F. Fernandez-Bernal

Model-based loss minimization for DC and AC vector controlled motors including core saturation

A generalized d-q loss model applicable to permanent magnet synchronous motors, synchronous reluctance motors, induction motors and DC motors is presented. A model-based loss minimization algorithm of easy implementation is proposed, based on the loss model. Core saturation is taken into account. The paper reviews the loss-minimization schemes previously presented in the literature for specific types of motor. It shows how all these can be derived from the generalized model and the algorithm presented here. Results are compared with those reported in the literature. Finally, experimental results from an interior permanent magnet synchronous motor are presented.

Determination of parameters in interior permanent magnet synchronous motors with iron losses without torque measurement

This paper proposes systematic procedures to estimate the circuit parameters of an inverter-fed vector controlled interior permanent magnet synchronous motor when torque measurement is not available. The methodology presented here does not neglect iron losses. New procedures have been developed and justified, because international standard recommendations (IEC standards) cannot be applied. Experimental results from a test rig are presented in the paper to validate the most important contributions. Thanks to the procedures proposed, secondary effects on the motor parameters, like saturation or frequency dependency, have been evaluated.

Maximum Frequency Deviation Calculation in Small Isolated Power Systems

Large frequency deviations due to a number of disturbances are frequent in small isolated power systems. The maximum frequency deviation in the system is limited to prevent other generator tripping. It is important to have an accurate model to calculate it, both for system planning and operation. A new simplified model to calculate the maximum frequency deviation when either a generator or load-related disturbance occurs in these systems is presented. This model takes into account the response of governor-prime mover even when different technologies are present in the power system. Model parameters can be easily obtained from either more complex models or from test records. Simulation results for an actual power system aimed at checking the model accuracy are presented. High accuracy is obtained while computation time is reduced due to the simplicity of the model.

Modeling of thermal generating units for automatic generation control purposes

A simple discrete time model of a thermal unit has been formally developed for designing automatic generation control (AGC) controllers. This model has been developed using data obtained from specific tests and historical records. This model consists of a nonlinear block followed by a linear one. The nonlinear block consists of a dead band and a load change rate limiter, while the linear block consists of a second-order linear model and an offset. Although most of these elements have already been included in unit models for AGC presented in the literature, a certain mix up exists about which of them are necessary. This is clarified in this paper. It has been found that the unit response is mainly determined by the rate limiter, while the other model components are used for a better fitting to the real response. An identification procedure is proposed to estimate the values of the models parameters.

Efficient control of reluctance synchronous machines

This paper shows that maximum efficiency control (ME) in reluctance synchronous machines (RSM) belongs to the class of constant angle control strategies. It is also shown that for all constant angle control strategies, efficiency is constant and independent of torque (current), being only a function of speed. Results are explored by simulation comparing ME to other typical control strategies from the efficiency viewpoint. Data from a standard RSM and an ALA-RSM (axially laminated anisotropic RSM) are used. Machine limits are taken into account. The paper presents the analytical solution in dq-currents for optimum efficiency, based on a per unit (pu) loss-model. A practical ME expression within a vector control scheme is also presented.

The Spanish AGC System: Description and Analysis

This paper describes and analyzes the Spanish AGC system. The differences with respect to a standard hierarchical structure are explained. A simple model useful for simulation is proposed. Using this model, the performance of the system and the influence of several parameters in system response is evaluated. The paper also suggests some changes in the configuration and parameter settings of the system to improve its performance.

Modeling, Sizing, and Control of an Excitation Booster for Enhancement of Synchronous Generators Fault Ride-Through Capability: Experimental Validation

This paper proposes a complete approach to modeling, sizing, and controlling ultracapacitor-based excitation boosters (EB) aimed at improving the fault ride-through capability of synchronous generators equipped with bus-fed static excitation systems. The EB model is a simplified one suitable for transient stability simulations. Sizing is performed using transient stability simulations. It is aimed at maximizing the machine critical clearing time subject to machine rotor insulation and ultracapacitor features. The developed control system includes fast voltage sag and loss of synchronism detectors. The proposed approach can be used to design ultracapacitor-based EB in real-world applications. A dedicated test environment based on 10-kVA synchronous machine has been used to validate the proposed approach.