Filter monitoring apparatus and filter monitoring system

Abstract

A filter monitoring apparatus (9) comprises: a first current sensor (7) that measures a first common mode current between an EMC filter provided between a power source and a power electronics device and the power source; a second current sensor (8) that measures a second common mode current between the EMC filter and the power electronics device; and a state diagnosis unit (95) that determines abnormality in the EMC filter on the basis of the first common mode current and the second common mode current.

Description

Filter monitoring device and filter monitoring system

[0001] The present disclosure relates to a filter monitoring device and a filter monitoring system for detecting an abnormality in an EMC (Electromagnetic Compatibility) filter.

[0002] In the fields of factory automation (FA) and robotics, a noise filter having a common mode choke coil has been installed in a power supply path as an EMC filter to suppress high-frequency noise generated during switching operations in power conversion. When a common mode current exceeding a specified level flows into the power supply path as high-frequency noise caused by switching operations, the common mode choke coil installed in the noise filter may become magnetically saturated. Regarding this problem, for example, Patent Document 1 discloses a method for detecting magnetic saturation of a common mode choke coil.

[0003] Japanese Patent Application Laid-Open No. 2022-136924

[0004] The method described in Patent Document 1 is capable of detecting magnetic saturation, but is not capable of detecting faulty grounding of capacitors built into EMC filters. Since faulty grounding of a capacitor also impairs the performance of the EMC filter, there is a need for technology that can also detect faulty grounding of capacitors.

[0005] The present disclosure has been made in view of the above, and aims to provide a filter monitoring device that can distinguish between and detect magnetic saturation of a coil and poor grounding of a capacitor in an EMC filter.

[0006] In order to solve the above-mentioned problems and achieve the object, the filter monitoring device according to the present disclosure is characterized by including: a first current sensor that measures a first common mode current between an EMC filter provided between a power supply and a power electronics device and the power supply; a second current sensor that measures a second common mode current between the EMC filter and the power electronics device; and a condition diagnosis unit that determines an abnormality in the EMC filter based on the first common mode current and the second common mode current.

[0007] The filter monitoring device according to the present disclosure has the advantage of being able to distinguish and detect magnetic saturation of a coil and poor grounding of a capacitor in an EMC filter.

[0008] FIG. 1 is a diagram showing an example of the configuration of an entire system including a filter monitoring device according to a first embodiment. FIG. 2 is a diagram showing an example of the configuration of an EMC filter used as the filter shown in FIG. 1. Block diagram showing an example of the configuration of a filter monitoring device according to a first embodiment. FIG. 3 is a diagram showing an example of hardware realizing a state diagnosis unit of the filter monitoring device according to the first embodiment. Flowchart showing an example of the operation of the state diagnosis unit constituting the filter monitoring device according to the first embodiment. FIG. 4 is a diagram showing an example of a common mode current signal in the frequency domain after Fourier transform. FIG. 5 is a diagram showing an example of the configuration of a filter monitoring system according to a second embodiment. FIG. 6 is a diagram showing an example of the configuration of a current measuring device included in the filter monitoring system according to the second embodiment. FIG. 7 is a diagram showing an example of the configuration of a determination device included in the filter monitoring system according to the second embodiment.

[0009] A filter monitoring device and a filter monitoring system according to an embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0010] First Embodiment Fig. 1 is a diagram showing an example of the configuration of an entire system 100 including a filter monitoring device 9 according to a first embodiment.

[0011] an overall system 100 shown in FIG. 1 includes: a circuit breaker 2 connected to a power source 1; a filter 3 which is an EMC filter connected to the load side of the circuit breaker 2; inverters 4 a to 4 c which are power electronics devices (hereinafter referred to as “power electronics devices”) connected to the secondary side of the filter 3; load devices 5 a to 5 c which are connected to the secondary sides of the inverters 4 a to 4 c, respectively; a controller 6 which controls the inverters 4 a to 4 c; a first current sensor 7 which is provided on an electric wire connecting the circuit breaker 2 and the filter 3 and measures a common mode current Icom_out which flows from the power source 1 to the filter 3; a second current sensor 8 which is provided on an electric wire connecting the filter 3 and the inverters 4 a to 4 c and measures a common mode current Icom_in which flows from the filter 3 to each of the inverters 4 a to 4 c; and a filter monitoring device 9 which is connected to the first current sensor 7 and the second current sensor 8 and which monitors the state of the filter 3 based on the common mode currents measured by the first current sensor 7 and the second current sensor 8. Hereinafter, the common mode current measured by the first current sensor 7 may be referred to as a first common mode current, and the common mode current measured by the second current sensor 8 may be referred to as a second common mode current.

