Energy storage system and protection device and protection method thereof

Abstract

An energy storage system includes a battery, a first battery terminal and a second battery terminal connected to the battery, a first inverter terminal and a second inverter terminal connected to an inverter, a switch connected between the second battery terminal and the second inverter terminal, and a protection circuit, the protection circuit is configured to determine whether to turn off the switch based on a difference between a first voltage detected at the first inverter terminal and a second voltage detected at the second inverter terminal, the first voltage, and the second voltage.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0163660 filed in the Korean Intellectual Property Office on November 22, 2023, the entire contents of which are incorporated herein by reference.

[0003] The present disclosure relates to an energy storage system and a protection device and a protection method thereof. Background Art

[0004] Energy storage systems (ESS), which store electricity and provide it when needed, are used in a variety of applications. For example, ESS can be used to store excess power from power plants and provide it when there is a temporary shortage. ESS can also be miniaturized and used in buildings, factories, and homes for outage preparedness or peak power reduction. ESS can also be used to store electricity generated from renewable energy sources and utilize the stored power when needed.

[0005] Inverters are used to store electricity in energy storage systems and deliver it to loads. Recently, when high-voltage power generation systems, such as solar power, are connected to inverters, a fault in the inverter could cause high voltage to be fed to the energy storage system, potentially damaging it. Summary of the Invention

[0006] Technical issues

[0007] Some embodiments may provide an energy storage system and a protection device and method thereof, which are used to protect the energy storage system in the event of an inverter failure.

[0008] Technical Solution

[0009] According to some embodiments, an energy storage system may include a battery, a first battery terminal and a second battery terminal connected to the battery, a first inverter terminal and a second inverter terminal connected to an inverter, a switch connected between the second battery terminal and the second inverter terminal, and a protection circuit configured to determine whether to disconnect the switch based on a difference between a first voltage detected at the first inverter terminal and a second voltage detected at the second inverter terminal, the first voltage, and the second voltage.

[0010] According to some embodiments, a protection device for an energy storage system includes a battery and a switch, the switch being configured to be connected between the battery and an inverter. The protection device may include a voltage divider circuit configured to divide a voltage at a first inverter terminal connected to a first terminal of the inverter to output a first voltage, and to divide a voltage at a second inverter terminal connected to a second terminal of the inverter to output a second voltage; an adder configured to calculate a difference between the first voltage and the second voltage; a first comparator configured to compare the difference between the first voltage and the second voltage with a first reference voltage; a second comparator configured to compare the first voltage with a second reference voltage; a third comparator configured to compare the second voltage with a third reference voltage; a logic circuit configured to perform a logic operation on a first output signal of the first comparator, a second output signal of the second comparator, and a third output signal of the third comparator; and a switch control circuit configured to control the switch based on a fourth output signal of the logic circuit.

[0011] According to some embodiments, a method for protecting an energy storage system includes a battery and a switch configured to control a connection between the battery and an inverter. The method may include: detecting a voltage at a first inverter terminal connected to a first terminal of the inverter to output a first voltage, detecting a voltage at a second inverter terminal connected to a second terminal of the inverter to output a second voltage, comparing a difference between the first voltage and the second voltage with a first reference voltage, comparing the first voltage with a second reference voltage, comparing the second voltage with a third reference voltage, and disconnecting the switch in response to the difference between the first voltage and the second voltage being greater than the first reference voltage, the first voltage being greater than the second reference voltage, or the second voltage being greater than the third reference voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a diagram illustrating an example of a power supply system according to some embodiments.

[0013] Figure 2 is a diagram illustrating an example of an energy storage system according to some embodiments.

[0014] Figure 3 is a diagram illustrating an example of a protection circuit of an energy storage system according to some embodiments.

[0015] Figure 4 is a diagram illustrating an example of a protection circuit of an energy storage system according to some embodiments.

[0016] Figure 5 is a flowchart illustrating an example of a protection method for an energy storage system according to some embodiments. DETAILED DESCRIPTION

[0017] In the following detailed description, only certain embodiments of the present invention are shown and described by way of illustration. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be regarded as illustrative and not restrictive. Throughout the specification, the same reference numerals represent the same elements.

