High-voltage cascade valve hall energy storage system and SOC balance control method thereof

Abstract

The invention relates to the technical field of energy storage systems, and discloses a high-voltage cascade valve hall energy storage system and an SOC balance control method thereof.In the system, a main controller receives SOC data from all energy storage modules and judges whether SOC imbalance occurs in bridge arms or not based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arms where the energy storage modules are located; based on the difference between the average SOC values of all the energy storage bridge arms in the phase units, whether SOC unbalance occurs between the bridge arms or not is judged; and if the SOC in the bridge arms is unbalanced or the SOC between the bridge arms is unbalanced, the main controller starts an SOC balance control strategy in the bridge arms or an SOC balance control strategy between the bridge arms. According to the invention, the SOC of the battery in the bridge arm and between the bridge arms is accurately controlled, and the electric quantity balance between each energy storage module and the bridge arm is ensured, so that the performance of the energy storage system is optimized, the service life of the battery is prolonged, the energy loss of the system is reduced, and the stability of the system is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and in particular to a high-pressure cascade valve hall energy storage system and a SOC balancing control method thereof. Background Art

[0002] In electrochemical energy storage systems, high-voltage cascade valve halls refer to facility areas dedicated to controlling, regulating and protecting the working environment of high-voltage energy storage modules or battery modules, especially when the battery voltage of high-voltage energy storage modules or energy storage units gradually increases and requires hierarchical management. High-voltage cascade valve halls usually involve precise control of the flow of gases and liquids (such as coolants) within the system to ensure that the battery system operates in a stable, safe and efficient environment.

[0003] High-voltage cascade energy storage technology has significant advantages in large-scale energy storage power stations, mainly in terms of high efficiency, economy, and safety. Compared with low-voltage energy storage, high-voltage cascade systems do not require step-up transformers and can be directly connected to high-voltage power grids (such as 6kV, 10kV, 35kV, 110kV and even higher voltage levels), greatly reducing system complexity and operating costs. In addition, high-voltage cascade energy storage systems have a small footprint and fast power response, avoiding the common parallel circulation and efficiency loss problems of low-voltage energy storage. The system efficiency is increased by 3% to 10%, effectively improving the economy and return on investment of the power station. With the advancement of battery technology, the market penetration rate of high-voltage cascade energy storage is expected to increase significantly in the future, becoming the mainstream technology in the field of large storage.

[0004] In the prior art, there is no effective solution for SOC balancing control of high-voltage cascade valve hall energy storage systems, especially for control methods involving SOC balancing within and between bridge arms. The SOC balancing control of high-voltage cascade energy storage systems mainly faces the following challenges:

[0005] 1. Imperfect balancing control methods: Although existing SOC balancing control methods can solve the SOC difference problem to a certain extent, these methods are less applicable in high-voltage cascade energy storage systems and cannot simultaneously meet the balancing requirements between multiple energy storage modules and bridge arms;

[0006] 2. Energy loss problem: Existing balancing control methods usually lead to certain energy loss, especially when passive balancing is adopted, the energy loss is more serious;

[0007] 3. High cost: Although active balancing solutions are accurate, they usually require a large number of power electronic devices, which increases the cost of the system.

[0008] Therefore, proposing a new control method to address the problem of SOC balancing control of a high-voltage cascade energy storage system becomes the research goal of the present invention. Summary of the invention

[0009] The purpose of the present invention is to provide a high-voltage cascade valve hall energy storage system and a SOC balancing control method thereof, which can ensure the balance of power between each energy storage module and the bridge arm by accurately controlling the battery SOC in and between the bridge arms, thereby optimizing the performance of the energy storage system, increasing the service life of the battery, reducing the system energy loss, and enhancing the stability of the system.

[0010] To achieve the above object, the present invention provides the following solutions:

[0011] A high-voltage cascade valve hall energy storage system comprises three phase units, wherein the three phase units are respectively connected to a three-phase AC power grid;

[0012] Each phase unit includes at least two energy storage bridge arms arranged in parallel, each energy storage bridge arm is connected in series with a reactor, the energy storage bridge arm includes a plurality of energy storage units arranged in series, each of the energy storage units includes an energy storage module and a power converter correspondingly connected to the energy storage module;

[0013] Each of the energy storage modules is equipped with a battery management system, which is used to monitor the SOC data of the energy storage module in real time and upload it to the main controller;

[0014] The main controller receives SOC data from each energy storage module, and judges whether SOC imbalance occurs within the bridge arm based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arm where the energy storage module is located, and judges whether SOC imbalance occurs between bridge arms based on the difference between the average SOC values ​​of each energy storage bridge arm in the phase unit; if SOC imbalance occurs within the bridge arm, the main controller starts the SOC balancing control strategy within the bridge arm, and if SOC imbalance occurs between bridge arms, the main controller starts the SOC balancing control strategy between bridge arms;

[0015] Among them, the main controller generates execution instructions based on the SOC balancing control strategy within the bridge arm or the SOC balancing control strategy between bridge arms, adjusts the working state of the power converters corresponding to different energy storage modules, adjusts the charging and discharging current of the energy storage module or the energy storage bridge arm, and realizes SOC balancing control.

[0016] Furthermore, the energy storage module is a flexible battery stack, which includes a plurality of battery clusters arranged in parallel, each battery cluster includes a plurality of battery PACKs arranged in series, and each of the battery PACKs is connected to a PACK controller.

[0017] Furthermore, the power converter is an H-bridge power module, comprising four fully-controlled semiconductor devices, and the four fully-controlled semiconductor devices form an H-bridge structure.

[0018] Furthermore, the fully-controlled semiconductor device adopts MOSFET or IGBT.

[0019] The present invention also provides a SOC balancing control method for a high-pressure cascade valve hall energy storage system, which is applied to any of the above-mentioned high-pressure cascade valve hall energy storage systems, comprising:

[0020] Real-time monitoring of the SOC data of each energy storage module;

[0021] Based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arm where the energy storage module is located, the SOC imbalance of the energy storage module is obtained. If the SOC imbalance of the energy storage module exceeds the set imbalance threshold, it is determined that the SOC imbalance in the bridge arm occurs, and the main controller starts the SOC balance control strategy in the bridge arm, adjusts the working state of the power converter corresponding to different energy storage modules, and adjusts the charge and discharge current of the energy storage module to achieve SOC balance in the bridge arm;

[0022] Based on the difference between the average SOC values ​​of each energy storage bridge arm in the phase unit, the relative size of the average SOC value of each energy storage bridge arm is determined. If the average SOC values ​​of each energy storage bridge arm are not equal, it is judged that the SOC imbalance between the bridge arms occurs. The main controller starts the SOC balancing control strategy between the bridge arms, adjusts the working status of the power converter corresponding to different energy storage modules, and adjusts the charging and discharging current of the energy storage bridge arm to achieve SOC balance between the bridge arms.

