Medium-high voltage direct hanging type flow battery energy storage system

Abstract

The utility model discloses a middle-high voltage direct hanging type flow battery energy storage system which comprises an energy storage converter, a positive electrolyte storage tank and a negative electrolyte storage tank, and the direct current side of the energy storage converter is respectively connected with the positive electrode and the negative electrode of a first electric pile group, the positive electrode and the negative electrode of a second electric pile group and the positive electrode and the negative electrode of a third electric pile group; according to the middle-high voltage direct hanging type flow battery energy storage system disclosed by the utility model, the electrolyte storage tank is divided into a plurality of independent areas, so that a pipeline of each series circuit group in the system is independent, and the energy storage converter is connected with a power grid at the alternating current side, and the first electric pile group, the second electric pile group and the third electric pile group are respectively formed by connecting five electric piles in series. And an electrolyte common channel is eliminated, so that the purpose of completely eliminating bypass current is achieved. Secondly, a step-up transformer is cancelled, and the cascade energy storage converter is directly boosted to middle-high voltage to be merged into a power grid, so that the energy efficiency of the flow battery system can be effectively improved, and the occupied area and investment are reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of liquid flow battery energy storage, in particular to a medium- and high-voltage direct-hanging liquid flow battery energy storage system. Background Art

[0002] Liquid flow battery energy storage systems, with their large energy storage capacity, flexible power configuration, long cycle life, safety, and environmental friendliness, are currently widely used in renewable energy generation, grid peak and frequency regulation, and smart microgrids. The open-circuit voltage of all-vanadium liquid flow batteries is 1.259V, making a single cell insufficient for the voltage requirements of power storage. In practical applications, multiple batteries are connected in series to form a stack to increase the voltage. These stacks are then connected in series and parallel to meet specific voltage and power requirements, and then connected to the grid via a power storage converter (PCS) and a power storage boost transformer.

[0003] The electrolyte circulates between the stacks and the electrolyte storage tanks through pumps and pipelines, connecting different potential points within the stack, forming a conductive path and generating leakage current. This leakage current generates leakage losses, which not only causes localized temperature rise within the stack and accelerates material aging, but also increases the system's heat dissipation burden and reduces system energy efficiency. Common methods to reduce leakage current include adding coils to the stack and creating voltage isobars on common pipelines.

[0004] In large-capacity liquid flow battery energy storage systems, a power storage converter (PCS) usually converts the DC power of the battery stack into low-voltage AC power. Multiple AC circuits are collected and then boosted to 10-220kV by a power storage step-up transformer and fed into the grid.

[0005] Patent CN102867975 uses a parallel circuit approach to create voltage isobaric points on common pipelines. However, in actual engineering applications, due to the inconsistencies in the layout of the battery stacks, electrolyte flow rates, and the battery stacks themselves, especially in large-scale 100-megawatt liquid flow battery energy storage systems, it is difficult to truly achieve isobaric points in parallel. Therefore, this method is not very effective in practical applications.

[0006] Patent CN201720196674 uses a shared storage tank for multiple battery stacks connected in series, while separate storage tanks are used for multiple battery stacks connected in series. This effectively creates a single, independent energy storage system connected by wires. This approach requires multiple storage tanks, increasing floor space and costs.

[0007] Traditional flow battery energy storage systems use a single-stage DC-AC converter or a two-stage DC-DC converter, followed by a step-up transformer to achieve the grid-connected voltage. This model uses a lower AC voltage, and the use of a step-up transformer increases system losses, reducing energy efficiency. It also increases the system's footprint and investment. Utility Model Content

[0008] The purpose of the present invention is to provide a medium- and high-voltage direct-mounted liquid flow battery energy storage system to solve the problems raised in the above-mentioned background technology.

