阅读说明：本技术 具有公共高压直流母线的级联多电平整流器及控制策略 (Cascaded multi-level rectifier with common high-voltage direct-current bus and control strategy ) 是由 王聪 程红 赵志浩 李瑶璞 田长庚 邓嘉卿 陶艳梅 于 2020-06-11 设计创作，主要内容包括：本发明具有公共高压直流母线的级联多电平整流器及控制策略,属于AC/DC变换技术及其控制技术。该变换器提供多种主功率电路,每种主功率电路都由若干个模块单元级联组成,用于构成一对公共高压直流母线,极大降低了功率开关管的电压应力,克服了传统整流器由于功率开关管电压应力限制而不能产生高直流母线电压的缺点。本发明提供的整流器及控制策略平衡了输出侧各串联电容电压,实现应用低耐压的功率开关管完成高电压下的大功率整流变换,且不需要使用庞大,笨重,接线复杂的工频移相变压器的隔离,极大简化了主功率电路拓扑,提高了系统的工作效率,体积小,重量轻,成本低,在中高压直流输电、大功率的中高压变频器等领域具有重要的应用价值。(The invention discloses a cascaded multi-level rectifier with a common high-voltage direct-current bus and a control strategy, and belongs to an AC/DC conversion technology and a control technology thereof. The converter provides various main power circuits, each main power circuit is formed by cascading a plurality of module units and is used for forming a pair of public high-voltage direct-current buses, the voltage stress of a power switch tube is greatly reduced, and the defect that the traditional rectifier cannot generate high direct-current bus voltage due to the limitation of the voltage stress of the power switch tube is overcome. The rectifier and the control strategy balance the voltage of each series capacitor at the output side, realize the high-power rectification conversion under high voltage by using the low-voltage-resistant power switching tube, do not need to use the isolation of a power frequency phase-shifting transformer which is huge, heavy and complex in wiring, greatly simplify the topology of a main power circuit, improve the working efficiency of the system, have small volume, light weight and low cost, and have important application value in the fields of medium-high voltage direct current transmission, high-power medium-high voltage frequency converters and the like.)

1. Cascaded many level rectifier with public high voltage direct current generating line includes main power circuit, main power circuit includes high frequency filter, single-phase diode rectifier bridge, boost inductance L and first module unit (A), its characterized in that: the first module unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filterInductor L_BAnd a load resistor R_BSaid switching device S_B1And said switching device S_B2Is connected to the first terminal (c), said switching device S_B2And said filter inductance L_BIs connected to one end of the filter inductor L_BAnd the other end of the capacitor is connected with the output direct current capacitor C in parallel_BAnd the load resistance R_BN of said second module units (B) are cascaded, wherein each of said second module units (B) has a switching device S_B1And a switching device S in the next said second module unit (B)_B1Is connected to the first terminal (a), the output dc capacitors C connected in parallel in the respective second module units (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel in the next second modular unit (B)_BAnd the load resistance R_BIs connected to the first terminal (e) of the first and second module unit (B) of the cascade connection_B1With said output dc capacitor C connected in parallel_BAnd the load resistance R_BAnd said switching device S₁Is connected to the second terminal (n), said switching device S₁And the fast recovery diode D₁Is connected to the anode of the fast recovery diode D₁And the output direct current capacitor C connected in parallel₁And the load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And the load resistance R₁And the other end of the first and second cascade-connected module units (B) is connected in parallel with the output DC capacitor C_BAnd the load resistance R_BIs connected to the first terminal (e), said switching device S₁The first terminal (m) of the boost inductor L is connected with one end of the boost inductor L, the other end of the boost inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂With said first terminal (m) of said second module unit (B) of the nth in cascadeSwitching device S_B1Is connected with the second terminal (B), and the output direct current capacitor C connected in parallel in the Nth cascaded second module unit (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel₂And the load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And the load resistance R₂And the other end of the diode and the fast recovery diode D₂Is connected to the anode of the switching device S₂And said fast recovery diode D₂The negative pole of the single-phase diode rectifier bridge is connected with the negative end of the rectification output of the single-phase diode rectifier bridge, and the alternating current input end of the single-phase diode rectifier bridge is connected with an alternating current power grid in series through the high-frequency filter.

2. The cascaded multi-level three-phase star-connected rectifier with the common high-voltage direct-current bus, which is formed by the cascaded multi-level rectifier with the common high-voltage direct-current bus, of claim 1, comprises a three-phase main power circuit, and is characterized in that: the three-phase main power circuit comprises three high-frequency filters and three third module units (C), wherein each third module unit (C) comprises a single-phase diode rectifier bridge, a boost inductor L and a first module unit (A), and each first module unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSaid switching device S_B1And said switching device S_B2Is connected to the first terminal (c), said switching device S_B2And said filter inductance L_BIs connected to one end of the filter inductor L_BAnd the other end of the capacitor is connected with the output direct current capacitor C in parallel_BAnd the negativeLoad resistor R_BN of said second module units (B) are cascaded, wherein each of said second module units (B) has a switching device S_B1And a switching device S in the next said second module unit (B)_B1Is connected to the first terminal (a), the output dc capacitors C connected in parallel in the respective second module units (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel in the next second modular unit (B)_BAnd the load resistance R_BIs connected to the first terminal (e) of the first and second module unit (B) of the cascade connection_B1With said output dc capacitor C connected in parallel_BAnd the load resistance R_BAnd said switching device S₁Is connected to the second terminal (n), said switching device S₁And the fast recovery diode D₁Is connected to the anode of the fast recovery diode D₁And the output direct current capacitor C connected in parallel₁And the load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And the load resistance R₁And the other end of the first and second cascade-connected module units (B) is connected in parallel with the output DC capacitor C_BAnd the load resistance R_BIs connected to the first terminal (e), said switching device S₁The first terminal (m) of the boost inductor L is connected with one end of the boost inductor L, the other end of the boost inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂And the switching device S in the Nth of the second module unit (B) in cascade connection_B1Is connected with the second terminal (B), and the output direct current capacitor C connected in parallel in the Nth cascaded second module unit (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel₂And the load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And the load resistanceR₂And the other end of the diode and the fast recovery diode D₂Is connected to the anode of the switching device S₂And said fast recovery diode D₂The negative pole of the single-phase diode rectifier bridge is connected with the rectification output negative end of the single-phase diode rectifier bridge, 2 residual alternating current input ends of the third module unit (C) of each phase are arranged, the first alternating current input end of the three-phase third module unit (C) forms a group of wiring terminals, the second alternating current input end of the three-phase third module unit (C) forms another group of wiring terminals, one group of wiring terminals are connected to a common neutral point, and the other group of wiring terminals are respectively connected with the three high-frequency filters in series and connected into a three-phase power grid to form star connection.

