High-voltage direct-hanging energy storage system and method with battery state self-balancing capability

Abstract

The invention provides a high-voltage direct-hanging energy storage system and method with a battery state self-balancing capability, and the method comprises the steps: enabling a battery module to be connected to a DC bus of a multi-level AC-DC power conversion circuit through a battery state self-balancing energy storage module, and enabling the multi-level AC-DC power conversion circuit to convert the electrochemical energy in the battery module into electric energy; the main control unit generates modulation information of the battery state self-balancing energy storage module through control by sampling voltage and current information of a power grid side and collecting battery state information uploaded by the battery state self-balancing energy storage module; the sub-module distributed control unit receives the modulation information generated by the main control unit, transmits the battery state information to the main control unit, and converts the received modulation information into a switching signal corresponding to the battery state self-balancing energy storage module. According to the invention, the number of switches of the system can be reduced, the state self-equalization of the batteries in the sub-modules is realized, the control difficulty of main control is reduced, and an energy storage system with a higher voltage level and a larger single-machine capacity is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical automation equipment. Specifically, it relates to a novel topology of a high-voltage direct-connected energy storage system with ultra-large single-machine capacity and automatic battery state balancing, and particularly to a high-voltage direct-connected energy storage system and method with the ability of self-balancing battery state. Background Art

[0002] The conventional battery energy storage system solution is limited by technologies such as battery safety, battery grouping method, and battery management system. The single-machine capacity generally does not exceed 0.5 MW. Multiple such battery energy storage systems are connected in parallel to form a larger-capacity energy storage power station, and finally, after being step-up transformed by a step-up transformer, they are connected to the medium-voltage and high-voltage power grids. In the energy storage power station based on the conventional battery energy storage system architecture, the battery stack has disadvantages such as large inter-cluster circulating current, obvious cask effect, low battery utilization rate, and easy occurrence of safety problems. In addition, the parallel connection of multiple energy storage converters will result in a complex structure of the energy storage power station, large floor area, long cable lines leading to complex distribution of parasitic parameters, communication delay leading to slow system response time, complex control system of the entire power station, and difficult coordinated control, making it difficult to meet the requirements of building 100-MW and GW-level energy storage power stations in the future.

[0003] The high-voltage direct-connected battery energy storage system based on cascaded H-bridge converters has a highly modular structure, which is convenient for capacity expansion and redundant design, and can eliminate the loss caused by the transformer by directly connecting to the high-voltage power grid without using a power frequency transformer. The large-capacity battery stack is dispersed and connected to each H-bridge circuit with a single battery cluster as a unit, avoiding the circulating current in the battery stack, reducing the system cycle loss and improving the system safety at the same time. Compared with the traditional energy storage system, the high-voltage direct-connected battery energy storage system realizes large single-machine capacity, requires fewer parallel units when forming a large-scale energy storage power station, reduces the floor area of the power station, has a simple power station structure and control strategy, fast system response speed and is not prone to system stability problems, and can meet the requirements of building a large-capacity battery energy storage power station.

[0004] However, with the large-scale application of high-voltage direct-connected energy storage, the single-machine capacity of the system and the connected voltage level are getting higher and higher. The traditional high-voltage direct-connected battery energy storage based on cascaded H-bridge converters faces the following three major challenges: 1) The number of sub-modules increases sharply, and the number of devices used in the cascaded H-bridge converter doubles, resulting in more prominent device reliability problems; 2) The increase in the number of H-bridge sub-modules leads to a sharp increase in the modulation and communication pressure of the main controller. Under the existing communication rate limit, it is difficult to solve the control stability problem caused by communication delay; 3) To achieve state balance for hundreds or thousands of battery clusters, the traditional inter-phase and intra-phase balancing needs to process a large amount of data, and it is difficult to achieve independent and precise control of all battery clusters. Therefore, it is urgent to solve the technical problems brought by the existing architecture through topology innovation.

[0005] In the prior art, the following grid-forming control methods have been proposed: The utility model patent with the publication number CN221058195U discloses a high-voltage direct-connected series three-level energy storage converter power unit, which solves the problems of a large number of series power units and a large volume of the direct-connected energy storage system in the existing solutions through a single-phase three-level sub-module topology structure, greatly reducing the number of power units in the direct-connected energy storage system, reducing the failure rate, and improving the reliability of the direct-connected energy storage system. However, the number of switching devices used in this topology to access two battery modules is the same as that of the traditional H-bridge scheme.

[0006] The invention patent with the publication number CN116581800A discloses a capacity-expanded high-voltage direct-connected energy storage power conversion system and a control method, providing a structural design of a stacked half-bridge sub-module. Each sub-module can be connected in parallel with two batteries. Therefore, in the case of the same number of sub-modules, the number of battery modules is doubled, which means that when designing the maximum capacity, the total output capacity of the batteries is doubled, enabling the energy storage system capacity to double, forming an expanded-capacity high-voltage direct-connected energy storage PCS, and greatly improving the total output capacity of a single high-voltage direct-connected energy storage system. However, each sub-module topology can only access two battery modules, and the state balance between the two battery modules cannot be achieved inside the sub-module and relies on external control means.

[0007] The invention patent with the publication number CN115459324A discloses a cascaded H-bridge energy storage circuit with an energy balance function and its energy balance method. The switching capacitor balance circuit is connected in parallel after the battery and is connected to the DC side of the DC / AC power conversion circuit. It can not only improve the capacity utilization rate of the battery pack, but also avoid safety problems caused by overcharging and discharging of the battery, increasing the number of battery cycle uses. However, this method adds an additional hardware balance circuit, and the insulation pressure between the balance circuits is extremely large in a high-voltage environment, making it very difficult to implement. Summary of the Invention

[0008] Aiming at the defects in the prior art, the present invention provides a high-voltage direct-connected energy storage system and method with the ability of self-balancing battery state.

