Three-phase

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

A Three-Phase Current-Fed DC/DC Converter With Active Clamp for Low-DC Renewable Energy Sources

Abstract: This paper focuses on a new three-phase high power current-fed DC/DC converter with an active clamp. A three-phase DC/DC converter with high efficiency and voltage boosting capability is designed for use in the interface between a low-voltage fuel-cell source and a high-voltage DC bus for inverters. Zero-voltage switching in all active switches is achieved through using a common active clamp branch, and zero current switching in the rectifier diodes is achieved through discontinuous current conduction in the secondary side. Further, the converter is capable of increased power transfer due to its three-phase power configuration, and it reduces the RMS current per phase, thus reducing conduction losses. Moreover, a delta-delta connection on the three-phase transformer provides parallel current paths and reduces conduction losses in the transformer windings. An efficiency of above 93% is achieved through both improvements in the switching and through reducing conduction losses. A high voltage ratio is achieved by combining inherent voltage boost characteristics of the current-fed converter and the transformer turns ratio. The proposed converter and three-phase PWM strategy is analyzed, simulated, and implemented in hardware. Experimental results are obtained on a 500-W prototype unit, with all of the design verified and analyzed.

Transient simulation and analysis of a three-phase five-limb step-up transformer following an out-of-phase synchronization

Abstract: Theoretical and experimental analyses are presented of the electromagnetic transient following the out-of-phase synchronization of a three-phase five-limb step-up transformer; this means an abnormal condition where the angle between phasors representing the generated voltages and those representing the power network voltages at the instant of closure of the connecting circuit breaker is not near zero, as normal, but may be as much as 180 degrees (phase opposition). When this happens, the peak values of the transient currents in the windings of the transformer might be sensibly higher than those of the failure currents estimated in a conventional way; in addition, they correspond to unbalanced magnetomotive forces (MMF) in the primary and secondary windings of each phase of the machine. The currents and fluxes during the transient are computed by a nonconventional circuital nonlinear model of the transformer simulated by the electromagnetic transient program (EMTP). The results of an experimental validation made on a specially built 100 kVA three-phase five-limb transformer are also reported. >

Design and performance of active power filters

Abstract: This article has demonstrated the feasibility of a three phase active filter based on a half-bridge topology. Design guidelines for the power circuit have been derived and applied to a 5 kVA IGBT laboratory prototype. In the single phase mode, the active filter can reduce the low frequency harmonic content in the AC line to below 1% excluding the harmonics due to switching action of the converter. In the three phase mode, line currents are corrected under balanced and unbalanced conditions. The neutral current is reduced significantly.

Application of Four-Switch-Based Three-Phase Grid-Connected Inverter to Connect Renewable Energy Source to a Generalized Unbalanced Microgrid System

Abstract: In this paper, a four-power-semiconductor-switch-based three-phase inverter is proposed for renewable energy source integration to a generalized microgrid system. The proposed topology b-4 of three-phase inverter is investigated to make the commercial microgrid system to be cost effective and hardware optimized. A simple sine-pulse-width-modulation-based (SPWM) control strategy is proposed for the b-4 inverter topology instead of the traditional complex four-switch-based space vector techniques. The overall control structure is implemented using the Lyapunov function-based nonlinear controller to track the inverter current directly in the a-b-c frame so that a specific amount of active and reactive grid power flow to the grid can be controlled in a decoupled manner along with low total harmonic distortion of grid currents in the presence of nonlinear load at the point of common coupling (PCC). A novel technique of using the spatial repetitive controller (SRC) is also proposed to eliminate the effect of midpoint voltage fluctuation of the dc link even in the case of asymmetrically split dc-link capacitors without any extra voltage or current sensors unlike conventional methods. Detailed experimental results are provided to show the efficacy of the proposed hardware system for grid-connected applications in the microgrid.

Bifurcation and Large-Signal Stability Analysis of Three-Phase Voltage Source Converter Under Grid Voltage Dips

Abstract: Three-phase voltage source converters (VSCs) are commonly used as power flow interface in ac/dc hybrid power systems. The ac power grid suffers from unpredictable short-circuit faults and power flow fluctuations, causing undesirable grid voltage dips. The voltage dips may last for a short time or a long duration, and vary the working conditions of VSCs. Due to their nonlinear characteristics, VSCs may enter abnormal operating mode in response to voltage dips. In this paper, the transient response of three-phase VSCs under practical grid voltage dips is studied and a catastrophic bifurcation phenomenon is identified in the system. The converter will exhibit an irreversible instability after the dips. The expanded magnitude of ac reactive current may cause catastrophic consequence for the system. A full-order eigenvalue analysis and a reduced-order mixed-potential-theory-based analysis are adopted to reveal the physical origin of the large-signal instability phenomenon. The key parameters of the system are identified and the boundaries of instability are located. The bifurcation phenomenon and a set of design-oriented stability boundaries in some chosen parameter space are verified by cycle-by-cycle simulations and experimental measurement on a practical grid-connected VSC prototype.