Battery energy storage system, method, controller, and medium based on cascaded h-bridges

Abstract

The application provides a battery energy storage system based on a cascade H-bridge, a method, a controller and a medium. The system comprises a first energy storage unit, a second energy storage unit and a third energy storage unit connected to a three-phase voltage of a power grid respectively, and a controller. Each energy storage unit comprises battery modules equal in number and connected in series. The controller is connected to the battery modules. The battery module comprises a direct-current battery and an H-bridge circuit. The direct-current side of the H-bridge circuit is connected to the direct-current battery through a direct-current line, and the alternating-current side is connected to the power grid through an alternating-current bus. The controller is configured to, after receiving a charge / discharge instruction, acquire a current modulation wave of each phase of the power grid and a current level number of the energy storage unit in the phase. According to the current modulation wave and the current level number, and the state of charge of each battery module in the phase, the controller controls the input / output of each battery module in the phase, so that each battery module in the phase is in a balanced state. The application improves the scalability and balance of the battery energy storage system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, and in particular to a battery energy storage system based on cascaded H-bridges, a method, a controller and a medium. BACKGROUND

[0002] With the large-scale application of power electronic devices in power systems, the inertia of new power grids is continuously reduced, and battery energy storage systems are introduced into power grids on a large scale to improve stability. In order to improve the capacity of the battery energy storage system, a large number of battery cells are deployed into the capacity of the battery energy storage system.

[0003] The battery energy storage system often adopts a series-parallel expansion architecture, Figure 1 The structure of the battery energy storage system in the related art is shown in FIG. 1, a plurality of battery packs are connected in series to form a battery cluster, and a plurality of battery clusters are connected in parallel, each battery cluster corresponds to a switch box, and the switch box is used to control the input and output of the battery cluster. Since the architecture controls the battery cluster based on the switch box, the battery is directly connected to the DC side, and therefore the expandability is poor, and there are inconsistencies between the battery cells caused by factors such as manufacturing process, use environment, and aging degree, which easily leads to an unbalanced state of the battery energy storage system. Figure 1

[0004] Therefore, there is a need for a battery energy storage solution that can improve the expandability and balance of the battery energy storage system. SUMMARY

[0005] The embodiments of the present application provide a battery energy storage system based on cascaded H-bridges, a method, a controller and a medium, which can improve the expandability and balance of the battery energy storage system.

[0006] In a first aspect, the embodiments of the present application provide a battery energy storage system based on cascaded H-bridges, comprising: a first energy storage unit, a second energy storage unit and a third energy storage unit connected to a three-phase voltage of a power grid, respectively, and a controller;

[0007] Each energy storage unit includes a plurality of battery modules connected in series, and the controller is connected to the battery modules;

[0008] The battery module includes a DC battery and an H-bridge circuit, the DC side of the H-bridge circuit is connected to the DC battery through a DC line, and the AC side is connected to the power grid through an AC bus;

[0009] The controller is configured to, after receiving a charge / discharge instruction, obtain a current modulation wave of each phase of the power grid and a current level number of the energy storage unit in the phase; and control the input / output of each battery module in the phase according to the current modulation wave, the current level number, and the state of charge (SOC) of the battery of each battery module in the phase, so that each battery module in the phase is in a balanced state. ​

[0010] In a possible implementation, each energy storage unit further comprises a DCDC conversion module, a left input end of the DCDC conversion module being a cascade battery voltage of the corresponding energy storage unit, a right output end of the DCDC conversion module being connected in series to an alternating current side of an H-bridge circuit of each battery module in the phase, and the DCDC conversion module being further connected with the controller.

[0011] The DCDC conversion module is configured to increase a discharge rate of the direct current battery when a discharge voltage of the energy storage unit is insufficient.

[0012] In a possible implementation, the DCDC conversion module is a two-stage isolated converter, and the two-stage isolated converter comprises a direct current high-frequency (HF) isolated converter and a DCDC converter connected in series with the HF isolated converter.

[0013] In a second aspect, an embodiment of the present application provides a balancing control method of a battery energy storage system, applied to a controller of the battery energy storage system based on a cascade H-bridge as described in any one of the first aspect, and the method comprises:

[0014] After receiving a charge / discharge instruction, for each phase of the grid side, a current modulation wave of the grid side and a current level number of the energy storage unit in the phase are obtained.

[0015] According to the current modulation wave and the current level number, and a battery state of charge (SOC) of each battery module in the phase, input / output of each battery module in the phase is controlled, so that each battery module in the phase is in a balanced state.

[0016] In a possible implementation, when the battery energy storage system is charging, the input / output of each battery module in the phase according to the current modulation wave and the current level number, and the battery SOC of each battery module in the phase comprises:

[0017] It is determined whether the current modulation wave is less than the current level number.

[0018] If yes, a first battery module currently input by the energy storage unit in the phase is determined, and a battery module with the largest SOC in the first battery module is cut off.

[0019] If no, a second battery module currently cut off by the energy storage unit in the phase is determined, and a battery module with the smallest SOC in the second battery module is input.

[0020] In a possible implementation, when the battery energy storage system is discharging, the input / output of each battery module in the phase according to the current modulation wave and the current level number, and the battery SOC of each battery module in the phase comprises:

[0021] determining whether the current modulation wave is less than the current level number;

[0022] If yes, determining a third battery module currently put into the intra-phase energy storage unit, and cutting off the battery module with the minimum SOC in the third battery module;

[0023] If no, determining a fourth battery module currently cut off the intra-phase energy storage unit, and putting into the battery module with the maximum SOC in the fourth battery module.

