New methodology to calculate DC voltage signature in n-phases TRUs under supply voltage sags

A new methodology based on the shadow projection has been developed to study any multipulse rectifier's dynamic behavior under balanced and unbalanced conditions. The proposed methodology calculates the DC average voltage and instantaneous values under balanced and unbalanced supply voltage conditions for multiphase Transformer Rectifier Units (TRUs). The calculation of the developed algorithms is more practical than the classical methods and other approaches based on Fourier series or symmetrical components that are difficult to apply under unbalanced conditions. Furthermore, classical methods are not simple to determine the limits of the integrals and calculate them to obtain the average value, so a more friendly and practical methodology has been developed to analyze rectifiers operating under supply voltage sags. This new methodology has been validated by simulation for a 12-pulse TRU in series and parallel connections, and it has also been validated for a 36-pulse TRU in parallel connection using interphase inductors. The accuracy of the calculations is validated by the experimental results for 12-pulse TRUs, series, and parallel connection, and 18-pulse TRU in series connection.This work was supported by the research project ‘‘Estabilidad de redes MVDC integrando tecnologías de energías renovables, almacenamiento de energía y convertidores de fuente de impedancia,’’ by the Ministerio de Ciencia, Innovación y Universidades and European Union, under Grant RTI2018-095720-B-C33.Peer ReviewedPostprint (published version

Comparative study of TEC for GISTM stations in the Peninsular Malaysia region for the period of January 2011 to December 2012

Total Electron Content (TEC) is a fundamental and the most prevalent parameter that affects Global Positioning System (GPS) signals, leading to delays, poor signals or total loss of signals. The gradients in TEC are frequently associated with disturbance in the ionosphere which explains the space weather behavior and indirectly causes inefficient operations of ground and space based Global Navigation Satellite System (GNSS) applications. The role of TEC variability is constructive in space weather prediction as it allows GNSS users to minimize rangerate errors in achieving highly reliable measurements. This paper therefore presents an analysis of the diurnal and seasonal activity dependence of TEC using data obtained from the GPS Ionospheric Scintillation and TEC Monitor (GISTM) at two stations in Peninsular Malaysia which are located at the Langkawi National Observatory, Langkawi, LGKW (06_19’N, 99_51’E) and Universiti Kebangsaan Malaysia, UKM (02_55’N, 101_46’E). Data for the two years (2011 and 2012), were recorded using the NovAtel GSV 4004B GISTM model equipment. Further investigations on a few more stations in the coast of Peninsular Malaysia will strengthen and consolidate the findings of this study

Analytical Evaluation of Surface-Mounted PMSG Performances Connected to a Diode Rectifier

This paper analyzes some operational issues of threephase surface-mounted permanent magnet synchronous generators (PMSGs) connected to a diode rectifier. This simple configuration coupled to a single-switch dc–dc converter is used in smallscale wind energy conversion systems, as well as in energy harvesting systems, to reduce costs. The diode rectifier causes an intrinsic limit for the maximum convertible power, which is related to the load impedance matching, and additional joule losses due to the distorted currents. By using an analytical steady-state model of the rectifier and of the PMSG, this paper discusses how to achieve two particularly meaningful operating conditions characterized respectively by the maximum power transfer and the maximum power per ampere. The theory is validated by simulation and test results on a prototype

MODELLING AND SIMULATION OF HIGH VOLTAGE DIRECT CURRENT TRANSMISSION SYSTEM

High voltage direct current (HVDC) is one of the technologies in electrical transmission system. It is established as an alternative to AC transmission system. The main purpose ofthis project is to model and simulate the HVDC system by using software. The scope of this project is to cover the concepts about transmission system, specifically HVDC.In fact, familiarization with softwaresuch as ATPwill be covered too as it will assist in the modeling and simulation stage. The systematic approaches such as research, modeling, simulation, validation and troubleshooting in accomplishing this project are discussed in the chapter of methodology. Assessments on several softwares were conducted in order to identify the best software in studying the behavior of HVDC system. Besides that, data taken from real HVDC project, which is EGAT/TNB HVDC Interconnection Project, will be discussed too. Comparison between the simulated results and the real data were carried out in order to validate the findings from the simulation. Based on the evaluation made on the relevant software, it is found that ATP is the best software to be utilized in this project. Subsequently, simulations were conducted by using ATP and desired waveforms were obtained since they managed to resemble the real data and consistent with the theoretical concept

