Distributed Power Generation Research Articles

Improving of electric network feeding nuclear facility based on multiple types DGs placement

Abstract Nuclear Facility (NF), during shutdown and startup, are in the essential need for reliable electric power that should be delivered by electric power grid to NF. Safe operation of NF needs a limited variation in both frequency and voltage.The reduction of power losses, improving voltage profile, and frequency in electric grid connected with NF can be achieved by optimally distributed generators (DGs) placement. This paper presents a mathematical model for multible types of DGs placement in electric grid feeding NF. Also, it proposes artificial intelligence solution methodology for active and reactive power DGs placement problem. The trained Adaptive Neuro-Fuzzy Inference System (ANFIS) with Cat Swarm Optimization algorithm (CSO) is used for optimal solution. The optimization technique is tested and validated by using different sizes of electric grid. Test results showed a more reliable and efficient approach compared with other approachs.

Economic dispatch in a stand-alone system using a combinatorial energy management system

In this paper, a new adaptive combinatorial model control strategy is designed for energy dispatch of a photovoltaic-diesel-battery hybrid of an island grid power system, where the battery is optimised to increase its usage time, considering the increase of the fuel cost. The distinguishing feature of the proposed combinatorial step model is that the constraints of batteries are constructed depending on the load control strategy to describe the batteries' different modes (charging and discharging). Parameters of the battery vary with the load estimation and are estimated by the combinatorial process. In the combinatorial model, the control horizon varies according to the method defined by load control. The process steps of the control strategy are effectively used to obtain the dispatching behaviour for the renewable system while optimally considering various constraints of distributed power generation. Therefore, the system performance of the developed optimal combinatorial scheme is validated through simulation and analysis. The designed combinatorial model reduces the diesel generator (DG) power by more than 73 % of its total energy supply to the load.

Loss allocation methods for unbalanced power distribution networks - a review

At present, the power industry is undergoing profound changes around the world. To improve the electricity market operations and further eliminate monopolies, it is pivotal to achieve fairness, equality and transparency among all electricity market participants. As the downstream sections of the power grid, the distribution network incurs a lot of losses, accounting for more than 70% of the total power losses. Consequently, investigation is required on how to ensure a reasonable effectiveness of power distribution network loss allocation. In practice, a distribution network does not always operate under balanced conditions, especially when considering single-phase distributed power generation, storage or loads, for example, PV panels and singlephase electric vehicle chargers. Therefore, the allocation of losses in this context will be based on analysis for unbalanced systems. In this paper, three methods of distribution network loss allocation for unbalanced systems will be reviewed in detail, including classical loss partitioning (CLP) method, resistive component-based losses partitioning (RCLP) method, and multiphase losses allocation procedure (MPLAP). It is summarised that the MPLAP method could be the most relevant for transactive energy applications in unbalanced power distribution networks. Further research areas based on this approach are listed for future research efforts.

Optimization of Intelligent Distribution of Distribution Network in the Presence of Distributed Sources

In order to improve the intelligent distribution effect of the distribution network in the presence of distributed generation, this study combines intelligent algorithms to analyze the intelligent distribution of the distribution network in the presence of distributed generation. Moreover, this study establishes an objective function composed of system network loss expectation, voltage stability index, and reactive power compensation equipment investment. In addition, this study improves the artificial bee colony algorithm through tabu search algorithm and genetic algorithm and obtains an improved TS-IABC algorithm. Finally, this study compares and tests the performance of different algorithms in the form of functions and simulations. The simulation results show that the optimal intelligent distribution method of the distribution network in the presence of distributed power generation proposed in this study has a good effect and can promote the intelligent distribution of the distribution network.

Secondary Voltage Collaborative Control of Distributed Energy System via Multi-Agent Reinforcement Learning

In this paper, a new voltage cooperative control strategy for a distributed power generation system is proposed based on the multi-agent advantage actor-critic (MA2C) algorithm, which realizes flexible management and effective control of distributed energy. The attentional actor-critic message processor (AACMP) is extended into the MA2C method to select the important messages from all communication messages adaptively and process important messages efficiently. The cooperative control strategy trained by centralized training and decentralized execution frame will take over the responsibility of the secondary control level for voltage restoration in a distributed manner. The introduction of the attention mechanism reduces the amount of information exchanged and the requirements of the communication network. Finally, a distributed system with six energy nodes is used to verify the effectiveness of the proposed control strategy.

