Search

The bearing wear and looseness are significant failures in induction machines. For accurate recognition of the bearing faults, a new comprehensive modeling and analysis of induction machines with three degrees of freedom along with an effective method for loose bearing signature are presented in this article. For these purposes, the electromagnetic radial force and rotating torques are determined and applied to Euler–Lagrange equations of an induction machine. Besides, to better identify the defective loose bearings, the spectral analysis of neutral voltage is utilized. Comparing the experimental results with the outcome of the numerical analysis validates the proposed model. The results show that the spectral analysis of the neutral voltage detects mechanical looseness with higher precision than the conventional techniques such as mechanical vibrations and stator currents. [ABSTRACT FROM AUTHOR]

This article proposes a mathematical model for a switched reluctance (SR) generator feeding a dc link through a power electronic converter. SR machines are operated in single-pulse mode at close to and above base speed. The SR generator is modeled as a current source, controllable with dc-link voltage $V_{\text{dc}}$ , prime mover speed $\omega _m$ , and switching angles ($\alpha _{\text{on}}$ and $\alpha _{\text{off}}$) of the converter. This current source model is used to predict the dc-link dynamics for constant resistance, constant current, and constant power loads. This is further utilized to derive the voltage build-up condition for an SR generator. The generator model, dc-link dynamics and voltage build-up conditions are validated through simulations and experiments. [ABSTRACT FROM AUTHOR]

In the application of electric railway traction, induction machines may suffer momentary power interruptions. Restarting control while machine running is a critical part of such applications, but residual flux in the free-running rotor deteriorates conventional controller performances, leading to inrush current and torque impact. Thus, this article proposes an improved feed-forward current controller that compensates voltage variations in the restart process. The residual rotor flux, as well as the induced back electromotive force, is estimated only with the measured speed in the free-running stage. The exact electromotive force is compensated at the restart moment, and the following current re-establishing stage. Based on the feed-forward compensation, the restart impact is eliminated and the restart current is controlled accurately in the predefined trajectories. Verified by experiments, the restart controller provides flexible restart manipulations. [ABSTRACT FROM AUTHOR]

This paper presents an improved rotating restart method for a sensorless permanent magnet synchronous motor (PMSM) drive system using repetitive zero voltage vectors. To restart the sensorless PMSM drive system, a method for estimating initial rotor position and speed is required due to the absence of sensors such as encoders and resolvers. The rotor position and speed can be estimated using the short-circuit current vectors generated by applying zero voltage vectors. However, the estimated rotor position and speed can be inaccurate. The inaccurate rotor position that causes the current is distorted by the back-electromotive force of the PMSM, and it is impossible to precisely control the system. Therefore, an improved rotating restart method for the sensorless PMSM drive system using repetitive zero voltage vectors is proposed. The effectiveness of the proposed method is verified through simulation and experimental results using a 5-kW PMSM drive system. [ABSTRACT FROM AUTHOR]

During the unbalance operation of a standalone brushless doubly-fed induction generator (BDFIG), the negative sequence component causes significant unbalanced effect on the voltage and current of the power winding (PW). In this paper, a new control strategy is proposed to minimize the voltage unbalance effect of a standalone BDFIG under unbalanced loads. The proposed control strategy consists of two parts. The first part represents the conventional direct voltage control strategy to control the frequency and magnitude of the positive sequence PW voltage. The second part is the proposed strategy to minimize the negative sequence component in the output voltage of PW with a negative sequence compensator in the machine side converter. The dual second-order generalized integrator is used to extract negative-sequence component of the PW voltage. Proportional integral controllers are used to obtain reference of the control winding (CW) current which compensate the negative sequence component of the PW voltage. The proportional-integral-resonant controller is applied to regulate the CW current in positive reference frame. A prototype 30 kVA BDFIG test platform is developed in the laboratory to verify the proposed strategy. [ABSTRACT FROM AUTHOR]

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]