[0024] In a possible implementation, if the current modulation wave is still not less than the current level number after all battery modules in the intra-phase energy storage unit are put in, the method further includes:

[0025] sending an opening signal to a DCDC conversion module corresponding to the energy storage unit, and the DCDC conversion module increases the discharge rate of each direct-current battery in the energy storage unit from a first discharge rate to a second discharge rate in response to the opening signal.

[0026] In a possible implementation, if the current modulation wave is still not less than the current level number after the DCDC conversion module is opened, the method further includes:

[0027] outputting a charging prompt information of the battery energy storage system to charge the battery energy storage system.

[0028] In a third aspect, an embodiment of the present application provides a controller of a battery energy storage system, including:

[0029] an acquisition module, configured to acquire, after receiving a charging / discharging instruction, for each phase of a grid side, a current modulation wave of the grid side and a current level number of an intra-phase energy storage unit;

[0030] a processing module, configured to control putting in / cutting off of each battery module in the intra-phase according to the current modulation wave and the current level number and a battery state of charge (SOC) of each battery module in the intra-phase, so that each battery module in the intra-phase is in a balanced state.

[0031] In a fourth aspect, an embodiment of the present application provides another controller of a battery energy storage system, including:

[0032] a processor, and a memory connected with the processor in communication;

[0033] the memory is configured to store host computer execution instructions;

[0034] the processor is configured to execute the host computer execution instructions stored in the memory, so that the processor performs the method in the second aspect and / or various possible implementation manners of the second aspect.

[0035] In a fifth aspect, an embodiment of the present application provides a host computer readable storage medium, the host computer readable storage medium storing host computer execution instructions, the host computer execution instructions, when executed by a processor, being configured to implement the method of the second aspect and / or various possible implementation manners of the second aspect.

[0036] In a sixth aspect, an embodiment of the present application provides a host computer program product, the host computer program product comprising a host computer program, the host computer program, when executed by a processor, being configured to implement the method of the second aspect and / or various possible implementation manners of the second aspect.

[0037] The embodiment of the present application provides a battery energy storage system based on a cascade H-bridge, a plurality of battery modules are connected in series to form an energy storage unit connected to a three-phase voltage of a power grid side, a direct-current battery and an H-bridge circuit are connected to form a battery module, a direct-current side of the H-bridge circuit is connected to the direct-current battery through a direct-current line, and an alternating-current side is connected to the power grid side through an alternating-current bus. Through such a setting, the H-bridge circuit can realize high-granularity management and control of the battery module, and the energy storage system architecture based on the cascade H-bridge can realize transformerless fast grid connection and flexible assembly, greatly improving the scalability of the battery energy storage system. In addition, during the charging and discharging process, the controller can obtain a current modulation wave of each phase of the power grid side and a current level number of the energy storage unit in the phase, and control the input / output of each battery module in the phase according to the current modulation wave, the current level number, and the battery state of charge of each battery module in the phase, so that each battery module in the phase is in a balanced state. Through such a setting, the battery state of charge can be used as the switching criterion of the battery module, different module sorting can be selected according to different system charging and discharging states, the battery modules in the phase are ensured to be in a balanced state, overcharging / overdischarging of the battery is avoided, and the balance of the battery energy storage system is improved. BRIEF DESCRIPTION OF DRAWINGS

[0038] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the application.

[0039] Figure 1 FIG. 1 is a structural schematic diagram of a battery energy storage system in the related art;

[0040] Figure 2 FIG. 2 is a structural schematic diagram of a battery energy storage system based on a cascade H-bridge according to an embodiment of the present application;

[0041] Figure 3 FIG. 3 is a structural schematic diagram of a DCDC conversion module according to an embodiment of the present application;

[0042] Figure 4 FIG. 4 is a flowchart of a balancing control method of a battery energy storage system according to an embodiment of the present application;

[0043] Figure 5The schematic diagram of the equalization control process of the battery energy storage system of an embodiment of the present application;

[0044] Figure 6 The schematic diagram of the structure of the controller of the battery energy storage system of an embodiment of the present application;

[0045] Figure 7 The schematic diagram of the structure of the controller of the battery energy storage system of another embodiment of the present application.

[0046] The figure mark: 1, the first energy storage unit; 2, the second energy storage unit; 3, the third energy storage unit; 4, the battery module; 5, the direct current battery; 6, H bridge circuit; 7, DCDC conversion module; 8, direct current line; 9, alternating current bus.

[0047] Through the above-mentioned drawings, the specific embodiments of the present application have been shown, and more detailed description will be given hereinafter. These drawings and textual descriptions are not intended to limit the scope of the concept of the present application by any means, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0048] The exemplary embodiments will be described in detail herein with reference to the accompanying drawings. In the following description, unless otherwise indicated, like numbers in the different drawings represent similar or analogous elements. The implementations described in the following exemplary embodiments are not meant to represent all implementations consistent with the present application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0049] The terms "first", "second", "third", "fourth" and the like in the description and claims of the present application and the above-mentioned drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the use of the terms so termed herein is to be interpreted to allow that the embodiments of the present application described herein can employ relative terms without necessarily preferring one order of sequence or chronology over another order of sequence or chronology. Moreover, the terms "comprising" and "having", and any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or apparatus that comprises a list of steps or units not necessarily limited to those steps or units that are clearly listed, but can include other steps or units not clearly listed or inherent to such processes, methods, products, or apparatuses.

