Power Quality in Electrified Transportation Systems

"Power Quality in Electrified Transportation Systems" has covered interesting horizontal topics over diversified transportation technologies, ranging from railways to electric vehicles and ships. Although the attention is chiefly focused on typical railway issues such as harmonics, resonances and reactive power flow compensation, the integration of electric vehicles plays a significant role. The book is completed by some additional significant contributions, focusing on the interpretation of Power Quality phenomena propagation in railways using the fundamentals of electromagnetic theory and on electric ships in the light of the latest standardization efforts

Doubly fed induction generator with integrated energy storage system for smoothening of output power

Wind energy is one of the fastest growing renewable energies in the world today. However, integration of wind power into the power system network is still confronting many challenges. One of the main challenges is the suppression of wind power fluctuations. This thesis focuses on integration of wind power with energy storage to overcome the integration challenges. The first part of this thesis investigates the suitability of energy storage systems for transmission, distribution and wind farm applications. A review on the available energy storage systems is performed considering several criteria. Efforts are made to investigate solutions that meet all the power system requirements. In the second part of the thesis, a wind turbine generator with integrated energy storage system is modeled and studied for smoothening of the output power fluctuations due to changes in wind velocity. An ultra-capacitor is used as an energy storage system which is integrated into the doubly-fed induction generator through a bidirectional buck-boost dc-dc converter. Different modes of operation for the integrated system are studied and the simulation results verify the effectiveness of the designed model using the software package MATLAB/Simulink. The last part of the thesis focuses on application of the doubly-fed induction machine. The grid-side converter of the machine is used to supply harmonics for nearby non-linear loads. A multiple reference frame synchronous estimator and controller are used to track and eliminate the dynamically changing 6k ±1 harmonics on the power system network. This complete system is developed and tested using the software package PSCAD/EMTDC. The simulation results and the harmonic analysis verify the correct operation of the system --Abstract, page iii

Solid state transformer technologies and applications: a bibliographical survey

This paper presents a bibliographical survey of the work carried out to date on the solid state transformer (SST). The paper provides a list of references that cover most work related to this device and a short discussion about several aspects. The sections of the paper are respectively dedicated to summarize configurations and control strategies for each SST stage, the work carried out for optimizing the design of high-frequency transformers that could adequately work in the isolation stage of a SST, the efficiency of this device, the various modelling approaches and simulation tools used to analyze the performance of a SST (working a component of a microgrid, a distribution system or just in a standalone scenario), and the potential applications that this device is offering as a component of a power grid, a smart house, or a traction system.Peer ReviewedPostprint (published version