[0009] According to a high-voltage direct-connected energy storage system and method with the ability of self-balancing battery state provided by the present invention, the solution is as follows: In the first aspect, a high-voltage direct-connected energy storage system with the ability of self-balancing battery state is provided. The system includes: The system is cascaded on the AC side through a multi-level AC-DC power conversion circuit and then connected to the high-voltage power grid through a filter inductor. The system includes: a battery state self-balancing energy storage module, a main control unit, and a sub-module distributed control unit; The battery state self - balancing energy storage module: Connect the battery module to the DC bus of the multilevel AC - DC power conversion circuit, and convert the electrochemical energy in the battery module into electrical energy through the multilevel AC - DC power conversion circuit; The main control unit: By sampling the grid - side voltage and current information and collecting the battery state information uploaded by the battery state self - balancing energy storage module, generate the modulation information of the battery state self - balancing energy storage module through control; The sub - module distributed control unit corresponds one - to - one with the battery state self - balancing energy storage module, receives the modulation information generated by the main control unit and transmits the battery state information to it, and converts the received modulation information into the switching signals corresponding to the battery state self - balancing energy storage module.

[0010] Preferably, the battery state self - balancing energy storage module includes: a switching module and a battery module; The switching module includes: the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, the tenth switch S10, the eleventh switch S11, and the twelfth switch S12; the battery module includes: the first battery module B1, the second battery module B2, the third battery module B3, and the fourth battery module B4; The specific circuit connection of the battery state self - balancing energy storage module includes: The half - bridge formed by the first switch S1 and the second switch S2 is connected to the positive and negative ports of the first battery module B1, the half - bridge formed by the fifth switch S5 and the sixth switch S6 is connected to the positive and negative ports of the first battery module B1, the half - bridge formed by the third switch S3 and the fourth switch S4 is connected to the positive and negative ports of the second battery module B2, the half - bridge formed by the seventh switch S7 and the eighth switch S8 is connected to the positive and negative ports of the second battery module B2, and the negative pole of the first battery module B1 is connected to the positive pole of the second battery module B2; The positive port of the third battery module B3 is connected to the mid - point of the half - bridge formed by the first switch S1 and the second switch S2, the negative port of the third battery module B3 is connected to the mid - point of the half - bridge formed by the third switch S3 and the fourth switch S4, and the half - bridge formed by the ninth switch S9 and the tenth switch S10 is connected to the positive and negative ports of the third battery module B3; The positive port of the fourth battery module B4 is connected to the mid - point of the half - bridge formed by the fifth switch S5 and the sixth switch S6, the negative port of the fourth battery module B4 is connected to the mid - point of the half - bridge formed by the seventh switch S7 and the eighth switch S8, and the half - bridge formed by the eleventh switch S11 and the twelfth switch S12 is connected to the positive and negative ports of the fourth battery module B4; The mid - point of the half - bridge formed by the ninth switch S9 and the tenth switch S10 and the mid - point of the half - bridge formed by the eleventh switch S11 and the twelfth switch S12 constitute the AC - side port of the battery state self - balancing energy storage module.

[0011] Preferably, the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, the tenth switch S10, the eleventh switch S11, and the twelfth switch S12 are power semiconductor devices, including insulated gate bipolar transistors, integrated gate-commutated thyristors, or metal-oxide semiconductor field-effect transistors.

[0012] Preferably, the battery state self-balancing energy storage module outputs five levels of voltage at the AC side port through the combination of the switch states of the switch network: +2 U B , -2 U B , + U B , - U B , 0; By turning on the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, the fourth switch S4, and the tenth switch S10, and closing the remaining switches, the battery state self-balancing energy storage module outputs +2 U B level at the AC side port; By turning on the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, the eighth switch S8, and the twelfth switch S12, and closing the remaining switches, the battery state self-balancing energy storage module outputs -2 U B level at the AC side port; By turning on the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, and the ninth switch S9, and closing the remaining switches, the battery state self-balancing energy storage module outputs + U B level at the AC side port; By turning on the twelfth switch S12, the second switch S2, the seventh switch S7, the fourth switch S4, and the tenth switch S10, and closing the remaining switches, the battery state self-balancing energy storage module outputs + U B level at the AC side port; By turning on the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, and the eleventh switch S11, and closing the remaining switches, the battery state self-balancing energy storage module outputs - U B level at the AC side port; By turning on the tenth switch S10, the third switch S3, the sixth switch S6, the eighth switch S8, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs a - U B level at the AC - side port; By turning on the tenth switch S10, the third switch S3, the sixth switch S6, and the eleventh switch S11, and closing the remaining switches, the battery state self - balancing energy storage module outputs a 0 - level at the AC - side port; By turning on the ninth switch S9, the second switch S2, the seventh switch S7, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs a 0 - level at the AC - side port.

[0013] Preferably, the battery state self - balancing energy storage module realizes the state - of - charge self - balancing between battery modules through the combination of the switch states of the switch network; By turning on the first switch S1 and the third switch S3, the state self - balancing between the first battery module B1 and the third battery module B3 is realized; By turning on the second switch S2 and the fourth switch S4, the state self - balancing between the second battery module B2 and the third battery module B3 is realized; By turning on the fifth switch S5 and the seventh switch S7, the state self - balancing between the first battery module B1 and the fourth battery module B4 is realized; By turning on the sixth switch S6 and the eighth switch S8, the state self - balancing between the second battery module B2 and the fourth battery module B4 is realized.

