CN105576687B - A kind of AC/DC energy storage PCU Power Conditioning Unit and its control method - Google Patents

Abstract

The invention discloses an AC and DC dual-purpose energy storage power regulating device and a control method thereof, including 3n cascaded H-bridge units, 3n energy storage units, an AC output interface circuit, a DC output interface circuit, and a central controller unit; The central controller unit controls the switching status of the AC circuit breaker of the AC output interface circuit and the DC circuit breaker of the DC output interface circuit, so that the energy storage device works in the energy storage inverter mode to connect to the AC grid, or works in the energy storage DC conversion mode The controller mode is used to connect to the DC grid; the central controller unit adopts the corresponding control strategy according to the working mode of the energy storage device to realize the two-way controllable flow of power. The invention can realize the flexible configuration and management of the energy storage system connected to the AC-DC hybrid microgrid by controlling the different working modes of the energy storage device, more efficiently utilize the conversion of electric energy between the AC and DC buses, and improve the efficiency of electric energy storage and transfer. Efficiency, easy to improve the stability of the AC-DC hybrid microgrid system.

Description

An AC and DC dual-purpose energy storage power adjustment device and its control method

technical field

The invention relates to the technical field of energy storage in a microgrid system, and more specifically relates to an AC and DC dual-purpose energy storage power regulating device and a control method thereof.

Background technique

As a new energy network supply and management technology, microgrid integrates distributed power generation units, renewable energy, energy storage devices, loads, monitoring and protection systems, etc., which can effectively optimize the operation and management of renewable energy and improve the efficiency of large power grids. The level of consumption of renewable energy. Microgrids can be divided into AC microgrids, DC microgrids, and AC-DC hybrid microgrids according to their structural characteristics. Among them, the AC-DC hybrid microgrid integrates the characteristics of the AC microgrid and the DC microgrid. The AC power supply and the AC load are connected in parallel to the AC bus, and the DC power supply and the DC load are connected in parallel to the DC bus. energy.

At present, there are AC distributed generation units, AC loads, AC energy storage systems, DC distributed generation units, DC loads, and DC energy storage units in the field of power system transmission and distribution, using a single AC microgrid or DC microgrid. It is difficult for the grid to meet the needs of the power system. As a network structure with both advantages, the AC-DC hybrid microgrid can well adapt to the development needs of the power system.

The energy storage system is an important part of the microgrid. Its unique two-way adjustment capability makes the operation of the microgrid more flexible and reliable. The smooth transition has an irreplaceable role for other power sources.

At present, most of the existing technologies are equipped with energy storage systems on both sides of the AC bus and DC bus of the AC-DC hybrid microgrid, and perform energy conversion through independent power adjustment devices, and the operation mode is relatively simple. The electric energy in the energy storage system between the AC micro-grid and the DC micro-grid needs to be converted through independent power regulation devices and bus interconnection inverters. On the one hand, the utilization efficiency of electric energy is reduced, and on the other hand, the response of electric energy conversion is reduced. speed.

Contents of the invention

The present invention aims to solve the problem that the traditional energy storage power adjustment device cannot satisfy the AC-DC power conversion at the same time, and proposes an AC-DC dual-purpose energy storage power adjustment device and its control method, in order to be able to be directly connected to the AC-DC bus and flexibly realized Energy conversion realizes flexible configuration and management of the energy storage system, so that the conversion of electric energy between the AC and DC buses can be used more efficiently, the efficiency of electric energy storage and transfer can be improved, and it is more beneficial to improve the stability of the AC-DC hybrid microgrid system .

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

The present invention is an AC-DC dual-purpose energy storage power adjustment device, which is applied in an AC-DC hybrid microgrid, and is characterized in that the energy storage power adjustment device includes: a power adjustment main circuit and a central controller unit;

The power regulation main circuit includes 3n cascaded H-bridge units, 3n energy storage units, an AC output interface circuit and a DC output interface circuit; n≥1; 1≤i≤n;

The 3n cascaded H-bridge units include n a-phase cascaded H-bridge units (H _a1 ~H _an ), n b-phase cascaded H-bridge units (H _b1 ~H _bn ) and n c-phase cascaded H bridge unit (H _c1 ~ H _cn );

The i-th a-phase cascaded H-bridge unit includes the i-th a-phase full-bridge inverter and the i-th a-phase filter capacitor (C _ai );

The i-th b-phase cascaded H-bridge unit includes the i-th b-phase full-bridge inverter and the i-th b-phase filter capacitor (C _bi );

The i-th c-phase cascaded H-bridge unit includes the i-th c-phase full-bridge inverter and the i-th c-phase filter capacitor (C _ci );

The 3n energy storage units include n a-phase energy storage units, n b-phase energy storage units and n c-phase energy storage units;

The i-th phase-a energy storage unit includes: the i-th phase-a energy storage device (V _ai ) and the i-th phase-a DC circuit breaker (K _DCai ) connected in series;

The i-th phase-b energy storage unit includes: the i-th phase-b energy storage device (V _bi ) and the i-th phase-b DC circuit breaker (K _DCbi ) connected in series;

The i-th phase-c energy storage unit includes: the i-th phase-c energy storage device (V _ci ) and the i-th phase-c DC circuit breaker (K _DCci ) connected in series;

The AC output interface circuit includes a-phase AC output interface circuit, b-phase AC output interface circuit and c-phase AC output interface circuit;

The a-phase AC output interface circuit includes: a-phase AC circuit breaker (K _ACa ) and its a-phase power frequency inductor (L _a ) connected in series;

The b-phase AC output interface circuit includes: a b-phase AC circuit breaker (K _ACb ) and a b-phase power frequency inductor (L _b ) connected in series;

The c-phase AC output interface circuit includes: a c-phase AC circuit breaker (K _ACc ) and a c-phase power frequency inductor (L _c ) connected in series;

The DC output interface circuit includes a first DC output interface circuit, a second DC output interface circuit, a third DC output interface circuit, a fourth DC circuit breaker (K _DC4 ) and a filter capacitor (C _DC );

The first DC output interface circuit includes: a first DC circuit breaker (K _DC1 ) and its first high-frequency inductor (L ₁ ) connected in series;

The second DC output interface circuit includes: a second DC circuit breaker (K _DC2 ) and a second high-frequency inductor (L ₂ ) connected in series;

The third DC output interface circuit includes: a third DC circuit breaker (K _DC3 ) and a third high-frequency inductor (L ₃ ) connected in series;

