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Fractional Order PI Controller Grid Connected PV System

Fractional Order PI Controller Grid Connected PV System

Introduction to the PV System

Our PV system consists of:

  • PV Panels: Each panel generates 13 watts with a maximum power point of 29 volts and 7.35 amps.

  • Configuration: 10 panels in series and 5 strings in parallel.

  • Maximum Power: Under standard conditions (1000 W/m², 25°C), the array generates up to 10.66 kW.

Boost Converter and MPPT Algorithm

To maintain voltage at 700 volts for efficient power transfer, a boost converter controlled by a Modified Perturb and Observe (MPPT) algorithm is used.

Three-Phase Inverter and Control

  • Inverter: Converts DC from the PV Panels to AC.

  • LCL Filter: Filters the output to reduce harmonics.

  • Control: Utilizes a fractional order PI controller for voltage control and a feedforward control approach to manage power flow to the grid.

Fractional Order PI Controller

The fractional order PI controller parameters used are:

  • Controller Constants: Kp=0.1K_p = 0.1Kp​=0.1, Ki=0.5K_i = 0.5Ki​=0.5, Kd=0.001K_d = 0.001Kd​=0.001.

  • Fractional Order: λ=1.5\lambda = 1.5λ=1.5.

Simulation Scenarios and Results

Simulation Scenario 1: Irradiance of 400 W/m²
  • PV Power: Achieves around 4307 watts.

  • Grid Current: Peaks at approximately 10 amps.

Simulation Scenario 2: Irradiance of 800 W/m²
  • PV Power: Peaks at around 8289 watts.

  • Grid Current: Peaks at about 16-17 amps.

Simulation Scenario 3: Irradiance of 600 W/m²
  • PV Power: Peaks at approximately 6465 watts.

  • Grid Current: Peaks at about 14-15 amps.

Comparison with PI Controller

We replicated the system using a traditional PI controller and observed the following:

  • PV Power: Slightly lower compared to the fractional order PI controller.

  • Grid Current: Shows more harmonic content due to reactive power flow management inefficiencies.

Total Harmonic Distortion (THD) Analysis

  • Fractional PI Controller: THD maintained below 1%.

  • PI Controller: THD exceeds 2.5%.


In conclusion, the fractional order PI controller demonstrates superior performance in maximizing PV power extraction while minimizing grid current harmonics compared to the conventional PI controller. This highlights its potential for enhancing grid-connected PV system efficiency and reliability.

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