An Electrochemical Energy Storage Inverter Voltage Regulation System and Control Method

Abstract

The present invention discloses an electrochemical energy storage converter voltage regulation system and a control method, belonging to the technical field of power systems. The electrochemical energy storage converter voltage regulation system includes a measurement module, a battery cabinet SOC equivalent calculation module, an energy storage reactive power calculation module, a voltage regulation mode judgment module, a power distribution module, etc. The control method includes: after voltage fluctuations occur, when the reactive power compensation demand of the power system is less than the current maximum reactive power capacity of the energy storage, an equal margin distribution strategy based on the maximum reactive power is adopted; when the reactive power compensation demand of the power system is greater than the current maximum reactive power capacity of the energy storage, a load shedding voltage regulation strategy considering the equivalent SOC is adopted; the load shedding voltage regulation strategy considering the equivalent SOC is: calculating the equivalent SOC values of each battery cabinet and determining the PCS load shedding priority, and adjusting the active power and reactive power commands of each PCS controller based on the energy storage load shedding method to maximize the excavation of the reactive power capacity of the energy storage system. The present invention makes full use of the cooperative control ability of multiple energy storage converters to enhance the voltage regulation effect of the energy storage system and can ensure the voltage stability of new energy power stations.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to an electrochemical energy storage converter voltage regulation system and a control method thereof. Background Art

[0002] Due to the large-scale access of new energy, the problems of power system frequency and voltage stability are prominent, and new technical means are urgently needed to participate in the stable control of the power grid. With many characteristics such as short construction period, strong response ability, and wide application, electrochemical energy storage plays an increasingly important role in the power system.

[0003] For new energy power stations, especially offshore wind farms, due to the long submarine cable connection to the onshore power grid, the voltage stability problem has always been prominent. In response to this problem, current research rarely involves the voltage regulation problem of the wind energy storage system. Summary of the Invention

[0004] The technical objective of the present invention is to construct an electrochemical energy storage converter voltage regulation system and a control method for system voltage stability in view of the insufficient excavation of the voltage regulation ability of the current energy storage system and the problem of coordinated and stable control of multiple energy storage converters; this method preferentially adopts an equal margin distribution strategy based on the maximum reactive power, and when the reactive power demand of the system is large, a load shedding voltage regulation strategy considering the equivalent SOC is adopted. This strategy takes into account the SOC of the battery cluster and the active load shedding ability, can fully exploit the reactive power capacity of the energy storage system, and ensure the voltage stability of the new energy power station.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A control method for an electrochemical energy storage converter voltage regulation system, which is applied to a power system connected to a new energy power station and an electrochemical energy storage system. The energy storage system includes a plurality of battery cabinets, each battery cabinet is connected to an energy storage converter, and the electric energy provided by it is connected to the power system through the energy storage converter. The method is characterized in that it includes the following steps:

[0007] Step S1, detecting the voltage fluctuation at the grid connection point of the new energy power station and determining the operation mode of the energy storage system:

[0008] When there is no voltage fluctuation signal at the grid connection point of the new energy power station, control the energy storage system to operate in a zero reactive power mode, that is, the energy storage system does not emit reactive power;

[0009] When it is detected that a voltage fluctuation signal occurs at the grid connection point of the new energy power station and the voltage fluctuation value is within a preset reasonable range, send an instruction to the energy storage system to enter the reactive power compensation mode to optimize the power of the power system, and then enter step S2;

[0010] If the voltage fluctuation value is not within the preset reasonable range, then control the energy storage system to enter the fault ride-through mode or the off-grid state;

[0011] Step S2: Compare the reactive power compensation demand Q generated by the voltage fluctuation at the grid connection point of the new energy power plant in the current operating state of the power system r with the maximum reactive power output capacity Q of the energy storage system s1 to determine the strategy for the energy storage system to participate in power optimization in the reactive power compensation mode:

[0012] When the reactive power compensation demand Q of the power system r is less than or equal to the maximum reactive power output capacity Q of the current energy storage system s1 , adopt the equal margin distribution strategy based on the maximum reactive power. At this time, the reactive power command value Q obtained by each energy storage converter of the energy storage system PCSm_r is as follows:

