Research On ZCS Single Switch Buck PFC Of Three Phase

The control and transform technology of electric energy is widely used.The traditional AC-DC converter uses the nonlinear combination of rectifier bridge and bus capacitor making the input current contain a large number of harmonics,which pollute the grid and affect the normal work of the electric equipment in the grid.In high power applications,three-phase PFC(power factor correction)converter is generally used as rectifier.Three-phase PFC combined with soft switching technique can enhance the power density and efficiency of converter.Firstly,the research status of PFC including the topology of three-phase PFC and control strategy at home and abroad is introduced.The working process and working waveforms of three-phase single switch zero current Buck PFC in a work period are analyzed.Secondly,the characters of the three-phase single switch zero current Buck PFC are studied.With the simulation analysis,a suitable hysteresis voltage control and duty ratio are found.The simulation results show that the hysteresis voltage control can reduce the THD(total harmonic distortion)of phase current.Capacitance of the delta connection is explored and the conclusion is given.The simulation about the hysteresis voltage control combined with correction capacitor delta connection is accomplished.The simulation results show that the combination can effectively reduce the THD of phase current.The content of THD is less than 5%.With the characteristics of the voltage and current waveforms in a work period,the efficiency of the converter is analyzed.The parameters of device are substituted in efficiency expression.Under the assumption of the input voltage and load having no change,the curve of duty cycle and efficiency is drawn,which provides the guidance on the choice of the efficiency and output power of converter.Finally,a 1.5kW experimental prototype is designed.The selection methods of main circuit device and the corresponding circuit design is given.The design about DSP control program and some of the important subroutines are described.An experimental platform is built and the experimental results show that at rated output power,the switch operates on zero current switch.The PF value of grid side is closed to 1 and the THD of phase current is 3.66%,which is lower than 5%.With the correction capacitor delta connection combined with the hysteresis voltage control,THD can be optimized.The efficiency of the converter is tested.The test results and test curves are given.The test data shows the efficiency at full power is 92.02%and the efficiency of the converter at 1.5kW is 93.35%according to the efficiency expression.The error between test value and calculated value is about 1%which shows the efficiency expression can make a good prediction.The error on the efficiency and power loss in full power are analyzed.The soft start function is tested and the experimental results are analyzed.The loss of prototype in the condition of no load is analyzed.The variation of phase current and the output voltage is tested in the condition of load mutation.The dynamic adjustment characteristics of the phase current and the output voltage demonstrate the rationality of program design.