Active Power Factor Correction (APFC) is a technique used in power electronics to improve the power factor of a load by actively controlling the input current waveform. Power factor is a measure of how effectively electrical power is being converted into useful work, and it's defined as the ratio of real power (active power) to apparent power.
In many electrical systems, especially those with non-linear loads such as computers, electronic devices, and motor drives, the current waveform can become distorted due to the non-linear characteristics of these loads. This distortion leads to a lower power factor, which can result in inefficient use of electrical power and increased energy costs.
Active Power Factor Correction aims to address this issue by adding a control circuit that actively adjusts the input current waveform to be more sinusoidal and in phase with the voltage waveform. This is typically achieved using a combination of sensing, control algorithms, and power electronic components like switching transistors.
Here's a simplified overview of how APFC works:
Sensing: The system monitors the input voltage and current waveforms. The goal is to ensure that the input current follows the shape of the input voltage waveform and is in phase with it.
Control: The control circuit uses feedback from the sensing stage to generate a control signal that adjusts the switching of power electronic components (typically transistors or thyristors) in the converter circuit.
Converter Circuit: The converter circuit operates to shape the input current waveform to match the input voltage waveform. This is done by adjusting the switching frequency, duty cycle, or other parameters of the power electronic components.
Correction: By actively adjusting the input current waveform, the load appears more resistive to the power source. This results in a higher power factor, reducing the reactive power drawn from the source and improving overall system efficiency.
Benefits of APFC:
Improved power factor: The main advantage of APFC is the improvement in power factor, which leads to better utilization of electrical power and reduced energy costs.
Reduced harmonic distortion: APFC can help reduce harmonic distortion in the current waveform, which is essential in maintaining the quality of the electrical supply and complying with regulations.
Increased system efficiency: A higher power factor means that less energy is wasted as reactive power, leading to more efficient power usage.
Active Power Factor Correction is commonly used in various applications, including industrial systems, data centers, commercial buildings, and any environment where non-linear loads can affect power quality and efficiency.