Time Variation Of Load Research Articles

An Optimization Method of Active Distribution Network Considering Time Variations in Load and Renewable Distributed Generation

Network optimization is one of an effective ways to enhance the performance of an active distribution network (ADN). Aiming to improve the operation and power quality of the ADN considering time variations in load and renewable distributed generation (RDG) power, a multi-time period optimization model and its dynamic solution method are proposed. Considering the real time load demand and power generation variation of RDG versus input parameters like wind speed and solar irradiance, the time variation models of load and RDG power output are developed. The minimum power loss and maximum absorption of RDG power are served as the optimization indexes to construct the dynamic muti-time period optimization model. A hybrid particle swarm optimization (HPSO) algorithm is presented based on integer coding and random coding technique, which can find the most satisfactory solutions for the proposed dynamic model. Considering the time variation of load and RDG power of ADN, the optimal network structure and RDG allocation scheme at any time interval are determined by analyzing the obtained solutions. Additionally, two ADNs with time variation in load and RDG are tested to verify the effectiveness and superiority of the proposed dynamic optimization model and HPSO algorithm. The simulation results show that the proposed method can improve the operation performance and RDG optimal utilization of the ADNs through muti-time period dynamic optimization.

In brief

PAGE 752 With security in free-space optical communications mounting in importance, a novel 2D encryption scheme for such channels has been proposed which uses two spatial patterns as encryption keys. The team from Japan, including one Electronics Letters Associate Editor, hopes the system will reduce the risk of unauthorised third-party intrusion. PAGE 723 Samsung Electronics researchers present a dual-layer substrate integrated waveguide cavity filtering antenna with a controllable radiation band and two radiation nulls. The designed and fabricated prototype exhibits good filtering performance, with a radiation band that can be independently controlled without affecting the radiation nulls. Simulated intensity results on varying patterns. PAGE 756 Dielectric metasurfaces composed of arrays of subwavelength structures can manipulate the properties of electromagnetic waves. These effects have been utilised by researchers from China to produce a metasurface grating with blazing behaviour which imitates saw-tooth gratings for use in an imaging spectrometer. Electric field distribution on the ground plane. PAGE 737 A team of researchers from China outline a finite element-based domain decomposition method with a novel transmission condition for electromagnetic (or other type of fields) computation. It operates by splitting an original large domain into several non-overlapping smaller sub-domains and is verified with calculations on 3D electro- and magnetostatic models. Schematic of the designed Metamaterial Blazed Grating (MBG). PAGE 749 A low-cost and passive medical examination solution based on near field communication technology has been proposed by Chinese researchers. The presented time-sharing control energy accumulation method is extended to a medical detection system temperature measuring prototype and demonstrates that this method can be used in conjunction with a smart phone for portable healthcare monitoring applications. Permanent magnet structure and computational model. Load time variation with charge time with different capacitors.

Efficient algorithm for transmission system energy loss allocation considering multilateral contracts and load variation

This study proposes a new analytical method for transmission power loss allocation in hybrid market power systems. It is based on circuit laws and the orthogonal projection. In this method, the current flow in each branch is divided into two components. The first one is due to the power transfer from generators to loads. The second component is due to the voltage differences between generator buses. The later currents are called no-load or circulating currents. These current components are computed by using the superposition principle. The responsibility of each load and generator to power losses in each branch of the network is derived analytically. Hence, the share of each load or generator in the overall transmission network losses is estimated. Furthermore, the impact of bilateral/multilateral contracts is included in the transmission network power loss allocation algorithm. The method is extended to consider the time variation of loads and wind generation. The proposed method is applied to four test systems and compared with other methods.

Comparison Study of the Clustering Analysis Methods in the Load Time-Variation Research

Load model has a great impact on the digital simulation result. In this paper, the measurement-based method is applied to model the load. If all the measured data are used for modeling respectively, the workload would be increased greatly. But if only one model is generated with the multi-curve fitting parameter identification method, the accuracy of modeling would be reduced greatly. The clustering analysis theory supplies an effective way to solve the problem above. There are some methods for clustering introduced in this paper. But a suitable method needs be studied firstly. The case study is presented to compare these methods. According to simulation result, it is concluded that the Kmeans method is best, while the usually adopted central clustering is actually not suitable for the load time-variation research.

A Wavelet Based Method for the Analysis of Impulsive Noise Due to Switch Commutations in Power Line Communication (PLC) Systems

The aim of this paper is to study the problem of load-time variation in power line communication (PLC) systems and to analyze asynchronous impulsive noise and related channel variations due to switch commutations. A numerical model of the time-varying communication channel is developed by using scattering parameters in the wavelet domain. The proposed method uses the N-port description of the elements that constitute a time-varying PLC system in terms of real matrices with constant elements. This represents a valid alternative to the time domain description usually adopted for analyzing time-varying networks. The comparison with results obtained from other numerical models and with experimental data has confirmed the accuracy and the efficiency of the proposed method.

Numerical Simulation and Deformation Research for Cold Enlarging Tube Diameter

This paper presented how to build finite element model based on UG NX, and simulated the cold expanding process by DEFORM software. The deformation, distribution and development trend of velocity, equivalent stress, equivalent strain and equivalent strain rate were predicted. The punch’s load-time variation curves in X, Y and Z direction were also obtained.

