Improved Bipolar-type AC-AC Converters Based On Non-Differential Dual-Buck AC Choppers

Under the background of the massive integration of renewable energy,the voltage fluctuation no longer only shows voltage sag,but also has the problem of voltage swell.At this time,the traditional power frequency transformer tap voltage regulation scheme has been unable to effectively adjust the voltage.With the rapid development of power electronic transformation technology,it is an effective voltage regulation scheme to solve the voltage problem in distribution network by using compensation equipment based on AC-AC converter,which has good feasibility and high cost performance.As one of the four basic power converters,the research and innovation of AC-AC converters is far less than that of other three kinds.With the continuous updating of higher performance power switching devices and digital chips such as FPGA?DSP,the current stage provides strong support for the research of AC-AC converters.In addition,the urgent demand of the world for the growing construction of high quality,high efficiency and environmentally friendly strong power grids also provides a good application prospect for practical engineering applications of AC-AC converters.Firstly,the research background and significance of this topic are expounded,and the advantages and disadvantages of several typical AC-AC converters are analyzed in detail.On this basis,a new type of bipolar AC-AC converter topology(DB-AC)and the corresponding PWM modulation strategy are proposed.The proposed converter can solve the converter problem in the traditional structure structurally,and can realize the bipolar voltage output.The PWM modulation strategy used is simple and reliable,no need to set the dead time,and has two adjustable freedom duty cycle,which makes the working mode more diverse.Combining the topology and PWM modulation strategy of the proposed DB-AC,the working process of its bipolar voltage output is analyzed concretely,and the closed-loop simulation is built based on PSIM to optimize the structural parameters;the loss of the power tube is analyzed concretely.In summary,the experimental prototype of 500W is built by using laboratory conditions,and the experimental verification is carried out for different load and different duty cycle,and the actual efficiency of the experimental prototype is measured by power analyzer.Finally,the situation of grid voltage fluctuation is simulated,thus the validity and engineering application of DB-AC converter for grid voltage fluctuation problem are verified.