Showing papers on "Voltage regulation published in 1994"

Dynamic compensation of AC transmission lines by solid-state synchronous voltage sources

Abstract: This paper describes a novel approach in which solid-state synchronous voltage sources are employed for the dynamic compensation and real time control of power flow in transmission systems. The synchronous voltage source is implemented by a multi-pulse inverter using gate turn-off (GTO) thyristors. It is capable of generating internally the reactive power necessary for network compensation, and is also able to interface with an appropriate energy storage device to negotiate real power exchange with the AC system. The paper develops a comprehensive treatment of power flow control using solid-state synchronous voltage sources for shunt compensation, series and phase angle control. It also describes the unique unified power flow controller that is able to control concurrently or selectively all three network parameters (voltage, impedance, transmission angle) determining power transmission. Comparison of the synchronous voltage source approach with the more conventional compensation method of employing thyristor-switched capacitors and reactors shows its superior performance (including the unmatched capability of using both reactive and real power compensation to counteract dynamic disturbances), uniform applicability, smaller physical size, and potentially lower overall cost. >

IC card with dual level power supply interface and method for operating the IC card

Abstract: An objective of the present invention is to provide a highly reliable IC card which is large in the scale of integration, fast, and low power-consuming, which contains the latest type of IC that has an operating voltage of 3.3 V and a maximum rated voltage of 5 V or less, and which can be used in either the latest equipment rated at 3.3 V or existing equipment rated at 5 V, or which does not cause this latest type of IC to be destroyed. The interface circuit comprises an analog switch, an external interface circuit, an interval interface circuit, and a high-voltage detection circuit. If the voltage of the power supply Vcc of the host system is less than or equal to an upper-limit voltage of 4 V, the power supply voltage is applied unchanged through the analog switch to a ROM that is the main circuit. On the other hand, if the power supply voltage is greater than this upper-limit voltage of 4 V, the analog switch is made non-conductive and thus the power supply voltage is not applied to the ROM. This prevents the ROM from being destroyed. If a regulated-voltage circuit is also provided, a power supply voltage regulated at 3.3 V can be applied to the ROM, even when the power supply voltage of host system is greater than the upper-limit voltage of 4 V.

Distributed current and voltage sampling function for an electric power monitoring unit

Abstract: A low voltage AC electric power monitoring system includes a processor which samples the current and circuit breaker system includes a processor which samples each of the current components at seventeen samples per cycle to obtain current samples representing a single period of the AC power signal. The processor samples the voltage component at different points in the voltage cycle over several cycles to obtain voltage samples representing a single period of the AC power signal.

Solar array maximum power tracker with arcjet load

Abstract: A solar array maximum power point tracking system for regulating the power output of a solar array associated with a spacecraft. An on-board computer measures the bus voltage and current from the solar array and generates a power calculation of the solar array power output. The on-board computer applies a first reference signal to a remote error amplifier representative of an incremental change in the solar array power. Additionally, the solar array bus voltage is applied to the remote error amplifier such that the remote error amplifier senses the solar array bus voltage and generates an output voltage indicative of the change of the solar array power. The output voltage of the error amplifier is applied to a power processor unit. The output voltage from the remote error amplifier and the bus voltage are applied to a power stage within the power processor unit. The power stage generates an output current that is applied to an arcjet thruster. The output current is also applied to a transconductive circuit that converts the output current to a voltage so as to condition the input voltage to the power stage.

Hybrid alternator with voltage regulator

Abstract: A hybrid alternator includes a stator (10) and a rotor (20), with the rotor (20) having longitudinally separate wound field (24) and permanent magnet (38) rotor portions. A rotor excitation circuit applies a forward polarity to the wound field rotor portion (24) to increase output in a boosting mode at low RPMs and a reverse polarity to decrease output at high RPMs in a bucking mode to maintain a constant voltage output. Alternative embodiments combine a magnetic flux concentrating design for efficient low speed operation with integral strength for high speed capability. Dual voltage output is provided using only one stator winding. A three state voltage regulator allows voltage regulation without inducing reverse currents onto the power bus in the lightly loaded or no battery conditions. The regulator has automatic interlocking to automatically turn on and off without risk.

