Research on Torque Control Current Injection Method of PMSM in Flywheel Energy Storage Based on Electromagnetic-Thermal Bidirectional Coupling Numerical Method

In the numerical calculation process of electromagnetic-thermal bidirectional coupling of permanent magnet synchronous motor (PMSM), as the temperature increases, the residual magnetism and coercive force of the PM gradually decrease, which leads to weakening of the magnetic field and further leads to electromagnetic (EM) torque decreasing in numerical calculation. However, the temperature rise caused by EM torque decreasing is not considered in numerical calculation process, which leads to weaker electromagnetic field and smaller motor loss than those of actual values. Therefore, the calculated temperature in motor is inaccurate. To solve this issue, a control method is proposed to keep the torque as a constant value during numerical calculation process to improve the accuracy of the numerical results of electromagnetic-thermal bidirectional coupling method.