Research On High Frequency Chain Full Bridge AC-AC Converter

With the transformation of China's power supply from quantity to quality,and more and more power equipment with higher power quality requirements are connected to the grid.In order to make such electrical equipment and systems run as efficiently and stably as possible and avoid the negative effects caused by grid fluctuations,it is necessary to add an AC voltage regulator to the consumers.Among various AC voltage regulators,AC-AC converters are used for voltage regulation,and have a large adjustment range and small waveform distortion.In order to further improve the converter power density and achieve isolation,the high-frequency chain AC-AC converter is studied to ensure that the converter has the ability to suppress the fluctuation of the power grid while converting power.The overall implementation of this function has important engineering implications.First,the steady-state characteristics of the high-frequency chain full-bridge AC-AC converter are studied.For the relationship between the input and output voltages;the voltage and current stress of the main components of the two phase shifting controls are calculated;at the same input voltage,the two phase shifting controls are the transformer turns ratio and the transformer when the same output voltage is reached.The parameters such as magnetic density change,copper loss and iron loss were compared and analyzed.Secondly,the analysis of the modulation and demodulation and soft switching process of the high-frequency chain full-bridge AC-AC converter is given.The converter operates in a high frequency state,and further obtains a mathematical expression of the output voltage waveform of the front and rear cycle converters through a switching function.The low-order harmonics contained in the output waveform after modulation and demodulation and low-pass filtering are analyzed and suppressed by introducing a compensation function.The modal and soft-switching process is analyzed for high-frequency isolated full-bridge AC-AC converters.Perform a simulation analysis on this.Again,combined with theoretical derivation,design hardware experimental platform for verification,software writing and hardware circuit construction.Design software processes and procedures,and select the DSP28335 controller to write software for the control core.The hardware design includes MOSFET selection,input and output filter selection,high frequency transformer design,and design of various functional circuits.The functional circuit includes a driving circuit,a signal sampling and conditioning circuit,and the like.Finally,it is verified by analyzing the experimental results that the designed converter characteristics are in agreement with the above theoretical analysis.Finally,the linear sliding mode control method is used to control the high-frequency chain full-bridge AC-AC converter.Thereby achieving suppression of disturbances.The general design flow of sliding mode control and the mathematical model of the high frequency chain full bridge converter are given.Finally,the design results are verified by simulink simulation to verify the correctness of the theory.