Error analysis and limit value design of a simple sensorless control for MW-level DDWT-PMSG

Given the characteristics of MW-level direct-drive wind turbines based on permanent magnet synchronous generator (DDWT-PMSG), a simple sensorless zero d-axis current control (ZDAC) method is introduced, which gets rotor flux linkage position using saturation feedback double integrator based on coordinate transform (SFDICT). Its implementation principle is introduced in detail. Furthermore, performance of SFDICT under different harmonic components and different amplitude limits is discussed in depth. Error expressions under different amplitude limits are proposed, which provide design principle for the selection of amplitude limits. Based on error analysis, small amplitude limit with angle compensation is proposed, which can get better accuracy and quality. Finally, experimental results indicate feasibility of the proposed method.