Variable Renewable Power Research Articles

Addressing the limitation of Operational Flexibility in Power Generation with Pumped Hydro Energy Storage System – Indian Perspective

The global climate change scenario has impacted and taken corrective measures in shifting the sourcing of primary energy and efficient end-use pattern with more focus to utilise renewable energy resources to replace the depleting fossil fuels. Electric power generation capacity in the Indian subcontinent has gradually been improved to substantially contribute to intermittent and variable renewable power generation mix up to 40% of grid demand. However, the injection of grid-integrated renewable power as per the availability of generation potential will necessitate limiting the power generation from generating plants running on fossil fuel. But the operational flexibility of fossil fuel power plants is mostly designed to run efficiently with a 55% minimum technical load on the machines. In the above situation, stable grid availability and operation with a desirable spinning reserve may be taken care of suitably with an on-grid energy storage system, and in the Indian context, a pumped hydro energy storage system may play a critical role to take care of grid operational variability with adequate measures on frequency and voltage correction through periodic power generation and power draw. In this paper, the feasibility of a pumped hydro storage system from an Indian power sector perspective has been reviewed about the present national power scenario.

Synergies of variable renewable energy and electric vehicle battery swapping stations: Case study for Beijing

Battery swapping technology has emerged as a promising option for simultaneously addressing electric vehicle (EV) range anxiety and uncoordinated charging impacts, thereby enabling a renewable-powered future at the city scale. This study aims to explore the potential synergies between variable renewable energy (VRE), including wind and solar power, and the city-scale operation of battery swapping stations (BSSs) under varying levels of VRE penetration. To this end, an integrated modeling framework that combines multisource traffic data with node-based BSS deployment optimization and hourly power system dispatch simulations was developed. Beijing in 2025 was selected as the case study due to its ambitious EV development goals and the substantial need for VRE integration. The simulation results reveal that system-optimized BSS operations, particularly through bidirectional charging (V2G), can significantly enhance VRE integration, reduce net load fluctuations, and mitigate carbon emissions. Specifically, increasing VRE penetration from 30 % to 70 % reduces VRE curtailment by 1.1 TWh to 6.4 TWh and avoids 3.0 t to 6.3 t of carbon emissions per vehicle annually. The economic analysis further indicates that while current time-of-use electricity pricing leads to higher costs for BSS operations, a real-time pricing mechanism offers a more economically viable solution, benefiting both power system operators and BSS operators. The integrated modeling framework developed in this study not only advances the understanding of city-scale BSS operations but also provides a valuable tool for analyzing the complex interactions between EV infrastructure, VRE integration, and urban power grids.

Driving factors of residential demand response for the integration of variable renewable power.

The large-scale integration of renewable power poses great challenges to grid stability. Among flexible resources, demand response (DR) stands out for its advantages in cost and efficiency. To identify key factors influencing DR, this study adopted the modified theory of planned behavior (TPB) to establish the conceptual model. Social norms were included as a front-end variable, and institutional factors and electricity consumption habits served as moderating variables. The model was subsequently tested and modified using the structural equation modelling (SEM). Results indicated that social norms can exert a substantial indirect effect on DR behavior. However, due to the deficiency of such norms, the formation of the positive attitude towards DR was hindered, resulting in a low standard coefficient of 0.16. Moreover, the influence of subjective norm on response intention was rejected due to limited perceived external pressure. Perceived behavior control exhibited the most significant direct influence on response intention (0.76). Additionally, the positive effects of situational factors and personal habits on the conversion from response intention to behavior were supported. Based on these findings, several policy suggestions including enhancing publicity and incentive policies were proposed.

Distributed Energy Resource Integration for Carbon Neutral Power Systems: Market‐Based Approaches to Ancillary Services and Microgrid Operation

Electricity, as a sustainable energy carrier, plays a central role in the transition scenarios for carbon neutralization of energy systems. Expanding the potential of electricity requires intelligent integration of electricity infrastructures and electricity markets with distributed energy resources (DERs) including roof‐top solar photovoltaics (PVs), controllable loads, and storage batteries. This integration will advance the management of power distribution grids, resulting in harmonization of the distribution grids and variable renewable generation. In the foreseeable future, the DERs will be actively used to perform advanced management of power distribution grids and compensate fluctuation in variable renewable power generation such as PVs and wind power. Market‐based coordination mechanisms are already practiced in large‐scale electricity production, electricity trading and transmission around the world. Using these mechanisms at the distribution grid level to integrate numerous flexible devices into the grids remains an important research topic. This paper reviews the role of DER integration toward carbon‐neutral power systems, the state‐of‐art and challenges associated with market‐based approaches for integrating flexible demand, distributed generation, and storage. Methods for assessing the value of DER aggregation such as virtual power plants and microgrids are also explored. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Public policies to foster green hydrogen seasonal storage: Portuguese study case model until 2040

