Leyte-Luzon

The Leyte-Luzon HVDC project is located in the Philippines, connecting the island of Leyte to the main island of Luzon. This 440 MW, 350 kV monopolar HVDC link transfers power from geothermal plants on Leyte to the southern part of Luzon, feeding into the existing AC grid in the Manila region.

Technical Specifications

The HVDC system operates at a rated power of 440 MW and a DC voltage of 350 kV. It consists of converter stations at Ormoc (Leyte) and Naga (Luzon), with Ormoc typically functioning as the rectifier and Naga as the inverter. The transmission line includes both overhead lines and submarine cables. The total length of the HVDC transmission is 455 kilometers, with overhead lines accounting 432km and submarine cable accounting for 23km.

System Design and Components

The Leyte-Luzon HVDC link employs a twelve-pulse converter group with three quadruple valves. Each thyristor valve consists of series-connected thyristors with auxiliary circuits. The system uses fiber optics for communication between the control equipment at ground potential and the thyristors at high potential.

The converter stations include transformers, AC filters, shunt capacitors, and DC filters. AC filters are installed to limit harmonics generated by the 12-pulse HVDC converter, specifically addressing the 11th, 13th, 23rd, 25th, and higher order harmonics.

Control Features

The Leyte-Luzon HVDC system incorporates special control features to ensure stability in both the Visayas and Luzon power systems. These include frequency control and emergency power control. The frequency control allows the Visayas system to operate with minimal spinning reserve, optimizing the use of geothermal resources.

An important feature of this HVDC system is its ability to operate continuously at 5% of rated current, which minimizes disturbances to the AC networks during start/stop operations. This capability is particularly important when the Leyte system is islanded.

Performance and Operation

The HVDC link has demonstrated high reliability since its commissioning. During its first 15 months of commercial operation, it achieved a converter availability of 98%. The system normally operates in power control mode, with current control available as a backup.

The Leyte-Luzon HVDC project exemplifies HVDC as a solution to address the unique challenges of island-based power systems and long-distance energy transfer.