Energy storage system and photovoltaic system

Abstract

Provided in the present application are an energy storage system and a photovoltaic system. The energy storage system comprises an energy storage unit and a power conversion system, a positive electrode end of the energy storage unit being used for connecting to a positive electrode end of the power conversion system by means of a first protection unit, and a negative electrode end of the energy storage unit being used for connecting to a negative electrode end of the power conversion system by means of a second protection unit. The second protection unit comprises a switch unit and a reverse polarity protection unit which are connected in parallel. The switch unit is closed during charging or discharging of the energy storage unit, so as to enable electrical connection between the energy storage unit and power conversion system. When the switch unit is off, the reverse polarity protection unit is used for unidirectionally conducting a current flowing from the negative electrode end of the power conversion system to the negative electrode end of the energy storage unit. When the power conversion system is short-circuited, the first protection unit is off, and, when the energy storage unit is short-circuited, the switch unit is off. The energy storage system provided by the present application can, when the power conversion system or the energy storage unit has had a short-circuit fault, isolate the short-circuit fault in a timely manner, thereby preventing fault propagation.

Description

Energy storage system and photovoltaic system

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on December 13, 2023, with application number 202311725487.5 and application name "A Energy Storage System and Photovoltaic System", the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of fault protection, and in particular to an energy storage system and a photovoltaic system. Background Art

[0004] Energy storage systems are widely used in various scenarios, including industrial and commercial applications, power stations, residential applications, and charging stations. The power conversion system (PCS) in an energy storage system primarily converts DC to AC power, controlling the charging and discharging of batteries. An energy storage system typically has multiple PCSs configured to simultaneously convert power. A PCS failure or a failure in the battery pack connected to the PCS can affect the normal operation of other PCSs in the energy storage system, thereby affecting the efficiency of the energy storage system.

[0005] Summary of the Invention

[0006] The present application provides an energy storage system and a photovoltaic system, which can promptly cut off the short-circuit fault when a short-circuit fault occurs in an energy storage converter or an energy storage unit, thereby preventing the fault from spreading.

[0007] In a first aspect, the present application provides an energy storage system, which includes an energy storage unit and an energy storage converter. The energy storage unit includes multiple battery packs. The energy storage unit is used to output discharge power to a power grid or a load through the energy storage converter, or to receive charging power input from a photovoltaic system or a power grid through the energy storage converter. The positive terminal of the energy storage unit is used to be connected to the positive terminal of the energy storage converter through a first protection unit, and the negative terminal of the energy storage unit is used to be connected to the negative terminal of the energy storage converter through a second protection unit. The second protection unit includes a switch unit and an anti-reverse unit connected in parallel. The switch unit is used to close when the energy storage unit is charging or discharging to make the electrical connection between the energy storage unit and the energy storage converter conductive. The anti-reverse unit is used to unidirectionally conduct current from the negative terminal of the energy storage converter to the negative terminal of the energy storage unit when the switch unit is disconnected. When the energy storage converter is short-circuited, the first protection unit is disconnected. When the energy storage unit is short-circuited, the switch unit is disconnected.

[0008] When the positive and negative terminals of the energy storage unit and the energy storage converter in the energy storage system are reversed, the anti-reverse current unit can prevent current from damaging the switching devices in the energy storage converter. Furthermore, if the energy storage converter short-circuits, the first protection unit can be disconnected to disconnect the positive terminal of the energy storage unit from the positive terminal of the energy storage converter, thereby protecting the energy storage unit. If the energy storage converter short-circuits, the switch unit can be disconnected to disconnect the negative terminal of the energy storage unit from the negative terminal of the energy storage converter, thereby protecting the energy storage converter.

[0009] As a possible implementation, when the energy storage converter is short-circuited, the switch unit is disconnected, and when the energy storage unit is short-circuited, the first protection unit is disconnected. When the energy storage converter is short-circuited, disconnecting the switch unit can disconnect the negative terminal of the energy storage converter from the negative terminal of the energy storage converter, thereby protecting the energy storage converter. When the energy storage converter is short-circuited, disconnecting the first protection unit can disconnect the positive terminal of the energy storage converter from the positive terminal of the energy storage converter, thereby protecting the energy storage converter.

[0010] As a possible implementation, a short circuit of the energy storage converter occurs when the voltage between the positive terminal and the negative terminal of the energy storage converter is less than a first voltage threshold, and the current flowing through the first protection unit is greater than a first current threshold. By detecting the voltage across the energy storage converter and the current between the energy storage converter and the energy storage unit, it can be determined whether the energy storage converter has a short circuit.

[0011] As a possible implementation, a short circuit in the energy storage converter occurs when the current flowing through the first protection unit is greater than a first current threshold, and the current flows from the positive terminal of the energy storage unit to the negative terminal of the energy storage unit. Because the short-circuit current flows unidirectionally when the energy storage converter is short-circuited, detecting the magnitude and direction of the current between the energy storage converter and the energy storage unit can determine whether the energy storage converter has a short circuit.

[0012] As one possible implementation, a short circuit in the energy storage unit occurs when the voltage between the positive terminal and the negative terminal of the energy storage unit is less than a second voltage threshold, and the current flowing through the second protection unit is greater than a second current threshold. By detecting the voltage across the energy storage unit and the current between the energy storage converter and the energy storage unit, it is possible to determine whether the energy storage unit has a short circuit.

[0013] As one possible implementation, a short circuit in the energy storage unit occurs when the current flowing through the second protection unit is greater than a second current threshold, and the current flows from the positive terminal of the energy storage converter to the negative terminal of the energy storage converter. Since the short-circuit current flows unidirectionally when the energy storage unit is short-circuited, detecting the magnitude and direction of the current between the energy storage converter and the energy storage unit can determine whether the energy storage converter has a short circuit.

