The Effects of Excitation Control Systems on Parallel Operation of DGs with the Main Grid

This paper presents actual cases of steady reactive power oscillation of Distributed Generations (DGs) during parallel operation with the main grid. The cause of the problem was found to be the adverse effects of excitation system voltage regulation. It is shown, through preliminary investigation and detailed simulation studies, that how the excitation control system can be modified to overcome this problem. On-site test results verify the analysis results and effectiveness of the remedial actions.  Finally, general practical recommendations are offered for excitation control of synchronous generator-based DG, such that it performs properly, both in grid connected and islanding conditions.