Utilities demonstration series

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A novel grid computing approach for probabilistic small signal analysis

Grid computing is an advanced technique for collaboratively solving complicated scientific problems using geographically and organisational dispersed computational, data storage and other recourses. Application of grid computing could provide significant benefits to all aspects of power system that involves using computers. Based on our previous research, this paper presents a novel grid computing approach for probabilistic small signal stability (PSSS) analysis in electric power systems with uncertainties. A prototype computing grid is successfully implemented in our research lab to carry out PSSS analysis on two benchmark systems. Comparing to traditional computing techniques, the gird computing has given better performances for PSSS analysis in terms of computing capacity, speed, accuracy and stability. In addition, a computing grid framework for power system analysis has been proposed based on the recent study.

Approximate, Average, Dynamic Models of Uncontrolled Rectifiers for Aircraft Applications

To carry out stability and voltage regulation studies on more electric aircraft systems in which there is a preponderance of multi-pulse, rectifier-fed motor-drive equipment, average dynamic models of the rectifier converters are required. Existing methods are difficult to apply to anything other than single converters with a low pulse number. Therefore an efficient, compact method for deriving the approximate, linear, average model of 6- and 12-pulse rectifiers, based on the assumption of a small duration of the overlap angle is presented. The models are validated against detailed simulations and laboratory prototypes.

Vertical and horizontal scope economies in the regulated US electricity power industry

This paper investigates vertical economies between generation and distribution of electric power, and horizontal economies between different types of power generation in the U.S. electric utility industry. Our quadratic cost function model includes three generation output measures (hydro, nuclear and fossil fuels), which allows us to analyze the effect that generation mix has on vertical economies. Our results provide (sample mean) estimates of vertical economies of 8.1% and horizontal economies of 5.4%. An extensive sensitivity analysis is used to show how the scope measures vary across alternative model specifications and firm types. © 2012 Blackwell Publishing Ltd and the Editorial Board of The Journal of Industrial Economics.

Hybrid power system intelligent operation and protection involving distributed architectures and pulsed loads

Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system. To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators. The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available protection concepts and devices for AC systems in a DC network, were presented. A study was also conducted on the effect of changing the distribution architecture and distributing the storage assets on the various zones of the network on the system's dynamic security and stability. A practical shipboard power system was studied as an example of a hybrid AC/DC power system involving pulsed loads. Generally, the proposed hybrid AC/DC power system, besides most of the ideas, controls and algorithms presented in this dissertation, were experimentally verified at the Smart Grid Testbed, Energy Systems Research Laboratory. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.

Reaproveitamento de condensado e vapor flash em uma planta têxtil com ênfase no setor de acabamento

This study focused object a steam generation system, steam distribution and condensate return a textile plant located in Rio Grande do Norte. The work was based on the following objectives: Knowing the use of saturated water vapor in the dyeing and finishing processes in a textile plant; To study the various aspects of a steam distribution system to identify the ways in which energy losses occur; Obtain quantitative information of the main loss in steam generation system and steam distribution and to measure the losses, water and steam system; Using the flash steam as a means of cost reduction. For it was made use of the calculation of financial gains made in their respective improvements. As a database for the development of working registers are used in industrial processes, data from utility systems, laboratory data analysis and on-line analyzers, covering the period 2013. Using the principles set conservation laws mass and energy, those data showed that the loss of water and energy in the steam system are significant and that the environmental and economic gains to be obtained with improvement actions are quite significant. Based on the data and results suggest that future studies deem the continuity approach to steam generation systems, distribution and mainly condensate return.

