Adaptive Duty-Ratio-Modulated Direct Torque Control Based on Extended Virtual Voltage Vectors for PMSM Drives

Duty-ratio-modulated direct torque control (DDTC) suffers from the limited phase resolution of voltage vectors and strong sensitivity to motor parameter variations, degrading its torque and flux control performance for permanent magnet synchronous motor (PMSM) drives. To address the issue, an adaptive DDTC strategy based on extended virtual voltage vectors is proposed. By analyzing the coupling effects of the duty ratio on torque and flux, an efficient vector combination mechanism is developed, in which the torque deadbeat response and the flux ripple are adopted as optimization criteria. This method dynamically extends virtual voltage vectors with continuously adjustable phases, achieving coordinated optimization of the output torque and flux. To overcome the dependency of duty-ratio calculations on accurate motor parameters, the torque production strategy is investigated to vectorially project torque control errors. Leveraging a voltage-vector phase-mapping scheme, the torque slope undergoes an equivalent linear correction and is integrated into the duty-ratio model to achieve adaptive regulation, thereby effectively suppressing torque ripples and enhancing the robustness. Experimental results on a 2.2-kW PMSM drive platform validate the effectiveness of the proposed strategy.