Method and system for controlling inter-phase charge state balance of high-voltage direct-hanging energy storage system

Abstract

The invention provides a control method and system for inter-phase charge state balance of a high-voltage direct-hanging energy storage system. The method comprises the following steps: receiving an active power instruction and a reactive power instruction of the system; measuring the charge state of each battery unit by the system; measuring by the system to obtain a power grid voltage effective value and a power grid current instantaneous value; calculating a power factor of the system according to the active power instruction and the reactive power instruction; calculating active power reference of each phase according to the active power instruction, the reactive power instruction and the charge state of each battery unit; according to the active power instruction, the reactive power instruction, the power grid voltage effective value, the power grid current instantaneous value, the power factor and the active power reference of each phase, calculating to obtain a zero-sequence voltage of the injected three-phase modulation signal; and calculating a three-phase modulation signal after zero-sequence voltage injection according to the zero-sequence voltage. According to the method, the convenience of a control algorithm can be improved, the operation range of inter-phase charge state balance is expanded, and the control efficiency of inter-phase charge state balance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage system control, and in particular relates to a control method and system for balancing the inter-phase charge state of a high-voltage direct-mounted energy storage system. Background Art

[0002] The high-voltage direct-mounted energy storage system forms a multi-level voltage output on the AC side by cascading multiple independent battery cells, and is directly connected to the medium-voltage grid without a step-up transformer. Compared with traditional two-level and three-level energy storage systems, the high-voltage direct-mounted energy storage system has some advantages such as high conversion efficiency, large single-cell capacity, low circulating loss, and high power quality.

[0003] At present, in high-voltage direct-mounted energy storage systems, in order to achieve consistent operation of each battery unit and improve the overall operating life and full-capacity operating capacity of the energy storage system, it is necessary to use a control algorithm to ensure that the state of charge of each battery unit is always consistent in charging mode and discharging mode. The widely used battery unit state of charge balancing control method consists of total power control, phase-to-phase state of charge balancing control, and phase-to-phase state of charge balancing control. Among them, total power control is used to achieve power interaction between the high-voltage direct-mounted energy storage system and the power grid, phase-to-phase state of charge balancing control is used to achieve consistent operation of the sum of the state of charge of all battery units in each phase, and phase-to-phase state of charge balancing control is used to achieve consistent operation of the state of charge of all battery units in a single phase.

[0004] However, the inter-phase state of charge balancing control method is implemented by injecting zero-sequence voltage into the three-phase modulation signal, and the indirect control of the state of charge of the three-phase battery unit is achieved by adjusting the distribution of the three-phase power. The calculation process of the existing zero-sequence voltage injection method is relatively cumbersome, involving complex calculations such as trigonometric functions and square roots. The calculation formula cannot be unified when targeting zero-sequence voltages of different phases. At the same time, only a single power factor operating condition can be considered, and the scope of application is single. Therefore, in summary, at present, in high-voltage direct-mounted energy storage systems, the inter-phase state of charge balancing control method can only consider a single power factor operating condition, the scope of application is relatively single, and the process is relatively cumbersome. The calculation formula cannot be unified when targeting zero-sequence voltages of different phases. Summary of the invention

[0005] The present invention provides a control method and system for balancing the interphase state of charge of a high-voltage direct-mounted energy storage system, aiming to solve the problem that the current interphase state of charge balancing control method in a high-voltage direct-mounted energy storage system can only consider a single power factor operating condition, has a relatively single scope of application, and a relatively cumbersome process, and cannot unify the calculation formula for zero-sequence voltages of different phases.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A control method for balancing the interphase charge state of a high-voltage direct-mounted energy storage system comprises the following steps:

[0008] S1, receiving active power instructions and reactive power instructions of the high-voltage direct-mounted energy storage system;

[0009] S2, the high-voltage direct-mounted energy storage system measures the state of charge of each battery unit;

[0010] S3, the high-voltage direct-mounted energy storage system measures the effective value of the grid voltage and the instantaneous value of the grid current;

[0011] S4. Calculate the power factor of the high-voltage direct-mounted energy storage system according to the active power command and the reactive power command;

[0012] S5. Calculate the active power reference of each phase according to the active power command, the reactive power command and the charge state of each battery unit;

[0013] S6. Calculate the zero-sequence voltage injected into the three-phase modulation signal according to the active power command, the reactive power command, the effective value of the grid voltage, the instantaneous value of the grid current, the power factor and the active power reference of each phase;

[0014] S7. According to the zero-sequence voltage, the three-phase modulation signal after the zero-sequence voltage is injected is calculated, and then the inter-phase charge state of the high-voltage direct-mounted energy storage system is balanced and controlled.

