Grid Synchronization of Photovoltaic System with Harmonics Mitigation Techniques for Power Quality Improvement

Abstract

This chapter proposes a modified composite observer-based instantaneous reactive power theory (IRPT) for grid-connected photovoltaic (PV) system to improve the power quality (PQ) of the power distribution system and grid risibility under weak grid voltage. The generated PV power feeds to the grid through voltage source inverters (VSIs). This grid-connected VSI is used for feeding the generated PV active power during day time and the same VSI acts as a shunt active power filter to mitigate various PQ problems during night-time when the PV generation is off. In the present scenario of the electrical power system network, it is having different kinds of loads such as high-frequency switching converters, AC arc-furnaces, healthcare equipment, telecommunication equipment, etc. These types of equipment create dominant even harmonics into the electric distribution system. Thus these dominant even harmonic currents create electromagnetic interferences (EMI) which will raise the temperature of power electronic devices of any converters and degrade their efficiency, create noise and vibration in the electrical machines, etc. A modified composite observer-based IRPT is designed to mitigate these types of harmonics from the system. The control strategy is compiling two things: one is the filtering of the fundamental frequency voltage signal and generating the reference currents for harmonic mitigation, and the second is to feed the PV active power to the grid with a better synchronizing technique. The modified composite observer is used to extract fundamental components of voltage from the distorted voltage without phase delay which is further used in the calculation of the reference source current by using IRPT. The IRPT is also working on the calculation of the active power of the PV array and feeds to the grid without grid synchronization problems. The proposed control technique is well designed for these types of critical loads which are modelled using MATLAB®/Simulink software and tested under various conditions of the load and supply voltage.