Solar PV System with MPPT Using Boost Converter Using MATLAB Simulink/Simscape

1. Panel sizing and string arrangement

• Target capacity: 2.00 kW total output feeding into a 400 V DC bus.
• Minimum panels per string (8 panels / 1.80 kW): Keeps the panel voltage high enough so the converter does not need an extreme, inefficient duty cycle above 80%.
• Maximum panels per string (10 panels / 2.25 kW): Prevents panel open-circuit voltage from rising above the 400 V bus, which would cause uncontrolled current to bypass the switch through the diode.
• Selected setup: 1 string containing 9 panels in series, producing 2.03 kW under standard conditions.
• Fast simulation model: Instead of calculating separate diode equations for all 9 panels, the model combines them into an equivalent controlled source, speeding up simulations by about 85%.

2. MPPT algorithms

The model includes two selectable algorithms via a variant setting:

• Perturb and observe (MPPT = 0):
  • Slightly nudges the panel voltage up or down.
  • Checks if output power went up or down compared to the previous step.
  • Keeps moving in the direction that increased power.
  • Simple to build, but it constantly wobbles around the peak at steady state and can briefly step the wrong way during fast cloud cover changes.
• Incremental conductance (MPPT = 1):
  • Compares how current changes relative to voltage changes.
  • Knows mathematically when it has reached the top of the power curve.
  • Stops adjusting once it hits the peak, eliminating the steady-state wobble and reacting faster to weather shifts.

3. Boost converter and dual-mode control

• Voltage step-up: Boosts panel voltage (around 270 V) up to the 400 V DC bus.
• MPPT mode: Active when the connected load or battery can take all the power the panels generate.
• De-rated voltage control mode: Activates when load power drops below solar output. Instead of pushing excess power and overcharging the 400 V bus, a PI controller steps the panels away from their peak, reducing generation to match the load.

4. PI controller tuning

• Boost converters naturally exhibit a temporary reverse response: when the switch duty cycle changes, output voltage momentarily dips before rising.
• The controller uses proportional gain and a phase-lead time constant to steady the loop.
• Proper tuning ensures the output voltage recovers quickly from load changes without ringing or tripping overvoltage protections.

Simulation output (MPPT mode)

Startup and tracking behavior

• Fast convergence: From zero power at startup, the system locks onto the maximum power point within 35 to 50 milliseconds.
• Operating values: The array settles at roughly 270 V and 7.5 A, delivering the expected 2.03 kW.
• Continuous current: Inductor current stays smooth and continuous throughout operation with small, well-filtered ripple.
• DC bus regulation: The output bus holds stable at 400 V with less than 0.5% voltage ripple.

Algorithm comparison

• Perturb and observe: Constantly steps back and forth across three operating points, causing about 12 W (0.6%) of power wobble at steady state.
• Incremental conductance: Stops stepping as soon as it reaches the peak, reducing power fluctuation to about 1.2 W and achieving 99.85% tracking efficiency.
• Sudden cloud response (1000 to 800 W/m²): Incremental conductance finds the new 1.62 kW operating point in 15 milliseconds without hesitation. Perturb and observe takes roughly 5 milliseconds longer due to an initial false step.