The global transition toward power-electronics dominated grids has significantly reduced system inertia, posing increasing challenges to frequency stability. This paper proposes a novel active inertia and damping reshaping strategy for the Synchronous Machine with Electromagnetically Coupled Fly wheel (SM-ECF) system, which is a promising new solution for transient grid support. By integrating a target swing equation with cascaded control loops, the proposed strategy reshapes the equivalent inertia and damping characteristics of the SM-ECF, thereby improving its response to grid-frequency disturbances and enhancing its transient stability under large disturbances. A parameter design procedure for the proposed strategy is further developed by accounting for the physical operating constraints of the system. Hardware-in-the-loop experiments covering active power tracking, frequency support, and short-circuit faults validate the dynamic performance and practical feasibility of the proposed strategy. The results demonstrate that the proposed strategy enables the SM-ECF to provide flexible and robust transient support for modern power grids.
Large-scale islanded hydropower is typically transmitted through independent HVDC links. The lack of interconnected power transmission results in hydropower curtailment during HVDC line faults, and renders the system incapable of providing adequate power support when generator units are under maintenance. Meanwhile, the grid strength of the hydropower stations varies from strong to extremely weak as the number of operating generators decreases, bringing challenges to stable operation of sending-end converters. To overcome the above challenges, this paper proposes an interactive synchronization and fault ride-through control for AC bundled multiple MMC HVDC system integrating large-scale islanded hydropower. The sending-end MMCs are interconnected via AC tie lines to achieve flexible power transfer among HVDC links and promote hydropower consumption. An interactive hybrid synchronization control for the sending-end MMCs is proposed to improve dynamic performance and damp power oscillations during power transmission. Besides, a synergistic sending-end AC fault ride-through strategy is developed to suppress overvoltage, overcurrent and unintended power reversal, ensuring reliable operation. Finally, the effectiveness of the proposed integration technology is verified in a 30GW/±800kV integration system by PSCAD/EMTDC simulation analysis.
In this article, an AC/DC/DC hybrid substation and the operation control strategy are proposed for cost-effective grid integration of multiple far-offshore wind farms (WFs). For large scale far-offshore wind power development, traditional point-to point or multi-terminal DC schemes face challenges in transmission corridor costs and energy conversion efficiency. The proposed hybrid substation collects and transmits power from both AC and DC WFs during normal operation. It also provides start-up power for WFs during initialization. Considering active power regulation and reactive power allocation, the substation control strategy is developed. Control parameters are determined based on substation stability. The proposed solution is evaluated against point-to-point, multi-port modular multilevel converter (MMC), and DC bus collection configurations in terms of cost and losses. Furthermore, the applicable scenarios of the proposed topology are investigated by considering different transmission capacities and distances. The effectiveness of the proposed topology and control strategy is verified through hardware-in the-loop (HIL) simulation.
The objective of this paper is to report some computational results for the theory of differential-algebraic equations (DAEs) stability boundary, with the aim of advancing applications in power system voltage stability studies. Firstly, a new regularization transformation for standard DAEs is proposed. Then the existence of anchor points on the voltage stability boundary is examined, and an optimization method for computing the controlling pseudo-saddle is suggested. Subsequently, a local representation of the stable manifold of the pseudo-saddle on the stability boundary is presented, and a voltage stability margin expression is obtained. Moreover, the impact of grid-forming (GFM) converters, including their current-limiting control, on voltage stability is analyzed within the proposed framework. Finally, the proposed results are verified using several examples, demonstrating the accuracy and effectiveness of the suggested methods.
The increasing penetration of renewable energy challenges power system adequacy. Relying solely on a single power reserve dimension fails to address coarse-grained energy deficits over long horizons and fine-grained ramping needs during short-term fluctuations. To bridge this gap, this paper proposes a multi-dimensional reserve coordination strategy that decouples reserve attributes into energy, power, and ramping dimensions. As the foundation of this strategy, the three-dimensional reserve capabilities are comprehensively modeled, and a unified mapping model is developed to match heterogeneous flexible resources with these three-dimensional capabilities. To coordinate these matched reserve capabilities across time, a hierarchical “month-ahead configuration—day-ahead scheduling” mechanism is established. Specifically, within the day-ahead stage, a Full-Scenario Residual Risk (FSRR) index is proposed, and an FSRR-guided robust iteration evaluates candidate strategies over the full scenario set and adaptively determines the representative scenario set for power–ramping reserve co-optimization. Case studies demonstrate that the proposed method effectively mitigates adequacy risks under diverse scenarios, validating its superiority over traditional single-dimension reserve schemes.
