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 Symmetrical DC-Link Multilevel Inverter With Reduced Number of DC Sources

Abstract: This paper presents a novel three-phase DC-link multilevel inverter topology with reduced number of input DC power supplies. The proposed inverter consists of series-connected half-bridge modules to generate the multilevel waveform and a simple H-bridge module, acting as a polarity generator. The inverter output voltage is transferred to the load through a three-phase transformer, which facilitates a galvanic isolation between the inverter and the load. The proposed topology features many advantages when compared with the conventional multilevel inverters proposed in the literatures. These features include scalability, simple control, reduced number of DC voltage sources, and less devices count. A simple sinusoidal pulse-width modulation technique is employed to control the proposed inverter. The performance of the inverter is evaluated under different loading conditions and a comparison with some existing topologies is also presented. The feasibility and effectiveness of the proposed inverter are confirmed through simulation and experimental studies using a scaled down low-voltage laboratory prototype.

SVPWM-based current controller with grid harmonic compensation for three-phase grid-connected VSI

Abstract: Voltage space vector pulse-width modulation (SVPWM) is widely used in the current control of three-phase voltage-source inverters (VSI). However, as a voltage-type modulator, SVPWM brings some drawbacks to controllers, such as the compromised output current due to the back EMF disturbance and nonlinearity of the system, the lack of inherent overcurrent protection, etc. In this paper, SVPWM-based current control strategy with grid harmonics compensation and dual-timer sampling scheme is proposed and implemented in a 30 kW three-phase grid-connected VSI. Both simulation and experimental results verify that the proposed current controller offers a high performance of current control even under the influence of the grid harmonics. At the same time, the proposed dual-timer sampling scheme not only minimizes the system control delay but also offers an improved response for overcurrent protection to the system.

Optimized Common-Mode Voltage Reduction PWM for Three-Phase Voltage-Source Inverters

Abstract: In this paper, two new optimized common-mode voltage reduction PWM (CMVRPWM) strategies based on solving the established constrained nonlinear programming models in the time domain are proposed and analyzed. The proposed current ripple losses-optimized CMVRPWM (CRLO-CMVRPWM) minimizes the mean-square values of the three-phase current ripples by calculating the optimized special solutions of the voltage–second balance equations under the designed switching sequences. CRLO-CMVRPWM can achieve better output waveform quality than the existing methods. The proposed switching losses-optimized CMVRPWM (SLO-CMVRPWM) online optimizes the bus-clamping styles according to the phase currents to minimize the switching losses under different load power factors. Compared to the near-state PWM with fixed bus-clamping styles, SLO-CMVRPWM can reduce more switching losses in broader range of the modulation index. Simulation and experimental results verify the superiority of the proposed strategies to the conventional ones.

Comparison of Two Three-Phase PLL Systems for More Electric Aircraft Converters

Abstract: The More Electric Aircraft power system is characterized by variable supply frequency, in general between 360Hz and 900Hz All equipment on board the aircraft have to operate delivering high performance under this variable frequency condition In particular, power electronic converters need accurate control algorithms able to track the fundamental phase and frequency in real time, both in normal and unusual conditions Phase Locked Loop (PLL) based algorithms are commonly used in traditional single and three phase power systems to provide phase and frequency estimations of the supply Despite the simplicity of those algorithms, large estimation errors can arise when power supply voltage has variable frequency or amplitude, presents unbalances or is polluted with harmonics To improve the quality of the phase and frequency real-time estimations, a robust PLL algorithm, based on a prediction-correction filter, is presented in this paper and compared with a Discrete Fourier Transform (DFT) based procedure The performances of the two algorithms, implemented in a floating-point DSP, have been compared through an experimental validation obtained on a laboratory power converter prototype

Three-phase four-leg flying-capacitor multi-level inverter-based active power filter for unbalanced current operation

Abstract: This study describes a new application of flying capacitor multi-level inverters whereby a three-phase, four-leg three-level inverter is used for harmonic current cancellation and unbalanced current compensation in a four-wire system. A direct three-dimensional-pulse-width modulation (3D-PWM) scheme is developed to deal with the increased state redundancy in the four-leg flying capacitor multi-level inverter. Test results show much superior performance in the four-leg case, which may allow the use of smaller DC supply capacitors. A new modified dead-beat current control algorithm is proposed and combined successfully with the 3D-PWM modulation technique in a hardware demonstrator of a complete active filter.