PV-ESS direct grid-connected energy management system and photovoltaic power generation system interlocking device

Abstract

A PV interlocking device according to an embodiment of the present invention is a device for interconnecting a DC bus connected to a DC power line of an energy storage system (ESS) and an inverter (PCS) with a photovoltaic power generation (PV) system, and includes an inverter connection terminal for connecting the photovoltaic power generation system with the inverter; an ESS connection terminal for connecting the photovoltaic power generation system with the ESS; and a disconnector for disconnecting the photovoltaic power generation system from the DC bus according to a control command based on an external condition.

Description

[Technical Field]

[0001] This application claims the benefit of the filing dates of Korean Patent Application No. 10-2022-0011267 filed with the Korean Intellectual Property Office on January 26, 2022, and Korean Patent Application No. 10-2023-0003808 filed with the Korean Intellectual Property Office on January 11, 2023, and all of the contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a PV interlocking device, an energy management system including the same, and a control method for the energy management system, and more particularly to an interlocking device that separates a photovoltaic power generation system from a battery system according to external conditions, an energy management system including the same, and a control method for the energy management system. [Background technology]

[0003] An energy storage system (ESS) is a system that connects renewable energy, batteries that store power, and an existing power grid. In recent years, as smart grids and renewable energy have become more widespread and emphasis has been placed on the efficiency and stability of power grids, 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 energy storage systems vary, and multiple battery systems can be connected to form a large-capacity energy storage system.

[0004] Energy storage systems generate and store electricity in the form of direct current (DC) voltage. When such energy storage systems are connected to a photovoltaic (PV) system, they are usually connected to the power grid via an AC coupling system, which is connected to an alternative current (AC) system via an inverter.

[0005] In recent years, DC coupled systems, in which a photovoltaic power generation system and an ESS are coupled to a DC power distribution system, are expected to increase in order to maximize photovoltaic power generation efficiency and reduce installation costs by minimizing the number of inverters. However, DC coupled systems, in which the PV system and ESS are commonly connected to a DC bus, can be plagued by problems such as system errors due to conflicts between the MPPT control of the photovoltaic power and the ESS voltage control, reduced power efficiency due to partial discharge due to the PV connection while the ESS is supplying power to the power grid at night, and increased system risk due to the inflow of fault current. Therefore, a separate method is needed to directly connect the PV system and ESS to the DC bus. Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a PV interlocking device.

[0007] Another object of the present invention to solve the above problems is to provide an energy management system including a PV interlocking device.

[0008] Another object of the present invention to solve the above problems is to provide a control method for an energy management system. [Means for solving the problem]

[0009] To achieve the above object, a PV interlocking device according to one embodiment of the present invention is a device for interconnecting a photovoltaic (PV) system with a DC bus connected to a DC power line of an energy storage system (ESS) and an inverter (PCS), and includes an inverter connection terminal for connecting the PV system with the inverter; an ESS connection terminal for connecting the PV system with the ESS; and a disconnector for disconnecting the PV system from the DC bus according to a control command based on an external condition.

[0010] The disconnector can receive a control command based on the external condition from the power management control device and operate accordingly.

[0011] The PV interlocking device may further include a current monitoring unit that measures the amount of power generated by the photovoltaic power generation system; and a ground fault detector that detects a ground fault in the photovoltaic power generation system.

[0012] The ESS connection terminal can be connected to a Battery DC Panel (BDCP) in the energy storage system.

[0013] The external conditions may include one or more of a time condition and a weather condition relating to whether solar power generation is possible.

[0014] More specifically, the external conditions may include whether the operating time period of the solar power generation system is daytime or nighttime.

[0015] The disconnector disconnects the photovoltaic power generation system from the DC bus during nighttime hours.

[0016] To achieve the above-mentioned other object, an energy management system according to one embodiment of the present invention includes a control device that interfaces with an energy storage system (ESS) and a photovoltaic (PV) system connected thereto and checks whether the PV system is capable of generating power based on external conditions; and a PV interlocking device that disconnects the PV system from a DC bus connected to the energy storage system and a DC power line of an inverter (PCS) in accordance with a control command of the power management control device.

[0017] The PV interlocking device may include an inverter connection terminal that connects the solar power generation system and the inverter; an ESS connection terminal that connects the solar power generation system and the ESS; and a disconnector that disconnects the solar power generation system from the DC bus in accordance with a control command of the power management control device based on external conditions.

