High-voltage direct-mounted system integrating reactive power compensation and energy storage

Abstract

The present invention provides a high-voltage direct-mounting system integrating reactive power compensation and energy storage, comprising: a module M1: calculating the amplitude and relative phase of a zero-sequence voltage based on parameter information of a cascaded H-bridge converter and a grid-side current; a module M2: calculating a given value of the output voltage of each phase of the cascaded H-bridge converter based on the given reactive power of the high-voltage direct-mounting energy storage system, and then calculating the modulation voltage of the output voltage of each phase of the cascaded H-bridge converter according to the battery charge state and capacitor voltage of each power module of each phase, and according to the modulation voltage of the output voltage of each phase of the cascaded H-bridge converter, calculating the number of sub-modules required to be put into operation under the nearest level modulation, and then sorting the battery charge state of each power module, and determining the driving signal of each power module according to the current direction of each phase and the number of power modules required to be put into operation under the nearest level modulation.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical automation equipment, and in particular, to a high-voltage direct-hung system integrating reactive power compensation and energy storage, and more particularly, to a reactive power compensation control system of a high-voltage direct-hung energy storage system based on optimal zero-sequence voltage injection and a reactive power compensation control system of a high-voltage direct-hung energy storage system based on intra-phase active power conversion. Background Art

[0002] The development of large-capacity battery energy storage technology is conducive to increasing the installed capacity of wind and solar power sources and promoting the transformation of energy structure, thereby helping to achieve the goals of carbon peak and carbon neutrality. Compared with traditional energy storage systems, high-voltage direct-mounted BESS achieves large-capacity single-machine while meeting the requirements of high efficiency, high reliability, economy and safety. When forming a large-scale energy storage power station, the number of parallel units required is small, the power station structure and control strategy are simple, the response speed is fast, it can meet the needs of 100 MW-level energy storage systems, and it is not easy to cause system stability problems.

[0003] According to the export power requirements of the wind farm, 30% of SVG needs to be configured at the wind farm export to provide reactive power compensation for the grid, and 15%-20% of energy storage facilities need to be configured. If the static energy storage equipment can not only provide the grid active power smoothing function during peak and frequency regulation, but also provide reactive power compensation capability of rated capacity, it will greatly reduce the demand and investment cost of SVG and have better economic benefits. However, when the high-voltage direct-mounted battery energy storage system outputs pure reactive power, if the traditional control method is used, there will be a double frequency current that quickly charges and discharges the battery cycle, affecting the battery life.

[0004] In the prior art, the following methods for solving the problem of reactive power compensation device and control based on cascaded H-bridge converter have been proposed:

[0005] Patent document CN103840474A (application number: 201410075640.9) discloses a main circuit topology structure of a medium- and high-voltage direct-mounted static synchronous VAR compensator, which can realize functions such as reactive voltage support, harmonic pollution control, and power oscillation damping, and can be directly mounted on a medium- and high-voltage AC power grid. It has the characteristics of good output waveform quality, low switching action frequency, relatively small number of required switching devices, high DC voltage utilization rate, and ability to suppress DC side fault current, etc. It can reduce the number of AC side filters, reduce the initial investment cost and control complexity of the compensator, improve the energy conversion efficiency of the reactive compensator, improve the fault survivability of the reactive compensator, improve the unit utilization rate of the reactive compensator, and expand the application occasions and functions of the reactive compensator. However, the synchronous VAR compensator cannot provide and absorb active power for the system, and cannot realize peak load and frequency regulation of the power grid.

[0006] Patent document CN110350564A (application number: 201910697341.1) discloses a high-voltage direct-mounted energy storage device and a power control method, which has the ability to adjust active and reactive power in four quadrants, realize independent control of active and reactive power, and adjust the voltage and frequency of the system at the same time. However, this method requires adding a DC / DC converter to each submodule, which increases the complexity of the system and control, increases the system cost and reduces the reliability of the system.

[0007] Patent document CN110350564B (application number: 201910697341.1) discloses a high-voltage direct-mounted energy storage device, including: an A-phase H-bridge power module, a B-phase H-bridge power module, and a C-phase H-bridge power module connected to the A-phase, B-phase, and C-phase lines, respectively, including two or more cascaded H-bridge power modules, and the A-phase, B-phase, and C-phase lines are star-connected; a DC side capacitor, and a DC side capacitor is connected in parallel to the DC side of each H-bridge power module; a battery and a supercapacitor, respectively as an energy-type energy storage element and a power-type energy storage element; and an isolated three-port active bridge converter, one side of which is connected to one side of the capacitor, and the other side is connected to the battery and the supercapacitor at the same time. The present disclosure also provides a power control method for a high-voltage direct-mounted energy storage device. Summary of the invention

[0008] In view of the defects in the prior art, the object of the present invention is to provide a high-voltage direct-hanging system integrating reactive power compensation and energy storage.

[0009] A high-voltage direct-mounted system integrating reactive power compensation and energy storage is provided according to the present invention, comprising:

[0010] Module M1: Calculate the amplitude and relative phase of the zero-sequence voltage based on the parameter information of the cascaded H-bridge converter and the grid-side current;

[0011] Module M2: Calculate the given value of the output voltage of each phase of the cascaded H-bridge converter based on the reactive power given by the high-voltage direct-mounted energy storage system, and then calculate the modulation voltage of the output voltage of each phase of the cascaded H-bridge converter according to the battery state of charge, the amplitude and relative phase of the zero-sequence voltage of each phase;

[0012] Module M3: Based on the battery charge state and capacitor voltage of each power module in each phase, according to the modulation voltage of each phase output voltage of the cascaded H-bridge converter, the number of power modules required for the nearest level modulation is calculated, and then the battery charge state of each power module is sorted. The drive signal of each power module is determined according to the current direction of each phase and the number of power modules required for the nearest level modulation.

[0013] Preferably, in the module M1:

[0014] Module M1.1: Calculate the battery current ripple rate γ;

[0015]

[0016] Where, ω2=4πf AC represents the angular velocity of the double frequency component; f AC Indicates the frequency of the grid voltage; R indicates the sum of the resistances of the battery and the DC side filter inductor; L indicates the inductance of the DC side filter inductor; C indicates the capacitance of the bus capacitor;

[0017] Module M1.2: Calculate the critical value ρ of the ratio of phase reactive power to active power;

[0018]

[0019] Module M1.3: Calculate the relative phase θ of the zero-sequence voltage;

[0020]

[0021] Module M1.4: Calculate the amplitude V0 of the zero-sequence voltage;

[0022]

[0023] Where ω=2πf AC Indicates the angular velocity of the grid voltage fundamental frequency; V s Indicates the phase voltage amplitude of the grid voltage; I s Indicates the amplitude of the grid current; L ac Indicates the inductance value of the AC side filter inductor.

[0024] Preferably, in the module M2:

[0025] Module M2.1: Obtain the current given value of the dq rotating coordinate system according to the reactive power required by the high-voltage direct-mounted energy storage system and

[0026] Module M2.2: Three-phase output current i of cascaded H-bridge converter A 、i b 、i c The actual current value i in the dq rotating coordinate system is obtained by abc / dq vector transformation and the phase-locking angle theta d and i q ;

[0027] Module M2.3: d-axis current given value The actual value of the d-axis current i d The difference is negative after passing through the PI controller and then cross-decoupled with the d-axis component ωL AC iq Add them together and add them to the actual value of the d-axis voltage u d The sum is used to obtain the d-axis voltage given value Q-axis current set value The actual value of the q-axis current i q The difference is negative after passing through the PI controller and then cross-decoupled with the q-axis component 2ωf AC L AC i d Subtract, and then add to the actual value of the q-axis voltage u q The sum is used to obtain the q-axis voltage given value

[0028] Module M2.4: voltage setpoint The three-phase output voltage given value of the cascaded H-bridge converter is obtained by dq / abc vector transformation and phase-locking angle theta

[0029] Module M2.5: If the high-voltage direct-mounted energy storage system generates pure inductive reactive power, the relative phase θ of the zero-sequence voltage is negative and then subtracted from the phase of the j-th phase current to obtain the phase θ of the zero-sequence voltage. q :

[0030] θ0=-θ-φ ij (5)

[0031] Among them, φ ij represents the phase of the j-th phase current; the subscript i represents the current;

[0032] If the direct-mounted energy storage system generates pure capacitive reactive power, the relative phase θ of the zero-sequence voltage is subtracted from the phase of the j-th phase current to obtain the phase θ0 of the zero-sequence voltage:

[0033] θ0=θ-φ ij (6)

[0034] Module M2.6: Calculate the battery state of charge SOC of phase j j Battery state of charge SOC of direct-mounted energy storage system sys The difference ΔSOC j ;

[0035] ΔSOC j =SOC j -SOC sys (7)

[0036] If ΔSOC j If the set lower limit is reached, the jth phase is changed to the phase with the highest battery state of charge, and step S2.5 is triggered repeatedly to recalculate the phase θ0 of the zero-sequence voltage; if the set lower limit has not been reached, the original zero-sequence voltage phase is maintained;

[0037] Module M2.7: Calculate the instantaneous value of zero-sequence voltage;

[0038]

[0039] Module M2.8: Calculate the three-phase output voltage modulation voltage v of the cascaded H-bridge converter a 、v b 、v c ;

[0040]

[0041] Preferably, in the module M3:

[0042] Module M3.1: Sampling the battery state of charge and capacitor voltage of each functional module in each phase, sorting the battery state of charge of each power module in each phase, and calculating the average value of the capacitor voltage of the total power module in each phase;

[0043] Module M3.2: Modulating the voltage v using the three-phase output voltage of the cascaded H-bridge converter a 、v b 、v c Divide by the average value of the total power module capacitor voltage in each phase to calculate the number of power modules N required for the three phases of the cascaded H-bridge converter a 、N b 、N c ;

[0044]

[0045] Among them, round() represents the nearest integer function; V a 、V b 、V c It represents the average value of the capacitor voltage of the three-phase total power module A, B, and C;

[0046] Module M3.3: The output current to the grid side is the phase current i x , x=a, b, c positive direction, when the phase current i x When the direction is positive, the number of power modules N required for the three phases is x It is also positive, and N is input from high to low according to the battery charge state. x Power modules, N x The power modules output positive level, and the other power modules output zero level;

[0047] When the phase current i x When the direction is positive, the number of power modules N required for the three phases is x When it is negative, the battery charge state is from low to high. x| power modules, put into use | N x | power modules output negative level, and other power modules output zero level;

[0048] When the phase current i x When the direction is negative, the number of power modules N required for the three phases x When it is negative, the battery charge state is input from high to low |N x | power modules, put into use | N x | power modules output negative level, and other power modules output zero level;

[0049] When the phase current i x When the direction is negative, the number of power modules N required for the three phases x When the battery is positive, N is input from low to high according to the battery charge state. x Power modules, N x The power modules output positive level, and the other power modules output zero level.

