Research On Waveform Control Strategy Of Off-grid Inverter Based On H6 Topology

Development and application of the new energy technologies have drawn more and more attention in the world because of the energy crisis and environment problems.With the development of power generation technology,inverters used in the power generation systems can be divided into two classes: grid-connected inverters and off-grid inverters.Off-grid power generation systems,which can run independently from the grid,are flexible and easy to use.They can reduce the electricity cost of remote areas such as communications bases,islands and so on.A comprehensive research on the off-grid power generation system has been conducted.First,main circuit structure and operation mode of the H6 topology were introduced.The advantage of H6 topology in suppressing common-mode current was presented by comparing with the full-bridge topology.Mathematical model of the single-phase off-grid inverters was established and the traditional double closed-loop control algorithm was presented which could eliminate the steady-state error of output voltage.Some issues were analyzed such as design of LC filter,method to reduce the THD of output voltage under nonlinear loads,improved deadbeat control method,no dead-time modulation and so on.Then,a simulation model of single-phase inverter based on H6 topology was constructed in the MATLAB/Simulink environment.The simulation results showed that the improved deadbeat control method and no dead-time modulation can obviously improve the system dynamic response and reduce the output voltage THD under nonlinear loads.Finally,an off-grid inverter was designed and experiments under linear loads and nonlinear loads were conducted.The experiment results showed that the improved deadbeat control method and no dead-time modulation can improve the waveform of output voltage.