海上换流站直流侧暂态过压应力抑制策略有效性分析

Analysis on the Effectiveness of Suppression Strategies for Transient Overvoltage Stress on the DC Side of Offshore Converter Station

欧洲北海等地区已经建设了多条基于柔性直流输电技术的海上风电并网工程,中国近些年也加速了该技术的工程实践。由于柔直系统阻尼低,直流侧暂态过电压、过电流发展快,需要采取必要的暂态应力抑制措施,降低对海上平台设备的技术要求,在尽可能减少设备尺寸的同时,保证足够的设备安全裕度。重点围绕暂态过电压应力,首先总结了海上柔直换流站直流侧暂态过电压应力的类型和关键指标,分别针对对称单极和对称双极结构系统,介绍了直流侧设备上承受过电压应力的机理,并梳理了影响直流侧过电压应力的主要因素。其次,总结了海上换流站直流侧过电压抑制策略,将其分为主动型抑制和被动型抑制两大类,其中主动型抑制措施包括功率不平衡抑制策略、直流耗能装置、电缆放电策略、保护加速和断路器快速跳闸策略以及组合策略等,被动型抑制措施包括优化接地方式、优化避雷器参数以及调整桥臂电抗位置等。最后,对相关暂态过压应力抑制措施进行了适用性、有效性和优缺点评估。

Several offshore wind power generation systems integrated with modular multilevel converter high-voltage direct current(MMC-HVDC)technology have been built in the North Sea and other regions of Europe;and China has also accelerated the engineering practice of this technology in recent years.Due to the low damping of the MMC-HVDC system,the transient overvoltage and overcurrent of the equipment develop rapidly on the DC-side.Thus,it is essential to take measures to suppress the transient stress,and optimize the technical requirements of equipment on the DC-side of the offshore converter station,while ensuring sufficient safety margin of the equipment.Considering the transient overvoltage stress,the types and key indicators of the overvoltage stress on the DC side of the offshore converter station were first summarized,and the transient stress mechanism was introduced based on symmetrical monopolar,and bipolar topology,and the factors influencing the overvoltage stress were listed.Further,the overvoltage suppression strategies of the were summarized,and divided into two categories:active suppression,and passive suppression.Active suppression measures included power imbalance suppression strategies,DC energy consuming devices,DC cable discharging strategies,acceleration of protection and circuit breaker trip strategies,and combination strategies.Passive suppression measures included optimizing the grounding method,optimizing the parameters of the DC arrester,and adjusting the position of the arm reactor.Lastly,the applicability,effectiveness,advantages,and disadvantages of the transient overvoltage stress suppression measures were evaluated.