Energy storage system and method for operating a protection circuit in an energy storage system

Abstract

An energy storage system (1) and a method for operating a protection circuit (3, 3n, 4) in an energy storage system (1). The energy storage system (1) comprises a plurality of energy storage units (2, 2n) and comprises one or more protection circuits (3, 3n, 4) which are capable of bypassing one or more of the energy storage units (2, 2n), wherein at least one of the protection circuits (3, 3n, 4) comprises a first switch (S1, Sn1, Sa) and a first resistor (R1, Rn1, Ra) which are electrically connected in series, and comprises a second switch (S2, Sn2, Sb) which is electrically connected in series with the first switch (S1, Sn1, Sa) and is electrically connected in parallel with the first resistor (R1, Rn1, Ra).

Description

Technical Field

[0001] This disclosure relates to an energy storage system and a method for operating the energy storage system, the method being used to bypass one or more energy storage units in the energy storage system. Such an energy storage system includes multiple energy storage units. Each energy storage unit may include one or more energy storage cells, such as supercapacitors or batteries. Background Technology

[0002] Energy storage systems can be used to supply power to the power grid. In grid applications, power demand ranges widely, from a few megawatts to hundreds of megawatts. This may require a large number of energy storage units, which can be constructed using different topologies. These energy storage units can be arranged, for example, in the form of rack or cabinet-style energy storage systems. The arrangement can be selected based on transportation or testing requirements.

[0003] Racks or cabinets can store very high levels of energy (e.g., megajoules) and output very high levels of power (e.g., megawatts). During discharge events, such as during a fault or maintenance, the forces and heat generated by the event can pose a risk to nearby personnel or equipment. Therefore, limiting current and ensuring safe discharge are crucial during the normal operation and maintenance of energy storage systems.

[0004] EP 4 170 852 A1 discloses a fault response bypass system for an energy storage group, which includes a discharge circuit for discharging modules of the energy storage group. The bypass system includes a discharge switch for bypassing the energy storage modules. WO 2022 / 100 822 A1 discloses a distributed protection and bypass circuit for an energy storage system, which includes a circuit for discharging energy storage units and a switch for disconnecting the energy storage units from the main circuit. US 9789782 B1 discloses a battery module disconnection arrangement including switches for bypassing and disconnecting the battery modules.

[0005] JP 2000 312442 A discloses a battery pack comprising multiple batteries connected in series, which can be connected and disconnected from a charging / discharging device via a charging / discharging circuit under the control of a controller. US 2013 / 278218 A1 and EP 3 806 271 A1 disclose battery packs including battery balancing circuits. Summary of the Invention

[0006] Embodiments of this disclosure relate to an energy storage system having improved protection circuitry that allows bypassing one or more energy storage units of the system.

[0007] According to a first aspect, an energy storage system includes a plurality of energy storage units and one or more protection circuits capable of bypassing one or more of the energy storage units. At least one of the protection circuits includes a first switch and a first resistor connected in series, and includes a second switch connected in series with the first switch and connected in parallel with the first resistor.

[0008] An energy storage unit may include one or more energy storage cells, such as capacitors (e.g., supercapacitors) or batteries. Energy storage units may be connected in series, parallel, or otherwise electrically connected to each other. Protection circuitry may be connected in parallel with one or more of these energy storage units.

[0009] By incorporating a first and second switch connected in series in the protection circuit, accidental direct short circuits caused by closing only one switch can be prevented. The energy storage system can be configured such that one or more associated energy storage units can be directly bypassed only when both the first and second switches are closed. The associated energy storage units are those to be bypassed by the protection circuit. In this respect, direct bypass means that there is no resistor in the current path used to bypass the energy storage unit. Direct bypass can also mean short-circuiting the energy storage unit.

[0010] It is also possible that, in addition to the first and second switches, other switches must be closed to bypass the energy storage unit. These additional switches can be connected in series with the first and second switches. By setting up additional switches, the risk of accidental short circuits can be further reduced.

