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.
