Ahmed Abdelhakim

Split source inverters (SSIs) have gained attention as potential alternatives to conventional two-stage systems in applications that require integrating a dc source into an inverter powertrain via a step-up operation such as in fuel cell-powered systems. By incorporating the voltage boost functionality directly into the inverter, SSIs eliminate the additional dc–dc stage which typically consists of semiconductor devices subjected to high current and/or voltage stresses. However, the conventional variant of the topology suffers from poor utilization of the dc-bus voltage and constraints over the dc voltage gain limiting its use in various applications. In this work, a novel variant of the converter $-$ buck-boost split source inverter (BSI), is introduced which improves the dc-bus utilization by modifying the conventional circuitry and enables control of power injection from multiple dc sources. Furthermore, the modification provides an extra degree of freedom allowing a larger variation of the voltage gain, which can be beneficial in applications requiring different voltage levels (e.g., with different fuel cell types). In this study, the operation of the topology is analyzed, and suitable modulation methods for the converter are developed analytically and validated through PLECS simulations. Finally, a SiC-based experimental prototype is designed and tested to validate the performance of the proposed converter.

Hydrogen has emerged as a pivotal resource in reshaping the global energy landscape and the transition toward a sustainable and carbon-neutral future, especially for hard-to-abate sectors. Two sides of this resource are explored. The first side is related to hydrogen production, while the second side is related to hydrogen utilization. Several methods can be employed in order to produce hydrogen, where water electrolysis is regarded as the most effective method in terms of minimal carbon dioxide (CO₂) emissions, particularly when powered by renewable energy sources. A critical aspect of this rapidly evolving technology is the utilized power supply with the electrolyzer, which is tasked with handling unregulated dc voltage efficiently at megawatt-scale power levels. On the flip side, hydrogen can be used directly as a feedstock in some applications, used with internal combustion engines (ICEs) to convert the stored chemical energy into mechanical output, or with fuel cells to convert the chemical energy into electrical energy, where power electronics are mandatory with the latter to control the flow of this energy and benefit from reduced noise and vibrations. Collectively, these electrified hydrogen systems represent remarkable possibilities and opportunities and present a unique set of challenges in terms of the risks associated with hydrogen along with the optimization of the surrounding power electronics technology, which is a key enabler for enhanced system performance and reduced capital cost and, potentially, a lower total cost of ownership. To accelerate this transition and promote the electrification of hydrogen systems, this article provides a comprehensive overview of the entire value chain of electrified hydrogen systems, focusing on the challenges and opportunities in hydrogen production, storage, and utilization and the provision for improvements in existing electric power trains.

Single-stage inverters, such as the proposed differentially structured flyback inverter (DSFI) offer many features including reduced component count, voltage step-up/down capability, minimized cost and footprint, as well as high power density operation. Differential-type inverters comprises three DC-DC converters that are linked in-parallel at the input side and differentially from the grid-side. These strutcures are commonly modulated using continuous modulation schemes (CMSs) for simpler operation and low-order harmonic suppression. In the CMS, the three DC-DC modules are activated for whole operating period, which increases the circulating power between the flyback modules and adversely affects the inverter efficiency. Therefore, this paper applies the discontinuous modulation scheme (DMS) scheme for single-stage three-phase DSFI and provides a comprehensive evaluation of the three-phase DSFI under CMS and DMS schemes. In addition, a simple single-pole selective harmonic compensation (SHC) loop is utilized for second-order harmonic compensation. The CMS reduces the low-order harmonic components in the grid currents; however, the voltage stress across the inverter different components is increased with increased circulating power. On the other hand, the proposed DMS reduces the voltage stress across the different components and reduces the circulating power between the inverter’s modules, resulting in an enhanced system efficiency as a consequence. The proposed DSFI system is experimentally validated under CMS and DMS based on a 1.6 kW prototype in grid connected mode.

This article proposes a framework for stability analysis of hydrogen fuel cell-based hybrid power systems (HPS) for zero-emission propulsion. An analytical model is developed and a comprehensive modal analysis is performed to address the HPS dynamic interactions. Sensitivity analysis assesses the impact of operating conditions, control parameters of the governor and converter controllers, and different control strategies. The case studies focus on how the parameters of the HPS state variables are coupled with the HPS modes through participation factors (PFs), thereby emphasizing which system state participates in determining the system’s dynamics. The modal analysis characterizes the influence of control parameters on poorly damped modes, and enables expanding the stable operating region of the HPS by appropriate control parameter selection. The results indicate a notable impact of the voltage control loop parameters on the system stability, a strong coupling between the subsystems’ current state variables and dc bus voltage dynamics, and a strong coupling between the governor dynamics and the FC current state. Additionally, the study demonstrates a PF of 0.9 between the dc bus voltage and the HPS’s critical modes within 15% deviation by changes in the voltage controller’s proportional gain. Finally, analytical analysis and time-domain simulations are validated with a real-time hardware-in-the-loop (HIL) test setup.

