Redox flow battery system and method of operation thereof

Abstract

The present invention relates to a redox flow battery system and a method of operation thereof, wherein the method of operation improves the reliability and availability of the redox flow battery system.

Description

Technology Field

[0001] The present invention relates to a redox flow battery system (RFBS) and a method of operation thereof, wherein the method of operation improves the reliability and availability of the redox flow battery system. Background Technology

[0002] DE 10 2020 108 068 A1 and DE 10 2020 108 053 ​​A1:

[0003] The above documents disclose a redox flow battery system (RFBS) comprising at least two battery modules (1), a bidirectional converter (7), and a control device (8), wherein the battery modules (1) are connected in series and connected to the converter (7), and each battery module (1) comprises a cell assembly (2) comprising a plurality of redox flow cells and a tank device (3) for storing electrolyte and supplying electrolyte to the cell assembly (2), the battery system comprises a DC-DC voltage converter (17) for each battery module (1), the first terminal of each DC-DC voltage converter (17) is connected to each battery module (1), and the second terminal of each DC-DC voltage converter (17) is connected to a shared DC bus, the battery system comprises an additional converter (16) connected to the DC bus, and the control device (8) is connected to the additional converter (16) and the DC-DC voltage converter (17) so that the control device (8) can control the additional converter (16) and the DC-DC voltage converter (17) (particularly FIG. 6 and FIG. 8 of the above documents). (See 7).

[0004] Disadvantages and limitations of the cited prior art:

[0005] In a redox flow battery system composed of a series circuit of multiple battery modules, the availability of the RFBS needs to be defined by the function of all battery modules. For this reason, switches are used in many of these systems (see (9) and (10) of the cited prior art), and their purpose is to bypass individual battery modules. One of the main causes of failure within individual battery modules is the lack of lifespan and reliability of the wiring of electronic components (e.g., converter (16) and DC-DC voltage converter (17) of the cited literature). Additionally, the aforementioned bypass switches (9) and (10) are subjected to high loads due to short-circuit currents, which consequently increases the failure rate. Furthermore, the configuration according to the prior art has the disadvantage that if the converter (16) fails, damage occurs to the shared DC bus, causing failure of multiple DC-DC voltage converters (17), and thus can lead to failure of the entire RFBS despite the configuration including bypass switches (9) and (10). In RFBSs disclosed in the prior art, when spatial dimensions and voltage levels are combined in a widely distributed shared DC bus, additional electrical losses occur in this type of RFBS, which reduces efficiency, or the cable cross-sectional area may need to be increased to avoid these losses, but this may result in increased costs for RFBSs configured in this way.

[0006] US 2023126285 A and DE 10 2020 108 053 ​​A1:

[0007] The cited literature discloses the following method for reducing imbalance occurring during charging and discharging of a redox flow battery system, comprising at least one of the following steps:

[0008] When charging the battery system, the DC-DC voltage converter (17) is operated by the control device (8) to reduce the difference between the first and second battery modules with respect to the control variable, so that the DC-DC voltage converter (17) delivers sufficient power to the DC bus so that one of the two battery modules charges slower than the other battery module.

[0009] When discharging the battery system, the DC-DC voltage converter (17) is operated by the control device (8) to reduce the difference between the first and second battery modules (1) with respect to the control variable, so that the DC-DC voltage converter (17) delivers sufficient power from the DC bus so that one of the two battery modules discharges more slowly than the other battery module.

[0010] At least where the converter (16) has a separate main power supply, the disclosed arrangement also enables the main power supply to assist the converter (7) during the charging and discharging of the battery module. This is particularly advantageous when the converter (7) reaches its capacity limit. Since this assistance by the DC-DC voltage converter (17) may be selectively provided for each battery module, it can, of course, also be used for balancing. This mechanism results in accelerated charging and discharging of the "slow" module.

[0011] Disadvantages and limitations of the cited prior art:

[0012] In particular, the same disadvantages and limitations described above arise with respect to the spatial dispersion, fault sensitivity, and loss of the shared DC bus. Additionally, in this embodiment, if a problem occurs in the converter (16) or the DC-DC voltage converter (17), the individual battery modules can be disabled only by the bypass switch (9) or (10). Another disadvantage of this configuration is the fact that only three favorable states can be achieved for the balancing logic circuit when the DC / DC converter (17) is designed to be bidirectional.

[0013] WO 2022033750 A1:

[0014] This document discloses a method of operation of a vanadium redox flow battery system, the method comprising the following steps: S1: connecting at least one battery module (1) to a converter (6, 7); S2: supplying current to the at least one battery module (1) connected to the converter (6, 7) in step S1, such that at least a portion of the electrolyte belonging to the battery module (1) reaches a charge state greater than or equal to a predefined threshold; S3: operating first and second switches (9, 10) so that all battery modules (1) form a series circuit connected to a bidirectional converter (6); S4: supplying current to the series circuit of step S3 while transferring the electrolyte from all battery modules (1) (see particularly FIG. 3 and FIG. 4).

[0015] Disadvantages and limitations of the cited prior art:

[0016] Since switches (11) and (12) can only be used to connect or disconnect the converter to one or more battery modules (1), the converter (7) cannot be used completely flexibly. However, it is impossible to charge and discharge different battery modules (1) simultaneously using the converter (7).

[0017] DE 10 2017 222 979 A1:

[0018] This document discloses a balancing unit that balances the voltages of a plurality of electric storage cells; and an electric transmission and reception unit that, without interrupting or switching the electrical connection between (a) a plurality of electric storage cells and (b-1) a load using power from the plurality of electric storage cells or (b-2) a charging device charging the plurality of electric storage cells, (i) transmits power from the plurality of electric storage cells to an external assembly different from the load and charging device, or (ii) receives power supplied to the plurality of electric storage cells from the external assembly.

