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Energy Conversion, IEEE Transactions on

Issue 3 • Date Sep 1989

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Displaying Results 1 - 25 of 37
  • A recursive approach to calculating derivatives of production cost and reliability of generation system

    Page(s): 358 - 367
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    A recursive computational procedure derived from the cumulant method for efficiently calculating production cost and reliability derivatives is proposed. The procedure is applicable to the derivatives with respect to load, unit capacity, or forced outage rate. Moreover, the procedure can handle any number of cumulants without additional theoretical development or software implementation effort. The general accuracy of cumulant method extended for calculating derivatives is evaluated. In addition to the proposed computational procedure, three extended applications of production simulation derivatives are presented View full abstract»

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  • Impact of cogeneration and small power producing facilities on the power system reliability indices

    Page(s): 368 - 374
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    The author describes the models and computational techniques that simulate the operational behavior of cogeneration and small power-producing facilities and evaluates their impact on the reliability indices of power system load-points. These techniques evaluate the five basic reliability indices of the system load-points and quantify the impact of these facilities on the system reliability performance. The increased information that can be gained from these improved techniques is illustrated by the analysis of a typical system based on the Hellenic interconnected transmission system. The results demonstrate the increased information that can be gained about the reliability indices of the system load-points and the impact of these facilities on them. By varying the operational features of cogeneration facilities, a system planner can assess a number of additional system configurations which are not possible using existing techniques View full abstract»

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  • Application of operations research in automatic generation control of hydropower plants

    Page(s): 375 - 381
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    An algorithm is presented to solve the problem of automatic generation control (AGC) for hydropower plants stage by stage, using in each stage a different method of operations research: dynamic programming, 0-1 integer programming, and the principle of equal incremental. The algorithm has the following advantages: short time of calculation, less computer memory required, the ability to take aspects of economic and safety requirements into consideration, flexibility, etc. This algorithm is suitable for real-time AGC. A brief description of the realization of AGC in the left powerhouse of the Gezhouba Hydropower Plant is presented View full abstract»

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  • A study of islanding in utility-connected residential photovoltaic systems. I. Models and analytical methods

    Page(s): 436 - 445
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    Models and methods for the analysis of the continued operation of a group of utility-connected photovoltaic systems even after loss of the utility source are presented. The methods involve an examination of steady-state power balance under islanded conditions, an examination of large-signal, limit-cycle behavior, and an examination of the effect of specific control systems on the small-signal stability of islanded conditions. In conjunction with each other these methods allow a determination of whether islanding can occur in a specific system. Although all such systems have a natural propensity to island, it is shown that the controls used in many commercially available units make islanding a rather unlikely phenomenon View full abstract»

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  • Use of single-point grounding for instrumentation and control systems installed in existing generating stations

    Page(s): 402 - 405
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    General guidelines for the design of single-point grounding systems for instrumentation and control (I&C) systems are presented, along with an example illustrating the practical difficulties often involved in trying to implement an ideal theoretical solution. The single-point grounding methods presented should be recognized as an ideal approach that often has practical limitations in implementation. When properly designed and installed, however, a single-point grounding system plays a vital role in the proper operation of modern I&C equipment View full abstract»

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  • Load rejection operation in conventional power plants in ENEL-Italy

    Page(s): 382 - 391
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    A description of the experience gained in establishing a procedure which trips all fuel input to the boiler and maintains house load operating the turbine on mass and energy stored in the boiler is presented. This procedure was qualified a few years ago and since then has been used in the 320 MW units in operation (the main bulk of ENEL's thermal capacity) whether equipped with subcritical once-through boilers or with assisted circulation drum boilers. A series of tests carried out on supercritical 660 MW units shows that by adopting the same procedure these large units can also sustain successfully the run back to house load. The procedure has been used in many other thermal units of size ranging between 70 MW to 240 MW and can be performed in most of ENEL's thermal power plants View full abstract»

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  • The operation of loads powered by separate sources or by a common source of solar cells