Application Study on Metal Forging Technology of Square Block Based on DEFORM

Much progress has achieved in forging technology, and it has become a popular process for preparation of intricate parts. As a case, a finite element model of the square block forging process was established by DEFORM software. The deformation, distribution and development trend of velocity, mean stress, equivalent strain and equivalent strain rate were predicted. The load-time variation curves in X, Y and Z direction were obtained too. Based on the numerical simulation result, we had a better understanding of the forging process.

Genetic algorithm-based approach for fixed and switchable capacitors placement in distribution systems with uncertainty and time varying loads

Installation of capacitors in primary and secondary networks of distribution systems is one of the efficient methods for energy and peak load loss reduction. Also voltage profile in the feeder is improved and static voltage stability is enhanced. The main challenge is the determination of optimal location and size of fixed and switchable capacitors with respect to network configuration, distribution of load in the feeder, time variation of load and uncertainty in load forecasting or load allocation process. To solve this complex problem, an efficient method for simultaneous allocation of fixed and switchable capacitors in radial distribution systems is presented. Energy and peak load loss reduction, and capacitor cost are considered in the cost function. Time variation and uncertainty of load are also involved in problem formulation. Genetic algorithm with a new coding as two rows chromosomes is used for optimisation. Numerical studies show the effectiveness of the proposed procedure.

Large deflection dynamic response of composite laminated plates under in-plane loads

An analytical solution is presented for the dynamic buckling behaviour of a laminate subjected to time-dependent uniformly distributed normal and shear in-plane loads based on the Classical Lamination Theory and accounting for moderately large deflections. The assumed load-time variation is either linear or of a pulse type. The Galerkin method is applied and the obtained nonlinear differential equations are solved numerically by the Runge-Kutta method. The parametric study performed revealed three distinct phases in the undamped centre deflection time-history of a laminate. No significant deformations are produced in phase I, while the subsequent phase II reflects the dynamic buckling behaviour, exhibiting a rapid increase of the deformations. These magnitudes follow an oscillating motion in phase III, analogous to the loading condition under consideration. Relatively large initial imperfection values change completely the response of the laminate, by eliminating both the characteristic dynamic buckling phase II and the oscillations of phase III.

Creep-fatigue interactions in glass fibre/polyester composites

Glass-reinforced plastics (GRP) are employed in the cooling water (CW) systems of coastal power stations, where they are exposed to an aggressive environment, sea water at temperatures up to 40°C, and to a complex loading pattern. This latter comprises a background static load, on which are superimposed sinusoidal variations and periodic unloads. The aim of this project was to ascertain the extent of any interaction between static and dynamic loading. Also examined were the effects of environment and of cyclic loading at low frequencies upon fatigue life. The material was modelled on the CEGB-preferred layup of mixed chopped-strand mat (csm) and woven-roving (wr) in polyester. Two loading regimes were used to model aspects of the CW system service conditions. Both used a frequency of 1 cycle per 2 min (0·0083 Hz). Periodic unloads were represented by a ‘rectangular’ load-time variation (R1), with a ratio of time under load to time off-load of 20:1. Tidal pressure variations were represented by a sinusoidal régime with load amplitude equal to 20% of mean load (S1). When the aggregate time at maximum load during the rectangular-wave test R1 was compared to life under static loading at the same level, intermittent unloading seemed to make no difference. This observation was contrary to some published work. Since the different behaviour might arise from the use of different loading frequencies, the effect of frequency of unloading was investigated over a range from 0·0005 Hz to 0·25 Hz. At the higher frequencies, failure occurs after a specific number of cycles, irrespective of the time under load; at low frequencies a time-at-load criterion is satisfied first. A ‘boundary frequency’ must exist between these régimes, and it is calculated to lie between 0·12 and 1·2 cycles/min (cpm). The frequency of R1 (0·5 cpm) lies within this range. The interaction between sinusoidal and static loading was investigated with two ratios of stress amplitude to mean stress; with frequencies of 1·0, 0·25 and 0·0083 Hz; in air and in water at 40°C. Results were assembled in the form of a partial Haigh diagram. From this it was possible to deduce: (a) that in tension, the effect of combined static and cyclic loading conforms to the expected pattern, (b) that the fatigue design limits of the material in water are less than in air for tests at the same frequency, as was expected, and (c) that a further reduction in limits is required in wet environments at low frequencies, relative to those at 1 Hz. Implications for BS4994, the principal GRP design code, are discussed.

Dynamic solution of distribution planning in intermediate time range

The time-phase mode of the long-range distribution planning model introduced in a recent publication by the authors (1985) is applied to an actual distribution system. The model incorporates an accurate formulation of the continuous nonlinear cost function. Once the load-time variation in the area under consideration is known, the model takes into account the different types of costs (fixed costs, variable costs, and the cost of energy losses) for all planned facilities (substations and feeders), and then either the optimum construction or expansion of the system is obtained to satisfy the network operational and security constraints. A realistic utility example is used to compare the dynamic and the static solutions. >