Investigation into the impact of wind generation on the inter-area and local oscillation modes of power systems

Abstract

The operation and dynamic characteristics of power system grids with mixed generation technologies in particular synchronous generators and wind turbine generators are receiving great attention towards the better understanding of the modern power system stability. Wind power generation introduces new types of non-conventional generators that are being operated in parallel with conventional generation. However, as the penetration of wind energy increases, the power system dynamics and behaviour are modified. It is thus important to understand and quantify the impact of wind energy technologies on the performance of the interconnected power systems. The investigation in this dissertation focuses on the impact of wind power generation on the power system small-signal stability. The focus is on the variable speed Type 4 Wind Turbine Generators (WTGs) and the Wind Power Plants (WPPs) impact on the inter-area and local oscillation modes of the power systems. An aggregated WPP model based on the generic IEC 61400-27-1 (2015) Type 4 WTG of varying capacities was used in this investigation together with a multi-machine small-scale power system comprising conventional synchronous generators and their associated controls. The Power System Stabilizer (PSS), an additional generator control, is widely used to resolve the power system small-signal stability problems by providing additional damping to the inter-area and local oscillation modes. This investigation considered the impact of wind power on the inter-area and local oscillation modes without and with PSSs installed on the synchronous generators. The procedure involved employing small-signal stability analysis through eigenvalue analysis and tracking the oscillation modes after the integration of wind power generation sources. The investigation has shown that the introduction of wind power in parallel with synchronous generators alter the generator operating conditions and the power flows causing the inter-area and local oscillation mode characteristics to change. As the wind power penetration increases, the inter-area and local mode frequencies decrease. The decrease in frequencies has been attributed to the change in the operating conditions of synchronous generators when operated in parallel with wind turbine generators. It was further found that wind power can have negative or positive impact on the damping of inter-area and local modes. However, for the particular case studies examined, this investigation suggests that PSSs already installed in the absences of wind power generation sources do not require retuning. The work recommends that power system small-signal stability requirements in the presence of wind power should be investigated as this is a unique characteristic for a given network.