S. V. Kulkarni

Placement and Penetration of Distributed Generation under Standard Market Design

Distributed Generation (DG) can help in reducing the cost of electricity to the costumer, relieve network congestion and provide environmentally friendly energy close to load centers. Its capacity is also scalable and it provides voltage support at distribution level. Hence, DG placement and penetration level is an important problem for both the utility and DG owner. The cost of electricity as a commodity depends upon market model. The restructured power markets are slowly maturing with standardizations like Standard Market Design (SMD). The key feature of SMD is the Locational Marginal Pricing (LMP) scheme. This paper examines placement and penetration level of the DGs under the SMD framework. The proposed approach is illustrated by case studies on MATPOWER 30 bus and IEEE 118 bus systems.

Evaluation of configuration plans for DGs in developing countries using advanced planning techniques

Many developing countries have emphasis on distributed generation (DG) technology for their generation expansion planning. The planning considerations and judicious choice of attributes are dictated by prevailing conditions. The attributes considered are capital costs, energy not served per annum, and profits from injecting power into the grid at peak load, all of which are important for a developing country. The uncertain futures considered are three possible loading conditions, which can be low, medium and high. Different scenarios (plans) are generated by various combinations of configurations. DGs can be configured as stand-alone mode, hybrid operation, or micro-grid formation with or without grid connection. With the increased complexities in DG planning options along with the multiple attributes to be accounted, more sophisticated techniques other than conventional economic analysis are needed to arrive at correct decisions by decision makers. The analytical hierarchy process (AHP) is used for obtaining relative weights in an objective way. Further, the statistical method like interval-based multi-attribute decision making with tradeoff analysis is used for shortlisting the feasible plans and identifying the most appropriate plan. It is proposed to use the weights obtained from AHP for finding the performance efficiencies in data envelopment analysis (DEA) for evaluating the plans. A new composite utility function is proposed to resolve cases where performance efficiency is insufficient for evaluation in DEA application. The sample system is derived with reference to a rural electrification scheme in India. The assessment of plans is presented and discussed. The comparative strengths and weaknesses of the methods are reported on the basis of the results obtained.

Analysis of Short-Circuit Performance of Split-Winding Transformer Using Coupled Field-Circuit Approach

Summary form only given. The split-winding arrangement requires special short circuit design considerations. During short circuit conditions, there is a considerable distortion of the leakage field, which in turn produces high axial short circuit forces. This paper deals with the computation and analysis of electromagnetic forces in windings of split-winding transformers. A nonlinear-transient field-circuit coupled finite element model is used to simulate the split-winding transformer. A 70 MVA, 3-phase, 220/6.9/6.9 kV split-winding transformer is modeled under pre-set and post-set short circuit test conditions. Under the pre-set condition, the transformer is analysed with one as well as both the LV windings short-circuited to compare the axial forces produced in the windings for these two cases. The results show that there is a considerable rise in the axial forces when one winding is short circuited as compared with the case when both windings are short-circuited. The effect of initial magnetization of core on axial short-circuit forces is calculated and discussed. It is also shown that even though post-set method eliminates inrush related problems there is not much respite in short circuit forces.

Optimal sizing of distributed generators in microgrid

Hybrid optimization model for electric renewables (HOMER), developed by National Renewable Energy Laboratory (NREL), enables economic analysis for single source and hybrid distributed energy resources (DERs). However, current version of HOMER does not support microgrid analysis. In this paper, economic analyzer for distributed energy resources (EADER) is developed. It finds minimum cost of energy (COE) and optimal mix of DERs with multiple sources and sinks. In addition to single source distributed generator (DG) and hybrid DG, EADER is also capable to analyze microgrid. EADER results are validated for single source DG and hybrid DG with results obtained from HOMER for the same systems. Further, a sample practical system from Western Maharashtra, India, is analyzed using EADER. The results which consider all practical constraints are presented and discussed

Stray loss evaluation in power transformers-a review

Survey of current research papers reveals the continued interest in application of advanced techniques for accurate estimation and control of stray losses in transformers. This paper gives an overview of research, development and application of various computational tools for stray loss analysis, based on over 50 published papers. All landmark papers are systematically classified. Practicality of application of methods by transformer designers is discussed. The report concludes with critical comments on efficacy of all approaches and directions for pursuing further research.