[0050] It should be noted that in the embodiments of the present application, some software, components, models and the like of the prior art may be mentioned, which should be considered as exemplary, and the purpose is only to illustrate the feasibility of the implementation of the technical solutions of the present application, but it does not mean that the applicant has or will necessarily use the scheme.

[0051] The battery energy storage system, method, controller and medium based on the cascaded H-bridge of the application can be used in the field of power electronics, and can also be used in any field other than the field of power electronics, such as the field of energy management. The application of the battery energy storage system, method, controller and medium based on the cascaded H-bridge of the application is not limited.

[0052] The battery energy storage system, method, controller and medium based on the cascaded H-bridge of the application can be applied to the charging / discharging scenarios of the battery energy storage system, and any scenarios involving high-voltage power grid energy conversion.

[0053] First, the terms involved in the application are explained:

[0054] H-bridge circuit, single-phase H-bridge inverter, composed of 4 power switches (such as IGBT or SiC MOSFET), when discharging (DC→AC), the switch tube is controlled by PWM to convert the battery DC voltage into an AC square wave, and then output a sinusoidal AC through an LC filter; when charging (AC→DC), the switch tube is controlled to realize the rectification function, and the AC is converted into DC to charge the battery.

[0055] Modulation wave, a reference signal (usually a sine wave) generated inside the controller, which approximates an ideal sine wave and is synchronized with the grid voltage, is used to guide PWM (pulse width modulation) and determines the phase, frequency and amplitude of the inverter output waveform. The modulation wave is the "blueprint" of the grid voltage, but the actual grid voltage waveform is the result of the modulation wave after PWM hardware implementation and physical filtering.

[0056] The number of levels refers to the number of voltage steps output on the AC side after the DC side (battery end) voltage of the H-bridge circuit is modulated by PWM. The number of levels is directly determined by the topology and battery configuration.

[0057] With the large-scale application of power electronic devices in power systems, the inertia of new power grids is continuously reduced, and battery energy storage systems are introduced into the power grid on a large scale to improve stability. In order to improve the capacity of the battery energy storage system, a large number of battery cells are deployed in the battery energy storage system.

[0058] The battery energy storage system often uses a series-parallel expansion architecture, Figure 1 The structure of the battery energy storage system in the related art is shown in FIG. Figure 1 As shown in FIG., a plurality of battery packs are connected in series to form a battery cluster, and a plurality of battery clusters are connected in parallel. Each battery cluster corresponds to a switch box, which is used to control the input and output of the battery cluster.

[0059] Since the architecture is based on switch box control battery cluster, the battery is directly connected to the DC side, so the scalability is poor, and there are inconsistencies between battery monomers caused by manufacturing process, use environment, aging degree and other factors, which easily leads to unbalanced state of the battery energy storage system.

[0060] Based on the above technical problems, the application concept of the present application is to provide a battery energy storage scheme capable of improving the scalability and balance of the battery energy storage system.

[0061] The embodiment of the present application provides a battery energy storage system and method based on cascaded H-bridge, a plurality of battery modules are connected in series to form an energy storage unit connected to a three-phase voltage of a power grid side, a DC battery and an H-bridge circuit are connected to form a battery module, the DC side of the H-bridge circuit is connected to the DC battery through a DC line, and the AC side is connected to the power grid side through an AC bus. Through such a setting, the H-bridge circuit can realize high-granularity management and control of the battery module, and the energy storage system architecture based on cascaded H-bridge can realize transformerless fast grid connection and flexible assembly, greatly improving the scalability of the battery energy storage system. In addition, during the charging and discharging process, the controller can obtain the current modulation wave of each phase of the power grid side and the current level number of the energy storage unit in the phase, and control the input / output of each battery module in the phase according to the current modulation wave, the current level number, and the state of charge of each battery module in the phase, so that each battery module in the phase is in a balanced state. Through such a setting, the state of charge of the battery can be used as the switching criterion of the battery module, different module sorting can be selected for switching according to the different system charging and discharging states, the battery modules in the phase are ensured to be in a balanced state, overcharging / overdischarging of the battery is avoided, and the balance of the battery energy storage system is improved.

[0062] The technical solutions of the present application and how the technical solutions of the present application solve the above technical problems will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes can not be described in detail in some embodiments. The embodiments of the present application will be described below with reference to the drawings.

[0063] Figure 2 The structure diagram of the battery energy storage system based on cascaded H-bridge of an embodiment of the present application is shown in Figure 2 As shown in the figure, the battery energy storage system comprises: a first energy storage unit 1, a second energy storage unit 2, and a third energy storage unit 3 connected to a three-phase voltage of a power grid side respectively, and a controller.

[0064] Each energy storage unit comprises a plurality of battery modules 4 connected in series, and the controller is connected to the battery modules 4.

[0065] The structure of each battery module 4 is the same, Figure 2The specific structure of the battery module 4 is described only by taking the structure of the module A1 as an example, and the structures of the modules A2-An, B1-Bn and C1-Cn are the same as that of the module A1, which is not described herein.

[0066] The battery module 4 includes a direct-current battery 5 and an H-bridge circuit 6, the direct-current side of the H-bridge circuit 6 is connected with the direct-current battery 5 through a direct-current line 8, and the alternating-current side is connected with the grid side through an alternating-current bus 9.

[0067] The controller is configured to, after receiving the charge / discharge instruction, acquire a current modulation wave of each phase of the grid side and a current level number of the energy storage unit in the phase; and control the input / output of each battery module 4 in the phase according to the current modulation wave, the current level number and a state of charge (SOC) of each battery module 4 in the phase, so that each battery module 4 in the phase is in a balanced state.

