Self-adaptation of MTPA tracking controller for IPMSM and SynRM drives based on on-line estimation of loop gain

Maximum Torque Per Ampere (MTPA) tracking techniques for the control of Interior Permanent Magnet Synchronous Machines (IPMSMs) and Synchronous Reluctance Machine (SynRMs) drives were introduced in the last decade, with the aim of overcoming the dependence on motor parameter knowledge accuracy. In fact, uncertainty due to identification errors, magnetic saturation or temperature variation results in undesired deviation from the optimal MTPA trajectory. A recent paper [14] addressed gain adaptation and closed-form design of the loop controller gain for the MTPA tracking method proposed in [11]. However, since adaptation was based on motor parameters, at least a coarse knowledge of them was required. Moreover, relatively intensive calculation resources had to be dedicated to the adaptation task. In order to overcome these issues, a novel technique is proposed in this paper, in which gain estimation is adopted in place of parameters-based calculation. The MTPA tracking process gain is estimated by proper demodulation and filtering of the current vector magnitude component at twice the injection frequency. The obtained signal is then used for gain adaptation of the MTPA tracking loop. The method theoretical basis will be first introduced and the concept demonstrated by means of simulations. Implementation has been carried out using the hardware of a standard industrial drive and a 2.2 kW IPMSM. Experimental test results show the effectiveness of the proposal, with performances comparable to the previously proposed parameter-based gain adaptation.