Marija Mirošević

Diesel-generator-units dynamic analysis during the start-up of induction motors drives

The paper analyses the dynamics of generator-units during start-up of the induction motor drives. A unique mathematical model of integral motor drives has been developed, consisting of: a diesel engine, a synchronous generator and two non-regulated motor drives fed directly from generator-unit terminals. The aim of this paper is to compare dynamics behaviours of the generator-units during starting the second induction motor at the moment when the instantaneous electromagnetic torque of the synchronous generator reached various values

Analysis of synchronous generator stability in case of separate and self-excitation system

The paper presents the mathematical model of the electric power system with several synchronous generators. It enables the analysis of stability in the circumstances of large disturbance in a power system. The analysis has been performed for the generator with separate excitation and the generator with self-excitation.

Effect of sudden change load on isolated electrical grid

The aim of this paper is to analyse effects of sudden change load as well as failures, such as short term interruption in power supply, on isolated electrical grid, e.g. ships electrical grid. The autonomous operation of the synchronous generator is characterized by a change in steady state which causes a change in voltage and frequency, what in turn affects the quality of electric power systems. The aim of this paper is to analyse dynamics during the transients.

Impact of interruption on power grid disturbances

The aim of this paper is to analyze behavior of isolated power system in case of short-term interruptions that is applied on one of the loads fed from the grid. Developed mathematical model of the system under consideration involves gen-set, prime mover and synchronous generator, and induction motors as active consumers. The aim of this paper is to analyse effect of short-term interruptions from the point of view of source and loads. Analysis includes connecting another load while the transition regime is not terminated.

Oscillations in hydropower bulb units

The paper presents the results of studying the specific problems that occurred during the exploitation of two 42 MVA bulb generators. The work focuses particularly on two groups of problems which were more pronounced on only one of the two hydropower units, and these are increased vibrations of the hydropower unit and electromechanical oscillations in the stationary and transition states, which significantly depend on the operating point of the drive. This paper shows a part of extensive generator measurements. A lot of probes were mounted on the generator measuring all electrical and mechanical physical quantities, as well as air gap width, induction in air-gap and others.

The dynamics of isolated electrical grid during short term interruptions

The aim of this paper is to analyze dynamics of isolated electrical grid during short term interruptions. The effect of short term interruptions of the power supply on the characteristic values of synchronous generator in autonomous operation is analyzed. Dynamical loads (two induction motors), are connecting to the grid. Short-term interruptions that occur in different moments allow analyze of this phenomenon on the generator and on the other uninterrupted motor.

The dynamics of diesel generator units with different voltage controller parameters

The aim of this paper is to analyze the dynamics of diesel generator units with different proportional-integral voltage controller parameters. Effect of changes of gain and time constant of voltage controller, during direct-on-line starting loaded induction motors connected to a synchronous generator in autonomous operation, is considered.

Torsional dynamics of generator-units during autonomous operation

The main objective of this paper is to analyse dynamic behavior of diesel-generator units due to electrical loads and due to torsional strains on the shaft cable. A flexible coupling between generator rotor and rotating mass of diesel engine allows masses to rotate at a different speed in transient. In order to investigate the dynamic behavior of synchronous generator as well as torsional strains in the shaft line a unique mathematical model of integral motor drives has been developed. The model involves a prime mover, a synchronous generator with its electrical and mechanical properties and optionally, generators control system. Mechanical coupling of a prima mover and a synchronous generator is considered a rotating system with two concentrated masses allowing thus the analysis of the torsional dynamics in the coupling.

Overvoltages and power oscillations in hydro generators

The paper describes two specific transient phenomena of different characteristic frequencies. First, a short overview of a calculation of overvoltages in the generator main electrical circuit of a hydro power station is presented. A case of a generator connected to the step-up transformer through encapsulated lines has been studied. The most critical cases have been considered: overvoltages at a single phase earth fault in the generator circuit and temporary overvoltages due to the single phase earth fault followed by the load rejection. The calculations have been carried out by EMTP-ATP and MicroTran program. Second, electric power oscillations in hydro power plants are not rare. The paper shows two cases in two different power plants. Each power plant has different generator positions (one vertical and one horizontal bulb type) and therefore different reasons for power oscillations. An overview of those cases is presented supported by measurements and calculated by Matlab.

Dual Heuristic Neural Programming Controller for Synchronous Generator

This chapter describes the development of voltage control system of a synchronous generator based on neural networks. Recurrent (dynamic) neural networks are used, as a type that has great capabilities in approximation of dynamic systems. Two algorithms are used for training – Dual Heuristic Programming (DHP) and Globalized Dual Heuristic Programming (GDHP). The algorithms have been developed for the optimal control of nonlinear systems using dynamic programming principles.