Abstract: A method and apparatus for controlling a selectable voltage audio power output stage provides a mechanism for raising the selected power amplifier output voltage in time for the arrival of signal peaks to avoid clipping. Signal peaks may either be delayed by delaying an increase in volume control level or enabling signal compression for a predetermined time period, so that sufficient time is provided for the amplifier power supply to stabilize at a higher operating voltage when an increase of power supply voltage is selected. Alternatively, a signal level may be determined at an upstream source, such as a decoder or filter that provides information in sufficient advance of the arrival of the peaks, and used to control the power supply selection, so that the higher power supply voltage level is selected in advance of arrival of the signal peaks that would otherwise cause clipping at the power amplifier output.

Abstract: An inductive power supply (9) includes a transceiver (28) for sending information between the remote device (11) and the inductive power supply. The remote device determines the actual voltage and then sends a command to the inductive power supply to change the operating frequency if the actual voltage is different from the desired voltage. In order to determine the actual voltage, the remote device determines a peak voltage (34) and then applies a correction factor.

Abstract: Voltage stability has become a very important issue of power systems analysis. This paper discusses some important aspects related to voltage stability indices in electric power systems. Some techniques previously studied in the literature are analyzed and a comparison of the performance of several indices is presented. The effectiveness of the analyzed methods are demonstrated through numerical studies in IEEE 14 busbar test system, using several different scenarios of load increase.

Abstract: There is provided a method for measuring a parameter of a power frequency current being carried by a power line. The method that includes (a) transducing a power frequency current flowing through a power line, into a power frequency voltage, via an inductive coupler that couples a communications signal from the power line, (b) separating the power frequency voltage from the communications signal, and (c) determining a value of a parameter of the power frequency current from the power frequency voltage. There is also provided a system and an apparatus for measuring the parameter.

Abstract: This paper addresses the congestion management problem avoiding offline transmission capacity limits related to stability. These limits on line power flows are replaced by optimal power flow-related constraints that ensure an appropriate level of security, mainly targeting voltage instabilities, which are the most common source of stability problems. Results from an illustrative case study based on the IEEE 24-bus Reliability Test System are analyzed. Conclusions are duly drawn.

Abstract: An apparatus and method of wirelessly sharing power by an inductive method are provided. The apparatus includes a first battery supplying power; a rectifier supplied with an AC voltage, converts the AC voltage into a DC voltage, and outputs the DC voltage; an inverter supplied with the DC voltage, converts the DC voltage into the AC voltage, and outputs the AC voltage; a power control/conversion unit connected to the rectifier or the inverter and supplying power to charge the first battery or a second battery that is provided in an external device as a power supply for the first battery; and a communication unit communicating with the external device.

Abstract: This paper presents a new online voltage stability index (VSI) that predicts the power system steady-state voltage stability limit. Starting with deriving a method to predict three types of maximum transferable power (real power, reactive power, and apparent power) of a single-source power system, a new VSI based on the calculated load margins is devised. In order to apply the VSI to large power systems, a method is developed to simplify the large network behind a load bus into a single source and a single transmission line using time-synchronized phasor measurements and network parameters. The simplified system model, to which the devised VSI can be applied, preserves power flow and voltage information of the particular load bus under study. The proposed VSI combined with the network simplification method provides the voltage stability margin of each individual load bus in an informative format and identifies the load bus that is the most vulnerable to voltage collapse. Test results from applying the VSI on two test systems validate its applicability for online applications

Abstract: Multilevel inverters with a large number of steps (more than 50 levels) can generate high quality voltage waveforms, good enough to be considered as suitable voltage template generators. Many levels or steps can follow a voltage reference with accuracy, and with the advantage that the generated voltage can be modulated in amplitude instead of pulse-width modulation. The main disadvantage of this type of topology is the large number of power supplies and semiconductors required to obtain these multistep voltage waveforms. This paper is focussed on minimizing the number of power supplies and semiconductors for a given number of levels. Different combinations of topologies are presented, and the corresponding mathematical relations have been derived. This paper shows optimized curves to obtain the relation between a minimum number of power semiconductors required for a given number of levels. Experimental results obtained from an optimized prototype, capable of generatng 81 levels of voltage with only four power supplies and 16 transistors per phase, are shown.

Abstract: In this paper, the maximum loading margin (MLM) approach is proposed in finding generation directions to maximize the static voltage stability margin, where the MLM is evaluated at various possible generation directions in the generation direction space. An approximate and simple model representing the relationship between the generation direction and the LM is used to obtain the MLM point. The proposed method is validated in the modified IEEE 14-bus test system and applied to the Thailand power system. LMs of the system with the generation directions are compared for different generator combinations using the proposed technique.

