Interlocking Device for NPC DC to AC Converter Short Circuit Prevention
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Solution Overview
Problem
Neutral-point-clamped (NPC) DC to AC converters face malfunctions and short circuits due to switching device errors, leading to potential damage from short circuit loops, especially when operating with high DC input voltages.
Innovation Solution
A high-level triggered interlocking device and a low-level triggered interlocking device are introduced, each comprising interlocking circuits that control switch activation based on logic levels of specific signals, preventing short circuits by generating locking signals to turn off switches when abnormal conditions are detected, thus preventing short circuit loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching devices are used to convert DC power into AC power in NPC DAC, then power loss is reduced and electromagnetic interference is minimized, but malfunctions and short circuits may occur leading to device damage
Solution Approach 1:
The interlocking device applies preliminary anti-action by detecting abnormal conditions (such as malfunction signals) before short circuits can occur and preemptively generating locking signals to turn off switching devices. This prevents the harmful short circuit loops from forming in the first place, thereby protecting the switching devices while maintaining the low power loss benefits of the NPC DAC configuration.
2Loss of energy
If switching devices operate at high DC input voltage, then power loss of switching devices is reduced, but the risk of short circuit damage increases
Solution Approach 1:
The interlocking device serves as an intermediary between the control signals and the switching devices. It monitors the operating conditions and intermediates the control by generating locking signals that prevent switching devices from operating under abnormal high-voltage conditions that could lead to short circuits, thus mediating between the beneficial low power loss operation and the harmful short circuit risk.
3Reliability
If interlocking device controls switching devices to prevent short circuits, then device safety is improved, but system complexity increases
Solution Approach 1:
The interlocking device is segmented into multiple independent interlocking circuits, with each circuit responsible for controlling specific switching devices. This segmentation allows the complex protection function to be distributed across simpler modular units, making the overall system more manageable and easier to implement while maintaining comprehensive device safety coverage.
Data Source
AI summary
The disclosure provides an interlocking device and a three-phase interlocking device for a DC to AC converter (DAC). The interlocking device includes a first interlocking circuit and a second interlocking circuit. The first interlocking circuit couples with a first switch and a second switch, controls whether to conduct the first switch according to the logic levels of a first signal, a second signal and a third signal, and controls whether to conduct the second switch according to the logic levels of the first signal and the second signal. The second interlocking circuit couples with a third switch and a fourth switch, controls whether to conduct the third switch according to the logic levels of the first signal, the third signal and a fourth signal, and controls whether to turn on the fourth switch according to the logic levels of the third signal and the fourth signal.