Dynamic Modeling And Control Strategy Optimization Of Range-Extender For Electric Vehicle

With the increasingly serious problems of environmental pollution and energy security,new energy vehicles have gradually become academic and commercial hotspots.Range-extended electric vehicles are ideal models for the transition from traditional fuel vehicles to pure electric vehicles at the current stage due to their long cruising range and pure electric drive.Range extender is one of the core power components of range-extended electric vehicles,and the quality of its control strategy plays a decisive role in the performance of range extender,such as power follow-up,fuel consumption,and emissions.In the V-mode development process of the modelbased range extender controller,the controlled object model of the range extender is an indispensable part,and it is the basis and the premise for carrying out the model-in-loop verification and the hardware-in-loop simulation verification of the range extenderrelated strategy.In this paper,a permanent magnet synchronous range extender is used as the modeling object,and its dynamic modeling and parameter identification are carried out.Model-in-loop simulation is used to optimize the existing range extender control strategy.According to the system structure and working principle of the range extender,the paper designs the overall scheme of the range extender modeling,and clarifies the boundary of the controlled object model of the range extender.Aiming at the accuracy and calculation speed requirements of the controlled object model based on the model development process,the paper chooses to establish a dynamic model of the range extender,including the engine and the generator,by combining experimental data and physical principles.The engine system model establishes a two-dimensional look-up table model based on the test data,and describes its torque dynamic performance with a first-order inertia link;the generator system model is constructed based on physical principles and appropriately simplified.The entire generator system model is divided into speed request processing module,control current module,body module,and output current module to describe the functions such as generator speed control,d-axis and qaxis control current output,torque and speed calculation,and DC bus current output respectively.Aiming at the range extender model established above,the paper collected steadystate and dynamic operating data of the engine and generator based on the test method of the range extender,engine and motor,and identified the range extender model-related parameters by using multiple linear regression and least squares method,including the time parameters of the first-order inertia link of engine torque,the moment of inertia of the engine,the time constant of the first-order inertia link of the generator current,etc.,and the dynamic step test of the torque and the speed is used to verify the engine,generator and range extender models.The comparison results of model prediction and bench test show that the maximum relative error of torque prediction of range extender model is 14%,the maximum relative error of speed prediction is 3.2%,and the maximum relative error of current prediction is 11.9%,indicating that the range extender model constructed in the paper has high accuracy.Aiming at the power reverse overshoot problem in the actual operation of the range extender,based on the controlled object model of the range extender,the problem is carried out by building a range extender model in the loop simulation analysis environment that includes the control strategy model of the range extender.After reproducing and simulation analysis,it is found that the root cause of the reverse power overshoot is that the response speed of the generator to the speed request is higher than the response speed of the engine to the torque request.On this basis,the paper proposes to add a first-order inertia filter to the generator speed request,and at the same time change the optimization method from the closed-loop control of the generated power based on the mechanical power request to the control based on the engine torque request.Model-in-loop simulation results show that the optimized range extender control strategy can reduce the power overshoot by up to 89.8% and the response time by up to38% compared to before optimization,indicating that the optimization method is effective in suppressing the power reverse overshoot of the range extender.