A Procedure to Determine the Droop Constants of Voltage Controllers Coping with Multiple DG Interactions in Active Distribution Systems

Abstract

In modern distribution systems, the presence of an increasing amount of Distributed Generation (DG) systems causes over-/under-voltage problems, due to the reverse power flows.To face these problems, the voltage-reactive power droop controllers of DG systems are commonly used for their simplicity and are required by international standards. On the other hand, the interaction among voltage droop controllers of different DG systems may introduce instability. The paper presents an effective procedure to determine the droop constants of voltage-reactive power controllers for multiple DG systems. Firstly, a multi-input multi-output model of the distribution system is introduced. Then, using the concept of the interaction measure under decentralized control, a simple constraint is added to the single-input single-output design of each droop controller. Such a constraint guarantees stability with respect to the interaction among the voltage droop controllers of all the DG systems. Eventually, the proposed procedure is applied to an LV test system with 24 nodes and six photovoltaic systems; the results of numerical simulations are presented, giving evidence of the effectiveness of the proposed procedure in various operating conditions of the distribution system.

Decentralized Voltage Control in Active Distribution Systems: Features and Open Issues

“…As a consequence, the controllers performance may result unsatisfactory, while, conversely, the adoption of a separate design without condition (4) may not guarantee overall stability due to the neglected off diagonal transfer functions in the matrix plant. Secondly, condition (4) must be applied assuming the largest value of ||E|| ∞ for all the possible scenarios and operating conditions of the distribution system [67]. Then the estimation of the largest value of ||E|| ∞ may result in an even more conservative condition, especially if the number of DERs increases, as shown in [67].…”

“…Secondly, condition (4) must be applied assuming the largest value of ||E|| ∞ for all the possible scenarios and operating conditions of the distribution system [67]. Then the estimation of the largest value of ||E|| ∞ may result in an even more conservative condition, especially if the number of DERs increases, as shown in [67].…”

On the Use of Robust Techniques in Smart Grid Control

“…Then using robust methods, the design of a suitable controller for each subsystem is designed by minimizing the weighted sensitivity functions and, as a consequence, the effect of subsystems would drop-off. A third approach, developed for input-output models, is proposed in [35] and applied in [36]. Let define P(s) the block diagonal matrix obtained from P(s), see (7).…”