| Abstract |
In high power applications, 3-phase ac/dc Voltage Source Converters (VSCs) are paralleled to increasethe overall aggregated converter power rating, number of voltage steps, effective switching frequencyand control bandwidth. For this, the interleaved Pulse Width Modulation (PWM) and current limitingconverter paralleling inductors are utilized. Interphase Transformers (ITRs) or Multi-WindingTransformers (MWTs) are often adopted for the converter paralleling because they provide largeinductances for the currents flowing among the converters while introduce relatively lower leakageinductances for the currents flowing from the converters to the power grid. However, large asymmetries in the inductances created by magnetic coupling in these transformers make it difficult to independently control active power flows in the converters. Thus, if the converter dc buses are not interconnected,instabilities in the active balancing control of the converter dc bus voltages are possible in certain operational conditions. In this paper MWT model and effects of magnetic coupling introduced by it on controllability of the power flows among the converters are presented. Operational condition leading to instability of the active balancing control is theoretically defined and validated in simulations. |
