Showing papers on "Voltage regulator published in 1990"

Shunt capacitor sizing for radial distribution feeders with distorted substation voltages

Abstract: An algorithm for optimizing shunt capacitor sizes on radial distribution lines with nonsinusoidal substation voltages such that the RMS voltages and their corresponding total harmonic distortion lie within prescribed values is presented. The problem is formulated as a combinatorial optimization problem with inequality constraints. A simple heuristic numerical algorithm that is based on the method of local variations is proposed to determine an optimal solution. An example shows that optimal capacitor sizes found by neglecting the harmonic components may result in unacceptable voltage distortion levels. >

Voltage stability condition in a power transmission system calculated by sensitivity methods

Abstract: A new method for determining the voltage stability condition in a power system is presented. The method is based on sensitivity techniques, taking into account the limits on reactive power generation capacities. A distance to voltage collapse in terms of MVAr is defined as a measure of system security. Results from calculations on a 480-bus network with 140 generators are presented. The method can be efficiently used for reactive power security evaluation in both system planning and operation. >

A voltage reduction technique for digital systems

Abstract: A self-regulating on-chip voltage-reduction circuit that adjusts the internal supply voltage to the lowest value compatible with chip speed requirements is described. Besides enhancing reliability, this technique allows power savings. The technique is based on regulation of the supply voltage of an equivalent critical path, a small circuit with delay V/sub dd/ properties proportional to those of the actual critical path. The output of this equivalent critical path is compared with the output of a second identical equivalent critical path which is connected to the full supply voltage and serves as a reference. In a first-order approximation the ratio of the delay of a critical path to the period of a ring oscillator is a constant that depends only on the number of gates, the dimensions of the transistors, and the load capacitances. This means that a ring oscillator can be used as an equivalent critical path for all digital circuits. Moreover, when the supply voltage of a ring oscillator (VCO) is changed the frequency changes. The voltage regulator principle can be implemented with a phase-locked loop (PLL). By adjusting the VCO supply voltage, the PLL causes the VCO to oscillate at N*f/sub in/. If the dimensions of the VCO transistors and the division ratio N are such that the critical path functions correctly at the regulated voltage, it will always function correctly, as changing parameters temperature or frequency f/sub in/ affect the VCO in the same way as the circuitry. >

Voltage angle lock loop control of the boost type PWM converter for HVDC application

Abstract: The advent of high-power, high-frequency, solid-state switches with fast gate turn-off capabilities suggests that pulse-width-modulated (PWM) techniques can soon be introduced into HVDC (high-voltage direct-current) applications. A boost-type PWM converter with voltage angle lock control that is tailored to the utility environment is described. Experimental test results for 1 kVA models show that the advantages are substantial. >

A drive device for driving a matrix-type LCD apparatus

Abstract: A drive device for driving a matrix-type LCD apparatus is disclosed. The drive device comprises a signal electrode drive circuit for converting an input digital video signal into a voltage signal having one of predetermined plural levels, and supplying the voltage signal to one of the signal electrodes. The signal electrode drive circuit comprises: a video signal memory (30) for storing the input digital video signals; a data decoder (40) for decoding the information contained in the stored digital video signals; a voltage signal supply circuit (50) for outputting a plurality of voltage signals with different levels; and a selection circuit (55) for selecting one of the plurality of voltage signals in accordance with the output of the data decoding circuit.

Cascaded voltage collapse

Abstract: The dynamic phenomena of power system voltage collapse are analyzed by the method of dynamic simulation using induction motor models. From the viewpoint of dynamic phenomena, the voltage collapse starts locally at the weakest node and spreads out to the other weak nodes. The main conclusions drawn from this study are as follows. The voltage can be recovered, even after the node voltage is lowered beyond its static critical value. The operating state corresponding to the lower voltage solution is not always unstable. It could be stable depending upon the dynamic characteristics of individual loads, even if they are not of constant impedance type. The voltage collapse is initiated at the weakest node and spreads out to the other weak nodes. These results can be applied to radial voltage collapse phenomena. >

Power supply with improved power factor correction

Abstract: A regulated voltage converter circuit includes a storage inductor and a controlled semiconductor switch connected in series circuit to a pair of input terminals that supply a full wave rectified voltage of a sinusoidal 50 Hz AC input voltage. A power factor amplifier receives a divided part of the rectified voltage and produces an output control voltage V M of a predetermined waveform (Fig. 2c). A comparison circuit compares the control voltage V M with a ramp voltage that is proportional to the current flowing through the semiconductor switch. The comparison circuit supplies PWM pulses to a control electrode of the semiconductor switch so as to regulate the output voltage of the converter circuit. The control voltage (V M ) waveform is chosen so as to produce near unity power factor correction at the input of the converter circuit.