[0019] The electric transceiver unit discloses an isolated bidirectional DC-DC voltage converter.

[0020] Disadvantages and limitations of the cited prior art:

[0021] The cited literature discloses embodiments that may result in reduced availability of RFBS due to dependency / coupling of the balancing correction unit (220) and / or protection unit (230) and / or DC-DC voltage converter (330), similar to the literature mentioned above.

[0022] Here, too, the function of all battery modules defines the availability of batteries connected in series. Here, too, conventional technology does not provide suitable options for improving availability and facilitating critical functions for establishing and maintaining operational capability. The problem to be solved

[0023] The problem that the present invention aims to solve is to provide a redox flow battery system having high reliability and availability and a method of operating the same.

[0024] The problem that the present invention aims to solve is, in particular, to improve upon the problems and limitations of the prior art and to enhance the availability of the RFBS. According to the present invention, this is achieved by a distributed improved balancing unit capable of maintaining and restoring operational capability. Furthermore, the assembly according to the present invention facilitates the deservice of individual battery modules supporting the service of the RFBS. Additionally, the assembly according to the present invention can be used to restore the performance of the battery mode.

[0025] According to the present invention, the above problem is solved by the configuration and method according to the independent claim. Further advantageous embodiments of the present invention can be found in the dependent claims. Brief explanation of the drawing

[0026] The present invention is described below based on the drawings, and details shown in the drawings are as follows: Figure 1 illustrates a battery module. FIG. 2 illustrates a redox flow battery system according to the present invention. FIG. 3 illustrates a balancing unit according to the present invention. FIG. 4 illustrates a switching device of the first embodiment. FIG. 5 illustrates a switching device of another embodiment. FIG. 6 illustrates a switching device of another embodiment. FIG. 7 illustrates a switching device of another embodiment. Specific details for implementing the invention

[0027] FIG. 1 illustrates a battery module labeled 1. The battery module includes a cell assembly labeled 2, a tank device for storing electrolyte liquid labeled 3, an optional measuring device for determining open circuit voltage labeled 4, and an optional measuring device for determining terminal voltage labeled 5. The battery module generally includes an auxiliary system represented by a square labeled 6. Additionally, the battery module (1) includes a pump for supplying electrolyte liquid from the tank device (3) to the cell assembly (2).

[0028] FIG. 2 is a schematic diagram of a redox flow battery system according to the present invention. The battery system comprises at least two battery modules (one of which is denoted as 1), a bidirectional power converter (bidirectional power conversion system (PCS)) denoted as 7, and a control device denoted as 8. To distinguish it from other converters of the battery system (see below), the bidirectional power converter is referred to as the "main converter" below. Battery modules (1) are connected in series and connected to the main converter (7). FIG. 2 illustrates four battery modules, and the dashed lines of the series circuit are intended to indicate any number of additional modules. The main converter (7) serves to connect the battery system to the main power supply or a higher-level electrical system. The battery system may optionally include a bypass switch for each battery module (1), which is denoted as 9 in FIG. 2. The bypass switch (9) is placed in parallel with the associated battery module (1) and can be used particularly for balancing (see e.g., DE 10 2022 109 193 B3). However, this may also be used to permanently short-circuit the defective battery module (1) and effectively isolate the module from the series circuit of the battery system, thereby ensuring the availability of the entire battery system even in the event of failure of one (or some) of the battery modules (1).

[0029] The redox flow battery system further includes a balancing unit denoted by 60. The balancing unit (60) may be assigned to a single battery module (1). The balancing unit (60) may be a distributed balancing unit. FIG. 2 illustrates three separate distributed balancing units (60) assigned to each illustrated battery module (1). In the redox flow battery system according to the present invention, the separate balancing unit (60) is preferably assigned to each battery module (1). However, it may also be considered that the separate balancing unit (60) is not assigned to each battery module (1). Generally, the separate balancing unit (60) may be assigned to at least two battery modules (1) in each case. Generally, the separate balancing unit (60) may be assigned to a) all battery modules (1) or a) each of all battery modules (1) excluding one battery module (1). That is, the redox flow battery system may include n battery modules (1) and a) n or b) n-1 separate balancing units (60). That is, the redox flow battery system may include n battery modules (1) and at least n-1 separate balancing units (60). The redox flow battery system may include, for example, at least two battery modules (1) and at least one separate balancing unit (60), wherein the at least one separate balancing unit (60) is assigned to one of the at least two battery modules (1).

[0030] In this case, the balancing unit (60) is powered by the power supply unit (30), and in a preferred variation of the invention, the power supply unit (30) is configured as an AC voltage source. In another embodiment, the power supply unit (30) may be configured as an uninterruptible power supply, which further improves availability by temporarily compensating for defects and transient malfunctions of the AC voltage source. An advantage of the uninterruptible power supply, which can be used as power for the auxiliary system (6) of the battery module (1), the auxiliary system of the main converter (7), and the control unit (8), is that it improves the RFBS for main power independent operation. This is particularly advantageous when the redox flow battery system is used for grid stabilization, standalone micro-grid operation, or public main network restoration (black start).

