ENERGY STORAGE SYSTEM AND GROUNDING STRUCTURE CONTROL DEVICE FOR ENERGY STORAGE SYSTEM

Abstract

An energy storage system according to an embodiment of the present invention includes a photovoltaic (PV) system and is connected to a power grid, and includes: a power conversion system (PCS) connected to the power grid and selectively connected to the photovoltaic power generation system; a first switch selectively connecting the photovoltaic power generation system to a DC side of the power conversion system; a first earth fault detector having one side terminal connected to ground; a second switch located between the first switch and the photovoltaic power generation system and selectively connecting the photovoltaic power generation system to the other side terminal of the first earth fault detector; and a switch control device that controls the first switch and the second switch according to a power generation state of the photovoltaic power generation system to change the grounding structure of one or more of the photovoltaic power generation system, the power conversion system, and a battery system included in the energy storage system.

Description

[Technical field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0047876 filed with the Korean Intellectual Property Office on April 19, 2022, and all of the contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an energy storage system and a ground structure control device for an energy storage system, and more particularly to an energy storage system including a solar power generation system, a ground structure control device for the energy storage system, and a switch control device for controlling the ground structure of the energy storage system. [Background technology]

[0003] An energy storage system (ESS) is a system that connects renewable energy, batteries that store power, and existing grid power. In recent years, smart grids and renewable energy have become more widespread, and as the efficiency and safety of the power system are emphasized, the demand for energy storage systems is increasing to regulate power supply and demand and improve power quality. Depending on the purpose of use, the output and capacity of the energy storage system vary, and multiple battery systems can be connected to each other to configure a large-capacity energy storage system.

[0004] Among ESS systems, ESS systems that are connected to PV (Photovoltaic) systems are changing from AC-coupled to DC-coupled systems. In DC-coupled ESS systems, the PV system and battery system are DC voltage, while the grid is AC voltage, so a power conversion system is essential.

[0005] Meanwhile, PV systems and battery systems generally use different grounding methods due to system efficiency or safety issues. In this case, the type of grounding method to be used in an energy storage system in which a PV system and a battery system are linked is a matter of choosing between system efficiency and safety, which causes difficulties in system operation in that one of system efficiency and safety must be given up. Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE PRESENT EMBODIMENT In order to solve the above problems, an object of the present invention is to provide an energy storage system including a solar power generation system.

[0007] Another object of the present invention to solve the above problems is to provide a ground structure control device for an energy storage system.

[0008] Another object of the present invention to solve the above problems is to provide a switch control device for controlling the ground structure of such an energy storage system. [Means for solving the problem]

[0009] To achieve the above object, an energy storage system according to one embodiment of the present invention includes a photovoltaic (PV) system, and is connected to a power grid, and includes: a power conversion system (PCS) connected to the power grid and selectively connected to the photovoltaic power generation system; a first switch for selectively connecting the photovoltaic power generation system to a DC side of the power conversion system; a first earth fault detector having one terminal connected to ground; a second switch located between the first switch and the photovoltaic power generation system for selectively connecting the photovoltaic power generation system to the other terminal of the first earth fault detector; and a switch control device that controls the first switch and the second switch according to a power generation state of the photovoltaic power generation system to change the grounding structure of one or more of the photovoltaic power generation system, the power conversion system, and a battery system included in the energy storage system, and selectively connects the photovoltaic power generation system to the DC side of the power conversion system.

[0010] When the solar power generation system is in a power generation state, the switch control device operates the first switch and the second switch in a closed state, thereby applying a grounding structure to the solar power generation system and the power conversion system, and the first ground fault detector detects whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

[0011] The switch control device applies a floating ground structure to the solar power generation system and the power conversion system by operating the second switch in an open state for a preset time after the solar power generation system is switched from a non-power generation state to a power generation state, and a second ground fault detector configured at the DC side input node of the power conversion system detects whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

[0012] When the solar power generation system is in a non-power generating state, the switch control device operates the first switch in an open state and the second switch in a closed state, thereby applying a grounding structure to the solar power generation system and applying a floating ground structure to the power conversion system, and the first ground fault detector detects whether or not a ground fault has occurred in the solar power generation system.

[0013] The energy storage system may further include a second ground fault detector configured at a DC side input node of the power conversion system, wherein the second ground fault detector detects whether or not a ground fault occurs in the power conversion system.

[0014] The first switch can operate as a normally open switch. Here, the switch control device can include a first switch drive circuit configured to drive the first switch by receiving power produced by the solar power generation system, and can operate the first switch in a closed state when the solar power generation system is in a power generation state.

[0015] The second switch may be a normally closed switch, and the switch control device may include a second switch drive circuit configured to drive the second switch by receiving power generated by the solar power generation system.

[0016] The second switch drive circuit is configured to operate using the supplied power when a control signal is received from an external control device, and when the solar power generation system is in a power generation state and the control signal is input, the second switch can be operated in an open state.

[0017] The energy storage system may further include a battery system connected to a DC side input node of the power conversion system.

[0018] The first ground fault detector may include a Ground Fault Detection Interrupter (GFDI).

[0019] The second ground fault detector may include an Insulation Monitoring Device (IMD).

[0020] In order to achieve the above-mentioned another object, a grounding structure control device for an energy storage system according to one embodiment of the present invention includes a photovoltaic (PV) system and a power conversion system (PCS) selectively connected to the photovoltaic power generation system, and is located in an energy storage system connected to a power grid, and includes a first switch for selectively connecting the photovoltaic power generation system to a DC side of the power conversion system; a first earth fault detector having one side terminal connected to ground; a second switch for selectively connecting the photovoltaic power generation system to the other side terminal of the first earth fault detector, and a switch control device for controlling the first switch and the second switch according to a power generation state of the photovoltaic power generation system to change the grounding structure of one or more of the photovoltaic power generation system, the power conversion system, and a battery system included in the energy storage system, and selectively connecting the photovoltaic power generation system to the DC side of the power conversion system.

[0021] When the solar power generation system is in a power generation state, the switch control device operates the first switch and the second switch in a closed state, thereby applying a grounding structure to the solar power generation system and the power conversion system, and the first ground fault detector detects whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

[0022] The switch control device applies a floating ground structure to the solar power generation system and the power conversion system by operating the second switch in an open state for a preset time after the solar power generation system is switched from a non-power generation state to a power generation state, and a second ground fault detector configured at the DC side input node of the power conversion system detects whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

[0023] When the solar power generation system is in a non-power generating state, the switch control device operates the first switch in an open state and the second switch in a closed state, thereby applying a grounding structure to the solar power generation system and applying a floating ground structure to the power conversion system, and causing the first ground fault detector to detect whether or not a ground fault has occurred in the solar power generation system.

