DATA ACQUISITION APPARATUS AND METHODOLOGY FOR SELF-DIAGNOSING OF AC MODULES

• US 20100106339A1
• Filed: 02/27/2008
• Published: 04/29/2010
• Est. Priority Date: 03/07/2007
• Status: Active Grant

• Current Assignee: FTC Solar, Inc.
• Original Assignee: Greenray, Inc.
• Inventors: Little, Ruel Davenport, King, Zachary Adam
• Granted Patent: US 8,300,439 B2
• Time in Patent Office: Days
• US Class Current: 700/293
• CPC Class Codes: G01D 9/005 Solid-state data loggers
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
• CPC Class Codes: H02S 50/00 Monitoring or testing of PV systems, e.g. load balancing or fault identification
• CPC Class Codes: H02S 50/10 Testing of PV devices, e.g. of PV modules or single PV cells testing of semiconductor devices during manufacturing H01L22/00
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

Method and apparatus for monitoring, measuring and recording the operating values of each of a plurality of inter-connected AC PV modules and performing a diagnostic analysis, including comparing the those operating values to each other and to operating values recorded at an earlier time to determine laminate degradation and the performance-attenuating effect of temperature, soiling, shading, and snow cover on the modules.

Claims

1. A power generating system comprising two or more solar cell modules, with each module comprising a PV laminate characterized by a plurality of electrically interconnected solar cells for generating a DC power output, and an inverter electrically connected to said PV laminate for converting said DC power output to an AC power output;

an AC power bus extending between said modules and connected to said inverter of each module for collecting the AC power output of said array of modules; and

a junction box electrically connected to said AC power bus;

said inverter also comprising means for sensing selected parameters from the group consisting of DC voltage, DC current, AC voltage, AC current, cumulative energy, inverter temperature, PV laminate temperature, and solar cell temperature;

means for digitizing said sensed parameters, and means for transmitting sensed parameters data over said AC power bus to said junction box; and

said junction box comprising means for receiving and storing sensed parameters data transmitted by said inverters over said AC power bus, and means for analyzing said stored parameters data on a module and array basis and storing the results of the analysis, and means for transmitting said digitized sensed parameters data and/or the results of said analysis to a remote receiver.

2. Apparatus according to claim 1 wherein each inverter comprises means for storing sensed parameters data.

3. Apparatus according to claim 1 wherein said junction box transmitting means comprises means for wirelessly transmitting said digitized sensed parameters data to a remote receiver.

4. Apparatus according to claim 1 wherein said junction box transmitting means is serially connected to a remote receiver by a wired connection.

5. Apparatus according to claim 1 in combination with at least a second array comprising two or more of solar cell modules, with said second array also having an inverter for each module, a second AC power bus extending between and connected to said inverter of each module of said second array of modules for collecting the AC power output of said second array;

and a second junction box electrically connected to said second AC power bus;

said inverters of said second array each comprising means for sensing selected parameters related to the power output of the modules of said second array, with said selected parameters being from the group consisting of DC voltage, DC current, AC voltage, AC current, cumulative energy, inverter temperature, PV laminate temperature, and solar cell temperature;

means for digitizing said sensed parameters, and means for transmitting said sensed parameters data over said AC power bus to said junction box; and

said second junction box comprising means for receiving and storing sensed parameters data transmitted by said inverters of said second array over said AC power bus, and means for analyzing said stored parameters data from said second array on a module and array basis and storing the results of the analysis, and means for transmitting said digitized sensed parameters data and/or the results of said analysis to a remote receiver.

6. Apparatus according to claim 5 further comprising means connecting the AC power bus of said first array of modules with the AC power bus of said second array of modules, whereby the combined power output of said first and second arrays is available for transmission to a power grid or other electrical load.

7. Apparatus according to claim 5 wherein said means for transmitting the sensed parameters data to a remote receiver from said junction box is a wireless transmitting device.

8. Apparatus according to claim 5 further including an AC power line connected to said AC bus via said junction box for transmitting the AC power output of said array to an AC power grid, and further including an AC filter interposed in AC power line downstream of said junction box for reducing the effect of grid noise on data transmitted over said AC power line.