[0013]

[0014] In the above formula, Q PCSm_max is the upper limit value of the reactive power of a single energy storage converter;

[0015] When the reactive power compensation demand Q of the power system r is greater than the maximum reactive power output capacity Q of the current energy storage system s1 , adopt the load shedding and voltage regulation strategy considering the equivalent SOC;

[0016] The load shedding and voltage regulation strategy considering the equivalent SOC is as follows: Select all or part of the battery cabinets to participate in power optimization. Based on the principle that the larger the equivalent SOC value, the higher the load shedding priority, determine the load shedding priority of the corresponding energy storage converter based on the equivalent SOC value of the battery cabinet, and dynamically adjust the active power and reactive power commands of the controller of the corresponding energy storage converter in the way of energy storage load shedding.

[0017] On the basis of the above scheme, further improved or optimized schemes also include:

[0018] Furthermore, in step S2:

[0019] The maximum reactive power output capacity Q of the energy storage system s1 is obtained through the following formula:

[0020]

[0021] In the above formula, M is the total number of battery cabinets included in the energy storage system;

[0022] The upper limit value Q of the reactive power of a single energy storage converter PCSm_max is obtained according to the capacity limit of a single energy storage converter, and the calculation method is as follows:

[0023]

[0024] In the above formula, S PCS is the apparent power of a single energy storage converter, and P PCSm_ref is the active power command value after the energy storage system participates in the active power balance of the power system. P PCSm_ref = P PCSm + k(SOC ref - SOC m ), where P PCSm is the active power command value of the m-th energy storage converter before load shedding, that is, the initial value of the active power. SOC ref is the SOC reference value corresponding to P PCSm_ref , and SOC m is the SOC reference value corresponding to P PCSm . k m is the energy storage active droop coefficient;

[0025] Among them, SOC m is obtained by the following formula:

[0026]

[0027] SOC L ≤ SOC x ≤ SOC H (5)

[0028] In the above formula, SOC mx is the equivalent SOC value of the x-th battery cluster, SOC my is the SOC value of the y-th battery cell. X is the number of battery clusters in a single battery cabinet, and Y is the number of battery cells included in a single battery cluster. SOC L and SOC H are the lower limit and upper limit of the state of charge of a single battery cell, respectively.

[0029] Furthermore, in step S2, the execution process of the load shedding and voltage regulation strategy considering the equivalent SOC includes the following steps:

[0030] First, select the battery cabinets with equivalent SOC values in a reasonable range to participate in power optimization compensation. The maximum reactive power support Q s2 of the energy storage system is:

[0031]

[0032] In the formula, η takes 1 or 0. When η takes 1, it means that all or part of the battery cabinets participate in power optimization, and A is the number of battery cabinets participating in power optimization. When η takes 0, it means that all battery cabinets do not participate in power optimization. At this time, Q s2 = Q s1 ; P PCSm_r is the active power command value of the m-th energy storage converter after load shedding, PPCSm_max is the upper limit of the active power of the m-th energy storage converter;

[0033] The active power shedding amount is:

[0034]

[0035] After that, an intelligent optimization algorithm is adopted, with the maximum reactive power support Q of the energy storage system s2 maximum and the active power shedding amount P de minimum as the objectives, and the double-objective solution of formulas (6) and (7) is carried out to obtain the reactive power command value Q of the energy storage converter corresponding to each battery cabinet participating in power optimization PCSm_r and the active power command value P PCSm_r , and the constraint conditions for the solution include the reasonable range of the equivalent SOC value of the battery cabinet, the apparent power limit of the energy storage converter, and the preset energy storage shedding limit;

[0036] Finally, according to the principle that the larger the equivalent SOC value, the higher the shedding priority, the shedding order of the energy storage converters of each battery cabinet participating in optimization is determined.

[0037] Furthermore, in the execution process of the load shedding and voltage regulation strategy considering the equivalent SOC, the battery cabinets with the equivalent SOC value in the interval [0.2, 0.8] are selected to participate in power optimization compensation.

[0038] Furthermore, in step S1, the preset reasonable range of the voltage fluctuation value U P is greater than or equal to 0.9 p.u. and less than or equal to 1.1 p.u., where p.u. represents the per-unit value.

