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Grid impedance is one of the most important parameters for the satisfactory operation of variable frequency drive (VFD) and their interaction with other utilities connected to the same grid. In this research investigation a new approach to analytical evaluation and verification of grid impedance, and short circuit current is discussed. VFD under identical operating and loading conditions is connected to different grid capacities and configurations, being considered in this investigation. Grid impedance variation in terms of measured or estimated values, due to different grid connectivity affects the commutation of uncontrolled front-end rectifiers. This impacts the nonlinearity of input current wave shape, causing a significant change in current harmonics (THDi) and ripple current of DC link. This paper comprehensively investigates the reduction of DC capacitor lifetime and losses of DC inductor, and diode with various grid capacity and configurations under standard load conditions. High-frequency harmonics impact (2-9 kHz) on DC inductor losses is also analyzed. A VFD of 250 kW is considered for entire practical measurement including distortion effects and MATLAB simulation. This research may give a good insight into the sizing of VFD front-end devices. The reliability impact of VFD is also one of the important outcomes of this research.

With the increasing penetration of renewable energy sources in the power system, the power electronic inverters are widely used to interface with the grid, which will reduce the inertia of the power system. This study proposes ancillary inertial service from single-phase rooftop solar photovoltaic (PV) based inverter to the grid. The inertia emulation control technique transforms the behaviour of inverter like a synchronous generator under power imbalances. A hybrid energy storage system consisting of battery and supercapacitor (SC) has been connected at the DC bus to take care of the variability in PV output power and load fluctuations. The SC absorbs/injects the fast-varying power and provides the inertial response to arrest the frequency deviation and battery charges/discharges to bring back the frequency to the nominal value. Real-time simulation is carried out to test the system behaviour for different operating conditions using OPAL-RT 5700.

The short-term variability in power produced by grid-integrated photovoltaic (PV) plants can adversely affect the power quality and reliability of the system. Hence, the variability of the generated power is one of the major challenges to integrating this solar resource into the electricity grid. The irregular nature of renewable sources and unpredictable load changes require high-energy and high-power density storage devices in the current microgrid (MG) environment. In this paper, an energy management scheme (EMS) is proposed for the control of solar PV fluctuations using ramp-rate control with a hybrid energy storage system (HESS). The ramp-rate control in the system mitigates fluctuating PV power and improves system reliability. The proposed EMS has the following key advantages: effective power-sharing between energy storage devices (ESSs), faster regulation of DC-link voltage to generation and load uncertainties, effective power distribution between battery and grid-based on the battery charge state, and reduced charging/discharging rate for battery current during steady and transient state power fluctuations. The performance of the system was validated using the MATLAB/Simulink environment.

Energy storage systems are becoming more and more important for integrating higher levels of varying and intermittent renewable power into the grid. As we have energy storages with different characteristics and applications, hybrid storage solutions combining various technologies to meet different applications are fast developing. In this paper, an efficient energy management strategy is proposed for a VRB and Li-ion hybrid battery system to be integrated with a grid-connected wind-PV Hybrid Renewable Energy System (HRES). The operation of the generating system and the storage batteries are evaluated using Matlab/Simulink and techno-economic analysis is carried out. The results demonstrated successful implementation of the hybrid system with improved deliver ability and storage lifetime.

This paper proposes a new approach for grid integration of solar photovoltaic system using modified incremental conductance maximum power point tracking algorithm with multi-output converter and multilevel inverter. The multi-output converter is a combination of boost converter and switched capacitor function to generate different self-balanced output voltages using single switch, single inductor, 2N-1 diodes and 2N-1 capacitors. This topology is proposed to be used as DC link in applications where several controlled voltage levels are required with self-balancing and unidirectional current flow, such as photovoltaic (PV) or fuel cell generation systems with multilevel inverter. The utilization of multilevel inverter in the proposed system provides better quality of output voltage and current waveform thereby reducing the size of passive filters. Also, it eliminates the requirement of bulky transformers for grid integration. Multicarrier unipolar phase disposition pulse width modulation technique is employed for triggering the switches of the multilevel inverter. The proposed system is tested with standard test conditions using MATLAB/SIMULINK.

