HVDC Converter Control for Leakage Current Reduction
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Solution Overview
Problem
High voltage direct current (HVDC) power transmission networks face issues with leakage currents, which cause thermal runaway and interfere with fault clearing processes, necessitating additional hardware for current reduction, increasing size, weight, and cost.
Innovation Solution
An electrical assembly with a converter, a circuit interruption device featuring switching elements and energy absorption elements, and a converter control unit that operates in a leakage current reduction mode to divert current through energy absorption elements, reducing leakage currents and allowing safe switching of the DC power transmission medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional hardware is added to reduce leakage current, then leakage current reduction is improved, but device complexity and cost increase
Solution Approach 1:
The energy absorption element automatically reduces leakage current through its inherent V-I characteristic without requiring additional control hardware. The element self-regulates the current based on the applied voltage, eliminating the need for external current reduction devices.
Solution Approach 2:
The converter control unit changes the DC voltage parameter to control the leakage current. By adjusting the DC voltage across the energy absorption element, the system exploits the nonlinear V-I relationship to reduce current without adding hardware complexity.
2Reliability
If additional hardware is added to reduce leakage current, then leakage current reduction is improved, but weight and cost increase
Solution Approach 1:
The converter and its control unit serve multiple functions: normal power conversion operation and leakage current reduction. The existing converter infrastructure is utilized for both purposes, eliminating the need for dedicated weight-bearing hardware for current reduction.
Solution Approach 2:
The energy absorption element provides self-regulating current reduction through its V-I characteristic, requiring no additional active components or control hardware that would add weight to the system.
3Reliability
If DC voltage is controlled to reduce leakage current, then leakage current is reduced, but converter control complexity increases
Solution Approach 1:
The converter control unit implements a feedback control mechanism that monitors the DC voltage and adjusts it to maintain the energy absorption element in a state that minimizes leakage current. The control unit continuously regulates the DC voltage based on the operational state of the circuit interruption device.
Solution Approach 2:
The system dynamically adjusts the DC voltage parameter in response to changing operational conditions. The converter control unit modulates the DC voltage to optimize the performance of the energy absorption element during different phases of circuit interruption and normal operation.
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
The solution effectively reduces leakage currents, preventing thermal runaway and fault interference, while eliminating the need for additional hardware, enhancing the reliability and performance of the power transmission network and enabling the use of cheaper, lower-rated switching apparatus.
Implementation Method 1
the energy absorption element to provide a back electromotive force (EMF) to reduce the flow of current in the DC power transmission medium
Implementation Method 2
control a voltage across the energy absorption element to reduce a leakage current flowing in the DC power transmission medium
Data Source
AI summary
There is provided an electrical assembly for use in a power transmission network. The electrical assembly includes a converter including terminals for connection to an electrical network, where the first terminal is a DC terminal. The assembly also includes a DC power transmission medium connected to the DC terminal, and a circuit interruption device including switching element(s) and an energy absorption element, each switching element being switchable to divert a flow of current in the DC power transmission medium through the energy absorption element in order to reduce the flow of current in the DC power transmission medium; The assembly also includes a converter control unit programmed to operate the converter to control a DC voltage at the DC terminal in a leakage current reduction mode to control a voltage across the energy absorption element.