Energy storage integrated power electronic transformer area device and control method thereof

Abstract

The invention discloses an energy storage integrated power electronic transformer area device and a control method thereof. The invention discloses an energy storage integrated power electronic transformer area device which comprises a four-winding transformer and a four-bridge-arm converter. The four-leg converter comprises an alternating current port, two direct current ports and a zero sequence port, the alternating current port is connected with a parallel port of the four-winding transformer through a three-phase filter, and the zero sequence port is connected with a neutral point of the four-winding transformer through the three-phase filter. The two direct current ports are a high-voltage direct current port and a low-voltage direct current port; and power flow between the alternating current port and the two direct current ports is realized through the four-bridge-arm converter control unit. According to the invention, unbiased voltage control of the energy storage device can be maintained, output AC voltage and current can be accurately controlled, overvoltage of a high-voltage DC port can be avoided, and the reliability and stability of the system can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronic converters, and in particular to an energy storage integrated power electronic stage device and a control method thereof. Background Art

[0002] The access of new energy power generation to the power grid makes the load characteristics volatile and intermittent. In addition, the new power load headed by new energy vehicles makes the trend of new energy power generation output and power load change significantly different, making power prediction difficult. The distribution network flow distribution is volatile. Traditional distribution network substations are prone to voltage over-limit problems under the influence of random flow, and traditional control methods are no longer applicable. More and more research focuses on intelligent distribution technology with flexible regulation capabilities. In order to prevent power fluctuations caused by new energy power generation, ensure reliable power supply and safe operation, it is necessary to cooperate with energy storage devices to realize the peak regulation, frequency regulation and voltage regulation capabilities of the grid-connected device itself.

[0003] Therefore, the use of a multi-port AC / DC / DC converter structure and its control method to flexibly regulate the power flow of photovoltaics, energy storage and the power grid will effectively improve the system operation stability.

[0004] The problems and defects of the prior art are:

[0005] (1) The simultaneous access of photovoltaic power generation and energy storage to the grid requires the introduction of multiple power electronic converter modules, which results in large size and high cost.

[0006] (2) Existing control methods are difficult to stabilize the output voltage and current of the energy storage device and the grid-connected current, which can easily lead to excessive DC voltage and threaten the safety of the device. In terms of control implantation, the energy storage device control is difficult to integrate into the existing grid-connected converter control, making it difficult to promote the composite energy storage control. Summary of the invention

[0007] In view of the problems existing in the above-mentioned prior art, the present invention provides an energy storage integrated power electronic substation device and a control method thereof, which can use fewer switching devices, realize power coordination between supercapacitors and batteries on different time scales, and transmit the power to the power grid and load through a transformer, so as to realize normal voltage transformation of the substation device, and output or absorb stable AC power for a period of time, as well as control of unbalanced current.

[0008] To this end, the present invention adopts the following technical solution.

[0009] In a first aspect, the present invention provides an energy storage integrated power electronic station area device, which includes a four-winding transformer and a four-bridge arm converter;

[0010] The four-bridge-arm converter comprises an AC port, two DC ports and a zero-sequence port, wherein the AC port is connected to the parallel port of the four-winding transformer through a three-phase filter, the zero-sequence port is connected to the neutral point of the four-winding transformer through a three-phase filter, and the two DC ports are a high-voltage DC port and a low-voltage DC port; the power flow of the AC port and the two DC ports is realized by a four-bridge-arm converter control unit;

[0011] The high voltage DC port is connected to a filter capacitor C dc , used to access supercapacitors; the high-voltage DC port is connected to the AC port through a four-arm converter;

[0012] The low voltage DC port is connected to a filter capacitor C d and a DC filter inductor L d , used to connect to the battery; the low-voltage DC port is connected to the DC filter inductor L through the secondary winding of the four-winding transformer zigzag connection d The neutral point of the four-winding transformer is connected to the DC filter inductor L d One end is connected to the DC filter inductor L d The other end of the filter capacitor C d One end connected.

[0013] Further, the four-winding transformer includes one set of primary windings and three sets of secondary windings;

[0014] The primary winding includes an A-phase primary winding, a B-phase primary winding and a C-phase primary winding; the three-phase winding adopts a triangle connection method, and the port is used as a high-voltage access port;

[0015] The three groups of secondary windings are a first secondary winding, a second secondary winding and a third secondary winding;

[0016] The first secondary winding and the second secondary winding are connected in a zigzag manner; the three-phase winding named ends of the first secondary winding are connected to form a secondary neutral point, the unnamed end of the A-phase winding of the first secondary winding is connected to the unnamed end of the C-phase winding of the second secondary winding, the unnamed end of the B-phase winding of the first secondary winding is connected to the unnamed end of the A-phase winding of the second secondary winding, the unnamed end of the C-phase winding of the first secondary winding is connected to the unnamed end of the B-phase winding of the second secondary winding, the named end of the A-phase winding of the second secondary winding is used as a parallel-end A-phase voltage port, the named end of the B-phase winding of the second secondary winding is used as a parallel-end B-phase voltage port, and the named end of the C-phase winding of the second secondary winding is used as a parallel-end C-phase voltage port;

[0017] The unnamed end of the A-phase winding of the third secondary winding is connected to the named end of the A-phase winding of the second secondary winding, and the named end of the A-phase winding of the third secondary winding serves as a low-voltage access port; the unnamed end of the B-phase winding of the third secondary winding is connected to the named end of the B-phase winding of the second secondary winding, and the named end of the B-phase winding of the third secondary winding serves as a low-voltage access port; the unnamed end of the C-phase winding of the third secondary winding is connected to the named end of the C-phase winding of the second secondary winding, and the named end of the C-phase winding of the third secondary winding serves as a low-voltage access port.

