The Flexible Operation of Coal Power and Its Renewable Integration Potential in China

At present time, China’s power systems face significant challenges in integrating large-scale renewable energy and reducing the curtailed renewable energy. In order to avoid the curtailment of renewable energy, the power systems need significant flexibility requirements in China. In regions where coal is still heavily relied upon for generating electricity, the flexible operations of coal power units will be the most feasible option to face these challenges. The study first focused on the reasons why the flexible operation of existing coal power units would potentially promote the integration of renewable energy in China and then reviewed the impacts on the performance levels of the units. A simple flexibility operation model was constructed to estimate the integration potential with the existing coal power units under several different scenarios. This study’s simulation results revealed that the existing retrofitted coal power units could provide flexibility in the promotion of the integration of renewable energy in a certain extent. However, the integration potential increment of 20% of the rated power for the coal power units was found to be lower than that of 30% of the rated power. Therefore, by considering the performance impacts of the coal power units with low performances in load operations, it was considered to not be economical for those units to operate at lower than 30% of the rated power. It was believed that once the capacity share of the renewable energy had achieved a continuously growing trend, the existing coal power units would fail to meet the flexibility requirements. Therefore, it was recommended in this study that other flexible resources should be deployed in the power systems for the purpose of reducing the curtailment of renewable energy. Furthermore, based on this study’s obtained evidence, in order to realize a power system with high proportions of renewable energy, China should strive to establish a power system with adequate flexible resources in the future.

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A Study on Optimal Power System Reinforcement Measures Following Renewable Energy Expansion

Energies ◽

10.3390/en13225929 ◽

2020 ◽

Vol 13 (22) ◽

pp. 5929

Author(s):

Hyuk-Il Kwon ◽

Yun-Sung Cho ◽

Sang-Min Choi

Keyword(s):

Renewable Energy ◽

Power Systems ◽

Power System ◽

Transmission Lines ◽

Large Scale ◽

Supply And Demand ◽

Electricity Supply ◽

Static And Dynamic Analysis ◽

The Future ◽

Reinforcement Measures

Renewable energy generation capacity in Korea is expected to reach about 63.8 GW by 2030 based on calculations using values from a power plan survey (Korea’s renewable energy power generation project plan implemented in September 2017) and the “3020” implementation plan prescribed in the 8th Basic Plan for Long-Term Electricity Supply and Demand that was announced in 2017. In order for the electrical grid to accommodate this capacity, an appropriate power system reinforcement plan is critical. In this paper, a variety of scenarios are constructed involving renewable energy capacity, interconnection measures and reinforcement measures. Based on these scenarios, the impacts of large-scale renewable energy connections on the future power systems are analyzed and a reinforcement plan is proposed based on the system assessment results. First, the scenarios are categorized according to their renewable energy interconnection capacity and electricity supply and demand, from which a database is established. A dynamic model based on inverter-based resources is applied to the scenarios here. The transmission lines, high-voltage direct current and flexible alternating current transmission systems are reinforced to increase the stability and capabilities of the power systems considered here. Reinforcement measures are derived for each stage of renewable penetration based on static and dynamic analysis processes. As a result, when large-scale renewable energy has penetrated some areas in the future in Korean power systems, the most stable systems could be optimally configured by applying interconnection measure two and reinforcement measure two as described here. To verify the performance of the proposed methodology, in this paper, comprehensive tests are performed based on predicted large-scale power systems in 2026 and 2031. Database creation and simulation are performed semi-automatically here using Power System Simulator for Engineering (PSS/E) and Python.

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Flexibility Evaluation Method of Power Systems with High Proportion Renewable Energy Based on Typical Operation Scenarios

Electronics ◽

10.3390/electronics9040627 ◽

2020 ◽

Vol 9 (4) ◽

pp. 627

Author(s):

Xiangying Tang ◽

Yan Hu ◽

Zhanpeng Chen ◽

Guangzeng You

Keyword(s):

