Compensation And Weight Distribution Of Influencing Factors Of Phase Accuracy Of Synchronous Sampling In Power System

Advanced phasor measurement unit (PMU) and wide-area measurement system (WAMS) is one of the developing trends of the future smart grid. It is considered as the main research interests that are developing new technologies and improving the accuracy of measurement and calculation. Data sampling system, as an important component of WAMS, is required to measure the data strictly synchronously. And its key technical indicator is that sampling data from different sampling system has comparability accuracy, which is also the indispensable part for promotion and safety reliability operation of smart grid. Significant amount of research at home and abroad have revealed that phasor from different measurement systems has lower"comparability"only in the steady state, and stressed that the phase delay and other errors must be compensated by sampling devices themselves. But so far, a kind of possible uniform measurement algorithm is not proposed. It is not clearly pointed out how the accuracy of specific power system applications are influenced by phase error based on"comparability". The accuracy of phase measurement device calibration is of significant ambiguity due to the lack of reliable calibration and unified configuration conditions for phase measurement instruments.A stable and reliable platform is developed for real-time data sampling. Taking the present phase measurement standard and precision requirement in typical application of power system into consideration, it is intended to make the phase error accumulation and spread to be limited in the pre-unit of wide-area measurement system with accuracy algorithm for phase measurement and compensation. Several key issues have been deeply analyzed in this paper that are data follow access mechanism, the measurement method of phase error, compensation algorithm and phase accuracy at fault time. And the study of phase accuracy measurement has important value for data analysis and application on real-time and off-line state.The power sampling system is studied based on multi-processor synchronous control to solve problems in current domestic sampling devices, such as, sampling data discontinuous, single function, analysis difficult, and so on. And the execution time of steady and transient recording functions in processor modules has been tested, and as well as the access speed between module interfaces. It can be achieved that long-term effective monitoring for power grid by accommodating the priority of all functions and setting high priority for fault sampling, synchronously controlling tasks logic switch of the internal and interface modules, and leaving enough time for data processing. The bottlenecks factors which affect the data processing speed and its optimization algorithm are analyzed by the processing procedure including data collection, storage, transmission and control logic. The real-time parallel processing mechanism is designed by taking both the real-time and reliability into consideration to assess and optimize the performance of power system comprehensively.The contribution and influence regularity of signal transmission characteristics on phase error of single channel is researched, and gain phase measurement method is adopted after comparing various measurement methods. The probability distribution of phase error due to different factors is achieved by synthetically estimating various errors and the measuring system's own error.The calculations and compensation methods for phase relative error are analyzed, and the FFT method with compensation is adopted when considering the affect of phasor calculation precision by synchronization error. Frequency measurement, as an important link in the compensation algorithm, is also studied. The frequency measurement algorithm with simple recursive software architecture is adopted considering real-time processing. Because calculation precision can be affected by sampling frequency, the allocation method of sampling frequency is given by making overall plans. The weight distribution of several factors which affect phase precision is analyzed, and the corresponding compensation algorithm is adopted in different frequency ranges to improve the comparability of sampling data from different power stations. In addition the data analysis algorithm has low computation complexity.Influence factors for phase accuracy at fault time are analyzed. The phase accuracy at fault time is improved by adopting hign-speed data sampling algorithm based on phase state estimation among the sampling systems. The phase difference forecasting model between asynchronous power stations is established based on the long-term effective monitoring for power grid. The phase difference is forecasted by setting the corresponding parameter. Further, two-terminal fault location is analyzed due to the asynchronous phase difference between two-end current and voltage signal. The relay protection accuracy is discussed by the initial phase in fault time.The power sampling system has been developed. The electrical properties and functions have satisfied the design requirements, and the partial research results have passed the certification in the relevant units. And it has been kept in good working condition in parts of power stations in China. At present, the power sampling system has been produced on a large scale.