Power Factor Correction in Power Conversion Applications
AN1106
Power Factor Correction in Power Conversion Applications Using the dsPIC® DSC
Author: Vinaya Skanda Microchip Technology Inc. The low cost and high performance capabilities of the DSC, combined with a wide variety of power electronic peripherals such as an Analog-to-Digital Converter (ADC) and a Pulse Width Modulator (PWM), enable the digital design and development of power related applications to be simpler and easier. Some advantages of using a digital implementation for PFC are: • Easy implementation of sophisticated control algorithms • Flexible software modifications to meet specific customer needs • Simpler integration with other applications
INTRODUCTION
Most of the power conversion applications consist of an AC-to-DC conversion stage immediately following the AC source. The DC output obtained after rectification is subsequently used for further stages. Current pulses with high peak amplitude are drawn from a rectified voltage source with sine wave input and capacitive filtering. The current drawn is discontinuous and of short duration irrespective of the load connected to the system. Since many applications demand a DC voltage source, a rectifier with a capacitive filter is necessary. However, this results in discontinuous and short duration current spikes. When this type of current is drawn from the mains supply, the resulting network losses, the total harmonic content, and the radiated emissions become significantly higher. At power levels of more than 500 watts, these problems become more pronounced. Two factors that provide a quantitative measure of the power quality in an electrical system are Power Factor (PF) and Total Harmonic Distortion (THD). The amount of useful power being consumed by an electrical system is predominantly decided by the PF of the system. Benefits from improvement of Power Factor include: • Lower energy and distribution costs • Reduced losses in the electrical system during distribution • Better voltage regulation •
Power Factor Correction in Power Conversion Applications Using the dsPIC® DSC
Author: Vinaya Skanda Microchip Technology Inc. The low cost and high performance capabilities of the DSC, combined with a wide variety of power electronic peripherals such as an Analog-to-Digital Converter (ADC) and a Pulse Width Modulator (PWM), enable the digital design and development of power related applications to be simpler and easier. Some advantages of using a digital implementation for PFC are: • Easy implementation of sophisticated control algorithms • Flexible software modifications to meet specific customer needs • Simpler integration with other applications
INTRODUCTION
Most of the power conversion applications consist of an AC-to-DC conversion stage immediately following the AC source. The DC output obtained after rectification is subsequently used for further stages. Current pulses with high peak amplitude are drawn from a rectified voltage source with sine wave input and capacitive filtering. The current drawn is discontinuous and of short duration irrespective of the load connected to the system. Since many applications demand a DC voltage source, a rectifier with a capacitive filter is necessary. However, this results in discontinuous and short duration current spikes. When this type of current is drawn from the mains supply, the resulting network losses, the total harmonic content, and the radiated emissions become significantly higher. At power levels of more than 500 watts, these problems become more pronounced. Two factors that provide a quantitative measure of the power quality in an electrical system are Power Factor (PF) and Total Harmonic Distortion (THD). The amount of useful power being consumed by an electrical system is predominantly decided by the PF of the system. Benefits from improvement of Power Factor include: • Lower energy and distribution costs • Reduced losses in the electrical system during distribution • Better voltage regulation •