Distributed Voltage Control and Power Management of Networked Microgrids (original) (raw)
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Distributed consensus-based control of multiple DC-microgrids clusters
IECON 2014 - 40th Annual Conference of the IEEE Industrial Electronics Society, 2014
This paper presents consensus-based distributed control strategies for voltage regulation and power flow control of dc microgrid (MG) clusters. In the proposed strategy, primary level of control is used to regulate the common bus voltage inside each MG locally. An SOC-based adaptive droop method is introduced for this level which determines droop coefficient automatically, thus equalizing SOC of batteries inside each MG. In the secondary level, a distributed consensus based voltage control strategy is proposed to eliminate the average voltage deviation while guaranteeing proper regulation of power flow among the MGs. Using the consensus protocol, the global information can be accurately shared in a distributed way. This allows the power flow control to be achieved at the same time as it can be accomplished only at the cost of having the voltage differences inside the system. Similarly, a consensus-based cooperative algorithm is employed at this stage to define appropriate reference for power flow between MGs according to their local SOCs. The effectiveness of proposed control scheme is verified through detailed hardware-in-the-loop (HIL) simulations.
An Accurate Power Sharing Method for Control of a Multi-DG Microgrid
This paper presents an accurate control scheme for active and reactive power sharing in a microgrid consisting of two distributed generation (DG) units. Each DG unit within the microgrid utilizes a structurally simple controller for adjusting its power components. The proposed method combines the droop, and average power sharing (APS) schemes to improve the accuracy of reactive power sharing control. This method also employs the low-bandwidth digital communications to achieve accurate power sharing and restoration process. The simulation results verify the accuracy and effectiveness of the proposed method as compared to the conventional droop and APS methods.
To meet several power objectives, the idea of organizing DGs into several clusters in a microgrid is proposed in this paper. Power objectives include maintaining active power flow to the main grid at a predetermined level, minimizing the reactive power flow to the main grid and maintaining a unified voltage profile across the microgrid. DGs are organized differently for active and reactive power control. All DGs realize active power objective in one group. As reactive power is used to maintain the unified voltage, DGs are grouped in several clusters to regulate multiple critical point voltages. The closest cluster to the point of common coupling, minimizes the reactive power flow and others manage their reactive power to regulate their critical points. Each cluster has a virtual leader which other DGs follow, utilizing the cooperative control. The cooperative law is also derived, based on the dynamics of the inverters.
Power sharing between parallel inverters in microgrid by improved droop control
2018
Microgrid is a main part of the future intelligent and sustainable power system. In order to improve the flexibility of a microgrid and realize the plug and play feature of distributed generation and load, this paper proposed an improved droop control to control the parallel inverters in microgrid to solve the problem that the traditional droop control cannot efficiently allot power between multiple inverters. In the proposed improved droop controller, new components are added to the reference voltage and frequency of each parallel inverter based on a feedback loop of the main bus voltage and frequency, respectively. The proposed control strategy is tested with Matlab/Simulink simulation model of a microgrid in the islanding mode which is more difficult to achieve power sharing in. Different supply and load variations are investigated in order to show the robustness of the proposed control. Results are compared with the traditional droop control showing superior performance of the p...
A review of droop control techniques for microgrid
Renewable and Sustainable Energy Reviews, 2017
Coordination of different distributed generation (DG) units is essential to meet the increasing demand for electricity. Many control strategies, such as droop control, master-slave control, and average current-sharing control, have been extensively implemented worldwide to operate parallel-connected inverters for load sharing in DG network. Among these methods, the droop control technique has been widely accepted in the scientific community because of the absence of critical communication links among parallel-connected inverters to coordinate the DG units within a microgrid. Thus, this study highlights the state-of-the-art review of droop control techniques applied currently to coordinate the DG units within a microgrid.
Hierarchical Control for Multiple DC-Microgrids Clusters
This paper presents a distributed hierarchical control framework to ensure reliable operation of dc Microgrid (MG) clusters. In this hierarchy, primary control is used to regulate the common bus voltage inside each MG locally. An adaptive droop method is proposed for this level which determines droop coefficients according to the state-of-charge (SOC) of batteries automatically. A small signal model is developed to investigate effects of the system parameters, constant power loads as well as line impedance between the MGs on stability of these systems. In the secondary level, a distributed consensus-based voltage regulator is introduced to eliminate the average voltage deviation over the MGs. This distributed averaging method allows the power flow control between the MGs to be achieved at the same time, as it can be accomplished only at the cost of having voltage deviation inside the system. Another distributed policy is employed then to regulate the power flow among the MGs according to their local SOCs. The proposed distributed controllers on each MG communicate with only the neighbor MGs through a communication infrastructure. Finally, the small signal model is expanded for dc MG clusters with all the proposed control loops. The effectiveness of proposed hierarchical scheme is verified through detailed hardware-in-the-loop (HIL) simulations.
Distributed Control of Microgrids
Power Systems, 2019
The aim of this chapter discusses the relationship between hierarchical control and review of distributed control systems that is used in microgrids. The microgrids are differs from the conventional power systems. Because of the widespread use of advanced control technologies with features such as power electronics devices, detection/measurement applications, and communication infrastructures. These features of microgrids make it easier for renewable energy sources that are included in the power systems. Therefore, distributed control methods are applied in addition to centralized and decentralized controls for reliable operation of the system in microgrids and between different microgrids. This section discusses the features of these methods.
IEEE Transactions on Power Electronics, 2000
DC microgrids are gaining popularity due to high efficiency, high reliability and easy interconnection of renewable sources as compared to ac system. Control objectives of dc microgrid are: (i) ensure equal load sharing (in per unit) among sources and (ii) maintain low voltage regulation of the system. Conventional droop controllers are not effective in achieving both the aforementioned objectives simultaneously. Reasons for this are identified to be the error in nominal voltages and load distribution. Though centralized controller achieves these objectives, it requires high speed communication and offers less reliability due to single point of failure. To address these limitations, this paper proposes a new decentralized controller for dc microgrid. Key advantages are high reliability, low voltage regulation and equal load sharing, utilizing low bandwidth communication. To evaluate the dynamic performance, mathematical model of the scheme is derived. Stability of the system is evaluated by eigenvalue analysis. The effectiveness of the scheme is verified through detailed simulation study. To confirm the viability of the scheme, experimental studies are carried out on a laboratory prototype developed for this purpose. Controller Area Network (CAN)