Analysis of harmonics issue in grid integration solar photovoltaic system and mitigation method

Abstract

Solar photovoltaics system is the most preferable green technology for energy saving especially in Malaysia and the demand of grid connected Photovoltaic system (PV) is increasing continuously to support the needs. Large penetration of harmonics that happened at the point of common coupling (PCC) will affect the overall efficiency and cause power quality issue at the downstream. Total harmonic distortion (THD) is the measurement of harmonic distortion that exist in power system. The acceptable level of THD as referring to the International Electrical and Electronics Engineers (IEEE), IEE 519-2014 has classified voltage harmonics (THDv) based on the voltage range and current harmonics (THDi) based on the range of short circuit current (Isc) over line current (IL). This report presents harmonics impact to power system due to the installation of solar photovoltaic system. The study involves few analysis techniques to identify the existence of harmonics in the existing power system before and after solar PV integration. Methodology that was approached involved desktop study, actual measurement using power quality analyzer and system modelling and simulation using ETAP software. Measurement was conducted at the PCC of low voltage hybrid PV system which is the integration of solar system with grid supply power system. In this report, the results of harmonics that was measured at PCC prior the integration of solar PV and after the integration of solar PV clearly shows significance difference where harmonics reading of THDi increased to 23.81% from 14.11%. Suitable mitigation method was proposed to control harmonics to below the standard for the purpose of energy optimization. The installation of passive harmonic filter in parallel with non-linear load was found capable to reduce harmonics readings. The capacity of passive harmonics filter was determined from reactance calculation. Based on the results from the improvement technique, it was proven that passive filter could reduce THDi from 23.81% to 7.43%, increased the current from 1206A to 2685A and increase voltage from 415V to 449V. The power factor of the power system has also increase from 0.7 to 0.99. High power factor means power system is run in high efficiency. Maintaining high power factor and efficiency is important to provide a solution for real-time cancellation of harmonic distortions. The implication of the improvement imposed to the system was benefits in terms of energy optimization by eliminate distortion and power quality issue.