Specific instrumentation and diagnostics for high-intensity hadron beams

An overview of various typical instruments used for high-intensity hadron beams is given. In addition, a few important diagnostic methods are discussed which are quite special for these kinds of beams.Comment: 58 pages, contribution to the CAS - CERN Accelerator School: Course on High Power Hadron Machines; 24 May - 2 Jun 2011, Bilbao, Spai

A Study on the Hierarchical Control Structure of the Islanded Microgrid

The microgrid is essential in promoting the power system’s resilience through its ability to host small-scale DG units. Furthermore, the microgrid can isolate itself during main grid faults and supply its demands. However, islanded operation of the microgrid is challenging due to difficulties in frequency and voltage control. In islanded mode, grid-forming units collaborate to control the frequency and voltage. A hierarchical control structure employing the droop control technique provides these control objectives in three consecutive levels: primary, secondary, and tertiary. However, challenges associated with DG units in the vicinity of distribution networks limit the effectiveness of the islanded mode of operation.In MV and LV distribution networks, the X/R ratio is low; hence, the frequency and voltage are related to the active and reactive power by line parameters. Therefore, frequency and voltage must be tuned for changes in active or reactive powers. Furthermore, the line parameters mismatch causes the voltage to be measured differently at each bus due to the different voltage drops in the lines. Hence, a trade-off between voltage regulation and reactive power-sharing is formed, which causes either circulating currents for voltage mismatch or overloading for reactive power mismatch. Finally, the economic dispatch is usually implemented in tertiary control, which takes minutes to hours. Therefore, an estimation algorithm is required for load and renewable energy quantities forecasting. Hence, prediction errors may occur that affect the stability and optimality of the control. This dissertation aims to improve the power system resilience by enhancing the operation of the islanded microgrid by addressing the above-mentioned issues. Firstly, a linear relationship described by line parameters is used in droop control at the primary control level to accurately control the frequency and voltage based on measured active and reactive power. Secondly, an optimization-based consensus secondary control is presented to manage the trade-off between voltage regulation and reactive power-sharing in the inductive grid with high line parameters mismatch. Thirdly, the economic dispatch-based secondary controller is implemented in secondary control to avoid prediction errors by depending on the measured active and reactive powers rather than the load and renewable energy generation estimation. The developed methods effectively resolve the frequency and voltage control issues in MATLAB/SIMULINK simulations

Cross-Coupling Effects of Interconnected DC-DC Converter System in PV Applications

Due to increase in global warming,the world is renewing its focus on renewable sources of energy.Among them, Photovoltaic(PV)generation has attracted vast interests worldwide.In PV generation, solar photovoltaic panels absorb solar radiation to generate power through photovoltaic effect.However,the PV systems are found to be vulnerable to mismatch conditions and other atmospheric conditions.So,to extract maximum power under partial shading condition and module mismatching,calls for new innovation methods and technologies.In this thesis,the modelling of a PV module is discussed.The characteristics of photo-voltaic module are observed for various solar irradiation and different atmospheric condition.The PV panel is operated at its maximum power point by using P & O method and the duty cycle control is being employed to get the peak power.The photovoltaic modules are connected in series to get the high voltage of system.The classical MPPT control method does not work when the photo-voltaic modules are connected in series,under extreme conditions and under partial shading.Thus,Distributed Maximum power point tracking(DMPPT)control method is used to extract power under such conditions.However,due to cascading of dc-dc converters,there is a surprise element of cross-coupling effects.The coupling effects are the disturbances which are present in the system because of cascading of dc-dc converters.Cross-coupling effects are studied in this thesis

Temperature profiles of field-aged photovoltaic modules affected by optical degradation

Moisture ingress into PV module in the presence of ultraviolet radiation, high temperature, and other environmental stressors can affect the optical integrity of the PV module. Optical degradation can take the form of delamination, discolouration of encapsulant, metal grids corrosion, and trapped moisture or chemical species. This can influence the photon absorption and current transport properties in the PV module bulk, which can affect the module operating temperature. In the present work, the relationship between optical degradation and temperature sensitivity of 20-year-old multicrystalline silicon field-aged PV modules have been investigated. The selected PV modules were characterized using visual inspection, current-voltage (I–V) characterization, temperature coefficients profiling, current resistivity profiling, infrared (IR) thermal, ultraviolet fluorescence (UV–F), and electroluminescence (EL) imaging. PV modules affected by optical degradation show weak fluorescence and luminescence signal intensities. The average difference in cell temperature (ΔT) between the warmest and coldest cell for the PV modules investigated was found to be around 10 ± 2 °C and the average power degradation rate was approximately 0.8% per year. The underlying factor for the observed degradation is attributed to the degradation in the temperature coefficients of open circuit voltage (βVoc) and maximum power point voltage (βVmpp). The average temperature coefficient of efficiency (βηm) of the modules was found to be around −0.5%/°C. Finally, a temperature dependent resistivity method for extracting temperature coefficients from IR thermal data of PV modules has been proposed.publishedVersio

A survey of islanding detection methods for microgrids and assessment of non-detection zones in comparison with grid codes

