Distributed Secondary Control of Islanded Microgrids for Fast Convergence Considering Arbitrary Sampling

This paper proposes a novel distributed secondary control of MGs for fast convergence considering asynchronous sampling. With the employment of the algorithm, optimal power sharing and voltage restoration are implemented simultaneously. First, the hierarchical control objectives concerned with economic operation and voltage quality are introduced. Then, the execution process of the fast convergence algorithm is described for weighted average state estimation, with the illustration of corresponding features and the application in cooperative control. Further, the relevant stability issue is discussed based on large-signal dynamic modeling and a sufficient stability condition is derived based on the Lyapunov–Krasovskii theory. Our approach offers superior reliability, flexibility and robustness because of the loose implementation in terms of its performance concern, which is essential when the distributed consensus protocol is likely to yield toward deviation or even instability under arbitrary sampling and delays. The effectiveness of the proposed methodology is verified via simulations.

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Secondary Control for Storage Power Converters in Isolated Nanogrids to Allow Peer-to-Peer Power Sharing

Electronics ◽

10.3390/electronics9010140 ◽

2020 ◽

Vol 9 (1) ◽

pp. 140 ◽

Cited By ~ 2

Author(s):

Eva González-Romera ◽

Enrique Romero-Cadaval ◽

Carlos Roncero-Clemente ◽

Mercedes Ruiz-Cortés ◽

Fermín Barrero-González ◽

...

Keyword(s):

Power Flow ◽

Control Method ◽

Low Voltage ◽

Hierarchical Control ◽

Power Converter ◽

Power Sharing ◽

Primary Control ◽

Secondary Control ◽

Control Loops ◽

Energy Interchange

It is usual in literature that power sharing among grid-forming sources of an isolated microgrid obeys their energy rating, instead of economic agreements between stakeholders, and circulating energy among them is usually avoided. However, these energy interchanges make strong sense and classical power sharing methods must be reformulated in the context of prosumer-based microgrids. This paper proposes a secondary control method for a prosumer-based low-voltage nanogrid that allows for energy interchange between prosumers, where storage systems, together with PV generators, are the controllable grid-forming sources. A power flow technique adapted to islanded microgrids is used for secondary control algorithm and the whole hierarchical control strategy for the prosumer converter is simulated and validated. This hierarchical control consists of three stages: tertiary control plans the energy interchange among prosumers, secondary obtains different voltage and power setpoints for each of the grid-forming sources, and, finally, primary control guarantees stable voltage and frequency values within the nanogrid with droop rules. Inner control loops for the power converter are also defined to track setpoints and assure stable performance. Simulation tests are carried out, which prove the stability of the proposed methods and the accuracy of the setpoint tracking.

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A Cooperative Control Scheme for AC/DC Hybrid Autonomous Microgrids

Processes ◽

10.3390/pr8030311 ◽

2020 ◽

Vol 8 (3) ◽

pp. 311 ◽

Cited By ~ 1

Author(s):

Wanxing Sheng ◽

Yinqiu Hong ◽

Ming Wu ◽

Yu Ji

Keyword(s):

Cooperative Control ◽

Control Strategies ◽

Power Sharing ◽

Secondary Control ◽

Hybrid Microgrid ◽

Bidirectional Converter ◽

Global Power ◽

Control Scheme ◽

Droop Characteristic ◽

High Flexibility

The AC/DC hybrid microgrid (MG) has been widely promoted due to its high flexibility. The capability to operate in islanding mode is an appealing advantage of the MG, and also sets higher requirements for its control system. A droop control strategy is proposed on account of its distinguishing feature of automatic power sharing between distributed generations (DGs), but it introduces some drawbacks. Therefore, distributed cooperative secondary control is introduced as an improvement. In order to optimize the active power sharing in AC/DC hybrid microgrids, a number of cooperative control strategies have been proposed. However, most studies of AC/DC hybrid microgrids have mainly focused on the control of the bidirectional converter, ignoring the effects of secondary control within subnets, which may make a difference to the droop characteristic. This paper extends the cooperative control to AC/DC hybrid microgrids based on normalizing and synthesizing the droop equations, and proposes a global cooperative control scheme for AC/DC autonomous hybrid microgrids, realizing voltage restoration within AC and DC subnets as well as accurate global power sharing. Ultimately, the simulation results demonstrate that the proposed control scheme has a favorable performance in the test AC/DC hybrid system.