[0014] Preferably, the sub - module distributed control unit selects a set of switch - state combinations of the switch network in each switching period to meet the output - level requirements of the AC - side of the battery state self - balancing energy storage module, and at the same time realizes the state self - balancing of the battery modules inside the battery state self - balancing energy storage module.

[0015] In a second aspect, a high - voltage direct - connection energy storage method with battery state self - balancing ability is provided, and the method includes: Step S1: Connect the battery module to the DC bus of the multi - level AC - DC power conversion circuit, and the battery state self - balancing energy storage module realizes the conversion of the electrochemical energy in the battery module into electrical energy through the multi - level AC - DC power conversion circuit; Step S2: The main control unit samples the voltage and current information on the grid side and collects the battery state information uploaded by the battery state self - balancing energy storage module, and generates the modulation information of the battery state self - balancing energy storage module through control; Step S3: Correspond the sub-module distributed control unit with the battery state self-balancing energy storage module one by one. Receive the modulation information generated by the main control unit through the sub-module distributed control unit, transmit the battery state information to it, and convert the received modulation information into switching signals corresponding to the battery state self-balancing energy storage module.

[0016] Preferably, in the step S1, the battery state self-balancing energy storage module includes: a switching module and a battery module; The switching module includes: the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, the tenth switch S10, the eleventh switch S11, and the twelfth switch S12; the battery module includes: the first battery module B1, the second battery module B2, the third battery module B3, and the fourth battery module B4; The specific circuit connection of the battery state self-balancing energy storage module includes: the half-bridge formed by the first switch S1 and the second switch S2 is connected to the positive and negative ports of the first battery module B1, the half-bridge formed by the fifth switch S5 and the sixth switch S6 is connected to the positive and negative ports of the first battery module B1, the half-bridge formed by the third switch S3 and the fourth switch S4 is connected to the positive and negative ports of the second battery module B2, the half-bridge formed by the seventh switch S7 and the eighth switch S8 is connected to the positive and negative ports of the second battery module B2, and the negative pole of the first battery module B1 is connected to the positive pole of the second battery module B2; the positive port of the third battery module B3 is connected to the midpoint of the half-bridge formed by the first switch S1 and the second switch S2, the negative port of the third battery module B3 is connected to the midpoint of the half-bridge formed by the third switch S3 and the fourth switch S4, and the half-bridge formed by the ninth switch S9 and the tenth switch S10 is connected to the positive and negative ports of the third battery module B3; the positive port of the fourth battery module B4 is connected to the midpoint of the half-bridge formed by the fifth switch S5 and the sixth switch S6, the negative port of the fourth battery module B4 is connected to the midpoint of the half-bridge formed by the seventh switch S7 and the eighth switch S8, and the half-bridge formed by the eleventh switch S11 and the twelfth switch S12 is connected to the positive and negative ports of the fourth battery module B4; the midpoint of the half-bridge formed by the ninth switch S9 and the tenth switch S10 and the midpoint of the half-bridge formed by the eleventh switch S11 and the twelfth switch S12 constitute the AC side port of the battery state self-balancing energy storage module.

[0017] Preferably, the battery state self-balancing energy storage module outputs five levels of voltage at the AC side port through the combination of the switching states of the switching network: +2 U B 、 -2 U B 、 + UB , - U B , 0; By turning on the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, the fourth switch S4, and the tenth switch S10, and closing the remaining switches, the battery state self - balancing energy storage module outputs +2 U B level at the AC - side port; By turning on the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, the eighth switch S8, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs - 2 U B level at the AC - side port; By turning on the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, and the ninth switch S9, and closing the remaining switches, the battery state self - balancing energy storage module outputs + U B level at the AC - side port; By turning on the twelfth switch S12, the second switch S2, the seventh switch S7, the fourth switch S4, and the tenth switch S10, and closing the remaining switches, the battery state self - balancing energy storage module outputs + U B level at the AC - side port; By turning on the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, and the eleventh switch S11, and closing the remaining switches, the battery state self - balancing energy storage module outputs - U B level at the AC - side port; By turning on the tenth switch S10, the third switch S3, the sixth switch S6, the eighth switch S8, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs - U <[BOS_never_used_51bce0c785ca2f68081bfa7d91973934]>{"name":"GodelPlugin","parameters":{"input":" U "}}<|FunctionExecuteEnd|><|FunctionExecuteResult|> U <|FunctionExecuteResultEnd|> B level at the AC - side port; By turning on the tenth switch S10, the third switch S3, the sixth switch S6, and the eleventh switch S11, and closing the remaining switches, the battery state self - balancing energy storage module outputs 0 level at the AC - side port; By turning on the ninth switch S9, the second switch S2, the seventh switch S7, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs 0 level at the AC - side port; The battery state self - balancing energy storage module realizes the self - balancing of the state of charge between battery modules through the combination of the switching states of the switching network; by turning on the first switch S1 and the third switch S3, the state self - balancing of the first battery module B1 and the third battery module B3 is realized; By turning on the second switch S2 and the fourth switch S4, the state self - balancing of the second battery module B2 and the third battery module B3 is realized; By turning on the fifth switch S5 and the seventh switch S7, the state self - balancing of the first battery module B1 and the fourth battery module B4 is realized; By turning on the sixth switch S6 and the eighth switch S8, the state self - balancing of the second battery module B2 and the fourth battery module B4 is realized.