3. The cascaded multi-level three-phase angle rectifier with the common high-voltage direct-current bus formed by the cascaded multi-level rectifier with the common high-voltage direct-current bus of claim 1 comprises a three-phase main power circuit, and is characterized in that: the three-phase main power circuit comprises three high-frequency filters and three third module units (C), wherein each third module unit (C) comprises a single-phase diode rectifier bridge, a boost inductor L and a first module unit (A), and each first module unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSaid switching device S_B1And said switching device S_B2Is connected to the first terminal (c), said switching device S_B2And said filter inductance L_BIs connected to one end of the filter inductor L_BAnd the other end of the capacitor is connected with the output direct current capacitor C in parallel_BAnd the load resistance R_BN of said second modular units (B) cascaded,wherein a switching device S is provided in each of said second modular units (B)_B1And a switching device S in the next said second module unit (B)_B1Is connected to the first terminal (a), the output dc capacitors C connected in parallel in the respective second module units (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel in the next second modular unit (B)_BAnd the load resistance R_BIs connected to the first terminal (e) of the first and second module unit (B) of the cascade connection_B1With said output dc capacitor C connected in parallel_BAnd the load resistance R_BAnd said switching device S₁Is connected to the second terminal (n), said switching device S₁And the fast recovery diode D₁Is connected to the anode of the fast recovery diode D₁And the output direct current capacitor C connected in parallel₁And the load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And the load resistance R₁And the other end of the first and second cascade-connected module units (B) is connected in parallel with the output DC capacitor C_BAnd the load resistance R_BIs connected to the first terminal (e), said switching device S₁The first terminal (m) of the boost inductor L is connected with one end of the boost inductor L, the other end of the boost inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂And the switching device S in the Nth of the second module unit (B) in cascade connection_B1Is connected with the second terminal (B), and the output direct current capacitor C connected in parallel in the Nth cascaded second module unit (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel₂And the load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And the load resistance R₂And the other end of the diode and the fast recovery diode D₂Is connected to the anode of the switchDevice S₂And said fast recovery diode D₂The negative pole of the three-phase diode rectifier bridge is connected with the rectification output negative end of the single-phase diode rectifier bridge, 2 residual alternating current input ends of the third module unit (C) of each phase are arranged, the first alternating current input end of the three-phase third module unit (C) forms a group of wiring ends, the second alternating current input end of the three-phase third module unit (C) forms another group of wiring ends, one group of wiring ends are respectively connected to the input end of the three-phase power grid through the three high-frequency filters, and the other group of wiring ends are sequentially connected to the input end of the next phase in the three-phase power grid to form an.

4. The cascaded multi-level three-phase double star rectifier with the common high-voltage direct-current bus formed by the cascaded multi-level current transformers with the common high-voltage direct-current bus of claim 1 comprises a three-phase main power circuit, and is characterized in that: the three-phase main power circuit comprises three high-frequency filters, six bridge arm inductors, a direct current capacitor and six third modular units (C), wherein the six third modular units (C) form two groups of butted star-shaped connections, namely in each group of star-shaped connections, each third modular unit (C) comprises a single-phase diode rectifier bridge, a boost inductor L and a first modular unit (A), and each first modular unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSaid switching device S_B1And said switching device S_B2Is connected to the first terminal (c), said switching device S_B2And said filter inductance L_BIs connected to one end of the filter inductor L_BAnd the other end of the capacitor is connected with the output direct current capacitor C in parallel_BAnd the load resistance R_BSecond connection ofA plurality of N cascaded second module units (B) connected with each other at the line end (f), wherein each second module unit (B) is provided with a switching device S_B1And a switching device S in the next said second module unit (B)_B1Is connected to the first terminal (a), the output dc capacitors C connected in parallel in the respective second module units (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel in the next second modular unit (B)_BAnd the load resistance R_BIs connected to the first terminal (e) of the first and second module unit (B) of the cascade connection_B1With said output dc capacitor C connected in parallel_BAnd the load resistance R_BAnd said switching device S₁Is connected to the second terminal (n), said switching device S₁And the fast recovery diode D₁Is connected to the anode of the fast recovery diode D₁And the output direct current capacitor C connected in parallel₁And the load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And the load resistance R₁And the other end of the first and second cascade-connected module units (B) is connected in parallel with the output DC capacitor C_BAnd the load resistance R_BIs connected to the first terminal (e), said switching device S₁The first terminal (m) of the boost inductor L is connected with one end of the boost inductor L, the other end of the boost inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂And the switching device S in the Nth of the second module unit (B) in cascade connection_B1Is connected with the second terminal (B), and the output direct current capacitor C connected in parallel in the Nth cascaded second module unit (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel₂And the load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And the load resistance R₂Another end of (2) andfast recovery diode D₂Is connected to the anode of the switching device S₂And said fast recovery diode D₂The cathode of the three-phase three-module unit (C) is connected with the rectification output negative end of the single-phase diode rectifier bridge, 2 alternating current input ends are remained in each phase of the third module unit (C), a group of wiring ends are formed by the first alternating current input ends of the three-phase third module unit (C), the second alternating current input ends of the three-phase third module unit (C) form another group of wiring ends, one group of wiring ends are connected to a common neutral point, the other group of wiring ends are respectively connected with one end of three bridge arm inductors, the other ends of the two bridge arm inductors on each phase of bridge arm are respectively connected with the input end of a three-phase power grid through one of the three high-frequency filters, and meanwhile, the common neutral point in the first group of star connection and the common neutral point in the second group of star connection are respectively connected with the two ends of the.

5. A control strategy of a cascaded multi-level rectifier with a common high-voltage direct-current bus is characterized in that the control strategy of the cascaded multi-level rectifier with the common high-voltage direct-current bus comprises the following steps:

(1) sampling the output side direct current voltage of a cascade multi-level rectifier with a public high-voltage direct current bus to obtain N +2 output side direct current voltage signals U_o1、U_o2And U_oB1、U_oB2...U_oBN；

(2) Calculating the N +2 output side direct-current voltage signals U in the step (1) by using the following formula_o1、U_o2And U_oB1、U_oB2...U_oBNAverage value of U_o：

(3) Mixing U in step (2)_oWith a given signal U of DC voltage_o ^*After comparison, the obtained signal is sent to a PI voltage regulator to obtain the amplitude I of the direct current signal output by the PI voltage regulator_d；

(4) The N +2 output side direct current voltage signals U in the step (1) are processed_o1、U_o2And U_oB1、U_oB2...U_oBNRespectively associated with a given signal U of DC voltage_o ^*After comparison, the obtained signal is sent to a PI voltage regulator to obtain the amplitude I of the direct current signal output by the PI voltage regulator_d1、I_d2And I_dB1、I_dB2...I_dBN；

(5) The amplitude I of the direct current signal in the step (4) is measured_d1、I_d2And I_dB1、I_dB2...I_dBNRespectively corresponding to the amplitude I of the DC current signal in the step (2)_dAdding the obtained DC current to obtain a given signal amplitude I_d1 ^*、I_d2 ^*And I_dB1 ^*、I_dB2 ^*...I_dBN ^*Setting the DC current to a signal amplitude I_d1 ^*、I_d2 ^*And I_dB1 ^*、I_dB2 ^*...I_dBN ^*Multiplying with a sinusoidal signal obtained by a Phase-Locked loop (PLL) and having the same Phase as the network voltage to generate an alternating current given signal i_d1 ^*、i_d2 ^*And i_dB1 ^*、i_dB2 ^*...i_dBN ^*；

