Low-frequency high-voltage alternating-current (LF-HVac) transmission scheme has been recently proposed as an alternative solution to conventional 50/60-Hz HVac and high-voltage direct-current (HVdc) schemes for bulk power transfer. This paper proposes an optimal planning and operation for loss minimization in a multi-frequency HVac transmission system. In such a system, conventional HVac and LF-HVac grids are interconnected using back-to-back (BTB) converters. The dependence of system MW losses on converter dispatch as well as the operating voltage and frequency in the LF-HVac is discussed and compared with that of HVdc transmission. Based on the results of the loss analysis, multi-objective optimization formulations for both planning and operation stages are proposed. The planning phase decides a suitable voltage level for the LF-HVac grid, while the operation phase determines the optimal operating frequency and power dispatch of BTB converters, generators, and shunt capacitors. A solution approach that effectively handles the variations of transmission line parameters with the rated voltage and operating frequency in the LF-HVac grid is proposed. The proposed solutions of the planning and operation stages are evaluated using a multi-frequency HVac system. The results show a significant loss reduction and improved voltage regulation during a 24-hour simulation.

中文翻译：

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多频 HVac 输电系统的优化规划和运行

低频高压交流 (LF-HVac) 传输方案最近被提出作为传统 50/60-Hz HVac 和高压直流 (HVdc) 方案的替代解决方案，用于大功率传输。本文提出了多频 HVac 输电系统损耗最小化的最佳规划和操作。在这样的系统中，传统的 HVac 和 LF-HVac 电网使用背对背 (BTB) 转换器互连。讨论了系统 MW 损耗对变流器调度以及 LF-HVac 中的工作电压和频率的依赖性，并与 HVdc 输电进行了比较。基于损失分析的结果，提出了针对规划和运营阶段的多目标优化公式。规划阶段为 LF-HVac 电网确定合适的电压水平，而运行阶段决定了 BTB 转换器、发电机和并联电容器的最佳运行频率和功率分配。提出了一种有效处理LF-HVac电网中输电线路参数随额定电压和工作频率变化的解决方案。使用多频 HVac 系统评估规划和运营阶段的建议解决方案。结果表明，在 24 小时模拟过程中，损耗显着降低并改善了电压调节。使用多频 HVac 系统评估规划和运营阶段的建议解决方案。结果表明，在 24 小时模拟过程中，损耗显着降低并改善了电压调节。使用多频 HVac 系统评估规划和运营阶段的建议解决方案。结果表明，在 24 小时模拟过程中，损耗显着降低并改善了电压调节。