Distributed Generation Systems Research Articles

Novel Integrated Zeta Inverter for Standalone Applications

In recent years, distributed generation systems based on renewable energy sources have gained increasing prominence. Thus, the DC/AC converters based on power electronics devices have become increasingly important. In this context, this article presents an integrated Zeta inverter for low-power conditions, which operates in continuous conduction mode (CCM), achieving efficiency greater than 95%. The proposed topology is composed of four power switches, two operating at high frequency and two operating at low frequency, i.e., at the output frequency. Compared with the topologies in the literature, these configurations make it a competitive solution from the point of view of efficiency, number of elements, and, consequently, implementation cost. The proposed converter operates as a sinusoidal voltage source for local loads and is supplied by a DC source, such as batteries or a photovoltaic array. A multi-resonant voltage controller was used to guarantee the sinusoidal voltage provided to the non-linear load while dealing with the complex dynamics of the Zeta converter in the CCM. Experimental results from a 324 W prototype show the converter’s implementation feasibility and the high efficiency of the DC/AC conversion.

Optimal coordination of directional over current relays for distribution systems using hybrid GWO-CSA

Coordination of protective relays is a critical aspect of electrical distribution systems, ensuring effective and reliable protection against faults. In modern power systems, the integration of distributed generation (DG) sources adds complexity to the coordination task. The dynamic nature of DG systems requires adaptive relay settings that can swiftly detect and isolate faults while minimizing potential damage and downtime. The purpose of this research is to improve the coordination of directional over current relays in electrical distribution systems, particularly in DG systems. An optimization technique combining the grey wolf optimization (GWO) and cuckoo search algorithm (CSA) is developed to identify the best relay settings that reduce overall operation time while ensuring excellent fault identification and isolation. To address relay faults caused by DG integration, a suitable primary and backup relay design is chosen, and the influence of time multiplier settings (TMS) on system performance and reliability is investigated. The proposed GWO-CSA technique is evaluated and implemented on IEEE 3, 8 and 15-bus systems using MATLAB. Simulation results show that the GWO-CSA strategy outperforms well compared to previous algorithms, enabling optimal coordination and increased protection in DG systems while drastically lowering relay operating time.

Design and verification of q-axis perturbation based active islanding detection schemes for DG systems

The penetration of grid integrated distributed generation (DG) in the present decade, has benefited rural communities, the environment, and the power sector. These renewable power sources based DGs could eliminate the need of extensive transmission networks, especially in remote areas, reduce emissions and improve power supply reliability. A significant drawback of grid integrated DG systems is the islanding of DG units, which puts workers' safety at risk and raises the possibility of damaging electrical infrastructure. Therefore, islanding detection techniques are used to reduce the danger associated with islanded functioning of DG units. Fast detection, small non detection area and less power quality disturbance are the major requirements of any islanding detection method. To address this issue of islanding, researchers have proposed various islanding detection strategies. This paper compares various q-axis controller-based islanding identification approaches: sub-harmonic perturbation (SHP), complementary reactive power perturbation (CRPP), and even harmonic perturbation (EHP). In all three proposed methodologies, the perturbations introduced result in frequency deviations surpassing the predefined threshold values. But the time of islanding detection is least in the CRPP approach. CRPP can also drift the total harmonic distortion (THD) beyond the corresponding threshold in an appreciable way. The performance of these (Islanding detection methods) IDMs is evaluated through simulations using MATLAB-Simulink on a PV fed DG. The efficacy of the comparative analysis is ensured with necessary waveforms.

The role of storage in energy security performance based on diversification and concentration for distributed energy systems

This work addresses the use of diversification and deconcentration strategies of primary sources of energy supply for the multi-objective design of distributed generation systems based on renewable sources. The Shannon–Wiener and Herfindahl–Hirschman indices are proposed as optimal design objectives. The utopia-tracking method is used to identify trade-offs between the total annual cost of the system and the efficiency of the storage system. The storage system is included in the assessment of diversification and deconcentration due to its functions as a backup unit in the event of adverse system operating conditions. Cases of interconnected and off-grid systems are addressed. The results show that, by including the storage system, an over-diversification of supply sources is generated and that, in the absence of various sources, as occurs in off-grid systems, storage generates sufficient flexibility to reach a trade-off among economic performance, diversification of supply sources and energy efficiency. The robust nonlinear programming model is fed with real data from a residential building.

