An improved PWM control of quasi-switched-boost inverter with reduced ripple magnitude and increased ripple frequency input current

摘要

This paper presents an improved PWM control for a Quasi-Switched Boost Inverter (qSBI), in order to achieve continuous input current with reduced ripple magnitude and increased ripple frequency. This increase in ripple frequency is accomplished without increasing switching frequency of inverter and its switching losses. Compared to conventional PWMs, the Z-source inductor in qSBI can be of reduced size because of the increase in ripple frequency for a given inverter switching frequency. The voltage boost in qSBI is achieved by allowing a shoot through mode of operation which puts a restriction on the maximum inverter modulation index, thus increasing harmonics at its output. In contrast, the proposed PWM maintains the same boost ratio as that of conventional PWM, but with a higher modulation index and lower THD. This improved performance is realised by introducing a phase shift between the shoot through control signals and the boost control signals. The concept of the proposed PWM is conceived, presented and tested with a simulated qSB-inverter of 700W rating. The performance and the features of the proposed PWM are assessed considering three shoot through conditions and the test results analysed in terms of voltage boost, and harmonic profile, challenging the usual paradox in the conventional PWM.