Research On Three-port Converter Topology And Control Strategy With Wide Voltage Range

In order to deal with the problem of instability and intermittent of renewable energy such as solar energy and wind energy,the method of using three-port converter to provide additional ports to connect energy storage equipment to stabilize power supply has been widely concerned in new energy generation.Compared with the traditional two-port converter,the non-isolated three-port converter has the advantages of smaller volume and lower cost.However,the voltage constraint between ports is often serious,and the lifting voltage between any ports cannot be realized,which greatly limits its application.Therefore,the study of non-isolated topologies with wider voltage range and their control strategies has become a hot topic.To solve the above problems,a non-isolated three-port topology with wide working voltage range is proposed,The topology can realize the voltage boost or buck between any ports and has higher power density.The topology evolved from the four-switch Buck-Boost,By adding capacitance between the ports,The output voltage of both ports connected to the capacitor can be reduced simultaneously.Therefore,under the same ripple requirement,the total amount of filter capacitance required by the topology is less and the power density of the system is higher.In addition,it is proved by theoretical analysis that the addition of the capacitor is also beneficial to reduce the total filtering loss of the two ports connected with it.A piecewise modeling compensation strategy was designed to solve the problem that the stability control of the circuit could not be realized with only a single controller parameter in a wide operating voltage range.When the voltage variation range is large,the control effect of the compensator designed by using the small signal model of a single working point is not good.Therefore,the voltage range is divided into three sections according to the relation of the port voltage,Each section is compensated separately,and the circuit determines the compensator parameters according to the working voltage.Based on the analysis of the working principle and considering the working characteristics of the circuit,the parameters of the circuit are designed,and the small signal model of the circuit before and after adding capacitance is established by the state space average method and compared,so as to analyze the influence of adding capacitance on the stability of the small signal of the system.Different work areas and voltage modes are divided according to the working characteristics of the circuit.In order to realize accurate identification of work areas and automatic switch of control loop,a controller output parallel competition logicis adopted.In order to ensure the smoothness of each working area and voltage mode switching,a mode switching strategy with memory function was designed to avoid the abrupt change of duty ratio in the switching process.In order to reduce the circuit conduction loss and switching loss,the sawtooth modulation strategy is designed for different bridge arms to minimize the RMS of inductance current and realize the ZVS of switches.Simulation tools are used to analyze the effect of the auxiliary capacitance on reducing ripple in each voltage mode and the soft switching process,simulation also verifies the dynamic response performance of the circuit when the load changes suddenly,which verifies the correctness of the above theoretical analysis.