Design Of High Voltage Gain Switched Coupled Inductor Quasi Z Source Inverter

The three-phase PWM inverter has been widely studied as an important part of the new energy power generation systems and AC motor drive system. The traditional PWM inverter can only work as buck inverter, and the three-phase H-bridge is not allowed to work in the shoot through state. A quasi-Z-source network is applied in the DC side of the traditional inverter to improve it. Quasi-Z-source inverter enables conventional PWM inverter function, but also to achieve the boost inverter. This greatly expands the range of applications of PWM inverter. The key parameter of quasi-Z-source inverter is its step-up ratio, the study and improvement of quasi-Z-source inverter improving its boost ability is very meaningful.This thesis transfers the quasi-Z-source inverter into two parts: the conventional PWM inverter AC side and DC side quasi-Z source boost network. The Mathematical Model of these two parts are calculated in this paper. The signal flow diagram modeling method to obtain the model of DC side quasi-Z-source network is studied in detail. Then this paper compares the different zero vector shoot-through modulation methods and selects the maximum gain SVPWM modulation method. The third harmonic is analyzed and eliminated by improving the modulation scheme.To improve the step-up ability, the subject uses the new switched-coupled-inductor structure in the quasi-Z-source network. It further improves the step-up capacity of the traditional quasi-Z-source. It works without increasing the number of magnetic components, through the ratio of the coupled inductor, the boost ratio of inverter improves significantly. The work process and features are analyzed in detail, and compares it to the traditional quasi-Z-source inverter. The timing operating process of the coupled inductor and the modal of the main structure are studied, and the design process of the coupled inductor is described.On the base of the AC small-signal model of the inverter, the design method of the main circuit parameters is given, and the current and voltage dual closed-loop control strategy is taken. Analysis of the dual closed-loop PI regulator parameters design method is given. The result of simulation proves the stability and dynamic performance of the inverter system.