Papers by Keyword: Microgrids (MGs)

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Authors: Xiao Dong Li, Zhong Xing Dong, Wei Zong, Zong Qi Liu
Abstract: This paper analyzes the battery dynamic characteristics as well as some existing battery models, then presents a universal battery model applicable to micro-grid simulation. The model is composed of a controlled voltage source in series with a constant resistance .The voltage of the controlled voltage source is a one-to-one correspondence with the state of charge (SOC) of the battery, which can effectively avoid the algebraic loop problem. The parameters of the model can be easily extracted from the battery discharge curve. The simulation results shows that the biggest advantage of this model is that the initial SOC of the battery can be set accordingly, which allows the battery to be charged or discharged from any SOC conveniently.
458
Authors: Cheng Liu, Zhe Li, Hui Wang, Lei Xia
Abstract: Nowadays we advocate low carbon economy, energy conservation and emission reduction, emphasize the harmonious development of human being and the nature. As a result, the clean, efficient microgrid with flexible use mode is widely payed attention to. A microgrid uses natural resources as electric power source, it can effectively relieve burden of the grid, and help to solve the problem of transporting electricity from the grid to remote suburb area. How to design the structure of a microgrid to make it run harmoniously with the grid while using clean energy efficiently and controlling the microgrid reasonably is the key to developing microgrid technique. Based on the construction of microgrids in China, this paper concludes the main key techniques in designing and constructing of microgrid, introduces several typical microgrids in China, and makes an outlook to the designing of microgrid structure and technique development.
931
Authors: Gui Ying Liu, Yong Guang Gui, Shi Ping Su, Qian Luo, Jiang Wu, Xue Rui Jia
Abstract: For the different operation mode of micro-grid, an improved droop control method and a parallel inverter was proposed depending on the study of micro-grid inverter. Grid-connected interface contains a series inverter and a parallel inverter, and can be switched to select different work mode. The parallel inverter can eliminate harmonic, compensate three-phase imbalanced current to improve the quality of the power delivered to the utility grid. In islanding operation mode, the improved droop control strategy was applied, where an integral controller was introduced. So it can reduce the inverter output voltage amplitude. Thereby it can restrain circulation and realize the power of self-distribution. The effectiveness and feasibility are verified by the simulation result.
677
Authors: Ling Xiao Hu, Jing Li Mao, Bi Ling Zhang, An Shi Zhou
Abstract: Micro-grid, which coordinates distributed energy resources in a decentralized way, is a promising approach to allow distributed energy resources to provide full benefits while reducing the control burden on the grid. By exploiting the concept of cyber-physical system (CPS), prediction can be easily incorporated into micro-grid, which helps the micro-grid work more effectively and safely. In such a case, in this paper, based on CPS, we propose a novel micro-grid model, within the framework of which, a more explicit wind-solar complementary power system is presented. Moreover, we show how the closed-loop control is implemented in the proposed model which is of benefit to the design of micro-grid.
2325
Authors: Dong Liang Nan, Xiu Fan Le, Peng Peng Kang
Abstract: With the development of micro-grid, the protection and control technologies for micro-grid have withdrawn broad attention. By analyzing the interactions between the micro-grid and the main grid, a dual-processor based coordinator is proposed in the paper. This coordinator achieves the functions of protection and control through two processors, utilizing the electrical information from the whole network, realizing the wide area data sharing and sound cooperation of the unit protection and regional control in the micro-grid. The proposed method enables smooth transition between grid-connected and islanded operation, which is adaptive to any operational modes. Implemented in a demonstrative project of the micro-grid in china, this novel method is verified to be efficient.
1677
Authors: Guan Qi Liu, Ting Hu, Jin Jiao Lin
Abstract: This paper investigates a frequency coordination control strategy for islanded microgrid. The dynamic process is divided into three levels including the dynamic support, droop control and zero error regulation. The control strategy is classified into primary and secondary frequency regulation. Simulation is performed on DIgSILENT and the results verify the effectiveness of the proposed control strategy and improve the performance of system frequency regulation.
3434
Authors: Wei Si Deng, Bu Han Zhang, Hong Fa Ding, Jian Shao, Bing Jie Jin
Abstract: Distributed renewable energy connected to the power grid in the form of micro-grid, which makes a great impact on the power quality of the grid. Active Power Filter (APF) is a kind of effective device, which can improve the power supply quality and purify the power pollution. It‘s particularly significant to improve the APF’s performance. Based on the selective harmonic current control strategy, which is used to solve the problem, that the main times of the harmonic current is not sufficiently compensated, this paper considers to adopt the LCL filter on the grid-side to further improve the compensation performance of active power filter. This improvement can reduce the high frequency harmonics caused by the way of PWM high frequency modulation. Finally a case study simulated by PSIM software verifies the superiority of the proposed measure.
1240
Authors: Xiao Qi Chen, Hong Jie Jia
Abstract: The droop control is commonly used as the control strategy in microgrid. The traditional droop control only considers the relation between the active power and voltage frequency; and the relation between the reactive power and voltage amplitude.This study proposes the improved droop control ; which considers the active and reactive power are simulatedly related with both the voltage amplitude and the voltage frequency. This improved droop control not only could satisfy the load sharing in according to the capability of the distributed generations; but also represents better stability than the conditional droop control.The simulation in MATLAB/simuliink validate the effectiveness of the proposed control strategy
2228
Authors: Zhang Xi, Gui Bin Zou, Tian Chun
Abstract: Based on the analysis of the disadvantages of the several protection schemes for microgrid, the paper proposes a novel current protection scheme for microgrid. The scheme treats the typical microgrid layout as a case study and analyses the principle of operation of adaptive protection in connected mode and islanded mode about three typical faults. In addition, the algorithm and program flow about the adaptive protection, as well as the information feedback mechanism and operation time limit about the bidirectional power flow characteristics have been provided. It improves the technical challenges faced with the protection in different modes to a great extent.
977
Authors: Lei Zhou, Hong Da Liu, Ming Jie Chen, Nai Jun Shen
Abstract: On the basis of analyzing the synthesis application of p-q (instantaneous reactive power) theory and unit vector template, a multi-functional grid-connected inverter (MFGCI) with auxiliary services on power quality enhancement in micro-grid (MG) is presented. The novel control strategy for achieving maximum benefits from these MFGCI when installed in AC MG access to 3-phase 4-wire distribution systems by isolated transformer at the point of common coupling (PCC). This kind of inverter can not only deliver the power generation of renewable energy sources (RESs), but also can perform as active power filter (APF) at their PCC as well as can improve the efficiency of inverter and decrease the hardware investment. Finally, both feasibility and effectiveness of this new topologies and control strategies of MFGCI are verified by PSCAD/EMTDC.
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