With the large penetration of renewable energy,fulfilling the balance between electricity demand and supply is a challenge to the modern power system.According to the UK government,the wind power penetration will reach 30%by the year 2020.The role of electric vehicles(EVs)contributing to frequency response was investigated.A dynamic frequency control strategy which considers the comfort level of vehicle owners was developed for EVs to regulate their power consumption according to the deviation of system frequency.A simulation model of a population of EVs equipped with such controlwas implemented inMatlab/Simulink platform.In this paper,a simplified Great Britain power system model is used to study the contribution of EVs to dynamic frequency control.The case study showed that using EVs as a demand response resource can greatly reduce the frequency deviations.And the rapid response from EVs can help reduce the operation cost of conventional generators.
This paper presents a novel LMI criterion for electric power system stability with multiple time-delays.Initially,the linear time-invariant model of the power system with multiple delays is constructed,subsequently,the former criteria and the novel criterion of this paper are demonstrated in this paper,and the novel criterion is fully proved according to Lyapunov direct method.Specifically,the proposed criterion utilizes a properly simplified Lyapunov-Krasovskii functional,and no free-weighting matrix is introduced in the formation of new criterion,as a consequence,the calculation efficiency is remarkably enhanced.A typical second-order delay system,a single-generator-infinite-bus system and the WSCC 3-generator-9-bus delay system are taken to validate the effectiveness and efficiency enhancement of the proposed criterion.The numerical results indicate that the criterion of this paper can generate the same stability margin with the former ones.Further,the numerical results also verify that the proposed criterion’s efficiency is substantially boosted and calculation time is greatly curtailed.
Distributed generation including wind turbine(WT) and photovoltaic panel increases very fast in recent years around the world, challenging the conventional way of probabilistic load flow(PLF) calculation. Reliable and efficient PLF method is required to take this chage into account.This paper studies the maximum entropy probabilistic density function reconstruction method based on cumulant arithmetic of linearized load flow formulation,and then develops a maximum entropy based PLF(MEPLF) calculation algorithm for power system integrated with wind power generation(WPG). Compared with traditional Gram–Charlier expansion based PLF(GC-PLF)calculation method, the proposed ME-PLF calculation algorithm can obtain more reliable and accurate probabilistic density functions(PDFs) of bus voltages and branch flows in various WT parameter scenarios. It can solve thelimitation of GC-PLF calculation method that mistakenly gains negative values in tail regions of PDFs. Linear dependence between active and reactive power injections of WPG can also be effectively considered by the modified cumulant calculation framework. Accuracy and efficiency of the proposed approach are validated with some test systems. Uncertainties yielded by the wind speed variations, WT locations, power factor fluctuations are considered.