[0018] When describing that an element is “connected” to another element, it should be understood that the element can be directly connected to the other element or connected to the other element through a third element. On the other hand, when describing that an element is “directly connected” to another element, it should be understood that the element is not connected to the other element through a third element.

[0019] As used herein, the singular form may be intended to include the plural form as well, unless an explicit expression such as "one" or "single" is used.

[0020] In the flowcharts described with reference to the accompanying drawings, the order of operations or steps may be changed, several operations or steps may be combined, a certain operation or step may be divided, and a specific operation or step may not be performed.

[0021] Figure 1 is a diagram illustrating an example of a power supply system according to some embodiments.

[0022] refer to Figure 1 , the power supply system may include a power generation unit 110 , an energy storage system (or energy storage device) 120 , an inverter 130 , a grid 140 and a load 150 .

[0023] Power generation unit 110 can generate electrical energy. Power generation unit 110 can be, for example, but not limited to, a solar power generation system, a wind power generation system, a tidal power generation system, or a geothermal power generation system. For example, if a solar power generation system is used, power generation unit 110 can include a solar cell array that converts solar energy into electrical energy. A solar cell array can include a plurality of solar cell modules, and a solar cell module can include a plurality of solar cells connected in series or parallel to convert solar energy into electrical energy and generate a predetermined voltage and current.

[0024] Energy storage system 120 can be charged with electric energy supplied from power generation unit 110 and discharge the charged electric energy to supply it to grid 140 or load 150. For example, when grid 140 or load 150 is lightly loaded, energy storage system 120 can receive idle power from power generation unit 110 and charge it with the idle power. If grid 140 or load 150 is overloaded, energy storage system 120 can discharge the charged electric energy and supply it to grid 140 or load 150.

[0025] The inverter 130 can convert direct current (DC) power into alternating current (AC) power. The inverter 130 can convert the DC power supplied by the power generation unit 110 or the DC power supplied by the energy storage system 120 into AC power. In some embodiments, the inverter 130 can be a three-phase inverter. In some embodiments, when the power generation unit 110 uses a high voltage, the inverter 130 can include an inverter 131 that converts DC power into AC power and a DC / DC converter 132 that converts the DC power supplied by the power generation unit 110 into DC power. The energy storage system 120 can be charged with the DC power supplied by the DC / DC converter 132. The inverter 131 can convert the DC power supplied by the energy storage system 120 or the DC power supplied by the DC / DC converter 132 into AC power, which is supplied to the grid 140 or the load 150.

[0026] The grid 140 may be an electric power network having power plants, substations, power transmission and distribution, etc. The load 150 may be a device that consumes electric power.

[0027] Energy storage system 120 may include a protection circuit (or protection device) 121 that detects faults in inverter 130 and protects energy storage system 120 in the event of a fault in inverter 130. In some embodiments, protection circuit 121 may disconnect the electrical connection between energy storage system 120 and inverter 130.

[0028] Figure 2 is a diagram illustrating an example of an energy storage system according to some embodiments.

[0029] refer to Figure 2 , the energy storage system 200 may include a battery 210, a switch 220, and a protection circuit 230. In some embodiments, the protection circuit 230 may be a battery management system of the energy storage system 200, or may be included in the battery management system.

[0030] Battery 210 may be a rechargeable battery. Battery 210 may be, for example, a lithium cell, such as a lithium-ion cell or a lithium-ion polymer cell, or a nickel cell, such as a nickel-cadmium (NiCd) cell or a nickel-metal hydride (NiMH) cell. In some embodiments, battery 210 may include an assembly of multiple battery cells, a battery module comprising multiple assemblies connected in series or in parallel, a battery pack (or battery rack) comprising multiple battery modules connected in series or in parallel, or multiple battery packs connected in series or in parallel.

