Research On VIENNA Rectifier Based On Fuzzy Fractional Order PID And Its Control Algorithm

Compared with the two level rectifier,the three level rectifier has the advantages of less input current harmonic content,lower voltage stress of power device and no bridge arm straight through.In many three level rectifiers,the topology of VIENNA rectifier is the most simple and the switch devices are the least,and it is widely used in charging pile,communication power supply and other fields.The thesis firstly introduces the working principle of VIENNA rectifier and analyzes the working mode of the rectifier in different switching states.Based on this,the mathematical models of VIENNA rectifier in abc,?? and dq coordinate system are established in turn.Secondly,in order to solve the problem that the conventional three-level space vector modulation has the disadvantages of complex vector judgment and large computation time of the basic vector,a three-level to two-level SVPWM modulation method is adopted in this paper.After analyzing the effect of each basic vector on the mid-point potential,it is shown that the positive short-term vector decreases the mid-point potential and the negative short-vector increases the mid-point potential,and then proposes to introduce a regulation factor in the positive and negative short-term vector,the coefficient is used to adjust the time of the action of the positive and negative short vector,and then the balance of the middle point potential is realized.Then,in view of the nonlinearity of VIENNA rectifier,a fractionalPID controller is proposed in this paper.Compared with integer PID,fractional PID has two parameters that affect the dynamic performance and robustness,and the controller design is more flexible.Aiming at the time-varying system,a fuzzy fractional PID controller is proposed in this paper.That is to say,combining fuzzy control with fractional PID controller,it has the better dynamic performance and robustness of fractional PID controller,and its parameters can be set online.Finally,the Simulink simulation model of VIENNA rectifier is built and the control algorithm is validated.Simulation and experimental results show that the proposed neutral point potential balance control strategy can achieve capacitor voltage balance,and the VIENNA rectifier has better dynamic performance when using the fuzzy fractional PID controller.