Portugal made a climate commitment when it ratified the Paris Climate Agreement in 2015. As a result, Portugal, along with other EU members, has created a national roadmap for the deployment of hydrogen as a crucial component of Portugal's energy transition towards carbon neutrality, creating synergies between the electric and gas systems.The increased variability of generation from variable renewable power sources will create challenges regarding the security of supply, requiring investment in storage solutions to minimize renewable energy curtailment and to provide dispatchability to the electric power system. Hydrogen can be a renewable energy carrier capable of ensuring not only the desired transformation of the infrastructures of the gas system but also an integrator of the Electric System, such as in Power-to-Power (P2P) systems. Hydrogen can be produced with a surplus of renewable electricity from wind and solar, allowing a long-term energy seasonal storage strategy, namely by using underground salt caverns, to be subsequently transformed into electricity when demand cannot be supplied due to a shortage of renewable generation from solar or wind.P2P investments are capital intensive and require the development of transitional regulation mechanisms to both create opportunities to market agents while fostering the energy surplus valuation and decreasing the energy dependency. In order to maintain the electric system's security of supply, the suggested methodology innovatively manages the importance of seasonal storage of renewable energy surplus using hydrogen in power systems. It suggests a novel set of regulatory strategies to foster the creation of a P2P solution that maintains generation adequacy while assisting in decarbonising the electric power industry. Such methodology combines long-term adequacy assessment with regulatory framework evaluation to evaluate the cost of the proposed solutions to the energy system.A case study based on the Portuguese power system outlook between 2030 and 2040 demonstrates that the considerable renewable energy surplus can be stored as hydrogen and converted back into electricity to assure adequate security of supply levels throughout the year with economic feasibility under distinct public policy models.

Investigation of Failures during Commissioning and Operation in Photovoltaic Power Systems

Considering global warming and environmental problems, the importance of renewable energy sources is increasing day by day. In particular, the effects of wind and solar power, which are variable renewable power sources, on the power system necessitate their evaluation in terms of the reliability of the power system. Photovoltaic panels, which enable the conversion of solar power into electrical power with semiconductors, have started to take an important place in global energy investments today. Photovoltaic power plants increase the demand for this energy source with continuous energy conversion depending on sunshine duration and radiation intensity. Among the renewable energy sources, the most easily utilized energy source, regardless of geographical conditions, is the sun. To prevent the energy production of PV power plants from being interrupted, it is necessary to address and analyze all kinds of faults that will affect power production in order to increase the reliability of the system. Academic studies in this field are generally grouped under two topics: classification of faults or modeling of electrical faults. Based on this, in this study, the problems that occur during the installation and operation of photovoltaic systems are classified, and the relevant faults are modeled and simulated in MATLAB Simulink version 23.2 (R2023b). Thus, a scientific approach to the problems of photovoltaic power plant operating conditions has been gained, which will be the basis for academic studies.

Long-term energy transition planning: Integrating battery system degradation and replacement for sustainable power systems

The transition towards sustainable energy systems has gained significant importance globally due to high levels of environmental pollution caused by the use of fossil fuels. This study addresses a critical aspect of the global transition towards sustainable energy systems. We emphasize the impact of considering energy storage system degradation and replacement in long-term energy transition planning. The importance of this lies in mitigating the challenges posed by the intermittency and variability of renewable energy sources, such as wind and solar, without failing to consider the negative effect that excessive use of batteries as a storage energy system would have. We propose an optimization model that integrates power systems generation and transmission infrastructure with strategic energy storage system implementation to optimize their size, operation, and location for maximum efficiency and benefits. This paper offers a comprehensive approach to take into account the environmental effect of the depth of the discharge and replacement of battery systems over a long-term planning horizon considering hourly operation of representative time periods. The electricity system of Baja California, Mexico, a region heavily reliant on fossil fuels, is presented as a case study to show the applicability of the model. Results demonstrate that continuous replacement of dispatchable generators (natural gas power plants) for non-dispatchable generators (variable renewable power plants) may cause an unexpected increase of indirect greenhouse gas emissions from the continuous replacement of batteries when degradation is not considered. The results of the case study show an average emissions factor of 0.325 Ton CO2eq/MWh, approximately 24 % lower than government expectations, using the proposed MILP model.

