Showing papers on "Voltage regulation published in 1992"

Apparatus and method for dynamic voltage restoration of utility distribution networks

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.

Voltage collapse proximity indicator: behaviour and implications

Abstract: With the increased loading and exploitation of the power transmission system, the problem of voltage stability and voltage collapse attracts more and more attention. A voltage collapse can take place in systems or subsystems, and can appear quite abruptly. Continuous monitoring of the system state is therefore required. This paper is concerned with the problem of voltage stability, and investigates a proposed voltage collapse proximity indicator applicable to the load points of a power system, based on the optimal impedance solution of a two-bus system. This indicator is generalised and applied to an actual system. The performance of this new indicator is investigated over both the stable and the unstable regions, as the load at a particular node or the system load increases. Tests show that the indicator can provide useful information at any operating point.

Method and apparatus for determination of battery run-time in uninterruptible power system

Abstract: The run-time on battery power available from an uninterruptible power system is accurately determined both during supply of power from the battery through an inverter to the load and during the time where power is supplied directly from an AC power system to the load. During power outages where power is supplied from the battery through the inverter to the load, the output voltage of the battery is directly measured as is the output current supplied to the load. The remaining run-time is determined utilizing the measured battery voltage, the measured output current, and system specifications including the full charge open circuit voltage of the battery, the allowable lower limit of battery voltage, and constants which are characteristic of the uninterruptible power supply and the battery. When power is supplied from the AC power system to the load, the open circuit voltage of the battery is measured initially, and then during the time that the battery is being recharged the open circuit battery voltage is calculated based on the initial open circuit voltage adjusted by a factor porportional to the time that the battery has been charged. The calculated open circuit voltage is used to calculate a battery voltage under load conditions by subtracting a term proportional to output current. These estimates are then utilized to calculate run-time in a manner similar to that used to calculate run-time when the battery is loaded. Thus, the inverter need not be turned on to supply power to the load solely for the purpose of testing the battery.

Switched mode power supply integrated circuit with start-up self-biasing

Abstract: An embodiment of the present invention is a switching power supply that includes a full-wave bridge rectifier to rectify incoming AC line voltage, a transformer having a primary winding and two secondary windings and a switched mode power supply chip that includes an integrated high voltage power MOSFET with a low voltage tap in the drift region. The MOSFET controls power switching of the primary winding of the transformer and has a high voltage present during initial power-up. This high voltage is dropped across the JFET part of the MOSFET and supplies a regulator with power either temporarily or continuously to operate a pulse width modulator in the chip that controls the switching of the MOSFET.

Integrated circuit monitor for storage battery voltage and temperature

Abstract: An apparatus for monitoring voltage as a function of temperature of a storage battery and an apparatus for controlling the charging voltage of the battery based on battery temperature, voltage, and charging system loads. The battery monitoring apparatus includes a comparator for comparing, at any temperature in the working temperature range of the battery, the actual battery voltage with a reference battery voltage. The reference battery voltage is the voltage gassing curve for the storage battery. The comparator is given a temperature coefficient provided by a temperature-sensitive band-gap voltage reference. A plurality of the temperature-sensitive band-gap reference cells may be connected together in order to accurately track any differently sloped battery gassing voltage curve. An apparatus for controlling charging voltage of the storage battery is also provided, which includes a comparator for comparing, at any temperature in a predetermined range, the actual charging voltage with a reference charging voltage. The reference charging voltage curve is a function of charging system component temperatures and electrical system loads. A plurality of comparators may be connected together in order to approximate any desired charging voltage reference curve or combination of curves.

