A method and device for controlling the charging and discharging depth of a cascade high-voltage direct-hanging energy storage system

Abstract

The application discloses a kind of cascade high-voltage direct hanging energy storage system charge-discharge depth control methods, comprising: during the operation of cascade high-voltage direct hanging energy storage system, SOC equalization control is carried out to each stage battery in cascade high-voltage direct hanging energy storage system, and the SOC of each stage battery is kept consistent during the operation of cascade high-voltage direct hanging energy storage system;At the end of charge-discharge, electronic bypass control is carried out to the battery that cannot continue to charge and discharge, so that the battery that cannot continue to charge and discharge exits the charge-discharge circuit, and the battery that is not full / empty continues to be charged and discharged, when the number of electronic bypass stages in a phase exceeds the bypassable stage threshold, the cascade high-voltage direct hanging energy storage system stops;During the operation of cascade high-voltage direct hanging energy storage system, the water machine working state, water outlet temperature and target temperature are dynamically controlled according to the real-time temperature parameters of the battery, to ensure that the battery is within the normal working temperature range.The method significantly improves the charge-discharge depth of the battery and improves the economy of the energy storage system.

Description

Technical Field

[0001] This invention relates to the field of power energy storage technology, specifically to a method and device for controlling the charge and discharge depth of a cascaded high-voltage direct-connected energy storage system. Background Technology

[0002] In commercial and industrial energy storage applications, profiting from electricity price differences by utilizing the "peak shaving and valley filling" principle is the core strategy for energy storage equipment to generate profits. Within energy storage equipment, the battery stack, as the carrier of electrical energy, has a warranty limit on the number of charge-discharge cycles. With a limited number of warranty cycles, the depth of charge-discharge determines the economic viability and payback period of the equipment. The depth of charge-discharge of a battery stack is often limited by the charging and discharging power at the maximum and minimum State of Charge (SOC) of the battery, as the latter is gradually limited to zero towards the end of the charge-discharge cycle. However, the consistency differences among the cells within the battery (initial SOC, voltage, temperature, charging and discharging current, etc.) mean that most cells are not fully charged or discharged when the charging and discharging power is limited to zero, resulting in "waste" of electrical energy. For example, the commonly used centralized PCS battery stacks in the market, to avoid over-discharge and overcharge of cells, employ a power limiting logic: when the voltage of a single cell falls below or exceeds a certain threshold, the charging and discharging power of the entire battery stack is limited to zero. Summary of the Invention

[0003] The purpose of this invention is to provide a method and device for controlling the charge and discharge depth of a cascaded high-voltage direct-connected energy storage system, which significantly improves the battery charge and discharge depth and enhances the economic efficiency of the energy storage system.

[0004] This invention is achieved through the following technical solution:

[0005] In a first aspect, the first embodiment of the present invention provides a method for controlling the charge and discharge depth of a cascaded high-voltage direct-connected energy storage system, comprising:

[0006] During the operation of the cascaded high-voltage direct-connected energy storage system, SOC equalization control is performed on each level of the battery in the cascaded high-voltage direct-connected energy storage system to maintain the consistency of SOC of each level of battery during the operation of the cascaded high-voltage direct-connected energy storage system.

[0007] At the end of the charging and discharging period, electronic bypass control is implemented for batteries that cannot continue to charge or discharge, so that the batteries that cannot continue to charge or discharge are removed from the charging and discharging circuit, and the batteries that are not fully charged / discharged continue to be charged and discharged. When the number of electronic bypass stages in a certain phase exceeds the threshold of the number of bypass stages, the cascaded high-voltage direct-connected energy storage system is shut down.

[0008] Throughout the operation of the cascaded high-voltage direct-connected energy storage system, the water turbine's operating status, outlet water temperature, and target temperature are dynamically controlled based on the battery's real-time temperature parameters to ensure that the battery remains within its normal operating temperature range.

