Dual transformer coupling voltage compensation system based on thyristor switching and its control method

Abstract

A dual transformer coupled voltage compensation system based on thyristor switching and a control method thereof, the control method comprising step 1, when a voltage drop occurs, switching S 1 , S 2 Disconnect and calculate the voltage required to compensate for each phase load; Step 2: Determine the voltage drop ratio k sag , control the anti-parallel thyristor to be switched on, through the multi-tap transformer T 2 Take energy from the three-phase AC power supply and then use the multi-tap transformer T 2 and transformer T 1 The voltage of each phase load is compensated once; Step 3, detect the compensation state of each phase load voltage, and control the voltage type H bridge inverter through the transformer T according to the difference between the current load voltage and the voltage standard value of the three-phase AC power supply. 1 Perform secondary compensation on the load voltage to achieve full compensation of the load voltage; Step 4, when the three-phase AC power supply voltage returns to the standard value, turn off the anti-parallel thyristor switching and switch S 1 , S 2 The present invention can not only reduce the investment cost, but also increase the compensation accuracy and compensation range.

Description

Technical Field

[0001] The present invention relates to the technical field of power quality voltage compensation, and in particular to a dual-transformer coupling voltage compensation system based on thyristor switching and a control method thereof. Background Art

[0002] With the rapid development of smart distribution networks and power electronics technology, as well as the application of a large number of power electronic equipment and the access of distributed energy, power quality issues in power grids have gradually become prominent. Among them, the number of accidents caused by voltage drops is about 10 times the number of accidents caused by voltage interruptions. Therefore, the voltage drop problem is considered to be one of the important issues affecting the stable operation of power loads.

[0003] In order to solve the problem of voltage drop in distribution network, the main method is to suppress or eliminate the occurrence of voltage drop by adding new compensation devices. Traditional compensation devices include standby generators, on-load tap-changing transformers, static VAR compensators, etc., but these devices are restricted by response speed and compensation accuracy and cannot effectively implement full compensation for voltage drop. With the rapid development of power electronics technology, various series power electronic devices based on power semiconductor devices continue to emerge. Among them, voltage source converters (VSC) based on fully controlled power devices are very popular in power electronic equipment due to their simple topology, mature control technology, and easy multi-level implementation. Dynamic voltage restorer (DVR) has become an important technical means to protect sensitive loads from power quality problems such as grid voltage sag and surge due to its advantages of high operating efficiency, high reliability and good rapidity. However, during voltage compensation, the output voltage range of DVR is limited by the inverter capacity, and the compensation range is limited. The dual DVR collaborative compensation device can improve the reliability and flexibility of the compensation voltage, but the device is expensive and the control strategy is complex. On the basis of traditional DVR, a capacitor is connected in series in the LC filter, which can effectively reduce the inverter capacity and DC side voltage level. However, improper matching of the series capacitor and the inductive device parameters can easily cause oscillation, which is not conducive to the safe and stable operation of the system.

[0004] Faced with the problem of fault voltage drop in the distribution network, although the series dynamic voltage restorer, dual DVR compensation device and series capacitor coupling dynamic voltage restorer can effectively compensate the load voltage to a certain extent, there are still problems such as high cost and insufficient compensation accuracy. Therefore, there is an urgent need for a voltage compensation device that has both compensation performance and cost. Summary of the invention

[0005] In order to solve the problems of limited compensation range and high cost of existing voltage compensation devices, the present invention provides a dual-transformer coupling voltage compensation system based on thyristor switching and a control method thereof.

