Band 4, Heft 1

This paper deals with a model to simulate the operating of an autonomous induction generator. The model used is a diphase one obtained by the application of the Park transform. This model permits, when adopting some simplifying hypothesis, to take account of the saturation effect. This is achieved using a variable inductance function of the magnetising current. The non linearity is then based on the approximation of the magnetising inductance with regards to the current. In our case, we use a polynomial function, of 12th degree to perform it. This approach is simple and very accurate. The developed model has been used to study the operating of an induction machine when a capacitive bank is connected to the stator windings. The simulation calculation was achieved using MATLAB®-SIMULINK® package. This paper presents transient analysis of the self-excited induction generator. In order to simulate the voltage build-up process and the dynamic behaviour of the machine, we first establish the machine's model based on a d-q axis considering the machine’s saturation effect. Secondly, effect of excitation capacitors or load imbalances on voltage build-up process is investigated. Simulations results for a 5.5 kW induction generator are presented and discussed. Several experimentations are presented to validate simulations and verify the effectiveness of the developed model.

Specially connected transformers can reduce the voltage unbalance in a High Speed Railway (HSR) power supply system. Differently connected transformers reduce unbalance differently. Traditionally, a two-dimensional figure is used to represent the degree of unbalance associated with specially connected transformers. However, such a figure cannot completely express the conditions under which the voltage unbalance factor (VUF) is maximized. This work proposes a new approach to creating figures that represent the VUF of specially connected transformers under different dispatch schedules. Besides helping engineers to estimate voltage unbalance associated with various connected transformers, the analytical results can also provide a valuable reference for train dispatchers of HSR to plan dispatching.

Reactive Power Dispatch (RPD) is one of the important tasks in the operation and control of power system. The objective is to apply Particle Swarm Optimization (PSO) algorithm for arriving optimal settings of RPD problem control variables. Incorporation of PSO as a derivative free optimization technique in solving RPD problem significantly relieves the assumptions imposed on the optimized objective functions. The proposed algorithm has been applied to find the optimal reactive power control variables in IEEE 30-bus system and in a practical Indian power system with different objectives that reflect loss minimization, voltage profile improvement and voltage stability enhancement. The results of this approach have been compared with the results of Genetic Algorithm (GA). The results are promising and show the effectiveness and robustness of the proposed approach.

In this paper, an adaptive fuzzy PI-sliding mode control (AFPISMC) is proposed for induction motor (IM) speed control. First, an adaptive sliding-mode controller (APISMC) with a proportional plus integral equivalent control action is investigated, in which a simple adaptive algorithm is utilized for generalised soft-switching parameters. The proposed control design uses the fuzzy logic techniques to dynamically control parameter settings of the SMC equivalent control action. The theoretical analyses for the proposed fuzzy PI-sliding-mode controller are described in detail. Simulated results show that the proposed controller provides high-performance dynamic characteristics and is robust with regard to plant parameter variations and external load disturbance.

The goal of this paper is to evaluate performances of a new hysteresis current control strategy for autonomous three phase parallel active filter in harmonic currents elimination (by simulation an experiment) as well as the reactive power compensation (by simulation). This strategy, called the Optimized Hysteresis Control Strategy, is based on currents errors and their derivatives calculation each time the zero voltage vector is set at the AC side of the inverter of the active filter. The harmonic currents are identified using the method of the instantaneous real and imaginary powers. A voltage regulation loop is used to regulate the condenser DC voltage which ensure a constant DC voltage to the inverter. A digital software C++ simulation program was developed and implemented via the data acquisition board (AT-MIO-16X DAQ from National Instruments). Simulation and experimental results are presented.

The aim of this paper is to present a novel method for the optimal placement of capacitor and reactor banks, with the objective of maximizing network capacity to absorb new generation. The method is an extension of the Optimal Power Flow used as a tool for network capacity analysis. It can be used to a) plot graphs of the bank investment cost with respect to the increase in network capacity and b) find the optimum investment for the network operator in order to maximize his revenue. A 12-bus low voltage network was used as a test case. The results demonstrate the efficiency of the method to allocate new banks. At a small investment cost, network capacity could nearly double.

Transient stability is recognized as a critical problem for modern electrical power systems, since the deregulation could involve more and more restricted margins. Continuous improvements in power electronics technology gives the possibility to improve significantly the dynamic behaviour. Recently, a great attention in the relevant literature has been paid to Superconducting Magnetic Energy Storage (SMES) devices, showing their intrinsic ability to improve power transmission capability. In the paper, a control strategy for these devices is derived starting from a Control Lyapunov function, thus determining reference values for SMES active and reactive powers injections, able to counteract the effects of large disturbances. Hence, a new topology of the power conditioning system for interfacing SMES device with a power system is proposed. Finally, a control law based upon quasi-sliding technique is employed for tracking the required active and reactive powers. In the last part of the paper an application is presented, with reference to a test system, allowing to outline the flexibility and the goodness of the proposed control strategy.