Abstract: An active filter unit comprising a first active filter which operates under low-frequency PWM control for controlling the fundamental and low-order harmonic capacity and a second active filter which operates under high-frequency PWM control for controlling the high-order harmonic capacity. The first and second active filters are connected in series through associated transformers that are in serial connection across the power lines. The divided filter arrangement reduces the required power rating of high-frequency switching devices.

Abstract: A harmonic suppressing device provided in a power system such as, for example, a transmission and distribution system or a power generating system, to filter higher harmonic currents generated by a higher harmonic current source of the power system such as, for example, a cycloconverter. The harmonic suppressing device comprises, as the principal components thereof, a passive filter serving as a high-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively high order among those generated by the higher harmonic current source, and an active filter serving as low-order higher harmonic filtering unit for filtering higher harmonic currents of comparatively low orders among those generated by the higher harmonic current source.

Abstract: In order to maintain low telephone interference (IT factor) during its normal operation and to establish rapid-post-fault voltage support to preserve the integrity of electric power transmission lines in the presence of degraded system impedance and harmonic instability, amplitude detection in a transmission voltage regulator (static VAR generator, SVG) is provided based on real time conventional, or fast, Fourier analysis, data samples being used to establish the fundamental voltage amplitude and collected during a specific, frequency tracking sliding window that precedes the amplitude reading by one line voltage cycle of the transmission line. The number of samples in the window is an integer multiple of the line frequency and, in the case of conventional analysis, the pulse number of the switching power circuit is used in the SVG. The amplitude value is updated after each sampling by shifting (sliding) the one cycle sample data base in a first in - first out manner.

Abstract: A triggering method for a thyristor switch which has at least two thyristors wired in series and a thyristor wired in antiparallel to each of these thyristors. The thyristor switch is triggered or cut off as a function of a specifiable on-off signal. At least a single triggering of a thyristor to be switched-on takes place at the earliest if a positive anode-cathode voltage is applied to it which exceeds a specifiable switch-on voltage limiting value. The method comprises generating a trigger standby signal if the on-off signal is in the switch-on condition and, with a specifiable minimum number of thyristors to be triggered wired in series, their anode-cathode voltage is greater than the specifiable switch-on voltage limiting value. At least a single triggering of each thyristor to be switched on takes place by means of a short-duration trigger pulse only during the duration of the trigger standby signal.

Abstract: A reactive power compensation apparatus for compensating for voltage fluctuation of an AC power supply system includes a first arithmetic circuit for synthesizing a positive-phase fundamental wave voltage signal from voltages of the AC power supply system, a second arithmetic circuit for synthesizing negative-phase voltage signals from the voltages of the AC power supply system, a third arithmetic circuit, coupled to the first and second arithmetic circuits, for synthesizing current instructions from the positive-phase fundamental wave voltage and the negative-phase voltage signals, and a circuit, coupled to the third arithmetic circuit, for generating a reactive power corresponding to the current instructions.

Abstract: A reactive power compensation device for a system including an AC power source and a load. The device comprises a first detection circuit for detecting reactive power in the load; a first reactive power compensation circuit, having a reactor, a thyristor and a capacitor, the thyristor being controlled based on the detected reactive power in the load; a second detection circuit for detecting total reactive power in the load and the first compensation circuit; a second reactive power compensation circuit having a self-commutated power converter connected in parallel to the load. The second compensation circuit is controlled to minimize the detected total reactive power in the load and the first compensation circuit.

Abstract: In a load commutated inverter system, the recovery time of the outgoing static switch is extended by applying an auxiliary commutation voltage in series with the associated phase line. This action is triggered in response to the gating signal of the on-coming switch during a time interval initiated before the expiration of the overlap time interval. Its duration extends by a predetermined amount beyond the normal recovery time of the outgoing switch.

Abstract: In a power distribution system, power line insulators have three electrodes, two of which are connected to the line and to ground, and the third of which forms a capacitively stepped down voltage corresponding to the line voltage, and use sensing coils to measure current. The sensing coils are inversely connected and differentially located to suppress noise.

