Engineering Technology Works

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Browsing Engineering Technology Works by Author "Akbari, Rasoul"

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    Economic Operation of Utility-Connected Microgrids in a Fast and Flexible Framework Considering Non-Dispatchable Energy Sources
    (MDPI, 2022) Akbari, Rasoul; Tajalli, Seyede Zahra; Kavousi-Fard, Abdollah; Izadian, Afshin; Engineering Technology, Purdue School of Engineering and Technology
    This paper introduces a modified consensus-based real-time optimization framework for utility-connected and islanded microgrids scheduling in normal conditions and under cyberattacks. The exchange of power with the utility is modeled, and the operation of the microgrid energy resources is optimized to minimize the total energy cost. This framework tracks both generation and load variations to decide optimal power generations and the exchange of power with the utility. A linear cost function is defined for the utility where the rates are updated at every time interval. In addition, a realistic approach is taken to limit the power generation from renewable energy sources, including photovoltaics (PVs), wind turbines (WTs), and dispatchable distributed generators (DDGs). The maximum output power of DDGs is limited to their ramp rates. Besides this, a specific cloud-fog architecture is suggested to make the real-time operation and monitoring of the proposed method feasible for utility-connected and islanded microgrids. The cloud-fog-based framework is flexible in applying demand response (DR) programs for more efficiency of the power operation. The algorithm’s performance is examined on the 14 bus IEEE network and is compared with optimal results. Three operating scenarios are considered to model the load as light and heavy, and after denial of service (DoS) attack to indicate the algorithm’s feasibility, robustness, and proficiency. In addition, the uncertainty of the system is analyzed using the unscented transformation (UT) method. The simulation results demonstrate a robust, rapid converging rate and the capability to track the load variations due to the probable responsive loads (considering DR programs) or natural alters of load demand.
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    Hybrid energy storage characterization for power profile enhancement in split-shaft wind energy conversion systems
    (Wiley, 2022) Akbari, Rasoul; Izadian, Afshin; Engineering Technology, Purdue School of Engineering and Technology
    This paper characterizes an integrated hybrid energy storage unit required to support the new generator excitation system developed for doubly-fed induction generators in the split-shaft wind energy conversion units. The goal is to improve the power quality while significantly reducing the generator excitation power rating and component counts. The rotor excitation circuit is modified to directly include the storage to its DC link. The output power fluctuation can be attenuated solely by utilizing the rotor-side converter making it self-sufficient from the grid connection. The storage characteristics are identified based on several system design parameters, including the system inertia, inverter capacity, and energy storage capacity. The obtained power generation characteristics suggest an energy storage mix of fast-acting types with a high energy capacity and moderate acting time. A feedback controller is designed to maintain the charge in the storage within the required limits. Adaptive model-predictive control is also developed to reduce power generation fluctuations. The proposed system is investigated and simulated in MATLAB Simulink at different wind speeds to validate the results and demonstrate the system's dynamic performance. It is demonstrated that the system's inertia is critical to damping the high-frequency oscillations of the wind power fluctuations. It is also shown that the bandwidth of the control system is determined by the system inertia and the size of the storage and inverter power rating.
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    Quasi Self-Excited DFIG-Based Wind Energy Conversion System
    (IEEE Xplore, 2021-05) Akbari, Rasoul; Izadian, Afshin; Weissbach, Robert S.; Engineering Technology, School of Engineering and Technology
    This article introduces a new configuration of the doubly-fed induction generator (DFIG) based wind energy conversion system (WECS) employing only a reduced-size rotor side converter (RSC) in tandem with a supercapacitor. In the proposed structure, the grid side converter (GSC) utilized in conventional DFIG-based WECSs is successfully eliminated. This is accomplished by employing the hydraulic transmission system (HTS) as a continuously variable and shaft decoupling transmission unit. This transforms the conventional constant-ratio drives by providing an opportunity to control the power flow through the generator's rotor circuit regardless of the wind turbine's shaft speed. This feature of HTS can be utilized to control the RSC power and ultimately regulate the supercapacitor voltage without a need for GSC. The proposed system is investigated and simulated in MATLAB Simulink at various wind speeds to validate the results and demonstrate the dynamic performance of the system.