SUPPRESSION OF THE DC COMPONENT IN GRID INJECTION CURRENT FOR PHOTOVOLTAIC GRID-TIED INVERTERS
This work deals with identifying the main causes of DC component appearance by analyzing the relationship between the DC component in grid injection current and the deviation existing in sampling value of AC voltage and AC current. Then the DC component is separated through a low-pass filter circuit. The DC component is eliminated by an appending closed-loop control. Simultaneously, a high pass filter (HPF) is introduced to filter sampling voltage value, which suppressed the deviation of the sampling voltage value. In addition, the phase delay existing in the current loop, which improves the power factor, will be compensated by the phase leading of the HPF. Eventually, the effectiveness of the proposed method is verified through the test of the total harmonic distortion (THD) index, the power factor, and the DC component index of the grid-injection current under different load conditions.
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