[0015] In some embodiments, in S2, the state of charge of each battery cell of the high-voltage direct-mounted energy storage system is SOC a1 -SOC cn , where n represents the number of battery cells per phase.

[0016] In some embodiments, in S4, the power factor of the high-voltage direct-mounted energy storage system is calculated according to the following formula (1):

[0017]

[0018] Where F is the power factor, P * is the active power command, Q * It is the reactive power command.

[0019] Further, in S4, the operating range of the power factor of the high-voltage direct-mounted energy storage system is 1 to -1.

[0020] In some embodiments, in S5, the high-voltage direct-mounted energy storage system has a charging mode and a discharging mode; wherein:

[0021] When the high-voltage direct-mounted energy storage system is in charging mode, the active power reference of each phase is calculated as follows:

[0022]

[0023] When the high-voltage direct-mounted energy storage system is in the discharge mode, the active power reference of each phase is calculated as follows:

[0024]

[0025] in, is the active power reference of each phase, SOC aj , SOC ij , SOC bj , SOC cj is the state of charge of each battery cell.

[0026] In some implementations, in S6, the zero-sequence voltage injected into the three-phase modulation signal is calculated using the following formula (4):

[0027]

[0028] Where v0 is the zero-sequence voltage, P * is the active power command, is the active power reference of each phase, Vg is the effective value of the grid voltage, i gi is the instantaneous value of the grid current, and F is the power factor.

[0029] In some implementations, in S7, the three-phase modulation signal after zero-sequence voltage injection is calculated according to the following formula (5):

[0030]

[0031] in, They respectively represent the positive sequence components of the three-phase modulation signals before zero sequence voltage injection.

[0032] The present invention also provides a control system for balancing the interphase charge state of a high-voltage direct-mounted energy storage system, the control system comprising a data acquisition module and a data analysis and calculation module; wherein:

[0033] The data acquisition module is used to collect various physical quantities in the high-voltage direct-mounted energy storage system and transmit them to the data analysis and calculation module;

[0034] The data analysis and calculation module is used to calculate the three-phase modulation signal after zero-sequence voltage injection based on various physical quantities in the high-voltage direct-mounted energy storage system.

[0035] The present invention also provides a computer device, including a memory, a processor, and a computer program stored and running on the memory. When the processor executes the computer program, the steps of the control method for balancing the inter-phase charge state of the above-mentioned high-voltage direct-mounted energy storage system are implemented.

[0036] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the control method for balancing the inter-phase charge state of the above-mentioned high-voltage direct-mounted energy storage system are implemented.

[0037] Compared with the prior art, the control method and system for balancing the interphase state of charge of a high-voltage direct-mounted energy storage system of the present invention have the following beneficial effects:

[0038] The present invention provides a control method for balancing the interphase state of charge of a high-voltage direct-mounted energy storage system, comprising the following steps: S1, receiving the active power command and reactive power command of the high-voltage direct-mounted energy storage system; S2, the high-voltage direct-mounted energy storage system measures the state of charge of each battery unit; S3, the high-voltage direct-mounted energy storage system measures the effective value of the grid voltage and the instantaneous value of the grid current; S4, according to the active power command and the reactive power command, the power factor of the high-voltage direct-mounted energy storage system is calculated; S5, according to the active power command, the reactive power command and the state of charge of each battery unit, the active power reference of each phase is calculated; S6, according to the active power command, the reactive power command, the effective value of the grid voltage, the instantaneous value of the grid current, the power factor and the active power reference of each phase, the zero-sequence voltage injected into the three-phase modulation signal is calculated; S7, according to the zero-sequence voltage, the three-phase modulation signal after the zero-sequence voltage is injected is calculated, and then the interphase state of charge of the high-voltage direct-mounted energy storage system is balanced. Based on the above, the present invention can achieve the balance of the interphase state of charge through the above method. The present invention first receives the active power command and reactive power command of the system, and then measures the state of charge of each battery unit and the voltage and current information of the power grid. The measured information is then used to calculate the power factor, the active power reference of each phase, and the zero-sequence voltage injected into the three-phase modulation signal, and finally the phase-to-phase state of charge balance is achieved by adjusting the three-phase modulation signal. On the basis of achieving the balanced operation of the phase-to-phase state of charge of the high-voltage direct-mounted energy storage system, the present invention can effectively reduce the complexity of the control algorithm implementation, expand the operating range of the phase-to-phase state of charge balance, unify the zero-sequence voltage calculation formula, improve the algorithm versatility and practicality, and improve the control efficiency of the phase-to-phase state of charge balance. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0040] Figure 1 A flow chart of a control method for balancing the interphase state of charge of a high-voltage direct-mounted energy storage system and a method in the system according to the present invention;