[0009] Furthermore, the SOC balancing control of each stage of the cascaded high-voltage direct-connected energy storage system includes inter-phase SOC control. This inter-phase SOC control controls the power of each phase, ultimately affecting the zero-sequence voltage and injecting a modulation wave, satisfying the following formula:

[0010] ;

[0011] in, This represents the power that needs to be added to each phase. This represents the control coefficient. Represents the target power. This represents the average SOC of all non-bypassed stages in a three-phase battery system, where the stage is... M represents the number of high-voltage direct-connected energy storage systems cascaded, while This represents the average SOC of the battery in each non-bypass stage, where Mi is the number of stages. j i j For each phase, there is a bypass series.

[0012] Furthermore, the SOC equalization control of each stage of the cascaded high-voltage direct-connected energy storage system also includes intra-phase SOC control. The intra-phase SOC control directly acts on the modulation wave through superposition, satisfying the following formula:

[0013] ;

[0014] in, This indicates the amount of superposition of the original modulated waves. This represents the control coefficient. Represents the original modulated wave, SOC i This represents the SOC value of a single-cell battery.

[0015] Furthermore, the specific method for electronically bypassing the battery that cannot continue to charge or discharge, thereby removing the battery from the charging / discharging circuit and continuing to charge / discharge the partially charged / discharged battery, includes:

[0016] Determine whether the cascaded high-voltage direct-connected energy storage system is in a charging or discharging state;

[0017] If it is in a discharge state, determine whether the dischargeable power of each phase and each stage is 0. If it is, control the converter unit and battery of that stage to enter electronic bypass, and control the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to conduct simultaneously. If not, release the electronic bypass state of that stage and continue discharging.

[0018] If it is in the charging state, determine whether the rechargeable power of each phase and each stage is 0. If it is, control the inverter unit and battery of that stage to enter electronic bypass, and control the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to conduct simultaneously. If not, release the electronic bypass state of that stage and continue charging.

[0019] After each bypass, the number of electron bypass stages in that phase is counted.

[0020] Furthermore, the specific method for dynamically controlling the water purifier's operating status, outlet water temperature, and target temperature based on the battery's real-time temperature parameters includes:

[0021] Calculate the average temperature T of each battery cell. av Maximum temperature T max and lowest temperature T min ;

[0022] The normal operating temperature range of the battery is set to T. idea1 ~T idea2 ;

[0023] Control the water turbine start / stop and target temperature T according to the following conditions. goal :

[0024] (1) When T av >T idea1 Then start the water chiller and set the operating mode to cooling. If T max >T idea2 Then T goal =T idea1 -10; if T max <T idea2 Then T goal =T idea1 -5;

[0025] (2) When T idea1 -10 <T av <T idea1 And T max <T goal +3℃, and T min >T idea1 -13℃, and at this time the cascaded high-voltage direct-connected energy storage system is in a shutdown state, and the water turbine return liquid temperature is >T idea1 If the temperature is -13℃, the temperature difference between the inlet and outlet liquids of the water chiller is less than 6℃, and the water chiller unit is functioning correctly, then the water chiller should be shut down. Otherwise, start the water chiller and set the operating mode to cooling. goal =T idea1 -5;

[0026] (3) When T av <T idea1 -10, and T min >T idea1-13℃, while the cascaded high-voltage direct-connected energy storage system is in a shutdown state, the water turbine is also shut down; otherwise, the water turbine is started and the operating mode is set to heating. goal =T idea1 -5.

[0027] Secondly, the second embodiment of the present invention provides a cascaded high-voltage direct-connected energy storage system charge and discharge depth control device for implementing the method described in the first embodiment above, including: a SOC equalization control module, an electronic bypass control module, a water turbine temperature control module, and a central control module;

[0028] The SOC equalization control module is used to perform SOC equalization control on each battery cell in the cascaded high-voltage direct-connected energy storage system to maintain the consistency of the SOC of each battery cell during system operation.

[0029] The electronic bypass control module is used to perform electronic bypass control on batteries that cannot continue to be charged or discharged at the end of the charging and discharging period, so that the batteries that cannot continue to be charged or discharged are removed from the charging and discharging circuit, and the batteries that are not fully charged / discharged continue to be charged and discharged. When the number of electronic bypass stages in a certain phase exceeds the threshold of the number of bypass stages, the cascaded high-voltage direct-connected energy storage system is shut down.

[0030] The water purifier temperature control module is used to dynamically control the water purifier's working status, outlet water temperature, and target temperature based on the battery's real-time temperature parameters, ensuring that the battery operates within its normal operating temperature range.