[0031] The positive electrode of the battery 210 may be connected to the positive battery terminal B+ of the energy storage system 200, and the negative electrode of the battery 210 may be connected to the negative battery terminal B- of the energy storage system 200. One of the positive battery terminal B+ and the negative battery terminal B- may be referred to as a first battery terminal, and the other may be referred to as a second battery terminal. In some embodiments, the positive battery terminal B+ and the negative battery terminal B- may be a positive battery receptacle B+ and a negative battery receptacle B-, respectively. The positive inverter terminal INV+ of the energy storage system 200 may be connected to an inverter (e.g., Figure 1 The positive terminal of inverter 130 is connected to the positive terminal of inverter 130, and the negative inverter terminal INV- of energy storage system 200 can be connected to the negative terminal of inverter 130. One of the positive inverter terminal INV+ and the negative inverter terminal INV- can be referred to as the first inverter terminal, and the other can be referred to as the second inverter terminal. Furthermore, one of the positive and negative terminals of the inverter can be referred to as the first terminal, and the other can be referred to as the second terminal. The positive inverter terminal INV+ and the negative inverter terminal INV- can be the positive inverter socket INV+ and the negative inverter socket INV-, respectively.

[0032] In some embodiments, the positive terminal and negative terminal of inverter 130 may be the positive output and negative output of DC / DC converter 132 of inverter 130, respectively. In some embodiments, the positive terminal and negative terminal of inverter 130 may be the positive input and negative input of inverter 131, respectively.

[0033] The switch 220 may be connected between the battery terminals of the energy storage system 200 and the inverter terminals of the energy storage system 200. In some embodiments, as Figure 2 As shown in , switch 220 can be connected between the negative battery terminal B- and the negative inverter terminal INV-. In some embodiments, switch 220 can be connected between the positive battery terminal B+ and the positive inverter terminal INV+. In some embodiments, switch 220 can include a switch connected between the positive battery terminal B+ and the positive inverter terminal INV+ and a switch connected between the negative battery terminal B- and the negative inverter terminal INV-. In some embodiments, switch 220 can be a conductor formed as a relay.

[0034] The ground of the energy storage system 200 may be connected to a ground terminal GND. The ground terminal GND may be referred to as a ground socket GND. In some embodiments, the ground terminal GND may be connected to a chassis ground of the energy storage system 200.

[0035] The protection circuit 230 may receive the voltage at the positive inverter terminal INV+ and the voltage at the negative inverter terminal INV-, and diagnose whether a fault occurs in the inverter 130 based on the voltage at the positive inverter terminal INV+ and the voltage at the negative inverter terminal INV-, and disconnect the switch 220 if the inverter 130 fails. For example, if the inverter 130 (e.g., Figure 1 If the DC / DC converter 132 (e.g., the DC / DC converter 132) is supplied with a voltage higher than the voltage actually to be supplied, the protection circuit 230 can diagnose a fault in the inverter 130 based on the voltage at the positive inverter terminal INV+ and the voltage at the negative inverter terminal INV-, and open the switch 220. Alternatively, if a short circuit occurs in the line connecting the inverter 130 to the grid 140, the protection circuit 230 can diagnose a fault (short circuit fault) in the inverter 130 based on the voltage at the positive inverter terminal INV+ and the voltage at the negative inverter terminal INV-, and open the switch 220.

[0036] In some embodiments, fuse 240 may be connected between the positive battery terminal B+ and the positive inverter terminal INV+. In some embodiments, fuse 250 may be connected between the negative battery terminal B- and the negative inverter terminal INV-.

[0037] Figure 3 is a diagram illustrating an example of a protection circuit of an energy storage system according to some embodiments.

[0038] refer to Figure 3 The protection circuit 300 may be connected to the positive inverter terminal INV+ and the negative inverter terminal INV− of the energy storage system and may include an adder 310 , comparators 320 , 330 and 340 , a logic circuit 350 and a switch control circuit 360 .

[0039] The adder 310 may calculate a difference Vip−Vin between a voltage Vip detected at the positive inverter terminal INV+ (referred to as “positive inverter voltage”) and a voltage Vin detected at the negative inverter terminal INV− (referred to as “negative inverter voltage”). The adder 310 may be referred to as a subtractor.

