Study On Transient Frequency Stability Of AC/DC Power System In The Background Of Asynchronous Networking

With the rapid development of the five provinces south power grid,southern power grid has become one of the world's most complex network.Yunnan power grid luxi dc back to back project has been built 2016 put into operation,implement the asynchronous Yunnan power grid and southern main electric power grid interconnection.Asynchronous networking,Yunnan power grid as the low level of space truss structure is relatively weak,load the multi-terminal dc to send end of the power grid,the grid frequency stability problems of risk is very serious.Aimed at this practical problem,based on the asynchronous network under the background of AC/DC power system as the research object,over load model,load parameters,speed regulation system and overlap timing effect on the stability of Yunnan power grid transient frequency conducted in-depth research,the main research content is as follows:The influence of load model on frequency stability.Analyzes the meter and frequency characteristics of the static load model,considering the load model of distribution network,and contains the comprehensive load model of induction motor and other three kinds of the mechanism of load model.In power system transient simulation program of PSD-BPA in 3 kinds of Yunnan power grid load model,the simulation analysis of asynchronous networking background,uhv DC system respectively unipolar and bipolar HVDC pole blocking fault occurs,the peak load model on the system frequency and the influence of the recovery process.The influence of load parameters on the frequency stability.Load on the Yunnan power grid industry,on the basis of full investigation of electrolyzer industrial load of typical electric equipment as the research object.In fully understand electricity utilization equipment production technology and its features,on the basis of establishing cell load model of electrical equipment,forming equivalent circuit.Theory and simulation analysis of power supply side frequency perturbation influence on load consumption power,calculating cell energy intensive frequency characteristic coefficient of electrical equipment.Combined with the research of electric arc furnace and intermediate frequency furnace frequency characteristic analysis of the results,as well as to the Yunnan power grid load data clustering and recommended load model parameters,correction of Yunnan power grid load simulation model,analysis of large disturbance under static and dynamic load model scale and frequency characteristic coefficient for asynchronous networking the effect on the stability of the system frequency.The influence of the speed regulation system of frequency stability.Combination of Yunnan power grid power supply for the most part for medium and large turbines installed features,analysis of hydro turbine governing system system transient stability,the influence of frequency and speed regulation system of differential coefficient,governor response time,soft feedback time and water hammer effect parameters such as time and frequency turbine units.With three machines nine nodes system and asynchronous networking system as an example,the simulation verifies the turbines transient frequency speed control system parameters on the asynchronous networking system.Overlap sequential effects on frequency stability.When the AC/DC power system of ac transmission line three-phase permanent fault occurs,by changing the system and admittance matrix of the normal operation condition,fault line coincides with the head end and the end of the coincidence of admittance matrix,Ward equivalent method is used to get the equivalence between the generator node admittance,according to the related theory,derive the expression of transient frequency under different three-phase reclosing time series,considering the factors such as system capacity and fault distance,the quantitative evaluation index system according to the frequency offset safety of transient frequency stability margin,thus put forward the system frequency stability of three-phase reclosing time sequence setting strategy.In the 2 machine system and asynchronous networking system to verify the effectiveness of the three-phase reclosing timing setting strategy and correctness.