[0018] Furthermore, the high-voltage DC port of the four-bridge-arm converter is connected to the AC port through a three-phase H-bridge, and is connected to the zero-sequence port through a half-bridge arm; the three-phase H-bridge includes 6 IGBT switch tubes Q g1 , Q g2 , Q g3 , Q g4 , Q g5 and Q g6 ; IGBT switch tube Q g1 With Q g2 Forming the a-phase bridge arm, Q g1 The source and Q g2 The drain of is connected to the a-phase grid-connected inductor, Q g1 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g2 The source of the switch tube Q is connected to the negative electrode of the high voltage DC port; g3 With Q g4 The b-phase bridge arm, Q g3 The source and Q g4 The drain of is connected to the b-phase grid-connected inductor, Q g3 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g4 The source of the switch tube Q is connected to the negative electrode of the high voltage DC port; g5 With Q g6 The c-phase bridge arm, Q g5 The source and Q g6 The drain of the capacitor is connected to the c-phase grid-connected inductor, Q g5 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g6 The source of the IGBT switch tube Q is connected to the negative electrode of the high voltage DC port; g7 With Q g8 Forming N-phase bridge arm, Q g7 The source and Q g8 The drain of the capacitor is connected to the c-phase grid-connected inductor, Q g7 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g8 The source is connected to the negative pole of the high voltage DC port.

[0019] Furthermore, the four-arm converter control unit generates a PWM signal to control the IGBT switch tube of the four-arm converter by combining the three-phase voltage at the parallel end of the four-winding transformer, the AC three-phase current and N-phase current of the four-arm converter, the load N-phase current and its reference value, the high-voltage DC port voltage and its reference value, the low-voltage DC port voltage and its reference value and the low-voltage DC port current using a phase-locked loop controller, a DC voltage controller, an AC current controller, a zero-sequence current controller, a low-voltage port voltage controller and a low-voltage port current controller.

[0020] Furthermore, the four-bridge-arm converter control unit comprises:

[0021] A first Parker transformation coordinate converter is used to transform the output three-phase current of the four-bridge-arm converter and the input phase through Parker transformation to output the d-axis current and the q-axis current in a two-phase synchronous rotating coordinate system;

[0022] The second Parker transformation coordinate converter is used to transform the three-phase voltage at the parallel end of the four-winding transformer and the input phase through Parker transformation to output the d-axis voltage and q-axis voltage in a two-phase synchronous rotating coordinate system;

[0023] A phase-locked loop controller is used to obtain the phase of a two-phase synchronous rotating coordinate system by using the three-phase voltage on the secondary side of a four-winding transformer through phase-locked calculation, and then obtain the electric vector phase θ through sine-cosine calculation;

[0024] A DC voltage controller, used for performing subtraction between a high-voltage DC port voltage reference value and a high-voltage DC port voltage through a first subtractor, and then outputting a d-axis current reference value through a first proportional-integral controller;

[0025] The first subtractor is used to subtract the high-voltage DC port voltage reference value from the high-voltage DC port voltage to obtain a DC voltage difference;

[0026] The first proportional-integral controller is used to use the value obtained by adding the DC voltage difference through proportional calculation and integral calculation as the d-axis current reference value in the two-phase synchronous rotating coordinate system;

[0027] An AC current controller is used to make a difference between the current reference value output by the four-arm converter and the output current through the second subtractor and the third subtractor, respectively, and the difference is input into the second proportional integral controller and the third proportional integral controller respectively. The output value is subjected to an inverse Pike transformation and added to the three-phase voltage at the parallel end of the four-winding transformer through the fourth subtractor and the fifth subtractor to obtain a three-phase PWM modulation voltage in a stationary coordinate system;

[0028] An anti-Peake transform coordinate converter, used for converting the modulation voltage of the two-phase synchronous rotating coordinate system and the input phase through anti-Peake transform to output a three-phase modulation voltage;

[0029] A low-voltage port voltage controller, used for inputting the low-voltage port voltage reference value and the low-voltage port voltage into a fourth proportional-integral controller through a sixth subtractor, and outputting a low-voltage DC port current reference value;

[0030] A low-voltage port current controller, used for inputting the low-voltage DC port current difference into a fifth proportional-integral controller through a seventh subtractor to obtain a low-voltage DC port modulation voltage;

[0031] The zero-sequence current controller is used to obtain the difference between the load N-phase current and the four-bridge arm converter N-phase current through the eighth subtractor, and then input it into the proportional integral resonant controller to obtain the zero-sequence port modulation voltage, and generate a half-bridge PWM signal through the comparator.

[0032] Furthermore, the second subtractor is used to subtract the d-axis current from the d-axis current reference value to obtain a d-axis current difference;

[0033] The third subtractor is used to subtract the q-axis current from the q-axis current reference value to obtain a q-axis current difference;

[0034] The second proportional-integral controller is used to obtain a value obtained by adding the d-axis current difference through proportional calculation and integral calculation as the d-axis voltage difference;

[0035] The third proportional-integral controller is used to obtain a value obtained by adding the q-axis current difference through proportional calculation and integral calculation as the q-axis voltage difference;

[0036] The fourth subtractor is used to add the inverse of the d-axis voltage difference to the d-axis voltage to obtain the d-axis modulation voltage;

[0037] The fifth subtractor is used to add the inverse of the q-axis voltage difference to the q-axis voltage to obtain the q-axis modulation voltage.

[0038] Furthermore, the sixth subtractor is used to subtract the low-voltage port voltage from the low-voltage port voltage reference value to obtain a low-voltage port voltage difference;

[0039] The fourth proportional-integral controller is used to use the value obtained by adding the low-voltage port voltage difference through proportional calculation and integral calculation as the low-voltage DC port current reference value.

[0040] Furthermore, the seventh subtractor is used to subtract the low-voltage DC port current from the low-voltage DC port current reference value to obtain a low-voltage DC port current difference;

[0041] The fifth proportional-integral controller is used to use the value obtained by adding the low-voltage DC port current difference through proportional calculation and integral calculation as the low-voltage DC port modulation voltage.

