A Building-Block Approach to State-Space Modeling of DC-DC Converter Systems

Round 1

Reviewer 1 Report

1. The writing of whole paper should be checked. Some language and grammar problems can be found. 

2. Is it possible for the authors to quantitatively evaluate how accurate is of the model to predict the dynamics? 

Author Response

Thanks to the reviewer for these suggestions, which have been incorporated in the revised version of the paper as follows:

1.

The following typos have been fixed in the revised version:

- page 1, line 23: "ouput" -> "output

- page 2, line 54: "lateron" -> "later on"

- page 5, line 149: "chosing" -> "choosing"

- page 8, line 190: comma added after "Furthermore"

- page 10, line 252: "abobe" -> "above"

- page 10, line 255: comma removed after "Figure 5"

- page 10, line 265: "ouput" -> "output

- page 18, line 493: capitalization of "Frequency" and "Mode"

2.

The connection operations as well as the overall small-signal system model proposed in this articles are all linear. The accuracy of the resulting system model will therefore not be compromised (compared to the accuracy of the building blocks). The prediction accuracy is only limited by the accuracy of the small-signal building blocks employed in creating a system model. For converter models, the references linked in Appendix B.1 contain state-of-the-art models. 

A paragraph regarding the small-signal accuracy has been added in both section 5.2 and the conclusions section.

Reviewer 2 Report

The paper is well written, the main ideas are carefully explained, the organisation is good and the list of references sound, complete and quite informative. The main contribution of the paper is the systematic treatment of the state-space modeling of converter systems in a modular building block structure that could be very helpful from a practical point of view in future research efforts in the area, particularly  in the formulation and mathematical description of more complex or multilevel converters and other more complicated topologies.

Some minor comments and typos are given below for improving the paper's presentation

1) The notation ctl for the control input used in most of the formulas and figures is not a good choice, I would prefer to see the most common  u, e, r  for the reference , error and control input

Moreover, terms like   ctl OL , CL  are not used, this is the reference signal   and the error etc.

2) The main formulas for connection are (10),(11),(12). No derivation details are given.

3) page 10,  line 247, replace "abobe" with "above"

4) page 2,  line 54, replace "lateron" with "later on"

Author Response

Thanks to the reviewer for these suggestions, which are answered in detail below and are all reflected in the revised version of the paper.

1)

I fully agree that the notation "ctl" is an uncommon choice, and it was not an easy one. However I settled on this notation for the following reasons. Depending on the modeling stage, the meaning of the control ("ctl") input of the converter (system) model given by equation (2) can be completely different. For a bare converter, it can be the duty cycle of the active switch (often denoted as "d"). For a model of a peak current mode controlled converter, it will be the reference (peak) current (denoted as "i_ctl" e.g. in reference [34]). For an open control loop, it will be the control error (typically denoted as "e"). For closed-loop control, it will be the reference signal (typically denoted as "r"). In order to represent the model structure with one set of equations (eqs. (2) and (4)) and graphics (Figures 2, 3, 4), a unified name "ctl" has been chosen. The subscripts "OL" (for open-loop) and "CL" for closed-loop control have been introduced to reflect the modeling stage accordingly.

For the reasons sketched above, I would like to maintain the "ctl" notation. However, extensions were made to the paper in line 122 (page 4) and equation (4) (page 5) in order to establish the link to the commonly used notation e(t) and r(t) (for control error and reference signal) more clearly.

2)

For a better understanding of the derivation of the main equations, the intermediate equations (11) and (12) have been added together with a new paragraph on page 7.

The matrix equations (14) and (15) [numbering was (11) and (12) in the first version] can be found from (13) [was (10) before] by inspection. A note has been added on line 182/183 (page 8) to reflect that.

3) and 4)

The following typos have been fixed in the revised version:

- page 1, line 23: "ouput" -> "output

- page 2, line 54: "lateron" -> "later on"

- page 5, line 149: "chosing" -> "choosing"

- page 8, line 190: comma added after "Furthermore"

- page 10, line 252: "abobe" -> "above"

- page 10, line 255: comma removed after "Figure 5"

- page 10, line 265: "ouput" -> "output

- page 18, line 493: capitalization of "Frequency" and "Mode"

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.