They are among 46 projects that have agreed to sell power to national utility Vietnam Electricity (EVN) at a temporary price rate while the government considers an official rate.
The temporary rate is VND754-908 (US$0.032-0.039) per kilowatt-hour, which is half the maximum price the government can offer.
The Ministry of Industry and Trade and EVN have been pushing for linking up the plants amid fears of a power shortage in the summer as water levels plummet in reservoirs.
Renewable energy plants with around 4,600-MW capacity are awaiting connection to the grid since they were built after the government ended its incentive buying price.
Their developers are in the process of negotiating new rates with the government.