High Proportion Of Renewable Energy Research Articles

Comparative Analysis of Combustion Characteristics of a CFB Boiler during the Changes Process between High-Rated Loads and Low-Rated Loads

In order to alleviate problems such as large fluctuations in grid load caused by the high proportion of renewable energy, circulating fluidized bed (CFB) power plants undertake the task of rated load regulation. This study discussed the combustion characteristics of a 100 KW CFB boiler during the operation process of varying loads and analyzes the combustion characteristics, load regulation rate and emissions variation law during the operation process of high- and low-rated load intervals. The experimental results showed that under the condition of a high-rated load, the average temperature of each area in the furnace was proportional to the size of the load. Under low-rated load conditions, the temperature change increased first and then decreased with the reduction in load. In the 30% load stage, the lowest temperature in the riser was 740 °C, while the temperature in the loop seal was even as low as 650 °C. The concentrations of O2, CO and unburned carbon mainly depended on the combustion reaction intensity under each load condition, which showed a higher trend at low load (30%). In terms of NOx emission, it was proportional to the load in the high-rated load range. However, the NOx generation at the 30% load was about 30 mg/Nm3(@6%O2) higher than the 50% load. In addition, the regulation load rate (2.5%/min) between high-load conditions exhibited significantly greater than that between low-load conditions (0.78%/min). Therefore, the low-load operation will face problems such as low furnace temperature, uneven gas–solid fluidization, and difficult control of pollutant generation, which need to be paid attention to during operation.

Review of Low Inertia in Power Systems Caused by High Proportion of Renewable Energy Grid Integration

With the power industry moving toward a green and low-carbon direction, renewable energy is occupying an increasingly larger share in the power system. However, compared with traditional thermal power generation, the instability of new energy generation is very prominent, which also leads to a decrease in the inertia of the power system after the grid integration of a high proportion of renewable energy. If no measures are taken, this may lead to frequency collapse accidents. Therefore, this paper first introduces two international major power outage accidents that have occurred in recent years, analyzing the causes, and then summarizes the inspiration obtained from the accidents. Subsequently, some research results on low inertia-related issues in the power system caused by the high proportion of new energy grid integration in recent years were summarized and analyzed from three aspects: inertia evaluation methods, optimal operation measures for the power system, and under frequency load-shedding (the abbreviation “ULFS” in the following text stands for it) schemes. Finally, suggestions were made for future research directions.

Day-ahead robust optimal dispatching method for urban power grids containing high proportion of renewable energy

Urban energy supply includes more renewable energy, but renewable energy, such as wind and photovoltaic, is intermittent and connected to the grid and impacts the safe operation of the power system. For urban multi-type energy dispatching, this paper proposed a day-ahead multi-energy robust optimization dispatching method for an urban power grid with a high proportion of renewable power. Firstly, the power supply and load operation scenarios of the urban energy supply system are constructed. Multiple typical scenarios are formed based on fully considering the uncertainties caused by renewable energy and load prediction. A robust optimal scheduling model with system constraints was constructed based on the tuning capacity of adjustable generator sets and energy storage devices in the power grid, with multi-system functional cost optimization as the objective function. Extending the augmented Lagrange multiplier Method, the Alternating Direction Method of Multipliers (ADMM) is proposed to solve the constructed model. The effectiveness of the proposed method is verified by some examples based on the data of an actual power grid in China.

Electricity price modeling from the perspective of start-up costs: incorporating renewable resources in non-convex markets

This paper constructs a comprehensive electricity market model in the context of China, highlighting the deviation caused by neglecting start-up costs from an engineering perspective. The model allows for the abandonment of excess wind and solar power generation, contributing to the achievement of research objectives in scenarios with a high proportion of renewable energy. Our method innovatively integrates fuel and carbon prices, clean energy expansion, and power system marginal prices according to the carbon trading rules of the Chinese power industry, providing a more accurate representation of market dynamics. Findings reveal that neglecting start-up costs can lead to significant biases in electricity prices. We demonstrate that the marginal price sometimes deviates from the fluctuation of the real value. While fuel and CO2 prices can be transmitted downstream, the value of new energy must be transmitted through its impact on the marginal unit. This insight is crucial for understanding the “missing money” problem in electricity markets. Based on these findings, we propose policy recommendations. We suggest considering fixed and average costs as pricing benchmarks and utilizing capacity utilization as a signal for demand response to adjust power pricing. Furthermore, we recommend trading different energy types separately in the spot market with different pricing benchmarks to ensure the homogeneity of marginal units.

