Decentralized coordination control of PV generators, storage battery, hydrogen production unit and fuel cell in islanded DC microgrid

Abstract

Renewable energy sources (RESs) have been limited to connect to main grid because of their inherent disadvantages such as the fluctuation and intermittence of the output power, the inconsistency with load curve and the impact on the relay protection. Hydrogen production unit (HPU) can address the above issues because it can achieve large-capacity and long-term power absorption, and requires not much of the RESs. In this paper, an adaptive coordination control strategy is proposed in the islanded DC microgrid containing PV generators, storage battery, fuel cell and HPU. As for HPU, the energy conversion efficiency from electric energy to hydrogen energy of HPU is derived and it reveals that there exists a peak value in the efficiency curve. Then an efficiency adaptive control is proposed to adjust the power absorption by regulating the efficiency point based on the dc bus voltage. As for storage battery, the state of charge (SoC) and the instantaneous charging and discharging power of the battery are considered, which can avoid the battery being overused or damaged. As for PV generator, the designed PV controller can adaptively regulate its output power from the maximum power point to the reference power point. As for fuel cell, it is designed that the fuel cell starts to supply power in low-SoC condition with constant power control strategy. Finally, the stability of the coordination control strategy is analyzed based on Nyquist stability criterion and the control effectiveness is verified with simulation and experimental results.