[0031] One option for facilitating an uninterruptible power supply is the use of a backup system, such as a diesel generator, battery, or capacitor. Such systems can provide the necessary power in the event of low voltage or a power outage to reactivate the power supply unit (30) and the battery power system. This ensures that the power supply remains stable even in the event of an unexpected event. Depending on the configuration, such backup systems have different voltage waveforms, either AC voltage or DC voltage. In a favorable configuration, the converter (20) is designed with the same voltage waveform provided by the uninterruptible power supply from the power supply unit (30). For AC voltage, the converter (20) is designed as AC-DC, and for DC voltage, the converter (20) is designed as DC-DC.

[0032] Another advantage of configuring the power supply unit (30) as an uninterruptible power supply is that when the volumetric flow from the tank unit (3) is deactivated, the voltage level of the cell assembly (2) is raised to a level where the main converter (7) can be activated and actively participate in grid stabilization with relatively low power consumption.

[0033] The balancing unit (60) further includes a protection and isolation unit indicated by 40 and a converter indicated by 20. The balancing unit (60) may further include an availability enhancement unit indicated by 50. In this case, the protection and isolation unit should be considered optional. The power supply unit (30) can be isolated from the potential of the battery module (1) by the protection and isolation unit (40).

[0034] The control unit (8) may be configured to control the balancing unit (60), the pump of the battery module (1), the main converter (7), and the potentially provided bypass switch (9). Alternatively, the control unit (8) may be configured to control the balancing unit (60) but not the main converter (7). The control of the main converter (7) may be handled by an upper control unit (not shown). The two control units may communicate with each other.

[0035] The availability enhancement unit (50) serves to improve the availability of the battery module (1), particularly in cases where a negative module voltage may occur intentionally or unintentionally. This will be explained in more detail with reference to FIGS. 3 through 7.

[0036] FIG. 3 illustrates a balancing unit (60) according to the present invention. To enable the protection and isolation unit (40) to isolate the power supply unit (30) from the potential of the battery module (1), the protection and isolation unit (40) includes a protection unit indicated by 41, which can isolate the power supply unit (30) from the converter (20), for example, via a suitable switch. Additionally, the protection unit (41) may include an upstream protection circuit to reduce the load on the power supply unit (30) before a temporarily high switch-on current may be generated by the balancing unit (60). The protection and isolation unit (40) may optionally include an isolation unit indicated by 42. In this case, the isolation unit (42) within the protection and isolation unit (40) is used to isolate the potentials of the battery module (1) and the power supply unit (30) from each other.

[0037] In a preferred embodiment of the present invention, the protection unit (41) is implemented by a passive circuit that dampens the high switch-on current when the entire pole relay and / or balancing unit (60) is activated and deactivated. Thus, it may be a switch-on current limiter. By connecting an AC relay upstream of the protection unit (41), losses in no-load operation can be prevented when the balancing unit is not in use.

[0038] In a preferred embodiment of the present invention, the insulation unit (42) is implemented by an insulation transformer, for example, in the form of a toroidal transformer. Other embodiments are also possible here and may be advantageous for, for example, other voltages or network configurations.

[0039] In another embodiment, if the converter (20) already has galvanic isolation, the protection and isolation unit (40) may be completely omitted.

[0040] The converter (20) facilitates a method for reducing imbalances occurring during the charging and discharging of a redox flow battery system. In this case, the converter may be designed to be unidirectional or bidirectional. The converter (20) may be used to accelerate, decelerate, or not affect the voltage rise of the battery module (1). In a preferred embodiment, individual components or all components of the protection and insulation unit (40) may be integrated into the converter (20) on the input or output side. The converter (20) may perform these effects through the main converter (7) in addition to external charging or discharging of the battery system (and thus the battery module (1)).

[0041] If the converter (20) is configured as a unidirectional or bidirectional converter, the operating capability can be restored during the initial commissioning or after discharge for service purposes. In this case, the voltage rise of the battery module (1) is provided by the respective balancing unit (60) and power supply unit (30).

[0042] If the converter (20) is configured as a bidirectional converter, the affected battery module (1) can be brought to a state that supports de-service without the need to provide more complex protection measures for energization operations, for example, during service or for service operations. In this case, the voltage reduction of the affected battery module (1) is achieved by the balancing unit (60) and the power supply unit (30).

[0043] The configuration of the converter (20) as a bidirectional converter also enables the recovery (restoration) of the performance of the battery module (1) by the balancing unit (60) and the power supply unit (30) by using a voltage drop used by the balancing unit (60) alone or in combination with an external discharge through the bidirectional main converter (7) to cause a reversal of the voltage polarity in the battery module (1).

[0044] As previously mentioned, the availability enhancement unit (50) serves the purpose of increasing the availability of the battery module (1). To this end, the availability enhancement unit (50) may include an integrated switching device indicated by 52. ​​The battery module (1) affected by the integrated switching device (52) may be isolated from the influence of the balancing unit (60). To this end, the integrated switching device (52) includes at least one switch, thereby enabling the blocking of one of the two DC connections to the battery module (1).

[0045] FIG. 4 illustrates a first embodiment of an integrated switching device (52). For this purpose, the illustrated integrated switching device (52) includes a switch labeled 53. The switch (53) can be used to block one of the two DC connections to the battery module (1).

[0046] FIG. 5 illustrates another embodiment of an integrated switching device (52). For this purpose, the illustrated integrated switching device (52) includes two switches labeled 54 and 55. Switches (54) and (55) can be used to disconnect both DC connections to the battery module (1).

[0047] FIGS. 6 and 7 illustrate two additional and particularly advantageous embodiments of the integrated switching device (52). In addition to separating the balancing unit (60) from the affected battery module (1), both embodiments enable changing the polarity of the balancing unit (60) with respect to the affected battery module (1).

