Generator Shaft Research Articles

Coupled Torsional Vibration and Fatigue Damage of Turbine Generator Due to Grid Disturbance

Crack failures continually occur in shafts of turbine generator, where grid disturbance is an important cause. To estimate influences of grid disturbance, coupled torsional vibration and fatigue damage of turbine generator shafts are analyzed in this work, with a case study in a 600MW steam unit in China. The analysis is the following: (i) coupled system is established with generator model and finite element method (FEM)-based shafts model, where the grid disturbance is signified by fluctuation of generator outputs and the shafts model is formed with lumped mass model (LMM) and continuous mass model (CMM), respectively; (ii) fatigue damage is evaluated in the weak location of the shafts through local torque response computation, stress calculation, and fatigue accumulation; and (iii) failure-prevention approach is formed by solving the inverse problem in fatigue evaluation. The results indicate that the proposed scheme with continuous mass model can acquire more detailed and accurate local responses throughout the shafts compared with the scheme without coupled effects or the scheme using lumped mass model. Using the coupled torsional vibration scheme, fatigue damage caused by grid disturbance is evaluated and failure prevention rule is formed.

Ship's Propulsion Neural Controller Main Engine - Pitch Propeller - Shaft Generator

The paper focuses on integration of monitoring and control of the main parts of ship propulsion plant - it means : main engine - shaft generator - pitch propeller. Each of these parts has its own controllers, but there is a lack of one supervisory, one level higher, device gathering and monitoring the whole system. This gap is fulfilled by the one supervisory controller based on neural network principles. (Iracki K., 2005); (Kruszewski J., 2002); (Kruszewski J. 1999);(Żurada J., Barski M., Jędruch W. 1996) The paper consist of three parts, the first one describes the problems and purposes of the controller usage, the second one presents the dynamic model of the ship basic parts and propulsion system and the third part presents the whole dynamic system with supervisory neural controller. Matlab/Simulink enclosing neural network data base was used as a main tool to realize computer simulation of the system.

Analysis of Turbine Generator Shaft Torsional Vibration Caused by Self-commutated Converters

SUMMARY This paper presents a simple analysis tool for torsional vibration of the rotor shaft of a turbine generator which is interconnected with a power system with self-commutated converters. The evaluation is based on analysis of measurement data in the field and instantaneous value-based power system simulation. A number of power converters with large capacity are installed in industrial power systems. Especially, interharmonics originating from self-commutated converters cause torsional vibration at the rotor shaft of rotating machines. The interaction between rotating machines and converters is known as sub-synchronous torsional interaction. The resonance between interharmonics from converters and the natural frequency of the rotor shaft causes large torsional vibrations, leading to shaft damage. In this paper, the influence of interharmonics on turbine generators is investigated. If there were air gap torque fluctuations with a frequency near the natural frequency caused by interharmonics, which have frequencies below 100 Hz of the sideband wave caused by asynchronous pulse width modulation, the rotor shaft may be damaged by the torsional vibration. In this paper, the emerging condition of the torsional vibration and the impact on the generator are investigated.

Adaptive Transmission of Wind Turbine

Adaptive transmission represents a wheelwork which is converting a variable rotational velocity of a wind wheel to constant rotational velocity of the generator shaft. Advantages of adaptive transmission: simplicity and reliability. The principle of act of adaptive transmission is based on use of the “Effect of force adaptation” in the kinematic chain with two degrees of freedom (at the science discovery). The research problem: to develop the scheme of the adaptive mechanism and regularity of interacting of its parameters for creation of highly effective wind turbines.

Performance Of Power System Stabilizerusing Fuzzy Logic Controller

Power system stabilizers (PSS) must be capable of providing appropriate stabilization signals over a broad range of operating conditions and disturbances. Traditional PSS rely on robust linear design methods. In an attempt to cover a wide range of operating conditions, expert or rule based controllers have been proposed. Recently, fuzzy logic as a novel robust control design method has shown promising results. In this paper a fuzzy logic based power system stabilizer for stability enhancement of a two-area four machine system are designed. In order to accomplish the stability enhancement, speed deviation (Δω) and active power deviation (ΔP) of the rotor synchronous generator were taken as the inputs to the fuzzy logic controller. These variables take significant effects on damping the generator shaft mechanical oscillations. The stabilizing signals were computed using fuzzy membership function depending on these variables. The performance of the system with fuzzy logic PSS is compared with the conventional PSS and the system without PSS.

