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The Great East Japan Earthquake in March 2011 caused a large-scale blackout. The scheduled outages in parts of the Kanto region was inevitable because power interchange from other power company areas could not be implemented due to the restricted capacity of the power interconnection lines and facilities that convert frequencies . In addition, during the Hokkaido Eastern Iburi earthquake that hit Hokkaido in September 2018, a blackout occurred across the region, which led to the establishment of committees and working groups by the government in relation to strengthen the resilience of the power supply infrastructure against large-scale disasters. It began to be discussed as one of the key energy measures.
Moreover, with respect to the spread of the use of renewable energy, which has attracted attention as a countermeasure against global warming, there is an issue of the uneven distribution of power source locations and areas that consume the supplied power. Accordingly, it is needed to transmit power from renewable energy sources in a remote area over long distance towards areas of power consumption, without electrical losses.. Furthermore, in the liberalized electric power market, it is expected that in order to eliminate the difference in the electricity market price among the regions, the electric power market will be activated and the economic benefit will be enhanced by strengthening the wide-area interconnection.
From the lessons from earthquake disasters and from the standpoint of the spread of the use of renewable energy and the activation of the electric power market, the enhancement of power interchange among the regions and a wide-area power interchange beyond the boundary of power companies are required. There were also a variety of issues that needed to be overcome in order to achieve this, including the difference in the frequencies between eastern Japan and western Japan, and the geographical restrictions between Hokkaido and Honshu (the main island).
One of the solutions that respond to the needs for enhancing the power grid interconnection is High Voltage Direct Current (HVDC).
HVDC is a direct current system for power transmission that ensures lower electric losses during power transmission. It is capable of transmitting a large amount of power over long distances and also enables interconnection between different frequency grids. In addition, the system is currently attracting attention as a solution for achieving the use of renewable energy as a main power source, such as the interconnection of large-scale renewable energy and the transmission of power to distant areas with high electricity demand .
Since 1970, in most HVDC projects installed within Japan, Hitachi has taken charge of the technical development and coordination of the projects, and has been contributing to operation of HVDC systems, which has maintained Japan’s high power quality and the world class operating rates.
Hitachi received an order for LCC-HVDC system*1 for Hida Conversion Station in the Hida-Shinano DC Bulk Project between TEPCO’s Shin Shinano Substation and Chubu Electric’s Hida Conversion Station, important bases of the two electric companies, with the aim of commencing operations in FY2020. Hida Conversion Station is an important facility that interchanges power between eastern Japan and western Japan with different frequencies. Hitachi’s HVDC system will play an important role.
Demand for voltage-sourced HVDC, which has an advantage in terms of grid stability, is expected to become greater, not only for the power interchange among the power company areas, but also for the interconnection of the large-scale renewable energy sources such as offshore wind and mega solar power, the long-distance transmission from power source locations to areas of high demand, and interconnection with remote islands.
In December 2014, Hitachi concluded a strategic partnership with ABB Ltd. (“ABB”), establishing the joint venture company Hitachi ABB HDVC Technologies in November 2015. Hitachi and ABB established a business structure in which each of the two companies capitalizes on its strengths in order to advance a project in a cooperative manner. With this partnership, Hitachi plans to proactively develop Voltage-Sourced HVDC that is capable of optimizing the entire structure of a system.
In 2019, Hitachi received an order for two Voltage-Sourced Frequency Convertors (300,000 kW each), which enhance the interconnection capacity of Chubu Electric Higashi Shimizu Substation from 300 MW to 900 MW, building the system with the combination of ABB’s AC/DC converter together with a control and protection system and Hitachi’s converter transformers.
Hitachi will contribute to stable power supply by utilizing its experience in HVDC and its world-class technology.
*1 Line Commutated Converter High-Voltage Direct Current Transmission HVDC (LCC-HVDC): A
system in which power semiconductor devices such as a thyristor, which requires zero transit
current when the power is off, are used. The grid interconnection should be strong and no black
start is possible.
*2 Voltage-Sourced Converter HVDC (VSC-HVDC): A system in which a power semiconductor that can
be set off/on at any one point in time is used. A black start is possible, and grid interconnection do
not need to be strong. A filtering facility is unnecessary or can be small. VSC-HVDC system has
been increasingly installed since around 2000, mainly in the market overseas.