Power converter for AC load

A power converter for an AC induction type load comprising:

• detector means for detecting whether or not the frequency of an AC output from the power converter falls within a predetermined frequency range, and for generating a detection signal when the frequency of said AC output falls within a predetermined frequency range;
• current control means coupled to said detector means, for determining an AC output current of the power converter in accordance with a given current reference, when said detection signal is generated, said AC output current being supplied to the AC load;
• a voltage controlled type main circuit including,
• rectifier means for converting an AC input from an AC power source, in accordance with said given current reference, and providing a DC current to a DC circuit of the power converter;
• filter means for filtering ripples in said DC output of said rectifier means;
• inverter means for re-converting the filtered DC output from said filter means, to generate an AC output voltage to be applied to said AC load;
• voltage control means coupled to said detector means and said inverter means, for regulating the DC output voltage in accordance with a given voltage reference when the detection signal disappears;
• a capacitor coupled in parallel to said DC circuit for filtering off ripples in said DC current;
• release means coupled to said capacitor and said detector means, for releasing said capacitor from said DC circuit when said detection signal is generated;
• and
• absorbing means coupled to said DC circuit, for absorbing reactive energy from said AC load when said release means releases said capacitor from said DC circuit.