Microgrid Islanding Stability via Grid Forming Support Mode
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Solution Overview
Problem
Microgrids experience power imbalances and system transients during islanding due to the loss of macrogrid connection, requiring DGs to switch from power control to voltage and frequency control, which can disrupt operations and stability.
Innovation Solution
Implementing a grid forming support mode where at least one DG assists a primary DG in controlling voltage and frequency during transient states after islanding detection, allowing the microgrid to stabilize without changing its power output, and then reverting to power control once stable, with the primary DG maintaining control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DGs switch from power control to voltage and frequency control during islanding, then voltage and frequency stability is improved, but operation disruption and system transients increase
Solution Approach 1:
The control mode of DGs is pre-configured to switch from power control to voltage and frequency control before islanding occurs. This preliminary preparation ensures that when islanding happens, the DGs are already in the appropriate control mode to maintain voltage and frequency stability, thereby reducing operation disruption and system transients.
2Reliability
If multiple DGs switch to grid forming mode during islanding, then microgrid stability is improved, but power output control flexibility is reduced
Solution Approach 1:
Different DGs are assigned different control modes based on their local characteristics and the specific islanding scenario. Some DGs switch to voltage and frequency control while others maintain power control, allowing each DG to contribute optimally to microgrid stability while preserving overall power output control flexibility.
3Reliability
If loads and DGs are disconnected during islanding to achieve power balance, then power imbalance is reduced, but system continuity and productivity decrease
Solution Approach 1:
The control system continuously monitors power balance, voltage, and frequency in real-time during islanding and dynamically adjusts the control modes of DGs accordingly. This feedback mechanism enables the system to maintain power balance without requiring load or DG disconnections, thereby preserving system continuity and productivity.
Data Source
Figure 1~3
Figure 4~5
AI summary
The present disclosure relates to a method of controlling a microgrid arrangement (1) comprising a microgrid (6), a plurality of Distributed Generators (DGs) (2a, 2b.2c) connected to the microgrid (6), and a switch (5) for, in a closed position, connecting the microgrid (6) to a power grid(4), and for, in an open position, disconnecting the microgrid(6) from said power grid (4). The method comprises detecting instability in the microgrid(6). The method also comprises, in response to the detection, switching operating mode of a first DG (2a) of the plurality of DGs from a grid following mode to a grid forming support mode and of a second DG (2b) the plurality of DGs to a grid forming mode. The method also comprises, when the first DG(2a) is in the grid forming support mode, controlling output to the microgrid (6) from the first DG (2a) based on a first voltage reference during a transient state of the microgrid and based on a power reference during a steady state of the microgrid, and controlling output to the microgrid from the second DG (2b) based on a second voltage reference during both the transient state and the steady state.