DC microgrid small-signal stability and control: Sufficient stability criterion and stabilizer design

Abstract

The behavior of constant power loads is known to be a potential cause of instability in DC microgrids. This issue is addressed by the DC microgrid stabilizer proposed in this paper. It relies on active stabilization through power electronic control by introducing a virtual positive resistance to counteract the negative incremental resistance of a constant power load. Compared with physical damping resistors, the virtual counterpart does not incur heat losses. It also has no adverse impact on microgrid power sharing nor on voltage regulation. The theoretical foundations for the design of the stabilizer were made possible thanks to the method of DC microgrid modeling and analysis also developed here. To obtain a model of general validity and practical value, the behavioral characteristics of all components connected to DC microgrid buses are mapped onto two elementary categories. With the DC microgrid model then obtained in nonlinear state-space format and subsequent linearization, a sufficient criterion of stability is readily obtained. It gives the rule for tuning the DC microgrid stabilizer. The simulation tests confirmed the validity of the modeling and analysis framework as well as the performance of the stabilizer.