Abstract: A transmission line power controller for controlling the flow of electric power in an alternating current three-phase transmission system is described. The power line controller includes a parallel inverter connected to a series inverter through a dc link. The parallel inverter is connected in shunt to the transmission system through a shunt transformer. The series inverter is connected in series with the transmission system through a series transformer. A transmission line power control circuit is used to specify a desired real power demand and reactive power demand for the transmission system. The power control circuit processes this information along with a transmission line voltage vector and a transmission line current vector to produce a voltage source reference signal that is applied to the series inverter. In response to the voltage source reference signal, the series inverter produces an injected voltage vector into the transmission system.

Abstract: An apparatus for use in the simultaneous deactivation of a set of series-connected switching devices includes gate command control logic to generate a gate command signal for application to a selected switching device of the set of series-connected switching devices. A command compensation circuit processes the gate command signal. The command compensation circuit includes a time differential measurement module that forms a time differential signal indicative of the time from the previous turn-off of the selected switching device and the previous turn-off of the last switching device in the set of series-connected switching devices. A time difference processing module of the command compensation circuit process the time differential signal and creates a delay signal. A delay module of the command compensation circuit delays the gate command signal in response to the delay signal. Each switching device of the set of series-connected switching devices includes a command compensation circuit.

Abstract: A series compensator for damping power oscillations in an electric power transmission system includes a switching power converter which injects a voltage into the transmission line having a phase angle relative to transmission line current which is controlled to provide reactive compensation and to inject virtual real impedance into the line. The switching power converter is a dc to ac converter which is capable of injecting virtual real impedance into the transmission line by virtue of the fact that it has a power exchange device connected to its dc terminals. Where the power exchange device is a resistor, the switching power converter is capable of absorbing real power during surges in power on the line. Alternatively, the power exchange device is a storage device such as a battery bank or a super conducting magnet, in which case the switching power converter can provide both virtual positive and negative real impedance.

Abstract: A method and apparatus for AC-to-AC power conversion wherein commutation from one switch in a switching group to a second switch is effected while both switches are enabled simultaneously without causing a short circuit between the phase input lines associated with each respective switch. Each switch in a switching group is bidirectional and polarity-controlled, and may be selectively enabled to conduct only negative-polarity or positive-polarity current, or may be disabled. An overvoltage clamping circuit is also provided with each switch. A switch gating control circuit is employed to provide selective operation of the switches in a particular switch group.

Abstract: A valve for rapidly switching high voltage at high currents includes several identical modules series-coupled between the high voltage rails. Each module includes a three-terminal semiconductor voltage controlled gate turn-off device ("VCGTO"), an input port for receiving a preferably optically coupled gate drive signal, input circuitry, two power switching ports coupled to the VCGTO device output terminals, and an output circuit coupled across the device output terminals. The input circuitry includes an interface circuit and a drive circuit for driving the VCGTO device in response to the gate drive signal, while the output circuit includes a clamping mechanism and regulated clamp voltage circuit that maintains a safe, regulated maximum differential potential across the VCGTO device.

Abstract: First and second dc linked, preferably voltage sourced, inverters are connected to an electric power transmission line in shunt and in series, respectively, by coupling transformers. Firing of the GTO-thyristors of the first inverter is controlled to regulate reactive power on the transmission line and to supply real power requirements of the second inverter. The second inverter is controlled to inject into the transmission line in series a voltage which can be adjusted in magnitude and from zero through 360 degrees in phase with respect to the transmission line voltage to selectively adjust any one or more of transmission line voltage magnitude, transmission line impedance and transmission line voltage phase angle.

Abstract: An advanced static VAR (volt ampere reactive) compensator (ASVC) system for coupling with and compensating a transmission line of a power system includes an ASVC controller. A voltage-sourced inverter has an AC side coupled through a series inductance to the transmission line, and a DC side coupled to a capacitor. By monitoring the DC side voltage, two line-to-line voltages and two line currents between the series inductance and the transmission lines, the ASVC controller determines an instantaneous reactive current component of the line current. The ASVC controller adjusts the phase angle of the inverter AC output voltages to compensates the transmission line by negating the instantaneous reactive current, and thus, the undesirable instantaneous reactive power on the transmission line. A method is also disclosed of compensating the instantaneous reactive power flowing over the transmission line.

Abstract: A system and method is provided compensating utility distribution line transients such as voltage sags in a dynamic manner, by inserting a voltage signal in series with the distribution signal having a magnitude and phase to effectively cancel out the voltage deviation caused by a network disturbance. An energy storage device such as a storage capacitor is used to provide energy to an inverter circuit which is controlled to generate the series-inserted signal. Preferably a converter such as a chopper is utilized between the storage element and the inverter, to provide a constant dc input to the inverter. A controller generates a corrective error signal based upon the deviation between the utility supply voltage as affected by the disturbance, and the nominal ideal voltage signal, and adjusts the insertion voltage so as to optimize real power delivery to the utility distribution line.

Abstract: A converter for synchronous motor starting rectifies the input voltage from a polyphase input power source to develop a starting current having a substantial DC component. The starting current is then sequentially applied to each of the phase windings in the synchronous motor, with the sequential rate of application occurring at a continuously increasing frequency. The angular velocity of the motor synchronously increases with the increasing frequency of the sequential rate of application of the starting current to the phase windings. By application of the starting current at an increasing frequency, the synchronous motor operates in a forced commutation mode. The starting current is removed when the angular velocity of the motor is synchronous with the constant frequency of the polyphase input power source. When the starting current is removed, and the motor is synchronous with the input power, the input power may then be applied directly to the motor in a natural commutation mode.

