Fault tolerant maximum power tracking solar power system

• US 6,433,522 B1
• Filed: 09/27/2001
• Issued: 08/13/2002
• Est. Priority Date: 05/02/2001
• Status: Expired due to Term

• Current Assignee: Aerospace Corporation
• Original Assignee: Aerospace Corporation
• Inventors: Siri, Kasemsan
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/966,139
• Time in Patent Office: 320 Days
• Field of Search: 323/271, 323/272, 323/284, 323/906, 320/101, 320/162, 136/244, 700/295
• US Class Current: 323/272
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• 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: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A maximum power tracker maximizes the power deliverable from a power source, such as a solar array using increasing, decreasing and maintaining states controlled by a set point signal modulated by a dither signal for stabilized regular power tracking during under demand conditions and maximum power tracking during periods with over demand conditions of a load. For multiple power sources, respective multiple sets of parallel-connected converters and respectively maximum power trackers can be coupled in parallel using shared bus and control signals for fault tolerant equalized power conversion among the parallel-connected converters. Among multiple solar array sources that can have quite different characteristics, some maximum power trackers may actively regulate maximum power flows from respective array sources that have deficient power while the remaining maximum power trackers are inactive because respective remaining solar array sources provide sufficient power to allow respective DC-DC converters to regulate the load voltage to a regulated level.

Claims

1. A system for providing power from at least one source providing source power at a source current at a source voltage to a load receiving load power at a load current at a load voltage, the load having variable amounts of load demand for the load power, the source providing variable amounts of the source power, the system comprising,

at least one converter coupled between the source and the load, the converter for converting the source power into the load power,

at least one source current sensor for sensing the source current for providing at least one source current signal,

at least one source voltage sensor for sensing the source voltage for providing at least one source voltage signal, and

at least one maximum power tracker connected to the at least one converter and the at least one source for controlling the source power and the load power, the maximum power tracker receiving the source current signal and source voltage signal and controlling the converter for maximizing the source power to a peak power point at a respective peak power source voltage when the load demand exceeds the source power, the maximum power tracker increasing the source voltage for increasing the source power toward the peak power point when the source power is below the peak power point and the source voltage is below the peak power source voltage and when the load demand exceeds the source power, the maximum power tracker decreasing the source voltage for increasing the source power toward the peak point when the source power is below the peak power point and when and the source voltage is above the peak power source voltage and when the load demand exceeds the source power, the maximum power tracker maintaining the source voltage constant at the peak power source voltage when the source power is at the peak power point and when the load demand exceeds the source power, the maximum power tracker generating a control signal for controlling the converter to control the source voltage for operating the source at the peak power point when the load demand exceeds the source power, the maximum power tracker controlling the converter for peak power tracking when increasing or decreasing or maintaining the source voltage when the load demand exceeds the source power, the maximum power tracker regulating the load voltage at a regulated load voltage when the source power exceeds the load demand.

2. The system of claim 1 wherein the at least one converter is a plurality of converters coupled between the at least one source and the load, each of the plurality of converters is coupled to the control signal serving as a bus signal to each of the converters to control the converters to provide equal current sharing contributions to the load current.

3. The system of claim 1 wherein the converter comprises,

a power stage having a converter input signal for controlling the load current and load voltage to the load,

an error amplifier for sensing the load voltage and generating an error signal for regulating the load voltage to a regulation voltage when the source powers exceeds the load demand, the error signal driving the converter input signal during load voltage regulation, and

a coupling means for coupling together the control signal and the converter input signal and the error signal, the converter input signal being the control signal when the control signal is lesser than the error signal during the peak power tracking when the load demand exceeds the source powers, the converter input signal being the error signal when the control signal is greater than the error signal during load voltage regulation when the source power exceeds the load demand, the maximum power tracker generating the control signal from the source voltage and a set point signal, the set point signal increasing when the source power is increasing and the source voltage is increasing, the set point signal decreasing when the source power is increasing and the source voltage is decreasing, the set point signal maintaining when the source power is at the peak power point at the peak power source voltage, the set point signal and source voltage combined into the control signal driving the converter connected to the source voltage for controlling the source voltage to the set point signal under closed loop control.

4. The system of claim 3 wherein,

the set point signal is dithered by a dither signal having a dither frequency for dithering the set point signal about a tracking signal, the set point signal serving to dither the source voltage and the source power about the dither frequency,

the maximum power tracker receiving the source voltage signal and the source current signal at repetitive present and previous times for continuously providing and updating present and previous source voltage signals and for continuously providing and updating present and previous source power signals as present and previous source power signals, the present and previous source voltage signals defining a changed source voltage signal, the present and previous source power signals providing a changed source power signal, and

the set point signal is increasing or decreasing or maintaining respectively when the tracking signal is increasing or decreasing or maintaining, the tracking signal increasing when the changed source power signal is increasing and when the changed source voltage signal is increasing, the tracking signal decreasing when the changed source power signal is increasing and the changed source voltage signal is decreasing, the tracking signal maintaining when an absolute value of the changed source power signal is less than a predetermined minimum value.

5. The system of claim 4 wherein the maximum power tracker comprises,

a first filter for filtering the source voltage having the dither frequency into a filtered source voltage signal,

a first sample and hold circuit for sampling the filtered source voltage signal into the present and previous source voltage signals,

a multiplier for multiplying the source current signal and the source voltage signal for generating a source power signal,

a second filter for filtering the source power having the dither frequency into a filtered power signal, and

a second sample and hold circuit for sampling the filtered power signal into the present and previous power signals.