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This paper studies the coordinated use of smart inverters with legacy voltage regulating devices to help increase the energy savings from conservation voltage reduction (CVR) in distribution systems with high photovoltaic penetration. Two voltage optimization algorithms are developed to evaluate the CVR benefit by considering two types of smart inverter functions: aggregated reactive power control and autonomous volt/VAR control. In each algorithm, smart inverters are coordinately controlled with the operation of legacy voltage regulating devices including load tap changers and capacitor banks. Both algorithms are tested on representative utility distribution system models. Simulation results demonstrate that the proposed algorithms can achieve around 1.8-3.6% energy savings when only using legacy voltage regulating devices and an additional 0.3-0.9% when adding smart inverters.

In regions such as hawai'i, south australia, Tasmania, Texas, and Ireland, power systems are commonly experiencing instantaneous penetration levels of inverter-based power sources (IBPSs) such as wind, solar photovoltaics (PV), and battery storage in excess of 50n60% relative to system demands.

The main purpose of this paper is to observe the effect PV variation of solar temperature and irradiance on different conditions and on the inverter output for a grid-connected system. Majorly temperature& solar irradiation effects the performance of a grid connected inverter, also on the photo-voltaic (PV) electric system. The simulation based study was carried out in order to evaluate the variation of inverter output with the variation of solar temperature and irradiance with the variation in climate. The analysis of Grid-connected inverter and their performance at various seasons and conditions is investigated. Solar power plant for a year. In solar power plant efficiency of inverter is also considered to calculate overall losses so, the inverter efficiency and plant performance are considered in this paper using MAT Lab software. In summer season the inverter performed efficiency is decreased because of peak temperature value and slightly increased with the increase in irradiance.

The double-bridge voltage source inverter (DB-VSI) is a promising inverter topology for high performing motor drives. A DB-VSI comprises two VSIs, connected to the opposite sides of an open-end winding motor (no floating neutral point). Thanks to its inherent properties, a DB-VSI requires only half DC supply voltage, compared to a simple VSI, in order to generate the same motor voltage. Thereafter, by processing/switching only half of the DC supply voltage, the DB-VSI benefits from significantly lower semiconductor devices’ switching losses. The DB-VSI technology is the main focus of this paper. Namely, two different DB-VSI variants and/or modulation strategies are comparatively evaluated. After detailing the operating principle of each modulation strategy, the stresses on the inverter components are analytically derived. It is shown that the selection of the DB-VSI modulation strategy impacts the efficiency/power density of the inverter and the voltage quality of the motor. The theoretical considerations are subsequently verified within the context of a high-speed motor drive. In the investigated drive system, a fuel-cell supplies the inverter, which in return controls a 280krpm 1kW electric compressor. Two DB-VSI hardware prototypes are purposely assembled and compared against a third state-of-the-art hardware prototype of the same specifications. It is shown that, thanks to the DB-VSI technology it is possible to reduce simultaneously the volume and the losses by up to 50% compared to the state-of-the-art solution. The low DB-VSI volume enables a seamless integration of the inverter in the motor housing. Accordingly, the open-end winding motor is directly attached to the inverter, eliminating the need for cumbersome and costly interconnecting cables. A final, integrated (inverter/motor) hardware prototype is presented, that further highlights the advantages of the DB-VSI technology.

This paper presents the design and development of Dynamic Adaptability (DA) feature, added to a multi-objective Model Predictive Control (MPC) of a basic grid-tied inverter with a secondary function for switching frequency reduction. The classical MPC is enhanced with dynamically varying secondary function weightage in accordance with the demand of the operating condition for self-reliant change-over across grid-tied mode and grid-forming modes in an Inverter Dominated Microgrids (IDM) environment. A customized DA database has been developed through prior investigation on the IDM, considering possible operating conditions with diverse combinations of the sampling frequency and the secondary function weight. Investigations unveiled that there is a unique value of secondary weight for every operating condition, beyond which the reference tracking is lost. This necessitated the dynamic assignment of the weight to achieve a desirable inverter performance. The dynamic weightage assignment is accomplished by accessing the DA database through the priority signals for harmonic standards, inverter losses and reference tracking, respectively. The DA imparted MPC is tested for its mode transfer capability with desired performance under all operating modes of IDM in simulations with a 15 kVA grid-tied/forming inverter and the results are presented. Further, the experimental investigations are conducted with a 10 kVA inverter on a 5-bus laboratory scale IDM emulator along with hardware-in-loop. Both inter-mode and intra-mode transitions were initiated in the IDM and the inverter performance are presented here. Both the simulation and the hardware results yielded competent values of reference tracking accuracy and mode transition times.

In this paper, a new 5-level inverter is developed by inserting a switched-capacitor (SC) unit into the traditional 3-level neutral-point-clamped (NPC) inverter phase-leg. The SC unit consists of two capacitors and one bidirectional switch, all of which withstand a quarter of the dc input voltage. Whilst increasing the output levels, the performance is also improved in terms of power loss, common-mode voltage, switching stress dv/dt and output filter. Compared to other 5-level inverters like the conventional NPC and active NPC 5-level topologies, the new solution not only reduces the number of components and simplifies the design, but also has the advantage of self-balanced capacitor voltages. The analysis, simulation and experiment indicate that the proposed inverter is suitable for a wide range of applications like renewable source grid-connected interfaces and motor drivers. Simulation and experimental results of grid-connected operation verify that the new inverter is capable of providing both active and reactive power to the grid. Its excellent performance is also experimentally evaluated by a 1.2 kW prototype and the measured efficiency is above 97% for a wide range of load.

