Power factor correction using SEPIC converter
Greetings, LMS Solution viewers! In today's session, we delve into the intricacies of power factor correction using semiconductor devices. Specifically, we explore the distinctions between open-loop and closed-loop control mechanisms.
In the open-loop model, our system comprises an AC source voltage, a diode bridge rectifier, and a SEPIC (Single-Ended Primary Inductor Converter) converter. The SEPIC converter operates with a fixed duty cycle, offering no control over load voltage and source current. Consequently, the source current deviates from sinusoidal due to the presence of non-linear loads, leading to a high Total Harmonic Distortion (THD) of around 66.24%.
A comprehensive examination through FFT analysis reveals a THD exceeding the acceptable IEEE/IEC standards of 5%. This emphasizes the need for improvement in both THD and power factor for optimal system performance.
To address these issues, we implement closed-loop control, introducing an outer voltage control loop and an inner current control loop. In the outer loop, a voltage controller regulates the load voltage, while an inner loop utilizes a current controller for source current control.
Outer Loop (Voltage Control): A Proportional-Integral (PI) controller compares the load voltage with a reference voltage, generating a reference current in DC form.
Inner Loop (Current Control): The reference current undergoes transformations and comparisons, resulting in a pulse for the IGBT to enforce sinusoidal source current.
The simulation demonstrates a remarkable transformation. The source current becomes sinusoidal, the load voltage stabilizes at the reference voltage, and the system power factor improves significantly. The THD reduces to a mere 3.72%, aligning with stringent IEEE/IEC standards.
In conclusion, the closed-loop control proves instrumental in achieving power factor correction, mitigating harmonic distortions, and aligning system parameters with international standards. The dynamic interplay of voltage and current control loops elevates the system's efficiency and performance.