Renewable Energy ◽

Power Systems ◽

Power System ◽

Power Flow ◽

Evaluation Method ◽

Comprehensive Evaluation ◽

Supply And Demand ◽

Flow Distribution ◽

Occurrence Probability ◽

Flexible Operation

The development of renewable energy represented by wind, photovoltaic and hydropower has increased the uncertainty of power systems. In order to ensure the flexible operation of power systems with a high proportion of renewable energy, it is necessary to establish a multi-scenario power system flexibility evaluation method. First, this study uses a modified k-means algorithm to cluster operating scenarios of renewable energy and load to obtain several typical scenarios. Then, flexibility evaluation indices are proposed from three perspectives, including supply and demand balance of the zone, power flow distribution of the zone and transmission capacity between zones. Next, to calculate the flexibility evaluation indices of each scenario—and according to the occurrence probability of each scenario—we multiplied the indices of each scenario by the scenario occurrence probability to obtain comprehensive evaluation indices of all scenarios. Based on the actual historical output data of renewable energy and load of a southern power system in China, a flexibility evaluation was performed on the modified IEEE 14 system and modified IEEE 39 system. The results show that the proposed clustering method and flexibility indices can effectively reflect the flexibility status of the power system.

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Voltage Coordination via Communication in Large-Scale Multi-Area Power Systems. Part II: Simulation Results

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.433-440.7183 ◽

2012 ◽

Vol 433-440 ◽

pp. 7183-7189

Author(s):

Mohammad Moradzadeh ◽

René Boel

Keyword(s):

Power Systems ◽

Power System ◽

Electricity Market ◽

Large Scale ◽

Test System ◽

Distributed Model ◽

Future Evolution ◽

Distributed Model Predictive Control ◽

Control Actions ◽

Simulation Results

This two-part paper deals with the coordination of the control actions in a network of many interacting components, where each component is controlled by independent control agents. As a case study we consider voltage control in large electric power systems where ever-increasing pressures from the liberalization and globalization of the electricity market has led to partitioning the power system into multiple areas each operated by an independent Transmission System Operator (TSO). Coordination of local control actions taken by those TSOs is a very challenging problem as poorly coordinated operation of TSOs may endanger the power system security by increasing the risk of blackouts. This second part of the paper presents simulation results on a 12-bus 3-area test system, using the distributed model predictive control paradigm in order to design a coordinating model-based feedback controller. Coordination requires that each agent has some information on what the future evolution of its power flows to and from its neighbors will be. It will be shown that how the communication between agents can avoid voltage collapse in circumstances where classical uncoordinated controllers fail.

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A Countermeasure for Preventing Flexibility Deficit under High-Level Penetration of Renewable Energies: A Robust Optimization Approach

Sustainability ◽

10.3390/su10114159 ◽

2018 ◽

Vol 10 (11) ◽

pp. 4159 ◽

Cited By ~ 1

Author(s):

Jinwoo Jeong ◽

Heewon Shin ◽

Hwachang Song ◽

Byongjun Lee

Keyword(s):

Renewable Energy ◽

Power Systems ◽

Power System ◽

Robust Optimization ◽

Storage System ◽

Initial Point ◽

Energy Storage System ◽

Optimization Approach ◽

Flexible Resources ◽

High Level

An energy paradigm shift has rapidly occurred around the globe. One change has been an increase in the penetration of sustainable energy. However, this can affect the reliability of power systems by increasing variability and uncertainty from the use of renewable resources. To improve the reliability of an energy supply, a power system must have a sufficient amount of flexible resources to prevent a flexibility deficit. This paper proposes a countermeasure for protecting nonnegative flexibility under high-level penetration of renewable energy with robust optimization. The proposed method is divided into three steps: (i) constructing an uncertainty set with the capacity factor of renewable energy, (ii) searching for the initial point of a flexibility deficit, and (iii) calculating the capacity of the energy storage system to avoid such a deficit. In this study, robust optimization is applied to consider the uncertainty of renewable energy, and the results are compared between deterministic and robust approaches. The proposed method is demonstrated on a power system in the Republic of Korea.

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Review of Power System Analysis Methods Considering Correlation of Wind-Photovoltaic-Load

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.860-863.2088 ◽

2013 ◽

Vol 860-863 ◽

pp. 2088-2094 ◽

Cited By ~ 1

Author(s):

Pan Yu Fang ◽

Xue Feng Fan ◽

Jie Ren ◽

Yi Xia ◽

De Zhi Chen ◽

...

