Parallel Connected Voltage Source Inverters without Intermodule Reactors

Connecting power converters in parallel is useful method for solving high power requirements. Parallel structure without intermodule reactors would be desirable because of its low cost and compact size. Due to the finite tolerances in power stages and delays in control circuits, switchings of the parallel connected units will not be absolutely simultaneous. Asynchronous switchings leads to a current imbalance at the parallel inverter legs. In the ideal situation switchings would be exactly simultaneous and each leg would take the same amount of the load current. In this paper simulation and measurement results of the parallel connected voltage source inverters (VSI) without intermodule reactors are presented. These results show that a method is needed to synchronize the parallel power converters to get a full use of the parallel system.