Discrete-Time Torque Control of High-Speed SPM Machine For Aircraft Electric Propulsion

High-speed permanent magnet machines are drawing attention in applications such as aircraft electric propulsion due to their high power density and high efficiency. However, the fundamental electrical frequency becomes higher because of high speed and high number of poles, which poses challenges for torque control. Issues caused by discrete time control implementation such as delay-induced input cross-coupling, incorrect complex pole cancellation, and phase lag introduced by update delay are the key factors that limit the control performance at high electrical frequencies. A control framework is presented that allows the machine to operate at high fundamental frequencies with good command tracking and disturbance rejection performance. After analyzing the effect of delay-induced input cross-coupling, the input decoupling including disturbance input decoupling (DID) and manipulated input decoupling (MID) is designed and evaluated based on an accurate discrete time model. This leads to derivation of a direct synthesized complex vector current regulator (CVCR) that is compared with the baseline PI-based CVCR. The direct synthesized CVCR exhibits excellent complex pole cancellation even at high speed with good command tracking and disturbance rejection capabilities.