[0009] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a medium- and high-voltage direct-mounted liquid flow battery energy storage system, comprising an energy storage converter, a positive electrode electrolyte storage tank, and a negative electrode electrolyte storage tank. The DC side of the energy storage converter is respectively connected to the positive and negative electrodes of the first battery stack group, the positive and negative electrodes of the second battery stack group, and the positive and negative electrodes of the third battery stack group. The AC side of the energy storage converter is connected to the power grid. The first battery stack group, the second battery stack group, and the third battery stack group are each composed of five battery stacks connected in series. The interior of the positive electrode electrolyte storage tank and the interior of the negative electrode electrolyte storage tank are evenly divided into zone I, zone II, and zone III by partitions. The five battery stacks in the first battery stack group are connected by The first positive electrode electrolyte pipeline is connected to zone III of the positive electrode electrolyte storage tank, the five battery stacks in the second battery stack group are connected to zone II of the positive electrode electrolyte storage tank through the second positive electrode electrolyte pipeline, the five battery stacks in the third battery stack group are connected to zone I of the positive electrode electrolyte storage tank through the third positive electrode electrolyte pipeline, the five battery stacks in the first battery stack group are connected to zone III of the negative electrode electrolyte storage tank through the first negative electrode electrolyte pipeline, the five battery stacks in the second battery stack group are connected to zone II of the negative electrode electrolyte storage tank through the second negative electrode electrolyte pipeline, and the five battery stacks in the third battery stack group are connected to zone I of the negative electrode electrolyte storage tank through the third negative electrode electrolyte pipeline.

[0010] Preferably, the first fuel cell stack group, the second fuel cell stack group and the third fuel cell stack group are arranged in parallel.

[0011] Preferably, circulation pumps are installed inside the positive electrolyte storage tank, zones I, II, and III, and the negative electrolyte storage tank, zones I, II, and III. The storage tank zones, circulation pumps, series piping, and multiple stacks in the series circuit form an independent circulation system.

[0012] Preferably, the first positive electrode electrolyte pipeline, the second positive electrode electrolyte pipeline and the third positive electrode electrolyte pipeline constitute a positive electrode pipeline network.

[0013] Preferably, the first negative electrode electrolyte pipeline, the second negative electrode electrolyte pipeline and the third negative electrode electrolyte pipeline constitute a negative electrode pipeline network.

[0014] Compared with existing technologies, the present invention offers the following advantages: by separating the electrolyte storage tank into multiple independent zones, the piping of each series circuit group in the system is independent, eliminating common electrolyte channels and completely eliminating bypass currents. Furthermore, by eliminating the step-up transformer and using a cascaded energy storage converter to directly boost the voltage to medium and high voltage for grid integration, the system can effectively improve the energy efficiency of the flow battery system while reducing floor space and investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of a flow battery system of the present utility model;

[0016] Figure 2 This is the topology diagram of the cascaded PCS of the present utility model.

[0017] Figure 1 Middle: 1. Positive electrode electrolyte storage tank; 2. Negative electrode electrolyte storage tank; 3. First positive electrode electrolyte pipeline; 4. Second positive electrode electrolyte pipeline; 5. Third positive electrode electrolyte pipeline; 6. First negative electrode electrolyte pipeline; 7. Second negative electrode electrolyte pipeline; 8. Third negative electrode electrolyte pipeline; 9. First fuel cell group; 10. Second fuel cell group; 11. Third fuel cell group; 12. Energy storage converter. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0019] Example 1.

