A Dynamic Equivalent Modeling For Regional Small Hydropower Generator Group

Water is pollution-free energy resource and the development potential of China’s small hydropower resource ranks first in the world. If we can make good use of the superiority ofsmall hydropower resource, it will play an important role in the sustainable developmentoneconomy and society.With a large number of small hydropower stations connecting to the grid, it’s necessary to analyze their impact on the main network. Considering the number of small hydropower units is large and the network structure iscomplex, if we take thedetailed parameters of every small hydropower units into account in the grid simulation model, it may appear "curse of dimensionality" problem, causing extremely large reduction in computational efficiency. And a large number of small hydropower units with unknown or inaccurate parameters, whose output will probably be influenced by seasonality, will make it difficult tobuild a dynamic equivalent modelwithdetailed parameters. Therefore, the dynamic equivalent model for regional small hydropower generator group is essential to build.This paperdiscusses how tobuild a dynamic equivalent model of small hydropower generating units, which is based on the equivalent generator coherent ideology and system identification to establish the equivalent model of small hydropower generator group, and is alsobased onthe parameters identificationby using the dynamic contact line power flow information to get parameters of the equivalent model.The main contents of this paper are as follows:(1) By comparing the existing dynamic equivalent methods and the equivalent models, a dynamic equivalent method has been presented, which is suitable for the regional small hydropower generator group.(2)Considering the characteristics of small hydropower generations, this paper proposes a method to classify the coherent generator group,which isbased on electrical generator group distances, and thenbuilds the equivalent model of regional small hydropower generator group- Virtual Synchronous Generator(VSG) model and establishes the model practical equations as well.(3) The parameters’ identifiability of the equivalent modelhas been analyzed, which is based onits mathematical equations, and a methodto identify the parameters has beenproposed based on the real-time dynamic powerflowdata. This paper introduces how toconvert the PMU(PhasorMeasurement Unit) data to the dynamic data which is required for parameters identification.(4) AnimprovedPSO(Particle Swarm Optimization)algorithm ispresentedtoidentifytheparametersoftheequivalentmodel with considering more information about the position of every particle.The improvedPSO is used for identifying the parameters of the VSG model.The algorithm for identificationhas been realizedthroughprogramming,and the validity of the algorithm has been proved in a single machine infinite bus system.For validation purposes, the proposed method is applied to a test IEEE system of 10 generators and 39 buses and the small hydropower generating units in the actual power system.Results show that the reduced systemretains the dynamic performance of the original system with good accuracy, which lays a foundation for dynamic equivalent modeling.