Study On The Dynamic State Estimation Of Power System Based On PMU

Modern power system requests to monitor the real-time state to make effective control decisions, in order to keep its safety. Power system state estimation can calculate the bus voltage amplitude and phase from system measurements, so as to estimate and forecast the state, which plays an important role in modern power system. The traditional static state estimation can only give the current state, while dynamic state estimation can provide the state of next step. Since the 1990s, the emergence of PMU based on the GPS technology provides a new opportunity and method for state estimation.Aimed to the dynamic state estimation of power system based on PMU, the paper did some research work mainly on the below aspects:(1)The concept of state estimation, why to study the state estimation and how the research is going on were firstly introduced. The traditional static state estimation algorithms, dynamic state estimation algorithms and algorithms considering the PMU measurements were covered. The basic dynamic state estimation algorithm and some improved algorithms were given an emphasis and their merits and defects were pointed out after careful analysis and comparison.(2)PMU provides a new way for state estimation. Its technical theory, the way to form WAMS system and some relevant problems were detailed in the paper. Because the SCADA system and PMU measurements will exist together for a long time, some algorithms based on data fusion of these two measurements were introduced in detail.(3)Based on the study above, a new algorithm which combines the merits of the static and dynamic state estimation algorithm was brought up. The algorithm uses WLS algorithm on the SCADA measurements first, then mix the result with node voltage from PMU measurements as mixed measurements data to do further dynamic estimation. The traditional WLS algorithm provides reliable results and the linear dynamic algorithm has a quick performance. Simulations on an IEEE 14 test system showed that the new algorithm is effective and superior. Simulations and analysis were carried out to study the effects of PMU deployment to the estimation accuracy, results show that those lines with PMU have higher accuracy; near deployment improves all lines'accuracy; deployment on the node with more branches improves all lines'accuracy.(4)An improved algorithm was brought up to reduce estimation time and error. The fast decoupled method was applied in the process of static estimation. Then the results, together with the voltage phasor measured by PMU, and some relevant voltage phasor transformed from branch current measured by PMU, formed the measured data for the linear dynamic state estimation. Simulations on an IEEE 14 bus test system demonstrated that the method has a better validity in filtering and forecasting the voltage phasor. Numerical experiments results were given to show the effects of different amount of PMU to estimation accuracy.