Edgar L. Moreno-Goytia

Fault Ride-Through Improvement of DFIG-WT by Integrating a Two-Degrees-of-Freedom Internal Model Control

A novel two-degree-of-freedom internal model control (IMC) controller that improves the fault ride-through (FRT) capabilities and crowbar dynamics of doubly fed induction generator (DFIG) wind turbines is presented. As opposed to other control strategies available in the open literature, the proposed IMC controller takes into account the power limit characteristic of the DFIG back-to-back converters and their dc-link voltage response in the event of a fault and consequent crowbar operation. Results from a digital model implemented in Matlab/Simulink and verified by a laboratory scale-down prototype demonstrate the improved DFIG FRT performance with the proposed controller.

Offshore Wind Energy Generation : Control, Protection, and Integration to Electrical Systems

The offshore wind sector’s trend towards larger turbines, bigger wind farm projects and greater distance to shore has a critical impact on grid connection requirements for offshore wind power plants. This important reference sets out the fundamentals and latest innovations in electrical systems and control strategies deployed in offshore electricity grids for wind power integration. Includes: All current and emerging technologies for offshore wind integration and trends in energy storage systems, fault limiters, superconducting cables and gas-insulated transformers Protection of offshore wind farms illustrating numerous system integration and protection challenges through case studies Modelling of doubly-fed induction generators (DFIG) and full-converter wind turbines structures together with an explanation of the smart grid concept in the context of wind farms Comprehensive material on power electronic equipment employed in wind turbines with emphasis on enabling technologies (HVDC, STATCOM) to facilitate the connection and compensation of large-scale onshore and offshore wind farms Worked examples and case studies to help understand the dynamic interaction between HVDC links and offshore wind generation Concise description of the voltage source converter topologies, control and operation for offshore wind farm applications Companion website containing simulation models of the cases discussed throughout Equipping electrical engineers for the engineering challenges in utility-scale offshore wind farms, this is an essential resource for power system and connection code designers and pratitioners dealing with integration of wind generation and the modelling and control of wind turbines. It will also provide high-level support to academic researchers and advanced students in power and renewable energy as well as technical and research staff in transmission and distribution system operators and in wind turbine and electrical equipment manufacturers.

Modelling of a wind turbine with permanent magnet synchronous generator

This investigation presents the implementation and simulation of a Simulink-based controlled permanent magnet synchronous generator (PMSG) wind turbine in the dq0 reference frame. The model consists of a current control subsystem, a PMSG model, a mechanical subsystem, a pitch angle controller and a wind turbine model. The current control subsystem makes use of PI controllers governing the wind turbine speed, the direct and quadrature stator currents and the pitch angle of the turbine blades. The pitch angle controller measures the speed and the active power from the generator limiting both in case of high-speed wind conditions. In order to verify the functioning and the effectiveness of the proposed controllers, simulations- for different operation conditions- are presented and discussed.

MMC technology and its participation in the integration of variable renewable energies and implementation of DC grids

The emerging Modular Multilevel Converters (MMC) technology is expected to play a key role in the construction of DC grids and integration of renewable energy sources (RESs) at bulk to medium and high voltage. The DC option is also perceived as solution to the steady increase in power demand and the collection of disperse conventional and variable generations. These can be achieved while maintaining the control and operation of the grid into the smart grid playground without affecting the environment. Therefore, this paper presents the characteristics of the MMC along with the modulation techniques as well as control methods for MMC-based high multilevel structures. Also the MMC-HVDC advantages for integrating RES are reviewed. At final section the technical and environmental benefits of using MMC for DC grids are discussed.

Analysis of the effects of a high power electronics controller on electrical Grids during faulted and post-faulted conditions using wavelets

FACTS controllers and HVDC links are high power electronics-based structures which have shown its strength in improving the operation and control of nowadays electrical networks worldwide. Alongside the many benefits they provide, there are also collateral effects on the grid as consequence of dynamically deviating localized network parameters, which affects the protection system for instance. This paper reviews some effects of the STATCOM, TCSC and UPFC on equivalent parameters of the grid on faulted and non-faulted conditions. As main point, this paper also analyses the dynamic effects of the TCSC on the equivalent reactance of the neighborhood of the controller in the transit from pre-faulted to faulted condition. The steady state waveforms and those from the transient oscillations emerged during the faulted state are processed using wavelets to determinate effective protection and control actions. The results presented have been obtained by combining the capabilities of PSCAD and MATLAB-Simulink.

Fault Detection in Electrical Grid on Power Electronic Controllers Environment Based on Wavelet Transform

This paper presents the applications of the Wavelet Transform (WT) for analyzing fast transient signals originated from fault events in power grids with presence of power electronics-based controllers and its protective devices. The study cases included emphasizes the wavelets ability to discriminate signals originated by the fault events from those injected by power controllers, like the TCSC and its associated protection, the MOV, and determine location and electrical distance of the fault to a reference point. The simulation and analysis are carried out cooperatively mean between PSCAD and MATLAB.

State of the art, modeling and simulation of an advanced power electronics transformer

This paper presents a state of the art on electronic transformer, whose structure is based on power electronic devices and high-frequency electromagnetic induction. It has the capability to handle bidirectional flow of active and reactive power for different input-output voltage ratios and mitigate voltage disturbances and harmonic voltage and / or current. These features overcome the current limitations of distribution transformers, thus improving power quality and preserving the characteristics of voltage conditioning. This paper describes the evolution of electronic transformers as a generational change in the traditional distribution transformers, with the advantage of control added capacity for the benefit of users and the electric network.

Arbitrary waveform power source for testing purposes in real-time using an H-cascaded multilevel converters and FPGA-based control

This paper presents the design and construction of a scaled-down arbitrary waveform power source which bases the synthesis of power signals at its output in two H converters multilevel with asymmetric sources in cascade. The aim of the power source is to mimic the disturbance-like signal for testing controls, instruments and electric devices and equipment in real-time. The electrical disturbances of interest are those related to power quality degradation and short-circuit events in power grids. A FPGA platform is the core element of the computational bed for the PWM multilevel scheme, and other control task, useful for implementing the waveforms as required for a particular application. As final part a number of experimental results are presented.

A transformerless, single DC-input, DC-AC 7-levels boost converter for PV applications

This paper introduces a new transformerless multilevel topology for PV arrays systems. The 7-levels structure ensembles the best characteristics of three basic topologies to obtain a step-up DC-AC converter with only a single DC input and nine power switches. The advantages of the proposed structure are a higher power density, lower harmonic distortion and higher efficiency as no transformer is needed for the grid interconnection. The topology does not require a control scheme for balancing the capacitors voltage. The cases of study clearly show the capabilities of the combination, in cascade, of a DC-DC multilevel boost converter, a DCDC multilevel buck converter and an H-bridge.

Novel closed loop control of a DAB converter for charge/discharge process of EV batteries

In this paper, a novel closed loop control for a Dual Active Bridge (DAB) converter, involved in the charge/discharge process of electric batteries of Electric Vehicles (EV), is presented. The modulation technique implemented is the Single Phase Shift Control (SPSC). The SPSC modulation can control the power flux direction, but it generates a return peak current doing the SPSC modulation suitable for the pulsed charge method. The closed loop control achieves the regulation of the power flux by controlling two variables during the charge/discharge process: the current and the state of charge (SoC) of the battery. The general performance of the closed loop control is analyzed by carrying out several cases of study in Matlab Simulink.