A Maximum Power Point Tracking (MPPT) Strategy Based on Harris Hawk Optimization (HHO) Algorithm
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors present an maximum power point tracking strategy based on improved HHO algorithm. The paper is interesting. I have some suggestions to help improve its quality.
1) More state-of-the art comparison should be implemented on the basis of the traditional HHO algorithm.
2) Stability should be analyzed.
3) Could the mathematical model be used in the isolated DC-DC converter, such as in [R1]? Since in the practical application, the isolated requirement is paramount.
[R1] H. Lin, C. Cai, J. Chen, Y. Gao, S. Vazquez and Y. Li, "Modulation and Control Independent Dead-Zone Compensation for H-Bridge Converters: A Simplified Digital Logic Scheme," in IEEE Transactions on Industrial Electronics, vol. 71, no. 11, pp. 15239-15244, Nov. 2024, doi: 10.1109/TIE.2024.3370975.
Author Response
（1）More state-of-the art comparison should be implemented on the basis of the traditional HHO algorithm.
I would like to express my sincere gratitude for your suggestion. The author has added the improved Particle Swarm optimization (IPSO) algorithm mentioned in the introduction section to the results part of this paper. The IHHO-INC algorithm proposed in this paper is further compared with the improved Particle Swarm optimization (IPSO) algorithm. From the simulation results, it can be seen that in both uniform and non-uniform lighting conditions, the IHHO-INC algorithm proposed in this paper has faster optimization speed and more accurate precision than the improved particle swarm optimization algorithm. Please refer to Figure. 11-13 in the original paper for details.
（2） Stability should be analyzed.
I would like to express my sincere gratitude for your valuable suggestions. In this paper, the author set up the stability performance of the algorithm when the light intensity suddenly increased and decreased. From the experimental results, it can be analyzed that, from both the tracking time of maximum power and the tracking precision of maximum power, the IHHO-INC algorithm proposed in this paper has better performance. In summary, when external conditions change, the algorithm still has good performance, which also indicates that the algorithm proposed in this paper has good stability.
（3) Could the mathematical model be used in the isolated DC-DC converter, such as in [R1]? Since in the practical application, the isolated requirement is paramount.
Thank you very much for your valuable advice. The author has replaced the BUCK converter in the PV system with an isolated DC-DC converter in the Figure 9, and the mathematical model still applies.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe English usage and Presentation of results must be improved.
The Conclusion is very limited. It needs to be elaborated.
What are the Contributions of the paper?
A copy of the marked paper is provided to help the authors.
Pay attention to acronyms used. See HHO and IHHO, Is it Harris Hawk or Harris eagle?
The References need to be re-formatted. See attached paper. Check Reference [1]. An additional reference is provided:
Faizan Khan, Ali Sunbul, Mohammad. Y. Ali, Haytham AbdEl-Gawad, Shahryar Rahnamayan, Vijay. K. Sood, "Maximum PowerPoint Tracking in PV Farms Using DE and PSO Algorithms: A Comparative Study", 8-13 July 2018 – IEEE World Congress on Computational Intelligence (WCCI ) 2018, Rio de Janeiro, Brazil.
The units need to be check in Figures etc. Units of Watts is (W). The units of Seconds is (s).
Check P (W) and not P/W. etc.
Check Equation and not formula.
Check in Table 2 : two decimal points or one decimal point?
Figure 11 a and b can be combined for better comparison purposes.
Figure # and figure #.
Pay attention to punctuation marks.
Comments for author File: 
Comments.pdf
English must be improved.
Author Response
（1） The English usage and Presentation of results must be improved.
Thank you very much for your suggestions. The author has already improved the English usage in this article, and the presentation has also been improved.
（2） The Conclusion is very limited. It needs to be elaborated.
The author has provided a detailed account of the conclusions in this paper, as follows:
Under partial shading conditions, the output characteristic curve of the photovoltaic array has multiple inflection points. By analyzing the MPP position pattern of the multi-peak curve, this paper proposes an improved MPPT method combining Harris Hawk optimization (HHO) and a variable step conductance increment method (INC) ,which solves the problem that the traditional maximum power point tracking(MPPT) method is easy to fall into a local optimum and difficult to balance the tracking precision and speed when faced with local shading. For the local development precision deficiency of the HHO algorithm, when the HHO algorithm reaches the maximum iteration number, the algorithm is terminated and the optimal solution is output, and then switched to the INC algorithm. This paper conducts simulation verification of the maximum power tracking HHO-INC algorithm, concluding that the algorithm has extremely small steady-state error and good steady-state and dynamic performance, with a significant improvement in convergence speed and efficiency compared to the HHO and PSO algorithms.
