Showing papers on "Voltage regulation published in 2006"

Power Management Strategies for a Microgrid With Multiple Distributed Generation Units

Abstract: This paper addresses real and reactive power management strategies of electronically interfaced distributed generation (DG) units in the context of a multiple-DG microgrid system. The emphasis is primarily on electronically interfaced DG (EI-DG) units. DG controls and power management strategies are based on locally measured signals without communications. Based on the reactive power controls adopted, three power management strategies are identified and investigated. These strategies are based on 1) voltage-droop characteristic, 2) voltage regulation, and 3) load reactive power compensation. The real power of each DG unit is controlled based on a frequency-droop characteristic and a complimentary frequency restoration strategy. A systematic approach to develop a small-signal dynamic model of a multiple-DG microgrid, including real and reactive power management strategies, is also presented. The microgrid eigen structure, based on the developed model, is used to 1) investigate the microgrid dynamic behavior, 2) select control parameters of DG units, and 3) incorporate power management strategies in the DG controllers. The model is also used to investigate sensitivity of the design to changes of parameters and operating point and to optimize performance of the microgrid system. The results are used to discuss applications of the proposed power management strategies under various microgrid operating conditions

Switching power supply circuit

Abstract: The present invention relates to a switching power-supply circuit comprising: rectifying and smoothing means for generating a rectified and smoothed voltage and outputting the rectified and smoothed voltage as a direct-current input voltage; an insulating converter transformer for transferring a primary-side output to a secondary side; switching means for intermittently passing on the direct-current input voltage to a primary winding of the insulating converter transformer; a primary-side resonance circuit for actuating the switching means in a voltage resonance mode; power-factor improvement means for improving a power factor by generating intermittently a rectified current based on the fed-back switching output voltage; a secondary-side resonance circuit on a secondary side of the insulating converter transformer; direct-current output voltage generation means carrying out a rectification operation in order to generate a secondary-side direct-current output voltage; and constant-voltage control means for executing constant-voltage control on the secondary-side direct-current output voltage.

A self-tuning DVS processor using delay-error detection and correction

Abstract: In this paper, we present a dynamic voltage scaling (DVS) technique called Razor which incorporates an in situ error detection and correction mechanism to recover from timing errors. We also present the implementation details and silicon measurements results of a 64-bit processor fabricated in 0.18-/spl mu/m technology that uses Razor for supply voltage control. Traditional DVS techniques require significant voltage safety margins to guarantee computational correctness at the worst case combination of process, voltage and temperature conditions, leading to a loss in energy efficiency. In Razor-based DVS, however, the supply voltage is automatically reduced to the point of first failure using the error detection and correction mechanism, thereby eliminating safety margins while still ensuring correct operation. In addition, the supply voltage can be intentionally scaled below the point of first failure of the processor to achieve an optimal tradeoff between energy savings from further voltage reduction and energy overhead from increased error detection and correction activity. We tested and measured savings due to Razor DVS for 33 different dies and obtained an average energy savings of 50% over worst case operating conditions by scaling supply voltage to achieve a 0.1% targeted error rate, at a fixed frequency of 120 MHz.

High-Quality Power Generation Through Distributed Control of a Power Park Microgrid

Abstract: Inverters are a necessary interface for several forms of distributed generation (DG) and where they form a microgrid they have the potential to offer high power quality. The challenge is to coordinate the actions of a group of inverters so that they offer the level of power quality known to be possible from fast local control of a single inverter. The case examined here is a power park of several inverter-based DG in relatively close proximity. A basic requirement is that the inverters regulate the grid voltage and share the real and reactive power demands according to their ratings. In small girds with high proportions of nonlinear and unbalanced loads it is also important to actively control the waveform quality in terms of harmonics, transient disturbances, and balance. Further, it is important that these duties are shared equally between the units rather than having one master unit taking the lead in the voltage control function. A constraint faced in designing a sharing system is the limited bandwidth of signal communication even over distances of a few meters. A control method is proposed that separates the control tasks in the frequency domain. Power sharing and voltage regulation are controlled centrally and commands are distributed through a low-bandwidth communication link. Waveform quality functions are controlled in high bandwidth controllers distributed to each local inverter. Experimental tests on a grid of three 10-kVA inverters are used to show that the method fully exploits the inherent fast response of the inverters while also ensuring voltage balance even with extreme load imbalance. It is shown that circulating currents are avoided during steady state and transients

