Abstract:
DC wind turbine is the key basic equipment of all-DC wind power system, its efficient topology and stable control strategy have an important impact on the operation of all-DC wind power system. In order to solve the problems of low efficiency caused by excessive power conversion links of DCWT, high difficulty of self-starting control and low reliability caused by dependence on auxiliary circuit during fault crossing, a new topology of DC wind turbine based on parallel charging and series discharging conversion was proposed in this paper. Based on the dynamic connection mode of the half-bridge and full-bridge arms in parallel on the low-voltage side and in series on the high-voltage side, this paper designed the operation control strategy of the DCWT under different working conditions and analyzed the operating characteristics of DCWT in loss, self-starting and DC fault handling. Through comparison and calculation, it was verified that the proposed new DCWT topology could effectively improve the energy transmission efficiency by reducing the power conversion link. In addition, PSCAD/EMTDC was used to build a simulation model of a parallel all-DC power generation system based on the new DCWT. Through the simulation of DCWT in the wind power system under normal operating conditions such as steady state and dynamic operation, as well as under fault operating conditions such as dynamic cut-in and cut-out of faulty DCWT and DC short circuit, it was verified that the new DCWT had a self-starting mode with low control difficulty and high reliability fault crossing capability under the premise of feasibility.