(6) Detecting a current t_kNetwork voltage e (t) at time_k) And an alternating current i (t)_k) Predicting t using the following equation_k+1Time of day alternating current i_d1(t_k+1)、i_d2(t_k+1) And i_dB1(t_k+1)、i_dB2(t_k+1)...i_dBN(t_k+1) The value of (c):

in the formula, L₁Is a boost inductor; r is a boost inductor L₁Internal resistance; t is_sIs a sampling period; u. of_d1(t_k)、u_d2(t_k) And u_dB1(t_k)、u_dB2(t_k)...u_dBN(t_k) The voltages of the alternating current sides corresponding to the applied switch states of the rectifier in the kth sampling period are respectively;

(7) calculating u in step (6) using the following formula_d1(t_k)、u_d2(t_k) And u_dB1(t_k)、u_dB2(t_k)...u_dBN(t_k)：

In the formula of U_o1(t_k)、U_o2(t_k) And U_oB1(t_k)、U_oB2(t_k)...U_oBN(t_k) Is t_kN +2 DC voltage signals, S, at the output side of the time rectifier_d1(t_k)、S_d2(t_k) And S_dB1(t_k)、S_dB2(t_k)...S_dBN(t_k) Is t_kThe corresponding switch state of the rectifier at the moment: s_d1(t_k)、S_d2(t_k) And

(8) constructing a cost function g_d1、g_d2And g_dB1、g_dB2...g_dBN：

g_d1＝|i_d1 ^*-i_d1(t_k+1)|

g_d2＝|i_d2 ^*-i_d2(t_k+1)|

g_dB1＝|i_dB1 ^*-i_dB1(t_k+1)|

g_dB2＝|i_dB2 ^*-i_dB2(t_k+1)|

g_dBN＝|i_dBN ^*-i_dBN(t_k+1)|

In the formula i_d1 ^*、i_d2 ^*And i_dB1 ^*、i_dB2 ^*...i_dBN ^*Setting a signal, i, for the alternating current in step (5)_d1(t_k+1)、i_d2(t_k+1) And i_dB1(t_k+1)、i_dB2(t_k+1)...i_dBN(t_k+1) Is t in step (6)_k+1Predicting the alternating current at the moment;

(9) by a cost function g_d1、g_d2And g_dB1、g_dB2...g_dBNEvaluating each switch state of the rectifier, selecting the switch state corresponding to the predicted current value which minimizes the cost function, and generating the driving signal Q of the switching device₁、Q₂And Q_1B1、Q_1B2...Q_1BN(ii) a Will drive signal Q₂And Q_1B2、Q_1B3...Q_1BNObtaining a driving signal Q after inverting_2B1、Q_2B2...Q_2BN；

(10) The driving signal Q in the step (9) is converted into a driving signal Q₁、Q₂And Q_1B1、Q_1B2...Q_1BNAnd the driving signal Q in step (9)_2B1、Q_2B2...Q_2BNAnd the voltage is sent to a corresponding switch device, so that active power factor correction is realized, input current is sinusoidal, and balance control over the voltage of N +2 cascaded output direct current capacitors is realized.

Technical Field

The invention belongs to the technical field of high-power high-voltage rectification and conversion, and particularly relates to a system implementation scheme of a cascaded multi-level current-smoothing circuit with a high-voltage common direct-current bus.

Background

In recent years, a multi-level power converter (multilevel converter) has been more and more successfully applied in the fields of medium-high voltage high-power frequency conversion speed regulation, active power filtering, High Voltage Direct Current (HVDC) power transmission, reactive power compensation of a power system and the like. The basic circuit topologies of multilevel converters can be roughly classified into a clamping type and a cell cascade type. Diode-clamped three-level medium-high voltage inverters manufactured by siemens corporation or ABB corporation and cascaded H-bridge medium-high voltage inverters manufactured by robinkon corporation or rituximab corporation, which are widely used in the industry at present, are typical representatives of the two types of products. In any of the two types of medium-high voltage frequency converters, in order to implement high-voltage power conversion by using low-voltage-resistant power electronic devices, an industrial frequency phase-shifting transformer with large volume, complex wiring and high price is required to be used at the input side of the rectifier to realize electrical isolation. This limits their use in many industrial applications [1 ].

The cascade multilevel converter [2] without the power frequency transformer has attracted wide attention in the technical field of power electronics in recent years, and is considered to be an ideal implementation scheme of an intelligent power grid interface or a new generation medium-high voltage frequency converter which is suitable for a new energy power generation system to access and meet the distributed power generation requirement. The converter uses a high-frequency transformer to replace a power frequency phase-shifting transformer in the traditional cascade converter to realize electrical isolation, and when the converter is used for bidirectional power transmission, a cascade full-control H bridge multi-level power converter structure is adopted on a rectifying side. When the power converter is used for unidirectional power transmission, a unidirectional cascade multilevel power converter structure (comprising a cascade diode + Boost rectifying circuit, a cascade bridgeless rectifying circuit, a cascade VIENNA rectifying circuit and the like) is adopted at the rectifying side. Compared with the traditional rectifier stage of a medium-high voltage frequency converter, the implementation scheme of the rectifier stage of the converter cancels a power frequency phase-shifting transformer which is large in size, complex in wiring and high in price, so that the size, the weight and the manufacturing cost of a system are effectively reduced. However, such converters also have significant drawbacks, mainly represented by: each phase of N cascade rectifier modules can generate N groups of direct current output ends, and the direct current output ends of the N groups of rectifier modules cannot be directly connected in series to form a pair of common high-voltage direct current output buses because the input ends are not isolated, so that the N groups of rectifier modules cannot be directly used for high-voltage direct current transmission and cannot be directly connected with a multi-level inverter circuit to be used for medium-high voltage frequency conversion speed regulation. In order to realize a common high-voltage direct-current output bus or realize flexible control of N groups of rectified output direct-current voltages, N groups of cascaded rectification modules are necessarily connected with N high-frequency isolation DC-DC conversion modules in sequence, so that the complexity of the topological structure and the control mode of the whole system is increased, and the working efficiency is reduced.

Disclosure of Invention

The invention aims to overcome the defects and provides a novel implementation scheme of a high-voltage high-power cascaded multilevel unit power factor rectifier, compared with the rectification stage of the traditional medium-high voltage frequency converter, the novel cascaded rectifier provided by the invention can finish high-power unit power factor rectification conversion under high voltage by using a low-voltage-resistant power switching tube without using a power frequency phase-shifting transformer at the input end. Compared with a cascade multilevel converter without a power frequency transformer, the novel cascade rectifier provided by the invention can form a pair of common high-voltage direct-current buses on the direct-current side, and can flexibly realize the balance control of the capacitor voltage on the output side of each cascade rectifier module. The novel main power circuit of the cascade rectifier provided by the invention has the advantages of simple topological structure, high system working efficiency, small volume, light weight and low cost, and has important application value in the fields of High Voltage Direct Current (HVDC), high-power electronic transformers, high-power medium-high voltage alternating current-direct current-alternating current frequency converters and the like.