[0012] 2 is a diagram showing an example of the configuration of an EMC filter used as the filter 3 shown in FIG. 1. The EMC filter shown in FIG. 2 includes input terminals IN1 and IN2, output terminals OUT1 and OUT2, an X capacitor Cx, a filter resistor R, a common mode choke coil L1, a differential mode inductance L2, and a Y capacitor Cy. IN1 and IN2 are connected to OUT1 and OUT2 via the common mode choke coil L1. The X capacitor Cx and the filter resistor R are connected between IN1 and IN2, and the X capacitor Cx is connected between OUT1 and OUT2. The Y capacitor Cy is connected between OUT1 and ground and between OUT2 and ground. Note that the leakage inductance component of the common mode choke coil L1 is usually used as the differential mode inductance L2.

[0013] FIG. 3 is a block diagram showing an example of the configuration of the filter monitoring device 9 according to the first embodiment.

[0014] As shown in FIG. 3 , the filter monitoring device 9 includes a first current measurement unit 91 that receives an output signal Icom_out from the first current sensor 7 and converts the signal Icom_out from an analog signal to a digital signal; a second current measurement unit 92 that receives an output signal Icom_in from the second current sensor 8 and converts the signal Icom_in from an analog signal to a digital signal; a first Fourier transform unit 93 that receives the digital signal converted by the first current measurement unit 91 and performs a Fourier transform on the input signal; a second Fourier transform unit 94 that receives the digital signal converted by the second current measurement unit 92 and performs a Fourier transform on the input signal; a condition diagnosis unit 95 that receives signals Fourier transformed by the first Fourier transform unit 93 and the second Fourier transform unit 94 and diagnoses the condition of the filter 3 based on the input signal; and an output unit 96 that outputs the diagnosis result by the condition diagnosis unit 95 to the outside.

[0015] The output destination of the diagnostic result by the output unit 96 corresponds to, for example, a display device for displaying the diagnostic result, a communication network to which other devices requiring the diagnostic result are connected, etc. The output unit 96 may have a function as a display device and display the diagnostic result.

[0016] The first current measuring unit 91 and the second current measuring unit 92 are configured by A / D (Analog to Digital) converters. The first Fourier transform unit 93 and the second Fourier transform unit 94 may perform processing by software or may perform processing using a DSP (Digital Signal Processor).

[0017] The state diagnosis unit 95 can be realized by, for example, a processing circuit configured with a processor 201 and a memory 202 shown in Fig. 4. Fig. 4 is a diagram illustrating an example of hardware that realizes the state diagnosis unit 95 of the filter monitoring device 9 according to the first embodiment.

[0018] The processor 201 is a CPU (Central Processing Unit, also called a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or processor). The memory 202 is, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read Only Memory).

[0019] The condition diagnosis unit 95 is realized by the processor 201 executing a program for operating as the condition diagnosis unit 95. The program for operating as the condition diagnosis unit 95 is stored in advance in the memory 202. The processor 201 operates as the condition diagnosis unit 95 by reading and executing the program stored in the memory 202. Note that the condition diagnosis unit 95 may be realized by a processing circuit that is dedicated hardware, specifically, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like.

[0020] Next, a description will be given of the operation of the state diagnosis unit 95. Fig. 5 is a flowchart showing an example of the operation of the state diagnosis unit 95 constituting the filter monitoring device 9 according to the first embodiment.

[0021] 5 , the condition diagnosis unit 95 of the filter monitoring device 9 first measures the peak values ​​of the frequency domain signals of the first common mode current Icom_out and the second common mode current Icom_in (step S11). That is, the first common mode current Icom_out and the second common mode current Icom_in measured by the first current sensor 7 and the second current sensor 8 are converted into digital signals by the first current measurement unit 91 and the second current measurement unit 92, and then the first Fourier transform unit 93 and the second Fourier transform unit 94 perform Fourier transforms on the digital signals. The condition diagnosis unit 95 measures the peak values ​​of each of the first common mode current Icom_out and the second common mode current Icom_in in the frequency domain.

[0022] Here, common mode current refers to current that flows in the same direction in multiple electric wires connected to a filter, etc., and means, for example, current that flows in the same direction in multiple electric wires connecting filter 3 to inverters 4a to 4c.

