Research On The Power Quality Problems Of The Micro-grid And Its Improvement Measures

In recent years,with more and more in-depth study of micro-grid,its range of applications has continued to expand,the variety and quantity of distributed generation power has also been greatly improved.Meanwhile,there are many power quality problems occur within the exercise of micro-grid.Therefore,it is necessary to make specific analysis of the correlation of the micro-grid system and its power quality problems.Moreover,propose improvement measures of micro-grid power quality problems in this context.Firstly,three kinds of commonly used control strategies of a single distributed generation power have been studied,namely PQ control,V/f control and Droop control,as well as two control strategies of overall micro-grid.Master-slave control and peer-to-peer control are involved in the strategies which have been studied.By using formulas,block diagrams and other methods,a detailed analysis of the fundamental contents,structures and control objectives of each control method is given,and the corresponding simulation models are established.The advantages disadvantages and suitable using places of each control method are summarized.All above lays out the foundation for the study of micro-grid power quality.Secondly,according to the existing micro-grid power quality problems,like harmonic current influence and voltage fluctuation,this paper proposes the comprehensive improvement measures by using active power filter(APF)and static var compensator(SVC)combined with micro-grid control strategy to improve the micro-grid power quality problems.Through the analysis of working principle,structure and application of APF and SVC,we focus on the APF harmonic current detection technology,the current tracking control technology and voltage control of direct current side and SVC.On this basis,this paper focuses on the micro power quality monitoring strategy based on multi-agent system(MAS).With the development of distributed generation technologies,lack of flexibility and scalability of traditional centralized intelligent control methods has been difficult to adapt to the rapid growth of distributed power.For the shortcomings of traditional solutions,this paper presents micro power quality monitoring system based on MAS.With the autonomy,collaboration,communication,perception of Agent and the distributed features of MAS,the system not only can unified control and manage the various distributed microgrid,but also be able to adapt to the distributed nature of the micro-grid itself has to reduce the difficulty of control.After the specific needs of the micro-grid power quality monitoring conducted detailed analysis,based on the overall system architecture of MAS;Analysis of the specific functions and implementation of Object-controlled Agent,Micro-grid Agent and Distribution Agent;Presented each Agent communication implementations based on the "Blackboard" and "point-to-point" between the ways of combining;Presented theimplementation of single Agent,based on the Reactive Agent and Deliberative Agent;Focuses on the coordinated control strategy of power quality,based on the coordinated interaction between Agent in the normal and emergency situations.Finally,we build the corresponding simulation models with PSCAD/EMTDC simulation software to verify the improvement measures of micro-grid proposed through this paper.The results not only shows that the integrated management measures proposed in this paper can make effective impacts on the power quality problems of micro-grid,but also proves the correctness and effectiveness of this measures.