Abstract: An apparatus for rapidly tracking fundamental frequency information in the signal of an electric grid is a cross-coupled phase-lock loop filter (CCPLL) that includes the use of a phase-lock-loop (PLL) apparatus having a plurality individual filters, wherein an input for a first filter in the plurality of individual filters comprises the signal of the electric grid and an output signal from at least a second filter in the plurality of individual filters. A method for using the CCPLL includes applying a signal to the CCPLL and monitoring the output of the CCPLL. Use of the CCPLL may be accomplished or modeled via computer instructions stored on machine readable media.

Abstract: An apparatus for rapidly tracking fundamental frequency information in the signal of an electric grid is a cross-coupled phase-lock loop filter (CCPLL) that includes the use of a phase-lock-loop (PLL) apparatus having a plurality individual filters, wherein an input for a first filter in the plurality of individual filters comprises the signal of the electric grid and an output signal from at least a second filter in the plurality of individual filters. A method for using the CCPLL includes applying a signal to the CCPLL and monitoring the output of the CCPLL. Use of the CCPLL may be accomplished or modeled via computer instructions stored on machine readable media.

Abstract: An apparatus for rapidly tracking fundamental frequency information in the signal of an electric grid is a cross-coupled phase-lock loop filter (CCPLL) that includes the use of a phase-lock-loop (PLL) apparatus having a plurality individual filters, wherein an input for a first filter in the plurality of individual filters comprises the signal of the electric grid and an output signal from at least a second filter in the plurality of individual filters. A method for using the CCPLL includes applying a signal to the CCPLL and monitoring the output of the CCPLL. Use of the CCPLL may be accomplished or modeled via computer instructions stored on machine readable media.

Abstract: Method and apparatus that provide a response to the negative sequence current demands during a disturbance of the grid system connected to power-generating equipment, such as a wind turbine system, provide for tracking components in the grid signal, orienting at least a portion of the signal, and injecting the oriented portion. Controlled injection of negative sequence current provides for extending small-signal control response, and also provides for modifications of the apparent impedance to the grid interconnect of the power conversion equipment.

Abstract: A method for providing a smooth transition to powered operation in a motor control system in which a variable voltage inverter regulates power to the motor on a volts per Hertz basis. The method is particularly applicable to systems for energizing and rapidly gaining control of a motor driving a load in which the motor armature is turning at the time that power is supplied from the variable voltage converter. The method is implemented by sweeping the frequency of the excitation applied to an alternating current motor while holding the magnitude of the excitation at a level sufficient to prevent over current excitation of the motor.

Abstract: A dynamic brake control system for an alternating current motor powered by a variable voltage, variable frequency inverter which regulates the speed of the motor. An AC to DC converter converts AC line power to DC power with the DC power being transferred to the inverter via a DC link. During electrical dynamic braking, the inverter functions to transfer power from the motor to the DC link. The torque available to the motor during braking is a function of the receptivity of the DC link. Link receptivity controlled by a resistance connected to the link in which the resistance is modulated at a frequency dependent upon the incoming AC line frequency at the converter. The modulation is binarily controlled so as to minimize ripple current on the DC link without the necessity of providing high frequency control of the modulating electronics.

Abstract: A method for developing current control signals from motor terminal voltage in the control of alternating current electric motors which utilize electric current control signals oriented to the phase of a flux component in a rotating field for applying current so as to control the flux and torque in the motor. The method includes developing flux signals from measurement of motor terminal voltage and integrating those signals to develop corresponding flux signals. In one form, the method eliminates DC components occuring in the resultant flux signals by locating local maxima and minima of the resultant flux signal and correcting the value of the flux integrator so as to provide maxima and minima flux signals having equal absolute values. The method also includes establishing an initial flux in the motor prior to startup which is oriented in a predetermined manner such that initial current applied to the motor can be applied so as to immediately develop torque, if required.

Abstract: An automated SCR cell test exercises each of the twelve SCRs in a dual, 3 phase, full wave SCR rectifier bridge singly to detect shorted SCRs and in pairs to detect open SCRs or faulty gate circuits.

Abstract: A method of adaptively controlling the time of rendering the individual controlled devices of a controllable power conversion bridge includes the sensing of the instant in time at which the current from the bridge to a load becomes discontinuous. From the time of this sensing, the time period to a predetermined time such as a normally calculated time of rendering the controlled devices conductive is derived. This time period is then multiplied by a multiplier and the resultant product is combined with the predetermined time to provide an actual time of rendering the controlled devices conductive.

Abstract: A fault protective system for a load commutated inverter motor drive including an AC to DC source side converter coupled from an AC source to a DC to AC load side converter via a DC link circuit and wherein the load side converter supplies AC power of varying magnitude and frequency to the synchronous motor load. A pair of microcomputers interlinked by a common digital memory respectively control the inverters and interface with hardware type sensor means for detecting the occurrence of a plurality of different types of faults. Additionally, a number of stored instructional sets or programs are respectively included in both microcomputers to detect by software means another plurality of faults. The detection of a fault on either side of the link circuit is communicated to the respective computer which subsequently communicates with the other microcomputer to effect a coordinated protective action in response to thyristor cell failures, circuit failures, and abnormal operating conditions.