[0018] The PV interlocking device may further include a current monitoring unit for measuring the amount of power generated by the photovoltaic power generation system; and a ground fault detector for detecting a ground fault in the photovoltaic power generation system.

[0019] The ESS connection terminal can be connected to a Battery DC Panel (BDCP) in the energy storage system.

[0020] The external conditions may include one or more of a time condition and a weather condition relating to whether solar power generation is possible.

[0021] More specifically, the external conditions may include whether the operating time period of the solar power generation system is daytime or nighttime.

[0022] The disconnector disconnects the photovoltaic power generation system from the DC bus during nighttime hours.

[0023] When solar power generation is possible, the solar power generation system is connected to the DC bus and the energy management system operates in a first operation mode, and when solar power generation is not possible, the solar power generation system is disconnected from the DC bus and the energy management system operates in a second operation mode.

[0024] In the first operation mode, the inverter supplies power by maximum power point tracking (MPPT) control, and the ESS can perform charging operation in a constant power (CP) mode.

[0025] Meanwhile, in a second operation mode, the ESS discharges in a constant voltage (CV) mode, and the PV inverter operates to supply power in a constant power (CP) mode.

[0026] To achieve the above-mentioned still another object, a control method for an energy management system according to one embodiment of the present invention includes a step of checking whether the photovoltaic (PV) system is capable of generating power based on external conditions; and a step of connecting or disconnecting the DC bus and the photovoltaic (PV) system using a PV interlocking device arranged between the photovoltaic (PV) system and a DC bus connected to a DC power line of the energy storage system (ESS) and an inverter (PCS) according to the checking result.

[0027] Connecting or disconnecting the DC bus from the photovoltaic (PV) system may include connecting the PV system to the DC bus and operating the energy management system in a first operational mode when solar power generation is available.

[0028] Connecting or disconnecting the DC bus from the photovoltaic (PV) system may include disconnecting the PV system from the DC bus and operating the energy management system in a second mode of operation when solar power generation is not possible.

[0029] In the first operation mode, the inverter supplies power by maximum power point tracking (MPPT) control, and the ESS can perform charging operation in a constant power (CP) mode.

[0030] Meanwhile, in a second operation mode, the ESS discharges in a constant voltage (CV) mode, and the PV inverter operates to supply power in a constant power (CP) mode. [Effects of the Invention]

[0031] According to the above-described embodiments of the present invention, power generation efficiency can be improved and installation costs can be reduced by constructing a solar-ESS direct grid-connected DC power distribution system.

[0032] In addition, the PV interlocking device monitors the PV system for ground faults while photovoltaic power generation is in progress, and isolates the PV system from the ESS while no power generation is in progress, preventing the inflow of fault current and a decrease in power efficiency.

[0033] This is expected to optimize the operation of energy management systems including solar power generation systems and battery systems. [Brief explanation of the drawings]

[0034] [Figure 1] This is a block diagram of an AC-coupled solar-ESS grid-connected system. [Figure 2] 1 is a block diagram showing an example of a DC-coupled solar-ESS grid-connected system to which the present invention can be applied. [Figure 3] 1 is a diagram showing the connection relationship between each system in a DC coupled solar photovoltaic-ESS grid-connected system according to an embodiment of the present invention. [Figure 4] 10 is a table illustrating a method for operating a solar power generation grid-tied DC coupled energy storage system according to external conditions according to an embodiment of the present invention. [Figure 5] FIG. 2 is a flow chart of an energy storage system operation method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] Since the present invention can be modified in various ways and can have 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 embodiments, but rather to include all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention. Like reference numerals are used to refer to like elements throughout the drawings.

[0036] Terms such as "first," "second," "A," and "B" may be used to describe various components, but the components should not be limited by these terms. These terms are used only to distinguish one component from another. For example, a first component may be termed a "second component," and similarly, a second component may be termed 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.

[0037] When a component is referred to as being "coupled" or "connected" to another component, it is understood that the component may be directly coupled or connected to the other component, but that there may be other components in between. In contrast, when a component is referred to as being "directly coupled" or "directly connected" to another component, it is understood that there are no other components in between.

[0038] The terms used in this application are merely used to describe specific embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise. It should be understood that in this application, the terms "comprise" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and do not preclude the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0039] 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 this invention pertains. 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.

[0040] Some terms used in this specification are defined as follows:

[0041] 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 [%].

