Yongji Cao

Shandong University

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Hengxu Zhang

Shandong University

Changgang Li

Shandong University

Hao Qin

China University of Geosciences

Ruicong Ma

Shandong University

Zhimin Gao

International Bamboo and Rattan Organization

Dong Yang

Chongqing University

Shihao Zou

Shandong University

Huan Ma

Zhaoqing University

Jian Zhang

University of Electronic Science and Technology of China

Jiacheng Ruan

Guangdong Ocean University

Cooperative Institutions

EY Technologies (United States)

219

Unchained Labs (United States)

214

Shandong University

Chinese Academy of Sciences

Tianjin Hi-Tech Superconducting Electronic Technology (China)

Artificial Intelligence in Medicine (Canada)

Shanghai Jiao Tong University

Tsinghua University

Zhejiang University

Peking University

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Coordination Planning of Multiple Energies in Distribution Networks

Jian Zhang Yongji Cao Hengxu Zhang Jiaying Wang Ruicong Ma

In the context of the large-scale integration of renewable energy units into the grid, the coordinated operation of multiple energy types has become imperative for grid development. This paper begins by analyzing the characteristics of distribution network components and models the distribution network using an alternating current flow model. Subsequently, considering the uncertainty of renewable energy output and the seasonal characteristics affecting cold and heat loads, typical daily data is generated. Addressing the uncertainties of electricity, heating, and cooling loads, along with the seasonal variations in renewable energy output, a multi-scenario planning scheme is proposed. Validation is conducted through a simulation example involving a 33-bus system, demonstrating that the proposed scheme reduces costs while improving system economics, all while ensuring the provision of cold and heat loads.

10.1109/iccect60629.2024.10546188

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Quantitative Analysis of Influence of Frequency Spatiotemporal Distribution on UFLS

2021 International Conference on Power System Technology (POWERCON) (2023)

Xuening Cao Hengxu Zhang Yongji Cao

The modern power system network topology is becoming more and more complex, and the spatiotemporal distribution characteristics of frequency are becoming more and more prominent, which makes the implementation of the under-frequency load shedding (UFLS) of the power system deviate from the ideal setting. In this paper, the spatiotemporal distribution characteristics of frequencies in modern complex power systems are quantified and its influence on UFLS is analyzed. Based on the inertia mechanism of the spatiotemporal distribution characteristics of power system frequency, a description method of frequency response based on observation space is established. The spatiotemporal distribution characteristics of frequency response are quantitatively described by calculating multiple indicators of each observation point. The PSASP is used for simulation, and to analyze the influence of the spatiotemporal distribution characteristics of frequency on different UFLS action scheme.

10.1109/powercon58120.2023.10330973

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Extending SFR model to incorporate the influence of thermal states on primary frequency response

IET Generation Transmission & Distribution (2020)

Yongji Cao Hengxu Zhang Yi Zhang Yuzheng Xie Changhui Ma

Due to the increasing penetration of variable renewable energies, the primary frequency response (PFR) capability of thermal power units is becoming more and more significant for power systems to tackle abrupt active power disturbances. Moreover, the actual thermal states of boilers that are usually assumed to keep rated and constant may degrade PFR capability, and incur unexpected severer frequency deviations and even instability. This study proposes an extended system frequency response (ESFR) model incorporating the influence of thermal states on PFR. The ESFR model is developed by extending the system frequency response (SFR) model with a boiler thermodynamic sub-model, of which a low-order and linear time-domain expression is derived. Then, a quantitative assessment framework is established to assess the influence of thermal states on PFR capability, in which the instantaneous and accumulative quantities are calculated via the expressions of the ESFR and SFR models. Furthermore, based on the developed ESFR model, an improved estimation approach of dynamic frequency response considering thermal states is provided for the preliminary application. Case studies are conducted to validate the proposed model and approach.

Primary (astronomy)

10.1049/iet-gtd.2020.0206

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Quantitative Analysis of Power System Flexibility Based on K-Means Method and Copula Function

2022 IEEE/IAS Industrial and Commercial Power System Asia (I&CPS Asia) (2022)

Ruicong Ma Yongji Cao Hengxu Zhang Ying Lü Xueliang Yu

Power system flexibility analysis is important for grid development. For solving this problem, this paper constructs a flexible resource model of the power system to analyze the flexibility. The k-means method is adopted to classify the data. The probability models of wind power, PV output and load fluctuation in each scenario are constructed based on the Copula function, and the conditional probability of adjacent moments is solved by the Bayesian formula. Random sampling is performed based on the probability to generate the time series. The system flexibility margin expectation, shortage expectation and shortage probability are considered, and the operational economy is taken into account to establish quantitative assessment indices. The probabilistic optimal power flow (P-OPF) model with flexibility resources is constructed, and Monte Carlo simulation method is used to calculate the values of the assessment indexes. The IEEE RTS-24 system is used as an example to analyze the system flexibility.