[0041] Figure 2A control method for balancing the inter-phase charge state of a high-voltage direct-mounted energy storage system and a schematic diagram of the topological structure of the high-voltage direct-mounted energy storage system in the system are provided in the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0044] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0045] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0046] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0047] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] How to reduce the complexity of control algorithm implementation and expand the range of balanced operation of phase-to-phase charge state based on the balanced operation of phase-to-phase charge state of high-voltage direct-mounted energy storage system.

[0049] like Figure 1 As shown, the present invention provides a control method for balancing the inter-phase charge state of a high-voltage direct-mounted energy storage system, comprising the following steps:

[0050] S1, receiving active power instructions and reactive power instructions of the high-voltage direct-mounted energy storage system;

[0051] S2, the high-voltage direct-mounted energy storage system measures the state of charge of each battery unit;

[0052] S3, the high-voltage direct-mounted energy storage system measures the effective value of the grid voltage and the instantaneous value of the grid current;

[0053] S4. Calculate the power factor of the high-voltage direct-mounted energy storage system according to the active power command and the reactive power command;

[0054] S5. Calculate the active power reference of each phase according to the active power command, the reactive power command and the charge state of each battery unit;

[0055] S6. Calculate the zero-sequence voltage injected into the three-phase modulation signal according to the active power command, the reactive power command, the effective value of the grid voltage, the instantaneous value of the grid current, the power factor and the active power reference of each phase;

[0056] S7. According to the zero-sequence voltage, the three-phase modulation signal after the zero-sequence voltage is injected is calculated, and then the inter-phase charge state of the high-voltage direct-mounted energy storage system is balanced and controlled.

[0057] The control method for balancing the interphase state of charge of the high-voltage direct-mounted energy storage system of the present invention can reduce the fluctuation of the high-voltage direct-mounted energy storage system caused by the inconsistency between the battery cells by balancing the state of charge of the battery cells of each phase, improve the stability and reliability of the high-voltage direct-mounted energy storage system, and the balanced state of charge helps to avoid overcharging or over-discharging of some battery cells, thereby extending the service life of the entire high-voltage direct-mounted energy storage system. The present invention improves the energy conversion efficiency of the high-voltage direct-mounted energy storage system by optimizing power distribution and modulation signals, and has better applicability.

[0058] like Figure 2 As shown, the high-voltage direct-mounted energy storage system targeted by the control method of the present invention consists of n power modules per phase, and each power module consists of an AC side bypass switch, an H-bridge unit, a DC bus capacitor, a DC side inductor, a DC side fuse, and a DC side pre-charging device. The DC side of the power module is connected to an independent battery unit, and the AC side is connected in series with a grid-connected inductor, an AC circuit breaker, and an AC fuse to be directly mounted on a medium-voltage grid for operation.

[0059] In the control method for balancing the state of charge between phases of a high-voltage direct-mounted energy storage system of the present invention, the state of charge of each battery cell measured by the high-voltage direct-mounted energy storage system is SOC a1 -SOC cn , where n represents the number of battery cells per phase. The present invention can achieve a more accurate control method by clarifying the charge state of each battery cell, thereby further improving the balance and stability of the high-voltage direct-mounted energy storage system.

[0060] In some embodiments, the power factor of the high-voltage direct-mounted energy storage system of the present invention is calculated according to the following formula (1):

[0061]

[0062] Where F is the power factor, P * is the active power command, Q * It is the reactive power command.

[0063] The control method for balancing the interphase charge state of a high-voltage direct-mounted energy storage system of the present invention reduces the calculation complexity by providing the above-mentioned concise power factor calculation formula. Accurate power factor calculation helps to more accurately control the power distribution and modulation signal of the system.

