A black start device and method for a flow battery energy storage system

Abstract

The application discloses a black start device and method for a liquid flow battery energy storage system. The device relates to the technical field of energy storage. The device comprises a plurality of liquid flow battery modules and a control module; the output ends of the liquid flow battery modules are connected to a common bus; each liquid flow battery module comprises a main liquid flow battery module and a plurality of slave liquid flow battery modules; the control module is used for synchronously controlling each liquid flow battery module to enter a black start hot standby mode when the bus is powered off; after each liquid flow battery energy storage system enters the black start hot standby mode, the main liquid flow battery module is controlled to enter a network construction mode according to target electrical parameters of the bus; the electrical parameters comprise voltage parameters and frequency parameters; after the main liquid flow battery module enters the network construction mode, the slave liquid flow battery modules are controlled to enter a grid-connected expansion mode based on a health degree droop control strategy and the network construction mode of the main liquid flow battery module. The scheme improves the stability and responsiveness of the black start of the liquid flow battery energy storage system.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a black start device and method for a flow battery energy storage system. Background Technology

[0002] Currently, the installed capacity of new energy sources continues to climb, and the proportion of renewable energy in the power system is constantly increasing. The penetration level of random and fluctuating power sources such as wind power and photovoltaics has risen significantly. Accompanying this structural change, the demand for flexible, adjustable, highly secure, and long-term energy storage technologies in the power system is growing rapidly. Among various technical routes, vanadium redox flow battery energy storage systems have advantages such as low maintenance costs, strong environmental adaptability, low operating noise, intrinsic safety, and zero pollution emissions, which can meet the application requirements of integrated generation, grid, load, and storage, as well as flexible dispatch. Currently, vanadium redox flow batteries have been demonstrated in multiple engineering projects in China and are gradually moving towards large-scale construction, showing an accelerated development trend in the industry.

[0003] Flow batteries are energy storage batteries that use a flowing electrolyte as the energy carrier. The electrolyte is stored in external tanks and circulated through the stack via a pump to complete the electrochemical reaction for charging and discharging. The power is determined by the stack size, and the capacity by the electrolyte volume, thus power and capacity can be configured independently. Flow batteries also have the following key advantages: 1) High safety and no risk of thermal runaway, suitable for deployment in high-safety-requirement scenarios; 2) Long cycle life, supporting high-frequency start-stop and long-term continuous power supply, with low standby maintenance requirements; 3) Simple maintenance and easy modular expansion; capacity expansion only requires adding electrolyte and storage tanks, and the system can be flexibly scaled up as needed, exhibiting good economic efficiency and sustainability throughout its entire life cycle.

[0004] Under conditions of high-proportion renewable energy grid integration, the grid support and islanded operation capabilities of energy storage are particularly critical: when the external power supply is interrupted, the energy storage needs to establish and maintain the bus voltage and frequency as a voltage / frequency source; when the external power supply is unavailable, it also needs to have black-start capability, that is, to establish a self-bootstrapping grid, step-by-step load-bearing, and restore critical loads without relying on the external grid. Traditional flow battery energy storage systems have the following drawbacks as black-start power sources, which greatly limit their engineering applications: slow black-start response speed; voltage / frequency overshoot and oscillation are prone to occur when multiple modules are connected in parallel; in addition, the circulating current and power imbalance caused by the difference between the stack and the line in the parallel system result in poor black-start stability and responsiveness. Summary of the Invention

[0005] This invention provides a black-start device and method for a flow battery energy storage system, which improves the stability and responsiveness of the black start of the flow battery energy storage system.

[0006] To achieve the above objectives, in a first aspect, embodiments of the present invention provide a black start device for a flow battery energy storage system. The device includes: multiple flow battery modules and a control module; the output terminals of each flow battery module are connected by a common bus; each flow battery module includes a main flow battery module and multiple slave flow battery modules.

[0007] The control module is used to synchronously control each flow battery module to enter a black-start hot standby mode when the bus loses power; wherein, the black-start hot standby mode includes a standard black-start hot standby mode and a fast black-start hot standby mode; the standard black-start hot standby mode is a mode that uses the remaining energy of the fuel cell stack in each flow battery module to start automatically; the fast black-start hot standby mode is a mode that uses the internal or external power source of each flow battery module to start automatically.

[0008] After each of the aforementioned flow battery energy storage systems enters the black-start hot standby mode, the main flow battery module is controlled to enter the grid-connected mode according to the target electrical parameters of the bus; wherein, the electrical parameters include voltage parameters and frequency parameters;

[0009] After the main flow battery module enters the grid connection mode, each slave flow battery module is controlled to enter the grid-connected expansion mode based on the health droop control strategy and the grid connection mode of the main flow battery module; wherein, the health droop control strategy is to determine the power parameters of each slave flow battery module according to the health parameters of each slave flow battery module.

[0010] Optionally, each of the flow battery modules includes: a flow battery unit, a bus pre-charging unit, and a power conversion unit; the flow battery unit includes an electrolyte circulation assembly and a battery stack;

[0011] The electrolyte circulation assembly is coupled to the fuel cell stack; the fuel cell stack is also electrically connected to the input terminal of the power conversion unit via the bus pre-charging unit; the output terminals of each power conversion unit are connected to a common bus; the output terminal of each power conversion unit is also electrically connected to the power supply terminal of the electrolyte circulation assembly; and each power conversion unit is communicatively connected.