[0018] Preferably, in step S3, the sub - module distributed control unit selects a set of switching state combinations of the switching network within each switching cycle to meet the output level requirements of the AC side of the battery state self - balancing energy storage module, and at the same time realizes the state self - balancing of the battery modules inside the battery state self - balancing energy storage module.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. By providing a topology of the battery state self - balancing energy storage module and connecting four battery modules, compared with the scheme in which each battery module of the traditional cascaded H - bridge circuit uses an H - bridge circuit, the system reduces the number of switches by 25%, has the advantages of compact structure and high integration, and improves the system reliability; 2. The present invention realizes the automatic balancing of the state of charge between battery modules. By reasonably selecting the switching state combinations of the switching network, the automatic balancing of the states of four batteries inside the topology of the battery state self - balancing sub - module can be realized; 3. Aiming at the problem that the implementation difficulty of the controller in the traditional cascaded H - bridge circuit scheme increases with the increase of the system capacity and voltage level, for the high - voltage direct - connection energy storage system with the ability of battery state self - balancing provided by the present invention, the number of sub - modules can be reduced to one - quarter of the original. Then, through the sub - module distributed control unit, the internal modulation of the sub - module and the state self - balancing of the battery module are realized, which can greatly simplify the implementation difficulty of the system main controller.

[0020] Other beneficial effects of the present invention will be described through the introduction of specific technical features and technical solutions in the specific implementation manner. Those skilled in the art should be able to understand the beneficial technical effects brought by the technical features and technical solutions through these introductions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] By reading the detailed description of the non - restrictive embodiments with reference to the following drawings, other features, objects and advantages of the present invention will become more obvious: Figure 1 This is the circuit diagram of the high-voltage direct-connected energy storage system with the ability of self-balancing battery state in the present invention; Figure 2 This is the circuit diagram of the energy storage module with self-balancing battery state in the present invention; Figure 3 This is the switch combination of the energy storage module with self-balancing battery state in the present invention at different output levels. Detailed implementation manners

[0022] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0023] An embodiment of the present invention provides a high-voltage direct-connected energy storage system with the ability of self-balancing battery state. Referring to Figure 1 as shown, this system is cascaded on the AC side through a multilevel AC-DC power conversion circuit and then connected to the high-voltage power grid through a filter inductor. This system includes: an energy storage module with self-balancing battery state, a main control unit, and a sub-module distributed control unit; Specifically, the energy storage module with self-balancing battery state: connects the battery module to the DC bus of the multilevel AC-DC power conversion circuit, and converts the electrochemical energy in the battery module into electrical energy through the multilevel AC-DC power conversion circuit.

[0024] The main control unit: generates the modulation information of the energy storage module with self-balancing battery state by sampling the voltage and current information on the grid side and collecting the battery state information uploaded by the energy storage module with self-balancing battery state.

[0025] The sub-module distributed control unit corresponds to the energy storage module with self-balancing battery state one by one, receives the modulation information generated by the main control unit and transmits the battery state information to it, and converts the received modulation information into the switch signal corresponding to the energy storage module with self-balancing battery state.

[0026] Referring to Figure 1 as shown, it is the structure diagram of the high-voltage direct-connected battery energy storage system with the ability of self-balancing battery state. The high-voltage direct-connected energy storage system with the ability of self-balancing battery state is directly connected to power grids of various voltage levels, including: a phase A power module, a phase B power module, and a phase C power module; each phase is cascaded by n energy storage modules with self-balancing battery state. The energy storage module with self-balancing battery state realizes the conversion of the electrochemical energy in the battery module into electrical energy. The energy storage module with self-balancing battery state is directly connected to the medium- and high-voltage power grid through a filter inductor, an AC side pre-charging device, and an AC fuse on the AC side; in the figure is the voltage of the three-phase power grid, is the output voltage of the cascaded H-bridge converter, is the output current of the converter.

[0027] The battery state self-balancing energy storage module includes: a switch module and a battery module; the switch module includes: the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, the tenth switch S10, the eleventh switch S11, and the twelfth switch S12; the battery module includes: the first battery module B1, the second battery module B2, the third battery module B3, and the fourth battery module B4. The first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, the tenth switch S10, the eleventh switch S11, and the twelfth switch S12 are power semiconductor devices, including but not limited to insulated gate bipolar transistors, integrated gate-commutated thyristors, metal oxide semiconductor field effect transistors, etc. The battery module is an electrochemical energy storage medium, including but not limited to lithium-ion batteries, sodium-ion batteries, etc.

[0028] Referring to Figure 2 As shown, the specific circuit connection of the battery state self-balancing energy storage module includes: the half-bridge formed by the first switch S1 and the second switch S2 is connected to the positive and negative ports of the first battery module B1, the half-bridge formed by the fifth switch S5 and the sixth switch S6 is connected to the positive and negative ports of the first battery module B1, the half-bridge formed by the third switch S3 and the fourth switch S4 is connected to the positive and negative ports of the second battery module B2, the half-bridge formed by the seventh switch S7 and the eighth switch S8 is connected to the positive and negative ports of the second battery module B2, and the negative electrode of the first battery module B1 is connected to the positive electrode of the second battery module B2; the positive port of the third battery module B3 is connected to the midpoint of the half-bridge formed by the first switch S1 and the second switch S2, the negative port of the third battery module B3 is connected to the midpoint of the half-bridge formed by the third switch S3 and the fourth switch S4, and the half-bridge formed by the ninth switch S9 and the tenth switch S10 is connected to the positive and negative ports of the third battery module B3; the positive port of the fourth battery module B4 is connected to the midpoint of the half-bridge formed by the fifth switch S5 and the sixth switch S6, the negative port of the fourth battery module B4 is connected to the midpoint of the half-bridge formed by the seventh switch S7 and the eighth switch S8, and the half-bridge formed by the eleventh switch S11 and the twelfth switch S12 is connected to the positive and negative ports of the fourth battery module B4; the midpoint of the half-bridge formed by the ninth switch S9 and the tenth switch S10 and the midpoint of the half-bridge formed by the eleventh switch S11 and the twelfth switch S12 constitute the AC side port of the battery state self-balancing energy storage module.

