Showing papers on "AC power published in 1979"

Reactive Power Generation and Control by Thyristor Circuits

Abstract: Generally, static var generators function as variable reactances (capacitive or inductive impedances) or controllable ac current and voltage sources. Possible methods of var generation and control by static thyristor circuits are reviewed, and new approaches are described in which power frequency changers (cycloconverters) are employed. Oscillographic recordings illustrate the operation and performance of practical systems, including a 35-Mvar arc furnace compensator.

Power plant for camping trailer

Abstract: A power plant for mobile homes, camping trailers, and the like, capable of capturing low powered aeolian energy, storing said energy in the form of compressed air, and delivering it on demand in the form of household electrical current. The device comprises a wind turbine driving an air compressor which feeds a storage tank. On demand, the compressed air drives a turbine coupled to an electrical generator. Various pressure regulators are used to regulate the speed of the generator. The wind turbine is also coupled to an alternator which maintains a bank of electrical batteries charged. A DC motor running on the batteries is used when necessary to boost the drive of the air compressor during periods of heavy or long power drain. Provision is made for rapidly recharging the power plant from either a supply of compressed air or from an AC power source.

A Pulsewidth Controlled AC-to-DC Converter to Improve Power Factor and Waveform of AC Line Current

Abstract: As a method for improving power factor and waveform of ac line current drawn by an ac-to-dc converter a new pulsewidth controlled converter is proposed, its commutation mechanism is described, and experimental results are given which show a good power factor, a good waveform of the line current, and a wide adjustable range of dc output voltage.

Supplemental electrical power generating system

Abstract: Hydrocarbon fuel energy is converted to AC electrical energy by a new system utilized to supplement AC power for household and similar limited size loads in synchronism with existing AC utility service via pre-existing wiring between the load and the utility lines. The system has an externally excited commutator AC motor-generator driven by an internal combustion engine to provide AC power at a magnitude which is a function of the drive shaft velocity and degree of excitation. An exciter circuit provides excitation for the motor-generator to cause the generated AC power to be in phase with utility power. A load demand sensor senses current flowing through the wiring to the load, providing a control signal signifying magnitude of the current, thus measuring load power requirements. Control circuitry interconnected with the exciter circuitry and the engine is responsive to the control signal to control excitation for causing the generated supplemental power substantially to meet load requirements. The control circuitry also controls engine speed to provide sufficient engine power to meet these load requirements. Mechanical elements of the system are contained by an insulated, sound-proofed enclosure. Air is drawn into the enclosure for cooling of the motor-generator and for recovering heat from the engine and the engine exhaust. The heated air is ducted out of the housing for use in household heating, etc. Various circuit features, including a phase sensitive detector, ensure that electrical power generated by the system does not flow back to the utility service. The system starts and stops automatically according to power demand.

Prediction Method for Buried Pipeline Voltages Due to 60 Hz AC Inductive Coupling Part I-Analysis

Abstract: The voltages induced on gas transmission pipelines by 60 Hz ac power transmission lines sharing a joint right-of-way are predicted using electrical transmission line theory. Thevenin equivalent circuits for pipeline sections are developed which allow the decomposition of complex pipeline-power line geometries. Programmable hand calculator techniques are used to determine inducing fields, pipeline characteristics, and Thevenin circuits.

Harmonic Analysis and Suppression for Electrical Systems Supplying Static Power Converters and Other Nonlinear Loads

Abstract: This paper is comprised of the proposed Chapter 9, entitled ``Harmonic Analysis,'' of the forthcoming IEEE Recommended Practice for Industrial and Commercial Power System Analysis (Brown Book).