[0011] By setting a first resistor in series with the first switch and in parallel with the second switch, the first resistor can be switched to the current path or removed from the current path in the protection circuit depending on the state of the switches, i.e., whether the switches are closed or open. When only a current path flows through the resistor, the current in the protection circuit is limited, thereby achieving a safe discharge process. When sufficient discharge has been achieved, a short-circuit current path can be formed by changing the state of one or more switches.

[0012] At least one of these protection circuits can be a unit protection circuit, which is used to bypass one of the energy storage units while simultaneously keeping the energy storage system operational. The unit protection circuit can allow simultaneous discharge and bypassing of the associated energy storage unit. The unit protection circuit can be connected in parallel only with the associated energy storage unit. When the unit protection circuit allows current flow, both operating current and discharge current can flow through it.

[0013] This ensures the availability of the energy storage system, eliminating the need for system shutdown when only a portion of the system is discharged while the rest continues to operate normally. For example, one or more protection circuits can be activated when an associated energy storage unit fails.

[0014] It is possible that each of these energy storage units has its own protection circuit. It is also possible that several energy storage units share a protection circuit, which bypasses several energy storage units when activated.

[0015] At least one of these protection circuits can be a system protection circuit that bypasses all energy storage units within the energy storage system. The system protection circuit can be configured to maintain the energy storage system. It can also be activated and allow discharge when one or more energy storage units fail.

[0016] An energy storage system may include one or more unit protection circuits and a system protection circuit. As an example, in addition to the system protection circuit, a unit protection circuit may be provided for each energy unit. These protection circuits can have different designs. For example, the unit protection circuit can have a more complex design than the system protection circuit.

[0017] At least one of these protection circuits may include at least one additional resistor for changing the resistance value of the current path in the protection circuit. The resistance value can be changed by altering the state of one or more of these switches. The protection circuit may include one or more additional switches for changing the resistance value by opening or closing a corresponding current path.

[0018] As an example, the current can be limited by gradually decreasing the resistance value according to the discharge current. By reducing the resistance value, the discharge process can be accelerated. Furthermore, the risk of exceeding the ratings of the switching device and / or energy storage unit, for example due to overvoltage and / or overcurrent, can be reduced. Simultaneously, high operating current can be achieved. The risk of exceeding the ratings of the energy storage unit can also be reduced.

[0019] The protection circuit can be configured such that an additional resistor can be connected in parallel with the first resistor by changing the state of one or more of these switches. As an example, in the first step, only a current path through the first resistor can be provided. In the second step, another switch can be closed to form another parallel current path through the other resistor. Thus, the total resistance value can be gradually reduced. As a final step, a current path can be achieved that passes only through the switches and not through the resistors.

[0020] It is also possible that several additional resistors are connected in parallel with the first resistor. The additional resistors can be connected in separate branches.

[0021] The protection circuit can be configured such that an additional resistor can be connected in series with the first resistor by changing the state of one or more of these switches. Similarly, the resistance value can be gradually increased by gradually disconnecting one or more additional resistors from the current path.

[0022] One or more additional switches in the protection circuit may be connected in parallel with the first switch. As an example, the protection circuit may include one or more parallel branches of the first switch and the first resistor, wherein each parallel branch includes an additional switch and an additional resistor.

[0023] Alternatively, one or more additional switches can be connected in series with the first switch. As an example, an additional resistor can be connected in parallel with the first resistor, and another additional switch can be connected in series with the first switch. Depending on the layout, activating the additional switch creates a current path for the additional resistor through the parallel resistor. As another example, an additional resistor can be connected in series with the first resistor, and another additional switch can be connected in series with the first switch. Depending on the layout, activating the additional switch creates a current path that bypasses the additional resistor.

[0024] It is also possible that the protection circuit allows additional resistors to be connected in series with the first resistor and in parallel with the first resistor by changing the state of one or more switches. In the first state, the additional resistors can be connected in series, and in the second state, the additional resistors can be connected in parallel.

[0025] The protection circuit may include an overvoltage protection device connected in parallel with the first resistor. This reduces the current stress passing through the associated energy storage unit.

