Self-disciplined stabilization of DC microgrids by passivity-based control

DC microgrids may have time-varying system structures and operation patterns due to the flexibility and uncertainty of microsources. This feature poses a challenge to conventional stability analysis methods, which are based on fixed and complete system models. To solve this problem, the concept of self-disciplined stabilization is introduced in this paper. A common stability discipline is established using the passivity-based control theory, which ensures that the microgrid is always stable as long as this discipline is complied with by each individual converter. In this way, the stabilization task is localized to avoid investigating the entire microgrid, thereby providing immunity against system variations. Moreover, a passivity margin criterion is proposed to further enhance the stability margin of the self-disciplined control. The modified criterion imposes a tighter phase restriction to provide explicit phase margins and prevent under-damped transient oscillations. In line with this criterion, a practical control algorithm is also derived, which increases the converter´s passivity through voltage feed forward. The major theoretical conclusions are verified by a laboratory DC microgrid test bench.