Broadband Simulation And Model Reduction Based On Dq Unified Frequency Transform

With the development of renewable energy and distributed energy,power electronic devices as grid connection interface have been connected to power system on a large scale,and the installed capacity is increasing.Compared with traditional electrical equipment,power electronic equipment often has significant differences in topology,control mode,dynamic response and other aspects,which leads to wide-band oscillation when the system is disturbed.However,the traditional quasi-static electromechanical simulation can not accurately reflect the characteristics of wide-band oscillation.At the same time,the speed of electromagnetic transient simulation is slow,which has the bottleneck of large-scale system application.Obviously,how to establish a reduced order state space model of power system with high reliability and good reduction degree according to the characteristics of modern power system broadband oscillation,and carry out modal analysis on this basis to realize the stable operation and optimal adjustment of power system has become a key problem to be solved,which is of great significance to the penetration of large-scale new energy and the construction of a new generation of power system.In this paper,the dq transform is used to establish the traditional generator,fan and line simulation model.Then,based on dq model,the fundamental differences between dq model and quasi steady state model in formula,principle and simulation accuracy are explained,and the reason why quasi steady state model can not be applied to power system with large-scale semiconductor is explained.Then,in the improved IEEE 3-machine 9-bus system,the sub / super synchronous oscillation curve of power system is reproduced by adjusting the controller parameters,and then compared with the electromagnetic transient simulation curve and eigenvalue calculation,the advantage of dq model is analyzed.Finally,the dq quasi steady state hybrid network model is proposed.For the area near the control system with inverter/ rectifier,the dq model is used to model and simulate the network to restore the dynamic response as much as possible.For the system near the traditional generator network,the phasor model is used.The two models are linked by Kirchhoff’s law to form the whole power network model,which makes up for the shortcomings of the two models.The modeling method is applied to the improved IEEE 3-machine 9-bus test system.By selecting three different partition regions,the advantages of the proposed method in eigenvalue calculation and broadband simul ation analysis are verified.