Power Reserve Research Articles

A new framework for using weather‐sensitive surplus power reserves in critical infrastructure

AbstractReserve power systems are widely used to provide power to critical infrastructure systems in the event of power outages. The reserve power system may be subject to regulation, typically focussing on a strict operational time commitment, but the energy involved in supplying reserve power may be highly variable. For example, if heating or cooling is involved, energy consumption may be strongly influenced by prevailing weather conditions and seasonality. Replacing legacy assets (often diesel generators) with modern technologies could offer potential benefits and services back to the wider electricity system when not in use, therefore supporting a transition to low‐carbon energy networks. Drawing on the Great Britain telecommunications systems as an example, this paper demonstrates that meteorological reanalyses can be used to evaluate capacity requirements to maintain the regulated target of 5‐days operational reserve. Across three case‐study regions with diverse weather sensitivities, infrastructure with cooling‐driven electricity demand is shown to increase energy consumption during summer, thus determining the overall capacity of the reserve required and the availability of ‘surplus’ capacity. Lower risk tolerance is shown to lead to a substantial cost increase in terms of capacity required but also enhanced opportunities for surplus capacity. The use of meteorological forecast information is shown to facilitate increased surplus capacity. Availability of surplus capacity is compared to a measure of supply–stress (demand‐net‐wind) on the wider energy network. For infrastructure with cooling‐driven demand (typical of most UK telecommunication assets), it is shown that surplus availability peaks during periods of supply–stress, offering the greatest potential benefit to the national electricity grid.

An Improved Photovoltaic Power Reserve Control With Rapid Real-Time Available Power Estimation and Drift Avoidance

An Improved Photovoltaic Power Reserve Control With Rapid Real-Time Available Power Estimation and Drift Avoidance

Exhaustive Intermittent Cycling Preferentially Decreases Explosive Over Maximal Voluntary Torque in the Knee Extensors, With No Difference Between Normoxia and Moderate to Severe Hypoxia.

To compare the effects of graded hypoxia during exhaustive intermittent cycling on subsequent rapid and maximal torque-production capacity. Fifteen well-trained cyclists repeated intermittent cycling bouts (15s at 30% of anaerobic power reserve; rest = 45s) until exhaustion at sea level (FiO2 ∼0.21/end-exercise arterial oxygen saturation ∼96%), moderate hypoxia (FiO2 ∼0.16/∼90%), and severe hypoxia (FiO2 ∼0.12/∼79%). Rapid (rate of torque development [RTD]) and maximal isometric torque-production capacities of the knee extensors were assessed at baseline (visit 1) and exhaustion (visits 2-4). Exercise capacity decreased with hypoxia severity (39 [30], 22 [13], and 13 [6] cycle efforts in sea level, moderate hypoxia, and severe hypoxia, respectively; P = .002). Changes in maximal-voluntary-contraction torque between baseline and postexercise in all conditions were not statistically significant (pooled values: -2.6% [5.7%]; P = .162). Peak RTD measured postexercise was reduced below baseline in all conditions (-21.5% [5.1%]; P ≤ .015). Compared with baseline, absolute RTD values were lower at 0- to 30-millisecond (-35.1% [5.3%], P ≤ .020), 0- to 50-millisecond (-40.0% [3.9%], P ≤ .002), 0- to 100-millisecond (-30.7% [3.7%], P ≤ .001), and 0- to 200-millisecond (-18.1% [2.4%], P ≤ .004) time intervals in all conditions. Exhaustive intermittent cycling induces substantial yet comparable impairments in RTD of knee extensors between normoxia and moderate to severe hypoxia.

