This research paper discusses the reliability analysis of Direct Current (DC) Electric Vehicle (EV) charging stations, focusing on their crucial role in advancing sustainable transportation. Utilizing Continuous Markov Processes, the methodology assesses the dependability of key components in DC charging systems, such as inverters, resonant circuits, transformers, and rectifiers. Real-world operational data and failure rates derived from MIL-HDBK-217 are employed for analysis, and the study utilizes the Markov process to model the system’s dynamic behavior, presenting results that affirm the high reliability (0.9993) of the DC charging infrastructure over a ten-year period. The impact of different Mean Time to Repair (MTTR) on system reliability is considered. The reliability analysis is conducted using dedicated software designed for Markov modeling and system reliability assessment.

In this study, we utilize a Nonlinear Auto-Regressive Exogenous (NARX) observer to estimate voltage and current states within an islanded DC microgrid across normal, load change, and attack scenarios. We implement a distributed cooperative control mechanism to synchronize distributed generation (DG) units for proportional load distribution. Specifically, we introduce a false data injection (FDI) attack to compromise control functions and system stability by intercepting sensor data or communication flows. Detecting such attacks is imperative for system resilience. Additionally, we compare Support Vector Machine (SVM), Neural Network (NN), and NARX methods to assess their estimation capabilities, finding that NARX outperforms in both estimation and attack detection. This study involves the initial operation of the DC microgrid under normal conditions, generating a dataset for training neural networks. This dataset incorporates load variations, enabling the distinction between load changes and potential cyber-attacks. Trained networks are subsequently applied in real-time to estimate the voltages and currents of Distributed Energy Resources (DER) units, allowing for the detection of cyber-attacks based on estimation errors. The efficacy of our approach is verified through MATLAB simulations and real-time validation using the OPAL-RT platform.

This study presents an active defense mechanism aimed at identifying cyber-attacks on an Islanded DC microgrid utilizing distributed consensus control. The proposed mechanism involves injecting a unique random signal, termed as a "watermark," into the control inputs of the system. This watermark signal is demonstrated to propagate through the actuator, converter, and microgrid components, thus becoming evident in all measurement data used for system control. The proposed method uses the gathered data to create a system identification model, which includes a constant system matrix for representing the system in state-space form, enabling accurate estimation of future states.Under normal operating conditions, the properties of the watermark signal remain unchanged, while they are altered during attack scenarios. Subsequently, two statistical sequence tests are employed to accurately detect cyber-attacks. This approach effectively detects any malicious manipulation of measurement data, such as false data injection or record and replay attacks, perpetrated by malicious actors seeking to gain control of the microgrid or disrupt its operations, potentially leading to significant grid damage.The robustness of the proposed active defense mechanism is verified through validation with various attack scenarios in the MATLAB environment.

This article introduces a data-driven approach to assessing failure mechanisms and reliability degradation in outdoor photovoltaic (PV) string inverters. The manufacturer's stated PV inverter lifetime can vary due to the impact of operating site conditions. To address limitations in degradation estimation through accelerated testing, condition monitoring, or degradation modeling, we propose a machine learning (ML) oriented approach. Utilizing data from a 1.4 MW PV power plant operational since 2016, with 46 string PV inverters tied to the grid, we employ the unsupervised one-class support vector machine ML technique to analyze inverter and sensor data, capable of classifying humidity cycling and temperature fluctuations as dominant failure mechanisms. Utilizing the anomaly alert relationship and alert details specific to the inverter, the level of PV inverter output is considered as its availability or available reliability. Subsequently, a continuous Markov model is applied to six-month alert data, revealing an average stated reliability of 20% after 20 years of continuous operation. These results support recommendations for time-bound preventive measures to enhance PV inverter reliability under diverse outdoor conditions. The approach provides a nondestructive, top–down, and generalized method for analyzing any commercial PV inverter exposed to outdoor conditions, contingent on the availability of relevant data.

This paper presents an improved single-stage, non-isolated dc to dc boost converter with a high voltage gain, and low voltage stress across the switch. The main features of the proposed converter are that it has a voltage gain four times the gain of the conventional boost converter and low voltage stress across switching devices. Two output ports are available which reduces stress on output capacitors. It employs two switches but uses the same gate pluses so control is easy. Other features include the continuous input current which makes it very useful for renewable energy applications. It does not require coupled inductor which makes it less costly. The proposed topology is compared with other existing boost topologies on the grounds of their gain, switch voltage stress, and the number of elements. The steady-state analysis is done in detail. A prototype of the proposed converter is developed in the lab for practical validation of theoretical results.