A Survey on Shaft Voltage of Large Generator

Shaft voltage is widely existed in the operation of generator and needed to pay more attentions. Based on the mechanism of generator shaft voltage, this paper analyses and expounds the harmfulness of shaft voltage and shaft current, then summarizes the prevention and control measures of shaft voltage and the research status. The direction of generator shaft voltage is prospected for further research.

Simulation of Power Plant Subsynchronous Resonance Possibility Based on ADPSS

The rotor shaft of a steam turbine generator consists of several masses, such as rotors of turbine sections, generator section and exciter section. When the generator is perturbed, it will cause torsional oscillation between different sections. In long-distance high-capacity transmission lines, series compensation with capacitors can enhance power transfer capability of power system, however it may cause subsynchronous resonance (SSR) between the turbine shaft and serial compensation., which produce large shaft torques can result in a reduction in the shaft fatigue life and possibly shaft failure, threatening the security of generator unit and stability of power system. In China the 1000kV HVAC transmission line with series compensation has been put in operation since 2009. Near the Nanyang substation, there has a power plant in Henan power grid. So it is necessary to model the power plant and HVAC transmission line to simulate the possibility of SSR problem. Based on the power system simulation software ADPSS developed by China Electric Power Research Institute (CEPRI), this paper built up the simulation model using the electromechanical-electromagnetic transient hybrid method, and simulated the SSR possibility between the power plant and HVAC transmission line series compensation. The simulation results showed that with the generator parameters given, there has no risk of SSR between them. This paper also gives an evaluation principle of generator SSR risk when connected into a power grid.

Simulation of Power Plant Subsynchronous Resonance Possibility Based on ADPSS

The rotor shaft of a steam turbine generator consists of several masses, such as rotors of turbine sections, generator section and exciter section. When the generator is perturbed, it will cause torsional oscillation between different sections. In long-distance high-capacity transmission lines, series compensation with capacitors can enhance power transfer capability of power system, however it may cause subsynchronous resonance (SSR) between the turbine shaft and serial compensation., which produce large shaft torques can result in a reduction in the shaft fatigue life and possibly shaft failure, threatening the security of generator unit and stability of power system. In China the 1000kV HVAC transmission line with series compensation has been put in operation since 2009. Near the Nanyang substation, there has a power plant in Henan power grid. So it is necessary to model the power plant and HVAC transmission line to simulate the possibility of SSR problem. Based on the power system simulation software ADPSS developed by China Electric Power Research Institute (CEPRI), this paper built up the simulation model using the electromechanical-electromagnetic transient hybrid method, and simulated the SSR possibility between the power plant and HVAC transmission line series compensation. The simulation results showed that with the generator parameters given, there has no risk of SSR between them. This paper also gives an evaluation principle of generator SSR risk when connected into a power grid.

Analysis on Torsional Stresses in Turbo-Generator Shafts due to Two-Phase Short-Circuit Fault

Taking a 660MW turbine generator shaft system as a target system, the torsional stresses responses are calculated under two-phase short-circuit fault by the finite element (FE) method which can obtain torsional stresses in local areas accurately. The results show that torsional stresses threaten the safety of shafts appear at the first several cycles of the vibration. And the amplitude of stress in weak cross sections located between the low pressure cylinder and the generator is much greater. In addition, the proportion of torsional stresses frequency components in different sections is distinct. The results are helpful to improve the safety management level of the unit.

Research on Main Performance of the Vehicle-Mounted Generator System under Variable Speed Condition

Vehicle-mounted shaft generator system with constant frequency and voltage under variable speed condition can adapt to a large speed range of working condition while the vehicle is moving. Its key technologies are a process of rectification-inversion and a composite staggered parallel DC converter. Test research shows that electrical performance of the shaft generator system meets the first kind electric power plant requirements according to GJB 5785-2006 of China, which indicates that the shaft generator system can provide uninterrupted high quality electric power to current general on-board electrical equipment on vehicles under all speed conditions.