[0040] The comparator 320 may compare the difference Vip-Vin between the positive inverter voltage Vip and the negative inverter voltage Vin calculated by the adder 310 with a reference voltage (or first reference voltage) Vref1. If the difference Vip-Vin between the positive inverter voltage Vip and the negative inverter voltage Vin is greater than the reference voltage Vref1, the comparator 320 may output an output signal (or first output signal) S1 having a first predetermined level (or first level). If the difference Vip-Vin between the positive inverter voltage Vip and the negative inverter voltage Vin is not greater than the reference voltage Vref1, the comparator 320 may output an output signal S1 having a second level different from the first predetermined level. Depending on the setting of the reference voltage Vref1, a case where the difference Vip-Vin between the positive inverter voltage Vip and the negative inverter voltage Vin is greater than the reference voltage Vref1 can be understood as a case where the difference Vip-Vin between the positive inverter voltage Vip and the negative inverter voltage Vin is greater than or equal to the reference voltage Vref1.

[0041] The comparator 330 may compare the positive inverter voltage Vip with a reference voltage (or second reference voltage) Vref2. In some embodiments, since a three-phase inverter may be used, the positive inverter voltage Vip compared by the comparator 330 may be relative to a ground terminal (e.g., Figure 2 In other words, the comparator 330 may compare the positive inverter voltage Vip obtained by subtracting the voltage at the ground terminal GND from the positive inverter voltage Vip with the reference voltage Vref2. If the positive inverter voltage Vip (e.g., the positive inverter voltage Vip obtained by subtracting the voltage at the ground terminal GND) is greater than the reference voltage Vref2, the comparator 330 may output an output signal (or a second output signal) S2 having a first predetermined level. If the positive inverter voltage Vip is not greater than the reference voltage Vref2, the comparator 330 may output an output signal S2 having a second level different from the first predetermined level. Depending on the setting of the reference voltage Vref2, the case where the positive inverter voltage Vip is greater than the reference voltage Vref2 may be understood as the case where the positive inverter voltage Vip is greater than or equal to the reference voltage Vref2.

[0042] Comparator 340 can compare the negative inverter voltage Vin with a reference voltage (or third reference voltage) Vref3. In some embodiments, since a three-phase inverter can be used, the negative inverter voltage Vip compared by comparator 340 can be the negative inverter voltage Vin relative to ground terminal GND. That is, comparator 340 can compare the negative inverter voltage Vin (e.g., the voltage at ground terminal GND) with reference voltage Vref3. If negative inverter voltage Vip (e.g., negative inverter voltage Vin (the voltage at ground terminal GND) is less than reference voltage Vref3) is greater than reference voltage Vref3, comparator 340 can output an output signal (or third output signal) S3 having a first predetermined level. In this case, the magnitudes of the negative inverter voltage Vip and reference voltage Vref3 to be compared can be the absolute values of negative inverter voltage Vip and reference voltage Vref3, respectively. If negative inverter voltage Vin is not greater than reference voltage Vref3, comparator 340 can output an output signal S3 having a second level different from the first predetermined level. According to the setting of the reference voltage Vref3 , the case where the negative inverter voltage Vin is greater than the reference voltage Vref3 may be understood as the case where the negative inverter voltage Vin is greater than or equal to the reference voltage Vref3 .

[0043] The logic circuit 350 may output an output signal S4 based on the output signals S1, S2, and S3 output from the comparators 320, 330, and 340. The logic circuit 350 may output the output signal S4 by performing a logical operation on the output signals S1, S2, and S3 output from the comparators 320, 330, and 340. When at least one of the output signals S1, S2, and S3 output from the comparators 320, 330, and 340 has a first predetermined level, the logic circuit 350 may output a control signal having a second predetermined level (or a third predetermined level). If the output signals S1, S2, and S3 output from the comparators 320, 330, and 340 have a second predetermined level, the logic circuit 350 may output a control signal having a fourth level different from the second predetermined level.

