Wind Farm Grid Integration Architecture using Unified Expandable Power Converter

IEEE This paper proposes a novel unified expandable low switch power electronic converter architecture for grid integration of direct drive variable speed wind turbine (VSWT) system using permanent magnet synchronous generator (PMSG). The proposed unified expandable power converter (UEPC) can interface two or more bidirectional output ports such as wind generators, energy storages and grid. The size of the power converter is compact because of low number of power electronic switches and protection devices and its architecture is easily expandable to accommodate more outputs, i.e., in this case, the wind turbines. A generalized sequential space vector modulation technique is developed based on the operational principle of the proposed converter to control of the outputs autonomously in order to track maximum power point for individual VSWTSs driven PMSG's. It is expected that the proposed approach will reduce the cost of power electronic converters in a wind farm compared to both AC- and DC-link based topologies, which are available for the momen

Combined Use of Sensitivity Analysis and Hybrid Wavelet-PSO- ANFIS to Improve Dynamic Performance of DFIG-Based Wind Generation

In the past few decades, increasing growth of wind power plants causes different problems for the power quality in the grid. Normal and transient impacts of these units on the power grid clearly indicate the need to improve the quality of the electricity generated by them in the design of such systems. Improving the efficiency of the large-scale wind system is dependent on the control parameters. The main contribution of this study is to propose a sensitivity analysis approach integrated with a novel hybrid approach combining wavelet transform, particle swarm optimization and an Adaptive-Network-based Fuzzy Inference System (ANFIS) known as Wavelet-ANFIS-PSO to acquire the optimal control of Doubly-Fed Induction Generators (DFIG) based wind generation. In order to mitigate the optimization complexity, sensitivity analysis is offered to identify the Unified Dominate Control Parameters (UDCP) rather than optimization of all parameters. The robustness of the proposed approach in finding optimal parameters, and consequently achieve a high dynamic performance is confirmed on two area power system under different operating conditions

Optimal Capacitor Allocation in Radial Distribution Networks for Annual Costs Minimization Using Hybrid PSO and Sequential Power Loss Index Based Method

In the most recent heuristic methods, the high potential buses for capacitor placement are initially identified and ranked using loss sensitivity factors (LSFs) or power loss index (PLI). These factors or indices help to reduce the search space of the optimization procedure, but they may not always indicate the appropriate placement of capacitors. This paper proposes an efficient approach for the optimal capacitor placement in radial distribution networks with the aim of annual costs minimization based on the sequential placement of capacitors and calculation of power loss index. In the proposed approach, initially, the number of capacitors location is estimated using the total reactive power demand and the average range of capacitors available in the market. Then, the high potential buses can be identified using sequential power loss index-based method. This method leads to achieve the optimal or near optimal locations for the capacitors and decrease the search space of the optimization procedure significantly. The particle Swarm Optimization (PSO) algorithm takes the final decision for the optimum size and location of capacitors. To evaluate the efficiency of the conducted approach, it is tested on several well-known distribution networks, and the results are compared with those of existing methods in the literature. The comparisons verify the effectiveness of the proposed method in producing fast and optimal solutions

Specific of Myocardial Perfusion Scintigraphy Compared to Invasive Coronary Angiography

Purpose: The NICE guidance has placed non-invasive ischaemia testing as the primary role for assessing patients with moderate pre test probability for obstructive coronary artery disease. Functional tests like MPI, have led to a reduced role for invasive coronary angiography (ICA) in initial patient assessment. Aim of our audit was to assess the specificity of our nuclear service compared with ICA retrospectively. The standard was set at a false positive rate of no more than 73%.Methods: A search was conducted (between Aug2012-Feb2013). MPIs were reported by a radiologist and a cardiologist. A standard 17-segment model was used for MPI interpretation. Coronary angiograms were interpreted for the absence/presence of epicardial luminal narrowing >50% by referencing the clinical report on the patient electronic record. The cases which were positive enough to warrant recommendation for ICA the true positive and false positive rate was determined.Results: This cross –sectional study included 51 cases.33 had a stenosis in a major coronary artery of>50% giving a true positive rate of 65%. There were18 false positive studies (35%). 5 cases were regarded as having evidence of transient ischaemic dilatation (TID), all of which had a subsequent negative angiogram.3 studies had notable artefact due to patient body habitus, or inability to position the patient optimally. The percentage of myocardium defects was determined for each case at stress. The average percentage in the true positive studies was 17%, in the false positive studies it was7%, excluding those regarding as having TID.Conclusions: MPI studies deemed sufficiently abnormal to justify a coronary angiogram have a moderate likelihood of predicting a significant stenosis being present on ICA. False positive scans are frequent when only TID and significant artefacts are present. It is likely that CT calcium scoring with MPI will increase the specifity of this imaging. It will also allow CT coronary angiography to be used in cases where artefact is present and the calcified atheroma burden is low.The audit standard was not met. Suggested changes in practice. 1. Greater caution in recommending ICA for cases where the only evidence for ischaemia is transient ischaemic cardiomyopathy. 2. Increased use of CT to determine cases where significant reversible ischaemia is present in the context of none or low burden of coronary calcification.Clinical Relevance/Application: MPI assesses myocardial perfusion by using radiotracers injected under stress/rest conditions

