Large-scale synchronous condenser (LSC) has a broad application prospect in China's ultra-high voltage direct current (UHVDC) to provide dynamic reactive power. Loss of excitation (LOE) is an important grid-relate...Large-scale synchronous condenser (LSC) has a broad application prospect in China's ultra-high voltage direct current (UHVDC) to provide dynamic reactive power. Loss of excitation (LOE) is an important grid-related fault of LSC, resulting in uncontrolled reactive power consumption. However, due to the un obvious fault feature and UHVDC's diverse reactive power demands, LSC's LOE protection faces challenges in criterion and action mode configurations. Thus, this paper proposes a complete LOE protection strategy for the LSC used in UHVDC, including effective criterion and proper action mode. First, the defect of existing reverse reactive power-based protection is presented through an in-depth analysis of the LOE LSC's reactive power behavior. Then, excitation current difference between the measured value and equivalent actual value is identified as the new fault feature. Compared with existing reverse reactive power features which also appear in healthy LSC's leading phase conditions, this current difference feature only appears in the LO E process and thus is more typical. Since actual excitation current is unmeasurable in practice, an estimation model is built and validated by experiment and simulation. Moreover, the novel LOE protection strategy including current-based criterion and improved action mode is proposed. Through comparative simulation studies in PSCADIEMTDC, the novel protection exhibits superior performances compared to existing protection in LOE detection and commutation failure immunity improvement, as well as overvoltage suppression.展开更多
单载波码分与频分多址(SC-CFDMA,single carrier code and frequency division multiple access)体制要求符号定时精确至码片级,同步难度高于普通体制。为此提出一种多速率星地闭环同步方法,通过适当提升部分环路元件的控制速率,在环路...单载波码分与频分多址(SC-CFDMA,single carrier code and frequency division multiple access)体制要求符号定时精确至码片级,同步难度高于普通体制。为此提出一种多速率星地闭环同步方法,通过适当提升部分环路元件的控制速率,在环路非采样点上延续闭环控制,从而提高对用户运动速度的适应能力。推导了控制速率提升后相关元件及环路的状态空间方程,进行了Matlab软件仿真,结果表明,即使在高轨卫星通信场景下,所提方法也能将多个超音速用户之间的SC-CFDMA上行符号定时偏差同步至码片宽度内,保证链路畅通。展开更多
大型同步调相机配套管道异常振动问题,不仅会降低管道的使用寿命,还会影响调相机润滑油和冷却液的供应,严重时甚至会造成重大安全事故,危害电力系统的稳定性。以某特高压换流站的同步调相机润滑油供油管道为研究对象,使用现场测量、流...大型同步调相机配套管道异常振动问题,不仅会降低管道的使用寿命,还会影响调相机润滑油和冷却液的供应,严重时甚至会造成重大安全事故,危害电力系统的稳定性。以某特高压换流站的同步调相机润滑油供油管道为研究对象,使用现场测量、流固耦合和谐响应分析等多种方法,研究了管道振动的产生原因和机制。结果表明,由调相机本身产生的周期性激振力是管道振动的主要原因。进一步提出基于调谐质量阻尼器(Tuned Mass Damper,TMD)的管道减振措施,试验和仿真数据表明,在润滑油供油管道系统4和5、6和7支吊架中间位置各安装一个TMD,减振效果最佳,可将该管系的振动加速度降低90%以上,具有良好的减振效果。展开更多
文摘Large-scale synchronous condenser (LSC) has a broad application prospect in China's ultra-high voltage direct current (UHVDC) to provide dynamic reactive power. Loss of excitation (LOE) is an important grid-related fault of LSC, resulting in uncontrolled reactive power consumption. However, due to the un obvious fault feature and UHVDC's diverse reactive power demands, LSC's LOE protection faces challenges in criterion and action mode configurations. Thus, this paper proposes a complete LOE protection strategy for the LSC used in UHVDC, including effective criterion and proper action mode. First, the defect of existing reverse reactive power-based protection is presented through an in-depth analysis of the LOE LSC's reactive power behavior. Then, excitation current difference between the measured value and equivalent actual value is identified as the new fault feature. Compared with existing reverse reactive power features which also appear in healthy LSC's leading phase conditions, this current difference feature only appears in the LO E process and thus is more typical. Since actual excitation current is unmeasurable in practice, an estimation model is built and validated by experiment and simulation. Moreover, the novel LOE protection strategy including current-based criterion and improved action mode is proposed. Through comparative simulation studies in PSCADIEMTDC, the novel protection exhibits superior performances compared to existing protection in LOE detection and commutation failure immunity improvement, as well as overvoltage suppression.
文摘单载波码分与频分多址(SC-CFDMA,single carrier code and frequency division multiple access)体制要求符号定时精确至码片级,同步难度高于普通体制。为此提出一种多速率星地闭环同步方法,通过适当提升部分环路元件的控制速率,在环路非采样点上延续闭环控制,从而提高对用户运动速度的适应能力。推导了控制速率提升后相关元件及环路的状态空间方程,进行了Matlab软件仿真,结果表明,即使在高轨卫星通信场景下,所提方法也能将多个超音速用户之间的SC-CFDMA上行符号定时偏差同步至码片宽度内,保证链路畅通。
文摘大型同步调相机配套管道异常振动问题,不仅会降低管道的使用寿命,还会影响调相机润滑油和冷却液的供应,严重时甚至会造成重大安全事故,危害电力系统的稳定性。以某特高压换流站的同步调相机润滑油供油管道为研究对象,使用现场测量、流固耦合和谐响应分析等多种方法,研究了管道振动的产生原因和机制。结果表明,由调相机本身产生的周期性激振力是管道振动的主要原因。进一步提出基于调谐质量阻尼器(Tuned Mass Damper,TMD)的管道减振措施,试验和仿真数据表明,在润滑油供油管道系统4和5、6和7支吊架中间位置各安装一个TMD,减振效果最佳,可将该管系的振动加速度降低90%以上,具有良好的减振效果。
