Development of Robust and Dynamic Control Solutions for Energy Storage Enabled Hybrid AC/DC Microgrids

Development of Robust and Dynamic Control Solutions for Energy Storage Enabled Hybrid AC/DC Microgrid

Hybrid AC/DC Microgrid Mode-Adaptive Controls

The lack of inertial response at microgrids is usually compensated by configuring primary controllers of converter‐interfaced devices to contribute in the transient response under power disturbances. The main purpose of this chapter is to study the modes of operation of primary level techniques of generation, storage, loads, and other devices attached to hybrid ac/dc microgrids. Although the chapter includes an analysis of the modes of operation of lower‐level regulators, the focus is on upper‐level or primary controllers. In this context, we analyze mode‐adaptive controls based on voltage and frequency levels and we evaluate their behavior by simulation in the Matlab/Simulink® environment. The results demonstrate that mode‐adaptive techniques are adequate for maximizing the energy extracted by distributed generation (DG) systems and limit demand side management actuations while ensuring an adequate regulation of the microgrid

Planning and Operation of Hybrid AC-DC Microgird with High Penetration of Renewable Energy Sources

A hybrid ac/dc microgrid is a more complex but practical network that combines the advantages of an AC and a DC system. The main advantage of this network is that it connects both alternating current and direct current networks via an interlinking converter (IC) to form a unified distribution grid. The hybrid microgrid (HMG) will enable the direct integration of both alternating current (AC) and direct current (DC) distributed generators (DGs), energy storage systems (ESS), and alternating current and direct current (DC) loads into the grid. The alternating current and direct current sources, loads, and ESS are separated and connected to their respective subgrids primarily to reduce power conversion and thus increase overall system efficiency. As a result, the HMG architecture improves power quality and system reliability. Planning a hybrid microgrid entails estimating the capacities of DGs while taking technical, economic, and environmental factors into account. The hybrid ac-dc microgrid is regarded as the distribution network of the future, as it will benefit from both ac and dc microgrids. This thesis presents a general architecture of a hybrid ac-dc microgrid, which includes both planning and design. The goal of the Hybrid ac-dc microgrid planning problem is to maximise social welfare while minimising total planning costs such as investment, maintenance, and operation costs. This configuration will assist Hybrid microgrid planners in estimating planning costs while allowing them to consider any type of load ac/dc and DER type. Finally, this thesis identifies the research questions and proposes a future research plan