[0024] The ground structure control device may further include a second ground fault detector arranged at a DC side input node of the power conversion system, wherein the second ground fault detector detects the occurrence of a ground fault in the power conversion system.

[0025] The first switch may be a normally open switch, and the switch control device may include a first switch drive circuit configured to drive the first switch by receiving power produced by the solar power generation system, and may operate the first switch in a closed state when the solar power generation system is in a power generation state.

[0026] The second switch may be a normally closed switch, and the switch control device may include a second switch drive circuit configured to drive the second switch by receiving power generated by the solar power generation system.

[0027] The second switch drive circuit is configured to be driven by the supplied power when a control signal is received from an external control device, and when the solar power generation system is in a power generation state and the control signal is input, the second switch can be operated in an open state.

[0028] The ground structure control device may further include a third switch that selectively connects the DC side input node of the power conversion system and a battery system.

[0029] The third switch can be operated in a closed state in a power generation state and a non-power generation state of the solar power generation system.

[0030] According to an embodiment of the present invention, there is provided a switch control device for an energy storage system connected to a power grid, the switch control device including a photovoltaic (PV) system, a power conversion system (PCS) selectively connected to the photovoltaic power generation system, a first switch selectively connecting the photovoltaic power generation system to a DC side of the power conversion system, a first earth fault detector having one terminal connected to ground, and a second switch selectively connecting the photovoltaic power generation system to the other terminal of the first earth fault detector, the switch control device being located in an energy storage system connected to a power grid, the switch control device including at least one processor and a memory storing at least one instruction executed by the at least one processor, wherein the at least one instruction includes an instruction to check a state of the photovoltaic power generation system, and an instruction to control the first switch and the second switch according to a power generation state of the photovoltaic power generation system to control one or more ground structures of the photovoltaic power generation system, the power conversion system, and a battery system included in the energy storage system.

[0031] The instruction to control the grounding structure may include an instruction to apply a grounding structure to the solar power generation system and the power conversion system by operating the first switch and the second switch in a closed state when the solar power generation system is in a power generation state, and to cause the first ground fault detector to detect whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

[0032] The command to control the grounding structure may further include a command to apply a floating grounding structure to the solar power generation system and the power conversion system by operating the second switch in an open state for a predetermined time after the solar power generation system is switched from a non-power generation state to a power generation state, and to cause a second ground fault detector configured at a DC side input node of the power conversion system to detect whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

[0033] The instruction to control the grounding structure may include an instruction to operate the first switch in an open state and the second switch in a closed state when the solar power generation system is in a non-power generation state, thereby applying a grounding structure to the solar power generation system and causing the first ground fault detector to detect whether or not a ground fault has occurred in the solar power generation system.

[0034] The instructions for controlling the grounding structure may include instructions for applying a floating grounding structure to the power conversion system and causing a second ground fault detector configured at a DC side input node of the power conversion system to detect whether or not a ground fault has occurred in the power conversion system. Effect of the Invention

[0035] According to the above-described embodiments of the present invention, it is possible to minimize PID generated in a solar power generation system and prevent a decrease in efficiency of the solar power generation system.

[0036] In addition, it is possible to monitor ground faults in the DC-Coupled energy storage system connected to the entire PV system, ensuring both efficiency and safety at the same time compared to existing technologies. [Brief description of the drawings]

[0037] [Figure 1] 1 is a block diagram of an example of a PV system-connected DC-Coupled energy storage system to which the present invention can be applied. [Figure 2a] FIG. 1 is a schematic diagram of a PV system-connected DC-Coupled energy storage system having a typical floating ground structure. [Figure 2b] FIG. 1 is a conceptual diagram showing a method of operating a PV system-interconnected DC-Coupled energy storage system having a general floating ground structure. [Figure 3a] FIG. 1 is a schematic diagram of a PV system-connected DC-Coupled energy storage system having a general grounding structure. [Figure 3b] FIG. 1 is a conceptual diagram showing an operation method of a PV system-connected DC-Coupled energy storage system having a general grounding structure. [Figure 4] 1 is a configuration example of an energy storage system having a grounding structure according to an embodiment of the present invention. [Diagram 5] FIG. 2 is a conceptual diagram showing an example of a method of operating an energy storage system having a grounding structure according to an embodiment of the present invention. [Figure 6] FIG. 13 is a conceptual diagram showing another example of a method for operating an energy storage system having a grounding structure according to an embodiment of the present invention. [Figure 7] 1 is a circuit diagram showing a switch control device according to an embodiment of the present invention; [Figure 8] 1 is a circuit diagram showing a ground structure control device including a switch control device according to an embodiment of the present invention; [Figure 9] 2 is a circuit diagram showing a PV system interconnection terminal of the ground structure control device according to the embodiment of the present invention; FIG. [Figure 10]2 is a circuit diagram showing a battery system interconnection terminal of a ground structure control device according to an embodiment of the present invention. FIG. [Figure 11] FIG. 11 is a block diagram of a switch control device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Since the present invention can be modified in various ways and has various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, it is understood that this is not intended to limit the present invention to the specific embodiment, but includes all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention. Similar reference numerals are used for similar components while describing each drawing.

[0039] Terms such as first, second, A, B, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only to distinguish one component from another. For example, a first component may be named a second component, and similarly, a second component may be named a first component, without departing from the scope of the present invention. The term "and / or" includes a combination of multiple associated listed items or any of multiple associated listed items.

[0040] When a component is referred to as being "coupled" or "connected" to another component, it should be understood that the component may be directly coupled or connected to the other component, but there may also be other components in between. In contrast, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that there are no other components in between.

[0041] The terms used in this application are merely used to describe certain embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless the context clearly indicates otherwise. In this application, the terms "include" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and are not intended to preclude the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0042] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. Terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted as having an ideal or overly formal meaning unless expressly defined in this application.

[0043] Some terms used in this specification are defined as follows:

[0044] Nominal capacity (Nominal Capa.) refers to the set capacity [Ah] of a battery that is set by the battery manufacturer at the time of development.

[0045] SOC (State of Charge) is the current charged state of the battery expressed as a percentage [%], and SOH (State of Health) is the current deterioration state of the battery expressed as a percentage [%].

