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In order to better describe the uncertainty of renewable energy output, this paper proposed a novel robust optimization method for new distribution systems based on adaptive data-driven polyhedral sets. First, an ellipsoidal uncertainty set was established using historical data on renewable energy output, and a data-driven convex hull polyhedral set was established by connecting high-dimensional ellipsoidal vertices; on this basis, an adaptive data-driven polyhedral set model was established to address the problem of high conservatism in the scaling process of convex hull polyhedral sets. Furthermore, a novel adaptive data-driven robust scheduling model for new distribution systems was established, and a column-and-constraint generation (C&CG) algorithm was used to solve the robust scheduling model. Finally, the improved IEEE-33 bus system simulation verification shows that the robust scheduling model for new distribution systems based on adaptive data-driven polyhedral sets can reduce conservatism and improve the robustness of optimization results. [ABSTRACT FROM AUTHOR]

With the gradual emergence of trends such as the asynchronous interconnection of power grids and the increasing penetration of renewable energy, the issues of ultra-low-frequency oscillations and low-frequency stability in power grids have become more prominent, posing serious challenges to the safety and stability of systems. The voltage-source converter-based HVDC (VSC-HVDC) interconnection is an effective solution to the frequency stability problems faced by regional power grids. VSC-HVDC can participate in system frequency stability control through a frequency limit controller (FLC). This paper first analyses the basic principles of how VSC-HVDC participates in system frequency stability control. Then, in response to the frequency stability control requirements of the sending and receiving power systems, a droop FLC strategy is designed. Furthermore, a multi-objective optimization method for the parameters of the droop FLC is proposed. Finally, a large-scale electromagnetic transient simulation model of the VSC-HVDC interconnected power system is constructed to verify the effectiveness of the proposed droop FLC method. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) play a crucial role in tertiary sectors due to their eco-friendliness and sustainability when powered by clean energy. Integrating EV charging stations with renewable energy systems is essential to alleviate energy issues and grid pressure. Exploring this integration's feasibility is imperative for sustainable transportation. This study aims to provide a clear approach and methodology for examining the potential of integrating renewable energy technologies with EV charging stations at the district level. Additionally, the study investigates the energy, economic, and environmental benefits of an integrated system comprising photovoltaic/wind turbines (PV/WTs) connected to the electricity grid to meet the energy demand of a tertiary district consisting of five hotels in Egypt. Through the development of a simulation model, the paper verifies whether the proposed energy system can meet the district's energy demand. In addition, the simulation model has been employed to conduct a sensitivity analysis for investigating the impact of different charging rates on economic feasibility. The results indicate that a hybrid renewable energy system (HRES) integrated with an EV charging station can effectively relieve pressure on the electricity grid and provide electricity at competitive prices compared to the national grid. Moreover, the proposed energy system significantly reduces environmental emissions by up to 510 tons of CO2 per year and has the potential to decrease fossil fuel usage by 248 tons per year. Sensitivity analysis highlights the significant impact of charging prices on project profitability. [ABSTRACT FROM AUTHOR]

In low-carbon energy systems, due to the high proportion of renewable energy access, the voltage regulation capacity of the system will decrease. Therefore, in the event of voltage violation, it is easy to cause large-scale renewable energy off-grid and power outages. In order to improve the voltage regulation ability of low-carbon energy system, this paper proposes a two-stage overvoltage suppression strategy for sending-end power grid. Firstly, the principle of overvoltage phenomenon in the sending end power grid of low-carbon energy system with high proportion of renewable energy access is studied, and an overvoltage control strategy composed of two stages of centralized control of rectifier station and flexible resource control of distributed power grid is proposed. Then, the PSO algorithm and consensus algorithm are used to solve the established control model. Finally, a simulation system is established based on actual operating power grid data to verify the proposed control strategy through simulation. The results indicate that the control strategy proposed in this paper can effectively suppress transient overvoltage of AC buses and improve the operational stability of the high proportion of renewable energy sending-end power grid under various operating conditions. In addition, during the daytime overvoltage regulation process, the potential of flexible regulation equipment can be fully utilized. Shortening the duration of voltage exceeding the limit and reducing the peak voltage exceeding the limit can help reduce the renewable energy waste rate of the power grid. [ABSTRACT FROM AUTHOR]

In this paper the concept of eco-maintenance is presented. The concept aims to improve lifetime while minimising environmental impact over the entire life cycle to ensure maximum performance. Offshore wind farms are subjected to severe weather conditions, which limits the vessels capabilities to access the wind farms. The interest of this paper is the investigation of the optimal maintenance strategy for different offshore wind farms. This objective is achieved by implementing a simulation model which includes, weather and failure analysis as well as operation and maintenance. This paper shows how different maintenance strategies can influence the environmental performance of a wind farm. [ABSTRACT FROM AUTHOR]

Biodiesel is a material serving as a promising energy alternative to cover the demand of clean sustainable energy sources. Conventional biodiesel production is done by transesterification method using stirred tank reactor and homogeneous base or acid catalyst then followed by purification process. However, there are some disavantages related with this method. They include soap formation, sensitivity to free fatty acid (FFA) content and purification difficulties. Transesterification process depends upon a number of process parameters which are required to be optimized in order to maximize the biodiesel yield. In this paper we have worked for flow sheet constructions of Biodiesel small plant using computer simulating software. All the conclusion results will be shown in simulation part of paper. The core objective of this paper would to design and develop a profitable biodiesel production plantby examining all models. [ABSTRACT FROM AUTHOR]