In this paper, a new synchronous machine model is developed for electromagnetic transients program type simulations. The stator circuit is expressed in the abc phase domain. The machine model is represented as a Norton equivalent with a current source in parallel with a constant Norton admittance. The machine equations are reformulated so that the computational effort required for the modeling of the machine is reduced. Test studies demonstrate the accuracy of the proposed synchronous machine model and show that the proposed model is computationally more efficient than the existing constant conductance phase domain model and voltage-behind-reactance model. [ABSTRACT FROM AUTHOR]

Copper-loss-minimizing torque control (CLMTC) method has been widely studied to reduce electromagnetic torque ripple and minimize copper loss of a brushless dc motor (BLDCM), but still suffers challenges to improve its performance. This paper presents a quantitative analysis of stator iron loss and current-loop delay effects on CLMTC. In the analysis, the iron-loss-included torque equation that only suits for sinusoidal back electromotive force (EMF) is modified to cover the case of nonsinusoidal back EMF. It is concluded that the iron loss effect brings about significant torque generation error and the delay effect leads to torque ripple that increases linearly with the delay angle. Two improvements are proposed, one of which redefines the condition of an optimal motor current vector to compensate for the iron loss effect. The other one aims to suppress the delay effect by preshaping current reference based on delay characteristic of the loop. The improvements can be performed effectively on a microprocessor to realize a better CLMTC method with reduced torque generation error and torque ripple. Both the analysis and improvements are experimentally validated on a 0.95 kW BLDCM setup. [ABSTRACT FROM AUTHOR]

Switched reluctance machines (SRMs) are witnessing increased interests and applications in the industry and scientific communities thanks to the advantages of rigid structures, high reliability and robustness, the absence of permanent magnets, fast dynamic response, and low manufacturing cost. SRMs have become a feasible and popular alternative to conventional electric machines, such as induction machines and permanent magnet machines, with variable speed drives in many applications. Since improving the electromagnetic and thermal performances of an SRM at the design stage is of significant value, this paper presents an in-depth literature review on the status and potential trends of the technology pertinent to the design and optimization of SRMs in the following aspects: the mathematical modeling of the electromagnetic and thermal fields in SRMs, the enhancement of the performances in terms of the torque ripple, acoustic noise, efficiency, and torque density, and the multiobjective design optimization incorporating all the above factors. Finally, the presence of SRMs and their design considerations for specific applications in electric vehicles, aircraft and aerospace systems, wind generators, high speed, and energy storage systems are extensively discussed in this paper. The existing approaches advancing the SRM technologies are systematically and comprehensively summarized and compared for each category. [ABSTRACT FROM AUTHOR]

This paper extends the application of a frame-angle-based (FAB) direct torque controller (DTC) for permanent magnet synchronous motor (PMSM) drives to low and very low speeds. The FAB-DTC is intended for PMSM drives that are fed by $3\phi$ six-pulse wavelet-modulated dc–ac converters. The foundations of the FAB-DTC are based on regulating the $d\text{--}q$ -axis stator voltages, in response to variations in the load torque and/or drive speed. The adjustments in $d\text{--}q$ -axis stator voltages are created by changing the angle $\vartheta$ of the frame spanned by the $d\text{--}q$ -axis stator voltages. In order to extend the FAB-DTC to low and very low speeds, the changes in $\vartheta$ are accompanied by changes in the maximum scale. The values of maximum scale and $d\text{--}q$ -axis stator voltages are used to update or change the reference signals employed by the wavelet modulation to generate switching pulses to operate a $3\phi$ dc–ac converter. The complete PMSM drive system incorporating the modified FAB-DTC is implemented for a 10-hp PMSM drive system. The performance of the FAB-DTC is investigated for different changes in the command torque for various low and very low speeds. Performance results demonstrate stable, fast, dynamic, and accurate responses, which have minor sensitivity to variations in load torque and/or drive speed. [ABSTRACT FROM AUTHOR]