[0042] Furthermore, the eighth subtractor is used to subtract the load N-phase current from the N-phase current of the four-bridge-arm converter to obtain a zero-sequence port current difference;

[0043] The proportional-integral resonant controller is used to use the value obtained by adding the zero-sequence port current difference through proportional calculation and integral calculation as the zero-sequence port modulation voltage.

[0044] In a second aspect, the present invention provides a four-arm converter control method based on the energy storage integrated power electronic station device, which comprises the steps of:

[0045] 1) The three-phase voltage at the parallel end of the four-winding transformer is converted from the three-phase stationary coordinate system to the dq-axis component U of the two-phase synchronous rotating coordinate system using Park transformation. kd , U kq , through U kq The proportional-integral controller is directly input, and the output electrical angular velocity deviation is added to the preset grid angular velocity. The obtained electrical angular velocity of the two-phase synchronous rotating coordinate system is integrated to obtain the phase θ of the two-phase synchronous rotating coordinate system; the Park transformation is used to convert the three-phase current of the four-leg converter from the three-phase stationary coordinate system to the dq-axis component I of the two-phase synchronous rotating coordinate system. kd ,I kq ;

[0046] 2) Subtracting the high-voltage DC port voltage reference value from the high-voltage DC port voltage to obtain a DC voltage difference;

[0047] 3) The DC voltage difference is calculated by proportional calculation and integral calculation to obtain a value obtained by adding the values ​​as the d-axis current in the two-phase synchronous rotating coordinate system;

[0048] 4) Subtract the current reference value of the four-bridge-arm converter from the output current, input the difference into the proportional-integral converter, add the output value to the voltage at the parallel terminal of the four-winding transformer, and obtain the three-phase PWM modulation voltage in the stationary coordinate system through the inverse Park transformation;

[0049] 5) Subtracting the low-voltage DC port voltage reference value from the low-voltage DC port voltage to obtain the low-voltage DC port voltage difference;

[0050] 6) The value obtained by adding the low voltage port voltage difference through proportional calculation and integral calculation is used as the low voltage DC port current reference value;

[0051] 7) Subtracting the low-voltage DC port current reference value from the low-voltage DC port current to obtain a low-voltage DC port current difference;

[0052] 8) The value obtained by adding the low-voltage DC port current difference through proportional calculation and integral calculation is used as the low-voltage DC port current reference value deviation, and then added to the low-voltage DC port current reference value to obtain the low-voltage DC port modulation voltage, and then the three-phase PWM modulation voltage is added to the low-voltage DC port modulation voltage, and pulse width modulation is performed to obtain a PWM signal to control the three-phase H-bridge of the four-bridge-arm converter;

[0053] 9) Subtracting the load N-phase current from the four-bridge-arm converter N-phase current to obtain the N-phase current difference;

[0054] 10) The value obtained by adding the N-phase current difference through proportional calculation, integral calculation and resonance calculation is used as the modulation voltage of the N-phase port, and a PWM signal is obtained through pulse width modulation to control the half-bridge arm of the four-bridge-arm converter.

[0055] The beneficial effects of the present invention are as follows: the present invention can use fewer switching devices, realize power coordination between supercapacitors and batteries on different time scales, and transmit it to the power grid and load through the transformer, so as to realize normal voltage transformation of the substation device, and output or absorb stable AC power for a period of time, as well as control of unbalanced current. Therefore, the present invention has good economy, and at the same time, the modulated current output by the energy storage control can be extended to any grid-connected converter using current loop control, and has good promotion and universality. The present invention can maintain unbiased voltage control of the energy storage device, accurately control the output AC voltage and current, and at the same time, the parallel terminal voltage of the four-winding transformer is slightly lower than the secondary voltage, which can avoid overvoltage at the high-voltage DC port and improve system reliability and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a structural schematic diagram of the energy storage integrated power electronic station area device of the present invention;

[0057] Figure 2 is a control block diagram of a four-bridge-arm converter control unit of the present invention;

[0058] Figure 3 It is the spatial voltage vector relationship diagram of the four-arm transformer of the present invention;

[0059] Figure 4 It is the secondary voltage and current output waveform diagram of the four-winding transformer of the present invention;

[0060] Figure 5 It is a waveform diagram of the voltage at the parallel terminals and the zigzag winding current output of the four-winding transformer of the present invention;

[0061] Figure 6 It is the primary voltage and current output waveform diagram of the four-winding transformer of the present invention;

[0062] Figure 7 It is an output waveform diagram of the load N-phase current of the four-winding transformer, the N-phase current of the four-bridge-arm converter and the neutral point N-phase current of the four-winding transformer of the present invention. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0064] This embodiment provides an energy storage integrated power electronic station area device, such as Figure 1 As shown, it includes a four-winding transformer and a four-leg converter.

[0065] The four-winding transformer includes a set of primary windings and three sets of secondary windings;

[0066] The primary winding includes an A-phase primary winding, a B-phase primary winding and a C-phase primary winding; the three-phase winding adopts a triangle connection method, and the port is used as a high-voltage access port;

[0067] The three groups of secondary windings are a first secondary winding, a second secondary winding and a third secondary winding;

[0068] The turns ratio of the primary winding, the first secondary winding, the second secondary winding and the third secondary winding is set to N1:N2:N3:N4.

