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The authors have declared that no competing interests exist.

Under the background of high-energy penetration of new energy into the power grid, this paper takes the ancillary service capability of photovoltaic energy integrated into the grid as the starting point and builds a photovoltaic system reactive power service impact evaluation model on the grid energy efficiency. This is based on the multi-temporal and spatial scale operation mode, in order to study the supporting principles of photovoltaic system reactive power services on the energy efficiency of grid operation and the law of influence on system energy efficiency changes. In this way, the space for power system energy efficiency improvement and the reactive power service market value of renewable energy are explored to improve the renewable energy auxiliary services participation in the theoretical system of electric power spot market transactions. The research conclusions can provide a decision-making reference for system dynamic energy efficiency management and can assist relevant market entities to make optimal decisions in spot market transactions, and provide empirical data for improving the theory of renewable energy participation in auxiliary service market transactions.

Under the background of high-energy penetration of new energy into the power grid, the impact of new energy on the safe operation of the power grid is one of the hot topics today. However, the research on the mechanism and effect of reactive power support capacity on the energy efficiency of grid operation lacks corresponding attention. Mostly, power grid companies do not have a full understanding of the relationship between reactive power support capacity and grid energy efficiency. Furthermore, the reactive power support function of the photovoltaic power generation system has not been fully tapped. The auxiliary service of photovoltaic power generation system is mainly to make full use of the residual capacity of the inverters in the photovoltaic power generation system and the SVG devices to provide reactive power for the power system, to realize the balance of reactive power of the power system and support for the voltage stability of the power system. The reactive power supporting equipment in the photovoltaic power generation system mainly includes inverters and SVG devices. When determining the plan for connecting the photovoltaic power generation system integrated to the power grid, there is a lack of effective methods to evaluate the impact of its reactive power support capacity on changes in the energy efficiency of grid operation. Therefore, the determined planning objectives for the photovoltaic power generation system integrated into the grid have a restrictive effect on the energy efficiency improvement in the grid company’s later grid operations. The real-time balance of reactive power plays an important role in stabilizing market transaction electricity prices. Renewable energy represented by photovoltaic power generation is widely integrated into the power grid, researches on economic operation control, power quality, energy efficiency evaluation, optimal utilization of reactive power resources, energy-saving and emission reduction, and their impact on grid stability after grid connection have achieved certain results. However, there is a lack of mechanism explanation for the degree of its impact on the energy efficiency of the power grid. Clarifying the relationship between the reactive power resources in the renewable energy power generation and the energy efficiency of the power grid operation can further promote room for improvement in the energy efficiency management of the power grid. Under the multi-temporal and spatial scales operation mode of the system, based on the supporting capability of auxiliary services of renewable energy, how market entities in the power system can make effective market trading strategies for changes in power system energy efficiency to improve its income is an urgent problem for all entities to solve. Especially under the background that renewable energy has fully penetrated the power grid and the energy utilization structure has been transformed, it still needs theoretical basic research to mine the value of the reactive power resources of renewable energy based on the perspective of energy efficiency management to realize the optimal allocation of system resources and energy-saving and emission reduction of the power system.

At present, academic scholars mainly focus on the following four aspects concerning the energy efficiency of the power grid, the reactive service capability of the photovoltaic power generation system, the new energy grid-connected operation control, and its optimized scheduling.

Firstly, some research focuses on the reactive power support capability of inverters and SVG devices in photovoltaic power system and their coordination and optimization. Research [

Secondly, some research focuses on comprehensive benefit and energy efficiency evaluation of photovoltaic power systems. Research [

Thirdly, the research focuses on the efficient utilization, and carbon emission reduction of renewable energy power generation after renewable energy is connected to the power grid. Research [

Fourth, some research focuses on the power quality of the power system after renewable energy is connected to the grid. Research [

Time | Research | Research content | Research solves the major problem | Research goal | Research method |
---|---|---|---|---|---|