In this paper, a new adiabatic logic family named as adiabatic differential cascode voltage-switch logic (A-DCVSL) for low power applications is presented. The family operates on a two-phase split level sinusoidal power clock instead of four-phase trapezoidal power clock. The proposed A-DCVSL circuits reduce the power dissipation by charge recovery and minimizing the peak current flow. The behavior of the inverter is analysed and the power dissipation of A-DCVSL circuit is mathematically modeled. The performance of A-DCVSL inverters is compared with other existing differential adiabatic logic families. A full subtractor is also designed to exhibit the benefits at the application level. The results confirm that the proposed A-DCVSL circuit outperforms in terms of power dissipation and can be adapted to the design of lower power applications. The simulations were performed on Tanner EDA tool using 32 nm PTM technology parameters.

Multisource inverters (MSIs) as a new approach for the integration of the energy and the power sources in electric vehicle applications have gained considerable attraction. Such structures offer the active control of the dc sources without using any dc/dc converters or magnetic elements, which reduces the weight, and the volume of the power electronics interface between the sources and the load. Moreover, high power density and improved efficiency due to the elimination of the magnetics are the other significant features of an MSI. This article proposes a novel three-phase MSI for integration and active control of a high-voltage dc source and a low-voltage dc source. The proposed MSI structure employs a smaller number of semiconductor devices at the current path in various operating modes in comparison to the previously published counterparts, which results in an improved efficiency operation. Performance of the proposed MSI using a modified space vector modulation technique for all possible operating modes is verified through simulations and experiments on a laboratory prototype

In this article, a hybrid asynchronous particle swarm optimization-genetic algorithm (APSO-GA) is proposed for the removal of unwanted lower order harmonics in the cascaded H-bridge multilevel inverter (MLI). The APSO-GA is applicable to all levels of MLI. In the proposed method, ring topology based APSO is hybrid with GA. APSO is applied for exploration and GA is used for the exploitation of the best solutions. In this article, optimized switching angles are calculated using APSO-GA for seven-level and nine-level inverter, and results are compared with GA, PSO, APSO, bee algorithm (BA), differential evolution (DE), synchronous PSO, and teaching–learning-based optimization (TLBO). Simulation results show that APSO-GA can easily find feasible solutions particularly when the number of switching angles is high; however, the rest of all stuck at local minima due to less exploration capability. Also, the APSO-GA is less computational complex than GA, BA, TLBO, and DE algorithms. Experimentally, the performance of APSO-GA is validated on a single-phase seven-level inverter.

Direct Torque Control (DTC) scheme introduces a robust and simple control of electrical drive. However, its shortcomings such as broad torque ripple and variable switching frequency have offered several improvements like Space Vector Modulation (SVM) strategy, multilevel inverter (MLI) topology, etc. The conventional DTC which is fed by the two-level inverter has limited voltage vector, results in some difficulties to optimize the operation, especially at low operating speed. In contrast to MLI, the abundant of voltage vector has provided various amplitudes and angles that can overcome the problem of conventional DTC. Thus, this paper introduces the selected optimal voltage vector obtained from five-level Cascaded H-Bridge (CHB) inverter that employs in DTC hysteresis-based to achieve better optimization that similar to the DTC-SVM. Initially, the research work begins with an investigation on the performance comparison between a DTC hysteresis-based between two-level inverter (conventional method) and a five-level CHB inverter (proposed method). Here, a DC generator acted as a load is employed to control the operating speed instead of the speed controller (speed controller is negligible). Hence, the DTC method is optimized by minimizing the torque ripple as well as retaining the torque control capability at constant torque region on several operating speed. The selected optimal vector from the look-up table DTC of five-level CHB inverter must be dynamically appropriate to any change of torque (increased or decreased torque). For simplicity, this paper will only discuss the experimental results for both topologies of drive system. From the experimental results, it is verified that the torque ripples by the proposed method have achieved 10% and 50% reduction at high and low operating speed respectively. It is found that the DTC hysteresis-based result simpler control method than DTC-SVM while maintaining similar output performance.

With the characteristics of module-level maximum power point tracking, module-level monitoring, and panel shut- off , single-phase cascaded H-bridge (CHB) inverter has outstanding advantages applied to household photovoltaic (PV) power generation occasion. However, unbalanced output powers among PV panels is an inherent problem of single-phase CHB PV inverter, which will make the H-bridges (HBs) with higher powers overmodulation, resulting in deteriorated grid current and even system instability. Aiming at this issue, this article proposes a power adaptive control strategy, which divides system operation into three modes, and calculates modulation waveforms by using different methods in different modes. By flexibly adjusting the transmission power of HBs in different modes, all the HBs are able to avoid overmodulation, and single-phase CHB PV grid-connected inverter can still operate normally even if the maximum powers among PV panels are seriously unbalanced. The effectiveness of the proposed control strategy is verified by simulation and experimental results.

Due to the rise of distributed energy resources, the control of networks of grid-forming inverters is now a pressing issue for power system operation. Droop control is a popular control strategy in the literature for frequency control of these inverters. In this paper, we analyze transient stability in droop-controlled inverter networks that are subject to multiple operating constraints. Using a physically-meaningful Lyapunov-like function, we provide two sets of criteria (one mathematical and one computational) to certify that a post-fault trajectory achieves frequency synchronization while respecting operating constraints. We show how to obtain less-conservative transient stability conditions by incorporating information from loop flows, i.e., net flows of active power around cycles in the network. Finally, we use these conditions to quantify the scale of parameter disturbances to which the network is robust. We illustrate our results with numerical case studies of the IEEE 24-bus system.

This paper proposes a model predictive control strategy for 15 level Packed-U-Cell inverter that satisfies multiple-objectives of low current total harmonic distortion (THD), capacitor voltage balances, supply of desired active and reactive power, as well as lower switching and lower voltage stresses on the switching devices. The proposed device performs well under dynamic conditions and can successfully track the current command during step changes in the power demand. A detailed modeling is presented and discussed. MATLAB/Simulink is used for obtaining the simulation results, and the results are validated in the real time by using a hardware-in-the-loop (HIL) Typhoon 402 real-time emulator.