[0020] See also Figure 1-2 The utility model provides a medium- and high-voltage direct-mounted liquid flow battery energy storage system, including an energy storage converter 12, a positive electrode electrolyte storage tank 1 and a negative electrode electrolyte storage tank 2. The DC side of the energy storage converter is respectively connected to the positive and negative electrodes of the first battery stack group 9, the positive and negative electrodes of the second battery stack group 10 and the positive and negative electrodes of the third battery stack group 11. The AC side of the energy storage converter 12 is connected to the power grid. The first battery stack group 9, the second battery stack group 10 and the third battery stack group 11 are each composed of five battery stacks in series. The interior of the positive electrode electrolyte storage tank 1 and the interior of the negative electrode electrolyte storage tank 2 are evenly divided into area I, area II and area III by partitions. The five battery stacks in the first battery stack group 9 are connected by the first positive electrode electrolyte. The liquid pipeline 3 is connected to the zone III of the positive electrode electrolyte storage tank 1, the five battery stacks in the second battery stack group 10 are connected to the zone II of the positive electrode electrolyte storage tank 1 through the second positive electrode electrolyte pipeline 4, the five battery stacks in the third battery stack group 11 are connected to the zone I of the positive electrode electrolyte storage tank 1 through the third positive electrode electrolyte pipeline 5, the five battery stacks in the first battery stack group 9 are connected to the zone III of the negative electrode electrolyte storage tank 2 through the first negative electrode electrolyte pipeline 6, the five battery stacks in the second battery stack group 10 are connected to the zone II of the negative electrode electrolyte storage tank 2 through the second negative electrode electrolyte pipeline 7, and the five battery stacks in the third battery stack group 11 are connected to the zone I of the negative electrode electrolyte storage tank 2 through the third negative electrode electrolyte pipeline 8.

[0021] The first stack group 9, the second stack group 10 and the third stack group 11 are arranged in parallel. Circulation pumps are provided inside the areas I, II and III of the positive electrode electrolyte storage tank 1 and the areas I, II and III of the negative electrode electrolyte storage tank 2.

[0022] Specifically, the positive electrode electrolyte storage tank 1 and the negative electrode electrolyte storage tank 2 are divided into zone I, zone II and zone III, the same number as the series circuits in the system, and each partition of the positive electrode electrolyte storage tank 1 and the negative electrode electrolyte storage tank 2 is equipped with a circulation pump. The tank partitions, circulation pumps, series pipes, and several battery stacks in the series circuit form an independent circulation system.

[0023] The first positive electrode electrolyte pipeline 3, the second positive electrode electrolyte pipeline 4 and the third positive electrode electrolyte pipeline 5 form a positive electrode pipeline network. The first negative electrode electrolyte pipeline 6, the second negative electrode electrolyte pipeline 7 and the third negative electrode electrolyte pipeline 8 form a negative electrode pipeline network.

[0024] When the embodiment of the present application is in use: the positive electrode electrolyte storage tank 1 is provided with 3 partitions, numbered I, II, and III, and the electrolyte in the storage tank is completely separated by the partition. The electrolyte in area I is connected to the liquid inlet of the third battery stack group 11 in a row of series battery stacks through the third positive electrode electrolyte pipeline 5, and then returns to area I from the liquid outlet of the third battery stack group 11 in a row of series battery stacks through the third positive electrode electrolyte pipeline 5; the electrolyte in area II is connected to the liquid inlet of the second battery stack group 10 in a row of series battery stacks through the second positive electrode electrolyte pipeline 4, and then returns to area II from the liquid outlet of the second battery stack group 10 in a row of series battery stacks through the second positive electrode electrolyte pipeline 4; the electrolyte in area III is connected to the first battery stack group 9 in a row of series battery stacks through the first positive electrode electrolyte pipeline 3, and then returns to area III from the liquid outlet of the first battery stack group 9 through the first positive electrode electrolyte pipeline 3. The partitions and pipelines of the negative electrode electrolyte storage tank 2 are the same as those of the positive electrode storage tank 1. The electrolyte pipelines of the three rows of battery stacks of the utility model all complete circulation independently, eliminating the common channel and achieving the purpose of completely eliminating the bypass current.

[0025] Example 2.