2021 | [ |
Optimal local voltage control strategy for photovoltaic inverters in active distribution networks | The problem of voltage exceeding the limit in the process of continuous increase of the penetration rate of photovoltaic power generation in the active distribution network. | Reduction of voltage overruns and minimization of power network losses as the goal | Convolution Neural Networks (CNN) |

2021 | [ |
A voltage adjustment method for active distribution network considering reactive power optimization of substations | Fluctuations in photovoltaic power generation lead to significant voltage fluctuations in active distribution grids | Running loss minimization as the goal | Non-dominated Sorting Genetic Algorithm-II (NSGA-II) |

2021 | [ |
Reactive power optimization algorithm of distribution network with the photovoltaic power generation system | After the photovoltaic power generation system is connected to the distribution network, the power quality decreases, the system’s active power loss increases, and the system is unstable. | System stability and the economy as a goal | Non-dominated Sorting Genetic Algorithm-Ⅲ (NSGA-III) |

2021 | [ |
Integrated energy system carbon emissions and carbon trading, as well as power-to-gas equipment and photovoltaic co-optimized configuration | How to improve the utilization efficiency of IES and the supporting capability of reasonable equipment configuration in IES for carbon neutrality | The goal is to minimize the total cost of system operation | K-means |

2020 | [ |
Voltage Coordinated Control Strategy of Distribution Network with Distributed Photovoltaic Generation | Distributed photovoltaic grid connection brings problems such as many centralized control dimensions and complex control process of voltage to the distribution network. | Realize fast control in case of system emergency and reach the voltage safety range | Clustering By Fast Search and Find Of Density Peaks (CFSFDP) |

2019 | [ |
Three-stage reactive power and voltage control strategy of inverter based on high-penetration photovoltaic power generation system | Uncertainty of PV power output and load demand | reducing energy loss and voltage deviation as a goal | Robust Optimization (RO) |

2019 | [ |
Simulation of consumption capacity of distribution network and research on voltage control strategy under high penetration rate of photovoltaic power generation | The imbalance between photovoltaic output and load leads to reverse the tide in the line current, causing voltage out-of-limit problem | improving photovoltaic consumption capacity as a goal | Monte Carlo method (MC) |

- | This research | Research on the supporting mechanism of photovoltaic system auxiliary service to grid energy efficiency | Mining of auxiliary service resource value of photovoltaic power generation system and its impact on the dynamic energy efficiency of the power grid | The correlation between the reactive power service of the photovoltaic system and the energy efficiency of the grid, and the law of dynamic changes in the energy efficiency of the system | Pearson correlation coefficient, mean-semi-absolute dispersion, and t-test |

Based on the research progress and shortcomings of existing literature, this paper may have the following academic contributions and values:

By analyzing the boundary operating characteristics of the photovoltaic power generation system after it is integrated into the grid, typical operation modes of power systems, typical operation load rates, different grid structures, and two boundary reactive power operation modes of inverter devices or SVG devices in photovoltaic power generation systems are simulated. The correlation effect analysis model of photovoltaic power system reactive power service to support grid energy efficiency support, which is based on Pearson method and power system voltage deviation, active loss, and line loss rate as the core indicators are designed. Taking the auxiliary service capability of the photovoltaic power generation system as the starting point, the mechanism of the reactive power service capability of the photovoltaic power generation system support the energy efficiency of the power grid operation is studied, and the effect of the reactive power supporting capability of the photovoltaic power generation system on the energy efficiency supporting of the power grid operation is planned to be verified. It provides decision-making reference for the planning and design, investment cost control, and energy efficiency management of the grid company before the photovoltaic power generation system is integrated into the power grid.