[0044] In some embodiments, when the first predetermined level is a high logic level, the logic circuit 350 may include an OR gate, and the second predetermined level may be a high level. In some embodiments, when the first predetermined level is a high logic level, the logic circuit 350 may include a NOR gate, and the second predetermined level may be a low level. In some embodiments, when the first predetermined level is a low logic level, the logic circuit 350 may include an AND gate, and the second predetermined level may be a low level. In some embodiments, when the first predetermined level is a low logic level, the logic circuit 350 may include a NAND gate, and the second predetermined level may be a high level.

[0045] The switch control circuit 360 may disconnect the switch 30 connecting the battery terminal of the energy storage system and the inverter terminal of the energy storage system in response to the output signal S4 having the second predetermined level.

[0046] As described above, if an abnormality occurs in the voltage supplied by the inverter, the protection circuit 300 can detect the fault in the inverter and disconnect the switch 30 controlling the connection between the inverter and the battery of the energy storage system to prevent the fault in the inverter from affecting the energy storage system. In addition, the protection circuit can determine whether an abnormality exists in the difference between the positive inverter voltage and the negative inverter voltage, or in each of the positive inverter voltage and the negative inverter voltage, so that the energy storage system can be protected even when the three-phase inverter is connected to the energy storage system.

[0047] In some embodiments, since the inverter can output a high voltage, the protection circuit 300 may further include a voltage divider circuit 370, so that a lower voltage can be used in the protection circuit 300. The voltage divider circuit 370 may include a first voltage divider circuit and a second voltage divider circuit. The first voltage divider circuit divides the voltage at the positive inverter terminal INV+ to output a positive inverter voltage Vip, and the second voltage divider circuit divides the voltage at the negative inverter terminal INV- to output a negative inverter voltage Vin. The voltage divider circuit 370 may include, for example, a first voltage divider circuit including a plurality of resistors connected in series between the positive inverter terminal INV+ and the ground terminal GND, and a second voltage divider circuit including a plurality of resistors connected in series between the negative inverter terminal INV- and the ground terminal GND.

[0048] In some embodiments, the protection circuit 300 may further include a high-voltage buffer (or first buffer) 381 and a low-voltage buffer (or second buffer) 382. The high-voltage buffer 381 may store the positive inverter voltage Vip detected by the voltage divider circuit 370, and the low-voltage buffer 382 may store the negative inverter voltage Vin detected by the voltage divider circuit 370.

[0049] In some embodiments, the protection circuit 300 may further include a power management device 391 and / or a power management device 392. The power management device 391 may be connected to the positive battery terminal B+ and the negative battery terminal B- to generate a voltage used by the components of the protection circuit 300 based on the voltage of the battery. The power management device 392 may be connected to the positive inverter terminal INV+ and the negative inverter terminal INV- to generate a voltage used by the components of the protection circuit 300 based on the voltage supplied by the inverter. In some embodiments, the power management devices 391 and / or 392 may include a DC / DC converter.

[0050] Figure 4is a diagram illustrating an example of a protection circuit of an energy storage system according to some embodiments.

[0051] refer to Figure 4 , the protection circuit 400 may include an adder 410, comparators 420, 430, and 440, a logic circuit 450, and a switch control circuit 460. In some embodiments, the protection circuit 400 may further include a voltage divider circuit 470, a high-voltage buffer 481, and a low-voltage buffer 482. In some embodiments, the protection circuit 400 may further include a power management device 491 and / or 492. The adder 410, the comparators 420, 430, and 440, the logic circuit 450, the voltage divider circuit 470, the high-voltage buffer 481, the low-voltage buffer 482, and the power management devices 491 and 492 are connected to the reference Figure 3 The described adder 310 , comparators 320 , 330 , and 330 , logic circuit 350 , voltage dividing circuit 370 , high voltage buffer 381 , low voltage buffer 382 , and power management devices 391 and 392 operate identically or similarly, and thus their description is omitted.

[0052] The switch control circuit 460 may include a latch 461 and a driver 462. The latch 461 may output a control signal S5 having a second predetermined level in response to an output signal S4 having a second predetermined level from the logic circuit 450.