Flexibility enhancement of multi-district DISCOs considering a trade-off between congestion and extractable reserve capacity from virtual energy storage systems

One of the fundamental concerns of distribution companies (DISCOs) is how to satisfy security requirements under uncertain conditions and real-time contingencies. To address this concern, it is vital to employ operational flexibility levers aimed at mitigating congestion and retaining optimal reserve capacity, particularly in critical feeders. Increased interaction between DISCOs and virtual energy storage systems (VESSs) offers an unparalleled opportunity to unlock the energy flexibility of distribution grids at the local level without increasing operational complexity. According to the state-of-the-art, models that tap the economic performance of VESSs while respecting the flexibility and security setpoints adopted by DISCOs in a distributed manner have remained scarce. This study goes beyond by developing a flexibility-oriented decision-making strategy as a single-leader multi-followers stochastic model; in which a multi-district DISCO involves the flexibility setpoints and congestion management strategy in the market participation plan of each VESS locally to enhance the energy flexibility of each district. In the upper level, DISCO aims to deal with stressful situations in real-time sessions by (i) determining the minimum reserve capacity requirements in each district to be provided by VESSs with respect to the existing uncertainty sources and the importance of each district, and (ii) alleviating the congestion in critical feeders to release the feeder capacity for deployment of the available reserve power promptly. In the lower level, each VESS makes optimal decisions on power and reserve bidding in day-ahead, reserve, and real-time markets that are affected by the flexibility services required by the DISCO. Inspired by the activity schedule of different users, it also examines how demand response programs can affect DISCO’s ability to unlock consumer-side flexibility in realizing congestion management strategies. The developed bi-level scheduling model is first reformulated as single-level mathematical program with equilibrium constraints (MPEC) by employing Karush–Kuhn–Tucker (KKT) optimality conditions and then linearized into a mixed-integer linear program (MILP). The proposed strategy is validated through extensive simulations conducted on the modified IEEE 33-bus test system consisting of three districts with different users. Furthermore, DIgSILENT PowerFactory is used to verify the feasibility of the proposed model under contingency cases and to provide insights for DISCOs to control multiple VESSs and capacity-correlated uncertainties.

Kamu Diplomasisi, Göç ve Mülteci Siyaseti: Türkiye Örneği

Public diplomacy, which is a candidate to replace the classical understanding of diplomacy, is based on the idea of explaining the ideas, ideals, values, institutions, culture, and policies of a country or nation to the public opinion of other countries. The aim here is to create a sphere of influence on other peoples and win their hearts and minds. Through public diplomacy, which is based on strategic communication logic, countries' foreign policies can find a wider area of legitimacy. Türkiye has a strong soft power reserve with its ancient history, culture, language, political system, geography, various TV series, and movies. It is also among the most generous countries in the world in terms of humanitarian diplomacy, which is a sub-dimension of public diplomacy. After the civil war in Syria, Türkiye has hosted more than 3.5 million Syrians and has been hosting more than a million irregular migrants and refugees from different countries. Türkiye's migration policies based on humanitarian values are supported by a kind of public diplomacy. Turkey has been hosting millions of Syrian refugees for more than 12 years. During this endless process of hosting Syrians, Turkey has been faced with significant economic, political, social and cultural problems. Turkey, which has to bear the economic, political and social costs of migrants and refugees on its own, has to create public opinion both for the global sharing of this burden and for the establishment of a peaceful environment in Syria and the repatriation of refugees. Public diplomacy activities are a holistic approach that includes the aforementioned public opinion building. This study analyzes Türkiye's migration and refugee policy from a public diplomacy perspective.

Fast power tracking control of PV power plants for frequency support

Abstract A power tracking controller for frequency support by photovoltaic power plants without battery storage is presented. Due to the decreasing inertia, regenerative systems such as wind turbines and photovoltaic power plants must provide an instantaneous reserve for fast frequency support in power systems. To provide grid support by PV power plants, a control scheme, and a design procedure are introduced to ensure power reserve by leaving the optimal operating point. A model-based generalized design procedure in the Takagi-Sugeno fuzzy framework for PV system with switched-mode DC-DC converter is presented to achieve the specified control objectives. Simulation studies show the applicability of the control scheme.