Self powering technique for integrated switched mode power supply

Abstract: A regulator circuit is connected to a transformer. The transformer has a primary winding connected to a rectified D.C. voltage signal and has a feedback winding. A feedback capacitor is coupled across the feedback winding of the capacitor. The regulator circuit includes a high voltage switching transistor, a pulse width modulator which controls the high voltage switching transistor and a high voltage power up transistor. At power up, the high voltage power up transistor connects the single high voltage pin to the feedback capacitor allowing the feedback capacitor to begin charging. When the feedback capacitor has charged past a first threshold voltage the pulse width modulator alternately turns the high voltage switching transistor on and off. When the high voltage switching transistor is turned on, the high voltage pin is connected to ground and current passes through the primary winding of the transformer, and thus current is generated through the feedback winding into the feedback capacitor. Additionally, when the high voltage power up transistor is on, the gate of the high voltage power up transistor is connected to ground turning the high voltage power up transistor off. Once the feedback capacitor has been charged to a second threshold voltage a transistor connects the gate of the high voltage power up transistor to ground thus permanently switching the high voltage power up transistor off.

Analysis of HVDC converters connected to weak AC systems

Abstract: A method of analysis is presented and applied to a model system which is well established and extensively used in studies of HVDC converters connected to weak AC systems. The method is based on fundamental frequency quantities. A variety of phenomena and interactions of the AC/DC system can be analyzed, and basic understanding of the mechanisms can be gained. Some important properties of the system, such as voltage/power stability in different control modes and stability of tap changer action, are analyzed. Furthermore, they dynamics of a system consisting of a static VAr compensator (SVC) and DC converters are analyzed, and the requirements for stable operation are derived within the framework of the method of analysis presented. These results are verified by time simulation done by a transient stability program. >

Adaptive compensating ramp generator for current-mode DC/DC converters

Abstract: A circuit (20, 40, 50, 60) for generating an optimal compensating ramp voltage signal V cramp , with the minimum necessary slope, m c for a current mode DC/DC converter is shown The adaptive compensating ramp generating circuit (20) is comprised of two voltage dividers (22, 24), the first voltage divider 22 divides an input voltage V IN and the second voltage divider 24 divides an output voltage V OUT The first voltage divider (22) has two resistors (26, 28) in series: the first resistor (26) has a resistance of (1/B-1) * R ohms and the second resistor (28) has a resistance of R ohms V OUT is divided by the second voltage divider (24) having two resistors (29, 30) in series: the first resistor (29) has a resistance of (1/A-1) * R ohms and the second resistor (30) has a resistance of R ohms The constants A, B, and C are selected for the particular type of DC/DC converter employed The divided voltages A * V OUT and B * V IN are input into a voltage controlled current source (32) The voltage controlled current source (32) has a scaling resistor R scale , an amplifier (36), a transistor Q, and a diode D1 The output of the current source (38) is coupled to a capacitor C ramp whose voltage realizes the slope of the compensating ramp signal, V cramp The capacitor C ramp is charged through R scale

Photovoltaic source switching regulator with maximum power transfer efficiency without voltage change

Abstract: For matching the electrical impedance of a photovoltaic power source and a load, a switching regulator circuit has properties especially suited to the conversion of photovoltaic power to electric power. The circuit regulates the source voltage for maximum power output and supplies a load voltage equal to the regulated source voltage. The circuit comprises two branches: one in which a switching transistor (38), a diode (40), and filter components (30) and (42) provide a positive voltage; and the other in which similar components (22, 32, 24, and 44) in a different configuration, provide a negative voltage. The load voltage is the sum of these and is equal to the input voltage. Since the source voltage is substantially constant, the switching regulator in effect converts the photovoltaic power source to a constant-voltage source. The circuit provides improved performance and thus enhances the utility of photovoltaic power sources.

