Voltage-Frequency Interaction Mechanism Under Short-Circuit Faults in a High Proportion of New Energy-Receiving Grids

An alternating current (AC) fault in the alternating current/direct current (AC/DC) receiving end of the grid with a high proportion of new energy access will cause problems such as direct current (DC) phase switching failure, new energy low-voltage ride-through(LVRT), and generate short time active and reactive power coupling impact(SA-RPCI). These issues can lead to significant alterations in the system voltage and frequency. In order to address this problem, this paper investigates the system frequency and voltage characteristics after an AC fault, divides the frequency-voltage interaction response process into three phases, and analyses the new energy, DC and load dynamics in each phase. New energy sources are investigated for changes in active and reactive power output under different voltage dips levels. It is highlighted that DC and induction motors absorb a substantial amount of reactive power during the recovery process, affecting the system voltage recovery. It is observed that the frequency exhibits two opposing response characteristics due to a change in fault location. A quantitative index of the frequency response trend is proposed to account for the influence of the source-load voltage, which can inform the formulation of the emergency control strategy. Finally, the conclusions are verified in a simplified AC/DC receiving grid with a high proportion of new energy sources.