[0068] In the embodiment, each energy storage unit of the battery energy storage system is connected with three-phase voltage of the grid side, and each battery module in the energy storage unit can realize ACDC conversion by using the H-bridge circuit in the battery module, and the battery energy storage system can be connected with a high-voltage grid for charging / discharging.

[0069] In the embodiment, the alternating-current side of each battery module 4 is connected with the grid in series through the alternating-current bus 9.

[0070] In the embodiment, the first energy storage unit 1 can be connected with A-phase voltage of the grid side, the second energy storage unit 2 can be connected with B-phase voltage of the grid side, and the third energy storage unit 3 can be connected with C-phase voltage of the grid side.

[0071] In the embodiment, the number of the battery modules included in each energy storage unit can be flexibly set by those skilled in the art, as long as the number of the battery modules included in each energy storage unit is equal.

[0072] In the embodiment, the battery energy storage system can be quickly expanded by adjusting the number of the battery modules of each energy storage unit, and the battery modules can be controlled in high granularity by the H-bridge circuit.

[0073] In the embodiment, the controller can be connected with the battery modules (battery management units) in each energy storage unit to acquire the state of charge of each battery module and control the input / output of each battery module.

[0074] In the embodiment, the current modulation wave of the grid side is synchronized with grid voltage and is obtained by PWM modulation, and the acquisition method of the grid-side modulation wave can refer to related prior art, which is not described herein.

[0075] In the embodiment, the current level number of the intra-phase energy storage unit can be the sum of the level numbers of the individual battery modules in the energy storage unit, and the energy storage unit level number can be obtained in the manner of the related prior art, which will not be described herein.

[0076] In the embodiment, the controller can determine the corresponding level in real time according to the battery module state. Although the low switching frequency may cause the problem of large output harmonics, the problem can be ignored in the case of a large number of battery modules and high voltage levels, and the control accuracy is ensured.

[0077] In the embodiment, the controller can select different battery module sequences according to different system charging and discharging states, preferentially discharge high-capacity modules, and charge low-capacity modules, so that the system balances the intra-phase module state in the working state.

[0078] In the embodiment, a plurality of battery modules are connected in series to form an energy storage unit connected to a three-phase voltage on the grid side, a DC battery and an H-bridge circuit are connected to form a battery module, a DC side of the H-bridge circuit is connected to the DC battery through a DC line, and an AC side is connected to the grid side through an AC bus. Through such a setting, the H-bridge circuit can realize high-granularity management and control of the battery module, and the cascaded H-bridge energy storage system architecture can realize transformerless fast grid connection and flexible assembly, greatly improving the scalability of the battery energy storage system. In addition, during the charging and discharging process, the controller can obtain the current modulation wave of each phase on the grid side and the current level number of the intra-phase energy storage unit, and control the input / output of each battery module in the intra-phase according to the current modulation wave, the current level number, and the battery state of charge of each battery module in the intra-phase, so that each battery module in the intra-phase is in a balanced state. Through such a setting, the battery state of charge can be used as the switching criterion of the battery module, different module sequences can be selected for switching according to different system charging and discharging states, the intra-phase battery modules can be ensured to be in a balanced state, overcharging / overdischarging of the battery can be avoided, and the balance of the battery energy storage system is improved.

[0079] In one possible implementation, as shown in Figure 2 each energy storage unit also includes a DCDC conversion module 7, the left input end of the DCDC conversion module 7 is the cascaded battery voltage of the corresponding energy storage unit, the right output end is connected in series to the AC bus 9 of the H-bridge circuit 6 of each battery module 4 in the intra-phase, and the DCDC conversion module 7 is also connected to the controller.

[0080] The DCDC conversion module 7 is used to increase the discharge rate of the DC battery 5 when the discharge voltage of the energy storage unit is insufficient.

[0081] In the embodiment, as shown in Figure 2 the two lines on the left side of the DCDC conversion module 7 form the left input end, and the two lines on the right side form the right output end.

[0082] In the embodiment, when all battery modules of the intra-phase energy storage unit are put into operation or the number of battery modules put into operation in a certain period of time is fixed, the discharge voltage of the energy storage unit can be considered as fixed, and therefore the discharge rate of each direct-current battery in the energy storage unit can be adjusted by using the DCDC conversion module.

[0083] In the embodiment, the DCDC conversion module corresponds to the energy storage unit one-to-one, and one DCDC conversion module can increase the discharge rate of the corresponding phase direct-current battery to adjust the discharge voltage of the corresponding phase.

[0084] In the embodiment, the left input end of the DCDC conversion module is the battery phase voltage, and the right output is directly connected in series to the AC bus end of the cascaded battery module, which has small loss, and the DCDC conversion module can increase the discharge rate of the direct-current battery when the discharge voltage of the energy storage unit is insufficient, thereby compensating the phase voltage and ensuring that the voltages among the phases are in a balanced state.

[0085] In one possible embodiment, the DCDC conversion module 7 is a two-stage isolation converter, which includes a direct-current high-frequency (HF) isolation converter and a DCDC converter connected in series with the HF isolation converter.