[0006] In order to solve the above technical problems, the present invention adopts the following technical methods:

[0007] A dual-transformer coupling voltage compensation system based on thyristor switching includes a three-phase compensation unit, each of which includes an active inverter circuit, a transformer T1, a multi-tap transformer T2, a thyristor switching circuit, a switch S1 and a switch S2; the active inverter circuit includes a voltage type H-bridge inverter, a filter capacitor C f and filter inductor L f ; The thyristor switching circuit includes a plurality of groups of anti-parallel thyristors;

[0008] The primary winding of the multi-tap transformer T2 is connected in parallel with the three-phase AC power grid, the tap of the secondary winding of the multi-tap transformer T2 is electrically connected to one end of the primary winding of the transformer T1 through an anti-parallel thyristor, and the other end of the primary winding of the transformer T1 and the other end of the secondary winding of the multi-tap transformer T2 are electrically connected to the filter capacitor C f The two ends of the voltage type H-bridge inverter are connected in series with the AC side filter inductor L f After the filter capacitor C f In parallel, the secondary winding of the transformer T1 is connected in series to a three-phase AC power grid, which includes a three-phase AC power supply and a load. The switch S1 is connected in parallel to the secondary winding of the transformer T1, and the switch S2 is connected in parallel to the secondary winding of the multi-tap transformer T2.

[0009] Furthermore, the thyristor switching circuit includes an anti-parallel thyristor Ts1, an anti-parallel thyristor Ts2 and an anti-parallel thyristor Ts3 connected in parallel in sequence, one end of the anti-parallel thyristor Ts1, the anti-parallel thyristor Ts2 and the anti-parallel thyristor Ts3 are respectively electrically connected to each tap of the secondary winding of the multi-tap transformer T2, and the other end of the anti-parallel thyristor Ts1, the anti-parallel thyristor Ts2 and the anti-parallel thyristor Ts3 are all electrically connected to the filter capacitor C f one end.

[0010] Furthermore, the voltage-type H-bridge inverter includes fully controlled devices V1, V2, V3, V4 on the AC side and capacitor C on the DC side. dc , the capacitor C dc They are respectively connected in parallel with the series circuit composed of the fully-controlled devices V1 and V2 and the series circuit composed of the fully-controlled devices V3 and V4.

[0011] Preferably, the fully-controlled devices V1, V2, V3, V4 are all NPN-type insulated gate bipolar transistors, and a diode is connected in series between the emitter and the collector of the insulated gate bipolar transistor.

[0012] In order to solve the above technical problems, the present invention also adopts the following technical methods:

[0013] A control method for a dual-transformer coupled voltage compensation system based on thyristor switching, comprising:

[0014] Step 1: Set the voltage standard value U of the three-phase AC power supply a_ref , U b_ref , U c_ref , real-time detection of the actual output voltage U of the three-phase AC power supply sa , U sb , U sc , when each phase voltage U sa , U sb , U sc Lower than the voltage standard value U of the corresponding phase a_ref , U b_ref , U c_ref When , it is determined that a voltage drop has occurred, switches S1 and S2 are disconnected, and the voltage required to compensate for each phase load is calculated;

[0015] Step 2: According to the detected voltage U sa , U sb , U sc And the set voltage standard value U a_ref , U b_ref , U c_ref Determine the voltage drop ratio k sag , control the conduction of the anti-parallel thyristor to be switched on, take energy from the three-phase AC power supply through the primary winding of the multi-tap transformer T2, then output the compensation voltage through the secondary winding of the multi-tap transformer T2, and inject the compensation voltage into the three-phase AC power grid through the transformer T1, so as to compensate the voltage of each phase load;

[0016] Step 3, detecting the compensation state of the load voltage of each phase, and controlling the voltage-type H-bridge inverter to perform secondary compensation on the load voltage through transformer T1 according to the difference between the current load voltage and the voltage standard value of the three-phase AC power supply, so as to achieve full compensation of the load voltage;

[0017] Step 4: When it is detected that the voltage of the three-phase AC power source is restored to the standard value, the anti-parallel thyristor is turned off and the switch S1 and the switch S2 are closed.

