Dynamic performance analysis of potential current control strategies for grid connected applications

Environmental concerns were raised due to the recent demand increase for energy which resulted in higher CO₂ emissions. Hence, it became essential to research a different energy source to meet the increasing demand. Since Photovoltaics (PV) were found to be a promising source, the governments started to support grid connected PV projects. However, grid connected PV systems cause many stability issues. Therefore, controlling methods must be implemented. Several control techniques have been proposed for grid connected applications in the last few decades. The controllers attempt to achieve stability, low harmonic content and fast dynamic response. However, tradeoffs are usually required. In order to understand the potential developments in this field, the paper will present three different current control strategies used in grid connected systems, compare them and recommend the usage of the most suitable. This was achieved by developing a MATLAB/Simulink model of a photovoltaic grid connected system in order to simulate case studies that tests Voltage Oriented Current Control (VOC), Direct Power Control (DPC), and PQ Synchronous Control (PQSC) topologies under different scenarios. The model configuration used ensures realistic simulation conditions in order to study the controllers thoroughly. Case studies are simulated in order to investigate the three controllers´ stability and dynamic response under variable irradiance, Single Line to Ground (SLG) fault and three phase fault. Such case studies results can act as benchmarks that can be used by other researchers to compare their controller´s performance against a standard system and check for improvements.