Research On Distributed Power Control And Energy Management Strategy Of DC Microgrid

With the increasingly serious problem of energy shortage, utilization of renewable source becomes a trend in social development. Therefore microgrid technology using distributed power generation systems gets more attention. But the electrical energy that distributed power supply are influenced by the environment greatly, it can’t be used directly. To reduce the negative influence caused by distributed power, and retain its original advantages, the microgrid is put forward.DC microgrid is a controllable system that provides power in DC supply and connects various distributed power generation by a DC bus. It can be connected to AC main grid by an AC/DC converter. Compared with AC microgrid, phase and frequency don’t need to be controlled and fewer converters using in the DC microgrid that make costs lower and improve reliability of the system. Therefore, DC microgrid has more research value.The stability of bus voltage is the important measure for the balance of DC micrigrid. When the microgrid is running, if the change of the bus voltage is very big, the DC/DC converters which connect the distributed sources and the DC bus have much more significant change in the duty cycle in the process of work, which leads to the serious nonlinear problem. To solve the problem, the double closed- loop control structure is adopted. Sliding mode variable structure control based on proportion switching is used for voltage loop and traditional PI is used for control in current loop. The simulation results show that the control schemes effectively improve the robustness of the converter, shorten the transition process, suppress the high frequency chattering and reduce the output voltage fluctuations, in order to meet quality and performance requirements.The generation of d istributed powers are influenced by the environment, and if they grid directly, with gradually increasing penetration of distributed generation, the grid will be impacted which will bring a series of problems and affect the stability of the grid. The traditional solution is that once the grid faces problems, then the distributed powers will be cut off immediately, which severely limits the use of new energy sources. To solve this problem, Grid Controllers are designed for different distributed powers to control them, and put forward hierarchical coordinated control strategy, to make all the power electronic converters can be coordinated to ensure power balance of the DC microgrid. The simulation results show that the DC microgrid can run steadily in different conditions, each of inverters will respond quickly to change based on the bus voltage, so that the stability of the DC microgrid system and the power supply quality are improved.