Switched Capacitor Based Cascaded Half-Bridge Multilevel Inverter with Voltage Boosting Feature

Abstract

Abstract: In many applications, cascading multilevel inverter (CMI) topologies are common. However, the biggest disadvantage of CMI is the need for many separate switches and DC sources. As a result, the CMI topology becomes more expensive, more complex, and larger, and its performance suffers. In the proposed SC-CHMI, only one DC source is used and the other DC sources are replaced by switched capacitor cells. Thanks to the self-balancing function, the capacitor charging process occurs naturally without the need for any auxiliary equipment. In the proposed SC-CHMI, the inrush current of the capacitor is attenuated using a load inductor or a front-end boost converter. To improve the performance of multi-level inverters, several types of techniques can be tested with existing multi-level inverters. Due to the modulation algorithm, modulation frequency, voltage drop on the switches and bus voltage modulation, the output voltage of the inverter has overall harmonic distortion, leading to overheating of the device and shortening the life of the device bag. In the proposed SC-CHMI, a level-shifted pulse width modulation technique is proposed to improve the output voltage quality and reduce the total harmonic distortion. This new control scheme is applicable to nine-level, eleven-level and fifteen-level SC-CHMI. The proposed topology can be used as a general-purpose inverter in renewable energy systems, due to its voltage gain characteristics, minimal number of switches, and single DC source. The effectiveness of the proposed inverter topology is confirmed by simulation results.