The carbon reduction effects of stepped carbon emissions trading and carbon capture and storage on hybrid wind-PV-thermal- storage generation operating systems.

To accelerate the low-carbon transformation of the power industry, a range of carbon emission reduction policies and technologies have emerged. However, the current China's carbon emissions trading (CET) policy is inadequate in encouraging power generation enterprises to take proactive measures towards emission reduction due to challenges like fixed and low carbon prices. The high proportion of renewable energy in electricity consumption also faces significant challenges due to the unpredictable nature of wind and PV energy. Therefore, this paper applies stepped CET mechanism, energy storage system (ES) system and carbon capture and storage (CCS) mechanism together to hybrid renewable energy system, aiming to study their synergistic carbon emission reduction effect. Firstly, the paper constructs the stepped CET model considering incentives and penalties. Secondly, the stepped CET model, ES system and CCS are jointly introduced into the hybrid renewable energy system. Finally, a scenario analysis is conducted to investigate the synergistic effect of various carbon emissions reduction policies and technologies in the operation of power generation systems. The results show that: i) compared with traditional CET, the stepped CET increases renewable energy consumption by 0.12% and reduces carbon emissions by 0.6%; ii) the introduction of stepped CET and ES equipment together consumes an additional 36.1% of renewable energy and reduces carbon emissions by 32.4%; iii) based on stepped CET model and ES equipment, the introduction of CCS system reduces carbon emissions by 29.4%.

Robust Planning of Distributed Generators in Active Distribution Network Considering Network Reconfiguration

The energy crisis and environmental concerns have accelerated the development of the active distribution network (ADN) with a high proportion of renewable energy, which poses a challenge to the operation of the power system. Moreover, using active management means to promote the consumption of renewable energy is an important task of ADN. Therefore, as an important operation means, the network reconfiguration is used to enhance the adjustable capacity of the power system at the planning stage. Firstly, a “wind–light–load” uncertain scenario set is constructed to address the uncertainty of wind speed, lighting, and load. On this basis, a robust optimization model for distributed power generation taking into account network reconstruction and in ADN is proposed. In addition, the distributed generator (DG) permeability indicator is introduced in the planning model to improve the ADN ability of absorbing renewable energy. A linearized AC power flow model is utilized to calculate the power flow. Finally, via simulation in an IEEE 33-bus system and IEEE 69-bus system, the influence of network reconfiguration and robustness on distributed generator planning, economy and reliability of ADN is analyzed, and the validity of the model is verified.

A novel day-ahead scheduling approach for multi-power system considering dynamic frequency security constraint

The ever-growing proportion of renewable energy results in the decrease of frequency regulation capability of the multi-power system. Hence, to ensure the stability of the multi-power system with a high proportion of renewable energy, a novel day-ahead scheduling approach is proposed considering the frequency security constraint. Firstly, the dynamic changing process of frequency due to the power disturbance is analyzed. Secondly, a frequency security constraint considering the dynamic process is modeled and incorporated into the scheduling model of the multi-power system. The proposed scheduling model ensures that the maximal frequency deviation of the dynamic process is kept within the permitted range. Next, to ensure the stable operation of the system and make full use of renewable energy, the proposed scheduling model aims at minimizing the net load fluctuation and intermittent new energy curtailment. Finally, simulation results show that the proposed optimal scheduling model considering dynamic frequency security constraint can maintain the stability and frequency security of the multi-power system under power disturbance.

A Comprehensive Review on Energy Storage System Optimal Planning and Benefit Evaluation Methods in Smart Grids

Smart grids are the ultimate goal of power system development. With access to a high proportion of renewable energy, energy storage systems, with their energy transfer capacity, have become a key part of the smart grid construction process. This paper first summarizes the challenges brought by the high proportion of new energy generation to smart grids and reviews the classification of existing energy storage technologies in the smart grid environment and the practical application functions of energy storage in smart grids. Secondly, optimization planning and the benefit evaluation methods of energy storage technologies in the three different main application scenarios, including the grid side, user side, and new energy side, are analyzed. The advantages and shortcomings of the current research are also pointed out. Furthermore, the paper sheds light on the pressing issues that demand further consideration in energy storage planning. Finally, the aspects that warrant attention in the future application and promotion processes are elucidated in detail, culminating in a comprehensive understanding of the energy storage technologies in smart grids.

