Power sharing of parallel operated DC-DC converters using current-limiting droop control

In this paper, a nonlinear current-limiting droop controller is proposed to achieve accurate power sharing among parallel operated DC-DC boost converters in a DC micro-grid application. In particular, the recently developed robust droop controller is adopted and implemented as a dynamic virtual resistance in series with the inductance of each DC-DC boost converter. Opposed to the traditional approaches that use small-signal modeling, the proposed control design takes into account the accurate nonlinear dynamic model of each converter and it is analytically proven that accurate power sharing can be accomplished with an inherent current limitation for each converter independently using input-to-state stability theory. When the load requests more power that exceeds the capacity of the converters, the current-limiting capability of the proposed control method protects the devices by limiting the inductor current of each converter below a given maximum value. Extensive simulation results of two paralleled DC-DC boost converters are presented to verify the power sharing and current-limiting properties of the proposed controller under several changes of the load

Control of DC power distribution system of a hybrid electric aircraft with inherent overcurrent protection

In this paper, a novel nonlinear control scheme for the on-board DC micro-grid of a hybrid electric aircraft is proposed to achieve voltage regulation of the low voltage (LV) bus and power sharing among multiple sources. Considering the accurate nonlinear dynamic model of each DC/DC converter in the DC power distribution system, it is mathematically proven that accurate power sharing can be achieved with an inherent overcurrent limitation for each converter separately via the proposed control design using Lyapunov stability theory. The proposed framework is based on the idea of introducing a constant virtual resistance at the input of each converter and a virtual controllable voltage that can be either positive or negative, leading to a bidirectional power flow. Compared to existing control strategies for on-board DC micro-grid systems, the proposed controller guarantees accurate power sharing, tight voltage regulation and an upper limit of each source's current at all times, including during transient phenomena. Simulation results of the LV dynamics of an aircraft on-board DC micro-grid are presented to verify the proposed controller performance in terms of voltage regulation, power sharing and the overcurrent protection capability

Control of DC power distribution system of a hybrid electric aircraft with inherent overcurrent protection

In this paper, a novel nonlinear control scheme for the on-board DC micro-grid of a hybrid electric aircraft is proposed to achieve voltage regulation of the low voltage (LV) bus and power sharing among multiple sources. Considering the accurate nonlinear dynamic model of each DC/DC converter in the DC power distribution system, it is mathematically proven that accurate power sharing can be achieved with an inherent overcurrent limitation for each converter separately via the proposed control design using Lyapunov stability theory. The proposed framework is based on the idea of introducing a constant virtual resistance at the input of each converter and a virtual controllable voltage that can be either positive or negative, leading to a bidirectional power flow. Compared to existing control strategies for on-board DC micro-grid systems, the proposed controller guarantees accurate power sharing, tight voltage regulation and an upper limit of each source's current at all times, including during transient phenomena. Simulation results of the LV dynamics of an aircraft on-board DC micro-grid are presented to verify the proposed controller performance in terms of voltage regulation, power sharing and the overcurrent protection capability

Analysis of the effect of clock drifts on frequency regulation and power sharing in inverter-based islanded microgrids

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Local hardware clocks in physically distributed computation devices hardly ever agree because clocks drift apart and the drift can be different for each device. This paper analyses the effect that local clock drifts have in the parallel operation of voltage source inverters (VSIs) in islanded microgrids (MG). The state-of-the-art control policies for frequency regulation and active power sharing in VSIs-based MGs are reviewed and selected prototype policies are then re-formulated in terms of clock drifts. Next, steady-state properties for these policies are analyzed. For each of the policies, analytical expressions are developed to provide an exact quantification of the impact that drifts have on frequency and active power equilibrium points. In addition, a closed-loop model that accommodates all the policies is derived, and the stability of the equilibrium points is characterized in terms of the clock drifts. Finally, the implementation of the analyzed policies in a laboratory MG provides experimental results that confirm the theoretical analysis.Peer ReviewedPostprint (author's final draft