[0023] Furthermore, the SOC imbalance of the energy storage module is obtained based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arm where the energy storage module is located, which specifically includes:

[0024] Energy storage module

[0025] Among them, SOC i Represents the SOC data of energy storage module i, Indicates the average SOC value of the energy storage bridge arm where the energy storage module is located.

[0026] Furthermore, the SOC balancing control strategy in the bridge arm specifically includes:

[0027] SOC balance in the bridge arm under discharge conditions:

[0028] If the SOC data of a certain energy storage module is lower than the average SOC value of the energy storage bridge arm where the energy storage module is located, the output voltage of the energy storage module is reduced by controlling the power converter corresponding to the energy storage module, thereby reducing the discharge current of the energy storage module;

[0029] If the SOC data of a certain energy storage module is higher than the average SOC value of the energy storage bridge arm where the energy storage module is located, the output voltage of the energy storage module is increased by controlling the power converter corresponding to the energy storage module, thereby increasing the discharge current of the energy storage module;

[0030] SOC balance in the bridge arm under charging conditions:

[0031] If the SOC data of a certain energy storage module is lower than the average SOC value of the energy storage bridge arm where the energy storage module is located, the input voltage of the energy storage module is increased by controlling the power converter corresponding to the energy storage module, thereby increasing the charging current of the energy storage module;

[0032] If the SOC data of a certain energy storage module is higher than the average SOC value of the energy storage bridge arm where the energy storage module is located, the input voltage of the energy storage module is reduced by controlling the power converter corresponding to the energy storage module, thereby reducing the charging current of the energy storage module;

[0033] SOC balance in the bridge arm under standby or shutdown conditions:

[0034] The main controller adjusts the working state of the power converters corresponding to different energy storage modules. Through the adjustment of the power converters, a voltage difference is formed between the energy storage modules in the same bridge arm, generating a current in the bridge arm.

[0035] Among them, if the SOC data of a certain energy storage module is lower than the average SOC value of the energy storage bridge arm where the energy storage module is located, a current in the bridge arm is generated to charge the energy storage module, and the energy storage module obtains electricity from other energy storage modules to increase its SOC value; if the SOC data of a certain energy storage module is higher than the average SOC value of the energy storage bridge arm where the energy storage module is located, a current in the bridge arm is generated to discharge the energy storage module, and the energy storage module releases electricity to charge other energy storage modules in the energy storage bridge arm to reduce their SOC values.

[0036] Furthermore, the calculation formula of the current in the bridge arm is as follows:

[0037] I balance,i =K balance ΔSOC i

[0038] Among them, I balance,i Indicates the current in the bridge arm, K balance Indicates the proportionality coefficient of the current in the bridge arm, ΔSOC i Indicates the difference between the SOC data of energy storage module i and the average SOC value of the energy storage bridge arm where the energy storage module is located:

[0039]

[0040] in, Indicates the average SOC value of the energy storage bridge arm where the energy storage module is located;

[0041] When ΔSOC i >0, I balance,i is positive, indicating that the energy storage module is discharged; when ΔSOC i <0, I balance,i If it is negative, it means that the energy storage module is charged.

[0042] Furthermore, the bridge arm SOC balancing control strategy specifically includes:

[0043] In the case where each phase unit includes two energy storage bridge arms arranged in parallel, namely bridge arm A1 and bridge arm A2, the SOC mean value of the two energy storage bridge arms is calculated;

[0044] During the discharge process, if the SOC average value of one energy storage bridge arm is lower than the SOC average value of another energy storage bridge arm, the output voltage of the energy storage bridge arm is reduced, and the discharge current of the energy storage bridge arm is reduced;

[0045] During the charging process, if the SOC average value of a certain energy storage bridge arm is lower than the average SOC value of the phase unit where the energy storage bridge arm is located, the input voltage of the energy storage bridge arm is increased and the charging current of the energy storage bridge arm is increased; if the SOC data of a certain energy storage bridge arm is higher than the average SOC value of the phase unit where the energy storage bridge arm is located, the input voltage of the energy storage bridge arm is reduced and the charging current of the energy storage bridge arm is reduced; wherein, the average SOC value of the phase unit is the average value of the SOC average values ​​of all energy storage bridge arms in the phase unit;

[0046] Under standby or shutdown conditions, if the SOC average of one energy storage bridge arm is lower than the SOC average of another energy storage bridge arm, the main controller adjusts the working state of the power converter corresponding to each bridge arm to form a voltage difference between the energy storage bridge arm with a higher SOC average and the energy storage bridge arm with a lower SOC average, thereby driving the power to transfer from the energy storage bridge arm with a higher SOC average to the energy storage bridge arm with a lower SOC average, thereby achieving power balance between the energy storage bridge arms within the phase.

[0047] Furthermore, the calculation of the SOC mean of the two energy storage bridge arms specifically includes:

[0048] Assume that the SOC values ​​of each energy storage module in bridge arm A1 and bridge arm A2 are SOC i1 and SOC i2 , the SOC mean values ​​of bridge arm A1 and bridge arm A2 are:

[0049]

[0050] Among them, n 1 and n 2 are the numbers of energy storage modules in bridge arm A1 and bridge arm A2 respectively.

[0051] According to the specific embodiment provided by the present invention, the high-pressure cascade valve hall energy storage system and the SOC balancing control method thereof provided by the present invention disclose the following technical effects:

[0052] (1) Each energy storage module is connected to a power converter to control the energy storage module individually to achieve voltage regulation and thus adjust the corresponding charging and discharging current;

[0053] (2) Based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arm where the energy storage module is located, it is determined whether there is an SOC imbalance in the bridge arm; the SOC balancing control strategy in the bridge arm uses the SOC of the energy storage module as the control target to achieve dynamic balancing of the power of each energy storage module;

[0054] (3) Based on the difference between the average SOC values ​​of each energy storage bridge arm in the phase unit, it is determined whether there is an SOC imbalance between the bridge arms. The SOC balancing control strategy between the bridge arms accurately controls the charging and discharging power of each energy storage bridge arm to achieve energy balance between the bridge arms. This not only improves the control accuracy of the system, but also avoids the performance degradation between the bridge arms due to SOC imbalance, thereby ensuring the efficient operation and safety of the energy storage system.

