A Frequency Adaptive Scheme Based on Newton Structure of PRRC for LCL-Type Inverter Connected with Weak Grid

Repetitive control (RC) is gradually used in inverters tied with weak grid. To achieve the zero steady-state error tracking of inverter current and compensate harmonic distortion caused by frequency fluctuation, a adaptive (FA) scheme for LCL-type connected grid proposed. This adopts proportional resonance (PR) controller parallel RC (PRRC) to overcome disadvantages inherent one-cycle time delay. A fractional delay (FD) filter based on Newton structure proposed approximate fraction item fs/f, where fs f are sample frequency, respectively. The FD relatively simple; moreover, coefficients maintain constant so as not need online tuning even when fluctuates, which decreases computational burden considerably. feasibility effectiveness FA scheme, named Newton-FAPRRC, all verified simulation experimental results.