Research And Analysis Of VIENNA Rectifier Circuit Control Technology

With the development of power electronic technology,especially the rapid development of power semiconductor devices and control technology,power electronic devices are increasingly used in industry.Power electronic devices in improving production efficiency and product quality plays an important role,become a important basis for production automation equipment.Because of the power electronic equipment has a strong nonlinear characteristics of power electronic devices,power electronics devices inject a large amount of harmonic and reactive power in grid,causing severe grid “pollution”.Therefore,how to improve the power factor of power electronic devices,and reduce the current total harmonic distortion rate become a problem which needs to be settled.VIENNA rectifier,as a typical three-level topology,is suitable in areas of high-voltage and high-power condition.Compared with traditional two-level structure,it reduces the switch voltage stress and the AC side of the harmonic content;In comparison with the diode clamped three-level structure,only a switch is needed in each leg,avoiding the dangers of the upper and lower bridge arm and simplifying the control links to obtain a wide range of applications.Therefore,from the view of the economic and security considerations the study of VIENNA rectifier control technology has a great engineering value.Firstly,this paper analyses the operation principle of VIENNA rectifier and present the operation mode on a different switch state.On the base of which,this paper analyses the operation feature of VIENNA rectifier,and deduces the mathematical mode and equivalent circuit based on switching function in three kinds of coordinate system.On the basis of the second,and then the last chapter,in the dq reference frame for the decoupling control of current,based on voltage loop,current double closed-loop control structure diagram of the inner ring.In-depth analyses the SVPWM control algorithm,and implements a there-level SVPWM and the equivalent of two level SVPWM,simplifies the complexity of the space vector synthesis algorithm,to facilitate the realization of the digital control.The influence of different vectors on the midpoint voltage balance of the output capacitor is analyzed,and the equilibrium control strategy of the midpoint of the capacitor based on the regulation factor is given.In this paper,a test prototype with a rated power of 7.5kW is set up.The design parameters of the experimental prototype,the structure of the control system and the software flow chart are given according to the experimental purpose.Waveform simulation and experiment indicate that: the VIENNA rectifier again based on SVPWM control algorithm of voltage and current double closed-loop control strategy,the advantages of voltage and current double closed-loop control strategy,the advantages of low harmonic content,high power factor,good dynamic performance and steady-state performance,neutral voltage balance control effect is good wait for a characteristic.