Regulated AC power for Josephson interferometer latching logic circuits

Abstract: We have developed an ac power distribution scheme which provides switched regulated power of alternating polarity (no rectification necessary) for Josephson interferometer latching logic circuits. Distribution from the power source relies on a tree system of thin film transformers having single primaries and multiple secondaries to maintain low current levels and small phase skews throughout the system. Power signals are clipped on chip to the desired voltage supply level by series connected large area Josephson junctions ("regulator" junctions) and distributed across the chip by voltage busses. Supply resistors between the regulated voltage bus and the logic circuits define the operating current level. A detailed design is presented for a specific interferometer latching circuit family. We report experimental data on the two major components of the power system design - the regulators and the transformers. A series string of four regulator junctions provides a trapezoidal waveform of 11 mV amplitude at > 66% logic duty cycle (that portion of the machine cycle in which logic operations can be performed). Thin film transformers have their designed inductance (350 pH) and coupling coefficient ( > .90).

Power source system

Abstract: A power source system, which comprises a converter for converting AC power on an AC bus into DC power, a damped filter connected between the AC bus and ground and including a capacitor and an inductor, a diode-rectifying circuit for taking out and rectifying fundamental and harmonic waves produced across the inductor in the damped filter and a circuit for connecting a DC output circuit in the diode-rectifying circuit in series with a DC output circuit in said converter, and in which the rectified output is regeneratively added to the output of the converter.

A Two-stage Approach To Solving Large-scale Optimal Power Flows

Abstract: A two stage optimization algorithm is developed for the solution of the large-scale optimal power flow (OPF) problem. The solution scheme is arrived at by exploiting the structural properties of the OPF problem formulation, including the physical characteristics of its variables. The algorithm incorporates certain features of the generalized reduced gradient and the penalty function methods. At each iteration a modified reduced gradient is used to provide a direction of movement. The use of penalty functions in the optimization is kept at a minimum. The generalized reduced gradient ideas are adapted in such a way that a routine power flow is used in the optimization. Numerical results of test cases including a 1410 bus system are given.

Electromagnetic flow meter

Abstract: PURPOSE:To measure the flow rate of fluid in high accuracy by providing difference between large and small energizing currents during ordinal value period and selecting the sampling interval for detecting both signal voltages at integer magnification of commerical power frequency. CONSTITUTION:An electromagnetic flow meter oscillator 4 consists of an exciting coil 5, a fluid flowing pipe 6 and electrodes 7, 7' and flows rectangular exciting current having two ordinal values at the coil 5 by a rectangular wave energizing circuit 1 to detect the difference between the signal voltage occurred at the larger ordinal exciting current and the signal voltage occurred at the smaller ordinal exciting current by a differential amplifier 12. It provides the difference between the period of the larger ordinal value of the exciting current and the period of the smaller ordinal value of the current and selects the interval from one sampling of the current to the other sampling thereof by a pulse generator 13 to the integer magnification of the period of commerical AC power supply so as to effectively remove the effects of the noise of the commerical power frequency and of electrochemical unbalance voltage.

Power line disturbance detector circuit

Abstract: A power line disturbance (PLD) detector circuit includes a digital counter which is driven by pulses provided by a clock in an associated data processing system The PLD detector circuit includes a comparator amplifier for comparing primary AC power to a DC reference voltage on a cycle-by-cycle basis The amplifier generates a reset pulse once during each AC cycle as long as the AC voltage exceeds the DC reference voltage When a decoder circuit detects a count outside the range of counts attained by the digital counter between normally occurring reset pulses, the decoder circuit responds by generating a PLD signal The PLD signal is provided both to the associated data processing system and to a Power On Reset circuit The Power On Reset circuit is initialized by the PLD signal, permitting the circuit to respond consistently upon subsequent restoration of power

Method for controlling power flow between an electrochemical cell and a power grid

Abstract: A method for controlling a force-commutated inverter coupled between an electrochemical cell and a power grid for adjusting the magnitude and direction of the electrical energy flowing therebetween. Both the real power component and the reactive power component of AC electrical energy flow can be independently varied through the switching waveform presented to the intermediately coupled inverter. A var error signal is derived from a comparison of a var command signal with a signal proportional to the actual reactive power circulating between the inverter and the power grid. This signal is presented to a voltage controller which essentially varies only the effective magnitude of the fundamental voltage waveform out of the inverter, thereby leaving the real power component substantially unaffected. In a similar manner, a power error signal is derived by a comparison of a power command signal with a signal proportional to the actual real power flowing between the electrochemical cell and the power grid. This signal is presented to a phase controller which varies only the phase of the fundamental component of the voltage waveform out of the inverter relative to that of the power grid and changes only the real power in proportion thereto, thus leaving the reactive power component substantially unaffected.

