Abstract: RF digital information signals are interfaced with a medium voltage power line data channel. An interface circuit connects between the medium voltage and low voltage sides of a step-down power transformer. The interface circuit includes a metal oxide arrestor (MOV) and an opto-coupler. The MOV provides the needed capacitance and voltage rating without the bulk of a capacitor having similar capacitance and voltage rating. The opto-coupler provides an added margin of safety for coupling communications data while isolating the medium voltage power from the low voltage side of the transformer.

Abstract: A new family of matrix converters is introduced, that employs relatively simple voltage-clamped buses and can generate multilevel voltage waveforms of arbitrary magnitude and frequency. The basic configuration includes a nine-switch matrix that uses four-quadrant switch cells. Each four-quadrant switch cell resembles a full-bridge inverter and can assume three voltage levels during conduction. Semiconductor devices in a switch cell are clamped to a known constant DC voltage of a capacitor. Control of the input and output voltage waveforms of the proposed converter can be achieved through space vector modulation. Simulation results show how the converter can operate with any input and output voltages, currents, frequencies, and power factors while maintaining constant DC voltages across all switch cell capacitors.

Abstract: In a three-phase system, voltage unbalance takes place when the magnitudes of phase or line voltages are different and the phase angles differ from the balanced conditions, or both. This letter reviews three definitions of voltage unbalance developed by NEMA, IEEE, and the power community, respectively. The differing definitions of voltage unbalance are analyzed in order to understand the implications of their use.

Abstract: The voltage lift technique is a popular method widely applied in electronic circuit design. Applying it has created six new DC-DC step-up power converters, namely, self-lift DC-DC power converters, which possess high output voltage with smooth ripple. Therefore, these converters can be used in computer peripheral equipment and industrial applications.

Abstract: The secondary voltage control of power systems initiated by EDF has been developed successfully and applied mainly for the generator AVRs to improve power system voltage stability. Work on secondary voltage control is presented involving various types of power system voltage controllers, AVRs, SVCs and STATCOMs, for a new application: power system voltage management in system contingencies. The secondary voltage control is proposed, to be implemented based on the principles of multi-agent system theory, an active branch of applications in distributed artificial intelligence. An example power system is presented to demonstrate the necessity of the secondary voltage control among an AVR, an SVC and a STATCOM installed in the power system, and also to illustrate the success of applying the multi-agent co-ordination for their secondary voltage control in system contingencies.

Abstract: In this paper, a novel control scheme compensating source voltage unbalance and current harmonics for hybrid active power filters is proposed. The reference voltage for compensation is derived from the differences between the fundamental source and load voltages and their instantaneous values, where the positive sequence component which is simply obtained by using digital all-pass filters is used as the fundamental voltages. The reference voltages for the 5/sup th/ and 7/sup th/ harmonic compensation are predicted a sampling period ahead to reduce the delay in the inverter voltage control loop. The validity of the proposed scheme has been verified by experimental results.

Abstract: Most of today's voltage regulation modules (VRMs) draw power from 5 V output of the silver box. For future applications, this voltage bus will be too low to be practical. In the future, distributed power systems (DPS) with 12 V or 48 V voltage bus, are more attractive solutions for servers and high-end workstations. This paper focuses primarily on the comparison of three 12 V VRM topology candidates: buck; tapped-inductor buck; and active-clamp couple-buck.

Abstract: A high frequency switched, power electronics based distribution transformer is introduced and described. Besides the definition of appropriate voltage and power ratings also several preferred topologies are discussed, favorable to replace the typical power frequency distribution transformer by a high frequency switched one with low number of variants. Special attention is paid to modularity and automated production capability of all individual components, very low first and operating costs e.g. low maintenance costs, long operation intervals and high efficiency especially at partial load.

