Riassunto analitico
This work addresses the analytical feasibility of an optimal reference current calculation (ORCC) and presents a unified and comprehensive theory for the computation of optimal reference currents in various operating strategies. The proposed method enables deterministic and memory-saving computation, while incorporating the influential factor of rotor temperature. By introducing the rotor temperature as a state variable, the study reduces the reliance on extensive testing for obtaining flux tables, utilizing interpolation and extrapolation for different temperatures.
The study extends existing knowledge by introducing the MTPL operating strategy and deriving the theory for optimal torque pre-control in anisotropic and nonlinear synchronous machines with constant excitation. The derived theory allows for analytical computation of optimal reference currents, considering stator resistance, magnetic cross-coupling, and iron losses. It accommodates angular velocity and temperature dependencies, ensuring guaranteed solvability of optimization problems and facilitating fast analytical computation.
The unified theory is based on the consistent application of Lagrange multipliers and the implicit formulation of physical limitations and torque equations in the (d,q)-plane as conic sections. The study highlights the limitations of the MTPF method and emphasizes the higher efficiency of the MTPV method, particularly in the presence of non-negligible stator resistances or magnetic cross-coupling. Neglecting stator resistance, magnetic cross-coupling, and iron losses can have detrimental effects on drive efficiency and the selection of the optimal operating strategy.
Furthermore, the study emphasizes the importance of considering the dependency of machine parameters on rotor temperature, as it affects the convergence of the algorithm and the optimal damping factor. By optimizing the damping factor for specific temperatures, the study replaces the need for extensive testing with the determination of the optimal damping factor for different temperatures.
Overall, this study contributes to the advancement of analytical techniques for optimal reference current computation and provides valuable insights for the design and control of synchronous machines across various operating strategies.
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