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Integration of new energy sources will continuously encroach upon the startup capacity of conventional units， reducing system’s rotational inertia and frequency regulation capabilities. This leads to accelerated frequency changes and increased fluctuation amplitudes. Therefore， it is imperative for new energy units to provide active inertia support. However， the dynamic characteristics of new energy units differ significantly from synchronous generators， making traditional swing equations inadequate to fully reflect the dynamic process of frequency response in new-type power systems after disturbances. Therefore， an inertia model for new-type power systems is established to accurately characterize the inertia response process of synchronous generators， grid-following inverters， and grid-forming inverters. A real-time inertia measurement method is proposed， which employs an improved polynomial curve fitting method （PCFM） and system identification method to accurately identify the system’s rotational inertia and regional inertia. Finally， through simulation， a quantitative assessment of the equivalent inertia of new-type power systems is conducted， and the effectiveness of the proposed measurement method and mathematical model is validated.

Because of the control complexity of voltage source converters (VSCs), transient stability analysis of multi-VSC parallel systems is challenging, and there are still no effective methods to solve this problem. Inspired by the decoupling principle and combined with the normal form method, an innovative coupling-factor-based nonlinear decoupling (CFND) method is proposed. According to the coupling factors that can be used to evaluate the nonlinear coupling degree among different state variables, the CFND method approximately transforms a high-order nonlinear multi-VSC parallel system into multiple decoupled low-order modes. Thus, the transient stability of the original high-order multi-VSC system can be reflected indirectly by the mature inversing trajectory method and the phase plane method. The CFND method has universality, flexibility, and insensitivity to system order, and no need to construct corresponding Lyapunov functions for different nonlinear systems, breaking through the inherent limitations of traditional analysis methods. Furthermore, this paper derives a reduced-order large-signal model and the corresponding truncated model for a single VSC grid-connected system. The effectiveness of the reduced-order model is verified through simulation waveforms and ROAs partitioning. Subsequently, a generalized model of the multi-VSC grid-connected system is developed. Finally, taking the grid-connected system with three VSCs as an example, the proposed CFND method is used to analyze typical operation cases, and the conclusions of transient stability analysis are verified using the hardware-in-loop (HIL) experiments. [ABSTRACT FROM AUTHOR]

Recently, distributed cooperative control has been popularly used in the secondary control of microgrids due to its reliability and flexibility. However, traditional distributed control schemes based on fixed‐cycle communication usually result in a waste of communication resources. Thus, this paper proposes an event‐triggered distributed control strategy that can significantly reduce the requirements of communication. In addition, compared with existing schemes, the proposed algorithm can achieve the secondary control goal in a directed graph, which can be applied to more scenarios, especially for weaker communication conditions. The stability of the strategy is investigated with the Lyapunov method. The simulation results verify the validity and effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Power to hydrogen (P2H) system with renewable energy sources is an important research point for sustainable development. Developing a comprehensive model to accurately capture the thermal-electric characteristics of an electrolyzer and utilizing it to optimize the system's performance pose a significant challenge. In this paper, we develop an energy conversion model of the Alkaline Water Electrolyzer (AWE), describing the impact of temperature on AWE's operation. Then, using experimental fitting methods, we fit the important formulas of the model: the maximum power (MMP) function and the efficiency function. Subsequently, based on the proposed energy conversion model, we propose an active variable temperature (AVT) operation strategy for the P2H system with renewable energy aimed at maximizing hydrogen production. At last, cases for both the day-ahead and hour-ahead situations are conducted with real photovoltaic power. The simulation results show that the AVT operation strategy achieves up to 3% higher hydrogen production and nearly 100% renewable energy utilization rates. • A detailed energy conversion model for alkaline water electrolyzer is proposed. • A novel operation strategy combined with the proposed energy conversion model is introduced. • Considering temperature in the alkaline water electrolyzer model and operation strategy is crucial. [ABSTRACT FROM AUTHOR]