IIU Activation Sequencing for Balanced FACTS Electrical Stress
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Solution Overview
Problem
High current handling FACTS devices in transformer-less flexible alternating current transmission systems (TL-FACTS) face reliability issues due to uneven electrical stress distribution across impedance injection units (IIUs), leading to variations in time-to-failure and reduced operational lifespan.
Innovation Solution
Implementing a method where IIUs are activated in sequences and the ordering of activation is repeatedly changed over time periods to equalize electrical stress across units, using a controller to manage the switching of IIUs in a rotational sequence, ensuring all units experience similar stress levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IIUs are activated simultaneously without rotational sequencing, then power flow control responsiveness is improved, but electrical stress distribution becomes uneven leading to reduced device reliability
Solution Approach 1:
The patent applies periodic action by implementing rotational sequencing where IIUs are activated in alternating sequences (odd-numbered IIUs in one sequence, even-numbered IIUs in the next sequence). This periodic switching pattern ensures that each IIU experiences electrical stress in a distributed manner over time, equalizing the stress distribution while maintaining continuous power flow control capability through the coordinated switching of different IIU groups.
2Duration of action of stationary object
If rotational sequencing is implemented to equalize stress, then device lifetime is extended, but control system complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the IIU system into distinct groups based on their switching sequences (odd-numbered IIUs forming one group, even-numbered IIUs forming another group). This segmentation allows the control system to manage complexity by treating each group as a manageable unit with predetermined switching patterns, while the overall system achieves equalized stress distribution through the coordinated operation of these segmented groups.
3Reliability
If continuous operation of all IIUs is maintained, then power flow control capability is maximized, but electrical stress on individual units increases leading to earlier failure
Solution Approach 1:
The patent applies dynamics by implementing time-varying switching sequences where the active IIU groups change over time. In the first time period, odd-numbered IIUs are activated; in the second time period, even-numbered IIUs are activated. This dynamic switching pattern ensures that no single IIU operates continuously under full stress, thereby extending operational lifespan while maintaining continuous power flow control capability through the alternating activation of different IIU groups.
Data Source
AI summary
An impedance injection unit (IIU) system is coupled to a high-voltage (HV) transmission line. The IIUs are activated in sequences of activation in successive time periods. This injects an impedance waveform onto the HV transmission line. The ordering of IIUs in the sequences of activation is repeatedly changed in successive time periods. This equalizes electrical stress across the IIUs used, leading to overall improvement in IIU system lifetimes.