Abstract
High-frequency injection (HFI) is widely used for zero-to-low speed self-sensing in machines with saliency. HFI algorithms use inductive saliency in the d- and q-axes to estimate the rotor position in permanent magnet synchronous machines (PMSMs). Generally speaking, surface PMSMs (SPMSMs), which are designed without inductive saliency, are not suitable for HFI inductive based self-sensing. In this article, a method to enhance HFI algorithms at zero-to-low speed for classically designed SPMSMs with low inductive saliency is presented. The proposed method is based on using intentional magnetic saturation under flux-intensifying (FI) operation, which will temporarily enable robust self-sensing operation in the zero-to-low speed region in machines that are not suitable for traditional HFI self-sensing.
Highlights
High-frequency injection (HFI) is a self-sensing technique widely used in machines with inductive saliency in the zeroto-low speed operational region [1]
To improve the use of HFI techniques in surface PMSMs (SPMSMs), research efforts have been focused on increasing the signal-to-noise ratio (SNR) [2][3][4], and increasing inductive saliency by modifying the design of SPMSMs [5][6][7][8]
Saturation and cross-saturation effects and self-sensing control strategies have been investigated in depth for interior permanent magnet synchronous machines (IPMSMs)
Summary
High-frequency injection (HFI) is a self-sensing technique widely used in machines with inductive saliency in the zeroto-low speed operational region [1]. Saturation and cross-saturation effects and self-sensing control strategies have been investigated in depth for interior permanent magnet synchronous machines (IPMSMs). This paper proposes a novel technique based on intentional magnetic saturation with PM flux-intensifying (FI) current, i.e., positive fundamental d-axis current, + id, injection, on SPMSMs. The physics-based model with variable inductance is developed from the machine design perspective of view considering characteristic current, Ich, offset biasing on d-axis flux path. The proposed technique utilizes positive fundamental d-axis current injection to intentionally increase the inductive saliency; making reliable use of classical HFI self-sensing techniques in machines with very low saliency, e.g., SPMSMs. FI operation with positive d-axis current in the estimated rotor reference frame will results in a decrease of d-axis incremental inductance which results in an increased inductive saliency; saliency-based self-sensing ability will be enhanced [17].
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