Research On Control Strategy Of The Quasi-Z Source Inverter With The Waveform Control Ability Of Load Voltage Under Nonlinear Load

Global energy shortage and environmental crisis has become the important factors which restrict the development of the human.The distributed generation system based on clean and renewable energy is widely concerned by countries all over the world,especially the remote areas where the grid is disconnected.Solar energy,wind energy and other new energies become one of the best choices of distributed generation system because of its adequate cleanliness,absolute security,relative wide range of resources and the flexibility in use.The operating state of the inverter directly affacts the working performance of the whole system,so the Quasi-Z source inverter is widely concerned owing to its boost/buck function.In this paper,for the off-grid type distributed generation system,the basic working principle of the circuit composed by the Quasi-Z source inverter and the single-phase full-bridge inverter are studied.A Quasi-Z source inverter control strategy with voltage waveform control ability under nonlinear load is deeply analyzed.In order to achieve voltage-boosting function,direct sample and control method of the DC-link peak voltage for the Quasi-Z source inverter is discussed,and the PWM modulation strategy based on constant switching frequency shoot-through zero vector of double arms is also discussed.In order to achieve good voltage quality,repetitive control and proportion control is used as the outer voltage loop,proportion control is utilized as the inner current loop.The THD of output voltage under nonlinear load can be improved and dynamic response speed of the system is increased.Finally,In order to verify the system design and control strategy,the simulation model of the single-phase off-grid inverter system based on a Quasi-Z source inverter is established by the PSIM simulation software.And the experimental platform is built,the experiments are done.Simulation results and experimental results verify the validity and superiority of the control strategy.