Current Issue : April - June Volume : 2017 Issue Number : 2 Articles : 5 Articles
Spikes frequently occur in power quality (PQ) disturbance signals due to various causes\nsuch as switching of the inductive loads and the energization of the capacitor bank. Such signals are\ndifficult to analyze using existing time-frequency (TF) methods as these signals have two orthogonal\ndirections in a TF plane. To address this issue, this paper proposes an adaptive TF distribution (TFD)\nfor the analysis of PQ signals. In the proposed adaptive method, the smoothing kernel�s direction\nis locally adapted based on the direction of energy in the joint TF domain, and hence an improved\nTF resolution can be obtained. Furthermore, the performance of the proposed adaptive technique\nin analyzing electrical PQ is thoroughly studied for both synthetic and real world electrical power\nsignals with the help of extensive simulations. The simulation results (specially for empirical data)\nindicate that the adaptive TFD method achieves high energy concentration in the TF domain for\nsignals composed of tones and spikes. Moreover, the local adaptation of the smoothing kernel in the\nadaptive TFD enables the extraction of TF signature of spikes from TF images, which further helps in\nmeasuring the energy of spikes in a given signal. This new measure can be used to both detect the\nspikes as well as to quantify the extent of distortion caused by the spikes in a given signal....
Solenoid valve is a very important hydraulic actuator for an automatic transmission\nin terms of shift quality. The same form of pressure for the clutch and the input\ncurrent are required for an ideal control. However, the gap between a pressure and a\ncurrent can occur which brings a delay in a transmission and a decrease in quality.\nThis problem is caused by hysteresis phenomenon. As the ascending or descending\nmagnetic field is applied to the solenoid, different thrust forces are generated. This\npaper suggests the calculation method of the thrust force considering the hysteresis\nphenomenon and consequently the accurate force can be obtained. Such hysteresis\noccurs in ferromagnetic materials, however the hysteresis phenomenon includes a\nminor hysteresis loop which begins with an initial magnetization curve and is generated\nby DC biased field density. As the core of the solenoid is ferromagnetic material, an\naccurate thrust force is obtained by applying the minor hysteresis loop compared to\nthe force calculated by considering only the initial magnetization curve. An analytical\nbackground and the detailed explanation of measuring the minor hysteresis loop are\npresented. Furthermore experimental results and finite element analysis results are\ncompared for the verification....
The electrical energy production capability of bimorph (Pb...
A high-voltage positive temperature coefficient (PTC) heater has a simple structure and a\nswift response. Therefore, for cabin heating in electric vehicles (EVs), such heaters are used either on\ntheir own or with a heat pump system. In this study, the sintering process in the manufacturing of\nPTC elements for an EV heating system was improved to enhance surface uniformity. The electrode\nproduction process entailing thin-film sputtering deposition was applied to ensure the high heating\nperformance of PTC elements and reduce the electrode thickness. The allowable voltage and\nsurface heat temperature of the high-voltage PTC elements with thin-film electrodes were 800 V\nand 172 ââ??¦C, respectively. The electrode layer thickness was uniform at approximately 3.8 Ã?¼m or\nless, approximately 69% less electrode materials were required compared to that before process\nimprovement. Furthermore, a heater for the EV heating system was manufactured using the\ndeveloped high-voltage PTC elements to verify performance and reliability....
A key issue in Low Voltage (LV) distribution systems is to identify strategies for the optimal\nmanagement and control in the presence of Distributed Energy Resources (DERs). To reduce the\nnumber of variables to be monitored and controlled, virtual levels of aggregation, called Virtual\nMicrogrids (VMs), are introduced and identified by using new models of the distribution system.\nTo this aim, this paper, revisiting and improving the approach outlined in a conference paper,\npresents a sensitivity-based model of an LV distribution system, supplied by an Medium/Low\nVoltage (MV/LV) substation and composed by several feeders, which is suitable for the optimal\nmanagement and control of the grid and for VM definition. The main features of the proposed\nmethod are: it evaluates the sensitivity coefficients in a closed form; it provides an overview of the\nsensitivity of the network to the variations of each DER connected to the grid; and it presents a\nlimited computational burden. A comparison of the proposed method with both the exact load flow\nsolutions and a perturb-and-observe method is discussed in a case study. Finally, the method is used\nto evaluate the impact of the DERs on the nodal voltages of the network....
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