Showing papers on "AC power published in 1981"

Optimal Control of Reactive Power flow for Improvements in Voltage Profiles and for Real Power Loss Minimization

Abstract: A mathematical formulation of the optimal reactive power control (optimal VAR control) problem and results from tests of the algorithm are presented in this paper. The model minimizes the real power losses in the system. The constraints include the reactive power limits of the generators, limits on the load bus voltages, and the operating limits of the control variables, i.e., the transformer tap positions, generator terminal voltages and switchable reactive power sources. Real power economic dispatch is accomplished by standard techniques.

Device for conversion of light power to electric power

Abstract: This invention relates to a high efficiency device for the direct conversion of light power to electrical power. Present photocells for accomplishing this purpose are well known to the art and have a theoretical efficiency not exceeding about 20%. In practice, realization of efficiency of about 10% has been achieved, but ultimately the theoretical limitation is an upper limit which cannot be exceeded by devices utilizing known construction. The present device differs from the prior art devices in that it utilizes a plurality of dipole antennae for absorbing light photons, employing an alternating electrical field of said photons to cause electrons in the dipole antenna to resonate therewith and absorb electrical power therefrom, with means for rectifying said AC power to DC, said DC being accumulated on conducting busbars from the plurality of antennae and associated rectifying circuits.

New Static VAR Control Using Forced-Commutated Inverters

Abstract: This paper describes the system outline and the operating results of a new type of 20MVA Static VAR Generator (SVG), which is already in operation in electric power field since January of 1980. This SVG consists of force-commutated inverters of the voltage source and can be operated in both, inductive and capacitive modes, by simple control of the output voltage of the inverter. Special emphasis is placed on the system outline, electrical designing features and the operating results which coincide with the theoretical analysis.

Television remote control system for selectively controlling external apparatus through the AC power line

Abstract: A remote control system utilizes a portion of television receiver system to control an external appliance through the AC power supply line. The user enters an appliance control command into the keyboard of the television remote control unit. Inside the television receiver, the appliance control command is encoded and modulated onto a carrier signal which is transmitted on the AC power supply line. An external appliance control module, also connected to the AC power supply line, is located near the external appliance for detecting the encoded appliance control command and for selectively controlling the AC power supplied to the external appliance.

Improvement of Transmission Capacity by Thyristor Controlled Reactive Power

Abstract: This paper shows that thyristor controlled reactive power can be used as an efficient tool to improve damping of large power systems. If thyristor switched capacitors are used there will also be positive contribution to transient stability. Examples of power systems where damping is the critical factor have been investigated. The use of supplementary control of generators and control of reactive power has been studied. Basic configurations of thyristor switched capacitors and thyristor controlled reactors are presented.

Electronic ballast for gaseous discharge lamps

Abstract: An electronic ballast for energizing one or more gaseous-discharge lamps and for regulating the power consumed thereby, the ballast including a power supply for providing a source of DC power between a pair of outputs, a pair of transistors connected as switches in series between the power-supply outputs, the transistors for selectively coupling to the juncture thereof positive and negative potentials, a voltage-conditioning and current-limiting network for energizing the lamp from the potential developed between the transistor juncture and a power-supply common, and a pulse generator for developing pulses for driving each of the transistors in turn whereby a potential is developed at the transistor juncture which alternates as positive-going and negative-going pulses each separated by a dead time, the pulse generator for monitoring the power consumption level of the lamp and responsive thereto operative to vary the frequency and/or the width of the transistor driving pulses whereby the lamp consumption is regulated. Also included is a third harmonic trap for coupling the power supply to the AC power line to improve the power factor.

A Simple and Efficient AC-DC Load-Flow Method for Multiterminal DC Systems

Abstract: A new ac-dc Load-flow method for multiterminal dc-ac systems that uses a novel approach to solve the equations of the multiterminal dc system is described. A simplified version of the ac-dc load-flow method with all of the capabilities of estabLished Newton's methods is shown to have the best qualities of simultaneous and sequential solution ac-dc methods combined. Next, important features such as discrete taps, distinction between scheduled voltage and scheduled angle controls, fixed taps and extended phase controls, and current limits are incorporated to enhance the versatility of the method, especially for transient stability studies. Numerical examples are used to illustrate the various features of the method. Its performance is compared with those of an established Newton's method and a recent method. The method is simpLe to program, economical and fast.