[0050] Preferably, it includes:

[0051] Module M4: Calculate the amplitude of the maximum zero-sequence voltage under the parameter constraints of the high-voltage direct-mounted energy storage system;

[0052] Module M5: Calculate the phase angle of the zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power;

[0053] Module M6: The amplitude of the maximum zero-sequence voltage under the parameter constraints of the high-voltage direct-mounted energy storage system and the phase angle of the zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power are used to obtain the passive parameter design criteria in the power module. The DC side filter inductor and bus capacitor in the power module are set based on the passive parameter design criteria in the power module.

[0054] Preferably, in the module M4,

[0055] Define the grid-side rated voltage as V s ', assuming that the rated capacity reactive output inductor voltage drop is σ L V s , the maximum voltage that the converter can output is βV s , zero-sequence voltage V0 lags behind phase b current -i sb The angle is θ', and the amplitude of the maximum zero-sequence voltage V0' is calculated;

[0056]

[0057] Among them, σ L It indicates the ratio of the rated capacity reactive output inductor voltage drop to the grid-side rated voltage; β indicates the ratio of the maximum voltage that the converter can output to the grid-side rated voltage;

[0058] The maximum zero-sequence voltage amplitude is

[0059]

[0060] Preferably, in the module M5,

[0061] Module M5.1: Solve the ratio of three-phase reactive power to active power;

[0062]

[0063] Among them, Q x (x=a,b,c) is the reactive power of phases A, B and C, P x (x=a,b,c) is the active power of phases A, B and C;

[0064] Module M5.2: Solve to obtain the phase angle of zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power;

[0065]

[0066] Preferably, in the module M6,

[0067] Module M6.1: Calculate the DC component of the battery current generated by the three-phase active power at the minimum zero-sequence voltage phase angle and maximum zero-sequence voltage amplitude |I x |For:

[0068]

[0069] Among them, V bat is the battery voltage;

[0070] Module M6.2: Calculate the current AC component generated by the three-phase apparent power under the minimum zero-sequence voltage phase angle and maximum zero-sequence voltage amplitude |i x |For:

[0071]

[0072] Module M6.3: Calculate the components of the AC current flowing into the battery after LC filtering for

[0073]

[0074] Module M6.4: In order to prevent the battery current from charging and discharging back and forth during the power frequency cycle, it is necessary to ensure

[0075]

[0076] in, is the margin factor;

[0077] Module M6.5: Assuming that the battery current ripple rate obtained by the design of the high-voltage direct-mounted energy storage system to emit pure active power is γ, the design parameters need to meet the following requirements:

[0078]

[0079] A high-voltage direct-mounted system integrating reactive power compensation and energy storage is provided according to the present invention, comprising:

[0080] Module S1: Calculate the voltage amplitude and relative phase of the two bridge arms in each phase based on the parameter information of the cascaded H-bridge converter and the grid-side current;

[0081] Module S2: Based on the reactive power given by the high-voltage direct-mounted energy storage system and the battery charge state of the two bridge arms in each phase, the given value of the output voltage of the two bridge arms in each phase of the cascaded H-bridge converter is calculated according to the voltage amplitude and phase of the two bridge arms in each phase;

[0082] Module S3: Based on the battery charge state and capacitor voltage of each power module in each phase, according to the given value of the output voltage of the two bridge arms in each phase of the cascaded H-bridge converter, the number of sub-modules required for the nearest level modulation is calculated, and then the battery charge state of each power module is sorted. The drive signal of each power module is determined according to the current direction of each phase and the number of sub-modules required for the nearest level modulation.

[0083] Preferably, in the module S1,

[0084] Module S1.1: Calculate the battery current ripple rate γ;

[0085]

[0086] Where, ω2=4πf AC represents the angular velocity of the double frequency component; f AC Indicates the frequency of the grid voltage; R indicates the sum of the resistances of the battery and the DC side filter inductor; L indicates the inductance value of the DC side filter inductor, and C indicates the capacitance value of the bus capacitor;

[0087] Module S1.2: Calculate the relative phase θ of the voltages of the two bridge arms in each phase;

[0088] θ=arcsin(γ)(23)

[0089] Module S1.3: Calculate the amplitudes V1 and V2 of the two bridge arms in each phase;

[0090]

[0091] Where ω=2πf AC is the angular velocity of the grid voltage fundamental frequency, V sis the phase voltage amplitude of the grid voltage, I s is the amplitude of the grid current, L AC is the inductance value of the AC side filter inductor;

[0092] In the module S2,

[0093] Module S2.1: Obtain the current given value of the dq rotating coordinate system according to the reactive power required by the high-voltage direct-mounted energy storage system and

[0094] Module S2.2: Three-phase output current i of cascaded H-bridge converter a 、i b 、i c The actual current value i in the dq rotating coordinate system is obtained by abc / dq vector transformation and the phase-locking angle theta d and i q ;

[0095] Module S2.3: d-axis current setpoint The actual value of the d-axis current i d The difference is negative after passing through the PI controller and then cross-decoupled with the d-axis component ωL AC i q Add them together and add them to the actual value of the d-axis voltage u d The sum is used to obtain the d-axis voltage given value Q-axis current set value The actual value of the q-axis current i q The difference is negative after passing through the PI controller and then cross-decoupled with the q-axis component 2πf AC L AC i d Subtract, and then add to the actual value of the q-axis voltage u q The sum is used to obtain the q-axis voltage given value

[0096] Module S2.4: Voltage setpoint The three-phase output voltage given value of the cascaded H-bridge converter is obtained by dq / abc vector transformation and phase-locking angle theta

[0097] Module S2.5: If the high-voltage direct-mounted energy storage system generates pure inductive reactive power, the first phase θ of the jth phase is obtained j1 , the second phase θ j2 :

[0098]

[0099] Among them, φ ijis the phase of the jth phase current, j = A, B, C; θ represents the relative phase of the voltages of the two bridge arms;

[0100] If the high-voltage direct-mounted energy storage system generates pure capacitive reactive power, the first phase θ of the jth phase is obtained. j1 , the second phase θ j2 :

[0101]

[0102] Module S2.6: Calculate the battery state of charge SOC of the first bridge arm of phase j j1 and the battery state of charge SOC of the second bridge arm j2 The battery state of charge SOC of the jth phase j The difference between

[0103] ΔSOC j1 =SOC j1 -SOC j ,ΔSOC j2 =SOC j2 -SOC j

[0104] When the state is the voltage phase of the first bridge arm of the jth phase Equal to the first phase θ of the jth phase j1 , the voltage phase of the second bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 , if ΔSOC j1 When the set lower limit is reached, the state changes to the voltage phase of the first bridge arm of the jth phase. Equal to the second phase θ of the jth phase j2 , the voltage phase of the second bridge arm of the jth phase is equal to the first phase θ of the jth phase j1 ;

[0105] When the state is the voltage phase of the first bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 , the voltage phase of the second bridge arm of the jth phase Equal to the first phase θ of the jth phase j1 , if ΔSOC j2 When the set lower limit is reached, the state changes to the voltage phase of the first bridge arm of the jth phase. Equal to the first phase θ of the jth phase j1 , the voltage phase of the second bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 .

[0106] Module S2.7: Calculate the given value of the voltage of the first bridge arm of phase j and the given value of the voltage of the second bridge arm of the jth phase

[0107]

[0108] In the module S3,

[0109] Module S3.1: Sampling to obtain the battery state of charge and capacitor voltage of each power module in each phase, sorting the battery state of charge of each power module in the first bridge arm and the second bridge arm in each phase, and calculating the average value of the capacitor voltage of the power module in the first bridge arm and the second bridge arm in each phase;

[0110] Module S3.2: Use the given value of the voltage of the first bridge arm of the jth phase of the cascaded H-bridge converter and the given value of the voltage of the second bridge arm of the jth phase Divide by the average value of the power module capacitor voltage in the first bridge arm and the second bridge arm in each phase, and calculate the number of power modules required in the first bridge arm and the second bridge arm in the three-phase cascaded H-bridge converter

[0111]

[0112] Among them, round() is the nearest integer function. is the average value of the capacitor voltage of the first bridge arm power module of phases A, B, and C, It is the average value of the capacitor voltage of the second bridge arm power module of the three phases A, B, and C.