[0026] According to another aspect, a method for operating a protection circuit in an energy storage system is disclosed. The protection circuit and the energy storage system may include any functional and structural features of the protection circuit and energy storage system disclosed above. The protection circuit includes two or more switches and a first resistor, wherein one of the switches is a first switch connected in series with the first resistor and in series with a second switch. The second switch is connected in parallel with the first resistor.

[0027] During normal operation of the energy storage system, at least two switches in the protection circuit can be disconnected. In some embodiments, the first and second switches are disconnected. Alternatively, all switches may be disconnected. By closing at least one of these switches, the protection circuit is activated to initiate a bypass of one or more of these energy storage units. Then, at least another switch is closed, either directly or simultaneously. As an example, the first switch may be closed first, followed by the second switch.

[0028] The protection circuit may include at least one additional resistor and at least one additional switch. The switches in the protection circuit may be closed sequentially to gradually reduce the resistance value in the bypass path.

[0029] This operating method allows for a controlled discharge process. Specifically, it prevents accidental short circuits caused by closing only a single switch. Furthermore, the resistance value of the current path in the protection circuit can be controlled, enabling the energy storage system to operate normally while simultaneously discharging one or more energy storage units. By adjusting the resistance value during operation, the risk of the switching devices and energy storage units exceeding their rated values ​​can be reduced, while simultaneously accelerating the discharge process.

[0030] This disclosure includes several aspects and embodiments. Each feature described with respect to one aspect and embodiment is also disclosed herein with respect to other aspects and embodiments, even if the corresponding feature is not explicitly mentioned in the context. Attached Figure Description

[0031] Further features, improvements, and conveniences will become clear from the following description of exemplary embodiments in conjunction with the accompanying drawings. In the drawings, elements with the same structure and / or function may be indicated by the same reference numerals. It should be understood that the embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale.

[0032] Figure 1 An embodiment / example of an energy storage system is illustrated in the diagram. Figure 2 An embodiment of the energy storage system is illustrated in the schematic diagram. Figures 3A to 3C A schematic diagram illustrates the process for operation. Figure 2 The energy storage system for discharging methods and steps, Figure 4 Another embodiment of a protection circuit for an energy storage system is illustrated in the schematic diagram. Figures 5A to 5F A schematic diagram illustrates the process for operation. Figure 4 The protection circuit is used for the method and steps of discharging. Figure 6Another embodiment of a protection circuit for an energy storage system is illustrated in the schematic diagram. Figure 7 Another embodiment of a protection circuit for an energy storage system is illustrated in the schematic diagram. Figure 8 Another embodiment of a protection circuit for an energy storage system is illustrated in the schematic diagram. Figure 9 Another embodiment of a protection circuit for an energy storage system is illustrated in schematic diagram. Detailed Implementation

[0033] Figure 1 A conceptual diagram of energy storage system 1 is shown. For example, energy storage system 1 may be in the form of a rack or cabinet. Energy storage system 1 can be configured to supply electrical energy to the power grid, electric or hybrid vehicles, or other electric systems or devices. Energy storage system 1 may include power terminals for connecting to external devices to supply electrical energy to those devices.

[0034] Energy storage system 1 includes multiple energy storage units 2, 2 n Each energy storage unit has 2,2 n It may include one or more energy storage cells, such as batteries, capacitors, or fuel cells. For example, the capacitor may be a supercapacitor. Energy storage unit 2, 2 n They can be connected in series or in parallel.

[0035] For each energy storage unit 2, 2n, an electrical protection circuit 3, 3n (also referred to as a unit protection circuit) can be provided. The corresponding protection circuit 3, 3n is connected in parallel with the associated energy storage unit 2, 2n. The corresponding electrical protection circuit 3, 3n can bypass the associated energy storage unit 2, 2n, for example, in the event of a failure of that energy storage unit 2, 2n. All other energy storage units in energy storage units 2, 2n are not bypassed. Therefore, each energy storage unit 2, 2n has its own protection circuit 3, 3n, which enables the other energy storage units 2, 2n to operate normally.

[0036] Therefore, healthy energy storage units can still operate normally, while defective energy storage units will be discharged. As an example, a defective energy storage unit could be a string of energy storage modules.

