Study on direct-drive PMSG converter systems for small wind turbines.

摘要

The research of this thesis is focused on the study of the common key techniques of small direct-drive, grid-connected permanent magnet synchronous generator (PMSG) wind energy generation systems (WEGSs). The research work is carried out in 4 aspects.;First, the dq-axis models of PMSGs are derived, which, combined with the equivalent magnetic circuit and the phasor diagram, are used to study and design PMSG. Improved methods for the calculations of PMSG reactance and performance, which can take the PMSG saturation into account, are developed. An improved analytical method for the air gap flux density calculation, which can take into account the PMSG saturation and the flux leakage, is developed to calculate the PMSG cogging torque. A practical PMSG CAD program is developed.;Then the finite element method (FEM) is used to calculate the PMSG parameters and performances, and used to fine-tune the PMSG design. An improved PMSG output voltage calculation method and two PMSG reactance calculation methods are developed; to obtain the precise flux leakage coefficient, the axial and radial 2-D flux leakage calculation models are found; using the 2nd -order FEM and through re-construction of integration region, an improved cogging torque FEM calculation method is developed. The influence of various design parameters on PMSG terminal voltage, flux leakage coefficient, reactance, air gap flux density and cogging torque, are studied using the developed methods.;Thirdly, the steady and dynamic performance for both the normal operation and fault operation of PMSG WEGSs are studied through simulation. Key design parameters of PMSG converter are studied and valuable design guidelines are proposed. Techniques to increase the DC-link voltage of PMSG converter are studied using simulation. The basic 2-phase rectifier topologies are proposed and studied through theoretical analysis and simulation. One practical "double-voltage" rectifier topology and one practical PWM boost rectifier topology are proposed, simulated and used to construct the 2-phase PMSG converter.;Finally, using the research results, two PMSGs and their converters are developed and tested. Satisfactory test results and the successful commercialization of the developed 3-phase PMSG WEGS validate the research of this thesis.