[0048] To this end, the embodiment illustrated in FIG. 6 includes two combined switches labeled 54a and 55b, each having three switching states. In the switching state illustrated in FIG. 6, a first polarity is present (the line simply passes through). In the second switching state, the two switches (54a and 55b) are connected to a central contact (neutral position), so that the balancing unit (60) is disconnected from the affected battery module (1). In the third switching state, the switches (54a and 55b) are connected to a lower contact, so that the polarity is reversed compared to the switching state illustrated in FIG. 6.

[0049] The embodiment illustrated in FIG. 7 has the same function. For this purpose, the illustrated integrated switching device (52) includes four switches labeled 56, 57, 58, and 59. In each case, two switches are coupled together. When both pairs of switches are open, the balancing unit (60) is disconnected from the affected battery module (1). Polarity can be affected by alternately opening and closing the two pairs of switches.

[0050] These particularly advantageous embodiments, having the polarity switching of the balancing unit (60) as an option, make it possible to use a unidirectional converter in the converter (20). Consequently, the converter (20) can be used to keep the battery module (1) in a state that allows for deservice, for example, during service. In this case, the voltage reduction of the affected battery module (1) is provided by the balancing unit (60) and the power supply unit (30). Additionally, the converter (20) can be used to restore the performance of the affected battery module (1) through the balancing unit (60) and the power supply unit (30), where the voltage reduction can be used only by the balancing unit (60) or combined with an external voltage reduction by the main converter (7) to reverse the voltage of the affected battery module (1).

[0051] Additionally, the unique function of the balancing unit (60) can be used to accelerate, decelerate, or not affect the voltage rise of the affected battery module (1). In this case, these three states can be implemented using a unidirectional converter (20) and a switching device (52) having a polarity inversion function. In this case, the control unit (8) can adjust the polarity of the balancing unit (60) to implement the desired function using the unidirectional converter (20) based on the desired state (accelerating or decelerating the voltage rise of the affected battery module (1)) and the current operating state of the RFBS (charging or discharging). Without a switching device (52) including a polarity inversion, a bidirectional converter (20) is always required for this, which entails lower availability, a higher probability of failure, and higher costs.

[0052] In the event of a malfunction or defect in the switch, the above-mentioned embodiments of the switching device (52) may cause a malfunction of the balancing unit (60) and / or the affected battery module (1). To prevent the above-mentioned problems, the availability enhancement unit (50) may be extended by a protection device indicated as 51 in FIG. 3, which prevents polarity reversal or forced current reversal at the output of the converter (20) through active or passive electronic components.

[0053] A redox flow battery system includes a computer system for enabling the method steps briefly described above and detailed below to be performed in an automated manner. The term “computer system” refers to any device suitable for performing the described method steps in an automated manner, including, in particular, programmable logic controllers, ICs, or microcontrollers specifically developed for this purpose, as well as application-specific integrated circuits (ASICs). In this case, the control unit (8) itself may include a suitable computer system. Alternatively, the computer system may constitute a separate device or part of a separate device. This application also relates to a computer program containing instructions for the battery system to perform the method steps described above. Furthermore, this application relates to a computer-readable medium storing such a computer program.

[0054] Description of a method that can be performed using a battery system according to the present invention:

[0055] Improved Availability:

[0056] If a defect occurs in at least one of the balancing units (60), a negative effect may occur on the associated battery module (1). To prevent this and improve the availability of the entire battery system, the affected balancing unit is electrically disconnected from the associated battery module (1) when a defect occurs.

[0057] Separating the battery module (1) or cell assembly (2) from the unidirectional or bidirectional converter (20) can be done through the switching device (52) by performing one of the following steps:

[0058] - Step of opening the switch (53) in a single switch configuration as shown in FIG. 4.

[0059] - A step of opening at least one of the switches (54 or 55) in a dual switch configuration as illustrated in FIG. 5.

[0060] - A step of moving at least one of the switches (54a or 55b) to a neutral position in a configuration including two switches (having a neutral position) as illustrated in FIG. 6.

[0061] - A step of opening all switches (56, 57, 58 and 59) in a configuration including four switches as illustrated in FIG. 7.

[0062] Alternatively or additionally, the availability enhancement unit (50) can protect the balancing unit, in particular the associated converter (20), from negative polarity and consequent damage caused by the negative voltage of the battery module (e.g., by applying the method described in DE 10 2022 113 939 B3). To prevent negative voltage in the converter (20), the availability enhancement unit may include a switching device (52) or reverse polarity protection (51) capable of separating the converter (20) from the module (1).

[0063] Initialization or restoration of operating capability after initial commissioning or discharge:

[0064] Initialization of the battery module (1) using a unidirectional or bidirectional converter (20) can be performed through a switching device (52) by performing one of the following steps:

[0065] - As illustrated in FIG. 4, the step of supplying charging power to the battery module (1) (specifically the cell assembly (2)) by closing the switch (53) in a single switch configuration, operating the pump to perform the initial charging of the battery module (1), and not operating the pump to perform the initial charging of the cell assembly (2).

[0066] - A step of supplying charging power to the battery module (1) (specifically the cell assembly (2)) while the pump is operated to perform initial charging of the battery module (1) and while the pump is not operated to perform initial charging of the cell assembly (2), as illustrated in FIG. 5.

[0067] - As illustrated in FIG. 6, the step of switching the two switches (54a and 55b) in a dual switch configuration to a first position, and supplying charging power to the battery module (1) (specifically the cell assembly (2)) while the pump is running to perform initial charging of the battery module (1), and while the pump is not running to perform initial charging of the cell assembly (2).