One side of the i-th a-phase full-bridge inverter is respectively connected in parallel with the a-phase filter capacitor (C _ai ) and the i-th a-phase energy storage unit;

The other side of the i-th a-phase full-bridge inverter is respectively connected in series with the i-1th a-phase full-bridge inverter and the i+1th a-phase full-bridge inverter to form an a-phase conversion unit Afterwards, they are respectively connected in parallel with the first DC output interface circuit and the a-phase AC output interface circuit;

One side of the i-th b-phase full-bridge inverter is respectively connected in parallel with the b-phase filter capacitor (C _bi ) and the i-th b-phase energy storage unit;

The other side of the i-th b-phase full-bridge inverter is respectively connected in series with the i-1th b-phase full-bridge inverter and the i+1th b-phase full-bridge inverter to form a b-phase conversion unit After that, they are respectively connected in parallel with the second DC output interface circuit and the b-phase AC output interface circuit;

One side of the i-th c-phase full-bridge inverter is respectively connected in parallel with the c-phase filter capacitor (C _ci ) and the i-th c-phase energy storage unit;

The other side of the i-th c-phase full-bridge inverter is respectively connected in series with the i-1th c-phase full-bridge inverter and the i+1th c-phase full-bridge inverter to form a c-phase conversion unit Afterwards, they are respectively connected in parallel with the third DC output interface circuit and the c-phase AC output interface circuit;

The a-phase AC output interface circuit is connected to a-phase of the AC grid;

The b-phase AC output interface circuit is connected to the b-phase of the AC grid;

The c-phase AC output interface circuit is connected to the c-phase of the AC grid;

The first DC output interface circuit, the second DC output interface circuit, the third DC output interface circuit and the filter capacitor are connected in parallel to the fourth DC circuit breaker (K _DC4 ) in series, and then connected to into both sides of the DC grid;

The central controller unit includes a sampling conditioning circuit, a control unit and a PWM modulation unit;

The sampling conditioning circuit respectively collects the phase voltage of the three-phase power grid at the AC output interface circuit, the three-way power frequency inductor current, the DC voltage at the DC output interface circuit, the three-way high-frequency inductor current, and the DC voltage of 3n energy storage units. The sampling signal formed by the voltage is transmitted to the control unit;

The control unit is based on the a-phase AC circuit breaker (K _ACa ), the b-phase AC circuit breaker (K _ACb ), the c-phase AC circuit breaker (K _ACc ) and the first DC circuit breaker ( K _DC1 ), the second DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) switch states to judge that the working mode of the energy storage power regulating device is energy storage Inverter mode or energy storage DC converter mode, so that according to the received sampling signal, the PWM control signal is obtained by using the energy storage inverter mode strategy or the energy storage DC converter mode strategy, and transmitted to the PWM modulation unit;

The PWM modulation unit controls the 3n cascaded H-bridge units to implement power conversion regulation according to the PWM control signal.

The characteristics of the AC/DC dual-purpose energy storage power regulating device of the present invention are also:

The energy storage device is a storage battery, a supercapacitor, a flywheel or a superconducting magnet.

The control unit judges whether the working mode of the energy storage power regulating device is the energy storage inverter mode or the energy storage DC converter mode in the following manner:

When the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are closed, and the first DC circuit breaker (K _DC1 ), the second If the DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are disconnected, it means that the energy storage power regulating device forms an energy storage inverter DC/AC structure, Therefore, it is judged that the working mode of the energy storage power regulating device is the energy storage inverter mode;

When the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are disconnected, and the first DC circuit breaker (K _DC1 ), the first When the second DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are closed, it means that the energy storage power regulating device forms an energy storage DC converter DC/DC structure, Therefore, it is judged that the working mode of the energy storage power regulating device is the energy storage DC converter mode.

The characteristic of the control method of a kind of AC and DC dual-purpose energy storage power regulating device of the present invention is to carry out according to the following steps:

Step 1. Collect phase a AC circuit breaker (K _ACa ), phase b AC circuit breaker (K _ACb ), phase c AC circuit breaker (K _ACc ), and the first DC circuit breaker (K _DC1 ), the second DC circuit breaker (K _DC2 ), the switch states of the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) and judge;

If the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are closed, and the first DC circuit breaker (K _DC1 ), the second If the DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are disconnected, it means that the energy storage power regulating device is working in the energy storage inverter mode, and executes Step 2;

If the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are disconnected, and the first DC circuit breaker (K _DC1 ), the first When the second DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are closed, it means that the energy storage power regulating device is working in the energy storage DC converter mode, and step 6 is performed ;

Step 2. Collect phase a phase voltage V _sa , phase b phase voltage V _sb , phase c phase voltage V _sc , and phase a inductance current i _a , phase b inductance current i _b , and phase _c inductance current ic of the AC grid; Voltages V _a1 -V _an of n a-phase energy storage units, voltages V _b1 -V _bn of n b-phase energy storage units, and voltages V _c1 -V _cn of n c-phase energy storage units;

Make abc/dq coordinate transformation for phase a phase voltage V _sa , phase b phase voltage V _sb , phase c phase voltage V _sc , phase a inductance current i _a , phase b inductance current i _b , and phase c inductance current i _c , respectively Obtain the grid voltage d-axis component V _sd , q-axis component V _sq and grid current d-axis component i _d , q-axis component i _q ;

Step 3. Using the power decoupling control method, given the active command P ^* and the reactive command Q ^* , calculate the given active current command i _d ^* and reactive current command i _q ^* according to formula (1):

Step 4. The difference between the active current command i _d ^* and the d-axis component i _d of the AC grid side current, the difference between the reactive current command i _q ^* and the q-axis component i _q of the AC grid side current, through the active and reactive current After decoupling control, the dq axis reference components u _d and u _q of the AC output voltage of the cascaded H-bridge unit are obtained; the dq axis reference components u _d and u _q are transformed by inverse coordinates to obtain the original voltage of the modulated wave in the PWM signal generation link _{signal_abc} ^* ;

Step 5. Utilize the carrier phase shift CPS-SPWM modulation method to calculate the modulated wave signal u _abc of the PWM signal generation link according to formula (2):

The obtained modulated wave signal u _abc is used as the sinusoidal modulated wave of n a-phase full-bridge inverters, and the sinusoidal modulated wave of the n a-phase full-bridge inverters is used as the modulated wave signal of the left bridge arm, and the obtained The sinusoidal modulation wave of n a-phase full-bridge inverters is phase-shifted by 180° as the modulation wave signal of the right bridge arm;