    Page(s): 351 - 357
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    A procedure is introduced for analyzing the interaction between different loads connected to a common solar cell (SC) source, and the performances of these loads when powered by separate and common sources are compared. It is shown that for identical loads (the same type and size), either optimal or nonoptimal, powered by identical SC arrays, and for loads of the same type but different sizes that are powered by proportional sizes of SC arrays, the operation of the loads is the same when powered either by separate sources or by a common SC source. The arrays in the separate source systems are of the same sizes, and in the common source system the arrays are of double size. The loads in both setups are of the same type. Two types of loads are considered in this study: two different ohmic loads; two different water electrolyzer loads. A comparison of the operation of the above two load types is performed for systems that incorporate a maximum-power point-tracker (MPPT), for both the separate and common SC sources. The criterion for comparing the performances is the energy utilization efficiency. It is shown that the performance of one load affects the performance of another load in a common source system. In systems not including MPPTs, the total performance of the loads in a common source system is improved as compared to the total performance of the loads when they are powered separately by individual sources. In systems including MPPTs, the total performance of the loads is the same when powered either by a common source or by single sources. MPPTs improve the performance of loads, the amount of improvement depending on the mismatch of the loads to the solar cells View full abstract»

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  • A study of islanding in utility-connected residential photovoltaic systems. II. Case studies

    Page(s): 446 - 452
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    For pt.I see ibid., vol.4, no.3, p.436-45 (1989). The methods and models developed in pt.I to study the problem of islanding are extended to study systems containing multiple inverters. The key issues addressed are whether multiple power conditioning systems (PCSs) are more prone to islanding and whether the destabilized feedback used in PCSs such as the APCC and Teslaco can prevent islanding even in the presence of other PCSs in the island. It is shown that islanding can be virtually eliminated through the use of destabilized feedback controls such as the ones available on some commercial units View full abstract»

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  • Modeling and dynamic performance of a line-commutated photovoltaic inverter system

    Page(s): 337 - 343
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    A three-phase line-commutated utility-interactive photovoltaic (PV) inverter system is described. A simplified computer model of this system is established and presented in block-diagram form. This model is suitable for use in transient stability programs. The accuracy of the simplified model is verified by comparing the response calculated therefrom with that of a highly detailed photovoltaic system model in which the inverter is represented in valve-by-valve detail. The computer studies indicate that the simplified model is reasonably accurate when used to predict the PV system response following, for example, step changes in the inverter delay angle, rapid increases or decreases in solar insolation, and step changes in AC voltage magnitude or phase. In each case, the PV system response predicted using the simplified model closely follows the average response of the detailed model exclusive of the harmonics, which are neglected in the simplified model View full abstract»

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  • Maximum likelihood estimation of solid-rotor synchronous machine parameters from SSFR test data

    Page(s): 551 - 558
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    Based on previous work (presented at the IEEE/PES 1989 Winter Meeting, New York) in which it was established that multiple parameter sets are obtained when the machine parameters are estimated from noise-corrupted frequency-domain data, the effects of noise on time-domain parameter estimation of synchronous machine models are studied. The proposed approach can be applied to the SSFR test data or time-domain test data. It is shown that a unique set of parameters can be obtained, and the noise effects can be dealt with effectively when the maximum-likelihood estimation technique is used to estimate machine parameters View full abstract»

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  • Enhancing the utilization of photovoltaic power generation by superconductive magnetic energy storage

    Page(s): 314 - 321
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    The authors demonstrate that a superconductive magnetic energy storage (SMES) system can enhance large-scale utilization of photovoltaic (PV) generation. Results show that power output from a SMES system can be used to smooth out PV power fluctuations so that the combined PV/SMES output is dispatchable and free from fluctuations. Power generated from PV arrays is shown to be fully utilized under different weather conditions, and PV penetration is increased to significant levels without adversely affecting the power system. Coupled with PV generation, a SMES system is even more effective in performing diurnal load leveling. A coordinated PV/SMES operation scheme is proposed, and its demonstration under different weather conditions is discussed View full abstract»

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  • A model for saturation effects in high-field permanent magnet synchronous motors

    Page(s): 487 - 494
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    A procedure is proposed to study and identify the model of a buried permanent-magnet synchronous motor which takes account of the nonlinear magnetic phenomena caused by the armature current. The experiment procedures are described, and the results of the measurement of the parameters of the linear d-q model of the motor considered are presented. A simple procedure is then proposed for using finite elements to study the saturation phenomena found, and the relative model is defined. A comparison between the experimental and simulation results shows them to be in good agreement View full abstract»

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  • Transient behaviour of a current-source inverter-fed synchronous motor with a solid rotor

