Failure diagnosis method for photovoltaic power generation system

Patent metadata

Field	Value
Publication number	US-9506971-B2
Application number	US-201313975826-A
Country	US
Kind code	B2
Filing date	Aug 26, 2013
Priority date	Aug 27, 2012
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

A low-cost failure diagnosis method, without addition of a measuring unit and a communication unit, provided for a solar battery system, of calculating a working temperature and the number of failed solar battery modules in a solar battery array, by calculating a solar radiation amount while updating a predetermined coefficient as a ratio between a short-circuit current and a working current in accordance with state of the solar battery array and using measured data having the working current and working voltage measured with a detection unit.

First claim

What is claimed is:

1. A failure diagnosis method for a photovoltaic power generation system, the method comprising:
detecting, by a detection unit, a working voltage and a working current of a solar battery array, formed by connecting in parallel a plurality of solar battery strings, each solar battery string formed by serially connecting a plurality of solar battery modules, each formed by serially connecting a plurality of solar battery cells and connecting a protective diode to both ends, as one unit;
calculating, by a failure information calculation unit, failure information of the solar battery array using the detected working voltage and the working current;
calculating, by the failure information calculation unit, a solar radiation intensity of radiation on the solar battery array using a predetermined coefficient, wherein the predetermined coefficient is a ratio between the working current and a short-circuit current of the solar battery array;
calculating, by the failure information calculation unit, a working temperature of the solar battery array using the working voltage and the solar radiation intensity;
updating, by the failure information calculation unit, the predetermined coefficient using the calculated working temperature and the failure information; and
identifying, by the failure information calculation unit, failure in the solar battery array.

2. The failure diagnosis method for a photovoltaic power generation system according to claim 1 , wherein the failure information is a number of failed solar battery modules.

3. The failure diagnosis method for a photovoltaic power generation system according to claim 1 , further comprising calculating, by the failure information calculation unit, a number of failed solar battery modules, as the failure information, using a wiring resistance value corresponding to a loss amount of the solar battery modules, the detected working current, and the solar radiation intensity.

4. The failure diagnosis method for a photovoltaic power generation system according to claim 3 , wherein the ratio of the predetermined coefficient is a ratio between the working current and the short-circuit current in a current-voltage characteristic of the solar battery array obtained by reflecting the wiring resistance value.

5. The failure diagnosis method for a photovoltaic power generation system according to claim 1 , wherein the working temperature of the solar battery array is calculated using the detected working voltage, an open-circuit voltage of the solar battery array at normal temperature in the calculated solar radiation intensity, a temperature characteristic of the open-circuit voltage, and the predetermined coefficient.

6. A photovoltaic power generation monitoring system for transmitting a working voltage and a working current detected from a detection unit to a monitoring device using a signal conversion-transmission unit,
wherein the monitoring device uses the failure diagnosis method according to claim 1 .

7. The failure diagnosis method for a photovoltaic power generation system according to claim 1 , further comprising calculating, by the failure information calculation unit, a number of solar battery strings in which the short-circuit current in the solar battery array is lowered based on time change of a ratio between the calculated solar radiation intensity and a reference solar radiation intensity.

8. The failure diagnosis method for a photovoltaic power generation system according to claim 7 , wherein the reference solar radiation intensity is calculated from an occurrence of a short-circuit current in a reference solar battery module.

9. A failure diagnosis method for a photovoltaic power generation system, the the method comprising:
detecting, by a detection unit, a working voltage and a working current of a solar battery array, formed by connecting in parallel a plurality of solar battery strings, each solar battery string formed by serially connecting a plurality of solar battery modules, each formed by serially connecting a plurality of solar battery cells and connecting a protective diode to both ends, as one unit;
calculating, by a failure information calculation unit, failure information of the solar battery array using the detected working voltage and the working current;
calculating, by the failure information calculation unit, a solar radiation intensity of radiation on the solar battery array using a predetermined coefficient, wherein the predetermined coefficient is a ratio between the working current and a short-circuit current of the solar battery array;
calculating, by the failure information calculation unit, a working temperature of the solar battery array using the working voltage and the calculated solar radiation intensity;
updating, by the failure information calculation unit, the predetermined coefficient by comparing a calculated value of electric power of the solar battery array based on the working temperature and the solar radiation intensity calculated while a wiring resistance value is decremented in the plurality of solar battery modules, with a measured value of electric power of the solar battery array based on the working voltage and the working current; and
identifying, by the failure information calculation unit, failure in the solar battery array.

10. The failure diagnosis method for a photovoltaic power generation system according to claim 9 , wherein the failure information is a number of failed solar battery modules.

11. The failure diagnosis method for a photovoltaic power generation system according to claim 9 , further comprising calculating, by the failure information calculation unit, a number of failed solar battery modules, as the failure information, using a wiring resistance value corresponding to a loss amount of the solar battery modules, the detected working current, and the solar radiation intensity.

12. The failure diagnosis method for a photovoltaic power generation system according to claim 11 , wherein the ratio of the predetermined coefficient is between the working current and the short-circuit current in a current-voltage characteristic of the solar battery array obtained by reflecting the wiring resistance value.

13. The failure diagnosis method for a photovoltaic power generation system according to claim 9 , wherein the working temperature of the solar battery array is calculated using the detected working voltage, an open-circuit voltage of the solar battery array at normal temperature in the calculated solar radiation intensity, a temperature characteristic of the open-circuit voltage, and the predetermined coefficient.

14. A photovoltaic power generation monitoring system for transmitting a working voltage and a working current detected from a detection unit to a monitoring device using a signal conversion-transmission unit,
wherein the monitoring device uses the failure diagnosis method according to claim 9 .

15. The failure diagnosis method for a photovoltaic power generation system according to claim 9 , further comprising calculating, by the failure information calculation unit, a number of solar battery strings in which the short-circuit current in the solar battery array is lowered based on time change of a ratio between the calculated solar radiation intensity and a reference solar radiation intensity.

Assignees

• Hitachi Ltd

Inventors

• Kohno Tohru
• Nakamura Akihiro
• Nakamura Tomoharu
• Morikawa Koki

Classifications

• H02S50/10 Primary

  Testing of PV devices, e.g. of PV modules or single PV cells (testing of semiconductor devices during manufacturing {H10P74/00}) · CPC title

• G01R31/02 Primary

  Physics · mapped topic

• Y02E10/50

  Photovoltaic [PV] energy · CPC title