This paper analyzes different models for evaluating investments in energy storage systems (ESS) in power systems with high penetration of renewable energy sources. First of all, two methodologies proposed in the literature are extended to consider ESS investment: a unit commitment model that uses the “system states” (SS) method of representing time; and another one that uses a “representative periods” (RP) method. Besides, this paper proposes two new models that improve the previous ones without a significant increase of computation time. The enhanced models are the “system states reduced frequency matrix” model which addresses short-term energy storage more approximately than the SS method to reduce the number of constraints in the problem, and the “representative periods with transition matrix and cluster indices” (RP-TM&CI) model which guarantees some continuity between representative periods, e.g., days, and introduces long-term storage into a model originally designed only for the short term. All these models are compared using an hourly unit commitment model as benchmark. While both system state models provide an excellent representation of long-term storage, their representation of short-term storage is frequently unrealistic. The RP-TM&CI model, on the other hand, succeeds in approximating both short- and long-term storage, which leads to almost 10 times lower error in storage investment results in comparison to the other models analyzed. [ABSTRACT FROM AUTHOR]

The integration of renewable energy sources, electric vehicles, and other electrical assets has introduced complexities in monitoring and controlling power networks. Consequently, numerous grid nodes have been equipped with sensors and complex measurement systems to enhance network observability. Additionally, real-time power network simulators have become crucial tools for predicting and estimating the behavior of electrical quantities at different network components, such as nodes, branches, and assets. In this paper, a new user-friendly model for Rogowski coils is presented and validated. The model's simplicity stems from utilizing information solely from the Rogowski coil datasheet. By establishing the input/output relationship, the output of the Rogowski coil is obtained. The effectiveness and accuracy of the proposed model are tested using both simulations and commercially available Rogowski coils. The results confirm that the model is simple, accurate, and easily implementable in various simulation environments for a wide range of applications and purposes. [ABSTRACT FROM AUTHOR]

This paper presents application guidelines for a new generic plant controller model that can be used for renewable plant dynamic system analysis that may include the control of static compensators (STATCOMs), static var compensators (SVCs), and/or energy storage devices. The authors originally presented the need for such a model to the Western Electricity Coordinating Council (WECC) and contributed to various stages of the new model development led by WECC. As Independent System Operators (ISOs)/Regional Reliability Organizations (RTOs)/Transmission Service Providers (TSPs) are moving toward acceptance and use of generic models only the authors have for the first time applied this new model for an operating renewable plant. The new model was configured, parameterized, and tuned to control two STATCOMs and multiple switched capacitors/reactors to represent a master/auxiliary control strategy as implemented in the plant. Dynamic simulations show that the configured and parameterized model is performing properly as expected. This tuned model was submitted to the system operator for compliance with the interconnection requirements of the plant. This is the first submission of the new generic model for this type of control for a renewable project. The submitted model is appropriate for dynamic simulations, which are routinely performed by ISOs/RTOs/TSPs in system impact studies or transmission planning studies. This paper provides useful guidelines in applying this new model for similar projects. [ABSTRACT FROM AUTHOR]

The objective of this paper is to explore the efficacy of applying risk-based security assessment (RBSA) to define reliability standards for electricity grids with high penetration of converter-interfaced generation. A novel approach to estimate the impact of transient instability is presented in this paper by modeling several important protection systems in the transient stability analysis. In addition, a probabilistic model is developed to capture the uncertainty of increased converter-interfaced renewable penetration. A synthetic test case is derived from a realistic power system to verify the proposed method. The simulation results show that RBSA not only provides significantly relaxed security limits, but also helps in identifying critical aspects of system reliability that are not possible using conventional deterministic methods. [ABSTRACT FROM AUTHOR]

To accomplish an enormous demand of power with solar energy, a cost effective and optimum system has to be developed which works in synchronisation with the existing grid. The Government in developing countries like India is providing momentous opportunities and marvellous schemes to promote renewable energy sources like solar for generating power. This paper aims to analyse the generation of power from solar photovoltaic (PV) systems economically and efficiently as it is always a challenge for the design engineer to develop an economical and efficient solar PV system. Apart from technical issues, structural aspects also affect the power generation from PV modules. This paper proposes an innovative design of non-movable tracking system that enhances the power generation of PV modules by just providing two grooves in the mounting structure in place of the tracking system. A formula for the optimum space calculation for PV installation is also proposed in this paper. A comparative analysis of total annual energy generated by the hardware setup and the results obtained using software of the rooftop solar PV system has also been analysed for practical consideration. To verify the results, first, the system has been simulated using the PVSYST software considering all practical and existing realistic losses like PV loss due to irradiance and temperature, array soil loss, module quality loss, array mismatch loss, ohmic wiring loss, and inverter loss which formulate a bonafide case of consideration and then hardware implementation of the proposed system. The hardware and software results have been compared to analyse the proposed topologies adopted to address the aforesaid problems. [ABSTRACT FROM AUTHOR]