[0113] Module S3.3: The output current to the grid side is the phase current i x , x=a, b, c positive direction, when the phase current i x When the direction is positive, the number of power modules required in the first bridge arm and the second bridge arm of the three-phase When the battery is positive, the bridge arm is put into operation from high to low according to the battery charge state. Power modules, put into The power modules output positive level, and the other power modules output zero level;

[0114] When the phase current i x When the direction is positive, the number of power modules required in the first bridge arm and the second bridge arm of the three-phase When it is negative, the bridge arm is put into operation from low to high according to the battery charge state. Power modules, put into The power modules output negative level, and the other power modules output zero level;

[0115] When the phase current i x When the direction is negative, the number of power modules required for the first bridge arm and the second bridge arm of the three-phase When it is negative, the bridge arm is put into operation from high to low according to the battery charge state. Power modules, put into The power modules output negative level, and the other power modules output zero level;

[0116] When the phase current i x When the direction is negative, the number of power modules required for the first bridge arm and the second bridge arm of the three-phase When the battery is positive, the bridge arm is put into operation from low to high according to the battery charge state. Power modules, put into The power modules output positive level, and the other power modules output zero level.

[0117] Compared with the prior art, the present invention has the following beneficial effects:

[0118] 1. When the chain battery energy storage system emits pure reactive power, the traditional control method will cause the battery to cyclically charge and discharge within the power frequency cycle time scale, and the rapid back and forth charging and discharging will cause the battery life to decay rapidly. The reactive power compensation control method of the high-voltage direct-mounted energy storage system based on the optimal zero-sequence voltage injection provided by the present invention can realize the four-quadrant operation of the chain battery energy storage system. When the system emits and absorbs pure reactive power, the battery current does not undergo the frequency doubling cycle charging and discharging, which is beneficial to the stable operation and life of the battery;

[0119] 2. The method for designing reactive compensation parameters of a high-voltage direct-mounted energy storage system based on optimal zero-sequence voltage injection provided by the present invention can guide the design of a battery DC side filter for a chain battery energy storage system considering four-quadrant operation;

[0120] 3. The reactive power compensation control of the high-voltage direct-mounted energy storage system based on intra-phase active power conversion provided by the present invention, compared with the traditional chain battery energy storage system, can realize the four-quadrant operation of the chain battery energy storage system through this control method. When the system emits and absorbs pure reactive power, the battery current does not undergo frequency doubling cycle charge and discharge, which is beneficial to the stable operation and life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0121] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0122] Figure 1 This is a structural diagram of a high-voltage direct-mounted battery energy storage system in a preferred embodiment of the present invention.

[0123] Figure 2 This is a reactive compensation control block diagram of a high-voltage direct-mounted energy storage system based on optimal zero-sequence voltage injection in a preferred embodiment of the present invention.

[0124] Figure 3 The present invention is a flowchart of reactive compensation parameter design for a high-voltage direct-mounted energy storage system based on optimal zero-sequence voltage injection in a preferred embodiment of the present invention.

[0125] Figure 4 The present invention is a reactive power compensation control block diagram of a high-voltage direct-mounted energy storage system based on intra-phase active power conversion in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0126] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0127] In view of the defects in the prior art, the purpose of the present invention is to propose a reactive power compensation control method and parameter design method for a high-voltage direct-mounted energy storage system based on optimal zero-sequence voltage injection, which can realize the active and reactive power control of a high-voltage direct-mounted BESS based on an existing cascaded H-bridge converter, and provide a grid active power smoothing function during peak and frequency regulation through innovation of the control method without increasing the cost, while providing reactive power compensation capability of the rated capacity.

[0128] Example 1

[0129] A high-voltage direct-hung system integrating reactive power compensation and energy storage provided by the present invention comprises: a reactive power compensation control system of a high-voltage direct-hung energy storage system based on optimal zero-sequence voltage injection and a reactive power compensation control system of a high-voltage direct-hung energy storage system based on intra-phase active power conversion;

[0130] Reference Figure 1 , is a structural diagram of a high-voltage direct-mounted battery energy storage system in an embodiment of the present invention. The high-voltage direct-mounted energy storage system is directly connected to power grids of various voltage levels, including: A-phase power module, B-phase power module and C-phase power module; each phase is cascaded by n power modules, each power module is mainly composed of an H-bridge power device and its drive circuit, a bus capacitor, a DC fuse, and a battery-side pre-charging device. The H-bridge power module is connected to the battery cluster on the DC side through a high-voltage cable and a DC-side filter inductor. The cascaded H-bridge converter is directly connected to the 35KV power grid on the AC side through a filter inductor, an AC-side pre-charging device and an AC fuse; v in the figure sa 、v sb 、v sc is the voltage of the three-phase grid, v a 、v b 、v c is the output voltage of the cascaded H-bridge converter, i a 、ib 、i c is the converter output current.

[0131] The reactive power compensation control system of the high-voltage direct-mounted energy storage system based on optimal zero-sequence voltage injection is as follows: Figure 2 As shown, including:

[0132] Module M1: Calculate the amplitude and relative phase of the zero-sequence voltage based on the parameter information of the cascaded H-bridge converter and the grid-side current;

[0133] Specifically, in the module M1:

[0134] Module M1.1: Calculate the battery current ripple rate γ;

[0135]

[0136] Where, ω2=4πf AC represents the angular velocity of the double frequency component; f AC Indicates the frequency of the grid voltage; R indicates the sum of the resistances of the battery and the DC side filter inductor; L indicates the inductance of the DC side filter inductor; C indicates the capacitance of the bus capacitor;

[0137] Module M1.2: Calculate the critical value ρ of the ratio of phase reactive power to active power;

[0138]

[0139] Module M1.3: Calculate the relative phase θ of the zero-sequence voltage;

[0140]

[0141] Module M1.4: Calculate the amplitude V0 of the zero-sequence voltage;

[0142]

[0143] Where ω=2πf AC Indicates the angular velocity of the grid voltage fundamental frequency; V s Indicates the phase voltage amplitude of the grid voltage; I s Indicates the amplitude of the grid current; L ac Indicates the inductance value of the AC side filter inductor.

[0144] Module M2: Calculate the given value of the output voltage of each phase of the cascaded H-bridge converter based on the reactive power given by the high-voltage direct-mounted energy storage system, and then calculate the modulation voltage of the output voltage of each phase of the cascaded H-bridge converter according to the battery state of charge, the amplitude and relative phase of the zero-sequence voltage of each phase;

[0145] Specifically, in the module M2:

[0146] Module M2.1: Obtain the current given value of the dq rotating coordinate system according to the reactive power required by the high-voltage direct-mounted energy storage system and

[0147] Module M2.2: Three-phase output current i of cascaded H-bridge converter a 、i b 、i c The actual current value i in the dq rotating coordinate system is obtained by abc / dq vector transformation and the phase-locking angle theta d and i q ;

[0148] Module M2.3: d-axis current given value The actual value of the d-axis current i d The difference is negative after passing through the PI controller and then cross-decoupled with the d-axis component ωL AC i q Add them together and add them to the actual value of the d-axis voltage u d The sum is used to obtain the d-axis voltage given value Q-axis current set value The actual value of the q-axis current i q The difference is negative after passing through the PI controller and then cross-decoupled with the q-axis component 2πf AC L AC i d Subtract, and then add to the actual value of the q-axis voltage u q The sum is used to obtain the q-axis voltage given value

[0149] Module M2.4: voltage setpoint The three-phase output voltage given value of the cascaded H-bridge converter is obtained by dq / abc vector transformation and phase-locking angle theta

[0150] Module M2.5: If the high-voltage direct-mounted energy storage system generates pure inductive reactive power, the relative phase θ of the zero-sequence voltage is negative and then subtracted from the phase of the j-th phase current to obtain the phase θ0 of the zero-sequence voltage:

[0151] θ0=-θ-φ ij (5)

[0152] Among them, φ ii represents the phase of the j-th phase current, j = A, B, C; the subscript i represents the current;

[0153] If the direct-mounted energy storage system generates pure capacitive reactive power, the relative phase θ of the zero-sequence voltage is subtracted from the phase of the j-th phase current to obtain the phase θ0 of the zero-sequence voltage:

[0154] θ0=θ-φij (6)

[0155] Module M2.6: Calculate the battery state of charge SOC of phase j j Battery state of charge SOC of direct-mounted energy storage system sys The difference ΔSOC j ;

[0156] ΔSOC j =SOC j -SOC sys (7)

[0157] If ΔSOC j If the set lower limit is reached, the jth phase is changed to the phase with the highest battery state of charge, and step S2.5 is triggered repeatedly to recalculate the phase θ0 of the zero-sequence voltage; if the set lower limit has not been reached, the original zero-sequence voltage phase is maintained;

[0158] Module M2.7: Calculate the instantaneous value of zero-sequence voltage;

[0159]

[0160] Module M2.8: Calculate the three-phase output voltage modulation voltage v of the cascaded H-bridge converter a 、v b 、v c ;

[0161]

[0162] Module M3: Based on the battery charge state and capacitor voltage of each power module in each phase, according to the modulation voltage of each phase output voltage of the cascaded H-bridge converter, the number of power modules required for the nearest level modulation is calculated, and then the battery charge state of each power module is sorted. The drive signal of each power module is determined according to the current direction of each phase and the number of power modules required for the nearest level modulation.

[0163] For example, if the number of power modules per phase is 10, the average value of the power module capacitor voltage is 1V, and the modulation voltage of the output voltage of phase A is 3.2V, the number of power modules N required for phase A can be obtained according to formula (10): a =3, the three power modules put into operation output positive level, if the A phase current i a When the direction is positive, the three power modules release electric energy, and the battery charge state of each power module in phase A is sorted. Because the three power modules put into use release electric energy, the three power modules put into use should be the three power modules with the highest battery charge state; if the phase A current i aWhen the direction is negative, the three power modules absorb electric energy, and the battery charge states of the power modules in phase A are sorted. Because the three power modules put into operation absorb electric energy, the three power modules put into operation should be the three power modules with the lowest battery charge states.

