Phase Compensation for Power Factor Correction Zero-Crossing Distortion
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Solution Overview
Problem
Conventional power factor correction circuits experience zero-crossing distortion and increased total harmonic distortion due to the forward voltage drop of bridge rectifier diodes and the placement of high-frequency filtering capacitors, leading to reduced power factor and efficiency.
Innovation Solution
A phase compensation method for power factor correction circuits that employs a control unit with a low-pass filter, differential controller, cosine multiplier, and adders to predict and adjust the input current waveform, generating a phase compensation signal to synchronize the phase of the input current and voltage, thereby suppressing zero-crossing distortion and reducing harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bridge rectifier diode and high frequency filtering capacitor are used in the power factor correction circuit, then the circuit can perform basic power factor correction, but zero-crossing distortion occurs and total harmonic distortion increases
Solution Approach 1:
The patent applies preliminary action by calculating and storing the compensation current values in advance for different input voltage levels before the actual power factor correction operation. The lookup table is pre-populated with compensation values that account for the non-linear characteristics of the rectifier diode, allowing the controller to quickly retrieve and apply the appropriate compensation current without real-time complex calculations, thereby preventing zero-crossing distortion before it occurs.
Solution Approach 2:
The patent introduces a compensation current as an intermediary element that mediates between the rectifier diode's non-linear characteristics and the desired sinusoidal input current. This compensation current, derived from the lookup table based on instantaneous input voltage, acts as a corrective signal that offsets the distortion caused by the diode's forward voltage drop, thereby reducing total harmonic distortion while maintaining the basic power factor correction function.
2Reliability
If feedforward control is used to adjust output current according to AC input voltage, then power factor is increased, but zero-crossing distortion occurs due to diode forward voltage drop
Solution Approach 1:
The patent implements feedback by continuously monitoring the instantaneous input voltage and using this information to retrieve the appropriate compensation current value from the lookup table. This feedback mechanism ensures that the compensation current dynamically adjusts to match the actual input voltage conditions, particularly during the zero-crossing region where distortion is most severe, thereby maintaining high power factor while eliminating zero-crossing distortion.
Solution Approach 2:
The patent applies parameter changes by varying the compensation current parameter based on the instantaneous input voltage level. The lookup table stores pre-calculated compensation current values that correspond to different input voltage amplitudes. By changing the compensation current parameter in real-time according to the input voltage, the system optimizes the power factor correction performance and eliminates zero-crossing distortion without compromising the overall power factor.
3Productivity
If conventional power factor correction circuit is used, then power transmission efficiency can be improved, but total harmonic distortion increases due to current cessation at zero-crossing point
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation current values that specifically address the zero-crossing region where current cessation and harmonic distortion occur. The lookup table is populated with compensation values that anticipate and counteract the distortion effects before they manifest in the actual current waveform, allowing the system to maintain continuous current flow and reduce total harmonic distortion while preserving power transmission efficiency.
Solution Approach 2:
The patent introduces a compensation current as an intermediary that mediates between the discontinuous current caused by diode forward voltage drop and the desired continuous sinusoidal current. This compensation current, retrieved from the lookup table based on instantaneous voltage, fills in the gaps during zero-crossing regions and smooths the current waveform, thereby reducing total harmonic distortion while maintaining the power transmission efficiency achieved by the conventional circuit.
Data Source
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AI summary
A method for phase compensating a power factor correction circuit (1) is provided. Firstly, a present current value of an input current (Iin) is sampled, and the sampled signal is filtered. Then, a present waveform of the input current (Iin) corresponding to the present current value of the filtered sampled signal and a previous waveform of the input current (Iin) corresponding to a previous current value of the filtered sampled signal are predicted, and a current error signal is generated according to a difference between the present waveform and the previous waveform. Then, the current error signal is adjusted, and an adjusted signal is generated. Then, a feedforward signal (D_ff) is added to the adjusted signal, and a phase compensation signal (D_comp). Then, a current control signal (D_curr_ctrl) is added to the phase compensation signal (D_comp), and a pulse width modulation signal (D_pwm) is generated to control a switching circuit (10).