In actual microgrids (MGs) networks, the information exchange between distributed energy resources (DERs) agents may be subject to various types of measurement noises and effected by communication time delays. This article proposes a resilient distributed multiagent control scheme for ac MG networks subject to additive noise and time-delay disturbances. The proposed multiagent control scheme is composed of three distributed consensus protocols, which is able to synchronize the output voltages and frequencies of inverter-based DERs to their reference values and achieve the optimal active power-sharing property by a low bandwidth communication network with noise and time-delay disturbances in almost sure convergence. By means of the stochastic analysis tools and algebraic graph theory, distributed consensus control protocols are designed to be employed for the secondary control level of MGs. On this basis, we deduce the stability criteria of the closed-loop MG system under noise and time-delay disturbances. As a result, the proposed consensus protocols can well restore the voltage and frequency's derivation produced at the primary control level, meanwhile, can well achieve the optimal power sharing even though there exist communication disturbances. Several simulation scenarios on an islanded MG network are provided to verify the proposed control protocols' performance.

The purpose of this article is to investigate the potential of obtaining an auxiliary dc output from the common-mode switching harmonics of a three-phase inverter without access to the neutral point of the ac load. To achieve this, the control of common-mode (CM) switching harmonics with space vector modulation is proposed. With this control, CM switching harmonics can be regulated independently from the differential mode power flow to the main three-phase load. To physically implement the CM power flow, a harmonic extraction circuit is placed in parallel with the main three-phase load. The extraction circuit is formed by series-connected inductance and capacitance. Due to the LC series resonance and the mutual coupling of the inductance, only common-mode switching harmonics can pass through the extraction circuit. The extracted harmonics are then rectified and delivered to the auxiliary dc output. The control and topology are verified in both simulations and experiments. In the end, it is shown in experiments that there is no significant difference of the inverter efficiency after the auxiliary dc load is connected. This method can be used for instance to drive an ac machine while charging a low voltage battery or powering a compressor simultaneously.

In this paper, a 13-level asymmetric configured cascaded H-bridge (CHB) inverter is used with a 54-pulse AC-DC converter to feed a medium voltage indication motor (IM). A thorough analysis is caried out to design an isolated multi-winding transformer (MWT) based 54-pulse converter. Accordingly, the main aim of this converter is to extract the power from the grid as per the power quality standard. Moreover, a higher number of voltage levels in CHB inverter is used to adhere the power quality due to asymmetric DC supplies, having 1:2:3 voltage ratio. Hence, a 13-leevl CHB-MLI is implemented with nine DC voltage sources. The converters of this drive system ensure that the quality of the grid currents and drive currents are excellent and meet the IEEE 519 power quality successfully. A nearest level control technique is implemented to generate the switching logic for a 13-level CHBCHB inverter. Simulated results demonstrate the performance of a 298.4kW induction motor drive in steady state and dynamic state. A validation study is conducted on an experimental setup with a 7.5kW IM at steady and dynamic states. Test results show a good agreement in terms of total harmonics distortions, power loss, and efficiency.

This paper introduces a novel configuration of electric spring based on the modified five-level packed u-cell (MPUC5) inverter for mitigating harmonics and voltage fluctuations at various points of a grid with unstable generated power from distributed renewable energy sources. Immanent merits of the proposed configuration include, but are not limited to, halved DC links voltages, boost mode operation, possibility of higher power applications, smooth five-level voltage waveform with low total harmonic distortion (THD) index, the smaller size of output low pass filter, and low switching frequency. The operation principles, design procedure, and configuration of the MPUC5-based electric spring (MPUC5-ES) are also presented. Besides, a simple and yet efficient controller without any extra control loop for regulating DC bus voltages has been proposed. Finally, the introduced multilevel electric spring is tested through extensive simulation and experimental studies to confirm its dynamic and steady-state performances in various operation modes in a weak grid fed by both conventional and intermittent renewable energy sources.

The installment of $LC$ filter between the voltage source inverter and motor terminal can reduce the value of $dv$ / $dt$ considerably, and further mitigate the surge voltage stress on the motor windings during the long-distance transmission. However, the sophisticated controller needs to be designed to solve the additional resonance problems caused by the filter. Conventional active damping (AD) scheme mainly introduce the multiloop feedback based on the analysis in $s$ -domain or $z$ -domain, which is realized with limited bandwidth and high tuning complexity. In this article, the finite-control-set model predictive control (FCS-MPC) is adopted to realize the $q$ -axis current reference tracking for motor and suppress the filter resonance simultaneously. Different from the transfer-function-based AD scheme, the mechanism of resonance generation is revealed in the time-domain, where the cost function of FCS-MPC is designed to directly regulate the multivariable trajectory of the system. Therefore, the proposed FCS-MPC controller expresses the intuitive design principle, a simple structure, and fewer tuning parameters, which could be an alternative to the existing AD scheme. To reduce the number of sensors, the Kalman-filter based state estimation is used by considering the one-step delay of the control input. The cost function is further optimized to a simplified form that suits the implementation of the digital platform, and the lower computational burden is obtained. The experimental results prove that the proposed FCS-MPC scheme can ensure the motor-friendly waveform and overcome the resonance problem effectively. The robustness of the controller to parameter variations of the filter is also verified.

The single-phase five-level transformerless inverters have been gradually applied in photovoltaic grid-connected systems due to low voltage stress and excellent waveform quality. However, they also suffer from serious leakage current as conventional three-level inverters. In order to reduce the leakage current, a single-phase five-level transformerless inverter is proposed in this article. The proposed inverter guarantees that the common-mode (CM) voltage is clamped to a half of the dc-link voltage when outputting ± V dc/2 and zero voltage levels. Consequently, the high-frequency CM voltage is avoided and the leakage current is suppressed. The voltage stresses of eight switches and two flying capacitors are only V dc/4, thus the system investment cost and total losses are reduced. The conduction and switching losses are analyzed in detail and a comparison with some existing topologies is also made. Finally, simulations and experiment are carried out based on a 1-kW prototype. The results show that the proposed single-phase five-level inverter can obtain both excellent differential-mode and CM performance.

