DC Microgrid Operation Control Based On Bus Voltage

In recent years,distributed energy technology has developed rapidly,in order to reduce the impact of direct grid connection of distributed energy on power quality,various distributed energy units are usually integrated into micro grid.Since most of the electric energy generated by photovoltaic,fuel cell,energy storage unit and fan is direct current or non-power frequency electricity,compared with AC microgrid,DC microgrid can well accept wind,light and other distributed renewable energy,and effectively reduce multi-stage energy conversion links such as DC/DC and DC/AC.DC bus voltage is the only standard for the internal power balance of dc microgrid system,which is different from the problem of stable frequency and reactive power in ac microgrid.It can effectively reduce cost and control difficulty.In the research process of microgrid,firstly,the photovoltaic,energy storage and other microgrid subsystems are studied and analyzed.On the basis of it,a DC microgrid prototype platform is built,which is mainly composed of photovoltaic curve simulation device,MPPT maximum power tracking device,bidirectional DC /DC device,battery simulator device and bidirectional DC / AC energy storage converter.Secondly,in the process of practice,it is found that with the access of multi-level power electronic equipment,the loss of energy conversion units such as DC/DC,DC/AC can not be ignored.Based on the analysis,it can be seen that the loss and the output voltage of the port converter are closely related to the bus voltage drop,and the minimum loss function is constructed by the loss and voltage difference,which provides a reference for the selection of bus voltage in multi bus structure.The hierarchical coordinated control strategy based on DC bus voltage signal is adopted to maintain the stability of bus voltage,and the application of droop control in DC microgrid is emphatically analyzed.Aiming at the problem of bus voltage drop caused by traditional droop control,an improved control strategy based on voltage compensation is proposed.The power proportional distribution is carried out in combination with SOC state of charge of energy storage unit,and the bus voltage is easy to wave For dynamic and low inertia problems,the control strategy is improved to mine the latent inertia in the microgrid,and the equivalent capacitance is virtualized to enhance the system inertia and improve the stability.Based on MATLAB / Simulink,the DC microgrid model is built,and the improved control strategy is verified by simulation.The results show that the improved droop control strategy can effectively reduce the voltage deviation and maintain the voltage stability of the bus;can reasonably distribute the power proportion between the energy storage units according to the SOC state of charge of the energy storage unit;can provideflexible and adjustable inertia support for the DC microgrid when disturbed,so as to improve the system stability.