阅读说明：本技术 一种ac/dc电源系统及控制方法 (AC/DC power supply system and control method ) 是由 彭国平 周治国 史奔 王红占 张�浩 刘会民 徐元龙 白代兵 李立冬 宋海军 于 2021-01-15 设计创作，主要内容包括：一种AC/DC电源系统及控制方法,AC/DC电源系统包括：移相变压器,其原边用于连接交流输入电源；电压调整柜,其内设置有N个维也纳三相整流器；N个维也纳三相整流器的交流输入端分别与移相变压器的N组副边连接,直流输出端并联；数据采集模块,用于采集维也纳三相整流器的输出电压、三相输入电压和三相输入电流,以及采集移相变压器的总输出功率；控制系统,分别与电压调整柜、数据采集模块连接。本发明实施例的系统的站用体积相较于传统的电源系统体积减少一半以上,有效的降低了占用体积、降低了成本、解决了低次谐波的问题。此外,本发明实施例的系统输出有冗余且可热插拔,系统整体可靠性极大地提高。本发明实施例的系统功率器件选型更容易。(An AC/DC power supply system and a control method, the AC/DC power supply system includes: the primary side of the phase-shifting transformer is used for connecting an alternating current input power supply; the voltage adjusting cabinet is internally provided with N Vienna three-phase rectifiers; the alternating current input ends of the N Vienna three-phase rectifiers are respectively connected with N groups of secondary sides of the phase-shifting transformer, and the direct current output ends are connected in parallel; the data acquisition module is used for acquiring the output voltage, the three-phase input voltage and the three-phase input current of the Vienna three-phase rectifier and acquiring the total output power of the phase-shifting transformer; and the control system is respectively connected with the voltage adjusting cabinet and the data acquisition module. Compared with the traditional power supply system, the volume of the system for the station is reduced by more than half, so that the occupied volume is effectively reduced, the cost is reduced, and the problem of low-order harmonic is solved. In addition, the system output of the embodiment of the invention has redundancy and can be hot-plugged, and the overall reliability of the system is greatly improved. The system power device of the embodiment of the invention is easier to select.)

1. An AC/DC power supply system, comprising:

the phase-shifting transformer (100) is provided with a group of primary sides and N groups of secondary sides, and the primary sides of the phase-shifting transformer are used for being connected with an alternating current input power supply;

a voltage adjustment cabinet (200) in which N Vienna three-phase rectifiers (210) are arranged; the alternating current input ends of the N Vienna three-phase rectifiers (210) are respectively connected with the N groups of secondary sides of the phase-shifting transformer (100), the direct current output ends of the N Vienna three-phase rectifiers (210) are connected in parallel, and each Vienna three-phase rectifier (210) is used for converting alternating current into direct current;

a data acquisition module (300) for acquiring the output voltage, the three-phase input voltage and the three-phase input current of the vienna three-phase rectifier (210) and acquiring the total output power of the phase-shifting transformer (100);

and the control system (400) is respectively connected with the voltage adjusting cabinet (200) and the data acquisition module (300).

2. The AC/DC power supply system according to claim 1, wherein the phase differences between the N sets of secondary sides of the phase-shifting transformer (100) are sequentially equal.

3. The AC/DC power supply system according to claim 1, further comprising a DC distribution cabinet (500), wherein the DC distribution cabinet (500) is connected to the DC output of the vienna three-phase rectifier (210) for distributing the DC power converted by the vienna three-phase rectifier (210) to electrical consumers.

4. The AC/DC power supply system according to claim 3, characterized in that said direct current distribution cabinet (500) comprises a plurality of switching assemblies all connected to the direct current output of said vienna three-phase rectifier (210).

5. The AC/DC power supply system according to claim 3 or 4, further comprising a battery unit (600) connected to said direct current distribution cabinet (500).

6. An AC/DC power supply system control method, characterized by comprising the steps of:

collecting the total output power of the phase-shifting transformer (100) and the output voltage, the three-phase input voltage and the three-phase input current of each vienna three-phase rectifier (210);

calculating an average active current carried by each said three-phase vienna rectifier (210) from said total output power;

determining a closed-loop D-axis set value according to the output voltage of the Vienna three-phase rectifier (210) and a preset first judgment parameter range;

dq conversion is carried out on the three-phase input voltage of the Vienna three-phase rectifier (210) to obtain a D-axis voltage direct-current component e_dAnd Q-axis voltage DC component e_q(ii) a Dq conversion is carried out on the three-phase input current of the Vienna three-phase rectifier (210) to obtain a D-axis current direct-current component i_dAnd Q-axis current DC component i_q；