[0068] - A step of supplying charging power to the battery module (1) (specifically the cell assembly (2)) while the pump is running to perform initial charging of the battery module (1) and while the pump is not running to perform initial charging of the cell assembly (2), as illustrated in FIG. 7, in a configuration including four switches.

[0069] For example, during the initial commissioning or re-commissioning (while the pump is stopped), the battery module can be charged to a minimum voltage required to allow the main converter (7) to start operation and continue to complete initialization through the associated converter (20). To this end, the converter (20) is intended to have a minimum DC voltage of 0 V, whereas the main converter (7) may have a minimum voltage much higher than 0 V.

[0070] Provides a state that supports initialization disable or service disabling (e.g., in service):

[0071] De-initialization of the affected battery module (1) or cell assembly (2) using a bidirectional converter (20) can be performed through a switching device (52) by performing one of the following steps:

[0072] - As illustrated in FIG. 4, the step of supplying discharge power to the battery module (1) (specifically the cell assembly (2)) while the switch (53) is closed in a single switch configuration, the pump is operated to perform the initialization release of the battery module (1), and the pump is not operated to perform the initialization release of the cell assembly (2).

[0073] - A step of supplying discharge power to the battery module (1) (specifically the cell assembly (2)) while the pump is operated to perform the initialization release of the battery module (1) and while the pump is not operated to perform the initialization release of the cell assembly (2), as illustrated in FIG. 5.

[0074] - A step of switching the two switches (54a and 55b) to a first position in a configuration including two switches as illustrated in FIG. 6, and supplying discharge power to the battery module (1) (specifically the cell assembly (2)) while the pump is operated to perform the initialization release of the battery module (1), and while the pump is not operated to perform the initialization release of the cell assembly (2).

[0075] - A step of supplying discharge power to the battery module (1) (specifically the cell assembly (2)) while the pump is operated to perform the initialization release of the battery module (1) and while the pump is not operated to perform the initialization release of the cell assembly (2), as illustrated in FIG. 7.

[0076] The de-initialization of an affected battery module (1) or cell assembly (2) using a unidirectional or bidirectional converter (20) (supporting only charging function) can be accomplished through a switching device (52) by performing one of the following steps:

[0077] - As illustrated in FIG. 6, in a dual switch configuration, the two switches (54a and 55b) are switched to a third position, and the pump is operated to perform the initialization release of the battery module (1), and the pump is not operated to perform the initialization release of the cell assembly (2), and the charging power is supplied to the battery module (1) (specifically the cell assembly (2)), in which case a reverse polarity protection circuit (51) is required.

[0078] - As illustrated in FIG. 7, in a configuration including four switches, two switches (56 and 59) are closed, and a pump is operated to perform the initialization release of the battery module (1), and a charging voltage is supplied to the battery module (1) (specifically the cell assembly (2)) while the pump is not operated to perform the initialization release of the cell assembly (2), in which case a reverse polarity protection circuit (51) is required.

[0079] For example, for discharge for service purposes, the battery modules can be discharged below a voltage threshold that supports de-service or service using their respective associated converters (20). For service technicians, re-energizing is possible only with special protective equipment and training. Working below a specific voltage threshold is much less complex. Since the main converter (7) does not function below a certain minimum voltage, this threshold cannot be achieved by simple discharge by the main converter (7). A value close to 0 volts can be obtained through the converter (20).

[0080] Reduction of imbalance occurring during charging and discharging in redox flow battery systems:

[0081] A redox flow battery system battery and / or method can be used to balance battery modules by charging or discharging individual battery modules through a converter (20) to balance the difference in charge state between battery modules.

[0082] State of Charge (SOC) balancing of a group of modules connected in a string configuration can be achieved by using a bidirectional converter (20) and a switching device (52) together to perform one of the following steps:

[0083] - As shown in FIG. 4, the step of closing the switch (53) in a single switch configuration and supplying charging or discharging power to the battery module (1).

[0084] - A step of closing the two switches (54 and 55) in a configuration including two switches as shown in FIG. 5, and supplying charging or discharging power to the battery module (1).

[0085] - As shown in FIG. 6, the step of switching the two switches (54a and 55b) in a dual switch configuration to a first position and supplying charging or discharging power to the battery module (1).

[0086] - A step of closing two switches (57 and 58) in a configuration including four switches as shown in FIG. 7, and supplying charging or discharging power to the battery module (1).

[0087] Additionally, state of charge (SOC) balancing of a group of modules connected in a string configuration can be achieved by using a unidirectional or bidirectional converter (20) (supporting only the charging function) and a switching device (52) together to perform one of the following steps:

[0088] - As shown in FIG. 6, a step of switching both switches (54a and 55b) in a dual switch configuration to a third position and supplying charging power to the battery module (1). In this case, a reverse polarity protection circuit (51) is required.

[0089] - A step of closing both switches (56 and 59) in a configuration including four switches as shown in FIG. 7 and supplying a charging voltage to the battery module (1). In this case, a reverse polarity protection circuit (51) is required.

[0090] Restoration of performance of battery module (1):

[0091] Reversing the polarity of the cell assembly (2) can be advantageous for cell aging recovery by charging the cell assembly (2) with a negative voltage. This can be achieved by using a unidirectional or bidirectional converter (20) (supporting only the charging function) together with a switching device (52) and a battery module (1) to perform one of the following steps:

[0092] - As shown in FIG. 6, in a dual switch configuration, both switches (54a and 55b) are switched to position 3, the rotational speed of the pump is adjusted to reduce or set the flow rate through the cell assembly (2) to zero, and charging power is supplied to the battery module (1). In this case, a reverse polarity protection circuit (51) is required.

