Mohapatra, Gopa Ranjan (1997) Voltage and stability analysis of distribution networks with non-conventional energy sources. Research Master thesis, Victoria University of Technology.

Abstract

The impact of renewable energy installations connected to the utility grid is an important issue concerning the technical and economic viability of harnessing these emerging energy sources. Distribution networks must be carefully controlled in order to maintain an acceptable power supply quality. The major sources of non-conventional energy are small scale generation and storage from mini hydro, photovoltaic, wind power, fuel cells, battery, flywheel, pump storage and biomass. The aim of this thesis is to analyse the variation in voltage of the distribution network when renewable energy sources are interconnected to the distribution network, in terms of it's stability. In particular this study analyses the impact of interconnection of small synchronous generators to the utility power grid. Dynamic stability analysis is mainly concerned with analysing the response of electrical power system to small perturbation about a given operating point. These studies are particularly important due to the growing interest in interconnecting small renewable energy sources to large and complex power systems. Simulation studies were carried out in order to find out the transient stability and voltage stability of the non-conventional energy sources under different operating conditions. A 5-second simulation was conducted using explicit numerical integration (Euler method) and an integration time step of 0.002 second. Power System Toolbox was used for analysis.The multimachine power system models used in this thesis are generated in MATLAB code. The load flow is performed on the multimachine power system correponding to the loading condition to be investigated. The machines are represented by the two-axis models, the exciters by IEEE Type-1 models and the loads are modelled as constant impedances. To save programming time, it has become common to limit the machine and exciter representations to some specified models. The network admittance matrix is reduced by retaining only the internal buses of the generators. The reduced network, machine and exciter data are then combined to form a linearised state-space model representing the entire system. The simulation studies are applied to a four machine ten bus system. It is clear from the analysis that much care should be taken based on the stability point of view while interconnecting the small renewable energy sources to the utility. The renewable energy sources should be interconnected at a point which provides higher stability margin.The renewable energy sources is a viable option if it is connected to the distribution network with necessary methods of improving transient stability and voltage stability.

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