Online Adaptive Set of Virtual Voltage Vectors for Stator Current Regulation of a Six-Phase Induction Machine Using Finite State Model Predictive Controllers

Abstract

Virtual voltage vectors (VVV) have been used for the control of multi-phase induction machines, where different sub-spaces appear related to the torque production and losses generation. In the literature, several sets of VVV have been used, aiming at reducing harmonic content while maintaining a low computational burden. This paper proposes the use of different sets of VVV to regulate the stator current of multi-phase drives using finite-state model predictive controllers. In the proposal, only one set is active at each control period. This active set is obtained through a preliminary analysis using performance maps. As a result, a method is derived for the online selection using the current operating point. The selection is based on a simple computation from variables usually measured on variable-speed drives. Results are provided for a symmetrical six-phase IM, showing that the proposal improves the closed-loop performance of the multi-phase drive with a low computational cost.

Guiding the Selection of Multi-Vector Model Predictive Control Techniques for Multiphase Drives

“…This fact can generate an undesired harmonic injection in the x-y plane when the regulation goal is achieved in the main plane, resulting in a low current quality and an inadequate control performance. To address these problems, inherent to the performance of standard FCS-MPC, different multi-vector approaches have been proposed [23][24][25][26][27][28][29][30][31][32][33]. Four of them are evaluated in this work as previously exposed in Table 1.…”

“…Following this approach and taking into account the number of available large voltage vectors, 12 active VVs can be generated for the considered 6PH-IM (Figure 4). (52,38) VV 3 (54,20) VV 4 (22,50) VV 5 (18,30) VV 6 (26,19) VV 7 (27,10) VV 8 (11,25) VV 9 (9,43) VV 10 (41, 13) VV 11 (45,33) VV 12 (44,37) The employment of these VVs also permits reducing the predictive model ( 9) and the cost function (11) (Figure 5), simplifying the control scheme and reducing the computational burden in relation to the standard version. Since the secondary currents can be regulated in open-loop mode with the null-average voltage production provided by the VVs in the secondary subspace, the following machine model and cost function can be employed:…”

“…However, MPC based on the application of a single switching state per control period presents an unacceptable current quality. Fortunately, this undesirable harmonic content has been mitigated with the development of multi-vector solutions [22][23][24][25][26][27][28][29][30][31][32][33]. In fact, ref.…”

“…Regardless of the selected family of controllers, it can be concluded that the last decade has witnessed success, where a high number of more competitive control techniques have been developed in diverse application fields such as renewable energy application [34] or electrical propulsion [35,36]. The most popular procedure in the field of electric drives to illustrate the goodness of an original proposal of the state of the art is an experimental comparison using a benchmark method as a basis for the verification [23][24][25][26][27][28][29][30][31][32][33]37,38]. Focusing on the necessary validation process, it is also common to carry out the mentioned comparison on a single test bench where the electric machine is characterized by specific values of its electrical parameters [18,20,[22][23][24][25][26][27]31].…”

“…Taking into account this last issue, a reasonable doubt can appear regarding the universality of the obtained conclusions. For instance, from the perspective of the signal quality in multiphase drives, the role of the secondary currents (x-y components) is crucial [27,33,[39][40][41], and the behavior of these components is highly dependent on the stator parameters [42,43]. In this regard, the implementation of a multi-vector solution can be considered as a mandatory task when a direct control strategy is implemented to regulate multiphase electrical machines with low values of the stator impedance.…”