In grid-connected PV systems, the inverter is one of the important components. Inverter efficiency may vary depending on the input power and voltage of the PV array. This paper analysed three factors affecting inverter efficiency. The first one was the effect of the duration of inverter operations. Analysis of the operation of a PV system that has been operating four years showed an annual average inverter efficiency of 0.90, almost equal to the manufacturer’s specification of 0.91. The study showed that there was no significant degradation in inverter efficiency because a cool temperature (of 25°C) was maintained for the inverter storage room through an air conditioning system. The second analysis investigated the effect of the power input from different types of PV module technology. The study showed that the inverter connected to p-Si PV modules operated the highest efficiency at 0.91. However, detailed analyses showed that PV module technology had less or minimal impact on inverter efficiency. It was the power input from the PV module that has influence on the inverter efficiency. The third analysis involved the study of the effect of irradiance distribution on inverter efficiency. The study shows that the inverter operates at the maximum efficiency of 0.90 at irradiance of above 350 W/m2, at which range solar energy potential is at its highest at around 85% of the total generation. This means that inverter converts almost all the energy supplied from solar PV at this irradiance range. In conducting the third analysis, a location-specific equation, η PHS, for determining inverter efficiency was also developed. The η PHS equation generates the actual inverter efficiency values based on the local irradiance conditions in Phitsanulok province.

Integration of solar photovoltaic systems to low-voltage distribution networks is witnessing an unprecedented growth in many parts of the world. Although solar photovoltaic generation is of significant benefit from a number of angles, exceedance of hosting capacity levels by such installations in low-voltage distribution networks continue to cause significant technical challenges in network operation, especially to the management of network voltage. Modern smart inverters are equipped with Volt-VAr and Volt-Watt control capabilities, which can assist in the management of network voltage levels. This paper provides a detailed analysis of the influence of different connection standards which cover these strategies on solar photovoltaic hosting capacity and their applicability in low-voltage distribution networks. Smart inverters with differing Volt-VAr and Volt-Watt control functions are modelled in the DIgSILENT PowerFactory platform. Influence of different connection standards on solar photovoltaic hosting capacity is analysed to investigate the most beneficial connection approach/es to address the issue of voltage violations. Furthermore, the work presented in this paper provides a greater understanding on the hosting capacity improvement by employing advanced inverter control functions where such improvements are subjected to locational aspects of inverters in low-voltage distribution systems.

To satisfy the demand for more compact medium-voltage motor drive systems, it is desirable to increase the frequency of the cascaded H-bridge inverters used in high-speed motor systems. However, in asynchronous pulse width modulation (PWM) systems, as the output frequency increases, the command voltage and triangular wave carrier frequencies get closer, making it impossible to accurately output the command voltage. This manifest itself as increased current harmonics, increased surge voltage at the motor terminals, and increased low-frequency ripple current due to the asynchronous nature of the system. In this study, we adopt a fixed pulse pattern modulation method to address these problems. In our method, a low-distortion output voltage is compiled in advance into a table, and subsequently output in synchronization with the fundamental voltage phase. We were able to confirm the effectiveness of the proposed method in simulations at fundamental wave frequencies of 700 Hz and 1000 Hz.

A local load connected with the grid-interfaced photovoltaic (GIPV) system demands reactive power compensation at the distribution level. The compensation either fulfilled by the PV inverter or grid side arrangements such as capacitor bank, static VAR compensator or tap-changing transformers. Amongst both, the inverter has merit to compensate reactive power without using an additional compensator or oversizing the inverter rating. However, it always depends upon the availability of irradiance and especially when the inverter transfers power with full capacity has no margin to generate the reactive power. Therefore, to make the system flexible according to the demand of the local loads and to create a margin to generate the reactive power at any time instant, a GIPV system with modified perturb & observe (MP&O) maximum power point tracking (MPPT) technique has been proposed. This proposed technique with an intermediate boost converter extracts maximum power more efficiently as compared to the traditional MPPT technique. On the other hand, it curtails the generated active power and provides margin for the PV inverter to generate the reactive power. Further, the PV inverter generates active and reactive power to the local loads as well as transfer power to the grid using inverter control. The inverter control comprises of decoupled instantaneous active and reactive power control. In this control scheme, it maintains the DC-link voltage and power flow between the GIPV system and the grid under all available irradiance conditions. In this respect, a 30 kW GIPV system is simulated and performance of the system is validated using real-time OP4510 hardware-in-loop (HIL) setup.

Refrigerators consume significantly high energy and the improvement on their efficiency is essential to minimize greenhouse gas emission. Understanding the power consumption patterns of refrigerators is a key element that is not thoroughly studied, especially in domestic PV system with an integrated battery-storage. Therefore, the main objective of the study is to develop strategies in decreasing the energy consumptions of systems including inverter-driven refrigerators in commercial and residential sectors. This paper compares measurements of the power consumption of two types of appliances, inverter-driven and traditional/non-inverter driven refrigerators when operating in DC and AC environment. The energy consumption was measured experimentally at four different temperatures from 10 °C to 40 °C to provide information on underlying energy changes due to changes during normal use. The work proposes an efficient configuration with DC environment appropriate for PV with battery storage applications. The overall system efficiency is adopted as a factor to evaluate the system performance for comparing two DC system topologies, DC-Load and DC-inverter-load. The comparison results of size equivalent refrigerators indicated that around 300 Wh of daily energy can be saved when just switching to the new inverter technology and smoother power pattern, especially at higher ambient temperatures. The results also found that the voltage level (310–325)VDC is the most appropriate value for the photovoltaic system integrated with battery storage of DC environment. This study provides researchers reasonable estimates on the daily energy consumption for other refrigerators at different operating conditions.