Applications of coupled field formulations to electrical machinery

Purpose – This paper aims to give a perspective about the variety of techniques which are available and are being further developed in the area of coupled field formulations, with selective bibliography and practical examples, to help postgraduate students, researchers and designers working in design or analysis of electrical machinery.Design/methodology/approach – This paper reviews the recent trends in coupled field formulations. The use of these formulations for designing and non‐destructive testing of electrical machinery is described, followed by their classifications, solutions and applications. Their advantages and shortcomings are discussed.Findings – The paper gives an overview of research, development and applications of coupled field formulations for electrical machinery based on more than 160 references. All landmark papers are classified. Practical engineering case studies are given which illustrate wide applicability of coupled field formulations.Research limitations/implications – Problems ...

Evaluation of flitch plate losses in power transformers

Summary form only given as follows. Although eddy current losses in pitch plates of large power transformers may form a small part of total transformer losses, they are important because they can appear concentrated in a small area and cause hazardous hot-spots. An analytical method to calculate pitch plate eddy loss is a very useful practical guide to a transformer designer, but for high power transformers, a more accurate analysis by techniques such as the finite element method (FEM) is desirable. A series of 2-D FEM simulations, using a statistical technique-orthogonal array design of experiments, have been carried out to find the effect of various factors on the losses in a mild steel pitch plate. The procedure for carrying out the experiments and the results obtained thereof are presented. The more involved analysis of slotted pitch plates, has been done using 3-D FEM. Loss and eddy current patterns in mild steel and stainless steel pitch plates have been studied. In both cases, the effect of the number of slots and slot length on the losses is discussed. Effect of slots on eddy current pattern is explained, Results of simulation of laminated pitch plate are presented. The eddy loss distribution obtained by 3-D FEM electromagnetic analysis is used in 3-D FEM thermal analysis to estimate temperature rise of the pitch plate. Verification of 3-D FEM analysis has been done by measurement of temperatures on a slotted mild steel pitch plate of a 33 MVA, single phase, 220/132/11 kV auto-transformer. The estimated temperatures have been found to be in good agreement with that obtained by measurements.

Numerical modeling of electromagnetic welding

Feasibility of electromagnetic welding of flat sheets is ascertained by comparing the minimum impact velocities determined by using software ANSYS/EMAG and ABAQUS with the required minimum velocity obtained from analytical considerations. Magnetic forces acting on the sheets are computed from ANSYS/EMAG simulations. The velocity of impact and the pressure profile acting on the sheets are found from ABAQUS simulations. A criterion for weld formation is subsequently arrived at based on the simulations, which is further validated using experimental results. The reasons for no-weld zone in Al-to-Al EM weld and complete metal continuity (absence of no-weld zone) in Al-to-SS EM weld have been analyzed based on the numerical and experimental results.

Three-phase load flow methods for radial distribution networks

A distribution system has certain distinguishing features which make it different and somewhat difficult to analyze as compared to a transmission system. Unbalanced loads, untransposed lines, single-phase and two-phase laterals are some of them. The distribution system needs to be analyzed on the three-phase basis instead of the single-phase basis. Hence, the three-phase load flow for the distribution system is significantly different from the conventional load flow for the transmission system. In this paper, various load flow methods for distribution systems are reviewed. These methods are applied on a sample 8-bus system. The results are reported. The performance of these methods is compared for various parameters.

Hysteresis modeling of the grain-oriented laminations with inclusion of crystalline and textured structure in a modified Jiles-Atherton model

Grain-oriented (GO) laminations owing to their crystalline and textured structure exhibit strong anisotropy in magnetic characteristics. GO laminations generally display highly steep, gooseneck, and narrow waist rolling direction (RD) hysteresis loops and complex-shaped transverse direction (TD) curves. The original Jiles-Atherton (JA) model needs improvisation while modeling such characteristics. The paper proposes a modified JA model for the hysteresis modeling of GO laminations with consideration of their crystalline and textured structure. The model is based on single crystal approximation of polycrystalline materials and modifies the anhysteretic magnetization on account of anisotropic energy. It takes into account the domain wall motion as well as domain magnetization rotation. The model provides a better prediction of RD hysteresis loops and also shows ability to characterize of TD hysteresis loops with reasonable accuracy. The model preserves simplicity of the original JA model.