Keyword(s):

Renewable Energy ◽

Power Systems ◽

Power System ◽

Wind Power ◽

Large Scale ◽

System Analysis ◽

Power System Analysis ◽

Systems Planning ◽

Photovoltaic Power ◽

Planning And Operation

Close attention has been paid to the power generation using renewable energy such as the widespread energy and solar energy. After the integration of large-scale renewable energy, more uncertain factors are brought to the power system, which badly influences systems planning and operation. The wind power, photovoltaic power and load are random but correlative, therefore, it is more logical to study the influence exerted by the integration of renewable energy when considering the uncertainty and it is meaningful to the power systems planning and operation. Based on the summary and survey of previous studies, the technical route of power system analysis concerning the correlation of wind power, photovoltaic power and load is proposed in this paper and some key technologies are discussed. The study of correlation offers valuable analysis and recommendations to the connection of large-scale wind and solar power base.

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Optimal Scheduling of a Multi-Energy Power System with Multiple Flexible Resources and Large-Scale Wind Power

Energies ◽

10.3390/en12183566 ◽

2019 ◽

Vol 12 (18) ◽

pp. 3566 ◽

Cited By ~ 2

Author(s):

Quanhui Che ◽

Suhua Lou ◽

Yaowu Wu ◽

Xiangcheng Zhang ◽

Xuebin Wang

Keyword(s):

Power Systems ◽

Power System ◽

Wind Power ◽

Large Scale ◽

Cost Model ◽

Supply And Demand ◽

Thermal Power ◽

Wind Farms ◽

Optimal Scheduling ◽

Flexible Resources

With the grid-connected operation of large-scale wind farms, the contradiction between supply and demand of power systems is becoming more and more prominent. The introduction of multiple types of flexible resources provides a new technical means for improving the supply–demand matching relationship of system flexibility and promoting wind power consumption. In this paper, multi-type flexible resources made up of deep peak regulation of thermal units, demand response, and energy storage were utilized to alleviate the peak regulation pressure caused by large-scale wind power integration. Based on current thermal plant deep peak regulation technology, a three-phase peak regulation cost model of thermal power generation considering the low load fatigue life loss and oil injection cost of the unit was proposed. Additionally, from the perspective of supply–demand balance of power system flexibility, the flexibility margin index of a power system containing source-load-storage flexible resources was put forward to assess the contribution from each flexibility provider to system flexibility. Moreover, an optimal dispatching model of a multi-energy power system with large-scale wind power and multi-flexible resources was constructed, aimed at the lowest total dispatching cost of the whole scheduling period. Finally, the model proposed in this paper was validated by a modified RTS96 system, and the effects of different flexibility resources and wind power capacity on the optimal scheduling results were discussed.

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Methodology for Implementing the State Estimation in Renewable Energy Management Systems

Energies ◽

10.3390/en14082301 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2301

Author(s):

Yun-Sung Cho ◽

Yun-Hyuk Choi

Keyword(s):

Renewable Energy ◽

Power Systems ◽

State Estimation ◽

Measurement Errors ◽

Large Scale ◽

Test System ◽

The State ◽

Inner Function ◽

Outer Function ◽

Bad Data

This paper describes a methodology for implementing the state estimation and enhancing the accuracy in large-scale power systems that partially depend on variable renewable energy resources. To determine the actual states of electricity grids, including those of wind and solar power systems, the proposed state estimation method adopts a fast-decoupled weighted least square approach based on the architecture of application common database. Renewable energy modeling is considered on the basis of the point of data acquisition, the type of renewable energy, and the voltage level of the bus-connected renewable energy. Moreover, the proposed algorithm performs accurate bad data processing using inner and outer functions. The inner function is applied to the largest normalized residue method to process the bad data detection, identification and adjustment. While the outer function is analyzed whether the identified bad measurements exceed the condition of Kirchhoff’s current law. In addition, to decrease the topology and measurement errors associated with transformers, a connectivity model is proposed for transformers that use switching devices, and a transformer error processing technique is proposed using a simple heuristic method. To verify the performance of the proposed methodology, we performed comprehensive tests based on a modified IEEE 18-bus test system and a large-scale power system that utilizes renewable energy.

