Nested dc-link balancer

摘要

Double-conversion UPS systems, as shown in Figure 1, are composed by 4 conversion stages: (ⅰ) rectifier stage to convert AC power from the grid to DC power, (ⅱ) inverter stage to convert DC power to AC power for the load, (ⅲ) DC/DC converter for the battery to convert DC power to DC power and (ⅳ) DC-link balancer circuit to convert dc power to dc power. For a modular UPS system, the reliability is high since each UPS module is independent to the other UPS modules. The DC rails are therefore on purpose not connected together, in order to avoid the loss of all UPS modules in case of a DC short-circuit (e.g., failure of one electrolytic capacitor).