Multirate model predictive current control of a permanent magnet synchronous machine for a flywheel energy storage system

Abstract

A flywheel energy storage system (FESS) achieves energy conversion through a permanent magnet synchronous machine (PMSM). The PMSM in a FESS requires low current total harmonic distortion (THD) and fast current response to obtain high performance. However, the PMSM in a FESS needs to operate at high speed, making it difficult to obtain a low current THD. One of the reasons for the high current THD is that the sampling frequency of the control system is limited. This paper proposes a new multirate model predictive current control (MRMPCC) for the PMSM in a FESS to achieve low current THD and fast current response. The proposed MRMPCC can obtain a high control frequency at a low sampling frequency, which can reduce the current THD. The MRMPCC can also compensate for control delay, which can offer a fast current response to the FESS. In addition, the MRMPCC employs feedforward decoupling to simplify the predictive model. The proposed MRMPCC is implemented on a 36000-rpm magnetic suspension FESS prototype. Compared to a conventional proportional integral differential (PID) control and common dead-beat model predictive current control (DBMPCC), the proposed MRMPCC can provide lower current THD, higher efficiency, and faster current response for a FESS. The proposed MRMPCC is verified experimentally.

Keywords

• High-speed PMSM
• FESS
• Multirate model predictive current control
• Low current THD