Distributed Power Generation Research Articles

VERCampus – Live Park of Renewable Energies

This paper presents the VERCampus Project – Live Campus of Renewable Energies – which integrates a set of technologies, infrastructures, and initiatives carried out in the Campus of the Polytechnic Institute of Bragança (IPB) regarding the renewable energies technologies and distributed power generation systems promotion and dissemination for IPB students and for other schools and education levels, stakeholders and all community in general. The aim is to create an attractive and innovative green Campus as a real platform for training, education and dissemination activities in order to understand the real cost of the energy and stimulate better behaviours in view of a rational use of energy. The results consist of an experimental framework based on commercial equipment with new and innovative functionalities developed by students and teaching staff of IPB in view of studies and transfer of practical information and technology for the community. This paper describes the main activities achieved for these purposes and some details are presented.

A novel approach to frequency control in an islanded microgrid by load shedding scheduling

A microgrid is composed of distributed power generation systems (DGs), distributed energy storage devices (DSs), and loads. To maintain a specific frequency in the island mode as an important requirement, the control of DGs output and charge action of DGs are used in supply surplus conditions and load-shedding and discharge action of DGs are used in supply shortage conditions. Recently, multiagent systems (MAS) for autonomous microgrid operation have been studied. Especially, load-shedding, which is intentional reduction of electricity use, is a critical problem in islanded microgrid operation based on the MAS. Therefore, effective schemes for load-shedding are required. A novel optimization algorithm called ICA has been used to optimize this load shedding procedure.

Analysis of Remote Islanding Detection Methods for Distributed Resources

Penetration of distributed generation in the power grid is increasing. This situation leads to new possibilities but also new issues, such as anti-islanding protection. During a loss-of-mains or islanding situation, distributed generation (DG) units remain feeding a part of the electrical network without connection to the main power system. Currently, DG units have to be disconnected from the grid during islanding as soon as possible, due to potential risks for repair crews and components, poor power quality in the island and reclosing problems. A fast and reliable islanding detection method could avoid mentioned issues. Among the many existing methods, remote schemes could meet these requirements. Hence, this paper presents the operating principles of remote islanding detection methods, as well as the current state of development of communication-based remote islanding detection methods to be applied in distributed power generation systems.

Current control of distributed generation power inverters for losses reduction in the distribution network

The main objective of the paper is to evaluate the power losses reduction that can be achieved in a low voltage distribution network when the inverters associated to the distributed generation are used as active power filters to compensate the non active currents produced by inductive and unbalanced loads. For that purpose, a hysteresis current control has been proposed and implemented. A real distribution threephase four-wire network has been simulated considering a large penetration of distributed generation. Power losses and the efficiency of the network have been quantified for different compensation cases.

Multilevel Convertors for Distributed Power Generation Systems with DC Voltage Sources.

The paper is related to the problem of generating the high qual-ity AC voltage waveforms in distributed power generating systems with DC voltage sources like photo-voltaic farms and fuel cells. A novel approach to the synthesis of AC voltage waveforms, applying chosen analytical methods like Fourier transform, Haar wavelets transform and orthogonal vectors method, is discussed. The simulation and experimental results for the proposed complex convertor’s structures are presented in the paper.

Защита электрогенераторов объектов распределенной генерации от аварийных режимов

Distributed generation is a good solution for areas remote from centralized power supply sources as it helps increase the reliability of consumer operation. Distributed generation power supply systems use renewable sources of electricity, diesel generators and gasoline generators in the form of mobile power stations, which in most cases are not equipped with modern means of protection. This study presents an analysis of existing means of protecting electric generators from abnormal and emergency operating conditions, including voltage asymmetry, which is one of the factors reducing the service life of generators and is typical for rural electrical networks. During the analysis, the authors determined the main types of generator protection against emergency operation modes: protection of stator windings, protection against underfrequency and overfrequency, protection against undervoltage and overvoltage, protection against voltage (current) asymmetry. It is noted that the main cause of voltage asymmetry leading to mechanical vibration and rapid overheating of the rotor is single-phase loads in the system, which are unevenly distributed over three phases. The problem of voltage asymmetry is mainly solved by redistributing loads in transmission lines and/or installing compensating devices. However, in rural power supply systems, unbalanced load distribution is rarely corrected. The voltage asymmetry can be compensated through the use of hybrid active power filters of series compensation and improved control methods of these filters. Voltage converters that are effective in equalizing voltage asymmetry in PV systems can effectively protect small capacity diesel power generators provided that the use of additional equipment is economically viable.