9. Apparatus according to claim 1 wherein said modules are mounted in proximity to one in substantially like angular positions relative to the roof and experiencing similar environmental conditions, and further wherein said means for analyzing stored parameters data comprises means for diagnosing operational faults.

10. Apparatus according to claim 1 wherein said module includes a frame surrounding and supporting said PV laminate, and further wherein said inverter is mounted to said frame.

11. Apparatus according to claim 10 wherein said frame is made of metal and functions as a heat sink for said inverter.

12. Apparatus according to claim 11 wherein said inverter has an enclosure that functions as a ground path in conjunction with said frame.

13. Apparatus according to claim 10 wherein said frame comprises a channel having a first wall defining the periphery of said module and a second wall disposed inwardly and running parallel to said first wall, and further wherein said inverted is mounted in an opening in said second wall.

14. Apparatus according to claim 1 further including a temperature sensor connected to said PV laminate for sensing the temperature of said PV laminate, and means for transmitting the temperature sensed by said sensor to said inverter for digitizing and transmittal to said junction box for storage.

15. Apparatus according to claim 1 wherein said means for analyzing stored parameters data comprises means for diagnosing inverter faults.

17. Apparatus according to claim 1 wherein said means for analyzing stored parameters data comprises means for identifying module faults caused by one of the following conditions:

module shading by vegetation or other factor, snow cover, soiling of the sun-receiving surfaces of the modules, excessive module temperature due to insufficient air venting, and modules in an array having differences in their orientation relative to the sun.

18. Apparatus according to claim 17 wherein said means for analyzing stored parameters data for identifying module faults comprises means for comparing the operating values of the modules in the cluster to one another and also to the operating values of the modules at an earlier time.

16. Apparatus according to claim 16 wherein said inverter faults consist of one or more of the following:

insufficient DC voltage, DC ground fault, AC under frequency, AC over frequency, insufficient AC voltage, excessive AC voltage, inverter excess temperature, and inverter start-up wait period.

19. Method for acquiring operating and environmental data from an array of PV modules where each module has a power output section and its own dedicated inverter connected to that power output section and using that data to evaluate module and array performance, said method comprising the following steps:

(a) operating each inverter to convert the DC output of the module to which it is dedicated to an AC output, measuring the current and voltage values of said DC and AC outputs and also the inverter temperature and the temperature of the PV laminate component of the module, converting those values and temperatures to digital data, and storing said digital data in said inverter;

(b) transmitting said AC output from each inverter to a common AC power output bus for further transmittal to a utility power grid or other electrical load;

(c) operating said inverter to transmit said stored digital data to a computer controlled datalogger over said common AC power bus aided by an AC filter designed to eliminate interference of said digital data by AC grid noise;

(d) operating said datalogger to selectively evaluate the stored digital data from each inverter to determine inverter DC faults, AC faults, and internal faults as herein defined and storing the results of that evaluation; and

(e) operating said datalogger to selectively evaluate the stored digital data from each module to determine module faults resulting from one or more of the following;

snow accumulation, shading of module, soiling of module front face, high module temperature, and non-uniform orientation of modules in the array, and storing the results of that evaluation.

20. Method according to claim 19 wherein said inverter DC faults are DC voltage below a predetermined minimum and a DC ground fault, and said AC faults are members of the following group:

AC frequency below a predetermined limit, AC frequency above a predetermined limit;

AC voltage;

below a predetermined limit, and AC voltage above a predetermined limit.

21. Method according to claim 19 wherein said internal faults consist of inverter excess temperature and an inverter start-up period.

