Simulation and evaluation of HERIC and H5 transformerless inverter topologies

Most of the inverters have an isolation transformer which prevents or limits fault current between AC and DC circuits under most fault conditions. If the transformer is excluded from the system, it would increase the PV system efficiency and decrease the size of its installations, which will lead to a lower cost for the whole investment. Thus, elimination of the transformer has to be considered carefully because a galvanic connection appears between the PV arrays and the ground in the absence of an isolation transformer. The galvanic connection causes the stray capacitance between the PV arrays structure and the ground to produce a leakage current. In this paper, a review of full bridge topology with bipolar and unipolar scheme and half bridge topology carried out in regard leakage current.in addition, HERIC and H5 topologies are simulated and leakage current in these topologies are evaluated.

Fault detection and diagnosis of induction motors using motor current signature analysis and a hybrid FMM-CART model

In this paper, a novel approach to detect and classify comprehensive fault conditions of induction motors using a hybrid fuzzy min-max (FMM) neural network and classification and regression tree (CART) is proposed. The hybrid model, known as FMM-CART, exploits the advantages of both FMM and CART for undertaking data classification and rule extraction problems. A series of real experiments is conducted, whereby the motor current signature analysis method is applied to form a database comprising stator current signatures under different motor conditions. The signal harmonics from the power spectral density are extracted as discriminative input features for fault detection and classification with FMM-CART. A comprehensive list of induction motor fault conditions, viz., broken rotor bars, unbalanced voltages, stator winding faults, and eccentricity problems, has been successfully classified using FMM-CART with good accuracy rates. The results are comparable, if not better, than those reported in the literature. Useful explanatory rules in the form of a decision tree are also elicited from FMM-CART to analyze and understand different fault conditions of induction motors.

The tax treatment of employee stock options : generous to a fault

In the 2000 budgets, both the federal and Ontario governments introduced changes to the tax treatment of employee stock options for the explicit purpose of making their tax treatment in Canada similar to or more favourable than that in the United States. The federal budget added a deferral, similar to that currently applicable to options granted by Canadian-controlled private corporations, for up to $100,000 per year of public company stock options. The Ontario budget introduced an exemption from tax for employees involved in research and development on the first $100,000 per year of employee benefits arising on the exercise of qualified stock options or on eligible capital gains arising from the sale of shares acquired by the exercise of eligible stock options. These proposals reflect the apparent acceptance by the two governments that there is a “brain drain” from Canada to the United States of knowledge workers in the “new” economy and that reductions in Canadian taxes should stem this drain. In the author’s view, the tax treatment of employee stock options, even without these changes, is overly generous. Both the federal and provincial proposals ignore the fact that most employee stock options are taxed more favourably in Canada than in the United States in any event. In particular, most employee stock option benefits in Canada are taxed at capital gains tax rates, whereas in the United States most are taxed at full rates. While the US Internal Revenue Code does provide capital gains tax treatment for certain employee stock option benefits, a number of preconditions must be met. Most important, the shares acquired pursuant to the options must be held for a minimum of one year after the option is exercised. In addition, there are monetary limits on the amount of options that qualify for capital gains treatment. In Canada, there are generally no holding period requirements or monetary limits that apply in order for the option holder to benefit from capital gains tax rates. Empirical evidence indicates that the vast majority of employees in the United States exercise their options and immediately sell the shares acquired. These “cashless exercises” do not benefit from capital gains treatment in the United States, whereas similar cashless exercises in Canada generally do. This empirical evidence suggests not only that the 2000 budget proposals are unwarranted, but also that the existing treatment of employee stock options in Canada is already more generous than that in the United States. This article begins with a theoretical “benchmark” for the taxation of employee stock options. The author suggests that employee stock options should be treated in the same manner as other income from employment. In theory, the value of the benefit should be included in income when the option is granted or vests. However, owing to the practical difficulty of valuing employee stock options, the theoretical benchmark proposed is that the value of the benefit (the difference between the fair market value of the shares acquired and the strike price under the option) be taxed when the shares are acquired, and the employer be entitled to a corresponding deduction. The employee stock option rules in Canada and the United States are then compared and contrasted with each other and the benchmark treatment. The article then examines the arguments that have been made for favourable treatment of employee stock options. Included in this critique is a review of the recent empirical work on the Canadian brain drain. Empirical studies suggest that the brain drain—if it exists at all—is small and that, despite what many newspapers and right-wing think-tanks would have us believe, lower taxes in the United States are not the cause. One study, concluding that taxes do have an effect on migration, suggests that even if Canada adopted a tax system identical to that in the United States, the brain drain would be reduced by a mere 10 percent. Indeed, even if Canada eliminated income tax altogether, it would not stop the brain drain. If governments here want to spend money in order to stem the brain drain, they should focus on other areas. For example, Canada produces fewer university graduates in the fields of mathematics, sciences, and engineering than any other G7 country except Italy. The short supply of university graduates in these fields, the apparent loss of top-calibre academics to US
universities, and the consequent lower levels of university research in these areas (an important spawning ground for new ideas in the “new” knowledge-based economy) suggest that Canada may be better served by devoting more resources to its university institutions, particularly in post-graduate programs, rather than continuing the current trend of budget cuts that universities have endured and may further endure if taxes are reduced.
As far as employee stock options are concerned, if Canada does want to look to the United States for guidance on tax reform (which it seems to do with increasing frequency of late), it should adopt the US rules applicable to nonstatutory options, which are close to the proposed benchmark treatment. In the absence of preferential tax treatment, employee stock options would still be included in compensation packages provided that there were sound business reasons for their use. No persuasive evidence has been put forward that the use of stock options, in the absence of tax incentives, is suboptimal. Indeed, the US experience suggests quite the opposite.

Application of the fuzzy min-max neural network to fault detection and diagnosis of induction motors

In this paper, an application of the motor current signature analysis (MCSA) method and the fuzzy min–max (FMM) neural network to detection and classification of induction motor faults is described. The finite element method is employed to generate simulated data pertaining to changes in the stator current signatures under different motor conditions. The MCSA method is then used to process the stator current signatures. Specifically, the power spectral density is employed to extract harmonics features for fault detection and classification with the FMM network. Various types of induction motor faults, which include stator winding faults and eccentricity problems, under different load conditions are experimented. The results are analyzed and compared with those from other methods. The outcomes indicate that the proposed technique is effective for fault detection and diagnosis of induction motors under different conditions.

Characteristics evaluation of an LMI-synthesis H∞ controller for a superconducting magnetic energy systems applied in power systems

© 2015 IEEE.This paper presents an H« controller synthesised based on linear matrix inequalities (LMI) for a current source converter based superconducting magnetic energy systems (SMESs) connected to a node of power systems where the regulation of grid current has considered as a control objective. To facilitate the control design, the system is represented in terms of state space realization with uncertainties. The control design involves selecting proper weighting functions and performing LMI-synthesis. The controller order is reduced by Henkel-norm method. Simulations are carried out to evaluate the characteristics of the controller under parametric uncertainties. It is found out that the proposed controller is inherently stable, possesses significantly small tracking error, and preserves robust performance for the SMES.