Showing papers on "Power factor published in 1970"

State Calculation of Power Systems From Line Flow Measurements

Abstract: This paper describes a new and efficient method for computing a real-time load flow solution of a power system network. The use of line flow measurements is proposed and it is shown that this measurement scheme shows superiority in speed, accuracy and numerical behavior together with advantages in error detection and identification.

Power System Dynamic Equivalents

Abstract: This paper describes a method for determining a simplified equivalent mathematical representation of portions of a power system for transient stability analysis The method leads to equations that do not correspond directly to a system composed of normal power system components Conditions under which it is possible to obtain such an equivalent are given, and the results of applying the method to the 118-bus IEEE test system are reported

Improvement of Power System Transient Stability Using Optimal Control: Bang-Bang Control of Reactance

Abstract: The problem of restoring a power system to its initial steady state in minimum time after a transient disturbance is identified as a minimum time problem in optimal control theory. The optimal control obtained to achieve this objective, by use of Pontryagin's maximum principle, is bang-bang control of line reactance. The implementation of this scheme on a simple power system model is shown, along with numerical results.

Self-Excited Oscillations in a Transmission System Using Series Capacitors

Abstract: Self-excitation can result from using series capacitors in EHV transmission circuits if the series compensation is large and the circuit resistance small. Such a condition can be realized in a highly compensated transmission line using bundle conductors. An analytical approach to solve for the borderline conditions between stability and instability is presented. The analysis presented is suitable for the simultaneous consideration of both electromechanical (hunting) and primarily electrical (self-excitation) oscillations using lumped circuit constants, or for cases of distributed circuit parameters (long lines and/or solid-rotor generators). Numerical examples are included.

The derivation and application of design equations for ferroresonant voltage regulators and regulated rectifiers

Abstract: Design equations for the most commonly used ferroresonant regulators and regulated rectifiers are derived. Expressions relating the physical size of the components and the short circuit characteristic of the circuit to the output power, frequency, input power factor, and voltage levels are developed. Frem these expressions, design equations that optimize the design are obtained and specific component values are recommended. For regulated rectifiers, the design of the filter and the effect of the filter on the design of the basic regulator are discussed. The effect of deviating from the recommended values and the effects of nonlinearities not considered in the derivations are discussed, Design examples and data are presented.

A feedback-controlled ferroresonant voltage regulator

Abstract: A new regulated rectifier which combines a ferroresonant regulator with a simple control circuit is described herein. The voltage regulating function normally provided in a ferroresonant regulator by the saturating core is provided by the control circuit in this new regulated rectifier. The control circuit provides regulation by varying the amplitude of the alternating voltage feeding the rectifier and filter. By incorporating feedback into the control circuit, regulation of better than ±1/2 percent for line, load, frequency, and temperature changes can easily be attained. The new feedback-controlled circuit retains many desirable properties of conventional ferroresonant regulators such as half-cycle transient response, good input power factor, ideal output waveform for rectification and filtering, high efficiency, short circuit protection, and suppression of input voltage spikes. Additional features are level set, improved efficiency, lower stray magnetic fields than observed with conventional ferroresonant regulators, and, primarily, precision regulation. Data on an 800-watt regulated rectifier employing the new circuit are also presented.

Direct current control circuit

Abstract: A control circuit for controlling the effective power to a load from a power source of substantially constant direct current voltage includes a first or main solid state switching device for placing the load and the power source in series. Suitable circuitry including a commutating capacitor chargable in a direction such that its discharge will terminate conduction of the main switching device further includes resistive means serving to maintain the capacitor in constant communication with the power source. Also provided is a means for providing dynamic braking of a direct current motor load through a resistive element such that the armature terminal voltage is adjusted linearly with the speed thereof.

Nondissipative power loss suppression circuit for transistor controlled power converters

Abstract: A nondissipative power loss suppression circuit for a transistor controlled DC power converter of the type having a pair of positive and negative input terminals for connection to a source of DC voltage, a power converter inductor having primary and secondary windings, one end of the primary windings being connected to the positive input terminal, a transistor having a base connected to a transistor drive circuit for control of the transistor with turn-on and turnoff pulses, a collector conducted to the other end of the power converter inductor primary winding, and an emitter connected to the negative input terminal, and an output diode in series arrangement for providing a DC voltage output across the arrangement. The power loss suppression circuit consists of an energy absorbing circuit connected to the terminals and the power converter inductor for absorbing input voltage power during a turn-on pulse while said output diode recovers and for transferring excess absorbed power to the source when the diode recovers. Also provided is an energy storage circuit connected to the positive terminal and collector for storing power in the power converter inductor and the energy absorbing circuit during a turnoff pulse. An energy transfer circuit connected to the negative terminal and the energy storage circuit provides for the transfer of energy stored by the energy storage circuit to the source during a succeeding turn-on pulse.

