An Extended Admittance Modeling Method with Synchronization Nodes for Stability Assessment of Converter-Interlinked Power Systems

Grunnleggende konsepter

The proposed extended admittance modeling method with explicit characterization of synchronization (sync) loops can intuitively reveal the impact of diverse sync dynamics on the oscillatory stability of converter-interlinked power systems.

Sammendrag

The paper proposes an extended admittance modeling method to explicitly characterize the sync loops in converter-interlinked power systems for improved stability assessment.

Key highlights:

1. An extended four-port impedance model (EIM) of a generic AC/DC converter is developed, which can explicitly represent the sync loop as a virtual port.
2. The extended impedance network (EIN) is formulated by assembling the EIMs according to the system topology, allowing the frequency-domain modal analysis (FMA) to be directly applied to the sync nodes/branches.
3. The interactions between typical grid-following (GFL) and grid-forming (GFM) sync loops on the system oscillatory stability are revealed through case studies of a point-to-point HVDC system.
4. The sync-node extended FMA method can intuitively identify the dominant sync loops and their participation in the system instability, which is not possible with the conventional FMA based on the pure electrical impedance network.

Statistikk

The following sentences contain key metrics or figures used to support the author's analysis:
"By decreasing the damping coefficient D, the EIN model will generate one pair of RHP-zeros at around 4.3974Hz (dq frame), indicating that the system is unstable."
"The predicted change Δλ is calculated by multiplying the theoretically calculated sensitivity with the corresponding component 5% increment, while the actual change is obtained by re-computing λ of the updated system model (replace the corresponding component value with 105% times of original value) and subtracting the original λ."

Sitater

"The proposed extended admittance modeling method with explicit characterization of synchronization (sync) loops can intuitively reveal the impact of diverse sync dynamics on the oscillatory stability of converter-interlinked power systems."
"The interactions between typical grid-following (GFL) and grid-forming (GFM) sync loops on the system oscillatory stability are revealed through case studies of a point-to-point HVDC system."

Viktige innsikter hentet fra

An Extended Admittance Modeling Method with Synchronization Node for Stability Assessment of Converters-Interlinked System

by Haoxiang Zon... klokken arxiv.org 10-02-2024

https://arxiv.org/pdf/2410.00619.pdf

Dypere Spørsmål

How can the proposed sync-node extended FMA method be extended to analyze the stability of multi-terminal HVDC systems with a larger number of converters?

The proposed sync-node extended Frequency-Domain Modal Analysis (FMA) method can be effectively extended to analyze the stability of multi-terminal HVDC (MTDC) systems by leveraging its modularity and scalability. The following steps outline this extension:

Modular Representation: Each converter in the MTDC system can be represented using the four-port Extended Impedance Model (EIM). This modular approach allows for the independent characterization of each converter's sync dynamics, including both grid-following (GFL) and grid-forming (GFM) behaviors.

Network Assembly: The Extended Impedance Network (EIN) can be constructed by interconnecting the individual four-port EIMs of all converters. This involves applying Kirchhoff's laws to ensure that the network adheres to the principles of electrical circuit theory, thus allowing for the integration of sync nodes as virtual branches.

Sensitivity Analysis: The sync-node extended FMA method can be applied to the assembled EIN to perform sensitivity analysis across the entire MTDC system. This analysis will identify how variations in sync loop parameters affect the overall system stability, enabling the assessment of oscillation propagation and the identification of critical components that contribute to instability.

Dynamic Simulation: Time-domain simulations can complement the frequency-domain analysis, providing a comprehensive view of the system's dynamic behavior under various operating conditions. This dual approach enhances the understanding of how sync dynamics interact with other control mechanisms in a multi-converter environment.

Scalability: The method's inherent scalability allows for the addition of more converters without significant modifications to the existing framework. Each new converter can be integrated into the EIN, and its sync dynamics can be analyzed in conjunction with the existing system.

By following these steps, the sync-node extended FMA method can effectively address the complexities associated with the stability analysis of multi-terminal HVDC systems, providing valuable insights into the interactions between multiple converters and their sync loops.

