To enhance power transmission efficiency in scenarios such as medium-to-long distance offshore wind power transmission

interconnected power supply for island groups

and large-scale renewable energy integration and transmission on land

low-frequency AC transmission technology has garnered significant attention. As an emerging power transmission technology

low frequency transmission can reduce line reactance and charging reactive power and improve line transmission capacity

and AC is easy to voltage regulation

easy to fault interrupting and easy to network. At the same time

voltage source converters (VSC) provide flexible control similar to VSC-HVDC for low-frequency AC transmission systems. On the basis of comparing the AC

DC and low-frequency AC transmission schemes of medium- and long-distance offshore wind power

the impact of frequency reduction on cables and overhead lines is studied

and the optimal frequency is recommended to be 20 Hz according to the capacity and distance of the wind farm. The effect of frequency reduction on major equipment such as converters

transformers and circuit breakers is analyzed

and after some modifications

the equipment can still be applied to low-frequency AC transmission systems. Three demonstration projects on flexible low-frequency power transmission are introduced

aiming to validate the feasibility of low-frequency transmission in small-capacity scenarios

the reliability of key equipment under high-voltage and large-capacity conditions

and the viability of high-voltage

large-capacity offshore low-frequency wind power transmission. Finally

the future development of flexible low-frequency transmission technology is envisioned.