MW Turbine Research Articles

Cooling analysis of an axial turbine for a direct fired sCO2 cycle and impacts of turbine cooling on cycle performance

In this paper, the details of the cooling analysis and design process of a 950 MW rated sCO2 turbine for a direct-fired sCO2 power plant are presented. An analytical cooled turbine algorithm for combustion gas turbines is modified for sCO2 coolant and mainstream flows to determine the coolant fractions. Inputs of the cooling technologies were determined from internal NETL studies and publicly available data for prototype axial turbines. A simplified thermal stress analysis method is used to down-select and determine the cooling configurations to be used by considering the disk and material properties and candidate stream coolant temperatures. The cooled turbine algorithm was first used to eliminate configurations that would require too much coolant from the cycle. The best cooling configurations for a single flow and a double flow turbine were determined by testing in a direct-fired sCO2 power plant performance model in Aspen Plus. A weighed scoring criteria was developed to help select amongst closely related performance outcomes. Results of the scoring gave the best option as a single flow turbine with a calculated turbine efficiency of 88%, and a resulting cycle LHV efficiency of 65.73% and plant LHV efficiency of 54.43% for a 601.58 net MW direct-fired sCO2 power plant (952 MW turbine).

Results of fatigue measurement campaign on XL monopiles and early predictive models

In the present contribution, data from a measurement campaign on XL monopiles (with 9.5 MW turbines and water depths of up to 36 m) is presented. This campaign is based on data collected by three types of sensors: strain gauges (installed at the TP-tower interface), accelerations (taken at bottom, mid and upper levels of the tower) and SCADA data, comprising of wind speed, yaw angle, power, pitch angle and rpm. Additionally, wave and tidal data from a public Flemish maritime weather database is added. In a comparative analysis of XL monopiles’ and standard monopiles it was seen that the fatigue behaviour of the former radically departs from the latter, with side-to-side damage surpassing fore-aft for nominal operational conditions, and standstill fatigue damage generally being bigger than nominal. Furthermore, following a methodology described in previous OWI-Lab research, artificial neural network models are trained using the aforementioned sensor data to estimate the fore-aft and side-side tower bending moment damage equivalent loads (DEL), through the use of three months worth of data with a comparative analysis ensuing. Finally, the models’ performance is investigated for concrete operating conditions by correlating it with environmental and operating conditions (EOCs).

Rapid approach for structural design of the tower and monopile for a series of 25 MW offshore turbines

The goal of further reducing the Levelized Cost of Energy (LCOE) has driven the investigation of large-scale wind turbines. This work presents a simple, rapid and detailed approach for the structural design of the tower and monopile without a controller, but with frequency and high fidelity structural verification. The approach uses an optimization to reduce the mass of the structures while meeting strength, buckling and geometric constraints by using analytical equations. A verification of frequency constraints is performed with BModes, and ANSYS Mechanical APDL is used for high fidelity verification of stress and buckling. The approach is applied to study the design space of three 25 MW offshore wind turbines with different rotor diameters and cone angles, and to evaluate the nacelle center of mass fore-aft location effect. Results obtained show that the tower and monopile are more susceptible to changes in the rotor thrust than the overturning moment even for designs with high pre-cone angle and large distance of the nacelle center of mass from the tower axis. But it is possible to obtain structurally feasible tower and monopile designs for the three 25 MW turbines studied while not exceeding diameter and wall thickness limits. However, mass penalties can be decreased by 0.8-14%, to further reduce the cost of energy, by increasing the diameter limit which may require manufacturing technology development. The approach applied and studies serve to understand the design space of the tower and monopile for a 25 MW turbine, and provide baseline designs that can be used in the development of a controller and evaluation of a full suite of design load cases.

Comparison of blade optimisation strategies for the IEA 15MW reference turbine

Reference wind turbine models are crucial for enabling the research community to advance technology and meet the challenges associated with upscaling. The IEA 15 MW is one such reference model, designed using NREL’s WISDEM tool, which enables researchers to perform system-level analysis and optimisation. However, the authors have found the blade to be structurally infeasible when subject to aero-servo-elastic simulations and finite-element (FE) analyses. Given the shortcomings, this work aims to develop an updated blade model for the 15 MW turbine platform using the design tool Aeroelastic Turbine Optimisation Methods (ATOM). Two optimisation processes, with a comprehensive suite of feasibility constraints, are applied: 1) a frozen-loads mass minimisation with fixed planform, and 2) an aero-servo-structural levelised cost of energy (LCoE) minimisation. Results show the frozen-loads optimised design results in a 0.93% increase in LCoE due to the mass penalty of attaining feasibility. In contrast, the aero-structural optimised design results in a 2.29% reduction in LCoE due to mass reductions and increased energy capture—highlighting the benefits of an integrated design process. FE shell analysis of the optimised blades indicates the strength predictions in ATOM are accurate and the main load-bearing spar caps are optimally utilised. Whilst an improvement on the baseline, buckling load factors do not satisfy the target values, indicating the lower fidelity checks in ATOM are non-conservative. The WindIO yaml files for these optimised designs are freely available online.