For field-oriented control (FOC) of induction motors, accurate estimation of flux is important. Among the various flux estimation methods, the voltage model flux observer exhibits superior performance in situations where there is detuning of rotor parameters, such as rotor resistance and mutual inductance, because this model is robust to the detuning of these parameters. However, it is difficult to implement the voltage model, which includes pure integration, because of the dc saturation and dc drift problems. A number of methods have been developed to overcome this problem, including the Gopinath model flux observer, which can completely solve these problems. However, this model has a critical weakness in terms of parameter sensitivity in the mid-speed region because of the property of its characteristic function. In this paper, an analysis of parameter sensitivity of existing flux observers is discussed. A method for a voltage model flux observer design based on the Gopinath model is presented. Through an analysis of the characteristic function of the observer, the voltage model is designed. Finally, the operation of the proposed method is proven by simulations and experiments. [ABSTRACT FROM AUTHOR]

A global parameter estimation method for a permanent magnet synchronous machines (PMSM) drive system is proposed, where the electrical parameters, mechanical parameters, and voltage-source-inverter (VSI) nonlinearity are regarded as a whole and parameter estimation is formulated as a single parameter optimization model. A dynamic learning estimator is proposed for tracking the electrical parameters, mechanical parameters, and VSI of PMSM drive by using dynamic self-learning particle swarm optimization (DSLPSO). In DSLPSO, a novel movement modification equation with dynamic exemplar learning strategy is designed to ensure its diversity and achieve a reasonable tradeoff between the exploitation and exploration during the search process. Moreover, a nonlinear multiscale based interactive learning operator is introduced for accelerating the convergence speed of the $Pbest$ particles; meanwhile a dynamic opposition-based learning strategy is designed to facilitate the $gBest$ particle to explore a potentially better region. The proposed algorithm is applied to parameter estimation for a PMSM drive system. The results show that the proposed method has better performance in tracking the variation of electrical parameters, and estimating the immeasurable mechanical parameters and the VSI disturbance voltage simultaneously. [ABSTRACT FROM AUTHOR]

This paper focuses on the estimation of the rotor speeds of synchronous machines by means of phasor measurement units. This estimation is aimed at online monitoring of electromechanical transients and transient stability analysis. The proposed technique is based on the concept of frequency divider formula recently published by the first two authors in these Transactions. The dynamic state estimation is formally stated as a convex optimization problem and a thorough discussion of the sensitivity analysis of the optimal solution is provided. The case study considers a dynamic 1479-bus model of the all-island Irish system and discusses the effect of bad data, noise, and latency on the proposed estimation technique. [ABSTRACT FROM AUTHOR]

This paper deals with the speed and position estimation for synchronous reluctance motors (SyRMs) and interior permanent-magnet synchronous motors (IPMs). A unified design and analysis framework for a class of back electromotive force-based observers is developed and the links between apparently different estimation methods are brought out. State observers equipped with a speed-adaptation law are shown to be mathematically equivalent to voltage-model-based flux observers equipped with a position-tracking loop. The error signal driving the adaptation law or the tracking loop is presented in a generalized form. Using the framework, a stabilizing gain design is reviewed and detailed design guidelines are given. Selected observer designs are experimentally evaluated using a 6.7-kW SyRM drive and a 2.2-kW IPM drive. [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]

In this paper, the model predictive current control is introduced in the semicontrolled open-winding permanent magnet synchronous motor (OW-PMSM) generation system with a common dc bus to suppress the zero-sequence current for the first time. Particularly, the basic voltage vectors of the semicontrolled OW-PMSM, which are synthesized by the three-phase full-controlled converter and the three-phase uncontrollable diode bridge, is analyzed and their influences on the zero-sequence current are investigated for the first time in this paper. Then the current-error-based cost function that includes dq-axis current error and zero-sequence current error is designed to evaluate all the voltage vectors. Moreover, to further improve the steady-state control performance of the whole generation system, a zero-sequence current suppression method based on the uncontrollable side voltage vector adjustment, which has the advantage of low computation burden, is developed. In this method, two voltage vectors of the controllable converter are applied during one control period. Based on the distribution character of the basic voltage vector in the semicontrollable OW-PMSM generation system, the first voltage vector is selected according to the three-phase current direction to adjust equivalent vector of the uncontrollable diode bridge, whereas for the second voltage vector, the selection method based deadbeat voltage vector sector is designed to reduce the range of the candidate voltage vector. In addition, the vector durations are also computed. Finally, simulation and experiment are carried out to validate the proposed control approaches. [ABSTRACT FROM PUBLISHER]

