Westinghouse Electric Corporation

Electric Power Research Institute Incorporated

Curtiss-wright Electro-mechanical Corporation

Michael B Brennen

Laszlo Gyugyi

Steven A Moran

Eric J Stacey

Alberto Abbondanti

Francis T Thompson

Thomas H Putman

Scott K Suko

Jiing-Liang Wu

Kenneth M Eichler

David Jonathan Hall

Miklos Sarkozi

Mark Peter Krefta

Robert Edward Strickler

Mark G Gernhardt

A control system for a linear motor adapted to accurately supply a moving window of power to the stator coils. A plurality of individually switched stator coils run the length of a linear motor to move a rotor down the long axis of the stator. Accurate inductive-based position sensors continuously provide position data for the moving rotor. A processing unit calculates a proper time delay from a source voltage peak in order to apply power to the next stator coil in the moving direction of the rotor such that no DC offshoot/undershoot occurs. The linear motor control system optionally includes a failure prevention switching scheme in which pairs of individual stator coils on opposite sides of a double-sided stator are switched together.

Linear position sensing system and coil switching methods for closed-loop control of large linear induction motor systems

An improved active power line conditioner is disclosed. A series inverter is controlled by a series filter controller which performs synchronous transformations on a load current to generate a series filter feedforward signal corresponding to the fundamental components of the load current. The series filter controller also generates a series filter reference signal corresponding to a negative sequence fundamental output voltage. The series filter feedforward signal and the series filter reference signal are combined to form a series filter compensation signal. The series filter compensation signal is applied to the series inverter to generate sinusoidal input currents, with negative sequence fundamental output voltage compensation, for a non-linear load. A parallel inverter is controlled by a parallel filter controller which performs synchronous transformations to generate a parallel filter feedforward signal corresponding to the harmonic ripple components of the load current. The parallel filter controller also generates a parallel filter reference signal corresponding to a negative sequence fundamental source current. The parallel filter feedforward signal and the parallel filter reference signal are combined to form a parallel filter compensation signal. The parallel filter compensation signal is applied to the parallel inverter to generate sinusoidal voltages, with source current negative sequence fundamental compensation, for the non-linear load.

Active power line conditioner with fundamental negative sequence

An improved active power line conditioner is disclosed. The active power line conditioner includes a series inverter coupled to an energy input source, and a parallel inverter coupled to a non-linear load. The non-linear load is powered by a three phase load current which includes fundamental components and harmonic components. An energy storage element is electrically connected between the series inverter and the parallel inverter. The series inverter is controlled by a series filter controller which performs synchronous transformations on the load current to generate a series filter feedforward signal corresponding to the fundamental components of the load current. The series filter feedforward signal is applied to the series inverter to generate sinusoidal input currents for the non-linear load. The parallel inverter is controlled by a parallel filter controller which performs synchronous transformations on the load current or series inverter input voltages to generate a parallel filter signal corresponding to the harmonic ripple components of the load current. The parallel filter signal is applied to the parallel inverter to generate sinusoidal voltages for the non-linear load.

Active power line conditioner with synchronous transformation control

A series-parallel active power line conditioner is provide having improved peak voltage regulation capability when compared with the prior art. The DC energy level in the DC link between the series and parallel inverters is temporarily increased when the AC input voltage is not within the linear regulation range of the active power line conditioner. To effect this energy boosting function, control circuitry first determines the amount by which the average value of the AC input voltage is without the linear regulation range of the active power line conditioner. This information is then utilized to control the parallel inverter such that the DC energy level in the link is proportionally increased. A preselected maximum DC energy level is preferably chosen such that excessive AC input voltage variations will not cause further increases in the DC energy level. In presently preferred embodiments, this maximum DC energy level is twice the level nominally maintained when the AC input voltages fall within the sinusoidal regulation range of the active power line conditioner.

Series-parallel active power line conditioner utilizing temporary link

An improved active power line conditioner with fast dynamic response is disclosed. The active power line conditioner includes a series inverter coupled to an energy input source, and a parallel inverter coupled to a non-linear load. The non-linear load is powered by a three phase load current which includes fundamental components and harmonic components. An energy storage element is electrically connected between the series inverter and the parallel inverter. The load current fundamental signal is derived and is multiplied by a derived voltage output/input ratio to render a current reference product. The current reference product may be further modified by a user-set displacement power factor correction ratio. The current reference product is applied to the series inverter for fast dynamic response within the active power line conditioner.

Active power line conditioner with a derived load current fundamental

An improved active power line conditioner is disclosed. The active power line conditioner includes a series inverter coupled to an energy input source, and a parallel inverter coupled to a non-linear load. The non-linear load is powered by a load current which includes fundamental components and harmonic components. An energy storage element is electrically connected between the series inverter and the parallel inverter. The parallel inverter is used for current control functions, while the series inverter is used for instantaneous output voltage regulation. In one embodiment of the invention, a parallel current limiter is used for the parallel inverter. The parallel current limiter is fixed to satisfy specified output voltage total harmonic distortion requirements or peak to rms output current ratios in the active power line conditioner. A series current limiter may be used for the series inverter. The series current limiter is set slightly above the peak of the active power line conditioner input current fundamental. This allows the onset of a small intentional peak output voltage distortion that in turn limits excessive nonlinear load peak currents without back feeding of current harmonics into the input supply of the active power line conditioner.