Wind field reconstruction using nacelle based lidar measurements for floating wind turbines

In this work we investigate the influence of floater motions on nacelle based lidar wind speed measurements. The analysis is focused on wind field characteristics which are most relevant for performance analysis, namely rotor effective wind speed, shear and turbulence intensity. A numerical approach, coupling the publicly available in-house lidar simulation framework ViConDAR (Virtual Constrained turbulence and liDAR measurements) with an aeroelastic floating offshore wind turbine simulation is employed. Synthetic turbulent wind fields are generated with the open source turbulence generator TurbSim. The dynamics of the floating offshore wind turbine are simulated in the aeroelastic simulation code OpenFAST. Turbine dynamics and the corresponding synthetic wind field are then passed to the lidar simulation module of ViConDAR, which has been adapted for the consideration of turbine dynamics in all six degrees of freedom to simulate the lidar measurements under influence of motion. The simulation framework is demonstrated in a case study, simulating a lidar system on the nacelle of the IEA 15 MW turbine in combination with the WindCrete floater concept. Two different realistic lidar patterns are investigated under different metocean conditions. Different motion cases are examined individually and combined to evaluate the influence of rotational and translational degrees of freedom. Results show an increase of mean absolute error between lidar estimated and full wind field rotor effective wind speed of 0 to 25% depending on the environmental conditions. Observed overestimation of mean rotor effective wind speed was found to be in the region of up to 1%.

Comparison of different fidelity aerodynamic solvers on the IEA 10 MW turbine including novel tip extension geometries

Lifting-line based solvers could supersede the blade element momentum (BEM) method as the industry standard in the near future as rotor sizes of modern wind turbines and computational resources continue to increase. A comparison study between both methods is presented where the IEA 10 MW wind turbine is evaluated in the aero-servo-elastic simulation tool QBlade, comparing the lifting-line free vortex wake method to an unsteady blade element momentum solver. Besides the baseline rotor of the IEA 10 MW turbine, the comparison includes several blade tip extensions, including a swept and a dihedral geometry, to further differentiate capabilities between both methods in aerodynamically complex flow fields. As a reference serve results from equivalent simulations performed with multiple fidelity solvers of the simulation tool HAWC2. Results of a rigid load case demonstrate considerable improvement regarding the aerodynamic accuracy of lifting-line based methods in below rated conditions over BEM codes. The aerodynamic loads on geometrically complex tip extensions in steady conditions prove good capabilities of lower fidelity codes to predict out-of-plane bend shapes but also clear limitations regarding loads on swept geometries. A quasi-steady aeroelastic load case further demonstrates the capability of both QBlade codes to produce comparable results to similar fidelity solvers of the HAWC2 tool on an integral level. A detailed comparison in the time domain shows a larger dependency of the results on the type of structural solver that is used in contrast to the fidelity level of the aerodynamic method.

Predicting tilting of monopile supported wind turbines during seismic liquefaction

Offshore Wind Turbines are increasingly being constructed in seismically liquefiable zones and monopile is one of the main foundation types for water depths of up to about 40 m. Due to the nature of the loading history from wind, wave, and machine loading (1P and 2P/3P), the governing loading on the monopile foundation is asymmetric cyclic overturning moment defined by maximum moment (Mmax) and minimum moment (Mmin). During earthquakes, additional lateral loads will be experienced by the foundation due to inertia as well as kinematic interaction. In addition, if the ground is liquefiable, the foundation will also lose moment carrying capacity. One of the design challenges is therefore the prediction of the long-term tilt during earthquake liquefaction. The paper proposes a framework to predict the permanent tilt for monopiles in seismically liquefiable soils. A 5 MW turbine is taken to show the applicability of the method. Parametric studies are also carried out to show the influence of different parameters affecting the tilt.