Review on Non-Isolated Multiport Converters for Residential DC Microgrids

Nowadays, energy sustainability needs drive the development of novel power system architectures that efficiently harvest and deliver green energy. Specifically, DC Microgrids (DC-MG) have emerged as promising bases for distributed power generation, especially in residential applications. The pivotal role of power conversion and the need for more affordable and compact converters has led to an increasing research interest. MultiPort Converters (MPCs) exhibit beneficial operational characteristics for these applications and, therefore, a plethora of different topologies is suggested in the literature. Even though there have been some attempts to organize and review the field status, the categorization is based on the existence or not of isolation between the converter’s ports, without providing insight on the topology conception. In this article, a literature review is conducted to specify the most suitable non-isolated MPC topologies for residential DC-MGs. Converters with a power rating ranging from 0.1 to 1 kW are compared based on technical features and categorized according to their topology derivation process. This procedure is performed separately for MPCs suitable for unipolar and bipolar DC Buses. The selected approach highlights the design basis for each MPC in a structured manner, facilitating further development of original converters by both new and experienced researchers.

A novel cost-based optimization model for electric power distribution systems resilience improvement under dust storms

A novel cost-based optimization model for electric power distribution systems resilience improvement under dust storms

Energy Storage Dynamic Configuration of Active Distribution Networks—Joint Planning of Grid Structures

The integration of distributed power generation mainly consisting of photovoltaic and wind power into active distribution networks can lead to safety accidents in grid operation. At the same time, climate change can also cause voltage fluctuations, direct current injection, harmonic pollution, frequency fluctuations, and other issues. To achieve economic and safe operation of the distribution network, an active distribution network-network planning model considering the dynamic configuration of energy storage system energy storage is constructed. This model focuses on energy storage batteries with high ease of use, high modularity, and strong mobility. The route location planning involving different load operating scenarios in spring, summer, autumn, and winter is constructed. The objective function includes the revenue from selling electricity in the distribution network, the expenditure on purchasing electricity in the distribution network, and the cost during the planned construction period. The constraints include three major constraints: distribution network operation, network topology, and energy storage system operation. Three numerical examples are set up to analyze the impact of energy storage system dynamic configuration on grid planning. The results confirmed the active distribution network-grid planning model for dynamic configuration of energy storage systems. Both Example 2 and Example 3 had 3 ESS configurations. Case 3 showed different access methods for ESS in different seasons. The access nodes for ESS in spring and winter were 4, 5, and 6, while the access nodes for summer and autumn were 3, 5, and 6. After applying the proposed method, the daily energy storage investment of commercial, residential, and industrial users gradually stabilized. The reliability of electricity consumption was improved, with an improvement rate of about 40%. The research has brought considerable economic benefits to distribution network operators. It has forward-looking academic value in the joint planning of grid structures and energy storage.

Mass and efficiency optimization of a He-Xe Brayton cycle for mobile, land-based nuclear microreactors

Mass and efficiency optimization of a He-Xe Brayton cycle for mobile, land-based nuclear microreactors

Investigation on Voltage Stability in a Distributed Generation Power Grid Influenced by PMSG and DFIG Based Wind Energy Conversion System

– Countries have pledged to meeting the demand for electricity while also generating electricity from renewable sources in order to slow environmental degradation. Compared to other forms of alternative energy, wind power has a comparatively small environmental impact despite its size. Instability on the grid is a common consequence of adding wind power. Voltage instability is a common type of stability issue. The wind is an unpredictable element of nature. Wind velocity shifts as a result of varying turbine rotation speeds. For back-to-back converters to effectively maintain a stable grid voltage, the DC link voltage and the grid voltage must be the same. In this study, we’ll look about how the DFIG and PMSG affect voltage stability. In this study, we test the voltage stability of WECS built on PMSG and DFIG in three distinct scenarios. The whole system is created and analyzed with the help of Matlab/Simulink. The results of this inquiry have far-reaching consequences. This research provides important insight into how renewable energy sources may be better integrated into the grid, which could radically alter the energy industry.

Organisation of the Structure and Functioning of Self-Sufficient Distributed Power Generation

During the operation of solar and wind power plants, it is necessary to solve issues related to the guaranteed capacity of these plants, as well as the frequency stabilisation in the power system where they operate, and maintain an operating mode of self-sufficiency conditions. One of the solutions to these problems is the use of energy storage systems. This article proposes a mathematical model for the study of frequency and power regulation processes in power systems with distributed generation, which includes renewable energy resources and energy storage systems. The novelty of the model lies in the possibility of determining energy cost indicators based on instantaneous energy power data. The model allows us to estimate the conditions under which distributed generation becomes self-sufficient. The results of the model calculations of two variants of power system operation, which includes wind generators with a capacity of 1500 MW, demonstrate the ability of the proposed model to accurately reproduce the dynamics of the frequency stabilisation process. The calculation results of the energy-economic indicators of a real power system combined with a powerful subsystem of wind generation and a battery-type energy storage system prove the competitiveness of self-sufficient renewable energy power plants.

