In this letter, a polar-coordinate-multi-signal-flux-observer (PCMFO) is proposed for permanent magnet synchronous motor (PMSM) sensorless control. PCMFO is constructed in polar coordinates and uses the orthogonality relations between αβ -axis active fluxes. It permits estimating the rotor position and the flux simultaneously, instead of obtaining the active flux first and then the rotor position, so the phase-locked loop is not necessary. Furthermore, PCMFO consists of paralleled multiple observers, which, respectively, estimate the dc bias, fundamental wave, and harmonics, thus eliminating the influence of these interfering signals on flux estimation. The theoretical analysis indicates that PCMFO can reduce the system order and suppress the estimation error caused by the varying rotor speed and discretization. Then, the PMSM sensorless control is constructed based on it. The experimental results verify the superiority of this method.

In the system of permanent magnet synchronous motor (PMSM) driven by indirect matrix converter (IMC), space vector pulsewidth modulation (SVPWM) technology is used in the inverter stage, which causes that the output current generates high-frequency harmonics around the integral multiples carrier frequency, thus generating high-frequency noise and electromagnetic interference. In order to suppress the high-frequency harmonics of output current in IMC-PMSM, a Markov chain random asymmetrical SVPWM (MRA-SVPWM) method is proposed in this article. Although random PWM (RPWM) technology have some effect to reduce the harmonic amplitude. There are still some inherent defects. Markov chain with nonaftereffect is applied to random switching frequency PWM in order to improve the performance of RPWM. Meanwhile, MRA-SVPWM changes the switching state by adjusting the vectors order and, thus, changes the coefficient of the harmonic. A better suppression performance around the integer multiples carrier frequency is achieved. Meanwhile, the principle of harmonic suppression is analyzed by using three-dimensional Fourier. Finally, the effectiveness of the proposed algorithm is verified by experiments.

Multiresonance phenomena occur in inverter clusters under weak grid, with more complex resonance characteristics. Traditional suppression methods are difficult to determine control parameters when considering dynamic resonance under the variation of grid impedance. To this end, this article proposes a hybrid multiresonances suppression method based on the improved dual-division-summation (D-D-Σ) method and virtual admittance strategy. Multiresonances are divided into dynamic resonance and static resonance, in which dynamic resonance frequency shifts with the variation of grid impedance, and static resonance frequency remains fixed. D-D-Σ method with strong adaptive ability and paralleled virtual admittance strategy reshaped the inverter output impedance are used to suppress dynamic resonance and static resonance, respectively. The proposed hybrid multiresonance suppression method can adapt to parameter changes and simplify the center frequency design process of traditional paralleled virtual admittance. The experimental results of a parallel system with three inverters verify the feasibility of the proposed method in this article.

Model predictive control (MPC) has emerged as a promising control scheme for power converters and motor drives. One of the major advantages of MPC is the possibility to control several system objectives with a single control law (cost function). However, the minimization selection of the cost function and its corresponding switching state is often achieved by using the enumeration method based on a simple element comparison that can lead to a local optimum solution and is time-consuming. In this article, a genetic algorithm (GA) optimum technique is applied to enable a global optimal solution to the cost function and its corresponding switching state in parallel implementation of MPC that ensures good performance in terms of the input reactive power and output current in an indirect matrix converter (IMC). Moreover, a performance comparison between using a GA and a conventional enumeration method is described. Meanwhile, a hybrid weighting factor searching method combining branch and bound algorithms with a strategy of precise searching over a small weighting range is proposed. Finally, the operation principles and validity of the proposed algorithm are analyzed and verified by using simulation and experimental results.

This study presents two methods of controlling neutral‐point voltage oscillation in a hybrid VIENNA rectifier, which is composed of the parallel association of a three‐phase single‐switch Boost rectifier with a VIENNA‐type rectifier. The neutral‐point oscillation reason has been analysed with a mathematical model. Meanwhile, the two neutral‐point control methods of a simplified method based on a zero‐sequence component injection and a dual‐carrier pulse‐width modulation (PWM) method are proposed to control the voltage deviation of the split DC‐link and three‐time fundamental frequency neutral‐point voltage fluctuation with a decrease from ±1.6 to ±1 V, respectively. Moreover, the significant oscillation in the neutral‐point voltage caused by unbalanced loads or asymmetric capacitor parameters can also be effectively suppressed by using the dual‐carrier PWM method. Furthermore, the performance comparison between these two methods is provided. The experimental results show that the system after being introduced the proposed two methods still exhibits a low‐order input current harmonic such as second, third, and fourth harmonics as well as the input current total harmonic distortion is lower than the standard 5%.

VIENNA rectifier has emerged as a promising topology for ac-dc power converter, but it has the problem of the dc-link output voltage surge under no-load condition. In this paper, a high reliability hardware auxiliary circuit and an easy-implement software regulation algorithm are proposed to achieve voltage stability. Firstly, voltage oriented current cross-decoupling control strategy is introduced and the reason of the voltage surge has been analyzed using equivalent circuit model. Secondly, the equivalent circuit model of different working state for auxiliary circuit in association with VIENNA rectifier are described, along with introducing the selection of device parameters in the auxiliary circuit. Meanwhile, the mechanism of two working mode in the software regulation algorithm are analyzed to make the VIENNA work in boost and buck mode to achieve dc-voltage stability. Finally, the feasibility and effectiveness of the proposed methods have been verified using experimental results. The proposed methods not only suppress the dc-voltage surge, but also exhibit a good performance in terms of supply-side power factor and dc-voltage in a VIENNA rectifier, meanwhile maintaining the system adaptability under circumstance of the load step.