[0014] As a possible implementation, the first protection unit is an exploding fuse, which is designed to disconnect when the temperature exceeds a temperature safety threshold. This serves as a last-ditch protection measure. If the current between the energy storage unit and the energy storage converter is excessive or the temperature exceeds a temperature safety threshold, and the fault remains uncorrected, the explosive device in the exploding fuse explodes, instantly severing the circuit and preventing the short-circuit current from continuing to flow, thus avoiding potential failures and dangers.

[0015] As a possible implementation, a controller is included, and when the energy storage converter is short-circuited, the first protection unit is disconnected under the control of the controller.

[0016] As a possible implementation, a controller is included, and when the energy storage unit is short-circuited, the switch unit is disconnected under the control of the controller.

[0017] As a possible implementation, the controller is used to obtain the magnitude of the voltage between the positive terminal of the energy storage inverter and the negative terminal of the energy storage inverter and the magnitude of the current flowing through the first protection unit, or the controller is used to obtain the magnitude and direction of the current flowing through the first protection unit.

[0018] As a possible implementation, the controller is used to obtain the magnitude of the voltage between the positive terminal of the energy storage unit and the negative terminal of the energy storage unit and the magnitude of the current flowing through the second protection unit, or the controller is used to obtain the magnitude and direction of the current flowing through the second protection unit.

[0019] As a possible implementation, a charging pile is included, and the energy storage converter is also used to convert the DC power output by the energy storage unit into AC power and output it to the charging pile. The energy storage system provided in this application is also used in scenarios where electric vehicles are charged. The energy storage converter converts the DC power provided by the energy storage unit into AC power and provides it to the charging pile, so that the charging pile can charge the electric vehicle with AC power.

[0020] In the second aspect, the present application provides a photovoltaic system, which includes a photovoltaic module, a power converter and an energy storage unit. The power converter is used to convert the direct current output by the photovoltaic module into a direct current voltage and then input the charging power into the energy storage unit. The positive terminal of the photovoltaic module is used to be connected to the positive terminal of the power converter through a first protection unit, and the negative terminal of the photovoltaic module is used to be connected to the negative terminal of the power converter through a second protection unit. The second protection unit includes a switch unit and an anti-reverse unit connected in parallel. The switch unit is used to close when the photovoltaic module is discharged to make the electrical connection between the photovoltaic module and the power converter conductive. The anti-reverse unit is used to unidirectionally conduct the current from the negative terminal of the photovoltaic module to the negative terminal of the power converter when the switch unit is disconnected. When the power converter is short-circuited, the first protection unit is disconnected. When the photovoltaic module is short-circuited, the switch unit is disconnected.

[0021] When the positive and negative terminals of the photovoltaic modules and power converters in the photovoltaic system are reversed, the anti-reverse current protection unit can prevent current from damaging the switching devices in the power converter. Furthermore, when the power converter short-circuits, the first protection unit can be disconnected to disconnect the positive terminal of the photovoltaic module from the positive terminal of the power converter to protect the photovoltaic module. When the photovoltaic module short-circuits, the switch unit can be disconnected to disconnect the negative terminal of the photovoltaic module from the negative terminal of the power converter to protect the power converter.

[0022] As a possible implementation, when the power converter is short-circuited, the switch unit is disconnected, and when the photovoltaic module is short-circuited, the first protection unit is disconnected. When the power converter is short-circuited, disconnecting the switch unit can disconnect the negative terminal of the photovoltaic module from the negative terminal of the power converter, thereby protecting the photovoltaic module. When the photovoltaic module is short-circuited, disconnecting the first protection unit can disconnect the positive terminal of the photovoltaic module from the positive terminal of the power converter, thereby protecting the power converter.

[0023] As a possible implementation, a short circuit of the power converter means that the voltage between the positive terminal of the power converter and the negative terminal of the power converter is less than a first voltage threshold, and the current flowing through the first protection unit is greater than a first current threshold, or a short circuit of the power converter means that the current flowing through the first protection unit is greater than the first current threshold and the current direction is from the negative terminal of the photovoltaic module to the positive terminal of the photovoltaic module.

[0024] As a possible implementation, a short circuit of a photovoltaic module is when the voltage between the positive terminal of the photovoltaic module and the negative terminal of the photovoltaic module is less than a second voltage threshold, and the current flowing through the second protection unit is greater than the second current threshold, or a short circuit of the photovoltaic module is when the current flowing through the second protection unit is greater than the second current threshold and the current direction is from the negative terminal of the power converter to the positive terminal of the power converter.

[0025] As a possible implementation, the first protection unit is an exploding fuse, which is configured to disconnect when the temperature is greater than a temperature safety threshold.

[0026] As a possible implementation, a controller is included, and when the power converter is short-circuited, the first protection unit is disconnected under the control of the controller; or when the photovoltaic module is short-circuited, the switch unit is disconnected under the control of the controller.

[0027] As a possible implementation, the controller is used to obtain the magnitude of the voltage between the positive terminal of the power converter and the negative terminal of the power converter, the magnitude of the current flowing through the first protection unit, and the magnitude and direction of the current of the first protection unit, and the controller is used to obtain the magnitude of the voltage between the positive terminal of the photovoltaic component and the negative terminal of the photovoltaic component, the magnitude of the current flowing through the second protection unit, and the direction of the current flowing through the second protection unit.

