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In this study, soybean straw (SS) as a promising source of glycolaldehyde-rich bio-oil production and extraction was investigated. Proximate and ultimate analysis of SS was performed to examine the feasibility and suitability of SS for thermochemical conversion design. The effect of the co-catalyst (CaCl2 + ash) on glycolaldehyde concentration (%) was examined. Thermogravimetric-Fourier-transform infrared (TG-FTIR) analysis was applied to optimize the pyrolysis temperature and biomass-to-catalyst ratio for glycolaldehyde-rich bio-oil production. By TG-FTIR analysis, the highest glycolaldehyde concentration of 8.57% was obtained at 500 °C without the catalyst, while 12.76 and 13.56% were obtained with the catalyst at 500 °C for a 1:6 ratio of SS-to-CaCl2 and a 1:4 ratio of SS-to-ash, respectively. Meanwhile, the highest glycolaldehyde concentrations (%) determined by gas chromatography–mass spectrometry (GC–MS) analysis for bio-oils produced at 500 °C (without the catalyst), a 1:6 ratio of SS-to-CaCl2, and a 1:4 ratio of SS-to-ash were found to be 11.3, 17.1, and 16.8%, respectively. These outcomes were fully consistent with the TG-FTIR results. Moreover, the effect of temperature on product distribution was investigated, and the highest bio-oil yield was achieved at 500 °C as 56.1%. This research work aims to develop an environment-friendly extraction technique involving aqueous-based imitation for glycolaldehyde extraction with 23.6% yield. Meanwhile, proton nuclear magnetic resonance (1H NMR) analysis was used to confirm the purity of the extracted glycolaldehyde, which was found as 91%.

Power grid pattern is expected to evolve from generator-based power systems towards converter-based systems in the forthcoming decades. Therefore, grid-forming converters will be pertinent to interconnected power grids in pursuance of enhancement their resilience against disturbances. This paper introduces a new efficient damping control method for grid-forming converters that provides a smooth power modulation and an efficient damping response against frequency and voltage deviations. First, an averaged state-space representation for a grid forming application in dq synchronization frame is derived. Based on this model, a new hybrid damping controller, including the concept of state feedback control and PI control, is proposed to address the main issues in existing controllers. The state feedback controller is optimally designed using a linear-quadratic regulator (LQR) approach to optimize the system performance. Moreover, the PI controller is optimally designed using the pattern search algorithm. The proposed damping control method integrates optimally between the control loops through a mapping matrix to rapidly synchronize with the grid and efficiently damp the oscillations. Simulations are carried out to prove the proposed method robustness. Finally, a comparative study using controller hardware-in-the-loop (CHiL) is employed against conventional system to validate the proposed damping method.

A second-order generalized integrator (SOGI) is a resonant regulator with a pair of complex-conjugate poles, and therefore, with infinite magnitude at its center frequency. Thanks to this property, one can put together a set of m SOGIs in an elegant way and decompose a single-phase signal into its constituent frequency components and detect their amplitude and phase angle. Such a configuration, which is often referred to as the multi-SOGI (MSOGI) structure, requires a frequency estimator to adapt the center frequency of SOGIs to frequency changes. This frequency estimation is often provided by interconnecting the MSOGI structure with a basic frequency-locked loop (FLL) or phase-locked loop (PLL). The resulting structures are known as the MSOGI-FLL and MSOGI-PLL. These structures and their close variants are mathematically difficult to analyze probably because of the lack of a linear model for these systems. This article aims to bridge this research gap. First, it is shown how linear time-periodic (LTP) models of the MSOGI-FLL and MSOGI-PLL can be obtained. The model verification, obtaining open-loop harmonic transfer function from the LTP model, and LTP stability assessment of MSOGI-based synchronization systems are the next parts of this article. Finally, some close variants of the MSOGI-FLL/PLL are considered and their modeling and stability assessment are briefly discussed.

