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• Transient stability of virtual synchronous generator (VSG) is discussed. • Active power-frequency loop of VSG is modified. • The modification consist on adding the auxiliary inertia and additional power into the active power-frequency loop. • Equal area criterion is used to analyze the proposed modification. • Simulation results shows that the proposed modification significantly improved the transient stability of VSG. Virtual synchronous generator (VSG) control scheme has received much attention from researchers as the introduction of rotational inertia to inverters. However, maintaining power-angle stability during the transient state of low inertia microgrids consisting of VSG based distributed generation units is a critical challenge. According to the equal-area criterion, the accelerating and decelerating area play an important role in power system stabilisation. Therefore, a new control strategy based on the equal-area criterion is proposed in this paper. According to the proposed control technique, the auxiliary inertia is incorporated into the governor unit of VSG with an additional power loop. The auxiliary inertia term minimises the difference between the governor unit of VSG and the governor unit of the conventional synchronous generator (SG). In contrast, the additional power loop supplies the auxiliary power during the transient process only when a significant fault occurs. Moreover, to enhance the transient stability, auxiliary inertia helps to improve the convergence time and dynamic characteristics of VSG, and additional power helps to shorten the acceleration area and widen the deceleration area. MATLAB/Simulink based simulations analysis and results validate the effectiveness of proposed control. [ABSTRACT FROM AUTHOR]

The electric power sector significantly contributes to China's economic growth. However, rapid industrialization and urbanization have led to energy shortage problems. More than 70% of customers' demand is fulfilled by fossil fuel sources that threaten the environment. The rapid increase in demand and the need for decarbonization has forced China to work on demand-side management (DSM) to fulfill the power needs of the country. DSM is receiving much importance in China over the past few years. However, it is still in the early phases of development in comparison to other developed countries. At first, this paper points out the need for demand response, which is an aspect of the DSM, for maintaining power system stability and integrating variable renewable energy resources such as wind (on-shore and off-shore) and solar (photovoltaic and concentrated solar power). Then, it assesses China's power sector reforms and changes in demand response policies over the period to promote demand response programs. It also reviews the current demand response pilot projects in China, identifies technical and policy barriers in implementing these projects and proposes recommendations to make it successful across the whole country. • Rapid industrialization and urbanization in China have led to energy shortages. More than 70% of customers' demand is fulfilled by fossil fuel sources that threaten the environment. • This paper assesses China's power sector reforms and changes in DR policies over the period of time to promote DR programs. • It also reviews current DR pilot projects in China, identifies barriers in implementing these projects and proposes recommendations to make it successful across the whole country. [ABSTRACT FROM AUTHOR]

• Virtual synchronous generator (VSG) and distributed generation is discussed. • Deeply discuss the current progress in distributed power generation and role of VSG. • Overview of the recent development in VSG control operation. • Difficulties and future research directions for VSG are discussed in detail. The renewable energy resources based distributed generation (DG) unit's integration into the power system is growing rapidly, and the power system experiencing low inertia and damping, which causes severe stability and performance issues of the power system. In order to facilitate the integration of DG into the existing power system, improved control schemes for grid-tied electronic converters are necessary to ensure the stability and support to the power system. The virtual-synchronous generator (VSG) control emulates the dynamics of the rotation synchronous generator and enhances the stability of the power system. In this paper, an overview of different topologies to virtual inertia is presented along with a detailed description of the VSG structure. Moreover, VSG control defining active and reactive power control, and voltage and frequency control is explained in detail. The VSG stability analysis methods, such as small signal stability and transient stability are presented in comprehensive manners. Later on, the VSG application fields are described. Finally, the VSG problems and future research directions such as centralised control, stability improvement, reliable modelling, the interface for VSG are discussed. [ABSTRACT FROM AUTHOR]

• Improve the response speed of the Magnetically Controllable Reactor. • Rapid Magnetization and demagnetization strategy for slow response Magnetically Controllable Reactor. • The strategy to improve the response speed without changing the structural windings of the Magnetically Controllable Reactor. • The proposed strategy is suitable for all the traditional Magnetically controllable reactor used in UHV transmission lines. Though the magnetically controllable reactor (MCR) has been used in dynamic reactive power compensation of high voltage long distance transmission lines, its dynamic compensation performance is restricted by the imperfection of its slow response in the transition process. Hence, based on the typical structure and working principle of MCR, a novel fast excitation control based on rapid magnetization and demagnetization (RMDM) strategy, which only needs to add augmented boost circuit in the control winding of an MCR, is proposed to improve the dynamic response characteristics of MCR. The mathematical model of the novel proposed RMDM strategy is built and analyzed, based on which, the associations between the estimated transition time and the parameters of the typical MCR structure with auxiliary circuit are considered. Furthermore, the simulation model of the RMDM strategy is established by PSCAD/EMTDC, and simulation findings indicated that the transient time of magnetization and demagnetization of the typical MCR is improved from 0.5sec and 1.0sec to 0.3 sec and 0.1 sec respectively, while the transient time of the reactive power compensation is improved by half. These results substantiate the precision of the theoretical analysis and efficacy of the proposed RMDM strategy of typical MCR. [ABSTRACT FROM AUTHOR]