Analysis of the Seismic Performance of ±500 kV Flexible DC Converter Valves

Abstract

The converter valve is the core equipment of flexible DC transmission, but it has been severely damaged in previous earthquakes. Therefore, the seismic performance of its structure has a significant impact on the safety and reliability of power transmission. To study the seismic performance of ±500 kV flexible DC converter valves and identify weak links in the supporting valve tower, this article first established a refined finite-element model of a valve tower based on its physical structure; then modal analysis on the valve tower was conducted; finally, time-domain analysis of the valve tower under three seismic excitations, namely Wenchuan, EI Centro, and artificial, was conducted, and the equivalent stress and directional displacement cloud maps of the key parts of the valve tower were obtained. The research results indicate that the dynamic characteristics of the valve tower are relatively complex, with low fundamental frequency and diverse natural vibration modes. Under earthquake action, the predominant frequency of EI Centro waves is close to the fundamental frequency of the valve tower, which is prone to resonance and causes significant damage to the valve structure. The improved design of the valve tower meets the seismic strength requirements of level 8 seismic intensity.