[0042] A battery rack is a system with the smallest single structure that can be monitored and controlled through a BMS by connecting pack units set by the battery manufacturer in series / parallel, and can be composed of multiple battery modules and one BPU or protection device.

[0043] 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.

[0044] A BSC (Battery System Controller) is a device that performs top-level control for a battery system including a bank-based battery system, and can also be used as a control device in a battery system with a multi-bank level structure.

[0045] 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 (unit: [kW]) set at the rack level, and can be set based on the battery's SOC and temperature.

[0046] The power limit can be divided into a charge power limit and a discharge power limit depending on whether it is charging or discharging. Also, depending on the structure of the battery system, a rack power limit per rack and a bank power limit per bank can be defined.

[0047] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0048] Figure 1 is a block diagram of an AC-coupled solar-ESS grid-connected system.

[0049] Referring to FIG. 1, the AC coupled solar-ESS grid-connected system is a form in which a PV system and a battery (or ESS) system are coupled to an AC bus via a solar (PV) inverter and an ESS inverter, respectively, and are connected to a power grid.

[0050] The PV inverter receives commands from the PMS (Power Management System) to generate electricity by forming a voltage that maximizes PV power generation efficiency, or during the night, it supplies energy stored in the battery to the power grid as needed.

[0051] However, in recent years, the demand for DC coupling systems, which are a type of system that is different from the AC coupling solar-ESS grid-connected system, has been increasing due to its advantages such as maximizing solar power generation efficiency and reducing installation costs by minimizing the number of inverters.

[0052] FIG. 2 is a block diagram showing an example of a DC-coupled solar-ESS grid-connected system to which the present invention can be applied.

[0053] In a DC-coupled solar-ESS grid-connected system, a DC / DC converter 500 capable of individually controlling the DC voltage / current for each battery system 100 is required. Because a DC / DC converter is installed in the battery system, the DC / AC converter used for linking with the solar system is no longer required, increasing efficiency. Furthermore, applying a DC / DC converter to each battery system not only protects and controls the existing battery system, but also enables control of the battery power amount taking into account the characteristics of each individual battery system, even if differences in SOC, SOH, and capacity occur between battery racks.

[0054] FIG. 2 shows an example of a DC coupled system in which the output side of a PV (Photovoltaic; solar power generation system) 700 is connected to the output side of a DC / DC converter 500 and the input side of a PCS 400 .

[0055] Batteries that store power in an energy storage system are typically implemented in the form of a battery rack made up of multiple battery modules, and multiple battery racks made up of multiple battery banks. Here, the battery rack may also 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. 2 may be in the form of a battery pack or a battery rack.

[0056] In this case, each battery 100 may be provided with a Battery Management System (BMS). The BMS monitors the current, voltage, and temperature of each battery rack (or pack) under its control, calculates the State of Charge (SOC) based on the monitoring results, and controls charging and discharging. In the system of FIG. 2, if 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. The PCS 400 may be understood to be the same component as the inverter or PV inverter in other parts of this specification.

[0059] Furthermore, the output of the DC / DC converter 500 can be connected to the PCS 400, which can be connected to the grid 600. The PCS 400 normally operates in a constant power mode. A power management system (PMS) / energy management system (EMS) 300 connected to the PCS can control the output of the PCS based on the monitoring and control results of the BMS or BSC.

[0060] 2, 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 outputs of the DC / DC converters corresponding to each battery are connected to PCS 400 via DC links.

[0061] The DC-DC converter may be a bidirectional converter, and when conversion is performed 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. Examples of DC-DC converters that can be used include various types of converters such as a full-bridge converter, a half-bridge converter, and a flyback converter.

[0062] Meanwhile, communication using a Controller Area Network (CAN) or Ethernet (shown by dotted lines in FIG. 2) can be performed between the BMS, BSC 200, PMS 300, and PCS 400.

[0063] According to one embodiment of the present invention shown in FIG. 2, the BSC 200, which is 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 (State of Charge), SOH (State of Health), voltage, and temperature 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, which is in charge of control of the entire ESS system, issues a charge or discharge command (via P_pcs_reference) to the PCS 400 during actual system operation.

[0064] Here, the BSC 200 determines the output reference for each DC / DC converter taking into account the state of each battery. In an embodiment of the present invention, the output reference of each DC / DC converter can be set differently depending on whether it is in droop mode or constant power (CP) mode.

