Periodic Traction Force Fluctuations Suppression Strategy of Maglev Train Based on Flux Linkage Observation and Harmonic Current Injection

To suppress the periodic traction force fluctuations of maglev train caused by the current harmonics and the excitation flux linkage harmonics of long stator linear synchronous motor (LSLSM), a strategy based on flux linkage observation and harmonic current injection is proposed in this article. First, the mathematical models of the LSLSM in single feed (SF) and double feed (DF) modes are established and simplified. Then, considering the characteristics of variable frequency and phase lag of the LSLSM, an improved discrete resonant controller (RSC) with pole correction and whole frequency domain phase compensation is designed to suppress the traction force fluctuation caused by current harmonics. To suppress the traction force fluctuations caused by the flux linkage harmonics, a sliding mode flux linkage observer (SMFO) is designed and combined with an adaptive notch filter (ANF) to estimate specific flux linkage harmonics in real time. By analyzing the flux linkage component in the traction force equation, appropriate harmonic currents are injected and tracked by the RSC. Hardware-in-the-loop (HIL) experiments verify the effectiveness of the proposed strategy.