Robust voltage model flux estimator design with parallel vector compensator for sensorless drive of induction motors
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ORIGINAL ARTICLE
Robust voltage model flux estimator design with parallel vector compensator for sensorless drive of induction motors Gwon‑Jae Jo1 · Jong‑Woo Choi2 Received: 7 May 2020 / Revised: 26 August 2020 / Accepted: 31 August 2020 © The Korean Institute of Power Electronics 2020
Abstract Flux estimator (FE) is critical for achieving high-performance sensorless drive of induction motors. A voltage model (VM) is an excellent candidate for a FE since it does not require speed information and has a simple structure. A VM using a closed-loop style has excellent sensorless drive capability over a wide speed range. However, it is limited by the uncertainties such as offset and parameter mismatch. This paper presents an improved a closed-loop style FE. To overcome the problems inherent in the conventional FE, a hybrid strategy for the changeover between control modes is applied. In the setting of the FE’s cutoff frequency (CF), the influences of the offset and parameter mismatch are analyzed. The phase distortion and acquisition of the back electromotive force are also analyzed. From this analysis, a vector compensation strategy for the flux linkage is applied. This strategy facilitates the CF setting, which improves the robustness against both the offset and parameter mismatch. Finally, the effectiveness of the proposed FE in a sensorless driven induction motor is verified using simulations and experiments under various conditions. Keywords Cutoff frequency (CF) · Induction motor · Sensorless drive · Flux estimator (FE) · Voltage model (VM) · Back electromotive force (back-EMF)
1 Introduction Induction motors have high durability as well as low initial and maintenance costs. Thus, they are ideal for use in a wide range of areas and have been shown to be excellent actuators in recent years. Information on speed and flux is essential for achieving field-oriented control of induction motors. However, speed sensors have the disadvantages of high installation costs and vulnerability to heat and mechanical vibrations. Moreover, their installment makes inverter drive system complex and bulky. As a result, many studies on the sensorless control of induction motors have been recently reported, where a number of methods of flux estimator (FE) design have been proposed. State observer-based flux estimations have been studied in [1–12]. However, these models * Jong‑Woo Choi [email protected] 1
School of Electronic and Electrical Engineering, Kyungpook National University, Daegu, South Korea
Department of Electrical Engineering, School of Electronic and Electrical Engineering, Kyungpook National University, Daegu, South Korea
2
require speed information and/or complex structures. Thus, they are not preferred for sensorless drives. Since a voltage model (VM) does not require speed information and has a simple structure, it is a very good estimator in sensorless drives. In practical inverter systems, the inverter nonlinear characteristic and current A/D measurement offset produce dc offset components in the voltage a
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