Variable Step Size Perturb-and-Observe MPPT Algorithm for Photovoltaic Systems
Overview of the Variable Step Size MPPT Algorithm
The Variable Step Size P&O MPPT algorithm is designed to enhance the performance of PV systems by dynamically adjusting the duty cycle based on real-time measurements. The process involves several key steps:
Parameter Measurement:
Measure the current voltage and current of the PV panel.
Record the previous instant’s voltage and current.
Compute both the current and previous instant power levels.
Power Difference Check:
Determine if the power difference between the current and previous instants is zero. If it is, the panel is operating at the maximum power point, and no adjustments are needed.
Power Change Analysis:
If the power difference is not zero, evaluate whether the change in power is positive or negative.
Depending on the sign and magnitude of the power change, adjust the duty cycle either by incrementing or decrementing it using two variable step sizes (Step 1 and Step 2).
Voltage and Current Change Evaluation:
Assess changes in voltage and current to guide the adjustment of the duty cycle. If the current change is positive, the duty cycle is incremented or decremented based on the magnitude of the changes.
Variable Step Size Calculation:
Step 1 and Step 2 values are updated using a specific formula that depends on the power, voltage, and current changes. These steps are adjusted dynamically to ensure optimal performance.
Algorithm Implementation
The Variable Step Size P&O MPPT algorithm is implemented using a control system comprising:
Solar PV Panel: Typically a 250-watt panel.
Boost Converter: Connected to the load and controlled by the MPPT algorithm.
Code and Control: The algorithm is coded to calculate and adjust Step 1 and Step 2 based on the system’s real-time performance data. The control system continuously updates the duty cycle to maximize power extraction.
Performance Analysis
To evaluate the effectiveness of the Variable Step Size MPPT algorithm, performance is assessed under varying conditions:
Load Variations: Load is changed every 0.3 seconds to observe the PV system’s response in maintaining power output.
Irradiation Changes: Irradiation levels are varied every 0.2 seconds to test how well the system adapts to changes in solar intensity. The maximum power extracted from the PV panel aligns with expected values for different irradiation levels, demonstrating the algorithm's robustness.
Conclusion
The Variable Step Size Perturb-and-Observe MPPT algorithm significantly enhances the efficiency of photovoltaic systems by dynamically adjusting the duty cycle to optimize power output. By continuously measuring and analyzing changes in power, voltage, and current, the algorithm ensures that the PV system operates close to its maximum power point, regardless of variations in load or solar irradiation.
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