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Direct torque control (DTC) has become a widely acceptable alternative to field-oriented control in permanent magnet synchronous motor (PMSM) drives. Deadbeat direct torque and flux control (DB-DTFC) is a significant improvement over the classical DTC. However, there are some aspects that can be improved, such as insufficiently small electromagnetic torque ripple, unsmooth dynamic response, heavy computation burden, and relatively weak robustness to motor parameters variation. To improve the operation performance, an advanced DB-DTFC strategy is proposed in this article. First, the algorithm model based on stator flux oriented coordinate system is deduced. On this basis, the basic principle of proposed DB-DTFC is presented. Second, a novel graphical analysis method is proposed to help illustrate the proposed strategy. Third, a general solution method is proposed to solve the reference stator voltage, which is a key variable for the DB-DTFC. Finally, the stability of system is analyzed. Theoretical and experimental comparisons between the proposed DB-DTFC and the conventional DB-DTFC are done. The results show that the performance in the aspects of electromagnetic torque and stator current ripples reduction, dynamic response, computation burden, and robustness to motor parameters variation are all improved in the proposed DB-DTFC. [ABSTRACT FROM AUTHOR]

This paper presents a five-phase dual random space vector pulsewidth modulation (FPDR-SVPWM) strategy with an optimized probability density function (PDF) for a five-phase voltage-source inverter, and its performance and evaluation are also analyzed. Based on the nearest four vectors modulation method, the FPDR-SVPWM strategy, combined with random switching frequency and random zero vector, is investigated to significantly reduce the amplitude of high-order harmonics near the switching frequency and its integer multiples. For the nonsinusoidal power supply, third harmonic injection is introduced in this modulation strategy as well. Considering the effect of random numbers on the performance, an optimized Beta distribution is studied in detail. In order to analyze harmonic dispersion degree qualitatively and quantitatively, the power spectral density and the harmonic spread factor are both employed to assess the performance of the FPDR-SVPWM strategy. A series of results of simulation in MATLAB and experiments based on field programmable gate array demonstrate that the proposed modulation strategy is correct and valid, and it distributes high-order harmonics into a wide range without affecting the fundamental wave and third harmonic. [ABSTRACT FROM AUTHOR]

Dual stator-winding induction generator (DWIG) is attractive in stand-alone power systems, and the aim of this paper is to develop the dc generating system of five-phase DWIG with an open phase. First, the relationship between flux and torque is constructed based on the reduced-order transformation, modified flux, and current. Second, the relation between modified voltage and current on the dq plane is constructed. The current of fundamental plane is used for the control loop of the power-winding voltage and control-winding voltage, respectively. Third, the current of the modified secondary subspace plane is used to control the five-phase DWIG operation at minimum control-winding loss. Finally, the simulation and experimental results are given to verify that the amplitude of phase current and output voltage can be regulated effectively by the proposed control strategy. [ABSTRACT FROM AUTHOR]

In this paper, the five-phase dual stator-winding induction generator dc generating system with the static excitation controller is presented, and two kinds of control strategies for this system are proposed. In this generator, the cage-type rotor is employed, and two sets of five-phase windings are placed in the stator, namely, the power winding and control winding. Using the instantaneous power theory, the control-winding-flux-oriented control (CWFOC) strategy without harmonic injection is obtained. To improve power density, the CWFOC with harmonic injection is proposed as well. For these two strategies, the detailed implementation is studied. The results (simulation and experiment) support the correctness and effectiveness of the proposed control strategies, and the corresponding results show that, using the CWFOC strategy with harmonic injection, the output power of this system can be improved by about 11%. [ABSTRACT FROM PUBLISHER]

In this paper, the performance of the dual stator-winding induction generator (DWIG) variable frequency ac (VFAC) generating system with unbalanced loads is analyzed, and an asymmetrical operation analysis method based on a three-port load network model is proposed. This method has four key steps: (1) deriving the three-port load network model for three-phase four-line unbalanced loads; (2) establishing the positive sequence, negative sequence, and zero sequence equivalent circuits for the DWIG; (3) combining the above model and circuits together to obtain the system whole equivalent model; and (4) writing the corresponding equations and solving them. The experimental results and the calculation results are almost consistent, which proves that the proposed method is correct and valid, and the DWIG VFAC generating system with unbalanced loads has a good performance. [ABSTRACT FROM PUBLISHER]

This letter presents a modulation technique for the modified coupled-inductor single-stage boost inverter (CL-SSBI)-based grid-connected photovoltaic (PV) system. This technique can reduce the system leakage current in a great deal and can meet the VDE0126-1-1 standard. To maintain the advantages of the impedance network, only a diode is added in the front of the original topology, to block the leakage current loop during the active vectors and open-zero vectors. On the other hand, the near-state pulse width modulation (NSPWM) technique is applied with one-leg shoot-through zero vectors in order to reduce the leakage current through the conduction path in the duration of changing from and to open-zero vectors. Simultaneously, the leakage current caused by other transitions can also be reduced due to the fact that the magnitude of common-mode voltages is reduced. Simulation results of the transformerless PV system are presented in two cases: modified CL-SSBI modulated by maximum constant boost (MCB) control method and NSPWM. Experimental results for both CL-SSBI topology modulated by the MCB control method and modified CL-SSBI topology modulated by NSPWM are also obtained to verify the accurateness of theoretical and simulation models. [ABSTRACT FROM AUTHOR]

This letter proposes an integrated ac and dc hybrid generation system based on the dual-stator-winding induction generator with the static excitation controller (SEC). In this generator, not only the power winding can output the variable-frequency ac power, but also the control winding can provide the high-voltage dc power through the dc bus of the SEC, which implements the electric integration by only one generator. An instantaneous slip frequency control strategy is employed to guarantee the system a good performance. The experimental results verify the correctness and effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]