摘要
研究了高压直流输电系统工频和二次谐振特性,建立了系统阻抗频率扫描模型。提出了交流系统和交流滤波器通过换流变和换流器折算到直流侧的等效模型和计算方法,分析了交流系统强弱和交流滤波器组数对系统阻抗频率特性的影响。结合可能导致直流系统谐振的故障工况,研究了扫描时谐波源的施加方法,分析了谐波源施加于不同位置对扫描结果的影响。针对同廊道交流线路的感应,提出扫描时谐波源应分别施加于线路端部和中间,并在扫描时考虑最严重的情况。以锦屏—苏南±800 kV工程为例,扫描了各种工况下系统的阻抗频率特性,结果表明在某些运行工况下系统谐振频率为48 Hz和100 Hz,可能存在一次、二次谐振。采用直流系统电磁暂态仿真模型仿真了可能在直流系统产生一次、二次谐波的故障,结果表明在发生交流相间短路故障时,直流侧二次过电压很严重,进一步验证了阻抗扫描结果。最后,提出了抑制二次谐振的措施。
The 50Hz and 100Hz DC resonance occurred in HVDC power transmission projects are studied, and a system impedance-frequency scan model for HVDC transmission project is build. Equivalent model and computing method, by which the AC system and AC filters are converted to DC side via converter transformer and converters, are proposed, and the impacts of AC system strength and the sets of AC filters on impedance-frequency characteristics of DC system are analyzed. Considering fault conditions that may cause resonance in DC system, the approach of exerting the harmonic source during the scanning is researched, and the influence of applying harmonic source to different positions on scanning results is analyzed. In allusion to the induction due to the AC transmission line arranged in the same corridor, it is proposed that the harmonic source should be applied to both terminals and the middle of the DC transmission line, and the most serious conditions should be taken into account during the scanning. Taking the ±800 kV UHVDC power transmission project from Jinping to Sunan for example, the impedance-frequency characteristics of the DC system under various operating conditions are scanned, and scanning results show that under certain operating conditions the frequencies of the resonance occurred in the DC system are 48 Hz and 100 Hz, so the power frequency resonance and the second harmonic resonance exist possibly. Some faults that may cause power frequency and second harmonic resonances in the DC system are simulated by electromagnetic transient model of the DC system, and simulation results show that the 100Hz overvoltage in the DC system is serious while phase to phase short circuit fault occurs in AC system, thus the impedance scanning results are further verified. Finally, some measures to suppress second harmonic resonance in the DC system are suggested.
出处
《电网技术》
EI
CSCD
北大核心
2012年第12期189-194,共6页
Power System Technology
关键词
高压直流输电
直流谐振
阻抗扫描
过电压
HVDC power transmission
DC resonance
impedance scan
overvoltage
