Diagnosis of the Static Excitation Systems of Synchronous Generators with the Use of Hardware-in-the-Loop Technologies

In this paper, testing and diagnosis methods for the static excitation systems of power plant synchronous generators using Hardware-In-the-Loop technology are described. These methods allow a physical excitation system to be connected to a real-time model of a power plant unit. A feature of a static excitation system is the presence of generator self-excitation—that is, when the input voltages of the excitation system are defined by a synchronous generator. These voltages are determining by the digital model, which creates additional difficulties with combining a digital model with a real excitation system. Various ways to solve this problem are described in this article; in particular, we focus on the option in which the gate-impulses of a thyristor converter are applied to the digital model by a real static excitation system. The real-time models are based on the method of average voltages in the integration step. This method is effective for providing numerical stability for the models of power schemes and their functioning in real time mode over a long period. A synchronization method for the calculation time of the model with real time is described. The adequacy of the described method is proved by the results of the static excitation system of synchronous generators testing in operating and fault modes.

Low Frequency AC Transmission for Offshore Wind Power

This paper presents a low frequency ac (LFAC) transmission system for offshore wind power. The LFAC system is interfaced with the main power grid with a cycloconverter. The wind power plant collection system is dc based, and connects to the LFAC transmission line with a 12-pulse thyristor converter. A method to design the system’s components and controls is set forth. Simulation results are provided to illustrate the system’s performance.

EVALUATION OF QUALITY INDICATORS OF MODERN CONTROL SYSTEMS OF DMZ WAGON TRANSMITTER DRIVE BY MATHEMATICAL MODELING

The results of the analysis of quality indicators of the proposed control systems for the electric drive of the DMZ ore yard with rheostatic tilt speed control, using alternative the system "thyristor converter - DC motor" and "frequency converter - induction motor", by studying the transients of these electric drive systems using the software product Matlab. It is established that the parameters of the control system "frequency converter - induction motor", are not inferior to the parameters of the control system "thyristor converter - DC motor", and even slightly exceed it, in particular, in the range of technological speeds of the wagon tipper drive, and energy losses during transient start-up processes are 2.3% less than the "thyristor converter - DC motor". It is expedient to use the offered decisions in case of modernization of the operating electric drive of the wagon tipper.

Estimation of Damage Rotor Shaft of Turbogenerators with a Diode Brushless Excitation System

The damage to the rotor shafts of high-power turbo generators is estimated as a result of the resonant in-teraction between the generator and the exciter caused by the operation of the automatic excitation regulator (AER) by mathematical modeling. The analysis covers turbo generators with a capacity of 300 to 1000 MW with a diode brushless excitation system (DBES). The simulated circuit includes a turbo generator with a block transformer, a power transmission line, an exciter in the form of a reversed synchronous generator with a rotat-ing rectifier diode converter unit, a static thyristor converter, and a sub-exciter in the form of a synchronous machine with permanent magnets. When modeling the electrical part, an approach is used from the positions of its own coordinates, which ensures maximum methodological consistency of the models of the listed devices and allows directly reproducing resonant phenomena at torsional vibration frequencies with the determination of instantaneous values of currents, voltages and electromagnetic moments of the turbo generator and exciter. The mechanical system is presented taking into account the exciter and sub-exciter as a seven-mass system. AER is introduced into the mathematical model by means of transfer functions with corresponding coefficients and time constants. The control system of the thyristor converter is represented in the model by a generator of line-arly increasing signals, a body for comparing these signals with the signal from the AER and a control pulse generator. To assess the damage rate, the deformation criterion for soft and hard loads in the zone of low-cycle fatigue and the force criterion in the zone of multi-cycle fatigue were used. A comparative quantitative assess-ment of the damage in the neck of the G-E shaft line in the resonant interaction between the exciter and the generator with different automatic excitation control systems is given. The influence of attenuation of electro-magnetic transients and damping of torsional vibrations on the damage values is analyzed. The results ob-tained can be used to analyze the functioning and determine the settings of the AER.

High power current pulse generator based on reversible thyristor converter

In metal forming using high power current pulses, it becomes necessary to control both reproduction frequency and pulse amplitude. Description of a generator of high power current pulses with controlled thyristor converter is provided as a power source of charging device (charger) for regulating voltage (pulse amplitude) of capacitor charge. Faults of the generators associated with inrush current in capacitor charge modes are revealed, which reduces quality of supply network. To reduce time of transient processes while lowering voltage across capacitors, application of reverse thyristor converter is applied as a power source. Structural diagram of generator is considered, which includes reversible thyristor converter with separate control, power unit, capacitor recharge device, charger parameters automatic control system and capacitor charge process control system. Calculation of parameters of automatic control system regulators is presented. To obtain optimal transients, standard methodology for setting regulators to a modular optimum was used. In order to reduce overshoot at time of disturbances appearance, which can reach 100 % and higher, socalled logical device was introduced into the automatic control system. It blocks control pulses on thyristors of converter and simultaneously reduces signal at the output of current regulator to zero. Simulation model of high power current pulse generator in MatLab – Simulink environment was synthesized. Analysis of the model was carried out, and graphs are given that explain principle of device operation and transition processes under various operating modes. Generator application will allow user to adjust amplitude of current pulses with high speed and to obtain sufficiently high-quality transient processes of capacitors charge (discharge), which will have beneficial effect on supply network. Application of better converters will significantly increase frequency of reproduction of current pulses.

Research and development of resonant electromagnetic vibration screen for intensive vibration technologies

In the article the development and use of controlled electromagnetic vibration drives used in the field of intensive vibration technologies are considered. Method is proposed for adjustment of amplitude and frequency of vibration of working element of vibrating screen, which improves efficiency of cutting, its dynamic and energy indices. By solving the differential equations of the system, its main characteristics, which can be used in the calculation and design of electromagnets, are determined. For experimental research, a vibrator was developed with a drive from a two-stroke electromagnetic exciter. Based on the results of the studies, it was established that the adjustment of the near-resonance mode when the load changes can always be provided by changing the frequency of the thyristor converter voltage pulses. Optimal combinations of amplitudes and oscillation frequencies of the developed vibration sieve are determined.