Research On Current-Sharing Control Technology For Distributed Parallel Inverters

The multi-module redundant inverter system becomes more and more popular forits capabilities of providing high power system and high reliability. Based on studyingthe parallel control theory and technology of the module inverters, a novel DSP-basedparallel inverter system is presented for engineering application.Firstly, the operation principle and mathematical model of the parallel inverter areanalyzed, and the characteristic of its circulation current is studied as well. In addition,factors such as reference voltage, voltage feedback coefficient, output voltageamplitude and DC offset which influence on circulation current are discussed, andcorresponding compensation schemes are proposed. All of them above offer theorybases for design and implementation of the parallel inverter system.Secondly, a novel control scheme is studied so as to suppress the circulationcurrent of parallel inverters. The reference signals of the parallel inverters are in phasewith each other via synchronous buses, which enable their output voltages are in phaselikewise. The AC steady-state circulation current can be suppressed by regulatingreference voltage amplitude according to average circulation current in half line cycle.The instantaneous circulation current is introduced to current loop to improve dynamiccirculation current rejecting capability. The DC circulation current caused by outputvoltage DC offset is suppressed by introducing DC offset compensation of referencesignal according to circulation current DC offset.Based on theory analysis and simulation, two 1 kW experimental prototypes aredeveloped which compose the parallel inverter system. Experimental results verifyeffectiveness of the studied control scheme.