The second-order-generalized-integrator-based freq-uency-locked loop (SOGI-FLL) is a well-known tool for filtering and synchronization purposes in the power and energy applications. The SOGI-FLL, nevertheless, has a limited ability in rejecting the grid voltage disturbances. To deal with this problem, two advanced SOGI-FLLs have been proposed recently. In the first one, a SOGI-based filter is included inside the standard SOGI-FLL control loop, and in the second one, a SOGI-based filter is employed as the prefiltering stage of the SOGI-FLL. The small-signal modeling, tuning procedure, and detailed performance comparison of these advanced SOGI-FLLs have not been carried out yet. The aim of this paper is to cover these issues.

The increasing demands for reducing greenhouse emissions and improving fuel efficiency of marine transportation have presented opportunities for electric ships. Due to the complexity of multiple power resources coordination, varied propulsion loads, changeable economical, and environmental requirements, power/energy management system (PMS/EMS) becomes essential in both designing and operational processes. The existing literature on PMS/EMS can be categorized into rule-based and optimization-based approaches. Compared to the rule-based PMS/EMS, which relies heavily on human expertise, as well as predefined strategies and priorities, the optimization-based approaches can offer more efficient solutions and are more widely used nowadays. This article provides a comprehensive review of the marine optimization-based power/energy management system and discusses the future trends of PMS/EMS in ship power systems.

This paper presents a techno-economic feasibility evaluation for a grid-connected photovoltaic energy conversion system on the rooftop of a typical residential building in Jeddah, one of the major cities in Saudi Arabia. In Saudi Arabia, electric energy consumption is the highest in the domestic sector, with 48.1% of the total electricity consumption. As the power generation in Saudi Arabia mainly relies on conventional resources, environmental pollution and energy sustainability are major concerns. To minimize these issues, the Saudi government is in the process of maximizing the utilization of renewable energy resources for power generation. Investing in solar energy in Saudi Arabia is important because the country is witnessing a rapid increase in load demand, with annual growth rates of 6%. In this paper, the system advisor model software for renewable energy modeling has been utilized to perform a techno-economic feasibility analysis of a residential grid-connected solar photovoltaic (PV) system, which is proposed for a typical apartment in Saudi Arabia, on the basis of various key performance indicators, namely: yield factor, capacity factor, performance ratio, levelized cost of energy, net present value, internal rate of return, and payback period. A sensitivity analysis that investigates the impact of varying techno-economic parameters on system performance and feasibility is also discussed. The size of the PV system for a typical Saudi Arabian apartment is estimated to be 12.25 kW. Results have shown that the proposed system can generate 87% of the electricity needs of an apartment. The technical analysis showed that the capacity factor and the performance ratio were 22% and 78% respectively. The levelized cost of energy and net present value revealed competitive figures of 0.0382 $/kWh and $4378, respectively. The investigations indicate that residential PV installations are an effective option for energy management in the country.

The design of reliable power filters that mitigate current and voltage harmonics to meet the power quality requirements of the utility grid is a major requirement of present-day power systems. In this paper, a detailed systematic approach to design a shunt active power filter (SAPF) for power quality enhancement is discussed. A proportional–integral (PI) controller is adopted to regulate the DC-link voltage. The instantaneous reactive power theory is employed for the reference current’s extraction. Hysteresis current control is used to obtain the gate pulses that control the voltage source inverter (VSI) switches. The detailed SAPF is developed and simulated for balanced nonlinear loads and unbalanced nonlinear loads using MATLAB/Simulink. The simulation results indicate that the proposed filter can minimize the harmonic distortion to a level below that deployed by the Institute of Electrical and Electronics Engineers (IEEE) standards.

Contrary to the phase-locked loop (PLL), which has almost reached a mature stage of development in power and energy applications (particularly in three-phase systems), the frequency-locked loop (FLL) is not a mature technique yet. This is probably because of the implementation of FLLs in the stationary reference frame, which makes their modeling, tuning, and performance enhancement more complicated than PLLs. The aim of this paper is conducting a research on three-phase FLLs. Providing a review of recent advances, introducing the concept of inloop filters for designing more advanced FLLs, demonstrating the FLL modeling and tuning in the presence of an inloop filter, analyzing the advantages and disadvantages of using an inloop filter in the FLL structure, and establishing a connection between FLLs and PLLs are the main parts of this research.

In recent years, single-phase frequency-locked loops (FLLs) are gaining more popularity as a signal processing and synchronization tool in a wide variety of engineering applications. In the power and energy area, a basic structure in designing the majority of available single-phase FLLs is the second-order generalized integrator-based FLL (SOGI-FLL), which is a nonlinear feedback control system. This nonlinearity makes the SOGI-FLL analysis complicated. To deal with this problem, some attempts to derive linear models for the SOGI-FLL have been made in very recent years. The available linear models, however, are not able to accurately predict the dynamic behavior, stability region, and robustness metrics of the SOGI-FLL. The situation is even worse for close variants of the SOGI-FLL because some of them have no linear model at all. Filling these gaps in research is the main goal of this article. To this end, the structural relationship among the SOGI-FLL and its variants is identified first. Based on this information and deriving the linear time-periodic (LTP) model of a recently proposed extended SOGI-FLL, the LTP models of the standard SOGI-FLL and its close variants are obtained. The accuracy assessment of these LTP models, discussion about their limitations, and performing the stability analysis using them are other contributions of this article.