scholarly journals Distributed Control Strategy for DC Microgrids of Photovoltaic Energy Storage Systems in Off-Grid Operation

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2637 ◽  
Author(s):  
Mingxuan Chen ◽  
Suliang Ma ◽  
Haiyong Wan ◽  
Jianwen Wu ◽  
Yuan Jiang
Keyword(s):  
Energy Storage ◽  
Power Systems ◽  
Distributed Control ◽  
Control Strategy ◽  
Storage System ◽  
Voltage Stabilizer ◽  
Dc Microgrid ◽  
Dc Microgrids ◽  
Photovoltaic Energy ◽  
Operation Conditions

DC microgrid systems that integrate energy distribution, energy storage, and load units can be viewed as examples of reliable and efficient power systems. However, the isolated operation of DC microgrids, in the case of a power-grid failure, is a key factor limiting their development. In this paper, we analyze the six typical operation modes of an off-grid DC microgrid based on a photovoltaic energy storage system (PV-ESS), as well as the operational characteristics of the different units that comprise the microgrid, from the perspective of power balance. We also analyze the key distributed control techniques for mode transformation, based on the demands of the different modes of operation. Possible reasons for the failure of PV systems under the control of a voltage stabilizer are also explored, according to the characteristics of the PV output. Based on this information, we propose a novel control scheme for the seamless transition of the PV generation units between the maximum PV power tracking and steady voltage control processes, to avoid power and voltage oscillations. Adaptive drooping and stabilization control of the state of charge of the energy storage units are also considered, for the protection of the ESS and for reducing the possibilities of overcharging and/or over-discharging. Finally, various operation conditions are simulated using MATLAB/Simulink, to validate the performance of the proposed control strategy.

scholarly journals An Energy Management System-Based Control Strategy for DC Microgrids with Dual Energy Storage Systems

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2992
Author(s):  
Subarto Kumar Ghosh ◽  
Tushar Kanti Roy ◽  
Md Abu Hanif Pramanik ◽  
Ajay Krishno Sarkar ◽  
Md. Apel Mahmud
Keyword(s):  
Energy Storage ◽  
Control Strategy ◽  
Storage Systems ◽  
Storage System ◽  
Energy Storage System ◽  
Energy Management System ◽  
Energy Storage Systems ◽  
Dc Microgrid ◽  
Dc Microgrids ◽  
Control Scheme

In this work, a control strategy is developed for different components in DC microgrids where set points for all controllers are determined from an energy management system (EMS). The proposed EMS-based control scheme is developed for DC microgrids with solar photovoltaic (PV) systems as the primary generation units along with energy storage systems. In this work, the concept of dual energy storage systems (DESSs) is used, which includes a battery energy storage system (BESS) and supercapacitor (SC). The main feature of this DESS is to improve the dynamic performance of DC microgrids during severe transients appearing from changes in load demands as well as in the output power from solar PV units. Furthermore, the proposed EMS-based control scheme aims to enhance the lifetime of the BESS in DC microgrids with DESSs and voltage stability as compared to the same without SCs. The proposed EMS-based control strategy uses proportional-integral (PI) controllers to regulate the switching control actions for different converters within the DC microgrid based on the decision obtained from the EMS in order to achieve the desired control objectives. The performance of the proposed scheme was analyzed through simulation results in terms of improving the voltage stability, maintaining the power balance, and enhancing the lifetime of BESSs within a DC microgrid framework incorporated with the DESS. The simulations are carried out in the MATLAB/SIMULINK simulation platform and compared with a similar approach having only a single energy storage system, i.e., the BESS.

scholarly journals Research on Control Strategy of Isolated DC Microgrid Based on SOC of Energy Storage System

Electronics ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 834
Author(s):  
Jiechao Lv ◽  
Xiaoli Wang ◽  
Guishuo Wang ◽  
Yuhou Song
Keyword(s):  
Energy Storage ◽  
Control Strategy ◽  
Storage System ◽  
Energy Storage System ◽  
Dc Microgrid ◽  
Battery Energy Storage ◽  
Distributed Power ◽  
Distributed Power Generation ◽  
Operation Control ◽  
Battery Energy

