Hybrid Phase Locked Loop for controlling Centralized inverters in large solar Photovoltaic power plants

Abstract

This paper presents a hybrid Phased Locked Loop (PLL) algorithm for 500kW–1MW grid-connected Centralized inverters for large Photovoltaic (PV) power plants. Proposed Hybrid PLL with ZCD enables faster synchronization during inverter start-up and can be used in high power master-slave based centralized inverters which are being used in large PV power plant. Three phase PLL structures such as Synchronous Reference Frame (SRF), Double Decoupled SRF (DDSRF), Enhanced PLL (EPLL), Double Second Order General Integral (DSOGI) and DSOGI with Frequency Locked Loop (FLL) are discussed and a comparative analysis of these PLL techniques is done with proposed PLL technique. The proposed PLL technique is simulated in MATLAB/SIMULINK and digitally implemented in TMS320F2812 based Discrete Signal Controller (DSC). The performance of the proposed PLL technique is experimentally validated with unbalanced and distorted grid signals.