José M. Cañedo

Discontinuous controller for power systems: sliding-mode block control approach

Based on the complete model of the plant, a sliding-mode stabilizing controller for synchronous generators is designed. The block control approach is used in order to derive a nonlinear sliding surface, on which the mechanical dynamics are linearized. This combined approach enables us to compensate the inherent nonlinearities of the generator and to reject high-level external disturbances. A nonlinear observer is designed for estimation of the rotor fluxes and mechanical torque.

DISCRETE-TIME SLIDING MODE CONTROL OF AN INDUCTION MOTOR

Abstract A discrete-time sliding mode with block control aided design is applied to a nonlinear discrete-time induction motor model where the load torque is considered as unknown perturbation. With full state measurements, both rotor speed and rotor flux amplitude tracking objectives are satisfied. Then, a reduced order observer is implemented where speed and current measurements provide the observation for the unreachable fluxes and load torque. The simulations predict the system to be robust with respect to external load torques.

Digital Sliding-Mode Sensorless Control for Surface-Mounted PMSM

In this work, a sampled-data model for surface-mounted permanent magnet synchronous motors (SMPMSMs) is proposed based on the symplectic Euler method. Then, based on the obtained model, a digital sliding-mode controller is designed for rotor velocity output tracking. Moreover, for rotor position and velocity and load estimation, a digital observer is designed. A separation principle is introduced in order to verify that the proposed controller can accomplish its task with estimated signals. Open-loop simulations predict that the sampled-data model obtained via the symplectic Euler method performs better than a model obtained with the classical explicit Euler method. Moreover, closed-loop simulations are carried on where the proposed controller is compared with a sampled continuous-time controller, where the controller here designed yields to better results even when the sampling period is increased. Finally, the performance of the proposed controller is verified by experimental tests.

High-Order Block Sliding-Mode Controller for a Synchronous Generator With an Exciter System

This paper deals with the design of robust regulation for both angular speed stability enhancement and voltage in synchronous generator machines with an excitation control system. The designed controller is based on the block control technique combined with a sliding-mode (SM) control approach. The block control is used to design a nonlinear sliding manifold with the desired stability property. In order to attenuate the chattering effect which can appear in the presence of the exciters unmodeled dynamics, a high-order SM algorithm and a robust exact differentiator are employed. The efficiency of the proposed controller, i.e., robustness and high accuracy, is verified via simulations.

A Novel Octagonal Wound Core for Distribution Transformers Validated by Electromagnetic Field Analysis and Comparison With Conventional Wound Core

This paper analyzes a novel configuration of transformer core, called octagonal wound core (OWC), and shows the minimization of the excitation current and the reduction of the eddy-current losses. The OWC is compared with the conventional wound core (CWC) configuration. The comparison is based on two-dimensional and three-dimensional finite-element method (FEM) simulations, taking into account the nonlinear properties of the magnetic material of the core. The results show that the OWC reduces the excitation current and the eddy-current losses when compared with CWC. Moreover, several combinations of grades of the grain-oriented silicon steel (GOSS) were investigated so as to further reduce the eddy-current losses and the excitation current.

Variable structure control of synchronous generator: singularly perturbed analysis

Synchronous generators have a natural different time scale dynamics. That is why, for modelling and control design in such systems, the methods of singular perturbations are widely used. In this paper the possibilities of sliding mode control design for synchronous generators are analysed. With this aim the concept of singular perturbation is revised in order to use it for relay control systems. The obtained results are used for sliding mode control of synchronous generator.

High-Order Sliding Mode Block Control of Single-Phase Induction Motor

A new sliding mode (SM) observer-based controller for single-phase induction motor is designed. The proposed control scheme is formulated using block control feedback linearization technique and high-order SM algorithms with measurements of the rotor speed and stator currents. The stability of the complete closed-loop system, including the rotor flux second-order SM observer, is analyzed in the presence of model uncertainty, namely, rotor resistance variation and bounded time-varying load torque.

Robust non-linear control of a wound rotor induction generator: Integral sliding modes

In this paper, we propose a sliding mode - based controller for a wind power system where an induction generator is connected to an infinity bus. To ensure robustness of the closed - loop system with respect to perturbations and plant parameter variations, first, we applied the conventional sliding mode (SM) control technique. Secondly, an integral sliding SM control is designed to reduce a chattering effect. Both the control schemes are proposed to control the electromagnetic torque and the stator reactive power of a wound rotor induction generator coupled with a wind turbine across a gear box. The performance of the designed controllers is validated through simulations.

Nested integral sliding modes of large scale power system.

A sliding mode decentralized excitation controller for multimachine power systems is designed to stabilize the power angle and regulate the terminal generators voltages. First, the block control approach is used to derive a nonlinear sliding manifold, on which the mechanical dynamics are linearized. Then, a combination of the integral and nested sliding mode techniques is applied to reject both the matched and unmatched perturbations. The designed controller was tested through simulation of WSCC (Western System Coordinating Council) under small and large perturbations. The presented simulations confirm effectiveness of the proposed controller.

Second Order Sliding Mode Block Control of Single-Phase Induction Motors

Abstract The authors propose a robust non-linear controller based on a block control linearization technique combined with a second order sliding modes super-twisting algorithm for controlling a rotor speed of single phase induction motors (SPIM). The controls objectives consist on the maximizing of the average torque operation and minimizing of the pulsating torque operation of the motor to achieve desirable performance. A nonlinear observer is designed to estimate the unmeasured variables (rotor flux linkages and torque load).