MODELING AND VALIDATION OF A SYNCHRONOUS-MACHINE/CONTROLLED-RECTIFIER SYSTEM

The hardware validation of a novel average-value model (AVM) for the simulation of a synchronous-generator/controlled rectifier system is presented herein. The generator is characterized using genetic algorithm techniques to fit standstill frequency response (SSFR) measurements to q and d-axis equivalent circuits representing the generator in the rotor reference frame. The generator parameters form the basis of a detailed model of the system, from which algebraic functions defining the parametric AVM are derived. The average-value model is compared to the physical system for a variety of loading and operating conditions including step load change, change in delay angle, and external closed-loop control, validating the model accuracy for steady-state and transient operation

On the integration of electromagnetic railguns with warship electric power systems

Electromagnetic railguns have reached levels of maturity whereby they are now being considered for installation on warships. A critical review of previous research in this field has highlighted the potential adverse impact that electromagnetic railguns may have on the supply quality of electric power systems. Currently, there is limited collective knowledge of this impact particularly when configured in a topology representative of a candidate warship. This research explores the impact of electromagnetic railguns on a candidate warship electric power system. This research employs a validated gas turbine alternator model of the Rolls-Royce MT30 capable of assessing performance when powering an electromagnetic railgun. A novel control circuit to interface the electromagnetic railgun with the gas turbine alternator and control the rate of fire was developed. A mathematical analysis of the system was then undertaken to understand the challenges in greater detail. A system model was then developed to explore the transient and harmonic impact of electromagnetic railgun firing on the warship electric power system using time-domain simulations. The key finding of this research is that the current practice of warship electric power system design is not robust enough to withstand electromagnetic railgun operations and that under-voltage, under-frequency, over-frequency and excessive waveform distortion result due to the high power demand of the electromagnetic railgun. To mitigate these consequences it is recommended that firing constraints be placed on the electromagnetic railgun and the maximum waveform distortion at the high voltage bus be limited to 8% total harmonic distortion. Failure to adhere to the recommended limits may result in the mal-operation, reduced efficiency and reduced life expectancy of the electric power system

EXPERIMENTAL ACTIVITY AND ANALYSIS OF PLC TECHNOLOGY IN VARIOUS SCENARIOS

Power line communications (PLCs) have become a key technology in the telecommunication world, both in terms of stand-alone technology or a technology that can complement other systems, e.g., radio communications. Since PLCs exploit the existing power delivery grid to convey data signals, the application scenarios are multiple. Historically, PLCs have been deployed in outdoor low voltage (< 1 kV) power distribution networks for the automatic metering and the management of the loads. Today, the evolution of the electrical grid toward an intelligent and smart grid that dynamically manages the generation, the distribution and the consumption of the power makes this technology still relevant in this scenario. Therefore, PLCs have raised significant interest in recent years for the possibility of delivering broadband Internet access and high speed services to homes and within the home. The increase in demand for such services has inspired the research activity in the in-home scenario, both toward the direction of the development of independent or integrated solutions, with respect to already existing technologies. Another application scenario that has not been deeply investigated yet is the in-vehicle one, which includes the in-car, in-plane and in-ship scenario. Since the power grid has not been designed for data communications, the transmission medium is hostile and exhibits high attenuation, multipath propagation and frequency selectivity, due to the presence of branches, discontinuities and unmatched loads. For the proper design of a power line communication (PLC) system, good knowledge of the grid characteristics in terms of propagation channel and disturbances is required. In this respect, we have performed experimental measurement campaigns in all the aforementioned scenarios. We aimed to investigate the grid characteristics from a telecommunication point of view. In this thesis, we present the results of our experimental activity. Firstly, we analyze the outdoor low voltage and industrial scenario. We have carried out a measurement campaign in an artificial network that can resemble either an outdoor low voltage power distribution network or an industrial or marine power system. We have focused on the channel frequency response, the line impedance and the background PLC noise, within the narrow band and the broad band frequency ranges. Then, we focus on the in-home scenario. In this context, we have studied the impact of the electrical devices (loads) connected to the power grid on the PLC medium characteristics and on the quality of the data communication. Their behavior has been investigated both in the time and frequency domain, in terms of load impedance and impulsive noise components that they inject into the network. Finally, we consider in-vehicle PLC, in particular the in-ship and in-car environment. Firstly, we summarize the results of a channel measurement campaign that we have carried out in a large cruise ship focusing on the low voltage power distribution network in the band 0-50 MHz. Thus, we present the results of an entire PLC noise and channel measurement campaign that we have performed in a compact electrical car