[0018] Preferably, in step 1, after the switches S1 and S2 are disconnected, the voltage U sa , U sb , U sc The voltage fundamental component U is obtained by Park transformation, filtering, and Park inverse transformation. Laq , U Lbq , U Lcq, and then the voltage fundamental component U Laq , U Lbq , U Lcq The voltage standard value U of the three-phase AC power supply is set a_ref , U b_ref , U c_ref Subtract the voltage U required to compensate for each phase load when the power supply voltage drops. ra , U rb , U rc ;

[0019] In step 2, according to the detected voltage U sa , U sb , U sc And the set voltage standard value U a_ref , U b_ref , U c_ref Determine the voltage drop ratio k sag , control the anti-parallel thyristor to be switched on, take energy from the three-phase AC power supply through the primary winding of the multi-tap transformer T2, and then output the power supply voltage k through the secondary winding of the multi-tap transformer T2 sag / k2 ratio compensation voltage U ka , U kb , U kc , and then the compensation voltage U ka , U kb , U kc Inject into the three-phase AC power grid to compensate the voltage of each phase load;

[0020] In step 3, the voltage U required to compensate the load of each phase obtained in step 1 is ra , U rb , U rc Subtract the compensation voltage U obtained in step 2 from the ka , U kb , U kc , get the active inverter circuit output voltage command signal U ai_a , U ai_b , U ai_c , the output voltage command signal U ai_a , U ai_b , U ai_c The voltage is subtracted from the actual output voltage of the active inverter circuit of each corresponding phase, and then a voltage modulation signal is obtained through a PI regulator. The voltage modulation signal is then SPWM modulated to obtain the drive signal pulses D1, D2, D3, and D4 of the voltage-type H-bridge inverter. The drive signal pulses D1, D2, D3, and D4 are given to the signal interface of the voltage-type H-bridge inverter. The voltage-type H-bridge inverter performs secondary compensation for the load voltage through transformer T1 to achieve full compensation of the load voltage.

[0021] Furthermore, in step 1, the formula of the Park transformation is:

[0022]

[0023]

[0024]

[0025] Among them, C 32 represents the transformation matrix from three-phase to two-phase stationary coordinate system; C 2s-2r represents the transformation matrix from the two-phase stationary to the two-phase rotating coordinate system; C abc / dq Represents the transformation matrix between the three-phase abc coordinate system and the dq axis of the two-phase coordinate system.

[0026] Furthermore, in step 2, the compensation voltage output by the secondary winding of the multi-tap transformer T2 is:

[0027]

[0028] Among them, U k is the compensation voltage output by the secondary winding of the multi-tap transformer T2, U k According to the phase ka , U kb , U kc ;k sag is the current voltage U of the three-phase AC power supply s With voltage standard value U s_ref The ratio of the voltage standard value U s_ref is the power supply voltage under normal working conditions; k2 is the transformation ratio of the multi-tap transformer T2, and k2 is related to the tap that is turned on.

[0029] Furthermore, in step 3, after the driving signal pulses D1, D2, D3, and D4 are given to the signal interface of the voltage-type H-bridge inverter, the voltage-type H-bridge inverter passes through the filter inductor L f 、Filter capacitor C f The output voltage after filtering is:

[0030]

[0031] Among them, U ai It is the output voltage of the active inverter circuit.

[0032] Preferably, in step 3, the voltage across the load after full voltage compensation is:

[0033] U L =U S +(U k +Uai ) / k1 (6)

[0034] Among them, U L is the voltage across the load, and k1 is the transformation ratio of transformer T1.

[0035] The control method of the dual-transformer coupled voltage compensation system based on thyristor switching involved in the present invention, when the voltage drops, by quickly detecting the voltage amplitude of the power supply voltage, when the power supply voltage drops, the isolating switch is disconnected in time and the voltage compensation system is put into operation. And according to the amplitude of the power supply voltage drop, the primary winding of the multi-tap transformer is controlled to take energy from the power grid, the anti-parallel thyristor of the tap corresponding to the tap of the secondary winding is turned on, and most of the compensation voltage is injected into the load through the multi-tap transformer. In addition, the compensation state of the load voltage is also detected, and a small part of the compensation voltage is output by the active inverter circuit to achieve accurate compensation of the load. When the power supply voltage returns to the standard value, the isolating switch is controlled to close. This control method can not only greatly reduce the voltage level on the DC side of the active inverter circuit and reduce the capacity of the inverter, reduce the investment cost, but also increase the compensation accuracy and compensation range for the voltage amplitude drop. At the same time, the isolating switch in the compensation system and its control method can effectively ensure the reliability of the device under short-circuit faults and increase the service life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a circuit principle diagram of a double transformer coupling type voltage compensation system based on thyristor switching involved in the present invention;