To achieve the above objects, the present invention provides cascaded multilevel converter with common high voltage dc busThe current device comprises a main power circuit, wherein the main power circuit comprises a high-frequency filter, a single-phase diode rectifier bridge, a boost inductor L and a first module unit (A), and is characterized in that: the first module unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSaid switching device S_B1And said switching device S_B2Is connected to the first terminal (c), said switching device S_B2And said filter inductance L_BIs connected to one end of the filter inductor L_BAnd the other end of the capacitor is connected with the output direct current capacitor C in parallel_BAnd the load resistance R_BN of said second module units (B) are cascaded, wherein each of said second module units (B) has a switching device S_B1And a switching device S in the next said second module unit (B)_B1Is connected to the first terminal (a), the output dc capacitors C connected in parallel in the respective second module units (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel in the next second modular unit (B)_BAnd the load resistance R_BIs connected to the first terminal (e) of the first and second module unit (B) of the cascade connection_B1With said output dc capacitor C connected in parallel_BAnd the load resistance R_BAnd said switching device S₁Is connected to the second terminal (n), said switching device S₁And the fast recovery diode D₁Is connected to the anode of the fast recovery diode D₁And the output direct current capacitor C connected in parallel₁And the negativeLoad resistor R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And the load resistance R₁And the other end of the first and second cascade-connected module units (B) is connected in parallel with the output DC capacitor C_BAnd the load resistance R_BIs connected to the first terminal (e), said switching device S₁The first terminal (m) of the boost inductor L is connected with one end of the boost inductor L, the other end of the boost inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂And the switching device S in the Nth of the second module unit (B) in cascade connection_B1Is connected with the second terminal (B), and the output direct current capacitor C connected in parallel in the Nth cascaded second module unit (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel₂And the load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And the load resistance R₂And the other end of the diode and the fast recovery diode D₂Is connected to the anode of the switching device S₂And said fast recovery diode D₂The negative pole of the single-phase diode rectifier bridge is connected with the negative end of the rectification output of the single-phase diode rectifier bridge, and the alternating current input end of the single-phase diode rectifier bridge is connected with an alternating current power grid in series through the high-frequency filter.

In order to achieve the purpose, the cascade multi-level three-phase star connection rectifier with the public high-voltage direct current bus, which is formed by adopting the cascade multi-level rectifier with the public high-voltage direct current bus, comprises a three-phase main power circuit and is characterized in that: the three-phase main power circuit comprises three high-frequency filters and three third module units (C), wherein each third module unit (C) comprises a single-phase diode rectifier bridge, a boost inductor L and a first module unit (A), and each first module unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascadedA second module unit (B), N being a positive integer, said second module unit (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSaid switching device S_B1And said switching device S_B2Is connected to the first terminal (c), said switching device S_B2And said filter inductance L_BIs connected to one end of the filter inductor L_BAnd the other end of the capacitor is connected with the output direct current capacitor C in parallel_BAnd the load resistance R_BN of said second module units (B) are cascaded, wherein each of said second module units (B) has a switching device S_B1And a switching device S in the next said second module unit (B)_B1Is connected to the first terminal (a), the output dc capacitors C connected in parallel in the respective second module units (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel in the next second modular unit (B)_BAnd the load resistance R_BIs connected to the first terminal (e) of the first and second module unit (B) of the cascade connection_B1With said output dc capacitor C connected in parallel_BAnd the load resistance R_BAnd said switching device S₁Is connected to the second terminal (n), said switching device S₁And the fast recovery diode D₁Is connected to the anode of the fast recovery diode D₁And the output direct current capacitor C connected in parallel₁And the load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And the load resistance R₁And the other end of the first and second cascade-connected module units (B) is connected in parallel with the output DC capacitor C_BAnd the load resistance R_BIs connected to the first terminal (e), said switching device S₁Is connected to one end of the boost inductor L, the other end of the boost inductor LOne end of the switching device S is connected with the positive end of the rectification output of the single-phase diode rectifier bridge₂And the switching device S in the Nth of the second module unit (B) in cascade connection_B1Is connected with the second terminal (B), and the output direct current capacitor C connected in parallel in the Nth cascaded second module unit (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel₂And the load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And the load resistance R₂And the other end of the diode and the fast recovery diode D₂Is connected to the anode of the switching device S₂And said fast recovery diode D₂The negative pole of the single-phase diode rectifier bridge is connected with the rectification output negative end of the single-phase diode rectifier bridge, 2 residual alternating current input ends of the third module unit (C) of each phase are arranged, the first alternating current input end of the three-phase third module unit (C) forms a group of wiring terminals, the second alternating current input end of the three-phase third module unit (C) forms another group of wiring terminals, one group of wiring terminals are connected to a common neutral point, and the other group of wiring terminals are respectively connected with the three high-frequency filters in series and connected into a three-phase power grid to form star connection.

In order to achieve the purpose, the invention provides a cascaded multi-level three-phase angle connection rectifier with a common high-voltage direct current bus, which is formed by cascaded multi-level rectifiers with the common high-voltage direct current bus, and comprises a three-phase main power circuit, and is characterized in that: the three-phase main power circuit comprises three high-frequency filters and three third module units (C), wherein each third module unit (C) comprises a single-phase diode rectifier bridge, a boost inductor L and a first module unit (A), and each first module unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S _B21 toAn output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSaid switching device S_B1And said switching device S_B2Is connected to the first terminal (c), said switching device S_B2And said filter inductance L_BIs connected to one end of the filter inductor L_BAnd the other end of the capacitor is connected with the output direct current capacitor C in parallel_BAnd the load resistance R_BN of said second module units (B) are cascaded, wherein each of said second module units (B) has a switching device S_B1And a switching device S in the next said second module unit (B)_B1Is connected to the first terminal (a), the output dc capacitors C connected in parallel in the respective second module units (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel in the next second modular unit (B)_BAnd the load resistance R_BIs connected to the first terminal (e) of the first and second module unit (B) of the cascade connection_B1With said output dc capacitor C connected in parallel_BAnd the load resistance R_BAnd said switching device S₁Is connected to the second terminal (n), said switching device S₁And the fast recovery diode D₁Is connected to the anode of the fast recovery diode D₁And the output direct current capacitor C connected in parallel₁And the load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And the load resistance R₁And the other end of the first and second cascade-connected module units (B) is connected in parallel with the output DC capacitor C_BAnd the load resistance R_BIs connected to the first terminal (e), said switching device S₁The first terminal (m) of the boost inductor L is connected with one end of the boost inductor L, the other end of the boost inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂First terminal (m) and stage (c)Said switching device S in the Nth of said second modular units (B) of the series_B1Is connected with the second terminal (B), and the output direct current capacitor C connected in parallel in the Nth cascaded second module unit (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel₂And the load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And the load resistance R₂And the other end of the diode and the fast recovery diode D₂Is connected to the anode of the switching device S₂And said fast recovery diode D₂The negative pole of the three-phase diode rectifier bridge is connected with the rectification output negative end of the single-phase diode rectifier bridge, 2 residual alternating current input ends of the third module unit (C) of each phase are arranged, the first alternating current input end of the three-phase third module unit (C) forms a group of wiring ends, the second alternating current input end of the three-phase third module unit (C) forms another group of wiring ends, one group of wiring ends are respectively connected to the input end of the three-phase power grid through the three high-frequency filters, and the other group of wiring ends are sequentially connected to the input end of the next phase in the three-phase power grid to form an.

