Energy storage system and its protection device and protection method

Abstract

The energy storage system includes a battery, first and second battery terminals to which the battery is connected, first and second inverter terminals to which an inverter is connected, a switch connected between the second battery terminal and the second inverter terminal, and a protection circuit that determines 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, and the first and second voltages.

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0163660, dated November 22, 2023, and all contents disclosed in the documents of this Korean Patent Application are incorporated herein by reference.

[0002] The disclosed subject matter relates to an energy storage system and a protection device and method thereof. [Background technology]

[0003] Energy storage systems (ESS), which store and provide electricity, are used in a variety of fields. For example, energy storage systems can be used to store surplus electricity from power plants and provide electricity during temporary power shortages. Compact energy storage systems can also be used to prepare for power outages or reduce peak power demand in buildings, factories, and homes. Energy storage systems can also be used to store electricity generated using renewable energy and use the stored electricity when it is needed.

[0004] Inverters are used to store power in energy storage systems and supply power from the energy storage systems to loads. Recently, power generation systems that use high voltage, such as solar power generation, have come to be connected to inverters. If a fault occurs in the inverter, high voltage will be supplied to the energy storage system, which may destroy the energy storage system. Summary of the Invention [Problem to be solved by the invention]

[0005] Some embodiments may provide an energy storage system and a protection device and method thereof that can protect the energy storage system in the event of an inverter failure. [Means for solving the problem]

[0006] In one embodiment, the energy storage system may include a battery, first and second battery terminals to which the battery is connected, first and second inverter terminals to which an inverter is connected, a switch connected between the second battery terminal and the second inverter terminal, and a protection circuit that determines 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, and the first and second voltages.

[0007] In one embodiment, a protection device for an energy storage system including a battery and a switch controlling a connection between the battery and an inverter may include a voltage divider circuit that divides a voltage at a first inverter terminal connected to a first terminal of the inverter to output a first voltage and divides a voltage at a second inverter terminal connected to a second terminal of the inverter to output a second voltage, an adder that calculates a difference between the first voltage and the second voltage, a first comparator that compares the difference between the first voltage and the second voltage with a first reference voltage, a second comparator that compares the first voltage with a second reference voltage, a third comparator that compares the second voltage with a third reference voltage, a logic circuit that performs a logical 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 that controls the switch based on a fourth output signal of the logic circuit.

[0008] In one embodiment, a method for protecting an energy storage system including a battery and a switch controlling a connection between the battery and an inverter may include the steps of detecting a voltage at a first inverter terminal connected to a first terminal of the inverter and outputting a first voltage, detecting a voltage at a second inverter terminal connected to a second terminal of the inverter and outputting 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 opening the switch if the difference between the first voltage and the second voltage is greater than the first reference voltage, or if the first voltage is greater than the second reference voltage, or if the second voltage is greater than the third reference voltage. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of a power supply system according to an embodiment. [Figure 2] 1 is a diagram illustrating an example of an energy storage system according to an embodiment. [Figure 3] 1 is a diagram illustrating an example of a protection circuit of an energy storage system according to an embodiment. [Figure 4] 10 is a diagram illustrating an example of a protection circuit of an energy storage system according to another embodiment. [Figure 5] 1 is a flowchart illustrating an example of a method for protecting an energy storage system, according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not relevant to the description will be omitted, and similar parts will be designated by similar reference numerals throughout the specification.

[0011] When a component is said to be "connected" to another component, it should be understood that there may be other components between them, although there may be direct connections between them. On the other hand, when a component is said to be "directly connected" to another component, it should be understood that there are no other components between them.

[0012] In the following description, expressions in the singular may be construed as singular or plural unless expressly stated otherwise, such as "one" or "single."

[0013] In the flowcharts described with reference to the figures, the order of operations may be changed, operations may be combined, certain operations may be split, or certain operations may not be performed.

[0014] FIG. 1 is a diagram illustrating an example of a power supply system according to an embodiment.