Abstract: In a reactive power compensation apparatus for compensating reactive power generated by a load connected to an AC power supply system, dual phase current signals obtained by dual phase-converting the load currents and unit dual phase voltage signals synchronized with voltages of an AC main line connected to the load are used, and arithmetic operations thereof are performed to separately detect an in-phase reactive component signal and opposite phase component signals of the load currents. Current commands are generated on the basis of the separately detected signals, thereby controlling the reactive power compensation apparatus on the basis of the current commands.

Abstract: A static var compensator connected to a line node in a power transmission system and having a capacitor and a first reactor for producing and absorbing reactive power, respectively, and a second reactor connected between the line node and the common node of the first reactor and the capacitor for providing, in combination with the capacitor and the first reactor, a maximum leading reactive capacity so as to effectively reduce the capacities of the elements and for compensating for changes in reactive power resulting from a current fluctuation in response to a load fluctuation. The second reactor increases the reactive power produced by the capacitor when the reactive power absorbed by the first reactor is low and decreases the reactive power produced by the capacitor when the reactive power absorbed by the first reactor is high.

Abstract: A method for attenuating at least one unwanted harmonic, particularly the second harmonic, with respect to the system frequency in a multi-phase alternating current system, wherein an additional stabilizing circuit is installed into a conventional current/voltage controller including a current/voltage controller and a three-phase firing pulse generator in a reactive-power compensator connected via a reactive-power transformer and a current transformer to a 50 Hz three-phase system. The reactive power compensator has for each phase of the three-phase current at least one air choke, which is connected via a current transformer and via an alternating-current switch via another sum-current transformer to a secondary winding of the reactive-power transformer. In addition, the reactive-power compensator has for each phase of the three-phase current at least one capacitor bank or a capacitor, which is connected via a current transformer and an alternating-current switch (13) to the sum-current transformer (20).

Abstract: The reactive power of an induction machine is compensated by providing fixed capacitors on each phase line for the minimum compensation required, sensing the current on one line at the time its voltage crosses zero to determine the actual compensation required for each phase, and selecting switched capacitors on each line to provide the balance of the compensation required.

Abstract: At least two active conditioners are connected in series with a common DC source, and are mounted as a unit between two pairs of AC terminals to act either as a tie-in link between two AC power sources, as a buck/boost regulator between one AC power source and its load, or as VAR compensator as well as active power conditioner between phases of a multiphase AC option.

Abstract: A constant voltage regulator involving a feedback loop by which frequency dependence may be eliminated and at the same time, hunting phenomenon in case of low load can be suppressed without inserting a dummy resistance or a reactor in its circuit, whereby high reliability may be compatible with low cost.The constant voltage regulator comprises a linear reactor and a resonance capacitor connected in series to an input power source, and a variable reactor connected in parallel with said resonance capacitor and involves a feedback loop, a saturable reactor being used as said variable reactor, and current flowing through said saturable reactor being subjected to feedback control in response to load or output voltage.

Abstract: A static VAR generator for providing reactive power compensation to an n-phase AC network subject to transient surge currents utilizing mechanically switched shunt circuits in parallel with the thyristor arrays.

Abstract: Apparatus for generating a signal indicative of a fault occurring in an AC electric circuit connected to an AC network (UW). The AC circuit (1) comprises a series connection of at least one inductance winding (L) and a two-way static switch having thyristors (5, 6) controlled by firing pulses .theta., and the capacitive impedance and the resistive impedance of said AC circuit are negligible relative to its inductive impedance L. The apparatus comprises a differential relay (15) receiving first and second input signals and providing an output signal (Id) when said input signals are unequal. The first input signal is a real image of the current flowing through said AC circuit as provided by the secondary winding of a current transformer (30) inserted in said AC circuit.

Abstract: The thyristor control pulse generator consists of a dual slope sawtooth signal generator (11, 13, 17) providing a signal U.sub.sy with slopes a and 2a, said sawtooth generator comprising an input (23) for resetting the signal to zero in response to each generated pulse .theta. and means (15) for controlling the switching of the signal slope from value a to value 2a at the time the current in the reactive power regulating inductor becomes cancelled. A comparator (19) compares said signal U.sub.sy to a control voltage U.alpha. to which a correcting signal .DELTA.U.alpha.

