Zero Sequence Voltage Modulation Strategy of Variable Flux Reluctance Machine Based on Single Leg Excitation Control

Abstract

Conventionally, the variable flux reluctance machines (VFRMs) are controlled by armature current and field current, which can be generated through a separated H-bridge. However, high switching losses in the H-bridge are not avoidable. To reduce the switching losses and improve efficiency, a VFRM control system based on single-leg excitation control is proposed. The field winding of VFRM is connected to the neutral point of armature winding by using single-leg to utilize the zero-sequence current as the DC excitation. A novel zero sequence voltage modulation technique is developed to generate the equivalent DC field excitation, i.e., the DC bias in the current of the armature winding. Compared with the separated DC field excitation, lower copper losses and higher efficiency can be obtained. Finally, experimental results on a prototype VFRM are presented for verification.