[0037] In addition, the energy storage system 1 includes a system protection circuit 4, which is electrically connected in parallel with all energy storage units 2 and 2n. The system protection circuit 4 is also electrically connected in parallel with all protection circuits 3 and 3n. The system protection circuit 4 can simultaneously bypass all energy storage units 2 and 2n. The system protection circuit 4 can also be used for maintenance.

[0038] Figure 2An embodiment of the energy storage system 1 is shown, in which protection circuits 3, 3n and system protection circuit 4 are shown in detail.

[0039] The protection circuit 3 includes a first switch S1 and a first resistor R1 connected in series. Furthermore, the protection circuit 3 includes a second switch S2. The second switch S2 is connected in parallel with the first resistor R1 and in series with the first switch S1.

[0040] The protection circuit 3 is configured as a dual bypass circuit, which allows the energy storage unit 2 to bypass via two paths when the corresponding switches S1 and S2 are closed. The first path passes through the first switch S1 and the first resistor R1, and the second path passes through the first switch S1 and the second switch S2.

[0041] The first path passes through the first resistor R1, while the second path provides a short circuit and contains no resistors. Since the second switch S2 is connected in parallel with the first resistor R1 but not with the first switch S1, a direct short circuit due to misoperation is less likely to occur compared to a design where the bypass switch is connected in parallel with the energy storage unit and there are no other switches in the path. In the illustrated embodiment, both the first switch S1 and the second switch S2 must be closed to short-circuit the energy storage unit 2.

[0042] Furthermore, a resistor R1 is provided in the first path to provide current limiting during the discharge of the first energy storage unit 2. In addition, when switch S1 is closed, current flows through resistor R1, or when the second switch S2 is also closed, the resistor is bypassed; in both cases, the energy storage system 1 can continue to operate.

[0043] In the illustrated embodiment, each protection circuit 3, 3n, 4 has the same structure. However, even in this case, the resistance value and type of the switches can differ for different protection circuits 3, 3n, 4. As an example, the first resistor Ra of the system protection circuit 4 can have a high resistance value to allow for slow discharge at very low currents, in which case low-cost switches Sa, Sb would suffice.

[0044] The resistance values ​​of unit protection circuits 3 and 3n may be low, and switches S1, S2, Sn1, and Sn2 may be expensive.

[0045] The design and operating mode of protection circuit 3 are described in detail below, but the same applies to other protection circuits 3n and 4. System protection circuit 4 includes a system first switch Sa, a system first resistor Ra, and a system second switch Sb. The additional protection circuit 3n includes a first switch Sn1, a first resistor Rn1, and a second switch Sn2. In other embodiments, the designs of protection circuits 3, 3n, and 4 may differ. As an example, system protection circuit 4 may have a design different from the protection circuits 3 and 3n of each energy storage unit 2, 2n.

[0046] It is also possible that the energy storage system 1 includes only one or more unit protection circuits 3, 3n, or only system protection circuit 4.

[0047] Protection circuits 3, 3n, and 4 can be controlled by a control unit. The control unit can be part of the energy storage system or an external component.

[0048] Figures 3A to 3C It shows the method for running Figure 2 Methods and steps for developing energy storage systems.

[0049] exist Figure 3A In this configuration, energy storage system 1 is in its operating mode, and all energy storage units 2 and 2n are operating normally. All first switches S1, Sn1, and Sa are open. Second switches S2, Sn2, and Sb are also open. The operating current Iop flows through energy storage units 2 and 2n without any bypass.

[0050] As from Figure 3B As can be seen, when energy storage unit 2 is bypassed, for example due to a fault, the first switch S1 closes. The discharge process begins, and the discharge current Idc flows through the first switch S1 and the first resistor R1. The second switch S2 remains open. This prevents accidental direct short circuits caused by closing the first switch S1. The first resistor R1 has a resistance value, which limits the current to the desired level.

[0051] Meanwhile, based on the fault of energy storage unit 2 and the resistance value of resistor R1, the operating current Iop is divided into a first current Iop1 that still flows through energy storage unit 2 and a second operating current Iop2 that flows through the first switch S1 and the first resistor R1.