The calls for actions to combat climate change have resulted in renewable energy adoption and, consequently, an emerging renewable energy industry. Of course, this has also precipitated the need for more renewable energy expert grounded in hybrid renewable energy system (HRES) software to support the growing industry. Hence, selecting particular software for teaching renewable energy modules for the training of students at a university level is essential. The appraisal and selection of HRES sizing and optimisation software have become crucial for instructors and learners being prepared for the industry. This paper's central contribution is to provide academics, tutors, and researchers in the field of renewable energy system sizing with an idea on how to proficiently and effectively deploy multi-criteria decision-making (MCDM) approaches in HRES sizing and optimisation software selection problems. A framework that combines fuzzy entropy method and fuzzy-VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) was used to rank HRES simulation software. The performance of the framework was compared with that of the complex proportional assessment (COPRAS) method. The article observed a difference between the fuzzy VIKOR and COPRAS solution for ranking the most preferred software; the most preferred option using the Fuzzy VIKOR is the BCHP screening tool, and HOMER for the COPRAS method. They ranked the least preferred software as RETScreen (VIKOR method) and ORCED (COPRAS method). [ABSTRACT FROM AUTHOR]

The development of micro-grid renewable energy system in China has achieved rapid growth in recent years, and the micro-grid renewable energy system has been drawing more and more attention by its flexible operation. Due to the randomness, fluctuation, uncertainty of the wind and photovoltaic renewable generation, abundant flexibility is required to meet the needs of safe, reliable and independent operation of the micro-grid energy system. We need to connect large energy systems to accept outside assistance when the micro-grid renewable energy system is short of adjustment capability. Independent operation and network operation will affect the economic benefit of the micro-grid energy system, so it is practically meaningful to study on the economic benefit evaluation of the micro-grid renewable energy system. This paper proposes a micro-grid energy system operation simulation model about wind and photovoltaic generation, the uncertainty of which is tackled based on the scenario generation and extraction techniques. Based on the proposed indices, the economic benefit could be evaluated by simulating the micro-grid energy system operation. The proposed method is validated by a real micro-grid energy system. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the cause of several unexpected high amplitude oscillations that occurred in the surge tank water level of a real hydropower plant during secondary load-frequency control (LFC) maneuvers, after the replacement of the turbine runner, and to propose solutions that allow the power plant to continue providing secondary LFC in a safe and reliable manner. For this purpose, a simulation model has been developed and calibrated from data gathered during several on-site tests. Two different solutions are proposed in order to cope with the observed problem: using a state-dependent load change rate limiter or modifying the hydro turbine governor gains; the turbine governor remains the same as before the runner replacement. The proposed solutions are tested against a set of realistic secondary LFC signals by means of simulations and compared to each other as a function of the probability that the surge tank water level descends below a minimum safe level and the quality of the secondary LFC response. The results presented in the paper demonstrate the validity of the methodology proposed to determine the state-dependent ramp limit, as well as its effectiveness to prevent the surge tank drawdown and to provide clear insight into the trade-off between response quality and power plant safety. [ABSTRACT FROM AUTHOR]

With the increasing penetration of variable renewable generations, independent system operators (ISOs)/regional transmission organizations (RTOs) are faced with new challenges for the secure and economic operation of power systems. This paper proposes an effective approach for deriving robust solutions to the security-constrained unit commitment (SCUC) problem, which considers load and wind uncertainties via interval numbers. Different from most robust optimization-based SCUC approaches in literature which explore robust unit commitment (UC) solutions for immunizing against the worst economic scenario in terms of the highest minimum dispatch cost, the proposed robust SCUC model minimizes operation cost for the base case while guaranteeing that the robust UC and dispatch solutions could be adaptively and securely adjusted in response to uncertain intervals. Thus, the proposed model achieves smaller unit commitment costs while maintaining the solution robustness as compared with literature. In addition, the proposed model describes base case dispatches and corrective actions in uncertain intervals, which is more consistent with the current day-ahead and real-time markets. Furthermore, besides budget constraints used in literature, this paper also considers load and wind variability correlations in constructing uncertain intervals, which would eliminate unlike-to-happen scenarios and further limit the level of conservatism of the robust solution. The proposed robust SCUC model is solved by Benders decomposition, which decomposes the original problem into a master UC problem for the base case and subproblems for the base case network evaluation and the security checking for uncertain intervals. Feasibility cuts are generated and fed back to the master problem for further iterations when violations are identified in subproblems. Numerical case studies on the modified IEEE 118-bus system illustrate the effectiveness of the proposed robust SCUC model for the secure and economic operation of power systems under various uncertainties. [ABSTRACT FROM AUTHOR]

Solar photovoltaic is clean and green energy for renewable power generation, which plays a vital role to fulfil the power shortage for any region. Photovoltaic array is quite expensive and has non-linear characteristics. Under varying conditions, it takes much time to give operating curves. Before mount photovoltaic for any application or at any location, there is a vital phase of analysis, modelling, and simulation of the photovoltaic system, which helps to understand the actual behaviour in real conditions. This paper emphasizes on the stepwise procedure of modelling and simulation for the photovoltaic panel, which is proposed to use for the small application. The proposed system provides a reliable, accurate, and simple method to model the photovoltaic system. It takes a flexible solar panel of 180 W as a reference model. The I–V and P–V characteristics are further investigated at different operating conditions such as a variation of irradiance from 1000 to 400 W/m2, variation of temperature from 15 to 70 °C, and vary shunt resistance from higher to low values. The equation-based modelling of the photovoltaic system is built in the MATLAB/Simulink. This methodology allows investigating the photovoltaic system on different operating conditions (varying temperature and irradiance) and physical parameters (ideality factor, series and shunt resistance) along with partial shading effect. [ABSTRACT FROM AUTHOR]

