General Interface for Power Management of Micro-Grids Using Nonlinear Cooperative Droop Control (original) (raw)
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2014 IEEE 23rd International Symposium on Industrial Electronics (ISIE), 2014
Control strategies of a microgrid which includes both synchronous generators and converter-based distribution generation (DG) units must be designed such that effective operation of the microgrid is achieved. The main objective of this paper is to develop a high performance control strategy for an islanded medium voltage (MV) microgrid consisting of inverter and non-inverter interfaced DG units. A new control method for the synchronous generator in an islanded microgrid is proposed based on a virtual droop scheme. The proposed strategy can effectively manage the real and reactive powers of the microgrid among the inverter and non-inverter based DG units. The steady state and dynamic responses of the MV microgrid is significantly improved by using the proposed power management scheme. The performance of the proposed control strategy is verified by using digital time-domain simulation study in the PSCAD/EMTDC software environment.
Applicability of Droop Regulation Technique in Microgrid - A Survey
Engineering Journal, 2014
Currently, the worth of power generation on the basis of renewable sources is rapidly growing. Correspondingly the microgrids and the DG units are impressed the researchers for their peculiar features. Power sharing is the major concern when various DGs are connected to the microgrid via power electronic converters. It is mandatory to achieve an appropriate power sharing when the manifold DGs are activated in parallel. For that, the two ultimate quantities-power angle δ and voltage magnitude V are regulated to acquire the real and reactive power sharing correspondingly. Many innovative control techniques have been used for load sharing. The most common method of local load sharing is the droop characteristics. Subsequently, there is a swift momentum in the advancement of researchers to meet the challenges of the droop control techniques in the power sharing concerns, an extensive literature review on active and reactive power sharing, voltage and frequency control in microgrid has been emphasized. The various conventional and modified droop control techniques/strategies that relates to power sharing issues have been highlighted in this work.
Sliding Droop Control For Distributed Generation In Microgrids
Eletrônica de Potência, 2017
This paper proposes a fully autonomous controller that slides the droop curves of a Static Synchronous Generator, avoiding the need of hierarchical controllers to perform power sharing and frequency and voltage regulation. The aim of this controller is to enhance the primary controller in order to perform additional functionalities in a similar way as those performed in a secondary control level hierarchy, avoiding the need of a communication-system and without mischaracterizing the primary behavior as a virtual synchronous machine. The proposed seamless controller is still compatible with conventional communication-systems, and can receive inputs from hierarchical controllers. In grid-connected microgrids, distributed generation (DG) units perform active-power supply and adequate voltage regulation, whereas the system frequency is imposed by the grid. Contrarily, in islanded microgrids, DG units have to perform activepower sharing between all units, reactive-power sharing, as well as to ensure adequate frequency control and voltage regulation. When static droop curves are employed, power dispatch planning along with coordinated set of DG units is required to achieve accurate active-power sharing. This drawback is mitigated with the proposed fully autonomous controller. Simulation results were obtained in a microgrid scenario to demonstrate the effective approach for power sharing. Experimental results are also presented.
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.
Distributed cooperative control system for smart microgrids
Electric Power Systems Research, 2016
This paper presents a decentralized control method for Electronically Interfaced Distributed Generations (EI-DGs) that controls their output frequencies, power generations, and voltages during grid-connected, islanding, and synchronizing modes. The proposed control system utilizes droop control to quickly balance generation and demand after sudden disturbances. It utilizes distributed cooperative control to stabilize the system frequency and voltage, and also to distribute the generation among DGs. Furthermore, the proposed control system adjusts the frequency and voltage to reconnect the microgrid to the main grid by utilizing only local measurements from the neighboring DGs. The proposed control system is verified on a modified IEEE Standard 399-1997 test system using MATLAB/SIMULINK and the advantages and disadvantages of the proposed method are discussed according to the results.
