A Study On Step-up Active Capacitor Converter

With the rapid development of power conversion technology,single-phase power converter(rectifier or inverter)has been widely applied in photovoltaic inverter,LED drive,locomotive traction,uninterruptible power supply,fuel cell,electric vehicle and other systems.Whether in the rectifier or inverter,instantaneous power are not balanced between AC and DC.In order to balance the DC and AC side instantaneous power and ensure the two times voltage ripple of the DC bus voltage is small enough(usually less than 5%),large value electrolytic capacitor is usually used as the DC bus capacitor.However,the electrolytic capacitor has short service life and poor reliability,which affects the life and reliability of the single-phase power converter.Therefore,to prolong the service life of the single-phase power converter and improve the stability of the work,this paper proposes a boost type active capacitor converter(Active Capacitor Converter,ACC),by controlling the port current and the port voltage of the ACC meet the rules of capacitor.The certain capacitance value of active capacitor to replacing the original electrolytic capacitor and the non-electrolytic capacitor single-phase power converter will be realised.Firstly,complete the accurate calculation method of single-phase power converter DC bus capacitor,analyze the working principle of active capacitor converter and realize modular design.A detailed and reasonable parameter design is uesd for main and control loop and the related simulation verification is realised.An experimental prototype is made,which is based on digital signal processor F28335.The main contents and achievements of this paper are listed as follows:First of all,this article used the single-phase power factor corrector as an example to calculate the required internal DC bus capacitor.It is used as the basic working platform of the active capacitor converter.An accurate calculation method of the DC bus capacitor of the single-phase power converter is presented,which provides the basis for subsequent design of the equivalent capacitance value of the active capacitor converter.Then,the main circuit topology and the closed-loop control method of the active capacitor converter that can realizes the standardization and modular design are given,which is based on a small capacitor that paralleled to the input of the Boost/Buck bidirectional DC/DC converter.The operating principle of the active capacitor converter and the method of designing the main circuit parameters are described in detail.Then the dual-loop control loop of the active capacitor converter is analyzed,and the controller design method of the current inner loop and the voltage outer loop is given.Finally,the realization of the principle of the active capacitor converter and the correctness of the design parameters of the main circuit are analyzed and verified.According to the main circuit parameter design results,the simulation model was built in the simulation software and the experimental prototype was made in the laboratory.The simulation and experimental results verify the feasibility of the scheme and the correctness of the parameter design.