Meshed HVDC Converter Control for AC Transient Stability
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Solution Overview
Problem
The integration of meshed DC networks into AC networks reduces the transient stability margin, making AC networks more prone to instability after disturbances, as existing control methods struggle to quickly adapt power settings while respecting electrical limitations.
Innovation Solution
A method for controlling electrical transmission networks that modulates active power between converters based on stored power references and adjusts setpoints using synchronizing and damping power corrections, even without point-to-point high-voltage DC links, by applying terms that account for angle differences and frequency measurements to maintain network stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If meshed DC networks are integrated into AC networks to enable power exchange between AC buses, then control of active and reactive power is improved and renewable power input is facilitated, but the transient stability margin of the AC network is reduced
Solution Approach 1:
The control method continuously measures the frequency on each AC bus and uses this feedback to dynamically adjust the active power setpoint of DC network converters. The frequency measurement serves as a real-time indicator of AC network stability, allowing the control system to respond to disturbances and maintain transient stability while enabling power exchange between AC buses through the meshed DC network.
Solution Approach 2:
The invention dynamically changes the active power setpoint parameter of DC converters based on measured frequency deviations. By adjusting the power setpoint as a function of frequency measurement, the system adapts to changing network conditions, correcting transient imbalances and restoring equilibrium without requiring point-to-point high-voltage DC links between all converter pairs.
2Reliability
If existing control methods are used to improve transient stability by measuring frequencies and applying corrections to active power setpoints, then some stability enhancement is achieved, but the increase in transient stability margin is insufficient during specific disturbances
Solution Approach 1:
The control method dynamically adjusts the active power setpoint of each DC converter based on real-time frequency measurements on connected AC buses. This dynamic adjustment allows the system to respond quickly to disturbances, providing sufficient transient stability improvement that static or pre-programmed control methods cannot achieve during specific disturbance scenarios.
3Reliability
If power settings are quickly adapted to meet network needs during disturbances, then transient stability is improved, but the electrical limitations of converters and high-voltage DC lines may be violated
Solution Approach 1:
The control system pre-establishes the relationship between frequency measurements and active power setpoint corrections, allowing converters to immediately apply appropriate corrections when disturbances occur. This preliminary configuration enables quick response to maintain transient stability without requiring complex real-time optimization calculations that would risk violating electrical limitations of converters and DC lines.
Data Source
AI summary
A method for controlling an electrical transmission network including a plurality of DC high-voltage lines and at least three AC/DC converters which are identified by a respective index i and are interconnected by the DC high-voltage lines. Each of the AC/DC converts are connected to an AC voltage bus identified by a respective index i as well as to one of the DC high-voltage lines.