[0052] Therefore, the healthy portion of the energy storage system 1 can continue to operate, while the affected energy storage unit 2 is discharged.

[0053] In this operation, the voltage level can be monitored to determine when the second switch S2 closes.

[0054] exist Figure 3CIn this process, the second switch S2 is closed. The first switch S1 remains closed. The closure of the second switch S2 may depend on the voltage level being reached. Now, all or almost all of the operating current Iop flows through the protection circuit 3. A small amount of operating current Iop may still flow through the energy storage unit 2, and / or a small amount of discharge current Idc may still flow through the protection circuit 3.

[0055] Therefore, the healthy portion of the energy storage system 1 can continue to operate, while the affected energy storage units 2 and 2n are bypassed.

[0056] The above method and steps are also applicable to bypassing other energy storage units 2n and / or the entire energy storage system 1.

[0057] Figure 4 Another embodiment of the protection circuit 3 in the energy storage system 1 is shown. Similarly, in this case, the protection circuit 3 can be an additional protection circuit 3n and / or a system protection circuit 4.

[0058] and Figure 2 The difference in this embodiment is that an additional resistor R2 (also referred to as the second resistor below) is provided in the protection circuit 3. In addition, an additional switch S3 (also referred to as the third switch below) is provided, which connects resistors R1 and R2 in series. The second resistor R2 allows for more flexible adjustment and limitation of the current flowing through the energy storage system 1 and / or energy storage units 2, 2n than using only one resistor. As an example, the rated current of energy storage units 2, 2n can be lower than the peak current generated by the sum of the system operating current Iop and the discharge current Idc.

[0059] When all switches S1, S2, and S3 are closed, energy storage units 2 and 2n are bypassed, and no current flows through any resistor in protection circuit 3. When the first switch S1 and the second switch S2 are closed, resistors R1 and R2 are connected in parallel, and current can flow through both resistors R1 and R2. When only one of the first switch S1 and the second switch S2 is closed and the third switch S3 is open, current flows through only one of the resistors R1 and R2. When only one of the first switch S1 and the second switch S2 is closed and the third switch S3 is closed, current flows through the two resistors R1 and R2 connected in series.

[0060] Figures 5A to 5F It shows the method for running Figure 4 The sequence of steps in one embodiment of the protection circuit 3.

[0061] Figure 5A The protection circuit 3 is shown when the associated energy storage units 2 and 2n are in normal operation. All switches in the protection circuit 3 are open. The entire operating current Iop flows through energy storage unit 2.

[0062] like Figure 5B As shown, when a fault is detected, the third switch S3 closes, while the first switch S1 and the second switch S2 remain open. Consequently, resistors R1 and R2 are connected in series, achieving the highest possible resistance value for the current flowing through the protection circuit 3. Therefore, the peak value of the discharge current Idc can be kept as low as possible.

[0063] After that, as Figure 5C As shown, the first switch S1 is closed. Alternatively, the second switch S2 is closed. This reduces the resistance value and accelerates the discharge. Therefore, the discharge time constant is reduced.

[0064] After that, as Figure 5D As shown, disconnect the third switch to prepare for the next step.

[0065] After that, as Figure 5E As shown, the second switch S2 is closed to further accelerate the discharge. Alternatively, where the previous situation was that the second switch S2 was closed and the first switch S1 was open, the first switch S1 is now closed.

[0066] After that, as Figure 5F As shown, the third switch is closed to complete the bypass. In this state, current flows through protection circuit 3, and there are no resistors R1 and R2 in the current path.

[0067] In the example shown, the resistance value of the current flowing through protection circuit 3 gradually decreases. This limits the peak value of the discharge current Iop that occurs at the beginning of discharge. As the discharge current decreases over time, the resistance value decreases, thereby accelerating the discharge.

[0068] In other embodiments, different operating sequences may be provided. The selected sequence may depend on current limits and the ratio of operating current to discharge current.

[0069] Figure 6 Another embodiment of the protection circuit 3 for the energy storage system 1 is shown. In this circuit variant, several branches are connected in parallel with a first switch S1 and a first resistor R1. Each parallel branch includes switches S11, S12, S1m and resistors R11, R12, R1m. This allows for further variation of the discharge resistance.