Temperature Regulation Strategy of Heterogeneous Air Conditioning Loads for Renewable Energy Consumption

In a power system with a high proportion of renewable energy, sudden increases in wind power or photovoltaic output can lead to huge challenges, such as difficulties in accommodating excess renewable energy and imbalances between supply and demand on the grid. As an important adjustable resource on the demand side, air conditioning load is a flexible load for realizing output consumption. In this paper, a heterogeneous air conditioning load regulation strategy for renewable energy consumption is proposed. Each air conditioning load regulation quantity is obtained based on the day-ahead dispatching mode. Then, the temperature setting value, rated power, and duty cycle are selected as the indexes. The load regulation sequence is obtained by the entropy weight method. Finally, the load regulation time of each air conditioning load is obtained based on the constraint of the quantity of loads during the possible adjustment time. The simulation analysis shows that the temperature regulation strategy presented in this paper can effectively reduce the power fluctuations of air conditioning loads, while ensuring that users with lower temperature settings are selected in the adjustment process.

Multi-objective optimization of an integrated energy system with high proportion of renewable energy under multiple uncertainties

With the development of integrated energy systems, the system energy demands become more complicated and the renewable energy proportion becomes higher. Under this background, integrated energy systems gradually present a state of high randomness and strong uncertainty, which affects the system collaborative optimization. In order to handle the multiple uncertainties’ effects effectively, multi-objective optimization considering uncertainties of energy demand and renewable energy using information gap decision theory (IGDT) method was carried out. By analyzing the optimization results and comparing the results of different weight coefficient of multiple uncertainties, the renewable energy uncertainty has a strong effect, while the energy demand uncertainty’s effect is more complex.

A Multi-objective Control Strategy of the Energy Storage System in Distribution Networks with a High Proportion of Renewable Energy

With the development of battery technology and power electronic technology, battery-based energy storage has been widely used in Peak Shaving and Valley Filling frequency and voltage regulation for the power system with a high proportion of renewable energy integration. However, the existing control strategies of the energy storage system (ESS) mostly take peak shaving and valley filling frequency and voltage regulation as a single control objective, causing the rest capacity of the energy storage in the single control working period to be wasted, which significantly reduces the utilization rate and economic benefits of energy storage. How to improve the utilization rate and economic benefits of the ESS while enhancing the support performance of ESS has not received much attention. This paper proposes a multi-objective control strategy of ESS to maximize energy storage’s benefit and ensure the distribution network’s safe and stable operation. First of all, this paper combines the auxiliary compensation benefits of the price system of distributed energy storage power stations and proposes a comprehensive index that comprehensively considers the economy of the ESS and the stable operation of the distribution network to support the evaluation needs of multi-objective control of energy storage. On this basis, this paper predetermines the multi-layer judgment logic for ESS operation control under different operating conditions, divides the ESS into different operating conditions according to the control objectives, and proposes a multi-objective control strategy based on variable droop coefficients. It effectively utilizes the idle capacity of the ESS and achieves an optimized control of energy storage that takes into account both technology and economy. The simulation verification based on the energy storage model built in Matlab/Simulink is conducted to validate the effectiveness of the proposed ESS multi-objective control strategy.

Cloud-Edge Collaborative Scheduling with a Focus on Clean Energy

With the promotion of the national "double carbon" goal, the power system is developing towards the direction of low-carbon transformation. In order to achieve the goal of "striving to peak carbon dioxide emissions by 2030 and striving to achieve carbon neutrality by 2060", we must actively promote the consumption of a high proportion of renewable energy from the grid, which is the most urgent issue to be addressed. In this chapter, access to clean energy will involve multiple aspects such as source, network, load and storage. However, due to the intermittent, random and volatile nature of wind power and photovoltaic power generation, the challenges faced by significant users of the power system are enormous. Traditional energy Internet dispatching adopts centralized dispatching. In this paper, by deploying edge nodes, the autonomous decision-making and autonomous collaboration of power grid nodes at all levels are enhanced, and the collaborative integration level of source, network, load and storage of smart power grid is improved. Aimed at the current power supply and demand imbalance, new energy access problems and energy storage problems. In this paper, a service adaptation algorithm based on dynamic priority is proposed based on the scenario of load storage integration of source network under renewable energy access. Experimental results show that, compared with other algorithms, this algorithm has lower scheduling time and execution time and better performance under the condition of ensuring the highest clean energy consumption rate and first-order load priority response.