Stability Analysis of Two Power Converters Control Algorithms Connected to Micro-Grids with Wide Frequency Variation.

Distributed power generation, micro-grids, and networks working in islanding mode have strong deviations in voltage quantities. These deviations can be divided into amplitude and frequency. Amplitude deviations are well-known and studied, as they are common in small and big grids. However, deviations on the ac mains frequency have not been widely studied. The literature shows control schemes capable of bearing these variations, but no systematic analysis has been performed to ensure stability. As the majority of power converters are designed for big grids, their analysis and design neglect frequency disturbances, therefore those devices allow a very small frequency operating window. For instance, in power converters that need to be synchronized to the grid, the standard deviation does not go beyond 0.5 Hz, and for grid-tied inverters it does not go beyond 1 Hz, whereas variations of around 8 Hz can be expected in micro-grids. This work presents a comprehensive analysis of the control system’s stability, where two different control schemes for a back-to-back static converter topology are implemented and studied under a wide variable grid frequency. Because the behavior of power converters is nonlinear and coupled, dynamic and static decouplers are usually introduced in the controller, being a key element on the scheme according to the findings. The results show that using just a static decoupler does not guarantee stability under frequency variations; meanwhile, when a dynamic decoupler is used, the operating window can be greatly extended. The procedure shown in this paper can also be extended to other control algorithms, making it possible to carefully choose the control system for a variable frequency condition. Simulated and experimental results confirm the theoretical approach.

Design of Novel HG-SIQBC-Fed Multilevel Inverter for Standalone Microgrid Applications

The growth of distributed power generation using renewable energy sources has led to the development of new-generation power electronic converters. This is because DC–DC converters and inverters form the fundamental building blocks in numerous applications, which include renewable integrations, energy harvesting, and transportation. Additionally, they play a vital role in microgrid applications. The deployment of distributed energy resources (DERs) with renewable sources such as solar has paved the way for microgrid support systems, thus forming an efficient electric grid. To enhance the voltage of such sources and to integrate them into the grid, high-gain DC–DC converters and inverter circuits are required. In this paper, a novel single-switch high-gain converter (HG-SIQBC) with quadratic voltage gain and wide controllable range of load is proposed, the output of which is fed to a modified multilevel inverter for conversion of voltage. The overall performance of the newly designed converter and inverter is analyzed and compared with the existing topologies. A prototype of the investigated multilevel inverter is designed and tested in the laboratory. Development and testing of such novel topologies have become the need of the hour as the grid becomes smarter with increased penetration of distributed resources.

Experimental Investigation and Performance Characteristics of Francis Turbine with Different Guide Vane Openings in Hydro Distributed Generation Power Plants

This article presents a study on the performance characteristics of a Francis turbine operating with various guide vane openings to determine the best operating point based on unit quantities. The guide vane openings were specified based on the width between the vanes at their exit, i.e., 10 mm, 13 mm, 16 mm, and 19 mm. The performance characteristic curves of the Francis turbine—head versus speed, torque versus speed, discharge versus speed, and efficiency versus speed—were obtained at various input power and guide vane openings. From these data, unit curves were plotted and the corresponding best efficiency points were obtained. The highest efficiency of 50.25% was obtained at a guide vane opening of 19 mm. The values of head, discharge, speed, and output power at BEP were 7.84 m, 13.55 lps, 1250 rpm, and 524 W, respectively.

Emerging and Advanced Green Energy Technologies for Sustainable and Resilient Future Grid

Future grid refers to the next generation of the electrical grid, which will enable smart integration of conventional, renewable, and distributed power generation, energy storage, transmission and distribution, and demand management [...]

