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This paper realizes a high power factor, high reliability, and low cost PMSM drive system with small DC-link capacitor. Compared with conventional bulky electrolytic capacitor for the regulation of DC-link voltage, a small-size film capacitor with capacitance reduction to 1% is used to realize a seneorless PMSM drive with high power factor, high reliability, and high compactness. To overcome high...
In railway traction applications, due to the limitation of switching frequency and the attempt to fully utilize the DC-link voltage, the traction inverters usually work in six-step (or quasi-square-wave) mode under heavy load or high frequency condition. Meanwhile, DC-link voltage fluctuation, stemming from a common single-phase grid-side power supply, has a great impact on the drive system. To maintain...
Although the wireless power transfer (WPT) has been used in a wide range of areas, there are many difficulties with the development of WPT. The load voltage quality problem caused by the high susceptibility of the delivered power to the surrounding is still a key issue to be solved. To guarantee a high quality of dc load voltage in WPT system, this paper proposes a novel voltage control strategy based...
Unpredictable power quality (PQ) events such as, balanced and unbalanced voltage sag/swell, frequency shift, phase jump and harmonic distortions in the utility grid voltage drastically affects the performance of a grid interfaced distributed generation (DG) systems due to unreliable synchronization. This paper presents adaptive synchronization based dq-current control technique for three-level NPC...
This paper proposes a two-stage three-level DC/AC converter, which consists a three-level inter-leaved dc/dc boost converter in the first stage, and a three-level neutral-point-clamped (NPC) inverter in the second stage. The boost converter regulates variable and/or wide-range dc source, then provides suitable and stable dc voltage to the NPC inverter. The NPC inverter generates variable frequency...
This paper proposes a novel control strategy for electrolytic capacitor-less quasi-Z-source inverter, which fed adjustable-speed drive (ASD) system with almost unit input power factor. The system has no shoot through issues and gains high reliability. By using E-caps-less topology, the life time can be greatly increased. In order to guarantee the high power factor and the ability of resisting grid...
In this work a three-phase power supply to emulate voltage disturbances that occur in an electrical network is presented. The type of disturbances that can be generated are voltage drop (voltage sags), over voltage (voltage swell). To maintain the value of the disturbance is necessary to implement a close loop with a control technique on it. Three control schemes were probed in this work: PI, PID...
This paper introduces a predictive voltage controller for multilevel inverter used in Dynamic Voltage Restorer, which is able to protect a sensitive load against grid voltage sags dynamically. The compensated voltages are obtained by using Phase-Lock Loop to detect the phase and the magnitude of the grid voltage then compare to the load reference voltage. A three-phase NPC inverter with output LC...
With the focus on environmental sustainability and energy security, policy makers and electric utility planners are looking at renewable energy both as supplements and alternatives. But such generation sources have their own challenges — primarily high variability, especially for solar and wind. This paper highlights the challenges and opportunities in grid integration of large-scale solar photovoltaic...
The neutral-point voltage balancing problem is a key issue for three-level three-leg neutral-point clamped (NPC) inverter used in three-phase four-wire system. In this paper, a detailed discussion on this issue and a mathematical model for the neutral-point voltage fluctuation are given. Then a novel neutral-point voltage control strategy based on the disassembly of zero level is proposed. To balance...
In this paper, a new configuration of a multi-functional grid-connected inverter is proposed to improve both voltage-based and current-based power quality issue. By implementing bidirectional switches using semiconductor devices, a multi-functional grid-connected inverter can be connected in series or parallel to the grid and provides three modes of operation. This paper presents the control scheme...
Voltage dips or sag creates useless conflict at the customer side as well as utility side. In this paper, dynamic voltage restorer device based on voltage source converter (VSC) topology is used to compensate voltage sag. Dynamic Voltage Restorer (DVR) is a power electronic device that is utilized to improve voltage stability i.e. to reduce the power quality problems in electrical power system network...
Modernized grid needs ancillary service as a variety of distributed energy resources are connected. Vehicle-to-grid (V2G) application is one of promising distributed energy resources, which enables to transfer bidirectional power between batteries of plug-in electric vehicle and the grid as well as offer ancillary service to the grid. Benefits of V2G application are voltage and frequency regulation,...
This paper investigates the transient voltage sags/swells subsequent to islanding of a PV-Battery microgrid. For an unplanned islanding and micro-grid formation, during islanding detection time, the microgrid is disconnected from main grid while the control mode of the BESS stays the same as before. Consequently the microgrid will undergo transient voltage sag or swell caused by the mismatch of the...
Renewable power generation such as rooftop solar PV is resulting in high number of installation due to incentives as drop in prices and environmental awareness. The uncertainty of solar irradiance and cell temperature cause its output power to be varied. Considering high penetration of rooftop solar cell and also load profile in LV distribution system will lead to much more voltage fluctuations. Then,...
Protection of Distributed Generation (DG) injected Distribution network (DN) is a challenging task in entire electrical ancestors. The connection of DG to the distribution network alters the nature of the network. Expose of DG can alter the fault current during the grid disturbance or external fault and perturb the existing distribution protection system, one of them in the event of a fault where...
Energy storage technologies are increasing their presence in the market and integration of these technologies into the power grid is slowly becoming a reality. An interline dynamic voltage restorer has used to provide sag and swell the compensation and improvement of displacement power factor during normal condition. The concept of integrating ultra-capacitor based energy storage into an interline...
Power Quality (PQ) is the most significant perspectives at transmission and distribution levels. The supply of high grade electrical services required to the customers illustrates this concept. The voltage sag and swell are the most frequent PQ problems that mainly occur in the distribution systems since it may cause equipment tripping, failure of drive systems, shutdown for domestic and industrial...
The Inrush Transient Current (ITC) in the output of the photovoltaic grid-connected inverters is usually generated when grid voltage sag occurs, which can trigger the protection of the grid-connected inverters, and even destroy the semiconductor switches. Then, the grid-connected inverters will thus fail to ride through the voltage sag and even further cause more serious grid faults. This paper analyzes...
This paper presents a new PAC-SRF based approach for UPQC to be used in single phase distribution systems. A necessary phase angle shift of load voltage is introduced with respect to the source voltage using the power angle control concept in order to integrate a reactive power sharing feature for series inverter part of UPQC. Synchronous reference frame (SRF) based controller is adapted for both...
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