[0053] The switch 40 connecting the battery terminal of the energy storage system and the inverter terminal of the energy storage system may include a relay switch 41 and a relay coil 42 .

[0054] The relay switch 41 may be connected between the battery terminal and the inverter terminal. A relay coil 42 may be provided for driving the relay switch 41. A driver 462 may be connected between a power supply supplying a power supply voltage Vs and a first terminal of the relay coil 42, and a second terminal of the relay coil 42 may be connected to a terminal having a lower potential than the power supply voltage Vs, such as a ground terminal GND. For convenience, the terminal having a lower potential than the power supply voltage Vs is described as the ground terminal GND. The power supply supplying the power supply voltage Vs may be, for example, the power management device 491 and / or 492.

[0055] Driver 462 controls the electrical connection between a power source supplying supply voltage Vs and the first terminal of relay coil 42 and may include, for example, a switch such as a transistor. Such a driver 462 is referred to as a high-side driver (HSD). When a power source supplying supply voltage Vs is connected to the first terminal of relay coil 42 via driver 462, current flows through relay coil 42, generating a magnetic field that connects the contacts of relay switch 41, thereby closing switch 40. In response to a control signal S5 having a second predetermined level from latch 461, driver 462 disconnects the power source supplying supply voltage Vs from the first terminal of relay coil 42. This disconnects current flowing through relay coil 42, disconnecting the contacts of relay switch 41 and opening switch 40.

[0056] In some embodiments, a first terminal of the relay coil 42 may be connected to a power supply supplying a power supply voltage Vs, and a driver 462 may be connected between a second terminal of the relay coil 42 and a ground terminal. Such a driver 462 may be referred to as a low-side driver (LSD). In some embodiments, the driver 462 may include a driver connected between the first terminal of the relay coil 42 and the power supply supplying the power supply voltage Vs, and a driver connected between the second terminal of the relay coil 42 and a ground terminal.

[0057] As described above, if an abnormality occurs in the voltage supplied by the inverter, the protection circuit 400 can detect the fault in the inverter and disconnect the switch 40 controlling the connection between the inverter and the battery of the energy storage system to prevent the fault in the inverter from affecting the energy storage system. In addition, the protection circuit can determine whether an abnormality exists in the difference between the positive inverter voltage and the negative inverter voltage, or in each of the positive inverter voltage and the negative inverter voltage, so that the energy storage system can be protected even when a three-phase inverter is connected to the energy storage system.

[0058] Figure 5 is a flowchart illustrating an example of a protection method for an energy storage system according to some embodiments.

[0059] refer to Figure 5 When the energy storage system or inverter is powered on (S510), the protection circuit may be powered on (S520), and the switch controlling the connection between the battery of the energy storage system and the inverter may be closed (S530). In some embodiments, when the energy storage system is powered on, the power management device may use the voltage from the battery of the energy storage system to provide power to the protection circuit. In some embodiments, when the inverter is powered on, the power management device may use the voltage from the inverter to provide power to the protection circuit.

[0060] The protection circuit may determine whether the voltage of the inverter (i.e., the positive inverter voltage and the negative inverter voltage) meets diagnostic conditions (S540). In some embodiments, the diagnostic conditions may include a first diagnostic condition in which the difference between the positive inverter voltage and the negative inverter voltage is greater than a first reference voltage, a second diagnostic condition in which the positive inverter voltage is greater than a second reference voltage, and / or a third diagnostic condition in which the negative inverter voltage is greater than a third reference voltage. In some embodiments, the positive inverter voltage compared to the second reference voltage may be a positive inverter voltage relative to a ground of the energy storage system (e.g., a chassis ground). In some embodiments, the negative inverter voltage compared to the third reference voltage may be a negative inverter voltage relative to a ground of the energy storage system (e.g., a chassis ground).