Operational Control and Analysis of a Hybrid AC/DC Microgrid

In light of the growing demand for electrical power around the globe, the need to increase electrical power generation in order to diminish total carbon emissions has led to the installation of renewable resources to replace traditional generators. Most of today’s microgrids are AC microgrids, whose advantages and shortcomings with respect to control techniques and stability assessment have been demonstrated through extensive studies reported in the literature. These considerations have led to the recent proposal and investigation of DC microgrids, accompanied by the introduction of the hybrid AC/DC microgrid as a means of combining the advantages and benefits of both types of microgrid. However, since a hybrid microgrid is viewed as a weak system with low inertia, controlling and assessing the performance of a hybrid microgrid constitutes a high-priority issue that requires further investigation. The lack of inertia of power electronics converters, especially in an islanded hybrid microgrid, poses a threat to stability and control. For these reasons, effective stability analysis has become a necessity with respect to the implementation of hybrid microgrids. Because of these challenges, the emulation of synchronous machine (SM) inertia and damping is now viewed as necessary for enhancing the effect of a VSC on an active distribution system and for facilitating its participation in voltage and frequency support. Improving the stability and performance of a hybrid microgrid therefore requires the introduction of a form of inertia into a hybrid microgrid. This research first proposes the incorporation of a novel form of virtual inertia into a hybrid microgrid using virtual synchronous machine (VSM) control of the intertying converter (IC) controller. The second proposal of this research is to employ the VSM control to establish autonomous control of the IC. A first research component, a novel control strategy for the Intertying converter in hybrid AC/DC microgrid has been proposed to ensure the benefit of a virtual synchronous machine (VSM) control algorithm in the hybrid AC/DC microgrid. The VSM controller application in hybrid AC/DC microgrid is capable to enable an IC converter to support the AC-side voltage and frequency as well as the DC-side voltage. The proposed control application of the VSM is chosen based on a comprehensive assessment of VSM control algorithms that are exist in the literature. Moreover, proposing an autonomous operation control of the VSM intertying converter based on dual droop characteristics which is quite different compared to using only current controller. The autonomous operation of the intertying converter based on dual droop control is modified and proposed to be capable to feed the VSM controller (swing equation) to ensure accurate power exchange management between the AC and DC sub-subsystems. The most important portion for the hybrid microgrid system is the stability study due to that fact that the behavior of the system when it is subjected to a temporary disturbance is the main concern. In hybrid microgrid, the disturbances take place continuously because of the load changing endlessly. Satisfying the hybrid microgrid operation during the disturbances conditions must be achieved in order to supply the demand. Therefore, the second part of the research introduces a generic small-signal state space model of the hybrid AC/DC microgrid system, and built to carry out the stability analysis. The development of the small-signal state-space model for the entire hybrid AC/DC microgrid was developed to investigate the overall system stability under different operating points. The final part of this thesis reveals three serious issues of operating hybrid AC/DC microgrid; some of these issues are temporary take a place based on the system operating conditions. In hybrid AC/DC microgrid, an Intertying converter (IC) becomes harmonics voltage source due to the antiparallel diodes and the shunt capacitor at its DC side. The nonlinearity behavior of ICs introduces another operation issue that is circulating current in case of parallel ICs. Reconnecting an IC after abnormal operation condition or schedule maintenance requires an extra challenging synchronization control due the variation of the AC subgrid voltages and frequency; which is the third issue. This part proposes a solution for all these issues by developing a new control strategy that combines the VSM control concept with a dual based droop control. The developed VSM controller on the IC solves these issues. The test system used in this research, which is simulated in a PSCAD/EMTDC environment, consisted of simulated voltage source converters with two AC voltage levels; while the stability analysis is conducted in MATLAB environment

Power Management of the DC Bus Connected Converters in a Hybrid AC/DC Microgrid Tied to the Main Grid

[EN] In this paper, a centralized control strategy for the efficient power management of power converters composing a hybrid AC/DC microgrid is explained. The study is focused on the converters connected to the DC bus. The proposed power management algorithm is implemented in a microgrid central processor which is based on assigning several operation functions to each of the generators, loads and energy storage systems in the microgrid. The power flows between the DC and AC buses are studied in several operational scenarios to verify the proposed control. Experimental and simulation results demonstrate that the algorithm allows control of the power dispatch inside the microgrid properly by performing the following tasks: communication among power converters, the grid operator and loads; connection and disconnection of loads; control of the power exchange between the distributed generators and the energy storage system and, finally, supervision of the power dispatch limit set by the grid operator.This work has been cofinanced by the Spanish Ministry of Economy and Competitiveness (MINECO) and by the European Regional Development Fund (ERDF) under Grant ENE2015-64087-C2-2.Salas-Puente, RA.; Marzal-Romeu, S.; González-Medina, R.; Figueres Amorós, E.; Garcerá, G. (2018). Power Management of the DC Bus Connected Converters in a Hybrid AC/DC Microgrid Tied to the Main Grid. Energies. 11(4):1-21. https://doi.org/10.3390/en11040794S12111

Operation Control and Analysis of a Hybrid AC/DC Microgrid

Distributed renewable energy production is making smart microgrid concepts based on AC, DC, and hybrid-MG design more attractive (DRE). In light of the growing population and the pressing need to minimize the load, research into effective control techniques and architectural solutions is a hot topic right now. However, a comprehensive and coordinated literature assessment of hierarchical control approaches based on diverse configurations of the microgrid (MG) architecture has been explored relatively little in the past.\u27\u27 Primary, secondary, and tertiary methods to MG system control are outlined in this suggested method. Primary, secondary and third-tier techniques are examined for each MG structure in a short literature review. In addition, the paper offers the best and worst aspects of current control methods. In addition, a simulation research connected to the literature review\u27s future trends in MG control is offered as a further contribution to this subject. Since renewable energy supplies are intermittent in nature, a hybrid microgrid is needed to minimize overall deficit inadequacies and increase system dependability. This is due to the depletion of natural resources and to the intermittent nature of renewable energy resources. Using a hybrid microgrid, the present distributed and concentrated load situations may be accommodated. In order to better understand how the hybrid microgrid may be integrated, optimized and controlled, there is a growing demand for research. It is necessary to do a thorough evaluation of the performance, efficiency, dependability, security, design flexibility, and cost-effectiveness of a hybrid microgrid. Issues such as AC and DC microgrids integrating into a single hybrid microgrid are discussed in this paper, as well as how to manage renewable energy resources in a cost-effective manner and how to place the optimal number of feeders in a microgrid. There is a quick overview of the primary research fields, with the goal of finding the research gap that may further enhance the grid\u27s performance. \u27\u27New hybrid microgrid solutions are being offered in light of current study trends that have been determined to be the most effective and most-friendly. Research, comparative analysis, and further development of new methodologies related to hybrid microgrids will be aided by this study as the foundation for future wor

