# US 12,119,786 B2 · Deterioration diagnosis device for solar cell string and photovoltaic power generation system provided with the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,119,786 B2 - Document ID: US12119786B2 - Status: Granted - Kind: B2 - Application number: 17/610,712 - Filed: 2019-06-03 - Published: 2022-07-14 - Granted: 2024-10-15 - Earliest claimed: 2019-06-03 - Assignees: Mitsubishi Electric Corporation - Applicants: Mitsubishi Electric Corporation - Inventors: Takayuki Morioka; Hidetada Tokioka - Web page: https://patentgrep.com/patent/US12119786B2 ## CPC - H02S 50/00: Monitoring or testing of PV systems, e.g. load balancing or fault identification - H02S 50/10: Testing of PV devices, e.g. of PV modules or single PV cells (testing of semiconductor devices during manufacturing {H10P74/00}) - G01R 31/367: Software therefor, e.g. for battery testing using modelling or look-up tables - G01R 31/389: Measuring internal impedance, internal conductance or related variables - G01R 31/392: Determining battery ageing or deterioration, e.g. state of health - H02S 40/36: characterised by special electrical interconnection means between two or more PV modules, e.g. electrical module-to-module connection - Y02E 10/50: Photovoltaic [PV] energy - H02S: GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES (obtaining electrical energy from radioactive sources G21H1/12; light sensitive inorganic semiconductor devices H10F; light sensitive organic semiconductor devices H10K30/00; thermoelectric devices H10N10/00; pyroelectric devices H10N15/00) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A deterioration diagnosis device for a solar cell string and a photovoltaic power generation system includes an impedance measuring instrument to measure a frequency characteristic of a first impedance between solar power generation units connected in the solar cell string and to measure a frequency characteristic of a second impedance, an analysis unit to calculate a first increment from an initial value of a series resistance component, and to calculate a second increment from an initial value of a resistance component between the first end of the plurality of solar power generation units connected in series and the frames in the solar cell string based on the frequency characteristic of the second impedance, and a deterioration determining unit to determine a position of a solar cell module having an increased resistance in the solar cell string based on the first increment and the second increment calculated by the analysis unit. ## Claims ### Claim 1 A deterioration diagnosis device for a solar cell string including a plurality of solar cell modules each of which has a solar power generation unit and a conductive frame, the solar power generation units of the plurality of solar cell modules being electrically connected in series, the frames of the plurality of solar cell modules being electrically connected in common, the deterioration diagnosis device comprising: an impedance measuring circuit to measure a frequency characteristic of a first impedance between a first end and a second end of the plurality of solar power generation units connected in series in the solar cell string and to measure a frequency characteristic of a second impedance between the first end of the plurality of solar power generation units connected in series and the frames in the solar cell string; a processing circuit configured as an analysis unit to calculate a first increment from an initial value of a series resistance component between the first end and the second end of the plurality of solar power generation units connected in series in the solar cell string based on the frequency characteristic of the first impedance, and to calculate a second increment from an initial value of a resistance component between the first end of the plurality of solar power generation units connected in series and the frames in the solar cell string based on the frequency characteristic of the second impedance, the initial value of the series resistance component between the first end and the second end of the plurality of solar generation units being a minimum impedance value obtained at a resonance point determined according to the frequency characteristic of the first impedance, and the initial value of the series resistance component between the first end of the plurality of solar power generation units and the frames in the solar cell string being a minimum impedance value obtained at a resonance point determined according to the frequency characteristics of the second impedance; and the processing circuit further configured as a deterioration determining unit to determine a position of a solar cell module having an increased resistance in the solar cell string based on the first increment and the second increment calculated by the analysis unit. ### Claim 2 (depends on 1) The deterioration diagnosis device for the solar cell string according to claim 1, wherein the initial value of the series resistance component and the initial value of the resistance component are values at the time of initial measurement of the solar cell string. ### Claim 3 (depends on 1) The deterioration diagnosis device for the solar cell string according to claim 1, wherein, when the first increment is ΔRs and the second increment is ΔRframe, the analysis unit calculates a value of ΔRframe/ΔRs, and the deterioration determining unit determines a position of the solar cell module having an increased resistance in the solar cell string based on the value of ΔRframe/ΔRs. ### Claim 4 (depends on 3) The deterioration diagnosis device for the solar cell string according to claim 3, wherein the impedance measuring circuit measures a frequency characteristic of a third impedance between the second end of the plurality of solar power generation units connected in series and the frames in the solar cell string; the analysis unit calculates a third increment from an initial value of a resistance component between the second end of the plurality of solar power generation units connected in series and the frames in the solar cell string based on the frequency characteristic of the third impedance; and the deterioration determining unit determines a position of the solar cell module having an increased resistance in the solar cell string based on the first increment, the second increment and the third increment calculated by the analysis unit. ### Claim 5 (depends on 4) The deterioration diagnosis device for the solar cell string according to claim 4, wherein, when ΔR′frame is defined as the third increment, the analysis unit calculates a value of ΔR′frame/ΔRs, and the deterioration determining unit determines a position of the solar cell module having an increased resistance in the solar cell string based on the value of ΔRframe/ΔRs and the value of ΔR′frame/ΔRs. ### Claim 6 (depends on 5) The deterioration diagnosis device for the solar cell string according to