Abstract: There has been much interest in embedding small generators deep within distribution systems. The steady-state voltage rise resulting from the connection of these generators can be a major obstacle to their connection at the lower voltage levels. This article summarises the results of some generic studies, explaining this voltage rise issue and how it may be overcome. Methods discussed to counteract voltage rise are primary substation voltage reduction, reactive power import, autotransformers installation, conductor upgrading, and generation constraints.

Abstract: A dynamic voltage restorer (DVR) is a power-electronic controller that can protect sensitive loads from disturbances in the supply system. In this paper, it is demonstrated that this device can tightly regulate the voltage at the load terminal against imbalance or harmonic in the source side. The behavior of the device is studied through steady-state analysis, and limits to achievable performance are found. This analysis is extended to the study of transient operation where the generation of the reference voltage of the DVR is discussed. Once the reference signals are generated, they are tracked using a switching band scheme. A suitable structure in which the DVR is realized by voltage-source inverters (VSIs) is also discussed. Particular emphasis to the rating of this device is provided. Extensive simulation results are included to illustrate the operating principles of a DVR.

Abstract: Since a couple of decades ago, voltage stability assessment has received increasing attention due to the complexity of power systems. With the increase in power demand and limited power sources has caused the system to operate at its maximum capacity. Therefore, a study that is able to determine the maximum capacity limit before voltage collapse must be carried out so that necessary precaution can be taken to avoid system capacity violation. This paper presents a novel fast voltage stability index (FVSI) simplified from a pre-developed voltage stability index referred to a line initiated from the voltage quadratic equation at the sending end of a representation of a 2-bus system. The line index in the interconnected system in which the value that is closed to 1.00 indicates that the line has reached its instability limit which could cause sudden voltage drop to the corresponding bus caused by the reactive load variation. The formulated index was tested on the IEEE reliability test system in order to verify the performance of the proposed indicator. Results showed that the proposed technique is indicative in predicting the occurrence of system collapse and hence necessary action can be taken to avoid such incident.

Abstract: The multicell converters introduced more than ten years ago make it possible to distribute the voltage constraints among series-connected switches and to improve the output waveforms (increased number of levels and apparent frequency). The balance of the constraints requires an appropriate distribution of the flying voltages. This paper presents some solutions for the active control of the voltages across the flying capacitors in the presence of rapid variation of the input voltage. The latter part of this paper is dedicated to the observation of these voltages using an original modeling of the converter.

Abstract: A method for power system impedance estimation is presented. The method employs a power converter to inject a voltage transient onto the supply system. As the technique employs controlled power electronic devices it may be used as a stand alone piece of a portable measurement equipment, or it may be embedded into the functions of an active shunt filter for improved harmonic control. The impedance is estimated through correlation of the measured voltage and current transients. Simulations and experimental results demonstrate the measurement technique is highly accurate and effective.

Abstract: The definitions for active, reactive, and apparent powers that are currently used are based on the knowledge developed and agreed upon during the 1940s. Such definitions served the industry well, as long as the current and voltage waveforms remained nearly sinusoidal. Important changes have occurred in the last 50 years. New definitions in the Trial-Use Standard were developed to give guidance with respect to the quantities that should be measured or monitored for revenue purposes, engineering economic decisions, and determination of major harmonic polluters. The panel will discuss these issues.

Abstract: This paper studies the recovery of the voltage after a voltage dip due to a fault in a three-phase system. The instant of voltage recovery corresponds to the instant of fault clearing. For single-phase and phase-to-phase faults, a single point-on-wave of voltage recovery can be defined. For two-phase-to-ground and three-phase faults, the recovery takes place in two or three steps. The voltage recovery is described in a systematic way by using a classification of three-phase unbalanced voltage dips. The voltage recovery needs to be modeled correctly for studies of equipment immunity against voltage dips.

