Research On Stability Of Distributed Power System

Distributed power system (DPS) has been widely applied in many areas such as aerospace, aviation, power system, new energy resource, etc., due to its advantages of modularization, integration, extensibility, maintainability and so on. However, with the development of power technology and increasing need, there is an increasing demand in the stability and reliability of DPS. The stability problem of DPS becomes a gradually outstanding problem. Aiming at the shortcoming of stability criterion, stability analysis, etc. of DPS, this thesis conducts a relatively deep research from sides of the model establishment, small-signal stability analysis, large-signal stability analysis, etc. In addition, this thesis also researches the impact of shading on the stability of spacecraft power system.The source model, load model and switching converter’s small-signal and large-signal models of the DPS are established, which are suitable for stability analysis. Especially, a new mode transition principle is proposed to solve the mode transition problem between CCM (Continuous Current Mode) and DCM (Discontinuous Current Mode) of the switching converter’s large-signal averaged model. The proposed mode transition principle can better reflect the large-signal dynamic behavior of the switching converters. Experiment validation is made to ensure the effectiveness of the model in the stability analysis, which laid the foundation for the stability study of the following parts.Among the small-signal stability study of the DPS, the impedance criterion is one of the most popular methods. For the conservative problem of the present impedance criterion, a necessary and sufficient impedance stability criterion for the two subsystems cascaded DPS is proposed. And this thesis also discusses the impedance criterion of complex connected DPS. The sector forbidden region, which is a new forbidden region and can be easily calculated in the Bode diagram, is proposed to solve the calculation problem of the round forbidden region in engineering application. Examples and simulations are provided to verify the necessary and sufficient impedance stability criterion and the proposed sector forbidden region for the load impedance specification.To overcome the disadvantages of the Lyapunov direct method and the direct simulation method in estimating the region of attraction of the DPS, a typical nonlinear system, the indirect numerical simulation method based on Monte Carlo analysis is proposed. And the upper envelope method is used to judge the convergence property of the state variables of the system. Taking the filter and converter cascaded DPS as an example, this thesis estimates the system’s region of attraction. The validity of this method has been proved by experimental approaches.Finally, this thesis analyzes the impact of shading on the stability of spacecraft power system. According to the features of spacecraft having complex structure and solar array having various kinds of installation methods,3D model of spacecraft is established to consider the relative movement of the component and an algorithm of precisely calculating the shadow graph of solar array using the modified shadow map method and the minimal rectangle method is proposed. The example of lunar rover’s shadow graph calculation is given to validate the correctness and rapidity of the proposed algorithm. Based on the shadow graph, the solar array’s output characteristic is calculated, and the impact of shading on stability of spacecraft power system is analyzed through estimating the region of attraction of the whole system with different shading conditions.