Minimization of active filter rating in high power hybrid filter systems

An approach for the optimization of a hybrid (combined) power filter by using the genetic algorithm (GA) method is presented. As the criterion for the optimization, the minimization of the active filter (AF) rating is adopted. The optimization studies are carried out for two characteristic situations of a DC rectifier load and a cycloconverter load. It is shown that a reduction of the active filter rating can be achieved if the load is a rectifier. However, a considerably higher active rating is required for a cycloconverter because of the presence of low frequency interharmonics and it is not possible to decrease it significantly by use of the passive filter optimization only. These examples clearly show why hybrid filter topologies and control techniques widely examined in the literature are suitable only for rectifier loads but not for loads with a broader spectrum. A possible modification of the AF filter control system which optimize the performance/rating ratio is proposed and discussed.