PWM Phase Correction for Power Conversion Harmonic Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power conversion devices face challenges in reducing input current harmonics due to delays between the input AC voltage and PWM signals, particularly in high-frequency applications like aircraft and ships, leading to distorted current waveforms and suboptimal power factor correction.
Innovation Solution
A power conversion device and method that include a voltage conversion circuit, input voltage and current detection circuits, and a control circuit to correct the phase of the PWM signal based on detection signals from these circuits, allowing for precise timing adjustments to synchronize with the AC voltage zero-crossing, thereby reducing harmonic distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power factor correction circuit is used to improve power factor, then power factor is improved, but input current harmonics are generated due to delay between AC voltage and PWM signal
Solution Approach 1:
The control circuit performs preliminary phase correction on the PWM signal before it is applied to the power conversion circuit. By detecting the phase difference between the AC voltage and PWM signal in advance and pre-adjusting the PWM signal phase, the system eliminates the delay that causes current harmonics, allowing the power factor correction to work effectively without generating harmful harmonics.
2Object-generated harmful factors
If switch control is adjusted based on voltage zero-cross detection to reduce harmonics, then harmonic components are reduced, but delay between detected voltage and actual voltage remains
Solution Approach 1:
The control circuit continuously monitors the phase relationship between the detected AC voltage and the PWM signal, and dynamically adjusts the PWM signal phase based on this feedback. This closed-loop control ensures that the phase correction remains accurate even as operating conditions change, maintaining low harmonic levels while compensating for detection delays in real-time.
Data Source
AI summary
A power conversion device includes: a voltage conversion circuit that converts an AC voltage input into a DC voltage by PWM control and outputs the DC voltage; an input voltage detection circuit that detects the AC voltage input to the voltage conversion circuit and outputs a detection signal; an input current detection circuit that detects an AC current input to the voltage conversion circuit and outputs a detection signal; an output voltage detection circuit that detects the DC voltage output from the voltage conversion circuit and outputs a detection signal; and a control circuit that corrects a phase of a PWM signal for the PWM control based on the detection signal from the input voltage detection circuit, the detection signal from the input current detection circuit, and the detection signal from the output voltage detection circuit, and outputs the PWM signal corrected to the voltage conversion circuit.