[0065] When the output of the DC / DC converter is controlled in droop mode, the BSC can set the droop curve for each DC / DC converter taking into account the state of each battery before system operation and provide it to the corresponding converter.On the other hand, when the DC / DC converter operates in CP mode, the BSC can determine the power reference of each DC / DC converter during system operation and provide it to the corresponding converter.

[0066] During the 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 (PV) system, grid, and battery in real time, and determines the operating mode and output reference of the components within the system based on the operating commands received from the EMS, which is the upper system.

[0067] This DC coupling system has the effect of storing surplus power in the ESS when the amount of PV power generation exceeds the capacity of the solar inverter. This is called energy recapture, and it has the effect of maximizing the amount of solar power generation.

[0068] FIG. 3 is a diagram showing the connection relationships between the systems in the DC coupled solar power-ESS grid-connected system according to the embodiment of the present invention.

[0069] FIG. 3 illustrates a system configuration focusing on hardware components required to actually implement the interconnection between the solar power generation system 700 and the energy storage system 100 when they are interconnected with the power grid 600 through DC coupling.

[0070] 3, the solar power generation system 700 includes a PV array 701 in which PV strings are connected in parallel, and a PV combiner 702 in the form of a distribution board that connects together multiple positive terminals and multiple negative terminals of the PV strings in the PV array. The switch connecting the positive side and the switch connecting the negative side in the PV combiner 702 are always kept connected except when necessary for operation, such as in the case of a malfunction or inspection.

[0071] Each PV string connects multiple PV panels in series to generate a DC bus voltage of 1000 V to 1500 V. The solar power generation system 700 generally generates a maximum voltage of 1000 V to 1500 Vdc, and in the case of a large-capacity power generation system, the output voltage can be increased to generate a lower current capacity for the same power, thereby reducing installation costs such as cable costs.

[0072] The energy storage system 100 can be configured using various energy sources as an energy storage device, but in this embodiment, a secondary battery (battery) is used as the energy source. In the case of a battery system, as previously described with reference to FIG. 2, a voltage of 1000V to 1500Vdc can be generated by connecting a number of battery packs in series to form a battery rack.

[0073] In such a DC power distribution system, the solar inverter performs MPPT control according to the PV power generation status to adjust the DC bus voltage. In this case, if the PV power generation system is directly connected to the battery, it is difficult to adjust the DC bus voltage. Therefore, in a DC coupling system, a separate DC / DC converter is required in the ESS, i.e., the battery system.

[0074] Here, Maximum Power Point Tracking (MPPT) control is a control method that obtains maximum power by appropriately adjusting the load according to external conditions. The point where maximum power is transmitted is called the maximum power operating point (MPP), and the MPPT can be changed depending on external conditions such as solar radiation and temperature.

[0075] 2 and 3 show 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. A rack-based DC / DC converter can result in a complex system, but has the advantage of being able to control each battery rack individually according to its status, and a central DC / DC converter has the advantage of simplifying the system configuration and reducing the number of parts.

[0076] The PV recombiner 710 serves as a distribution board for physically connecting the photovoltaic power generation system and the energy storage system. The PV recombiner 710 may include a remote disconnector, a PV inverter connection terminal, and an ESS connection terminal. The PV recombiner should be understood to be the same component as the PV interlocking device mentioned elsewhere in this specification.

[0077] To prevent a decrease in power generation efficiency, a PV re-combiner can isolate the photovoltaic power generation system from the DC bus, for example, during nighttime using a remote disconnector. Even when the photovoltaic power generation system is not generating power, a voltage is applied to the DC bus connected to the ESS. However, if a voltage is applied to the photovoltaic power generation system when the photovoltaic power generation system is not generating power, a reverse current in the opposite direction to the power generation direction occurs. This is the same as continuous discharge in the battery system, which reduces power generation efficiency. Therefore, according to the present invention, the PV system is isolated from the DC bus during nighttime when the photovoltaic power generation system is not generating power, thereby increasing the power generation efficiency of the ESS.

[0078] In this case, the remote disconnector can be realized using a motorized disconnector.

[0079] The PV recombiner 710 may further include a fuse, a ground fault detection interrupter (GFDI) for preventing ground faults, a current monitor for checking the amount of PV power generation, an IO port, and the like.