Abstract: An improved single-phase line-interactive uninterruptible power supply (UPS) is proposed for low-power applications with low cost. The proposed UPS is comprised of two push-pull converters based on a low-voltage battery for reduced cost: one in series with the input and the other in parallel with the load. In the presence of input power, the UPS acts as an output voltage regulator and at the same time as an active filter while charging the battery. In case of loss of input power, the UPS supplies a regulated sinusoidal voltage to the load, drawing power from the battery. The series converter compensates only a small percentage of the input voltage carrying the input current and, therefore, a reduced rating is made. The parallel converter always supplies a nominal voltage and makes a seamless transition to backup mode. In the voltage determination of the parallel converter, the nominal voltage is derived using the feedback linearization concept and then a perturbed voltage is determined for the reactive power control or output voltage regulation. Experimental results obtained from a 1-kVA prototype are discussed.

Abstract: We demonstrate a novel algorithm for assigning the threshold voltage to the gates in a digital random logic complementary metal-oxide-semiconductor (CMOS) circuit for a dual-threshold voltage process The tradeoff between static and dynamic power consumption has been explored When used along with device sizing and supply voltage reduction techniques for low power, the proposed algorithm can reduce the total power dissipation of a circuit by as much as 50%

Abstract: This paper compares two different optimal power flow (OPF) formulations that consider voltage security in power systems. The techniques are both based on multi-objective optimization methodologies, so that operating costs and losses can be minimized while maximizing the "distance" to voltage collapse. The techniques are described in detail and compared to study their similarities, as well as advantages and disadvantages. The comparisons are based on the results obtained by applying these two methods to a modified version of the 118-bus IEEE test system.

Abstract: A charge pump power converter efficiently provides electrical power by dynamically controlling a switch matrix of the charge pump. Instead of open-loop oscillator-based control, a dynamic controller provides power upon demand by sensing the output voltage and changing the operating frequency of the charge pump in response. Moreover, this closed-loop dynamic control intrinsically voltage regulates the output voltage of the charge pump power converter without the inefficient addition of a step-down voltage regulator, downstream of the power converter. Additional efficiencies are achieved through maintaining the voltage ripple across the fly capacitor and/or the load capacitor. Also, a three-state control scheme is used to charge the fly capacitor, wait for the output voltage to drop to a predetermined level, and discharge the fly capacitor. Furthermore, a multiple-output charge pump power converter provides multiple voltage levels for devices such as portable communication electronic devices.

Abstract: A power system stabilization system is provided between power generation equipment significantly fluctuating in output and a power system required to maintain a predetermined voltage. In the power system stabilization system, a voltage detection device and a current detection device detect voltage and current, respectively, of the power system and voltage and current thus detected are used to calculate a level of active power required and that of reactive power required which are referred to to provide charging and discharging from a rechargeable battery to the power system via an A-D converter.

Abstract: A charge pump power converter efficiently provides electrical power by dynamically controlling a switch matrix of the charge pump. Instead of open-loop oscillator-based control, a dynamic controller provides power upon demand by sensing the output voltage and changing the operating frequency of the charge pump in response. Moreover, this closed-loop dynamic control intrinsically voltage regulates the output voltage of the charge pump power converter without the inefficient addition of a step-down voltage regulator, downstream of the power converter. In addition, this closed-loop dynamic control allows for maintaining a desired output voltage even with variations in the input voltage. Also, the dynamic control accommodates the advantages of using ultra-capacitors in the charge pump. The power converter is capable of operating with a sub-one volt input voltage incorporating low-threshold, low on-resistance power MOSFET switches in the switch matrix of the charge pump. A progressive start-up circuit further allows the power converter to start from a discharged state even with a sub-one volt input voltage.

Abstract: Buck+Half Bridge (d=50%) topology is a very suitable circuit for low output voltage, high output current applications with a wide input voltage range. Its small signal transfer function is very complex and should be considered to optimize the dynamic response, efficiency and size of the power converter. Small signal and large signal behavior of this topology are analyzed through their corresponding average models. Design guidelines, drawn from this analysis, are applied on two low-voltage (1.5 V) wide input voltage prototypes to validate the goodness of this topology.

Abstract: This letter presents a new method for the generation of reference voltage for a dynamic voltage restorer (DVR). These volt- ages, when injected in series with a distribution feeder by a voltage source inverter, can tightly regulate the voltage at the load terminal against imbalance or harmonics in the source side. It is stipulated that the DVR does not supply any real power in the steady state. The refer- ence voltage generation scheme is validated through digital computer simulation studies.

