It is widely accepted that renewable energy sources are the key to a sustainable energy supply infrastructure since they are both inexhaustible and nonpolluting. A number of renewable energy ...technologies are now commercially available, the most notable being wind power, photovoltaic, solar thermal systems, biomass, and various forms of hydraulic power. In this paper, a methodology has been proposed for optimally allocating different types of renewable distributed generation (DG) units in the distribution system so as to minimize annual energy loss. The methodology is based on generating a probabilistic generation-load model that combines all possible operating conditions of the renewable DG units with their probabilities, hence accommodating this model in a deterministic planning problem. The planning problem is formulated as mixed integer nonlinear programming (MINLP), with an objective function for minimizing the system's annual energy losses. The constraints include the voltage limits, the feeders' capacity, the maximum penetration limit, and the discrete size of the available DG units. This proposed technique has been applied to a typical rural distribution system with different scenarios, including all possible combinations of the renewable DG units. The results show that a significant reduction in annual energy losses is achieved for all the proposed scenarios.
This paper addresses the low-frequency relative stability problem in paralleled inverter-based distributed generation (DG) units in microgrids. In the sense of the small-signal dynamics of a ...microgrid, it can be shown that as the demanded power of each inverter changes, the low-frequency modes of the power sharing dynamics drift to new locations and the relative stability is remarkably affected, and eventually, instability can be yielded. To preserve the power sharing stability, an adaptive decentralized droop controller of paralleled inverter-based DG units is presented in this paper. The proposed power sharing strategy is based on the static droop characteristics combined with an adaptive transient droop function. Unlike conventional droop controllers, which yield 1-DOF tunable controller, the proposed droop controller yields 2-DOF tunable controller. Subsequently, the dynamic performance of the power sharing mechanism can be adjusted, without affecting the static droop gain, to damp the oscillatory modes of the power sharing controller. To account for the power modes immigration at different loading conditions, the transient droop gains are adaptively scheduled via small-signal analysis of the power sharing mechanism along the loading trajectory of each DG unit to yield the desired transient and steady-state response. The gain adaptation scheme utilizes the filtered active and reactive powers as indices; therefore, a stable and smooth power injection performance can be obtained at different loading conditions. The adaptive nature of the proposed controller ensures active damping of power oscillations at different operating conditions, and yields a stable and robust performance of the paralleled inverter system.
Environmental concerns and fuel cost uncertainties associated with the use of conventional energy sources have resulted in rapid growth in the amount of wind energy connected to distribution grids. ...However, based on Ontario's standard offer program (SOP), the utility has the right to curtail (spill) wind energy in order to avoid any violation of the system constraints. This means that any increase in wind energy production over a specific limit might be met with an increase in the wind energy curtailed. In spite of their cost, energy storage systems (ESSs) are considered to be a viable solution to this problem. This paper proposes a methodology for allocating an ESS in a distribution system with a high penetration of wind energy. The ultimate goal is to maximize the benefits for both the DG owner and the utility by sizing the ESS to accommodate all amounts of spilled wind energy and by then allocating it within the system in order to minimize the annual cost of the electricity. In addition, a cost/benefit analysis has been conducted in order to verify the feasibility of installing an ESS from the perspective of both the utility and the DG owner.
This paper presents a summary of Demand Response (DR) in deregulated electricity markets. The definition and the classification of DR as well as potential benefits and associated cost components are ...presented. In addition, the most common indices used for DR measurement and evaluation are highlighted, and some utilities’ experiences with different demand response programs are discussed. Finally, the effect of demand response in electricity prices is highlighted using a simulated case study.
Keen interest in the development and utilization of renewable distributed generation (DG) has been currently observed worldwide. The reliability impact of this highly variable energy source is an ...important aspect that needs to be assessed as renewable power penetration becomes increasingly significant. Distribution system adequacy assessment including wind-based and solar DG units during different modes of operation is described in this paper. Monte Carlo simulation (MCS) and analytical technique are used in this work with a novel utilization of the clearness index probability density function (pdf) to model the solar irradiance using MCS. The results show that there is no significant difference between the outcomes of the two proposed techniques; however, MCS requires much longer computational time. The effect of islanding appears in the improvement of the loss of load expectation (LOLE) and loss of energy expectation (LOEE).
