Analysis and Measures of Ultralow-Frequency Oscillations in a Large-Scale Hydropower Transmission System

Mo, Weike; Chen, Haoyong; Liu, Yingshang; Zhang, Yong; Hou, Jun; Gao, Qin; Li, Chongtao

doi:10.1109/jestpe.2017.2759810

Cited by 48 publications

(21 citation statements)

References 18 publications

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“…Yang and Yang and Zhao and Ren also studied the role of pumped storage units in enhancing power system stability and frequency control [7,8]. It can be seen from some accidents in the power system that the units with the input of primary frequency regulation function and the correct setting of primary frequency regulation parameters can greatly restrain the expansion of the accident and ensure the stability of the power system [9][10][11]. e pumped storage unit regulation system (PSURS) has strong nonlinear and time-varying characteristics [12], and PSU has "S" characteristic area, which leads to the frequency oscillation of the unit under low water head [13,14].…”

Section: Introductionmentioning

confidence: 99%

Characteristic Analysis and Optimal Regulation of Primary Frequency Regulation Condition in Low Water Head Area Based on Hydraulic-Mechanical-Electrical Coupling Model of Pumped Storage Unit

et al. 2020

Complexity

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Pumped storage power station is an important regulating tool for peak load regulation and frequency regulation of the power grid, especially its primary frequency regulation function, which is of profound significance for the safety and stability of the power grid. As the core equipment of the pumped storage power station, the reversible design of the pump turbine makes it easy to have hydraulic fluctuation and mechanical instability when the unit runs to the “S” characteristic area, which will cause the frequency oscillation of the generator under the condition of primary frequency regulation. Therefore, some innovative work is studied in this paper: (1) an accurate hydraulic-mechanical-electrical coupling system mathematical model of pumped storage unit regulation system (PSURS) is established based on full characteristic curve of the pump turbine and seventh-order synchronous generator and excitation system; (2) the dynamic response characteristics of primary frequency regulation of pumped storage unit (PSU) under different water heads and different frequency disturbances are analyzed by numerical simulation; (3) in view of the unstable condition of the unit under the large frequency disturbance when it operates in the low head and small load area, the objective optimization function considering the ITAE index of hydraulic, mechanical, and electrical factors is proposed; and (4) fractional-order PID controller and the bacterial-foraging chemotaxis gravitational search algorithm (BCGSA) combined optimization strategy is used for PSURS optimization regulation and parameter optimization. The results show that the joint optimization strategy proposed in this paper has smaller objective function value, and makes the PSURS pass through the unbalanced area quickly, with better primary frequency regulation speed and smaller regulation depth.

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Section: Introductionmentioning

confidence: 99%

Characteristic Analysis and Optimal Regulation of Primary Frequency Regulation Condition in Low Water Head Area Based on Hydraulic-Mechanical-Electrical Coupling Model of Pumped Storage Unit

et al. 2020

Complexity

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“…It was concluded that the turbine and governing system would produce negative damping and weaken the stability of the system. Especially, differing from thermal units, the hydropower units' water hammer effect plays a negative role in ultra-low frequency band [8]- [13]. Furthermore, the influences of different governor control modes and governor parameters on damping torque were analyzed.…”

Section: Introductionmentioning

confidence: 99%

The Mechanism of Ultra-Low Frequency Oscillations With the Same Mode Shapes

et al. 2020

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The ultra-low frequency oscillation (ULFO) problem reappears in China recently. Different from the classical low frequency oscillation (LFO), the generators in ULFO have the same mode shapes, namely oscillating in the same pace. To reveal the reason why ULFO generators do not oscillate inversely as classical LFO does, this paper investigates the mechanism of ULFO based on improved Philips-Heffron model of two-machine system. Through this model, the phase angle relationship between different generators is obtained. Based on the bode diagram, it is found that the phase angle difference of the two machines is around zero in ultra-low frequency band however the generator parameters change. On the contrary, the situation is different in classical low frequency band, which reveals the mechanism that generators in ULFO always oscillate in the same pace. Finally, the analysis above is validated through a 2area 4-machine system and a 6-machine system established in PSASP software. INDEX TERMS ultra-low frequency oscillation, mode shape, dynamic mechanism NOMENCLATURE E '' di, E '' Y Complex admittance matrix (p.u.). yij, βij Amplitude of Y, phase angle of Y (p.u.). δij Difference between δi and δj, in rad. Cij,Sij cos(βij-δij), sin(βij-δij) (p.u.).

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“…In 2016, an extremely low frequency oscillation (about 0.05 Hz) occurred in China Southern Power Grid during asynchronous testing [2]. Simulation indicates that the parameters of governors may lead to substantial effects [3]. An ultra-low frequency eigenmode with 0.08 Hz was motivated in the second stage of the north Brazil blackout in 2018 [4].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Mode Interaction in Ultra-low Frequency Oscillation Based on Trajectory Eigenvalue

Xue

Bin

2020

Journal of Modern Power Systems and Clean Energy

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Complex phenomena such as prolongedly undamped ultra-low frequency oscillation (ULFO) and eigenmode re-excitation are observed in the simulations of hydroelectric power systems. Emphases are put on nonlinearities and mode interactions, which cannot be analyzed by traditional eigen-analysis methods. In order to investigate the mechanism of the evolvement of the nonlinear dynamic process in ULFO, this paper proposes a method to analyze the mode interactions quantificationally. First, a disturbed trajectory is decoupled into a set of time-varying components. Second, transfer matrices of eigenmodes are extracted along the trajectory. Third, consecutive sequences of eigenvalues and trajectories of components are formed by a proposed technique. Based on the decoupled components and transfer matrices, the mechanisms of mode interactions and inheritance relationships between eigenmodes are analyzed. The causes and developments of the above complex phenomena are revealed by the proposed method in a test two-machine system. Meanwhile, the accuracy of the eigenmode matching technique is verified in the New England system.

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Analysis and Measures of Ultralow-Frequency Oscillations in a Large-Scale Hydropower Transmission System

Cited by 48 publications

References 18 publications

Characteristic Analysis and Optimal Regulation of Primary Frequency Regulation Condition in Low Water Head Area Based on Hydraulic-Mechanical-Electrical Coupling Model of Pumped Storage Unit

Characteristic Analysis and Optimal Regulation of Primary Frequency Regulation Condition in Low Water Head Area Based on Hydraulic-Mechanical-Electrical Coupling Model of Pumped Storage Unit

The Mechanism of Ultra-Low Frequency Oscillations With the Same Mode Shapes

Analysis of Mode Interaction in Ultra-low Frequency Oscillation Based on Trajectory Eigenvalue

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