### Browsing by Department "Electric Drives"

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Item Analysis and design of a position observer with resistance adaptation for synchronous reluctance motor drives(2013-01-16) Tuovinen, Toni; Hinkkanen, Marko; Luomi, Jorma; Electric DrivesA back-electromotive-force-based reduced-order position observer with stator-resistance adaptation is analyzed for motion-sensorless synchronous reluctance motor (SyRM) drives. Analytical equations for steady-state estimation errors and stability conditions are derived (with and without resistance adaptation), taking into account errors in the parameter estimates. The effect of the observer gain on the noise reduction is studied by means of eigenvector analysis. A robust gain selection is proposed, which maximizes the allowed uncertainties in the parameter estimates. The proposed observer design is experimentally evaluated using a 6.7-kW SyRM drive; stable operation is demonstrated at low speeds under various parameter errors.Item An Approach Utilizing Converters for Locating Faults in LV Distribution Grids(2021-10-25) Pitkäniemi, Sami; Routimo, Mikko; Kukkola, Jarno; Pirsto, Ville; Pouresmaeil, Edris; Department of Electrical Engineering and Automation; Renewable Energy in Electrical Power; Electric Drives; Renewable Energies for Power SystemsThis paper proposes an approach for locating faults in a distribution grid by utilizing data measured and gathered by distributed converters. The data, comprising grid voltages and impedances from multiple locations, is processed using multinomial logistic regression, a machine learning algorithm, to classify a fault location in the grid. The algorithm is ﬁrst trained with simulation data, followed by evaluation of its predictive performance using a set of test data previously unseen by the algorithm. The fault location accuracy of the proposed approach is found resonable and encourages further studies of the unused potential in the converters.Item A combined position and stator-resistance observer for salient PMSM drives(2012) Hinkkanen, Marko; Tuovinen, Toni; Harnefors, Lennart; Luomi, Jorma; Electric DrivesA reduced-order position observer with stator-resistance adaptation is proposed for motion-sensorless permanent-magnet synchronous motor drives. A general analytical solution for the stabilizing observer gain and stability conditions for the stator-resistance adaptation are derived. Under these conditions, the local stability of the position and stator-resistance estimation is guaranteed at every operating point except the zero frequency, if other motor parameters are known. Furthermore, the effect of inaccurate model parameters on the local stability of the position estimation is studied, and an observer gain design that makes the observer robust is proposed. The proposed observer is experimentally tested using a 2.2-kW motor drive; stable operation at very low speeds under different loading conditions is demonstrated.Item Comparative analysis of the effects of integral action and disturbance feedforward on current control of voltage-source converters(2021-10-25) Pirsto, Ville; Kukkola, Jarno; Hinkkanen, Marko; Electric Drives; Department of Electrical Engineering and AutomationThis paper presents a comparison between integral action and disturbance feedforward in current control of grid converters. The current controllers are designed directly in the discrete-time domain with the objective of similar reference-tracking and disturbance-rejection performance under nominal conditions.Partial compensation of time delays is included in the controller designs. The analytically and experimentally compared properties, in addition to reference tracking and disturbance rejection, are noise sensitivity and robustness to grid impedance variations. The controllers are found to have comparable dynamic performance, although the realized disturbance-rejection performance of the integrator-based controller is slightly better. The disturbance-feedforward-based controller is found to be less susceptible to current measurement noise at the cost of having an additional entry point for noise through the voltage measurement. The integrator-based controller is found more robust to grid impedance variations.Item Comparative study of inner and outer rotor bearingless synchronous reluctance motors(INST ENGINEERING TECHNOLOGY-IET, 2019-01-22) Mukherjee, Victor; Sokolov, Maksim; Pippuri-Mäkeläinen, Jenni; Hinkkanen, Marko; Belahcen, Anouar; Department of Electrical Engineering and Automation; Electric Drives; VTT Technical Research Centre of FinlandIn this study, the authors presented a systematic design procedure of outer rotor bearingless synchronous reluctance motor (SynRM). The proposed motor is compared with an already prototyped inner rotor bearingless SynRM at different operation points. It has been shown that a properly designed outer rotor SynRM can produce higher levitation forces than the inner rotor counterpart. The inner rotor motor produces higher torque and