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Integrating Retired Electric Vehicle Batteries with Photovoltaics in Microgrids

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2014, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
It is expected that by 2020, there will be a large number of battery packs retired from Electric Vehicles (EVs). These retired EV batteries may be utilized as energy storage systems in a Microgrid to help with the integration of renewable energy resources and provide different functions, such as Time-of-Use energy management, frequency and voltage regulation, emergency power supply, etc. In this dissertation, both system and circuit level studies are performed on the implementation of retired EV batteries with Photovoltaic (PV) systems in Microgrid applications. First, an optimization algorithm is presented to determine the usage profile of the retired EV battery and the size of the PV system for a residential application. The electrical and economic models of the Battery Energy Storage System (BESS) and the PV system are derived. In addition, irradiance, load profile, and electricity price information are collected as calculation input. An Energy Management Strategy (EMS) is implemented to minimize the yearly system operation cost under different PV sizes. The proposed optimization algorithm is realized in Matlab, and simulation results are provided to validate the effectiveness of the algorithm. Then, a hybrid Microgrid testbed is developed for the study on experimental implementation of the retired EV battery in a Microgrid. The testbed combines Power Hardware-in-the-Loop (PHIL) simulation of an electric power network and System-in-the-Loop (SITL) simulation of a communication network with real hardware. The PHIL system can interface with other power hardware and emulate different systems connected to the testbed, such as renewable energy conversion systems, different topologies of utility grid, and other Microgrids, etc. The SITL system is a component of the real-time Supervisory Control and Data Acquisition (SCADA) system. It is able to accept real-time traffic from a physical network and simulate different communication networks and phenomena. In addition, multiple power electronics converters and programmable power sources/loads are integrated in the testbed to emulate different renewable energy conversion systems. System-level experimental results are presented to demonstrate the functionality of the testbed. Next, a full-bridge current-source isolated Quasi-Switched-Capacitor (QSC) dc/dc converter is proposed for PV applications. The proposed converter features reduced input current ripple and improved performance under partial shading, reduced number of switches and voltage stress on the high voltage side QSC circuit, and soft switching for both primary side and secondary side switches. The operation principle is presented and the design guidelines are studied. A 1.2 kW, 1 MHz, 40 V/ 400 V prototype utilizing Gallium Nitride (GaN) switching devices is built in the lab, and a peak efficiency of 92.7% at 500 kHz and 89.0% at 1 MHz is achieved. Compared to other current-source isolated dc/dc converters in the literature, a comparable efficiency is achieved with a much higher switching frequency. In the end, a family of dual-input dc/dc converters derived from the current-source isolated QSC dc/dc converter is proposed for integration of the PV and battery. This family of converters utilizes a current-source full-bridge or half-bridge topology as the primary side, and the QSC topology as the secondary side. The proposed converters have a similar operation principle as the full-bridge current-source isolated QSC PV converter, and inherit all the merits of it. In addition, a secondary battery is integrated in the QSC circuit to realize a dual-input operation. A 1.3 kW half-bridge circuit prototype based on Silicon Carbide (SiC) switching devices and a 2 kW full-bridge circuit prototype, based on GaN switching devices, are built in the lab. The full-bridge prototype achieves a peak efficiency of 95.9% at 500 kHz and 93.5% at 1 MHz under the dual-input operation condition. Compared to other isolated multiple-input dc/dc converters in the literature, the proposed converter achieves a higher efficiency at a much higher switching frequency.
Jin Wang (Advisor)
Longya Xu (Committee Member)
Mahesh Illindala (Committee Member)
156 p.

Recommended Citations

Citations

  • Guo, F. (2014). Integrating Retired Electric Vehicle Batteries with Photovoltaics in Microgrids [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408969201

    APA Style (7th edition)

  • Guo, Feng. Integrating Retired Electric Vehicle Batteries with Photovoltaics in Microgrids. 2014. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1408969201.

    MLA Style (8th edition)

  • Guo, Feng. "Integrating Retired Electric Vehicle Batteries with Photovoltaics in Microgrids." Doctoral dissertation, Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408969201

    Chicago Manual of Style (17th edition)