[0012] The control module is used to synchronously control each flow battery module to enter a black-start hot standby mode when the bus loses power. The black-start hot standby mode includes a standard black-start hot standby mode, specifically:

[0013] When the bus loses power, the bus pre-charging unit is kept closed and the remaining energy output by the stack is distributed to each component in the electrolyte circulation assembly through the bus pre-charging unit and the power conversion unit to synchronously control each flow battery module to enter the black start hot standby mode.

[0014] Optionally, each of the flow battery modules includes: a flow battery unit, a bus pre-charging unit, and a power conversion unit; the flow battery unit includes an electrolyte circulation assembly, a UPS assembly, a diode, and a battery stack;

[0015] The electrolyte circulation assembly is coupled to the fuel cell stack; the fuel cell stack is also electrically connected to the input terminal of the power conversion unit through the bus pre-charging unit; the output terminals of each power conversion unit are connected to a common bus; the UPS assembly is electrically connected to the power supply terminal of the electrolyte circulation assembly through the diode; and each power conversion unit is communicatively connected.

[0016] The control module is used to synchronously control each of the flow battery modules to enter the black start hot standby mode when the bus loses power. The black start hot standby mode includes a fast black start hot standby mode, specifically: when the bus loses power, the control module controls the bus pre-charging unit to remain closed and controls each of the UPS components to power the electrolyte circulation component through the diode to synchronously control each of the flow battery modules to enter the black start hot standby mode.

[0017] The control module is also used to control the UPS component to stop powering the electrolyte circulation component after each of the flow battery modules enters the grid-connected expansion mode, so that the energy continuously output by the stack can be used to power the electrolyte circulation component through the power conversion unit.

[0018] Optionally, the health sag control strategy specifically includes:

[0019] The SOC, SOH, and temperature parameters of each flow battery cell are acquired in real time.

[0020] Based on the SOC parameter, SOH parameter and temperature parameter of each flow battery cell, the health weight parameters of each flow battery cell are determined and normalized.

[0021] The frequency droop parameter is determined based on the normalized health weight parameters.

[0022] The active power parameters of each flow battery unit are determined based on the frequency droop parameters and the active-frequency model.

[0023] Optionally, the health sag control strategy further includes:

[0024] Each voltage droop parameter is determined based on the normalized health weight parameters.

[0025] The reactive power parameters of each flow battery unit are determined based on the voltage droop parameters and the reactive-voltage model.

[0026] Control each of the flow battery units to output the corresponding reactive power parameters and active power parameters.

[0027] Optionally, based on the target electrical parameters of the bus, each slave flow battery module is controlled to enter the grid-connected expansion mode according to the grid configuration mode and health droop control strategy of the main flow battery module, including:

[0028] Based on the target electrical parameters of the bus, each slave flow battery module is controlled to enter the grid-connected expansion mode according to the grid configuration mode of the main flow battery module, the health droop control strategy, and the virtual impedance control strategy.

[0029] Optionally, after each of the aforementioned flow battery energy storage systems enters black-start hot standby mode, the main flow battery module is controlled to enter grid-connected mode according to the target electrical parameters of the bus, including:

[0030] The main flow battery module is controlled to output preset voltage parameters and target frequency parameters according to the target voltage parameters and target frequency parameters of the bus to enter the grid construction mode.

[0031] Optionally, after the main flow battery module enters the grid-connected mode, based on the health droop control strategy and the grid-connected mode of the main flow battery module, each slave flow battery module is controlled to enter the grid-connected expansion mode, including:

[0032] Based on the health droop control strategy, the main flow battery module outputs preset voltage parameters and target frequency parameters to control each slave flow battery module to output preset voltage parameters and target frequency parameters to enter the grid-connected capacity expansion mode.

[0033] Optionally, the control module is further configured to determine the fault state of the flow battery unit based on the SOC parameter, SOH parameter and temperature parameter of each flow battery unit;

[0034] When it is determined that the flow battery unit is in a faulty state, the flow battery unit is controlled to be isolated.

[0035] Secondly, embodiments of the present invention also provide a black-start method for a flow battery energy storage system. This method is applied to the black-start device for the flow battery energy storage system described in the first aspect above. The black-start method for the flow battery energy storage system includes:

[0036] When the busbar loses power, each flow battery module is synchronously controlled to enter a black-start hot standby mode; wherein, the black-start hot standby mode includes a standard black-start hot standby mode and a fast black-start hot standby mode; the standard black-start hot standby mode is a mode that uses the remaining energy of the fuel cell stack in each flow battery module to start automatically; the fast black-start hot standby mode is a mode that uses the internal and external power sources of each flow battery module to start automatically.

[0037] After each of the aforementioned flow battery energy storage systems enters the black-start hot standby mode, the main flow battery module is controlled to enter the grid-connected mode according to the target electrical parameters of the bus; wherein, the electrical parameters include voltage parameters and frequency parameters;

[0038] After the main flow battery module enters the grid connection mode, each slave flow battery module is controlled to enter the grid-connected expansion mode based on the health droop control strategy and the grid connection mode of the main flow battery module; wherein, the health droop control strategy is to determine the power parameters of each slave flow battery module according to the health parameters of each slave flow battery module.

