Research On High Frequency Isolated Quasi-Z-Source Inverter And Application

Compared with the traditional inverters, Z-source/quasi-Z-source inverters have better electrical transmission characteristics, which can overcome some theoretical limitations in traditional ones. On the basis of study of the high frequency transformer isolated quasi-Z-source inverter recently proposed, an innovative structure is proposed to improve its characteristic in this paper, which can significantly reduce the voltage stress of DC-bus support capacitor. The high frequency isolated quasi-Z-source inverter with this innovative structure is studied in-depth in this paper.First, basic working principle about the inverter is given in the paper. Formulas of voltage and current across and through the key components are deduced. And an abnormal working state is analyzed at the same time. Second, the paper gives the small signal modeling process about the inverter by using state space averaging method. By using the transfer function got from the small signal model, a grid-connected PV system is be designed. The control strategy of the system used here is to keep the peak voltage of the DC-bus constant. The dual closed-loop of DC-bus voltage and output current is designed to be the feedback control loop. The method of how to design and achieve the PI regulator and PR regulator used in dual closed-loop is given at the same time.In order to prove that the system is correct and feasible, the paper gives the result of co-simulation of the system in detail by using saber and simulink. And the parameters of components in inverter are optimized through simulation, which make it more precise for design and selection of components. At last a500VA prototype is produced by using the chip of TMS320F2808from TI company. Then a group of experimental waveforms are given by the test of the prototype.