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This paper proposes a novel mesh-based equivalent magnetic network (EMN) model for performance analysis and optimal design of permanent magnet (PM) machines. The key contribution of the EMN model is that a generalized air-gap model solution is proposed by considering the machine motion of PM machines. Meanwhile, a modular modeling method is presented, and then the optimal design of PM machines can be investigated without repetitive programming and modeling. Two kinds of mesh elements are comprehensively utilized in the EMN model, and a hybrid rotor PM (HRPM) machine with interior PM and surface PM configuration is selected as an example to illustrate the development processes of EMN model. Meanwhile, the electromagnetic characteristics of HRPM machine are calculated by the proposed EMN model, such as back electromotive force, air-gap flux density distribution, and average torque. Finally, the accuracy and effectiveness of the proposed EMN model are verified through comparisons with finite element analysis and experimental tests. [ABSTRACT FROM AUTHOR]

In this paper, by solving the Maxwell's equations, an analytical model is developed for the prediction of the air gap flux density in the eccentric permanent magnet (PM)-inset machines at no-load and on-load conditions. Since in this model neither Schwartz–Christoffel transformation nor perturbation analysis is used, it is fast and accurate. In the modeling process, the stator of the eccentric machine is replaced with an equivalent surface current (ESC), which is injected at the stator bore. Distribution of the ESC is unknown and must be selected, such that the resultant tangential field satisfies the boundary condition at the stator bore contour. To apply this condition, the flux density of the PMs, armature current, and the ESC are obtained by applying the subdomain analysis and using a conformal transformation. The armature current and ESC are considered as a surface current sheet at the stator bore. The back electromotive force and inductances of the eccentric machine are obtained in the proposed model. In addition, using the Maxwell stress tensor, the unbalanced magnetic force, and the electromagnetic torque are computed. Finally, the model is verified by means of finite element analysis. [ABSTRACT FROM AUTHOR]

Dual stator-winding induction generator (DWIG) is one kind of emerging multiport electrical machine. It has become a promising direction in the last two decades, especially for stand-alone power systems and renewable energy power systems. This paper mainly focuses on the DWIG with similar-poles stator windings and cage-type rotor. An overview of DWIG and its system is given. Recent advances of this generator in system topologies, mathematical model, optimal design, control strategies, and performance analysis are presented. The developments and potential applications of the DWIG-based system are also discussed. [ABSTRACT FROM AUTHOR]

A parameter estimation method for deep-bar induction machines is presented. The parameters are estimated using two instantaneous voltage and current waveforms during a direct startup. The instantaneous input impedance is used as a stator indicator to solve a constrained nonlinear optimization problem that outputs the model's parameters. For such purposes, a novel analytical expression for the instantaneous input impedance is introduced. The method is validated in two distinct National Electrical Manufacturers Association (NEMA) design type induction machines (designs A and B), and the accuracy of the obtained parameters is determined by comparing the instantaneous input impedance magnitude and angle errors between the deep-bar and single-cage models with experimental data. The two tested motors showed an improvement when implementing the deep-bar model with the estimated parameters. The error decrease is more significant for the NEMA design B motor which corresponds to a deep-bar rotor construction. Finally, the single-cage and deep-bar models are simulated and their outputs are compared to experimental waveforms. The deep-bar model with the estimated parameters outperforms the single-cage model, showing excellent agreement between the experimental and simulated mechanical speed, stator currents, and electromagnetic torque. The results endorse the accuracy of the method and its applicability for transient studies. [ABSTRACT FROM PUBLISHER]

Six-phase electrical machines have received significant attention in the literature due to their use in special purpose applications (e.g., aircraft, naval, and vehicular systems). Recently, such machines have also been considered for renewable energy systems including wind generators. Modeling of such machines in commonly available transient simulation programs is not straightforward, especially when the machine model is interfaced with external inductive network and/or power electronic converters. The available modeling approaches include the classical qd 0 model, the coupled-circuit-phase-domain and the voltage-behind-reactance (VBR) models (each having its interfacing challenges). This paper extends the prior research in this area and proposes a constant-parameter VBR model that has a very convenient constant RL−branch interfacing circuit (even for salient pole machines), which makes it simple to implement in most state-variable-based simulations programs. The presented computer studies demonstrate significant numerical advantages of the new model over the existing alternative models. [ABSTRACT FROM PUBLISHER]

This paper presents and experimentally validates a new control scheme for electrical drive systems, named cascaded predictive speed and current control. This new strategy uses the model predictive control (MPC) concept. It has a cascaded structure like that found in field-oriented control or direct torque control. Therefore the control strategy has two loops, external and internal, both implemented with model predictive control. The external loop controls the speed, while the inner loop controls the stator currents. The inner control loop is based on Finite Control Set Model Predictive Control, and the external loop uses MPC deadbeat, making full use of the inner loop's highly dynamic response. Experimental results show that the proposed strategy has a performance that is comparable to the classical control strategies but that it is overshoot-free and provides a better time response. [ABSTRACT FROM PUBLISHER]