Conventional finite control set-model predictive control (FCS-MPC) applies single voltage vector within each control period. This leads to relatively high steady-state ripples and requires fast sampling rate. Additionally, enumeration-based optimal vector selection is computationally intensive. Recently, double-vector-based schemes have been proposed to improve the steady-state performance of FCS-MPC. However, they are usually complicated in vector selection and duty ratio calculation. In this paper, a universal multiple-vector-based MPC (UMV-MPC) is proposed, which achieves the same performance as the state-of-the-art double-vector-based MPC, but executes in a much more efficient and universal way. Unlike conventional FCS-MPC, enumerating process and state predictions for candidate voltage vectors are not required in the proposed UMV-MPC to select the best voltage vectors. In UMV-MPC, the optimal vectors and duty ratios are directly constructed from deadbeat control (DBC) based on space vector modulation (SVM), which is easy to follow and quick to use. The proposed UMV-MPC is not only more efficient than prior methods, but also reveals the inherent relationship between double-vector-based MPC and DBC with SVM. A comparative study of UMV-MPC and prior double-vector-based MPC is carried out in this paper. The theoretical analysis as well as simulation and experimental tests on a 2.2-kW induction motor drive are demonstrated to validate the effectiveness of the proposed UMV-MPC. [ABSTRACT FROM AUTHOR]

In spite of the wide improvement in computer simulation packages, analyzing, and optimizing the simulation model, particularly under uncertainty can still be computationally expensive and time-consuming. This paper aims to tackle these features by proposing a comprehensive methodology applied to black-box stochastic simulation models under uncertainty. For this purpose, the common surrogate model as Kriging metamodel is served to fit the simulation input–output data produced by Latin hypercube sampling experimental design. Taguchi terminology of robust design enables the optimization methods to control uncertainty and uncontrollable environmental factors. So as to formulate robust counterpart optimization, three different models in the class of dual-response surface are integrated with metamodel and robust design. Leave-one-out cross-validation is applied to validate the Kriging metamodel. Finally, a numerical case study as a direct speed control of dc motor under uncertainty is served to demonstrate the applicability of the proposed method in real engineering problems. This simplified and practical mechatronics case illustrates how the proposed procedure can be expanded for analyzing and optimizing the real complex systems. [ABSTRACT FROM AUTHOR]

A basic, fast, and accurate steady-state finite-element analysis (FEA) based parameter and performance calculation method for the wound-rotor induction motor is presented. The method couples the circuit equations with field equations using the principle of frozen permeabilities to present the voltage-fed induction motor. The effects of saturation saliency and cross-magnetization are accurately taken into account. The method is verified by direct comparison with the current- and torque-slip frequency curves obtained from a commercial FEA package. [ABSTRACT FROM PUBLISHER]

This paper presents a fundamental study of voltage collapses that occur on a post-fault trajectory of a stressed power system in seconds after large disturbances. The focus of the study are voltage collapses that are induced by certain load models. Using an n-machine-N-bus power system model, the paper explicitly shows that the voltage collapse is caused by the non-existence of a real, positive solution for a load voltage magnitude in different areas of a relative rotor angle space when the load is of non-linear type. These “areas without voltage solution” are denoted as Voltage Impasse Regions (VIR) and are mathematically characterized as trigonometric functions of (n -1) relative rotor angles. Once the post-fault trajectory enters a VIR, voltage magnitude solutions become complex or negative, the algebraic Jacobian becomes singular, and the behaviour of a system becomes undefined. The case study has been carried out using a simple 3-machine-1-load system with static load models. In the study, VIR appeared and enlarged as the non-linear (constant power and constant current) load increased. Furthermore, the non-convergence of time-domain solution occurred exactly at VIR, thereby confirming that the problem is of structural nature. [ABSTRACT FROM PUBLISHER]

