Active filter for DC-link low frequency ripple filtering and passive components reduction

Contemporary Alternating Current to Direct Current converters (AC-DC) and Direct Current to Alternating Current converters (DC-AC) include a DC-link with a relative big DC-link capacitor to filter the ripple. AC-DC converters represent a fundamental component of battery chargers for battery energy storage systems since they allow to charge and possibly discharge the battery. The main drawbacks of AC-DC converters or more in detail of conventional battery chargers are the dimension and the weight, but also the durability over the years. Essentially a battery charger that works using grid power is composed by a Power Factor correction (PFC) bridgeless rectifier that rectifies the current from alternating to direct, in order to charge the battery. This stage is often equipped with a bulk filter made of electrolytic capacitors connected in parallel to the DC-link, in order to smooth out the double line frequency current ripple and obtain a direct current. A Direct Current to Direct Current converter (DC-DC) then regulates voltage and current levels according to the specific requirements of the battery. The main drawback of conventional battery chargers are the capacitors that, apart from the size and weight, because of being electrolytic, are not so well suited for long time and safety critical application. This study aims to analyse a new concept of DC-link filter and, in particular, an active buck topology filter that uses film capacitors. Simulation and analysis using PLECS are conducted in order to verify the functionality of the proposed filter. In addition, a physical prototype will be implemented in order to validate the obtained simulation results and confirm the feasibility of this kind of filter.