A Thyristor Controlled Static Phase-Shifter for AC Power Transmission

Abstract: The paper outlines the importance of a fast, fully controllable phase - shifter for AC power systems. It proposes new designs, based-on power thyristor technology, analyzes them and proves their viability both by analytical and practical tests. A number of resulting problems are highlighted which need further investigation. In conclusion the paper shows that thyristor controlled phase-shifters may be the next major advance in power transmission technology.

The Effects of Distribution Voltage Reduction on Power and Energy Consumption

Abstract: Voltage reduction is a practice which has long been used by electric power companies during emergencies to reduce peak demand. Since 1973, some have suggested that it can also be an effective energy conservation method. Others disagree. The purposes of this paper are to: 1) present what is known about the effects of voltage reductions on real power, reactive power, and energy, for individual and composite loads; 2) discuss the problems associated with conservation voltage reduction proposals; and 3) suggest promising approaches for further study. Tests were conducted to determine the real and reactive power dependencies on voltage of a three-phase 5 hp induction motor. The following conclusions are derived from the information presented in this paper. 1) Appliances, motors, and feeders generally show initial reductions of power consumption at reduced voltage, but little reliable information concerning energy exists. 2) Because of the lack of hard evidence and the problems associated with conservation voltage reduction programs, it would be premature for any regulatory agency to mandate such programs at the present time.

Large Scale Induction Generators for Power Systems

Abstract: Induction generators coupled with controlled static var sources can replace the function of synchronous alternators. They can operate in systems composed exclusively of induction generators or in mixed systems of induction and synchronous sources.

Method and circuit for controlling a hybrid contactor

Abstract: A method and circuit for minimizing DC current offset generated by the voltage-integrating property of an inductive load. First, second and third hybrid contactors connect first, second, and third output lines of an AC power source to first, second, and third input lines of an inductive load. Each hybrid contactor includes a pair of relay contacts in parallel with a semiconductor switching unit having two antiparallel-connected silicon-controlled-rectifiers. A latching circuit and several delay circuits are used to turn on and off the hybrid contactors; the timing of the turn-on points is controlled relative to a zero-crossing of a voltage from the AC power source such that minimal DC offset current occurs.

Generalized theory of electric power

Abstract: The paper presents the generalized theory of electric power, which makes it possible to estimate the operation of complex electric circuits. Use has been made of the correlation analysis and new definitions have been found for various kinds of power occurring in such systems. It has been shown that both the active and the reactive power depend on the voltage-current correlation of the system. A new definition has been found for the distortion power, together with the condition which leads to its minimization.

Remote AC power control with control pulses at the zero crossing of the AC wave

Abstract: A remote control for the control of AC power uses the AC power wave of an existing AC power line for the transmitting control signals from a control location to a remote location. A transmitter at the control location provides a predetermined number of control pulses to the AC power line and includes at least one breakdown device and at least one capacitor in series across the AC power line. The actuation of the transmitter provides triggering of the one or more breakdown devices at at least one peak point of the AC power wave and with the triggering corresponding to the predetermined number of control pulses for providing a charging of the one or more capacitors substantially to one half of the peak to peak value of the AC power wave at the predetermined number of points and triggering of the one or more breakdown devices at the zero crossing points of the AC power wave to discharge the one or more capacitors to provide high frequency pulses having amplitudes substantially equal to one half of the peak to peak value of the AC power wave. A receiver at the remote location includes a detector which is enabled only at the zero crossing points so as to detect the presence of the control pulses only at that time.

Low Voltage Bulk Power System Restoration Simulation

Abstract: Time is the crucial element in restorative state control for electric power systems. One method for reenergizing large portions of a blacked out electric power system with a minimum of switching and thus time to restoration, is described. Results of a simulated system restart utilizing actual power system facilities are compared to power flow studies. The simulation tests were performed on the Los Angeles Department of Water and Power (LADWP) system in order to verify the concept of utilizing generation operating at extremely low voltage to energize as large a part as possible of the unloaded bulk power transmission system located within the service area.

Idenntification of Parameters for Power System Stability Analysis Using Kalman Filter

Abstract: We propose that parameters on generators and the control units, used for power stability analysis, should be identified on the field data for reliable analysis in planning and operation of power supply systems. We apply Kalman filter technique in estimating the parameters. The identified data are compared with the design data and are well verified by analyzing the dynamic stability under line switching condition. Which deviation of designed values from identified values has the largest influence on the analysis, is also investigated.

Optimal Reactive Power Planning

Abstract: This paper discusses development of a computer algorithm which can select one overall reactive power installation pattern that will satisfy system performance constraints for both base case and contingency conditions. The cost of installation and base case losses are minimized. In addition, existing controllers are fully utilized prior to any addition of new installation. The computing algorithm employs a reduced gradient method of optimization in conjunction with simplex and integer routines to solve the reactive power allocation problem. The resulting program has been tested on a sample Consolidated Edison system.

