Madi Zholbaryssov with adviser A. Dominguez-Garcia


Figure 37: 9-bus lossless microgrid

In this research, we propose a distributed controller for voltage regulation in islanded ac microgrids with lossy lines and present stability analysis without assuming decoupled operation of the frequency and voltage controllers; the frequency controller achieves the active power load sharing by driving the power ows to a certain manifold, and the voltage controller moves along this manifold and adjusts the voltage magnitudes at the inverter buses to maintain a healthy voltage prole throughout the microgrid,i.e., voltage magnitudes at all buses are within some prescribed limits. Since voltage regulation and reactive power sharing are known to be conflicting objectives, we pursue voltage regulation objective. However, reactive power sharing can be recovered to some extent by tuning a certain parameter in the voltage controller.



Figure 38

Consider a 9-bus microgrid, the topology of which is shown in Fig. 37 Nodes G1, G2, and G3 correspond to inverters, with the remaining nodes corresponding to loads. In Fig. 38, because of the load perturbation at time t = 0:05 s, the voltage at bus 5 drops below the lower limit and that at bus 7 rises above the upper limit, which triggers the proposed voltage controller, and after a certain time, the voltage controller is

Figure 39

able to push the voltage magnitudes at buses 5 and 7 back within their operational limits. Note that in Fig. 3, the secondary frequency controller is able to drive the
active power injections to the desired references while the voltage controller is being executed.