Neutral Current Injection for Three-Phase Source Side Identification
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Solution Overview
Problem
Existing methods struggle to accurately identify the source and load side in dynamic three-phase power systems, particularly in scenarios with bi-directional power flow and complex grid configurations, and there is a need for systems and methods to characterize various aspects of such systems.
Innovation Solution
A method and system that utilize a zero-sequence circuit to inject a known shunt current change at a point of interconnection, measure neutral current values before, during, and after the injection, and determine the source and load sides based on the network response to this injection, using sensitivity indices to differentiate between the two.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional methods are used to identify source and load side in three-phase power systems, then the system operation continues, but accurate identification of source and load side cannot be achieved in dynamic configurations with bi-directional power flow
Solution Approach 1:
The patent introduces a zero-sequence circuit as an intermediary device that injects known shunt current changes into the neutral line. This intermediary enables the system to actively probe and characterize the network topology, allowing accurate source identification even in complex bi-directional power flow scenarios where traditional passive measurement methods fail.
Solution Approach 2:
The system implements feedback by measuring neutral current values before, during, and after the injection of known shunt current changes. By analyzing the network's response (changes in neutral current) to the injected signals, the system determines whether the source is on the first or second side of the point of interconnection, enabling accurate identification in dynamic configurations.
2Measurement precision
If neutral current injection is implemented to characterize the power system, then source identification accuracy is improved, but device complexity increases
Solution Approach 1:
The zero-sequence circuit serves multiple functions: it characterizes network topology for source identification, measures impedance, and provides data for power flow analysis. By making this single device multi-functional, the patent reduces the need for multiple separate measurement systems, thereby limiting the increase in overall device complexity while achieving accurate source identification.
3Device complexity
If the system uses passive monitoring without active injection, then device complexity remains low, but the ability to characterize dynamic power systems and identify sources accurately is insufficient
Solution Approach 1:
The system performs preliminary characterization by injecting known shunt current changes before attempting to identify the source or analyze power flow. This active probing action beforehand reveals network topology information that would otherwise be inaccessible, enabling subsequent accurate source identification and power flow determination without requiring continuously complex monitoring infrastructure.
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
Enables accurate identification of the source and load sides in dynamic three-phase power systems, facilitating proper network phase balancing and substation control, even in complex grid configurations.
Implementation Method 1
causing the zero-sequence circuit to: (i) inject a known shunt current change into the point of interconnection
Implementation Method 2
obtaining neutral current values while the known shunt current change is injected
Data Source
AI summary
A system and method of identifying the source in a three-phase power system, wherein a zero-sequence circuit is coupled between the phase lines and the neutral line at a point of interconnection. The zero-sequence circuit to: (i) injects a known shunt current change into the point of interconnection and (ii) ceases injection of the known shunt current change into the point of interconnection. Neutral current values are obtained while the known shunt current change is injected and at least one of (i) before the known shunt current change is injected and (ii) after the known shunt current change is injected and ceased. A determination is made as to whether the source is on the first side of the point of interconnection or the second side of the point of interconnection based on the known shunt current change and the neutral current values.