摘要
目前,针对柔性直流输电系统在交流电网电压波动时的稳定运行问题,一般采用通过调节有载分接开关保证变压器阀侧空载电压的恒定,但这种方法没有充分发挥有载分接开关的作用,导致正常运行时换流器损耗偏高。为此,提出一种有效降低换流器损耗的新型有载分接开关调节策略。首先,考虑柔性直流输电系统的运行特性,分析所提有载分接开关调节策略的原理,即以最大调制比限制和阀侧最高持续运行电压限制两方面综合确定变压器阀侧空载电压的上限值,再根据网侧电压的实际情况计算分接开关档位。其次,针对具体算例,分析不同交流电压下系统无功功率的要求,根据所提策略计算得到各种实际工况的分接开关档位需求,并且计算对比新型调节策略与传统策略在多种系统传输功率下的换流器损耗,数据显示新型调节策略可有效降低换流器损耗。最后,搭建典型海上风电柔性直流输电系统的PSCAD仿真模型,针对交流电压波动和变压器运行台数变化2种关键工况验证所提新型分接开关调节策略的稳定性和有效性。
At present,in view of the stable operation of the VSC-HVDC transmission system under grid voltage fluctuation,the on-load tap-changer(OLTP)is generally adjusted to ensure the constant no-load voltage on the valve side of the transformer.But the method does not take full use of the OLTP,leading to a relatively higher converter loss during normal operation.In this paper,a novel OLTP regulation strategy to effectively reduce converter losses is proposed.Firstly,the principle of the proposed OLTP regulation strategy is analyzed based on the operation characteristics of the VSC-HVDC system.The maximum modulation ratio limit and the maximum continuous operating voltage limit of transformer valve side are used to comprehensively determine the upper limit of no-load transformer valve side voltage,and then the OLTP position is calculated according to the actual grid side voltage.Secondly,for a specific example,the reactive power requirements under different AC voltages are analyzed,and then the OLTP requirements under different working conditions are calculated according to the proposed strategy.The converter losses of the novel regulation strategy and the traditional strategy under various transmission powers are calculated and compared,and the losses data show that novel regulation strategy could effectively reduce converter losses.Finally,a PSCAD simulation model of a typical offshore wind power VSC-HVDC transmission system is established,and the stability and effectiveness of the proposed novel OLTP regulation strategy are verified under two key conditions of AC voltage fluctuation and change in the number of operating transformers.
作者
张勇
季兰兰
袁艺嘉
王民警
黄玮
ZHANG Yong;JI Lanlan;YUAN Yijia;WANG Minjing;HUANG Wei(China Nuclear Power Engineering Corporation,Shenzhen 518100,China;State Key Laboratory of Advanced Power Transmission Technology,State Grid Smart Grid Research Institute Co.,Ltd.,Beijing 102200,China)
出处
《电力科学与技术学报》
CAS
CSCD
北大核心
2023年第4期35-45,共11页
Journal of Electric Power Science And Technology
基金
深圳中广核工程设计有限公司科技项目(K-A2021.001)。
关键词
分接开关
调节策略
空载电压
损耗
on-load tap changer
adjustment strategy
no-load voltage
losses
