Review Reports - Cooperative Frequency Control of a Small-Scale Power System between Diesel Engine Driven Adjustable Speed Generator and Battery

Round 1

Reviewer 1 Report

1. In table 2, please include parameter units.

2. In Fig.8, membership functions have been determined by trial and error method.

-Please provide more details on the procedure used in the trail and error method. -This is important because the readers may apply the method to their system.

3. Cooperative control has its specific definition.

-In section 4, the reviewer is not sure why the authors call their method 'cooperative control'. The method seems to be a classical controller.

Author Response

Response to Reviewer 1 Comments

Thank you very much for your time in reviewing the paper. Also, thank you for your valuable comments which will be definitely improve the paper quality.

The authors tried to address all the comments as follows;

Comments and Suggestions for Authors,

Point 1 : 1. In table 2, please include parameter units.

Author’s response 1: Thank you for your pointing out. We made a mistake about the units. The parameter units were added in table 2 in the revised manuscript.

Point 2 : 2. In Fig.8, membership functions have been determined by trial and error method.

-Please provide more details on the procedure used in the trial and error method. -This is important because the readers may apply the method to their system.

Author’s response 2: The fuzzy control systems are excellent at intuitively designing a controller for nonlinear systems, but the desired response cannot be obtained unless it is designed appropriately. In this study, the values of gains G_P, G_D and G_O in Figure 7, and the values on the horizontal axes in the membership functions shown in Figure 8(a) and (b) in the manuscript have been repeatedly tried in various patterns, and the values making the system response more stable (i.e., non-oscillatory) and improving the frequency fluctuation suppression effect have been selected.

The following sentences were inserted from line 183 of the revised manuscript.

“Specifically, the gains G_P, G_D and G_O shown in Figure 7, and the values on the horizontal axes in the membership functions shown in Figure 8(a) and (b) have been repeatedly tried in various patterns, and the values making the system response more stable (i.e., non-oscillatory) and improving the frequency fluctuation suppression effect have been selected. “

Point 3 : 3. Cooperative control has its specific definition.

-In section 4, the reviewer is not sure why the authors call their method 'cooperative control'. The method seems to be a classical controller.

Author’s response 3:

As the reviewer pointed out, there was no detailed explanation about "Cooperative control". In this study, in addition to the proposed adjustable speed DFIG, the Battery Energy Storage System (BESS) directly monitors the system frequency fluctuation, and then suppresses the fluctuation by charging and discharging power in the same way as the DFIG. At this point, as described in Point 2 above, the gains G_P, G_D in Figure 10, and the values on the horizontal axes in the membership function of the fuzzy control system of the BESS in Figure 11(a), (b) have been repeatedly tried in various patterns in order to further enhance the effect of DFIG control.

In this paper, the specific diagram of control configuration that clearly indicates that it is "Cooperative" is not included, but this is called "Cooperative control" in this study because DFIG and BESS operate simultaneously and cooperatively to suppress system frequency fluctuations under different fuzzy control parameters.

The following sentences were inserted in Section 4 (revised manuscript, line 212).

“However, the control gain for the input signal and the membership function of the fuzzy control system in the BESS are different from those of DFIG, and they are tuned to behave cooperatively to further enhance the effectiveness of the control by DFIG.”

Reviewer 2 Report

The addressed topic is very much important and refers at an isolated small scale power system including renewable power sources.

The authors propose a simulated application that analyses the possibility of using adjustable speed diesel engine-driven power plant with employing doubly-fed induction generator for contribute to fast and flexible power balancing regulation in a power system with renewable power sources. Installation of a battery system is also considered by the authors.

In the paper, the authors present the topology of the small scale power system and the models for the diesel engine driven power plant, the battery energy storage system, the wind power station.

Using these models, the authors analyze the efficacy of the proposed approach to suppress the frequency fluctuations in small scale power system by the adjustable speed diesel engine-driven generator, system behavior under vacillated power from a wind power station in the power system.

However, I will provide some comments to improve this paper:

The authors must improve the introduction section in order to present related works in this topic.
The fonts used in Fig 5, 13 and 14 are too big. Please reduce the fonts.
The results obtained by simulation are not validated by experiments.
It is suggested to upgrade the references and add some new references.
Please renumber the conclusions section with 6.
Please add more references because the number of scientific references is too low.

Author Response

Response to Reviewer 2 Comments

Thank you very much for your time in reviewing the paper. Also, thank you for your valuable comments which will be definitely improve the paper quality.

The authors tried to address all the comments as follows;

Comments and Suggestions for Authors,

The addressed topic is very much important and refers at an isolated small scale power system including renewable power sources.

In the paper, the authors present the topology of the small scale power system and the models for the diesel engine driven power plant, the battery energy storage system, the wind power station.

However, I will provide some comments to improve this paper:

Point 1: The authors must improve the introduction section in order to present related works in this topic.

Author’s response 1: In most of other research reports related to this study, the main control target is storage batteries. Therefore we selected articles of which contents are close to the purpose of this study and listed them in the reference list. Revised parts are shown in the manuscript by red colored characters and yellow highlighting.

Point 2: The fonts used in Fig 5, 13 and 14 are too big. Please reduce the fonts.

Author’s response 2: According to your comment, size of the fonts in Figure 5, 13 and 14 are reduced. In addition, we checked size of the fonts in other figures and reduced some of them.

Point 3: The results obtained by simulation are not validated by experiments.

Author’s response 3: We agree with your pointing out. However, this paper is mainly aiming to propose ‘concepts’ that form the basis of this research, and therefore, the verification of validity by experimental consideration will be performed in the next stage. In addition, the simulation is performed by the power system analysis software PSCAD/EMTDC which is recognized worldwide, and the accuracy of the simulation is considered to be reliable enough.

Point 4: It is suggested to upgrade the references and add some new references.

Author’s response 4: As mentioned in ‘author’s response 1’ above, references related to this study have been added.

Point 5: Please renumber the conclusions section with 6.

Author’s response 5: Thank you for your pointing out. We made a mistake about the number. It has been corrected as ‘6’.

Point 6: Please add more references because the number of scientific references is too low.

Author’s response 6: As mentioned in ‘author’s response 1’ above, references related to this study have been added.