PWM Control Scheme for Quasi-Switched-Boost Inverter to Improve Modulation Index

The typical two stage power inverters, a boost DC – DC converter is utilized to make a constant DC bus voltage. Then a DC – AC inverter (H- Bridge) is used to invert the DC voltage to AC voltage but in this type both of the power switches in the leg of the H – bridge cannot be turned on at the same time because it makes a short circuit and thus may damage the device. Shoot-through protection is a way used to prevent and solve this problem by controlling the shoot through state in a single phase stage quasi-switched boost inverter (qSBI). However, it has different methods, the most common is the simple boost control (SBC). This thesis presents a new pulse width modulation (PWM) control scheme to improve the modulation index for the qSBI. In this thesis, a circuit is designed with 400W and 110V and 50 HZ output. The related circuits and the operating principles were analyzed using Matlab/Simulink. The analysis simulation results proved that the control scheme can enlarge the modulation index, reduce the voltage stress on the capacitor, diode and switches, as well as reduce the frequency of the inductor current, ripples of the capacitor voltage, lowering the shoot through current. Keywords: Pulse-Width Modulation (PWM), quasi-Z-Source Inverter (qZSI), quasi-Switched-Boost Inverter (qSBI), shoot-through, Simple Boost Control (SBC).