不同桥臂电抗配置海上风电柔直换流站暂态应力与绝缘配合对比

Comparison Study on Transient Stresses and Insulation Coordination on Offshore VSC-HVDC Converter Station Considering Different Arm Reactor Arrangements

全球海上风电柔性直流并网工程总容量已达10 GW,随着单位投资成本不断降低,柔性直流在未来一段时间内仍然是远海风电并网工程的首选方案。由于海上换流站交流电网主要由风电场构成,其暂态电气应力相比陆上换流站有所不同;此外,不同桥臂电抗配置方案会产生不同暂态电气应力。为此,重点针对对称单极系统,对比分析了阀交流侧和直流侧两种桥臂电抗配置方案海上换流站的暂态电气应力。通过建立PSCAD/EMTDC仿真模型,详细分析了海上换流阀交流侧单相接地、两相短路等关键性故障暂态应力特性差异与产生机理,并对主要设备操作过电压与绝缘耐受进行了对比研究。结果表明,直流侧配置方案将显著减小换流阀瞬态电压、电流应力,但暂态应力耐受能力要求更高。

The total capacity of the VSC-HVDC projects used for offshore wind farms integration in the world presently has reached up to 10 GW.As the unit investment cost continues to decrease,the VSC-HVDC will still be the primary option when it comes to integration of far-away offshore wind farms during a period in the future.Because the offshore AC gird is mainly composed by the offshore wind farms,the electrical transients of offshore converter station are different to some degree compared to the onshore side.Moreover,different arm reactor configurations also result in different transient characteristics.Hence,focusing on the symmetric monopole system,this paper compares the transient electrical stresses imposed on offshore converter station considering the two arm reactor arrangements,i.e.,valve AC side and valve DC side.By establishing the simulation models based on PSCAD/EMTDC platform,the differences of transient characteristics and mechanism in case of the key faults,e.g.,valve AC side single-phase grounding faults and two-phase short circuit faults,are analyzed in detail.Then,a comparative study on switching overvoltage and withstand levels of the key equipment in the offshore converter station are carried out.As a result,the valve DC side arm reactor arrangement significantly reduce the valve transient overvoltage and overcurrent.But this is at the sacrifice of the higher requirements of transient stresses withstand capability of arm reactors.