[0023] For example, if the common mode current signal in the frequency domain obtained by performing the Fourier transform has the waveform shown in Fig. 6, the condition diagnosis unit 95 detects the carrier frequency of the inverters 4a to 4c (10.7 kHz in the example of Fig. 6) and peak currents that appear at frequencies that are integer multiples of the carrier frequency. Fig. 6 is a diagram showing an example of the common mode current signal in the frequency domain after the Fourier transform.

[0024] 6, the common mode current signals in the frequency domain obtained by performing Fourier transforms on the first Fourier transform unit 93 and the second Fourier transform unit 94 are up to 100 kHz. The maximum frequency depends mainly on the sampling frequencies of the first current measurement unit 91 and the second current measurement unit 92, and therefore on the hardware used for the first current measurement unit 91 and the second current measurement unit 92.

[0025] Next, the condition diagnosis unit 95 compares, of the peak values ​​measured in step S11, a peak value Icom_out_peak that appears at the carrier frequency of the first common mode current Icom_out in the frequency domain output from the first Fourier transform unit 93 with a peak value Icom_in_peak that appears at the carrier frequency of the second common mode current Icom_in in the frequency domain output from the second Fourier transform unit 94 (step S12). If Icom_out_peak<Icom_in_peak (step S12: No), the condition diagnosis unit 95 diagnoses that the operation of the filter 3 is normal (step S14). On the other hand, if Icom_out_peak≧Icom_in_peak (step S12: Yes), the condition diagnosis unit 95 determines whether the peak value Icom_out_peak2 of the first common mode current Icom_out and the peak value Icom_in_peak2 of the second common mode current Icom_in, which appear at positions that are integer multiples of the carrier frequency within a range below a predetermined frequency, are equal to each other (step S13). The predetermined frequency is the upper limit of the frequency domain Fourier transformed by the first Fourier transform unit 93 and the second Fourier transform unit 94. In the example shown in FIG. 6 , this is 100 kHz. The equality is determined not by whether they completely match, but by whether the difference between the peak value Icom_out_peak2 and the peak value Icom_in_peak2 is equal to or less than a predetermined value. That is, the condition diagnosis unit 95 determines that the peak values ​​Icom_out_peak2 and Icom_in_peak2 are equal to each other if the difference between the peak values ​​Icom_out_peak2 and Icom_in_peak2 is equal to or less than the predetermined value. When multiple peak values ​​exist within a range equal to or less than a predetermined frequency, the condition diagnosis unit 95 may determine whether any one of the peak values ​​is equal, or may determine whether the averages of the multiple peak values ​​are equal, or may determine whether the sums of the multiple peak values ​​are equal.

[0026] If the peak value Icom_out_peak2 and the peak value Icom_in_peak2 are equal (step S13: Yes), the state diagnosis unit 95 determines that the filter 3 is poorly grounded, i.e., that the capacitor built in the filter 3 is poorly grounded (step S15). On the other hand, if the peak value Icom_out_peak2 and the peak value Icom_in_peak2 are not equal (step S13: No), the state diagnosis unit 95 determines that the filter 3 is magnetically saturated, i.e., that the common mode choke coil built in the filter 3 is magnetically saturated (step S16).

[0027] If magnetic saturation is determined in step S13, the user is notified of the abnormality in step S16 via an LED lamp mounted on the output unit 96 of the filter monitoring device 9, or via a host control computer or cloud screen connected to an output signal from the output unit 96. This makes it possible to prevent noise leaking to the outside when the filter 3 is not functioning normally from adversely affecting other devices.

