MATLAB

Conventionally, the simulation of power engineering applications can be a challenge for both undergraduate and postgraduate students. For the easy implementation of several kinds of power structure and control structures of power engineering applications, simulators such as MATLAB/(Simulink and coding) are necessary, especially for students, to develop and test various circuits and controllers in all branches of the field of power engineering. This book presents three different applications of MATLAB in the power system domain. The book includes chapters that show how to simulate and work with MATLAB software for MATLAB professional applications of power systems. Moreover, this book presents techniques to simulate power matters easily using the related toolbox existing in MATLAB/Simulink

Adaptive vector control based wave-to-wire model of wave energy converters

This study presents a complete wave-to-wire model in which a novel wave energy converter control approach based on adaptive vector control is introduced. The proposed control for maximum power absorption of the primary resource is included, as well as the grid interconnection topology and required controllers, needed for processing the power over the entire wave energy conversion chain. Thanks to the adaptive performance of the proposed controller, maximum energy extraction can be instantaneously achieved regardless of the current irregular wave characteristics of the resource. Finally, the proposed electrical configuration arises as a suitable grid interconnection solution, as it not only provides maximum power supply from the wave energy resource, but it also contributes towards further reducing its output power oscillations.Peer ReviewedPostprint (author's final draft

Control of Wind Energy Conversion Systems for Large-Scale Integration with the Power System

This thesis is mainly focused on (i) mathematical modeling and real power control of a direct-drive wind energy conversion system (WECS) that employs a high-pole permanent-magnet synchronous generator (PMSG), and (ii) the contribution of the WECS to the frequency regulation process in a host power system. In the first part, a strategy is proposed for real power control of the WECS, which augments the maximum power-point tracking (MPPT) feature of modern WECSs. The proposed strategy is based on rapid torque control, rather than the (slow) pitch-angle control. Moreover, a supplementary damping scheme is presented and tuned for the proposed power control strategy, based on a detailed mathematical model and eigenvalue analysis of the WECS. The supplementary mechanism damps the WECS drive-train oscillations and maintains its internal stability, even if its output power is regulated. The thesis also presents an alternative control structure for the WECS which mitigates the sensitivity of the WECS output power to power fluctuations caused by wind speed variations and drive-train oscillatory modes. Thus, a damping strategy and a tuning procedure are proposed for the aforementioned control structure, such that a stable performance of the WECS over the operating range is ensured. In the second part of the thesis, an enhanced control strategy is proposed that enables a WECS to contribute to frequency regulation process by effectively using its available generation reserve and the kinetic energy of its rotor, such that the stability of the WECS is maintained over the operating range. The performances of direct-drive PMSG-based WECSs with the proposed control strategy are examined in an example host power system and the impact of wind speed intermittency on the frequency responses of WECSs is assessed, based on which the parameters of the proposed control are adjusted to maintain the reliability of the example power system in response to a specific contingency event, under different wind speed regimes. The effectiveness of the proposed control strategies is demonstrated through time-domain simulation studies conducted in the PSCAD/EMTDC software environment

Small-Signal Stability Analysis of The Hydrokinetic Energy Harnessing connected to The Grid

This paper presents the modelling of the hydrokinetic system for the small-signal stability analysis under the small disturbances due to variation and fluctuation of water velocity in the river or marine. The complete modelling of the hydrokinetic system consists of vertical axis H-Darrieus turbine, direct-drive permanent magnet synchronous generator (PMSG), back-to-back converter and the grid network. By linearising all the equation around the steady-state value, the dynamic equation of the hydrokinetic system is derived. The stability of the system is tested with and without the PI controller. The eigenvalues analysis-based approaches have been used to investigate the stability of the system under the small disturbances. The findings show, the stability of the hydrokinetic system with PI controller is improved up to 57.82% by reducing the oscillation frequency at the Rotor Side Converter (RSC)

Control of distributed renewable energy generation systems in converter-dominated microgrid applications

