Abstract
This paper discusses the modeling of nonlinear electrical loads used in domestic and small scale industrial distribution systems. Harmonic analysis of the distribution system is essential to study the behavior of equipments connected in the non-sinusoidal system environment for designing and optimal location of filters. Simulation models are developed for various nonlinear loads based on practical waveforms of voltage and current obtained in the laboratory. Analysis of voltage and current harmonics is performed for these loads individually. These models are used for harmonic analysis of typical domestic and industrial loads. THD is used as the harmonic index to study the effect of these nonlinear loads at the utility. Validation of the load models is done by performing case study for an industrial supply system and comparing the THDs obtained from simulation using PSCAD/EMTDC package with the THD values obtained by measurement.
I. INTRODUCTION
This the objective of the electric utility to supply its customers with a sinusoidal voltage of fairly constant magnitude and frequency. The generators that produce the electric power generate a very close approximation to a sinusoidal signal. However, there are loads and devices on the system which have nonlinear characteristics and result in harmonic distortion of both the voltage and current signals. As more nonlinear loads are introduced within a facility, these waveforms get more distorted.
V.CONCLUSION
Harmonic analysis of power system is performed to study the system behavior under harmonics and take preventive action to improve the pf or minimize losses. This paper presented the simulation modeling of various nonlinear loads used for both domestic and industrial applications. Case study of harmonic analysis is performed using these models for Cartosat-2A distribution system at ISRO, Bangalore. THD is used as the harmonic index and harmonic spectrum is presented for each load and for the industrial distribution system. Simulation result of power factor improvement by the addition of capacitor bank is also presented. The simulation results of THD and pf are acceptable with the practical measurement values. These models can hence be employed for harmonic analysis of a practical system and to design a suitable filter to mitigate harmonics in the distribution system.
