An Analytical Approach to Harmonic Analysis and Controller Design of a STATCOM

An analytical approach to harmonic analysis of a static synchronous compensator (STATCOM) based on Bessel functions of the first kind is described and a novel STATCOM controller with a fixed modulation index reference to minimize voltage and current harmonics is presented in this paper. Harmonic analysis of the STATCOM using the proposed analytical approach reveals that the total harmonic distortion of the STATCOM output voltage is minimal as the modulation index is fixed at unity at steady state. Then, a STATCOM controller with an adjustable modulation index during the transient period is designed by the pole assignment method to regulate ac system bus voltage in a very efficient manner. By comparing results obtained from the analytical approach, the computer simulations, and the experiments, it is concluded that the proposed analytical approach gives harmonic spectra which are very close to those from simulations and experiments. In addition, the step load change testings demonstrate the effectiveness of the proposed STATCOM controller in regulating ac bus voltage.