Phase current reconstruction and regulation for three-phase AC motor drives using DC-link single current sensor and measurement voltage vectors

This thesis presents a novel method for the DC-link single current sensor technique (SCST). The new method, measurement vector insertion method (MVIM), overcomes the inherent problem of the DC-link SCST created by unmeasurable intervals. The concept of MVIM is to introduce three zero-sum measurement voltage vectors (e.g (100), (010), and (001)) between regular PWM switching cycles for current measurements in the unmeasurable area. By using three measurement vectors, all three phase currents can be sequentially measured with close time proximity within a short time interval.; MVIM provides improved current regulation in the unmeasurable area as well as complete phase current reconstruction. The advantages of MVIM also include the predictability in the timing of the current sampling, and minimal modification of existing PWM algorithms due to easy incorporation into familiar space-vector PWM (SVPWM) algorithms.; MVIM causes the increased number of switching events, resulting in the increased switching losses, due to insertion of three measurement vectors. To minimize the number of added switching events and associated switching losses, various MVIM enhancement techniques such as combining MVIM with discontinuous PWM (DPWM) are presented.; To enhance current regulation performance of the system using MVIM, the extended application of MVIM (EMVIM) to the entire voltage space vector plane is proposed. By doing so, valuable advantages such as reduced control delay and improved predictability in the timing of the current sampling are achieved. However, EMVIM also brings some disadvantages such as the increased voltage harmonics. The increased voltage disturbances are resolved by employing a modified current regulator design using virtual active resistance state feedback to improve the disturbance rejection capability of the system.; MVIM and EMVIM are evaluated compared to alternative methods of the DC-link SCST as well as the conventional three-leg current sensor technique using the standard SVPWM. Primary comparative metrics are total harmonic distortion (THD) of phase currents and power loss, including switching losses.; A combination of analysis, simulation, and experimental results is applied to evaluate performance of the system using MVIM, EMVIM and MVIM enhancement techniques, including phase current reconstruction and current regulation using reconstructed currents.