Accurate modeling techniques for power delivery

“Power delivery is essential in electronic systems to provide reliable power from voltage sources to load devices. Driven by the ambitious user demands and technology evolutions, the power delivery design is posed serious challenges. In this work, we focus on modeling two types of power delivery paths: the power distribution network (PDN) and the wireless power transfer (WPT) system. For the modeling of PDN, a novel pattern-based analytical method is proposed for PCB-level PDN impedance calculations, which constructs an equivalent circuit with one-to-one correspondences to the PCB’s physical structure. A practical modeling methodology is also introduced to optimize the PDN design. In addition, a topology-based behavior model is developed for the current-mode voltage regulator module (VRM). This model includes all the critical components in the power stage, the voltage control loop, and the current control loop of a VRM device. A novel method is also proposed to unify the modeling of the continuous and discontinuous conduction modes for transient load responses. Cascading the proposed VRM model with the PCB-level PDN model enables a combined PDN analysis, which is much needed for modern PDN designs. For the modeling of WPT system, a system-level model is developed for both efficiency and power loss of all the blocks in WPT systems. A rectifier characterization method is also proposed to obtain the accurate load impedance. This model is capable of deriving the power capabilities for both the fundamental and higher order harmonics. Based on the system model, a practical design methodology is introduced to simultaneously optimize multiple system parameters, which greatly accelerates the design process”--Abstract, page iv

Optimised design of isolated industrial power systems and system harmonics

This work has focused on understanding the nature and impact of non-linear loads on isolated industrial power systems. The work was carried out over a period of 8 years on various industrial power systems: off-shore oil and gas facilities including an FPSO, a wellhead platform, gas production platforms, a mineral processing plant and an LNG plant. The observations regarding non-linear loads and electrical engineering work carried out on these facilities were incorporated into the report.A significant literature describing non-linear loads and system harmonics on industrial power systems was collected and reviewed. The literature was classified into five categories: industrial plants and system harmonics, non-linear loads as the source of current harmonics, practical issues with system harmonics, harmonic mitigation strategies and harmonic measurements.Off-shore oil and gas production facilities consist of a small compact power system. The power system incorporates either its own power generation or is supplied via subsea cable from a remote node. Voltage selection analysis and voltage drop calculation using commercially available power system analysis software are appropriate tools to analyse these systems. Non-linear loads comprise DC rectifiers, variable speed drives, UPS systems and thyristor controlled process heaters. All nonlinear loads produce characteristic and non-characteristic harmonics, while thyristor controlled process heaters generate inter-harmonics. Due to remote location, harmonic survey is not a common design practice. Harmonic current measurements during factory acceptance tests do not provide reliable information for accurate power system analysis.A typical mineral processing plant, located in a remote area includes its own power station. The power generation capacity of those systems is an order of magnitude higher than the power generation of a typical off-shore production facility. Those systems comprise large non-linear loads generating current and voltage interharmonics. Harmonic measurements and harmonic survey will provide a full picture of system harmonics on mineral processing plants which is the only practical way to determine system harmonics. Harmonic measurements on gearless mill drive at the factory are not possible as the GMD is assembled for the first time on site.LNG plants comprise large non-linear loads driving gas compressor, however those loads produce integer harmonics. Design by analysis process is an alternative to the current design process based on load lists. Harmonic measurements and harmonic survey provide a reliable method for determining power system harmonics in an industrial power system