Control Strategy Of Multi-Port Converter With AC Source

Multi-port converter has become a hot topic of domestic and foreign scholars,especially in the fields of energy Internet,distributed generation systems and vehicle-to-grid energy technologies,because of its high integration,flexible expansion and high power density.In this paper,a multi-port converter is choosen as the research object,and a typical three-port converter topology with an AC source is proposed.Based on this topology,the corresponding control strategy is studied,and the simulation and hardware experiment are carried out to demonstrate the effectiveness of the proposed strategies.Firstly,Same typical topologies of the multi-port converter and DC-AC converter are introduced,and same typical control strategies used in multi-port converters are introduced briefly.Then taking three-port converter as an example,a specific solution for using one port as a harmonic compensation and storage port is proposed to solve two main problems including double-frequency harmonic and energy storage in three-port converter with an AC grid.Secondly,in the specific solution,a three-port converter topology with an AC source is proposed,and a central symmetric phase shift modulation strategy is adopted.The power transfer equation of the dual-active bridge converter is firstly derived by the fundamental approximation method.Then the power transfer equation and the terminal current equation of the three-port converter with an AC source are derived.To simplify the mathematical model and the power coupling relationship,Internal shift angles are selected as the control variable while outer shift angles are fixed.Then,the small signal model on the DC side and AC side are formulated respectively,where the small signal model on the AC side is established in dq synchronous frame.Finally,four typical working modes are analyzed and related typical applications are introduced.Then,a frequency division control strategy is applied to the three-port converter,where a high bandwidth controller is designed on the DC side while a low bandwidth controller is designed on the AC side.Specific controllers are designed by frequency domain analysis.Both active and reactive power on the AC side can be controlled by adjusting the d-axis component and q-axis component in dq synchronous frame.The essential reason of the resonance on the closed-loop system caused by the LC filter of the DC side and the AC side port is analyzed,and corresponding virtual damping controllers are designed to suppress the resonance.A three-port converter simulation model with an AC source is built in the MATLAB/Simulink simulation environment,and the control strategies including the comparison of actual damping and the virtual damping,the influence of different controller bandwidth,and two typical work are simulated,which verify the correctness of the design controller.Finally,a 300 W experimental prototype is built for comprehensive verification.The key components such as the power switch and the equivalent leakage inductor in the hardware circuit were selected and designed respectively.At the same time,the discrete control system is designed based on the ARM+FPGA dual-core controller.The scientific and correctness of the topology and corresponding control strategies proposed in this paper are verified by comprehensive comparison of experimental waveforms and simulation waveforms.