With the increased installation of voltage source converters (VSCs) into the power grid, concerns about resonance/stability issues associated with interactions among converters, and between them and the ac grid is growing. The prevailing method for investigating these issues is the impedance modeling of VSCs, which involves linearizing all their control elements, such as their current control and grid synchronization system among others. In this process, most often a phase-locked loop (PLL) is considered for the grid synchronization of VSCs in the literature. The available options for the grid synchronization, however, are not limited to PLLs; a large number of frequency-locked loops (FLLs) for the grid synchronization of VSCs may also be found in the literature. The impedance modeling of three-phase VSCs equipped with FLL-based grid synchronization systems can be quite challenging as FLLs have different structures compared to PLLs. This article aims to address this difficulty. The general idea is obtaining the PLL counterparts of FLLs, which makes the VSC impedance modeling very straightforward. To make this idea clear, several case studies are presented and investigated.

Biomass is one of the key components for bioenergy generation in recent epoch as traditional resources and depleting swiftly. Going through this fact, the present study aims to appraise the feasibility of Holy Thistle (HT) to produce energy and valuable organic chemicals through pyrolysis. The HT was pyrolyzed at four heating rates including, 10, 20, 30, and 40 °C min−1 to perform thermo kinetic modeling and estimate thermodynamics parameters to establish the pyrolysis reaction process. The pyrolysis process of HT illustrated about 85–88 % of thermal degradation achieved through three different stages from 30 to 800 °C. The major degradation stage was observed from 170 to 450 °C with 55% to 60 % product formation from mainly cellulose and hemicelluloses components. Moreover, the average activation energy and pre-exponential factors demonstrated to be 183–184 kJ mol−1 and 1010 min−1 to 1025 min−1, respectively. The pyrolytic products exhibited agreement to the cleaner production of bio-gas, char and bio-oil which is evident for the potential and productivity of the feed combination.

Microgrid is one of the promising green transition technologies that will provide enormous benefit to the seaport, as a solution to the major concerns in this sector, namely energy crisis, economical and environmental pollution. However, finest design of the microgrid is a challenging task considering different objectives, constraints and uncertainties involved. To ensure the optimal operation of the system, determining the right configuration framework and size for each component in the seaport microgrid at the minimum cost is a vital decision at the design stage. This paper aims to design a hybrid system of seaport microgrid with optimally sized component .The selected case study is the Port of Aalborg, Denmark. The proposed grid-connected structure consists of renewable energy sources (photovoltaic system and wind turbines), an energy storage system and cold ironing as seaport’ loads. The architecture is then optimized by utilizing HOMER to meet the maximum load demand by considering a few parameters such as solar global horizontal irradiance, temperature and wind resources. Then, the best configuration framework is analyzed in terms of economic feasibility, energy reliability and environmental impact.

This paper presents a comprehensive study that aims to establish the meaningful range for the ratios of full-bridge cells to the total number of cells per arm, in which the performance of the mixed cells modular multilevel converter (MC-MMC) can be customized by trading the number of FB cells for high value features such as: resiliency to DC faults, reduced capital costs of DC circuit breakers (DCCBs) and running costs of the semiconductor, and continued operation. The MC-MMC design for particular ratio of FB cells to total number of cells per arm to achieve tailored features at system level is termed as an customized modular multilevel converter (CMMC). The primary motivation for the CMMC is to facilitate the use of low-cost and relative slow mechanical DC circuit breakers, with fault isolation times in the order of 8 ms to 12.5 ms. With these objectives to be achieved, interruption of power flows across the DC grid and surrounding AC grids must be minimized. It has been found that after certain ratios of FB cells to total cells per arm, the CMMC starts to exhibit current limiting mode, which helps to reduce DCCBs current breaking capacities and extend critical fault clearance times for remote converters from the fault point. Results of the pole-to-ground and pole-to-pole DC faults, semiconductor loss studies, and extended control range indicate that the presented CMMC is promising for future realization of DC grids.

