Research On Impacts Of Voltage Stability Of Distribution Network Due To Distributed Generation Embedded

Under the pressure from both energy supply and environmental problems, distributed generation (DG) which use clean and renewable energy have been widely used in the world.With the development of power electronics and control technology, it is possible to integrate DG into local distribution network. However, the structure of the existing power distribution network is also changed by DG, and the size and direction of power flow may be changed, which makes a series of inevitable effect on system stability. Therefore, it is quite necessary to study the effect of DG systems on power distribution network, especially on voltage stability.This article introduces the international and domestic status applications of DG firstly. And it analyzes the principle and characteristics of DG which the types are commonly used. Then the research results of DG on distribution systems which discussed by the domestic and foreign scholars are presented.Secondly, the principle and control strategy are analyzed in detail based on doubly Fed induction wind turbine (DFIG). And then the mathematical model of Wind power generation system are built. The continuous operation process oriented simulation language DSL are used to control DFIG model which can be transient stability analysis in the simulation environment of DIgSILENT. There are pitch angle module, shaft module, wind turbine control module, maximum power tracking control module, protection control module and the PWM convertercontrol module with double closed loop control strategy in this model. The model can work well under the environment of variable wind speed.Furthermore, the thesis analyzes the principle and structure of photovoltaic power generation system (PV), and then builts the mathematical model of PV. The engineering analytical model of PV is established based on the DIgSILENT software and use DSL language to build a dc power supply module which control by illumination,temperature conditions. The paper uses the voltage outer loop control and current inner loop control strategy to built the inverter control module. Moreover, added MPPT control strategy to the outer loop control in inverter control module. In the end, the function of MPPT is realized on PV.Finally, the simulation and the theory of voltage loss are used to analyze the voltage distribution of distribution network with DG. After analyzing the quiescent voltage stability, figures out the indexes to the quiescent voltage stability based on power flow solvability. In DIgSILENT simulation environment, the thesis studies the influence of the DFIG and PV when they connect to IEEE 33-bus system. The indexes on the quiescent voltage stability of the power distribution system are studied, which include following aspects:the output power, location, power factors and types of DG systems.Summarizing the law from the above analysis can provide guidance for the optimalsitting and sizing of DG.