Harmonics elimination PWM based direct control for 23-level multilevel distribution STATCOM using differential evolution algorithm.

This work describes the application of a soft computing technique—known as the differential evolution (DE) to implement the harmonics elimination pulse-width modulation (HEPWM) for the direct control of distribution static synchronous compensator (D-STATCOM). The main contribution of the work is the application of DE to solve eleven HEPWM switching angles to synthesize a 23-level cascaded multilevel voltage source inverter (MVSI). The key feature of this algorithm is the wide modulation index ( M I ) range that can be produced (i.e. 5.40–8.15 p.u) with very small step size (0.01), while maintaining the total harmonic distortion (THD) of the MVSI output voltage below 5%. Furthermore, the utilization of high levels MVSI allows for the output voltage of the D-STATCOM to be sufficiently high, thus avoiding the use of step-up transformer. The correctness of the computed HEPWM angles is validated using single phase 23-level cascaded MVSI experimental rig. Then, the proposed method is compared to the phase-shifted PWM (PS-PWM) using a ±6.5 MVAr/11 kV D-STATCOM modelled in MATLAB-Simulink. For the same switching frequency, the HEPWM switching results in a superior harmonics spectra and lower switching losses. Furthermore, if the switching frequency is fixed to a particular value, the size of the series coupling inductor can be reduced to at least half. Dynamically, the steady state value of the reactive current ( i Cq ) is reached in less than one mains cycle when a transition from the full inductive to full capacitive modes is imposed. [ABSTRACT FROM AUTHOR]