[0037] Figure 2 It is a structural block diagram of voltage compensation performed by a dual transformer coupling type voltage compensation system based on thyristor switching according to the present invention;

[0038] Figure 3 It is a flow chart of a control method of a dual-transformer coupling type voltage compensation system based on thyristor switching according to the present invention;

[0039] Figure 4 It is a waveform diagram of active power outputted by the compensation system, the multi-tap inverter T2 and the active inverter circuit respectively when the compensation system compensates the load voltage in the embodiment of the present invention;

[0040] Figure 5 The waveform diagrams of the fundamental voltage and compensation voltage of each part when the power supply voltage drops by 10%, 20%, 30%, and 40% respectively in the embodiment of the present invention (where Figure 5 a is the fundamental voltage waveform of the three-phase AC power supply. Figure 5 b is the waveform of the compensation voltage required by the load, Figure 5 c is the load voltage waveform, Figure 5 d is the output compensation voltage waveform of the multi-tap transformer T2, Figure 5e is the output compensation voltage waveform of the active inverter circuit). DETAILED DESCRIPTION

[0041] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments and drawings. The contents mentioned in the implementation modes are not intended to limit the present invention.

[0042] like Figure 1 As shown, the dual-transformer coupling voltage compensation system based on thyristor switching includes three-phase compensation units, each of which includes an active inverter circuit, a transformer T1, a multi-tap transformer T2, a thyristor switching circuit, a switch S1 and a switch S2.

[0043] The active inverter circuit includes a voltage-type H-bridge inverter, a filter capacitor C f and filter inductor L f The voltage-type H-bridge inverter includes fully controlled devices V1, V2, V3, V4 on the AC side and capacitor C on the DC side. dc The fully controlled devices V1, V2, V3, and V4 are all NPN insulated gate bipolar transistors, with a diode in series between the emitter and the collector, and a capacitor C dc The AC side of the voltage type H-bridge inverter is connected in parallel with the series circuit composed of the fully controlled devices V1 and V2 and the series circuit composed of the fully controlled devices V3 and V4. f After the filter capacitor C f in parallel.

[0044] The primary winding of the multi-tap transformer T2 is connected in parallel with the three-phase AC power grid. The tap of the secondary winding of the multi-tap transformer T2 is electrically connected to one end of the primary winding of the transformer T1 through an anti-parallel thyristor. The other end of the primary winding of the transformer T1 and the other end of the secondary winding of the multi-tap transformer T2 are electrically connected to the filter capacitor C f At both ends of the transformer T1, the secondary winding is connected in series to the three-phase AC power grid, which includes a three-phase AC power supply and a load. The switch S1 is connected in parallel to the secondary winding of the transformer T1, and the switch S2 is connected in parallel to the secondary winding of the multi-tap transformer T2.

[0045] The thyristor switching circuit includes an anti-parallel thyristor Ts1, an anti-parallel thyristor Ts2 and an anti-parallel thyristor Ts3 which are sequentially connected in parallel. One end of the anti-parallel thyristor Ts1, the anti-parallel thyristor Ts2 and the anti-parallel thyristor Ts3 is electrically connected to each tap of the secondary winding of the multi-tap transformer T2, and the other end of the anti-parallel thyristor Ts1, the anti-parallel thyristor Ts2 and the anti-parallel thyristor Ts3 is electrically connected to the filter capacitor C. f one end.

