Studies Of Distribilted Generation On Voltage Stability In Distribution Systems

With the constant decrease of fossil energy and its impact on the environment in recent years, it is necessary to develop clean, renewable energies. As a result, distributed generation (DG) technology is one of the development tendencies of the modern power network. However, DG has also changed the structure of the existing power distribution network, thus producing a series of inevitable influences on system stability. Hence, it is quite necessary to study the effect of DG systems on power distribution network, especially on voltage stability.Firstly, the thesis introduces several common DGs as well as the background and status quo of the research on the effect of DG systems on the voltage of the power distribution network. After that, the thesis analyzes the quiescent voltage stability of the power distribution network with DGs. Based on the working principles and operating mode of DGs, the thesis divides the DG system into four node types:PQ, P-Q (V), PI, and PV. On the basis, the thesis works out the load flow calculation model after the DGs are connected to the power distribution network and the way of load flow calculation.Secondly, the thesis, after analyzing the quiescent voltage stability, figures out the indexes to the quiescent voltage stability based on power flow solvability. In the MATLAB environment, two models for the wind turbine generator system and the photovoltaic power generator system have been fulfilled respectively. The forward-backward sweep method is used in power flow calculation through IEEE33-bus system based on the square incidence matrix. Thus, the thesis calculates the indexes and carries out the stimulation verification of its validity.Finally, based on the calculation of indexes, the thesis studies the influence of different DGs on the quiescent voltage stability of the power distribution system from the following aspects:the capacity, location, power factors, and types of DG systems. After summarizing the law from the above analysis, the thesis finds out the sensitive voltage nodes in the system.