Abstract: The problem of minimizing DC content in a dual converter system (18) is addressed with dual inverters (36,38) having outputs connected in parallel through an interphase transformer (42). In order to minimize DC current flow through the transformer (42) caused by non-ideal switching characteristics, a current transducer (44) senses primary current out of each inverter (36,38). Particularly, the current transducer (44) comprises a current transformer which senses the currents differentially. This sensing removes load current so that the sensed current represents interphase transformer excitation current and DC current. The excitation current is eliminated by filtering and averaging resulting in a DC signal proportional to DC current through the interphase transformer (42), which is transferred to a control processor (40) which modifies PWM patterns sent to the inverters (36,38) to reduce the DC current.

Abstract: A system for receiving DC input and for providing AC output is disclosed having first and second inverters. The first inverter has an input for receiving DC input and an output for providing a first inverter output and the second inverter has an input for receiving DC input and an output for providing a second inverter output. An inverter controller is connected to the first and second inverters for controlling the first and second inverters such that the first and second inverter outputs are separated in phase by a predetermined number of degrees in order to suppress harmonics in the AC output. An output circuit is arranged to combine the first inverter output and the second inverter output into the AC output.

Abstract: The problem of minimizing DC content in a dual converter system (18) is addressed with dual inverters (36,38) having outputs connected in parallel through an interphase transformer (42). The outputs for each phase are connected through a neutral forming transformer (43) to develop a reference. The output voltage at each phase is sensed, filtered and averaged to develop a signal representing DC content in each of the output phase voltages. A master controller (40-1) develops switching signals for the master inverter (36) which signals are modified based on the DC content of the output phase voltages to minimize the same. A current transducer (44) for each phase senses differential current output from the master and slave inverters (36 and 38) for each phase. This signal is used to modify PWM patterns from a slave controller (40-2) for minimizing DC content through the interphase transformers (42).

Abstract: An inverter arrangement for converting DC to AC having a first inverter with an input for receiving DC and an output for providing a first inverter output, a second inverter having an input for receiving DC and an output for providing a second inverter output, an AC output circuit having a first input for receiving the first inverter output, a second input for receiving the second inverter output, and an AC output for providing AC based upon the first inverter output and the second inverter output, and a controller for controlling the first inverter to minimize DC content in a first inverter output, and for controlling the second inverter output based upon DC content between the first inverter output and the second inverter output to minimize DC content in the second inverter output.