[0031] The central control module is communicatively connected to the SOC equalization control module, the electronic bypass control module, and the water turbine temperature control module, and is used to coordinate the operation and state switching of each module.

[0032] Furthermore, the SOC equalization control module includes inter-phase SOC control, which is used to control the power of each phase, ultimately acting on the zero-sequence voltage and injecting a modulation wave, satisfying the following formula:

[0033] ;

[0034] in, This represents the power that needs to be added to each phase. This represents the control coefficient. Represents the target power. This represents the average SOC of all non-bypassed stages in a three-phase battery system, where the stage is... M represents the number of high-voltage direct-connected energy storage systems cascaded, while This represents the average SOC of the battery in each non-bypass stage, where Mi is the number of stages. j i j For each phase, there is a bypass series.

[0035] Furthermore, the SOC equalization control module includes in-phase SOC control, which directly acts on the modulated wave through a superposition amount, satisfying the following formula:

[0036] ;

[0037] in, This indicates the amount of superposition of the original modulated waves. This represents the control coefficient. Represents the original modulated wave, SOC i This represents the SOC value of a single-cell battery.

[0038] Furthermore, the electronic bypass control module includes a judgment unit, a first control unit, a second control unit, and a statistics unit;

[0039] The judgment unit is used to determine whether the cascaded high-voltage direct-connected energy storage system is in a charging or discharging state.

[0040] The first control unit is used to determine whether the dischargeable power of each phase and each stage of the cascaded high-voltage direct-connected energy storage system is 0 when the system is in a discharge state. If so, it controls the converter unit and battery of that stage to enter electronic bypass and controls the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to be turned on simultaneously. If not, it releases the electronic bypass state of that stage and continues to discharge.

[0041] The second control unit is used to determine whether the rechargeable power of each phase and each stage is 0 when the cascaded high-voltage direct-connected energy storage system is in the charging state. If it is, it controls the converter unit and battery of that stage to enter electronic bypass and controls the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to be turned on at the same time. If not, it releases the electronic bypass state of that stage and continues charging.

[0042] The statistical unit is used to count the number of electron bypass stages in that phase after each bypass.

[0043] Furthermore, the water purifier temperature control module includes a calculation unit, a temperature setting unit, and a control unit. The calculation unit is used to calculate the average temperature, maximum temperature, and minimum temperature of each battery cell.

[0044] The temperature setting unit is used to set the normal operating temperature range of the battery.

[0045] The control unit is used to control the start / stop of the water purifier and the target temperature based on the relationship between the average temperature, maximum temperature and minimum temperature of each battery cell.

[0046] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0047] This invention provides a method and apparatus for controlling the charge and discharge depth of a cascaded high-voltage direct-connected energy storage system. It combines SOC equalization control with electronic bypass control, solving the problem in traditional solutions where individual cells prematurely reach their voltage thresholds, causing the entire stack to stop charging and discharging. At the end of the charge and discharge cycle, the system can electronically bypass cells that cannot continue charging or discharging, utilizing the capacity of other partially charged or partially discharged batteries, thereby increasing the overall battery charge and discharge depth by approximately 1%. Under a complete charge and discharge cycle, the user's effective power capacity can be increased by more than 2%, significantly improving the utilization rate and return on investment of the energy storage system. By introducing water chiller temperature control logic, the system dynamically adjusts the start / stop and target temperature of the water chiller based on the average, maximum, and minimum battery temperatures, ensuring that the battery always operates within a suitable temperature range. Through precise thermal management, battery aging is effectively delayed, battery cycle life is extended, and maintenance costs due to battery replacement are reduced. Attached Figure Description

[0048] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0049] Figure 1 This is a schematic diagram of a cascaded high-voltage direct-connected energy storage system.