After the Fukushima nuclear accident, nuclear policy has become uncertain in Japan, and alternatively, variable renewable (VR) energy, such as wind and photovoltaic (PV), is highlighted for addressing climate change and energy security issues. This paper attempts to assess the massive integration of VR into Japan’s long-term power-generation mix, employing the dynamic multiregional optimal powergeneration mix model, which is a large-scale linear programming model including 200 million constraints. The feature of the model enables explicit consideration of the actual variability of wind and PV outputs in a 10-min temporal resolution and to analyze the impact of those variabilities on long-term expansion planning of power plants. Simulation results show that both nuclear decommission and carbon regulation policies make VR economically justified and encourage its expansion in Japan’s long-term power-generation mix. When nuclear is totally decommissioned and CO2 is mitigated by 50% from 2010 levels by 2050, the power-generation cost in 2050 shows a doubling compared with that in the scenario where nuclear power is not decommissioned and carbon regulation is not assigned. [ABSTRACT FROM AUTHOR]

In this paper, we present a decentralized load estimation approach to support real-time volt/var optimization in distribution networks with high penetration of distributed generation. The decentralized load estimation scheme relies on local information and on a limited amount of information from neighbor areas. We defined a procedure for measurement selection and feeder partitioning so as to limit communication needs and allow prioritizing the estimation accuracy for selected loads. The measurement selection and feeder partitioning methods are based on the mutual information and minimum-redundancy-maximum-relevance concepts. We tested the proposed approach with a modified radial IEEE 34-node test feeder and a weakly meshed IEEE 123-node test feeder. The effectiveness of the method is validated using a hardware-in-the-loop simulation platform. [ABSTRACT FROM AUTHOR]

Considering the increasing penetration of renewable energy sources and electrical vehicles in utility distribution feeders, it is imperative to study the impacts of the resulting increasing uncertainty on the delivery capability of a distribution network. In this paper, probabilistic available delivery capability (ADC) is formulated for a general distribution network integrating various renewable energy sources (RES) and load variations. To reduce the computational efforts by using conventional Monte Carlo simulations, we develop and employ a computationally efficient method to assess the probabilistic ADC, which combines the up-to-date sparse polynomial chaos expansion (PCE) and the continuation method. Particularly, the proposed method is able to handle a large number of correlated random inputs with different marginal distributions. Numerical examples in the IEEE 13 and IEEE 123 node test feeders are presented, showing that the proposed method can achieve accuracy and efficiency simultaneously. Numerical results also demonstrate that the randomness brought about by the RES and loads indeed leads to a reduction in the delivery capability of a distribution network. [ABSTRACT FROM AUTHOR]

This paper presents a distributed wind power virtual simulation experiment system for cultivating students' ability to solve complex engineering problems. The experiment system was designed with complex engineering problems of real wind farms, both in a steady state and transient process. On the basis of the system, comprehensive practical contents were developed. According to engineering education certification, the virtual simulation practical contents provide support for improving students' ability to solve complex engineering problems. The system has been applied to a comprehensive practical course of renewable energy. From the designed assessment, the experiment system helped students to master the advanced technologies applied to real wind farms visually and enhanced their ability to solve complex engineering problems. After practical learning on the system, students' performance has been improved in graduation projects. It is proved that the virtual simulation experiment system is effective in cultivating students' ability to solve complex engineering problems. [ABSTRACT FROM AUTHOR]

This paper describes a methodology for applying geographical information systems (GIS) tools to site a photovoltaic (PV) park inside a sustainable community, in order, not only to meet all siting restrictions, such as environmental protection, but also to operate a PV park more efficiently reducing the shading effect erection and cabling cost. Additionally, the PV operation impact on the grid is investigated, integrating GIS maps into power systems analysis software, such as the PowerWorld®Simulator. In other words, this paper also stresses the importance of GIS for the design, installation and monitoring of power systems. A case study considering the Campus of the Technical University of Crete has been performed showing that siting properly a PV installation meeting 20% of the demand can gain significant savings in both peak and regular energy demands, especially on peak summer days. [ABSTRACT FROM PUBLISHER]

This paper introduces a new proposed design and optimization simulation program for the techno-economic sizing of a stand-alone hybrid photovoltaic/wind/diesel/ battery energy system using the iterative optimization. The main function of the new proposed simulation program is to determine the optimum size of each component of a hybrid renewable energy system for the lowest price of generated energy and the lowest value of dummy energy at highest reliability. An accurate methodology for pairing between five Saudi Arabia sites and ten wind turbines from different manufacturers to maximize energy production and minimize the price of the generated power is introduced. This methodology changes the penetration ratio of the renewable energy sources in certain increments to meet the load requirements of the sites under study. A detailed economic methodology to obtain the price of the generated energy is introduced. The new proposed simulation program is implemented in flexible fashion, which is not possible for the market-available software, such as HOMER, INSEL, TRNSYS, and RETScreen. The results obtained from the new proposed simulation program are compared with those from genetic algorithm and HOMER software to evaluate the effectiveness of the proposed program. Many valuable results can be extracted from the proposed program to assist researchers and decision makers. [ABSTRACT FROM AUTHOR]

