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Power and Energy Society General Meeting, 2011 IEEE

Date 24-29 July 2011

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Displaying Results 1 - 25 of 987
  • [Front cover]

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    Freely Available from IEEE
  • Incorporating short-term stored energy resource into Midwest ISO energy and ancillary service market

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    Summary form only given. The purpose of this paper is to analyze various approaches to incorporate short-term stored energy resources into the Midwest ISO co-optimized energy and ancillary service market. Based on the analysis, the best approach is to utilize short-term stored energy resources for regulating reserve with the real-time energy dispatch to be set in such a way that the maximum regulating reserve can be cleared. Results on a five-bus system are used to illustrate the clearing and pricing on short-term stored energy resources with the proposed approach. Monte Carlo simulation on the five-bus system is used to illustrate the AGC regulation deployment. View full abstract»

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  • Dynamic performance of a modular multilevel back-to-back HVDC system

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    The modular multilevel converter (MMC) is a newly introduced switch-mode converter topology with the potential for high-voltage direct current (HVDC) transmission applications. This paper focuses on the dynamic performance of an MMC-based, back-to-back HVDC system. A phase-disposition (PD) sinusoidal pulsewidth modulation (SPWM) strategy, including a voltage balancing method, for the operation of an MMC is presented in this paper. Based on the proposed PD-SPWM switching strategy, a mathematical model for the MMC-HVDC system, under both balanced and unbalanced grid operation modes, is developed. Dynamic performance of the MMC-based back-to-back HVDC converter system, based on time-domain simulation studies in the PSCAD/EMTDC environment, is then evaluated. The reported time-domain simulation results show that based on the adopted PD-SPWM switching strategy, the MMC-HVDC station can respond satisfactorily to the system dynamics and control commands under balanced and unbalanced conditions while maintaining voltage balance of the dc capacitors. View full abstract»

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  • Damping inter-area oscillations using phase imbalanced series compensation schemes

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    Summary form only given. The recently proposed phase imbalanced series capacitive compensation concept has been shown to be effective in enhancing power system dynamics as it has the potential of damping power swing as well as subsynchronous resonance oscillations. In this paper, a comparative effectiveness of two “hybrid” series capacitive compensation schemes in damping inter-area oscillations is evaluated. A hybrid scheme is a series capacitive compensation scheme, where two phases are compensated by fixed series capacitor (C) and the third phase is compensated by either a TCSC or SSSC in series with a fixed capacitor (Cc). The effectiveness of both schemes in damping inter-area oscillations for various network conditions, namely different system faults and tie-line power flows is evaluated using the EMTP-RV time simulation program. View full abstract»

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  • A Naïve multiple linear regression benchmark for short term load forecasting

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    Benchmarking issue in short term load forecasting has not received as much attention as it deserves. Although dozens of techniques have been reported to be applied to short term load forecasting, most of them are still on the theoretical level with insignificant practical value. None of them has been established to produce benchmarking models for comparative assessment. This paper proposes a naïve multiple linear regression benchmark for short term load forecasting, which is from the experience of helping a US utility develop the first in-house short term load forecasts. The proposed model has been served as a benchmark for this utility since 2009, and was in production use for a year with satisfying performance before a major upgrade. It has also been used for a Canadian utility for load forecasting purposes. In addition, it was reproduced by a group of graduate students from a creditable US university following the documented procedure. View full abstract»

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  • Effect of various parameters on the inductive induced voltage and current on pipelines

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    Considerable research has been conducted on the issues of induced voltage on the pipelines which are close to the high voltage power lines. It has been found that the induced voltage and current on the pipeline are determined by many parameters. This paper presents a comprehensive study on how the various parameters affect the induced voltage and current on the pipelines. In the system modeling part, a circuit model for multiple-pipeline section-model is employed. In this model, not only the perfect parallel case, but also a more realistic case with approaches, crossing as well as removals is considered. 2 cases are studied in this paper. The results of steady state induced voltage and current have demonstrated the effect of different parameters. View full abstract»

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  • System-wide inertial response from fixed speed and variable speed wind turbines

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    As wind penetration levels on power systems increase worldwide, the dynamic characteristics of these systems are changing due to the displacement of synchronous generation. One issue, of particular concern, is the resulting reduction in system inertia. Modern, variable speed wind turbines are controlled by power electronics and so do not inherently contribute to the inertial response of the system. Such devices can however be fitted with a control loop which provides an active power response to significant frequency deviations, similar to the inertial response of fixed speed wind turbines and synchronous generation. However, the response of variable speed turbines is dependent on local wind speeds and so cannot be quantified deterministically by system operators. This paper examines the potential for wind generation to contribute to system inertial response and considers the aggregated inertial response capabilities of fixed speed and variable speed wind generation. View full abstract»

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  • Real-time ampacity and ground clearance software for integration into smart grid technology