Abstract: Paisan Boonchiam and Nadarajah MithulananthanElectric Power System Management, Energy Field of Study, Asian Institute of Technology,PO Box 4, Klong Luang, Pathum Thant 12120, Thailand;E-mail : mithu lan(@,ait ac t hAbstractThis paper presents the application of dynamic voltage restorers (DVR) on power distributionsystems for mitigation of voltage sags/swells at critical loads DVR is one of the compensating typesof custom power devices An adequate modeling and simulation of DVR, including controls inMATLAB, show the flexibility and easiness of the MATLAB environment in studying andunderstanding such compensating devices The DVR, which is based on forced-commutated voltagesource converter (VSC) has been proved suitable for the task of compensating voltage sags/swellsSimulation results are presented to illustrate and understand the performances of DVR in supportingload voltages under voltage sags/swells conditionsKeywords: custom power, power quality, voltage sags, voltage swells, DVR1 IntroductionModem power systems are complexnetworks, where hundreds of generating stationsand thousands ofload centers are interconnectedthrough long power transmission anddistribution networks [1] The main concern ofconsumers is the quality and reliability of powersupplies at various load centers where they arelocated at Even though the power generation inmost well-developed countries is fairly reliable,the quality of the supply is not so reliablePower distribution systems, ideally, shouldprovide their customers with an unintemrptedflow of energy at smooth sinusoidal voltage atthe contracted magnitude level and frequencyl2l However, in practice, power systems,especially the distribution systems, havenumerous nonlinear loads, which significantlyaffect the quality of power supplies As a resultof the nonlinear loads, the purity of thewaveform of supplies is lost This ends upproducing many power quality problems Aparlfrom nonlinear loads, some system events, bothusual (eg capacitor switching, motor starling)and unusual (eg faults) could also inflict powerquality problems [3] The consequence of powerquality problems could range from a simplenuisance flicker in the electrical lamps to loss ofthousands ofdollars due to production shutdownA power quality problem is defined as anymanifested problem in voltage/current or leadingto frequency deviations that result in failure ormisoperation of customer equipment 13-41Power quality problems are associated with anextensive number of electromagneticphenomena in power systems with broad rangesof time frames such as long duration variations,short duration variations other disturbancesShort duration variations are mainly caused byeither fault conditions or energization of largeloads that require high starting currentsDepending on the electrical distance related toimpedance, type ofgrounding and connection oftransformers between the faulted/load locationand the node, there can be a temporary loss ofvoltage or temporary voltage reduction (sag) orvoltage rise (swell) at different nodes of thesystem [5]Voltage sag is defined as a suddenreduction of supply voltage down 90% to 10Vonominal, followed by a recovery after a shortperiod of time A typical duration of sag is,according to the standard, l0 ms I minuteVoltage sag can cause loss of production inautomated processes since voltage sag can trip amotor or cause its controller to malfunctionVoltage swell, on the other hand, is defined as asudden increasing of supply voltage up I l0% to180% in rms voltage at the network fundamentalfrequency with duration from 10 ms to 1 minuteSwitching off a large inductive load orenergizing a large capacitor bank is a typical

Abstract: This paper presents an automatic system for real-time detection and analysis of voltage events in power systems. The voltage events considered are those that cause a temporary increase or decrease in the rms voltage magnitude over the limits recommended in the international standards. The system proposed uses three Kalman filters to detect when a voltage event begins and to estimate the three-phase voltage supply during the event. The results obtained from real measurements in a low-voltage distribution network show that the system accurately detects and analyzes in real time different types of voltage events in power systems

Abstract: The authors propose a control algorithm for a single-phase active-power filter working under a non-stiff voltage source. The method provides compensation for harmonics and reactive power and has an excellent dynamic performance. A detailed synchronization circuit is presented for proper sequencing of operation of the active power filter even when the source voltage contains multiple zero crossings. Experimental study has been carried out under a non-stiff voltage source to verify the proposed control scheme

Abstract: A progammable power supply for providing a regulated DC output power is disclosed. The power supply provides the output power to any one of a plurality of electronic devices adapted for receiving the output power at an operational voltage or an operational current. The power supply receives a programming signal to maintain the output power at the operational voltage or operational current associated with a particular selected electronic device. Accordingly, by varying the programming signal, the power supply can be programmed to provide output power to any one of several electronic devices having differing input power requirements.

