We assumed the charging power to be 3200 MW, which is
equivalent to the maximum fluctuation of wind power shown
in Fig. 9. When the charging power per car is 500 W, the value
of 3200 MW is achieved by 6.4 million PHEVs; in addition,
when the frequency characteristic per PHEV is 2,500 [W/Hz],
total frequency characteristic of 6.4 million PHEVs becomes
16,000 [MW/Hz].