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.

The proposed technique focuses on the non -sinusoidal power supply control strategy aiming to obtain the optimal air-gap flux density distribution. The electrical constraints for the alignment between rotated fundamental and harmonic air-gap flux are illustrated in detail. The supporting simulation is performed to analyze the misaligned angles between fundamental and harmonic air-gap flux for the traditional methods. Different from traditional flux-oriented methods, the improved algorithm for harmonic currents injection is designed based on rotor flux orientated control (RFOC) in fundamental plane and air-gap flux orientated control (AFOC) in harmonic planes. The synchronous and aligned control of the fundamental and harmonic air-gap flux is achieved regardless of load condition. The experimental verification is implemented based on a multiphase driving platform using a 7-phase induction machine (IM) as prototype. Various performance is provided for the proposed control strategy comparing with the traditional ones in terms of induced electromotive force (EMF) waveforms, harmonic currents and advance angles of air-gap flux. The simulated and experimental results validate the theoretical assumption and the effectiveness of the proposed method.

The numerical technique for parameters estimation is applicable for the induction machine (IM) with arbitrary number of stator phases and arbitrary number of rotor bars. The self‐inductance and mutual inductance matrices for the stator side and rotor side are constructed through the magnetic vector potential method. The Clarke transformation is implemented to separate the magnetising inductance and slot leakage inductance of each sequence plane, where the orthogonality theory of trigonometric function is used. The harmonic leakage inductance of each plane is calculated based on the ratios of the harmonic components among air‐gap flux density. The 2D eddy current field solver is conducted to obtain the rotor resistance based on the IM equivalent circuit. A classical mathematical model is established using the acquired parameters under Simulink environment to accomplish the comparisons between the simulated and experimental performance. The non‐sinusoidal power supply based on the rotor field‐orientated control, which is highly dependent on the precision of parameters, is carried out under no‐load and heavy load conditions to indirectly verify the accuracy of parameters.

The traditional direct torque control (DTC) strategy utilizes the largest fourteen voltage vectors for a seven-phase induction machine (7PIM) which is directly extended from the three-phase counterparts. This method suffers from the issues of severe harmonic currents and torque ripple for multiphase ones. This paper firstly puts forward the concept of virtual vectors for a 7PIM. This can efficiently eliminate the third and fifth order harmonic currents. However, the DTC strategy based on the virtual voltage vector has insignificant effect on reducing torque ripple. The torque ripple caused by these virtual vectors in different torque and speed conditions is investigated. Analysis shows that there are some additional degrees of freedom while choosing the applied voltage vector. A novel sequential strategy integrated with duty ratio optimization algorithm is proposed to select the optimal voltage vector which can significantly alleviate the torque ripple. Experimental results verified that the proposed method can effectively reduce dynamic and steady-state torque ripple as well as harmonic current. This paper uses a 7PIM for an illustration, but it should be mentioned here that the proposed strategy is applicable for multiphase machines with any number of phases.

The proposed technique focuses on the online estimations of multiplane rotor resistances for the multiphase induction machine operating under the flux-oriented frame. The deviations in regard to the steady-state performance caused by the mismatched fundamental and harmonic rotor resistances are analyzed in detail. The reactive-power-based model referenced adaptation system (MRAS) is formulated for the third harmonic plane, which is air gap flux-oriented. The quasi-normalized method with respect to the error terms between the referenced and adjustable models is addressed to improve the adaptive mechanism under various load conditions. Experimental validations have been performed to confirm the effectiveness of the proposed algorithm. The simultaneous online identifications for the fundamental and harmonic rotor resistances are achieved. The approximate convergence processes and steady performance can be obtained for a large range of load conditions by using constant adaptive gains. The estimated results are indirectly verified by the comparisons between command and actual flux. In addition, the dynamic performance for the proposed MRAS is conducted with the sudden change of load. The effects of inverter nonlinearity and temperature rise are taken into account.

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.