Abstract: A method for controlling dynamic power factor or the reactive power of a wind farm is provided. The wind farm comprises a number of wind turbines connected to a utility grid driven with a requested power factor or a requested reactive power. The wind turbine output voltage is controlled to a specific voltage set point. In the method, the wind farm power factor is measured and compared with the power factor requested for the utility grid, or the wind farm reactive power is measured and compared with the reactive power requested for the utility grid, respectively; the ratio of the wind farm voltage to the utility grid voltage is adjusted, and the output voltage of the individual wind turbines is regulated to correspond to the specific voltage set point; the steps are repeated until the power factor of the wind farm electricity corresponds to the requested reactive power.

Abstract: A dual-input power converter comprises two power stages using a common low-side element, a first input for coupling a first input voltage to the first power stage, a second input for coupling a second input voltage to the second power stage, and a controller for driving the first and second power stages to convert the first or second input voltage to an output voltage.

Abstract: This paper presents a simple, fast, and efficient method for determining the maximum loading point (MLP) and the voltage stability security margin of electric power systems. The proposed method is based on nonlinear programming techniques. The MLP is accurately obtained after a few load change steps. The computational procedure involves two kinds of load changes. Initially, load increases toward the MLP are defined for minimizing an objective function based on sensitivities. In case an overestimated load increase drives the system outside the feasible (stable) operating region, another very simple optimization-based procedure aimed to minimize the power mismatches determines the load adjustment (curtailment) to pull the system back onto the feasibility boundary. Simulation results for small test to large realistic systems are shown to validate the proposed method.

Abstract: The static var compensator (SVC) has fast dynamic characteristics that can support effective system voltage following disturbances. Keeping reactive power reserve in an SVC during steady-state operation is always needed to provide reactive power requirements during system dynamics. This paper presents a new SVC control strategy with two stages of regulation slopes and two voltage regulation controls, which are fixed-voltage reference control and variable (floating) voltage reference control. The aim of this control is to limit the reactive power output from the SVC to the desired value during the steady-state voltage range and compensate the reactive power requirement from the upstream networks via the coordination with the under-load tap changer (ULTC). However, when the voltage deviates the steady-state voltage range, the SVC will react to support the system voltage using the SVC reactive power reserve. When a disturbance results in a new operating point, with a steady-state reactive-power output, the variable voltage reference control effectively changes the SVC output slowly and returns it within the steady-state margin.

Abstract: A method for controlling power flow of an electric power generation system (10) includes generating or dissipating electric power to maintain a predetermined grid voltage and frequency. The electric power is transmitted to a grid (20); and the current and voltage of the electric power thus transmitted are sensed. The frequency of the grid (20) and the power transmitted to the grid (20) is determined based on the sensed current or voltage. A grid-side converter (42) is then controlled to regulate the voltage and frequency of an electric grid (20) via a compensating circuit (52) when the sensed voltage is outside a predetermined voltage range or the determined frequency is outside a predetermined frequency range.

Abstract: The low voltage ride through (LVRT) requirement that has recently been imposed on the majority of new wind park projects has direct implications on the design and sizing of the power electronic conversion component. This paper considers three wind energy conversion systems and compares them in terms of the additional power electronic infrastructure and control that is required to meet the LVRT requirement. The complete detailed models are developed using electromagnetic transients programming and are compared for various low voltage events. The results convincingly show that the turbine that is interfaced through a full converter, using a dump load to limit dc over voltages, is simple in terms of realization and demonstrates superior performance.

Abstract: A power source is disclosed. The power source includes a first power source applying a first voltage to a control unit and a second power source applying a second voltage to a unit controlled by the control unit. The power source includes a first power supplying unit, which includes a main power switch and a first relay and supplies electric power to the first power source, and a second power supplying unit, which includes the main power switch and a second relay and supplies the electric power to the second power source. The electric power is supplied to the first power source by turning on the main power switch, and the first relay is turned on by a voltage output from the second power source. The electric power is supplied to the second power source by turning on the second relay by a voltage output from the first power source.

Abstract: One key component of the future automation is replacement of conventional distribution transformers by an all-solid-state (power-electronic) alternative. In this paper, the optimum design of a Power Electronic Transformer (PET) will be investigated. In the design process, the PFC and DC-DC converters have been integrated to achieve higher efficiency. The proposed PET performs typical functions and has advantages such as power factor correction, voltage regulation, voltage sag and swell elimination, voltage flicker reduction and protection capability in fault situations. In addition, it has other benefits such as light weight, low volume and no toxic dielectric coolants.