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Decentralized Fast Delayed Signal Cancelation Secondary Control for Low Voltage Ride-Through Application in Grid Supporting Grid Feeding Microgrid

Frontiers in Energy Research ◽

10.3389/fenrg.2021.643920 ◽

2021 ◽

Vol 9 ◽

Author(s):

Elutunji Buraimoh ◽

Innocent E. Davidson ◽

Fernando Martinez-Rodrigo

Keyword(s):

Low Voltage ◽

Hierarchical Control ◽

Voltage Regulation ◽

Power Sharing ◽

Primary Control ◽

Distributed Energy ◽

Secondary Control ◽

Low Voltage Ride Through ◽

Control Scheme ◽

Real Time Digital Simulator

In this study, a distributed secondary control is proposed alongside the conventional primary control to form a hierarchical control scheme for the Low Voltage Ride-Through (LVRT) control and applications in the inverter-based microgrid. The secondary control utilizes a fast Delayed Signal Cancelation (DSC) algorithm for the secondary control loop to control the reactive and active power reference by controlling the sequences generated. The microgrid consists of four Distributed Energy Resources (DER) sources interfaced to the grid through interfacing inverters coordinated by droop for effective power-sharing according to capacities. The droop also allows for grid supporting application for microgrid’s participation in frequency and voltage regulation in the main grid. The proposed decentralized fast DSC performance is evaluated with centralized secondary and traditional primary control using OPAL-RT Lab computation and MATLAB/SIMULINK graphical user interface for offline simulations and real-time digital simulator verification. This study presents and discusses the results.

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Fuzzy-Based Distributed Cooperative Secondary Control with Stability Analysis for Microgrids

Electronics ◽

10.3390/electronics10040399 ◽

2021 ◽

Vol 10 (4) ◽

pp. 399

Author(s):

Mahmuda Begum ◽

Mohsen Eskandari ◽

Mohammad Abuhilaleh ◽

Li Li ◽

Jianguo Zhu

Keyword(s):

Control System ◽

Stability Analysis ◽

Cooperative Control ◽

Dynamic Behaviour ◽

Reactive Power ◽

Control Method ◽

Power Sharing ◽

System Stability ◽

Control Technique ◽

Secondary Control

This research suggests a novel distributed cooperative control methodology for a secondary controller in islanded microgrids (MGs). The proposed control technique not only brings back the frequency/voltage to its reference values, but also maintains precise active and reactive power-sharing among distributed generation (DG) units by means of a sparse communication system. Due to the dynamic behaviour of distributed secondary control (DSC), stability issues are a great concern for a networked MG. To address this issue, the stability analysis is undertaken systematically, utilizing the small-signal state-space linearized model of considering DSC loops and parameters. As the dynamic behaviour of DSC creates new oscillatory modes, an intelligent fuzzy logic-based parameter-tuner is proposed for enhancing the system stability. Accurate tuning of the DSC parameters can develop the functioning of the control system, which increases MG stability to a greater extent. Moreover, the performance of the offered control method is proved by conducting a widespread simulation considering several case scenarios in MATLAB/Simscape platform. The proposed control method addresses the dynamic nature of the MG by supporting the plug-and-play functionality, and working even in fault conditions. Finally, the convergence and comparison study of the offered control system is shown.

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Secondary Control of Microgrids via Neural Inverse Optimal Distributed Cooperative Control

IFAC-PapersOnLine ◽

10.1016/j.ifacol.2020.12.1973 ◽

2020 ◽

Vol 53 (2) ◽

pp. 7891-7896

Author(s):

Carlos J. Vega ◽

Larbi Djilali ◽

Edgar N. Sanchez

Keyword(s):

Cooperative Control ◽

Secondary Control ◽

Distributed Cooperative Control

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Coordinated Frequency Control Strategy with the Virtual Battery Model of Inverter Air Conditionings

Applied Sciences ◽

10.3390/app9153052 ◽

2019 ◽

Vol 9 (15) ◽

pp. 3052

Author(s):

Jiafu Yin ◽

Dongmei Zhao

Keyword(s):