[0061] If at least one of the first, second, and third diagnostic conditions is met (S540: Yes), the protection circuit may disconnect the switch (S550). In some embodiments, the protection circuit may disconnect the switch (S550) if the difference between the positive inverter voltage and the negative inverter voltage is greater than a first reference voltage, the positive inverter voltage is greater than a second reference voltage, or the negative inverter voltage is greater than a third reference voltage. If the diagnostic condition is not met (S540: No), the protection circuit may monitor the inverter voltage to determine whether the diagnostic condition is met.

[0062] In some embodiments, after the switch is turned off, the protection circuit may determine whether the voltage of the inverter satisfies a diagnostic release condition (S560). In some embodiments, the diagnostic release condition may include a condition that the difference between the positive inverter voltage and the negative inverter voltage is no greater than a first reference voltage, a condition that the positive inverter voltage is no greater than a second reference voltage, and a condition that the negative inverter voltage is no greater than a third reference voltage. In other words, if the difference between the positive inverter voltage and the negative inverter voltage is no greater than the first reference voltage, the positive inverter voltage is no greater than the second reference voltage, and the negative inverter voltage is no greater than the third reference voltage, the protection circuit may determine that the diagnostic release condition is satisfied (S560: Yes).

[0063] If the diagnostic release condition is satisfied (S560: Yes), the protection circuit may de-energize the energy storage system (S570) and then re-energize the energy storage system (S510) to close the switch. In some embodiments, if the diagnostic release condition is satisfied (S560: Yes), the protection circuit may de-energize the inverter (S570) and then re-energize the inverter (S510).

[0064] While the invention has been described in connection with what are presently considered to be practical embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. An energy storage system comprising: Battery; a first battery terminal and a second battery terminal connected to the battery; a first inverter terminal and a second inverter terminal connected to the inverter; a switch connected between the second battery terminal and the second inverter terminal; as well as A protection circuit is configured to determine whether to open the switch based on a difference between a first voltage detected at the first inverter terminal and a second voltage detected at the second inverter terminal, the first voltage, and the second voltage.

2. The energy storage system according to claim 1, wherein: The protection circuit is further configured to: determining a first diagnostic condition, a second diagnostic condition, and a third diagnostic condition, wherein in the first diagnostic condition the difference between the first voltage and the second voltage is greater than a first reference voltage, in the second diagnostic condition the first voltage is greater than a second reference voltage, and in the third diagnostic condition the second voltage is greater than a third reference voltage; as well as The switch is opened in response to at least one of the first diagnostic condition, the second diagnostic condition, and the third diagnostic condition being satisfied.

3. The energy storage system according to claim 2, wherein: The protection circuit is further configured to, after opening the switch, de-energize the energy storage system and then energize the energy storage system again in response to the difference between the first voltage and the second voltage being not greater than the first reference voltage, the first voltage being not greater than the second reference voltage, and the second voltage being not greater than the third reference voltage.

4. The energy storage system according to claim 1, wherein: The inverter is a three-phase inverter, and The first voltage is a voltage relative to a ground of the energy storage system, and the second voltage is a voltage relative to the ground of the energy storage system.

5. The energy storage system according to claim 1, wherein: The protection circuit comprises: an adder configured to calculate the difference between the first voltage and the second voltage; a first comparator configured to compare the difference between the first voltage and the second voltage with a first reference voltage; a second comparator configured to compare the first voltage with a second reference voltage; a third comparator configured to compare the second voltage with a third reference voltage; a logic circuit configured to perform a logic operation on a first output signal of the first comparator, a second output signal of the second comparator, and a third output signal of the third comparison circuit; and A switch control circuit is configured to control the switch based on a fourth output signal of the logic circuit.

6. The energy storage system according to claim 5, wherein: The switch comprises: a relay switch connected between the second battery terminal and the second inverter terminal; and a relay coil configured to drive the relay switch, and Wherein, the switch control circuit includes: a latch configured to output a control signal in response to the fourth output signal; and A driver is connected to terminals of the relay coil and is configured to disconnect the relay coil from a power source in response to a predetermined level of the control signal.