Limiting imbalance settlement costs from variable renewable energy sources in the Nordics: Internal balancing vs. balancing market participation

Due to the market gate closures in the Nordic energy markets, producers with variable renewable energy (VRE) assets, e.g., PV and wind power plants, must forecast their production prior to delivery, leaving room for significant forecast errors. These forecast errors can lead to imbalances between the contractual market agreements and physical delivery, which have to be financially accounted for through the imbalance settlement. The increasing shares of VREs in the Nordic energy mix and the increasing variability in the price of regulating the imbalances, can lead to potential large revenue losses for the producers.This study investigates how different producer balancing strategies can limit the uncertainty and potential revenue losses in the imbalance settlement. The study focuses on available balancing measures the producers are able to use in the period starting from the last energy market gate closure, i.e., the manual Frequency Restoration Reserve (mFRR, tertiary reserves) balancing market, and throughout the subsequent settlement period. During this settlement period, producers have the option within the Nordic imbalance settlement framework to prevent VRE imbalances by performing internal balancing, i.e., ramping up or down their dispatchable assets which are located in the same bidding area as the VRE assets. However, this study shows both theoretically and quantitatively that such internal balancing is not economically beneficial compared to offering this regulating energy to the mFRR market.

VRE Integrating in PIAT grid with aFRR using PSS, MPPT, and PSO-based Techniques: A Case Study Kabertene

The Fluctuations in demand and weather conditions have a significant impact on the frequency and the voltage of Algeria's isolated PIAT power grid. To maintain stability and reliable power supply, it is crucial to keep these quantities close to their expected levels. An automatic (FRR) is employed to regulate real-time frequency deviations caused by integrating variable renewable energy (VRE), specifically wind and solar power in the Kabertene region. In order to mitigate wind power fluctuations, a power system stabilizer is implemented, which helps dampen oscillations. The use of Maximum Power Point Tracking (MPPT) techniques optimizes the extraction of power from solar panels under varying conditions. For efficient scheduling and dispatch of VRE generation, particle swarm optimization (PSO)-based algorithms are used. These algorithms ensure optimal utilization of renewable energy sources by considering their intermittent nature. This study proves the effectiveness of these techniques in enhancing grid stability, reducing frequency deviations, and improving VRE integration. Valuable insights are provided on their practical implementation, playing a crucial role in transitioning to a cleaner and more sustainable energy system.

Simultaneous design and operational optimization for flexible carbon capture process using ionic liquids

Carbon capture and storage is an effective way to abate CO2 emissions during the transition to zero-carbon power generation technologies. As renewable electricity sources such as wind and solar photovoltaics become more prevalent, conventional power generation systems are increasingly required to operate at highly variable rates in order to balance intermittent renewable power supply. As a result, post-combustion carbon capture systems integrated with fossil fuel power plants must also operate at variable load. In addition, the solvent regeneration and CO2 compression in capture plants requires substantial amounts of energy and such flexible operation can present an opportunity for operators to take advantage of fluctuating electricity prices, potentially offsetting the cost of carbon capture. This can be achieved through, among others, variable capture rates and utilization of solvent storage. In this paper, we consider a carbon capture system using ionic liquids as a chemical absorption solvent. We study the optimal flexible operation of this system when connected to a natural gas combined cycle power plant under high variable renewable power generation rates. The results show significant cost savings relative to the case of inflexible capture system operation.

Strategies for Continuous Balancing in Future Power Systems with High Wind and Solar Shares

The use of wind power has grown strongly in recent years and is expected to continue to increase in the coming decades. Solar power is also expected to increase significantly. In a power system, a continuous balance is maintained between total production and demand. This balancing is currently mainly managed with conventional power plants, but with larger amounts of wind and solar power, other sources will also be needed. Interesting possibilities include continuous control of wind and solar power, battery storage, electric vehicles, hydrogen production, and other demand resources with flexibility potential. The aim of this article is to describe and compare the different challenges and future possibilities in six systems concerning how to keep a continuous balance in the future with significantly larger amounts of variable renewable power production. A realistic understanding of how these systems plan to handle continuous balancing is central to effectively develop a carbon-dioxide-free electricity system of the future. The systems included in the overview are the Nordic synchronous area, the island of Ireland, the Iberian Peninsula, Texas (ERCOT), the central European system, and Great Britain.

