Aditya Shekhar

Verified

Aditya verified their affiliation via an institutional email.

Learn more

Verified

Aditya verified their affiliation via an institutional email.

Learn more

• Dr. ir.
• Assistant Professor at Delft University of Technology

A practical issue faced by today's ac grid is the rapidly growing power demand on its aging infrastructure. One possibility to maximize the capacity of the existing infrastructure is to refurbish the ac links to operate under dc conditions using modular multilevel converters. In this paper, the idea is applied to restructure an actual medium voltag...

While the scientific community recognizes the benefits of DC power transfer, the distribution network operators point out the practical and economic constraints in refurbishing the existing AC network at a medium-voltage level. Some apprehensions like reliability, cost of ownership, and safety in adopting a universal DC distribution may merit consi...

It is anticipated that with the thrust towards use of clean energy resources such as electric vehicles, future distribution grids will face a steep increase in power demand, forcing the utility operators to invest in enhancing the power delivering capacity of the grid infrastructure. It is identified that the critical 5– 20 km medium voltage (MV) u...

Modular Multilevel Converters (MMCs) offer significant advantages in the medium to high-voltage settings. The modular architecture of MMCs allows for redundant submodules (SMs) to improve overall reliability. These redundant SMs can be deployed using various redundancy strategies, such as Load-Sharing Active Redundancy Strategy (LS-ARS), Fixed-Leve...

Targeting a climate-neutral maritime sector drives the adoption of the All-Electric Ship (AES). While AESs can utilize both ac and dc Shipboard Power Systems (SPS), a dc system offers advantages in efficiency, power density, and source synchronization. However, the enhanced network complexity of dc grids combined with the high penetration of power...

High-power flexible dc links employ modular multilevel converters (MMC) for compact active power redirection in medium and high voltage grids. During contingencies, such converters may need to provide an enhanced active power capacity to avoid overload in vulnerable grid locations. This paper achieves this target by using the capacitor voltage ripp...

In this article, we provide a comprehensive review of defect formation at the atomic level in interfaces and gate oxides, focusing on two primary defect types: interface traps and oxide traps. We summarize the current theoretical models and experimental observations related to these intrinsic defects, as they critically impact device performance an...

Identifying faulty lines and their accurate location is key for rapidly restoring distribution systems. This will become a greater challenge as the penetration of power electronics increases, and contingencies are seen across larger areas. This paper proposes a single terminal methodology (i.e., no communication involved) that is robust to variatio...

Power electronics converters are essential for power generation, transmission, and distribution. The modular multilevel converter (MMC) is highly valued for its versatility, high efficiency, and robust control capabilities. Since MMC is composed of many components, its reliability is crucial for maintaining the availability of electrical power syst...

Modular Multilevel Converter (MMC) is favorable for high-power grid-connected power electronic applications to achieve efficient operation. The required number of components significantly increases when higher modularity is introduced for the given voltage level, thus reducing the system reliability. This paper suggests a Mixed Redundancy Strategy...

The rising demand for electric vehicles (EVs) in the face of limited grid capacity encourages the development and implementation of smart charging (SC) algorithms. Experimental validation plays a pivotal role in advancing this field. This paper formulates a hierarchical mixed integer programming (MIP) EV SC algorithm designed for low voltage (LV) d...

Modular multilevel converters are favorable for efficiently operating high-power usages. The required number of components significantly increases when higher modularity is introduced for the given voltage level, thus reducing the system's reliability. This article suggests a mixed redundancy strategy (MRS) that combines the operational concepts us...

In the realm of electric mobility, fast chargers for electric vehicles (EVs) play a critical role in mitigating range anxiety while driving. The converter in these chargers usually has a load profile consisting of a high-current pulse to swiftly recharge the EV battery, followed by a cooling-off phase when the charging process is over. This pattern...

In DC shipboard power systems (DC-SPS), the high penetration of power electronic devices combined with the ship's harsh operating conditions make the system-level reliability a critical design concern. However, the enhanced network structure of a meshed DC grid imposes an intricate relation between component and system functionality, complicating t...

