Conventional space vector pulse width modulation (SVPWM) would degrade the operating performance of the multiphase motor drives under open-phase fault. To resolve this issue, existing solutions require the reconfiguration of transformation matrices. However, for the variable positions of faulty phases, the structure of matrices needs to be redefined, which is a restraint to the industrial implementation of such technologies. This study examined the offset of the voltage vectors after fault occurrence. Accordingly, a universal fault-tolerant SVPWM strategy is proposed for the purpose of natural fault-tolerance, as well as a simplified fault detection scheme. Compared with conventional fault-tolerant SVPWM, it is highlighted with the characteristics of minimum reconfiguration, torque-ripple free operation, and applicability to handle various types of open-phase faults using a single transformation matrix. Besides, proposed strategy eliminates the redundant controllers and also reduces the degree of difficulty for fault diagnosis. Finally, the effectiveness of proposed approach is evaluated experimentally with a seven-phase induction machine, which shows that the torque ripple could be reduced by about 40% in the presence of multiple faults compared to the conventional SVPWM strategy.

This paper proposes a novel model predictive control scheme for dual three-phase permanent magnet synchronous machines to further suppress the x – y current harmonics caused by unmodeled disturbances such as inverter nonlinearity and back-EMF harmonics, in which the average deception effect is taken into account to avoid larger x – y current spikes. Instead of following the conventional virtual vectors to synthesize a zero-average voltage in the x – y subspace, the rotating non-zero voltage vector is dynamically modulated in a control period by scheduling the dwell times of the three adjacent large vectors and zero vectors to realize the closed-loop current control in the x – y subspace. In the implementation of synthetic vectors, to ensure that large vectors with a higher ratio of α–β/ x – y voltage are applied directly to the inverter, the compare registers A and B of the PWM module are configured to solve the state conflicts issue in the switching sequence. Since the x – y unmodeled disturbances have considerable periodic components, a resonant extended state observer (RESO) is employed to provide a more accurate estimate within a limited bandwidth, resulting in more targeted suppression of the 5th and 7th harmonics. Experimental results validate the superiority of the proposed strategy.

This paper presents the development and hovering control of a tailsitter unmanned aerial vehicle (UAV) that merges long endurance and vertical takeoff and landing (VTOL) abilities. The designed tailsitter contains one flying-wing with two motors and two elevons. Vehicle aerodynamics and a six-degrees-of-freedom (6-DOF) model are especially developed for the tailsitter. To achieve a good performance in outdoor stationary hovering and accurate vertical flying, the active disturbance rejection control (ADRC) for attitude controller is proposed. With signals from extended state observer (ESO) and tracking differentiator (TD), ADRC decouples the system model into a controllable chain of integrators. Based on the decoupled system dynamics, the motion of tailsitter can be easily handled by developed position controller. Experimental results are presented to corroborate the effectiveness of the controller in disturbance rejection.

The cascade system stability and grid side power quality are significant concerns for the single phase input interior permanent magnet synchronous motor (IPMSM) drive system with small film capacitor. The characteristic of port equivalent circuit of grid side--dc link--inverter side is analyzed, and the model of inverter side equivalent admittance is established considering the power fluctuation and motor dynamic. The essence of the cascaded system instability is investigated, which reveals the mismatch between the front and rear ports, and hence simplifies the stability judgment with Nyquist criterion. To deal with the cascade system instability and LC resonance, an admittance reshaping method based on the adaptive minimum value of dc-link voltage is proposed, which avoids extra sensors for grid current detection and maintains the inherent active damping effect of dc-link voltage. The resonance component under different cases of minimum value is analyzed in detail, and is obtained based on the adaptive minimum value of dc-link voltage, which removes the phase delay and reduces inevitable compensation error to a large degree. In addition, the grid side power quality is evaluated through the grid side input admittance. Experimental validations have been presented to confirm the effectiveness of the proposed method.

This article is focused on the current harmonic suppression of a permanent magnet machine with the enhanced extended state observers (ESOs). For traditional ESO, there are three defects: coupling issue between fundamental current regulation (FCR) and disturbance attenuation (DA), limited periodic disturbance attenuation (PDA) property, and coupling issue between aperiodic disturbance attenuation (APDA) and PDA. Three kinds of enhanced ESOs are then proposed. That is decoupling-type ESO (DESO), resonance-type DESO (RDESO), and notch-type DESO (NDESO). For DESO, the structure of traditional ESO is redesigned. Decoupling between FCR and DA is, thus, achieved but the other two defects still exist. For RDESO, an additional link is inserted into DESO. Foregoing decoupling property and enhanced PDA are thus achieved simultaneously. Whereas, decoupling between APDA and PDA still cannot be reached. For NDESO, the added link in RDESO is redesigned. Foregoing three defects are thus all solved. Experiments on a test rig have verified the effectiveness of proposed methods.

Active discharge circuit is of great significance for discharging the dc-bus capacitor voltage to safe voltage in the electric vehicles (EVs) based PMSM drive system when EVs encounter an emergency such as a crash event. However, when electric vehicle occurs a collision, the active discharge circuit may be damaged or failed, which poses a great electric threat to the passengers and succors. In order to resolve the problem, this article proposes a winding-based dc-bus capacitor discharge method. To quickly discharge the dc-bus capacitor energy, the machine windings are used as discharge resistance with active discharge circuit fault. For the purpose of reducing the bus voltage to safe voltage as soon as possible, the discharge method can be divided into two phases, rapid discharge stage and bus voltage regulation stage. Firstly, the dc-bus voltage will be dropped to safe voltage due to the large flux-weakening current applied to the d-axis. Secondly, in order to stabilize the bus voltage at safe voltage, an extended observer state (ESO) is designed to estimate and compensate the total power loss that is regarded as disturbance in bus voltage regulation stage. The parameters of the proposed ESO are designed and the tracking performance is analyzed. Finally, the proposed discharge technique is validated by both simulation and experiments, which are conducted on a three-phase SPMSM drive platform.