[0039] Furthermore, the intelligent optimization algorithm is one of the whale optimization algorithm, the grey wolf optimization algorithm, or the ant colony optimization algorithm.

[0040] Furthermore, when using the whale optimization algorithm to solve formulas (6) and (7), first set the whale population size and the number of iterations, then map the whale population control variables to the reactive power of each energy storage converter, then establish an enclosure, hunting, and searching prey model based on the active power / reactive power optimization, and finally screen the optimal solution from the Pareto solution set to obtain the maximum reactive power support Q of the energy storage s2 , where the active power / reactive power optimization means that Q s2 is maximum and the active power shedding amount is minimum. An electrochemical energy storage converter voltage regulation system applying the control method as described above, characterized in that it includes a measurement module, a battery cabinet SOC equivalent calculation module, an energy storage reactive power calculation module, a voltage regulation mode judgment module, and a power distribution module;

[0041] The measurement module is used to detect the voltage at the grid connection point of the new energy power plant, the active power and reactive power of the energy storage converter, and the SOC value of the battery unit;

[0042] The signal input end of the battery cabinet SOC equivalent calculation module is connected to the signal output end of the measurement module, and is used to determine the equivalent SOC value of each battery cabinet of the energy storage system. Its calculation equation is:

[0043]

[0044] SOC L ≤SOC x ≤SOC H

[0045] In the formula, SOC mx is the equivalent SOC value of the xth battery cluster, SOC my is the SOC value of the yth battery unit, X is the number of battery clusters in a single battery cabinet, Y is the number of battery units included in a single battery cluster respectively, SOC L and SOC H are the lower limit value and upper limit value of the state of charge of a single battery unit respectively;

[0046] The signal input end of the energy storage reactive power calculation module is respectively connected to the signal output ends of the measurement module and the battery cabinet SOC equivalent calculation module, and is used to determine the maximum reactive power Q s1 of the energy storage system under the current operating state. The implementation process is as follows:

[0047] First, calculate the active power of a single energy storage converter according to the equivalent SOC value:

[0048] P PCSm_ref =P PCSm +k(SOC ref -SOC m )

[0049] In the formula, P PCSm_ref is the active power command value after the energy storage system participates in the active power balance of the power system, P PCSm is the initial active power value of the energy storage converter m, SOC ref is the SOC reference value corresponding to the active power command value, SOC m is the SOC reference value corresponding to the initial active power value, k m is the energy storage active droop coefficient;

[0050] According to the capacity limit of the energy storage converter, the upper limit value of the reactive power of a single energy storage converter can be obtained:

[0051]

[0052] In the formula, S PCS is the apparent power of the energy storage converter;

[0053] Then the current maximum reactive power output capacity Q of the entire energy storage system s1 is:

[0054]

[0055] The signal input end of the voltage regulation mode judgment module is connected to the signal output ends of the measurement module and the energy storage reactive power calculation module, and is used to determine the reactive power compensation demand Q of the power system r and the current maximum reactive power output capacity Q of the energy storage system s1 , and compare the magnitude relationship between the two, and determine the reactive power operation instruction of the energy storage system according to the comparison result, including the zero reactive power mode, the equal margin distribution strategy mode based on the maximum reactive power in the reactive power compensation mode, and the load shedding voltage regulation strategy mode considering the equivalent SOC;

[0056] The signal input end of the power distribution module is connected to the signal output end of the voltage regulation mode judgment module. After receiving the reactive power operation instruction sent by the voltage regulation mode judgment module, the power distribution module converts the corresponding reactive power distribution result into a corresponding control instruction and inputs it into the controllers of each energy storage converter.

