Implementation and Stability Study of Dynamic Droop in Islanded Microgrids (original) (raw)
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International Journal of Renewable Energy Research, 2019
Conventional droop-control scheme shares the load amongst energy sources in proportion to their ratings. The scheme suffers from the issue of ineffective utilization of the sources when performance of some of the sources is dependent on environmental conditions. Hence, a modified droop-control strategy is proposed for a microgrid comprising of photovoltaic (PV) based distributed generators (DG) operating in parallel with other DGs. Dynamic nature applied to the droop characteristic by the primary control unit (PCU) sets the frequency reference such that the PV sources operate at their maximum power point and the energy demanded from the auxiliary source is the minimum. The margin available after supplying the active power is used to allocate the references for reactive power sharing. The reactive power sharing algorithm employed in secondary control unit (SCU) ensures that the standard deviation of the percentage utilization of the inverters is kept the minimum. Even in case of the failure of the communication between the PCU and SCU, a reasonably good performance is ensured as the control shifts to the master-slave control having dynamic droop adjustment feature. The effectiveness of the proposed strategy against other approaches is justified through the simulation results obtained in MATLAB/Simulink.
2013 IEEE Power & Energy Society General Meeting, 2013
Microgrids provide a coordinated integration of distributed generation units in the electrical power system. By operating in islanded mode, they can increase the reliability of the system or electrify remote areas. For the power sharing and voltage control in low-voltage microgrids, active power/grid voltage droop control is highly suitable. In order to optimize the integration of renewable energy sources in the microgrid, a variant of this droop control, the voltage-based droop (VBD) control, has been presented. A well-known concern about droop controllers is the inherent trade-off between voltage control and power sharing. Therefore, in this paper, an additional control loop is included in the VBD control to improve the active power sharing ratio. In this way, accurate power sharing is achieved, i.e., the DG units respond to load changes exactly according to their droops. Although this modification relies on communication, it does not jeopardize the reliability of the microgrid as if the communication is lost, the basic VBD control still ensures a stable microgrid operation, while operating without the need for communication.
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.
IET Generation, Transmission & Distribution
This study proposes a new frequency control of islanded and storage independent wind-powered microgrid based on coordinated robust dynamic droop power sharing. The islanded microgrid includes wind turbine as undispatchable distributed generation (DG) and fuel cell as dispatchable DG. In the first layer of control, the reverse and direct droop controls are considered for wind turbine and fuel cell, respectively. Accordingly, the outputs of reverse droop control are active and reactive powers, which are used for wind turbine. Simultaneously, the outputs of direct droop control are frequency and voltage, which are used for the fuel cell. Since the generated power of wind turbine is not constant, so the coordinated dynamic droop coefficients for both DGs are modified as a function of available wind power. Then in the second layer, robust sliding mode control is designed for setpoints tracking of both DGs to control the frequency and voltage of islanded microgrid. The effectiveness evaluation of the proposed control scheme is performed by simulation studies on the islanded microgrid in different conditions such as single-phase fault, load step change and variety of wind speeds in MATLAB/Simulink environment. Finally, results are validated experimentally through the implementation of real-time hardware-in-the-loop system.
Reactive Power Sharing in Islanded Microgrid by Droop Control Method
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.
IRJET, 2021
Recent climatic changes have led to the increase in utilization of sustainable Distributed Generation (DG) resources such as fuel cells using natural or biogas, wind, solar etc. To meet the ever increasing energy requirement, society is moving to renewable sources like solar energy, wind energy etc, as it is pollution free, clean and available in plenty. In this paper , a micro grid model is designed using PV cell by using two different control strategies have been analyased. Droop control and advanced dynamic droop control methods have been explained in this paper In both these techniques, there is no need of communication line and maximum power is extracted from solar panel using Perturb and Observe method. The LC filters are designed to eliminate harmonic current. The conventional droop control has poor voltage regulation at heavy load condition and poor power sharing performance at light load condition. The conventional P-Q droop methods shares the active power based on fixed droop coefficient irrespective of available energy from non conventional energy source. The disadvantages of the conventional droop control can be reduced with the use of advanced dynamic droop control. PV models with droop control and advanced dynamic droop control have been designed and compared using matlab/simulink models
Droop control technique for equal power sharing in islanded microgrid
International Journal of Power Electronics and Drive System (IJPEDS), 2019
This paper presents a droop control technique for equal power sharing in islanded microgrid. In this study, the proposed controller is based on the frequency droop method, is applied to a robust droop controller in parallel connected inverters. The previous robust droop controller deals with voltage droop method. A modification has been formed against this controller by adding a fuzzy logic controller with the frequency droop method. The only sharing error which is concentrated in this paper is the error in sharing the rated frequency among the inverters. By adapting fuzzy in the robust droop, it tries to eliminate the frequency error, hence that the frequency reference of the inverters keeps maintain at 50Hz. A derivation of generalized models of a single-phase parallel-connected inverter system is shown. The simulation results show that the proposed controller with FLC is able to improve the stability of frequency reference and the performance of power sharing between the inverters under the inductive line impedance.
Adaptive Fuzzy Droop Control for Optimized Power Sharing in an Islanded Microgrid
Energies, 2018
With the serious environment pollution and power crisis, the increasing of renewable energy resource (RES) becomes a new tendency. However, the high proportion of RES may affect the stability of the system when using the conventional droop control with a fixed droop coefficient. In order to prevent the power overloading/curtailment, this paper proposes an adaptive fuzzy droop control (AFDC) scheme with a P-f droop coefficient adjustment to achieve an optimized power sharing. The droop coefficient is adjusted considering the power fluctuation of RES units and the relationship of power generation and demand, which can realize the stability requirements and economic power sharing for the islanded microgrid. What is more, a secondary control is considered to restore the frequency/voltage drop resulting from the droop control. The proposed strategy improves the stability and economics of microgrid with a droop-based renewable energy source, which is verified in MATLAB/Simulink with three...
Journal of Operation and Automation in Power Engineering, 2023
The widespread adoption of microgrids in electric power systems has brought numerous advantages such as decentralized control, reliability, cost-effectiveness, and environmental benefits. However, one of the most critical challenges faced by islanded microgrids is ensuring frequency and voltage stability. This paper addresses these stability issues that arise when microgrids operate independently, disconnected from the main network through the point of common coupling (PCC). These microgrids rely on renewable resources like photovoltaic (PV) systems, wind turbines, and energy storage systems, which often require DC to AC conversion through inverters to simulate synchronous generators. To overcome the frequency and voltage stability challenges, this research utilizes the droop control technique to regulate the active and reactive power of distribution generators (DGs). The droop control technique is implemented and simulated using MATLAB software, specifically employing a multi-DC bus-based inverter. The simulation results demonstrate that the DGs successfully supply the required total power to meet load demands while maintaining frequency and voltage stability. Through the droop control technique, active and reactive power sharing is achieved, ensuring stability at nominal values. The DGs can effectively maintain a constant power profile at desired values, even in the presence of static and dynamic loads.