Research And Realization Of A Grid-Connected And Stand-alone Dual Mode Inverter

Recently, as the environmental pollution getting worse and the appearance of energy crisis, renewable resources and new energy development are becoming more and more important, especially in the area of solar power. With the support of national policy, large-scale photovoltaic power plants and household photovoltaic systems continue to build, greatly promoted the development of the solar power generation. Especially in recent years, the government supports the household photovoltaic systems and allows household photovoltaic power generation to connect to the grid system, the user also can get the money from the government. Since the grid-connected photovoltaic inverter only has a single function and hybrid household photovoltaic systems has a complex structure, it does not meet the user’demand for the versatile, compact PV system.The papers focus on the gird-connected/stand-alone dual mode inverter and analysis the circuit topology, control and other key technologies. In the circuit, the MPPT controller used the Boost circuit topology. The battery charge and discharge used the Buck-Boost circuit topology. The bridge of inverter used the H6topology, which can solve the problem of leakage current, and the work status are detailed analysis.One-cycle control is a nonlinear control strategy based on large-signal system, with control circuit is simple, fast response, good stability. This paper analyzes the method of one-cycle control by means of analog circuit. Based on the principle of one-cycle control, the digital formulas can be derived and used in off-grid inverter, reflecting the stability of single-cycle control strategy. In the end, the one-cycle control is simulated in the MATLAB.The paper analysis the grid and off-grid control strategy of the dual-mode inverter. Furthermore, on the basis of current loop, a special method join the network voltage loop in the gird-connect strategy. In order to improve the steady-state performance, the system used PR controllers. The paper also analysis the switch of dual-mode and proposed the step of switch method, the method can achieve two-mode operation strategy and get good performance. In the grid-connected mode switching to the stand-alone mode, the current controller can set the load current as give and can accelerate the speed of the turn-off thyristor, the system can cut the connecting with the power network immediately.Finally, the designed control algorithm was verified in a5KW inverter. According to the experimental results, the papers proposed the disadvantage of the research and make a summary of the task. For the uncomplicated task and the problems, the future work is designed.