Analysis and design of a series voltage unbalance compensator based on a three-phase VSI operating with unbalanced switching functions

Abstract: Voltage unbalance in AC supply systems is typically corrected by means of a shunt connected thyristor-controlled static VAr compensator. This approach has the disadvantage of slow response, harmonic injection into the AC system, and the requirement for large passive components. The proposed system consists of a three-phase PWM voltage source inverter, connected in series with the line through a three-phase transformer. The unbalance compensation is achieved by canceling the negative sequence component of the line-to-line voltages of the source. It is also shown that by having the inverter operate with unbalanced switching functions, it is possible to balance the load voltage and to control the amplitude of the positive sequence component in order to perform load voltage regulation. A complete mathematical description of the method is presented, demonstrating that the compensation can be achieved with low kVA inverters and low harmonic injection. Implementation procedures, design equations, and a design example are also included in order to illustrate the proposed method. Experimental results of a 1.5 kVA laboratory prototype system confirm the feasibility of the technique. >

Optimized modulation techniques for the generalized N-level converter

Abstract: A balancing control strategy that allows the voltage differences among the DC link capacitors of the generalized n-level power converter to be minimized is presented. The case n=3 is treated, but the technique can be generalized to larger n values. The balancing algorithm does not achieve correct voltage sharing of the capacitors under all operating conditions, but it provides a great improvement. This strategy appears to be very promising in single-phase applications, for which nonredundant switching configurations do not affect the capacitor voltage balance. >

Physical origins of input filter oscillations in current programmed converters

Abstract: Addition of an input filter to a current-programmed converter can cause the controller to oscillate. Two instability mechanisms can typically occur: (1) the current programmed controller effective current feedback loop may become unstable, or (2) the controller effective input voltage feedforward loop, which becomes a positive feedback loop when an input filter is added, may oscillate. Three design criteria for preventing oscillations are derived and interpreted. When all three criteria are well satisfied, then the output voltage regulation loop gain is unchanged. Hence, input filters of current programmed converters can be designed in essentially the same manner as for duty-ratio programmed converters. Results are summarized in tabular form for the basic buck, boost, and buck-boost converters. Experimental measurements for a buck converter with different input filters support the theoretical predictions. >

Robust nonlinear controller design for transient stability enhancement of power systems

Abstract: A robust DFL (direct feedback linearization) nonlinear excitation controller is proposed to enhance transient stability for power systems. A robust control technique for linear systems is extended to design this controller. The design of the controller is independent of the operating point. Simulation results show that the controller has the following advantages: the fault location does not need to be known and the controller can overcome the variation of the reactance of the transmission line. Both transient stability enhancement and voltage regulation can be achieved. >

Electric power unit

Abstract: The electric power unit of the present invention for a battery-powered electronic appliance comprises a chopper-controlled nonisolated DC-DC converter (2) for converting the output voltage of a battery into a required voltage, a bypass switch (4) for bypassing the DC-DC converter, a comparator (5) for comparing the output voltage of the battery with a reference voltage (Vb) corresponding to the required voltage of the load circuit, and a controller (6) for controlling the bypass switch (4) on the basis of the output signal of the comparator (5). When the output voltage of the battery is higher than the reference voltage, the battery is connected directly to the load circuit, so that the power of the battery can be supplied to the load circuit without loss due to the operation of the DC-DC converter (2). When the output voltage is lower than the reference voltage, the output voltage of the battery is converted into a voltage nearly equal to the required voltage of the load circuit by the DC-DC converter (2), so that substantially all the energy stored in the battery (1) can effectively be used.

Quick-start and overvoltage protection for a switching regulator circuit

Abstract: A switching regulator controls the pulse width to a gate of a switching power transistor to maintain an average output voltage. An error amplifier in the regulation loop detects the difference between the actual output voltage and its desired value and maintains the proper regulation voltage at a loop node to control the pulse width to the gate of the power transistor. A quick-start circuit establishes a minimum loop regulation voltage at the loop node during power up allowing the error amplifier to begin regulating immediately thereby reducing start-up delay. The quick-start circuit is disabled after the loop node reaches the minimum loop regulation voltage. The switching regulator also monitors the output voltage by the same input pin to detect an overvoltage condition and shuts down the power switching transistor accordingly.

Varying the supply voltage in response to the current supplied to a computer system

Abstract: Disclosed is a power system for use with a computer, the power system having incorporated in it circuitry for automatically varying the supply voltage output to the computer system based upon the magnitude of the current being supplied to the computer by the power system. Also included in the computer system is a variable frequency clock circuit, the frequency of which changes based upon the supply voltage produced by the power system. This permits, during computer system operation where low voltage and low clock speeds will be sufficient to provide the performance needed, achievement of a power saving since both the voltage and frequency at which the system operates is reduced, thereby markedly reducing the power consumption.

