scholarly journals A Generalized and Mode-Adaptive Approach to the Power Flow Analysis of the Isolated Hybrid AC/DC Microgrids

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2253 ◽  
Author(s):  
Yu Xiao ◽  
Chunguang Ren ◽  
Xiaoqing Han ◽  
Peng Wang
Keyword(s):  
Power Flow ◽  
Operation Mode ◽  
Flow Analysis ◽  
Dc Microgrid ◽  
Dc Microgrids ◽  
Operation Modes ◽  
Load Fluctuation ◽  
Practical Operation ◽  
Binary Matrices ◽  
The Time Domain

Hybrid AC/DC microgrids (HMG) are emerging as an attracting method for integrating AC/DC distributed energy resources (DERs). In the isolated hybrid AC/DC microgrid (IHMG), the key problem is how to balance power variation and regulate voltage and frequency. Various energy storage systems (ESS) and interlinking converter (IC) technologies are viable for this application. The present study proposes a novel unified power flow (PF) model which can be applied to compare and analyze the practical operation modes of the IHMG and, further, to evaluate and compare the abilities of the ESS with different connection topologies and ICs with different control approaches to maintain the voltage and frequency stability of the IHMG. Five operation modes of the IHMG are defined and explained. Then, a set of generic PF equations are derived. Moreover, three binary matrices are applied as input parameters of the unified power equations. These matrices enable a single operation mode of the IHMG at a time to be constructed in the power equation. Finally, the accuracy and effectiveness of the proposed scheme are verified against the time domain simulation result. The quasi-steady-state behaviors of multi-DC subgrids IHMG in different modes after a range of load fluctuation are investigated. The results show that the use of multiple grid-forming units in the AC and DC subgrids, when IC adopted normalized.

scholarly journals A Generalized and Mode-adaptive Approach to the Power Flow Analysis of the Isolated Hybrid AC/DC Microgrids

2019 ◽  
Author(s):  
Yu Xiao ◽  
Chunguang Ren ◽  
Xiaoqing Han ◽  
Peng Wang
Keyword(s):  
High Performance ◽  
Power Flow ◽  
Low Cost ◽  
External Disturbance ◽  
Flow Analysis ◽  
Distributed Energy ◽  
Dc Microgrid ◽  
Dc Microgrids ◽  
Binary Matrices ◽  
And Control

HybridAC/DC microgrids(HMG) are emerging as an attracting method for integrating the AC/DC distributed energy resources(DERs) with the features of high-performance and low-cost. In the isolated hybrid AC/DC microgrid (IHMG), the key problem is how to balance the power variation and regulate the voltage and frequency. Various energy storage systems (ESS)and interlinking converter (IC) technologies are viable for this application. The present study proposes a novel unified power flow model to evaluate and compare the abilities of the ESS with different connection topologies and ICs with different control approaches to maintain the voltage and frequency stability of the IHMG. In order to investigate the performance of the proposed scheme, five operation modes of the IHMG are defined and explained. The classification is based on the connection topologies and control modes of the ESS/IC in the IHMG. Then, a set of generic PF equations are derived. Moreover, three binary matrices are applied in the construction of the unified power equations. These matrices are used for describing the running state of the IHMG. Finally, in order to verify the proposed scheme, it is applied to several case studies of the IHMG. The operation characteristics of multi-DC subgrids IHMG in different modes, particularly when an external disturbance occurs, are investigated.

scholarly journals A Bus-Sectionalized Hybrid AC/DC Microgrid: Concept, Control Paradigm, and Implementation

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3508
Author(s):  
Jing Li ◽  
Hongda Cai ◽  
Pengcheng Yang ◽  
Wei Wei
Keyword(s):  
Hierarchical Control ◽  
Mode Switching ◽  
Stable Operation ◽  
Service Reliability ◽  
Test Results ◽  
Dc Microgrid ◽  
Dc Microgrids ◽  
Operation Modes ◽  
Control Paradigm ◽  
Operational Data

In the last several years, the coordination control of hybrid AC/DC microgrids (HMGs) has been gaining increasingly more attention. However, most of these discussions are focused on single-bus HMGs whose AC or DC bus is not sectionalized by AC or DC breakers. Compared with these single-bus HMGs, the bus-sectionalized HMG has more flexible topologies, more diverse operation modes, and consequently higher service reliability. However, meanwhile, these benefits also bring challenges to the stable operation of bus-sectionalized HMGs, particularly for mode switching. Relying on the national HMG demonstrative project in Shaoxing, China, this paper makes efforts to present the hierarchical control paradigm of a typical bus-sectionalized HMG toward standardization. The test results demonstrate that the proposed system provides seamless switching and uninterrupted power supply without controller reconfiguration among different operation modes. The operational data are also brought forth and analyzed to provide significant and useful experiences for designing and developing similar HMGs in the future.

scholarly journals Stability and reliability of low voltage hybrid AC-DC microgrids power flow model in islanding operation

