| In recent years,the far coast wind power has been continuously constructed through MMC-HVDC delivery project.Although the far coast wind power grid can solve the energy crisis,environmental pollution and other problems,it will also bring a certain impact on the system,make the system oscillation,serious may damage the equipment,and even make the whole system unlist.Therefore,it is imperative to study how to suppress the power system oscillations.Hydrogen energy storage can provide power compensation for the system according to the needs,but also make the damping characteristics of the system develop in a favorable direction,eliminate the factors that may stimulate the oscillation.Reasonable allocation of hydrogen energy storage device is of great significance to the governance of the oscillation phenomenon of the power system.However,there are few studies on the use of hydrogen energy storage system to suppress the oscillation of the power system.In this paper,the principle of harmonic linearization is used to model the small signal impedance of AC side of MMC of wind farm and VSC of wind farm respectively,and obtain the analytical formula of the impedance model.The program was written in MATLAB and the port diagram corresponding to the impedance model was obtained,and the simulation diagram of the far coast wind power electrical model was built in PSCAD was obtained.The correctness of the model was verified by comparative analysis of the two.The impedance model reveals the influence of MMC circulation control and MMC main circuit parameters on the stability of the flexible DC transmission system,and changes the parameters of the main circuit and circulation control in the MATLAB program.The results show that increasing the equivalent inductance or the stability of circulation control can increase the damping of the system and suppress the oscillation better.The electrical model of hydrogen energy storage system is established,which is added to the electrical model of far coast wind power system,and a control strategy is proposed to suppress the oscillation of the system.In the PSCAD time domain simulation,the oscillation of hydrogen-free energy storage system is analyzed.The results show that the hydrogen energy storage equipment and its control strategy can effectively suppress the system oscillation.At the same time,the influence of changing the wind speed,the number of hydrogen energy storage stations and the control parameters of the hydrogen energy storage system on the system stability is observed in the simulation.The results show that the increase of wind speed will increase the active power at the contact line and decrease the system stability;selecting different number of hydrogen energy storage stations and control parameters will have different effects on oscillation suppression.According to the results,the best choice to meet the system stability requirements is given. |
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