Dual-Loop Dynamic Fast-Tracking MPPT Control Method, Device, and System

• US 20110175454A1
• Filed: 01/20/2011
• Published: 07/21/2011
• Est. Priority Date: 01/20/2010
• Status: Active Grant

• Current Assignee: Also Energy Incorporated
• Original Assignee: Draker Laboratories Incorporated (Also Energy Incorporated)
• Inventors: Sandbote, Sam B., Williams, Bertrand J.
• Granted Patent: US 8,975,783 B2
• Time in Patent Office: Days
• US Class Current: 307/82
• 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 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A converter unit to improve the response dynamics and 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 control operation of a power converter to output modified voltage and current corresponding to the solar panel onto a bus coupling the converter units. The controller may operate as an analog or (digital) firmware control system to regulate the input voltage of each power converter unit under indirect guidance of a Maximum Power Point Tracking (MPPT) controller to optimize and regulate the resultant power, and achieve very fast dynamic response to environmental transients. Input voltage and output voltage management may be achieved by way of a fast inner control loop and a corresponding MPPT control system configured as an outer guidance loop providing a reference signal to the inner control loop.

Claims

1. A control system for controlling a power converter configured to couple to a solar panel to provide an output voltage to a voltage bus, the control system 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 provided by the solar panel;

a second parameter indicative of an input voltage of the power converter provided by the solar panel;

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

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

an inner control loop configured to regulate based on a reference value one or more of;

the input current of the power converter;

the input voltage of the power converter;

the output voltage of the power converter; and

the output current of the power converter; and

an outer control loop configured to perform Maximum-Power-Point-Tracking (MPPT) control of the power converter based on the plurality of parameters, and further configured to generate the reference value based on the plurality of parameters.

2. The control system of claim 1, wherein the inner control loop is an analog voltage regulation loop, and the reference value is a reference voltage set-point signal.

3. The control system of claim 1, wherein the outer loop is a digital MPPT loop.

4. The control system of claim 1, wherein the inner control loop is configured to operate in current-mode.

5. The control system of claim 1, wherein the reference value corresponds to a desired value of the input voltage of the power converter;

wherein the outer control loop is configured to determine the desired value, and further configured to instruct the inner control loop, via analog signaling, to regulate the input voltage of the power converter to the desired value.

6. The control system of claim 1, wherein the outer control loop is configured to implement a three-point derivative plus peak detection and tracking MPPT algorithm.

7. The control system of claim 1, wherein the outer control loop is configured to implement an MPPT algorithm that incorporates dynamic dithering magnitude, dependent upon sensed dynamic and static conditions.

8. The control system of claim 1, wherein the inner control loop is a digital control regulation loop, and the reference value is a digital signal corresponding to a reference voltage set-point.

9. The control system of claim 1, wherein the inner control loop is configured to adjust a duty cycle value of a pulse width modulated (PWM) control signal to adjust the input voltage of the power converter.

10. The control system of claim 9, wherein the inner control loop is configured to hold an on-time of an output stage of the power converter constant while increasing an off-time of the output stage of the power converter when the duty cycle value of the PWM control signal drops below a specified level.

11. A control system for controlling a power converter configured to couple to a solar panel to provide an output voltage to a voltage bus, the control system comprising:

a sensing circuit configured to sense input current and input voltage of the power converter derived from the solar panel, and further configured to sense output voltage and output current of the power converter;

an inner control loop configured to adjust, according to a corresponding reference signal, at least one of;

the input voltage of the power converter;

the input current of the power converter;

the output voltage of the power converter; and

the output current of the power converter;

an outer control loop configured to perform Maximum-Power-Point-Tracking (MPPT) control of the power converter based on the input voltage, input current, output voltage, and output current of the power converter, and further configured to generate the reference signal based on the input voltage, input current, output voltage, and output current of the power converter to maintain MPPT of the power converter.

12. The control system of claim 11, wherein the inner control loop is configured to operate at a bandwidth that is greater than a frequency of transients that affect the output voltage of the power converter.

13. The control system of claim 11, wherein the outer loop is a digital MPPT loop.

14. The control system of claim 11, wherein the inner control loop is configured to operate in current-mode.

15. The control system of claim 11, wherein the reference signal corresponds to a desired value of the input voltage of the power converter;

wherein the outer control loop is configured to determine the desired value, and further configured to instruct the inner control loop, via analog signaling, to adjust the input voltage of the power converter to the desired value.

16. The control system of claim 11, wherein the outer control loop is configured to implement an MPPT algorithm that incorporates dynamic dithering magnitude, dependent upon sensed dynamic and static conditions.

