Micro-satellite cluster enables a whole new class of missions for communications, remote sensing, and scientific research for both civilian and military purposes. Synchronizing the time of the satellites in a cluster ...Micro-satellite cluster enables a whole new class of missions for communications, remote sensing, and scientific research for both civilian and military purposes. Synchronizing the time of the satellites in a cluster is important for both cluster sensing capabilities and its autonomous operating. However, the existing time synchronization methods are not suitable for microsatellite cluster, because it requires too many human interventions and occupies too much ground control resource. Although, data post-process may realize the equivalent time synchronization, it requires processing time and powerful computing ability on the ground, which cannot be implemented by cluster itself. In order to autonomously establish and maintain the time benchmark in a cluster, we propose a compact time difference compensation system（TDCS）, which is a kind of time control loop that dynamically adjusts the satellite reference frequency according to the time difference. Consequently, the time synchronization in the cluster can be autonomously achieved on-orbit by synchronizing the clock of other satellites to a chosen one＇s. The experimental result shows that the standard deviation of time synchronization is about 102 ps when the carrier to noise ratio（CNR） is 95 d BHz, and the standard deviation of corresponding frequency difference is approximately0.36 Hz.展开更多
The Radial Basis Functions Neural Network （RBFNN） is used to establish the model of a response system through the input and output data of the system. The synchronization between a drive system and the response syst...The Radial Basis Functions Neural Network （RBFNN） is used to establish the model of a response system through the input and output data of the system. The synchronization between a drive system and the response system can be implemented by employing the RBFNN model and state feedback control. In this case, the exact mathematical model, which is the precondition for the conventional method, is unnecessary for implementing synchronization. The effect of the model error is investigated and a corresponding theorem is developed. The effect of the parameter perturbations and the measurement noise is investigated through simulations. The simulation results under different conditions show the effectiveness of the method.展开更多
可编程约瑟夫森电压基准(programmable Josephson voltage standard,PJVS)已被初步应用于谐波信号的测量与分析,在克服过渡过程和吉布斯效应对测量结果的影响后,仍存在无法避免的非同步采样问题,这会在测量结果中引入较大误差,且影响信...可编程约瑟夫森电压基准(programmable Josephson voltage standard,PJVS)已被初步应用于谐波信号的测量与分析,在克服过渡过程和吉布斯效应对测量结果的影响后,仍存在无法避免的非同步采样问题,这会在测量结果中引入较大误差,且影响信号的分析频谱。针对上述问题,提出了基于准同步采样的二次加权傅里叶变换方法,所提方法将准同步采样改进后与加权傅里叶变换结合,通过对原始信号进行两次不同的加权和分步修正,实现了对谐波信号的准确测量。经实验验证,使用该方法对谐波电压测量分析,测量标准偏差可达10^(-7)量级。展开更多
随着风电、光伏的不断接入,电网电压支撑能力不足等问题愈发严重,在新能源场站中配置静止无功发生器(static var generator,SVG)是解决上述问题的有效手段之一。传统跟网型SVG采用低带宽电压控制,难以满足宽频带下的电压支撑需求,而构网...随着风电、光伏的不断接入,电网电压支撑能力不足等问题愈发严重,在新能源场站中配置静止无功发生器(static var generator,SVG)是解决上述问题的有效手段之一。传统跟网型SVG采用低带宽电压控制,难以满足宽频带下的电压支撑需求,而构网型SVG具有理想的电压源特性,近年来受到广泛关注。然而,构网型SVG在模拟同步发电机同步特性的同时,存在大扰动下暂态功角失稳的风险。为此,在新能源联合送出系统控制结构的基础上,建立了基于直流电容动态方程的构网型SVG同步分析模型。其次,解析了新能源联合送出系统等效分析模型的功角特性,揭示了新能源动态影响下系统的暂态功角失稳机理。进一步,提出一种基于自适应功角补偿原理的稳定增强型自同步控制策略,可有效提升系统的暂态稳定性能。最后,通过数字仿真和RT-LAB硬件仿真验证了机理分析的正确性和稳定提升策略的有效性。展开更多