[0039] Optionally, each of the grid-type flow battery modules includes: a flow battery unit, a bus pre-charging unit, and a power conversion unit; the flow battery unit includes an electrolyte circulation assembly and a battery stack;

[0040] When the busbar loses power, each flow battery module is synchronously controlled to enter a black-start hot standby mode. This black-start hot standby mode includes a standard black-start hot standby mode, comprising:

[0041] When the busbar loses power, the busbar pre-charge unit is kept closed and the remaining energy output by the stack is distributed to each component in the electrolyte circulation assembly through the busbar pre-charge unit and the power conversion unit to synchronously control each flow battery module to enter the standard black start hot standby mode.

[0042] Optionally, each of the grid-type flow battery modules includes: a flow battery unit, a bus pre-charging unit, and a power conversion unit; the flow battery unit includes an electrolyte circulation assembly, a UPS assembly, and a battery stack;

[0043] When the busbar loses power, each flow battery module is synchronously controlled to enter a black-start hot standby mode, wherein the black-start hot standby mode includes a fast black-start hot standby mode, including:

[0044] When the bus loses power, the bus pre-charging unit is kept closed and each UPS component is powered on to the electrolyte circulation component to synchronously control each flow battery module to enter the fast black start hot standby mode.

[0045] In this embodiment of the invention, when the busbar loses power, the control module synchronously controls each flow battery module to enter the black-start hot standby mode. After each flow battery module enters the black-start hot standby mode, the main flow battery module is controlled to enter the grid-connected mode according to the target electrical parameters of the busbar. The electrical parameters include voltage and frequency parameters. After the main flow battery module enters the grid-connected mode, based on the health droop control strategy and the grid-connected mode of the main flow battery module, each slave flow battery module is controlled to enter the grid-connected expansion mode. In this way, by entering the black-start hot standby mode in advance, the start-up speed of the flow battery energy storage system is improved. Furthermore, the distributed grid-connected mode of one main and multiple slave flow battery modules avoids voltage or frequency overshoot and oscillation that would occur if each flow battery module were connected to the grid simultaneously. At the same time, the health droop control strategy suppresses the circulating current between each flow battery module to the target qualified value, realizing adaptive current sharing among multiple flow modules. This improves the stability of the black start of the flow battery energy storage system.

[0046] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of a black start device for a flow battery energy storage system provided in an embodiment of the present invention;

[0049] Figure 2 This is a schematic diagram of the specific structure of a black start device for a flow battery energy storage system provided in an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of the specific structure of another black start device for a flow battery energy storage system provided in an embodiment of the present invention;

[0051] Figure 4 This is a schematic flowchart of a black start method for a flow battery energy storage system provided in an embodiment of the present invention;

[0052] Figure 5 This is a schematic flowchart of another black start method for a flow battery energy storage system provided in an embodiment of the present invention;

[0053] Figure 6This is a schematic flowchart of another black start method for a flow battery energy storage system provided in an embodiment of the present invention. Detailed Implementation

[0054] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0055] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0056] Figure 1 This is a schematic diagram of the structure of a black start device for a flow battery energy storage system provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the starting device includes multiple flow battery modules 10 and a control module 20; the output terminals of each flow battery module 10 are connected by a common bus A; each flow battery module 10 includes a main flow battery module 11 and multiple slave flow battery modules 12.

[0057] The control module 20 is used to synchronously control each flow battery module 10 to enter the black start hot standby mode when the bus loses power; after each flow battery module 10 enters the black start hot standby mode, it controls the main flow battery module 11 to enter the grid-connected mode according to the target electrical parameters of the bus; wherein, the electrical parameters include voltage parameters and frequency parameters; after the main flow battery module 11 enters the grid-connected mode, it controls each slave flow battery module 12 to enter the grid-connected expansion mode based on the health droop control strategy and the grid-connected mode of the main flow battery module 11.

[0058] Generally, during normal operation, the busbar of a flow battery energy storage system is continuously energized by an external auxiliary AC power source (such as the plant power grid or mains power). The power source for each flow battery module in the flow battery energy storage system is the voltage on the busbar. In this embodiment, the busbar de-energization operation occurs when some situation suddenly occurs during the normal operation of the flow battery energy storage system, and the busbar disconnects from the external auxiliary AC power source (such as the plant power grid or mains power), and the flow battery energy storage system is in an unstarted state (completely dark state). In some embodiments, a rapid power failure detection mechanism (typical detection delay <100ms) can accurately identify that the busbar is in a de-energized state.

[0059] Black start hot standby mode is a working mode in which the flow battery energy storage system can automatically start up initially without relying on the external power grid, relying only on its own stored energy, so that the bus gradually restores the power-on state. Black start hot standby mode includes standard black start hot standby mode and fast black start hot standby mode. Standard black start hot standby mode is a mode of self-starting using the remaining energy of the stack in each flow battery module. Fast black start hot standby mode is a mode of self-starting using the internal and external power sources of each flow battery module.

[0060] When the main flow battery module 11 enters the grid construction mode, the control module 20 controls the main flow battery module 11 to first establish a mode for the bus reference voltage and bus reference frequency for the isolated grid according to the target electrical parameters of the bus (the electrical parameters include voltage parameters and frequency parameters); the bus reference voltage is the same as the target voltage parameter; the bus reference frequency is the target frequency parameter;

[0061] When each slave flow battery module 12 enters the grid-connected capacity expansion mode, it means that each slave flow battery module 12 follows the main flow battery module 11 to establish the same bus reference voltage and the same bus reference frequency for the isolated grid, thereby expanding the capacity of the bus.