As intermittent energy resources become more significant in power production, traditional capacity planning may be insufficient to ensure reliable system operation. A system planner must ensure that flexibility solutions are available to respond to large and uncertain ramping events. These solutions may be operational, such as improved unit commitment and dispatch, curtailment of renewables, or demand response; procurement based, such as new fast ramping resources or batteries; or involve market reform. This paper outlines a new methodology for modeling the economic tradeoffs in implementing flexibility solutions for integrating renewables. The proposed model includes both a stochastic treatment of system states to account for a wide range of operating conditions and an adapted production simulation methodology that weighs the cost of reliability and subhourly flexibility violations against the cost of the operational flexibility solutions available to mitigate them. The model's functionality is demonstrated with a case study of California at a 50% RPS in 2030. The model tests the value of 1088 MW of generic flexible units, relative to the same capacity of must-run resources, finding an expected annual value of \$347\pm 42 million/yr. Potential applications of the model for resource planning and procurement are also discussed. [ABSTRACT FROM PUBLISHER]

The high costs of fuel cell stacks are often prohibitive for research applications. Instead, researchers tend to either perform tests on individual cells under emulated load conditions, or they use model-based emulated fuel cell stacks to test realistic loads. This paper presents an alternative technique that allows the simultaneous investigation of both cell and hardware. In this technique, an amplifier takes as input the voltage of a reference fuel cell and reproduces the “scaled-up” voltage that would be provided by a stack of similar cells. The output terminals of this simulated stack can be connected to realistic loads, which are series connected with the reference cell to maintain a one-to-one correspondence of cell and load currents. This technique allows the simultaneous investigation of stack/load interactions, stack electrochemical performance characteristics, and stack durability under load. The amplifier electronics are independent of the fuel cell allowing its use with all fuel cell types, e.g., solid oxide fuel cells (SOFCs) or proton exchange membrane fuel cells. We demonstrate the emulator using a single planar SOFC and under several real loads. The data collected reveal good steady-state and dynamic accuracy, and the observed electrical interactions highlight the utility of the emulator in cell and hardware-in-the-loop testing. Ultimately, this technique provides fuel cell system researchers and developers a low-cost, easily implemented tool for rapid assessment of novel fuel cell technologies under real-world loading conditions. [ABSTRACT FROM AUTHOR]

Intentional islanding is an effective approach to avoid large-area blackouts and minimize outage losses through making full use of renewable energy sources. This paper proposes a novel strategy based on node electrical relevance and artificial bee colony algorithm. The node electrical relevance is defined with equivalent electrical distance and traditional line weight, which can reflect the electrical characteristics of power systems, differentiating the proposed strategy from most existing strategies which are based on graph theory. The artificial bee colony (ABC) algorithm employed has fewer control parameters, strong robustness, and high accuracy; therefore, more loads can be incorporated into islands and restored. The constraints of load priority, load controllability, line capacity, and stable operation requirements of power systems are considered to tally with the actual distribution networks. The strategy is tested using the IEEE 69-bus distribution system and compared with other strategies from the literature. The simulation results demonstrate that the proposed strategy is more feasible and efficient. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

A reliable approach based on a multi-verse optimization algorithm (MVO) for designing load frequency control incorporated in multi-interconnected power system comprising wind power and photovoltaic (PV) plants is presented in this paper. It has been applied for optimizing the control parameters of the load frequency controller (LFC) of the multi-source power system (MSPS). The MSPS includes thermal, gas, and hydro power plants for energy generation. Moreover, the MSPS is integrated with renewable energy sources (RES). The MVO algorithm is applied to acquire the ideal parameters of the controller for controlling a single area and a multi-area MSPS integrated with RES. HVDC link is utilized in shunt with AC multi-areas interconnection tie line. The proposed scheme has achieved robust performance against the disturbance in loading conditions, variation of system parameters, and size of step load perturbation (SLP). Meanwhile, the simulation outcomes showed a good dynamic performance of the proposed controller. [ABSTRACT FROM AUTHOR]

This paper describes the integration of a photovoltaic (PV) renewable energy source with a superconducting magnetic energy storage (SMES) system. The integrated system can improve the voltage stability of the utility grid and achieve power leveling. The control schemes employ model predictive control (MPC), which has gained significant attention in recent years because of its advantages such as fast response and simple implementation. The PV system provides maximum power at various irradiation levels using the incremental conductance technique (INC). The interfaced grid side converter of the SMES can control the grid voltage by regulating its injected reactive power to the grid, while the charge and discharge operation of the SMES coil can be managed by the system operator to inject/absorb active power to/from the grid to achieve the power leveling strategy. Simulation results based on MATLAB/Simulink® software prove the fast response of the system control objectives in tracking the setpoints at different loading scenarios and PV irradiance levels, while the SMES injects/absorbs active and reactive power to/from the grid during various events to improve the voltage response and achieve power leveling strategy. [ABSTRACT FROM AUTHOR]