Microwave Kinetic Inductance Detector (MKID) Camera Testing for Submillimeter Astronomy

Developing kilopixel focal planes for incoherent submm- and mm-wave detectors remains challenging due to either the large hardware overhead or the complexity of multiplexing standard detectors. Microwave kinetic inductance detectors (MKIDs) provide a efficient means to produce fully lithographic background-limited kilopixel focal planes. We are constructing an MKID-based camera for the Caltech Submillimeter Observatory with 576 spatial pixels each simultaneously sensitive in 4 bands at 230, 300, 350, and 400 GHz. The novelty of MKIDs has required us to develop new techniques for detector characterization. We have measured quasiparticle lifetimes and resonator Qs for detector bath temperatures between 200 mK and 400 mK. Equivalent lifetime measurements were made by coupling energy into the resonators either optically or by driving the third harmonic of the resonator. To determine optical loading, we use both lifetime and internal Q measurements, which range between 15,000 and 30,000 for our resonators. Spectral bandpass measurements confirm the placement of the 230 and 350 GHz bands. Additionally, beam maps measurements conform to expectations. The same device design has been characterized on both sapphire and silicon substrates, and for different detector geometries. We also report on the incorporation of new shielding to reduce detector sensitivity to local magnetic fields

The cryomechanical design of MUSIC: a novel imaging instrument for millimeter-wave astrophysics at the Caltech Submillimeter Observatory

MUSIC (Multicolor Submillimeter kinetic Inductance Camera) is a new facility instrument for the Caltech Submillimeter Observatory (Mauna Kea, Hawaii) developed as a collaborative effect of Caltech, JPL, the University of Colorado at Boulder and UC Santa Barbara, and is due for initial commissioning in early 2011. MUSIC utilizes a new class of superconducting photon detectors known as microwave kinetic inductance detectors (MKIDs), an emergent technology that offers considerable advantages over current types of detectors for submillimeter and millimeter direct detection. MUSIC will operate a focal plane of 576 spatial pixels, where each pixel is a slot line antenna coupled to multiple detectors through on-chip, lumped-element filters, allowing simultaneously imaging in four bands at 0.86, 1.02, 1.33 and 2.00 mm. The MUSIC instrument is designed for closed-cycle operation, combining a pulse tube cooler with a two-stage Helium-3 adsorption refrigerator, providing a focal plane temperature of 0.25 K with intermediate temperature stages at approximately 50, 4 and 0.4 K for buffering heat loads and heat sinking of optical filters. Detector readout is achieved using semi-rigid coaxial cables from room temperature to the focal plane, with cryogenic HEMT amplifiers operating at 4 K. Several hundred detectors may be multiplexed in frequency space through one signal line and amplifier. This paper discusses the design of the instrument cryogenic hardware, including a number of features unique to the implementation of superconducting detectors. Predicted performance data for the instrument system will also be presented and discussed

Optimization of MKID Noise Performance Via Readout Technique for Astronomical Applications

Detectors employing superconducting microwave kinetic inductance detectors (MKIDs) can be read out by measuring changes in either the resonator frequency or dissipation. We will discuss the pros and cons of both methods, in particular, the readout method strategies being explored for the Multiwavelength Sub/millimeter Inductance Camera (MUSIC) to be commissioned at the CSO in 2010. As predicted theoretically and observed experimentally, the frequency responsivity is larger than the dissipation responsivity, by a factor of 2-4 under typical conditions. In the absence of any other noise contributions, it should be easier to overcome amplifier noise by simply using frequency readout. The resonators, however, exhibit excess frequency noise which has been ascribed to a surface distribution of two-level fluctuators sensitive to specific device geometries and fabrication techniques. Impressive dark noise performance has been achieved using modified resonator geometries employing interdigitated capacitors (IDCs). To date, our noise measurement and modeling efforts have assumed an onresonance readout, with the carrier power set well below the nonlinear regime. Several experimental indicators suggested to us that the optimal readout technique may in fact require a higher readout power, with the carrier tuned somewhat off resonance, and that a careful systematic study of the optimal readout conditions was needed. We will present the results of such a study, and discuss the optimum readout conditions as well as the performance that can be achieved relative to BLIP