An optimal reactive power planning strategy against voltage collapse

Abstract: This paper introduces a method of determining the minimum amount of shunt reactive power (VAr) support which indirectly maximizes the real power transfer before voltage collapse is encountered. Using a relaxation strategy that operates with a predictor-corrector/optimization scheme, a voltage stability index that serves as an indirect measure to the closeness of reaching the steady state voltage stability limits is obtained. Sensitivity information that identifies weak buses is also available for locating effective VAr injection sites. >

Integrated circuit device that selects its own supply voltage by controlling a power supply

Abstract: The specification describes an integrated circuit device that selects its own supply voltage by controlling a programmable power supply. The programmable power supply provides a supply voltage in response to one or more voltage control signals generated by the integrated circuit device. The integrated circuit device includes a voltage control circuit for generating the voltage control signals according to one or more predetermined operational voltages programmed into the integrated circuit device such that the supply voltage is substantially equal to a selected one of the predetermined operational voltages. The integrated circuit device may include a temperature sensor to allow selection of the predetermined operational voltage according to device temperature to avoid speed-limiting voltage and temperature combinations.

Generalized fast, power flow controller

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. In a high power configuration of the controller each of the inverters includes a plurality of six-pulse inverter modules connected by interstage transformers to form balanced higher order pulse groups controlled through pulse width modulation or through adjustment of the phase between opposite groups to generate the appropriate ac voltages.

Boost-input backed-up uninterruptible power supply

Abstract: A boost-input backed-up uninterrupted power supply provides an uninterrupted output voltage to a load. The backed-up power supply has an input rectifier and filter for converting an input voltage source voltage into at least an unregulated positive dc voltage source, and an unregulated negative dc voltage source. Batteries provide respective positive and negative battery voltages at corresponding positive and negative battery output terminals. A diode isolates the unregulated positive and negative dc voltage sources from their respective battery voltages for unregulated voltage source values equal to or greater than their respective battery voltages and clamps the unregulated dc voltage values to their respective battery voltages in response to loss of the sinusoidal input voltage source. A pair of boost regulators receives power from the unregulated positive and negative dc voltage sources and provide positive and a negative regulated dc voltage with respect to the return. A dc-to-ac converter receives a reference signal and converts the positive and negative regulated dc voltage into a first uninterrupted output voltage for application to the load. The uninterrupted output voltage is continuously sampled and scaled to provide an output voltage sense signal. The output voltage sense signal is combined with the reference signal to provide an amplified error signal. The dc-to-ac converter is further characterized to continuously adjust and scale the output voltage in amplitude and phase to minimize the amplified error signal.

Power control apparatus and method and power generating system using them

Abstract: Power control apparatus and method for fetching the maximum electric power from a battery power source and a system using such apparatus and method are provided. For this purpose, the power control method comprises the steps of fluctuating an output voltage of the battery power source and obtaining (m) power values from at least (m) voltage signals from voltage detecting means and at least (m) current signals from current detecting means which were sampled at desired intervals, calculating a formula of function with a polar to approximate the relations between the (m) voltage values and (m) power values, obtaining a voltage at which a power is set to an extreme value from the formula of function with a polar, and setting the power at such a voltage into an output power set value and controlling the output power of the battery power source.

Investigation of the output droop characteristics of parallel-connnected DC-DC converters

Abstract: The analytical proof that output voltage droop characteristics of parallel-connected DC-DC power converters are only appropriate for very limited applications is presented. Because the converters are rarely made to be identical, near-uniform current-sharing without additional control can be achieved only when converters connected in parallel have similar characteristics of being very close to the ideal current sources. This can occur at a cost of poor voltage regulation. As an alternative, the current-sharing control technique, which requires no remote-sensing, is proposed. The technique ensures uniform or designated current distribution throughout the specified load range. A control circuit module is independently implemented without any preliminary knowledge or any circuit modification of the source converters. >

Low and medium voltage PWM AC/DC power conversion method and apparatus

Abstract: A power supply apparatus and method for supplying direct current power to low and medium voltage DC loads wherein a multi-phase transformer having multiple secondary windings provides multi-phase power to multiple power cells, each of which have a single DC output and are controllable by a modulation controller. The primary and secondary windings in the power transformer may be star- or mesh-connected; the secondary windings may be shifted in phase. Because the power cells can be connected in series, the maximum output voltage for each cell may be less than the maximum line-to-line voltage. The power cell output can have variable DC voltage and current which can be controlled using pulse-width modulation techniques. AC input power is converted to DC output power for each power output line. Output power modulation can be produced by interdigitating a selected number of carrier signals so that harmonic components reflected back to the input are attenuated.

