Provisional Microgrid Research Articles

Belbic frequency control of provisional microgrid with hybrid AC/DC microgrid and renewable energy sources

Nowadays, intelligent control methods play an important role in the advancement of technology and the human movement towards further evolution. The development of new frameworks for power generation and distribution systems by designing a microgrid structure with economic capabilities is one of these areas of progress. Therefore, this paper introduces a new practical method for controlling the frequency of provisional microgrid and is able to cover the following issues at the same time including (1) It considers the nonlinear model of provisional microgrid which has a hybrid structure (AC and DC) in addition to renewable energy sources; (2) Introduces a method for microgrid frequency control under different operational conditions that performs based on the brain emotional learning; (3) Ensures the operation and applicability of the control method for the provisional microgrid through implementation of FPGA for the first time; (4) Confirms the robustness of the proposed method under severe load changes and generation from renewable sources. So, the effects of wind turbines and solar energy are considered in the simulation scenario and under the influence of various changes in load and system uncertainties, the robustness and efficiency of the proposed method are well demonstrated.

Provisional Microgrid Frequency Regulation by Brain Emotional Learning Based Intelligent Controller and Implementation Through FPGA

With the advancement of technology and human movement towards evolution, intelligent control methods are becoming more important. One of the areas of progress is related to the development of new frameworks for electricity generation and distribution systems, and the microgrid structure with economic capabilities is one of the frameworks. Accordingly, this paper presents a new practical method for controlling the frequency of microgrids and is able to cover the following issues at the same time. 1- It considers the nonlinear model of provisional microgrid which has a hybrid structure (AC and DC) in addition to renewable energy sources. 2- Introduces a method for microgrid frequency control under different operational conditions that performs based on the brain emotional learning. 3- Ensures the operation and applicability of the control method for the provisional microgrid through implementation of FPGA for the first time 4- Confirms the robustness of the proposed method under extreme load changes. So, in the simulation scenarios, the effects of wind turbine and solar energy are considered and under the influence of various changes in load and system uncertainties, the robustness and efficiency of the proposed method are well demonstrated.

A novel control scheme for load current components sharing improvement, and unbalanced and harmonic voltage compensation, in islanded provisional-microgrids

Microgrids (MGs) are the building blocks of future smart distribution grids, bringing several benefits to both utilities and consumers. In recent years a new class of MGs has been introduced, called provisional-microgrid (P-MG), consisting of master-MG and slave-MG. Slave-MG cannot operate isolated from master-MG. However, power quality is of the major challenges in MG investigations. In this study, a novel hierarchical and distributed control scheme is proposed for the improvement of unbalanced and harmonic load current components sharing among the distributed generation (DG) units as well as voltage quality (VQ) enhancement of sensitive load bus (SLB) in provisional-microgrid. Compared to the previous works, the proposed control strategy takes the instantaneous free capacity of DGs and multi-voltage-quality level (MVQL) indices of different buses into account for both load current sharing and voltage quality improvement functions. Furthermore, it considers the nature of variable power generation-renewable energy resources (VPG-RERs) and does not need any information about the loads or lines impedances. The efficiency of the proposed control scheme is evaluated by simulation of a typical islanded P-MG under several cases. Simulations are carried out in MATLAB/Simulink environment, and their results demonstrate the appropriate speed and accuracy of the presented method.

Robust Frequency Control of Provisional Microgrid by Using of a Combined Fuzzy Reset Approach

Robust Frequency Control of Provisional Microgrid by Using of a Combined Fuzzy Reset Approach

Microgrid Energy Management during High-Stress Operation

We consider the energy management of an isolated microgrid powered by photovoltaics (PV) and fuel-based generation with limited energy storage. The grid may need to shed load or energy when operating in stressed conditions, such as when nighttime electrical loads occur or if there is little energy storage capacity. An energy management system (EMS) can prevent load and energy shedding during stress conditions while minimizing fuel consumption. This is important when the loads are high priority and fuel is in short supply, such as in disaster relief and military applications. One example is a low-power, provisional microgrid deployed temporarily to service communication loads immediately after an earthquake. Due to changing circumstances, the power grid may be required to service additional loads for which its storage and generation were not originally designed. An EMS that uses forecasted load and generation has the potential to extend the operation, enhancing the relief objectives. Our focus was to explore how using forecasted loads and PV generation impacts energy management strategy performance. A microgrid EMS was developed exploiting PV and load forecasts to meet electrical loads, harvest all available PV, manage storage and minimize fuel consumption. It used a Model Predictive Control (MPC) approach with the instantaneous grid storage state as feedback to compensate for forecasting errors. Four scenarios were simulated, spanning a stressed and unstressed grid operation. The MPC approach was compared to a rule-based EMS that did not use load and PV forecasting. Both algorithms updated the generator’s power setpoint every 15 min, where the grid’s storage was used as a slack asset. While both methods had similar performance under unstressed conditions, the MPC EMS showed gains in storage management and load shedding when the microgrid was stressed. When the initial storage was low, the rule-based EMS could not meet the load requirements and shed 16% of the day’s electrical load. In contrast, the forecast-based EMS managed the load requirements for this scenario without shedding load or energy. The EMS sensitivity to forecast error was also examined by introducing load and PV generation uncertainty. The MPC strategy successfully corrected the errors through storage management. Since weather affects both PV energy generation and many types of electrical loads, this work suggests that weather forecasting advances can improve remote microgrid performance in terms of fuel consumption, load satisfaction, and energy storage requirements.

