Showing papers on "Voltage regulation published in 1973"

Optimum Network Var Planning by Nonlinear Programming

Abstract: Controllable network VAr compensators are required in high voltage transmission networks for system loss reduction and voltage maintenance during normal and emergency operation. Long term planning of network compensators is generally based on contingencies which cause the system voltage to move out of the desired operational range. A non-linear analysis based on multi-contingency states is presented for optimum network VAr planning. The proposed approach is critically evaluated and compared with the existing techniques and is illustrated by an application to a high voltage model system.

High speed control of reactive power for voltage stabilization in electric power systems

Abstract: In a multiphase alternating current electric power system subject to erratic and unbalanced reactive load current demand, reactive load current compensation is provided by a balanced multiphase reactive compensating impedance having equal but limited reactive current capability in all phases. To increase reactive current capability of any one selected phase of the reactive compensator in response to severe load unbalance a supplementary single phase compensating impedance is connected through a load current controlled switching bridge in parallel circuit relation with any one phase arm of the multiphase compensator. When any one such parallel connection is operative the switching bridge is prevented from connecting the supplementary impedance in any other phase arm of the multiphase compensator.

Power-system load representation

Abstract: The paper concerns the representation of distributed loads of mixed but known composition. A general load model is employed which relates relative changes in active-and reactive-load demand to relative changes in applied voltage and frequency in terms of a set of four characteristic parameters. The object is to identify analytically the resultant characteristic parameters at a principal load busbar, taking into account the effects of feeders and distribution transformers as well as load composition. The analysis may start at any network level where load characteristics are known. An example is given, illustrating the application of the method.

Overcurrent protection circuit utilizing peak detection circuit with variable dynamic response

Abstract: A DC to DC converter includes voltage regulation, overcurrent limit and symmetry correction circuitry. The converter includes a pulse-width modulation control including a timing circuit. The regulator, overcurrent limit, and symmetry correction circuitry all modify the timing therein to control the duty cycle of the converter switching devices. The overcurrent limit circuitry includes a variable response peak detection circuit to improve its response and feedback stability.

Power supply keep alive system

Abstract: A power supply system comprising a plurality of parallel connected voltage regulators, each regulator having a voltage control loop. Each voltage regulator is provided with a circuit which increases the reference voltage supplied to the voltage control loop so that the control loop of each regulator is prevented from being cut off during standby operation.

Real and Reactive Power Optimization by Suboptimum Techniques

Abstract: The short-term real and reactive power optimization of a large system is a non-linear programming problem and its solution requires a considerable amount of computational effort. In actual practice separate real and reactive power suboptimization techniques may be more suitable than a complete optimization(1). The results obtained by the suboptimal techniques under ideal conditions coincide with those from a real and reactive power optimization. In this paper, complete real and reactive optimization has been solved by suboptimization techniques. The proposed approach decomposes the complete problem into two halves, i. e. the optimum voltage evaluation and the real power optimization with optimally determined voltages. A theoretical treatment of the technique along with a qualitative and analytical discussion is provided. The method is applied to a small system and the results obtained are compared with a real and reactive power optimization.

Power inverter circuit

Abstract: A power supply is provided which is capable of operation from either of two power sources, such as on normal power from the usual alternating-current mains, or emergency power from a standby battery; and which will automatically switch from one source to another as the need arises. The power supply includes a transformer having at least two primary windings, and first and second input circuits respectively connected to the two primary windings and to the two sources. The preferred source will be selected by the power supply so long as its voltage is equal to or greater than the voltage of the secondary source.

High dc voltage generating circuit

Abstract: A high DC voltage generating circuit is provided with an impedance element connecting a switching element with the primary winding of a fly-back transformer, and a capacitive element is connected to the primary winding of the fly-back transformer to form a resonance circuit therewith, so that the fly-back transformer delivers, as its output, a sinusoidal high voltage which is subjected to a voltage doubler rectification to provide a high DC voltage with improved regulation.

Temperature responsive battery charging circuit

Abstract: A battery charging circuit for use in aircraft wherein a voltage-regulated alternator is employed to maintain a nickel cadmium battery charged. A temperature-dependent resistance element thermally coupled to the battery provides a reference voltage against which battery terminal voltage is compared. When the terminal voltage falls below the reference voltage application of sensing voltage to the alternator voltage regulator is interrupted, causing full charging current to be applied to the battery. When the terminal voltage exceeds the reference voltage, sensing voltage is reapplied to reduce charging current. The alternator switches between maximum and minimum charging efforts to maintain a voltage level dictated by the battery temperature.

