Applying Improved Droop Control to Hybrid Microgrid Control (original) (raw)
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An Improved Droop Control Method to Enhance Dynamic Performance of AC Microgrid
2018 20th National Power Systems Conference (NPSC), 2018
The sources, interfaced with the microgrid using power electronic converters have inherently low physical inertia. With step variation in load demand, voltage and frequency difference are created among the sources during transient and the low frequency oscillations appear in the power supplied through the interconnecting lines. This may even lead to false triggering of fault protection system. To suppress these transient in powers and to improve dynamic response of microgrid in islanded mode, a modified droop controller which uses dynamic variation in droop gains of active power frequency (P − ω) characteristics is proposed. The variation of droop gains is based on the rate of change of active power supplied by the corresponding source. Key advantages offered by the modified droop controller are improved dynamic response with reduced peaks in power supplied by the sources during step change in load power demand. The effectiveness of the proposed technique is demonstrated using linearized model derived for microgrid taking into account the dynamics of proposed controller, loads and distribution network. The root loci plots are used to study the behavior of the ac microgrid with respect to variation in parameters of proposed controller. The effectiveness of the controller is validated using simulation study in Simulink/Matlab for a microgrid test model.
A Droop Controlled Operation of Interlinking Converters for Power Sharing in Hybrid AC/DC Subgrids
2018 20th National Power Systems Conference (NPSC), 2018
In this paper, the power sharing among ac and dc subgrids (ACS and DCSs) which are connected through a droop controlled interlinking converter (IC) is studied. A new method is proposed to manage the power sharing in hybrid ac/dc microgrids and to reduce the complexity in delivering efficient load power during islanded mode of operations. In this work, both ac and dc droop gain values are used to regulate ac frequency and dc voltage at the point of IC. A reliable power sharing method for hybrid system is evaluated at all the operating scenarios of loading and generation conditions. Finally, MATLAB/Simulink based timedomain simulation results are presented to demonstrate the effectiveness of the proposed method under the different power flow conditions.
IEEE Access
This work analyzes interlinking converter control in hybrid AC/DC microgrids. The paper addresses the state-of-the-art general hybrid microgrid structure. The key power electronics topologies are used as bidirectional interface converters in the AC and DC parts. Different control structures of hybrid microgrids are categorized, followed by the classification of the main control functions, their control strategies, and the control techniques and a summary of their positive and negative aspects and applications. Control functions, strategies and techniques are classified in the interlinking-converter based. Finally, overall control objectives, time-scaled control structures, and their strategies are outlined. The prospects, main challenges, research gaps, and the trend of the hybrid microgrid structure and control are reviewed and summarized in the conclusions. INDEX TERMS Bidirectional interface converter, control objectives, distributed generator, droop, hierarchical control, hybrid microgrid, island detection, power-sharing, power quality.
Modelling and simulation for energy management of a hybrid microgrid with droop controller
International Journal of Electrical and Computer Engineering (IJECE), 2023
The most efficient and connected alternative for increasing the use of local renewable energy sources is a hybrid microgrid, these systems face additional challenges due to the integration of power electronics, energy storage technologies and traditional power plants. The hybrid alternating currentdirect current (AC-DC) microgrid that is the subject of this research uses a primary-droop control system to regulate state variables and auxiliary services, thus, it is composed of batteries, solar panels and a miniature wind turbine (PDC) and controls how each energy source in a microgrid contributes to the final product. To achieve the given objectives, this paper will create appropriate models for each part of the microgrid design and define, among them, the energy storage batteries and power electronic converters required for each level of each of these systems. Finally, the dynamic nature of the system will be critically evaluated and characterized, to distribute the load and reduce imbalances, modify the primary drop of the resulting microgrid using MATLAB simulation.
Due to various technical, economic and environmental concerns the concept of Microgrid has become popular in the electric energy industry. It's capability to operate in both grid-connected as well as an autonomous system in islanded mode is the distinct feature of the Microgrid concept. Hence, Microgrid control should provide seamless transition between grid-connected and islanded operations. Active-reactive (PQ) power control and voltage source inverter (VSI) control are two popular techniques employed in Microgrid control. This paper proposes a simplified VSI controller for dynamic analysis of the Microgrid operation. The proposed control algorithm is explained, modeled in MATLAB Simulink and the simulation results are presented for various operating scenarios to demonstrate the effectiveness of the proposed control scheme in providing a desirable dynamic performance for both the grid-connected and islanded operation mode of the Microgrid.
