A Simple Modified Deadbeat Direct Thrust Control for Permanent Magnet Linear Synchronous Machine Considering Parameter Asymmetry

Permanent magnet linear synchronous machine (PMLSM) has the inherent drawbacks of end effect which would cause phase winding asymmetry, viz., electromagnetic parameter asymmetry (EMPA). In order to achieve fast and precise thrust response, traditional deadbeat direct thrust control (DB-DTC) is suitable for PMLSM, however it cannot be directly applied to PMLSM since it is constructed based on symmetrical machine mathematical model. Moreover, if EMPA is considered in traditional DB-DTC strategy, it is hard to calculate the required change of load angle since the primary flux linkage should be kept constant, especially when the salient-pole effect exists. Based on this, this paper proposed a simple modified DB-DTC strategy for a salient-pole PMLSM considering EMPA. Firstly, the mathematical model with and without considering asymmetrical inductance are derived. Then the influence of EMPA on traditional deadbeat direct thrust control (DB-DTC) is fully investigated. In order to compensate the effect of EMPA, this paper proposes a simple modified DB-DTC by compensating the error in both prediction and deadbeat control processes. Finally, the prototype experiments are carried out to validate the proposed control strategy. The results show that the phase current unbalance that caused by EMPA is largely suppressed controlled with the proposed control strategy. Moreover, both good steady and transient performances can be obtained compared with traditional DB-DTC strategy. The effectiveness of the proposed control strategy is validated.