Direct current component i of D-axis current_dInputting the given value of the closed-loop D axis into a first proportional integral controller and outputting a closed-loop D axis regulating voltage; direct Q-axis currentComponent i_qInputting the preset given value of the closed-loop Q shaft to a second proportional-integral controller and outputting a closed-loop Q shaft regulating voltage;

adjusting the closed-loop D-axis voltage with the D-axis voltage DC component e_dObtaining a D-axis component of the modulated wave through addition operation; adjusting the closed-loop Q-axis voltage with the Q-axis voltage DC component e_qObtaining a Q-axis component of a modulated wave through addition operation;

three-phase sinusoidal modulation waves Varef1, Vbref1 and Vcref1 are obtained by carrying out dq transformation inverse transformation on the D-axis component and the Q-axis component of the modulation wave, and the operation of the Vienna three-phase rectifier (210) is controlled according to the three-phase sinusoidal modulation waves Varef1, Vbref1 and Vcref 1.

7. The AC/DC power supply system control method according to claim 6, wherein the determining a closed-loop D-axis setpoint according to the output voltage of the vienna three-phase rectifier (210) and a preset first decision parameter range comprises the steps of:

if the output voltage of the Vienna three-phase rectifier (210) is within a preset first judgment parameter range, the average borne active current is used as a closed-loop D-axis given value;

and if the output voltage of the Vienna three-phase rectifier (210) is not within the preset first judgment parameter range, calculating the closed-loop D-axis set value according to a preset reference voltage and the output voltage of the Vienna three-phase rectifier (210).

8. The AC/DC power supply system control method according to claim 6, wherein the conversion formula for dq converting the three-phase input voltage of the vienna three-phase rectifier (210) is:

in the formula, e_a、e_b、e_cIs the three-phase input voltage of the vienna three-phase rectifier (210).

9. The AC/DC power supply system control method according to claim 6, wherein the conversion formula for dq converting the three-phase input current of the vienna three-phase rectifier (210) is:

in the formula i_a、i_b、i_cIs the three-phase input current of the vienna three-phase rectifier (210).

10. The AC/DC power supply system control method according to claim 6, wherein the three-phase sinusoidal modulation waves Varef1, Vbref1 and Vcref1 adopt SVPWM modulation mode to obtain the on-off logic of each phase of switching tube of the Vienna three-phase rectifier (210).

Technical Field

The invention belongs to the field of power supplies, and particularly relates to an AC/DC power supply system and a control method.

Background

In recent years, technologies such as internet, cloud computing, artificial intelligence, block chaining and the like are vigorously developed, demands for fields such as storage, exchange, calculation and the like of data are also explosively increased, data becomes a new production element, and society is rapidly crossing the era of data economy. The sustainable development of the data economy era cannot be realized without the important support of the brain, namely the data center, and the rapid development of the data center industry is a necessary trend of the data era. In a data center, its power supply system is the throat, which is one of the most important components in the infrastructure. With the rapid development of data centers in the future, higher requirements are put forward on the reliability, energy conservation, sustainability and the like of a power supply system.

Several common uninterrupted power supply technologies of the current data center include AC UPS, HVDC, and a direct mains supply + BBU, but these schemes all have some disadvantages. The AC UPS scheme belongs to an alternating current power supply mode, the equipment structure is complex, and the equipment reliability is low; the HVDC scheme belongs to a direct current power supply mode, the reliability is greatly improved compared with an alternating current power supply mode, but the defect of complex structure still exists; the scheme of the commercial power direct supply and BBU is high in power supply efficiency, but each server needs a lithium battery as a backup power supply, so that the number of fault points is large, the maintenance is difficult, and the cost is high. Therefore, the existing power supply system of the data center has the defects of large occupied space, high cost, complex maintenance and management and the like. In addition, with the continuous development of new energy industry and power electronic technology, more and more power electronic devices are connected to a power grid, but due to the fact that the power electronic devices have the characteristic of strong nonlinearity, a large number of harmonic components are brought to the power grid in the using process.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides an AC/DC power supply system which solves the problems that a data center power supply system is large in occupied space and high in cost, and harmonic waves cannot be eliminated. The invention also provides an AC/DC power supply system control method.