The resulting modulated wave signal u _abc is lagged by 120° as the sinusoidal modulated wave of n b-phase full-bridge inverters, and the sinusoidal modulated wave of the n b-phase full-bridge inverters is used as the modulated wave signal of the left bridge arm , shifting the sinusoidal modulation waves of the n b-phase full-bridge inverters by 180° as the modulation wave signal of the right bridge arm;

Advance the obtained modulated wave signal u _abc by 120° as the sinusoidal modulated wave of n c-phase full-bridge inverters, and use the sinusoidal modulated wave of the n c-phase full-bridge inverters as the modulated wave signal of the left bridge arm , shifting the sinusoidal modulation waves of the n c-phase full-bridge inverters by 180° as the modulation wave signal of the right bridge arm;

The original triangular carrier signal of a full-bridge inverter is given, and the original triangular carrier signal is sequentially phase-shifted by π/n carrier cycles, so as to obtain n triangular carrier signals of full-bridge inverters, and respectively serve as n A triangular carrier signal of a-phase full-bridge inverters, a triangular carrier signal of n b-phase full-bridge inverters, and a triangular carrier signal of n c-phase full-bridge inverters;

Comparing the sinusoidal modulation waves of the n a-phase full-bridge inverters with the triangular carrier signals of the n a-phase full-bridge inverters to obtain the n a-phase full-bridge inverter PWM drive signals;

Comparing the sinusoidal modulation waves of the n b-phase full-bridge inverters with the triangular carrier signals of the n b-phase full-bridge inverters, obtaining n PWM drive signals of the b-phase full-bridge inverters;

Comparing the sinusoidal modulation waves of the n c-phase full-bridge inverters with the triangular carrier signals of the n c-phase full-bridge inverters to obtain the n c-phase full-bridge inverter PWM drive signals;

Control the energy storage inverter according to the PWM driving signals of the n a-phase full-bridge inverters, the PWM driving signals of the n b-phase full-bridge inverters and the n c-phase full-bridge inverters. Two-way controllable flow of power;

Step 6. Collect the DC grid voltage V _o , the first high-frequency inductor current i _L1 , the second high-frequency inductor current i _L2 , and the third high-frequency inductor current i _L3 ; collect the voltages V _a1 ~ of n a-phase energy storage units V _an , voltages V _b1 -V _bn of n phase-b energy storage units, and voltages V _c1 -V _cn of n phase-c energy storage units;

Step 7. Control the upper tube of the right bridge arm of the full-bridge inverter in the 3n cascaded H-bridge units to always turn off and the lower tube to always be turned on, so that the output of n cascaded H-bridge units in each phase can be connected in series to the DC power grid ;

Step 8. Using the method of controlling the charging and discharging power of the energy storage system, given the power command P _ref of the energy storage system, according to the DC bus voltage V _o obtained by sampling, calculate the reference value I _ref of the charging and discharging current of the energy storage system through formula (3) :

Step 9. Comparing the charge and discharge current reference value I _ref of the energy storage system with the first high-frequency inductor current i _L1 , the second high-frequency inductor current i _L2 , and the third high-frequency inductor current i _L3 , the obtained difference The values are obtained through the PI link to obtain the modulated wave signals of the three channels;

Given an original triangular carrier wave, the original triangular carrier wave is sequentially phase-shifted by 2π/3 phases using a three-phase interleaved parallel control method, thereby obtaining triangular carrier waves of 3 channels; The modulated wave signals are compared to generate a PWM driving signal for the full-bridge inverter, and the PWM driving signal is used to control the bidirectional controllable power flow of the energy storage DC converter.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. The energy storage power adjustment device of the present invention enables the energy storage system to use a set of power adjustment devices to connect to both the AC power grid and the DC power grid, and flexibly control the energy storage power adjustment device to work in DC according to the operating conditions of the AC-DC hybrid micro-grid system. Two different operating modes: /AC inverter or DC/DC conversion, which overcomes the problem that the existing technology needs to independently configure energy storage systems and corresponding power adjustment devices on both sides of the AC bus and DC bus of the AC-DC hybrid microgrid system. It realizes the flexible configuration and management of the energy storage system, improves the conversion efficiency of electric energy between the AC and DC buses, improves the stability and reliability of the AC-DC hybrid micro-grid system, and reduces the investment cost and equipment installation space, ensuring Make full use of the equipment under different operating modes.

2. The present invention controls the energy storage power adjustment device to flexibly switch between the DC/AC structure of the energy storage inverter and the DC/DC structure of the energy storage DC converter by adjusting the switch state of the circuit breaker of the AC output interface circuit and the DC output interface circuit , to overcome the problem of single operation mode of the traditional power adjustment device, and realize the diversification of the operation mode of the power adjustment device; at the same time, the working mode of the energy storage power adjustment device is judged by using the switch state of the circuit breaker as the basis for judging the working mode of the energy storage power adjustment device It is an energy storage inverter mode or an energy storage DC converter mode; the device structure switching method is simple and flexible, and the control judgment basis is intuitive and reliable, which improves the applicability and operability of the energy storage power adjustment device.

3. The present invention adopts the power decoupling control method and the carrier phase shift CPS-SPWM modulation method as the control method of the energy storage power adjustment device in the energy storage inverter mode; the power decoupling control method realizes the control of the energy storage inverter Fast and precise control of the output power; the carrier phase shift CPS-SPWM modulation method is simple to control, which can greatly reduce the harmonics of the inverter output voltage and reduce the requirements for the output filter circuit.

4. The present invention adopts the method of controlling the charge and discharge power of the energy storage system and the three-phase interleaved parallel control method as the control method of the energy storage power adjustment device in the mode of the energy storage DC converter; the method of controlling the charge and discharge power of the energy storage system realizes the The fast and precise control of the output power of the DC converter makes the energy storage power adjustment device suitable for the occasion of stabilizing the fluctuation of renewable energy; the three-phase interleaved parallel control mode reduces the total output current ripple and increases the ripple frequency, thereby reducing The parameter values of the output filter inductor and capacitor are reduced, which is conducive to improving the dynamic response capability of the circuit and improving the system efficiency.

