Research On Robust Scheduling Of Distributed Generation In Stand-alone Microgrid

Nowadays,human economy and civilization are in an unprecedented period of rapid development,but the good situation is accompanied by the aggravation of energy crisis,the deterioration of the earth's environment and other problems.In order to make people get rid of the dilemma of over dependence on traditional energy,a batch of distributed generation technology based on renewable energy was born.With the concept of "micro grid" put forward,the original decentralized single distributed power generation forms a system scale in an efficient and orderly combination form,which is conducive to control and regulation,and plays an increasingly important role in the modern power system structure.Therefore,how to design a set of control system which can ensure the stable operation of micro grid in the conventional island or grid mode and realize the smooth switching between island / grid mode is the inevitable requirement of human development in the new energy field.Firstly,this paper summarizes the structure and characteristics of micro-grid by analyzing the development of micro-grid technology at home and abroad.This paper analyzes the advantages and disadvantages of three kinds of conventional micro grid control structures,points out the important advantages of the master-slave structure in the current micro grid technology application and research,and takes it as the theoretical basis of the research experiment.Then,three kinds of conventional inverter control strategies are analyzed in detail,and their control principles and application limitations are described in detail.Then,the performance and characteristics of the inverter based on power electronic devices are described,which shows that it does not have the physical advantages of traditional synchronous generator to deal with the transient problems of the system,and leads to the virtual synchronous generator control.By introducing the control principle of the traditional synchronous generator,the control strategy of the virtual synchronous generator is designed according to the mathematical model of its rotor motion.The inverter successfully simulates the traditional synchronous generator,which has certain external characteristics and damping characteristics,and improves the ability of the micro grid to deal with the sudden change of load.Based on the results of mathematical model derivation and simulation experiments,the specific role of key parameters in the regulation process is analyzed in detail.This paper analyzes the problems in the process of parallel / off network switching in detail,and then puts forward the corresponding solutions to these problems.Firstly,aiming at the problem of steady-state error in traditional PI control pre-synchronization,an improved pre-synchronization regulation method is proposed to improve the steady-state error accuracy of pre-synchronization regulation;secondly,aiming at the problem of power fluctuation in VSG control at the time of grid connection,an improved PQ control is proposed to weaken the power impact of inverter switching from VSG to PQ control at the time of grid connection;aiming at grid connection In the process of switching to islanding operation mode,an off grid phase tracking control method is proposed to reduce the phase mutation in off grid micro-grid..Finally,according to the proposed control theory,the corresponding simulation experiment model is designed with Matlab/Simulink software platform to verify the effectiveness of the theory.The theory of this paper can solve the transient problem of the micro-grid mode switching,which can not only ensure the stable operation of the micro-grid when it is in island or grid mode,but also realize the smooth switching between the two modes.