Single-stage grid-connected photovoltaic (PV) systems have advantages such as simple topology, high efficiency, etc. However, since all the control objectives such as the maximum power point tracking (MPPT), synchronization with the utility voltage, and harmonics reduction for output current need to be considered simultaneously, the complexity of the control scheme is much increased. This paper presents the implementation of a single-stage three-phase grid-connected PV system. In addition to realize the aforementioned control objectives, the proposed control can also remarkably improve the stability of the MPPT method with a modified incremental conductance MPPT method. The reactive power compensation for local load is also realized, so as to alleviate grid burden. A DSP is employed to implement the proposed MPPT controller and reactive power compensation unit. Simulation and experimental results show the high stability and high efficiency of this single-stage three-phase grid-connected PV system. Index Terms-Grid-connected inverters, maximum power point tracking (MPPT), photovoltaic (PV), solar energy.

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This paper proposes an adaptive low dc-link voltage controlled LC coupling hybrid active power filter (LC-HAPF) with a neutral inductor, which can compensate both dynamic reactive power and current harmonics in the three-phase four-wire distribution power systems. Due to its adaptive low dc-link voltage characteristic, it can obtain the least switching loss and switching noise and the best compensating performances, compared with the conventional fixed and newly adaptive dc voltage controlled LC-HAPFs. The design procedures of the dc-link voltage controller are discussed, so that the proportional and integral (PI) gains can be designed accordingly. And the general design procedures for the adaptive dc voltage controlled LC-HAPF with neutral inductor are also given. The validity and effectiveness of the adaptive dc-link voltage controlled LC-HAPF with neutral inductor are confirmed by experimental results obtained from a 220V, 10kVA laboratory prototype compared with the conventional fixed and adaptive dc-link voltage controlled LC-HAPFs without neutral inductor.Index Terms-Active power filters, current harmonics, dc-link voltage control, hybrid active power filters, passive power filters, reactive power. 1