[0029] Referring to Figure 3As shown, the battery state self - balancing energy storage module can output five - level voltages at the AC - side port through the combination of the switching states of the switching network: +2 U B 、 - 2 U B 、 + U B 、 - U B 、0; By turning on the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, the fourth switch S4, and the tenth switch S10, and closing the remaining switches, the battery state self - balancing energy storage module outputs +2 U B level at the AC - side port; By turning on the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, the eighth switch S8, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs - 2 U B level at the AC - side port; By turning on the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, and the ninth switch S9, and closing the remaining switches, the battery state self - balancing energy storage module outputs + U B level at the AC - side port; By turning on the twelfth switch S12, the second switch S2, the seventh switch S7, the fourth switch S4, and the tenth switch S10, and closing the remaining switches, the battery state self - balancing energy storage module outputs + U B level at the AC - side port; By turning on the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, and the eleventh switch S11, and closing the remaining switches, the battery state self - balancing energy storage module outputs - U B level at the AC - side port; By turning on the tenth switch S10, the third switch S3, the sixth switch S6, the eighth switch S8, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs - U B level at the AC - side port; By turning on the tenth switch S10, the third switch S3, the sixth switch S6, and the eleventh switch S11, and closing the remaining switches, the battery state self - balancing energy storage module outputs 0 level at the AC - side port; By turning on the ninth switch S9, the second switch S2, the seventh switch S7, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs 0 level at the AC - side port.

[0030] Referring to Figure 3 as shown, the battery state self - balancing energy storage module can achieve the self - balancing of the state of charge between battery modules through the combination of the switching states of the switching network; By turning on the first switch S1 and the third switch S3, the state self - balancing of the first battery module B1 and the third battery module B3 is achieved; By turning on the second switch S2 and the fourth switch S4, the state self - balancing of the second battery module B2 and the third battery module B3 is achieved; By turning on the fifth switch S5 and the seventh switch S7, the state self - balancing of the first battery module B1 and the fourth battery module B4 is achieved; By turning on the sixth switch S6 and the eighth switch S8, the state self - balancing of the second battery module B2 and the fourth battery module B4 is achieved.

[0031] The sub - module distributed control unit selects a combination of the switching states of a group of switching networks within each switching cycle to meet the output level requirements of the AC side of the battery state self - balancing energy storage module, and at the same time realizes the state self - balancing of the battery modules inside the battery state self - balancing energy storage module.

[0032] The present invention also provides a high - voltage direct - connection energy storage method with the ability of battery state self - balancing, which specifically includes: Step S1: Connect the battery module to the DC bus of the multi - level AC - DC power conversion circuit, and the battery state self - balancing energy storage module realizes the conversion of the electrochemical energy in the battery module into electrical energy through the multi - level AC - DC power conversion circuit; Step S2: The main control unit samples the voltage and current information on the grid side and collects the battery state information uploaded by the battery state self - balancing energy storage module, and generates the modulation information of the battery state self - balancing energy storage module through control; Step S3: Correspond the sub - module distributed control unit and the battery state self - balancing energy storage module one by one. The sub - module distributed control unit receives the modulation information generated by the main control unit and transmits the battery state information to it, and converts the received modulation information into the switching signal corresponding to the battery state self - balancing energy storage module.

[0033] Referring to Figure 1As shown in the figure, it is the structure diagram of a high-voltage direct-connected battery energy storage system with the ability of self-balancing battery state. The high-voltage direct-connected energy storage system with the ability of self-balancing battery state is directly connected to power grids of various voltage levels, including: A-phase power module, B-phase power module and C-phase power module; Each phase is cascaded by n battery state self-balancing energy storage modules. The battery state self-balancing energy storage module realizes the conversion of electrochemical energy in the battery module into electrical energy. The battery state self-balancing energy storage module is directly connected to the medium-high voltage power grid through a filter inductor, an AC side pre-charging device and an AC fuse on the AC side; In the figure is the voltage of the three-phase power grid, is the output voltage of the cascaded H-bridge converter, is the output current of the converter.

[0034] The battery state self-balancing energy storage module includes: a switch module and a battery module; The switch module includes: first switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, sixth switch S6, seventh switch S7, eighth switch S8, ninth switch S9, tenth switch S10, eleventh switch S11 and twelfth switch S12; The battery module includes: first battery module B1, second battery module B2, third battery module B3 and fourth battery module B4. The first switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, sixth switch S6, seventh switch S7, eighth switch S8, ninth switch S9, tenth switch S10, eleventh switch S11 and twelfth switch S12 are power semiconductor devices, including but not limited to insulated gate bipolar transistors, integrated gate-commutated thyristors, metal-oxide-semiconductor field-effect transistors, etc. The battery module is an electrochemical energy storage medium, including but not limited to lithium-ion batteries, sodium-ion batteries, etc.