[0069] The first secondary winding and the second secondary winding are connected in a zigzag manner; the three-phase winding named ends of the first secondary winding are connected to form a secondary neutral point, the unnamed end of the A-phase winding of the first secondary winding is connected to the unnamed end of the C-phase winding of the second secondary winding, the unnamed end of the B-phase winding of the first secondary winding is connected to the unnamed end of the A-phase winding of the second secondary winding, the unnamed end of the C-phase winding of the first secondary winding is connected to the unnamed end of the B-phase winding of the second secondary winding, the named end of the A-phase winding of the second secondary winding is used as a parallel-end A-phase voltage port, the named end of the B-phase winding of the second secondary winding is used as a parallel-end B-phase voltage port, and the named end of the C-phase winding of the second secondary winding is used as a parallel-end C-phase voltage port;

[0070] The unnamed end of the A-phase winding of the third secondary winding is connected to the named end of the A-phase winding of the second secondary winding, and the named end of the A-phase winding of the third secondary winding serves as the low-voltage access port of the substation transformer; the unnamed end of the B-phase winding of the third secondary winding is connected to the named end of the B-phase winding of the second secondary winding, and the named end of the B-phase winding of the third secondary winding serves as the low-voltage access port of the substation transformer; the unnamed end of the C-phase winding of the third secondary winding is connected to the named end of the C-phase winding of the second secondary winding, and the named end of the C-phase winding of the third secondary winding serves as the low-voltage access port of the substation transformer.

[0071] The four-bridge-arm converter comprises an AC port, two DC ports and a zero-sequence port; the power flow between the AC port and the two DC ports is realized by a four-bridge-arm converter control unit.

[0072] The AC port of the four-arm converter is connected to the transformer parallel access port through an L-type filter;

[0073] The zero-sequence port of the four-bridge-arm converter is connected to the neutral point access port through an L-type filter;

[0074] The two DC ports of the four-arm converter are a high-voltage DC port and a low-voltage DC port; the high-voltage DC port is connected to a filter capacitor C dc , used to connect to the supercapacitor; the high-voltage DC port is connected to the AC port through a four-arm converter; the low-voltage DC port is connected to a filter capacitor C d and a DC filter inductor L d , used to access the battery.

[0075] The high-voltage DC port of the four-bridge-arm converter is connected to the AC port through a three-phase H-bridge, and is connected to the zero-sequence port through a half-bridge arm; the three-phase H-bridge includes 6 IGBT switch tubes (Q g1 ~Q g6 );Switch tube Q g1 With Q g2 Forming the a-phase bridge arm, Q g1 The source and Q g2 The drain of is connected to the a-phase grid-connected inductor, Q g1 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g2 The source of the switch tube Q is connected to the negative electrode of the high voltage DC port; g3 With Q g4 The b-phase bridge arm, Q g3 The source and Q g4 The drain of is connected to the b-phase grid-connected inductor, Q g3 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g4 The source of the switch tube Q is connected to the negative electrode of the high voltage DC port; g5 With Q g6 The c-phase bridge arm, Q g5 The source and Q g6 The drain of the capacitor is connected to the c-phase grid-connected inductor, Q g5 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g6 The source of the switch tube Q is connected to the negative electrode of the high voltage DC port; g7 With Q g8 Forming N-phase bridge arm, Q g7 The source and Q g8The drain of the capacitor is connected to the c-phase grid-connected inductor, Q g7 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g8 The source electrode is connected to the negative electrode of the high voltage DC port;

[0076] The low voltage DC port of the four-arm converter is connected to the DC filter inductor L through the secondary winding of the four-winding transformer zigzag connection method. d The neutral point of the four-winding transformer is connected to the DC filter inductor L d One end is connected to the DC filter inductor L d The other end of the filter capacitor C d One end connected.

[0077] The four-arm converter control unit generates a PWM signal to control the IGBT switch tube of the four-arm converter by combining the three-phase voltage at the parallel end of the four-winding transformer, the AC three-phase current and the N-phase current of the four-arm converter, the load N-phase current and its reference value, the high-voltage DC port voltage and its reference value, the low-voltage DC port voltage and its reference value and the low-voltage DC port current, using a phase-locked loop controller, a DC voltage controller, an AC current controller, a zero-sequence current controller, a low-voltage port voltage controller and a low-voltage port current controller.

[0078] Specifically, the four-arm converter control unit includes a first Parker transform coordinate converter, a second Parker transform coordinate converter, a phase-locked loop controller, a DC voltage controller, an AC current controller, an inverse Parker transform coordinate converter, a low-voltage port current controller and a zero-sequence current controller.

[0079] The first Parker transform coordinate converter is used to convert the three-phase output current of the converter and the input phase through Parker transform to output the d-axis current and q-axis current in a two-phase synchronous rotating coordinate system.

[0080] The second Parker transform coordinate converter is used to transform the parallel end three-phase voltage and the input phase through Parker transform to output the d-axis voltage and q-axis voltage in a two-phase synchronous rotating coordinate system.

[0081] The phase-locked loop controller is used to obtain the phase of the two-phase synchronous rotating coordinate system by phase-locked calculation using the three-phase voltage on the secondary side of the transformer, and then obtain the electric vector phase θ by sine-cosine calculation.

[0082] The DC voltage controller is used to perform a difference between the high-voltage DC port voltage reference value and the high-voltage DC port voltage through a first subtractor, and then output a d-axis current reference value through a first proportional-integral controller;

[0083] The first subtractor is used to subtract the high-voltage DC port voltage reference value from the high-voltage DC port voltage to obtain a DC voltage difference; the first proportional-integral controller is used to use the value obtained by adding the DC voltage difference through proportional calculation and integral calculation as the d-axis current reference value in the two-phase synchronous rotating coordinate system.

[0084] The AC current controller is used to make a difference between the current reference value output by the four-arm converter and the output current through the second subtractor and the third subtractor, respectively, and the difference is input into the second proportional integral controller and the third proportional integral controller respectively. The output value is subjected to an inverse Pike transformation and added to the voltage at the parallel terminal of the transformer through the fourth subtractor and the fifth subtractor to obtain a three-phase PWM modulation voltage in a stationary coordinate system;

[0085] The second subtractor is used to subtract the d-axis current from the d-axis current reference value to obtain the d-axis current difference; the third subtractor is used to subtract the q-axis current from the q-axis current reference value to obtain the q-axis current difference; the second proportional-integral controller is used to use the value obtained by adding the d-axis current difference through proportional calculation and integral calculation as the d-axis voltage difference; the third proportional-integral controller is used to use the value obtained by adding the q-axis current difference through proportional calculation and integral calculation as the q-axis voltage difference; the fourth subtractor is used to add the inverse of the d-axis voltage difference to the d-axis voltage to obtain the d-axis modulation voltage; the fifth subtractor is used to add the inverse of the q-axis voltage difference to the q-axis voltage to obtain the q-axis modulation voltage.