[0050] Figure 2 A flowchart of a method for controlling the charge and discharge depth of a cascaded high-voltage direct-connected energy storage system provided in the first embodiment of the present invention;

[0051] Figure 3 This is a flowchart of the electronic bypass control logic;

[0052] Figure 4 The diagram below shows a structural block diagram of a cascaded high-voltage direct-connected energy storage system charge and discharge depth control device, which is provided in another embodiment of the present invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0054] like Figure 1The diagram illustrates a cascaded high-voltage direct-connected energy storage system, wherein the number of cascades in the high-voltage direct-connected energy storage system is M, and each stage includes a converter unit, a high-voltage box, and a battery. The converter unit comprises two mechanical bypass switches, an H-bridge consisting of four fully controlled semiconductor devices, a DC bus capacitor, and an LC filter. The high-voltage box includes fuses and a soft-start circuit. The battery consists of multiple cells. A water chiller provides liquid cooling for the converter and battery, keeping their temperatures within the ideal operating range. The fully controlled semiconductor devices are IGBTs or IGCTs; in this embodiment, IGBTs are used.

[0055] like Figure 2 As shown, the first embodiment of the present invention provides a method for controlling the charge and discharge depth of a cascaded high-voltage direct-connected energy storage system, comprising:

[0056] Before the cascaded high-voltage direct-connected energy storage system is put into operation, the water turbine will keep the outlet water temperature at the ideal temperature of the battery in advance.

[0057] During the operation of the cascaded high-voltage direct-connected energy storage system, SOC equalization control is performed on each level of the battery in the cascaded high-voltage direct-connected energy storage system to maintain the consistency of SOC of each level of battery during the operation of the cascaded high-voltage direct-connected energy storage system.

[0058] At the end of the charging and discharging period, electronic bypass control is implemented for batteries that cannot continue to charge or discharge, so that the batteries that cannot continue to charge or discharge are removed from the charging and discharging circuit, and the batteries that are not fully charged / discharged continue to be charged and discharged. When the number of electronic bypass stages in a certain phase exceeds the threshold of the number of bypass stages, the cascaded high-voltage direct-connected energy storage system is shut down.

[0059] Throughout the operation of the cascaded high-voltage direct-connected energy storage system, the water turbine's operating status, outlet water temperature, and target temperature are dynamically controlled based on the battery's real-time temperature parameters to ensure that the battery remains within its normal operating temperature range.

[0060] Specifically, during the operation of the cascaded high-voltage direct-connected energy storage system, the SOC balancing algorithm is used to maintain the SOC difference among the three-phase 3M-level batteries within a small range. However, differences will always exist at the end of the charge and discharge cycle. Some battery cells in certain stages will discharge or fully charge before other battery cells, meaning their cell voltage is below or above a certain threshold (dischargeable or rechargeable power is 0). Therefore, electronic bypass temporarily blocks the non-chargeable / dischargeable stages, allowing other partially charged or discharged batteries to continue charging and discharging. Finally, when the number of electronically bypassed stages in a certain phase exceeds the threshold for bypassable stages, the system shuts down.

[0061] The bypass stage threshold is set to N, and the number of bypass stages for each phase is i. jState of Charge (SOC) balancing control of each stage of the battery in a cascaded high-voltage direct-connected energy storage system includes inter-phase SOC control. Inter-phase SOC control is used to control the power of each phase, ultimately affecting the zero-sequence voltage and injecting a modulation wave, satisfying the following formula:

[0062] ;

[0063] in, This represents the power that needs to be added to each phase. This represents the control coefficient. Represents the target power. This represents the average SOC of all non-bypassed stages in a three-phase battery system, where the stage is... M represents the number of high-voltage direct-connected energy storage systems cascaded, while This represents the average SOC of the battery in each non-bypass stage, where Mi is the number of stages. j i j For each phase, there is a bypass series.

[0064] SOC balancing control for each stage of batteries in a cascaded high-voltage direct-connected energy storage system also includes intra-phase SOC control. Intra-phase SOC control directly acts on the modulation wave through superposition, satisfying the following formula:

[0065] ;

[0066] in, This indicates the amount of superposition of the original modulated waves. This represents the control coefficient. Represents the original modulated wave, SOC i This represents the SOC value of a single-stage battery. SOC equalization control ensures that the SOC of the three-phase M-stage batteries remains relatively close during the remaining time, except at the end of the charge / discharge cycle.

[0067] By employing intra-phase and inter-phase SOC balancing control methods, and through power regulation and modulation wave superposition, the SOC of each battery cell is continuously dynamically balanced during charging and discharging. This control strategy effectively reduces the SOC differences between battery cells, avoiding local overcharging or over-discharging caused by inconsistency, thereby improving the overall operating efficiency and safety of the energy storage system.