[0046] A battery rack is a system with the smallest structure that can be monitored and controlled through a battery management system (BMS) by connecting pack units set by the battery manufacturer in series / parallel. A battery rack can be composed of multiple battery modules and one battery protection unit or any other protection device.

[0047] A battery bank can refer to a large-scale collection of battery rack systems consisting of multiple racks connected in parallel. The battery bank BMS can monitor and control the rack BMS (RBMS) for each battery rack.

[0048] A BSC (Battery Section Controller) is a device that performs top-level control of a battery system including a bank-based battery system, and can also be used as a control device in a battery system having a multi-bank level structure.

[0049] Power limit refers to the output limit preset by the battery manufacturer according to the battery condition. Rack power limit refers to the output limit (in kW) set at the rack level, and can be set based on the battery's SOC and temperature.

[0050] The power limit can be divided into a charge power limit and a discharge power limit depending on whether the battery is charging or discharging. Also, a rack power limit for each rack and a bank power limit for each bank can be defined depending on the structure of the battery system.

[0051] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0052] FIG. 1 is a block diagram of an example of a PV system-connected DC-Coupled energy storage system to which the present invention can be applied.

[0053] In a DC-Coupled energy storage system, a DC / DC converter 500 capable of individually controlling the DC voltage / current is essential for each battery system 100. Since a DC / DC converter is installed in each battery system, not only can each battery system be protected and controlled through the DC / DC converter as in existing battery systems, but also the battery power can be controlled based on the characteristics of each individual battery system even when the SOC, SOH, and capacity differ between each battery rack.

[0054] FIG. 1 shows an example of a DC coupled system in which an output terminal of a PV (Photovoltaic; solar power generation system) 700 is connected to an output terminal of a DC / DC converter 500 and an input terminal of a PCS 400 .

[0055] Batteries that serve to store power in an energy storage system (ESS) may be embodied in a form in which a number of battery modules form a battery rack, and a number of battery racks form a battery bank. Here, the battery rack may be called a battery pack depending on the device or system in which the battery is used. Battery #1, battery #2, ..., battery #N shown in FIG. 1 may be in the form of a battery pack or a battery rack.

[0056] At this time, each battery 100 may be provided with a Battery Management System (BMS). The BMS may monitor the current, voltage, and temperature of each battery rack (or pack) under its management, calculate a Status Of Charge (SOC) based on the monitoring results, and control charging and discharging. In the system of FIG. 1, when each battery is a battery rack, the BMS may be a rack BMS (RBMS).

[0057] Each battery section, which includes a number of batteries and peripheral circuits and devices, is provided with a Battery Section Controller (BSC) 200, which can monitor and control control targets such as voltage, current, temperature, circuit breakers, etc.

[0058] In addition, a power conversion / conditioning system (PCS) 400 provided for each battery section controls power supplied from the outside and power supplied from the battery section to the outside, and may include a DC / AC inverter. In addition, an output of the DC-DC converter 500 may be connected to the PCS 400, and the PCS 400 may be connected to a grid 600. The PCS 400 usually operates in a constant power mode. A power management system (PMS) / energy management system (EMS) 300 connected to the PCS may control the output of the PCS based on the monitoring and control results of the BMS or BSC.

[0059] 1, battery #1 is connected to DC-DC converter #1, battery #2 is connected to DC-DC converter #2, and battery #N is connected to DC-DC #N. The output of the DC-DC converter corresponding to each battery is connected to PCS 400 via a DC link.

[0060] The DC-DC converter may be a bidirectional converter, and when conversion is performed in the direction from the battery to the load, the input of the DC-DC converter may be connected to the battery (battery unit, battery rack, or battery pack), and the output of the DC-DC converter may be connected to the load. As examples of the DC-DC converter, various types of converters such as a full-bridge converter, a half-bridge converter, and a flyback converter may be used.

[0061] Meanwhile, communication using a Controller Area Network (CAN) or Ethernet (shown by dotted lines in FIG. 1) can be performed between the BMS, BSC 200, PMS 300, and PCS 400.

[0062] According to an embodiment of the present invention shown in FIG. 1, the BSC 200 in charge of overall control of the battery area can report the status of each battery to the PMS 300. Here, the status of each battery can include information such as the SOC (Status Of Charge), SOH (Status Of Health), voltage, temperature, etc. of each battery. The BSC 200 can provide information such as the limit power (P_battery_limit) and actual power (P_battery_real) of each battery to the PMS 300. The PMS 300 in charge of control of the entire ESS system issues a charge or discharge command (through P_pcs_reference) to the PCS 400 during actual system operation.

[0063] Here, the BSC 200 determines the output reference for each individual DC / DC converter taking into account the state of each battery. In an embodiment of the present invention, the output reference of each individual DC / DC converter can be set in different manners depending on whether the mode is droop or constant power (CP).

[0064] When the output of the DC / DC converter is controlled by the droop mode, the BSC can set a droop curve for each DC / DC converter considering the state of each battery before the system operation and provide it to the corresponding converter. On the other hand, when the DC / DC converter operates in the CP mode, the BSC can determine the power reference of each DC / DC converter during the system operation and provide it to the corresponding converter.

[0065] During actual operation of the energy storage system, the PMS transmits charge and discharge commands to the PCS and BSC. At this time, the PMS monitors the status of the photovoltaic power system (PV), grid, and battery in real time, and can determine the operation mode and output reference of the components in the system based on the operation command received from a higher-level system, such as an energy management system (EMS).

[0066] Meanwhile, FIG. 1 shows an example of a system in which a separate DC / DC converter is applied to each battery rack, but the present invention can also be applied to a system in which a central DC / DC converter commonly connected to multiple battery racks is applied.

[0067] In the DC Coupled Energy Storage System as explained in Figure 1, the grounding structure is determined by whether the negative power line of the PV system is grounded or not. The method of monitoring a ground fault varies depending on the grounding structure, and the impact of the fault appears in different forms depending on the grounding structure.

[0068] The structure of grounding-related systems can be broadly divided into grounding systems and floating systems. In a grounding system, a fault current flows when a single-line ground fault occurs, which can damage equipment. In contrast, in a floating system, a fault current does not flow when a single-line ground fault occurs, but current flows when a second ground fault occurs.

[0069] FIG. 2a is a schematic diagram of a PV system-connected DC-Coupled energy storage system having a typical floating ground structure.