Hybrid AC/DC Provisional Microgrid Planning Model Considering Converter Aging

Renewable energy deployment through distributed energy resources is among the central goals of future power systems. Microgrids have proven to be an economically viable solution for distributed energy resources’ integration into the power system and benefits customers with uninterrupted power supply. In this context, provisional microgrids have been introduced with the main goal of rapid renewable energy resource deployment. Since a considerable portion of renewable energy resources, as well as residential loads, are DC, and this portion is expected to grow even further, hybrid AC/DC design of provisional microgrids can improve both efficiency and economic benefit through an optimal arrangement of AC/DC feeders and converters. This paper presents a planning model for hybrid provisional microgrids considering the long-term influence of energy storage and the aging process of converters on economic revenues. Due to several intrinsic uncertainties involved in provisional microgrid operation, robust optimization is applied to the problem to ensure optimality under worst-case conditions. Results show the economic benefits of a hybrid provisional microgrid compared to a provisional microgrid and independent microgrid. Several sensitivity analyses are carried out to identify critical factors in planning.

A three‐stage stochastic planning model for enhancing the resilience of distribution systems with microgrid formation strategy

In recent years, severe outages caused by natural disasters such as hurricanes have highlighted the importance of boosting the resilience level of distribution systems. However, due to the uncertain characteristics of natural disasters and loads, there exists a research gap in the selection of optimal planning strategies coupled with provisional microgrid (MG) formation. For this purpose, this study proposes a novel three-stage stochastic planning model considering the planning step and emergency response step. In the first stage, the decisions on line hardening and Distributed Generation (DG) placement are made with the aim of maximising the distribution system resilience. Then, in the second stage, the line outage uncertainty is imposed via the given scenarios to form the provisional MGs based on a master-slave control technique. In addition, the non-anticipativity constraints are presented to guarantee that the MG formation decision is based on the line damage uncertainty. Last, with the realisation of the load demand, the cost of load shedding in each provisional MG is minimised based on a demand-side management program. The proposed method can consider the step-by-step uncertainty realisation that is near to the reality in MG formation strategy. Two standard distribution systems are utilised to validate the correctness and effectiveness of the presented model.

Presentation of an H ∞ based frequency control for islanding provisional microgrid consisting of hybrid AC / DC microgrid

Presentation of an H _∞ based frequency control for islanding provisional microgrid consisting of hybrid <scp>AC</scp> / <scp>DC</scp> microgrid

Robust Line Hardening Strategies for Improving the Resilience of Distribution Systems With Variable Renewable Resources

Line hardening refers to strengthening certain distribution lines that will not be subject to outages during extreme conditions. Line hardening provides a resilient solution in the case of major faults in a radial or meshed distribution system. We propose a robust optimal line hardening method coupled with multiple provisional microgrids to improve the distribution system resilience against worst N-k contingencies. In this case, provisional microgrids, which are interconnected by hardened liens, do not have the islanding capability and depend on the supply provided by one or more electrically connected microgrids for islanding purposes. A trilevel optimal model is considered with the objectives of minimizing the costs of line hardening and the operation of multiple islanded provisional microgrids, which could include the cost of load shedding in each provisional microgrid considering the worst N-k contingencies. Specifically, a two-stage robust optimization model is formulated and Benders decomposition (BD) algorithm coupled with iterative relaxation procedure (IRP) is developed to enable the tractable computation. In our work, the master problem determines line hardening strategies and the subproblem discovers the impact of the worst N-k contingencies corresponding to the optimal operation of reformed provisional microgrids. The second-stage which includes the max–min subproblem is solved efficiently using linearization techniques, duality theory, and IRP. Our numerical results for the IEEE distribution test systems validate the effectiveness of the proposed model and reveal that distributed generation is critical in increasing the resilience of distribution systems corresponding to the worst N-k contingencies in provisional microgrids.

Provisional Microgrid Planning

The optimal planning problem of provisional microgrids, as a new class of microgrids, is investigated in this paper. Unlike traditional microgrids, provisional microgrids do not possess the islanding capability and are dependent on one or more electrically connected microgrids, called coupled microgrids, for islanding purposes. Provisional microgrids can be considered as enablers of rapid integration of renewable energy resources in distribution networks, while at the same time providing economic benefits for local consumers and environmental benefits for the entire system. The provisional microgrid planning problem is defined and formulated in this paper, considering anticipated interactions between the provisional microgrid, the coupled microgrid, and the utility grid during grid-connected and islanded modes. Robust optimization is used to efficiently consider physical and financial uncertainties in the problem. Numerical simulations study a test provisional microgrid for exploring its merits, as well as demonstrating its benefits when compared with deployment of a traditional microgrid.