[0046] When the voltage U of the three-phase AC power supply s (including U sa , U sb , U sc ) does not drop, switches S1 and S2 are turned on, and the system is in bypass mode; and when the voltage U s When a drop occurs, switches S1 and S2 are turned off. At this time, the system is in compensation mode. Most of the load drop voltage is compensated by the multi-tap transformer T2, and the remaining load drop voltage is compensated by the active inverter circuit. It is worth mentioning that the switches S1 and S2 in the present invention have the function of selecting the system mode, and can also be called isolation switches. In the compensation system involved in the present invention, the multi-tap transformer T2 bears the main drop voltage, which can greatly reduce the voltage level on the DC side of the active inverter circuit and reduce the capacity of the inverter.

[0047] As another aspect of the present invention, Figure 2 and 3 As shown, the control method of the dual-transformer coupled voltage compensation system based on thyristor switching includes:

[0048] Step 1: Set the voltage standard value U of the three-phase AC power supply a_ref , U b_ref , U c_ref , real-time detection of the actual output voltage U of the three-phase AC power supply sa , U sb , U sc , when each phase voltage U sa , U sb , U sc Lower than the voltage standard value U of the corresponding phase a_ref , U b_ref , U c_ref When a voltage drop occurs, the switches S1 and S2 are disconnected, and the voltage U of the detected three-phase AC voltage is sa , U sb , U sc After Park transformation, the power supply voltage U containing harmonics is obtained sd , U sq , and then filtered through a low-pass filter to obtain the DC component U sd ′、U sq ′, then the DC component U sd ′、U sq ′Perform Park inverse transformation to obtain the voltage fundamental component U of the three-phase AC power supply Laq , U Lbq , U Lcq , and then the voltage fundamental component U Laq , U Lbq , U LcqThe voltage standard value U of the three-phase AC power supply is set a_ref , U b_ref , U c_ref Subtract the voltage U required to compensate for each phase load when the power supply voltage drops. ra , U rb , U rc .

[0049] The formula for the aforementioned Park transformation is:

[0050]

[0051]

[0052]

[0053] Among them, C 32 represents the transformation matrix from three-phase to two-phase stationary coordinate system; C 2s-2r represents the transformation matrix from the two-phase stationary to the two-phase rotating coordinate system; C abc / dq Represents the transformation matrix between the three-phase abc coordinate system and the dq axis of the two-phase coordinate system.

[0054] Step 2: According to the detected voltage U sa , U sb , U sc And the set voltage standard value U a_ref , U b_ref , U c_ref Determine the voltage drop ratio k sag , control the anti-parallel thyristor to be switched on to take energy from the three-phase AC power supply through the primary winding of the multi-tap transformer T2, and then output the power supply voltage k through the secondary winding of the multi-tap transformer T2 sag / k2 ratio compensation voltage U ka , U kb , U kc , and then the compensation voltage U ka , U kb , U kc Injected into the three-phase AC power grid to compensate the voltage of each load.

[0055] It is necessary to point out that if Figure 2 As shown, when the voltage drops by k sag When the voltage drop ratio k is less than 0.72, the anti-parallel thyristors Ts1 and Ts2 are turned off, and the anti-parallel thyristor Ts3 is turned on. sag When the voltage drops to the range of [0.72, 0.82], the anti-parallel thyristors Ts1 and Ts3 are turned off, and the anti-parallel thyristor Ts2 is turned on. sagWhen it is in the range of [0.82, 0.92], the anti-parallel thyristors Ts2 and Ts3 are controlled to be turned off, and the anti-parallel thyristor Ts1 is turned on.

[0056] The compensation voltage output by the secondary winding of the aforementioned multi-tap transformer T2 is:

[0057]

[0058] Among them, U k is the compensation voltage output by the secondary winding of the multi-tap transformer T2, U k According to the phase ka , U kb , U kc ;k sag is the current voltage U of the three-phase AC power supply s With voltage standard value U s_ref The ratio of the voltage standard value U s_ref is the power supply voltage under normal working conditions; k2 is the transformation ratio of the multi-tap transformer T2, and k2 is related to the tap that is turned on.

