Showing 6 results for Askari
F. Askarian, Dr. S.m. Razavizadeh, Dr. F. Haddadi,
Volume 11, Issue 4 (December 2015)
Abstract
In this channel,we study rate region of a Gaussian two-way diamond channel which operates in half-duplex mode. In this channel, two transceiver (TR) nodes exchange their messages with the help of two relay nodes. We consider a special case of the Gaussian two-way diamond channels which is called Compute-and-Forward Multiple Access Channel (CF-MAC). In the CF-MAC, the TR nodes transmit their messages to the relay nodes which are followed by a simultaneous communication from the relay nodes to the TRs. Adopting rate splitting method in the terminal encoders and then using Compute-and-Forward (CF) relaying and decoding the sum of messages at the relay nodes, an achievable rate region for this channel is obtained. To this end, we use a superposition coding based on lattice codes. Using numerical results, we show that our proposed scheme has better performance than other similar methods and achieves a tighter gap to the outer bound.
M. Kamali, F. Sheikholeslam, J. Askari,
Volume 13, Issue 2 (June 2017)
Abstract
In this paper, a robust adaptive actuator failure compensation control scheme is proposed for a class of multi input multi output linear systems with unknown time-varying state delay and in the presence of unknown actuator failures and external disturbance. The adaptive controller structure is designed based on the SPR-Lyapunov approach to achieve the control objective under the specific assumptions and the SDU factorization method of the high frequency gain matrix is employed to drive the suitable form of the error equation. The two component controller structure with an integral term is used in order to compensate the effect of unknown state delay and external disturbance. Using a suitable Lyapunov-Krasovskii functional, it is shown that despite existing external disturbance and actuator failures, all closed loop signals are bounded and the plant Output asymptotically tracks the output of a stable reference model. Simulation results are provided to demonstrate the effectiveness of the proposed theoretical results.
S. R. Hosseini, M. Karrari, H. Askarian Abyaneh,
Volume 15, Issue 4 (December 2019)
Abstract
This paper presents a novel impedance-based approach for out-of-step (OOS) protection of a synchronous generator. The most popular and commonly used approaches for detecting OOS conditions are based on the measurement of positive sequence impedance at relay location. However, FACTS devices change the measured impedance value and thus disrupt the performance of impedance-based relay function. In this paper, the performance of synchronous generator OOS protection function connected to the transmission line in the presence of a static synchronous compensator (STATCOM) is investigated. Moreover, an analytical adaptive approach is used to eliminate the effect of STATCOM. This approach requires only the remote bus voltage and current phasors to be sent to the relay location via a communication channel. Simulation results show that STATCOM changes impedance trajectory and causes the incorrect operation of OOS relay. Furthermore, the proposed approach corrects the relay mal-operation and improves the accuracy of OOS impedance-based function when the STATCOM is used in the system.
S. R. Hosseini, M. Karrari, H. Askarian Abyaneh,
Volume 17, Issue 1 (March 2021)
Abstract
In this paper, a novel approach based on the Thévenin tracing is presented to modified conventional impedance-based out-of-step (OOS) protection. In conventional approach, the OOS detection is done by measuring positive sequence impedance. However, the measured impedance may be change due to different factors such as capacitor bank switching and reactive power compensators that it can cause the relay to malfunction. In this paper, first, an on-line Thévenin equivalent (TE) approach based on the recursive least square (RLS) is presented. Then, a protection function is developed based on online network Thévenin equivalent parameters to correct the measured impedance path. The main feature of this method is the use of local voltage and current measurements for Thévenin equivalent estimation and OOS protection. The performance of the proposed method is investigated by simulation of synchronous generator OOS protection function in the presence of a static synchronous compensator (STATCOM). The simulation results show that, STATCOM changes the impedance path and can cause the incorrect diagnosis of OOS relay. Furthermore, the proposed method corrects the impedance path and improves the accuracy of OOS impedance-based function when the STATCOM is installed in system.
F. Askari, A. Khoshkholgh,
Volume 17, Issue 2 (June 2021)
Abstract
The battery of electric vehicles (EV) can be charged from the power grid or discharged back to it. Parking lots can aggregate hundreds of EVs which makes them a significant and flexible load/generation component in the grid. In a smart grid environment, the smart parking lot (SPL) can benefit from the situation of the simultaneous connection to the EVs and power grid. This paper proposes a new algorithm to maximize SPL profit from participation in the forward and spot markets. Monte-Carlo simulation is used to determine the participation of the SPL in the forward market. Then an economic model is proposed to optimize the charging or discharging time table of EVs at any hours of a day and SPL participation in the spot market in a way that maximum SPL profit and satisfaction of EV owners can be gained. The Genetic Algorithm (GA) is used to solve this optimization problem.
Kaveh Askari, Soolmaz Abbasalizadeh,
Volume 22, Issue 3 (September 2026)
Abstract
This paper proposes a new one-cell single-port microstrip bandpass filter (BPF) named the main cell, which consists of a band-pass section connected with one band-stop section at the input port. Considering the main cell, this paper provides a new two-cell two-port BPF with quasi-reflectionless behavior at its input and output ports. This two-cell two-port BPF is constructed with three sections of a series bandpass filter at the center and two shunt-connected bandstop filters at the input and output ports. Moreover, this paper analyzes the BPF’s S-parameters and, to the best of the authors’ knowledge, derives its formulas in a closed form, for the first time. Furthermore, to the best of the authors’ knowledge, this paper presents a novel approach for determining the filter’s cut-off frequency by utilizing the derived S-parameters. This paper compares the calculated results with the simulated to evaluate the analysis. In addition, this paper proposes a three-cell two-port BPF to increase the out-of-band attenuation loss. Finally, this paper manufactures the two-cell and three-cell BPFs on an FR-4 substrate to evaluate the efficiency of the presented concepts. The comparisons between the electromagnetic simulation and the measurement results have good agreements with each other. The measurement results of the three-cell two-port BPF show a center frequency of 2.6 GHz, a bandwidth of 0.27 GHz, and a minimum in-band insertion loss of -3 dB. Also, the fabricated filter has an in-band return loss lower than -8 dB over the entire bandwidth and a stopband attenuation level better than 50 dB.
