1,721,219 research outputs found
Compact Integration of Battery Storage System for a Micro Wind Turbine Generator
No full textAs wind turbine (WT) power fluctuates due to the intermittent nature of the wind, batteries can help smooth out this variation. Traditionally, multiple conversion stages are used to manage the power flow between the wind source and the storage device. This paper investigates the feasibility of a dual-port inverter (DPI) as single conversion stage to connect a battery and a micro-WT and shows how the DPI can be controlled to ensure that the most power possible is harvested from the wind turbine. Numerical simulations demonstrate that the DPI has the capability to deliver power to the grid with a unity power factor, even under conditions of highly variable speed, while always extracting maximum power from the WT. The simple DPI-based configuration enables smoothing wind power variations with the battery without employing multiple dc-dc and dc-ac conversion stages
Single-Stage NPC-Type Dual-Port Inverter for Integrated Wind/Battery Hybrid System
No full textWind power is inherently intermittent and poses challenges to the stable integration of wind turbines (WTs) into a power system. Battery energy storage systems (BESSs) are often used to mitigate wind power fluctuations, charging and discharging batteries depending on wind conditions. Like every multisource system, the WT-BESS hybrid system requires power electronic converters to control the dc and ac power flows. Multiple dc-dc and dc-ac power conversion stages enable high control flexibility, but have a low energy conversion efficiency and require several bulky passive filters. Single-stage multiport inverters (MPIs) that connect multiple sources to the ac grid in a single conversion stage have been increasingly investigated in recent years as a potential alternative. This paper examines the performance of the NPC-type Dual-Port Inverter (DPI) for a wind energy system based on a permanent magnet synchronous generator and battery storage device. The modulation of the DPI and the integrated BESS and WT maximum power point tracking control are presented and discussed. As proved by numerical simulations, the single-stage DPI can inject smooth electrical power into the grid at a unity power factor under highly variable speed conditions while always extracting the maximum power from the turbine
Optimal Torque Curve Tracking for Wind Turbine Generators Using Adaptive Extremum Seeking
No full textOptimal torque control is a common technique for tracking the maximum power point of wind energy systems without direct wind measurements. However, it relies on the precise knowledge of the turbine's aerodynamic characteristics and air density. Since these parameters can significantly differ from their nominal value due to variable ambient conditions and turbine aging, suboptimal operation of the wind generator can occur. In this paper, a sensorless and model-free Adaptive Extremum Seeking (ES) parameter optimization is considered to track in real-time the optimal torque trajectory and achieve maximum wind energy harvesting. Differently from the conventional approach, adaptive ES is here used to drive the generator torque toward its optimal trajectory rather than to define a variable speed setpoint for the turbine. By doing so, maximum power operation can be reached with reduced oscillations of electrical power. Simulations on a 1.5 MW wind energy system are reported to demonstrate the effectiveness of the technique
Bona Sforza a Venezia: l'orazione di Cassandra Fedele e le lodi di una regina
No full textIl contributo prende in esame le orazioni di Cassandra Fedele e del Cieco d'Adria (Luigi Groto) pronunciate in lodo di Bona Sforza nel 1556, quando la Regina di Polonia fece rientro in Italia
Size, Efficiency, Reliability and Cost Analysis of a Multiport Traction Inverter with Downsized DC-DC Converter for a Catenary/Battery Tram
Full text linkThe use of a NPC-type multilevel converter as multiport inverter (MPI) has recently been considered a promising solution for the compact integration of multisource systems in various applications. Despite increasing research interest in this topic, a comprehensive study of an MPI-based power conversion system for multisource rail applications is still lacking in the literature. This paper presents a broad analysis of a quasi-single stage propulsion system (QSS) that employs an NPC-type MPI and a downsized boost dc-dc converter for an urban tram vehicle with overhead line connection and onboard batteries. The control and dynamic performance are detailed and validated experimentally. Furthermore, the efficiency, weight, volume, reliability and cost of the QSS system are evaluated and benchmarked against a conventional architecture for a case-study catenary/battery tram model. To this aim, analytical design equations, manufacturers’ data, electrothermal time-domain simulations, finite element method (FEM) simulations, and Monte Carlo-based lifetime analyses are employed. The analysis reveals that the QSS system can achieve significant savings in volume, weight, and round-trip energy efficiency, higher reliability due to intrinsic redundancy, but with increased part count, complexity, and cost
Experimental Validation of a Semi-Two-Stage Traction System Based on the NPC Multi-Source Inverter for Fuel Cell Rail Vehicles
No full textHydrogen trains have been increasingly considered as an alternative to diesel-powered trains on long-range medium-traffic routes, for which electrification lacks economic attractiveness. In fact, very long autonomies can be reached by hydrogen fuel cell plants with a single refueling. In fuel cell systems, a high-power dc/dc converter must be included to boost the voltage of the fuel cell, which can vary significantly from no load to full load condition. In this paper, a semi-two-stage traction system for hydrogen-powered rail vehicles is investigated and tested. The architecture employs an NPC multi-source inverter as main traction converter to provide an additional connection between the fuel cells and the traction motors. With the coordinated control of the two power converters, the boost converter can be partly bypassed during operation, and its peak power rating and round-trip energy losses reduced. Experimental tests on a lab prototype show significant reductions in the peak current and round-trip energy processed by the dc/dc converter, with expected benefits in terms of weight and volume of its passive filters and heatsinks
Sizing approach of high torque density motors for aircraft application
No full textThe paper deals with PM-brushless radial flux machines with high torque density suitable for aircraft application where a high specific torque in a reduced range of operating speeds is needed. In particular, the goal is to obtain some useful relations among geometric, electrical, magnetic and thermal variables, to define an analytical expression of the torque density as a function of both the maximum thermal and magnetic stresses allowed by the active materials
Semi-Two-Stage Traction System based on the NPC Multisource Inverter for Tram Vehicles with Onboard Supercapacitors
No full textThis paper proposes an innovative semi-two-stage topology for the traction system of trams equipped with supercapacitors, with the aim to downsize the onboard dc/dc converters. The configuration is obtained through a non-conventional connection of a half-bridge chopper and 3L Neutral Point Clamped (NPC) inverter to the dc sources and ac traction motors. By means of a proper modulation strategy, the NPC converter works as a Multi-Source Inverter and can independently control the power absorbed or supplied by the catenary and supercapacitors. Due to limitations in the power-processing domain of the NPC circuit, a chopper must be also included in the traction circuit. However, it processes only a fraction of the total power of the supercapacitors. The proposed solution is compared against a traditional two-stage architecture, where a dc/dc converter processes the entire power of the capacitors and a 2L Voltage Source Inverter drives the traction motors. Extensive numerical analyses testify that the envisioned architecture shows encouraging performance and can yield a significant reduction of the dc/dc converter ratings, losses, volume, and weight
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