[0028] As a possible implementation method, including a charging pile, the power converter is also used to convert the DC power output by the energy storage unit or photovoltaic module into a DC voltage and then output it to the charging pile. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a structural diagram of an energy storage converter provided by the present application;

[0030] Figure 2 is a short circuit fault schematic diagram 1;

[0031] Figure 3 is a second schematic diagram of a short circuit fault;

[0032] FIG4A is a schematic diagram of the layout structure of each protection unit;

[0033] FIG4B is a second schematic diagram of the layout structure of each protection unit;

[0034] FIG4C is a third schematic diagram of the layout structure of each protection unit;

[0035] FIG4D is a fourth schematic diagram of the layout structure of each protection unit;

[0036] Figure 5 is a third schematic diagram of a short circuit fault;

[0037] FIG6 is a fourth schematic diagram of a short circuit fault;

[0038] FIG7 is a fifth schematic diagram of a short circuit fault;

[0039] FIG8 is a sixth schematic diagram of a short circuit fault;

[0040] FIG9 is a schematic diagram of a short-circuit protection structure provided by the present application;

[0041] FIG10 is a schematic diagram of the structure of the energy storage system provided by this application;

[0042] FIG11 is a schematic diagram of a short circuit detection structure provided by the present application;

[0043] FIG12 is a schematic structural diagram of a photovoltaic system. DETAILED DESCRIPTION

[0044] Below, some of the terms involved in the embodiments of the present application are explained to facilitate understanding by those skilled in the art.

[0045] A pyrofuse is a protective device used in power systems, primarily to protect against overloads or short-circuit failures. It consists of a small explosive device connected to a fuse or fuse element in a circuit. When the current exceeds the rated current of the fuse or fuse element, the explosive device explodes, instantly severing the circuit and preventing further current flow, thus avoiding potential failures and dangers.

[0046] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings. The specific operating methods in the method embodiments can also be applied to device embodiments or system embodiments. It should be noted that in the description of the present application, "at least one" refers to one or more, wherein multiple refers to two or more. In view of this, "multiple" can also be understood as "at least two" in the embodiments of the present invention. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / ", unless otherwise specified, generally indicates that the previous and next associated objects are in an "or" relationship. In addition, it should be understood that in the description of the present application, words such as "first" and "second" are only used to distinguish the purpose of description, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0047] It should be noted that in the embodiments of the present application, "connection" refers to electrical connection, and the connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be either a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For example, the connection between A and B can also be a direct connection between A and C, and C and B can be directly connected, with A and B connected through C.

[0048] In an energy storage system, if an energy storage converter fails, if it is not removed in time, it will affect the operation of other energy storage converters in the energy storage system, thereby causing the fault to spread. Therefore, for an energy storage system, if a short-circuit fault occurs in an energy storage converter, the energy storage converter can be actively removed so as not to affect the normal operation of the entire energy storage system. When a short-circuit fault occurs in an energy storage unit connected to an energy storage converter, it is necessary to actively separate the energy storage unit from the energy storage system and reconnect it to the energy storage system after the energy storage unit fault is repaired.

[0049] To achieve the above requirements, the present application provides an energy storage system, as shown in Figure 1, which is a structural schematic diagram of the energy storage system provided by the present application. The energy storage system 100 includes an energy storage unit 101 and an energy storage converter 102. The energy storage unit 101 includes one or more batteries connected in series or in parallel. The battery may include a lead-acid battery (or lead-acid storage battery), a sodium battery, or a lithium-ion battery (such as a lithium iron phosphate battery or a ternary lithium battery), etc. The present application does not limit the specific type of battery.

[0050] The energy storage converter 102 of the present application is a bidirectional conversion circuit. When electric energy is transmitted from a first end of the energy storage converter 102 to a second end of the energy storage converter 102, the first end of the energy storage converter 102 serves as an input end of the energy storage converter 102 to receive electric energy, and the second end of the energy storage converter 102 serves as an output end of the energy storage converter 102 to output electric energy. When electric energy is transmitted from the second end of the energy storage converter 102 to the first end of the energy storage converter 102, the second end of the energy storage converter 102 serves as an input end of the energy storage converter 102 to receive electric energy, and the first end of the energy storage converter 102 serves as an output end of the energy storage converter 102 to output electric energy.

[0051] It is understandable that the energy storage converter 102 can receive charging power from the photovoltaic system to charge the energy storage unit 101, and can also convert the DC power of the energy storage unit 101 into AC power to supply the grid or load.

[0052] Referring to FIG. 2 , FIG. 2 is a schematic diagram of a short-circuit fault. When a short-circuit fault occurs in energy storage unit 101, since grid voltage still exists on the grid side, the short-circuit current will flow counterclockwise from the negative busbar to the positive busbar. At this time, if the faulty energy storage unit 101 and the energy storage converter 102 are disconnected, the short-circuit fault in energy storage unit 101 can be promptly eliminated.

[0053] Refer to Figure 3, which shows a second schematic diagram of a short-circuit fault. When a short-circuit fault occurs in the energy storage converter 102, due to the voltage present in the energy storage unit 101, the short-circuit current will flow clockwise from the positive busbar to the negative busbar. At this point, if the faulty energy storage converter 102 is disconnected from the energy storage unit 101, the short-circuit fault in the energy storage converter 102 can be promptly eliminated, thereby preventing the fault from spreading to the faulty energy storage converter 102.

[0054] Therefore, the energy storage system 100 provided in the present application adds a first protection unit 103 and a second protection unit 104, so that when a short circuit fault occurs in the energy storage unit 101 or the energy storage converter 102, the faulty part can be promptly cut off by controlling the first protection unit 103 and the second protection unit 104.

