| Summary: | 碩士 === 國立中央大學 === 電機工程學系 === 104 === High penetration level of the photovoltaic (PV) inverters in low voltage (LV) distribution grid will impact the stability and reliability of the grid. The main objective of the control strategy of the grid-connected inverter is to maintain or improve the grid stability, reliability and power quality. Therefore, in this study, a novel active and reactive power control strategy of a single-stage three-phase grid-connected photovoltaic (PV) system is proposed to mitigate the voltage variation at the point of common coupling (PCC). The single-stage three-phase grid-connected PV system introduces a current-controlled voltage-source inverter (CCVSI) to achieve the maximum power point tracking (MPPT) control of the PV panel and the function of power control. Moreover, a modified variable step-size incremental conductance (VSSIC) method is proposed to improve the tracking speed and accuracy of the MPPT control of the PV panel. Furthermore, the single-stage three-phase grid-connected PV system will inject or absorb the reactive power into or from the grid to mitigate the voltage variation at the PCC according to the grid codes. In the meantime, an economics optimization method is proposed to determine the control values of the active and reactive power with guaranteeing the output power of the three-phase inverter within the rating of itself. Finally, some experimental tests are realized to validate the effectiveness of the proposed control strategy.
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