In this paper, a mean-semi-absolute deviation and t-test system operation energy efficiency correlation effect evaluation model is constructed. Through calculating the deviation of voltage or energy consumption, the difference in the impact of the reactive service capability of inverters or SVG devices in the photovoltaic power generation systems on changes in the energy efficiency of grid operations is verified. Based on the comparison of different combined operation modes, the effect of reactive power support capacity of photovoltaic power generation system on energy efficiency support of grid operation is verified. It is expected to provide decision-making references for planning and design, investment cost control, and energy efficiency management of grid companies before and after the photovoltaic power generation system is integrated into the grid. Meanwhile, taking the supporting effect of the reactive power service of the photovoltaic power generation system on the grid operation energy efficiency as an example, it is intended to reveal the general law of the impact of renewable energy on the grid operation energy efficiency after grid connection, to prove that renewable energy has participated in the auxiliary services of the power system to the system, to prove the extent of renewable energy’s impact on the energy efficiency of the system after participating in auxiliary services of the power system. It provides a theoretical basis for the construction of a market mechanism for auxiliary services containing renewable energy and transaction optimization decisions.

The research on the supporting mechanism of a single photovoltaic power generation system to the grid energy efficiency and the dynamic energy efficiency analysis method of multi-temporal and spatial scales can be further applied to the dynamic energy efficiency analysis in the grid cluster mode such as photovoltaic cluster or wind and solar cluster. Through the coupling mechanism and division of different cluster modes research realize the power grid lean energy efficiency management, and provide ideas and methods for power grid energy conservation and loss reduction.

The reactive power demand of photovoltaic power plants mainly originates from the transformer, collector line, and delivery line. The active power output of photovoltaic power plants fluctuates and is random. At the same time, the reactive power demand for photovoltaic power plants will change with the actual power output of photovoltaic power plants. The SVG device in a photovoltaic system is connected in parallel to the bus of low voltage side of the main transformers, which mainly compensates the reactive power requirement of main transformer and transmission line, and SVG generates the maximum reactive power to support the grid voltage in case of power grid failure. Based on the reactive power regulation capability of the inverter itself (i.e., when the active power of the inverter is at full load, i.e., 1 pu (per unit), its reactive power output can be adjusted between—0.484 pu and + 0.484 pu), the reactive power demand of transformer and collector can be compensated locally. Due to the different capacities of the photovoltaic power system connected to the power grid, the photovoltaic power system has an impact on the node voltage and active power loss.

On the other hand, after the photovoltaic power generation system is connected to the grid, a high-order harmonic current will be generated, and the harmonic current will have a certain impact on the energy consumption of the grid. Research [

Balanced regulation of active and reactive power of each node in the system under steady-state operation should be mainly considered during power grid energy efficiency management, and corresponding stability requirements should be met to ensure the safe operation of the power grid.

In the process, N is the number of nodes: _{GI}, _{Li}is the generator and load reactive power, kVar; _{i} is the voltage amplitude of node i, kV; _{ij} is the phase angle difference between two nodes, rad; _{ij}, _{j} are the real and imaginary parts of node admittance, S. ^{1} is the probabilities of different operation modes, ι is the all column 1 vector.

The Newton-Raphson method is used to calculate the power flow of the power grid. The Newton-Raphson modified equation is as follows:

In the formula, Δ

The voltage deviation formula is as follows:

In the formula, _{i} is the node voltage, kV; _{s} is the system nominal voltage, kV. Under normal operation mode, the absolute sum of positive and negative deviations of supply voltage does not exceed 10% of nominal system voltage.

The nodal equivalent power method is used to calculate the active power loss. The formula is as follows:

In the formula, R is the branch resistance, Ω; t is time, s; P is the node active power, kW; Q is the node reactive power, kVar.

The comprehensive energy efficiency of the system is calculated by subtracting the statistical line loss rate by 100%. The formula for calculating the statistical line loss rate is as follows:

In the formula, _{loss} is the line loss power, kW‧h; Ag is the power supply, kW‧h.