[0055] 4A is a schematic diagram of the layout structure of each protection unit. The positive terminal of the energy storage unit 101 is used to connect to the positive terminal of the energy storage converter 102 through the first protection unit 103, and the negative terminal of the energy storage unit 101 is used to connect to the negative terminal of the energy storage converter 102 through the second protection unit 104.

[0056] The second protection unit 104 includes a switch unit 1041 and an anti-reverse unit 1042 connected in parallel. The switch unit 1041 is used to close when the energy storage unit 101 is charging or discharging to make the electrical connection between the energy storage unit 101 and the energy storage converter 102 conductive. The anti-reverse unit 1042 is used to unidirectionally conduct the current from the negative end of the energy storage converter 102 to the negative end of the energy storage unit 101 when the switch unit 1041 is disconnected.

[0057] Using this approach, if a short-circuit current flows from the negative terminal of energy storage unit 101 to the negative terminal of energy storage converter 102, the unidirectional conduction characteristics of anti-reverse unit 1042 will still prevent the short-circuit current from flowing. If the short-circuit current flows from the negative terminal of energy storage converter 102 to the negative terminal of energy storage unit 101, first protection unit 103 can be controlled to disconnect the positive terminal of energy storage converter 102 from the positive terminal of energy storage unit 101, thus achieving short-circuit protection.

[0058] In addition, when the energy storage converter 102 is short-circuited, the switch unit 1041 may be controlled to be disconnected. When the energy storage unit 101 is short-circuited, the first protection unit 103 may be controlled to be disconnected.

[0059] Among them, the short circuit of the energy storage converter 102 is when the voltage between the positive terminal of the energy storage converter 102 and the negative terminal of the energy storage converter 102 is less than the first voltage threshold, and the current flowing through the first protection unit 103 is greater than the first current threshold, or, the short circuit of the energy storage converter 102 is when the current flowing through the first protection unit 103 is greater than the first current threshold and the current direction is from the positive terminal of the energy storage unit 101 to the negative terminal of the energy storage unit 101, or, the short circuit of the energy storage unit 101 is when the voltage between the positive terminal of the energy storage unit 101 and the negative terminal of the energy storage unit 101 is less than the second voltage threshold, and the current flowing through the second protection unit 104 is greater than the second current threshold, or, the short circuit of the energy storage unit 101 is when the current flowing through the second protection unit 104 is greater than the second current threshold and the current direction is from the positive terminal of the energy storage converter 102 to the negative terminal of the energy storage converter 102.

[0060] Referring to FIG. 4B , FIG. 4B is a second schematic diagram of the layout structure of each protection unit. As one possible implementation, the anti-reverse unit 1042 is connected between the positive terminal of the energy storage converter 102 and the positive terminal of the energy storage unit 101, and is used to unidirectionally conduct current from the positive terminal of the energy storage unit 101 to the positive terminal of the energy storage converter 102. The switch unit 1041 is connected in parallel with the anti-reverse unit 1042. The first protection unit 103 is connected between the negative terminal of the energy storage converter 102 and the negative terminal of the energy storage unit 101, and is used to connect or disconnect the negative terminal of the energy storage converter 102 and the negative terminal of the energy storage unit 101.

[0061] Using this approach, if a short-circuit current flows from the positive terminal of the energy storage converter 102 to the positive terminal of the energy storage unit 101, the unidirectional conduction characteristics of the anti-reverse unit 1042 will still prevent the short-circuit current from flowing. If the short-circuit current flows from the positive terminal of the energy storage unit 101 to the positive terminal of the energy storage converter 102, the first protection unit 103 can be controlled to disconnect the negative terminal of the energy storage converter 102 from the negative terminal of the energy storage unit 101, thus achieving short-circuit protection.

[0062] In addition, the first protection unit 103 and the second protection unit 104 can also be located on the same side of the DC bus, as shown in FIG4C , which is a third schematic diagram of the layout structure of each protection unit. The anti-reverse unit 1042 is connected between the positive terminal of the energy storage converter 102 and the positive terminal of the energy storage unit 101, and is used to unidirectionally conduct the current from the positive terminal of the energy storage unit 101 to the positive terminal of the energy storage converter 102. The switch unit 1041 is connected in parallel with the anti-reverse unit 1042. The first protection unit 103 is also connected between the positive terminal of the energy storage converter 102 and the positive terminal of the energy storage unit 101, and is used to connect or disconnect the positive terminal of the energy storage converter 102 and the positive terminal of the energy storage unit 101.

[0063] In this way, when the short-circuit current flows from the positive terminal of the energy storage unit 101 to the positive terminal of the energy storage converter 102, the first protection unit 103 can be controlled to disconnect the positive terminal of the energy storage converter 102 and the positive terminal of the energy storage unit 101, thereby achieving short-circuit protection.

[0064] Referring to FIG. 4D , FIG. 4D is a fourth schematic diagram of the layout structure of each protection unit. The anti-reverse flow unit 1042 is connected between the negative terminal of the energy storage converter 102 and the negative terminal of the energy storage unit 101, and is used to unidirectionally conduct current from the positive terminal of the energy storage converter 102 to the positive terminal of the energy storage unit 101. The switch unit 1041 is connected in parallel with the anti-reverse flow unit 1042. The first protection unit 103 is also connected between the negative terminal of the energy storage converter 102 and the negative terminal of the energy storage unit 101, and is used to connect or disconnect the positive terminal of the energy storage converter 102 and the positive terminal of the energy storage unit 101.