[0059] Step 3: Detect the voltage compensation status of each phase load, and according to the difference between the current load voltage and the voltage standard value of the three-phase AC power supply, specifically, the voltage U required for compensation of each phase load obtained in step 1 is ra , U rb , U rc Subtract the compensation voltage U obtained in step 2 from the ka , U kb , U kc , and obtain the output voltage command signal U of the active inverter circuit in each phase compensation unit ai_a , U ai_b , U ai_c , and then the output voltage command signal U ai_a , U ai_b , U ai_c The voltage is subtracted from the actual output voltage of the active inverter circuit of each corresponding phase, and then the voltage is regulated by the PI regulator to obtain a voltage modulation signal. Finally, the voltage modulation signal is SPWM modulated to obtain the drive signal pulses D1, D2, D3, and D4 of the voltage-type H-bridge inverter. The drive signal pulses D1, D2, D3, and D4 are given to the signal interface of the voltage-type H-bridge inverter. The voltage-type H-bridge inverter performs secondary compensation on the voltage of each phase load through the transformer T1, thereby realizing full compensation of the load voltage.

[0060] After the driving signal pulses D1, D2, D3, and D4 are given to the signal interface of the voltage-type H-bridge inverter, the voltage-type H-bridge inverter passes through the filter inductor L f 、Filter capacitor C f The output voltage after filtering is:

[0061]

[0062] Among them, U ai It is the output voltage of the active inverter circuit.

[0063] For the load, the voltage across its two ends after full voltage compensation is:

[0064] U L =U S +(U k +U ai ) / k1 (6)

[0065] Among them, U L is the voltage across the load, and k1 is the transformation ratio of transformer T1.

[0066] It is worth mentioning that Figure 1 As shown, the aforementioned drive signal pulse D1 is the drive signal of the fully-controlled device V1, the drive signal pulse D2 is the drive signal of the fully-controlled device V2, the drive signal pulse D3 is the drive signal of the fully-controlled device V3, and the drive signal pulse D4 is the drive signal of the fully-controlled device V4.

[0067] In order to verify the effectiveness and feasibility of the dual transformer coupled voltage compensation system based on thyristor switching proposed in the present invention, this embodiment is built in Matlab / simulink as follows: Figure 1 The simulation model shown in the figure and the system simulation parameters are shown in Table 1 below, wherein the DC side voltage of the voltage-type H-bridge inverter is provided by an ideal DC voltage source, the transformation ratio parameter of the transformer T1 is 1, and the implementation mode of the present invention is described by taking phase A as an example.

[0068] Table 1 System simulation parameters

[0069]

[0070] The simulation system sets the power supply voltage to drop at 0.15s and return to the standard value at 0.45s.

[0071] Figure 4 and Figure 5 It can be seen that at 0.15-0.25s, the power supply voltage drops by 10%, and the voltage drop ratio k sagis 0.9, which is in the range of [0.82, 0.92], and the phase voltage amplitude drops from 311V to 280V. The compensation system of the present invention controls the anti-parallel thyristor Ts1 to be turned on, and the compensation voltage amplitude of the multi-tap transformer T2 is 36.5V, which is greater than the grid voltage drop value and is in an over-compensation state. The voltage amplitude output by the active inverter circuit is 5.5V, and the phase is opposite to the voltage phase output by the multi-tap transformer T2. At this time, the system compensation voltage is equal to the grid drop voltage, so that the load side voltage amplitude reaches the standard value.

[0072] At 0.25 to 0.35 seconds, the power supply voltage drops by 20%, and the voltage drop ratio is k sag is 0.8, which is within the range of [0.72, 0.82], that is, the phase voltage amplitude drops from 311V to 248.9V. The compensation system of the present invention controls the anti-parallel thyristor Ts1 to turn off, the anti-parallel thyristor Ts2 to turn on, and the compensation voltage amplitude of the multi-tap transformer T2 is 65.5V, which is greater than the grid voltage drop value and is in an over-compensation state. The output voltage amplitude of the active inverter circuit is 3.4V, and the phase is opposite to the output voltage of the multi-tap transformer T2. At this time, the system compensation voltage is approximately equal to the grid drop voltage, and the load side voltage amplitude reaches the standard value.