Multicomputer Control of System Voltage and Reactive Power on Real-Time Basis

Abstract: This paper concerns a real-time control scheme of voltage and reactive power in power systems when more than two control computers as well as one central coordinating computer are involved. When a large number of voltage and/or reactive power regulating devices are involved in a power system and the number of nodes or lines in which the voltages or reactive power flows are observed and controlled increases, the necessary computing time and memory requirement increase exponentially if the central computer installed at the central dispatching office should take care of all control functions. In addition, the number of channels of the data transmission network becomes very large because the voltage and reactive power flow at each electric station must be transmitted to the central computer and the optimum operating values of regulating devices should be transmitted back to the regulating stations.

Power-factor compensation of thyristor-controlled single-phase load

Abstract: It is found that an effective way to obtain a, good power factor with a thyristor-controlled load is to use a parallel-connected uncontrolled resistive load of similar rating. The use of parallel-connected capacitance alone gives no significant degree of power-factor improvement, even when the capacitance is adjusted to the optimum value for each step of thyristor firing angle.

Alarm circuit for monitoring the amplitude of a-c voltages

Abstract: A circuit for rapidly and accurately indicating whether an a-c voltage has a magnitude greater than a predetermined minimum value. A two-state voltage comparing circuit establishes a first output voltage when the rectified a-c input voltage exceeds a preset reference voltage and establishes a second output voltage state when the rectified a-c input voltage is less than that reference voltage. A two-state switching circuit forces the comparing circuit to assume and remain in its first state for a preset time after it assumes its second state, the preset time being greater than the time required for an acceptably high a-c voltage to pass through the reference voltage region established by the comparing circuit, as the a-c voltage varies through zero volts twice during each full cycle thereof. A two-state output control circuit indicates an a-c voltage fault if and when the comparing circuit returns to its second state within a relatively short time after having been forced to assume its first state. In this manner actual a-c voltage faults are distinguished from the apparent a-c voltage faults which tend to occur each time the a-c voltage varies through zero.

Barrier isolator device employing an overload protection circuit

Abstract: A barrier isolator device is disclosed for interconnecting a voltage source in a safe area, a load (such as a sensing element) in a hazardous area, and a load-associated device (such as a recorder) in a safe area. The barrier isolator device includes an overload protection circuit arranged to transmit signals between the load and the load-associated device, a first isolating circuit connecting the voltage source with the overload protection circuit, and a second isolating circuit connecting the load-associated device with the overload protection circuit. The protective circuit is characterized by low voltage losses in normal operation, low power consumption in a fault condition, and automatic resetting. The protective circuit comprises a current control means, such as a transistor, in series with the load and controlling the current flowing through the load by varying its conductivity. A current detection means, such as a low valued resistor, is connected in series with the load to detect the predetermined limiting value of current, and a voltage detection means, such as a resistive voltage divider, is connected parallel to the voltage source for detecting the predetermined limiting value of voltage. The current control means is arranged to be responsive to the current and voltage detection means to react to either a current or voltage overload condition by reducing its conductivity to limit current flow through, and voltage across, the load. Under normal conditions the current control means inserts a conducting transistor's collector-emitter circuit in series with the load, and the current detecting means inserts a low valued resistor in series with the load, and hence the overload protection circuit introduces only a small series voltage loss. The voltage detecting means places large valued resistors in parallel with the voltage source, and any bias voltages provided to the current control means by the voltage source can be supplied through similar large valued resistors, and hence there is little power consumption during a voltage overload condition. The current control means and the voltage and current detection means are arranged to automatically restore themselves when overload conditions vanish. Accordingly, the overload protection circuit is highly suitable for use in intrinsically safe circuitry arranged to prevent excess energy from entering a hazardous environment, such as an explosive environment.

Switching voltage regulator with optical coupling

Abstract: An improved voltage regulator has a transistor connected to switch on and off the current to the load with a variable waveform that establishes the effective current level. A voltage detector circuit adjusts the regulated current level to the level required to maintain the selected load voltage.