[0065] In this way, when the short-circuit current flows from the negative terminal of the energy storage converter 102 to the negative terminal of the energy storage unit 101, the first protection unit 103 can be controlled to disconnect the negative terminal of the energy storage converter 102 and the negative terminal of the energy storage unit 101, thereby achieving short-circuit protection.

[0066] Based on the structure of FIG4A , refer to FIG5 , which is a third schematic diagram of a short-circuit fault. When a short-circuit fault occurs in the energy storage converter 102, since grid voltage still exists on the grid side, the short-circuit current will flow counterclockwise from the negative busbar to the positive busbar. At this time, by controlling the first protection unit 103 or the switch unit 104 to disconnect the faulty energy storage unit 101 from the energy storage converter 102, the short-circuit fault in the energy storage unit 101 can be promptly eliminated.

[0067] Refer to FIG6 , which is a fourth schematic diagram of a short-circuit fault. When a short-circuit fault occurs in the energy storage converter 102, due to the voltage in the energy storage unit 101, the short-circuit current will flow clockwise from the positive busbar to the negative busbar. At this time, the short-circuit current is consistent with the unidirectional conduction direction of the anti-reverse unit 1042. Since the anti-reverse unit 1042 is connected in parallel with the switch unit 1041, even if the switch unit 1041 is disconnected, the short-circuit fault of the energy storage converter 102 cannot be promptly removed. At this time, by disconnecting the first protection unit 103, the connection between the energy storage unit 101 and the energy storage converter 102 can be disconnected, and the short-circuit fault of the energy storage converter 102 can be promptly removed.

[0068] Considering the different operating states of the energy storage converter 102 before a short-circuit fault occurs, refer to Figure 7, which is a fifth schematic diagram of a short-circuit fault. If the energy storage unit 101 is in a discharging state before a short-circuit fault occurs in the energy storage converter 102, the normal operating current flows clockwise from the positive busbar to the negative busbar. In this case, the energy storage converter 102 operates in inverter mode, converting the DC power input from the energy storage unit 101 into AC power and outputting the AC power to the grid. However, when a short-circuit fault occurs in the energy storage converter 102, due to the battery voltage in the battery of the energy storage unit 101, the short-circuit current will also flow clockwise from the positive busbar to the negative busbar. Therefore, by controlling the switch unit 1041 or the first protection unit 103 to disconnect, the short-circuit fault in the energy storage converter 102 can be promptly eliminated, thereby preventing the fault from spreading.

[0069] Refer to Figure 8, which is a sixth schematic diagram of a short-circuit fault. If the energy storage converter 102 is in a charging state before a short-circuit fault occurs, the normal operating current flows counterclockwise from the negative busbar to the positive busbar. In this case, the energy storage converter 102 is operating in rectification mode, converting AC power from the grid into DC power and outputting the DC power to the energy storage converter 101, thereby charging the energy storage converter 101. When a short-circuit fault occurs in the energy storage converter 102, it is necessary to first disconnect the negative terminal of the faulty energy storage converter 101 from the negative terminal of the energy storage converter 102, thereby cutting off the normal operating current. At this point, the corresponding control switch unit 1041 disconnects the negative terminal of the energy storage converter 101 from the negative terminal of the energy storage converter 102, thereby cutting off the normal operating current. After disconnection, due to the battery voltage in the energy storage converter 101, the short-circuit current will flow clockwise from the positive busbar to the negative busbar. Therefore, it is necessary to control the positive terminal of the faulty energy storage unit 101 to be disconnected from the positive terminal of the faulty energy storage converter 102. At this time, the first protection unit 103 is correspondingly controlled to disconnect the positive terminal of the energy storage unit 101 from the positive terminal of the energy storage converter 102, thereby cutting off the short-circuit current, thereby timely removing the short-circuit fault of the energy storage converter 102 to prevent the fault from spreading.

[0070] The first protection unit 103 is connected between the negative terminal of the energy storage converter 102 and the negative terminal of the energy storage unit 101, and is used to unidirectionally conduct the current from the negative terminal of the energy storage converter 102 to the negative terminal of the energy storage unit 101. The switch unit 1041 is connected in parallel with the anti-reverse unit 1042. The first protection unit 103 is connected between the positive terminal of the energy storage converter 102 and the positive terminal of the energy storage unit 101, and is used to conduct or disconnect the connection between the positive terminal of the energy storage converter 102 and the positive terminal of the energy storage unit 101.

[0071] Using this approach, if a short-circuit current flows from the negative terminal of energy storage unit 101 to the negative terminal of energy storage converter 102, the unidirectional conduction characteristics of first protection unit 103 will still prevent the short-circuit current from flowing. If the short-circuit current flows from the negative terminal of energy storage converter 102 to the negative terminal of energy storage unit 101, first protection unit 103 can be controlled to disconnect the positive terminal of energy storage converter 102 from the positive terminal of energy storage unit 101, thus achieving short-circuit protection.

[0072] The switch unit 1041 and the anti-reverse unit 1042 can be used for overload protection and short circuit protection. The switch unit 1041 and the first protection unit 103 can be mechanical control devices or electronic control devices, such as a switch device with a controller. The anti-reverse unit 1042 can be a diode, etc.

[0073] In order to further implement short-circuit fault protection, as a possible implementation, the switch unit 1041 is a switch tube, the anti-reverse unit 1042 is a diode, and the first protection unit 103 is an exploding fuse.

[0074] The diode in the anti-reverse unit 1042 can be connected between the negative terminal of the energy storage unit 101 and the negative terminal of the above-mentioned energy storage converter 102, and is used to unidirectionally conduct the current from the negative terminal of the energy storage converter 102 to the negative terminal of the energy storage unit 101.

