Parallel Operation of Permanent Magnet Synchronous Generators under Six-Step Operation Mode

In the shipboard dc power system, dc bus voltage regulation through six-step operation of active front end (AFE) can conspicuously reduce converter loss, compared to PWM operation of AFE. Despite of the superior efficiency of the six-step operation, there have been few researches on the parallel operation of generators under the six-step operation. This paper proposes a framework for the parallel operation of permanent magnet generators (PMGs) under the six-step operation. In addition, a method for deriving the optimal dc bus voltage to minimize the total copper loss of paralleled PMGs with different parameters is proposed. The proposed optimal voltage regulation method is compared with methods only minimizing copper loss of a single PMG among the paralleled PMGs. By the optimal voltage regulation, the total copper loss can be reduced by up to 9.1 % and 29 %, in the simulation and the experiment, respectively.