Line-to-line voltage based modulation scheme for single-phase reduced switch ac-dc-ac converters to achieve improved performance

Modulation methods can significantly influence the performance of the converter in steady state, which is therefore very important. With different objectives like the minimum current ripple, minimum power loss or maximum DC link voltage utilization, SVPWM or DPWM are normally applied. With the SVPWM or DPWM proposed in literatures, the generation of the references is phase voltage based. But the phase voltages actually cannot be controlled directly by the PWM converter, since they can be influenced by both of terminal voltages and the load network while the PWM converter can only control the former. It thus introduces complexity to the generation of the references, especially in unbalanced source or load condition. In this paper, a line-to-line voltage based PWM reference generation method is proposed. The proposed method is easy to be implemented to maximize the DC link voltage utilization, reduce current ripple, or improve the loss distribution. Analysis and experimental test are also given to verify the proposed method.