An Improved SVM Strategy to Reduce DC Current Ripple for AC-DC Matrix Converter

The AC-DC matrix converter can facilitate the bidirectional interconnection between the utility grid and a relatively low voltage DC source/loads. To fulfill the grid codes and DC source/loads requirements, AC-DC matrix converters shall produce low ripples in DC current and low THD in AC current, which can be a challenge due to the absence of DC-link capacitor in AC-DC matrix converter. To improve the AC and DC current quality, this paper proposes a new 9-segment SVM, which optimizes the duty cycle of zero vector. Compared with the conventional 9-segment SVM strategy, lower THD of AC current and smaller DC current ripple can be achieved in the improved SVM strategy under any voltage condition with arbitrary power factor. To address the commutation problems, which is an important challenge to safely operate AC-DC matrix converters, a two-step voltage based commutation strategy is applied to reduce commutation time. Experimental results are provided to verify the effectiveness of the improved SVM strategy.