Energy Management Using a Rule-Based Control Strategy of Marine Current Power System with Energy Storage System
Round 1
Reviewer 1 Report
This paper proposes energy management based on rules to compensate for the fluctuating power caused by tidal motion and improve the operation efficiency of VRB by incorporating supercapacity.
Several comments on this submission:
1) Using the hybrid energy storage system is not a new topic; the super-capacity can improve the battery's efficiency and reduce the ageing capacity of the battery has been investigated in the literature long time, more than 10 years. So the novelty of this manuscript is not very strong, according to my knowledge.
2) I suggest authors merge figures 8, 9, 10 into one big figure. In this way, the current flow, power flow and the corresponding efficiency profile within 24 hours can be read more clearly. The same suggestion to the figures of showing the results of the proposed rule-based stragety.
3) On line216, son[29], The power of VRB (P_VRB) flows to compensate
4) In figure 7, there should be some description for the box with k parameters and box of nomarlization.
5)Concerning the proposed rule-based strategy, why name the threshold voltage delta I? Difference is the most common meaning of the uppercase delta; I do not think there is a difference here. These two threshold current values just the maximum points in figure 5, right?
6)Last but not least, have the authors considered that it would be worthwhile to add supercapacitors to the entire system to increase the efficiency of the battery? From an economic point of view, can the cost of adding supercapacitors be compensated by the increased battery efficiency? Just a suggestion one paper to analyze the cost of the electrical energy system "Cost-aware design and simulation of electrical energy systems."
7)Why considering the VRB battery? Because it is more adapted to the marine environment than lithium or lead batteries? Or is there some other reason?
Author Response
Dear reviewer:
Please see the attachment.
Sincerely
Author Response File: 
Author Response.pdf
Reviewer 2 Report
- In the introduction, the importance of renewable energy is given, however, there should be a short description of other renewable energy sources, such as wind and solar. Next, the significance of ocean energy can be provided and the major reason for the need to benefit from ocean energy. This can be embedded at the beginning of the introduction in one paragraph.
- In lines 58 and 85, PMSG is described properly, while, it is advisable to briefly Squirrel Cage Induction Generator (SCIG) compared with PMSG. By efficiency, and some characteristic.
- 4.2. Simulation results based on rules control strategy can be converted to the discussion while describing its relevant content. However, it is not a must and can lead to a better flow of the text.
- Grammar and vocabulary choice are both properly written. In addition, the reference numbers match the work volume.
- I show no objection to the publication of this work.
Author Response
Dear reviewer:
Please see the attachment.
Sincerely
Author Response File: Author Response.pdf
Reviewer 3 Report
This paper proposes an energy management control strategy based on rules to compensate for the fluctuating power caused by tidal motion. The hybrid energy storage system composed of vanadium redox flow battery (VRB) is applied to reallocate power. Supercapacitor banks (SCB) is applied as the auxiliary power source to absorb or release required power according to energy management strategy based on control rules in the marine current power system.
The article is written in quite simple way, without using complicated math operations. The article should be useful for practical applications.
Below you find the list of comments and spotted irregularities, that should be corrected.
1) L.10 The authors use the comparative form in the sentence, but do not specify what they are comparing here. Higher reliability, but from what? Better control performance, but from what?
2) L.36 In the Line 36 the denotation MCT was introduced. But this denotation was not explained here, but only in the Line 58.
3) L.38 In the Line 38 the denotation MPC was introduced. But this denotation was not explained in the article. It should be given, that MPC means Model Predictive Control.
4) L.44 In the Line 44 the denotation PSO was introduced. But this denotation was not explained in the article. It should be given, that PSO means Particle Swarm Optimization.
5) The terms used by the authors are not always precise and unambiguous. The used term: “bidirectional DC/DC circuit” should be changed for: “bidirectional DC/DC converter”. The better name for the converter connected to PMSG is the Machine Side Converter (MSC). The better name for the converter connected to AC grid is the Grid Side Converter (GSC).
6) In Line 71 it should be more precisely stated that the water mass density is considered. In Line 71-72 it should be stated, that the R means the length of blade radius given in m.
7) The Authors in Eq.(1)-(2) present the relationships for determining the power of marine current turbine and the mechanical power coefficient. Similar equations are widely presented in the literature for the wind turbines. The Authors should give citations for the validity of the presented dependencies. The exponential model for turbine power coefficient was used. In similar equations for wind turbines the angle beta is given in degrees, not in radians. How is in this case?
8) It is not stated in the article whether the gear or gearless mechanical system of turbine is considered. For gear system wref in (3) is the rotational speed of the turbine rotor. Only for the direct gearless system wref can be treated as the rotational speed of the generator rotor because it is equal to the rotational speed of the turbine rotor.
9) In Eq.(4) a receiver arrow system was adopted for the circuits of PMSG. For this arrow system the torque Te is positive for the motor operation , but it is negative for the generator operation. It should be included in the motion equation in (5). In the motion equation (5) there is a direct summation of the turbine torque and the generator torque. It is valid only for the gearless system. The relationship for the electromagnetic torque Te in (5) is valid only when Ld=Lq, it means only for the cylindrical rotor of PMSG.
10) It is not described or cited how the coefficients presented in (6) were obtained. All these factors are expressed as percentages. But in the denominator of the coefficient d2 there is the sum of the absolute quantity and the product of the absolute quantity and the percentage.
11) In Equations (9) the components of grid current vector have the same symbols as the components of PMSG stator current vector. In this equations the source arrow system is adopted. The dq system for the grid is not the same dq system for PMSG. In Eq.(9) rotation voltages have mistakenly the same signs. The meaning of variables and parameters in Eq.(9) should be described.
12) The system presented in Fig.1 is quite empty. It is desirable to mark the individual currents on the circuits in Fig. 1: Iger, IHESS and other currents.
13) In Line 303 there is incorrect reference to Fig. 15, and it should be to Fig. 16.
14) In the analysis of energy management control strategy the influence of the capacitance in the DC bus is neglected. But this capacitance can be also charging and discharging and influence on the flow of energy.
15) The control strategy seems to be limited only to the control of DC/DC converters. The description of the control of the main converters – machine and grid side converters is not described.
16) The presented energy management control strategy is based on the algebraic dependencies and it is not quick control, as it is necessary in power electronic converters.
17) The dimension of Pn in Table A1 is not given. There are not data of rated voltages and currents of the PMSG and used converters.
Author Response
Dear reviewer:
Please see the attachment.
Sincerely
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
In my opinion, the paper reached the proper level, however, I strongly recommend that authors improve the novelty of their article.