[0086] An exemplary structure of the DCDC conversion module of an embodiment of the present application is shown in FIG. 2, which is a two-stage isolation converter composed of an HF isolation converter and a DCDC converter connected in series. Figure 3 As shown in FIG. 2, the DCDC conversion module is a two-stage isolation converter composed of an HF isolation converter and a DCDC converter connected in series. Figure 3

[0087] In the embodiment, the DCDC conversion module can be a partial power converter, and the LLC + Buck or DAB architecture can be selected in terms of topology.

[0088] In the embodiment, the DCDC conversion module can be a two-stage isolation converter composed of an HF isolation converter and a DCDC converter connected in series. On the one hand, the isolation converter can realize phase-to-phase voltage isolation to avoid the generation of three-phase circulating current. On the other hand, the two-stage converter can realize high-gain voltage conversion to adapt to the demand of high-voltage power grid.

[0089] Figure 4 A flowchart of the equalization control method of the battery energy storage system of an embodiment of the present application is shown in FIG. 3, and the embodiment takes the controller of the battery energy storage system as the execution subject. Figure 2 The equalization control method of the battery energy storage system is described below with reference to the controller of the battery energy storage system. Figure 4 As shown in FIG. 3, the equalization control method of the battery energy storage system can include the following steps:

[0090] ​S401: After receiving the charge / discharge instruction, for each phase of the grid side, the current modulation wave of the grid side and the current level number of the energy storage unit in the phase are obtained.

[0091] In the embodiment, the current modulation wave of the grid side is synchronized with the grid voltage and is obtained through PWM modulation. The obtaining method of the grid side modulation wave can refer to related prior art, which is not described here in detail.

[0092] In the embodiment, the current level number of the energy storage unit in the phase can be the sum of the level numbers of each battery module in the energy storage unit. The obtaining method of the energy storage unit level number can refer to related prior art, which is not described here in detail.

[0093] S402: According to the current modulation wave and the current level number, and the battery state of charge SOC of each battery module in the phase, the input / output of each battery module in the phase is controlled to make each battery module in the phase in a balanced state.

[0094] In the embodiment, the controller of the battery energy storage system can be connected with the battery module (battery management unit) in each energy storage unit to obtain the battery state of charge of each battery module and control the input / output of each battery module.

[0095] In the embodiment, the input of the battery module can be to control the battery module to charge / discharge, and the output of the battery module can be to control the battery module to stop charging / discharging.

[0096] In the embodiment, the controller can select different battery module sequences according to different system charge / discharge states, preferentially discharge high-capacity modules and charge low-capacity modules, so that the system balances the module states in the phase in the working state.

[0097] In the embodiment, during the charging and discharging process, the controller can obtain the current modulation wave of each phase of the grid side and the current level number of the energy storage unit in the phase, and according to the current modulation wave and the current level number, and the battery state of charge of each battery module in the phase, the input / output of each battery module in the phase is controlled to make each battery module in the phase in a balanced state. Through such a setting, the battery state of charge can be used as the switching criterion of the battery module, different module sequences can be selected for switching according to different system charge / discharge states, the battery modules in the phase can be kept in a balanced state, overcharging / overdischarging of the battery can be avoided, and the balance of the battery energy storage system is improved.

[0098] In one possible implementation, when the battery energy storage system is charging, the step 4502 above of controlling the input / output of each battery module in the phase according to the current modulation wave and the current level number, and the battery state of charge SOC of each battery module in the phase can include:

[0099] S11: determining whether the current modulation wave is less than the current level number.

[0100] S12: if yes, determining a first battery module currently put in by the in-phase energy storage unit, and cutting out a battery module with the largest SOC in the first battery module.

[0101] S13: if no, determining a second battery module currently cut out by the in-phase energy storage unit, and putting in a battery module with the smallest SOC in the second battery module.

[0102] In the embodiment, the first battery module currently put in can be a battery module currently being charged by the energy storage unit, and the second battery module currently cut out can be a battery module currently not being charged by the energy storage unit.

[0103] In the embodiment, when the battery energy storage system is charging, the grid-side voltage is high, if the current modulation wave is less than the current level number, it indicates that the in-phase battery is overcharged, the battery module should be controlled to be cut out, and the battery module with the largest SOC in the currently put-in battery module is preferentially controlled to be cut out; if the current modulation wave is not less than the current level number, it indicates that the in-phase battery voltage can be too low, the battery module should be controlled to be put in, and the battery module with the smallest SOC in the currently cut-out battery module is preferentially controlled to be put in, so that each battery module of the in-phase energy storage unit is in a balanced state during charging.

[0104] In one possible embodiment, when the battery energy storage system is discharging, the step S402 of controlling the put-in / cut-out of each battery module in the in-phase according to the current modulation wave and the current level number, and the battery state of charge SOC of each battery module in the in-phase can include:

[0105] S21: determining whether the current modulation wave is less than the current level number.

[0106] S22: if yes, determining a third battery module currently put in by the in-phase energy storage unit, and cutting out a battery module with the smallest SOC in the third battery module.

[0107] S23: if no, determining a fourth battery module currently cut out by the in-phase energy storage unit, and putting in a battery module with the largest SOC in the fourth battery module.

[0108] In the embodiment, the third battery module currently put in can be a battery module currently being discharged by the energy storage unit, and the fourth battery module currently cut out can be a battery module currently not being discharged by the energy storage unit.

[0109] In this embodiment, when the battery energy storage system discharges, the grid-side voltage is low. If the current modulation wave is less than the current level, it indicates that the battery in the phase may be over-discharged. The battery module should be switched out, and priority should be given to switching out the battery module with the lowest SOC among the currently activated battery modules. If the current modulation wave is not less than the current level, it indicates that the grid-side voltage may be too low. The battery module should be switched in, and priority should be given to switching in the battery module with the highest SOC among the currently switched-out battery modules, so that the battery modules of the energy storage unit in the phase are in a balanced state during discharge.

