Abstract: An electric power flow controller for controlling an electric power flow of a power system includes a semiconductor switch for controlling a series reactance of the power system. The electric power flow controller includes a first winding having at least one Y-connection, a second winding mating with the first winding, an electric power flow compensator connected in series to the Y-connection of the first winding and for compensating a transmission state of the electric power system. The electric power flow compensator provides a compensating capacitor inserted onto an electric power line. The compensation of the capacitor is controlled by the semiconductor switch. The semiconductor switch keeps an application of a voltage that is equal to or lower than a voltage to ground of the electric power line.

Abstract: Disclosed is an active power factor correction integrated circuit for a boost converter, comprising a bias voltage generator coupled to an external power source through a first pin, for generating internal bias voltages used for the integrated circuit; a zero crossing detector coupled magnetically to the inductor through a second pin, for detecting a time at which a voltage across the inductor is zero to provide a zero crossing detection signal; an oscillator reset by the zero crossing detection signal for generating a pulse signal; a flip-flop for generating a first control signal in response to the zero crossing detection signal or the pulse signal; a switching element responsive to the first control signal for enabling a boosted voltage to be provided to the load; an over-current detector for generating an over-current signal when a current flowing through the switching element is over a predetermined value; and a voltage variation detector for detecting variation of a load voltage to generate a variation

Abstract: A method and apparatus for controlling power transferred and regulating voltage in a multi-phase transmission line includes generating a first plurality of voltages, a second plurality of voltages displaced in phase from the first plurality of voltages, and a third plurality of voltages displaced in phase from the first and second plurality of voltages. The first, second and third plurality of voltages are selectively connected in series in each line of the multi-phase transmission line.

Abstract: Voltage flicker is a power quality problem in power distribution circuits which is caused by the operation of fluctuating loads such as AC and DC electric arc furnaces, spot welders, starting of large ac motors, and the like. Converters based on Voltage Source technology (VSC) connected in shunt close to the fluctuating load are found to have the capability of reducing the voltage flicker level. Flicker control systems responsive to the active and reactive power components are used to exploit the capabilities of VSC in accordance with the invention. The flicker control systems reduce the voltage flicker observed at the point of common coupling by adapting, e.g., H-infinity, Linear Quadratic Gaussian, Minimum Variance Control, and self-tuning design methods for flicker control in power systems having fixed or self-tuning flicker controller parameters.

Abstract: In operation, DC arc furnaces generate undesired reactive load fluctuations which are compensated for by a power controller without special compensation reactance. In order to permit a melting operation of the arc furnace in weak AC systems the DC furnace is operated with at least two melting electrodes. A current controller is connected to each cathode via rectifiers. Each cathode is controlled with respect to its spacing from a melt by an electrode adjusting device and an electrode controller. Only one current controller one electrode controller are operationally connected, on an input side, to a power factor controller. Power factor control is thus performed with only one electrode assembly.

Abstract: A load management and control apparatus comprising a control unit in which system voltage and a power flow state are measured to make an arithmetic decision by using the resultant variations in voltage and reactive power so as to estimate system reactance, and the estimated system reactance is used to carry out control operation while establishing unique relationship between tap changing operation of the transformer and connection or disconnection of the reactive power supply unit in the receiving side sub-station so as to set voltage and power factor of the receiving side of power system in desired ranges, whereby in a receiving end side substation, it is possible to prevent frequent tap changing operation of the transformer, and adjust system voltage not only to reduce the voltage deviation but also to provide integrated and reasonable management of the reactive power.

Abstract: A method and apparatus for receiving, monitoring and characterizing network power information in real time through the use of a specialized display system. A processor receives three phase current and voltage information from a network power relay, converts and scales that data into a two-dimensional vector having coordinates that are represented by, and displayed as, a single pixel on a display screen. The repeated monitoring provides a Feature Map (FM) of the network system that can be easily read and understood by operating personnel.