[0164] Specifically, in the module M3:

[0165] Module M3.1: Sampling the battery state of charge and capacitor voltage of each functional module in each phase, sorting the battery state of charge of each power module in each phase, and calculating the average value of the capacitor voltage of the total power module in each phase;

[0166] Module M3.2: Modulating the voltage v using the three-phase output voltage of the cascaded H-bridge converter a 、v b 、v c Divide by the average value of the total power module capacitor voltage in each phase to calculate the number of power modules N required for the three phases of the cascaded H-bridge converter a 、N b 、N c ;

[0167]

[0168] Among them, round() represents the nearest integer function; V a 、V b 、V c It represents the average value of the capacitor voltage of the three-phase total power module A, B, and C;

[0169] Module M3.3: The output current to the grid side is the phase current i x , x=a, b, c positive direction, when the phase current i x When the direction is positive, the number of power modules N required for the three phases is x It is also positive, and N is input from high to low according to the battery charge state. x Power modules, N x The power modules output positive level, and the other power modules output zero level;

[0170] When the phase current i x When the direction is positive, the number of power modules N required for the three phases is x When it is negative, the battery charge state is from low to high. x | power modules, put into use | N x | power modules output negative level, and other power modules output zero level;

[0171] When the phase current i x When the direction is negative, the number of power modules N required for the three phases xWhen it is negative, the battery charge state is input from high to low |N x | power modules, put into use | N x | power modules output negative level, and other power modules output zero level;

[0172] When the phase current i x When the direction is negative, the number of power modules N required for the three phases x When the battery is positive, N is input from low to high according to the battery charge state. x Power modules, N x The power modules output positive level, and the other power modules output zero level.

[0173] Among them, Figure 3 As shown, it also includes:

[0174] Module M4: Calculate the amplitude of the maximum zero-sequence voltage under the parameter constraints of the high-voltage direct-mounted energy storage system;

[0175] Specifically, in the module M4,

[0176] Define the grid-side rated voltage as V s ′, assuming that the rated capacity reactive output inductor voltage drop is σ L V s , the maximum voltage that the converter can output is βV s , zero-sequence voltage V0 lags behind phase b current -i sb The angle is θ′, and the amplitude of the maximum zero-sequence voltage V0′ is calculated using the cosine theorem;

[0177]

[0178] Among them, σ L It indicates the ratio of the rated capacity reactive output inductor voltage drop to the grid-side rated voltage; β indicates the ratio of the maximum voltage that the converter can output to the grid-side rated voltage;

[0179] The maximum zero-sequence voltage amplitude is

[0180]

[0181] Module M5: Calculate the phase angle of the zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power;

[0182] Specifically, in the module M5,

[0183] Module M5.1: Solve the ratio of three-phase reactive power to active power;

[0184]

[0185] Among them, Q xis the reactive power of phases A, B, and C, P x is the active power of phases A, B, and C; x = a, b, c;

[0186] Module M5.2: Solve to obtain the phase angle of zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power;

[0187]

[0188] Module M6: The amplitude of the maximum zero-sequence voltage under the parameter constraints of the high-voltage direct-mounted energy storage system and the phase angle of the zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power are used to obtain the passive parameter design criteria in the power module. The DC side filter inductor and bus capacitor in the power module are set based on the passive parameter design criteria in the power module.

[0189] Specifically, in the module M6,

[0190] Module M6.1: Calculate the DC component of the battery current generated by the three-phase active power at the minimum zero-sequence voltage phase angle and maximum zero-sequence voltage amplitude |I x |For:

[0191]

[0192] Among them, V bat is the battery voltage;

[0193] Module M6.2: Calculate the current AC component generated by the three-phase apparent power under the minimum zero-sequence voltage phase angle and maximum zero-sequence voltage amplitude |i x |For:

[0194]

[0195] Module M6.3: Calculate the components of the AC current flowing into the battery after LC filtering for

[0196]

[0197] Module M6.4: In order to prevent the battery current from charging and discharging back and forth during the power frequency cycle, it is necessary to ensure

[0198]

[0199] in, is the margin factor;

[0200] Module M6.5: Assuming that the battery current ripple rate obtained by the design of the high-voltage direct-mounted energy storage system to emit pure active power is γ, the design parameters need to meet the following requirements:

[0201]

[0202] The reactive power compensation control system of the high-voltage direct-mounted energy storage system based on intra-phase active power conversion is as follows: Figure 4 As shown, including:

[0203] Module S1: Calculate the voltage amplitude and relative phase of the two bridge arms in each phase based on the parameter information of the cascaded H-bridge converter and the grid-side current;

[0204] Specifically, in the module S1,

[0205] Module S1.1: Calculate the battery current ripple rate γ;

[0206]

[0207] Where, ω2=4πf AC represents the angular velocity of the double frequency component; f AC Indicates the frequency of the grid voltage; R indicates the sum of the resistances of the battery and the DC side filter inductor; L indicates the inductance value of the DC side filter inductor, and C indicates the capacitance value of the bus capacitor;

[0208] Module S1.2: Calculate the relative phase θ of the voltages of the two bridge arms in each phase;

[0209] θ=arcsin(γ)(23)

[0210] Module S1.3: Calculate the amplitudes V1 and V2 of the two bridge arms in each phase;

[0211]

[0212] Where ω=2πf AC is the angular velocity of the grid voltage fundamental frequency, V s is the phase voltage amplitude of the grid voltage, I s is the amplitude of the grid current, L AC is the inductance value of the AC side filter inductor;

[0213] Module S2: Based on the reactive power given by the high-voltage direct-mounted energy storage system and the battery charge state of the two bridge arms in each phase, the given value of the output voltage of the two bridge arms in each phase of the cascaded H-bridge converter is calculated according to the voltage amplitude and phase of the two bridge arms in each phase;

[0214] In the module S2,

[0215] Module S2.1: Obtain the current given value of the dq rotating coordinate system according to the reactive power required by the high-voltage direct-mounted energy storage system and

[0216] Module S2.2: Three-phase output current i of cascaded H-bridge converter a、i b 、i c The actual current value i in the dq rotating coordinate system is obtained by abc / dq vector transformation and the phase-locking angle theta d and i q ;

[0217] Module S2.3: d-axis current setpoint The actual value of the d-axis current i d The difference is negative after passing through the PI controller and then cross-decoupled with the d-axis component ωL AC i q Add them together and add them to the actual value of the d-axis voltage u d The sum is used to obtain the d-axis voltage given value Q-axis current set value The actual value of the q-axis current i q The difference is negative after passing through the PI controller and then cross-decoupled with the q-axis component 2πf AC L AC i d Subtract, and then add to the actual value of the q-axis voltage u q The sum is used to obtain the q-axis voltage given value

[0218] Module S2.4: Voltage setpoint The three-phase output voltage given value of the cascaded H-bridge converter is obtained by dq / abc vector transformation and phase-locking angle theta

[0219] Module S2.5: If the high-voltage direct-mounted energy storage system generates pure inductive reactive power, the first phase θ of the jth phase is obtained j1 , the second phase θ j2 :

[0220]

[0221] Among them, φ ij is the phase of the jth phase current, j = A, B, C; θ represents the relative phase of the voltages of the two bridge arms;

[0222] If the high-voltage direct-mounted energy storage system generates pure capacitive reactive power, the first phase θ of the jth phase is obtained. j1 , the second phase θ j2 :

[0223]

[0224] Module S2.6: Calculate the battery state of charge SOC of the first bridge arm of phase j j1 and the battery state of charge SOC of the second bridge arm j2 The battery state of charge SOC of the jth phase jThe difference between

[0225] ΔSOC j1 =SOC j1 -SOC j ,ΔSOC j2 =SOC j2 -SOC j

[0226] When the state is the voltage phase of the first bridge arm of the jth phase Equal to the first phase θ of the jth phase j1 , the voltage phase of the second bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 , if ΔSOC j1 When the set lower limit is reached, the state changes to the voltage phase of the first bridge arm of the jth phase. Equal to the second phase θ of the jth phase j2 , the voltage phase of the second bridge arm of the jth phase is equal to the first phase θ of the jth phase j1 ;

[0227] When the state is the voltage phase of the first bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 , the voltage phase of the second bridge arm of the jth phase Equal to the first phase θ of the jth phase j1 , if ΔSOC j2 When the set lower limit is reached, the state changes to the voltage phase of the first bridge arm of the jth phase. Equal to the first phase θ of the jth phase j1 , the voltage phase of the second bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 .

[0228] Module S2.7: Calculate the given value of the voltage of the first bridge arm of phase j and the given value of the voltage of the second bridge arm of the jth phase

[0229]

[0230] Module S3: Based on the battery charge state and capacitor voltage of each power module in each phase, according to the given value of the output voltage of the two bridge arms in each phase of the cascaded H-bridge converter, the number of sub-modules required for the nearest level modulation is calculated, and then the battery charge state of each power module is sorted. The drive signal of each power module is determined according to the current direction of each phase and the number of sub-modules required for the nearest level modulation.

[0231] For example, if the number of power modules per phase is 10, the average value of the power module capacitor voltage is 1V, and the modulation voltage of the output voltage of phase A is 3.2V, the number of power modules N required for phase A can be obtained according to formula (10): a =3, the three power modules put into operation output positive level, if the A phase current i a When the direction is positive, the three power modules release electric energy, and the battery charge state of each power module in phase A is sorted. Because the three power modules put into use release electric energy, the three power modules put into use should be the three power modules with the highest battery charge state; if the phase A current i a When the direction is negative, the three power modules absorb electric energy, and the battery charge states of the power modules in phase A are sorted. Because the three power modules put into operation absorb electric energy, the three power modules put into operation should be the three power modules with the lowest battery charge states.