Assessment of flexibility options in electric power systems based on maturity, environmental impact and barriers using Fuzzy Logic method and Analytic Hierarchy Process

The rapid integration of variable renewable energy sources (vRES) in conjunction with the reduction of coal-fired power plants increase the need for flexibility in electric power systems. In a previous research paper, twenty-three (23) flexibility options were assessed, based on their technical and economic characteristics, using Fuzzy Logic (FL) method and Analytic Hierarchy Process (AHP). Through this research paper the same Flexibility Options (FO) are assessed based on their maturity level, their environmental impact and the technical, economic, social and political/regulatory barriers they encounter in their deployment in Greece, using again FL and AHP methods. Data concerning maturity level and environmental impact are obtained through literature review while data concerning barriers are collected through a survey of energy expert’s opinions. In both methods (FL and AHP), Demand Response from Large Industrial Plants (DRLIP) is ranked 1st among the flexibility options having FSI 0.745 and GPV 0.483 while variable Renewable Energy Power Plants (vRE) and Biogas Power Plants (BGPP) are ranked 2nd and 3rd respectively. On the contrary, Power to Gas (PtG) is ranked 23rd (lowest in rank) using FL method and 22nd using AHP method. The results of the research are very important for the policymakers as they can identify in which sectors (commercial, environmental, technical, economic, social etc.) should take action in order to promote specific flexibility options according to their policy.

Barriers and opportunities for the deployment of CO2 electrolysis in net-zero emissions energy systems

As energy systems across the globe transition toward net-zero emissions, the decarbonization of hard-to-decarbonize sectors, e.g., industry and transportation, is becoming more crucial. Renewable power-driven carbon dioxide (CO2) electrolysis has the potential to facilitate this transition by (1) substituting carbon-intensive petrochemical and fuel production and (2) using CO2 otherwise emitted from industrial processes or CO2 from the atmosphere; however, because of existing technical and economic challenges, the industrial deployment of this technology is not yet imminent. Here, we present an overview of CO2 electrolysis technologies to identify key hurdles in view of the industrial deployment of this technology in net-zero emissions energy systems. From the technology standpoint, catalysts should be developed with enhanced activity, selectivity, and stability/durability as well as membranes and reactors that prevent carbonate formation or crossover, achieve higher reaction rates, e.g., >1 A/cm2, and demonstrate long-term stability, e.g., >5 years. Conversely, from the system integration standpoint, impurity-tolerant CO2 electrolysis systems need to be developed and tested under relevant conditions, e.g., CO2 streams with traces of impurities (NOx, SOx, O2, N2, H2S, etc.). Additionally, the quantification of pros and cons of different integration pathways for CO2 capture and CO2 electrolysis requires further research. Moreover, the integration with variable renewable power sources—e.g., wind and solar photovoltaic power—and electricity markets requires a better understanding. For instance, the value of CO2 electrolysis flexibility in view of variable renewable power supply or dynamic electricity prices is not well understood. As energy systems across the globe transition toward net-zero emissions, the decarbonization of hard-to-decarbonize sectors, e.g., industry and transportation, is becoming more crucial. Renewable power-driven carbon dioxide (CO2) electrolysis has the potential to facilitate this transition by (1) substituting carbon-intensive petrochemical and fuel production and (2) using CO2 otherwise emitted from industrial processes or CO2 from the atmosphere; however, because of existing technical and economic challenges, the industrial deployment of this technology is not yet imminent. Here, we present an overview of CO2 electrolysis technologies to identify key hurdles in view of the industrial deployment of this technology in net-zero emissions energy systems. From the technology standpoint, catalysts should be developed with enhanced activity, selectivity, and stability/durability as well as membranes and reactors that prevent carbonate formation or crossover, achieve higher reaction rates, e.g., >1 A/cm2, and demonstrate long-term stability, e.g., >5 years. Conversely, from the system integration standpoint, impurity-tolerant CO2 electrolysis systems need to be developed and tested under relevant conditions, e.g., CO2 streams with traces of impurities (NOx, SOx, O2, N2, H2S, etc.). Additionally, the quantification of pros and cons of different integration pathways for CO2 capture and CO2 electrolysis requires further research. Moreover, the integration with variable renewable power sources—e.g., wind and solar photovoltaic power—and electricity markets requires a better understanding. For instance, the value of CO2 electrolysis flexibility in view of variable renewable power supply or dynamic electricity prices is not well understood.