[0015] Referring to FIG. 1 , the power supply system may include a power generation device 110 , an energy storage system (or energy storage device) 120 , an inverter 130 , a grid 140 , and a load 150 .

[0016] The power generation device 110 can generate electrical energy. The power generation device 110 can be, for example, but is 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, the power generation device 110 can include a solar cell array that converts solar energy into electrical energy. The solar cell array includes multiple solar cell modules, and the solar cell module can convert solar energy into electrical energy and generate a predetermined voltage and current by connecting multiple solar cells in series or in parallel.

[0017] The energy storage system 120 can store electrical energy supplied from the power generation device 110 and discharge the stored electrical energy to supply to the grid 140 or the load 150. For example, when the grid 140 or the load 150 is lightly loaded, the energy storage system 120 can be charged by receiving idle power from the power generation device 110. When the grid 140 or the load 150 is overloaded, the energy storage system 120 can discharge the stored power to supply power to the grid 140 or the load 150.

[0018] The inverter 130 can convert DC power to AC power. The inverter 130 can convert the DC power supplied by the power generation device 110 or the DC power supplied by the energy storage system 120 into AC power. In one embodiment, the inverter 130 may be a three-phase inverter. In one embodiment, when the power generation device 110 uses a high voltage, the inverter 130 can include an inverter 131 that converts the DC power to AC power and a DC / DC converter 132 that converts the DC power supplied by the power generation device 110 into DC power. The energy storage system 120 can charge the DC power supplied from the DC / DC converter 132. The inverter 131 can convert the DC power supplied from the energy storage system 120 or the DC power supplied from the DC / DC converter 132 into AC power to supply to the grid 140 or the load 150.

[0019] The grid 140 may be an electric power network including connected power plants, substations, transmission and distribution stations, etc. The loads 150 may be devices that consume electric power.

[0020] The energy storage system 120 may include a protection circuit (or protection device) 121 that detects a fault in the inverter 130 and protects the energy storage system 120 in the event of a fault in the inverter 130. In one embodiment, the protection circuit 121 may interrupt the electrical connection between the energy storage system 120 and the inverter 130.

[0021] FIG. 2 is a diagram illustrating an example of an energy storage system according to an embodiment.

[0022] 2, energy storage system 200 may include a battery 210, a switch 220, and a protection circuit 230. In some embodiments, protection circuit 230 may be included in a battery management system or a battery management system of energy storage system 200.

[0023] Battery 210 may be a secondary battery. Battery 210 may be, for example, a lithium battery, such as a lithium-ion battery or a lithium-ion polymer battery, or a nickel battery, such as a nickel-cadmium (NiCd) battery or a nickel-metal hydride (NiMH) battery. In some embodiments, battery 210 may include an assembly of multiple battery cells, a battery module in which multiple assemblies are connected in series or parallel, a battery pack (or battery rack) in which multiple battery modules are connected in series or parallel, or multiple battery packs connected in series or parallel.

[0024] 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 a first battery terminal, and the other may be a second battery terminal. In one embodiment, the positive battery terminal (B+) and the negative battery terminal (B-) may be a positive battery socket (B+) and a negative battery socket (B-), respectively. The positive inverter terminal (INV+) of the energy storage system 200 may be connected to the positive terminal of the inverter (e.g., 130 in FIG. 1 ), and the negative inverter terminal (INV-) of the energy storage system 200 may be connected to the negative terminal of the inverter 130. One of the positive inverter terminal (INV+) and the negative inverter terminal (INV-) may be a first inverter terminal, and the other may be a second inverter terminal. Also, one of the positive terminal and the negative terminal of the inverter may be a first terminal, and the other may be a second terminal. The positive inverter terminal (INV+) and the negative inverter terminal (INV-) may be a positive inverter socket (INV+) and a negative inverter socket (INV-), respectively.