[0028] As described above, the filter monitoring device 9 according to the present embodiment determines the peak values ​​in the frequency domain of the common mode currents Icom_out and Icom_in measured on the power supply side and on the inverter 4a-4c side of the filter 3, which is an EMC filter connected to the inverters 4a-4c, which are power electronics devices, and compares the peak value of the first common mode current Icom_out with the peak value of the second common mode current Icom_in in the frequency domain to determine whether the state of the filter 3 is normal or abnormal. If an abnormal state is determined, the filter monitoring device 9 further determines the type of abnormal state, i.e., whether the abnormality is due to magnetic saturation of the common mode choke coil that constitutes the filter 3 or poor grounding of the capacitor that constitutes the filter 3. Specifically, the filter monitoring device 9 determines the normal state when the peak value Icom_in_peak of the second common mode current Icom_in that appears at the carrier frequency is greater than the peak value Icom_out_peak of the first common mode current Icom_out. Furthermore, the filter monitoring device 9 compares the peak value Icom_out_peak2 of the first common mode current Icom_out with the peak value Icom_in_peak2 of the second common mode current Icom_in, which appear between the carrier frequency and a predetermined frequency, and determines that there is poor grounding of the capacitor that constitutes the filter 3 if the difference between the two is equal to or less than the predetermined value, and determines that there is magnetic saturation of the common mode choke coil that constitutes the filter 3 if the difference between the two is greater than the predetermined value. In this way, the filter monitoring device 9 can detect an abnormal state of the EMC filter, and can also determine whether the abnormal state is due to magnetic saturation of the common mode choke coil in the EMC filter or poor grounding of the capacitor.

[0029] The reasons why magnetic saturation and poor capacitor grounding can be determined in step S13 will be explained. When magnetic saturation occurs, the L of the common mode choke coil that constitutes filter 3 decreases, resulting in a higher LC resonance frequency within the filter. When the effect of this resonance overlaps with the carrier frequency band of the inverter, the magnitude relationship of the common mode current, in which Icom_in is greater than Icom_out under normal conditions, is reversed (corresponding to step 13: No). Furthermore, when poor capacitor grounding occurs, the input current Icom_in to filter 3 and the output current Icom_out from filter 3 match. When Icom_in and Icom_out match, this simply means that the capacitor grounded between them is not functioning (corresponding to step 13: Yes).

[0030] Second Embodiment In this embodiment, a filter monitoring system that can obtain the same effects as the filter monitoring device 9 described in the first embodiment will be described.

[0031] Fig. 7 is a diagram showing a configuration example of a filter monitoring system 101 according to the second embodiment. In Fig. 7, the same components as those in the overall system 100 (see Fig. 1) including the filter monitoring device 9 according to the first embodiment are assigned the same reference numerals as in Fig. 1. In this embodiment, the description of the components assigned the same reference numerals as in Fig. 1 will be omitted.

[0032] 7 , a filter monitoring system 101 according to the present embodiment has a server 10 provided on a network 50 such as the cloud, and the server 10 operates as a determination device 12 having a first Fourier transform unit 93, a second Fourier transform unit 94, and a state diagnosis unit 95 that were provided in the filter monitoring device 9 in the first embodiment. Also, a current measurement device 11 having a first current measurement unit 91 and a second current measurement unit 92 that were provided in the filter monitoring device 9 in the first embodiment is provided instead of the filter monitoring device 9. That is, the filter monitoring system 101 is configured to realize the functions of the filter monitoring device 9 described in the first embodiment by the current measurement device 11 and the determination device 12.

[0033] 8 is a diagram illustrating an example of the configuration of a current measurement device 11 included in a filter monitoring system 101 according to the second embodiment. As illustrated in Fig. 8, the current measurement device 11 includes a first current measurement unit 91 that receives an output signal Icom_out from the first current sensor 7, converts the signal Icom_out from an analog signal to a digital signal, and outputs the digital signal; a second current measurement unit 92 that receives an output signal Icom_in from the second current sensor 8, converts the signal Icom_in from an analog signal to a digital signal, and outputs the digital signal; and a communication unit 97 that transmits the digital current signal output from the first current measurement unit 91 and the digital current signal output from the second current measurement unit 92 to the server 10. The first current measurement unit 91 and the second current measurement unit 92 of the current measurement device 11 are circuits similar to the first current measurement unit 91 and the second current measurement unit 92 of the filter monitoring device 9 according to the first embodiment.

[0034] 9 is a diagram illustrating an example of a configuration of a determination device 12 included in a filter monitoring system 101 according to a second embodiment. As illustrated in Fig. 9, the determination device 12 includes a communication unit 98 that receives each digital signal transmitted from a communication unit 97 of the current measuring device 11, a first Fourier transform unit 93 that performs a Fourier transform on a digital signal converted by a first current measuring unit 91 of the current measuring device 11 out of the digital signals received by the communication unit 98, a second Fourier transform unit 94 that performs a Fourier transform on a digital signal converted by a second current measuring unit 92, a condition diagnosis unit 95 that receives the signals Fourier transformed by the first Fourier transform unit 93 and the second Fourier transform unit 94 and diagnoses the condition of the filter 3 based on the input signals, and an output unit 96a that outputs a diagnosis result by the condition diagnosis unit 95 to an external device. The first Fourier transform unit 93, the second Fourier transform unit 94, and the status diagnosis unit 95 of the determination device 12 are circuits similar to the first Fourier transform unit 93, the second Fourier transform unit 94, and the status diagnosis unit 95 of the filter monitoring device 9 according to the first embodiment. Therefore, a description of the first Fourier transform unit 93, the second Fourier transform unit 94, and the status diagnosis unit 95 of the determination device 12 will be omitted. The output unit 96a outputs the diagnosis result by the status diagnosis unit 95 to another device connected to the network 50, such as a tablet terminal with a display function or an external server that manages data.

