抄録
Under high renewable energy penetration, increasing power-electronic interfacing, and the accelerated deployment of new-type power systems, conventional synchronous-machine-dominated AC grids are facing growing limitations in long-distance bulk power transmission, flexible power regulation, and system resilience, which has promoted VSC-based HVDC transmission and DC grids as major research frontiers. In recent years, substantial progress has been achieved in key enabling technologies, including converter devices and topologies, system control and multi-terminal coordination, DC fault detection and protection, and AC/DC coupled stability mechanisms. In particular, the engineering maturity of modular multilevel converters has established a solid foundation for high-voltage, high-capacity, and multi-terminal DC systems, enabling the transition from point-to-point HVDC links to networked DC grids. However, pronounced trade-offs persist among different technical routes, such as control accuracy versus reliability, power losses versus investment cost, protection speed versus selectivity, and overall system complexity. The coordinated design of converter topologies, system-level control strategies, and DC protection schemes has therefore become a key bottleneck for large-scale and interconnected DC grid deployment. Moreover, several fundamental challenges remain, including fast and reliable DC fault isolation, stable operation under weak-grid and passive-network conditions, and planning and economic evaluation methodologies for DC grids. From a system perspective, this paper reviews the core enabling technologies of VSC-based DC grids, summarizes recent advances in devices and topologies, control and coordination, protection and stability, and representative applications, and comparatively analyzes the applicability and inherent limitations of different technical schemes. Finally, current research bottlenecks and future development trends are identified to support engineering practice, standard development, and frontier research on DC grids.