Abstract: A microprocessor (42) is coupled to sense the current and voltage in an AC line (11) at a high sampling rate and to determine the power factor. In one embodiment the primary (83) of a transformer (84) is coupled across the power lines, and at least two capacitors (86, 88), forming separate switching paths, are coupled to the secondary (85) of the transformer. High speed switching circuitry under the control of the microprocessor alternately charges and discharges the capacitors (86, 88) at varying frequencies, to alternately store energy from the power lines (11) when the variable load (32) is returning energy to the power lines, and to supply the stored energy back to the power lines when the variable load (32) is absorbing energy from the power lines (11). This corrects the power factor since the frequency of the high speed switching circuitry is varied with the varying reactance of the load.

Abstract: In a power system wherein a plurality of power plants, load systems and power transmission components are connected to each other for increasing the power transmission capacity of the power system, the power system is stabilized and power swings are suppressed, by controlling a semiconductor switch used in a power system stabilizing apparatus which is provided at the power system in an applying manner adequately corresponding to its operation characteristics and function, in accordance with a stabilizing command signal generated by using state values (for example, voltage, current, power, frequency, phase angle) of the power system, detected by detecting circuits provided in the power system.

Abstract: An active filter for compensation of polluting harmonics on an electricity distribution network comprising a source of energy (19, 20), a bridge converter (21) connected between the energy source and the network, control means which control the bridge converter in order to compensate for the polluting harmonics, characterized in that the state of the energy source (19, 20) is independant of the control of the bridge converter carried out by the control means (22) and in that the control means (22) control the injection of the harmonic components independantly of the state of the energy source.

Abstract: A static reactive power compensating equipment includes a circuit for preventing harmonic currents generated by adjusting lag compensation current from phase control from flowing out of the equipment. A first reactor and a controller are connected to a switching circuit. A second reactor is connected between an output terminal and a connection node. The first reactor is also connected to the connection node such that the first and second reactors are series connected. A resonant circuit including a third reactor connected in series with a capacitor is connected to the connection node such that the resonant circuit is series connected with the second reactor and parallel connected to the first reactor. The resonant circuit is constructed to resonate at a predetermined frequency which substantially absorbs harmonic currents flowing from the static reactive power compensating equipment.

Abstract: The invention relates to a method and a device for reducing imbalances (.DELTA.V.sub.12, .DELTA.V.sub.23, .DELTA.V.sub.31) in a three-phase network (42) by means of a static compensator. According to the invention, a correction signal (.DELTA.B.sub.12, .DELTA.B.sub.23, .DELTA.B.sub.31) is in each case superimposed on a mean susceptance value (B.sub.SVC), which is produced, of the static compensator, which correction signals (.DELTA.B.sub.12, .DELTA.B.sub.23, .DELTA.B.sub.31) are in each case proportional to an imbalance (.DELTA.V.sub.12, .DELTA.V.sub.23, .DELTA.V.sub.31), which imbalances are determined from measured line to earth voltages (V.sub.01, V.sub.02, V.sub.03) by comparisons, in pairs, of the determined line to line voltages (V.sub.12, V.sub.23, V.sub.31). Imbalances (.DELTA.V.sub.12, .DELTA.V.sub.23, .DELTA.V.sub.31) in the three-phase network (42) can thus be reduced in a simple manner.

Abstract: A power capacitor controller that adaptively and/or automatically determines a variety of operational parameters, including adaptively and automatically establishing the line phase angle correction value; adaptively and automatically establishing the appropriate electrical levels determining connection and disconnection of the capacitor bank relative to the line; adaptively and automatically establishing appropriate guard voltage levels determining connection and disconnection of the capacitor bank relative to the line; automatically determining when the capacitor bank is inoperative; automatically determining when a reverse power line condition and a reverse current line condition exists; automatically determining when a capacitor bank switching operation is a result of multiple capacitor banks on the line, and automatically determining when the operational set points of the controller are reversed.

Abstract: A system and method for providing harmonic currents to a harmonic generating load connected to a multiphase alternating current power system includes a zig-zag transformer and a current generator. The zig-zag transformer is electrically connected to the multiphase alternating current power system. The current generator is electrically connected between a neutral of the zig-zag transformer and a neutral return path of the multiphase alternating current power system. The current generator injects a harmonic current into the neutral of the zig-zag transformer which in turn, reduces the harmonic currents provided to the load from the multiphase alternating current power system.