A Method of Improving Power System Transient Stability Using Controllable Parameters

Abstract: Controllable parameters in a power system include generator terminal voltage, generator input power, and network admittances. These parameters can be controlled to damp mechanical rotor oscillation in the generators and thereby improve system transient stability. Explicit equations are derived for the control of these parameters to introduce damping uniformly throughout a large power system. These equations are derived on the basis of minimizing a positive definite error function. Decision functions are included which inhibit damping action when it leads to system instability. This method can be used to coordinate the application of locally based damping techniques.

Capacitive compensation of thyristor-controlled slip-energy-recovery system

Abstract: The steady-state performance of a slip-energy-recovery scheme incorporating an induction motor and a static frequency changer is described. A considerable improvement in the low-speed efficiency may be obtained at the expense of a poor power factor. Power-factor correction by the use of primary-side capacitance is found to increase slightly the 5th-harmonic component of the supply current and to double the torque/supply-current ratio. Compensation by the use of fixed secondary capacitance is found to give increased torque at low speeds, increased torque/supply-current ratio, higher efficiency at some speeds, better speed regulation, much improved step response to changes of control signal and good power-factor correction at low speeds. The closed-loop steady-state performance is that of a good stable variable-speed drive, with speed regulation of the order of within 1?3% over the entire speed range.

Generalized theory of static power frequency changers

Abstract: The thesis is concerned with static frequency changers, using solid-state switching devices, capable of directly (i.e. without an intermediate dc link) converting polyphase ac power of a given frequency to single or polyphase power of a chosen frequency. The thesis consists of two parts. The first part, comprising five chapters, is devoted to the study of ideal frequency changers operated from ac Sources having zero internal impedance. The second part, comprising two chapters, considers sources with finite internal impedances . Chapter 1 introduces the basic concepts of static frequency conversion, outlines the basic mathematical models representing static frequency changers and defines the output and input performance indicators. Chapter 2 presents a detailed investigation of that class of three-pulse frequency changers which will be studied in the thesis. A large portion of the chapter is devoted to the study of output waveform generation. The mathematical tools of the investigation, existence matrices and modulating functions, are introduced and defined. Analytical expressions for output waveforms corresponding to various practical modulating functions are derived and the related performance indicators are computed. Assuming a given desired output performance, criteria for an optimal modulating function are established. It is proved that only one system can generate an output waveform conforming to the postulated prerequisites. This system is termed the "Unrestricted" Frequency Changer. Expressions for the input current waves are also derived in this chapter and the corresponding input performance indicators are determined . The concept of a new frequency changer having the unique property of providing unity input power factor, regardless of the load, is introduced. This system is termed the "Unity Power Factor" Frequency Changer. In Chapter 3 the previous results are extended to systems having pulse numbers which are integral multiples of three. Chapter 4 is devoted to the study of output voltage control. Three basic methods are analysed and detailed quantitative data for output voltage and input current waves, and the related performance indicators, are presented in graphical form. In Chapter 5 special aspects of static frequency changing are investigated. It is shown that the input displacement factor is variable. The concept of the "Controlled Displacement Factor" Frequency Changer is introduced It is proven that the naturally commutated cycloconvertor is theoretically equivalent to a particular "Controlled Displacement Factor" Frequency Changer. Chapter 6 presents a detailed analysis of the "Unrestricted" Frequency Changer, operated from an ac source with finite internal impedance. The basic conditions are defined and an outline is given of the techniques of symmetrical components used for the analysis. The input current, input terminal voltage and output voltage waveforms are expressed in terms of the input terminal impedance and the positive, negative and zero sequence components of the output currents. The equivalent sequence impedances and the output impedance matrix are derived . The output voltage unbalance is computed under various conditions and presented in graphical form. The relationships between the amplitudes of the unwanted components in the output waveform and the resonant frequency of the input terminal circuit are also graphically presented. The results obtained are verified by computer simulations. In Chapter 7 a similar analysis of the "Unity Power Factor" Frequency Changer is carried out . The computed data are also graphically presented. Again, the results are verified by appropriate computer simulations.

A Static Power Supply for Induction Heating

Abstract: Static power supplies, incorporating solid state switching devices, are rapidly becoming commonplace in the induction heating industry. Several different system approaches have been described in the literature (see Bibliography) from both the design and application viewpoint. The present paper covers a functionally similar system, but one which incorporates circuitry different from that previously described. This approach is intended for use in the 1 to 3 KHz range. At lower frequencies, the economics of other systems are more favorable whereas at higher frequencies currently available SCR switching speeds are inadequate.

