Vulnerability Assessment Of New Energy Power System Based On Cascading Failure Simulation

With the steady progress of "carbon peaking and carbon neutral",the change of energy structure on the discharge side and the increase of autonomy on the user side are accelerated,and the construction of new power systems is promoted.The dynamic characteristics of the power system have become more complex,the interaction between source,network and load has led to an increase in the uncertainty level of the system tide.The reduction in the rotational inertia of the system has led to a reduction in the frequency stability of the power system.The nature of the new energy field station through the converter and the grid for energy decoupling transformation also makes its voltage regulation support capacity reduced,the probability of chain failures in the power system has increased significantly,thus putting forward higher requirements for the safe,stable and reliable operation of the power system.In response to the lack of dynamic analysis in the current research on the vulnerability of new energy power systems,this paper assesses the vulnerability of new energy power systems from the perspective of simulating chain failures in new energy power systems,taking into account system currents,frequencies and voltages,and establishing vulnerability indicators through dynamic simulation analysis.The work done is as follows:Firstly,the new energy power system characteristics are modelled and wind power,photovoltaic power and load power prediction models are established.By analysing the link between the power electronics of the new energy power system and the weak immunity to frequency and voltage in the cascading failure,the probability of failure models of the power electronics when the system frequency,the frequency change rate and the voltage crosses the limit are established respectively.Then,the cascading failure process of the new energy power system is simulated,and a DC current-based branch stochastic current overload model is established based on the cascading failure mechanism,including the branch overload probability,action time,new energy off-grid criterion under different scenarios as well as the cascading failure termination criterion and propagation time,and the cascading failure incident chain search process of the new energy power system is described in detail.Finally the calculation method of the occurrence probability and occurrence consequence of the accident chain is proposed,in which the occurrence consequence of the accident chain is characterised by four consequence functions such as parallel network voltage,system frequency,system frequency change rate and load loss of the accident chain,from which the risk value of the accident chain is calculated,and the vulnerability assessment index of the accident chain and the power system and its calculation model are established by considering the risk and system structure importance comprehensively.The IEEE39 node system is used as an example to analyse and validate the research method proposed in this paper.The results of the algorithm show that the stability of the power system voltage and frequency under the penetration of new energy has been reduced,and the vulnerability has been increased,which may lead to the off-grid of new energy equipment.Moreover,the comparative analysis of the scenarios shows that the impact of centralised energy on the vulnerability of the power system is more serious compared with distributed energy.It proves the effectiveness of the vulnerability assessment method of new energy power system based on chain fault simulation proposed in this paper.