[0025] In some embodiments, the positive and negative terminals of inverter 130 may be the positive and negative outputs, respectively, of DC / DC converter 132 of inverter 130. In some embodiments, the positive and negative terminals of inverter 130 may be the positive and negative inputs, respectively, of inverter 131.

[0026] The switch 220 may be connected between the battery terminal of the energy storage system 200 and the inverter terminal of the energy storage system 200. In one embodiment, as shown in FIG. 2, the switch 220 may be connected between the negative battery terminal (B-) and the negative inverter terminal (INV-). In one embodiment, the switch 220 may be connected between the positive battery terminal (B+) and the positive inverter terminal (INV+). In one embodiment, the switch 220 may 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 one embodiment, the switch 220 may be a conductor formed into a relay.

[0027] The ground of the energy storage system 200 can be connected to the ground terminal (GND). The ground terminal (GND) can be a ground socket (GND). In one embodiment, the ground terminal (GND) can be connected to the chassis ground of the energy storage system 200.

[0028] The protection circuit 230 receives the voltage at the positive inverter terminal (INV+) and the voltage at the negative inverter terminal (INV-), diagnoses whether or not there is 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 can open the switch 220 if there is a fault in the inverter 130. For example, if a voltage higher than the voltage actually provided by the inverter 130 (e.g., the DC / DC converter 132 in FIG. 1) is 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 can open the switch 220. Alternatively, if a short circuit occurs in the line connecting the inverter 130 and the grid 140, the protection circuit 230 can diagnose a fault (short circuit) in the inverter 130 based on the voltage at the positive inverter terminal (INV+) and the voltage at the negative inverter terminal (INV-) and can open the switch 220.

[0029] In some embodiments, a fuse 240 may be connected between the positive battery terminal (B+) and the positive inverter terminal (INV+). In some embodiments, a fuse 250 may be connected between the negative battery terminal (B-) and the negative inverter terminal (INV-).

[0030] FIG. 3 is a diagram illustrating an example of a protection circuit of an energy storage system according to an embodiment.

[0031] Referring to FIG. 3 , the protection circuit 300 is connected to the positive inverter terminal (INV+) and the negative inverter terminal (INV−) of the energy storage system, and may include a summer 310, comparators 320, 330, 340, a logic circuit 350, and a switch control circuit 360.

[0032] The adder 310 can calculate the difference (Vip-Vin) between the voltage (Vip) detected at the positive inverter terminal (INV+) (referred to as the "positive inverter voltage") and the voltage (Vin) detected at the negative inverter terminal (INV-) (referred to as the "negative inverter voltage") The adder 310 may also be referred to as a subtractor.

[0033] 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). 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 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 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). If the difference (Vip-Vin) between the positive inverter voltage (Vip) and the negative inverter voltage (Vin) is greater than the reference voltage (Vref1) due to the setting of the reference voltage (Vref1), this can be interpreted as the difference (Vip-Vin) between the positive inverter voltage (Vip) and the negative inverter voltage (Vin) being greater than or equal to the reference voltage (Vref1).

[0034] 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 the positive inverter voltage (Vip) relative to a ground terminal (e.g., GND in FIG. 2). That is, the comparator 330 may compare a voltage obtained by subtracting the voltage of the ground terminal (GND) from the positive inverter voltage (Vip) with the reference voltage (Vref2). The comparator 330 may output an output signal (or second output signal) (S2) having a first predetermined level when the positive inverter voltage (Vip) (e.g., a voltage obtained by subtracting the voltage of the ground terminal (GND) from the positive inverter voltage (Vip)) is 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 when the positive inverter voltage Vip is not greater than the reference voltage Vref2. Depending on the setting of the reference voltage Vref2, when the positive inverter voltage Vip is greater than the reference voltage Vref2, this may be interpreted as the positive inverter voltage Vip being equal to or greater than the reference voltage Vref2.

