Reduction of converter rating for new induction generator system by 3rd harmonic injection

The wind power generation system connected to DC line has been investigated recently. We have proposed new converter exciting induction generator system for dc output to reduce the system cost. This paper shows that the rating of the converter can be reduced by using the 3rd harmonic injection control. 3rd harmonic injection control can increase the ac output voltage with same dc voltage. Both experimental and simulation results are shown. The experimental results show the reduction of dc voltage does not affect the output voltage and current of VSC. Therefore the reduction of voltage rating of the switching device of VSC is possible. The simulation results confirm the same performance with the reduced dc voltage. The simulation results show that the 3rd harmonic injection can allow the reduction of the VSC rating about 13%. It is also shown that the 3rd harmonic component of the current from the VSC is suppressed. This also reduced the peak current value about 16%. These effects can reduce the total VSC rating up to 72% of that without 3rd harmonic injection.