Advances in wind power generation, transmission, and simulation technology

Wind is an increasingly important piece of electricity generation portfolios worldwide. This dissertation describes advances related to the electromechanical energy conversion system of wind turbines, and the electric transmission system for offshore wind power plants. The contributions of this work are the following: (i) We propose that the power electronics topology commonly called the Vienna rectifier can be used for improved variable-speed wind energy conversion. Theoretical analysis is conducted to show how a Vienna rectifier could drive either a squirrel-cage induction generator or a permanent-magnet synchronous generator-based wind turbine. Computer simulations and experimental results demonstrate the feasibility of the proposed topology and potential improvements in energy conversion efficiency. (ii) We propose a novel low-frequency ac (LFAC) transmission system for offshore wind power plants. A system design and control method is set forth, and key system operational characteristics are illustrated via computer simulations. The LFAC system constitutes a promising option for medium- or long-distance transmission, and could be an alternative to high-voltage dc (HVDC) transmission. (iii) We develop a technique that utilizes a field programmable gate array (FPGA) as a dynamic simulation platform for wind turbines. A doubly fed induction generator-based wind turbine simulation is implemented on an FPGA board, in order to verify the effectiveness and performance advantage of this approach

Analiza dizajna LCLC rezonantnog invertera za dvostupanjsko dvofazno napajanje

This paper deals with the design analysis and synthesis of power resonant inverter with sinusoidal output voltage for sensitive loads. The proposed filter must be capable of removing higher harmonic components from the supplying voltage to reach a harmonic distortion of roughly 5% in the whole range of the load (0 − 100%). The inverter can be supplied from either single-phase voltage inverter in full- or half- bridge connection, or from simple DC/DC buck converter. Non-symmetrical control causes higher harmonic content, both odd and even. Simulation and experimental results based on designed parameters and subsequently obtained from Matlab and OrCad models confirm good quality of output quantities, voltage and current.Tema je ovog članka analiza dizajna i sinteza učinskog rezonantnog invertera sa sinisuidalnim izlaznim naponom za osjetljive terete. Predloženi filtar mora moći filtrirati više harmonike ulaznog napona kako bi distorzija harmonika bila oko 5% u čitavom radnom području (0−100%). Inverter se može napajati ili iz jednofaznog naponskog invertera u mosnom ili uzrokuje pojavu viših harmonika u signalu, kako parnih tako i neparnih. Simulacijski i eksperimentalni rezultati temeljeni na sintetiziranim parametrima dobivenim od modela napravljenih u programskim paketima Matlab i OrCad potvr.uju dobru kvalitetu izlaznih veličina napona i struje

The analysis, simulation and control of cycloconverter drives for ship propulsion

Naval expeditionary forces of the future will require new, technologically advanced, multi-mission surface combatants. The design philosophy for future surface combatants stresses survivability, efficiency, and modularity through the use of a modern open architecture consisting of commercial off the shelf and dual use systems. An integrated propulsion and electrical power generation system which utilizes advanced, commercially viable power electronics and state of the art control and monitoring systems is viewed as the appropriate system for the future surface combatant. This study provides the designing naval engineer with technical background information and design considerations for the application of a cycloconverter drive for ship propulsion in an integrated power system. The cycloconverter is a power electronic circuit which performs a single stage conversion of an ac input voltage at one frequency to an ac output voltage of variable frequency and amplitude. Cycloconverters are generally used for low speed, very large horsepower applications and with suitable closed loop control can develop torque and speed responses suitable for ship propulsion. External performance characteristics and control issues for the cycloconverter are discussed, followed by a time domain computer simulation of an integrated ship propulsion drive utilizing a cycloconverter. From the technical background information, external performance characteristics and computer simulation analysis, the designing naval engineer can make educated decisions on the application of a cycloconverter drive for ship propulsion.http://archive.org/details/thenalysissimula1094532014NAU.S. Navy (U.S.N.) authorApproved for public release; distribution is unlimited

Computer model of hybrid compensator of fast varying loads

A computer model of the hybrid compensator of fast varying loads was developed in this dissertation. The computer model was implemented in MFC Visual C++ compiler version 6.0. The classification of fast varying loads and effects of their operation in distribution systems were described in this dissertation. The power properties of fast varying loads were expressed in terms of the Currents\u27 Physical Components Theory. Therefore, the Currents\u27 Physical Components Theory was applied to systems with non-periodic voltages and currents. The supply current of the fast varying loads was decomposed into the useful and the useless components using an algorithm based in the Currents\u27 Physical Components Theory. The current components resulting from this decomposition were used to generate the reference signals for compensator control. The systems of equations that modeled the integrated operation of the distribution system, the fast varying load and the hybrid compensator were developed in detail. The computer model was developed with sequential subroutines that allowed both the analytical solution of the compensation of fast varying loads and the incorporation of the hybrid compensator in the compensation of fast varying loads. The performance of the computer model was verified by comparison between the analytical results with the results obtained with the effect of the hybrid compensator. Finally, the computer model provided reduction of the active and reactive power variation and reduction of the distorted component of the supply current of the fast varying loads tested