[0093] - As shown in FIG. 7, in a configuration including four switches, the two switches (56 and 59) are closed, the rotational speed of the pump is adjusted to reduce or set the flow rate through the cell assembly (2) to zero, and charging power is supplied to the battery module (1). In this case, a reverse polarity protection circuit (51) is required.

[0094] Degradation of the battery module can be at least partially restored by operating it with reverse polarity for a certain period of time. This type of polarity reversal (i.e., charging in the opposite direction after discharging the module) can be implemented through a balancing unit. To do this, the battery string can be cut off and the pump can be deactivated.

[0095] To this end, for example, the affected battery modules can each be discharged to ~0 V (below the minimum diode voltage of the converter). The switching device of FIG. 6 or FIG. 7 can then be switched. Afterward, the modules can each be charged (in the reverse polarity direction) for a certain period of time. Then, they can be discharged again to ~0 V, the switching device is switched again, and the pump is turned on again.

[0096] Separate the affected battery module (1) from the balancing unit (60):

[0097] Separating the affected battery module (1) or associated cell assembly (2) from the unidirectional or bidirectional converter (20) is accomplished through a switching device (52) by performing one of the following steps:

[0098] - Step of opening the switch (53) in a single switch configuration as shown in FIG. 4.

[0099] - A step of opening at least one of the switches (54 or 55) in a dual switch configuration as illustrated in FIG. 5.

[0100] - A step of moving at least one of the switches (54a or 55b) to a neutral position in a configuration including two switches (having a neutral position) as illustrated in FIG. 6.

[0101] - A step of opening all switches (56, 57, 58 and 59) in a configuration including four switches as illustrated in FIG. 7.

[0102] Examples

[0103] In one embodiment, the redox flow battery system may include at least two battery modules (1), a main converter (7), a power supply unit (30), and a control unit (8), wherein the battery modules (1) are connected in series and connected to the main converter (7), and each battery module (1) includes a cell assembly (2) comprising a plurality of redox flow cells, a tank device (3) for storing an electrolyte liquid, and a pump for supplying the electrolyte liquid to the cell assembly (2), and the battery system includes a balancing unit (60) for each of the at least two battery modules (1), wherein the terminal of each balancing unit (60) is connected to the associated battery module (1), and the second terminal of each balancing unit (60) is connected to the power supply unit (30), and each balancing unit (60) includes a converter (20) and a availability enhancement unit (50), wherein the availability enhancement unit (50) is connected to the converter (20) on the first side and to the associated battery module (1) on the second side. The control device (8) is configured to control the balancing unit (60), the pump of the battery module (1), and the main converter (7).

[0104] In one embodiment, the converter (20) may be designed to be bidirectional or unidirectional and may be connected to the power supply unit (30) with a DC voltage or an AC voltage, and the availability enhancement unit (50) may each include a switching device (52), and each switching device may include at least one switch (53, 54, 55, 54a, 55b, 56, 57, 58, 59).

[0105] In one embodiment, the power supply unit (30) may be configured as an uninterruptible power supply, each battery module (1) includes an auxiliary system (6), and the main converter (7) includes an auxiliary system, and the auxiliary system (6) of the battery module (1), the auxiliary system of the main converter (7), and the control device (8) are powered by the power supply unit (30).

[0106] In one embodiment, the power supply unit (30) can provide AC voltage, and the converter (20) is configured as an AC-DC converter.

[0107] In one embodiment, the power supply unit (30) can provide a DC voltage, and the converter (20) is configured as a DC-DC converter.

[0108] In one embodiment, each balancing unit (60) may include a protection and isolation unit (40) configured to galvanically isolate the potential of the power supply unit (30) from the potential of the associated battery module (1).

[0109] In one embodiment, each switching device (52) may include at least two switches (54, 55, 54a, 55b, 56, 57, 58, 59), the converter (20) is optionally designed to be unidirectional and connected to a power supply unit (30) with a DC voltage or an AC voltage, each switching device (52) is optionally designed to switch the polarity of a balancing unit (60) for an associated battery module (1), and each availability enhancement unit (50) includes a protection device (51) configured to protect the associated converter (20) from an unacceptable polarity state.

[0110] In one embodiment, a battery system for each battery module (1) may include a bypass switch (9), the first switch (9) is arranged in parallel with the battery module (1) associated in each case, and a control device (8) is connected to each bypass switch (9) to determine each switch position of the bypass switch (9) to connect the battery module (1) to the series circuit or disconnect it from the series circuit.

[0111] In one embodiment, a method for improving the availability of a battery module in a redox flow battery system of the type described above may be provided, and in the method, if at least one fault occurs in at least one of the balancing units (60), the control device (8) operates at least one switch (53, 54, 55, 54a, 55b, 56, 57, 58, 59) of a switching device (52) associated with the affected battery module (1) to prevent further impact on the affected battery module (1) by disconnecting the connection between the associated balancing unit (60) and the affected battery module (1).

[0112] In one embodiment, a method for reducing imbalance occurring during charging and discharging in a redox flow battery system of the type described above may be provided, wherein the control device (8) may control a balancing unit (60) and optionally a main converter (7), and the method comprises at least one of the following steps:

[0113] - When charging the battery system, the balancing unit (60) is operated by the control device (8) to reduce the difference between the first and second battery modules (1) with respect to the control variable, so that at least one converter (20) delivers sufficient power to the battery module (1) so that one of the two battery modules (1) charges more slowly than the other battery module (1);

[0114] - When discharging the battery system, the balancing unit (60) is operated by the control device (8) to reduce the difference between the first and second battery modules (1) with respect to the control variable, so that at least one converter (20) delivers sufficient power from the battery module (1) so that one of the two battery modules (1) discharges more slowly than the other battery module (1).

