# Japan OCCTO and Chubu Electric Advance Higashi-Shimizu 50 Hz/60 Hz Frequency Converter Expansion to 3,000 MW

> The Organization for Cross-regional Coordination of Transmission Operators (OCCTO) and Chubu Electric Power Grid have advanced key equipment delivery and converter transformer installation at the Higashi-Shimizu Frequency Converter Station, expanding interchange capacity between Eastern Japan (50 Hz) and Western Japan (60 Hz) to 3,000 MW.

- **Publish Date:** 2026-09-27
- **Category:** transmission-substations
- **Reading Time:** 5 min
- **Original Source Citation:** [Organization for Cross-regional Coordination of Transmission Operators (OCCTO) & Chubu Electric Power Grid](https://www.occto.or.jp/en/news/press-releases/2026-09-higashi-shimizu-converter-expansion.html)
- **Tags:** Japan, Frequency Converter, Higashi-Shimizu, 50Hz 60Hz Interconnection, VSC HVDC, OCCTO, Chubu Electric, TEPCO
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## Bridging the Historic 50 Hz / 60 Hz Split in Japan’s Grid

Japan’s national power grid remains historically split between a 50 Hz synchronous zone in Eastern Japan (served by TEPCO and Tohoku Electric) and a 60 Hz synchronous zone in Western Japan (served by Chubu, Kansai, and Kyushu). This geographical divide severely limits mutual emergency power assistance during natural disasters and nuclear/thermal outages.

Under OCCTO’s strategic national master plan, the Higashi-Shimizu station is undergoing a massive capacity multiplication, adding two new 300 MW Voltage Source Converter (VSC-HVDC) back-to-back blocks alongside existing facilities.

## Advanced VSC Converter Transformers and Black-Start Capabilities

The expansion integrates state-of-the-art converter transformers manufactured by domestic heavy electric OEMs, designed with low acoustic signatures and specialized high-voltage damping circuits to absorb high-frequency harmonic stresses generated by fast-switching IGBT valves.

Unlike older line-commutated facilities, the new VSC blocks possess full black-start capability, enabling either frequency grid to restart neighboring isolated islands or blackout-affected metropolitan centers following catastrophic earthquakes or tsunami events.

## Enabling Nationwide Renewable Energy Wheeling

The expanded intertie is scheduled for full commercial energization in early FY2027, unlocking cross-island wheeling of abundant solar generation from Western Japan to Tokyo, while channeling northern offshore wind energy southward.

The project serves as a cornerstone of Japan’s energy transition, reducing fossil-fuel peaking reliance and significantly elevating grid resilience.

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