The all-electric ship (AES) with DC-grid configuration has demonstrated advantages compared to the traditional AC system and has become the state-of-the-art for ships with electric propulsion in the low to medium power range during the past decade. However, the integration with different power sources, such as fuel cells, batteries and diesel gen-sets, increases the system complexity and requires an advanced power management system (PMS) to handle vessel operation and to achieve optimal power control. This paper presents an optimized power management strategy to reduce the total cost of ownership of such vessels, considering not only the fuel cost and emission penalty, but also the power device degradation and equipment replacement cost. In this study, Model Predictive Control (MPC) and Reinforcement Learning (RL)-based PMS control methods are approached respectively. In order to demonstrate the performance of MPC and RL techniques, a typical tugboat load profile is simulated. The testing results are also compared with a traditional rule-based power management control.

Compact and efficient power converter solutions are seen to be the backbone of future transportation systems in order to cope with the ongoing transition toward greener systems. Such systems usually comprise a main load section, in which one or more propulsion or traction motors are connected, in addition to an auxiliary load, which might comprise the hotels and air conditioning for example. This auxiliary load can be as low as 5–10% of the main load power. Therefore, it can be challenging to drive this power from a typical high-power system that employs a medium-voltage (MV) dc (MVDC) grid, which is typical in high-power systems. In such MVDC-integrated systems, neutral-point-clamped and active neutral-point-clamped (ANPC) converters are commonly used, where the auxiliary load converter is overrated in this case, resulting in a bulky and inefficient power system. Thus, in order to enable a lighter and efficient transportation power system, a multiport hybrid converter (MHC) is presented in this article. This converter can feed the main MV motor, in addition to two auxiliary low-voltage loads. Compared with the state-of-the-art ANPC converter, the proposed MHC utilizes only two extra switches per phase leg in order to achieve this multiport operation along with increasing the voltage rating of another two switches. The proposed MHC is analyzed in this article, where its operation, modulation, and mathematical derivation are presented. These analyses are supported by simulation and experimental results utilizing a reduced-scale 5-kW system.

Environmentally driven regulations are significantly affecting shipping in recent years, where the shipbuilding industry is required to comply with upcoming restrictions concerning polluting emissions. The all-electric ship (AES) is one of the most promising technologies for complying with the increasingly strict environmental regulations, improving fuel efficiency, and enhancing system dynamic performance. In this study, the dc-distributed power grid of an AES integrated with fuel cells and batteries has been configured using extensive electrification technology, where the system-level shipboard power plant has been modeled with the average modeling method. The model not only incorporates the hybrid power source integration but also the primary and secondary power management as a whole. In addition, a hardware-in-the-loop (HIL) has been set up to replicate the real-time system behavior, which is essential for the verification of any optimal power management control algorithms to be developed in future work. Finally, both the mathematical and real-time models are validated against the full-scale hybrid shipboard power system.

Transportation electrification is undergoing a significant transition toward the utilization of efficient and reliable energy sources and smart integration schemes, where this transitioning is continuously facing ever-tightening challenges in order to comply with the increased environmental regulations. Among the different means of transportation, global maritime transport is responsible for 2%–3% of global greenhouse gas (GHG) emissions, and it is predicted to increase to 17% by 2050 if no changes are adapted. Hence, the international maritime organization (IMO) has targeted to reach a 50% reduction in GHG emissions by 2050 compared to 2008. Hence, alternative energy sources shall be utilized in order to meet these strict GHG emissions reduction targets, where battery- and hydrogen-fed fuel cells can play a vital role in such aspects. Since the output of these two energy sources is unregulated dc voltage, their connection to the whole ship power system can be accomplished in several ways, where each way has its features, in addition to utilizing different power conditioning stages (PCSs), and these features are not well clarified and compared in the literature. Hence, this article presents an overview of the possible integration schemes that can be utilized in fuel cell- and battery-fed vessels, which is supported with a comparative assessment. This is also presented along with highlighting the state-of-the-art PCSs that are available in the market and can be utilized in these integration schemes within marine vessels. Such overview and comparative assessment are seen to be of significant importance and added value for researchers and developers in both the academic and industrial sides in order to accelerate the adoption of fuel cells in marine systems for zero-emission shipping.

To satisfy the ever-increasing requirement from load-side and improve the power quality, the paralleled converters structure is seen to be an interesting solution for such purpose. However, paralleled converters suffer from a major challenge related to the excessive circulating currents due to the difference in the induced CMV in each converter. This voltage difference is due to the instantaneous potential difference between paralleled phase-legs. Consequently, ZSCC as well as DMCC shall appear between the paralleled converters. In this context, this paper utilizes the interleaved PWM concept for the ZSCC and DMCC reduction in paralleled SSIs, where this SSI is a single-stage dc-ac converter and the prior mentioned operation and associated issues have never been investigated yet. This paper describes the three-phase SSI structure and its basic operation, and shows the corresponding CMV waveform. Then, based on the shown analysis, an interleaved DPWM strategy is proposed to restrain the CMV amplitude and reduce the induced circulating currents. Furthermore, the effect of changing the modulation index and interleaving angle on the overall converter behavior has also been evaluated in case of using SSI. The analysis and simulations revealed the effectiveness of the proposed modulation strategy compared to counterparts. Finally, the shown simulation results are validated experimentally.