AC/DC Converter Inrush Current Control via Dynamic Pulse Width
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Solution Overview
Problem
The existing AC/DC conversion process for aircraft electrical distribution experiences transient phenomena such as current peaks (inrush current) during the transition from pre-charge to regulation, which stress power components and fail to meet network quality standards, especially when multiple converters are in parallel.
Innovation Solution
A method and device that include a transition step between pre-charge and regulation, utilizing control signals generated from alternating input voltages to manage switch states, reducing inrush current by gradually widening pulse widths and employing logic signals and AND circuits to control switches, thereby minimizing current peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pre-charge resistors are used to limit inrush current during pre-charge stage, then inrush current is limited, but transient current peaks occur during transition to regulation stage
Solution Approach 1:
The patent applies dynamics by making the pulse width of control signals variable over time. During the transition from pre-charge to regulation stage, the pulse width gradually increases from a narrow initial width to a wider steady-state width. This dynamic adjustment allows the converter to smoothly transition between operating modes without generating transient current peaks, while still maintaining inrush current limitation throughout the process.
Solution Approach 2:
The patent changes the parameter of pulse width in the control signals from a fixed value to a time-varying parameter. By gradually increasing the pulse width during the transition period, the control method adjusts the effective resistance seen by the AC network, enabling continuous inrush current limitation while avoiding the abrupt transitions that cause transient peaks.
2Object-generated harmful factors
If pulse width is gradually widened during transition, then transient current peaks are reduced, but control circuit complexity increases
Solution Approach 1:
The patent uses periodic pulse signals with varying widths to control the switches. The pulse train is generated with a fixed frequency but with pulse widths that evolve over time from narrow to wide. This periodic action simplifies the control circuitry compared to generating arbitrary waveforms, as it only requires a pulse generator with adjustable duty cycle and a timing mechanism.
Data Source
Figure 1~2A
Figure 2B
Figure 3~4
AI summary
The invention relates to a method for converting alternating current into direct current, implemented by a conversion device that includes a three-phase bridge in which at least one arm consists of a first switch and a second switch mounted in series, the method including a step of adjusting the direct voltage output by the conversion device, characterised in that said method includes a transition step which precedes the adjustment step, the transition step including the formation of signals for controlling the first and second switches capable of limiting the amplitude of the inrush currents when switching the conversion device to the alternative network.