Micro-grid Power Control During Islanding Transitions
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Solution Overview
Problem
Existing methods for controlling micro-grids during the transition from grid-connected to islanded operation are not optimal, leading to balancing problems due to simultaneous power supply regulation and load shedding, and lack a fast response when disconnected from the main grid.
Innovation Solution
A method for controlling electrical power in a micro-grid that includes determining load shedding during grid-connected mode, monitoring the grid switch status, and performing frequency-based regulation and load shedding upon entering islanding mode, with faster response times for load shedding compared to power production adjustments, and adjusting control speeds based on stabilization criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power supply regulation and load shedding are performed simultaneously during transition phase, then power balance is attempted to be maintained, but balancing problems occur due to interaction of operations
Solution Approach 1:
The control method segments the transition phase into two distinct sequences: first performing load shedding to reduce power consumption, then performing power supply regulation to match remaining load. This segmentation eliminates the harmful interaction between simultaneous operations while achieving power balance through coordinated sequential actions.
Solution Approach 2:
Load shedding is performed as a preliminary action before power supply regulation during the transition phase. By first reducing the load to match available power supply capacity, the system prevents overloading and stabilizes power balance before adjusting power supply levels, ensuring a controlled transition.
2Speed
If fast response is implemented when disconnected from main grid, then transition stability is improved, but control precision may be compromised
Solution Approach 1:
The control method dynamically adjusts the sequence and timing of control actions based on the transition phase detection. Upon detecting grid disconnection, the system immediately executes load shedding with high speed to prevent power imbalance, then transitions to precision power supply regulation. This dynamic sequencing maintains both fast response and control precision at appropriate stages.
Solution Approach 2:
Load shedding is executed as a preliminary fast-acting measure to immediately address power imbalance upon disconnection. This preliminary action with fast response prevents system instability, followed by more precise power supply regulation to fine-tune the balance, thus combining speed and precision in a two-stage approach.
3Adaptability or versatility
If load shedding is performed without pre-determination, then flexibility is maintained, but transition time increases
Solution Approach 1:
The controller pre-determines the load shedding plan during grid-connected operation by monitoring power supply status and calculating required load reductions. This preliminary determination stores control instructions ready for immediate execution upon disconnection, eliminating calculation delays during transition while maintaining flexibility through real-time monitoring and adaptive planning.
Solution Approach 2:
The system continuously monitors power supply status and load conditions during grid-connected operation, using feedback to pre-calculate and prepare load shedding instructions. When disconnection occurs, the pre-determined plan based on actual monitored conditions is executed immediately, achieving fast transition while maintaining adaptability to real-time system state.
Data Source
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AI summary
A method and system (17) for controlling electrical power in a micro-grid (1), especially during islanding when the micro-grid is disconnected from a main grid (3) is described. A potential load shedding for islanding is determined when the micro grid is connected to the main grid. The potential load shedding is performed when a grid switch (9) that connects the micro-grid to a main grid (3) opens. A frequency based load shedding and a frequency based control of power injections to the micro grid (1) may also be performed. The frequency based load shedding is performed with a faster response than the power injection control during islanding. The frequency based power injection control is performed with a faster response than the frequency based load shedding when the micro grid (1) is connected to the main grid (3). A load shedding controller (19), an energy storage controller (18) and methods performed by the load shedding controller, and the energy storage controller, respectively, is also provided.