Abstract: Subsynchronous resonance is detected in an electric a.c. power supply system by determining changes in wave parameters of substantially successive half cycles and applying said changes as a relationship of said subsynchronous resonance. The parameter change measured is the wave period, and changes in the ratio of the difference of the period of positive and period of negative half cycles over the sum of the period positive and the period of negative half cycles is related to detection of subsynchronous resonance.

Abstract: An alternating current motor drive in which the motor is furnished with electrical excitation from an alternating current source through a controllable power converter also includes first and second capacitor circuits connected to the common point between the converter and the motor. The first capacitor circuit is connected to the common point through an isolating inductor circuit. The second capacitor circuit is connected to the common point via the parallel combination of an inductor circuit and a resistor circuit. A further embodiment includes a variable VAR generator connected to the junction of the second capacitor circuit and the parallel combination of the inductor and resistor circuits.

Abstract: In a reactive power compensator used for capacitive or inductive reactive powers in alternating-voltage networks, a capacitor is connected to an alternating-voltage network for a short time by means of a thyristor switch. In order to reduce the voltage load on the thyristor switch, a discharge circuit is connected in parallel with the capacitor. Via this circuit, the capacitor can discharge, after being disconnected from the alternating-voltage network, with such a speed that the voltage occurring at the thyristor switch is no greater than about 1.5 times the maximum network voltage. In the discharge circuit, a variable inductive reactive resistance can be a discharge circuit choke having an iron core or the primary winding of a transformer. When the capacitor is connected to the alternating-voltage network, the discharge circuit choke is unsaturated and its reactive resistnace is large (or the transformer secondary is open) so that no significant leakage current can flow via the discharge circuit.

Abstract: There is provided a static VAR generator employing a bank of series-connected inductors, each inductor being supplied by different secondary taps of a step-down transformer. The voltage rating of each inductor is appropriately decreased so as to make their sum correspond to the supply voltage. All but one of the inductors are controlled by thyristors in an on-off fashion to supply reactive power to the network in incremental steps. One of the thyristors is continuously phase-angle fired in combination with the incremental insertion of the other inductors to vary the VAR output over the full range, but generating harmonics that are proportional only to the continuously controlled inductor.

Abstract: A compensation circuit for reactive power balance includes a capacitor, inductor and rectifier connected in series to a power system. In order to protect the rectifier from misfires of the thyristors, two discharge devices are connected in parallel to the series circuit from the common points in the series circuit. This protects the thyristors in case of a double misfire.

Abstract: A static VAR generator utilizing a multitude of reactor banks each having different computation circuits and firing angle control circuits is provided. The different computation and firing angle control circuits allows the VAR generator the flexibility of being able to change the reactor power in an A.C. network repetitively in any cycle in response to rapid changes in load demand. This is accomplished by each reactor bank having progressively longer computation times and later insertion of additional banks into the network after the first bank has responded to load demand.

Abstract: A static reactive-power compensating apparatus in which transients having a frequency below a predetermined frequency are not compensated for while all other variations are fully compensated for. A reset filter circuit is connected between the output of a rectifier circuit and a thyristor control circuit, the latter controlling the firing of thyristors which couple a reactive energy storage bank to the power system for compensating for voltage variations in the system. Preferably, the reset filter has a transfer characteristic of sT.sub.1 /(1+sT.sub.1).

Abstract: Power factor regulating method and an apparatus embodying the method in which each of three condensers, which are to be connected to each phase of a three phase distribution line, is preliminarily charged with approximately peak line voltage while a load connected to a distribution line is opened in order to lessen impulse waves that are brought about at the time of connection of the condenser to the appropriate phase of the power line. The present method needs no conventional discharging coil.

