Research On Unsolvable Power Flow And Its Regulation Method In Electric Power System

The load flow calculation is the base of power system analysis. It has been successfully applied into actual networks. However, as modern power networks becomming heavily loaded and larger interconnected, transmission distance is getting longer, along with competition mechanism has been introduced, power flow equations are apt to have no real solutions. Conventional load flow algorithm can neither give the reason nor the way to convergence. Therefore, it is important to research on unsolvable power flow, and put forward regulation method. The paper study on this problem. The main research content include theory analyse, regulation method research, and software development.Firstly, in chapter two, the related theories of unsolvable power flow are summarized. The characteristics of calculation is showed when Jacobian Matrix of power flow equations reached singularity point, then two nonlinear dynamic theories——feasible region theory and bifurcation theory were simply introduced, so did their effect on regulation. The relation between steady-state voltage stability and unsolvable power flow is studied. After introducing three steady-state voltage stability methods, the feasibility of adopting these methods into the research of unsolvable power flow is discussed.Secondly, two regulation methods are proposed. The first one is based on primal-dual interior point nonlinear programming, and the second is based on sensitivities and dropping power injections. In chapter three, The non-linear programming model of the problem and the solving process, is given. Besides, several suggestions, such as improving the non-linear programming model, and the algorithm, are given. However, this method has a disadvantagement of lack of practical value. According to this, chapter four propose a practical algorithm based on sensitivities and dropping power injections. This method find the weakest transmission path by reducing generators and loads, and reschedule the active power of generators and shed loads based on the sensitivities to get the convergent solution of the power flow. Finally, in chapter five, the software which can solve unsolvable power flow are introduced. The framework of the software, and the characteristics of the regulation module are given. Examples on practical Power Grid testify that the software can effectively solve the unsolvable power flow in power networks.