The High-Frequency Base Converter-A New Approach to Static High-Power Conversion

Abstract: A new approach to high-power conversion in which two naturally commutated converters (cycloconverters) are used in tandem, each with its input connected to a (passive) high-frequency (HF) source (``base'') is presented. The arrangement approximates an ideal converter; its ``input'' and ``output'' frequency can be equal or different, and the power factor at both external terminals can be maintained at unity or any other value. Potential utility applications in which the HF base converter functions as an asynchronous intertie between two ac power systems and as a tie between a dc transmission line and a weak ac system are discussed, and technical and economic comparisons with conventional approaches are given.

Dual speed control circuit for power flow through an inverter

Abstract: A control circuit for a force-commutated inverter connected intermediate a regenerative DC power source and a power grid, the power source/inverter combination operative to supply AC electrical energy to, or receive AC electrical energy from or adjust the power factor of, the AC electrical energy of the power grid. The control circuit of the present invention varies the real power component and the reactive power component of the electrical energy flowing between the electrochemical cell and the power grid through the use of two feedback loops with separate time constants. The first feedback loop allows for the independent control of the magnitude and direction of both the real power component and the reactive power component of the AC electrical energy flowing to or from the power grid. The first feedback loop also has a relatively slow time constant so that the power flow between the DC source and the power grid is substantially unaffected by transients. The second feedback loop has a fast time constant for rapidly adjusting the effective magnitude and phase of the voltage waveform from the inverter to compensate for instantaneous or short duration voltage surges which periodically appear on the power grid.

Metering and protection system for an A.C. power system

Abstract: A system for electronically metering an A.C. electrical power system to derive performance parameters such as real and reactive power useful in revenue metering and fault protection applications. Voltage and current sensors associated with the power system provide isolated output signals proportional to the voltage and current in the system. From these signals finite-duration impulse-response filters periodically determine Walsh function correlation coefficients by integrating the voltage and current signals at least once during each period of the power system and periodically sampling and holding the integrated signal in sequence with the integration. The present and a plurality of immediately preceding correlation coefficient values are stored in memory, and by combination of the correlation coefficients by addition, subtraction or multiplication, power system performance parameters, such as real power, reactive power, voltage, current, or power factor, are obtained for utilization in revenue metering or overload protection applications. Related methods are also disclosed.

Remote control circuit for coded receivers - operates with direct modification of power supply waveform by positive and negative half-wave clipping

Abstract: The application is to the remote control of loads connected to an AC power supply. The necessary control signals for the loads(2, 3) are generated by clipping either the positive or negative half waves of the power supply in a predetermined pattern. A sensor(6) in the load circuit detects the wave sequence and switches the load(7) accordingly. The signal transmitter(1) may be linked with a zero cross-over detector(8) in order to operate with minimum losses. The waveshape modifications may be applied to either voltage or current components of the supply.

Dc power transmission control

Abstract: OF THE DISCLOSURE A pair of thyristor converters are connected by a DC power transmission line, and their AC terminals are connected through tapped transformers to AC systems respectively. The output signal of a constant-current circuit in a converter control unit associated with the forward converter is selected to control the gate of the forward converter, while the output signal of a constant-voltage circuit in a converter control unit associated with the reverse converter is selected to control the gate of the reverse converter. When the reactive power is to be controlled, a reactive power signal is applied for the gate control. A voltage limit indication circuit in each control unit receives the AC terminal voltage e2 of the transformer and the DC current Id so as to increase the control angle limit with a decrease in the values of e2 and Id. When the control advance angle or control delay angle determined by the output signals of the control circuits is larger than the control angle limit, this angle is limited to the control angle limit. When the reactive power is to be controlled, the tap position of either transformer is lowered to decrease e2 and to increase the control angle limit thereby widening the controllable range of the reactive power. During the start-stop stage or during the protective operation, the output of the voltage limit indication circuit in each control unit is inhibited to permit free variations of the control angle.