SIMULATION ANALYSIS OF POWER CONTROL USING DROOP CONTROL METHOD IN AC-DC MICROGRID
Due to the fast proliferation of distributed generators (DGs) in power systems, managing the power of different DGs and the grid has become crucial, and microgrid provides a promising solution. Therefore, focus on ac and dc microgrids has grown rapidly with their architectural, modeling, stability analysis and enhancement, power quality improvement, power sharing control, and other issues. Most developments mentioned above on micro grids are, however, directed at DG control mainly within one microgrid.
An improved control scheme based in droop characteristic for microgrid converters
Electric Power Systems Research, 2010
Power-quality a b s t r a c t In the present work, an improved version of the conventional-droop control for microgrid converter is presented. The modifications added to the control are based on a feed-forward current control that allows the converter to work in several modes, both when it is grid connected or in island. The use of this control represents the main contribution of this paper, permitting the inverter to work as a grid supporting source or ancillary services provider when it works grid connected. In this mode the converter varies the injected active and reactive power with the variation of voltage module and frequency using the same main control loop as when it is working in island mode.
Hierarchical Control of Parallel AC-DC Converter Interfaces for Hybrid Microgrids
IEEE Transactions on Smart Grid, 2000
In this paper, a hierarchical control system for parallel power electronics interfaces between ac bus and dc bus in a hybrid microgrid is presented. Both standalone and grid-connected operation modes in the dc side of the microgrid are analyzed. Concretely, a three-level hierarchical control system is implemented. In the primary control level, the decentralized control is realized by using the droop method. Local ac current proportional-resonant controller and dc voltage proportional-integral controller are employed. When the local load is connected to the dc bus, dc droop control is applied to obtain equal or proportional dc load current sharing. The common secondary control level is designed to eliminate the dc bus voltage deviation produced by the droop control, with dc bus voltage in the hybrid microgrid boosted to an acceptable range. After guaranteeing the performance of the dc side standalone operation by means of the primary and secondary control levels, the tertiary control level is thereafter employed to perform the connection to an external dc system. Meanwhile, the impact of the bandwidth of the secondary and tertiary control levels is discussed. The closed-loop model including all the three control levels is developed in order to adjust the main control parameters and study the system stability. Experimental results of a kW parallel ac-dc converter system have shown satisfactory realization of the designed system. Index Terms-Hierarchical control, hybrid microgrid, parallel power electronics converter interface.
Analysis of voltage droop control method for dc microgrids with Simulink: Modelling and simulation
2012 10th IEEE/IAS International Conference on Industry Applications, 2012
This work presents a perfomance study of a dc microgrid when it is used a voltage droop technique to regulated the grid voltage and to control the load sharing between different sources. A small model of a dc microgrid comprising microsources and loads was implemented in the SimulinklMatlab environment. Some aspects about centralized (master-slave) and descentralized (voltage droop) control strategies as well as the procedures to design the controllers, with and without droop control, are presented and discussed. Simulation results obtained with the digital model of the dc microgrid with three microsources will be presented to validate the effectiveness of the voltage droop strategy, applied to proportional and proportional-integral controllers, to regulate the microgrid voltage.
IET Smart Grid, 2021
Hybrid AC-DC microgrids (HMGs) are formed by interconnecting AC microgrids (MGs) and DC microgrids via AC-DC interlinking converters (ICs). In the islanded mode, apart from power sharing in a single MG, power sharing expansion throughout HMG is desirable. Conventionally, this is achieved by employing an IC control mechanism in coordination with the droop characteristics of sources. Because the conventional control strategy of IC relies on measuring the frequency variations in AC MG, accurate coordination necessitates a wide range of frequency deviation. Also, this strategy employs the current-controlled method, which fails to accomplish superior voltage quality during load transients and in the presence of an unbalanced load obtainable by the voltage-controlled method (VCM). An IC control strategy for single IC HMGs is proposed that does not require the measurement of frequency variation and employs VCM in the inner control loop. As a consequence, the power quality of AC MG is improved. The proposed control strategy is phase locked-loop-less. In addition, by supporting the related MG with the disconnection of sources in AC MG or DC MG, it provides a uniform control property. Time domain simulations and experimental results are provided to verify the efficacy of the proposed strategy. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.