Analysing the Performance of Distributed Generation System Based on Renewable Energy through ANN-Tuned UPQC

This article presents an advanced approach to enhancing power quality in a three-phase, low-voltage network that is integrated with a hybrid renewable energy system. This system utilizes an Artificial Neural Network (ANN)-based Unified Power Quality Conditioner (UPQC). A thorough performance analysis was carried out on this system, which harnesses energy from solar photovoltaic (PV) and wind sources and is regulated by an ANN-controlled UPQC. This novel ANN controller aims to exceed the capabilities of the conventional proportional-integral (PI) controller, and particularly the proportional-integral-derivative (PID) controller, by improving both the steady-state and dynamic performance. The system, referred to as UPQC-ANN-RE, directs energy from wind turbines and photovoltaic arrays into a 3-phase, 4-wire electrical distribution network. In its role as a UPQC, it significantly enhances key power quality metrics such as voltage and current harmonics and power factor. A detailed examination of the active-real power flow through the converters provides further insights into the operational dynamics of the system.

Characteristics of Various Single Wind-Power Distributed Generation Placements for Voltage Drop Improvement in a 22 kV Distribution System

A major challenge in distribution systems is the issue of voltage drop along the distribution line resulting from an increased load capacity connected to the utility. A significant voltage drop can affect the performance of a distribution system and cause quality issues for end users, impacting the system’s long-term sustainability and reliability. Therefore, regulations have been set stating that the voltage level should not be more that 5% higher or lower than the rated voltage. Thus, in this study, we aimed to evaluate the voltage level characteristics of a 22 kV distribution system that replicates the actual distribution system in the Provincial Electricity Authority. A voltage improvement technique based on distributed generation placement was proposed. In addition, the distribution system characteristics with and without distributed generation placement were evaluated under fault conditions. The results indicate that distributed generation placement in the distribution system can improve the voltage level along the distribution line. However, the level of increase in voltage depends on the size of the load, the capacity of the distributed generation, and the location of the distributed generation system on the distribution line. Furthermore, placing a distributed generation system with a minimum capacity at the proposed location can improve the voltage within the utility’s standard level. Thus, the installation of a distributed generation system in the distribution system is beneficial in terms of voltage improvement in the distribution system and provides the power system with a sustainable method to address the issue of voltage drop.

Power Flow Analysis Using Fuzzy for Single Phase Transformer Less PV System Connected with a Nine-Level Converter

Power electronics technology advancements and growing environmental concerns worldwide have made photovoltaic (PV) systems more visible in distributed generation systems. Photovoltaics, or solar PV, is an important component of solar energy for generating electricity. Grid-connected inverters must be able to regulate the amount of power they inject into the grid, track maximum power points, be highly efficient, and inject currents into the grid with minimal harmonic distortion. Two step-down converters were used to construct an inverter without a single-phase transformer. This study investigates two multi-sequence inverter types that use different voltages and are based on single-phase grid-connected photovoltaic (PV) technology. A new nine-level grid-connected transformer-less photovoltaic converter was proposed in this study. MATLAB was used to construct the complicated FFT simulation using fuzzy logic controls. Analyzing efficiency through simulation in order to enhance efficiency. This work aims to replace PI controllers with fuzzy controlled systems so that single-stage operation can be improved with reduced switches in an economic manner. An improvement of 10% over the existing system is achieved by implementing fuzzy computing.

Experimental Characterization of Commercial Scroll Expander for Micro-Scale Solar ORC Application: Part 1

In order to reduce greenhouse gas emissions and achieve global decarbonisation, it is essential to find sustainable and renewable alternatives for electricity production. In this context, the development of distributed generation systems, with the use of thermodynamic and photovoltaic solar energy, wind energy and smart grids, is fundamental. ORC power plants are the most appropriate systems for low-grade thermal energy recovery and power conversion, combining solar energy with electricity production. The application of a micro-scale ORC plant, coupled with Parabolic Trough Collectors as a thermal source, can satisfy domestic user demand in terms of electrical and thermal power. In order to develop a micro-scale ORC plant, a commercial hermetic scroll compressor was tested as an expander with HFC-245fa working fluid. The tests required the construction of an experimental bench with monitoring and control sensors. The aim of this study is the description of the scroll performances to evaluate the application and develop optimization strategies. The maximum isentropic effectiveness is reached for an expansion ratio close to the volumetric expansion ratio of the scroll, and machine isentropic effectiveness presents small variations in a wide range of working conditions. The filling factor is always higher than one, due to leakage in the mechanical seals of the scroll or other inefficiencies. This study demonstrates that using a commercial scroll compressor as an expander within an ORC system represents a valid option for such applications, but it is necessary to improve the mechanical seals of the machine and utilize a dedicated control strategy to obtain the maximum isentropic effectiveness.