Pearson correlation coefficient is used to calculate the correlation. The formula is as follows:

In the formula,

The correlation coefficient can describe the degree of correlation between variables and the positive and negative attributes. The positive and negative values of r represent the positive and negative correlation of variables. 丨r丨 represents the degree of correlation of variables. The larger 丨r丨 is, the stronger the correlation degree is, and the smaller 丨r丨 is, the weaker the correlation degree is.

Mean-semi-absolute deviation [

In the formula, p is the simulation calculation values of voltage and energy consumption,

The test is used to test the hypothesis of the deviation of voltage deviation and active power loss under different operation modes to verify the difference of positive and negative correlation between reactive power support capability of the photovoltaic power system and power grid operation efficiency under different combined operation modes.

In the formula, _{a/2}, the original hypothesis is negated. Otherwise, the original hypothesis is accepted.

There are 7 main conditions as follows:

In the future, the popularization and utilization of reactive power optimization system software for photovoltaic power generation systems will be more extensive, that is, it is assumed that the reactive power optimization control system in photovoltaic power stations can realize the coordination of reactive power support functions of SVG or inverter devices.

It is assumed that the harmonic current generated by the grid connection of a single photovoltaic power generation system has a negligible impact on the energy consumption of the grid.

It assumes that the load characteristics of a randomly selected system are specific, the peak-valley difference rate (percentage of the difference between maximum load and minimum load divided by maximum load) corresponding to the load characteristic curve is not affected by load rate (percentage of the average load to the maximum load ratio in the specified time) of the operating system. It also assumes three different load rates (see

It assumes that photovoltaic power system is connected to the 14-node system (a grid structure in the International Power System Database) of the IEEE (Institute of Electrical and Electronics Engineers), and it simulates photovoltaic power system connected to the IEEE 57-node system for further theoretical verification;

In different node systems, the position of the photovoltaic power generation system incorporated into the node is different, and the impact on the energy efficiency of the power system is different. This article assumes that the merged node position is randomly selected. For two (IEEE57, IEEE14) node systems, choose to merge from node 7 respectively.

It is assumed that the fundamental operation data of IEEE14 and IEEE57 bus systems are used to calculate corresponding energy efficiency indexes as the initial state for analysis and comparison (i.e. the state without connection to photovoltaic power system), hereinafter referred to as the initial state;

This paper assumes that under different combinations of operation modes, there is a difference in terms of the correlation between voltage deviation and power loss of inverters or SVG devices with reactive power support capability in the photovoltaic power system. When the original hypothesis is negated. Otherwise, the original hypothesis is accepted. The test level is generally less than 0.05, indicating that the probability does not exceed 0.05.

Operation mode | Large operation in summer | Large operation in winter | Small operation in summer |
---|---|---|---|

Load rate | 60% | 40% | 22% |

The total installed capacity of a photovoltaic power plant is 60 MW with six collector lines in total. Each collector line is connected with 10 groups of PVGU (Photovoltaic Generation Unit) in series, and each group of PVGU has a capacity of 1 MW, which is connected to collector lines of 10 kV through step-up transformers. The capacity of the 110 kV main transformer is 63 MVA (capacity unit), and the length of transmission lines is 80 km. The LGJ-185 conductor (line model) is used. SVG devices can be directly parallel connected to a 10 kV bus in a photovoltaic booster plant. Based on the 110 kV high-voltage side, SB = 100MVA, and in order to simplify the calculation, it is set to be 1pu. The equivalent circuit of the photovoltaic power system connected to the power grid (due to the limited length of the article, the parameter derivation of the equivalent circuit is omitted) is shown in

With the goal of quantitative analysis and calculation, the system load ratio under three operation modes of Large-scale Winter, Large-scale Summer, and Small-scale Summer is assumed as shown in

Mode | Photovoltaic active power | Inverter reactive power | SVG reactive power |
---|---|---|---|

Mode 1 | 0.6 | 0.29 | 0 |

Mode 2 | 0.6 | 0 | 0.1 |

According to formulas (1), (2), (3), and (6), the voltage deviation correlation between the combination mode in