Solid state electric power usage meter and method for determining power usage

Abstract: A digital solid state electric power usage meter for determining power usage by a load attached to an electric power network. The meter has a current sensor coupled to each phase of the electric power network for sensing current in each phase, a voltage divider coupled to each phase of the power network for detecting the voltage level on each phase, an analog to digital (A/D) converter coupled to the current sensors and voltage dividers receiving signals from the current sensors related to the current in each phase and signals from the voltage dividers related to the voltage on each phase. The A/D converter samples the current and voltage related signals at predetermined times at a rate which insures that samples of the current and voltage related signals do not repeat for a large number of cycles of the network frequency or never repeat and which rate is at least twice as fast as the rate of change of the current and voltage related signals and converts the samples to digital signals representing the voltage levels and current at the predetermined times. A processor calculates instantaneous values of power at the predetermined times from the digital signals and a memory accumulates the instantaneous values so as to form a value representative of electric power usage by the load attached to the network.

Analysis of a new power electronics interface with approximately sinusoidal 3-phase utility currents and a regulated DC output

Abstract: A three phase rectification scheme that draws line currents with reduced distortion and provides a regulated DC output voltage is analyzed. The scheme employs two boost DC-DC converters to modulate the DC link currents. The modulation current is injected into the AC side through an impedance network consisting of series tuned L-C branches. The theoretical analysis and the basic simulation results, which can be used to carry out the design of a system based on this approach, are presented. >

Voltage interfacing buffer with isolation transistors used for overvoltage protection

Abstract: A voltage interfacing buffer for interfacing a low voltage integrated circuit to a high voltage environment, wherein the integrated circuit contains only low voltage transistors. To drive the high voltage environment at the low voltage swing, the voltage interfacing circuit employs protection circuits and novel n-well biasing of MOS transistors. To drive the high voltage environment at the high voltage swing, the voltage interfacing circuit employs a bias generator circuit to bias buffer transistors supplied with the high voltage. As example applications, the voltage interfacing buffer enables a 3 volt or 3.3 volt integrated circuit chip to drive TTL as well as CMOS voltage levels. Moreover, the voltage interfacing buffer enables a 2 volt integrated circuit chip to drive TTL voltage levels.

Voltage collapse in power systems

Abstract: The stages of a voltage collapse in a power system are described. Circuit and system techniques for analyzing voltage collapse that relate it to the changing number of solutions for the power-flow equations, due to slow changes in system parameters are presented. It is shown that to fully analyze voltage collapse for small- and large-disturbance cases, the essential dynamic mechanisms are considered. Several algorithms developed to detect how close a system is to voltage collapse are discussed. A voltage-collapse scenario based on the interaction among dynamic mechanisms is outlined. >

Automated voltage and VAR control in power transmission and distribution networks

Abstract: Controlling a customer voltage and VAR flow in a power transmission and distribution system includes measuring first voltages in a power line directed to a first location related to customers. Both the customer voltage and the VAR flow for the network is determined in relation to the number of capacitors associated with the first location which are switched in or out of the network. The measured voltages are communicated to a voltage control. Voltage deviations of the measured first voltage are determined relative to a predetermined voltage range intended to be present at the first locations. Switching the capacitor means into or out of the network is determined by the voltage control in accordance with a voltage rise table. A VAR flow controller is responsive to the voltage at the first locations, the effect of the VAR generation by the capacitors and the change of VAR generation by the capacitor. A decrease in voltage at the customers saves energy use. A decrease in the VAR generated upstream of the customer results in greater efficiency of energy generation.

Diesel Generator Handbook

Abstract: Reciprocating internal combustion engines Power rating and performance A C Generators - general A.C. generators - performance characteristics Load considerations Engine governing Automatic voltage regulation Parallel operation of generating sets Switchgear and controlgear Prime mover and generator protection Emergency and standby AC power supplies Fuels and lubricating oils Installation and commissioning Plant noise reduction Operation and maintenance. Appendices. Index.