[0232] In the module S3,

[0233] Module S3.1: Sampling to obtain the battery state of charge and capacitor voltage of each power module in each phase, sorting the battery state of charge of each power module in the first bridge arm and the second bridge arm in each phase, and calculating the average value of the capacitor voltage of the power module in the first bridge arm and the second bridge arm in each phase;

[0234] Module S3.2: Use the given value of the voltage of the first bridge arm of the jth phase of the cascaded H-bridge converter and the given value of the voltage of the second bridge arm of the jth phase Divide by the average value of the power module capacitor voltage in the first bridge arm and the second bridge arm in each phase, and calculate the number of power modules required in the first bridge arm and the second bridge arm in the three-phase cascaded H-bridge converter

[0235]

[0236] Among them, round() is the nearest integer function. is the average value of the capacitor voltage of the first bridge arm power module of phases A, B, and C, It is the average value of the capacitor voltage of the second bridge arm power module of the three phases A, B, and C.

[0237] Module S3.3: The output current to the grid side is the phase current i x , x=a, b, c positive direction, when the phase current i x When the direction is positive, the number of power modules required in the first bridge arm and the second bridge arm of the three-phase When the battery is positive, the bridge arm is put into operation from high to low according to the battery charge state. Power modules, put into The power modules output positive level, and the other power modules output zero level;

[0238] When the phase current i x When the direction is positive, the number of power modules required in the first bridge arm and the second bridge arm of the three-phase When it is negative, the bridge arm is put into operation from low to high according to the battery charge state. Power modules, put into The power modules output negative level, and the other power modules output zero level;

[0239] When the phase current i x When the direction is negative, the number of power modules required for the first bridge arm and the second bridge arm of the three-phase When it is negative, the bridge arm is put into operation from high to low according to the battery charge state. Power modules, put into The power modules output negative level, and the other power modules output zero level;

[0240] When the phase current i x When the direction is negative, the number of power modules required for the first bridge arm and the second bridge arm of the three-phase When the battery is positive, the bridge arm is put into operation from low to high according to the battery charge state. Power modules, put into The power modules output positive level, and the other power modules output zero level.

[0241] Among them, it also includes:

[0242] Module S4: Calculate the maximum voltage amplitude under the parameter limitation of the high-voltage direct-mounted energy storage system;

[0243] Specifically, in the module S4,

[0244] Define the grid-side rated voltage as V s ′, assuming that the rated capacity reactive output inductor voltage drop is σ L V s , the maximum voltage that the converter can output is βV s , voltage V0 lags behind phase b current -i sb The angle is θ′, and the amplitude of the maximum voltage V0′ is calculated;

[0245]

[0246] Among them, σ L It indicates the ratio of the rated capacity reactive output inductor voltage drop to the grid-side rated voltage; β indicates the ratio of the maximum voltage that the converter can output to the grid-side rated voltage;

[0247] The maximum voltage amplitude is

[0248]

[0249] Module S5: Calculate the phase angle of the voltage that minimizes the ratio of three-phase reactive power to active power;

[0250] Specifically, in the module S5,

[0251] Module S5.1: Solve the ratio of three-phase reactive power to active power;

[0252]

[0253] Among them, Q x is the reactive power of phases A, B, and C, x = a, b, c, P x is the active power of phases A, B, and C (x = a, b, c);

[0254] Module S5.2: Solve to obtain the voltage phase angle that minimizes the ratio of three-phase reactive power to active power;

[0255]

[0256] Module S6: The amplitude of the maximum voltage under the parameter constraints of the high-voltage direct-mounted energy storage system and the phase angle of the voltage that minimizes the ratio of three-phase reactive power to active power are used to obtain the passive parameter design criteria in the power module. The DC side filter inductor and bus capacitor in the power module are set based on the passive parameter design criteria in the power module.

[0257] Specifically, in the module S6,

[0258] Module M6.1: Calculate the DC component of the battery current generated by the three-phase active power at the minimum voltage phase angle and maximum voltage amplitude |I x |For:

[0259]

[0260] Among them, V bat is the battery voltage;

[0261] Module S6.2: Calculate the current AC component of the three-phase apparent power generated at the minimum voltage phase angle and maximum voltage amplitude |i x |For:

[0262]

[0263] Module S6.3: Calculate the components of the AC current flowing into the battery after LC filtering for

[0264]

[0265] Module S6.4: In order to prevent the battery current from charging and discharging back and forth during the power frequency cycle, it is necessary to ensure

[0266]

[0267] Among them, θ is the margin coefficient;

[0268] Module S6.5: Assuming that the battery current ripple rate obtained by the design of the high-voltage direct-mounted energy storage system to emit pure active power is γ, the design parameters need to meet the following requirements:

[0269]

[0270] A high-voltage direct-hanging method integrating reactive power compensation and energy storage provided by the present invention comprises: a reactive power compensation control method of a high-voltage direct-hanging energy storage system based on optimal zero-sequence voltage injection and a reactive power compensation control method of a high-voltage direct-hanging energy storage system based on intra-phase active power conversion;

[0271] Reference Figure 1 , is a structural diagram of a high-voltage direct-mounted battery energy storage system in an embodiment of the present invention. The high-voltage direct-mounted energy storage system is directly connected to power grids of various voltage levels, including: A-phase power module, B-phase power module and C-phase power module; each phase is cascaded by n power modules, each power module is mainly composed of an H-bridge power device and its drive circuit, a bus capacitor, a DC fuse, and a battery-side pre-charging device. The H-bridge power module is connected to the battery cluster on the DC side through a high-voltage cable and a DC-side filter inductor. The cascaded H-bridge converter is directly connected to the 35KV power grid on the AC side through a filter inductor, an AC-side pre-charging device and an AC fuse; v in the figure sa 、v sb 、v sc is the voltage of the three-phase grid, v a 、v b 、v c is the output voltage of the cascaded H-bridge converter, i a 、i b 、i c is the converter output current.

[0272] The reactive power compensation control method of a high-voltage direct-mounted energy storage system based on optimal zero-sequence voltage injection includes:

[0273] Step M1: Calculate the amplitude and relative phase of the zero-sequence voltage based on the parameter information of the cascaded H-bridge converter and the grid-side current;

[0274] Specifically, in step M1:

[0275] Step M1.1: Calculate the battery current ripple rate γ;

[0276]

[0277] Where, ω2=4πf AC represents the angular velocity of the double frequency component; f AC Indicates the frequency of the grid voltage; R indicates the sum of the resistances of the battery and the DC side filter inductor; L indicates the inductance of the DC side filter inductor; C indicates the capacitance of the bus capacitor;

[0278] Step M1.2: Calculate the critical value ρ of the ratio of phase reactive power to active power;

[0279]

[0280] Step M1.3: Calculate the relative phase θ of the zero-sequence voltage;

[0281]

[0282] Step M1.4: Calculate the amplitude V0 of the zero-sequence voltage;

[0283]

[0284] Where ω=2πf AC Indicates the angular velocity of the grid voltage fundamental frequency; V s Indicates the phase voltage amplitude of the grid voltage; I s Indicates the amplitude of the grid current; L ac Indicates the inductance value of the AC side filter inductor.

[0285] Step M2: Calculate the given value of the output voltage of each phase of the cascaded H-bridge converter based on the reactive power given by the high-voltage direct-mounted energy storage system, and then calculate the modulation voltage of the output voltage of each phase of the cascaded H-bridge converter according to the battery state of charge, the amplitude and relative phase of the zero-sequence voltage of each phase;

[0286] Specifically, in step M2:

[0287] Step M2.1: Obtain the current given value of the dq rotating coordinate system according to the reactive power required by the high-voltage direct-mounted energy storage system and

[0288] Step M2.2: Three-phase output current i of cascaded H-bridge converter a 、i b 、i c The actual current value i in the dq rotating coordinate system is obtained by abc / dq vector transformation and the phase-locking angle theta d and i q ;

[0289] Step M2.3: d-axis current given value The actual value of the d-axis current id The difference is negative after passing through the PI controller and then cross-decoupled with the d-axis component ωL AC i q Add them together and add them to the actual value of the d-axis voltage u d The sum is used to obtain the d-axis voltage given value Q-axis current set value The actual value of the q-axis current i q The difference is negative after passing through the PI controller and then cross-decoupled with the q-axis component 2πf AC L AC i d Subtract, and then add to the actual value of the q-axis voltage u q The sum is used to obtain the q-axis voltage given value

[0290] Step M2.4: Voltage setpoint The three-phase output voltage given value of the cascaded H-bridge converter is obtained by dq / abc vector transformation and phase-locking angle theta

[0291] Step M2.5: If the high-voltage direct-mounted energy storage system generates pure inductive reactive power, the relative phase θ of the zero-sequence voltage is negative and then subtracted from the phase of the j-th phase current to obtain the phase θ0 of the zero-sequence voltage:

[0292] θ0=-θ-φ ij (5)

[0293] Among them, φ ii represents the phase of the j-th phase current, j = A, B, C; the subscript i represents the current;

[0294] If the direct-mounted energy storage system generates pure capacitive reactive power, the relative phase θ of the zero-sequence voltage is subtracted from the phase of the j-th phase current to obtain the phase θ0 of the zero-sequence voltage:

[0295] θ0=θ-φ ij (6)

[0296] Step M2.6: Calculate the battery state of charge SOC of phase j j Battery state of charge SOC of direct-mounted energy storage system sys The difference ΔSOC j ;

[0297] ΔSOC j =SOC j -SOC sys (7)

[0298] If ΔSOC jIf the set lower limit is reached, the jth phase is changed to the phase with the highest battery state of charge, and step S2.5 is triggered repeatedly to recalculate the phase θ0 of the zero-sequence voltage; if the set lower limit has not been reached, the original zero-sequence voltage phase is maintained;

[0299] Step M2.7: Calculate the instantaneous value of the zero-sequence voltage;

[0300]

[0301] Step M2.8: Calculate the three-phase output voltage modulation voltage v of the cascaded H-bridge converter a 、v b 、v c ;

[0302]

[0303] Step M3: Based on the battery charge state and capacitor voltage of each power module of each phase, according to the modulation voltage of each phase output voltage of the cascaded H-bridge converter, calculate the number of power modules required for the nearest level modulation, and then sort the battery charge state of each power module, and determine the drive signal of each power module according to the current direction of each phase and the number of power modules required for the nearest level modulation.