Control Strategy ◽

Frequency Control ◽

Hierarchical Control ◽

Frequency Regulation ◽

Consensus Protocol ◽

Consensus Control ◽

Response Characteristics ◽

Battery Model ◽

Control Framework ◽

Control Scheme

Due to the potential of thermal storage being similar to that of the conventional battery, air conditioning (AC) has gained great popularity for its potential to provide ancillary services and emergency reserves. In order to integrate numerous inverter ACs into secondary frequency control, a hierarchical distributed control framework which incorporates a virtual battery model of inverter AC is developed. A comprehensive derivation of a second-order virtual battery model has been strictly posed to formulate the frequency response characteristics of inverter AC. In the hierarchical control scheme, a modified control performance index is utilized to evaluate the available capacity of traditional regulation generators. A coordinated frequency control strategy is derived to exploit the complementary and advantageous characteristics of regulation generators and aggregated AC. A distributed consensus control strategy is developed to guarantee the fair participation of heterogeneous AC in frequency regulation. The finite-time consensus protocol is introduced to ensure the fast convergence of power tracking and the state-of-charge (SOC) consistency of numerous ACs. The effectiveness of the proposed control strategy is validated by a variety of illustrative examples.

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A novel distributed event-triggered control for reactive power sharing based on hierarchical structure in islanded microgrid

Measurement and Control ◽

10.1177/0020294020924754 ◽

2020 ◽

pp. 002029402092475

Author(s):

Yingwen Long ◽

Yanxiang Zhu ◽

Wei Zhang

Keyword(s):

Hierarchical Structure ◽

Reactive Power ◽

Hierarchical Control ◽

Power Sharing ◽

Control Algorithms ◽

Centralized Control ◽

Nonlinear Loads ◽

Distributed Generator ◽

Islanded Microgrid ◽

Event Triggered

Due to line impedance mismatches, nonlinear loads and other reasons, the traditional droop control algorithms have great limitations on the control of reactive power sharing. Distributed control algorithms based on hierarchical structure have become an effective approach for reactive power sharing compared with traditional centralized control methods. In this paper, an event-triggered control algorithm based on stability analysis of Lyapunov method is put forward in order to satisfy the demand of low-bandwidth communication for distributed generator in islanded microgrid. Subsequently, a distributed hierarchical control scheme adopting proposed event-triggered strategy is designed to achieve proportional reactive power sharing in an islanded microgrid. Finally, the feasibility and validity of the proposed algorithm are further verified in MATLAB/Simulink environment.

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Hierarchical control of DC microgrid with dynamical load power sharing

Applied Energy ◽

10.1016/j.apenergy.2019.01.081 ◽

2019 ◽

Vol 239 ◽

pp. 1-11 ◽

Cited By ~ 9

Author(s):

Minghan Yuan ◽

Yang Fu ◽

Yang Mi ◽

Zhenkun Li ◽

Chengshan Wang

Keyword(s):

Hierarchical Control ◽

Power Sharing ◽

Dc Microgrid ◽

Load Power

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Consensus Control for Reactive Power Sharing Using an Adaptive Virtual Impedance Approach

Energies ◽

10.3390/en13082026 ◽

2020 ◽

Vol 13 (8) ◽

pp. 2026 ◽

Cited By ~ 2

Author(s):

Ahmed S. Alsafran ◽

Malcolm W. Daniels

Keyword(s):

Rate Of Convergence ◽

Reactive Power ◽

Impedance Control ◽

Power Sharing ◽

Control Methods ◽

Triangle Mesh ◽

Secondary Control ◽

Consensus Control ◽

Communication Topology ◽

Virtual Impedance

Reactive power sharing among distributed generators (DGs) in islanded microgrids (MGs) presents control challenges, particularly in the mismatched feeder line condition. Improved droop control methods independently struggle to resolve this issue and centralized secondary control methods exhibit a high risk of collapse for the entire MG system under any failure in the central control. Distributed secondary control methods have been recently proposed to mitigate the reactive power error evident in the presence of mismatched feeder lines. This paper details a mathematical model of an adaptive virtual impedance control that is based on both leaderless and leader-followers consensus controls with a novel triangle mesh communication topology to ensure accurate active and reactive power sharing. The approach balances an enhanced rate of convergence with the anticipated implementation cost. A MATLAB/Simulink model with six DG units validates the proposed control performance under three different communication structures: namely, ring, complete, and triangle mesh topologies. The results suggest that leaderless consensus control is a reliable option with large DG systems, while the leader-followers consensus control is suitable for the small systems. The triangle mesh communication topology provides a compromise approach balancing the rate of convergence and the expected cost. The extensibility and scalability are advantages of this topology over the alternate ring and complete topologies.

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