Abstract: A switched mode power supply having a regulated reflected voltage. In one embodiment, a switched mode power supply includes a power supply regulator coupled between a positive input supply rail of the power supply and a primary winding of an energy transfer element. The reflected voltage across the primary winding of the transfer element is related to the output voltage across a secondary winding of the energy transfer element according to the turns ratio of the energy transfer element. The power supply regulator is coupled to regulate the reflected voltage across the primary winding, thereby regulating the output voltage across secondary winding. In one embodiment, the reflected voltage across the primary winding is sensed through a current representative of the reflected voltage received by the power supply regulator.

Abstract: A dynamic voltage restorer (DVR) is a power electronic controller that can protect sensitive loads from disturbances in the supply system. This device can tightly regulate the voltage at the load terminal against imbalance or harmonic in the source side. The behavior of the device is studied through steady-state analysis, and limits to achievable performance are found. This analysis is extended to the study of transient operation where the generation of the reference voltage of the DVR is discussed. Once the reference signals are generated, they are tracked using a switching band scheme. A suitable structure in which the DVR is realized by voltage source inverters is also discussed. Particular emphasis on the rating of this device is given. Extensive simulation results are included to illustrate the operating principles of a DVR.

Abstract: As the power consumption of modern high-performance microprocessors increases beyond 100 W, power becomes an increasingly important design consideration. This paper presents a novel technique to simulate power supply voltage variation as a result of varying activity levels within the microprocessor when executing typical software. The voltage simulation capability may be added to existing microarchitecture simulators that determine the activities of each functional block on a clock-by-clock basis. We then discuss how the same technique can be implemented in logic on the microprocessor die to enable real-time computation of current consumption and power supply voltage. When used in a feedback loop, this logic makes it possible to control the microprocessor's activities to reduce demands on the power delivery system. With on-die voltage computation and di/dt control, we show that a significant reduction in power supply voltage variation may be achieved with little performance loss or average power increase.

Abstract: The performance and dynamic characteristics of a three-phase parallel active power filter (APF) with point of the common coupling (PCC) voltage compensation with consideration for an unbalanced load is presented and analyzed in this paper. The proposed scheme employs a pulse-width modulation (PWM) voltage-source inverter and has two operation modes. First, it operates as a conventional active filter with reactive power compensation when PCC voltage is within the 15% voltage drop range. Second, it operates as a voltage compensator when PCC voltage is not within the 15% voltage drop range. Both the APF and the voltage compensator compensate asymmetries caused by nonlinear loads. Finally, the validity of this scheme is investigated through the analysis of simulation and experimental results for a prototype APF system rated at 10 kVA.

Abstract: Power amplifiers are significant contributors to current consumption within mobile phones resulting in continued focus on design techniques to improve power amplifier efficiency. The techniques presented here use variable bias current and supply voltage, which allow enhanced efficiency at low power levels, and variable load impedance, which provides tradeoffs for optimum linearity and efficiency as a function of power level and battery voltage.

Abstract: A system for improving the power efficiency of an electronic device includes a threshold voltage selector and a supply voltage selector. The threshold voltage selector selects a value of a threshold voltage for operation of the device in response to a present operating condition of the device. The supply voltage selector selects a value of a supply voltage to be applied to the device in response to the present operating condition of the device. The value of the threshold voltage and the value of the supply voltage control a power consumption of the device.

Abstract: The single-phase pq theory is used for instantaneous reactive power and current harmonics compensation of single-phase loads. A new definition of single-phase instantaneous active power p(t), and reactive power q(t), is used in control circuits. Generation of reference compensating current of single-phase active filter is based on canceling the alternating component of p(t) for harmonic compensation and q(t) for reactive power compensation. The principle of operation is explained using analytical and simulation results.

Abstract: The concept of "standards" is introduced for the design of power acceptability curves. The power acceptability curves are aides in the determination of whether the supply voltage to a load is acceptable for the maintenance of a load process. The construction of the well-known Computer Business Equipment Manufacturing Association (CBEMA) power acceptability curve is discussed, and issues of 3-phase and rotating loads are discussed.

