Economic Operation Of Microgrid Research Articles

Cooperative Hierarchical Control of Isolated Microgrids Considering Energy Storage System Aggregation

The integration of numerous energy storage systems (ESSs) improves the reliable and economic operation of microgrids but also enlarges the burden of control and communication systems. This paper proposes a cooperative hierarchical control for isolated microgrids with ESSs, which fully frees from the centralized paradigm and is therefore superior in flexibility and scalability. Firstly, the ESS cooperative control based on the distributed frequency controller is introduced for the state of charge (SoC) balance and the frequency regulation. Then, the ESS aggregation is considered. The aggregated ESS model is established and the real-time model parameters are derived by proposed distributed state observers. Finally, energy management is employed to allocate the output power between generators and the aggregated ESS. A detailed theoretical analysis of the dynamic and steady-state performance of proposed controllers and observers is provided. Simulations on the IEEE 33-bus and the 69-bus system verify the effectiveness of proposed methods.

Privacy-reserved economic dispatch of micro-grid considering flexible regulation of air-conditioning load

An economic dispatch model of Micro-grids (MGs) considering flexible regulation demand response of central air-conditioning load is proposed in this paper. In the modeling of air-conditioning load interaction, the operation characteristics of air conditioning load and user's energy satisfaction requirements are considered in this paper. Moreover, to protect user’s information privacy, a distributed solution strategy based on alternating direction method of multipliers with self-adaptive parameters (ADMM-SAP) is presented to achieve a distributed solution of MGs scheduling sub-problem and air-conditioning load scheduling sub-problem. Case studies demonstrate that the proposed model can achieve a better economic operation of MGs without violating central air-conditioning user’s energy satisfaction, which can reduce total operation costs by 4.2%. And the ADMM-SAP based distribution solution strategy can achieve a distributed solution of two sub-problems without knowing the global information, which behaves a better convergence performance than standard ADMM.

Applying a Theta-Krill Herd Algorithm to Energy Management of a Microgrid Considering Renewable Energies and Varying Weather Conditions

Abstract Recently, researchers have shown an increased interest in using renewable-based distributed generations (DGs) in microgrids (MGs). Therefore, the economic operation of MGs plays a vital role in reducing total daily costs and greenhouse gas emissions in the modern power system. This study presents a day-ahead optimization management for a grid-tied MG supplied by small-scale renewable energy sources (RESs) like photovoltaic (PV) systems. The major aim of the suggested optimal energy management system is to minimize the cost of RERs and storage facilities in the MG for power generation while satisfying technical constraints. In addition, an improved mathematical model is suggested for the PV power generation using real data for four dissimilar days. To attain accurate results, uncertainties in the generations, load demand, and market price are probabilistically modeled. To handle the optimization problem, the θ-modified krill herd (θ-MKH) algorithm is used. The suggested algorithm for solving the optimization problem is investigated on numerical examples with different RESs and storages in the MG and compared with conventional approaches. The results attained illustrate that the recommended algorithm can utilize the cheapest sources while covering technical constraints.

Multi-objective Planning of the Economic Operation of Microgrid Considering the Energy Loss and the Start-up Cost of Conventional Units

The fluctuation of load and new energy will have an important impact on the operation mode of microgrid. In order to balance the economy and reliability of microgrid, a chance constrained model of microgrid is established firstly. Based on the reliability cost, the operation cost of microgrid under different confidence levels is calculated, and a reasonable confidence level of rotating reserve is obtained. This paper analyzes the impact of energy storage charge and discharge loss and conventional unit start-up cost on the economic operation of the isolated micro grid; for the grid connected micro grid, the economy of its own operation and the effect of auxiliary large grid peak load shedding are taken as the objective function, and the multi-objective programming method proposed in this paper is used to solve the problem. The example analysis shows that the multi-objective programming method in this paper, by combining with particle swarm optimization algorithm, can optimize the weight of different objectives reasonably, which can not only help the large power grid to cut peak and fill valley, but also realize the economy of microgrid operation.

