Power Flow Optimization Of AC/DC Hybrid System Considering Wind Power Integration

With the increasingly prominent global energy and environmental issues,the development and use of renewable energy has received widespread attention.This article focuses on wind power,which is strongly random and volatile,and the forecast of wind power is still inaccurate.Therefore,the uncertainty of large-scale wind power connection is still a huge challenge for power systems.At the same time,with the rapid development of power electronics technology,AC/DC hybrid systems based on flexible DC technology are also more complex and changeable than traditional power grids.Optimal power flow(OPF)is an important method to solve the optimization of power system operation.However,the traditional optimal power flow calculation is difficult to apply in the face of the complex and changeable operating environment of the power system.Therefore,for large-scale uncertain wind power access to AC/DC hybrid system,this paper studies the optimization of AC/DC hybrid power systems considering wind power access.Firstly,considering the impact of uncertain wind power on the operation of AC systems through VSC-based multi-terminal DC(VSC-MTDC)grid connection,the wind power probability scenario is used to characterize wind power uncertainty.The steady-state model of the parallel system,an AC/DC optimal power flow model with VSC-MTDC transmission systems considering wind power uncertainty is proposed.The primal-dual interior point method based on automatic differentiation(AD)is used to solve the model,and the validity and feasibility of the proposed model are verified by a modified IEEE30 nodes example.Due to the day-ahead wind power forecast error,a multi-time scale scheduling mechanism for a VSC-MTDC AC/DC hybrid system with wind power integration is proposed,and the two-stage dispatch optimal flow model of the VSC-MTDC AC/DC interconnection system taking into account wind power uncertainty is established.Based on the dispatching thinking of “multi-level coordination and level-by-level refinement”,this model mainly focuses on the optimization of real-time dispatching based on multi-terminal flexible participation.The running cost of generators is optimized based on short-term forecast data of wind power during the daily rolling stage.And the ultra-short-term forecast data is continuously adjusted to optimize the control of the VSC converter station and the output of the buffer units,which timely correct the impact of short-term forecast errors of wind power on the network loss and voltage level of the AC system.Finally,the proposed model is applied to modified IEEE30 and IEEE118 nodes calculation examples.The analysis results show that the two-stage dispatching optimal power flow model proposed in this paper can reduce the impact of short-term forecast errors of wind power on system operation,and optimize the system while ensuring the economic operation of the power flow distribution.