Encoderless Predictive Flux Control of Three-level NPC Converter-fed Induction Motor with SMO

In this work, we proposed an encoderless finite control set predictive flux control (FCS-PFC) method for an induction motor (IM) fed by a three-level neutral-point clamped (3L-NPC) power converter. The FSC-PFC employs stator flux vector as control objective to eliminate the weighting factor(s) between torque and flux commonly used in the predictive torque control (PTC) approach. An improved sliding-mode observer (SMO) is applied to achieve encoder-less control, where the feedback speed signal is not necessary, which is novel add-on to the state-of-the-art solutions. Simulation and experimental results verify the effectiveness of the proposed encoderless PFC method.

I. Introduction

Advanced control techniques for electrical drives are important and have been attracting increasingly much attention in facing the new era of electrical-mobilities and introduction of wide-band-gap power electronic devices. With the explosive development of the electrical vehicles in recent years, effective motor control strategy plays a key role to achieve high efficiency, reliability with low cost. Field oriented control (FOC) and direct torque control (DTC) are two widely used control strategies for high performance electrical drives. However, the transient performance of the FOC is limited because of the constrained bandwidth using cascaded PI controllers. While the control variable ripples for the DTC are considerable and system performances can only be partially optimized with less flexibility, involving an offline designed switching table [1]. Rapid development of the digital controller enables the realization of model predictive control (MPC), which was developed/applied to power electronics and electrical drives in the early 1980s. Well recognized advantages of MPC include simple and intuitive concept, easy inclusion of the multiple objectives and constraints, global optimization and fast dynamics [2]. Many contributions with respect to MPC have been reported, covering different topologies and applications [3]–[5].