Hybrid Voltage Control in Distribution Networks Under Limited Communication Rates

Voltage regulation in distribution networks is challenged by increasing penetration of distributed energy resources (DERs). Thanks to advancement in power electronics, DERs can be leveraged to regulate the grid voltage by quickly changing their reactive power outputs. This paper develops a hybrid voltage control (HVC) strategy that can seamlessly integrate both local and distributed designs to effectively coordinate the network-wide DERs. By minimizing a special voltage mismatch objective, we achieve the proposed HVC design by adopting partial primal-dual gradient updates that can allow for a distributed and online implementation. The proposed HVC design improves over existing distributed approaches by reliably integrating local voltage feedback. As a result, it can dynamically adapt to varying system operating conditions while being fully cognizant of the instantaneous availability of communication links. Under the worst-case scenario of total link outages, the proposed design naturally boils down to a surrogate local control implementation. Numerical tests on realistic feeder cases have been made to corroborate our analytical results and demonstrate the algorithmic performance.