Life cycle greenhouse gas emissions of cogeneration energy hubs at Japanese paper mills with thermal energy storage

Variable renewable energy-based power is expected to increase toward a sustainable society, although the power cannot be dispatched effectively due to its intermittent nature. To accelerate renewable energy implementation, we simulated energy flows of paper mills installing wind energy and evaluated their potentials to function as energy hubs for appropriate early-stage design. We targeted 39 Japanese paper mills assumed to have thermal energy storage, wind–thermal energy converters and regional woody biomass installed, and analyzed the amount of power and heat selling and life cycle greenhouse gas emissions. The results for the paper mills were compared with conventional mills to examine effective conditions for greenhouse gas reduction. The amount of power or heat selling depended on the capacity of the paper mill and the installed equipment. Most paper mills could reduce greenhouse gas using thermal energy storage, wind energy, and woody biomass. The paper mill with the highest life cycle greenhouse gas reduction, compared with conventional mills, could achieve a 190% reduction. To function as a cogeneration energy hub, the equipment installed in paper mills should be designed according to the conditions of the paper mills and their regions.

Integrated planning method of green hydrogen supply chain for hydrogen fuel cell vehicles

To satisfy the growing refueling demand of hydrogen fuel cell vehicles (HFCVs) with carbon-free hydrogen supply, this paper proposes an integrated planning method of green hydrogen supply chain. First, the k-shorted path method is introduced to analyze HFCV refueling load considering vehicle travel habits and routing diversity. Second, based on it, a two-stage integrated planning model is established to minimize the total investment and operation cost. The construction of hydrogen refueling stations, electrolysis-based hydrogen generation stations and hydrogen pipelines are coordinated with their operating constraints, constituting the green hydrogen supply chain, in which hydrogen storage is also an important part for consideration to address variable renewable power. Then, the proposed model is reformulated as a mixed integer linear programing (MILP) problem solved efficiently. Finally, the case studies are carried out on an urban area in Xi'an China to verify the validity and correctness of the proposed method. The results show that the integrated planning can realize synergy benefits. The influence of electricity prices and k values is also discussed.

Improving combustion and lowering NO emissions of an industrial coal swirl burner by optimizing its nozzle structure

• Simulation and comparison are conducted for the burner before and after optimization. • Entrained effect of secondary air on primary air is enhanced with retrofitting ISACS. • Retrofitting ISACS has significant effects on the combustion characteristics. • Optimized burner performs better in NOx reduction, flame stability and burnout rate. To accommodate rapidly growing but highly variable renewable power in the grid and large variations in power demand, coal-fired power plants need to be flexibly operated through fast and wide load changes, still with high efficiency and reliability and low emissions. Towards reliable implementation in a power plant under flexible operation, this paper comprehensively investigates the improvement of an industrial low-NO x swirl burner via numerical simulation and various field tests. Burner aerodynamics, which play a vital role in its performance, are largely affected by the burner nozzle structure. For the low-NO x swirl burner under study, the inner secondary air cone structure is found to have the most significant impact on the burner aerodynamics and the combustion performance. For the coal fired in the power plant, the newly designed inner secondary air cone structure, which is a kind of an extended smooth diverging duct, greatly facilitates the entrainment of the primary air into the surrounding swirl secondary air stream and largely enhances lateral mixing. A large recirculation zone is formed between the primary air and the inner secondary air stream, stabilizing ignition and combustion under flexible operation conditions. This is particularly important for low-load operation. Comparatively, reducing the secondary air duct area for a higher axial momentum of the secondary air stream and adding a new particle separation ring for more dispersed particle distribution are found to have a minor impact on the burner aerodynamics. The optimized burner nozzle structure via numerical simulation has been finally adopted by the power plant for the burner retrofit, on which various field tests have been performed on the retrofitted burner. The tests show that the nozzle structure optimization remarkably improves the burner performance, which is also consistent with the numerical prediction. This study also provides useful guidance for optimizing the swirl burners of the similar type.

