Research On Inverter Interfaced Distributed Generation Control Strategy And Islanding Detection

With the increasing impact of the energy crisis on social progress,the development of green clean renewable energy is getting more attention.Distributed generation technology can convert dispersed clean renewable energy into electricity,so as to facilitate the use of nearby users.Distributed generation has pointed out the direction for the efficient use of renewable energy.The inverter interfaced distributed generation through the power electronic device access to the grid,its related technology has also been a popular research field because of its flexible and rapid regulation performance and strong controllability.Based on three-phase inverter interfaced distributed generation grid-connected system,this paper conducts the detailed analysis and intense research on the control strategies under unbalance grid voltage and islanding detection of inverter after disconnection.The analysis of grid-connected inverter is the basis of the research of inverter interfaced distributed generation system.Firstly,this paper analyzes the structure of the inverter,and designs the grid-connected filter according to the system parameters.Then introducing several basic control methods based on double closed-loop control and selecting constant power control method for the grid-connected control mode.A simulation model of grid-connected distributed generation system with constant power control method is built.As the core component of inverter interfaced distributed generation,studying the control strategy of inverter has important research significance,which is the basis for safe and efficient use of electric energy.Under grid voltage unbalance,this paper analyzes the shortcomings of traditional PI regulator,and the control strategy based on dual dq-PI regulator is given to realize the non-static tracking control of positive and negative sequence currents independently.In view of its control structure is complex and the feedback current needs to be positive and negative sequence decomposition.So an improved control strategy based on PR regulator was adopted.This control method simplifies the unbalanced control system design,with good steady-state performance while transient performance is better than the former.A unified reference current instruction is deduced for different control targets.By adjusting the control parameter can realize the coordinated control between different targets.Simulation results verifythe effectiveness of these methods.In order to solve the islanding problem when the grid is disconnected,this paper firstly introduces the basic principle,testing standards and testing circuit of islanding detection,briefly compares the characteristics and application of several commonly used islanding detection methods.The analysis found that the traditional islanding detection method can not achieve the balance between power quality and non-detection zone.On this basis,in view of the photovoltaic grid-connected inverter,a new method of islanding detection based on the second harmonic of active power was proposed.This method can realize the islanding detection in non-detection zone without affecting power quality,and also applies to multi-inverter parallel operation.The simulation verify the effectiveness of the proposed method.