[0062] Specifically, the grid-connected expansion mode can be entered based on a health droop control strategy. This strategy ensures that each slave flow battery module outputs the same voltage and frequency. More specifically, the health droop control strategy is a power allocation strategy based on the health parameters of each slave flow battery module, thereby suppressing circulating currents between slave flow battery modules and between slave flow battery modules and the master flow battery module, ensuring that all flow battery modules share the current. It should also be noted that in this embodiment, any one of the multiple flow battery modules is designated as the master flow battery module, and the rest are slave flow battery modules. The master / slave role of the flow battery modules is configured by the control module during the black start process.

[0063] In this embodiment of the invention, when the busbar loses power, the control module 20 synchronously controls each flow battery module to enter the black-start hot standby mode. After each flow battery module enters the black-start hot standby mode, the main flow battery module is controlled to enter the grid-connected mode according to the target electrical parameters of the busbar. After the main flow battery module enters the grid-connected mode, based on the health droop control strategy and the grid-connected mode of the main flow battery module, each slave flow battery module is controlled to enter the grid-connected expansion mode. In this way, by entering the black-start hot standby mode in advance, the start-up speed of the flow battery energy storage system is improved. Furthermore, by using a distributed grid-connected mode with one main and multiple slave flow battery modules, voltage or frequency overshoot and oscillation that would occur if each flow battery module were connected to the grid simultaneously are avoided. At the same time, the health droop control strategy ensures that the circulating current suppression between each flow battery module is zero, achieving adaptive current sharing among multiple flow modules. This improves the stability of the black start of the flow battery energy storage system.

[0064] Optionally, based on the above embodiments, the specific configuration of the flow battery module further details how each flow battery module 10 enters the black-start hot standby mode; in some embodiments, Figure 2 This is a schematic diagram of the specific structure of a black start device for a flow battery energy storage system provided in an embodiment of the present invention, as shown below. Figure 2 As shown, each flow battery module 10 includes: a flow battery unit 01, a bus pre-charging unit 02, and a power conversion unit 03; the flow battery unit 01 includes an electrolyte circulation assembly 011 and a battery stack 012; the electrolyte circulation assembly 011 is coupled to the battery stack 012; the battery stack 012 is also electrically connected to the input terminal of the power conversion unit 03 through the bus pre-charging unit 02; the output terminals of each power conversion unit 03 are connected to a common bus; the output terminal of each power conversion unit 03 is also electrically connected to the power supply terminal of the electrolyte circulation assembly 011; each power conversion unit 03 is communicatively connected.

[0065] The control module 20 is used to synchronously control each flow battery module 10 to enter the black start hot standby mode when the bus loses power. The black start hot standby mode includes the standard black start hot standby mode, which is as follows: when the bus loses power, the control module 20 keeps the bus precharge unit 02 closed and makes the remaining energy output by the stack 012 power each component in the electrolyte circulation assembly 011 through the bus precharge unit 02 and the power conversion unit 03 to synchronously control each flow battery module 10 to enter the black start hot standby mode.

[0066] Among them, the power conversion unit 03 is a PCS converter; it can convert DC power into AC power; in order to enable the flow battery energy storage system to start automatically without relying on the external power grid and only relying on its own stored energy, in this embodiment, when the bus loses power, the bus pre-charging unit 02 can be controlled to remain closed, so that the remaining energy output by the stack 012 is output to the DC side of the PCS converter, so that the DC side voltage of the PCS converter is gradually stabilized and established.

[0067] Simultaneously, the remaining energy output by the stack 012 can be distributed to various components within the electrolyte circulation assembly 011 through the bus pre-charging unit 02 and the power conversion unit 03, thus providing initial start-up power for the electrolyte circulation assembly 011. Subsequently, after the electrolyte circulation assembly 011 has been stably started, the stack 012 can stably release energy. With the stable establishment of the DC side voltage of the PCS converter and the distributed power supply to various components within the electrolyte circulation assembly 011, each flow battery module 10 can be synchronously controlled to enter the black start hot standby mode, thereby improving the start-up speed of the flow battery energy storage system.

[0068] It should be noted that the components within the electrolyte circulation assembly 011 may include an electrolyte control pump, an electrolyte control valve, and an electrolyte controller, etc.; the power-on of each component within the electrolyte circulation assembly 011 is performed with each component at its lowest power, which ensures the pre-start of each component within the electrolyte circulation assembly 011; and the distributed power-on of each component within the electrolyte circulation assembly 011 avoids excessive impact on the DC side voltage of the PCS converter.

[0069] Optionally, in other embodiments, Figure 3 This is a schematic diagram of the specific structure of another black-start device for a flow battery energy storage system provided in an embodiment of the present invention, as shown below. Figure 3 As shown, each flow battery module 10 includes: a flow battery unit 01, a bus pre-charging unit 02, and a power conversion unit 03; the flow battery unit 01 includes an electrolyte circulation assembly 011, a battery stack 012, a diode D, and a UPS assembly 013.

[0070] The electrolyte circulation assembly 011 is coupled to the fuel cell stack 012; the fuel cell stack 012 is also electrically connected to the input terminal of the power conversion unit 03 through the bus pre-charging unit 02; the output terminals of each power conversion unit 03 are connected to the common bus; the UPS assembly 013 is electrically connected to the power supply terminal of the electrolyte circulation assembly 011 through the diode D; each power conversion unit 03 is communicatively connected.