Robust controller structure for coordinated power system voltage regulator and stabilizer design

Abstract: This paper analyzes the inherent conflict between voltage regulation and damping improvement for synchronous generators and develops an effective robust controller structure, which allows coordinated direct trade-off between these requirements. >

Control of front-end three-phase boost rectifier

Abstract: Modeling and control of a three-phase PWM boost rectifier is presented. A current controller in rotating coordinates assures unity input power factor and fast output voltage regulation. Sensitivity of stability margins to different loads is analyzed. Two typical loads, a DC-DC power converter and an inverter supplying an AC motor, are considered. Linear and nonlinear current controllers in the direct axis are compared. With the nonlinear controller, which employs load current feedforward, the rectifier sensitivity to load variations is greatly reduced and a single optimal output voltage compensator can be designed for all load conditions. Small-signal output impedance is significantly improved, and faster transient response is obtained. The results are illustrated with simulations of a practical 10 kW rectifier. >

Control of DC-DC converters with linear optimal feedback and nonlinear feedforward

Abstract: This paper describes a new control design procedure for PWM DC-DC converters. The control action has two components: a linear feedback, designed via the LQ approach, and a nonlinear feedforward. The proposed control scheme guarantees excellent regulation of the output voltage, even in the presence of large variations of the input reference signal, as pointed out by numerous simulations carried out on different converter topologies. Good performances are also achievable when a suitably designed estimator is inserted into the control loop to reconstruct internal variables and input voltage disturbances from output voltage measurements. >

Method and apparatus for regulating the output voltage of negative charge pumps

Abstract: A regulation circuit which includes circuitry for furnishing a reference voltage, a voltage divider for furnishing a voltage provided by a charge pump circuit, a comparator for comparing the output of the charge pump circuit with the reference voltage, and apparatus for operating the charge pump when the voltage drops below the reference level and for interrupting operation of the charge pump when the voltage produced by the charge pump becomes greater than the reference voltage.

An improved voltage vector control method for Neutral-Point-Clamped inverters

Abstract: A new PWM method for Neutral-Point-Clamped (NPC) inverters is introduced. The method is based on closed-loop control of the line-to-line voltage vectors. It uses independent hysteresis comparator controllers to regulate the direct and quadrature axis components of the three phase output voltages. The controllers select the appropriate inverter output voltage vectors through an EPROM table. The closed-loop control allows a high performance over the whole range of operation, even when low speed devices such as the GTO are used. A neutral-point potential control is described, which is capable of stabilizing the variations within fixed limits during steady and transient states. The principle of the method is discussed and the vector selection technique is presented. The effectiveness in the output-voltage-waveform generation and the balance of the DC-link capacitor voltages are verified by simulation and experiment. >

Power supply start up booster circuit

Abstract: A power supply start up booster circuit for providing an increased startup voltage for a switch mode control integrated circuit including a boost portion for combining a first input voltage that has a predetermined minimum value and a second input voltage that transitions from 0 volts to the predetermined minimum value to make a minimum threshold voltage, a control portion having an integrated circuit for using the minimum threshold voltage to temporarily provide a voltage input at the integrated circuit, and an output portion for providing a permanent voltage input at the integrated circuit and an output supply voltage to an external circuit.

Three level power converting apparatus having means for balancing DC component thereof

Abstract: In order to equalize voltage shares of DC-side voltage dividing capacitors of a three-level power converting apparatus for converting a DC voltage to a three-level AC phase voltage, there is provided an arrangement for compensating for rising and falling instances of a three-level AC voltage pulse depending on a difference voltage between the two voltage dividing capacitors and the polarity of the AC current, thereby adjusting a zero-voltage period of the AC voltage.

Switching regulator with improved Dynamic response

Abstract: A switching regulator having improved dynamic response to load variations includes a load compensation circuit coupled to the output terminal. The load compensation circuit supplies current to a load coupled to the output terminal when the output voltage is less than a first predetermined level and/or diverts current away from the load when the output voltage is greater than a second predetermined level. The load compensation circuit operates in this manner until the output voltage is between the first and second predetermined levels. The load compensation circuit responds faster to load variations than the switching regulator to accommodate sudden changes in the load demand.

