29 research outputs found
Negative Reactance Impacts on the Eigenvalues of the Jacobian Matrix in Power Flow and Type-1 Low-Voltage Power-Flow Solutions
It was usually considered in power systems that power flow equations had multiple solutions and all the eigenvalues of Jacobian matrix at the high-voltage operable solution should have negative real parts. Accordingly, type-1 low-voltage power flow solutions are defined in the case that the Jacobian matrix has only one positive real-part eigenvalue. However, an important issue that has not been well addressed yet is that the \u27negative reactance\u27 may appear in the practical power system models. Thus, the negative real-part eigenvalues of the Jacobian matrix at the high-voltage operable solution may be positive and also the type-1 low-voltage solutions could have more than one positive real-part eigenvalues, being a major challenge. Therefore, in this paper, the recognition of the type-1 low-voltage power flow solutions is re-examined with the presence of negative reactance. Selected IEEE standard power system models and the real-world Polish power systems are then tested to verify the analysis. The results reveal that the negative reactance in the practical power systems has a significant impact on the negative real-part eigenvalues of the Jacobian matrix at the high-voltage operable solution as well as the number of positive real-part eigenvalues at the type-1 low-voltage power flow solutions
A Hybrid Method for Load flow Calculation based on LVDC Power Distribution Networks
Low voltage direct current (LVDC) distribution system stability, supply security and power quality are evaluated by computational modelling and measurements on an LVDC research platform. Computational models for the LVDC organize investigation are created. The LVDC arrange control misfortune model is produced in a MATLAB domain and is prepared to do quick estimation of the system and segment influence misfortunes. The model integrates analytical equations that describe the power loss mechanism of the network components with power flow calculations. For an LVDC network research platform, a monitoring and control software solution is developed. The solution is used to deliver measurement data for verification of the developed models and analysis of the modelling results. In the work, the power loss mechanism of the LVDC network components and its main dependencies based on hybrid method is described. Energy loss distribution of the LVDC network components is presented
Recent Advances in Computational Methods for the Power Flow Equations
The power flow equations are at the core of most of the computations for
designing and operating electric power systems. The power flow equations are a
system of multivariate nonlinear equations which relate the power injections
and voltages in a power system. A plethora of methods have been devised to
solve these equations, starting from Newton-based methods to homotopy
continuation and other optimization-based methods. While many of these methods
often efficiently find a high-voltage, stable solution due to its large basin
of attraction, most of the methods struggle to find low-voltage solutions which
play significant role in certain stability-related computations. While we do
not claim to have exhausted the existing literature on all related methods,
this tutorial paper introduces some of the recent advances in methods for
solving power flow equations to the wider power systems community as well as
bringing attention from the computational mathematics and optimization
communities to the power systems problems. After briefly reviewing some of the
traditional computational methods used to solve the power flow equations, we
focus on three emerging methods: the numerical polynomial homotopy continuation
method, Groebner basis techniques, and moment/sum-of-squares relaxations using
semidefinite programming. In passing, we also emphasize the importance of an
upper bound on the number of solutions of the power flow equations and review
the current status of research in this direction.Comment: 13 pages, 2 figures. Submitted to the Tutorial Session at IEEE 2016
American Control Conferenc