[0070] The first resistor R1 and the other resistors R11, R12, and R1m in the parallel branch can have the same resistance value or different resistance values. As an example, the resistance value of the first resistor R1 can be different from the resistance values ​​of each of the other resistors R11, R12, and R1m.

[0071] The bypass process is accomplished by simultaneously closing the first switch S1 and turning on the second switch S2.

[0072] The following are some examples of the working modes.

[0073] An example of an operating mode is to gradually reduce the discharge resistance to accelerate the discharge process. This reduction can be achieved by turning on the first switch S1 and then sequentially turning on the parallel switches S11, S12, and S1m. That is, first, the first switch S1 is closed to introduce the first resistor R1 into the current path, then S11 is closed to connect R11 in parallel with R1, then S12 is closed to connect R1, R11, and R12 in parallel, and so on.

[0074] Another operating mode can be achieved by slowly discharging using only one of the resistors R1, R11, R12, and R1m, for example, by switching the first switch S1 to use only the first resistor R1. This operating mode can be used to discharge faulty energy storage units that should not be exposed to high current. It is worth noting that several resistors can be used to avoid rating the first resistor R1 at its full energy capacity. For example, after closing S12, discharge can begin through R12, then S12 can be opened and S11 closed to continue using R11, and then S11 can be opened and S1 closed to continue discharging using R1. This mode requires switches S1 to S1m to have current-disconnecting capability.

[0075] Another operating mode could be to increase the discharge resistance when the discharge current flowing through energy storage unit 2 needs to be increased to a very high value. In this case, increasing the resistance will reduce the discharge current and thus reduce the current stress on energy storage unit 2.

[0076] The following text summarizes Figure 6 and Figure 2 Some differences in the circuit variants.

[0077] To achieve the same discharge time, as long as the correct selection is made... Figure 6 The resistance in Figure 6 The current-carrying capacity of S1 to S1m can be lower than Figure 2 The current-carrying capacity of S1 in the circuit. This will bring the disadvantage of increasing the number of switches, but the total cost of the switches may not be higher.

[0078] Figure 6One drawback of the circuit is that the first switch S1, connected in series with the second switch S2 that completes the bypass process, must have a high current-carrying capacity so that it remains closed even during short circuits in other non-bypass energy storage units. The current-carrying capacity of the first resistor S1 can be reduced by using a second switch connected in parallel with each resistor R11, R12, R1m in the parallel branch as the second switch S2. However, in this case, all second switches may need to have the same current-carrying capacity, as simultaneous switching is challenging.

[0079] Figure 7 Another embodiment of the protection circuit 3 for the energy storage system 1 is shown. Also in this embodiment, several branches are provided having resistors R11, R12, and R1m that can be connected in parallel with the first resistor R1. However, additional switches S3, S4 to Sm-2 ensure that the resistance value can only be decreased sequentially by adding resistors R11, R12, and R1m. Therefore, the discharge process can be gradually accelerated.

[0080] for Figure 7 The circuit begins the discharge process by turning on the first switch S1. Then, the resistance value can be reduced sequentially by closing S3, S4 to Sm-2, thereby connecting resistors R11, R12, and R1m in parallel with the first resistor R1.

[0081] The first switch S1 can have a lower current-carrying capacity because it can be turned on while all other switches are in the off position (i.e., at the maximum resistance equal to R1). Finally, bypassing is achieved by closing the second switch S2 simultaneously with the first switch S1.

[0082] and Figure 6 The disadvantage of this circuit compared to the previous one is that, in the event of a faulty switch, the achievable reduction in resistance is highly dependent on the position of the faulty switch. For example, if the first additional switch S3 fails to connect, the resistance cannot be reduced at all, and the circuit effectively becomes... Figure 2 The circuit.

[0083] Figure 8 Another embodiment of the protection circuit 3 for the energy storage system 1 is shown. Also here, the discharge resistance can be changed by opening and closing additional switches S3 to Sm+1.