Description of drawings

Fig. 1 is a schematic structural diagram of the energy storage power regulating device of the present invention;

Fig. 2 is a schematic diagram of the topological structure of the working mode of the energy storage inverter of the energy storage power regulating device of the present invention;

Fig. 3 is a schematic diagram of the topological structure of the working mode of the energy storage DC converter of the energy storage power regulating device of the present invention;

Fig. 4 is a schematic diagram of the working mode control structure of the energy storage inverter of the energy storage power regulating device of the present invention;

Fig. 5 is a schematic diagram of the working mode control structure of the energy storage DC converter of the energy storage power regulating device of the present invention.

Detailed ways

In this embodiment, an AC-DC dual-purpose energy storage power adjustment device is applied to an AC-DC hybrid microgrid, and mainly includes a power adjustment main circuit and a central controller unit;

As shown in Figure 1, the power regulation main circuit includes 6 cascaded H-bridge units, 6 energy storage units, AC output interface circuit and DC output interface circuit; 1≤i≤2;

The 6 cascaded H-bridge units include 2 a-phase cascaded H-bridge units (H _a1 ～H _a2 ), 2 b-phase cascaded H-bridge units (H _b1 ～H _b2 ) and 2 c-phase cascaded H-bridges units (H _c1 ～H _c2 ); wherein, the i-th a-phase cascaded H-bridge unit includes the i-th a-phase full-bridge inverter and the i-th a-phase filter capacitor (C _ai ); the i-th b-phase The cascaded H-bridge unit includes the i-th b-phase full-bridge inverter and the i-th b-phase filter capacitor (C _bi ); the i-th c-phase cascaded H-bridge unit includes the i-th c-phase full-bridge inverter and the i-th c-phase filter capacitor (C _ci );

The 6 energy storage units include 2 a-phase energy storage units, 2 b-phase energy storage units and 2 c-phase energy storage units; among them, the i-th a-phase energy storage unit includes: the i-th a-phase energy storage device (V _ai ) and its i-th phase a DC circuit breaker (K _DCai ) in series; the i-th phase b energy storage unit includes: the i-th phase b energy storage device (V _bi ) and its i-th b-phase DC circuit breaker (K _DCbi ); the i-th c-phase energy storage unit includes: the i-th c-phase energy storage device (V _ci ) and the i-th c-phase DC circuit breaker (K _DCci ) connected in series; where The energy storage device is a battery, a supercapacitor, a flywheel or a superconducting magnet;

The AC output interface circuit includes a-phase AC output interface circuit, b-phase AC output interface circuit and c-phase AC output interface circuit; a-phase AC output interface circuit includes: a-phase AC circuit breaker (K _ACa ) and its series a-phase work frequency inductor (L _a ); the b-phase AC output interface circuit includes: b-phase AC circuit breaker (K _ACb ) and its b-phase power frequency inductor (L _b ) connected in series; the c-phase AC output interface circuit includes: c-phase AC breaker device (K _ACc ) and its c-phase power frequency inductor (L _c ) connected in series;

The DC output interface circuit includes a first DC output interface circuit, a second DC output interface circuit, a third DC output interface circuit, a fourth DC circuit breaker (K _DC4 ) and a filter capacitor (C _DC ); the first DC output interface The circuit includes: a first DC circuit breaker (K _DC1 ) and its first high-frequency inductor (L ₁ ) in series; the second DC output interface circuit includes: a second DC circuit breaker (K _DC2 ) and its second series inductance A high-frequency inductor (L ₂ ); the third DC output interface circuit includes: a third DC circuit breaker (K _DC3 ) and a third high-frequency inductor (L ₃ ) connected in series;

The entire power conditioning main circuit is connected as follows:

One side of the i-th a-phase full-bridge inverter is connected in parallel with the a-phase filter capacitor (C _ai ) and the i-th a-phase energy storage unit; the other side of the i-th a-phase full-bridge inverter is respectively connected to The i-1th a-phase full-bridge inverter and the i+1th a-phase full-bridge inverter are connected in series to form an a-phase conversion unit, and then respectively connected to the first DC output interface circuit and the a-phase AC output interface The circuits are connected in parallel; one side of the i-th b-phase full-bridge inverter is connected in parallel with the b-phase filter capacitor (C _bi ) and the i-th b-phase energy storage unit respectively; the other side of the i-th b-phase full-bridge inverter The side is connected in series with the i-1th b-phase full-bridge inverter and the i+1th b-phase full-bridge inverter respectively to form a b-phase conversion unit, and then communicates with the second DC output interface circuit and the b-phase respectively The output interface circuits are connected in parallel; one side of the i-th c-phase full-bridge inverter is connected in parallel with the c-phase filter capacitor (C _ci ) and the i-th c-phase energy storage unit respectively; the i-th c-phase full-bridge inverter’s The other side is respectively connected in series with the i-1th c-phase full-bridge inverter and the i+1th c-phase full-bridge inverter to form a c-phase conversion unit, and then respectively connected with the third DC output interface circuit and the c-phase The phase AC output interface circuits are connected in parallel;

The a-phase AC output interface circuit is connected to a-phase of the AC grid; the b-phase AC output interface circuit is connected to b-phase of the AC grid; the c-phase AC output interface circuit is connected to c-phase of the AC grid;

The first DC output interface circuit, the second DC output interface circuit, the third DC output interface circuit and the filter capacitor (C _DC ) are connected in parallel and then connected in series with the fourth DC circuit breaker (K _DC4 ), and then connected to both sides of the DC grid;

The topological structure shown in this implementation can control the energy storage power adjustment device in the DC/AC structure of the energy storage inverter and the DC/DC structure of the energy storage DC converter by adjusting the switch state of the circuit breaker of the AC output interface circuit and the DC output interface circuit. Flexible switching between energy storage inverters and energy storage DC converters is realized in a set of power regulation devices, which makes the operation mode of power regulation devices diversified; at the same time, energy storage units realize distributed operation, which is convenient for energy storage units to realize Balanced control improves the reliability of large-scale energy storage systems; energy storage units and cascaded H-bridge units form independent sub-modules, and the system can be modularized to facilitate expansion of energy storage systems.