[0075] When the positive and negative terminals of the energy storage unit 101 are reversely connected to the positive and negative terminals of the energy storage converter 102, the diode included in the anti-reverse unit 1042 can act as a bypass for the reverse current flowing into the energy storage converter 102, so that the current output from the positive terminal of the energy storage unit 101 flows back to the negative terminal of the energy storage unit 101 through the diode in the anti-reverse unit 1042, thereby preventing the reverse current from damaging the switch tube of the energy storage converter 102. Furthermore, because the switch unit 1041 and the anti-reverse unit 1042 are connected in parallel, the switch unit 1041 and the anti-reverse unit 1042 will not operate simultaneously.

[0076] When a short-circuit fault occurs in the energy storage unit 101, the switch tube included in the anti-reverse unit 1042 is disconnected, thereby eliminating the short-circuit fault. Moreover, when the current between the energy storage converter 102 and the energy storage unit 101 is greater than the first current threshold and the duration is greater than or equal to the first time threshold, it indicates that the short-circuit current has not been eliminated. The explosive fuse in the first protection unit 103 can still play a final protective role. That is, when the current between the energy storage converter 102 and the energy storage unit 101 is too large and has not been eliminated after the first time threshold, the explosive device in the explosive fuse explodes to instantly cut off the circuit, thereby preventing the short-circuit current from continuing to flow and avoiding faults and dangers.

[0077] Furthermore, since the embodiment of the present application uses a switch to disconnect the failed energy storage unit 101 from the energy storage converter 102, when the energy storage unit 101 returns to normal, the controller can also reclose the switch in the anti-reverse unit 1042 to restore the connection between the energy storage unit 101 and the energy storage converter 102.

[0078] The switch tube may be an insulated gate bipolar transistor (IGBT) and its anti-parallel diode, or a metal oxide semiconductor field effect transistor (MOSFET), etc. The present application does not impose any restrictions on the specific structure inside the switch tube.

[0079] For the above-mentioned short-circuit scenarios, Figure 9 is a schematic diagram of the short-circuit protection structure provided by the present application. If a short-circuit fault occurs in the energy storage unit 101, since the grid voltage still exists on the grid side, the short-circuit current will flow counterclockwise from the negative busbar to the positive busbar. At this time, since the direction of the short-circuit current is opposite to the conduction current direction of the switch tube in the anti-reverse unit 1042, the short-circuit fault in the energy storage unit 101 can be removed in time, thereby avoiding affecting the normal operation of the energy storage system.

[0080] If the energy storage unit 101 is in a discharging state before a short-circuit fault occurs in the energy storage converter 102, the current in normal operation flows clockwise from the positive busbar to the negative busbar. At this time, the energy storage converter 102 operates in the inverter mode. The energy storage converter 102 is used to convert the direct current input by the energy storage unit 101 into alternating current and output the alternating current to the power grid. When a short-circuit fault occurs in the energy storage converter 102, due to the battery voltage in the energy storage unit 101, the short-circuit current will flow clockwise from the positive busbar to the negative busbar. At this time, since the direction of the short-circuit current is consistent with the conduction current direction of the diode in the anti-reverse unit 1042, even if the switch unit 1041 is disconnected, the short-circuit current will still flow through the diode in the anti-reverse unit 1042. Therefore, the explosion fuse in the first protection unit 103 can be controlled to disconnect the positive terminal of the faulty energy storage converter 102 from the positive terminal of the energy storage unit 101. In this way, the short-circuit fault in the energy storage converter 102 can be promptly removed, thereby preventing the fault from spreading.

[0081] If the battery of the energy storage converter 102 is in a charging state before a short-circuit fault occurs, the normal operating current flows counterclockwise from the negative busbar to the positive busbar. At this time, the energy storage converter 102 operates in a rectification mode. The energy storage converter 102 is used to convert the AC power input from the power grid into DC power and output the DC power to the energy storage unit 101 side, thereby charging the energy storage unit 101. When a short-circuit fault occurs in the energy storage converter 102, it is necessary to first control the switch tube in the switch unit 1041 to disconnect the negative terminal of the energy storage unit 101 from the negative terminal of the faulty energy storage converter 102, thereby cutting off the normal operating current. And because there is a battery voltage on the energy storage unit 101 side, the short-circuit current will flow clockwise from the positive busbar to the negative busbar. Therefore, controlling the explosion fuse to disconnect can disconnect the positive terminal of the faulty energy storage converter 102 from the positive terminal of the energy storage unit 101, so that the short-circuit fault of the energy storage converter 102 can be promptly removed, thereby preventing the fault from spreading.

[0082] Referring to FIG. 10 , which is a schematic diagram of the energy storage system structure provided in the present application, as a possible implementation, the energy storage system 100 includes: a controller 105, the controller 105 being configured to obtain the magnitude of the voltage between the positive terminal and the negative terminal of the energy storage converter 102 and the magnitude of the current flowing through the first protection unit 103; alternatively, the controller 105 being configured to obtain the magnitude and direction of the current flowing through the first protection unit 103. The controller 105 being configured to obtain the magnitude of the voltage between the positive terminal and the negative terminal of the energy storage unit 101 and the magnitude of the current flowing through the second protection unit 104; alternatively, the controller 105 being configured to obtain the magnitude and direction of the current flowing through the second protection unit 104.

[0083] The controller may be a general-purpose central processing unit (CPU), a general-purpose processor, a digital signal processing (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It may implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The aforementioned processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, and the like. Furthermore, the controller may also include a battery management system (BMS), which may monitor and estimate the status of the batteries in the energy storage converter 102 online, and may also use the current status and certain algorithms to balance the batteries in the energy storage converter 102 and determine whether a short circuit fault has occurred in the energy storage converter 102.

