Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

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: 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.

Abstract: 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.

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 timing reference generator for producing a multi-phase timing reference signal in synchronism with a multi-phase source voltage signal is disclosed. The timing reference generator uses an N stage array of series connected phase-locked loop (PLL) circuits to preserve the prefault condition of an input source signal by open circuiting at least the Nth stage prior to the propagation of the fault condition signal through the array. The open circuited stage acts like a flywheel to preserve the prefault condition of the source signal. This output can be used to replace the lost source signal until the fault condition has cleared. The output of the first PLL is used to provide the timing reference signals. This arrangement allows for sensing delays in establishing the occurrence of a fault and the consequent delay in activation of the flywheel.

Abstract: A static VAR generator for providing reactive compensation incorporating a malfunction detector. The static VAR generator comprises a reactance which is linearly responsive to a first linearized control signal and produces an output signal proportional to the reactive compensation which provides a feedback signal. A director control uses the feedback signal and an adjustable reference signal to provide the first linearized control signal based on the difference between the reference and feedback signals. A tracker controller provides a second linearized control signal based on the reference and feedback signals. The second control signal is compensated by an equalizer that determines the difference between the first and second control signals. The compensation counters the difference between the first and second control signals caused by the offset and component tolerances in the two controllers and makes the second control signal substantially equal to and track the first control signal.

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 only 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: 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 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 voltage regulator and flicker compensator is taught which utilizes a simulated light bulb in the feedback control. The simulated light bulb utilizes an analog voltage squaring module the output of which is filtered to reduce the second harmonic of the input signal. An error generator is provided as part of the control loop. The error generator utilizes an adaptive voltage reference which tends to conserve VAR generator capacity. A voltage preconditioner is also utilized which reduces spurious non-flicker transients and the like in the feedback signal.