In the existing power system architecture of military aircraft (such as F-35), electrical loads are fed from two 270V-HVDC buses. These two HVDC buses are completely isolated from each other. In existing architecture, there is no possibility of power transfer between the two buses. This inability reflects as overdesigning of the system to meet the dynamic loads and possible power quality deterioration during operation (occurring due to unequal loading of the two HVDC buses). This paper attempts to address this inability by introducing the concept of dynamic power balancing between the buses. As military aircraft design criteria are sensitive to weight and size, the introduction of the proposed feature must not add additional weight to the system. To ensure this, the authors have studied the existing architecture and have attempted to replace the two 270V to 28V Dual-Active Bridge (DAB) converter (used for charging the 28V battery) with the proposed Triple-Active Bridge (TAB) converter. This converter must be capable of achieving power balancing in addition to the conventional 28V battery charging operation. To achieve this, a modulation strategy to achieve bidirectional power flow and soft-switching is also discussed. Simulation results verifying the feasibility of the proposed converter and control are also presented.

This paper focusses on three phase Cascaded H bridge Multi-level Inverter (MLI) topology fed by solar Photovoltaic (PV) module. For maintaining maximum power as well as constant voltage for MLI, Perturb and Observe (P&O) technique is applied. Sine Pulse Width Modulation (SPWM) is implemented along with unipolar and bipolar switching scheme. Performance parameters like Total Harmonic Distortion (THD), switching loss, switching stress, Root Mean Square (RMS) fundamental voltage and efficiency of MLI output voltage is calculated and graphically compared for both unipolar as well as bipolar schemes. It is found that unipolar scheme outperforms bipolar scheme in all parameters and hence is better than the later. The control algorithm is also validated in Hardware-in-the-Loop using Typhoon HIL 402 emulator and results are presented and discussed.

The multilevel converters (MLC) are utilized from less switching loss point of view from low, medium to high power applications. The paper discuss, about the SPV grid tied applications by using neutral point clamped (NPC) converter. Power quality is the major attribute by getting the system worked in closed loop control . Neutral point voltage fluctuations are kept within limit with the help of controller. Power flow from DC to AC grid side is investigated for unity power factor correction. PV is fed to the grid for three phase applications and promising results gives the validation for the system performance.

This paper presents Third Harmonic Operation (THO) of Current Fed Parallel Resonant Push-pull Inverter (CFPRPI) for Inductive Power Transfer (IPT) systems. THO is proposed for CFPRPI to achieve higher voltage ratio with lower switching frequency, which is essential for low input voltage IPT systems. The IPT system is considered based on PS compensation method, i.e. parallel compensation for the primary side and series compensation for the secondary side. Moreover, a phase-shift control method is presented based self-oscillating tuning loop for output voltage or power regulations. The tuning loop and IPT system are modeled and formulated in THO mode. To verify the validity of the proposed method, a laboratory prototype with resonant frequency of about 120 kHz and maximum output power of about 50 W has been implemented.

Due to the surge in the renewable energy and distributed power source in the electric grid and with the increase in demand of the electric traction system, much research on power quality improvement in the grid has been seen in the last few years. The conventional transformer which has been used for very long years becomes inefficacious for voltage, current, and frequency control. Furthermore, we cannot integrate dc supply, bulky as well as heavy due to low-frequency operation and have other limitations. It can be bridled by using solid-state transformer which has been named in the top 10 prominent technologies by MIT in 2010 for upcoming years. Global Solid State Transformers Market has estimated the compound annual growth rate of the Solid-state transformer to be around appealing 24.75 % during 2016-2023. This paper presents the analysis of the dual transformer-based dual active bridge for solid-state transformer in the distribution system.

Torque pulsations and harmonics are the problems in the three phase system drives systems. But, in higher phase system, smooth operation of the machines with greater power capacity takes place. Many applications like electric traction, more electric aircraft, more electric ships, conveyor belt drive system etc. uses five phase variable-speed induction motor drives. In this work, a comparative analysis of the modulation schemes such as IPD, POD and APOD in triangular carrier waves applied on the five level five phase PUC inverter fed induction motor drives is presented. Different parameters were analyzed and reported in the paper. The simulation is performed in MATLAB®/Simulink environment and the results obtained are reported and discussed in the paper.

The increase in electrical power requirement in the more electric aircraft (MEA) leads to the deployment of a high energy density battery energy storage system (BESS). In the presented work, a high energy density Lithium Ion (Li-ion) “Li-ion phosphate” battery is selected and is designed as per the requirements of MEA. The proposed Li- ion BESS comprises of 5 Li-ion batteries, which are connected in series and integrated with MEA power distribution bus with a bidirectional isolated DC-DC converter as a charger. A Li-ion battery model based on a modified Shepherd curve-fitting with the addition of the voltage polarization term is also investigated in the paper. The modeled Li-ion battery is integrated to the 270 V DC MEA power distribution bus using the optimal harmonic number based harmonic model of DC-DC converter. The values of duty cycle and coupling inductor used in the modeling is selected in order to achieve maximum power transfer and wide range zero voltage switching (ZVS) operation. The harmonic model representation results for different harmonic number are obtained and are compared with the detailed switch model simulation done in MATLAB®/Simulink simulation environment.