Subsynchronous Impact of Series Compensation on Induction Generator Based Wind Farm

Series compensation of transmission networks is being increasingly considered for integration of large wind farms to transfer bulk power. This article presents an extensive analysis of the potential of subsynchronous resonance in wind farms connected to a series-compensated line. The impact of symmetrical faults at different locations in the network is studied in detail. An equivalent circuit model is presented to calculate the resonant speeds of the aggregated induction generator for varying power outputs and series compensation levels. This study is validated by electromagnetic transient simulations using PSCAD/EMTDC software. Two sets of results are presented: one for wind farms of different megawatt ratings, and the other for a wind farm with different megawatt outputs. Scenarios are described for a wind farm connected to a line with a realistic level of series compensation, when a symmetrical fault at the wind plant terminal may result in high shaft torques. Recurrence of such faults can potentially lead to generator shaft failure due to cyclic fatigue. To mitigate subsynchronous resonance, a static synchronous compensator (STATCOM) is proposed at the terminals of the wind farm. The STATCOM not only stabilizes the wind farm but also reduces the peak shaft torque, thereby obviating the potential of shaft damage due to subsynchronous resonance.

Studies on a Wind Turbine Generating System that Employs a Thyristor Inverter

SummaryA new wind turbine generating system that employs a current‐source thyristor inverter is proposed, and the steady‐state and dynamic performances for a practical system are discussed. The proposed system is essentially based on the shaft generator system that is widely used in large ships, and it has many features such as high reliability and generation of output power of high quality. It is shown that electric power with constant frequency and voltage with low distortion can be obtained by using this novel system despite the changes in the velocity of natural wind. A dynamic model of the system is also developed, and a good agreement between simulated and experimental performances is obtained, thereby confirming the validity of the model.

Water Lubricated Guide Bearing with Self-aligning Segments

Abstract Water lubricated guide bearing was newly leased and has been applied to actual hydro turbines with vertical shaft. reAs a result, they can have not only high bearing performance but environmental advantages in meeting the demand for reducing river pollution by oil leakage from oil lubricated guide bearing. The PTFE composite guide bearing was tested by experimental equipment operated under conditions similar to those of actual hydro turbines. Circumferential and axial tilting bearing segments help to improve the bearing performance and efficiency due to low friction loss in the bearing system. Furthermore, bearing cooling systems could be eliminated and maintenance periods could be extended, thus the initial investment and operating costs of the hydroelectric power plant are reduced. Keywords : Water lubricated guide bearing, PTFE, Tilting segment, Vertical shaft hydro turbine, Hydrodynamic lubrication 1. Introduction Hydroelectric power generation, which provides electricity from clean and renewable energy without CO2 emissions, has the highest conversion efficiency and the fastest response in providing a stable power supply at low operating cost. In Japan there is not much room left for development of large capacity hydropower plants. In order to fulfill market demand for clean and renewable energy supply, small and medium capacity hydropower plants have been recently developed. The service intervals for hydropower plants have been extended and in other words, their long maintenance intervals strongly request that the radial and thrust bearings must have extremely high stability and reliability for supporting the rotating parts such as runner, turbine shaft, generator shaft and rotor. The oil lubricated radial bearings (hereinafter to be called guide bearings instead of radial bearing) have been usually applied to the hydro turbines and generators, but on the other hand the water lubricated guide bearings have recently had a strong background in construction of the hydro plants in order to prevent oil pollution in river water. The turbine guide bearing for multi-nozzle vertical Pelton turbine must have high stability throughout all kinds of operation enough to withstand high bearing pressure during operation driven with only one active nozzle. In case that shaft alignment is out of tolerance, there are possibilities of shaft vibration or partial contact between the bearing segment and the rotating shaft and, therefore, the turbine guide bearing must have preventive measures against abnormal wear and significant damage on the bearing sliding surfaces.

