Negative Sequence Converter for IBR Fault Detection
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Solution Overview
Problem
Inverter-based resources (IBRs) in electrical power systems produce insufficient negative sequence current with incorrect phase relationships, making it difficult for conventional protective relays to detect and respond to unbalanced faults effectively, as they rely on predictable magnitudes and phase angles not met by IBRs.
Innovation Solution
A negative sequence converter (NSC) device is connected to the power system to monitor phase voltages, determine the reference magnitude and phase angle of negative sequence voltage, and generate model currents with appropriate magnitudes and phase angles to ensure sufficient negative sequence current is injected into the bus, enabling conventional protective relays to function properly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inverter-based resources are used in power systems, then renewable energy integration is improved, but negative sequence current magnitude and phase angle accuracy deteriorate
Solution Approach 1:
The patent introduces a negative sequence current injection device as an intermediary component between the IBR and the protective relay. This device synthesizes negative sequence current with accurate magnitude and phase angle relationships, mediating the interface between the IBR's insufficient negative sequence output and the relay's requirements for accurate fault detection.
2Device complexity
If conventional protective relays are used with IBRs, then existing infrastructure is preserved, but fault detection reliability deteriorates
Solution Approach 1:
The negative sequence current injection device serves as a mediator that enables conventional protective relays to reliably detect faults in IBR-based systems. It transforms the IBR's insufficient negative sequence current into adequate current with correct phase relationships, allowing existing relay infrastructure to function reliably without replacement.
3Reliability
If negative sequence current is injected to improve fault detection, then protective relay performance is improved, but device complexity increases
Solution Approach 1:
The negative sequence current injection device is designed to perform multiple functions: it monitors system conditions, synthesizes negative sequence current with accurate phase relationships, and interfaces with conventional protective relays. This multi-functionality reduces the need for separate devices for each function, thereby limiting the increase in overall system complexity.
Data Source
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AI summary
A method for providing negative sequence current to a bus of an IBR-based power system includes the steps of monitoring phase voltages at terminals connected to the power system and determining a reference phasor of a negative sequence voltage incident on the terminals. A rotation phasor is applied to the reference phasor based on an angular offset between a negative sequence voltage and a corresponding negative sequence current to obtain a first outbound negative sequence current having a first magnitude and a first phase angle. The first outbound negative sequence current is scaled to obtain a second outbound negative sequence current having a second magnitude that is different from the first magnitude and is oriented at the first phase angle. The second outbound negative sequence is provided to the bus of the power system.