Modeling of Time-Delayed Distributed Cyber-Physical Power Systems for Small-Signal Stability Analysis
Abstract : Compared with a power system under centralized control, a power system under fully distributed control has stronger interdependence between its physical side and cyber side. Such a system is a typical cyber-physical system (CPS). The time delay problem is one of the most critical issues in the application of distributed control for power systems. First, a distributed information flow model is established considering multiple sources of time delay, especially the communication delay between neighboring agents. Second, combining the dynamics of physical power systems, a general model of time-delayed CPS under fully distributed control is proposed, especially for inverter-based microgrids. Third, the stability of the time-delayed CPS is analyzed based on the proposed model with a critical eigenvalue tracking algorithm. A real-world microgrid with DGs under fully distributed frequency control is tested for small-signal stability analysis. The findings show that the stability of the distributed CPS with multiple sources of time delay depends on not only the absolute value of time delays but also the coordination of time delays and that the delay merging property in centralized mode is not relevant in a distributed CPS. The accuracy of the model and the obtained stability margin are verified by Simulink simulations.
? This information can be used as a complexity and communication cost index (owing to the number of external cybernetic signals are proportional to the information channels required).
? In a similar way, we can see that although the centralized communication architecture requires less cybernetic outputs and inputs, it requires a higher number of Inventions communication links and could be more vulnerable to single point failure events.
? A generalization of these results, integrating the CPES module developed in this paper, is an area for further research.
? The development of the cybernetic and physical network models required for the second step of the CPES modeling methodology is the next stage of our research.
? In particular, time delays are among the most critical issues in information systems.
? The time delay problem remains one of the main obstacles of the revolution of WAMSs and the industrial implementation of wide area control systems (WACSs).
? Given the lack of frequency and voltage regulation capabilities of power systems with high-penetration renewable energy, especially low-inertia microgrids, conventional operation and control methods are unable to cope with the active control problem in high-penetration renewable generation.
? The time delay problem in a DCPPS is especially critical and is nonnegligible under distributed control.
• Some variations of the conventional droop control strategy have been proposed including the virtual impedance approach , which can achieve an important reduction of the reactive power sharing error but requires accurate feeder impedance estimation through online or offline methods.
• Different alternatives for modeling the physical process of an inverter based distributed generator have been proposed, which include detailed temporary models and reduced models.
• However, a characterization of cybernetic components such as communication topologies and a model structure that allows an integration with networked constraints have not been proposed.
? To achieve improved stability performance, multiple sources of time delay in a DCPPS must be simultaneously considered. In addition, the delay merging property in centralized mode cannot be applied to a timedelayed CPPS under fully distributed control.
? With the application of advanced and high-performance information and communication technology (ICT) in modern power systems, the operational efficiency of the cyber-physical power system (CPPS) has undergone a qualitative leap.
? Due to ubiquitous measurement units, control systems and advanced information systems such as the energy management system (EMS) and the wide area measurement system (WAMS), the awareness of modern power systems has become increasingly comprehensive, and the control philosophy is more efficient than ever.
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