In recent years, power systems have undergone significant changes in voltage management due to the increasing penetration of renewable energy sources (RES), both at the distribution level, such as rooftop solar panels, and at the sub-transmission level, through large-scale wind and solar farms. The increasing penetration of RES is reducing system inertia and the availability of traditional frequency and voltage regulation resources. As a result, Transmission System Operators (TSOs), including TenneT NL, are increasingly encountering voltage management challenges, including voltage violations and quality degradation, compared to historical conditions.

TenneT NL is actively addressing these challenges by exploring improvements in control schemes, operational procedures, and network reinforcements to support reactive power compensation. In particular, the implementation of automatic secondary voltage control (SVC) strategies is being investigated as a means to maintain voltage stability and optimize reactive power distribution in the evolving grid.

This study presents a systematic review of existing secondary voltage control methodologies and evaluates their applicability to the Dutch grid. The analysis includes both theoretical analysis and case study reviews to identify gaps, assess technical performance, and outline implementation challenges.

Two main types of secondary voltage control are considered: pilot node control and averaged voltage control. While pilot node control is more commonly applied due to its simplicity, lower cost, and faster response, the findings suggest that averaged voltage control offers greater ease of compliance and can more effectively enhance system-wide voltage stability.

This study provides valuable insights for policymakers, grid operators, and system designers aiming to develop robust and adaptive secondary voltage control strategies tailored to the Dutch power system’s evolving needs.