Showing papers by "Juan C. Vasquez published in 2021"

Standard SOGI-FLL and Its Close Variants: Precise Modeling in LTP Framework and Determining Stability Region/Robustness Metrics

Abstract: 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.

Energy management system optimization in islanded microgrids: An overview and future trends

Abstract: Islanded microgrids (IMGs) provide a promising solution for reliable and environmentally friendly energy supply to remote areas and off-grid systems. However, the operation management of IMGs is a complex task including the coordination of a variety of distributed energy resources and loads with an intermittent nature in an efficient, stable, reliable, robust, resilient, and self-sufficient manner. In this regard, the energy management system (EMS) of IMGs has been attracting considerable attention during the last years, especially from the economic and emissions point of view. This paper provides an in-depth overview of the EMS optimization problem of IMGs by systematically analyzing the most representative studies. According to the state-of-the-art, the optimization of energy management of IMGs has six main aspects, including framework, time-frame, uncertainty handling approach, optimizer, objective function, and constraints. Each of these aspects is discussed in detail and an up-to-date overview of the existing EMSs for IMGs and future trends is provided. The future trends include the need for improved models, advanced data analytic and forecasting techniques, performance assessment of real-time EMSs in the whole MG’s control hierarchy, fully effective decentralized EMSs, improved communication and cyber security systems, and validations under real conditions. Besides, a comprehensive overview of the widely-used heuristic optimization methods and their application in EMSs of IMGs as well as their advantages and disadvantages are given. It is hoped that this study presents a solid starting point for future researches to improve the EMS of IMGs.

Large-Signal Stability Improvement of DC-DC Converters in DC Microgrid

Abstract: In DC microgrids, constant power loads (CPLs) reduce the effective damping of the DC-DC converter and may induce destabilizing effects into the DC-DC converter. To overcome such problems regarding CPL and ensure large-signal stability of DC-DC converters in DC microgrids, some feedforward terms are added to $V$ - $I$ droop-based dual-loop controller for a DC-DC converter based on the large-signal model. It is proven that the feedforward terms can not only improve the transient response but also guarantee the exponential stability of the closed-loop system in the whole operating range in regards to a large-signal manner, which is verified by using a singular perturbation model. Moreover, a disturbance observer is designed to estimate the output current, thereby enabling the removal of the current measurement sensor. The proposed technique can be easily plugged into a pre-defined $V$ - $I$ droop-based dual-loop controller without an additional sensor being required. Ultimately, both simulation and experimental tests verify the effectiveness of the proposed method.

A Microgrid Energy Management System Based on Non-Intrusive Load Monitoring via Multitask Learning

Abstract: Non-intrusive load monitoring (NILM) enables to understand the appliance-level behavior of the consumers by using only smart meter data, and it mitigates the requirements such as high-cost sensors, maintenance/update and provides a cost-effective solution. This article presents an efficient NILM-based energy management system (EMS) for residential microgrids. Firstly, smart meter data are analyzed with a multi-task deep neural network-based approach and the appliance-level information of the consumers is extracted. Both consumption and operating status of the appliances are obtained. Afterward, the energy consumption behaviors of the end-users are analyzed using these data. Accordingly, average power consumption, operation cycles, preferred usage periods, and daily usage frequency of the appliances were obtained with an average accuracy of more than 90%. The obtained results were integrated into an EMS to create an efficient and user-centered microgrid operation. The developed model not only provided the optimum dispatch of distributed generation plants in the microgrid but also scheduled the controllable loads taking into account customers’ satisfaction. It was demonstrated with the help of simulation that the proposed NILM-based EMS model improves the operation cost/customer satisfaction ratio between 45% and 65% compared to a traditional EMS.

Optimization-Based Power and Energy Management System in Shipboard Microgrid: A Review

Abstract: 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.

dq -Frame Impedance Modeling of Three-Phase Grid-Tied Voltage Source Converters Equipped With Advanced PLLs

Abstract: With the increased prevalence of power converters in power systems, especially three-phase voltage source converters (VSCs), the stability analysis of power electronics-based power systems has received much attention recently To this end, different impedance models, such as the dq -domain, sequence-domain, and phasor-domain impedance models among others, have been developed for three-phase VSCs in recent years A common trend in all these impedance models, which have no noticeable practical advantage compared to each other, is considering a standard synchronous reference frame phase-locked loop (SRF-PLL) for the synchronization of the VSC with the power grid The standard SRF-PLL, however, has a limited filtering ability and, therefore, may not be very practical in most applications To deal with this shortcoming of the SRF-PLL, a great number of advanced three-phase PLLs have been proposed in the literature These advanced PLLs may have different feedback/feedforward loops and filters in their structures, which make including their dynamics in the available impedance models complicated Bridging this gap in research is the objective of this article To this end, it is demonstrated that advanced three-phase PLLs have an alternative representation, which can be easily obtained and included in the available dq -frame impedance model Several case studies are presented to verify this idea

