Abstract
The central Tibet AC interconnection project (CTAIP), which connects the Tibet power grid and the Sichuan power grid through a long distance transmission line of more than 1400 km, has a significant problem of voltage regulation. In order to improve the voltage regulation performance, six sets of ±60 Mvar static VAR compensators (SVC) were installed in the CTAIP. However, the SVCs may lead to electromagnetic oscillation below 50 Hz while improving voltage regulation capability. In this paper, the electromagnetic oscillation modes and the sensitivity of control parameters of SVC are analyzed. Then, the characteristics and influencing factors of the oscillation are discussed. It was found that there is an inherent electromagnetic oscillation mode below 50 Hz in the ultra-long distance transmission system. The employ of SVCs weaken the damping of this mode. Large proportional gain and integral gain (PI) parameters of SVCs can improve the voltage regulation performance, but weaken the electromagnetic oscillation mode damping. Therefore, a suppression method based on SVC PI parameters optimization is proposed to damp the oscillation. The essential of this method is to use the rising time of voltage response and setting time of SVCs as performance indicators of voltage regulation, and take the damping level of the electromagnetic oscillation mode as the performance index of SVC electromagnetic oscillation suppression ability. Combining the two indicators to form a comprehensive optimization index function, an intelligent optimization algorithm is applied. The process of SVC parameter optimization and the steps of multi-SVC parameter optimization in large power grids is proposed. Finally, PSCAD and real-time digital simulation (RTDS) simulation results verified the correctness of the proposed method. The optimization strategy was applied to CTAIP. The artificial grounding short circuit experimental results proved the effectiveness of the proposed strategy.
Highlights
The central Tibet AC interconnection project (CTAIP) connects the central Tibet, Changdu, and Sichuan power grids of China
The electromagnetic oscillation mode of the power system furnishing with static VAR compensators (SVC) can be calculated by solving this generalized eigenvalue problem
The following part of this paper parameter optimization method which can suppress electromagnetic oscillation and maintain focuses on the oscillation modes with angular frequencies smaller than 314 rad/s, so this defect of this enough reactive power regulation performance of the SVC
Summary
The central Tibet AC interconnection project (CTAIP) connects the central Tibet, Changdu, and Sichuan power grids of China. There has been a large number of studies focused on SSCI It has been pointed out in [5] that a power system stabilizer may deteriorate the subsynchronous oscillation mode damping of power systems. In [19], coordinated control of SVCs and TCSCs for voltage profile improvement employing particle swarm optimization was proposed, but oscillation suppression was not discussed. There is no systematic method to optimize the PI parameters of SVCs considering both the electromagnetic oscillation suppression and voltage regulation capability. An optimization strategy of SVC is proposed, considering both the suppressing of oscillation and voltage regulation capability. The contradiction between reactive power regulation ability and electromagnetic oscillation suppression ability of the SVC is revealed, which provides a basis for the definition of a comprehensive optimization objective function.
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