Energy Storage Power and Energy Sizing and Specification Using HSSPFC

Round 1

Reviewer 1 Report

The authors are commended for addressing concerns for the sizing of energy storage elements in power systems that are subjected to uncertainties of renewable resources. The method of Hamiltonian Surface Shaping and Power Flow Control is a beneficial method in this application. The results are well developed and explained in detail. There is a rigorous analytical development that allows engineering practitioners to apply the methods developed in the paper. The paper would be improved if some discussion of the difficulties in determined the power spectra density (PSD). The authors provide reference [28], however there are difficulties in quantifying the PSD. In particular, the paper would be improved is some discussion was included that describes how to account for nonstationary behavior of electric power systems. 

Author Response

Thank you for your feedback. In this work, the PSD is determined by performing the frequency analysis on the reference power signal. The power signal itself is obtained from the Hamiltonian controller that makes use of the defined constraints in eqs (15) to (25). From which, eq (20) accounts for power smoothing through the energy storage elements.

Most of the assumptions in this work can be challenged as future work. One major assumption here is that the average value of the renewable source is already known (stationary behavior). This is a strong assumption that is added for the sake of simplification and to maintain focus on the main objectives of the article. However, this assumption can be challenged considering the baseline approach in this work. For example, the overall design can be re-iterated for multiple source profiles with corresponding ES sizing based on “estimated” forecast. Then, further deterministic and probabilistic methods could be leveraged to determine the sizing overhead or perform various optimization based on cycle duration, size (overall system), topology etc. which are considered as future work.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear author

The following comments will imrove the paper quality:

1) Please provide a subsection to introduce the HSSPFC method.

2) Different energy storages has different response time. How do you consider the effect of energy storage type in your model? In your model you have represented the energy storage just as a DC link.

3) Please provide more explanation on your model in fig. 2. Please also provide your reference if you got it from other resourses.

4) what does (line,i ) represent in your equations.

5) please give more explanation on equations 33 and 34. Please also provide their references

6) The scenario which is applied in your simulation in completely unclear. you need to provide a much better explanation and in an organized way. You need to completely change this section in a better way.

7) In section (4), Please explain how you determined the droop voltage settings.

8) The paper contribution is not clear throughout the paper.

 

 

 

Author Response

1. The authors would like to thank you for your detailed feedback.An introduction to HSSPFC is added to the introduction section (line 21-highlighted in blue). Moreover, the corresponding paragraph includes 7 ([4]-[10]) references (books and publications) around the HSSPFC topics in the field.
2. Thank you for your attention to detail. The ESS in the dc-link in Fig. 1 is connected to a source in a series connection. This is a specific form (starting point of this work) that is appropriate for HSSPFC design and analysis for stability and performance. It is important to note the overall system is a power-flow and energy transfer model. Therefore, different topologies can eventually be derived from this model, however practical constraints should be met since the series and parallel conversion is not always valid. One of the contributions of this work is relevant to the same; to move one step ahead and fill the gap between the theoretical analysis and practical implementation. In the article, equations 14 to 25 are dedicated to specifying these constraints for a parallel connection. Brief description is added to section 3, the second paragraph.
3. More explanations are added to figure 1 (highlighted in blue) and the relevant reference [10] is added to where Fig. 1 was first mentioned.  
4. Thank you for your attention to detail. More descriptions and a major assumption are added to equation 31 (highlighted in blue).
5. More details about the representation of the ESSs in equations (33) and (34) are added (highlighted in blue).
6. Thank you for your attention to detail. The contents of the example section are reformed and detailed explanations about the simulation examples are added to Section 9 (highlighted in blue).
7. Further explanations are added to Section 4. Droop setting are chosen arbitrarily for a droop slope changing method. Alternative methods such as curve shifting can be used but will not directly affect ESS results.
8. Stronger statements were added to the introduction section to highlight the contributions of this work.

Author Response File: Author Response.pdf

Reviewer 3 Report

The presented work is very interesting and the manuscript is well organized and presented. However, although the aim of the work is the demonstration of the sizing methodology, both presented examples refer to a microgrid with predefined the characteristics of the storage system. Therefore, the addition of a section demonstrating the selection of the specific storage system parameters is required.

Furthermore, figures 20, 21 and 22 should be moved before the references section.

Author Response

Thank you for your attention to detail. Detailed explanations about the simulation examples are added to Section 9 (highlighted in blue). It is important to note that the aim of ESS sizing in these examples is not to determine BESS or FESS device component parameters. Instead, the intent is to analyze the power split using the sizing criteria proposed in (40) and observe the subsequent energy allocation. Hence, the power and energy sizing are done from the perspective of the Point of Common Coupling (PCC) between the DC-link and individual BESS and FESS subsystems. Sizing an energy storage device for its specific components and parameters under various DLCs and Energy Management Systems (EMSs) requires device-specific design measures, rigorous analysis and addressing multiple trade-offs at device and control levels which are out of the capacity of this work. Hence, the simulation cases are designed to serve the objective of the proposed control rather than to dictate detailed device-specific component sizing.

Thank you for your attention. Figures are rearranged so that all appear before the reference section.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The comments are well addressed and the paper quality is improved.

Reviewer 3 Report

thanks for the clarification and congratulations on the very interesting work