An Improved T-type Switched-Capacitor Based 3-level 3-Phase Inverter with Common Mode Voltage Elimination and Voltage Boosting Capability

Zero common mode voltage (ZCMV) space vector modulation (SVM) strategy applied to a three-phase multilevel inverter (MLI) eliminates the common mode voltage (CMV). However, the usage of ZCMV-SVM strategy reduces the number of levels in the output voltage and requires higher magnitude dc voltage source due to the reduced modulation depth of the employed PWM scheme. Moreover, the usage of a single dc-source in such systems may have issues with respect to capacitor voltage balancing. Taking into account all the above issues, a 3-level inverter solution is proposed in this manuscript. The complete details of the method used for developing the proposed solution using the ZCMV space vectors is also included in this paper. The proposed topology utilizes a unique combination of a T-type 3-level inverter and a switched-capacitor (SC) circuit to achieve ZCMV performance with a single dc-source of low magnitude at a reduced component count. Analysis of the CMV and terminal voltages along with the design of the SCs are presented in this paper. The proposed topology is compared with the existing topologies to prove its unique merits over the other 3LI solutions with ZCMV capability. All the claims are validated using simulation and experimental results.