An AC/DC power supply system according to an embodiment of the first aspect of the invention includes:

the phase-shifting transformer is provided with a group of primary sides and N groups of secondary sides, and the primary sides of the phase-shifting transformer are used for being connected with an alternating current input power supply;

the voltage adjusting cabinet is internally provided with N Vienna three-phase rectifiers; the alternating current input ends of the N Vienna three-phase rectifiers are respectively connected with the N groups of secondary sides of the phase-shifting transformer, the direct current output ends of the N Vienna three-phase rectifiers are connected in parallel, and each Vienna three-phase rectifier is used for converting alternating current into direct current;

the data acquisition module is used for acquiring the output voltage, the three-phase input voltage and the three-phase input current of the Vienna three-phase rectifier and acquiring the total output power of the phase-shifting transformer;

and the control system is respectively connected with the voltage adjusting cabinet and the data acquisition module.

The AC/DC power supply system provided by the embodiment of the invention has the following technical effects: the phase-shifting transformer is provided with a plurality of groups of secondary sides, the short-circuit current of the secondary side winding can be greatly reduced, the short-circuit current capacity of a downstream switch of the phase-shifting transformer is reduced, the switch with a smaller volume can be selected, the volume of the whole AC/DC power supply system is greatly reduced, the phase-shifting transformer can offset most of low-order harmonics, the low total harmonic current content and the high power factor are realized, the power factor correction link in a rectification power module in the traditional AC UPS or HVDC power supply scheme can be optimized and removed, and the overall volume of the AC/DC power supply system is further reduced. Compared with the traditional rectifying module, the Vienna three-phase rectifier can further reduce the occupied volume of rectification, so that the volume of an AC/DC power supply system is further reduced; and the vienna three-phase rectifier structure has the advantages of the traditional three-level topology: the problem of bridge arm direct connection is avoided, dead time of a switching tube does not need to be set, voltage stress of the switching tube is only half of that of a three-phase full-bridge switching tube, and the type selection of a power device is easier. The direct current positive and negative electrodes on the output sides of all Weijina three-phase rectifiers are mutually connected in parallel to form positive and negative direct current buses, and the rectifiers are mutually redundant and can be plugged in and pulled out, so that the reliability of the system is greatly improved. Compared with the volume of a traditional power supply system, the volume of the AC/DC power supply system is reduced by more than half, so that the occupied volume is effectively reduced, the cost is reduced, and the problem of low-order harmonic is solved.

According to some embodiments of the first aspect of the present invention, the phase differences between the N sets of secondary sides of the phase shifting transformers are sequentially equal.

According to some embodiments of the first aspect of the present invention, the AC/DC power supply system further comprises a DC distribution cabinet connected to the DC output of the vienna three-phase rectifier for distributing the DC power converted by the vienna three-phase rectifier to the electric devices.

According to some embodiments of the first aspect of the present invention, the dc distribution cabinet comprises a plurality of switching assemblies each connected to a dc output of the vienna three-phase rectifier.

According to some embodiments of the first aspect of the present invention, the AC/DC power supply system further comprises a battery unit connected to the DC distribution cabinet.

The AC/DC power supply system control method according to the embodiment of the second aspect of the invention comprises the following steps:

collecting the total output power of the phase-shifting transformer and the output voltage, the three-phase input voltage and the three-phase input current of each Vienna three-phase rectifier;

calculating the average active current born by each Vienna three-phase rectifier according to the total output power;

determining a closed-loop D-axis given value according to the output voltage of the Vienna three-phase rectifier and a preset first judgment parameter range;

carrying out dq conversion on the three-phase input voltage of the Vienna three-phase rectifier to obtain a D-axis voltage direct-current component e_dAnd Q-axis voltage DC component e_q(ii) a Carrying out dq conversion on the three-phase input current of the Vienna three-phase rectifier to obtain a D-axis current direct-current component i_dAnd Q-axis current DC component i_q；

Direct current component i of D-axis current_dInputting the given value of the closed-loop D axis into a first proportional integral controller and outputting a closed-loop D axis regulating voltage; direct current component i of Q axis current_qInputting the preset given value of the closed-loop Q axis into a second proportional-integral controller and outputting a closed-loop Q axis regulating voltage;

adjusting the closed-loop D-axis voltage with the D-axis voltage DC component e_dObtaining a D-axis component of the modulated wave through addition operation; adjusting the closed-loop Q-axis voltage with the Q-axis voltage DC component e_qObtaining a Q-axis component of a modulated wave through addition operation;

and carrying out dq transformation inverse transformation on the D-axis component and the Q-axis component of the modulation wave to obtain three-phase sinusoidal modulation waves Varef1, Vbref1 and Vcref1, and controlling the operation of the Vienna three-phase rectifier according to the three-phase sinusoidal modulation waves Varef1, Vbref1 and Vcref 1.