[0080] A GFDI is a device connected between a power line and ground that cuts off the current when the current flowing from the power line to ground exceeds a reference value. In addition to a GFDI, other devices that can be used to detect ground faults include an insulation monitoring device (IMD) and a residential current monitoring device (RCM). An IMD is a device that measures and monitors the insulation resistance between the positive terminal and ground and between the negative terminal and ground. An RCM is a device that detects leakage current by monitoring whether the sum of the currents flowing through the positive and negative power lines is zero.

[0081] Another role of the PV recombiner is to prevent fault current from flowing in. Because the solar power generation system and ESS are interconnected without a separate device, fault current may flow in when a ground fault occurs. Therefore, in the present invention, the PV recombiner monitors PV ground faults during power generation and separates the PV from other systems when power generation is not in progress, thereby preventing fault current from flowing in and optimizing ground fault monitoring.

[0082] In this case, the power management control device or energy management system (PMS / EMS) 300 may be a main body that controls the operations of the PV recombiner 710, the PV inverter 400, and the ESS 100 in conjunction with them.

[0083] According to the embodiment, when the PV system and the DC bus are connected via the PV re-combiner 710 under the control of the power management control device, the entire energy management system can operate in a first operation mode. In the first operation mode, the PV inverter supplies power according to an MPPT algorithm. Since this is a section where solar power generation is performed, the ESS 100 can be in a charging state. At this time, the ESS can operate in a constant power (CP) mode. The GFDI included in the PV re-combiner 710 constantly monitors the ground fault of the PV system.

[0084] According to another embodiment, when the PV system is disconnected from the DC bus via the PV recombiner 710 under the control of the power management control device, the entire energy management system can operate in a second operation mode. In the second operation mode, the ESS 100 discharges in a constant voltage (CV) mode, and the PV inverter supplies power in a constant power (CP) mode. The GFDI also monitors the ground fault of the PV system at this time. Meanwhile, the IMD located on the DC bus can be activated to monitor the insulation of the DC bus (ESS and PV inverter) during the nighttime hours.

[0085] Meanwhile, the DC / DC converter 500 can be connected to the PV recombiner 710 via a BDCP (Battery DC Panel) 170.

[0086] In FIG. 3, the EMS is expressed as a single entity that manages the entire system in conjunction with the PMS. However, the energy management system described in this specification can also be understood as a concept including a power management controller (PMS) that interfaces with an energy storage system (ESS) and a photovoltaic (PV) system connected thereto and checks whether the PV system is capable of generating power based on external conditions; and a PV interlocking device that disconnects the DC bus connected to the DC power line of the energy storage system and the inverter (PCS) from the PV system in accordance with a control command from the power management controller, or as a system concept for managing energy that includes all the components shown in FIG. 3.

[0087] FIG. 4 is a table illustrating a method for operating a grid-tied DC coupled energy storage system according to external conditions according to an embodiment of the present invention.

[0088] In the embodiment of Fig. 4, the operation method is explained by dividing the external conditions into time conditions, i.e., day and night. However, the external conditions may include not only time conditions but also weather conditions. That is, the operation method equivalent to the night operation method of this embodiment can be applied even in conditions where sunlight cannot be expected for a long period of time, such as during the rainy season.

[0089] First, during the daytime when sufficient sunlight required for power generation can be expected, the PV recombiner 710 maintains the connection between the PV system and the DC bus in an ON state. The PV inverter supplies power through MPPT control. Since this is the section where solar power generation is performed, the ESS 100 may be charging. At this time, the ESS can operate in CP (Constant Power) mode. The GFDI included in the PV recombiner 710 constantly monitors the PV system for ground faults.

[0090] On the other hand, during the nighttime when solar power generation is not possible, the PV recombiner 710 disconnects the PV system from the DC bus. The ESS 100 discharges in CV (Constant Voltage) mode, and the PV inverter supplies power in CP (Constant Power) mode. The GFDI also monitors the PV system for ground faults.

[0091] Meanwhile, the system according to the present invention may further include an IMD (Insulation Monitoring Device), which is disposed on the DC bus and can monitor the insulation of the DC bus (ESS and PV inverter) during the nighttime hours, and can be turned off during the daytime hours.

[0092] FIG. 5 is a flow diagram of a method for controlling an energy management system according to an embodiment of the present invention.

[0093] The method for controlling an energy management system according to the present invention can be performed by a control device that is linked to an energy storage system (ESS) and a solar power generation (PV) system connected thereto. The control device checks whether the solar power generation (PV) system is capable of generating power based on external conditions (S510).