A two-stage two-layer optimization approach for economic operation of a microgrid under a planned outage

Microgrids (MGs) are a promising and viable solution for sustainable cities and community development. However, it is challenging to achieve the economic operation of MGs due to the uncertainties of generation, load demand, and outage occurrence. Consequently, this paper proposes a novel two-stage two-layer optimization approach to minimize the total operation cost of an MG under a high dimension of uncertainties of generation, load demand, and planned outages. In the upper layer, the binary chance-constrained (CC) for outage planning under the n-1 criterion is developed considering the outage uncertainty. Then, the CC for optimal day-ahead scheduling is introduced to deal with the uncertainties of generation and load demand. Since the prediction error means are not perfectly known, we propose an efficient second order cone formulation via the distributionally robust optimization method to solve the MG economic operation problem. The lower layer performs real-time optimization to compensate for the power deviation and determines a fair benefit sharing for the use of the external devices. To validate the proposed approach, we conducted simulations with different uncertainty levels and outage scenarios. The simulation results illustrate the effectiveness of the proposed approach, resulting in a remarkable operational cost reduction.

Real-time dispatch strategy of microgrid based on fuzzy control of energy storage

Microgrid (MG) is effective to absorb the distributed renewable energy source (RES). Considering the uncertainty of RES and load, this paper proposes a fuzzy rule of energy storage system (ESS) and gets its output by anti-fuzzification in the real-time dispatch stage after receiving the actual load and RES value. Based on the envelope principle and fuzzy control, a grid-connected MG scheduling model is established. Considering the ultra-short-term forecasted data at the beginning of an hour, a receding-horizon scheduling model which includes the constraints of ladder price, ESS, RES, etc. and aims at the lowest operating cost, is established to correct the day-ahead scheduling error as the basic value of real-time scheduling at subsequent times. Taking a MG in Shaanxi Province as an example, the proposed strategy ensures the rapid and economic operation of MG.

Optimal Energy Management of a Microgrid Incorporating a Novel Efficient Demand Response and Battery Storage System

In this paper, optimal economic management of a grid-connected microgrid (MG) with distributed energy resource (DER) and its interaction with incentive-based demand response programs (DRPs) is studied. The use of DR makes energy management system (EMS) of the MG an efficient tool in balancing the demand and supply, and therefore ensuring the network reliability. In this work, the cost function of customers is developed in the incentive-based DRP with the aim of receiving a more realistic incentive and then it is combined with EMS. Accordingly, the consumers offer hourly power reduction bids based on which they are sorted and then incentive-based payment model is implemented. At times, due to full utilization of grid and MG resources, the supply–demand balance cannot be maintained by respecting the consumer offers. Specific energy policies and contracts are required in this case for mandatory power curtailment in exchange for higher incentive payments by MG operator (MGO). The objective function attempts to minimize operation costs of the MG units such as Diesel Generator fuels costs, cost of power exchange with the main grid, battery energy storage system (BESS) costs and in the mean time, maximize MGO DR benefit. On the other hand, simultaneous EMS and DR management leads to a complex non-linear problem, which can be solved using whale optimization algorithm (WOA) in MATLAB software. To assess the performance of the proposed new approach, a grid-connected MG with DERs and reducible power of consumers is studied within a 24-h time cycle. Also, to verify the scalability of the implemented system, an MG with aggregators and a large scale battery is considered. Simulation results show that incorporating a developed DR into EMS is an efficient way in optimal performance of both demand and supply sides in conjunction with the goals of economic operation of MGs.

Multi-Objective Optimization Scheduling Considering the Operation Performance of Islanded Microgrid

In recent years, with the increase of distributed generation (DG) penetration rate, the economic operation of microgrid (MG) has been fully developed, but the energy consumption system based on fossil energy has increased the contradiction of the economy, energy and environment. The process of accelerating the development and utilization of renewable energy are a new focus of social concern. This paper first analyzes the basic characteristics and related policies of the distributed power and demand response (DR) in MG, and introduces the evaluation index of the islanded microgrid. Then, established a multi-objective optimization scheduling model considering the operation performance of islanded microgrid. In model, considered the generation cost of microsources, environmental management cost and power supply reliability of MG, and selected different scene analysis and verification. Used the improved particle swarm optimization-exterior point method (IPSO-EPM) to solve the problem. When the constraint condition is included in the objective function, the problem of falling into the local extremum during planning is avoided as much as possible. Finally, an islanded microgrid is taken as an example to verify the rationality of the proposed model and the effectiveness of the algorithm.

