Fault Protection In DC Distribution Systems Via Coordinated Control of Power Supply Converters and Bus Tie Switches

A new fault protection method responds to the current needs of emerging dc power distribution systems by coordinating electronic power converters and mechanical contactors to rapidly isolate short circuit faults while maintaining continuity of power to loads. This work is important because the increasing performance, higher efficiency, and decreasing cost of electronic power converters have spurred a rediscovery and proliferation of dc power distribution systems. Although dc distribution offers advantages such as higher transmission efficiency, higher power density, higher reliability, and ease of interfacing asynchronous sources, enthusiasm for adopting dc technologies suffers from widespread concern over the means to protect dc distribution systems against short-circuit faults. The developed fault protection method rapidly limits the fault current, de-energizes the main distribution bus, reconfigures the bus via mechanical contactors, and re-energizes the system. The entire process can be accomplished fast enough to comply with the requirements of CBEMA and IEEE standards on power quality. A fast and reliable fault detection method has been developed in order to coordinates power converters and contactors. With this method the source power converters independently enter into current-limiting mode as soon as they recognize a fault condition. The bus segmentizing contactors autonomously decide whether to open or not based on their local interpretation of time-to-trip curves as functions of apparent equivalent circuit resistance. This method allows converter and contactors to coordinate to provide fault protection for dc distribution systems independently on communication failures. Simulation and experimental results show that fault current can be limited within few milliseconds, faults can be isolated within 20 ms and that the system can be re-energized within 100 ms. Moreover, this work provides system design considerations and limitations on components and system parameters

Application of the computing environment maple To the calculation of the dynamics of the electromagnets in the complicated systems of forced control

The authors propose a technique for calculating the dynamics of electromagnets operating in complex forced systems. Such forced electromagnets are widely used in electromechanical switching devices, in particular in vacuum contactors, to reduce their size, energy consumption and to increase speed, which indicates the relevance of this topic. A mathematical model of the dynamics of a forced electromagnetic system, which takes into account the peculiarities of behavior in transients of its individual elements – the mechanical system, the magnetic and electrical circuits, taking into account the interaction of the electromagnet with a control device when the apparatus is activated, contains certain signs of scientific novelty and is the purpose of the paper. The technique of calculating the dynamics of forced electromagnets uses the computing environment Maple. The calculation is based on a mathematical model, which is a system of nonlinear differentialequations of the magnetic and electric circuits, supplemented by the equations of motion of the elements of a mechanical system. The use of the computing environment Maple, applied here to automatically perform the mathematical transformations, allowsavoiding the complicated processes of choosing the numerical integration method, programming of complex and cumbersome equations and numerical integration procedures, to obtain results of calculations in convenient tabular and/or graphic form. This specifically indicates the practical significanceof this work. The results of the comparison of calculations with previously published experimental data presented in the paper indicate the high efficiencyof the proposed models and techniques.Розглядається запропонована авторами методика розрахунку динаміки електромагнітів, що працюють у складних форсованих системах. Подібні форсовані електромагніти широко застосовуються в електромеханічних комутаційних апаратах, зокрема у вакуумних контакторах, для зменшення їх розмірів, споживання енергії та для підвищення швидкодії, що свідчить про актуальність даної теми. Математична модель динаміки форсованої електромагнітної системи, що враховує особливості поведінки у нестаціонарних процесах її окремих елементів – механічної системи, магнітного та електричного кіл з урахуванням взаємодії електромагніта з пристроєм керування під час спрацьовування апарата, містить певні ознаки наукової новизни і є метою статті. Методика розрахунку динаміки форсованих електромагнітів застосовує математичний пакет Maple. В основу розрахунку покладено математичну модель, яка представляє собою систему нелінійних диференційних рівнянь магнітного і електричного кіл, доповнених рівняннями руху елементів механічної системи. Застосування пакетуMaple, який багато в чому бере на себе складнощі математичного опису різних процесів, автоматично здійснюючи дуже складні і громіздкі математичні перетворення, дозволяє, уникаючи складних процесів вибору способу чисельного інтегрування, програмування складних й громіздких рівнянь та процедур їх чисельного інтегрування, отримувати результати розрахунків у зручній табличній та/або графічній формі, що свідчить про практичну значущість даної роботи. Наведені у статті результати зіставлення розрахунків з опублікованими раніше експериментальними даними, свідчать про високу ефективність запропонованих моделей та методи

Modelling, analysis and verification of a resonant llc converter as a power supply for the electromagnetic driving mechanism of an electromagnetic contactor

The paper presents model based analysis and experimental verification of a half-bridge resonant LLC converter for suppling power to the electromagnetic driving mechanism of an electromagnetic contactor. In the proposed application the convertor - powered either by AC or DC voltage - supplies the coil of the contactor with DC voltage. Analytical and experimental results presented, show several important advantages of the proposed topology: versatility in terms of input voltages – both AC and DC are accepted; stability over wide voltage range; omission of overvoltages – common to electromagnetic systems; reduced power consumption

A Contract-Based Methodology for Aircraft Electric Power System Design

In an aircraft electric power system, one or more supervisory control units actuate a set of electromechanical switches to dynamically distribute power from generators to loads, while satisfying safety, reliability, and real-time performance requirements. To reduce expensive redesign steps, this control problem is generally addressed by minor incremental changes on top of consolidated solutions. A more systematic approach is hindered by a lack of rigorous design methodologies that allow estimating the impact of earlier design decisions on the final implementation. To achieve an optimal implementation that satisfies a set of requirements, we propose a platform-based methodology for electric power system design, which enables independent implementation of system topology (i.e., interconnection among elements) and control protocol by using a compositional approach. In our flow, design space exploration is carried out as a sequence of refinement steps from the initial specification toward a final implementation by mapping higher level behavioral and performance models into a set of either existing or virtual library components at the lower level of abstraction. Specifications are first expressed using the formalisms of linear temporal logic, signal temporal logic, and arithmetic constraints on Boolean variables. To reason about different requirements, we use specialized analysis and synthesis frameworks and formulate assume guarantee contracts at the articulation points in the design flow. We show the effectiveness of our approach on a proof-of-concept electric power system design

