The loads of dc–dc converter (DDC) are mostly constant power loads (CPLs) in dc microgrid. Due to the negative impedance characteristic, CPLs may lead to the nonpassive factor in DDC. Thus, it may result in DDC, not operating reliably at the desired operating point. In this article, a nonlinear controller based on passivity-based stability theory is proposed for the DDC with CPL, which will improve the stability of the converter. Through damping and interconnection injecting, the alternating component passivity-based controller (PBC) is designed to realize the unified control of output voltage and inductor current. It could realize the passivation of alternating component. Furthermore, this controller can solve the problem of traditional PBCs to control inductor current or output voltage only. Moreover, a power observer is adopted, which could fast estimate the variation of the CPL and improve the adaptability of DDC when CPL changes. The proposed controller not only ensures the stability of DDC under large variation of CPL, but also features fast dynamic response with accurate tracking over wide operating range. Finally, the feasibility and effectiveness of the proposed controller are verified by simulation and experimental results.

DC-DC converters with constant power loads are mostly used in DC microgrids. Negative impedance and large disturbances of constant power loads may lead to the instability of DC-DC converters. To address this issue, a nonlinear control strategy consisting of an improved passivity-based controller and nonlinear power observer is proposed in this paper. First, an improved passivity-based controller is designed based on the port-controlled Hamiltonian with dissipation model. By proper damping and interconnection injecting, the fast dynamic response of output voltage and stability of the DC-DC converter is achieved. Second, the constant power load is observed by a nonlinear power observer, which is adopted to estimate the power variation of the constant power load within a small settling time and improve the adaptability of the DC-DC converter under power disturbance. Finally, the simulation and experimental results are presented, which illustrate the proposed control strategy not only ensures the stability of the DC-DC converter under large disturbances, but also can track the desired operating point with low voltage overshoot in no more than 10 milliseconds.

Nowadays distributed energy has been widely developed and applied in various fields, especially in DC micro-grids. However, for many reasons, such as the realization of high voltage and small ripple of output voltage on the DC-bus side in DC micro-grids, Energy Storage System (ESS) is faced with challenges and also opportunities. This paper proposes a novel cascaded modular topology applied to ESS with interleaved control method to solve the problems above. Finally, simulation has been performed on Matlab to validate the effectiveness of the proposed topology, strategy of charging, discharging and interleaved control.