Integration of Grid Forming Inverter Based Resources in Power Systems

The rising global commitment into zero carbon emissions technologies for the future of energy security has led to increased investment in and adoption of renewable energy sources. This transition characterized by the rapid shift toward distributed energy resources and simultaneous the displacement of fossil fuel based synchronous generation has introduced specific challenges to the signal quality and operational stability of the electric grid.

The wide adoption of inverter-based resources for the integration of renewable energy on to the grid has led to the requirement of incorporating power quality and grid stability features in new smart inverters used in microgrids that connect to the wider power system. Though this is achievable on the large-scale generation of renewable power sources such as photovoltaic (PV) and wind, smaller utility scale distributed energy generation still requires more work.

This thesis presents the end-to-end design, implementation and real time hardware-in-loop (HIL) based simulation of a grid forming inverter capable of ancillary services and fault tolerance in order to maintain the power quality and system stability when integrated into the power grid. The MATLAB/Simulink based software environment, and the OPAL-RT HIL platform was used to implement a 100kW grid-forming inverter which was integrated into and grid connected microgrid to establish the core results of this thesis. The empirical data validated the efficacy of the implemented grid-forming inverter in maintaining transient and steady state stability in islanded and grid connected operational modes. The inverter asset demonstrated precise frequency and voltage regulation within the dynamic boundaries mandated by the New Zealand grid code. Furthermore, the inverter exhibited exceptional fault tolerance by successfully executing low voltage ride through (LVRT) during transient anomalies. Crucially, this structural reliance was achieved at the local inverter interface removing the need for load shedding schemes or the deployment of auxiliary flexible AC transmission system (FACTS) devices, while simultaneously satisfying New Zealand grid compliance and power quality benchmarks through the alignment with IEEE 519-2022 standard for harmonic compliance.

The research provides a blueprint for commercial operators to meet the operation constraints and grid compliance with the high-fidelity modelling of systems to evaluate and benchmark capabilities prior to commissioning of their renewable energy assets onto the power grid.