Influence mechanism of backlash nonlinearity on dynamic regulation stability of hydropower units

Liao, Yiwen; Yang, Weijia; Zhao, Zhigao; Li, Xudong; Ci, Xiaohu; Bidgoli, Mohsen Alizadeh; Yang, Jiandong

doi:10.1016/j.seta.2021.101917

Cited by 4 publications

(5 citation statements)

References 35 publications

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“…From these results, it can be observed that for the 50% load drop, the system will not be able to settle for constant operation, as the frequency will continue to oscillate with a fixed amplitude and period. This is coherent with the results discussed in [9], where it is stated that with an increase of backlash from 0, the frequency will "evolve into an oscillation with equal amplitude". It is also observed that all the other load variation cases eventually will stabilize after about 1200s, even though the backlash is 5%.…”

Section: Frequency Testssupporting

confidence: 89%

“…The period of the oscillations is given as The oscillation periods given in Equations 3 and 5 will be used to validate the SIMSEN model's ability to show the physical phenomena in the waterways as described in Section 4. With the hydropower plants and their belonging governors aging, the magnitude of mechanical backlash in the system will increase [9]. This means that the governing equations will have to include effects from the backlash, and cause challenges for both constructors and operators of power plants.…”

Section: Theorymentioning

confidence: 99%

“…Backlash can be described as one of the most important non-linearities that limit the accuracy and swiftness of the mechanical motions in a control system [10]. This is also the case for a hydro turbine governor, where mechanical backlash can occur between the servo motor and the guide vanes [9]. This is because of the multiple links and joints, shown in Figure 1, which all have a certain engineering fit clearance for dynamic motion.…”

Section: Theorymentioning

confidence: 99%

See 2 more Smart Citations

Governing of a Francis Turbine Model Subjected to Load Variations

Haugum

2023

J. Phys.: Conf. Ser.

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In this work, the problem of mechanical backlash in the governor system for the Francis test rig at the Waterpower Laboratory, NTNU Trondheim, is investigated. Through numerical simulations on a digital model of the test rig, done in the software SIMSEN, the maximum allowable backlash which still enables stable governing was detected. This was done by further developing the model used in the work by A. Ingranata [1], to perform load variation tests presented by Statnett [2]. From these frequency control tests it was concluded that the maximum mechanical backlash which still enables stable governing, is 1% of maximum stroke length of the servomotor present in the governor system. To design a system which can achieve the requirements of 1% backlash, a more conventional layout which utilizes links instead of the slots present in the existing governor ring, is suggested.

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Section: Frequency Testssupporting

confidence: 89%

Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

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Governing of a Francis Turbine Model Subjected to Load Variations

Haugum

2023

J. Phys.: Conf. Ser.

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“…In the field of operational stability, 32 Shang et al 33 explored the characteristics of discharge and pressure fluctuation of VSPSU under different operating speeds in turbine mode and revealed that with the increase of unit speed, the stability decreases. Cavazzini et al 34 illustrated the influence of the S‐shape zone and the hump zone on the power regulation of VSPSU and proposed that not only both pump mode and turbine mode should be considered at the same time when optimizing the stability of the pump–turbine.…”

Section: Introductionmentioning

confidence: 99%

Quantifying power regulation characteristics in pump mode of variable‐speed pumped storage unit with DFIM

Liu,

Yang,

Yang

et al. 2024

Energy Science & Engineering

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Pumped storage plants (PSPs) play an important role in renewable energy consumption in power systems. Variable‐speed technology is a new and critical direction for the development of PSPs. In pump mode, variable‐speed pumped storage units (VSPSUs) have wider power regulation ranges and more flexible power responses than fixed‐speed pumped storage units (FSPSUs); however, the corresponding quantification study of VSPSUs is rare. Therefore, this study aims to quantify the static and dynamic power regulation characteristics of VSPSU in pump mode. First, the modeling of the fast speed control strategy of VSPSU in pump mode is improved. Then, the power regulation range of the VSPSU is explored. The factors (i.e., power command, governor, and converter) affecting the power response rapidity are quantified through the engineering case of a variable‐speed PSP adopting the doubly fed induction machine. Accordingly, suggestions on the settings of the parameters are provided. Quantification results show that parameter tuning based on this study effectively solves the problem of low regulation rate caused by great power fluctuations under typical power regulation cases in pump mode. This VSPSU has the fastest regulation rate of 13.75%/s when adjusting 40% power. This study could provide technical support to the practical operation of VSPSU.

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“…The finite element method is used to evaluate the performance of the turbine. Article [17] analyzes the influence of backlash nonlinearity on the stability of island power systems, where the Nyquist stability criterion and the numerical modeling method are used to control hydraulic turbines. Another focus of the study is on the mechanism of the influence of four important hydromechanical time constants on the stability of a nonlinear system of a hydraulic unit.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Simulation of Starting and Emergency Conditions of a Hydraulic Unit Based on a Francis Turbine

et al. 2022

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The Francis hydro-turbine is a typical nonlinear system with coupled hydraulic, mechanical, and electrical subsystems. It is difficult to understand the reasons for its operational failures, since the main cause of failures is due to the complex interaction of the three subsystems. This paper presents an improved dynamic model of the Francis hydro-turbine. This study involves the development of a nonlinear dynamic model of a hydraulic unit, given start-up and emergency processes, and the consideration of the effect of water hammer during transients. To accomplish the objectives set, existing models used to model hydroelectric units are analyzed and a mathematical model is proposed, which takes into account the dynamics during abrupt changes in the conditions. Based on these mathematical models, a computer model was developed, and numerical simulation was carried out with an assessment of the results obtained. The mathematical model built was verified on an experimental model. As a result, a model of a hydraulic unit was produced, which factors in the main hydraulic processes in the hydro-turbine.

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Influence mechanism of backlash nonlinearity on dynamic regulation stability of hydropower units

Cited by 4 publications

References 35 publications

Governing of a Francis Turbine Model Subjected to Load Variations

Governing of a Francis Turbine Model Subjected to Load Variations

Quantifying power regulation characteristics in pump mode of variable‐speed pumped storage unit with DFIM

Dynamic Simulation of Starting and Emergency Conditions of a Hydraulic Unit Based on a Francis Turbine

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