Research On DC-Bus Nanogrid Control Strategy

With the diversification of the new energy generation and the maturity of the power electronic technique, the small-scale smart grid consisting of different functional units has become a new research point. DC-Bus structure has many advantages such as the easier grid-connection way, the higher utilization efficiency and the more stable control method. As a result, DC-Bus structure becomes an ideal choice for the low-voltage and small-scale smart grid.This paper firstly provided a DC-Bus nanogrid structure aiming at the future power supply for smart building and house. From the inner aspect, it consists of the new energy generation unit, the grid-connection unit, the storage unit and the load unit. From the outer aspect, it is the subnet of the upper microgrid. A distributed DC-Bus nanogrid control strategy was provided, based on the voltage droop control and the voltage level control. This control strategy realized the stability of the DC-Bus voltage and the ordered power flow both inside and outside the nanogird. At the same time, with the distributed control strategy, each module can change its mode automatically, which increased the robustness and the expansibility of the modular nanogrid.Also, the detailed design of the grid-connection units had been done using the parallel structure of the T-type three-level converters. The SVPWM modulation method was used, and by adding the regulator factor and the zero-sequence current feedback loop, the voltage-sharing of the DC capacitors and the restraint of the parallel circulating current have been realized.Finally, with the models’ construction through the Matlab Simulink platform and the pertinent simulation, the feasibility and validity of the DC-bus nanogrid control strategy and the other provided methods had all been confirmed.