Green energy solution for grid integrated solar PV system for water storage towers

In India, water storage towers are present almost everywhere, especially across small towns to rural areas. The storage tanks either utilize diesel powered or utility grid fed induction motor (IM) water pumps. The large spaces available with water storage towers can be utilized to plant solar PV panel for large storage towers water pumping operation, hence, making a switch from diesel or grid run storage towers to solar operated storage towers. This paper presents a robust control of grid integrated solar PV-based water pump system with efficient and smooth transition between standalone and grid interfaced modes. A smart DC link voltage control is presented for distributed generation system (DGS), which provides full control on DC link voltage for both modes of operation at all dynamic load conditions. An enhanced phase-locked loop (EPLL) control is utilized for grid source converter (GSC) in grid control operation, making it flexible to different grid scenarios and power quality. It works for harmonics suppression, load balancing and grid side converter control. An enhanced phase-locked loop (EPLL) is implemented for synchronization control algorithm, which provides an accurate estimation of voltage angle even during frequency ramps and exhibiting superior performance particularly in terms of robustness against DC offsets. The primary requirement for smooth operation of grid-tied solar PV system is effective power management between different sources. The issues of power management and power quality, are discussed in this work, and solutions are presented. The implemented control algorithms are tested successfully for dynamic solar insolation, varying load conditions, unbalance in load, sudden grid outage condition. The system appropriateness is validated by experimental results.

Low/Middle-Frequency Positive External- Damping Design Under Self-Stability Constraint for Inner Control Loop of Grid-Forming Converters

The inner voltage control loop and inductor current active damping loop of grid-forming (GFM) converters perform the output voltage control and filter resonance damping, and their stability design has been widely developed in the literature. However, the equivalent external-damping characteristics have not been fully explored. In this paper, the analysis shows that inappropriate design focusing only on self-stability would lead to negative external-damping in a wide low/middle-frequency band when LC resonant frequency is greater than one-sixth sampling frequency and less than one-third sampling frequency, which may cause system instability when interacting with loads or grids. Therefore, a low/middle-frequency positive external-damping design method under self-stability constraint is proposed for inner control loop of GFM converters. Detailed design process is presented with simple implementation. The key feature is the use of negative proportional gain of voltage controller. Through the proposed design method, the GFM converters can improve system damping capability, which is beneficial to promoting large-scale integration of distributed generation systems based on power electronics. Simulation and experimental results are finally provided to verify the feasibility and effectiveness of the design method.

АНАЛІЗ ПОТОЧНОГО СТАНУ ЕНЕРГОСИСТЕМИ ТА СТРАТЕГІЇ РОЗВИТКУ РОЗОСЕРЕДЖЕНОЇ ГЕНЕРАЦІЇ В УКРАЇНІ

The article analyzes the state of the Unified Energy System (UES) of Ukraine as of the beginning of 2023. The main focus of the article is on the issue of energy security and the consequences for the UES of Ukraine after mass attacks on energy facilities from the beginning of a full-scale invasion until the beginning of 2023. The assessment of the main shortcomings of the current model of the operation of the power system was carried out and the current short-term strategies for its modernization were considered in order to prepare for the heating season of 2023-2024. During the analysis of potentially possible short-term strategies, the main attention was paid to the recovery plan of Ukraine, available capacities of the Gas Transport System (GTS) of Ukraine, potential of using "Floating Power Plants", poten-tial possibilities of the operation of distribution networks (DM) in the "island mode" and stimulating an increase in the share of distributed sources generation (DSG) and energy storage systems (ESS). The current results of the implemen-tation of the above-mentioned strategies and the potential of their development after the end of a full-scale war in ac-cordance with the energy strategy of Ukraine until 2035 and the main theses of the energy strategy of Ukraine until 2050 were presented. Based on the results of the analysis, the recommendation regarding the implementation of the preparation of the UES of Ukraine for the next heating season were formed. Bibl. 10, fig. 2.