The variability of the output power of distributed renewable energy sources (DRESs) that originate from the fast-changing climatic conditions can negatively affect the grid stability. Therefore, grid operators have incorporated ramp-rate limitations (RRLs) for the injected DRES power in the grid codes. As the DRES penetration levels increase, the m...

Power electronics converters are crucial for power generation, transmission, and distribution. The modular multi-level converter (MMC) is highly valued for its ability to handle high power levels, versatility in reconfiguration, high efficiency through small-capacity submodules (SMs), and robust control capabilities. A failure of a power electronic...

Power electronics converters are crucial for power generation, transmission, and distribution. The modular multilevel converter (MMC) is highly valued for its ability to handle high power levels, versatility in reconfiguration, high efficiency through small-capacity submodules (SMs), and robust control capabilities. A failure of a power electronics...

Modular Multilevel Converters (MMCs) find increasing applications in medium to high-voltage systems. In such systems, reliability-oriented selection of power electronic switches becomes essential because higher modularity implies an increased number of components. The trade-off between the impact of higher modularity on converter reliability is qua...

This paper benchmarks the performance of three practical electric vehicle (EV) charging scheduling methods relative to uncontrolled charging (UNC) in low-voltage (LV) distribution grids. The charging methods compared are the voltage droop method (VDM), price-signal-based method (PSM) and average rate method (ARM). Trade-offs associated with the gri...

Modular Multilevel Converters (MMCs) find increasing applications in medium to high voltage systems. In such systems, reliability-oriented selection of power electronic switches becomes essential because higher modularity implies an increased number of components. The trade-off between this impact of higher modularity on converter reliability is qu...

Power electronics converters will play a crucial role in power grid expansion. Superior advantages offered by MMC make it the most popular candidate amongst various converter topologies. However, due to a large number of components installed within MMC, reliability analysis is an unavoidable task that needs to be carried out to maximize the MMC's a...

Modular Multilevel Converter (MMC) is favorable for high-power grid-connected power electronic applications to achieve efficient operation. The required number of components significantly increases when higher modularity is introduced for the given voltage level, thus reducing the system reliability. This paper suggests a Mixed Redundancy Strategy...

Power electronic converters (PECs) are workhorses of emerging distribution networks. PEC interfaced grids can function as flexible power corridors facilitating compact and efficient energy exchange between distribution generation, load and storage elements. Introducing adequate Reconfigurability, Modularity, and Redundancy (RMR) in such PEC-driven...

In this paper, the impact of EV uncontrolled charging with four levels of EV penetration in overall 21 real low voltage distribution grids in two seasons are analyzed. The employed real grid data is provided by distribution system operators from three European countries: Austria, Germany and the Netherlands. At least six grids in each country were...

Low-voltage direct current (LVdc) systems are a promising technology for systems with a high penetration of renewable sources and storage that operate with bidirectional power flow. In this article, a fundamental building block for LVdc is presented for different applications, such as charge controllers, voltage regulation in street-lighting system...

Future office buildings are expected to be integrated with energy intensive, inherently DC components such as photovoltaic panels (PV), electric vehicles (EV), LED lighting, and battery storage. This paper conceptualizes the interconnection of these components through a 750 V DC nanogrid as against a conventional three-phase 400 V AC system. The fa...

DC links with back to back voltage source converters are usually built alongside the existing medium voltage ac distribution grids for infrastructure reinforcement. The distribution network operators need to run multiple of such parallel ac and dc links between two substations at optimal efficiency. This paper shows that the active power steering c...

Hybrid ac-dc distribution systems with multiple parallel operating ac and dc links are being developed to maximize system capacity during (n-1) contingencies. This paper shows that post-fault reconfigurability between such ac and dc links allows an additional design flexibility of reducing the required substation converter rating to maintain the sa...

Energy transition will inevitably lead to greater electrification. For example, it is anticipated that electrical energy demand will rise by at least 2-3 times by 2050 with increasing share of electric vehicles and heat pumps. This will translate to significant increase in power demand on the existing medium voltage distribution grid, resulting in...