[0035] Refer to Figure 2As shown, the specific circuit connection of the battery state self - balancing energy storage module includes: A half - bridge composed of the first switch S1 and the second switch S2 is connected to the positive and negative ports of the first battery module B1. A half - bridge composed of the fifth switch S5 and the sixth switch S6 is connected to the positive and negative ports of the first battery module B1. A half - bridge composed of the third switch S3 and the fourth switch S4 is connected to the positive and negative ports of the second battery module B2. A half - bridge composed of the seventh switch S7 and the eighth switch S8 is connected to the positive and negative ports of the second battery module B2. The negative pole of the first battery module B1 is connected to the positive pole of the second battery module B2. The positive port of the third battery module B3 is connected to the mid - point of the half - bridge composed of the first switch S1 and the second switch S2. The negative port of the third battery module B3 is connected to the mid - point of the half - bridge composed of the third switch S3 and the fourth switch S4. A half - bridge composed of the ninth switch S9 and the tenth switch S10 is connected to the positive and negative ports of the third battery module B3. The positive port of the fourth battery module B4 is connected to the mid - point of the half - bridge composed of the fifth switch S5 and the sixth switch S6. The negative port of the fourth battery module B4 is connected to the mid - point of the half - bridge composed of the seventh switch S7 and the eighth switch S8. A half - bridge composed of the eleventh switch S11 and the twelfth switch S12 is connected to the positive and negative ports of the fourth battery module B4. The mid - point of the half - bridge composed of the ninth switch S9 and the tenth switch S10 and the mid - point of the half - bridge composed of the eleventh switch S11 and the twelfth switch S12 constitute the AC - side port of the battery state self - balancing energy storage module.

[0036] As shown in Figure 3 , the battery state self - balancing energy storage module can output five - level voltages at the AC - side port through the combination of the switch states of the switch network: +2 U B , - 2 U B , + U B , - U B , 0; By turning on the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, the fourth switch S4, and the tenth switch S10, and closing the remaining switches, the battery state self - balancing energy storage module outputs +2 U B level at the AC - side port; By turning on the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, the eighth switch S8, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs - 2 U B level at the AC - side port; By turning on the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, and the ninth switch S9, and closing the remaining switches, the battery state self - balancing energy storage module outputs +U B Level; By turning on the twelfth switch S12, the second switch S2, the seventh switch S7, the fourth switch S4, and the tenth switch S10, and closing the remaining switches, the battery state self - balancing energy storage module outputs + at the AC - side port U B Level; By turning on the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, and the eleventh switch S11, and closing the remaining switches, the battery state self - balancing energy storage module outputs - at the AC - side port U B Level; By turning on the tenth switch S10, the third switch S3, the sixth switch S6, the eighth switch S8, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs - at the AC - side port U B Level; By turning on the tenth switch S10, the third switch S3, the sixth switch S6, and the eleventh switch S11, and closing the remaining switches, the battery state self - balancing energy storage module outputs 0 level at the AC - side port; By turning on the ninth switch S9, the second switch S2, the seventh switch S7, and the twelfth switch S12, and closing the remaining switches, the battery state self - balancing energy storage module outputs 0 level at the AC - side port.

[0037] Referring to Figure 3 As shown, the battery state self - balancing energy storage module can achieve the self - balancing of the state of charge between battery modules through the combination of the switch states of the switch network; by turning on the first switch S1 and the third switch S3, the state self - balancing of the first battery module B1 and the third battery module B3 is achieved; By turning on the second switch S2 and the fourth switch S4, the state self - balancing of the second battery module B2 and the third battery module B3 is achieved; By turning on the fifth switch S5 and the seventh switch S7, the state self - balancing of the first battery module B1 and the fourth battery module B4 is achieved; By turning on the sixth switch S6 and the eighth switch S8, the state self - balancing of the second battery module B2 and the fourth battery module B4 is achieved.

[0038] The sub - module distributed control unit selects a set of switch - state combinations of the switch network within each switching period to meet the output - level requirements of the battery - state self - balancing energy storage module at the AC side, and at the same time realizes the state self - balancing of the battery modules inside the battery - state self - balancing energy storage module.

[0039] An embodiment of the present invention provides a high-voltage direct-connected energy storage system and method with battery state self-balancing ability. Through the battery state self-balancing sub-module topology, the number of switches in the system is reduced, the self-balancing of the battery state inside the sub-module is achieved, the control difficulty of the main control is reduced, and it is beneficial to realize an energy storage system with a higher voltage level and a larger single-unit capacity.

[0040] Those skilled in the art know that in addition to implementing the system and its various devices, modules, and units provided by the present invention in the form of pure computer-readable program code, the method steps can be logically programmed to enable the system and its various devices, modules, and units provided by the present invention to be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers to achieve the same function. Therefore, the system and its various devices, modules, and units provided by the present invention can be regarded as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be regarded as the structure inside the hardware component; the devices, modules, and units for implementing various functions can also be regarded as either software modules for implementing the method or the structure inside the hardware component.

[0041] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined arbitrarily with each other.

Claims

1. A high-voltage direct-mounted energy storage system with battery state self-balancing capability, characterized in that: The system is cascaded on the AC side through a multi-level AC / DC power conversion circuit, and then connected to the high-voltage power grid through a filter inductor. The system includes: a battery state self-balancing energy storage module, a main control unit, and a sub-module distributed control unit; The battery state self-balancing energy storage module: connects the battery module to the DC bus of the multi-level AC / DC power conversion circuit, and converts the electrochemical energy in the battery module into electrical energy through the multi-level AC / DC power conversion circuit; The main control unit: by sampling the voltage and current information on the grid side and collecting the battery status information uploaded by the battery status self-balancing energy storage module, generates the modulation information of the battery status self-balancing energy storage module through control; The submodule distributed control unit corresponds one-to-one to the battery state self-balancing energy storage module, receives the modulation information generated by the main control unit and transmits the battery state information to it, and converts the received modulation information into a switch signal corresponding to the battery state self-balancing energy storage module.

