Torque ripple reduction based on harmonic current injection has been widely applied to surface-mounted permanent-magnet synchronous machine (SPMSM) drive systems. However, additional voltages are typically required for harmonic injection, and the dc-link voltage limit should be considered in practical drive systems. This article proposes a novel harmonic control for SPMSMs in which the torque ripple reduction and high dc-link voltage utilization can be achieved simultaneously. The influence of harmonic injection on voltage utilization is investigated in detail. In addition to injecting the appropriate q -axis harmonic currents to suppress torque ripple, the d -axis harmonics are also optimized and injected. The geometric principle is applied to obtain the analytical expression for the optimal d -axis harmonic voltage, which can minimize the maximum magnitude of the stator voltage vector. Since the reference harmonic voltage is directly calculated in accordance with the analytical solution, the implementation complexity of harmonic voltage regulation is relatively low. Moreover, a virtual dual three-phase system with auxiliary currents is developed to decompose the fundamental and harmonic currents without low-pass filters, thus avoiding additional delay in the control loop. Finally, the experimental results are provided to verify the validity of the proposed method.

In this article, a novel harmonic subspace signature-based method is proposed for real-time detection and localization of inter-turn short circuit fault (ITSCF) in dual three-phase permanent magnet synchronous machines (DTP-PMSMs) which are driven by the vector space decomposition (VSD) control scheme. The method is independent of additional equipment, machine parameters, and prerecorded faulty data. Based on VSD theory, the ITSCF model of DTP-PMSMs is derived first. It reveals that the ITSCF can introduce an extra fundamental pulsating voltage vector to harmonic subspace, which has diverse locations in harmonic subspace according to the different faulty phases. Then, with different VSD transformation orientations, the ITSCF can be detected and located by comprehensively utilizing the fundamental components of harmonic subspace currents and reference voltages. Finally, the experimental results are given to verify the effectiveness of the proposed method.

The rapid development of machine drive systems is closely tied to advancements in signal sampling technology. Accurate measurement results, especially current measurement results, are crucial for high-performance machine drive systems. However, current measurement errors (CME) caused by circuit parameter inconsistencies, aging, and temperature variations can significantly affect the control performance of drive systems, thus necessitating compensation. To better understand the mechanisms of CME in drive systems, this paper reviews existing research on CME analysis and compensation techniques. Based on the source of CME, this paper classifies CME into high-frequency and low-frequency components and discusses their causes and compensation methods, respectively. Additionally, the influence of different types of CME on other control strategies, such as sensorless and model predictive control, is discussed. The characteristics of CME compensation strategies for special current sensor installation positions are also explored. Finally, the paper summarizes the state of the art in CME analysis and compensation and discusses future trends in this field.

Current measurement errors (CMEs) including offset and gain errors can lead to the first- and second-order harmonics in dq-axes currents of permanent magnet synchronous machine (PMSM) drives. The Thermal drift-caused CME can change during the operation of the PMSM, which should be compensated online. This paper proposed a CME online compensation strategy based on a modified multiple complexcoefficient filter (MMCCF). This compensator has two improvements based on MCCF. Firstly, the reference model of PMSM is employed to replace the original CCF to achieve fast fundamental current feedforward, which effectively suppresses the additional disturbance caused by working condition variation. In addition, the gain error coefficient is directly compensated instead of the negative sequence current to further improve the adaptability of variable operating conditions. Compared with MCCF, the proposed strategies can greatly expand the practical application under variable conditions. The effectiveness of the proposed method is verified by simulation and experiment.

The multiple synchronous reference frame controller is a common method for harmonic control in permanent magnet synchronous machines (PMSMs), but its low-pass filter deteriorates the harmonic regulation dynamics and system stability. The virtual winding structure, as a novel alternative, can quickly separate each harmonic by vector space decoupling transformation. However, past studies have often assumed that the virtual winding structure does not affect closed-loop system performance or stability. This article constructs the equivalent transfer function of the virtual winding structure of a PMSM under resistance asymmetry. It is revealed that this structure is essentially a special filter. The stability of the closed-loop system is then studied in both continuous and discrete domains. The influence of speed and controller bandwidth on the stability boundary is analyzed. A parameter design method for the harmonic controller is proposed to optimize dynamic response while ensuring system stability. Finally, experimental results show that the theoretical and experimental stability boundaries have an error of less than 4%, validating the accuracy of the stability analysis and the effectiveness of the parameter design.

Harmonic current control is a key research area in permanent magnet synchronous machines (PMSMs). The virtual winding-based harmonic current controller, as a novel approach, exhibits outstanding dynamic characteristics. To construct the virtual windings, this method requires delaying the currents by a fixed angle. However, since the actual delay angle must be an integer multiple of the switching period, rounding operation is required. This paper reveals that this rounding error can result in incomplete decoupling between the fundamental and harmonic current components, which deteriorates the harmonic current control performance. It is found that lower switching frequencies, higher electrical frequencies, and smaller delay angles lead to larger rounding errors. Moreover, a modified vector space decoupling (VSD) transformation that accounts for rounding errors is derived. The Taylor series approximation is employed to simplify the matrix into the original VSD matrix and an additional compensation matrix to avoid additional real-time trigonometric calculations. Finally, simulations and experimental results confirm that the proposed algorithm significantly mitigates the incomplete harmonic decoupling caused by rounding errors.