Research on design for the grid connection converter of AC PEL

The AC power source can be tested by the PEL (Power Electronic Load) expediently and economically. The GCC(Grid-Connection Converter) of the PEL should send back the recycling energy to the utility grid with high power factor and low harmonics components. Considering that the single phase PEL can be widely used to test the single phase or three phase power source, the single phase PEL is analyzed in the paper. The paper gives the electrical model and the control scheme based on the GCC´s circuits, and analyzes the harmonic components based on the structure and the function of the PEL. The effects of the notch filter, low-pass filter and mean filter are compared, and the mean filter has been chosen to filter the harmonics components mixed with the dc voltage, for its perfect steady-state characteristics. Large inertia links such as DC capacitor with large capacity and means filter deteriorate the dynamic characteristics, a small signal model based on active power balance is constructed, and feedforward control strategy is applied to ensure the whole system with perfect dynamic response when the input voltage, input current and grid voltage flicker fluctuate. The improved repetitive controller is employed to ensure the inner current loop with zero-errors track characters and hold the GCC with near unity power factor. The experimental and simulation results show that the analysis in the paper is right and the new control scheme is effective. The conclusion can be applied in the control strategy of GCCs, which are used in the distributed power supply system such as Photovoltaic power generations.