Three-level VSI based low switching frequency 10 MVA STATCOM in reactive power and harmonics compensation

This paper examines the reactive power and harmonics compensation performance of a low switching frequency three-level voltage-source inverter based 10 MVA STATCOM. The intention is to mitigate supply current harmonics up to the 13^th order using a switching frequency between 600-1200 Hz. However, due to the low switching frequency the STATCOM response time is not adequate for harmonics compensation because PWM modulation adds a notable delay to the current control loop. Four different harmonic detection methods equipped with control delay compensation feature are examined to improve the STATCOM performance. The STATCOM operation is studied by means of Simulink/Simplorer simulations in steady-state load conditions, during step load changes and in electric arc furnace compensation. The results show that the STATCOM performance can be extended to harmonics mitigation under steady-state load conditions. Under non-periodic load conditions the accuracy of harmonic detection and delay compensation decreases and reduces the STATCOM performance.