Day-Ahead Optimization Scheduling for Islanded Microgrid Considering Units Frequency Regulation Characteristics and Demand Response

With the increase of distributed generation penetration, the economic operation of microgrid has been fully developed. For islanded microgrid, due to the lack of large grid support and the limited capacity of the distributed generation (DG), the energy supply of microgrid may not meet the need of users in real time. Therefore, it is of great significance to solve the problem of insufficient power supply of islanded microgrid and improve the economy of its operation. Firstly, this paper analyses the frequency characteristics of DG, and establishes power models oriented to the frequency regulation characteristics of microgrid and introduces the mathematical model of DG. Then, an islanded microgrid day-ahead optimization scheduling model considering frequency regulation characteristics of units and demand response (DR) is proposed. The frequency characteristics of controllable units and DR are considered in the model, and different strategies are selected to analyze their impact on microgrid economy. The example shows that the optimization scheduling model of microgrid established in this paper can reduce the power supply pressure during peak load periods, alleviate the problem of insufficient power supply, and effectively improve the overall benefit of microgrid, which verifies the rationality of the model.

Simulation of Composite Energy Storage Optimization Configuration of Micro-grid Based on PSO

The micro-grid studied in this paper contains photovoltaic power generation, wind power generation and energy storage devices composed of super capacitors and storage batteries. Although this method of composite energy storage can effectively utilize new energy sources, the cost is relatively expensive. So, under the condition of normal load and overall normal operation, combined with power balance and other constraints, how to allocate capacity configuration can minimize the overall operating cost of the micro-grid, and improving the economics of micro-grid operation becomes a key issue. In this paper, for the micro-grid with island operation mode, using Matlab to build distributed power model and micro-grid model in micro-grid, aiming at the economical operation of micro-grid, using the basic particle swarm optimization algorithm to obtain the optimal solution, the grid is optimized for configuration and combined with an example for simulation analysis.

Consensus-based economic hierarchical control strategy for islanded MG considering communication path reconstruction

In the islanded microgrid (MG), to improve the control effect of the output voltages of DERs and keep the economical operation of MG, a consensus-based economic hierarchical control strategy is proposed in this paper. The corresponding control structure is divided into physical and cyber layers, where the cyber layer is mainly composed by communicators. In these two layers, there are two main designs: the consensus-based primary control (CBPC) method and the secondary control (CBSC) method. In CBPC: Firstly, the undirected communication path among communicators is designed by path planning. Then, based on the constructed path, an economic P–U droop control method considering with line loss and flexible load is realized by using consensus control. In CBSC: Firstly, a cyber-physical vulnerability assessment method is designed. Based on this method, the DER with the lowest vulnerability is selected to be connected with the “virtual leader”. And when the data transmission behavior of the undirected communication path is selected, the undirected network can be transferred as a directed network. Thus, it can make the virtual leader-following consensus control (VLFCC) and the secondary control on voltage accomplished. Finally, the simulation results show the effectiveness of the proposed strategy.

Stability Constrained Economic Operation of Islanded Droop-Controlled DC Microgrids

This paper proposes a method to determine optimal droop values of dispatchable distributed generation (DG) units in an islanded droop-controlled dc microgrid. Objectives are to minimize fuel cost and maximize small signal stability of the system. In this paper, a detailed state-space model of an islanded droop-controlled dc microgrid including the converter, network parameters, and network interconnection is developed. The developed model is then used to obtain the dominant eigen value of the system. Particle swarm optimization is used to determine the optimal droop values of the dispatchable DG units in order to simultaneously reduce the fuel cost, increase system damping, and push the most dominant eigen value away from the imaginary axis to the left of the s -plane. The bi-objective optimization is solved using a fuzzy max–min based approach. The proposed method is validated on a sample three-bus droop-controlled DCMG test system. Comparison of the result obtained by the fuzzy max–min approach with that of controlled elitist genetic algorithm is also presented in this paper.

