Power conversion systems and methods are provided for ride through of abnormal grid conditions or disturbances, in which a system rectifier is operated in a first mode to regulate a DC voltage of an intermediate DC circuit, an inverter is operated in the first mode to convert DC power from the intermediate DC circuit to provide AC output power to drive a load. In response to detecting an abnormal grid condition, the system changes to a second mode in which the rectifier is turned off and the inverter regulates the DC voltage of the intermediate DC circuit using power from the load.

A converter circuit converts AC electric power into DC power. An inverter circuit converts the DC power into AC power. A capacitor is connected in parallel to each of the converter circuit and the inverter circuit between these circuits. The capacitor allows variation of an output voltage from the converter circuit, and absorbs variation of an output voltage from the inverter circuit due to a switching operation. An overvoltage protection circuit includes a resistor and a semiconductor element connected in series to each other. The overvoltage protection circuit is connected in parallel to the capacitor to protect the inverter circuit from an overvoltage. First and second control units respectively control the inverter circuit and the overvoltage protection circuit.

A converter circuit converts AC electric power into DC power. An inverter circuit converts the DC power into AC power. A capacitor is connected in parallel to each of the converter circuit and the inverter circuit between these circuits. The capacitor allows variation of an output voltage from the converter circuit, and absorbs variation of an output voltage from the inverter circuit due to a switching operation. An overvoltage protection circuit includes a resistor and a semiconductor element connected in series to each other. The overvoltage protection circuit is connected in parallel to the capacitor to protect the inverter circuit from an overvoltage. First and second control units respectively control the inverter circuit and the overvoltage protection circuit.

The present invention relates a method for optimizing electrical current in a DC link busbar of a power converter system, wherein the power converter system comprises, a first inverter bridge, connected to the DC link busbar at a first end, the first inverter bridge having a first pulse width modulation signal, and a second inverter bridge, connected to the DC link busbar at a second end, the second inverter bridge having a second pulse width modulation signal, measuring a current flowing in the DC link busbar from the first end to the second end, optimizing the current flowing in the DC link busbar by delaying the first pulse width modulation signal and the second pulse width modulation signal from each other with a carrier delay, the invention also relates to power converter and wind turbine with optimizing electrical current in a DC link busbar.

A power conversion apparatus includes a rectification unit that rectifies a first alternating-current power supplied from a commercial power supply; a capacitor connected to output terminals of the rectification unit; an inverter that is connected across the capacitor, converts power output from the rectification unit and the capacitor into a second alternating-current power and, outputs the second alternating-current power to a load including a motor; and a control unit that performs operation control on the inverter to cause the second alternating-current power that includes a pulsation based on a pulsation of power that flows into the capacitor from the rectification unit to be output from the inverter to the load, to restrain a current that flows into the capacitor.

A power conversion apparatus includes a rectification unit that rectifies a first alternating-current power supplied from a commercial power supply; a capacitor connected to output terminals of the rectification unit; an inverter that is connected across the capacitor, converts power output from the rectification unit and the capacitor into a second alternating-current power and, outputs the second alternating-current power to a load including a motor; and a control unit that performs operation control on the inverter to cause the second alternating-current power that includes a pulsation based on a pulsation of power that flows into the capacitor from the rectification unit to be output from the inverter to the load, to restrain a current that flows into the capacitor.

The present disclosure includes a precision voltage and frequency converter, comprising of a power factor correction circuit configured to correct the conduction angle of input AC current, in phase with AC voltage source, a reserve DC filter and energy storage unit, a multi-phase unfolding bridge circuit configured to receive a rectified, isolated, and filtered DC voltage derived from the input AC, a voltage and current feedback pulse-width modulator circuit and compensation circuit configured to modify a signal from the multi-phase unfolding bridge circuit, an isolation transformer having a first side and a second side, wherein the isolation transformer is configured to receive an unfolded half-sine signal generated by the multi-phase unfolding bridge on the first side, the second side of the transformer is regulated via an isolated feedback voltage control circuit and compensation circuit to generate on the second side a first output precision voltage and frequency converted AC signal.

The present disclosure includes a precision voltage and frequency converter, comprising of a power factor correction circuit configured to correct the conduction angle of input AC current, in phase with AC voltage source, a reserve DC filter and energy storage unit, a multi-phase unfolding bridge circuit configured to receive a rectified, isolated, and filtered DC voltage derived from the input AC, a voltage and current feedback pulse-width modulator circuit and compensation circuit configured to modify a signal from the multi-phase unfolding bridge circuit, an isolation transformer having a first side and a second side, wherein the isolation transformer is configured to receive an unfolded half-sine signal generated by the multi-phase unfolding bridge on the first side, the second side of the transformer is regulated via an isolated feedback voltage control circuit and compensation circuit to generate on the second side a first output precision voltage and frequency converted AC signal.