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In the shaft and end windings of large turbogenerators, unacceptably high mechanical stresses can occur as a result of subsynchronous resonances (SSRs) in the system network-generator-shaft. These stresses can cause severe damages. Subsynchronous resonances are characterized by the occurrence of currents and electromagnetic torques in the air gap of the generator with frequencies that are significantly below the synchronous frequency. When simulating the balancing processes in multi-machine networks, the generators are represented by Canay’s equivalent circuit diagrams. The parameters used here are determined from geometric dimensions of the generator, taking into account material properties, and verified by means of surge short-circuit tests in which the 50 and 100 Hz components are dominant. This paper aims to examine whether the parameters of the equivalent circuit diagram determined in this way reproduce correctly the dynamic behavior of a synchronous machine, even if the SSR occur.

The simulation program NETOMAC is used to simulate the SSRs for different parameters. The results of these simulations are then compared with those obtained by the finite difference (FD) method calculations.

The comparison of the waveforms calculated with NETOMAC and FELMEC for an SSR shows that the original equivalent circuit diagram parameters provide satisfactory results. An extension of Canay’s equivalent circuit diagram is not necessary. Optimization of the discussed parameters leads to a significant improvement in comparison to the calculation with the parameters from the generator data sheet.

The unresolved doubt has been proven, that the Parka generator model with the manufacturer’s parameters can also be used for subsynchronous studies of electromechanical resonances of systems. However, it was advisable to improve the simulation results by optimizing the generator parameters used in the calculations. By optimizing the parameters for the SSRs, the calculation of the occurring torques has been significantly improved.

Subsynchronous resonance (SSR) problem is often created in generator rotor systems with long shafts (non‐rigid shaft) and large inertias constituting a weakly damped mechanical system. When the electrical network resonance frequency (in which the transmission line is compensated by series capacitors) approaches shaft natural frequencies, the electrical system increases torsional torques amplitude on the shaft. The purpose of this paper is to propose a self‐tuning proportional, integral, derivative (PID) controller to damp the SSR oscillations in the power system with series compensated transmission lines.

To accommodate the PID controller in all power system loading conditions, the gradient descent (GD) method and a wavelet neural network (WNN) are used to update the PID gains on‐line. All parameters of the WNN are trained by the gradient descent method using adaptive learning rates (ALRs). The ALRs are derived from discrete Lyapunov stability theorem, which are applied to guarantee the convergence of the proposed control system. Also, the suggested controller is designed based on a non‐linear model.

The proposed self‐tuning PID controller is applied to a power system non‐linear model. Simulation results are used to demonstrate the effectiveness and performance of the proposed controller. It has been shown that self‐tuning PID is able to damp the SSR under any circumstances, because the WNN ensures the robustness of the controller. Simplicity and practicality of the proposed controller with its excellent performance make it ideal to be implemented in real excitation systems.

The proposed self‐tuning PID approach is interesting for the design of an intelligent control scheme based on non‐linear model to damp the torsional oscillations. In this suggested controller, the system conditions and requirements adjust on‐line the PID gains. On other words, to damp the SSR, PID gains are intelligently computed by the controlled system. The main contributions of this paper are: the overall control system is globally stable and hence, the SSR is controlled; the control error can be reduced to zero by appropriate chosen parameters and learning rates; and the self‐tuning PID can achieve favorable controlling performance.

Series capacitive compensation in electrical power systems is generally recognized as a very economical and powerful means for increasing the transmission capability of long‐distance transmission lines, resulting in relevant technical advantages in power system behavior: increased steady‐state and transient stability margins, reduced voltage drop in receiving systems during occurrence of severe contingencies and reduction of transmission losses. In this paper, a general method for choosing the series compensation degree is proposed, focusing the attention on the transient stability aspect. The approach, based upon a probabilistic framework, allows to properly select – at the design stage – the optimal degree of series compensation in order to contain the instability risk at an acceptable value. The transient stability problem is formulated by using the transient energy function method. In order to show the feasibility of the proposed approach, a numerical application to the Cigre test network is performed in the final part of the paper.

Due to the installation of the new, more powerful gearbox and the dismantling of the exciter machine, the vibration characteristics of the shaft train will be changed. Therefore, it is necessary to reassess the shaft train. It is to be investigated if the shaft train of the compressor meets the general requirements for bending and torsional vibrations and can be safely operated within the electrical network. The purpose of this paper is to show the necessary alignment of modification, calculation and measurement in such a project..

After some modification work on the shaft train of an air compressor, it was necessary to do some engineering calculations regarding the bending natural and torsional natural frequencies and their mode shapes. The correctness of the calculated values was proven by vibration measurements performed at the shaft train in operation.

It can be concluded that the change and replacement of rotating equipment in a shaft train never should be done without any engineering calculations in advance and measurements after the component modification. Most important is that the calculation results have to be compared with the measurement results for verifying the calculation assumptions. In the case described above, one can see that theory and practice match well. In addition to this, the very low damping of torsional vibrations is proved again, which can be a significant problem in some situations.

