Sliding Mode Controller Based P&O MPPT for Solar PV System
Explanation of Simulink Model
This model tests the Sliding Mode Controller based P&O MPPT algorithm for a solar PV system. It consists of:
250W PV Panel
Open Circuit Voltage: 37.3V
Voltage at Maximum Power Point: 30.7V
Short Circuit Current: 8.66A
Current at Maximum Power Point: 8.15A
PV Panel Characteristics
The IV and PV characteristics of the 250W PV panel vary with different irradiation conditions. For example:
1000 W/m²: Peak power ~ 250.2W
800 W/m²: Peak power ~ 199.9W
600 W/m²: Peak power ~ 149.6W
The peak point varies based on the irradiation level and is extracted using the MPPT algorithm.
Boost Converter Design
The PV panel is connected to a variable load via a boost converter. The design of the boost converter (inductor and capacitor values) depends on:
PV Power (250W)
Voltage across the PV panel (30.7V at standard test conditions)
Desired Output Voltage (e.g., 60V)
Based on these values and the inductor ripple current percentage and capacitor voltage ripple percentage, the values for L and C are determined.
Sliding Mode Controller Based P&O MPPT
The P&O MPPT algorithm provides a reference voltage based on the measured PV voltage and current. The reference voltage helps in extracting maximum power from the PV panel.
Control Logic
The control logic combines the P&O method with the sliding mode control concept, thus forming the Sliding Mode Controller based P&O MPPT algorithm.
Simulation Results
Varying Irradiance Condition
The model is tested with a constant load and varying irradiation every 0.2 seconds (1000, 800, 600, 400 W/m²). The results are as follows:
1000 W/m²: Max power ~ 250W
800 W/m²: Max power ~ 200W
600 W/m²: Max power ~ 150W
The PV voltage, load voltage, PV current, load current, PV power, and load power are recorded for these varying conditions.
Varying Load Condition
The model is tested with a constant irradiation and varying load every 0.3 seconds.
After 0.3 seconds, an additional load is added to the system. The results show:
Load current changes from ~2.8A to ~3.5A.
PV power is maintained at the maximum power point (250W for 1000 W/m²).
The variations in PV voltage, load voltage, PV current, and load current are observed for changing load conditions.
Conclusion
The Sliding Mode Controller based P&O MPPT effectively extracts maximum power from the PV panel under varying irradiation and load conditions.
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