High frequency link Uninterruptible Power Supply (UPS) system

This thesis was submitted for the degree of Master of Philosophy and awarded by Brunel University.The main aim of this thesis is to propose, design, simulate and build a new UPS system which can be used for compact applications. The idea of the proposed system is to operate the transformers within the UPS at high frequency so that the size and the weight are kept to minimum. In order to achieve this aim, the transformer within the UPS system is operated at high frequency; however it also carries two 50 Hz waveforms at 180 phase shift so that the transformer does not see this 50 Hz frequency. A cycloconverter is then used to reconstruct the 50 Hz waveform for the UPS output. The UPS system is simulated using PSPICE software at high frequency link of 500 Hz, 1 kHz, 5 kHz and 10 kHz. The simulation results show that the transformer only passes the high frequency component while the 50 Hz frequency is ‘hidden’ within the transformer. The proposed UPS system is then built using MOSFETs IRF740 as the main switches for the inverter and cycloconverter circuits. A Chipkit-uno32-development-board is used to control the MOSFET switches. Simulated and practical results show the viability of the proposed UPS system.This study is funded by Dubai Aluminium

Simulation and performance of a high frequency cycloconverter

With modern naval vessels headed in the direction of integrated power systems, new attention must be paid to efficiency of both power and space. However, modern designs for ship power systems often incorporate DC link converters, or synchroconverters, into their design. Not only does this add extra steps into the power conversion process, it also adds the DC link, which requires large capacitors and can aggravate problems experienced in a short circuit. Modern research for cycloconverters is showing that they have many advantages over the synchroconverter when used in a ship power system. However, cycloconverters also have downsides. One of these problems is the incorporation of harmonics into the supply current, distorting the generator output, as well as voltage harmonics at the output of the converter, which can cause problems at the various loads. Most disastrous of all, additions of subharmonics, or interharmonics which occur below the fundamental can appear. Subharmonics are nearly unfilterable and they can cause serious problems for any power system. This study specifically considers higher frequency inputs to see if these subharmonics can be mitigated in a cycloconverter system.http://archive.org/details/simulationndperf109452773US Navy (USN) author.Approved for public release; distribution is unlimited

Study of the generator/motor operation of induction machines in a high frequency link space power system

Static power conversion systems have traditionally utilized dc current or voltage source links for converting power from one ac or dc form to another since it readily achieves the temporary energy storage required to decouple the input from the output. Such links, however, result in bulky dc capacitors and/or inductors and lead to relatively high losses in the converters due to stresses on the semiconductor switches. The feasibility of utilizing a high frequency sinusoidal voltage link to accomplish the energy storage and decoupling function is examined. In particular, a type of resonant six pulse bridge interface converter is proposed which utilizes zero voltage switching principles to minimize switching losses and uses an easy to implement technique for pulse density modulation to control the amplitude, frequency, and the waveshape of the synthesized low frequency voltage or current. Adaptation of the proposed topology for power conversion to single-phase ac and dc voltage or current outputs is shown to be straight forward. The feasibility of the proposed power circuit and control technique for both active and passive loads are verified by means of simulation and experiment

New hybrid cycloconverters: an evaluation of their performance

Nowadays, power electronic converters based exclusively on IGBTs seem to have achieved excellent load side performance up to megawatt powers range in the low voltage range (200-690Vrms) and are steadily gaining good performance in the medium voltage range as well. However, the medium and high voltage/high power range remains dominated by converters using naturally commutated thyristors, such as line-commutated cycloconverters, line-commutated current source inverters, which provide comparatively poorer output side performance. The purpose of this thesis is to investigate both the conventional cycloconverter, which will be referred as standard cycloconverter in the thesis, and the new hybrid cycloconverter topologies, which are capable of improving the performance of the standard cycloconverter by adding an auxiliary forced commutated inverter with reduced installed power. It will be shown that the new topology is not only able to improve the quality of the output voltage, but also to enhance the control over the circulating current and therefore, for some of the standard cycloconverter arrangements, to improve the input power quality. To realize the evaluation of the standard cycloconverter and validate the feasibility of the new hybrid cycloconverter in both circulating current and circulating current-free mode, SABER simulation models are developed in the first place to perform the initial analysis. A configurable three-phase input to three-phase output cycloconverter prototype which can be easily changed via a switch box to test four different cycloconverter topologies (standard and hybrid) is designed and implemented in the laboratory. Finally, the whole system is debugged and tested. All the relevant results obtained from both the simulation and experiment will be thoroughly analyzed in the thesis

Induction Motors

AC motors play a major role in modern industrial applications. Squirrel-cage induction motors (SCIMs) are probably the most frequently used when compared to other AC motors because of their low cost, ruggedness, and low maintenance. The material presented in this book is organized into four sections, covering the applications and structural properties of induction motors (IMs), fault detection and diagnostics, control strategies, and the more recently developed topology based on the multiphase (more than three phases) induction motors. This material should be of specific interest to engineers and researchers who are engaged in the modeling, design, and implementation of control algorithms applied to induction motors and, more generally, to readers broadly interested in nonlinear control, health condition monitoring, and fault diagnosis