Standalone PV fed induction motor for water pump application
System Overview
The model we developed consists of two main parts: a standalone inverter and an induction motor load, which functions as a water pump. The setup ensures that the induction motor operates efficiently to pump water, driven by solar power.
Components of the System
Standalone Inverter:
Solar PV Array: Captures solar energy.
Boost Converter with MPPT Control: Steps up the voltage from the PV array and maximizes power extraction.
Grid Inverter with Harmonic Filters and Transformer: Converts DC to AC power for the motor.
Inverter Control: Manages the operation of the inverter to supply the induction motor.
Induction Motor Load:
Water Pump: The motor's speed is controlled to operate a centrifugal pump effectively.
PV Array Specifications
Each solar panel in the array has a power rating of 414 watts with the following characteristics:
Open Circuit Voltage: 85.3 volts
Voltage at Maximum Power Point: 72.9 volts
Short Circuit Current: 6.09 amps
Current at Maximum Power Point: 5.69 amps
For this model, we used 7 panels in series to achieve a total voltage around 510 volts. The panels are configured to generate approximately 5.8 kilowatts of power.
Boost Converter and MPPT Control
The boost converter steps up the voltage from 510 volts to 1000 volts. This is achieved using an incremental conductance MPPT algorithm, which calculates the optimal duty cycle to maximize power extraction from the PV array. The generated duty cycle controls the boost converter, ensuring efficient energy conversion.
Inverter and Control Mechanism
The neutral point clamping inverter, controlled by the inverter control block, converts the DC power to AC. This control mechanism includes:
PV Power Measurement: Converts PV power to reference speed for the motor.
PID Controller: Manages the operating frequency of the inverter based on the speed error of the induction motor.
V/f Control: Generates three-phase sinusoidal waveforms to control the motor speed.
Simulation and Results
We tested the system under different irradiation conditions to observe its performance.
1000 W/m² Irradiation
Under 1000 watts per meter square and 25 degrees Celsius:
PV Power Output: Approximately 5.5 kilowatts
Induction Motor Power: Around 4.5 kilowatts
Motor Speed: Maintained around 1500 RPM
Operating Frequency: 50 Hz
800 W/m² Irradiation
Under 800 watts per meter square and 25 degrees Celsius:
PV Power Output: Approximately 4 kilowatts
Induction Motor Power: Around 2.7 kilowatts
Motor Speed: Maintained around 1200 RPM
Operating Frequency: 40 Hz
Variable Irradiation
We also tested the system with variable irradiation, starting at 1000 watts per meter square and dropping to 800 watts per meter square after three seconds:
Initial PV Power Output: 5.5 kilowatts
Initial Motor Power: 4.2 kilowatts
Motor Speed: 1500 RPM
After Irradiation Drop:
PV Power Output: 4.5 kilowatts
Motor Power: 3 kilowatts
Motor Speed: 1200 RPM
Operating Frequency: 42 Hz
Conclusion
The standalone solar PV system with an induction motor effectively pumps water under varying irradiation conditions. This setup is ideal for agricultural applications, ensuring reliable and sustainable water supply.
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