Model Predictive Control Of Multilevel Converter Based On Finite Control Set

Along with the rapid development of economy,the problems of energy crisis and environment pollution become more serious.The new energy technology has become the focus of the development of the energy.Multilevel inverter for converting DC to AC is an important part of the new energy power generation grid connection.The traditional control strategy of multilevel converter generally adopts double closed loops PI control,while there is no fixed way to design the PI parameters and the adjustment is difficult.FCS-MPC is a powerful control technique that has several advantages such as high accuracy,flexibility and stability,easy implementation,simple and understandable concepts,all the control requirements can be considered by one controller at the same time.This paper in the view of the finite control set model predictive control which was used in the multilevel converter,the main research is as follows:1)The research background and significance of the model predictive control based on the finite control set is introduced in this paper,presented a finite control set model predictive control,which is applied to improve the dynamic and steady state performance of the system.2)The theory of model predictive control has been described systematically.Firstly,the basic principle and mathematical model of FCS-MPC are expounded.Secondly,introduces the design process of FCS-MPC,including three kinds of discrete system model method(forward Euler,backward Euler method,midpoint Euler method),cost function definition and system constraints.3)The topology and basic working principle of the three-level inverter are introduced,and the corresponding FCS-MPC control algorithm is given.Through the comparison of three kinds of discrete system model of output current tracking the reference variable results.The feasibility of the model is verified by the three-level inverter and the performance of the system model by three discretization methods is compared.4)The working principle of MMC is described,the MMC mathematical model in three kinds of coordinates(abc,αβ,dq)is analyzed,the traditional double closed loop PI control and linear quadratic regulator control are introduced,the controller design process is deduced.The performance of the two control methods are compared by simulation.5)The model predictive control is applied to the six-level MMC.The objective function defined by FCS-MPC is used to control the output current of MMC,maintain the capacitor voltage balance and suppress the circulating current.