Method and apparatus for preventing loss of data from volatile memory

Abstract: Normal line voltage, such as 115 volts AC available on a standard home or office receptacle (or single or three phase 230 volts AC), is surge protected and filtered prior to monitoring for voltage deviations outside of a voltage "window" such as 105-125 volts AC. Deviations outside of this voltage "window", are sensed and a deviation output signal is generated. The filtered AC supply and an auxiliary AC supply are selectively connected to the user equipment through a power distribution panel, with the selection being determined by the deviation output signal. By the method and apparatus of the invention, the computer equipment is supplied with primary input power from the utility company or the like as long as the voltage remains within this adjustable voltage window of 105-125 volts AC. If the line voltage moves outside of this "window", due to drift, brown-out, drop-out (complete voltage failure), or a surge creating an overvoltage condition, there is a transference of the power supplied to the computer equipment from the normal AC supply to an auxillary AC supply to maintain the contents of RAM and allow the program to continue running. Visual and audible indicators are actuated upon the occurrence of the deviation output signal to notify the user of the equipment that primary power has been disconnected and data should be transferred from volatile memory to non-volatile memory to prevent data loss. If the failure is temporary, the device automatically recovers and switches back to primary AC power when the filtered line voltage is within its "window".

Optimal Hydrothermal Scheduling with Cascaded Plants Using Progressive Optimality Algorithm

Abstract: This paper presents an application of the 'Progressive Optimality Algorithm' (POA) to the problem of short range optimal hydrothermal scheduling in a power system consisting of ca. caded plants with time delay. Head variation and constraints imposed due to equipment ratings and operating conditions on hydro as well as thermal-electric subsystems have been considered. Electrical subsystem has been represented in detail through ac power flows. Resulbs for a sample 5 bus system consisting of two hydro (cascaded) and two thermal stations clearly reveal the simplicity, effectiveness and distinct superiority of the progressive optamility algorithm over many of the existing techniques. The algorithm requires minimal storage and is extremely fast. It is envisaged thst POA technique would greatly appeal to the utility engineers for practical application.

A Doublesided Cycloconverter

Abstract: A power converter with reversible power flow, which transforms polyphase ac or dc power of one form and voltage level to ac or dc power of another form and voltage level, is presented. Use of a modulated high-frequency link between two sets of matrices of switches at the output terminals allows the application of active filtering processes and the elimination of all low-frequency filters and transformers; it allows, furthermore, arbitrary and independent programming of the power factors at the two ports. Low weight and cost of apparatus is enhanced by the time proven reliability of its significant functional elements. The potential for the construction of megawatt capacity systems is derived from experience with the basic class of these converters and is reinforced by the report of reduction to practice of some of the described techniques in the form of a 3-kW model in a companion paper [15].

Diode assisted relay contactor

Abstract: A switching circuit having hybrid contactors connects the three output lines of a 3 phase AC power source to three input lines of a load, such as a motor and the like. A single pair of relay contacts is used to directly connect one output line of the AC power source to one input line of the load, whereas each of the other two phases of the AC power source are supplied to the load by one of a pair of pilot relay contacts in series with a diode-shunted one of a pair of master relay contacts. Only two extra pilot relays are used to provide a reversing function. The switching circuit further includes a zero-crossing detector, a phase-sequence detector, a control circuit including four flip-flops arranged in a tumble-down chain and a single distribution circuit having a data select circuit. The control circuit causes the making and breaking of the contacts at particular times, and in a sequence, such that arcing is prevented.

Explicit Load Flow Series and Functions

Abstract: When expressed in rectangular coordinates, the basic load flow equations consist of n quadratic equations for power in: terms of n voltage variables. In this paper, a series reversion technique is employed to express the-n voltage variables as an explicit-power series in the power variables. Two different series are presented. The first is a Taylor series for voltage in terms of power while the second has a fixed point iteration origin with near Newton properties. The series have the potential to generate explicit load flow functions which can evaluate alternate loading conditions very rapidly.

Monitoring system for an LC filter circuit in an AC power network

Abstract: A monitoring system for measuring the phase currents of a filter circuit, the monitoring system having current measuring transformers coupled to respective filter sections for suppressing the harmonic content. Voltage measuring transformers are provided for measuring the network phase voltages, each such voltage measuring transformer being coupled to an electronic filter simulator and a filtering section for suppressing harmonic content. The fundamental frequency component of the measured phase currents and the simulated phase currents are conducted to transient comparator circuitry which is coupled to indicating and triggering circuitry having individual counter stages. Only rapid variations between the measured and simulated phase currents will result in fault indications, thereby preventing false indications resulting from variations in temperature.

