Reduced-Order Model Of Brushless Doubly-Fed Generator With Rotary Transformer

To follow the trend of sustainable development,it is of great significance to develop the renewable energy for power generation,such as wind energy.Doubly-fed induction generators(DFIG)is the main equipment of the wind field.However,due to the existence of brushes and slip-ring structure,it limits the application of the doubly-fed induction generators.This paper proposes a brushless doubly-fed generator with rotary transformer as its research object,supported by National Natural Science Foundation of China.It has systematically studied the principle of operation,model construction,simulation analysis,physical reduction,and numerical reduction.First of all,this paper proposes a brushless doubly-fed generator with rotary transformer and analyzes its principle.Then,its full-order mathematical model in the d-q rotating coordinate system is established,whose dynamic response was simulated and analyzed under different operating conditions.Since the full-order model will increase the simulation time and complexity,this paper brings out two solutions to reduce the order via physical and mathematical way respectively.The former reduces the model to a low-order model of different degrees by ignoring the faster part of the machine dynamic change.The latter uses the Arnoldi reduction algorithm based on Krylov subspace to simulate the system's various responses and simplify the model.The simulation results show that the operation state of the generator model proposed is similar to that of the common doubly-fed generator.It accords with the expected value of the theory,which verifies the validity of the model proposed in this paper.It is found that both reduced-order methods have an ideal reduction effect and eventually reach a stable expected value,which lays a theoretical foundation for the promotion and application of this type of generators.