Flow battery energy storage system of 30MW and above

Abstract

Disclosed in the present invention is a flow battery energy storage system of 30 MW level and above, which comprises more than eight fluid process systems. A positive electrolyte storage tank and a negative electrolyte storage tank of each fluid process system are respectively connected to a positive electrode current equalizer and a negative electrode current equalizer by means of transfer pumps, the current equalizers supplying electrolyte to positive electrodes and negative electrodes of all battery stacks in the system simultaneously, and the electrolyte from an electrolyte outlet of each battery stack being combined and flowing back to the electrolyte storage tanks by means of another positive electrode current equalizer and negative electrode current equalizer separately. The battery stacks with the corresponding serial numbers in the fluid process systems are connected in series, and each string of battery stacks is externally connected to a converter device. The present invention adds current equalizers or multi-stage distribution pipelines for battery stacks, so as to achieve uniform fluid distribution, and reduce the flow difference. In addition, using advanced converter devices overcomes the problems of system energy loss or low reliability and stability caused by a circuit topology between a conventional battery stack and DC / DC and / or AC / DC, as well as the limitations of low integration and small power scale, generally not greater than 500 kW of individual energy storage systems.

Description

30MW and above flow battery energy storage system Technical Field

[0001] The present invention relates to the field of liquid flow batteries, and in particular to a liquid flow battery energy storage system with a capacity of 30MW or above. Background Art

[0002] Flow batteries are a new type of electrochemical energy storage system. They charge and discharge through redox reactions between active ions in the positive and negative electrolytes. For large-scale energy storage systems, the output power of a single battery stack falls far short of meeting the system's output requirements. Multiple battery stacks are typically connected in series or parallel to increase the system's output power and meet these requirements.

[0003] In the technologies related to liquid flow battery energy storage systems above 30MW, in order to ensure the consistency of charging and discharging of all battery stacks, all battery stacks are usually connected in parallel on the liquid pipeline, so that the parameters such as the electrolyte charge state of each battery stack are the same. However, the existing liquid connection mode does not take into account the fluid distribution between battery stacks and the upper and lower limits of the battery stack series voltage. The consistency of battery stack performance is difficult to guarantee, and there may be series current limitation issues. Or, during the charging and discharging process, when the battery stack series current is the same, the liquid pipeline system will still form a liquid conductive network under different battery stack voltages, resulting in liquid bypass current between battery stacks, causing energy loss. Moreover, this large-scale energy storage system is usually composed of a simple combination of multiple small energy storage systems. The power of each small energy storage system generally does not exceed 500kW. The system is decentralized and complex, which seriously affects the reliability and stability of the energy storage system.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to provide a liquid flow battery energy storage system with a capacity of 30MW or above, solve the problem of efficient integration of liquid flow battery energy storage systems, eliminate bypass current, and at the same time, the battery stacks within the system are integrated, installed, and operate in a consistent manner; at the same time, it adopts advanced current conversion technology, namely conventional AC / DC and phase-shifting transformer combined current conversion technology, to overcome the system energy loss or low reliability and stability caused by the current loop of conventional DC / DC or AC / DC; finally, it solves the problem that the low voltage liquid flow battery energy storage system cannot be directly connected to the high voltage power grid; and it can make the scale of a single energy storage system exceed 30MW, forming an ultra-large-scale, highly integrated single energy storage system.

[0006] The technical solution of the present invention is:

[0007] Liquid flow battery energy storage systems above 30MW include more than 8 sets of fluid process systems. Each fluid process system includes: multiple battery stacks, positive and negative electrolyte storage tanks, positive and negative electrolyte pumps, and a pair of positive and negative current equalizers.

[0008] The positive and negative electrode electrolyte storage tanks are connected to a positive and negative electrode current equalizer respectively through the positive and negative electrode electrolyte delivery pumps, and the positive and negative electrode current equalizers respectively supply liquid to the positive and negative electrodes of all battery stacks in the group at the same time. The positive and negative electrode supply outlets of each battery stack are respectively collected and refluxed to the positive and negative electrode electrolyte storage tanks through another positive and negative electrode current equalizer;

[0009] The number of battery stacks in each fluid process system is the same, and the battery stacks of corresponding sequences between each fluid process system are connected in series to form a string of battery stacks, and each string of battery stacks is externally connected to a set of converter equipment.

[0010] Preferably, in the fluid process system, if the positive electrode or negative electrode of the flow battery is in a solid state, the electrolyte storage tank, electrolyte delivery pump, pipeline and flow equalizer in the fluid process system are only on one side.

[0011] Preferably, in the fluid process system, the number of the fluid process systems is represented by N, that is, N>8; the serial number of the fluid process system is represented by i, 1≤i≤N; the positive and negative electrolytes in each group of fluid process systems are independent of each other.

[0012] Preferably, in the fluid process system, the battery stacks in each group of process systems are installed in a module at a rate of K units per group to form an energy storage power module, where K≥16, and the serial number of the battery stack in the power module is represented by k, 1≤k≤K; the total number of power modules is represented by M, where M≥16, and the serial number of the power module is represented by j, 1≤j≤M; by reasonably selecting large-scale fluid pumps for the positive and negative electrode electrolytes, the large flow rate of the delivered electrolyte can support stable charging and discharging operation of the M power modules with a total power of not less than 4MW.

