An Improved Droop Control Method for Accurate Power Sharing and Bus Voltage Restoration in DC Microgrid

2019 ◽  
Author(s):  
Haifeng Liang ◽  
Ji Bian ◽  
Yuxi Huang
Keyword(s):  
Control Method ◽  
Power Sharing ◽  
Droop Control ◽  
Dc Microgrid ◽  
Bus Voltage

scholarly journals Capacity Limitation Control of Multiple Bi-directional DC-DC Converters for Micro Grid Application

2015 ◽  
Vol 2 (1) ◽  
pp. 61 ◽  
Author(s):  
S. J. Chiang ◽  
Yu-Min Liao ◽  
Ke-Chih Liu
Keyword(s):  
Power Management ◽  
Control Method ◽  
Droop Control ◽  
Control Methods ◽  
Power Capacity ◽  
Capacity Limitation ◽  
Current Sharing ◽  
Parallel Control ◽  
Micro Grid ◽  
Bus Voltage

The micro grid system requires battery for energy storage and power management. In which, the bi-directional DC to DC converter is the key component for maintaining the DC bus voltage and controlling the charge and discharge of the battery with or without grid support. Parallel control of multiple DC to DC converters is a critical technique to enlarge the power capacity. This paper presents two capacity limitation control methods that multiple DC to DC converters can be paralleled with distributed battery banks. The first method is the capacity limitation control with cascaded load current sense needing no control interconnection. The second method is the capacity limitation control with master-slave and cascaded current command limitation. Two methods are presented to solve the limitation of droop control method and active current sharing method respectively, and can be extended without converter number limitation theoretically. Three prototype 240W bidirectional half-bridge DC to DC converters are built and paralleled in this paper. The proposed method is confirmed with some measured results.

scholarly journals New adaptive droop control with combined line impedance estimation method for parallel inverters

2016 ◽  
Vol 19 (4) ◽  
pp. 45-64
Author(s):  
Phuong Minh Le ◽  
Duy Vo Duc Hoang ◽  
Hoa Thi Xuan Pham ◽  
Huy Minh Nguyen
Keyword(s):  
Kalman Filter ◽  
Control Method ◽  
Least Squares Method ◽  
Estimation Method ◽  
Load Sharing ◽  
Phase Lock Loop ◽  
Power Sharing ◽  
Voltage Source ◽  
Droop Control ◽  
Voltage Source Inverters

This paper presents a new load sharing control between paralleled three-phase inverters in an islanded-microgrid based on the line impedance estimation online by the use of the Kalman filter. We can solve the mismatch of power sharing when the line impedance changes due to the temperature and frequency, significant differences of line parameters and requirements of Plug-and-Play mode of inverters connected to the microgrid. Moreover, the paper also presents a new Droop control method working with the line impedance which is different from the Droop traditional algorithm when the line impedance is assumed pure resistance R or pure inductance X. In the paper, the line impedance estimation for parallel inverters uses the least squares method combined with Kalman filter. In addition, secondary control loops are designed to restore the voltage amplitude and frequency of the microgrid by using a combined nominal value SOGI-PLL with generalized integral block and phase lock loop to exactly monitor the voltage magnitude and frequency phase at common PCC. Control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of the power sharing. The simulation results have shown the accuracy of the proposed control method. Therefore, the proposed adaptive droop control method based on line impedance estimation can be an alternative one for load sharing control in islanded microgrids.

scholarly journals Robust Control Method for DC Microgrids and Energy Routers to Improve Voltage Stability in Energy Internet

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1622 ◽  
Author(s):  
Haochen Hua ◽  
Yuchao Qin ◽  
Hanxuan Xu ◽  
Chuantong Hao ◽  
Junwei Cao
Keyword(s):  
Power Transmission ◽  
Control Method ◽  
Voltage Regulation ◽  
Normal Operation ◽  
Local Network ◽  
Linear Matrix ◽  
Dc Microgrid ◽  
Voltage Stabilization ◽  
Energy Internet ◽  
Bus Voltage

The energy internet (EI) is a wide area power network that efficiently combines new energy technology and information technology, resulting in bidirectional on-demand power transmission and rational utilization of distributed energy resources (DERs). Since the stability of local network is a prerequisite for the normal operation of the entire EI, the direct current (DC) bus voltage stabilization for each individual DC microgrid (MG) is a core issue. In this paper, the dynamics of the EI system is modeled with a continuous stochastic system, which simultaneously considers related time-varying delays and norm-bounded modeling uncertainty. Meanwhile, the voltage stabilization issue is converted into a robust H ∞ control problem solved via a linear matrix inequality approach. To avoid the situation of over-control, constraints are set in controllers. The problem of finding a balance between voltage regulation performance and constraints for the controllers was also extensively investigated. Finally, the efficacy of the proposed methods is evaluated with numerical simulations.

scholarly journals Multi-level bus voltage compensation of droop control with enhanced load-sharing capability for DC microgrid

2019 ◽  
Vol 2019 (16) ◽  
pp. 3056-3061 ◽  
Author(s):  
Sucheng Liu ◽  
Zhongpeng Li ◽  
Wenjie Liu ◽  
Xiaodong Liu
Keyword(s):  
Load Sharing ◽  
Droop Control ◽  
Dc Microgrid ◽  
Voltage Compensation ◽  
Multi Level ◽  
Bus Voltage

scholarly journals The Hierarchical Control Algorithm for DC Microgrid Based on the Improved Droop Control of Fuzzy Logic

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2995 ◽  
Author(s):  
Liang Zhang ◽  
Kang Chen ◽  
Shengbin Chi ◽  
Ling Lyu ◽  
Guowei Cai
Keyword(s):  
Fuzzy Logic ◽  
Control Algorithm ◽  
Voltage Drop ◽  
Hierarchical Control ◽  
Voltage Regulation ◽  
Droop Control ◽  
Dc Microgrid ◽  
Current Sharing ◽  
The Difference ◽  
Bus Voltage

In the direct current (DC) microgrid composed of multiple distributed generations, due to the different distances between various converters and the DC bus in the system, the difference of the line resistance will reduce the current sharing accuracy of the system. The droop control was widely used in the operation control of the DC microgrid. It was necessary to select a large droop coefficient to improve the current sharing accuracy, but a too large droop coefficient will lead to a serious bus voltage drop and affect the power quality. In view of the contradiction between the voltage regulation and load current sharing in the traditional droop control, a hierarchical control algorithm based on the improved droop control of the fuzzy logic was proposed in this paper. By improving the droop curve, the problems of voltage regulation and current sharing were solved simultaneously. The effectiveness of the algorithm was verified by simulation.

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