[0068] Electronic bypass function logic for improving battery charge / discharge depth, such as Figure 3As shown in the figure, when the cascaded high-voltage direct-connected energy storage system enters the operating state, it is determined whether the cascaded high-voltage direct-connected energy storage system is in the discharging state or the charging state (i.e., the active power given value is not 0, and the given value determines the charge-discharge state). If it is in the discharging state, it is judged whether the dischargeable power of each phase and each level (a total of M levels) is 0; if it is 0, the converter unit and the battery of this level enter the electronic bypass, and the upper-arm IGBTs of the H-bridge are turned on simultaneously. If it is not 0, the electronic bypass state of this level is released, and the discharging continues; after the converter unit and the battery of this level enter the electronic bypass, it is judged whether the number of electronic bypass levels of this phase is greater than the total number of bypassable levels N. If > N, the system enters the shutdown state. If < N, it continues to judge whether the dischargeable power of each phase and each level (a total of M levels) is 0. When the system is in the charging state, similar to the discharging state, it is judged whether the chargeable power of each phase and each level is 0. If so, the converter unit and the battery of this level are controlled to enter the electronic bypass, and the full-controlled semiconductor devices of the upper arm of the H-bridge of this level are turned on simultaneously. If not, the electronic bypass state of this level is released, and the charging continues. It should be noted that the levels bypassed electronically during the discharging stage will have their electronic bypass states released during the charging stage, and vice versa.

[0069] The temperature of the battery is also related to the charge-discharge depth and cycle life. Therefore, in order to keep the battery at a suitable temperature all the time (it is known that this temperature range is the suitable temperature of the battery), and in combination with the current state of the system, the operating logic of the water chiller is designed. First, the average temperature of 3M batteries is set as T av , the highest temperature is T max , the lowest temperature is T min , the suitable temperature range of the battery is T idea1 ~T idea2 , and the target temperature of the water chiller is T goal . The start-stop of the water chiller and the target temperature T goal are controlled according to the following conditions

[0070] (1) When T av >T idea1 , the water chiller is started, and the working mode is set to refrigeration. If T max >T idea2 , then T goal =T idea1 -10; if T max <T idea2 , then T goal =T idea1 -5;

[0071] (2) When T idea1 -10<T av <T idea1 , and T max <T goal , and T min >Tidea1 -13℃, and the system is in a shutdown state at this time, the water return temperature is >T idea1 If the temperature is -13℃ and the temperature difference between the inlet and outlet liquids of the water chiller is less than 6℃, the water chiller unit is functioning correctly and will shut down. Otherwise, start the water chiller and set its operating mode to cooling. goal =T idea1 -5;

[0072] (3) When T av <T idea1 -10, and T min >T idea1 If the temperature is -13℃ and the system is in a shutdown state, the water chiller will also shut down. Otherwise, start the water chiller and set its operating mode to heating. goal =T idea1 -5.

[0073] This invention provides a method for controlling the charge and discharge depth of a cascaded high-voltage direct-connected energy storage system. By combining SOC equalization control and electronic bypass control, it solves the problem in traditional solutions where the entire stack stops charging and discharging due to individual cells reaching their voltage threshold prematurely. At the end of the charge and discharge cycle, the system can electronically bypass cells that cannot continue charging or discharging, continuing to utilize the capacity of other partially charged or partially discharged batteries, thereby increasing the overall battery charge and discharge depth by approximately 1%. Under a complete charge and discharge cycle, the user's effective power capacity can be increased by more than 2%, significantly improving the utilization rate and return on investment of the energy storage system. For practical applications of industrial and commercial energy storage (e.g., two charge and two discharge cycles per day), annual cost savings can exceed tens of thousands of yuan. By introducing water purifier temperature control logic, the start / stop and target temperature of the water purifier are dynamically adjusted based on the average, maximum, and minimum battery temperatures, ensuring that the battery always operates within a suitable temperature range. Through precise thermal management, battery aging is effectively delayed, battery cycle life is extended, and maintenance costs due to battery replacement are reduced.