[0013] Preferably, there are N groups of fluid process systems, and each group of process systems has M power modules, so the total power of the single energy storage system can be much greater than 8X 4MW=32MW.

[0014] Preferably, the modules of the fluid process system are constructed using frames or containers, and are stacked in a building block-like manner during construction, thereby improving the construction efficiency of the energy storage power station.

[0015] Preferably, the converter device adopts a bidirectional AC / DC converter and an isolation transformer. Each string of battery stacks is connected to the AC bus or transformer interval through the bidirectional AC / DC converter and isolation transformer connected in sequence to achieve the function of power storage or release.

[0016] Preferably, the converter device uses an AC / DC converter and a phase-shifting transformer. Each battery stack is connected to an AC / DC converter, and all AC / DC converters are then connected to a high-voltage bus or a transformer bay to a power grid through the same phase-shifting transformer.

[0017] Preferably, the converter device adopts a bidirectional high-frequency isolated AC / DC converter, and each battery stack is connected to the AC bus or the AC bus output is connected to the power grid through the bidirectional high-frequency isolated AC / DC converter.

[0018] The advantages of the present invention are:

[0019] 1. The liquid flow battery energy storage system of the present invention adds a flow equalizer or multi-stage distribution pipeline to the battery stack to achieve uniform distribution of the fluid and reduce the flow difference to no more than 5%;

[0020] 2. The present invention limits the series voltage of the battery stack to no less than 500V but no more than 1500V to avoid insufficient insulation performance of the system and the occurrence of leakage faults;

[0021] 3. The present invention adopts AC / DC and phase-shifting transformer combined conversion technology, the output voltage level can be higher than 35kV, realizing high-voltage direct connection;

[0022] 4. Due to the flow limitation of the liquid pump in actual engineering, the present invention cannot support too many battery stacks. Of course, this is related to the power size and required flow size of the battery stack itself. The number of battery stacks in each fluid process system is generally 256;

[0023] 5. The present invention uses the energy storage converter PCS to limit the power, and the total power of the battery stack after series connection is no more than 2.5MW;

[0024] 6. This technology breaks through the bottleneck of small scale and low power of conventional single-cell flow battery energy storage systems, enabling the construction of ultra-large-scale single-cell energy storage systems with a total power far exceeding 32MW, reaching over 64MW, significantly improving the integration, reliability, and stability of energy storage systems.

[0025] 7. The power of each battery stack of the present invention can be within 150kW, realizing the system integration of high-power battery stacks. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0027] FIG1 is a topology diagram of a flow battery energy storage system according to the present invention;

[0028] Figure 2 shows the topology of a battery stack string connected to an AC bus or transformer bay via a bidirectional AC / DC converter and an isolation transformer;

[0029] Figure 3 shows the topology of a battery stack string connected to a high-voltage bus or a transformer bay through an AC / DC converter and a phase-shifting transformer to connect to the grid.

[0030] Figure 4 shows the topology of a battery stack string connected to the AC bus or the AC bus output connected to the grid through a bidirectional high-frequency isolated AC / DC converter. DETAILED DESCRIPTION

[0031] As shown in Figure 1, the liquid flow battery energy storage system of the present invention includes more than 8 groups of fluid process systems, each group of fluid process systems includes: multiple battery stacks, positive and negative electrolyte storage tanks, positive and negative electrolyte pumps, and a pair of positive and negative current equalizers; the positive and negative electrolyte storage tanks are respectively connected to a positive and negative current equalizer through the positive and negative electrolyte delivery pumps, and the positive and negative current equalizers respectively supply liquid to the positive and negative electrodes of all battery stacks in the group at the same time. The positive and negative electrode supply outlets of each battery stack are respectively collected and refluxed to the positive and negative electrolyte storage tanks through another positive and negative current equalizer to ensure that the positive and negative electrolyte flow rates of all battery stacks in each process system are the same.

[0032] In liquid flow battery energy storage systems above 30MW, the number of fluid process systems is represented by N, that is, N>8, and the serial number of the fluid process system is represented by i, 1≤i≤N; the positive and negative electrolytes in each group of fluid process systems are independent of each other.

[0033] The battery stacks within each process system are installed in a container-sized frame or container, each containing 16 stacks (when the number of battery stacks does not exceed 16, a single frame or container is sufficient). This facilitates construction using a modular stacking method, improving the efficiency of energy storage power station construction. The total number of frames or containers is represented by M, which is generally no less than 16. The total number of frames or containers M is an even number, and the serial number of the frame or container is represented by j, with 1≤j≤M. The number of battery stacks within each frame or container is represented by K, which should be an even number, that is, K≥16. The serial number of the battery stacks within each frame or container is represented by k, with 1≤k≤K.