    Page(s): 509 - 517
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    A calculation method is presented which allows the transient behavior of a 2×three-phase current-source inverter-fed synchronous motor to be investigated, taking into account the eddy currents arising in the solid rotor iron. The set of equations for the synchronous machine is derived on the basis of a two-dimensional numerical field calculation and system-theoretical expressions. The theory is converted into a digital simulation program, also incorporating the regulation for constant buffer-circuit current and constant machine flux. The results of simulation computations show the characteristic shapes of currents, voltages, and torque. A comparison between measurement and computation shows good agreement View full abstract»

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  • Understanding modern generator control

    Page(s): 453 - 458
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    A simple discussion about generator control without bode plots and other sophisticated references necessary to equipment design is presented. Two kinds of control schemes used for most generator drives, droop control, and frequency control are discussed. Synchronous and induction generators, and their differences in control, are also discussed. The operation of generators both connected to and disconnected from the utility grid is also examined View full abstract»

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  • Experience with AC hipot and partial discharge tests for commissioning generating station cables and switchgear

    Page(s): 392 - 396
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    Test equipment is described which is suitable for AC hipot and partial discharge testing of 5 and 15 kV shielded cables of lengths up to about 600 m. The equipment can be used to test 5 and 15 kV metal-clad switchgear. Ontario Hydro's experience at two nuclear generating stations using this AC test equipment is presented. The equipment can be used to assure the integrity of cable systems (less than 600 m long) already in service. The reasons for switching to AC testing of cable systems are outlined. Practical experience shows that the partial-discharge test is very effective in identifying installation problems in cables and switchgear. A number of problems are identified with the AC tests that a DC test would have missed View full abstract»

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  • High speed AC generator (7200 RPM, 60 Hz) for autonomous power systems

    Page(s): 544 - 550
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    The authors analyze the features of an electric generator whose angular speed is twice that of the rotating field. Two versions are studied: series- and parallel-connected windings. A technical analysis is presented in order to determine which type of machine to choose for specific applications. The relevant mathematical models are deduced. Self-excitation of the machine feeding an autonomous power system is ensured by two sets of capacitors. The on-load characteristic curves of the machine when operating as a generator are presented, and the strategies to be used to maintain constant voltage are described. The experimental results, obtained on a small power machine at Rome University's Department of Electric Energy, are given View full abstract»

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  • Damping subsynchronous resonance by phase shifters

    Page(s): 344 - 350
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    A method is presented to damp subsynchronous resonance (SSR) using a thyristor-controlled phase shifter to modulate the generator real power. A control approach is proposed in which generator speed and/or modal speed deviations are used as the control signals for the phase shifter. Location of the phase shifter in the network to damp subsynchronous oscillations effectively is also investigated. An eigenvalue analysis method is used to study the effectiveness of this approach. It is shown that all torsional modes of system-1 of the second IEEE benchmark can be successfully suppressed by the use of the phase shifter with proper control signals and location. To verify the analytical results, a digital computer study on the second IEEE benchmark for SSR studies was conducted using a detailed nonlinear generator model. Results of the study are reported View full abstract»

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  • Analysis and modeling of a single-phase brushless DC motor drive system

    Page(s): 473 - 479
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    A single-phase brushless DC motor drive system with a bifilar stator winding and asymmetrical stator pole faces is investigated. The form of the permanent-magnet component of the stator winding flux linkage is analyzed considering the asymmetry of the stator pole faces. Equations describing the electromechanical dynamics of the motor are then derived along with an expression for the electromagnetic torque. These equations are expressed in state-model form, and a mathematical model of the inverter is developed for use in a computer simulations. The computer simulation is used to demonstrate steady-state and dynamic operation of the motor. Comparison of simulation results with measurements of an actual motor-inverter system indicate that the computer model is reasonably accurate View full abstract»

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  • Improving nuclear generating station response for electrical grid islanding

    Page(s): 406 - 413
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    A description of problems associated with the performance characteristics of nuclear generating stations which do not have their overall plant control design functions coordinated with the other grid controls is presented. Also presented are some design changes to typical nuclear plant controls which result in a significant improvement in both the performance of the grid island and the chances of the nuclear units staying online following a disturbance. Four areas of the overall unit controls and turbine governor controls which could be modified to better coordinate the control functions of the nuclear units with the electrical grid are emphasized. Some simulation results are presented to show the performance of a typical electrical grid island containing a nuclear unit with and without the changes View full abstract»

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  • Optimal PID gain schedule for hydrogenerators-design and application