Today, interests on hybrid ac/dc microgrids, which contain the advantages of both ac and dc microgrids, are growing rapidly. In the hybrid ac/dc microgrid, the parallel-operated ac/dc bidirectional interfacing converters (IFCs) are increasingly used for large capacity renewable energy sources or as the interlinking converters between the ac and dc subsystems. When unbalanced grid faults occur, the active power transferred by the parallel-operated IFCs must be kept constant and oscillation-free to stabilize the dc bus voltage. However, under conventional control strategies in unbalanced grid conditions, the active power transfer capability of IFCs is affected due to the converters’ current rating limitations. Moreover, unbalanced voltage adverse effects on IFCs (such as output power oscillations, dc-link ripples, and output current enhancement) could be amplified by the number of parallel converters. Therefore, this paper investigates parallel operation of IFCs in hybrid ac/dc microgrids under unbalanced ac grid conditions and proposes a novel control strategy to enhance the active power transfer capability with zero active power oscillation. The proposed control strategy employs a new current sharing method which introduces adjustable current reference coefficients for parallel IFCs. In the proposed control strategy, only one IFC, named as redundant IFC, needs to be designed and installed with higher current rating to ensure the constant and oscillation-free output active power of parallel IFCs. Simulation and experimental results verify the feasibility and effectiveness of the proposed control strategy. [ABSTRACT FROM PUBLISHER]

The inertia of modern power systems is decreasing and becoming more variable as more inverter-connected renewable energy sources and loads are integrated. This leads to a low and time-varied inertia power system that is more sensitive to disturbances and may not be robust enough to survive large disturbances. How to protect such a low and time-varied inertia system from blackouts is in question. This paper tries to answer this question using a graph spectra-based controlled islanding method. Eigenvector sensitivity, with respect to inertia, is used to identify the impact of reduced inertia on the spectral properties of power system graphs and, thus, coherent generator grouping. Constrained spectral clustering is then used to find the islanding boundary with minimal power-flow disruption to island low inertia systems. Simulation results, obtained using the IEEE 9-bus and 118-bus test systems, validate the effectiveness of the proposed algorithm in the case of low inertia systems. [ABSTRACT FROM AUTHOR]

When a hexagonal converter (Hexverter) is applied to high-power renewable energy generation such as offshore low-frequency transmission, using traditional PID control to ensure the stable global operation and strong robustness of the system is difficult due to the random fluctuation of renewable energy, system parameter uptake, its non-linear characteristics, and the possible unbalanced grid situation. This paper proposes a non-linear passivity-based control (PBC) strategy for Hexverter under an unbalanced grid. First, the passivity and stability of Hexverter objects are analyzed based on PBC theory. The unbalanced PBC strategy of Hexverter is then designed and derived. Three control objectives are designed according to different control requirements. Finally, the simulation system of the Hexverter under an unbalanced grid is built on Matlab/Simulink to verify the effectiveness and superiority of the proposed unbalanced PBC method. The simulation results show that the proposed method has fewer control parameters, faster response, lower harmonic content, and better overall control effect than PID control. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems have become an integral and widespread part of renewable energy generation. In combination with energy storage, they offer a variety of advantages such as increased self-sufficiency or improved grid stability. However, geographic location, subsidies, energy tariffs, size of PV panels and battery, and other factors significantly influence the overall performance and profitability of the system. Solving this complex task of system design and component dimensioning is not easy. The diversity and multitude of parameters therefore usually requires the help of, more or less complex, computer simulations. This led and still leads to a high publication activity on techno-economic and other optimizations for such systems. However, the operating strategies and component models are often oversimplified, leading to results with significant errors. The goal of this paper is to provide in-depth insight into component modeling and parametrization for PV module, battery energy storage, and inverter, as well as giving suggestions on appropriate control strategies. The focus lies on the description of suitable simple-but-accurate models and their parametrization. In order to avoid the effort of having to conduct measurements for component characterization, an approach relying on values presented in product data sheets is considered. Furthermore, the effects of model simplifications, as they are found in many publications, are shown. Finally, the importance of an uncertainty analysis for the entire simulation is discussed in order to gain insight into the accuracy of the calculated simulation results and their dependency on model- and input-parameters. • Photovoltaic system modeling/simulation. • Component modeling for PV module, battery energy storage and inverter. • Suitable simple-but-accurate models and their parametrization • Characterization relying on product data sheets with minimal informations. [ABSTRACT FROM AUTHOR]