[0035] The comparator 340 may compare the negative inverter voltage (Vin) with a reference voltage (or third reference voltage) (Vref3). In some embodiments, since a three-phase inverter may be used, the negative inverter voltage (Vip) compared by the comparator 340 may be the negative inverter voltage (Vin) relative to the ground terminal (GND). That is, the comparator 340 may compare the reference voltage (Vref3) with a voltage obtained by subtracting the voltage of the ground terminal (GND) from the negative inverter voltage (Vin). The comparator 340 may output an output signal (or third output signal) (S3) having a first predetermined level if the negative inverter voltage (Vip) (e.g., the voltage obtained by subtracting the voltage of the ground terminal (GND) from the negative inverter voltage (Vin)) is greater than the reference voltage (Vref3). In this case, the magnitudes of the negative inverter voltage (Vip) and the reference voltage (Vref3) may be the absolute values ​​of the negative inverter voltage (Vip) and the reference voltage (Vref3), respectively. The comparator 340 may output an output signal S3 having a second level different from the first predetermined level when the negative inverter voltage Vin is not greater than the reference voltage Vref3. Depending on the setting of the reference voltage Vref2, when the positive inverter voltage Vip is greater than the reference voltage Vref2, this may be interpreted as the positive inverter voltage Vip being equal to or greater than the reference voltage Vref2.

[0036] The logic circuit 350 can output an output signal (S4) based on the output signals (S1, S2, S3) output from the comparators 320, 330, and 340. The logic circuit 350 can output an output signal (S4) by performing a logical operation on the output signals (S1, S2, S3) output from the comparators 320, 330, and 340. The logic circuit 350 can output a control signal having a second predetermined level (or a third level) when at least one of the output signals (S1, S2, S3) output from the comparators 320, 330, and 340 has a first predetermined level. The logic circuit 350 can output a control signal having a fourth level different from the second predetermined level when the output signals (S1, S2, S3) output from the comparators 320, 330, and 340 have a second level.

[0037] In one embodiment, when the first predetermined level is a high logic level, logic circuit 350 may include a logical sum (OR) gate and the second predetermined level may be a high level. In one embodiment, when the first predetermined level is a high logic level, logic circuit 350 may include a logical negative sum (NOR) gate and the second predetermined level may be a low level. In one embodiment, when the first predetermined level is a low logic level, logic circuit 350 may include a logical negative sum (AND) gate and the second predetermined level may be a low level. In one embodiment, when the first predetermined level is a low logic level, logic circuit 350 may include a logical negative sum (NAND) gate and the second predetermined level may be a high level.

[0038] The switch control circuit 360 can open 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) of the second predetermined level.

[0039] In this way, if an abnormality occurs in the voltage supplied from the inverter, the protection circuit 300 detects the inverter failure and opens the switch 30 that controls the connection between the battery of the energy storage system and the inverter, thereby preventing the inverter failure from affecting the energy storage system. In addition, the protection circuit determines whether there is an abnormality in the difference between the positive inverter voltage and the negative inverter voltage, and in each of the positive inverter voltage and the negative inverter voltage, so that the energy storage system can be protected even if a three-phase inverter is connected to the energy storage system.

[0040] In one embodiment, since the inverter can output a high voltage, the protection circuit 300 can further include a voltage divider circuit 370 so that the protection circuit 300 can use a lower voltage. The voltage divider circuit 370 can include a first voltage divider circuit that divides the voltage at the positive inverter terminal (INV+) and outputs a positive inverter voltage (Vip), and a second voltage divider circuit that divides the voltage at the negative inverter terminal (INV-) and outputs a negative inverter voltage (Vin). The voltage divider circuit 370 can include, for example, a first voltage divider circuit including a plurality of resistors connected in series between the positive inverter terminal (INV+) and a ground terminal (GND), and a second voltage divider circuit including a plurality of resistors connected in series between the negative inverter terminal (INV-) and a ground terminal (GND).

[0041] In one embodiment, the protection circuit 300 may 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.