[0055] In summary, the present invention realizes the SOC balanced control within the bridge arm and between the bridge arms of the high-voltage cascade valve hall energy storage system. Through a reasonable control strategy, the SOC of the energy storage module in each bridge arm and the SOC between the bridge arms are accurately adjusted to achieve the voltage and capacity balance of the entire energy storage system, improve the charging and discharging efficiency of the energy storage system, extend the battery life, reduce the risk of overcharging and over-discharging of the battery, and ensure the stability and efficiency of the energy storage system under various working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0057] Figure 1 This is a hardware topology diagram of the high-pressure cascade valve hall energy storage system according to an embodiment of the present invention;

[0058] Figure 2 The hardware topology diagram of the energy storage bridge arm of the embodiment of the present invention;

[0059] Figure 3 The hardware topology diagram of the flexible battery stack according to an embodiment of the present invention;

[0060] Figure 4A hardware topology diagram of an energy storage unit according to an embodiment of the present invention;

[0061] Figure 5 This is a flow chart of the SOC balancing control method of the high-pressure cascade valve hall energy storage system according to an embodiment of the present invention;

[0062] Description of the drawings: 1. Energy storage bridge arm; 2. Energy storage unit; 3. Energy storage module; 4. Power converter; 5. PACK controller; 6. Battery PACK; 7. Battery cluster. DETAILED DESCRIPTION

[0063] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] The purpose of the present invention is to provide a high-voltage cascade valve hall energy storage system and a SOC balancing control method thereof, which can accurately control the battery SOC in and between bridge arms to ensure that the charging state between each energy storage module and the bridge arm is balanced, thereby optimizing the performance of the energy storage system, increasing the service life of the battery, reducing system energy loss, and enhancing system stability.

[0065] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0066] Example 1

[0067] like Figure 1-Figure 4 As shown, the present invention takes the star-connected energy storage topology as an example. The high-voltage cascade valve hall energy storage system adopts two groups of three-phase 6-bridge arms to form a 1GW / 2GWh energy storage system. Specifically, each phase unit includes two energy storage bridge arms arranged in parallel, and one end of the three energy storage bridge arms located on the same side of the three phase units are connected together to form a neutral point, and the other ends are connected to the three-phase AC power grid through reactors.

[0068] In the high-voltage cascade valve hall energy storage system provided in Example 1 of the present invention, each phase unit includes two energy storage bridge arms 1 arranged in parallel, each energy storage bridge arm 1 is connected in series with a reactor, and the energy storage bridge arm 1 includes a plurality of energy storage units 2 arranged in series, each of the energy storage units 2 includes an energy storage module 3 and a power converter 4 (such as a DC-DC converter or inverter) correspondingly connected to the energy storage module 3;

[0069] Each of the energy storage modules 3 is equipped with a battery management system (BMS), which is used to monitor the SOC data of the energy storage module 3 in real time and upload it to the main controller; for example, each energy storage module 3 is equipped with an independent BMS, which includes a voltage sensor, a current sensor, a temperature sensor, etc., responsible for monitoring the battery voltage, current, temperature and other state parameters of the energy storage module 3. By accurately measuring these electrical parameters, the BMS can calculate the SOC data of each energy storage module according to a preset algorithm (Kalman filter) and transmit the data to the main controller. The main controller assumes the decision-making and control functions of the energy storage system. The main controller receives the SOC data from each energy storage module through the communication interface (CAN bus and Ethernet bus).

[0070] The main controller receives SOC data from each energy storage module 3, and judges whether SOC imbalance occurs within the bridge arm based on the difference between the SOC data of each energy storage module 3 and the average SOC value of the energy storage bridge arm where the energy storage module is located, and judges whether SOC imbalance occurs between bridge arms based on the difference between the average SOC values ​​of each energy storage bridge arm in the phase unit; if SOC imbalance occurs within the bridge arm, the main controller starts the SOC balancing control strategy within the bridge arm, and if SOC imbalance occurs between bridge arms, the main controller starts the SOC balancing control strategy between bridge arms;

[0071] Among them, the main controller generates execution instructions based on the SOC balancing control strategy within the bridge arm or the SOC balancing control strategy between bridge arms, adjusts the working state of the power converter corresponding to different energy storage modules 3, adjusts the charging and discharging current of the energy storage module 3 or the energy storage bridge arm 1, and realizes SOC balancing control.

[0072] For example, the energy storage module 3 is a flexible battery stack, and the charging and discharging power of the flexible battery stack can be controlled by a power converter to achieve balanced power control of each flexible battery stack.

[0073] like Figure 3 As shown, the flexible battery stack includes a plurality of battery clusters 7 arranged in parallel, each battery cluster 7 includes a plurality of battery PACKs 6 arranged in series, and each of the battery PACKs 6 is connected to a PACK controller 5 .

[0074] like Figure 4 As shown, the battery PACK adopts the 1P104S connection method, every 6 battery PACKs are connected in series to form a battery cluster 7, every 4 battery clusters 7 are connected in parallel to form a flexible battery stack, and each H-bridge power module is connected in series with a flexible battery stack to form an energy storage unit; the H-bridge power module is the power converter, including four fully-controlled semiconductor devices, and the four fully-controlled semiconductor devices form an H-bridge structure.

[0075] For example, the fully controlled semiconductor device uses MOSFET or IGBT. In the energy storage bridge arm of the cascaded multiple energy storage modules, the power converter usually uses a DC-DC converter (such as a buck-boost converter) to adjust the output voltage of each energy storage module. Specifically, the power converter adjusts the output of current and voltage by controlling the on and off of the fully controlled semiconductor device (such as MOSFET).

[0076] Example 2

[0077] The present invention also provides a SOC balancing control method for a high-pressure cascade valve hall energy storage system, which is applied to the above-mentioned high-pressure cascade valve hall energy storage system, comprising:

[0078] Real-time monitoring of the SOC data of each energy storage module;

[0079] Based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arm where the energy storage module is located, the SOC imbalance of the energy storage module is obtained. If the SOC imbalance of the energy storage module exceeds the set imbalance threshold, it is determined that the SOC imbalance in the bridge arm occurs, and the main controller starts the SOC balance control strategy in the bridge arm, adjusts the working state of the power converter corresponding to different energy storage modules, and adjusts the charge and discharge current of the energy storage module to achieve SOC balance in the bridge arm;

[0080] Based on the difference between the average SOC values ​​of each energy storage bridge arm in the phase unit, the relative size of the average SOC value of each energy storage bridge arm is determined. If the average SOC values ​​of each energy storage bridge arm are not equal, it is judged that the SOC imbalance between the bridge arms occurs. The main controller starts the SOC balancing control strategy between the bridge arms, adjusts the working status of the power converter corresponding to different energy storage modules, and adjusts the charging and discharging current of the energy storage bridge arm to achieve SOC balance between the bridge arms.

[0081] The SOC balancing control method of the high-voltage cascade valve hall energy storage system mainly involves the balancing of the power in the bridge arm and the balancing of the battery clusters between the bridge arms. The specific analysis is as follows:

[0082] 1. Balance of power in the bridge arm

[0083] 1. Cluster balancing within flexible battery stack

[0084] The internal balancing of the flexible battery stack is mentioned in the previously applied patent CN117713314A - "A system and method for balancing clusters of energy storage systems with a common DC bus", which will not be elaborated here.