The introduction of a decentralized energy system in remote rural areas with limited or no access to power supply can improve the quality of life of people living in these areas. Renewable energy technology can play a key role in electricity generation, as grid expansion is not a cost-effective option. In this study, we focused on the techno-economic feasibility and optimal design of a hybrid micro-hydro-photovoltaic-diesel-battery-wind power system designed to electrify a typical remote village located in the southern part of Nigeria. We aimed at achieving the electrification at minimal cost while taking into cognizance the constraints of environmental pollutant emission. In this study, the technical details, as well as the economic feasibility of setting up such a power system, were determined using the hybrid optimization of multiple energy resources (HOMER) simulation tool. Different combinations of energy resources including solar, wind, hydro, and diesel were compared and analyzed. The system performance and economics using some determinant factors such as the cost of energy, operation, and maintenance cost, net present cost, excess electricity, capacity shortage, generator fuel consumption rates, and cost, load fulfillment, and CO2 and other pollutant gas emission savings were determined. The experimental results and the comparative analysis revealed that a hybrid hydro/PV/wind/diesel/battery system was the most ideal and preferred option for off-grid rural electrification. The simulation results also indicated that the optimal system had a net present cost (NPC) and cost of energy (COE) of $1.01 m and $0.106/kWh, respectively, with a renewable fraction of 77.4% and environmental pollutant emission of 228,945 kg/year. This system was found to be environmentally friendly as it emitted the least pollutant gas among all the considered configurations. Bearing in mind the recent advocacy towards the actualization of Sustainable Development Goal (SDG) number 7, this work was found to be in alignment with the tenet of “Affordable and Clean Energy”.

Most photovoltaic (PV) plants conduct operation and maintenance (O&amp, M) by periodical inspection and cleaning. Such O&amp, M is costly and inefficient. It fails to detect system faults in time, thus causing heavy loss. To ensure their operations are at an ideal state, this work proposes an unsupervised method for intelligent performance evaluation and data-driven fault detection, which enables engineers to check PV panels in time and implement timely maintenance. It classifies monitoring data into three subsets: ideal period A, transition period S, and downturn period B. Based on A and B datasets, we build two non-continuous regression prediction models, which are based on a tree ensemble algorithm and then modified to fit the non-continuous characteristic of PV data. We compare real-time measured power with both upper and lower reference baselines derived from two predictive models. By calculating their threshold ranges, the proposed method achieves the instantaneous performance monitoring of PV power generation and provides failure identification and O&amp, M suggestions to engineers. It has been assessed on a 6.95 MW PV plant. Its evaluation results indicate that it is able to accurately determine different functioning states and detect both direct and indirect faults in a PV system, thereby achieving intelligent data-driven maintenance.

The dc component, which may be caused by different factors in the grid voltage, is one of the disturbances that may severely affect the performance of grid synchronization systems and, therefore, grid-tied power converters. In the phase-locked loop (PLL) and frequency-locked loop (FLL)-based grid synchronization systems, which this article focuses on, some solutions to deal with this challenge have been proposed in the literature. One of the best available solutions is adding dc rejection/estimation loop(s) to a standard PLL and FLL structure. This approach provides an estimation of the dc component and, at the same time, makes the PLL and FLL immune to disturbance effects of the dc component. Despite their implementation simplicity, no linear model for the grid synchronization systems with the dc rejection/estimation capability has yet been presented. The main aim of this article is to fill this research gap. It will be shown that developing such models facilitates the examination and the performance enhancement of the grid synchronization systems under study.