The correlation coefficients of voltage deviation are calculated based on the comparison of three load rates in

Active power is calculated according to formulas (1), (2), (4), and (6), and the initial active power loss of the IEEE14 system is 0.1318 pu. The variation of active power loss under different operation modes and different load rates is shown in

The correlation coefficient of active power loss is shown in

Mode 1 and mode 2 | Large operation in summer and winter | Large operation in summer and a small operation in summer | Large operation in winter and a small operation in summer |
---|---|---|---|

1 | 0.9998 | 0.9956 | 0.9972 |

Based on the operation modes of Tables

From

Based on the results of correlation analysis between reactive power support of the photovoltaic system and the energy efficiency index of power grid under different operation modes, the t-test is used to verify the difference of correlation effects. According to formula (8) and its hypothesis, the three operation modes of mode 1, mode 2, and

In order to further verify the difference of the influence of reactive power support of a photovoltaic system on the energy efficiency index of power grid under various combined operation modes, node 7 of the IEEE57 system is simulated to connect to the photovoltaic power system. The t-test values of voltage deviation and energy consumption are shown in

In mode 1 and mode 2 of

After the photovoltaic power generation system is integrated into the power grid, within 00:00–24:00, the correlation coefficient between the voltage deviation value and the initial state voltage deviation in a variety of operating states fluctuates between 0–1, and the fluctuation trend changes greatly. This generally shows a positive correlation indicating that it is greatly affected by changes in system load.

After the photovoltaic power generation system is integrated into the power grid, under different combinations of operation modes, the correlation coefficient indicators of active loss and voltage deviation are above 0.9 within 00:00–24:00, showing a positive correlation. Its correlation coefficient fluctuates with the change of the load rate, which shows that the active power loss and voltage deviation of the system are closely related to the change of the load rate.

When the active power of a photovoltaic power generation system is constant, within 00:00–24:00, the correlation coefficient of active loss in different operating modes is above 0.99, that is, the reactive power support capacity of the photovoltaic power generating system is basically not affected by different operating modes and it affects the power system. The trend of the effect of active power loss is consistent; at the same time, the overall energy efficiency change trend of the system can reflect that at the lowest point of the initial value of energy efficiency (at 20:00) and other times, the energy efficiency values of different operating modes are higher than the initial value of energy efficiency; At the same time, the comprehensive energy efficiency change trend of the system can reflect that at the lowest point of the initial value of energy efficiency (at 20:00) and at other times, the energy efficiency values of different operating modes are higher than the initial energy efficiency value.

Based on the T-test effect in the statistics, that is, the analysis in H shows that there is no significant difference between the positive correlation of reactive power support capacity of the photovoltaic power generation system to the improvement of grid energy efficiency, and the improvement effect of the different operation combination modes, that is, the combination operation mode is not affected by most of the time.

The positions of the merged nodes of the photovoltaic system assumed in this article are randomly selected, and the selected node system is representative. When different nodes are merged, the energy efficiency change curve and correlation index are different. The access point based on the best energy efficiency can be determined by the system-wide node access simulation according to the analysis model constructed in this paper. In general, the integration of photovoltaic power generation systems from different nodes is effective in improving the energy efficiency of system operations.

Different types of renewable energy, under the assumptions in C, are simulated and verified based on different reactive power support boundary conditions, the system’s multi-time scale load demand, and multiple operating modes. Therefore, similar results can be obtained.

The above results are based on six assumptions in C and the operation modes designed according to the operation characteristics of the power grid (Tables

Due to the differences in reactive power equipment and reactive power support capabilities of other renewable energy sources, the changing trend and correlation index values of the system energy efficiency will be different from the results of this paper. This research provides an energy efficiency evaluation and analysis method based on the multi-temporal and spatial scale operation mode, however, in the process of selecting the location of renewable energy to be integrated into the grid, due to the constraints of power construction channels, investment costs, and other factors, the operating energy efficiency of the system may not be fully considered. Therefore, research based on multiple operating scenarios and constraints of planning and construction needs to be further expanded. At the same time, the application of this method needs to be combined with the actual operating data of the power grid to analyze and compare. It also provides data support for the market value of renewable energy reactive auxiliary services based on the perspective of system energy efficiency analysis and verifies the improvement effect of system operation efficiency.