（3） What are the Contributions of the paper?
In response to the multi-peak phenomenon of photovoltaic arrays under uneven illumination, which leads to an imbalanced problem of traditional maximum power point tracking, a MPPT control based on Harris Hawk algorithm was proposed. Due to the shortcomings of low convergence accuracy, slow tracking speed, and easy falling into local optimum of Harris Hawk Optimization (HHO) algorithm, the HHO algorithm is combined with the variable step conductance increment method (INC), and after the HHO algorithm reaches the maximum iteration number, it switches to the variable step conductance method for local exploration to improve the algorithm's convergence accuracy and tracking speed.
In summary, the contributions of this paper is to use the variable step conductance increment method (INC) to compensate for the shortcomings of the HHO algorithm, and the proposed HHO-INC algorithm in this paper has excellent steady-state and dynamic performance, which can quickly and accurately track the maximum power point and thus improve the efficiency of photovoltaic power generation.
（4） Pay attention to acronyms used. See HHO and IHHO, Is it Harris Hawk or Harris eagle?
The full name of HHO is Harris Hawk optimization, and the author has already made changes to the original text.
（5） The References need to be re-formatted. See attached paper. Check Reference [1]. An additional reference is provided:
The author has reorganized the reference list format for this article.
(6）The units need to be check in Figures etc. Units of Watts is (W). The units of Seconds is (s).
Check P (W) and not P/W. etc.
Check Equation and not formula.
Check in Table 2 : two decimal points or one decimal point?
The author has carefully revised the text and changed all instances of " P/W " to " P (W)" throughout the article. The author has carefully revised the text and changed all instances of "formula " to " Equation" throughout the article. The author has checked Table 2:one decimal point.
（7）Figure 11 a and b can be combined for better comparison purposes.
The author has combined Figure 11(a) and (b) and superimposed the I, U, and P curves from both figures for a more intuitive comparison, showing that the variable-step length conductance incremental method has better output characteristics.
（8）Figure # and figure #.
The author has replaced the figures in this article with Figure.
（9）Pay attention to punctuation marks.
Thank you very much for your suggestions. The author has carefully reviewed the use of punctuation in this article and has made corrections to any improper punctuation found.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe work is well organized and, at the same time, well written. Good structuring of the work helps the authors to take their logical approach from simple to complex. The results obtained by the authors are validated by simulation in Matlab/Simulink environment. This work opens new avenues of research in the future. Nevertheless, some comments should be taken into account before publishing:
1) Aim to avoid acronyms in the abstract. Additionally, provide a clearer explanation of the significance of your findings. What advances the field does your study address? Why is switching to variable step incrementing method important?
2) Indicate in the opening section exactly which problem or knowledge gap your research aims to fill. Although you touch on a number of IPSO and PSO, a clearer problem definition will assist highlight the significance of your study. To set the scene for your research, summarize the limitations and contributions of several studies rather than simply listing them.
3) In Figure 1, please correct the symbol on the left to a current source (not a voltage) since you are showing it as a source of photocurrent - Iph.
4) For Figure 9, explain the meaning of LPF (low pass filter) in the text.
5) Line -271. Better to call this section "Simulation Analysis or Discussion" than just "results".
6) If possible to convert Figures 11 ito vector format to improve the quality and avoid pixelation.
Author Response
（1） Aim to avoid acronyms in the abstract. Additionally, provide a clearer explanation of the significance of your findings. What advances the field does your study address? Why is switching to variable step incrementing method important?
The author has carefully revised the abstract section of the article, replacing all abbreviations with their full forms. Due to the shortcomings of the Harris Hawk algorithm, such as low convergence precision, slow tracking speed, and easy entrapment in local optimum, it must be optimized and improved. To solve these problems, the author adopts the switching to the variable-step length conductance increment method for local development when the Harris Hawk algorithm, algorithm converges, achieving the rapid and precise tracking of the photovoltaic array MPPT. In summary, this paper utilizes the variable-step length conductance incremental method to solve the shortcomings of the Harris Hawk algorithm, which is the main contribution of this paper and highlights the importance of switching the conductance and variable-step length incremental method.
