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Energy Conversion, IEEE Transactions on

Issue 1 • Date Mar 1988

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Displaying Results 1 - 25 of 28
  • A frequency domain method for tuning hydro governors

    Publication Year: 1988 , Page(s): 14 - 17
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    A frequency domain method to determine the optimum values for the parameters of a proportional-integral-derivative (PID) governor is presented. The method readily handles detailed models of turbine-penstock, gate dynamics, and other system components. The main advantages of the method are that it is computationally simple, that it does not involve any iterations, and that the designer can prespecify a speed response for load rejection View full abstract»

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  • Developing a mini-hydro plant in the remote Canadian North

    Publication Year: 1988 , Page(s): 18 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    The implementation of a 1150 kW mini-hydro-generation plant at Wemindji, a remote community in Northern Canada, is described. A number of studies and investigations of the overall costs of energy to the community led to the choice of a mixed energy-supply system consisting of hydro, diesel, and firewood. The 1150 kW hydro power plant constitutes the main element in this energy supply. Details are given of the design and implementation of the mini-hydro-power facility and its related equipment, with descriptions of constraints that were overcome from conception through to commissioning and initial operation View full abstract»

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  • The time variation of wind speeds and windfarm power output in Kansas

    Publication Year: 1988 , Page(s): 44 - 49
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    On the Kansas plains, 1-min average wind speeds have high autocorrelations, with a value of about 0.9 with a lag of 32 min. In the winter, spring, and fall, 10 min average wind speed autocorrelation functions drop to 0 in 20 to 30 hr. Some cyclic behavior is noticed in the winter and fall correlations, with a period of several days. It is believed that this cyclic behavior is due to the passage of fronts. Only the summer season data showed a marked diurnal cycle. For short lag times up to about 30 min, the autocorrelation function of 1 min averaged wind machine output dropped more rapidly than that of wind speed. For longer lag times the 10 min averaged output autocorrelation was very similar to that of the wind speed. Wind speeds averaged for 1 min has a cross-correlation across a wind site which was a function of distance. The correlation dropped to about 0.83 at a distance of 21.7 km (13.5 mi). Wind machine output was less well correlated with a drop to about 0.69 at a spacing of 21.7 km. The autocorrelation function of a windfarm consisting of a large number of wind machines dropped much less rapidly than that of a single wind machine, as would be expected. A windfarm consisting of 100 MOD-2 wind machines with a spacing of 1.61 km by 0.80 km had a correlation of about 0.98 for a 10 min lag time when 1 min averaged output was considered View full abstract»

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  • Speed loop cancellation governor for hydrogenerators. II. Application

    Publication Year: 1988 , Page(s): 91 - 94
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    For pt.I see ibid., vol.3, no.1, p.85-90 (1988). The essential dynamics for a hydrogenerator supplying a large grid may be represented by two control loops: the first for power and the second for speed. Previously, the authors developed a governor design intended to neutralize the speed loop's destabilizing effects while tuning for improved load tracking. The practical implementation of such a controller by computer is considered. An approximate system is used to develop analytical expressions for the control parameters. These parameters are functions of load level throughout the operating range and may be computed in real time. The effectiveness of the approximate-system-derived control is verified by simulation. Computed transients are indistinguishable from transients for the optimally tuned control View full abstract»

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  • Parasitic torques in saturated induction motors

    Publication Year: 1988 , Page(s): 157 - 163
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    A method for analyzing the performance of induction machines for parasitic torques is described. Such torques arise from the interactions of fundamental and harmonic components of air flux density due to geometrical considerations such as slotting, and saturation effects. Parasitic torques arise under balanced sinusoidal drive conditions. However, they are greatly exacerbated under nonsinusoidal drive conditions. The technique described for analysis is applicable to both cases View full abstract»

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  • A feasibility study of photovoltaic-fuel cell hybrid energy system

    Publication Year: 1988 , Page(s): 50 - 55
    Cited by:  Papers (19)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    The concept and feasibility study results of applying fuel cells to provide operational support to photovoltaic (PV) arrays are presented. Through simulation using actual data, it is shown that it is feasible to use fuel cells in coordination with PV to meet variable loads to either utility or stand-alone applications. The dynamic response required of the fuel cell to support the hybrid operation is found to be well within the capabilities of the prototype designs that have been tested in the United States and Japan. The hybrid operation overcomes the intermittency problem inherent with PV and makes possible novel applications for the fuel cell technology View full abstract»

