Conventional Current Control System Research Articles

Discretization Error Compensation Method in High‐Speed Motor Drive System by using Direct Torque Control

SUMMARYIn this paper, a discretization error compensation method in a motor drive system by using direct torque control (DTC) is proposed. Similar to a conventional current control system, DTC allows an efficient drive and a wide range drive. Furthermore, it has the advantage that its control system can be simple and theoretically it can realize sensorless position control. Therefore, a reference flux vector calculator (RFVC) DTC is studied as a system for the ultra‐high‐speed drive control of permanent magnet synchronous motors (PMSMs). In high‐speed drive, we revealed that a discretization error in the DTC generates an error in the instruction magnetic flux and stator magnetic flux. In addition, we revealed that current detection timing generates an error in the estimated torque and real torque. Then, we propose a compensation method to cancel the flux and torque error focusing on the phase of the stator magnetic flux and experimentally verifying its effectiveness.

直接トルク制御を用いた高速モータドライブシステムの離散化誤差補償方法

SUMMARY In this paper, a discretization error compensation method in a motor drive system by using direct torque control (DTC) is proposed. Similar to a conventional current control system, DTC allows an efficient drive and a wide range drive. Furthermore, it has the advantage that its control system can be simple and theoretically it can realize sensorless position control. Therefore, a reference flux vector calculator (RFVC) DTC is studied as a system for the ultra-high-speed drive control of permanent magnet synchronous motors (PMSMs). In high-speed drive, we revealed that a discretization error in the DTC generates an error in the instruction magnetic flux and stator magnetic flux. In addition, we revealed that current detection timing generates an error in the estimated torque and real torque. Then, we propose a compensation method to cancel the flux and torque error focusing on the phase of the stator magnetic flux and experimentally verifying its effectiveness.

An Adjusted Current Control System for Signal Injection‐Based Position Sensorless Control and Parameter Identification

SUMMARYThis paper proposes a current controller for signal injection‐based control schemes such as those for parameter identification and position sensorless control. In a conventional current control system with voltage signal injection, the separation of the injected frequency components from the current is carried out by using band stop filters. However, the separation is not accurate, especially when the system is in the transient state and/or when the current controller bandwidth is close to the injected signal frequency. This leads to distortion of the transient response and affects the stability of the current control system. The proposed controller estimates the injected frequency components in the current on the basis of a motor model by using the injected signal as the input. Therefore, accurate signal separation is accomplished even in the transient state. The current controller's stability and dynamic performance are improved significantly. Experimental results are presented to validate the proposed method. Factors that play an important role in the implementation of the controller, such as time delay and parameter variation, are discussed. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(1): 58–66, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22416

An Adjusted Current Control System for Signal-injection-based Position Sensorless Control and Parameter Identification

This paper proposes a current controller for signal-injection-based control schemes such as those for parameter identification and position sensorless control. In a conventional current control system with voltage signal injection, the separation of the injected frequency components from the current is carried out by using band stop filters. However, the separation is not accurate, especially when the system is in the transient state and/or when the current controller bandwidth is close to the injected signal frequency. This leads to the distortion of the transient response and affects the stability of the current control system. The proposed controller estimates the injected frequency components in the current on the basis of a motor model by using the injected signal as the input. Therefore, accurate signal separation is accomplished even in the transient state. Moreover, the current controller's stability and dynamic performance are improved significantly. Experimental results are presented to validate the proposed method. Factors that play an important role in the implementation of the controller, such as time delay and parameter variation, are discussed.

Current Control System for PMSM in Overmodulation Range of Inverter

This paper proposes a novel current control system for a PMSM that can stably operate even in the overmodulation range of an inverter. Because an inverter generates harmonic components in this range, an instability problem in the conventional current control system usually occurs. For solving this instability problem, the idea of harmonic current compensation scheme has already been proposed. However, the effectiveness of this method depends directly on the harmonic current estimation accuracy.There are two new topics in harmonic component estimation that we use in our proposed current control system as follows: (1) the harmonic voltage estimation method that is based on the conventional sinusoidal PWM modulation technique, and (2) the harmonic current estimation method that estimates correctly both in the steady state and transient condition. The effectiveness of the proposed methods is confirmed by computer simulation and experimental results.