[0085] 2. Balance of power between energy storage modules

[0086] The SOC balancing control of the energy storage module inside the bridge arm of the present invention uses the SOC of the energy storage module as the control target to achieve dynamic balancing of the power of each energy storage module. The SOC of the energy storage module is the average SOC of all battery cells inside the energy storage module.

[0087] The present invention divides the device working states into three working conditions: discharging, charging, and standby / stopping, and designs corresponding control strategies for each working condition to ensure SOC balance, extend the battery life, and improve the system efficiency.

[0088] Discharging working condition: During the discharging process, the discharging rate is dynamically adjusted through an intelligent adjustment strategy, and the current distribution is optimized in real time according to the load change to prevent over-discharging of the energy storage module.

[0089] Charging working condition: A strategy of dynamically adjusting the charging current is adopted to optimize the current distribution during the charging process, reduce the temperature rise and energy loss during the battery charging process, and at the same time ensure that the energy storage module maintains a good balanced state during the charging process.

[0090] Standby working condition: When in the standby mode, the SOC state of the energy storage module is monitored regularly, and the SOC balance of the energy storage modules inside each energy storage bridge arm is maintained through timely fine-tuning of the charge and discharge strategies.

[0091] A number of energy storage units are cascaded inside an energy storage bridge arm. Each energy storage unit contains a flexible battery stack and a power converter inside, and the charge and discharge power of the flexible battery stack can be controlled through the power converter to achieve the power balance of the flexible battery stack.

[0092] In the embodiment of the power balance between energy storage modules, the balance current (referring to the adjusted charge and discharge current under the charging or discharging working condition, or the internal current inside the bridge arm or between bridge arms under the standby or stopping working condition) limit is set to 5% of the rated current. This limit value is determined through tests on different battery types (such as standard lithium batteries, lithium iron phosphate batteries). The tests show that this value can effectively avoid overheating or damage of the battery during the balancing process. The test data show that when the balance current is limited to 5% of the rated current, not only can the balance efficiency of the battery be improved, but also the battery life can be effectively extended. Under high load conditions, the balance current limit value can be appropriately adjusted to adapt to the charge and discharge characteristics of different batteries.

[0093] In the design of the battery protection mechanism, the charging protection voltage is set to 4.2V, which is the maximum charging voltage for most lithium batteries. In order to cope with the differences in batteries from different manufacturers, the charging protection voltage is adjustable, and users can adjust it according to the actual battery type and manufacturer's requirements. The discharge protection voltage is set to 3.0V, which can effectively avoid damage caused by excessive discharge of the battery. The setting of the discharge protection voltage can also be adjusted according to the specific requirements of the battery to ensure the safety of the battery in different usage scenarios. Among them, the charge and discharge protection voltage refers to the voltage threshold of the battery cell, which is monitored and protected by the battery management system (BMS).

[0094] 2.1 SOC balance in the bridge arm under discharge conditions

[0095] Based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arm where the energy storage module is located, the SOC imbalance of the energy storage module is obtained, which specifically includes:

[0096] Energy storage module

[0097] Among them, SOC i Represents the SOC data of energy storage module i, Indicates the average SOC value of the energy storage bridge arm where the energy storage module is located.

[0098] If the SOC imbalance of the energy storage module exceeds the set imbalance threshold, it is determined that the SOC imbalance in the bridge arm occurs, and the main controller starts the SOC balance control strategy in the bridge arm, which specifically includes:

[0099]

[0100] Among them, ΔSOC threshold To set the imbalance threshold, for example, it is usually 5%.

[0101] After starting the SOC balance control strategy in the bridge arm, the SOC balance in the bridge arm under the discharge condition specifically includes:

[0102] If the SOC data of a certain energy storage module is lower than the average SOC value of the energy storage bridge arm where the energy storage module is located, the output power of the energy storage module is reduced by controlling the power converter corresponding to the energy storage module to slow down its discharge rate and avoid over-discharge;

[0103] The power converter adjusts the output current and voltage by controlling the on and off of fully controlled semiconductor devices (such as MOSFET). In order to reduce the output voltage of a certain energy storage module, the power converter usually achieves this by adjusting the duty cycle. By adjusting the control signal of the power converter, the output voltage of the energy storage module can be reduced.

[0104] During the battery discharge process, there is a certain relationship between the battery voltage and the discharge current. For a storage module, the magnitude of the discharge current depends on the voltage of the module and the resistance (or current demand) of the external load. Reducing the output voltage of the module through the power converter means that the module's ability to drive the external load is reduced, thereby reducing the discharge current. Especially in a series configuration, reducing the voltage of a single module means that the module's contribution to the overall current is reduced.

[0105] At the same time, the current of other cascaded energy storage modules will not be directly affected by the voltage reduction of a single energy storage module, unless the system design is uniformly controlled by sharing the total current. In a typical parallel energy storage system, the power converter dynamically adjusts the current distribution according to the SOC of each energy storage module. The voltage of the energy storage module with a low SOC decreases during discharge, which reduces the discharge current of the energy storage module, thereby avoiding over-discharge, while other energy storage modules still discharge according to their SOC and system load conditions.

[0106] Specifically, the regulated discharge current is:

[0107]

[0108] Among them, I out,i is the output current of energy storage module i, I out,avg is the average discharge current of all energy storage modules in the energy storage bridge arm. In this way, the discharge rate of energy storage modules with low SOC will be slowed down to prevent over-discharge.

[0109] On the contrary, if the SOC data of a certain energy storage module is higher than the average SOC value of the energy storage bridge arm where the energy storage module is located, the output voltage of the energy storage module is increased by controlling the power converter corresponding to the energy storage module, thereby increasing the discharge current of the energy storage module; the purpose is to accelerate the discharge process of the energy storage module and ensure that energy can be evenly distributed to all energy storage modules. The voltage difference is the main factor driving the current. When the battery voltage is higher, it can release energy more easily. By increasing the voltage of the energy storage module, the power converter accelerates the discharge process of the energy storage module, ensuring that its SOC gradually decreases and approaches the average SOC value of the energy storage bridge arm. At this time, the calculation formula for the discharge current is:

[0110]

[0111] This ensures that modules with higher SOC can release energy faster and balance the SOC of each module.

[0112] By adjusting the output voltage of each energy storage module in real time, the system can ensure that the SOC of each battery cluster gradually tends to be balanced, thereby avoiding excessive discharge of a module or waste of capacity.

[0113] 2.2 SOC balance in the bridge arm under charging conditions

[0114] Under charging conditions, the control strategy is similar to that under discharging conditions, but the operation direction is opposite to that during discharging.

