Majlesi Journal of Energy Management
Volume:4 Issue: 2, Jun 2015

Increasing the share of wind energy in supplying load demand of power grid has created new challenges in the field of power system stability. So that, the stable operation of each units of wind power producer on interaction with grid could be affected by power system instability. Among them we can mention the phenomenon of voltage instability in power system which eventually will lead to voltage collapse if stability controls are not applied. In this paper the impact of reactive power control on improvement of SCIG-based wind farms operation has been studied. With regard to the asynchronous operation of induction machine, the increment of wind power generation will be possible only by absorption of more reactive power. Increasing in the power reactive consumption of induction generator leads to reduction of voltage in point of common connection (PCC) which the wind farm connects to the grid. Ultimately, this process in lack of proper reactive power control can be lead to instability in whole of power system. The conducted studies in this paper are in framework of quasi-static time-domain simulations (QSTDS) and continuation power flow (CPF) algorithm. The results indicate with increment of wind power penetration in power system if the proper support of reactive power is not used, the stable performance of the wind farm will be threatened and caused to over speed of SCIGs. Another task done in this paper is the employment of SVC and STATCOM as a practical solution in improvement of wind farms-based power system stability.

Elictric power utilities are facing with high infrastructure costs to supply the increasing demand of customers. Demand side management has a beneficial role to help the utilities overcome this problem. This program, among the various demand side management programs, studies the impact of interruptible load and load shifting program on the distribution transformer lifetime. The programs are performed on a 1600KVA transformer of the distribution network in Rasht city, with three industrial customers and some residential customer. To assess the impact of demend side management on the transformer lifetime, the aging is acalculated with the basic load curve and the modified load curves by DSM programs and the results are compared.

Applications of Distributed Generation (DG) are taken into account more seriously due to the growth of cities, ever-increasing demand for electrical energy, and economic constraints affecting the installation of new substations and power plants. Distributed Generation unlike centralized electrical generation aims to generate electrical energy on small scale as near as possible to the load centers, interchanging electric power with the network. The installation of DG units at non-optimal places can result in an increase in system losses, implying in an increase in costs and, therefore, having an effect opposite to the desired. On the other hand, presence of the DG in a radial distribution network, in which all the currents are flowed from the source to the consumers, may this pure radial nature is lost. Thus the protection of distribution networks becomes a challenging task due to the change in the fault current levels and direction. Therefore the Optimal distributed generation sizing and placement, also negative effects of the DG on the protection system of the distribution network will be reviewed in this paper.

Optimal reactive power dispatch (ORPD) is a multi-variable problem with nonlinear constraints and continuous/discrete variables. Due to the stochastic behavior of loads, the ORPD requires a probabilistic mathematical model. In this paper, Monte Carlo simulation (MCS) is used for modeling of load uncertainties. Multi objective (MO) model is used for this aim. The objective functions of the proposed MO-ORPD are the real power losses and voltage stability (L-index). Since these two objectives are conflicted, the MO-ORPD problem is solved by weighted sum method. The problem is solved by considering bus voltage limits, the limits of branches power flow; transformers’ tap changers and the amount of reactive power compensation at weak buses. The optimization models are implemented and solved in GAMS environment and the proposed method is examined on IEEE 14–bus test system. The obtained results illustrate the effectiveness of the proposed MO-ORPD problem for dealing with uncertainties of loads.

One of the most important parts of the reliability study of power systems are transmit and ultra-transmit substations. Aim of this paper is to calculate the reliability of high voltage substations considering kinds of busbar that was used in the substations. The main objective of this article is to simplify the reliability inputs, electrical parameters and load information. In this simplification, it is assumed that time of a variable repair was random and repair time is usually so small that it can be neglected in anywhere of time hence to reliability analysis is corrected by removing the repair time and availability, and non-availability can be obtained in each point of feeder using simple methods of probability and set theory.

One of the most important challenging task of doubly fed induction generator (DFIG) is performance under island conditions. Voltage drop caused grid fault occurrence increase stator current and, due to magnetic couple between stator and rotor, it induces the same current in the rotor. The excessive current can increase voltage of DC link and damage used power electronic converter. This paper investigates transient behavior of a DFIG in a 9MW wind plant with 10m/s fixed wind speed, during symmetrical three phase short circuit using d-q vector control method in MATLAB environmental. Simulation results show proposed control method improves frequency and voltage characteristics of microgrid in islanding mode by individual control of produced active/reactive power of generator.

Smart Grid’s foundation is accorded to the development of innovation power technology as in two-way communication, smart control of grid’s conditions and particularly modern consumers’ penetration. Electric vehicles’ Presence in this new field of power (PEV, PHEV), in spite of its ability for energy storage and energy regain usage, obviation of energy demands for electric vehicles owners in 24 hours of a day is a challenge. In this article, Scenario arranging of electric vehicle similar to fact, is analyzed via focus on the relation between minimum energy demand, presence of electric vehicles during a day and technical specifications of relatives. That used for the simulation of the smart grid, this scenario has been illustrated on a 33- bus power system.