AC Line Distance Protection for Commutation-Failure Fault Location
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In AC/DC hybrid power grids, traditional distance protection methods fail to accurately isolate faults due to nonlinear and time-varying fault characteristics caused by commutation failures in DC systems, leading to misoperation or refusal to operate, compromising grid safety and stability.
Innovation Solution
A method and system for AC line distance protection that collects operation parameters from inverter-side converters, determines conduction states, calculates currents fed into the AC system, and computes virtual fault locations and transition resistances to accurately identify fault positions, reducing the likelihood of misoperation by using specific equations for different valve arm states and fault types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional distance protection methods are used in AC/DC hybrid power grids, then the protection system can operate with simple principles, but the accuracy of fault location determination deteriorates due to nonlinear and time-varying fault characteristics caused by commutation failures
Solution Approach 1:
The patent transforms the complex nonlinear fault characteristics into equivalent linear parameters by introducing virtual fault location and virtual transition resistance concepts. By calculating these virtual parameters based on measured currents and comparing them with actual fault characteristics, the system achieves accurate fault location without requiring complex real-time nonlinear analysis, thus resolving the contradiction between simple system structure and high measurement precision
Solution Approach 2:
The patent introduces virtual fault location and virtual transition resistance as intermediary parameters that bridge the gap between traditional protection methods and the actual nonlinear fault conditions. These virtual parameters serve as mediators that allow conventional protection algorithms to accurately identify faults in AC/DC hybrid systems without directly confronting the complexity of nonlinear time-varying characteristics
2Adaptability or versatility
If traditional distance protection is applied without considering converter conduction states, then the protection method remains simple and universal, but the reliability deteriorates due to misoperation or refused operation caused by DC system commutation failures
Solution Approach 1:
The patent dynamically adapts the protection algorithm by determining the converter conduction state (number of conducting valve arms) in real-time and selecting different calculation equations accordingly. This dynamic adjustment allows the protection system to maintain high reliability under varying operating conditions while preserving the simplicity and universality of the overall protection framework through a standardized decision-making structure
Solution Approach 2:
The patent segments the protection algorithm into distinct calculation paths based on converter conduction states (different numbers of conducting valve arms). Each segment uses an appropriate equation tailored to that specific state, allowing the system to handle the complexity of different operating conditions through modular, state-specific calculations rather than a single complex universal algorithm
Data Source
AI summary
The disclosure relates to a method and system for AC line distance protection in AC/DC hybrid power grid, and storage medium. The method comprises: collecting the operation parameters of inverter-side converter, AC parameters, converter bus voltage, current at distance protection installation and operation parameters of the smoothing reactor of inverter station; determining the conduction state of the inverter-side converter according to the operation parameters of the inverter-side converter; determining the current fed into the AC system from the DC system corresponding to the conduction state according to the operation parameters of the inverter-side converter, the operation parameters of the smoothing reactor of the inverter station and the converter bus voltage; determining the virtual fault location and virtual transition resistance according to fault types and AC parameters; controlling the corresponding protection device to perform the protection action according to the virtual fault location and virtual transition resistance.