Aditya Shekhar

Series arc extinction in DC microgrids using load side voltage drop detection

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 detection method is proposed. It detects the load side input voltage drop due to the initial electrode specific minimum arc voltage. Only the local input voltage has to be measured and selectivity is given. The arc can be extinguished by shutting down the loads power electronics converter. The proposed method is elaborated through simulation of arc behaviour for constant resistor and constant power loads with input capacitors. First experimental results correspond with the theoretical analysis.

Generic methodology for driving range estimation of electric vehicle with on-road charging

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 developed to estimate the driving range of any EV by defining a set of formulae linearly dependant on vehicle mass, frontal area, IPT system configuration, power level and road coverage area. Driving cycle constants are defined to take into account the variation in the consumption pattern of the EV with the velocity profile.

DC microgrid protection by selective detection of series arcing using load side power electronic devices

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 point of common coupling with a stable voltage dc micro-grid during accidental unplugging. The influence of the variations in the grid parameters on the load capacitor voltage characteristics and the response of the designed detection algorithm is discussed, thereby, offering insight into the maximum voltage drop and rise time with different circuit configurations due to series arc initiation.

Comparison of Hierarchical Control and Distributed Control for Microgrid

Abstract 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 control method adopts hierarchical structure. Each controllable resource is complied with a local controller and the microgrid is managed and optimized by a central supervisor controller. The second control method adopts the distributed structure. Distributed controller of each energy resource can communicate with each other to achieve global goals. This paper discusses the main features of these two methods and provides recommendations on how to choose appropriate control for different types of microgrids. A case study illustrates the performance difference of the two methods from economic point of view.

Experimental design of a series arc load side detection algorithm for DC microgrid protection

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 associated with the intial electrode dependent series arc voltage. The original contribution of this work includes the experimental analysis of response of the arc detection algorithm with different discrete bandpass filter configurations and time constants. Experiments are conducted by generating series arcs for a stable 100V supply and noisy 600V supply with 300 Hz noise. The design requirements like robustness to low frequency grid voltage fluctuations, high frequency switching noise, detection time, and the threshold detection voltage are achieved and the most favourable design choices are highlighted.

Characterization of series arcs in LVdc microgrids

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 multiple times under similar conditions to gain statistical significance. Thereby, insight on percentage occurrence and burn time of initiated series arcs is provided. Load side voltage response is studied to gain insight on the expected peak drop and fall time. This empirical evidence was judged to be a necessary requirement in developing a novel series arc extinguishing method from load side power electronic devices.

Detection of Series Arcs using Load Side Voltage Drop for Protection of Low Voltage DC Systems

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 proposed arc detection algorithm is described along with the structure and time constants of the designed bandpass filter. The operational boundaries of the arc detection algorithm are defined for copper electrodes depending on the set threshold voltage and the system parameters, like grid inductance, resistance and the load capacitance. Further, the detection time and the zone of guaranteed positive detection are depicted. These are validated through test simulations on the state space model of the system. Finally, experimental validation of the proposed scheme is carried out, wherein, a series arc is generated in the dc circuit and the programmed microcontroller provides a real time signal upon detecting the arcing event. The results on variation in detection time with set threshold voltage is also presented experimentally.

Refurbishing existing mvac distribution cables to operate under dc conditions

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 voltage rating based on the temperature dependent electric field is developed. The proposed algorithm can be incorporated in the dc link converters to obtain additional efficiency and capacity gains. Finally, challenges in the presented concept are highlighted.

Green energy based inductive Self-Healing highways of the future

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. Solaroads along the emergency lanes are also investigated. A Dutch highway A12 is considered as a case study and sizing of these energy sources for electric mobility is considered. A grid power demand profile is considered and number of EVs that can be charged hourly is calculated. A preliminary investigation of the combination of IPT and Self-Healing roads is considered in this study.

Power transfer computations for medium voltage AC link by imposing rated current at sending end

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, conductor cross-sectional area and load power factor. The percentage error in transmitted power computation due to simplification by neglecting the cable capacitance is quantified. The merit of the developed theory for future use is highlighted.