This article implements a real-time digital twin (RTDT) of a 10 kW Dual Active Bridge (DAB)-electrolyzer system. The electrical model of a 10 kW alkaline electrolyzer is presented to understand its I–V characteristics. A sensitivity analysis is performed to assess the impact of various parameters on the electrolyzer’s electrical characteristics. The series inductance, crucial for power transfer within a DAB converter, is examined using PLECS software to study the impact of the electrolyzer load on the peak and RMS currents. Based on this, the value of series inductance is optimized, resulting in a minimum overall RMS current throughout the operating power range. RTDT of the DAB electrolyzer system is developed using an OP4610XG real-time simulator to validate the presented model and simulation parameters. A comparison with the PLECS simulation results shows that the developed RTDT accurately operates within the 10 kW alkaline electrolyzer’s electrical characteristics. Thus, this setup exhibits the potential to evaluate power electronics converter designs without a physical electrolyzer system.

This article presents a detailed procedure for deriving the generalized average model (GAM) of a dual active bridge converter. The proposed model incorporates higher orders of harmonic components to increase accuracy. Moreover, the turn ratio of the high-frequency transformer (N_t) is considered for realistic modeling, which removes the conventional assumption of unity turn ratio. A detailed model of the DAB will ensure an accurate control design. Required mathematical expressions are derived and explained thoroughly, with an example showcasing a GAM model of the DAB converter up to the ninth harmonics. Several GAM models using different harmonic orders (first, third, fifth, seventh, and ninth harmonics) are derived and compared to the PLECS simulation model and a real-time simulation of the DAB converter on the PLECS RT-Box-2. Results show that including up to the ninth harmonics in the proposed model of the DAB converter leads to achieving accurate voltage and current amplitudes that are almost identical to the simulation outputs and even better than the experimental results.

Power electronics converters (PEC) play a crucial role in interfacing renewable energy systems and electrolyzers to ensure a high production yield of green hydrogen. The design of such PEC is not straightforward due to the safety hazards of using multiple electrolyzer stacks and converter modules at industrial levels. Therefore, real-time simulations should be conducted to ensure the converter design satisfies all the requirements before deploying it on-site. This paper presents a real-time digital twin (RTDT) of a 10 kW dual-active bridge converter interfaced with an electrolyzer. OPAL-RT simulator (eHS toolbox) is used for RTDT. Finally, the voltage across the series inductance and current flowing through it are presented for the open-loop operation of DAB.

Electrolysis requires a high DC current at low voltage to produce hydrogen from water. Designing power converters for such a load requirement could be challenging while fulfilling the galvanic isolation needs. Therefore, prior knowledge of the electrolyzer's impact on the converter operation should be needed. In this context, this paper investigates the behavior of the Dual Active Bridge (DAB) converter when utilized for electrolysis. A MATLAB simulation of DAB with a 10 kW alkaline electrolyzer is developed. Several converter parameters, such as the phase shift angle, series inductance, peak and RMS currents, and voltage gain, are analyzed during electrolysis. Distinct operating behavior is observed from the analysis.

When operating a modular multilevel converter (MMC), a margin appears between the arm voltage and sum capacitor voltage corresponding to the power dependent ripple. This margin can be used to enhance the DC link voltage and increase the transfer capacity of an MMC-based distribution link while keeping the submodule (SM) stresses fixed. Consequently, this dynamic enhancement in transfer capacity can be achieved with the same submodule switch and capacitor voltage ratings. Using an arm-level averaged simulation model of a 10MW MMC-based MVDC link, the enhancement concept is verified and shown to be beneficial to a practical link application. Besides, a dependency is discovered between the enhancement limit and the grid-injected reactive power, which defines the basis of the proposed control for dynamic enhanced operation.

Reliable Power Electronic Systems (PES) are vital for enabling energy transition technologies of the future. Power hardware-in-the-Loop (PHIL) test bed can be used to validate such systems cost-effectively and time-efficiently. In general, the Real Time Digital Twin (RTDT) is a virtual representation of the PES and its operating environment that mimics its behavior in real-time to provide adequate flexibility to the test bed. The workflow of alternating between the prototype and twin, for instance, overcomes the dilemma of needing 100 % details (due to fast dynamics), but optimization during design choices requires cheap flexibility. In this paper, some use cases in applications of RTDT-based PHIL test bed such as fault tolerant converters, power electronic interface for green technologies, survivable all-electric ships, mission profile-based reliability testing, protection of multi terminal dc systems and reconfigurable hybrid ac-dc links is discussed. Furthermore, the co-simulation potential of real-time platforms is briefly described.

Electrolysis holds tremendous potential in reducing the carbon footprint and providing energy dense fuels such as methane. Such systems can be integrated with renewable energy systems with the aid of power electronics interfaces. However, this integration is not straight-forward and imposes various converter design challenges. This paper presents the current state-of-the-art electrolyzer systems, and a simple model of an alkaline regenerative stack with four degrees of freedom. To gain insights with regards to limitations/trade-offs, a sensitivity analysis is conducted on this model. Based on these insights, the challenges associated with power electronics converter design for this application have been discussed along with the trade-offs associated with the electrolyser system. Furthermore, the concept of adaptive modularity for efficiency and reliability improvement has been discussed.