Analytic and Iterative Algorithms for Online Estimation of Coupling Inductance in Direct Power Control of Three-Phase Active Rectifiers

One of the best known control methods for three-phase active rectifiers is the so-called direct power control (DPC). The control algorithm of the DPC is primarily based on the regulation of instantaneous active and reactive power. Because the DPC method can operate without any grid voltage sensors, instantaneous power and grid phase voltages must be estimated. The value of the essential coupling inductor between the rectifier and its three-phase supply play an important role in these estimations. This value is theoretically known; however, the grid inductance, which is sometimes difficult to determine precisely, or the coupling inductor tolerance, among other factors, may lead to errors in the inductance value. These errors have a negative and considerable effect on the instantaneous power and grid voltage estimation. Therefore, they provoke an improper operation of the DPC algorithm and the rectifier itself. To avoid these drawbacks, two simple, fast and robust inductance online estimation algorithms (analytic and iterative) are proposed in this paper. The proper operation of both methods is shown by simulation and experimental results.