The integration of high proportion of new energy into distribution networks poses significant challenges for voltage control of distribution network. Traditional voltage control methods cannot ensure satisfactory control performance in scenarios with high penetration of new energy. Additionally， traditional voltage control relies on mechanical voltage regulation equipment， and frequent operation of these equipment significantly affects their lifespan. To address these issues， this paper proposes a multilayer voltage control method based on model predictive control (MPC). In the proposed method， mechanical voltage regulation equipment， such as transformers and shunt capacitors， is controlled in the upper layer with a longer control period， while active and reactive power outputs of distributed generations are rapidly adjusted in the lower layer with a shorter timescale. The objective of the upper-layer control is to reduce the number of operation of mechanical voltage regulation equipment， while the lower-layer control aims to minimize network losses and active power curtailment， ensuring the economic operation of the distribution network. The proposed method considers both the current and future states of the distribution network， ensuring that voltage operates within allowed limits under high penetration of new energy. Simulation results show that the proposed method can effectively address the voltage violation issues introduced by the high penetration of new energy in the distribution network， decreasing the system voltage mean square error from 3.9% to 0.97%. Additionally， the proposed method significantly reduces operation number of mechanical voltage regulation equipment， which is only 40% and 16.4% of those under traditional voltage control methods， respectively.

Energy storage plays an important role in establishing a modern energy system with clean energy as the core. In the new power system, the energy storage technology is mainly applied to promote the consumption of new energy, participate in the auxiliary service of the power market and support the construction of grid-load storage system. Firstly, the structure and classification of energy storage are summarized, and the application characteristics of energy storage are introduced according to power side, grid side and user side respectively. Then, it discusses the way of energy storage promoting new energy consumption on the grid side, and introduces the technology of "electric hydrogen production" to promote new energy consumption. Secondly, the construction of grid-load storage and its typical projects are introduced. The diversification of source grid load storage subjects greatly promotes the development of new energy and realizes the maximization of energy utilization. Finally, the development of power auxiliary services at home and abroad and typical energy storage cases are summarized, and the future development trend of energy storage is prospected.

With the significant increase in the use of renewable power generators, future power systems face stability challenges, including subsynchronous oscillation (SSO), which is a crucial issue. This study proposes subsynchronous damping control (SDC) strategies based on a grid-forming controlled battery energy storage system (BESS) to effectively suppress the SSOs induced by the interaction between nearby direct-drive wind farms and a weak AC grid. The BESS not only offers a range of grid services, including load shifting, peak shaving, and frequency regulation, but also provides positive damping for possible unstable SSO modes from grid-connected wind power. Different SDC structures were designed based on a low-pass filter, notch filter, and phase shifter, and their installed locations and filter/gain parameters were selected. Finally, the results were verified based on electromagnetic simulations, the damping performances of the three SDCs were compared, and the influence of the BESS capacity on oscillation damping was investigated. Specifically, the NF-SDC with a second-order notch filter and the PS-SDC based on a phase shifter exhibited superior performance under the given system conditions. The damping target SSO modes required at least 5% BESS capacity.

Studies in recent years have shown that in addition to the ability to provide frequency and voltage support for AC system, the voltage-controlled virtual synchronous generators (VSG) are also of good adaptability to the operation conditions of weak grid. To improve the stability of a grid-connected VSG and exploit its advantages to the full, in this paper, a method to determine the critical short-circuit ratio (SCR) of the gird-connected VSG system and related stability criteria are explored considering small-signal stability (SSS). To do so, the small-signal model of a grid-connected VSG system is established and sorted into a form of negative feedback system with two-input and two-output units at first. Secondly, according to the generalized Nyquist criterion, a SSS criterion for the system considering impact of grid strength is proposed and a critical SCR is defined, which can provide guidance and reference for planning of gird-connected VSG systems in the future. Finally, methods proposed in the paper are validated through study cases.