1. System Overview: Components and Connections
The system consists of a solar PV panel, a battery, and various power converters connected to a common DC bus. The PV panel generates power from sunlight, which is transferred to the DC bus. The battery is also connected to this bus to store energy for later use. Additionally, a bidirectional converter allows power to flow between the DC bus and the battery, ensuring both charging and discharging can occur efficiently.
2. MPPT Algorithm: Maximizing Solar Power Extraction
The heart of the system lies in the MPPT algorithm, which maximizes the power extracted from the PV panel. The algorithm operates by measuring the voltage and current from the PV, converting these values into power changes, and then adjusting the duty cycle of the converter. By continuously adjusting based on the slope of the power curve, the system ensures the maximum amount of energy is captured from the solar panel.
3. Fuzzy Logic Control for Power Optimization
A fuzzy logic controller is used to fine-tune the MPPT algorithm. The controller relies on membership functions that take into account both the error and the rate of change of the error. By evaluating these parameters, the fuzzy logic controller adjusts the duty cycle to extract the optimal amount of power from the PV panel. This enables the system to respond dynamically to changes in solar radiation and ensure maximum efficiency in energy conversion.
4. Battery Charging Control: Maintaining Steady Power Flow
The battery is charged through a DC-DC converter, which controls the charging process by maintaining a constant voltage of 400V. The power needed for battery charging is first supplied by the PV panel. If the PV output is insufficient, the system can draw additional power from the grid to meet the battery's charging needs. This ensures that the battery remains charged, regardless of fluctuations in solar power generation.
5. Inverter Control: Managing Grid Power Flow
An inverter is used to control the power flow from the battery and the grid. The inverter’s current is regulated based on the power output from the battery and the PV panel. If the PV power is enough to meet the charging requirements (e.g., 2,000 W), the inverter will direct the power to the EV battery. If PV power is low, the inverter adjusts to supply power from the grid, ensuring that the charging power remains constant.
6. Grid Power Management: Ensuring Reliable Charging
When the PV power is insufficient (for example, due to cloudy conditions), the grid power steps in to supply the remaining energy required for the battery. The system ensures that the battery continues to charge at a stable rate (around 2,000 W), regardless of the changes in PV output. The grid supply is seamlessly integrated into the system, preventing any interruptions in charging.
7. Reference Current Generation for Battery Charging
A reference current is generated to regulate the battery charging process. This current is used to guide the inverter's operation, ensuring that the battery is charged efficiently. The system employs phase modulation techniques to ensure smooth power flow from the grid, maintaining a stable charging rate even when solar power decreases.
8. Simulation and Power Management in Action
The system is designed to handle variations in solar power efficiently. Through simulation, the system tracks key parameters such as DC bus voltage, current, and the power from both the PV panel and the battery. When solar power fluctuates, the system adjusts the power flow, ensuring that the battery receives a constant 1,900–2,000 W. If the PV output is low, the system draws power from the grid, demonstrating the flexibility and resilience of the charging station.
9. Power Sharing Between PV, Grid, and Battery
As the PV power decreases due to reduced sunlight, the grid will begin to supply power to ensure that the battery charging rate remains constant. For example, if PV power drops to 1,000 W, the grid will supply an additional 1,000 W to maintain the charging power for the battery. This dynamic power-sharing ensures that the battery is charged at the desired rate, regardless of the available solar power.
10. Conclusion: Efficient and Flexible EV Charging
The MATLAB-based implementation of a solar PV-based EV charging station with fuzzy MPPT control offers an efficient and flexible solution for charging electric vehicles. By dynamically adjusting power flows between the PV panel, battery, and grid, the system ensures that the battery is always charged optimally. This integration of renewable energy, energy storage, and power management systems provides an environmentally friendly and reliable solution for EV charging, reducing reliance on the grid and maximizing the use of solar energy.
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