Research On Dynamic Equivalent And Generalization Capability Of Small And Medium Hydropower Generator Group

Hydropower generators are considered to be the most advantage and widely applicable environmentally-friendly energy because they are flexible, economic and convenient. The dynamic performance of the power system would be affected by the small and medium hydropower generator group so that the requirement of this simulation model is higher and higher correspondingly in the power system simulation. It is difficult to establish the detailed model because the parameters of each generating unit can be obtained hardly if there is small and medium hydropower generator group in the power system. The point location is not easy to construct in simulation software, the power flow calculation may not be converged and the dimension is too large for dynamic analysis even if the typical parameters are used. At present, the common practice in the power system of China is to represent the small and medium hydropower generator group as a negative load simply, but the simulation results are not accurate. Dynamic equivalence is an accurate way to represent the characteristics of the equivalent system while there is a problem about generalization ability of equivalent model. Therefore, the dissertation studies dynamic equivalent and generalization ability of small and medium hydropower generator group.Firstly, dynamic equivalent method of small and medium hydropower generator group is proposed based on estimation-based equivalent method. The equivalent model is composed of a 3rd order generator model and a constant power load model. Based on the tie line phasor measurements when disturbance occurs, that are voltage, frequency, active power and reactive power, parameters of the equivalent model are obtained by combining nonlinear 4th order Runge-Kutta method and dynamic multi-swarm particle swarm optimizer (DMS-PSO) algorithm.Secondly, the sensitivity of equivalent model parameters is analyzed, the parameter identification of the method is verified, and the influence to identification results of disturbance type is compared. The proposed method is used to construct the hydropower generator group with simulation data. Compared with the negative load model, the proposed method is more accurate and more practical. Based on the actual data of PMU, the equivalent model of small and medium hydropower generator group is constructed. It is verified that there are some practical engineering value of the proposed method.Finally, a method is proposed to improve generalization capability of equivalent model based on multi-curve fitting method. Taking the measurements of disturbances occur in different time as the inputs, the equivalent model parameters which considering different dynamic characteristics are obtained based on 4th order Runge-Kutta method and DMS-PSO. The hydropower generator group is equivalent modeling based on the proposed method. And the comparison with single disturbance parameters identification method and mean value method are analyzed. Results show that the equivalent model based on proposed method in this paper is provided with stronger generalization capability, which can satisfy the situations of different disturbances and change in equivalent area slightly. It can be considered as another kind of typical operation modes to utilize the proposed method when equivalent area massively changed.