This paper presents a mathematical model of smart loads in demand response (DR) schemes, which is integrated into centralized unit commitment (UC) with optimal power flow coupled energy management ...systems for isolated microgrids for optimal generation and peak load dispatch. The smart loads are modeled with a neural network (NN) load estimator as a function of the ambient temperature, time of day, time of use price, and the peak demand imposed by the microgrid operator. To develop the NN-based smart load estimator, realistic data from an actual energy hub management system is used for supervised training. Based on these, a novel microgrid energy management system (MEMS) framework based on a model predictive control approach is proposed, which yields optimal dispatch decisions of dispatchable generators, energy storage system, and peak demand for controllable loads, considering power flow and UC constraints simultaneously. To study the impact of DR on the microgrid operation with the proposed MEMS framework, a CIGRE benchmark system is used that includes distributed energy resources and renewables based generation. The results show the feasibility and benefits of the proposed models and approach.
This paper presents practical energy management system (EMS) models which consider the operational constraints of distributed energy resources, active-reactive power balance, unbalanced system ...configuration and loading, and voltage dependent loads. A novel linearization approach is proposed and validated based on the fact that, for isolated microgrids, due to the characteristics of feeders, network losses, and voltage drops across feeders are relatively small. The proposed EMS models are mixed integer quadratic programming problems, requiring less computation time and thus suitable for online applications. The practical EMS models are compared with a typical decoupled unit commitment and optimal power flow-based EMS with and without consideration of system unbalancing. The models, along with "standard" EMS models, are tested, validated, and compared using a CIGRE medium voltage benchmark system and the real isolated microgrid of Kasabonika Lake First Nation in Northern Ontario, Canada. The presented results demonstrate the effectiveness and practicability of the proposed models.
In this paper, the impact of electric thermal storage (ETS) systems on the operation of Northern Communities' microgrids is analyzed. A mathematical model of the ETS system is developed and ...integrated into an energy management system (EMS) for isolated microgrids, in which the problem is divided into unit commitment and optimal power flow subproblems, to dispatch fossil-fuel-based generators, energy storage systems, and ETS charging. To account for the deviations in the forecast of renewables, a model predictive control technique is used. The proposed ETS-EMS framework is tested and studied on a modified CIGRE medium voltage benchmark system, which comprises various kinds of distributed energy resources, and on the real Kasabonika Lake First Nation isolated microgrid system. It is shown that the ETS significantly reduces operating costs, and allows for better integration of intermittent wind and solar sources.
In this paper, the equivalent CO 2 emission models for fossil-fuel-based distributed generator units are developed considering their individual emission characteristic and fuel consumption. These ...models are then integrated within a microgrid energy management system (EMS) model. Constant energy, demand shifting load models are further integrated in the EMS to examine the possible impact of demand response (DR) on the total system emissions and economics of a microgrid. Thus, the impacts of including the developed emission models on the operation of an isolated microgrid, equivalent CO 2 emissions, and costs are examined considering five different operating strategies. The proposed operating strategies are validated on a modified CIGRE medium voltage benchmark system. The results obtained highlight the effectiveness of the proposed EMS and also demonstrate the impact of DR on emissions and costs.
As the penetration of variable renewable generation increases in power systems, issues, such as grid stiffness, larger frequency deviations, and grid stability, are becoming more relevant, ...particularly in view of 100% renewable energy networks, which is the future of smart grids. In this context, energy storage systems (ESSs) are proving to be indispensable for facilitating the integration of renewable energy sources (RESs), are being widely deployed in both microgrids and bulk power systems, and thus will be the hallmark of the clean electrical grids of the future. Hence, this article reviews several energy storage technologies that are rapidly evolving to address the RES integration challenge, particularly compressed air energy storage (CAES), flywheels, batteries, and thermal ESSs, and their modeling and applications in power grids. An overview of these ESSs is provided, focusing on new models and applications in microgrids and distribution and transmission grids for grid operation, markets, stability, and control.
This paper proposes an integrated energy management system (IEMS) for isolated microgrids considering demand response, fossil-fuel-based and renewable-based distributed generators (DGs), and energy ...storage systems (ESS). In the proposed approach, the unit commitment (UC) and optimal power flow (OPF) constraints are jointly included in the IEMS model, and to account for forecasting errors in renewable generation and electricity demand, a model predictive control (MPC) technique is adopted. The proposed IEMS model is compared with a "standard" decoupled energy management system (DEMS) in which the dispatch problem is decomposed into UC and OPF sub-problems, and the impact of MPC implementation and forecast errors are also analyzed. Both IEMS and DEMS approaches are tested and compared using a modified CIGRE medium voltage benchmark system. The results demonstrate the effectiveness of the proposed IEMS and MPC techniques.
Driven by global environmental emission issues, energy access in remote communities, and tighter requirements for system resilience and reliability, electricity production is shifting from a ...centralized paradigm to a decentralized one. In this context, renewable energy sources (RESs) have proliferated over the past decade, exhibiting a steadily increasing trend. Thus, today, a large number of wind turbines and photovoltaic (PV) panels are connected to medium- (1-69 kV) and low-voltage (=1 kV) grids, with traditional integrated bulk power systems becoming decentralized in the presence of active distribution networks, where the flow of power is bidirectional between generators and "prosumers." In particular, with decreasing RES s costs, these technologies are becoming attractive solutions to bring energy to remote communities and/or replace expensive fossil-fuel-based generators. However, RES s such as wind and solar are intermittent sources of energy, difficult to predict, and prone to large output fluctuations-therefore, significantly affecting system voltage and frequency.
ObjectivesThis study aimed to assess the coverage and explore enablers and challenges in implementation of direct benefit transfer (DBT) cash incentive scheme for patients with tuberculosis ...(TB).DesignThis is a mixed methods study comprising a quantitative cohort and descriptive qualitative study.SettingThe study was conducted in City TB Centre, Vadodara, Western India.ParticipantsWe used routinely collected data under the National TB Programme (NTP) on patients with TB notified between April and September 2018 and initiated on first-line anti-tuberculosis treatment (ATT) to assess the coverage of DBT. We interviewed NTP staff and patients to understand their perceptions.Primary and secondary outcome measuresThe study outcomes are receipt of DBT (primary), time to receipt of first instalment of DBT and treatment outcome.ResultsAmong 1826 patients, 771 (42.2%) had received at least one instalment. Significantly more patients from the public sector had received DBT (at least one instalment) compared with those from private sector (adjusted relative risk (adjRR)=16.3; 95% CI 11.6 to 23.0). Among public sector patients, 7.3% (49/671) had received first instalment within 2 months of treatment initiation. Median (IQR) time to receipt of first instalment was 5.2 (3.4, 7.4) months. Treatment in private sector, residing outside city limits and being HIV non-reactive were significantly (p<0.001) associated with longer time to receipt. Timely and sufficient fund release, adequate manpower and adequate logistics in TB centre were the enablers. Inability of patients to open bank accounts due to lack of identity/residence proof, their reluctance to share personal information and inadequate support from private providers were the challenges identified in implementation.ConclusionDuring the early phase of DBT implementation, the coverage was low and there were delays in benefit transfer. Facilitating opening of bank accounts for patients by NTP staff and better support from private providers may improve DBT coverage. Repeat assessment of DBT coverage after streamlining of implementation is recommended.
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