Generation Expansion Planning Considering Weakness Reinforcement of Power Grids Based on Robust Model

Large-scale integration of variable renewable energy and power electronic device has raised great changes in the physical characteristics of power systems. It is urgent to strengthen system weaknesses in system evolution study. To fill the gap, a generation expansion planning model considering weakness identification and reinforcement is proposed. An efficient outer-inner loop algorithm is designed based on the structure of the model. An IEEE 6-bus test case is carried out to show the effectiveness of the proposed model and methodology. The test case reveals that weakness reinforcement schemes are robust against the worst-case contingency and the unserved demand can be reduced to 20.6% after the weakness reinforcement process.

Hybrid solar PV-wind-battery system bidding optimisation: A case study for the Iberian and Italian liberalised electricity markets

The coupling of electrical batteries with variable renewable power generation can increase the production flexibility and revenue of power plant operators. This study focuses on developing an optimisation model to manage the operational revenue of a renewable power unit comprising a wind farm, solar photovoltaic (PV) power plant, and electrical battery. The power system integration was conducted by formulating a mixed-integer linear programme to schedule the day-ahead operation of the renewable power unit in two liberalised power markets: the Italian and Iberian day-ahead power markets. Several scenarios and case studies have been analysed to assess the value of storage for revenue maximisation. The proposed methodology results reveal that the average yearly net revenue of the hybrid PV-wind-storage power plant can increase by 4% compared to the standalone operation of the wind and solar PV power plants. Additionally, the results indicate that in the markets analysed the coupling of storage to wind power generates a higher revenue than coupling storage systems with solar power. The study demonstrated a correlation between the increase in revenue and the capacity installed in the battery and concluded that the use of hybrid VRE storage systems would be feasible in the Iberian Peninsula and Italy for battery installation costs ranging from €14,804/MW to €38,267/MW.

Cross-regional electricity and hydrogen deployment research based on coordinated optimization: Towards carbon neutrality in China

In order to achieve carbon neutrality in a few decades, the clean energy proportion in power mix of China will significantly rise to over 90%. A consensus has been reached recently that it will be of great significance to promote hydrogen energy, that is produced by variable renewable energy power generation, as a mainstay energy form in view of its potential value on achieving carbon neutrality. This is because hydrogen energy is capable of complementing the power system and realizing further electrification, especially in the section that cannot be easily replaced by electric energy. Power system related planning model is commonly used for mid-term and long-term planning implemented through power installation and interconnection capacity expansion optimization. In consideration of the high importance of hydrogen and its close relationship with electricity, an inclusive perspective which contains both kinds of the foresaid energy is required to deal with planning problems. In this study, a joint model is established by coupling hydrogen energy model in the chronological operation power planning model to realize coordinated optimization on energy production, transportation and storage. By taking the carbon neutrality scenario of China as an example, the author applies this joint model to deploy a scheme research on power generation and hydrogen production, inter-regional energy transportation capacity, and hydrogen storage among various regions. Next, by taking the technology progress and cost decrease prediction uncertainty into account, the main technical–economic parameters are employed as variables to carry out sensitivity analysis research, with a hope that the quantitative calculation and results discussion could provide suggestion and reference to energy-related companies, policy-makers and institute researchers in formulating strategies on related energy development.

Assessing the integration effect of inter-regional transmission on variable power generation under renewable energy consumption policy in China

Integrating a high share of variable renewable energy into multi-region power systems is essential and requires an interconnected transmission grid to coordinate regional power system operations. This paper proposes a multi-region power system optimization model to evaluate the role of interconnection in China's power sector for economic benefit, variable renewable energy power generation and allocation, transmission line efficiency and carbon emission transfer in the context of renewable energy consumption policy. The results show that inter-regional power transmission coupled with flexibility technology can facilitate renewable power generation and delivery. The renewable energy consumption policy would intensify this effect, although it leads to a slight drop in economic efficiency. Improving the compatibility of transmission network with variable power is crucial because wind and solar power are expected to make up 60% of the total inter-regional power transmission, particularly the share in the outward transmission lines from the northwest region reaching 91%. Renewable energy integration policy targets in northwest, north, Inner-Mongolia and northeast regions can be improved to 37.5%, 31.5%, 35.3%, and 36.9%, respectively.