Uma metodologia para geração otimizada de ambientes virtuais baseados em usinas hidrelétricas

Based on the possibility of real-time interaction with three-dimensional environments through an advanced interface, Virtual Reality consist in the main technology of this work, used in the design of virtual environments based on real Hydroelectric Plants. Previous to the process of deploying a Virtual Reality System for operation, three-dimensional modeling and interactive scenes settings are very importante steps. However, due to its magnitude and complexity, power plants virtual environments generation, currently, presents high computing cost. This work aims to present a methodology to optimize the production process of virtual environments associated with real hydroelectric power plants. In partnership with electric utility CEMIG, several HPPs were used in the scope of this work. During the modeling of each one of them, the techiniques within the methodologie were addressed. After the evaluation of the computional techniques presented here, it was possible to confirm a reduction in the time required to deliver each hydroelectrical complex. Thus, this work presents the current scenario about development of virtual hydroelectric power plants and discusses the proposed methodology that seeks to optimize this process in the electricity generation sector.

Distributed Power balance and damping control for high power multiport LCL DC hub

This project is funded by European Research Council in FP7; grant no 259328, 2010 and EPSRC grant no EP/K006428/1, 2013.

Distributed Power balance and damping control for high power multiport LCL DC hub

This project is funded by European Research Council in FP7; grant no 259328, 2010 and EPSRC grant no EP/K006428/1, 2013.

Identification of Microturbine Model for Long-term Dynamic Analysis of Distribution Networks

As one of the most successfully commercialized distributed energy resources, the long-term effects of microturbines (MTs) on the distribution network has not been fully investigated due to the complex thermo-fluid-mechanical energy conversion processes. This is further complicated by the fact that the parameter and internal data of MTs are not always available to the electric utility, due to different ownerships and confidentiality concerns. To address this issue, a general modeling approach for MTs is proposed in this paper, which allows for the long-term simulation of the distribution network with multiple MTs. First, the feasibility of deriving a simplified MT model for long-term dynamic analysis of the distribution network is discussed, based on the physical understanding of dynamic processes that occurred within MTs. Then a three-stage identification method is developed in order to obtain a piecewise MT model and predict electro-mechanical system behaviors with saturation. Next, assisted with the electric power flow calculation tool, a fast simulation methodology is proposed to evaluate the long-term impact of multiple MTs on the distribution network. Finally, the model is verified by using Capstone C30 microturbine experiments, and further applied to the dynamic simulation of a modified IEEE 37-node test feeder with promising results.

Transformada wavelet aplicada a análise automática de oscilografias de curta duração em unidades geradoras

The focus of this work is the automatic analysis of disturbance records for electrical power generating units. The main proposition is a method based on wavelet transform applied to short-term disturbance records (waveform records). The goal of the method is to detect the time instants of recorded disturbances and extract meaningful information that characterize the faults. The result is a set of representative information of the monitored signals in power generators. This information can be further classified by an expert system (or other classification method) in order to classify the faults and other abnormal operating conditions. The large amount of data produced by digital fault recorders during faults justify the research of methods to assist the analysts in their task of analysing the disturbances. The literature review pointed out the state of the art and possible applications for oscillography records. The review of the COMTRADE standard and wavelet transform underlines the choice of the method for solving the problem. The conducted tests lead to the determination of the best mother wavelet for the segmentation process. The application of the proposed method to five case studies with real oscillographic records confirmed the accuracy and efficiency of the proposed scheme. With this research, the post-operation analysis of occurrences is improved and as a direct result is the reduction of the time that generators are offline.

Arquitetura para o desenvolvimento de unidades de medição fasorial sincronizada no monitoramento a nível de distribuição

This work presents a low cost architecture for development of synchronized phasor measurement units (PMU). The device is intended to be connected in the low voltage grid, which allows the monitoring of transmission and distribution networks. Developments of this project include a complete PMU, with instrumentation module for use in low voltage network, GPS module to provide the sync signal and time stamp for the measures, processing unit with the acquisition system, phasor estimation and formatting data according to the standard and finally, communication module for data transmission. For the development and evaluation of the performance of this PMU, it was developed a set of applications in LabVIEW environment with specific features that let analyze the behavior of the measures and identify the sources of error of the PMU, as well as to apply all the tests proposed by the standard. The first application, useful for the development of instrumentation, consists of a function generator integrated with an oscilloscope, which allows the generation and acquisition of signals synchronously, in addition to the handling of samples. The second and main, is the test platform, with capabality of generating all tests provided by the synchronized phasor measurement standard IEEE C37.118.1, allowing store data or make the analysis of the measurements in real time. Finally, a third application was developed to evaluate the results of the tests and generate calibration curves to adjust the PMU. The results include all the tests proposed by synchrophasors standard and an additional test that evaluates the impact of noise. Moreover, through two prototypes connected to the electrical installation of consumers in same distribution circuit, it was obtained monitoring records that allowed the identification of loads in consumer and power quality analysis, beyond the event detection at the distribution and transmission levels.

