Extremely Low Frequency PS-PWM Based Technique for Cascaded H-Bridge Converters With Grid Voltage Compensation Capability

Cascaded H-bridge (CHB) converters are good candidates for many industrial applications. Among the modulation techniques that can be applied to CHB converters, the phase-shifted pulse width modulation (PWM) method (PS-PWM) provides very good harmonic quality being the most popular modulation technique at the expense of presenting high switching losses. On the contrary block switching technique as well as selective harmonic elimination/mitigation techniques provides lower switching frequency and losses with a lower harmonic quality. Additionally, with these techniques the converter operation becomes stiff. In this work a modification of PS-PWM based on an extremely low frequency carrier is proposed with the objective of achieving both low switching losses and an acceptable harmonic quality, simultaneously. The main advantage of the proposed solution is the capability of adjusting the phase-shift angle among the carriers to compensate for harmonic grid voltage disturbance. Several experimental results have been reported to demonstrate the good performance of the proposed modulation technique.