An Inverse Method for Wind Turbine Blade Design with Given Distributions of Load Coefficients

It is shown in the literature that wind turbine designs with different load distributions have different wake features. To systematically study how different load distributions affect turbine wakes, a method for designing variants of blades with different radial load distributions, but with approximately the same power (CP) or thrust coefficient (CT), is needed. In this work, an inverse design method based on the blade element momentum method and the multi-dimensional Newton’s method, with the normal and tangential force coefficients as the design objective and iterations for satisfying the CP or CT constraint, is developed. The proposed method is validated using the two-bladed small-scale NREL phase VI S809 wind turbine blade design and the three-bladed utility-scale NREL 5 MW wind turbine blade design. Four variants of the NREL 5 MW wind turbine, i.e., the Root-CP, Tip-CP, Root-CT, and Tip-CT designs, which represent the variants of the original design (NREL-Ori) with a higher load near the blade root and tip regions with approximately the same power coefficient (CP) or thrust coefficient (CT) as that of the NREL-Ori design, respectively, are then designed using the proposed method. At last, the flapwise blade bending moment and the power coefficients from different variants of the NREL 5 MW turbine are compared for different tip speed ratios, showing that the “Root” designs are featured by a wider chord near the root, lower blade bending moment, and higher power coefficients for tip-speed ratios greater than nine.

Adaptive envelope protection control of wind turbines under varying operational conditions

This study introduces a new Envelope Protection System (EPS) algorithm for wind turbines. The algorithm is adaptive to turbine-changing operational conditions and can effectively reduce turbine excessive/ultimate loads. Through an adaptive neural network, the proposed algorithm continuously monitors instantaneous wind and turbine states. Simultaneously, it predicts the near future response of the turbine load and detects its future crossing with a predefined safe envelope limit by comparing the actual wind speed to a theoretically estimated wind speed. When required, a protection action is applied based on the comparison to keep the turbine load response within the safe limit. In this paper, the thrust force is used as the critical load and is chosen as the limit parameter. Simulations are carried out using the MS (Mustafa Sahin) Bladed Wind Turbine Simulation Model for the National Renewable Energy Laboratory (NREL) 5 MW turbine under normal turbulent winds with different mean values. Simulations show that the EPS algorithm adapts to varying operational conditions such as changes in turbine operating point in the below rated, transition, and above rated regions, as well as rotor blade icing and successfully reduces the excessive thrust forces. Performance analyses indicate that, for keeping the thrust force within the limit, the proposed EPS algorithm reduces the thrust force by 98.89%, 98.43%, 99.26% relative to standard baseline controls in the aforementioned regions, respectively and by 99.61% under blade icing. Also, the mean value and the fluctuations of thrust force are reduced up to 5.52% and 68.7%, respectively. Depending on the operating region, the mean power decreases up to 2.07% or increases up to 1.21%, while power fluctuations decrease up to 30.97%.

Lyapunov stability of grid-connected wind turbines with permanent magnet synchronous generator

Dynamic stability across a range of operating conditions and disturbances is an essential requirement in the control of wind turbines. To analyse and design for closed-loop stability, existing methods typically rely on the numerical evaluation of a small-signal model of the system around each operating condition. This approach, however, is an inefficient way to capture and shape dynamic behaviour over the wide ranges of operating conditions and parameter values arising in practical implementations. This work presents an analytic stability analysis for presents an analytic stability analysis for (PMSG) wind turbines. The proposed methodology, based on a Lyapunov function constructed from an analytic expression of the system Jacobian, enables the identification of regions of operation and parameter values for the wind turbine system within which its stability can be guaranteed. A feedback linearisation control strategy is adopted to deal with the nonlinear relationship between the generator speed and the DC-link voltage in the turbine back-to-back converter. The closed-loop response performance of the design based on the proposed methodology is compared to that of a conventional PI control design via simulation tests conducted on a 2 MW turbine model and a 5 MW (PMSG) reference turbine model on the FAST physics-based simulation tool developed by NREL.

