System Planners Research Articles

Influence of business models on PV-battery dispatch decisions and market value: A pilot study of operating plants

PV-battery hybrid projects dominate interconnection queues in some regions in the United States. But few large-scale projects have been in use long enough to assess how the hybrid capabilities may be used in practice and the existing literature scantly discusses observed operational strategies. We interview plant operators and analyze empirical dispatch data for eleven large-scale PV-battery hybrids in three organized wholesale markets in the United States. We estimate the market value of our sample hybrids in 2020. The empirical increase in market value of a PV-battery hybrid relative to a standalone PV plant varies by project and ranges from $1 to $48/MWhsolar, often aided by a large boost in capacity value. This premium is driven by market, location, technical characteristics of the PV and battery asset, and battery dispatch strategies. In contrast to the widespread assumptions in the PV-battery hybrid modeling literature, only three of the eleven project operators optimize battery usage for wholesale market revenue as merchant plants. Instead, load-serving entities target peak load reductions, incentive program participants focus on compliance with program requirements, and large energy consumers prioritize resiliency and utility bill minimization. These alternative business models can result in high revenues for the project operators, but do not optimize the storage dispatch from a grid perspective. Understanding real-world dispatch signals and aligning them closer with system-wide grid needs will be important for electric grid operators and system planners, and can increase the market value of PV-battery hybrids.

Investigation on Temperature Rise Characteristic and Load Capacity of Amorphous Alloy Vegetable Oil Distribution Transformers with 3D Coupled-Field Method

The large differences in the load peak and valley of rural distribution networks always bring severe problems to system planners and operators. Given this issue, this paper deals with the hot-spot temperature (HST) of the transformer and its overload capability, and proposes a modeling method-based online monitoring of practical parameters. In the current work, a temperature-fluid coupling field of the 315 kVA vegetable oil distribution transformer is developed in both the two-dimensional and three-dimensional geometry, by which the convection and heat dissipation process can be studied. The grid of the model is divided into regions to increase the calculation speed and ensure the accuracy of the calculation. Secondly, tests related to the temperature rise of the transformer are carried out. The accuracy of the three-dimensional model is later discussed in terms of temperature and fluid velocity distribution. Finally, the temperature distribution laws of the amorphous alloy vegetable oil distribution transformers (AVDT) are compared and analyzed under different load conditions. Findings reveal that the AVDT has low no-load loss and strong overload capacity, which is capable of reducing the internal overheating accidents of the transformer.

Grid Connection Studies for Large-Scale Offshore Wind Farms Considering High Penetration of Regional Renewables

There is a global focus on adding renewable energy sources to the mix of energy supplies. In this study, the grid connections for large-scale offshore wind farms in areas that have high penetration of renewable energy sources were examined. System strength evaluation considering the interaction of wind farms and inverter-based resources (IBRs) was performed; the fault current was then analyzed to determine their contribution to the total fault current at a bus level. These studies revealed that the interaction between offshore wind farms and IBRs may make the power system weaker, and it is possible that fault current contributions from offshore wind farms can violate the capacity limit of existing circuit breakers. The results of steady-state analysis were verified through case studies focused on the southwest area of the Korea Electric Power Corporation (KEPCO) system where large-scale offshore wind farms are planned to be established and connected. Power system planners will benefit from the results of this study with a better understanding of the factors to consider when integrating large-scale wind farms in areas with high penetration of renewables.

Comprehensive Overview of Power System Flexibility during the Scenario of High Penetration of Renewable Energy in Utility Grid

Increased deployment of variable renewable energy (VRE) has posed significant challenges to ensure reliable power system operations. As VRE penetration increases beyond 80%, the power system will require long duration energy storage and flexibility. Detailed uncertainty analysis, identifying challenges, and opportunities to provide sufficient flexibility will help to achieve smooth operations of power system networks during the scenario of high share of VRE sources. Hence, this paper presents a comprehensive overview of the power system flexibility (PSF). The intention of this review is to provide a wide spectrum of power system flexibility, PSF drivers, PSF resources, PSF provisions, methods used for assessment of flexibility and flexibility planning to the researchers, academicians, power system planners, and engineers working on the integration of VRE into the utility grid to achieve high share of these sources. More than 100 research papers on the basic concepts of PSF, drivers of the PSF, resources of PSF, requirement of the PSF, metrics used for assessment of the flexibility, methods and approaches used for measurement of flexibility level in network of the power system, and methods used for the PSF planning and flexibility provisions have been thoroughly reviewed and classified for quick reference considering different dimensions.