An analytical model for predicting the remaining battery capacity of lithium-ion batteries

Abstract: Predicting the residual energy of the battery source that powers a portable electronic device is imperative in designing and applying an effective dynamic power management policy for the device This paper starts up by showing that a 30% error in predicting the battery capacity of a lithium-ion battery can result in up to 20% performance degradation for a dynamic voltage and frequency scaling algorithm Next, this paper presents a closed form analytical expression for predicting the remaining capacity of a lithium-ion battery The proposed high-level model, which relies on online current and voltage measurements, correctly accounts for the temperature and cycle aging effects The accuracy of the high-level model is validated by comparing it with DUALFOIL simulation results, demonstrating a maximum of 5% error between simulated and predicted data

Natural Balance of Multicell Converters: The Two-Cell Case

Abstract: The multicell converter topology is said to possess a natural voltage balancing property. This paper is the first of a two-part series in which multicell converters are modelled for the general case of p-cells. This paper focuses on the development of the natural balancing theory for the two-cell case. An understanding of the two-cell case is fundamental to understanding the general balancing theory. The switching functions used in switching these converters are mathematically analyzed. Equivalent circuits are derived and presented. The switching and balancing properties of these converters are mathematically analyzed. The main conclusion of the analysis is that the natural balancing of these converters are influenced by three factors namely, the harmonic content of the reference waveform, the switching frequency and the load impedance. Mathematical tools are presented that can help designers to predict if balancing problems would occur for a particular set of operating conditions. As a result of the detailed understanding of the balancing mechanism that is gained through this theory it is shown that by adding a balance booster, the load impedance can be manipulated to improve the natural balancing of the converter. Simulation results are included to verify the presented balance theory and properties

Methods and apparatus for high power factor controlled power delivery using a single switching stage per load

Abstract: Methods and apparatus for high power factor power transfer to a load using a single switching stage. In exemplary implementations, a controllable variable power may be delivered to a load using a single switching stage while maintaining high power factor, in some cases without requiring any feedback information relating to the load conditions (i.e., without monitoring load voltage and/or current) to control normal switching operations in the single switching stage, and without requiring regulation of load voltage and/or load current. In one example, a single stage high power factor driver is used to control power delivery to an LED-based light source.

Multi-voltage CMOS Circuit Design

Abstract: List of Tables. List of Figures. Preface. 1 Introduction. 1.1 Evolution of Integrated Circuits. 1.2 Outline of the Book. 2 Sources of Power Consumption in CMOS Integrated Circuits. 2.1 Dynamic Switching Power. 2.2 Leakage Power. 2.3 Short-Circuit Power. 2.4 Static DC Power. 3 Supply and Threshold Voltage Scaling Techniques. 3.1 Dynamic Supply Voltage Scaling. 3.2 Multiple Supply Voltage CMOS. 3.3 Threshold Voltage Scaling. 3.4 Multiple Supply and Threshold Voltage CMOS. 3.5 Dynamic Supply and Threshold Voltage Scaling. 3.6 Circuits with Multiple Voltage and Clock Domains. 3.7 Chapter Summary. 4 Low Voltage Power Supplies. 4.1 Linear DC-DC Converters. 4.2 Switched-Capacitor DC-DC Converters. 4.3 Switching DC-DC Converters. 4.4 Chapter Summary. 5 Analysis of Buck Converters for On-Chip Integration with a Dual Supply Voltage Microprocessor. 5.1 Circuit Model of a Buck Converter. 5.2 Efficiency Analysis of a Buck Converter. 5.3 Simulation Results. 5.4 Chapter Summary. 6 Low Voltage Swing Monolithic DC-DC Conversion. 6.1 Circuit Model of a Low Voltage Swing Buck Converter. 6.2 Low Voltage Swing Buck Converter Analysis. 6.3 Chapter Summary. 7 High Input Voltage Step-Down DC-DC Converters for Integration in a Low Voltage CMOS Process. 7.1 Cascode Bridge Circuits. 7.2 High Input Voltage Monolithic Switching DC-DC Converters. 7.3 Chapter Summary. 8 Signal Transfer in Integrated Circuits with Multiple Supply Voltages. 8.1 A High Speed and Low Power Voltage Interface Circuit. 8.2 Voltage Interface Circuit Simulation Results. 8.3 Experimental Results. 8.4 Chapter Summary. 9 Domino Logic with Variable Threshold Voltage Keeper. 9.1 Standard Domino Logic Circuits. 9.2 Domino Logic with Variable Threshold Voltage Keeper. 9.3 Simulation Results. 9.4 Domino Logic with Forward and Reverse Body Biased Keeper. 9.5 Chapter Summary. 10 Subthreshold Leakage Current Characteristics of Dynamic Circuits. 10.1 State Dependent Subthreshold Leakage Current Characteristics. 10.2 Noise Immunity. 10.3 Power and Delay Characteristics in the Active Mode. 10.4 Dual Threshold Voltage CMOS Technology. 10.5 Chapter Summary. 11Sleep Switch Dual Threshold Voltage Domino Logic with Reduced Standby Leakage Current. 11.1 Previously Published Sleep Mode Circuit Techniques. 11.2 Dual Threshold Voltage Domino Logic Employing Sleep Switches. 11.3 Simulation Results. 11.4 Noise Immunity Compensation. 11.5 Chapter Summary. 12 Conclusions. Bibliography. Index. About the Authors.