IEEE Transactions on Power Electronics, 2000
This paper addresses the low-frequency relative stability problem in paralleled inverter-based distributed generation (DG) units in microgrids. In the sense of the small-signal dynamics of a microgrid, it can be shown that as the demanded power of each inverter changes, the low-frequency modes of the power sharing dynamics drift to new locations and the relative stability is remarkably affected, and eventually, instability can be yielded. To preserve the power sharing stability, an adaptive decentralized droop controller of paralleled inverter-based DG units is presented in this paper. The proposed power sharing strategy is based on the static droop characteristics combined with an adaptive transient droop function. Unlike conventional droop controllers, which yield 1-DOF tunable controller, the proposed droop controller yields 2-DOF tunable controller. Subsequently, the dynamic performance of the power sharing mechanism can be adjusted, without affecting the static droop gain, to damp the oscillatory modes of the power sharing controller. To account for the power modes immigration at different loading conditions, the transient droop gains are adaptively scheduled via small-signal analysis of the power sharing mechanism along the loading trajectory of each DG unit to yield the desired transient and steady-state response. The gain adaptation scheme utilizes the filtered active and reactive powers as indices; therefore, a stable and smooth power injection performance can be obtained at different loading conditions. The adaptive nature of the proposed controller ensures active damping of power oscillations at different operating conditions, and yields a stable and robust performance of the paralleled inverter system. Index Terms-Adaptive control, decentralized control, distributed generation (DG), microgrid, parallel operation, power sharing stability.
An Overview on Microgrid Control Strategies
—In response to the ever increasing energy demand, integrating distributed energy resource-based microgrid will be the most promising power system improvement in the near future. Microgrid system implementation provides significant advantages for both electric utility provider and end customer user. This paper performs a comprehensive literature review on the current key issues on control strategies of microgrid islanded mode operation. Brief descriptions are provided for typical microgrid control methods, PQ control, droop control, voltage/frequency control, and current control, which are associated with microgrid mode of operation. This review also covers microgrid control issues such as islanded mode, stability, and unbalanced voltages to provide adequate power quality. In addition, this paper discusses the challenges of microgrid islanded mode issues, such as load sharing, distributed generation losses, and non-linear /unbalanced load. Finally, research conclusions of the important microgrid control requirements for future development are also described.
The energy sector is moving into the era of distributed generation (DG) and microgrids (MGs). The stability and operation aspects of converter-dominated DG MGs, however, are faced by many challenges. To overcome these difficulties, this paper presents a new large-signal-based control topology for DG power converters that is suitable for both grid connected and islanding modes of operation without any need to reconfigure the control system and without islanding detection. To improve MG stability and to guarantee stability and high performance of the MG system during sudden harsh transients such as islanding, grid reconnection, and large load power changes, a nonlinear MG stabilizer is proposed. We propose a novel control topology for microgrids which can work in both grid connected and islanding modes without reconfiguration so it does not require islanding detection technique, the controller is based on the concept of synchronverter In this paper, a radical step is taken to improve the synchronverter as a self-synchronized synchronverter by removing the dedicated synchronization unit.
Reactive Power Sharing Droop Control Strategy for DG Units in an Islanded Microgrid
The proposed method mainly includes two important operations: error reduction operation and voltage recovery operation. The sharing accuracy is improved by the sharing error reduction operation, which is activated by the low-bandwidth synchronization signals. However, the error reduction operation will result in a decrease in output voltage amplitude. Therefore, the voltage recovery operation is proposed to compensate the decrease., due to increasing the demand of electricity as well as rapid depletion of fossil fuels, and the government policies on reduction of greenhouse gas emissions , renewable energy technologies are more attractive and various types of distributed generation sources, such as wind turbine generators and solar photo voltaic panels are being connected to low-voltage distribution networks. Micro grid is an integrated system that contain in s distributed generation sources, control systems, load management, energy storage and communication infrastructure capability to work in both grid connected and island mode to optimize energy usage. The paper presents a advanced control technique for a micro grid system which works efficiently under a decentralized control system.