Delay Compensated Multifold Table (DCMST) Direct Power Control (DPC) with Duty Ratio Control

Abstract

The DPC approach for controlling ac-dc converters has a number of benefits over traditional methods. Even with the advancement of PWM control techniques, the look-up-table based DPC presents a good substitute when a low computational load is the criteria for the system design. By using an appropriate switching table matching to the demand and eliminating the error due to control delay, the DCMST provides good steady-state performance at low computation complexity. However, as the two-level converter has a limited set of voltage vectors, the sampling frequency must be higher to ensure adequate accuracy and grid power quality. Hence this work proposes the use of multiple switching vectors in the same control period by designating one fragment of the control period for one switching vector and rest time for a zero vector to achieve improved steady-state behavior. It presents the user with a highly accurate control for an ac-dc converter at a low computational burden. The duration of the application is estimated using the power error minimization method. The performance of the proposed duty regulated DCMST-DPC is presented and compared to that of the traditional DCMST-DPC using extensive simulation study in MATLAB/Simulink.