Distributed voltage control strategy for LV networks with inverter-interfaced generators

• New grid codes require MV and LV active users to provide reactive power support and participate to the network regulation.
• Participation of both single and three-phase inverter-interfaced DGs for reactive power control is here investigated.
• A current control based procedure for network voltage unbalance correction by three-phase inverters is proposed.
• A similar principle is adopted for an original distributed network regulation strategy, using conservative control variables.
• Simulations on a case study representing a typical Italian LV network demonstrate the validity of the approach.

Low voltage distribution networks are characterized by an ever growing diffusion of single and three phase distributed generators whose unregulated operation may deplete the power quality levels, in particular as regard voltage profiles and unbalances. This issue is at present under discussion by several national and international standardization bodies and the general trend is to require, for the new connections of generators to medium and low voltage grids, their participation to the reactive power network management. In this paper a novel strategy proposes to control the network voltage unbalance suitably for coordinating single and three-phase inverter interfaced embedded generators, concurrently with a local volt/var regulation action as foreseen by the new grid connection requirements. Simulations conducted on case study network representing a typical Italian 4-wire LV distribution system under different load/generation conditions, demonstrate that the coordinated action of single-phase and three-phase inverters may considerably reduce the degree of unbalance thus improving the network power quality levels.