Abstract: Apparatus and process for the selective cancellation of harmonic frequencies of current produced in a multiphase dynamic stabilizer. A plurality of multiphase dynamic stabilizers providing electrical stabilization are interconnected to a multiphase AC electrical network via a coupling transformer. The leakage reactances and turns ratios of the windings of the transformer are such that the phases of selected harmonic frequencies of current produced in each of the stabilizer means are rotated with respect to those of the other stabilizer means with the selected harmonic frequencies being substantially cancelled in each of the stabilizer means. The harmonics are not the cause of subsynchronous resonance. The cancelled harmonic frequencies are dependent upon the number of dynamic stabilizers used.

Abstract: A polyphase static reactive compensator comprising a main saturated reactor (SR1) connected in series with a number of smaller saturated reactors (SR2-4) of graded voltage rating. The smaller reactors are shunted by respective thyristor switches (TV2-TV4) so that selected combinations of reactors can be obtained to provide control of the overall operating voltage. The slope of the overall characteristic can be controlled by switching through successive reactor combinations. Further refinement of the overall characteristic can be obtained by phase control of the smallest reactor (SR4) thyristor switches (TV3) or, in an alternative form of the invention, by the use of a single reactor (SR1) having a primary winding, a closed mesh secondary winding (19) and a phase-controlled auxiliary reactor (AR, ACR) constituting a load on the closed mesh winding. The two forms of the invention may be combined in one equipment.

Abstract: The non-linear control characteristic of a force commutated current source inverter operating as a var generator is linearized to provide a similar dynamic response in both leading and lagging modes of operation by two inter-related control schemes. The first control scheme comprises a linear closed loop feedback which controls a thyristor firing circuit in response to a difference or error signal between a var command signal and an actual var feedback signal while the second control comprises a feed-forward non-linear network having a signal transfer function which models the non-linear control characteristic of the var generator and is operative to control the thyristor firing circuit in response to the summation of scaled values of the var command signal and the actual var feedback signal and wherein the scaled values provide a combined gain which is equal to unity.

Abstract: A secondary arc extinction device in an electric power system, including a bus bar; an electric power line connected to the bus bar; protective relaying means connected to the bus bar; first reactance means having two terminals, one terminal of which is connected to the electric power line; a transformer having a primary winding and a secondary winding connected between the other terminal of the first reactance means and ground; second reactance means connected to the secondary winding of the transformer; and means for controlling the second reactance means in response to the protective relaying means.

Abstract: A secondary arc extinction device is disclosed for an electrical power system which includes a bus bar, an electrical power line connected to the bus bar and a protective relay device. A first reactance is provided with each phase so that one terminal of the first reactance is connected to a respective phase of the power line. A transformer which has a primary winding connected between the second terminal of the first reactance and ground is further provided and a second reactance is connected to the secondary winding of the transformer. A control device provides for control of the second reactance in response to a signal from the protective relay.

Abstract: A method of static reactive power compensation is disclosed wherein the system voltage is compensated by supplying advanced-phase or retarded phase reactive power in dependence upon the difference between the system voltage and a reference voltage. The difference is formed by a comparator which receives a variable reference voltage from a filter containing a time lag circuit and which receives the system voltage as an input. For transients, the output of the filter does not change and thus reactive power is applied. For smooth variations, the output of the filter follows that of the system voltage so that the output of the power compensation circuit is maintained at zero.

Abstract: A secondary arc extinction device in an electric power system, including a bus bar; an electric power line connected to said bus bar; protective relaying means connected to said bus bar; a first reactance means having a first terminal connected to said electric power line; a second reactance means connected between a second terminal of said first reactance means and ground; line voltage detecting means connected to said electric power line for detecting the voltage of said electric power line; current detecting means coupled to said second reactance means for detecting the current flowing in said second reactance means; and controlling means connected to said second reactance means for controlling the reactance of said second reactance means in response to said protective relaying means, line voltage detecting means and current detecting means.

Abstract: An auxiliary thyristor control circuit inserts a zinc oxide varistor in series with the capacitor bank of a static VAR generator for discharging the capacitor bank when the static VAR generator is subjected to high transient voltages.