[0074] like Figure 4As shown, another embodiment of the present invention provides a charge / discharge depth control device for a cascaded high-voltage direct-connected energy storage system, used to implement the method described in the first embodiment of the present invention. The device includes: a SOC equalization control module, an electronic bypass control module, a water turbine temperature control module, and a central control module. The SOC equalization control module is used to perform SOC equalization control on each battery cell within the cascaded high-voltage direct-connected energy storage system, maintaining the consistency of the SOC of each battery cell during system operation. The electronic bypass control module is used to perform electronic bypass control on batteries that cannot continue charging / discharging at the end of the charge / discharge period, causing these batteries to exit the charge / discharge circuit and allowing the charging / discharging of batteries that are not fully charged / discharged to continue. When the number of electronic bypass stages in a certain phase exceeds the bypass stage threshold, the cascaded high-voltage direct-connected energy storage system shuts down. The water turbine temperature control module is used to dynamically control the water turbine's operating status, outlet water temperature, and target temperature based on the real-time temperature parameters of the batteries, ensuring that the batteries are within the normal operating temperature range. The central control module is connected to the SOC... The equalization control module, electronic bypass control module, and water turbine temperature control module are connected to each other for overall control of the operation and status switching of each module.

[0075] The SOC equalization control module includes inter-phase SOC control, which is used to control the power of each phase, ultimately acting on the zero-sequence voltage and injecting a modulation wave, satisfying the following formula:

[0076] ;

[0077] in, This represents the power that needs to be added to each phase. This represents the control coefficient. Represents the target power. This represents the average SOC of all non-bypassed stages in a three-phase battery system, where the stage is... M represents the number of high-voltage direct-connected energy storage systems cascaded, while This represents the average SOC of the battery in each non-bypass stage, where Mi is the number of stages. j i j For each phase, there is a bypass series.

[0078] The SOC equalization control module includes in-phase SOC control, which directly acts on the modulated wave through superposition, satisfying the following formula:

[0079] ;

[0080] in, This indicates the amount of superposition of the original modulated waves. This represents the control coefficient. Represents the original modulated wave, SOC i This represents the SOC value of a single-cell battery.

[0081] The electronic bypass control module includes a judgment unit, a first control unit, a second control unit, and a statistics unit. The judgment unit is used to determine whether the cascaded high-voltage direct-connected energy storage system is in a charging or discharging state. The first control unit is used when the cascaded high-voltage direct-connected energy storage system is in a discharging state to determine whether the dischargeable power of each phase and each stage is 0. If yes, it controls the converter unit and battery of that stage to enter electronic bypass and controls the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to conduct simultaneously. If no, it deactivates the electronic bypass state of that stage and continues discharging. The second control unit is used when the cascaded high-voltage direct-connected energy storage system is in a charging state to determine whether the rechargeable power of each phase and each stage is 0. If yes, it controls the converter unit and battery of that stage to enter electronic bypass and controls the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to conduct simultaneously. If no, it deactivates the electronic bypass state of that stage and continues charging. The statistics unit is used to count the number of electronic bypass stages for that phase after each bypass.

[0082] The water purifier temperature control module includes a calculation unit, a temperature setting unit, and a control unit. The calculation unit is used to calculate the average temperature, maximum temperature, and minimum temperature of each battery cell. The temperature setting unit is used to set the normal operating temperature range of the battery. The control unit is used to control the start / stop of the water purifier and the target temperature based on the relationship between the average temperature, maximum temperature, and minimum temperature of each battery cell.

[0083] This invention provides a cascaded high-voltage direct-connected energy storage system charge / discharge depth control device. It combines SOC equalization control with electronic bypass control, solving the problem in traditional solutions where individual cells prematurely reach their voltage thresholds, causing the entire stack to stop charging / discharging. At the end of the charge / discharge cycle, the system can electronically bypass cells that cannot continue charging / discharging, utilizing the capacity of other partially charged or partially discharged batteries, thereby increasing the overall battery charge / discharge depth by approximately 1%. Under a complete charge / discharge cycle, the user's effective power capacity can be increased by more than 2%, significantly improving the utilization rate and return on investment of the energy storage system. By introducing water chiller temperature control logic, the system dynamically adjusts the start / stop of the water chiller and the target temperature based on the battery's average, maximum, and minimum temperatures, ensuring the battery always operates within a suitable temperature range. Through precise thermal management, battery aging is effectively delayed, battery cycle life is extended, and maintenance costs due to battery replacement are reduced.

