Research On Nonlinear Backstepping Control Strategy Of Three-phase Three-level Vienna Rectifier

With the continuous growth of electric vehicle ownership and ship electrical load,the power level of off-grid battery and energy storage device rises sharply,which makes the demand for medium and high power charging infrastructure increase sharply.The three-phase Vienna rectifier,as a three-level unidirectional transmission rectifier topology,has the advantages of higher power density,better input current quality,fewer switching devices and higher reliability.It is widely used in medium and high power charging facilities.In this paper,the three-phase Vienna rectifier is taken as the research object,and a nonlinear inverse direct power control method is designed.In view of differential expansion,parameter drift and external interference in operation,zero crossing current distortion and other problems,the following are studied:Firstly,the topology and working principle of the three-phase Vienna rectifier are analyzed,the mathematical model of the Vienna rectifier in the DQ rotating coordinate system is derived,the physical meaning and realization of the control quantity in the mathematical model are explained,and the simplified space vector modulation is further introduced as the controller output method.On this basis,analyzes the basic principle and design method of nonlinear backstepping method,starting from the model of instantaneous power dc output voltage is derived,the reflex control active power and reactive power backstepping control,analyzes the backstepping direct power controller in virtual control problems of the differential expansion,joined the second-order filter instruction and redesigned the active power controller,The calculation amount is reduced effectively,making the algorithm more practical.Then,in view of the uncertainties of external disturbance and filter parameter variation in the operation of three-phase Vienna rectifier,the sliding mode design idea is introduced.In the last step of controller design,the sliding mode control rate is adopted and the exponential switching rate is used to reduce chattering.A nonlinear disturbance observer for backward direct power control is designed to reduce the gain of the switching rate and further improve the robustness of backward direct power controller.Meanwhile,aiming at the inherent zero-crossing current distortion of threephase Vienna rectifier,the current hysteresis caused by current vector hysteresis is analyzed.By compensating the current hysteresis caused by inductance potential,a zero-crossing distortion compensation mechanism suitable for adaptive sliding mode reverse direct power is proposed.Finally,in order to further verify the effectiveness of the proposed algorithm,a hardware-in-the-loop experiment platform was built based on NI PXI chassis and Starsim software,and the hardware-in-the-loop experiment was carried out to verify the backsliding control strategy.Meanwhile,an experimental prototype of three-phase Vienna rectifier is designed and the proportional integral control strategy,backward direct power control strategy and adaptive sliding mode backward direct power control strategy are tested.The effectiveness and practicability of the proposed method are verified to some extent.