Abstract: A frequency domain self-synchronization controller for solid state switches is disclosed. The controller analyzes a measured power signal in the frequency domain to identify a frequency domain firing angle and then converts the frequency domain firing angle to a time-domain firing signal command. The time-domain firing signal command is used to fire selected solid state switches of, for example, a static VAR compensator, precisely when the voltage across the selected solid state switches is at or near zero volts, so that the solid state switches are not damaged. The controller also calculates the line voltage level of the power system and in response to the voltage level it automatically executes either a high voltage coarse line conditioning strategy, a high voltage fine line conditioning strategy, a low voltage coarse line conditioning strategy, or a low voltage fine line conditioning strategy.

Abstract: During operation, DC arc furnaces (8) produce undesired reactive load fluctuations which are compensated by means of a power factor compensator (31). An AC power controller (28) of the power factor compensator (31) is controlled as a function of a stabilization striking angle signal (.alpha..sub.st) which is controlled in accordance with the reactive power of filter branches (4, 4') by a function generator (26) as a function of a desired reactive power signal (Q.sub.des8), of a reactive power actual value signal (Q.sub.8) of the arc furnace (8) and of a filter reactive power signal (Q.sub.F). The desired reactive power signal (Q.sub.des8) is formed by means of a phase-angle controller (35) as a function of a total current intensity (i.sub.33) which, in addition to the current actual value (i.sub.act) of the arc furnace (8) also comprises the current of the filter branches (4, 4') and that of any auxiliaries.

Abstract: An overload management system is provided, including a method and an apparatus, for controlling the operation of electrical equipment in a short-term overload region above the equipment's continuous capability operation curve, without suffering significant loss of equipment life. This overload management system is particularly beneficial for use with equipment having load management capability, such as a modular thyristor controlled series capacitor (TCSC) system using phase controlled firing based on monitored capacitor voltage and line current. For vernier operation, the system predicts an upcoming firing angle for switching a switching device to govern the current received by the electrical device, such as to bypass line current around a series capacitor of the TCSC system. The overload management system may serve as one of several higher-level controllers providing input to a vernier controller for accommodating competing objectives of various system demands.

Abstract: A power factor correction circuit in which an inductor current is detected separately as a charging current indication signal and a discharging current indication signal by using a current sense resistor and a current sense circuit. A scaled-down output DC voltage is compared with a predetermined reference DC voltage by using an error amplifier which serves to produce an output voltage error signal. The output voltage error signal is then multiplied with a divided-down rectified input line voltage through the use of the multiplier to generate a sinusoidal reference signal. The sinusoidal reference signal is used by peak and valley comparators which also receive the charging and the discharging current indication signals. The outputs from the peak and the valley comparators are used to control a FET transistor which controls the input line current. As a result, the power factor correction circuit is capable of effectively eliminating a dead time and thereby achieving a near unity power factor.

Abstract: The invention is a static VAR compensator (SVC) which provides optimized power factor correction in the presence of resonant line conditions and large amplitude harmonics. A gate drive signal is applied to the solid state devices of the SVC during only a minor fraction of the fundamental cycle to prevent damage to the solid state devices and the capacitors of the SVC, otherwise caused by resonant line conditions or large amplitude harmonics. This relatively short gate drive signal, in the presence of large amplitude harmonics, will force the solid state electronic components to turn-off prematurely. As a result, the capacitors of the SVC provide incomplete reactive power compensation. Feedback from a capacitor polarity circuit is used to determine switched capacitor status at a specific instant in each cycle. A VAR correction controller, responsive to the feedback, executes a control scheme to account for incomplete reactive power compensation.

Abstract: This invention provides various methods and techniques for adaptive control of pole-top capacitors to compensate for inductive customer loads along distribution lines together with control of Var flow into supply lines to a distribution substation by a load tapchanging transformer control using measures of said Var flow as a voltage control bias.

Abstract: A method and apparatus is described for generating a synchronizing signal for a firing-circuit subassembly to trigger a power converter valve of a controlled series compensator. According to the invention, a sinusoidal substitute variable is provided, which can be either a measured line current or the sum of a capacitor current and a valve current, such that the zero crossings of said substitute variable do not vary. This substitute variable is modified in terms of its phase position so that a synchronizing signal that corresponds to the phase position of the capacitor voltage of the series capacitor of the controlled series compensator is made available to the firing-circuit subassembly. The result, even in the bypassed state, is a sinusoidal synchronizing signal whose zero crossings do not vary, so that operating stability problems no longer occur in the transient state during operation close to resonance.

