The Application And Research Of Fuzzy Logic For Soft-Switching Power Converter

In recent years, with the rapid progress of power electronics, switchingfrequency must be increased in order to acquire good performance,high efficiency,high security,small size and light weight of power converters. But the higher theswitching frequency is, the greater the loss wastage of switching is, so thesoft-switching must be achieved. The technology of soft-switching of power converterutilizes inductances and capacitances to change the switching slot of the switch, itneeds adding inductances and capacitances to the circuit. Because of the strongnon-linearity of the systems themselves and the addition of the resonant components,the modeling of these system becomes difficult, its effect sometimes is unideal eveninvalid that applying conventional controlling methods. The strategy of fuzzy controlneedn't constituting mathematics model and control the system based on controlexperience completely, fuzzy control is fit for controlling the systems of non-linearand uncertain. The dissertation probes into applying fuzzy control to soft-switchingpower converters.The most content of dissertation is followed:(1) Dissertating the necessity of power converters' working under the state ofsoft-switching, introducing the actuality of the controlling of the systems of non-linearand uncertain like soft-switching power converters.(2) Adopting quasi-resonant technology in realizing soft-switching andintroducing the working principle of the quasi-resonant converter. Setting zero-currentswitching quasi-resonant SEPIC converter as example, it analyzing the switchingmode of SEPIC converter in detail based on the instance of switches' on-off.(3) Based on the working principle of fuzzy control and characters ofsoft-switching technology, it applies fuzzy control to soft-switching power converterand designs a normal fuzzy controller for SEPIC power converter introduced former.By simulating the fuzzy control system,it validates the availability and rationality ofthis fuzzy controller.(4) Taking zero-current switching quasi-resonant SEPIC power converter ascontrolled object, this dissertation designs an on-line adjustable modification factorα PID controller. This controller exerts on-line modification of KP,KI,KD of PIDcontroller taking advantages of fuzzy control and PID control fully and utilizing thethinking of fuzzy reasoning. Because factor α modifies the quantification ke,kec,the parameters of PID controller are optimized.