[0115] If the SOC data of a certain energy storage module is lower than the average SOC value of the energy storage bridge arm where the energy storage module is located, the input voltage of the energy storage module is increased by controlling the power converter corresponding to the energy storage module, thereby increasing the charging current of the energy storage module;

[0116] For example, for energy storage module i, if its SOC is lower than the average SOC value of the energy storage bridge arm where it is located, the power converter will increase the input voltage of the energy storage module and increase the charging current, so that the charging of the energy storage module is accelerated and gradually consistent with the SOC of other energy storage modules. According to Ohm's law (I=V / R), the current is proportional to the voltage difference and inversely proportional to the internal resistance. The internal resistance of the battery changes with the SOC, but usually in the early stages of charging (when the SOC is low), the internal resistance of the battery is small. When the charging voltage is increased, the voltage difference across the energy storage module (i.e., the charging voltage) increases, and the current also increases accordingly. A higher charging voltage allows more current to flow into the energy storage module, thereby accelerating the charging process. The charging current formula at this time is:

[0117]

[0118] Among them, I in,i is the charging current of energy storage module i, I in,avg It is the average charging current of the energy storage module in the bridge arm.

[0119] On the contrary, if the SOC data of a certain energy storage module is higher than the average SOC value of the energy storage bridge arm where the energy storage module is located, the input voltage of the energy storage module is reduced by controlling the power converter corresponding to the energy storage module, thereby reducing the charging current of the energy storage module.

[0120] If the SOC of energy storage module i is higher than the average SOC value of the energy storage bridge arm, the power converter will reduce its charging current by lowering the input voltage of the module. Also according to Ohm's law, reducing the charging voltage (the voltage applied to the battery) will reduce the current flowing into the battery. When the SOC is higher, the charging demand of the energy storage module becomes smaller, and reducing the voltage helps to reduce the charging rate to prevent overcharging and avoid battery damage. At this time, the charging current will be reduced according to the following formula:

[0121]

[0122] During the charging process, the system will dynamically adjust the charging current according to the real-time SOC of each energy storage module to ensure that the SOC difference between energy storage modules always remains within an acceptable range, avoiding shortening of battery life due to uneven charging.

[0123] 2.3. SOC balance in the bridge arm under standby or shutdown conditions

[0124] In the standby or shutdown state, since there is no actual charge and discharge current flowing, SOC balancing cannot be performed by the traditional charge and discharge method. In order to solve this problem, the present invention proposes to adjust the SOC by generating a current in the bridge arm. The specific implementation method is as follows:

[0125] In the standby or shutdown state, when the difference between the SOC of a certain energy storage module and the average SOC value of the energy storage bridge arm in which it is located exceeds the set imbalance threshold, the balancing strategy is started; at this time, the main controller adjusts the working state of the power converters corresponding to different energy storage modules. Through the adjustment of the power converter, a voltage difference is formed between the energy storage modules in the same bridge arm, generating a current in the bridge arm to adjust the SOC of the energy storage module.

[0126] Assume that the difference between the SOC data of energy storage module i and the average SOC value of the energy storage bridge arm where the energy storage module is located is:

[0127]

[0128] in, Indicates the average SOC value of the energy storage bridge arm where the energy storage module is located;

[0129] When ΔSOC i >0, I balance,i is positive, indicating that the energy storage module is discharged; when ΔSOC i <0, I balance,i If it is negative, it means that the energy storage module is charged.

[0130] Then the current in the bridge arm can be expressed as:

[0131] I balance,i =K balance ΔSOC i

[0132] Among them, K balance is the proportional coefficient of the current in the bridge arm, which is adjusted according to actual needs to ensure that the rate of the balancing process is reasonable.

[0133] Here are some examples:

[0134] Battery capacity: 100Ah

[0135] SOC difference: 5%

[0136] Target: Recover 1% SOC difference per hour

[0137] calculate:

[0138] It takes 1Ah of electricity to restore 1% SOC, and the balancing current is 1A within 1 hour.

[0139] Formula: I balance,i =K balance ΔSOC i

[0140] 1A=K balance 0.05

[0141] K balance =20A / %

[0142] Conclusion: K balance = 20A / % can make a 100Ah battery equalize 1% SOC per hour, which is a reasonable rate. In practice, it is recommended that K balance The value is 5-50A / %, adjusted according to demand.

[0143] Note: 20A / % is a unit that represents the relationship between current and SOC (State of Charge) difference. Specifically, every 1% SOC difference corresponds to a balancing current of 20 amperes (A).

[0144] If the SOC of a certain energy storage module is lower than the average SOC value of the energy storage bridge arm where it is located, the power converter is adjusted to form a voltage difference between the energy storage modules in the same bridge arm, so that the energy storage module absorbs energy from other energy storage modules for charging and improves its SOC. If the SOC of a certain energy storage module is higher than the average SOC value of the energy storage bridge arm where it is located, the voltage difference is adjusted to make the energy storage module release power for discharge and reduce its SOC. The generation of current in the bridge arm is adjusted in real time according to the SOC difference of each energy storage module. In standby or shutdown conditions, since there is no actual charge and discharge flow, the system cannot achieve SOC balance through conventional charge and discharge methods. Therefore, the power converter controls the voltage difference between the energy storage modules, generates current in the bridge arm, and thus adjusts the SOC. Assuming that the SOC of energy storage module i is lower than the average SOC, the power converter will adjust the voltage of the energy storage module so that its voltage is lower than that of other energy storage modules. At this time, the voltage of energy storage module i is lower than the voltage of other modules, resulting in a voltage difference, which drives current to flow into energy storage module i, thereby achieving charging.

[0145] In standby or shutdown conditions, the time period of the balancing process is very critical. For example, if the estimated balancing time is T, the system will automatically reverse the bridge arm current strategy after maintaining T / 2 time to ensure the effect of SOC balancing.

[0146] In standby or shutdown conditions, the duration of the SOC balancing process is critical to system management. The system monitors the SOC differences of each energy storage module in real time. Once the difference exceeds the preset threshold, the balancing strategy is activated by adjusting the power converter. This strategy uses the directional current generated in the bridge arm to transfer power from the high SOC module to the low SOC module in one direction. This process continues until the SOC difference is reduced to within the set range. This unidirectional adjustment method effectively realizes the gradual balancing of SOC between modules and is suitable for internal optimization in standby or shutdown conditions.