[0070] The energy storage system in Fig. 2a includes a battery system 10, a DC / DC converter 50, a PV system 70, and a power conversion system 40 connected to them, and has a floating earth structure. In general, a floating earth (ungrounded) structure is recommended for battery systems to ensure safety in the event of a ground fault.

[0071] The connection between the PV system 70 and the power conversion system 40 can be controlled through switch 1 (SW1), but the PV system 70 is usually isolated from the DC grid at night. The connection between the battery system 10 including the DC / DC converter 50 and the power conversion system 40 is made through switch 2 (SW2), which is usually kept in the on state when the system is operating normally.

[0072] In the system structure of Fig. 2a, the positive and negative terminals of the PV system and the battery system are not connected to ground. Such a ground structure in which the positive and negative terminals of the power line are not connected to ground is called floating (or ungrounded) ground. In order to monitor ground faults in such a system structure, insulation resistance and ground faults can be monitored using an insulation monitoring device such as an IMD (Insulation Monitoring Device). The IMD is a device that measures and monitors the insulation resistance value between the positive terminal and ground and between the negative terminal and ground, and can be located on the DC power line of the power conversion system 40 as shown in Fig. 2a.

[0073] The IMD, which is a ground fault monitoring device, detects insulation resistance and ground faults depending on the open / close state of switch 1, but such a structure has limitations as described below.

[0074] FIG. 2b is a conceptual diagram showing an operation method of a PV system-connected DC-Coupled energy storage system having a typical floating ground structure.

[0075] 2b shows the state of each component (power conversion system, PV system, battery system) according to the operating state of the energy storage system with a floating ground structure. When the system is charging, switch 1 is closed and the PV system is connected to the battery system and the power grid. At this time, the power conversion system 40, PV system 70, and battery system 10 are all in a floating state, and the insulation resistance can be measured by the IMD, and a ground fault can be monitored.

[0076] However, when switch 1 is opened at night to separate the PV system from the DC system, it is not possible to detect a ground fault occurring in the system. In addition, PID (potential induced degradation) occurs in the solar cells in the floating PV system, causing gradual system degradation. As degradation progresses, the amount of energy generated by the solar cells decreases, ultimately resulting in a decrease in system efficiency.

[0077] For this reason, negative grounding is mainly used in PV systems to prevent potential induced degradation (PID), which adversely affects power generation efficiency.

[0078] FIG. 3a is a schematic diagram of a PV system-connected DC-Coupled energy storage system having a typical grounding structure.

[0079] The energy storage system of Fig. 3a includes a battery system 10, a DC / DC converter 50, a PV system 70, and a power conversion system 40 connected to them, and has a negative grounding structure among one-pole grounding structures. The negative grounding structure refers to a structure in which the negative (-) terminal of the power line is connected to the ground. It can be seen from Fig. 3a that the negative terminal of the PV system and the negative terminal of the battery system can be connected to the ground via a switch.

[0080] The connection between the PV system 70 and the power conversion system 40 can be controlled through switch 1 (SW1), but the PV system 70 is usually isolated from the DC grid at night. The connection between the battery system 10 including the DC / DC converter 50 and the power conversion system 40 is made through switch 2 (SW2), which is usually kept on when the system is operating normally. The system of Fig. 3a further selectively connects the negative terminals of the battery system and the PV system to ground through switch 3 (SW3).

[0081] In such a system structure, insulation resistance and ground faults can be monitored using insulation and ground fault monitoring devices such as IMD, RCM (Residential Current Monitoring) devices, and GFDI (Ground Fault Detection Interrupter) to monitor ground faults.

[0082] The IMD is a device that measures and monitors the insulation resistance between the positive terminal and ground and between the negative terminal and ground, and can be located on the DC power line of the power conversion system 40 or between the battery rack and the DC / DC converter as shown in Fig. 3a. The RCM is a device that monitors whether the sum of the currents flowing through the positive power line and the negative power line is zero to detect whether leakage current occurs, and is located between the battery rack and the DC / DC converter in Fig. 3a. The GFDI is a device that is connected between the power line and ground, and cuts off the current when the current flowing from the power line to the ground is equal to or greater than a reference value.

[0083] On the other hand, even such a negative grounding structure has limitations, as will be explained below.

[0084] FIG. 3b is a conceptual diagram showing an operation method of a PV system-connected DC-Coupled energy storage system having a general grounding structure.

[0085] FIG. 3b shows the state of each component (power conversion system, PV system, battery system) according to the operating state of an energy storage system having a grounding structure. Here, when the battery is being charged or is in a standby state after charging, switch 1 is in a closed state, and the PV system is connected to the battery system and the power grid. Switch 3 is also in a closed state, and the negative electrodes of the power conversion system 40, PV system 70, and battery system 10 are in a grounded state. If a ground fault occurs in this state, a fault current will be generated.

[0086] After that, when the power generation of the PV system is finished, the switches 1 and 3 are opened, and the power conversion system 40, the PV system 70, and the battery system 10 are all in a floating ground state. At this time, since the PV system 70 is in a floating ground state, PID occurs, and as a result, the PV power generation efficiency decreases. In addition, since the switch 1 is open, insulation reduction and earth faults cannot be detected.

[0087] Therefore, in an energy storage system including a PV system and a battery system, the choice of which grounding method to use is a matter of choosing between system efficiency and safety. In the end, system efficiency and safety are in a trade-off relationship and are determined by the system designer's choice, and no matter which method is selected, problems will occur.

[0088] In order to solve this problem, the present invention aims to ensure both the safety and efficiency of a DC-Coupled energy storage system connected to a PV system by changing the grounding mode according to the power generation state of the photovoltaic power generation system and operating the energy storage system.

[0089] FIG. 4 is a configuration example of an energy storage system having a grounding structure according to an embodiment of the present invention.

[0090] The energy storage system according to the embodiment of the present invention may include a PV system 700 and a power conversion system 400 operating in conjunction therewith, and may further include a battery system 100 and a DC / DC converter 500 .

[0091] The connection between the PV system 700 and the power conversion system 400 is controlled through a first switch S1. A first ground fault detector may be configured between the first switch and the PV system (including a plurality of PV panels) as a device for detecting a ground fault. Here, the first ground fault detector may include a Ground Fault Detection Interrupter (GFDI).

[0092] One terminal of the first ground fault detector (GFDI) may be connected to ground, and the other terminal may be connected to a node between the PV system on the negative power line and the first switch, where the connection between the first ground fault detector (GFDI) and the negative power line may be controlled through the second switch S2.