[0071] The control module 20 is used to synchronously control each flow battery module to enter the black-start hot standby mode when the bus loses power. The black-start hot standby mode includes a fast black-start hot standby mode. Specifically, when the bus loses power, the control module 2 keeps the bus pre-charging unit 02 closed and controls each UPS component 013 to power the electrolyte circulation component 011 through diode D to synchronously control each flow battery module to enter the black-start hot standby mode. In some embodiments, in order to enable the flow battery energy storage system to start automatically without relying on the external power grid and only relying on its own stored energy, this embodiment can control the bus pre-charging unit 02 to keep closed when the bus loses power. This allows the remaining energy output by the stack 012 to be output to the DC side of the PCS converter, so that the DC side voltage of the PCS converter gradually stabilizes and is established.

[0072] Simultaneously, each UPS component 013 can be controlled to supply power to the electrolyte circulation component 011 via diode D. This allows each UPS component 013 to seamlessly take over power supply to the electrolyte circulation component 011 directly through diode D, ensuring continuous operation of the electrolyte circulation component 011. This also allows for synchronous control of each flow battery module 10 to enter black-start hot standby mode, thereby improving the startup speed of the flow battery energy storage system. It can be understood that in this embodiment, during islanded operation, the seamless takeover of power supply to the electrolyte circulation component 011 via each UPS component 013 significantly improves the startup speed compared to using the remaining energy of the battery stack to provide startup power to the electrolyte circulation component 011. This method is a fast black-start hot standby mode; the above embodiment is a standard black-start hot standby mode. It should be noted that diode D is configured between the UPS component 013 and the electrolyte circulation component 011. Diode D is an anti-backflow diode / ideal diode to prevent backflow.

[0073] Additionally, it should be noted that after the rapid black start hot standby mode, the main flow battery module is controlled to enter the grid-connected mode according to the target electrical parameters of the bus. After the main flow battery module enters the grid-connected mode, the slave flow battery modules are controlled to enter the grid-connected expansion mode based on the health droop control strategy and the grid-connected mode of the main flow battery module. That is, after the bus voltage is stabilized, the control module 20 is also used to control the UPS component to stop powering the electrolyte circulation component 011 so that the energy continuously output by the stack is powered to the electrolyte circulation component 011 through the power conversion unit 03, thereby improving the service life of the UPS component 013.

[0074] Optionally, the health sag control strategy in the above embodiments will be further described; refer to Figures 1 to 3The health droop control strategy is as follows: Real-time acquisition of the SOC, SOH, and temperature parameters of each flow battery unit 01; determination and normalization of the health weight parameters of each flow battery unit 01 based on the SOC, SOH, and temperature parameters; determination of the frequency droop parameters based on the normalized health weight parameters; and determination of the active power parameters of each flow battery unit based on the frequency droop parameters and the active power-frequency model.

[0075] Among them, due to the SOC parameter It can directly reflect the concentration of active materials within the flow battery cell, thus reflecting the energy storage capacity of the flow battery cell; SOH parameter It can directly reflect the changes in the stack time, capacity retention rate and polarization characteristics within the flow battery cell; that is, it reflects the maximum discharge capacity of the flow battery cell; temperature parameters can affect the operating efficiency of the flow battery cell; therefore, this embodiment comprehensively considers the influence of SOC parameters, SOH parameters and temperature parameters on the flow battery cell, thereby establishing health weight parameters;

[0076] Based on the SOC parameters of each flow battery cell 01 SOH parameters and temperature parameters Determine the health weight parameters for each flow battery cell. Specifically:

[0077]

[0078] in: For each parameter, there is a normalization function; , , These are the weighting coefficients for each normalization function; For reference temperature;

[0079] Each health score weight parameter is normalized, specifically as follows:

[0080]

[0081] Where n is the number of flow battery cells;

[0082] The frequency droop parameters are determined based on the normalized health score weights, specifically:

[0083]

[0084] in, The droop parameter of the fundamental frequency; The droop parameters for each frequency;

[0085] The active power parameters of each flow battery cell are determined based on the frequency droop parameters and the active-frequency model, specifically:

[0086]

[0087] in, The target frequency output by the main flow battery unit; These are the active power parameters of each flow battery unit; The base frequency parameter.

[0088] It is understandable that, as can be seen from the above formula, the health score weighting parameter... When the frequency droop parameter is large, the flow battery cell is more sensitive to changes in active power distribution and can handle more active power; health weighting parameter When the frequency droop is small, the frequency droop parameter is large, the power distribution is reduced, and automatic derating operation is initiated; this allows each flow battery unit to output the target frequency to the bus. Maintain consistency.

[0089] Optional, continue to refer to Figures 1 to 3 The health droop control strategy is further defined as follows: determining each voltage droop parameter based on the normalized health weight parameters; determining the reactive power parameters of each flow battery unit based on each voltage droop parameter and the reactive-voltage model; and controlling the corresponding output of each reactive power parameter and each active power parameter of each flow battery unit.

[0090] Specifically, each voltage droop parameter is determined based on the normalized weighted parameters of each health status; as follows:

[0091]

[0092] in, For each voltage droop parameter; Based on the base voltage droop parameter;

[0093] The reactive power parameters of each flow battery cell are determined based on the voltage droop parameters and the reactive-voltage model, specifically:

[0094]

[0095] in, The target voltage output by the main flow battery unit; These are the reactive power parameters for each flow battery unit; Based on the base voltage parameter.