[0064] In some embodiments, the control method for balancing the state of charge between phases of a high-voltage direct-mounted energy storage system of the present invention clarifies that the operating range of the power factor is 1 to -1. This is determined by the definition and physical meaning of the power factor, that is, the power factor represents the ratio of active power to apparent power, and its value is between -1 and 1. By clarifying the operating range of the power factor, the present invention helps to consider all possible operating conditions when designing the control algorithm.

[0065] In some embodiments, the control method for balancing the interphase charge state of a high-voltage direct-mounted energy storage system of the present invention, the high-voltage direct-mounted energy storage system has a charging mode and a discharging mode; wherein:

[0066] When the high-voltage direct-mounted energy storage system is in charging mode, the active power reference of each phase is calculated as follows:

[0067]

[0068] When the high-voltage direct-mounted energy storage system is in the discharge mode, the active power reference of each phase is calculated as follows:

[0069]

[0070] in, is the active power reference of each phase, SOC aj , SOC ij , SOC bj , SOC cj is the state of charge of each battery cell.

[0071] The present invention is based on the active power instruction of the high-voltage direct-mounted energy storage system and the charge state of each battery unit, and realizes the balance of the charge state between phases through a reasonable allocation strategy. Different calculation formulas are designed for the charging and discharging modes respectively, which improves the adaptability and flexibility of the control algorithm. Through a reasonable power allocation strategy, the balance of the charge state between phases is achieved, and the overall performance of the system is improved.

[0072] In some embodiments, the control method for balancing the interphase state of charge of a high-voltage direct-mounted energy storage system of the present invention uses the following formula (4) to calculate the zero-sequence voltage injected into the three-phase modulation signal:

[0073]

[0074] Where v0 is the zero-sequence voltage, P * is the active power command, is the active power reference of each phase, Vg is the effective value of the grid voltage, i gi is the instantaneous value of the grid current, and F is the power factor.

[0075] The above formula is based on the active power reference of each phase, the effective value of the grid voltage, the instantaneous value of the grid current, the power factor, and the active power command, and obtains the zero-sequence voltage value through mathematical operation. The present invention provides an accurate zero-sequence voltage calculation formula, which helps to achieve more accurate phase-to-phase charge state balance control, and improves the stability and efficiency of the high-voltage direct-mounted energy storage system by optimizing the injection of zero-sequence voltage.

[0076] In some embodiments, the control method for balancing the state of charge between phases of a high-voltage direct-mounted energy storage system of the present invention calculates the three-phase modulation signal after zero-sequence voltage injection according to the following formula (5):

[0077]

[0078] in, They respectively represent the positive sequence components of the three-phase modulation signals before zero sequence voltage injection.

[0079] The present invention reduces the calculation complexity through the above concise three-phase modulation signal calculation formula, adjusts the three-phase modulation signal after calculation, thereby realizing balanced control of the charge state between phases, and has better applicability.

[0080] The present invention provides a control system for balancing the interphase charge state of a high-voltage direct-mounted energy storage system to implement the above control method. The control system includes a data acquisition module and a data analysis and calculation module; wherein:

[0081] The data acquisition module is used to collect various physical quantities in the high-voltage direct-mounted energy storage system and transmit them to the data analysis and calculation module;

[0082] The data analysis and calculation module is used to calculate the three-phase modulation signal after zero-sequence voltage injection based on various physical quantities in the high-voltage direct-mounted energy storage system.

[0083] The present invention provides a computer device, comprising a memory, a processor and a computer program stored and running on the memory. When the processor executes the computer program, the steps of the control method for balancing the inter-phase charge state of the high-voltage direct-mounted energy storage system are implemented.

[0084] The present invention provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the control method for balancing the interphase charge state of the high-voltage direct-mounted energy storage system are implemented.

[0085] The present invention adopts a modular design, and separates data acquisition and data analysis and calculation, thereby improving the scalability and maintainability of the system. The present invention realizes the automatic control of the interphase charge state of the high-voltage direct-mounted energy storage system through the coordinated work of the data acquisition and data analysis and calculation modules, so as to realize the control method of the interphase charge state balance of the high-voltage direct-mounted energy storage system of the present invention, improve the realization of the interphase charge state balance operation of the high-voltage direct-mounted energy storage system, simplify the control algorithm, and improve the operating range of the interphase charge state balance, thereby providing technical support for the high-voltage direct-mounted energy storage system.