[0115] In one embodiment, a method for reducing imbalance occurring during charging and discharging in a redox flow battery system of the type described above may be provided, wherein the control device (8) may control a balancing unit (60) and a bidirectional main converter (7), and the method comprises at least one of the following steps:

[0116] - When charging the battery system, the balancing unit (60) is operated by the control device (8) to reduce the difference between the first and second battery modules (1) with respect to the control variable, so that at least one converter (20) delivers sufficient power to the battery module (1) so that one of the two battery modules (1) is charged faster than the other battery module (1);

[0117] - When discharging the battery system, the balancing unit (60) is operated by the control device (8) to reduce the difference between the first and second battery modules (1) with respect to the control variable, so that at least one converter (20) delivers sufficient power to at least one interface with the battery module (1) so that one of the two battery modules (1) is discharged faster than the other battery module (1).

[0118] In one embodiment, the control device (8) controls the balancing unit (60) and the bidirectional main converter (7) so that the control device (8) operates at least one availability enhancement unit (50) through the switching device (52), thereby allowing power to be maintained within the battery module (1) without being transferred to the power supply unit (30) by changing the polarity of the balancing unit (60).

[0119] In one embodiment, the control device (8) can control the transfer of electrolyte within the battery module (1) from the balancing unit (60), the main converter (7), and the tank device (3) to the cell assembly (2), and the cell assembly (2) can be discharged by the balancing unit (60) in each battery module (1) independently or in combination with the main converter (7), and there may or may not be a transfer of electrolyte to the cell assembly (2), and by discharging the cell assembly (2), the voltage level in the affected cell assembly in at least one battery module (1) becomes below a specific threshold value, thereby supporting de-service or service operation without more complex protection measures for active operation.

[0120] In an embodiment, the control device (8) can control the transfer of electrolyte within the battery module (1) from the balancing unit (60), the main converter (7), and the tank device (3) to the cell assembly (2), and when the voltage potential of the affected cell assembly (2) is too low to activate the main converter (7), the affected cell assembly (2) in each battery module (1) is independently charged by the associated balancing unit (60), and there may or may not be a transfer of electrolyte to the cell assembly (2), and is charged until at least one voltage level appears at which the main converter (7) can be activated.

[0121] In one embodiment, a method for restoring the performance of a battery module (1) of a redox flow battery system of the type described above may be provided, and a control device (8) may control a main converter (7), a battery module (1), and / or a balancing unit (60) to cause the voltage in at least one battery module (1) to be reversed during the discharge process of the redox flow battery system.

[0122] In one embodiment, the control device (8) controls the balancing unit (60) and the main converter (7) to operate at least one availability enhancement unit (50) through the switching device (52) associated with the control device (8), so that the unidirectional converter (20) of each balancing unit (60) can be used to increase the voltage and / or decrease the voltage of the associated battery module (1) by changing the polarity of the balancing unit (60). Explanation of the symbols

[0123] 1: Battery module 2: Cell Assembly 3: Tank device 4: Measuring device for determining open circuit voltage 5: Measuring device for determining terminal voltage 6: Battery Module Auxiliary System 7: Bidirectional Power Converter / Main Converter 8: Control unit 9: Bypass switch 20: AC-DC Converter 30: Power supply unit 40: Protection and insulation unit 41: Protection Unit 42: Insulation unit 50: Availability Enhancement Unit 51: Reverse polarity protection circuit 52: Switching device 53: Switch 54: Switch 54a: Switch 55: Switch 55b: Switch 56: Switch 57: Switch 58: Switch 59: Switch 60: Switch