[0073] At 0.35-0.45s, the power supply voltage drops by 30%, and the voltage drop ratio k sag is 0.7, that is, less than 0.7, and the phase voltage amplitude drops from 311V to 217.8V. The compensation system of the present invention controls the anti-parallel thyristor Ts2 to turn off, the anti-parallel thyristor Ts3 to turn on, and the compensation voltage amplitude of the multi-tap transformer T2 is 86.3V, which is less than the grid voltage drop value and is in an under-compensated state. The output voltage amplitude of the active inverter circuit is 6.9V, and the phase is in phase with the output voltage of the multi-tap transformer T2. At this time, the system compensation voltage is approximately equal to the grid drop voltage, and the load side voltage amplitude reaches the standard value.

[0074] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present technical solution is within the protection scope of the present invention.

[0075] In order to make it easier for ordinary technicians in the field to understand the improvements of the present invention over the prior art, some drawings and descriptions of the present invention have been simplified, and for the sake of clarity, some other elements are omitted in this application document. Ordinary technicians in the field should realize that these omitted elements may also constitute the content of the present invention.

Claims

1. A dual transformer coupled voltage compensation system based on thyristor switching, characterized by: It includes three-phase compensation units, each of which includes an active inverter circuit, a transformer , Multi-tap transformer , thyristor switching circuit, switch and switch The active inverter circuit includes a voltage-type H-bridge inverter, a filter capacitor and filter inductor ; The thyristor switching circuit includes a plurality of groups of anti-parallel thyristors; The multi-tap transformer The primary winding of the multi-tap transformer is connected in parallel with the three-phase AC grid. The secondary winding tap is connected to the transformer through an anti-parallel thyristor One end of the primary winding is electrically connected to the transformer The other end of the primary winding is connected to the multi-tap transformer The other end of the secondary winding is electrically connected to the filter capacitor The two ends of the voltage type H-bridge inverter are connected in series with the AC side filter inductor After the filter capacitor In parallel, the transformer The secondary winding is connected in series to a three-phase AC power grid, wherein the three-phase AC power grid includes a three-phase AC power source and a load, and the switch With transformer The secondary windings are connected in parallel, the switch With multi-tap transformer The secondary windings are connected in parallel.

2. The dual transformer coupled voltage compensation system based on thyristor switching according to claim 1 is characterized in that: The thyristor switching circuit comprises anti-parallel thyristors connected in parallel in sequence , Anti-parallel thyristor and anti-parallel thyristors , the anti-parallel thyristor , Anti-parallel thyristor and anti-parallel thyristors One end of each of the two terminals is electrically connected to a multi-tap transformer Each tap of the secondary winding, the anti-parallel thyristor , Anti-parallel thyristor and anti-parallel thyristors The other end is electrically connected to the filter capacitor one end.

3. The dual transformer coupled voltage compensation system based on thyristor switching according to claim 2 is characterized in that: The voltage-type H-bridge inverter includes a fully controlled device on the AC side. , and the capacitor on the DC side , the capacitor Fully controlled devices Series circuits and fully controlled devices The series circuits are connected in parallel.

4. The dual transformer coupled voltage compensation system based on thyristor switching according to claim 3 is characterized in that: The fully controlled device All are NPN-type insulated gate bipolar transistors, and a diode is connected in series between the emitter and the collector of the insulated gate bipolar transistor.

