Power Factor Corrector Control Method for Harmonic Distortion
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Solution Overview
Problem
Conventional power factor correctors experience significant total harmonic distortion (THD) in the input current during transitions between discontinuous conduction mode (DCM) and continuous conduction mode (CCM), leading to poor power quality.
Innovation Solution
A control method that includes a computing circuit to generate a current control signal by adding a feedforward signal and an adjusted current error signal during transition intervals between DCM and CCM, reducing the change in the duty cycle of the switch control signal and thereby minimizing harmonic distortion in the input current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the power factor corrector is operated in transition interval between DCM and CCM, then the power factor is improved, but the total harmonic distortion of input current increases significantly
Solution Approach 1:
The patent applies preliminary action by detecting the transition interval between DCM and CCM in advance, and preemptively adjusting the current control signal through feedforward compensation. This prevents the large transient changes that would otherwise cause harmonic distortion, rather than reacting after the distortion occurs.
Solution Approach 2:
The patent implements feedback by continuously monitoring the operating mode of the power factor corrector and using the detected transition interval information to dynamically adjust the current control signal. The feedback mechanism enables real-time compensation to maintain low harmonic distortion while operating in transition intervals.
2Object-generated harmful factors
If the change amount of current control signal is reduced during mode transition, then the harmonic distortion is inhibited, but the response speed of the control system may be affected
Solution Approach 1:
By detecting the transition interval in advance and applying feedforward compensation, the system prepares the current control signal before the actual transition occurs. This preliminary action smooths the transition and prevents large changes in the control signal, thereby inhibiting harmonic distortion while maintaining fast response through proactive rather than reactive control.
Solution Approach 2:
The patent changes the parameter of the current control signal by applying feedforward compensation specifically during transition intervals. This parameter adjustment modifies the signal characteristics to reduce transient changes and harmonic distortion, while the selective application during transitions ensures that normal response speed is maintained outside these intervals.
Data Source
AI summary
A control method is used in a power factor corrector. Firstly, a current command signal from a computing circuit is received. Then, the current command signal is compared with an input signal of the power conversion circuit, so that a current error signal is generated. If the power factor corrector is operated in a transition interval between the first mode and the second mode, an addition operation is performed on the unadjusted current error signal, a feedforward signal and the adjusted current error signal, thereby generating a current control signal. A switch control signal is generated according to the current control signal. A switching element of a power conversion circuit is controlled according to the switch control signal. Consequently, the harmonic distortion of the input current is inhibited.