[0094] Here, the external conditions may include one or more of a time condition and a weather condition that determine whether solar power generation is possible.

[0095] Depending on the confirmation result, the connection between the DC bus and the photovoltaic power generation (PV) system is maintained (S520) or disconnected (S530) using a PV recombiner arranged between the DC bus connected to the DC power line of the energy storage system (ESS) and the inverter (PCS) and the photovoltaic power generation system.

[0096] That is, for example, during the daytime when sufficient sunlight required for power generation can be expected, the PV recombiner 710 maintains the connection between the PV system and the DC bus ON. Conversely, during the nighttime when solar power generation is not possible, the PV recombiner releases the connection between the PV system and the DC bus.

[0097] When the PV system and the DC bus are connected, the entire energy management system can operate in a first operation mode (S521). In the first operation mode, the PV inverter supplies power according to an MPPT algorithm. Since this is the section where solar power generation is performed, the ESS 100 can be in a charging state. At this time, the ESS can operate in a constant power (CP) mode. The GFDI included in the PV recombiner 710 constantly monitors the ground fault of the PV system.

[0098] On the other hand, if the PV system is disconnected from the DC bus, the entire energy management system can operate in a second operation mode (S531). In the second operation mode, the ESS 100 discharges in a constant voltage (CV) mode, and the PV inverter supplies power in a constant power (CP) mode. The GFDI also monitors the PV system for ground faults in this mode. Meanwhile, the IMD installed on the DC bus can be activated to monitor the insulation of the DC bus (ESS and PV inverter) during the nighttime hours.

[0099] According to the above-described embodiment of the present invention, it is possible to monitor a ground fault in the PV system through the PV recombiner during solar power generation, and to isolate the PV system from the ESS during no power generation, thereby achieving optimization of fault current inflow and ground fault monitoring.

[0100] The operations of the methods according to the embodiments of the present invention can be embodied as a computer-readable program or code on a computer-readable recording medium. The computer-readable recording medium includes all kinds of storage devices in which data that can be read by a computer system is stored. In addition, the computer-readable recording medium can be distributed among computer systems connected via a network, so that the computer-readable program or code can be stored and executed in a distributed manner.

[0101] Some aspects of the invention have been described in the context of an apparatus, but they may also be described in terms of a corresponding method, where a block or apparatus corresponds to a method step or feature of a method step. Similarly, aspects described in the context of a method may be described 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 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.

[0102] Although the present invention has been described above with reference to preferred embodiments, 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]

[0103] 100: Energy Storage System (ESS) 200 Battery Section Controller (BSC) 300 Energy Management System (PMS / EMS) 400 Power Conversion / Conditioning System (PCS) 500 DC / DC Converter 600 Power system 700 Solar Power Generation System 701 PV array 702 PV Combiner 710 PV Recombiner

Claims

1. An apparatus for interconnecting a DC bus connected to a DC power line of an energy storage system (ESS) and an inverter (PCS) with a photovoltaic (PV) system, comprising: an inverter connection terminal for connecting the solar power generation system and the inverter; an ESS connection terminal for connecting the solar power generation system and the ESS; a disconnector that disconnects the solar power generation system from the DC bus according to a control command based on an external condition; a ground fault detector connected to one or more of the DC power line and ground to detect a ground fault in the solar power system; and an insulation monitoring device (IMD) on the DC bus; the ESS connection terminal is connected to one terminal of a DC / DC converter in the ESS via a BDCP (Battery DC Panel) in the ESS, the DC / DC converter has another terminal connected to a battery in the ESS; The IMD is monitoring the insulation of the DC bus during nighttime hours; It operates as off during the daytime and does not monitor the insulation of the DC bus. PV interlocking device.

2. The PV interlocking device according to claim 1 , wherein the disconnector operates by receiving a control command based on the external condition from a power management control device.

3. a current monitoring unit for measuring the amount of power generated by the solar power generation system; The PV interlocking device of claim 1 further comprising:

4. The external conditions are: The PV interlocking device according to claim 1 , comprising at least one of a time condition and a weather condition relating to whether or not solar power generation is possible.

5. The PV interlocking device according to claim 4 , wherein the external conditions include whether the operating time period of the photovoltaic power generation system is daytime or nighttime.

6. The PV interlocking device according to claim 5 , wherein the disconnector disconnects the photovoltaic power generation system from the DC bus during nighttime hours.

