Research On Grid-connected Inverter Stability Control Strategy Based On Lyapunov Theory

As an important part of microgrid,the inverter is vulnerable to large transient disturbances due to its model nonlinearity and low electrical inertia,thus threatening the safe operation of microgrid.Therefore,as the basis of the study on the operation stability of microgrid,the operation stabilit y of a single inverter should be fully understood first.However,up to now,the stability of inverters has been mainly focused on the stability of small si gnals,while few scholars have been involved in the operation stability of inverters under large signal disturbances.Therefore,so as to perfect the stability analysis of the inverter and improve its anti-disturbance ability,it is necessary to fully understand the large signal stability of a single inverter.In this paper,a single-phase grid-connected inverter based on droop control is studied.For the sake of simplifying the model,the dc side voltage of the inverter is equivalent with a constant voltage source.By selecting appropriate circuit parameters and steady-state operating points,the stable domain of the inverter system is estimated by combining the Takagi-Sugeno(T-S)fuzzy model approach and Lyapunov stability theory,the large-signal disturbance range that the system can bear is quantified,and the conservatism of the estimated stable domain based on Lyapunov stability theory is analyzed.So as to verify the estimation results of the stable domain,the simulation circuit of single-phase grid-connected inverter is built in PLECS and the validity of the estimated stable domain obtained by using Lyapunov stability theory is verified by simulation.Furthermore,in order to provide guidance for parameter selection,this paper also analyzes the infl uence of relevant parameter changes on the system’s large-signal stability.It is found that the grid-connected inverter with traditional PI control structure can only bear small power disturbance under the fixed parameters and steady operating point.Therefore,in order to expand the range of power disturbance the inverter system is subjected to,and improve the system’s large-signal stability.In this paper,Lyapunov stability theory is used to design a kind of stabilization controller for grid-connected inverter,and the design idea of the controller and the selection principle of control parameters are given.As the structural parameters of the system are involved in the design of the stabilization controller,it is considered that the structural parameters will vary with the operating conditions.Therefore,the influence of structure parameter mismatch on the stability of the system and the control effect of the controller is analyzed.Finally,PLECS simulation verifies that the grid-connected inverter with the stabilization controller can bear more power disturbance and effectively improve the stability of the system under the large signal disturbance.