[0096] It is understandable that, as can be seen from the above formula, the health score weighting parameter... When the voltage droop is large, the voltage droop parameter is small, the module is more sensitive to changes in reactive power distribution, and it handles more reactive power; health weight parameter When the voltage is low, the voltage droop parameter is large, the distributed reactive power is reduced, and automatic derating operation is initiated; this allows each flow battery unit to output the target voltage to the bus. Maintain consistency.

[0097] Optional, continue to refer to Figures 1 to 3 In some embodiments, based on a health droop control strategy, each slave flow battery module is controlled to enter the grid-connected expansion mode according to the grid configuration mode of the main flow battery module. This includes: based on a health droop control strategy and a virtual impedance control strategy, each slave flow battery module is controlled to enter the grid-connected expansion mode according to the grid configuration mode of the main flow battery module.

[0098] The virtual impedance control strategy adjusts the impedance of each flow battery cell according to its state, thereby suppressing the circulating current between slave flow battery modules and between slave flow battery modules and the main flow battery module, thus enabling the flow battery modules to share the current. By using the health droop control strategy and the virtual impedance control strategy, the accuracy of the current sharing control can be further improved, thereby further improving the stability of the black start device.

[0099] Optional, continue to refer to Figures 1 to 3 The control module 20 is also used to determine the fault state of the flow battery unit based on the SOC parameter, SOH parameter and temperature parameter of each flow battery unit; when it is determined that the flow battery unit is in a fault state, it controls the flow battery unit to be isolated.

[0100] Before synchronously controlling each flow battery module 10 to enter the black start hot standby mode, the control module 20 can also determine the fault state of each flow battery unit based on its SOC, SOH, and temperature parameters. When a flow battery unit is determined to be in a fault state, the control module 20 controls the flow battery unit to be isolated, thus controlling the main flow battery module 11 to enter the grid-connected mode based on the target electrical parameters of the bus. After the main flow battery module 11 enters the grid-connected mode, the control module 20, based on the health droop control strategy and the grid-connected mode of the main flow battery module 11, controls each slave flow battery module 12 to enter the grid-connected expansion mode, thereby further improving the black start stability of the black start device.

[0101] Based on the same inventive concept, this invention also provides a black-start method for a flow battery energy storage system, which is applied to the black-start device for the flow battery energy storage system described in the above embodiments. Figure 4 This is a schematic flowchart of a black start method for a flow battery energy storage system provided in an embodiment of the present invention; as shown below. Figure 4As shown, the black-start method of the flow battery energy storage system includes the following steps:

[0102] S110. When the busbar loses power, the flow battery modules are synchronously controlled to enter the black start hot standby mode.

[0103] The black start hot standby mode includes a standard black start hot standby mode and a fast black start hot standby mode. The standard black start hot standby mode is a mode that uses the remaining energy of the fuel cell stack in each flow battery module to start automatically. The fast black start hot standby mode is a mode that uses the internal and external power sources of each flow battery module to start automatically.

[0104] S120. After each flow battery energy storage system enters the black start hot standby mode, the main flow battery module is controlled to enter the grid-connected mode according to the target electrical parameters of the bus; wherein, the electrical parameters include voltage parameters and frequency parameters.

[0105] S130. After the main flow battery module enters the grid-connected mode, based on the health droop control strategy and the grid-connected mode of the main flow battery module, each secondary flow battery module is controlled to enter the grid-connected expansion mode.

[0106] The health droop control strategy determines the power parameters of each slave flow battery module based on its health parameters. After each slave flow battery module enters grid-connected expansion mode, i.e., after the bus voltage output stabilizes, the control module can also adopt a segmented closing strategy based on the importance and impact of the load (e.g., connecting critical loads first, then general loads; or, for example, with a 5-10 second interval between segments and a smooth power ramp increase), thus avoiding excessive fluctuations in bus voltage / frequency. Specifically, for high-impact loads (such as transformers and rectifiers), the overload of the power conversion unit can be adjusted to dynamically allocate redundant capacity and ensure stable bus voltage and frequency.

[0107] In this embodiment of the invention, the startup speed of the flow battery energy storage system is improved by entering the black-start hot standby mode in advance. Furthermore, the distributed grid configuration of the one master and multiple slave flow battery modules avoids voltage or frequency overshoot and oscillation that would occur if all flow battery modules were connected to the grid simultaneously. At the same time, the health droop control strategy ensures that the circulating current suppression between the flow battery modules is zero, achieving adaptive current sharing among multiple flow battery modules. This improves the stability of the black start of the flow battery energy storage system.

[0108] Optionally, based on the above method embodiments, step S110 in the black start method of the flow battery energy storage system is further refined. In some embodiments, Figure 5 This is a schematic flowchart of another black-start method for a flow battery energy storage system provided in an embodiment of the present invention; as shown below. Figure 5 As shown, the black-start method of the flow battery energy storage system includes the following steps:

[0109] S210. When the busbar loses power, the control busbar pre-charge unit is kept closed and the remaining energy output by the stack is distributed to each component in the electrolyte circulation assembly through the busbar pre-charge unit and the power conversion unit to synchronously control each flow battery module to enter the standard black start hot standby mode.