In this paper, by analyzing the harmonic control function of the photovoltaic grid-connected inverters themselves and the contribution of the harmonic distortion rate of current of the photovoltaic power generation system to the energy efficiency of the power grid, the research case ignores the impact of harmonics generated by a single photovoltaic power station on the line loss of the power grid. Due to its small contribution, the photovoltaic power generation system has little influence on the changing trend of the grid energy efficiency; although the research method in this paper has laid a theoretical foundation for the dynamic energy efficiency analysis of the grid under the photovoltaic cluster mode, in the actual grid operation, the load is constantly changing where changes and differences in power load characteristics will affect the content of harmonic currents in the power system. Especially in the mode where the power system is connected to a large number of photovoltaic clusters, the harmonic superposition or cancellation effect of different photovoltaic clusters after grid connection will cause an impact on the energy consumption and reliability of power grid operation. Therefore, the degree of influence of photovoltaic power generation clusters on the dynamic energy efficiency change trend of the power grid needs further research.

The SVG capacity of photovoltaic power systems is usually 20%-30% of the capacity of power plants. Assuming that 100 MW photovoltaic power plants are equipped with 20 MVar SVG devices, the SVG loss is set as 0.2% of the output capacity during system operation, and the average power cost is 0.0714 USD/kW‧h, then the annual power consumption of 20 MVar SVG is 350,400 kW‧h (20000Var*0.2%*24h*365days), and the operation loss will be 625,464 USD (350400‧h*0.0714USD*25Years) after 25 years. Through research on the correlation between reactive power support of inverters and SVG devices and power grid, inverters can substitute SVG devices for their equivalent reactive power support. Therefore, the capacity configuration of SVG can be reduced during design. At present, the unit cost of 35 kV suspended SVG is about 14.2857USD/kVar. By reducing 10 MVar capacity allocation, the cost will be reduced to 142857USD, and the operating loss will also be reduced.

This paper takes the reactive power capabilities of the photovoltaic power generation systems as the starting point to study the role of its reactive power capabilities in supporting grid energy efficiency. By analyzing the boundary operating characteristics of the photovoltaic power generation system after it is integrated into the grid, the typical operation load rate and multi-spatial-temporal operation mode of reactive power service in photovoltaic power generation systems are simulated. The correlation effect analysis model of photovoltaic power system reactive power service to support grid energy efficiency support based on the Pearson method and power system voltage deviation, active loss, and line loss rate as the core indicators are designed. At the same time, a mean-semi-absolute deviation and t-test system operation energy efficiency correlation effect evaluation model is constructed. Through calculating the deviation of voltage or energy consumption, the difference in the impact of the reactive service capability of inverters or SVG devices in the photovoltaic power generation systems on changes in the energy efficiency of grid operations is verified. The mechanism of the photovoltaic system reactive power service to the energy efficiency support of grid operation is revealed. Research conclusions show that: (1) The model constructed in this paper can effectively analyze the impact and change trend of renewable energy on the system operation energy efficiency after it is integrated into the power grid. The research data can provide a decision basis for tapping the energy efficiency improvement space and has a certain reference value on optimizing the design of renewable energy grid-connected projects and investment cost control. (2) Under the combination of different operation modes of the system based on multi-spatial-temporal scales and the reactive power support of the photovoltaic power generation system, the reactive power support capacity of the photovoltaic power generation system can generally improve the operational energy efficiency of the power grid, that is, the impact on the power efficiency of the power system operation is the positively correlated effect. This conclusion provides a theoretical basis for promoting its increase in the proportion of consumption in power transactions. Research-based on the market value of reactive power services has enriched the theoretical system of renewable energy participating in auxiliary service market transactions. (3) Taking the effect of the reactive power service of the photovoltaic power generation system on the grid energy efficiency as an example, this article reveals the mechanism of the impact of renewable energy on the grid energy efficiency after grid connection. The energy efficiency change data of the multi-spatial-temporal operation mode can provide theoretical support for the auxiliary service transaction decision in the real-time power balance market. (4) The analysis method based on the auxiliary service of the photovoltaic power generation system to support the dynamic energy efficiency of the power grid provides ideas and theoretical references for the research on the energy efficiency management decision-making of the photovoltaic cluster or the wind and solar cluster.