Abstract: High-speed AC electric railways, such as Shinkansen, require large single-phase AC electric power. So, if the short circuit capacity of the power system is not large enough, therefore, railway operation causes large voltage unbalance at the three-phase side. In this paper, a railway static power conditioner (RPC), a new system for reducing voltage unbalance and fluctuation, is described. To reduce voltage unbalance and fluctuation, the RPC balances effective power of different phase and compensates reactive power and harmonics. It enables operation of high-speed AC electrified railways even if the short circuit capacity of the power system is rather small.

Abstract: This paper deals with unified power quality conditioner (UPQC), which aims at the integration of series-active and shunt-active power filters. The main purpose of a UPQC is to compensate for voltage imbalance, reactive power, negative-sequence current and harmonics. This paper discusses the compensation principle and control strategy of the UPQC in detail. Experimental results obtained from a laboratory prototype of 20 kVA are shown to verify the viability and effectiveness of the UPQC.

Abstract: A low-cost high-frequency power supply for ozone generation is presented in this paper. The paper addresses two important issues. Firstly, the ozone reactor is tested at high frequency and a new model of this type of load is proposed. Secondly, the power supply stage is presented and analyzed, obtaining some important characteristics that allow the correct design of this power converter. Simulation and experimental results are also provided to evaluate the possibilities of the proposed converter.

Abstract: Power consumption is a key issue in highperformanceinterconnection network design. Communicationlinks, already a aignificant consumer of power now,will take up an ever larger portion of the power budgetas demand for network bandwidth increases. In this paper,we motivate the use of dynamic voltage scaling (DVS)for links, where the frequency and voltage of links are dynamicallyadjusted to minimize power consumption. Wepropose a history-based DYS algorithm that jjlidiciously adjustsDVS poIicies based on past link utilization. Despitevery conservative assumptions about DVS link characteristics,our approach realizes up to 4.5X power savings (3.2Xaverage), with just an average 27.4% Iatency increase and2.5% throughput reduction. To the best of our knowledge,this is the first study that targets dynamic power optimizationof interconnection networks.

Abstract: When paralleled to the utility bus, synchronous generators can be controlled using either terminal voltage or VAr/power factor control. Selection is dependent upon the size of the generator and the stiffness of the connecting utility bus. For large generators where the kVA is significant, these machines are usually terminal voltage regulated and dictate the system's bus voltage. When smaller terminal voltage regulated generators are synchronized to a stiff utility bus, the system voltage will not change as the smaller generator shares reactive loading. However, if the system voltage changes significantly, the smaller generator, with its continuous acting terminal voltage regulator, will attempt to maintain the voltage set point. As the voltage regulator follows its characteristic curve, it may cause either over or under excitation of the smaller generator. Excessive system voltage may cause a small generator to lose synchronizing torque, while low system voltage may cause excessive heating on the generator or excessive overcurrent operation of the excitation system. Maintaining a constant reactive load on the smaller generating unit can reduce the generator field current variations and, thus, reduce the maintenance of the collector rings and brushes. This paper illustrates the effect of changing system bus voltage on small generators utilizing voltage versus VAr/power factor regulation.

Abstract: A power charging system for charging portable electric devices. The power charging system includes a plurality of transformers for transforming a plurality of different input voltages into a standard DC (direct current) voltage. The charging system also includes a power cord for inputting and outputting the standard DC voltage. The charging system also includes a plurality of converters for converting the standard DC voltage into the working voltage of the portable electric devices. Users connect the corresponding converters to the power cord and then connect the power cord to any one of the transformers to use the standard DC voltage to charge the portable electric devices.

Abstract: A processor power supply voltage controller. The controller includes a temperature sensor configured to sense a temperature of a processor and generate a temperature signal in accordance therewith. A regulator is coupled to provide a power supply voltage to the processor. The regulator is coupled to receive the temperature signal and control the power supply voltage to maintain a substantially stable crosstalk level within the processor.