Power supply over voltage protection system

Abstract: A power supply system is disclosed having a plurality of voltage regulator circuits connected in parallel with each other between a source of unregulated voltage and a load. Each of the voltage regulators includes an over voltage protection circuit whereby a particular regulator is taken out of service when the current in that regulator exceeds a certain level and the voltage across the load is at a first level. The regulator is not taken out of service when the current through the regulator is below the certain level and the voltage across the load is above the first level but below a second, higher, level.

Monolithic integrable series stabilization circuit for generating a constant low voltage output

Abstract: A series stabilization circuit for generating a regulated voltage in the order of one volt. In order to reduce variations in the output voltage due to changes in temperature, the reference voltage used is a combination of the outputs of two reference voltage sources. The first reference source has a negative coefficient of voltage such that its output will decrease when temperatures increase. The second reference source has a positive coefficient of voltage such that its output will increase as temperature increases thereby resulting in a balanced overall reference voltage.

Voltage, current, or power controller utilizing a switched reactance A.C. shunt regulator

Abstract: Apparatus is described that regulates the transfer of voltage, current, or power from an AC line to a load. The basic controller comprises an inductive element and a switch whose closing converts the inductive element from a series inductance between line and load to a step-down auto-transformer between line and load thus reducing the voltage available to the load and thereby reducing or terminating energy transfer to the load. The switch is connected in series with the inductive element and the combination of the switch and one winding of the auto-transformer is connected in parallel with the load. The controller can therefore be thought of as a switched reactance AC shunt regulator. Theoretically, shunt power in the controller is losslessly returned to the source. The controller is used to regulate any parameter related to the current through the load, the voltage across the load, or the power dissipated by the load simply by controlling the switch with any suitable means for sensing that parameter.

Direct curent supply with ribble suppression

Abstract: A circuit arrangement for supplying a direct current, which is free from interruptions, from an alternating line current. The circuit includes: a first rectifier which initially rectifies the line current; an energy store, which helps compensate for variations in the rectified voltage; an inverter for chopping up the recitified voltage; a transformer; a second rectifier arrangement; a smoothing filter; and a control device. The voltage which is generated at the output of the smoothing filter is fed to the direct current load. When the voltage across the direct current load falls below a rated value, a first electrical switching device provides an extra current to the direct current load. On the other hand, when the voltage across the direct current load increases above the rated value, a second electrical switching device diverts a portion of the current through the direct current load. In this manner, any changes in the current and voltage across the load are compensated.

Machine work sensor

Abstract: An improved work sensor circuit for single or multiphase electric motors wherein a change in work load produces a test voltage, thereby providing a convenient and sensitive way of measuring load and load changes. According to the invention, a vectorial combination of voltage signals representing motor current and motor voltage is produced in a first circuit portion to provide a test voltage which is operated on by additional circuitry to indicate changes in motor load, the rate of change, and the direction of change.

Voltage failure sensing circuit

Abstract: A circuit for sensing voltage failure in a multiphase conductor electric power supply. Voltage failure of any of the phase conductors to a value less than a predetermined voltage serves to de-energize a sensing means, which preferably comprises a solenoid in control circuit relationship with a load connected to the power supply.

Temperature control device for thermostatic oven

Abstract: A temperature control device for a thermostatic oven or the like is provided with an input temperature-sensitive, resistive bridge network. Any imbalance voltage in the bride network is integrated by an electronic integrator to provide an output intergrated voltage. The output integrated voltage is amplified by a power amplifier which supplies the heater element in the oven. The effect of the arrangement is such as to minimize the offset voltage in the feedback loop with the result that changes in the ambient temperature and power supply voltage have less effect on the operation of the device.

Voltage-regulated power supply unit

Abstract: Voltage-regulated power supply unit provided with first and second d.c. voltage sources of different voltage levels and first and second regulators. The first regulator delivers a stabilised output voltage. In general, the input voltage of the first regulator is derived from the first source. However, if the output voltage of the first source drops below the working voltage of the first regulator, an additional supply of energy is provided by the second source via the second regulator. A smoothing filter having a certain ripple factor, is inserted in the first source, thus increasing the efficiency of the supply unit.

