Gorislav Erceg

The influence of body position on cerebrospinal fluid pressure gradient and movement in cats with normal and impaired craniospinal communication

Intracranial hypertension is a severe therapeutic problem, as there is insufficient knowledge about the physiology of cerebrospinal fluid (CSF) pressure. In this paper a new CSF pressure regulation hypothesis is proposed. According to this hypothesis, the CSF pressure depends on the laws of fluid mechanics and on the anatomical characteristics inside the cranial and spinal space, and not, as is today generally believed, on CSF secretion, circulation and absorption. The volume and pressure changes in the newly developed CSF model, which by its anatomical dimensions and basic biophysical features imitates the craniospinal system in cats, are compared to those obtained on cats with and without the blockade of craniospinal communication in different body positions. During verticalization, a long-lasting occurrence of negative CSF pressure inside the cranium in animals with normal cranio-spinal communication was observed. CSF pressure gradients change depending on the body position, but those gradients do not enable unidirectional CSF circulation from the hypothetical site of secretion to the site of absorption in any of them. Thus, our results indicate the existence of new physiological/pathophysiological correlations between intracranial fluids, which opens up the possibility of new therapeutic approaches to intracranial hypertension.

Load angle estimation of a synchronous generator

The article is focused on a load angle estimation method in excitation regulation systems of synchronous generators. The estimation method is based on synchronous generator parameters given by the corresponding voltage-current vector diagram. The estimation results were compared with the measured ones. The estimation method gives satisfactory accuracy for load angles less than 120/spl deg/ el. Load angle regulation in excitation systems improves the stability of a synchronous generator in capacitive operating mode.

Excitation control of a synchronous generator using fuzzy logic stabilizing controller

This article is focused on the implementation of simple fuzzy logic excitation control of a synchronous generator. A simple fuzzy logic control scheme for voltage control and generator stabilization is tested on the real laboratory model that includes digital system for excitation control (based on four DSPs) and synchronous generator connected to an AC system through transformer and two parallel transmission lines. The behaviour of the excitation system with fuzzy logic stabilizing controller is compared with excitation system based on the PI voltage controller and conventional power system stabilizer

Simulation model of Neural Network based synchronous generator excitation control

Usage of neural network (NN) based excitation control on single machine infinite bus and its simulation studies are reported in this paper. The proposed feed forward neural network integrates a voltage regulator and a power system stabilizer. It is trained on-line from input and output signals of a synchronous generator. A modified error function used for training the neural network by the back propagation algorithm uses the reference and terminal voltage as controlling voltage and active power deviation to provide stabilization. The complete algorithm is simulated in Matlab Simulink. Synchronous generator (83 kVA, 50 Hz, 400V) is connected over transmission lines to AC power system. The proposed algorithm shows advantages of this method and satisfactory results.

Using digital signal processor for excitation system of brushless synchronous generator

In the paper digitally based excitation systems for the synchronous brushless generators are presented. A digital control system is realized with a digital signal processor ADSP-2001. System configuration, control functions with their structure functions are also presented. The control system has two feedback loops: the main one is based on a generators voltage and the inner one based on excitation current of the exciter. Beside basic function of a voltage controller the digital system has some other control functions, like: limits of minimal and maximal exciter current, compensation of the voltage (based on reactive and active current characteristics), voltage/frequency characteristic, and possibility of communicating with higher system levels.

The appliance of the estimated load angle in the fuzzy power system stabilizer

This paper investigates the application of the fuzzy logic power system stabilizer. Proposed stabilizer use estimated load angle of synchronous generator as the input. The load angle estimation is based on the real parameters of a synchronous generator, which are given by the corresponding voltage-current vector diagram. A fuzzy logic control scheme for synchronous generator stabilization is tested on the real laboratory model that includes digital system for excitation control (based on four DSPs) and synchronous generator connected to an AC system through transformer and two parallel transmission lines. The experiments were performed for step change of voltage reference. The behavior of the excitation system with fuzzy logic stabilizer is compared with excitation system based on the PI voltage controller and conventional power system stabilizer

The use of programmable automation controller in synchronous generator excitation system

Synchronous generator voltage control system with a programmable automation controller (PAC) is presented in the paper. Such digital control can be used on both separately excited and self-exciter for generators with slide rings and brushless. As a power converter for a generators excitation an IGBT chopper is used. Function of the synchronous generator voltage control system with a PAC was experimentally verified on a separately excited generator.

Concepts of synchronous generator's digital control

In this paper new concepts of synchronous generator control using up-to-date digital systems are shown. For excitation and speed (active power) controls of synchronous generator same hardware and software support are used. In this concept the difference between excitation control and speed control is the control algorithm. This new concept of generators control is used on the aggregate in hydro power station Vinodol (Croatia). For realization of this generators control a digital system DIRES 21 is used. The CPU contains 4 digital signal processors ADMC 3000 (analog devices). Functions of the generators control system are experimentally verified.

Starting of diesel electrical aggregate loaded with an induction motor

Switching larger induction motors on the buses of a diesel electrical aggregate causes large voltage and frequency drops. Also, it can cause severe disturbances to any locally connected loads on the aggregates buses. In this paper, a method of starting an induction motor, loaded on the aggregate, by simultaneously changing voltage and frequency is presented. Besides the mathematical model of the diesel electrical aggregate, a mathematical model of the induction motor is also given. Results obtained with simulation are compared with experimental results obtained from a laboratory model. With this method, the starting of larger induction motors can be realized without using special starters (soft start).