Voltage control improvement through capacitor and transformer tap optimization

Abstract: The authors present a study of the existing and planned voltage control devices on the Ohio Edison (OE) transmission and subtransmission system. These devices included 104 transformers, most of which are fixed tap, and over 100 sites for new or additional capacitor bank installations. The intent was to determine the transformer tap settings and reactive allocation to provide the best possible voltage profile for all foreseeable system conditions while minimizing losses and reactive imports. Due to the large number of voltage control devices being studied, an optimal power flow (OPF) was used for most of the analysis. The use of an OPF eliminated a significant amount of the trial and error work normally associated with this type of study. This study demonstrates the benefit of an OPF for transmission planning studies in addition to previously demonstrated system operation benefits. >

Multiple-voltage control circuit of battery or multiple independent DC power

Abstract: Circuit of multi-voltage control circuit of battery of multiple independent DC power consists of a diode compound switch contact for resisting sparkle and segmented current when multi-voltage switches add the non-sparkle switch for series of solid switch member which forms linear voltage adjustment of basic grade and voltage of low loss, or chopped wave voltage adjustment of low pulse. The advantages of the present invention are that it loses less thermal, is highly efficient, and has low pulse. It can provide fine quality graded voltage and a voltage adjustment between further grades.

Reactive power dispatch incorporating voltage stability

Abstract: The cause of the 1977 New York blackout has been proved to be the reactive-power problem. The 1987 Tokyo blackout was believed to be due to a reactive-power shortage and a voltage collapse at the summer peak load. These events have confirmed the importance of reactive-power planning and dispatching in maintaining the security of modern power systems. Appropriate control of system voltage profiles can enhance system security and may also reduce system losses. Previous investigations by the same authors have shown that a voltage collapse proximity indicator based on the optimal impedance solution of a two-bus system can be extended to an actual network. The authors describe a linear reactive power dispatch algorithm which incorporates this indicator to minimise the possibility of voltage collapse in the system.

Power inverter for generating voltage regulated sine wave replica

Abstract: A power inverter formed by several transformers having their secondary windings wired in series and their primary windings connected to respective switching bridges. The turns ratios of each of the primary windings vary from each other by a factor of 3 to provide good voltage resolution over a wide dynamic range. The switching bridges are controlled by a decoder and timing circuit which is, in turn, controlled by a microprocessor. The microprocessor closes the switches in the switching bridges in up to 27 different combinations to produce 27 different output voltages, thereby generating a relatively accurate replica of a sine wave. Voltage regulation is accomplished by sampling the A.C. voltage, comparing the magnitude of the A.C. voltage to a reference voltage, and adjusting the selection of output voltage values so that the A.C. voltage matches the reference voltage. The switching bridge may also be controlled to convert an A.C. voltage applied to the transformer secondaries to a D.C. voltage for battery charging purposes.

Voltage pumping circuit for semiconductor memory devices

Abstract: A high density semiconductor device is provided with an improved voltage pumping (bootstrapping) circuit. The voltage pumping circuit generates at an initial power-up state a first output voltage which is substantially identical to the memory device source supply voltage. The pumping circuit then pumps the first output voltage up to a second output voltage which is higher than the first output voltage. The pumping operation is achieved prior to or upon the semiconductor memory device being enabled in response to a series of pulses output from an oscillator.

Electric power system for marine vehicles

Abstract: An electric power system for large marine vehicles in which one or more AC generators are shared as the ship's propulsion power source and the ship's electrical service power source. The voltage from the AC generator(s) is rectified to a reduced DC voltage such that voltage transients in the propulsor motor do not reflect into the ship service power system. Silicon controlled rectifier (SCR) bridges are utilized to convert the generator's AC voltage into a reduced DC voltage. As a supplement for emergency power, a rechargeable battery is included to provide power for propulsion and ship service.

