柔性低频交流输电关键技术与应用

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.