In order to achieve the above object, the cascaded multi-level three-phase double star rectifier with a common high-voltage direct-current bus, which is formed by cascaded multi-level rectifiers with a common high-voltage direct-current bus, provided by the invention comprises a three-phase main power circuit, and is characterized in that: the three-phase main power circuit comprises three high-frequency filters, six bridge arm inductors, a direct current capacitor and six third modular units (C), wherein the six third modular units (C) form two groups of butted star-shaped connections, namely in each group of star-shaped connections, each third modular unit (C) comprises a single-phase diode rectifier bridge, a boost inductor L and a first modular unit (A), and each first modular unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSaid switching device S_B1And said switching device S_B2Is connected to the first terminal (c), said switching device S_B2And said filter inductance L_BIs connected to one end of the filter inductor L_BAnd the other end of the capacitor is connected with the output direct current capacitor C in parallel_BAnd the load resistance R_BN of said second module units (B) are cascaded, wherein each of said second module units (B) has a switching device S_B1And a switching device S in the next said second module unit (B)_B1Is connected to the first terminal (a), the output dc capacitors C connected in parallel in the respective second module units (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel in the next second modular unit (B)_BAnd the load resistance R_BIs connected to the first terminal (e) of the first and second module unit (B) of the cascade connection_B1With said output dc capacitor C connected in parallel_BAnd the load resistance R_BAnd said switching device S₁Is connected to the second terminal (n), said switching device S₁And the fast recovery diode D₁Is connected to the anode of the fast recovery diode D₁And the output direct current capacitor C connected in parallel₁And the load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And the load resistance R₁And the other end of the first and second cascade-connected module units (B) is connected in parallel with the output DC capacitor C_BAnd the load resistance R_BIs connected to the first terminal (e), said switching device S₁The first terminal (m) of the boost inductor L is connected with one end of the boost inductor L, the other end of the boost inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂And the switching device S in the Nth of the second module unit (B) in cascade connection_B1Is connected with the second terminal (B), and the output direct current capacitor C connected in parallel in the Nth cascaded second module unit (B)_BAnd the load resistance R_BWith said output dc capacitor C connected in parallel₂And the load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And the load resistance R₂And the other end of the diode and the fast recovery diode D₂Is connected to the anode of the switching device S₂And said fast recovery diode D₂The cathode of the three-phase three-module unit (C) is connected with the rectification output negative end of the single-phase diode rectifier bridge, 2 alternating current input ends are remained in each phase of the third module unit (C), a group of wiring ends are formed by the first alternating current input ends of the three-phase third module unit (C), the second alternating current input ends of the three-phase third module unit (C) form another group of wiring ends, one group of wiring ends are connected to a common neutral point, the other group of wiring ends are respectively connected with one end of three bridge arm inductors, the other ends of the two bridge arm inductors on each phase of bridge arm are respectively connected with the input end of a three-phase power grid through one of the three high-frequency filters, and meanwhile, the common neutral point in the first group of star connection and the common neutral point in the second group of star connection are respectively connected with the two ends of the.

In order to achieve the above object, the present invention provides a control strategy for a cascaded multi-level rectifier with a common high voltage dc bus, which is characterized in that the control strategy for the cascaded multi-level rectifier with the common high voltage dc bus comprises the following steps:

(1) sampling the output side direct current voltage of a cascade multi-level rectifier with a public high-voltage direct current bus to obtain N +2 output side direct current voltage signals U_o1、U_o2And U_oB1、U_oB2...U_oBN；

(2) Calculating the N +2 output side direct-current voltage signals U in the step (1) by using the following formula_o1、U_o2And U_oB1、U_oB2...U_oBNAverage value of U_o：

(3) Mixing U in step (2)_oWith a given signal U of DC voltage_o ^*After comparison, the obtained signal is sent to a PI voltage regulator to obtain the amplitude I of the direct current signal output by the PI voltage regulator_d；

(4) The N +2 output side direct current voltage signals U in the step (1) are processed_o1、U_o2And U_oB1、U_oB2...U_oBNRespectively associated with a given signal U of DC voltage_o ^*After comparison, the obtained signal is sent to a PI voltage regulator to obtain the amplitude I of the direct current signal output by the PI voltage regulator_d1、I_d2And I_dB1、I_dB2...I_dBN；

(5) The amplitude I of the direct current signal in the step (4) is measured_d1、I_d2And I_dB1、I_dB2...I_dBNRespectively corresponding to the amplitude I of the DC current signal in the step (2)_dAdding the obtained DC current to obtain a given signal amplitude I_d1 ^*、I_d2 ^*And I_dB1 ^*、I_dB2 ^*...I_dBN ^*Setting the DC current to a signal amplitude I_d1 ^*、I_d2 ^*And I_dB1 ^*、I_dB2 ^*...I_dBN ^*Multiplying with a sinusoidal signal obtained by a Phase-locked loop PLL (Phase-Lockedloop) and having the same Phase with the network voltage to generate an alternating current given signal i_d1 ^*、i_d2 ^*And i_dB1 ^*、i_dB2 ^*...i_dBN ^*；

(6) Detecting a current t_kNetwork voltage e (t) at time_k) And an alternating current i (t)_k) Predicting t using the following equation_k+1Time of day alternating current i_d1(t_k+1)、i_d2(t_k+1) And i_dB1(t_k+1)、i_dB2(t_k+1)...i_dBN(t_k+1) The value of (c):

in the formula, L₁Is a boost inductor; r is a boost inductor L₁Internal resistance; t is_sIs a sampling period; u. of_d1(t_k)、u_d2(t_k) And u_dB1(t_k)、u_dB2(t_k)...u_dBN(t_k) The voltages of the alternating current sides corresponding to the applied switch states of the rectifier in the kth sampling period are respectively;

(7) calculating u in step (6) using the following formula_d1(t_k)、u_d2(t_k) And u_dB1(t_k)、u_dB2(t_k)...u_dBN(t_k)：

u_d1(t_k)＝S_d1(t_k)^*U_o1(t_k)

u_d2(t_k)＝S_d2(t_k)^*U_o2(t_k)

u_dB1(t_k)＝S_dB1(t_k)^*U_oB1(t_k)

u_dB2(t_k)＝S_dB2(t_k)^*U_oB2(t_k)

u_dBN(t_k)＝S_dBN(t_k)^*U_oBN(t_k)

In the formula of U_o1(t_k)、U_o2(t_k) And U_oB1(t_k)、U_oB2(t_k)...U_oBN(t_k) Is t_kN +2 DC voltage signals, S, at the output side of the time rectifier_d1(t_k)、S_d2(t_k) And S_dB1(t_k)、S_dB2(t_k)...S_dBN(t_k) Is t_kThe corresponding switch state of the rectifier at the moment: s_d1(t_k)、S_d2(t_k) And

(8) constructing a cost function g_d1、g_d2And g_dB1、g_dB2...g_dBN：

g_d1＝|i_d1 ^*-i_d1(t_k+1)|

g_d2＝|i_d2 ^*-i_d2(t_k+1)|

g_dB1＝|i_dB1 ^*-i_dB1(t_k+1)|

g_dB2＝|i_dB2 ^*-i_dB2(t_k+1)|

g_dBN＝|i_dBN ^*-i_dBN(t_k+1)|

In the formula i_d1 ^*、i_d2 ^*And i_dB1 ^*、i_dB2 ^*...i_dBN ^*Setting a signal, i, for the alternating current in step (5)_d1(t_k+1)、i_d2(t_k+1) And i_dB1(t_k+1)、i_dB2(t_k+1)...i_dBN(t_k+1) Is t in step (6)_k+1Predicting the alternating current at the moment;