[0093] A second ground fault detector may be configured as a device for monitoring or detecting a ground fault at the DC side input node of the power conversion system 400. Here, the second ground fault detector may include an insulation monitoring device (IMD).

[0094] The battery system 100 including the DC / DC converter 500 can be connected to a DC side input node of the power conversion system 400. Here, the connection between the battery system 100 including the DC / DC converter 500 and the power conversion system 400 can be controlled through a third switch S3, which is normally maintained in a closed state when the system operates normally.

[0095] In the present invention, the DC / DC converter 500 is in the form of a rack DC / DC converter as shown in FIG. 4, and may be in the form of a central DC / DC converter commonly connected to a plurality of battery racks.

[0096] The energy storage system according to the embodiment of the present invention includes a switch control device that controls one or more of the first to third switches. Here, the switch control device controls one or more of the first to third switches to change the grounding structure of one or more of the PV system 700, the battery system 100, and the power conversion system 400, and selectively connects the PV system 700 to the DC side of the power conversion system 400.

[0097] Hereinafter, a method for operating the energy storage system according to the embodiment of the present invention will be described in detail with reference to FIGS.

[0098] FIG. 5 is a conceptual diagram showing an example of a method of operating an energy storage system having a grounding structure according to an embodiment of the present invention.

[0099] 5, the switch control device controls the first switch and the second switch according to the power generation state of the PV system 700 to change the grounding structure of one or more of the PV system 700, the battery system 100, and the power conversion system (PCS) 400. Here, the third switch is maintained in a closed state regardless of the power generation state of the PV system.

[0100] According to the operation method of the energy storage system shown in FIG. 5, the PV system 700 is operated in a grounded structure except for a certain period of time (td) immediately after switching to a power generation state, and the battery system 100 and the power conversion system 400 are operated in a floating ground structure except when the PV system 700 is in a power generation state.

[0101] Specifically, when the PV system 700 is not generating power (e.g., at night), the first switch is operated in an open state, the second switch is operated in a closed state, the PV system 700 is operated in a grounded structure, and the battery system 100 and the power conversion system 400 are operated in a floating ground structure. In this case, the PV system 700 can detect the occurrence of a ground fault using a first ground fault detector (GFDI) located between the first switch and the PV system 700. In addition, the battery system 100 and the power conversion system 400 can detect the occurrence of a ground fault using a second ground fault detector (IMD) configured at a DC side input node of the power conversion system 400.

[0102] When the PV system 700 is in a power generating state (e.g., daytime), the first switch and the second switch are operated in a closed state, and the PV system 700, the battery system 100, and the power conversion system 400 are all operated in a grounded structure. In this case, the first ground fault detector (GFDI) can detect the presence or absence of a ground fault in the PV system 700, the battery system 100, and the power conversion system 400.

[0103] Here, the second switch may be operated in an open state (the first switch may be operated in a closed state) for a preset time (td) after the PV system 700 is switched from a non-power generating state to a power generating state. Thus, the PV system 700, the battery system 100, and the power conversion system 400 may all be operated in a floating ground structure during the corresponding time (td). In this case, a second earth fault detector (IMD) may detect the occurrence of a ground fault in the PV system 700, the battery system 100, and the power conversion system 400. That is, the energy storage system may be temporarily switched to a floating ground structure immediately after the PV system 700 is switched from a non-power generating state to a power generating state, and the insulation state of all the components 100, 400, and 700 may be monitored through the IMD. At this time, if an abnormality occurs in the insulation state and the system is shut down, additional measures such as an on-site inspection may be taken to confirm and resolve the abnormal state, and if no abnormality is detected, the energy storage system may be switched to a grounded structure and operated.

[0104] According to this embodiment, the PV system 700 is operated in a grounded structure except for a certain time (td) immediately after switching to a power generation state, thereby minimizing the occurrence of PID in the PV system 700 and preventing a decrease in efficiency.

[0105] In addition, the battery system 100 is operated in a floating ground structure except when the PV system 700 is in a power generation state, thereby minimizing the possibility of fault current flowing in the event of a ground fault, thereby ensuring system safety.

[0106] 6 is a conceptual diagram showing another example of an operation method of the energy storage system having the grounding structure according to the embodiment of the present invention, in which the PV system 700 is temporarily in a non-power generating state.

[0107] Specifically, when the PV system 700 is not generating power (e.g., at night), the first switch is operated in an open state, the second switch is operated in a closed state, the PV system 700 is operated in a grounded structure, and the battery system 100 and the power conversion system 400 are operated in a floating ground structure. In this case, the PV system 700 can detect the presence or absence of a ground fault using a first ground fault detector (GFDI), and the battery system 100 and the power conversion system 400 can detect the presence or absence of a ground fault using a second ground fault detector (IMD).

[0108] After the PV system 700 is switched from a non-power generating state to a power generating state (e.g., daytime), the first switch is operated in a closed state and the second switch is operated in an open state for a preset time (td), and the PV system 700, the battery system 100, and the power conversion system 400 can all be operated in a floating ground structure during the time (td). In this case, the second earth fault detector (IMD) can detect whether or not a ground fault occurs in the PV system 700, the battery system 100, and the power conversion system 400.

[0109] If there is no abnormality in the insulation state of all the components 100, 400, 700, the first switch and the second switch are operated in a closed state, and the PV system 700, the battery system 100, and the power conversion system 400 are all operated in a grounded structure. In this case, the first ground fault detector (GFDI) can detect the presence or absence of a ground fault in the PV system 700, the battery system 100, and the power conversion system 400.

[0110] Here, when the PV system 700 is switched from a power generating state to a temporary non-power generating state (e.g., a non-power generating state due to weather conditions such as clouds or rain), the first switch is operated in an open state, the second switch is operated in a closed state, the PV system 700 is operated in a grounded structure, and the battery system 100 and the power conversion system 400 are operated in a floating ground structure. In this case, the PV system 700 can detect the presence or absence of a ground fault using a first ground fault detector (GFDI), and the battery system 100 and the power conversion system 400 can detect the presence or absence of a ground fault using a second ground fault detector (IMD).

[0111] Thereafter, when the PV system 700 is switched from the temporary non-power generating state to the power generating state, the first switch and the second switch are operated in a closed state, and the PV system 700, the battery system 100, and the power conversion system 400 are all operated in a grounded structure. That is, when the temporary non-power generating state is released, the pre-monitoring process through the second earth fault detector (IMD) performed when switching from the non-power generating state to the power generating state can be omitted.