There is an increasing focus on integrating flexible dc links for bulk power routing in medium voltage distribution grids. In such applications, the ac-dc Modular Multilevel Converter (MMC) devised for medium voltage and high-power ratings can be an interesting choice. This paper highlights some less explored design trade-offs arising due to the li...

During the operation of a three line ac link in parallel with a ac-dc-ac link system that employs Back-to-Back (B2B) Medium Voltage Modular Multilevel Converters (MMC), a path for the low frequency zero sequence currents is shown to exist. Apart from causing additional losses, these currents can result in limitations on power capacity. A detailed a...

Flexible dc interlinks can be used for compact and efficient active power redirection by creating a meshed structure in existing radial distribution network. It is shown that with optimal location and sizing of a back-to-back voltage sourced converter based point-to-point dc link connecting two ac buses of the test 33-bus radial distribution system...

Parallel ac-dc reconfigurable link technology can find interesting applications in medium voltage power distribution. A given system can operate in different configurations while maintaining equivalent capacity during (n-1) contingencies using reconfigurability. This paper provides a method for the ideal selection of the link configuration by defin...

An important step in Voltage-Source Modular Mul-tilevel Converter (MMC) design is the selection of adequate semiconductor blocking voltage class. This paper highlights that particularly for grid connected medium voltage applications, the choice of suitable switch blocking voltage class is not so straightforward. The market available switch voltage...

Back-to-back Modular multilevel converters (MMC) for medium voltage dc (MVDC) distribution link applications offer exciting opportunities due to its superior harmonic performance and high efficiency. Based on the steady state equations, it is shown that under specific active and reactive power operation, an increase in dc link voltage can be achiev...

This chapter is a part of the book that highlights the emerging concepts in DC Distribution systems and Microgrids.

Parallel ac-dc reconfigurable link technology can find interesting applications in medium voltage power distribution. A given system can operate in different configurations while maintaining equivalent capacity during (n-1) contingencies. It is proved that within the defined operating boundaries, a parallel ac-dc configuration has higher efficiency...

The role of MVDC links for distribution network expansion is important. The distribution network operators (DNOs) can maximize the power transfer capacity of existing grid infrastructure during (n-1) contingencies using reconfigurable parallel ac-dc architecture. In addition this concept involves a range of efficiency, reliability and economic trad...

Solar road technology provides an opportunity to harvest the vast, albeit dispersed, photovoltaic (PV) energy, while maximizing the land utilization. Deriving experience from the pioneering 70-m solar bike path installed in the Netherlands, this paper highlights the operational challenges and performance parameters using the first-year measured dat...

Development of electric mobility and sustainable energy result in new technologies such as contactless electric vehicle charging and roadway energy harvesting methods, but also self-healing asphalt roads. By combining these technologies a new concept of Future Sustainable Roads for Electric Mobility is created and presented in the paper. This paper...

A scientific consensus is emerging on the benefits of direct current (DC) distribution in medium voltage (MV) power systems of ships and cities. At least 50% space savings and increased power transfer capacity are estimated with enhanced voltage DC operation of electric cables. The goal of this research is to contribute to developing the empirical...

A scientific consensus is emerging on the benefits of dc distribution in medium voltage power systems of ships and cities. At least 50% space savings and increased power transfer capacity are estimated with enhanced voltage dc operation of electric cables. The goal of this research is to contribute to developing the empirical knowledge on the insul...

Localization of series arc faults in dc microgrids is an important requirement to guarantee operational safety and uninterrupted power to end users. In the previous EPE-ECCE proceeding, a theoretical proof was provided for the selective series arc detection using a novel algorithm. In the current paper, the concept is validated by showcasing real t...

This paper provides an empirical study on series arc behavior in low voltage dc microgrids. The response of an R-L-C dc microgrid abstraction towards series arcs is studied experimentally for varying grid inductance, dc voltages, load capacitances and load currents. In order to account for the stochastic nature of arcs, experiments are repeated mul...

