Converter Active Current Control During Single-Phase Tripping
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Solution Overview
Problem
Single-pole auto-reclose (SPAR) events in electrical power grids can cause instability and overvoltage tripping in converters due to changes in grid characteristics, particularly when the grid impedance is high and zero sequence impedance is low, leading to critically high phase voltages that risk converter tripping.
Innovation Solution
The method involves controlling the active current in the three-phase output of the converter to keep the negative sequence voltage at or below a predetermined level during a SPAR event, thereby preventing unnecessary tripping and optimizing power transfer capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the converter operates normally during a SPAR event, then power transfer capability is maintained, but overvoltage tripping occurs due to high negative sequence voltage
Solution Approach 1:
The invention changes the operating parameters of the converter during a SPAR event by controlling the active current to maintain negative sequence voltage below a predetermined level. This parameter adjustment allows the converter to ride through the SPAR event without tripping, resolving the contradiction between maintaining power transfer and avoiding overvoltage tripping
Solution Approach 2:
The invention implements dynamic control of the active current during the SPAR event, continuously adjusting the current to keep negative sequence voltage within acceptable limits. This dynamic adaptation enables the converter to respond to changing grid conditions and maintain stability throughout the event
2Object-affected harmful factors
If the converter trips during a SPAR event, then overvoltage protection is activated, but power transfer capability is lost
Solution Approach 1:
The invention converts the potentially harmful SPAR event into a manageable condition by using the negative sequence voltage control mechanism. Instead of allowing the event to cause tripping and power loss, the control method utilizes the relationship between active current and negative sequence voltage to maintain stable operation, effectively turning a harmful grid disturbance into a controllable operating condition
3Reliability
If reactive current is injected into faulty phases, then voltage support is provided, but device complexity increases
Solution Approach 1:
The invention segments the control approach by treating each phase independently during the SPAR event. The active current control is applied specifically to the three-phase output to manage negative sequence voltage, while reactive current injection is used selectively in faulty phases. This segmented control strategy provides targeted voltage support without requiring complete system redesign, thus managing device complexity while maintaining reliability
Data Source
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AI summary
A method for operating an electric power converter and an electric power converter (10) configured to convert DC power into AC power supplied to a three-phase AC network (30), conclude, during the converting, that a single-phase tripping has started in the three-phase AC network (30) connected to the three-phase output of the converter (10), and after the concluding that the single-phase tripping has started in the three-phase AC network (30), control an active current in the three-phase output of the converter (10) such that a negative sequence voltage in the three-phase output of the converter (10) remains at or below a predetermined level, wherein the converter (10) is configured to perform the controlling until concluding that the single-phase tripping has ended in the three-phase AC network (30).