[0112] According to this embodiment, similar to the operation method shown in FIG. 5, the PV system 700 is operated in a grounded structure except for a certain period of time (td) immediately after switching to a power generation state, and the battery system 100 is operated in a floating ground structure except when the PV system 700 is in a power generation state, thereby minimizing the occurrence of PID in the PV system 700 and ensuring system safety.

[0113] In addition, the pre-monitoring process through the second earth fault detector (IMD) is performed when switching from a non-power generating state to a power generating state, and is omitted when switching from a temporary non-power generating state to a power generating state, thereby improving the operational efficiency of the energy storage system.

[0114] Hereinafter, a switch control device embodied as a circuit and a ground structure control device including the same will be described with reference to FIGS.

[0115] FIG. 7 is a circuit diagram showing a switch control device according to an embodiment of the present invention.

[0116] The switch control device controls the first switch and the second switch according to the power generation state of the PV system 700 to change the grounding structure of one or more of the PV system 700, the battery system 100, and the power conversion system 400, and selectively connects the PV system 700 to the DC side of the power conversion system 400.

[0117] The switch control device may include a first switch driving circuit configured to drive a first switch and a second switch driving circuit configured to drive a second switch, where the first and second switch driving circuits may include devices for switching between open / closed states of each switch, and may include one or more of a power supply device, a switch driving device, and a logic circuit.

[0118] The first switch driving circuit may be configured to drive the first switch by receiving power generated by the PV system 700. As shown in Fig. 7, the first switch driving circuit may include a power supply device (e.g., SMPS; Switched Mode Power Supply) connected to the output side of the PV system 700, and a switch driving device that switches the state of the first switch through the power supplied by the power supply device (SMPS).

[0119] Here, the first switch may be a normally open switch, in which case the first switch driving circuit operates the first switch in an open state when no power is supplied to the PV system 700 in a non-power generating state, and switches the first switch to a closed state when power is supplied to the PV system 700 in a power generating state.

[0120] The second switch driving circuit may be configured to drive the second switch by receiving power generated by the PV system 700, and to drive the second switch through the supplied power when a control signal is received from an external control device. As shown in Fig. 7, the second switch driving circuit may include a power supply device (SMPS) connected to an output side of the PV system 700, an AND circuit that outputs the power supplied by the power supply device (SMPS) to the outside when a control signal (S2 control signal from external) is received from the external control device, and a switch driving device that switches the state of the second switch through the power supplied from the output side of the AND circuit.

[0121] Here, the second switch may be a normally closed switch. In this case, when the PV system 700 is not generating power, the second switch driving circuit operates the second switch in a closed state without supplying power, and when the PV system 700 is generating power, the second switch driving circuit switches the second switch to an open state only when an external control signal is input.

[0122] FIG. 8 is a circuit diagram showing a ground structure control device including a switch control device according to an embodiment of the present invention.

[0123] The ground structure control device according to the embodiment of the present invention is electrically connected to the PV system 700, the battery system 100, and the power conversion system 400, and changes the ground structure of one or more of the PV system 700, the battery system 100, and the power conversion system 400 according to the power generation state of the PV system 700. Here, the ground structure control device (shown by a dotted box in FIG. 8) may be embodied as a PV-ESS coupling box including first to third switches, first and second ground fault detectors, and a switch control device.

[0124] In FIG. 8, the first switch S1 can be configured as a normally open switch, the second switch S2 can be configured as a normally closed switch, and the third switch S3 can be configured as a switch that is manually opened and closed (e.g., a disconnector).

[0125] The switch control device may include a first switch driving circuit configured to drive the first switch and a second switch driving circuit configured to drive the second switch. Here, the first switch driving circuit may be configured to drive the first switch by receiving power produced by the PV system 700, and the second switch driving circuit may be configured to drive the second switch by receiving power produced by the PV system 700, and to drive the second switch through the supplied power when a control signal is received from an external control device.

[0126] The method of operating the energy storage system using the ground structure control device shown in Figure 8 is as follows.

[0127] When the PV system 700 is not generating power (e.g., at night), no power is supplied to the first and second switch drive circuits, and the first switch is operated in an open state and the second switch is operated in a closed state, so that the PV system 700 is operated in a grounded structure, and the battery system 100 and the power conversion system 400 are operated in a floating ground structure.

[0128] When the PV system 700 is switched from a non-power generating state to a power generating state (e.g., daytime), a control signal (S2 control signal from external) for switching the second switch to an open state is input for a preset time (td). Here, the control signal can be input by an administrator or set to be input when a power generating state is detected. In this case, power is supplied to the first and second switch driving circuits, and an external control signal is input, so that the first switch is switched to a closed state and the second switch is switched to an open state. As a result, the PV system 700, the battery system 100, and the power conversion system 400 can all be operated in a floating ground structure during the corresponding time (td). In this case, the second earth fault detector (IMD) can detect whether or not a ground fault occurs in the PV system 700, the battery system 100, and the power conversion system 400.

[0129] After the corresponding time (td) has elapsed, the second switch is switched to a closed state, and the PV system 700, the battery system 100 and the power conversion system 400 are all operated in a grounded configuration.

[0130] Here, when the PV system 700 is switched from a power generating state to a temporary non-power generating state (e.g., a non-power generating state due to weather conditions such as clouds or rain), no power is supplied to the first and second switch drive circuits, the first switch is switched to an open state, and the second switch maintains a closed state. As a result, the PV system 700 is operated in a grounded structure, and the battery system 100 and the power conversion system 400 are operated in a floating ground structure.

[0131] Thereafter, when the PV system 700 is switched from the temporary non-power generating state to the power generating state, power is supplied to the first and second switch drive circuits, but no external control signal is input, the first switch is switched to a closed state, and the second switch maintains a closed state, so that the PV system 700, the battery system 100, and the power conversion system 400 are all operated in a grounded structure.

[0132] FIG. 9 is a circuit diagram showing a PV system grid-connection terminal of a ground structure control device according to an embodiment of the present invention.

[0133] The ground structure control device according to an embodiment of the present invention may be embodied as a PV-ESS coupling box, and a DC input port for electrically connecting to the PV system 700 may be provided on the outside of the coupling box.

[0134] The DC input port may include a positive input port connected to each of the positive terminals of the multiple PV modules (PV1, PV2, ...) and a negative input port connected to each of the negative terminals of the multiple PV modules (PV1, PV2, ...), where each of the positive input port and the negative input port may be electrically coupled inside the PV-ESS coupling box.