claim 5, wherein the deterioration determining unit determines a first position of the solar cell module having an increased resistance in the solar cell string based on the value of ΔRframe/ΔRs, determines a second position of the solar cell module having an increased resistance in the solar cell string based on the value of ΔR′frame/ΔRs, and determines that the solar cell module closer to the output terminal used for measurement is the solar cell module having an increased resistance when the first position and the second position are different from each other. ### Claim 7 (depends on 5) The deterioration diagnosis device for the solar cell string according to claim 5, wherein the deterioration determining unit determines a first position of the solar cell module having an increased resistance in the solar cell string based on the value of ΔRframe/ΔRs, determines a second position of the solar cell module having an increased resistance in the solar cell string based on the value of ΔR′frame/ΔRs, and determines that resistances of the plurality of solar cell modules in the solar cell string have increased when the first position and the second position are different from each other. ### Claim 8 (depends on 1) The deterioration diagnosis device for the solar cell string according to claim 1, wherein the initial value of the series resistance component is the series resistance component of the solar cell string measured last time and the initial value of the resistance component is the resistance component of the solar cell string measured last time; the analysis unit calculates the first increment and the second increment based on the series resistance component and the resistance component of the solar cell string measured last time; and the deterioration determining unit adds the first increment to the series resistance value measured last time of the solar cell module at a position determined based on the first increment and the second increment to record the sum. ### Claim 9 (depends on 1) A photovoltaic power generation system comprising: a solar cell string provided with a plurality of solar cell modules each of which has a solar power generation unit and a conductive frame, the solar power generation units of the plurality of solar cell modules being electrically connected in series, the frames of the plurality of solar cell modules being electrically connected in common; and the deterioration diagnosis device for the solar cell string according to claim 1. ### Claim 10 A deterioration diagnosis method using a deterioration diagnosis device for a solar cell string including a plurality of solar cell modules each of which has a solar power generation unit and a conductive frame, the solar power generation units of the plurality of solar cell modules being electrically connected in series, the frames of the plurality of solar cell modules being electrically connected in common, the deterioration diagnosis method comprising: measuring a frequency characteristic of a first impedance between a first end and a second end of the plurality of solar power generation units connected in series in the solar cell string and measuring a frequency characteristic of a second impedance between the first end of the plurality of solar power generation units connected in series and the frames in the solar cell string by using the deterioration diagnosis device; calculating a first increment from an initial value of a series resistance component between the first end and the second end of the plurality of solar power generation units connected in series in the solar cell string based on the frequency characteristic of the first impedance, and calculating a second increment from an initial value of a resistance component between the first end of the plurality of solar power generation units connected in series and the frames in the solar cell string based on the frequency characteristic of the second impedance by using the deterioration diagnosis device, the initial value of the series resistance component between the first end and the second end of the plurality of solar generation units being a minimum impedance value obtained at a resonance point determined according to the frequency characteristic of the first impedance, and the initial value of the series resistance component between the first end of the plurality of solar power generation units and the frame in the solar cell string being a minimum impedance value obtained at a resonance point determined according to the frequency characteristics of the second impedance; and determining a position of a solar cell module having an increased resistance in the solar cell string based on the calculated first increment and the calculated second increment by using the deterioration diagnosis device. ### Claim 11 A deterioration diagnosis device for a battery string including a plurality of battery modules each of which has a plurality of battery cells and a conductive frame, the plurality of battery modules being electrically connected in series, the frames of the plurality of battery modules being electrically connected in common, the deterioration diagnosis device comprising: an impedance measuring circuit to measure a frequency characteristic of a first impedance between a first end and a second end of the plurality of battery modules connected in series in the battery string and to measure a frequency characteristic of a second impedance between the first end of the plurality of battery modules connected in series and the frames in the battery string; a processing circuit configured as an analysis unit to calculate a first increment from an initial value of a series resistance component between the first end and the second end of the plurality of battery modules connected in series in the battery string based on the frequency characteristic of the first impedance, and to calculate a second increment from an initial value of a resistance component between the first end of the plurality of battery modules connected in series and the frames in the battery string based on the frequency characteristic of the second impedance, the initial value of the series resistance component between the first end and the second end of the plurality of solar generation units being a minimum impedance value obtained at a resonance point determined according to the frequency characteristic of the first impedance, and the initial value of the series resistance component between the first end of the plurality of solar power generation units and the frames in the solar cell string being a minimum impedance value obtained at a resonance point determined according to the frequency characteristics of the second impedance; and the processing circuit further configured as a deterioration determining unit to determine a position of a battery module having an increased resistance in the battery string based on the first increment and the second increment calculated by the analysis unit.