Smart sensors for solar panels

• US 8,294,451 B2
• Filed: 11/18/2008
• Issued: 10/23/2012
• Est. Priority Date: 12/03/2007
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hasenfus, Gary D.
• Primary Examiner(s): Dole, Timothy J
• Application Number:
  US12/272,990
• Publication Number:
  US 20090140719A1
• Time in Patent Office: 1,435 Days
• Field of Search: 136/290, 324/72
• US Class Current: 324/72
• 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: H04Q 2209/84 Measuring functions
• CPC Class Codes: H04Q 2209/886 using energy harvesting, e.g. solar, wind or mechanical
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A solar panel smart sensor system is disclosed. The sensor system permits solar power system owners and operators to monitor the voltage of individual panels in a solar array. The system uses a low wire-count bus in which the order of sensors on the bus is automatically determined. A novel technique is used to measure DC voltages of panels that may be floating hundreds of volts above ground. Bypass diodes are monitored to detect lost power generation capacity.

Claims

1. A solar power generating system comprising:

multiple photovoltaic panels, each panel connected to its own voltage sensor that is configured to transmit voltage information to a controller via a bus;

wherein each voltage sensor comprises;

a voltage-to-frequency converter configured to generate a pulse data signal based on an output voltage of an associated photovoltaic panel; and

a multiplexer connected to the bus and configured to receive the pulse data signal, the multiplexer comprising;

a sense-in terminal configured to receive a sense-out signal associated with another solar panel, a sense-out terminal, a ground terminal, a power terminal, and a control terminal;

wherein the multiplexer is configured to connect the sense-out terminal to the pulse data signal in response to a first signal received at the control terminal, to the sense-in terminal in response to a second signal received at the control terminal, to the ground terminal in response to a third signal received at the control terminal, and to the power terminal in response to a fourth signal received at the control terminal, wherein

the bus comprises ground, power, and control wires;

the ground wire is connected to the ground terminal of the multiplexer in each voltage sensor;

the power wire is connected to the power terminal of the multiplexer in each voltage sensor;

the control wire is connected to the control terminal of the multiplexer in each voltage sensor;

the sense-out terminal of the multiplexer in each voltage sensor, except a last voltage sensor in a string, is connected to the sense-in terminal of the multiplexer in a succeeding voltage sensor in the string; and

the sense-out terminal of the multiplexer in the last voltage sensor in the string is connected to a bus master.

2. The solar power generating system of claim 1, wherein each voltage sensor is electrically isolated from earth ground.

3. The solar power generating system of claim 1, wherein each voltage sensor further comprises a digital temperature sensor.

4. The solar power generating system of claim 3, wherein the digital temperature sensor of each voltage sensor is configured to respond to changes in a temperature of a bypass diode for its associated solar panel.

5. The solar power generating system of claim 1, wherein the voltage-to-frequency converter in at least one of the voltage sensors has voltage inputs that are optically isolated from a pulse data output.

6. The solar power generating system of claim 1, wherein the voltage-to-frequency converter in at least one of the voltage sensors comprises:

a precision capacitor;

a comparator configured to sense when the capacitor is charged to a specified level;

a light-emitting diode (LED) through which the capacitor is discharged when the capacitor is charged to the specified level; and

a photodiode configured to create an electrical pulse when the LED turns on.

7. The solar power generating system of claim 1, wherein each voltage sensor further comprises:

an input/output device configured to interface the multiplexer of that voltage sensor to the bus.