Design and performance evaluation of subsynchronous damping controller with STATCOM

Abstract: A long transmission line needs controllable series as well as shunt compensation for power flow control and voltage regulation. This can be achieved by suitable combination of passive elements and active FACTS controllers. In this paper, series passive compensation and shunt active compensation provided by a static synchronous compensator (STATCOM) connected at the electrical center of the transmission line are considered. It is possible to damp subsynchronous resonance (SSR) caused by series capacitors with the help of an auxiliary subsynchronous damping controller (SSDC) on STATCOM. The objective of this paper is to investigate the SSR characteristics of the system and propose a new design procedure for SSDC based on nonlinear optimization to meet the specifications on the damping torque in the range of critical torsional frequencies. The SSDC uses the Thevenin voltage signal to modulate the reactive current reference of STATCOM. The Thevenin voltage signal is derived from the locally available STATCOM bus voltage and reactive current signals. The STATCOM configurations considered in this paper are 12 pulse, two- and three-level voltage source converter with Type-2 and Type-1 control, respectively. The controller regulates either reactive current (supplied by the STATCOM) or the bus voltage. The 3-phase model of the STATCOM is based on switching functions. By neglecting harmonics in the switching function, D-Q model is derived which is combined with similar models of the other system components for linear analysis. The results of the linear analysis are validated by carrying out transient simulation based on the detailed nonlinear models. The study is performed on the system adapted from the IEEE First Benchmark Model.

Method and apparatus for controlling current supplied to electronic devices

Abstract: The present invention provides a drive and control apparatus provides a desired switched current to a load including a string of one or more electronic devices. A voltage conversion means, based on an input control signal converts the magnitude of the voltage from the power supply to another magnitude that is desired at the high side of the load. A dimming control means provides control for activation and deactivation of the load and may further provide a means for current limiting. A feedback means is coupled to the voltage conversion means and a current sensing means and provides a control signal to the voltage conversion means that is indicative of voltage drop across the current sensing means which represents the current flowing through the load. Based on the control signal received, the voltage conversion means can subsequently adjust its output voltage such that a constant switched current is provided to the load.

STATCOM-Based Voltage Regulator for Self-Excited Induction Generator Feeding Nonlinear Loads

Abstract: This paper deals with the performance analysis of a static compensator (STATCOM)-based voltage regulator for self-excited induction generators (SEIGs) supplying nonlinear loads. In practice, a number of loads are nonlinear in nature, and therefore, they inject harmonics in the generating systems. The SEIG's performance, being a weak isolated system, is very much affected by these harmonics. The additional drawbacks of the SEIG are poor voltage regulation and that it requires an adjustable reactive power source with varying loads to maintain a constant terminal voltage. A three-phase insulated-gate-bipolar-transistor-based current-controlled voltage source inverter working as STATCOM is used for harmonic elimination, and it provides the required reactive power for the SEIG, with varying loads to maintain a constant terminal voltage. A dynamic model of the SEIG-STATCOM feeding nonlinear loads using stationary d-q axes reference frame is developed for predicting the behavior of the system under transient conditions. The simulated results show that SEIG terminal voltage is maintained constant, even with nonlinear balanced and unbalanced loads, and free from harmonics using STATCOM-based voltage regulator

