Six-Step Operation of PMSM With Instantaneous Current Control

Abstract

Six-step operation has many advantages in permanent-magnet synchronous machine (PMSM) drives such as maximum power utilization and widened flux-weakening region. However, due to the maximum utilization of inverter output, saturation of current regulator makes it difficult to maintain instantaneous current control capability. Accordingly, in most of conventional research studies, the six-step operation has been implemented by voltage angle control without current regulation, whose dynamic performance is quite unsatisfactory. This paper proposes a control scheme for the six-step operation of PMSM with enhanced dynamic performance of current control. By collaborative operation of dynamic overmodulation, flux weakening, and a technique for enhanced dynamic performance, the six-step operation is realized without losing instantaneous current control capability. Simulations and experiments are carried out to verify the effectiveness of the proposed control scheme. The experimental results show 17% extension of the constant torque region and 27% enhancement of torque capability at three times of the base speed. Index Terms-Current control, flux weakening, motor drives, overmodulation, permanent-magnet synchronous machines (PMSMs), six-step operation. NOMENCLATURESuperscript s Stationary reference frame. Superscript r Synchronously rotating rotor reference frame. Superscript * Reference value. P Number of poles. ω r Electrical rotor speed. V * s Magnitude of voltage reference. V s1 Fundamental component of inverter output voltage. v r ds , v r qs d−q components of inverter output in rotor reference frame. i r ds , i r qs d−q components of phase current in rotor reference frame. R s Stator resistance. L ds , L qs d−q components of stator self-inductance.

Control Strategies for Induction Motors in Railway Traction Applications

“…However, its use at high speeds presents multiple problems, including the lack of a voltage margin in the inverter for proper operation of the current regulator, distortions in the currents due to overmodulation, and delays intrinsic to the reduced switching frequency. The modification of RFOC to enable operation at the voltage limit was discussed in [16]. Ideally, (13) will produce the voltage needed to obtain the desired torque and rotor flux with no error.…”

DSP Implementation of a Neural Network Vector Controller for IPM Motor Drives

“…In over-modulation region II, corresponding to MI ranging from 0.952 up to 1, both the amplitude and angle of the control voltage vector are modified [6,16,17], in which the inverter can just provide even more limited partial control ability when compared to over-modulation region I. When MI reaches 1, the control voltage generated from the controller needs to be saturated, since the inverter has reached the maximum possible voltage and the inverter works on the six-step modulation [18]. Thus, the inverter can only provide the tracking of the reference dand q-axis currents according to the six-step modulation rule in the six-step modulation region, which means that more oscillation would appear in the actual dand q-axis currents as shown by the hardware experimental results in Section 6.…”

Derivation of Motor Mean Phase Currents in PMSM Drives Operating with Low Switching-to-Fundamental Frequency Ratio

“…Hence, the SFFR is not likely to be substantially reduced in the longer time horizon. Moreover, in some cases, six-step control is applied to mitigate the voltage constraint in order to increase the available torque at high speeds (Kwon et al, 2014). In such a case, the SFFR is 6, independently from the dynamic properties of transistors.…”