In practice, because of different factors, the supply voltage (especially in the distribution level) almost always has some degrees of imbalance and harmonic pollution. With increasing the level of these power quality issues in recent years, their monitoring and compensation using custom power devices have received much attention. In addition, modern power converter based renewable energy sources are expected to provide some ancillary services to mitigate these power quality issues. These tasks and requirements often involve using a signal processing tool for the online detection of the fundamental sequence components and harmonics of the voltage and/or current signals. The typical choice for this purpose is the discrete Fourier transform as it offers a fast computational speed. It, however, may not be a very attractive solution for applications where the selective extraction of a few frequency components is required as it demands a high computational effort. In such scenarios, using time-domain signal decomposition algorithms is more desirable. Generally speaking, these algorithms are nonlinear feedback control systems, which include two or more dynamically interactive frequency-Adaptive filters tuned to concerned frequency components. The complex structure of these algorithms, however, makes them complicated to analyze, especially for those who are not experienced in this field. This article aims to address this difficulty by developing harmonic models for these algorithms and investigating them. To this end, three case studies are considered. Through a harmonic linearization procedure, developing harmonic models for them is shown. The accuracy of these models is then investigated, and performing the harmonic stability analysis using them is demonstrated.

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.

Recent advances in using renewable energy resources make them more accessible and prevalent in microgrids (MGs) and nano grids (NGs) applications. Accordingly, much attention has been paid during the past few years to design and operate MGs with high renewable energy sources (RESs) penetration. Energy storage (ES) is the crucial enabler for reliable MG operation to help MGs become more resistant to disruptions, particularly with the increased penetration of RESs. In this regard, this paper formulates a two-stage optimization framework to improve a grid-connected MG performance. Firstly, the optimal allocation decisions of the battery ES systems (BESSs) are provided to enhance the self-consumption rate of the RESs and the hosting capacity (HC) of the MG. Secondly, an operation strategy with the results (number, location, and capacity) of the BESSs obtained from the first stage is handled as an objective function to minimize the MG&rsquo, s total operation cost. The IEEE 33-bus radial system is modified to act as the MG with high RESs penetration. The problem is solved using a recent swarm intelligence optimization algorithm called the Harris hawks optimization (HHO) algorithm. The proposed optimal operation strategy considers numerous constraints, such as the charge-discharge balance, number and capacity limitations of the BESSs, and the different technical performance constraints of the MG. The results obtained verify the proposed optimization framework&rsquo, s effectiveness for grid-connected MGs and validate the benefits gained from the appropriate allocation of BESSs. The results also indicate that oversized storage or using many unneeded storage units may adversely influence the MG&rsquo, s total power losses.

This paper proposes an enhanced energy management system (EEMS) for a residential AC microgrid. The renewable energy-based AC microgrid with hybrid energy storage is broken down into three distinct parts: a photovoltaic (PV) array as a green energy source, a battery (BT) and a supercapacitor (SC) as a hybrid energy storage system (HESS), and apartments and electric vehicles, given that the system is for residential areas. The developed EEMS ensures the optimal use of the PV arrays’ production, aiming to decrease electricity bills while reducing fast power changes in the battery, which increases the reliability of the system, since the battery undergoes fewer charging/discharging cycles. The proposed EEMS is a hybrid control strategy, which is composed of two stages: a state machine (SM) control to ensure the optimal operation of the battery, and an operating mode (OM) for the best operation of the SC. The obtained results show that the EEMS successfully involves SC during fast load and PV generation changes by decreasing the number of BT charging/discharging cycles, which significantly increases the system’s life span. Moreover, power loss is decreased during passing clouds phases by decreasing the power error between the extracted power by the sources and the required equivalent; the improvement in efficiency reaches 9.5%.

This paper proposes an enhanced modular multilevel converter as an alternative to the conventional half-bridge modular multilevel converter that employs a reduced number of medium-voltage cells, with the aim of improving waveforms quality in its AC and DC sides. Each enhanced modular multilevel converter arm consists of high-voltage and low-voltage chain-links. The enhanced modular multilevel converter uses the high-voltage chain-links based on medium-voltage half-bridge cells to synthesize the fundamental voltage using nearest level modulation. Although the low-voltage chain-links filter out the voltage harmonics from the voltage generated by the high-voltage chain-links, which are rough and stepped approximations of the fundamental voltage, the enhanced modular multilevel converter uses the nested multilevel concept to dramatically increase the number of voltage levels per phase compared to half-bridge modular multilevel converter. The aforementioned improvements are achieved at the cost of a small increase in semiconductor losses. Detailed simulations conducted in EMPT-RV and experimental results confirm the validity of the proposed converter.