Abstract: Voltage stability is a security concern for modern power systems. It can be analyzed using detailed or equivalent models. In this paper a new approach is presented for voltage stability analysis using synchronized phasor measurement data. Simple equivalent models of the interconnected system and load side at a measurement point are estimated from the data, and then used for calculating PV curves and predicting the stability limit. Two different models are proposed, and compared based on the analyses performed on the event recordings from US western power system. Minimal modeling and formulation makes the method suitable for online calculations. The models are continuously updated to reflect the effects of different system components and changes

Abstract: Solar power tracking techniques are described herein. In one aspect of the invention, a solar power tracking apparatus includes, but is not limited to, a voltage converter and a controller coupled to the voltage converter. The voltage converter includes an input capable of being coupled to a solar power source and an output capable of being coupled to an electronic load, such as, for example, a portable electronic device. The voltage converter is configured to monitor or detect an amount of power drawn by the electronic load at the output of the voltage converter. In response to the monitored power drawn, the controller is configured to control the voltage converter to reduce amount of power to be drawn subsequently if the monitored amount of power exceeds a predetermined threshold. As a result, the output voltage from the solar power source is maintained within a predetermined range. Other methods and apparatuses are also described.

Abstract: High power consumption will shorten battery life for handheld devices and cause thermal and reliability problems. One way to lower the dynamic power consumption is to reduce the supply voltage. Multi-supply voltage (MSV) is introduced to provide higher flexibility in controlling the power and performance trade-off. In region-based MSV, circuits are partitioned into "voltage islands" where each island occupies a contiguous physical space and operates at one supply voltage. In a work by Wu et al. (2005), this supply voltage partitioning problem is addressed, and the input circuit is partitioned into a slicing structure with every voltage island rectangular in shape. This unnecessary restriction on the structure and island shapes has caused a significant degradation in the solution quality. In this paper, we propose a method to solve this voltage island generation problem without these restrictions. Experimental results have shown that our approach is fast and can improve the solution quality significantly. In some data sets, only two voltage islands are needed to satisfy the same power consumption bound while the approach by Wu et al. (2005) will generate nineteen

Abstract: Bootstrapped switches are used in a variety of applications including DC-DC converters, pipelined analog-to-digital converters and high voltage switches and drivers. Current work on highly integrated power management applications often requires the ability to measure voltage quantities that exceed the supply voltage in magnitude. This is primarily due to a basic need to maximize efficiency by running the power management IC on as low supply voltage as possible, while still maintaining the ability to sample and measure quantities from the surroundings that could well exceed the battery voltage. In this paper, a new bootstrapped switch is presented. The switch enables the precise sampling of input signals well greater than the chip supply voltage with no static power consumption, and without activating on-chip parasitic body diodes. The bootstrapped switch, presented here, is designed to sample an input signal with a 0-5.5-V range at a supply voltage of 2.75 V. Measurement data shows functionality for a 0-6-V input signal range with a supply voltage as low as 1.2 V

Abstract: Multiple power supply voltages are often used in modern high-performance ICs, such as microprocessors, to decrease power consumption without affecting circuit speed. To maintain the impedance of a power distribution system below a specified level, multiple decoupling capacitors are placed at different levels of the power grid hierarchy. The system of decoupling capacitors used in power distribution systems with multiple power supplies is described in this paper. The noise at one power supply can propagate to the other power supply, causing power and signal integrity problems in the overall system. With the introduction of a second power supply, therefore, the interaction between the two power distribution networks should be considered. The dependence of the impedance and magnitude of the voltage transfer function on the parameters of the power distribution system is investigated. An antiresonance phenomenon is intuitively explained in this paper. It is shown that the magnitude of the voltage transfer function is strongly dependent on the parasitic inductance of the decoupling capacitors, decreasing with smaller inductance. Design techniques to cancel and shift antiresonant spikes out of range of the operating frequencies are presented. It is also shown that it is highly desirable to maintain the effective series inductance of the decoupling capacitors as low as possible to decrease the overshoots of the response of the dual-voltage power distribution system over a wide range of operating frequencies. A criterion for an overshoot-free voltage response is presented in this paper. It is noted that the frequency range of the overshoot-free voltage response can be traded off with the magnitude of the response.

Abstract: The dependence of the system voltage stability on reactive power distribution forms the basis for reactive power optimisation. The technique attempts to utilise fully the reactive power sources in the system to improve the voltage stability and profile as well as meeting the reactive power requirements at the AC-DC terminals to facilitate the smooth operation of DC links. The method involves successive solution of steady-state power flows and optimisation of reactive power control variables using linear programming techniques. The proposed method has been applied to a few systems and the results obtained on a real-life equivalent 96-bus AC and a two-terminal DC system are presented for illustration.