نشریه مهندسی برق
سال چهل و پنجم شماره 1 (پیاپی 71، بهار 1394)

Adaptive notch filter is a well-known approach for frequency estimation and extraction of sinusoidal signals. The structure of ANF is composed of a second order band-pass filter (BPF) (and its complementary notch filter) and a frequency update law that continuously adjusts the center frequency of the BPF. The performance of the ANF degrades when the sinusoidal input is polluted by some harmonics. In this paper، a method has been proposed to improve the performance of the ANF in the presence of harmonics. The proposed method is based on the use of a window function in the frequency update law. Window functions have extensively been used in some algorithms like discrete Fourier transform and phase-locked loop to provide better estimation of the parameters of sinusoidal signal in the presence of harmonics. It was shown that using a rectangular window enhances the ANF performance.

In Smart grids, how to manage the energy stored in the smart parking can lead to a variety of service for improvement the network status in both active and reactive power provisions. On the other hand, increasing the use of distributed generation sources like wind power plants, makes solving their problems (specially in the transient state) be very important issues in the reactive power provision of the smart grids. Therefore, in order to improve the efficiency of SmartParks, the selection of an appropriate and robust controller for various network conditions is very important. In this paper, a sliding mode controller is proposed to control the SmartPark on the provision of reactive power. The improvement of the voltage profile and also the improvement of the wind power performance in the transient condition is investigated by using the proposed control method. The proposed control method, is simulated on the standard IEEE-9 Bus network and productivity of smartParks in the reactive power provision is studied. simulation results show the desired goals can be achieved in natural condition of the network and show the robustness of SmartParks in the both transient state and in the parameter changing of the network.

Partial Discharge is one of the main causes of premature aging of electrical machines insulations, which are using power electronic drives. An appropriate model can prepare a better recognition of influences of different parameters on partial discharge behavior. Partial discharge has been modeled with different kind of methods, but no one modeled this phenomena under pulses of power electronic devices. In this paper, modeling of partial discharge using Finite Element Method (FEM) in order to calculate electric field is presented. Accordingly, COMSOL MultiphysicsTM 3.5a software is used to calculate electric field with FEM which is connected simultaneously to MATLAB software to implement the proposed algorithm. The influence of different parameters such as, rise time of each surges, the high repetition rate of PWM pulses and the amount of overshoots of each pulses on behavior of partial discharge is examined.

Nowadays the role and impact of renewable energy resources (RER) penetration in power system operation and scheduling is increased dramatically. Because of intermittent and probabilistic behavior of RER power and uncertainty in RER output power, unit commitment (UC) at the presence of RER is a more complicated optimization problem. This paper proposes an innovative and effective modeling procedure based on modification of the Harmony Search Algorithm (HSA) to solve the UC in power systems with and without RER. The proposed algorithm is easy in application compared to the other heuristic methods and has a high capability in reaching to optimal solution with reasonable time. The proposed method is tested on 10 units test system for base case and modification to new test case including wind and solar power plant. To preserve the general structure of economic dispatch equation, the wind and solar power plant operating cost is modeled with a quadratic equation similar to thermal units. Simulations were done for daily units scheduling. Numerical results show the lower operating cost for 10 units system at the presence of RER. The efficiency and improvement of the solution in cost and execution time compared to the results of the other powerful heuristic algorithms is compared.

In this paper, the results of providing and implementation of the state estimation (SE) program and also input/output required information has been presented for the first time in North-West dispatching center of the country. The SE program has been written based on weighted least square (WLS) in the MATLAB software and is able to estimate amplitudes and phase angles of all 132kV, 230kV and 400kV power stations voltages in North-West region of country, every instant. Moreover, in order to convert the measured information and identify the close/open status of the power stations circuit breakers, a special program was written in the C++ software. This program delivers the mentioned information in a desired order to the SE program, in each program execution cycle. Output of the proposed SE program provides two options for the experts and operators of the dispatching center. In the first option, output of SE program can be used in the form of a special monitoring system unsig Bitmap figures without using any other programs. While for the second option, SE program output is imported to the well-known DIgSILENT software using a special input script data file, which can be presented with the DIgSILENT software and used for the other of power network calculations.

Within the next years, energy demand at the residential sector has been increased as a result of economic developments. On the other hand, intelligent and programmable household appliances and smart metering have been widely used. This paper proposes an energy management system for residential consumer to minimize its electricity cost. A framework is presented to determine i) the optimal operation and scheduling of household appliances; ii) charging/discharging cycles of battery storage and plug-in hybrid electric vehicles; and iii) optimal operation of distributed resources renewable (small wind turbines and photoVoltaic systems). The smart home is connected to the grid and the power consumption can be balanced by exchanging the electricity between them at real time pricing. The problem is formulated as a mixed integer linear programming (MILP) and solved by commercial software (GAMS). A realistic case study is presented to verify the efficiency and usefulness of the developed models.