Insulation monitoring device and insulation monitoring system including insulation monitoring device

Abstract

The present invention relates to an insulation monitoring device comprising: a signal generation unit for applying a pulse signal having a preset voltage to a power line connecting a power conversion device and a load or the power conversion device and a power source; a signal measurement unit for receiving a measurement signal corresponding to the applied pulse signal from a connected protective earth and measuring a detection voltage for calculating an insulation resistance from the received measurement signal; a memory in which a plurality of reference values having different insulation resistance values are stored; and a control unit for calculating the magnitude of the insulation resistance on the basis of the detection voltage, the voltage of the pulse signal, and the magnitude of an internal resistance, detecting the operation state of the power conversion device, and determining the insulation state of the power line by comparing a first reference value among the plurality of reference values with the calculated magnitude of the insulation resistance or comparing a second reference value among the plurality of reference values with the calculated magnitude of the insulation resistance according to the detected operation state of the power conversion device.

Description

Insulation monitoring device and insulation monitoring system including the insulation monitoring device

[0001] The present invention relates to an insulation monitoring system comprising an insulation monitoring device and a plurality of insulation monitoring devices.

[0002] The IT (Insulation Terra) grounding method is a grounding system in which neither side of the power line is grounded, and grounding is achieved solely through the load's enclosure. This IT grounding method has the advantage of ensuring continuous system operation because, even if a ground fault occurs on any of the power lines, system operation is not halted, and there is sufficient time to locate the fault site.

[0003] Since the system can be operated even in the event of a ground fault, it is necessary to continuously monitor the insulation status of power lines while the system is in operation. Accordingly, the International Electrotechnical Commission (IEC) 61557 standard mandates the installation of insulation monitoring devices capable of monitoring the insulation status of power lines.

[0004] This insulation monitoring device (IMD) may include a pulse signal generator that forms a circuit between the transmission line and the ground through an insulation resistance formed between the transmission line and the ground, and injects a square wave (pulse) signal into the formed circuit, and a detection resistor for detecting a voltage according to the square wave signal. When the pulse signal generator applies a signal (voltage: Vp) to the ground (Protective Earth, PE), the insulation resistance (Re) is calculated based on a signal (voltage: Vm) in which the voltage is distributed by the virtual resistance (insulation resistance (Re)) between the ungrounded line and the ground and the internal resistance (Ri) of the IMD from the applied signal (Vp), thereby enabling monitoring of the insulation status of the ungrounded line.

[0005] Meanwhile, as the penetration rate of renewable energy increases, there is a trend toward constructing power grids for load management and the stabilization of renewable energy. As part of this trend, energy storage systems are being installed in power grids. These energy storage systems store excess power generated and, when there is an energy shortage in the power grid, discharge the stored power, thereby enabling more stable and efficient power supply to loads.

[0006] As such, the energy storage device is installed in the power grid and is connected to an ungrounded line through which alternating current supplied from the power source flows. In this case, the line section from the power source to the energy storage device and the line section connecting the power conditioning system (PCS) installed in the energy storage device and the battery can be connected. In this case, the entire line section from the power source to the battery can be divided into a first line section through which alternating current flows (the line section from the power source to the energy storage device) and a second line section through which direct current flows (the line section from the PCS to the battery), with the PCS as the boundary.

[0007] In this case, if the above-mentioned PCS is not operated, the first line section and the second line section are not connected to each other and can be divided into separate sections. In this case, the insulation status of each section can be monitored through separate insulation monitoring devices installed in each section, and the insulation status of each section can be monitored according to the insulation resistance reference value set in each insulation monitoring device and the magnitude of the insulation resistance calculated in each section.

[0008] On the other hand, if the above-mentioned PCS is in operation, the first line section and the second line section are connected to each other, so they can be integrated into a single line section. In this case, any one of the insulation monitoring devices placed in each section can calculate the insulation resistance from the integrated section, and the insulation status of the integrated section can be monitored according to the magnitude of the calculated insulation resistance and the magnitude of the preset insulation resistance.

[0009] However, when the insulation status of the aforementioned integrated section is monitored, there is a problem in that the magnitude of the insulation resistance calculated may be reduced due to the influence of other integrated line sections. Consequently, even if no leakage current or similar issues occur, the insulation status of the aforementioned integrated section may be falsely detected as damaged, leading to a problem where a false alarm may be output.

[0010] The present invention aims to solve the aforementioned problem by providing an insulation monitoring device capable of accurately monitoring the insulation status of an ungrounded line even when the line section is extended to an energy storage device through the operation of the power conversion device, and an insulation monitoring system including said insulation monitoring device.

[0011] Furthermore, the present invention aims to provide an insulation monitoring device capable of preventing an incorrect insulation condition damage alarm from being output by an integrated line section when the line section is extended to an energy storage device through the operation of the power conversion device, and an insulation monitoring system including the insulation monitoring device.

[0012] An insulation monitoring device according to an embodiment of the present invention for achieving the above-described purpose comprises: a signal generating unit that applies a pulse signal having a preset voltage to a power line connecting a power conditioning system (PCS) and a load or between the power conditioning system and a power source; a signal measuring unit connected to ground, receiving a measurement signal corresponding to the applied pulse signal from the connected ground, and measuring a detection voltage for calculating insulation resistance from the received measurement signal; a memory in which a plurality of reference values ​​having different insulation resistance values ​​are stored; and a control unit that calculates the size of the insulation resistance based on the detection voltage, the voltage of the pulse signal, and a preset internal resistance size, detects the operating state of the power conditioning system, and determines the insulation state of the power line by comparing a first reference value among the plurality of reference values ​​with the size of the calculated insulation resistance or comparing a second reference value among the plurality of reference values ​​with the size of the calculated insulation resistance according to the detected operating state of the power conditioning system.

[0013] In one embodiment, the control unit is characterized by detecting a voltage change of the power line that increases or decreases above a certain level, and determining the operating state of the power conversion device based on the detected voltage change of the power line.

[0014] In one embodiment, the insulation monitoring device further includes a communication unit that performs a communication connection with another insulation monitoring device placed on another power line connected through the power converter, and the control unit receives a result of detecting a voltage change of the other power line from the other insulation monitoring device, and determines the operating state of the power converter based on the received result of the voltage change of the other power line and the result of detecting the voltage change of the power line.

[0015] In one embodiment, the load is a battery, the insulation monitoring device calculates the magnitude of the insulation resistance from a power line through which a direct current flows between the power converter and the battery, and the other insulation monitoring device calculates the magnitude of the insulation resistance from the other power line through which an alternating current flows between the power converter and the power source.

[0016] In one embodiment, the insulation monitoring device further includes a communication unit that collects information related to the driving state of the power converter from the power converter, and the control unit determines the driving state of the power converter based on the driving state-related information collected from the power converter.

[0017] In one embodiment, the control unit is characterized by changing a reference value for determining the insulation state of the power line according to the determined operating state of the power conversion device when the operating state of the power conversion device changes as a result of the determination.

[0018] In one embodiment, the first reference value is an insulation resistance reference value for determining the insulation state of a first power line section connecting the power converter and the load or the power converter and the power source when the power converter is not operating, and the second reference value is an insulation resistance reference value for determining the insulation state of an integrated section in which the first power line section and a second power line section, which is another section connected through the power converter, are integrated when the power converter is operating, and is characterized by having a value smaller than the first reference value.

[0019] In one embodiment, the memory further stores information regarding the intrinsic resistance value of the power converter and information regarding the internal resistance magnitude of another insulation monitoring device placed in the second power line section, and the control unit inversely calculates the detection voltage based on the internal resistance of the insulation monitoring device, the detection resistance of the insulation monitoring device, the magnitude of the insulation resistance corresponding to the first reference value, and the voltage of the pulse signal, and adds the intrinsic resistance of the power converter and the magnitude of the internal resistance of the insulation monitoring device placed in the second power line section to the internal resistance magnitude of the insulation monitoring device, and calculates the second reference value based on the summed internal resistance magnitude and the inversely calculated detection voltage, and the voltage of the pulse signal and the magnitude of the detection resistance of the insulation monitoring device.

[0020] To achieve the above-mentioned purpose, an insulation monitoring system for monitoring the insulation status of a line section to which an energy storage system (ESS) is connected, according to an embodiment of the present invention, comprises: an insulation monitoring device connected to a first power line section connecting a power source and a power conditioning system (PCS) of the energy storage system and determining the insulation status of the first power line section; and an insulation monitoring device connected to a second power line section connecting the power conditioning system and a battery of the energy storage system and determining the insulation status of the second power line section. One of the insulation monitoring devices is a first insulation monitoring device whose operating state is determined based on whether the power conditioning system is operating, and the other of the insulation monitoring devices is a second insulation monitoring device that determines the insulation status of either the first power line section or the second power line section based on a first reference value for determining the insulation status of either the first power line section or the second power line section, or a second reference value for determining the insulation status of an integrated section in which the first power line section and the second power line section are integrated, depending on whether the power conditioning system is operating. It is characterized as an insulation monitoring device.