Validation of a coupled atmospheric–aeroelastic model system for wind turbine power and load calculations

Abstract. The optimisation of the power output of wind turbines requires the consideration of various aspects including turbine design, wind farm layout and more. An improved understanding of the interaction of wind turbines with the atmospheric boundary layer is an essential prerequisite for such optimisations. With numerical simulations, a variety of different situations and turbine designs can be compared and evaluated. For such a detailed analysis, the output of an extensive number of turbine and flow parameters is of great importance. In this paper a coupling of the aeroelastic code FAST (fatigue, aerodynamics, structures, and turbulence) and the large-eddy simulation tool PALM (parallelised large-eddy simulation model) is presented. The advantage of the coupling of these models is that it enables the analysis of the turbine behaviour, among others turbine power, blade and tower loads, under different atmospheric conditions. The proposed coupling is tested with the generic National Renewable Energy Laboratory (NREL) 5 MW turbine and the operational eno114 3.5 MW turbine. Simulating the NREL 5 MW turbine allows for a first evaluation of our PALM–FAST coupling approach based on characteristics of the NREL turbine reported in the literature. The basic test of the coupling with the NREL 5 MW turbine shows that the power curve obtained is very close to the one when using FAST alone. Furthermore, a validation with free-field measurement data for the eno114 3.5 MW turbine for a site in northern Germany is performed. The results show a good agreement with the free-field measurement data. Additionally, our coupling offers an enormous reduction of the computing time in comparison to an actuator line model, in one of our cases by 89 %, and at the same time an extensive output of turbine data.

Large eddy simulations of curled wakes from tilted wind turbines

One control strategy to increase power production in wind farms is angling wind turbine rotors, in order to steer wakes away from downwind turbines. Although rotor yaw is the most common approach to wake steering, tilting the rotor vertically to steer the wake downward can also increase total farm power. In this study, large eddy simulations of a 15 MW turbine are performed for rotor tilt angles of 0°, 15°, and 30° with below-rated turbulent inflow. Wake characteristics are analyzed, including using circulation to quantify the curled wake's counter-rotating vortex pair and quantifying wake shapes by fitting Legendre polynomials to wake edge polar coordinates. Tilting the rotor causes downward wake steering, wider and vertically compressed wake cross-sections, and stronger counter-rotating vortices. Although the wake velocity deficit recovers similarly for tilted and non-tilted wakes, the power available to a downwind rotor recovers faster because the tilted wake is steered away from the downwind rotor area and is replaced by high-speed air from above. This also causes higher effective wind shear across the downwind rotor. Additional simulations double the gap between the ground surface and the rotor bottom, which affects the wake geometry as well as the downwind power recovery and wind shear.

Blade-Resolved CFD Simulations of a Periodic Array of NREL 5 MW Rotors with and without Towers

A fully resolved (FR) NREL 5 MW turbine model is employed in two unsteady Reynolds-averaged Navier–Stokes (URANS) simulations (one with and one without the turbine tower) of a periodic atmospheric boundary layer (ABL) to study the performance of an infinitely large wind farm. The results show that the power reduction due to the tower drag is about 5% under the assumption that the driving force of the ABL is unchanged. Two additional simulations using an actuator disc (AD) model are also conducted. The AD and FR results show nearly identical tower-induced reductions of the wind speed above the wind farm, supporting the argument that the AD model is sufficient to predict the wind farm blockage effect. We also investigate the feasibility of performing delayed-detached-eddy simulations (DDES) using the same FR turbine model and periodic domain setup. The results show complex turbulent flow characteristics within the farm, such as the interaction of large-scale hairpin-like vortices with smaller-scale blade-tip vortices. The computational cost of the DDES required for a given number of rotor revolutions is found to be similar to the corresponding URANS simulation, but the sampling period required to obtain meaningful time-averaged results seems much longer due to the existence of long-timescale fluctuations.

Principal Modernization Solutions for a 300 MW Power Unit to be Converted to Operate at Ultra-Supercritical Steam Parameters

This paper analyses the state of power engineering in Ukraine and the main trends in the development of the world market in the field of converting high-capacity powerful power units of thermal power plants into ultra-supercritical (USC) ones. It is shown that the energy sector of Ukraine requires special attention and the introduction of new modern technical solutions. Worldwide trends indicate that the emphasis is now on increasing the steam parameters before a turbine to ultra-supercritical ones. This allows one both to increase the efficiency of power units and to reduce thermal emissions, fighting the global environmental problem of climate warming. The implementation of this approach is proposed taking into account the realities of the Ukrainian economy and the available technical capabilities of the power engineering industry. This paper presents the results of variational computational studies of the thermal scheme of the 300 MW power unit of the K-300-23.5 turbine to be converted into a USC one. The problem was solved under the condition of maximizing the preservation of the thermal scheme, increasing the efficiency of the power unit and minimizing capital investments during the modernization of the turbine. It was chosen to preserve the regeneration system, as well as the medium-pressure (MP) and low-pressure (LP) cylinders. Considered and calculated were variants with the addition to the existing turbine of a USC cylinder and the creation of a new high-pressure cylinder (HPC) with insignificant changes in its overall characteristics. The results of computational studies showed that the most rational variant for modernizing the 300 MW turbine plant is the creation of a new HPC designed for operation at USC steam parameters as well as the addition to the IPC of a new cylinder with the purpose of increasing the reheat steam parameters while preserving the regeneration system.