Abstract: A new input current shaper is proposed in this paper. The operating principle is based on the connection of a voltage source and a loss-free resistor (LFR) between the input rectifier and the bulk capacitor in a conventional switching mode power supply with no power-factor correction. Both the voltage source and the LFR are obtained as an additional output from the converter's transformer. This additional output is a forward-type one with one extra inductor. With the final topology, a good tradeoff between capacitor voltage, recycling energy, and harmonic content can be established in order to comply with IEC 1000-3-2 specifications.

Abstract: A system and method to parasitically take electrical power from a source of ac load power to provide a voltage source to directly power an associated control device is described. The system utilizes a controllable transconductance device to both selectively provide power to a controlled load and to develop a predetermined voltage to directly power the control device in a system where the ac load power is applied at one terminal and is passed through the transconductance device to be returned through the load. The system includes a means for establishing the predetermined voltage level to power the control device and for continuously monitoring that voltage level to maintain it as required, whether power is applied to the load or not. Alternative voltage regulators to provide isolated or non-isolated power to the control device irrespective of whether or not power is applied to the load are also described.

Abstract: With each technology generation, delivering a timevarying current with reduced nominal supply voltage variation is becoming more difficult due to increasing current and power requirements. The power delivery network design becomes much more complex and requires accurate analysis and optimizations at all levels of abstraction in order to meet the specifications. In this paper, we describe techniques for estimation of the supply voltage variations that can be used in the design of the power delivery network. We also describe the decoupling capacitor hierarchy that provides a low impedance to the increasing high-frequency current demand and limits the supply voltage variations. Techniques for high-level power estimation that can be used for performance vs. power trade-offs to reduce the current and power requirements of the circuit are also presented.

Abstract: AC railway traction systems are particularly susceptible to harmonic distortion. They are weak single phase networks often loaded with severely distorting SCR-based locomotive drives which continually change their point of physical connection to the network. For a public distribution system the total harmonic distortion is a clear measure of supply quality. However, for a traction system the more important parameter is the voltage form factor, which is directly related to the maximum power a locomotive can deliver. To minimise this form factor, this paper proposes the use of a shunt active filter that minimises the 3rd, 5th and 7th harmonic voltage components at the point of filter coupling. It is shown that the filter is effective in both compensating the pantograph voltage form factor, and providing reactive power to maintain the feeder voltage. The results are confirmed by detailed simulation using the EMTDC package.

Abstract: Recently developed power quality mitigation equipment, like the static transfer switch, needs methods for fast and reliable detection of voltage dips. Such a detection scheme must be able to detect a voltage dip as fast as possible and be immune to other types of disturbances. In this paper, the authors address the problem of voltage dip detection regarding Kalman filtering, the characteristics of fault-induced voltage dips and other power system disturbances. They investigate how the voltage dip characteristics influence the speed of detection and show that disturbances other than fault-induced dips could trigger a detection scheme. Special attention is given to trans former-related events. Their characteristics are presented using measurements. Kalman filtering modelling issues are discussed. Statistics on the characteristics of fault-induced dips and transformer events are presented from medium voltage networks.

Abstract: The last portion of the electrical distribution system is used to provide high-speed communications to residential homes. An aggregation point interfaces a medium voltage power line with a point-of-presence, and a power line bridge enables flow of communications signals between the medium voltage power line and a low voltage power line across a distribution transformer.

Abstract: A universal power converter for generating a regulated voltage, current or power with a large input voltage range. The power converter has a voltage boost function configured to boost the rectified input voltage and provide power factor correction. The power converter also includes a voltage chop function to chop the boosted voltage to form an AC voltage. The power converter further includes at least one relay in electrical communication with the AC voltage and a transformer. The primary winding has at least two inputs operative to selectively vary the voltage generated on a secondary winding thereof selected by the relay. Accordingly, the power converter can generate different voltages at the output based upon the position of the relay and the boosted voltage. The power converter provides maximum power operation at a wide output voltage range, maximizing the charging energy.

