Modelling of STATCOM and its Control for Power System Stability Improvements

Abstract

Power system stability study has been one of the major concerns of the alternating current (AC) power system operation over the past decades. STATCOMs have been widely applied for voltage stability enhancement due to its fast response to system disturbances. Conventional Static Synchronous Compensators (STATCOMs) used for voltage regulation are capable of compensating reactive power only. Thus, the applications of STATCOM such as frequency regulation are limited by the lack of real power compensation ability. For a power system with relatively low inertia, real power compensation becomes more important. STATCOMs equipped with DC sources with large real power energy can significantly improve the AC power system dynamics. This thesis focuses on the frequency stability and voltage dynamic stability improvements provided by a STATCOM with ability of real power compensation. In this thesis, a STATOM with controllability over AC power system voltage and frequency has been modelled together with an AC power system which comprises of one generator, a transmission line and loads. The model has been simplified and some ideal assumptions have been made in order to analyse the performance without undesired effects caused by system dynamics or unwanted components behaviour. The STATOM external real and reactive power control in dq frame and internal Space Vector Pulse Width Modulation (SVPWM) control are designed and presented. Power system performances during disturbances with and without STATCOM support have been simulated. Simulation results show that both voltage and frequency can be regulated to a certain degree within the STATCOM capacity and the system stability has been improved with the STATCOM support. Comparison between Sinusoidal Pulse Width Modulation (SPWM) and SVPWM in terms of total harmonic distortion in the STATCOM current during real power compensation has been discussed as well.