Microprocessor based harmonic elimination in chopper type AC voltage regulators

Abstract: A control strategy for firing instances in pulse-width-modulated (PWM) AC voltage regulators is presented. In this type of regulator, output voltage is controlled by varying the on/off time ratios of a series-controlled switch. Using a microprocessor as a controller makes it possible to vary firing instances at will according to a predetermined timing regime. One of these regimes, proposed here, involves adjusting firing instances so that selected dominant lower-order harmonics can be eliminated. This in turn leads to improved system power factor and efficiency. The theoretical principles used in evaluating firing instances are described, and experimental results verifying the analysis are presented. >

An adaptive generator excitation controller based on linear optimal control

Abstract: An adaptive excitation controller for a synchronous generator based on the linear optimal control theory is proposed. The generator operating conditions are tracked by a model whose parameters are identified every sampling interval using the actual input and output of the generator. The control is computed by solving a third-order Riccati equation and the identified model parameters. Studies on a single-machine infinite-bus system and a three-machine infinite-bus system show that the proposed controller exhibits better performances than an automatic voltage regulator (AVR) with a conventional power system stabilizer (PSS). >

Implementation of conservation voltage reduction at Commonwealth Edison

Abstract: The implementation of a conservation voltage reduction program is described. Such a program involves the calibration of substation voltage-regulating equipment so that distribution system voltages are maintained at as low a level as possible within the standard acceptable range. Initial distribution system voltmeter data were used to estimate potential voltage reductions. Program results show that an average reduction of 1.6 V was achieved. Comparison of this result with the initial estimate indicates that the feasibility of additional voltage reductions depends on the definition of acceptable service quality. >

High frequency link DC-AC converter for UPS with a new voltage clamper

Abstract: A power conversion system for a UPS (uninterruptible power supply) using a high-frequency link is described. The proposed UPS consists of a high-frequency inverter, a high-frequency transformer, and a cycloconverter with a new voltage clamper. The clamper effectively reduces the power loss of the conversion system. The voltage clamper gave an improved DC-AC conversion efficiency of about 10% more than when a conventional RC snubber was used. When source-commutation was used, DC-AC conversion efficiency was improved by about 5%. When the voltage clamper was used both DC-AC conversion efficiency and the output voltage characteristic without the automatic voltage regulator were improved to source commutation. Fabrication of a 10 kVA high-frequency-link DC-AC power converter is described and its loss reduction effect is demonstrated. >

Lighting circuit for high-pressure discharge lamp for vehicles

Abstract: A lighting circuit for high-pressure discharge lamp or high-pressure discharge lamp for vehicular use including a DC voltage booster circuit, a voltage detector, a current detector, an a control circuit. The booster circuit boosts the input voltage from a DC voltage input terminal to provide an output voltage that is converted into an AC voltage to be applied to a high-pressure discharge lamp. The voltage detector detects the output voltage of the booster circuit. The current detector detects an output current of the booster circuit. The control circuit applies a control signal corresponding to signals from the voltage detector and the current detector to control the output voltage of the booster circuit. The control circuit, the voltage detector and the current detector constitute a feedback system for the booster circuit. Also, in lighting the discharge lamp from a cool state, therefore, the operation of the timer circuit causes transition to constant power control using rated power after execution of control so as to supply power exceeding the rated power to the output voltage detector and the output current detector sequentially.

Electrical power supply for short term power interruptions

Abstract: A direct current power supply for instantaneously providing tens of kilows of electrical energy for brief periods, such as 100 ms, during momentary power interruptions between a load and an electrical power source having a supply voltage includes a capacitor having an initial voltage charge preferably greater than the supply voltage. The cathode of a zener diode is operably coupled to the capacitor. The anode of a second diode is operably coupled to the anode of the zener diode. A solid state switch has a power input operably coupled between the capacitor and the cathode of the zener diode, a power output operably coupled between the anodes of the zener diode and second diode, and an enabling input, so that the switch may be triggered to conduct electrical power whereby voltage from the capacitor is conducted through the switch to the anode of the second diode when an enabling signal is provided to the enabling input. The anode of a third diode is operably coupled to the voltage supply, and the cathode of the third diode is connnected to the load. The cathode of the second diode is connected between the cathode of the third diode and the load. A low supply voltage detecting circuit operably coupled between the enabling input of the solid-switch and the supply voltage provides the enabling signal to trigger the switch into a conduction mode when the supply voltage is below a predetermined voltage level. t

High frequency surgery device for cutting and/or coagulating biologic tissue

Abstract: A high frequency AC electro-surgery apparatus is equipped with an automatic regulation loop for controlling the output voltage (U a ) rather than the output power. An electrically isolating coupling in the form of an isolation transformer (5) is followed by a voltage converter (6) to provide DC voltage signal (a) proportional to a measure of the high frequency AC output voltage (U a ). The DC voltage signal (a) is supplied to a regulating amplifier (7) to which a reference voltage signal (b) is supplied by a reference voltage source (8), to produce an output signal (c) that is furnished to the control input of an electronically controlled power supply (16). The latter controls the operating voltage (U b ) for the amplifier (2) of the high frequency AC generator in such a manner that the output AC voltage (U a ) at the output terminals (10, 11) corresponds to a desired value set by the reference voltage signal (b).