Abstract: A circuit for sensing the voltage across a power device, such as an insulated gate bipolar transistor (IGBT), that provides a power signal, such as to a motor. Where power devices are connected in a half bridge configuration, the sensing circuitry provides low side and high side sense signals. The signals indicate respectively when voltage changes across the low side and high side power devices. If on times of the devices are separated by deadtime, one sense signal can indicate the beginning of deadtime and the other can indicate the ending of the deadtime. The sensing circuitry can provide a sense result signal indicating whether voltage across the power device is greater than a reference voltage. The sense result signal can be received both by feedback signal circuitry that provides a signal indicating when voltage changes and also by shutdown circuitry that causes driving circuitry to turn off the power device if it is turned on when voltage across it is greater than the reference voltage, which occurs in a short circuit condition. The circuitry can be combined in an integrated circuit in which low side and high side sense signals are used both to provide voltage feedback signals and also to turn off the low or high side device if it is on when the voltage across it exceeds its reference voltage.

Abstract: A charge pump power converter efficiently provides electrical power by dynamically controlling a switch matrix of the charge pump. Instead of open-loop oscillator-based control, a dynamic controller provides power upon demand by sensing the output voltage and changing the operating frequency of the charge pump in response. Moreover, this closed-loop dynamic control intrinsically voltage regulates the output voltage of the charge pump power converter without the inefficient addition of a step-down voltage regulator, downstream of the power converter. In addition, this closed-loop dynamic control allows for maintaining a desired output voltage even with variations in the input voltage. Also, the dynamic control accommodates the advantages of using ultra-capacitors in the charge pump. The power converter is capable of operating with a sub-one volt input voltage incorporating low-threshold, low on-resistance power MOSFET switches in the switch matrix of the charge pump. A progressive start-up circuit further allows the power converter to start from a discharged state even with a sub-one volt input voltage.

Abstract: The neutral-point-clamped multilevel converter is an attractive implementation of the unified power flow controller because it facilitates back-to-back operation, high-voltage operation (without direct series connection of devices), and low distortion (without the use of multipulse transformers). A UPFC using three converters is proposed. Two phase-shifted converters are required to provide a full range of voltage control of the series connection while ensuring low distortion and a balanced dc link. A single shunt converter is used. A commutation angle solution that balances the voltages of the multiple dc link capacitors is analyzed in terms of the active power balance at each node. Control of shunt reactive power requires a variable dc link voltage. Control schemes for both shunt and series converters are developed and verified in terms of voltage balancing and power flow control on a micro-scale experimental system using five-level converters.

Abstract: A computer system incorporates distributed power control. In particular, the computer system comprises a power supply for providing at least one voltage, a power distribution system, and N boards, or modules (where N>1) coupled to the power supply via the power distribution system. Each board comprises a voltage regulator, which receives the voltage from the power supply and provides a regulated voltage to the board, and a processor for controlling the voltage regulator for varying the regulated voltage.

Abstract: Modern computing devices, featuring extremely fast load current transients, impose severe issues to the design of voltage regulation modules (VRM) interfacing the microprocessor power bus with the main board power supply. Using conventional design techniques bulk and expensive high quality output filter capacitors are required to cope with load current slew rates higher than 10 A//spl mu/s. This paper proposes an alternative approach to improve the performance of voltage regulation modules, without requiring impractical output filter capacitors. The proposed approach is based on introducing a very low inductance current path on a voltage regulation module based on a multiphase converter.

Abstract: In this paper, different system topologies for dynamic voltage restorers are analyzed with the emphasis put on methods to acquire the necessary energy during a voltage sag Four different system topologies are analyzed and tested Two, which can be realized with insignificant energy storage and the energy is taken from the grid and two topologies, which are based on stored energy are compared Experimental tests on a 10 kVA rated dynamic voltage restorer shows that the no-energy storage concept is feasible, but an improved performance can for certain voltage sags, be achieved with stored energy In the comparison, the no-storage topology with a passive shunt converter at the load side is ranked highest followed by an energy storage topology with constant DC-link voltage