An important way to integrate renewable energy sources into the current electrical system is the hybrid AC/DC grid. To increase power supply efficiency, reliability, and resilience, they integrate the benefits of AC and DC distribution systems. This system is a complex network of distributed energy resources such as solar photovoltaic (PV) systems, wind turbines, fuel cells, batteries, and other energy storage systems, which work together to provide reliable and sustainable power. The advantages of hybrid AC/DC grids over conventional AC grids include lower transmission losses and higher energy efficiency.

Interlinking converters (ILC) manage the power flow between the AC/DC grids. The stability and performance of hybrid AC/DC grids are, therefore, highly dependent on the control of the interlinking converters. While hybrid grids and microgrids have numerous advantages, there are significant unresolved issues regarding how to control and stabilise the uninterrupted power flow between these grids. To tackle these problems, various control strategies have been implemented over time, of which droop-based schemes are predominant. In this research, we are going to focus on such strategies, specifically on the droop-based control strategies of interlinking control for the power flow.

In this research project, various models of an AC/DC grid connected through Interlinking Converters are constructed using MATLAB and MATLAB/Simulink. Droop-based (dual droop and matching) control strategies are implemented in the model with various gains, and the results are compared. A key objective is to gain insight into the behaviour of AC/DC grids and assess how different control strategies for the ILC can affect their performance and stability under varying conditions.

While it is impossible to accurately predict all scenarios, statistical analysis can be used to assess the robustness of network stability to parameter variation and changing conditions. In this thesis, therefore, a Monte-Carlo analysis is conducted on several hybrid AC/DC test systems in order to investigate four issues: the use of grid-forming vs grid-following interlinking converters, the modelling of grid-following phase-locked loops (PLLs), the effect of network topology and interconnectedness on stability and finally, the comparison between matching control vs dual droop. The conclusion presents the key findings of the work and discusses their application to power system design and converter control choices. Verification of the PLL model for a grid-following inverter is crucial for ensuring stability. The choice between a grid-following and a grid-forming ILC depends on grid strength. However, due to the coupling of DC voltage dynamics with AC frequency, GFM ILCs may require a higher stability threshold compared to battery-based GFM converters. Network topology also plays a significant role in stability, with additional interconnections potentially increasing the likelihood of interactions between converters. Matching control is found to be a better choice for grid-forming ILCs compared to dual droop, as the latter can cause destabilizing interactions with other converters and ILCs.