In power distribution systems, with their great vastness and various outage causes, one of the most important problems of power distribution companies is to select a suitable maintenance strategy of system elements and method of financial planning for the maintenance of system elements with the two objectives of decrease in outage costs and improvement of system reliability. In this article, a practical method is introduced for the selection of a suitable system elements maintenance strategy; moreover, to plan the preventive maintenance budget for the system elements, two methods are offered: the cost optimization method and the fuzzy Analytic Hierarchy Process (AHP) method. In the former method, a new model of system maintenance cost is offered. This model, based on system outage information, the elements maintenance costs are determined as functions of system reliability indices and preventive maintenance budget. The latter method, too, a new guideline is introduced for considering the cost and reliability criteria in the trend of preventive maintenance budget planning. In this method, the preventive maintenance budget for the elements is determined based on relative priority of elements with reliability criteria. © 2015 Wiley Periodicals, Inc. Complexity 21: 70–88, 2016

In this study, a novel approach for dynamic modeling and closed-loop control of hybrid grid-connected renewable energy system with multi-input multi-output (MIMO) controller is proposed. The studied converter includes two parallel DC-DC boost converters, which are connected into the power grid through a single-phase H-bridge inverter. The proposed MIMO controller is developed for maximum power point tracking of photovoltaic (PV)/fuel-cell (FC) input power sources and output power control of the grid-connected DC-AC inverter. Considering circuit topology of the system, a unique MIMO model is proposed for the analysis of the entire system. A unique model of the system includes all of the circuit state variables in DC-DC and DC-AC converters. In fact, from the viewpoint of closed-loop controller design, the hybrid grid-connected energy system is an MIMO system. The control inputs of the system are duty cycles of the DC-DC boost converters and the amplitude modulation index of DC-AC inverters. Furthermore, the control outputs are the output power of the PV/FC input power sources as well as AC power injected into the power grid. After the development of the unique model for the entire system, a decoupling network is introduced for system input-output linearization due to inherent connection of the control outputs with all of the system inputs. Considering the decoupled model and small signal linearization, the required linear controllers are designed to adjust the outputs. Finally, to evaluate the accuracy and effectiveness of the designed controllers, the PV/FC based grid-connected system is simulated using the MATLAB/Simulink toolbox. Index Terms--Multi-input multi-output (MIMO) converter, maximum power point tracking, grid-connected inverter, conversion function matrix.

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Reactive power, generated during connection of lag/lead phase loads to a system, circulates between the generation sector and the load side. This power has undesirable effects, including occupation of transmission capacity, generation capacity, increasing transmission line active losses and finally reduction of power quality and load reliability due to active power deficiency. In this paper, non-electrical description and definition of reactive power and a marked difference with active power is presented. Also the effect of reactive power mitigation using a capacitor bank is investigated. For educational purposes of teaching compensation advantages to undergraduate students the well-known software MATLAB-Simulink was used to simulate and investigate the effects of reactive power mitigation.

This paper proposes a model to allocate photovoltaic unit (PVU) and distribution static compensator (DSTATCOM) that incorporate the operation effect of PVU in sizing and sitting problem. The model is based on the dynamic assessment of PVU production and the effect of it on placement of PVU and DSTATCOM. Geographical conditions are interfered in placement problem of PVU and DSTATCOM simultaneously. The model is verified in a multi-objective form. The multi-objective problem is formulated based on voltage stability, liability, power loss and total cost of PVU and DSTATCOM. This problem is solved by employing optimization technique and the results of optimization processes are tested in different scenarios. Uncertainty in network loads is an inevitable task that should be considered in network planning. Uncertainty in the presented model has been defined as a set of divided parts in the presented model. The proposed model has been evaluated on two test system, 33-bus and 69-bus. The obtained results indicate that the presented model can be employed to study the intermittent behavior of PVU in placement problem.