Two-Layer Optimization Method for Sharing Energy Storage and Energy considering Subjectivity

The high level of integration of distributed generation systems (DGSs), especially distributed wind and solar, significantly affects the flexibility and controllability of the power system. Aggregating local DGSs and shared energy storage systems (ESSs) within an energy community offers an economically and environmentally viable solution. However, the coupling of shared ESSs with the energy community, while considering subjectivity, is often overlooked. Therefore, this study introduces a two-layer optimization framework that enables DGSs to trade energy freely, voluntarily, and independently and to share ESSs within the energy community, considering participants’ subjectivity. The upper layer optimizes the size of shared ESSs, while the lower layer, structured as a two-layer model, simulates participant interactions. The numerical case shows that, compared to DGSs operating individually, the shared ESS case indicates that community self-sufficiency and self-consumption rates increase by 16.22% and 21.98%, respectively. Additionally, the annual operating cost is reduced by approximately 27.10%, and CO2 emissions are decreased by about 33.24%. Considering DGS’ subjectivity, the self-sufficiency and self-consumption rates are 3.04% lower, and the total operating costs and CO2 emissions are 3.26% and 6.86% higher, respectively.

Integration of Artificial Intelligence for Enhanced Coordination of DOCR Protection in Distributed Generation Systems

Distributed generation (DG) is an approach that involves adding decentralized power generation within a distribution network. Distributed generation systems can reduce transmission losses, increase the reliability of energy supply, minimize carbon emissions, and enable the active participation of consumers in energy production. However, with the increase in distributed generation, electric power systems face new challenges in maintaining operational reliability and safety. Disruptions such as short circuits or overcurrent can occur in the system, and appropriate protective responses are required to protect the power grid from more significant damage. The addition of DG also causes the short circuit current to vary and results in system protection coordination having to be redone. Carrying out coordination will take a long time. This research uses modeling and simulation of a distributed generation system with various operating conditions and works adaptively according to changes in the system due to the addition of DG. The results obtained from the simulation are used in neural network training to study the relationship patterns between directional overcurrent relays (DOCR) parameters and system operating conditions. The backpropagation algorithm is used in the Artificial Neural Network (ANN) training process. The training process utilizes the maximum Short Circuit Current (ISC) input obtained through generation, fault location, and fault type. Time Dial Setting (TDS) and Ipickup values are used as ANN training targets. After testing, the results obtained are in accordance with the target data. The efficacy of this method is further demonstrated through ETAP simulations, which confirm that ANN is a suitable approach for modeling adaptive and optimal relay coordination systems.

PSO-enhanced discrete-time integrated sliding mode-based control of three-level NPC converter for grid-connected PV-FC distributed generation system

This study proposes the control of a three-level NPC converter applied in a PV-FC hybrid generation system based on discrete-time integral sliding mode control (DISMC) combined with the particle swarm optimization (PSO) technique. First, the comprehensive depiction and modeling of the system's main components are initially presented. Then, the controller's detailed design procedure is given. The sliding manifold is designed to have a fast dynamic response, and its stability analysis is verified using the Lyapunov direct method. Next, the optimization procedure is introduced to calculate the optimal values of the DISMC gains. Furthermore, a power management strategy is examined within the proposed control system to maximize the utility of the power produced by the hybrid system; the control is done through the designed PSO-DISMC to allow decoupled control of the active and reactive powers in two distinct modes of operation (the feeder-flow control (FFC) and the unit-power control (UPC) modes). The simulation of the approach is conducted in MATLAB/Simulink, and the findings demonstrate the effectiveness and robustness of the proposed control strategy.

Energy Policies and Interconnection Standards for Energy generation Distributed: Global Status, Development Trends and Perspectives in Peru

Energy policies and interconnection standards play a key role in promoting and regulating distributed energy generation globally. The work should examine the current state of global interconnection policies and standards, emerging trends and their impact on clean energy adoption. Globally, energy policies for distributed generation typically focus on marketing renewable energy sources and improving energy efficiency. Many countries implement tax incentives, subsidies and support programs to stimulate the adoption of distributed generation technologies, such as solar panels and small wind systems. The rules of Interconnections often focus on establishing technical standards to ensure the security, stability and reliability of electrical grids, as well as facilitating the connection and seamless integration of distributed generation systems

Methodology to Estimate the Financial Impacts of the Integration of PV Generators in Distribution Systems on Voltage Sags and Energy Losses

