Abstract: There has been considerable interest in the development and applications of active filters because of the increasing concern over power quality, at both distribution and consumer levels, and the need to control reactive power and voltage stability at transmission levels. The existing approaches are classified and assessed to provide a framework of references for both researchers in this field and for generators, suppliers and consumers of electrical power who are, or may be, concerned about the problems associated with power quality and are considering installing active filters for their particular sets of problems.

Abstract: Summary form only given, as follows. Voltage sags are one of the most important power quality problems challenging the utility industry. Voltage sags can be compensated for by voltage and power injection into the distribution system. By injecting voltage with a phase advance with respect to the sustained source-side voltage, reactive power can be utilized to help voltage restoration. Hence, the consumption of real power, from the perspective of the energy supply device, can be reduced. This energy-saving voltage injection comes at the expense of an increased voltage injection magnitude, load power swing phase shift and discontinuity of voltage wave-shape. For this reason, several proposed compensation strategies are examined, in term of satisfying custom power while taking into consideration the capacity of the energy-storage device and the voltage injection constraint of the dynamic voltage restorer. Numerical examples are included to illustrate the efficacy of the proposed control strategies.

Abstract: In this paper, graph theory is used to calculate the contributions of individual generators and loads to line flows and the real power transfer between individual generators and loads that are significant to transmission open access. Related lemmas are proved which present necessary conditions required by the method. Based on AC load flow solution a novel method is suggested which can decide downstream and upstream power flow tracing paths very fast and can calculate the contribution factors of generations and loads to the line flows efficiently. The power transfer between generators and loads can also be determined. The suggested method is suitable for both active and reactive power tracings of real power systems.

Abstract: The droop current sharing method is analyzed, and a general design procedure is proposed. It is shown that the current-sharing accuracy of N+1 power supplies is a function of the output-voltage set-point accuracy, the slope of the output-voltage droop, and gains of the control loop. It was found that to achieve a current sharing accuracy of 10% the output voltage of the paralleled power supplies needs to be set within 0.35%. The accuracy of the design procedure was compared against measured results of three power supplies operating in parallel.

Abstract: The paper presents design considerations for a 12 V/1.5 V, 50 A voltage regulator module (VRM) for the next generation of microprocessors. The module has stringent power-density and transient-response specifications, which are hard to meet with traditional design techniques. The proposed design solutions increase the VRM efficiency, as well as achieve the desired transient response with a minimum amount of the output capacitance.

Abstract: Closed-form formulas are presented for optimum supply voltage (VDD) and threshold voltage (VTH) that minimize power dissipation when technology parameters and required speed are given. The formulas take into account short-channel effects and the variation of VTH and temperature. Using typical device parameters, it is shown that a simple guideline to optimize the power consumption is to set the ratio of maximum leakage power to total power about 30%. Extending the analysis, the future VLSI design trend is discussed. The optimum VDD coincides with the SIA roadmap and the optimum VTH for logic blocks at the highest temperature and at the lowest process variation corner is in the range of 0V~0.1V over generations.

Abstract: The always-increasing switching frequency of modern solid-state power switches, together with the application of multi-converter topologies, make it possible to use pulse width modulation (PWM) in high power applications of STATCOMs (static synchronous compensators). This paper investigates the control system for a PWM-based STATCOM. First of all, a discrete-time model of the STATCOM is derived to take into account the discrete-time implementation of the controller. Secondly, the control algorithm is detailed. It ensures decoupled control of the real and reactive power exchanged between the power converter and the electric-energy system. This is necessary to control the DC capacitor voltage during transients of the exchanged reactive power. Finally, the control of the capacitor voltage is explained in detail. The controller is tailored to keep the capacitor voltage almost constant in spite of the fast control of the reactive power. This helps to reduce the capacitor size significantly. The main contributions are illustrated using a 15 kVA laboratory prototype.

