A Research On Paralleled Coordinated Control And Power Sharing Strategy For Single-phase Voltage Source Inverters

With the development of social economy and the increasing use of electrical equipment,the demand for power generation system is becoming more and more important.Nowadays,inverters have been widely applied in the fields of communication,computer,medical,and aerospace.In order to realize the coordinated operation of multi paralleled inverters,the coordinated control strategies of single-phase paralleled inverters are studied in this paper,including the modeling and analysis of the system,the small-signal model and stability analysis.An improved droop control based on washout filter is proposed in this paper,both of the linear and nonlinear load conditions are taken into account.Mainly includes the sharing of active and reactive power and the coordinated control strategy for voltage / frequency.The main contents are as follows:(1)The equivalent circuit model,transfer function model,small signal model and stability analysis for the paralleled multiple single-phase voltage source inverters are analyzed in this paper.Furthermore,the PI controller based on dq axis is proposed to used in the system of paralleled multiple single-phase voltage source inverters.The modeling and analyzing of the inner current loop and outer voltage loop based on dq axis are presented.The comparison between the PI control based on dq axis and ?? axis are carried out,and the results of simulation analysis are given.(2)The application of hierarchical control in distributed generations is introduced,including droop control and secondary control.The introduction and analysis of these strategies are presented respectively.Furthermore,an improved droop control based on washout filter is proposed in this paper,and the detailed analysis and parameter design are carried out.(3)The paralleled single-phase inverters under the condition of linear load is studied in this paper.The conditions for active power and reactive power sharing are discussed,and an improved droop control based on washout filter is put forward to achieve the power sharing.Through the detailed simulation analysis among traditional droop control,improved droop control and secondary control,it is verified that the improved droop control proposed in this paper is superior to the traditional droop and the two control in the effect of power sharing under linear loads condition.At the same time,the coordinated control on voltage and frequency under linear load condition is discussed.The improved droop control strategy is used to deal with the issue of voltage and frequency caused by the change of linear loads.Through the detailed simulation analysis among traditional droop control,improved droop control and secondary control,confirmed that the improved droop control proposed in this paper is better than the traditional droop and the secondary control in the effect on the coordinated control of voltage and frequency under linear load condition.(4)The paralleled single-phase inverters under the condition of nonlinear load is studied in this paper.A harmonic suppression strategy is proposed,which can effectively suppress 3,5 and 7 harmonics caused by nonlinear loads in paralleled single-phase inverters system.The rationality of parameter selection in the harmonic suppression measures is discussed through theoretical analysis,and detailed simulation analysis waveforms and experimental verification waveforms are given.Furthermore,the sharing effect of active power and reactive power under nonlinear loads condition is discussed in this paper.Through the detailed simulation analysis among traditional droop control,improved droop control and secondary control,it is verified that the improved droop control proposed in this paper is superior to the traditional droop and the two control in the effect of power sharing under nonlinear loads condition.At last,the coordinated control for voltage and frequency under nonlinear loads condition is presented,the improved droop control based on washout filter is proposed to deal with the issue of voltage and frequency caused by the change of nonlinear loads.Through the detailed simulation analysis among traditional droop control,improved droop control and secondary control,confirmed that the improved droop control proposed in this paper is better than the traditional droop and the secondary control in the effect on the coordinated control of voltage and frequency under nonlinear load condition.