Direct Current Control of a multi-pole synchronous machine

The paper presents an application of direct current control (DCC) in a multi-pole synchronous drive. The DCC scheme was modified for application in rotating reference frame. Thus the reluctance of the drive is easier to account for. There are two possible variants of DCC. Property of the first variant is the selection between an active and zero voltage space vector to be impressed throughout the entire sampling interval. The minimal current error is obtained following a simple and fast algorithm. As a consequence, the switching frequency becomes very low, but current and torque ripple are increased considerably. The second DCC variant enables more accurate current generation by applying an active vector merely throughout precalculated time interval within a sampling interval, thus requiring higher switching frequency. The method has been tested on a 24 pole, 2 kW synchronous machine with extra low inductance. The experimental results confirm the validity of the approach.