Analysis of Frequency Regulation Capability of Doubly Fed Induction Generator and Supercapacitor Energy Storage Based on Dynamic Power Flow

The grid-integrated doubly fed induction generator (DFIG) is required to participate in the frequency regulation of the power system. The supercapacitor energy storage (SES) is capable of enhancing the frequency regulation capability of the DFIG in a coupled manner. The SES is connected to the DC capacitor of the DFIG and provides active power response through the droop control. The dynamic power flow (DPF) model is established to quantify the frequency response of the power system when the DFIG-SES system participates in the frequency regulation. The integration of the SES affects the internal power flow distribution of the DFIG; thus, the detailed model of the DFIG is incorporated into the DPF analysis. Considering the different response speeds of the synchronous generator (SG), the SES, and the DFIG to the frequency regulation, the first-order inertia delay in the governor control of the SG is included in the DPF model. The impact of the delay time constant on the continued operation time of the SES is analyzed. With the same deloading percentage, the output power of the DFIG is adjusted based on a variable droop coefficient scheme to fully utilize its active power reserve. The feasibility and effectiveness of the DFIG-SES scheme to participate in the frequency regulation are analyzed based on the DPF and verified through numerical analysis.

A Robust Optimization Model of Aggregated Resources Considering Serving Ratio for Providing Reserve Power in the Joint Electricity Market

As the share of distributed generation increases, so do the opportunities for aggregators to participate in the electricity market. In particular, aggregators participating in both the day-ahead and real-time markets contribute to improving the reliability of the power system. In addition, aggregators seeking additional revenue can benefit from providing reserves in a joint electricity market environment. However, aggregated resources with uncertainty are limited because of the uncertain nature of both reserve provision and the amount of reserves they can provide. Therefore, this study proposes a robust optimization model for an aggregator to formulate a strategy for participation in the day-ahead markets and deploys energy control in the real-time operation. The serving ratio reflects the availability of the aggregator’s reserve participation. Both the deployed up/down power and renewable energy in the real-time operation are considered as uncertain parameters to reflect the uncertainty. In the case study, we analyze the profit-maximization strategy of an aggregator that owns renewable energy resources and energy-storage systems under the variation interval for uncertain parameters and the serving ratio. The bidding strategies vary by the variation interval and the serving ratio.

Power Flow Management of Interconnected AC Microgrids Using Back-to-Back Converters

Microgrids have limited renewable energy source (RES) capacity, which can only supply a limited amount of load. Multiple microgrids can be interconnected to enhance power system availability, stability, reserve capacity, and control flexibility. This paper proposes a novel structure and control scheme for interconnecting multiple standalone microgrids to a common alternating current (AC) bus using back-to-back converters. The paper presents a high-level global droop controller that exchanges power between interconnected microgrids. Each microgrid considered in this paper comprises RES, battery, auxiliary unit, and load. The battery maintains the AC bus voltage and frequency and balances the difference in power generated by the RES and that consumed by the load. Each microgrid battery’s charge/discharge is maintained within the safest operating limit to maximize the RES power utilization. To achieve balance and continuity of supply, renewable power curtailment and auxiliary power supplement mechanism is designed based on the bus frequency signalling technique. Performance evaluation shows that the proposed controller maximizes renewable power utilization and minimizes auxiliary power usage while providing better load support. The performance validation of the proposed structure and control strategy has been tested using MATLAB/Simulink.

Multi-Area and Multi-Period Optimal Reactive Power Dispatch in Electric Power Systems