Designing and Energy Estimation of Photovoltaic Energy Generation System and Prediction of Plant Performance with the Variation of Tilt Angle and Interrow Spacing

The focus of this research is to design a ground-mounted photovoltaic system at optimal tilt angle and interrow space to meet high demand of electrical energy. The Department of Electrical Engineering and Technology, GC University Faisalabad has been considered to perform the simulation test. This study is conducted using Meteonorm software for solar resource assessment. Furthermore, HelioScope software is used for modeling of a ground-mounted photovoltaic system, study of PV system’s performance in terms of annual generation, system losses and performance ratio and analysis of photovoltaic module’s performance, current-voltage and power-voltage curves for different irradiance levels. From SLD, it is seen that 11 strings are connected to each inverter and inverters output power are combined by using 20.0 A circuit interconnects. The performance of photovoltaic systems is impacted by tilt angle and interrow spacing. From simulation results of all cases, it is concluded that the PV system installed at 15° tilt angle with 4 feet interrow spacing are more efficient than the other installed PV systems, because total collector irradiance is maximum (1725.0 kWh/m2) as compared to other tilt angles. At 15° tilt angle, the annual production of photovoltaic system is 2.265 GWh and performance ratio of PV system is 82.0%. It is envisioned that this work will provide the guidance to energy system designers, planners and investors to formulate strategies for the installation of photovoltaic energy systems in Pakistan and all over the world.

Bi-Level Multi-Objective Planning Model of Solar PV-Battery Storage-Based DERs in Smart Grid Distribution System

This paper presents a novel bi-level multi-objective model for planning solar PV-battery storage (PV-BS) based DERs in Smart grid distribution system (SGDS). The planning of Solar PV and battery storage (BS) in the distribution system presents severe complexities for the system planner due to their inherent attributes. The detailed analysis considering all three planning aspects, namely technical, economics, and environmental, is presented, assisting in the efficient and reliable planning operation. The four test cases are formulated based upon the life cycle cost, unserved energy, penetration level, and social welfare. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">level-1</i> proceeds with evaluating the DERs sizing along with penetration level and serves as an input to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">level-2</i> for computing the optimal placement for DERs. The proposed model is implemented on the IEEE-33 bus distribution system and solved using Butterfly-PSO (BF-PSO) algorithm. The detailed parametric and sensitivity analysis presented may aid the system planners in terms of planning preview. The simulation results validate the effectiveness of the proposed work by showing significant improvement in bus voltage profiles (up to 4%) and reduction in total power losses (up to 45%). The highest penetration level is observed for Case 2 (70%), which also corresponds to the highest LCC (k <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\$ $ </tex-math></inline-formula> 147094) and thus results in the lowest emission cost (k <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\$ $ </tex-math></inline-formula> 4920).

Management and development of a residential energy storage system: A case study Jordan

The use of renewable energy generation (REG) and energy storage systems (ESSs) strategies have a considerable possibility in delivering resilience for renewable energy sources (RESs). Thus, combining REG and ESSs strategies to fix operational, economic, ecological, and power-concerning governmental issues have been received particular concern from power system (PS) operators and planners globally. In this concern, developing countries (Jordan), which are poor in traditional energy resources, have proposed different supportive issues and experiences for the common use of ESSs strategies in the situation of distribution PSs. Therefore, this article performs a universal solution to this problem possessed to construct the infrastructure substantially to achieve high penetration of RE in the PS. Based on this, the article firstly studies the necessity of using REG and ESSs strategies in RE-based distribution PS. So, the current approaches and motivation programs used in various countries for the growth of RERs in optimum composition with ESSs and REG strategies are offered. The results of this study suggest that the use of an ESS is very important for the management and development of residential Solar Energy (SE) applications. Most respondents (85.3%) said that the use of a domestic ESS is critical to the management and growth of demand and supply for RE. To improve main grid efficiency and reduce demand for conventional power supplies, Jordanian engineers and experts recommend that consumers should install ES devices in their homes.

