DC Capacitor Precharge Circuit for Inrush Current Suppression
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Solution Overview
Problem
The existing power conversion systems require a high-rating charging resistance for initial charging of a direct-current capacitor to suppress inrush current, which is inefficient.
Innovation Solution
A power conversion system that includes a power converter, a direct-current capacitor, a first and second alternate-current switch, an inrush current suppressor with a charging resistance or reactor, and a control device to manage the switches and voltage to achieve initial charging without high-rated components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a charging resistance with high rating is used for initial charging of the direct-current capacitor, then inrush current is suppressed, but the device complexity and component rating requirements increase
Solution Approach 1:
The patent applies dynamics by making the switch configuration changeable over time. The first switch connects the capacitor to the AC power supply for initial charging, while the second switch provides a bypass path. The control device dynamically switches between these configurations based on charging status, allowing the system to adapt its impedance characteristics during the charging process rather than relying on a fixed high-rating resistance.
Solution Approach 2:
The patent segments the charging function into two distinct paths: one through the first switch for initial charging and another through the second switch for bypass. This segmentation allows the system to divide the charging task into phases, using lower-rating components in each segment rather than requiring a single high-rating component to handle the entire charging process.
2Productivity
If a charging resistance is used for initial charging, then the capacitor can be charged, but inrush current suppression requires high-rated components
Solution Approach 1:
The patent introduces a control device as an intermediary that manages the switching between the first and second switches. This control intermediary coordinates the charging process by activating the first switch initially and then switching to the second switch, enabling the system to achieve both charging capability and inrush current suppression without requiring high-rated power components throughout the entire process.
3Reliability
If high-rated components are used to suppress inrush current, then charging is reliable, but the system becomes less efficient and more complex
Solution Approach 1:
The patent implements periodic action through time-based switching control. The first switch is activated during the initial charging period, and after a predetermined time or when charging is complete, the control device switches to the second switch. This periodic switching pattern ensures reliable charging while avoiding the need for continuously high-rated components, thereby reducing overall system complexity.
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
Enables initial charging of a direct-current capacitor while effectively suppressing inrush current without using high-rated components, optimizing power conversion efficiency.
Implementation Method 1
an inrush current suppressor connected in parallel to the first alternate-current switch, between the power converter and the alternate-current power supply, the inrush current suppressor including a charging resistance or a charging reactor
Implementation Method 2
an inrush current suppressor connected in parallel to the first alternate-current switch, between the power converter and the alternate-current power supply, the inrush current suppressor including a charging resistance or a charging reactor
Data Source
AI summary
A power conversion system includes: a power converter connected to an alternate-current power supply; a direct-current capacitor connected to a direct-current side of the power converter; a first alternate-current switch connected between the power converter and the alternate-current power supply; an inrush current suppressor connected in parallel to the first alternate-current switch, between the power converter and the alternate-current power supply, and including a charging resistance or a charging reactor; a second alternate-current switch connected in parallel to the first alternate-current switch and in series to the inrush current suppressor, between the power converter and the alternate-current power supply; and a control device configured to control the power converter so that the first alternate-current switch is open, the second alternate-current switch is closed, and a voltage applied to the direct-current capacitor reaches a voltage that is equal to or exceeds a preset voltage.