Factors such as persistent demand growth, expansion project delays, and the rising adoption of renewable energy sources highlight the importance of operating power systems within safe operational margins. The optimal reactive power dispatch (ORPD) seeks to find operating points that allow greater flexibility in reactive power reserves, thus ensuring the safe operation of power systems. The main contribution of this paper is a multi-area and multi-period ORPD (MA-MP-ORPD) model, which seeks the minimization of the voltage deviation in pilot nodes, the reactive power deviation of shunt elements, and the total reactive power generated, all taking into account the operational constraints for each area. The MA-MP-ORPD was implemented in the Python programming language using the Pyomo library; furthermore, the BONMIN solver was employed to solve this mixed-integer nonlinear programming problem. The problem was formulated from the standpoint of the system operator; therefore, it minimizes the variations of critical variables from the desired operative values; furthermore, the number of maneuvers of the reactive compensation elements was also minimized to preserve their lifetimes. The results obtained on IEEE test systems of 39 and 57 buses validated its applicability and effectiveness. The proposed approach allowed obtaining increases in the reactive power reserves of up to 59% and 62% for the 39- and 57-bus test systems, respectively, while ensuring acceptable operation values of the critical variables.

Improvement of Myocardial Structure after Developed Fibrous Degeneration Under the Use of Allogenic Biomaterial

Introduction. The question of the possibility of recovery of postischemic myocardium remains relevant.Aim. The aim of the study was to study the effect of dispersed decellularized allogeneic extracellular matrix (allogeneic biomaterial, DAB) on the developed fibrous degeneration of the myocardium, as well as to reveal the possible mechanisms of cellular regeneration.Materials and methods. The muscular wall of the heart of rats was subjected to cryodestruction. After 45 days, the rats of the main group were intramyocardially injected with a suspension of allogeneic biomaterialinto the area of the affected myocardium, and the rats of the control group were injected with saline.Results and discussions. In the experimental group, there was a regression of the formed fibrous connective tissue, chemoattraction of progenitor cells, their differentiation and integration into the myocardium. The thickness of the muscular part of the wall of the left ventricle was three orders of magnitude higher than in the control group.Conclusion. Analysis of the results of the study indicates that the heart in adult mammals has a powerful regenerative reserve. It is likely that, based on the use of DAB, a protocol can be developed that allows the restoration of the heart muscle even in conditions of already developed fibrous degeneration.

The Anaerobic Speed Reserve Influences Speed And Power Improvements From Repeated-sprint Training In Hypoxia (RSH) In World-class Short-track Speed Skaters

The Anaerobic Speed Reserve Influences Speed And Power Improvements From Repeated-sprint Training In Hypoxia (RSH) In World-class Short-track Speed Skaters

Determination of required instantaneous power reserve for power system inertia enhancement, based on the unit commitment

Determination of required instantaneous power reserve for power system inertia enhancement, based on the unit commitment

Dynamic Modelling and Mutual Coordination of Electricity and Watershed Networks for Spatio-Temporal Operational Flexibility Enhancement Under Rainy Climates

This paper proposes a watershed-electricity nexus model to unlock the flexibility of watershed networks (WSNs) for supporting the operation of power distribution networks (PDNs) under rainy climates. The proposed model exploits the spatio-tem-poral flexibility of geographically dispersed pump clusters to pro-vide reserve services to PDNs, and a hyperbolic partial differential function derived from Saint-Venant hydrodynamic equations is formed to describe the dynamic processes of river stream flows. Be-sides, a flexibility evaluation method based on a composite sensitiv-ity matrix of water levels with respect to power injections is pre-sented to quantify the time-varying adjustable power domain of pump loads. Then, a multi-stage interactive coordinated scheduling strategy is developed for the mutual operation of WSNs and PDNs, where drainage pumps are jointly optimized to provide flexible power reserves, while an optimal PDN economic dispatch is per-formed to improve the power supply voltage of pump loads. Fur-thermore, an equivalent mixed-integer linear programming refor-mulation method is derived to cope with the original nonlinear par-tial differential optimization problem for computational tractabil-ity improvements. Comparative results have validated the effective-ness of the proposed strategy in eliminating voltage violations and shaving peak loads.

