| 摘要 |
Method of controlling a voltage controlled PWM (Pulse Width Modulated) frequency converter comprising a single phase rectifier bridge ( 10 ) connectable to a sinusoidal single phase supply, a DC intermediate circuit ( 11 ) and a controlled inverter bridge ( 12 ) for generating an AC output voltage with varying amplitude and frequency to a load, said inverter bridge ( 12 ) having PWM controlled semiconductor switches (V 11- V 16 ) and flywheel diodes (D 11- D 16 ) connected in inverse-parallel with the semiconductor switches, wherein the DC intermediate circuit ( 11 ) is provided with a DC capacitor unit, and wherein the frequency converter is controlled so that the supply line current (I<SUB>in</SUB>) is essentially sinusoidal and in phase with the supply line voltage (U<SUB>in</SUB>). The inverter bridge is controlled so that the curve of filtered average current (I<SUB>dc</SUB>) in the DC intermediate circuit follows essentially the curve of the rectified AC supply voltage (U<SUB>dc</SUB>), the rectifier bridge is ( 10 ) connected to the inverter bridge ( 12 ) directly without a DC capacitor unit acting as an intermediate energy storage, and the curve of the power fed to the load has essentially the form sin<SUP>2</SUP>(2pift) (f=line frequency t=time).
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