The embedded HVDC system is a form of DC power system that enhances regional power grids. This paper innovatively categorizes the typical application scenarios of embedded HVDC into three types: transmission section reinforcement, new energy delivery, and power supply zone interconnection. It further pioneers an exploration of the planning approach by breaking it down into three key aspects: identifying embedded HVDC construction demands, determining capacity, and selecting embedding points. For each scenario, specific planning steps are proposed to advance the practical application in reginal power grids. Finally, the planning methods are applied and verified through a case study in Jiangsu, China. Viable embedded HVDC schemes are obtained and compared with the AC approaches.

This paper explores how different control strategies—grid-forming and grid-following—impact the transient stability of modular multilevel converters (MMCs) interfacing with AC power grids. By employing electromagnetic transient simulation tools (PSCAD/EMTDC) on an adapted IEEE three-machine, nine-bus system, various scenarios are analyzed, including faults of differing types and locations. In the simulation, traditional synchronous generators (SGs) are replaced by MMCs configured under distinct control modes. Results indicate that grid-forming (GFM) control enhances the receiving-end grid’s transient stability by providing superior phase support and extended fault-clearing times compared to grid-following (GFL) control, with hybrid approaches yielding intermediate performance. These findings underline the importance of converter control selection in achieving robust dynamic operation in modern power systems with a high penetration of renewable energy.

In response to the growing need for efficient and sustainable energy systems, phase shifters are pivotal in enhancing the flexibility and reliability of power grids while facilitating the integration of renewable energy sources. This paper conducts a comprehensive economic evaluation of various phase shifter technologies, including symmetrical dual-core mechanical phase shifters, electronic phase shifters, and controllable phase shifters, using a lifecycle cost (LCC) analysis framework tailored for the energy sector. The assessment employs probability distributions and Monte Carlo simulation methods to analyze their economic performance, considering key energy-related cost factors such as initial investment, operational efficiency, maintenance, and decommissioning. An uncertainty analysis is introduced to refine the accuracy of LCC calculations, while sensitivity analysis highlights the influence of cost fluctuations—especially in initial investment and operating costs—on overall performance. The results reveal that while large-capacity phase shifters involve higher upfront costs, their superior operational efficiency and lower long-term unit costs can provide substantial economic advantages for sustainable energy applications. These findings offer valuable insights for optimizing energy equipment selection and guiding investment decisions in the transition toward greener and more resilient energy systems.

The rising integration of renewable energy sources has resulted in a diminished capacity for voltage support within the system, which is characterized by low inertia and a reduced short circuit ratio (SCR). In order to improve grid strength and enhance the capacity for renewable energy integration, an initial analysis was conducted on the grid support capabilities of grid-forming (GFM) stations, followed by an investigation into how grid strength influences the dominant operational modes of GFM converters. Subsequently, leveraging the definition of the multi-infeed short circuit ratio, a calculation method for the SCR, applicable to new energy base stations featuring GFM substations, is developed. Additionally, a strategic approach to optimal location selection and sizing of these substations aimed at enhancing the SCR within new energy grids is proposed, with the model being solved through genetic algorithms. Finally, the effectiveness of the proposed method is verified based on the IEEE39-node system and a real new energy station. The results show that the system strength is greatly improved after the optimized configuration of the GFM equipment, and the maximum tolerable space of 90% new energy stations reaches 95% of the theoretical maximum tolerable space of each new energy station.