eccentric forces than the outer rotor motor.Item Comparison of finite-element based state-space models for PM synchronous machines(2014-05-16) Rasilo, Paavo; Lemesle, Marc-Antoine; Belahcen, Anouar; Arkkio, Antero; Hinkkanen, Marko; Computational Electromechanics; Electric Drives; Department of Electrical Engineering and AutomationAn 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.Item Dynamic emulation of multi-mass mechanical loads in electric drives(2011-08-30) Saarakkala, Seppo; Alahäivälä, Antti; Hinkkanen, Marko; Luomi, Jorma; Electric DrivesThis paper presents a straightforward method for dynamic emulation of multi-mass systems. The test bench consists of a driving motor coupled rigidly to a load servo motor, and the torque reference of the servo motor is controlled based on the dynamic model to be emulated. No additional measurements are needed, but the mechanical parameters of the test bench and the torque estimate of the driving motor have to be known. The use of the torque estimate makes it possible to avoid using any differentiations or controller compensation terms in the emulator. The experimental results show that the emulator can model the dynamics of the multi-mass mechanical load with a good accuracy. In addition, the robustness against the mechanical parameter inaccuracies is good.Item A dynamic model for bearingless flux-switching permanent-magnet linear machines(IEEE, 2020-02-19) Sokolov, Maksim; Saarakkala, Seppo E.; Hosseinzadeh, Reza; Hinkkanen, Marko; Electric Drives; Department of Electrical Engineering and AutomationThis article deals with dynamic models for three-phase bearingless flux-switching permanent-magnet (FSPM) linear machines. This machine type can be used to build a magnetically levitating long-range linear drive system, whose rail does not need any active materials apart from iron. A dynamic machine model is developed by means of equivalent magnetic models, taking into account air-gap variation and magnetic saturation. The effects of these phenomena are analyzed using finite-element method (FEM) simulations of a test machine. The parameters of the proposed model can be identified using the FEM or measured data. The model can be applied to real-time control and time-domain simulations. The model is validated by means of experiments.Item A dynamic model for saturated induction machines with closed rotor slots and deep bars(Institute of Electrical and Electronics Engineers, 2020-03) Mölsä, Eemeli; Saarakkala, Seppo E.; Hinkkanen, Marko; Arkkio, Antero; Routimo, Mikko; Electric Drives; Department of Electrical Engineering and Automation; ABB Oy DrivesThis paper deals with a dynamic model for three-phase induction machines equipped with closed rotor slots and deep rotor bars. The thin bridges closing the rotor slots saturate highly as a function of the rotor current. The impedance of the rotor bars also varies much as a function of the rotor current frequency. An extended dynamic model, which takes into account the slot-bridge saturation and the deep-bar effect, is developed. The model extensions can be plugged into a standard machine model and parametrized easily. The proposed model can be applied to time-domain simulations, real-time control, and identification. The model is validated by means of finite-element analysis and experiments using a four-pole 5.6-kW induction machine. The results show that the accuracy of the proposed model is superior to the standard model, particularly under transient excitation typically used in standstill self-commissioning tests of induction motor drives.Item A dynamic model for six-degree-of-freedom bearingless linear motor systems(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2021-11) Hosseinzadeh, Reza; Martin, Floran; Hinkkanen, Marko; Electric Drives; Computational Electromechanics; Department of Electrical Engineering and AutomationThis article develops a dynamic model for six-degree-of-freedom bearingless linear motor systems by means of lumped-element modeling. A four-sided motor system, containing eight three-phase motor units fed by their own inverters, is considered as an example system, but the modeling approach can be applied to other motor systems as well. The mechanical subsystem of the model comprises the rigid-body dynamics. The electromagnetic subsystem governs the electrical dynamics of the motor units and the production of the resultant electromagnetic force and its associated torque. In order to model the unbalanced magnetic torque due to tilting of the mover, the motor units are spatially discretized into a number of identical submotor models having a uniform air gap. The submotor models of each motor unit are electrically connected in series, i.e., they share the same current, but their flux linkages and forces differ in tilted positions. The electromagnetic subsystem can be parameterized based on simple static two-dimensional finite-element method computations at a range of uniform air-gap and current values. The developed model is validated through a comparison between