Improving the efficiency of room air conditioners (RACs) could provide significant energy and associated emissions savings, particularly in emerging economies with hot climates where the cooling demand is expected to increase dramatically. To help accelerate efficiency improvements, this study identifies “best-in-class” high-efficiency RAC components and products. The findings show that manufacturers tend to minimize manufacturing costs by using RAC designs that are readily available or standardized to their production, and they share components across various models. High-efficiency RAC models use advanced compressor technologies optimized at a low frequency, large heat exchangers with thermodynamically effective materials and designs, highly efficient direct current fan motors, advanced metering devices, and smart sensors for temperature and humidity control. Recently RAC manufacturers have been improving seasonal efficiency – better reflecting part-load operation – especially via variable-speed (inverter) drives for compressor motors. Recent highest-efficiency RAC models use low global warming potential (GWP) refrigerants, having transitioned from conventional high-GWP refrigerants, in regions where RACs that use these low-GWP refrigerants are commercially available. Recently demonstrated innovative technologies show trends toward smart hybrid designs, evaporative cooling, and solid-state materials beyond the conventional vapor-compression technology. This information could help policymakers improve their RAC market-transformation programs to align with the most-efficient global technology.

Single-phase H-bridge inverters provide a convenient and flexibly modulated solution to the dc–ac power conversion at once undergoing an inherent power mismatch between dc and ac sides. This article introduces a novel hybrid modulation technique that combines conventional sinusoidal pulsewidth modulation (SPWM) with pulse energy modulation (PEM) for a new single-phase bridge inverter with active power decoupling based on the front-end buck-boost converter. The proposed single-phase bridge inverter diverts the second-order ripple power into a small film capacitor at the buck-boost converter. The proposed hybrid modulation technique modulates the bridge inverter with PEM under discontinuous conduction mode (DCM) and with SPWM under continuous conduction mode (CCM), thus achieving zero-current turn-on compared with SPWM under DCM and removes a sampling circuit as compared with PEM under CCM. A 400-W single-phase inverter system has been built in Power Simulation (PSIM 11.0) to validate the theoretical analysis. Both hybrid modulation and active power decoupling control have been implemented in the experimental prototype using DSP TMS320F28335. The simulation and experimental results show that the second-order ripple power has been successfully mitigated with active power decoupling control, and the bridge inverter is able to work under both DCM and CCM with hybrid modulation.

In this article, a novel online optimal tracking method is proposed for permanent magnet synchronous machine drives for maximum torque per ampere (MTPA) and flux-weakening (FW) operations. The conventional model-based optimal tracking methods impose heavy computational burden, because the optimality criteria are usually used along with related boundaries to develop different optimization problems for different operation regions. Compared with the conventional methods, the proposed method reduces the mathematical complexity of the optimization problem and improves the computational efficiency in real-time implementation. Only one optimization problem is solved in both MTPA and FW regions, while the enhanced projection operations are developed to ensure the current references are within the voltage and current constraints. Magnetic saturation, phase winding resistance, nonlinearity of the inverter, and dc-link voltage variation are all taken into consideration. The feasibility of the proposed online optimal tracking method has been validated on an interior permanent magnet synchronous machine (IPMSM) test bench with an off-the-shelf motor control unit. The execution time and convergence rate of the proposed method have also been evaluated with benchmark conventional methods and presented in this article.

This paper presents a simple yet effective method for locating faults in radial distribution networks where impedance-based methods are known to have limitations, especially in the presence of inverter-based power sources (IBPS). The proposed approach utilizes the Discrete Wavelet Transform (DWT) to capture the first arrival times of the fault-generated traveling waves. It is assumed that a digital fault recorder (DFR) exists at the terminal node of every lateral, as well as the beginning and end of the main feeder. The detailed derivation of the fault location method is presented, and illustrative fault scenarios are simulated to experimentally verify the proposed algorithm's performance under very diverse conditions. It is shown that the proposed approach performs successfully irrespective of the unknown fault impedance, inception angle, and type.

In this article, a parallel open-circuit fault diagnosis method (POFDM) is proposed for cascaded full-bridge neutral-point clamped inverters (CFNPCIs) employing the model predictive control. It can be inferred that the open-circuit fault will cause abnormal capacitor voltage changes in the submodule. Therefore, eight count variables are configured to correspond to the eight Insulated gate bipolar transistors (IGBTs) for each submodule. In the POFDM, the eight variables count all the abnormal changes, and the variables corresponding to the healthy switches are cleared to 0. Then, the switch whose corresponding variable is first added to the maximum is diagnosed as the fault device. Because the independent and parallel structure is adopted, the proposed POFDM can diagnose not only a single fault but also multiple faults in different submodules. And it can be easily extended to CFNPCIs with arbitrary submodules due to its parallel structure and modular software. Finally, the feasibility and validity of the POFDM are verified on the experimental prototype.

Integrated modular motor drives (IMMDs) have a compact and high fault-tolerant structure compared to their conventional counterparts. The most challenging issue in the implementation of these drives is the thermal management of the inverter modules due to the small space available for each module and its physical proximity to the machine windings with their high heat production. The electrothermal design of a discrete half-bridge inverter module for a radially stator-mounted (RSM) axial flux integrated drive is introduced in this article. The inverter modules are mounted on the stator, radially along the circumference. The converter is implemented using GaN technology, and the size is optimized. The structure of the presented integration topology from the case of the switches to the cooling ambient is optimized from the thermal point of view. The converter is modeled using steady-state and transient lumped parameter thermal networks to estimate the steady state and the instantaneous temperature of the switches. The converter parasitics are extracted using FEM simulations, and their influence on the switch loss and temperature is evaluated. The lumped parameter modeling is validated with computational fluid dynamics (CFD) simulations and experimental measurements.