[0034] The corresponding battery stacks within each fluid process system are connected in series to form a string of battery stacks. Each string of battery stacks corresponds to one or more converter devices, including high-frequency isolated DC / DC, high-frequency isolated DC / DC, conventional AC / DC, and high-frequency isolated AC / DC. For example, the kth battery stack in the jth frame or container of the first fluid process system is connected in series with the kth battery stack in the jth frame or container of the second fluid process system, and then with the kth battery stack in the jth frame or container of the i-th fluid process system, and so on, until it is connected in series with the kth battery stack in the jth frame or container of the N-th fluid process system. Here, 1≤j≤M, M≥16; 1≤k≤K, K≥16; and 1≤i≤N, N>8.

[0035] In the fluid process system, if the positive electrode or negative electrode of the flow battery is in a solid state, such as there is no flow of electrolyte, the electrolyte storage tank, electrolyte delivery pump, pipeline and flow equalizer in the fluid process system are only on one side.

[0036] Example 2

[0037] As shown in Figure 2, when the total voltage of each battery stack string is no less than 500V, each battery stack string can be connected to a conventional AC / DC bidirectional converter to convert the DC current of the battery stack string to three-phase AC. Each AC / DC line can then be connected to an isolation transformer and then to a 10kV to 35kV AC bus or transformer bay. Under certain control logic, the liquid flow battery energy storage system can store or release electricity.

[0038] Example 3

[0039] As shown in Figure 3, the converter equipment uses an AC / DC converter and a phase-shifting transformer. Each battery stack is connected to an AC / DC converter, and all AC / DC converter outputs are then connected to a 35kV high-voltage bus or transformer interval to access the grid through the same phase-shifting transformer.

[0040] Example 4

[0041] As shown in FIG4 , the converter device adopts a bidirectional high-frequency isolated AC / DC converter. Each battery stack is connected to a 400V to 10kV AC bus or an AC bus output to the power grid through the bidirectional high-frequency isolated AC / DC converter.

[0042] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any modifications made based on the spirit of the main technical solution of the present invention shall be included in the scope of protection of the present invention.

Claims

1. 30MW or above liquid flow battery energy storage system, characterized by: Including more than 8 groups of fluid process systems, each group of fluid process systems includes: multiple battery stacks, positive and negative electrolyte storage tanks, positive and negative electrolyte pumps, and a pair of positive and negative current equalizers; The positive and negative electrolyte storage tanks are connected to a positive and negative current equalizer through positive and negative electrolyte delivery pumps, respectively. The positive and negative current equalizers supply liquid to the positive and negative electrodes of all battery stacks in the group at the same time. The positive and negative electrode liquid supply outlets of each battery stack are respectively collected and refluxed to the positive and negative electrolyte storage tanks through another positive and negative current equalizer. The number of battery stacks in each group of fluid process systems is the same, and the battery stacks of corresponding sequences between each group of fluid process systems are connected in series to form a string of battery stacks, and each string of battery stacks is externally connected to a set of inverter equipment.

2. The liquid flow battery energy storage system according to claim 1, characterized in that: In the fluid process system, if the positive electrode or negative electrode of the flow battery is in a solid state, the electrolyte storage tank, electrolyte delivery pump, pipeline and flow equalizer in the fluid process system are only on one side.

3. The liquid flow battery energy storage system according to claim 1, characterized in that: In the fluid process system, the number of the fluid process systems is represented by N, that is, N>8; the serial number of the fluid process system is represented by i, 1≤i≤N; the positive and negative electrolytes in each group of fluid process systems are independent of each other.

4. The liquid flow battery energy storage system according to claim 1, characterized in that: In the fluid process system, the battery stacks in each group of process systems are installed in a module at K units each to form an energy storage power module, K≥16, the serial number of the battery stack in the power module is represented by k, 1≤k≤K; the total number of power modules is represented by M, M≥16, the serial number of the module is represented by j, 1≤j≤M; by reasonably selecting large-scale fluid pumps for positive and negative electrolytes, stable charging and discharging operation of the M power modules with a total power of not less than 4MW can be supported.

5. The liquid flow battery energy storage system according to claim 4, characterized in that: The modules of the fluid process system are constructed in frames or containers, and are stacked in a building block-like manner during construction, thereby improving the construction efficiency of the energy storage power station.

6. The liquid flow battery energy storage system according to claim 4, characterized in that: The converter device adopts a bidirectional AC / DC converter and an isolation transformer. Each string of battery stacks is connected to an AC bus or a transformer interval through the bidirectional AC / DC converter and the isolation transformer connected in sequence to achieve the function of power storage or release.

7. The liquid flow battery energy storage system according to claim 4, characterized in that: The converter equipment adopts an AC / DC converter and a phase-shifting transformer. Each battery stack is connected to an AC / DC converter, and all AC / DC converters are then connected to a high-voltage bus or a transformer interval to a power grid through the same phase-shifting transformer.

8. The liquid flow battery energy storage system according to claim 4, characterized in that: The converter device adopts a bidirectional high-frequency isolated AC / DC converter, and each battery stack is connected to the AC bus or the AC bus output is connected to the power grid through the bidirectional high-frequency isolated AC / DC converter.

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