[0304] For example: if the current level is 3.2V, then the nearest level is 3V, and 3 power modules are required.

[0305] Specifically, in step M3:

[0306] Step M3.1: Sampling the battery state of charge and capacitor voltage of each functional module in each phase, sorting the battery state of charge of each power module in each phase, and calculating the average value of the capacitor voltage of the total power module in each phase;

[0307] Step M3.2: Modulate the voltage v using the three-phase output voltage of the cascaded H-bridge converter a 、v b 、v c Divide by the average value of the total power module capacitor voltage in each phase to calculate the number of power modules N required for the three phases of the cascaded H-bridge converter a 、N b 、N c ;

[0308]

[0309] Among them, round() represents the nearest integer function; V a 、V b 、V c It represents the average value of the capacitor voltage of the three-phase total power module A, B, and C;

[0310] Step M3.3: Take the output current to the grid as the phase current i x , x=a, b, c positive direction, when the phase current i x When the direction is positive, the number of power modules N required for the three phases is x It is also positive, and N is input from high to low according to the battery charge state. x Power modules, N x The power modules output positive level, and the other power modules output zero level;

[0311] When the phase current i x When the direction is positive, the number of power modules N required for the three phases is x When it is negative, the battery charge state is from low to high. x | power modules, put into use | N x | power modules output negative level, and other power modules output zero level;

[0312] When the phase current i x When the direction is negative, the number of power modules N required for the three phases x When it is negative, the battery charge state is input from high to low |N x | power modules, put into use | N x | power modules output negative level, and other power modules output zero level;

[0313] When the phase current i x When the direction is negative, the number of power modules N required for the three phases x When the battery is positive, N is input from low to high according to the battery charge state. x Power modules, N x The power modules output positive level, and the other power modules output zero level.

[0314] Among them, Figure 3 As shown, it also includes:

[0315] Step M4: Calculate the amplitude of the maximum zero-sequence voltage under the parameter constraints of the high-voltage direct-mounted energy storage system;

[0316] Specifically, in step M4,

[0317] Define the grid-side rated voltage as V s ', assuming that the rated capacity reactive output inductor voltage drop is σ L V s , the maximum voltage that the converter can output is βV s , zero-sequence voltage V0 lags behind phase b current -i sb The angle is θ', and the amplitude of the maximum zero-sequence voltage V0' is calculated;

[0318]

[0319] Among them, σ L It indicates the ratio of the rated capacity reactive output inductor voltage drop to the grid-side rated voltage; β indicates the ratio of the maximum voltage that the converter can output to the grid-side rated voltage;

[0320] The maximum zero-sequence voltage amplitude is

[0321]

[0322] Step M5: Calculate the phase angle of the zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power;

[0323] Specifically, in step M5,

[0324] Step M5.1: Calculate the ratio of three-phase reactive power to active power;

[0325]

[0326]

[0327] Among them, Q x (x=a,b,c) is the reactive power of phases A, B and C, P x (x=a,b,c) is the active power of phases A, B and C;

[0328] Step M5.2: Solve to obtain the phase angle of the zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power;

[0329]

[0330] Step M6: The amplitude of the maximum zero-sequence voltage under the parameter constraints of the high-voltage direct-mounted energy storage system and the phase angle of the zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power are used to obtain the passive parameter design criteria in the power module, and the DC side filter inductor and bus capacitor in the power module are set based on the passive parameter design criteria in the power module.

[0331] Specifically, in step M6,

[0332] Step M6.1: Calculate the DC component of the battery current generated by the three-phase active power under the minimum zero-sequence voltage phase angle and maximum zero-sequence voltage amplitude |I x |For:

[0333]

[0334] Among them, V bat is the battery voltage;

[0335] Step M6.2: Calculate the current AC component |i generated by the three-phase apparent power at the minimum zero-sequence voltage phase angle and maximum zero-sequence voltage amplitude x |For:

[0336]

[0337] Step M6.3: Calculate the components of the AC current flowing into the battery after LC filtering for

[0338]

[0339] Step M6.4: To prevent the battery current from charging and discharging back and forth during the power frequency cycle, ensure that

[0340]

[0341] Among them, θ is the margin coefficient;

[0342] Step M6.5: Assuming that the battery current ripple rate obtained from the design of the high-voltage direct-mounted energy storage system to emit pure active power is γ, the design parameters need to meet the following requirements:

[0343]

[0344] The reactive power compensation control system of the high-voltage direct-mounted energy storage system based on intra-phase active power conversion is as follows: Figure 4 As shown, including:

[0345] Step S1: Calculate the voltage amplitude and relative phase of two bridge arms in each phase based on the parameter information of the cascaded H-bridge converter and the grid-side current;

[0346] Specifically, in step S1,

[0347] Step S1.1: Calculate the battery current ripple rate γ;

[0348]

[0349] Where, ω2=4πf AC represents the angular velocity of the double frequency component; f AC Indicates the frequency of the grid voltage; R indicates the sum of the resistances of the battery and the DC side filter inductor; L indicates the inductance value of the DC side filter inductor, and C indicates the capacitance value of the bus capacitor;

[0350] Step S1.2: Calculate the relative phase θ of the voltages of the two bridge arms in each phase;

[0351] θ=arcsin(γ) =(23)

[0352] Step S1.3: Calculate the amplitudes V1 and V2 of the two bridge arms in each phase;

[0353]

[0354] Where ω=2πf AC is the angular velocity of the grid voltage fundamental frequency, V s is the phase voltage amplitude of the grid voltage, I s is the amplitude of the grid current, L AC is the inductance value of the AC side filter inductor;

[0355] Step S2: Based on the reactive power given by the high-voltage direct-mounted energy storage system and the battery charge state of the two bridge arms in each phase, the given value of the output voltage of the two bridge arms in each phase of the cascaded H-bridge converter is calculated according to the voltage amplitude and phase of the two bridge arms in each phase;

[0356] In step S2,

[0357] Step S2.1: Obtain the current given value of the dq rotating coordinate system according to the reactive power required to be generated by the high-voltage direct-mounted energy storage system and

[0358] Step S2.2: The three-phase output current i of the cascaded H-bridge converter a 、i b 、i c The actual current value i in the dq rotating coordinate system is obtained by abc / dq vector transformation and the phase-locking angle theta d and i q ;

[0359] Step S2.3: d-axis current given value The actual value of the d-axis current i d The difference is negative after passing through the PI controller and then cross-decoupled with the d-axis component ωL AC i q Add them together and add them to the actual value of the d-axis voltage u d The sum is used to obtain the d-axis voltage given value Q-axis current set value The actual value of the q-axis current i q The difference is negative after passing through the PI controller and then cross-decoupled with the q-axis component 2πf AC L AC i d Subtract, and then add to the actual value of the q-axis voltage u q The sum is used to obtain the q-axis voltage given value

[0360] Step S2.4: Voltage setpoint The three-phase output voltage given value of the cascaded H-bridge converter is obtained by dq / abc vector transformation and phase-locking angle theta

[0361] Step S2.5: If the high-voltage direct-mounted energy storage system generates pure inductive reactive power, the first phase θ of the jth phase is obtained. j1 , the second phase θ j2 :

[0362]

[0363] Among them, φ ij is the phase of the jth phase current, j = A, B, C; θ represents the relative phase of the voltages of the two bridge arms;

[0364] If the high-voltage direct-mounted energy storage system generates pure capacitive reactive power, the first phase θ of the jth phase is obtained. j1 , the second phase θ j2 :

[0365]

[0366] Step S2.6: Calculate the battery state of charge SOC of the first bridge arm of the jth phase j1 and the battery state of charge SOC of the second bridge arm j2 The battery state of charge SOC of the jth phase j The difference between

[0367] ΔSOC j1 =SOC j1 -SOC j ,ΔSOC j2 =SOC j2 -SOC j

[0368] When the state is the voltage phase of the first bridge arm of the jth phase Equal to the first phase θ of the jth phase j1 , the voltage phase of the second bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 , if ΔSOC j1 When the set lower limit is reached, the state changes to the voltage phase of the first bridge arm of the jth phase. Equal to the second phase θ of the jth phase j2 , the voltage phase of the second bridge arm of the jth phase is equal to the first phase θ of the jth phase j1 ;

[0369] When the state is the voltage phase of the first bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 , the voltage phase of the second bridge arm of the jth phase Equal to the first phase θ of the jth phase j1 , if ΔSOC j2When the set lower limit is reached, the state changes to the voltage phase of the first bridge arm of the jth phase. Equal to the first phase θ of the jth phase j1 , the voltage phase of the second bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 .

[0370] Step S2.7: Calculate the given value of the voltage of the first bridge arm of the jth phase and the given value of the voltage of the second bridge arm of the jth phase

[0371]

[0372] Step S3: Based on the battery charge state and capacitor voltage of each power module in each phase, according to the given value of the output voltage of the two bridge arms in each phase of the cascaded H-bridge converter, calculate the number of sub-modules required for the nearest level modulation, and then sort the battery charge state of each power module, and determine the drive signal of each power module according to the current direction of each phase and the number of sub-modules required for the nearest level modulation.

[0373] For example: if the current level is 3.2V, then the nearest level is 3V, and 3 power modules are required.

[0374] In step S3,

[0375] Step S3.1: Sampling to obtain the battery state of charge and capacitor voltage of each power module in each phase, sorting the battery state of charge of each power module in the first bridge arm and the second bridge arm in each phase, and calculating the average value of the capacitor voltage of the power module in the first bridge arm and the second bridge arm in each phase;

[0376] Step S3.2: Using the given value of the voltage of the first bridge arm of the jth phase of the cascaded H-bridge converter and the given value of the voltage of the second bridge arm of the jth phase Divide by the average value of the power module capacitor voltage in the first bridge arm and the second bridge arm in each phase, and calculate the number of power modules required in the first bridge arm and the second bridge arm in the three-phase cascaded H-bridge converter

[0377]

[0378] Among them, round() is the nearest integer function. is the average value of the capacitor voltage of the first bridge arm power module of phases A, B, and C, It is the average value of the capacitor voltage of the second bridge arm power module of the three phases A, B, and C.