[0026] This embodiment eliminates the step-up transformer and uses an energy storage converter 12 to directly connect to the medium and high voltage grid. The energy storage converter 12 adopts a cascade structure, with one end of the three-phase commutation chain connected in a star shape, and the other end is connected to the grid through a grid-connected reactor; the number of commutation links per phase N is determined according to the voltage level and capacity requirements of the grid; each link contains 4 power electronic devices (IGBT) to form an H-bridge circuit, and the DC side is connected to the battery stack. The number of links in the three phases A, B, and C is the same. The cascaded PCS topology is shown in the attached figure. Figure 2 As shown. Among them, m = 5 means a row of 5 stacks in series; N = 24, which means there are 24 sets Figure 1 Device

[0027] This system utilizes a cascaded energy storage converter 12. The first row of five series-connected battery stacks is connected to the DC side of the first link of the H-bridge circuit in phase A. The second row of five series-connected battery stacks is connected to the DC side of the first link of the H-bridge circuit in phase B. The third row of five series-connected battery stacks is connected to the DC side of the first link of the H-bridge circuit in phase C. Each H-bridge contains four IGBTs, and the H-bridge circuit uses five battery stacks connected in series, with a DC side voltage of 484V-682V. In a large-capacity, high-voltage, grid-connected liquid flow battery energy storage system composed of multiple units of these devices, the series-connected battery stacks of the second unit are connected to the second link, the series-connected battery stacks of the third unit are connected to the third link, and so on and so forth.

[0028] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A medium- and high-voltage direct-mounted liquid flow battery energy storage system, comprising an energy storage converter (12), a positive electrode electrolyte storage tank (1) and a negative electrode electrolyte storage tank (2), characterized in that: The DC side of the energy storage converter (12) is respectively connected to the positive and negative electrodes of the first stack group (9), the positive and negative electrodes of the second stack group (10), and the positive and negative electrodes of the third stack group (11). The AC side of the energy storage converter is connected to the power grid. The first stack group (9), the second stack group (10), and the third stack group (11) are each composed of five stacks connected in series. The interior of the positive electrode electrolyte storage tank (1) and the interior of the negative electrode electrolyte storage tank (2) are evenly divided into zone I, zone II, and zone III by partitions. The five stacks in the first stack group (9) are connected to zone III of the positive electrode electrolyte storage tank (1) through the first positive electrode electrolyte pipeline (3). The interior of the second stack group (10) is connected to zone III of the positive electrode electrolyte storage tank (1). The five battery stacks are connected to the II zone of the positive electrode electrolyte storage tank (1) through the second positive electrode electrolyte pipeline (4), the five battery stacks in the third battery stack group (11) are connected to the I zone of the positive electrode electrolyte storage tank (1) through the third positive electrode electrolyte pipeline (5), the five battery stacks in the first battery stack group (9) are connected to the III zone of the negative electrode electrolyte storage tank (2) through the first negative electrode electrolyte pipeline (6), the five battery stacks in the second battery stack group (10) are connected to the II zone of the negative electrode electrolyte storage tank (2) through the second negative electrode electrolyte pipeline (7), and the five battery stacks in the third battery stack group (11) are connected to the I zone of the negative electrode electrolyte storage tank (2) through the third negative electrode electrolyte pipeline (8).

2. A medium- and high-voltage direct-mounted liquid flow battery energy storage system according to claim 1, characterized in that: The first battery stack group (9), the second battery stack group (10) and the third battery stack group (11) are arranged in parallel.

3. The medium- and high-voltage direct-mounted flow battery energy storage system according to claim 1, characterized in that: Circulation pumps are provided inside the zones I, II and III of the positive electrode electrolyte storage tank (1) and the zones I, II and III of the negative electrode electrolyte storage tank (2).

4. A medium- and high-voltage direct-mounted liquid flow battery energy storage system according to claim 1, characterized in that: The first positive electrode electrolyte pipeline (3), the second positive electrode electrolyte pipeline (4) and the third positive electrode electrolyte pipeline (5) constitute a positive electrode pipeline network.

5. The medium- and high-voltage direct-mounted liquid flow battery energy storage system according to claim 1, characterized in that: The first negative electrode electrolyte pipeline (6), the second negative electrode electrolyte pipeline (7) and the third negative electrode electrolyte pipeline (8) form a negative electrode pipeline network.

Images