Voltage regulation with STATCOMs: modeling, control and results

Abstract: This paper presents system modeling and control design for fast load voltage regulation using static compensators (STATCOMs). The modeling strategy gives a clear representation of load voltage magnitude and STATCOM reactive current on an instantaneous basis. The particular coordinate transformation employed here also facilitates extraction of linearized system dynamics in conjunction with circuit simulators. It is rigorously shown that the control problem of load voltage regulation using reactive current is nonminimum phase. Linear and nonlinear controllers for the regulation problem are designed and compared via simulation results. Internal dynamics of the STATCOM are modeled using the same strategy. Lyapunov based adaptive controllers are designed for controlling the STATCOM reactive current while maintaining its dc bus voltage. Simulation results of the controlled STATCOM integrated with the load bus voltage controller are presented to show efficacy of the modeling and control design.

Coordinated control of an HVDC link and doubly fed induction generators in a large offshore wind farm

Abstract: Doubly fed induction generators (DFIGs) are an economic variable-speed solution for large wind turbines while high-voltage dc (HVdc) transmission is being considered for the grid connection of some offshore wind farms. This paper analyzes the need for coordinating the control of the DFIGs and the HVdc link so that the two topologies can work together, giving system designers and operators a choice that may be useful in some applications. It is desired that individual generators be controlled for power tracking in a way similar to that used when they are connected directly to an ac grid, although a grid voltage reference for the DFIG control is no longer available as an independent source in this case. The study shows that machine control should explicitly maintain the flux level, which then allows the HVdc link to regulate the local system frequency and, indirectly, voltage amplitude. Interactions between DFIGs and the HVdc link are investigated and simulations performed to verify the proposed control strategy.

Operation and control of a dynamic voltage restorer using transformer coupled H-bridge converters

Abstract: The dynamic voltage restorer (DVR) as a means of series compensation for mitigating the effect of voltage sags has become established as a preferred approach for improving power quality at sensitive load locations. Meanwhile, the cascaded multilevel type of power converter topology has also become a workhorse topology in high power applications. This paper presents the detailed design of a closed loop regulator to maintain the load voltage within acceptable levels in a DVR using transformer coupled H-bridge converters. The paper presents system operation and controller design approaches, verified using computer simulations, and a laboratory scale experimental prototype.

Modeling and design of a neutral-point voltage regulator for a three-level diode-clamped inverter using multiple-carrier modulation

Abstract: The three-level diode-clamped multilevel converter commonly called the neutral-point-clamped converter has become established to be a preferred topology for high-power motor drive applications operating at several kilovolts. Although solutions to the problem of maintaining a stable neutral-point voltage in the converter continue to be the topic of research, a simple solution based on a design-oriented dynamic model of the system is not widely known. This paper presents the design, analysis, and implementation of a simple neutral-point voltage regulator for a three-level diode-clamped multilevel inverter, which uses a multiple-carrier sine-triangle modulator in conjunction with a closed-loop controller for neutral-point regulation. Redundant state choices are controlled via a continuous offset voltage that regulates the dc injection into the midpoint of the dc bus. A small-signal transfer function is developed in closed form, for neutral-point regulation, with the voltage offset as the control variable. Besides maintaining dc-bus voltage balance, the use of the approach leads to a significant reduction in the voltage distortion at the neutral point, allowing a definitive reduction in the required dc bus capacitance. Analytical, computer simulation, and experimental results verifying the approach are presented in this paper.

Apparatus and method of wirelessly sharing power by inductive method

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.

