Three-phase

About: Three-phase is a research topic. Over the lifetime, 16801 publications have been published within this topic receiving 159477 citations.

Implementation of the Three-Phase Switched Reluctance Machine System for Motors and Generators

Abstract: This paper presents two three-phase switched reluctance machine systems. One is the dual motors drive for the electric locomotive traction; the other is the variable-speed generator system for wind power applications. The principles of the switched reluctance machine system operated at four quadrants, the scheme of the symmetrical traction at quadrant I and quadrant III, and the scheme of the symmetrical regenerative braking control at quadrant II and quadrant IV, are given. The transient phase current analysis and the energy analysis of the switched reluctance machine system at the operational state of braking or generating are evaluated, and the rotor position and the peak value of the phase current at three different conditions are given. The closed-loop rotor speed control of the main motor, synchronization of the rotor speed, and balance distribution of loads between the main motor and the subordinate motor have been implemented by the fuzzy logic algorithm. The closed-loop output power control of the switched reluctance wind power generator system implemented by regulating the turn-on angle of the main switches with fuzzy logic algorithm and fixed turn-off angle of the main switches is also presented. The major components of the two prototypes are explained in detail. The experimental results of the dual 7.5-kW three-phase 6/4 structure switched reluctance motors (SRMs) parallel drive system prototype are included. It is shown that the maximum difference in the output torque of the two motors at the same given rotor speeds is within 10.00% and the maximum difference in the practical rotor speed of the two motors is within 5.00%. The tested results of three-phase 12/8 structure switched reluctance variable-speed wind power generator system show that the error of the closed-loop output power control is within 2.2%, while the rotor speed range is close to the ratio of 1:3 with the low rotor speed 405 r/min. The average dc line current of the power converter can be utilized as a feedback signal for the actual output torque of SRM drive or a feedback signal for the actual output power of switched reluctance generator system.

Optimal Predictive Control of Three-Phase NPC Multilevel Converter for Power Quality Applications

Abstract: This paper presents the optimal control of the AC currents, the DC voltage regulation, and the DC capacitor voltage balancing in a three-level three-phase neutral point clamped multilevel converter for use in power quality applications as an active power filter. The AC output currents and the DC capacitor voltages are sampled and predicted for the next sampling time using linearized models and considering all the 27 output voltage vectors. A suitable quadratic weighed cost function is used to choose the voltage vector that minimizes the AC current tracking errors, the DC voltage steady-state error, and the input DC capacitor voltage unbalancing. The obtained experimental results show that the output AC currents track their references showing small ripple, a total harmonic distortion (THD) of less than 1%, harmonic contents that are 46 dB below the fundamental, and almost no steady-state error (0.3%). The capacitor voltages are balanced within 0.05%, and the balancing is assured even when redundant vectors are not chosen. Near-perfect capacitor DC voltage balancing is obtained while reducing current harmonic distortion. Some experimental evidence of robustness concerning a parameter variation was also found, with the optimum controller withstanding parameter deviations from +100% to -50%. Compared to a robust sliding mode controller, the optimal controller can reduce the THD of the AC currents or reduce the switching frequency at the same THD, being a suitable controller for power quality in medium-voltage applications.

Reduction of Both Harmonic Current and Torque Ripple for Dual Three-Phase Permanent-Magnet Synchronous Machine Using Modified Switching-Table-Based Direct Torque Control

Abstract: Due to the fixed and limited sampling period in the real-time system, three-phase permanent-magnet synchronous machine (PMSM) drives using switching-table-based direct torque control (ST-DTC) usually suffer from steady-state error and ripple of torque For the case of the dual three-phase system that has been widely investigated recently, the harmonic currents inevitably occur, which can be regarded as the third issue This harmonic currents lead to the increase of losses and the decrease of system efficiency Previous literature has addressed the aforementioned issues but only deals with either the torque ripple issues or harmonic currents Therefore, this paper first introduces two types of synthetic vectors, which can reduce the harmonic currents effectively, as well as the most suitable switching sequences Then, a modified five-level torque regulator has been proposed to improve the torque performance With the proposed method, not only the harmonic currents have been suppressed, but also the steady-state error and ripple of torque can be considerably reduced, whereas the merits of classical ST-DTC, such as simple structure and excellent dynamic performance, are preserved The experimental results validate the effectiveness of the proposed strategy

DC-Link Harmonics of Three-Phase Voltage-Source Converters Influenced by the Pulsewidth-Modulation Strategy—An Analysis

Abstract: DC-link current harmonics are the predominant factor to be considered for dimensioning dc capacitors in three-phase pulsewidth-modulation (PWM) voltage-source converters. In this paper, an analysis of the dc-link current harmonics applying a double Fourier series is derived. The analytical results for the dc-link current spectra of continuous and discontinuous PWMs are presented and compared with measurement results taken from a converter test setup. A good match between theoretically expected and actually obtained experimental results can be stated. Moreover, characteristic differences between the investigated modulation strategies regarding their dc-link current spectra become evident.