The Study Of Distributed PMU System Based On IEEE1588Precision Time Protocol And Its Networking Synchronization Scheme

With the growing scale of power systems and the increasing level of voltage, it is very important to monitor the real-time status of the power system effectively. So, it is quite necessary for the PMU-based WAMS system to establish a unified time synchronization system in power grid. However, traditional PMU measures the synchronized phasor by using in the GPS in the whole power system, so some problems such as high cost and potential security risks caused by GPS.Formulated at year2002, IEEE1588precision time protocol (PTP) is a network time synchronization protocol, which can achieve time scale of sub-microsecond synchronization accuracy. So PTP will provide another way for power system to synchronize its inner clocks precisely. Meanwhile, with the proposal and development of digital substation, both electronic transformers and merging unit begin to put into use, which will greatly influence the structure of PMU.Firstly, the background and the meaning for this issue are analyzed, and an IEEE1588-based PMU is proposed. Secondly, both the principle of PMU and two basic synchronized phasor measurement algorithms are introduced showing that the time synchronization is critical for the precision of synchronized phasor measurement. Thirdly, both the development of current time synchronization technology in power system and several commonly used time synchronization methods are described. The paper points out that time synchronization by IEEE1588has many advantages and IEEE1588protocol is comprehensively introduced including the difference between IEEE1588version1and version2, PTP device, PTP message, and the principle of PTP time synchronization. Fourthly the paper proposes a new IEEE1588-based PMU relayling on electronic transformers and merging unit to precisely achieve time synchronization between PMU substations and main station so that the dependence on GPS for PMU can be eliminated and the structure of PMU can be simplified. Finally, the paper proposes several networking programs between PMU substation and main station. Under different synchronous networking programs, the process of time synchronization is studied, and the paper points out that the time synchronization between PMU substation and main station by IEEE1588protocol is the inevitable trend in the future.