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Position sensorless control of interior permanent magnet synchronous motors (IPMSMs) is of great importance for the sake of the cost reduction and robustness improvement. An improved position sensorless method based on adjustable high-frequency (HF) square-wave voltage injection has been proposed for the IPMSM drive under zero- and low-speed regions. The general detection method of position from positive- and negative-sequence HF current response has been developed by the simple algebraic operations of data at some adjacent sampling instants. In addition, the proposed method not only can retain the advantage of the removal of low-pass filters in current feedback but also can increase the voltage margin of inverter with adjustable frequency setting of HF signal compared with existing square-wave voltage injection methods. Comprehensive experimental results have been given to verify the proposed theoretical analysis. [ABSTRACT FROM AUTHOR]

In standalone brushless doubly-fed induction generator (BDFIG) power generation systems, unbalanced and nonlinear loads can produce distorted power winding (PW) voltage, and consequently affects the normal operation of other loads and degrades the performance of the power generation system. Although the negative-sequence and harmonic components of the PW voltage can be eliminated by the conventional control methods implemented in either machine-side converter (MSC) or load-side converter (LSC), it causes higher voltage rating of converters and needs more current sensors. In this article, the detailed analysis for the impact of conventional control methods on the voltage rating of the two converters is presented. And then, an improved collaborative control method considering the power converter voltage rating is proposed, in which the MSC can be employed to eliminate the seventh-harmonic voltage of PW, and the LSC can be used to reject the negative-sequence and fifth-harmonic components of PW voltage without extra current sensors. The proportional-integral-resonant controller is applied to the current control loops in both MSC and LSC so as to obtain good current track ability. Comprehensive experimental results based on a 30-kVA BDFIG demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]