With the rapid development of renewable energy technologies, islanded DC microgrids have received extensive attention in the field of distributed power generation due to their plug-and-play, flexible operation modes and convenient power conversion, and are likely to be one of the mainstream structures of microgrids in the future. The islanded DC microgrid contains multiple distributed power generation units. The battery energy storage system (BESS) is the main controlled unit used to smooth power fluctuations. The main parameter of concern is the state of charge (SOC). In order to maintain the stability of the microgrid, this paper takes the islanded DC microgrid as the research object and designs a control strategy based on the SOC of the BESS. Additionally, in the control strategy, the BESS’s energy balance control strategy and the microgrid’s operation control strategy are emphatically designed. The designed BESS control strategy adjusts the droop coefficient in real time according to the SOC of the battery energy storage unit (BESU), and controls the charge and discharge power of the BESU to achieve the SOC balance among the BESUs. The microgrid operation control strategy takes the energy storage system (ESS) as the main controlled unit to suppress power fluctuations, and distributes the power of distributed power sources according to the SOC of the BESS to achieve power balance in the microgrid, and control the DC bus voltage fluctuation deviation within 4.5%.

Energy Storage Analysis to Increase Large Ship Fuel Efficiency

2009 ◽  
Author(s):  
Benjamin H. Gully ◽  
Michael E. Webber ◽  
Carolyn C. Seepersad ◽  
Richard C. Thompson
Keyword(s):  
Energy Storage ◽  
Power Systems ◽  
Fuel Consumption ◽  
Control Strategy ◽  
Storage System ◽  
Fuel Efficiency ◽  
Primary Objective ◽  
Hybrid Powertrain ◽  
Power Load ◽  
Large Ship

The marine transportation industry is a significant contributor to global emissions of CO2 and other pollutants. Although marine emission standards have become increasingly stringent, increasing fuel efficiency remains the primary objective in terms of further reducing emissions and overall marine energy use. In this paper, a hybrid powertrain is investigated as a means of increasing fuel efficiency for a modern, 100 m class, passenger vessel. The hybrid powertrain includes an Energy Storage System (ESS) based on sodium sulfur (NaS) batteries and commercially available Caterpillar diesel engine-generator sets. The ship’s power load profile is based on annual averages for similar vessels. A control strategy and simulation models are developed and implemented in Simulink to analyze the power and energy flows in the hybrid powertrain. The Simulink model is used to compare the base scenario of a ship without energy storage to a hybrid scenario employing a 7.5 MWh NaS battery pack with related control strategy. Annual fuel consumption is the primary measure that is used to assess efficiency. Unlike hybrid powertrains for light-duty surface vehicle transportation, which achieve efficiency gains on the order of 10–20% [8, 9, 10], the hybrid powertrain for a large ship is estimated to lower annual fuel consumption by approximately 2%. The surprisingly small level of fuel savings is explained largely by the granularity of marine power systems, which include multiple generators that can be switched on and off to maximize fuel efficiency.

scholarly journals Island DC Microgrid Hierarchical Coordinated Multi-Mode Control Strategy

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 3012 ◽  
Author(s):  
Zhongbin Zhao ◽  
Jing Zhang ◽  
Yu He ◽  
Ying Zhang
Keyword(s):  
Power Systems ◽  
Control Strategy ◽  
Voltage Stability ◽  
Dc Microgrid ◽  
Dc Microgrids ◽  
Mode Control ◽  
Load Power ◽  
Power Dispatch ◽  
Operation Modes ◽  
Multi Mode

As renewable energy sources connecting to power systems continue to improve and new-type loads, such as electric vehicles, grow rapidly, direct current (DC) microgrids are attracting great attention in distribution networks. In order to satisfy the voltage stability requirements of island DC microgrids, the problem of inaccurate load power dispatch caused by line resistance must be solved and the defects of centralized communication and control must be overcome. A hierarchical, coordinated, multiple-mode control strategy based on the switch of different operation modes is proposed in this paper and a three-layer control structure is designed for the control strategy. Based on conventional droop control, a current-sharing layer and a multi-mode switching layer are used to ensure the stable operation of the DC microgrid. Accurate load power dispatch is satisfied using a difference discrete consensus algorithm. Furthermore, virtual bus voltage information is applied to guarantee smooth switching between various modes, which safeguards voltage stability. Simulation verification is carried out for the proposed control strategy by power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC). The results indicate that the proposed control strategy guarantees the voltage stability of island DC microgrids and accurate load power dispatch under different operation modes.

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