Semiconductor device, display device, and electronic device

Abstract: A pixel includes a load, a transistor which controls a current supplied to the load, a storage capacitor, and first to fourth switches. By inputting a potential in accordance with a video signal into the pixel after the threshold voltage of the transistor is held in the storage capacitor, and holding a voltage of the sum of the threshold voltage and the potential, variations of a current value caused by variations of threshold voltage of a transistor can be suppressed. Consequently, a predetermined current can be supplied to the load such as a light-emitting element. Further, by changing the potential of a power supply line, a display device with a high duty ratio can be provided.

A comparison of voltage stability indices

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.

Congestion management ensuring voltage stability

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.

Switch mode power supply controllers

Abstract: This invention relates to SMPS controllers employing primary side sensing. We describe a system for identifying a knee point in a sensing waveform, at which the output voltage of the SMPS may be sampled accurately on the primary side. The system identifies the knee point by fitting a tangent to a portion of a power transformer voltage waveform, and samples the voltage waveform at the knee point to determine the SMPS output voltage. In preferred embodiments this technique is implemented using a decaying peak detector, providing a timing signal indicating detection of the knee point. Sample/hold and error amplifier circuits may be employed to achieve output voltage regulation.

Primary-side feedback switching power supply

Abstract: The present invention discloses a primary-side feedback switching power supply that uses a sample-and-hold circuit to obtain a corner voltage of a harmonic wave voltage while the primary-side auxiliary winding is operating at a discontinuous mode as a feedback control, and provides both voltage regulation and current limit functions. A stable voltage output is provided within the nominal input voltage and nominal output load, such that when the output reaches a current limit, the output voltage drops but the output current is controlled to remain unchanged, so as to provide an over-current protection.

Controller design for an induction generator driven by a variable-speed wind turbine

Abstract: This paper presents the modeling, controller design and a steady-state analysis algorithm for a wind-driven induction generator system. An output feedback linear quadratic controller is designed for the static synchronous compensator (STATCOM) and the variable blade pitch in a wind energy conversion system (WECS) in order to reach the voltage and mechanical power control under both grid-connection and islanding conditions. A two-reference-frame model is proposed to decouple the STATCOM real and reactive power control loops for the output feedback controller. To ensure zero steady-state voltage errors for the output feedback controller, the integrals of load bus voltage deviation and dc-capacitor voltage deviation are employed as the additional state variables. Pole-placement technique is used to determine a proper weighting matrix for the linear quadratic controller such that satisfactory damping characteristics can be achieved for the closed-loop system. Effects of various system disturbances on the dynamic performance have been simulated, and the results reveal that the proposed controller is effective in regulating the load voltage and stabilizing the generator rotating speed for the WECS either connected with or disconnected from the power grid. In addition, proper steady-state operating points for an isolated induction generator can be determined by the proposed steady-state analysis algorithm. Constant output frequency control using the derived steady-state characteristics of the isolated induction generator is then demonstrated in this paper

Wind-driven self-excited induction generator with voltage and frequency regulated by a reduced-rating voltage source inverter

Abstract: This paper discusses the regulation of the voltage and frequency of a stand-alone fixed-pitch wind energy conversion system (WECS) based on a self-excited squirrel-cage induction machine. A shunt connected voltage source inverter (VSI) and a controllable dump load are used for regulation purposes. A battery bank is included in the dc side of the VSI so that it can absorb and inject active power thus increasing the efficiency and availability of the system. A control scheme for the VSI with independent control of active and reactive power allows the state of charge of the batteries to be kept in a safe range while maximizing the voltage regulating capabilities of the VSI. The characteristics of the wind turbine, self-excited generator, and the ratings of the VSI are considered in order to determine the load range for which voltage and frequency can be regulated for a given wind speed range. The feasibility of the proposed system is verified by simulations.

Synchrophasor-Based Real-Time Voltage Stability Index

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

Three-Level Inverter Scheme With Common Mode Voltage Elimination and DC Link Capacitor Voltage Balancing for an Open-End Winding Induction Motor Drive

Abstract: A dc link capacitor voltage balancing scheme along with common mode voltage elimination is proposed for an induction motor drive, with open-end winding structure. The motor is fed from both the ends with three-level inverters generating a five level output voltage space phasor structure. If switching combinations, with zero common mode voltage in the pole voltage, are used, then the resultant voltage space vector combinations are equivalent to that of a three-level inverter. The proposed inverter vector locations exhibit greater multiplicity in the inverter switching combinations which is suitably exploited to arrive at a capacitor voltage balancing scheme. This allows the use of a single dc link power supply for the combined inverter structure. The simultaneous task of common mode voltage elimination with dc link capacitor voltage balancing, using only the switching state redundancies, is experimentally verified on a 1.5-kW induction motor drive

