DSOGI Based Performance Evaluation of D-STATCOM for Load Harmonic Compensation in Three-Phase Three-wire Polluted Utility System

摘要

DSTATCOM is one of the compensating custom power device available to solve power quality issues in the electrical power system. Basically, it is shunt connected bidirectional converter device, where accurate control of DSTATCOM depends on accuracy of reference signal generation. This reference signal can be obtained through either by Instantaneous Reactive Power (IRP) theory or Synchronous Reference Frame (SRF) theory. In case of SRF theory based control algorithm, it is essential to obtain phase-angle θ for transforming signal from two-phase to three-phase system. Hence, it is must to have proper phase-angle (fundamental frequency) information to generate accurate reference signals. This fundamental frequency information can be obtained by time domain (TD) or frequency domain (FD) techniques. However, the studies proves that the time-domain (TD) approach based on phase-locked loop (PLL)/frequency-locked loop (FLL) is accurate and fast to estimate the phase-angle information from the grid signal which is very important parameter for DSTATCOM to operate in synchronism with the grid. Amongst the various PLL, the SRF-PLL detects accurate fundamental frequency (phase angle) when the supply is balanced but during unbalanced supply condition it gives the oscillatory response in estimated frequency. Ultimately, it affects to the reference signal generation which should be accurate for proper operation and control of DSTATCOM. Hence, this problem is resolved by estimating the phase angle information by another techniques based frequency-locked loop. In this paper, the 9 is accurately detected based on Dual Second Order Generalized Integrator FLL (DSOGI-FLL) and reference signal. The percentage of THD (total harmonic reduction) reduction in source current before and after compensation by D-STATCOM is compared under the various grid abnormal conditions using different method by the MATLAB simulink model here.