[0110] In one possible implementation, if the current modulation wave is still not less than the current level after all battery modules of the in-phase energy storage unit are put into operation, the method may further include:

[0111] An enable signal is sent to the DC-DC converter module corresponding to the energy storage unit. In response to the enable signal, the DC-DC converter module increases the discharge rate of each DC battery in the energy storage unit from the first discharge rate to the second discharge rate.

[0112] In this embodiment, the first discharge rate and the second discharge rate can be flexibly set by those skilled in the art according to actual conditions. For example, the first discharge rate can be 0.5 and the second discharge rate can be 0.6, as long as the first discharge rate is less than the second discharge rate. Preferably, the difference between the first discharge rate and the second discharge rate is not large, so as to avoid over-discharge of the battery.

[0113] In this embodiment, when all battery modules of the energy storage unit within the phase are put into operation, or when the number of battery modules put into operation within a certain period of time is fixed, the discharge voltage of the energy storage unit can be considered to be fixed. Therefore, the discharge rate of each DC battery in the energy storage unit can be adjusted by using the DC-DC converter module.

[0114] For example, Figure 5 This is a schematic diagram of the equalization control process of a battery energy storage system according to an embodiment of this application, as shown below. Figure 5 As shown, the gray arcs represent the modulation waves, and the black stepped lines represent the stepped waves generated by the gradual connection / disconnection of battery modules. The left side of the figure shows the gradual connection of battery modules, and the right side shows the gradual disconnection of battery modules. Figure 5 As shown, when all battery modules in the energy storage unit within the battery module phase are activated, the current modulation wave is still not less than the current level number ( Figure 5 (The peak of the modulated wave is higher than the second highest step wave). After the DC-DC converter module is turned on, it compensates for the discharge voltage, making the second highest step wave the highest step wave. At this time, the step wave is greater than the modulated wave, and the energy storage unit can continue to discharge.

[0115] For example, after all the battery modules of the energy storage unit in the phase are put in, the current modulation wave is still not less than the current level number, at this time the discharge rate of each direct current battery in the energy storage unit for the power grid is 0.5, the controller sends an opening signal to the DCDC conversion module corresponding to the energy storage unit, after the DCDC conversion module is opened, the direct current battery adds a discharge rate of 0.1 for the DCDC conversion module, since the discharge rate of the direct current battery for the power grid is 0.5, the discharge rate of 0.6 can be obtained by superimposing the alternating current bus connected to the battery module on the grid side, which is slightly higher than before the DCDC conversion module is not opened. At the same time of compensating the discharge voltage, the battery damage caused by the too high discharge rate is avoided.

[0116] In the embodiment, the current modulation wave of the battery energy storage system discharge is not less than the current level number, which indicates that the energy storage unit is fed, which may be caused by the limited battery discharge rate or the insufficient energy storage unit power. Therefore, if the current modulation wave is still not less than the current level number after all the battery modules of the energy storage unit in the phase are put in, the controller can send an opening signal to the DCDC conversion module corresponding to the energy storage unit, so that the DCDC conversion module increases the discharge rate of each direct current battery in the energy storage unit, and compensates the discharge voltage of the energy storage unit in the phase to ensure the balance of the inter-phase voltage.

[0117] In one possible embodiment, if the current modulation wave is still not less than the current level number after the DCDC conversion module is opened, the method can further include:

[0118] Outputting the charging prompt information of the battery energy storage system to charge the battery energy storage system.

[0119] In the embodiment, the charging prompt information can be one or more of text information, image information and sound information.

[0120] In the embodiment, if the energy storage unit is still fed after the DCDC conversion module is opened, it indicates that the battery energy storage system is insufficient in power, and the controller can output the charging prompt information of the battery energy storage system to prompt the operator to charge the battery energy storage system in time.

[0121] The application process of the battery energy storage system based on the cascaded H-bridge will be described below with a specific embodiment.

[0122] In one specific embodiment, the battery energy storage system based on the cascaded H-bridge includes: a first energy storage unit connected to the A-phase voltage of the power grid side, a second energy storage unit connected to the B-phase voltage of the power grid side, a third energy storage unit connected to the C-phase voltage of the power grid side, and a controller.

[0123] Each energy storage unit includes an equal number of battery modules connected in series, and the controller is connected with the battery modules.

[0124] Each energy storage unit also includes a DCDC conversion module, the left input end of the DCDC conversion module is the cascade battery voltage of the corresponding energy storage unit, the right output end is connected in series to the AC side of the H-bridge circuit of each battery module in the phase, and the DCDC conversion module is also connected with the controller.

[0125] The DCDC conversion module is used to increase the discharge rate of the DC battery when the discharge voltage of the energy storage unit is insufficient.

[0126] The battery module includes a DC battery and an H-bridge circuit, the DC side of the H-bridge circuit is connected with the DC battery through a DC line, and the AC side is connected to the grid side through an AC bus.

[0127] The DCDC conversion module is composed of a HF isolation converter and a DCDC converter in series.

[0128] (1) When the battery energy storage system is charged, the charging process is as follows:

[0129] (1) The controller of the battery energy storage system receives a charging instruction, and for each phase of the grid side, obtains the current modulation wave of the grid side and the current level number of the energy storage unit in the phase.

