Abstract: This present invention provides a bridge battery voltage equalizer to equalize the voltages of the serially connected battery strings, comprising at least one battery crossing over an energy-transferring circuit. A plurality of the energy-transferring circuits are interconnected in a bridge architecture. Each energy-transferring circuit having four nodes comprises a first semiconductor switch, a first diode, a second semiconductor switch, a second diode, and an inductor. One end of the first element switch is connected to a negative pole of the first diode thereto. A positive pole of the second diode is connected to one end of the second element switch thereto. The inductor is an energy storing element that crosses over between the negative pole of the first diode and the positive pole of the second diode.

Abstract: An islanding detection method is proposed to overcome the incapability of detecting islanding operations in accordance with prior arts. A distortion for causing a variation of an AC power system is performed, and an AC power system frequency and a voltage variation are detected as the bases for determining the occurrence of an islanding operation.

Abstract: A transformerless power conversion circuit is interconnected with an electric grid and converts an input DC power provided by a power generator into an AC power and feeding the AC power into the grid. The power conversion circuit includes a buck-boost converter converting the input DC power into two sets of DC power levels; and at least one half-bridge inverter converting the two sets of DC power levels into the AC power for feeding into the grid. The isolating transformer can be eliminated and the common ground problem for DC side and AC side is also solved. The power conversion circuit has significant improvement for device size, manufacture cost and conversion efficiency.

Abstract: This present invention provides a bridge battery voltage equalizer to equalize the voltages of the serially connected battery strings, comprising at least one battery crossing over an energy-transferring circuit. A plurality of the energy-transferring circuits are interconnected in a bridge architecture. Each energy-transferring circuit having four nodes comprises a first semiconductor switch, a first diode, a second semiconductor switch, a second diode, and an inductor. One end of the first element switch is connected to a negative pole of the first diode thereto. A positive pole of the second diode is connected to one end of the second element switch thereto. The inductor is an energy storing element that crosses over between the negative pole of the first diode and the positive pole of the second diode.

Abstract: A method and a system for detecting stand-alone operation of a distributed generating system having a generating source connected in shunt with an independent power distribution system via a first branch breaker are proposed. A voltage or a frequency signal on the independent power distribution system is read. The wavelet transformation is performed on the voltage or frequency signal to form a time versus high-frequency component window and a time versus low-frequency component window for conveniently detecting the perturbation in the time domain of the signal. Next, whether the absolute value of the high-frequency component is greater than a threshold value and whether the duration is longer than another threshold value are determined. If both answers are yes, a stand-alone operation occurs. An alarm signal is immediately generated and sent to the first branch breaker to release the connection between the generating source and the power distribution system.

Abstract: An islanding detection and protection method of a parallel-type power converter is proposed, which performs perturbation to a power system to detect the frequency of the system voltage and the variation of the magnitude of the negative-sequence voltage as the basis for deciding the occurrence of an islanding operation. When the system operates normally, the frequency or phase and magnitude of the system voltage and the magnitude of the negative-sequence voltage won't be affected by the perturbation. On the other hand, if an islanding operation occurs, this perturbation will cause an apparent drift of the frequency or phase and magnitude of the system voltage and the magnitude of the negative-sequence voltage. Through detection of this apparent drift, the perturbation can be amplified by means of positive feedback to quickly detect the islanding operation phenomenon and trigger the protection mechanism.

Abstract: An islanding detection and protection method of a parallel-type power converter is proposed, which performs perturbation to a power system to detect the frequency of the system voltage and the variation of the magnitude of the negative-sequence voltage as the basis for deciding the occurrence of an islanding operation. When the system operates normally, the frequency or phase and magnitude of the system voltage and the magnitude of the negative-sequence voltage won't be affected by the perturbation. On the other hand, if an islanding operation occurs, this perturbation will cause an apparent drift of the frequency or phase and magnitude of the system voltage and the magnitude of the negative-sequence voltage. Through detection of this apparent drift, the perturbation can be amplified by means of positive feedback to quickly detect the islanding operation phenomenon and trigger the protection mechanism.

Abstract: A transformerless power conversion circuit is interconnected with an electric grid and converts an input DC power provided by a power generator into an AC power and feeding the AC power into the grid. The power conversion circuit includes a buck-boost converter converting the input DC power into two sets of DC power levels; and at least one half-bridge inverter converting the two sets of DC power levels into the AC power for feeding into the grid. The isolating transformer can be eliminated and the common ground problem for DC side and AC side is also solved. The power conversion circuit has significant improvement for device size, manufacture cost and conversion efficiency.

Abstract: The present invention provides a hierarchical battery potential equalizing device to equalize the voltage of a plurality of serial batteries. The batteries are divided into a plurality of groups, one potential equalizer is provided for each group to make potential equalization among batteries, and at least one potential equalizer is provided for different groups to make potential equalization among groups. Wherein the potential equalizers have a hierarchical architecture, the first level of potential equalizers of the hierarchical architecture are respectively corresponding to one group to make potential equalization, and the other levels of potential equalizers make potential equalization among groups.

Abstract: An islanding detection method is proposed to overcome the incapability of detecting islanding operations in accordance with prior arts. A distortion for causing a variation of an AC power system is performed, and an AC power system frequency and a voltage variation are detected as the bases for determining the occurrence of an islanding operation.

Abstract: A method and a system for detecting stand-alone operation of a distributed generating system having a generating source connected in shunt with an independent power distribution system via a first branch breaker are proposed. A voltage or a frequency signal on the independent power distribution system is read. The wavelet transformation is performed on the voltage or frequency signal to form a time versus high-frequency component window and a time versus low-frequency component window for conveniently detecting the perturbation in the time domain of the signal. Next, whether the absolute value of the high-frequency component is greater than a threshold value and whether the duration is longer than another threshold value are determined. If both answers are yes, a stand-alone operation occurs. An alarm signal is immediately generated and sent to the first branch breaker to release the connection between the generating source and the power distribution system.

Abstract: A solar cell array control device has a plurality of solar cell modules, a bidirectional DC converter, at least a voltage sensor and a control unit. The bidirectional DC converter corresponds to and is electrically connected to the solar cell modules to connect these solar cell modules in series to form a solar cell array. The voltage sensor is electrically connected to the solar cell modules, and can generate an abnormal voltage when detecting that one of the solar cell modules is abnormal. The control unit is electrically connected to the voltage sensor and the bidirectional DC converter, and outputs a pulse width modulation signal by detecting the abnormal voltage to control the bidirectional DC converter for compensating the conversion current and thus enhancing the output power of this solar cell module.