Energy Management Strategy for a Standalone Solar PV based DC Community Grid
28 Sep 2020-
TL;DR: In this paper, an adaptive droop control algorithm based on the existing source converted as the reference current for operating the converters to meet the demand is presented, where the changes in the output potential of each converter are controlled and maintained constant throughout the operation of DC community grid and makes it stable.
Abstract: The coordinated and efficient operation of Solar PV system combined with battery storage systems makes a standalone DC Community Grid stable and reliable. The accurate power sharing between the distributed renewable energy sources of a DC community grid according to the available source and load demand is managed through droop control algorithm and droop resistance adaptable to the variations in the sources (Uncertainties in Solar Power). This paper presents an adaptive droop control algorithm developed based on the existing source converted as the reference current for operating the converters to meet the demand. The changes in the output potential of each converter is controlled and is maintained constant throughout the operation of DC community grid and makes it stable. The proposed control algorithm is implemented to the system individually to make it a communication less control. The adaptive droop control algorithm relies on the local measurement data from each converter like, output voltage, current, rated load current and DC Bus voltage. The control strategy is applied to a simple DC microgrid representing a local community grid with solar PV as the source and battery as the support system on standalone mode of operation developed using MATLAB-Simulink® and is validated for three different power sharing scenarios.
References
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TL;DR: In this paper, a review of control strategies, stability analysis, and stabilization techniques for dc microgrids is presented, where overall control is systematically classified into local and coordinated control levels according to respective functionalities in each level.
Abstract: This paper presents a review of control strategies, stability analysis, and stabilization techniques for dc microgrids (MGs). Overall control is systematically classified into local and coordinated control levels according to respective functionalities in each level. As opposed to local control, which relies only on local measurements, some line of communication between units needs to be made available in order to achieve the coordinated control. Depending on the communication method, three basic coordinated control strategies can be distinguished, i.e., decentralized, centralized, and distributed control. Decentralized control can be regarded as an extension of the local control since it is also based exclusively on local measurements. In contrast, centralized and distributed control strategies rely on digital communication technologies. A number of approaches using these three coordinated control strategies to achieve various control objectives are reviewed in this paper. Moreover, properties of dc MG dynamics and stability are discussed. This paper illustrates that tightly regulated point-of-load converters tend to reduce the stability margins of the system since they introduce negative impedances, which can potentially oscillate with lightly damped power supply input filters. It is also demonstrated that how the stability of the whole system is defined by the relationship of the source and load impedances, referred to as the minor loop gain. Several prominent specifications for the minor loop gain are reviewed. Finally, a number of active stabilization techniques are presented.
1,131 citations
"Energy Management Strategy for a St..." refers background in this paper
...Therefore, it can be seen as a small-scale electrical distribution network which can guarantee affordable and reliable local electricity for urban and rural communities, islands and remote activities that have limited or no access to electricity [2]....
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TL;DR: This paper presents an overview of power management strategies for a hybrid ac/dc microgrid system, which includes different system structures, different operation modes, a thorough study of various power management and control schemes in both steady state and transient conditions, and examples of powermanagement and control strategies.
Abstract: Today, conventional power systems are evolving to modern smart grids, where interconnected microgrids may dominate the distribution system with high penetration of renewable energy and energy storage systems. The hybrid ac/dc systems with dc and ac sources/loads are considered to be the most possible future distribution or even transmission structures. For such hybrid ac/dc microgrids, power management strategies are one of the most critical operation aspects. This paper presents an overview of power management strategies for a hybrid ac/dc microgrid system, which includes different system structures (ac-coupled, dc-coupled, and ac–dc-coupled hybrid microgrids), different operation modes, a thorough study of various power management and control schemes in both steady state and transient conditions, and examples of power management and control strategies. Finally, discussion and recommendations of power management strategies for the further research are presented.
707 citations
"Energy Management Strategy for a St..." refers methods in this paper
...The renewables considered here is solar PV system and is represented by the PV array connection to the boost converter with the MPPT algorithm [7]....
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15 Sep 2011
TL;DR: In this article, the authors investigated on the active and reactive power sharing of an autonomous hybrid microgrid, which comprises dc and ac sub-grids, interconnected by power electronic interfaces.
Abstract: This paper investigates on the active and reactive power sharing of an autonomous hybrid microgrid. Unlike existing microgrids which are purely ac, the hybrid microgrid studied here comprises dc and ac sub-grids, interconnected by power electronic interfaces. The main challenge here is to manage the power flow among all the sources distributed throughout the two types of sub-grids, which certainly is tougher than previous efforts developed for only either ac or dc microgrid. This wider scope of control has not yet been investigated, and would certainly rely on the coordinated operation of dc sources, ac sources and interlinking converters. Suitable control and normalization schemes are therefore developed for controlling them with results presented for showing the overall performance of the hybrid microgrid.
620 citations
Additional excerpts
...The stable operation of a DC MGs during standalone operation is ensured by the proper connection and operation of Battery Energy Storage System (BESS) and is controlled to integrate it further to the conventional grid [3]....
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TL;DR: In this paper, a figure of merit called droop index (DI) is introduced in order to improve the performance of dc microgrid, which is a function of normalized current sharing difference and losses in the output side of the converters.
Abstract: This paper addresses load current sharing and cir- culating current issues of parallel-connected dc-dc converters in low-voltage dc microgrid. Droop control is the popular technique for load current sharing in dc microgrid. The main drawbacks of the conventional droop method are poor current sharing and drop in dcgrid voltage due tothe droop action. Circulating current issue will also arise due to mismatch in the converters output voltages. In this work, a figure of merit called droop index (DI) is introduced in order to improve the performance of dc microgrid, which is a function of normalized current sharing difference and losses in the output side of the converters. This proposed adaptive droop con- trol method minimizes the circulating current and current sharing difference between the converters based on instantaneous virtual resistance Rdroop .U singRdroop shifting, the proposed method also eliminates the tradeoff between current sharing difference and voltage regulation. The detailed analysis and design procedure are explained for two dc-dc boost converters connected in paral- lel. The effectiveness of the proposed method is verified by detailed simulation and experimental studies.
343 citations
TL;DR: A hierarchical active power management strategy for a medium voltage (MV) islanded microgrid including a multihybrid power conversion system (MHPCS) and the performance of the proposed control strategy is verified by using digital time-domain simulation studies in the PSCAD/EMTDC software environment.
Abstract: This paper proposes a hierarchical active power management strategy for a medium voltage (MV) islanded microgrid including a multihybrid power conversion system (MHPCS). To guarantee excellent power management, a modular power conversion system is realized by parallel connection of small MHPCS units. The hybrid system includes fuel cells (FC) as main and supercapacitors (SC) as complementary power sources. The SC energy storage compensates the slow transient response of the FC stack and supports the FC to meet the grid power demand. The proposed control strategy of the MHPCS comprises three control loops; dc-link voltage controller, power management controller, and load current sharing controller. Each distributed generation (DG) unit uses an adaptive proportional resonance (PR) controller for regulating the load voltage, and a droop control strategy for average power sharing among the DG units. The performance of the proposed control strategy is verified by using digital time-domain simulation studies in the PSCAD/EMTDC software environment.
145 citations
"Energy Management Strategy for a St..." refers background in this paper
...The hybrid power community proposes to combine both AC and DC power in homes because of the presence of DC loads like lighting and plug loads, home entertainment, appliances for domestic use, indoor and outdoor health and recreation and security purposes, EV charging, electrical storage and home utilities and so on in the residential community [4]....
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