Power supply devices

Abstract: A power supply for producing a.c. power at low voltage from conventional a.c. supply mains, without heavy-duty mains transformers. The supply is rectified, and switched at high frequency, transformed to low or other voltage and rectified. Control of the switching means is by comparison of voltage ramps with a threshold voltage and the threshold voltage is controlled in accordance with variables including voltage and current output, to vary the duty cycle of the switching means and hence the output.

Erratum: Rectifier action with constant load voltage: infinite-capacitance condition

Abstract: The paper presents an analysis of a 3-phase fullwave bridge-rectifier system with constant load voltage, and with series resistance and inductance in the a.c. source. It is shown that four different operating modes or conducting patterns may occur, according to the phase angle of the source impedance and the magnitude of the load voltage. The results given include a complete set of output voltage/current characteristics from open circuit to short circuit, for the full range of possible source impedances, together with details of the source and bridge currents.

Direct current power converter

Abstract: A power regulation system for use in electric drive vehicles having a direct current power supply of a relatively high voltage and which requires a source of relatively low direct current for auxiliary purposes, such as for charging a 12 volt auxiliary battery which operates an electrical system in the vehicle other than the drive train. The system includes a converter having a full wave transistor bridge oscillator operable to apply high frequency input to the primary of a step-down power transformer. The rectified output of the secondary of the power transformer is connected across the low voltage battery. Charging current control is achieved by a Schmitt trigger voltage sensor connected across the low voltage battery to deactivate or activate the converter at the upper or lower ends of a predetermined low voltage range.

Remote sensing voltage clamping circuit

Abstract: Apparatus for sensing the actual voltage at a load circuit remotely located from its power source and clamping the power source output level to prevent overvoltage levels at the remote load, including a high impedance sensing lead and a detector-clamping circuit coupled intermediate the sensing lead and the power source. The detector responds to attempts of the voltage level at the remote load to exceed the overvoltage level so as to actuate a drive signal and clamp the power source output.

Solar electric propulsion thrust subsystem development

Abstract: The Solar Electric Propulsion System developed under this program was designed to demonstrate all the thrust subsystem functions needed on an unmanned planetary vehicle. The demonstration included operation of the basic elements, power matching input and output voltage regulation, three-axis thrust vector control, subsystem automatic control including failure detection and correction capability (using a PDP-11 computer), operation of critical elements in thermal-vacuum-, zero-gravity-type propellant storage, and data outputs from all subsystem elements. The subsystem elements, functions, unique features, and test setup are described. General features and capabilities of the test-support data system are also presented. The test program culminated in a 1500-h computer-controlled, system-functional demonstration. This included simultaneous operation of two thruster/power conditioner sets. The results of this testing phase satisfied all the program goals.

AC power source voltage regulator including outward voltage slope control

Abstract: An AC power source voltage regulator is disclosed in which the instantaneous AC power source voltage is detected by a filter and a phase shift circuit, and the output voltage of the filter is compared by a comparator with a reference voltage. A pulse generator is actuated to give the output pulse in response to the output of the comparator and of the output of a slope regulating circuit so that in response to the output pulse a thyristor inserted in a power source circuit may be triggered.

High voltage regulators

Abstract: A television scan horizontal deflection circuit of the solid state switch variety also provides for the generation of high voltage to operate the display tube A regulator circuit, connected into the deflection circuit, serves to regulate the high voltage in terms of low voltage power supply variations, such as would result from ordinary power line varitions When pincushion correction signals are applied to such a circuit the high voltage value tends to vary as a function of the pincushion currents This introduces raster distortions resulting from capacitive lag in the high voltage power supply In an improved circuit, the regulator function is established so that it senses the magnitude of the high voltage power supply input pulses thereby maintaining the high voltage constant and avoiding the above-mentioned raster distortions By incorporating a partial sensing of the deflection into the regulator, good response to changing power supply voltage is also achieved

Voltage generating circuit for a gas turbine fuel control system

Abstract: In a fuel control system for a gas turbine engine, a fuel flow limiting signal is obtained from the difference between a voltage proportional to turbine inlet temperature and a voltage produced by an ambient temperature modified speed reference circuit. In the latter circuit, a first differential comparator passes the greater of a voltage proportional to compressor speed and a first reference voltage. A second differential comparator passes to the circuit output the lowest of the output of the first differential comparator, a second reference voltage and a third reference voltage which varies with ambient air temperature.