[0147] 2.4 SOC imbalance and balance judgment

[0148] In all the above working conditions, the SOC balance is determined by comparing the SOC of each energy storage module with the average SOC of all energy storage modules in the entire bridge arm. The specific judgment criteria are as follows:

[0149] Imbalance judgment: When the difference between the SOC of a certain energy storage module and the average SOC of the entire bridge arm exceeds the set imbalance threshold, the SOC of the energy storage module is judged to be unbalanced, and the system starts the balancing strategy. The conditions are:

[0150]

[0151] Balance judgment: When the difference between the SOC of a certain energy storage module and the average SOC of the entire energy storage bridge arm is less than the set balance threshold, it is judged that the SOC of the energy storage module is in a balanced state and the balancing operation can be stopped. The conditions are:

[0152]

[0153] Typically, the imbalance threshold ΔSOC threshold is set to a higher value (e.g. 5%), while the balance threshold ΔSOC balancethreshold It is set to a lower value (such as 2%) to ensure that the balancing operation is started only when the SOC difference is obvious, thereby avoiding unnecessary energy loss and over-regulation.

[0154] 2. Battery cluster balancing between bridge arms

[0155] The present invention achieves the balance of the energy storage bridge arm by accurately controlling the charge and discharge power of each energy storage bridge arm. This method not only improves the control accuracy of the system, but also avoids the performance degradation caused by SOC imbalance between energy storage bridge arms, ensuring the efficient operation and safety of the energy storage system.

[0156] The intra-phase bridge arm balancing method avoids the problem of intra-phase bridge arm SOC imbalance by accurately controlling the bridge arm current, thereby achieving effective energy distribution. This method adjusts the current between different bridge arms according to the SOC state of each energy storage module to achieve battery stack balance.

[0157] The SOC balancing control strategy between bridge arms includes:

[0158] 1. Data collection and transmission

[0159] Each energy storage bridge arm collects the SOC data of the energy storage module in real time and transmits it to the main controller. The SOC data of the energy storage module is collected in real time through the battery management system (BMS).

[0160] First, calculate the SOC mean SOC of the energy storage module in each bridge arm avg and compare it with the mean SOC of other bridge arms.

[0161] Assume that there are two energy storage bridge arms in the phase, namely bridge arm A1 and bridge arm A2, and the SOC value of each energy storage module in the bridge arm is SOC i1 and SOC i2 , then the mean SOC of each bridge arm is:

[0162]

[0163] Among them, n 1 and n 2 are the number of energy storage modules in the A1 and A2 bridge arms respectively.

[0164] 2. Balance control during charging and discharging

[0165] During the discharge process, if the SOC of a certain energy storage bridge arm is lower than the average SOC of other energy storage bridge arms avg , the system will achieve balance by adjusting the discharge current of the energy storage bridge arm. A1 Lower than the SOC of the other bridge arm A2 By reducing the discharge current I out,A1 To reduce its discharge rate, specifically, the system adjusts the output voltage of the bridge arm through the power converter to adjust the discharge current. According to the current-voltage relationship, reducing the output voltage of the bridge arm will reduce the discharge current of the bridge arm, thereby slowing down its discharge rate. The current regulation in this process monitors the SOC state of each bridge arm in real time through the controller, and adjusts the output voltage of the power converter according to the calculation results.

[0166]

[0167] Among them, I outis the total system discharge current, SOC avg,A1 and SOC avg,A2 are the average SOC values ​​of the A1 and A2 bridge arms respectively. The total system discharge current I out It refers to the total current flowing to the grid during the phase unit discharge process. It is the sum of the discharge currents of all parallel energy storage bridge arms in the phase unit, which is determined by the power demand of the grid and the system dispatching instructions. The main controller is based on I out And the SOC state of each energy storage bridge arm, adjust the output voltage and current of each energy storage bridge arm in real time to achieve balanced control of the SOC between the bridge arms.

[0168] During the charging process, if the average SOC value of a certain energy storage bridge arm is lower than the average SOC value of the phase unit where the energy storage bridge arm is located, the system will increase the charging current I of the bridge arm. in,A1 To accelerate charging. If the SOC data of a certain energy storage bridge arm is higher than the average SOC value of the phase unit where the energy storage bridge arm is located, the charging current is reduced to prevent overcharging. Among them, the average SOC value of the phase unit is the average value of the SOC averages of all energy storage bridge arms in the phase unit.

[0169] The charging current regulation formula is:

[0170]

[0171] Among them, I in is the total system charging current, SOC avg,A1 and SOC avg,A2 is the average SOC of the A1 and A2 bridge arms.

[0172] 3. Balanced current and overload protection

[0173] In order to prevent the balancing current (referring to the internal current generated in the SOC balancing control strategy between bridge arms to adjust the SOC difference of battery modules) from causing bridge arm overload, the system sets a maximum balancing current limit value, which is usually 5% of the rated current. Therefore, the main controller will limit the current to prevent the balancing current from being too large and damaging the system. Specifically, the balancing current limit is:

[0174] I balance =min(I balance,max ,I balance,calc )

[0175] Among them, I balance,max is the maximum balancing current limit value, I balance,calc is the calculated balancing current.

[0176] In addition, when the voltage of a bridge arm reaches the protection threshold, the system will enter the protection mode and stop the charging and discharging operation of the bridge arm to protect the battery from damage. The discharge protection voltage and charging protection voltage are:

[0177] V protect,discharge =2.69V

[0178] V protect,charge =3.70V

[0179] If the bridge arm voltage is lower than the discharge protection voltage or higher than the charge protection voltage, the system will automatically stop the charging and discharging operation of the energy storage bridge arm and enter the protection mode.

[0180] 4. Intra-phase bridge arms and energy transfer

[0181] During system operation, in order to achieve power balance in the bridge arms within the phase, the main controller will dynamically adjust the energy flow between the bridge arms to ensure the balance of SOC. For example, if the SOC of bridge arm A1 is higher and the SOC of bridge arm A2 is lower, the main controller will adjust the distribution of discharge current based on real-time monitoring data, so that bridge arm A1 transfers power to bridge arm A2, thereby reducing the difference in SOC between the two. Assuming that the SOC of bridge arm A1 is SOC A1 , the SOC of bridge arm A2 is SOC A2 , and the SOC imbalance threshold is set to ΔSOC threshold =3%. When the SOC difference between the two is greater than the threshold, the main controller will adjust the current distribution of the bridge arm so that the current of A1 increases slightly and the current of A2 decreases slightly until the SOC difference is lower than the threshold.

[0182] Under standby or shutdown conditions, if the SOC average of one energy storage bridge arm is lower than the SOC average of another energy storage bridge arm, the main controller adjusts the working state of the power converter corresponding to each bridge arm to form a voltage difference between the energy storage bridge arm with a higher SOC average and the energy storage bridge arm with a lower SOC average, thereby driving the power to transfer from the energy storage bridge arm with a higher SOC average to the energy storage bridge arm with a lower SOC average, thereby achieving power balance between the energy storage bridge arms within the phase.

