Research Of Power Factor Correction Based On Digital Control

The traditional PFC convert generally consist of a main power circuit and a controller.The controller of PFC typically is the analog controllers which consist of op amps and analog device such as capacitors and resistors.Because of the limitation of the limitation of the analog circuit,the performance of the traditional PFC has already approached the limit.In order to further enhance the performance and efficiency of PFC convert,more and more research turned to the digital PFC control method,which performs signal calculations through microprocessors to achieve more sophisticated control methods.The digital control method has good flexibility and can achieve higher performance.Therefore,it has become a hot research area of power electronics.This article summarizes and analyzes some existing PFC control methods and sampling methods,and analyzes their advantages and disadvantages.And then,design a digital-controlled single-phase power factor convert based on average current mode control.It use FPGA as the control microprocessors and Boost topology as the main power circuit.The PFC system in this paper is a double-loop control system,which consists of a voltage outer loop and a current inner loop.The control algorithm use a variable parameter PI control algorithm and add a feed-forward control to make the input impedance closer to a pure resistance.In this paper,the small signal model of PFC circuit is analyze and simplified.According to the small signal model,PI parameter adjustment method is given to ensure the dynamicity and stability of the system.The sampling method uses the current transformer to sample the upper edge and set the sampling threshold to avoid the sampling point at the switch time,thereby suppressing the influence of high frequency switching noise.The software part uses Verilog as the programming language and divides the whole system into several modules such as the soft start module,the protection module,the PI parameter adjustment module,the sampling current correction module and so on.Divide the system into module can make the system easy to modify,expand and upgrade.Finally,build an actual platform to implement the system.Measure its actual performance and efficiency to verify its feasibility.