High-voltage direct-connected energy storage system and method with battery state self-balancing ability

Abstract

The present invention provides a high-voltage direct-connected energy storage system and method with battery state self-balancing ability, including: 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 the multi-level AC-DC power conversion circuit converts the electrochemical energy in the battery module into electrical energy; 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 modulation information for the battery state self-balancing energy storage module through control; 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 signals of the corresponding battery state self-balancing energy storage modules. The present invention can reduce the number of switches in the system, achieve self-balancing of the battery states inside the sub-modules, reduce the control difficulty of the main control, and is beneficial to energy storage systems with higher voltage levels and larger single-unit capacities.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical automation equipment, and in particular, 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 more 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 are connected to the medium-voltage and high-voltage power grids through step-up transformers step by step. In the energy storage power station based on the conventional battery energy storage system architecture, there are disadvantages such as large inter-cluster circulating current, obvious cask effect, low battery utilization rate, and easy occurrence of safety problems in the battery stack. In addition, the parallel connection of multiple energy storage converters will result in a complex structure of the energy storage power station, a large floor area, a long cable line leading to complex distribution of parasitic parameters, a slow system response time caused by communication delay, a complex control system of the whole 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 omit the industrial-frequency transformer and be directly connected to the high-voltage power grid, and the loss caused by the transformer can be eliminated. 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, a fast system response speed and is not easy to cause 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 access 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 problems 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, some network - forming control methods have been proposed as follows:

[0006] The utility model patent with the publication number CN221058195U discloses a high - voltage direct - hanging series three - level energy - storage converter power unit. By using a single - phase three - level sub - module topology, it solves problems such as a large number of series power units and a large volume of the direct - hanging energy - storage system in the existing solutions, greatly reducing the number of power units of the direct - hanging energy - storage system, reducing the failure rate, and improving the reliability of the direct - hanging energy - storage system. However, the number of switching devices used when this topology accesses two battery modules is the same as that of the traditional H - bridge scheme.

[0007] The invention patent with the publication number CN116581800A discloses a capacity - expanded high - voltage direct - hanging energy - storage power conversion system and control method. The provided structure design of the stacked half - bridge sub - modules allows each sub - module to be connected in parallel with two batteries. Therefore, with 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 and forming an expanded - capacity high - voltage direct - hanging energy - storage PCS, greatly improving the total output capacity of a single - machine high - voltage direct - hanging 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 requires external control means.

[0008] The invention patent with the publication number CN115459324A discloses a cascaded H - bridge energy - storage circuit with an energy - balancing function and its energy - balancing method. Through a switched - capacitor balancing circuit, the switched - capacitor balancing 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 over - charging and over - discharging of the battery and increase the number of battery charge - discharge cycles. However, this method adds an additional hardware balancing circuit, and the insulation pressure between the balancing circuits is extremely large in a high - voltage environment, making it very difficult to implement. Summary of the Invention

[0009] Aiming at the defects in the prior art, the present invention provides a high - voltage direct - hanging energy - storage system and method with the ability of self - balancing battery states.

[0010] According to a high - voltage direct - hanging energy - storage system and method with the ability of self - balancing battery states provided by the present invention, the solutions are as follows:

[0011] In the first aspect, a high - voltage direct - hanging energy - storage system with the ability of self - balancing battery states is provided. The system includes:

[0012] 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;

[0013] The battery state self-balancing energy storage module: connects battery modules to the DC bus of the multi-level AC-DC power conversion circuit and converts the electrochemical energy in the battery modules into electrical energy through the multi-level AC-DC power conversion circuit;

[0014] The main control unit: generates modulation information for the battery state self-balancing energy storage module by sampling grid-side voltage and current information and collecting battery state information uploaded by the battery state self-balancing energy storage module;

[0015] The sub-module distributed control unit corresponds to the battery state self-balancing energy storage module one by one, receives the modulation information generated by the main control unit, transmits battery state information to it, and converts the received modulation information into switch signals corresponding to the battery state self-balancing energy storage module.

[0016] Preferably, the battery state self-balancing energy storage module includes: a switch module and a battery module;

[0017] 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;

[0018] 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 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. The 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. The 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.

[0019] 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.

[0020] Preferably, the battery state self - balancing energy storage module outputs 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;

[0021] 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;

[0022] 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 - equalizing energy storage module outputs - 2 at the AC - side port U B level;

[0023] 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 - equalizing energy storage module outputs + U B level;

[0024] 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 - equalizing energy storage module outputs + U B level;

[0025] 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 - equalizing energy storage module outputs - U B level;

[0026] 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 - equalizing energy storage module outputs - U B level;

[0027] 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 - equalizing energy storage module outputs 0 level;

[0028] 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 - equalizing energy storage module outputs 0 level.