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  • System performance improvement provided by a power conditioning subsystem for central station photovoltaic-fuel cell power plant

    Publication Year: 1988 , Page(s): 64 - 70
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    An augmented power conditioning subsystem (APCS), which can improve the power system performance besides performing DC/AC power conversion, is proposed. With the benefits provided by the APCS, connecting photovoltaic cells, fuel cells, or their combination to a power system would provide not only additional sources and control of real power, but also additional economic reactive power control as well. The basic principle of the APCS, its operation and control, economic considerations, and the results of a preliminary study are presented View full abstract»

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  • Intelligent user interface for expert systems applied to power plant maintenance and troubleshooting

    Publication Year: 1988 , Page(s): 71 - 77
    Cited by:  Papers (2)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    A research and development project is under way to specify, design, construct, and evaluate a user interface system to meet the requirements of a knowledge-based system for gas turbine electronics equipment maintenance and troubleshooting. The user interface is a portable device with text display, video and overlay graphics display, voice recognition and speech production, special-function keypad, and printer. A modular software structure based on a serial communications protocol between the user interface device and expert system host computer provides flexibility, expandability, and a simple, effective user-interface dialog View full abstract»

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  • Determination of negative-sequence resistance of turbo-generators from rated-frequency standstill tests

    Publication Year: 1988 , Page(s): 132 - 139
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    Systematic analysis and comparison of standstill and rotational test results for a large number of turbogenerators in the range of 30 to 1300 MVA and having various damper systems, shows that the ratio of negative-sequence resistance to mean subtransient resistance varies in a narrow range of ±10% around 0.85. This corresponds to an increase of about 1.5 to 1.85 times in the equivalent rotor resistance when the frequency is doubled, in contrast to the figure of √2 quoted in literature. Additional verification is obtained from frequency-response tests on one of the machines investigated View full abstract»

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  • Theoretical development and experimental verification of a DC-AC electronically rectified load-generator system model compatible with common network analysis software packages

    Publication Year: 1988 , Page(s): 123 - 131
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    A method for modeling electronically commutated DC-AC load-rectifier-generator systems is presented. The method is based on a modified form of Park's d-q-o transformation, and yields an equivalent system network which is compatible with most commonly known network analysis software packages. The method was used to develop a model for the simulation of the dynamic steady-state performance of a DC-AC system consisting of a 30 kVA, three-phase, 208 V, four-pole, 400 Hz generator feeding a rectifier-load system. The system was tested in the laboratory under various DC and combined DC-AC load conditions. The results of the simulation model reveal a dynamic steady-state performance of the load-rectifier-generator system, in very good agreement with the test results. The applicability of the method and model to other electronically controlled machine systems is discussed in the light of those results View full abstract»

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  • Steady-state performance of the DC motor supplied from single-phase rectifier with step-up converter-a unity power factor converter

    Publication Year: 1988 , Page(s): 172 - 178
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    It is shown that the voltage step-up converters supplying DC motors can be operated at a unity power factor when supplied from single-phase rectifiers. If the duty ratio of the main switching device in the step-up converter is continuously adjusted, it is possible to maintain the line current almost sinusoidal and in phase with the input voltage. This remarkable property can be obtained from a certain minimum critical current up to values in excess of the rated armature current View full abstract»

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  • Automatic generation control for hydro systems

    Publication Year: 1988 , Page(s): 33 - 39
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    The authors present the decision of an automatic generation control (AGC) system implemented with digital computers that periodically sample tie-line real power flows, line frequency, and generator power outputs. These analog signals are measured at 2-5 intervals and combined with desired interchange to obtain the area control error (ACE). The ACE digital quantity is allocated to regulating hydro turbines and transmitted via telemetry to the remote terminal units (RTU). The RTUs convert the raise/lower megawatts (MW) into timed relay contact closures to the governor which result in wicket gate open/close movement to change the generator output power. The output power of each generator is monitored by the digital AGC, which closes a feedback loop around the governor-turbine-generator to assure that the desired power level is attained. The feedback loop design, which is essentially a sampled-data control, is described. Additional feedback loops due to the ACE and load regulation are also analyzed. A method for allocating water usage between reservoirs on a generator command-time basis is presented. The theoretical designs are verified by online measurements View full abstract»

