Quasi Resonant DC Link Converters - Analysis and
Design for a Battery Charger Application
Another option is that the battery charger could be able to support the grid with peak power during periods of stability problems or emergency situations. This means that energy is borrowed from the batteries of vehicles connected to a charger. The price for energy supplied by the batteries is likely to be several times higher than the normal electric energy price, due to the wear costs of the batteries. Therefore, the battery charger losses also represents a high cost. It is often stated that resonant converters have a high efficiency compared to hard switched. Since carrier based pulse width modulation is employed, quasi resonant DC link converters are of interest.
Four of the most promising quasi resonant DC link topologies reported in the literature are compared. A fair comparison is obtained by designing them to meet certain common design criteria, in this case the duration of the zero voltage interval and the maximum output voltage time derivative. The derivation of the design expressions are given, and also the simulation results, by means of efficiency.
A 10 kW battery charger, equipped with one of the quasi
resonant DC links investigated is implemented. A hard switched battery charger with the
same rating is also tested to compare the measured efficiency with the simulated. Both the
simulations and measurements shows that the efficiency decrease for quasi resonant battery
chargers compared to the hard switched case. Furthermore, low frequency harmonics appear
in the battery charger input and output currents. However, full control of the output
voltage derivatives is obtained.
Last updated 1999-12-06