Interleaved Zero-CMV Zero-DMV PWM for Parallel Operation of Two Three-level Converters

Interleaved operation of parallel converters are preferred for better grid current quality but it contribute to high frequency circulating current flow. Space vector modulation (SVM) methods are developed for minimising circulating currents and other parameters while guaranteeing interleaved operation. This work proposes a four-vector interleaved SVM for two three-level (3l) flying capacitor (FC) converters in parallel for eliminating both common-mode voltage (CMV) and differential mode voltage (DMV). The zero CMV vectors of a single 3l-FC alone are utilised for reference generation. Zero DMV also eliminates the zero-sequence circulating current flow. The switching state redundancy of ‘0 ’state of 3l-FC is utilised for voltage balancing in the flying capacitors. With the interleaved SVM, the parallel operation of two 3l converters is equivalent to a single five-level converter. Simulation analysis using MATLAB/Simulink is provided to substantiate the efficacy of the proposed interleaved four-vector SVM.