Constraint weighted regulation of DC/DC converters

• US 9,142,960 B2
• Filed: 02/03/2011
• Issued: 09/22/2015
• Est. Priority Date: 02/03/2010
• Status: Active Grant

• Current Assignee: Also Energy Incorporated
• Original Assignee: Draker Laboratories Incorporated (Also Energy Incorporated)
• Inventors: Williams, Bertrand J., Sandbote, Sam B.
• Primary Examiner(s): Amrany, Adi
• Application Number:
  US13/020,641
• Publication Number:
  US 20110187198A1
• Time in Patent Office: 1,692 Days
• Field of Search: 307/151
• US Class Current: 1/1
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H02J 1/12 Parallel operation of dc generators with converters, e.g. with mercury-arc rectifier
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 3/02 without intermediate conversion into ac
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A converter unit to improve overall recovered power in a photovoltaic array configuration. Each photovoltaic panel in the photovoltaic array may be coupled to a respective converter unit, which may include a controller to sense an output voltage and output current produced by the solar panel, and manage the output voltage of a corresponding power converter to optimize and regulate the resultant bus voltage to a point which reduces overall system losses, maintains a low loss condition, and removes series-string non-idealities when the panels are series connected. The controller may also adapt to output condition constraints. Instead of single-port regulation, a combination of input voltage and output voltage management and regulation may be performed within the converter. The source voltage and current characteristic may be shaped to correspond to an optimized power curve at the desired bus voltage to allow MPPT tracking according to the DC voltage bus. The optimized power curve may be tracked to hold the DC-bus voltage at the desired operating point.

Claims

1. A controller for controlling a power converter, the controller comprising:

at least four input ports, each respective input port of the at least four input ports configured to receive a respective one of a plurality of parameters comprising;

a first parameter indicative of a value of an input current of a power converter;

a second parameter indicative of a value of an input voltage of the power converter originating from the solar panel;

a third parameter indicative of a value of an output voltage of the power converter; and

a fourth parameter indicative of a value of an output current of the power converter;

wherein the power converter is coupled between a solar panel and a voltage bus and is configured to provide an output voltage and an output current to the voltage bus, the input current originating from the solar panel; and

control circuitry configured to set a value of a control signal that controls the output voltage of the power converter, according to;

a first function corresponding to a maximum power point tracking (MPPT) signal path and configured to set a nominal value of the control signal according to a corresponding MPPT algorithm; and

a second function corresponding to an output voltage signal path of the power converter and configured to adjust the value of the control signal from the nominal value to an adjusted value that establishes a weak control path that provides a sloping output power characteristic of the power converter on either side of a flat output power characteristic of the power converter, wherein the flat output power characteristic corresponds to a preferred voltage range of the output voltage of the power converter within which the output voltage of the power converter is generated according to the nominal value of the control signal.

2. The controller of claim 1, wherein the control circuitry is configured to regulate the output voltage of the power converter according to a specified mathematical function.

3. The controller of claim 1, wherein the control circuitry is configured to regulate the input voltage of the power converter by setting a dominant value for a first control signal used for adjusting the output voltage of the power converter.

4. The controller of claim 1, wherein the control circuitry is configured to regulate the output voltage of the power converter such that the output voltage of the power converter does not exceed a specified maximum value.

5. The controller of claim 1, wherein the control circuitry is configured to regulate the input voltage of the power converter and suspend regulating the output voltage of the power converter when the output voltage of the power converter is within the preferred voltage range.

6. The controller of claim 1, wherein the control circuitry is configured to regulate output power of the power converter according to a weighted constraint corresponding to the output voltage of the power converter.

7. A controller for controlling a power converter, the control system comprising:

a sensing circuit configured to sense input current and input voltage of a power converter, and further configured to sense output voltage and output current of the power converter,

wherein the power converter is coupled between a solar panel and a voltage bus, and is configured to provide an output voltage and an output current to the voltage bus, wherein the input current and the input voltage derive from the solar panel; and

control circuitry configured to set a value of a control signal that controls the output voltage of the power converter, based on;

a first function corresponding to a maximum power point tracking (MPPT) signal path and configured to set a nominal value of the control signal according to a corresponding MPPT algorithm; and

a second function corresponding to an output voltage signal path of the power converter and configured to adjust the value of the control signal from the nominal value to an adjusted value that establishes a weak control path that provides a respective sloping output power characteristic of the power converter on either side of a flat output power characteristic of the power converter, wherein the flat output power characteristic corresponds to a preferred voltage range of the output voltage of the power converter within which the output voltage of the power converter is generated according to the nominal value of the control signal.

