Publications

Analysis of incremental LMS adaptive algorithm over wireless sensor networks with delayed-links

Abstract

Wireless sensor networks (WSN) are used for many delay-sensitive applications, e.g. military surveillance, emergency response, city management, etc. Therefore, modeling of delay is very important. This paper presents a study of the impact of sensors' sensing delay, process delay and transmission delay in the estimation of the desired unknown parameter in the WSN. Recently proposed wireless sensor networks, in the literature, assume perfect nodes and links, in view of delay. It means that no consideration has been made about the delay in the sensing, processing and, transmission procedures. The proposed method in this paper analyzes the behavior of the distributed incremental estimation algorithm in the presence of delay in wireless sensor networks. Weighted spatio-temporal energy conservation method is used to evaluate the transient and steady state behavior of the wireless sensor networks with delay without putting any restriction on regressor's distribution. The equations that illustrate mean square deviation (MSD), excess mean square error (EMSE) and mean square error (MSE) behavior of individual nodes, are driven. Also, simulations show that overall delay could be calculated to turn off nodes in some iterations without affecting the performance of the distributed estimation algorithm or adding extra latency to the network, which can improve power management strategies by modifying sleep-wake scheduling protocols. Eventually, it is shown that simulation results have a good match with derived theoretical expressions.

Authors:

AmirAslan Haghrah - Mohammad Ali Tinati - Tohid Yousefi Rezaii

A Voltage Equalizer Circuit to Reduce Partial Shading Effect in Photovoltaic String

Abstract

Partial shading is one of the main causes in reducing the output power of photovoltaic (PV) systems. This paper proposes a circuit to recover the energy of shaded PV modules during partial shading condition (PSC). The proposed circuit, which is a combination of a buck–boost converter and the switched-capacitor (BBSC) circuits, equalizes the voltage of PV modules and prevents bypass diodes from bypassing the shaded modules in a string. Hence, shaded PV modules can have a contribution in output generated power instead of being bypassed. The main features of the BBSC are the utilization of the reduced number of switches in comparison with buck–boost and switched-capacitor circuits, a simple switching control strategy, and fast voltage equalization. In addition, a BBSC circuit is almost a lossless circuit during uniform shading conditions. To validate the effectiveness of the proposed BBSC circuit, both simulation results in PSCAD/EMTDC software and experimental results are presented.

Authors:
Majid TahmasbiFard - Mehrdad TarafdarHagh - Saman Pourpayam - AmirAslan Haghrah