Grid Connection Research Articles

Thermodynamic integration in combined fuel and power plants producing low carbon hydrogen and power with CCUS

Demand for low-carbon sources of hydrogen and power is expected to rise dramatically in the coming years. Individually, steam methane reformers (SMRs) and combined cycle gas power plants (CCGTs), when combined with carbon capture utilisation and storage (CCUS), can produce large quantities of on-demand decarbonised hydrogen and power respectively. The ongoing trend towards the development of CCUS clusters means that both processes may operate in close proximity, taking advantage of a common infrastructure for natural gas supply, electricity grid connection and the CO2 transport and storage network. This work improves on a previously described novel integration process, which utilizes flue gas sequential combustion to incorporate the SMR process into the CCGT cycle in a single “combined fuel and power” (CFP) plant, by increasing the level of thermodynamic integration through the merger of the steam cycles and a redesign of the heat recovery system. This increases the 2nd law thermal efficiency by 2.6% points over un-integrated processes and 1.9% points the previous integration design. Using a conventional 35% wt. monoethanolamine (MEA) CO2 capture process designed to achieve two distinct and previously unexplored CO2 capture fractions; 95% gross and, 100% fossil (CO2 generated is equal to the quantity of CO2 captured). The CFP configuration reduces the overall quantity of flue gas to be processed by 36%–37% and increases the average CO2 concentration of the flue gas to be treated from 9.9% to 14.4% (wet). This decreases the absorber packing volume requirements by 41%–56% and decreases the specific reboiler duty by 5.5% from 3.46–3.67 GJ/tCO2 to 3.27–3.46 GJ/tCO2, further increasing the 2nd law thermal efficiency gains to 3.8%–4.4% points over the un-integrated case. A first of a kind techno economic analysis concludes that the improvements present in a CO2 abated CFP plant results in a 15.1%–17.3% and 7.6%–8.0% decrease in capital and operational expenditure respectively for the CO2 capture cases. This translates to an increase in the internal rate of return over the base hurdle rate of 7.5%–7.8%, highlighting the potential for substantial cost reductions presented by the CFP configuration.

Assessment of Possibilities of Using Local Renewable Resources in Road Infrastructure Facilities—A Case Study from Poland

The rising demand for water and energy is driving the overuse of natural resources and contributing to environmental degradation. To address these challenges, the focus has shifted to low- and zero-emission technologies that utilize alternative sources of water and energy. Although such systems are commonly applied in residential, commercial, and industrial buildings, facilities along transportation routes generally depend on grid connections. This study aimed to enhance operational independence and reduce environmental impacts by modernizing the Rest Area Stobierna (RAS) along Poland’s S19 expressway, part of the Via Carpatia road. A comprehensive technical, economic, and environmental analysis was conducted using HOMER Pro software (3.18.3 PRO Edition) and a simulation model based on YAS operating principles. The proposed Hybrid Renewable Energy System (HRES) incorporates photovoltaic panels, battery storage, and a rainwater harvesting system (RWHS). Two configurations of the HRES were evaluated, a prosumer-based setup and a hybrid-island mode. Optimization results showed that the hybrid-island configuration was most effective, achieving a 61.6% share of renewable energy in the annual balance, a 7.1-year return on investment, a EUR 0.77 million reduction in Net Present Cost (NPC), and a 75,002 kg decrease in CO2 emissions over the system’s 25-year lifecycle. This study highlights the potential of integrating renewable energy and water systems to improve sustainability, reduce operational costs, and enhance service quality in road infrastructure facilities, offering a replicable model for similar contexts.

Energy Enhancement for Grid Connection by Boost Inverter in Tripolar Operation with Novelty Quadcoupling Control

In this paper a single-phase differential boost inverter is presented that has two functions, first is boost up and second is active power quadcoupling without adding active power electronics components for smart grid system. There are three operating principals: First is pulse energy modulation which operates converter in continuous conduction mode (CCM), Second is quadcoupler which is designed by adding four boost converters and third is Tripolar technique which used to add two inductors and one capacitor for each boost converter. The proposed model consist of four boost converters in parallel with interleaving switching technique to get lower duty cycle. The energy is delivered to the quadcoupler through tripolar technique. When two grids are connected through DC to AC conversion the boost inverter can increase voltages on required demand. A Simulink model is designed that shows and proves properties of proposed system with high energy, high efficiency and power control with lower voltage stress.