[0042] In one embodiment, the protection circuit 300 may further include a power management device 391 and / or a power management device 392. The power management device 391 is connected to the positive battery terminal (B+) and the negative battery terminal (B-) and can generate a voltage used by the components of the protection circuit 300 based on the battery voltage. The power management device 391 is connected to the positive inverter terminal (INV+) and the negative inverter terminal (INV-) and can generate a voltage used by the components of the protection circuit 300 based on the voltage supplied from the inverter. In one embodiment, the power management devices 391 and 392 may include a DC / DC converter.

[0043] FIG. 4 is a diagram illustrating an example of a protection circuit of an energy storage system according to an embodiment.

[0044] 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 power management units 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 units 491 and 492 operate in the same manner as or similarly to the adder 310, the comparators 320, 330, and 330, the logic circuit 350, the voltage divider circuit 370, the high-voltage buffer 381, the low-voltage buffer 382, ​​and the power management units 391 and 392 described with reference to FIG. 3, and therefore, description thereof will be omitted.

[0045] The switch control circuit 460 may include a latch 461 and a driver 462. The latch 461 may output a control signal (S5) of a second predetermined level in response to an output signal (S4) having a second predetermined level from the logic circuit 450.

[0046] The switch 40 connecting the battery terminals of the energy storage system and the inverter terminals of the energy storage system may include a relay switch 41 and a relay coil 42 .

[0047] The relay switch 41 may be connected between a battery terminal and an inverter terminal. A relay coil 42 may be provided to drive the relay switch 41. A driver 462 may be connected between a power source that supplies a 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 potential lower than the supply voltage (Vs) (e.g., a ground terminal (GND)). For convenience of explanation, the terminal having a potential lower than the supply voltage (Vs) will be described as the ground terminal (GND). The power source that supplies the supply voltage (Vs) may be, for example, a power management device 491 and / or 492.

[0048] The driver 462 controls the electrical connection between the power supply that supplies the supply voltage (Vs) and the first terminal of the relay coil 42 and may be implemented as a switch, such as a transistor. The driver 462 may be a high-side driver (HSD). When the driver 462 connects the power supply that supplies the supply voltage (Vs) and the first terminal of the relay coil 42, a current flows through the relay coil 42, generating a magnetic field. The magnetic field connects the contacts of the relay switch 41, thereby closing the switch 40. The driver 462 electrically disconnects the power supply that supplies the supply voltage (Vs) from the first terminal of the relay coil 42 in response to a control signal (S5) having a second predetermined level from the latch 461. This interrupts the current flowing through the relay coil 42, disconnects the contacts of the relay switch 41, and opens the switch 40.

[0049] In one embodiment, a first terminal of the relay coil 42 may be connected to a power source that provides a supply voltage (Vs), and the driver 462 may be connected between a second terminal of the relay coil 42 and ground. Such a driver 462 may be a low-side driver (LSD). In one embodiment, the driver 462 may include a driver connected between the first terminal of the relay coil 42 and the power source that provides the supply voltage (Vs) and a driver connected between the second terminal of the relay coil 42 and ground.

[0050] In this way, if an abnormality occurs in the voltage supplied from the inverter, the protection circuit 300 detects the inverter failure and opens the switch 30 that controls the connection between the battery of the energy storage system and the inverter, thereby preventing the inverter failure from affecting the energy storage system. In addition, the protection circuit determines whether there is an abnormality in the difference between the positive inverter voltage and the negative inverter voltage, and in each of the positive inverter voltage and the negative inverter voltage, so that the energy storage system can be protected even if a three-phase inverter is connected to the energy storage system.

[0051] FIG. 5 is a flowchart illustrating an example method for protecting an energy storage system according to an embodiment.

[0052] 5, when the energy storage system or the inverter is powered on (S510), the protection circuit is powered on (S520), and a switch controlling the connection between the battery of the energy storage system and the inverter is closed (S530). In one embodiment, when the energy storage system is powered on, the power management device can provide power to the protection circuit using the voltage of the battery of the energy storage system. In another embodiment, when the inverter is powered on, the power management device can provide power to the protection circuit using the voltage of the inverter.

