Reduced Part Count Multiplexed Five-Level Inverters: Effect of Varied Modulation Index

This paper presents two simple and cost-effective minimum device count three-phase five-level voltage source inverters based on hybrid clamping principle. The proposed multiplexed five-level inverters (M-FLIs) construct five-level output voltage using two different clamping approaches and only 16 active switches, as opposed to 24 switches in a conventional five-level inverter. Furthermore, compared to other five-level inverters, MPFLIs have fewer available switching states and form discrete space vector diagrams. A new modulation scheme based on virtual vectors is developed to compensate for the unavailable switching states. Each inverter can be operated at a suitable modulation index, where the performance is identical to that of a conventional five-level inverter, with the proper selection of DC link voltage. An auxiliary circuit is connected to the inverter's input side to balance the dc-link capacitor voltages like other five-level inverters. The proposed M-FLIs may find applications in electrical vehicle drivetrain, fast charging infrastructure and renewable energy grid integration etc. The paper investigates and compares the performance of the two proposed inverters for variation in the modulation index using simulation results.