Low-Frequency AC Multiport Asynchronous Grid Connection System to Optimize Generation Costs and Mitigate Bottlenecks

Renewable energy sources continue to increase due to the energy transition; thus, the generation output of conventional power sources is decreasing. The installation of renewable energy sources can lead to the concentration of these sources depending on geographical characteristics, which may cause bottlenecks between the renewable energy generation sites and load centers, and such bottlenecks can result in power shortages in load centers and may cause issues that limit the integration of renewable energy. Thus, this paper proposes the application of an LFAC multiport asynchronous grid connection system to solve these problems, where the frequency conversion device uses a variable frequency transformer (VFT). In addition, the installation location of the proposed LFAC multiport asynchronous grid connection system is selected using a grid partitioning technique, and the optimal power flow is performed to minimize the generation costs. The grid partitioning was conducted using the IEEE 39 bus system, and the feasibility of the proposed LFAC multiport asynchronous grid connection system was verified through simulation tests of the generation and load demands in the grid. In addition, the VFT control and optimal power flow control performances were confirmed through MATLAB/Simulink.

Scatter Search for Optimal Sizing of a Hybrid Renewable Energy System for Scheduling Green Hydrogen Production

At present, energy demands are mainly covered by the use of fossil fuels. The process of fossil fuel production increases pollution from oil extraction, transport to processing centers, treatment to obtain lighter fractions, and delivery and use by the final consumers. Such polluting circumstances are aggravated in the case of accidents involving fossil fuels. They are also linked to speculative markets. As a result, the trend is towards the decarbonization of lifestyles in advanced societies. The present paper addresses the problem of the optimal sizing of a hybrid renewable energy system for scheduling green hydrogen production. A local system fully powered by renewable energies is designed to obtain hydrogen from seawater. In order to monetize excess energy, the grid connection of the system is considered under realistic energy market constraints, designing an hourly purchasing strategy. This crucial problem, which has not been taken into account in the literature, is solved by the specific dispatch strategy designed. Several optimization methods have been used to solve this problem; however, the scatter search method has not previously been employed. In this paper, the problem is faced with a novel implementation of this method. The implementation is competitive in terms of performance when compared to, on the one hand, the genetic algorithm and differential evolution methods, which are well-known state-of-the-art evolutionary algorithms, and, on the other hand, the optimal foraging algorithm (OFA), a more recent algorithm. Furthermore, scatter search outperformed all other methods in terms of computational cost. This is promising for real-world applications that require quick responses.

Coordinated optimization of control parameters for suppressing transient overvoltage in wind power DC transmission systems

With the increasing proportion of new energy in power systems, the instability issues of novel power systems become more prominent. This paper addresses the transient overvoltage problem in wind power DC transmission systems by proposing a method for transient overvoltage suppression based on doubly-fed wind turbines, high-voltage DC transmission systems, and SVC control parameter optimization. The electromagnetic transient model of the wind power DC transmission system is combined with intelligent optimization algorithms through joint invocation to achieve coordinated optimization of control parameters. Case studies validate the effectiveness of the proposed model and method. The results indicate that the improved genetic algorithm, SEGA, proposed in this paper, effectively suppresses overvoltage at the grid connection point of wind turbines. Furthermore, by simultaneously applying coordinated control strategies based on DFIG and SVC and optimizing parameters of HVDC, DFIG, and SVC, transient overvoltage phenomena can be effectively eliminated.

A comparative study of virtual synchronous generator and sinusoidal pulse width modulation in a wind high power conversion chain

The virtual synchronous generator (VSG) and sinusoidal pulse width modulation (SPWM) are two prominent control strategies that have attracted particular interest recently. In this paper, we compare these two inverter control strategies in a 5MW wind power conversion chain. The studied conversion chain includes a wind turbine, a permanent magnet synchronous generator, the power converters, namely the uncontrolled rectifier, and a two-stage inverter connected to the grid via an LCL filter. Our study of the two control methods shows that both strategies reduce the total harmonic distortion (THD) while respecting the grid connection conditions. The simulation results manifest that the VSG strategy has a better THD reduction of 0.99 % which is improved compared to the SPWM with a THD of 1.33%.