Methodology to Estimate the Financial Impacts of the Integration of PV Generators in Distribution Systems on Voltage Sags and Energy Losses

An Islanding Detection Method Based on the Reactive Power Disturbance for Multiple Inverter-Based DG Systems

In this paper, an islanding detection method for multiple inverter-based distributed generation systems is proposed, which is based on perturbing reactive power output. An asymmetric form of positive and negative reactive power disturbance is presented so that there always exists a certain total amount of disturbance in the system. To decrease the disturbance amplitude without expanding the non-detection zone, a positive feedback of frequency difference is added to the disturbance. A reactive power disturbance synchronization method without communication among inverters is proposed so that the averaging effect caused by unsynchronized reactive disturbances can be eliminated and the island can be detected in a multiple-DG system. Additionally, the islanding detection criterion is improved by establishing the relationship between the direction of disturbance and the numerical symbol of frequency difference, so there is no misjudgment of islanding detection in a weak grid. Finally, an experimental platform consisting of three 6kW three-phase grid-connected inverters and a 99.9kVA islanding detection test device is established. The experimental and simulation results indicate that the proposed method performs fast and precise islanding detection for the multiple-DG system with small NDZ and little impact on power quality. Additionally, no misjudgment happens in a weak grid.

Optimization and analysis of distributed generation units in distributed system for minimizing losses

The proposed study presents a novel methodology aimed at mitigating losses in distributed generation (DG) systems within distributed networks. This methodology involves the integration and implementation of DG units that utilize non-conventional, sustainable resources, potentially enhancing traditional DG systems. When DG units are located near the point of consumption, they create favorable conditions for voltage support, reduction in energy losses, and lower emissions. The strategic placement of DG units, in terms of both size and location within an existing generation network, is critical for the construction, execution, and operational planning of real-time distribution networks. This optimal positioning is key to maximizing voltage stability and minimizing power loss. The study proposes an innovative strategy to decrease real power losses and improve voltage profiles, which includes optimizing substation capacity by introducing DG units.

Smart landscaping design for sustainable net-zero energy smart cities: Modeling energy hub in digital twin

In our study, we introduce an innovative energy management system optimized for energy hubs in net-zero energy smart cities, emphasizing sustainability as a core objective. Our approach intricately integrates distributed generation systems and storage facilities within a digital twin framework, incorporating landscape considerations to promote environmental harmony. By prioritizing sustainability, our strategy aims to minimize operational costs while maximizing energy efficiency and reducing carbon emissions. We employ specialized energy flow algorithms for each grid, designing energy hubs that leverage renewable resources and mobile storage to enhance sustainability. To address complexity, our model utilizes a non-convex mixed-integer nonlinear programming structure and robust adaptive optimization techniques, combining the Gray Wolf and Krill Herd algorithms. Through simulations, we demonstrate significant improvements in power system efficiency, including notable reductions in power loss, peak voltage fluctuations, and temperature variations. Our research underscores the critical role of smart landscaping in advancing sustainable energy management for net-zero energy smart cities, facilitating seamless integration of energy hubs with the surrounding landscape within a digital twin paradigm.

Optimal sizing and siting of distributed generation systems incorporating reactive power tariffs via water flow optimization

Distributed generation (DG) systems are gaining popularity because they generate electricity closer to the point of consumption. This reduces transmission and distribution losses and enhances system reliability. For the efficient and cost-effective use of these systems, optimal sizing and siting of DGs is crucial. This paper introduces a Water Flow Optimization (WFO)-based method for the optimal placement and sizing of DG systems capable of injecting both active and reactive power simultaneously. This study assesses both the technical and economic facets of the system, taking into account power losses and the comprehensive annual economic costs, including capital investment, deployment, operation, and maintenance. A significant aspect of this research is the DG units' capability to enhance voltage and minimize losses, factoring in the reactive power tariff. The findings show that the WFO method surpasses other optimization techniques, such as particle swarm optimization, whale optimization algorithm, genetic algorithm and gray wolf optimization. Furthermore, the study emphasizes the cost advantages of injecting reactive power. The minimum annual economic losses (AEL) recorded in this study are $19,207 and $13,852 for IEEE-33 and IEEE-69 bus systems, respectively. In comparison, for DGs only injecting active power, the AEL increases to $24,749 and $41,381 for the corresponding systems.