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    Output from a real-time sag, tension and ampacity program was compared with measurements collected on an outdoor test span. The test site included a laser range-finder, load cells and weather station. A fiber optic distributed temperature sensing system was routed along the conductor and thermocouples were attached to the conductor's surface. Nearly 40 million data points were statistically compared with the computer output. The program provided results with a 95% confidence interval for conductor temperatures within ±10°C and sags within ±0.3m for a conductor temperature of 75°C. Test data were also used to determine the accuracy of the IEEE Standard 738 models. The computer program and the Standard 738 transient model gave comparable temperatures for temperatures up to 160°C. Measured temperatures were used to estimate the radial and axial temperature gradients in the ACSR conductor. The effect of insulators and instrumentation attached to the conductor on the local conductor temperature was determined. The real-time rating program is an alternative to installing instrumentation on the conductor for measuring tension, sag or temperature. The program avoids the problems of installing and maintaining expensive instrumentation on the conductor, and it will provide accurate information on the conductor's temperature and ground clearance in real-time. View full abstract»

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  • No title

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    The number of semiconductor switches in a modular multilevel converter (MMC) for HVDC transmission is typically two orders of magnitudes larger than that in a two or three level voltage-sourced converter (VSC). The large number of devices creates a computational challenge for electromagnetic transient simulation programs, as it can significantly increase the simulation time. The paper presents a method based on partitioning the system's admittance matrix and deriving an efficient time-varying Thévenin's equivalent for the converter part. The proposed method does not make use of approximate interfaced models, and mathematically, is exactly equivalent to modelling the entire network (converter and external system) as one large network. It is shown to drastically reduce the computational time without sacrificing any accuracy. The paper also presents control algorithms and other modelling aspects. The efficacy of the proposed method is demonstrated by simulating a point-to-point VSC-MMC-based HVDC transmission system. View full abstract»

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  • The development of a smart distribution grid testbed for integrated information management systems

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    This paper presents a smart distribution grid testbed to test or compare designs of integrated information management systems (I2MSs). An I2MS extracts and synthesizes information from a wide range of data sources to detect abnormal system behaviors, identify possible causes, assess the system status, and provide grid operators with response suggestions. The objective of the testbed is to provide a modeling environment with sufficient data sources for the I2MS design. The testbed includes five information layers and a physical layer; it generates multi-layer chronological data based on actual measurement playbacks or simulated data sets produced by the physical layer. The testbed models random hardware failures, human errors, extreme weather events, and deliberate tampering attempts to allow users to evaluate the performance of different I2MS designs. Initial results of I2MS performance tests showed that the testbed created a close-to-real-world environment that allowed key performance metrics of the I2MS to be evaluated. View full abstract»

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  • A combined state-space nodal method for the simulation of power system transients

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    Summary form only given. This paper presents a new solution method that combines state-space and nodal analysis for the simulation of electrical systems. The presented flexible clustering of state-space described electrical subsystems into a nodal method offers several advantages for the efficient solution of switched networks, nonlinear functions and for interfacing with nodal model equations. This paper extends the concept of discrete companion branch equivalent of the nodal approach to state-space described systems and enables natural coupling between them. The presented solution method is simultaneous and allows to benefit from the advantages of two different modeling approaches normally exclusive from one another. View full abstract»

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  • Synchronous machine modeling precision and efficiency in electromagnetic transients

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    Summary form only given. This paper presents various synchronous machine models implemented in the computation of electromagnetic transients. The paper proposes new models for achieving better computational efficiency while maintaining precision. In addition to simple infinite bus analysis, the machine models are also compared for a more sophisticated and practical case study. Precision analysis includes the surrounding network accuracy constraints. View full abstract»

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  • Evaluating risk indices of weak lines and buses causing static voltage instability

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    A set of risk indices of weak lines and buses causing static voltage instability and an assessment technique to evaluate the risk indices are proposed. The assessment technique is based on the integration of a quadratic optimization model combined with a line-based voltage stability index into Monte Carlo simulation. The proposed risk indices can be used to differentiate the risk responsibilities among the weak lines and buses and are useful information in determining locations of operational and planning measures for improving static voltage stability. The simulation results for the IEEE 30-bus system and Polish power grid system with 2383 buses demonstrate the effectiveness of the presented technique and usefulness of the proposed risk indices. View full abstract»

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  • Study of transformer resonant overvoltages caused by cable-transformer high-frequency interaction

