Deterioration diagnosis device for solar cell string and photovoltaic power generation system provided with the same

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.

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.