Principle of a Dual Current Source Converter for AC Motor Drives

Abstract: The principle of operation of a dual current source converter is briefly explained. The combination of two single current source converters (SCSC) to form a ``dual (duplex) current source converter'' (DCSC) is proposed. The DCSC is shown to have the following merits: 1) it retains all the advantages of the SCSC; 2) it reduces the harmonic content of the current waveform considerably; and 3) since the load current is shared equally between two current source converters, ratings of the individual components employed in the circuit are considerably lowered. A DCSC can be an attractive choice for sophisticated large horsepower drives where a good performance of the drive rather than cost is a prime factor. An open-loop control scheme employing the DCSC for an ac motor drive has been successfully implemented in the laboratory. Oscillograms of the improved load current waveforms are shown.

Mitigation of Buried Pipeline Voltages due to 60 Hz AC Inductive Coupling Part I-Design of Joint Rights-of-Way

Abstract: Useful mitigation techniques are presented for the reduction of voltages induced on gas transmission pipelines by 60 Hz ac power transmission lines sharing a joint right-of-way Part I describes how a joint pipeline/power line corridor can be designed to minimize inductive coupling This allows installation of the utilities with significantly reduced requirements for pipeline voltage mitigation using grounding techniques

Power supply system for linear motor

Abstract: A power supply system for a linear motor comprising a plurality of driving coils disposed along the track for a running body for generating a shifting magnetic field to drive the running body, power converter means for feeding the plurality of driving coils with electrical energy, a plurality of switches responsive to the movement of the running body for selectively electrically connecting each of the driving coils to the power converter means, a first reactive power controller continuously electrically connected to the power input side of the power converter means, and a second reactive power controller selectively electrically connected to the power input side of the power converter means in accordance with the movement of the running body, whereby the steady reactive-power is compensated for by the first reactive power controller and the reactive power which varies with the movement of the running body is compensated for by the second reactive power controller

Average power control apparatus and method

Abstract: A power control method and apparatus maintains a constant average power at an electrical load, such as a fuser in an electrophotocopy machine. A power monitor measures the average power delivered to the load and compares the measured power to a predetermined power. A digital network receives an input signal from the power monitor and controls the coupling of power from an ac source to the load. When load power is less than a predetermined level, the digital network couples every half cycle of the ac power source to the load. When the load power is equal to or greater than the predetermined power, the digital network couples every third ac half cycle to the load. As a result, only half cycles of sequentially opposite polarity are coupled to the load.

Touch dimmer circuit

Abstract: A touch dimmer switch incorporating an integrated circuit for controlling a thyristor dimming circuit, has a touch control connected in a high impedance, unidirectionally conducting circuit, and a filter circuit for filtering out ambient electrical noise. The touch control is isolated from the AC power source so that the polarity of connection to the power source is not critical.

Reverse Phase-Controlled Dimmer for Incandescent Lighting

Abstract: The reverse phase-controlled dimmer is an alternate method for varying the intensity of incandescent lights. Unlike conventional phase-controlled dimmers, the thyristors are triggered into conduction immediately following the zero crossing of the ac line rather than being delayed into the half-cycle. After an appropriate delay the silicon-controlled rectifiers (SCR's) are turned off by forced commutation. Manufacturers of conventional phase-controlled dimmers place a large inductor in series with the lamp load to reduce both lamp acoustical noise and radio-frequency interference (RFI) to acceptable levels. Instead of an inductor, reverse phase control connects a snubber capacitor in parallel with the main SCR's. The capacitor filters the output much like an inductor would, but without the inherent disadvantages. Eliminating the inductor makes more power available to the load since there is no reactive power loss in the main current path. Furthermore, without the inductor the dimmer will run quieter, because the inductor is a major source of acoustical noise. The control circuit incorporates an open loop scheme that provides line voltage regulation and fast response. A combination of analog and digital techniques tracks the amount of power available from the power line and meters out only the desired amount of the load. The dimmer responds to changes in control signal and line voltage within one half-cycle. Power levels are programmed by an 8 bit data word.