CONTROL STRATEGIES OF DC MICROGRID TO ENABLE A MORE WIDE-SCALE ADOPTION

Microgrids are gaining popularity in part for their ability to support increased penetration of distributed renewable energy sources, aiming to meet energy demand and overcome global warming concerns. DC microgrid, though appears promising, introduces many challenges in the design of control systems in order to ensure a reliable, secure and economical operation. To enable a wider adoption of DC microgrid, this dissertation examines to combine the characteristics and advantages of model predictive control (MPC) and distributed droop control into a hierarchy and fully autonomous control of the DC microgrid. In addition, new maximum power point tracking technique (MPPT) for solar power and active power decoupling technique for the inverter are presented to improve the efficiency and reliability of the DC microgrid. With the purpose of eliminating the oscillation around the maximum power point (MPP), an improved MPPT technique was proposed by adding a steady state MPP determination algorithm after the adaptive perturb and observe method. This control method is proved independent with the environmental conditions and has much smaller oscillations around the MPP compared to existing ones. Therefore, it helps increase the energy harvest efficiency of the DC microgrid with less continuous DC power ripple. A novel hierarchy strategy consisting of two control loops is proposed to the DC microgrid in study, which is composed of two PV boost converters, two battery bi-directional converters and one multi-level packed-u-cell inverter with grid connected. The primary loop task is the control of each energy unit in the DC microgrid based on model predictive current control. Compared with traditional PI controllers, MPC speeds up the control loop since it predicts error before the switching signal is applied to the converter. It is also free of tuning through the minimization of a flexible user-defined cost function. Thus, the proposed primary loop enables the system to be expandable by adding additional energy generation units without affecting the existing ones. Moreover, the maximum power point tracking and battery energy management of each energy unit are included in this loop. The proposed MPC also achieves unity power factor, low grid current total harmonics distortion. The secondary loop based on the proposed autonomous droop control identifies the operation modes for each converter: current source converter (CSC) or voltage source converter (VSC). To reduce the dependence on the high bandwidth communication line, the DC bus voltage is utilized as the trigger signal to the change of operation modes. With the sacrifice of small variations of bus voltage, a fully autonomous control can be realized. The proposed distributed droop control of different unit converters also eliminates the potential conflicts when more than two converters compete for the VSC mode. Single-phase inverter systems in the DC microgrid have low frequency power ripple, which adversely affects the system reliability and performance. A power decoupling circuit based on the proposed dual buck converters are proposed to address the challenges. The topology is free of shoot-through and deadtime concern and the control is independent with that of the main power stage circuit, which makes the design simpler and more reliable. Moreover, the design of both PI and MPC controllers are discussed and compared. While, both methods present satisfied decoupling performances on the system, the proposed MPC is simpler to be implemented. In conclusion, the DC microgrid may be more widely adopted in the future with the proposed control strategies to address the current challenges that hinder its further development

Industrial and Technological Applications of Power Electronics Systems

The Special Issue "Industrial and Technological Applications of Power Electronics Systems" focuses on: - new strategies of control for electric machines, including sensorless control and fault diagnosis; - existing and emerging industrial applications of GaN and SiC-based converters; - modern methods for electromagnetic compatibility. The book covers topics such as control systems, fault diagnosis, converters, inverters, and electromagnetic interference in power electronics systems. The Special Issue includes 19 scientific papers by industry experts and worldwide professors in the area of electrical engineering

Measurements, Models, Systems and Design

531 s.

Modeling and Controller Design of a Wind Energy Conversion System Including a Matrix Converter

In this thesis, a grid-connected wind-energy converter system including a matrix converter is proposed. The matrix converter, as a power electronic converter, is used to interface the induction generator with the grid and control the wind turbine shaft speed. At a given wind velocity, the mechanical power available from a wind turbine is a function of its shaft speed. Through the matrix converter, the terminal voltage and frequency of the induction generator is controlled, based on a constant V/f strategy, to adjust the turbine shaft speed and accordingly, control the active power injected into the grid to track maximum power for all wind velocities. The power factor at the interface with the grid is also controlled by the matrix converter to either ensure purely active power injection into the grid for optimal utilization of the installed wind turbine capacity or assist in regulation of voltage at the point of connection. Furthermore, the reactive power requirements of the induction generator are satisfied by the matrix converter to avoid use of self-excitation capacitors. The thesis addresses two dynamic models: a comprehensive dynamic model for a matrix converter and an overall dynamical model for the proposed wind turbine system. The developed matrix converter dynamic model is valid for both steady-state and transient analyses, and includes all required functions, i.e., control of the output voltage, output frequency, and input displacement power factor. The model is in the qdo reference frame for the matrix converter input and output voltage and current fundamental components. The validity of this model is confirmed by comparing the results obtained from the developed model and a simplified fundamental-frequency equivalent circuit-based model. In developing the overall dynamic model of the proposed wind turbine system, individual models of the mechanical aerodynamic conversion, drive train, matrix converter, and squirrel-cage induction generator are developed and combined to enable steady-state and transient simulations of the overall system. In addition, the constraint constant V/f strategy is included in the final dynamic model. The model is intended to be useful for controller design purposes. The dynamic behavior of the model is investigated by simulating the response of the overall model to step changes in selected input variables. Moreover, a linearized model of the system is developed at a typical operating point, and stability, controllability, and observability of the system are investigated. Two control design methods are adopted for the design of the closed-loop controller: a state-feedback controller and an output feedback controller. The state-feedback controller is designed based on the Linear Quadratic method. An observer block is used to estimate the states in the state-feedback controller. Two other controllers based on transfer-function techniques and output feedback are developed for the wind turbine system. Finally, a maximum power point tracking method, referred to as mechanical speed-sensorless power signal feedback, is developed for the wind turbine system under study to control the matrix converter control variables in order to capture the maximum wind energy without measuring the wind velocity or the turbine shaft speed