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  • Load-level-sensitive governor gains for speed control of hydrogenerators

    Publication Year: 1988 , Page(s): 78 - 84
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    The application of load-level-sensitive gains to proportional-plus-integral speed control of hydrogenerators is discussed. Appropriate root configuration gain functions of wicket gate position are derived for isolated resistive loads. Computer programs are used to calculate these gains from model turbine data and system parameters. Root locus tuning is used to determine appropriate gains for infinite bus loads. Simulations are presented which compare the use of constant gains to the use of these variable gains for isolated resistive and infinite bus loads. Additional resistive load simulations show the effect of a one-second digital filter on the gain function. Results indicate that the variable gain responses resemble 0.707 damping at each load level. Sample speed-transient comparisons between variable and constant gains show decreases of up to 45% in speed peak overshoot and 80% in power settling time. Load and pressure time-responses are included View full abstract»

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  • Subsynchronous resonance phenomena considering skin effects in solid iron rotor turbo-generators

    Publication Year: 1988 , Page(s): 140 - 148
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    The question of how the skin effects of the eddy current in the rotor of a synchronous generator influence the induction generation modes and the torsional interaction modes of the subsynchronous resonance (SSR) phenomena is addressed. The 3-D magnetic diffusion equation is solved in a round solid iron rotor to provide data for comparison and discussion purposes. The problem of representing skin depth, which is frequency dependent, in the time-domain stability analysis based on dx/dt=[A]x is examined View full abstract»

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  • An investigation of magnesium rotors in motor operated valve actuators

    Publication Year: 1988 , Page(s): 40 - 43
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    Failure mechanisms of induction motors in the valve actuators of motor operated valves are investigated. It is found that motors which contain cast magnesium rotors are susceptible to cracking and melting after carrying locked rotor current for as little as 61 s. Safety-related valve actuator motors may be thermally protected near this value to ensure operability of valve actuators. Corrosion is also discussed as a failure mechanism. An inspection procedure which allows a simple examination to be made to determine whether degradation may have occurred in in-service motors is provided View full abstract»

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  • Performance prediction and design modifications of superconducting generators using parameter sensitivity analysis results

    Publication Year: 1988 , Page(s): 187 - 191
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Many significant parameters of the superconducting alternator vary considerably from that of a conventional generator because of the rotating shields and very long field time constants. The effects of these parameter values on the dynamic performance of superconducting alternators could be obtained using parameter sensitivity analysis results. Here, results from a companion paper by A.H.M.S. Ula, J.M. Stephenson, and P.J. Lawrenson (see ibid., vol.3, no.1, p.179-86, 1988) are used to predict the dynamic performance of a 2000 MVA superconducting alternator, first with a single rotor screen and then with double rotor screens. It is shown how the parameter survey results can be used for design modifications resulting in significantly improved dynamic performance. Finally, a novel design which further improves the dynamic performance of the alternator is presented View full abstract»

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  • Impulse voltage withstand capability of rotating machine insulation as determined from model specimens

    Publication Year: 1988 , Page(s): 149 - 156
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    An evaluation of present-day turn and groundwall insulation is discussed. The surge breakdown voltage of unaged insulated specimens was evaluated at two rates of surge voltage rise; the values of breakdown voltage were compared to those obtained by direct voltage and 60 Hz alternating voltage. The insulations were then aged by voltage from conductor to ground and periodically evaluated for surge breakdown values. Finally, the specimens were tested for surge voltage endurance, and this endurance was compared to alternating voltage endurance View full abstract»

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  • Relationship between stator core buckling, core losses, vibration and local over-temperatures

    Publication Year: 1988 , Page(s): 56 - 63
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB)  

    Measurements on a hydrogenerator stator core during core test with higher-than-normal magnetic flux and extended test time provided the base for a study of interaction between buckling, local heat generation, hot spots, and vibration. The mechanism of buckling is analyzed. Curves were developed showing how the buckling influences the temperature at the bottom of the slot and between the stator coils. There is clear evidence that the core does not behave as a homogeneous structure. The upper and lower halves of the core may vibrate independently of each other, with different node numbers. The node number may be an odd number, contrary to the accepted theory. The magnitude and position of buckling does not seem to have any influence on the distribution of vibration nodes View full abstract»

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  • Application and testing of a fiber optic communication system at Grand Coulee

