Due to the threat posed by fossil fuels to human existence; many countries around the world have turned attention to renewable sources for power generation to reduce the emission of greenhouse gases and stop ozone layer depletion. This has increased the exploitation of various renewable energy sources which include: hydro, biomass, solar, geothermal and wind in many developed countries. However, most African countries seem not to have awakened to this new reality. This work presents a comprehensive review of available renewable energy capacity in Nigeria, the level of utilization of renewables in Nigeria in comparison to other countries, comparison of renewable energy scenarios among African countries, factors hindering the development of renewables in Nigeria, the country’s renewable energy policy and ways of improving its status in the country. A lot of peer-reviewed journal articles, and grey literatures were gathered from which the most suitable ones were selected for reviews. In addition, opinions of people across the country and beyond, regarding renewable energy status in Nigeria were sought through a questionnaire. It is found that Nigeria is greatly endowed with different renewable energy sources but the level of utilization has been very low due to a myriad of factors such as non-implementation of renewable energy policies, financial issues, unfavorable government policies and lack of adequate research. It is expected that the findings in this work will awaken policies makers in Nigeria to reshape her renewable energy policies and speed up its implementation as well as guide individuals wishing to invest in the nation’s vast renewable resources.
Due to the rising trends in the adoption of smart systems such as smart grids, smart homes, and vehicle-to-grid, there has been a lot of research interest in these areas. To manage these complex systems effectively and intelligently, a reliable, high-speed, and secure data communication network is very essential. The key distinguishing feature between smart systems and traditional ones is that smart systems use a two-way communication system while traditional systems usually use one-way communication. The requirements and techniques needed to ensure safe, secure, and reliable communication in smart systems have been the focus of many researchers in recent times. This work is aimed at providing a comprehensive, all-encompassing, up-to-date review of smart systems communication to ascertain the research directions as well as challenges. This review will guide other researchers in delving into smart systems communication to identify potential research problems and future research directions or research gaps.
A robust high-speed sliding mode control (SMC) of three phase permanent magnet synchronous motor (PMSM) is presented. The SMC served for inner speed control while a simplified hysteresis current control (HCC) scheme was used in the outer current control to generate gating signals for the inverter switches. The present research leverages on the ability of SMC to directly access system speed error which it attempts driving to zero by cancelling modelling uncertainties and disturbances. Performance comparison was done for the SMC model and an existing model having classical PI controller. With the initial positive speed command of 200 rpm at 5 Nm constant loading, rotor speed with SMC neatly settled to the reference speed at 0.085 seconds without overshoot while the rotor speed of the model with PI controller settled at 0.217 seconds after overshoot. This translates to 155.3% speed enhancement. Similar superior speed performance of the SMC was also observed during recovering from sudden speed reversal. While the SMC model recovered and settled to the reference speed of -200 rpm at 0.369 seconds, the model with PI controller settled at 0.482 seconds. From the results, it can be seen that SMC demonstared superiority over the conventioanl PI controller for complex drives systems.
<span lang="EN-US">This work presents a novel direct torque and flux control (DTFC) of permanent magnet synchronous motor (PMSM) with analytically-tuned proportional integral (PI) controllers. The proportional (K_p) and integral (K_i) gains of the PI controllers were accurately determined, from first principle, using the model of the control system. The PI flux and torque controllers were then developed in rotor reference frame. The designed PI controllers, together with the torque and flux controllers, were tested on a permanent magnet synchronous motor (PMSM). The results obtained were compared with results from conventional DTFC system using manually-tuned PI controllers. The total harmonic distortion (THD) of motor phase currents is 18.80% and 4.81% for the conventional and proposed models respectively. This confirms a significant reduction in torque ripples. The control system was tested for step torque loading and found to offer excellent performance both during load changes, speed reversal, and constant load conditions.</span>
<p>Automatic voltage regulator (AVR) is used at each generating station or synchronous generators to maintain voltage supply at steady state or at a constant value otherwise the performance of the generator will be affected. The combination of AVR system with controllers clears fluctuation due to variation in load, speed, temperature, and power factor. This causes deviation in generator’s voltage and damage to power equipment. This work presents performance enhancement of AVR system using Proportional Integral and Derivative (PID) with pre-filter control technique. The enhanced performance was achieved by designing a nonlinear model of a synchronous generator, a PID controller and a low pass filter or pre-filter using MATLAB/Simulink model. The introduction of the proposed PID controller with LPF at load variation of 20 seconds, reduces the rise time and the peak time to 5.2975 seconds and 12.31 seconds respectively. This increases the overshoot and the settling time to 4.28 seconds and 17.60 seconds. However, the developed scheme provides a stable time response performance for various desired generator voltages considered. The performance of the proposed scheme was compared with conventional PID controlled AVR system without LPF. The proposed scheme provides more stability as indicated by the percentage overshoot, which is 4.5788% (for PID) and 4.2765% (for PID with prefilter). This has contributed to knowledge an AVR control system with better performance in terms of rise time, peak time, overshoot and settling time for stabilized generator output voltage.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.