Abstract: This paper describes the novel technology of an integral motor with the associated driver and wireless transmission of power and information (WTPI), which is effectively applied to autonomous spindle drive for the sophisticated workpiece machining. The power supply to the integral motor is made by way of a separable WTPI coupling. In addition, calculation for variable voltage and variable frequency (VVVF) control is done at the primary side of the coupling, and then the frequency command is transmitted to the secondary side by an overlapped transmission of the data on the power transmission through the WTPI coupling. At the secondary side, direct power conversion from the induced high-frequency voltage to the motor terminal voltage is conducted using a bidirectionally controllable power switch. The amplitude of the terminal voltage is adjusted by changing the inverter voltage at the primary side. In this way, the VVVF drive is made through the WTPI coupling, thus providing the integral subspindle with the autonomy for sophisticated machining.

Abstract: This paper gives an overview of methods used in the mitigation of voltage sags. Different solutions for improving the performance of the power system, as well as the immunity of the equipment, are described. Finally, mitigation devices to be installed at the system-load interface for power quality enhancement are presented.

Abstract: Summary form only given as follows. DSGs (dispersed storage and generation systems) in power distribution systems impact on the conventional voltage regulation method. Therefore, there is the possibility that the customers' voltage violates the permissible limits. In this paper, we propose the MLDC (multiple line drop compensation) voltage regulation method which considers the unbalanced load diversity among feeders, the operations of DSGs, and the hysteretic tap changing mechanism of ULTC (under load tap changer). The result from a case study shows that the proposed MLDC method can be practically applied to the voltage regulation method at the power distribution system interconnected with DSGs and severely unbalanced load diversity among feeders.

Abstract: In previous work concerning the Voltage Instability Predictor (VIP), the proximity to voltage collapse (or instability) was expressed in terms of distance between two voltage curves or between two impedance curves. In this paper, a new measure, power margin, is introduced to describe the proximity to collapse in terms of power. The results of work on the effects of contingencies and system dynamics on the VIP are also presented, extending the prior work that assessed the effectiveness of the VIP under conditions of increased power transfers, using power flow simulations to examine voltage collapse conditions. These results show that the VIP algorithm successfully predicted voltage instability where conventional protection devices, using only voltage inputs, did not.

Abstract: Due to the quadratic reduction in the switching power dissipation, lowering supply voltage is obviously one of the most effective ways to reduce power consumption. However, the performance will degrade. In order to satisfy the high performance requirements, threshold voltage has to be scaled. Unfortunately, such scaling leads to a dramatic increase in leakage current, which becomes a new concern for low voltage and high performance circuit designs. Multiple transistor threshold and supply voltages can be used to achieve low power and high performance while maintaining low leakage current. In this tutorial, different multiple-V/sub th/, multiple-V/sub dd/ and standby leakage control techniques are presented.

Abstract: Improvements in the automation of transmission network voltage control has become a challenging problem. In this framework, the paper preliminarily describes the basic concepts of the secondary voltage regulation (SVR) and the hierarchical control system under application to the overall Italian transmission network for the voltage and reactive power regulation. At the power plant level this hierarchical control system operates through an innovative, microprocessor based, voltage and reactive power regulator, named REPORT. At the regional load dispatcher level, a regional voltage regulator (RVR) controls in real time and closed-loops through the REPORTs, the voltages of the main EHV buses in the region. Both the REPORT and RVR control apparatus have been designed and developed by CESI. The Italian Independent System Operator (ISO) has under way the general application of the REPORT apparatus to all the main power plants, a large amount of them being already in operation, as well as of the RVR regulators at the regional dispatchers control rooms. The paper describes the main characteristics and performances of the mentioned control apparatus, the progress of their application in the field, their impact with the traditional operation, and comparison with alternative voltage control service; significant field test results are also shown. Some considerations about the influence on the voltage service of the power system restructuring process are also given.

Abstract: This paper proposes microarchitecture-driven dynamic voltage scaling as a viable solution to power efficient architectures, with little or no performance penalty. The run-time behavior exhibited by common applications, with active periods, alternated with stall periods due to cache misses, is exploited to reduce the dynamic component of power consumption via selective voltage scaling. As it is shown by experimental results, up to 20% reduction in total energy consumption, 22% in average power and 14% in peak power have been achieved with less than 6% penalty in performance. The study shows that microarchitecture-driven dynamic voltage scaling can become an effective tool for energy reduction in high-performance processors.

