| As the fossil energy crisis is becoming more and more serious,the environmental problem caused by the consumption of fossil energy is becoming increasingly prominent. In the meantime, the distributed power supply and the electric car industry has entered a fast track of development because of the wide support from all walks of life. The rapid development of distributed power and electric vehicle industry accelerate structure change of power generation and electricity end of the current distribution system. Facing the change of the electric terminal structure of the power network, low voltage AC power distribution network has shown a lot of disadvantages such as not suitable for distributed power access, wasted a large number of converter equipment, etc. On the contrary, the DC power distribution network has become a new research focus, which is suitable for distributed power access, large power supply capacity and so on, when facing the same situation.First of all, this paper discusses the development status and research background of DC distribution network, analyzes the changes of the future low-voltage distribution network. Through comparing characteristics of DC and AC distribution network, shows the advantages of DC micro grid when faced with the increasing of the distributed power supply and the DC load: lower cost, higher transmission efficiency and more suitable for distributed power access etc. All these show that the DC power distribution network is an effective way to solve the problem of low voltage distribution in the future.Secondly, by studying the topology of DC power distribution network and the method of determining the voltage level, the low-voltage DC distribution network voltage is selected as the radiation type structure, so as 380 V and 48 V is selected as the voltage level. Two kinds of distributed energy generation and control model of photovoltaic cells and small wind turbines are detail designed in this paper. The super capacitor is selected as the energy storage device of the system. The models are established in PSCAD/EMTDC simulation software to verify the characteristics of distributed power independent operation and the control effect are good,through simulation of separated photovoltaic power generation system, power generation system of small fan, charging and discharging experiment of super capacitor.At last, this paper studies the operation characteristics under different operating conditions of the distributed power supply, when connected in the DC distribution network. The PSCAD/EMTDC simulation software is used to simulate the topology of DC distribution network, which is under conditions of steady state, load mutation and power grid fault. Through simulation, it is proved that distributed power supply can run very well in DC power distribution network; can Coordinate with energy storage devices and grid connected converters; can quickly restore stability under the sudden increasing of DC load and fault condition as well. The simulation results show that the distributed power supply can run stably under different conditions in DC power distribution network... |
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