Transient Maneuvers and Pressure Analysis on an Automotive Torque Converter

This work involves an investigation of internal fluid behavior of an automotive torque converter in a front-wheel drive automatic 6-speed transmission. The fluid behavior is identified through 29 pressure transducers instrumented throughout the torus, acquired through IR Telemetrics multiplexed channels, and analyzed with custom MATLAB code. The main vehicle operating conditions studied in this research are back drive scenarios or low motoring torques. Findings showed speed and torque limits for open converter coast down conditions as well as pressure field behavior with negative input torque

Power quality services provided by virtually synchronous FACTS

The variable and unpredictable behavior of renewable energies impacts the performance of power systems negatively, threatening their stability and hindering their efficient operation. Flexible ac transmission systems (FACTS) devices are able to emulate the connection of parallel and series impedances in the transmission system, which improves the regulation of power systems with a high share of renewables, avoiding congestions, enhancing their response in front of contingencies and, in summary, increasing their utilization and reliability. Proper control of voltage and current under distorted and unbalanced transient grid conditions is one of the most critical issues in the control of FACTS devices to emulate such apparent impedances. This paper describes how the synchronous power controller (SPC) can be used to implement virtually synchronous FACTS. It presents the SPC functionalities, emphasizing in particular the importance of virtual admittance emulation by FACTS devices in order to control transient unbalanced currents during faults and attenuate harmonics. Finally, the results demonstrate the effectiveness of SPC-based FACTS devices in improving power quality of electrical networks. This is a result of their contribution to voltage balancing at point of connection during asymmetrical faults and the improvement of grid voltage quality by controlling harmonics flow.Postprint (published version

A new model of electromechanical relays for predicting the motion and electromagnetic dynamics

In this paper, a novel multiphysics and nonlinear model for electromechanical relays is presented. The electromagnetic dynamics is analyzed by calculating the total reluctance of the magnetic equivalent circuit (MEC), which is composed of a fixed length iron core and an angular air gap. Magnetic saturation and angular dependency of the reluctance are considered in the analysis. Then, an energy balance over the electromagnetic components of the system is used to obtain the torque which drives the movable armature. A planar mechanism of four rigid bodies, including spring-damping torques that restrict the motion and model the contact bounces that occur in the switchings, is proposed to explain the dynamics of the movable components. Experimental tests show the accuracy of the model in both the electromagnetic and the mechanical parts

Measurement realities of current collection in dynamic space plasma environments

Theories which describe currents collected by conducting and non-conducting bodies immersed in plasmas have many of their concepts based upon the fundamentals of sheath-potential distributions and charged-particle behavior in superimposed electric and magnetic fields. Those current-collecting bodies (or electrodes) may be Langmuir probes, electric field detectors, aperture plates on ion mass spectrometers and retarding potential analyzers, or spacecraft and their rigid and tethered appendages. Often the models are incomplete in representing the conditions under which the current-voltage characteristics of the electrode and its system are to be measured. In such cases, the experimenter must carefully take into account magnetic field effects and particle anisotropies, perturbations caused by the current collection process itself and contamination on electrode surfaces, the complexities of non-Maxwellian plasma distributions, and the temporal variability of the local plasma density, temperature, composition and fields. This set of variables is by no means all-inclusive, but it represents a collection of circumstances guaranteed to accompany experiments involving energetic particle beams, plasma discharges, chemical releases, wave injection and various events of controlled and uncontrolled spacecraft charging. Here, an attempt is made to synopsize these diagnostic challenges and frame them within a perspective that focuses on the physics under investigation and the requirements on the parameters to be measured. Examples include laboratory and spaceborne applications, with specific interest in dynamic and unstable plasma environments

Experimental validation of Power Plant Control architectures

This project deals with the experimental validation of different power plant control architectures for Large-Scale Photovoltaic power plants (LS-PVPP). Central and hierarchical are the two main control architectures studied in the thesis. The central architecture controls the inverters of the power plant from a centralized unit and the hierarchical also takes into consideration the local controllers of the converters. Various of the standard control services for this type of power plants are introduced and tested. An experimental platform consisting of three voltage source converters (VSC) is used for the tests. The controls and services are implemented in an external software called LabVIEW and connected to the platform via National Instruments hardware. The experimental data is contrasted and validated with the simulation data from simulations performed in Simulink and PLECS. The first part of this thesis introduces the LS-PVPPs and the architectures and services considered in the project. The main elements forming a LS-PVPP, different topologies and the general plant and inverters controls are shown in this part. Also, the architectures and services are explained in depth. The second part describes the modelling of the system and the design of the power plant controller. There, the case of study is presented and the different models used in the simulations are defined. Then, the design and tuning of the control is described. The next part shows the experimental setup used in the project. A definition of the real platform set in the lab and the inverters is presented here. An important part of the experimental setup is the communication protocols and the LabVIEW implementation, also shown in this part. Finally, some experimental and simulation tests are performed for each architecture and service previously presented. A comparison is made in order to validate experimental with simulated dataObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura::9.1 - Desenvolupar infraestructures fiables, sostenibles, resilients i de qualitat, incloent infraestructures regionals i transfrontereres, per tal de donar suport al desenvolupament econòmic i al benestar humà, amb especial atenció a l’accés assequible i equitatiu per a totes les persone