[0130] (2) The controller determines whether the current modulation wave is less than the current level number; if yes, the first battery module currently put into the energy storage unit in the phase is determined, and the battery module with the largest SOC in the first battery module is cut out; if not, the second battery module currently cut out of the energy storage unit in the phase is determined, and the battery module with the smallest SOC in the second battery module is put in.

[0131] (2) When the battery energy storage system is discharged, the charging process is as follows:

[0132] (1) The controller of the battery energy storage system receives a discharge instruction, and for each phase of the grid side, obtains the current modulation wave of the grid side and the current level number of the energy storage unit in the phase.

[0133] (2) The controller determines whether the current modulation wave is less than the current level number; if yes, the third battery module currently put into the energy storage unit in the phase is determined, and the battery module with the smallest SOC in the third battery module is cut out; if not, the fourth battery module currently cut out of the energy storage unit in the phase is determined, and the battery module with the largest SOC in the fourth battery module is put in.

[0134] (3) If the current modulation wave is still not less than the current level number after all battery modules of the energy storage unit in the phase are put in, the controller starts the DCDC conversion module corresponding to the energy storage unit, and the DCDC conversion module increases the discharge rate of each DC battery in the energy storage unit from 0.5 to 0.6 in response to the start signal.

[0135] (4) If the current modulation wave is still not less than the current level number after the DCDC conversion module is turned on, the controller outputs the charging prompt information of the battery energy storage system to prompt the operator to charge the battery energy storage system in time.

[0136] Figure 6 A structural schematic diagram of the controller of the battery energy storage system of an embodiment of the present application is shown in FIG. 1. The controller of the battery energy storage system includes an acquisition module 61, which is configured to acquire the current modulation wave of the grid side and the current level number of the energy storage unit in each phase of the grid side after receiving the charge / discharge instruction. Figure 6 A processing module 62 is configured to control the input / output of each battery module in the phase according to the current modulation wave and the current level number and the battery state of charge (SOC) of each battery module in the phase, so that each battery module in the phase is in a balanced state.

[0137] The controller of the battery energy storage system provided in the embodiments of the present application can implement the technical solutions shown in the method embodiments, and the implementation principles and beneficial effects are similar, which will not be described here in detail.

[0138] Figure 7 A structural schematic diagram of the controller of the battery energy storage system of another embodiment of the present application is shown in FIG. 2. The controller of the battery energy storage system includes a processor 701 and a memory 702 in communication connection with the processor 701. Figure 7 The memory 702 stores the host computer execution instructions, and the processor 701 executes the host computer execution instructions stored in the memory 702 to implement the steps of the balancing control method of the battery energy storage system in the above method embodiments.

[0139] In the controller of the battery energy storage system, the memory 702 and the processor 701 are directly or indirectly electrically connected to realize the transmission or interaction of data. For example, these elements can be electrically connected to each other through one or more communication buses or signal lines, such as through bus connection. The memory 702 stores the host computer execution instructions for realizing the data access control method, including at least one software function module stored in the memory 702 in the form of software or firmware. The processor 701 executes various functional applications and data processing by running the software program and the module stored in the memory 702.

[0140] The memory 702 can be, but is not limited to, a Random Access Memory (RAM), a Read Only Memory (ROM), a Programmable Read-Only memory (PROM), an Erasable Programmable Read-Only Memory (EPROM), an Electric Erasable Programmable Read-Only Memory (EEPROM), etc. The memory 702 is configured to store programs, and the processor 701 executes the programs upon receiving an execution instruction. Further, the software programs and modules in the memory 702 can also include an operating system, which can include various software components and / or drivers for managing system tasks (such as memory management, storage device control, power management, etc.), and can communicate with various hardware or software components to provide an operating environment for other software components.

[0141] The processor 701 can be an integrated circuit chip with a processing capability. The processor 701 can be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc. The processor 701 can implement or execute the disclosed methods, steps and logic block diagrams in the embodiments of the present application. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0142] An embodiment of the present application further provides a host computer readable storage medium, and the host computer readable storage medium stores host computer execution instructions. The host computer execution instructions are executed by a processor to implement the steps of the method embodiments of the present application.

[0143] An embodiment of the present application further provides a host computer program product, and the host computer program product includes a host computer program. The host computer program is executed by a processor to implement the steps of the method embodiments of the present application.

[0144] It should be noted that, for the foregoing method embodiments, in order to simply describe, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the action order described, because according to the present application, certain steps can be performed in other order or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily required by the present application.

[0145] It should be further understood that, although the steps of the flowchart are shown in a sequential order, these steps are not necessarily performed in the order shown. Unless explicitly stated, the steps of the flowchart can be performed in any order. Further, at least some of the steps of the flowchart can include multiple sub-steps or multiple stages, which can be performed at different times, and in which the order of execution can be altered.

[0146] It should be understood that the above-mentioned apparatus embodiments are only illustrative, and the apparatus of the present application can also be implemented in other manners. For example, the division of the units / modules in the above-mentioned embodiments is only a logical function division, and actual implementation can be in another division manner. For example, a plurality of units / modules or components can be combined, or can be integrated into another system, or some features can be omitted or not executed.

[0147] In addition, unless specifically stated, each functional unit / module in each embodiment of the present application can be integrated in one unit / module, or can be physically present separately, or two or more units / modules can be integrated together. The above-mentioned integrated unit / module can be realized in the form of hardware or in the form of a software program module.

