Research On Power System State Estimation

In order to guarantee the safety, stability and economy of power system, power system dispatching center must grasp the actual operation state of electric power system quickly and accurately and fully. Thus solutions could be accuratly proposed in time to solve all sorts of problems.Nowadays, the SCADA (supervisory control and data acquisition) is widely used in power system to collect and transmiss data. Some of its processes, such as ADC and transmission process are likely to produce errors. Each process possibly still sometimes interference or malfunction. Therefore there are some unavoidable differences between data received by computer in dispatch center and real data. These differences could affect the judging conclusion gained by scheduling centre on the running state of power system, and generate decision-making errors, and lead to serious consequences sometimes.Applying state estimation to process the data received by computer in dispatch center, may make these data have better approximation of the real value, and make more accurate judgment of running state on power system in the scheduling centre, and reduce the economic losses.With the PMU (phasor measurements units) successfully applied in the power system, power system state estimation has entered a new stage.Because PMU device can provide phasor measurement, and high data precision, and short of data sampling period, and the possibility of realization of linear dynamic state estimation e. But due to the high cost and the little number of installation quantity, PMU device will coexist for quite a long time with SCADA.Now the wide-area measurement system (WAMS) based on PMU measurement device and modern energy management system (EMS) based on SCADA measurement device are independent of each other, but in the engineering application of the system can transfer WAMS's data to EMS system database. If the data of these two systems could be used at the same to state estimation, the state estimation accuracy can be effectively improved, and grantee the efficiency power grid operation. This paper studies how to use PMU measurement data and SCADA measuring data in the mixed state estimation.Based on the existing theory, this paper proposes a hybrid measurement of linear and nonlinear model. This model divids power system into linear and nonlinear area, and utilize PMU voltage measurement and electricity flow measurement in the area of linear area, and compute phasor of voltage at node where PMU device connected, the calculated value as indirect measurement of introducing nonlinear area in the state estimation, and weights, PMU measurement using sampling period is short, the phasor voltage will be calculated as the initial state estimation of nonlinear area in computing, thus effectively increase state estimation accuracy.Through doing the emulation experiment in IEEE-14 system, this algorithm put forward in this article is on the basis of guaranteeing computational speed, have improved systematic redundancy degree, thus improved the precision of calculating, it offers theory support for using PMU datas in the traditional estimate state, have certain practical value.