Rigid Bipole HVDC Energization for Ground Current Balance
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Solution Overview
Problem
In rigid bipole HVDC systems, uncoordinated energization of converters leads to energy imbalances between DC electrical poles, resulting in ground currents that cause electromagnetic interference, equipment damage, and corrosion, which existing technologies fail to adequately address.
Innovation Solution
A control logic is implemented to balance the DC voltage outputs of converters by modifying the energization rate and switching of converter valve capacitors, ensuring synchronous energization and minimizing ground currents to near-zero levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If converters are energised simultaneously without coordinated control, then energisation speed is improved, but ground current imbalance increases causing electromagnetic interference and equipment damage
Solution Approach 1:
The control logic performs preliminary assessment of converter energy levels before simultaneous energisation, and pre-coordinates the switching sequences to prevent ground current imbalance from the outset
Solution Approach 2:
The control logic continuously monitors the energy levels of converter valves and dynamically adjusts switching sequences based on real-time feedback, ensuring balanced ground currents while maintaining fast energisation
2Object-affected harmful factors
If converter energisation is coordinated to balance energy levels, then ground current imbalance is reduced, but energisation time increases
Solution Approach 1:
The control logic dynamically adjusts the energisation sequence based on real-time converter states, optimizing the balance between speed and ground current minimisation rather than using fixed sequential energisation
Solution Approach 2:
The control logic modifies switching parameters and energy level thresholds to enable faster coordinated energisation that maintains ground current balance without excessive time delay
3Object-affected harmful factors
If converter valve capacitor charging is controlled to match DC voltage outputs, then ground current is minimized, but control complexity increases
Solution Approach 1:
The control logic automatically monitors converter energy levels and self-adjusts switching sequences without external intervention, reducing the perceived complexity while achieving ground current minimisation
Solution Approach 2:
The control logic uses simplified parameter adjustments to capacitor charging rates and switching timing to achieve DC voltage matching and ground current minimisation
Data Source
AI summary
There is provided a method of energising electrical poles of a rigid bipole power transmission network, the rigid bipole power transmission network comprising a first pair of converters connected to a second pair of converters via first and second electrical poles, and further comprising a ground return path. The method includes determining one or more parameters associated with either of the first or second pair of converters, wherein the one or more parameters indicate a difference in energy between the first and second electrical poles. The method further includes controlling, based on the one or more parameters, at least one converter of the associated first or second pair of converters to regulate the difference in energy between the first and second electrical poles such that a ground current flowing in the ground return path is below a predetermined threshold value.