This study presents a grid-tied photovoltaic (PV) system based on the series Z-source inverter. The grid-tied current control strategy, the dc-link voltage control, as well as the maximum power point tracking scheme is realised in the single-stage system. The current control strategy is performed based on dq rotating frame. Indirect dc-link control is adopted to achieve constant peak dc-link voltage and thus can simplify the controller design in inversion stage. The overall control strategy is given and analysed in detail. Simulation and experimental results demonstrate that the proposed system can be applied in PV system with a wide input voltage range, which verify the correctness and validity of the analysis.
This paper proposes a new direct peak dc-link voltage control strategy of Z-source inverters. For Z-source inverters, the peak dc-link voltage is the actual voltage fed to the inversion stage. Controlling the peak dc-link voltage at the constant level can effectively decrease the voltage stress and simplify the design process of the inversion stage. A direct peak dc-link voltage detection method is developed with a simple sampling circuit, and then controlled directly. Therefore, the constant peak dc-link voltage can be achieved in different input and load conditions. The peak ac output is calculated in real-time by sampling the ac phase voltage, and it is controlled to the desired value without steady-state error. With the proposed direct peak dc-link voltage control and peak ac output control, both the peak dc-link voltage and ac output is controlled to a desired level under different input and load condition. Experimental results are presented to demonstrate the feasibility of the proposed control strategy.
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