NGCP backs MTerra Solar, warns of grid stability risks

The National Grid Corp. of the Philippines said Tuesday it welcomes the entry of the 2,500-MW MTerra Solar Power Project into the country’s power system, while warning that the expanding share of large-scale solar generation could create new operational challenges for grid stability.

NGCP said heavier reliance on intermittent sources such as solar may cause fluctuations in system frequency and voltage that, if not properly managed, could lead to under-frequency load shedding or rotating power interruptions in some areas.

“Renewable energy initiatives such as the MTerra Solar Power Project are welcome. Any new power source introduced into the system will help keep supply stable. However, not all renewable energy technologies are equal,” NGCP said.

The grid operator said wind and solar output are variable by nature and require closer operational management to keep the power system within safe operating limits.

MTerra Solar is a venture by Meralco PowerGen (MGEN) supported by investors including Actis, with a total capacity of 2,500 MW backed by a 1,125-MW battery energy storage system (BESS) that can sustain output for about four hours.

NGCP said the project adds to the country’s renewable energy capacity and supports national goals for a cleaner energy mix.

The company said grid stability depends not only on transmission operations but also on the readiness of generating plants to address the inherent variability of renewable energy.

NGCP said all facilities required on the plant side, as identified in system impact studies, must be fully complied with to ensure reliable integration into the grid.

The grid operator pointed to a recent voltage fluctuation incident in parts of North Luzon, which it said was caused by unstable output from renewable energy sources in the area.

NGCP said it implemented mitigating measures after the incident to prevent further disturbances to the power system.

Citing operational experience at the San Marcelino Solar Farm in Zambales, NGCP said short-term solar variability of up to 300 MW can occur due to brief cloud cover.

“While such variability can be effectively managed with fast-acting resources, conventional generation (such as coal power plants) has limited capability to respond quickly due to longer ramping times,” the company said.

NGCP said battery energy storage systems are among the “fast-acting resources” that can help maintain frequency stability as solar penetration in the grid increases.

Under its power supply arrangements, MTerra Solar will supply 850 MW to Manila Electric Co. (Meralco) through a power supply agreement, mainly during daytime hours.

NGCP said the remaining 1,650 MW will be injected into the grid and traded through the Wholesale Electricity Spot Market (WESM).

As a variable renewable energy source, MTerra Solar operates on a must-dispatch basis under Republic Act 9513, which requires priority dispatch for renewable energy facilities such as solar farms.

MTerra Solar has been in development since 2022, with construction ramping up in 2024.

The project is being implemented in multiple phases across North and Central Luzon and is one of the largest solar initiatives in Southeast Asia.

NGCP said MTerra Solar is expected to begin partial operations later this year, with full capacity targeted for 2027.

NGCP reiterated its call on the Department of Energy to adopt more progressive policies governing the entry of variable renewable energy, saying grid stability should be a primary consideration.

The grid operator said integrating bulk renewable energy capacity should be supported by dependable baseload and fast-ramping resources to keep power supply reliable.