The Impact of Variable Renewable Energy Integration on Total System Costs and Electricity Generation Revenue

Variable renewable energy (VRE) integration creates additional costs, called “integration costs.” These costs have grown with VRE penetration, potentially increasing the total system costs delivered to customers (direct integration costs) and decreasing electricity generation revenue, discouraging generators’ investment (indirect integration costs). Thus, integration costs can be an economic barrier to integrate high shares of VRE. This paper proposes a method to determine the impact of VRE integration on total system costs and electricity generation revenue. The method is a combination of the unit-commitment model, the optimal generation mix and optimal generation schedule analysis, and merit-order simulations. The results show that the total system costs are minimal at 70% VRE penetration. In addition, after 20% VRE penetration, the combination of solar and wind generation provided minimal total system costs rather than relying on wind or solar individually. Moreover, the profitability of generators from supplying energy to the energy market is declined by VRE penetration. Combined cycle gas turbines (CCGT), hydro, and wind generators face higher impacts on their electricity generation revenue than coal and solar generators. Electricity system planners and policymakers need to consider and prioritize the severity of VRE impacts on each technology grown with VRE penetration to enact consistent plans and policies.

Stochastic AC Transmission Expansion Planning: A Chance Constrained Distributed Slack Bus Approach With Wind Uncertainty

Integrating more renewable energy sources into the grid leads to a more vulnerable power system and presents challenges for power system planners. This paper proposes a probabilistic overload constraint based AC transmission expansion planning model. In terms of economic dispatch, generation adequacy and network constraints are assessed using a probabilistic participation factor power flow. Generation participation factors, which are handled in the AC power flow equations, are used to manage mismatch power that comes from uncertainties as well as transmission loss of the system in a distributed slack bus concept. Combinations of load, wind and N-1 contingency uncertainties are evaluated with Monte Carlo Simulation and the loading limits for the existing and candidate lines and violations on bus voltages are enforced as probabilistic constraints using chance constraint programming. The investment decisions taken under various operating conditions are re-evaluated under a new set of wind power uncertainty that differs from those utilized in the optimization process, and the resulting TEP decisions are analyzed from a risk perspective. The proposed method allows for the uncertain operating conditions to be easily and accurately adapted to the ACTEP optimization. The optimization results show that the participation factor power flow is a promising tool for evaluating probabilistic operating conditions, which can be used to explore the possibility of violations under different uncertainty conditions.

A Novel Four-Level Approach for Improving Power System Resilience Against Intentional Attacks

This study proposes a new four-level model to enhance power system resilience against human attacks. The model considers human attacks, such as intelligent attackers and power system planners, as defenders. The attackers want to maximize the impacts of actions, while the defender tries to avoid imposed costs and damages due to budget limitations. To this end, a new four-level model defense-defense-attack-defense (DDAD) is proposed, in which a new defense layer is added to the common three-level model defense-attack-defense (DAD). Looking at the model more closely, new power plants and substations are added to the power system to improve its resilience, while the most important power plants and substations are determined. Subsequently, the conventional three-level model was applied. In this research, the defender and attacker have some strategies with their own costs for every power system component, such as power plants and substations, and their own interactions. The power system model includes the load, power plant and substation, and substation priority, which are defined as a combination of the value of the load and network topology. The proposed model was applied to the IEEE-30 bus test system, and the results indicated the effectiveness of the proposed method.

Cost-effectiveness of Extracorporeal Cardiopulmonary Resuscitation (ECPR) for Out-of-Hospital Cardiac Arrest—A Systematic Review

The use of extracorporeal membrane oxygenation for out-of-hospital cardiac arrests (OHCA) has increased significantly. Extracorporeal cardiopulmonary resuscitation (ECPR) is resource intensive, costly and technically challenging, presenting significant challenges for health system planners. We sought to review the cost-effectiveness of using ECPR compared with conventional CPR for OHCA.