[0057] The beneficial effects of the present invention are:

[0058] Based on the voltage regulation problem of offshore new energy power stations, the present invention fully considers the four-quadrant operation characteristics of the energy storage system converter, and through the coordinated control of multiple energy storage converters and the load shedding voltage regulation ability, ensures that the energy storage participates in the system reactive power balance and voltage stability control. Since the state of charge SOC of each battery cluster and battery unit in the energy storage system is different, it is necessary to take into account the differences in the SOC states of the battery clusters connected to different energy storage converter PCSs, and dynamically adjust the active and reactive power commands of the PCS, so as to improve the energy storage voltage regulation ability and ensure the stable operation of the system. Description of the Drawings

[0059] Attached Figure 1 is the flow chart of the control method of the voltage regulation system of the electro-chemical energy storage converter of the present invention;

[0060] Attached Figure 2 is the topology diagram of the grid-connected system of an offshore wind farm containing an electro-chemical energy storage system;

[0061] Attached Figure 3 is the droop system curve of the PCS power and SOC;

[0062] Attached Figure 4 is the block diagram of the load shedding voltage regulation strategy considering the equivalent SOC. Detailed Embodiments

[0063] The present invention will now be further described in detail with reference to the accompanying drawings and specific embodiments.

[0064] Embodiment 1:

[0065] A control method for a voltage regulation system of an electro - chemical energy storage converter is applied to a power system connected to a new - energy power plant and an electro - chemical energy storage system. The electro - chemical energy storage system includes multiple power conversion systems (PCS), each power conversion system is connected to a battery cabinet, and the electric energy provided by it is connected to the power system through the power conversion system. Taking a wind farm as an example, the technical solution of this embodiment is described as follows. The control method of this embodiment includes the following steps:

[0066] Step S1: Detect the voltage fluctuation at the grid - connection point of the wind farm and determine the operation mode of the energy storage system:

[0067] When the power system is stable and no voltage fluctuation signal is detected at the grid - connection point of the wind farm, control the energy storage system to operate in a zero - reactive - power mode, that is, the energy storage system does not emit reactive power;

[0068] When a voltage fluctuation signal is detected at the grid - connection point of the wind farm and the voltage fluctuation value is in the range of greater than or equal to 0.9 p.u. and less than or equal to 1.1 p.u., send an instruction to the energy storage system to enter the reactive - power compensation mode to optimize the power of the power system, and then enter the next step, where p.u. is the per - unit value;

[0069] If the voltage fluctuation value is less than 0.9 p.u. or greater than 1.1 p.u., control the energy storage system to enter the fault - ride - through mode or the off - grid state.

[0070] Step S2: Compare the reactive - power compensation demand Q r generated by the power system due to the voltage fluctuation at the grid - connection point of the wind farm in the current operating state s1 and the maximum reactive - power generation capacity Q

[0071] of the energy storage system to determine the strategy for the energy storage system to participate in power optimization in the reactive - power compensation mode: s1 The maximum reactive - power generation capacity Q

[0072]

[0073] of the energy storage system is obtained through the following formula: PCSm_max In the above formula, M is the total number of power conversion systems included in the energy storage system, Q

[0074]

[0075] In the above formula, SPCS is the apparent power of a single energy storage converter, P PCSm_ref is the active power command value after the energy storage system participates in the active power balance of the power system, P PCSm_ref = P PCSm + k(SOC ref - SOC m ), P PCSm is the active power command value before load shedding of the m-th energy storage converter, that is, the initial value of the active power, SOC ref is the SOC reference value corresponding to P PCSm_ref , SOC m is the SOC reference value corresponding to P PCSm , k m is the energy storage active droop coefficient.

[0076] Among them, SOC m is obtained by the following formula:

[0077]

[0078] SOC L ≤ SOC x ≤ SOC H

[0079] In the above formula, SOC mx represents the equivalent SOC value of the x-th battery cluster, SOC my represents the SOC value of the y-th battery cell, X is the number of battery clusters in a single battery cabinet, Y is the number of battery cells (or single cells) included in a single battery cluster, SOC L and SOC H are the lower and upper limit values of the state of charge of a single battery cell respectively.

[0080] When the reactive power compensation demand Q of the power system r is less than or equal to the maximum reactive power output capacity Q of the current energy storage system s1 , an equal margin distribution strategy based on the maximum reactive power is adopted. At this time, the reactive power command value Q obtained by each energy storage converter of the energy storage system PCSm_r is as follows:

[0081]

[0082] When the reactive power compensation demand Q of the power system r is greater than the maximum reactive power output capacity Q of the current energy storage system s1 , a load shedding and voltage regulation strategy considering the equivalent SOC is adopted.