8. The controller of claim 7, wherein the control circuitry is configured to regulate output power of the power converter according to a specified mathematical function corresponding to an overall output power transfer characteristic of the power converter that comprises the sloping output power characteristic and the flat output power characteristic.

9. The controller of claim 7, wherein the power converter is a switching power converter and the control signal is a pulse width modulated (PWM) signal provided as a switching signal to the power converter;

and

wherein the control circuitry is configured to regulate the input voltage of the power converter by setting a dominant pulse timing corresponding to the nominal value for the (PWM) signal.

10. The controller of claim 9, wherein the first function is configured such that regulation of the input voltage of the power converter according to the MPPT algorithm causes an output of the power converter to operate as a virtual constant power port corresponding to the flat output power characteristic, wherein in controlling the output voltage of the power converter, the control circuitry is configured to adjust the dominant pulse timing of the PWM signal to provide the sloping output power characteristic at the virtual constant power port around the preferred voltage range of the output voltage of the power converter.

11. The controller of claim 7, wherein the control circuitry is configured to regulate the output voltage of the power converter such that the output voltage of the power converter does not exceed a specified maximum value.

12. The controller of claim 7, wherein the control circuitry is configured to regulate the input voltage of the power converter and suspend regulating the output voltage of the power converter when the output voltage of the power converter is within preferred voltage range.

13. A method for controlling a power converter coupled between a solar panel and a voltage bus and configured to provide an output voltage and an output current to the voltage bus, the method comprising:

monitoring input voltage and input current of the power converter;

monitoring output voltage and output current of the power converter;

setting a value of a control signal that controls the output voltage of the power converter, according to a first function corresponding to a maximum power point tracking (MPPT) signal path and configured to set a nominal value of the control signal according to a corresponding MPPT algorithm; and

adjusting the value of the control signal from the nominal value to an adjusted value according to a second function corresponding to an output voltage signal path of the power converter, wherein the adjusted value of the control signal creates a sloping output power characteristic of the power converter on either side of a flat output power characteristic of the power converter, wherein the flat output power characteristic corresponds to a preferred voltage range of the output voltage of the power converter within which the output voltage of the power converter is generated according to the nominal value of the control signal.

14. The method of claim 13, wherein said monitoring the input voltage and input current and said monitoring the output voltage and output current comprise obtaining digitized values corresponding to the input voltage and input current of the power converter and the output voltage and output current of the power converter, and using the digitized values as the parameters.

15. The method of claim 13, further comprising regulating output power of the power converter according to a specified function of the output voltage of the power converter.

16. A converter unit comprising:

a power converter having an input configured to couple to a solar panel to receive an input voltage and input current from the solar panel, and an output configured to couple to a voltage bus to provide a converter output voltage and a converter output current to the voltage bus; and

a control unit comprising;

one or more input ports, each given input port of the one or more input ports configured to receive one of a plurality of parameters comprising;

a first parameter indicative of an input current of the power converter;

a second parameter indicative of an input voltage of the power converter;

a third parameter indicative of the converter output voltage; and

a fourth parameter indicative of the converter output current; and

a controller configured to set a value of a control signal that controls the converter output voltage according to;

a first function corresponding to a maximum power point tracking (MPPT) signal path and configured to set a nominal value of the control signal according to a corresponding MPPT algorithm; and

a second function corresponding to an output voltage signal path of the power converter and configured to adjust the value of the control signal from the nominal value to an adjusted value that establishes a weak control path that provides a sloping output power characteristic of the power converter on either side of a flat output power characteristic of the power converter, wherein the flat output power characteristic corresponds to a preferred voltage range of the output voltage of the power converter within which the output voltage of the power converter is generated according to the nominal value of the control signal.

17. The converter unit of claim 16, wherein the power converter is a switching DC/DC converter.