Based on green energy prediction and storage, a novel green base station (GBS) offloading model is proposed and can be employed with multiple objectives in this paper to save energy. By predicting the value of green energy collected by GBS and updating the residual energy of each GBS, we can obtain the maximum number of users that each GBS can offload theoretically. Then, the optimum number of users should be calculated in order to achieve different network performance. Eventually, under the restrictions of the maximum number of users and the optimum number of users, we can finish offloading for traditional base station in the network. Simulation results demonstrate that through the proposed GBS offloading model, we can fulfill compromise between maximizing green energy utilization and load balancing in the offloading process, and the effect of energy saving is remarkable. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An advanced control scheme for managing a hybrid energy generation system (HEGS) is presented in this paper. A hierarchical management and control architecture based on multi-agent systems (MAS) is discussed. MAS will account for the complex behavior of a hybrid energy supply system. The management and control strategies are implemented through a system of agents based on three tiers. The upper level agents develop overall energy management strategies for a hybrid energy supply system. The middle-level agents integrate coordinated switching controllers. The lower level agents are responsible for dealing with local control strategies. Coordinated switching controllers within the middle-level agents are designed as event-triggered hybrid controllers based on differential hybrid Petri-net (DHPN) models. The operation modes of distributed energy resources (DERs) can smoothly transfer in a coordinated manner due to the coordinated action of the switching controllers according to variation in operating conditions. Finally, simulation results from different scenarios verifying the feasibility of the proposed scheme are offered. [ABSTRACT FROM PUBLISHER]

Dramatic mobile data traffic growth has spurred a dense deployment of small cell base stations (SCBSs). Small cells enhance the spectrum efficiency and thus enlarge the capacity of mobile networks. Although SCBSs consume much less power than macro BSs (MBSs) do, the overall power consumption of a large number of SCBSs is phenomenal. As the energy harvesting technology advances, base stations (BSs) can be powered by green energy to alleviate the on-grid power consumption. For mobile networks with high BS density, traffic load balancing is critical in order to exploit the capacity of SCBSs. To fully utilize harvested energy, it is desirable to incorporate the green energy utilization as a performance metric in traffic load balancing strategies. In this paper, we have proposed a traffic load balancing framework that strives a balance between network utilities, e.g., the average traffic delivery latency, and the green energy utilization. Various properties of the proposed framework have been derived. Leveraging the software-defined radio access network architecture, the proposed scheme is implemented as a virtually distributed algorithm, which significantly reduces the communication overheads between users and BSs. The simulation results show that the proposed traffic load balancing framework enables an adjustable trade-off between the on-grid power consumption and the average traffic delivery latency, and saves a considerable amount of on-grid power, e.g., 30%, at a cost of only a small increase, e.g., 8%, of the average traffic delivery latency. [ABSTRACT FROM AUTHOR]

With different structures and control strategies, inverter-interfaced renewable energy generators (IIREGs) have different fault characteristics from synchronous generators. This makes the conventional distance protection used in networks with synchronous generators not applicable for transmission lines emanating from IIREGs. Therefore, supported by the fault current analysis, operating performances of distance relays on both sides of the transmission line are unveiled. It reveals the problem that the conventional distance relay on the IIREG side has a high risk of malfunction or refusing to operate. To cope with this adaptability problem, an improved scheme based on time delay and zero-sequence impedance is proposed in this paper. To validate the operating performances of the scheme, a detailed IIREG model is built in a real-time digital simulator, and simulation tests are carried out. Apart from these, a field short-circuit test is performed in a real wind power plant to examine the practical feasibility of the proposed scheme. Both the simulation results and the field test confirm the problem of the conventional distance protection and verify the reliability of the improved scheme. [ABSTRACT FROM AUTHOR]

Reversible solid oxide cells (rSOCs) are highly efficient devices, which allow either the generation of electric power or the storage of energy via fuel production. In this paper, the characteristics of the mode switch are investigated by applying a dynamic 3D stack model. The responses of temperature, current density, and species mole fractions regarding a switch from storage (SOEC) to generation mode (SOFC) are examined in detail. Additionally, the impact of using excess air and continuous voltage variations to limit temperature gradients and fluctuations during the mode switch are analyzed. [ABSTRACT FROM AUTHOR]

Highlights • Variable renewable energy integration diminishes synchronous inertia of power systems, resulting in vulnerable frequency instability. • Alternative options of fast frequency resources are required for secure and stable grid operation under high penetration of renewables. • This paper provides a critical review of potential sources of fast frequency reserves, and way forward to maintain secure and stable grid operation. Abstract The last few decades have seen renewable energy source (RES) integration growing at a rapid pace and this trend is likely to continue. The displacement of conventional synchronous plant, particularly at higher RES shares, is resulting in a 'lighter' system with low system inertia and reduced governor droop stiffness, leading to increased vulnerability to fast frequency stability. This paper presents a review of literature from the research and industry communities on possible sources of non-synchronous fast frequency reserve, considered as a potential solution to address diminishing synchronous reserve in RES integrated systems. The wide range of potential sources includes wind turbines, solar photovoltaic plant, energy storage, high voltage direct current (HVDC) systems, and demand response. The challenges and limitations associated with each approach are highlighted, and alternative strategies to maintain a minimum volume of security constrained fast frequency reserve are discussed based on the recent industry trends. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Various predictive models about the residential energy demand and residential renewable energy production have been proposed. Recent studies have confirmed that they are not normally distributed over time. The increase in renewable energy installation has brought the issue of energy storage charge and discharge control. Thus, storage control methods that properly address non-normality are required. In this paper, we formulated the economically optimal storage control problem using Markov decision process (MDP) and the conditional value at risk (CVaR) measure to deal with the non-normality of predictive distribution about the household's net load. The CVaR measure was employed to treat with the chance constraint on the battery capacitor, in other words, overcharge risk and over-discharge risk. We conducted a simulation to compare the annual economic saving performances between two MDPs: one is the MDP with a Gaussian predictive distribution and the other is the MDP with a normalized frequency distribution (non-normal). We used the real time series of 35 residential energy consumption and PV generation data in Japan. The importance of addressing the non-normality of random variables was shown by our simulation. [ABSTRACT FROM AUTHOR]