[0021] In one embodiment, the first insulation monitoring device and the second insulation monitoring device are characterized by determining the operating state of the power converter based on a voltage change of the first power line or the second power line that increases or decreases above a preset level for a certain period of time, or based on operating state information collected from the power converter.

[0022] In one embodiment, the first insulation monitoring device is characterized by operating in a standby state that does not monitor the insulation state of the first power line when the power converter is in a driven state, and operating in an insulation monitoring state that monitors the insulation state of the first power line when the power converter is not in a driven state.

[0023] In one embodiment, the first insulation monitoring device is an insulation monitoring device that monitors the insulation status of the first power line section through which alternating current flows, and the second insulation monitoring device is an insulation monitoring device that monitors the insulation status of the second power line section through which direct current flows.

[0024] In one embodiment, the first reference value includes a plurality of insulation resistance sizes for determining the insulation state of a power line as one of a plurality of different states according to the calculated insulation resistance, and the second reference value includes a plurality of insulation resistance sizes for determining the insulation state of a power line as one of a plurality of different states according to the calculated insulation resistance, wherein each of the insulation resistance sizes included in the second reference value has a value smaller than each of the insulation resistance sizes included in the corresponding first reference value.

[0025] In one embodiment, the first reference value is determined based on 1000 Ohm per 1 volt of power line voltage (1000 Ohm / V), and the second reference value is determined based on 100 Ohm per 1 volt of power line voltage (100 Ohm / V).

[0026] In one embodiment, the second insulation monitoring device further comprises a memory including information on the intrinsic resistance size of the power converter and the internal resistance size of the first insulation monitoring device, and calculates the size of the internal resistance corresponding to the integrated section based on the intrinsic resistance size of the power converter, the internal resistance size of the first insulation monitoring device, and the internal resistance of the second insulation monitoring device, and calculates the second reference value based on the calculated internal resistance size of the integrated section and the insulation resistance size corresponding to the first reference value.

[0027] The effects of the insulation monitoring device according to the present invention and the insulation monitoring system including the insulation monitoring device are described as follows.

[0028] According to at least one embodiment of the present invention, the present invention has a configuration in which, when an energy storage device is connected and a line section from a power converter to a battery is integrated with a line section from a power source to an energy storage device through a power converter, an insulation resistance reference value is determined by reflecting the resistance value according to the insulation monitoring device of another line section integrated with the line section in which an insulation monitoring device for monitoring the insulation state is installed, and the resistance value according to the power converter, and the insulation state of the integrated line section is monitored according to the determined insulation resistance reference value.

[0029] Therefore, the present invention has the effect of being able to monitor the insulation status of the integrated line section more accurately, and has the effect of preventing false insulation damage alarms from being output due to the reduced insulation resistance based on the resistance value according to the insulation monitoring device of the other integrated line section and the resistance value according to the power conversion device.

[0030] FIG. 1 is a block diagram illustrating the configuration of an insulation monitoring system that includes an insulation monitoring device for monitoring the insulation status in each line section separated by a power conversion device.

[0031] FIGS. 2a and 2b are exemplary diagrams illustrating line sections in which the insulation status is monitored according to the operating status of the power converter, and the operating status of insulation monitoring devices placed in each line section.

[0032] FIG. 3 is a block diagram illustrating the configuration of an insulation monitoring device according to an embodiment of the present invention in more detail.

[0033] FIG. 4 is an exemplary diagram illustrating an example in which a voltage lower than a preset pulse voltage is detected by an insulation resistance in an insulation monitoring device according to an embodiment of the present invention.

[0034] FIG. 5 is an illustrative diagram showing examples of information stored in the memory of an insulation monitoring device according to an embodiment of the present invention.

[0035] FIG. 6 is a flowchart showing the operation process of a first insulation monitoring device in which the insulation resistance reference value is not changed in an insulation monitoring system according to an embodiment of the present invention.

[0036] FIG. 7 is a flowchart showing the operation process of a second insulation monitoring device in which the insulation resistance reference value is changed according to the operating state of the power converter in an insulation monitoring system according to an embodiment of the present invention.

[0037] FIGS. 8A and FIGS. 8B are exemplary drawings illustrating examples of determining the operating status of a power converter based on information collected from a power converter in an insulation monitoring system according to an embodiment of the present invention.

[0038] FIG. 9 is an example diagram showing the change in the magnitude of insulation resistance according to the SOC of the battery in an insulation monitoring system according to an embodiment of the present invention.

[0039] FIG. 10 is a flowchart illustrating the operation process in which insulation monitoring devices determine the operating status of a power converter based on voltage changes detected from a power line in an insulation monitoring system according to an embodiment of the present invention.

[0040] FIG. 11 is a flowchart illustrating the operation process in which the second insulation monitoring device directly calculates an insulation resistance reference value to be applied to an integrated line section based on the resistance values ​​of the insulation monitoring device and the power converter placed on another line.

[0041] It should be noted that technical terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Additionally, singular expressions used in this specification include plural expressions unless the context clearly indicates otherwise. The suffixes "module" and "part" for components used in the following description are assigned or used interchangeably solely for the ease of drafting the specification and do not inherently possess distinct meanings or roles.

[0042] In this specification, terms such as "composed of" or "comprising" should not be interpreted as necessarily including all of the various components or steps described in the specification, and should be interpreted as potentially excluding some of the components or steps, or including additional components or steps.

[0043] In addition, when describing the technology disclosed in this specification, if it is determined that a detailed description of related prior art could obscure the essence of the technology disclosed in this specification, such detailed description is omitted.

[0044] In addition, the attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification, and the technical concept disclosed in this specification is not limited by the attached drawings; it should be understood that they include all modifications, equivalents, and substitutions that fall within the concept and technical scope of the present invention. Furthermore, not only each of the embodiments described below, but also combinations of embodiments may fall within the concept and technical scope of the present invention as modifications, equivalents, and substitutions that fall within the concept and technical scope of the present invention.

[0045] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings.

[0046] FIG. 1 is a block diagram illustrating the configuration of an insulation monitoring system according to an embodiment of the present invention, wherein each line section classified by a power conversion device includes an insulation monitoring device for monitoring the insulation status. FIG. 2a and FIG. 2b are exemplary diagrams illustrating line sections where the insulation status is monitored according to the operating state of the power conversion device, and the operating states of the insulation monitoring devices placed in each line section. FIG. 3 is a block diagram illustrating the configuration of an insulation monitoring device according to an embodiment of the present invention in more detail. FIG. 4 is an exemplary diagram illustrating an example in which a voltage lower than a preset pulse voltage is detected by an insulation resistance in an insulation monitoring device according to an embodiment of the present invention.

[0047] As described above, the current power grid can be connected to an energy storage device (ESS) capable of storing excess power supplied to the power grid and supplying the stored power to the power grid when there is a power shortage. In this case, the energy storage device may be configured to include a battery capable of storing power and a power conversion device (PCS) for converting alternating current supplied from a power source into direct current, or for converting direct current supplied from a battery into alternating current. Accordingly, as shown in FIG. 1, an energy storage device (30) can be connected to the power grid in such a manner that alternating current is supplied from the power source (1) to the power conversion device (2), and direct current is supplied from the power conversion device (2) to the battery (3).

[0048] Meanwhile, the power conversion device (2) may be connected to a power line connected to the power source (1) and a power line connected to the battery (3) depending on the state of the power grid or the state of charging (SOC) of the battery (3). To this end, a first circuit breaker (CB) (31) formed to connect or disconnect between the power source (1) and the power conversion device (2) may be provided on the AC power line connecting the power conversion device (2) and the power source (1). Additionally, a second circuit breaker (CB) (32) formed to connect or disconnect between the battery (3) and the power conversion device (2) may be provided on the DC power line connecting the power conversion device (2) and the battery (3). In this case, the first circuit breaker (31) and the second circuit breaker (32) may be an Air Circuit Breaker (ACB) using air as the arc extinguishing medium.

[0049] Meanwhile, the first cutoff switch (31) and the second cutoff switch (32) can operate as a single unit and determine the operating state of the power conversion device (2). That is, when the first cutoff switch (31) and the second cutoff switch (32) open the circuit to electrically disconnect the power conversion device (2) from the power lines, the power conversion device (2) may be in a non-operating state, i.e., an off state. However, when the first cutoff switch (31) and the second cutoff switch (32) close the circuit to electrically connect the power lines and the power conversion device (2), the power conversion device (2) may be in an operating state, i.e., an on state.

[0050] In this case, the first cutoff switch (31) and the second cutoff switch (32) may be components of the power conversion device (2), and the circuit may be opened when the operation of the power conversion device (2) is turned off, and the circuit may be closed when the operation of the power conversion device (2) is turned on. Accordingly, in the following description, the first cutoff switch (31) and the second cutoff switch (32) will be described as components of the power conversion device (2), and when the operation state of the power conversion device (2) is turned on, the power conversion device (2) may be connected to each power line, and when the operation state of the power conversion device (2) is turned off, the power conversion device (2) may be disconnected from each power line.