5. The control method of the dual transformer coupled voltage compensation system based on thyristor switching according to any one of claims 1 to 4, characterized in that: include: Step 1: Set the voltage standard value of the three-phase AC power supply , real-time detection of the actual output voltage of the three-phase AC power supply , when each phase voltage Lower than the voltage standard value of the corresponding phase When a voltage drop occurs, the switch Disconnect and calculate the voltage required to compensate for each phase load; Step 2: According to the detected voltage And the set voltage standard value Determine the voltage drop ratio , control the conduction of the anti-parallel thyristor to be switched, through the multi-tap transformer The primary winding of the transformer takes energy from the three-phase AC power supply and then The secondary winding outputs the compensation voltage and passes through the transformer The compensation voltage is injected into the three-phase AC power grid to compensate the voltage of each phase load; Step 3: Detect the compensation state of the load voltage of each phase, and control the voltage type H-bridge inverter through the transformer according to the difference between the current load voltage and the voltage standard value of the three-phase AC power supply. Perform secondary compensation on the load voltage to achieve full compensation of the load voltage; Step 4: When the voltage of the three-phase AC power supply is detected to be restored to the standard value, the anti-parallel thyristor is turned off and the switch and switch closure.

6. The control method of the dual transformer coupled voltage compensation system based on thyristor switching according to claim 5 is characterized in that: In step 1, switch After disconnection, the voltage of the three-phase AC power supply will be detected The voltage fundamental component is obtained by Park transformation, filtering, and Park inverse transformation. , and then the voltage fundamental component The voltage standard value of the three-phase AC power supply is set Subtract the voltage from each other to get the voltage required to compensate for the load on each phase when the power supply voltage drops. ; In step 2, based on the detected voltage And the set voltage standard value Determine the voltage drop ratio , control the conduction of the anti-parallel thyristor to be switched, through the multi-tap transformer The primary winding of the transformer takes energy from the three-phase AC power supply and then The secondary winding output power supply voltage Ratio of compensation voltage , then through the transformer The compensation voltage Inject into the three-phase AC power grid to compensate the voltage of each phase load; Current voltage of three-phase AC power supply With voltage standard value Ratio, voltage standard value is the power supply voltage under normal working conditions; For multi-tap transformer The transformation ratio, Related to the tap that is turned on; In step 3, the voltage required to compensate the load of each phase obtained in step 1 is Subtract the compensation voltage obtained in step 2 from the , get the active inverter circuit output voltage command signal , the output voltage command signal The voltage modulation signal is obtained by subtracting the actual output voltage of the active inverter circuit of each corresponding phase, and then passing through the PI regulator. Then, the voltage modulation signal is modulated by SPWM to obtain the driving signal pulse of the voltage type H-bridge inverter. , the driving signal pulse The signal interface of the voltage-type H-bridge inverter is given to the voltage-type H-bridge inverter through the transformer Perform secondary compensation on the load voltage to achieve full compensation of the load voltage.

7. The control method of the dual transformer coupled voltage compensation system based on thyristor switching according to claim 6 is characterized in that: In step 1, the formula of the Park transformation is: （1） （2） （3） in, Represents the transformation matrix from three-phase to two-phase stationary coordinate system; Represents the transformation matrix from two-phase stationary to two-phase rotating coordinate system; Represents the transformation matrix between the three-phase abc coordinate system and the dq axis of the two-phase coordinate system.

8. The control method of the dual transformer coupled voltage compensation system based on thyristor switching according to claim 7 is characterized in that: In step 2, the multi-tap transformer The compensation voltage output by the secondary winding is: （4） in, For multi-tap transformer The compensation voltage output by the secondary winding, According to the phase ; Current voltage of three-phase AC power supply With voltage standard value Ratio, voltage standard value is the power supply voltage under normal working conditions; For multi-tap transformer The transformation ratio, Depends on the tap that is conducting.

9. The control method of the dual transformer coupled voltage compensation system based on thyristor switching according to claim 8, characterized in that: In step 3, the driving signal pulse After being sent to the signal interface of the voltage-type H-bridge inverter, the voltage-type H-bridge inverter passes through the filter inductor 、Filter capacitor The output voltage after filtering is: （5） in, It is the output voltage of the active inverter circuit.

10. The control method of the dual transformer coupled voltage compensation system based on thyristor switching according to claim 9, characterized in that: In step 3, the voltage across the load after full voltage compensation is: （6） in, is the voltage across the load, For transformer The transformation ratio.

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