Showing papers on "Automatic frequency control published in 1978"

Multilevel load-frequency control of interconnected power systems

Abstract: This paper presents a two-level optimal control for the load-frequency control of interconnected power systems using modern optimal control and multilevel system techniques. The controller minimises the deviations in frequency and scheduled tie-line power resulting from sudden disturbances. The interconnected power system considered in the paper is decomposed into subsystems each of which has a first level local controller. The local controller controls each subsystem according to the interaction variables provided by a second level controller (co-ordinator). The co-ordinator improves the interaction variables to satisfy interaction feasibility by means of an iteration technique. This paper differs from previous works in that the proposed controller is fast and simple and usually only a few iterations are required. Using the proposed controller the instability problem of subsystems is eliminated. Moreover, the proposed controller guarantees practically zero steady-state error in both frequency and tie-line power at the final time.

Limited position, non-volatile memory tuning system

Abstract: A limited-position television tuning system includes a read-only memory (ROM) dedicated to VHF channel coarse tuning information UHF coarse tuning information and VHF/UHF fine tuning information are contained in an electrically alterable ROM (EAROM) Equalization information for equalizing both fine tuning information and automatic frequency control (AFC) information for VHF is contained in another ROM The memories are addressed by a viewer-operated switch Information is read out as pulse-width modulated (PWM) signals by counter-interrogated comparators A hybrid scaling circuit includes a pair of operational amplifiers (Op Amps) and three transistors, with each PWM signal being applied to a separate transistor The fine tune transistor, along with the receiver AFC signal, drives the first Op Amp which, in turn, supplies operating potential to the equalization transistor, the output of which is coupled to the input of the second Op Amp The output of the coarse tuning information transistor also drives an input of the second Op Amp, the output of which is used to develop the tuning voltage

Single-mode collapse in 6328-A He--Ne lasers

Abstract: Internal-mirror 6328-A He-Ne lasers have an intramode frequency difference when placed in a transverse magnetic field. When the magnetic field strength is increased until the Zeeman frequency shift approaches the mode spacing, mode coupling is nduced. In some multimode lasers, this mode coupling results in a collapse into single-mode operation with no loss of over-all laser power in the output. The intramode frequency difference can be exploited to produce a simple frequency stabilization system whose frequency variation is less than 1 part in 10(10). Plots of beat frequency variation and single-mode tuning range are included.

Frequency Offset Due to Spectral Impurities in Cesium-Beam Frequency Standards

Abstract: Theoretical expressions for the frequency offset due to spectral impurities in beam-tube frequency standards are given for the case of small sideband to carrier power ratios. They are valid for any value of the separation between the extraneous sideband and the carrier which interrogates the atomic transition, as well as for any value of the power in the carrier. Useful approximations are given in special cases of interest. The effects of the velocity distribution of the detected atoms and of the frequency modulation technique (sine or square wave) are considered.

Circuit arrangement for the automatic frequency control of an ultrasonic transducer

Abstract: Circuit arrangement for inducing oscillations in an ultrasonic transducer approximating its natural resonance frequency, and comprising an oscillator for generation of an excitation AC voltage. A pulse gate circuit is connected to supply pulse wise application of the AC voltage to the transducer. The oscillator frequency is controlled by an auxiliary pulse generator connected to the transducer in parallel with the oscillator. A gate circuit and a phase discriminator are employed to produce favorable excitation for the particular oscillation mode of the transducer. The transducer is made preferably from a piezo electric ceramic. The circuit includes means capable of automatically finding the resonance frequency of the transducer.

A Nonlinear Load-Frequency Control Design

Abstract: A load frequency control for a two-area interconnected system is designed taking into account the nonlinearity and stochasticy of the load and using an optimal linear strategy aided by stability analysis. An observer is proposed for its implementation. A coordinating control for the two area system based on acceleration feedback is suggested.

Acceleration sensitivity compensation in high performance crystal oscillators

Abstract: Two approaches to achieving reduced acceleration sensitivity of crystal oscillators are discussed. The first involves electronic compensation within the frequency control loop. The second utilizes two resonators of comparable acceleration sensitivity to compensate each other. Problems encountered in matching and tuning the resonators are discussed, as well as orientation symmetry of the frequency deviation patterns. Results on frequency stability which reflect an improved static sensitivity are presented.

