超低频率振荡是高比例水电系统面临的突出挑战,大量水电机组调速系统及水力系统的负阻尼聚合是激发全网频率振荡的主要原因.频率振荡期间,水轮机接力器往复动作会导致液压系统油压下降,严重时将导致机组低油压而停机,负阻尼振荡将导致系统频率增幅振荡,控制不及时可能触碰系统高/低周控制动作.传统的降低机组有功出力、提高系统电压水平等振荡控制手段对超低频频率振荡抑制没有明显效果,这对系统安全稳定运行带来严重危害.为准确定位超低频振荡强相关机组,提出了利用发电机速度偏差与机械功率获取调速系统振荡能量的计算方法.同时,针对工程中发电机机械功率难以直接测量的难题,研究提出了利用广域测量系统(wide area measurement system,WAMS)实测的发电机转速和电磁功率合成发电机机械功率的实用算法,可准确计算动态过程中发电机机械功率值,并在电网超低频频率振荡案例分析和大电网超低频振荡预控中验证了该实用算法的有效性.该方法可综合应用同步相量测量装置(phasor measurement unit,PMU)/故障录波/WAMS 等广域信息,实现电力系统发生超低频振荡时,可对机组控制设备进行精细化定位,对发电机控制系统性能进行准确探察评估,从而对大电网频率振荡形态和机组动态行为进行全景式感知监测,为电网安全稳定运行构筑坚强的安全屏障.

This paper presented a comprehensive coordinated control strategy of centralized condenser in highvoltage DC converter station which participated in automatic voltage control（AVC） to perform the reactive power optimization in high proportion new energy areas of Northwest Power Grid. Firstly, the general control idea of AVC was analyzed, and the three-level voltage control mode based on “soft partition” was given. According to the actual situation of Northwest power grid and Qinghai power grid,the coordinated control variables between them were established. Combined with the optimal power flow model,the comprehensive coordinated control strategy of Qaidam condenser participating in AVC was formed. The good applicability of the control strategy was demonstrated by the example of power grid large disturbance encountered during the AVC joint commissioning test of Qaidam condenser. The presented strategy enhances the condenser’s reactive power source effect in the case of steady-state operation. Meanwhile,it ensures instantaneous strong reactive power support capability in the case of power grid fault. As a result, the strategy gives full play to the performance of the condenser,and improves the level of reactive power and voltage regulation of power grid.

特高压直流输电系统单极运行会导致临近变压器出现直流偏磁现象,而变压器感应电动势会对电网电压产生重要影响.为了研究直流偏磁对不同铁心结构和联结组别变压器感应电动势的影响,本文将三相三柱式和五柱式变压器时步有限元模型与YNy和YNd连接的外部电路相结合,建立了能够反映不同联结组别和铁心结构的变压器场-路耦合模型.研究了变压器感应电动势和励磁电流的基波及谐波含量随直流偏磁程度的变化规律,揭示了感应电动势波形畸变率与铁心结构及联结组别之间的关系;最后通过实验验证了结果的正确性.结果 表明,直流偏磁对三相五柱式变压器感应电动势的影响较大,采用YNd联结会减小感应电动势波形的畸变率;而直流偏磁对三相三柱式变压器感应电动势基本没有影响.

Excitation curves of ultra-high-voltage-transformers under conditions of deep saturation are difficult to obtain accurately. In addition, it is difficult to directly measure the remanence of the transformer cores after de-energizing. In this paper researches are made on the above problems. By theory analysis, changes of flux linkage are calculated during energizing and de-energizing processes of transformers. The flux linkage coupling, caused by electric connection of tertiary windings of single phase transformers, is proposed. Methods are proposed to obtain excitation curves and remanences by energizing and de-energizing tests. Results of simulations and experiments show that excitation curve of the transformers under conditions of deep saturation can be corrected by above method, and the remanence after de-energizing can be estimated accurately, thus a good practicability is found for the proposed methods.

变压器空载合闸励磁涌流注入电网可能引起严重的电压暂降或谐波过电压问题,对交直流系统及设备的正常安全运行造成不利影响,目前国内多次出现超、特高压主变空载合闸励磁涌流引起电网异常的问题。选相合闸技术已在国内电厂升压变、高压直流系统换流变等场景有实际应用,但在特高压交流系统中尚属空白。针对国内在晋北特高压交流变电站示范开展的特高压主变选相合闸技术应用实践,介绍了基于剩磁测算的特高压变压器选相合闸技术原理,并结合晋北站特高压交流工程调试系统工况开展建模仿真,比较分析了不同措施抑制变压器励磁涌流的效果,并结合现场实测结果进行验证分析。结果表明,特高压主变断路器采用选相合闸技术可以有效抑制合空变励磁涌流,推广应用价值良好。研究成果可为特高压交流工程设计、设备选型提供参考。

Rapid and accurate real-time monitoring method is the foundation to analyze and inhibit power system subsynchronous oscillation(SSO).This paper presents a real-time SSO monitoring method based on Mallat algorithm of wavelet analysis,which analyzes the generator speed and stator current with multi-solution,extracts the SSO component,detects the SSO strangeness at different scales,so that improves the resolution level of SSO monitoring in time and frequency domain.Field application suggests that the method has good engineering practical value.