Research On Series Z-Source Grid-connected Inverter With The Capability Of Reactive Compensation

The Series Z-Source inverter overcomes the disadvantages of the Voltage-Source inverter and the traditional Z-Source inverter. The boost/buck function which is traditionally reached only by two-stage topology can be reached, so the Series Z-Source inverter has a broad prospect in the field of new energy generation whose input voltage range is wide.The operation principle of the Series Z-Source inverter is introduced first. The Z-Source Network is utilized to realize the function of boost by inserting the shoot-through state. Then the existing SVPWM strategies for the Series Z-Source inverter are summarized and an improved modulation strategy is proposed. It can reduce the ripple of Z-Source inductor current and improve the efficiency. The circuit parameters are designed when this improved modulation strategy is used.Two control methods are introduced for the special state that the DC-link voltage is not a constant. They both can control the DC-link peak voltage as a constant which is helpful for designing the adjustment of the inverter part. The indirect control method is employed in this paper. The conception of instantaneous reactive power is introduced and used to detect the reactive current of load. The grid current is decoupled, so grid-connected generation and reactive power compensation are realized. By simulation, the indirect control method of the DC-link peak voltage, the detection of reactive current and grid current decoupling control are verified.At last, the control circuit and power circuit are designed, and a 3kVA experimental prototype is developed. The operational principle, the improved modulation strategy, the indirect control method of the DC-link peak voltage, the reactive current detection and grid current decoupling control are verified by experiment based on this prototype.