(DOCX)

PONE-D-22-00222Research on Supporting Mechanism of Reactive Power Service of PV System to Grid Energy Efficiency Based on Multi-time and Space-time OperationPLOS ONE

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Reviewer #1: The author presented a study on Mechanism of Reactive Power Service of PV System to Grid Energy Efficiency Based on Multi-time and Space-time Operation. The study is interesting, which I think merits a publication. However, I have the following comments:

1) The authors should consider harmonic issue and discusses how the proposed solution can mitigate the said problem. An extensive review of research in harmonic mitigation effort has been published in ["Advances in reduction of total harmonic distortion in solar photovoltaic systems: A literature review", International journal of energy research] and this can serve as a starting point for carrying out this addition. A research article on harmonic mitigation of PV system has also been published in ["Predictive Adaptive Filter for Reducing Total Harmonics Distortion in PV Systems", Energies]. The author can choose to either discuss the harmonic mitigation effort in a new section or perform an additional harmonic analysis.

2) The authors should benchmark their work with similar studies performed in ["A high-gain reflex-based bidirectional DC charger with efficient energy recycling for low-voltage battery charging-discharging power control", Energies], ["A new combined boost converter with improved voltage gain as a battery-powered front-end interface for automotive audio amplifiers", Energies] and ["Study of a Bidirectional Power Converter Integrated with Battery/Ultracapacitor Dual-Energy Storage", Energies].

Reviewer #2: The article presents an interesting Research on Supporting Mechanism of Reactive Power Service of PV System to Grid Energy Efficiency Based on Multi-time and Space-time Operation. the article is well written, but it may be let down at its current form due the lack of flow or presentation quality:

1- The main contribution of the article is not clearly highlighted.

2- The introduction is too long and as a reader we may loss the main point of the article. Please revise it with better flow that highlights the issue and the contribution of the research.

3- All figures quality are not acceptable especially Fig 1. Please redraw this figure and enhance the fonts quality in others.

4- Ref 2 is not cited in the text, and there is no any reference of last 3 years!!!.

5- Adding a table of abbreviation could clear many points to readers.

6. Table of comparison of conducted work and related works in literature will point out the improvement of the findings.

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Research on Supporting Mechanism of Ancillary Service of PV System to Grid Energy Efficiency Based on Multi-time and Space-time Operation

PONE-D-22-00222R1

Dear Dr. Shao,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Ziqiang Zeng, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Based on the referees' review comments, this paper could be accepted.

Reviewers' comments:

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Reviewer #1: All comments have been addressed

Reviewer #3: All comments have been addressed

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Reviewer #1: Yes

Reviewer #3: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #3: Yes

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The

Reviewer #1: Yes

Reviewer #3: Yes

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Reviewer #1: Yes

Reviewer #3: Yes

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Reviewer #1: All comments have been addressed and there is no more additional comments. Thank you for the addressing the comments.

Reviewer #3: (No Response)

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Reviewer #1: No

Reviewer #3: No

PONE-D-22-00222R1

Research on Supporting Mechanism of Ancillary Service of PV System to Grid Energy Efficiency Based on Multi-time and Space-time Operation

Dear Dr. Shao:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact

If we can help with anything else, please email us at

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Ziqiang Zeng

Academic Editor

PLOS ONE