22. A photovoltaic power generating apparatus comprising:

a plurality of PV modules clustered together in an array, each of said modules comprising a PV laminate that converts solar energy to DC power, and a like plurality of inverters each electrically connected to the PV laminate of a different one of said modules and comprising a converter structured to convert the DC power output of said connected PV laminate to AC power,

an AC power bus connected to said inverters for combining the AC power outputs of said inverters; and

means connecting said AC power bus to a power line for transmittal of AC power to a power utility circuit via said power line;

each inverter being characterized by a microprocessor for controlling operation of said inverter and for converting current values of the collected DC and AC electric power to data in digital form, means for storing said data and also storing as data in digital form the temperature of said inverter and the temperature of the PV laminate to which the inverter is connected, and means for transmitting said electric power and temperature data over said power bus;

a programmable datalogger that is programmed to receive said transmitted data via said power bus, store said transmitted data, compare said transmitted data to data transmitted at an earlier time, determine inverter and module faults on the basis of said comparison, store the results of said comparison, and transmit said data and said stored results to a separate data collection device.

23. A photovoltaic power generating apparatus according to claim 22 wherein said datalogger transmits said data and stored results to a separate data collection device by wireless means.

24. Method for acquiring operating and environmental data from a cluster of PV modules where each module is constructed to generate a DC power output in response to received solar radiation, said method comprising the following steps:

(a) convert the DC power output of each PV module individually to an AC power output using a separate dedicated inverter for each PV module;

(b) collect the AC power output of all of the modules in said cluster via a common AC power bus;

(c) for each PV module, measure the voltage, electric current and energy values of said DC and AC power outputs and also the current temperature of said each PV module and the current temperature of its dedicated inverter;

(d) store the said values and said temperatures for each module in the form of digital format data at the site of said each module;

(e) transmit said digital format data from all of the PV modules of said cluster to a cluster data collection point;

(f) store said digital format data from all of said PV modules at said cluster data collection point;

(g) at said cluster data collection point, evaluate said digital format data to determine faults occurring in step (a);

(h) at said cluster data collection point, compare said digital format data from each module with the digital format data of the other modules in the cluster and also compare said digital format data with like digital format data derived from said PV modules at a previous time to evaluate individual and relative performance of the modules in the cluster to determine event-caused performance faults; and

(i) record all of said faults.

25. Method according to claim 24 wherein said data collection point comprises a datalogger.

26. Method according to claim 25 wherein said AC power output is transmitted by said AC power bus to an electricity-using grid, and further wherein in step (e) said data is transmitted to said data logger via said AC power bus.

27. Method according to claim 24 further including transmitting all of said digital data and data identifying said faults to a data collection device at a location remote from said PV modules and said datalogger.

28. Method according to claim 27 wherein the transmission of data to said data collection device is accomplished wirelessly.

29. Method according to claim 25 wherein said datalogger is embodied in the dedicated inverter of one of said modules.

30. Method for acquiring operating and environmental data from a cluster of n AC PV modules where n is a number greater than 1 and each module is constructed to generate a DC power output in response to received solar radiation and includes a dedicated inverter for converting said DC power output to an AC power output, said method comprising the following steps:

(a) converting the DC power output of each PV module individually to an AC power output using the dedicated inverter for said each PV module;

(b) for each AC PV module, measuring the voltage, electric current and energy values of said DC and AC power outputs and also the current temperature of said each AC PV module and the current temperature of its dedicated inverter;

(c) storing the said values and said temperatures for each module in the form of digital format data at the site of said each module;

(d) evaluating said digital format data of all of said n modules on a module by module basis to determine faults occurring in step (a);

(e) comparing said digital format data of said modules to determine those modules that fail to meet a predetermined power output level;

(f) comparing said digital format data of those modules that fail to meet said predetermined power output level with like digital format data derived from those modules at a previous time to determine and characterize event-caused performance faults; and

(g) recording data indicative of all of said faults in memory.

31. Method according to claim 30 wherein said steps (d) to (f) are carried out in a data logger spaced from said n modules.

32. Method according of claim 30 wherein steps (d) to (f) are carried out by the dedicated inverter of one of said n modules.

33. Method according to claim 30 further including transmitting said recorded data indicative of said faults to a remote data collection device.

34. Method according to claim 30 wherein said recorded data indicative of said faults is transmitted wirelessly to a remote collection device.

35. Method according to claim 32 wherein said recorded data is transmitted by said dedicated inverter of said 1 PC module via an AC power bus to a wireless interface capable of transmitting data wirelessly to a remote collection device, and further wherein said AC power bus also line carries the combined AC power outputs of said n AC PV modules.