  High penetration of photovoltaic (PV) generators can lead to voltage issues
in distribution networks. Various approaches including the real power control
through PV inverters have been proposed to address voltage issues. However,
among different control strategies, communication delays are inevitably
involved and they need to be carefully considered in the control loop. Those
delays can significantly deteriorate the system performance with undesired
voltage quality, and may also cause system instability. In this paper,
according to the inverter based active power control strategy, a linearized
state space model with communication delay is presented. A delay dependent
stability criterion using linear matrix inequality (LMI) approach is used to
rigorously obtain the delay margins based on different system parameters. The
method can handle multiple PVs in the distribution network as well.
