Combined PV-Wind Hosting Capacity Enhancement of a Hybrid AC/DC Distribution Network Using Reactive Control of Convertors and Demand Flexibility

Round 1

Reviewer 1 Report

1.       Title is too long, which should be shortened;

2.       A more comprehensive literature review should be undertaken;

3.       Sampling size should be provided;

4.       What are the main advantages and disadvantages of the proposed model?

5.       The suitability of the proposed model should be elaborated.

Author Response

The authors would like to thank the respected Reviewer 1 for her/his valuable comments and suggestions. In this letter, the Reviewer’s comments and the authors’ responses are presented.

Comment 1 - Reviewer 1

Title is too long, which should be shortened;

Comment 1 - Authors

In order to answer this comment, the title has been shortened from 24 words to 19 words. The new selected title is as follows:

Combined PV-Wind Hosting Capacity Enhancement of a Hybrid AC/DC Distribution Network Using Reactive Control of Convertors and Demand Flexibility

Comment 2 - Reviewer 1

A more comprehensive literature review should be undertaken;

Comment 2 - Authors

For responding this comment, some new references are investigated in the literature review with detailed explanations. Also, a summary of the differences between the most related works in the field and the present paper is presented as a new table.

The added text to the various parts of the literature review is as follows (note that the references [16], [18], [20], [27] are the newly added ones):

Using various ANM schemes is one of the possible approaches for handling the variability of RESs and increasing the HC. ANM schemes mainly organize the connection between DGs and network equipment using various control mechanisms to facilitate a larger output from the DGs [11]. Voltage control via Under-Load Tap Changer (ULTC) transformers [12], voltage regulators [13], active/reactive management strategies such as DGs active power curtailment [14], network reconfiguration [15, 16], and energy storage [17] are some of the ANM schemes used for the HC enhancement. Most of the studies either consider one type of RESs or do not examine the effect of combining them for the HC improvement. Also, reactive power control strategies are included as an ANM scheme which is applied in various studies for HC enhancement. Reactive power control of inverters in DGs [6], smart inverter, i.e., STATCOM, considering both dynamic and static HC [18], Volt/VAr control process of electric vehicles [19], and capacitor bank [20] are the HC enhancement studies which consider reactive power control strategies. However, the new ANM potentials of hybrid AC/DC distribution network, such as reactive power control of the VSCs, is not utilized for the HC purpose.

Also, an economic evaluation between single location and multiple locations deployment of RESs in the hybrid AC/DC distribution network has been undertaken.

Reference [26] deals with the effect of DFP on HC in terms of energy losses in the form of a multi-objective nonlinear programming model. Reference [27] examines different ANM schemes on HC enhancement considering DFP based on a mixed integer second-order cone programming model in which, the optimization of energy losses is neglected.

Table 1 reviews some recent studies regarding the above-mentioned perspectives. This table also presents the novelties of the current work compared to these most related studies in the field.

Table 1. Summary of existing studies in the literature and the contribution of the present paper.

Comments 3, 4, and 5 - Reviewer 1

Sampling size should be provided;

What are the main advantages and disadvantages of the proposed model?

The suitability of the proposed model should be elaborated.

Comment 3, 4, and 5 - Authors

Based on these comments, a new section entitled ‘Discussion’ is added to the end of the simulation results section in which, it is tried to investigate these valuable aspects. Hence, this newly added section describes the sampling size, advantages and disadvantages, and suitability of the proposed model, as follows:

5.8. Discussion

The proposed model in this paper is a multi-objective framework for increasing the HC and decreasing the energy losses. This model considers the hybrid RESs deployment mathematical model that can incorporate any kind of DGs considering their uncertainties using the scenario-based stochastic programing. In this model both DSM and ANM schemes have been considered simultaneously which makes the proposed model more comprehensive. ANM schemes are DGs curtailment, DGs reactive power control, and VSCs reactive power control. Nevertheless, without loss of generality, other ANM schemes such as OLTC transformer, storage, and network reconfiguration are not considered, which can be straightforwardly added to the model.

In general, for HC studies, 8760 h of the year should be considered to demonstrate the accurate performance of the proposed model. However, due to the computation burden, one specific day of each season (totally, 96 h) is chosen to consider the frequent variability of RESs throughout the year. In addition, in order to be more realistic, the uncertainty of RESs output which may occur in any specific time is modeled via scenario-based stochastic programming.

The developed model was originally formulated as NonLinear Programming (NLP). Therefore, due to the noticeable size of the investigated test network, the nonlinearity and complexity of the accurate power flow equations, and the absolute expressions, the solution time was about 29 hours. So, in order to reduce this computational burden, the proposed NLP model has been converted to a Mixed Integer Linear Programming (MILP) model. After providing a MILP model, the solution time has decreased considerably to 11 hours which shows the efficiency of the proposed model. It should be noted that the HC studies are conducted for planning purposes and consequently, this solution time can be considered acceptable. However, it is worth noting that the conversion process of the NLP to MILP is based on some hypothesis which makes the proposed model non-accurate. However, the simulation studies have demonstrated that both MILP and NLP models have reached to the same results.

The authors would like to thank the respected Reviewer 1 for her/his valuable and accurate comments besides professional suggestions, which helped us to improve and revise the paper.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is well formulated in its present form. The description of the optimization method for assessing hosting capacity is very detailed, and provides a good insight for those interested in this topic.

Author Response

The authors would like to thank the respected Reviewer 2 for her/his valuable comments and suggestions. In this letter, the Reviewer’s comments and the authors’ responses are presented.

Comment 1 - Reviewer 2

The paper is well formulated in its present form. The description of the optimization method for assessing hosting capacity is very detailed, and provides a good insight for those interested in this topic.

Comment 1 - Authors

The authors would like to appreciate the reviewer’s positive comment and thank her/him for taking the time to review the paper. It shpuld be mentioned that based on the suggestions of the respected reviewer, a complete grammar and spell check has been done for the English language.

Author Response File: Author Response.pdf

Reviewer 3 Report

It is an excellent research manuscript an has been carefully peer-reviewed. My suggestion is to make it more usual the nomenclature, however, such details of the mathematical operators are useful.

Author Response

The authors would like to thank the respected Reviewer 3 for her/his valuable comments and suggestions. In this letter, the Reviewer’s comments and the authors’ responses are presented.

Comment 1 - Reviewer 3

It is an excellent research manuscript and has been carefully peer-reviewed. My suggestion is to make it more usual the nomenclature, however, such details of the mathematical operators are useful.

Comment 1 - Authors

First of all, the authors would like to thank the reviewer 3 for taking the time to review the paper and appreciate his/her positive feedback. The nomenclature has been rewritten in the word editor, and hence a better structure has been provided as suggested. Also, based on the suggestions of the respected reviewer, a complete grammar and spell check has been done for the English language.

Author Response File: Author Response.pdf