Anti-Islanding Method Development Based on Reactive Power Variation under Grid Support Environments

As the proportion of distributed generation (DG), including Photovoltaic (PV) generation, in the power grid system increases, there are dropouts of large-scale distributed power generation sources due to some transient conditions that negatively affect the power grid stability and power quality. Accordingly, the inverter for DG generation is in a transition period, requiring more complex control performance. Anti-islanding function requirements in particular are becoming more strict because sophisticated grid-connection requirements are demanded, such as voltage ride-through, frequency ride-through, rate of change of frequency, and other functions. Thus, highly advanced anti-islanding methods are required to detect the islanding condition quickly and accurately to stop the inverter. This paper presents the improved anti-islanding method based on reactive power variation (RPV) under grid-support environments for single-phase DG inverters. In order to verify the validity of the proposed method, PSIM simulation was conducted. The proposed method meets the requirements of IEEE Std. 1547-2018 and KS C 8564:2021 by preventing islanding within 0.007 s under the newly adopted voltage/frequency trip setting, while the conventional RPV method fails.

Towards an Internet of Energy for smart and distributed generation: applications, strategies, and challenges

AbstractThe global demands for clean and sustainable energy are rapidly increasing because of population and economic growth. The future of energy essentially requires novel thinking and new systems to transform energy generation, distribution, and consumption. The Internet of Energy (IoE), as a new concept, transforms the way of energy production, supply, and consumption to fulfill high-energy demands via a smart network of industrial energy producers and consumers. The main objective of this paper is to address how the Internet of Things (IoT) would meet the requirements of smart and distributed power generation. We did a comprehensive literature review to provide insights into the IoE applications and enlighten the current challenges. Furthermore, the paper provides deep insights into the existing research challenges to address the current limitations of the IoE security issues, and potential directions are also pointed for future work. The findings of this study include identifying the requirements and enabler factors influencing the IoT-based distributed generation that would be useful for policymakers and decision-makers in the field.

Large-Signal Stabilization Method for Islanded DC Microgrids Considering Battery and Supercapacitor Hybrid Energy Storage Systems

Islanded DC microgrids composed of distributed generators (DGs), constant power loads (CPLs), parallel converters, batteries and supercapacitors (SCs) are typical nonlinear systems, and guaranteeing large-signal stability is a key issue. In this paper, the nonlinear model of a DC microgrid with a hybrid energy storage system (HESS) is established, and large-signal stability criteria are obtained. The HESS consists of batteries and SCs. The derived criteria reveal the influences of the filter parameters, CPL power, DG power and the proportional control parameters of the battery converter and the SC converter on the system large-signal stability. Furthermore, important large-signal stabilization methods for regulating the HESS converter’s control parameters can easily achieve the large-signal stabilization of islanded DC microgrids without extra equipment. The paper is summarized as follows: First, the topology of and control strategy for a DC microgrid with an HESS and CPLs are proposed. Then, according to the characteristics of the HESS, the DGs and the CPLs, the system is equivalently simplified. Finally, the nonlinear model and large-signal stability criteria are both derived using the mixed potential theory, and a large-signal stabilization design method for the HESS converter’s control parameters is proposed. The experimental and simulation results show the effectiveness of the proposed large-signal stabilization method.

Distributed Energy Resources Electrical Systems: Current status and Future prospective

Distributed generation (DG) is an approach that utilizes small scale technologies to generate electricity close to the consumer side. Generally, DG can provide high reliability, high security, low cost electricity, and less environment impact. This paper gives an overview of some of the most significant issues related to the distributed generation (DG). It discusses different aspects of DG, such as definitions, technologies, motivation for moving to DG, some drawbacks associated with the centralized systems which have led to DG. DGs challenges, standards and polices are also presented. In addition, the economic impact and a price comparison between central power plants and DGs are discussed. Also a case study was conducted in order to study the impact of using distributed generations in Edmonton downtown. Three distributed generations, combustion turbine types with 25 MW capacities each have been implemented in Edmonton power system. The total cost estimations have been studied in this case, and the results have revealed that this type of distributed generation is inexpensive and more economic compared with price from the utility. It was estimated from the calculation that the price for the energy is about ¢6.27/kWh while the current electricity price from the utility is ¢8.561/kWh, for long term estimation it is found that the proposed CTs in this project has 11 years for a payback period, after that the project start earning money which is relatively good and wroth investment. The second part of the study analyses the impact of DGs on the system losses using Power-World software, and the result have proven that the loss is significantly decreases when the DG systems are in operation, hence DGs help reducing the costs that associated with the system’s losses.

