Incisive selection of the LCL filter parameters for a grid-connected inverter (GCI) is crucial to meet the grid interconnection standards with a reduced hardware footprint. Various design methods are available in the literature for selecting the LCL filter parameters. While the grid-side inductor of the LCL filter can utilize an iron core and follow the standard grid frequency inductor design, the inverter-side inductor design needs attention since it has significant switching frequency harmonics. This paper presents an extensive discussion on the design of the inverter-side inductor for GCIs. The inverter-side inductor (L i) is calculated based on the allowable inverter peak-peak ripple current to reduce the losses due to the ripple component. The value or size of L i depends on the inverter configuration, switching technique, and the application. The initial sections of the paper present a comprehensive analysis, comparing the value and hence the size of L i for different wiring configurations and applications. Closed-form expressions are developed for L i and are used in selecting the minimum value of L i. The suitability of an amorphous core for the inverter-side inductor is discussed. The amorphous-core inductor designs in literature can lead to a wide variation of inductance with current and have been analyzed to cause differential and common mode noise. To address this, a novel amorphous-core inductor design is proposed in the later sections of this work. The proposed approach ensures a minimal variation in the inductance over the operating current range. Experimental results are provided to support the various theoretical assertions.

LCL filters with passive damping are widely used for grid-connected inverter (GCI) applications. This work proposes a novel non-iterative component selection procedure for the LCL filter with passive RC damping. While the primary goal of the filter is to effectively attenuate the switching frequency components of the inverter, there are several other desirable constraints that make the selection procedure challenging. In this work, eight such desirable constraints are identified from the existing literature and the proposed method meets all the identified constraints. Besides being non-iterative, the novelty of the work primarily lies in the selection of the damping resistor Rd and the ratio n in which the total shunt capacitor is split. The primary intent of Rd being to damp the resonance, a methodical approach that ensures a high impact of the resistance at the resonance frequency is proposed. The proposed approach also ascertains a minimum possible quality factor. The selection of the ratio n is leveraged as an additional degree of freedom. An analytical method to find the range for n that offers a critically flat resonance peak is proposed. A critically flat resonance peak is important for control stability. The final value of n is chosen from the available range to meet all the constraints.