This paper addresses power management strategies, including technical issues and control methodologies, for a wind-dominated hybrid remote area power supply (RAPS) system. The system consists of a doubly fed induction generator, a diesel generator, a hydrogen-based generation scheme, and mains loads. The goal is to maximize power extraction from the wind generator under generation uncertainty. For active power management, a hydrogen-based generation scheme consisting of an electrolyser and a fuel cell system is integrated to the RAPS system. Developed control strategies contribute to achieve the following objectives: 1) load side voltage and frequency regulation; 2) maximum power extraction from wind; and 3) regulating diesel generator operation at low load conditions. Simulation studies with a real-life data set are used to evaluate the proposed architecture and prove the control objectives, and it has been observed that all the proposed objectives are met within satisfactory limits. [ABSTRACT FROM PUBLISHER]

SUMMARY This paper investigates Japan's long-term energy outlook to 2050 taking into consideration the massive deployment of solar photovoltaic (PV) systems and wind power generation under a nuclear energy scenario. The extensive introduction of PV systems and wind power systems is expected to play an important role in enhancing electricity supply security after the Fukushima nuclear power accident, which has increased the uncertainty of the future additional construction of nuclear power plants in Japan. Against this background, we develop an integrated energy assessment model composed of both an econometric energy demand and supply model and an optimal power generation mix model. The latter model is able to explicitly analyze the impact of output fluctuations for various renewable energy sources at a detailed time resolution of 10 min on 365 consecutive days, incorporating the role of stationary battery technology. The simulation results reveal that intermittent fluctuations derived from a high penetration level of those renewables are controlled by quick load following operation by natural gas combined cycle power plants, pumped-storage hydro power, stationary battery technology, and output suppression of PV and wind power generation. The results show as well that massive penetration of renewables does not necessarily require a comparable scale of stationary battery capacity. Additionally, in the scenario, which assumes the decommissioning of nuclear power plants with a lifetime of over 40 years, the required PV capacity in 2050 amounts to more than double the PV installation potential in both buildings and abandoned farmland areas. [ABSTRACT FROM AUTHOR]

In composite expansion planning, improving the efficiency and power quality of power supplied from Renewable Energy Sources (RES) is highly essential. Therefore, this paper focuses on developing an optimal power flow optimization model for minimizing power loss and harmonics emanating from RES with emphasis on reducing their impact on the Locational Marginal Prices. In order to assess the magnitude of harmonics, grid modelling and simulation with RES such as wind and solar energy were carried out using the Electrical Transient Analyzer Program 12.6.0 software. The proposed mixed integer nonlinear programming mathematical model was solved using the Outer Approximation Algorithm solver in the advanced interactive multidimensional modelling system, and the efficiency of the model was tested on the modified IEEE 6 bus and 24 bus system. The results obtained from simulations reveal the efficiency of the proposed model in terms of effective cost reduction, nodal marginal price reduction, minimization of harmonic losses, and additional lines in the power system network. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a microgrid control strategy to unify the control topology for energy storage systems and renewable energy sources inverters in an ac microgrid and to protect the microgrid reliability from unintentional islanding instability using control loops, which use thedc link voltage as a feedback. This bounds the dc link voltage and provides reliable operation in the microgrid. Simulation validates the proposed control strategy, and experiment results extol the concept. [ABSTRACT FROM PUBLISHER]

SUMMARY: Due to the rapid spread of renewable energy power sources in recent years, voltage rise problems in distribution systems caused by reverse power flow from these renewable energy power sources especially from photovoltaic (PV) power generation systems are of great concern. To cope with this kind of problems, conventional voltage regulation devices such as load‐ratio transformers in the substation and step voltage regulators (SVRs) on the distribution line are basically used. If their voltage regulation capability is not sufficient, the power conditioning systems of PV power generation systems may be modified so as to supply reactive power and a static synchronous compensator (STATCOM) may be applied to the distribution system. Therefore, the coordination of these conventional and new voltage regulation devices is necessary for the design of smarter distribution systems, and electromagnetic transient (EMT) simulations of distribution systems with these devices have to be carried out to assess power quality. To this end, the authors have developed EMT simulation models of distribution substations, SVRs and distribution STATCOMs, and they are routinely used for power quality assessment studies. This paper presents these simulation models and a simulation example. [ABSTRACT FROM AUTHOR]

This paper the effect of demand side management (DSM) on the sizing of hybrid PV/wind/battery energy in system has been considered. The pigeon inspired algorithm (PIO) has been used for optimization purpose and additionally an energy filter algorithm has been developed to minimize the fluctuations of power injected into the grid. The levelized cost of energy (LCE) has been taken as the objective function while maintaining the system reliability, healthy charge on the battery as well as the less fluctuations in the power injected into the grid. The simulation has been performed for both actual load and modified load after the DSM has been performed. To verify the results a case study has been considered and the simulations are carried out in MATLAB environment. The results indicate that the DSM considerably reduces the storage requirements and there by reducing the unit cost. [ABSTRACT FROM AUTHOR]