2. The high-voltage direct-mounted energy storage system with battery state self-balancing capability according to claim 1 is characterized in that: The battery state self-balancing energy storage module includes: a switch module and a battery module; The switch module includes: a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a seventh switch S7, an eighth switch S8, a ninth switch S9, a tenth switch S10, an eleventh switch S11 and a twelfth switch S12; the battery module includes: a first battery module B1, a second battery module B2, a third battery module B3 and a fourth battery module B4; The specific circuit connection of the battery state self-balancing energy storage module includes: the half bridge composed of the first switch S1 and the second switch S2 is connected to the positive and negative ports of the first battery module B1, the half bridge composed of the fifth switch S5 and the sixth switch S6 is connected to the positive and negative ports of the first battery module B1, the half bridge composed of the third switch S3 and the fourth switch S4 is connected to the positive and negative ports of the second battery module B2, the half bridge composed of the seventh switch S7 and the eighth switch S8 is connected to the positive and negative ports of the second battery module B2, the negative electrode of the first battery module B1 is connected to the positive electrode of the second battery module B2; the positive electrode port of the third battery module B3 is connected to the midpoint of the half bridge composed of the first switch S1 and the second switch S2, and the negative electrode port of the third battery module B3 is connected to The midpoint of the half bridge formed by the third switch S3 and the fourth switch S4, and the half bridge formed by the ninth switch S9 and the tenth switch S10 are connected to the positive and negative ports of the third battery module B3; the positive port of the fourth battery module B4 is connected to the midpoint of the half bridge formed by the fifth switch S5 and the sixth switch S6, the negative port of the fourth battery module B4 is connected to the midpoint of the half bridge formed by the seventh switch S7 and the eighth switch S8, and the half bridge formed by the eleventh switch S11 and the twelfth switch S12 is connected to the positive and negative ports of the fourth battery module B4; the midpoint of the half bridge formed by the ninth switch S9 and the tenth switch S10 and the midpoint of the half bridge formed by the eleventh switch S11 and the twelfth switch S12 constitute the AC side port of the battery state self-balancing energy storage module.

3. The high-voltage direct-mounted energy storage system with battery state self-balancing capability according to claim 2 is characterized in that: The first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, the eighth switch S8, the ninth switch S9, the tenth switch S10, the eleventh switch S11 and the twelfth switch S12 are power semiconductor devices, including insulated gate bipolar transistors, integrated gate-commutated thyristors or metal oxide semiconductor field effect transistors.

4. The high-voltage direct-mounted energy storage system with battery state self-balancing capability according to claim 2 is characterized in that: The battery state self-balancing energy storage module outputs 5 levels of voltage at the AC side port through the switch state combination of the switch network: +2 U B , -2 U B 、+ U B 、- U B , 0; By opening the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, the fourth switch S4 and the tenth switch S10, and closing the remaining switches, the battery status is outputted from the balancing energy storage module at the AC side port +2 U B Level; By opening the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, the eighth switch S8 and the twelfth switch S12, and closing the remaining switches, the battery status is output from the balancing energy storage module at the AC side port. U B Level; By opening the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7 and the ninth switch S9, and closing the remaining switches, the battery status is outputted from the balancing energy storage module at the AC side port + U B Level; By opening the twelfth switch S12, the second switch S2, the seventh switch S7, the fourth switch S4 and the tenth switch S10, and closing the remaining switches, the battery status is outputted from the balancing energy storage module at the AC side port + U B Level; By opening the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6 and the eleventh switch S11, and closing the remaining switches, the battery status is output from the balancing energy storage module at the AC side port. U B Level; By opening the tenth switch S10, the third switch S3, the sixth switch S6, the eighth switch S8 and the twelfth switch S12, and closing the remaining switches, the battery status is output from the balancing energy storage module at the AC side port. U B Level; By opening the tenth switch S10, the third switch S3, the sixth switch S6 and the eleventh switch S11, and closing the remaining switches, the battery status self-balancing energy storage module outputs a 0 level at the AC side port; By opening the ninth switch S9, the second switch S2, the seventh switch S7 and the twelfth switch S12, and closing the remaining switches, the battery status self-balancing energy storage module outputs a 0 level at the AC side port.

5. The high-voltage direct-mounted energy storage system with battery state self-balancing capability according to claim 2 is characterized in that: The battery state self-balancing energy storage module realizes self-balancing of the charge state between battery modules through the switch state combination of the switch network; By turning on the first switch S1 and the third switch S3, the states of the first battery module B1 and the third battery module B3 are self-balanced; By turning on the second switch S2 and the fourth switch S4, the state of the second battery module B2 and the third battery module B3 are self-balanced; By turning on the fifth switch S5 and the seventh switch S7, the states of the first battery module B1 and the fourth battery module B4 are self-balanced; By turning on the sixth switch S6 and the eighth switch S8, the states of the second battery module B2 and the fourth battery module B4 are self-balanced.

6. The high-voltage direct-mounted energy storage system with battery state self-balancing capability according to claim 1 is characterized in that: The submodule distributed control unit selects a switch state combination of a set of switch networks in each switching cycle to meet the output level requirements of the AC side of the battery state self-balancing energy storage module, and simultaneously realizes the state self-balancing of the battery modules inside the battery state self-balancing energy storage module.