[0083] The load shedding and voltage regulation strategy considering the equivalent SOC is as follows: Select all or part of the battery cabinets to participate in power optimization. Based on the principle that the larger the equivalent SOC value, the higher the load shedding priority, determine the load shedding priority of each energy storage converter based on the equivalent SOC value of the battery cabinet corresponding to a single energy storage converter. Then, consider dynamically adjusting the active power and reactive power commands of the controller of the corresponding energy storage converter in the way of energy storage load shedding. The specific implementation process is as follows:

[0084] First, select the battery cabinets with equivalent SOC values in the range of [0.2, 0.8] to participate in power optimization compensation. The maximum reactive power support Q of the energy storage system s2 is:

[0085]

[0086] In the formula, η takes 1 or 0. When η takes 1, it means all or part of the battery cabinets participate in power optimization, A is the number of PCSs participating in power optimization, and when η takes 0, it means all battery cabinets do not participate in power optimization. At this time, Q s2 = Q s1 ; P PCSm_r is the active power command value after load shedding of the m-th energy storage converter, and P PCSm_max is the upper limit value of the active power of the m-th energy storage converter.

[0087] The active power load shedding amount is:

[0088]

[0089] In the formula, P PCSm is the active power command value of the m-th energy storage converter before load shedding.

[0090] After that, through the intelligent optimization algorithm, with the maximum reactive power support Q of the energy storage system s2 being the maximum (or the maximum reactive power output of the energy storage system) and the minimum active power load shedding amount P de as the objectives, perform a two-objective solution for formulas (6) and (7) to obtain the reactive power command value Q PCSm_r and the active power command value P PCSm_r of the energy storage converter corresponding to each battery cabinet participating in power optimization, so that when the energy storage system provides the maximum reactive power support Q s2 , it has the smallest possible active power load shedding amount P de . The constraints of the above solution include the reasonable range of the equivalent SOC value of the battery cabinet, the apparent power limit of the PCS, and the energy storage load shedding limit.

[0091] The reasonable range of the equivalent SOC value of the battery cabinet is generally [0, 1]. When the equivalent SOC = 0, it means the battery is completely discharged, and when the equivalent SOC = 1, it means the battery is fully charged. Considering that the battery cabinet with over-full charge or nearly exhausted power has weak adjustment ability, in this embodiment, the reasonable range of the equivalent SPC value of the battery cabinet participating in the adjustment is set to [0.2, 0.8].

[0092] The intelligent optimization algorithm can adopt existing whale optimization algorithm, grey wolf optimization algorithm, ant colony optimization algorithm, etc. Taking the whale optimization algorithm as an example, a double-objective optimization model based on the whale optimization algorithm is established. First, the scale of the whale population and the number of iterations are set, then the control variables of the whale population are mapped to the reactive power of each energy storage converter, and then a surrounding, hunting and searching prey model based on the optimal active power / reactive power (i.e., Q s2 maximum and minimum active power load shedding amount) is established. Finally, the optimal solution is selected from the Pareto solution set to obtain the maximum reactive power support amount Q s2 .

[0093] The intelligent optimization algorithm includes but is not limited to the above optimization algorithms. Since the above optimization algorithms are all existing technologies, those skilled in the art are familiar with their principles and usage. Under the condition of determining the optimization goal, those skilled in the art can know how to use the above algorithms to achieve the purpose of double-objective optimization of formulas (6) and (7), and thus will not be elaborated here.

[0094] Finally, according to the current reactive power compensation demand Q r , the load shedding order of the energy storage converters connected to each battery cabinet is determined according to the principle that the larger the equivalent SOC value of the battery cabinet, the higher the load shedding priority. Finally, each energy storage converter reduces the load in turn to improve the reactive power output ability of the energy storage system until the total reactive power output by the energy storage system meets the voltage regulation demand of the power system and the voltage at the grid connection point of the wind farm is restored to stability.

[0095] Embodiment 2:

[0096] An electro-chemical energy storage converter voltage regulation system applying the control method described in Embodiment 1 includes a measurement module, a battery cabinet SOC (state of charge) equivalent calculation module, an energy storage reactive power calculation module, a voltage regulation mode judgment module, and a power distribution module.

