Studies on ECR4 for the CERN ion programme

The CERN heavy ion community, and some other high energy physics experiments, are starting to demand other ions, both heavy and light, in addition to the traditional lead ions. Studies of the behaviour of the afterglow for different operation modes of the ECR4 at CERN have been continued to try to understand the differences between pulsed afterglow and continuous operation, and their effect on ion yield and beam reproducibility. The progress in adapting the source and ion beam characteristics to meet the new demands will be presented, as will new information on voltage holding problems in the extraction

Torsional vibration analysis of crank train with low friction losses

High level of mechanical efficiency is exacted from internal-combustion engines. The reduction of friction losses of crankshaft main bearings can significantly contribute to the enhancement of this efficiency. For this purpose, an innovative design of a crankshaft is developed. The potential of computational modelling during the development of this innovative crank train is described in the article. The dynamics of the whole crank train is solved by using a multi-body system software, where flexible finite-element bodies along with hydrodynamic bearings are incorporated. Regarding the simulation results, attention is paid to the torsional vibration and its analysis, including concept design of a torsional damper, because a reduction of friction losses is associated with the improvement of torsional vibration in this case

Discussing Different Clustering Methods for the Aggregation of Demand Response and Distributed Generation

With the introduction of the Smart Grid context in the current network, it will be necessary to improve business models to include the use of distributed generation and demand response programs regarding the remuneration of participants as a form of incentive. Throughout this article a methodology is presented which will aggregate generation units and consumers participating in DR programs. A comparison of clustering methods will be carried out in order to understand which one of them will be the most appropriate for the scenario studied. After grouping all the resources, the remuneration of the groups are made considering the maximum rate in each group. The hierarchical clustering proved to be the most appropriate because it grouped the resources so that the total cost for the aggregator was the minimum.The present work was done and funded in the scope of the following projects: CONTEST Project (P2020-23575), and UID/EEA/00760/2013 funded by FEDER Funds through, COMPETE program and by National Funds through FCT.info:eu-repo/semantics/publishedVersio

Analytical and simulation comparison of sinusoidal and resistive modulation strategies for network-friendly three-phase grid-connected inverters

The growing numbers of consumers distort AC networks with harmonics. Therefore suppression of the network pollution should be considered. This problem can be solved by using ``network-friendly´´ converters. In our study we examined two modulation strategies of three-phase grid-connected inverters. If these methods are used, converters behave like sinusoidal or resistive current loads of the network, which enables ``network-friendly´´ operation. The examined sinusoidal and the resistive modulation strategies are known, but the differences between the two methods have not been studied before [1,2]. This paper deals with the comparison of these two strategies. First, the analytical examination is presented. By comparing their consumed RMS currents we defined a coefficient (k[%]), which depends only on the total harmonic distortion of the network voltage (THD_u). We demonstrated that at high THD_u resistive modulation method is more favorable. Then simulation examination is discussed, by presenting our model of the three-phase four quadrant converter. Finally simulation results are represented in this article

A novel fuzzy based controller to reduce circulating currents in parallel interleaved converter connected to the grid

This paper exhibits suppression strategy of low frequency circulating current components for parallel inter-leaved converters. Here inverters are parallelized by magnetically coupled inductors. Traditionally, carrier interleaved technique was used to get lower distorted output voltage, but it gives a higher circulating currents to flow through the Two-VSC‘s. The mutual inductance of the coupled inductors (CI) is utilized for minimizing circulating currents of high frequency components. Nevertheless, CI can‘t have capability to riddle the components generated by low frequency. When these circulating currents extremely increases may leads to CI saturation, elevated switching losses and diminishes the entire performance of system. Here author identified a novel control technique for a grid-connected parallel inter-leaved converter depending on approach of energy shaping control (ECS). This controller diminishes the value of the low frequency components of circulating current (LFCC). The performance of the proposed circuit is evaluated in simulation mode and correlated with the conventional proportional integral control (PIC) and the linear quadratic control (LQC). The Fuzzy controller is also included in this work to enhance the converter performance effectively and to diminish the circulating currents along with the healthy harmonic performance analysis

Multi-task control strategy for grid-tied inverters based on conservative power theory

In recent years, the concept of decentralizing power generation through the deployment of distributed generators (DGs) has been widely accepted and applied, driven by the growing market of renewable energy sources, in particular photovoltaic, wind and small hydro. These distributed generators are normally equipped with a switching power interface (inverter), acting as front end with the grid. In this scenario this paper proposes a multi-task control strategy for distributed generation inverters that simultaneously allows the DG system to inject the available energy, as well as to work as a voltage drop compensator or as an active power filter, mitigating load current disturbances and improving power quality of the grid. The main contribution of the proposed system, with respect to other solutions in the literature, is that the proposed control loops are based on the Conservative Power Theory decompositions. This choice provides decoupled power and current references for the inverter control, offering a very flexible, selective and powerful control strategy for the DG system. The paper also discusses the choice of the current waveform for injecting/absorbing active power into/from the grid, and both sinusoidal and resistive references have been compared in terms of damping capability. Finally, simulation and experimental results are provided in order to validate the proposed functionalities of the DG control system

