Optimum Voltage Droop Control in Transmission Systems to Support the Local Voltage Stability with High Share of RES

Abstract

Controlling the voltage profile in transmission systems with a high share of Renewable Energy Sources (RES) is becoming a challenge especially in areas where the presence of RES connected to (Very High Voltage) VHV substations is high. In fact, the local management of the reactive power of each wind power plant connected to a VHV/HV substation should be coordinated not only at the Point of Interconnection through tap regulation, amid others, but also at the individual wind power plant and photovoltaic plant. Based on a real case study in the Portuguese national transmission system, this paper presents the advantage of applying a voltage droop control strategy to avoid conflictual set-point for each wind power plant or photovoltaic plant. Different scenarios, both topological and operational, will be analyzed and developed in order to come up with a robust voltage droop control strategy that mitigates voltage fluctuations at the point of interconnection (POI) by fully utilizing the voltage regulation capability of each Wind Power Plant and photovoltaic plant. The main aim is to ensure that with the implemented control strategy the voltage stays within its steady-state limits in all performed scenarios.