Abstract: A DC power-supply unit convening AC into DC power is provided to, when AC voltage and/or AC current of an AC power supply passes through a zero point, close a switch after a preset first delay time from a passing through time, and open the switch after a preset second delay time from a passing through time. The unit includes a rectifier switch for convening AC power output from the AC power supply into DC power, an inductive element connected to the rectifying element, a switching element connected to the inductive element, and the rectifying element, a smoothing unit connected in parallel with the switching element, and a switch control unit for controlling the switch according to the predetermined delay times.

Abstract: A microprocessor is coupled to sense the current and voltage in a power phase at a high sampling rate such as two hundred fifty-five (255) times per cycle, and to determine the power factor. The primary of a transformer is coupled across the power lines, and at least two capacitors, forming separate switching paths, are coupled to the secondary of the transformer. High speed switching circuitry under the control of the microprocessor alternately charges and discharges the capacitors, at varying frequencies, to alternately store energy from the power lines when the variable load is returning energy to the power lines, and to supply the stored energy back to the power lines when the variable load is absorbing energy from the power lines. This corrects the power factor since the frequency of the high speed switching circuitry is varied with the varying reactance of the load.

Abstract: In one form of the invention, a method for improving power factor in a multiple phase power distribution system coupled to a load is disclosed, comprising the steps of (a) sensing an actual voltage of each of the multiple phases, (b) sensing an actual current being sourced by each of the multiple phases, (c) calculating an ideal current value for each of the multiple phases such that each the ideal current is in phase with a respective one of the actual voltages, (d) coupling at least one energy storage device for sinking current from at least one of the multiple phases wherein the actual current is less than the ideal current and (e) coupling the energy storage device for sourcing current to at least one of the multiple phases wherein the actual current is greater than the ideal current. Other systems, devices and methods are disclosed.

Abstract: A modular thyristor controlled series capacitor (TCSC) system, including a method and apparatus, uses phase controlled firing based on monitored capacitor voltage and line current. For vernier operation, the TCSC system predicts an upcoming firing angle for switching a thyristor controlled commutating circuit to bypass line current around a series capacitor. Each bypass current pulse changes the capacitor voltage proportionally to the integrated value of the current pulse. The TCSC system promptly responds to an offset command from a higher-level controller to control bypass thyristor duty to minimize thyristor damage, and to prevent capacitor voltage drift during line current disturbances. In a multi-module TCSC system, the higher level controller accommodates competing objectives of various system demands, including minimizing losses in scheduling control, stabilizing transients, damping subsynchronous resonance (SSR) oscillations, damping direct current (DC) offset, and damping power-swings.

Abstract: Controlling a customer voltage and VAR flow in a power transmission and distribution system includes measuring first voltages in a power line directed to a first location related to customers. Both the customer voltage and the VAR flow for the network is determined in relation to the number of capacitors associated with the first location which are switched in or out of the network. The measured voltages are communicated to a voltage control. Voltage deviations of the measured first voltage are determined relative to a predetermined voltage range intended to be present at the first locations. Switching the capacitor means into or out of the network is determined by the voltage control in accordance with a voltage rise table. A VAR flow controller is responsive to the voltage at the first locations, the effect of the VAR generation by the capacitors and the change of VAR generation by the capacitor. A decrease in voltage at the customers saves energy use.

Abstract: A snubber network for a power conversion circuit operated in discontinuous conduction mode includes a snubber capacitor, an isolation diode and an active reset circuit. The snubber capacitor is connected to the output of the isolation diode, both of which are connected across a main switch of the power conversion circuit. The active reset circuit, connected between the input and output of the isolation diode as well as the input and output of a boost diode, is responsive to a reset signal for active resetting of the snubber capacitor within the normal boost cycle of the power conversion circuit. Upon receipt of the reset signal, energy held by the snubber capacitor is recovered by the reset circuit and subsequently transferred to the output of the power conversion circuit with turn-off of the main switch of the power conversion circuit. This occurs contemporaneous with the power conversion circuit's delivery of converted power to its output.