This paper reviews the energy storage participation for ancillary services in a microgrid (MG) system. The MG is used as a basic empowering solution to combine renewable generators and storage systems distributed to assist several demands proficiently. However, because of unforeseen and sporadic features of renewable energy, innovative tasks rise for the consistent process of MGs. Power management in MGs that contain renewable energy sources (RES) can be improved by energy storage. The energy storage systems (ESSs) have several merits, such as supply and demand balancing, smoothing of RES power generation, enhancing power quality and reliability, and facilitating the ancillary services like voltage and frequency regulation in MG operation. The integration of ESS technology has become a solution to the challenges the power distribution networks face in achieving improved performance. By simplifying a smooth and robust energy balance within the MG, storage devices match energy generation to consumption. MG, and its multidisciplinary portrait of current MG drivers, tasks, real-world applications, and upcoming views are elucidated in this paper.

This paper presents the design of a new single-Phase 9- and 17-level inverters with sinking the components. The 17-level inverter topology is designed by cascading the two nine-step inverters. The topology produces the complex number of output voltage levels with high reliability and reduced total harmonic distortion. We develop numerical modeling of the converters using MATLAB/Simulink block sets, and we realize experimental prototype in a laboratory-scale model using digital processor dSPACE RTI 1104. Set of experimental and numerical results are provided in this paperwork to ensure and validate the feasibility as per IEC standards. Proposed inverters are well apt for low/high voltage renewable and hybrid electric vehicle applications.

Water hammering is a significant problem in pumping systems. It damages the pipelines of the pump drastically and needs to identify with an intelligent method. Various conventional methods such as the method of characteristics and wave attenuation methods are available to identify water hammering problems, and the predictive control method is one of the finest and time-saving methods that can identify the anomalies in the system at an early stage such that the device can be saved from total damage and reduce energy loss. In this research, a machine learning (ML) algorithm has used for a predictive control method for the identification of water hammering problems in a pumping system with the help of simulations and experimental-based works. A linear regression algorithm has been used in this work to predict water hammering problems. The efficiency of the algorithm is almost 90% compared to other ML algorithms. Through a Vib Sensor app-based device at different pressures and flow rates, the velocity of the pumping system, a fluctuation between healthy and faulty conditions, and acceleration value at different times have been collected for experimental analysis. A fault created to analyze a water hammering problem in a pumping system by the sudden closing and opening of the valve. When the valve suddenly closed, the kinetic energy in the system changed to elastic resilience, which created a series of positive and negative wave vibrations in the pipe. The present work concentrates on the water hammering problem of centrifugal pumping AC drive systems. The problem is mainly a pressure surge that occurs in the fluid, due to sudden or forced stops of valves or changes in the direction and momentum of the fluid. Various experimental results based on ML tool and fast Fourier transformation (FFT) analysis are obtained with a Vib Sensor testbed set-up to prove that linear regression analysis is the less time-consuming algorithm for fault detection, irrespective of data size.

This paper proposes a new multilevel inverter (MLI) topology that utilizes trinary sequence for the dc sources. It gives maximum output voltage level with minimum dc source and switch count when compared to other sequences, such as symmetric, natural, binary, and quasi-linear. This is due to the fact that the trinary sequence generates of all additive and subtractive combinations of input dc levels in the output voltage waveform. The concept is implemented on a 9-level asymmetric MLI using only four active devices. Multicarrier unipolar pulsewidth modulation technique is adopted to create the switching pulses. Theoretical calculation of total harmonic distortion in both voltage and current waveforms has been performed using asymptotic time domain formula. These values are compared with simulation and experimental values for different modulation indices. Power loss calculation for proposed topology is discussed with appropriate mathematical equations.

Renewable power generation becomes more popular nowadays due to the low availability of fuels. This paper proposes an integration of single DC source reduced switch multilevel inverter topology for grid connected photovoltaic system to achieve a good quality output waveform. The proposed configuration requires less number of power semiconductor devices when compared to conventional multilevel inverter configurations for generating higher output voltage level with lower total harmonic distortion. A sine reference with phase disposition triangular carrier arrangement is utilized for generating the switching pulses to the proposed multilevel inverter. A single diode model in photovoltaic system and dual output boost converter is utilized in the proposed system to reduce the complexity. Also, the improved incremental and conductance maximum power point tracking is selected in this work. The proposed system is tested only in standard test condition using MATLAB/Simulink. Hence, the proposed system is well suitable for grid connected in photovoltaic system.

