Impedance Injection Units for High-Voltage Line Oscillation Control
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Solution Overview
Problem
Current transformerless flexible alternating current transmission systems (TL-FACTS) based impedance injection units generate high-frequency oscillations when injecting rectangular impedance waveforms into high-voltage transmission lines, interfering with control systems and user premises, and there is a need for improved methods to manage disturbances and optimize waveform injection.
Innovation Solution
The method involves controlling impedance injection units to form multiple connection configurations in sequence, generating rectangular impedance injection waveforms, and combining them to produce a pseudo-sinusoidal waveform on the high-voltage transmission line, thereby reducing oscillations and utilizing idle time to inject additional waveforms for disturbance management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rectangular impedance injection waveforms are injected into high voltage transmission lines, then disturbance management and line balancing control are improved, but high-frequency oscillations are generated that interfere with control systems and user premises
Solution Approach 1:
The patent applies periodic action by using a sequence of rectangular impedance injection waveforms with specific timing and duration patterns. The control module generates multiple rectangular waveforms that are injected in a periodic sequence, where each waveform has a defined start time and duration. This periodic injection pattern allows the system to achieve effective disturbance management while the structured timing enables cancellation of high-frequency oscillations through constructive and destructive interference of the waveform edges.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the duration and timing parameters of the rectangular impedance injection waveforms. The control module varies the duration of each rectangular waveform in the sequence, and adjusts the time intervals between consecutive waveforms. By changing these temporal parameters, the system optimizes the injection pattern to achieve both disturbance management effectiveness and oscillation reduction, transforming the fixed-parameter injection approach into a flexible, adaptive solution.
2Power
If multiple impedance injection units are connected in series-parallel configuration, then current carrying capacity and injected impedance voltage are increased, but system complexity and coordination requirements increase
Solution Approach 1:
The patent applies segmentation by dividing the impedance injection system into multiple independent impedance injection units that can be connected in series-parallel configurations. Each unit operates as a separate module with its own control capabilities, allowing the system to achieve higher current carrying capacity through parallel connections and increased voltage injection through series connections. The segmentation enables modular scalability and simplifies the control architecture by allowing independent operation of each unit.
Solution Approach 2:
The patent implements merging by combining multiple impedance injection units into a coordinated system where series-connected units provide cumulative impedance voltage injection and parallel-connected units provide increased current carrying capacity. The control module coordinates the operation of merged units by synchronizing their waveform injection timing and duration, allowing the combined system to achieve enhanced power capability while maintaining controlled complexity through unified waveform generation and sequencing.
3Stability of the object's composition
If impedance injection units are used for localized control of disturbances, then grid stability is improved, but oscillations may still interfere with control systems and user premises
Solution Approach 1:
The patent applies the intermediary principle by using a sequence of rectangular waveforms as an intermediate mechanism between the impedance injection units and the power line. Instead of directly injecting single large-amplitude waveforms that cause oscillations, the system uses a sequence of smaller rectangular waveforms with specific timing and duration patterns. This intermediary waveform sequence acts as a buffer that achieves the necessary impedance injection for disturbance management and grid stability while reducing the amplitude and duration of oscillatory components that would interfere with control systems and user premises.
Data Source
AI summary
A control module controls impedance injection units (IIUs) to form multiple connection configurations in sequence. Each connection configuration has one IIU, or multiple IIUs in series, parallel or combination of series and parallel. The connection configurations of IIUs are coupled to a high-voltage transmission line. The control module and the IIUs generate rectangular impedance injection waveforms. When the waveforms are combined and injected to the high-voltage transmission line, this produces a pseudo-sinusoidal waveform.