Abstract: A static VAR compensator (11) is connected across a power transmission line (10) and includes a capacitor (12) connected to transmission line (10). The static VAR compensator (11) includes a capacitor (12) connected to the AC transmission line (10) and thyristor switches (18, 22) for controllably switching the capacitor (12) across the transmission line (10). The thyristors (18, 22) are fired based on signals generated by control circuitry (26, 28, 30). A substantially constant or DC voltage exists across the capacitor (12) after the thyristor switches have been turned-off. Discharge control circuitry (30) generates firing pulses to activate the thyristor switches (18, 22) in order to discharge the capacitor (12) and reduce the voltage across the capacitor (12) to zero. In one embodiment, the capacitor (12) is discharged gradually using a series of discharge pulses.

Abstract: A power transfer method and apparatus for efficient transfer of power are disclosed. Input power is converted in an essentially lossless manner to an intermediate form having a voltage or current in excess of that desired at the load. The intermediate power form is split into first and second parts, where the first part of the intermediate power form approximately matches an output power form desired at an output of the power transfer apparatus and the second part represents an excess power form. The first part of the intermediate power form is transferred to the output of the power transfer apparatus and the excess part is stored. Part or all of the stored excess energy is recycled in an essentially lossless manner, converted into a form that approximately matches the output power form desired at the output of the power transfer apparatus and transferred to the output of the power transfer apparatus.

Abstract: A boost-type power factor correction circuit is disclosed in which output voltage of the convertor is proportional to the peak input voltage. To achieve this, the circuit includes a peak rectifier D2, C2 which senses peak input voltage and provides a reference to which the output voltage derived through resistors R3, R4 is compared to give an error signal dependent upon variation from the peak input voltage derived reference. The error signal is used to control a MOSFET switch 120 to provide an output voltage V.sub.out dependent upon the reference.

Abstract: An automatic voltage control circuit by using reactive power is disclosed. The circuit comprises a proportional integrator, a triangular wave generator, a comparing circuit having first and second comparators, an inventer, and a reactive power control circuit, wherein the proportional integrator proportionally integrates the differences between output voltages and a reference voltage, the triangular wave generator outputs first and second triangular waves with a difference of phase angle 90.degree., the comparing circuit compares the output from the proportional integrator with the first and second triangular waves, the inverter controls the effective power by the output from the first comparator, and the reactive power control circuit controls the reactive power due to the variations of the load in response to the output from the second comparator, so that the output voltage can be maintained stably regardless of the variations of the load.

Abstract: A subsynchronous resonance mitigation system, including a method and apparatus, for damping undesirable subsynchronous resonance oscillations in a generator, which, if left unchecked, may damage the shafts of a turbine-generator set. A remote coupling apparatus, such as a thyristor controlled series capacitor (TCSC) system, a sourced inverter device, or a static phase shifter, is coupled to the generator by a transmission line. In response to a firing command, the coupling apparatus introduces subsynchronous resonance mitigating currents into the transmission line. Sensors monitor power line parameters and/or the generator speed, and in response thereto, a higher-level controller generates a voltage command. A vernier controller responds to the monitored power line parameters and the voltage command to provide the firing command to the coupling apparatus.

Abstract: An optically triggered solid state switch and method for switching a high voltage electrical current. A plurality of solid state switches (350) are connected in series for controlling electrical current flow between a compensation capacitor (112) and ground in a reactive power compensator (50, 50') that monitors the voltage and current flowing through each of three distribution lines (52a, 52b and 52c), which are supplying three-phase power to one or more inductive loads. An optical transmitter (100) controlled by the reactive power compensation system produces light pulses that are conveyed over optical fibers (102) to a switch driver (110') that includes a plurality of series connected optical triger circuits (288). Each of the optical trigger circuits controls a pair of the solid state switches and includes a plurality of series connected resistors (294, 326, 330, and 334) that equalize or balance the potential across the plurality of trigger circuits.