СУЧАСНІ РІШЕННЯ ДЛЯ ПРИЄДНАННЯ ВІДНОВЛЮВАНИХ ДЖЕРЕЛ ЕНЕРГІЇ ДО СИСТЕМИ ЕЛЕКТРОПОСТАЧАННЯ

According to the Energy Strategy of Ukraine, the development of renewable energy sources (RES) is expected to be the most dynamic compared to other types of generation. However, the existing energy problems and threats require the development of new and amendment of existing legislative and by-laws, as well as a number of sectoral norms regulat-ing activities in the energy sector. The article provides an overview of the world's current trends in renewable energy, as well as the formation of areas that should be focused on when reforming the energy sector. The long-term energy policy of the state should be focused on the effective integration of RES into the power supply system. To this end, it is necessary to stimulate and control the implementation of distributed power generation management systems, virtual power plants, and energy storage systems. The gradual growth of electric vehicles leads to the use of Vehicle-to-Grid technology, especially when considering modern microgrids or "smart grids" with RES. And the concept of an "active building" is a key step towards decarbonizing the construction sector. Ref. 9, fig. 2. Keywords: renewable energy sources, distributed energy resource management systems, virtual power plant, energy storage system, Vehicle-to-Grid, Plus Energy Buildings.

Power quality disturbance mitigation in grid connected photovoltaic distributed generation with plug-in hybrid electric vehicle

In the last twenty years, electric vehicles have gained significant popularity in domestic transportation. The introduction of fast charging technology forecasts increased the use of plug-in hybrid electric vehicle and electric vehicles (PHEVs). Reduced total harmonic distortion (THD) is essential for a distributed power generation system during the electric vehicle (EV) power penetration. This paper develops a combined controller for synchronizing photovoltaic (PV) to the grid and bidirectional power transfer between EVs and the grid. With grid synchronization of PV power generation, this paper uses two control loops. One controls EV battery charging and the other mitigates power quality disturbances. On the grid connected converter, a multicarrier space vector pulse width modulation approach (12-switch, three-phase inverter) is used to mitigate power quality disturbances. A Simulink model for the PV-EV-grid setup has been developed, for evaluating voltage and current THD percentages under linear and non-linear and PHEV load conditions and finding that the THD values are well within the IEEE 519 standards.

Research on Optimal Configuration of Integrated Energy Storage for Source Network, Load Storage Considering Carbon Emissions

This study endeavors to construct an optimized operation model for a Combined Heat and Power Microgrid that utilizes renewable distributed power generation. The model decouples the thermoelectric connection via energy storage equipment and takes into account carbon emissions based on multi-energy complementarity. This approach offers an optimization space for the thermal and electrical production of microgrids. Numerical simulation verification demonstrates that the optimization strategy proposed in this study enhances the flexibility of the system’s energy supply and improves the operational economy. Furthermore, the study explores the optimal storage battery capacity under the integration of a specific area’s source-grid-load-storage.

Power Flow Calculation of Integrated Transmission and Distribution Networks

As smart grids develop by leaps and bounds, the distribution network (DN) shows a more flexible and ever-changing trend. The continuous integration of distributed power generation, electric vehicles, and other new energy generation has led to an increasingly close relationship among the transmission and distribution networks (TDNs). The traditional method of independently calculating power flow in TDNs is no longer applicable. This paper proposes a power flow calculation algorithm for integrated transmission and distribution networks (ITDNs) based on the master-slave-splitting (MSS) method in response to this problem. This method is based on the electrical connection relationship between TDNs and the characteristics of their respective network structures. It decomposes the global power flow calculation problem into transmission network (TN) power flow calculation, multiple DN power flow calculation, and boundary node information coordination sub-problems. And achieve power flow calculation of ITDNs by exchanging the voltage and equivalent power of boundary nodes. Finally, the global power system constructed by the IEEE30 node system and IEEE33 node system is used to confirm the validity and correctness of the proposed algorithm and model.

