阅读说明：本技术 一种基于Boost原理的非隔离型桥臂交替式直流变压器 (A kind of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle ) 是由 刘沈全 王钢 于 2019-08-01 设计创作，主要内容包括：本发明公开了一种基于Boost原理的非隔离型桥臂交替式直流变压器,包括：两个不同电压等级的直流电压源,分别为高压侧电源和低压侧电源；两个高压电容器,分别为高压侧电容和低压侧电容；三条桥臂,分别为低压侧桥臂、高压侧桥臂和中间桥臂,所述三条桥臂均由桥臂电感和若干全桥型子模块级联而成；两个导向开关DS<Sub>1</Sub>和DS<Sub>2</Sub>,两个导向开关均由若干换流阀串联而成。相比现有的主流技术路线,本发明提供的直流变压器的子模块数量大大减少,显著降低了设备的体积与成本,且不依赖次级功率回路实现桥臂功率平衡,导通损耗低,具备更高的换流效率。(The invention discloses a kind of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle, comprising: the DC voltage source of two different voltages grades, respectively high side power and low-side power；Two high-voltage capacitors, respectively high pressure lateral capacitance and low pressure lateral capacitance；Three bridge arms, respectively low-pressure side bridge arm, high-pressure side bridge arm and intermediate bridge arm, three bridge arms are formed by bridge arm inductance and several bridge-type sub-module cascades；Two director switch DS 1 And DS 2 , two director switch are connected in series by several converter valves.Compared to existing mainstream technology route, the submodule quantity of commutator transformer provided by the invention greatly reduces, and significantly reduces the volume and cost of equipment, and does not depend on secondary power circuit and realize bridge arm power-balance, and conduction loss is low, has higher change of current efficiency.)

1. a kind of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle characterized by comprising two are not With the DC voltage source of voltage class, respectively high side power and low-side power；Two high-voltage capacitors, respectively high pressure Lateral capacitance and low pressure lateral capacitance；Three bridge arms, respectively low-pressure side bridge arm, high-pressure side bridge arm and intermediate bridge arm, three bridges Arm is formed by bridge arm inductance and several bridge-type sub-module cascades；Two director switch DS₁And DS₂, two director switch by Several converter valves are connected in series；

The cathode of two capacitors and the cathode of two DC voltage sources are connected, and low-pressure side bridge arm connects low-side power anode With low-pressure side capacitance cathode, high-pressure side bridge arm connects high side power anode and high-pressure side capacitance cathode, one end of intermediate bridge arm It is connected with low-pressure side capacitance cathode, the other end is connected with two director switch；Director switch DS₁With intermediate bridge arm and height Pressure lateral capacitance anode is connected, director switch DS₂It is connected with intermediate bridge arm and ground terminal；

The bridge-type submodule includes four converter valves and a sub- module capacitors C_SM, four converter valves are respectively first to change Flow valve, the second converter valve, third converter valve and the 4th converter valve；Submodule capacitor C_SMAnode with the first converter valve and third The collector of converter valve is connected, submodule capacitor C_SMCathode be connected with the emitter of the second converter valve and the 4th converter valve It connects；The emitter of first converter valve and the collector of the second converter valve are connected and constitute the first port of bridge-type submodule, The emitter of third converter valve and the collector of the 4th converter valve are connected and constitute the second port of bridge-type submodule.

2. a kind of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle according to claim 1, special Sign is that the converter valve for including in bridge-type submodule and director switch is the insulated gate bipolar with anti-paralleled diode Transistor.

