Record-Breaking DC Transformer Aims to Shield Power Grid From Renewable Energy Instability

China has unveiled a record-setting smart DC transformer designed to stabilise power grids as renewable energy expands. Rated at 750 million volt-amperes, it supports ultra-high-voltage, long-distance transmission, delivering over 36 billion kWh annually across 2,370km. By efficiently converting AC to DC, it reduces losses, absorbs fluctuations, and strengthens grid safety, flexibility, and reliability after recent grid instability exposed vulnerabilities nationwide.

Engineers in China have unveiled the world’s most powerful smart direct current (DC) transformer, marking a major advance in protecting large power grids from instability caused by fluctuating renewable energy supply. The breakthrough comes just over a year after a serious grid disturbance nearly escalated into a nationwide blackout.

The incident, which occurred in August of the previous year, was triggered by low-frequency oscillations linked to insufficiently integrated wind power in a major renewable energy hub in the country’s northwest. The event exposed vulnerabilities in the national grid as renewable generation continues to expand rapidly.

The newly developed transformer boasts a capacity of 750 million volt-amperes, setting a global benchmark for single-unit converter transformers used in flexible direct current transmission systems. Engineers involved in the project say the technology directly addresses instability that can arise when large volumes of renewable electricity are injected into the grid at transmission points.

By significantly improving operational flexibility, safety, and stability, the system is designed to absorb sudden power fluctuations and prevent cascading failures across long-distance transmission networks.

Backbone of a Long-Distance Clean Power Corridor

The transformer was engineered to support an ultra-high-voltage DC transmission corridor linking renewable-rich western regions with electricity-hungry eastern industrial centers. Spanning approximately 2,370 kilometers (1,473 miles), the line is expected to deliver over 36 billion kilowatt-hours of clean electricity annually once fully operational.

Such projects are central to the national strategy of channeling renewable power from less-developed inland regions—where wind and solar capacity is expanding rapidly—to densely populated coastal and industrial zones with high energy demand.

Why Direct Current Matters

For long-distance transmission, high-voltage direct current (HVDC) systems are increasingly favored over traditional alternating current (AC) lines. HVDC offers lower energy losses, better control over power flows, and greater resilience when integrating variable energy sources such as wind and solar.

Renewables depend heavily on weather conditions, making their output inherently intermittent. Without advanced transmission and control technologies, these fluctuations can undermine grid reliability and trigger instability.

The new transformer plays a critical role by converting AC electricity—which periodically reverses direction—into steady, one-directional DC power that can travel vast distances more efficiently. At the receiving end, the current is converted back to AC for local distribution.

Engineering for Extreme Conditions

To ensure long-term reliability, engineers incorporated advanced methods to manage magnetic flux leakage and deployed fiber-optic systems to continuously monitor internal temperatures. These features allow the transformer to operate safely under extreme electrical and environmental conditions.

Extensive testing was conducted, including simulations of lightning strikes and repeated switching between AC and DC modes. According to the development team, performance indicators such as temperature rise and energy loss exceeded design expectations, confirming the system’s robustness.

A New Global Benchmark

While earlier ultra-high-voltage transformers enabled multi-gigawatt power transmission over distances exceeding 3,000 kilometers, the latest system surpasses previous designs in capacity and flexibility. It represents a significant step forward in adapting national power grids to a future dominated by renewable energy.

As renewable penetration continues to rise, innovations like this large-capacity flexible DC transformer are expected to play a critical role in maintaining grid stability while accelerating the transition to cleaner energy systems worldwide.