Research On A Bidirectional AC/DC Converter With Secondary Ripple Suppression

Nowadays,the energy problem in the world is serious.The use of traditional fossil energy will bring air pollution,surface collapse,greenhouse effect and other problems.Under the pressure of energy and environment,distributed power generation represented by solar and wind power generation has been paid attention to.As a small intelligent power supply and distribution system,microgrid realizes the large-scale access of distributed generation to the main network,avoids the problems of threephase imbalance and island effect,and gives full play to the advantages of clean energy distributed generation.As an important part of microgrid,bidirectional AC / DC converter plays a key role in ensuring the reliable operation of power grid and the energy interaction between DC bus and main network,and has important research value.Most of the traditional bidirectional AC / DC converters are of bridge structure.Because the two power switches on one bridge arm are connected in series,there is a risk of short circuit.The body diode of the switch is used as the freewheeling circuit,and the loss at high frequency will seriously affect the efficiency of the converter.To solve the above problems,this paper studies a double buck bidirectional converter,which has no bridge arm through problem,avoids the body diode freewheeling and realizes the two-way flow of energy.For the double frequency fluctuation of output voltage in rectification mode,this paper proposes a boost source filtering method to suppress voltage fluctuation and reduce the size of bus capacitance.Firstly,this paper introduces the working principle of the bidirectional AC / DC converter studied,analyzes the zero crossing distortion of the converter current and the bus voltage ripple,establishes a small signal model,designs the control loop,and verifies the correctness of the controller design through the frequency characteristics of the closed-loop system.Aiming at the bus voltage ripple,a boost active filter circuit is proposed to suppress the double frequency fluctuation,The effectiveness of the filter is verified by simulation.Finally,the parameters of the converter,the driving circuit and sampling circuit are designed,and the experimental platform is built.The experimental results verify the correctness of the theory.