Active and Reactive Power Joint Optimization Dispatch of islanded Microgrid Based on SCCSA Algorithm

Based on the requirements of the economic reliability of the operation of islanded micro grid, a joint optimal dispatch model of the active power and reactive power of the islanded micro grid is proposed in this paper, which considers the constraints of upper and lower limits of output force and power balance of each micro source. In order to minimize the cost of operation and the penalty cost of voltage deviation of each node, an improvement is made on the basis of the original crow search algorithm, and combined with the advantages of the sine cosine algorithm, the improved sine cosine crow search algorithm is used to solve the model and the results of the active reactive power output of the island are obtained. The simulation results show that the proposed method can effectively control the voltage of each node in the micro grid within the allowable range, and is more beneficial to the economic operation of micro grid.

A Multi-Agent-Based Optimization Model for Microgrid Operation Using Dynamic Guiding Chaotic Search Particle Swarm Optimization

The optimal operation of microgrids is a comprehensive and complex energy utilization and management problem. In order to guarantee the efficient and economic operation of microgrids, a three-layer multi-agent system including distributed management system agent, microgrid central control agent and microgrid control element agent is proposed considering energy storage units and demand response. Then, based on this multi-agent system and with the objective of cost minimization, an operation optimization model for microgrids is constructed from three aspects: operation cost, environmental impact and security. To solve this model, dynamic guiding chaotic search particle swarm optimization is adopted and three scenarios including basic scenario, energy storage participation and demand response participation are simulated and analyzed. The results show that both energy storage unit and demand response can effectively reduce the cost of microgrid, improve the operation and management level and ensure the safety and stability of power supply and utilization.

Techno-economic and business case assessment of multi-energy microgrids with co-optimization of energy, reserve and reliability services

In this work a new techno-economic framework to model and assess business cases for energy, reserve and novel reliability services provided by Microgrids (MGs) is presented. The framework combines a bespoke Transactive Energy (TE) approach that aims at co-optimizing these potentially conflicting services. In this context, MGs aggregate, coordinate and exploit flexibility from emerging distributed energy resources and multiple energy vectors (e.g., electricity, heat and gas) as a means to partake in different services in response to price signals associated with markets and network needs. For example, MGs can provide reliability services to both the distribution network and their internal customers, owing to their ability to ride through contingencies by operating as islands. Further, MGs could coordinate with the network restoration scheme to reconnect to the network after a contingency occurs, and use their spare generation capacity to restore ‘blocks’ of other affected customers outside the MG. This novel application for MGs to improve network reliability has not yet been quantified from an economic perspective, especially in a TE context where conflicts with other services may arise. In this regard, it is clear that energy, reserve and reliability services may be economically attractive under specific conditions when assessed in isolation. However, their business case is still unclear in a pragmatic context where the provision of given services affects the economic operation of MGs, and may keep them from partaking in other services. On the above premises, this paper proposes a framework that combines a bespoke Mixed Integer Linear Programming (MILP) model for the operation of MGs, and a stochastic approach for simulating nonlinear and dynamic reliability price signals in light of MG reliability contributions assessed through Monte Carlo simulation. The framework is demonstrated on case studies based on pragmatic energy information, a real UK distribution network, sets of price signals for co-optimization of different services, and multi-energy MGs designed with Combined Heat and Power (CHP) units, Photovoltaic (PV) panels, Gas Boilers (GBs). Thermal Energy Storage (TES) and/or Battery Energy Storage (BES). The results demonstrate that, even though the operation schedule of devices within aMG can change based on the different technologies and price signals under consideration, the services are largely synergistic. This is a key finding, as it demonstrates that, for example, even without price signals from a reliability service the MG will have significant spare export capacity which, if accessible to the DNO, can improve the reliability of customers outside the MG.

A Novel Decentralized Economic Operation in Islanded AC Microgrids

Droop schemes are usually applied to the control of distributed generators (DGs) in microgrids (MGs) to realize proportional power sharing. The objective might, however, not suit MGs well for economic reasons. Addressing that issue, this paper proposes an alternative droop scheme for reducing the total active generation costs (TAGC). Optimal economic operation, DGs’ capacity limitations and system stability are fully considered basing on DGs’ generation costs. The proposed scheme utilizes the frequency as a carrier to realize the decentralized economic operation of MGs without communication links. Moreover, a fitting method is applied to balance DGs’ synchronous operation and economy. The effectiveness and performance of the proposed scheme are verified through simulations and experiments.

