Showing papers on "Voltage regulation published in 1989"

Optimal capacitor placement on radial distribution systems

Abstract: The problem of capacitor placement on a radial distribution system is formulated and a solution algorithm is proposed. The location, type, and size of capacitors, voltage constraints, and load variations are considered. The objective of capacitor placement is peak power and energy loss reduction, taking into account the cost of the capacitors. The problem is formulated as a mixed integer programming problem. The power flows in the system are explicitly represented, and the voltage constraints are incorporated. A solution method has been implemented that decomposes the problem into a master problem and a slave problem. The master problem is used to determine the location of the capacitors. The slave problem is used by the master problem to determine the type and size of the capacitors placed on the system. In solving the slave problem, and efficient phase I-phase II algorithm is used. >

Optimal sizing of capacitors placed on a radial distribution system

Abstract: A capacitor sizing problem for capacitors placed on a radial distribution system is formulated as a nonlinear programming problem, and a solution algorithm is developed. The object is to find the optimal size of the capacitors so that the power losses will be minimized for a given load profile while considering the cost of the capacitors. The formulation also incorporates the AC power flow model for the system and the voltage constraints. The solution algorithm developed for the capacitor sizing problem is based on a Phase I-Phase II feasible directions approach. Novel power flow equations and a solution method, called DistFlow, for radial distribution systems are introduced. The method is computationally efficient and numerically robust, especially for distribution systems with large r/x ratio branches. DistFlow is used repeatedly as a subroutine in the optimization algorithm for the capacitor sizing problem. The test results for the algorithm indicate that the method is computationally efficient and has good convergence characteristics. >

Structural analysis of the electrical system: application to secondary voltage control in France

Abstract: The voltage control of the French EHV power system is organized in three levels (primary, secondary, and tertiary) which concern distinct geographical areas and time constants. The authors present studies conducted to reach an automatic determination of zones and pilot nodes based on the examination of the structure of the network. The concept of electrical distance has been developed, and its close relationship with the theory of information is underlined. This concept allows the concept of structural controllability and observability of proximity to be extended to the power system. The combined use of this electrical distance and typological analysis algorithms has proven an effective method for the identification of the secondary voltage control zones of the French grid. >

Combined low-cost, high-efficient inverter, peak power tracker and regulator for PV applications

Abstract: A novel compound power converter that serves as a DC-to-AC inverter, maximum power point tracker (MPPT), and battery charger for stand-alone photovoltaic (PV) power systems is introduced. A theoretical analysis of the proposed converter is performed, and the results are compared with experimental results obtained from a 1.5 kW prototype. The overall cost of PV systems can thus be reduced by using load management control and efficiency-optimization techniques. Power flow through the converter is controlled by means of a combination of duty cycle and output frequency control. With load management, large domestic loads, such as single phase induction motors for water pumping, hold-over refrigerators, and freezers, can be driven by day at a much higher energy efficiency. This is due to the high efficiency of the inverter with high insolation, and because the inverter uses the energy directly from the solar array. The battery loss component is thus reduced. >

Application of Newton's optimal power flow in voltage/reactive power control

Abstract: The authors consider an application of Newton's optimal power flow to the solution of the secondary voltage/reactive power control in transmission networks. An efficient computer program based on the latest achievements in sparse matrix/vector techniques has been developed for this purpose. It is characterized by good robustness, accuracy and speed. A combined objective function appropriate for various system load levels with suitable constraints for the treatment of power system security and economy is also proposed. For the real-time voltage/receiver power control, a suboptimal power flow procedure has been derived by using the reduced set of control variables. This procedure is based on sensitivity theory applied to the determination of zones for the secondary voltage/reactive power control and a corresponding reduced set of regulating sources, whose reactive outputs represent control variables in the optimal power flow program. As a result, the optimal power flow program output becomes a schedule to be used by operators in the process of the real-time voltage/reactive power control in both normal and emergency operating states. >

Discrete pulse modulation strategies for high-frequency inverter systems

Abstract: High-performance, high-frequency inverter systems for UPS (uninterruptible power system) applications cannot be easily realized using conventional hard-switched PWM inverter topologies. Adoption of typical soft-switched inverters such as the resonant DC link inverter, require the use of discrete pulse modulation strategies. New controller structures are necessary to cope with stringent voltage regulation and distortion constraints in the presence of unbalanced and nonlinear loads. A controller that utilizes a load current feedforward strategy with a cost function current regulator to achieve excellent transient performance characteristics is presented. Voltage regulation is ensured using a synchronous frame regulator. Detailed simulation and experimental results verifying the concepts are presented. Although this work focuses on soft-switching inverters, the control concepts can be applied to conventional hard-switching inverters as well. >

