Research On Key Technologies Of Bidirectional AC/DC Converter For Electrical Energy Router

Owing to the advantages integration of information techniques and trandition energy system,energy internet becomes the next generation electrical system of the tranditional energy system.As an essential device in energy internet,electrical energy router can smooth the uncertainty fluctuations caused by the access to grid by the uncertain feedbackable loads such as renewable resources and electric vehicles,realizing peak-shaving and valley-filling.The bidirectional AC/DC converter is the bridge between electrical energy router and power grid,which is important for the safe and stable operation of the energy router.This thesisi takes home for the main applications,the hardware circuit design,adaptive frequency estimation based multi-mode control strategy,active power decoupling techniques for bidirectional AC/DC converter,are studied.First of all,the hardware circuit of bidirectional AC/DC converter is finished.The function of the bidirectional AC/DC converter in household eletrical energy router is analyzed.The single-phase full-bridge topology is selected as the main topology of the converter,the working principles in rectifier and inverter mode are analezed,the parameters of the filter inductance and filter capacitance are calculated and the semiconductor devices and driving circuit are designed.Finally,he power loss distribution are calculated and analyzed in theory and tested by experiments.Besides,the adaptive frequency estimation based multi-mode control strategy for bidirectional AC/DC converter is studied.Aiming at the poor frequency estimation performance of the conventional frequency lock loop under phase angle jump in input signal,the new frequency estimation law that considering the error square terms is introduced to enhance the phase angle jump rejection capability.The second order linear time-invariant model of the proposed frequency lock loop is established to fix out the nonlinearity introduced by the error square terms.The parameters design method is also given based on the linearized model.Based on this,the current control loop of bidirectional AC/DC converter is modeling and the influence of the parameters of controllers on the performance of the close-loop system are studied.Outer loop controllers are designed to achieve stable operation of the converter in grid-connected rectifier mode,grid-connected inverter mode and standalone inverter mode.The proposed frequency lock loop is adopted to estimate the grid frequency on time to enhance the performance of the converter under non-nominal situation and achieve smoothly mode switching.The excellent performance are tested by simulation and experimental results.Finally,the active power decoupling techniques for single-phae AC/DC system is studied.First,the generation of the double line frequency power ripple is analyzed.Based on this,the working principle of the power decoupling circuit,the decoupling capacitance and filter inductance design method and the voltage and current stress of the passive components are analyzed.The voltage based power decoupling control strategy is proposed,achieving active power decoupling without introducing extra sampling devices in both rectifier and inverter mode.The performance of the proposed methods are tested by experimental results.