Abstract: A secondary arc extinction device in an electric power system including a bus bar; an electric power line connected to the bus bar; protective relaying means connected to the bus bar; a transformer having a primary winding and a secondary winding, one terminal of the primary winding being connected to the electric power line; first reactance means connected between the other terminal of the primary winding of the transformer and ground; second reactance means connected to the secondary winding of the transformer; and means for controlling the reactance of the second reactance means in response to the protective relaying means.

Abstract: There is provided a static VAR generator having voltage regulation in combination with the capability to damp subsynchronous resonance should it occur. A novel method for controlling subsynchronous resonance is provided by monitoring the frequency of the electrical generating system and controlling the insertion of compensating inductance in response to disturbances that may result in voltage and frequency pulsations.

Abstract: There is provided a static VAR generator having a novel method for controlling subsynchronous resonance by monitoring the frequency of the electrical generating system and controlling subsynchronous resonance by phase-firing thyristor controlled inductance.

Abstract: There is provided a static VAR generator generally comprised of a fixed capacitor bank and a first and second switched conductor bank whereby said second switched inductor bank is operated at voltages leading the first inductor bank by 30 electrical degrees to allow the VAR generator to adjust its output current twice in each half cycle of operation.

Abstract: Subsynchronous oscillations and DC offset in an electrical power system are dampened by measuring the half-cycle period of current or voltage line waves, comparing the measured half-cycle time periods to a desired half-cycle time period and dissipating the line waves in measured half-cycle time periods which are longer than the desired half-cycle time period. Damping apparatus includes a reactance connected in a power line with selectively bidirectional conductors in parallel with the reactance whereby the reactance can be shorted. Alternatively, the selectively bi-directional conductors can connect a power line to ground or neutral when half-cycle time periods exceed a desired half-cycle time period.

Abstract: The invention contemplates a cord set involving a plug unit connected to one end of a multiple-conductor cord or cable, and destined to concurrently serve different electrical loads within a given utilization device. A suitably miniaturized power-factor control circuit is embodied within the plug, so that when plugged into a conventional a-c power outlet receptacle, a first two of the cable conductors can deliver suitably modified voltage appropriate to the instantaneous load requirements served by the modified voltage, while one of these first two cable conductors and a third cable conductor can concurrently deliver voltage appropriate to the different electrical load which it serves.

Abstract: A regulating system for delivering a leading or lagging current to compensate for a load varying reactance is disclosed. The regulating system has an RMS composite controller for regulating the voltages at a critical area in a power system at which good voltage regulation is desired. In various embodiments the RMS composite controller has an arrangement to develop RMS quantities representative of the sequence components of the three phase power system. Each of the various RMS composite controllers provides an accurate control signal for the desired voltage regulation.

Abstract: There is provided by this invention a static VAR generator having an auxiliary shutdown firing pulse generator that initiates a thyristor controlled inductive current to cancel any capacitive current supplied by the static VAR generator in the event of failure of the VAR generator's control means monitoring the capacitive current requirements.

Abstract: A circuit for controlling the voltage of a network which supplies electrical power to a load having a rapidly varying impedance. The circuit contains a pair of controlled electric valves which are connected in parallel between two conductors of the network and poled for condition in opposite directions. A voltage transformer produces a signal corresponding to the network voltage, which signal is conducted to an integrator and subsequently compared to a preset mean value. The preset mean value corresponds to a desired amplitude at which the positive and negative half-wave cycles of the network voltage are desired to be maintained. In one embodiment, the controlled electric valves are caused to conduct current during respective half-waves of network voltage so as to maintain the amplitudes of the half-waves at the present mean value. Other features are described for compensating for long term drift of the network voltage and for controlling the controlled electric valves by means of logic circuitry.

