Experience with 3-phase sinusoidal regenerative front-ends

Most electric motor drives involve conversion of alternating current from the supply to direct current within the drive using controlled or uncontrolled rectifiers. Less frequently, but in a growing number of cases the ability to reverse this process and provide a regenerative capability is also necessary. The conversion process creates unwanted harmonics in the supply system which in some cases lead to problems. This aspect has been brought to the fore recently with the introduction of new regulations which set maximum values for the generated harmonics. This paper provides an overview of a project to develop regenerative line-side power converters which are capable of transferring power between the AC supply and a DC link with sinusoidal line-side current at unity power factor. Such converters have aroused much interest in recent times and a number of papers have been published on the topic. However, it was decided at the outset of this project that, in order to achieve enhancement in performance, modern control techniques would be employed. Prototypes have been built at 10 kW, 22 kW and 150 kW and the paper highlights experience in developing the power circuitry, including thermal management and parallel operation of the power switches, together with comparisons of the performance of the converter with a number of different control schemes