(9) by a cost function g_d1、g_d2And g_dB1、g_dB2...g_dBNEvaluating each switch state of the rectifier, selecting the switch state corresponding to the predicted current value which minimizes the cost function, and generating the driving signal Q of the switching device₁、Q₂And Q_1B1、Q_1B2...Q_1BN(ii) a Will drive signal Q₂And Q_1B2、Q_1B3...Q_1BNObtaining a driving signal Q after inverting_2B1、Q_2B2...Q_2BN；

(10) The driving signal Q in the step (9) is converted into a driving signal Q₁、Q₂And Q_1B1、Q_1B2...Q_1BNAnd the driving signal Q in step (9)_2B1、Q_2B2...Q_2BNAnd the voltage is sent to a corresponding switch device, so that active power factor correction is realized, input current is sinusoidal, and balance control over the voltage of N +2 cascaded output direct current capacitors is realized.

The cascaded multi-level rectifier with the common high-voltage direct-current bus has the advantages and positive effects that: compared with the traditional rectifier stage of the medium-high voltage frequency converter, the novel cascade rectifier provided by the invention does not need to use a power frequency phase-shifting transformer at the input end, and can use a low-voltage-resistant power switching tube to finish high-power unit power factor rectification conversion under high voltage. Compared with a cascade multilevel converter without a power frequency transformer, the novel cascade rectifier provided by the invention can form a pair of common high-voltage direct-current buses on the direct-current side, and can flexibly realize the balance control of the capacitor voltage on the output side of each cascade rectifier module. The novel main power circuit of the cascade rectifier provided by the invention has the advantages of simple topological structure, high system working efficiency, small volume, light weight and low cost, and has important application value in the fields of High Voltage Direct Current (HVDC), high-power electronic transformers, high-power medium-high voltage alternating current-direct current-alternating current frequency converters and the like.

The following detailed description is made with reference to the accompanying drawings in conjunction with the embodiments.

Drawings

Fig. 1 is a circuit diagram of a second modular unit (B) of the cascaded multi-level rectifier with a common high voltage dc bus and control strategy of the present invention;

fig. 2 is a circuit diagram of a first modular unit (a) of the cascaded multi-level rectifier with a common high voltage dc bus and control strategy of the present invention;

fig. 3 is a circuit diagram of a third modular unit (C) of the cascaded multi-level rectifier with a common high voltage dc bus and control strategy of the present invention;

FIG. 4 is a circuit diagram of a three-phase star-connected rectifier of the present invention with a cascaded multi-level rectifier with a common high voltage DC bus and control strategy;

FIG. 5 is a circuit diagram of a three-phase angle rectifier with a cascaded multi-level rectifier and control strategy of the present invention having a common high voltage DC bus;

FIG. 6 is a circuit diagram of a three-phase dual-star rectifier of the present invention with a cascaded multi-level rectifier with a common high voltage DC bus and control strategy;

FIG. 7 is a schematic diagram of a cascaded multi-level rectifier with a common high voltage DC bus and control strategy according to the present invention;

FIG. 8 is a flow chart of a cascaded multi-level rectifier with a common high voltage DC bus and control strategy of the present invention;

FIG. 9 is an overall block diagram of the cascaded multi-level rectifier with common high voltage DC bus and control strategy of the present invention;

Detailed Description

The embodiments and the working principle of the present invention will be further described with reference to the accompanying drawings:

referring to fig. 1 and 2, a cascaded multi-level rectifier with a common high voltage dc bus includes a main power circuit including a high frequency filter, a single phase diode rectifier bridge, a boost inductor L, and a first module unit (a) including two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSwitching device S_B1And the second terminal (b) of the switching device S_B2Is connected to the first terminal (c) of the switching device S_B2And the second terminal (d) and the filter inductance L_BIs connected to one end of a filter inductor L_BAnd the other end of the capacitor is connected with an output direct current capacitor C in parallel_BAnd a load resistance R_BN cascaded second module units (B), wherein each second module unit (B) has a switching device S_B1And the switching device S in the next second module unit (B)_B1Are connected to each other, and output dc capacitors C connected in parallel in the respective second module units (B)_BAnd a load resistance R_BAnd an output dc capacitor C connected in parallel in the next second module unit (B)_BAnd a load resistance R_BIs connected to the first terminal (e), and the switching device S in the first and second module units (B) are cascaded_B1With an output dc capacitor C connected in parallel_BAnd a load resistance R_BAnd a switching device S₁Is connected to the second terminal (n), the switching device S₁First terminal (m) and fast recovery diode D₁Is connected with the anode of the fast recovery diode D₁And an output DC capacitor C connected in parallel₁And a load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And a load resistance R₁And the other end of the first and second cascade module units (B) is connected with an output direct current capacitor C in parallel_BAnd a load resistance R_BIs connected to the first terminal (e), the switching device S₁The first terminal (m) of the voltage boosting inductor L is connected with one end of the voltage boosting inductor L, the other end of the voltage boosting inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂And a switching device S in the cascaded Nth second module unit (B)_B1Is connected with the second terminal (B), and an output direct current capacitor C connected in parallel in the Nth second module unit (B) in cascade connection_BAnd a load resistance R_BWith a second terminal (f) connected in parallel with an output dc capacitor C₂And a load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And a load resistance R₂And the other end of the diode D and the fast recovery diode D₂Is connected to the anode of the switching device S₂And a fast recovery diode D₂The negative pole of the single-phase diode rectifier bridge is connected with the negative end of the rectification output of the single-phase diode rectifier bridge, and the alternating current input end of the single-phase diode rectifier bridge is connected in series with an alternating current power grid through a high-frequency filter.