The AC/DC power supply system control method provided by the embodiment of the invention at least has the following technical effects: the subsequent closed-loop control of the vienna three-phase rectifier can be facilitated by collecting the output voltage, the three-phase input voltage and the three-phase input current of each vienna three-phase rectifier, and the total output power of the phase-shifting transformer. Dq change is carried out on three-phase input voltage and current of the vienna three-phase rectifier, active power and reactive power on the network side of the rectifier can be conveniently and subsequently controlled respectively, accordingly, the difficulty of a subsequent operation process is reduced, and the stability and accuracy of control are improved. The control method of the AC/DC power supply system can reduce the influence caused by sampling errors and control the AC/DC power supply system to realize stable output.

According to some embodiments of the second aspect of the present invention, the determining a closed-loop D-axis setpoint from the output voltage of the vienna three-phase rectifier and a preset first decision parameter range comprises the steps of:

if the output voltage of the vienna three-phase rectifier is within a preset first judgment parameter range, taking the average borne active current as a closed-loop D-axis given value;

and if the output voltage of the vienna three-phase rectifier is not within the preset first judgment parameter range, calculating the closed-loop D-axis given value according to the preset reference voltage and the output voltage of the vienna three-phase rectifier.

According to some embodiments of the second aspect of the present invention, the conversion equation for dq converting the three phase input voltage of the vienna three phase rectifier is:

in the formula, e_a、e_b、e_cIs the three-phase input voltage of the vienna three-phase rectifier.

According to some embodiments of the invention, the conversion equation for dq converting the three phase input current of the vienna three phase rectifier is:

in the formula i_a、i_b、i_cIs the three-phase input current of the vienna three-phase rectifier.

According to some embodiments of the second aspect of the present invention, the three-phase sinusoidal modulation waves Varef1, Vbref1, and Vcref1 adopt an SVPWM modulation method to obtain on-off logic of each phase switching tube of the vienna three-phase rectifier.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic configuration diagram of a conventional AC UPS power supply system;

fig. 2 is a schematic structural diagram of a conventional HVDC power supply system;

FIG. 3 is a schematic diagram of the AC/DC power supply system according to an embodiment of the first aspect of the present invention;

fig. 4 is a schematic structural diagram of a vienna three-phase transformer according to an embodiment of the first aspect of the present invention;

FIG. 5 is a schematic diagram of a bidirectional switch tube in a three-phase Vienna transformer;

fig. 6 is a flow chart of a control method of the AC/DC power supply system according to the embodiment of the second aspect of the invention.

Reference numerals:

a phase-shifting transformer 100,

A voltage adjustment cabinet 200, a Vienna three-phase rectifier 210,

A data acquisition module 300,

A control system 400,

A direct current power distribution cabinet 500,

Battery cell 600.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, it is to be understood that the directional descriptions, such as the directions of upper, lower, front, rear, left, right, etc., are merely provided for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be considered as limiting the present invention.

In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If there is a description of the first and second for the purpose of distinguishing technical features, it is not to be understood as indicating or implying a relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, unless explicitly defined otherwise, terms such as setting, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the terms in the present invention by combining the specific contents of the technical solutions.

An AC/DC power supply system according to an embodiment of the first aspect of the invention is described below with reference to fig. 3 to 6.

An AC/DC power supply system according to an embodiment of the present invention includes:

a phase-shifting transformer 100 having a set of primary sides and N sets of secondary sides, wherein the primary sides are used for connecting an alternating current input power supply;

a voltage adjustment cabinet 200 in which N vienna three-phase rectifiers 210 are disposed; the ac input ends of the N vienna three-phase rectifiers 210 are respectively connected to the N sets of secondary sides of the phase-shifting transformer 100, the dc output ends of the N vienna three-phase rectifiers 210 are connected in parallel, and each vienna three-phase rectifier 210 is configured to convert ac power to dc power;

a data acquisition module 300, configured to acquire an output voltage, a three-phase input voltage, and a three-phase input current of the vienna three-phase rectifier 210, and acquire a total output power of the phase-shifting transformer 100;

the control system 400 is connected to the voltage adjustment cabinet 200 and the data acquisition module 300, respectively.

Before describing the AC/DC power system of the embodiment of the present invention, a brief description will be given of several conventional power systems.

