AN1106, Power Factor Correction in Power Conversion Applications Using the dsPIC® DSC

AN1106 Power Factor Correction in Power Conversion Applications ® Using the dsPIC DSC The low cost and high performance capabilities of the Author: Vinaya Skanda DSC, combined with a wide variety of power electronic Microchip Technology Inc. peripherals such as an Analog-to-Digital Converter (ADC) and a Pulse Width Modulator (PWM), enable the digital design and development of power related INTRODUCTION applications to be simpler and easier. Most of the power conversion applications consist of an Some advantages of using a digital implementation for AC-to-DC conversion stage immediately following the PFC are: AC source. The DC output obtained after rectification is * Easy implementation of sophisticated control subsequently used for further stages. algorithms Current pulses with high peak amplitude are drawn * Flexible software modifications to meet specific from a rectified voltage source with sine wave input and customer needs capacitive filtering. The current drawn is discontinuous * Simpler integration with other applications and of short duration irrespective of the load connected to the system. SIGNIFICANCE OF POWER FACTOR Since many applications demand a DC voltage source, IN POWER AND CONTROL SYSTEMSa rectifier with a capacitive filter is necessary. However, this results in discontinuous and short duration current To understand PF, it is important to know that power spikes. When this type of current is drawn from the has two components: mains supply, the resulting network losses, the total * Working, or Active Powerharmonic content, and the radiated emissions become * Reactive Powersignificantly higher. At power levels of more than 500 watts, these problems become more pronounced. Working Power is the power that is actually consumed and registered on the electric meter at the consumer'sTwo factors that provide a quantitative measure of the location. It performs the actual work such as creatingpower quality in an electrical system are Power Factor heat, light and motion. Working power is expressed in(PF) and Total Harmonic Distortion (THD). The amount kilowatts (kW), which registers as kilowatt hour (kWh)of useful power being consumed by an electrical on an electric meter.system is predominantly decided by the PF of the system. Reactive Power does no useful work, but is required to maintain and sustain the electromagnetic fieldBenefits from improvement of Power Factor include: associated with the industrial inductive loads such as * Lower energy and distribution costs induction motors driving pumps or fans, welding * Reduced losses in the electrical system during machines and many more. Reactive Power is distribution measured in kilovolt ampere reactive (kVAR) units. * Better voltage regulation The total required power capacity, including Working * Increased capacity to serve power requirements Power and Reactive Power, is known as Apparent This application note focuses primarily on the study, Power, expressed in kilovolt ampere (kVA) units. design and implementation of Power Factor Correction Power Factor is a parameter that gives the amount of