In this article, a self-organizing power electronic converter with control intelligence at the edge of the distribution network is proposed. The proposed converter is called power electronics intelligence at the network edge (PINE), and it has the potential to add intelligence at the network edge to the electricity delivery system of the present and in the future. The proposed approach consists of a power electronic converter (rectifier/dc-link/inverter) termed PINE to supply residential loads. The rooftop solar and battery energy storage system is connected to the dc link. With the bidirectional characteristic of the PINE, the load voltage is regulated via feedback, whereas input distribution voltage can be allowed to vary in a range. This type of configuration allows for control of input power factor to be unity and reactive power to be injected at the grid edge to regulate the voltage and also enable energy budgeting, i.e., limit the amount of power to the residential load under disaster situations. With the PINE converter at the distribution edge that can communicate with other PINEs as well as to the distribution system operator, intelligence at the distribution edge can be established. Such a system has many advantages that are discussed in this article. Furthermore, the impacts of increased penetration levels of PINE are shown using a test feeder based on the IEEE-37 test node feeder. Simulation and experimental results on a laboratory prototype system validate the PINE converter concept.

A novel inverter-based digital floating-gate MOSFET sensor design for commercial X-ray dosimetry is presented. The biomedical healthcare industry sterilizes blood products for storage purposes using Gamma and X-ray radiations. This requires an ultra-low-power dosimeter that ensures irradiation does not exceed the maximum allowable 50 Gy while providing the required minimum levels of 25 Gy. In this work, minimum-sized MOS transistor devices are employed in an inverter configuration, eliminating the continuous flow of current and reducing power consumption significantly. Maximum measured currents, which flow only during the transition period, are in the nA range, compared to continuous currents of conventional sensor designs in the μA range. Final measured results show the viability of the proposed design for radiation dosimetry applications.

This paper deals with the estimation of parameters of a Thevenin equivalent in an AC grid. We consider the practically relevant case of measurements coming from a grid-connected inverter. Our focus is on non-intrusive measurements, as we postulate and later experimentally observe transients that occur in normal operation as the primary source of information. We notice that even during quiet, after work hours there are typically enough variations in the grid to enable successful convergence of our procedure. For completeness, we also consider the artificial case of no external variations and show that injection of very small current perturbations suffices for convergence. Our procedure is based on real-time monitoring of the estimated determinant of the regression matrix. Regression matrix properties are also used to evaluate the integrity of the estimates and to initiate a brief sequence of perturbation in rare cases of the exceptionally restful grid. The estimation algorithm is simple enough to be implementable on standard industrial controllers, yet robust and reliable in terms of speed of convergence.

The trial and error method is the conventional method for LCL parameter design. Its efficiency is low and it is difficult to obtain the optimal parameter. Furthermore, due to the lack of detailed analysis of the high-frequency harmonics in the inverter output voltage, the designed LCL filter cannot effectively filter them, resulting that the quality of the grid-connected current cannot fully meet IEEE 519 standard. Based on the above-mentioned problems, the high-frequency harmonics of inverter output voltage is analyzed in detail in this article, and the multiobjective optimization function, including five optimization objectives, is constructed. Combined with the particle swarm optimization, a screening method is proposed to realize the multiobjective optimization process. Under the proposed method, the LCL parameter, which happens to meet the requirement of IEEE 519 for the high-frequency harmonic distortion rate of the grid-connected current, can be obtained, and the greatest tradeoff of LCL filtering performance and filter cost is achieved. In addition, the proposed method considers the problem of weak grid and provides a complete engineering solution for LCL parameter design in different degrees of weak grid. Finally, the effectiveness and accuracy of the proposed design method are verified by contrast simulation and experiment.

This Article Presents a Versatile Multi Objective Control Approach to Control Photovoltaic (PV) Powered Micro-grid side Multipurpose Grid Integrated inverter (µ11 A.Naveen Kumar, Dr I. JacobRaglendG-MPGII). This envisaged system uses SRF Theory to establish Modified Multi-objective Flexible Synchronous reference frame (MMOFSRF) based control strategy to control µG-MPGII. This µG-MPGII can be employed to 1) Establish complete control on grid real power based on State of charge of battery (SOC) & load profile, 2) Works as distributed power quality enhancer with features of eliminating dominant harmonics produced by nonlinear loads at point of common coupling (PCC), injecting required reactive power for the load and improving power factor 3) Balance the utility grid currents under unbalanced load system. The transfer function model of proposed system is derived and analyzed for stability assessment through frequency response characteristics. The efficacy, dynamic Pursuance and multifunctional features of proposed system are verified by conducting comprehensive simulation studies in MATLAB/SIMULINK.

Frequency responses are nonidentical between the positive and the negative frequency range for symmetric three-phase systems modeled with complex transfer functions, which shows unbalanced stability margins. The unbalanced stability margins limit the system performance, as the system dynamics are restricted by the worst one. This article extends the discussion of unbalanced stability margins to asymmetric three-phase systems, i.e., three-phase grid-tied inverters, which are described by transfer matrices. The reason for unbalanced stability margins is analytically investigated, and different impacts are analyzed. It is found that both the control delay and asymmetric control loops can lead to the unbalanced stability margins. To improve the performance limited by the worst stability margin, a margin balancing control is proposed. By implementing a phase correction term, the worst stability margin can be increased by reducing the best one. As a result, the overall stability margin of the system can be improved. The design procedure is elaborated based on a 2-MW inverter system. Verifications are presented based on a 1-kW prototype including simulations, experimental results, and Nyquist analyses. This method applies to all types of grid-tied inverters with multiple control loops.