[0086] The inverse Pike transform coordinate converter is used to output a three-phase modulated voltage by inverse Pike transforming the modulation voltage of the two-phase synchronous rotating coordinate system and the input phase.

[0087] The low-voltage port voltage controller is used to input the low-voltage port voltage reference value and the low-voltage port voltage into the fourth proportional-integral controller through the sixth subtractor, and output the low-voltage DC port current reference value;

[0088] The sixth subtractor is used to subtract the low-voltage port voltage from the low-voltage port voltage reference value to obtain the low-voltage port voltage difference; the fourth proportional-integral controller is used to add the low-voltage port voltage difference through proportional calculation and integral calculation to obtain a value as the low-voltage DC port current reference value.

[0089] The low-voltage port current controller is used to input the low-voltage DC port current difference into the fifth proportional-integral controller through the seventh subtractor to obtain the low-voltage DC port modulation voltage;

[0090] The seventh subtractor is used to subtract the low-voltage DC port current from the low-voltage DC port current reference value to obtain the low-voltage DC port current difference; the fifth proportional-integral controller is used to add the low-voltage DC port current difference through proportional calculation and integral calculation to obtain a value as the low-voltage DC port modulation voltage;

[0091] The zero-sequence current controller is used to obtain the difference between the load N-phase current and the converter N-phase current through the eighth subtractor, and then input it into the proportional integral resonant controller to obtain the zero-sequence port modulation voltage, and generate a half-bridge PWM signal through the comparator;

[0092] The eighth subtractor is used for subtracting the load N-phase current from the converter N-phase current to obtain a zero-sequence port current difference;

[0093] The proportional-integral resonant controller is used to use the value obtained by adding the zero-sequence port current difference through proportional calculation and integral calculation as the zero-sequence port modulation voltage.

[0094] This embodiment also provides a control method for the above four-arm converter to achieve simultaneous grid connection of photovoltaic and energy storage devices, and the steps are as follows:

[0095] (1) The three-phase voltage at the parallel end of the transformer is converted from the three-phase stationary coordinate system to the dq-axis component U of the two-phase synchronous rotating coordinate system using Park transformation. kd , U kq , through U kq Directly input the proportional integral controller, add the output electrical angular velocity deviation to the preset grid angular velocity, and perform integration operation on the obtained electrical angular velocity of the two-phase synchronous rotating coordinate system to obtain the phase θ of the two-phase synchronous rotating coordinate system; use Park transformation to convert the three-phase current of the converter from the three-phase stationary coordinate system to the dq-axis component I of the two-phase synchronous rotating coordinate system kd ,I kq ;

[0096] (2) subtracting the high-voltage DC port voltage reference value from the high-voltage DC port voltage to obtain a DC voltage difference;

[0097] (3) The DC voltage difference is calculated by proportional calculation and integral calculation to obtain a value obtained by adding the values ​​as the d-axis current in the two-phase synchronous rotating coordinate system;

[0098] (4) Subtract the current reference value of the four-bridge-arm converter from the output current, input the difference into the proportional-integral converter, add the output value to the voltage at the parallel terminal of the transformer, and obtain the three-phase PWM modulation voltage in the stationary coordinate system through the inverse Park transformation;

[0099] (5) subtracting the low-voltage DC port voltage reference value from the low-voltage DC port voltage to obtain a low-voltage DC port voltage difference;

[0100] (6) The value obtained by adding the low-voltage port voltage difference through proportional calculation and integral calculation is used as the low-voltage DC port current reference value;

[0101] (7) subtracting the low-voltage DC port current reference value from the low-voltage DC port current to obtain a low-voltage DC port current difference;

[0102] (8) The value obtained by adding the low-voltage DC port current difference through proportional calculation and integral calculation is used as the low-voltage DC port current reference value deviation, and then added to the low-voltage DC port current reference value to obtain the low-voltage DC port modulation voltage, and then the three-phase PWM modulation voltage is added to the low-voltage DC port modulation voltage, and pulse width modulation is performed to obtain a PWM signal to control the three-phase H-bridge of the four-bridge-arm converter;

[0103] (9) Subtracting the load N-phase current from the converter N-phase current to obtain an N-phase current difference;

[0104] (10) The value obtained by adding the N-phase current difference through proportional calculation, integral calculation and resonance calculation is used as the modulation voltage of the N-phase port, and a PWM signal is obtained through pulse width modulation to control the half-bridge arm of the four-bridge-arm converter.

[0105] Combine the following Figures 1 to 7 The specific implementation process of the present invention is introduced.

[0106] Figure 1 In the circuit, a four-leg converter, a three-phase passive L-type filter (referred to as a three-phase filter), and a filter capacitor C dc And a three-phase four-winding transformer constitutes the main circuit;

[0107] In the main circuit, the three-phase voltage of the transformer primary side is: u AN 、u BN 、u CN , the three-phase voltage at the parallel end is: u kAN 、u kBN 、u kCN ; The three-phase voltage of its secondary side is: u aN 、u bN 、u cN ; The output three-phase current and N-phase current of the four-bridge-arm converter are: i ka 、i kb 、i kc 、i kN ; Load three-phase current is: i La 、i Lb 、i Lc 、i LN ; The primary three-phase current is: i ga 、i gb 、i gc; The three-phase current of the zigzag winding is: i sa 、i sb 、i sc ; Low voltage DC port voltage: U B ; The low voltage DC port current is: I B ; The N-phase current at the neutral point of the transformer is: I TN ; High voltage DC port voltage: U dc .