Flexible control of grid-connected renewable energy systems inverters under unbalanced grid faults

The sustainable energy opportunity of the future lies in the renewable energy-based distributed Power Generation systems (DPGSs). However, there are different concerns and integration issues that surround them. To increase the rate at which renewable energy can be used, this paper focuses on an integrated utility grid system. A novel strategy to control the grid side inverter is developed for a DPGS when considering an unbalanced grid. First, an analysis of the consequences of the occurrence of a fault on the grid is performed. Secondly, a control strategy is proposed to ensure the operation of the DPGS connected to the grid even if the latter is unbalanced. The proposed approach consists in developing control loops for each of the three symmetrical sequences in a specific reference frame to ensure the operation of the grid-connected DPGS even during asymmetrical grid voltage fault. The found results are promising in terms of the guarantee of service continuity during faulty conditions.

Distributed Generation Power Systems in Wastewater Management

The article concerns the energy security of a wastewater treatment process caused by unforeseen situations related to the risk of electrical power outages. In this case, renewable energy sources based on distributed generation power systems can solve this problem in each wastewater treatment plant. The article highlights e related challenges and proposes the direction of solutions in this regard based on Czech conditions. The first part of the paper deals with the consequences of long-term outage of wastewater treatment plants on the population and the environment. There are several solutions presented for blackout conditions, and model calculations are made based on data from a Czech wastewater treatment plant. Diesel engine-generators, biogas as a cogeneration source of heat and electricity, solar panels with storage systems and combined biogas and solar systems were considered as approaches to provide energy autonomy during a blackout in a wastewater treatment plant. Special attention was paid to a combination of CHP units with solar panels and batteries. The results were evaluated for three different locations for this combination. It was concluded that biogas combustion in the CHP unit was the most profitable option, allowing the production of electricity independently of the grid for its own consumption and possibly for other operations. The last part of the paper deals with the transition to island operation, which must occur during a blackout. This transition is more difficult for both solar panels and cogeneration units if they were to supply electricity to the grid before a blackout. The transition to energy island operation could be ensured by frequency relay and processor devices to control the circuit breaker. Then, to maintain island operation, it would be necessary to have an automatic load shedding/application system.

Two-Stage Research on AC/DC Hybrid High-Voltage Distribution Network Based on Network Reconfiguration and SOP Coordinated Control

DC power grid has the advantages of large power supply capacity, easy access to clean energy, low loss, and easy power control. With the increasing penetration rate of distributed generation and DC load in low-voltage transmission network, the traditional radial AC distribution form develops into AC-DC hybrid form. Large-scale distributed energy access is an important feature of future distribution system. Aiming at the AC-DC hybrid distribution system with soft tie-in switch and voltage source converter, considering the network congestion caused by large-scale access of distributed energy, a two-stage congestion management mechanism is proposed. This strategy solves the congestion problem of AC/DC hybrid transmission network with the help of the power flow control ability of AC/DC transmission network’s own optimization control means and congestion management services provided by distributed energy sources. According to the experiment, the total distributed generation power of DC link is 15 MW, and the load power is 10 MW, that is, the remaining power of DC link is 5 MW, the total distributed generation power of AC link is 8 MW, and the load power is 15 MW, that is, the power shortage of AC link is 7 MW. In the first stage, the tie-in switch, SOP and VSC are coordinated and optimized, and in the second stage, the flexible adjustment ability provided by distributed energy makes up for the deficiency of the adjustment ability of direct control means in some periods of severe congestion and meets the requirements of congestion management of AC-DC hybrid transmission network under high-permeability distributed generation.