（2）Indicate in the opening section exactly which problem or knowledge gap your research aims to fill. Although you touch on a number of IPSO and PSO, a clearer problem definition will assist highlight the significance of your study. To set the scene for your research, summarize the limitations and contributions of several studies rather than simply listing them.
The author has carefully revised the introduction of this paper and listed the advantages and disadvantages of existing algorithms one by one, for example:
PSO: Although the maximum power tracking speed has been improved, there is still fluctuation in the output power.
immune firefly algorithm: However, this algorithm has slow convergence speed, easy to fall into local optimum, and early convergence, which limit its effectiveness and efficiency.
A composite algorithm combining PSO, genetic algorithm and fuzzy control: However, the control model of this composite algorithm is complex, the computation is large, and the optimization speed is not significantly improved.
And so on.
（3）In Figure 1, please correct the symbol on the left to a current source (not a voltage) since you are showing it as a source of photocurrent - Iph.
The author has corrected the voltage source in Figure 1 of this paper to a current source.
（4）For Figure 9, explain the meaning of LPF (low pass filter) in the text.
The role of a photovoltaic low-pass filter is to attenuate or eliminate these high-frequency noises, making the system more stable and reliable. In addition, a low-pass filter can also prevent reverse current from flowing into the photovoltaic module, protecting it and extending its service life.
（5）Line -271. Better to call this section "Simulation Analysis or Discussion" than just "results".
The author has revised the title of section 5 to Simulation Analysis.
（6）If possible to convert Figures 11 ito vector format to improve the quality and avoid pixelation.
The author has converted Figure 11 to vector format in this article.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors provide a significant revised version of the paper.
I have one suggestion that the authors should list the reference [R1] in the introduction or the corresponding section in the paper to discuss extensibility of the proposed technique to the isolated converter.
[R1] H. Lin, C. Cai, J. Chen, Y. Gao, S. Vazquez and Y. Li, "Modulation and Control Independent Dead-Zone Compensation for H-Bridge Converters: A Simplified Digital Logic Scheme," in IEEE Transactions on Industrial Electronics, vol. 71, no. 11, pp. 15239-15244, Nov. 2024, doi: 10.1109/TIE.2024.3370975, so that the discussion would be more complete.
Author Response
I have one suggestion that the authors should list the reference [R1] in the introduction or the corresponding section in the paper to discuss extensibility of the proposed technique to the isolated converter.
Thank you very much for your valuable advice! The author has added the reference [R1] to the corresponding section and they can be found in the References [18] of this paper.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript provided to the Reviewers is a PDF file, so that some of the changes that have been made are not visible to the Reviewer; these changes, such as to equations and figures, are not obvious.
I find that some requested corrections have been made, but not all of them. This is disappointing that the authors have not been able to do all the corrections.
Figure 9 has been modified. But the description/explanation of the figure is not improved.
A new Figure 10 has been added, but no description is provided. This must be corrected.
The correct notation for an equation (#) is not used. See equation 12.
The unit symbol of Watts is W and not w. See Table 2.
Comments on the Quality of English LanguageThe English grammar used in the manuscript still needs improvement.
Author Response
Thank you very much for your valuable suggestions. The specific changes are as follows:
- Figure 9 has been modified. But the description/explanation of the figure is not improved.The author has provided corresponding explanations for the modified parts in Figure 9. Since isolation is a very important factor in practical applications, the author changed the DC-DC converter in the PV system to an isolated DC-DC converter.
- A new Figure 10 has been added, but no description is provided. This must be corrected.
Figure 10 shows the simulation model of the PV system built in Simulink by author. The specific introduction in the original article is as follows: The simulation model diagram is shown in Figure 10, mainly composed of four modules: photovoltaic array model, DC-DC converter, PWM pulse signal model, and MPPT controller model. Among them, the battery is used instead of the load. - The correct notation for an equation (#) is not used. See equation 12.The author has replaced "equation 12" in the original text with "equation(12)".
- The unit symbol of Watts is W and not w. See Table 2.
The author has replaced the "w" in Table 2 with "W".