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Application of Battery Energy Storage Systems for Primary Frequency Control in Power Systems with High Renewable Energy Penetration

Energies ◽

10.3390/en14051379 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1379

Author(s):

Md Ruhul Amin ◽

Michael Negnevitsky ◽

Evan Franklin ◽

Kazi Saiful Alam ◽

Seyed Behzad Naderi

Keyword(s):

Renewable Energy ◽

Power Systems ◽

Power System ◽

Storage Systems ◽

Frequency Control ◽

Battery Energy Storage ◽

Battery Energy Storage Systems ◽

Battery Energy ◽

Primary Frequency ◽

Primary Frequency Control

In power systems, high renewable energy penetration generally results in conventional synchronous generators being displaced. Hence, the power system inertia reduces, thus causing a larger frequency deviation when an imbalance between load and generation occurs, and thus potential system instability. The problem associated with this increase in the system’s dynamic response can be addressed by various means, for example, flywheels, supercapacitors, and battery energy storage systems (BESSs). This paper investigates the application of BESSs for primary frequency control in power systems with very high penetration of renewable energy, and consequently, low levels of synchronous generation. By re-creating a major Australian power system separation event and then subsequently simulating the event under low inertia conditions but with BESSs providing frequency support, it has been demonstrated that a droop-controlled BESS can greatly improve frequency response, producing both faster reaction and smaller frequency deviation. Furthermore, it is shown via detailed investigation how factors such as available battery capacity and droop coefficient impact the system frequency response characteristics, providing guidance on how best to mitigate the impact of future synchronous generator retirements. It is intended that this analysis could be beneficial in determining the optimal BESS capacity and droop value to manage the potential frequency stability risks for a future power system with high renewable energy penetrations.

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A Novel Methodology for Adaptive Coordination of Multiple Controllers in Electrical Grids

Mathematics ◽

10.3390/math9131474 ◽

2021 ◽

Vol 9 (13) ◽

pp. 1474

Author(s):

Ruben Tapia-Olvera ◽

Francisco Beltran-Carbajal ◽

Antonio Valderrabano-Gonzalez ◽

Omar Aguilar-Mejia

Keyword(s):

Power Systems ◽

Power System ◽

Electric Power ◽

Large Scale ◽

Short Circuit ◽

Dynamic Performance ◽

Low Frequency ◽

Electric Power System ◽

Design Stage ◽

Positive Interaction

This proposal is aimed to overcome the problem that arises when diverse regulation devices and controlling strategies are involved in electric power systems regulation design. When new devices are included in electric power system after the topology and regulation goals were defined, a new design stage is generally needed to obtain the desired outputs. Moreover, if the initial design is based on a linearized model around an equilibrium point, the new conditions might degrade the whole performance of the system. Our proposal demonstrates that the power system performance can be guaranteed with one design stage when an adequate adaptive scheme is updating some critic controllers’ gains. For large-scale power systems, this feature is illustrated with the use of time domain simulations, showing the dynamic behavior of the significant variables. The transient response is enhanced in terms of maximum overshoot and settling time. This is demonstrated using the deviation between the behavior of some important variables with StatCom, but without or with PSS. A B-Spline neural networks algorithm is used to define the best controllers’ gains to efficiently attenuate low frequency oscillations when a short circuit event is presented. This strategy avoids the parameters and power system model dependency; only a dataset of typical variable measurements is required to achieve the expected behavior. The inclusion of PSS and StatCom with positive interaction, enhances the dynamic performance of the system while illustrating the ability of the strategy in adding different controllers in only one design stage.

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Decentralized H ∞ control for damping power system oscillations

Open Engineering ◽

10.2478/s13531-011-0054-1 ◽

2012 ◽

Vol 2 (1) ◽

Author(s):

Guo-Jie Li ◽

Tek Lie

Keyword(s):

Power Systems ◽

Power System ◽

Large Scale ◽

Digital Simulation ◽

Design Procedure ◽

Disturbance Attenuation ◽

System Stability ◽

Frequency Noise ◽

Stability Robustness ◽

Norm Bound

AbstractInter-area oscillations are serious problems to large-scale power systems. A decentralized H ∞ generator excitation controller of a power system is proposed to damp the inter-area oscillations and to enhance power system stability. The design procedure for a linear composite system is presented in terms of positive semi-definite solutions to modified algebraic inequalities. The resulting controller guarantees closed-loop stability, robustness and an H ∞-norm bound on disturbance attenuation even under uncertainties such as high frequency noise. The control is decentralized in the sense that the control of each generator depends on local information only. The effectiveness of the H ∞ controller is demonstrated through digital simulation studies on a two-machine power system.

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