Study On The Topology Analysis And One-cycle Control Strategy Based On Z-source Grid-connected Inverter

Z-source inverter topology is a kind of single-stage boost inverter circuit, the advantage of it is high efficiency, high reliability and low cost, and it can be widely used in solar photovoltaic power generation, wind power generation, and other new energy on the occasion of higher change input voltage. Compared with traditional bridge inverter, Z-source inverter source network allows the inverter working in the shoot through state and has no damage to the circuit element, and can use the shoot through state boost regulator function of the input voltage to ensure the inverter DC side input conditions. At the same time, the switch tube that control PWM signal has no dead time, it improves stability of system and quality of output waveform. But traditional Z-source inverter has defects, Its limitation is that there is impact of starting circuit, the large volume and the boost ability is insufficient.This paper introduces two kinds of improving Z-source grid-connected inverter based on the analysis of the limitations of the traditional inverter, aiming at improving the defects of traditional Z-source inverter. At the same time, the paper analysis the application of direct one-cycle control and indirect weekly control in Z-source inverter by using the idea of one-cycle control.At first, the deficiency of traditional bridge inverter bridge and the advantages of Z-source inverter. Introduces the improved topological structure of Z-source inverter and research status of control method, one-cycle control had been widely used in real industrial cases. The output power quality was verified by establishing state equation of Z-source grid-connected inverter system through the state average method and setting up control circuit based on d-q coordinate system.Secondly, this paper analysis the limitations of traditional Z-source grid-connected inverter, introduces topological structure and working principle of two kinds of circuit. The state equation was deduced and control circuit was built for the purpose of controling the grid current and stabling capacitance voltage of Z-source network. The two kinds of circuit is verified by building simulation model and analyzing the output waveform which were in the situation of changing the grid power or disturbing the steady state input waveform and so on.Then this paper expounds the idea of one-cycle control and the working principles of switch circuit, analyses the model of Z-source grid-connect inverter combined with the principle of three-phase one-cycle control. The equation of three-phase one-cycle control directly and indirect control in a single week were deduced, the control circuit is built. Finally,the correctness and feasibility of one-cycle control was verified by analyzing the output waveform which were in the situation of changing the grid power or disturbing the steady state input waveform and so on.Finally, the experimental prototype was designed based on the Z-source inverter and indirect one-cycle control theory, the inductance and capacitance in Z-source network and filter inductance parameters of grid side were also designed. The circuit of voltage sampling and PWM drive unit were designed by control circuit which was built by the minimum control system of DSP2808. Finally, the experimental results were analyzed.