[0379] Step S3.3: Take the output current to the grid side as the phase current ix , x=a, b, c positive direction, when the phase current i x When the direction is positive, the number of power modules required in the first bridge arm and the second bridge arm of the three-phase When the battery is positive, the bridge arm is put into operation from high to low according to the battery charge state. Power modules, put into The power modules output positive level, and the other power modules output zero level;

[0380] When the phase current i x When the direction is positive, the number of power modules required in the first bridge arm and the second bridge arm of the three-phase When it is negative, the bridge arm is put into operation from low to high according to the battery charge state. Power modules, put into The power modules output negative level, and the other power modules output zero level;

[0381] When the phase current i x When the direction is negative, the number of power modules required for the first bridge arm and the second bridge arm of the three-phase When it is negative, the bridge arm is put into operation from high to low according to the battery charge state. Power modules, put into The power modules output negative level, and the other power modules output zero level;

[0382] When the phase current i x When the direction is negative, the number of power modules required for the first bridge arm and the second bridge arm of the three-phase When the battery is positive, the bridge arm is put into operation from low to high according to the battery charge state. Power modules, put into The power modules output positive level, and the other power modules output zero level.

[0383] Among them, it also includes:

[0384] Step S4: Calculate the maximum voltage amplitude under the parameter limitation of the high-voltage direct-mounted energy storage system;

[0385] Specifically, in step S4,

[0386] Define the grid-side rated voltage as V s ', assuming that the rated capacity reactive output inductor voltage drop is σ L V s , the maximum voltage that the converter can output is βV s , zero-sequence voltage V0 lags behind phase b current -i sb The angle is θ', and the amplitude of the maximum zero-sequence voltage V0' is calculated;

[0387]

[0388] Among them, σ L It indicates the ratio of the rated capacity reactive output inductor voltage drop to the grid-side rated voltage; β indicates the ratio of the maximum voltage that the converter can output to the grid-side rated voltage;

[0389] The maximum zero-sequence voltage amplitude is

[0390]

[0391] Step S5: Calculate the phase angle of the voltage that minimizes the ratio of three-phase reactive power to active power;

[0392] Specifically, in step S5,

[0393] Step S5.1: Calculate the ratio of three-phase reactive power to active power;

[0394]

[0395] Among them, Q x is the reactive power of phases A, B, and C, x = a, b, c, P x is the active power of phases A, B, and C (x = a, b, c);

[0396] Step S5.2: Solve to obtain the phase angle of the voltage that minimizes the ratio of three-phase reactive power to active power;

[0397]

[0398] Step S6: Obtain the passive parameter design criteria in the power module from the maximum voltage amplitude under the parameter constraints of the high-voltage direct-mounted energy storage system and the voltage phase angle that minimizes the ratio of three-phase reactive power to active power, and set the DC side filter inductor and bus capacitor in the power module based on the passive parameter design criteria in the power module.

[0399] Specifically, in step S6,

[0400] Step M6.1: Calculate the DC component of the battery current generated by the three-phase active power at the minimum voltage phase angle and maximum voltage amplitude |I x |For:

[0401]

[0402] Among them, V bat is the battery voltage;

[0403] Step S6.2: Calculate the current AC component |i generated by the three-phase apparent power at the minimum voltage phase angle and maximum voltage amplitude x |For:

[0404]

[0405] Step S6.3: Calculate the components of the AC current flowing into the battery after LC filtering for

[0406]

[0407] Step S6.4: To prevent the battery current from charging and discharging back and forth during the power frequency cycle, ensure that

[0408]

[0409] in, is the margin factor;

[0410] Step S6.5: Assuming that the battery current ripple rate obtained by the design of the high-voltage direct-mounted energy storage system to emit pure active power is γ, the design parameters need to meet the following requirements:

[0411]

[0412] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0413] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A high voltage direct hanging system integrating reactive power compensation and energy storage, characterized in that: include: Module M1: Calculate the amplitude and relative phase of the zero-sequence voltage based on the parameter information of the cascaded H-bridge converter and the grid-side current; Module M2: Calculate the given value of the output voltage of each phase of the cascaded H-bridge converter based on the reactive power given by the high-voltage direct-mounted energy storage system, and then calculate the modulation voltage of the output voltage of each phase of the cascaded H-bridge converter according to the battery state of charge, the amplitude and relative phase of the zero-sequence voltage of each phase; Module M3: Based on the battery state of charge and capacitor voltage of each power module of each phase, according to the modulation voltage of each phase output voltage of the cascaded H-bridge converter, the number of power modules required for the nearest level modulation is calculated, and then the battery state of charge of each power module is sorted, and the driving signal of each power module is determined according to the current direction of each phase and the number of power modules required for the nearest level modulation; In the module M2: Module M2.1: Obtain the current given value of the dq rotating coordinate system according to the reactive power required by the high-voltage direct-mounted energy storage system and Module M2.2: Three-phase output current i of cascaded H-bridge converter a 、i b 、i c The actual current value i in the dq rotating coordinate system is obtained by abc / dq vector transformation and the phase-locking angle theta d and i q ; Module M2.3: d-axis current given value The actual value of the d-axis current i d The difference is negative after passing through the PI controller and then cross-decoupled with the d-axis component ωL AC i q Add them together and add them to the actual value of the d-axis voltage u d The sum is used to obtain the d-axis voltage given value Q-axis current set value The actual value of the q-axis current i q The difference is negative after passing through the PI controller and then cross-decoupled with the q-axis component 2πf AC L AC i d Subtract, and then add to the actual value of the q-axis voltage u q The sum is used to obtain the q-axis voltage given value Where, ω represents the angular velocity of the grid voltage fundamental frequency, L AC Indicates the inductance of the AC side filter inductor, f AC Indicates the frequency of the grid voltage; Module M2.4: Voltage setpoint The three-phase output voltage given value of the cascaded H-bridge converter is obtained by dq / abc vector transformation and phase-locking angle theta Module M2.5: If the high-voltage direct-mounted energy storage system emits pure inductive reactive power, the relative phase θ of the zero-sequence voltage is negative and then subtracted from the phase of the j-th phase current to obtain the phase θ0 of the zero-sequence voltage: θ0=-θ-φ ij (5) Among them, φ ij represents the phase of the j-th phase current; the subscript i represents the current; If the direct-mounted energy storage system generates pure capacitive reactive power, the relative phase θ of the zero-sequence voltage is subtracted from the phase of the j-th phase current to obtain the phase θ0 of the zero-sequence voltage: θ0=θ-φ ij (6) Module M2.6: Calculate the battery state of charge SOC of phase j j Battery state of charge SOC of high voltage direct-mounted energy storage system sys The difference ΔSOC j ; ΔSOC j =SOC j -SOC sys (7) If ΔSOC j If the set lower limit is reached, the jth phase is changed to the phase with the highest battery state of charge, and step S2.5 is triggered repeatedly to recalculate the phase θ0 of the zero-sequence voltage; if the set lower limit has not been reached, the original zero-sequence voltage phase is maintained; Module M2.7: Calculate the instantaneous value of zero-sequence voltage; Among them, V0 represents the amplitude of zero-sequence voltage; Module M2.8: Calculate the three-phase output voltage modulation voltage v of the cascaded H-bridge converter a 、v b 、v c ; 2. The high-voltage direct-mounted system integrating reactive power compensation and energy storage according to claim 1 is characterized in that: In the module M1: Module M1.1: Calculate the battery current ripple rate γ; Where, ω2=4πf AC represents the angular velocity of the double frequency component; f AC Indicates the frequency of the grid voltage; R indicates the sum of the resistances of the battery and the DC side filter inductor; L indicates the inductance of the DC side filter inductor; C indicates the capacitance of the bus capacitor; Module M1.2: Calculate the critical value ρ of the ratio of phase reactive power to active power; Module M1.3: Calculate the relative phase θ of the zero-sequence voltage; Module M1.4: Calculate the amplitude V0 of the zero-sequence voltage; Where ω=2πf AC Indicates the angular velocity of the grid voltage fundamental frequency; V s Indicates the phase voltage amplitude of the grid voltage; I s Indicates the amplitude of the grid current; L AC Indicates the inductance of the AC side filter inductor.

3. The high-voltage direct-mounted system integrating reactive power compensation and energy storage according to claim 1 is characterized in that: In the module M3: Module M3.1: Sampling the battery state of charge and capacitor voltage of each functional module in each phase, sorting the battery state of charge of each power module in each phase, and calculating the average value of the capacitor voltage of the total power module in each phase; Module M3.2: Modulating the voltage v using the three-phase output voltage of the cascaded H-bridge converter a 、v b 、v c Divide by the average value of the total power module capacitor voltage in each phase to calculate the number of power modules N required for the three phases of the cascaded H-bridge converter a 、N b 、N c ; Among them, round() represents the nearest integer function; V a 、V b 、V c It represents the average value of the capacitor voltage of the three-phase total power module A, B, and C; Module M3.3: The output current to the grid side is the phase current i x , x=a, b, c positive direction, when the phase current i x When the direction is positive, the number of power modules N required for the three phases is x It is also positive, and N is input from high to low according to the battery charge state. x Power modules, N x The power modules output positive level, and the other power modules output zero level; When the phase current i x When the direction is positive, the number of power modules N required for the three phases is x When it is negative, the battery charge state is from low to high. x | power modules, put into use | N x | power modules output negative level, and other power modules output zero level; When the phase current i x When the direction is negative, the number of power modules N required for the three phases x When it is negative, the battery charge state is input from high to low |N x | power modules, put into use | N x | power modules output negative level, and other power modules output zero level; When the phase current i x When the direction is negative, the number of power modules N required for the three phases x When the battery is positive, N is input from low to high according to the battery charge state. x Power modules, N x The power modules output positive level, and the other power modules output zero level.

