# US 11,442,115 B2 · Method and apparatus for circuit monitoring > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,442,115 B2 - Document ID: US11442115B2 - Status: Granted - Kind: B2 - Application number: 17/223,423 - Filed: 2021-04-06 - Published: 2021-07-22 - Granted: 2022-09-13 - Earliest claimed: 2018-10-09 - Assignees: ABB Schweiz AG - Applicants: ABB Schweiz AG - Inventors: Jinlei Meng; Bo Wang; Haitao Deng - Web page: https://patentgrep.com/patent/US11442115B2 ## CPC - G01R 31/64: Testing of capacitors - G01R 27/2605: {Measuring capacitance (capacitive sensors G01D5/24)} - G01R 31/42: AC power supplies - H02M 1/4225: {using a non-isolated boost converter} - H02M 5/458: using semiconductor devices only - Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract A method for circuit monitoring includes detecting a waveform of first voltage at a DC-link capacitor in a power converter, the first voltage being generated by turning on a chopper circuit coupling in parallel to the DC-link; determining a phase angle shift of the waveform of first voltage with respect to a waveform of second voltage at a rectifier in the power converter or a power supply for the power converter; determining magnitude of the waveform of first voltage; and determining, based on at least one of the magnitude and the phase angle shift, a parameter indicative of a health condition of the DC-link capacitor. An apparatus is also provided. ## Claims ### Claim 1 A method for circuit monitoring, comprising: detecting a waveform of first voltage at a DC-link capacitor in a power converter, the first voltage being generated by turning on a chopper circuit coupling in parallel to the DC-link; determining a phase angle shift of the waveform of first voltage with respect to a waveform of second voltage at a rectifier in the power converter or a power supply for the power converter; determining magnitude of the waveform of first voltage; and determining, based on at least one of the magnitude and the phase angle shift, a parameter indicative of a health condition of the DC-link capacitor. ### Claim 2 (depends on 1) The method of claim 1, wherein determining the parameter comprises at least one of the following: determining capacitance of the DC-link capacitor based on the magnitude; and determining equivalent series resistance (ESR) of the DC-link capacitor based on the phase angle shift. ### Claim 3 (depends on 2) The method of claim 2, wherein: determining the capacitance comprises determining, based on the magnitude, the capacitance with a lookup table storing relationship between capacitances and magnitudes; and determining the ESR comprises determining, based on the phase angle shift, the ESR with a lookup table storing relationship between ESRs and phase angle shifts. ### Claim 4 (depends on 1) The method of claim 1, further comprising: comparing the determined parameter with a threshold; and generating an alert signal in response to the determined parameter exceeding the threshold. ### Claim 5 (depends on 2) The method of claim 2, further comprising: determining a first ratio of the capacitance to an initial capacitance of the DC-link capacitor; determining a second ratio of the ESR to an initial ESR of the DC-link capacitor; and determining residue time based on at least one of the first ratio and second ratio. ### Claim 6 (depends on 1) The method of claim 1, wherein determining the phase angle shift comprises: detecting a first phase angle of the waveform of first voltage and a second phase angle of the waveform of second voltage simultaneously; and determining difference between the first phase angle and the second angle as the phase angle shift. ### Claim 7 (depends on 1) The method of claim 1, further comprising: detecting a phase angle of the waveform of second voltage; and detecting the waveform of first voltage in response to the detected phase angle arriving at a predetermined angle. ### Claim 8 (depends on 7) The method of claim 7, wherein determining the phase angle shift comprises: detecting a first phase angle of the waveform of first voltage; and determining a difference between the first phase angle and the predetermined angle as the phase angle shift. ### Claim 9 (depends on 1) The method of claim 1, wherein the method is performed in case that no load of the power converter is present and the voltage at the DC-link capacitor is stable. ### Claim 10 (depends on 1) The method of claim 1, further comprises: filtering the waveform of first voltage with a high pass filter; and determining, based on the filtered waveform of first voltage, the phase angle shift and the magnitude. ### Claim 11 A non-transitory computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, cause the at least one processor to perform circuit monitoring operation, comprising: detecting a waveform of first voltage at a DC-link capacitor in a power converter, the first voltage being generated by turning on a chopper circuit coupling in parallel to the DC-link; determining a phase angle shift of the waveform of first voltage with respect to a waveform of second voltage at a rectifier in the power converter or a power supply for the power converter; determining magnitude of the waveform of first voltage; and determining, based on at least one of the magnitude and the phase angle shift, a parameter indicative of a health condition of the DC-link capacitor. ### Claim 12 A computer program product being tangibly stored on a non-transitory computer readable storage medium and comprising instructions which, when executed on at least one processor, cause the at least one processor to perform circuit monitoring operation, comprising: detecting a waveform of first voltage at a DC-link capacitor in a power converter, the first voltage being generated by turning on a chopper circuit coupling in parallel to the DC-link; determining a phase angle shift of the waveform of first voltage with respect to a waveform of second voltage at a rectifier in the power converter or a power supply for the power converter; determining magnitude of the waveform of first voltage; and determining, based on at least one of the magnitude and the phase angle shift, a parameter indicative of a health condition of the DC-link capacitor. ### Claim 13 An apparatus for circuit monitoring, comprising: a voltage detector configured to detect a waveform of first voltage at a DC-link capacitor in a power converter, the first voltage being generated by turning on a chopper circuit coupling in parallel to the DC-link; a voltage sensor configured to detect a waveform of second voltage at a rectifier; and a controller configured to: determine a phase angle shift of the waveform of first voltage with respect to the waveform of second voltage at the rectifier in the power converter or a power supply for the power converter; determine magnitude of the waveform of first voltage; and determine, based on at least one of the magnitude and the phase angle shift, a parameter indicative of a health condition of the DC-link capacitor. ### Claim 14 (depends on 13) The apparatus of claim 13, wherein the controller is further configured to determine at least one of the following: capacitance of the DC-link capacitor based on the magnitude; and equivalent series resistance (ESR) of the DC-link capacitor based on the phase angle shift. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein the controller is further configured to: determine, based on the magnitude, the capacitance with a lookup table storing relationship between capacitances and magnitudes; and determine, based on the phase angle shift, the ESR with a lookup table storing relationship between ESRs and phase angle shifts. ### Claim 16 (depends on 13) The apparatus of claim 13, wherein the controller is further configured to: compare the determined parameter with a threshold; and generate an alert signal in response to the determined parameter exceeding the threshold. ### Claim 17 (depends on 13) The apparatus of claim 13, wherein the controller is further configured to: detect a first phase angle of the waveform of first voltage and a second phase angle of the waveform of second voltage simultaneously; and determine a difference between the first phase angle and the second angle as the phase angle shift. ### Claim 18 (depends on 13) The apparatus of claim 13, wherein the controller is configured to operate in case that no load of the power converter is present and the voltage at the DC-link capacitor is stable. ### Claim 19 (depends on 13) A power conversion system, comprising: a power converter; and an apparatus of claim 13, configured to monitor a direct current (DC)-link capacitor in the power converter.