Electrical control apparatus using direction of current and power flow to gate switching devices

Abstract: Electrical control apparatus including a transformer having a winding connectable in a power circuit which includes a source of alternating potential and a load circuit. The transformer winding includes at least two tap connections which are selectively connected into the power circuit with solid-state switching devices. The solid-state switching devices are gated at a firing angle responsive to an error signal. Tap-to-tap short circuits are obviated, regardless of the type of connected load, by firing control which senses the direction of instantaneous power flow, and the direction of instantaneous current flow in the power circuit.

Power control timing circuits with power line compensation

Abstract: Line voltage compensation is provided by a power control timing circuit for gated power control devices, which utilizes a negative resistance impedance for establishing the timing capacitor charging voltage, thereby determining the conduction angle to maintain power applied to a load relatively constant, notwithstanding fluctuations in the power line voltage.

Plurality of programmable regulated power supplies share the load in a predetermined ratio with overall stability determined by the master supply

Abstract: A plurality of programmable power supplies are connected in cascade and are interconnected in such manner as to provide that they share the load in predetermined ratios and so that the overall stability is determined substantially solely by the characteristics of the master supply. Prior art combinations of power supplies have been of two general kinds. The first kind has been called ''''piggy-back'''' where an unregulated power supply is connected in series with a programmable regulated power supply. An overall feedback circuit has been used to control the voltage across the load. Such an arrangement, however, cannot provide output voltage less than the output of the unregulated power supply and voltage ratio load sharing cannot be provided. The second kind uses two programmable regulated power supplies in a master-slave combination. The master power supply is used to control the slave power supply. There is no overall feedback and hence, the accuracy and stability of the system is governed by the less stable and accurate of the two power supplies. Offset and drift, for example, may be degraded by the slave power supply.

Input Filter Design with Static Power Converters

Abstract: Most static power converters are nonlinear systems which produce undesired harmonics in the three-phase input lines of the supply power system. These harnonics cause distorted voltage waveforms and must be reduced specially in large power applications. The methods of reducing undesired hannonics with special emphasis on designing input filters to reduce the undesired harmonics are discussed. The design of the input filters in general affects the performance of the converter. These effects are discussed for a single-phase voltage controller with an input filter.

Ac-to-ac power regulation circuits having low e.m.i. and shorted load protection

Abstract: AC-to-AC power regulation circuits with power switch means in series with the line and load, the conduction period or angle of the power switch means being controlled to regulate the power output Transistor type power switch means is turned on at zero current phase and turned off at the end of the desired conduction period Capacitative line filtering is employed to minimize electromagnetic interference (emi), with marked weight reduction as compared with conventionally used inductive line filtering, rendering the circuits especially advantageous for aircraft use, such as for lamp dimmers, windshield temperature controllers, and aircraft AC power supplies in general Bi-directional transistor type power switch means in circuits of the present invention, with proper bias, are inherently current-limiting and therefore can be operated into a short circuit load without damage to the power regulation circuit Such power switch means, as contemplated by the invention, are power transistors, in contrast to conventionally used silicon controlled rectifiers (SCRs)

Display power system

Abstract: A display and power supply system in which the power supply uses a switching frequency which is higher than the highest linear deflection rate used in a cathode ray tube display device supplied by the power supply and in which the frequency of the power supply and the information repetitively displayed on the display are synchronized to eliminate interference of the power supply frequency with the display characteristics.

Method and system for controlling electric furnaces as a function of power factor

Abstract: In an electric furnace control system of the type wherein an electrode driving mechanism is operated by the electrode control signals provided by an automatic current regulator responsive to the current flowing through the electrode, there are provided a program control connected between the automatic current regulator and the electrode driving mechanism for transmitting the electrode control signals to the electrode driving mechanism, and a power factor regulator responsive to the actual power factor of the furnace for controlling the program control.

H.V.D.C. Stations Connected to Weak A.C. Systems

Abstract: The operation of a h.v.d.c. converter station connected to a three- phase power system having a low short-circuit capacity gives rise to a series of special problems which must be treated together in order to produce an economic solution for the whole transmission system. The design of the reactive power supply for such a system is given particular attention and the question of a suitable grid control method for the converters is discussed in connection with the problem as a whole. In this way the complete technical and economic framework for the economic layout of a h.v.d.c. station fed by a weak a.c. system is demonstrated.

Regulator apparatus responsive to generator output power factor and voltage

Abstract: Regulator apparatus for a synchronous machine having a field winding, and terminals connected to an electrical system. The regulator apparatus utilizes the power factor at the terminals of the synchronous machine to control the excitation of the field winding during normal circuit conditions, and the voltage at the terminals to control the excitation during system voltage disturbances.

Connectionless electrical meter for measuring voltage or power factor

Abstract: A connectionless electrical meter is described which is capable of measuring the power carried by a conductor at a voltage with respect to ground, or the power factor thereof, without the necessity for any ohmic connection between the meter and the circuit being measured. Conductor current is measured by magnetic induction with an openable transformer core which surrounds the conductor. A signal in-phase with the voltage is obtained by electrostatic induction. In certain embodiments of the invention, a unique voltage probe is used for obtaining a signal proportional to the conductor voltage. Apparatus described herein employing such voltage probe is additionally useful for measurement of voltage independently of power or power factor.