[0051] Meanwhile, referring to FIG. 2a, which illustrates the state in which the first blocking switch (31) and the second blocking switch (32) are open, i.e., the state in which the operation of the power converter (2) is turned off, when the power converter (2) is cut off from the power grid, the line section from the power source (1) to the power converter (2), i.e., the AC section (210) through which alternating current flows, and the line section from the power converter (2) to the battery (3), i.e., the DC section (220) through which direct current flows, can be isolated as separate sections. That is, as the operation of the power converter (2) is turned off, the DC section (220) can be isolated from the alternating current section (210).

[0052] Here, the lines of the isolated line sections may each be implemented as ungrounded lines. In addition, insulation monitoring devices (10 or 20) for monitoring the insulation status of each line section may be provided to monitor the insulation status of the power lines constituting each of the isolated line sections.

[0053] Furthermore, each insulation monitoring device is connected to power lines connecting each line section and can calculate the magnitude of insulation resistance from each line section. Depending on whether the calculated insulation resistance is below a preset threshold, the insulation condition of the power lines to which the insulation monitoring device is connected—that is, whether there is insulation damage—can be monitored.

[0054] FIG. 3 is a block diagram illustrating the configuration of an insulation monitoring device according to an embodiment of the present invention in more detail.

[0055] Referring to FIG. 3, an insulation monitoring device (10 or 20) of an insulation monitoring system according to an embodiment of the present invention comprises: a coupler resistor (Rc, 370) connected to power lines of a system (hereinafter power lines, 50); a signal generation unit (330) that applies a square wave-shaped pulse signal to the power lines (50) through the coupler resistor (370); a signal measurement unit (320) including a virtual insulation resistor (Re, 340) formed between the power lines (50) and ground, and a detection resistor (Rm) connected to the ground; an Analog-Digital Converter (ADC) (302) connected to the signal measurement unit (320) and converting the voltage measured by the signal measurement unit (320) into a digital value; an average voltage calculation unit (310) that receives the digital value converted by the ADC (302) and calculates an average voltage according to the pulse signal applied to the power lines (50) during a preset sampling interval; and other connected components, and the average voltage It may be configured to include a control unit (300) that detects a plurality of normal state voltages according to the applied pulse signal based on a plurality of average voltages calculated by a calculation unit (310), and an insulation resistance calculation unit (308) that calculates the magnitude of the insulation resistance (340) based on the plurality of normal state voltages detected by the control unit (300). It may also be configured to include a memory (306) in which various data input to the control unit (300) or output from the control unit (300) are stored. Additionally, it may be configured to include a communication unit (304) capable of performing a communication connection with another device that has been set up.

[0056] The signal generation unit (330) can generate a pulse signal having a constant positive (+) voltage or a constant negative (-) voltage according to the control of the control unit (300). The generated pulse signal can be applied to the power line (50). Accordingly, a pulse signal in which positive and negative voltages alternate can be applied to the power line (50) according to the control of the control unit (300).

[0057] Meanwhile, the power line (50) and the ground can be connected to each other through a virtual circuit. A virtual insulation resistance (Re, 340) can be formed between the power line (50) and the ground. Additionally, a virtual capacitor (Ce, 350) can be formed between the power line (50) and the ground. The capacitor (350), together with the insulation resistance (340), can form an insulation impedance (360) between the power line (50) and the ground.

[0058] Accordingly, the pulse signal applied to the power line (50) can be input to the signal measuring unit (320) through a circuit formed between the power line (50) and ground. Then, the signal measuring unit (320) can detect the voltage of the virtual circuit reflecting the insulation impedance (360) based on the voltage across the detection resistor (Rm). The detection result of the signal measuring unit (320) can be amplified through an amplifier (Amp, Amplifier) ​​and converted into a digital value through an ADC (302). It can then be input to the control unit (300).

[0059] And the control unit (300) can control the insulation resistance calculation unit (308) so that the insulation resistance is calculated based on the virtual circuit voltage of the different polarity when the voltage of the virtual circuit for the pulse signal of the different polarity is calculated. And the control unit (300) can calculate the magnitude of the insulation resistance for the power line (50) by averaging the magnitudes of the insulation resistances calculated from the calculated virtual circuit voltage of the different polarity.

[0060] Meanwhile, the communication unit (304) can receive data transmitted from another device or transmit data to another device through a communication connection formed with another device that is pre-configured. In this case, the communication unit (304) can receive data related to the operating status of the other device from the other device and can provide the received data to the control unit (300). That is, the control unit (300) can collect data related to the operating status of the other device through the communication unit (304). And based on the collected data, it can determine whether the other device is in an operating state or not. In this case, the power conversion device (2) may be included in the other device that is pre-configured.

[0061] Meanwhile, to calculate the magnitude of the insulation resistance, the insulation monitoring device may apply a pulse signal having a preset voltage to the connected power line as described above. Then, a measurement signal corresponding to the applied pulse signal may be detected from the ground (PE). In this case, a measurement signal having a voltage attenuated compared to the voltage of the pulse signal due to the insulation impedance existing between the power line and the ground may be detected, such as the voltage of the preset pulse signal (Vp) and the voltage of the detection signal (Vm) shown in FIG. 4.

[0062] Then, the insulation monitoring device can calculate the voltage attenuated by the insulation impedance from the voltage of the measurement signal and the voltage of the preset pulse signal. And based on the magnitude of the attenuated voltage, the internal resistance of the insulation monitoring device, and the magnitude of the detection resistance, the magnitude of the insulation resistance can be inversely calculated.

[0063] In this case, if there is no insulation damage, the magnitude of the insulation resistance may be sufficiently large (above the reference value), but if there is insulation damage, such as leakage current, the insulation impedance is significantly reduced, so the magnitude of the calculated insulation resistance may be reduced to below the reference value. Accordingly, the insulation monitoring device can determine the insulation status of the power line and output an alarm indicating insulation damage according to the determined insulation status. In this case, the control unit (300) may drive a circuit breaker (not shown) to disconnect the energy storage device (30) from the power line (in the case of the insulation monitoring device (10)) or disconnect the battery (3) (in the case of the insulation monitoring device (20)).

[0064] Accordingly, as shown in FIG. 2a, when each line section is isolated from one another, the insulation resistance of the power lines connecting the AC current section (210) can be calculated based on the resistance values ​​(internal resistance and detection resistance) of the insulation monitoring device (10) in the AC current section (210). On the other hand, in the DC current section (220), the insulation resistance of the power lines connecting the DC current section (220) can be calculated based on the resistance values ​​of another insulation monitoring device (20).

[0065] Therefore, depending on the magnitude of the internal resistance and detection resistance according to each insulation monitoring device, the insulation resistance reference value applied to the AC current section (210) and the insulation resistance reference value applied to the DC current section may differ from each other. That is, the insulation monitoring device (10) monitors the insulation status of the AC current section (210) according to the insulation resistance reference value pre-set for the AC current section (210), and another insulation monitoring device (20) can monitor the insulation status of the DC current section (220) independently of the insulation monitoring device (10) according to the insulation resistance reference value pre-set for the DC current section (220).

[0066] However, as shown in FIG. 2b, when the first cutoff switch (31) and the second cutoff switch (32) are closed, that is, when the operation of the power converter (2) is turned on, the alternating current section (210) and the direct current section (220) can be connected to each other by the power converter (2). That is, as the operation of the power converter (2) is turned on, the line sections are connected to each other, and the alternating current section (210) and the direct current section (220) can be integrated into a single line section (alternating current / direct current integrated section (250)).

[0067] As shown in FIG. 2b above, when a plurality of line sections are integrated into a single section by driving the power conversion device (2), at least one of the insulation monitoring devices that monitor the insulation status of each of the plurality of line sections may be switched to a standby state. In this case, all other insulation monitoring devices may be switched to a standby state, except for one insulation monitoring device placed in any one of the line sections among the plurality of line sections integrated by the power conversion device (2). Here, the standby state may mean a state in which the operation of the insulation monitoring device is stopped or the operation is turned off.

[0068] Then, any one of the insulation monitoring devices can calculate the insulation resistance of the entire integrated section (250) and determine the insulation status of the integrated section (250) according to the magnitude of the calculated insulation resistance. In this case, the other insulation monitoring device (20) can be set to calculate the insulation resistance of the integrated section (250). Then, as shown in FIG. 2b, the insulation monitoring device (10) that calculates the insulation resistance in the other integrated line section, i.e., the alternating current section (210), can be switched to the standby state. And the other insulation monitoring device (20) can calculate the insulation resistance of the entire integrated section (250) and determine the insulation status of the integrated section (250) according to the magnitude of the calculated insulation resistance.

[0069] In this case, as described above, the insulation monitoring device typically uses the internal resistance and detection resistance within the insulation monitoring device to calculate the insulation resistance. Therefore, when multiple insulation monitoring devices are simultaneously connected to a single line section, they may be affected by the internal resistance and detection resistance within other insulation monitoring devices. For example, the internal resistance of another insulation monitoring device placed within the integrated section (250), i.e., an insulation monitoring device in a standby state (e.g., insulation monitoring device (10)), may be added to the internal resistance of the insulation monitoring device (e.g., another insulation monitoring device (20)) that calculates the insulation resistance.

