Research on the Nonlinearity Characteristics of VRB-Boost Converter System

The nonlinear behavior of VRB-Boost converter system is crucial to the safety and stability of microgrid. Furthermore, the nonlinear behavior can be influenced by the state variables, such as the state of charge(SOC) and the load impedance. Firstly, a mathematical model of the vanadium redox flow batteries (VRB) is established based on VRB’s electrical characteristics with consideration of the state of charge. Then, a discrete iterative mapping model of the current-controlled Boost converter is developed based on the stroboscopic mapping method. Thus, an unified model of the VRB-Boost converter system is established based on the above mentioned models. The unified model is then used to analyze the causes of the system’s nonlinear behavior induced by the SOC and load R. Simulation is conducted to obtain the bifurcation diagram of the system output varying with the SOC of VRB and the load R. Through comparison of the bifurcation diagrams under different conditions of state variables, the impact characteristics of the SOC of VRB and load R on the system’s nonlinear behavior are obtained. The experimental results proves the correctness of the theoretical analysis.