Analysis And Control Of Three Phase Imbalance In Microgrid System With Islanding Operation

The three-phase balance of power system is one of the important indicators of power quality,it is necessary to solve three phase equilibrium problem,and the unbalanced three-phase is a very old problem,but the emergence of micro-grid makes the problem become more prominent and diversified.The so-called three-phase imbalance,which is caused by a number of factors,such as poor design,asymmetric parameters,users use large-power single-phase load.If the power system appears three-phase imbalance,it will cause the related electrical equipment in this area to enter the bad working state,such as the additional heat and vibration of the rotating motor,the increase of power line loss,the reduction of equipment efficiency,and even cause the equipment to burn down.The huge power system will be affected by three-phase imbalance,the relatively small micro-grid is overwhelmed,or may cause extinction,not to mention the micro-grid in the single-phase load tends to occupy a higher proportion.In order to control and improve three-phase unbalanced state,this paper combines various methods and uses modern optimization technology theory to analyze,authenticate and combine the simulation data to make the whole system be unified into a system of maintaining the relative balance.In order to solve the three-phase imbalance problem in micro-power grid,and in view of the difference between the micro-grid and the traditional power grid,this paper puts forward a multi-level strategy to solve this problem,and maintains the system balance more perfectly and more effectively through three different principles and different technical means.First of all,this paper briefly introduces the calculation methods of the damage and unbalance of three-phase unbalance in the micro-power grid,and combines the local compensation principle with the single support system as the reference model to discuss the recovery condition of the balance in various cases.The control of inverter is used as a measure to solve the unbalanced problem of three-phase power network.Then,the theory analysis and simulation based on symmetrical component method and instantaneous power method are given respectively.According to the specific model,the three-phase compensation is calculated,and the compensation network is controlled by the distributed network compensation principle and the PWM control pulse.Finally,this paper puts forward the characteristics of the unique single-phase power supply with the micro-grid,and puts the single-phase power into the system in the initial stage of unbalanced production to maintain the balance of parameters,but it will cause unbalance of Transformers along the line and discuss the advantages of using single-phase transformer at the last stage.In this paper,the Matlab/simulink software is used to simulate and analyze to find the best balance point.Conclusion: Through the above multilevel control strategy,we can solve the three-phase unbalance problem in the micro-power grid,and have good coping ability for the three-phase unbalanced state.Meet the requirements of modern power system for power supply reliability and power supply quality.