A Multilevel Inverter Topology for Inductively Coupled Power Transfer

Abstract: This paper describes a multilevel inverter that can synthesize quantized approximations of arbitrary ac waveforms. This converter could be used to deliver power over multiple frequencies simultaneously. Unlike traditional multilevel inverters, this topology does not require an external voltage balancing circuit, a complicated control scheme, or isolated dc sources to maintain its voltage levels while delivering sustained real power. In this paper, we use this circuit for heating frequency selectable induction targets designed to stimulate temperature sensitive polymer gel actuators. For this application our multilevel inverter offers higher efficiency than a pulse width modulated full-bridge inverter (a more conventional power supply solution) at comparable levels of total harmonic distortion

A 10-kW SOFC low-Voltage battery hybrid power conditioning system for residential use

Abstract: This paper proposes a 10-kW power conditioning system for a 5-kW solid oxide fuel cells (SOFCs) low-voltage battery hybrid power generation that has been developed for participation in the 2003 Future Energy Challenge Competition organized by the U.S. Department of Energy and the IEEE. The objective of the competition was to develop a fuel cell inverter with minimum requirement for cost of $40/kW and efficiency of 90%. The proposed power conditioning system consists of the front-end dc-dc converter, the dc-ac inverter and the bidirectional dc-dc converter. Practical issues such as component rating calculation, high-frequency transformer design, heat sink design, and protection are detailed aiming at the cost and efficiency targets. A low-cost implementation of controllers is discussed along with current-mode control, output voltage regulation with capacitor balancing and an SOC control for battery management. A 10-kW hardware prototype was successfully built and tested in the steady-state as well as in the transient-state. Experimental performances are compared to minimum target requirements of the fuel cell inverter. The cost analysis is done based on the spreadsheets evaluation forms provided in the competition.

Advanced control of PWM converter with variable-speed induction generator

Abstract: This paper describes simple control structures for the vector-controlled stand-alone induction generator (IG) used to operate under variable speeds. Different control principles, indirect vector control and deadbeat current control, are developed for a voltage source pulsewidth-modulation (PWM) converter and the three-phase variable-speed squirrel-cage IG to regulate dc link and generator voltages with the newly designed phase-locked loop circuit. The required reactive power for the variable-speed IG is supplied by means of the PWM converter and a capacitor bank to buildup the voltage of the IG without the need for a battery, to reduce the rating of the PWM converter with the need for only three sensors, and to eliminate the harmonics generated by the PWM converter. These proposed schemes can be used efficiently for variable-speed wind energy conversion systems. The measurements of the IG systems at various speeds and loads are given and show that these systems are capable of good ac and dc voltage regulations

An adaptive local learning-based methodology for voltage regulation in distribution networks with dispersed generation

Abstract: This paper proposes a computational architecture for the voltage regulation of distribution networks equipped with dispersed generation systems (DGS). The architecture aims to find an effective solution of the optimal regulation problem by combining a conventional nonlinear programming algorithm with an adaptive local learning technique. The rationale for the approach is that a local learning algorithm can rapidly learn on the basis of a limited amount of historical observations the dependency between the current network state and the optimal asset allocation. This approach provides an approximate and fast alternative to an accurate but slow multiobjective optimization procedure. The experimental results obtained by simulating the regulation policy in the case of a medium-voltage network are very promising

Methods and systems for intentionally isolating distributed power generation sources

Abstract: A method and system for operating a mini-grid including one or more power generation sources and one or more loads independently from a utility grid is provided, where the mini-grid is disconnected from the utility grid in response to a power disruption over the utility grid. A universal interconnect device forms a connection between the mini-grid and the utility grid. In the disconnected state, the mini-grid operates independently from the utility grid, such that the power generation sources of the mini-grid supply the loads. Frequency and voltage regulation are provided by the universal interconnect device through a monitoring function performed by a controller in conjunction with at least an energy storage device, which can absorb or generate power as needed.