Power factor correction circuits and methods including partial power factor correction operation for boost and buck power converters
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Solution Overview
Problem
Existing power factor correction (PFC) circuits in compressor drives face inefficiencies due to reactive power storage and return, leading to suboptimal use of electrical power, particularly in HVAC systems where compressors and electric motors require efficient power management.
Innovation Solution
A PFC circuit comprising a bridge rectification circuit, a power converter with a switch, and a control module that transitions between high activity and inactive modes based on AC voltage, phase angle, and current detection to optimize power usage, reducing reactive power storage and enhancing power factor correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PFC circuit operates continuously in full activity mode, then the power factor is maintained at optimal levels, but energy losses increase due to continuous reactive power storage and return
Solution Approach 1:
The PFC circuit switches between active and inactive modes periodically based on the AC waveform phase and load conditions. The controller activates the PFC circuit during periods when power factor correction is needed and deactivates it when not needed, converting continuous operation into periodic operation to reduce energy losses while maintaining correction effectiveness when required
Solution Approach 2:
The PFC circuit transitions from static continuous operation to dynamic variable operation, adjusting its activity state based on real-time detection of AC voltage, current, and phase angle. This dynamic adaptation allows the circuit to optimize between maintaining power factor correction and reducing energy consumption based on instantaneous system conditions
2Loss of energy
If the PFC circuit operates in partial correction mode with mode transitions, then energy losses are reduced, but control complexity increases
Solution Approach 1:
The controller uses feedback from detectors monitoring AC voltage, current, and phase angle to automatically determine when to transition between active and inactive modes. This feedback mechanism simplifies the control logic by using sensor data to trigger pre-defined control actions, reducing the perceived complexity despite the dynamic operation
Solution Approach 2:
The PFC circuit monitors its own operating conditions through integrated detectors and automatically adjusts its mode without external intervention. The system self-regulates by detecting when power factor correction is needed and activating accordingly, reducing control complexity by eliminating the need for external control signals
3Productivity
If the switch transitions frequently between open and closed states, then power factor correction responsiveness improves, but switching losses increase
Solution Approach 1:
The switch operates in periodic bursts rather than continuous high-frequency switching. The controller activates the switch in synchronized periods with the AC waveform when correction is needed, and keeps it inactive during periods when correction is not required, reducing overall switching frequency and associated losses while maintaining responsiveness during active periods
Solution Approach 2:
The PFC circuit applies correction partially rather than continuously, activating the switch only during portions of the AC cycle when power factor correction is beneficial. This partial action approach reduces unnecessary switching events and associated losses while maintaining adequate correction performance during critical periods
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves the power factor of compressor drives, increasing actual electrical power usage while minimizing reactive power return to the source, leading to more efficient energy utilization and reduced energy losses in HVAC systems.
Implementation Method 1
a bridge rectification circuit configured to (i) receive an AC voltage, and (ii) generate a rectified AC voltage
Implementation Method 2
a power converter configured to convert the rectified AC voltage to a first DC voltage
Data Source
AI summary
A PFC circuit is provided. A bridge rectification circuit receives an AC voltage and generates a rectified AC voltage. A power converter converts the rectified AC voltage to a first DC voltage, where the power converter includes a switch and supplies the first DC voltage to a DC bus to power a compressor. A current sensor detects an amount of current. A control module, while operating in a correction mode: based on the rectified AC voltage, a phase angle of the rectified AC voltage, a second DC voltage of the DC bus, or the detected amount of current, control operation of the switch to transition between operating in a high activity mode and an inactive or low activity mode; transition the switch between open and closed states while in the high and low activity modes; and maintain the power converter in an OFF state while in the inactive mode.