In this paper, Dynamic Voltage Restorer (DVR) based series compensation of the voltage to provide Fault Ride Through (FRT) and reactive power support is discussed. The control of DVR is crucial in order to improve the FRT capability in Doubly Fed Induction Generator (DFIG) based wind turbines. This is observed in terms of voltage sag mitigation capability, active and reactive power support without tripping and fault current control. To achieve a flexible control solution for balanced and unbalanced fault conditions, a combination of Feed-forward and Feed-back control is discussed in this paper. The advantage of utilizing this combined control is verified through MATLAB/Simulink based simulation results of a 1.5 MW grid connected DFIG based wind turbine. The results show good transient and steady-state response and good reactive power support during various fault scenarios. The results are verified for the recent updated grid code standards.

Recently multilevel inverters (MLI) have attracted more attention in research and industry, as they are changing into a viable technology for several applications. The concept of MLI was introduced for high power and high/medium voltage applications as they can provide an effective interface with renewable energy sources. Developing of reduced switch MLI topology has been a rapid research topic since the past decade, which has not been reviewed so far. Therefore, this review article focuses on the different reduced switch MLI topologies under three categories such as symmetric, asymmetric and hybrid configurations. The important knowledge on these topologies is carefully tabulated based on the three categories in the comparison tables to understand the essential parameters of the MLI topologies. These configurations are not only generating higher voltage levels to improve the power quality but also to reduce the passive filter requirements. Also, this review includes a detailed perspective of various modulation techniques and control strategies for MLI topologies. In addition to that, the different performance parameters of MLI and its calculation methods are discussed with appropriate mathematical expression. This review will help in the selection of appropriate MLI topology for FACTS, motor drives and renewable applications.

A Model Predictive Current Control (MPCC) of single phase Shunt Active Power Filter (SAPF) is introduced in this paper. A single phase Voltage Source Inverter (VSI) is used as a SAPF to compensate the current harmonic and reactive power. A DC link capacitor voltage regulation based Proportional - Integral (PI) control algorithm is adopted for determining the reference current. A bridge rectifier with RL and RC loads are acting as a Non-Linear Loads (NLL). The harmonic compensation performance of SAPF and associated control methods like switch on response and transient responses were verified through a simulation with MATLAB software.

Introduction Bowel obstruction occurs when the normal flow of intraluminal content is interrupted. The most common cause of small bowel obstruction is adhesion but other rare causes of intestinal obstruction have also been reported as fecolith, foreign body or bezoar, GIST, and abdominal cocoon. Laparoscopy as diagnostic as well as therapeutic tool in small bowel obstruction seems to be useful. Methods We described two rare causes of intestinal obstruction. The aim of the present article is to stress the role of laparoscopy associated with computed tomography (CT) in diagnostic confirmation of causes of intestinal obstruction as well as reasons for conversion. We also reviewed the relevant published literature. Result CASE 1: A 63-year-old female presented with history of recurrent episodes of pain in left side of abdomen for 1 year. Contrast Enhanced Computed Tomography (CECT) showed rounded radiopaque foreign body in distal jejunum. Laparoscopic adhesiolysis and reduction of hernial content were done. Laparoscopic surgery converted to open for removal of foreign body and hernioplasty. CASE 2 64 year elderly male presented with history of intermittent episodes of colicky pain in periumbilical region for 1 month. CECT abdomen showed abdominal cocoon. Pneumoperitoneum access was not succeeded, thus exploratory laparotomy and adhesiolysis was done. Conclusion In small bowel obstruction, diagnostic laparoscopy has to be done for confirmation of diagnosis and if possible to release the cause of obstruction, but conversion to open by giving either small incision or exploratory laparotomy should be the choice to completely remove the cause for the further prevention of recurrence and complications.

