Linearized power flow models are of great interest in power system studies such as contingency analyses and reliability assessments, especially for large-scale systems. One of the most popular models—the classical DC power flow model—is widely used and praised for its state independence, robustness, and computational efficiency. Despite its advantages, however, the DC power flow model fails to consider reactive power or bus voltage magnitude. This paper closes this gap by proposing a decoupled linearized power flow (DLPF) model with respect to voltage magnitude and phase angle. The model is state independent but is distinguished by its high accuracy in voltage magnitude. Moreover, this paper presents an in-depth analysis of the DLPF model with the purpose of accelerating its computation speed, leading to the fast DLPF (FDLPF) model. The approximation that is applied to obtain the FDLPF model from the DLPF model is justified by a theoretical derivation and numerical tests. The proposed methods are provably accurate and robust for several cases, including radial distribution systems, meshed large-scale transmission systems and ill-conditioned systems. Finally, expressions for sensitivity with regard to MW flow and bus voltage are provided as a potential application.

A State-Independent Linear Power Flow Model With Accurate Estimation of Voltage Magnitude

https://pureadmin.qub.ac.uk/ws/files/95437154/Manuscript.pdf

Optimal day-ahead scheduling of integrated urban energy systems

At present, the problem of abandoning wind and PV power in “Three North” region of China is particularly significant, and how to alleviate this problem has become the focus of universal attention. Calculation of renewable energy accommodation capacity is the basis to solve the problem of abandoning wind and PV power. Main problems of Chinese renewable energy accommodation is analyzed from power supply, power grid and load side aspects, and it focuses on the effect of inter-provincial tie-line to renewable energy accommodation capacity. At present, the inter-provincial tie-line utilization level is limited, which affected renewable energy accommodation to a certain extent. Based on the sequential production simulation model, a new kind of renewable energy accommodation capacity model is put forward considering the utilization level of inter-provincial tie-line. According to different system stability constraints and different electricity constraints of inter-provincial tie-line, 4 schemes are designed for comparative analysis, and the evaluation model is used to calculate renewable energy accommodation capacity of “Three North” region of China in 2020. Example analysis results verify validity of the model that releasing curve constraints, electricity constraints and stability constraints in turn can significantly enhance renewable energy accommodation capacity through effective use of inter-provincial tie-line transmission capacity. Research work in this paper can provide strong support for the planning and scheduling control of power grid.

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Model and application of renewable energy accommodation capacity calculation considering utilization level of inter-provincial tie-line

To describe the impact of uncertainties, such as fluctuation of bus loads and intermittent behavior of renewable generations, on the available load supply capability (ALSC) of distribution system accurately and comprehensively, this paper defines a series of meaningful indices for the probabilistic evaluation of ALSC. An efficient simulation method, Latin hypercube sampling-based Monte Carlo simulation (LHS-MCS), combined with step-varied repeated power flow method is proposed to compute the defined indices. Compared with simple random sampling-based Monte Carlo simulation (SRS-MCS), LHS-MCS is found to be more suitable for the probabilistic evaluation of ALSC. It can achieve more accurate and stable ALSC indices under relatively small sample sizes. The calculation speed of LHS-MCS is comparable with that of SRS-MCS under the same sample sizes, and the required CPU time of LHS-MCS is far less than SRS-MCS under the same calculation accuracy. Case studies carried out on the modified Baran & Wu 33-bus and the modified IEEE 123-bus distribution systems verify the feasibility of the defined indices and high performance of the proposed method.

Probabilistic Evaluation of Available Load Supply Capability for Distribution System

The region-based method has been successfully applied in transmission systems. This study proposes the definition, model and applications of security region for distribution systems. With the ongoing smart grid initiatives, a large amount of real-time network information will be available. This is the motivation of an accurate calculation of the security boundary. First, this study presents the concepts of distribution system security region (DSSR); and discusses N -1 contingency scenarios for both substation transformers and feeders. Second, distribution system security boundary is modelled in the Euclidean space as several intersected hyperplanes. Furthermore, DSSR for substation transformer contingency is modelled as the space surrounded by the security boundaries and the set of all operating points that ensure the distribution system N -1 security. Third, distance from an operating point to a security boundary is formulated and a new index is also presented for security evaluation. The proposed DSSR-based security assessment method provides a new approach for future smart distribution system operation. Finally, the results from a real distribution system have demonstrated the effectiveness of the proposed concepts and methods; and the geometric characteristics of DSSR are also illustrated by means of two-dimensional visualisation of the test system.

Distribution system security region: definition, model and security assessment

Rapid evaluation method for power supply capability of urban distribution system based on N − 1 contingency analysis of main-transformers

In order to overcome the shortages of diagnostic method for distribution networks considering the reliability assessment, this paper proposed a method based on power supply safety standards. It profoundly analyzed the security standard of supply for urban power networks, and established quantitative indicators of load groups based on different fault conditions. Then a method suitable for diagnostic evaluation of urban distribution networks in China was given. In the method, “N-1” calibration analysis of the distribution network was conducted. Then the results are compared with quantitative indicators of load groups on different conditions deriving the diagnostic conclusions and the standard revision is discussed. The feasibility and accuracy of the method is finally verified in the case study.

/pdf/a-diagnostic-method-for-distribution-networks-based-on-power-4ao3g5ltuf.pdf

A diagnostic method for distribution networks based on power supply safety standards

Joint energy market design for local integrated energy system service procurement considering demand flexibility

Improved analytical method of power supply capability on distribution systems

The computer-supported decision-making system has become an essential tool for the sustainable growth and expansion planning of modern urban power distribution network. Current packages with planning functions are independent packages, which are limited in the academic research. Presently, in Shanghai Municipal Electric Power Company and its subordinate units, a geographic information system(GIS)-based production management system(PMS) has been applied successfully as the working platform in most departments, which makes the further research on the computer-aided decision-making system possible and feasible. Taking the PMS as the graphics supporting platform, this paper studies and develops a practical GIS-based decision-making support system for urban distribution network expansion planning, which establishes a primary foundation for information-based planning, daily-frequent planning and elaborate planning. Firstly, the physical structure of the system is designed with a four-layer hierarchical architecture, including the data layer, platform layer, application layer and performance layer, which is suitable for object-oriented development to ensure the security and stability of the system. Secondly, to satisfy the requirements of distribution expansion planning, the main functions of the system are divided into seven modules according to the planning process abstracted in the computer, including the module of current situation analysis, load forecasting, substation locating and sizing, network planning, cable channel planning, economic evaluation of planning and so on. There is at least one or one set of practical mathematical models and methods for planning adopted in each module to ensure the accuracy and reasonableness of the final planning results. Finally, an actual planning of Shanghai, China is accomplished with the expansion planning system. The practical application achievements show that the system can not only optimize the expansion planning results of urban power distribution network, but also reduce the workload of computation, analysis and graphics drawing dramatically.

Shaoyun Ge

Papers

Rapid evaluation method for power supply capability of urban distribution system based on N − 1 contingency analysis of main-transformers

A diagnostic method for distribution networks based on power supply safety standards

Joint energy market design for local integrated energy system service procurement considering demand flexibility

Improved analytical method of power supply capability on distribution systems

A practical GIS-based decision-making support system for urban distribution network expansion planning