The Comparison of Full Link Energy Efficiency between Low Voltage AC and DC Distribution Power System

The energy efficiency level of low voltage distribution network is strongly related with the consumption on electricity. With the rapid development of DC distribution power system and the integration of variety kinds of distributed resources, the quantitative evaluation and comparison of low voltage AC and DC distribution power system energy efficiency level is of great significance. However, there lacks the evaluation indices of energy efficiency for DC power distribution system, as well as the comparison of energy efficiency level between AC and DC system. According to the difference of topology structure of AC/DC distribution system, the energy efficiency evaluation indices and method is proposed. The power loss is mainly divided into line loss and device loss. The power loss and transmission efficiency of AC/DC distribution system are calculated by combining the load type and the characteristics of power electronic devices. By decomposes the loss and compares the loss composition and time sequence characteristics of AC and DC distribution system, the weak links affecting the efficiency of distribution system are explored. Furthermore, with the gradual increase of renewable energy access ratio and DC load ratio, the overall transmission efficiency of the AC/DC distribution network presents an upward trend within a certain range, indicating that the increase of dc components will be conducive to the improvement of distribution network efficiency to some extent.