Design And Implementation Of Improved Quasi-z-source Inverter Based On DSP

Traditional inverters have shortcomings such as single buck-boost,limited output voltage range,large influence of electromagnetic interference,and low efficiency.In 2003,the Z-source inverter proposed by Professor Fangzheng Peng has solved these problems.Since then,improved topologies based on Z-source inverters have appeared one after another,achieving engineering goals such as increasing the boost ratio,reducing the voltage stress of switching devices,and reducing current ripple.Affected by the ambient temperature and light intensity,the output voltage of photovoltaic cells and the output current present a non-linear relationship.The photovoltaic output voltage has a large degree of variability,and the output voltage is low and the current ripple is large.Therefore,there is a need for an inverter system that can improve the output voltage gain.This inverter also needs to adapt to a wide range of input voltage fluctuations,and eliminate input ripple as much as possible.This topic is based on the topological structure of the quasi-Z-source inverter,and uses the coupled-inductor to design a coupled-inductor switched quasi-Z-source inverter.By adopting the straight-through boost modulation and closed-loop control strategy,the output voltage remains stable under the condition of input voltage fluctuations,and has a higher boost ratio and lower voltage stress of switching device.The paper compares and analyzes the characteristics of several inverters from the three aspects of boost capacity,current ripple,and voltage stress,and proves that the improved quasi-Z source inverter has better performance.Aiming at the control of active switching devices in the impedance network,an improved SVPWM through modulation method is proposed,and a simulation experiment platform is built through MATLAB.Compared with the signal that is synchronized with the through time,the improved through modulation method has larger adjustment range.With a smaller shoot-through duty ratio,a higher voltage is output and the switching frequency is reduced.Aiming at the problem that the volatility of the output voltage of photovoltaic cells affects the stability of the output voltage of the inverter,a closed-loop control of the DC link voltage is proposed,and a small-signal modeling is performed on the improved quasi-Z-source inverter.The simulation results show that the closed-loop control strategy plays a role in constant output voltage.The parameters of the main circuit components are calculated,then the Protues software is used for circuit design.The TMS320F28027 DSP chip is used as the core control device of the DSP control system,and the peripheral control circuit and control program are designed.Finally,a hardware experiment platform was built to verify the rationality of the improved Z-source inverter and the feasibility of the SVPWM modulation strategy.