[0084] In the circuit, additional resistors R2 to Rm are connected in series with the first resistor R1. Each of the additional resistors R2 to Rm can be bypassed by closing the associated switches S3 to Sm+1, thereby forming a current path bypassing the associated resistors R2 to Rm in the protection circuit 3.

[0085] As an example of operation, the discharge resistance can be gradually reduced by sequentially closing switches S2 to Sm+1. The bypass operation is completed by closing all switches S1 to Sm+1.

[0086] and Figure 2 , Figure 6 and Figure 7 The disadvantage of this circuit compared to the previous one is that if any one of the switches S1 to Sm+1 fails, the bypass circuit without resistors R1 to Rm in the current path will fail. Figure 2 The advantage of this circuit compared to the previous one is that the resistance value can be lower in the event of a failure of the second switch S2.

[0087] Figure 9 Another embodiment of the protection circuit 3 for the energy storage system 1 is shown. (Compared to...) Figure 2 Compared to the previous embodiment, the protection circuit 3 here includes an overvoltage protection device 5, which is connected in parallel with the first resistor R1 and in parallel with the second switch S2.

[0088] The overvoltage protection device 5 can be, for example, a varistor. The overvoltage protection device 5 is configured to prevent overvoltage of the energy storage unit 2 during high discharge current bypass. This allows for the selection of a high resistance value for the first resistor R1, which can be used to reduce the current stress on the energy storage unit 2 when a high discharge current is required during bypass operation. When the voltage exceeds a certain level, the overvoltage protection device 5 becomes a low-impedance conductor, and current flows not through the resistor but instead through the overvoltage protection device 5. Under normal voltage conditions, the overvoltage protection device 5 acts as a high-impedance component.

[0089] Any of the protection circuits 3 and 3n for energy storage units 2 and 2n and the system protection circuit 4 can have the following characteristics for combination Figures 2 to 9 The specific embodiments described disclose the structure and operating mode. The protection circuits 3 and 3n for energy storage units 2 and 2n may have a different structure than the system protection circuit 4. As an example, the system protection circuit 4 may have... Figure 2 The basic structure shown is provided, and the unit protection circuits 3 and 3n can have the features shown in Figure 3 to 3n. Figure 9 This is one of the more complex structures. It is also possible that unit protection circuits 3 and 3n have different structures.

[0090] Figure Labels 1. Energy Storage System 2 Energy Storage Units 2n Other energy storage units 3. Protection Circuit 3n Additional protection circuits 4 System Protection Circuit 5. Overvoltage protection device S1 (the first switch of the first energy storage unit) R1 (the first resistor of the first energy storage unit) S2 (the second switch of the first energy storage unit) S11, S12, S1m (other switches in the parallel branch) R11, R12, R1m (the other resistors in the parallel branch) R2, R3, Rm The other resistor (connected in series with the first resistor). S3, S4, Sm+1 are additional switches (connected in series with the first / second switch). The first switch of the nth energy storage unit Sn1 Rn1, the first resistor of the nth energy storage unit The second switch of the nth energy storage unit of Sn2 The first switch of the Sa system The second switch of the Sb system The first resistor in the Ra system Iop operating current The first part of the operating current of Iop1 The second part of the Iop2 operating current Idc discharge current.

Claims

1. An energy storage system (1), The energy storage system (1) is configured to supply electrical energy to the power grid. It includes multiple energy storage units (2, 2n) and one or more protection circuits (3, 3n, 4), which are capable of bypassing one or more of the energy storage units (2, 2n). in, At least one of the protection circuits (3, 3n, 4) includes a first switch (S1, Sn1, Sa) and a first resistor (R1, Rn1, Ra) connected in series, and includes a second switch (S2, Sn2, Sb) connected in series with the first switch (S1, Sn1, Sa) and connected in parallel with the first resistor (R1, Rn1, Ra).

2. The energy storage system (1) as described in claim 1. It is configured such that the associated one or more energy storage units (2, 2n) can be short-circuited only when both the first switch (S1, Sn1, Sa) and the second switch (S2, Sn2, Sb) are closed.