Computational Modelling of Piston Ring Dynamics

Pístní kroužky jsou instalovány do pístu a vložky válce, která nemá dokonale kruhový tvar v důsledku výrobních tolerancí a vnejšího zatížení jako například utažení šroubů hlavy motoru. Jestli se kroužek není schopen přizpůsobit těmto deformacím, nastane lokální ztráta kontaktu a následně zvýšený profuk spalin a spotřeba oleje. Současné 2D výpočtové metody nedokáží implementovat tyto efekty – více komplexní model je nevyhnutelný. Předkládaná diplomová práce je zaměřená na vývoj 3D poddajného modelu pístního kroužku schopného zachytit lokální deformace. Ten je založený na Timoshenkové teorii prutů v kooperaci s MBS softwarem Adams. Model je následně porovnaný se softwarem ANSYS využívající metodu konečných prvků. Ověřený model pístního kroužku je vložený do sestavy píst/vložka válce a jsou provedeny základní simulace. Nakonec jsou navrhnuty další zlepšení.Piston rings are installed in the piston and cylinder wall, which does not have a perfect round shape due to machining tolerances or external loads e.g. head bolts tightening. If the ring cannot follow these deformations, a localized lack of contact will occur and consequently an increase in the engine blow-by and lubricant oil consumption. Current 2D computational methods can not implement such effects – more complex model is necessary. The presented master’s thesis is focused on the developement of a flexible 3D piston ring model able to capture local deformations. It is based on the Timoshenko beam theory in cooperation with MBS software Adams. Model is then compared with FEM using software ANSYS. The validated piston ring model is assembled into the piston/cylinder liner and very basic simulations are run. Finally, future improvements are suggested.

Piston secondary motion measurement by laser displacement sensors

Measurement of the piston group behavior is still a challenge. Achieved accuracy and complexity go hand in hand with the financial requirements. This paper presents an unconventional measurement of the piston secondary motion using laser displacement sensors. Two sensors help capture the piston tilt angle, while the third sensor is used for the piston lateral motion measurement. These sensors are aimed at the piston crown. The passage between the laser source and the target spot has to be transparent. Therefore, side-valve internal combustion engine is employed. It enables the cylinder head to be made of the transparent material such as cast plexiglass. In the initial stage, the experimental engine is motored during the measurement. As for the measurement of the piston tilt angle, the results are within the physical limits. However, the same does not apply for the piston lateral results, where the measured values are too high, so the piston would penetrate the liner

Flywheel energy storage and dump load to control the active power excess in a wind diesel power system

Wind Diesel Power Systems (WDPS) are isolated microgrids which combine Wind Turbine Generators (WTGs) with Diesel Generators (DGs). The WDPS modelled in this article is composed of a DG, a WTG, consumer load, Dump Load (DL) and a Flywheel Energy Storage System (FESS). In the Wind-Diesel (WD) mode both the DG and WTG supply power to the consumers. The WDPS is simulated in the WD mode in the case that the WTG produced power exceeds the load consumption. This WTG excess power case is simulated in the subcases of DL and FESS turned off, only-DL and only-FESS. Simulations for the DL and FESS-off case show that the WTG excess power leads to a continuous system frequency increase, so that the tripping of the WTG Circuit Breaker (CB) is required to guarantee the WDPS power supply continuity. Simulations for the only-DL/only-FESS cases show that commanding the DL/FESS to consume controlled power, so that the required DG power to balance the system active power is positive, enables the DE speed governor to regulate the system frequency. Furthermore, the frequency and voltage variations in the DL/FESS cases are moderate and there is no need to trip the WTG-CB, so that the WDPS reliability and power quality are greatly improved. Additionally, the only-FESS case obtains better WDPS relative stability than the only-DL case

Control strategy for a grid-connected inverter under unbalanced network conditions—a disturbance observer-based decoupled current approach

Abstract: This paper proposes a new approach on the novel current control strategy for grid-tied voltage-source inverters (VSIs) with circumstances of asymmetrical voltage conditions. A standard grid-connected inverter (GCI) allows the degree of freedom to integrate the renewable energy system to enhance the penetration of total utility power. However, restrictive grid codes require that renewable sources connected to the grid must support stability of the grid under grid faults. Conventional synchronously rotating frame dq current controllers are insufficient under grid faults due to the low bandwidth of proportional-integral (PI) controllers. Hence, this work proposes a proportional current controller with a first-order low-pass filter disturbance observer (DOb). The proposed controller establishes independent control on positive, as well as negative, sequence current components under asymmetrical grid voltage conditions. The approach is independent of parametric component values, as it estimates nonlinear feed-forward terms with the low-pass filter DOb. A numerical simulation model of the overall power system was implemented in aMATLAB/Simulink (2014B, MathWorks, Natick, MA, USA). Further, particular results show that double-frequency active power oscillations are suppressed by injecting appropriate negative-sequence currents. Moreover, a set of simulation results provided in the article matches the developed theoretical background for its feasibility