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MATLAB Simulation of Off-grid Solar PV Battery System

MATLAB Simulation of Off-grid Solar PV Battery System


Overview of the Off-Grid Solar PV Battery System

An off-grid solar PV battery system operates independently of the main power grid, relying entirely on solar panels and battery storage to provide electricity. This setup is particularly useful in remote areas or for individuals seeking energy independence.



Components of the System

Our simulation model includes several key components:

  1. Solar Panels:

  • Total capacity: 2000 watts.

  • Each panel capacity: 250 watts.

  • Voltage at maximum power point: 30.9 volts.

  • Current at maximum power point: 8.1 amps.

  • Configuration: 4 series panels per string and 2 parallel strings.

  1. Battery:

  • Voltage: 48 volts.

  • Capacity: 200 Ah.

  1. DC-DC Converter and Bidirectional Converter:

  • These converters manage the flow of electricity between the solar panels, battery, and AC load.

  1. AC Load:

  • Represents household or home load appliances powered by the system.

  1. Backup Generator or AC Input:

  • Provides power to the load and charges the battery when solar power is insufficient.

Operation Modes

Solar Power Mode

When the solar panels are generating power, the system operates as follows:

  • Primary Supply: Solar PV panels directly supply power to the AC load.

  • Excess Power: Any surplus power charges the battery via the bidirectional converter.

  • Performance: The voltage and current generated by the panels are monitored and adjusted using an MPPT (Maximum Power Point Tracking) algorithm to ensure optimal performance.

Battery Mode

If solar generation drops to zero (e.g., during nighttime), the system switches to battery mode:

  • Primary Supply: The battery discharges to provide power to the AC load.

  • Monitoring: Battery voltage and state of charge (SOC) are constantly monitored to prevent over-discharge.

Backup Generator Mode

When both solar generation is low and the battery's SOC is low, the backup generator kicks in:

  • Primary Supply: The generator provides power to the AC load and charges the battery.

  • Control: The generator's output is managed by a rectifier and LC filter to ensure a stable DC supply to the system.

Control Strategies

Voltage and Current Control

The system employs both voltage and current control mechanisms:

  • Voltage Control: Maintains the inverter output voltage within desired levels.

  • Current Control: Ensures the current supplied to the load is within safe limits.

Simulation Results

Let's analyze the system's performance under different conditions:

  1. High Solar Irradiation:

  • Solar panels generate significant power.

  • Excess power charges the battery.

  • The AC load receives continuous power from the solar panels.

  1. No Solar Power:

  • Solar power generation drops to zero.

  • The battery discharges to supply power to the AC load.

  • The SOC of the battery decreases as it supplies power.

  1. Low Battery SOC and No Solar Power:

  • The backup generator activates.

  • The generator supplies power to the AC load and charges the battery.

  • The system ensures uninterrupted power supply.

Conclusion

This simulation demonstrates the robustness of an off-grid solar PV battery system. By effectively managing power from solar panels, batteries, and a backup generator, the system ensures a reliable power supply under varying conditions. Whether you're considering an off-grid system for remote living or energy independence, understanding these dynamics is crucial.

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