Abstract: A flicker compensating apparatus for compensating for flickering due to a variation in the reactive power generated from a DC arc furnace connected by an AC/DC converter to an AC power system, comprises: a current detector for detecting a DC current flowing in the DC arc furnace; a controller for determining the phase control angle of a thyristor included in the AC/DC converter in accordance with the difference between the detected DC current and a predetermined reference current; a calculator for calculating reactive power to be generated by the DC arc furnace, from the detected DC current, the determined phase control angle, and a no-load DC voltage; a compensator including a reactive load connected via thyristor to the power system; and a controller for controlling the phase control angle of the thyristor of the compensator in accordance with the calculated reactive power, for controlling a current flowing across the reactive load, and for permitting the compensator to generate such reactive power as to co

Abstract: An improved control system for static volt ampere reactance compensator provides for a transformation of the three phases into a two-variable system which thus isolates any common mode in the associated delta. Improved control is provided by utilizing the flux change as an advance indication of a disturbance. Lastly, the two-variable system, as it is inverse transformed into a three variable system, has its phasors rotated to prevent oscillation.

Abstract: A reactive power compensation apparatus includes a power system with a given voltage, a controller for controlling the voltage of the power system to a predetermined target voltage, using a predetermined transfer function, a reactive element, a switch for connecting the reactive element to the power system, a detector for detecting an impedance of the power system in accordance with a change in the voltage of the power system, the voltage change being defined by a difference between the voltage of the power system obtained when the reactive element is connected to the power system and the voltage of the power system obtained when the reactive element is disconnected from the power system, and a circuit for changing the transfer function of the controller in accordance with the impedance detected by the detector.

Abstract: A gate pulse generator for a static var compensator (SVC) constituted by a thyristor switched capacitor (TSC) comprises voltage detectors for respectively detecting forward and reverse voltages applied to antiparallel-connected thyristors in the TSC. The antiparallel-connected thyristors comprise a plurality of series-connected forward thyristors and a plurality of series-connected reverse thyristors. The gate pulse generator monitors the forward and reverse voltages and determines whether a period in which both the forward and reverse voltages are zero continues for a predetermined period while reverse-phase sides of the antiparallel-connected thyristors are held in conduction periods, respectively. The gate pulse generator prolongs an active period of a forward conduction period signal by the predetermined period.

Abstract: When there are variations in the short-circuit power of a system, the operating conditions can change, particularly in a controller of a compensating device. To automatically adapt the controller and to avoid or suppress oscillations or voltage variations in the system, a method is provided according to a first solution, where the circuit state of a compensating element is modified for testing purposes. The reaction of the system is detected in a device and, then a parameter which determines the damping of the controller is modified by means of a computing device. According to a second solution, an oscillation of the controller is established by detecting a signal which is dependent on the system voltage and by comparing specific variations. To suppress the oscillations, the hysteresis of the controller is damped by means of the computing device.

Abstract: Apparatus for controlling the reactive impedance of a transmission line where capacitive reactance is inserted in series in the line to compensate inductive reactance includes a plurality of three or more capacitor modules connected to each other in series to form a series combination of capacitor modules. Each module is individually bypassed by fast acting thyristor bypass switches so that a central automatic control system can selectively place all of the modules in series where a maximum compensation level is achieved (meaning that the total reactive impedance is at a minimum level), or to provide a minimum change with just one capacitor module.

Abstract: A fully automatic phase controller for non-coil armature type generator includes a starting control circuit and an automatic voltage control circuit, to fully automatically control the phase according to the range of the amplitude or the forward and backward movement of a pulse train, by means of magnetic saturation using a TRIAC and a voltage stabilizer. According to the present invention, the controller is very compact and inexpensive to manufacture, which helps to provide a stable voltage while the phase is fully automatically controlled.

Abstract: The present invention pertains to a line voltage regulator for a cable which is electrically connected to at least one load. The line voltage regulator includes a device for producing a cable voltage drop signal that corresponds to a voltage drop across the cable which separates the line voltage regulator and the load. The line voltage regulator also includes a sensor circuit for determining distortion voltage across the cable which separates the power supply and the line voltage regulator and the fundamental frequency signal required for regulation. The sensor circuit produces a drive signal that corresponds to the distortion voltage and the fundamental frequency signal required for regulation. Additionally, there is a device for providing voltage to the cable such that the voltage is regulated and distortion voltage across the cable is essentially eliminated as applied to the load. The device for providing voltage is electrically connected to the sensor circuit and controlled by the drive signal therefrom.