[0029] Preferably, the battery state self - equalizing energy storage module realizes the self - equalization of the state of charge between battery modules through the combination of the switch states of the switch network;

[0030] By turning on the first switch S1 and the third switch S3, the state self - equalization of the first battery module B1 and the third battery module B3 is realized;

[0031] 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;

[0032] 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;

[0033] 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.

[0034] Preferably, the sub - module distributed control unit selects a combination of the switch states of a group of switch networks within 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.

[0035] In a second aspect, a high - voltage direct - connection energy storage method with battery state self - balancing ability is provided. The method includes:

[0036] Step S1: Connect the battery modules to the DC bus of the multi - level AC - DC power conversion circuit. The battery state self - balancing energy storage module realizes the conversion of the electrochemical energy in the battery modules into electrical energy through the multi - level AC - DC power conversion circuit;

[0037] 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;

[0038] 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, conveys the battery state information to it, and converts the received modulation information into the switch signals corresponding to the battery state self - balancing energy storage module.

[0039] Preferably, in step S1, the battery state self - balancing energy storage module includes: a switch module and a battery module;

[0040] 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;

[0041] 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 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. The 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. The 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.

[0042] Preferably, in step S1, the battery state self - balancing energy storage module outputs 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;

[0043] 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;

[0044] 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;

[0045] 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 a + U B level at the AC - side port;

[0046] 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 a + U B level at the AC - side port;

[0047] 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 a - U B level at the AC - side port;

[0048] 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;

[0049] 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;

[0050] 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;

[0051] 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 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 realized;

[0052] 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;

[0053] 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;

[0054] 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.

[0055] Preferably, in step S3, the sub - module distributed control unit selects a combination of switch states of a group of switch networks within 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.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] 1. By providing a topology of a battery state self - balancing energy storage module and connecting four battery modules, compared with the traditional cascaded H - bridge circuit where each battery module uses an H - bridge circuit, the system reduces the number of switches by 25%. It has the advantages of compact structure, high integration, etc., and improves the system reliability.

[0058] 2. The present invention realizes the automatic state - of - charge balancing between battery modules. By reasonably selecting the combination of switch states of the switch network, the automatic state - balancing of the four battery states inside the battery state self - balancing sub - module topology can be achieved.

[0059] 3. Aiming at the problem that the implementation difficulty of the controller in the traditional cascaded H - bridge circuit increases with the increase of system capacity and voltage level, for the high - voltage direct - connected energy storage system with battery state self - balancing ability 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.

[0060] Other beneficial effects of the present invention will be described in the specific implementation manners through the introduction of specific technical features and technical solutions. 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

[0061] 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:

[0062] Figure 1 It is the circuit diagram of the high - voltage direct - connected energy storage system with battery state self - balancing ability of the present invention;

[0063] Figure 2 It is the circuit diagram of the battery state self - balancing energy storage module of the present invention;

[0064] Figure 3This is the switching combination of the battery state self - balancing energy storage module of the present invention at different output levels. Detailed implementation manners

[0065] 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.

[0066] An embodiment of the present invention provides a high - voltage direct - connected energy storage system with battery state self - balancing ability. Referring to Figure 1 as shown, this 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;

[0067] Specifically, the battery state self - balancing energy storage module: connects a 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.

[0068] 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.

[0069] The sub - module distributed control unit corresponds to the battery state self - balancing energy storage module 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 switching signal corresponding to the battery state self - balancing energy storage module.

[0070] Referring to Figure 1 as shown, it is the structure diagram of a high - voltage direct - connected battery energy storage system with battery state self - balancing ability. The high - voltage direct - connected energy storage system with battery state self - balancing ability is directly connected to power grids of various voltage levels, including: an A - phase power module, a B - phase power module, and a 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 the 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.

[0071] 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 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.

[0072] 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, 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 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, 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, 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.

[0073] Referring to Figure 3 As 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;

[0074] 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;

[0075] 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;

[0076] 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;

[0077] 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;

[0078] 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;

[0079] 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;

[0080] 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;

[0081] 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.

[0082] 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;

[0083] 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;

[0084] 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;

[0085] 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;

[0086] 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.

[0087] 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.

[0088] The present invention also provides a high - voltage direct - connection energy storage method with the ability of battery state self - balancing, which specifically includes:

[0089] 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;

[0090] 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;

[0091] Step S3: One - to - one correspondence is established between the sub - module distributed control unit and the battery state self - balancing energy storage module. 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.