Designing a model of academic depression based on the psychological-social atmosphere of the class With the mediation of motivational self-regulation among 10th grade female students

Background and Aim: Academic activities require academic enthusiasm and motivation that sometimes students show a kind of disillusionment in doing homework and in fact this issue is very important in the path of their academic achievement, therefore, the main purpose of this study was to design a model of academic distress based on the psychosocial atmosphere of the class with motivational self-regulation mediation. Methods: The research method was descriptive correlational and the statistical population consisted of female students in the 10th grade of high schools in District 2 of Arak in the academic year 2021-2022. The sample size was determined by modeling method of 300 people who were selected by cluster random sampling method. Data collection tools were: Pekran Academic Distress Questionnaire (2005), Misho Class Psychosocial Climate (1985), Boufard Self-Regulation Questionnaire (1995). Data analysis method was the exploitation of descriptive statistics indicators, structural equations including path analysis, t-statistics, bootstrap and sobel. In this regard, PLS software was used. Results: The results showed that academic disillusionment based on psychosocial climate with motivational self-regulation mediation with coefficient of -0.681 at the level (P&lt;0.05), It is fitting that by increasing the psychosocial climate with the mediation of motivational self-regulation, academic heartache decreases by 0.681, so the model of academic heartache based on the psychosocial atmosphere of the class is mediated by the mediator. Gray himself has fitted motivational discipline. This fit had an indirect effect equivalent to -0.532 coefficient. Conclusion: Based on the results, it can be concluded that psychosocial climate has a significant relationship with academic distress directly and through the mediation of motivational self-regulation, and therefore, educational system planners can pay attention to these relationships and make teachers more aware of these results.

Generation Capacity Expansion Problem Considering Different Operation Modes of Combined-Cycle Gas Turbines

The design of future decarbonized power systems is one of the most relevant and challenging problems that power system planners are facing nowadays. It is expected that Combined-Cycle Gas Turbines (CCGTs) play a relevant role in these systems to provide peak power and reserve capacity when intermittent power units be unavailable. However, the large computational size of planning problems has prevented so far from modeling the actual operation of CCGTs accurately. This paper intends to quantify the effect of the modeling of CCGTs in the generation capacity expansion problem. For doing that, the operation of CCGTs is modeled using a mixed-integer linear formulation that considers different operation modes. Afterwards, generation expansion decisions in a realistic case study are analyzed using different accuracy degrees for modeling the operation of CCGTs. The numerical results suggest that the simplification of the modeling of the operation of CCGTs overestimates the flexibility provided by these units, which increases the capacity installed from renewable units.

Perceived Problems of Patients with Chronic Respiratory Failure: a Qualitative Study

Chronic respiratory failure is one of the concerns of the World Health Organization because of its widespread prevalence in the world. This disease has led to individual, family, and social dysfunction in these patients with a wide impact on physical, mental, and psychological dimensions. Considering the importance of this issue, the present study was conducted to explain the patients' perceived problems with chronic respiratory failure. The present qualitative study was performed using the conventional content analysis approach. Target targeted sampling selected chronic patients with respiratory failure from Shahid Sayyad Shirazi Hospital in Gorgan, Iran. Semi-structured face-to-face interviews were conducted with 15 patients. Graneheim and Lundman content analysis approach analyzed data. Data management was performed by MAXQDA 10. Data analysis was summarized in 2 main categories and eight subcategories. Patients' perceived problems with chronic respiratory failure were extracted in two main categories and eight subclasses. The first main category of "perceived economic problems" with the instability subclasses of treatment costs, unemployment and insufficient income, unable to cover expenses, and the second main category of " unable to measure basic needs " with the subclasses of sexual dysfunction, defecation problems, eating disorders, sleep disorders and health problems. Policymakers and stakeholders, health system planners, welfare organizations, and support organizations should use supportive strategies to reduce or eliminate the problems of patients with chronic respiratory failure using the knowledge and understanding of their perceived problems.