Grid-connected double-stage PV system with space vector PWM inverter and MPPT

Because of the increasing demand for non-conventional energy sources, photovoltaic system integration into the electrical grid is becoming more crucial. It is advised to employ a double-stage grid-connected PV system. This can be employed with the main parts boost converter, which helps to boost the DC output from the PV channels. And next one is the space vector pulse width modulation (SVPWM) inverter which can provide better harmonic performance and higher efficiency compared to traditional PWM methods. The SVPWM technique is employed to modulate the inverter output, generating a sinusoidal AC waveform that matches the grid frequency and voltage. By adjusting the pulse width to achieve effective and trustworthy grid integration. To maximize power extraction takes place by using maximum power point tracking (MPPT). The SVPWM inverter is crucial in converting DC power to AC power and enabling grid connection. Utilizing SVPWM allows exact control of voltage magnitude, frequency, and phase angle to provide high-quality sinusoidal AC output voltage. The power quality of the electricity pumped into the grid is improved by this precise management, which also ensures adherence to grid standards and reduces harmonic interference.

Grid connection barriers to renewable energy deployment in the United States

Grid connection barriers to renewable energy deployment in the United States

Analytic Design of an EV Charger Controller for Weak Grid Connection

Analytic Design of an EV Charger Controller for Weak Grid Connection

Improved differential protection for two-terminal weak feed AC system considering negative sequence control coordination strategy

The flexible DC transmission project of renewable energy has become an inevitable development trend for large-scale renewable energy grid connection. Its two-terminal weak feed AC system is often composed of 100 % power electronic power equipment. The fault control strategy is used at both ends of the line to change the fault current characteristics, leading to a decrease in the performance of traditional differential protection. Based on analyzing the adaptability of current differential protection in the two-terminal weak feed AC system under traditional control strategy (TCS), this paper proposed an improved differential protection for two-terminal weak feed AC system considering negative sequence control coordination strategy. Firstly, the fault characteristics of the two terminal weak feed AC systems are analyzed. On this basis, the adaptability of differential protection under TCS is analyzed, and the quantization function that can quantify the operation performance of differential protection is given. Secondly, based on the problem of the traditional negative sequence control strategy, an improved control strategy is introduced and the operation performance of differential protection under the improved control strategy is studied. Finally, an improved differential protection scheme based on the change of current amplitude is proposed. Simulation results show that the proposed protection scheme can resist higher fault impedance(300 Ω) and noise interference(25 dB). In addition, the proposed differential protection scheme is suitable for the protection requirements of the two terminal weak feed AC systems in different scenarios and has higher sensitivity.

Comparative Analysis of Community Energy Projects: Policy Lessons for Kenya from the United Kingdom

Assuming a scope for policy learning across jurisdictions, this paper compared policies relevant to community energy projects (CEPs) in a developed country where they have been adopted (i.e. the UK), against policies in an emerging country where CEPs are scarce (i.e. Kenya). Through comparative analysis, successes and failures in the policies’ landscapes were examined, with the aim of distilling lessons that could enhance CEPs adoption in Kenya. Both countries have some similar core functional mechanisms in their policies, e.g. Feed-in-Tariffs, energy auctions, and grid access. These are demand-side in nature and create a market for CEPs while derisking investments to local communities. However, key differences exist, reflecting the levels of maturity in the energy mix and policy-making in either country. The UK has more demand-side and ‘implementation oriented’ policies, compared to Kenya. For Kenya, key lessons include incentives prioritising appropriate grant programs, Feed-in-Tariffs targeting CEPs, adopting Smart Export Guarantee, implementing grid connection agreements, and fostering centres for data and knowledge exchange. However, these require a laser-focus to make them bespoke to the Kenyan context. Our recommendations envisaged a carefully calibrated confluence of pull-push policy factors, involving: a CEPs-friendly policy landscape, CEPs targets under a long-term strategy, natural abundance of different RE sources, and, Kenya’s appetite for using different policy solutions for different needs. Two key areas for relevant research are worth mentioning: exploring where the equilibrium for cost-effective energy mix integrating CEPs lies, in Kenya’s future, and; empirically exploring systems-wide analyses to reveal the inter-dependencies and inter-relations of the various contextual and policy factors, aimed at CEPs as an outcome.

Design and analysis of two-stage bidirectional power converter for vehicle-to-grid technology with fuel cell-battery electric vehicle

This paper presents the design and analysis of an isolated bidirectional two-stage power converter for vehicle-to-grid (V2G) technology with a fuel cell (FC) battery electric vehicle (FCBEV). In the first stage, the primary side employs a quadratic boost converter to achieve higher voltage levels, while the secondary side uses a voltage balancer circuit to equalize the DC subgrid terminal voltages. In the second stage, a T-type inverter is used for grid connection, effectively minimizing total harmonic distortion (THD). An Artificial Neural Network (ANN)-based maximum power point tracking technique combined with a Genetic Algorithm (GA) has been used to extract the maximum energy from the FC under changing temperature and pressure conditions in the system. The performance of the proposed converter has been evaluated and validated through simulation studies using MATLAB/Simulink software. The results demonstrate that the performance of the proposed converter is satisfactory under varying operating conditions. The grid current THD is maintained below 2.35 % in accordance with IEEE 519 standards. The proposed converter and control strategy facilitate the integration of EVs with renewable energy sources and bipolar hybrid AC/DC microgrids.

