Tap Changing Transformer Circulating Current Minimization
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Solution Overview
Problem
Circulating currents in microgrids occur due to voltage drops along distribution lines, leading to inefficiencies and potential equipment failures, as traditional droop control methods do not effectively minimize these currents.
Innovation Solution
Implementing a system where droop-controlled distributed energy resources (DERs) maintain local voltage quality by injecting reactive current, while tap-changing transformers adjust to maximize distribution line efficiency and minimize circulating currents, with autonomous or controlled tap changes based on power factor measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If droop control is used to autonomously share load among parallel generators, then load sharing is achieved, but circulating currents are generated due to voltage drops on distribution lines
Solution Approach 1:
The system measures the power factor at each generator and uses this feedback to dynamically adjust the droop control parameters. By continuously monitoring and adjusting based on actual operating conditions, the system optimizes load sharing while minimizing circulating currents that arise from voltage drops on distribution lines.
Solution Approach 2:
The invention changes the control parameters by adjusting the droop characteristics based on measured power factor. This parameter adaptation allows the system to maintain effective load sharing while compensating for voltage drops, thereby reducing the harmful circulating currents between generators.
2Stability of the object's composition
If generators attempt to support target voltage despite voltage drops, then voltage stability is maintained, but circulating current increases between generators
Solution Approach 1:
The system applies different control strategies to different generators based on their local conditions, specifically their measured power factor. Each generator adjusts its droop characteristics according to its local voltage drop conditions, maintaining voltage stability locally while avoiding the generation of circulating currents through coordinated local adjustments.
3Stability of the object's composition
If tap-changing transformers are used to adjust voltage, then voltage quality is improved, but mechanical stress and maintenance requirements increase
Solution Approach 1:
The invention replaces the mechanical tap-changing system with an electronic control system that adjusts generator output through droop control modification. This substitution eliminates the mechanical wear and stress associated with frequent tap changes while maintaining voltage quality through electronic regulation of generator performance.
Data Source
AI summary
A method and apparatus for minimizing circulating currents on a power distribution line. In one embodiment, the method comprises dynamically adjusting a turns ratio of a tap changing transformer, the tap changing transformer coupled to a power grid distribution line that is also coupled to a plurality of microgrid branches wherein at least one microgrid branch of the plurality of microgrid branches comprises a distributed energy resource (DER), based on a reactive power measured locally to the tap changing transformer, to minimize current circulating on the power grid distribution line.