Development of inverters with synchronization and inertial forces that can be operated integrally with conventional generators - Enabling the expansion of the amount of renewable energy introduced into microgrids.

PACIFIC CONSULTANTS CO., LTD.
PACIFIC POWER CO., LTD.

PACIFIC CONSULTANTS CO., LTD. (Address: Chiyoda-ku, Tokyo; President: Tomoyuki Shigenaga) and PACIFIC POWER CO., LTD. (Address: Chiyoda-ku, Tokyo; President: Michiko Godu), a member of the Pacific Consultants Group (hereafter referred to as the Group), have announced that they have developed an inverter with synchronized power and inertial force that will enable the introduction of renewable energy into microgrids between FY 2019 and FY 2021. As a part of the Ministry of the Environment's project for the development and demonstration of technologies to induce enhanced CO2 emission reduction measures, the company is collaborating with the Institute for Sustainable Energy Technologies Corporation, Toshiba Corporation and the National Institute of Advanced Industrial Science and Technology to develop an inverter for interconnection based on the virtual synchronous generator concept for the use of variable renewable energy. As a result of this development, the Grid Forming Inverter (GFM), an inverter with synchronization and inertia power that can be operated together with a synchronous generator in a microgrid, and the microgrid control system Grid Editor (Grid Editor), a system that controls the microgrid, have been developed. The system is based on the Grid Editor.

Introduction to the developed systems
In order to realize a low-carbon society, it is necessary to promote the use of renewable energy sources such as solar and wind power instead of fossil fuel-dependent thermal power generation. However, the introduction of a large number of these power sources, whose output varies irregularly according to weather conditions, into a microgrid will require energy management to maintain stable power system frequencies and efficient power utilization. In the demonstration project associated with this development, new inverter control technology that can maintain synchronization power and inertial effects comparable to those of conventional thermal power generators (synchronous generators) was developed, and a prototype GFM with a voltage control system that is actually compatible with renewable energy sources and storage devices was built to verify its functions. In addition, development was carried out with a particular focus on off-grid areas (micro-grids independent of the power systems of general transmission and distribution companies, isolated islands, etc.), where issues associated with volatile renewable energies will become apparent at an early stage, and not only inverters but also the control technology and system for the entire off-grid area in which they are installed, the Grid Editor, were developed as an integral part of the system. The Grid Editor was developed as an integral part of the system.

What was confirmed by the demonstration project
In this demonstration project, a small-scale simulated microgrid (with a variable renewable energy ratio of 70%, based on installed capacity) was constructed in the Fukushima Renewable Energy Centre of the National Institute of Advanced Industrial Science and Technology (AIST), where these systems were implemented, and it was demonstrated that the system can actually be operated under various conditions. It was confirmed for the first time in the world that a synchronous generator with an internal combustion engine and a GFM could operate in parallel off-grid, and that the GFM combined with storage batteries could contribute to the stabilization of the microgrid by demonstrating synchronization and inertia in response to changes in the grid frequency as expected. The frequency deviation was also confirmed to be generally stable, with a stay rate of more than 90% at ±0.5 Hz over a long period of time.

Furthermore, the microgrids that are connected to the grid under normal conditions can be used to further increase profitability by aggregating their regulating power and providing it to the wholesale power market and the supply-demand adjustment market, as well as to general distributed energy resources.

The system developed and demonstrated this time will be offered mainly to new municipal power companies in which Pacific Power Co., Ltd. participates, and will also be offered as a series of service packages, including GFM, to microgrids nationwide. In particular, the system is expected to be introduced in regional microgrid projects and power distribution projects being developed in areas where decarbonization has already taken place.

Pacific Consultants Group will continue to contribute to the revitalization and development of towns through community energy projects.