Generalized Integrator Based Two Degrees of Freedom PID Control for LCL Filter-Based Grid Connected Inverter
Traditional active damping control can suppress the resonance of LCL inverter,but it needs to add additional voltage or current sensors.A sensorless generalized integrator based two degrees of freedom proportional integral derivative(GI-2DoF-PID)control strategy for LCL-type grid-connected inverter with single current feedback is proposed.The proportional and integral(PI)control in the GI-2DoF-PID is used to track the grid current without static error,while the generalized integrator enhances the damping characteristic of the LCL inverter.Based on the derived transfer function of the GI-2DoF-PID controller,the system stability margin and dynamic response charac-teristics are analyzed,and the controller parameters are selected according to the proposed parameter guideline for tracking and anti-dis-turbance optimization.Finally,the simulation model in PLECS is built,and the simulation results validate the effectiveness of resonance suppression in LCL-type grid-connected inverter with the proposed GI-2DoF-PID controller.Meanwhile,the total harmonic distortion(THD)of the full load grid-connected current is only 3%under seriously distorted grid voltage conditions,which is far below the national standard.When there is a step change from half load to full load,the system overshoot is low,demonstrating a fast dynamic response.
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