Flux-switching permanent magnet machine typically suffers from relatively high cogging torque due to its special doubly salient structure and high air-gap flux density, causing undesired torque ripples, as well as acoustic noise and vibration, especially at low speeds. In this paper, an analytical expression of cogging torque is derived based on a magnetomotive force-permeance model, through which the optimal design parameters and dimensions, such as combinations of stator slots and rotor poles, skewing angle, stator tooth width, rotor tooth width, and magnet thickness, can be determined. Based on the derived analytical model, two novel approaches for cogging torque reduction are proposed, i.e., asymmetric magnetomotive force and asymmetric permeance, respectively, and consequently, the optimal designs are also acquired analytically. However, it is also found that the optimal choice of the proposed techniques depends on the combinations of stator slots and rotor poles of the machines. Finally, the effectiveness of the proposed approaches is verified by both finite element analytical predictions and experimental results. [ABSTRACT FROM PUBLISHER]

Back-electromotive force (back-EMF) self-sensing is commonly used in induction machine (IM) drive systems for its maintenance cost and safety considerations. In recent years, compared with standard indirect field oriented control, deadbeat-direct torque and flux control (DB-DTFC) has been shown to be a highly effective method for IM control with a fixed switching frequency. It has advantages such as fast torque dynamics with one step dynamic response for torque and flux with no current regulator. This paper evaluates the synergy between back-EMF self-sensing technology and DB-DTFC for IM drive systems. In this paper, an observer-based closed-loop back-EMF tracking self-sensing control in an IM DB-DTFC drive system is presented. It includes a back-EMF state filter, back-EMF tracking observer, and cascaded motion observer. Back-EMF harmonic decoupling is explored to improve the low-speed performance. The band-pass filter method (BPF) for back-EMF self-sensing is also presented. Finally, the closed loop system dynamic stiffness at very low speeds, with and without the BPF method, is experimentally evaluated. [ABSTRACT FROM AUTHOR]

This paper proposes a resonant-based backstepping direct power control (BS-DPC) strategy for doubly-fed induction generator (DFIG) under both balanced and unbalanced grid conditions. Proper formulae for the BS-DPC strategy are obtained based on the elaborated analysis of the mathematical model of DFIG. The influence of the unbalanced grid voltage on the normal BS-DPC is analyzed. Furthermore, a resonant-based improved strategy is proposed to achieve different control targets under unbalanced grid condition without the need of decomposition of positive- and negative-sequence components. Comparative experimental studies of the resonant-based BS-DPC and the normal BS-DPC for DFIG are conducted to validate the effectiveness of the proposed strategy under both balanced and unbalanced grid conditions. In addition, the experimental results also prove that the proposed resonant-based BS-DPC can achieve a satisfying transient performance. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous machines (PMSMs) are popular due to their high efficiency and favorable dynamic properties. In practice, these machines often have a back-electromotive force (EMF) waveform, which deviates from a theoretically ideal sinusoid or trapezoid. In the past, current waveform shaping techniques were developed for these machines to calculate nonconventional current waveforms to reduce the torque ripple. However, in the light of global warming, energy efficiency has become more important than torque ripple in many applications. Therefore, current waveform shaping techniques can be used to focus on maximum efficiency. In this paper, a technique is presented that maximizes the efficiency of both the PMSM and the drive simultaneously. A time domain approach is used instead of the classical frequency domain approach, which allows us to include many machine aspects that had to be neglected previously, i.e., armature reaction, reluctance, zero-sequence components, and iron losses. [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 proposes a zero-sequence model-based sensorless control strategy for open-winding permanent-magnet synchronous machine (OW-PMSM) with common dc bus. The third harmonic back electromotive force (EMF) in zero-sequence is utilized to estimate the rotor position information. The novelty is that the third harmonic back EMF is reconstructed based on the zero-sequence model together with zero-sequence current, instead of using voltage transducer and three phase resistance network which can be eliminated from the control system. Due to the essence of back EMF, the developed method is appropriate for the applications including wind power generation and motor drives operating above certain speed. Meanwhile, the phase shift-based space vector pulse width modulation method for OW-PMSM is also presented for easier implementation to form zero voltage disturbance in zero-sequence from the inverter side and hence the corresponding influence can be consequently minimized. The torque ripple, loss, and parameter sensitivity analysis are also carried out, as confirmed by predictions of two-dimensional finite element analysis. Due to the essence of decouple, the estimation can be more robust than the conventional fundamental model-based sensorless methods. Finally, the effectiveness of the proposed method is validated experimentally on a 3-kW OW-PMSM drive system with 2.5 kg·m2 total inertia. [ABSTRACT FROM AUTHOR]