[0035] Although the filter monitoring system 101 has been described as having a configuration in which both the first current sensor 7 and the second current sensor 8 are connected to the current measurement device 11, the first current sensor 7 and the second current sensor 8 may be connected to different current measurement devices. That is, the filter monitoring system may be configured to include a first current measurement device to which the first current sensor 7 is connected and a second current measurement device to which the second current sensor 8 is connected.

[0036] The filter monitoring system 101 according to the present embodiment includes a current measuring device 11 that executes processing similar to the processing related to measuring a current value executed by the filter monitoring device 9 according to the first embodiment, and a determining device 12 that executes processing similar to the processing related to diagnosing the operation of the filter 3 executed by the filter monitoring device 9 according to the first embodiment. Therefore, the filter monitoring system 101 can achieve the same effects as the filter monitoring device 9 according to the first embodiment.

[0037] Third Embodiment Fig. 10 is a diagram showing an example of the configuration of a filter monitoring system 102 according to a third embodiment. In Fig. 10, the same components as those in the filter monitoring system 101 according to the second embodiment (see Fig. 7) are assigned the same reference numerals as in Fig. 7. In this embodiment, the description of the components assigned the same reference numerals as in Fig. 7 will be omitted.

[0038] The filter monitoring system 102 of this embodiment has a configuration in which the circuit breaker 2 of the filter monitoring system 101 of the second embodiment is replaced with a circuit breaker 21 having a built-in current sensor 7a that measures the current on the power supply 1 side of the filter 3, the controller 6 of the filter monitoring system 101 is replaced with a controller 61, and the inverters 4a to 4c of the filter monitoring system 101 are replaced with inverters 41a to 41c that each have a built-in current sensor 8a to 8c that measures the current flowing through them.

[0039] The determination device 12 receives, from the circuit breaker 21, a current signal indicating a current measurement value by the current sensor 7a included in the circuit breaker 21, and also receives, via the controller 61, current signals indicating current measurement values ​​by the current sensors 8a to 8c included in each of the inverters 41a to 41c, and diagnoses the operation of the filter 3 based on the received current signals. The current signals received by the determination device 12 from the circuit breaker 21 and the inverters 41a to 41c are the same as the current signals received by the determination device 12 from the current measuring device 11 in the filter monitoring system 101 according to the second embodiment.

[0040] The determination device 12 of the filter monitoring system 102 according to this embodiment performs a Fourier transform on each of the current signals received from the inverters 41a to 41c, sums up the current peak values ​​in the frequency domain, and then performs the diagnostic operation described in the first embodiment (operation according to the flowchart in FIG. 5) using the result.

[0041] The filter monitoring system 102 according to this embodiment can obtain the same effects as the filter monitoring device 9 according to the first embodiment and the filter monitoring system 101 according to the second embodiment.

[0042] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0043] 1 Power supply, 2, 21 Circuit breaker, 3 Filter, 4a, 4b, 4c, 41a, 41b, 41c Inverter, 5a, 5b, 5c Load equipment, 6, 61 Controller, 7 First current sensor, 7a, 8a, 8b, 8c Current sensor, 8 Second current sensor, 9 Filter monitoring device, 10 Server, 11 Current measurement device, 12 Determination device, 50 Network, 91 First current measurement unit, 92 Second current measurement unit, 93 First Fourier transform unit, 94 Second Fourier transform unit, 95 Status diagnosis unit, 96, 96a Output unit, 97, 98 Communication unit, 100 Overall system, 101, 102 Filter monitoring system.

Claims

1. A filter monitoring device comprising: a first current sensor that measures a first common mode current between an EMC filter provided between a power source and a power electronics device and the power source; a second current sensor that measures a second common mode current between the EMC filter and the power electronics device; and a status diagnosis unit that determines an abnormality in the EMC filter based on the first common mode current and the second common mode current.