In this study, a new multilevel inverter configuration which introduces a combination of cascaded H-bridge multilevel inverter with a double level circuit is proposed. The double level circuit is a half-bridge inverter when combined with a cascaded H-bridge multilevel inverter, will increase the output voltage level to nearly twice that of a conventional cascaded H-bridge multilevel inverter. The effectiveness of the proposed configuration is demonstrated with five different cases of cascaded H-bridge multilevel inverter configurations. Phase disposition carriers arrangement with sinusoidal reference has been utilised in pulse width modulation for generating the gating signal of switches to achieve high-quality output voltage waveform. A comparison is carried out with different parameters such as %total harmonic distortion, distortion factor, the maximum voltage step of output voltage level and peak inverse voltage. Analysis of power loss and theoretical calculation of %total harmonic distortion is described. Also, a new method for calculating the overall component count is discussed. As a result, the proposed configuration requires lesser component count for generating higher output voltage level with lower %total harmonic distortion. Selected simulation and experimental results are shown to verify and validate the proposed multilevel inverter configuration.

This paper proposes an interleaved boost converter for renewable energy application with energy storage system approach. In this, the IBC is employed to sustain the steady DC link voltage and remove the current ripples in the system. The boost converter is utilized in low voltage applications provided by the battery. For high powered systems, the boost converter is not effective to control the system because of its high input current ripple appended to the current circling out from the source and this input current cause diminution in battery lifetime. The IBC is formed by connecting two switches, diodes and inductors in parallel provided with phase shift switching operation. The total load current is the addition of two inductor currents which is having small peak-to-peak ripples. It comprises a fast response and increases the overall system stability. The IBC provides high efficacy, reduced input, and output ripples and maintains high power density. Hence, the IBC is most preferable in high power applications. The aimed system is validated by using a Simulink environment.

This paper investigates the influence of the grid-connected renewable energy sources and their effect on the utilities having diode front-end rectifiers. The grid interface in the renewable energy converters generally has PWM Inverters with LCL filters. These LCL filters are tuned for different resonance frequencies based on their switching frequency and system parameters. With multiples of renewable energy source converters connected in parallel, the grid parameters and harmonic interaction change differently based on the individual LCL filter design and operating conditions. This condition becomes worse if inverters connected in the same PCC are significantly increased. The utility rectifiers are designed for a specific range of grid specification according to various international standards. Effect of grid parameter variation such as voltage and current harmonic injection due to these inverters in a specific grid configuration and application from earlier studies is referenced. Grid model is generated from earlier studies and simulation was carried out for a specific diode front-end model of VFD. Reliability variation in front-end rectifier utilities such as variable frequency drives with a special emphasis on DC filter capacitor and DC link inductor is also discussed.

Electric Vehicle is one of the most effective solution for reducing the Green House Effect and Global Warming. It is the alternative way of conventional vehicle. In Power Electronic circuit battery, charging unit is used to deliver high performance with less power consumption. LCC compensation network is used with the Converter circuit of the battery-charging unit of EV. It has high efficiency with reduced circulating current, output voltage and output current consists of wide range regulation. In Design consideration of Battery Charging unit, Bi- directional power flow is required Grid to Vehicle (G2V) power transformation or vice versa. The paper focuses on Bi-directional Converter LCC compensation with double sided for charging Topology of the EV. In this proposed method, depending on coupling coefficient resonant frequency is independent and is used between transmitting and receiving coil where zero voltage switching (ZVS) is achieved. This proposed method is used as a charging system which is wireless with maximum resistive load of 7.77 KW instead of battery load with an achieved efficiency of 86.2%.

This paper investigates the high frequency effects (2-9 kHz) on the DC link inductor of Variable Frequency Drive (VFD) connected to the grid with Shunt Active Filter (SAF) for harmonic mitigation at common point of coupling (PCC). Active filter generally operates in different conditions including voltage imbalance up to 3% and varying rated load. Most of available active filters in market operate efficiently with switching frequency in the range of 3-5 kHz. Although harmonic mitigation is the focus point of SAF use, impedance seen by diode bridge rectifier is significantly reduced which in turn increases stresses on DC link inductor and DC filter capacitor ripple current. Effects of these parameter variations in frequency range of 2–9 kHz predominantly are DC link inductor core loss, DC filter capacitor life time and increased conduction losses of diode bridge rectifier. 130 Amperes SAF connected to grid driving 132 kW VFD under different operating conditions is analyzed through MATLAB simulation and practical test measurements. Reliability variation in front end rectifier utilities such as variable frequency drives with special emphasis on DC link inductor is discussed in detail.