Referring to fig. 1, 2, 3 and 4, a cascaded multi-level three-phase star rectifier with a common high-voltage direct current bus formed by cascaded multi-level rectifiers with a common high-voltage direct current bus comprises a three-phase main power circuit, wherein the three-phase main power circuit comprises three high-frequency filters and three third module units (C), the third module units (C) comprise single-phase diode rectifier bridges, boost inductors L and a first module unit (A), and the first module unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSwitching device S_B1Second connection line ofTerminal (b) and switching device S_B2Is connected to the first terminal (c) of the switching device S_B2And the second terminal (d) and the filter inductance L_BIs connected to one end of a filter inductor L_BAnd the other end of the capacitor is connected with an output direct current capacitor C in parallel_BAnd a load resistance R_BN cascaded second module units (B), wherein each second module unit (B) has a switching device S_B1And the switching device S in the next second module unit (B)_B1Are connected to each other, and output dc capacitors C connected in parallel in the respective second module units (B)_BAnd a load resistance R_BAnd an output dc capacitor C connected in parallel in the next second module unit (B)_BAnd a load resistance R_BIs connected to the first terminal (e), and the switching device S in the first and second module units (B) are cascaded_B1With an output dc capacitor C connected in parallel_BAnd a load resistance R_BAnd a switching device S₁Is connected to the second terminal (n), the switching device S₁First terminal (m) and fast recovery diode D₁Is connected with the anode of the fast recovery diode D₁And an output DC capacitor C connected in parallel₁And a load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And a load resistance R₁And the other end of the first and second cascade module units (B) is connected with an output direct current capacitor C in parallel_BAnd a load resistance R_BIs connected to the first terminal (e), the switching device S₁The first terminal (m) of the voltage boosting inductor L is connected with one end of the voltage boosting inductor L, the other end of the voltage boosting inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂And a switching device S in the cascaded Nth second module unit (B)_B1Is connected with the second terminal (B), and an output direct current capacitor C connected in parallel in the Nth second module unit (B) in cascade connection_BAnd a load resistance R_BWith a second terminal (f) connected in parallel with an output dc capacitor C₂And a load resistance R₂Are connected at one end, outputs connected in parallelDC capacitor C₂And a load resistance R₂And the other end of the diode D and the fast recovery diode D₂Is connected to the anode of the switching device S₂And a fast recovery diode D₂The negative pole of the three-phase third module unit (C) and the rectification output negative end of the single-phase diode rectifier bridge are connected, 2 residual alternating current input ends of the three-phase third module unit (C) are arranged on each phase, the first alternating current input end of the three-phase third module unit (C) forms a group of wiring ends, the second alternating current input end of the three-phase third module unit (C) forms another group of wiring ends, one group of wiring ends is connected to a common neutral point, and the other group of wiring ends are respectively connected with three high-frequency filters in series to be connected into a three-phase power grid to form.

Referring to fig. 1, 2, 3 and 5, a cascaded multi-level three-phase angle rectifier with a common high-voltage direct current bus formed by cascaded multi-level rectifiers with a common high-voltage direct current bus comprises a three-phase main power circuit, wherein the three-phase main power circuit comprises three high-frequency filters and three third module units (C), the third module units (C) comprise single-phase diode rectifier bridges, boost inductors L and a first module unit (A), and the first module unit (A) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSwitching device S_B1And the second terminal (b) of the switching device S_B2Is connected to the first terminal (c) of the switching device S_B2And the second terminal (d) and the filter inductance L_BIs connected to one end of a filter inductor L_BAnd the other end of the capacitor is connected with an output direct current capacitor C in parallel_BAnd a load resistance R_BN cascaded second module units (B), wherein each second module unit (B) has a switching device S_B1And the switching device in the next second module unit (B)S_B1Are connected to each other, and output dc capacitors C connected in parallel in the respective second module units (B)_BAnd a load resistance R_BAnd an output dc capacitor C connected in parallel in the next second module unit (B)_BAnd a load resistance R_BIs connected to the first terminal (e), and the switching device S in the first and second module units (B) are cascaded_B1With an output dc capacitor C connected in parallel_BAnd a load resistance R_BAnd a switching device S₁Is connected to the second terminal (n), the switching device S₁First terminal (m) and fast recovery diode D₁Is connected with the anode of the fast recovery diode D₁And an output DC capacitor C connected in parallel₁And a load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And a load resistance R₁And the other end of the first and second cascade module units (B) is connected with an output direct current capacitor C in parallel_BAnd a load resistance R_BIs connected to the first terminal (e), the switching device S₁The first terminal (m) of the voltage boosting inductor L is connected with one end of the voltage boosting inductor L, the other end of the voltage boosting inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂And a switching device S in the cascaded Nth second module unit (B)_B1Is connected with the second terminal (B), and an output direct current capacitor C connected in parallel in the Nth second module unit (B) in cascade connection_BAnd a load resistance R_BWith a second terminal (f) connected in parallel with an output dc capacitor C₂And a load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And a load resistance R₂And the other end of the diode D and the fast recovery diode D₂Is connected to the anode of the switching device S₂And a fast recovery diode D₂The cathode of the three-phase third module unit (C) is connected with the rectification output negative terminal of the single-phase diode rectifier bridge, 2 AC input terminals are remained in each phase of the third module unit (C), the first AC input terminal of the three-phase third module unit (C) forms a group of wiring terminals, the second AC input terminal of the three-phase third module unit (C) forms another group of wiring terminals,one group of the terminals is connected to the input end of the three-phase power grid through three high-frequency filters, and the other group of the terminals is sequentially connected to the input end of the next phase in the three-phase power grid to form an angular connection.

Referring to fig. 1, 2, 3 and 6, a cascaded multi-level three-phase double-star rectifier with a common high-voltage direct-current bus, which is formed by cascaded multi-level rectifiers with a common high-voltage direct-current bus, comprises a three-phase main power circuit, wherein the three-phase main power circuit comprises three high-frequency filters, six bridge arm inductors, a direct-current capacitor and six third module units (C), the six third module units (C) form two groups of star connections which are in butt joint, namely in each group of star connections, the third module unit (C) comprises a single-phase diode rectifier bridge, a boost inductor L and a first module unit (a), and the first module unit (a) comprises two switching devices S₁、S₂Two fast recovery diodes D₁、D₂Two output DC capacitors C₁、C₂Two load resistors R₁、R₂And N cascaded second module units (B), N being a positive integer, the second module units (B) comprising two switching devices S_B1、S_B2An output DC capacitor C_BA filter inductor L_BAnd a load resistor R_BSwitching device S_B1And the second terminal (b) of the switching device S_B2Is connected to the first terminal (c) of the switching device S_B2And the second terminal (d) and the filter inductance L_BIs connected to one end of a filter inductor L_BAnd the other end of the capacitor is connected with an output direct current capacitor C in parallel_BAnd a load resistance R_BN cascaded second module units (B), wherein each second module unit (B) has a switching device S_B1And the switching device S in the next second module unit (B)_B1Are connected to each other, and output dc capacitors C connected in parallel in the respective second module units (B)_BAnd a load resistance R_BAnd an output dc capacitor C connected in parallel in the next second module unit (B)_BAnd a load resistance R_BAre connected to the first terminal (e) of the first series of terminalsA switching device S in a second modular unit (B)_B1With an output dc capacitor C connected in parallel_BAnd a load resistance R_BAnd a switching device S₁Is connected to the second terminal (n), the switching device S₁First terminal (m) and fast recovery diode D₁Is connected with the anode of the fast recovery diode D₁And an output DC capacitor C connected in parallel₁And a load resistance R₁Is connected with one end of the output direct current capacitor C in parallel connection₁And a load resistance R₁And the other end of the first and second cascade module units (B) is connected with an output direct current capacitor C in parallel_BAnd a load resistance R_BIs connected to the first terminal (e), the switching device S₁The first terminal (m) of the voltage boosting inductor L is connected with one end of the voltage boosting inductor L, the other end of the voltage boosting inductor L is connected with the positive end of the rectification output of the single-phase diode rectifier bridge, and the switching device S₂And a switching device S in the cascaded Nth second module unit (B)_B1Is connected with the second terminal (B), and an output direct current capacitor C connected in parallel in the Nth second module unit (B) in cascade connection_BAnd a load resistance R_BWith a second terminal (f) connected in parallel with an output dc capacitor C₂And a load resistance R₂Is connected with one end of the output direct current capacitor C in parallel connection₂And a load resistance R₂And the other end of the diode D and the fast recovery diode D₂Is connected to the anode of the switching device S₂And a fast recovery diode D₂The cathode of the three-phase diode rectifier bridge is connected with the rectification output negative end of the single-phase diode rectifier bridge, 2 alternating current input ends are remained in each phase of the third module unit (C), the first alternating current input end of the three-phase third module unit (C) forms a group of wiring ends, the second alternating current input end of the three-phase third module unit (C) forms another group of wiring ends, one group of wiring ends is connected to a common neutral point, the other group of wiring ends is respectively connected with one end of three bridge arm inductors, the other ends of the two bridge arm inductors on each phase of bridge arm are respectively connected to the three-phase power grid input end through one of three high-frequency filters, and simultaneously, the common neutral point in the first group of star connection andand a common neutral point in the star connection is respectively connected with two ends of the direct current capacitor to form double star connection.

