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Grid-connected PV System with Partial Shading Effect

Grid-connected PV System with Partial Shading Effect

System Overview

Our system consists of two parallel strings of PV panels, each supplying 1.5 megawatts (MW) of power, for a total of 3 MW. Each string is composed of three groups of arrays. The first two groups have 6650 parallel strings with four series-connected modules, while the third group has three series-connected modules.

MPPT Algorithm Implementation

The MPPT algorithm used is the Perturb and Observe (P&O) method. This method adjusts the duty cycle of the boost converter to find the maximum power point (MPP). Key steps in the algorithm include:

  1. Measure PV Voltage and Current: Calculate the power and compare it with the previous value.

  2. Adjust Duty Cycle: If the power increases with an increase in voltage, continue increasing the duty cycle; otherwise, decrease it.

  3. Limit Duty Cycle: Ensure the duty cycle stays within preset minimum and maximum limits.

Partial Shading and Irradiation Effects

To simulate real-world conditions, partial shading effects are introduced by varying the irradiation levels on different groups of arrays. For instance, after one second, the irradiation levels might change from 1000 to 800, 600, and 500 watts per square meter. The system adjusts the MPPT algorithm accordingly to maintain optimal power extraction.

Grid Integration

The system includes a voltage source inverter and a filter inductor to connect the boost converter output to the grid. The inverter is controlled based on the DC link voltage and grid current to ensure synchronized and efficient power injection.

Results and Observations

The system is tested under varying conditions to observe its performance. Initially, with standard irradiation, the PV arrays operate at 1000 watts per square meter, producing around 3 MW of power. When irradiation levels drop, the system adjusts to extract maximum power despite reduced sunlight, maintaining efficient energy conversion and grid supply.

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