Mitigation of harmonics in power distribution systems using distribution static compensator

Abstract

The quality of electric power is of major concern for both electric utilities and the end users of electric power in the wake of widespread use of nonlinear loads. Nonlinear loads normally draw non-sinusoidal (also called harmonics) currents and voltages at the point of connection with the utility grid and distribute them throughout the system causing protective relays and switchgear malfunctions, communication interference, incorrect meter readings, overheating of conductors, insulation degradation, and power transformer failures. In this research, focus was given to the harmonics generated by nonlinear loads using synchronous reference frame theory-based distribution static compensator. A distribution system having a stiff power source, linear and nonlinear loads, has been modelled in MATLAB/Simulink version 2017a software environment. For the control system design, proportional integral controllers were used for both voltage and current controls. Voltage source inverter with sinusoidal pulse width modulation was also employed for generating the alternating current. The investigation of harmonics by way of simulations, was carried out using the fast fourier transform from the MATLAB software to evaluate the total harmonic distortion generated by the nonlinear load with and without DSTATCOM connected. The simulation results indicated that at steady state voltage values of Vdc of 489 V, 555 V and 575 V, the current THD stood at 5.71%, 6.89% and 6.26%, respectively after mitigation giving a minimum of 55.8% reduction of harmonics in the source current. The distribution static compensator stands to be recommended for current harmonics mitigation in low voltage distribution systems.