A Risk-Averse Approach for Distribution Grid Expansion Planning

Recent episodes of natural disasters have challenged the resilience of power grids. Adequate distribution grid planning that properly captures the risk aversion of the utility system planner is a key factor to increase the flexibility of distribution networks to circumvent these events. In this paper, we propose a methodology to determine the optimal portfolio of investments in lines and storage devices in order to minimize a convex combination between expected value and CVaR of operational costs, including energy not served, while taking into account the multistage nature of the energy storage management within this context. While the expected value of energy not served has been traditionally employed to tackle routine failures, we also minimize the CVaR of energy not served to address high-impact, low-probability (HILP) events. We illustrate the performance of the proposed methodology with a 54-Bus system test case.

Performance benchmarking of power-to-gas plants using Composite Indicators

Driven by the need for decarbonizing energy carriers across sectors, and the increasing availability of low-cost renewable electricity generation future energy systems will see a rise of power-to-gas technology. For example, hydrogen and its derivates can make enable the usage of carbon-neutral electricity for hard-to abate industry sectors and serve as long-term seasonal storage. Given recent drafts of ambitious political hydrogen strategies around the world, the question arises which power-to-gas configurations provide the highest value for money from a power system perspective. This work provides a flexible framework to compare the performance of current power-to-gas sites all over the world. Power-to-gas technologies are assessed with a benchmarking framework based on Composite Indicators to compare the system value of existing conversion technologies, plant sizes, cost structures, and configurations. Our analysis confirms recent research that suggests that plant performance is higher for larger projects and improves as projects move from research stage over pilot stage to commercial stage. Our findings inform policy makers and electricity system planners who aim to identify the economically and technically most promising solutions for investment.

Cost of Energy Losses for Distributed Generation Using Hybrid Evolutionary Programming-Firefly Algorithm

The cost of energy losses analysis for distributed generation (DG) is presented in this paper using a Hybrid Evolutionary Programming-Firefly Algorithm (EPFA). The proposed method was created to determine the optimal DG sizing in the distribution system while accounting for the system’s energy losses. This study presents an investigation into hybrid optimization techniques for DG capabilities and optimal operating strategies in distribution systems. The objectives of this study were to reduce the cost of energy losses while increasing the voltage profile and minimize distribution system losses. In this study, the analysis was done by consider DG type I which is DG-PV. The suggested methodology was tested using the IEEE 69-bus test system, and the simulation was written in the MATLAB programming language. Power system planners can use appropriate location and sizing from the results obtained for utility planning in terms of economic considerations. From the simulation, the result shows the proposed method can identify the suitable sizing of DG while reduce cost of energy losses and total losses in the system.

Integrated Modelling of Decentralised Energy Supply in Combination with Electric Vehicle Charging in a Real-Life Case Study

Intelligent integration of decentralised energy resources, local storage and direct consumption are key factors in achieving the transformation of the energy system. In this study, we present a modular simulation concept that allows the planning of decentralised energy systems for buildings and building blocks. In comparison to related studies, we use a simulation model for energy planning with a high time-resolution from the perspective of the energy system planner. In this study, we address the challenges of the grid connection in combination with an increasing number of electric vehicles (EV) in the future. The here developed model is applied for an innovative building block in Germany with a photovoltaic (PV) system, a combined heat and power (CHP) unit, battery storage and electric vehicles. The results of the simulation are validated with real-life data to illustrate the practical relevance and show that our simulation model is able to support the planning of decentralised energy systems. We demonstrate that without anticipating future electric vehicle charging, the system configurations could be sub-optimal if complete self-sufficiency is the objective: in our case study, the rate of self-sufficiency of the net-zero energy building will be lowered from 100% to 91% if considering electric vehicles. Furthermore, our simulation shows that a peak minimising operation strategy with a battery can prevent grid overloads caused by EV charging in the future. Simulating different battery operation strategies can further help to implement the most useful strategy, without interruption of the current operation.