Offshore wind resource in the context of global climate change over a tropical area

Understanding the future offshore wind energy is crucial for making an appropriate energy strategy. Yet how offshore wind energy will respond to the rapidly intensifying global warming remains inconclusive. Focusing on a tropical sea in Vietnam, this study assesses the climatic impact of global warming on the local offshore wind potential. Dynamically downscaled wind data obtained by an edge-cutting fine-resolution regional climate model with two greenhouse-gases Representative Concentration Pathway (RCP) scenarios 8.5 and 4.5 were biased-corrected with a quantile mapping method before using for assessment. Results revealed a changing trend of the annual-mean offshore wind speed and power potential in Vietnam under both scenarios. However, the change is seasonally asymmetric with decreases of about 2 – 10% in September-October-November and slight increases of about 2 – 4% in December-January-February. The turbine-based assessment showed that the cumulative annual energy obtained from the 12 MW and 8 MW turbines could reach the highest about 50.9 GWh and 30.7 GWh (2080–2099 average under scenario RCP8.5) but the difference in their capacity factor is much smaller, suggesting that turbine 8 MW should be considered in the sense of cost-effectiveness in some areas.

Numerical modelling and dynamic response analysis of a 10 MW semi-submersible floating offshore wind turbine subjected to ship collision loads

The number of installed offshore wind turbines is continuously growing worldwide in recent years. Offshore wind farms are generally located near the coast close to traffic lanes and are exposed to the risk of collisions from visiting and passing ships. Potential consequences of collisions may vary from local structural damage to the detachment of turbine nacelles and rotors, and even tower collapse and capsizing of the turbine platform, causing significant economic loss and fatalities.This paper investigates ship collision responses of a semi-submersible floating offshore wind turbine (FOWT), i.e. the OO-STAR floater with the DTU 10 MW blades, using the nonlinear finite element code USFOS. The OO-STAR floater is made of post-tensioned concrete designed by Dr. techn. Olav Olsen. The striking ships are selected to be a modern supply vessel of 7500 tons and a shuttle tanker of 150,000 tons, representing respectively service/coastal merchant vessels and large passing vessels. Modelling of the FOWT in USFOS is described in detail including the OO-STAR floater, the DTU 10 MW turbine blade, the turbine tower, and the mooring system. The modelled hydrodynamic loads include buoyancy loads and motion induced radiation loads using the Morrison equation. The effects of external waves and currents are assumed to be small and ignored in all directions. Eigenmode analysis of the turbine model is performed to verify the established model.Global collision response analyses of the FOWT were performed in both parked and operating conditions. The ship resistance is modelled as nonlinear springs in USFOS containing force displacement curves simulated in LS-DYNA. In operating conditions, wind loads are introduced including wind thrust loads and wind induced torque to rotate the turbine blades. The changes of upstream wind speeds and rotor/wake interactions during collisions are neglected. The results are discussed with respect to energy absorption of the ship and the FOWT, and structural responses of the FOWT including global motions, nacelle accelerations, tower clearance, tower vibrations, and responses of the mooring system.

Estimation of blade forces in wind turbines using blade root strain measurements with OpenFAST verification

This paper introduces an inference method for computing the forces and bending moments on operating wind turbine blades using strain measurements and supervisory control and data acquisition (SCADA) data. Operational data from four months of a Clipper Liberty C96 2.5 MW turbine instrumented with interferometric strain sensors at the blade roots as well as SCADA data such as wind speed, rotor hub speed, and blade pitch angle allow for accurate calculation of blade forces and moments. To perform such calculations, certain structural properties of the turbine blades must be inferred in the absence of detailed, proprietary information. This is done by inferring missing information from the National Renewable Energy Laboratory (NREL) 3 MW WindPACT reference wind turbine specifications. The derived forces and moments computed on the blades of the Clipper turbine are compared with the behavior of the NREL 3 MW reference turbine according to OpenFAST simulation outputs. Comparison of blade root reaction forces to OpenFAST outputs match closely, demonstrating that this inference method can be used to successfully estimate the internal forces and bending moments acting on the blades. These methods are useful on turbines for which all the structural information is not available.

