Controlled Interior Permanent Magnet Research Articles

Direct torque and flux control of an IPM synchronous motor drive using a backstepping approach

A novel direct torque and flux controlled interior permanent magnet synchronous motor (IPMSM) drive using an adaptive backstepping technique is presented. Closed-loop regulation of the speed, torque and stator flux linkage is achieved by a non-linear controller. Using Lyapunov analysis, the stability of the controller is guaranteed. The reference voltage vectors are generated by a space vector modulation (SVM) unit, which replaces the switching table in the conventional direct torque control (DTC) scheme. While retaining its main advantages, the proposed backstepping controller features reduced torque and flux ripples as compared to the classical DTC. On the one hand, a comparison with the proportional–integral (PI) direct torque and flux control (DTFC) scheme shows that the proposed approach is superior. Experimental results confirm the effectiveness of the proposed method.

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.

Direct Flux Field-Oriented Control of IPM Drives With Variable DC Link in the Field-Weakening Region

This paper presents the direct flux control of an interior permanent-magnet (IPM) motor drive in the field-weakening region. The output torque is regulated by the coordinated control of the stator flux amplitude and the current component in quadrature with the flux, and it is implemented in the stator flux reference frame. The control system guarantees maximum torque production taking into account voltage and current limits, in particular in case of large dc-link variations. The field-oriented control does not necessarily require an accurate magnetic model of the IPM motor, and it is able to exploit the full inverter voltage at different dc-link levels with no additional voltage control loop. The feasibility of the proposed control method is investigated in discrete-time simulation, then tested on a laboratory rig, and finally implemented on board of an electric scooter prototype. The motor under test is an IPM permanent-magnet-assisted synchronous reluctance machine, with high-saliency and limited permanent-magnet flux.

Application of neural networks for permanent magnet synchronous motor direct torque control

Neural networks require a lot of training to understand the model of a plant or a process. Issues such as learning speed, stability, and weight convergence remain as areas of research and comparison of many training algorithms. The application of neural networks to control interior permanent magnet synchronous motor using direct torque control (DTC) is discussed. A neural network is used to emulate the state selector of the DTC. The neural networks used are the back-propagation and radial basis function. To reduce the training patterns and increase the execution speed of the training process, the inputs of switching table are converted to digital signals, i.e., one bit represent the flux error, one bit the torque error, and three bits the region of stator flux. Computer simulations of the motor and neural-network system using the two approaches are presented and compared. Discussions about the back-propagation and radial basis function as the most promising training techniques are presented, giving its advantages and disadvantages. The system using back-propagation and radial basis function networks controller has quick parallel speed and high torque response.

Feedback-Linearizing Control of IPM Motors Considering Magnetic Saturation Effect

This paper describes feedback-linearizing control of interior permanent magnet (IPM) motors which operate in magnetic saturation. First, we propose a current tracking controller for direct control of stator currents. Then, we explicitly characterize all torque controllers that can make the motor torque of an IPM motor exactly linear with respect to torque command even if magnetic saturation occurs. In particular, our torque controller contains a free function that can be used to achieve other control objectives as well as linear dynamic characteristics. Finally, the free function is chosen so optimal as to maximize power efficiency. The practical use of our control method is demonstrated through various simulation and experimental results.

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.

On Considering Magnetic Saturation with Maximum Torque to Current Control in Interior Permanent Magnet Synchronous Motor Drives

The influence of magnetic saturation on maximum torque to current controlled interior permanent magnet synchronous motor drives is discussed in this paper. A maximum torque to current condition that takes into account magnetic saturation and determines the optimal d-axis current is derived. For the implementation of the proposed controller, an experimental procedure is used to adjust its parameters, therefore, the knowledge of the exact motor model is not required. Selected experimental results are presented to verify the theoretical considerations and to confirm the high performance of the suggested controller.

On considering magnetic saturation with maximum torque to current control in interior permanent magnet synchronous motor drives

The influence of magnetic saturation on maximum torque to current controlled interior permanent magnet synchronous motor drives is discussed in this paper. A maximum torque to current condition that takes into account magnetic saturation and determines the optimal d-axis current is derived. For the implementation of the proposed controller, an experimental procedure is used to adjust its parameters, therefore, the knowledge of the exact model is not required. Selected experimental results are presented to verify the theoretical considerations and to confirm the high performance of the suggested controller.

High Efficiency Controlled Interior Permanent Magnet Synchronous Motor for Air conditioner fed by Sine-wave PWM Inverter

High Efficiency Controlled Interior Permanent Magnet Synchronous Motor for Air conditioner fed by Sine-wave PWM Inverter