[0070] In this case, since the insulation resistance can be reduced as the magnitude of the internal resistance increases, even if no insulation damage occurs, the magnitude of the insulation resistance calculated in the integrated section (250) may be reduced due to the influence, i.e., interference, of another insulation monitoring device connected to the integrated section (250) in the standby state.

[0071] In addition, since the integration of the line sections is achieved by the operation of the power conversion device (2), the state in which the line sections are integrated may be the state in which the power conversion device (2) is operated. In this case, the power conversion device (2) may have a unique resistance value, and the unique resistance of the power conversion device (2) may be reflected in the insulation impedance, thereby further reducing the magnitude of the insulation resistance calculated.

[0072] Accordingly, even though insulation damage such as leakage current has not occurred, an insulation resistance lower than the preset insulation resistance reference value may be calculated due to interference by the other insulation monitoring device and the inherent resistance value of the power converter. Therefore, an alarm indicating insulation damage may be output even though no insulation damage has occurred.

[0073] Meanwhile, in order to prevent such misjudgment and false alarm output, the insulation monitoring system according to an embodiment of the present invention allows the insulation resistance reference value applied to the insulation monitoring device that determines the insulation status of the integrated section (250) when the line section is integrated to have different values ​​depending on whether the line section is integrated or not.

[0074] Hereinafter, the insulation resistance reference value for determining whether insulation damage exists for an individual line section that is not integrated (e.g., an AC current section (210) or a DC current section (220)) will be referred to as the first reference value, and the insulation resistance reference value applied to the integrated section (250) will be referred to as the second reference value. In this case, the insulation resistance reference value for determining the insulation state of the individual line section that is not integrated, i.e., the first reference value, may have a value greater than the insulation resistance reference value applied to the integrated section (250), i.e., the second reference value.

[0075] Accordingly, any insulation monitoring device that calculates the insulation resistance for the integrated section (250) may have different reference values ​​for determining insulation damage depending on whether the line section is integrated. That is, when the line section is not integrated and each insulation monitoring device determines the insulation status of each line section, the first reference value may be used as an insulation resistance reference value for determining the insulation status of the line section. However, when the line section is integrated, the second reference value may be used as a reference value for determining the insulation status of the integrated line section. In this case, the first reference value and the second reference value may be different values. That is, the reference value for determining insulation damage may differ depending on whether the line section is integrated.

[0076] On the other hand, an insulation monitoring device that switches to a standby state when line sections are integrated can monitor the insulation status of a specific line section based on a preset insulation resistance threshold before the line sections are integrated. However, when the line sections are integrated, it switches to a standby state and does not monitor the insulation status. In other words, an insulation monitoring device that switches to a standby state monitors only the insulation status of a specific line section according to the preset insulation resistance threshold, and the threshold for determining insulation damage may not change depending on whether the line sections are integrated.

[0077] Accordingly, in the following description, the insulation monitoring device in which the insulation resistance reference value does not change will be referred to as the first insulation monitoring device, and the insulation monitoring device in which the insulation resistance reference value changes according to the integration of the line section will be referred to as the second insulation monitoring device.

[0078] For example, as shown in FIG. 2b, when a line section is integrated, the insulation monitoring device that switches to a standby state is an insulation monitoring device (10) that monitors the insulation state of an alternating current section (210). In this case, the insulation monitoring device (10) that monitors the insulation state of the alternating current section (210) may be the first insulation monitoring device. On the other hand, when a line section is integrated, the insulation monitoring device that monitors the insulation state of the integrated line section by changing the insulation resistance reference value according to the integration of the line section is an insulation monitoring device (20) that monitors the insulation state of a direct current section (220). In this case, the insulation monitoring device (20) that monitors the insulation state of the direct current section (220) may be the second insulation monitoring device.

[0079] Meanwhile, FIG. 2b describes an example in which an insulation monitoring device (insulation monitoring device (20)) that monitors the insulation state of the DC current section (220) is a second insulation monitoring device that monitors the insulation state of the integrated section (250), but it goes without saying that the present invention is not limited thereto. That is, instead of an insulation monitoring device (insulation monitoring device (20)) that monitors the insulation state of the DC current section (220), an insulation monitoring device (insulation monitoring device (10)) that monitors the insulation state of the AC current section (210) may be a second insulation monitoring device that monitors the insulation state of the integrated section (250).

[0080] Meanwhile, the first insulation monitoring device and the second insulation monitoring device constituting the insulation monitoring system according to an embodiment of the present invention can detect whether the line section is integrated in various ways. For example, the first insulation monitoring device and the second insulation monitoring device can detect whether the line section is integrated based on a change in voltage detected in the power line.

[0081] For example, when a power converter (2) is driven and the line of the DC current section (220) connected to the battery (3) is connected to the line of the AC current section (210), if the battery (3) is discharged, the voltage of the DC current section (220) may be lowered above a certain level by the voltage of the battery (3) being discharged into the connected AC current section (210). On the other hand, the voltage of the AC current section (210) may be raised above a certain level by the power supplied from the power converter (2).

[0082] Meanwhile, if the voltage charged in the battery (3) is below a preset level and power from the power source (1) is supplied to the battery (3) for charging, the voltage of the AC current section (210) may be lowered above a certain level while having the same voltage as the power source (1). On the other hand, the voltage of the DC current section (220) may be raised above a certain level by the power supplied from the AC current section (210) while having a low voltage according to the low battery charging voltage. That is, based on the voltage change over a certain period of time detected from the power line, the first insulation monitoring device and the second insulation monitoring device according to the embodiment of the present invention can determine whether the line section is integrated.

[0083] Meanwhile, whether the above-mentioned line section is integrated can be determined based on whether the power conversion device (2) is operating. Accordingly, the first insulation monitoring device and the second insulation monitoring device according to the embodiment of the present invention may detect the operating state of the power conversion device (2) and determine whether the above-mentioned line section is integrated based on the detection result. To this end, the first insulation monitoring device and the second insulation monitoring device according to the embodiment of the present invention may be equipped with a communication unit (304) that performs a communication connection with the power conversion device (2), and may determine whether the above-mentioned line section is integrated based on the operating state detection signal of the power conversion device (2) detected by the communication unit (304).

[0084] FIG. 5 is an exemplary diagram illustrating examples of information stored in the memory of a second insulation monitoring device, in which the insulation resistance reference value changes depending on whether the line section is integrated among the insulation monitoring devices according to an embodiment of the present invention.

[0085] Referring to FIG. 5, FIG. 5(a) illustrates an example of information contained in the memory (306-2) of the second insulation monitoring device. The memory (306) of the second insulation monitoring device may be configured to include a first reference value storage unit (510) in which a first reference value is stored and a second reference value storage unit (520) in which a second reference value is stored.

[0086] In this case, the first reference value may be a reference value applied to determine the insulation state of the power line before the line sections are integrated, that is, when the power conversion device (2) is not in operation. And the second reference value may be a reference value applied to determine the insulation state of the power line for the integrated line section (integrated section (250)) after the line sections are integrated.

[0087] Meanwhile, the second insulation monitoring device may have a plurality of insulation resistance reference values ​​as a first reference value or a second reference value. In this case, the plurality of reference values ​​belonging to the first reference value may form a first reference value group, and the plurality of reference values ​​belonging to the second reference value may form a second reference value group. In the following description, the first reference value may be any one of the reference values ​​included in the first reference value group, and the second reference value may be any one of the reference values ​​included in the second reference value group.

[0088] Meanwhile, the reference values ​​of the first reference value group may be stored in the first reference value storage unit (510), and the reference values ​​of the second reference value group may be stored in the second reference value storage unit (520). Additionally, each different reference value of one group may correspond to each different reference value of another group. In this case, each reference value of the second group may have a value smaller than the corresponding reference value of the first group.

[0089] And the second insulation monitoring device can determine the insulation status of the connected power line as one of a plurality of preset states based on a plurality of reference values ​​according to one reference value group, depending on whether the line section is integrated.

[0090] For example, the second insulation monitoring device can check whether the insulation condition of the power line meets the first reference value by comparing the magnitude of the insulation resistance with the first reference value. In this case, if the insulation resistance is greater than the first reference value, the insulation condition of the power line can be determined to be good.

[0091] On the other hand, if the magnitude of the insulation resistance is smaller than the first reference value, the second insulation monitoring device may compare the magnitude of the insulation resistance with a second reference value having a value smaller than the first reference value. Furthermore, if the magnitude of the insulation resistance is less than the first reference value and greater than or equal to the second reference value, the insulation status of the power line can be determined as a 'caution state'. In this case, the 'caution state' indicates that the power line insulation is not damaged, but there is a possibility of insulation damage, and an alarm may be output to indicate the insulation status (caution state) of the power line.

[0092] Furthermore, if the magnitude of the insulation resistance is smaller than the second reference value, the second insulation monitoring device can compare the magnitude of the insulation resistance with a third reference value having a value smaller than the second reference value. In this case, if the magnitude of the insulation resistance is less than the second reference value and greater than or equal to the third reference value, the insulation status of the power line can be determined as a 'warning state'. In this case, the 'warning state' may be a state where there is a very high possibility of insulation damage to the power line and urgent inspection or repair is required, and an alarm may be output to indicate the insulation status (warning state) of the power line. In this case, the 'caution state' and 'warning state' may be states where inspection or repair is required, but the connection of the power line may be maintained.

