Dynamic Properties and Stability Assessment of Current-Fed Converters in Photovoltaic Applications

Abstract

This paper presents the general dynamic descriptions of current-fed converters applied in the solar or photovoltaic applications including an impedance-based method to assess the stability of the corresponding interconnected system. Several earlier unknown general parameters are indentified governing either the low-frequency behavior of the closedloop converter or affecting the source or load interactions. Experimental evidence is provided to support the theoretical findings based on current-fed superbuck and boost converters both in time and frequency domains.

Review of PV Generator as an Input Source for Power Electronic Converters

“…The analysis methods are developed further in many publications (e.g., [28,42,[117][118][119][120][121][122][123][124][125][126][127]). The further developments are mainly concentrated on enlarging of the allowed area in complex plane, where the impedance ratio is allowed to lie without causing instability [117,118,122], on making the special parameters governing the interactions in the converters to be explicitly solvable [119,122], and on extending the methods into the grid-connected three-phase converters as well [123][124][125][126][127].…”

Impedance coordinative control for cascaded converter in bidirectional application

“…If the source sub system is the current fed converter, which means the output A is current controlled, then the minor loop gain m T becomes as [14]:…”

Impedance-Based Stability and Transient-Performance Assessment Applying Maximum Peak Criteria

“…Since then, the minor-loop gain composing of the internal impedances of the downstream and upstream subsystems has been frequently used to assess the stability of interconnected systems in different application areas [3]- [23]. It has been recently noticed that the impedance ratio has to be computed in a certain way for predicting correctly the stability in the voltage-and current-fed applications [22], [23]: the numerator impedance has to be the internal impedance of the subsystem containing the voltage source or sink, and the denominator impedance the internal impedance of the subsystem containing the current sink or source, respectively. It has been earlier customary to present the impedance-ratiobased stability regions as certain forbidden regions in the complex plane out of which the minor-loop gain shall stay for robust stability to exist as shown in Fig.…”

“…1, and maintains the same level of robustness or even better. Although the discussions in this letter are limited to the conventional voltage-fed (VF) converters, the presented ideas and discussions are equally valid for different applications when the minor-loop gain and the relevant impedances are correctly defined as discussed in [13]- [15], [22], and [23]. The validity of the impedance-based minor-loop gain in assessing the stability of a general interconnected system at an arbitrary interface is proved explicitly in [11] and [22] based on system theory.…”

“…Although the discussions in this letter are limited to the conventional voltage-fed (VF) converters, the presented ideas and discussions are equally valid for different applications when the minor-loop gain and the relevant impedances are correctly defined as discussed in [13]- [15], [22], and [23]. The validity of the impedance-based minor-loop gain in assessing the stability of a general interconnected system at an arbitrary interface is proved explicitly in [11] and [22] based on system theory. The main contributions of this letter are the explicit revelation of the basis for the MPC-based forbidden region and the validity of the information extractable from the application of the criteria in terms of robustness of the stability in respect to the interface the minor-loop gain is determined.…”