[0084] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the charge and discharge depth of a cascaded high-voltage direct-connected energy storage system, characterized in that, include: During the operation of the cascaded high-voltage direct-connected energy storage system, SOC equalization control is performed on each level of the battery in the cascaded high-voltage direct-connected energy storage system to maintain the consistency of SOC of each level of battery during the operation of the cascaded high-voltage direct-connected energy storage system. At the end of the charging and discharging period, electronic bypass control is implemented for batteries that cannot continue to charge or discharge, so that the batteries that cannot continue to charge or discharge are removed from the charging and discharging circuit, and the batteries that are not fully charged / discharged continue to be charged and discharged. When the number of electronic bypass stages in a certain phase exceeds the threshold of the number of bypass stages, the cascaded high-voltage direct-connected energy storage system is shut down. Throughout the operation of the cascaded high-voltage direct-connected energy storage system, the water turbine's operating status, outlet water temperature, and target temperature are dynamically controlled based on the battery's real-time temperature parameters to ensure that the battery remains within its normal operating temperature range.

2. The method according to claim 1, characterized in that, The SOC balancing control of each stage of the cascaded high-voltage direct-connected energy storage system includes inter-phase SOC control. The inter-phase SOC control is used to control the power of each phase, ultimately acting on the zero-sequence voltage and injecting a modulation wave, satisfying the following formula: ； in, This indicates the power that needs to be added to each phase. Indicates the control coefficient. Represents the target power. This represents the average SOC of all non-bypassed stages in a three-phase battery system, where the stage is... M represents the number of high-voltage direct-connected energy storage systems cascaded, while This represents the average SOC of the battery in each non-bypass stage, where Mi is the number of stages. j i j For each phase, there is a bypass series.

3. The method according to claim 2, characterized in that, The SOC equalization control of each stage of the cascaded high-voltage direct-connected energy storage system also includes intra-phase SOC control. The intra-phase SOC control directly acts on the modulation wave through superposition, satisfying the following formula: ； in, This indicates the amount of superposition of the original modulated waves. Indicates the control coefficient. Represents the original modulated wave, SOC i This represents the SOC value of a single-cell battery.

4. The method according to claim 3, characterized in that, The specific method for electronically bypassing batteries that cannot continue charging or discharging, thereby removing them from the charging / discharging circuit and allowing the partially charged / discharged batteries to continue charging and discharging, includes: Determine whether the cascaded high-voltage direct-connected energy storage system is in a charging or discharging state; If it is in a discharge state, determine whether the dischargeable power of each phase and each stage is 0. If it is, control the converter unit and battery of that stage to enter electronic bypass, and control the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to conduct simultaneously. If not, release the electronic bypass state of that stage and continue discharging. If it is in the charging state, determine whether the rechargeable power of each phase and each stage is 0. If it is, control the inverter unit and battery of that stage to enter electronic bypass, and control the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to conduct simultaneously. If not, release the electronic bypass state of that stage and continue charging. After each bypass, the number of electron bypass stages in that phase is counted.

5. The method according to claim 4, characterized in that, The specific method for dynamically controlling the water purifier's operating status, outlet water temperature, and target temperature based on the battery's real-time temperature parameters includes: Calculate the average temperature T of each battery cell. av Maximum temperature T max and lowest temperature T min ; The normal operating temperature range of the battery is set to T. idea1 ~T idea2 ; Control the water turbine start / stop and target temperature T according to the following conditions. goal ; (1) When T av >T idea1 Then start the water chiller and set the operating mode to cooling. If T max >T idea2 Then T goal =T idea1 -10; if T max <T idea2 Then T goal =T idea1 -5; (2) When T idea1 -10 <T av <T idea1 And T max <T goal +3℃, and T min >T idea1 -13℃, and at this time the cascaded high-voltage direct-connected energy storage system is in a shutdown state, and the water turbine return liquid temperature is >T idea1 If the temperature is -13℃, the temperature difference between the inlet and outlet liquids of the water chiller is less than 6℃, and the water chiller unit is functioning correctly, then the water chiller should be shut down. Otherwise, start the water chiller and set the operating mode to cooling. goal =T idea1 -5; (3) When T av <T idea1 -10, and T min >T idea1 -13℃, while the cascaded high-voltage direct-connected energy storage system is in a shutdown state, the water turbine is also shut down; otherwise, the water turbine is started and the operating mode is set to heating. goal =T idea1 -5.

