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With the evolution of renewable energies, many doubly fed induction generators (DFIGs) are being connected to the power grid, whose operation and grid‐connection stability have a major impact on the power grid. Currently, most studies focus on either modeling the mechanical–electrical section or the electrical‐grid section, and discussions have been limited to shaft oscillation or frequency coupling problems. In this study, a mechanical–electrical‐grid model of a DFIG was established to examine the impacts of wind speed and system control parameters on electrical damping and grid‐connection stability. The accuracy of the proposed model and validity of the analyses were verified using simulations. The following were observed: (1) In the case of changing wind speeds, the wind speed and the applied control model determine the shaft oscillation of DFIG, whereas the grid‐connected impedance on the rotor side is dependent on the wind speed. (2) At a constant wind speed, changes in control parameters under different control modes affect the dynamic characteristics of the drive train differently, whereas the grid‐connected impedance on the rotor side is primarily determined by the proportional gain of the inner/outer loop of the control system. The conclusions drawn from this study can further improve the safe and stable operation of DFIG wind power generation systems as well as their connection to the power grid.

Battery energy storage systems have gained increasing interest for serving grid support in various application tasks. In particular, systems based on lithium-ion batteries have evolved rapidly with a wide range of cell technologies and system architectures available on the market. On the application side, different tasks for storage deployment demand distinct properties of the storage system. This review aims to serve as a guideline for best choice of battery technology, system design and operation for lithium-ion based storage systems to match a specific system application. Starting with an overview to lithium-ion battery technologies and their characteristics with respect to performance and aging, the storage system design is analyzed in detail based on an evaluation of real-world projects. Typical storage system applications are grouped and classified with respect to the challenges posed to the battery system. Publicly available modeling tools for technical and economic analysis are presented. A brief analysis of optimization approaches aims to point out challenges and potential solution techniques for system sizing, positioning and dispatch operation. For all areas reviewed herein, expected improvements and possible future developments are highlighted. In order to extract the full potential of stationary battery storage systems and to enable increased profitability of systems, future research should aim to a holistic system level approach combining not only performance tuning on a battery cell level and careful analysis of the application requirements, but also consider a proper selection of storage sub-components as well as an optimized system operation strategy.

To ensure the stability and reliability of the power network operation, a number of Grid Codes have been used to specify the technical boundary requirements for different countries and areas. With the fast propagation of the usage of Electrical Energy Storage (EES), it is quite important to study how the EES technology with its development can help the Grid Code realization. The paper provides a comprehensive study of Great Britain (GB) Grid Code mainly on its voltage and frequency relevant specifications, with a comparison of other countries’ grid operation regulations. The different types of EES technologies with their technical characteristics in relation to meeting Grid Codes have been analysed. From the study, apart from direct grid-connection to provide grid services on meeting Grid Codes, EES devices with different technologies can be used as auxiliary units in fossil-fuelled power plants and renewable generation to support the whole systems’ operation. The paper also evaluates the potentials of different types of EES technologies for implementing the relevant applications based on the Grid Codes. Some recommendations are given at the end, for the EES technology development to help the Grid Code realization and to support the relevant applications.

With the steady annual growth of grid-connected photovoltaic (PV) power generation, the intermittent nature of this energy source has been increasingly drawing attention for its impact on grid stability. The output of photovoltaic power generation is highly influenced by weather factors and seasonal changes. The 24 solar terms are widely recognized as a reliable method for predicting weather conditions and seasonal shifts in China. Based on an analysis of the 24 solar terms, this work investigated their impact on PV power generation in China and established a correlation coefficient between PV output and solar terms. Subsequently, this paper proposed a grid connection method based on average values derived from the 24 solar terms and optimized it using a transfer learning model. The effectiveness of the proposed method was validated through a case study on a small-scale PV power station. It was validated that the proposed grid connection method increases power grid stability by 17.75%. The average grid connection method developed in this paper, which more accurately aligns with seasonal solar radiation variations, contributes to advancing grid-connected PV systems and provides a practical strategy for large-scale PV power integration.

In the coming decades, the European energy system is expected to become increasingly reliant on non-dispatchable generation such as wind and solar power. Under such a renewable energy scenario, a better characterization of the extreme weather condition ‘Dunkelflaute’, which can lead to a sustained reduction of wind and solar power, is important. In this paper, we report findings from the very first climatological study of Dunkelflaute events occurring in eleven countries surrounding the North and Baltic Sea areas. By utilizing multi-year meteorological and power production datasets, we have quantified various statistics pertaining to these events and also identified their underlying meteorological drivers. It was found that almost all periods tagged as Dunkelflaute events (with a length of more than 24 h) are in November, December, and January for these countries. On average, there are 50–100 h of such events happening in each of these three months per year. The limited wind and solar power production during Dunkelflaute events is shown to be mainly driven by large-scale high-pressure systems and extensive low-cloud coverage. Even though the possibility of simultaneous Dunkelflaute events in neighboring countries can be as high as 30–40%, such events hardly occur simultaneously in all the eleven countries. Through an interconnected EU-11 power system, the mean frequency of Dunkelflaute drops from 3–9% for the individual countries to approximately 3.5% for the combined region, highlighting the importance of aggregating production over a wide area to better manage the integration of renewable energy generation.