Abstract: The electric power acceptability curves are an empirical set of curves that represent the intensity and duration of bus voltage disturbances. These curves are discussed with regard to the energy delivered to the load, and alternatives for the assessment and measurement of bus voltage sags. Special attention is given to the three phase case.

Abstract: This paper presents the design, analysis, and experimental results of a vibration-induced power generator with total volume of -1 cm3 that uses laser-micromachined springs as resonating structures. The goal of our research is to create a minimally sized electric power generator capable of producing enough voltage to drive low-power IC circuit systems or micro sensors for robotic and automation applications where mechanical vibrations are present. Potential applications for the generator may also include mobile phone and heart-pacers where human motions can be used as a source of mechanical energy. Thus far, we have produced a generator capable of producing 2V DC with 64Hz input frequency with <200pm input vibration amplitude.

Abstract: In a multiple power source system of the present invention that has an inverter connected to a reactance, such as three-phase coils in a motor, a high voltage battery is connected with a low voltage battery via one transistor (Tr2) and one diode (D2) included in the inverter and one phase coil (U-phase coil) of the three-phase motor. The transistor Tr2 is turned on to make the electric current flow from the low voltage battery to the U-phase coil. The transistor Tr2 is subsequently turned off at a preset timing, so that the electric energy accumulated in the reactance, that is, the U-phase coil, flows through the diode D1 into the high voltage battery and thereby charges the high voltage battery. This arrangement enables the charging process from the low voltage battery to the high voltage battery without any complicated circuit structure for the voltage step-up. The three-phase motor may be unipolar driven with transistors connected to one side of the inverter. The arrangement of the present invention does not require any complicated structure, which undesirably increases the size of the multiple power source system, in order to ensure mutual supplement of the electric energy between electric systems having a large difference in voltage, for example, an electric system for driving a hybrid vehicle and an electric system for its control circuit.

Abstract: An internal power supply voltage generation circuit includes a main amplifier that supplies a current from an external power supply node to an internal power supply line in accordance with the difference between a reference voltage from a reference voltage generation circuit and an internal power supply voltage on the internal power supply line. The current supply amount by the main amplifier is adjusted by a level adjust circuit, according to the difference between the external power supply voltage and the reference voltage. The internal power supply voltage generation circuit can suppress reduction in the internal power supply voltage in the vicinity of the lower limit area of the differential power supply voltage.

Abstract: The invention is a load voltage and power control and supply system for the supply of power to a load for which, over particular periods of time, usually on a daily basis, it is desired to reduce power. The invention has particular application to street lighting systems in which, for a period of several hours during the night (when traffic is minimal and many people are asleep), the luminaires of the lighting system can operate at reduced power. The power control system is able to act as a voltage stabilizer as well as a controlled power reduction system. The power control system may operate the bank of spaced luminaires from a single control location. Moderately reduced power (say a 30% reduction in power) supplied to luminaires does not noticeably diminish the adequacy of the illumination provided. Further, the power control system reduces power in stepwise decrements each of which reduces power by a small amount insufficient to diminish noticeably the ambient illumination.

Abstract: A computer algorithm for optimal voltage control with voltage regulators, suitable for large radial distribution networks is given in this paper. An objective function concerning the total cost of the voltage regulators (investment and maintenance cost) as well as the cost of losses of the examined networks is developed and constitutes the base of the algorithm. This algorithm makes the initial selection, installation and tap setting of the voltage regulators, which provide a smooth voltage profile along the network, utilizing former algorithms suitably modified and optimized. Then it attempts to minimize the number of the initially selected voltage regulators as much as possible, by moving them in such a way as to control the network voltage at the minimum possible cost (maximization of the objective function). The algorithm is fast, efficient and reliable as its application to practical distribution networks shows.

Abstract: The method and system for managing power supplied from a charging circuit to a power source in an implantable device having the steps of and circuitry for: measuring the current drain of the device; measuring the elapsed time since last full charge and calculating the actual capacity based on the elapsed time and the current; calculating the operating time; signaling and disconnecting the the device when the source voltage falls below a value and further disconnecting the device when the source is overcharged; sensing when the RF transmitter/charger transmits the EM waves induced a voltage level above a value and reconnecting the device upon sensing the induced high voltage level; further monitoring the temperature of the source and halting charging the source when the temperature is above a value and further halting discharging when temperature is above a value.

