The dc grid system is attracting attention as a new electric power distribution method for several vessel kinds due to its high fuel efficiency compared with the ac grid. The combination of a wound rotor generator (WRG) and a diode rectifier [diode front end (DFE)] has been typically applied as a generation part of the dc grid. Still, the combination of a permanent magnet generator (PMG) and a DFE has been recently studied to take advantage of their simplicity, cost-effectiveness, robustness, high reliability, and high efficiency. However, although a single-operation mode of the “PMG + DFE” system was analyzed in the literature, research for the parallel operation of the “PMG + DFE” system has not yet been conducted. The “PMG + DFE” system should be operated along the optimal operating line (OOL) in the power–voltage ( PP – VV ) domain to minimize fuel consumption. This OOL in the PP – VV domain includes negative, zero, and positive slopes under light, medium, and heavy loads, respectively. Therefore, if the conventional droop control is applied to this system, it cannot be operated along the OOL. This article introduces modified droop control for operating paralleled “PMG + DFE” system along the OOL in the PP – VV domain. Furthermore, a mode change strategy from the single-operation mode to the parallel-operation mode is proposed. The validity of the proposed modified droop control is verified by computer simulation and a small-scaled experimental test.

中文翻译：

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考虑燃油经济性的海上直流电力系统永磁发电机与二极管整流器并联运行


直流电网系统由于其与交流电网相比具有较高的燃料效率，作为多种船舶的新型电力分配方法而受到关注。绕线转子发电机 (WRG) 和二极管整流器 [二极管前端 (DFE)] 的组合通常用作直流电网的发电部分。尽管如此，最近仍对永磁发电机 (PMG) 和 DFE 的组合进行了研究，以利用其简单性、成本效益、稳健性、高可靠性和高效率。然而，虽然文献中对“PMG+DFE”系统的单一运行模式进行了分析，但尚未对“PMG+DFE”系统的并行运行进行研究。 “PMG + DFE”系统应沿着功率-电压（PP – VV）域中的最佳运行线（OOL）运行，以最大限度地减少燃料消耗。 PP – VV 域中的 OOL 分别包括轻负载、中负载和重负载下的负斜率、零斜率和正斜率。因此，如果将传统的下垂控制应用于该系统，则不能沿OOL运行。本文介绍了改进的下垂控制，用于在 PP – VV 域中沿着 OOL 运行并行“PMG + DFE”系统。此外，提出了从单操作模式到并行操作模式的模式转换策略。通过计算机仿真和小规模实验测试验证了所提出的改进下垂控制的有效性。