the time-domain simulation results and the experimental results. The model can be applied to time-domain simulations, real-time control system development, and various analyses of the system.Item Dynamic Model of a Virtual Air Gap Variable Reactor(2021) Sevsek, David; Hinkkanen, Marko; Kukkola, Jarno; Lehtonen, Matti; Power Systems and High Voltage Engineering; Department of Electrical Engineering and Automation; Electric DrivesThis paper presents a dynamic model of a virtual air gap variable reactor (VGR). In contrast to traditionally mechanically operated variable reactors, which have been used as arc suppression coils in compensated networks for centuries, VGRs have shown an enhanced response speed. However, the harmonics created by VGRs are considerably higher than those created by mechanically operated reactors. This study’s dynamic model considers the magnetic saturation behavior of VGRs, enabling a detailed examination of VGRs. Furthermore, the model can be utilized to develop an effective controller for a VGR. A VGR prototype has been used to validate the dynamic model. It is shown that the dynamic model replicates the actual behavior of a VGR well.Item Equivalence of the integrator-based and disturbance-observer-based state-space current controllers for grid converters(IEEE, 2021-06) Rahman, F M Mahafugur; Pirsto, Ville; Kukkola, Jarno; Hinkkanen, Marko; Pérez-Estévez, Diego; Doval-Gandoy, Jesús; Electric Drives; Department of Electrical Engineering and Automation; University of VigoThis article deals with discrete-time state-space current controllers for three-phase grid converters equipped with an LCL filter. The integral action in the controller can be implemented either using an integrator or a disturbance observer. The results show that the disturbance-observer-based and integrator-based controllers become mathematically equal if the feedforward gains are selected to be equal, the feedforward zero is placed to cancel the pole originating from the integral action, and the closed-loop poles are placed identically. The equivalent performance in both designs is verified by means of analyses and experiments. The equivalence is also shown for double-frequency current controllers.Item Estimation of an unbalanced grid impedance using a three-phase power converter(2020-09-07) Kukkola, Jarno; Pirsto, Ville; Routimo, Mikko; Hinkkanen, Marko; Electric Drives; Renewable Energy in Electrical Power; Department of Electrical Engineering and AutomationThis paper proposes a real-time method for estimating an unbalanced grid impedance using a three-phase converter. In the method, a periodic single-frequency or multi-frequency excitation signal is added to the converter voltage reference. The converter measures currents and voltages at the point of common coupling. The impedance estimate is obtained from the measurements using sliding discrete Fourier transform (SDFT). The method is experimentally validated.Item Flux-Linkage-Based Current Control of Saturated Synchronous Motors(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019-05-27) Awan, Hafiz Asad Ali; Saarakkala, Seppo E.; Hinkkanen, Marko; Department of Electrical Engineering and Automation; Electric DrivesMagnetic saturation characteristics of synchronous reluctance motors (SyRMs), with or without permanent magnets (PMs), are highly nonlinear. These nonlinear effects can be included in the current controller by changing its state variable from the stator current to the stator flux linkage using the known saturation characteristics. A direct discrete-time variant of the flux-linkage based current controller is developed in a state-space framework. If the magnetics are modeled to be linear, the proposed control structure reduces to the standard current controller in this special case. Experimental results on a 6.7-kW SyRM drive demonstrate that the proposed flux-linkage based controller enables a higher closed-loop bandwidth and is more robust against parameter errors, as compared to the standard current controller.Item Gain scheduling of a full-order observer for sensorless induction motor drives(2014-11-20) Qu, Zengcai; Hinkkanen, Marko; Harnefors, Lennart; Electric Drives; ABB Corporate Research; Department of Electrical Engineering and AutomationThis paper deals with the design of a speed-adaptive full-order observer for sensorless induction motor (IM) drives. A general stabilizing observer gain matrix, having three free design parameters, is used as a design framework. A gain-scheduled selection of the free design parameters is proposed. Furthermore, the full-order observer is augmented with the stator-resistance adaptation, and the local stability of the augmented observer is analyzed. The performance of the proposed full-order observer design is experimentally compared with a reduced-order observer using a 2.2-kW IM drive.Item Identification of mechanical impedance of an electric machine drive for drivetrain design(2023-05-15) Hartikainen, Hannu; Tiitinen, Lauri; Laine, Sampo; Hinkkanen, Marko; Electric