    Publication Year: 1988 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    The rationale for applying fiber-optic technology in this application is discussed with emphasis on the related design considerations important in control and protection of this large hydroelectric facility. Brief summaries of hardware used and installation considerations are given. A discussion of factory and unique field testing, including electromagnetic-interference (EMI)-induced transient influence and timing tests, is included. Operating experience and projected future use are summarized View full abstract»

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  • Identification of parameters for superconducting generators having free or fixed outer rotor, based on tests and calculations

    Publication Year: 1988 , Page(s): 164 - 171
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    The generator, with its concentric and in part solid and conductive parts, is represented by a shell model, and the parameters of the system of equivalent windings are first obtained approximately using a two-dimensional analytical field calculation. The effect of the finite length, which is neglected in this field calculation, is taken into account by variation of the model geometry and material conductivity so that Nyquist plots of the model impedances are optimally matched to those of the real system. The resulting machine model is checked and confirmed by comparing the simulation results with test measurements. It is further shown that an outer damper cylinder (that is free to rotate independently) provides significant mechanical relief of the shaft line during transient processes View full abstract»

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  • Damping of subsynchronous resonance using excitation controllers and static VAr compensations: a comparative study

    Publication Year: 1988 , Page(s): 6 - 13
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The results of a comparative study on the application of two countermeasures, i.e. the excitation controller and the static VAr compensator (SVC), for damping of subsynchronous resonance (SSR) are presented. To stabilize all the SSR modes, a unified approach based on modal control theory is proposed for the design of the excitation controller and the SVC, which are essentially dynamic output feedback compensators. The two damping schemes differ in the way they modulate the reactive power flow in the system to damp out the subsynchronous oscillations. To demonstrate the effectiveness of the proposed damping schemes under disturbance conditions, time-domain simulations based on a nonlinear system model are also performed. The relative merits of the two countermeasures are compared with respect to their validities under various loading conditions and different degrees of series compensations and their capabilities to expand the stable region on the real-capacitive reactance plane View full abstract»

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  • Speed loop cancellation governor for hydrogenerators. I. Development

    Publication Year: 1988 , Page(s): 85 - 90
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    Speed control governors for hydrogenerators utilize a proportional-integral (PI) control with constant gains. Given the nonlinear characteristics of the installations, the result is compromised speed and power transients for step load changes. The PI control is not able to provide a responsive power response while maintaining the desired speed transient. The development of a control strategy that essentially neutralizes the speed dynamics in order to achieve improved power tracking is discussed. This technique results in up to a fifty percent reduction in the magnitude of the offspeed. The power transient is also more responsive as demonstrated by a twenty percent decrease in the settling time while maintaining acceptable damping and overshoot View full abstract»

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  • Economic-emission load dispatch through goal programming techniques

    Publication Year: 1988 , Page(s): 26 - 32
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    The economic-emission load dispatch problem which accounts for minimization of both cost and emission is a multiple, conflicting-objective function problem. Goal programming techniques are most suitable for such type of problems. Here, the economic-emission load dispatch problem is solved through linear and nonlinear goal programming algorithms. The application and validity of the proposed algorithms are demonstrated for a sample system having six generators View full abstract»

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  • The effect of design parameters on the dynamic behavior of the superconducting alternators

    Publication Year: 1988 , Page(s): 179 - 186
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The air-gap nature of a superconducting alternator coupled with the complex shielding system required to protect the superconducting field winding results in many of its significant parameters to vary considerably from that of a conventional alternator. The effects of these parameter values on the dynamic performance of the alternator are presented so that the effects of the resulting changes due to mechanical or screening considerations can be readily anticipated. These parameter sensitivity analysis results are presented for future use in optimal superconducting alternator design View full abstract»

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  • A finite element technique for calculating the magnet sizes and inductances of permanent magnet machines

    Publication Year: 1988 , Page(s): 116 - 122
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    A method for calculating the magnet size, and the direct and quadrature axis reactances of permanent magnet synchronous machines, using the finite-element method is presented. In this method the machine is modeled by its equivalent d-q representation of armature MMF and the appropriate reactances are calculated from the magnetic energy in the magnetic field. This is in contrast to the conventional approach of using an abc phase current model, solving the model and then converting the resulting quantities to respective d -q-o quantities. The method is applied to a permanent magnet motor design 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.

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Meet Our Editors

Editor-in-Chief
Juri Jatskevich
University of British Columbia