Analytical and numerical study on centrifugal stiffening effect for large rotating wind turbine blade based on NREL 5 MW and WindPACT 1.5 MW models

To pursue high efficiency for wind turbine and harness more energy from wind, the wind power generation system has been designed larger and larger. With length scale increasing, the natural frequency of blade will be lower and changing dramatically with rotational speed, which will threaten the stability of the blade and turbine. However, in the previous research, the parametric, analytical, and quantitative study of centrifugal stiffening effect is rare to see. As a result, the current research has comprehensively studied the centrifugal stiffening effect on the structural characteristics of large wind turbine blade. Specifically, the equivalent rotating wedge beam model has been proposed for composite wind turbine blade. Based on the proposed wedge beam model and Rayleigh-Ritz method, the natural frequency variation curve has been derived and verified by ANSYS 3D simulation results. The parameters, including blade length, stiffness-mass ratio, and aspect ratio, affecting the natural frequency curve have been uncovered and analysed. It was found that the centrifugal stiffening effect has a great impact on the fundamental frequency of blade, e.g. 10% for NREL 5 MW, while it has less impact on other modal frequencies. The variation curve of fundamental natural frequency can be approximated by parabola. The product of the parabola curvature and fundamental frequency is found to be approximately constant for both NREL 5 MW and WindPACT 1.5 MW turbine blades. This research will provide guidelines for the resonance avoidance design of large wind turbine blade in the future.

Data-driven yaw misalignment correction for utility-scale wind turbines

In recent years, wind turbine yaw misalignment that tends to degrade the turbine power production and impact the blade fatigue loads raises more attention along with the rapid development of large-scale wind turbines. The state-of-the-art correction methods require additional instruments such as laser imaging detection and ranging to provide the ground truths and are not suitable for long-term operation and large-scale implementation due to the high costs. In the present study, we propose a framework that enables the effective and efficient detection and correction of static and dynamic yaw errors by using only turbine supervisory control and data acquisition data, suitable for a low-cost regular inspection for large-scale wind farms in onshore, coastal, and offshore sites. This framework includes a short-period data collection of the turbine operating under multiple static yaw errors, a data mining correction for the static yaw error, and ultra-short-term dynamic yaw error forecasts with machine learning algorithms. Three regression algorithms, i.e., linear, support vector machine, and random forest, and a hybrid model based on the average prediction of the three, have been tested for dynamic yaw error prediction and compared using the field measurement data from a 2.5 MW turbine. For the data collected in the present study, the hybrid method shows the best performance and can reduce the total yaw error by up to 85% (on average of 71%) compared to the cases without static and dynamic yaw error corrections. In addition, we have tested the transferability of the proposed method in the application of detecting other static and dynamic yaw errors.

Shafting Torsional Vibration Analysis of 1000 MW Unit under Electrical Short-Circuit Fault

Taking a 1000 MW turbine generator as the research object, the short-circuit fault in electrical disturbance is analyzed. Since it is very difficult to carry out fault analysis experiments and research on actual systems, simulation analysis is one of the more effective means of electrical fault diagnosis; the simulation’s results approach the actual behavior of the system and are ideal tools for power system analysis, and can provide an empirical basis for practical applications. The short-circuit fault model of the SIMULINK power system is built to analyze the two types of faults of generator terminals short-circuit and power grid short-circuit. The impact load spectrum, fault current and speed fluctuation between low-voltage rotors were extracted and analyzed. The conclusion is that the impact value of electromagnetic torque at the generator terminal is greater than that on the power grid side. The impact value of a two-phase short-circuit at the generator terminal is the largest, and that of a three-phase short-circuit on the power grid side is the smallest. The transient impulse current of a three-phase short-circuit at any fault point is greater than that of a two-phase short-circuit; the impulse current of the grid side short-circuit is much greater than that of the generator terminal short-circuit; the speed fluctuation and fluctuation difference caused by the three-phase short-circuit in the grid side are the largest. The alternating frequency of the transient electromagnetic force of the four kinds of faults avoids the natural frequency of the torsional vibration of the shaft system, and the torsional resonance of the shaft system in the time domain of the short-circuit fault will not appear. However, after the fault is removed, the residual small fluctuation torque in the system has a potential impact on the rotor system. This research shows an analysis of the structural integrity and safe operation of turbine generator units after a short-circuit fault, which can not only be applied to engineering practice, but also provide a theoretical basis for subsequent research.