System-Level Large-Signal Stability Analysis of Droop-Controlled DC Microgrids

Abstract: In the literature, many studies on stability analysis of dc microgrids have been conducted. However, most of them mainly focus on small-signal stability. On the other hand, few works analyze large-signal stability, but the major part of these works is based on a single unit or a simple cascaded system as a case study. Different from those, this article aims to address the large-signal stability analysis of a dc microgrid from a system-level perspective. First, the equivalent model of a droop-controlled dc microgrid is developed. Subsequently, the Lyapunov-based large-signal stability analysis and the stability criterion are derived, and mixed potential theory is used to make comparisons to verify the effectiveness of the derived criterion. The equilibrium point stability for different operation stages was obtained by means of theoretical calculation. Furthermore, the instabilities principle as well as their physical interpretation is revealed. In this article, the bus voltage is used as the only index to assess the microgrid power balance. Hence, the power load limit can be obtained by taking into consideration the stability and voltage deviation constraints. Finally, simulation and experimental results from a four-converter dc microgrid system verify the feasibility of the proposed theoretical analysis.

A Communication-Less Multimode Control Approach for Adaptive Power Sharing in Ship-Based Seaport Microgrid

Abstract: The increase in greenhouse gas emissions from the transportation sector together with the continued depletion of fossil fuels in general has encouraged an increase in the use of energy storage systems and renewable energy sources at seaports and also on short route yachts and ferries. At present, most seaports, particularly smaller ones, are not provided with cold-ironing facilities—shore-based power facilities, which provide electric power to ships from the national grid. Because of the lack of cold-ironing facilities at most ports, auxiliary diesel engines and diesel generators on ships must be kept operating and online while at berth to supply auxiliary loads of ship. To address these requirements, one possible solution would be to provide cold-ironing facilities at all ports. However, in many circumstances, this is not cost-efficient as a port might be far from the national grid. To overcome these limitations, a seaport microgrid can be formed through the integration of multiple shipboard microgrids (SMGs) with decentralized control together with a charging infrastructure that is located on-shore. This integration of multiple SMGs and port-based charging stations is termed a ship-based seaport microgrid. Typically, power is shared among different microgrids using data communication techniques, which adds to the cost and the complexity of the overall system. This article proposes a communication-less approach based on multimode, decentralized droop control that enables power sharing among several SMGs in both charging and discharging modes based on the state of charge of battery banks—electric power is either supplied or consumed. The proposed approach would be potentially useful for future autonomous ships and also for islands where port electrification is either not technically feasible or an economically viable solution. A simulation and hardware-in-the-loop results are provided to verify the control robustness of the proposed control strategy.

A Linear Quadratic Regulator With Optimal Reference Tracking for Three-Phase Inverter-Based Islanded Microgrids

Abstract: This article proposes a power sharing control method based on the linear quadratic regulator with optimal reference tracking (LQR-ORT) for three-phase inverter-based generators using inductor-capacitor-inductor (LCL) filters islanded mode. Compared to single-input single-output (SISO)-based controllers, the LQR-ORT controller increases robustness margins and reduces the quadratic value of the power error and control inputs during transient response. Supplementary loops are used to reduce frequency and voltage deviations in the ac bus without communications. The supplementary loop for voltage regulation is based on the droop controller by reducing direct and quadrature output voltages according to the active and reactive power demand. A model in a synchronous reference frame that integrates power sharing and voltage–current dynamics is also proposed. In addition, a methodology to develop an islanded microgrid model in a synchronous reference frame is proposed. Robustness analysis demonstrates stability of the LQR-ORT controller under variations in the frequency and the LCL filter components. Experimental results demonstrate accuracy of the proposed model and the effectiveness of the LQR-ORT controller on improving transient response and robustness in islanded mode.

A comprehensive overview of framework for developing sustainable energy internet: From things-based energy network to services-based management system

Abstract: Energy Internet (EI) envisions a future energy system with sustainable concerns of efficiency, economy and environment by achieving flexibility of multi-energy-integrated physical space, digitalization of data-driven cyber space and interaction of customer-aware social space. To systemically understand how EI manages energy, data and information flows, a comprehensive investigation from multi-angle perspectives is presented in this paper. The core building blocks are categorized into three-layered framework: energy-oriented network, communication-oriented network and service-oriented management. Furthermore, this paper provides a multi-disciplinary portrait of today's EI in terms of architecture, technologies, standards, services and platforms. Finally, open issues, future trends and challenges for development of sustainable EI are discussed.

