This article proposes a novel sensorless control strategy for permanent magnet synchronous motor drives using reduced order quasi resonant-based extended state observer (ROQR-ESO) and Newton–Raphson method-based phase-locked loop (NRM-PLL). Due to the low-pass filtering characteristics, the conventional linear extended state observer (LESO) is not adequately able to track the fast-varying back electromotive forces (BEMFs). On this basis, the ROQR-ESO, which plants a ROQR controller into the internal model of conventional LESO, is presented to obtain BEMFs without phase lag. Moreover, the NRM-PLL, regarded as an improved finite position set-PLL, is proposed. After the rotor position is divided into four parts by utilizing a position quartering method, the extremely accurate rotor position can be obtained only by three iterations. In this method, no parameters need to be adjusted and great dynamic response can be achieved. The capacity of the proposed scheme is verified on a 750 W permanent magnet synchronous motor drive platform.

In this paper, the properties and operation of the virtual-space-vector pulse-width modulation (PWM) for a three-level neutral-point-clamped inverter with unbalanced dc-links are studied. By quantitatively analyzing the characteristics of the revised space-vector diagram (SVD) with unbalanced dc-links, the defined virtual SVD (VSVD) for the unbalanced case is theoretically proven identical to the VSVD of the conventional virtual-space-vector PWM (VSVPWM) strategy with balanced dc-links. The well-developed and fast-processing methods to calculate the durations of the nearest three virtual vectors for the conventional VSVPWM can be directly utilized. In addition, a control strategy to realize the asymmetric control of the dc-link voltages with VSVPWM is also studied, and this method can adjust the unbalancing degree with a high accuracy for any modulation indexes and load power factors. Simulated and experimental results are given to validate the effectiveness.

In this article, a common-mode voltage reduction pulsewidth modulation (CMV-R PWM) for three-level neutral point clamped inverter based on the simplification of the three-level space-vector diagram into that of a two-level inverter is studied. By replacing the switching sequence of two-level space-vector PWM with that of CMV-R PWM, the common-mode voltage of the proposed method can be restricted to one-sixth of the dc-link voltage. With the new switching sequences, the neutral-point voltage control by calculating an optimized injected zero-sequence voltage is introduced. Simulation and comparative analysis is given to illustrate the features of the proposed method. The effectiveness and correctness of the proposed method is verified by experiment.

Saliency tracking based sensorless control schemes of interior permanent magnet synchronous motor (IPMSM) are generally troubled by the audible noise induced by high-frequency (HF) signal injection and the estimation error caused by voltage distortions. Aiming at that, a novel sensorless control strategy of IPMSM drives using HF pulse voltage injection with random pulse sequence (HFPVI-RPS) is proposed. First, the conventional HFPVI method could restrain the impact of voltage distortions, and its mechanism is briefly reviewed. Then, based on that, a novel injected form that injecting HF pulse signals with random pulse sequence into the estimated d -axis is designed to eliminate discrete harmonics in the current power spectra density (PSD) and broaden the current PSD to a wide range. The audible noise can be reduced as much as possible. Furthermore, a signal demodulation scheme matched with the injected form of HFPVI-RPS is proposed for the accurate extraction of rotor position. The PSD analysis of the HFPVI and proposed HFPVI-RPS methods is carried out, and the PSD comparison between reported methods and HFPVI-RPS method is given. Eventually, the effectiveness of the proposed sensorless control strategy is verified on a 750 W IPMSM drive platform.

A new model predictive control scheme, Optimized Switching Finite Control Set Model Predictive Control (OS-FCS-MPC), is studied in this paper for NPC single-phase three-level pulse width modulation (PWM) rectifiers. To ensure the actual stability of the power converter, the ac-side current error of single-phase PWM rectifier and the neutral point voltage of the converter are both converged to the bounded invariant set, and the adjustment of system performance is thus realized by setting the bounded invariant set. Based on the NPC single-phase three-level PWM rectifier model, the ac-side current, the neutral point voltage and the current error in the future time can be predicted in advance. The above objectives are achieved by optimizing the selection of switch combinations. The advantage of the proposed method is that it can reduce the average switching frequency of the converter when the ac-side current error and the neutral point voltage of the converter are controlled within a certain range, which makes it suitable for the application of high-power single-phase PWM rectifier.

This letter proposes a novel finite position set-phase-locked loop (FPS-PLL) for permanent magnet synchronous motors sensorless drives. A novel cost function is designed to combine with the dichotomy of position for ensuring the astringency of iteration. After the dichotomy of position, through adopting the Newton iteration, the accurate rotor position is obtained only by three iterations. The convergence analysis and calculation accuracy expression are given. Moreover, no parameters need to be adjusted and fast dynamic response is achieved. Compared with reported FPS-PLLs, the calculated burden is markedly reduced. Eventually, the effectiveness of proposed scheme is verified by experiments.