Current sharing modular power supply

Abstract: A regulator circuit for equalizing the load currents of a plurality of power supply modules connected in common to feed a common load. Each of the modules includes a pulse-width modulator for adjusting the duty cycle of the module, thereby to adjust the voltage regulation point and corresponding current output of the module. A current sensor produces a current level signal proportional to the current output of the module. The current level signal is applied through a current amplifier to generate a corresponding variable error voltage. A fixed reference voltage derived from the output voltage and the variable error voltage are applied to the pulse-width modulator to vary the duty cycle so as to produce a decrease in load voltage with an increase in current output and an increase in the load voltage with a decrease in current output thereby equalizing the current output of the module with modules having substantially equal output voltages. A low pass filter interposed in the regulator feedback path assures current sharing under quasi steady-state conditions without degradation of high frequency response to dynamic load changes.

A line voltage regulator/conditioner for harmonic-sensitive load isolation

Abstract: A technique is presented for the isolation of harmonic-sensitive loads from harmonic-producing loads, such as rectifiers and power converters. The solution, referred to as a line voltage regulator/conditioner (LVRC), utilizes a combination of a series and a parallel active power filter. The series filter isolates the sensitive loads on the output side of the LVRC from the nonlinear, distortion-producing loads on the input side by correcting for the harmonic voltage distortion present at the input. In addition, the series filter is utilized to regulate the output voltage. The parallel filter acts to generate the harmonic current required by the loads connected on the output side, therefore reflecting a linear load to the source. >

AC to DC power conversion circuit with low harmonic distortion

Abstract: In an AC to DC power conversion circuit including a boost inductor connected in series between a full-wave rectifier and a DC load, a switch is connected to selectively shunt boost inductor current from the load. Switch conduction is controlled by a pulse width modulator generating switching pulses at a high fixed frequency. The pulse widths are automatically varied as a function of boost inductor current, load voltage, and an ideal sinusoidal waveform derived from the AC input voltage to force the boost inductor current to closely conform to the ideal sinusoidal waveform and thus minimize harmonic distortion, while achieving load voltage regulation and near unity power factor.

Voltage Compensation of an Induction Generator with Long-Shunt Connection

Abstract: Preliminary studies of voltage vs. speed relationships, stability of generated voltage, and voltage compensation of the self-excited induction generator are presented. In order to improve the voltage regulation, the long-shunt connection of the capacitors to the generator is used. The magnetizing inductance of the machine is used as a saturable reactor. The values of the capacitors for series and parallel connections are obtained from the saturation characteristics of the machine. Experimental results are reported. The maximum voltage drop is about 4%. >

Switched power supply with current mode regulation

Abstract: A switched mode power supply operating with current mode regulation comprises an output switch coupled to a first winding of a transformer and to a source of input supply voltage. The switch is responsive to a control signal for initiating a pulse width modulated pulse voltage in a second winding of the transformer. A supply circuit coupled to the second winding generates an operating voltage. A feedback signal source monitors both current flowing through the first winding and the operating voltage. A control circuit coupled to the feedback signal source includes an oscillator for generating the control signal at a substantially constant frequency during normal operation and at a variable frequency during abnormal operation. The control circuit is responsive both to the current and to variations of the operating voltage over a regulating range, in a negative feedback loop. The control signal varies the on-time conduction of the output switch in each cycle to stabilize the operating voltage. The oscillator has a frequency control responsive to variations of the operating voltage outside of the regulating range, in a positive feedback loop. The on-time conduction of the output switch is limited to a maximum value by comparing the current to an error signal related to the operating voltage. The error signal varies when the operating voltage is within the regulating range but is limited in magnitude when the operating voltage falls below the regulating range. A DC feedback voltage forms a part of both the negative and positive feedback loops.