[0093] Meanwhile, the second insulation monitoring device can determine that insulation damage has occurred in the power line and leakage current has occurred when the magnitude of the insulation resistance is smaller than the third reference value. Accordingly, the second insulation monitoring device may drive a circuit breaker simultaneously with the output of an alarm indicating the insulation damage state to disconnect the electrical connection between the power line and the load.

[0094] Meanwhile, the second insulation monitoring device according to an embodiment of the present invention may directly calculate the second reference value based on information from another insulation monitoring device connected to the integrated line section and information from the power conversion device (2). To this end, the memory (306-2) of the second insulation monitoring device (20) may further include an IMD resistance information storage unit (550) that stores information related to the internal resistance of another insulation monitoring device connected to the integrated line section when the line is integrated, and a PCS information storage unit (560) that stores resistance value information of the power conversion device (2), as shown in FIG. 5 (b).

[0095] In this case, the IMD resistance information storage unit (550) may include a table-type database in which unique information of a plurality of insulation monitoring devices and information of internal resistance corresponding to each insulation monitoring device are stored. In this case, the communication unit (304) of the second insulation monitoring device may receive unique information from another insulation monitoring device connected to the integrated line section and obtain the internal resistance value of the other insulation monitoring device connected to the integrated line section through the received unique information.

[0096] Likewise, the PCS information storage unit (560) may include a table-type database in which unique information of a plurality of power conversion devices and information of unique resistance values ​​corresponding to each power conversion device are stored. In this case, the communication unit (304) of the second insulation monitoring device may receive unique information of the power conversion device (2) from the power conversion device (2) and obtain the unique resistance value of the power conversion device (2) through the received unique information.

[0097] Then, the second insulation monitoring device can inversely calculate the insulation resistance reference value to be used during line integration, i.e., the second reference value, based on the internal resistance value of the other insulation monitoring device obtained above, the intrinsic resistance value of the power conversion device (2), and the insulation resistance value according to the first reference value. The inversely calculated second reference value may also be stored in the second reference value storage unit (520).

[0098] Referring to Figure 11 below, we will examine the operation process of inversely calculating the second reference value in more detail.

[0099] Meanwhile, as described above, the insulation monitoring devices (10, 20) placed in each line section, where the integration status is determined based on whether the power conversion device (2) is driven according to an embodiment of the present invention, may operate differently depending on whether the line section is integrated.

[0100] With reference to FIGS. 6 and 7 below, we will examine in detail the different operation processes of the first insulation monitoring device and the second insulation monitoring device constituting the insulation monitoring system according to an embodiment of the present invention.

[0101] First, FIG. 6 is a flowchart showing the operation process of a first insulation monitoring device in which the insulation resistance reference value is not changed in an insulation monitoring system according to an embodiment of the present invention.

[0102] Referring to FIG. 6, the control unit of the first insulation monitoring device can first collect information related to the operating status of the power conversion device (2) (S600). In this case, the information related to the operating status of the power conversion device (2) is information collected from the power conversion device (2), and may be the operating status information of the power conversion device (2) received from the power conversion device (2) through the communication unit (304). Then, the control unit of the first insulation monitoring device can determine whether the power conversion device (2) is operating based on the collected operating status information of the power conversion device (2) (S602).

[0103] Below, we will examine an example of determining the driving state by collecting driving state information of the power conversion device (2) from the above-mentioned power conversion device (2) with reference to FIGS. 8a and 8b.

[0104] Alternatively, the information collected in step S600 may be information regarding the voltage detected from the power line connected to the first insulation monitoring device. In this case, the control unit of the first insulation monitoring device can detect a voltage change occurring within a certain period of time based on the voltage detection information collected in step S600. Then, proceeding to step S602, it can determine whether the line section is integrated, that is, whether the power conversion device (2) is operated, based on the detected voltage change.

[0105] The operation process of detecting power changes in the power line and determining whether the power conversion device (2) is driven will be examined in more detail with reference to FIGS. 9 and FIGS. 10 below.

[0106] If, as a result of the determination in step S602, the power conversion device (2) is not in operation, the control unit of the first insulation monitoring device can calculate the insulation resistance of the line section to which the first insulation monitoring device is connected based on the voltage (Vp) of the pulse signal applied to the power line, the magnitude of the internal resistance (Ri) and detection resistance (Rm) of the first insulation monitoring device, and the voltage of the measurement signal corresponding to the applied pulse signal (detection voltage, Vm) (S604). Then, the calculated insulation resistance can be compared with the insulation resistance reference value pre-set in the first insulation monitoring device (S606). Then, based on the comparison result in step S606, the insulation status of the line section to which the first insulation monitoring device is connected can be determined depending on whether the calculated insulation resistance is less than the pre-set insulation resistance reference value (S608).

[0107] In this case, if the magnitude of the insulation resistance calculated above is greater than or equal to the insulation resistance reference value pre-set in the first insulation monitoring device, the control unit of the first insulation monitoring device can determine that the insulation condition of the line section is good. Then, the control unit of the first insulation monitoring device can proceed again to step S600 to collect information related to the operating status of the power conversion device (2), and proceed to step S602 to determine the operating status of the power conversion device (2).

[0108] On the other hand, if the magnitude of the insulation resistance calculated as a result of determining the insulation status in step S608 is less than a preset insulation resistance threshold, the control unit of the first insulation monitoring device may determine that there is an abnormality in the insulation status of the line section to which the first insulation monitoring device is connected. Accordingly, the control unit of the first insulation monitoring device may output an alarm to notify of the insulation abnormality that occurred in the line section (S610). In this case, the alarm may be output in the form of an alarm or notification information transmitted to a higher-level system managing the insulation monitoring system according to an embodiment of the present invention, or to another preset server or a preset terminal.

[0109] Meanwhile, if the power converter (2) is in an operating state as a result of the determination in step S602, the control unit of the first insulation monitoring device may switch the operating state to a standby state (S612). Then, the control unit of the first insulation monitoring device may proceed again to step S600 to collect information related to the operating state of the power converter (2), and proceed to step S602 to determine the operating state of the power converter (2). Then, depending on the result of the determination in step S602, it may proceed to step S604 to calculate the insulation resistance and proceed to subsequent steps, or proceed to step S612 to maintain the operating state that has been switched to a standby state. Therefore, if the power converter (2) is in an operating state, the first insulation monitoring device may be continuously maintained in a standby state.

[0110] As seen in Figure 6 above, in an insulation monitoring system according to an embodiment of the present invention, an insulation monitoring device (first insulation monitoring device) that does not perform insulation monitoring for the integrated line section when the line section is integrated has a configuration that switches from a standby state to an operating state depending on whether the line section is integrated, and may have a configuration that compares a preset insulation resistance reference value with the magnitude of the calculated insulation resistance.

[0111] In contrast, in an insulation monitoring system according to an embodiment of the present invention, an insulation monitoring device (second insulation monitoring device) that performs insulation monitoring for an integrated line section when a line section is integrated can determine the insulation state of the integrated line section by comparing different insulation resistance reference values ​​depending on whether the line section is integrated with the magnitude of the insulation resistance calculated for the integrated line section.

[0112] FIG. 7 is a flowchart showing the operation process of a second insulation monitoring device in which the insulation resistance reference value is changed according to the operating state of the power converter in an insulation monitoring system according to an embodiment of the present invention.

[0113] Referring to FIG. 7, as in FIG. 6, the control unit of the second insulation monitoring device can first collect information related to the operating status of the power conversion device (2) (S700). In this case, the information related to the operating status of the power conversion device (2) is information collected from the power conversion device (2), and may be the operating status information of the power conversion device (2) received from the power conversion device (2) through the communication unit (304). Then, the control unit of the second insulation monitoring device can determine whether the power conversion device (2) is operating based on the collected operating status information of the power conversion device (2) (S702).

[0114] Below, we will examine an example of determining the driving state by collecting driving state information of the power conversion device (2) from the above-mentioned power conversion device (2) with reference to FIGS. 8a and 8b.

[0115] Alternatively, the information collected in step S700 may be information regarding the voltage detected from the power line connected to the second insulation monitoring device. In this case, the control unit of the second insulation monitoring device can detect a voltage change occurring within a certain period of time based on the voltage detection information collected in step S700. Then, proceeding to step S702, it can determine whether the line section is integrated, that is, whether the power conversion device (2) is operated, based on the detected voltage change.

[0116] The operation process of detecting power changes in the power line and determining whether the power conversion device (2) is driven will be examined in more detail with reference to FIGS. 9 and FIGS. 10 below.

[0117] Based on the result of the judgment in step S702 above, the control unit of the second insulation monitoring device may select different insulation resistance reference values ​​depending on whether the power conversion device (2) is in operation. For example, if the power conversion device (2) is not in operation, the control unit of the second insulation monitoring device may select the first reference value among the first reference value and the second reference value as the insulation resistance reference value for determining the insulation state (S703). On the other hand, if the power conversion device (2) is in operation, the control unit of the second insulation monitoring device may select the second reference value among the first reference value and the second reference value as the insulation resistance reference value for determining the insulation state (S704). Here, the second reference value may have a value smaller than the first reference value.

