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US 7,843,082 B2Granted
Islanding detection apparatus for a distributed generation power system and detection method therefor
AssigneeAblerex Electronics Co., Ltd.
InventorsHung-Liang Chou, Wen-Jung Chiang, Chin-Chang Wu, Ya-Tsung Feng
Life of this patent
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Abstract
An islanding detection apparatus for a distributed generation power system and a detection method therefor operates a power converter to act as a virtual capacitor or inductor at a frequency close to but unequal to that of a utility power system under abnormal condition of the utility power system. When power failure occurs in the utility power system, only the distributed generation power system supplies power to a load so that a load voltage has been changed in at least one of amplitude and frequency which can be immediately detected islanding phenomenon.
Claims12
An islanding detection method for a distributed generation power system, comprising the steps of:
- a utility power system connecting with the distributed generation power system, the distributed generation power system including a power converter to connect with the utility power system;
- and
- controlling the power converter of the distributed generation power system to adopt a current-mode control, to have an output current tracing a reference signal including a real-power control signal and a virtual-capacitor control signal, and to act as a virtual capacitor at a frequency close to but unequal to a fundamental frequency of the utility power system for detecting islanding phenomenon under abnormal conditions of the utility power system;
- wherein when power failure occurs in the utility power system, only the distributed generation power system supplies power to a load such that the virtual capacitor of the power converter is enabled, thereby causing a significant change of a load voltage in at least one of amplitudes and frequencies;
- wherein the step of controlling the power converter to adopt the current-mode control, to have the output current tracing the reference signal including the real-power control signal and the virtual-capacitor control signal, and to act as the virtual capacitor comprises:
- detecting the load voltage by a voltage detector;
- filtering the load voltage by a first band-pass-filter having a center frequency the same with a fundamental frequency of the utility power system, so that an output of the first band-pass-filter is a sine-wave signal with a frequency and a phase identical with a frequency and a phase of a voltage of the utility power system;
- multiplying the output of the first band-pass-filter by an amplitude signal in a multiplier to obtain the real-power control signal;
- subtracting the output of the first band-pass-filter from the load voltage detected by the voltage detector by a first subtracter and sending the result of the first subtracter to a second band-pass-filter having a center frequency higher than the fundamental frequency of the utility power system;
- sending an output of the second band-pass-filter to a differentiator to generate the virtual-capacitor control signal;
- adding the real-power control signal and the virtual-capacitor control signal by an adder to obtain the reference signal;
- detecting an output current of the power converter by a current detector;
- subtracting the output current of the power converter from the reference signal by a second subtracter and sending an output of the second subtracter to a current controller;
- and
- sending an output of the current controller to a driving circuit to generate driving signals for power electronic switches of the power converter.
12 more elements
An islanding detection method for a distributed generation power system, comprising the steps of:
- a utility power system connecting with the distributed generation power system, the distributed generation power system including a power converter to connect with the utility power system;
- and
- controlling the power converter of the distributed generation power system to adopt a current-mode control, to have an output current tracing a reference signal including a real-power control signal and a virtual-inductor control signal, and to act as a virtual inductor at a frequency close to but unequal to a fundamental frequency of the utility power system for detecting islanding phenomenon under abnormal conditions of the utility power system;
- wherein when power failure occurs in the utility power system, only the distributed generation power system supplies power to a load such that the virtual inductor of the power converter is enabled, thereby causing a significant change of a load voltage in at least one of amplitudes and frequencies;
- wherein the step of controlling the power converter to adopt the current-mode control, to have the output current tracing the reference signal including the real-power control signal and the virtual-inductor control signal, and to act as the virtual inductor comprises:
- detecting the load voltage by a voltage detector;
- filtering the load voltage by a first band-pass-filter having a center frequency the same with a fundamental frequency of the utility power system, so that an output of the first band-pass-filter is a sine-wave signal with a frequency and a phase identical with a frequency and a phase of a voltage of the utility power system;
- multiplying the output of the first band-pass-filter by an amplitude signal in a multiplier to obtain the real-power control signal;
- subtracting the output of the first band-pass-filter from the load voltage detected by the voltage detector by a first subtracter and sending the result of the first subtracter to a second band-pass-filter having a center frequency higher than the fundamental frequency of the utility power system;
- sending an output of the second band-pass-filter to an integrator to generate the virtual-inductor control signal;
- adding the real-power control signal and the virtual-inductor control signal by an adder to obtain the reference signal;
- detecting an output current of the power converter by a current detector;
- subtracting the output current of the power converter from the reference signal by a second subtracter and sending an output of the second subtracter to a current controller;
- and
- sending an output of the current controller to a driving circuit to generate driving signals for power electronic switches of the power converter.
12 more elements
Dependencies are inferred from the claim text.