3. a kind of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle according to claim 1, special Sign is that the transformer includes four kinds of operation modes, is respectively as follows:

(1) working condition I: DS₁Conducting, DS₂Shutdown, intermediate bridge arm is connected between two lateral capacitances at this time, the output of intermediate bridge arm Voltage is the difference of two sides capacitance voltage, low-pressure side power grid and intermediate bridge arm to high-pressure side power grid and high-pressure side capacitances to supply power；

(2) working condition II: DS₁Shutdown, DS₂Conducting, intermediate bridge arm is in parallel with low pressure lateral capacitance at this time, the output of intermediate bridge arm Voltage is low-pressure side capacitance voltage, and low-pressure side power grid charges to intermediate bridge arm, and high pressure lateral capacitance is powered to high-pressure side power grid；

Transition state is the transition stage between working condition I and II, for realizing each branch voltage between two working conditions The zero-current switching and no-voltage conducting of smooth transition with electric current and two director switch；With the variation of working condition I and II For, transition state includes two stages:

(3) transition state I: the electric current of intermediate bridge arm is gradually decrease to 0, turns off DS₁；

(4) transition state II: the output voltage for adjusting intermediate bridge arm is the voltage of next working condition, and DS is connected₂, then will in Between bridge arm current be gradually promoted to the instruction value of subsequent work state.

4. a kind of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle according to claim 1, special Sign is that the transformer uses the three-layer type classic control framework of power electronic equipment " outer ring-inner ring-modulation "；Wherein, Outer ring is responsible for realizing the power-balance control of input-output power control and each energy storage branch, output low pressure, centre and high pressure The current instruction value of side bridge arm；Inner ring, which is responsible for controlling each bridge arm current, follows corresponding instruction value, exports each bridge arm voltage Instruction value；Modulation link is responsible for generating all converter valves according to the demand that submodule is pressed in voltage instruction value and bridge arm Trigger pulse.

5. a kind of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle according to claim 4, special Sign is, for the on high-tension side power control in outer loop control, high-pressure side power can pass through high voltage side current, i.e. high-pressure side Bridge arm current i_HAIt is controlled, governing equation are as follows:

In formula, p_HFor high-pressure side power；K_PAnd K_IThe respectively ratio and integral gain of PI controller；Subscript ref is indicated to strain The reference value of amount, s are Laplace transform operator；

Average voltage control for the pressure lateral capacitance low/high in outer loop control, can separately design according to formula (8) and be based on i_LAAnd i_MA1Low pressure side and high pressure side capacitor average voltage governing equation:

In formula, Section 2 is to control the feedback modifiers amount of target on the right side of equal sign, and first item is feedforward compensation component, is changed for being promoted Device dynamic responding speed is flowed, similarly hereinafter；

For the bridge arm in outer loop control be averaged submodule capacitor voltage control, according to formula (7), low-pressure side bridge arm and high-pressure side bridge The mean power of arm respectively with v_CLAnd v_CHIt is related, pass through v_CLAnd v_CHRealize the average submodule capacitor voltage control of two bridge arms, Governing equation are as follows:

In formula, v_CLAAnd v_CHAThe respectively average submodule capacitor voltage of low-pressure side bridge arm and high-pressure side bridge arm；

It can design to obtain based on i according to formula (8)_MA2Intermediate bridge arm be averaged the control strategy of submodule capacitor voltage:

In formula, v_CMAFor the average submodule capacitor voltage of intermediate bridge arm.

6. a kind of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle according to claim 4, special Sign is, for inner loop control, according to formula (1), the current control equation of low pressure side and high pressure side bridge arm are as follows:

K_hysTo control gain.

Technical field

The present invention relates to D.C. high voltage transmission, DC grid and commutator transformer fields, more particularly to one kind to be based on Boost The non-isolation type bridge arm alternative expression commutator transformer of principle.

Background technique

DC grid is the important technical for constructing the energy internet of high proportion renewable energy access, is power train One of future thrust of system.Commutator transformer is the core equipment for building multi-voltage grade DC grid, must be met following Technical requirements: 1) it can be realized the Power Exchange between different voltages grade DC grid, and watt level and side can be controlled To；2) side harmonics content is few, can be realized the power output of high quality；3) economic cost is suitable, has industrial application and pushes away Wide value.

In high pressure occasion, generally can using module-cascade inverter technology (Modular Multilevel Converter, MMC) to mitigate the voltage stress that individual devices undertake.By the further retrieval to the prior art, presently, there are based on MMC The commutator transformer technology path of technology has following several: isolated, resonant mode, direct-type and bridge arm alternative expression.

