Abstract
To address the issue that the phasor measurement units (PMUs) of wide area measurement system (WAMS) are not sufficient for static state estimation in most existing power systems, this paper proposes a mixed power system weighted least squares (WLS) state estimation method integrating a wide-area measurement system and supervisory control and data acquisition (SCADA) technology. The hybrid calculation model is established by incorporating phasor measurements (including the node voltage phasors and branch current phasors) and the results of the traditional state estimator in a post-processing estimator. The performance assessment is discussed through setting up mathematical models of the distribution network. Based on PMU placement optimization and bias analysis, the effectiveness of the proposed method was proved to be accurate and reliable by simulations of different cases. Furthermore, emulating calculation shows this method greatly improves the accuracy and stability of the state estimation solution, compared with the traditional WLS state estimation.
Highlights
Electric power is essential to modern society
phasor measurement units (PMUs) are used to measure data such as voltages, current, angle and frequency, and can provide real-time information about the state of large portions of national and transnational grids and allow one to obtain a state estimate which is a true snapshot of the power system, making the technology for real-time supervision of power systems clearly at hand [35], but because of the high relative cost and inconvenience of installation, we cannot install PMUs in each part of power grid, and we still need state estimation technology using supervisory control and data acquisition (SCADA) and other technologies to get the full state of power grid, and the algorithm and application of state estimation will still need to be explored, proposed and tested in the coming years
The covariance matrix of traditional measurement errors Rt and PMU voltage phasor measurement errors can be calculated by diag σ12, σ22, K, σm
Summary
Electric power is essential to modern society. Economic prosperity, national security, and standard of living depend on reliable electric power systems, and it is very important for the power systems to obtain operating condition information about the state of the electric grid [1]. The control center receives the system-wide device information and measurement mainly through a supervisory control and data acquisition (SCADA) system [6,7]. The collected measurements may not allow direct extraction of the corresponding real-time AC operation state of the system These concerns drive the development of power system technology. The algorithm has a fast computation speed due to the linear measurement equations and the constant Jacobian matrix [27,28] It requires the installation of enough PMU measuring to ensure the system is predictable. A mixed power system weighted least squares (WLS) state estimation method, which uses the PMU measurements to supplement SCADA measurements, has a practical significance.
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