17. The control system of claim 11, wherein the inner control loop is a digital control regulation loop, and the reference signal is a digital value corresponding to a reference voltage set-point representative of one of:

a desired value of the input voltage of the power converter; and

a desired value of the output voltage of the power converter.

18. A method for controlling a power converter coupled to a solar panel to provide an output voltage to a voltage bus, the control system comprising:

determining a desired set-point according to a Maximum-Power-Point-Tracking (MPPT) algorithm applied to the power converter based on one or more of;

input voltage and input current of the power converter; and

output voltage and output current of the power converter; and

adjusting one of;

the input voltage of the power converter to regulate to the desired set-point when the desired set-point corresponds to a desired value of the input voltage of the power converter; and

the output voltage of the power converter to regulate to the desired set-point when the desired set-point corresponds to a desired value of the output voltage of the power converter.

19. The method of claim 18, wherein said adjusting comprises:

setting a duty-cycle value of a pulse width modulated (PWM) control signal; and

controlling the output voltage of the power converter using the PWM control signal.

20. The method of claim 18, wherein said adjusting is performed at a rate that is faster than a frequency of transients that affect the output of the voltage regulator.

21. 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 at the input of the power converter;

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

a third parameter indicative of the converter output voltage; and

a fourth parameter indicative of the converter output current;

an inner control loop configured to regulate based on a reference value one or more of;

the input current at the input of the power converter;

the input voltage at the input of the power converter;

the converter output voltage; and

the converter output current; and

an outer control loop configured to perform Maximum-Power-Point-Tracking (MPPT) control of the power converter based on the plurality of parameters, and further configured to generate the reference value based on the plurality of parameters.

22. The converter unit of claim 21, wherein the power converter is a switching DC/DC converter.

23. The converter unit of claim 22, wherein the inner control loop is configured to regulate the input voltage at the input of the power converter by adjusting a duty cycle of a pulse width modulated (PWM) signal according to the reference value, wherein the PWM signal controls the converter output voltage.

24. A solar power array, comprising:

a plurality of solar power panels, wherein each given solar panel of the plurality of solar panels provides a respective output current and a respective output voltage;

a plurality of converter units, wherein each given solar panel is coupled to a corresponding converter unit of the plurality of converter units to provide its respective output current and its respective output voltage as inputs to its corresponding converter unit, wherein each corresponding converter unit comprises a switching power module that produces a respective converter output voltage and respective converter output current, and wherein each of one or more corresponding converter units is configured to;

determine a desired set-point according to a Maximum-Power-Point-Tracking (MPPT) algorithm applied to the switching power module based on one or more of;

input voltage and input current of the switching power module; and

the respective converter output voltage, and the respective converter output current; and

adjust one of;

the input voltage of the switching power module to regulate to the desired set-point when the desired set-point corresponds to a desired value of the input voltage of the switching power module; and

the converter output voltage to regulate to the desired set-point when the desired set-point corresponds to a desired value of the converter output voltage;

a DC voltage bus coupled to the plurality of converter units and configured to receive each respective converter output voltage to provide a DC bus voltage; and

a DC/AC inverter that inverts the DC bus voltage to an AC power signal for distribution to one or more AC loads.

25. The solar power array of claim 24, wherein the plurality of converter units are series connected to the DC voltage bus via their respective outputs, and wherein the desired set-point corresponds to a desired value of the input voltage of the switching power module.

26. The solar power array of claim 24, wherein the plurality of converter units are parallel connected to the DC voltage bus via their respective outputs, and wherein the desired set-point corresponds to a desired value of the converter output voltage.

27. A solar power array, comprising:

a plurality of solar power panels, wherein each given solar panel of the plurality of solar panels provides a respective output current and a respective output voltage;

a plurality of converter units, wherein each given solar panel is coupled to a corresponding converter unit of the plurality of converter units to provide its respective output current and its respective output voltage at an input of its corresponding converter unit, wherein each corresponding converter unit comprises a switching power module that produces a respective converter output voltage and a respective converter output current, and wherein each of one or more corresponding converter units comprises;

an inner control loop configured to adjust, according to a corresponding reference signal, at least one of;

an input voltage at the input of the switching power module;

an input current at the input of the switching power module;

the respective converter output voltage; and

the respective converter output current; and

an outer control loop configured to perform Maximum-Power-Point-Tracking (MPPT) control of the switching power module, and further configured to generate the reference signal based on one or more of;

the input voltage at the input of the switching power module and the input current at the input of the switching power module; and

the respective converter output voltage and the respective converter output current;

a DC voltage bus coupled to the plurality of converter units and configured to receive each respective converter output voltage to provide a DC bus voltage; and

a DC/AC inverter that inverts the DC bus voltage to an AC power signal for distribution to one or more AC loads.