Three-phase

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

Power Component Fault Detection Method and Improved Current Order Limiter Control for Commutation Failure Mitigation in HVDC

Abstract: A power component detection (PCD) method and an improved current order limiter control (improved COL) are proposed to mitigate the commutation failure in a line-commutated converter-based high-voltage direct current (LCC-HVDC). Integrating the instantaneous voltage and instantaneous current characteristics under single-phase and three-phase-to-ground faults, a fault detection method based on the power component is proposed, and the corresponding setting principle is presented. Then, an improved dc current order limiter is introduced. To evaluate the effectiveness of the proposed methods, a dual-infeed HVDC system is developed in PSCAD/EMTDC, and the presented methods are also implemented. The transient performances of dual-infeed HVDC, under single-phase and three-phase-to-ground faults at the inverter ac busbar of one LCC-HVDC link, are investigated. Simulation results show that the PCD method, with the voltage and current components as an additional judgment criterion, is more sensitive to detect the single-phase and three phase faults, and even more reliable than the detect method taking only voltage or current components for faults recognition. It can also be concluded that the improved COL that is integrated with the advancing firing angle control has the ability to make the LCC-HVDC less susceptible to commutation failure. Finally, the improvement of commutation process by improved COL is further demonstrated.

Unity power factor control for three phase three level rectifiers without current sensors

Abstract: Three level rectifiers with reduced number of switches (such as the Vienna rectifier) have been receiving wide interest in the past years to improve the input power quality of rectifier systems. In this paper, a new carrier-based pulse width modulation (PWM) control algorithm is proposed for such converters to eliminate the low frequency harmonics in the line current while achieving unity power factor at the rectifier input terminals. The operating constraints of the Vienna rectifier with the carrier-based modulation strategy are examined carefully and the proposed control algorithm ensures that appropriate voltage/current directional constraints are met. A promising cost reduction opportunity can be seen with elimination of input current sensing to operate the Vienna rectifier. The control algorithm is verified via Saber simulation and experimental results.

Operation of One-Cycle Controlled Three-Phase Active Power Filter With Unbalanced Source and Load

Abstract: The power quality of the ac electric system has become a great concern due to the rapidly increasing numbers of electronic equipment being connected to the grid. In order to reduce harmonic contamination in power lines and to improve its transmission efficiency, the research on active power filters (APF) has become a hot topic. Many control methods for APF were proposed in recent years. Among them, one-cycle control (OCC) has shown great promise featuring excellent harmonic suppression, simple circuitry, robust performance, and low cost for the control of three-phase APFs. Theory and experiments in previous papers have demonstrated the validity of OCC-controlled APFs working with balanced line voltages and balanced nonlinear loads. However, in reality, neither three-phase grid voltages nor three-phase nonlinear loads are balanced at all times; therefore, it is vital for an APF to be able to handle unbalanced sources and/or loads. In this paper, the OCC-controlled three-phase APF working with unbalanced three-phase line voltages and unbalanced loads are studied, respectively. Theoretical analyses and experimental results indicate that with OCC control, sinusoidal input currents can be realized, whether the input voltages and/or the nonlinear loads are balanced or unbalanced

New current control concept-minimum time current control in the three-phase PWM converter

Abstract: In this paper, a new current controller that guarantees the fastest transient response is proposed. The basic concept is to find the optimal control voltage for tracking the reference current with minimum time under the voltage limit constraint. Though this minimum time control concept is also applicable to all the machine drive systems, this paper focuses on the current regulation in the three-phase pulse width modulation (PWM) converter. In the simulation and experimental results, it is observed that the proposed controller has much less transient time than the conventional synchronous PI regulator and the performance of the DC link voltage control is also greatly improved with the proposed current controller.

Digital Control of Three Phase Three-Stage Hybrid Multilevel Inverter

Abstract: Three-stage 18-level hybrid inverter design with novel control method is presented. The inverter consists of main high-, medium-, and low-voltage stages connected in series from the output side. The high-voltage stage is a three-phase, six-switch conventional subinverter. The medium- and low-voltage stages are made of three-level subinverters constructed by H-bridge units. The proposed control strategy assumes a reference input voltage vector and aims to approximate it to the nearest inverter vector. The control concept is based on holding the high-voltage state as long as it is feasible to do so. The reference voltage vector has been represented in a 60°-spaced two axis coordinate system to reduce the computational effort. The concept of the staged-control has been presented, the transformed inverter vectors and their relation to the switching variables have been defined, and the implementation process has been described. The test results verify the effectiveness of the proposed strategy in terms of computational efficiency as well as the capability of the inverter to produce very low distorted voltage with low switching losses.