Isolated DC transformer by inversion-boosting-rectification method, by AC transformer realize voltage transformation with And the isolation of two sides DC grid, technology is more mature, but that there are switch-over units is more, component demand is big, equipment volume compared with The disadvantages of big.

Resonant mode commutator transformer use LC resonance principle transformation, the higher occasion of voltage change ratio can be with lifting means Power density reduces equipment volume, but the electrical stress of resonance link is larger, and in high pressure occasion, and the one of resonant network parameter Cause property is difficult to ensure, constrains its popularization and application.

Direct-type commutator transformer is directly connected to two sides power grid using sub-module cascade bridge arm, passes through control bridge arm output electricity Pressure compensation two sides voltage difference, it is only necessary to one-stage transfor-mation can realize voltage transformation, and structure is simple, and the change of current is high-efficient, but due to The voltage and current polarity of direct current system will not be overturn, in order to maintain the submodule voltage of each bridge arm, it is necessary to design secondary function Rate circuit is to maintain the power-balance of each bridge arm, and number of devices needed for leading to inverter and capacity are sharply increased, economic indicator Declined.

The defect that bridge arm power-balance is realized in secondary power circuit is relied on for direct-type commutator transformer, there is scholar's proposition The concept of bridge arm alternative expression commutator transformer (Alternate Arm DC-DC Transformer, AADCT).AADCT includes Three circuit units, each circuit unit are made of a module-cascade bridge arm and two director switch, are opened by controlling guiding The switch state of pass, thus it is possible to vary the connection type and charging and discharging state of bridge arm.Compared with direct-type commutator transformer, AADCT Varying-voltage principle it is similar, but the operation reserve for using bridge arm alternating charge and discharge realizes the power-balance of each bridge arm, does not need time Grade loop of power circuit.However, alternately the operating mode of charge and discharge means that the operation of single circuit unit is interrupted, it is necessary to rely on The method of three circuit unit phase shifts operation is to guarantee that the lasting, stable of net side electric energy conveys, average each circuit unit work Make for 1/3 time, utilization rate of equipment and installations is lower.

Summary of the invention

It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of non-isolation type bridges based on Boost principle Arm alternative expression commutator transformer.

The purpose of the present invention can be achieved through the following technical solutions:

A kind of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle, comprising: two different voltages grades DC voltage source, respectively high side power and low-side power；Two high-voltage capacitors, respectively high pressure lateral capacitance and low Press lateral capacitance；Three bridge arms, respectively low-pressure side bridge arm, high-pressure side bridge arm and intermediate bridge arm, three bridge arms are by bridge arm Inductance and several bridge-type sub-module cascades form；Two director switch DS₁And DS₂, two director switch are by several converter valves It is connected in series；

The cathode of two capacitors and the cathode of two DC voltage sources are connected, and low-pressure side bridge arm connects low-side power Anode and low-pressure side capacitance cathode, high-pressure side bridge arm connect high side power anode and high-pressure side capacitance cathode, intermediate bridge arm One end is connected with low-pressure side capacitance cathode, and the other end is connected with two director switch；Director switch DS₁With intermediate bridge arm with And high-pressure side capacitance cathode is connected, director switch DS₂It is connected with intermediate bridge arm and ground terminal.

The bridge-type submodule includes four converter valves and a sub- module capacitors C_SM, four converter valves are respectively One converter valve, the second converter valve, third converter valve and the 4th converter valve；Submodule capacitor C_SMAnode with the first converter valve and The collector of third converter valve is connected, submodule capacitor C_SMCathode and the second converter valve and the 4th converter valve emitter It is connected；The emitter of first converter valve and the collector of the second converter valve are connected and constitute the first end of bridge-type submodule Mouthful, the collector of the emitter of third converter valve and the 4th converter valve is connected and constitutes the second port of bridge-type submodule.