What are the potential limitations of the four-port EIM in accurately capturing the complex interactions between sync loops and other control dynamics in practical converter systems?

While the four-port Extended Impedance Model (EIM) offers significant advantages in explicitly characterizing sync loops, it also has potential limitations in accurately capturing the complex interactions between sync loops and other control dynamics in practical converter systems:

Simplified Assumptions: The four-port EIM may rely on simplified assumptions regarding the behavior of sync loops and their interactions with other control dynamics. In real-world scenarios, the dynamics of converters can be influenced by non-linearities, time delays, and varying operating conditions that may not be fully represented in the model.

Parameter Variability: The parameters used in the four-port EIM, such as inertia constants and damping ratios, can vary significantly across different operating conditions and converter types. This variability may lead to inaccuracies in the model if the parameters are not updated to reflect real-time conditions.

Neglect of Higher-Order Dynamics: The four-port EIM primarily focuses on the first-order dynamics of sync loops. However, higher-order dynamics, such as those arising from complex control strategies or interactions with external disturbances, may not be adequately captured, potentially leading to an incomplete understanding of system stability.

Coupling Effects: The interactions between sync loops and other control dynamics can be highly coupled and may exhibit emergent behaviors that are difficult to predict. The four-port EIM may not fully account for these coupling effects, particularly in systems with multiple converters operating under different control strategies.

Scalability Challenges: While the four-port EIM is designed for modularity, as the number of converters increases, the complexity of the EIN can grow significantly. This complexity may lead to challenges in computational efficiency and the ability to perform real-time stability assessments.

Overall, while the four-port EIM is a powerful tool for analyzing sync dynamics, its limitations must be acknowledged, and complementary methods may be necessary to achieve a comprehensive understanding of the interactions within practical converter systems.

Could the insights gained from the sync-node extended FMA be leveraged to develop novel control strategies for improving the overall stability and resilience of converter-dominated power systems?

Yes, the insights gained from the sync-node extended Frequency-Domain Modal Analysis (FMA) can be leveraged to develop novel control strategies aimed at improving the overall stability and resilience of converter-dominated power systems. The following points illustrate how these insights can be utilized:

Targeted Control Design: By identifying the specific sync dynamics and their contributions to system instability through participation factors and sensitivity analysis, control strategies can be tailored to address the most critical components. For instance, if a particular sync loop is found to significantly influence oscillations, control parameters can be adjusted to enhance damping or modify the response characteristics of that loop.

Adaptive Control Mechanisms: The insights from the sync-node extended FMA can inform the development of adaptive control strategies that dynamically adjust control parameters based on real-time system conditions. This adaptability can enhance the system's resilience to disturbances and varying operational scenarios, thereby improving overall stability.

Coordination of GFL and GFM Controls: Understanding the interactions between GFL and GFM converters can lead to the design of coordinated control strategies that optimize the benefits of both types of converters. For example, hybrid control schemes that leverage the fast response of GFL converters alongside the inertia response of GFM converters can be developed to enhance system stability.

Implementation of Active Damping: The analysis can reveal opportunities for implementing active damping strategies that specifically target identified oscillation modes. By integrating damping controls into the sync loops, the system can be made more robust against oscillatory instabilities.

Resilience to Grid Disturbances: Insights from the sync-node extended FMA can also guide the design of control strategies that enhance the resilience of converter-dominated power systems to external disturbances, such as faults or sudden changes in load. By understanding how sync dynamics interact with grid conditions, control strategies can be developed to maintain stability during such events.

Simulation and Validation: The proposed control strategies can be validated through simulation studies that utilize the EIN framework. This allows for the assessment of the effectiveness of the new strategies in improving stability and resilience before implementation in real-world systems.

In summary, the insights gained from the sync-node extended FMA provide a valuable foundation for developing innovative control strategies that enhance the stability and resilience of converter-dominated power systems, ultimately contributing to more reliable and efficient energy systems.