Photovoltaic array systems, methods, and devices and improved diagnostics and monitoring

• US 8,446,043 B1
• Filed: 12/05/2012
• Issued: 05/21/2013
• Est. Priority Date: 11/30/2010
• Status: Active Grant

• Current Assignee: CE+T Group SA
• Original Assignee: Ideal Power Converters, Inc.
• Inventors: Bundschuh, Paul, Alexander, William C.
• Primary Examiner(s): Fleming, Fritz M
• Application Number:
  US13/705,230
• Time in Patent Office: 167 Days
• Field of Search: 307/64, 307/80, 307/85, 307/151
• US Class Current: 307/80
• CPC Class Codes: G01R 31/2603 for curve tracing of semiconductor characteristics, e.g. on oscilloscope
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H01L 31/02021 for solar cells electrical connection means, e.g. junction boxes, specially adapted for structural association with photovoltaic modules H02S40/34
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/388 Islanding, i.e. disconnection of local power supply from the network
• CPC Class Codes: H02M 7/66 with possibility of reversal
• 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 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

Devices, systems and methods for operating, monitoring and diagnosing photovoltaic arrays used for solar energy collection. The system preferably includes capabilities for monitoring or diagnosing an array by automatically disconnecting portions of the array during normal service (when load is not maximum, and observing the resulting change in electrical characteristics. More intensive diagnostic procedures can be launched if needed. One embodiment provides for performing monitoring or diagnostic operations on the array in daylight or at night. Another embodiment allows monitoring or diagnostic operations to be performed on a portion of the array while other parts of the array continue to collect energy. Yet another embodiment provides a safety mode for an array for maintenance or during emergencies.

Claims

1. A method of monitoring a photovoltaic array with a plurality of strings of photovoltaic cells comprising the following steps:

automatically electrically disconnecting one or more strings of photovoltaic cells from a photovoltaic array;

performing a diagnostic test on the strings remaining connected using a bidirectional AC-DC converter to apply a DC potential to said at least one string of photovoltaic cells;

wherein said diagnostic test performs an IV curve trace on ones of said cells;

initiating an alert condition if results of the diagnostic test are outside of an expected range; and

automatically electrically reconnecting the one or more strings.

2. The method of claim 1, wherein said steps are repeated, from time to time during normal operation, for each said string.

3. The method of claim 1, wherein said automatically disconnecting step is performed at regular intervals.

4. The method of claim 1, wherein said automatically disconnecting step is performed only when electrical load is below a ceiling value.

5. A photovoltaic power generation system comprising:

a plurality of photovoltaic cells;

a power converter which is connected to groups of said photovoltaic cells through a plurality of switches;

wherein said converter is a bidirectional AC-DC converter; and

,

control logic which operates said switches such that;

during normal operation, most or all of said photovoltaic cells are connected to provide power to a power converter;

at some but not all times during normal operation, some but less than all, of said cells are automatically disconnected from power converter;

wherein one or more diagnostic tests are run while some of said cells are disconnected; and

said diagnostic test uses said converter to apply a DC potential to at least some ones of said photovoltaic cells; and

,

wherein said diagnostic test performs an IV curve trace on ones of said cells.