Abstract: A variable speed a-c drive motor is controlled by a current feedback pulse width modulation scheme which effectively isolates the controlled motor current from variations in the input d-c voltage. An additional control loop is provided to superimpose a control signal on the amplitude command input circuit of the pulse width modulation control scheme. The additional loop responds to line current and particularly line current resonance between the input d-c filter and the line inductance. Instantaneous line current is then maintained at the minimum required to support instantaneous power flow to the a-c motor so that resonance current is suppressed.

Abstract: A system, for use with a controlled current inverter to prevent malfunction of inverter action resulting from an insufficient capacitor voltage to effect commutation of an inverter bridge controlled rectifier, provides that the capacitor voltage is sensed and, if it is of insufficient value to effect rectifier commutation, the application of gating signals to the next to be rendered conductive controlled rectifier is inhibited. In order to achieve initial inverter operation, the inverter current is also sensed and the inhibit function is rendered ineffective until such time as the current reaches a predetermined value.

Abstract: Flux signals suitable for use in a control of an ac motor are generated as a function of the voltages and currents furnished to the motor. From sensed values of motor phase voltages and currents, signals representing the direct and quadrature values of motor voltage and current as well as total motor current are developed. Employing a closed loop path, these signals are utilized to develop signals representing the direct and quadrature components of the value of motor flux. The closed path develops a resistance signal representing the instantaneous motor resistance as a function of the total motor current and flux which resistance signal is employed in the development of the various flux signals.

Abstract: A control system for an AC motor drive including a source side converter and a load side converter coupled together by means of a DC link circuit wherein the current in the DC link circuit is controlled by either the source side converter or load side converter depending upon which converter is capable of control. This is achieved by crosstieing a signal from the normal regulating path in the source side converter control to the alternate regulating path in the load side converter control. This signal is chosen to be indicative of the source side converter controller being unable to control current, and may be derived from current error. This signal operates to alter the firing angle of the load side thyristor bridge to regulate the DC link current in the event the source side converter is unable to maintain the required current regulation.

Abstract: A plurality of arbitrarily loaded induction machines are operated from a single, controlled current inverter by regulating the amplitude of inverter output current in response to the average of the individual induction machine phase angles, the machine phase angle being the phase relationship magnitude between machine air gap flux and current, and by regulating the frequency of inverter output current in response to the average of the individual induction machine phase angle and the slip frequency of the most heavily loaded induction machine. The most heavily loaded induction machine is thus assured of having sufficient flux, thereby greatly reducing the possibility of machine pull-out and resultant inverter instability.

Abstract: An a-c induction motor powered from an adjustable frequency and adjustable magnitude power source is provided with a feedback control system whose gain is varied as a function of the magnitude of flux developed in the motor in order to normalize system response throughout the motor operating range. The control system is a two-loop system in which one loop adjusts excitation frequency and the other loop adjusts excitation magnitude with the excitation frequency loop being responsive to a torque command signal and a torque feedback signal to generate an error signal which is utilized to adjust the excitation frequency of the power source. System gain is varied by modifying the error signal as a function of the magnitude of flux developed in the motor. Preferably this modification is performed by dividing the error signal by a signal representative of the magnitude of motor flux.

Abstract: Dynamic response of an a-c induction motor control system including an adjustable frequency and adjustable magnitude power source is made more stable during the transition from a motoring to an electrical braking mode by modifying the system characteristics as a function of rate of change of motor flux and torque magnitude during electrical braking. The control system responds to a torque command signal and a torque feedback signal to generate an error signal which controls the frequency of the excitation supplied to the motor and thus the torque developed by the motor. During electrical braking this error signal is modified as a direct function of the rate of change of motor flux and as an inverse function of the magnitude of torque developed by the motor. During the transition from motoring to electrical braking, when the system tends to be unstable, the rate of change of flux is relatively high while the motor torque is at a relatively low value.

Abstract: An a-c electric induction motor control system having apparatus for balancing motor air-gap flux against motor stator current in a manner to derive a motor excitation command signal which tends to cause the control system to force the motor to operate on a predetermined torque versus slip frequency characteristic. The motor excitation command signal is utilized to regulate the magnitude of excitation supplied to the motor such that the air-gap flux level assumes a predetermined magnitude as a function of the motor slip frequency. Above motor corner point velocity, the balancing is modified in favor of flux such that the motor is operated in a constant horsepower mode.

Abstract: For use with an adjustable speed a-c electric motor having a stator adapted to be coupled to a source of variable frequency excitation and a rotor in which torque is developed when the motor is excited, the strength of said torque being dependent on interacting current and flux in the motor, a scheme is provided that comprises means for deriving an angle feedback signal representative of the actual phase angle between the aforesaid current and flux and means responsive to said angle feedback signal for controlling the source of variable frequency excitation so as to control the frequency of stator excitation as a function of the angle feedback signal.

Abstract: For use with an adjustable speed a-c electric motor comprising a stator having effective direct and quadrature axes and a rotor spaced from the stator by a gap, said stator including windings adapted to be connected to a source of excitation of variable frequency and amplitude, a scheme is provided that comprises means for deriving a "torque angle" feedback signal representative of the phase angle between current and flux that interact in the motor to develop electromagnetic torque tending to move the rotor relative to the stator, in combination with means responsive to the torque angle feedback signal for controlling the source of excitation so as to control the frequency of stator excitation as a function of the torque angle feedback signal. In one aspect of the invention, means is provided for controlling the source of excitation so as to control the amplitude of stator excitation as a function of a variable command signal that is prevented from deviating below a predetermined limit.