A Methodology to Evaluate Reactive Power Reserves Scarcity During the Energy Transition

The lack of reserves for reactive power production and absorption is an envisioned, still basically unexplored, threat to the voltage profile adequacy and thereby secure operation of transmission grids during the energy transition toward renewable-dominated power production. This paper proposes a novel, generic, comprehensive, and realistic methodology to identify when this issue of reactive power reserves (RPRs) scarcity during plausible scenarios of the energy transition would become severe. The computational core of the proposed methodology comprises four different AC security-constrained optimal power flow (SCOPF) problems: one conventional, two tailored ones that assess the RPRs scarcity in production and absorption modes, respectively, and an optimal reactive power dispatch. The methodology is versatile, offering the possibility to assess RPRs in different timescales, ranging from day-ahead short-term operation to years-ahead long-term operation, and considering appropriate renewable energy production forecasts and day-dependent load profiles. The proposed methodology can serve as a decision support tool for the transmission system operator (TSO), allowing to plug and play different plausible energy transition scenarios (e.g., differing in terms of sequence and timing of: phased out power plants as well as location, type, and size of renewable energy sources deployed) and ultimately informing the TSO about the timing where RPRs become insufficient to maintain security. Without loss of generality, the value of the proposed methodology is extensively demonstrated in a 60-bus Nordic32 system, considering 52 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N-1$</tex-math></inline-formula> line and generator contingencies, while the tractability of AC SCOPF problems is assessed in a 1,203-bus system.

Modeling the Reserve Capacity of Wind Power and the Inherent Decision-Dependent Uncertainty in the Power System Economic Dispatch

The ever-increasing penetration of renewable generation is demanding additional flexibility for the operation of power systems. In this sense, it has been proved that wind power generators (WPGs) can provide part of the required operating reserve through pitch angle control (PAC) under a deloaded strategy. Unlike conventional operating reserve sources, however, the operating reserve provided by WPGs can't always be considered reliable, which renders the power system dispatch more challenging. In this research, the reserve capacity of the WPGs is modeled considering the decision-dependent uncertainty (DDU). The random wind speed introduces uncertainty to the available reserve capacity of the WPGs while the decisions on the deloading degrees of the WPGs directly affect their coefficients between wind speed and usable wind power, making the uncertainty decision-dependent. Moreover, the operational technical limits of the WPGs and the multiple possible wind speed scenarios are also considered in the wind power reserve capacity modeling. Then, a two-stage reliability constrained stochastic economic dispatch model with WPGs' reserve provision (SED-WRP) is developed to jointly dispatch the generation and reserve. A group-based multi-cut Benders decomposition method is applied to improve the convergence performance of the solution algorithm. Case studies are solved to quantify the impact of considering the reserve provision of WPGs and the inherent DDU in power system dispatch decisions.

Design and implementation of Hybrid Renewable energy (PV/Wind/Diesel/Battery) Microgrids for rural areas.

This study examines the variation in sensitivity of a microgrid system comprised of photovoltaics, wind turbines, diesel engines, and batteries. The primary objective is to increase our knowledge of renewable energy resources (RERs) and their technical and economic factors in the context of the conceptual design of a microgrid system. The investigation employs Typhoon HIL software for simulation and testing, concentrating on hybrid PV/Wind/Diesel/Battery systems and devising a perturb &amp; observe (P&amp;O) maximum power point tracking (MPPT) strategy. Additionally, the study investigates the Optimal Power Controlling MPPT technique and the development and implementation of hybrid renewable energy resources (HRES). The Typhoon HIL system is utilized in the power, automotive, and aerospace industries, among others, to simulate and test control systems in real-time. This study presents a control strategy for a microgrid system that combines renewable energy sources such as solar and wind power with reserve power options such as diesel generators and batteries. The coordinated control technique is implemented by employing a centralized control method, effectively managing the flow of electricity from diverse distributed energy resources (DER) and ensuring the microgrid's stability. The findings indicated that the coordinated control method and dynamic models could be utilized to design and optimize microgrid systems. Future research can concentrate on refining the accuracy of the models and verifying the proposed coordinated control method in microgrid systems that operate in the real world.