Role of flexible alternating current transmission systems devices in mitigating grid fault‐induced vibration of wind turbines

ABSTRACTThis paper focuses on the modeling of mechanical and structural vibrations in wind turbines due to the occurrence of electrical faults and an effective means of suppressing the vibrations with flexible alternating current transmission systems (FACTS) devices. A detailed model describing the dynamic interaction between the mechanical and the electrical subsystems of the turbine is presented. The model captures the effect of grid faults on the mechanical vibrations of drivetrain, flexible rotor blades and tower. Numerical investigation reveals that electrical disturbances have a significant impact on the mechanical/structural vibrations. In fact, the occurrence of severe vibrations due to voltage sags may compromise safe operation of the overall plant. The application of FACTS devices is then considered to suppress the effect of electrical fault‐induced vibrations. The performance comparison of static synchronous compensator and unified power quality conditioner devices in improving the mechanical/structural response has been carried out. A fault scenario compliant with Irish grid code has been simulated. Simulation results show that FACTS devices are successfully able to mitigate vibrations due to electrical faults, and they can be conveniently applied to stabilize the generator shaft speed, drivetrain oscillations, edgewise blade vibrations and tower responses. Further, superior performances of the unified power quality conditioner as compared with static synchronous compensator are also observed under certain conditions with increased fault duration. Copyright © 2013 John Wiley & Sons, Ltd.

Simulation and study on mitigation measures of frequent subsynchronous oscillation with low amplitude at multi-power plants

Subsynchronous oscillation (SSO) with low amplitude that exceeds cumulative fatigue threshold of the generator shaft frequently could significantly reduce the shaft’s service life, which is a new SSO problem that emerges in recent years. According to the real recording oscillograph, the basic reason for frequently over-threshold SSO with low amplitude at multi-power plants was analyzed based on Hulunbuir League system. The sensitivities of the electrical damping to the main electrical parameters in the contributing loop of subsynchronous torsional interaction were calculated. Based on the sensitivities, a simulation method was presented, which was used to excite the same oscillation as the actual case by exerting disturbance on the firing angle. The limitation of wide-band and narrow-band supplementary subsynchronous damping controller (SSDC) for mitigating this kind of SSO was analyzed based on the electromagnetic transient simulation model of Hulunbuir League system. The difference of supplementary excitation damping controller (SEDC) and parallel-form FACTS connected to the generator terminal was compared from the aspects of response time and the ability of damping torque supplying. The analysis indicates that their response time is similar but FACTS has stronger ability of damping torque supplying than SEDC. Time-domain simulation method was used to compare the mitigation effects of SEDC, static var compensator (SVC) and static synchronous compensator (STATCOM). Considering the mitigation effect, the floor space limit of the power plant and so on, STATCOM was considered as the best mitigation measure. A control strategy of cascaded STATCOM for engineering application was presented and the capacity for SSO mitigation as well as output characteristics was analyzed. The analysis indicates that STATCOM using the proposed control strategy has better mitigation effect and output characteristics with smaller capacity.

MASS MODEL OF MICROGASTURBINE SINGLE SPOOL TURBOJET ENGINE

Presented paper consists detailed mass model of micro gas turbine single spool turbojet in well-known Scheckling design layout (1R/1A). One of major criteria in aviation is weight that is granted by airworthiness requirements. At present, exempt from certification process are RC airplanes or UAV with total take-off weight less than 22.5 kg. From the 70's mass model was added as a part of aero engines design process. Engine weight affects airplane or UAV weight greatly, because it is a source of variety structure loads. Weight reduction efficiency factor, verifying in terms of design quality a micro gas turbine, and the flying object as a system. Developed computational model allows to estimate weight of the components (gas generator shaft, compressor rotor, compressor diffuser, combustor, turbine nozzle, turbine rotor, jet pipe, casings and housings) and whole engine as well. Model inputs are related to technological axisymmetric dimensions obtained from thermo gas dynamic and construction equations, making it easy to use. Obtained results was presented for several micro gas turbines (mSO1-designed by author, FD3-64, TK-50, JF-50, MW-54, KJ-66, AMT Olympus). Advantage of this model allows to avoid time consuming CAD modelling process at design study level. Presented algorithm can be used also in the design of UAV as well as issues related to the preliminary multidisciplinary design and optimization PMDO cases.