Mención Internacional en el título de doctorThere is a growing interest in the use of renewable Distributed Energy Resources (DERs) that increase the efficiency of the transmission system and reduce the ecological impact of renewable energy infrastructures. At the same time, they reduce the associated capital requirements, thus increasing the potential installation of renewable energy. Microgrids have been proposed as a solution to improve the integration of renewable DERs. By the use of advanced control techniques, they provide a reliable frame for DERs to support the power system operation. As such, Microgrids can be a promising solution to increase renewable energy penetration. However, since renewable DERs are usually interfaced by Power Electronic Converters (PECs), they do not provide the common stabilization characteristics of traditional generation interfaced by Synchronous Generators (SGs). Therefore, there are concerns about the stability of converter-dominated Microgrids. This Thesis focus on the specific requirements of PEC-interfaced renewable DERs operating in Microgrids. An overview of available solutions show that, for PECs to support the Microgrid operation in both grid-connected and islanded modes, they require a synchronizing mechanism that does not rely on the measurement of an external frequency. A promising alternative is to emulate the behavior of traditional SGs in the PEC control system with the so-called Virtual Synchronous Machine (VSM) solutions. The synchronization system underlying to these proposals is analyzed. A comparison with the use of traditional frequency measurement systems, namely Phase-Locked Loops (PLLs), in the support of the Microgrid power balance is addressed, showing that the PEC synchronization system has a direct effect on the Microgrid stability. The Thesis includes a new proposal to ensure synchronous operation based on the use reactive power, instead of active power as in VSMs, that does not require frequency measurements. A dynamic model of a grid-connected PEC is used to demonstrate that reactive power can be used to ensure synchronism. This Reactive Power Synchronization system is used to propose a solution for the black-start of Wind Energy Conversion Systems (WECSs), so that they can contribute to the restoration of the power system following a blackout. The proposed control systems are validated with experimental results of a grid connected PEC and an isolated WECS.Programa Oficial de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidente: Luis Rouco Rodríguez.- Secretario: Emilio José Bueno Peña.- Vocal: Roberto Alves Baraciart

A Discrete-Time Direct-Torque Control for Direct-Drive PMSG-Based Wind Energy Conversion Systems

This paper proposes a novel flux space vector-based direct-torque control (DTC) scheme for permanent magnet synchronous generators (PMSGs) used in variable-speed direct drive wind energy conversion systems (WECSs). The discrete time control law, which is derived from the perspective of flux space vectors and load angle, predicts the desired stator flux vector for the next time-step with the torque and stator flux information only. The space-vector modulation (SVM) is then employed to generate the reference voltage vector, leading to a fixed switching frequency as well as lower flux and torque ripples when compared to the conventional DTC. Compared with other SVM-based DTC methods in the literature, the proposed DTC scheme eliminates the use of PI regulators and is less dependent on machine parameters, e.g., stator inductances and permanent magnet flux linkage, while the main advantages of the DTC, e.g., fast dynamic response and no need of coordinate transform, are preserved. The proposed DTC scheme is applicable for both nonsalient-pole and salient-pole PMSGs. The overall control scheme is simple to implement and is robust to parameter uncertainties and variations of the PMSGs. The effectiveness of the proposed discrete-time DTC scheme is verified by simulation and experimental results on a 180 W salient-pole PMSG and a 2.4-kW nonsalient-pole PMSG used in variable-speed direct-drive WECSs

The control of power electronic converters for grid code compliance in wind energy generation systems

This research report reviews some of the latest control schemes for the power electronic converters found in modern variable speed wind turbines in order to comply with various grid codes. Various control schemes, in order to comply with low voltage ride-through requirements, active and reactive power control and frequency control, are presented. The report first investigates the South African grid code requirements for wind energy generation, and then makes a comparison to grid codes of countries with significant penetration levels and vast experience in wind energy generation. This is followed by a review of the state of the art in fixed and variable speed wind turbine technologies. The research revealed that Type 3 generators offer significant advantages over others but suffer due to grid faults. Various active control schemes for fault ride-through were researched and the method of increasing the rotor speed to accommodate the power imbalance was found to be the most popular. It was found that Type 4 generators offer the best fault ride-through capabilities due to their full scale converters. The research will assist power system operators to develop appropriate and effective grid codes to enable a stable and reliable power system. The research will also provide turbine manufacturers and independent power producers with a comprehensive view on grid codes and relate them to the associated turbine technologies