Small-signal modeling and wide-band oscillation analysis with the high proportion of renewable energy integrated through LCC-HVDC

With the high proportion of renewable energy through high-voltage direct current (HVDC) transmission into the grid and the application of high proportion of power electronic equipment, in the modern power system, the traditional electromagnetic conversion equipment represented by synchronous generators is gradually replaced by power electronic equipment, which in a high level has been affecting the dynamic behavior of the power system. In recent years, the wide-band oscillation problem of unknown mechanism continues to appear in power systems, which poses a major threat to the security, stability, and operation of power systems. Therefore, based on the typical oscillation event, this paper constructs a typical small-signal model of the new power system which is composed of synchronous generator, HVDC transmission equipment, and renewable energy generation equipment. The model is suitable for the analysis of wide-band oscillation problem of the new power system with renewable energy as the main body. The comparison of time-domain response with the detailed time-domain model shows that the proposed small-signal model can well reflect the dynamic behavior of the detailed time-domain model. Based on the model, the influence of access distance, access proportion, and operation and control modes of renewable energy integrated through LCC-HVDC on the wide-band oscillation characteristics of the system is analyzed, and the correctness of the analysis is verified by the detailed time-domain model.

An improved multi-timescale coordinated control strategy for an integrated energy system with a hybrid energy storage system

In view of the complex energy coupling and fluctuation of renewable energy sources in the integrated energy system, this paper proposes an improved multi-timescale coordinated control strategy for an integrated energy system (IES) with a hybrid energy storage system (HESS). The power response characteristics of various devices in IES at different time scales are analyzed which shows that the multi-timescale coordinated control method can be well coupled with the IES including HESS. The advantages of HESS over single energy storage system in stabilizing power fluctuation and extending energy storage life are compared and analyzed while the control method of supercapacitor under multi-time scale coordinated control strategy is proposed. The primary energy consumption, operating costs, carbon dioxide emissions and load shedding costs are considered the optimization objectives in the day-ahead rolling optimization stage according to the day-ahead forecast renewable energy (RE) data. In the intraday rolling adjusting stage, the proposed method can reduce the effect of the RE day-ahead forecasting errors to achieve the intraday energy scheduling balance and ensure the safe operation of the devices of IES. Considering the background of IES with a high proportion of renewable energy, this paper makes innovative use of the advantages of HESS to improve the power response characteristic of the system. The high-frequency part of RE is balanced by HESS in the real-time coordinated control stage. A typical structure of IES is applied and the simulation results are analyzed to show the performance of the proposed method in this paper. Moreover, general rules for sizing of HESS are also proposed. The influence of the hybrid energy storage capacity allocation ratio on battery capacity loss and carbon emission reduction is discussed. The Pareto front including the configuration and cost of supercapacitor has been obtained. As shown in the case, the application of HESS in the IES can improve the power response characteristic, extend the lithium-ion battery (LiB) life and has more benefits in reducing carbon emissions.

An extended modeling of frequency security constraints for unit commitment model

Under the background of high proportion of renewable energy, the frequency security of the power system is facing challenges, which makes it necessary to consider and respond in the optimal dispatching. In this paper, the frequency security constraint is introduced into the basic unit commitment model and the unit commitment model considering the frequency security constraint is proposed. Different from the traditional research, a dynamic modeling method for the unbalanced power of the system is presented. Based on the system frequency response model of primary frequency response, the analytic and linearized frequency safety constraint sets are constructed for the frequency nadir, quasi steady frequency and maximum rate-of-change-of-frequency. The experimental results show that the proposed model not only ensures sufficient frequency security, but also fully considers the actual operation state of the frequency response unit. Compared with the traditional model whose unbalanced power is constant, the proposed model can save operating costs.

A review of key issues in planning AC/DC distribution systems for renewable energy

New requirements have been put forward for the construction of an AC/DC power distribution system under the targets of carbon peaking and carbon neutrality. It is urgent to build a new AC/DC power distribution system featuring low carbonization to realize the coordinated, green development of a high proportion of renewable energy. The low carbonization of the power industry is the key to coping with global warming and realizing the sustainable development of China’s society and economy. The reasonable and effective system planning and operation method will be the powerful means to ensure the AC/DC distribution system attain efficient carbon emission reduction under the premise of safe and stable operation. This paper combines the connotation and characteristics of renewable energy interconnection and mutual benefit, analyses the key technology features of AC/DC distribution systems for renewable energy, establishes a complete overall research framework of key technology for planning and operation of AC/DC distribution systems for renewable energy from two aspects of system planning and system operation, and gives an overview and outlook on each key research direction.

