Analysis and Design of a C-type Filter for a Wind or Solar Power Plant

The quality of the physical output must comply with local laws before a new wind or solar energy plant is connected to the grid. New harmonics and natural oscillation frequencies can be produced in a power system when a wind or solar power plant is added, which can result in a decrease in the quality of the power or the stability of the system. This study uses a passive filter to eliminate any new harmonics and natural oscillation frequencies. These values of new harmonics and natural oscillation frequencies are related to all-element parameters in a power system as the electrical network, the controllers and the machines. The new harmonic and natural oscillation frequencies are respectively identified using FFT in Matlab/Simulink and a Small Signal Analysis Tool. A passive filter is added to the PCC point. This study considers various AC filters which are initially used to remove harmonic resonance, in order to reduce or remove new harmonic or natural oscillation frequencies. A test system uses a modified section of a Taiwan power system. The eigenvalues and the total harmonic distortion (THD) percentage are used to compare the performance before and after the filter is added. The simulation results show that a C-type filter reduces harmonics and eliminates the natural oscillation frequency, which reduce the THD and increases the stability of the power system.