7. The energy storage system according to claim 5, wherein: The first comparator is further configured to output the first output signal having a first predetermined level in response to the difference between the first voltage and the second voltage being greater than the first reference voltage, The second comparator is further configured to output the second output signal having the first predetermined level in response to the first voltage being greater than the second reference voltage. The third comparator is further configured to output the third output signal having the first predetermined level in response to the second voltage being greater than the third reference voltage. wherein the logic circuit is further configured to output the fourth output signal having a second predetermined level in response to at least one of the first output signal having the first predetermined level, the second output signal, and the third output signal; and The switch control circuit is further configured to turn off the switch in response to the second predetermined level of the fourth output signal.

8. The energy storage system according to claim 5, wherein: The protection circuit further includes a voltage dividing circuit configured to divide the voltage at the first inverter terminal to output the first voltage, and to divide the voltage at the second inverter terminal to output the second voltage.

9. A protection device for an energy storage system, the energy storage system comprising a battery and a switch, the switch being configured to be connected between the battery and an inverter, the protection device comprising: a voltage dividing circuit configured to divide a voltage at a first inverter terminal connected to a first terminal of the inverter to output a first voltage, and to divide a voltage at a second inverter terminal connected to a second terminal of the inverter to output a second voltage; an adder configured to calculate a difference between the first voltage and the second voltage; a first comparator configured to compare the difference between the first voltage and the second voltage with a first reference voltage; a second comparator configured to compare the first voltage with a second reference voltage; a third comparator configured to compare the second voltage with a third reference voltage; a logic circuit configured to perform a logic operation on a first output signal of the first comparator, a second output signal of the second comparator, and a third output signal of the third comparator; as well as A switch control circuit is configured to control the switch based on a fourth output signal of the logic circuit.

10. The protection device according to claim 9, wherein: The first comparator is further configured to output the first output signal having a first predetermined level in response to the difference between the first voltage and the second voltage being greater than the first reference voltage; wherein the second comparator is further configured to output the second output signal having the first predetermined level in response to the first voltage being greater than the second reference voltage; wherein the third comparator is further configured to output the third output signal having the first predetermined level in response to the second voltage being greater than the third reference voltage; wherein the logic circuit is further configured to output the fourth output signal having a second predetermined level in response to at least one of the first output signal having the first predetermined level, the second output signal, and the third output signal; and The switch control circuit is further configured to turn off the switch in response to the second predetermined level of the fourth output signal.

11. The protection device according to claim 9, wherein: The logic circuit is further configured to output the fourth output signal having a predetermined level in response to the first output signal indicating that the difference between the first voltage and the second voltage is greater than the first reference voltage, the second output signal indicating that the first voltage is greater than the second reference voltage, or the third output signal indicating that the second voltage is greater than the third reference voltage, and The switch control circuit is further configured to turn off the switch in response to the predetermined level of the fourth output signal.

12. The protection device according to claim 9, further comprising: a first buffer configured to store the first voltage; as well as A second buffer is configured to store the second voltage.

13. The protection device according to claim 9, wherein: The inverter is a three-phase inverter, and The first voltage is a voltage relative to a ground of the energy storage system, and the second voltage is a voltage relative to the ground of the energy storage system.

14. A method for protecting an energy storage system, the energy storage system comprising a battery and a switch, the switch being configured to control a connection between the battery and an inverter, the method comprising: detecting a voltage at a first inverter terminal connected to a first terminal of the inverter to output a first voltage; detecting a voltage at a second inverter terminal connected to a second terminal of the inverter to output a second voltage; comparing a difference between the first voltage and the second voltage with a first reference voltage; comparing the first voltage with a second reference voltage; comparing the second voltage with a third reference voltage; as well as The switch is opened in response to the difference between the first voltage and the second voltage being greater than the first reference voltage, the first voltage being greater than the second reference voltage, or the second voltage being greater than the third reference voltage.

15. The method according to claim 14, further comprising: After opening the switch, in response to the difference between the first voltage and the second voltage being not greater than the first reference voltage, the first voltage being not greater than the second reference voltage, and the second voltage being not greater than the third reference voltage, the energy storage system is powered off and then powered on again.

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