Abstract
This paper aims to present a robust passivity-based control (PBC) strategy to solve the instability problem caused by the constant power loads (CPLs) in dc microgrid systems. This strategy is designed to stabilize and regulate the dc-bus voltage of the dc microgrid and to eliminate the dc-bus voltage deviations caused by the system disturbances such as load and input voltage variations. To this end, the control robustness of the PBC strategy is improved by adding the nonlinear disturbance observer (NDO). Whereas, the PBC is applied to damp the system oscillation caused by the CPLs and to ensure that each parallel subsystem in dc microgrid is passive (stable). Based on estimation technique, the NDO works in parallel with the PBC strategy to compensate the system disturbances through a feed-forward compensation channels. Furthermore, the PBC strategy provides self-( I-V ) droop characteristics, which able to eliminate the voltage mismatch between the parallel converters and obtain equal current sharing between them. This control strategy ensures large-signal stability, globally asymptotically stabilization and reacts extremely fast against system disturbances as compared with other PBC strategies. The MATLAB simulation and hardware-in-loop (HIL) experimental results are presented to verify the control robustness of the proposed controller.
Highlights
With the development of the dc-distributed generation (DG) systems based on the renewable resources and fast growing of dc loads, the dc microgrids are becoming an effective alternative networks compared with the traditional ac-networks [1]–[3]
This paper aims to achieve the following three targets: (i) Stabilize and regulate the DC-bus voltage of the DC microgrid using passivity-based control (PBC) strategy, (ii) By combining the nonlinear disturbance observer (NDO) to work in parallel with the PBC strategy, this paper aims to eliminate the steady-state error caused by the system disturbances such as load and input voltage variations, and (iii) Eliminate the voltage mismatch between the parallel connected converters in DC microgrid using the self I-V droop control property of the PBC strategy
The main feature provided by the PBC is that it has self-(I-V) droop characteristic which able to reshape the energy across output terminals of the parallel-connected dc-dc power converter through additional of virtual resistances
Summary
With the development of the dc-distributed generation (DG) systems based on the renewable resources and fast growing of dc loads, the dc microgrids are becoming an effective alternative networks compared with the traditional ac-networks [1]–[3]. This controller is presented to ensure both voltage regulation and equal current sharing between the parallel buck power converters locally without any communication. The main feature provided by the PBC is that it has self-(I-V) droop characteristic which able to reshape the energy across output terminals of the parallel-connected dc-dc power converter through additional of virtual resistances This virtual gain can eliminate the voltage mismatch between the parallel-connected converters through the control of the reference currents and equal current sharing to the CPL. The overall energy balance of the dc-microgrid is always positive
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