As shown in Figure 1, the central controller unit includes a sampling conditioning circuit, a control unit and a PWM modulation unit;

The sampling and conditioning circuit respectively collects the three-phase grid phase voltage (V _sa , V _sb , V _sc ) at the AC output interface circuit and the three-way power frequency inductor current ( _ia , _ib , _ic ), and the three-phase power frequency inductor current at the DC output interface circuit. DC voltage (V _o ) and three high-frequency inductor currents (i _L1 , i _L2 , i _L3 ), DC voltages of six energy storage units (V _a1 , V _a2 , V _b1 , V _b2 , V _c1 , V _c2 ) and transmit the sampling signal to the control unit; the control unit according to the phase a AC circuit breaker (K _ACa ), the b phase AC circuit breaker (K _ACb ), the c phase AC circuit breaker (K _ACc ) and the first DC The switching status of the circuit breaker (K _DC1 ), the second DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) is judged. The working mode of the energy storage power regulating device is storage Energy inverter mode or energy storage DC converter mode, so that according to the received sampling signal, use the energy storage inverter mode strategy or energy storage DC converter mode strategy to obtain the PWM control signal, and transmit it to the PWM modulation unit; PWM The modulation unit controls six cascaded H-bridge units to realize power conversion regulation according to the PWM control signal.

During the working process of the device, the control unit determines whether the working mode of the energy storage power regulating device is the energy storage inverter mode or the energy storage DC converter mode as follows:

When the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are closed, and the first DC circuit breaker (K _DC1 ), the second DC circuit breaker ( K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are disconnected, which means that the energy storage power adjustment device forms an energy storage inverter DC/AC structure, as shown in Figure 2, Therefore, it is judged that the working mode of the energy storage power regulating device is the energy storage inverter mode;

When the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are disconnected, and the first DC circuit breaker (K _DC1 ), the second DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are closed, which means that the energy storage power regulator forms a DC/DC structure of the energy storage DC converter, as shown in Figure 3, Therefore, it is judged that the working mode of the energy storage power regulating device is the energy storage DC converter mode.

In this embodiment, the control method applicable to the AC and DC dual-purpose energy storage power adjustment device is shown in Figure 4 and Figure 5, Figure 4 is a schematic diagram of the control structure of the energy storage inverter working mode of the energy storage power adjustment device, and Figure 5 is Schematic diagram of the working mode control structure of the energy storage DC converter of the energy storage power regulating device, and the overall control method is carried out as follows:

Step 1. Collect phase a AC circuit breaker (K _ACa ), phase b AC circuit breaker (K _ACb ), phase c AC circuit breaker (K _ACc ), and the first DC circuit breaker (K _DC1 ), the second DC circuit breaker (K _DC2 ), the switch states of the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) and judge;

If the AC circuit breaker of phase a (K _ACa ), AC circuit breaker of phase b (K _ACb ) and AC circuit breaker of phase c (K _ACc ) are closed, and the first DC circuit breaker (K _DC1 ), the second DC circuit breaker ( K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are disconnected, which means that the energy storage power regulating device is working in the energy storage inverter mode, and step 2 is performed;

If the phase a AC circuit breaker (K _ACa ), the phase b AC circuit breaker (K _ACb ) and the phase c AC circuit breaker (K _ACc ) are disconnected, and the first DC circuit breaker (K _DC1 ), the second DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are closed, which means that the energy storage power regulating device is working in the energy storage DC converter mode, and step 6 is performed;

Step 2. Collect phase a phase voltage V _sa , phase b phase voltage V _sb , phase c phase voltage V _sc , and phase a inductance current i _a , phase b inductance current i _b , and phase _c inductance current ic of the AC grid; The voltages V _a1 and V _a2 of the two a-phase energy storage units, the voltages V _b1 and V _b2 of the two b-phase energy storage units, and the voltages V _c1 and V _c2 of the two c-phase energy storage units;

Make abc/dq coordinate transformation for phase a phase voltage V _sa , phase b phase voltage V _sb , phase c phase voltage V _sc , phase a inductance current i _a , phase b inductance current i _b , and phase c inductance current i _c , respectively Obtain the grid voltage d-axis component V _sd , q-axis component V _sq and grid current d-axis component i _d , q-axis component i _q ;

Step 3. Commonly used power control strategies for cascaded H-bridge energy storage converters include active and reactive power decoupling control and phase-separation control based on zero-sequence component separation method. Based on the power decoupling strategy, fast and precise control of the output power of the energy storage converter can be realized. Therefore, in this embodiment, the power decoupling control is used as the basic control method of the energy storage inverter.

The power decoupling control method is adopted, the active command P* and the reactive command Q* are given, and the grid voltage vector orientation is adopted to make V _sq always equal to zero, which simplifies the solution process of active and reactive currents. According to formula (1), the given active current command id* and reactive current command iq* are obtained:

Step 4. The difference between the active current command i _d ^* and the d-axis component i _d of the AC grid side current, the difference between the reactive current command i _q ^* and the q-axis component i _q of the AC grid side current, through the active and reactive current After the decoupling control, the dq axis reference components u _d and u _q of the AC output voltage of the cascaded H bridge unit are obtained; the dq axis reference components u _d and u _q are transformed by inverse coordinates to obtain the modulation wave signal U _abc ^* of the PWM signal generation link ;

Step 5. Currently, the PWM modulation methods of cascaded H-bridge multilevel converters include ladder pulse width modulation, pulse ladder modulation, multi-carrier SPWM modulation, carrier phase shift CPS-SPWM modulation, space vector SVPWM modulation, and time-staggered sampling SVPWM modulation, etc. A variety of technologies, among which the carrier phase shift CPS-SPWM modulation has superior performance, simple control, and is suitable for modular control structures. Therefore, this embodiment uses the carrier phase shift CPS-SPWM modulation method as the pulse formation method of the energy storage inverter.