Microgrid concept has been widely adopted by power and energy community to boost the resilience and enhance the economics of the energy system. Stability control and economic control are two main factors to enable the reliable and efficient operation of microgrids. This paper presents two different control approaches for microgrids. The first contr...

Low voltage dc distribution grids face issues associated with arc faults, aggravated by the absence of current zero crossing. The focus of this work is to comprehensively develop a method of series arc fault detection at the load side power electronics, based on the electrode dependent initial voltage drop occurring at the arc initiation. The propo...

Need of compact and efficient energy distribution has garnered interest in dc for electric cables in ships and cities. There is a general consensus that a higher dc voltage can be imposed as compared to ac, but a proper quantification and its consequences in terms of lifetime cable performance is an open research question that this study attempts t...

This paper derives the mathematical expressions for computation of the load impedance magnitude, such that rated cable current is imposed at the sending end, with sending end voltage as the reference phasor. Thereby, the variation in maximum power transferred to the receiving end of a medium voltage cable link is described for varying link length,...

Refurbishing existing ac distribution cables to operate under dc conditions can offer several advantages in terms of capacity enhancement, efficiency and flexibility in power and voltage control, among others. In this paper, technical aspects such as insulation ageing, capacity and efficiency enhancement are explored. A novel idea of dynamic cable...

This paper proposes a method to mitigate the problems related to series arcing in low voltage dc (LVdc) micro-grids by performing voltage drop detection using the power electronic device at the load-side. Specifically, the selectivity of the designed series arc detection algorithm is shown for two constant power loads connected in parallel at the p...

This paper deals with a green energy highway in the Netherlands. Here, the development of electric mobility and self- driving cars is introduced. The ideas of wireless power integration with green energy technologies - solar and wind is considered. In case of wind energy, conventional turbines and bladeless vortex are considered as options. Solaroa...

Unplugging of energized loads in dc microgrids can cause safety concerns to users in residential areas. Sustained series arcs are more relevant in dc systems than in ac due to absence of current zero crossing. In this paper, the series arcs are detected from the load side, wherein, the proposed algorithm monitors the drop in load capacitor voltage...

In this paper, a state space model for n-parallel connected dc-dc buck converters is developed, and a predictive current control strategy is derived. A better dynamic response by Eliminating the transient overshoot in the output current is incorporated in the prediction algorithm. Finally, a corrective term for output converter resistance is Introd...

The economic viability of on-road wireless charging of electric vehicles (EVs) strongly depends on the choice of the inductive power transfer (IPT) system configuration (static or dynamic charging), charging power level and the percentage of road coverage of dynamic charging. In this paper, a case study is carried out to determine the expected inve...

One of the first of its kind, a pilot project involving the instalment of solar roads in Krommenie, was successfully implemented by the consortium of the province of North Holland, TNO, Ooms and Imtech. Seen as a living lab for knowledge gathering in this nascent application area, with a potential of widening the proliferation of PV technologies, t...

Advancements in power electronics has sparked the adaptability of dc systems in varied application fields. The phenomenon of electric arcing in such dc systems, arising due to the absence of zero crossing of current during normal operation, has impeded the widespread proliferation of dc-based technologies in the market. Considering the advantages p...

An analytical estimation of driving range of electric vehicles (EVs) with contactless on-road charging system is presented in this paper. Inductive power transfer (IPT) systems with different configurations (static, dynamic), power levels and road coverage have different (and non-linear) impact on the driving range. A generic methodology has been d...

Due to the absence of current zero crossing, dc arcs do not extinguish as easily as ac ones. It is essential to detect and eliminate series arc faults in dc microgrids in order to ensure safety, particularly while unplugging loads. Several detection and extinction methods using various means are known in literature. In this paper a novel arc detect...

Economic viability of on-road charging strongly depends on the choice of inductive power transfer (IPT) system configuration (static or dynamic charging), charging power level and the percentage road coverage of dynamic charging. In this paper, a case study is carried out to determine the expected investment costs involved in installing the on-road...