Innovative and Useful Laboratory Experiments of Electrical Machines

This work consists of simple and innovative experiments at the beginning and, as work advances, the experiments become themselves bigger and with more details. The last topics show the analysis of induction and synchronous generators in parallel operation mode and their transients. This work intends to present some innovative and relevant experiments and concepts to electrical machines applications. All chapters show innovations and they are interconnected so that the readers have a wide understanding about these new ways of electrical machines control and operation. Then, the main required topics to reach the cited understanding about new ways of electrical machines control and operation are, in summary, the followings: the project of current and voltage regulators to DC machines, implementation of control system and devices to DC machines, the newest technique to project and optimization of filters and regulators parameters of synchronous generator, an analysis of induction and synchronous generators in parallel operation mode and finalizing with a study about contingencies about synchronous and induction generators in parallel operation mode under load's transients and generation's transients

Ultra-low losses SiC based shunt active power filter for harmonics mitigation and harmonics power recovery in industrial power systems

The classical method to suppress resonances in power systems is by installing passive dampers in parallel to the loads. However, observations indicate significant power losses due to harmonic currents flowing over passive dampers. Certainly, passive dampers absorb harmonic active power and dissipate this power as heat on their resistive elements leading to energy waste. On the other hand, the passive damper counterpart is the active damper. The latter is also known in technical literature as Voltage driven shunt active power filter (VSAPF). The active damper is a power-electronics-based system that emulates a virtual resistance at harmonic frequencies. Truly, very little was known about the harmonic power absorption on active dampers. Therefore, this dissertation delves into a profound analysis of the capability of an ultra-low losses active damper based on SiC semiconductor technology to process the harmonic power intake and perform harmonic power recovery. Harmonic power recovery in this context is understood as the process of transforming the harmonic active power absorbed into fundamental power that is injected back into the power system. The next topic that is addressed is the reduction in the fundamental power demanded by an industrial facility due to the recovery of harmonic active power. To this end, this dissertation analyzes the power balance flow of a distribution power system (e.g., industrial grid) that includes an ultra-low losses active damper. Arising out of the power balance flow analysis, it was found that the active damper with harmonic recovery function achieves a 1.4% reduction on the fundamental power demanded compared to a passive damper. Naturally, the lower the active damper´s power losses, the higher will be the amount of harmonic active power\ud that can be recovered from the power system. Therefore, during this research work, various power electronics converters topologies are analysed to find the best possible design for the active damper with harmonic power recovery functionality. Arising out of this investigation, it was found that the conventional three-level neutral point piloted converter (3L-TNPC) and the asymmetrical three-level converter (3L-ASYM) are the most suitable power circuit topologies for the ultra-low losses active damper. The former topology, the 3L-TNPC, exhibits the lowest power losses for switching frequencies up to 60 kHz. And then, the 3L-ASYM topology presents the lowest losses among all the studied power circuits for switching frequencies beyond 70 kHz. Furthermore, as an active damper forms a closed loop between harmonic voltages and compensating currents, its stability must be ensured. Thus, a careful design of the VSAPF control system and its inner current controllers is essential. On account of this, this dissertation proposes using the Ragazzini method to design the VSAPF’s inner current controllers. Furthermore, the direct design of the inner current controllers on the discrete domain using the Ragazzini method increases the current controllers’ bandwidth by a factor of three compared to the controllers’ design with conventional methods. Consequently, the increased current controller’s bandwidth achieved through the Ragazzini method pushes the stability limit of the active damper forward compared with traditional current controller designs