HVDC Terminal Fault Control Using Buffered DC Voltage Reference
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Solution Overview
Problem
In multi-terminal high-voltage direct current transmission systems, faults in one alternating current power grid can cause undesirable voltage, current, and power fluctuations in interconnected grids, necessitating a method to mitigate these impacts.
Innovation Solution
A method and terminal configuration that includes DC voltage measurement buffering and regulation using a DC voltage controller to restore DC voltage to its pre-fault value, converting excess electrical energy into thermal energy via an energy converter with adjustable resistance elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If DC voltage is actively regulated during AC grid faults, then DC voltage stability is improved, but system complexity increases due to additional control mechanisms
Solution Approach 1:
The system stores the last valid DC voltage measurement in a buffer before faults occur. When a fault is detected, this pre-stored value is immediately used as the reference for voltage regulation, eliminating the need for complex real-time reference generation during fault conditions.
Solution Approach 2:
The control system continuously monitors DC voltage and compares it against the buffered reference value. This feedback mechanism automatically adjusts the converter operation to maintain voltage stability, providing a simple yet effective closed-loop control during fault conditions.
2Speed
If buffered DC voltage measurement is used for regulation, then response time to fault is improved, but information accuracy may deteriorate due to use of historical data
Solution Approach 1:
The buffer continuously updates the stored DC voltage measurement during normal operation, so that when a fault occurs, the most recent valid measurement is already available. This preliminary storage action enables immediate use of accurate historical data without waiting for new measurements during the fault event.
Solution Approach 2:
The buffer acts as a cushion that protects the control system from the sudden unavailability of voltage reference data during faults. By having a pre-stored valid measurement ready, the system avoids the harmful effect of missing or inaccurate real-time measurements during critical fault periods.
3Stability of the object's composition
If energy is converted to thermal energy during faults, then DC voltage control capability is improved, but energy loss increases
Solution Approach 1:
The system converts the harmful effect of excess energy during faults into a beneficial control mechanism. By directing surplus energy through the braking resistor, the system gains additional control capability to maintain DC voltage stability, transforming what would be a destabilizing factor into a useful regulatory tool.
Solution Approach 2:
The control system changes the operational parameters of the converter during faults, switching from normal power transmission mode to a mode where the braking resistor is activated. This parameter change enables active DC voltage control by adjusting the energy dissipation level to match the fault condition and maintain voltage within acceptable ranges.
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
Reduces fault-induced voltage fluctuations in connected AC power grids by maintaining DC voltage stability, minimizing disruptions and allowing seamless energy transmission.
Implementation Method 1
the terminal comprises an energy converter for converting electrical energy into thermal energy (by means of at least one electrical resistance element)
Data Source
AI summary
A method for handling faults in a terminal of a multi-terminal high-voltage direct current transmission system. A DC voltage arising at a DC voltage connection of the terminal is continuously measured so as to form a DC voltage measurement value and information about the DC voltage measurement value is temporarily stored for a predetermined period of time. If a fault arises in an AC grid, a DC voltage measurement value which was measured before the fault arose is used as a setpoint value for a DC voltage controller and the DC voltage controller is used to regulate the DC voltage arising at the DC voltage connection to the setpoint value.