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Fuzzy Logic Control of V2G and G2V in Single Phase Grid

Fuzzy Logic Control of V2G and G2V in Single Phase Grid


Introduction to the System

The system consists of a single-phase grid with a peak amplitude of the previous voltage and a frequency of 50 Hz. The main components of the system include a series inductance on the source side, a single-phase converter, and a bidirectional converter. The converter can operate in both directions, converting AC to DC and vice versa, depending on the battery's condition.

Key Components

  • Series Inductance: 2.3 Henry.

  • Single Phase Converter: Operates in both directions.

  • Bidirectional Converter: Comprises two IGBT switches and an LC filter.

  • Battery: 120V nominal voltage, 48Ah capacity, 15% initial state of charge, lithium-ion type.



Fuzzy Logic Control

The system uses a fuzzy logic controller to manage the current of the battery. The battery current is measured and compared with a reference current, which is determined by whether the system is in V2G or G2V mode.

Fuzzy Logic Controller Design

The fuzzy logic controller is designed with error and rate of change of error as inputs, each having five membership functions. The output is the duty cycle, which also has five membership functions, resulting in 25 rules in total. This controller helps in maintaining the desired battery current by generating appropriate duty cycles for the bidirectional converter's IGBT switches.

Converter Control Logic for Unity Power Factor

The converter control logic ensures that the source current remains sinusoidal and in phase with the voltage, maintaining unity power factor. This involves:

  1. Measuring the DC link voltage.

  2. Comparing it with a reference voltage (380V).

  3. Processing the difference through a PI controller to generate a current reference magnitude.

  4. Multiplying the current reference with a sinusoidal waveform generated using the grid voltage phase angle from a Phase-Locked Loop (PLL).

Simulation Results

We tested the model with two operating conditions: starting with V2G and switching to G2V, and vice versa. The results show the behavior of source voltage, source current, battery SOC, battery current, battery voltage, and DC link voltage.

Key Observations

  • Vehicle-to-Grid Mode (V2G): Battery supplies power to the grid, indicated by a decrease in battery SOC and a 180-degree phase shift between source voltage and current.

  • Grid-to-Vehicle Mode (G2V): Grid supplies power to the battery, indicated by an increase in battery SOC and in-phase source voltage and current.

During the transition from V2G to G2V and vice versa, the DC link voltage experiences a transient before settling back to 380V.

Conclusion

This single-phase grid system with fuzzy logic control effectively manages the V2G and G2V operations, maintaining unity power factor. The simulation results validate the system's performance under different operating conditions.

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