Sustainable Charging Stations for Electric Vehicles

In this work, we develop a detailed analysis of the current outlook for electric vehicle charging technology, focusing on the various levels and types of charging protocols and connectors used. We propose a charging station for electric cars powered by solar photovoltaic energy, performing the analysis of the solar resource in the selected location, sizing the photovoltaic power plant to cover the demand completely, and exploring different configurations such as grid connection or physical and virtual electric energy storage. Despite the current development applying for specific working conditions, operating voltage, charging rate, power demand, etc., the proposed configuration is modular, adaptable, and resilient. The simulated system operates within the 360 V to 800 V range of direct current for charging the electric vehicles, with a selectable power range between 20 and 180 kW. The basic layout includes four charging poles, each servicing all working voltages. An oversized PV plant powers the charging station at any time of the year, saving money compared to the alternative of the electric storage unit. In addition, we build simulation tools and algorithms that optimize the design of future projects, providing a solid basis for sustainable energy infrastructure planning and design.

The impact of current-loop control parameters on the electromagnetic transient voltage performance of voltage-source converter

Since the large-scale integration of renewable energy sources into the AC grid has led to a relative decline in the voltage support capacity of the grid and the deterioration of the voltage dynamic at the grid connection point, especially under fast-scale conditions, the voltage disturbance has become more obvious. To improve the dynamic characteristics of the electromagnetic transient voltage at the grid connection point, this paper uses a practical dynamic damping method to analyze the impact of the converter current inner loop, feedforward voltage, and other links on the dynamic performance of the electromagnetic transient voltage. First, the current inner loop dynamic in the converter’s synchronous coordinate is converted into an equivalent transfer function in the stationary coordinate, and the transfer function between the transient voltage disturbance at the grid connection point and the inner loop current output is established. On this basis, the Bode diagram and the vector diagram of the transfer function in the weak damping frequency band are used to analyze the dynamic damping of the current inner loop parameters and voltage feedforward filter parameters on the voltage disturbance at the grid connection point. The results indicate that moderately increasing the current inner loop bandwidth or reducing the feedforward filter bandwidth can help enhance the electromagnetic transient voltage stability of the grid connection point, but increasing the current inner loop bandwidth will worsen the low-frequency damping characteristics and reduce the feedforward filter bandwidth will still help increase low-frequency damping.

Does the incentive policy for renewable energy grid connection affect the technical efficiency of power grid companies? Empirical analysis based on China and Japan

The widespread adoption of renewable energy sources, which are characterized by intermittency, uncertainty, and uneven geographical distribution, has significantly influenced power grid operating efficiency. This study employs the meta-frontier model to assess the impact of varying degrees of renewable energy development in China and Japan from 2008 to 2022 on the efficiency of 40 power grid companies. The research reveals that the rapid increase in renewable energy generation has posed significant challenges to grid management, leading to a decline in grid company technical efficiency. Despite implementing entirely different renewable energy incentive policies, both China and Japan have encountered a detrimental effect on the efficiency of their power grids. However, over time, the adverse impact of renewable energy on grid efficiency has shown signs of attenuation. This positive trend is partly attributable to measures such as enhanced infrastructure development and improved technical standards, which have effectively mitigated the negative effects of renewable energy integration on grid operations. Based on these findings, the study emphasizes the importance of bolstering grid infrastructure and fostering technological innovations to minimize the disruptive effects of renewable energy on grid efficiency.