Abstract: A voltage regulator is taught for maintaining the terminal voltage of a three phase transmission line at a fixed reference value. The voltage regulator system utilizes the reactance of the transmission line in conjunction with reactive current from a VAR generator to compensate for the voltage effect of line current as it flows through the line reactance. The VAR generator is of the parallel capacitor-inductor type where the inductor is controlled by a thyristor switch. The conduction of the thyristor is controlled by utilizing a control system which generates an error signal based on the half period average of line voltage. The error signal is converted to a signal which is proportional to flux linkages by an integrator and then compared with the integral of the voltage signal for determining the conduction angle of the thyristor switches.

Abstract: A discrete-time, closed loop power factor corrector system controls the coupling of a delta-connected switched capacitor array to a 3- or 4-wire power line which may have time-varying, unbalanced, inductive loads. For inductive loads that cannot be exactly compensated with a delta-connected capacitance, the corrector system minimizes the total RMS reactive current drawn from the power line.

Abstract: A VAR generator of the switched capacitor controlled reactor type is shown utilized for a power transmission system. The control arrangement is such that the thyristor controlled capacitor and reactor banks are kept switched out for small terminal voltage variations which can be tolerated without compensation in order to minimize standby or no load losses in the region of the nominal voltage of the transmission system. Outside of this region VAR compensation is provided.

Abstract: A thyristor-switched inductor circuit is connected across a portion of a power system at which good regulation is desired. The thyristor-switched circuit delivers a leading or lagging current to compensate for a load of varying reactance and provides proper regulation at the desired portion of the power system. The thyristor-switched circuit comprises two parallel circuit branches each comprising an inductor and a thyristor in series, the thyristors being oppositely poled. The thyristor-switched circuit is operated during both the normal and the transient overvoltage conditions of the power system. During normal conditions the thyristor-switched circuit is operated at a conduction angle of less than 180.degree. so that the forward and reverse currents, related to the thyristors, are not in an overlapped condition. Conversely, during transient overvoltage conditions the thyristor-switched circuit is operated at a conduction angle of greater than 180.degree.

Abstract: A control system for automatically adding and subtracting capacitors to and from an electrical supply line for regulating the power factor of the supply line. A three-phase transducer is connected to the supply line and supplies a signal in direct proportion to the VARs of the supply line to a double setpoint meter relay. The meter relay is connected to a pair of timing relays which are selectively energized in response to a capacitor "add" or "subtract" signal from the transducer. If the signal is maintained for a predetermined period of time on one of the timing relays, a motor of a respective "add" or "subtract" cam-actuated switch is activated. The cam switches are programmed to energize or deenergize control relays, which in turn actuate capacitor contactors to add or subtract the next available capacitor.

Abstract: A control system for a VAR generator is taught in which a thyristor controlled inductive element is used to provide lagging VAR's and a bank of parallel capacitors, each of which may be switched into and out of circuit cooperation independent of the other, is used to provide discrete levels of leading VAR's. The inductive element is utilized in conjunction with the discrete levels of leading VAR's to provide a continuum of VAR generation in the region between the discrete levels by providing continuously variable compensating or cancelling current for interaction with the discrete levels to provide an overall continuous range of VAR generation in the leading VAR region.

Abstract: The two secondary windings of a transformer the primary winding of which is connected to an AC power supply are each provided with a controlled rectifying circuit. The DC sides of the rectifying circuits are connected in series to supply power to DC motors. One of the secondary windings is detachably connected with a capacitor bank. The capacity of the capacitor bank is selected so that the power factor of the converter can be improved to a satisfactory value when the two rectifying circuits are both controlled to produce output voltages. The capacitor bank becomes connected in response to the fact that the current in the primary winding of a transformer has arrived at a predetermined value.

Abstract: This concerns a compensator for electrical lines fed by a turbine-generator. The mechanical properties of the turbine-generator are such that modulation of the terminal voltage is possible due to subsynchronous mechanical torsional oscillations. If the carrier frequency or synchronous frequency of the generator minus the torsional oscillation frequency is equal to the resonant frequency of the electrical line driven thereby, a relatively large side band current may flow in the electrical line at the resonant frequency. The effect of this current may feedback through the air gap of the generator to increase the torsional oscillation. A boot strapping effect between the electrical properties of the line and the torsional oscillation may thus result which could ultimately end in shaft breakage.