  High penetrations of photovoltaic (PV) systems can cause severe voltage
quality problems in distribution networks. This paper proposes a distributed
control strategy based on the dynamic formation of coalitions to coordinate a
large number of PV inverters for voltage regulation. In this strategy, a
rule-based coalition formation scheme deals with the zonal voltage difference
caused by the uneven integration of PV capacity. Under this scheme, PV
inverters form into separate voltage regulation coalitions autonomously
according to local, neighbor as well as coalition voltage magnitude and
regulation capacity information. To coordinate control within each coalition,
we develop a feedback-based leader-follower consensus algorithm which
eliminates the voltage violations caused by the fast fluctuations of load and
PV generation. This algorithm allocates the required reactive power
contribution among the PV inverters according to their maximum available
capacity to promote an effective and fair use of the overall voltage regulation
capacity. Case studies based on realistic distribution networks and
field-recorded data validate the effectiveness of the proposed control
strategy. Moreover, comparison with a centralized network decomposition-based
scheme shows the flexibility of coalition formation in organizing the
distributed PV inverters. The robustness and generalizability of the proposed
strategy are also demonstrated.