[0110] S220. After each flow battery energy storage system enters the standard black start hot standby mode, the main flow battery module is controlled to enter the grid-connected mode according to the target electrical parameters of the bus; among which, the electrical parameters include voltage parameters and frequency parameters.

[0111] S230. After the main flow battery module enters the grid connection mode, based on the health droop control strategy and the grid connection mode of the main flow battery module, each secondary flow battery module is controlled to enter the grid connection expansion mode.

[0112] In this embodiment of the invention, by establishing a stable DC-side voltage in the power conversion unit and distributing the power on each component within the electrolyte circulation assembly, the flow battery modules can be synchronously controlled to enter the black-start hot standby mode, thereby improving the start-up speed of the flow battery energy storage system. In addition, by using a master-slave flow battery module distributed grid configuration, voltage or frequency overshoot and oscillation that would occur if all flow battery modules were connected to the grid simultaneously are avoided. At the same time, based on the health droop control strategy, the circulating current suppression between flow battery modules is reduced to zero, achieving adaptive current sharing among multiple flow battery modules, thus improving the black-start stability of the flow battery energy storage system.

[0113] Optionally, based on the above method embodiments, step S110 in the black start method of the flow battery energy storage system is further refined. In other embodiments, Figure 6 This is a schematic flowchart of another black-start method for a flow battery energy storage system provided in an embodiment of the present invention; as shown below. Figure 6 As shown, the black-start method of the flow battery energy storage system includes the following steps:

[0114] S310. When the busbar loses power, the busbar pre-charging unit is kept closed and each UPS component is powered on to the electrolyte circulation component to synchronously control each flow battery module to enter the fast black start hot standby mode.

[0115] S320. After each flow battery energy storage system enters the fast black start hot standby mode, the main flow battery module is controlled to enter the grid-connected mode according to the target electrical parameters of the bus; among which, the electrical parameters include voltage parameters and frequency parameters.

[0116] S330: After the main flow battery module enters the grid connection mode, based on the health droop control strategy and the grid connection mode of the main flow battery module, each slave flow battery module is controlled to enter the grid connection expansion mode.

[0117] In this embodiment of the invention, by establishing a stable DC-side voltage in the power conversion unit and powering the electrolyte circulation components through each UPS component, the flow battery modules can be synchronously controlled to enter the black-start hot standby mode, thereby improving the start-up speed of the flow battery energy storage system. In addition, by using a master-slave flow battery module distributed network mode, voltage or frequency overshoot and oscillation that would occur if all flow battery modules were connected to the grid simultaneously are avoided. At the same time, based on the health droop control strategy, the circulating current suppression between flow battery modules is reduced to 0, realizing adaptive current sharing among multiple flow battery modules, thus improving the black-start stability of the flow battery energy storage system.

[0118] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A flow battery energy storage system black start apparatus, characterized by, include: Multiple flow battery modules and control modules; The output terminals of all the flow battery modules are connected by a common bus; each flow battery module includes a main flow battery module and multiple slave flow battery modules. The control module is used to synchronously control each flow battery module to enter a black-start hot standby mode when the bus loses power; wherein, the black-start hot standby mode includes a standard black-start hot standby mode and a fast black-start hot standby mode; the standard black-start hot standby mode is a mode that uses the remaining energy of the fuel cell stack in each flow battery module to start automatically; the fast black-start hot standby mode is a mode that uses the internal or external power source of each flow battery module to start automatically. After each of the flow battery modules enters the black-start hot standby mode, the main flow battery module is controlled to enter the grid-connected mode according to the target electrical parameters of the bus; wherein, the electrical parameters include voltage parameters and frequency parameters; After the main flow battery module enters the grid connection mode, based on the health droop control strategy and the grid connection mode of the main flow battery module, each slave flow battery module is controlled to enter the grid-connected expansion mode. Specifically, the health droop control strategy determines the power parameters of each slave flow battery module based on its health weight parameters. The SOC, SOH, and temperature parameters of each flow battery module are acquired in real time. Based on the SOC, SOH, and temperature parameters of each flow battery module, the health weight parameters of each flow battery module are determined and normalized. Specifically, the health weight parameters of each flow battery module are determined based on its SOC, SOH, and temperature parameters, as follows: wherein: is the SOC parameter is the SOH parameter is the temperature parameter is a corresponding normalization function; is a normalization function weight coefficient corresponding to the SOC parameter; is a normalization function weight coefficient corresponding to the SOH parameter; is a normalization function weight coefficient corresponding to the temperature parameter; is a reference temperature; is the health weight parameter; The normalization process for each of the aforementioned health weight parameters is as follows: Where n is the number of the flow battery modules; The frequency droop parameter and the voltage droop parameter are determined based on the normalized health weight parameters. The active power parameters of each flow battery module are determined based on the frequency droop parameters; and the reactive power parameters of each flow battery unit are determined based on the voltage droop parameters and the reactive-voltage model. Control each of the flow battery modules to output the corresponding reactive power parameters and active power parameters.

