In this paper, a novel instantaneous control strategy for the AC control loop of voltage-type converter is proposed in which two switching vectors are selected sequentially in one sampling period. Vector selection is based on control error minimization theorem to bring both fast response and low ripple. Switching timing is determined in real time according to the THD(Total Harmonic Distortion) minimization theorem with instantaneous THD definition as a direct evaluation function. With this algorithm, instantaneous control can be realized in almost constant switching frequency. For DC output voltage control, voltage square feedback with load power compensated algorithm is introduced to obtain global stability with fixed gain. Experimental investigation confirmed the validity of proposed control algorithms.
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