Study on the characteristic of the grounding fault on the cascaded midpoint side of the hybrid cascaded HVDC system

Abstract

The hybrid cascaded high-voltage direct current (HVDC) system combines the system support capabilities of the modular multilevel converter (MMC) with the capacity of the line-mutated converter’s (LCC’s) advantage of high-power transmission. The HVDC system is among the key elements of a smart grid where artificial intelligence is applied extensively. However, the characteristics of a grounding fault on the cascaded midpoint side of a hybrid cascaded HVDC system remain unclear. This study analyzes fault characteristics and the impact of faults using analytical methods. First, the topology and basic control strategy are presented. The fault response process is then analyzed by dividing systems into the MMC and LCC parts at the inverter side. A separate theoretical analysis is also conducted. In addition, the impacts of faults on HVDC and alternating current (AC) networks are analyzed. Therefore, even after the HVDC system is disabled, the AC network can supply fault currents using an antiparallel diode. The simulation results show that the proposed analysis method is feasible, and the theoretical analysis is correct. The proposed method can provide a theoretical basis for the selection of equipment for HVDC systems and smart grid construction.

Planning and Operation Strategies for Enhancing Power System Flexibility in Low-Carbon Energy Transition

“…In the references (Yao et al, 2019;, the realtime post-disaster dispatching strategies for transportable energy storage are proposed in view of the power outages caused by disasters. The efficient dispatching strategies of maintenance crews and restoration crews are developed restore electricity customers after the disasters (Zhang et al, 2020a;Sun et al, 2023). In the reference (Hafiz et al, 2019), load restoration is combined with direct load control and demand response to improve system resilience through the flexibility provided by load.…”

A decision-making method for the operation flexibility enhancement of hybrid cascaded MTDC

“…In addition, issuing appropriate control instructions to ensure system stability according to operational demands is a problem that cannot be ignored in decision-making. Under abnormal operating conditions, permanent faults occur on the AC or DC side of the system, leading to changes in the topology (Ren et al, 2023). To reduce the impact of faults, decision-making methods are also needed to provide the corresponding combinations of control strategies and solve the allocation problem of transmission power of faulty poles.…”