[0086] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0087] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the specification and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A control method for balancing the interphase charge state of a high-voltage direct-mounted energy storage system, characterized in that: The steps include: S1, receiving active power instructions and reactive power instructions of the high-voltage direct-mounted energy storage system; S2, the high-voltage direct-mounted energy storage system measures the state of charge of each battery unit; S3, the high-voltage direct-mounted energy storage system measures the effective value of the grid voltage and the instantaneous value of the grid current; S4. Calculate the power factor of the high-voltage direct-mounted energy storage system according to the active power command and the reactive power command; S5. Calculate the active power reference of each phase according to the active power command, the reactive power command and the charge state of each battery unit; S6. Calculate the zero-sequence voltage injected into the three-phase modulation signal according to the active power command, the reactive power command, the effective value of the grid voltage, the instantaneous value of the grid current, the power factor and the active power reference of each phase; S7. According to the zero-sequence voltage, the three-phase modulation signal after the zero-sequence voltage is injected is calculated, and then the inter-phase charge state of the high-voltage direct-mounted energy storage system is balanced and controlled.

2. The control method for balancing the interphase state of charge of a high-voltage direct-mounted energy storage system according to claim 1 is characterized in that: In S2, the state of charge of each battery cell of the high-voltage direct-mounted energy storage system is SOC a1 -SOC cn , where n represents the number of battery cells per phase.

3. The control method for balancing the state of charge between phases of a high-voltage direct-mounted energy storage system according to claim 1 is characterized in that: In S4, the power factor of the high-voltage direct-mounted energy storage system is calculated according to the following formula (1): Where F is the power factor, P * is the active power command, Q * Reactive power command.

4. The control method for balancing the interphase state of charge of a high-voltage direct-mounted energy storage system according to claim 3 is characterized in that: In S4, the operating range of the power factor of the high-voltage direct-mounted energy storage system is 1 to -1.

5. The control method for balancing the interphase state of charge of a high-voltage direct-mounted energy storage system according to claim 1 is characterized in that: In S5, the high-voltage direct-mounted energy storage system has a charging mode and a discharging mode; wherein: When the high-voltage direct-mounted energy storage system is in charging mode, the active power reference of each phase is calculated as follows: When the high-voltage direct-mounted energy storage system is in the discharge mode, the active power reference of each phase is calculated as follows: in, is the active power reference of each phase, SOC aj , SOC ij , SOC bj , SOC cj is the state of charge of each battery cell.

6. The control method for balancing the interphase state of charge of a high-voltage direct-mounted energy storage system according to claim 1 is characterized in that: In S6, the zero-sequence voltage injected into the three-phase modulation signal is calculated using the following formula (4): Where v0 is the zero-sequence voltage, P * is the active power command, is the active power reference of each phase, Vg is the effective value of the grid voltage, i gi is the instantaneous value of the grid current, and F is the power factor.

7. The control method for balancing the state of charge between phases of a high-voltage direct-mounted energy storage system according to claim 1 is characterized in that: In S7, the three-phase modulation signal after zero-sequence voltage injection is calculated according to the following formula (5): in, They respectively represent the positive sequence components of the three-phase modulation signals before zero sequence voltage injection.

8. A control system based on the control method for balancing the interphase state of charge of the high-voltage direct-mounted energy storage system according to any one of claims 1 to 7, characterized in that: The control system includes a data acquisition module and a data analysis and calculation module; wherein: The data acquisition module is used to collect various physical quantities in the high-voltage direct-mounted energy storage system and transmit them to the data analysis and calculation module; The data analysis and calculation module is used to calculate the three-phase modulation signal after zero-sequence voltage injection based on various physical quantities in the high-voltage direct-mounted energy storage system.

9. A computer device comprising a memory, a processor and a computer program stored and executed on the memory, characterized in that: When the processor executes the computer program, the steps of the control method for balancing the inter-phase charge state of the high-voltage direct-mounted energy storage system as described in any one of claims 1-7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of a control method for balancing the inter-phase state of charge of a high-voltage direct-mounted energy storage system as claimed in any one of claims 1 to 7 are implemented.

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