THE RELATIONSHIP BETWEEN THE INPUT CURRENT HARMONIC DISTORTION OF ASYNCHRONOUS MOTOR AND THE SWITCHING FREQUENCY IN PHOTOVOLTAIC POWER SYSTEM

Abstract

This paper deals with the design, modelling, analysis and simulation input current harmonics distortion of induction motor depending on switching frequency (fsw) in off-grid photovoltaic (PV) power system. The proposed solar system is a combination of a boost DC–DC boost converter, DCAC solar inverter;three-phase squirrel cage induction motor.Harmonic currents generated by power electronics based devices, and cause serious power quality problems in off- grid PV systems. Harmonics are being increased day by day in off-grid PV power systems. As a result, heat losses, power bills, and reduction in the efficiency occur in the system. Harmonic components should be measured and calculated correctly in order to solve the energy quality problems.The relationship between carrier frequency of PWM and total harmonic distortion for current (THDI) are examined in this article.The analytical expression between fsw and THDI of induction motor are obtained by using the curve fitting method. It is observed that THDI value decreases as value of fsw increases. The design, modelling and simulation of this topology are performed using Matlab/Simulink program for range of 200 Hz to 51 kHz switching frequency.This shows the satisfactory performance of harmonic distortion mitigation higher than 0, 70 kHz switching frequency of PWM. It is observed that the PWM carrier frequency is inversely proportional changes with load current total harmonic distortion. Inverse proportionality constant is found by curve fitting method.