Operation Of Standalone Microgrids Research Articles

Optimal Operation of Stand-Alone Microgrid Considering Emission Issues and Demand Response Program Using Whale Optimization Algorithm

Microgrids are new technologies for integrating renewable energies into power systems. Optimal operation of renewable energy sources in standalone micro-grids is an intensive task due to the continuous variation of their output powers and intermittant nature. This work addresses the optimum operation of an independent microgrid considering the demand response program (DRP). An energy management model with two different scenarios has been proposed to minimize the costs of operation and emissions. Interruptible/curtailable loads are considered in DRPs. Besides, due to the growing concern of the developing efficient optimization methods and algorithms in line with the increasing needs of microgrids, the focus of this study is on using the whale meta-heuristic algorithm for operation management of microgrids. The findings indicate that the whale optimization algorithm outperforms the other known algorithms such as imperialist competitive and genetic algorithms, as well as particle swarm optimization. Furthermore, the results show that the use of DRPS has a significant impact on the costs of operation and emissions.

Peer‐to‐peer load allocation using potential field concept for optimal operation of standalone microgrids

The operation of a standalone microgrid is often optimised by the central controller that decides the set-points of the local controllers of the distributed generators. However, the optimised set-points may not remain optimal for a longer period due to the variability of loads and renewable generations. This study proposes a technique for readjusting the dispatch of the suitable generation units, between the optimisations carried out by the central controller, to support load changes. To this end, the potential field concept has been suggested to be adopted by the loads to select the appropriate generation units. The decision is made based on different criteria, such as their cost, reliability, emission, and power loss. This process requires low computational efforts, and thus, can act and make decisions immediately. This is valid as far as the change in the loads is not substantial. For a change above a predetermined level, the microgrid's central controller steps in to optimise the system. The central controller also performs the regular optimisation periodically to retune the whole system and reconfirm the optimal operation. The performance of the proposal has been evaluated by numerical analysis and validates the success and efficacy of the proposal.

Impact of scaled fitness functions on a floating‐point genetic algorithm to optimise the operation of standalone microgrids

Standalone hybrid remote area power systems, also known as microgrids (MGs), can provide reasonably priced electricity in geographically isolated and the edge of grid locations for their operators. To achieve the reliable operation of MGs, whilst consuming minimal fossil fuels and maximising the penetration of renewables, the voltage and frequency should be maintained within acceptable limits. This can be accomplished by solving an optimisation problem. Floating-point genetic algorithm (FP-GA) is a heuristic technique that has a proven track record of effectively identifying the optimal solutions. However, in addition to needing appropriate operators, the solver needs a fitness function to yield the most optimal control variables. In this study, a suitable fitness function is formulated, by including the operational, interruption and technical costs, which are then solved with an FP-GA, with different combinations of operators. The developed fitness function and the considered operators are tested for the non-linear optimisation problem of a 38-bus MG. Detailed discussions are provided on the impact, which different operators have upon the outcomes of the fitness function.

Mitigation of harmonics and unbalanced source voltage condition in standalone microgrid: positive sequence component and dynamic phasor based compensator with real-time approach

Penetration of Distributed Energy Resources (DER) is in high demand to supply power to the load where the grid is not available. Many of these sources are a single phase source used to form standalone Microgrid (MG). Single phase connectivity of these sources results in an unbalanced source voltage condition (UbSVC). Interfacing power electronic devices also inject the harmonics into Point of Common Coupling (PCC) voltage. The effect of this unbalance and harmonics on the operation of standalone MG is analysed in this paper in a twofold manner. One at a reduced power transfer from DER to load and the other is an error produced in Phase Locked Loop (PLL) operation. Positive Sequence Component (PSC) based and Dynamic Phasor (DP) based compensation techniques are proposed in this paper to mitigate the effect of UbSVC. Simulation validates that both the proposed methods are capable to provide balanced load voltage condition under UbSVC in terms of Voltage Unbalance Factor (VUbF). It also enhances the power transferred from DER to load during an UbSVC. The performance of the proposed compensator during UbSVC and harmonic presence is validated in real-time simulation using Opal-RT and dSPACE simulators.

Operation of Stand-Alone Microgrids Considering the Load Following of Biomass Power Plants and the Power Curtailment Control Optimization of Wind Turbines

Various stand-alone hybrid power systems are widely used to fulfil the electric loads for remote, rural villages. Although there are many investigations based on various aspects of renewable hybrids energy microgrids, the discussions about the application of biomass combustion power plants are rare. Also, detailed investigations of the system steady and transient stability analysis, and the power curtailment control optimization of wind turbines in these stand-alone hybrid systems are seldom found. This paper focuses on wind/biomass/diesel/battery stand-alone microgrids and discusses the system operation, energy management and dispatch issues detailed. The renewable and controllable biomass power is localized to follow the load fluctuations over a long timescale to decrease the power production from diesel and the peak-load shifting demands of the battery banks. An optimization strategy of the wind power curtailment control is also proposed to effectively decrease the frequency and amplitude of the pitch actor and, to some extent, improve the power generation through the combination of the active turbine speed control and pitch regulation. Then a parallel double-mode optimal operation strategy with a “fault detector” is presented to realize economic optimization dispatch under the normal mode and emergency power control for large disturbance scenarios. Finally, case studies of a microgrid on a remote Canadian aboriginal community are conducted to demonstrate the performance of the proposed methods.