2020 ◽  
Vol 19 (1) ◽  
pp. 32
Author(s):  
Hasti Afianti ◽  
Ontoseno Penangsang ◽  
Adi Soeprijanto
Keyword(s):  
Power Flow ◽  
Low Voltage ◽  
Flow Analysis ◽  
Steady State Condition ◽  
Dc Microgrids ◽  
Load Power ◽  
Bidirectional Converter ◽  
Islanding Operation ◽  
Stable Frequency ◽  
The Stability

The problem of decreasing and increasing power flow in hybrid AC-DC microgrids in island operations is the concern of this research. This condition arises if one sub-microgrid cannot supply load power requirements, either due to a decrease in power at the source or an increase in load on the sub-microgrid network. As a result, in this research used the bidirectional converter as an interlinking converter, the converter can change the power flow from the ac sub microgrid to the dc sub microgrid and vice versa. With this bidirectional converter, load power requirements can be met even though there is a power change in one of the sub microgrid. The simulation in this research support by Simulink/Matlab software. The model is built in a low voltage system, and the power flow analysis is in steady-state condition with two different cases. The simulation results show the stability and reliability of the power flow in both sub microgrid with stable frequency and voltage when power and load change occur.

scholarly journals Power Flow Analysis for Low-Voltage AC and DC Microgrids Considering Droop Control and Virtual Impedance

2017 ◽  
Vol 8 (6) ◽  
pp. 2754-2764 ◽  
Author(s):  
Chendan Li ◽  
Sanjay K. Chaudhary ◽  
Mehdi Savaghebi ◽  
Juan C. Vasquez ◽  
Josep M. Guerrero
Keyword(s):  
Power Flow ◽  
Low Voltage ◽  
Flow Analysis ◽  
Droop Control ◽  
Dc Microgrids ◽  
Power Flow Analysis ◽  
Virtual Impedance

scholarly journals Design and Implementation of an Energy-Management System for a Grid-Connected Residential DC Microgrid

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4074
Author(s):  
Alfredo Padilla-Medina ◽  
Francisco Perez-Pinal ◽  
Alonso Jimenez-Garibay ◽  
Antonio Vazquez-Lopez ◽  
Juan Martinez-Nolasco
Keyword(s):  
Energy Management ◽  
Management System ◽  
Operation Mode ◽  
Maximum Energy ◽  
Energy Management System ◽  
Dc Microgrid ◽  
Design And Implementation ◽  
Operation Modes ◽  
Dc Bus ◽  
Bus Voltage

The design and implementation of an energy-management system (EMS) applied to a residential direct current microgrid (DC-µG) is presented in this work. The proposed residential DC-µG is designed to provide a maximum power of one kilowatt by using two photovoltaic arrays (PAs) of 500 W, a battery bank (BB) of 120 V–115 Ah, a supercapacitor module of 0.230 F and a bidirectional DC–AC converter linked to the AC main grid (MG). The EMS works as a centralized manager and it defines the working operation mode for each section of the DC-µG. The operation modes are based on: (1) the DC-link bus voltage, (2) the generated or demanded power to each section of the DC-µG and (3) the BB’s state of charge. The proposed EMS—during the several working operation modes and at the same time—can obtain the maximum energy from the PAs, reduce the energy consumption from the main grid and keep the DC-link bus voltage inside a range of 190 V ± 5%. The EMS and local controllers are implemented by using LabVIEW and NI myRIO-1900 platforms. Moreover, experimental results during connection and disconnection of each DC-µG sections and different on-the-fly transitions are reported, these results focus on the behavior of the DC bus, which shows the DC bus robustness and stability. The robustness of the DC-µG is demonstrated by maintaining a balance of energy between the sources and loads connected to the DC bus under different scenarios.

scholarly journals Island DC Microgrid Hierarchical Coordinated Multi-Mode Control Strategy

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 3012 ◽  
Author(s):  
Zhongbin Zhao ◽  
Jing Zhang ◽  
Yu He ◽  
Ying Zhang
Keyword(s):  
Power Systems ◽  
Control Strategy ◽  
Voltage Stability ◽  
Dc Microgrid ◽  
Dc Microgrids ◽  
Mode Control ◽  
Load Power ◽  
Power Dispatch ◽  
Operation Modes ◽  
Multi Mode

As renewable energy sources connecting to power systems continue to improve and new-type loads, such as electric vehicles, grow rapidly, direct current (DC) microgrids are attracting great attention in distribution networks. In order to satisfy the voltage stability requirements of island DC microgrids, the problem of inaccurate load power dispatch caused by line resistance must be solved and the defects of centralized communication and control must be overcome. A hierarchical, coordinated, multiple-mode control strategy based on the switch of different operation modes is proposed in this paper and a three-layer control structure is designed for the control strategy. Based on conventional droop control, a current-sharing layer and a multi-mode switching layer are used to ensure the stable operation of the DC microgrid. Accurate load power dispatch is satisfied using a difference discrete consensus algorithm. Furthermore, virtual bus voltage information is applied to guarantee smooth switching between various modes, which safeguards voltage stability. Simulation verification is carried out for the proposed control strategy by power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC). The results indicate that the proposed control strategy guarantees the voltage stability of island DC microgrids and accurate load power dispatch under different operation modes.

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