Research On Some Key Problems Of Wide Area Synchronized Phasor Measurements Of Power Systems

The wide Area Synchronized Phasor Measurement (WASPM) is an important technology. Coordinated by uniform timing clock, it can be used to realize the real-time synchronized measurement of power networks, and is going to be the prerequisite and foundation of security and stability control of power systems. For lacking of a precise uniform timing system, and local synchronized measurement of dynamic frequency has not been solved completely yet, the development of this technology was obviously limited. In 1990's, with the popularization of applications of Global Position System (GPS), the problem of uniform timing system has been solved perfectly, that brings a big progress to the developing of WASPM, and the research focus is now moved to the local synchronized measurement.Based on the former works of other researchers, some key problems of WASPM, include properties of distributed frequency, precise measurements of dynamic frequency, high precise measurements of voltage phasors, influence of disturbance on measurement accuracy and its checking, etc. are analyzed systematically in this dissertation. The main works and innovations are as follows:1. Based on the model of two mixed signals, the properties of distributed frequency are analyzed, and the general expressions with universal applicability are also derived, which can be as a referential guiding function for the selecting of measurement positions in power systems.2. The accuracy of phasor measuring is determined by that of system frequency measuring, and the frequency deviation will give more influence to the phasor computing than to the amplitude of DFT. Further analysis's on the uncertainty of dynamic frequency measurement show, that the theoretical accuracy is only related to the character of disturbances, and different measuring methods can just approach but can not reach accurate point.3. Circle Center Fitting (CCF), a phasor method of frequency measurement, is innovated and proved, and it has the practical value of engineering.4. According to the characteristic that the group delay of linear-phase FIR(MA) filters can be compensated completely, a FIR(MA) filtering based method of frequency precisely measuring is put forward, and it can give more precise results. Combining with a Partial-Linearized Estimating method, it can estimate the error degree of disturbed signal frequency, and an IER(AR) filter can be used in a further frequency processing to improve accuracy. This method is a numerically stable method with high linearity and accuracy. It needn't track the dynamic frequency, and can be used in those near-realtime applications.5. Based on the second order PLL, which uses a first order RC filter as loop filter, the characteristic of dynamic tracking of PLL and its influence on the accuracy of synchronized measurement are analyzed and simulated. Four important problems, such as parameters optimizing problem, influence of filtering ripple, loop-delay and pre-filter delay, are pointed out and they will give harmful influence to frequency measurements. The conclusion is that PLL is not a high performance method of hardware in dynamically tracking, and is not suitable to be used in wide area synchronized phasor measurement systems.6. A method based on the integral de-multiplication technique and GPS synchronized clock to generate the global synchronized checking reference signal of PMU is proposed. It can effectively solve the problem of global synchronized checking and self-checking of PMU precision in synchronized measurement networks. This checking method is reliable and realizable, and can be...