| In recent years,as the inter-regional interconnection pattern of the power system has been increasingly improved,the problem of low-frequency oscillation remains a key issue that cannot be ignored.Especially the phenomenon of inter-regional oscillation severely limits the power transmission capacity of the contact line,restricts the rapid development of the power economy and affects the safe and stable operation of the power system.At the same time with the vigorous development of renewable energy,the proportion of renewable energy in the energy structure led by wind power and photovoltaic gradually increases,leading to the decline of the inertia of the power system and the prominent problem of transient stability.As a result,the wide-area damping control method with renewable energy devices as the controlled object has come into being.However,the deterioration of the control effect due to the communication delay and the dependence of the control method on the system model are the two major obstacles to the practical application of the wide-area damping control method,so this thesis is funded by the National Natural Foundation of China under the project "Analysis of low-frequency ultralow-frequency oscillation characteristics and unified control strategy of enriched hydropower system with fusion of physics-data driven"(52277083),this thesis focuses on the system model identification method and stability control method for inter-area oscillation of renewable energy integrated power system:(1)Firstly,around the low-frequency oscillation problem,a simplified model of the multi-machine system incorporated with renewable energy is established,and the mechanism of the wide area damping controller to improve the transient stability performance of the system and the control effect of communication delay deterioration is revealed based on the small disturbance power angle stability analysis method as the theory.(2)A novel noise-like signal-based online system model identification method is proposed to identify the open-loop state matrix and control input matrix containing multimodal information in real time for a wide-area control closed-loop system with communication time delay.Based on this,the model identification theory of the wide area control closed-loop system is proposed for different types of communication delays by combining the nodal power injection method;finally,the corresponding recursive estimation algorithm is designed to realize the model identification of the system and the low-frequency oscillation mode on the basis of improving the computational efficiency.Finally,the corresponding recursive estimation algorithm is designed to achieve the accurate identification of the system model and low-frequency oscillation modes with improved computational efficiency.(3)A multi-dimensional robust power oscillation suppression strategy based on damping apportionment is proposed,which can improve the inter-area oscillation problem and enhance the robustness of the system against various dimensions such as communication delay,discrimination error,external disturbance and communication line blockage.Firstly,a wide-area damping controller with the renewable energy device as the controlled object is designed from both physical and mathematical structure perspectives to realize the quantification of damping performance corresponding to sub-control modules and the decoupling control of specific modes;secondly,a safety constraint considering multi-dimensional robustness is constructed based on Razmising-type theory and robustness theory;a complete control strategy is designed to realize the damping apportionment of sub-control modules,and thus The complete control strategy is designed to realize the damping sharing of sub-control modules and thus enhance the ability of the system to deal with control channel blocking. |
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