The virtual synchronous generator (VSG) has gained a more attention since it can emulate the essential inertial characteristics of the synchronous generator to the power electronic inverter based distributed generators (DG). VSG allows the inverter to participate actively in the frequency regulation. However, the stability analysis of VSG under parameter variations and critical value of the inertia value have not yet been discussed. To handle this issue, a small signal model of VSG is framed. The impact of parameters involving inertia, damping on dynamic response is analysed with Pole Zero map and the critical value of inertia is determined. Finally, the MATLAB/Simulink simulation results illustrates the perfection and viability of the theoretical analysis.

In association with increasing in penetration of distributed generation sources (DGs) into power systems, and their power management of different DGs and the grid has elevated as a major concern. Though, Microgrid (MG) is the extensively an accepted concept for the association of DGs in power system networks. Integrating renewable energy sources (RESs), which are often connected via power electronic interfaces into the power grid, can sometimes be a stimulating task just from a purely technical point of view. Thus, the MG is a promising option for future power system interfaces. Evolving the challenges has taken place in terms of the power system control, power quality improvement, reliability, and energy management. The MG operational performance, stability, basic control issues and, concept of MGs are presented in this paper.

Multilevel inverters (MLIs) are gaining familiarity in industries for high-voltage applications. This study is a comparison of symmetric and asymmetric reduced switch MLI topologies which require a lesser number of switches for generating the desired number of voltage levels. In both symmetric and asymmetric conditions, output voltage levels are generated using the same number of switches with different DC source magnitudes. Unipolar pulse width modulation strategy is adapted in these topologies to generate the switching pulses. Three different unipolar references (sine, trapezoidal, 60°) and three different carrier arrangements (phase disposition, alternative phase opposition and disposition and variable frequency) are taken and each reference is compared with three different carrier signals. The performance parameters such as total harmonic distortion (THD), crest factor and distortion factor are evaluated for different modulation indices and compared with both conditions. The proposed topology in symmetric and asymmetric conditions can generate 9-level and 31-level output voltages, respectively, which are simulated using MATLAB/Simulink and verified with the experimental setup. The calculation of %THD using analytical asymptotic formula is also carried out. The theoretical value of %THD is verified to match closely with the simulation and experimental results.

This paper introduces a new single phase hybrid multilevel inverter with a minimum number of switches for a Photovoltaic application. A Perturb and observe maximum power point tracking is used for tracking maximum power from solar panel. A boost converter is used for boosting the generated voltage because proposed inverter operates at the asymmetric condition. The proposed inverter is the combination of reduced switch topology and cascaded H-Bridge topology. Two types of Phase Disposition carrier arrangement with sinusoidal reference is utilized for generating the gating pulses for proposed inverter. It generates a 15-level output voltage with 8.12% of total harmonic distortion.

A quasi-linear Cascaded H-Bridge multilevel inverter is introduced for solar application. In this paper, a separate solar panel with boost converter is placed instead of DC sources in the proposed configuration. The Incremental and Conductance maximum power point algorithm method is implemented for tracking maximum power with a fast response. Sinusoidal reference with triangular carriers is utilized in pulse width modulation for generating the switching pulses for proposed inverter. The proposed inverter can generate a 19-level output voltage with total harmonic distortion of 6.10% which is simulated using MATLAB/Simulink. Cost analysis of power switches is discussed.

This paper proposes a single phase multilevel inverter configuration that conjoins three series connected full bridge inverter and a single half bridge inverter for renewable energy application especially photo-voltaic system. This configuration of multilevel inverter reduces the value of total harmonic distortion. The half bridge inverter utilized in the proposed configuration increases the output voltage level to nearly twice the output voltage level of a conventional cascaded H-bridge multilevel inverter. This higher output voltage level is generated with lesser number of power semiconductor switches compared to conventional configuration, thus reducing the total harmonic distortion and switching losses. The effectiveness of the proposed configuration is illustrated by replacing the isolated DC sources in multilevel inverter with individual photo-voltaic panels using separate perturb and observer based maximum power point tracking and boost converters. The verification of the proposed system is demonstrated successfully using MATLAB/Simulink based simulation with different irradiation and temperature conditions. Also, the transient operation of the system is verified with results depicted using step change in standard test condition. In the proposed system, total harmonic distortion of the output voltage is 9.85% without using passive filters and 3.91% with filter inductance. Theoretical calculation of the power losses and total harmonic distortion with mathematical equations are discussed. Selective experimental results are presented to prove the effectiveness of proposed system.