6. A charge / discharge depth control device for a cascaded high-voltage direct-connected energy storage system, characterized in that, The method for implementing the method as described in any one of claims 1-5 includes: a SOC equalization control module, an electronic bypass control module, a water chiller temperature control module, and a central control module; The SOC equalization control module is used to perform SOC equalization control on each battery cell in the cascaded high-voltage direct-connected energy storage system to maintain the consistency of the SOC of each battery cell during system operation. The electronic bypass control module is used to perform electronic bypass control on batteries that cannot continue to be charged or discharged at the end of the charging and discharging period, so that the batteries that cannot continue to be charged or discharged are removed from the charging and discharging circuit, and the batteries that are not fully charged / discharged continue to be charged and discharged. When the number of electronic bypass stages in a certain phase exceeds the threshold of the number of bypass stages, the cascaded high-voltage direct-connected energy storage system is shut down. The water purifier temperature control module is used to dynamically control the water purifier's working status, outlet water temperature, and target temperature based on the battery's real-time temperature parameters, ensuring that the battery operates within its normal operating temperature range. The central control module is communicatively connected to the SOC equalization control module, the electronic bypass control module, and the water turbine temperature control module, and is used to coordinate the operation and state switching of each module.

7. The apparatus according to claim 6, characterized in that, The SOC equalization control module includes inter-phase SOC control, which is used to control the power of each phase, ultimately acting on the zero-sequence voltage and injecting a modulation wave, satisfying the following formula: ； in, This indicates the power that needs to be added to each phase. Indicates the control coefficient. Represents the target power. This represents the average SOC of all non-bypassed stages in a three-phase battery system, where the stage is... M represents the number of high-voltage direct-connected energy storage systems cascaded, while This represents the average SOC of the battery in each non-bypass stage, where Mi is the number of stages. j i j For each phase, there is a bypass series.

8. The apparatus according to claim 7, characterized in that, The SOC equalization control module includes in-phase SOC control, which directly acts on the modulated wave through superposition, satisfying the following formula: ； in, This indicates the amount of superposition of the original modulated waves. Indicates the control coefficient. Represents the original modulated wave, SOC i This represents the SOC value of a single-cell battery.

9. The apparatus according to claim 8, characterized in that, The electronic bypass control module includes a judgment unit, a first control unit, a second control unit, and a statistics unit; The judgment unit is used to determine whether the cascaded high-voltage direct-connected energy storage system is in a charging or discharging state. The first control unit is used to determine whether the dischargeable power of each phase and each stage of the cascaded high-voltage direct-connected energy storage system is 0 when the system is in a discharge state. If so, it controls the converter unit and battery of that stage to enter electronic bypass and controls the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to be turned on simultaneously. If not, it releases the electronic bypass state of that stage and continues to discharge. The second control unit is used to determine whether the rechargeable power of each phase and each stage is 0 when the cascaded high-voltage direct-connected energy storage system is in the charging state. If it is, it controls the converter unit and battery of that stage to enter electronic bypass and controls the fully controlled semiconductor devices of the upper arm of the H-bridge of that stage to be turned on at the same time. If not, it releases the electronic bypass state of that stage and continues charging. The statistical unit is used to count the number of electron bypass stages in that phase after each bypass.

10. The apparatus according to claim 9, characterized in that, The water purifier temperature control module includes a calculation unit, a temperature setting unit, and a control unit. The calculation unit is used to calculate the average temperature, maximum temperature, and minimum temperature of each battery cell. The temperature setting unit is used to set the normal operating temperature range of the battery. The control unit is used to control the start / stop of the water purifier and the target temperature based on the relationship between the average temperature, maximum temperature and minimum temperature of each battery cell.

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