A novel topology based on linear power amplifiers (PAs) and real-time sinusoidal voltage-adjustment power supply systems (RTSPSs) for a permanent magnet synchronous motor (PMSM) drive system is proposed in this article. Here, PAs are applied to achieve high-precision motor drive control and minimize the motor torque ripple and harmonic loss caused by nonlinearities of the inverter in traditional space vector pulsewidth modulation. Meanwhile, in order to improve the conversion efficiency of PAs, the traditional dc power supply system of PAs is replaced by the RTSPSs, which is based on the wide-band-gap devices. The experimental results show that the efficiency of PAs in the motor system is increased from 58.88% to 79.25% and the fluctuation of the motor speed at a given speed of 2 r/min is reduced from 27 to 0.5 r/min.

This paper presents improved energy management for grid-inverter of a hybrid photovoltaic (PV)/fuel cell (FC) energy system with unbalanced sensitive loads. In the system, unbalanced loads draw unbalanced currents at each phase and consume power from energy units at different levels. This condition makes the grid unbalanced, which cannot be compensated by a conventional energy management controller used in grid inverters. For this, a phase balancing control method is proposed in order to improve the grid quality under unbalanced loading conditions. The proposed method calculates power differentiation values based on multiple-frame ab/dq transform instead of abc/dq transform in the conventional method. Thus, it eliminates negative & zero sequence components in addition to power flow control. Under unbalanced loading conditions, the proposed method removes the deficiency of the conventional energy management method which generates the symmetrical current references to trigger the switching elements of the inverter. In performance results, the system with unbalanced loads is tested for different case studies, which supply different power from energy units to grids. The results show that the proposed method provides power balancing at the grid-side and eliminates negative & zero sequence components at grid-side currents. (C) 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Ain Shams University.

Arc fault detection is an important process for ensuring the safety of PV and grid-connected inverters and is essential for producing PV systems in real applications. However, it is difficult to detect series dc arc faults using conventional fuses because these faults produce only small current variations. In addition, the arc fault detection devices have limited performance, because they focused on arc fault detection between PV arrays and inverter. Moreover, they require the additional current and voltage sensors to implement the arc fault detection algorithm. This article proposes an arc fault detection algorithm employing differential power processing (DPP) structure. The proposed algorithm only uses intrinsic voltage sensors of DPP and inverter, which can improve the cost-effectiveness of PV systems. In addition, the proposed algorithm can integrate the functionality of maximum power processing for each PV panel and arc fault detection. The voltage relationship between DPP and inverter is analyzed to detect the arc fault condition according to the DPP voltage sensing type. The performance of DPP units and its voltage relationship are verified with the control hardware-in-the-loop system. The arc fault detection performance is verified with the prototype PV system.

The concept of open-current vector for sparse matrix converter is put forward along with its application constraints in this article. Based on the open-current vector, an improved space vector modulation (SVM) strategy is proposed to reduce the peak magnitude of common-mode voltage (CMV) by 42.3% without sacrificing the performance of input and output waveforms and the voltage transfer ratio (VTR). First, the application constraints and common-mode equivalent circuit of the open-current vector in the rectifier stage of the sparse matrix converter are analyzed. After that, in accordance with the principle of minimum switching action and two adjacent active vector synthesis, the improved SVM strategy used a suitable open-current vector instead of the active-current vector in the rectifier stage when the zero-voltage vector is used in the inverter stage, which contributes to CMV reduction. The improved SVM strategy not only reduces the peak magnitude of the CMV, but also ensures that the performance of input and output waveforms and the VTR are the same with those of traditional SVM. Finally, the effectiveness of the improved SVM strategy is verified by simulation and experiments.

Multilevel inverters with a common-ground structure and voltage step-up feature are beneficial for transformerless grid-connected photovoltaic applications. In this article, a novel topology of such converters with a five-level output voltage generation is presented. The proposed topology comprises of an integrated switched-boost (SB) module and a dual T-type (D2T) cell constructed with 10 power switches (six unidirectional and two bidirectional). An inductor in the integrated SB module is used to boost the voltage across two involved capacitors of the D2T cell. Therefore, a desirable ac voltage magnitude for the grid-connected application can be achieved over a wide range of input voltage changes. Current stress is also kept within a permissible input current range by the soft-charging operation of the involved capacitors through the inductor. A corresponding dead-beat continuous-current-control-set controller with a sinusoidal PWM modulator is implemented for controlling the real and reactive powers. The controller has an added benefit of achieving constant switching frequency for power switches. Circuit description, theoretical analyses, and comparative study are discussed. Simulation and experimental results are also presented to confirm the feasibility and correctness of the proposed topology.

Large-scale integration of renewable generation, usually interfaced to the network through power electronics, has led to drastic changes in power system dynamics. This paper presents novel insights into stability properties of such systems. For that purpose, a high-fidelity dynamic model of a generic low-inertia power system has been developed. The full-order, state-of-the-art control schemes of both synchronous and converter-based generators are included, with the latter differentiating between grid-forming and grid-following mode of operation. Furthermore, the dynamics of transmission lines and loads are captured in the model. Using modal analysis techniques such as participation factors and parameter sensitivity, the most vulnerable segments of the system are determined and the adverse effects of timescale coupling and control interference are investigated. More precisely, this work characterizes the maximum permissible penetration levels of inverter-based generation as well as the nature of the associated unstable modes and the underlying dynamics. Finally, potential directions for improving the system stability margin under different generation portfolios are proposed for several benchmark systems.

A new transformer-less three-level grid-tied inverter is proposed in this article. By employing the switched-capacitor (SC) modules, a new topology is derived. The proposed topology has some features which are high efficiency, the capability of voltage boosting without utilization of any additional boost stage, and suppressing the leakage current by using common grounded strategy. In this article, a peak current control is employed to generate the gate pulses of power semiconductor switches and adjustment of both active and reactive powers. By doing so, the grid injected current is controlled and adjusted to have a proper quality. The operation modes, design consideration, and a comparison with some recently proposed grid-connected topologies are done through this paper. Finally, the performance and feasibility of the proposed inverter are confirmed with a 500 W experimental prototype.

