Torque Controlled Interior Permanent Magnet Research Articles

Direct Torque Control of Interior Permanent Magnet Synchronous Motors Based on Full-order Sliding-mode Flux Observer

This paper proposes a full-order sliding-mode stator observer. The observer takes the stator current and “active flux” as the state variables in the stationary reference frame, and can realize “active flux” estimation in the direct torque controlled interior permanent magnet synchronous motor driving system. Therefore, the stator and electromagnetic torque can be calculated with estimated active flux according to the relationship between active flux, stator and electromagnetic torque. As a result, the IPMSM high-performance speed closed-loop control is achieved. Simulation results are presented to validate the effectiveness of the proposed method.

An Inverter Nonlinearity-Independent Flux Observer for Direct Torque-Controlled High-Performance Interior Permanent Magnet Brushless AC Drives

This paper introduces a novel flux observer for direct torque controlled interior permanent magnet brushless AC (IPM-BLAC) drives over a wide speed range including standstill. The observer takes machine nonlinearities into account and is independent of inverter nonlinearities, dead time, and armature resistance variation at steady states since such inaccuracies are compensated quickly by measured phase currents. Magnetic saturations in the stator and rotor cores, cross-coupling effects of flux linkages of the motor, and spatial harmonics in the magnetomotive force are all considered in the novel scheme. There is no filter; hence, no delays and oscillatory responses like in conventional schemes where filters are employed to prevent integrator drift issue. Superiority of the observer when compared to the state-of-the-art schemes has been illustrated by both extensive simulations and experimental results of a 10-kW IPM-BLAC machine designed for traction applications.

Rotor Position and Speed Estimation of a Variable Structure Direct Torque Controlled Ipm Synchronous Motor Drive at Very Low Speeds

The performance of a speed sensorless variable structure direct torque controlled interior permanent magnet synchronous motor drive at very low speeds including standstill is investigated in this paper. The rotor position and speed are estimated using a high frequency signal injection algorithm at low speeds and a sliding observer at medium to high speeds. The changeover between these two algorithms is performed using a weighting function that smoothly hands over estimated flux and speed information for torque estimation and speed feedback purposes, respectively. Experiments were performed to test the effectiveness of the proposed high frequency signal injection algorithm, and results show that the sensorless drive is capable of accurately estimating position and speed at very low speeds, including standstill.

Variable Speed Wind Power Generation System Using Direct Torque Control Suited for Maximum Power Control within Voltage and Current Limitations of Converter

This paper proposes a variable speed wind generation system using a direct torque controlled interior permanent magnet synchronous generator. The proposed system has no wind speed and generator position sensors, and thus, it is considered that the proposed system has cost and reliability advantages. The proposed direct torque control (DTC) system in wind power generation has several advantages over conventional current control. First, DTC is well suited for the maximum power point tracking (MPPT) control that is implemented by controlling the generator torque. Second, the method of flux-weakening to maintain the terminal voltage at the limiting value of the converter is simple. Finally, a novel method is proposed for torque limiting, which makes it easy to maintain the armature current at the limiting value. The proposed method accomplishes current limiting using the reactive torque, which is calculated as the inner product of the flux and current. This does not require generator parameters such as magnet flux and inductances. Experimental results demonstrate the effectiveness of the proposed system using a wind turbine emulator instead of the actual wind turbine.

A Novel Direct Torque Controlled Interior Permanent Magnet Synchronous Machine Drive With Low Ripple in Flux and Torque and Fixed Switching Frequency

A modified direct torque control (DTC) scheme for interior permanent magnet synchronous machine (IPMSM) is investigated in this paper, which features in very low flux and torque ripple and almost fixed switching frequency. It is based on the compensation of the error flux linkage vector by means of space vector modulation. Modeling and experimental results show that the flux and torque ripples are greatly reduced when compared with those of the basic DTC. With the new scheme, very short sampling time is not essential. All the advantages of the basic DTC are still retained. In addition, fixed switching frequency at different operating conditions becomes possible. The field-weakening control of this drive is also studied; an IPM DTC drive with a wider operation range and lower flux and torque ripple has been achieved experimentally.

An improved flux linkage estimator for a direct torque controlled interior permanent magnet synchronous machine drive

In a direct torque controlled (DTC) drive, accurate flux estimation is the key to achieve good steady-state and dynamic performance. The effects of the stator resistance variation of the stator resistance and the forward voltage drops of the power switches are analysed and mitigated in this paper. Modelling and experimental results confirm the effectiveness of the proposed flux estimator.

A sensorless initial rotor position estimation scheme for a direct torque controlled interior permanent magnet synchronous motor drive

In direct torque control (DTC) scheme, the requirement of the continuous rotor position sensor and coordinate transformation is eliminated since all the calculation is done in stator reference frame. However, the DTC scheme requires the position sensor to determine the initial position of the rotor at starting. Elimination of the shaft-mounted position encoder is a very desirable objective in many applications since this sensor is often one of the most expensive and fragile components in the entire drive system. This paper presents a sensorless method of determining the initial rotor position of a direct torque controlled interior permanent magnet (IPM) synchronous motor drive. The method consists of injecting a high frequency voltage to the windings and examining the effects of the saliency on the amplitude of the corresponding stator current components. This method does not depend on the level of static load and on any motor parameters. The magnet polarity of the rotor at its initial position is also identified using the effect of saliency. Modeling and experimental results verify the effectiveness of the proposed method.