Referring to fig. 1, an AC UPS scheme of a conventional Power supply system belongs to an AC Power supply mode, and in the scheme, a large-capacity 3-phase PFC (Power Factor Correction) is required inside a UPS to convert AC Power into dc Power, and the dc side needs to be processed by inversion/filtering and other links, so that the AC UPS has a complex device structure and low reliability. Particularly, the energy of the energy storage battery needs to be converted to load equipment through an inversion link, so that the power supply availability of a single AC UPS device cannot meet the requirement of a data center, and the power supply availability of the AC UPS device needs to be improved through redundancy of the AC UPS device.

Referring to fig. 2, the HVDC power supply architecture of the conventional power supply system adopts a dc power supply method, which improves reliability, but still has the disadvantages of complex structure and low equipment efficiency. For example, a switching device of a low-voltage distribution cabinet needs to have a short-circuit current breaking capability, an alternating-current input side of HVDC also needs three-phase PFC, and a direct-current side needs to be changed by DC/DC. These factors all result in bulky and costly HVDC power supply architectures.

An AC/DC power supply system of an embodiment of the present invention is briefly described below.

Referring to fig. 3 to 5, the phase-shifting transformer 100 includes N (N ≧ 2) secondary low-voltage windings, the primary side of which is connected to the high-voltage grid, and can convert the high-voltage ac in the high-voltage grid into N low-voltage ac to be provided to the voltage regulation cabinet 200. The voltage adjustment cabinet 200 is internally provided with N vienna three-phase rectifiers 210, and an alternating current input end of each vienna three-phase rectifier 210 is connected with one secondary side of the phase-shifting transformer 100. The vienna three-phase rectifier 210 converts low-voltage ac power into controllable dc power and outputs the dc power from a dc output terminal. The positive and negative dc poles of the dc output terminal of all vienna three-phase rectifiers 210 are connected in parallel to form a positive and negative dc bus, and then output from the voltage regulation cabinet 200, so as to supply power to the outside.

Compared with the schemes in fig. 1 and fig. 2, the AC/DC power supply system according to the embodiment of the present invention employs the phase-shifting transformer 100 having a plurality of low-voltage windings, so that the capacity of each low-voltage winding is much smaller than the total capacity, and further, the short-circuit current of the low-voltage winding can be greatly reduced, so as to reduce the requirement of the short-circuit switching capability of the downstream switching device, and further, the switching device having smaller withstand voltage capability and current-carrying capability can be selected, so as to reduce the cost, and in most cases, the size of the switching device having smaller withstand voltage capability and current-carrying capability is also smaller, so as to effectively reduce the overall size of the AC/DC power supply system according to the embodiment of the present invention.

For further understanding of the principles of the AC/DC power system of the present embodiment, the structure and operation of the vienna three-phase rectifier 210 will be briefly described.

The structure of the vienna three-phase rectifier 210 is shown in fig. 4 and 5, wherein e_a、e_b、e_cRepresenting the three-phase input voltage, i, of a Weiner three-phase rectifier 210_a、i_b、i_cRepresenting the three-phase input current, L, of the Vienna three-phase rectifier 210_a、L_b、L_cIs a three-phase filter inductor. The direct current output side is connected with two capacitors C1 and C2 with equal capacitance values in series, and the midpoint of the two capacitors is a central point N; the three-phase bridge arm is formed by 6 clamping diodes, the midpoint of each bridge arm is respectively connected with two bidirectional switching tubes Ka, Kb and Kc, each bidirectional switching tube is formed by connecting two switching tubes in an anti-series mode, and the other ends of the three bidirectional switching tubes are connected with a central point N.

When the action frequency of the bidirectional switch tube is far greater than the fundamental frequency of the ac input power supply, the vienna three-phase rectifier 210 operates under a steady-state condition, and the following two steady-state circuit equations are established according to Kirchhoff's Voltage Law (KVL):

in the above two equations, V is the amplitude of the three-phase AC input voltage, ω₀Is the fundamental angular frequency of the grid voltage. In a three-phase grid balancing system, there may be:

taking phase a of the three phases as an example for analysis: when the bidirectional switch tube Ka is conducted, the voltage of the input end relative to the midpoint of the direct-current bus is 0; when the switching tube is turned off and the input current flows in the positive direction (or negative direction), the alternating current input side is connected with the positive (or negative) end of the direct current output side through the fly-wheel diode, and the voltage of the input end to the midpoint of the direct current bus is V_dcA/2 or-V_dc/2. Therefore, the voltage V is applied across the bidirectional switch tube_kNThe current polarity and the switching state of the phase bridge arm jointly determine the current polarity. The three operating states, operating levels and switching states are shown in table one.