[0097] The measurement module is used to detect and measure the voltage at the grid connection point of the wind farm, the active power and reactive power of the energy storage converter (PCS), and the SOC value of the battery unit;

[0098] The signal input end of the battery cabinet SOC equivalent calculation module is connected to the signal output end of the measurement module, and is used to determine the equivalent SOC value of each battery cabinet of the energy storage system. Its calculation equation is:

[0099]

[0100] SOC L ≤SOC x ≤SOC H

[0101] Wherein, SOC mx is the equivalent SOC value of the x-th battery cluster, SOC my is the SOC value of the y-th battery cell, X is the number of battery clusters in a single battery cabinet, Y is the number of battery cells (or single cells) included in a single battery cluster, SOC L and SOC H are the lower limit value and the upper limit value of the state of charge of a single battery cell, respectively.

[0102] The signal input end of the energy storage reactive power calculation module is respectively connected to the signal output ends of the measurement module and the battery cabinet SOC equivalent calculation module, and is used to determine the maximum reactive power value Q of the energy storage system under the current operating state s1 , and its implementation process is as follows:

[0103] First, it is necessary to calculate the active power of a single energy storage converter according to the equivalent SOC:

[0104] P PCSm_ref = P PCSm + k(SOC ref - SOC m )

[0105] Wherein, P PCSm_ref is the active power command value after the energy storage system participates in the active power balance of the power system, P PCSm is the initial value of the active power of the m-th energy storage converter, SOC ref is the SOC reference value corresponding to the active power command value, SOC m is the SOC reference value corresponding to the initial value of the active power, and k m is the energy storage active power droop coefficient.

[0106] According to the capacity limit of the energy storage converter, the upper limit value of the reactive power of a single energy storage converter can be obtained:

[0107]

[0108] Wherein, S PCS is the apparent power of the energy storage converter.

[0109] Then the current maximum reactive power output capacity Q of the entire energy storage system s1 is:

[0110]

[0111] The signal input end of the voltage regulation mode judgment module is connected to the signal output ends of the measurement module and the energy storage reactive power calculation module, and is used to determine the reactive power compensation demand Q of the power system. r and the maximum reactive power output capacity Q of the current energy storage system s1 , and compare the magnitude relationship between the two, and determine the reactive power operation instruction of the energy storage system according to the comparison result, including the zero reactive power mode, the equal margin distribution strategy mode based on the maximum reactive power in the reactive power compensation mode, and the load reduction voltage regulation strategy mode considering the equivalent SOC.

[0112] The signal input end of the power distribution module is connected to the signal output end of the voltage regulation mode judgment module. After receiving the reactive power operation instruction sent by the voltage regulation mode judgment module, the power distribution module converts the corresponding reactive power distribution result into a corresponding control instruction and inputs it into the controllers of each energy storage converter.