Drives; Mechatronics; Department of Electrical Engineering and Automation; Department of Mechanical EngineeringThis paper proposes a method for identifying mechanical impedance of an electric machine drive for drivetrain design and analysis. The mechanical impedance describes the dynamics of an electric machine as seen from its mechanical terminals. It depends not only on the electric machine but also on the control system, which should be taken into account when analyzing torsional vibrations. If the black-box input-output time-domain models of the electric machine and its control system are available, the mechanical impedance can be extracted from simulations. The proposed identification method is based on signal injection in time-domain simulations. At steady-state operating points, an excitation signal is injected into the rotor speed and the response is observed in the electromagnetic torque. The method is validated by comparing the identified mechanical impedances with the corresponding analytical solutions.Item Levitation control for a double-sided bearingless linear motor based on feedback linearization(IEEE, 2019-09-29) Saarakkala, Seppo E.; Sokolov, Maksim; Hosseinzadeh, Reza; Hinkkanen, Marko; Electric Drives; Department of Electrical Engineering and AutomationThis paper deals with levitation control for a double-sided bearingless linear-motor system. Analytical design rules for a state-feedback gain and a state observer are derived. To decouple the production of forces in thrust- and normal-force directions, feedback-linearizing control based on the magnetic model is proposed. The proposed control design is tested in an experimental system consisting of four individually supplied linear-motor units in a double-sided configuration. The results from time-domain simulations and experimental tests suggest that the proposed control design can successfully provide smooth transition to contactless operation and retain the stable levitation during the movement in the thrust-force direction.Item Loss-minimizing flux level control of induction motor drives(2012-05-15) Qu, Zengcai; Ranta, Mikaela; Hinkkanen, Marko; Luomi, Jorma; Electric DrivesThis paper applies a dynamic space-vector model to loss-minimizing control in induction motor drives. The induction motor model, which takes hysteresis losses and eddy-current losses as well as the magnetic saturation into account, improves the flux estimation and rotor-flux-oriented control. Based on the corresponding steady-state loss function, a method is proposed for solving the loss-minimizing flux reference at each sampling period. A flux controller augmented with a voltage feedback algorithm is applied for improving the dynamic operation and field weakening. Both the steady-state and dynamic performance of the proposed method is investigated using laboratory experiments with a 2.2-kW induction motor drive. The method improves the accuracy of the loss minimization and torque production, it does not require excessive computational resources, and it shows fast convergence to the optimum flux level.Item Modeling of a bearingless synchronous reluctance motor with combined windings(IEEE, 2019-09-29) Sokolov, Maksim; Gruber, Wolfgang; Saarakkala, Seppo E.; Hinkkanen, Marko; Electric Drives; Johannes Kepler University Linz; Department of Electrical Engineering and AutomationThis paper deals with modeling of bearingless synchronous reluctance motors with a combined winding. A method to link an existing model used for the separated windings structure to the combined winding structure is proposed. A dynamic model applicable for the purposes of time-domain simulation, model-based control design, and real-time control is presented. The finite-element method (FEM) is used to validate the proposed model and to show the feasibility of the considered slice motor type, including passive stability of axial movement and tilting, force and torque production, and ripple. Applicability of the developed model in control design is demonstrated. The model is validated by means of experiments.Item Modeling of saturation due to main and leakage flux interaction in induction machines(2010-05-18) Tuovinen, Toni; Hinkkanen, Marko; Luomi, Jorma; Electric DrivesSaturation due to main flux and rotor leakage flux interaction appears in induction machines, particularly if rotor slots are skewed or closed. Conventional saturation models used in connection with dynamic equivalent-circuit models do not take this phenomenon into account. In this paper, explicit functions for modeling this mutual saturation are proposed. These functions are physically reasonable and are easy to fit, and the number of their parameters is small. The proposed functions can be used in real-time applications and in computer simulations if high accuracy and physical consistency are preferable. The model fits well to the data obtained from finite-element analysis or experimental data of a 2.2-kW motor. The model predicts the stator current with good accuracy both in steady state and in transients.