2. A filter monitoring device as described in claim 1, comprising: a first Fourier transform unit that performs a Fourier transform on the first common mode current; and a second Fourier transform unit that performs a Fourier transform on the second common mode current, wherein the condition diagnosis unit diagnoses an abnormality in the condition of the EMC filter based on a peak value that appears at a carrier frequency of the first common mode current and a peak value that appears at the carrier frequency of the second common mode current in the frequency domain.

3. The filter monitoring device according to claim 2, characterized in that, when the EMC filter is in an abnormal state, the status diagnosis unit determines whether the abnormality in the EMC filter is due to magnetic saturation of a coil or poor grounding of a capacitor, based on a peak value appearing between the carrier frequency of the first common mode current and a determined frequency and a peak value appearing between the carrier frequency of the second common mode current and the determined frequency.

4. The filter monitoring device according to claim 3, characterized in that the condition diagnosis unit determines that the EMC filter is in an abnormal state when a peak value appearing at the carrier frequency of the first common mode current is equal to or greater than a peak value appearing at the carrier frequency of the second common mode current.

5. The filter monitoring device according to claim 4, characterized in that the condition diagnosis unit determines that the EMC filter has a grounding failure when a difference between a peak value appearing between the carrier frequency of the first common mode current and a predetermined frequency and a peak value appearing between the carrier frequency of the second common mode current and the predetermined frequency is equal to or less than a predetermined value, and determines that the EMC filter has magnetic saturation when the difference is greater than the predetermined value.

6. A current measuring device that measures a current flowing through an EMC filter provided between a power source and a power electronics device; and a determination device that is connected to the current measuring device via a network and determines a state of the EMC filter based on a measurement result of the current by the current measuring device, wherein the current measuring device comprises: a first current sensor that measures a first common mode current between the EMC filter and the power source; and a second current sensor that measures a second common mode current between the EMC filter and the power electronics device, and the determination device comprises: a first Fourier transform unit that performs a Fourier transform on the first common mode current; and a second Fourier transform unit that performs a Fourier transform on the second common mode current. and a condition diagnosis unit that diagnoses a state of the EMC filter based on a peak value that appears at the carrier frequency of the first common mode current and a peak value that appears at the carrier frequency of the second common mode current in a frequency domain, and when the EMC filter is in an abnormal state, determines whether the abnormality of the EMC filter is due to magnetic saturation of a coil or a grounding fault of a capacitor based on a peak value that appears between the carrier frequency of the first common mode current and a determined frequency and a peak value that appears between the carrier frequency of the second common mode current and the determined frequency.

7. A determination device that determines a state of an EMC filter provided between a power source and a power electronics device based on a measurement result of a current flowing through the EMC filter; a first current sensor that is built into a circuit breaker provided between the power source and the EMC filter and measures a first common mode current flowing from the power source to the EMC filter; and a second current sensor that is built into the power electronics device and measures a second common mode current flowing from the EMC filter to the power electronics device, wherein the determination device comprises a first Fourier transform unit that performs a Fourier transform on the first common mode current, and a second Fourier transform unit that performs a Fourier transform on the second common mode current. and a condition diagnosis unit that diagnoses a state of the EMC filter based on a peak value that appears at the carrier frequency of the first common mode current and a peak value that appears at the carrier frequency of the second common mode current in a frequency domain, and when the EMC filter is in an abnormal state, determines whether the abnormality of the EMC filter is due to magnetic saturation of a coil or a grounding fault of a capacitor based on a peak value that appears between the carrier frequency of the first common mode current and a determined frequency and a peak value that appears between the carrier frequency of the second common mode current and the determined frequency.

8. The filter monitoring system according to claim 6 or 7, characterized in that the condition diagnosis unit determines that the EMC filter is in an abnormal state when a peak value appearing at the carrier frequency of the first common mode current is equal to or greater than a peak value appearing at the carrier frequency of the second common mode current.

9. The filter monitoring system according to claim 8, characterized in that the condition diagnosis unit determines that the EMC filter has a grounding failure when a difference between a peak value appearing between the carrier frequency of the first common mode current and a predetermined frequency and a peak value appearing between the carrier frequency of the second common mode current and the predetermined frequency is equal to or less than a predetermined value, and determines that the EMC filter has magnetic saturation when the difference is greater than the predetermined value.

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