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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Design of a Hybrid Active Filter to Suppress Harmonic Distortion in Industrial Facilities

Wnag, Yen-ching 26 July 2010 (has links)
Due to the drastic development of semiconductor, nonlinear loads are widely used in high-power applications, which results in harmonic distortion of current and voltage in the power system. Installation of passive filter is one of the conventional solutions to harmonic distortion. But line impedance, load inductors and/or filter components may result in harmonic resonance, which amplifies the harmonic components, and worsens the harmonic distortion and power quality. This thesis proposed a control algorithm of shunt hybrid active filter to suppress the harmonics and prevent harmonic resonance in industrial facilities. The hybrid active filter is composed of an active filter and a seventh-harmonic frequency tuned passive filter. The hybrid active filter functions as damping conductance for harmonic frequencies. A dynamical tuning control is realized to adjust the damping conductance for maintaining the voltage harmonic distortion. The suppressed harmonic distortion is conformed to the harmonics limitation, such as IEEE std. 519-1992. The capacitors of the hybrid filter sustain fundamental grid voltage and allow the inverter to operate in lower kVA rating. In addition, a dc bus controller was designed to hold the capacitor voltage by controlling the fundamental leading current. The simulations and laboratory results are provided to verify the effectiveness on suppressing harmonic resonance.
2

Third harmonic management and flexible charging for the integration of electric vehicles into the grid

Hernandez, Jorge Eliezer 08 June 2015 (has links)
Electric vehicle (EV) development has gone into an accelerated pace in recent years to address pressing concerns on energy security, the environment, and the sustainability of transportation. The future market success of EVs is still uncertain, but the current shift in the automotive industry is indicating a possible bright future for EVs. Because of its unique load characteristics, an extensive deployment of EVs will not only bring challenges to power systems, but will enable new opportunities as well. The objective of this work is to address the increased third harmonic currents expected with the introduction of EVs and to explore the potential of leveraging flexible EV charging to increase wind power production. Since EV chargers rely on a nonlinear power conversion process to obtain a controllable DC source from the utility AC supply, it is expected that these devices will aggravate third harmonic current issues. In fact, utility harmonic field data show that, even without EVs, distribution feeders are already experimenting elevated levels of third harmonic currents. To address present and future utility harmonic filtering needs, a practical third harmonic hybrid active filter for medium voltage (MV) applications is proposed. Its design is based on strict utility requirements of cost, reliability, and ease of system implementation. The operation and performance of the proposed filter is verified through simulations and two experimental setups, one tested at 7.2 kV. Furthermore, a system impact study of the proposed filter is performed using actual data for a typical residential/small commercial distribution feeder. Because vehicles remain stationary most of the time, EVs have the potential of being flexibly charged, providing a spectrum of opportunities for system operators. The recent increase in wind power penetration in the U.S. is raising concerns on how to accommodate this stochastic renewable energy resource in day-ahead scheduling operations. In this work, a detailed integrated day-ahead scheduling framework is developed to explore the impact of leveraging flexible EV charging to balance out the variability and uncertainty of wind power generation. It is determined that the full benefits of balancing wind power generation with flexible EV charging may not be achieved in congested power systems. A potential solution based on deploying power routers (PRs) to augment the flexibility of the transmission system is proposed. Simulation results are presented for a test system based on the IEEE 39-bus system.

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