High-frequency interleaved three-phase inverter with novel single reference six pulse modulation (SRSPM) technique

This paper presents a hybrid modulation technique consisting of singe-reference six-pulse-modulation (SRSPM) for front-end dc/dc converter and 33% modulation for three-phase inverter. Employing proposed novel SRSPM by front-end dc/dc converter, high frequency (HF) pulsating dc voltage waveform is produced, which is equivalent to six-pulse output at 6× line frequency (rectified 6-pulse output of balanced three-phase ac waveforms) once averaged. It reduces the control complexity owing to single-reference three-phase modulation as compared to conventional three-reference three-phase SPWM. In addition, it relives the need of dc link capacitor reducing the cost and volume. Eliminating dc link capacitor helps in retaining the modulated information at the input of three-phase inverter. It needs only 33% (1/3^rd) modulation of the inverter devices to generate balanced three-phase voltage waveforms resulting in significant saving in (at least 66%) switching losses of inverter semiconductor devices. At any instant of line cycle, only two switches are required to switch at HF and remaining switches retains their unique state of either ON or OFF. Besides, inverter devices are not commutated when current through them is at its peak value. Drop in switching loss accounts to be around 86.6% in comparison with a standard voltage source inverter (VSI) employing standard three-phase sine pulse width modulation (SPWM). This paper explains operation and analysis of the HF two-stage inverter modulated by proposed novel modulation scheme. Analysis has been verified by simulation results using PSIM9.0.4. Experimental results demonstrate effectiveness of the proposed modulation.