Javad Ebrahimi

Neutral Point Clamped (NPC) converters are widely adopted in high-power wind energy conversion systems due to their ability to handle high voltages with reduced device stress. However, one of the main challenges of NPC topology is the unequal distribution of switching losses, which leads to thermal imbalances and reliability concerns. This paper proposes a modulation scheme for NPC converter in wind power applications, aiming to achieve active thermal control, loss balancing, and capacitor voltage regulation. The key idea is to reconstruct the middle voltage level of each phase through a linear combination of the three available levels, ensuring volt-second balance while reducing neutral-point current. This approach not only equalizes the switching losses among devices but also decreases the RMS current stress on DC-link capacitors, enabling the use of smaller and more cost-effective capacitors. Unlike conventional methods, the proposed scheme maintains its effectiveness across the entire range of modulation indexes, including those typical of low-voltage ride-through (LVRT) conditions in wind turbines. Importantly, all semiconductor devices operate at the same switching frequency, without a significant increase, ensuring equalized loss distribution. Experimental results validate that the applicability of the proposed method over the entire range of modulation indexes.

Hybrid energy storage systems (HESSs), combining batteries and supercapacitors (SCs), have emerged as a promising solution to address the conflicting demands of high energy density, power density, and cycle life in electric vehicles (EVs). This article presents a comprehensive and up-to-date review of power converter topologies and energy management strategies (EMSs) for HESS integration in EVs. First, this article systematically classifies converter architectures into dual-stage, single-stage, and quasi-stage topologies to analyze their operational principles, control flexibility, efficiency, and suitability for modern EV applications. Detailed comparisons of semiactive, fully active, multi-input, and reconfigurable dual-stage converters, as well as advanced single-stage multisource inverter (MSI) configurations along with quasi-single-stage and quasi-dual-stage topologies, are provided. Next, the EMSs applicable to HESSs in EVs are reviewed and categorized into rule-based, optimization-based, machine learning (ML)-based, and hybrid methodologies. Recent advances in ML, particularly reinforcement learning algorithms, are critically examined for their potential in enabling adaptive, model-free energy management under complex and uncertain driving conditions. Comprehensive tables and comparative analyzes highlight the strengths, limitations, and validation methods of leading techniques. Finally, this article identifies key trends, technical challenges, and research gaps, and discusses future research directions to guide the codesign of converter topologies and intelligent EMSs for next-generation EVs.

Parallel operation of inverters is one method to increase power ratings of motor drives for high power applications. This paper proposes a novel variation of Field-Oriented Control for parallel inverters driving AC machines. The proposed strategy is implemented directly in the natural (abc) reference frame and overcomes many issues faced by conventional controllers for parallel motor drives. At the core of this control strategy is a proposed Resonant Proportional Integral (RPI) controller, which uses integrated plant dynamics to achieve the functionality of a second-order Proportional Resonant (PR) controller using only a first-order Proportional Integral (PI) controller. Hence the proposed control strategy is very simple, requiring only an inner first-order RPI controller for the the stator currents, and an outer PI controller for motor speed and maximum torque per ampere (MTPA) operation. A theoretical analysis of the RPI controller is given, which is supported by simulation and experimental results.

Three-phase four-level three-capacitor converter (3P4L3C) employs a single flying capacitor per phase, eliminating redundant switching states. However, this topology presents a significant challenge in capacitor voltage regulation, as conventional modulation techniques, including carrier-based SPWM and SVM, fail to maintain voltage balance. This article proposes a supervised voltage regulation method that dynamically adjusts duty ratios to compensate for capacitor voltage deviations, ensuring stable operation. Beyond regulation, a unified electrothermal lifetime evaluation framework is introduced to quantify how improved regulation impacts capacitor reliability. The framework integrates ripple-spectrum-based ESR loss calculation, hotspot temperature estimation, nonlinear damage accumulation, and Monte Carlo simulation under realistic mission profiles. Simulation and experimental results confirm that the proposed supervised voltage regulation achieves stable capacitor voltage regulation while reducing ripple current and thermal stress. As a result, the 3P4L3C converter demonstrates approximately 20% longer capacitor lifetime compared to the conventional 3P4L6C topology, highlighting the benefit of integrating control and reliability assessment within a single design framework.

Alternate arm converters (AAC) are emerging as one of the most efficient voltage source converter (VSC) topologies in high-voltage direct current (HVDC) systems due to their advantages over conventional modular multilevel converters (MMCs). Compared to conventional MMC, they benefit from fewer number of submodules (SMs), lower capacitance per submodule and DC fault ride-through capability. However, the AAC VSC controller must ensure appropriate regulation of AC currents in both overlap and non-overlap modes while maintaining minimal harmonic distortion. This paper presents an optimized control design method for the half-bridge (HB) AAC VSC using a Fuzzy Logic (FL) controller. The average modeling of multilevel converters is used to reduce computational burden, and the proposed FLC scheme is employed to regulate AC and circulating currents. The performance of the proposed control architecture is evaluated under short and extended overlap operating modes. Sensitivity analysis of the proposed controller against changes in VSC design parameter of overlap period is also investigated to examine the proposed scheme usefulness in different operating conditions. A two-terminal HVDC link using AAC VSC converters is modeled in MATLAB/Simulink and simulation results under different operating conditions are presented to demonstrate the effectiveness of the proposed scheme.

Having single stage conversion and combining different energy sources, hybrid source inverters (HSIs) are recognized as a viable solution for driving electric vehicles (EV). With only one path between each source and motor, efficiency and power density increase in these inverters. For modulation, in the literature, the classic space vector modulation (SVM) technique is employed. Although this modulation is simple, it suffers from high switching frequency, high switching loss, high and uneven thermal distribution between switches. In this article, a new reconstructed vector-based modulation technique for enhanced operation of HSIs is proposed and verified with simulation and experimental prototype. This modulation takes advantage of using reconstructed space vectors, and instead of using only one dc voltage level for each mode, it uses different dc voltage sources to construct the reference voltage, which leads to switching frequency distribution, better thermal junction profile and improved efficiency. These two modulation techniques are compared across various metrics, including junction temperature profile, efficiency, output total harmonic distortion (THD), and switching and conduction losses and significant improvements are demonstrated.

Hybrid energy sources in electric vehicles are a well-established approach to mitigating pollution caused by fossil fuels, thanks to their integration of batteries and ultra-capacitors. While various hybrid source inverters (HSIs) have been introduced in the literature to enable single-stage conversion, further advancements in topology and operation are still achievable. This article proposes a novel HSI structure that utilizes four shared IGBTs across three phases, complemented by a secondary two-level voltage source inverter. Compared to conventional HSIs, the proposed topology reduces the number of switches and eliminates the need for diodes. The shared-switch configuration leads to lower switching and conduction losses, enhancing overall efficiency. In addition to the new topology, a modified space vector modulation technique tailored for HSIs is introduced. This modulation strategy is applied to the proposed topology, and its performance is evaluated across multiple metrics, including junction temperature profile, efficiency, output total harmonic distortion, and switching and conduction losses. The results demonstrate significant performance improvements. Furthermore, both simulation and experimental results are presented to validate the functionality of the proposed topology and modulation scheme.