Preset tuning apparatus using floating gate type field effect device

Abstract: A preset tuning apparatus adapted for selecting a preset channel among a plurality of channels, comprising a tuner including a tuning circuit including a voltage controlled variable capacitance diode, a manually adjustable tuning voltage generator for providing a tuning voltage to the voltage controlled variable capacitance diode, a non-volatile analog storage including a plurality of floating gate type field effect memory devices, a band selection switch, a preset selection switch, a preset memory switch, addressing circuits coupled to the band selection and preset selection switches for addressing a corresponding one of the plurality of memory devices, an erase/write/read voltage generator, and a mode control coupled to the erase/write/read voltage generator and responsive to the band selection, preset selection and preset memory switches for alternately and repetitively writing and reading the analog value in the addressed memory device until the data corresponding to the tuning voltage of the tuning voltage generator is written in the memory device in the write and read modes and for reading thereafter the data in the memory device for providing the same as a tuning voltage to the voltage controlled variable capacitance diode in the preset mode, whereby the preset selection is achieved based on the data as written in and read out from the addressed memory device. Preferably, the data concerning the tuning voltage is divided into a rough tuning voltage and a fine tuning voltage, which are separately stored in separate memory devices. Preferably, the read tuning voltage is once stored in a buffer memory and the tuning voltage in the buffer memory is corrected responsive to an automatic frequency control signal.

Fast digital frequency synthesiser

Abstract: A new phase-locked-loop type frequency synthesiser is described and tested which employs a digital-analogue convertor to give very rapid coarse frequency switching and optimum lock in speed anywhere in a wide frequency range. The experimental results are in good agreement with theory.

Frequency control of asynchronous generator - has turbine driven asynchronous machine, rotor phase current is controlled, so that power passes via converter-network path

Abstract: The arrangement is designed to convert kinetic energy into electrical energy. The asynchronous machine, whose stator is connected to a constant frequency network, is driven by a turbine. The machine rotor is connected through a static convertor to the same network as the stator. Convertor frequency is so changed, that the sum of the frequency impressed on the rotor and the frequency proportional to the rotor variable speed is always equal to the network frequency. Rotor current phase is so controlled, that when its speed is above the synchronous speed, rotor power is delivered through the convertor to the network. when the speed drops below, the network (1) supplies the rotor power through the convertor. The reactive load or the rotor fed asynchronous machine (3, 4) can be adjusted using a regulator, which varies the amount of rotor current, such that the reactive laod i.e. the voltage or the asynchronous machine, corresp. to the network (1) requirement, is regulated independently from the 'effective' output.

Automatic gain control circuit and system for using same

Abstract: An automatic gain control circuit and system for using same provides linear attenuation response to input data signals of multiplexed frequencies of high and low signal amplitudes to eliminate frequency intermodulation products generated by the data signals of high amplitude from interfering with the reception of the proper data signals by a tuned receiver communicating with the automatic gain control circuit.

The Optimal Decentralized Control of a Large Power System: Load and Frequency Control

Abstract: The load and frequency control of a multi-area intemn- nected power system is studied. In this problem, the system is assrrmed to be subject to unknom constant dktmhnces, and it is desired to obtain, if possible, robust decentralized controllers so that the frequency and tie- line/net-area power flow of the power system are regulated. 'Ihe problem is solved by using some strudmal results recently obtained in decentra- lid control, in conjnndion with a parameter optimization method which minimizes the dominant eigenvalue of the closed-lo~p system A dass of minimum order robust decentralized controllers wbi& solves this general multi-area load and frequency control problem is obtained. Application of these resalts is then made to solve the load and frequency control problem for a power system comisting of nine syncbrowus machines (desaibed by a 119th-order system). It is shown that the load and frequency controller obtained in this c~se is not likely to be significantly improved by usiog more complex controllers; in particular, it is shown that the conventional controller, used in regulating the net-area power flow of a system, is not likely to be signifimnliy improved upon by using more complex con- trollerS

Multiband radio receiver with electronic preset tuning system

Abstract: A multiband radio receiver having an electronic preset tuning system is provided with a switch which is ganged with a preset switch in the electronic preset tuning system, so that an automatic frequency control is interrupted from a local oscillator in preset operation. During preset operation, no automatic frequency control is provided, as a result of which fine-tuning can be accomplished to memorize a digital signal representative of a completely tuned frequency in a read-write memory.