Abstract: A voltage-reactive power control apparatus provided together with VAR (volt-ampere reactive) supply equipment at principal points of the power system, such as load area substations. This voltage-reactive power control apparatus monitors the power-flow and load voltage at the load area. The apparatus quickly controls VAR supply equipment etc. upon detecting of voltage abnormalities, information that otherwise would be sent to the control point at a higher level station in the power system upon making decision to provide necessary countermeasures for wider range operation of the power system.

Abstract: A power converter includes an input primary switching system with its output connected to phase shift or impedance inversion circuit. These two circuits cooperate to function as a current source at the output of the impedance inversion circuit. A secondary switching system is connected in parallel with the output of the impedance inversion circuit and is switched synchronously with a controlled phase delay to the input primary switching system to synchronously charge a charge storage capacitor. The phase delay determines the voltage of the charge storage capacitor. An output load circuit is connected in parallel with both the output of the impedance inversion circuit and the input to the secondary switching system so that the capacitor voltage determined by the phase delay is controlling of the output voltage of the output load circuit.

Abstract: A reactive power compensator for an electric power system includes a voltage control circuit which amplifies a differential voltage between the potential command value and a potential signal corresponding to the voltage of the electric power system detected by a potential detector. The voltage control circuit outputs a reactive power compensation control signal. The control signal is fed to a reactive power output circuit which controls the voltage of the power system in order to compensate for reactive power in the power system. A gain calculation circuit is provided for setting the gain of the voltage control circuit to a value proportional to the level of short-circuit capacity of the system power on the system power supply side of the reactive power output circuit.

Abstract: In a computer controlled power factor control system switches are activated and deactivated in a predetermined order so that each capacitor is electrically connected to the power distribution system for substantially the same total time throughout the life of the capacitors.

Abstract: A static var compensator which includes a transformer with one end connected to an electric power system and a series circuit constituted by a reactor and a thyristor bulb connected between the other end of the transformer and ground. A voltage detection device detects the voltage of the electric power system and the output of the voltage detection device is sample an even number of times for every cycle of the voltage. A register is provided for storing sampled values an adder is provided for adding absolute values of the sampled values stored in the register. A firing angle of the thyristor bulb is controlled by a control device in accordance with a deviation of an output of the adder from an output of a voltage setting device. A deviation deriving device obtains a deviation of an output of the control device from a predetermined value corresponding to a present var, and an output of the deviation deriving devices is fed back to an input side of the control device.

Abstract: A power source device for high-frequency induction heating is disclosed. In this power source device, a plurality of high-frequency electric powers of different frequencies are supplied to the heating coil of a high-frequency induction heating appartus successively and repeatedly in time-division fashion at a very short period, to create a heating situation similar to multiple-frequency simultaneous heating, whereby the uniform quenching of an object to-be-treated having a complicated shape can be realized.

Abstract: In a power distribution system, in order to maximize efficiency and to provide protection in the event of a lightning strike or other transient, a fiber optic drive is utilized to transmit measured parameter signals through a fiber optic link to a control system. The fiber optic drive is powered only in timed, short bursts at ten second to ten minute intervals with a power supply that capacitively draws small amounts of energy over the long intervals and energizes the drive with accumulated high power pulses.

Abstract: A gate signal generator comprises U- and X-phase set circuits for discriminating, after the conduction period of every cycle, whether OFF time intervals of U- and X-phase thyristors are greater or smaller than a predetermined value, a reset circuit for detecting that both the U- and X-phase circuits do not provide outputs, a flip-flop set in response to an output from the U- or X-phase set circuit and reset in response to an output from the reset circuit, AND gates for calculating AND products of an output from the flip-flop and U- and X-phase forward voltage signals and for outputting the signals at a start of the forward voltage application after setting the flip-flop, and OR gates for calculating OR sums of outputs from the AND gates and outputs from the normal gate circuits. Gate signals are applied to the thyristors in response to the outputs from the OR gates.

Abstract: The reactive power compensation system used for preventing the power voltage fluctuation includes an inverter which operates in response to a high-frequency PWM signal based on the reactive power determined from the voltage and current at the receiving point to compensate a sharp varying component of reactive power created by the load, and a capacitor which is connected or disconnected with the power system through a semiconductor switch on the basis of comparison of the load reactive power with preset values so as to supply the leading reactive power back to the power system.