Research And Design On Associate Z-source Grid-connected Inverter

In a distributed power generation system,PV grid connected solar panels to the grid,its performance is directly related to the success of photovoltaic grid.In this one,quasi-Z-source photovoltaic grid-connected inverter is a new type of inverter converter structure in recent years,which make up the traditional inverter inverter structures such as poor reliability in the topology,efficiency and low defect.Especially in the new energy inverter system,the traditional voltage source and current source inverters due to their own characteristics,there is a small range of applications,anti-interference ability and weak.This paper analyzes the single-phase quasi-Z-source inverter,the topology of the network impedance capacitors withstand voltage is significantly reduced,and the topology of the network can be used soft-start capacitor voltage impedance eliminates the start-impact way to improve the stability of the system sex.Simulation and experimental waveforms also show that the quasi-Z-source photovoltaic grid inverters can be achieved in time to capture the maximum power point of solar panels,and work on this point,but also to work with unity power factor mode,power to the grid side,active islanding protection method in this paper,with islanding protection function.By analyzing the network impedance state,the alignment of the Z-source inverter mathematical modeling to obtain the transfer function and the impedance of the network control block,a source of direct control of the quasi Z AC side of the inverter output current,the load current regulator Z network can achieve quasi-capacitor voltage control purposes,i.e.the indirect control of the inverter DC bus voltage peak arm control strategy,the inductor current according to a function,the DC bus voltage and output current,the voltage across the capacitor,adjust parameters setting the controller to complete the design.Active duty cycle control to achieve a quasi-Z-source inverter in photovoltaic grid power factor units to the grid feeding purposes.Firstly,after a detailed analysis of the working conditions quasi-Z-source inverter for output voltage and current requirements,the design of the output of the filter.Secondly,this paper analyzes the quasi-Z-source inverter control strategy,using a simple step-modulation method,by unipolar SPWM modulation,inserted through state expected to achieve a buck purposes;proposed a based on the direct control of straight disturbance observation duty cycle control strategy,thus completing the MPPT function;then,for photovoltaic grid inverters several PLL comparative analysis,for single-phase synchronous phase-locked loop,advantages and disadvantages of the three-phase synchronous phase-locked loop,the proposed method,a virtual three-phase synchronous phase-locked loop,and the establishment of the phase-locked loop corresponding loop model for the stability analysis,design of the controller parameters,and finally the simulation and the actual operating results proved that the phase-locked loop has better performance.Through the above research and design strategies for the quasi-Z-source photovoltaic grid-connected inverter is designed for active frequency drift method of combining active islanding control method to achieve the islanding protection.