Also, today one can find torsional vibration measurements of rotating machines, including frequency, magnitude and damping factor, very seldom. Especially for smaller machines, there are no real comparisons between calculation and measurement are usual. This paper shows that an alignment between theoretical and practical approaches is necessary to avoid operational problems for rotating machines.

The purpose of this paper is to investigate the dynamic stability of liquid hydrogen turbopump rotor system in rocket engine under the effects of seal and internal rotor damping.

The dynamic modeling of a liquid hydrogen turbopump rotor system in rocket engine is presented in this paper with the aid of the finite element technique. The mathematical model takes into account the seal hydrodynamic forces described by Muszynska model and the internal rotor damping, viscous damping, and hysteretic damping. The shooting method and Floquet theory are employed to investigate the effects of seal and internal rotor damping on the nonlinear dynamic stability of two turbopump designs, the original and the modified design with a flexible bearing support.

The numerical results, which are in good agreement with test data, show that the destabilizing effect of internal rotor damping play a key role in the original design. In the modified design, the stability margins are enhanced and the vibration response levels are minimized. The onset speed of instability increases in original design and decreases in modified design as the effects of seal nonlinearities are considered. The predicted results indicate that the seals have a great destabilizing effect in the modified design and the turbine end bearing is the most dangerous hardware in both designs. The system stability analysis shows that the effect of seal length on the system stability is significant comparing with that of seal radius.

The results can be used in the design and operation of a liquid hydrogen turbopump rotor system to improve its stability performance and eliminate its subsynchronous problem.

Since seal and internal damping are two key destabilizing factors in liquid hydrogen turbopumps and the seal nonlinearities are inevitable, the use of nonlinear theory to study their effects on nonlinear stability and dynamic performance can lead to accurate prediction and explain the nature of the subsynchronous motion.

The purpose of this paper is to propose a new control strategy based on adaptive inverse control aiming at high performance control of permanent magnet synchronous motor (PMSM).

This scheme adopts the vector control with double closed-loop structure and introduces a multi-dimensional Taylor network (MTN) inverse control method into velocity-loop. First, the invertibility of PMSM’s mathematical model is proved. Second, a novel dynamic network (MTN) is presented, which has simple structure and faster computing speed. Besides, to realize the high-precision speed control, three MTNs are applied to achieve system modeling, inverse modeling and noise disturbance elimination which correspond to the function of the adaptive identifier, adaptive feed-forward controller and nonlinear adaptive filter, respectively.

This scheme is designed with the full consideration of the PMSM’s particularity. For the PMSM’s unknown dynamics and time-varying characteristics, the variable forgetting factor recursive least squares algorithm is adopted to improve identification ability, and the weight-elimination algorithm is used to remove redundant regression items in the MTN identifier and inverse controller. In addition, to reduce the influence arose from measurement noise and other stochastic factors, adaptive MTN filter is introduced to eliminate noise disturbance. The computational results show that the proposed scheme possesses excellent control performance and better robustness against the load disturbance.

The paper presents a new inverse control scheme with MTN which is practical and flexible, and the MTN-based control system is very promising for real-time applications.

As a core rotating component of power machinery and working machinery, the rotor system is widely used in the fields of machinery, electric power and aviation. When the system operates at high speed, the system stability is of great importance. To enhance the system stability, squeeze film damper (SFD) is being installed in the rotor system to alleviate vibration. The purpose of this paper is to first classify the rotor system into two types, the dual rotor system and the single rotor system, and to comprehensively and specifically mention the method of generating the dynamic model. Next, based on the establishment of a dynamic model with and without SFD in the rotor system, the optimization design of the rotor system with SFD was carried out using a genetic algorithm. Through sensitivity analysis, SFD clearance, shaft stiffness and oil viscosity were determined as design variables of the rotor system, and the objective function was the minimization of the maximum amplitude of the rotor system with SFD within the operation speed range.

In this paper, first, the rotor system was classified into two types, namely, the dual rotor system and the single rotor system, and the method of creating a dynamic model was comprehensively and specifically mentioned. Here, the dynamic model of the rotor system was derived in detail for the single rotor system and the dual rotor system with and without SFD. Next, based on the establishment of a dynamic model with and without SFD in the rotor system, the optimization design of the rotor system with SFD was carried out using a genetic algorithm. The sensitivity analysis of the unbalanced response was carried out to determine the design variables of the optimization design. Through sensitivity analysis, SFD clearance, shaft stiffness and oil viscosity were determined as design variables of the rotor system, and the objective function was the minimization of the maximum amplitude of the rotor system with SFD within the operation speed range.

SFD clearance, shaft stiffness and oil viscosity were determined as design variables of the rotor system through sensitivity analysis of the unbalanced response. These three variables are basic factors affecting the amplitude of the rotor system with SFD.

In the existing studies, only a dynamic model of a single rotor system with SFD was created, and the characteristic values of pure SFD were selected as optimization variables and optimization design was carried out. But in this study, the rotor system was classified into two types, namely, the dual rotor system and the single rotor system, and the method of creating a dynamic model was comprehensively and specifically mentioned. In addition, optimization design variables were selected and optimized design was performed through sensitivity analysis on the unbalanced response of factors affecting the vibration characteristics of the rotor system.