天广HVDC换流阀阻尼电容器加速老化试验及使用寿命研究

Study on Accelerated Aging and Service Life of Damping Capacitor for Tianguang HVDC Converter Valve

阻尼电容器是HVDC换流阀内关键组成元器件,可实现晶闸管开通、关断和截止等不同状态下的动态和静态均压,吸收阀端过电压,降低晶闸管器件参数一致性要求,使不同参数的晶闸管串联使用成为可能。阻尼电容器采用自愈式电容器,自愈现象持续发生,电容值持续下降的同时损耗角正切值不断增加。随着使用年限增加,阻尼电容器老化直至失效,进而导致阀串分压不均、器件过载甚至阀体损坏的严重后果。本文通过研究换流阀阻容电容器老化机理,提出了换流阀阻尼电容器加速老化试验方案及试验数据的处理建议,在不改变试品失效机理和不增加新失效因子前提下,提高试验应力(电压、温度),加速试品失效进程,再根据试验数据,确定寿命模型中的待定参数,进而估算出试品在实际使用应力下的预期使用寿命。

Damping capacitor is a key element in HVDC converter valve,which can realize dynamic and static voltage sharing of thyristors in such different states as on and off,absorb over-voltage at valve end,reduce the requirement of parameter consistency of thyristors and make series application of different thyristors with different parameters possible. The damping capacitor adopts self-healing capacitor,the self-healing phenomenon occurs continuously,and the tangent of loss angle increases continuously while the capacitance value decreases continuously. With the increase of service life,the damping capacitor ages until failure,which leads to such serious consequences as uneven voltage sharing of valve string,overload of elements and even damage of valve body. In this paper,by studying the aging mechanism of resistive-capacitive capacitor of the converter valve,the accelerated aging test scheme of damping capacitor of converter valve and suggestions for processing test data are proposed. Under the premise of not changing the failure mechanism and not adding new failure factors,the test stress(voltage and temperature)is increased to accelerate the failure process of the sample. Then,the undetermined parameters to be determined in the life model is determined in accordance with the test data,and thereby the expected service life of the sample under the actual service stress is estimated.