[0118] And the control unit of the second insulation monitoring device can calculate the insulation resistance of the line section to which the second insulation monitoring device is connected based on the voltage (Vp) of the pulse signal applied to the power line, the magnitude of the internal resistance (Ri) and detection resistance (Rm) of the second insulation monitoring device, and the voltage of the measurement signal corresponding to the applied pulse signal (detection voltage, Vm) (S705). In this case, if the power converter (2) is in a running state, the line section to which the second insulation monitoring device is connected may be a line section in which a plurality of line sections are integrated through the power converter (e.g., integrated section (250)). However, if the power converter (2) is not in a running state, the line section to which the second insulation monitoring device is connected may be a part of the integrated line section that is isolated by the power converter (e.g., DC current section (220)).

[0119] And the control unit of the second insulation monitoring device can compare the insulation resistance calculated in step S705 with the first reference value selected in step S703 or the second reference value selected in step S704 (S706). And based on the comparison result in step S706, the insulation status of the line section to which the second insulation monitoring device is connected can be determined depending on whether the magnitude of the calculated insulation resistance is less than the currently selected reference value (S708).

[0120] In this case, if the magnitude of the insulation resistance calculated above is greater than or equal to the currently selected reference value, the control unit of the second insulation monitoring device can determine that the insulation condition of the line section is good. Then, the control unit of the second insulation monitoring device can proceed again to step S700 to collect information related to the operating status of the power conversion device (2), and proceed to step S702 to determine the operating status of the power conversion device (2).

[0121] On the other hand, if the magnitude of the insulation resistance calculated as a result of determining the insulation status in step S708 is less than the currently selected reference value, the control unit of the second insulation monitoring device may determine that there is an abnormality in the insulation status of the line section to which the second insulation monitoring device is connected. Accordingly, the control unit of the second insulation monitoring device may output an alarm to notify of the insulation abnormality that occurred in the line section (S710). In this case, the alarm may be output in the form of an alarm or notification information transmitted to a higher-level system managing the insulation monitoring system according to an embodiment of the present invention, or to another pre-configured server or pre-configured terminal.

[0122] As seen in FIG. 7 above, in an insulation monitoring system according to an embodiment of the present invention, an insulation monitoring device (second insulation monitoring device) that performs insulation monitoring for an integrated line section when a line section is integrated determines the insulation state of the power line according to a first reference value when the line section is not integrated, i.e., when the power converter (2) is not operating, and determines the insulation state of the power line according to a second reference value when the line section is integrated, i.e., when the power converter (2) is operating.

[0123] In this case, the second reference value may be intended to determine the insulation status of the integrated line section by reflecting the internal resistance value of the insulation monitoring device of another line section, i.e., the first insulation monitoring device, to which the second insulation monitoring device is not connected among the integrated line sections. Additionally, the second reference value may be intended to determine the insulation status of the integrated line section by reflecting the unique resistance value of the power converter included in the line section along with other line sections when the line sections are integrated.

[0124] Therefore, the second reference value may have a resistance value smaller than the resistance value according to the first reference value. That is, since the first reference value and the second reference value have different values, the second insulation monitoring device may have the characteristic that the reference value for determining the insulation status of the power line differs depending on whether the line section is integrated, i.e., whether the power converter is operated.

[0125] Meanwhile, FIGS. 8a and 8b are exemplary drawings illustrating examples of determining the operating state of a power conversion device (2) based on information collected from a power conversion device (2) in an insulation monitoring system according to an embodiment of the present invention.

[0126] First, as shown in FIG. 8a, in an insulation monitoring system according to an embodiment of the present invention, a first insulation monitoring device (10) and a second insulation monitoring device (20) can each be connected to a power conversion device (2) via communication. In this case, the first insulation monitoring device (10) and the second insulation monitoring device (20) can receive a driving signal indicating the driving status of the power conversion device (2) from the power conversion device (2) and determine whether the power conversion device (2) is being driven.

[0127] For example, when the power converter (2) is in a standby state, that is, when the drive is off, as shown in FIG. 8a, it can transmit a signal indicating that the drive of the power converter (2) is off to the first insulation monitoring device (10) and the second insulation monitoring device (20).

[0128] Then, the first insulation monitoring device (10) and the second insulation monitoring device (20) determine that the power converter (2) is in an off state based on the received driving signal, calculate the insulation resistance for each connected power line, and determine the insulation state based on the reference value stored in each insulation monitoring device. In this case, the second insulation monitoring device (20) can determine the insulation state of the power line according to the first reference value among the preset reference values.

[0129] Alternatively, although not shown, if the power converter (2) is in a standby state, i.e., the operation is turned off, a signal indicating the operation of the power converter (2) may not be received from the power converter (2) to the first insulation monitoring device (10) and the second insulation monitoring device (20). In this case, the first insulation monitoring device (10) and the second insulation monitoring device (20) may determine that the power converter (2) is not operating when a signal indicating the operation of the power converter (2) is not received.

[0130] In addition, as shown in FIG. 8b, the first insulation monitoring device (10) and the second insulation monitoring device (20) can determine whether the power conversion device (2) is being operated by receiving a driving signal indicating that the power conversion device (2) is being operated when the power conversion device (2) is being operated.

[0131] For example, when the power converter (2) is in a running state, as shown in FIG. 8b, the power converter (2) can transmit a signal indicating that the operation is turned on to the first insulation monitoring device (10) and the second insulation monitoring device (20).

[0132] Then, the first insulation monitoring device (10) and the second insulation monitoring device (20) can determine that the power converter (2) is in an ON state based on the received driving signal. Then, the first insulation monitoring device (10) can be switched to a standby state, and the second insulation monitoring device (20) can change the reference value for determining the insulation state to a second reference value, which is a reference value for determining the insulation state for the integrated line section. Therefore, in the case of the second insulation monitoring device (20), the reference value for determining the insulation state may vary depending on the driving state of the power converter (2).

[0133] Alternatively, although not shown, if the power converter (2) is in an ON state, a signal indicating the OFF state of the power converter (2) may not be received from the power converter (2) to the first insulation monitoring device (10) and the second insulation monitoring device (20). In this case, the first insulation monitoring device (10) and the second insulation monitoring device (20) may determine that the power converter (2) is not operating if a signal indicating the OFF state of the power converter (2) is not received.

[0134] Alternatively, although not shown, the communication unit (304) may perform a communication connection between the first insulation monitoring device (10) and the second insulation monitoring device (20). In this case, either the first insulation monitoring device (10) or the second insulation monitoring device (20) may determine the operating status of the power conversion device (2) and share information regarding the determined operating status with the other insulation monitoring device.

[0135] Meanwhile, FIGS. 9 and FIGS. 10 are drawings for explaining whether the power conversion device (2) is driven based on a voltage change detected from the power line.

[0136] First, FIG. 9 is an example diagram showing the change in the magnitude of the insulation resistance calculated by the insulation monitoring device according to the SOC of the battery (3) when the battery (3) is connected according to the operation of the power conversion device (2) while the insulation state of the power line is maintained at a constant state in an insulation monitoring system according to an embodiment of the present invention.

[0137] Referring to FIG. 9, when the power conversion device (2) is driven as the SOC of the battery (3) is low and power supplied from the power source (1) is supplied to the battery (3), that is, when charging takes place, it can be seen that the magnitude of the insulation resistance calculated by the insulation monitoring device decreases significantly at the time charging begins. Then, it can be seen that the magnitude of the insulation resistance calculated while charging of the battery (3) continues gradually decreases, and then recovers when charging is completed.

[0138] In this case, since the voltage of the line section connecting the power converter (2) and the battery (3), i.e., the DC current section (220), is the same as the voltage of the battery (3), the voltage can gradually increase as the SOC of the battery (3) increases. Accordingly, an insulation monitoring device (e.g., a second insulation monitoring device (20)) that monitors the insulation status of the line section between the power converter (2) and the battery (3) can determine whether the power converter (2) is operating based on the voltage change of the line section between the power converter (2) and the battery (3).

[0139] Additionally, when charging the battery (3), power is supplied to the battery (3) through the power converter (2), so the voltage of the line section connecting the power source (1) to the power converter (2) may be slightly reduced. Accordingly, an insulation monitoring device (e.g., a first insulation monitoring device (10)) that monitors the insulation status of the line section between the power source (1) and the power converter (2) can determine whether the power converter (2) is operating based on the voltage change of the line section between the power source (1) and the power converter (2).

[0140] Meanwhile, when the power converter (2) is operated while the SOC of the battery (3) is high, the power of the battery (3) can be discharged through the power converter (2). In this case, it can be observed that the magnitude of the insulation resistance calculated by the insulation monitoring device decreases significantly at the time the discharge begins. Then, it can be observed that the magnitude of the insulation resistance calculated while the discharge of the battery (3) continues gradually decreases, and then recovers when the discharge is completed.

