AC-DC Converter Neutral-Point Control for Stable DC Output
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Solution Overview
Problem
Conventional power conversion devices struggle to stabilize output voltage when converting three-phase AC voltage to desired DC voltage for DC distribution systems, which is essential for reliable power supply to DC loads.
Innovation Solution
A power conversion device incorporating a power conversion circuit with semiconductor switching elements, an AC filter capacitor unit, a full-bridge chopper circuit, a DC filter capacitor unit, and a neutral point line that connects the neutral points of the AC and DC filter capacitors, along with a controller to manage the switching elements based on output current commands, ensuring common-mode current is inhibited and output voltage stability is maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the neutral points of filter capacitors are connected to suppress common-mode current, then common-mode current is reduced, but output voltage stability to DC loads cannot be achieved
Solution Approach 1:
The patent extracts the common-mode current component from the output current using a detection unit, and separates it from the normal output current. The controller then uses only the normal current component for control purposes, effectively removing the harmful common-mode component while maintaining proper output voltage control.
Solution Approach 2:
The patent implements a feedback control mechanism where the output current is detected, the common-mode component is removed through signal processing, and the corrected current signal is fed back to the controller. This feedback loop enables precise control of the semiconductor switching elements to maintain stable output voltage while suppressing common-mode current.
2Object-generated harmful factors
If a neutral point line connecting AC and DC filter capacitor neutral points is introduced, then common-mode current is inhibited, but device complexity increases
Solution Approach 1:
The patent introduces a neutral point line as an intermediary connection between the neutral points of the AC-side and DC-side filter capacitors. This intermediary structure provides a reference potential path that inhibits common-mode current flow without requiring direct grounding of both neutral points, thus balancing common-mode suppression with circuit simplicity.
3Device complexity
If current detection is performed without removing common-mode component, then control is simplified, but output voltage cannot be stabilized
Solution Approach 1:
The detection unit extracts and removes the common-mode current component from the detected output current signal. This extracted normal current component is then used by the controller for feedback control, enabling stable output voltage regulation while the removed common-mode component is prevented from affecting the control system.
Data Source
AI summary
An object is to obtain a power conversion device that can stabilize output voltage to a DC load. A power conversion device includes an AC/DC conversion unit having a power conversion circuit composed of a plurality of first semiconductor switching elements connected in a full-bridge form, and a full-bridge chopper circuit unit having a full-bridge chopper circuit composed of a plurality of second semiconductor switching elements connected in a full-bridge form, and connected to a positive terminal and a negative terminal. A neutral point of an AC filter capacitor unit and a neutral point of a DC filter capacitor unit are connected via a neutral point line.