同步相量测量单元(phasor measurement unit, PMU)为电网运行监测提供了精准数据,然而通信中断、设备故障等原因导致数据质量问题愈发显著。某工程现场PMU上送主站数据出现功率振荡异常现象,分析发现直接原因是母线电压选取错误,工程现...同步相量测量单元(phasor measurement unit, PMU)为电网运行监测提供了精准数据,然而通信中断、设备故障等原因导致数据质量问题愈发显著。某工程现场PMU上送主站数据出现功率振荡异常现象,分析发现直接原因是母线电压选取错误,工程现场复杂的电网配置使得电压选取面临挑战。基于层次分析法对各电压选取方案的决策效果进行量化评估,综合考虑方案的优劣及适应性,最终推荐在特定场景下使用电压切换装置选取母线电压。该装置通过接入一次设备的刀闸,从而自动选择最佳电压源以保障母线电压随一次设备的运行方式同步切换,保障了PMU数据采集的准确性和一致性,进而提升了PMU数据质量。研究结果为涉及母线电压选取的实际应用场景提供了科学的决策支持,结合当地电网运行状况,为提升数据质量和优化电网监控提供有效方案。展开更多
基金supported by the National Natural Science Foundation of China(61401389)the Joint Fund of the Ministry of Education of China(6141A02033310)
文摘Micro-satellite cluster enables a whole new class of missions for communications, remote sensing, and scientific research for both civilian and military purposes. Synchronizing the time of the satellites in a cluster is important for both cluster sensing capabilities and its autonomous operating. However, the existing time synchronization methods are not suitable for microsatellite cluster, because it requires too many human interventions and occupies too much ground control resource. Although, data post-process may realize the equivalent time synchronization, it requires processing time and powerful computing ability on the ground, which cannot be implemented by cluster itself. In order to autonomously establish and maintain the time benchmark in a cluster, we propose a compact time difference compensation system（TDCS）, which is a kind of time control loop that dynamically adjusts the satellite reference frequency according to the time difference. Consequently, the time synchronization in the cluster can be autonomously achieved on-orbit by synchronizing the clock of other satellites to a chosen one＇s. The experimental result shows that the standard deviation of time synchronization is about 102 ps when the carrier to noise ratio（CNR） is 95 d BHz, and the standard deviation of corresponding frequency difference is approximately0.36 Hz.
基金This project was supported in part by the Science Foundation of Shanxi Province (2003F028)China Postdoctoral Science Foundation (20060390318).
文摘The Radial Basis Functions Neural Network （RBFNN） is used to establish the model of a response system through the input and output data of the system. The synchronization between a drive system and the response system can be implemented by employing the RBFNN model and state feedback control. In this case, the exact mathematical model, which is the precondition for the conventional method, is unnecessary for implementing synchronization. The effect of the model error is investigated and a corresponding theorem is developed. The effect of the parameter perturbations and the measurement noise is investigated through simulations. The simulation results under different conditions show the effectiveness of the method.
文摘可编程约瑟夫森电压基准(programmable Josephson voltage standard,PJVS)已被初步应用于谐波信号的测量与分析,在克服过渡过程和吉布斯效应对测量结果的影响后,仍存在无法避免的非同步采样问题,这会在测量结果中引入较大误差,且影响信号的分析频谱。针对上述问题,提出了基于准同步采样的二次加权傅里叶变换方法,所提方法将准同步采样改进后与加权傅里叶变换结合,通过对原始信号进行两次不同的加权和分步修正,实现了对谐波信号的准确测量。经实验验证,使用该方法对谐波电压测量分析,测量标准偏差可达10^(-7)量级。
文摘随着风电、光伏的不断接入,电网电压支撑能力不足等问题愈发严重,在新能源场站中配置静止无功发生器(static var generator,SVG)是解决上述问题的有效手段之一。传统跟网型SVG采用低带宽电压控制,难以满足宽频带下的电压支撑需求,而构网型SVG具有理想的电压源特性,近年来受到广泛关注。然而,构网型SVG在模拟同步发电机同步特性的同时,存在大扰动下暂态功角失稳的风险。为此,在新能源联合送出系统控制结构的基础上,建立了基于直流电容动态方程的构网型SVG同步分析模型。其次,解析了新能源联合送出系统等效分析模型的功角特性,揭示了新能源动态影响下系统的暂态功角失稳机理。进一步,提出一种基于自适应功角补偿原理的稳定增强型自同步控制策略,可有效提升系统的暂态稳定性能。最后,通过数字仿真和RT-LAB硬件仿真验证了机理分析的正确性和稳定提升策略的有效性。
文摘同步相量测量单元(phasor measurement unit, PMU)为电网运行监测提供了精准数据,然而通信中断、设备故障等原因导致数据质量问题愈发显著。某工程现场PMU上送主站数据出现功率振荡异常现象,分析发现直接原因是母线电压选取错误,工程现场复杂的电网配置使得电压选取面临挑战。基于层次分析法对各电压选取方案的决策效果进行量化评估,综合考虑方案的优劣及适应性,最终推荐在特定场景下使用电压切换装置选取母线电压。该装置通过接入一次设备的刀闸,从而自动选择最佳电压源以保障母线电压随一次设备的运行方式同步切换,保障了PMU数据采集的准确性和一致性,进而提升了PMU数据质量。研究结果为涉及母线电压选取的实际应用场景提供了科学的决策支持,结合当地电网运行状况,为提升数据质量和优化电网监控提供有效方案。
