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| Quantitative Analysis and Evaluation Method for the Impact of Static Loads on Voltage Stability in Multi-Infeed Direct Current Systems |
| Wang Yixin1, Tang Yu1, Ye Lin2, Zhou Jinghao2, Liu Ang3, Xin Huanhai1 |
1. College of Electrical Engineering Zhejiang University Hangzhou 310027 China;
2. State Grid Zhejiang Electric Power Co. Ltd Hangzhou 310000 China;
3. Huzhou Power Supply Company State Grid Zhejiang Electric Power Co. Ltd Huzhou 313000 China |
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Abstract With the continuous growth of load and the expanding scale of HVDC projects, the spatial resources of HVDCs are gradually being occupied. The situation where new HVDC receiving-end converter stations are established in proximity to load centers has become increasingly unavoidable. Therefore, to ensure the safe and stable operation of the multi-infeed system, the quantification of voltage stability margin in the AC/DC system must take into account the influence of the load. The difference between the generalized short-circuit ratio (gSCR) and the critical generalized short-circuit ratio (CgSCR) is used to quantify the voltage stability margin of the AC/DC system. However, the existing definition of the gSCR has not taken into account the influence of the load, limiting its applicability. When considering the impact of the load in actual systems, the definition and calculation of the gSCR need to be changed. To address this issue, this paper proposes a method for analyzing and calculating the gSCR that considers the impact of the load. The new gSCR is a modification based on the original gSCR, and the modification is determined by various factors such as the size and type of the load. Firstly, considering a single infeed system, the impact of load on the short-circuit ratio is studied based on the system Jacobi matrix. Analytical expressions for the new short-circuit ratio are derived too. Secondly, for multi-infeed systems, a load equivalent modeling method is proposed which can unify the internal loads of the system onto the HVDC converter bus to avoid the dimension disaster caused by excessive loads. On this basis, the Jacobi matrix for the multi-infeed system is established by clustering the load-related components. Then, based on the modal perturbation method, the multi-infeed system Jacobi matrix is approximately decoupled, and the generalized short-circuit ratio considering the load impact is defined. Moreover, for practical computation of the generalized short-circuit ratio, a data-driven method for calculating the admittance matrix of the multi-infeed system is proposed. Finally, the effectiveness of the proposed methods is validated through a single infeed system and the IEEE 39-bus system simulation cases. The main contributions of the paper are as follows: (1) The adoption of the load equivalent modeling method overcomes the difficulty of individually modeling and analyzing loads in the system. This makes it possible to quantify the impact of loads in large systems. Since the load equivalent conversion process is independent of load scale, it can avoid the dimension disaster problem in large system analysis. (2) The proposed new gSCR can consider the impact of loads, extending the original gSCR and thereby improving the accuracy of voltage stability analysis. (3) Addressing the challenge of difficult computation of the generalized short-circuit ratio in large systems, a data-driven identification algorithm for the admittance matrix of the multi-infeed system is proposed. The algorithm, combined with the load equivalent modeling method mentioned above, enables the analysis and computation of the gSCR in large systems.
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Received: 08 November 2023
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2024, Vol. 39 
