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These days the number of nonlinear loads in power systems is increasing dramatically. These nonlinear loads inject harmonic currents and the voltages. Accordingly, the modeling of these loads and analysis of their effects on power quality has gained much attention. This paper presents harmonic models for residential appliances. The model is based on Norton equivalent technique. The parameters of appliances...
In order to solve mode mixing, an improved HHT (IHHT) is proposed to identify modes of low frequency oscillation (LFO) in power systems. Firstly, by means of Fourier transform the approximate frequency range of every mode is determined; then methods such as masking signals or filters are chosen to separate mixing modes. Finally mode parameters can be calculated by linear least quadratic fitting. Simulated...
It is generally accepted that the diesel engine crankshaft strength analysis is of importance in evaluating the performance and lifetime of the crankshaft and then acquire the overall engine mechanical information. However it is significant to apply a suitable model on the calculation including force analysis, simplification of the crankshaft geometry model, etc. In this paper, a single-cylinder crankshaft...
Nowadays, the Fast Fourier transform (FFT) has been widely adopted for harmonic analysis in power system. However, a direct application of FFT-based algorithms may bring about inaccurate results because of spectral leakage and picket-fence effects. In this paper, a high accuracy method based on the all-phase and interpolated FFT is presented for harmonic analysis. Firstly, the input signal is preprocessed...
The technology of horizontal-tube falling film evaporation is widely used in low temperature multi-effect distillation evaporators. The heat transfer coefficient of it depends on many factors, such as steam velocity, sprinkle density, evaporation temperature, etc. In the engineering design of evaporator, much smaller sprinkle density may led to "dry points on tube", while much bigger sprinkle...
Voltage sag has became the most concerned about power quality problems. Voltage sag source detection for power quality fault detection, diagnosis and to ease the formulation of strategy is necessary. This paper proposes a new method about voltage sag disturbance source location based on real current component. The product of the RMS current and the power factor angle at the monitoring point is employed...
The vacuum circuit breakers are used to switch shunt capacitors which are used as a reactive compensator. Due to capacitors' energy storage characteristic and asynchronous closing of vacuum circuit breakers, system will produce high overvoltage during switching off the shunt capacitors especially when a beaker is restriked. It's harmful to the insulation and lifecircle of the equipments and even threatens...
Numerical simulation of unsteady three-dimensional turbulent flow in a mixed flow reactor coolant pump was achieved by using a phased-lagged method. Based on Reynolds averaged Navier-Stokes equations with S-A turbulence models in commercial software Numeca, pressure distribution in impeller, diffuser and volute was obtained, and focused on pressure fluctuations caused by impeller-diffuser interaction...
A SOFC/GT hybrid system is difficult to operate on design conditions all the time. Adjustment methods of output power from a gas turbine (GT) and a solid oxide fuel cell (SOFC) are necessary and very important which influence the performance characteristics of an SOFC/GT hybrid system. In this paper, performance analyses of the hybrid system with two different control modes are conducted based on...
As is well known, Smart Grid is a complex nonlinear system whose dynamical behavior has many complicated forms such as low frequency oscillation, subsynchronous oscillation and even chaos. Thus this paper focuses on the chaotic phenomenon of the widely concerned Smart Grid and presents its stabilization condition via establishing generalized fuzzy hyperbolic model. Firstly, the concept of Smart Grid...
With fatty acid as raw material, using the two-step method, first, we use concentrated H2SO4 as a catalyst for esterification of fatty acid and methanol to reduce AV (acid value), and then we added methanol into the peristaltic pump to make its AV drop to below 1 mg KOH /g oil. The best condition of first stage: the temperature is 65±2°C, the catalyst dosage is 1%, the methanol to fatty acid ratio...
Laminar natural convection arising from horizontal rectangle cylinder to its concentric cylindrical enclosure is numerically studied. The Rayleigh number is varied in the range of 103≤Ra≤106. According to the form of isotherms and the streamline patterns, the basic features of flow and heat transfer for four rectangle cylinders with different aspect ratios are reported. And the local and average Nusselt...
The manufacturing industry of Suzhou is developing on the basis of carrying on the foreign capital with the characteristics of ample scale but deficient supporting industry, being pulled by foreign capital but weak resisting risk ability, producing with the head and end outside and low add-value and so on. This low-end manufacturing industry is the basic pattern of entering international producing...
In model based selective catalytic reduction (SCR) control, because of the nonlinearities and immeasurable properties of the SCR physical background, model parameterization is always a problem to be solved. In this paper, a new method based on the nonlinear least square method is developed to estimate the parameters in a SCR model. The SCR system state functions are specially designed in terms of...
Nitrogen oxides (NOx) reduction technique is one of the hot topics for Diesel engine developers. In the SCR system, the required urea dosing quantity is calculated from the diesel engine raw emissions, so the estimation of the engine raw emissions is very important,. Because of the complexity and the nonlinearity of the engine model, the estimation results are always not satisfied, especially when...
In this paper, the reaction kinetics of the selective catalytic reduction (SCR) is briefly introduced, and a non-cell mathematical model describing the thermal and chemical process of the SCR catalytic converter is given. Based on the one-cell model, identical SCR cell models can be seriously connected to simulate a real SCR converter performance. Consequently, the SCR catalytic converter model in...
Experimental study of the uniaxial automatic solar tracking device towards sun comparison with fixed bracket and the two devices to solar radiation quantity of receiving test had been presented. The results showed that the uniaxial automatic tracking device towards sun receive solar radiation quantity than fixed bracket improved 25%-28%.
For estimating moisture of oil-paper insulation, the frequency domain spectroscopy measurements were used to model oil-paper insulation system. Then the dielectric spectroscopy of oil-paper insulation system was tested. And give the formula of the moisture. The influence of oil gap on the test results of oil-paper insulation response was discussed. The results showed that the influence of oil gap...
Denitrification (De-NOx) agents using activated carbon (AC) as the support have a large specific surface area, good pore structure, low reaction temperature and low price, amongst others. In this work, CuO/AC catalysts with coconut AC supported copper were prepared. De-NOx experiments were conducted in a fixed-bed reactor using a simulated flue gas stream to investigate the effects of calcination...
It is very desirable to achieve high accuracy in fault location due to the increasing demands of fast detection and clearance of fault of transmission line. Most fault location algorithms incorporated in the fault recorders are based on the lumped parameter single-ended circuit model. Therefore, their accuracy is not satisfactory in many scenarios. A new revising scheme which can improve the accuracy...
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