Solar array inverter with maximum power tracking
First Claim
1. A bi-directional power supply adapted to supply AC power to a utility grid or stand-alone load, comprising:
- a DC power source;
a bi-directional inverter that provides output power through a single power stage of DC-AC conversion;
an output filtering grid interface that filters and supplies the output power from the bi-directional inverter into the utility grid; and
a system controller for regulating the voltage of the DC power source at its maximum power voltage, controlling the waveform of the inverter output current to be sinusoidal, and reducing the output power when the utility grid voltage exceeds a predetermined threshold;
wherein the output power;
tracks the maximum power output of the DC power source; and
is sinusoidal AC current that is controlled to be other in phase with or optimally phase-shifted with the utility grid voltage;
wherein the bi-directional inverter comprises a cascade connection of an input bulk capacitor for sufficient energy storage to limit voltage ripple across the DC power source to a predetermined level, a line-filter for filtering the inverter input current to suppress the conducted and radiated switching noise produced by the inverter, and the bi-directional inverter power stage; and
wherein the output filtering grid interface comprises an output filter, a fuse, and an output relay switching network for transferring power to either the utility grid or the stand-alone load.
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Accused Products
Abstract
An inverter for use in connecting a DC power source to the utility grid includes a single DC-AC conversion stage, maximum (source) power tracking, and current control based on feed-forward compensation as a function of input power voltage error, rectified utility line voltage, and a scaled inverse of RMS utility line voltage. Various topologies of the inverter power stage are developed for bi-directional power-flow operation after those developed for unidirectional power-flow operation. Various embodiments also include over-voltage protection, over-current protection, under-voltage protection, over-temperature protection, and stand-by battery with battery management control, while still others are adapted for a multiple-channel front-end distributed power system with distributed maximum power tracking for serving as a single DC power source input to the inverter system downstream with controllers, emergency or auxiliary loads, and alternative current feedback control systems. Improved control architectures are developed with bipolar sensing of the inverter output current and a bipolar sinusoidal reference signal.
334 Citations
18 Claims
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1. A bi-directional power supply adapted to supply AC power to a utility grid or stand-alone load, comprising:
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a DC power source; a bi-directional inverter that provides output power through a single power stage of DC-AC conversion; an output filtering grid interface that filters and supplies the output power from the bi-directional inverter into the utility grid; and a system controller for regulating the voltage of the DC power source at its maximum power voltage, controlling the waveform of the inverter output current to be sinusoidal, and reducing the output power when the utility grid voltage exceeds a predetermined threshold; wherein the output power; tracks the maximum power output of the DC power source; and is sinusoidal AC current that is controlled to be other in phase with or optimally phase-shifted with the utility grid voltage; wherein the bi-directional inverter comprises a cascade connection of an input bulk capacitor for sufficient energy storage to limit voltage ripple across the DC power source to a predetermined level, a line-filter for filtering the inverter input current to suppress the conducted and radiated switching noise produced by the inverter, and the bi-directional inverter power stage; and wherein the output filtering grid interface comprises an output filter, a fuse, and an output relay switching network for transferring power to either the utility grid or the stand-alone load. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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5. A bi-directional power supply adapted to supply AC power to a utility grid or stand-alone load, comprising:
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a DC power source; a bi-directional inverter that provides output power through a single power stage of DC-AC conversion; an output filtering grid interface that filters and supplies the output power from the bi-directional inverter into the utility grid; and a system controller for regulating the voltage of the DC power source at its maximum power voltage, controlling the waveform of the inverter output current to be sinusoidal, and reducing the output power when the utility grid voltage exceeds a predetermined threshold; the stand-by battery management control circuit controls a first and a second semiconductor battery switch to operate a stand-by battery in an isolation mode, a stand-by mode, a charging mode, an input voltage clamping mode, and a battery-dominated input mode; the stand-by battery is in the isolation mode when the first and second semiconductor battery switches are turned off; the stand-by battery is in the stand-by mode when the first semiconductor battery switch is turned on, the second semiconductor battery switch is turned off, and the inverter and output filtering grid interface provide transient power to the stand-alone load; the stand-by battery is in the charging mode when the first semiconductor battery switch is turned off and the second semiconductor battery switch is linearly regulated to maintain a healthy state of charge in the stand-by battery at low power, while the system controller regulates the DC power source output voltage at a level that is typically above the battery voltage; the stand-by battery is in the input voltage clamping mode when the first semiconductor battery switch is turned off, the second semiconductor switch is turned on continuously or linearly regulated with a pulse-width modulation control, and the inverter and output filtering grid interface are shut down, to restore a healthy state of charge to the stand-by battery without power transfer to the inverter; and the stand-by battery is in the battery-dominated input mode, when the first semiconductor battery switch is turned on and the second semiconductor switch is turned on continuously or linearly regulated with a pulse-width modulation control, for providing power transfer either to the stand-alone load when there is no power available from the DC power source, or for fast battery charging while the inverter is shut down; wherein the output power is controlled to track the maximum-power voltage of the DC power source and to have an output sinusoidal AC current that is controlled to be in phase with or optimally phase-shifted with the utility grid voltage when the DC power source is active and the stand-by battery management control circuit operates in any of the following modes;
the battery-charging mode, the battery stand-by mode, the battery isolation mode;wherein the output power is controlled to have a regulated AC output voltage across the stand-alone load when the DC power source is inactive and the stand-by battery management control circuit operates in a battery-dominated input mode; wherein the output power is cut off from both the utility grid and the stand-alone load when the stand-by battery management control circuit operates in an input-voltage clamping mode for maintaining the stand-by battery; wherein the bi-directional inverter comprises a cascade connection of an input bulk capacitor for sufficient energy storage to limit voltage ripple across the DC power source to a predetermined level, a line-filter for filtering the inverter input current to suppress the conducted and radiated switching noise produced by the inverter, and the bi-directional inverter power stage; and wherein the output filtering grid interface comprises an output filter, a fuse, and an output relay switching network for transferring power to either the utility grid or the stand-alone load.
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Specification