[0183] Among them, the power converter corresponding to each bridge arm refers to the power converter corresponding to all energy storage units in the bridge arm. The main controller coordinates the working status of all power converters in the bridge arm and adjusts the output voltage of the entire bridge arm to achieve SOC balance between the bridge arms.

[0184] 5. Real-time feedback and optimization

[0185] During the entire charging and discharging process, the main controller will dynamically adjust the balancing strategy based on real-time data. Assume that at a certain moment, the SOC of bridge arm A1 is 80%, while the SOC of bridge arm A2 is 76.8%, and the SOC difference is 3.2%. At this time, the main controller will optimize the current distribution, reduce the charging current of bridge arm A1, and increase the charging current of bridge arm A2 until the SOC difference between the two is reduced to within the set threshold.

[0186] 6. Balancing between battery stacks is completed

[0187] When the SOC differences of all bridge arms are consistent, the system will consider the balancing operation in the charging process to be completed. For example, assuming that the SOC of each bridge arm is stable between 78% and 80%, the main controller will turn off the balancing operation and switch to normal charging and discharging mode.

[0188] Example 3

[0189] like Figure 5 As shown, for a high-voltage cascade valve hall energy storage system consisting of 6 bridge arms, each phase unit has two energy storage bridge arms, including bridge arm A1 and bridge arm A2. Each energy storage bridge arm consists of multiple flexible battery stacks, including M1, M2, M3...M40. The power of each flexible battery stack is accurately managed by the main controller. The following is a specific method for balancing between flexible battery stacks during charging:

[0190] Monitor and detect battery stack status:

[0191] During system operation, the main controller monitors the SOC (state of charge) of each flexible battery stack in real time. For example, assume that the SOC of flexible battery stack M1 is 85%, the SOC of flexible battery stack M2 is 78%, the SOC of flexible battery stack M3 is 80%, and the SOC of the remaining flexible battery stacks is between 75% and 78%. The system sets the SOC imbalance threshold to 3%, that is, when the SOC difference between any two flexible battery stacks exceeds 3%, the system will automatically trigger the balancing operation.

[0192] Flexible battery stack charging power adjustment:

[0193] Assume that the system is in charging mode at this time, and the charge of the flexible battery stack M1 is too high, exceeding the set SOC balance threshold. For example, the charge of the flexible battery stack M1 has reached 90%, exceeding the average threshold of the flexible battery stack in the bridge arm. The system controller will detect this situation and reduce the output voltage amplitude of the flexible battery stack by controlling the internal power converter of the flexible battery stack M1. For example, assuming that the output voltage of the flexible battery stack A1 is 1.2kV, the system controller will reduce the output voltage to 1.1kV or even lower (can be 0), thereby reducing the charging power of the flexible battery stack M1.

[0194] Since the current of the flexible battery stack in each bridge arm is consistent, the charging power of the flexible battery stack will decrease after the flexible battery stack with high power reduces its voltage. In this way, the SOC of the flexible battery stack M1 will gradually fall back to the set balance range. Assuming that the SOC of the flexible battery stack M1 eventually returns to 87%, the SOC difference with other flexible battery stacks remains within 3%.

[0195] Intra-phase bridge arms and energy transfer:

[0196] In order to achieve power balance between the bridge arms in the phase, the main controller will adjust the current of bridge arm A1 and bridge arm A2 in a timely manner. For example, suppose the SOC of bridge arm A1 is high (for example, reaching 88%), while the SOC of bridge arm A2 is low (for example, reaching 77%). At this time, the main controller will control the power converter to slightly increase the discharge current of bridge arm A1, for example, from 1PU to 1.05PU. Since the discharge current of bridge arm A1 is higher than that of bridge arm A2, part of the energy of bridge arm A1 will be automatically transferred to bridge arm A2 until the SOC of bridge arm stack A2 rises to a level where the difference with bridge arm A1 does not exceed the set SOC imbalance threshold (3%).

[0197] Real-time feedback and optimization:

[0198] During the entire charging process, the main controller will continuously optimize the charging strategy based on real-time feedback data. Assuming that the controller finds that the SOC difference between bridge arm A1 and bridge arm A2 is 3.2% (for example, bridge arm A1 is 80% and bridge arm A2 is 76.8%), the main controller will immediately adjust the charging current of bridge arm A1 and reduce its charging power, so that bridge arm A2 can get more charging current to narrow the difference between the two.

[0199] Balancing between battery stacks is completed:

[0200] In the final balancing stage, assuming that the SOC of all bridge arms tends to be consistent, for example, the SOC of each energy storage bridge arm is stable between 78% and 80%, the system will consider that the power between the energy storage bridge arms has reached equilibrium. At this time, the main controller will turn off the balancing operation and switch to normal charging and discharging mode.

[0201] The above-mentioned balancing control method can effectively avoid the situation where the power of a single bridge arm is too high or too low, thereby ensuring the stable operation of the energy storage system. The battery module in each bridge arm dynamically adjusts the voltage and current to achieve energy transfer and SOC balance, thereby maximizing the efficiency of the system and the battery life.

[0202] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A high-voltage cascade valve hall energy storage system, comprising three phase units, the three phase units are respectively connected to a three-phase AC power grid, characterized in that: Each phase unit includes at least two energy storage bridge arms arranged in parallel, each energy storage bridge arm is connected in series with a reactor, the energy storage bridge arm includes a plurality of energy storage units arranged in series, each of the energy storage units includes an energy storage module and a power converter correspondingly connected to the energy storage module; Each of the energy storage modules is equipped with a battery management system, which is used to monitor the SOC data of the energy storage module in real time and upload it to the main controller; The main controller receives SOC data from each energy storage module, and determines whether SOC imbalance occurs within the bridge arm based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arm where the energy storage module is located, and determines whether SOC imbalance occurs between bridge arms based on the difference between the average SOC values ​​of each energy storage bridge arm in the phase unit; If an SOC imbalance occurs within a bridge arm, the main controller starts the SOC balancing control strategy within the bridge arm. If an SOC imbalance occurs between bridge arms, the main controller starts the SOC balancing control strategy between bridge arms. Among them, the main controller generates execution instructions based on the SOC balancing control strategy within the bridge arm or the SOC balancing control strategy between bridge arms, adjusts the working state of the power converters corresponding to different energy storage modules, adjusts the charging and discharging current of the energy storage module or the energy storage bridge arm, and realizes SOC balancing control.

2. The high-pressure cascade valve hall energy storage system according to claim 1 is characterized in that: The energy storage module is a flexible battery stack, which includes a plurality of battery clusters arranged in parallel, each battery cluster includes a plurality of battery PACKs arranged in series, and each of the battery PACKs is connected to a PACK controller.

3. The high-pressure cascade valve hall energy storage system according to claim 1 is characterized in that: The power converter is an H-bridge power module, comprising four fully-controlled semiconductor devices, and the four fully-controlled semiconductor devices form an H-bridge structure.