Multi-timescale hierarchical dispatch strategy of hybrid energy storage for multiple auxiliary service markets

As a flexible regulatory resource, hybrid energy storage system (HESS) is capable of providing multiple reliable ancillary services, which improves the adaptability of the distribution system to large-scale grid connection of the distributed generation (DG) and alleviate the pressure of peak load and frequency response. In this context, this paper proposes an optimal dispatch strategy of a HESS for DG electricity production and multiple auxiliary service markets to create stackable benefits for HESS operators. Firstly, different types of energy storage system (ESS) (energy-based and power-based) are unified to the joint optimal framework of peak shaving (PS), frequency containment reserves (FCR), and secondary frequency regulation (SFR). By constructing a virtual ESS model based on the idle-time reuse response, an optimal bidding strategy for HESS under this revenue combination is proposed to achieve the optimal utilization of resource allocation. Furthermore, an “hourly–minute–secondly” progressive time series is introduced, and a multi-timescale hierarchical dispatch model named “daily baseline–regulation basepoint–real-time regulation” is constructed. Specifically, the PS capacity is allocated day-ahead and a two-stage capacity allocation method for FCR and SFR is proposed in the intraday, which realizes the parallel optimal of HESS at the scale of full clearance in the auxiliary service markets. Results show that compared to the combined benefits of two types of ESS, the proposed method achieved the comprehensive income increased by 4.87 % and the auxiliary services income increased by 15.2 %. Under this revenue combination, the SFR market can create an additional 60 %–90 % economic value for HESS operators. The proposed hierarchical optimal model can better adapt to the trading rules of different auxiliary service markets and provide guidance for HESS and DG to further participate in the electricity market.

A Multiscale Adaptive Fusion Network for Modular Multilevel Converter Fault Diagnosis

Modular Multilevel Converters (MMCs) play a crucial role in new energy grid connection and renewable energy conversion systems due to the significant merits of good modularity, flexible scalability, and lower operating loss. However, reliability is a significant challenge for MMCs, which consist of a large number of Insulated Gate Bipolar Transistors (IGBTs). Failures of the IGBTs in submodules (SMs) are a critical issue that affect the performance and operation of MMCs. The insufficient ability of convolutional neural networks to learn key fault features affects the accuracy of MMC fault diagnosis. To resolve this issue, this paper proposes a novel deep fault diagnosis framework named the Multiscale Adaptive Fusion Network (MSAFN) for MMC fault diagnosis. In the proposed MSAFN, the fault features of the raw current in an MMC are extracted by employing multiscale convolutional neural networks (CNNs) firstly, and then a channel attention mechanism is added to adaptively select the channel containing key features, so as to improve the fault diagnosis ability of the MMC in a noisy environment. Finally, the adaptive size of a one-dimensional CNN is adopted to adjust the weight of the feature channels of different scales, which are adaptively fused for fault diagnosis. Experimental validation is performed on two different MMC datasets. Experimental results confirm that the introduction of an attention mechanism of the multiscale feature adaptive fusion channel improves the recognition accuracy of the model by an average of 15.6%. Moreover, comparative experiments under different signal-to-noise ratios (SNRs) demonstrate that the MSAFN maintains accuracy levels above 96.7%, highlighting its excellent performance, particularly under noisy conditions.

Not yet connected

This article demonstrates how infrastructures generate anxiety as a socially constituted experience in a context of infrastructural development and unreliability. Based on the case of a newly electrified trading centre in northern Uganda, I reflect on the anxiety expressed by a man who had not yet connected his house to the grid. Strikingly, the danger posed by a “weak” infrastructure and the uncertainty that those who had been connected to the grid faced seemed less important in generating anxieties. What mattered was the feeling of being left out of the development associated with grid connection. This points to the strong symbolic value that people attach to infrastructures even when they do not work as they are supposed to. I argue that infrastructural anxieties are grounded in such values to the extent that people internalize them.

A comprehensive framework of the decomposition-based hybrid method for ultra-short-term wind power forecasting with on-site application

Ultra-short-term wind power forecasting (UWPF) is crucial for the large-scale grid connection of wind energy. The state grid in China has strict multi-step forecasting requirements, which pose challenges to on-site efficiency and accuracy. This paper proposes a comprehensive framework of the hybrid method for UWPF with on-site application, consisting of data decomposition, model prediction, and post-processing. In the first stage, rolling decomposition and feature reconstruction are employed to decompose the wind power data into sub-components without future information leakage. The feature extraction and model matching processes are then performed to make full use of different machine learning prediction models and distinct characteristics of wind power components. Finally, a novel error tracking strategy is proposed to enable real-time error correction for multi-step forecasting by capturing the fluctuation characteristics of wind power data. The proposed framework is evaluated on two field wind power datasets through comparative experiments with five benchmark methods and nine reference methods. The experimental results demonstrate that (a) Each module of the proposed method effectively contributes to improving forecasting accuracy. (b) The proposed method significantly outperforms traditional machine learning methods in both single-step and multi-step forecasts, indicating its capability to handle practical UWPF tasks effectively.