Cycloconverter operation under a new scalar control algorithm

Abstract: A thorough analysis is conducted of a novel scalar control method for the operation of direct frequency changers using bidirectional switches that operate at high switching frequencies. The method uses the instantaneous voltage ratio of specific input phase voltages to generate the active and zero states of the various switches. A voltage transfer ratio as high as 0.87 is obtained under synchronous and asynchronous operation with a conventionally connected three-phase load. Moreover, the converter operation can be set to produce almost any power displacement factor, independently of load power factor. >

Intelligent battery charging system

Abstract: The present invention is a battery charging system that provides automaticoltage selection, short circuit protection, and delayed output to prevent arcing or pitting. A second embodiment of the invention provides a homing beacon which transmits a signal so that a battery powered mobile robot may home in on and contact the invention to charge its battery. The invention includes electric terminals isolated from one another. One terminal is grounded and the other has a voltage applied to it through a resistor connected to the output of a DC power supply. A voltage scaler is connected between the resistor and the hot terminal. An On/Off controller and a voltage mode selector sense the voltage provided at the output of the voltage scaler. The On/Off controller provides an output whenever Va

Two wire low voltage dimmer

Abstract: A low voltage two wire dimming circuit comprises a voltage compensating circuit for regulating the RMS value of an AC voltage applied to a load and a correcting circuit for eliminating damaging DC current that may flow through the load. The voltage compensating circuit adjusts the firing angle of an electronic switch disposed in the dimming circuit to compensate for fluctuations in the AC supply voltage. The correcting circuit advances or retards the firing angle during selected half cycles to correct for asymmetries in the AC load voltage waveform caused by excessive DC current. According to the invention, there is also provided a two wire low voltage dimming circuit without voltage compensation but having improved dimming ability at low load currents and improved resistance to the flow of damaging DC currents.

Hybrid high speed voltage regulator with reduction of Miller effect

Abstract: A linear regulator employing a field effect transistor (FET) pass element to supply a pulsed load is programmed by a cooperating switching regulator such that an increased voltage differential is maintained across the FET to reduce response time during the leading edge of the load pulse and to thereafter reduce the voltage differential to achieve reduced power consumption and increased efficiency during the remainder of the load pulse.

Line voltage monitor and controller

Abstract: A line voltage monitor and controller disconnects AC-powered user equipment from an AC power line whenever the AC power line voltage is outside a predetermined operating voltage window. The equipment is automatically reconnected to the power line only after the power line voltage remains continuously within the operating voltage window for a predetermined delay period. The controller protects the user equipment from both over-voltage and under-voltage (brownout) conditions.

Load voltage detecting device for use in an apparatus for supplying a current variable with time to a load section

Abstract: A load voltage detecting device for use in an apparatus for supplying a current variable with time to a load section. The load voltage detecting device for an apparatus such as a pulsed are welding machine can accurately detect the load voltage from the output voltage of the pulse current supplying section without being affected by the reactor component and the resistance component of the load section and the elements extended to the load section such as the cables and the welding torch.

Electric power supply system for automobile

Abstract: This specification discloses an electric power supply system for an automobile having a load which needs a higher voltage than the normal battery voltage. The electric power supply system of the present invention includes: a multi-phase AC generator having an armature winding, a field winding, a first rectifier for rectifying a multi-phase AC output of the armature winding, and a voltage regulation circuit for controlling a current in the field winding in accordance with a control signal to regulate an output voltage of the first rectifier; a battery charged by a DC output voltage of the first rectifier; a low-voltage load to be powered by the battery; a multi-phase transformer including a primary winding connected to a multi-phase AC output of the armature winding and a secondary winding for inducing a secondary multi-phase voltage higher than the voltage in the primary winding, the primary and secondary windings being electrically insulated from each other; a second rectifier for rectifying the multi-phase secondary voltage from the multi-phase transformer; and a high-voltage load to be powered by a DC output of the second rectifier.

Delay circuit for semiconductor integrated circuit devices

Abstract: A delay circuit for an IC device is disclosed, which comprises a charging/discharging circuit, a voltage divider and a comparator. The charging/discharging circuit selectively effects a charging/discharging operation in response to an input sigal to thereby generate a variable output voltage. The voltage divider divides a source voltage of the IC device to provide a reference voltage having a predetermined constant potential. The comparator is coupled to the charging/discharging circuit and voltage divider at its inverting input and non-inverting input, respectively, and compares the output voltage of the charging/discharging circuit with the reference voltage. A switch circuit is provided which performs a switching operation in response to the input signal to thereby electrically disconnect the non-inverting input of the comparator from the voltage divider. A capacitor is provided which retains the reference voltage at the non-inverting input of the comparator while the comparator is electrically disconnected from the voltage divider.