This paper proposes a new simplified model of a doubly fed induction generator (DFIG) that is integrated with a rotor-side converter for studies of large-scale transient stability. This model accurately considers the rotor field dynamics of an induction generator to yield simulation results that are more accurate in terms of voltage stability, as well as angle stability. The purpose of this paper is to provide a simple but effective DFIG model for the study of large-scale transient stability, and to examine the important aspects of rotor voltage and rotor slip power. This new simplified DFIG model with an electric/turbine control system was tested against a six-machine and 23-bus system, and the responses obtained in case studies of transient stability were compared with those of a PSS/E program. Finally, the proposed DFIG model was also validated by comparing the simulation results for a single-machine and infinite-bus system with those of PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

A new method of hierarchically partitioning the numerical calculations associated with the finite-element analysis of rotating electrical machinery is set forth. In this method, the device is partitioned geometrically and hierarchically into its constituent subsystems. Each Newton–Raphson iteration in a magnetically nonlinear device involves the hierarchical solution of relatively compact linear algebraic equations. This is contrasted with conventional approaches involving the formation or updating and solution of a single but large-dimensional sparse equation. In addition to an improvement in the computational efficiency, this approach facilitates efficient management of rotation. The proposed approach is demonstrated to require less than one-fourth the computation time, while producing identical results to those of a conventional formulation when solving for cogging torque and back electromotive force (back-EMF) of a permanent-magnet synchronous machine. The numerical results are also shown to be in agreement with the measured data. [ABSTRACT FROM AUTHOR]

An interior permanent-magnet (PM) motor is modeled by a combined analytical–numerical approach, in which the relationships between the stator currents and flux linkages are identified with static finite-element (FE) analysis. In addition to the previous approaches using the current space vector as the state variable, new models are also developed using the flux-linkage space vector, which leads to more convenient time-integration of the voltage equations. In order to account for the zero-sequence effects in delta connection, the models also include either the zero-sequence flux or current as an additional state variable. Finally, the possibilities of deriving the required quantities as partial derivatives of the magnetic field energy are discussed. The energy-based approaches avoid inaccuracies related to torque computation and thus allow better satisfying the power balance in the state-space model. We show the ability of the developed state-space models to predict the currents and torque equally to a nonlinear time-stepping FE model with much less computational burden. The results are validated by means of measurements for a prototype machine in both star and delta connections. In addition, we also demonstrate the effect of the zero-sequence current on the torque ripple in case of a delta-connected stator winding. [ABSTRACT FROM PUBLISHER]

The doubly fed induction generator (DFIG) is normally controlled with stator-flux orientation. The DFIG is a poorly damped system with a natural frequency near the grid frequency. This leads to natural oscillations on the stator flux and on other variables. When voltage dips occur, there are oscillations on the stator flux that produces electromotive forces and consequently disturbances on the rotor currents. This paper presents a comprehensive study of the DFIG during voltage dips. The method presented in this paper, valid for symmetric and for asymmetric voltage dips, is based on the classical model of the induction machine with stator flux orientation and neglects only a small part of the cross-coupling terms. The response depends on the design methodology of the proportional-integral inner controllers. Analytical, simulation, and experimental results are shown. The analysis and results can be divided into two sets depending if the voltage dip magnitude is smaller or deeper than 0.5 p.u. [ABSTRACT FROM PUBLISHER]

This paper presents a nonlinear parameter estimator for synchronous machines based on the unscented Kalman filter. The proposed methodology uses voltages and current signals recorded from the stator and the field winding to update the parameters of the classical model of the synchronous machine for stability studies. The methodology can be applied without interrupting the normal operation of the generator. Park's Transformation is included in the estimation process to relate the stator measurements (in abc components) to the nonlinear voltage equations in the qd0 reference frame. The proposed robust methodology has been validated using real and simulated data to estimate the model parameters of a 483-MVA round rotor machine. [ABSTRACT FROM PUBLISHER]

The application of the synthetic loading technique to permanent magnet (PM) synchronous machines is investigated. Mathematical equations for synthetic loading are developed. From the equations, a quadrature-axis current algorithm is proposed from which rotor speed and the stator direct- and quadrature-axis voltage and current equations are derived. The impact that synthetic loading frequency has on the dc-link voltage and the inverter phase-leg volt-ampere rating are analyzed. This shows that the synthetic loading technique requires an increased dc-link voltage and inverter volt-ampere rating compared to the standard efficiency test method. Synthetic loading is verified experimentally using a surface-mount PM synchronous machine. Simulation and experimental results are compared with the standard efficiency test. The simulation and the experimental results show that the synthetic loading technique is capable of evaluating the losses in the PM synchronous machine. [ABSTRACT FROM PUBLISHER]

This paper investigates the opportunity for energy saving in a three-phase induction motor (IM) driving pump load and proposes an improved loss model control (LMC). Compared with other power-loss reduction algorithms for IM, the presented one has the advantages of fast and smooth flux adaptation, high accuracy, and versatile implementation. The performance of LMC depends mainly on the accuracy of modeling the motor drive and losses. In this paper, the derived loss model considers the surplus power loss caused by inverter voltage harmonics using closed-form equations and also includes the magnetic saturation. An artificial neural network controller is synthesized and trained offline to determine the optimal flux level that achieves maximum drive efficiency. The drive's voltage and speed control loops are connected via the actual stator frequency, making the scheme comparatively reliable. Simulation and experimental studies are performed on 5.5-kW test motor using the proposed control method. The test results are provided and compared with the fixed flux operation to validate the effectiveness. [ABSTRACT FROM PUBLISHER]