Conditional probability

10.1109/icpsasia55496.2022.9949646

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Enhancing Event-Driven Load Shedding by Corrective Switching With Transient Security and Overload Constraints

IEEE Access (2019)

Fang Shi Hengxu Zhang Yongji Cao Huadong Sun Yun Chai

Sudden loss of bulk power generation will result in significant power shortage and power flow redistribution, which may lead to insecurity and/or stability problems. Under this condition, load shedding (LS) and corrective line switching (CLS) can be used to guarantee a reliable electricity supply. However, at present, the above two procedures are implemented separately, which may deteriorate each other and cause unnecessary load loss. To address this issue, a coordination optimization method is proposed to coordinate event-driven LS and CLS for enhancing power system security and stability as well as reducing LS amount simultaneously. A two-loop integrated algorithm is designed to solve the constrained optimization problem, which takes the transient frequency/voltage deviation and overload capacity of the transmission lines as constraints. In the inner loop, iterative optimization of the LS for frequency/voltage security is achieved based on linearized sensitivity analysis, and then step-by-step summation is employed to get the LS amount for alleviating overload. Neighbor search is used in the outer loop to coordinate event-driven LS and CLS so as to optimize the total LS amount. The effectiveness of the proposed method is validated in a modified IEEE 39 bus test system and an industrial power system. The results show that the proposed scheme can decrease the LS amount without improve the transient security while maintaining the transient security and alleviating overload.

Transient (computer programming)

10.1109/access.2019.2929304

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Citations (19)

Influence Analysis of Dual Carbon Goals on Industrial Load Based on System Dynamics

Xiu‐Qing Li Mo Zhou Yongji Cao Tao Liao Jian Zhang

The carbon peaking and carbon neutrality goals have been set for sustainable development and changed the behavior of energy consumption. In the phase of industrial production, the electrical load is high, and affected by the dual carbon goals. Thus, this paper proposes an influence analysis scheme of dual carbon goals on industrial load. The intensity of the government policy on decarbonization is assessed by the analytic hierarchy process (AHP). Then, the indices measuring the coupling between the low-carbon policy and industrial load is built for quantitative analysis. The system dynamic model is established to simulate the interaction between the intensity of the low-carbon policy and industrial load. A feedback loop depending on the industrial carbon emission is added to describe the changes in low-carbon policy. A case study is presented to validate the feasibility and effectiveness of the proposed scheme.

Carbon fibers

10.1109/iccect60629.2024.10545763

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Iterative Direction Expansion of Power Flow and Convergence Analysis Based on Deep Learning

Shang Cao Baoliang Li Yongji Cao Hengxu Zhang Lingyu Liang

Power flow calculation is essential for optimizing control actions and analyzing the running state of power systems. The development of smart grids has led to more complex power systems, challenging the convergence and computational efficiency of conventional algorithms. This study focuses on the limitations of current power flow algorithms in terms of iteration direction and proposed a method to extend the iteration direction in power flow calculation. Moreover, this method incorporated deep learning techniques to ease the computational burden while improving the convergence. This study aims to provide a useful reference for the analysis of complex power flows in power systems.

10.1109/iccect60629.2024.10545810

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Stability Assessment Approach Based on Trajectory Section Eigenvalue

E3S Web of Conferences (2021)

Jiacheng Ruan Hengxu Zhang Yongji Cao

Eigenvalue Method can analyze the operating features of the system. The trajectory section eigenvalue method combines the model and trajectory, and extends the equilibrium point eigenvalue to the unbalanced point of the cross section at any time on the disturbed trajectory, which well solves the non-linearity and the time-varying issues of the system. Based on the theoretical basis of clarifying the trajectory section eigenvalue (TSE) method, the paper establishes a stability evaluation framework based on the time-varying second-order resonant circuit, which extrates the damping feature and frequency feature information in the eigenvalue sequence of the trajectory section, then compares it with the results of signal processing. The influence mechanism of time-varying factors on system stability is clarified, and the advantages of the trajectory section eigenvalue method in stability evaluation are demonstrated.

Section (typography)

Feature (linguistics)

10.1051/e3sconf/202125602042

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A Coordinated Control Strategy of Multi-Type Flexible Resources and Under-Frequency Load Shedding for Active Power Balance

Symmetry (2024)

Jian Zhang Jiaying Wang Yongji Cao Baoliang Li Changgang Li

With the increasing expansion of power systems, there is a growing trend towards active distribution networks for decentralized power generation and energy management. However, the instability of distributed renewable energy introduces complexity to power system operation. The active symmetry and balance of power systems are becoming increasingly important. This paper focuses on the characteristics of distributed resources and under-frequency load shedding, and a coordinated operation and control strategy based on the rapid adjustment of energy storage power is proposed. The characteristics of various controllable resources are analyzed to explore the rapid response capabilities of energy storage. The energy storage types are categorized based on the support time, and the final decision is achieved with power allocation and adjustment control of the energy storage system. Additionally, a comprehensive control strategy for under-frequency load shedding and hierarchical systems is provided for scenarios with insufficient active support. The feasibility of the proposed model and methods is verified via a multi-energy system case.

Load Shedding

Power Balance

10.3390/sym16040479

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Citations (3)

Quantitative Assessment for Static Voltage Stability Considering Accumulative Effect

Lecture notes in electrical engineering (2025)

Zhiwen Liu Yongji Cao Shihao Zou

10.1007/978-981-96-1671-8_23

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