4. The high-pressure cascade valve hall energy storage system according to claim 3 is characterized in that: The fully controlled semiconductor device adopts MOSFET or IGBT.

5. A SOC balancing control method for a high-pressure cascade valve hall energy storage system, applied to the high-pressure cascade valve hall energy storage system according to any one of claims 1 to 4, characterized in that: include: Real-time monitoring of the SOC data of each energy storage module; Based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arm where the energy storage module is located, the SOC imbalance of the energy storage module is obtained. If the SOC imbalance of the energy storage module exceeds the set imbalance threshold, it is determined that the SOC imbalance in the bridge arm occurs, and the main controller starts the SOC balance control strategy in the bridge arm, adjusts the working state of the power converter corresponding to different energy storage modules, and adjusts the charge and discharge current of the energy storage module to achieve SOC balance in the bridge arm; Based on the difference between the average SOC values ​​of each energy storage bridge arm in the phase unit, the relative size of the average SOC value of each energy storage bridge arm is determined. If the average SOC values ​​of each energy storage bridge arm are not equal, it is judged that the SOC imbalance between the bridge arms occurs. The main controller starts the SOC balancing control strategy between the bridge arms, adjusts the working status of the power converter corresponding to different energy storage modules, and adjusts the charging and discharging current of the energy storage bridge arm to achieve SOC balance between the bridge arms.

6. The SOC balancing control method of the high-pressure cascade valve hall energy storage system according to claim 5 is characterized in that: The SOC imbalance of the energy storage module is obtained based on the difference between the SOC data of each energy storage module and the average SOC value of the energy storage bridge arm where the energy storage module is located, specifically including: Among them, SOC i Represents the SOC data of energy storage module i, Indicates the average SOC value of the energy storage bridge arm where the energy storage module is located.

7. The SOC balancing control method of the high-pressure cascade valve hall energy storage system according to claim 5 is characterized in that: The SOC balancing control strategy within the bridge arm specifically includes: SOC balance in the bridge arm under discharge conditions: If the SOC data of a certain energy storage module is lower than the average SOC value of the energy storage bridge arm where the energy storage module is located, the output voltage of the energy storage module is reduced by controlling the power converter corresponding to the energy storage module, thereby reducing the discharge current of the energy storage module; If the SOC data of a certain energy storage module is higher than the average SOC value of the energy storage bridge arm where the energy storage module is located, the output voltage of the energy storage module is increased by controlling the power converter corresponding to the energy storage module, thereby increasing the discharge current of the energy storage module; SOC balance in the bridge arm under charging conditions: If the SOC data of a certain energy storage module is lower than the average SOC value of the energy storage bridge arm where the energy storage module is located, the input voltage of the energy storage module is increased by controlling the power converter corresponding to the energy storage module, thereby increasing the charging current of the energy storage module; If the SOC data of a certain energy storage module is higher than the average SOC value of the energy storage bridge arm where the energy storage module is located, the input voltage of the energy storage module is reduced by controlling the power converter corresponding to the energy storage module, thereby reducing the charging current of the energy storage module; SOC balance in the bridge arm under standby or shutdown conditions: The main controller adjusts the working state of the power converters corresponding to different energy storage modules. Through the adjustment of the power converters, a voltage difference is formed between the energy storage modules in the same bridge arm, generating a current in the bridge arm. Among them, if the SOC data of a certain energy storage module is lower than the average SOC value of the energy storage bridge arm where the energy storage module is located, a current in the bridge arm is generated to charge the energy storage module, and the energy storage module obtains electricity from other energy storage modules to increase its SOC value; if the SOC data of a certain energy storage module is higher than the average SOC value of the energy storage bridge arm where the energy storage module is located, a current in the bridge arm is generated to discharge the energy storage module, and the energy storage module releases electricity to charge other energy storage modules in the energy storage bridge arm to reduce their SOC values.

8. The SOC balancing control method of the high-pressure cascade valve hall energy storage system according to claim 7 is characterized in that: The calculation formula of the current in the bridge arm is as follows: I balance,i =K balance ·ΔSOC i Among them, I balance,i Indicates the current in the bridge arm, K balance Indicates the proportionality coefficient of the current in the bridge arm, ΔSOC i Indicates the difference between the SOC data of energy storage module i and the average SOC value of the energy storage bridge arm where the energy storage module is located: in, Indicates the average SOC value of the energy storage bridge arm where the energy storage module is located; When ΔSOC i >0, I balance,i is positive, indicating that the energy storage module is discharged; when ΔSOC i <0, I balance,i If it is negative, it means that the energy storage module is charged.

9. The SOC balancing control method of the high-pressure cascade valve hall energy storage system according to claim 5, characterized in that: The bridge arm SOC balancing control strategy specifically includes: In the case where each phase unit includes two energy storage bridge arms arranged in parallel, namely bridge arm A1 and bridge arm A2, the SOC mean value of the two energy storage bridge arms is calculated; During the discharge process, if the SOC average value of a certain energy storage bridge arm is lower than the SOC average value of another energy storage bridge arm, the output voltage of the energy storage bridge arm is reduced, and the discharge current of the energy storage bridge arm is reduced; During the charging process, if the SOC average value of a certain energy storage bridge arm is lower than the average SOC value of the phase unit where the energy storage bridge arm is located, the input voltage of the energy storage bridge arm is increased and the charging current of the energy storage bridge arm is increased; if the SOC data of a certain energy storage bridge arm is higher than the average SOC value of the phase unit where the energy storage bridge arm is located, the input voltage of the energy storage bridge arm is reduced and the charging current of the energy storage bridge arm is reduced; wherein, the average SOC value of the phase unit is the average value of the SOC average values ​​of all energy storage bridge arms in the phase unit; Under standby or shutdown conditions, if the SOC average of one energy storage bridge arm is lower than the SOC average of another energy storage bridge arm, the main controller adjusts the working state of the power converter corresponding to each bridge arm to form a voltage difference between the energy storage bridge arm with a higher SOC average and the energy storage bridge arm with a lower SOC average, thereby driving the power to transfer from the energy storage bridge arm with a higher SOC average to the energy storage bridge arm with a lower SOC average, thereby achieving power balance between the energy storage bridge arms within the phase.

10. The SOC balancing control method of the high-pressure cascade valve hall energy storage system according to claim 9, characterized in that: The calculation of the SOC mean of the two energy storage bridge arms specifically includes: Assume that the SOC values ​​of each energy storage module in bridge arm A1 and bridge arm A2 are SOC i1 and SOC i2 , the SOC mean values ​​of bridge arm A1 and bridge arm A2 are: Among them, n1 and n2 are the numbers of energy storage modules in bridge arm A1 and bridge arm A2 respectively.

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