High dynamic quasi-direct converter with very low DC-link capacity

Frequency converters with a controllable input stage are increasingly used in electrical drive technology. Besides the mains and the load side pulse converters they also require passive components like input inductances and the capacitor in the DC-link. Reducing the DC-link capacity to a minimum leads to a quasi-direct converter. In order to maintain a constant DC-link voltage in quasi-direct converters, even during a dynamically changing load, a new high dynamic state control has been developed. Furthermore the power factor is adjustable. Simulations and practical results demonstrate the high performance of the state controlled converter