A New Controlled Current Type Inverter with Improved Performance

Abstract: A new current-commutating method applying the action of the mutually coupled inductances is described and is termed the coupled reactor commutating (CRC) method. With this method a unique self-excited controlled current type inverter is constructed. The CRC inverter not only gives an efficient voltage adjustment function, but it also liberates men from the task of treating reactive powers. An example of the application to the induction motor drives is described in which an overall efficiency as high as 85 percent has been reached. The troublesome problem of parasitic torque pulsation in the low-revolution range, which is inherent in the controlled current type inverters, is also resolved by the torque-smoothing current control method with the CRC inverter.

Generalised polyphase fault-analysis program: calculation of cross-country fault

Abstract: A general computer program using the phase co-ordinate technique has been developed for analysing series, shunt and simultaneous faults on balanced and unbalanced polyphase electrical networks. The program eliminates the need for maintaining numerous fault analysing subroutines, one for each kind of fault, and makes the solution of many difficult and previously unsolvable problems possible. It is employed to analyse the cross-country fault involving different phases. The solution method, program outlines and postfault results of voltages, currents and apparent power of an actual power system are given.

Damping of Power Swings in AC Tie Lines Using a Parallel DC Link Operating at Constant Reactive Power Control

Abstract: This paper presents a method for the damping of power swings in the ac lines interconnecting two power systems, utilising the fast electronic power flow control characteristics of a parallel dc link. The basic principle of the method is that the dc link is operated in order to maintain constant active power flow in the ac tie lines and constant reactive power consumption at the converter terminals. The proposed control strategy was tested using dynamic simulation techniques and the results obtained show that, under certain conditions, the contribution of a parallel dc link to the stability the ac system can be significant.

Power supply and control circuit for series connected controller

Abstract: A control circuit for a power threshold switch, like a power triac, to be connected in series with a load device, at a situs where only one AC power conductor and a conductor extending to the load device is available, is energized from a DC power supply energized from these conductors. The power supply includes a rectifier connected in series with an energy storage means, such as a capacitor, the terminals of which constitute the DC output terminal of the DC power supply, an impedance of much greater resistance than that of the load device and through which the capacitor is charged when the triac is in its non-conductive mode, and preferably a low power control triac shunting the high impedance and triggered momentarily into conduction each half cycle as the applied AC voltage goes through zero when the power triac is to be in its conductive mode, to effect charging of said energy storage means and subsequently the triggering of said power threshold switch into conduction.

The development of a guide on surge voltages in low-voltage ac power circuits

Abstract: Surge voltages in ac power circuits become more significant with the increased application of miniaturized electronics in consumer and industrial products. A Working Group of IEEE has prepared a Guide describing the nature of these surges in ac power circuits up to 600 V, and is currently developing an Application Guide for using the environmental data defined in the Guide to improve protection. The Guide proposes two waveforms, one oscillatory, the other unidirectional, depending on the location within the power system. It also includes recommendations for source impedance or short-circuit current. This paper describes the data base and approach used by the Working Group and the recommendations proposed to represent typical surges, in order to obtain feedback for writing the Application Guide.

Triac output asymmetry detector

Abstract: A circuit for protecting an AC driven load that is controlled by a solid state device, such as a triac, or inverse SCR's, or the like. Whenever the AC power output of the control is asymmetrical to the load, the circuit produces a signal capable of shutting down the AC power to the load, sounding an alarm, switching to a different controller, or signaling another load protecting reaction. The protection circuit continuously measures each individual half cycle of the AC output from the controller to the load and provides for phase shifting about a reference point, resulting in summing (or nulling) of the AC output half waves (positive and negative) at the reference point. The summing (or nulling) reference point is coupled to the gate of a switching element connected across the AC input line, the switching element being responsive to a positive or negative voltage above a predetermined threshold value. Half wave failure of the load controller resulting in an asymmetrical power output from the controller to the load creates a net charge, positive or negative (at the reference point). Whenever the net voltage at the reference point reaches the threshold voltage of the response switch, the load protecting response switch will be triggered.