Uncontrolled generator fault protection of novel hybrid-excited doubly salient synchronous machines with field excitation current control

In the safe-critical applications such as electric/hybrid electric vehicles, reliability of the machine drive system is vital. Among the various machine fault types, the uncontrolled generator fault (UCGF) at high speed is one of the most serious faults that could damage the machine drive system. In this paper, the fault protection capability of a novel hybrid-excited doubly salient synchronous machine is examined to illustrate its great capability to prevent the dangerous overvoltage issue from the UCGF. PM flux of the novel hybrid-excited doubly salient synchronous machine is inherently short-circuited when the field excitation current is not fed into the excitation windings. Therefore, when the UCGF is detected in the high speed region, the DC-link overvoltage issue can be effectively reduced by forcing the field excitation current to zero. Since only the field excitation current is utilized to protect the machine and power inverter from the UCGF, it is easy to implement and the concept of proposed control strategy can also be applied to other hybrid-excited machines. Finally, the proposed control strategy is verified by both simulation and experimental results on the hybrid-excited doubly salient synchronous machine.