Harmonic Linearization and Investigation of Three-Phase Parallel-Structured Signal Decomposition Algorithms in Grid-Connected Applications

Abstract: 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.

Linear Time-Periodic Modeling, Examination, and Performance Enhancement of Grid Synchronization Systems With DC Component Rejection/Estimation Capability

Abstract: 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.

A Cascaded H-Bridge With Integrated Boosting Circuit

Abstract: This letter proposes a multilevel inverter (MLI), which can be considered to be belonging to the cascaded H-bridge (CHB) family. In the proposed MLI, some of the H-bridges are connected to dc-sources, whereas most of the H-bridges are connected to only floating capacitors. A boosting circuit is integrated in the CHB, which permits charging the floating capacitors, enabling a higher voltage at the inverter's output with respect to the dc-sources total one. This boosting feature is essential in some applications, such as photovoltaic and fuel cell systems. Compared to the popular solutions in the literature, the proposal still offers a high boosting ratio with fewer employed components. A prototype of the proposed MLI has been built, and the results confirming its validity are shown in this letter. Efficiency analysis and evaluation with respect to one of the conventional solutions is also presented, where it is demonstrated that the proposal shows an improvement of 3.94% according to the European efficiency.

Inverter Parallelization for an Islanded Microgrid Using the Hopf Oscillator Controller Approach With Self-Synchronization Capabilities

Abstract: Nonlinear dynamical systems such as weakly coupled oscillators are an interesting approach to be adopted for the regulation of power inverters inside microgrids. Aiming at the synchronization and load sharing in islanded mirogrid, this article is inspired by oscillator synchronization property to propose a Hopf oscillator controller for the single-phase inverters. The Hopf oscillator dynamic equations are used for providing the inverter's frequency and amplitude voltage references, which lead to a robust nonlinear droop behavior for driving the system without using communications. The Hopf oscillator provides better sharing of the load between inverters with higher robustness, less harmonic distortion, and faster time response of the associated limit cycle than the achieved by the other approach made with a Van der Pol oscillator. In addition, global asymptotic synchronization of system is proven by Lyapunov approach. Simulation results of a system composed by paralleled inverters are provided and compared with a Van der Pol oscillator approach reported in literature. Experimental results are also provided to prove the Hopf oscillator based controller under different circumstances.

Space Microgrids for Future Manned Lunar Bases: A Review

Abstract: Several space organizations have been planning to establish a permanent, manned base on the Moon in recent years. Such an installation demands a highly reliable electrical power system (EPS) to supply life support systems and scientific equipment and operate autonomously in a fully self-sufficient manner. This paper explores various technologies available for power generation, storage, and distribution for space microgrids on the Moon. Several factors affecting the cost and mass of the space missions are introduced and analysed to provide a comprehensive comparison among the available solutions. Besides, given the effect of base location on the design of a lunar electrical power system and the mission cost, various lunar sites are introduced and discussed. Finally, the control system requirements for the reliable and autonomous operation of space microgrids on the Moon are presented. The study is complemented by discussing promising future technological solutions that could be applied upon a lunar microgrid.

Smart-Building Applications: Deep Learning-Based, Real-Time Load Monitoring

Abstract: Google's Director of Research Peter Norvig said, "We don't have better algorithms than anyone else; we just have more data." This inspiring statement shows that having more data is directly related to better decision making and foresight about the future. With the development of Internet of Things (IoT) technology, it is now much easier to gather data. Technological tools, such as social media websites, smartphones, and security cameras, can be considered as "data generators." When the focus is shifted to the energy field, these generators are "smart meters."

Effective Controls of Fixed Capacitor-Thyristor Controlled Reactors for Power Quality Improvement in Shipboard Microgrids

Abstract: Addressing power quality issues in shipboard microgrids (SMs), which are mainly attributable to the increased installation of power converters, has received much attention recently. To this end, static VAR compensators, such as thyristor-switched capacitors and fixed capacitors-thyristor controlled reactors (FCs-TCRs), can be effective solutions. Controlling these compensators, however, is not a trivial task as it involves sophisticated operations, especially estimating the firing angle, which should be carried out based on some nonlinear equations. This article aims to propose the application of some simple yet numerically efficient algorithms based on bisection, Newton–Raphson, false position, and secant methods for estimating the firing angle of the FC-TCR. The effectiveness and robustness of these algorithms are demonstrated via modeling of the FC-TCR with the electrical power system of a practical hybrid ferry under MATLAB/Simulink environment, where the results proved that the enhanced power quality issues respect the IEC standards 61000-4-7/30. Furthermore, an experimental setup consists of a digital signal processor and a programmable source is used to demonstrate that these techniques can be effectively applied in real-time applications.

