Study Of AC Plus DC Distribution Network Suitable For Distributed Generation Connection

As the dominant energy pattern, traditional fossil fuels deeply pollute the environment. The energy crisis is increasingly prominent. The rapid economic development promotes the rapid growth of load density and load demand. The penetration of distributed generation(DG), DC load, energy-storage device is increasing. Traditional passive and single radial distribution network faces the problems of lower power quality, insufficient power supply capacity, higher line power loss, lower reliability of power supply and so on. DG connection focused new diversified power-supply system gradually changes the configuration of traditional distribution network. Based on the suitable for DG connected AC plus DC distribution network, certain problems have been studied in this paper.Based on the future distribution network development pattern and AC plus DC power transmission technology, the topology of suitable for DG connected AC plus DC distribution network is proposed. The operating principle of network and DG connection mode are analyzed. The advantages of AC plus DC distribution network are summarized. Aiming at the critical equipment zigzag transformer, the principle of saturation phenomenon avoidance is studied by analyzing the winding vector relation and equivalent circuit. The simulation by Ansoft software verifies the correctness of theoretical analysis. The operating principle of converter circuit in the topology is analyzed and corresponding control strategy is given. The feasibility and correctness of suitable for DG connected AC plus DC distribution network is verified by Matlab/Simulink.AC plus DC distribution network adopts the power transmission line of 10kV MV AC distribution network. Taking equally distributed power as benchmark, taking line insulation level as comparison precondition, considering two cases of adopting overhead line and cable line, the comparison is made with 10kV MV AC distribution network from line power loss, line voltage drop and maximum power supply capacity. Taking lower line power loss, lower voltage drop and higher maximum power supply capacity of AC plus DC distribution network as constraint condition and considering future load ratio, the voltage overlapped scheme of AC plus DC distribution network is proposed.Compared with lOkV AC distribution network, the reliability and economy of proposed AC plus DC distribution network are analyzed. Minimal cut-set method is used to analyze the reliability of two networks. The effect of DC load, micro grid and backup power on load reliability index is analyzed. Combined with actual example, the reliability index of network is obtained. Annual expense method is used to analyze the economy of two networks from investment construction cost and transmission loss cost. Taking new area network construction as standard, investment construction cost is analyzed. Transmission loss cost is analyzed by considering the transfer efficiency of line, transformer and converter. The comprehensive economic result of two networks is obtained.