Superconductive voltage stabilizer

Abstract: A superconductive voltage stabilizer comprises an AC/DC converter, a voltage regulator, an energy storage cell and a superconducting energy storage coil. Alternating current is converted to direct current and stored in a superconducting coil. The stored direct current is selectively delivered to an energy storage cell to satisfy the energy requirements of a load. A voltage regulator senses the energy drawn from the energy storage cell and when appropriate releases stored energy from the superconducting coil to maintain a constant supply of energy to the load.

Load response control and method

Abstract: A regulator is responsive to an input signal proportional to the system supply voltage for adjusting the current flowing in the field windings of an electrical alternator which controls the output power thereof. The primary regulation loop of the regulator generates a pulse train having a duty cycle inversely proportional to the amplitude of the input signal while an oscillator provides a sawtooth signal at a predetermined frequency which controls the response frequency of the regulator. The regulator limits the rate of increase in the duty cycle of pulse train upon detecting a decrease in the system supply voltage by converting the duty cycle of the pulse train to a charging signal for developing a voltage across a capacitor proportional to the duty cycle of the pulse train. The voltage across the capacitor is compared to the sawtooth signal and triggers a latch which disables the output signal of the regulator as the duty cycle lengthens in response to the decrease in the system supply voltage. The voltage across the capacitor is increased each oscillator cycle until the duty cycle reaches the value required to support the output power of the alternator.

High frequency quasi-resonant DC voltage notching inverter for AC motor drives

Abstract: A high-frequency quasi-resonant DC voltage notching inverter derived from a resonant DC link inverter is discussed. The quasi-resonant link circuit provides a DC voltage with resonant notches to the inverter such that inverter switches can switch at zero voltage crossing. Compared to resonant DC link inverters, the size of passive components is reduced. Compared to traditional pulse-width modulation (PWM) inverters, the efficiency and performance are largely improved because high-frequency switching occurs at zero voltage crossing. The resonant voltage notches can be created at any instant, which permits the inverter to operate at standard or optimized PWM control. A least current error square method is proposed to incorporate the quasi-resonant DC voltage notching inverter, resulting in minimum output current ripples. For regenerative-type AC drive operation, a bidirectional current initialization is included in the circuit. The complete system was simulated using PC-SIMNON and fabricated as a laboratory prototype. >

Semiconductor integrated circuit chip having an identification circuit therein

Abstract: A semiconductor integrated circuit chip has an identification circuit connected between a power voltage supply terminal and one of the input terminals of the chip. The identification circuity includes a voltage limiter to limit the input potential difference between the power voltage supply terminal and the input terminal to a predetermined voltage level. The identification circuit further includes an option device connected to the voltage limiter to provide identification information of the chip. According to the identification circuit, chip identification testing may be achieved with existing input/output and power supply terminals, thereby eliminating the need for extra test and diagnosis pins or additional identification equipment employed during testing.

Hydro-Quebec multiple SVC application control stability study

Abstract: A report is presented on the SVC (static VAR compensator) control stability studies undertaken as part of an overall system improvement project. It is shown that for an all-shunt network, a regulator setting of T/sub r/=0.5 s would be stable for many contingencies, but some contingencies would require gain-supervisor action and transfer-trip automatisms to ensure system security. The transfer-trip automatisms would be complex and require much study to identify. Thus, from the perspective of SVC voltage regulator stability, the all-shunt option is the least desirable. For a mostly series network, a regulator setting of T/sub r/>0.25 s provides good stability margin for all system contingencies. This means that system security is not dependent upon a complex set of transfer-trip automatisms. A few new design considerations for the power system have been identified, due to adding series compensation. The major new phenomenon is a low-frequency oscillation between shunt reactors and the series capacitors, which has very little natural damping. The SVC voltage regulators will decrease the damping of these modes, and may cause them to become unstable. To insure against such instability, it is proposed that high-pass filters with a break frequency of 20 Hz be applied to all SVCs. >

New challenge: Voltage stability

Abstract: Line and transformer thermal limits have become less restrictive as our networks have become more dense. Static VAR systems (SVSs) and excitation stabilizers have raised transfer limits in stability limited systems. The resulting transmission capacity is being used to ship economy purchases among neighbors, and to support new generation remote from load centers. Today, the average transmission line is loaded more heavily than ever before, and this has given rise to a new problem, voltage instability. The author discusses the problem of voltage instability. Techniques to improve voltage stability are presented.

