Power System Static State N-1Verification Based On Probability Analysis

As modern industry and economy are developing all the time, the demand of electric power is increasing fast, which makes the scale of power system and opening degree of electricity market greater, power network structure and operation mode more complex day by day. The power industry is presenting a development trend of interconnected large power and international power network. The more sophisticated the electric power system is, the higher various fault probability is. If the fault can’t be treated timely, it is possible to give rise to system stability failure, a large area blackout and huge economic losses. Therefore, the safety analysis and reliability analysis of power system become more and more important. The static state security analysis of power system is one of important measures improving power system security. Static state security analysis is applied to estimate whether over-voltage or over-load condition exists at branches aiming at a set of expected contingency or not.The uncertain feature has been increased severely due to the scale of the power system expanding, such as network structure, bus load, et al. The weakness of traditional analysis method of static state security analysis is exposed, and the uncertain analysis approach begins to pay people’s attention. The probabilistic load flow method is one of uncertain analysis methods, and has been successfully used in many aspects of power system analysis. But it is applied less in N-1verification of static state security analysis. The probabilistic load flow study applies probabilistic theory to describe uncertain feature of power system, and explore corresponding mathematical modeling, computer algorithm and practical application.The probabilistic load flow analysis is introduced into the N-1verification of static state security analysis. Firstly, expected contingency ranking economic indicator is elaborated. The operating curves of nodal injections are obtained according to load forecasting. Based on expectation of each nodal injection power, the DC load flow approach is used to rank expected contingency quickly according to expected contingency ranking economic indicator. The list of expected contingency is formed.Secondly, in order to improve the calculation efficiency, linearized probabilistic load flow model is used in accurate N-1verification. Based on operating curves of nodal injection power, PV nodal voltages and the slack nodal voltage, line power changes during a period of time are processed in this thesis. The equations of expectation and variance of branch power are derived. The economic indicator and risk indicator reflecting the static security of branch powers are calculated accurately to estimate grid performance in the case of multi-operation modes.Finally, calculation program is compiled in Visual Fortran6.5platform. The proposed method is verified by an eight-machine system and one provincial power system. Statistical property of branch power could be obtained by it calculated only once, which can reflect the operation conditions of power system and provide comprehensive information to power system operation personnel. Results prove that the proposed method has much higher running speed, meanwhile, validity and practicability of the proposed approach could be also shown.