Watch 1

Switching state k ═ a, b, c	Working state	Bridge arm output level
			Sk＝0ik>0，	P	vdc/2
Sk＝1	O	0
			Sk＝0，ik<0	N	-vdc/2

Therefore, the topology structure of the vienna three-phase rectifier 210 belongs to a three-level structure, the bridge arm direct-current problem is avoided, the dead time of the switching tube does not need to be set, the voltage stress of the switching tube is only half of that of the switching tube of the three-phase full-bridge structure, and the type selection of a power device is easier.

According to the AC/DC power supply system provided by the embodiment of the invention, the phase-shifting transformer 100 is provided with a plurality of groups of secondary sides, so that the short-circuit current of the secondary side winding can be greatly reduced, the short-circuit current capacity of a downstream switch of the phase-shifting transformer is reduced, a switch with a smaller size can be selected, the size of the whole AC/DC power supply system is greatly reduced, most low-order harmonics can be counteracted by the phase-shifting transformer 100, the low total harmonic current content and the high power factor are realized, and therefore, a power factor correction link inside a rectification power module in the traditional AC UPS or HVDC power supply scheme can be optimized and removed, and the whole size of the AC/DC power supply system is further reduced. Compared with the traditional rectification module, the adoption of the Wei-Zener three-phase rectifier 210 can further reduce the volume occupied by rectification, so that the volume of an AC/DC power supply system is further reduced; and the vienna three-phase rectifier 210 structure combines the advantages of the conventional three-level topology: the problem of bridge arm direct connection is avoided, dead time of a switching tube does not need to be set, voltage stress of the switching tube is only half of that of a switching tube of a three-phase full-bridge structure, and the type selection of a power device is easier. The direct current positive and negative poles at the output sides of all the vienna three-phase rectifiers 210 are connected in parallel to form positive and negative direct current buses, the rectifiers are mutually redundant and can be plugged in and pulled out, and the reliability of the system is greatly improved. Compared with the traditional power supply system, the station volume of the AC/DC power supply system provided by the embodiment of the invention is reduced by more than half, so that the occupied volume is effectively reduced, the cost is reduced, and the problem of low-order harmonic is solved.

In some embodiments of the present invention, the core controller of the control system 400 may employ a PLC, DSP, or ARM. In some embodiments of the present invention, a Siemens S7 series PLC is specifically employed as the core controller.

In some embodiments of the present invention, the phase differences between the N sets of secondary sides of phase shifting transformer 100 are sequentially equal. The phase difference between the low-voltage windings of the N groups of secondary sides is equal, so that 6N +/-1 subharmonics can be mutually offset, and the low total harmonic current content is realized. Furthermore, compared with the traditional power supply system, the three-phase PFC power factor correction link of a downstream rectifier module can be optimized and omitted, and the reduction of the volume and the cost of the equipment are realized.

In some embodiments of the present invention, the AC/DC power supply system further includes a DC distribution box 500, and the DC distribution box 500 is connected to the DC output terminal of the vienna three-phase rectifier 210 for distributing the DC power converted by the vienna three-phase rectifier 210 to the electric devices. The dc distribution cabinet 500 may be convenient for distributing power to a plurality of electric devices, respectively.

In some embodiments of the present invention, the dc distribution cabinet 500 comprises a plurality of switching assemblies connected to the dc output of the vienna three-phase rectifier 210. The plurality of switch assemblies can be arranged to respectively supply power to the plurality of electric devices.

In some embodiments of the present invention, the AC/DC power supply system further includes a storage battery unit 600 connected to the DC distribution cabinet 500. The battery unit 600 generally includes a plurality of batteries and a plurality of correspondingly disposed battery shunt switches, and the batteries are directly connected to the dc bus in the dc distribution cabinet 500 through the battery shunt switches, that is, connected to the dc output terminal of the vienna three-phase rectifier 210; compared with the traditional power supply system, the method optimally saves the links such as inversion/filtering of the AC UPS scheme and the DC/DC change link of the HVDC scheme, greatly reduces the equipment volume and reduces the cost.