On the one hand, the application of microgrid can effectively cut down the effect of distributed generation on distribution network, on the other hand, it helps to improve the power quality of distribution network. However, for the distribution network, a single multi-functional inverter has limited effect on the improvement of its power quality. Therefore, the allocation control of power quality by decentralized multi-functional inverters can further improve the utilization of inverters. This paper proposes to calculate the output current of multiple multi-functional inverters according to the harmonic and reactive current of the parallel node and the residual capacity of the multi-functional inverter. The simulation results show that the allocation control strategy proposed in this paper can effectively control the compensation capacity of the multi-functional inverter, so as to control the harmonic at the grid connection in place.

The numerical simulation of flow around a three dimensional moving body faces different problems in several methods, such as disruption of the structure of the grid, the need for deletion and insertion of nodes, interpolation, and data transfer between different parts of grid. In order to tackle the above-mentioned problems, a new configuration has been developed for meshing domain, which besides providing the body with the capability of rotational and oscillatory motions in large displacements, saves the grid's primitive quality. In the introduced method, the grid connections are manipulated with the motion of the body, but the general form of the grid is not changed or disrupted. This needs a special form for nodes of the grid, which is explained in this paper. The three dimensional unsteady form of the Euler equations is solved and the properties over each cell faces are evaluated using an averaging method. For time integration of the equations an implicit dual time method is used. It can prove that the volume of all elements is constant in the introduced grid. Therefore, there is no need to calculate elements volume in every time step. Several test cases are solved and the results are compared with experimental or other numerical data.

Solar energy generated by grid-connected photovoltaic (GCPV) systems is considered an important alternative electric energy source because of its clean energy production system, easy installation, and low operating and maintenance costs. This has led to it becoming more popular compared with other resources. However, finding optimal sites for the construction of solar farms is a complex task with many factors to be taken into account (environmental, social, legal and political, technical-economic, etc.), which classic site selection models do not address efficiently. There are few studies on the criteria that should be used when identifying sites for solar energy installations (large grid-connected photovoltaic systems which have more than 100 kWp of installed capacity). It is therefore essential to change the way site selection processes are approached and to seek new methodologies for location analysis. A geographic information system (GIS) is a tool which can provide an effective solution to this problem. Here, we combine legal, political, and environmental criteria, which include solar radiation intensity, local physical terrain, environment, and climate, as well as location criteria such as the distance from roads and the nearest power substations. Additionally, we use GIS data (time series of solar radiation, digital elevation models (DEM), land cover, and temperature) as further input parameters. Each individual site is assessed using a unique and cohesive approach to select the most appropriate locations for solar farm development in the Valencian Community, a Spanish region in the east of Spain.

This paper presents an enhanced Maximum Power Point Tracking (MPPT) algorithm for Quadratic-Boost Split Source Inverters (QB-SSI), designed for grid-connected Photovoltaic (PV)-powered smart charging stations for Electric Vehicles (EVs). The proposed algorithm integrates advanced control strategies and adaptive techniques to address the limitations of traditional MPPT techniques. By dynamically adjusting to operating conditions and environmental factors, the enhanced algorithm achieves accurate and rapid tracking of the maximum power point (MPP) under dynamic conditions. The paper provides a comprehensive overview of the QB-SSI topology, a detailed mathematical model, and simulation results. These findings demonstrate the superior performance of the enhanced MPPT algorithm, offering significant improvements in tracking accuracy, convergence time, and efficiency, thereby enhancing the overall performance of QB-SSI-based PV systems. A modified space vector modulation (SVPWM) is utilized to enhance the inverter switching characteristics and dc-boosting capability. The overall system is modeled via MATLAB/Simulink ™ , and the experimental results providing valuable insights into the performance and functionality of the proposed algorithm. This allows for a comprehensive analysis of its capabilities and potential advantages in practical applications.

Rural electrification can have many benefits-not only bringing lighting, but improving the quality of health care, spreading information and supporting productive enterprises. The extent of these benefits has been questioned, arguing that they may be insufficient to justify the investment costs. This book quantifies these benefits. It finds that the benefits can indeed be high, substantially outweighing the costs, and that consumer willingness to pay is generally sufficient to achieve financial sustainability. However, benefits could be increased further by providing smart subsidies to assist connections for poorer households, promote productive uses and further consumer education.