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&ndash, integral (PI) controller is adopted to regulate the DC-link voltage. The instantaneous reactive power theory is employed for the reference current&rsquo, 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.

The SOGI-FLL (Second-Order Generalized Integrator&ndash, Frequency-Locked Loop) is a well-known and simple adaptive filter that allows for estimating the parameters of grid voltage with a small computational burden. However, the SOGI-FLL has been shown to be especially sensitive to voltage sags and voltage swells, which deeply distort the estimated parameters, especially the frequency. This problem can be alleviated by simply using a saturation block at the Frequency-Locked Loop (FLL) output to limit the impact of distortion on the estimated frequency. Improving upon this straightforward approach, in this paper we propose the use of a finite state machine (FSM) for the definition of the different states of the SOGI-FLL frequency response during a voltage sag or swell fault. The FSM approach allows for applying different gains during the fault, enhancing the SOGI-FLL transient response. The performance of the FSM-based SOGI-FLL is evaluated by using simulation results, which show a better and faster response to these kinds of faults.

All-pass filter (APF) passes all frequency components of a signal without altering their amplitude, but changes their phase. This feature has made the APF a versatile building block in different signal processing applications. The focus of this article is on APF-based phase-locked loops (PLLs), where the APF is required for creating a $\text{90}^\circ$ phase shift at the fundamental frequency. Such a phase shift is needed for generating a fictitious orthogonal signal in single-phase applications and rejecting the grid voltage imbalance in three-phase systems. To the best of authors’ knowledge, none of the APF-based PLLs have an accurate model yet. This gap in knowledge makes the analysis of these synchronization systems and identifying their advantages/disadvantages compared to state-of-the-art structures complicated. The main objective of this article is to bridge this knowledge gap.

Frequency-locked loops (FLLs) create a rather large category of closed-loop synchronization techniques, which have received considerable attention in different engineering applications, particularly for synchronization, signal processing, and control purposes. Focusing on single-phase grid applications, designing FLLs is often based on a second-order generalized integrator (SOGI), and the SOGI-FLL is regarded as a standard structure. Using the linear Kalman filter (LKF), complex bandpass filter (CBF), and circular limit-cycle oscillator (CLO) are some alternative approaches. FLLs based on these filters/elements, which are briefly referred to as the LKF-FLL, $1\phi$-CBF-FLL, and CLO-FLL, have not been well analyzed in the literature, and limited knowledge about their real advantages/disadvantages compared to the SOGI-FLL exists. Covering this gap is the objective of this paper.

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.

This paper proposes a critical analysis of the literature addressed to modelling and simulations of human crowds with the aim of selecting the most appropriate scale out of the microscopic (individual based), mesoscopic (kinetic), and macroscopic (hydrodynamical) approaches. The selection is made focusing on possible applications of the model. In particular, model validation and safety problems, where validation consists of studying the ability of models to depict empirical data and observed emerging behaviors. The contents of the paper look forward to computational applications related to the flow crowds on the Jamarat bridge.

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.

