Economic Comparison of AC and DC Distribution System

The load in the present distribution network is classified and the maximum transmission capacity of AC distribution network and that of DC distribution network are derived respectively. The manufacturing cost and transmission efficiency of main equipments for DC distribution network are calculated and analyzed, as for such equipments as the DC circuit breaker and the DC transformer, whose commercial use is not yet implemented, their market prices in future are estimated according to their research and development expenditure. Taking distribution network with typical structure as example, its investment costs and transmission losses under following three situations, namely supplying power by AC distribution network, ±7.5kV DC distribution network and ±15 kV DC distribution network, are calculated respectively, and then the economic comparison among the three situations is performed. Research results show that both maximum transmission capacity and investment cost of DC distribution network is higher than those of AC distribution network, and the higher the voltage class is, the higher the maximum transmission capacity and investment cost will be; the transmission loss DC distribution network is lower than that of AC distribution network, and it will decrease with the increase of voltage class; the higher the proportion of medium-voltage DC load is, the lower the investment cost of DC distribution network and the lower transmission loss will be.