[0141] In this case, the voltage of the DC current section (220) may gradually decrease as the battery (3) discharges, just like the voltage of the battery (3). Accordingly, an insulation monitoring device (e.g., a second insulation monitoring device (20)) that monitors the insulation status of the line section between the power converter (2) and the battery (3) can determine whether the power converter (2) is operating based on the voltage change of the line section between the power converter (2) and the battery (3).

[0142] Additionally, when the battery (3) is discharged, the power discharged from the battery (3) is supplied to the AC power grid through the power conversion device (2), so the voltage of the line section connecting the power source (1) to the power conversion device (2) may increase slightly. Accordingly, an insulation monitoring device (e.g., a first insulation monitoring device (10)) that monitors the insulation status of the line section between the power source (1) and the power conversion device (2) can determine whether the power conversion device (2) is operating based on the voltage change of the line section between the power source (1) and the power conversion device (2).

[0143] FIG. 10 is a flowchart illustrating the operation process in which insulation monitoring devices determine the operating status of a power converter based on voltage changes detected from a power line in an insulation monitoring system according to an embodiment of the present invention.

[0144] First, each insulation monitoring device can detect a change in voltage of the power line at a predetermined time interval (S1000). Then, it can check whether the voltage of the power line has decreased or increased by more than a predetermined level during the said predetermined time interval (S1002). And if the voltage of the power line has not decreased or increased by more than the said predetermined level, it can be determined that the power converter (2) is not in operation (S1006). In this case, the first insulation monitoring device or the second insulation monitoring device can determine that the power converter is not in operation at step S602 of FIG. 6 or step S702 of FIG. 7.

[0145] However, if, as a result of the check in step S1002 above, the voltage of the power line decreases or increases above the preset level, the first insulation monitoring device or the second insulation monitoring device can determine that the power converter (2) is in a running state (S1004). In this case, the first insulation monitoring device or the second insulation monitoring device can determine that the power converter is in a running state in step S602 of FIG. 6 or step S702 of FIG. 7.

[0146] Here, the above S1004 step may be a step of detecting a voltage change resulting from the interaction of interconnected line sections, rather than a voltage change of a power line detected in a single line section.

[0147] That is, as described in FIG. 9 above, if the power converter (2) is operated and the battery (3) is charged, the voltage of the line section between the power source (1) and the power converter (2), i.e., the alternating current section (210), may decrease, and conversely, the voltage of the line section between the power converter (2) and the battery (3), i.e., the direct current section (220), may increase. Alternatively, if the power converter (2) is operated and the battery (3) is discharged, the voltage of the alternating current section (210) may increase, and conversely, the voltage of the direct current section (220) may decrease. Therefore, if the voltages of the line sections connected to each other through the power converter (2) change in opposite directions, and the voltage change in opposite directions is above a preset level, the insulation monitoring device of each section may determine that the power converter (2) is in an operating state.

[0148] Meanwhile, the second insulation monitoring device of the insulation monitoring system according to an embodiment of the present invention may use a first reference value as a reference value for determining the insulation state of the DC current section (220) when the power converter (2) is not in operation. On the other hand, it has been mentioned that when the power converter (2) is in operation, the size of an insulation resistance having a value smaller than the first reference value may be used as a second reference value for determining the insulation state of the integrated section (250), by considering the inherent resistance of the power converter (2) and the internal resistance of the insulation monitoring device connected to another line section, i.e., the first insulation monitoring device (10).

[0149] In this case, when the power converter (2) is in operation, the insulation resistance of the line must have an insulation resistance of 1M Ohm or more for a line with a voltage of 1000 V, since the leakage current must not exceed 1 mA. Accordingly, for a line with a voltage of 1000 V, the first reference value can be determined based on 1M Ohm, that is, 1000 Ohm / V.

[0150] Meanwhile, regarding overseas standards for the operation of the power conversion device (2), in the case of Germany, the standard is 100 Ohm per volt, i.e., 100 Ohm / V, so a line with a voltage of 1000 V must have an insulation resistance of 100K Ohm or more. Therefore, 100K Ohm can be used as the second reference value for a line with a voltage of 1000 V. In this case, the second insulation monitoring device (20) according to the embodiment of the present invention can select either the first reference value (1M Ohm) or the second reference value (100K Ohm) depending on whether the power conversion device (2) is operated, and can determine the insulation status of the line by comparing the selected reference value with the size of the insulation resistance detected from the measurement signal.

[0151] Meanwhile, the magnitude of the insulation resistance can be determined according to the voltage of the preset pulse signal (Vp), the detection resistance (Rm), the detection voltage of the measurement signal (Vm), and the known internal resistance (Ri) of the insulation monitoring device, as shown in Equation 1 below.

[0152]

[0153] In this case, the insulation resistance (Re) is expressed in relation to the detection voltage (Vm) as shown in Equation 2 below.

[0154]

[0155] Here, the voltage of the pulse signal (Vp) is a known voltage as the voltage of the pulse signal applied to the line to calculate the insulation resistance, and the internal resistance (Ri) and the detection resistance (Rm) may also be known resistances as internal resistance values ​​of the insulation monitoring device. In this case, if the insulation resistance (Re) is set to a value according to a pre-set first reference value, the detection voltage (Vm) corresponding to the first reference value can be inversely calculated. In this case, the inversely calculated detection voltage (Vm) may be the detection voltage corresponding to the first reference value.

[0156] Meanwhile, the above detection voltage may be a voltage that is measured identically when a pulse signal having the same pulse voltage is applied to the line, and when the line section having the same insulation resistance and the internal resistance values ​​(Ri, Rm) of the insulation monitoring device are identical. Therefore, assuming that the above detection voltage (Vm) is identical and that the insulation state of the line section is identical, if the fixed resistance values ​​that change when the line section is integrated, i.e., the internal resistance values ​​(Ri, Rm) of the insulation monitoring device are different, the magnitude of the insulation resistance corresponding to the above-calculated detection voltage (Vm) can be calculated. In this case, the magnitude of the insulation resistance calculated may be the magnitude of the insulation resistance that changes according to the internal resistance of the insulation monitoring device that changes according to the integration of the line section when a pulse signal having the same voltage is applied to a line having the same insulation state. In this case, the internal resistance of the insulation monitoring device that changes according to the integration of the line section may include the intrinsic resistance value of the power conversion device (2).

[0157] Accordingly, the second reference value can be calculated based on the result of inversely calculating the detection voltage (Vm) corresponding to the preset first reference value by reflecting the internal resistance of at least one other connected insulation monitoring device and the intrinsic resistance value of the power conversion device (2).

[0158] FIG. 11 is a flowchart illustrating the operation process in which the second insulation monitoring device directly calculates an insulation resistance reference value to be applied to an integrated line section based on the resistance values ​​of the insulation monitoring device and the power converter placed in another line.

[0159] Referring to FIG. 11, the second insulation monitoring device of the insulation monitoring system of the present invention first considers a preset first reference value as the magnitude of the insulation resistance (Re), and based on a preset pulse voltage (Vp) and the magnitudes of the internal resistance (Ri) and detection resistance (Rm) known in advance by the second insulation monitoring device, it can inversely calculate the detection voltage (Vm) corresponding to the first reference value according to Equation 2 (S1100).

[0160] And the second insulation monitoring device can detect information on the internal resistance values ​​of at least one other insulation monitoring device installed in the other line section being integrated when the line section is integrated (S1102). Here, the second insulation monitoring device can utilize information on at least one other insulation monitoring device that is stored in memory (306) (e.g., IMD resistance information storage unit (550) of FIG. 5(b)). To this end, the second insulation monitoring device (20) can obtain the internal resistance values ​​of at least one other insulation monitoring device installed in the other line section through the communication unit (304), and in this case, the internal resistance values ​​may include the internal resistance (Ri) and detection resistance (Rm) of the other insulation monitoring device.

[0161] And the second insulation monitoring device (20) can sum internal resistance values ​​(Ri, Rm) detected by at least one other insulation monitoring device. Then, by summing the internal resistance value of the power converter to the summed internal resistance value, the total internal resistance value corresponding to the integrated line section can be calculated. Then, the internal resistance of the second insulation monitoring device known in advance is summed according to the calculated total internal resistance, and the internal resistance (Ri) for calculating the insulation resistance of the integrated line section can be updated according to the summed value (S1104). In this case, the internal resistance value of the power converter (2) can be received from the power converter (2) and may be a value stored in memory (306-2) (e.g., PCS information storage unit (560) of FIG. 5b).

[0162] Meanwhile, when the internal resistance (Ri) is updated in step S1104, the second insulation monitoring device can calculate the insulation resistance (Re) according to Equation 1 based on the inversely calculated detection voltage (Vm) corresponding to the first reference value, the updated internal resistance (Ri), the detection resistance (Rm) inside the second insulation monitoring device, and the voltage (Vp) of the preset pulse signal (S1108). In this case, the insulation resistance (Re) calculated in step S1108 may be the size of the insulation resistance corresponding to the first reference value when the size of the internal resistance (Ri) is increased according to the internal resistance values ​​of different insulation monitoring devices and the size of the intrinsic resistance of the power conversion device (2), assuming that the insulation state is the same.