Color television receiver AFPC circuit

Abstract: A color television receiver includes an automatic phase control circuit (which will be hereinafter referred to simply as an APC circuit) with a voltage controlled oscillator for controlling the phase of a reference carrier supplied to a color demodulator so that the phase and frequency of the reference carrier are locked to those of a color burst signal. In addition to the APC circuit, an auxiliary frequency control loop drives the frequency of the voltage controlled oscillator until its frequency falls within the lock-in range of the APC loop. The auxiliary frequency control loop includes a counter circuit for counting cycles of the output signal of the voltage controlled oscillator during a reference time interval and a decoding circuit for decoding the output of the counter circuit to produce an auxiliary control signal for frequency control of the voltage controlled oscillator.

Load frequency control using a governor and voltage controls vis a new approach

Abstract: This letter reports the decentralized load frequency control through a governor and voltage controls by a new approach based on Siljak's theory [1]. The design of the optimal feedback gains in each area can be made using the state variables belonging to the corresponding decoupled area.

Frequency discriminator producing at least one of two pulse sequences representing in average the result of frequency discrimination

Abstract: In a frequency discriminator for a first and a second input signal of a first and a second frequency, a phase detector produces first and second rectangular pulse sequences. When the first input signal leads the second by 0° through 180°, the first pulse sequence takes a predetermined peak value with an instantaneous frequency corresponding to the phase difference while the second one continuously has the peak value. When the first input signal lags behind the second by 0° through 180°, the second pulse sequence takes the peak value with the instantaneous frequency while the first one continuously has the peak value. A low-pass filter rejects components of the first pulse sequence which are higher than the first and second frequencies. A high-pass filter has a prescribed cutoff frequency for rejecting lower-frequency components of the low-pass output to produce an output pulse sequence representing in average the difference between the first and second frequencies when the first frequency is higher than the second. Alternatively or additionally, a similar set of a low-pass and a high-pass filter produces a like output pulse sequence when the first frequency is lower than the second. At least one of the output pulse sequences is used as a discriminator output signal either per se or after conversion to a substantially d.c. signal. The frequency discrimination characteristics depend on the prescribed cutoff frequency. In an automatic frequency control (AFC) loop, both d.c. signals may be supplied to a voltage controlled oscillator through a differential circuit.

Tuning apparatus for selecting preset broadcast frequencies

Abstract: In a tuning apparatus for a broadcast receiver having a dial scale calibrated to represent broadcast frequencies over a predetermined frequency band, and along which an indicator is movable for indicating the broadcast frequency to which the tuning apparatus is actually tuned; a sensor is movable with the indicator, at least one presetting element is movable along the dial scale for indicating a respective preset broadcast frequency and each such element coacts with the sensor whenever the broadcast frequency to which the tuning apparatus is tuned corresponds to the respective preset broadcast frequency, a control signal generator produces a control signal in response to the coaction of the sensor with each of the presetting elements, and a control circuit is responsive to the control signal to control a function of the tuning apparatus, such as, a muting and/or automatic frequency control operation of the tuning Johnson 310 239

Suboptimal control for load-frequency control system using an area-decomposition method

Abstract: The feedback control theory has been applied successfully to the Load-Frequency Control (LFC) in the power system. At present, however, because of the large-scale power system, peculiar power flow phenomena due to flow variation in the tie line have been discovered. The optimum control theory has been developed to solve these problems with the assumption that the information for all systems is always available. Various techniques such as Kalman filters, observers, and the hierarchy control method have been studied. These techniques, however, require complicated algorithms and long computation time. The area-decomposition method is applied to the multiarea LFC system and the optimum control is performed in each subsystem. At the area decomposition, the tie-line variables generates the subordinate vector and the decomposed subsystems become unstable. For these subsystems, a peculiar matrix is transformed to a regular matrix by the power flow calculation. These unstable subsystems are stabilized and the suboptimal control is applied to the entire system. Further, the conventional tie-line power control method (TBC) is also adopted. The present method is applied to a 4-area cascaded system and the cost rate. The computation time for transient response, etc., is compared with those in the optimal and suboptimal control methods.more » Further, the present method is applied to the 4-area tie-line system containing a loop to confirm the effectiveness of the present method.« less

Television picture receiver

Abstract: PURPOSE:To reduce the generation of a pseudo carrier signal within the video IF circuit system and not to increase this signal to much so that a mulfunction is caused in the automatic fine tuning circuit. Thus, a malfunction caused by an aural carrier signal is prevented from occurring in the automatic fine tuning circuit.

