Optimal low switching frequency pulse width modulation of current-fed three-level inverter for solar integration

In high power conversion, low device switching frequency operation is preferred in order to satisfy the thermal constraints of the semiconductor devices and also to improve efficiency. However, low device switching frequency operation leads to higher total harmonic distortion (THD) of the converter output currents. Synchronous optimal pulse-width modulation (SOP) technique is an emerging low device frequency modulation technique that maintains minimal THD on converter output currents. The state-of-the-art generalized SOP has only been applied to voltage source inverters so far. Hence, the aim of this paper is to propose a modified SOP technique for current source inverter (CSI). In addition, a simple conversion technique has been introduced in the modulation stage to incorporate additional switching constraints of CSI. The experimental results show effectiveness of the proposed modified SOP technique on CSI by achieving better total harmonic distortion for range of modulation indexes without compromising on device switching frequency.