Meeting IEEE-519 harmonic voltage and voltage distortion constraints with an active power line conditioner

Abstract: This paper addresses the use of an active power line conditioner (APCL) for holding voltage harmonics and voltage distortion within IEEE-519 guidelines at a set of power system busses. The following two related problems are solved: (1) what size APLC is needed to meet IEEE-519 voltage constraints at each bus; and (2) where an APLC should be placed for maximum performance. Straightforward techniques for finding optimal or near-optimal solutions to these problems are presented, and an example is used to illustrate the solution procedure. >

Constant Voltage Circuit and a Stabilized Power Supply Unit

Abstract: A DC constant voltage circuit comprises a rectifier and a boosting chopper circuit controlled by a general purpose PWM control IC. The general purpose PWM control IC receives a reference voltage Vref which regulates the output voltage by pulse width modulation and produces a voltage having the same waveform and phase as the input current to improve the power factor of the output voltage. An AC constant voltage circuit comprises a common line connecting an AC input terminal and an output terminal, positive and negative boosting chopper circuits for boosting and chopping a half-wave rectified respectively in both positive and negative sides into a DC voltage and a DC-AC inverter for inverting the DC voltage into the AC output voltage. The positive and negative boosting chopper circuits are used as a filter for improving the power factor and adjusting the waveform and phase of the output voltage to be the same as the sine full waveform of the input voltage.

Power factor control circuit having a boost current for increasing a speed of a voltage control loop and method therefor

Abstract: An integrated power factor control circuit (12) for keeping an average AC line current sinusoidal and in phase with the line voltage. The integrated power factor control circuit (12) provides a boosted DC voltage greater than the amplitude of the line voltage. A transconductance amplifier (16) provides a boosted source and sink current when an output voltage is significantly out of regulation. The boosted source and sink current of the transconductance amplifier (16) increases the speed in which the voltage control loop can react to an output voltage change and reduces the time needed to generate the regulated voltage under startup. A comparator (17) provides a boost current at start up and senses a no-load condition during normal operation. The comparator (17) senses the no-load condition and stops switching to eliminate further output charging before an out of range condition occurs.

Semiconductor IC device having a voltage conversion circuit which generates an internal supply voltage having value compensated for external supply voltage variations

Abstract: A voltage conversion circuit of the present invention is equipped with means for generating a first voltage stabilized with respect to ground potential of a semiconductor integrated circuit device including the circuit, means for generating second voltage stabilized with respect to an external supply voltage of the semiconductor integrated circuit device, and selection means for selecting either the first voltage or the second voltage. The first voltage age, stabilized with respect to the ground potential, is selected and used as the voltage at the time of normal operation, and the second voltage, stabilized with respect to the external supply voltage, is selected and used at the time of aging test. In this case, means for trimming the first voltage and/or the second voltage is, preferably, provided to raise the voltage accuracy.

Low power, slew rate insensitive power-on reset circuit

Abstract: An improved power-on reset circuit is provided for controlling reset signal transition until after the power supply has achieved operational levels. Specifically, the reset signal is designated to transition from a high to a low state after the power supply exceeds a fixed reference voltage. The reference voltage is set at a voltage value greater than the operational voltage level of devices within a load circuit connected to the output of the power-on reset circuit. The power-on reset circuit includes numerous subcircuits used to define the reference voltage, trigger the reference voltage in relation to the power supply voltage, delay the triggered voltage, and buffer the delayed, triggered voltage to a reset value capable of driving load circuit impedances.

Design and implementation of a fuzzy controller based automatic voltage regulator for a synchronous generator

Abstract: Fuzzy controllers are increasingly being accepted by engineers and scientists alike as a viable alternative for classical controllers. The processes involved in fuzzy controllers closely imitate human control processes. Human responses to stimuli are not governed by transfer functions and neither are those from fuzzy controllers. This study involves the design and application of fuzzy control to the problem of automatic voltage regulation of a synchronous generator. The method explored deals with the use of binary input-output fuzzy associative memories for control. Error and rate of change of voltage are used to maintain a constant output voltage. Software routines were written in the 'C' language and were fast enough for real time computer control. The fuzzy controller was implemented in an IBM compatible personal computer to control an industrial size 5 kVA synchronous machine. >

Power regulation system for controlling voltage excursions

Abstract: An apparatus and method for providing dynamic voltage regulation for a system with a fluctuating current demand are disclosed A first voltage regulator is used for producing regulated output to the system A control circuit activates a second voltage regulator with faster transient response than the first voltage regulator to help source current when the first voltage regulator is unable to adequately respond to an increase in current demand from the system The control circuit activates a load element to help sink current at the output of the first voltage regulator when the first voltage regulator is unable to adequately respond to a decrease in current demand from the system