4. The high-voltage direct-mounted system integrating reactive power compensation and energy storage according to claim 1 is characterized in that: include: Module M4: Calculate the amplitude of the maximum zero-sequence voltage under the parameter constraints of the high-voltage direct-mounted energy storage system; Module M5: Calculate the phase angle of the zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power; Module M6: The amplitude of the maximum zero-sequence voltage under the parameter constraints of the high-voltage direct-mounted energy storage system and the phase angle of the zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power are used to obtain the passive parameter design criteria in the power module. The DC side filter inductor and bus capacitor in the power module are set based on the passive parameter design criteria in the power module.

5. The high-voltage direct-mounted system integrating reactive power compensation and energy storage according to claim 4 is characterized in that: In the module M4, Define the grid-side rated voltage as V' s , assuming that the rated capacity reactive output inductor voltage drop is σ L V' s , the maximum voltage that the converter can output is βV' s , zero-sequence voltage lags behind phase b current -i sb The angle is θ′, and the amplitude of the maximum zero-sequence voltage V'0 is calculated; Among them, σ L It indicates the ratio of the rated capacity reactive output inductor voltage drop to the grid-side rated voltage; β indicates the ratio of the maximum voltage that the converter can output to the grid-side rated voltage; The maximum zero-sequence voltage amplitude is 6. The high-voltage direct-mounted system integrating reactive power compensation and energy storage according to claim 5 is characterized in that: In the module M5, Module M5.1: Solve the ratio of three-phase reactive power to active power; Among them, Q x is the reactive power of phases A, B, and C, P x is the active power of phases A, B, and C; x = a, b, c; Module M5.2: Solve to obtain the phase angle of zero-sequence voltage that minimizes the ratio of three-phase reactive power to active power; 7. The high-voltage direct-mounted system integrating reactive power compensation and energy storage according to claim 6 is characterized in that: In the module M6, Module M6.1: Calculate the DC component of the battery current generated by the three-phase active power at the minimum zero-sequence voltage phase angle and maximum zero-sequence voltage amplitude |I x |For: Among them, V bat is the battery voltage; Module M6.2: Calculate the current AC component generated by the three-phase apparent power under the minimum zero-sequence voltage phase angle and maximum zero-sequence voltage amplitude |i x |For: Module M6.3: Calculate the components of the AC current flowing into the battery after LC filtering for Wherein, ω2 represents the angular velocity of the double frequency component; R represents the sum of the resistances of the battery and the DC side filter inductor; C represents the capacitance of the bus capacitor; L represents the inductance of the DC side filter inductor; Module M6.4: In order to prevent the battery current from charging and discharging back and forth during the power frequency cycle, it is necessary to ensure Among them, θ is the margin coefficient; Module M6.5: Assuming that the battery current ripple rate obtained by the design of the high-voltage direct-mounted energy storage system to emit pure active power is γ, the design parameters need to meet the following requirements: Where γ represents the battery current ripple rate.

8. A high voltage direct hanging system integrating reactive power compensation and energy storage, characterized in that: include: Module S1: Calculate the voltage amplitude and relative phase of the two bridge arms in each phase based on the parameter information of the cascaded H-bridge converter and the grid-side current; Module S2: Based on the reactive power given by the high-voltage direct-mounted energy storage system and the battery charge state of the two bridge arms in each phase, the given value of the output voltage of the two bridge arms in each phase of the cascaded H-bridge converter is calculated according to the voltage amplitude and phase of the two bridge arms in each phase; Module S3: Based on the battery charge state and capacitor voltage of each power module in each phase, according to the given value of the output voltage of the two bridge arms in each phase of the cascaded H-bridge converter, the number of sub-modules required for the nearest level modulation is calculated, and then the battery charge state of each power module is sorted. The drive signal of each power module is determined according to the current direction of each phase and the number of sub-modules required for the nearest level modulation.

9. The high-voltage direct-mounted system integrating reactive power compensation and energy storage according to claim 8 is characterized in that: In the module S1, Module S1.1: Calculate the battery current ripple rate γ; Where, ω2=4πf AC represents the angular velocity of the double frequency component; f AC Indicates the frequency of the grid voltage; R indicates the sum of the resistances of the battery and the DC side filter inductor; L indicates the inductance value of the DC side filter inductor, and C indicates the capacitance value of the bus capacitor; Module S1.2: Calculate the relative phase θ of the voltages of the two bridge arms in each phase; θ=arcsin(γ)(23) Module S1.3: Calculate the amplitudes V1 and V2 of the two bridge arms in each phase; Where ω=2πf AC is the angular velocity of the grid voltage fundamental frequency, V s is the phase voltage amplitude of the grid voltage, I s is the amplitude of the grid current, L AC is the inductance value of the AC side filter inductor; In the module S2, Module S2.1: Obtain the current given value of the dq rotating coordinate system according to the reactive power required by the high-voltage direct-mounted energy storage system and Module S2.2: Three-phase output current i of cascaded H-bridge converter a 、i b 、i c The actual current value i in the dq rotating coordinate system is obtained by abc / dq vector transformation and the phase-locking angle theta d and i q ; Module S2.3: d-axis current setpoint The actual value of the d-axis current i d The difference is negative after passing through the PI controller and then cross-decoupled with the d-axis component ωL AC i q Add them together and add them to the actual value of the d-axis voltage u d The sum is used to obtain the d-axis voltage given value Q-axis current set value The actual value of the q-axis current i q The difference is negative after passing through the PI controller and then cross-decoupled with the q-axis component 2πf AC L AC i d Subtract, and then add to the actual value of the q-axis voltage u q The sum is used to obtain the q-axis voltage given value Module S2.4: Voltage setpoint The three-phase output voltage given value of the cascaded H-bridge converter is obtained by dq / abc vector transformation and phase-locking angle theta Module S2.5: If the high-voltage direct-mounted energy storage system generates pure inductive reactive power, the first phase θ of the jth phase is obtained. j1 , the second phase θ j2 : Among them, φ ij is the phase of the jth phase current, j = A, B, C; θ represents the relative phase of the voltages of the two bridge arms; If the high-voltage direct-mounted energy storage system generates pure capacitive reactive power, the first phase θ of the jth phase is obtained. j1 , the second phase θ j2 : Module S2.6: Calculate the battery state of charge SOC of the first bridge arm of phase j j1 and the battery state of charge SOC of the second bridge arm j2 The battery state of charge SOC of the jth phase j The difference between ΔSOC j1 =SOC j1 -SOC j ,ΔSOC j2 =SOC j2 -SOC j When the state is the voltage phase of the first bridge arm of the jth phase Equal to the first phase θ of the jth phase j1 , the voltage phase of the second bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 , if ΔSOC j1 When the set lower limit is reached, the state changes to the voltage phase of the first bridge arm of the jth phase. Equal to the second phase θ of the jth phase j2 , the voltage phase of the second bridge arm of the jth phase is equal to the first phase θ of the jth phase j1 ; When the state is the voltage phase of the first bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 , the voltage phase of the second bridge arm of the jth phase Equal to the first phase θ of the jth phase j1 , if ΔSOC j2 When the set lower limit is reached, the state changes to the voltage phase of the first bridge arm of the jth phase. Equal to the first phase θ of the jth phase j1 , the voltage phase of the second bridge arm of the jth phase Equal to the second phase θ of the jth phase j2 ; Module S2.7: Calculate the given value of the voltage of the first bridge arm of phase j and the given value of the voltage of the second bridge arm of the jth phase In the module S3, Module S3.1: Sampling to obtain the battery state of charge and capacitor voltage of each power module in each phase, sorting the battery state of charge of each power module in the first bridge arm and the second bridge arm in each phase, and calculating the average value of the capacitor voltage of the power module in the first bridge arm and the second bridge arm in each phase; Module S3.2: Use the given value of the voltage of the first bridge arm of the jth phase of the cascaded H-bridge converter and the given value of the voltage of the second bridge arm of the jth phase Divide by the average value of the power module capacitor voltage in the first bridge arm and the second bridge arm in each phase, and calculate the number of power modules required in the first bridge arm and the second bridge arm in the three-phase cascaded H-bridge converter Among them, round() is the nearest integer function. is the average value of the capacitor voltage of the first bridge arm power module of phases A, B, and C, is the average value of the capacitor voltage of the second bridge arm power module of the three phases A, B, and C; Module S3.3: The output current to the grid side is the phase current i x , x=a, b, c positive direction, when the phase current i x When the direction is positive, the number of power modules required in the first bridge arm and the second bridge arm of the three-phase When y=1,2 is also positive, the bridge arm is put into operation from high to low according to the battery charge state. Power modules, put into The power modules output positive level, and the other power modules output zero level; When the phase current i x When the direction is positive, the number of power modules required in the first bridge arm and the second bridge arm of the three-phase When it is negative, the bridge arm is put into operation from low to high according to the battery charge state. Power modules, put into The power modules output negative level, and the other power modules output zero level; When the phase current i x When the direction is negative, the number of power modules required for the first bridge arm and the second bridge arm of the three-phase When it is negative, the bridge arm is put into operation from high to low according to the battery charge state. Power modules, put into The power modules output negative level, and the other power modules output zero level; When the phase current i x When the direction is negative, the number of power modules required for the first bridge arm and the second bridge arm of the three-phase When the battery is positive, the bridge arm is put into operation from low to high according to the battery charge state. Power modules, put into The power modules output positive level, and the other power modules output zero level.

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