The principle techniques of current harmonics reduction and power factor improvement for power plants and the utilities: A review

Abstract

The applications of nonlinear loads are increasing worldwide, most of them are consisting power electronics devices. These nonlinear loads have made the power quality problems, a big challenge than ever before. An effective control of power quality parameters is highly dependent on their accurate and timely monitored system. Harmonics affects accurate estimation and effective control of power quality problems. In this paper, several methods of power system harmonics elimination are critically reviewed and classified based on the type of analysis tool and applications. Various estimation techniques are discussed in brief; comparison of available approaches are deeply examined and presented with the simulation models. The major issues and challenges in harmonics elimination are highlighted. The need to improve power quality in AC-to-DC converters has become the most important issue at present. Passive filters are not a solution to this as the harmonics are very high. So power electronics equipment has been used. A number of control strategies based on PWM method have emerged which cause a reduction in the harmonics and also achieves sinusoidal input current, unity power factor and high dynamic response. Some of the most important PWM control schemes include hysteresis current control (HCC)(1.3), Sinusoidal pulse width modulation (SPWM)(1.2), indirect current control (IDC)(2), space vector modulation (SVM)(3). The principle of operation and implementation of each scheme is discussed in detail and the advantages and disadvantages of each scheme are stated. A closed loop control system has been designed for each control strategy and the converters are simulated using the MATLAB/SIMULINK program. The performance of the converter under each control strategy is evaluated. The next phase is to calculate various parameters of the converter like DC output voltage, THD of output voltage, THD of input current, Input current distortion factor, input power factor, input displacement factor, input harmonic factor, voltage ripple factor have been calculated. All the strategies are then compared on the basis of these parameters and graphs have been plotted to make a comparative analysis of the schemes studied.