    Page(s): 300 - 307
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    The development and testing of a digital gain switching governor for hydrogenerators are described. Optimal gains are found at different load points by minimizing a quadratic performance criterion prior to controller operation. During operation, the gain sets are switched in depending on gate position and speed error magnitude. It is shown that, with gain switching operating, the digital governor has a substantial reduction of noise on the command signal and up to 42% faster responses to power requests. Nonlinear control strategies enable the digital governor to have a 2.5% to 2% reduction in speed overshoot on start-ups and an 8% to 1% reduction in undershoot on load rejections as compared to the analog View full abstract»

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  • Output error identification of hydrogenerator conduit dynamics

    Page(s): 329 - 336
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    Two output error model reference adaptive identifiers are considered for estimating the parameters in a reduced-order gate position to pressure model for the hydrogenerator. Gradient and sensitivity function identifiers are discussed for hydroelectric applications, and connections are made between their structural differences and relative performance. Simulations are presented to support the conclusion that the latter algorithm is more robust, having better disturbance rejections and less plant model mismatch sensitivity. For identification from recorded plant data from step gate inputs, the other algorithm fails to converge. A method of checking the estimated parameters is developed by relating the coefficients in the reduced-order model to head, an externally measurable parameter View full abstract»

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  • Multi-stage dual priority regulator for photovoltaic systems

    Page(s): 308 - 313
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    The design and application are investigated of an array shedding voltage regulator for use in photovoltaic (PV) systems with two separate loads of different priority. The multistage dual-priority regulator charges two separate battery systems for high- and low-priority loads. This controller switches the array modules from the main battery to the auxiliary battery as the main battery nears full charge, thus utilizing the PV panels to the maximum without jeopardizing the reliability of the critical load. Both the main and auxiliary voltage settings are adjustable, allowing the use of different types of batteries. A dual-priority voltage regulator is useful in any stand-alone system with multiple loads. Uses include PV-powered homes, medical clinics, and recreational vehicles View full abstract»

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  • Circuit representation of inverter-fed synchronous motors

    Page(s): 531 - 537
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    A study of the prediction of commutation time of current in inverter-fed synchronous motor drives is presented. The natural commutation from one thyristor to the next is brought about by the machine voltage, and performance is commonly expressed in terms of a commutating reactance, xc. The commutation behavior of solid salient poles is explored in terms of the magnetic structure of the motor. It is shown that the behavior can be closely modeled using a circuit-solving computer package, SPICE View full abstract»

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  • Voltage deterioration of XLPE wires in water under gamma ray irradiation

    Page(s): 466 - 472
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    Three types of cross-linked polyethyline (XLPE) wire were developed for insulation of internal pump motors (wet type) used in an advanced boiling water reactor. By applying gamma ray irradiation of 10 4 to 106 Gy and electric stress in hot water simultaneously or sequentially, the effect of gamma ray irradiation is examined. The effect of combined stresses in a large scale functional test is also described. It is proved that the gamma ray irradiation less than 106 Gy does not deteriorate the properties of the insulation of the wires. In the irradiational environment of 5×10 4 Gy where the internal pump motor is served, it is concluded that the wires have sufficient reliability View full abstract»

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  • Adaptive tracking control for high performance DC drives

    Page(s): 502 - 508
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    An application is presented of a modified adaptive controller to a DC motor for high-performance tracking applications, such as robotics, actuation, and manipulation. By the proposed technique, the rotor position and/or the speed of the DC motor is forced to follow preselected tracks, even when the load condition varies. An algorithm based on minimum variance self-tuning control is developed for this purpose. The adaptive controller is effective even in the presence of external disturbances, provided that the system exhibits minimum phase characteristics. The effectiveness of the controller is demonstrated by using general-purpose nonlinear simulation software. The simplicity of the algorithm and the promising simulation results prove that this proposed controller is very effective in high-performance tracking applications View full abstract»

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Aims & Scope

The IEEE Transactions on Energy Conversion includes in its venue the research, development, design, application, construction, installation, operation, analysis and control of electric power generating and energy storage equipment (along with conventional, cogeneration, nuclear, distributed or renewable sources, central station and grid connection). The scope also includes electromechanical energy conversion, electric machinery, devices, systems and facilities for the safe, reliable, and economic generation and utilization of electrical energy for general industrial, commercial, public, and domestic consumption of electrical energy.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Juri Jatskevich
University of British Columbia