To utilize electronic power converters for water electrolysis in industrial electrical networks, reliable testing methods are required to ensure safe control operation as malfunctions can instigate hydrogen explosion and fierce electrical hazards. In this thesis, Digital Twin modeling via OPAL-RT software and hardware is compared to Simulink and PLECS simulation methods by creating the same power-to-power hydrogen network for all three with a Dual Active Bridge, a Medium Voltage DC grid, and an Alkaline electrolyzer whilst utilizing PI control via single phase shift modulation.

The Digital Twin model showed great control tuneability, while the PLECS model showed superior control performance, modeling complexity, error occurrence, and time-based performance for the designed specifications. It was concluded that the Digital Twin model needs to be developed further or reassessed
to outperform the other modeling methods. The recommendations made included re-evaluating the OPAL-RT Digital Twin results for different signal measurement methods and validating the OPAL-RT Digital Twin’s performance by comparing the results with other Digital Twin brands. Future work suggestions included creating a hardware-in-the-loop system and expanding on the current network design to include all components of a power-to-power hydrogen network.

With the increasing appearance of DC loads and DC sources in the MVAC distribution grids, the need for DC power systems is getting more and more pronounced. As a result, the MMC has become a promising and innovative technology that can serve as the interface between a DC and AC network. The MMC-based MVDC distribution link is one of the solutions to incorporate DC in power grids. This link consists of two back-to-back configured MMCs connecting two possibly asynchronous AC networks. Generally, an MVDC distribution link is operated at a fixed rated DC voltage set through the MMC. This work explores the possibility of enhancing the DC link voltage beyond the nominal value to improve the power transfer capacity of the distribution link. The enhancement is achieved while preserving the average energy stored in the MMC and maintaining the AC-side harmonic performance.
First, a control strategy was developed that qualified for the static operation of back-to-back configured MMCs. This control strategy was designed using multiple sub-control modules, each regulating one or multiple circuit quantities using a closed-loop PI or PR control strategy. Second, the analytical limitation to the DC link voltage enhancement was determined. This provided the enhancement boundary expression, which revealed the dependence between the enhancement limit and the grid-injected reactive power. Third, the MMC control strategy was adapted to dynamically incorporate the DC link voltage enhancement. This was performed using the open-loop DC link voltage control, which dynamically enhanced the link voltage by using the reactive power input reference. The controller is realised using a finite state machine that provides an event-driven control system with conditional state transitions. Simulations verified the performance of this controller. Finally, the dynamic DC link voltage controller is implemented for a lab-scale MMC and optimally tuned using the MO tuning method. This is to provide experimental verification of the DC link voltage enhancement. Three experiments were performed to: demonstrate the workings of the enhancement concept, verify the analytical enhancement boundary expression, and show the performance of the dynamic DC link voltage controller. The experiments concluded that the open-loop dynamic control successfully achieved the DC link voltage enhancement and limited the grid injection of harmonic elements during system transients.
So it is concluded that the power transfer capacity of an MMC-based MVDC distribution link can be enhanced by applying dynamic DC link voltage control. This while operating with the same submodule stresses and preserving the AC-side harmonic performance. When the DC current of the distribution link is fixed at the rated value, the power transfer capacity of the link increases linearly with the controller enhancement function. For system transients, the dynamic controller uses smart control logic to avoid harmonic element injection. Combined, this concludes that the dynamic DC link voltage control achieves a proper DC link capacity enhancement that meets the requirements for both steady state and dynamic conditions.