Controle de uma microrrede ilhada baseada em geração eólica-diesel com alto nível de inserção de geração eólica

The insertion of distributed generation units in the electric power systems have contributed to the popularization of microgrid concepts. With the microgrids, several potential benefits can be achieved in regard to power quality and supply reliability. However, several technical challenges related to the control and operation of microgrids, which are associated with high insertion of generation systems based on static converters, must be overcame. Among the opportunities in the context of microgrids, there is the islanded operation of microgrids temporarily disconnected from the electric power systems and also the autonomous operation of geographically isolated microgrids. The frequency in large power systems is traditionally controlled by the generation units based on traditional synchronous generator. The insertion of distributed generation units based on static power converters may bring difficulties to the frequency control in microgrids, due to the reduction of the equivalent inertia of conventional synchronous generators present in islanded and isolated microgrids. In this context, it becomes necessary the proposition of new operational and control strategies for microgrids control, taking into account the presence of distributed generation units based on full-rated converter. This paper proposes an operational and control strategy for the islanded operation of a winddiesel microgrid with high insertion level of wind generation. The microgrid adopted in this study comprises of a wind energy conversion system with synchronous generator based on full rated converter, a diesel generator (DIG) and a dump load. Due to the high insertion level of wind generation, the wind unit operates in Vf mode and the diesel generator operates in PQ mode. The diesel generator and the dump load are used to regulate the DC-link voltage of the wind generation unit. The proposed control allows the islanded operation of the microgrid only with wind generation, wind-only mode (WO), and with wind-diesel generation, wind-diesel mode (WD). For the wind-only mode, with 100% of penetration level of wind generation, it is proposed a DC-link voltage control loop based on the use of a DC dump load. For the winddiesel mode, it is proposed a DC-link voltage control loop added to the diesel generator, which is connected to the AC side of the microgrid, in coordinated action with the dump load. The proposed operational and control strategy does not require the use of batteries and aims to maximize the energy production from wind generation, ensuring the uninterrupted operation of the microgrid. The results have showed that the operational and control strategy allowed the stable operation of the islanded microgrid and that the DC-link voltage control loop added to the diesel generator and the dump load proved to be effective during the typical variations of wind speed and load.

Hybrid Power System Intelligent Operation and Protection Involving Distributed Architectures and Pulsed Loads

Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system. To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators. The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available protection concepts and devices for AC systems in a DC network, were presented. A study was also conducted on the effect of changing the distribution architecture and distributing the storage assets on the various zones of the network on the system’s dynamic security and stability. A practical shipboard power system was studied as an example of a hybrid AC/DC power system involving pulsed loads. Generally, the proposed hybrid AC/DC power system, besides most of the ideas, controls and algorithms presented in this dissertation, were experimentally verified at the Smart Grid Testbed, Energy Systems Research Laboratory. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.

Avoided losses on LV networks as a result of microgeneration

In the scope of the discussions about microgeneration (and microgrids), the avoided electrical losses are often pointed out as an important value to be credited to those entities. Therefore, methods to assess the impact of microgeneration on losses must be developed in order to support the definition of a suitable regulatory framework for the economic integration of microgeneration on distribution networks. This paper presents an analytical method to quantify the value of avoided losses that microgeneration may produce on LV networks. Intervals of expected avoided losses are used to account for the variation of avoided losses due to the number, size and location of microgenerators, as well as for the kind of load distribution on LV networks.