2. The flow battery energy storage system black start device of claim 1, wherein, Each of the aforementioned flow battery modules includes: a flow battery unit, a bus pre-charging unit, and a power conversion unit; the flow battery unit includes an electrolyte circulation assembly and a battery stack; The electrolyte circulation assembly is coupled to the fuel cell stack; the fuel cell stack is also electrically connected to the input terminal of the power conversion unit via the bus pre-charging unit; the output terminals of each power conversion unit are connected to a common bus; the output terminal of each power conversion unit is also electrically connected to the power supply terminal of the electrolyte circulation assembly; and each power conversion unit is communicatively connected. The control module is configured to synchronously control each of the flow battery modules to enter a black-start hot standby mode when the bus is in a power-off operation, wherein the black-start hot standby mode includes a standard black-start hot standby mode, and specifically includes: When the bus is in a power-off operation, the bus pre-charging unit is controlled to remain in a closed state, and the remaining energy output by the stack is distributed to each component in the electrolyte circulation assembly through the bus pre-charging unit and the electrical energy conversion unit to synchronously control each of the flow battery modules to enter a black-start hot standby mode.

3. The flow battery energy storage system black start device of claim 1, wherein, Each of the flow battery modules includes a flow battery unit, a bus pre-charging unit, and an electrical energy conversion unit; the flow battery unit includes an electrolyte circulation assembly, a diode, a UPS assembly, and a stack; The electrolyte circulation assembly is coupled to the stack; the stack is electrically connected to the input ends of the bus pre-charging unit and the electrical energy conversion unit; the output ends of each of the electrical energy conversion units are connected in common to the bus; the UPS assembly is electrically connected to the power supply end of the electrolyte circulation assembly through the diode; and each of the electrical energy conversion units is communicatively connected; The control module is configured to synchronously control each of the flow battery modules to enter a black-start hot standby mode when the bus is in a power-off operation, wherein the black-start hot standby mode includes a fast black-start hot standby mode, and specifically includes: When the bus is in a power-off operation, the bus pre-charging unit is controlled to remain in a closed state, and each of the UPS assemblies is controlled to be powered on to the electrolyte circulation assembly through the diode to synchronously control each of the flow battery modules to enter a black-start hot standby mode. The control module is further configured to, after each of the slave flow battery modules enters a grid-connected expansion mode, control the UPS assemblies to stop being powered on to the electrolyte circulation assembly so that the energy continuously output by the stack is powered on to the electrolyte circulation assembly through the electrical energy conversion unit.

4. The flow battery energy storage system black start device of claim 2, wherein, The control module is further configured to, based on the target electrical parameter of the bus, control each of the slave flow battery modules to enter a grid-connected expansion mode according to the network configuration mode and the health degree droop control strategy of the master flow battery module, including: The control module is further configured to, based on the target electrical parameter of the bus, control each of the slave flow battery modules to enter a grid-connected expansion mode according to the network configuration mode, the health degree droop control strategy, and the virtual impedance control strategy of the master flow battery module.

5. The flow battery energy storage system black start device of claim 1, wherein, The control module is further configured to determine a fault state of each of the flow battery units according to an SOC parameter, an SOH parameter, and a temperature parameter of each of the flow battery units. When it is determined that the flow battery unit is in a fault state, the flow battery unit is controlled to be isolated.

6. A method of black start of a flow battery energy storage system, characterized in that, The flow battery energy storage system black-start method is applied to the flow battery energy storage system black-start device of any one of claims 1-5. Synchronously control each of the flow battery modules to enter a black start hot standby mode when the busbar is operated without power supply; wherein the black start hot standby mode comprises a standard black start hot standby mode and a fast black start hot standby mode; the standard black start hot standby mode is a mode of self-starting by using residual energy of the stack in each of the flow battery modules; the fast black start hot standby mode is a mode of self-starting by using external power supply in each of the flow battery modules; After each of the flow battery energy storage systems enters the black start hot standby mode, control the main flow battery module to enter a network construction mode according to a target electrical parameter of the busbar; wherein the electrical parameter comprises a voltage parameter and a frequency parameter; After the main flow battery module enters the network construction mode, control each of the slave flow battery modules to enter a network expansion mode based on a health degree droop control strategy and the network construction mode of the main flow battery module; wherein the health degree droop control strategy is to determine a power parameter of each of the slave flow battery modules according to a health degree parameter of each of the slave flow battery modules.

7. The flow battery energy storage system black start method of claim 6, wherein, Each of the flow battery modules comprises a flow battery cell, a busbar pre-charging unit and an electric energy conversion unit; the flow battery cell comprises an electrolyte circulating assembly and a stack; Synchronously control each of the flow battery modules to enter a black start hot standby mode when the busbar is operated without power supply, wherein the black start hot standby mode comprises a standard black start hot standby mode, which comprises: When the busbar is operated without power supply, control the busbar pre-charging unit to remain in a closed state and make residual energy output by the stack be distributed to each component in the electrolyte circulating assembly through the busbar pre-charging unit and the electric energy conversion unit to synchronously control each of the flow battery modules to enter the standard black start hot standby mode.

8. The flow battery energy storage system black start method of claim 6, wherein, Each of the flow battery modules comprises a flow battery cell, a busbar pre-charging unit and an electric energy conversion unit; the flow battery cell comprises an electrolyte circulating assembly, a UPS assembly and a stack; Synchronously control each of the flow battery modules to enter a black start hot standby mode when the busbar is operated without power supply, wherein the black start hot standby mode comprises a fast black start hot standby mode, which comprises: When the busbar is operated without power supply, control the busbar pre-charging unit to remain in a closed state and control each of the UPS assemblies to power on the electrolyte circulating assembly to synchronously control each of the flow battery modules to enter the fast black start hot standby mode.

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