Survey based characterisation of energy services for improved design and operation of standalone microgrids

Microgrids for rural electrification are expected to play a key role in achieving global energy access goals. However, the high cost of stand-alone microgrids intended to serve generally poor communities remains a key barrier to their deployment, while design and operation is challenging, given generally low diversity of loads and generators, and often high penetrations of variable renewable generation.Current practices for providing electricity access still often focus on the supply side with an emphasis on ensuring the reliability, affordability and security of electricity supply to meet user demand. This supply focus misses some key opportunities on the demand-side for providing low cost and reliable energy service delivery. In particular, rural communities may place very different relative values on various energy services, while there may be considerable flexibility in terms of when some of these energy services are delivered; due to inherent energy storage in the end-use equipment, or user willingness to shift the energy service itself.This paper presents a novel characterisation framework for energy services based on their relative flexibility and consumer prioritisation. Detailed survey data from 154 households across five microgrid sites in Nepal is used to test this framework, and assess the potential insights that it can provide for microgrid designers and operators seeking to reduce costs and improve reliability when serving poor rural communities. The five microgrids represent very different energy services and microgrid technology contexts, yet all would appear to have demand-side management opportunities that can trade-off cost and reliability and prioritise loads according to user preferences.

An Improved Multi-Timescale Coordinated Control Strategy for Stand-Alone Microgrid with Hybrid Energy Storage System

A scientific and effective coordinated control strategy is crucial to the safe and economic operation of a microgrid (MG). With the continuous improvement of the renewable energy source (RES) penetration rate in MG, the randomness and intermittency of its output lead to the increasing regulation pressure of the conventional controllable units, the increase of the operating risk of MG and the difficulty in improving the operational economy. To solve the mentioned problems and take advantage of hybrid energy storage system (HESS), this study proposes a multi-time scale coordinated control scheme of “day-ahead optimization (DAO) + intraday rolling (IDR) + quasi-real-time correction (QRTC) + real-time coordinated control (RTCC).” Considering the shortcomings of existing low prediction accuracy of distributed RES and loads, the soft constraints such as unit commitment scheduling errors and load switching scheduling errors are introduced in the intraday rolling model, allowing the correction of day-ahead unit commitment and load switching schedule. In the quasi-real-time coordinated control, an integrated criterion is introduced to decide the adjustment priority of the distributed generations. In the real-time coordinated control, the HESS adopts an improved first order low pass filtering algorithm to adaptively compensate the second-level unbalanced power. Compared with the traditional coordinated control strategy, the proposed improved model has the advantages of good robustness and fast solving speed and provides some guidance for the intelligent solution for stable and economic operation of stand-alone MG with HESS.

Improved Particle Swarm Algorithm in the Optimal Capacity Configuration of Micro-grid System

The characteristics of random fluctuation and uncontrollable solar illumination, in addition, the matching and coordination between power supply and load in micro grid is more complex in the off-grid type optical photovoltaic/storage/diesel micro grid system. Therefore, solving the problem of energy matching between the two is the primary condition for preserving stability operation of standalone microgrid. In this paper, the mathematical model of various power supply in independent photovoltaic/storage/diesel microgrid system is established, and the system's equivalent annual cost is the minimum economic optimization objective function. Using the simulated annealing (SA) improved particle swarm algorithm (PSO) to obtain the optimal configuration result of microgrid. Verify the SAPSO has the characteristics of global optimization ability.

에너지 자립섬 EMS 어플리케이션의 기능적 특성

For many past years, research in the operation of stand-alone Microgrid, which provides electric power generated from renewable energy sources and energy storage system instead of diesel generators, has been a major issue in order to prepare the exhaustion of fossil fuel and to protect environment, in island grids. Samso Island, known as the world's first stand-alone Microgrid in Denmark, is connected to the mainland grid through AC system, which has different technical conditions with Korea's isolated power system. Korea's first stand-alone Microgrid has been built in Ga-sa island, Chun-la-nam-do, based on Energy Management System (EMS) operation, and other islands are under construction to follow the next step. These stand-alone Microgrid's has large capacity of Battery Energy Storage System (BESS) and the proportion of the renewable energy sources are large, which makes it necessary to use a Microgrid-Energy Management System (MG-EMS) to operate the grid effectively and economically. However, since the main subject of MG-EMS is different from EMS, specific characteristics and functions must be different as well. In this paper, the necessary characteristics and functions are explained for a general MG-EMS compared to a large power system EMS.