Pulse density modulation (PDM) is often applied in inductively coupled power transfer (ICPT) systems to improve high-frequency inverter (HFI) efficiency. However, the PDM may cause the inverter output current fluctuation, even interruption for light load or low-quality factor system. This may result in the difficulty for the implementation of soft switching in ICPT. In this article, an improved PDM (IPDM) strategy is proposed by optimizing the distribution of switch sequences. Through the current fluctuation numerical analysis and Fourier decomposition, IPDM can reduce the current fluctuation and improve the system efficiency. The experimental results on a 20 kW ICPT system prototype show that the proposed IPDM strategy reduces the HFI output current ripple coefficient is 40% to 65% lower than PDM, and the efficiency is also improved.

In this paper, a Four Dimensional Space Vector Modulation (4D-SVM) is implemented for five phase Voltage Source Inverter (VSI) to improve the performance of the inverter. The 4D-SVM control technique generates switching pulses for five phase VSI system. The reference vector for 4D-SVM is identified by tracking subcubes and prisms located in the complex 4D-cubic region. The 4D-SVM for five phase inverter includes 32 switching state vectors; all the switching states are non-redundant switching states, which are located in 32 vertices of the 4D-cube. The proposed five phase inverter with 4D-SVM reduces CMV and Total Harmonic Distortion (THD) and minimized neutral current value. The minimization of CMV leads to avoid the damage of the winding and increases the life time of the motor. So for in two level inverter, the CMV is reduced up to Vdc/3 times of input voltage; In this proposed system, made an attempt to reduce the CMV level below this reported value. The simulation and hardware results are verified using matlab simulink and Field Programmable Gate Array (FPGA) processor.

This article proposes a method to compensate for the nonlinearity of an inverter through the estimation of the deadtime effect. The deadtime effect varies with the manufacturing tolerance of the inverter circuit itself and operating conditions, such as conducting current, dc-link voltage, and temperature. For the accurate compensation of the nonlinearity, the effect of the deadtime should be estimated in realtime. That effect on the control of the inverter is significantly affected by the pulsewidth modulation (PWM) scheme because the deadtime occurs only at the switching instant of the inverter, and the PWM scheme solely decides the switching. The proposed method exploits the difference of voltage error from the deadtime effect according to different PWM schemes. By comparing the effects with two different PWM schemes, namely continuous PWM and discontinuous PWM, the voltage error to a specific inverter caused by the deadtime can be identified. Several experimental tests are carried out to verify the validity of the proposed method. The results reveal that the voltage error due to the deadtime can be identified in the range of 100 mV at 300-V dc link. It is equivalent to 30 ns resolution in deadtime.

Conventional model predictive control (C-MPC) usually leads to considerable torque and current ripples since only one voltage vector is applied. In addition, the C-MPC applied in the hybrid-inverter) driven open-winding permanent magnet synchronous motor (OW-PMSM) suffers from complex tuning work of weighting factors and iterated evaluation work of all potential vectors because the capacitor voltage constraint in cost function is related to the switching states. In this article, an improved three-vector MPC based on energy storage model is proposed for the HI-OW-PMSM system. Firstly, a new prediction model of dc-link capacitor voltage based on energy storage model is proposed thus the capacitor voltage constraint is decoupled to the three-phase switching states. Furthermore, a novel restructured cost function without weighting factors can be obtained. Accordingly, by using the new prediction model and the novel cost function, the voltage reference can be easily obtained and a three-vector based prediction strategy without sector division can be carried out to achieve optimal voltage vectors selection and duty cycle calculation. Therefore, the system performance is improved and the calculation burden is also reduced. Finally, comparative experimental studies are carried out to validate the effectiveness of the proposed improved three-vector MPC method.

In this article, a multilevel inverter scheme to generate a 30-sided space vector structure (SVS) with congruent triangles is proposed. The 30-sided SVS eliminates all the lower order harmonics till 25th order from motor phase voltage throughout the modulation range. The proposed scheme is implemented using a single dc-link on an open-end induction motor (OEIM). The OEIM is fed with primary inverter from one end and secondary inverter from the other end. Primary inverter is fed from an active dc-link and supplies all the required active power for the scheme. Secondary inverter is a capacitor fed inverter, which acts as the switched capacitive filter. In this work, a simple algorithm is proposed, which calculates the timings required for a 2-level 30-sided SVS from sampled reference voltages. The algorithm requires only simple operations such as addition, multiplication, and comparisons. From the obtained timing values, the space vector location of three nearest multilevel 30-sided vectors and its time duration can be identified. The feasibility of the proposed scheme is proved by experimental results.

Direct power control (DPC) is widely used in grid-connected inverters. First, considering the effects of phase-locked loop (PLL), voltage outer loop, power inner loop, control delay, and frequency coupling, a broadband admittance model of the grid-connected inverter with DPC is established. The admittance characteristics of grid-connected inverters with DPC and closed-loop current control (CCC) are compared and analyzed. Due to the different inner loop control objects, the components produced by the power calculation in DPC and the Park's transformation in CCC cause the admittance differences between the grid-connected inverters with DPC and CCC. Then, the effects of grid impedance, output power, and control parameters on system stability are analyzed. It is revealed that the stability of the grid-connected inverter with DPC is very sensitive to grid impedance and easily affected by output power and inner loop bandwidth, while the grid-connected inverter with CCC has a better adaptability to weak grid, high output power, and inner loop bandwidth. Moreover, the PLL bandwidth has little effect on the stability of the grid-connected inverter with DPC, but has a great impact on the stability of the grid-connected inverter with CCC when the inverter is connected to weak grid. Finally, the correctness of the analysis is verified by experiments.