Power system services have traditionally largely been an inherent by-product of synchronous generators (SGs). These machines provided a naturally bundled service portfolio including physical inertia, short-circuit level, and reactive power support that were relatively independent, abundant and temporally decoupled. Moreover, SGs were typically electrically close to load centres, yielding a relatively homogenous provision of services and a homogeneous response to disturbances. Here, homogeneity denotes not only that nodal frequency and voltage deviations remain within defined stability regions across the grid but that the difference in frequency and voltage between two nodes during a transient is minimized, regardless of the disturbance location. Inverter based resources (IBRs) such as wind and batteries, are rapidly replacing SGs. However, they do not naturally provide services, have temporally coupled dynamics, are heavily influenced by control algorithms and operating points and can add to the need for additional services. As IBR penetration increases, the services landscape is more fragmented and heterogeneous. This creates a complex spatial-temporal challenge for the system service requirements: for example, a specific inverter may deliver fast frequency response yet contribute negligible fault current reducing system strength and creating weak-stability zones that can jeopardise wider system integrity. As a result the grid shifts from inherent homogenous stability to one defined by vulnerability pockets where services are atomised and dependant on the local technology mix. Furthermore, the interplay between system needs and services introduces an added layer of complexity: providing one service (e.g., frequency support) can result in an immediate demand for another (e.g., voltage regulation), and a single system need may require multiple bundled services to be met.

Through heterogeneous deployment of system services, this work synthesizes a uniform system response in IBR grids that matches the resilience of legacy grids. This is achieved by designing a framework for the optimal heterogeneous placement of services, by strategically varying the type and volume of support based on local grid characteristics. The approach centres on three components: One, characterisation and mapping, heterogeneous zones are identified by mapping the local vulnerabilities utilising spatial trajectory sensitivity metrics as a measure for homogeneity in system response. Two, critical cross-service interactions are identified by quantifying service interdependencies utilising the Dynamic Relative Gain Array, determining when satisfying one system need necessitates another and when bundled services are required. Three, spatial optimisation, strategic placement of technology-agnostic service bundles based on the results of the preceding analysis facilitating in the realisation a homogeneous response across the entire grid. The framework, validated on high a IBR penetration network, demonstrates the benefits of heterogeneous service placement in effectively mitigating localized weak-stability regions.