[0135] A fuse may be provided on the path between the ground structure control device and the PV system 700 for protection.

[0136] FIG. 10 is a circuit diagram showing a battery system interconnection terminal of a ground structure control device according to an embodiment of the present invention.

[0137] The ground structure control device according to an embodiment of the present invention may be embodied as a PV-ESS coupling box, and a DC input port for electrically connecting to the battery system 100 including the DC / DC converter 500 may be provided on the outside of the coupling box.

[0138] The DC input port may include a positive input port connected to each of the positive terminals of the multiple DC / DC converters 500 (DC / DC #1, DC / DC #2, ...) and a negative input port connected to each of the negative terminals of the multiple DC / DC converters 500 (DC / DC #1, DC / DC #2, ...). Here, each of the positive input port and the negative input port may be electrically coupled inside the PV-ESS coupling box and connected to a third switch.

[0139] A fuse and a surge protection device for protection may be provided on a path to which the battery system 100 including the ground structure control device and the DC / DC converter 500 are electrically connected.

[0140] FIG. 11 is a block diagram of a switch control device according to another embodiment of the present invention.

[0141] Referring to FIG. 11, the switch control device can be embodied as a computer device, unlike the switch control device embodied as a circuit shown in FIG.

[0142] The switch control device 300 according to the embodiment of the present invention may be a PMS or EMS included in an energy storage system, but may be any type of control device located in or linked to the energy storage system. Here, the energy storage system includes a photovoltaic (PV) system, a battery system, and a power conversion system (PCS) selectively connected to at least one of the photovoltaic power generation system and the battery system, and is connected to a power grid.

[0143] The switch controller 300 may include at least one processor 310, a memory 320 for storing at least one instruction executed by the processor, and a transceiver 330 for communicating with a network.

[0144] The at least one instruction may include an instruction to check a status of a solar power generation system; and an instruction to control the first switch and the second switch according to a power generation status of the solar power generation system to control one or more grounding structures of the solar power generation system, the power conversion system, and a battery system included in the energy storage system.

[0145] The instruction to control the grounding structure may include an instruction to apply a grounding structure to the solar power generation system and the power conversion system by operating the first switch and the second switch in a closed state when the solar power generation system is in a power generation state, and to cause the first ground fault detector to detect whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

[0146] The command to control the grounding structure may further include a command to apply a floating grounding structure to the solar power generation system and the power conversion system by operating the second switch in an open state for a predetermined time after the solar power generation system is switched from a non-power generation state to a power generation state, and to cause a second ground fault detector configured at a DC side input node of the power conversion system to detect whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

[0147] The instruction to control the grounding structure may include an instruction to operate the first switch in an open state and the second switch in a closed state when the solar power generation system is in a non-power generation state, thereby applying a grounding structure to the solar power generation system and causing the first ground fault detector to detect whether or not a ground fault has occurred in the solar power generation system.

[0148] The instructions for controlling the grounding structure may include instructions for applying a floating grounding structure to the power conversion system so that a second ground fault detector configured at a DC side input node of the power conversion system detects whether or not a ground fault has occurred in the power conversion system.

[0149] The switch control device 300 of the energy storage system may further include an input interface device 340, an output interface device 350, a storage device 360, etc. Each component included in the switch control device 300 may be connected by a bus 370 to communicate with each other.

[0150] The processor 310 can execute program commands stored in at least one of the memory 320 and the storage device 360. Here, the processor can refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which the method according to the embodiment of the present invention is performed. The memory (or storage device) can be composed of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory can be composed of at least one of a read only memory (ROM) and a random access memory (RAM).

[0151] The operation of the method according to the embodiment of the present invention can be embodied as a computer readable program or code in a computer readable recording medium. The computer readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. In addition, the computer readable recording medium can be distributed to computer systems connected via a network, and the computer readable program or code can be stored and executed in a distributed manner.

[0152] Some aspects of the invention have been described in the context of an apparatus, but it may also be presented in terms of a corresponding method, where a block or apparatus corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method may be presented in terms of a corresponding block or item or feature of a corresponding apparatus. Some or all of the method steps may be performed by (or using) a hardware apparatus, such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the most important method steps may be performed by such an apparatus.

[0153] Although the present invention has been described with reference to preferred embodiments thereof, those skilled in the art will understand that various modifications and variations of the present invention can be made without departing from the spirit and scope of the present invention as set forth in the following claims. [Explanation of symbols]

[0154] SW1 Switch SW2 switch SW3 Switch 10 Battery System 40 Power Conversion Systems 50 DC / DC Converter 70 PV systems 100, 400, 700 configurations 100 Battery System 200 Battery Section Controller (BSC) 300 Switch control device 310 Processor 320 Memory 330 Transmitting and Receiving Equipment 340 Input Interface Device 350 Output Interface Device 360 storage device 370 Bus 400 Power Conversion / Conditioning System (PCS) 400 Power Conversion System 400 configurations 500 DC / DC Converter 600 Grid 700 PV system

Claims

1. 1. An energy storage system including a photovoltaic (PV) system and connected to a power grid, comprising: a power conversion system (PCS) connected to the power grid and selectively connected to the solar power generation system; a first switch for selectively connecting the solar power generation system to a DC side of the power conversion system; a first ground fault detector having one terminal connected to ground; a second switch located between the first switch and the solar power generation system, for selectively connecting the solar power generation system to the other terminal of the first ground fault detector; and a switch control device that controls the first switch and the second switch according to a power generation state of the solar power generation system to change a ground structure of one or more of the solar power generation system, the power conversion system, and a battery system included in the energy storage system, and selectively connects the solar power generation system to a DC side of the power conversion system; Energy storage systems.

2. The switch control device includes:

2. The energy storage system according to claim 1, wherein when the solar power generation system is in a power generation state, a grounding structure is applied to the solar power generation system and the power conversion system by operating the first switch and the second switch in a closed state, and the first ground fault detector detects whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

3. The switch control device includes:

3. The energy storage system according to claim 2, wherein after the solar power generation system is switched from a non-power generation state to a power generation state, the second switch is operated in an open state for a preset time, thereby applying a floating ground structure to the solar power generation system and the power conversion system, and a second ground fault detector configured at a DC side input node of the power conversion system detects whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

4. The switch control device includes:

2. The energy storage system according to claim 1, wherein, when the solar power generation system is not generating power, the first switch is operated in an open state and the second switch is operated in a closed state, thereby applying a grounding structure to the solar power generation system and applying a floating ground structure to the power conversion system, and the first ground fault detector detects whether or not a ground fault has occurred in the solar power generation system.