Detection of unintentional islanding is critical in microgrids in order to guarantee personal safety and avoid equipment damage. Most islanding detection techniques are based on monitoring and detecting abnormalities in magnitudes such as frequency, voltage, current and power. However, in normal operation, the utility grid has fluctuations in voltage and frequency, and grid codes establish that local generators must remain connected if deviations from the nominal values do not exceed the defined thresholds and ramps. This means that islanding detection methods could not detect islanding if there are fluctuations that do not exceed the grid code requirements, known as the non-detection zone (NDZ). A survey on the benefits of islanding detection techniques is provided, showing the advantages and disadvantages of each one. NDZs size of the most common passive islanding detection methods are calculated and obtained by simulation and compared with the limits obtained by ENTSO-E and islanding standards in the function of grid codes requirements in order to compare the effectiveness of different techniques and the suitability of each one

Full characterization and analysis of a terahertz heterodyne receiver based on a NbN hot electron bolometer

We present a complete experimental characterization of a quasioptical twin-slot antenna coupled small area (1.0×0.15 µm^2) NbN hot electron bolometer (HEB) mixer compatible with currently available solid state tunable local oscillator (LO) sources. The required LO power absorbed in the HEB is analyzed in detail and equals only 25 nW. Due to the small HEB volume and wide antenna bandwidth, an unwanted direct detection effect is observed which decreases the apparent sensitivity. Correcting for this effect results in a receiver noise temperature of 700 K at 1.46 THz. The intermediate frequency (IF) gain bandwidth is 2.3 GHz and the IF noise bandwidth is 4 GHz. The single channel receiver stability is limited to 0.2–0.3 s in a 50 MHz bandwidth

An Islanding Detection Method for Micro-Grids With Grid-Connected and Islanded Capability

With the increasing prevalence of renewable energy and distributed generation (DG) in distribution systems, micro-grids are becoming more popular and an attractive option for enhancing system operation and reliability. This can be attributed to the micro-grid ability to operate in both connected and disconnected modes. Equally important, micro-grids are the best solution to meet the increasing demand of electric power in a cost effective manner due to the close proximity to the load demand and thus minimizing system losses. Islanding detection methods have been proposed for inverter based distributed generation with only grid-connected capability. Micro-grids are composed of DGs that are capable of operating in two modes: grid connected and islanded. This thesis introduces and proposes the concept of micro-grid transition detection where the status of the micro-grid is detected based on adaptively modifying the droop slope. The droop coefficient is chosen such that the micro-grid is stable while grid connected and in the contrary Unstable once an islanded micro-grid operation is initiated. The droop coefficient is adaptively modified, once the micro-grid transitions from grid-connected to islanded operation, to stabilize the micro-grid for the islanded mode of operation. The proposed method is capable of detecting micro-grid transition in less than 600 ms under various active and reactive power mismatches. The proposed micro-grid transition detection method is tested on a micro-grid equipped with inverter based DGs controlled using the droop approach. The main objective of this thesis is to develop a novel islanding detection method for micro-grids with grid connected and islanded capability. A micro-grid model was developed using power system computer aided design/ electromagnetic transient and DC (PSCAD/EMTDC) as a platform for testing the proposed method. Simulation results were conducted considering the Institute of Electrical and Electronics Engineers Standard 1547(IEEE Std. 1547) standard islanding detection testing procedure

Developing A Medium-Voltage Three-Phase Current Compensator Using Modular Switching Positions

The objective of this thesis is to present the context, application, theory, design, construction, and testing of a proposed solution to unbalanced current loading on three-phase four-wire systems. This solution, known as the Medium-Voltage Unbalanced Current Static Compensator or MV-UCSC, is designed to recirculate currents between the three phases of adistribution system. Through this redistribution of the currents negative- and zero-sequence current components are eliminated and a balanced load is seen upstream from the point of installation. The MV-UCSC as it operates in the distribution system is presented followed by its effect on traditional compensation equipment. The construction of the MV-UCSC as well as 13.8 kV simulations are then shown. Development of the switching positions required by the MVUCSC is then given followed by a variation on this switching position with the intent to reduce part count. Finally, the testing the 13.8 kV three-phase four-wire, neutral-point-clamped, elevenlevel, flying-capacitor-based MV-UCSC connected directly to the grid is presented

Voltage-based droop control of converter-interfaced distributed generation units in microgrids

Sinds de laatste jaren is er in het elektrisch energienet een enorme toevloed aan kleine decentrale generatoren, vaak op basis van hernieuwbare energiebronnen. De distributienetten werden echter niet gebouwd om injectie van energie toe te laten. Hierdoor komen steeds meer problemen in de distributienetten voor, zoals bijvoorbeeld overspanningen tijdens zonnige periodes. Dit bemoeilijkt de verdere integratie van hernieuwbare energiebronnen. In deze context werd het microgrid concept voorgesteld om een gecoordineerde koppeling van decentrale generatoren in het net mogelijk te maken. Microgrids zijn kleine subnetten die lokaal hun elementen, zoals de generatoren en de lasten regelen om bepaalde doeleinden te bereiken. Ze kunnen bijvoorbeeld de spanningsregeling in hun net verzorgen of als een geheel meespelen in de energiemarkten. Een karakteristiek van microgrids is dat ze onafhankelijk van het net kunnen werken, in het zogenaamde eilandbedrijf. In eilandbedrijf moeten het verbruik en de opwekking op ieder tijdstip op elkaar afgesteld zijn. Aangezien microgrids erg verschillende eigenschappen hebben van het gewone elektrisch net, zijn hier specifieke regelstrategieen voor vereist. In deze doctoraatsverhandeling wordt een dergelijke regelstrategie uitgewerkt, de zogenaamde spanningsgebaseerde droop (proportionele) regeling. Het spanningsniveau wordt als de niet-conventionele parameter gebruikt om het microgrid te regelen