[0113] The above is only the preferred implementation mode of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art in this technical field, several improvements and refinements made without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A control method for a voltage regulation system of an electro-chemical energy storage converter, which is applied to a power system connected to a new energy power plant and an electro-chemical energy storage system. The energy storage system includes multiple battery cabinets, each battery cabinet is connected to an energy storage converter, and the electric energy provided by the energy storage converter is connected to the power system. It is characterized in that, The method includes the following steps: Step S1: Detect the voltage fluctuation at the grid connection point of the new energy power station and determine the operation mode of the energy storage system: When there is no voltage fluctuation signal at the grid connection point of the new energy power station, control the energy storage system to operate in the zero reactive power mode, that is, the energy storage system does not emit reactive power; When it is detected that a voltage fluctuation signal occurs at the grid connection point of the new energy power station and the voltage fluctuation value is within the preset reasonable range, send an instruction to the energy storage system to enter the reactive power compensation mode to optimize the power of the power system, and then enter step S2; If the voltage fluctuation value is not within the preset reasonable range, control the energy storage system to enter the fault ride-through mode or the off-grid state; Step S2: Compare the reactive power compensation demand Q generated by the voltage fluctuation at the grid connection point of the new energy power plant in the current operating state of the power system r with the maximum reactive power output capacity Q of the energy storage system s1 , and determine the strategy for the energy storage system to participate in power optimization in the reactive power compensation mode: When the reactive power compensation demand Q of the power system r is less than or equal to the maximum reactive power output capacity Q of the current energy storage system s1 at this time, an equal margin allocation strategy based on the maximum reactive power is adopted, and the reactive power command value Q obtained by each energy storage converter of the energy storage system PCSm_r is as follows: In the above formula, Q PCSm_max is the upper limit of the reactive power of a single energy storage converter; When the reactive power compensation demand Q of the power system r is greater than the maximum reactive power output capacity Q of the current energy storage system s1 a load shedding voltage regulation strategy considering the equivalent SOC is adopted; The load shedding voltage regulation strategy considering the equivalent SOC is as follows: Select all or part of the battery cabinets to participate in power optimization. Based on the principle that the larger the equivalent SOC value, the higher the load shedding priority, determine the load shedding priority of the corresponding energy storage converter based on the equivalent SOC value of the battery cabinet, and dynamically adjust the active power and reactive power commands of the controller of the corresponding energy storage converter in the way of energy storage load shedding.

2. The control method of a voltage regulation system for an electrochemical energy storage converter according to claim 1, characterized in that, In step S2: The maximum reactive power output capacity Q of the energy storage system s1 is obtained through the following formula: In the above formula, M is the total number of battery cabinets included in the energy storage system; The upper limit value Q of the reactive power of a single energy storage converter PCSm_max , obtained according to the capacity limit of a single energy storage converter, and the calculation method is as follows: In the above formula, S PCS is the apparent power of a single energy storage converter, and P PCSm_ref is the active power command value after the energy storage system participates in the active power balance of the power system. P PCSm_ref = P PCSm + k(SOC ref - SOC m ), where P PCSm is the active power command value of the m-th energy storage converter before load shedding, SOC ref is the SOC reference value corresponding to P PCSm_ref , SOC m is the SOC reference value corresponding to P PCSm , and k m is the energy storage active droop coefficient; Among them, SOC m is calculated by the following formula: SOC L ≤ SOC x ≤ SOC H (5) In the above formula, SOC mx is the equivalent SOC value of the x-th battery cluster, SOC my is the SOC value of the y-th battery cell, X is the number of battery clusters in a single battery cabinet, Y is the number of battery cells included in a single battery cluster, SOC L and SOC H are the lower limit value and the upper limit value of the state of charge of a single battery cell, respectively.

3. The control method of a voltage regulation system for an electro-chemical energy storage converter according to claim 2, characterized in that, In step S2, the execution process of the load shedding voltage regulation strategy considering the equivalent SOC includes the following steps: First, select the battery cabinets with equivalent SOC values in a reasonable range to participate in power optimization compensation. The maximum reactive power support of the energy storage system Q s2 is as follows: Where η takes 1 or 0. When η takes 1, it means that all or part of the battery cabinets participate in power optimization, A is the number of battery cabinets participating in power optimization. When η takes 0, it means that all battery cabinets do not participate in power optimization. At this time, Q s2 = Q s1 ; P PCSm_r is the active power command value after load reduction of the m-th energy storage converter, and P PCSm_max is the upper limit value of the active power of the m-th energy storage converter; The active power load shedding amount is: After that, an intelligent optimization algorithm is adopted to take the maximum reactive power support Q of the energy storage system s2 maximum and the active power shedding P de minimum as the objectives, and the bi-objective solution of formulas (6) and (7) is carried out to obtain the reactive power command value Q of the energy storage converter corresponding to each battery cabinet participating in power optimization PCSm_r and the active power command value P PCSm_r . The constraint conditions for the solution include the reasonable range of the equivalent SOC value of the battery cabinet, the apparent power limit of the energy storage converter, and the preset energy storage shedding limit; Finally, determine the load shedding order of the energy storage converters of each battery cabinet participating in the optimization according to the principle that the larger the equivalent SOC value, the higher the load shedding priority.