Using the carrier phase shift CPS-SPWM modulation method, the modulation wave signal u _abc of the PWM signal generation link is calculated according to formula (2):

The obtained modulated wave signal u _abc is used as the sinusoidal modulated wave of n a-phase full-bridge inverters, and the sinusoidal modulated wave of the n a-phase full-bridge inverters is used as the modulated wave signal of the left bridge arm, and the obtained The sinusoidal modulation wave of n a-phase full-bridge inverters is phase-shifted by 180° as the modulation wave signal of the right bridge arm;

The resulting modulated wave signal u _abc is lagged by 120° as the sinusoidal modulated wave of n b-phase full-bridge inverters, and the sinusoidal modulated wave of the n b-phase full-bridge inverters is used as the modulated wave signal of the left bridge arm , shifting the sinusoidal modulation waves of the n b-phase full-bridge inverters by 180° as the modulation wave signal of the right bridge arm;

Advance the obtained modulated wave signal u _abc by 120° as the sinusoidal modulated wave of n c-phase full-bridge inverters, and use the sinusoidal modulated wave of the n c-phase full-bridge inverters as the modulated wave signal of the left bridge arm , shifting the sinusoidal modulation waves of the n c-phase full-bridge inverters by 180° as the modulation wave signal of the right bridge arm;

The original triangular carrier signal of a full-bridge inverter is given, and the original triangular carrier signal is sequentially shifted by π/2 carrier cycles, so as to obtain the triangular carrier signals of two full-bridge inverters, and respectively serve as two a The triangular carrier signal of the phase full-bridge inverter, the triangular carrier signal of the 2 b-phase full-bridge inverters and the triangular carrier signal of the 2 c-phase full-bridge inverters;

Comparing the sinusoidal modulation waves of the two a-phase full-bridge inverters with the triangular carrier signals of the two a-phase full-bridge inverters, the PWM driving signals of the two a-phase full-bridge inverters are obtained;

Comparing the sinusoidal modulation waves of the two b-phase full-bridge inverters with the triangular carrier signals of the two b-phase full-bridge inverters, the PWM driving signals of the two b-phase full-bridge inverters are obtained;

Comparing the sinusoidal modulation waves of the two c-phase full-bridge inverters with the triangular carrier signals of the two c-phase full-bridge inverters, the PWM driving signals of the two c-phase full-bridge inverters are obtained;

According to the PWM driving signals of 2 a-phase full-bridge inverters, the PWM driving signals of 2 b-phase full-bridge inverters and the PWM driving signals of 2 c-phase full-bridge inverters, the power of the energy storage inverter is controlled bidirectionally controlled flow;

Step 6. Collect the DC grid voltage V _o and the first high-frequency inductor current i _L1 , the second high-frequency inductor current i _L2 , and the third high-frequency inductor current i _L3 ; collect the voltages V _a1 , V _a2 , the voltages V _b1 and V _b2 of the two b-phase energy storage units, and the voltages V _c1 and V _c2 of the two c-phase energy storage units;

Step 7. Control the upper tube of the right bridge arm of the full-bridge inverter in the six cascaded H-bridge units to always turn off and the lower tube to always be turned on, so that the output of the two cascaded H-bridge units in each phase can be connected in series to the DC power grid ;

Step 8. Using the strategy of controlling the charge and discharge power of the energy storage system, given the power command P _ref of the energy storage system, and according to the DC bus voltage V _o obtained by sampling, calculate the reference value I _ref of the charge and discharge current of the energy storage system through formula (3) :

Step 9. Comparing the charge and discharge current reference value I _ref of the energy storage system with the first high-frequency inductor current i _L1 , the second high-frequency inductor current i _L2 , and the third high-frequency inductor current i _L3 , the obtained difference The values are obtained through the PI link to obtain the modulated wave signals of the three channels;

Given an original triangular carrier wave, the original triangular carrier wave is sequentially shifted by 2π/3 phases using a three-phase interleaved parallel control method to obtain triangular carrier waves of 3 channels. Compared with the three-phase synchronous parallel control mode, the three-phase interleaved parallel control mode can reduce the total output current ripple and increase the ripple frequency, thereby reducing the parameter values of the output filter inductance and capacitance, which is conducive to improving the dynamic response of the circuit ability to improve system efficiency;

Comparing the triangular carrier waves of the 3 channels with the modulation wave signals of the 3 channels respectively, the PWM driving signal of the full-bridge inverter is generated, and the PWM driving signal is used to control the power bidirectional controllable flow of the energy storage DC converter, which can be used for smooth and reliable Where the output power of renewable energy fluctuates.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be covered. Within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (3)