The average active and reactive powers, P and Q, are crucial parameters that have to be calculated when sharing common loads between parallelized droop-operated single-phase inverters. However, the droop method algorithm should employ low-pass filters (LPF) with very low cut-off frequency to minimize the distortion impact in the provide droop amplitude and frequency references. This situation forces the droop control to operate at a very low dynamic velocity, degrading the stability of the parallelized system. For this reason, different solutions had been proposed in literature to increase the droop velocity, but the issues derived from the sharing of nonlinear loads had not been properly considered. This work proposes a novel method to calculate P and Q based on the fundamental components of the inverter's output voltage and current and using the measured phase angle between the output voltage and current. The method is used under normal and highly distorting conditions due to the sharing non-linear loads. The fundamental components are obtained by means of the highly filtering capability provided by norder cascaded second order generalized integrators (nSOGI). The proposed method leads to faster and more accurate P and Q calculations that enhances the droop-method dynamic performance. Simulations are provided to validate the proposal.

The quadrature signal generation based phase-locked loops (QSG-PLLs) are highly popular for synchronization purposes in single-phase systems. The main difference among these PLLs often lies in the technique they use for creating the fictitious quadrature component. One of the easiest QSG approaches is delaying the original single-phase signal by a quarter of a cycle. The PLL with such QSG technique is often called the transfer delay based PLL (TD-PLL). The TD-PLL benefits from a simple structure, rather fast dynamic response, and a good detection accuracy when the grid frequency is at its nominal value, but it suffers from a phase offset error and double frequency oscillatory error in the estimated phase and frequency in the presence of frequency drifts. In this paper, a simple yet effective approach to remove the aforementioned errors of the TD-PLL is proposed. The resultant PLL structure is called the adaptive TD-PLL (ATD-PLL). The stability of the ATD-PLL is evaluated by the derivation of its small-signal model. Parameter design guidelines are also presented. Finally, the effectiveness of the ATD-PLL is confirmed using numerical results.

Bi3.25La0.75Ti3O12 thin film was prepared on p-type silicon substrate by sol-gel spin coating method. The film indicates a ferroelectric behavior with a remanent polarization of similar to 18.2 mu C/cm(2). Electronic parameters such as ideality factor and barrier height of the diode were calculated to be 3.80 and 0.75 eV, respectively. The photocurrent results in the reverse bias of the diode indicate that photocurrent under illumination is higher than the dark current. The diode exhibited a substantial visible-light photovoltaic effect. The capacitance-voltage and conductance-voltage measurements were carried out in the frequency range of 10 kHz-1 MHz. The observed decrease in the capacitance and increase in the conductance with the increasing frequency were explained on the basis of interface states. The interface states density of the structure was determined using Hill-Coleman method and observed to decrease with increasing frequency. The obtained results indicate that ferroelectric Bi3.25La0.75Ti3O12/P-type silicon junction is a new class of photoconductive devices with low-cost fabrication and high photoresponsivity. (C) 2014 Published by Elsevier B.V.

Designing an effective phase-locked loop (PLL) for three-phase applications is the objective of this paper. The designed PLL structure is able to provide an accurate estimation of the grid voltage frequency and the phase, even in the presence of all harmonic components of both positive and negative sequences and the dc offset in its input. In addition to offering a high disturbance rejection capability, the suggested PLL structure has a fast transient response and provides a settling time of around two cycles of the fundamental frequency. The effectiveness of the suggested PLL structure is confirmed using numerical results.

The performance of Dual-Axis Solar Tracker (DAST) and Static Solar System (SSS) with respect to clearness index in Malaysia is presented. An attempt to investigate the correlation between clearness index with energy gain and efficiency of DAST over SSS is being done experimentally. A good correlation could not be found out from the daily clearness index. It is due to the more profound advantage of DAST in the morning and evening compared to midday as it is able to follow the sun’s position. Hence, the daily clearness index is divided into three segments which are morning, midday, and evening to interpret the energy gain and efficiency better. A clearer correlation with low standard deviation can be observed on the segmented clearness index analysis. The energy gain and efficiency of seven cities in Malaysia is being estimated with the segmented clearness index and compared to the result generated from anisotropic radiation model. A similar trend is obtained and it has shown that the segmented clearness index could be utilized as a graphical method for estimation of energy gain and efficiency of DAST over SSS.