A SVPWM Control Strategy for Capacitor Voltage Balancing of Flying Capacitor Based 4-Level NPC Inverter

Abstract

A Space Vector Pulse Width Modulation (SVPWM) control strategy is implemented for capacitor voltage balancing of Flying Capacitor (FC) based 4-level Neutral Point Clamped (NPC) inverter. This flying capacitor based 4-level NPC inverter is developed for medium voltage and high power applications. This system includes 6 power switching devices, 2 clamping diodes and 2 flying capacitors per leg. The flying capacitors ensure to operate inverter normally and all the switching devices share the voltage stresses in identical manner. Also it controls the voltage across each capacitor and maintained at Vdc/3 times of applied dc voltage. The proposed SVPWM method takes advantage of utilizing redundancy switching states to control and balance the voltage across the capacitor using nearest switching state vector selection method. Moreover, this system provides reduced total harmonic distortion (THD), and minimized voltage stress. The control technique is implemented without using any look-up tables or effective logic tables or trigonometric functions. The simulation and experimental results of this proposed verified are verified using Matlab-simulink and FPGA controller respectively.