An Optimal PWM Technique for Dual-Output Nine-Switch Boost Inverters with Minimum Passive Component Count

Abstract

Nine-Switch inverter (NSI) has been recently introduced for independent control of dual ac motors. Although this topology reduces the number of active switches by 25% compared to conventional inverters, it has a main conceptual shortcoming due to voltage gain limitations. In NSI, the voltage gains of both outputs are relatively low, while their maximum achievable magnitudes depend on the phase angle between the two sets. In order to mitigate this problem, this article introduces a new dual output nine-switch boost inverter (NSBI) topology with a minimum number of passive elements. The detailed analysis of NSBI is presented, while the required modifications to conventional pulsewidth modulation (PWM) strategies of the NSI are explained to ensure an acceptable voltage boosting ratio while a high-quality voltage output is obtained. Among different PWM schemes, a modified discontinuous PWM scheme is found optimum with this proposed topology to minimize the voltage stress across switches and improve the input current and output voltage quality. The proposed topology is also validated under both common-frequency and different-frequency modes of operations. Moreover, a clear picture of the NSBI performance compared with other possible counterparts is introduced. The theoretical findings have been corroborated using simulation and experiments.