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 describes a self-sensing control scheme based on pulse-voltage-injection for permanent-magnet synchronous machines (PMSMs). Multiple saliencies, as well as the saturation and reluctance-based coupling effects, are studied by means of analytical methods, and are proved with finite element method simulations and measurements. These phenomena cause a constant estimated error of the rotor angle, as well as periodic errors with harmonics of order 6 k. The primary saliency of the considered interior PMSM with concentrated windings is strongly dependent on the load, so that the self-sensing capability disappears at some critical operating points. In this study, the parameters of the multiple saliencies are identified based on the proposed self-sensing method. The secondary saliencies are compensated with a closed loop control structure. The effectiveness of the proposed method is confirmed by experimental results. [ABSTRACT FROM PUBLISHER]

As wind power technology points to increase power ratings, the implementation based on a permanent-magnet synchronous generator (PMSG) with a full-power converter is expanding its market share. Multilevel converters, as for example, neutral-point clamped (NPC) converters, are therefore well suited for this application. Predictive current control presents similar dynamic response and reference tracking than other well-established control methods, but working at lower switching frequencies, and providing extensive flexibility to apply either online or offline different control laws to the same plant. In this work, the predictive current control is applied to both sides of the back-to-back NPC converter connecting a permanent-magnet synchronous wind power generator to the grid. DC-link neutral-point balance is achieved by means of the predictive control algorithm, which considers the redundant switching states of the back-to-back NPC converter. Reduced number of commutations, current spectrum control, and compliance with the low-voltage ride-through (LVRT) requirement are carried out with the predictive control. The obtained experimental results confirm the suitability of the proposed control approach. [ABSTRACT FROM PUBLISHER]

The transition to a deregulated electric power system industry has created a highly competitive electricity market with immense power transfer activity performed between the market participants. A poorly-damped oscillation of small-signal instability is usually imminent during a stress power system condition attributed by the base case power transfer or available transfer capability (ATC) compounded with an outage of critical line. The contingency ranking by means of lowest damping ratio is introduced so that execution of the most critical line outage will incite to a poorly-damped oscillation during the base case ATC. The rescheduling of few critical generators determined by using the normalized participation factor is presented in this paper as a novel, non-intricate and cost-effective solution for estimating a new value of ATC while ensuring a secure power system operating condition. Sturdiness of the proposed method is verified through comparison with the weighted-average sensitivity of stability index required for rescheduling the critical generators performed in a case study of 39-bus New England system. Comparative study on the results of cost minimization in generators rescheduling has also been done based on the critical generators selected by the two methods. [ABSTRACT FROM AUTHOR]

A widely used method for the magnetic field calculation in permanent magnet (PM) machines is the harmonic modeling (HM) method. Despite its many advantages, the application of this method is limited to machines in which armature currents, as a source of the magnetic field, are known. Since most of the PM machines are supplied with three-phase voltages, any variation of parameters in the armature electric circuit could lead to the uncertainty in knowing the armature currents, and therefore, limit use of the HM method. In this paper, an approach for overcoming this limitation is presented, which enables the calculation of the magnetic field in the PM machines without a priori knowledge of the armature currents. [ABSTRACT FROM AUTHOR]

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]

This paper presents a load torque estimation method for self-sensing brushless dc drives. Torque ripples in brushless dc machines can be reduced using load torque information. This method uses the terminal voltage, the virtual neutral point voltage, and the dc bus current of the machine. The algorithm uses the variation of successive back electromotive force (back EMF) samples to estimate the rotor speed. The rotor position is estimated by defining an intermediate function of estimated speed and back EMF samples. An estimate of acceleration is used to estimate load torque. The load torque information is used for increasing the dynamic stiffness of the drive. The mathematical background is given and discussed, and the simulations and the experimental results prove the performance of the proposed method. [ABSTRACT FROM PUBLISHER]

