Compensation of Selective Current Harmonics for Switching-Table-Based Direct Torque Control of Dual Three-Phase PMSM Drives

Advances in Dual-Three-Phase Permanent Magnet Synchronous Machines and Control Techniques

“…Direct torque control (DTC) aims to control directly the stator flux and the torque by selecting the appropriate inverter state. DTCs can be classified into three categories: switching-table based DTC (ST-DTC) [85][86][87][88][89][90][91][92][93][94][95], the duty-ratio-based ST-DTC (D-DTC) [96,97] and space vector modulation DTC (SVM-DTC) [98,99].…”

“…The values V s and I s represent the stator voltage and current after transformation. The method offers the benefits of fast response and dynamic performance, but suffers from large current harmonics, as concluded in [86][87][88][89][90][91]. The Redesign of the torque and flux regulators is investigated in [86], where it reduced current harmonics and torque ripples effectively, albeit with at the cost of complicating the control structure.…”

“…The switching look-up table in [87] is shown in Figure 21 and Table 12. Further, the back-EMF harmonics are considered and selectively [90] and fully [91] compensated in an ST-DTC employing a virtual vector based on two or three groups of VVs, respectively. Additionally, the authors of [100] introduced an additional current loop to determine the optimal dwell times of applied voltage vectors; the current harmonics caused by back-EMF distortion were reduced as well.…”

“…Furthermore, in order to implement standard centralization PWM sequences, three adjacent vectors in the L group are employed to synthesize the virtual vectors, which are equivalent to the virtual vectors synthesized by the vectors in the L and ML groups. For example, the virtual vectors synthesized by V9-V11-V27 in the L groups are employed to replace the virtual vectors synthesized by V11-V25 to obtain standard PWM sequences, as shown in Figure 28c,d In [90,91], the 5th and 7th back-EMF harmonics are considered in DTP machines. Because the 5th and 7th back-EMF harmonics that possess phase shifts are unaligned with the VVs in the L and ML groups, the ST-DTC based on the VVs in the L and ML groups can only compensate for the selective order back-EMF harmonics, as concluded in [90].…”

“…For example, the virtual vectors synthesized by V9-V11-V27 in the L groups are employed to replace the virtual vectors synthesized by V11-V25 to obtain standard PWM sequences, as shown in Figure 28c,d In [90,91], the 5th and 7th back-EMF harmonics are considered in DTP machines. Because the 5th and 7th back-EMF harmonics that possess phase shifts are unaligned with the VVs in the L and ML groups, the ST-DTC based on the VVs in the L and ML groups can only compensate for the selective order back-EMF harmonics, as concluded in [90]. Hence, in order to obtain composite vectors aligned with back-EMF harmonic components, the VVs in the M group are employed to combine with the VVs in the L and ML groups (STDTC-L + ML + M) in [91], due to their different directions with VVs in the L and ML groups, as shown in Figure 29a,b.…”