Claims

Claim 1 A redox flow battery system comprising at least two battery modules (1), a main converter (7), a power supply unit (30), and a control unit (8), wherein the battery modules (1) are connected in series and connected to the main converter (7), and each battery module (1) comprises a cell assembly (2) comprising a plurality of redox flow cells, a tank device (3) for storing an electrolyte liquid, and a pump for supplying the electrolyte liquid to the cell assembly (2), and wherein the battery system comprises a separate balancing unit (60) for each of the at least two battery modules (1), wherein one terminal of each balancing unit (60) is connected to the associated battery module (1), and a second terminal of each balancing unit (60) is connected to the power supply unit (30), and each balancing unit (60) comprises a converter (20). Claim 2 A redox flow battery system according to claim 1, wherein the converter (20) is designed to be bidirectional or unidirectional and is connected to the power supply unit (30) by a DC voltage or an AC voltage. Claim 3 A redox flow battery system according to claim 1 or 2, wherein each balancing unit (60) comprises a availability enhancement unit (50) connected to a converter (20) on the first side and connected to a battery module (1) on the second side. Claim 4 In paragraph 3, the availability enhancement unit (50) each comprises a switching device (52) to isolate the associated battery module (1) from the influence of the balancing unit (60), and each switching device comprises at least one, preferably at least two, switches (53, 54, 55, 54a, 55b, 56, 57, 58, 59); and / or each of the availability enhancement unit (50) comprises a protection device (51) configured to protect the associated converter (20) from an unacceptable polarity state, in a redox flow battery system. Claim 5 In any one of the preceding paragraphs, the power supply unit (30) is configured as an uninterruptible power supply, each battery module (1) preferably includes an auxiliary system (6), the main converter (7) preferably includes an auxiliary system, and the auxiliary system (6) of the battery module (1), the auxiliary system of the main converter (7), and the control device (8) are a redox flow battery system that receives electric power from the power supply unit (30). Claim 6 In any one of the preceding paragraphs, the power supply unit (30) provides AC voltage, and the converter (20) is a redox flow battery system composed of an AC-DC converter. Claim 7 In any one of the preceding paragraphs, the power supply unit (30) provides a DC voltage, and the converter (20) is a redox flow battery system composed of a DC-DC converter. Claim 8 A redox flow battery system in which, in any one of the preceding paragraphs, each balancing unit (60) comprises a protection and isolation unit (40) configured to galvanically isolate the potential of the power supply unit (30) from the potential of the associated battery module (1). Claim 9 In any one of the preceding paragraphs, where applicable to at least paragraph 4, each switching device (52) comprises at least two switches (54, 55, 54a, 55b, 56, 57, 58, 59), and the converter (20) is preferably designed to be unidirectional and is a redox flow battery system connected to the power supply unit (30) by a DC voltage or an AC voltage. Claim 10 In claim 8, each switching device (52) is designed to switch the polarity of the balancing unit (60) in relation to the associated battery module (1) in a redox flow battery system. Claim 11 A redox flow battery system in which, in any one of the preceding claims, the battery system includes a bypass switch (9) for each battery module (1), wherein the bypass switch (9) is arranged in parallel with the associated battery module (1) in each case, and the control device (8) is connected to each of the bypass switches (9) to determine each switch position of the bypass switch (9) to connect or disconnect the battery module (1) to a series circuit. Claim 12 In any one of the preceding paragraphs, the control device (8) is configured to control the balancing unit (60), the pump of the battery module (1), and the main converter (7) in a redox flow battery system. Claim 13 In any one of the preceding claims, the redox flow battery system comprises n battery modules (1) and at least n-1 separate balancing units (60). Claim 14 A method for improving the availability of a battery module (1) in a redox flow battery system subject to at least one of the preceding claims, wherein when at least one defect occurs in at least one of the balancing units (60), the control device (8) prevents further damage to the affected battery module (1) by operating at least one switch (53, 54, 55, 54a, 55b, 56, 57, 58, 59) of a switching device (52) associated with the affected battery module (1) to block the connection between the associated balancing unit (60) and the affected battery module (1). Claim 15 A method for reducing an imbalance occurring during charging and discharging in a redox flow battery system according to any one of claims 1 to 13, wherein the control device (8) can control the balancing unit (60) and the main converter (7), and the method comprises at least one of the following steps: - when charging the battery system, the balancing unit (60) is operated by the control device (8) to reduce the difference between the first and second battery modules (1) with respect to a control variable, so that at least one converter (20) delivers sufficient power to the battery module (1) so that one of the two battery modules (1) charges slower than the other battery module (1); - when discharging the battery system, the balancing unit (60) is operated by the control device (8) to reduce the difference between the first and second battery modules (1) with respect to a control variable, so that at least one converter (20) delivers sufficient power from the battery module (1) so that one of the two battery modules discharges slower than the other battery module. Claim 16 A method for reducing an imbalance occurring during charging and discharging in a redox flow battery system according to any one of claims 1 to 13, wherein the control device (8) can control the balancing unit (60) and the bidirectional main converter (7), and the method comprises at least one of the following steps: - when charging the battery system, the balancing unit (60) is operated by the control device (8) to reduce the difference between the first and second battery modules (1) with respect to a control variable, so that at least one converter (20) delivers sufficient power to the battery module (1) so that one of the two battery modules (1) is charged faster than the other battery module (1); - when discharging the battery system, the balancing unit (60) is operated by the control device (8) to reduce the difference between the first and second battery modules (1) with respect to a control variable, so that at least one converter (20) delivers sufficient power to at least one interface with the battery module (1) so that one of the two battery modules (1) is discharged faster than the other battery module (1). The stage of transmitting power. Claim 17 A method according to claim 15 or 16, wherein the control device (8) controls the balancing unit (60) and the bidirectional main converter (7) so that the control device (8) operates at least one availability enhancement unit (50) through the switching device (52), thereby preventing power from being transferred to the power supply unit (30) and maintaining it within the battery module (1) by changing the polarity of the balancing unit (60). Claim 18 In any one of claims 14 to 17, the control device (8) can control the transfer of electrolyte within the battery module (1) from the balancing unit (60), the main converter (7), and the tank device (3) to the cell assembly (2), and the cell assembly (2) can be discharged by the balancing unit (60) in each battery module (1) independently or in combination with the main converter (7), and there may or may not be a transfer of electrolyte to the cell assembly (2), and by discharging the cell assembly (2), the voltage level in the cell assembly affected in at least one battery module (1) becomes below a threshold value, thereby enabling service release or service support. Claim 19 A method characterized in that, in any one of claims 14 to 18, the control device (8) can control the transfer of electrolyte within the battery module (1) from the balancing unit (60), the main converter (7), and the tank device (3) to the cell assembly (2), and the affected cell assembly (2) in each battery module (1) is independently charged by the associated balancing unit (60) while the voltage potential of the affected cell assembly (2) is too low to activate the main converter (7), and there may or may not be a transfer of electrolyte to the cell assembly (2), and the charging continues until at least one voltage level appears at which the main converter (7) can be activated. Claim 20 A method for restoring the performance of a battery module (1) of a redox flow battery system according to any one of claims 1 to 13, wherein the control device (8) controls the main converter (7), the battery module (1), and / or the balancing unit (60) to cause the voltage in at least one battery module (1) to be reversed during the discharge process of the redox flow battery system.

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