Power systems
Mehrdad Manshor; Mahmood Joorabian; Afshin Lashkarara
Abstract
Power management in microgrids is a major challenge due to its low total inertia and capacity. The lower the microgrid generation capacity is, the higher the share of each generation unit in total power will be, and the higher the frequency deviation in less time will be when an outage occurs. So, preventive ...
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Power management in microgrids is a major challenge due to its low total inertia and capacity. The lower the microgrid generation capacity is, the higher the share of each generation unit in total power will be, and the higher the frequency deviation in less time will be when an outage occurs. So, preventive actions can be more reasonable and affordable than corrective actions for microgrid power and frequency control. In this regard, a new primary frequency response-constrained unit commitment model is presented here to prevent excessive frequency deviations by more commitment of higher inertia power plants and more contribution of renewable energy resources or energy storage systems’ fast inertia response. To have a mixed-integer linear programming model, the primary frequency response constraints are linearized. The model is solved by the combination of two commercial solvers named MOSEK and YALMIP in the MATLAB 2018 environment. The proposed model is examined on a real isolated microgrid (an island). The results show that by activating the primary frequency support of distributed energy resources, the power can be managed with lower costs because there will be less need to start up fast (and expensive) gas turbine generation units. In addition, although comparing the model with others shows the more expensive management procedure, better frequency stability is obtained in contingencies.
Power systems
Shervin Bikdeli; Mohammad Farshad
Abstract
Developments in power systems like the installation of new generation resources and interconnections may increase short-circuit current levels and consequently, impose additional costs of replacing circuit breakers and equipment. In these cases, one of the best methods to reduce short-circuit currents ...
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Developments in power systems like the installation of new generation resources and interconnections may increase short-circuit current levels and consequently, impose additional costs of replacing circuit breakers and equipment. In these cases, one of the best methods to reduce short-circuit currents in power systems and avoid significant replacement costs is to use fault current limiters (FCLs). This paper suggests a new method for optimally locating and sizing FCLs using an imperialist competitive algorithm (ICA). The ICA finds the optimal locations and sizes of FCLs such that not only are short-circuit currents reduced, but the size of the installed FCLs is also minimized, and the system reliability is increased. Indeed, three indices including the short-circuit level, the economic cost of FCLs, and the lost power are integrated into an objective function with a new formulation. The results obtained from multiple executions of the suggested procedure for the 39-bus New England benchmark system confirm that the formulation of indices in the objective function is suitable and the indices can be prioritized easily. Also, the results indicate that the ICA can find the optimal locations and sizes of FCLs with good convergence and accuracy considering the specified objectives and priorities.
Power systems
Sanaz Ghanbari; Hamdi Abdi
Abstract
The advent of DG and SEGs has led to fundamental changes in various fields of power system operation. The current paper is aimed to investigate the reliability of SEGs considering DGRs based on the self-healing concept. Due to the emergence of new uncertainties in the power system resulted from the presence ...
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The advent of DG and SEGs has led to fundamental changes in various fields of power system operation. The current paper is aimed to investigate the reliability of SEGs considering DGRs based on the self-healing concept. Due to the emergence of new uncertainties in the power system resulted from the presence of DGRs, this paper is dedicated to comparing network reliability indices before and after the entry of DGRs and analyzing their effect on improving network reliability. To do so, improving the indices based on customer satisfaction, such as reducing the SAIFI, and SAIDI, is evaluated. More specifically, the improvement of the most important index based on load and energy, namely energy not supplied (ENS), is investigated. To do this, the MCS method is used given the pdf of the samples due to the presence of uncertainty created by the presence of DGRs, demanded load change and network restoration time after the presence of DG. Also, after providing an appropriate model for problem analysis, results of applying this model to the case study system are investigated using reliability indices. Subsequently, in order to improve performance of the system, impacts of the changes of various parameters on the given indices are reported. One of the most important points in this regard is to investigate the impacts of the changes in the system configuration on the results. It is observed that self-healing positively affects the reduction of the electrical energy restoration time as well as the system reliability.
Power systems
Ali Karimabadi; Mohammad Ebrahim Hajiabadi; Ebadollah Kamyab; Ali Asghar Shojaei
Abstract
Over the recent years, a number of new maintenances methods for high voltage substations have been introduced to reduce the number of substation events. The primary purpose of the present study is to presents a Cost-benefit analysis for Circuit-Breakers (CBS) in a substation equipped with Condition Monitoring ...
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Over the recent years, a number of new maintenances methods for high voltage substations have been introduced to reduce the number of substation events. The primary purpose of the present study is to presents a Cost-benefit analysis for Circuit-Breakers (CBS) in a substation equipped with Condition Monitoring (CM) devices. To this end, a mathematical formulation to categorize and model equipment failures based on their severity is developed. By CM, some of severity failures, named major failures, can be detected early, and corrected as the minor failure. This formulation quantifies the effect of CM devices on the outage rate and Predictive Maintenance (PDM) rate of the equipment. The PDM rate is used to modify the Markov maintenance model for the equipment. The proposed modified Markov model quantifies the effect of CM on the maintenance costs and lifetime of CB. The New Markov model is compared with the Preventive Maintenance (PM) model. Expected Energy Not Supply (EENS) and reliability Cost are calculated with and without CM on CBs. Finally, the proposed model is applied on the CBs of 400/132/20KV substation in the Khorasan Regional Electricity Company (KREC) in Iran. The obtained results show that CM on CBs of substations improves the EENS and reliability cost by 82.43 %. Moreover, the maintenance cost of the proposed model shows an improvement of 9.07 % compared to PM model. Finally, the total annual costs show an improvement of 80.67% due to CM on CBs.
Industrial Electronics
Mahdi Radmehr; Mohammad Mojibi
Abstract
Reliability consideration is always important among the manufacturers of power modules and converters. Before using of power electronic converters into the related application, it is necessary to predict its reliability over time. In the meanwhile, the power loss and heat generated within the power semiconductors ...
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Reliability consideration is always important among the manufacturers of power modules and converters. Before using of power electronic converters into the related application, it is necessary to predict its reliability over time. In the meanwhile, the power loss and heat generated within the power semiconductors play a key role in the lifespan of the whole system. In this paper, a method for assessing the reliability of a step-down DC-DC converter is employed based on the thermal modeling of power semiconductors. As is evident from the used reliability approach, the junction temperature of power semiconductors – diodes and insulated-gate bipolar transistors (IGBTs) – is the most influential factor on the lifetime of power converters. Therefore, the simultaneous influence of switching frequency and duty cycle is analyzed at the same time as a factor for evaluating reliability. A cut-off of 150°C is considered for the maximum allowable junction temperature for the examined IGBT power module. The results show that a failure can be expected after 46,000 hours of operation of the considered power converter. Additionally, 3D curves are presented to illustrate the influence of duty cycle and switching frequency on the reliability of circuit’s components and the overall system. The obtained results confirmed that an increase in switching frequency from 1 kHz to 10 kHz can decrease the circuit’s lifetime almost 22%.