[0108] Figure 2 It is a control block diagram of a four-bridge-arm converter control unit of the present invention, and the control method comprises the following steps:

[0109] The three-phase voltage u at the parallel end of the transformer is converted into kABCN The dq-axis component U is converted from the three-phase stationary coordinate system to the two-phase synchronous rotating coordinate system kd , U kq , through U kq Directly input the proportional integral controller, add the output electrical angular velocity deviation to the preset grid angular velocity, and perform integration operation on the electrical angular velocity of the two-phase synchronous rotating coordinate system to obtain the phase θ of the two-phase synchronous rotating coordinate system; use Park transformation to convert the three-phase current i kabc The dq axis component I converted from the three-phase stationary coordinate system to the two-phase synchronous rotating coordinate system kd ,I kq ;

[0110] The high voltage DC port voltage reference value U dcN With the high voltage DC port voltage U dc Subtract the DC voltage difference ΔU dc ;

[0111] The DC voltage difference ΔU dc The value obtained by adding the proportional calculation and the integral calculation is taken as the d-axis current I in the two-phase synchronous rotating coordinate system. kdr ;

[0112] The four-leg converter current reference value I kdr ,I kqr The difference between them and the output current is ΔI kd , ΔI kq The proportional integral converter is input respectively, and the output value is respectively connected to the transformer parallel terminal voltage U kd , U kq Add them together and obtain the three-phase PWM modulation voltage U in the stationary coordinate system through the inverse Park transformation. kabcr ;

[0113] The low voltage DC port voltage reference value U BN With low voltage DC port voltage U BSubtract to get the low voltage DC port voltage difference ΔU B ;

[0114] The voltage difference of the low voltage port ΔU B The opposite number of is calculated by proportional calculation and integral calculation, and the value obtained is used as the low-voltage DC port current reference value I Br ;

[0115] The low voltage DC port current I B and the low voltage DC port current reference value I Br Subtract the current difference ΔI of the low voltage DC port B ;

[0116] The low voltage DC port current difference ΔI B The value obtained by adding the proportional calculation and the integral calculation is used as the low-voltage DC port current reference value deviation U k0r , and then add it to the low-voltage DC port current reference value to obtain the low-voltage DC port modulation voltage, and then add the three-phase PWM modulation voltage to the low-voltage DC port modulation voltage, and through pulse width modulation, obtain the PWM signal G Qg1-6 , for the three-phase H-bridge converter switch tube Q g1 To Q g6 To exercise control;

[0117] The load N phase current i LN The N-phase current i kN Subtract the current difference Δi of the N phases N ;

[0118] The N-phase current difference Δi N The value obtained by adding the proportional calculation, integral calculation and resonance calculation is used as the modulation voltage u of the N-phase port. kn , and through pulse width modulation, the PWM signal G is obtained Qg7-8 , for the half-bridge converter switch tube Q g7 With Q g8 To exercise control;

[0119] Figure 3 This is the spatial voltage vector relationship diagram of the transformer of the power electronic substation provided by the present invention. Taking the A phase line as an example, the primary side line voltage U BA The A-phase winding is excited, and the sum of the voltage vectors of the first secondary winding and the second secondary winding is the parallel end A-phase voltage U kAN , lagging primary line voltage U BA ; The excitation generating device of the third secondary winding generates the secondary A phase voltage U aN , leading parallel terminal A phase voltage U kAN; When the winding ratio satisfies N1:N2:N3:N4=17320:173:173:90, the primary line voltage is 10kV, the parallel end line voltage is 300V, and the secondary line voltage of the device is 380V.

[0120] The solution of the present invention is verified using the MATLAB / Simulink simulation experiment platform. The simulation results are as follows: Figures 4 to 7 The simulation process is as follows: the primary side of the power electronic area is connected to the AC grid with a line voltage of 10kV, and the secondary side is connected to the resistive inductive load; the DC voltage of the high-voltage DC port of the four-leg converter is set to 750V; the device is phase-locked before 0.02s, and the device is running after 0.02s, and the energy storage does not output power; after 1s, the energy storage starts to output power; the secondary voltage and current output waveforms of the power electronic area device are as follows Figure 4 , the parallel terminal voltage and current output waveforms are as follows Figure 5 , the primary voltage and current output waveforms are as follows Figure 6 As shown, the output waveforms of the load N-phase current, the converter N-phase current and the transformer neutral point N-phase current are as follows: Figure 7 shown.

[0121] Figure 4 During the entire operation process, since the load is fixed and a fixed three-phase current flows through the load, it can be found that severe unbalanced load leads to severe unbalanced current. Figure 5 Before 0.02s, a large amount of unbalanced current flows through the transformer due to unbalanced load. After 0.02s, the device is running and the converter controls the unbalanced current of the line. The unbalanced current flowing through the transformer decreases rapidly. After 1s, the energy storage starts to charge and the line current increases. These show that the converter controls the unbalanced current of the line, and the battery can quickly change the photovoltaic power at any time, reflecting its superiority. Figure 6 Before 0.02s, a large amount of unbalanced current flows through the transformer due to the unbalanced load, and most of the unbalanced current also flows through the primary side. After 0.02s, the device is operational and the converter controls the unbalanced current in the line. The unbalanced current flowing through the transformer decreases rapidly. After 1s, the energy storage starts to charge and the line current increases. Figure 7 In the case of a large amount of zero-sequence current flowing through the N-phase line of the transformer before 0.02s, after the device is started, the zero-sequence current is quickly compensated and drops from 50A to less than 2A. During the 0.02-2s change process, the active power changes smoothly and the output is stable in steady state, which reflects the superiority of the device in the flexible regulation of multi-energy storage grid-connected power.