Emergency apparatus for elevator

Abstract: An emergency apparatus for elevator which converts a DC power into an AC power by an inverter device in an emergency state to feed the AC power to an AC traction motor and an AC motor for door-opening and closing which have different rated voltages so as to drive a cage of the elevator and to open and close a door of the cage comprises selectively feeding a power through said inverter device to either of said traction motor or said motor for door-opening and closing, in an emergency state.

Analysis of Certain Aspects of Forced Commutated HVDC Inverters

Abstract: Previous researchers have analyzed the forced commutated HVDC Inverter and have concluded that it could be used to meet the reactive power requirements, and even to supply reactive power at the inverter terminals.

Dynamic Stability of Static Compensator - Synchronous Generator Combination

Abstract: An automatic static compensator shunt connected at the synchronous generator terminals using an appropriate control strategy is shown to yield superior dynamic stability limits than that of a conventional or a dual excited machine. The control signal to actuate the static compensator is derived from a comparison of the reactive power flow on the tie line and that produced by the compensator. A state spacs mathematical model for the proposed system is formulated and the dynamic stability limits for various studies are obtained using sigenvalue technique.

Power supply for an ac discharge lamp

Abstract: A power supply for an ac discharge lamp utilizes a switching transistor for turning on and off the dc current from a dc power circuit. The dc current is then fed to a low pass filter for supplying the dc power to the lamp with alternating polarity. A voltage and a current sensing circuits effective to control the dc power to a substantially constant level is connected to a control circuit for controlling the on and off times of the switching transistor. In such a power supply, the voltage and current sensing circuits are made up of transformers whereby the high-voltage circuit section is effectively separated and insulated from the low-voltage circuit section so as to prevent any possible electrical shocks.

Circuit for injecting simulating-noise signals in a power line

Abstract: A simulated-noise signal is injected in the power line of equipment under test without loss of AC power by the use of a series resonance circuit having a resonance frequency equal to the frequency of the AC power supply. The series resonance circuit is connected in the power line in parallel with the equipment, and a capacitor is connected to the power line in parallel with the series resonance circuit and the equipment. A switching element is used to short-circuit the resonance circuit when noise simulation is not carried out. For the simulation of lightening strikes the circuit further comprises a simulated-noise signal generator including a capacitor charged by a DC power supply, a first switching element to discharge the charge of the capacitor to the equipment, and a second switching element for establishing a by-pass of the discharging current. By closing the second switching element after the first switching element is closed, a square-wave signal is fed to the equipment. In order to simulate ringing-surge signals, the circuit includes a generator to generate a damped-wave signal similar to a ringing signal. This generator has a capacitor charged by a DC power supply, a switching element for discharging the charge of the capacitor to the equipment, and an inductance coil connected to the discharging circuit. When the switching element is closed, a damped-wave signal is fed to the equipment.

AC Fail-detect and battery switchover circuit for multi-bus power supply

Abstract: A power supply having reliable means to detect the failure of an AC power source and to provide an AC fail signal in response thereto includes error-free switchover circuitry to supply emergency power from a standby battery. The power supply comprises a comparator circuit, a Schmitt trigger-inverter circuit, and a feedback circuit which provides positive regeneration to ensure error-free battery switching under AC power fail or restore conditions.

Flow rate measuring device

Abstract: PURPOSE:To obtain a flow rate measuring device having a small amount of consumption and multiplied reliability with a simple constitution, by performing a time division multiplexing process. CONSTITUTION:A switch 33 of an energizing circuit 31, a switch 51 of an electromagnetic flow rate converter 11, etc. are switched via a timer 23. Then the energizing coils 5A and 5B of electromagnetic flow rate detectors 1A and 1B are energized with time division by the DC power which is obtained by converting the AC power supplied from a commercial power supply 21 with a rectifier 25, a capacitor 27, etc. Then the frequency signals corresponding to the flow rates which are detected with time division by the detectors 1A and 1B are multiplied via the switch 51 and processed by an F/V converting circuit 55, a reversible counter 59, a pulse code converter 63 and an optical signal converter 67 to be transmitted via an optical fiber without receiving any effect of noises. The circuits and component parts can be shared with each other, and the number of transmission lines is not increased. As a result, the power consumption is reduced with multiplied reliability for a flow rate measuring device with a simple constitution.