LTP Modeling of Single-Phase $T/4$ Delay-Based PLLs

Abstract: A large number of single-phase phase-locked loops (PLLs) require generating a 90° phase-shifted version of their single-phase input signal. Among the wide variety of options, using a quarter-cycle transfer delay is particularly popular. In recent years, several single-phase transfer delay-based PLLs (TD-PLLs) have been proposed in the literature. The major difference between different TD-PLLs lies in the way they have adapted to frequency changes. Regardless of this structural difference, a common trend in investigating TD-PLLs is obtaining a linear time-invariant (LTI) model and analyzing it. Obtaining such a model, however, is often based on neglecting the input signal amplitude variations and double-frequency oscillations in the transient behavior of TD-PLLs, which results in some inaccuracies. To deal with this problem, the linear time-periodic (LTP) modeling of TD-PLLs is presented in this letter. It is demonstrated that the LTP model does not have the limitations of the LTI one and can provide much higher accuracy, but at the cost of a higher model complexity.

Coordinated Control of Diesel Generators and Batteries in DC Hybrid Electric Shipboard Power System

Abstract: Hybrid electric ships powered by diesel generators and batteries are the main configuration for shipboard microgrids (SMGs) in the current maritime industry. Extensive studies have been conducted for the hybrid operation mode, whereas the all-electric operation mode and the switching between the aforementioned two modes in a system with multiple generators and batteries have not been tested. In this paper, a coordinated approach for a hybrid electric ship is proposed, where two operation modes have been simultaneously considered. More specifically, for achieving an efficient operation with reduced generator wear losses, the governor-less diesel-engine-driven generators have been adopted in the study. According to the practical operation conditions, two operation modes, the all-electric and hybrid modes, are preset. Based on these, the coordination of the generators acting as the main power sources and batteries regulating the power flow and improving the generator efficiency is studied. The governor-less diesel generators are regulated to inject the rated power in order to maximize the generator efficiency, while the DC bus voltage is regulated by DC/DC converters. For the benefit of the overall lifespan of battery banks, power sharing during charging and discharging states have been realized by the state of charge (SoC)-based adaptive droop regulator. For the test of two operation modes, as well as the mode switching, a simulation assessment in a 1 kV DC SMG has been conducted. The simulation results show that the DC bus voltage can be controlled well, and that the power sharing among batteries follows the design. Additionally, smooth transients can be observed during mode switching when the proposed control scheme is applied.

Hierarchical Control of Space Closed Ecosystems: Expanding Microgrid Concepts to Bioastronautics

Abstract: One of the main challenges of human space exploration is the development of artificial ecosystems, which can be used as life support systems (LSSs) to enable long-duration human space missions. In an open LSS, no food generation or waste treatment is provided in space, and supplies from Earth are necessary. According to Figure 1, considering the approximate metabolic consumables and hygiene water as well as the number of crewmembers [1], a huge mass would be required to be transported from Earth, which brings the necessity of a regenerative or closed LSS [2]-[4]. Closed ecological systems (CESs) are ecosystems without any matter exchange with the outside environment [2]. The most advanced humanmade CESs include Advanced Life Support System Test Bed (ALSSTB) (the NASA Johnson Space Research Center, Houston, Texas), Biosphere 2 (Oracle, Arizona), BIOS-3 (Krasnoyarsk, Russia-no longer operative), the Closed Ecology Experiment Facility (CEEF) complex (Rokkasho, Japan), the Micro-Ecological Life Support System Alternative (MELiSSA) Pilot Plant (MPP) (Universitat Aut?noma de Barcelona, Spain), and the Concordia Antarctica Station, which are different from one another with respect to their complexity, size, and degree of closure [2]. CESs are necessary for long-term manned space missions, which aim to minimize support from Earth. They are composed of several specific compartments that, together, reproduce the main functionalities of an ecological system in a continuous mode of operation and under controlled conditions.