The AC/DC power supply system control method according to the embodiment of the second aspect of the invention comprises the following steps:

the total output power of the phase-shifting transformer 100 and the output voltage Udc and the three-phase input voltage e of each vienna three-phase rectifier 210 are collected_a、e_b、e_cAnd three-phase input current i_a、i_b、i_c；

The average active current i borne by each vienna three-phase rectifier 210 is calculated according to the total output power_ref；

Determining a closed-loop D-axis given value according to the output voltage of the Vienna three-phase rectifier 210 and a preset first judgment parameter range;

the three-phase input voltage of the vienna three-phase rectifier 210 is dq-converted to obtain a D-axis voltage direct-current component e_dAnd Q-axis voltage DC component e_q(ii) a The three-phase input current of the vienna three-phase rectifier 210 is dq-converted to obtain a D-axis current direct-current component i_dAnd Q-axis current DC component i_q；

Direct current component i of D-axis current_dInputting the given value of the closed-loop D axis into a first proportional integral controller and outputting a closed-loop D axis regulating voltage; direct current component i of Q axis current_qInputting the preset given value of the closed-loop Q shaft to a second proportional-integral controller and outputting a closed-loop Q shaft regulating voltage;

regulating voltage of closed loop D axis and D axis voltage direct current component e_dObtaining a D-axis component of the modulated wave through addition operation; regulating voltage of closed loop Q axis and direct current component e of Q axis voltage_qObtaining a Q-axis component of a modulated wave through addition operation;

three-phase sinusoidal modulation waves Varef1, Vbref1 and Vcref1 are obtained by the D-axis component and Q-axis component of the modulation wave through dq transformation and inverse transformation, and the operation of the Vienna three-phase rectifier 210 is controlled according to the three-phase sinusoidal modulation waves Varef1, Vbref1 and Vcref 1.

Referring to fig. 3 to 6, the output voltage, the three-phase input voltage and the three-phase input current of each vienna three-phase rectifier 210, and the total output power of the phase-shifting transformer 100 are collected by the data collection module 300; the total output power can be calculated by collecting the total output voltage and the total output current. The control method of the AC/DC power supply system of the embodiment of the invention adopts a power balance control mode, so that the average active current born by each Vienna three-phase rectifier 210 can be calculated according to the total output power, and each Vienna three-phase rectifier 210 can be accurately controlled conveniently.

In order to facilitate control of the vienna three-phase rectifier 210, dq change is adopted in the AC/DC power supply system control method according to the embodiment of the present invention, three-phase inputs of the vienna three-phase rectifier 210 correspond to a D axis and a Q axis after the dq change, and the D axis and the Q axis respectively represent an active component reference axis and a reactive component reference axis, so that respective control of active power and reactive power can be achieved. Three-phase input voltage e of the vienna three-phase rectifier 210_a、e_b、e_cD, carrying out dq conversion to obtain D-axis voltage direct-current component e_dAnd Q-axis voltage DC component e_q(ii) a Three-phase input current i of the vienna three-phase rectifier 210_a、i_b、i_cD, carrying out dq conversion to obtain D-axis current direct current component i_dAnd Q-axis current DC component i_q。

Closed-loop control also requires the use of a closed-loop D-axis setpoint i_dcrefAnd closed loop Q axis set value i_qcrefClosed loop D axis set value i_dcrefThe closed-loop D-axis set value i is determined according to the output voltage of the Vienna three-phase rectifier 210 and a preset first judgment parameter range_dcrefIt can be preset directly. Determining a closed loop D axis set value i_dcrefThen, the D-axis current direct current component i_dAnd closed loop D axis set value i_dcrefThe voltage is input into a first proportional integral controller, so that an output closed-loop D-axis regulating voltage can be obtained; direct current component i of Q axis current_qAnd closed loop Q axis set value i_qcrefThe output closed-loop Q-axis regulating voltage can be obtained by inputting the voltage into a second proportional-integral controller. Further, the closed loop D-axis regulating voltage and the D-axis voltage direct current component e can be adjusted_dObtaining D-axis component of modulation wave by addition operation, regulating voltage of closed-loop Q-axis and Q-axis voltage direct-current component e_qAnd obtaining the Q-axis component of the modulated wave through addition operation.

Finally, three-phase sinusoidal modulation waves Varef1, Vbref1 and Vcref1 are obtained by performing dq conversion inverse transformation on the D-axis component and the Q-axis component of the modulation wave, and the operation of the vienna three-phase rectifier 210 is controlled according to the three-phase sinusoidal modulation waves Varef1, Vbref1 and Vcref 1.

