Three-phase Short-circuit Current Calculation Of Power System Integrated Wind-solar Considering Low Voltage Ride-through

With the proposal of carbon peaking and carbon neutrality strategy,photovoltaic and wind power is the choice of the grid’s development.When large-scale wind and photovoltaic power connect to the grid,the error of short-circuit current calculation power system with the synchronous generations delaminated increases,and the inaccurate calculation will impact the relay protection operating,then the security of the power system is weakened.Therefore,this paper takes wind power with double fed induction generator(DFIG)and photovoltaic,which currently account for a large proportion of the clean energy,as the research object and investigates the aggregated equivalence of the systems containing both wind farms with DFIG and photovoltaic farms,the selection of low-voltage ride-through(LVRT)control strategies for wind farms with DFIG and photovoltaic farms under three-phase faults,and the calculation of short-circuit currents for wind farms with DFIG and photovoltaic farms under three-phase faults.The fault analysis theory of hybrid wind farms with DFIG and photovoltaic farms connected to the grid is enriched,and a reference for the relay protection and rectification is provided.The main research of the paper is as follow.An equivalent aggregated equivalence model of wind farm with DFIG and photovoltaic farm is proposed.Firstly,analyze the detailed equivalence models of DFIG with stator magnetic chain directional control and PV inverter with voltage directional control.Secondly,select the variables under fluctuating as the classification indictor.Thirdly,use the TSNE algorithm to classify the wind farm with DFIG.Lastly,establish the equivalent aggregation model of wind farm with DIFG and the simplified aggregation photovoltaic farm model,based on the conversion rule of line parameter and transformer parameter.The detailed and aggregated equivalence model of wind farm with DFIG and photovoltaic farm are built;the effectiveness of the model is verified with a simulation.An equivalence grid-connected model is proposed for the hybrid wind farm with DFIG and a photovoltaic farm under the influence of a low voltage ride-through control strategy.For the wind farm with DFIG,the LVRT control strategy of injecting reactive power into the rotor side and judging whether to put in the crowbar circuit according to the magnitude of the DC voltage in the converter is adopted;for the photovoltaic farm,an shed-loading circuit is added on the DC side and the voltage on the network side line is used as the threshold for the opening and closing control of the unloading circuit to realize the LVRT control of the photovoltaic farm.The effectiveness of the model is verified with the equivalence grid-connected simulation model.A three-phase short-circuit current calculation method for hybrid wind and photovoltaic grid-connected power systems is proposed based on the realization of LVRT in the wind farm with DFIG under symmetrical short-circuit faults,considering the aggregation model of the wind farm and photovoltaic farm.The effectiveness of the method is validated by the simulation of the equivalence grid-connected model under three phrase faults.The error of the calculation in temporary state and steady state is within reasonable limits.