5. The energy storage system includes: Further comprising a second ground fault detector arranged at a DC side input node of the power conversion system; The energy storage system of claim 4 , wherein the second ground fault detector detects the presence or absence of a ground fault in the power conversion system.

6. the first switch is a normally open switch; 2. The energy storage system of claim 1, wherein the switch control device includes a first switch drive circuit configured to drive the first switch by receiving power produced by the solar power generation system, and operates the first switch in a closed state when the solar power generation system is in a power generation state.

7. the second switch is a normally closed switch, The energy storage system of claim 1 , wherein the switch control device includes a second switch drive circuit configured to be supplied with power produced by the solar power generation system to drive the second switch.

8. 8. The energy storage system according to claim 7, wherein the second switch drive circuit is configured to be driven using the supplied power when a control signal is received from an external control device, and when the solar power generation system is in a power generation state and the control signal is input, the second switch is operated in an open state.

9. The energy storage system according to claim 1 , further comprising a battery system connected to a DC side input node of the power conversion system.

10. The first ground fault detector includes:

10. The energy storage system of claim 1, comprising a Ground Fault Detection Interrupter (GFDI).

11. The second ground fault detector includes: The energy storage system of claim 3 or 5, comprising an Insulation Monitoring Device (IMD).

12. 1. A ground structure control device located within an energy storage system connected to a power grid, the energy storage system including a photovoltaic (PV) system and a power conversion system (PCS) selectively connected to the photovoltaic (PV) system, the ground structure control device comprising: a first switch for selectively connecting the solar power generation system to a DC side of the power conversion system; a first ground fault detector having one terminal connected to ground; a second switch located between the first switch and the solar power generation system, for selectively connecting the solar power generation system to the other terminal of the first ground fault detector; and a switch control device that controls the first switch and the second switch according to a power generation state of the solar power generation system to change the grounding structure of one or more of the solar power generation system, the power conversion system, and a battery system included in the energy storage system, and selectively connects the solar power generation system to a DC side of the power conversion system.

13. The switch control device includes:

13. The grounding structure control device of claim 12, wherein when the solar power generation system is in a power generation state, the first switch and the second switch are operated in a closed state to apply a grounding structure to the solar power generation system and the power conversion system, and the first ground fault detector detects whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

14. The switch control device includes: The ground structure control device of claim 13, wherein after the solar power generation system is switched from a non-power generation state to a power generation state, the second switch is operated in an open state for a preset time, thereby applying a floating ground structure to the solar power generation system and the power conversion system, and a second ground fault detector configured at a DC side input node of the power conversion system detects whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

15. The switch control device includes:

13. The grounding structure control device of claim 12, wherein when the solar power generation system is not generating power, the first switch is operated in an open state and the second switch is operated in a closed state, thereby applying a grounding structure to the solar power generation system, applying a floating ground structure to the power conversion system, and causing the first ground fault detector to detect whether or not a ground fault has occurred in the solar power generation system.

16. The ground structure control device includes: Further comprising a second ground fault detector arranged at a DC side input node of the power conversion system; The ground structure control device of claim 15 , wherein the second ground fault detector detects the presence or absence of a ground fault in the power conversion system.

17. the first switch is a normally open switch; The ground structure control device of claim 12, wherein the switch control device includes a first switch drive circuit configured to drive the first switch by receiving power produced by the solar power generation system, and operates the first switch in a closed state when the solar power generation system is in a power generation state.

18. the second switch is a normally closed switch, The ground structure control device of claim 12 , wherein the switch control device includes a second switch drive circuit configured to be supplied with power produced by the solar power generation system to drive the second switch.

19. The ground structure control device of claim 18, wherein the second switch drive circuit is configured to be driven using the supplied power when a control signal is received from an external control device, and when the solar power generation system is in a power generation state and the control signal is input, the second switch is operated in an open state.

20. The ground structure control device of claim 12 further comprising a third switch selectively connecting a DC side input node of the power conversion system and a battery system.

21. The third switch is The ground structure control device of claim 20 , wherein the ground structure control device is operated in a closed state during power generation and non-power generation of the solar power generation system.

22. A switch control device is provided in an energy storage system connected to a power grid, the switch control device including: a photovoltaic (PV) system; a power conversion system (PCS) selectively connected to the photovoltaic power generation system; a first switch selectively connecting the photovoltaic power generation system to a DC side of the power conversion system; a first earth fault detector having one side terminal connected to ground; and a second switch located between the first switch and the photovoltaic power generation system and selectively connecting the photovoltaic power generation system to the other side terminal of the first earth fault detector, the switch control device being provided in an energy storage system connected to a power grid, the second switch comprising: at least one processor; a memory for storing at least one instruction to be executed by said at least one processor; The at least one instruction: instructions to verify the status of the solar power system; and A switch control device for an energy storage system, the switch control device including an instruction for controlling the first switch and the second switch according to a power generation state of the solar power generation system to control one or more grounding structures of the solar power generation system, the power conversion system, and a battery system included in the energy storage system.

23. The instructions for controlling the ground structure include:

23. The switch control device for an energy storage system according to claim 22, further comprising instructions to apply a grounding structure to the solar power generation system and the power conversion system by operating the first switch and the second switch in a closed state when the solar power generation system is in a power generation state, and to cause the first ground fault detector to detect whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

24. The instructions for controlling the ground structure include:

24. The switch control device for an energy storage system according to claim 23, further comprising an instruction to apply a floating ground structure to the solar power generation system and the power conversion system by operating the second switch in an open state for a preset time after the solar power generation system is switched from a non-power generation state to a power generation state, and to cause a second ground fault detector configured at a DC side input node of the power conversion system to detect whether or not a ground fault has occurred in the solar power generation system and the power conversion system.

25. The instructions for controlling the ground structure include:

23. The switch control device for an energy storage system according to claim 22, further comprising instructions to operate the first switch in an open state and the second switch in a closed state when the solar power generation system is in a non-power generation state, thereby applying a grounding structure to the solar power generation system, and to cause the first ground fault detector to detect whether or not a ground fault has occurred in the solar power generation system.

26. The instructions for controlling the ground structure include: The switch control device for an energy storage system according to claim 25, further comprising instructions for applying a floating ground structure to the power conversion system and for causing a second ground fault detector configured on a DC input node of the power conversion system to detect the presence or absence of a ground fault in the power conversion system.

Images