[0148] In the above-mentioned embodiments, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments. Each technical feature of the above-mentioned embodiments can be combined arbitrarily, and in order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0149] Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The present application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice in the art to which the application pertains. The specification and examples are to be regarded as exemplary only, and the true scope and spirit of the application are indicated by the appended claims.

[0150] It is to be understood that the application is not limited to the precise construction already described above and shown in the drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the application. The scope of the application should only be limited by the claims appended hereto.

Claims

1. A battery energy storage system based on cascaded H-bridges, characterized in that, The application relates to a battery energy storage system based on a cascaded H-bridge, which comprises a first energy storage unit, a second energy storage unit and a third energy storage unit connected to a three-phase voltage of a power grid, and a controller. Each energy storage unit comprises battery modules connected in series, and the controller is connected to the battery modules. The battery module comprises a direct-current battery and an H-bridge circuit, the direct-current side of the H-bridge circuit is connected to the direct-current battery through a direct-current line, and the alternating-current side is connected to the power grid through an alternating-current bus. The controller is used for obtaining a current modulation wave of each phase of the power grid and a current level number of the energy storage unit in the phase after receiving a charge / discharge instruction, controlling the input / output of each battery module in the phase according to the current modulation wave, the current level number and a battery state of charge (SOC) of each battery module in the phase, so that each battery module in the phase is in a balanced state, and when the battery energy storage system is charged, the method of controlling the input / output of each battery module in the phase according to the current modulation wave, the current level number and the battery SOC of each battery module in the phase comprises the following steps. If yes, a first battery module currently input by the energy storage unit in the phase is determined, and a battery module with the maximum SOC in the first battery module is cut off; and if no, a second battery module currently cut off by the energy storage unit in the phase is determined, and a battery module with the minimum SOC in the second battery module is input. Each energy storage unit further comprises a DC / DC conversion module, the left input end of the DC / DC conversion module is connected to the cascaded battery voltage of the corresponding energy storage unit, the right output end is connected to the alternating-current side of the H-bridge circuit of each battery module in the phase in series, and the DC / DC conversion module is further connected to the controller.

2. The cascaded H-bridge based battery energy storage system of claim 1, wherein, The DC / DC conversion module is used for increasing the discharge rate of the direct-current battery when the discharge voltage of the energy storage unit is insufficient. The DC / DC conversion module is a two-stage isolated converter, which comprises a direct-current high-frequency (HF) isolated converter and a DC / DC converter connected to the direct-current HF isolated converter in series.

3. The cascaded H-bridge based battery energy storage system of claim 2, wherein, The application relates to a controller applied to the battery energy storage system based on the cascaded H-bridge, and the method comprises the following steps.

4. A method of equalization control of a battery energy storage system, characterized by, After receiving a charge / discharge instruction, for each phase of the power grid, a current modulation wave of the power grid and a current level number of the energy storage unit in the phase are obtained. According to the current modulation wave, the current level number and the battery SOC of each battery module in the phase, the input / output of each battery module in the phase is controlled, so that each battery module in the phase is in a balanced state. When the battery energy storage system is charged, the method of controlling the input / output of each battery module in the phase according to the current modulation wave, the current level number and the battery SOC of each battery module in the phase comprises the following steps. If yes, a first battery module currently input by the energy storage unit in the phase is determined, and a battery module with the maximum SOC in the first battery module is cut off; and if no, a second battery module currently cut off by the energy storage unit in the phase is determined, and a battery module with the minimum SOC in the second battery module is input. ​ ​ If not, a second battery module currently cut out by the in-phase energy storage unit is determined, and the battery module with the minimum SOC in the second battery module is put into.

5. The equalization control method of a battery energy storage system according to claim 4, wherein, When the battery energy storage system is discharging, the input and output of each battery module in the in-phase energy storage unit is controlled according to the current modulation wave, the current level number, and the SOC of each battery module, and the control method comprises the steps of: determining whether the current modulation wave is less than the current level number; If yes, a third battery module currently put into the in-phase energy storage unit is determined, and the battery module with the minimum SOC in the third battery module is cut out; If not, a fourth battery module currently cut out by the in-phase energy storage unit is determined, and the battery module with the maximum SOC in the fourth battery module is put into.

6. The balancing control method of a battery energy storage system according to claim 5, wherein, If the current modulation wave is still not less than the current level number after all the battery modules in the in-phase energy storage unit are put into, the method further comprises the steps of: sending an opening signal to a DCDC conversion module corresponding to the energy storage unit, and increasing the discharge rate of each direct-current battery in the energy storage unit from a first discharge rate to a second discharge rate in response to the opening signal.

7. The balancing control method of a battery energy storage system according to claim 6, wherein, If the current modulation wave is still not less than the current level number after the DCDC conversion module is opened, the method further comprises the steps of: outputting a charging prompt information of the battery energy storage system to charge the battery energy storage system.

8. A controller for a battery energy storage system, characterized by, The method comprises the steps of: a processor and a memory connected to the processor in communication; the memory is used to store host computer execution instructions; the processor is used to execute the host computer execution instructions stored in the memory, so that the processor executes the equalization control method of the battery energy storage system as claimed in any one of claims 4-7.

9. A host computer readable storage medium, characterized by, The host computer readable storage medium stores host computer execution instructions, and the host computer execution instructions are executed by the processor to implement the equalization control method of the battery energy storage system as claimed in any one of claims 4-7. The host computer readable storage medium stores host computer execution instructions, and the host computer execution instructions are executed by the processor to implement the equalization control method of the battery energy storage system as claimed in any one of claims 4-7.

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