[0053] The protection circuit may determine whether the inverter voltages (i.e., the positive inverter voltage and the negative inverter voltage) satisfy a diagnostic condition (S540). In one embodiment, the diagnostic condition may include a first diagnostic condition in which a 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 one embodiment, the positive inverter voltage compared to the second reference voltage may be the positive inverter voltage relative to a ground (e.g., chassis ground) of the energy storage system. In one embodiment, the negative inverter voltage compared to the third reference voltage may be the negative inverter voltage relative to a ground (e.g., chassis ground) of the energy storage system.

[0054] If at least one of the first diagnostic condition, the second diagnostic condition, and the third diagnostic condition is met (S540: Yes), the protection circuit can open the switch (S550). In one embodiment, if the difference between the positive inverter voltage and the negative inverter voltage is greater than a first reference voltage, if the positive inverter voltage is greater than a second reference voltage, or if the negative inverter voltage is greater than a third reference voltage, the protection circuit can open the switch (S550). If the diagnostic conditions are not met (S540: No), the protection circuit can monitor the inverter voltage to determine whether the diagnostic conditions are met.

[0055] In one embodiment, after opening the switch, the protection circuit may determine whether the inverter voltage satisfies a diagnosis termination condition (S560). In one embodiment, the diagnosis termination condition may include a condition that the difference between the positive inverter voltage and the negative inverter voltage is not greater than a first reference voltage, a condition that the positive inverter voltage is not greater than a second reference voltage, and a condition that the negative inverter voltage is not greater than a third reference voltage. That is, if the difference between the positive inverter voltage and the negative inverter voltage is not greater than the first reference voltage, the positive inverter voltage is not greater than the second reference voltage, and the negative inverter voltage is not greater than the third reference voltage, the protection circuit may determine that the diagnosis termination condition is satisfied (S560: YES).

[0056] If the diagnostic release condition is met (S560: YES), the protection circuit may turn off the power to the energy storage system (S570) to close the switch, and then turn on the power to the energy storage system again (S510). In one embodiment, if the diagnostic release condition is met (S560: YES), the protection circuit may turn off the power to the inverter (S570), and then turn on the power to the inverter again (S510).

[0057] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these examples, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the claims below also fall within the scope of the present invention.

Claims

1. battery, a first battery terminal and a second battery terminal to which the battery is connected; a first inverter terminal and a second inverter terminal to which an inverter is connected; a switch connected between the second battery terminal and the second inverter terminal; a protection circuit that determines 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; an energy storage system including:

2. 2. The energy storage system of claim 1, wherein the protection circuit determines a first diagnostic condition in which a difference between the first voltage and the second voltage is greater than a first reference voltage, a second diagnostic condition in which the first voltage is greater than a second reference voltage, and a third diagnostic condition in which the second voltage is greater than a third reference voltage, and opens the switch when at least one of the first diagnostic condition, the second diagnostic condition, and the third diagnostic condition is satisfied.

3. 3. The energy storage system of claim 2, wherein the protection circuit turns on the power of the energy storage system after turning it off if, after the switch is opened, a difference between the first voltage and the second voltage is not greater than the first reference voltage, the first voltage is not greater than the second reference voltage, and the second voltage is not greater than the third reference voltage.

4. the inverter is a three-phase inverter, 2. The energy storage system of claim 1, wherein the first voltage is a voltage relative to a ground of the energy storage system and the second voltage is a voltage relative to a ground of the energy storage system.

