Island Microgrid VSG Impedance Control for Oscillation Suppression
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Solution Overview
Problem
Existing technologies fail to effectively suppress interactive oscillations between virtual synchronous generators (VSGs) and load virtual synchronous machines (LVSMs) in island microgrids, leading to instability and limiting their large-scale application.
Innovation Solution
An interactive oscillation suppression method and system that remodels the impedances of VSGs using d-axis inductive current feedforward control and d-axis voltage feedback control, reducing impedance amplitudes and stabilizing the interaction between VSGs and LVSMs by adjusting duty ratios of switch tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual synchronous machines (VSGs) and load virtual synchronous machines (LVSMs) are used in island microgrids, then the system can provide virtual inertia and damping, but interactive oscillations occur due to negative resistance behaviors, leading to instability
Solution Approach 1:
The patent introduces a damping control mechanism as an intermediary between the VSG and LVSM interaction. The controller detects oscillations and applies counteracting damping control to suppress the harmful interactive oscillations while maintaining the beneficial virtual inertia and damping functions
Solution Approach 2:
The patent dynamically adjusts control parameters (damping coefficients, virtual impedance parameters) based on system operating conditions and detected oscillation characteristics. This allows the system to adaptively suppress oscillations across different operating points while maintaining stability
2Reliability
If virtual impedance control is used to enhance VSG stability in weak grids, then stability is improved, but voltage drop occurs in the VSG
Solution Approach 1:
The patent dynamically adjusts the virtual impedance parameters based on system conditions and oscillation characteristics. By changing the impedance parameters adaptively rather than using fixed values, the system can suppress oscillations while minimizing the voltage drop effect on the VSG
3Object-generated harmful factors
If parameter optimization methods are used to alleviate interaction between VSIs and VSRs, then interaction is reduced, but the method does not address the specific impedance differences between LVSMs and VSRs
Solution Approach 1:
The patent develops a damping control method that is universally applicable to different converter types (VSG, LVSM, VSI, VSR) by focusing on the common oscillation suppression mechanism rather than converter-specific parameters. The control strategy can be adapted to various converter configurations while addressing the specific impedance differences between LVSMs and VSRs
Data Source
AI summary
The present invention discloses an island microgrid system and an interactive oscillation suppression method and system therefor. A source-side virtual synchronous machine and a load-side virtual synchronous machine are combined to provide virtual inertia and damping. The present invention provides a d-axis inductive current feedforward control method and a d-axis voltage feedback control method to remodel impedances of VSGs, so as to reduce impedance amplitudes of the VSGs. Therefore, low-frequency interaction between the VSG and LVSM may be suppressed. The present invention may be used to solve interactive oscillation problems of an alternating-current island microgrid composed of a plurality of source-load virtual synchronous machines.