[0122] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0123] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. An energy storage integrated power electronic station device, characterized in that: It includes a four-winding transformer and a four-bridge-arm converter; The four-bridge-arm converter comprises an AC port, two DC ports and a zero-sequence port, wherein the AC port is connected to the parallel port of the four-winding transformer through a three-phase filter, the zero-sequence port is connected to the neutral point of the four-winding transformer through a three-phase filter, and the two DC ports are a high-voltage DC port and a low-voltage DC port; the power flow of the AC port and the two DC ports is realized by a four-bridge-arm converter control unit; The high voltage DC port is connected to a filter capacitor C dc , used to access supercapacitors; the high-voltage DC port is connected to the AC port through a four-arm converter; The low voltage DC port is connected to a filter capacitor C d and a DC filter inductor L d , used to connect to the battery; the low-voltage DC port is connected to the DC filter inductor L through the secondary winding of the four-winding transformer zigzag connection method d The neutral point of the four-winding transformer is connected to the DC filter inductor L d One end is connected to the DC filter inductor L d The other end of the filter capacitor C d One end connected.

2. The energy storage integrated power electronic substation device according to claim 1, characterized in that: The four-winding transformer includes a set of primary windings and three sets of secondary windings; The primary winding includes an A-phase primary winding, a B-phase primary winding and a C-phase primary winding; the three-phase winding adopts a triangle connection method, and the port is used as a high-voltage access port; The three groups of secondary windings are a first secondary winding, a second secondary winding and a third secondary winding; The first secondary winding and the second secondary winding are connected in a zigzag manner; the three-phase winding named ends of the first secondary winding are connected to form a secondary neutral point, the unnamed end of the A-phase winding of the first secondary winding is connected to the unnamed end of the C-phase winding of the second secondary winding, the unnamed end of the B-phase winding of the first secondary winding is connected to the unnamed end of the A-phase winding of the second secondary winding, the unnamed end of the C-phase winding of the first secondary winding is connected to the unnamed end of the B-phase winding of the second secondary winding, the named end of the A-phase winding of the second secondary winding is used as a parallel-end A-phase voltage port, the named end of the B-phase winding of the second secondary winding is used as a parallel-end B-phase voltage port, and the named end of the C-phase winding of the second secondary winding is used as a parallel-end C-phase voltage port; The unnamed end of the A-phase winding of the third secondary winding is connected to the named end of the A-phase winding of the second secondary winding, and the named end of the A-phase winding of the third secondary winding serves as a low-voltage access port; The unnamed end of the B-phase winding of the third secondary winding is connected to the named end of the B-phase winding of the second secondary winding, and the named end of the B-phase winding of the third secondary winding serves as a low-voltage access port; the unnamed end of the C-phase winding of the third secondary winding is connected to the named end of the C-phase winding of the second secondary winding, and the named end of the C-phase winding of the third secondary winding serves as a low-voltage access port.

3. The energy storage integrated power electronic substation device according to claim 1 or 2, characterized in that: The high-voltage DC port of the four-bridge-arm converter is connected to the AC port through a three-phase H-bridge, and is connected to the zero-sequence port through a half-bridge arm; the three-phase H-bridge includes 6 IGBT switch tubes Q g1 , Q g2 , Q g3 , Q g4 , Q g5 and Q g6 ; IGBT switch tube Q g1 With Q g2 Forming the a-phase bridge arm, Q g1 The source and Q g2 The drain of is connected to the a-phase grid-connected inductor, Q g1 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g2 The source of the switch tube Q is connected to the negative electrode of the high voltage DC port; g3 With Q g4 The b-phase bridge arm, Q g3 The source and Q g4 The drain of is connected to the b-phase grid-connected inductor, Q g3 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g4 The source of the switch tube Q is connected to the negative electrode of the high voltage DC port; g5 With Q g6 The c-phase bridge arm, Q g5 The source and Q g6 The drain of the capacitor is connected to the c-phase grid-connected inductor, Q g5 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g6 The source of the IGBT switch tube Q is connected to the negative electrode of the high voltage DC port; g7 With Q g8 Forming N-phase bridge arm, Q g7 The source and Q g8 The drain of the capacitor is connected to the c-phase grid-connected inductor, Q g7 The drain of the device is connected to the positive electrode of the high voltage DC port, Q g8 The source is connected to the negative pole of the high voltage DC port.

4. The energy storage integrated power electronic substation device according to claim 1 or 2, characterized in that: The four-arm converter control unit generates a PWM signal to control the IGBT switch tube of the four-arm converter by combining the three-phase voltage at the parallel end of the four-winding transformer, the AC three-phase current and the N-phase current of the four-arm converter, the load N-phase current and its reference value, the high-voltage DC port voltage and its reference value, the low-voltage DC port voltage and its reference value and the low-voltage DC port current, using a phase-locked loop controller, a DC voltage controller, an AC current controller, a zero-sequence current controller, a low-voltage port voltage controller and a low-voltage port current controller.