Method and apparatus for high voltage level shifting

Abstract: A voltage level shifter circuit (10) for outputting an output high (18) and output low (18) signal is provided which accommodates multiple power supplies (12 and 22) at different relative voltage to each other. The voltage level shifter (10) includes an input stage (24) which is characterized by voltage ranges applicable to the process used to make the circuit. The voltage level shifter circuit includes an output stage (18) which is also characterized by the same voltage ranges which cannot be exceeded. The output stage outputs the translated output high (16) and output low (18) voltage signals. A clamping network (20) is employed to ensure that the output stage voltage ranges are not exceeded. The present invention implements a high voltage level shifter (10) using low voltage components by extending the breakdown capability of the voltage level shifter circuit (10) past the breakdown voltage of any single component in the circuit.

Electrical line-fault detector and circuit breaker device

Abstract: An electrical circuit breaker device for connection between a load device and a power source, capable of disconnecting the load device from the power source upon detection of an electrical fault condition present in the wiring between the load and the power source is provided. A time delay prevents the load from being disconnected due to the reporting of a temporary voltage fluctuation. One embodiment of the present invention measures a voltage value representative of the voltage across the source and compares it with the voltage drop across the load to determine the voltage drop due to the wiring between the source and the load. The load device is disconnected from the power source if the resulting power loss or voltage difference due to the resistance of the wiring indicates a power loss in the wiring sufficient to cause combustion. Another embodiment of the present invention compares an arbitrary voltage to the voltage drop across the load device to determine whether a fault condition exists within the wiring, and if such a fault condition is detected, the load device is disconnected from the power source.

Voltage regulator for field programmable gate arrays

Abstract: A voltage regulator especially adaptable for use with field-programmable gate arrays (FPGA). The voltage regulator is configurable as a true voltage regulator or, alternatively, as a pseudo-voltage regulator. The voltage regulator includes circuitry to rapidly generate an operating voltage for the core or nucleus logic elements. Additional circuitry is provided to reduce the steady-state power consumption once the operating voltage is reached. To compensate for die-to-die variations, additional circuitry is also provided to adjust the compensation delays or switching rates.

Power supply apparatus for a vehicle having batteries of different voltages which are charged according to alternator speed

Abstract: A power supply apparatus for a vehicle includes an alternator for generating an output voltage for charging a first battery and a second battery having a higher voltage than the first battery. The output voltage of the alternator is controlled by a voltage regulator in accordance with the rotational speed of the alternator. When the rotational speed is in a low speed range, the voltage regulator controls the output voltage of the alternator to a first value suitable for charging the first battery. When the rotational speed is in a high speed range, the voltage regulator controls the output voltage of the alternator to a second value higher than the first value and suitable for charging the second battery. The output voltage of the alternator is switched between the first value and the second value at a rotational speed at which the output power of the alternator at the first output voltage equals the output power at the second output voltage. The apparatus may include a voltage converter which reduces the output voltage of the alternator to a voltage suitable for charging the first battery when the alternator is generating power at the second voltage. Alternatively, when the alternator is generating power at the second voltage, a point of the armature winding of the alternator having a voltage less than the output voltage of the alternator may be connected to the first battery to charge the first battery.

High voltage dc-dc converter with dynamic voltage regulation and decoupling during load-generated arcs

Abstract: A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

Engine-driven generator

Abstract: An engine-driven generator includes an internal combustion engine, a permanent magnet alternator and an AC to AC converter. The output frequency and voltage of the permanent magnet alternator are largely dependent on engine speed and the alternator load. The AC to AC converter converts the speed-dependent alternating potential developed by the alternator to another alternating potential whose frequency and voltage are largely independent of engine speed. Voltage regulation is provided by varying the engine speed in accordance with the load current. Frequency regulation is provided by frequency dividing the alternator output by an integer divisor that varies in accordance with engine speed. Additional voltage regulation is provided by deleting selected cycles of the alternator output current as needed to maintain the RMS output voltage within predetermined limits. A stepper motor coupled to the throttle of the internal combustion engine controls the speed of the engine in accordance with commands received from an electronic system control.