Virtual Resistance Tradeoff Design for DCMG Grid-Forming Converters Considering Static- and Large-Signal Dynamic Constraints

Abstract: This article brings forward a design method of virtual resistance for droop-controlled dc microgrids (DCMGs). Although droop control is widely employed in coordinated DCMGs to coordinate different energy sources, few works address thoroughly the principles for a proper virtual resistance design. In this article, dynamic stability and static voltage deviation constraints are taken into consideration as the main criteria to be complied with by the virtual resistance design. In critical cases, constant power loads (CPLs) may substantially decrease system damping and adversely affects the stability of the system. In this sense, the large-signal stability model is developed including CPLs by using the Lyapunov function, and it is subsequently analyzed to infer the stability criterion. Theoretically, bus voltage is the most important index when addressing the DCMG control; hence, the impact of virtual resistance on the voltage deviation is explored as well. The research presented in this article finds out that virtual resistance influence on system stability is opposite to that on voltage deviation; thus, a tradeoff method based on the containment principle is developed. Throughout the proposed compromised design, we can adjust the weight coefficient to satisfy different performance requirements of DCMGs. The effectiveness of the proposed scheme is validated through experimental results.

An Accurate Physical Model for PV Modules With Improved Approximations of Series-Shunt Resistances

Abstract: An accurate model to represent the photovoltaic modules is essential to facilitate the efficient deployment of these systems in terms of design, analysis, and monitoring considerations. In this respect, this study proposes a new approach to improve the accuracy of the widely used five-parameter single-diode model. Two new physical equations are introduced to represent the series and shunt resistances, while the other parameters are represented by well established physical expressions. In the proposed model, most of the parameters are in terms of the cell temperature, irradiance, and datasheet values, while a few parameters need to be tuned. The model is compared with four well-known methodologies to extract the parameters of the single-diode and double-diode models. The simulation studies make use of the different I–V characteristics provided in the photovoltaics (PVs) datasheets, characteristics extracted from an outdoor module, as well as the ones simulated with the software PC1D. The results show an improved precision of the proposed model to estimate the power characteristics for a wide range of temperatures and irradiances, not only in the maximum power point but also in the whole range of voltages. Furthermore, the proposed physical model can be easily applied to other kind of studies where a physical meaning of the PV parameters is of great importance.

A cascaded DC-AC-AC grid-tied converter for PV plants with AC-link

Abstract: Cascaded multilevel converters based on medium-frequency (MF) AC-links have been proposed as alternatives to the traditional low-voltage inverter, which uses a bulky low-frequency transformer step-up voltage to medium voltage (MV) levels In this paper, a three-phase cascaded DC-AC-AC converter with AC-link for medium-voltage applications is proposed Three stages integrate each DC-AC-AC converter (cell): a MF square voltage generator; a MF transformer with four windings; and an AC-AC converter Then, k DC-AC-AC converters are cascaded to generate the multilevel topology This converter’s topological structure avoids the per-phase imbalance; this simplifies the control and reduces the problem only to solve the per-cell unbalance Two sets of simulations were performed to verify the converter’s operation (off-grid and grid-connected modes) Finally, the papers present two reduced preliminary laboratory prototypes, one validating the cascaded configuration and the other validating the three-phase configuration

Coordinated Adaptive Directional Overcurrent Protection System for AC Microgrids

Abstract: In this research work, an adaptive scheme for the coordinated protection of AC Microgrids using directional overcurrent (DOCR) relays is presented. Protection of AC MGs is a complex and challenging issue due to the dynamic nature of the network including, a) its capability to reconfigure the modes of operation ranging from grid-connected to the islanded mode, c) bidirectional-power flow capability, and c) integration of intermittent renewable energy resources with real-time variations in the resource availability. Consequently, the fault current contributions may largely vary depending upon the incident conditions on the network. Conventional protection schemes, generally designed for radial networks, and unidirectional power flow from the source end to the load may either mal-operate or exhibit very poor performance, if not adapted according to the dynamic conditions of the network. To address this issue, a communication-based adaptive protection scheme capable to adapt its settings according to the generation resource availability and network configuration is presented in this work. The proposed scheme consists of an intelligent central protection unit (ICPU) capable to update the settings and communicate it to the individual relays based on the pre-calculated offline settings. The directional overcurrent relays employed in the scheme use two-stage settings, i.e. definite time and inverse definite minimum time characteristics for the effective coordination among the downstream and upstream relays. An adaptive algorithm for ICPU operation is presented and a case study is implemented for a modified IEEE 9-bus system using DigSilent Power factory. The results for various scenarios including, a) grid-connected mode of operation, b) islanded mode of operation, and c) variable distributed generation mode are obtained and compared to the static scheme, which validates the effectiveness of the proposed scheme.