4. Referring to fig. 7, 8 and 9, a control strategy for a cascaded multi-level rectifier with a common high voltage dc bus comprises the following steps:

(1) sampling the output side direct current voltage of a cascade multi-level rectifier with a public high-voltage direct current bus to obtain N +2 output side direct current voltage signals U_o1、U_o2And U_oB1、U_oB2...U_oBN；

(2) Calculating the N +2 output side direct-current voltage signals U in the step (1) by using the following formula_o1、U_o2And U_oB1、U_oB2...U_oBNAverage value of U_o：

(3) Mixing U in step (2)_oWith a given signal U of DC voltage_o ^*After comparison, the obtained signal is sent to a PI voltage regulator to obtain the amplitude I of the direct current signal output by the PI voltage regulator_d；

(4) The N +2 output side direct current voltage signals U in the step (1) are processed_o1、U_o2And U_oB1、U_oB2...U_oBNRespectively associated with a given signal U of DC voltage_o ^*After comparison, the obtained signal is sent to a PI voltage regulator to obtain the amplitude I of the direct current signal output by the PI voltage regulator_d1、I_d2And I_dB1、I_dB2...I_dBN；

(5) The amplitude I of the direct current signal in the step (4) is measured_d1、I_d2And I_dB1、I_dB2...I_dBNRespectively corresponding to the amplitude I of the DC current signal in the step (2)_dAdding the obtained DC current to obtain a given signal amplitude I_d1 ^*、I_d2 ^*And I_dB1 ^*、I_dB2 ^*...I_dBN ^*Setting the DC current to a signal amplitude I_d1 ^*、I_d2 ^*And I_dB1 ^*、I_dB2 ^*...I_dBN ^*Multiplying with a sinusoidal signal obtained by a Phase-locked loop PLL (Phase-Lockedloop) and having the same Phase with the network voltage to generate an alternating current given signal i_d1 ^*、i_d2 ^*And i_dB1 ^*、i_dB2 ^*...i_dBN ^*；

(6) Detecting a current t_kNetwork voltage e (t) at time_k) And an alternating current i (t)_k) Predicting t using the following equation_k+1Time of day alternating current i_d1(t_k+1)、i_d2(t_k+1) And i_dB1(t_k+1)、i_dB2(t_k+1)...i_dBN(t_k+1) The value of (c):

in the formula, L₁Is a boost inductor; r is a boost inductor L₁Internal resistance; t is_sIs a sampling period; u. of_d1(t_k)、u_d2(t_k) And u_dB1(t_k)、u_dB2(t_k)...u_dBN(t_k) The voltages of the alternating current sides corresponding to the applied switch states of the rectifier in the kth sampling period are respectively;

(7) calculating u in step (6) using the following formula_d1(t_k)、u_d2(t_k) And u_dB1(t_k)、u_dB2(t_k)...u_dBN(t_k)：

u_d1(t_k)＝S_d1(t_k)^*U_o1(t_k)

u_d2(t_k)＝S_d2(t_k)*U_o2(t_k)

u_dB1(t_k)＝S_dB1(t_k)*U_oB1(t_k)

u_dB2(t_k)＝S_dB2(t_k)*U_oB2(t_k)

u_dBN(t_k)＝S_dBN(t_k)*U_oBN(t_k)

In the formula of U_o1(t_k)、U_o2(t_k) And U_oB1(t_k)、U_oB2(t_k)...U_oBN(t_k) Is t_kN +2 DC voltage signals, S, at the output side of the time rectifier_d1(t_k)、S_d2(t_k) And S_dB1(t_k)、S_dB2(t_k)...S_dBN(t_k) Is t_kThe corresponding switch state of the rectifier at the moment: s_d1(t_k)、S_d2(t_k) And

(8) constructing a cost function g_d1、g_d2And g_dB1、g_dB2...g_dBN：

g_d1＝|i_d1 ^*-i_d1(t_k+1)|

g_d2＝|i_d2 ^*-i_d2(t_k+1)|

g_dB1＝|i_dB1 ^*-i_dB1(t_k+1)|

g_dB2＝|i_dB2 ^*-i_dB2(t_k+1)|

g_dBN＝|i_dBN ^*-i_dBN(t_k+1)|

In the formula i_d1 ^*、i_d2 ^*And i_dB1 ^*、i_dB2 ^*...i_dBN ^*Setting a signal, i, for the alternating current in step (5)_d1(t_k+1)、i_d2(t_k+1) And i_dB1(t_k+1)、i_dB2(t_k+1)...i_dBN(t_k+1) Is t in step (6)_k+1Predicting the alternating current at the moment;

(9) by a cost function g_d1、g_d2And g_dB1、g_dB2...g_dBNEvaluating each switch state of the rectifier, selecting the switch state corresponding to the predicted current value which minimizes the cost function, and generating the driving signal Q of the switching device₁、Q₂And Q_1B1、Q_1B2...Q_1BN(ii) a Will drive signal Q₂And Q_1B2、Q_1B3...Q_1BNObtaining a driving signal Q after inverting_2B1、Q_2B2...Q_2BN；

(10) The driving signal Q in the step (9) is converted into a driving signal Q₁、Q₂And Q_1B1、Q_1B2...Q_1BNAnd the driving signal Q in step (9)_2B1、Q_2B2...Q_2BNThe power factor correction is carried out to the corresponding switch device, so that the active power factor correction is realized, the input current is sinusoidal, and meanwhile, the cascade connection is realizedAnd (3) balancing and controlling the voltage of the N +2 output direct-current capacitors.

In other embodiments of the invention for applications of cascaded unity power factor rectifiers with a common high voltage dc bus, the described three-phase star, corner and three-phase double star rectifiers, in addition to the third modular unit (C), may also be a combination of different circuits derived from the third modular unit (C).

The described cascade unit power factor rectification application circuit with the common high-voltage direct current bus can simplify the circuit topological structure of a power electronic rectifier applied to a high-power occasion, can improve the working efficiency of a system through a proper control strategy, can stabilize and balance the capacitance voltage at the direct current side, provides favorable conditions for the later-stage electric energy conversion, and has important application value in the application fields of high-voltage direct current transmission, high-power electronic transformers, high-power medium-high voltage alternating current-direct current-alternating current frequency converters and the like.

The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the spirit and scope of the present invention, and various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design solutions of the present invention shall fall within the protection scope of the present invention, and the technical contents of the present invention as claimed are all described in the claims.