Combination of input/output control using matrix converter for islanded operation for AC generator

Abstract

This paper proposes a control method of a matrix converter in a micro grid system to obtain stable islanded operation. The islanded operation using a matrix converter needs a voltage feedback control to assume the matrix converter as a constant voltage power supply for the load. On the other hand, the islanded operation also requires a generator current control with a feedback to determine provided power. However, when the matrix converter is applied two feedback controls on the generator side and the load side, the interference between both controls occurs and the matrix converter becomes unstable. This instability occurs due to difference of instantaneous active powers between the generator side and the load side; therefore, the active power is determined by the voltage source converter only. The active current which is needed to control the filter capacitor voltage should be converted to the generator current command as an active power command. Thereby, the proposed control method avoids the interference, and achieves a stable islanded operation. In addition, the proposed control also offers a constant three-phase voltage to the load even if the load power is light because of a compensation of a reactive current into the filter capacitor. As a result, the proposed control method achieves stable islanded operation and unity displacement power factor of the load side. The load current THD (Total harmonic distortion) is 1.4%, and the filter capacitor voltage THD is 1.5%. In the experiment, the load voltage is a sinusoidal waveform of 200 V. In addition, the load voltage THD is 4.56%. Therefore, it is confirmed that the proposed control method achieves stable operation without the interference. This paper confirms validity of the proposed control in the islanded operation by simulation and fundamental experiment.