[0084] Referring to FIG. 11 , FIG. 11 is a schematic diagram of the short-circuit detection structure provided by the present application. As a possible implementation, the energy storage system 100 further includes: an energy storage converter short-circuit detection unit 1101 and an energy storage unit short-circuit detection unit 1102. The energy storage converter short-circuit detection unit 1101 is used to detect whether a short circuit has occurred in the energy storage converter, and the energy storage unit short-circuit detection unit 1102 is used to detect whether a short circuit has occurred in the energy storage unit. The present application does not limit the specific structures of the energy storage converter short-circuit detection unit 1101 and the energy storage unit short-circuit detection unit 1102; these may be any method capable of detecting whether a short circuit has occurred in each unit in the energy storage system 100.

[0085] As a possible implementation, the energy storage system 100 further includes: a charging pile, and the energy storage converter is further configured to convert the direct current output by the energy storage unit into alternating current and output it to the charging pile.

[0086] Based on the same concept, the present application provides a photovoltaic system, as shown in FIG12, which is a schematic diagram of the structure of a photovoltaic system. The photovoltaic system 120 includes a photovoltaic module 121, a power converter 122, and an energy storage unit 123; the power converter 122 is used to convert the DC power output by the photovoltaic module 121 into a DC voltage and then input the charging power to the energy storage unit 123. The positive terminal of the photovoltaic module 121 is used to connect to the positive terminal of the power converter 122 through a first protection unit 124, and the negative terminal of the photovoltaic module 121 is used to connect to the negative terminal of the power converter 122 through a second protection unit 125; the second protection unit 125 It includes a switch unit 126 and an anti-reverse unit 127 connected in parallel. The switch unit 126 is used to close when the photovoltaic component 121 is discharged to make the electrical connection between the photovoltaic component 121 and the power converter 122 conductive. The anti-reverse unit 127 is used to unidirectionally conduct the current from the negative end of the photovoltaic component 121 to the negative end of the power converter 122 when the switch unit 126 is disconnected; when the power converter 122 is short-circuited, the first protection unit 124 is disconnected; when the photovoltaic component 121 is short-circuited, the switch unit 126 is disconnected.

[0087] As a possible implementation, when the power converter is short-circuited, the switch unit is disconnected; when the photovoltaic module is short-circuited, the first protection unit is disconnected.

[0088] As a possible implementation, a short circuit of the power converter means that the voltage between the positive terminal of the power converter and the negative terminal of the power converter is less than a first voltage threshold, and the current flowing through the first protection unit is greater than a first current threshold; or a short circuit of the power converter means that the current flowing through the first protection unit is greater than the first current threshold and the current direction is from the negative terminal of the photovoltaic module to the positive terminal of the photovoltaic module.

[0089] As a possible implementation, a photovoltaic module short circuit occurs when the voltage between the positive terminal and the negative terminal of the photovoltaic module is less than a second voltage threshold, and the current flowing through the second protection unit is greater than a second current threshold; or a photovoltaic module short circuit occurs when the current flowing through the second protection unit is greater than the second current threshold and the current direction is from the negative terminal of the power converter to the positive terminal of the power converter.

[0090] As a possible implementation, the first protection unit is an exploding fuse; the exploding fuse is configured to disconnect when the temperature is greater than a temperature safety threshold.

[0091] As a possible implementation, a controller is included; when the power converter is short-circuited, the first protection unit is disconnected under the control of the controller; or when the photovoltaic module is short-circuited, the switch unit is disconnected under the control of the controller.

[0092] As a possible implementation, the controller is used to obtain the magnitude of the voltage between the positive terminal of the power converter and the negative terminal of the power converter, the magnitude of the current flowing through the first protection unit, and the magnitude and direction of the current in the first protection unit; and, the controller is used to obtain the magnitude of the voltage between the positive terminal of the photovoltaic component and the negative terminal of the photovoltaic component, the magnitude of the current flowing through the second protection unit, and the direction of the current flowing through the second protection unit.

[0093] As a possible implementation method, including a charging pile, the power converter is also used to convert the DC power output by the energy storage unit or photovoltaic module into a DC voltage and then output it to the charging pile.

[0094] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. An energy storage system, characterized in that: The energy storage system includes an energy storage unit and an energy storage converter, wherein the energy storage unit includes a plurality of battery packs; the energy storage unit is used to output discharge power to a power grid or a load through the energy storage converter, or to receive charging power input from a photovoltaic system or a power grid through the energy storage converter; The positive terminal of the energy storage unit is used to be connected to the positive terminal of the energy storage converter through the first protection unit, and the negative terminal of the energy storage unit is used to be connected to the negative terminal of the energy storage converter through the second protection unit; The second protection unit includes a switch unit and an anti-reverse unit connected in parallel, wherein the switch unit is used to close when the energy storage unit is charged or discharged so as to conduct the electrical connection between the energy storage unit and the energy storage converter, and the anti-reverse unit is used to unidirectionally conduct the current from the negative terminal of the energy storage converter to the negative terminal of the energy storage unit when the switch unit is disconnected; When the energy storage converter is short-circuited, the first protection unit is disconnected; When the energy storage unit is short-circuited, the switch unit is disconnected.

2. The energy storage system according to claim 1, characterized in that: When the energy storage converter is short-circuited, the switch unit is disconnected; When the energy storage unit is short-circuited, the first protection unit is disconnected.

