General Parameter Tuning Method for Impedance Shaping of the Grid-Tied Inverter

The inverter's impedance is influenced by its control algorithm and control parameters simultaneously. It is important to obtain a proper impedance shape for an inverter to achieve the design purpose, e.g., sufficient stability margin and strong filtering ability. Different control schemes and corresponding parameter tuning have been proposed to realize these design purposes against different adverse grid conditions. However, these control schemes may have to be combined in practice because different grid conditions may be coupled in the real world. Under this situation, all the control parameters have to be re-tuned to coordinate the control schemes. Impedance-based analysis provides a general vision to test the stability margin and harmonic suppression ability of the grid-inverter system. However, the existing impedancebased analyses cannot realize the quantitative parameter tuning for further improvement. In this paper, three common design purposes are formulated as impedance shaping problems, including stability margin improvement, filtering ability enhancement, and phase-angle shaping. Then, a general parameter tuning method based on optimization theory is proposed for impedance shaping, which can provide a quantitative tuning result directly after an iteration<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup>.