Speed Sensorless Model Predictive Control Of Three-level Inverter-fed Induction Motor Drives

There are many characteristics for model predictive control(MPC),such as intuitive concept and dealing nonlinear constraints easily.It has obtained increasing attention and research in both academia and industry.In this thesis,MPC is deeply studied for the application of the adjustable-speed induction motor(IM)drive fed by a three-level Neutral-point-clamped(3L-NPC)inverter.Meanwhile,the speed sensorless operation is achieved.Neutral point(NP)fluctuation is an inherent problem in 3L-NPC topologies and usually needs considering in modulation strategies.Therefore,the modulation strategy of 3L-NPC inverters is more complicated than the traditional two-level one.In this paper,sinusoidal pulse width modulation(SPWM)and space vector modulation(SVM)are studied and the previous studies are summarized.Based on the research results,a novel zero-sequence component injection strategy is proposed,which can make SPWM equivalent to SVM.Further,a unified judgment conditions and injection formulas in the entire complex plane are given.The adaptive full-order observer(AFO)can realize the observation of the flux linkage and the rotation speed of the induction motor,and has the characteristics of high robustness and high estimation accuracy.The design of the feedback gain matrix is a research hotspot.This paper summarizes the common pole-moving class design scheme and proposes a new pole configuration strategy to achieve the unification of pole-moving class configuration schemes.The traditional MPC applied to a 3L-NPC inverter needs to tune 3 weighting factors and does not limit the shift of voltage vectors,which is not conducive to practical industrial applications.This paper presents a low switching frequency MPC with only two weighting factors.Then,two types of switching vector table are designed and verified experimentally.The average switching frequency of the system under various operating conditions is 600 Hz.At the same time,this thesis also proposes an MPC method from the perspective of directly suppressing switching losses,and carries out simulation verification.Based on the idea of deadbeat control,this paper proposes two kinds of no coefficient MPC strategy,which is suitable for high-performance adjustable-speed applications without strict restrictions on switching frequency.Without current loop parameter and weighting factors tuning,both of these methods are implemented in a stationary reference frame.At the same time,they have good dynamic performance and steady state performance.What’s more,this article takes one of the methods as an example to analyze the parameter robustness briefly.All methods proposed in this thesis can achieve speed sensorless operation and achieve NP voltage balance.In this paper,some of the more outstanding schemes are selected for experiment.The detailed comparisons of the current harmonics with field oriented control(FOC)and direct torque control(DTC)are performed,through which the effectiveness and superiority of the proposed MPC are validated.