Highly fault tolerant active power line conditioner

A novel active power line conditioner is disclosed. The apparatus includes a parallel inverter, with a dc-link, coupled to an output line. The parallel inverter is controlled by a parallel inverter controller which forces the parallel inverter to act as a variable capacitor or inductor. The parallel inverter controller identifies and feeds-forward a desired phase shift value between an active power line conditioner voltage output signal and an active power line conditioner voltage input signal. Utilization of the desired phase shift value results in voltage control of the dc-link of the parallel inverter. The parallel inverter controller also produces a tuning capacitance current reference signal which reduces voltage magnitude errors of the output voltage.

Low cost active power line conditioner

The present invention provides an active power line conditioner (APLC) which has improved peak voltage regulation capability when compared with similarly-sized devices constructed according to current teachings. The invention utilizes a control function which, when the AC input voltage is not within a given sinusoidal regulation range of the APLC, superimposes selected harmonics of the fundamental frequency on the reference voltage signal used to control voltage regulation action. This causes the AC output voltage of the APLC to have a nonsinusoidal, but peaking waveform shape. The magnitude of the harmonics are preferably controlled to increase as the amount by which the AC input voltage falls outside the linear regulation range of the active power-line conditioner. In presently preferred embodiments, the chosen harmonic frequency is preferably an odd harmonic of the fundamental frequency, with third or fifth harmonics believed to be particularly useful. To Lessen the potential for unwanted zero crossings of the AC output voltage, means may be provided to modulate the harmonic reference with an envelope frequency equal to twice the fundamental frequency.

Active power line conditioner utilizing harmonic frequency injection for

The present invention provides an APLC which has improved common-mode disturbance rejection capability when compared with similarly-sized devices constructed according to current teachings. The need for an isolation transformer is, in many cases, eliminated by the invention. The invention alters the coupling transformer of the series parallel APLC or the isolation inductor of the newly-proposed inductor-parallel APLC to create a balun effect in the high and low conductors of the electrical supply network. Particularly, first and second windings are substituted for the single winding of the transformer primary or the isolation inductor. These two windings are serially-connected on the high and low conductors, respectively, with appropriate polarity such that self-inductance values of each are additive. Low pass capacitors and surge protectors may also be added to further protect the APLC and the load.

Active power line conditioner having capability for rejection of

The present invention provides an improved active power line conditioner which achieves a significant improvement in peak voltage regulation capability when compared with a similarly-sized device of the prior art. Enhanced peak voltage regulation capability is achieved by reducing the number of turns on the transformer winding connected to the series inverter. As a result, the AC regulation voltage induced across the transformer primary and added to or subtracted from the AC supply voltage will be capable of achieving higher peak levels of short duration. When a reduced-turns-ratio transformer is utilized according to the invention, variations of the AC supply voltage which are within the sinusoidal regulation range of a prior art active power line conditioner having a similarly-sized transformer, the output voltage will remain sinusoidal. When, however, the input voltage variation is outside of this sinusoidal regulation range, the reduced-turns-ratio transformer will create a peaking but nonsinusoidal AC output voltage. This allows rejection of higher magnitude input voltage disturbances of short duration.

Series-parallel active power line conditioner utilizing

These and other objects are achieved by an improved active power line conditioner in accordance with the invention. The active power line conditioner includes series inverter coupled to an energy input source, and a parallel inverter coupled to a non-linear load. The non-linear load is powered by a load current which includes fundamental components and harmonic components. An energy storage element is electrically connected between the series inverter and the parallel inverter. A fault condition shorting circuit is supplied in accordance with the invention. The fault condition shorting circuit is coupled to a secondary transformer winding within the series inverter. The fault condition shorting circuit includes a diode bridge which conveys diode bridge current only in the presence of an overvoltage or overcurrent condition. A threshold device is connected to the diode bridge and conducts threshold device current in response to the diode bridge current. The circuit also includes a thyristor with its gate coupled to the threshold device. The thyristor is fired by the first threshold device current so as to short the secondary transformer winding in the presence of an overvoltage or overcurrent condition.

Active power line conditioner with low cost surge protection and fast

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.

Transmission line voltage detector for static VAR generator

To a static VAR generator of the split reactor type, a scaled down model is associated to be controlled concurrently with the static switches of the split reactor and to generate under proportional line voltage a simulated reactive current which is matched with the actual reactive current to detect a flashover across one of the two halves of the split reactor.

Protection system for thyristor-controlled reactors

In a hybrid switched-capacitor controlled-reactor static VAR compensator including a fixed-capacitor, hysteresis on switching-OFF a switchable capacitor of the capacitance bank is performed with a minimal fixed-hysteresis at the entrance of the standby region and with a temporary and variable-hysteresis in relation to any operating point in the standby region whenever maintaining the capacitor OFF is required. Since the fixed-hysteresis operates most often to prevent switching-OFF of the capacitor while the variable-hysteresis will operate less often, the losses at standby are minimized during thyristor-switched capacitor operation through most of this.

VAR generator system with minimal standby losses

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.

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Pittsburgh, PA, United States of America

Michael B Brennen