Internal low voltage transformation circuit of static random access memory

Abstract: In a static RAM having an internal low voltage transformation circuit, a word line drive circuit is provided which applies a low voltage, from an internal low voltage transformation circuit to a word line during read-out to improve the static RAM operating margin. The internal low voltage transformation circuit is formed by a reference voltage supply circuit and an internal voltage control circuit. A data hold voltage is supplied, when the static RAM is operating at a lower voltage, by a power pull-down device having a lower power consumption than the internal low voltage transformation circuit so as to achieve power consumption savings.

An expert system for load allocation in distribution expansion planning

Abstract: The load demand in Taiwan power system has been increasing during the past decade due to rapid economic growth on the island. To meet the ever-increasing demand, effective expansion plans for distribution systems are essential. The increasing load density can be met by either increasing the capacities of existing substations or planning a new substation. The load allocation problem arising from the latter approach will be addressed in the paper. The purpose of a load allocation plan is to reallocate some loads in the study system to the new substation such that certain desirable features of the distribution system such as minimum loss, minimum investment cost, high reliability, satisfactory voltage regulation, etc., can be met. Several approaches based on mathematical programming have been reported in the literature for the load allocation problem. However, these approaches require considerable computational effort and can not take many practical constraints into account. After an intensive interview with system planners in Taiwan Power Company, it was found that current practice of load allocation is a combination of hand calculations on such items as losses, voltage regulation, investment cost, reliability, etc. and some heuristic rules, which has been established based on past experience. The use of these rules in the utility motivated the development of a rule-based expert system for the load allocation problem. Considerable progress in the application of artificial intelligence (Al) technology to power system problems has been achieved during the past decade.

Data protection system in a data processing system

Abstract: A data protection system for protecting the data stored in a memory (10) in a data processing system having at least a channel system, a device controller (2) and an external storage device (6), includes: a memory (10) provided in the device controller and supplied to a power source voltage from a power source (1), and temporarily storing a data to be transferred; a battery (12) connected to the power source (11) and the memory (10), and charged by the power source (11) when the power source (11) is normal, and supplying a battery voltage to the memory (10) when the power source is accidentally interrupted. The data protection system also includes a first voltage check circuit (13) connected to the battery (12) which compares the battery voltage with a first reference voltage and generates a battery error signal when the battery voltage is lower than the first reference voltage and, a second voltage check circuit (14) connected to the battery (12), which compares the battery voltage with a second reference voltage and generates a battery charging signal when the battery voltage lies between the first reference voltage and the second reference voltage. The data protection system also includes a control circuit (2) for selectively determining two modes, one mode being a write-back mode for transferring the data from the memory to the external storage device after the data is stored in the memory, and the other being a write-through mode for directly transferring the data from the channel system to the external storage device (6) not through the memory (10) when the battery error signal and/or the battery charging signal is input to it.

Control circuit for heat fixing device for use in an image forming apparatus

Abstract: A control circuit for heat fixing device for use in an image forming apparatus is disclosed. The control circuit comprises device for detecting a power source voltage, device for detecting zero-crossing points of the power source voltage, device for determining frequency of the source voltage from the detected zero-crossing points, device for determining a power supplying time based on the detected power supply voltage and the power source frequency, device for controlling the power supply to a load based on the determined power supply line, in such a manner that a given power is automatically applied to the load against the change or fluctuation of the power supply source.

Noise reduction in CMOS driver using capacitor discharge to generate a control voltage

Abstract: A pull-up or pull-down transistor in an output buffer or the like is controlled to limit dI/dt and thus reduce noise. This control employs a series transistor in the driver circuit which has a modulating voltage applied to its gate. This modulating voltage is generated in a circuit which uses precision-timed clocks as a reference so that variations in electrical parameters (process, temperature and power supply dependent) will not cause variation in circuit noise. A dummy driver circuit is used to discharge a capacitor at a rate dependent upon the modulating voltage, and the capacitor voltage is compared with a reference at a time determined by the precision clock. The result of the comparison is used to increment or decrement the modulating voltage.

An electrical circuit, particularly an electronic power circuit for motor vehicle injection systems, with a function for the detection and diagnosis of faults, and method related thereto

Abstract: During the piloting of the load, the current intensity and the voltage present in the load are monitored by the comparison of their values with a current threshold and with a window of permissible voltage values. When the voltage is outside the window of permissible values and/or the current falls below its threshold, a fault message is generated and the nature of the fault (open load, short circuit to earth, short circuit to the supply voltage) is also identified by the emission of a corresponding signal of a diagnostic nature. The identification of the faulty stage or stages is also provided for in the case of a circuit including several stages in parallel.