Adaptive Neural Network-Based Control of a Hybrid AC/DC Microgrid

In this paper, the behavior of a grid-connected hybrid ac/dc microgrid has been investigated. Different renewable energy sources - photovoltaics modules and a wind turbine generator - have been considered together with a solid oxide fuel cell and a battery energy storage system. The main contribution of this paper is the design and the validation of an innovative online-trained artificial neural network-based control system for a hybrid microgrid. Adaptive neural networks are used to track the maximum power point of renewable energy generators and to control the power exchanged between the front-end converter and the electrical grid. Moreover, a fuzzy logic-based power management system is proposed in order to minimize the energy purchased from the electrical grid. The operation of the hybrid microgrid has been tested in the MATLAB/Simulink environment under different operating conditions. The obtained results demonstrate the effectiveness, the high robustness and the self-adaptation ability of the proposed control system

Techno-Economic Feasibility Study of Autonomous Hybrid AC/DC Microgrid System

Distributed generation technology based on diesel generators often has been considered as a viable solution to providing power to remote areas, but the sky‐rocketing of diesel fuel price and the increasing cost of delivery to such remote sites have called for providing a sustainable solution that is environmentally friendly, economical, affordable, and easily accessible. To this end, the use of locally available energy resources is accepted as a sustainable solution in providing electricity for rural and remote settlements. The system cost of wind and solar energy systems is continuously decreasing because of the increase in the acceptance and deployment of the energy systems based on these renewable energy resources. A standalone hybrid AC/DC electric power system is designed, modeled, simulated, and optimized in HOMER Pro. HOMER is a Hybrid Optimization Model of Electric Renewable that enables the comparison of electric and thermal power production technologies across an extensive variety of applications. Both cycle‐charging and load‐following dispatched strategies are investigated. Plausible selected system components ratings are chosen for the simulation to ensure that there is enough search space for HOMER Pro to obtain an optimal system configuration. Net present cost (NPC) is used as an economic metric to assess the optimal configuration that is technically feasible

Modeling and control of hybrid ac/dc microgrid

Renewable energy based distributed generators (DGs) play a dominant role in electricity production, with the increase in the global warming. Distributed generation based on wind, solar energy, biomass, mini-hydro along with use of fuel cells and microturbines will give significant momentum in near future. Advantages like environmental friendliness, expandability and flexibility have made distributed generation, powered by various renewable and nonconventional microsources, an attractive option for configuring modern electrical grids. A microgrid consists of cluster of loads and distributed generators that operate as a single controllable system. As an integrated energy delivery system microgrid can operate in parallel with or isolated from the main power grid. The microgrid concept introduces the reduction of multiple reverse conversions in an individual AC or DC grid and also facilitates connections to variable renewable AC and DC sources and loads to power systems. The interconnection of DGs to the utility/grid through power electronic converters has risen concerned about safe operation and protection of equipment’s. To the customer the microgrid can be designed to meet their special requirements; such as, enhancement of local reliability, reduction of feeder losses, local voltages support, increased efficiency through use of waste heat, correction of voltage sag or uninterruptible power supply. In the present work the performance of hybrid AC/DC microgrid system is analyzed in the grid tied mode. Here photovoltaic system, wind turbine generator and battery are used for the development of microgrid. Also control mechanisms are implemented for the converters to properly co-ordinate the AC sub-grid to DC sub-grid. The results are obtained from the MATLAB/ SIMULINK environment