Multi-Machine Power System Stabilizer Design using Quantitative Feedback Theory

Power System Stabilizers (PSSs) are used to enhance damping of power system oscillations through excitation control of synchronous generator. The objective of the PSS is to generate a stabilizing signal, which produces a damping torque component on the generator shaft. Conventional PSSs are designed with the phase compensation technique in the frequency domain and include the lead-lag blocks whose parameters are determined according to a linearized power system model. The performance of Conventional PSSs (CPSSs) depends upon the generator operating point and the system parameters, but a reasonable level of robustness can be achieved depending on the tuning method. To overcome the drawbacks of CPSS, numerous techniques have been proposed in literatures. In this paper a robust method based on Quantitative Feedback Theory (QFT) Algorithm is used for tuning the PSS parameters. The proposed QFT-PSS is evaluated at a multi machine electric power system. The simulation results clearly indicate the effectiveness and validity of the proposed method.

A Design of Single Phase Induction Generator for Waterfall-hydro Turbine

This paper presents the design of the single phase induction generator for hydro turbine that driven by waterfall power. By the principle, when the water from the waterfall flows along the 1 inch pipe until to the nozzle, after that the nozzle directs water jet along a tangent to the circle through the center of the buckets. Finally, the buckets drive the rotor shaft of the single phase induction generator and generated 220V a.c. voltage for distributing electric load.The design of single phase induction generator is modified by rewiring the winding of an old 1 HP, 220V, 50Hz motor from 4 poles to 6 poles. For impulse turbine design, this paper use the information model from Baan Kiriwong waterfall, Nakhorn Sri Thammarat province, south of Thailand for designing the dimension of the components of Pelton turbine with 9 ½ inches diameter and 18 buckets.The result in laboratory test, at on-load test, the generator can distribute the load at 115.96W, 223V, 0.52A, 0.96P.F. - lagging with 1,200rpm of shaft speed. For the applications test, the water pump are set the pressure as similar as the Baan Kiriwong waterfall and when the water jet against the bucket for moving the generator, at on-load test, the generator can distribute the load at 77.9W, 190V, 0.41A, 0.98P.F. - lagging with 1,100rpm of shaft speed. It should be suitable for light load rural area and really far from electric distribution system.

Design and Performance of Brushless Doubly-fed Machine Based on Wound Rotor with Star-polygon Structure

The star-polygon brushless doubly-fed machine (SPBDFM) is a new type of wound-rotor machine and is attractive for variable-speed constant-frequency shaft generation system. The structure of rotor for the machine may be improving the conductor availability of the rotor windings. The kirchhoff laws is employed to illuminate the principle and some combinations of different slots and poles are presented as the examples. Harmonic analysis is also employed to analyze the magnetic motive force (MMF) waveform of rotor winding with the structure of star- polygon. Finally, the results are used to reveal that the SPBDFM is attractive for shaft generation system.

Analytical and Numerical Deflection Study on the Structure of 10 kW Low Speed Permanent Magnet Generator

Analytical and numerical studies of the deflection in the structure of 10 kW low speed permanent magnet generator (PMG) have been discussed in this paper. This study is intended to prevent failure of the structure when the prototype is made. Numerical analysis was performed with the finite-element method (FEM). Flux density, weight and temperature of the components are the required input parameters. Deflection observed were the movements of the two main rotor components, namely the rim and shaft, where the maximum deflection allowed at the air gap between rotor and stator should be between 10% to 20% of the air gap clearance or 0.1000 mm to 0.2000 mm. Base on the analysis, total deflection of the analytic calculation was 0.0553 mm, and numerical simulation was 0.0314 mm. Both values were in the acceptable level because it was still below the maximum allowed deflection. These results indicate that the structure of a permanent magnet generator (rim and shaft) can be used safely.