Generator excitation controller

Abstract: PURPOSE:To remove the malfunction at transient time and enable generator excitation control through which a voltage/frequency control function is provided by adding the output of the frequency detector section which increases in proportion to the reduction of frequency when the frequency does not reach a specified value, to that of the voltage detector section.

Frequency Synthesis Tuning Systems With Automatic Offset Tuning

Abstract: This paper describes a new closed-loop tuning system utilizing custom large scale integrated circuits to control the selection of the 82 U.S. television channels. The system is designed to minimize hardware but yet support multiple user features. No frequency adjustment or prealignment is needed for operation. A crystal frequency reference is continually used on each channel, but full compatibility with automatic fine tuning is maintained to cope with transmitters operating off FCC assigned frequencies. Channel selection is easily remoted and is either by digital keyboard or by up-down scan of a user selected list of channels stored in non-volatile digital memory. Channel number display is either on screen with time of day or off screen using a digital display.

Phase locked loop circuit - has constant voltage added to error voltage and switchable capacitor connected to control input of VCO

Abstract: The phase locked loop consists of a VCO (1) controlled by the output of a phase comparator (2). An adder (4) adds a constant DC voltage to the phase comparator's output error voltage and applies the sum to the VCO's control input via a resistor (31). The frequency control input of the VCO is also connected via a second resistor (32) to an earthed capacitor (33). The capacitor is shunted by a controlled discharging switch (37).

Carrier frequency sound transmission system

Abstract: A carrier frequency sound transmission system which utilizes sound channels which correspond approximately to the bandwidth of three separate telephone channels and wherein a pilot tone is added to each of the sound channels and four sound channels are transmitted on a suitable carrier to a receiver where the pilot tone is utilized as an automatic frequency control signal to control a local injection oscillator for demodulating the four incoming sound channels.

Automatic frequency control circuit

Abstract: PURPOSE:To simply obtain the output of oscillating frequency corresponding to a given time point, by controlling the oscillating frequency thru the comparison of the hold signal in the hold circuit and the oscillating output of the oscillating circuit.

Electronic multiple function watch

Abstract: PURPOSE:To simplify the constitution of an electronic multiple function watch by providing an information processing control high speed timing pulse generator for processing information at high speed to thereby process the information in series. CONSTITUTION:A high frequency oscillator 15 for generating higher frequency control pulse than that from a standard time pulse generator 1 is started through a starting circuit 3 by the signal corresponding to a key operation for outputting from a key input circuit 2 connected to the generator 1 upon operation of a key, and program is read from a ROM5 responsive to the key operation through a program counter 4. Information is shortly processed via a RAM6, an arithmetic circuit 7, and discriminator 8 or the like by the high speed pluse from the oscilllator 15 with the result that the time is displayed on a display unit 13. This high speed short time processor can serially process the information with one arithmetic circuit and memory commonly used to thus simplify the multiple functions imparted with stop watch, alarm functions.

Frequency control circuit

Abstract: PURPOSE:At a variable frequency oscillator, the lock state of an AFC circuit is discriminated by pulses obtained according to existence of a pulse interval, thereby stopping the phase-comparing operation of the AFC circuit at the time of the variation of the interval of regenerated horizontal synchronous signals.

Multiplex communication equipment with common automatic frequency control function

Abstract: PURPOSE:At a ground station for satellite communication, two frequency synthesizers are given a specific frequency relation in order to improve the function of a receiving common circuit by a common AFC, thereby acieving the flexibility of an equipment and the reduction of its manufacturing cost.

Controlling method of capacity of air conditioner

Abstract: PURPOSE: To improve the comfortability in a room with an air conditioner by controlling to increase or decrease the output frequency of a frequency converter in the magnitude of varied frequency to meet the temperature deviation value to thereby stably control the temperature in the vicinity of the set temperature. CONSTITUTION: A room temperature signal from a room temperature sensor 1 and a set signal from a room temperature setting potentiometer 2 are fed to a temperature deviation detector 3 to thus calculate the temperature deviation ΔT, a signal of the temperature deviation ΔT is fed to a frequency controller 4 at the time receiving the signal intermittently from a time setting potentiometer 6, a frequency control instruction is fed to a frequency converter 5 to thus control the output frequency f to a motor 7 for a compressor. When the temperature deviation ΔT becomes larger than the set value, the output frequency f is increased or decreased in the control magnitude Δf corresponding to the temperature deviation ΔT. COPYRIGHT: (C)1980,JPO&Japio