Grid‐connected operation and control of single‐phase asymmetrical multilevel inverter for distributed power generation

In recent times, multilevel inverters (MLIs) are gaining popularity for grid integration of distributed power generation sources. In this paper, a proportional-resonant (PR) controller based on current control logic is proposed for a single-phase eleven-level inverter topology, enabling the integration of distributed power generation sources into the grid. The presented topology utilizes eight two-quadrant switches and three dc sources to produce an eleven-level output voltage. The level-shifted pulse width modulation (LS-PWM) scheme is used for providing switching signals to the inverter under grid-connected operation. Simulation and real-time results are presented for the eleven-level inverter to validate the presented current control logic under the grid-connected mode of operation. The hardware-in-loop emulator (Typhoon HIL-402) is used for taking real-time results of the presented grid-connected topology. The total harmonic distortion (THD) of the eleven-level inverter voltage and grid current is 12.10% and 0.46%, respectively. The efficiency of the inverter while supplying 2 kW active power to the grid is 98.4%.

Research on Reconfiguration of Distribution Network considering Three-Phase Unbalance

In the distribution network, the addition of distributed power sources can improve the voltage part of the distribution system, provide uninterrupted power supply, and reduce network losses. The location of the power supply and its output will also directly affect the system voltage and power loss. Therefore, determining the optimal installation location and capacity of distributed power generation is of great significance to the distribution network. However, in the actual system, due to the unbalanced load distribution and the three-phase unbalance of the transmission line, the power distribution system presents the characteristics of unbalanced distribution. As the number of electric vehicles increasing, the imbalance of the distribution network has become more prominent.

Effect of Sputtering Pressure on the Nanostructure and Residual Stress of Thin-Film YSZ Electrolyte

Solid oxide fuel cells are energy conversion devices that contribute to carbon neutrality, with the advantages of high efficiency, clean emissions production, and distributed power generation. However, the high operating temperature of the solid oxide fuel cells causes system stability and material selection problems. In this study, we aimed to lower the operating temperature of a solid oxide fuel cell by reducing the thickness of the electrolyte via sputtering. The deposition process was conducted under various pressure conditions to find the optimal sputtering process for a gas-tight YSZ thin-film electrolyte. The gas-tightness of the YSZ electrolytes was evaluated by observing the nanostructure and cell performance. As a result, the YSZ thin-film deposited at 3 mTorr showed the best gas-tightness and cell performance. At 500 °C, 1.043 V of OCV and a maximum power density of 1593 mW/cm2 were observed. Then, X-ray diffraction was used to calculate the residual stress of the YSZ films. As a result, it was confirmed that the gas-tight film showed compressive residual stress. Through this study, we were successful in developing a room-temperature YSZ electrolyte fabrication process with excellent gas-tightness and performance. It was also proven that there is a strong relationship between the gas-tightness and residual stress. This study is expected to contribute to cost reductions and the mass production of solid oxide fuel cells.

Investment strategies under stochastic electricity prices and implications for charging infrastructure network coverage: A case of photovoltaic pavements

For enhancing the charging infrastructure network coverage in populated areas, photovoltaic pavement (PVP) has been considered an innovative option that caters to distributed power generation and electric vehicles (EVs) charging in motion. However, the promotion of PVP has not yet served its intended purpose. This paper develops a gross net present value (GNPV) model to investigate the optimal timing to invest in PVP under stochastic electricity prices and time-dependent investment costs. Based on the photovoltaic highway project in Shandong, China, our numerical results reveal that the volatility of electricity prices, construction investment costs, and solar panels’ energy conversion efficiency significantly restricts the diffusion of PVP, resulting in the current dilemma of PVP adoption. However, the rapid decline in investment costs and the rapid increase in the number of EVs are not always effective in accelerating the PVP investment process, especially in some high electricity price regions, such as the southern areas of China. The findings of this paper will provide theoretical support and decision-making recommendations for the management evaluation of PVP projects, the optimization of charging facility networks, and the formulation of EV incentive measures.