7. A high-voltage direct-mounted energy storage method with battery state self-balancing capability, based on the high-voltage direct-mounted energy storage system with battery state self-balancing capability according to any one of claims 1 to 6, characterized in that: include: Step S1: connecting the battery module to the DC bus of the multi-level AC / DC power conversion circuit, and the battery state self-balancing energy storage module converts the electrochemical energy in the battery module into electrical energy through the multi-level AC / DC power conversion circuit; Step S2: the main control unit samples the voltage and current information on the grid side and collects the battery status information uploaded by the battery status self-balancing energy storage module, and generates modulation information of the battery status self-balancing energy storage module through control; Step S3: The submodule distributed control unit and the battery state self-balancing energy storage module are matched one by one, the modulation information generated by the main control unit is received by the submodule distributed control unit and the battery state information is transmitted to it, and the received modulation information is converted into a switch signal corresponding to the battery state self-balancing energy storage module.

8. The high-voltage direct-mounted energy storage method with battery state self-balancing capability according to claim 7 is characterized in that: The battery state self-balancing energy storage module in step S1 includes: a switch module and a battery module; The switch module includes: a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a seventh switch S7, an eighth switch S8, a ninth switch S9, a tenth switch S10, an eleventh switch S11 and a twelfth switch S12; the battery module includes: a first battery module B1, a second battery module B2, a third battery module B3 and a fourth battery module B4; The specific circuit connection of the battery state self-balancing energy storage module includes: the half bridge composed of the first switch S1 and the second switch S2 is connected to the positive and negative ports of the first battery module B1, the half bridge composed of the fifth switch S5 and the sixth switch S6 is connected to the positive and negative ports of the first battery module B1, the half bridge composed of the third switch S3 and the fourth switch S4 is connected to the positive and negative ports of the second battery module B2, the half bridge composed of the seventh switch S7 and the eighth switch S8 is connected to the positive and negative ports of the second battery module B2, the negative electrode of the first battery module B1 is connected to the positive electrode of the second battery module B2; the positive electrode port of the third battery module B3 is connected to the midpoint of the half bridge composed of the first switch S1 and the second switch S2, and the negative electrode port of the third battery module B3 is connected to The midpoint of the half bridge formed by the third switch S3 and the fourth switch S4, and the half bridge formed by the ninth switch S9 and the tenth switch S10 are connected to the positive and negative ports of the third battery module B3; the positive port of the fourth battery module B4 is connected to the midpoint of the half bridge formed by the fifth switch S5 and the sixth switch S6, the negative port of the fourth battery module B4 is connected to the midpoint of the half bridge formed by the seventh switch S7 and the eighth switch S8, and the half bridge formed by the eleventh switch S11 and the twelfth switch S12 is connected to the positive and negative ports of the fourth battery module B4; the midpoint of the half bridge formed by the ninth switch S9 and the tenth switch S10 and the midpoint of the half bridge formed by the eleventh switch S11 and the twelfth switch S12 constitute the AC side port of the battery state self-balancing energy storage module.

9. The high-voltage direct-mounted energy storage method with battery state self-balancing capability according to claim 8, characterized in that: In step S1, the battery state self-balancing energy storage module outputs 5 voltage levels at the AC side port through the switch state combination of the switch network: +2 U B , -2 U B 、+ U B 、- U B , 0; By opening the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7, the fourth switch S4 and the tenth switch S10, and closing the remaining switches, the battery status is outputted from the balancing energy storage module at the AC side port +2 U B Level; By opening the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, the eighth switch S8 and the twelfth switch S12, and closing the remaining switches, the battery status is output from the balancing energy storage module at the AC side port. U B Level; By opening the fifth switch S5, the eleventh switch S11, the second switch S2, the seventh switch S7 and the ninth switch S9, and closing the remaining switches, the battery status is outputted from the balancing energy storage module at the AC side port + U B Level; By opening the twelfth switch S12, the second switch S2, the seventh switch S7, the fourth switch S4 and the tenth switch S10, and closing the remaining switches, the battery status is outputted from the balancing energy storage module at the AC side port + U B Level; By opening the first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6 and the eleventh switch S11, and closing the remaining switches, the battery status is output from the balancing energy storage module at the AC side port. U B Level; By opening the tenth switch S10, the third switch S3, the sixth switch S6, the eighth switch S8 and the twelfth switch S12, and closing the remaining switches, the battery status is output from the balancing energy storage module at the AC side port. U B Level; By opening the tenth switch S10, the third switch S3, the sixth switch S6 and the eleventh switch S11, and closing the remaining switches, the battery status self-balancing energy storage module outputs a 0 level at the AC side port; By opening the ninth switch S9, the second switch S2, the seventh switch S7 and the twelfth switch S12, and closing the remaining switches, the battery status self-balancing energy storage module outputs a 0 level at the AC side port; The battery state self-balancing energy storage module realizes self-balancing of the state of charge between the battery modules through the switch state combination of the switch network; by opening the first switch S1 and the third switch S3, the state of the first battery module B1 and the third battery module B3 is self-balancing; By turning on the second switch S2 and the fourth switch S4, the states of the second battery module B2 and the third battery module B3 are self-balanced; By turning on the fifth switch S5 and the seventh switch S7, the states of the first battery module B1 and the fourth battery module B4 are self-balanced; By turning on the sixth switch S6 and the eighth switch S8, the states of the second battery module B2 and the fourth battery module B4 are self-balanced.

10. The high-voltage direct-mounted energy storage method with battery state self-balancing capability according to claim 7, characterized in that: In step S3, the submodule distributed control unit selects a switch state combination of a switch network in each switch cycle to meet the output level requirement of the AC side of the battery state self-balancing energy storage module, and simultaneously realizes the state self-balancing of the battery modules inside the battery state self-balancing energy storage module.

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