5. The energy storage integrated power electronic substation device according to claim 1 or 2, characterized in that: The four-bridge-arm converter control unit comprises: A first Parker transformation coordinate converter is used to transform the output three-phase current of the four-bridge-arm converter and the input phase through Parker transformation to output the d-axis current and the q-axis current in a two-phase synchronous rotating coordinate system; The second Parker transformation coordinate converter is used to transform the three-phase voltage at the parallel end of the four-winding transformer and the input phase through Parker transformation to output the d-axis voltage and q-axis voltage in a two-phase synchronous rotating coordinate system; A phase-locked loop controller is used to obtain the phase of a two-phase synchronous rotating coordinate system by using the three-phase voltage on the secondary side of a four-winding transformer through phase-locked calculation, and then obtain the electric vector phase θ through sine-cosine calculation; A DC voltage controller, used for performing subtraction between a high-voltage DC port voltage reference value and a high-voltage DC port voltage through a first subtractor, and then outputting a d-axis current reference value through a first proportional-integral controller; The first subtractor is used to subtract the high-voltage DC port voltage reference value from the high-voltage DC port voltage to obtain a DC voltage difference; The first proportional-integral controller is used to use the value obtained by adding the DC voltage difference through proportional calculation and integral calculation as the d-axis current reference value in the two-phase synchronous rotating coordinate system; An AC current controller is used to make a difference between the current reference value output by the four-arm converter and the output current through the second subtractor and the third subtractor, respectively, and the difference is input into the second proportional integral controller and the third proportional integral controller respectively. The output value is subjected to an inverse Pike transformation and added to the three-phase voltage at the parallel end of the four-winding transformer through the fourth subtractor and the fifth subtractor to obtain a three-phase PWM modulation voltage in a stationary coordinate system; An anti-Peake transform coordinate converter, used for converting the modulation voltage of the two-phase synchronous rotating coordinate system and the input phase through anti-Peake transform to output a three-phase modulation voltage; A low-voltage port voltage controller, used for inputting the low-voltage port voltage reference value and the low-voltage port voltage into a fourth proportional-integral controller through a sixth subtractor, and outputting a low-voltage DC port current reference value; A low-voltage port current controller, used for inputting the low-voltage DC port current difference into a fifth proportional-integral controller through a seventh subtractor to obtain a low-voltage DC port modulation voltage; The zero-sequence current controller is used to obtain the difference between the load N-phase current and the four-bridge arm converter N-phase current through the eighth subtractor, and then input it into the proportional integral resonant controller to obtain the zero-sequence port modulation voltage, and generate a half-bridge PWM signal through the comparator.

6. The energy storage integrated power electronic substation device according to claim 5, characterized in that: The second subtractor is used to subtract the d-axis current from the d-axis current reference value to obtain a d-axis current difference; The third subtractor is used to subtract the q-axis current from the q-axis current reference value to obtain a q-axis current difference; The second proportional-integral controller is used to obtain a value obtained by adding the d-axis current difference through proportional calculation and integral calculation as the d-axis voltage difference; The third proportional-integral controller is used to obtain a value obtained by adding the q-axis current difference through proportional calculation and integral calculation as the q-axis voltage difference; The fourth subtractor is used to add the inverse of the d-axis voltage difference to the d-axis voltage to obtain the d-axis modulation voltage; The fifth subtractor is used to add the inverse of the q-axis voltage difference to the q-axis voltage to obtain the q-axis modulation voltage.

7. The energy storage integrated power electronic substation device according to claim 5, characterized in that: The sixth subtractor is used to subtract the low-voltage port voltage from the low-voltage port voltage reference value to obtain a low-voltage port voltage difference; The fourth proportional-integral controller is used to use the value obtained by adding the low-voltage port voltage difference through proportional calculation and integral calculation as the low-voltage DC port current reference value.

8. The energy storage integrated power electronic substation device according to claim 5, characterized in that: The seventh subtractor is used to subtract the low-voltage DC port current from the low-voltage DC port current reference value to obtain a low-voltage DC port current difference; The fifth proportional-integral controller is used to use the value obtained by adding the low-voltage DC port current difference through proportional calculation and integral calculation as the low-voltage DC port modulation voltage.

9. The energy storage integrated power electronic substation device according to claim 5, characterized in that: The eighth subtractor is used to subtract the load N-phase current from the N-phase current of the four-bridge-arm converter to obtain a zero-sequence port current difference; The proportional-integral resonant controller is used to use the value obtained by adding the zero-sequence port current difference through proportional calculation and integral calculation as the zero-sequence port modulation voltage.

10. A four-arm converter control method based on the energy storage integrated power electronic substation device according to any one of claims 1 to 9, characterized in that: Includes steps: 1) The three-phase voltage at the parallel end of the four-winding transformer is converted from the three-phase stationary coordinate system to the dq-axis component U of the two-phase synchronous rotating coordinate system using Park transformation. kd , U kq , through U kq The proportional-integral controller is directly input, and the output electrical angular velocity deviation is added to the preset grid angular velocity. The obtained electrical angular velocity of the two-phase synchronous rotating coordinate system is integrated to obtain the phase θ of the two-phase synchronous rotating coordinate system; the Park transformation is used to convert the three-phase current of the four-leg converter from the three-phase stationary coordinate system to the dq-axis component I of the two-phase synchronous rotating coordinate system. kd ,I kq ; 2) Subtracting the high-voltage DC port voltage reference value from the high-voltage DC port voltage to obtain a DC voltage difference; 3) The DC voltage difference is calculated by proportional calculation and integral calculation to obtain a value obtained by adding the values ​​as the d-axis current in the two-phase synchronous rotating coordinate system; 4) Subtract the current reference value of the four-bridge-arm converter from the output current, input the difference into the proportional-integral converter, add the output value to the voltage at the parallel terminal of the four-winding transformer, and obtain the three-phase PWM modulation voltage in the stationary coordinate system through the inverse Park transformation; 5) Subtracting the low-voltage DC port voltage reference value from the low-voltage DC port voltage to obtain the low-voltage DC port voltage difference; 6) The value obtained by adding the low voltage port voltage difference through proportional calculation and integral calculation is used as the low voltage DC port current reference value; 7) Subtracting the low-voltage DC port current reference value from the low-voltage DC port current to obtain a low-voltage DC port current difference; 8) The value obtained by adding the low-voltage DC port current difference through proportional calculation and integral calculation is used as the low-voltage DC port current reference value deviation, and then added to the low-voltage DC port current reference value to obtain the low-voltage DC port modulation voltage, and then the three-phase PWM modulation voltage is added to the low-voltage DC port modulation voltage, and pulse width modulation is performed to obtain a PWM signal to control the three-phase H-bridge of the four-bridge-arm converter; 9) Subtracting the load N-phase current from the four-bridge-arm converter N-phase current to obtain the N-phase current difference; 10) The value obtained by adding the N-phase current difference through proportional calculation, integral calculation and resonance calculation is used as the modulation voltage of the N-phase port, and a PWM signal is obtained through pulse width modulation to control the half-bridge arm of the four-bridge-arm converter.

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