5. The protection circuit includes: an adder that calculates the difference between the first voltage and the second voltage; a first comparator that compares a difference between the first voltage and the second voltage with a first reference voltage; a second comparator that compares the first voltage with a second reference voltage; a third comparator that compares the second voltage with a third reference voltage; a logic circuit that performs a logical 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; a switch control circuit that controls the switch based on a fourth output signal of the logic circuit; 10. The energy storage system of claim 1, comprising:

6. The switch is a relay switch connected between the second battery terminal and the second inverter terminal; and a relay coil for driving the relay switch; The switch control circuit a latch that outputs a control signal in response to the fourth output signal; a driver connected to a terminal of the relay coil for interrupting a connection between the relay coil and a power source in response to a predetermined level of the control signal; 6. The energy storage system of claim 5, comprising:

7. the first comparator outputs the first output signal having a first predetermined level when a difference between the first voltage and the second voltage is greater than the first reference voltage; the second comparator outputs the second output signal having the first predetermined level when the first voltage is greater than the second reference voltage; the third comparator outputs the third output signal having the first predetermined level when the second voltage is greater than the third reference voltage; the logic circuit outputs the fourth output signal having a second predetermined level when at least one of the first output signal, the second output signal, and the third output signal has the first predetermined level; 6. The energy storage system of claim 5, wherein the switch control circuit opens the switch in response to the second predetermined level of the fourth output signal.

8. 6. The energy storage system of claim 5, wherein the protection circuit further comprises a voltage divider circuit that divides a voltage at a terminal of the first inverter to output the first voltage and divides a voltage at a terminal of the second inverter to output the second voltage.

9. 1. A protection device for an energy storage system including a battery and a switch controlling a connection between the battery and an inverter, a voltage divider circuit that divides a voltage at a first inverter terminal connected to a first terminal of the inverter to output a first voltage, and that divides a voltage at a second inverter terminal connected to a second terminal of the inverter to output a second voltage; an adder that calculates the difference between the first voltage and the second voltage; a first comparator that compares a difference between the first voltage and the second voltage with a first reference voltage; a second comparator that compares the first voltage with a second reference voltage; a third comparator that compares the second voltage with a third reference voltage; a logic circuit that performs a logical 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; a switch control circuit that controls the switch based on a fourth output signal of the logic circuit; Protective devices including:

10. the first comparator outputs the first output signal having a first predetermined level when a difference between the first voltage and the second voltage is greater than the first reference voltage; the second comparator outputs the second output signal having the first predetermined level when the first voltage is greater than the second reference voltage; the third comparator outputs the third output signal having the first predetermined level when the second voltage is greater than the third reference voltage; the logic circuit outputs the fourth output signal having a second predetermined level when at least one of the first output signal, the second output signal, and the third output signal has the first predetermined level; 10. The protection device of claim 9, wherein the switch control circuit opens the switch in response to the second predetermined level of the fourth output signal.

11. the logic circuit outputs the fourth output signal having a predetermined level when the first output signal indicates that a difference between the first voltage and the second voltage is greater than the first reference voltage, or when the second output signal indicates that the first voltage is greater than the second reference voltage, or when the third output signal indicates that the second voltage is greater than the third reference voltage; The switch control circuit opens the switch in response to the predetermined level of the fourth output signal.

10. The protection device of claim 9.

12. a first buffer for storing the first voltage; a second buffer for storing the second voltage; 10. The protection device of claim 9, comprising:

13. the inverter is a three-phase inverter, 10. The protection device of claim 9, wherein the first voltage is a voltage relative to a ground of the energy storage system and the second voltage is a voltage relative to a ground of the energy storage system.

14. 1. A method for protecting an energy storage system including a battery and a switch controlling a connection between the battery and an inverter, comprising: detecting a voltage at a first inverter terminal connected to a first terminal of the inverter and outputting a first voltage; detecting a voltage at a second inverter terminal connected to a second terminal of the inverter and outputting 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; opening the switch when a difference between the first voltage and the second voltage is greater than the first reference voltage, or when the first voltage is greater than the second reference voltage, or when the second voltage is greater than the third reference voltage; Protection methods including:

15. 15. The protection method of claim 14, further comprising: if, after the switch is opened, a difference between the first voltage and the second voltage is not greater than the first reference voltage, the first voltage is not greater than the second reference voltage, and the second voltage is not greater than the third reference voltage, then powering the energy storage system off and then on again.

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