Research On Short Circuit Calculation And Static Voltage Stability Of Distribution Network With Distributed Generation

With the pressure of energy crisis and environmental pollution problems,distributed generation (DG) technologies using clean and renewable energy have beenfacing great opportunities and challenges, and also have been experiencingapplication widely in power supply system. Large scale penetration of DG will lead tosome influence on the operation of local distribution network. This paper mainlystudies the issues that how to calculate short circuit current for the distribution systemwith DGs and analyze the influence of different types DG on the system static voltagestability.For large scale penetration of DGs integrated to the local distribution grid, theradial structure of the traditional distribution will be changed, which affects the powerflow distribution and the short-circuit current level of the system. All kinds ofelectrical equipment need to be re-evaluated, and relay protection setting values needto be adjusted. All these jobs are based on the calculation of short-circuit current. As aconsequence, this paper proposes a short circuit current calculation method for thedistribution system with DG. Firstly, the method builds the short-circuit model of theDG according to its interface characteristic. Secondly, State variables can keepunchanged during faults, which can be got by power flow calculation. Based on thischaracteristic of state variables, the short circuit current supplied by DG can becalculated with the value of state variables. Eventually, the presented method has beenverified in the testing example, and the results indicate the feasibility and validity ofthe proposed method.A stable voltage is the necessary condition for normal operation of the powersystem. Various disturbances occurring at any time in the system, such as the abruptchange of the load, faults, and the out of service of generators, will lead to the systemvoltage deviate from its normal value, even lead to voltage collapse. A scenario withdifferent types of DG connected to testing example has been studied to analyze thesystem static voltage stability comparatively. The results have shown that the systemstability will be enhanced if some DG with active and reactive power output supportconnected to the regions with weak voltage stability, while wind power generationswill lower the system static voltage stability, unless using additional reactive powercompensation devices.