Research On Loss Analysis And Common Mode Current Suppression Of Dual Buck Grid-Connected Inverter Based On GaN

With the rapid development of industrial economy, the environmental problems have become increasingly prominent in our country, therefore to develop renewable energy power generation, particularly the solar power is to solve our energy crisis and ensure the sustainable development of our country’s important strategy. In recent years, photovoltaic power generation has been more and more concern and attention. Currently photovoltaic grid-connected inverter on the market, according to whether isolation can be divided into isolated and non-isolated. Isolated grid-connected inverter with electrical isolation to ensure the PV panels and the AC side of the grid, improve the security of the system, but it has large volume, low efficiency, and control complex. Non-isolated grid-connected inverter without transformer, reducing the energy loss of the transformer, low cost, small size, high efficiency, it received widespread attention.The main object of the thesis is Dual Buck grid-connected inverter. First of all, summarize the advantages and disadvantages of Dual Buck grid-connected inverter, by the third generation of wide bandgap semiconductor devices Cascode GaN transistor solve the problem of Dual Buck grid-connected inverter’s inductor is larger. Analyzing its working principle, grid-connection control strategy and the design of the main circuit parameters, and simulation verification. By double pulse test circuit, the Cascode GaN transistor drive circuit and dynamic performance was tested, and the mathematical models of Cascode GaN transistor turn on and turn off loss and silicon carbide schottky diode turn off loss are presented, based on this result, the loss of the whole circuit are analyzed. Then analyzed the Dual Buck grid-connected inverter’s common model, proposed a reactive power generation control method which can make Dual Buck grid-connected inverter to realize bi-directional flow of power, and analyzed its working principle and common model, and simulation verification. Finally set up a 500W Dual Buck grid-connected inverter prototype based on the Cascode GaN transistors and silicon carbide schottky diode, and on the prototype of Dual Buck grid-connected inverter with experimental verification.The theoretical analysis, simulation and experiment of this thesis show that the Dual Buck grid-connected inverter has simple structure, high efficiency and low common-mode current. And the use of GaN transistors to achieve high frequency circuits can solve the problem of lager inductance. Finally, reactive power generation control method is proposed which can make Dual Buck grid-connected inverter with bi-directional flow of power, expanding the range of applications.