7. A power management control device that interfaces with an energy storage system (ESS) and a solar photovoltaic (PV) system connected thereto and determines whether the solar photovoltaic (PV) system is capable of generating power based on external conditions; and a PV interlocking device that disconnects a DC bus connected to a DC power line of an energy storage system and inverter (PCS) from the solar power generation system in accordance with a control command of the power management control device; The PV interlocking device is a disconnector that disconnects the photovoltaic power generation system from the DC bus according to a control command based on an external condition; a ground fault detector connected to one or more of the DC power line and ground to detect a ground fault in the photovoltaic power system; an inverter connection terminal for connecting the solar power generation system and the inverter; an ESS connection terminal that connects the solar power generation system and the ESS; and an insulation monitoring device (IMD) on the DC bus; the ESS connection terminal is connected to one terminal of a DC / DC converter in the ESS via a BDCP (Battery DC Panel) in the ESS, the DC / DC converter has another terminal connected to a battery in the ESS; The IMD is monitoring the insulation of the DC bus during nighttime hours; It operates as off during the daytime and does not monitor the insulation of the DC bus. Energy management system.

8. The PV interlocking device is a current monitoring unit for measuring the amount of power generated by the solar power generation system; and a ground fault detector for detecting a ground fault in the solar power generation system; The energy management system of claim 7 .

9. The external conditions are: The energy management system according to claim 7 , further comprising one or more of a time condition and a weather condition relating to whether solar power generation is possible or not.

10. The energy management system according to claim 9 , wherein the external conditions include whether the operating time period of the photovoltaic power generation system is daytime or nighttime.

11. The energy management system according to claim 7 , wherein the disconnector disconnects the solar power generation system from the DC bus during nighttime hours.

12. 8. The energy management system of claim 7, wherein when solar power generation is possible, the solar power generation system is connected to a DC bus and the energy management system operates in a first operation mode, and when solar power generation is not possible, the solar power generation system is disconnected from the DC bus and the energy management system operates in a second operation mode.

13. In a first mode of operation, The energy management system according to claim 12 , wherein the inverter supplies power by maximum power point tracking (MPPT) control, and the ESS performs a charging operation in a constant power (CP) mode.

14. In a second mode of operation, The energy management system of claim 12 , wherein the ESS discharges in a constant voltage (CV) mode, and the inverter supplies power in a constant power (CP) mode.

15. A method for controlling an energy management system including an energy storage system (ESS) and a photovoltaic (PV) system connected thereto, comprising: determining whether the solar power generation system is capable of generating power based on external conditions; and According to the confirmation result, connecting or disconnecting the DC bus and the solar power generation system using a PV interlocking device disposed between the DC bus connected to the DC power line of the energy storage system and inverter (PCS) and the solar power generation system; The PV interlocking device is a disconnector that disconnects the photovoltaic power generation system from the DC bus according to a control command based on an external condition; a ground fault detector connected to one or more of the DC power line and ground to detect a ground fault in the photovoltaic power system; an inverter connection terminal for connecting the solar power generation system and the inverter; an ESS connection terminal that connects the solar power generation system and the ESS; and an insulation monitoring device (IMD) on the DC bus; the ESS connection terminal is connected to one terminal of a DC / DC converter in the ESS via a BDCP (Battery DC Panel) in the ESS, the DC / DC converter has another terminal connected to a battery in the ESS; The IMD is monitoring the insulation of the DC bus during nighttime hours; operating the DC bus in an off state without monitoring the insulation during daytime hours; Contains Control methods for energy management systems.

16. The step of connecting or disconnecting the DC bus and the solar power generation system includes:

16. The method of claim 15, further comprising the step of connecting the solar power generation system to a DC bus and operating the energy management system in a first operational mode when solar power generation is possible.

17. The step of connecting or disconnecting the DC bus and the solar power generation system includes:

16. The method of claim 15, further comprising disconnecting the solar power generation system from a DC bus and operating the energy management system in a second operational mode when solar power generation is not possible.

18. In a first mode of operation, 17. The control method for an energy management system according to claim 16, wherein the inverter supplies power by maximum power point tracking (MPPT) control, and the ESS performs a charging operation in a constant power (CP) mode.

19. In a second mode of operation, 18. The control method for an energy management system according to claim 17, wherein the ESS discharges in a constant voltage (CV) mode, and the inverter supplies power in a constant power (CP) mode.

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