[0092] 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.

[0093] 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.

[0094] 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 electrode of the first battery module B1 is connected to the positive electrode of the second battery module B2. The positive terminal 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 terminal 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 terminal 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 terminal 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.

[0095] 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;

[0096] 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;

[0097] 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;

[0098] 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 a + U B level at the AC - side port;

[0099] 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 a + U B level at the AC - side port;

[0100] 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 a - U B level at the AC - side port;

[0101] 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;

[0102] 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;

[0103] 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.

[0104] Refer 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;

[0105] 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;

[0106] 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;

[0107] 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.

[0108] The sub-module distributed control unit selects a set of switching state combinations of the switching network in each switching cycle, which meets 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.

[0109] The embodiment of the present invention provides a high-voltage direct-connected energy storage system and method with the ability of battery state self-balancing. Through the battery state self-balancing sub-module topology, the number of switches in the system is reduced, the state self-balancing of the batteries inside the sub-module is realized, 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.

[0110] 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 make the system and its various devices, modules, and units provided by the present invention be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers, etc. 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 both software modules for implementing the method and the structure inside the hardware component.

[0111] 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 with each other arbitrarily.

Claims

1. A high-voltage direct-connected energy storage system with the ability of self-balancing battery state, 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 a 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 grid-side voltage and current information and collecting the battery state information uploaded by the battery state self-balancing energy storage module, generates the modulation information of the battery state self-balancing energy storage module through control; The sub-module distributed control unit corresponds to the battery state self-balancing energy storage module 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 switching signal corresponding to the battery state self-balancing energy storage module; The battery state self-balancing energy storage module includes: a switching module and a battery module; The switching 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, 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 composed of 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 composed of the third switch S3 and the fourth switch S4, and the 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 midpoint 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 midpoint of the half-bridge composed of the seventh switch S7 and the eighth switch S8, and the 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 midpoint of the half-bridge composed of the ninth switch S9 and the tenth switch S10 and the midpoint 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.

2. The high-voltage direct-connected energy storage system with the ability of self-balancing battery state according to claim 1, wherein 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.

3. The high-voltage direct-connected energy storage system with battery state self-balancing ability according to claim 1, characterized in that The battery state self - balancing energy storage module outputs 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 turning off the remaining switches, the battery state self - balancing energy storage module outputs a +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 turning off 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 turning off the remaining switches, the battery state self - equalizing energy storage module outputs a + U B level on 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 turning off 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 first switch S1, the ninth switch S9, the third switch S3, the sixth switch S6, and the eleventh switch S11, and turning off 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 turning off 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 turning off 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 turning off the remaining switches, the battery state self-balancing energy storage module outputs a 0 level at the AC side port.

4. The high-voltage direct-connected energy storage system with battery state self-balancing ability according to claim 1, characterized in that, 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 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.

5. The high-voltage direct-connected energy storage system with battery state self-balancing ability according to claim 1, characterized in that, The sub-module distributed control unit selects a set of switch state combinations of the switch network in 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.

6. A high-voltage direct-connected energy storage method with battery state self-balancing ability, based on the high-voltage direct-connected energy storage system with battery state self-balancing ability according to any one of claims 1-5, characterized in that, Including: 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 generates the modulation information of the battery state self-balancing energy storage module 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. Step S3: Corresponding 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 switch signal corresponding to the battery state self-balancing energy storage module.

7. The high-voltage direct-connected energy storage method with battery state self-balancing ability according to claim 6, characterized in that, In step S1, 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 specific circuit connection of the battery state self - balancing energy storage module is as follows: 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 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.

8. The high-voltage direct-connected energy storage method with battery state self-balancing ability according to claim 7, wherein In the step S1, the battery state self - balancing energy storage module outputs 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 turning off 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 turning off 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 turning off the remaining switches, the battery state self-balancing energy storage module outputs a + U B level on 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 turning off the remaining switches, the battery state self - balancing energy storage module outputs a + U B level on 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 turning off 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, the eighth switch S8, and the twelfth switch S12, and turning off 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 turning off the other 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 turning off the other switches, the battery state self - balancing energy storage module outputs a 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 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 of the second battery module B2 and the fourth battery module B4 is achieved.

9. The high-voltage direct-connected energy storage method with battery state self-balancing ability according to claim 6, characterized in that, In step S3, the sub-module distributed control unit selects a combination of switch states of a group of switch 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.

Images