Distributed Power High Dynamic Group Control Technology and Grid Connection Demonstration

Abstract Currently, high penetration distributed power generation group control technology makes it difficult to effectively regulate complex power grids. Therefore, on the ground of the division of distributed photovoltaic power generation clusters, this study proposes a dual-layer control model for distribution networks that integrates the cuckoo particle swarm algorithm and verifies its effectiveness. The experiment showcases that the standard deviations of the research algorithm on the four benchmark functions under the 50 dimension are 2.95e-02, 6.73e+02, 6.48e-04, and 6.45e-06, respectively, most of which are lower than the comparison algorithm. On the basis of connecting to the photovoltaic system, the voltage amplitude fluctuation of the double-layer control model designed through research using control algorithms is relatively small, basically maintaining around 1.05. In addition, after implementing control in practical applications, the actual line loss of the distribution network decreased from the maximum of 15.3% to 8.9%, meeting the line loss requirements of the actual distribution network, indicating the effectiveness of the double-layer control model. Meanwhile, after applying the double-layer control model, the voltage fluctuation of node 42 significantly decreased, and the numerical value remained at 1.05 p.u., achieving a good voltage condition effect. The voltage fluctuation of grid connection in distributed power generation has been significantly improved when applied to the actual grid connection. Overall, the proposed dual-layer control model for the distribution network is effective and practical, which can effectively promote the construction of practical grid connection demonstration projects.

Технології електрогенерації та теплопостачання для підвищення енергетичної незалежності окремих територіальних громад

Russian attacks on Ukraine's energy system, which led to the blackout of entire cities and the termination of district heating, highlighted the risks and disadvantages of relying on large-scale district energy supply for communities. In this context, it is important to consider the development of the energy supply of communities in the direction of their energy independence. The purpose of the article is to form a list of electricity generation and heat supply technologies for increasing the energy independence of individual territorial communities, which are appropriate for implementation in Ukraine. The article considers the criteria for the analysis and selection of technologies for distributed power generation and heat supply. An analytical overview of the following power generation and heat supply technologies is presented: solar and wind power plants, gas piston and gas turbine plants, generators, batteries, co- and trigeneration plants, biofuel power plants and heat-generating boilers, heat pumps and electric boilers, and their grouping is performed according to the established criteria. All the considered technologies contribute to reducing the external supply of communities with energy resources and reducing losses during the transmission and distribution of electricity. Technologies that use renewable energy sources and local fuels are appropriate for implementation in communities in accordance with the availability of sufficient amounts of resources. Still, in most cases, they are not able to fully provide communities with electrical and thermal energy due to their insufficient quantity and high cost of equipment, such as batteries and heat pumps. Decisions regarding the implementation of a specific technology of distributed generation should be made after a thorough analysis of the conditions and possibilities of the energy supply of each individual community. This article is aimed at discussing the options of increasing energy independence and ensuring the reliability of the energy supply of territorial communities in Ukraine. Keywords: distributed generation, power generation, heat supply, renewable energy sources, cogeneration, biofuels, heat pumps.

Full Operating Range Optimization Design Method of LLC Resonant Converter in Marine DC Power Supply System

The marine DC power supply system is the key to a ship’s power supply, which needs to convert the energy from storage batteries or distributed power generation units into stable DC voltage for electric propulsion or the ship’s electronics. The LLC resonant converter can be used as the key power conversion link in the marine DC power supply system due to its ability to realize electrical isolation in a high-power environment and soft switching within a wide load range. Aiming at the problem of sudden changes in voltage gain at a high switching frequency under light load conditions and the problem of insufficient voltage gain under heavy load conditions due to the parasitic parameters of power devices (mainly referring to the junction capacitor), this paper first proposes a full operating range performance optimization design method. By adding an auxiliary circuit that can be opened according to the operating conditions and a multi-objective particle swarm parameter optimization method that considers the converter loss and voltage gain under heavy load conditions, the performance of the LLC resonant converter can be improved in a full range of operating conditions. Finally, the effectiveness of the proposed method is verified by an experimental prototype and compared with the conventional methods and existing solutions to highlight the superiority of the proposed method in this paper.

Impact of Grid-Connected Inverter Parameters on the Supraharmonic Emissions in Distributed Power Generation Systems

In this paper, a mathematical analysis is presented to show the effect of grid-connected inverter (GCI) parameters on its emissions in the supraharmonic range. This analysis is extended to explain the effect of asymmetry on the emissions of parallel-connected GCIs on distributed power generation systems. The switching harmonics of a GCI appear as bands around the switching frequency and its multiples. A MATLAB/Simulink model is built to perform two studies. In the first study, we use one GCI to examine the effect of the parameters on the emissions, while in the second study, we examine the effect of the asymmetry of two parallel-connected GCIs on the total emission toward the grid. An actual setup is built to verify the results of the mathematical analysis and the simulation study. It is found that the SHs of single-phase GCI amplitude are strongly dependent on the DC-link voltage and the coupling inductor, while the phases of the sideband harmonics only change with changing the injected power. The variation of the injected power does not have any tangible effect on the carrier harmonics.