Visit to Plant

Japan's Largest Wind Turbines Begin Operation With Batteries in Hokkaido (page 3)

Power transmitted to grid as planned by charging, discharging batteries

2019/07/20 18:52
Kenji Kaneko, Nikkei BP Intelligence Group, CleanTech Labo
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2MW/unit NAS batteries used

The grid substation and the storage battery system were both set up in the same site. In addition, an administration building with a SCADA (supervisory control and data acquisition) room and an office was also constructed on-site.

Nine 2MW NAS batteries were installed. Power conditioners with a total output of 2MW control each battery's charging and discharging. Compared with normal power conditioners for solar power generation, which only convert direct current (DC) electricity from solar panels into alternate current (AC), power conditioners for storage batteries are, to control power charging and discharging, bidirectional-type that feature both functions to convert AC from wind turbines into DC and to convert DC from storage batteries into AC (Fig. 6 & 7).

Fig. 6: NGK Insulators NAS batteries (source: Nikkei BP)

Fig. 7: TMEIC power conditioners for storage batteries (source: Nikkei BP)

The wind turbines and batteries are connected using the "AC link" method, in which output combining AC from wind turbines and AC from storage batteries is transmitted to the grid of Hokkaido Electric Power Co Inc (Hokuden). Smoothing short-term fluctuations on a second scale and long-term fluctuations on an hour scale by charging and discharging the batteries to make up for changes in the amount of wind power generation, the plant alleviates Hokuden's grid operation load.

To be more specific, the plant formulates and submits in advance a power generation plan (power transmission plan), in which output fluctuations are kept below a certain rate, to Hokuden and charges and discharges the batteries in accordance with the plan. There are displays for real-time monitoring of such battery operation in the SCADA room inside the administration building. This was also exhibited to visitors during the tour (Fig. 8).

Fig. 8: Remote monitoring displays in SCADA room (source: Nikkei BP)