[0163] Accordingly, the second insulation monitoring device can determine the magnitude of the insulation resistance (Re) calculated in step S1108 as the second reference value and store it in the second reference value storage unit (420). Then, depending on the operating state of the power conversion device (2), either the first reference value stored in the first reference value storage unit or the second reference value stored in the second reference value storage unit can be used as a reference value for determining the insulation state of the connected line section. That is, the reference value for determining the insulation state of the connected line section can be changed depending on the operating state of the power conversion device (2).

[0164] In this way, when the second reference value is calculated directly, the second insulation monitoring device can automatically calculate the second reference value according to the resistance values ​​of the new power conversion device or other insulation detection device, based on the intrinsic resistance value of the changed power conversion device (2) and the internal resistance values ​​(Ri, Rm) of the changed other insulation monitoring device when the power conversion device (2) or another insulation monitoring device (e.g., first insulation monitoring device) placed in another line section is changed.

[0165] To this end, the memory of the second insulation monitoring device (e.g., memory (306-2) in Fig. 5 (b)) stores information on resistance values ​​for each of the model information of a plurality of different types of power conversion devices and model information for a plurality of different types of insulation monitoring devices, and can detect information on resistance values ​​of the power conversion device (2) and the other insulation monitoring device (e.g., first insulation monitoring device) connected to the integration section (250) based on the model information of the power conversion device (2) or the other insulation monitoring device (e.g., first insulation monitoring device) received through the communication unit (304).

[0166] Meanwhile, although specific embodiments have been described in the above description of the present invention, various modifications may be made without departing from the scope of the present invention. In particular, in the embodiment of the present invention, an example was given in which an insulation monitoring device placed in a DC current section (220) is used as a second insulation monitoring device to monitor the insulation status of the integrated line section when the line section is integrated; however, this is merely one example of the present invention and the present invention is not limited thereto.

[0167] The present invention described above can be implemented as computer-readable code on a medium on which a program is recorded. A computer-readable medium includes all types of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable media include HDD (Hard Disk Drive), SSD (Solid State Disk), SSD (Silicon Disk Drive), ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc., and also include implementation in the form of a carrier wave (e.g., transmission over the Internet).

[0168] Additionally, the computer may include a control unit for each insulation monitoring device. Accordingly, the above detailed description should not be interpreted restrictively in all respects and should be considered exemplary. The scope of the invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the invention are included within the scope of the invention.

Claims

1. A signal generating unit that applies a pulse signal having a preset voltage to a power line connecting a power conditioning system (PCS) and a load or between the power conditioning system and a power source; A signal measuring unit connected to ground, receiving a measurement signal corresponding to the applied pulse signal from the connected ground, and measuring a detection voltage for calculating insulation resistance from the received measurement signal; A memory storing a plurality of reference values ​​having different insulation resistance values; and, The magnitude of the insulation resistance is calculated based on the above detection voltage, the voltage of the above pulse signal, and the preset internal resistance magnitude, and An insulation monitoring device characterized by including a control unit that detects the operating state of the power converter and, depending on the detected operating state of the power converter, compares a first reference value among the plurality of reference values ​​with the magnitude of the calculated insulation resistance or compares a second reference value among the plurality of reference values ​​with the magnitude of the calculated insulation resistance to determine the insulation state of the power line.

2. In paragraph 1, the control unit is, An insulation monitoring device characterized by detecting a voltage change of the power line that increases or decreases above a certain level, and determining the operating state of the power converter based on the detected voltage change of the power line.

3. In Paragraph 2, The above insulation monitoring device is, It further includes a communication unit that performs a communication connection with another insulation monitoring device placed on another power line connected through the power conversion device, and The above control unit is, An insulation monitoring device characterized by receiving a result of detecting a voltage change of the other power line from the other insulation monitoring device, and determining the operating state of the power converter based on the received result of the voltage change of the other power line and the result of detecting the voltage change of the power line.

4. In Paragraph 3, The above load is a battery, and The above insulation monitoring device is, The magnitude of the insulation resistance is calculated from the power line through which direct current flows between the power converter and the battery, and The above other insulation monitoring device is, An insulation monitoring device characterized by calculating the magnitude of insulation resistance from another power line through which alternating current flows between the power conversion device and the power source.

5. In Paragraph 1, The above insulation monitoring device is, It further includes a communication unit that collects information related to the operating status of the power conversion device from the power conversion device, The above control unit is, An insulation monitoring device characterized by determining the operating state of the power converter based on operating state-related information collected from the power converter.

6. In paragraph 2 or 5, the control unit, An insulation monitoring device characterized by changing a reference value for determining the insulation state of the power line according to the determined operating state of the power conversion device when the operating state of the power conversion device changes as a result of the above determination.

7. In Paragraph 1, The above first standard value is, It is an insulation resistance reference value for determining the insulation state of a first power line section connecting the power converter and the load or the power converter and the power source when the power converter is not operating, and The above second standard value is, An insulation monitoring device characterized by having a value smaller than the first reference value as an insulation resistance reference value for determining the insulation state of an integrated section in which a second power line section and the first power line section, which are other sections connected through the power conversion device, are integrated, as the power conversion device is driven.

8. In Paragraph 7, The above memory is, Further storing information on the intrinsic resistance value of the power conversion device and information on the internal resistance magnitude of another insulation monitoring device placed in the second power line section, The above control unit is, The detection voltage is inversely calculated based on the internal resistance of the insulation monitoring device, the detection resistance of the insulation monitoring device, the magnitude of the insulation resistance corresponding to the first reference value, and the voltage of the pulse signal, and An insulation monitoring device characterized by adding the magnitude of the intrinsic resistance of the power conversion device and the magnitude of the internal resistance of the other insulation monitoring device placed in the second power line section to the magnitude of the internal resistance of the insulation monitoring device, and calculating the second reference value based on the magnitude of the added internal resistance and the inversely calculated detection voltage, and the voltage of the pulse signal and the magnitude of the detection resistance of the insulation monitoring device.

9. An insulation monitoring system for monitoring the insulation status of a line section to which an Energy Storage System (ESS) is connected, An insulation monitoring device connected to a first power line section connecting a power source and a power conditioning system (PCS) of the energy storage device, and determining the insulation status of the first power line section; and, It includes an insulation monitoring device connected to a second power line section connecting the power conversion device and the battery of the energy storage device, and determining the insulation status of the second power line section. One of the above insulation monitoring devices, It is a first insulation monitoring device whose operating state is determined based on whether the above-mentioned power conversion device is driven, and Another one of the above insulation monitoring devices is, An insulation monitoring system characterized by being a second insulation monitoring device that determines the insulation state of either one of the first power line section and the second power line section based on a first reference value for determining the insulation state of either one of the first power line section and the second power line section, or a second reference value for determining the insulation state of the integrated section in which the first power line section and the second power line section are integrated, depending on whether the power conversion device is driven.

10. In Paragraph 9, The first insulation monitoring device and the second insulation monitoring device are An insulation monitoring system characterized by determining the operating state of a power converter based on a voltage change of the first power line or the second power line that increases or decreases above a preset level for a set period of time, or based on operating state information collected from the power converter.

11. In paragraph 9, the first insulation monitoring device is, When the above power conversion device is in a driven state, it operates in a standby state that does not monitor the insulation state of the first power line, and An insulation monitoring system characterized by operating in an insulation monitoring state that monitors the insulation state of the first power line when the above power conversion device is not in operation.

12. In Paragraph 9, The above-mentioned first insulation monitoring device is, It is an insulation monitoring device that monitors the insulation status of the first power line section through which alternating current flows, and The above second insulation monitoring device is, An insulation monitoring system characterized by being an insulation monitoring device that monitors the insulation status of the second power line section through which direct current flows.

13. In Paragraph 9, The above first standard value is, It includes a plurality of insulation resistance sizes for determining the insulation state of a power line as one of a plurality of different states according to the calculated insulation resistance, and The above second standard value is, It includes a plurality of insulation resistance sizes for determining the insulation state of a power line as one of a plurality of different states according to the calculated insulation resistance, and Each of the insulation resistance magnitudes included in the above second reference value is, An insulation monitoring system characterized by having a value smaller than each of the insulation resistance magnitudes included in the corresponding first reference value.

14. In Paragraph 9, The above first standard value is, It is determined based on 1000 Ohm per 1 volt of power line voltage ((1000 Ohm / V)), and The above second standard value is, An insulation monitoring system characterized by determining 100 Ohm per 1 volt of power line voltage ((100 Ohm / V)).

15. In paragraph 9, the second insulation monitoring device is, The device further comprises a memory including information on the intrinsic resistance size of the power conversion device and the internal resistance size of the first insulation monitoring device, and An insulation monitoring system characterized by calculating the size of the internal resistance corresponding to the integrated section based on the intrinsic resistance size of the power conversion device, the internal resistance size of the first insulation monitoring device, and the internal resistance of the second insulation monitoring device, and calculating the second reference value based on the calculated internal resistance size of the integrated section and the insulation resistance size corresponding to the first reference value.

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