High-speed current vector control of PWM inverter minimizing current error at every sampling point

This paper proposes a novel digital current control technique of a PWM inverter. The key feature of this method is minimization of a current error vector norm at every sampling point with no predetermined current error tolerance, such as a spatial circular area or hysteresis bands. In order to make the current vector trajectory until the next sampling point as close as possible to a predicted current command vector, one of the six nonzero-voltage vectors is appropriately selected in the inverter A zero-voltage vector is inserted once a sampling period to adjust the current vector velocity and to move the current vector to the closest position to the predicted current command vector. Although manipulating variables in the current loop during the sampling period are limited by the discrete voltage vectors as described above, the proposed method achieves a dead-beat response in a two-dimensional space without the predetermined current error tolerance. Also, on-line identification of a load inductance is introduced to the system to overcome degradation of the response caused by the parameter mismatch. Resultant data obtained from computer simulations and experiments prove the feasibility of the proposed technique.