1. An AC-DC dual-purpose energy storage power adjustment device, which is applied in an AC-DC hybrid microgrid, is characterized in that the energy storage power adjustment device includes: a power adjustment main circuit and a central controller unit; The power regulation main circuit includes 3n cascaded H-bridge units, 3n energy storage units, an AC output interface circuit and a DC output interface circuit; n≥1; 1≤i≤n; The 3n cascaded H-bridge units include n a-phase cascaded H-bridge units (H _a1 ~H _an ), n b-phase cascaded H-bridge units (H _b1 ~H _bn ) and n c-phase cascaded H bridge unit (H _c1 ~ H _cn ); The i-th a-phase cascaded H-bridge unit includes the i-th a-phase full-bridge inverter and the i-th a-phase filter capacitor (C _ai ); The i-th b-phase cascaded H-bridge unit includes the i-th b-phase full-bridge inverter and the i-th b-phase filter capacitor (C _bi ); The i-th c-phase cascaded H-bridge unit includes the i-th c-phase full-bridge inverter and the i-th c-phase filter capacitor (C _ci ); The 3n energy storage units include n a-phase energy storage units, n b-phase energy storage units and n c-phase energy storage units; The i-th phase-a energy storage unit includes: the i-th phase-a energy storage device (V _ai ) and the i-th phase-a DC circuit breaker (K _DCai ) connected in series; The i-th phase-b energy storage unit includes: the i-th phase-b energy storage device (V _bi ) and the i-th phase-b DC circuit breaker (K _DCbi ) connected in series; The i-th phase-c energy storage unit includes: the i-th phase-c energy storage device (V _ci ) and the i-th phase-c DC circuit breaker (K _DCci ) connected in series; The AC output interface circuit includes a-phase AC output interface circuit, b-phase AC output interface circuit and c-phase AC output interface circuit; The a-phase AC output interface circuit includes: a-phase AC circuit breaker (K _ACa ) and its a-phase power frequency inductor (L _a ) connected in series; The b-phase AC output interface circuit includes: a b-phase AC circuit breaker (K _ACb ) and a b-phase power frequency inductor (L _b ) connected in series; The c-phase AC output interface circuit includes: a c-phase AC circuit breaker (K _ACc ) and a c-phase power frequency inductor (L _c ) connected in series; The DC output interface circuit includes a first DC output interface circuit, a second DC output interface circuit, a third DC output interface circuit, a fourth DC circuit breaker (K _DC4 ) and a filter capacitor (C _DC ); The first DC output interface circuit includes: a first DC circuit breaker (K _DC1 ) and its first high-frequency inductor (L ₁ ) connected in series; The second DC output interface circuit includes: a second DC circuit breaker (K _DC2 ) and a second high-frequency inductor (L ₂ ) connected in series; The third DC output interface circuit includes: a third DC circuit breaker (K _DC3 ) and a third high-frequency inductor (L ₃ ) connected in series; One side of the i-th a-phase full-bridge inverter is respectively connected in parallel with the a-phase filter capacitor (C _ai ) and the i-th a-phase energy storage unit; The other side of the i-th a-phase full-bridge inverter is respectively connected in series with the i-1th a-phase full-bridge inverter and the i+1th a-phase full-bridge inverter to form an a-phase conversion unit Afterwards, they are respectively connected in parallel with the first DC output interface circuit and the a-phase AC output interface circuit; One side of the i-th b-phase full-bridge inverter is respectively connected in parallel with the b-phase filter capacitor (C _bi ) and the i-th b-phase energy storage unit; The other side of the i-th b-phase full-bridge inverter is respectively connected in series with the i-1th b-phase full-bridge inverter and the i+1th b-phase full-bridge inverter to form a b-phase conversion unit After that, they are respectively connected in parallel with the second DC output interface circuit and the b-phase AC output interface circuit; One side of the i-th c-phase full-bridge inverter is respectively connected in parallel with the c-phase filter capacitor (C _ci ) and the i-th c-phase energy storage unit; The other side of the i-th c-phase full-bridge inverter is respectively connected in series with the i-1th c-phase full-bridge inverter and the i+1th c-phase full-bridge inverter to form a c-phase conversion unit Afterwards, they are respectively connected in parallel with the third DC output interface circuit and the c-phase AC output interface circuit; The a-phase AC output interface circuit is connected to a-phase of the AC grid; The b-phase AC output interface circuit is connected to the b-phase of the AC grid; The c-phase AC output interface circuit is connected to the c-phase of the AC grid; The first DC output interface circuit, the second DC output interface circuit, the third DC output interface circuit and the filter capacitor are connected in parallel to the fourth DC circuit breaker (K _DC4 ) in series, and then connected to into both sides of the DC grid; The central controller unit includes a sampling conditioning circuit, a control unit and a PWM modulation unit; The sampling conditioning circuit respectively collects the phase voltage of the three-phase power grid at the AC output interface circuit, the three-way power frequency inductor current, the DC voltage at the DC output interface circuit, the three-way high-frequency inductor current, and the DC voltage of 3n energy storage units. The sampling signal formed by the voltage is transmitted to the control unit; The control unit is based on the a-phase AC circuit breaker (K _ACa ), the b-phase AC circuit breaker (K _ACb ), the c-phase AC circuit breaker (K _ACc ) and the first DC circuit breaker ( K _DC1 ), the second DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) switch states to judge that the working mode of the energy storage power regulating device is energy storage Inverter mode or energy storage DC converter mode, so that according to the received sampling signal, the PWM control signal is obtained by using the energy storage inverter mode strategy or the energy storage DC converter mode strategy, and transmitted to the PWM modulation unit; The PWM modulation unit controls the 3n cascaded H-bridge units according to the PWM control signal to realize power conversion regulation; The control unit judges whether the working mode of the energy storage power regulating device is the energy storage inverter mode or the energy storage DC converter mode in the following manner: When the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are closed, and the first DC circuit breaker (K _DC1 ), the second If the DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are disconnected, it means that the energy storage power regulating device forms an energy storage inverter DC/AC structure, Therefore, it is judged that the working mode of the energy storage power regulating device is the energy storage inverter mode; When the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are disconnected, and the first DC circuit breaker (K _DC1 ), the first When the second DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are closed, it means that the energy storage power regulating device forms an energy storage DC converter DC/DC structure, Therefore, it is judged that the working mode of the energy storage power regulating device is the energy storage DC converter mode. 2. The AC and DC energy storage power regulating device according to claim 1, wherein the energy storage device is a storage battery, a supercapacitor, a flywheel or a superconducting magnet. 