Corona cell for nitrogen and other reactions

Abstract: A concentric-electrode type of electric chemical reactor cell using high voltages of A.C. current between a central wire and an outer insulated metallic cylinder, such as in an ozone generator, is adapted for achieving higher energy gas state chemical reactions by the use of higher voltages and fields thereby producing chemically reactive ionized species which are unattainable and undesirable from the standard ozone generator. The A.C. voltage between the electrodes is provided with a D.C. bias of such amplitude as to insure periods of time when there is a greater number of ions in the cell having a charge that is of the same electric sign as the sign on the central ionizing wire for the chemical advantage of reacting that ionized species when the reacting species is more chemically reactive in its ionized form than in its electrically neutral form, and finally the capacitive reactance of the cell is made part of a resonant circuit with the secondary of the current supply transformer to insure a favorable power factor and efficient operation.

Bipolar capacitor driver

Abstract: This specification discloses a bipolar driver which will charge a capacitive load to substantially the potential supplied to the driver. The driver includes two transistors that couple the load to a source of potential. One transistor is connected in shunt with the load while the other transistor is connected in series with the load and the source of potential. The shunt-connected transistor is used to discharge the capacitive load while the serially connected transistor is used to charge the capacitive load with charge from the source of potential. To allow the capacitive load to be charged to the full potential of the source, the driver includes circuitry which decouples the base of the serially connected transistor from the source of potential and drives the transistor with charge accumulated in the base-to-emitter junction of the transistor so that the serially connected transistor will not be turned off until the potential across the capacitive load reaches the potential of the driving source.

Automatic power transfer switch

Abstract: A static switch is operated upon sensing a loss of a primary power supply for providing a rapid temporary connection of a secondary power supply to a load. Slower acting power contactors are also energized and their operation provides a permanent connection of the secondary power supply to the load and also provides means for disconnecting the path of secondary power through the static switch.

Mos integrated circuit driver system

Abstract: An integrated circuit driver system utilizing Metal-OxideSilicon Field-Effect Transistors (MOS FET''s) is disclosed for operation in a two-phase mode for driving a substantially capacitive load. A preferred embodiment of the invention makes use of an alternating current (ac) voltage having a peak-to-peak magnitude somewhat greater than the direct current (dc) supply potential. An auxilliary dc power supply is implemented for converting the ac voltage to an operating potential for inverters which in turn provide the phase inverted signals required by a pair of drivers. The latter generate the alternate phases of the output voltage presented to the load. Additionally, the system exploits the MOS threshold voltage dropping properties to realize a threshold shift of suitable magnitude to insure the required duty cycle of the driver output pulse waveforms.

A wide-band wattmeter for the measurement and analysis of power dissipation in semiconductor switching devices

Abstract: A technique is presented for accurately measuring and displaying the magnitude and time function of the exchange and absorption of electrical energy in linear and nonlinear circuit elements such as semiconductor power switches. A novel electronic wattmeter with a wide-band (dc to 10 MHz) linear multiplier is used to observe the instantaneous product of the time-varying voltage and current in an arbitrary load. Experimental data show that the peaks of power dissipation during the turn-on and turn-off phases of a switching power transistor are much greater than the power dissipated during the time intervals of settled current flow. Furthermore, it is verified experimentally that the average power dissipation increases linearly with the transistor pulse-repetition frequency beyond a static (dc) value. The absence of such a frequency-dependent component of power dissipation in switches of resonant-current circuits is also confirmed.

Voltage doubler starting circuit for discharge lamp

Abstract: A voltage doubler starting circuit converting the AC voltage impressed on the lamp to a DC voltage of twice the peak AC amplitude which is fed back to the lamp terminals. The circuit includes two diodes and two capacitors arranged in a voltage doubling configuration along with a bleeder resistor, and may, if desired, be built into the lamp base or into the lamp itself in the case of a double envelope lamp. The circuit is used with a ballast of the magnetic type having a series secondary power factor correcting capacitor.

Apparatus for boosting a direct current voltage

Abstract: A plurality of rectifiers are connected in series from the positive terminal of a DC power source to one plate of an output capacitor which supplies a load. The opposite plate of the output capacitor is connected to the negative terminal of the power source. Capacitors are connected to the output of each rectifier and to a switch which selectively connects the capacitors to either the positive or negative side of the power source. The switch operates to accomplish successive switching operations, and when the capacitors connected to the outputs of the source are connected to the positive power source terminal, the remaining rectifier output capacitors are connected to the power source negative terminal. The switch operates to successively change these reverse relationships.