Autonomous transient power management strategy based on improved droop control for DC microgrid

Most of the renewable energy sources in DC microgrids are intermittent in nature, have a slow dynamic response, and lack a power reserve, resulting in power imbalance and difficulty to supply transient power. To address these problems, implementation of a proper transient power management strategy is a must, so that different nature of power demand can be dealt with by competent energy sources. An improved droop control strategy with DC bus signaling (DBS) is proposed in this paper to obtain autonomous transient power management for an islanded or grid-connected DC microgrid, without the use of central controller and communication networks. Furthermore, the proposed improved droop control splits load power into transient power and steady-state power for SC, battery, and grid. Here, virtual impedance droop, acting as a high pass filter, controls the SC converter and makes SC only supply transient power, while virtual resistor droop, behaving as a low pass filter, regulates the battery converter and grid rectifier to provide steady-state average power in islanded and grid-connected modes of the DC microgrid, respectively. In addition, a smooth shift of the DC microgrid from islanded mode to grid-connected mode is facilitated by DBS. And SoC recovery of battery and SC is achieved, and dynamic restoration of DC bus voltage is also obtained. The operational methods of the proposed control strategy, the system detail design, and the impedance analysis are presented. Then, the efficacy of the proposed method and theoretical analyses are validated by results obtained from PLECS simulation and RT box real-time simulation.