Optimal management of static volt‐ampere‐reactive devices and distributed generations with reconfiguration capability in active distribution networks

Recently, power system planners and operators are of interest to maximize distribution automation investments. Optimal operation of control centers of fully automated distribution systems enables it to control all switches as well as dispatching connected controllable apparatuses. Most previously enhanced distribution systems, which include additional enhancement apparatuses, such as distribution static VAr compensators, capacitor banks, and distributed generators, cannot take advantage of the features of these apparatuses because there is no efficient and reliable control. Accordingly, this article presents a robust and efficient technique using Manta ray foraging optimization algorithm (MRFOA) for optimal coordination and control of such apparatuses as well as distribution network reconfiguration simultaneously. The proposed procedure is employed for the dynamic operation of automated distribution systems, considering daily load variations, for losses minimization and emissions reduction with diverse cases of both the 33-bus and 69-bus distribution test systems. To manifest, these cases are developed to validate the proposed technique and to achieve optimum control and operation of the distribution systems. Despite the complexity of this problem, the proposed technique can achieve the optimal solution for the various considered cases. As well, the comparative assessment of the proposed MRFOA with relevant techniques demonstrates its effectiveness as an effective tool used in the control centers of modern automated distribution systems. One of the most complex challenges to distribution systems operators in the practical daily load variations is the control and optimal operation of the associated dispatchable enhancement apparatuses such as DGs and DSVCs. The DNR makes the utilization and control of such aforementioned enhancement apparatuses more feasible for distribution systems, but this is in return for increasing the complexity of the problem. Significant technical and environmental benefits have been achieved. Great power losses reduction (about 80%) and voltage enhancement are achieved using the MRFOA. In addition, the emission levels are kept at the lowest levels.

The impact of PV generation and load types on the impedance relays during both balanced and unbalanced faults

Photovoltaic (PV) power generation and the types of connected loads both have an effect on protective impedance relays’ readings. This paper investigates this effect in a real distribution system installed in the State of Kuwait. It is found that, both the dynamic loads and the PV plants have considerable effects in the relay impedance value which vary according to the load type, PV connection and fault locationplace. Both single phase to ground fault (unsymmetrical fault) and three phase fault (symmetrical fault) are investigated. When single line to ground fault occurs at the PV bus (far from relay location), the dynamic loads increase the relay impedance while the PV plant decreases the relay impedance. When a single phase to ground fault occurs at the relay bus (load bus), the dynamic load decreases the relay impedance and the PV plant increases it. For a three-phase to ground fault at the relay bus, both dynamic load percentages and PV plant power generation have no effect on the protective relay impedance readings. At this condition, the relay impedance totally depends on the fault resistance. The main finding of this paper is that both the load type (especially dynamic load) and the PV plant have dominant effects on the protective impedance relay reading and setting. The distribution system planners and operators must consider the PV plant and types of load during designing, setting and adjusting the protective impedance relays. The most important point in this paper is considering real case study. This means that, the obtained results are more realistic than the assumed system in the other research. If the fault occurs at the location of the PV system’s bus when no PV power is generated, the dynamic load causes the relay impedance to increase, while connecting the PV decreases the relay impedance. The relay’s resistance and reactance increase from 0.3153Ω and 1.4950Ω, to 0.3456Ω and 1.6617Ω respectively when the dynamic load increases from 25% to 90% of the total load at constant high fault resistance. The relay resistance and reactance decrease from 0.2849Ω and 0.3443Ω (without PV plant), to 0.2195Ω and 0.3137Ω (with PV), respectively. When the dynamic load percentage increases from 25% to 90%, the resistance and reactance of the relay decrease from 1.0488Ω and 0.0051Ω, to 0.9526Ω and 0.0008Ω, respectively. This phenomenon is valid for all expected fault resistances. When considering constant dynamic load percentage and constant fault resistance, the relay resistance and reactance increase from 1.375Ω and 0.0022Ω (without PV) to 1.5745Ω and 0.0726 Ω (with PV), respectively. Based on those results, the impedance relay setting must be adjusted according to the percentage of the dynamic loads percentage, the PV penetration level, and the fault location.