Applicability of Droop Regulation Technique in Microgrid - A Survey (original) (raw)
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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...
Modified droop control scheme for load sharing amongst inverters in a micro grid
Advances in Energy Research, 2015
Microgrid, which can be considered as an integration of various dispersed resources (DRs), is characterized by number of DRs interfaced through the power electronics converters. The microgrid comprising these DRs is often operated in an islanded mode. To minimize the cost, reduce complexity and increase reliability, it is preferred to avoid any communication channel between them. Consequently, the droop control method is traditionally adopted to distribute active and reactive power among the DRs operating in parallel. However, the accuracy of distribution of active and reactive power among the DRs controlled by the conventional droop control approach is highly dependent on the value of line impedance, R/X i.e., resistance to reactance ratio of the line, voltage setting of inverters etc. The limitations of the conventional droop control approach are demonstrated and a modified droop control approach to reduce the effect of impedance mis-match and improve the time response is proposed. The error in reactive power sharing is minimized by inserting virtual impedance in line with the inverters to remove the mis-match in impedance. The improved time response is achieved by modifying the real-power frequency droop using arctan function. Simulations results are presented to validate the effectiveness of the control approach.
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.
Improvement of Reactive Power Sharing and Control in Networked Microgrid
2013
An important task of microgrid is to share the load demand using multiple Distributed Generation (DG) units. The total load demand shared by multiple DG units with different conventional droop control and its variants have been reported in literature. Frequency droop control and voltage droop control methods are introduced to share real and reactive power in microgrid. The power sharing at the steady state is always accurate while reactive power sharing is sensitive to the impacts of mismatched feeder impedance. Due to the mismatched feeder impedance in microgrid, the reactive power sharing errors and power control stability problem occur. For a networked microgrid configuration with linear and non linear loads, the reactive power sharing is more challenging. For improvement of reactive power sharing and control in networked microgrid, a control method is introduced to reduce reactive power sharing errors by injecting a small real power disturbance, which is activated by the low-ban...
Enhanced Droop Control Technique for Parallel Distributed Generations in AC Microgrid
2021
In a microgrid, distributed generations (DGs) such as solar photovoltaic and energy storages(ESs) are interfaced with the AC network through power electronic-based inverters. Due to the low inertia of the solar photovoltaic system, the inverter controls become crucial for improving the power quality. State-of-the art conventional droop control in the inverters face problems such as large voltage and frequency deviations and improper reactive power sharing during various contingencies. This paper presents a simulation model of a stand-alone microgrid with solar photovoltaic source with an enhanced droop control technique which is able to mitigate the constraints of conventional droop control. In order to improve the transient response and appropriate reactive power sharing, proposed control technique explores the addition of derivative of active power for the frequency droop control and the rms output voltage from the inverter for the reactive power control. The simulation results of the proposed controller are obtained and compared with the conventional droop control methods using MATLAB/Simulink.
A Novel Approach for Active and Reactive Power Sharing in Microgrids
2016
The parallel action of inverters in microgrids is supported on droop process. The actual droop process comprises of rectifying the final voltage frequency and size to obtain self-standing power sharing without control wire interconnections. The actual voltage droop process reveals several drawbacks such as interior multiloop feedback control, frequency and voltage deviations. This paper intends a modern control tactic in microgrid applications by bringing down the substantial flux in place of the inverter final voltage. Firstly, the substantial flux and the active and reactive powers are mathematically obtained and a relationship is established between them which are employed to promote a modern flux droop technique. A small signal model is improved in direction to sketch the main control parameters and to study the steadiness as well as the system dynamics. A direct flux control step by step technique is used to adjust the substantial flux agreeing to the droop controller to evade ...
IEEE Transactions on Power Systems, 2010
- Improvement of stability and load sharing in an autonomous microgrid using supplementary droop control loop. IEEE Transactions on Power Systems. (Unpublished) ABSTRACT: This paper investigates the problem of appropriate load sharing in an autonomous microgrid. High gain angle droop control ensures proper load sharing, especially under weak system conditions. However it has a negative impact on overall stability. Frequency domain modeling, eigenvalue analysis and time domain simulations are used to demonstrate this conflict. A supplementary loop is proposed around a conventional droop control of each DG converter to stabilize the system while using high angle droop gains. Control loops are based on local power measurement and modulation of the d-axis voltage reference of each converter. Coordinated design of supplementary control loops for each DG is formulated as a parameter optimization problem and solved using an evolutionary technique. The supplementary droop control loop is shown to stabilize the system for a range of operating conditions while ensuring satisfactory load sharing.
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.