Abstract: P -V and Q - V curves are commonly used to determine the steady state voltage stability limit of a power system. In this letter, a new method of determining the voltage stability limit using the P -Q curve is presented. The boundary of the voltage stability region is first determined and then presented in the P -Q plane. For a given operating point, the voltage stability margin can easily be determined from the stability boundary in the P -Q plane. The proposed method of determining the voltage stability limit was tested on a simple system and very interesting results were found.

Abstract: This paper presents a positive sequence voltage detector based on a new "synchronous double reference frame PLL" (SDRF-PLL). This PLL exhibits a fast, precise and robust behavior under unbalanced utility conditions. When amplitude and phase of the positive sequence source voltage are known, various compensation strategies are feasible for the control of the unified power quality conditioner. Four suitable control strategies are shown. The performance of the proposed SDRF-PLL is verified by means of its application in the control of a unified power quality conditioner. In this paper, an analytical study and a verification by simulation are conducted.

Abstract: This paper relates the potential energy savings to the energy profile of a circuit. These savings are obtained by using gate sizing and supply voltage optimization to minimize energy consumption subject to a delay constraint. The sensitivity of energy to delay is derived from a linear delay model extended to multiple supplies. The optimizations are applied to a range of examples that span typical circuit topologies including inverter chains, SRAM decoders and adders. At a delay of 20% larger than the minimum, energy savings of 40% to 70% are possible, indicating that achieving peak performance is expensive in terms of energy.

Abstract: A switching power supply consists of the power stage and the control circuit. The power stage performs the basic power conversion from the input voltage to the output voltage and includes switches and the output filter. This report addresses the buck-boost power stage only and does not cover control circuits. Detailed steady-state and small-signal analysis of the buck-boost power stage operating in continuous and discontinuous mode is presented. Variations in the standard buck-boost power stage and a discussion of power stage component requirements are included.

Abstract: This paper describes a new economical sag/swell voltage generator suitable for the evaluation of high power custom power devices such as DVR (dynamic voltage restorer) and DSTATCOM (distribution static compensator). Proposed system was designed to generate the several power quality disturbances in MVA power ratings-sag, swell, under voltage, over voltage and harmonic distortions. The sag and the under voltage can be generated by voltage drop across a reactor, while its magnitude and durations can be controlled by the firing angle of TCR (thyristor controlled reactor). In the case of the swell and the over voltage, we need a step-up transformer. Output of the step-up transformer is regulated by TCR to obtain nominal voltage level. At any given instant, if the firing angle of TCR is retarded or stopped, then we can obtain the swell voltage or the over voltage disturbance. Also we can generate harmonic current by controlling firing angles of TCR, while keeping the system voltage level within the specified limits. In this paper, two identical three-phase wye-connected TCRs are connected to the secondary windings of two step-down transformers, one operated from wye-wye transformer, the other from delta-wye transformer. Harmonic filters (11/sup th/ and 13/sup th/) are added to reduce the voltage distortion when TCRs are operated. Simulation results are given for several cases of voltage sag and swell generations. Design guidelines are given for the TCR. Finally, conclusions are given.

Abstract: There is disclosed an adaptive voltage power supply that finely adjusts VDD to an optimum level. The adaptive voltage power supply comprises: 1) a first charging circuit capable of increasing a reference voltage on a charge capacitor in response to receipt of a first VDD control signal; 2) a second charging circuit capable of decreasing the reference voltage on the charge capacitor in response to receipt of a second VDD control signal; and 3) a power supply capable of receiving the reference voltage on the charge capacitor and generating an output power level, VDD, determined by a level of the reference voltage.

Abstract: A method of analyzing the power distribution in a chip containing one or more voltage islands, each voltage island having a power distribution network connected to a chip-level power distribution network by one or more voltage translation interface circuits. The method comprising: analyzing the voltage-island power distribution networks independently of the chip-level power distribution network to obtain voltage translation interface circuit currents; using the voltage translation interface circuit currents as input to a model of the chip-level power distribution network to obtain voltage translation interface circuit input voltages; and calculating voltage translation interface circuit output voltages based on the voltage translation interface circuit input voltages, the voltage translation interface circuit currents, and current-voltage characteristics of the voltage translation interface circuits.