Abstract: Voltage stability has become a challenging problem for many power systems. Contingency screening and ranking (CS&R) is one of the important components of on-line voltage stability assessment. The objective of CS&R is to quickly and accurately select a short list of critical contingencies from a large list of potential contingencies and rank them according to their severity. Suitable preventive control actions can be implemented considering contingencies that are likely to affect the power system performance. An effective method for contingency ranking is proposed in this paper. This method calculates the voltage stability margin considering branch outages. Test results based on the IEEE 300 bus power system, a 600 bus power system as well as two utility systems (197 bus and 1254 bus) are presented.

Abstract: Most converter designs assume that a closed power switch has zero volts across it. In general, this is a valid assumption that reduces the design complexity. However the fact that a power switch does have a finite resistance means that there will be a nonzero voltage across it during its on time. This voltage can be taken advantage of. This paper proposes a simple control technique that utilizes the variable resistance of the power MOSFET in a dc-dc converter. This is the first switched mode power supply that uses the power switch in more than two states or operating points. It is also the first switched mode power supply that uses the power switch as a variable control device as well as a power device. A 48-5-V 20-W forward converter is implemented to confirm the theory and demonstrate its practicality. The proposed technique provides self oscillation, self overload protection, zero voltage switching (ZVS), input voltage feedforward, and a reduced component count and cost.

Abstract: Fuel cell power systems, direct current voltage converters, fuel cell power generation methods, power conditioning methods and direct current power conditioning methods are provided. According to one aspect of the invention, a fuel cell power system includes a plurality of terminals adapted to couple with a load; a fuel cell configured to convert chemical energy into direct current electrical energy having a variable voltage potential; and a converter coupled intermediate the fuel cell and the terminals, the converter being configured to convert the direct current electrical energy having the variable voltage potential into direct current electrical energy having a substantially constant voltage potential.

Abstract: Apparatus and methods are described for the voltage control of power converters in which the input and output voltages of the converter are not sensed directly but are derived from an inductor voltage which in turn is derived by sensing an instantaneous inductor current.

Abstract: This paper presents a global overview of the state of the art techniques in active power filters and reactive power compensation. The presentation and the subdivisions of these power system conditioners, presented in this paper, show the merits and drawbacks of each type and technique used. This is important for design engineers and researchers in power quality to enable them to select the correct system for their specific applications.

Abstract: The important systems issues surrounding the circuit of a dynamic voltage restorer using battery energy storage for voltage dip mitigation are discussed by the authors. The connection arrangement, filtering, system control and effect of real power storage are examined. Simulation results for single and two-phase voltage sags indicate that the system responds quickly to changes in voltage phase and magnitude with only small system transients.

Abstract: A proposal is presented for characterization of voltage dips as experienced by a three-phase load. The primary result of the method is a so-called "characteristic magnitude" which corresponds to the magnitude (remaining voltage) as used for the existing methods to characterize dips experienced by a single-phase load. The proposed method may be extended by adding additional parameters where further accuracy is needed for characterization. The method is applied to the analysis of multi-stage voltage dips.

Abstract: Generators typically regulate terminal voltage via automatic voltage regulator and exciter equipment. The desired high side (transmission side) voltage schedule is usually maintained by the power plant operator or by slow SCADA-type process control computers. Power system dynamic performance, however, can be improved by faster regulation of the transmission voltage. Contrasted to generators, static VAr compensators are designed specifically for transmission voltage regulation. The transmission voltage is directly regulated at high speed. Total SVC and medium voltage component reactive power ratings are referred to the transmission side. All medium voltage equipment are designed to support the transmission side reactive power and voltage regulation requirements. The droop (slope) setting is usually small compared to generators regulating terminal voltage. This paper introduces the panel session on secondary voltage control. The author outline various methods for tighter high side voltage control, with emphasis on control of hydro generation in the US Pacific Northwest.