3. The energy storage system according to claim 1 or 2, characterized in that: The short circuit of the energy storage converter means that the voltage between the positive terminal of the energy storage converter and the negative terminal of the energy storage converter is less than a first voltage threshold, and the current flowing through the first protection unit is greater than a first current threshold.

4. The energy storage system according to claim 1 or 2, characterized in that: The short circuit of the energy storage converter is when the current flowing through the first protection unit is greater than a first current threshold and the current direction flows from the positive terminal of the energy storage unit to the negative terminal of the energy storage unit.

5. The energy storage system according to claim 1 or 2, characterized in that: The short circuit of the energy storage unit means that the voltage between the positive terminal of the energy storage unit and the negative terminal of the energy storage unit is less than a second voltage threshold, and the current flowing through the second protection unit is greater than a second current threshold.

6. The energy storage system according to claim 1 or 2, characterized in that: The short circuit of the energy storage unit is when the current flowing through the second protection unit is greater than a second current threshold and the current direction flows from the positive terminal of the energy storage converter to the negative terminal of the energy storage converter.

7. The energy storage system according to any one of claims 1 to 6, characterized in that: The first protection unit is an exploding fuse; the exploding fuse is used to disconnect when the temperature is greater than a temperature safety threshold.

8. The energy storage system according to claim 7, characterized in that: Including controller; When the energy storage converter is short-circuited, the first protection unit is disconnected under the control of the controller.

9. The energy storage system according to claim 7, characterized in that: Including controller; When the energy storage unit is short-circuited, the switch unit is disconnected under the control of the controller.

10. The energy storage system according to claim 8, characterized in that: The controller is used to obtain the magnitude of the voltage between the positive terminal of the energy storage converter and the negative terminal of the energy storage converter and the magnitude of the current flowing through the first protection unit; or The controller is used to obtain the magnitude and direction of the current flowing through the first protection unit.

11. The energy storage system according to claim 9, characterized in that: The controller is used to obtain the magnitude of the voltage between the positive terminal of the energy storage unit and the negative terminal of the energy storage unit and the magnitude of the current flowing through the second protection unit; or The controller is used to obtain the magnitude and direction of the current flowing through the second protection unit.

12. The energy storage system according to any one of claims 1 to 11, characterized in that: Including a charging pile, the energy storage converter is also used to convert the direct current output by the energy storage unit into alternating current and output it to the charging pile.

13. A photovoltaic system, characterized in that: The photovoltaic system includes a photovoltaic module, a power converter and an energy storage unit; the power converter is used to convert the direct current output by the photovoltaic module into a direct current voltage and then input the charging power to the energy storage unit; The positive terminal of the photovoltaic assembly is used to be connected to the positive terminal of the power converter through the first protection unit, and the negative terminal of the photovoltaic assembly is used to be connected to the negative terminal of the power converter through the second protection unit; The second protection unit includes a switch unit and an anti-reverse unit connected in parallel, wherein the switch unit is used to close when the photovoltaic component is discharged so as to conduct the electrical connection between the photovoltaic component and the power converter, and the anti-reverse unit is used to unidirectionally conduct the current from the negative end of the photovoltaic component to the negative end of the power converter when the switch unit is disconnected; When the power converter is short-circuited, the first protection unit is disconnected; When the photovoltaic assembly is short-circuited, the switch unit is disconnected.

14. The photovoltaic system according to claim 13, characterized in that: When the power converter is short-circuited, the switch unit is disconnected; When the photovoltaic assembly is short-circuited, the first protection unit is disconnected.

15. The photovoltaic system according to claim 13 or 14, characterized in that: The power converter is short-circuited when the voltage between the positive terminal of the power converter and the negative terminal of the power converter is less than a first voltage threshold, and the current flowing through the first protection unit is greater than a first current threshold; or The short circuit of the power converter is when the current flowing through the first protection unit is greater than a first current threshold and the current direction flows from the negative terminal of the photovoltaic component to the positive terminal of the photovoltaic component.

16. The photovoltaic system according to claim 13 or 14, characterized in that: The photovoltaic component is short-circuited when the voltage between the positive terminal of the photovoltaic component and the negative terminal of the photovoltaic component is less than a second voltage threshold, and the current flowing through the second protection unit is greater than a second current threshold; or The photovoltaic component short circuit occurs when the current flowing through the second protection unit is greater than a second current threshold and the current direction flows from the negative terminal of the power converter to the positive terminal of the power converter.

17. The photovoltaic system according to any one of claims 13 to 16, characterized in that: The first protection unit is an exploding fuse; the exploding fuse is used to disconnect when the temperature is greater than a temperature safety threshold.

18. The photovoltaic system according to any one of claims 13 to 17, characterized in that: Including controller; When the power converter is short-circuited, the first protection unit is disconnected under the control of the controller; or When the photovoltaic assembly is short-circuited, the switch unit is disconnected under the control of the controller.

19. The photovoltaic system according to claim 18, characterized in that: The controller is used to obtain the magnitude of the voltage between the positive terminal of the power converter and the negative terminal of the power converter, the magnitude of the current flowing through the first protection unit, and the magnitude and direction of the current of the first protection unit; and, The controller is used to obtain the magnitude of the voltage between the positive terminal of the photovoltaic component and the negative terminal of the photovoltaic component, the magnitude of the current flowing through the second protection unit, and the direction of the current flowing through the second protection unit.

20. The photovoltaic system according to any one of claims 13 to 19, characterized in that: A charging pile is included, and the power converter is also used to convert the direct current output by the energy storage unit or the photovoltaic component into a direct current voltage and output it to the charging pile.

Images