Abstract: An electrical control system includes multiple frames of reference in the error path of a controller. In each such frame, a particular chosen component of the error vector appears as a constant vector and is passed through a pure integrator thus acquiring infinite gain. In the steady state, the net error vector can then be forced to have zero content at each of the targeted frequencies (as set by the rotational velocity of the frames of reference). Both parallel and series configuration of the controller are provided, as well as the control methods used by the controllers.

Abstract: A three-phase flat-top waveform generator which may be utilized in a pulse-width modulator. Transfer function means receive a three-phase input signal and produce therefrom a zero sequence signal. Under steady-state and balanced conditions, the zero sequence signal will generally have a fundamental frequency three times the frequency of the input signal. Summing means add the zero sequence signal to each phase of the input signal to produce the desired flat-top signal.

Abstract: A series impedance compensation system for a set of transmission lines which are used for electrical power transmission, with these parallel lines being protected from the transient faults and dynamic subsynchronous oscillation problems. These problems can become aggravated by the introduction of capacitor banks which thus serve as only a partial solution to the disturbances of transient faults during conventional recovery modes of operation. The impedance compensation system is coupled in series to each transmission line to dynamically balance the inductor impedance on the transmission line, responsive to demand, by injecting a voltage component determined to be optimized substantially at quadrature leading or lagging phase angles (.+-.90.degree.) with respect to the transmission line voltage and current components.

Abstract: A drive system for a battery-powered vehicle is selectively operable in either a drive mode or an alternative battery-charging mode. In the drive mode, vector control circuitry is used to control instantaneous stator currents in an AC induction motor. The motor is preferably constructed having a pair of separately excitable three-phase windings spatially displaced by thirty electrical degrees. In the battery-charging mode, many of the same components are used to control battery charging current obtained as AC from a typical AC mains source.

Abstract: A motor torque and flux controller usable with a battery-powered vehicle drive regulates the flux in the drive motor so that a constant fraction of available battery voltage is used throughout the constant-power operating range. The controller is responsive to a scalar voltage reference signal and a torque demand reference signal to produce direct and quadrature components of a current demand vector as well as a signal representative of rotor slip. Feedback for the controller is provided by a scalar signal preferably representative of a fraction of the demanded motor terminal voltage. The controller limits the magnitude of the current demand vector to a predetermined maximum while providing flux dominance.

Abstract: An AC-to-AC converter operating as a current-source between an AC input line and an AC output line connected to a load, for instance an AC motor, includes three groups of bilateral switches controlled selectively within each group so as to generate a quasi square-wave current in each output phase while establishing a DC voltage between two of the output phases at a time, the third phase being idle, the magnitude of the output voltage being controlled in relation to the firing angle of the switches and the frequency being established by controlling the duration of each square-wave alternance. The duration of such alternances is set to 120 degrees of the output wave, followed and preceded by a 60 degree zero-current period.

Abstract: A feedback controlled elevator system driven by a traction drive motor in response to a speed pattern provided by a car controller. The speed pattern is limited when the car approaches a terminal floor within a predetermined terminal slowdown zone adjacent to the terminal floor. A pattern limiting signal is provided in response to digital integration of shaft encoder signals which provides a digital position "x" of the car within a terminal zone. The position "x" of the car is then used to access a read-only-memory which contains the maximum car speed for the specific location of the elevator car. The value from the read-only memory is used to limit the speed pattern.

Abstract: An induction motor torque/flux control system the motor flux is forced down while accelerating and force up while decelerating to maintain a required flux level at all speeds. This is achieved through vector control by generating a direct current component in relation to the flux demand while imposing limits thereto corresponding to the maximum desirable resultant current vector, and by generating a quadrature current component which is held between limits defined by the sum of the squares of the two current components. The three-phase currents of the motor generated by vector control transformation are used to control a voltage-source inverter in a bang-bang fashion. The conventional bang-bang technique is improved by typing up one pole while controlling in the bang-bang mode the two other poles. To this effect the motor back emf is detected when the poles are simultaneously tied to one of the DC link terminals, and the tied-up pole is selected by the emf so detected.

Abstract: A bridge between the inductor and the capacitor of the DC-Link of a voltage-source inverter AC motor drive includes a GTO (or transistor) device used for forced-commutation in the regenerating mode, while the current is controlled ON and OFF according to a duty-cycle defined by an hysteresis circuit to hold the current flowing into the inductor to a magnitude which establishes a boost on the capacitor voltage, so that in the motoring, as well as the regenerating mode of operation, the voltage of the capacitor is kept constant and higher than upon the converter output.

Abstract: An inductio motor torque/flux control system the motor flux is forced down while accelerating and force up while decelerating to maintain a required flux level at all speeds. This is achieved through vectory control by generating a direct current component in relation to the flux demand while imposing limits thereto corresponding to the maximum desirable resultant current vector, and by generating a quadrature current component which is held between limits defined by the sum of the squres of the two current components. The three-phase currents of the motor generated by vector control transformation are used to control a voltage-source inverter in a bang-bang fashion. The conventional bang-bang technique is improved by tying up one pole while controlling in the bang-bang mode the two other poles. To this effect the motor back emf is detected when the poles are simultaneously tied to one of the DC link terminals, and the tied-up pole is selected by the emf so detected.

Abstract: Adaptive control is used in an asynchronous motor drive. A reference model based on the model equation of the motor is combined with an adjustable model responsive to the direct and quadrature components of the current and to an estimated speed. An adaptive mechanism counting in a P-I amplifier expands to the direct deviation between the direct and quadrature components of the flux outputed by the two models and generates a feedback signal representing the estimated speed. The adjustable model reacts to such feedback signal so that the estimated speed readily becomes the actual speed of the motor. As a result, a tacho-less AC motor drive is obtained in which under any running conditions the motor immediately takes the required speed.