According to the AC/DC power supply system control method of the embodiment of the present invention, the subsequent closed-loop control of the vienna three-phase rectifier 210 can be facilitated by collecting the output voltage, the three-phase input voltage and the three-phase input current of each vienna three-phase rectifier 210, and the total output power of the phase-shifting transformer 100. Dq change is performed on three-phase input voltage and current of the vienna three-phase rectifier 210, so that active power and reactive power on the network side of the rectifier can be conveniently and respectively controlled subsequently, the difficulty of the subsequent operation process is reduced, and the stability and accuracy of control are improved. The control method of the AC/DC power supply system can reduce the influence caused by sampling errors and control the AC/DC power supply system to realize stable output.

In some embodiments of the present invention, referring to fig. 6, the closed-loop D-axis set point i is determined according to the output voltage of the vienna three-phase rectifier 210 and the preset first decision parameter range_dcrefThe method comprises the following steps:

when the output voltage Udc of the vienna three-phase rectifier 210 is within a preset first judgment parameter range, the average borne active current is used as a closed-loop D-axis given value i_dcref。

If the output voltage Udc of the vienna three-phase rectifier 210 is not within the preset first determination parameter range, the output voltage Udc is determined according to a preset reference voltage u_dcrefAnd the output voltage Udc of the vienna three-phase rectifier 210 calculates the given value i of the closed-loop D axis_dcref。

If the output voltage Udc of the vienna three-phase rectifier 210 is within the preset first judgment parameter range, the Udc can be considered to be within the normal range, and at the moment, the average borne active current is taken as the given value i of the closed-loop D axis_dcrefThus, the method is completed. When the output voltage Udc of the vienna three-phase rectifier 210 is not within the preset first determination parameter range, the Udc is considered not to be within the normal range, and at the moment, the control mode is switched to the direct-current voltage control mode to use the reference voltage u_dcrefTaking actually sampled Udc as a feedback value as a given value, and taking a closed-loop output result as a closed-loop D-axis given value i_dcref. Closed loop Q axis given value i_qcrefIt can be directly preset to 0.

In some embodiments of the present invention, the conversion formula for dq converting the three-phase input voltage of the vienna three-phase rectifier 210 is:

in the formula, e_a、e_b、e_cIs the three-phase input voltage of the vienna three-phase rectifier 210.

The conversion equation for dq conversion of the three-phase input current of the vienna three-phase rectifier 210 is:

in the formula i_a、i_b、i_cIs the three-phase input current of the vienna three-phase rectifier 210.

In some embodiments of the present invention, the three-phase sinusoidal modulation waves Varef1, Vbref1, and Vcref1 adopt an SVPWM modulation method to obtain on-off logic of each phase of switching tubes of the vienna three-phase rectifier 210. Accurate and stable control over all vienna three-phase rectifiers 210 can be achieved through an SVPWM modulation mode, and stability of overall output is guaranteed.

The specific process of obtaining the on-off logic of each phase of switching tube of the vienna three-phase rectifier 210 by adopting the SVPWM modulation mode is as follows:

step S1: the three-phase sine modulation waves Varef1, Vbref1 and Vcref1 are changed by dq/alpha beta to obtain u_α、 u_βThen, the sector is determined according to the following formula:

A＝u_α

sector number N ═ sign (a) + sign (b) + sign (c), where sign denotes the symbol "+" or "-".

Step S2: the vector control time is determined according to the following formula and table two:

table two T1, T2 valuation table

Ⅰ

Ⅱ

Ⅲ

Ⅳ

Ⅴ

Ⅵ

T1

Z

Y

-Z

-X

X

-Y

T2

Y

-X

X

Z

-Y

-Z

And (3) saturation judgment: if T1+ T2> T, T1 is T1T/(T1 + T2), and T2 is T2T/(T1 + T2).

Step S3: determining the on-time and the off-time of each phase of the switching tube according to the following formula and the third table:

T_a＝(T-T₁-T₂)/4

T_b＝T_a+T₁/2

T_C＝T_b+T₂/2

table three Tcom value assigning table

Ⅰ

Ⅱ

Ⅲ

Ⅳ

Ⅴ

Ⅵ

Tcom1

Tb

Ta

Ta

Tc

Tc

Tb

Tcom2

Ta

Tc

Tb

Tb

Ta

Tc

Tcom3

Tc

Tb

Tc

Ta

Tb

Ta

Finally, the switching control of each vienna three-phase rectifier 210 is realized through the control strategy obtained through the steps, and stable direct current output is obtained.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an exemplary embodiment," "an example," "a specific example," or "some examples" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to the embodiments, and those skilled in the art will understand that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.