One of the requirements for safe, stable, sustainable, and profitable operation of doubly fed induction generators (DFIGs)-based wind energy conversion systems (WECSs) is the accurate and reliable protection against electrical faults, in particular, ground faults. The performance of protective devices employed to achieve this requirement is highly dependent on the grounding configuration of the DFIG-based WECS. This paper investigates impacts of the grounding configuration on the performance of protective devices used to protect DFIGs-based WECSs from electrical ground faults. Investigated grounding configurations include solid grounding, low-resistance grounding, high-resistance grounding, and no grounding. This paper also investigates the use of a capacitor in parallel with a low resistance, as a grounding configuration, to limit ground potentials, reduce ground currents, and minimize impacts on responses of ground protective relays. The impacts of the grounding configurations on protective devices are observed through their ability to identify faults, as well as their speed to respond to identified faults. Simulation and experimental results reveal that adequately designed low-resistance grounding offers the minimum impacts on protective devices used for ground protection of DFIG-based WECSs. [ABSTRACT FROM PUBLISHER]

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]

This work deals with the differential-evolution (DE)-based method for simultaneous identification of the electric, magnetic, and mechanical subsystem parameters of a line-start interior permanent magnet synchronous motor (LSIPMSM). The parameters are determined in the optimization procedure using the dynamic model of the LSIPMSM; the time behavior of voltages, currents, and speed measured on the tested LSIPMSM; and the DE, which is applied as the optimization tool. During the optimization procedure, the DE changes the parameters of the LSIPMSM dynamic model in such a way that the differences between the measured and calculated time behaviors of individual state variables are minimized. This paper focuses on the objective function definition, the constraint settings for individual parameters, the normalization of parameters, and, above all, the test and measurement procedures performed on the LSIPMSM, which all together make it possible to determine the LSIPMSM dynamic model parameters valid for a broad range of operation, thus ensuring proper evaluation of the LSIPMSM's line-starting capability. Some of the LSIPMSM parameters that can be determined by finite-element analysis and experimental methods are compared to the values obtained by the DE, thus validating the DE-based approach. [ABSTRACT FROM PUBLISHER]

This paper presents a rotor speed observer for induction-machine drives based on a sliding-mode approach and magnetizing current estimation. The back electromotive force (EMF) is calculated from the stator current and the stator voltage signals. The magnetizing currents are obtained from the back EMF. A theorem which gives the rotor speed estimate in the continuous-time domain is formulated using the magnetizing current estimation. The stability analysis is achieved based on the Lyapunov approach. Moreover, the discrete-time approach of the method is discussed, and a theorem for the discrete-time implementation is proposed. The limits that ensure the system stability for the switching gains and for the observer gain are discussed. This paper shows that the limits for the gains of the discrete-time algorithm are different from the limits for the gains of the continuous-time algorithm. Simulation results are presented to validate the theoretical analysis. In addition, experimental results based on a fixed-point digital signal processor (DSP) platform (DSP TMS320F2812) demonstrate the performance of the proposed scheme. [ABSTRACT FROM PUBLISHER]

In speed sensorless induction machine control, the reduced-order observer, i.e., the combined voltage and current (UI) mode flux observer, obtains good flux estimation results in the full-speed range but has some drawbacks in the stability characteristics. This paper constructs the small-signal model of the UI mode flux observer and derives the characteristic matrix to realize the stability analysis, based on which the stable range with corresponding conditions has been calculated explicitly. Furthermore, a cross-coupling feedback mechanism is proposed to solve the instability problem when the machine runs in the low-speed regenerating or plugging-in mode. The cross-coupling feedback coefficient is adjusted by the estimated speed or the speed command (conditional) for further simplification and is easy to be implemented. The improvement strategy is well verified by both the simulation in MATLAB and corresponding experimental results. [ABSTRACT FROM AUTHOR]