Power supply with automatic input voltage doubling

Abstract: An automatic input switching circuit for a power supply includes a transformer with two primary windings, normally connected in series and connectible in parallel by relay contacts for operation in a doubler mode. The secondary winding supplies a rectifier for developing a DC output voltage and a voltage doubler for developing a higher voltage than the output voltage. The voltage doubler charges a capacitor that stores energy for operating the relay when a transistor switch is closed. The transistor switch is normally held in a nonconductive state by an inhibit transistor driven from a comparator that switches states when the voltage across the capacitor reached a predetermined level. A voltage sensing arrangement compares the rectifier output voltage with a reference voltage and when it reaches a certain level, another comparator switches states to activate a disable transistor. The activated disable transistor prevents cutting off of the inhibit transistor, thus preventing operation of the transistor switch. The arrangement may be used above as an automatic voltage doubler power supply with line isolation or, by adding additional relay contacts, as a relay control device for controlling normal doubling mode switching in a high current, switched mode power supply.

Control circuit for an inductive load

Abstract: The circuit according to the invention controls the supply to an inductive load by a power transistor of the N-channel MOS type, placed on the side of the positive terminal of a supply source delivering a voltage +Vbat. The conduction of the transistor is maintained by means of a gate voltage Vs>+Vbat supplied by a voltage multiplier. On cutting off this voltage, there is blocking of the transistor and discharge of the load, which rapidly develops a high negative voltage. An interconnecting transistor than prevents the return to conduction of the power transistor while, according to the invention, a transistor of the P-channel MOS type isolates the gate of the interconnecting transistor to authorize the application to said gate of the negative voltage developed by the inductive load. The invention has application to the control of actuators for the automobile industry.

Input translating circuit for CMOS device

Abstract: An input translating circuit for a CMOS device is disclosed which can be operated without being influenced by a level of the supply voltage. This is made possible by providing a supply voltage level discriminating means consisting of a voltage dividing network for dividing the supply voltage into predetermined voltages and a level comparing means for comparing the divided voltage with the reference voltage level, and further by providing a constant voltage supply means, so that a trip voltage, used in the operation of the circuit, can be maintained at a constant level regardless of the variations of the supply voltage. Further, the circuit according to the present invention eliminates corresponding mask work requirements for the option of the power voltage in the manufacturing process, thereby lowering production complexity costs.

Measuring and analyzing the impact of voltage and capacitor control with high speed data acquisition (distribution system)

Abstract: Experimental results on the effects of capacitor switching on feeder operating variables as measured in the substation by a high-speed data acquisition system are presented. Consistent with the modeling of feeder loads as constant power, the switching in of a capacitor bank to improve power factor results in decreased reactive power injection and increased phase voltage. However, a reduction in real power injection reflecting reduced line losses is not observable at the substation. Similarly, the switching out of a capacitor bank results in increased reactive power, decreased phase voltages, and decreased real power. Analysis of the experimental results, using voltage-sensitive load models shows that while feeder losses are reduced following feeder power factor correction, the attendant improvement in voltage profile results in an increase in load that exceeds the amount of loss reduction. Consequently, distribution system operators using supervisory control and data acquisition systems will not be able to observe the loss reduction associated with capacitor switching to improve power factor. >

Maximum power transfer limited by voltage stability in series and shunt compensated schemes for AC transmission systems

Abstract: The planning, operation and control of a power system are to a significant extent governed by stability considerations. Transient or steady-state stability of a power system is its capability to operate stably without loss of synchronism after a large or a small disturbance respectively. Voltage stability, on the other hand, is the ability of the system to provide adequate reactive power support under all operating conditions so as to maintain stable load voltage magnitudes within specified operating limits in the steady-state. Since long distance transmission systems for the transport of bulk power, in addition to the use of series capacitors, require shunt reactors to control power frequency voltage, it is necessary to determine the maximum power transfer PRcrit Of such compensated systems when they are operating on the verge of voltage stability. The determination of such limits is the objective of the present paper. Five different schemes. using series and shunt compensation have been considered. These schemes are the same as those discussed by lliceto and Cinieri [1] from the angular steady-state point of view. In the present paper, an expression for the critical clearing angle bcrit, when the system is operating on the verge of voltage stability, is derived in terms of the load power factor angle, and the generalized circuit constants of the line. Next, assuming the sending-end voltage to be fixed, the critical voltage, VRcrit, when the system is on the verge of voltage stability, is determined in terms of ?crit and the line constants.