A Probabilistic Modeling Method for Joint Output of Multi Energy Combined Generation System

Existing methods cannot accurately establish the joint output probabilistic model of the Wind-PV-CSP multi-energy complementary generation system. Therefore, based on the analysis of the correlation and complementarity among wind power, PV, and CSP output, a method of establishing the joint output probability model of Wind-PV-CSP multi-energy complementary system by using Copula theory and Gaussian mixture model is proposed. Considering the operational history data of wind power, PV, and CSP, the Copula function based on the correlation between PV and CSP output is adopted to establish the probabilistic model of CSP-PV combined output. Moreover, the probabilistic model for the joint output of PV-wind power generation is set up using the mixed Gaussian model based on the complementarity of wind power and PV output. Subsequently, based on the probabilistic models for the combined outputs of wind power-PV and CSP-PV, the probabilistic model for the combined output of wind power-PV-CSP mixed Gaussian model was established. Moreover, three evaluation metrics-the Nash efficiency coefficient (NSE), root mean square error (RMSE), and Euclid coefficient, are used to judge the quality of the model. The operational history data of CSP-PV-wind power in Jiuquan high proportion renewable energy base is taken as examples; the simulation results verify the validity and usability of the proposed method.

Flexibility-enhanced strategies of generations to improve the integration of renewable energy considering uncertainties

Power systems with a high proportion of renewable energy are confronted with immense challenges and a huge amount of renewable energy has been curtailed. To promote the integration of renewable energy, this paper focus on exploiting the generation flexibilities. For hydropower units, a high-resolution dynamic regulation model of reservoir volume is proposed, in which the real-time situation of inflow is considered. The reservoir’s flexibility which is hindered by the static flood water limit level (FLWL) is exploited by this method. For thermal units, a deep peak regulation of thermal is constructed to enhance the system’s flexibility. Furthermore, considering the uncertainties of renewable energy, a chance-constrained reservoir flexible model influenced by random reservoir inflow and a chance-constrained spinning reserve and power flow model influenced by the wind uncertainty are developed. Based on those models and their coordination, an optimal dispatching model considering generation flexibilities and uncertainties is proposed. Simulation results on the IEEE 30-bus system show that the proposed model with multiple flexible resources can increase wind power penetration by 10% and save half of the cost compared with the conventional dispatching methods. These results demonstrated the efficiency of the proposed method whether the integration of renewable energy or the saving of operation costs.

Operational risk assessment on power system based on weather regionalization considering power ramp of renewable energy generation

With the ever-increased installed capacity of renewable energy generation (REG) units, the power ramp of REG has become a common event, introducing an operational risk to the power system. In order to quantify the operational risk, this paper proposes a novel method for assessing the operational risk of power systems with a high proportion of renewable energy, taking into account the power ramp of REG. Firstly, a weather regionalization is proposed to divide the region of the power system into multiple areas, and then the weather data from the weather stations in these areas will be utilized to forecast the power of REG probabilistically. Moreover, an operational risk assessment model based on the cumulative prospect theory is built to reflect the irrational psychological factors of dispatchers, and two typical indices are introduced to show the operational risk of renewable energy curtailment and load curtailment caused by the power ramp of REG. Finally, numerical simulations are conducted in the actual CEPRI-RE power system in the northwest region of China, and the actual weather data from the meteorological agencies is used. The results show that the proposed method is able to assess the operational risk of the power system with a high proportion of renewable energy effectively, and achieve the early warning 30 min in advance. Besides, it can be found that the power system at the turning point between the power ramp and normal operation has a higher operational risk.

Pre-disaster and mid-disaster resilience improvement strategy of high proportion renewable energy system considering frequency stability

This paper aims to investigate the influence of dynamic system frequency changes on the resilience improvement process of high proportion renewable energy systems (HPRES). To this end, a module mobile energy storage system (MMESS) is considered to participate in primary frequency modulation and two types of system frequency stability constraints are established to guarantee the safety of frequency nadir and maximum frequency drop rate. Furthermore, taking into account the uncertainty of fault components caused by extreme weather, a two-stage stochastic mixed-integer programming (SMIP) is proposed for pre-disaster preventive control. By using progressive hedging method, generator and MMESSs scheduling plans can be converged after multiple iterations. For a deterministic fault scenario, a single-stage mixed-integer linear programming is adopted for mid-disaster emergency dispatch. Based on results from pre-disaster process, generators and MMESSs are coordinated to optimize load reduction while ensuring system frequency stability. Finally, case studies are conducted to demonstrate that the proposed strategy can effectively improve HPRES resilience while reducing renewable energy threat to frequency stability.