Research On Control Strategies Of Inverter Under Mixed Conduction Mode

The inverter can convert DC voltage into voltage, frequency and phase-controlled AC voltage, which is an integral part of modern society. With the increasing awareness of energy saving and environmental protection, the efficiency of the inverter also has higher requirements. An inverter operates in discontinuous inductor current mode is studied in this article, and the control strategy is designed to stabilize the circuit. The discontinuous inductor current mode can realize zero current switching, optimize the overall efficiency of the circuit.The working state of inverter in discontinuous inductor current mode is analyzed, and the mathematical model is made and compared with the inverter in continuous inductor current mode. In terms of controlling strategies, a PID controller based on quantity of electric charge is proposed. The simulation and experiment result shows that this control strategy has great stability. Up to three control strategies are proposed and compared with each other.When the inverter works in discontinuous inductor current mode, the peak current of the inductor is three times higher than the normal inverter. The influence of parasitic inductance on the switching process will be particularly great because of the higher peak current. The calculation formula of parasitic inductance in bus line is deduced in detail, and the influence of parasitic inductance on the switching loss is analyzed. Several measures to reduce parasitic inductance are proposed.In order to make the circuit work in discontinuous inductor current mode firmly, more demand is needed when designing the LC filter parameter. The factors should be considered in the design process are given, and the formulas of designing the LC filter parameter are deduced, in the perspective of maximum instantaneous power. The type of switching devices is selected for the half bridge inverter. The experiments have been made to verify the correctness of the theory.