3. The energy storage system (1) as described in any of the preceding claims. in, At least one of the protection circuits (3, 3n, 4) is a unit protection circuit (3, 3n), which is capable of bypassing one of the energy storage units (2, 2n) and enabling the energy storage system (1) to continue operating simultaneously.

4. The energy storage system (1) as described in any of the preceding claims. in, At least one of the protection circuits (3, 3n, 4) is a system protection circuit (4) which is capable of bypassing all energy storage units in the energy storage units (2, 2n).

5. The energy storage system (1) as described in any of the preceding claims. in, At least one of the protection circuits (3, 3n, 4) includes at least one additional resistor (R2 to Rm, R11 to R1m) for allowing the resistance value of the current path flowing through the protection circuit (3, 3n, 4) to be changed.

6. The energy storage system (1) as described in claim 5. in, By changing the state of one or more switches (S1, S2, S3 to Sm+1, S11 to S1m), the additional resistors (R2 to Rm, R11 to R1m) can be electrically connected in parallel with the first resistor (R1).

7. The energy storage system (1) as described in any one of claims 5 or 6. in, By changing the state of one or more switches (S1, S2, S3 to Sm+1, S11 to S1m), the additional resistors (R2 to Rm, R11 to R1m) can be connected in series with the first resistor (R1).

8. The energy storage system (1) as described in any one of claims 5 to 7. in, By changing the state of one or more switches (S1, S2, S3 to Sm+1, S11 to S1m) respectively, the additional resistors (R2 to Rm, R11 to R1m) can be connected in series and in parallel with the first resistor (R1).

9. The energy storage system as described in any one of claims 5 to 8, in, The protection circuit (3, 3n, 4) includes at least one additional switch (S3 to Sm+1, S11 to S1m) for changing the resistance value of the current path.

10. The energy storage system as described in claim 9, in, The other switches (S3 to Sm+1, S11 to S1m) are connected in parallel with the first switch (S1).

11. The energy storage system as described in claim 9, in, The other switches (S3 to Sm+1, S11 to S1m) are connected in series with the first switch (S1).

12. The energy storage system as described in any of the preceding claims, in, The protection circuit (3, 3n, 4) includes an overvoltage protection device (5) connected in parallel with the first resistor (R1).

13. A method for operating a protection circuit (3, 3n, 4) for one or more energy storage units (2, 2n) in a bypass energy storage system (1), The energy storage system (1) is configured to supply electrical energy to the power grid. The energy storage system (1) includes multiple energy storage units (2, 2n) and one or more protection circuits (3, 3n, 4), which are capable of bypassing one or more of the energy storage units (2, 2n). in, At least one of the protection circuits (3, 3n, 4) includes two or more switches (S1, Sn1, Sa, S2, S3 to Sm+1, S11 to S1m) and includes a first resistor (R1, Rn1, Ra), wherein the two or more switches include a first switch (S1, Sn1, Sa) and a second switch (S2, Sn2, Sb). Wherein, the first switch (S1, Sn1, Sa) and the first resistor (R1, Rn1, Ra) are connected in series, and wherein the first switch (S1, Sn1, Sa) and the second switch (S2, Sn2, Sb) are connected in series, and wherein the second switch (S2, Sn2, Sb) and the first resistor (R1, Rn1, Ra) are connected in parallel. The method includes the following steps: Close at least one of the switches (S1, Sn1, Sa, S2, S3 to Sm+1, S11 to S1m) to initiate a bypass to one or more of the energy storage units (2, 2n), and Then close at least one of the switches (S1, Sn1, Sa, S2, S3 to Sm+1, S11 to S1m) simultaneously.

14. The method as described in claim 13, in, The first switch (S1) is closed to initiate a bypass, and the second switch (S2) is closed after or simultaneously with the first switch (S1).

15. The method as described in any one of claims 13 or 14, in, The protection circuit includes at least one additional resistor (R2 to Rm, R11 to R1m) and at least one additional switch (S3 to Sm+1, S11 to S1m), wherein the switches (S3 to Sm+1, S11 to S1m) are closed sequentially such that the resistance value in the bypass path gradually decreases.

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