Research On Modeling And Simulation Of Large Offshore Wind Power System

In recent years,in response to the increasingly tight energy demand and environmental pollution in the world,the country has vigorously developed new energy construction,especially wind power generation systems.At present,the development of onshore wind power is gradually saturated due to topographic and environmental factors.China has a vast coastal area,and there are abundant wind energy resources in the offshore area.Compared with the onshore wind power,offshore wind power has higher average air density and better power generation efficiency.It is the key development direction of the country's future new energy power generation.Permanent magnet synchronous generator is still a research hotspot of scholars at home and abroad due to its advantages of simple structure,high power density,and low operation and maintenance costs.Taking the Jiangsu Rudong Offshore Wind Power Project as the background,this thesis studies the aggregation method and equivalent modeling problem of large offshore wind farms.At the same time,the problem of low voltage ride through of the entire wind farm is studied,and real-time simulation verification is carried out.The research work is carried out as follows:First,an equivalent model of an offshore AC pooled wind farm is established.Taking the actual wind farm as a reference,the circuit structure,main transformer and main wiring form of the AC convergent wind farm are analyzed;The equivalence method of the collecting line of the offshore wind turbine is studied,and a simulation model is built to compare the power before and after the line is equivalent;The establishment method of equivalent model of wind farm is studied,and a double-layer equivalent method combining single-machine equivalent method and multi-machine equivalent method is proposed according to the actual wind farm fan collection method;The equivalent model of the offshore AC wind farm is built and compared with the wind speed equivalent model and the detailed model,which verifies the correctness and high accuracy of the equivalent method.Second,an equivalent model of an offshore DC-concentrated wind farm is established.Aiming at the problems of high cost of AC collection and large line loss,the line structure of wind farms with DC collection is studied.The uncontrolled rectification and fully controlled rectification of the wind turbine are simulated and compared.A series-parallel DC collection test model is built to verify the effectiveness of the wind turbine control and collection methods;The large-scale DCconcentration offshore wind farm is equivalent to the double-layer equivalent method,which verifies the superiority of the DC-concentration wind farm with less loss.Third,the low-voltage fault ride-through test model for offshore wind farms is established.The low-voltage ride-through technology of wind turbines is studied,and the coordinated control strategy of Braking Chopper and grid-side reactive power compensation is analyzed.In the real-time simulation system of offshore wind power,the voltage drop experiment is carried out on the grid connection point of the wind turbine to verify the effectiveness of the low-voltage ride-through control strategy.The hardware-in-the-loop simulation test platform is built with the actual controller of the wind turbine.After comparative experiments,it is verified that the semi-physical simulation is closer to the control effect of the on-site wind turbine,and the test accuracy of the actual project is improved.Low-voltage fault ride-through experiments are carried out on the equivalent models of offshore AC sink and DC sink wind farms to verify the effectiveness of this control strategy in the offshore wind farm equivalent model.