Abstract
Once the motor stator winding is opened, balanced three-phase windings turn into unbalanced two-phases windings. Unfortunately, by conducting Clarke and Park transformation for open-phase PMSM, complete decoupling of the torque and flux cannot achieve. To maintain the rated torque, the two remained phase currents have to be modified as sinusoidal currents with 60° phase difference (not 120°). As a result, the current controller design becomes complicated. In order to solve this problem, a new fault tolerance method for the open-phase PMSM is proposed in this paper. It is designed based on a novel reference frame transformation. Through proposed frame transformation, the modified sinusoidal time-varying current commands are turned into dc variables in the redefined synchronous rotating frame. Hence, the design of the open-phase PMSM current controller can be simplified. This method can deal with different phase open fault and different current control mode ( $i_{d}=0$ or $i_{d}\ne 0$ mode). In addition, considering that the neutral current ripple at usual switching frequencies may be very high, an optimal additional inductance that inserted into the neutral wire is designed. With the designed additional inductance, complete decoupling can be achieved. Experimental results confirm that the reliability and the performance of the PMSM drive can be improved distinctly with the proposed open-phase fault tolerance strategy.
Highlights
Permanent magnet synchronous motor (PMSM) is attractive for a variety of applications owing to its high efficiency and power density
With the designed additional inductance, complete decoupling can be achieved and the stronger nonlinear induced by the unbalanced three-phase windings can be eliminated
The Control moment gyros (CMGs) gimbal is driven by PMSM
Summary
Permanent magnet synchronous motor (PMSM) is attractive for a variety of applications owing to its high efficiency and power density. Gaeta proposed a three-phase induction motor modeling and field-oriented control method under open-phase fault [17] It is designed based on the three-leg inverter with the neutral wire connected to the middle point of a split capacitor. The analysis and modeling of the open-phase induction motor presented in [17] are very complicated and it is not suitable for the PMSM fault-tolerant system with four-leg inverter [19]–[23]. Most of the PMSM open-phase fault-tolerance methods are designed based on the four-leg inverter [19]–[23], the design theory of the additional inductance is rarely discussed in the existing literatures, further studies are still necessary.
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