Position estimating method of IPMSM at low speed region using dq-axis current derivative without high frequency component

Various methods have been proposed to identify the flux position in an interior permanent magnet synchronous motor (IPMSM) without the use of mechanical sensors. To achieve this, a method that uses both the back electromotive force (EMF) and the saliency to identify the flux position in the IPMSM without the injection of high-frequency components at low speeds has been reported [1]. We propose the extended method by controlling current derivative during zero voltage vector. Our method uses d-axis current derivative which has the unstable region where q-axis current derivative can be applied.