Single-phase Three-level Rectifier Operated With Improved Model Predictive Power Control Based On Repetitive Control

High-speed railways play a vital role in China’s "Belt and Road" strategy,and the core power transmission technology of high-speed electric locomotives is a link that cannot be ignored.The CHR2 motor car uses a three-level topology.Therefore,this paper chooses a single-phase three-level rectifier topology as the research object.In the process of converting electrical energy from AC to DC with specific requirements,people have higher and higher requirements for power quality.From the perspective of single-phase three-level rectifier system power factor improvement,control accuracy optimization,and harmonic situation improvement,the following work was done:First,the working principle and mathematical model of the single-phase three-level rectifier are analyzed,and the double closed-loop control based on the voltage outer loop and the current inner loop and the direct hysteresis direct power control which are suitable for the rectification system are studied.Secondly,in order to improve the power factor and speed up the response,Model Predictive Control(MPC)has been applied to replace the existing control and modulation methods.However,traditional model prediction has problems such as low control accuracy and large tracking error.Aiming at these problems,an improved scheme based on two-step prediction is proposed,and the iterative control based on the inner membrane principle is used to optimize the given value of the reference power to improve the tracking error of the instantaneous power.At the same time,the causes of the modeling errors of traditional model predictive control are analyzed,and the compensation error values ??are corrected by feedback.Thirdly,on the single-phase three-level rectification system,an improved method is applied to derive the prediction model and evaluation function of the model predictive power control.A simulation model was built for comparative simulation.The simulation results show that the single-phase three-level rectifier uses model predictive control instead of the traditional modulation link,which is capable of achieving fast dynamic response at low switching frequencies.The rectifier system can significantly reduce the tracking error of active and reactive power after adding repetitive control and modeling error compensation,improve the harmonic situation on the grid side,and improve the control effect of the system.Finally,a single-phase three-level topology experimental platform is built on the basis of the simulation result,and a comparative experiment is performed on the above control methods by using DSP as the core control hardware.Experimental results and simulation results confirm each other.