| As a solution that combines the advantages of low emission,high efficiency,and long range,the extended-range electric vehicle is currently a research hotspot in the new energy vehicle industry.The fast response and stable operation of the range extender system is the premise of the vehicle energy management,which is of great significance to improve the efficiency of the range extender and even the vehicle efficiency.In this dissertation,the control strategy of the range extender system is studied to improve the response performance of the engine speed and generator torque at the same time,so as to improve the rapidity and stability of the power output.The main research contents are as follows:In order to establish an accurate model of the range extender system and reduce the influence of the engine feedback torque error on the model,an improved modeling method of the range extender system is proposed.By adding the delay time uncertainty into the engine torque transfer function,the accuracy of the engine torque response model is improved,and by increasing the freedom of the speed model,the accuracy of parameter identification is optimized.The model response curve and the experimental data curve under the same torque command are compared,which verifies the accuracy of the model.Aiming at the problems of parameter uncertainty in the system model and the coupling relationship between the speed and torque of the range extender,a multi-input and multi-output range extender control strategy based on the robust algorithm and parameter uncertainty is proposed.The control scheme considers the interval estimation of model parameters,and coordinates the engine and the generator to reach the optimal speed and torque synchronously,achieving the purpose of fast output of the required power.In addition,the problem of power reverse undershoot is solved by increasing the constraint of generator torque command and adopting the constraint treatment method of anti-saturation.The Simulink platform is built for testing,and the results show that,the proposed method improves the dynamic performance of the range extender system.In order to reduce the influence of torque constraints on the system control performance and further improve the dynamic performance of range extender system when the reference power changes frequently,a range extender model predictive control strategy considering the torque command error is proposed.The strategy adds the error between the current torque command and the steady-state torque command into the cost function,and improve the power response speed and the engine torque control performance by dealing with the constraints online.The explicit expressions of MPC under different constraints are obtained by considering the characteristics of quadratic penalty function,and the stability of the system is analyzed by calculating the eigenvalues.The simulation results verify the effectiveness of the proposed range extender control strategy.Aiming at the problem of long online solution time and high computational load of model prediction controller,a range extender model predictive control strategy based on Gerschgorin Circle Theorem and eigenvalue estimation is proposed.In this strategy,a new iterative algorithm of penalty coefficient is provided on the basis of adding quadratic penalty function for the specific range extender system.The algorithm establishes a state space equation related to the penalty coefficient,which ensures the convergence and convergence rate of the algorithm by limiting the eigenvalues of the system matrix within the unit circle.Simulation results verify the effectiveness of the proposed algorithm.Finally,in order to further verify the effectiveness and practicability of the proposed algorithm,the experimental results and comparative analysis are given by building a range extender bench system and designing a series of experimental test schemes.The bench experiment results show that,the proposed control strategy can effectively improve the dynamic performance of the extender system,which have high practical value. |
