An event-trigger two-stage architecture for voltage control in distribution systems

With the increasing penetration of distributed generations (DGs) in distribution systems, new challenges are introduced into voltage control of distribution systems, such as the frequent switching operations of traditional voltage control devices, resulted from rapid voltage fluctuations, and coordination between traditional voltage control devices and fast controllers such as inverters in DGs. In order to solve the challenges above, an event-trigger based two-stage architecture is presented, taking the characteristics of inverters and conventional devices, such as on-load tap-changers (OLTCs) and shunt capacitor banks (CBs), into account. An event-trigger mechanism is designed to make a fast response to large voltage deviations and reduce unnecessary switching operations of traditional devices, compared with periodic methods. The integration of inverter-based voltage control, in the proposed two-stage architecture, can provide a fast and continuous response to voltage deviation. Moreover, as reactive capacities in DGs, determined by inverters, are reserved in global voltage optimization, it can further reduce the switching operations of traditional devices in the following voltage control process. Simulations in a IEEE 33-bus distribution system show that the proposed architecture can ensure a higher voltage quality and reduce the number of switching operations of OLTCs and CBs by the event-trigger mechanism, the integration of inverter-based local voltage control, and the inverter's reserved reactive power capacity in global voltage optimization.