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Micro-grid Based On Virtual Impedance Inverter Control Strategies

Posted on:2016-09-14Degree:MasterType:Thesis
Country:ChinaCandidate:G S WuFull Text:PDF
GTID:2272330479950490Subject:Electrical engineering
Abstract/Summary:PDF Full Text Request
A systematic organization which contains the DG systems, energy storage devices and inverters forms a microgrid. The microgrid has two operational modes: the grid-connected mode and islanding mode. With the characteristic of flexible power supply, the microgrid provides enhanced reliability and power quality. Most of the microsources in microgrid connect into the ac power grid side through inverters which is an important part for energy exchange, so inverter control is the key to the stable and reliable operation of microgrid.The traditional control strategy of interfacing inverter in mircogrid was studied in this paper firstly. In the islanding mode, when the distributed generations are operating in parallel, the circulating current would appear and the stability of the system would be affected,which were due to the inconsistency between the line impedance and the point of common coupling. Then the problems from the resolution of traditional virtual impedance was analyzed and the adaptive virtual impedance methodwhich is able to calculate the virtual resistance based on inverter output power and the actual value of the line resistance was discussed. Afterwards,the method was simulated and proved that the adaptive virtual impedance method permits the resistance of smaller value,when comparing with traditional method which includes virtual impedance aimed to achieving power-sharing,so as to maintain the precision of the output voltage from the result.The strategy of Dropping control in distributed generation was specified in this paper,which was introduced virtual impedance. And the active voltage-port(P-U) virtual impedance of drooping closed-loop correction was also studied, virtual impedance is introduced at the same time, lowered down slope and closed-loop control ports voltage droop characteristic, eliminates virtual impedance Voltage dips and increase the stability of the system. The microgrid Simulation model is established by using MATLAB/simulink software and proved the validity and rationality of the improved control method in terms of averaging current and stabilizing the value of the voltage.The experimental platform was set up which consists of two three-phase inverters controlled by DSP.The experimental of the proposed control strategy was completed based on the platform.The experimental results show that the control method can not only improve the voltage steady-state value,but also achieve precise power sharing.
Keywords/Search Tags:microgrid, inverters in parallel, virtual resistance, power sharing
PDF Full Text Request
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