3. A control method for the AC/DC dual-purpose energy storage power regulating device according to claim 1 or 2, characterized in that the following steps are performed: Step 1. Collect phase a AC circuit breaker (K _ACa ), phase b AC circuit breaker (K _ACb ), phase c AC circuit breaker (K _ACc ), and the first DC circuit breaker (K _DC1 ), the second DC circuit breaker (K _DC2 ), the switch states of the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) and judge; If the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are closed, and the first DC circuit breaker (K _DC1 ), the second If the DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are disconnected, it means that the energy storage power regulating device is working in the energy storage inverter mode, and executes Step 2; If the a-phase AC circuit breaker (K _ACa ), b-phase AC circuit breaker (K _ACb ) and c-phase AC circuit breaker (K _ACc ) are disconnected, and the first DC circuit breaker (K _DC1 ), the first When the second DC circuit breaker (K _DC2 ), the third DC circuit breaker (K _DC3 ) and the fourth DC circuit breaker (K _DC4 ) are closed, it means that the energy storage power regulating device is working in the energy storage DC converter mode, and step 6 is performed ; Step 2. Collect phase a phase voltage V _sa , phase b phase voltage V _sb , phase c phase voltage V _sc , and phase a inductance current i _a , phase b inductance current i _b , and phase _c inductance current ic of the AC grid; Voltages V _a1 -V _an of n a-phase energy storage units, voltages V _b1 -V _bn of n b-phase energy storage units, and voltages V _c1 -V _cn of n c-phase energy storage units; Make abc/dq coordinate transformation for phase a phase voltage V _sa , phase b phase voltage V _sb , phase c phase voltage V _sc , phase a inductance current i _a , phase b inductance current i _b , and phase c inductance current i _c , respectively Obtain the grid voltage d-axis component V _sd , q-axis component V _sq and grid current d-axis component i _d , q-axis component i _q ; Step 3. Using the power decoupling control method, given the active command P ^* and the reactive command Q ^* , calculate the given active current command i _d ^* and reactive current command i _q ^* according to formula (1): <mrow><mfenced open = "{" close = ""><mtable><mtr><mtd><mrow><msubsup><mi>i</mi><mi>d</mi><mo>*</mo></msubsup><mo>=</mo><msup><mi>P</mi><mo>*</mo></msup><mo>/</mo><msub><mi>V</mi><mrow><mi>s</mi><mi>d</mi></mrow></msub></mrow></mtd></mtr><mtr><mtd><mrow><msubsup><mi>i</mi><mi>q</mi><mo>*</mo></msubsup><mo>=</mo><msup><mi>Q</mi><mo>*</mo></msup><mo>/</mo><msub><mi>V</mi><mrow><mi>s</mi><mi>d</mi></mrow></msub></mrow></mtd></mtr></mtable></mfenced><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow></mrow> Step 4. The difference between the active current command i _d ^* and the d-axis component i _d of the AC grid side current, the difference between the reactive current command i _q ^* and the q-axis component i _q of the AC grid side current, through the active and reactive current After decoupling control, the dq axis reference components u _d and u _q of the AC output voltage of the cascaded H-bridge unit are obtained; the dq axis reference components u _d and u _q are transformed by inverse coordinates to obtain the original voltage of the modulated wave in the PWM signal generation link _{signal_abc} ^* ; Step 5. Utilize the carrier phase shift CPS-SPWM modulation method to calculate the modulated wave signal u _abc of the PWM signal generation link according to formula (2): <mrow><msub><mi>u</mi><mrow><mi>a</mi><mi>b</mi><mi>c</mi></mrow></msub><mfrac><mrow><mn>3</mn><msubsup><mi>U</mi><mrow><mi>a</mi><mi>b</mi><mi>c</mi></mrow><mo>*</mo></msubsup></mrow><mrow><msub><mi>V</mi><mrow><mi>a</mi><mn>1</mn></mrow></msub><mo>+</mo><mo>...</mo><mo>+</mo><msub><mi>V</mi><mrow><mi>a</mi><mi>n</mi></mrow></msub><mo>+</mo><msub><mi>V</mi><mrow><mi>b</mi><mn>1</mn></mrow></msub><mo>+</mo><mo>...</mo><mo>+</mo><msub><mi>V</mi><mrow><mi>b</mi><mi>n</mi></mrow></msub><mo>+</mo><msub><mi>V</mi><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo>+</mo><mo>...</mo><mo>+</mo><msub><mi>V</mi><mrow><mi>c</mi><mi>n</mi></mrow></msub></mrow></mfrac><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mrow> The obtained modulated wave signal u _abc is used as the sinusoidal modulated wave of n a-phase full-bridge inverters, and the sinusoidal modulated wave of the n a-phase full-bridge inverters is used as the modulated wave signal of the left bridge arm, and the obtained The sinusoidal modulation wave of n a-phase full-bridge inverters is phase-shifted by 180° as the modulation wave signal of the right bridge arm; The resulting modulated wave signal u _abc is lagged by 120° as the sinusoidal modulated wave of n b-phase full-bridge inverters, and the sinusoidal modulated wave of the n b-phase full-bridge inverters is used as the modulated wave signal of the left bridge arm , shifting the sinusoidal modulation waves of the n b-phase full-bridge inverters by 180° as the modulation wave signal of the right bridge arm; Advance the obtained modulated wave signal u _abc by 120° as the sinusoidal modulated wave of n c-phase full-bridge inverters, and use the sinusoidal modulated wave of the n c-phase full-bridge inverters as the modulated wave signal of the left bridge arm , shifting the sinusoidal modulation waves of the n c-phase full-bridge inverters by 180° as the modulation wave signal of the right bridge arm; The original triangular carrier signal of a full-bridge inverter is given, and the original triangular carrier signal is sequentially phase-shifted by π/n carrier cycles, so as to obtain n triangular carrier signals of full-bridge inverters, and respectively serve as n A triangular carrier signal of a-phase full-bridge inverters, a triangular carrier signal of n b-phase full-bridge inverters, and a triangular carrier signal of n c-phase full-bridge inverters; Comparing the sinusoidal modulation waves of the n a-phase full-bridge inverters with the triangular carrier signals of the n a-phase full-bridge inverters to obtain the n a-phase full-bridge inverter PWM drive signals; Comparing the sinusoidal modulation waves of the n b-phase full-bridge inverters with the triangular carrier signals of the n b-phase full-bridge inverters, obtaining n PWM drive signals of the b-phase full-bridge inverters; Comparing the sinusoidal modulation waves of the n c-phase full-bridge inverters with the triangular carrier signals of the n c-phase full-bridge inverters to obtain the n c-phase full-bridge inverter PWM drive signals; Control the energy storage inverter according to the PWM driving signals of the n a-phase full-bridge inverters, the PWM driving signals of the n b-phase full-bridge inverters and the n c-phase full-bridge inverters. Two-way controllable flow of power; Step 6. Collect the DC grid voltage V _o , the first high-frequency inductor current i _L1 , the second high-frequency inductor current i _L2 , and the third high-frequency inductor current i _L3 ; collect the voltages V _a1 ~ of n a-phase energy storage units V _an , voltages V _b1 -V _bn of n phase-b energy storage units, and voltages V _c1 -V _cn of n phase-c energy storage units; Step 7. Control the upper tube of the right bridge arm of the full-bridge inverter in the 3n cascaded H-bridge units to always turn off and the lower tube to always be turned on, so that the output of n cascaded H-bridge units in each phase can be connected in series to the DC power grid ; Step 8. Using the method of controlling the charging and discharging power of the energy storage system, given the power command P _ref of the energy storage system, according to the DC bus voltage V _o obtained by sampling, calculate the reference value I _ref of the charging and discharging current of the energy storage system through formula (3) : <mrow><msub><mi>I</mi><mrow><mi>r</mi><mi>e</mi><mi>f</mi></mrow></msub><mo>=</mo><mfrac><msub><mi>P</mi><mrow><mi>r</mi><mi>e</mi><mi>f</mi></mrow></msub><mrow><mn>3</mn><msub><mi>V</mi><mn>0</mn></msub></mrow></mfrac><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>3</mn><mo>)</mo></mrow></mrow> Step 9. Comparing the charge and discharge current reference value I _ref of the energy storage system with the first high-frequency inductor current i _L1 , the second high-frequency inductor current i _L2 , and the third high-frequency inductor current i _L3 , the obtained difference The values are obtained through the PI link to obtain the modulated wave signals of the three channels; Given an original triangular carrier wave, the original triangular carrier wave is sequentially phase-shifted by 2π/3 phases using a three-phase interleaved parallel control method, thereby obtaining triangular carrier waves of 3 channels; The modulated wave signals are compared to generate a PWM driving signal for the full-bridge inverter, and the PWM driving signal is used to control the bidirectional controllable power flow of the energy storage DC converter.