| Wind energy is a clean and friendly new energy source,therefore it is rapidly developed worldwide.In recent years,the offshore wind power has developed rapidly and has broad prospects.In terms of power transmission,the flexible high-voltage DC transmission(VSC-HVDC)system represented by fully-controlled devices has become the main transmission mode for the offshore wind power system.At present,the doubly-fed wind power generation system applied to the VSC-HVDC system for offshore wind power has many defects,which restricts the healthy development of offshore wind power.For this reason,we propose a novel VSC-HVDC topology with DFIGs to meet the requirements with the development of offshore wind power.This paper has carried out the related researches on the transmitting end station converter and the receiving end station converter in novel VSC-HVDC wind power generation system with DFIGs.First,the bidirectional Buck/Boost circuit is used as the topology of the transmitting end station converter.Its operating principle is analyzed in detail.Based on this,the mathematical model is established.The double closed-loop control strategy of the converter is studied.The overall simulation model of this converter is built on the Matlab/Simulink platform.The simulation results show that the expected control requirements are met.A set of 3kW converter prototype was designed based on the main performance parameters.The experiment was carried out on the experimental platform,and the proposed control strategy of the converter was verified.Second,the research on the receiving end station converter was carried out.The two-level voltage source converter(VSC)is chosen to be the topology of the receiving end station converter.Its operating principle is introduced,and its mathematical model is established.This converter employes the control strategy based on grid voltage orientation,and the inner loop and voltage outer loop are controlled.The Matlab simulation study was carried out to verify the feasibility of the control strategy theoretically.A set of 5kW converters was designed,and the experimental verification was carried out on the experimental platform under the different working conditions such as off-grid,grid-connected and rectified.Finally,by analyzing the working process of the new offshore wind power high-voltage flexible DC transmission system,the cooperative control targets of the transmitting end station converter and the receiving end station converter are determined,and the experimental platform of the transmitting end station and the receiving end station converter system is set up.Thecollaborative control of the two converters was experimentally studied to verify the reliability of the whole system. |
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