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    Summary form only given. Power transformers can fail from dielectric stresses caused by electromagnetic transients. In this paper we focus on a special phenomenon where excessive overvoltages arise due to resonance. This situation can take place when a transformer on the high-voltage side is connected to a cable and the low-voltage side is unloaded. Very high overvoltages can then result on the low-voltage side from transient events that cause a weakly attenuated overvoltage on the cable with a dominant frequency matching a resonance peak in the transformer voltage ratio. Laboratory tests on a 11 kV/230 V distribution transformer show that a step voltage excitation on a 27-m cable produces a 24 p.u. overvoltage on the open low-voltage side. The voltage waveforms are accurately reproduced by a black-box model obtained from frequency sweep measurements. Simulations show that overvoltages as high as 43 p.u. could occur with the most unfavorable cable length. It is further shown that the following situations can lead to high overvoltages on an unloaded transformer low-voltage side: 1) ground fault initiation at the far cable end, 2) cable energization from a busbar with several other cables connected, and 3) cable energization from another cable of same length. View full abstract»

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  • A hybrid measurement approach for wide-band characterization and modeling of power transformers

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    Summary form only given. This paper describes a hybrid procedure for wide-band characterization and modeling of power transformer behavior from frequency sweep measurements. The approach is based on measuring corresponding sets of voltage and current vectors that are associated with short circuit and open circuit conditions. These vectors are stacked side-by-side in two matrices which are used for computing the short circuit admittance matrix. This hybrid approach is shown to give more information about the transformer behavior than the traditional approach of measuring the admittance matrix directly under short-circuit conditions, which tends to corrupt the small eigenvalues associated with open-circuit conditions. From the obtained admittance matrix, a pole-residue model is extracted via vector fitting and passivity enforcement, thereby giving a model ready for EMTP simulation. The accuracy of the small eigenvalues is retained by using a modal formulation in the fitting and passivity enforcement step. Application to a distribution transformer shows that the hybrid approach can greatly improve the accuracy of time domain simulations involving high-impedance terminations. View full abstract»

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  • A gas turbine model for studies on distributed generation penetration into distribution networks

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    Summary form only given: The paper proposes a detailed model of a gas turbine for a CHP (Combined Heat and Power) plant. The prime mover is endowed with several controls: first of all, a speed control which can be either droop type or isochronous type according to the status of connection to the distribution grid. An acceleration limiter and an exhaust gases temperature limiter intervene to cut the fuel request respectively in case of an excessive rotor acceleration and of a too high temperature of the exhaust gases. A further control regulates IGV (Inlet Guide Vanes) in order to keep the exhaust temperature almost constant. This is important in a cogeneration plant where the heat recovery from the exhaust gases is used to satisfy the demand of the thermal load. Some validation simulations on a model of cogeneration plant connected to a MV distribution grid are carried out and commented. View full abstract»

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  • Impact of imbalanced phase operation of SSSC on damping subsynchronous resonance

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    The paper investigates the impact of using Static Synchronous Series Compensator (SSSC) in phase imbalanced operation modes on damping subsynchronous resonance in series capacitive compensated transmission grid. Phase imbalance has the potential of reducing the energy exchange between the electrical and mechanical sides of the turbine-generator and, therefore, damps subsynchronous oscillations. The validity and effectiveness of different proposed phase imbalanced modes have been demonstrated on the IEEE first benchmark model by means of time domain simulation analysis using the EMTP-RV program. View full abstract»

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  • Development of ultra — Low noise transformer technology

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    Strict limits of the revised Noise Ordinance of NY City require Power Transformers to have ultra - low levels at each of the frequencies of the transformer noise at full load and over-excitation. This paper describes the development of the technology that allowed successful design and production of Ultra - Low noise Power Transformers recently delivered to ConEd (Consolidated Edison) of NY City. The paper presents results achieved by this development effort in the areas of accurate calculation of core resonance frequencies, frequency spectrum of core noise, and load noise. It also presents other aspects of the technology development such as de - coupling of Active Parts vibrations from the tank, proper design of tank plate fields and tank bracing, proper transformer mounting techniques, and accurate measurement of low noise levels in the factory. Finally, the paper presents the difference in design of the generations of these transformers produced at different stages of this development effort. View full abstract»

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  • Accommodating large amounts of variable generation in North America

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    To accommodate higher penetrations level of variable generation, changes will be required to the traditional methods used by system planners and operators in order to maintain ongoing bulk power system reliability. While the focus of this paper is on the integration of wind generation, the conclusions and recommended actions may also apply to the integration of all types of variable generation technologies. In 2006, natural gas-fired generation produced 20% of the electricity in the United States while representing 41% of the installed summer generating capacity. Coal-fired generation produced 49% of the electrical energy in North America and represented 32% of the installed summer capacity. Heavy and light oil is primarily used as a back-up fuel for natural gas. Fossil fuels are nonrenewable, that is, they draw on finite resources. In contrast, renewable energy resources - such as wind, solar, ocean, biomass, hydro, etc. can be replenished at a generally predictable rate. Government policy is the key driver for renewable energy expansion in the US and Canada. For example, over 50% of (non-hydro) renewable capacity additions in the US from the late 1990s through 2007 have occurred in states with mandatory Renewable Portfolio Standards. The proposed level of commitment to renewables offers many benefits as well as certain challenges. View full abstract»