4. The control method of a voltage regulation system for an electro-chemical energy storage converter according to claim 3, wherein: The execution process of the load shedding voltage regulation strategy considering the equivalent SOC selects the battery cabinets with the equivalent SOC value in the range of [0.2, 0.8] to participate in power optimization compensation.

5. The control method of a voltage regulation system for an electro-chemical energy storage converter according to claim 1, characterized in that: In step S1, the voltage fluctuation value U P has a preset reasonable range of greater than or equal to 0.9 p.u. and less than or equal to 1.1 p.u., where p.u. represents per-unit value.

6. The control method of a voltage regulation system for an electrochemical energy storage converter according to claim 3, characterized in that: The intelligent optimization algorithm is one of the whale optimization algorithm, the grey wolf optimization algorithm or the ant colony optimization algorithm.

7. The control method of a voltage regulation system for an electro-chemical energy storage converter according to claim 6, characterized in that, When using the whale optimization algorithm to solve formulas (6) and (7), first set the scale of the whale population and the number of iterations. Then, map the control variables of the whale population to the reactive power of each energy storage converter. Next, establish models for surrounding, hunting, and searching for prey based on the optimal active power / reactive power. Finally, screen the optimal solution from the Pareto solution set to obtain the maximum reactive power support Q of the energy storage s2 , where the optimal active power / reactive power means Q s2 is the maximum and the active power load shedding amount P de is the minimum.

8. An electrochemical energy storage converter voltage regulation system applying the control method as described in claim 1, characterized in that, It includes a measurement module, a battery cabinet SOC equivalent calculation module, an energy storage reactive power calculation module, a voltage regulation mode judgment module and a power distribution module; The measurement module is used to detect and measure the voltage at the grid connection point of the new energy power station, the active power and reactive power of the energy storage converter, and the SOC value of the battery unit; The signal input end of the battery cabinet SOC equivalent calculation module is connected to the signal output end of the measurement module, and is used to determine the equivalent SOC value of each battery cabinet of the energy storage system. Its calculation equation is: SOC L ≤SOC x ≤SOC H In the above formula, SOC mx is the equivalent SOC value of the xth battery cluster, SOC my is the SOC value of the yth battery cell, X is the number of battery clusters in a single battery cabinet, Y is the number of battery cells included in a single battery cluster, SOC L and SOC H are the lower limit value and upper limit value of the state of charge of a single battery cell, respectively; The signal input end of the energy storage reactive power calculation module is respectively connected to the signal output ends of the measurement module and the battery cabinet SOC equivalent calculation module, and is used to determine the maximum reactive power value Q of the energy storage system under the current operating state s1 , and the implementation process is as follows: First, calculate the active power of a single energy storage converter according to the equivalent SOC value: P PCSm_ref = P PCSm + k(SOC ref - SOC m ) In the above formula, P PCSm_ref is the active power command value after the energy storage system participates in the active power balance of the power system, P PCSm is the initial value of the active power of the energy storage converter m, SOC ref is the SOC reference value corresponding to the active power command value, SOC m is the SOC reference value corresponding to the initial value of the active power, k m is the energy storage active droop coefficient; According to the capacity limit of the energy storage converter, the upper limit value of the reactive power of a single energy storage converter can be obtained: Where S PCS is the apparent power of the energy storage converter; Then the current maximum reactive power output capacity Q of the entire energy storage system s1 is as follows: The signal input end of the voltage regulation mode judgment module is connected to the signal output ends of the measurement module and the energy storage reactive power calculation module, and is used to determine the reactive power compensation demand Q of the power system r and the maximum reactive power output capacity Q of the current energy storage system s1 , and compare the magnitude relationship between the two, and determine the reactive power operation instruction of the energy storage system according to the comparison result, including the zero reactive power mode, the equal margin allocation strategy mode based on the maximum reactive power amount in the reactive power compensation mode, and the load reduction voltage regulation strategy mode considering the equivalent SOC; The signal input end of the power distribution module is connected to the signal output end of the voltage regulation mode judgment module. After receiving the reactive power operation instruction sent by the voltage regulation mode judgment module, the power distribution module converts the corresponding reactive power distribution result into a corresponding control instruction and inputs it into the controller of each energy storage converter.

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