بایگانی برچسب برای: microgrid

Intelligent Frequency Control in an AC Microgrid[taliem.ir]

Intelligent Frequency Control in an AC Microgrid: Online PSO-Based Fuzzy Tuning Approach

Modern power systems require increased intelligence and flexibility in the control and optimization to ensure the capability of maintaining a generation-load balance, following serious disturbances. This issue is becoming more significant today due to the increasing number of microgrids (MGs). The MGs mostly use renewable energies in electrical power production that are varying naturally. These changes and usual uncertainties in power systems cause the classic controllers to be unable to provide a proper performance over a wide range of operating conditions. In response to this challenge, the present paper addresses a new online intelligent approach by using a combination of the fuzzy logic and the particle swarm optimization (PSO) techniques for optimal tuning of the most popular existing proportional-integral (PI) based frequency controllers in the ac MG systems. The control design methodology is examined on an ac MG case study. The performance of the proposed intelligent control synthesis is compared with the pure fuzzy PI and the Ziegler-Nichols PI control design methods .
Benefits of Power Electronic Interfaces[taliem.ir]

Benefits of Power Electronic Interfaces for Distributed Energy Systems

With the increasing use of distributed energy (DE) systems in industry and its technological advancement, it is becoming more important to understand the integration of these systems with the electric power systems. New markets and benefits for DE applications include the ability to provide ancillary services, improve energy efficiency, enhance power system reliability, and allow customer choice. Advanced power electronic (PE) interfaces will allow DE systems to provide increased functionality through improved power quality and voltage/volt–ampere reactive (VAR) support, increase electrical system compatibility by reducing the fault contributions, and flexibility in operations with various other DE sources, while reducing overall interconnection costs. This paper will examine the system integration issues associated with DE systems and show the benefits of using PE interfaces for such applications.
Power Management Strategies for a Microgrid With[taliem.ir]

Power Management Strategies for a Microgrid With Multiple Distributed Generation Units

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 lso used to investigate sensitivity of the design to changes of parameters and operating point and to ptimize performance of the microgrid system. The results are used to discuss applications of the proposed power management strategies under various microgrid operating conditions.
An Accurate Power Control Strategy for[taliem.ir]

An Accurate Power Control Strategy for Power-Electronics-Interfaced Distributed Generation Units Operating in a Low-Voltage Multibus Microgrid

In this paper, a power control strategy is proposed for a low-voltage microgrid, where the mainly resistive line impedance, the unequal impedance among distributed generation (DG) units, and the microgrid load locations make the conventional frequency and voltage droop method unpractical. The proposed power control strategy contains a virtual inductor at the interfacing inverter output and an accurate power control and sharing algorithm with consideration of both impedance voltage drop effect and DG local load effect. Specifically, the virtual inductance can effectively prevent the coupling between the real and reactive powers by introducing a predominantly inductive impedance even in a lowvoltage network with resistive line impedances. On the other hand, based on the predominantly inductive impedance, the proposed accurate reactive power sharing algorithm functions by estimating the impedance voltage drops and significantly improves the reactive power control and sharing accuracy. Finally, considering the different locations of loads in a multibus microgrid, the reactive power control accuracy is further improved by employing an online estimated reactive power offset to compensate the effects of DG local load power demands. The proposed power control strategy has been tested in simulation and experimentally on a low-voltage microgrid prototype.
Control of a Multiple Source Microgrid With Built-in[taliem.ir]

Control of a Multiple Source Microgrid With Built-in Islanding Detection and Current Limiting

An approach for the control of a voltage-sourced converter-interfaced distributed energy resource microgrid environment with multiple energy sources is analyzed and experimentally validated. The control approach is designed to operate in grid-connected and islanded modes of operation, as well as provide a smooth transition between the two modes. Additional features including islanding detection with positive feedback and dynamic overcurrent limiting are also evaluated. Validation is achieved through the results obtained from a scaled down prototype system with further results from the time-domain simulation of a medium-voltage microgrid.
Design, Analysis, and Real-Time Testing[taliem.ir]

Design, Analysis, and Real-Time Testing of a Controller for Multibus Microgrid System

This paper concentrates on the design and analysis of a controller for multibus microgrid system. The controller proposed for use with each distributed generation (DG) system in the microgrid contains inner voltage and current loops for regulating the three-phase grid-interfacing inverter, and external power control loops for controlling real and reactive power flow and for facilitating power sharing between the paralleled DG systems when a utility fault occurs and the microgrid islands. The controller also incorporates synchronization algorithms for ensuring smooth and safe reconnection of the micro and utility grids when the fault is cleared. With the implementation of the unified controller, the multibus microgrid system is able to switch between islanding and grid-connected modes without disrupting critical loads connected to it. The performance of this unified controller has been verified in simulation using a real-time digital simulator (RTDS1 ) and experimentally using a scaled laboratory prototype.
Microgrid Protection Using Communication-Assisted[taliem.ir]

Microgrid Protection Using Communication-Assisted Digital Relays

Microgrids have been proposed as a way of integrating large numbers of distributed renewable energy sources with distribution systems. One problem with microgrid implementation is designing a proper protection scheme. It has been shown that traditional protection schemes will not work successfully. In this paper a protection scheme using digital relays with a communication network is proposed for the protection of the microgrid system. The increased reliability of adding an additional line to form a loop structure is explored. Also a novel method for modeling high impedance faults is demonstrated to show how the protection scheme can protect against them. This protection scheme is simulated on a realistic distribution system containing a high penetration of inverter connected Distributed Generation (DG) sources operating as a microgrid. In all possible cases of operation the primary and secondary relays performed their intended functions including the detection of high impedance faults. This system is simulated using Matlab Simulink’s SimPowerSystems toolbox to establish the claims made in this paper
Microgrid Protection Using Communication-Assisted[taliem.ir]

Microgrid Protection Using Communication-Assisted Digital Relays

Microgrids have been proposed as a way of integrating large numbers of distributed renewable energy sources with distribution systems