Droop control strategy of the AC/DC hybrid micro‐grid based on quasi‐PR control

With the developments of renewable energies and integrations of new loads into distribution system, the hybrid of AC and DC has been becoming the typical existing form of the micro-grid. Studying on the droop control strategy will be very important for improving the safe and economic operation of micro-grid. Therefore, this study aims at thoroughly analysing a novel droop control strategy of the hybrid AC/DC micro-grid. First of all, the analysis model of the hybrid AC/DC micro-grid is built by connecting the traditional AC and DC micro-grid. Next, the typical droop control strategy of AC and DC micro-grid is introduced, respectively. Then, the voltage outer loop of quasi-proportional resonance (PR) control strategy and its optimal parameters are presented based on the analysis of the voltage–current double-loop control strategy. Finally, the simulation model of AC/DC micro-grid in Matlab/Simulink is utilised to compare the performances of the Proportional Integral (PI) and quasi-PR droop control strategies. The results show that the proposed quasi-PR has better performances in control accuracy and harmonic suppression.

Selecting a Meta-Heuristic Technique for Smart Micro-Grid Optimization Problem: A Comprehensive Analysis

In current epoch, the economic operation of micro-grid under soaring renewable energy integration has become a major concern in the smart grid environment. There are several meta-heuristic optimization techniques available under different categories in literature. One of the most difficult tasks in cost minimization of micro-grid is to select the best suitable optimization technique. To resolve the problem of selecting a suitable optimization technique, a rigorous review of six meta-heuristic algorithms (Whale Optimization, Fire Fly, Particle Swarm Optimization, Differential Evaluation, Genetic Algorithm, and Teaching Learning-based Optimization) selected from three categories (Swarm Intelligence, Evolutionary Algorithms, and Teaching Learning) is conducted. It presents, a comparative analysis using different performance indicators for standard benchmark functions and proposed a smart micro-grid (SMG) operation cost minimization problem. A proposed SMG is modeled which incorporates utility connected power resources, e.g., wind turbine, photovoltaic, fuel cell, micro-turbine, battery storage, electric vehicle technology, and diesel power generator. The proposed work will help researchers and engineers to select an appropriate optimization method to solve micro-grid optimization problems with constraints. This paper concludes with a detailed review of micro-grid operation cost minimization techniques based on an exhaustive survey and implementation.

Energy management strategy for microgrids including heat pump air‐conditioning and hybrid energy storage systems

The stable and economic operation of microgrids always requires the participation of hybrid energy storage systems (HESSs). In order to reduce the capacity and investment cost of HESSs, the application of heat pump air-conditioning systems (HPACSs) is a feasible solution to the problem. This study proposes a microgrid energy management strategy based on the coordination of HPACSs and HESSs. The strategy is devised to regulate the peak-valley loads on demand side and to smooth the power fluctuation of renewable energy sources in the microgrids. Peak-valley load difference is reduced through the heat capacity model of HPACS and battery energy storage system. Power fluctuation is allocated between HPACS and HESS by using fuzzy control theory. A simulation of a microgrid including HPACS and HESS demonstrates the effectiveness of the proposed strategy.

考虑可控负荷停电成本的微电网经济调度策略

微电网中的负荷具有灵活而易于控制管理的特点。将负荷积极参与到微电网调度计划中，可以有效提高微电网运行的经济性。本文根据影响可控负荷停电成本的各要素，建立可控负荷停电成本模型，并将其与常见的微电网调度模型结合，制定了多时间尺度下的考虑可控负荷停电成本的微电网经济调度方案，有效地将可控负荷参与到微电网经济调度中。通过对其进行仿真分析，验证了该方法的合理性和有效性。 The loads in microgrid are flexible and easy to control. The economical operation of microgrid would become more economic by loads actively participating in. A cost model of controllable load was built based on factors affecting the outage costs. Combining it and the traditional microgrid operating model, a multi-time scale microgrid operating model was constructed, engaging controllable loads in the operation effectively. By simulation analysis, the rationality and validity of the model were proved.