Tap-Changing Transformer Control for HVDC Converter Availability
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Solution Overview
Problem
In high voltage direct current (HVDC) transmission networks, converter-based electrical devices often require shutdown or disconnection during abnormal operating states due to voltage support capability changes, leading to reliability issues and increased costs.
Innovation Solution
A transformer with a tap changer and controller that selectively modifies the transformer's turn ratio to adjust AC voltage at the converter-based electrical device's side, allowing continued operation during abnormal states by matching voltage support capabilities and reducing or increasing AC voltage as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the converter-based electrical device operates in abnormal states, then the voltage support capability changes, but the device must be shut down or disconnected, reducing reliability
Solution Approach 1:
The transformer incorporates a tap changer mechanism that dynamically adjusts the turn ratio in response to abnormal operating states. The controller detects changes in voltage support capability and selectively connects different taps to modify the transformer's turn ratio, thereby adapting the AC voltage output to match the converter device's reduced capability while maintaining continuous operation
Solution Approach 2:
The system changes the electrical parameter (AC voltage) by modifying the transformer's turn ratio through tap selection. When the converter-based electrical device enters an abnormal state with reduced voltage support capability, the controller adjusts the turn ratio parameter to produce an AC voltage that corresponds to the modified working voltage, allowing the device to continue operating in a degraded but functional state
2Reliability
If the turn ratio is modified to adjust AC voltage, then the device can continue operating, but the transformer complexity increases
Solution Approach 1:
The tap changer introduces dynamic adjustability to the transformer, allowing the turn ratio to be modified based on operating conditions. This dynamic capability enables the transformer to adapt to abnormal states without requiring complete system shutdown, accepting the trade-off of increased structural complexity for improved reliability
Solution Approach 2:
The tap changer acts as an intermediary mechanism between the AC electrical network and the converter-based electrical device. It provides a controlled interface that can adjust voltage levels to match the device's capabilities, mediating the interaction between the fixed transformer structure and the variable operational requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures the continued availability and reliability of converter-based electrical devices by dynamically adjusting AC voltage in response to module failures or power overload demands, reducing the need for shutdowns and optimizing module usage.
Implementation Method 1
a transformer for connecting the converter-based electrical device to an AC electrical network, a first transformer side of the transformer connected to the converter-based electrical device, a second transformer side of the transformer for connection to the AC electrical network
Data Source
AI summary
An electrical assembly includes a converter-based electrical device and a transformer for connecting the converter-based electrical device to an AC electrical network, a first transformer side of the transformer connected to the converter-based electrical device, a second transformer side of the transformer for connection to the AC electrical network, the transformer including a number of taps, the transformer including a tap changer operable to selectively connect to the or each tap to modify a turn ratio of the transformer. The transformer includes a controller configured to selectively operate the tap changer in an AC voltage modification mode, responsive to an abnormal operating state of the electrical assembly, to modify the turn ratio of the transformer so as to modify an AC voltage at the first transformer side.