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  • Evaluation of DER adoption in the presence of new load growth and energy storage technologies

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    This study considers potential system effects from the addition of Plug-in Electric Vehicle (PEV) load to individually metered residential customers together with a concurrent market adoption of Distributed Energy Resources (DER) and energy storage technologies to offset the associated load growth. To evaluate various renewable energy source conditions, a prototypical circuit is evaluated in Detroit, Los Angeles, and Orlando locations for both summer and winter loading conditions. Various load adoption scenarios are simulated by randomly assigning specified loading to target customer classes on the circuit. View full abstract»

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  • Distribution network short term scheduling in Smart Grid context

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    The large increase of Distributed Generation (DG) in Power Systems (PS) and specially in distribution networks makes the management of distribution generation resources an increasingly important issue. Beyond DG, other resources such as storage systems and demand response must be managed in order to obtain more efficient and “green” operation of PS. More players, such as aggregators or Virtual Power Players (VPP), that operate these kinds of resources will be appearing. This paper proposes a new methodology to solve the distribution network short term scheduling problem in the Smart Grid context. This methodology is based on a Genetic Algorithms (GA) approach for energy resource scheduling optimization and on PSCAD software to obtain realistic results for power system simulation. The paper includes a case study with 99 distributed generators, 208 loads and 27 storage units. The GA results for the determination of the economic dispatch considering the generation forecast, storage management and load curtailment in each period (one hour) are compared with the ones obtained with a Mixed Integer Non-Linear Programming (MINLP) approach. View full abstract»

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  • A pattern recognition approach for detecting power islands using transient signals — Part I: Design and implementation

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    Summary form only given. A novel, pattern-recognition-based approach for fast detection of power islands in a distribution network is investigated. The proposed method utilizes transient signals generated during an islanding event to detect the formation of the island. A decision-tree classifier is trained to categorize the transient generating events as “islanding” or “non-islanding.” The feature vectors required for classification were extracted from the transient current and voltage signals through discrete wavelet transform. The proposed technique is tested on a medium-voltage distribution system with multiple distributed generators. The results indicate that this technique can accurately detect islanding events very fast. View full abstract»

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  • No title

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    Positive feedback anti-islanding methods have been widely applied to inverter-based distributed generators recently due to their high cost-performance ratio. The effectiveness of these anti-islanding methods is usually demonstrated by means of steady-state non-detection zones (NDZs) represented in a load parameter space (LPS). However, such NDZs cannot accurately describe the impact of the inverter interface controls on the anti-islanding methods! detection performance, especially in multi-inverter systems. In addition, the intrinsic destabilization characteristic of the positive feedback anti-islanding scheme cannot be exhibited by these NDZs. This paper proposes an improved dynamic NDZ in the LPS to evaluate the islanding detection effectiveness of the positive feedback anti-islanding methods. Modal analysis approach is employed to determine the critical RLC load quality factor which is defined as the small-signal stability limit index of the islanded distributed generation (DG) systems for the dynamic NDZs. The sensitivity analysis of the dynamic NDZs for different DG system parameters are conducted in the paper. The applications of the proposed dynamic NDZs in multi-DG systems are also presented. View full abstract»

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  • Modeling the Trans Bay Cable Project as Voltage-Sourced Converter with Modular Multilevel Converter design

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    This paper introduces a model developed for modeling the steady-state and the dynamic behavior of the Trans Bay Cable Project as Voltage-Sourced Converter based on the Modular Multilevel Converter design. The model is intended for time domain simulations in an electromechanical simulation program with a balanced positive sequence network representation. Typical applications are transient stability studies and performance analysis of the HVDC link within a large scale AC network. The new developed model is validated against a much more accurate electro-magnetic model comprising all parts of the complex converter control and the protection circuits. View full abstract»

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  • Analysis of coupling effects on overhead VSC-HVDC transmission lines from ac lines with shared right of way

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    Summary form only given: The coupling of fundamental frequency voltages and currents on VSC-HVDC overhead transmission lines from neighboring ac lines is analyzed. The complementary modulation components at dc and 2nd harmonic frequencies on the ac side of the converter resulting from the fundamental frequency coupling are analyzed. A mathematical model is developed for the VSC converter that accurately represents modulation effects to and from its ac and dc sides. This model is shown to be significantly different from that of a conventional Line Commutated Converter. This model is validated using electromagnetic transients simulation. The model is then combined with an accurate frequency-domain model of the transmission lines and the converter ac side equipment, and used to conduct parametric analysis of the coupling effects. As the induced 0 Hz (dc) modulation component on the ac side is of serious concern, parametric plots are presented showing its variation with factors such as ac/dc separation distance, paralleled length, transposition and VSC operating point. View full abstract»

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