A tunable CMOS-DRAM voltage limiter with stabilized feedback amplifier

Abstract: The authors present two developments for a CMOS-DRAM voltage limiter: a precise internal-voltage generator, and a stabilized driver composed of a feedback amplifier with compensation. The voltage limiter's features include generating a PMOS-V/sub T/ difference, being capable of voltage tuning with fuse trimming, and compensation in the driver circuit through zero insertion. It provides a voltage impervious to supply-voltage and substrate-voltage boundings, temperature variation, and process fluctuation, while ensuring the feedback-loop stability with a phase margin of 55 degrees for a time-dependent load of DRAM circuit. The proposed circuits are experimentally evaluated through their implementation in a 16-Mb CMOS DRAM. A temperature dependency of 1.4 mV/ degrees C and a voltage deviation within +or-10% for process fluctuation are achieved. The voltage is stabilized within +or-3% for V/sub CC/ bounce and +or-10% for memory operation. >

Frequency synthesizer allowing rapid frequency switching

Abstract: A frequency synthesizer is designed to modify voltage value data read out of a memory in accordance with the output voltage of a filter, and apply a d.c. voltage corresponding to the modified data to a second variable-capacitance diode at the control input of a VCO, thereby allowing the VCO frequency switching without imposing a significant fluctuation of the application voltage to a first variable-capacitance diode and accomplishing a short channel switching time and stable operation against temperature fluctuation. The device is further designed to supply a voltage setup value read out of the memory to the second variable-capacitance diode thereby to reduce the frequency matching time at channel switching, and to determine such another voltage setup value as to reduce the time of phase matching based on the trend of change in the filter output voltage and supply the value to the second variable-capacitance diode.

A new synchronous-switch post regulator for multi-output forward converters

Abstract: A synchronous-switch post regulator (SSPR) circuit based on a novel charge-pump gate drive is described. It resolves the technical barriers due to the difficulty of designing an effective gate drive and synchronized trailing-edge pulse width modulation (PWM) in a straightforward manner. It has been demonstrated that in the medium current range, the power loss of this SSPR is much less than when the linear regulator approach is used. With additional advantages of easy on/off control, better overcurrent protection, and the potential of being integrated into a monolithic IC, this SSPR compares favorably with the magnetic amplifier post regulators. >

Open loop motor control with both voltage and current regulation

Abstract: An open-loop pulse width modulation (PWM) motor control for an induction motor includes a voltage regulator loop which is wrapped around a current regulator. When a load is suddenly encountered by the motor, voltage drops at the output of the current regulator. This is sensed and fed back to a voltage regulator and to a current limiter which then adjust the input signal to the current regulator to prevent an overcurrent that will trip a circuit protection device. The voltage regulator and current limiter may be implemented in either analog or digital circuitry.

Electric power system with line drop compensation

Abstract: An electric power system having line drop compensation includes a controllable electric power source 10 having an output for supplying voltage to a power bus 14, a local voltage regulator 12 for monitoring the output voltage of the power source and for producing a control signal representative of a desired nominal output voltage of the power source, and a remote voltage regulator 20 for sensing voltage on the power bus at a point of regulation located away from the power source. The remote voltage regulator produces a pulse width modulated signal having a duty cycle representative of the voltage at the point of regulation. A pulse width to trim bias converter 26 receives the pulse width modulated signal and produces the trim signal having a magnitude representative of the duty cycle of the pulse width modulated signal. This trim signal is combined with the control signal of the local voltage regulator to produce a modified control signal for controlling the output voltage of the power source to produce a predetermined voltage at the point of regulation.

Vehicle AC generator control system

Abstract: A control device for a vehicle AC generator provided with a rectifier and a battery connected to the latter comprises a voltage regulator with a switching element connected to the field coil of the generator, to adjust the output voltage of the generator to a predetermined value in which a field current is controlled to eliminate a load torque which otherwise occurs immediately after the start of the engine, to stabilize the rotation of the engine, and to prevent the production of belt slip noises at low temperatures. Further, when the generator output is restored, the production of a belt slip noise is prevented, and the decrease in the speed of rotation of the engine is prevented.