This paper proposes a multi-year multi-objective planning algorithm for enabling distribution networks to accommodate high penetrations of plug-in electric vehicles (PEVs) in conjunction with ...renewable distributed generation (DG). The proposed algorithm includes consideration of uncertainties and will help local distribution companies (LDC) better assess the expected impacts of PEVs on their networks and on proposed renewable DG connections. The goal of the proposed algorithm is to minimize greenhouse gas emissions and system costs during the planning horizon. An approach based on a non-dominated sorting genetic algorithm (NDSGA) is utilized to solve the planning problem of determining the optimal level of PEV penetration as well as the location, size, and year of installation of renewable DG units. The planning problem is defined in terms of multi-objective mixed integer nonlinear programming. The outcomes of the planning problem represent the Pareto frontier, which describes the optimal system solutions, from which the LDC can choose the system operating point, based on its preferences.
Recent development in small renewable/clean generation technologies such as wind turbines, photovoltaic, fuel cells, microturbines and so on, has drawn distribution utilities' attention to possible ...changes in the distribution system infrastructure and policy by deploying distributed generation (DG) in distribution systems. In this study, a methodology has been proposed for optimally allocating wind-based DG units in the distribution system so as to minimise annual energy loss. The methodology is based on generating a probabilistic generation-load model that combines all possible operating conditions of the wind-based DG units and load levels with their probabilities, hence accommodating this model in a deterministic planning problem. The planning problem is formulated as mixed integer non-linear programming, with an objective function for the system's annual energy losses minimise. The constraints include voltage limits at different buses (slack and load buses) of the system, feeder capacity, discrete size of the DG units, maximum investment on each bus, and maximum penetration limit of DG units.
Although integrating a large amount of wind power is technically possible, higher integration costs might be incurred when the penetration level of this intermittent power increases. This paper ...reviews wind power variability and its different impacts on power systems. In addition, an up-to-date overview of wind power balancing costs is presented.
Keen interest in the development and utilization of wind-based distributed generation (DG) has been currently observed worldwide. The reliability impact of this highly variable energy source is an ...important aspect that needs to be assessed as wind power penetration becomes increasingly significant. Distribution system adequacy assessment including wind-based DG units during different modes of operation is described in this paper. Monte Carlo simulation (MCS) and analytical technique are used in this work with a new implementation of the islanding mode of operation in the assessment. The results show that there is no significant difference between the outcomes of the two proposed techniques; however, MCS requires much longer computational time. Moreover, the effect of islanding appears in the improvement of the loss of load expectation (LOLE) and loss of energy expectation (LOEE).
•Techno-economic viability of distributed and centralized electrolysis-based hydrogen generation and storage systems (eHGSS) is assessed.•eHGSSs are operated to meet hydrogen demand and participate ...to the provision of multiple ancillary services to the grid.•Slack variables, penalty terms, and soft constraints are utilized for the management of ancillary services contribution.•Both the distributed and centralized eHGSSs offer maximum financial benefit when operated for multiple ancillary services concurrently.•Participation to the ancillary service market does not significantly increase the grid losses in both systems.
The interest in producing hydrogen from electricity has been recently identified as a potential means for large-scale energy storage, proliferation of hydrogen mobility, and decarbonization of several processes that require hydrogen. Such interest is growing due to the increase of the renewable energy penetration levels and the significant drop in their costs. The rollout of hydrogen-based applications increases the global demand for hydrogen and thus necessitates the deployment of reliable and cost-effective hydrogen infrastructure, i.e., generation, storage, and delivery. Based on its application, hydrogen fuel could be generated and stored in either distributed onsite or centralized offsite compositions. Yet, the operation of both distributed and centralized electrolysis-based hydrogen generation and storage systems (eHGSS) needs to be optimally managed not only to supply the hydrogen demand but also to provide appropriate services to improve the flexibility of power grids. To that end, this paper aims to develop a unified formulation for the optimal operation management of distributed and centralized eHGSS. The objective of the developed formulation is to maximize the net revenue of eHGSS via sale of the produced hydrogen and participation in the provision of multiple grid’s ancillary services. The developed optimization model is utilized to conduct qualitative techno-economic analysis for the two composition forms of eHGSS, i.e., centralized and distributed. The applications of the two arrangements under various operating scenarios including sole services to the hydrogen market and concurrent ancillary services provision to an electricity market are numerically investigated. These studies are significantly valuable to private investors and grid operators that would like to assess the techno-economic variability of distributed and centralized eHGSS. The superiority of the proposed operation management model has been substantiated with numerical investigation, discussions, and analysis.