Participation of battery energy storage system for frequency control in wind dominated power systems: An analytical approach

The frequency performance of a power grid is effectively maintained through the utilization of inertia and power reserve provided by synchronous generators. The growing concerns surrounding global warming and the greenhouse effect have led to a significant increase in the integration of wind energy into the grid. But the system may face frequency instability following a contingency due to lack of sufficient inertia and headroom of wind generators. Therefore, the grid operator may require shedding some loads to prevent the system from severe frequency excursion. In this paper, we have estimated proper amount of load shedding through the formulation of analytical expression that will keep a highly wind penetrated & Battery Energy Storage System (BESS) integrated system stable. For this purpose, the maximum amount of wind power penetration level (WPPL) is first calculated using a fast analytical approach which utilizes two frequency response performance metrics, frequency nadir and Rate of Change of Frequency (ROCOF). In scenarios where the wind penetration level exceeds the calculated allowable threshold, it becomes necessary to implement load shedding measures following a contingency event. After installation of BESS, grid frequency response is much enhanced, hence, the required load shedding amount is also different. Therefore, we have derived an analytical expression for a quick measurement of frequency response enhancement attained by BESS. Finally, a frequency nadir-based load shedding scheme, being the goal of this paper, is proposed for a heavily wind penetrated grid with BESS, using the previously derived expression, to retain the grid at its nominal operating condition following a severe contingency. Our proposed scheme incorporates an analytical method to prevent over load shed. We have used DIgSILENT PowerFactory to validate our proposed analytical approaches through dynamic simulation. Results obtained from the proposed approaches nearly resemble the simulated one. Hence, this paper can help generating simplified yet effective models to conduct analysis on a wind integrated grid. This paper can also be regarded as a guide to ensure a wind penetrated resilient grid in view of frequency stability.

Clustering Combined Multi-Objective Optimal Operation of Transmission Systems Considering Voltage Stability

In recent years, power systems have undergone major changes called energy transitions during which synchronous generators have been replaced with power electronics-based generation. Therefore, the voltage stability of power systems has become a major concern owing to the absence of synchronous generators. This study proposes multi-objective optimization using the non-dominated sorting genetic algorithm III to achieve optimal reactive power reserve procurement and improve the voltage stability of the overall system. These systematic approaches require high computational power and are unsuitable for the operational frameworks currently used for large-scale power systems. Previous works have rarely considered the local characteristics of reactive power or generation de-commitment with sufficient re-dispatch owing to greater renewable energy integration. We propose a framework for achieving systematic optimization by considering various objective functions while utilizing the regional aspect of reactive power via spectral clustering-based voltage control area (VCA) identification. The proposed method comprises systematic and regional approaches to optimizing systems for voltage stability improvement based on VCAs. The results demonstrate that the proposed method shows satisfactory performance. These results will be helpful for decision making for power system operations in harsher environments with more renewable energy.

Perancangan PLTS Untuk Sumber Daya Lampu Penerangan Jalan Desa Iringmulyo Metro

The increasing activity of the people at night makes the need for lighting sources also increase, especially in public places. One part that requires lighting is the Iringmulyo Metro village road. Roads are the main infrastructure that must be considered for their condition and use, if the road conditions are good for passage it will certainly reduce the level of accidents and crime, so village roads also need lighting. Public street lighting using solar energy is a cheap and economical alternative to use as a source of lighting electricity because it uses a free and unlimited source of energy from nature, namely solar energy. The Iringmulyo Metro village road lighting system uses a solar cell of 200 wp and a lamp load of 40 watts. When the weather is clear the battery can charge up to 720wh and can run a light load for up to 18 hours. If the solar panel is unable to receive light, the battery still has a power reserve of 240wh/6 hours. Lighting a solar street light using a 40 watt LED lamp produces an illumination of 4.58 lux. The power efficiency of the solar cell module panel is 14.5% determined by the tilt position of the solar cell panel and the intensity of sunlight. The higher the sunlight intensity, the higher the output efficiency of the solar cell module