Bridge-type submodule can export ± v_CWith 0 three kinds of level, wherein v_CFor the module capacitance voltage of full-bridge submodule；n A concatenated submodule can be with output voltage range for-nv_CTo nv_C。

How many bridge-type submodules are specifically needed in each bridge arm, export electricity when being operated normally as inverter needed for the bridge arm The range of pressure determines.For example, it is assumed that certain bridge arm must export the up to voltage of 100kV, and the electricity of single bridge-type submodule Pressure grade is 2kV, then the bridge arm must include 100/2=50 submodule.It is similar with bridge-type submodule, each director switch In required converter valve quantity when must be disconnected according to the switch the maximum back-pressure that be born of its both ends determine

Preferably, the converter valve for including in bridge-type submodule and director switch is the insulation with anti-paralleled diode Grid bipolar junction transistor (IGBT).

The method of operation of the non-isolation type bridge arm alternative expression commutator transformer based on Boost principle in the present invention includes four Kind operation mode, is respectively as follows:

(1) working condition I: DS₁Conducting, DS₂Shutdown, intermediate bridge arm is connected between two lateral capacitances at this time, intermediate bridge arm Output voltage is the difference of two sides capacitance voltage, low-pressure side power grid and intermediate bridge arm to high-pressure side power grid and high-pressure side capacitances to supply power.

(2) working condition II: DS₁Shutdown, DS₂Conducting, intermediate bridge arm is in parallel with low pressure lateral capacitance at this time, intermediate bridge arm Output voltage is low-pressure side capacitance voltage, and low-pressure side power grid charges to intermediate bridge arm, and high pressure lateral capacitance is powered to high-pressure side power grid.

Transition state is the transition stage between working condition I and II, for realizing each branch between two working conditions The smooth transition of voltage and current and zero-current switching and the no-voltage conducting of two director switch.With working condition I and II Variation for, transition state include two stages.

(3) transition state I: the electric current of intermediate bridge arm is gradually decrease to 0, turns off DS₁。

(4) transition state II: the output voltage for adjusting intermediate bridge arm is the voltage of next working condition, and DS is connected₂, then Intermediate bridge arm current is gradually promoted to the instruction value of subsequent work state.

When commutator transformer of the invention operates normally, the operating frequency of two director switch is lower, generally it is tens of extremely Hundreds of hertz, and the Sofe Switch movement of zero-current switching and no-voltage conducting is realized, it avoids the pressure of series IGBT and leads Logical consistency problem.

The voltage of high pressure lateral capacitance and low pressure lateral capacitance can fluctuate near rated value, and high pressure lateral capacitance will be in working condition I charging is discharged in working condition II, and the fundamental frequency of capacitance voltage ripple is identical as the working frequency of Boost AADCT, and low pressure Lateral capacitance will charge in transition state, discharge in working condition, since transition state twice must be undergone in a duty cycle, because The working frequency that the fundamental frequency of this low-pressure side capacitance voltage ripple is twice.

Output voltage by adjusting high-pressure side and low-pressure side bridge arm can carry out Contrary compensation to capacitance voltage ripple, disappear Influence except capacitance voltage ripple to extraneous operation of power networks, to guarantee the power quality of net side.

The present invention compared to the prior art, have it is below the utility model has the advantages that

1, the present invention can satisfy the application demand of the high-voltage direct current power grid of the following multi-voltage grade in technological layer, pass through Electrical component quantity and capacity needed for Ji level significantly reduce, and have compared to mainstream technology route at this stage certain excellent Gesture has very big application potential.

Detailed description of the invention

Fig. 1 is the topology diagram of the non-isolation type bridge arm alternative expression commutator transformer based on Boost principle.

Variable wave when Fig. 2 is each operation mode of non-isolation type bridge arm alternative expression commutator transformer based on Boost principle Shape schematic diagram.

Fig. 3 is the control system block diagram of the non-isolation type bridge arm alternative expression commutator transformer based on Boost principle.

Fig. 4 is in the non-isolation type bridge arm alternative expression commutator transformer based on Boost principle based in hystersis controller Between bridge arm current control block diagram.

Specific embodiment

Present invention will now be described in further detail with reference to the embodiments and the accompanying drawings, but embodiments of the present invention are unlimited In this.