Title: Fuzzy Logic Control for Charging/Discharging Interface of Electrical Vehicle to Grid (V2G) Technology
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Date
2020-11
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Addis Ababa University
Abstract
In this thesis, a two-stage non-isolated bidirectional electric vehicle chartering system used for charging and discharging electric vehicle battery developed and presented. On the modern definition, the system named V2G /G2V power flow. Allowing EV to charge or discharge without proper control may lead to voltage variation and instability on the power network. However, the EV is charge and discharge in an effective controlled manner, it can support the electrical power network for peak load levelling, peak load shaving, and frequency regulation.
Using FLC for the first stage of the system under direct current control mode to minimize the error between the measured battery current and reference battery current, also to level the current that supplied to DC-DC converter through the PWM pulse generation, to determine bidirectional power flow between the electric vehicle battery and the electrical power grid. SPWM technique also applied for the second stage of the system, which is a single-phase bidirectional AC-DC inverter, to make its output current and voltage have a true sinusoidal wave shape.
MATLAB-based experiments are conducted to verify the system’s feasibility and validate the theoretical analysis. From G2V operation the BSoC increasing from its initial state, which indicates the battery gains an additional percentage of charging capacity on its initial BsoC. In V2G BSoC decreased from its initial state, which indicates the battery loses its initial percentage of charging capacity. The battery terminal current for charging is negative and for dischargin is positive the opposite sign of the current is indicated fuzzy logic controlled DC-DC converter is work efficiently for the bidirectional power flow. Besides, the V2G simulation verifies that the SPWM is effective to make inverter output current and voltage are in phase. In general, the selected topology within the proposed controller can supply 230V AC voltage with 5.60% THD and 1.048A AC Current with 5.57% THD to the AC grid. FFT analysis shows that inserted LCL filter is better to comply with IEEE 519 current and voltage total harmonic distortion standard
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Keywords
battery charger, Electric Vehicle Battery, Electric Power Grid, Bidirectional power electronics Converter, Grid to Vehicle(G2V), vehicle to grid (V2G), fuzzy logic controller (FLC), sinusoidal pulse width modulation (SPWM)