Research On Power Decoupling Technologies Of Single-phase AC/DC Converter

In a single-phase PFC AC/DC converter,the instantaneous input fluctuating power flowing into dc side is buffered by bulky electrolytic-capacitors which are added to the dc link in parallel.However,there exists secondary ripple voltage in dc side of the converter.In addition,short service lifetime of electrolytic-capacitors will directly affect the operation reliability of system.Furthermore,in order to suppress dc voltage ripple and improve system reliability,power decoupling technique based on film capacitors have received attentions and several applications.Therefore,this dissertation will mainly study the control techniques of power decoupling circuit integrated single-phase PFC AC/DC converter to improve control precision and robustness of power decoupling control system.The research results have theoretical research value and engineering application value.Full-bridge power decoupling circuit paralleled to the dc side of single-phase Boost PFC converter is adopted in this dissertation.Firstly,the working principle of fullbridge power decoupling circuit is analyzed;secondly,PR controller is designed by the derived transfer function of power decoupling circuit,and its parameters tuning is carried out by root-locus method;and then the advanced design strategy of PR controller for delay compensation is given in the discrete time state.On the basis of the designed and developed experiment prototype of power decoupling circuit integrated Boost PFC converter,through the system simulation and experimental study,the proposed PR controller turns out to be reasonable and valid.In view of that PR controller has dependence on the system parameters of power decoupling circuit,and its control performance is easy to be affected by parameter variations and unknown disturbances.Through algebraic parameter identification technique,the second-order ultra-local model of full-bridge type power decoupling circuit is established in this paper;and the model-free deadbeat predictive controller is designed for real time generation of duty cycle signal applied to regulate conducting and shutting off states of switch tubes in power decoupling circuit.Through the system simulation and experimental study,the performance comparison research with PR controller is implemented and proves that proposed model-free deadbeat predictive controller has technical advantages of better control performance with stronger robustness.Considering that the accuracy of decoupling capacitor voltage reference generated by the calculation formula-based open-loop scheme is easily affected by parameter variations.The closed-loop reference generation method based on model-free controller design is proposed in this paper.Its implementation idea is to analyze the relationship between the voltage ripple existing in dc side of PFC converter and double line frequency ripple power;and then the corresponding first-order ultra-local is built up;the model-free controller is designed,and the capacitor voltage reference is determined based on residual fluctuating power at dc side generated by the acquired dc voltage ripple.Finally,through system simulation and experimental study,the performance comparison research with open-loop reference generation is implemented,and the technical advantage of proposed closed-loop generation scheme is confirmed.