This paper presents a comparative study of modulation strategies for a full-bridge based unidirectional step-down partial power converter (PPC), focusing on a newly proposed Buck Modulation (BM) scheme. Unlike traditional Phase-Shift Modulation (PSM), BM disables transformer utilization by applying identical PWM signals to all switches in the converter’s full-bridge, effectively converting the topology into an equivalent buck converter. Thermal simulations were conducted to evaluate efficiency performance across different transformer turns ratios and load conditions. Results demonstrate that BM achieves superior efficiency at light loads when the transformer ratio is below unity, and consistently outperforms PSM across the entire power range when the ratio exceeds unity. Furthermore, BM offers a wider and more flexible operating voltage range.

Photovoltaic (PV) grid-connected system is nowa-days a well established industry. For PV inverters, European (EURO) efficiency and California Energy Commission (CEC) efficiency have been defined, as Figures of Merit (FoM) allowing easy PV inverter efficiency estimation, while including consideration on PV variability. This paper explores the applicability of weighted efficiencies for off-grid H2production system with DC-DC connection of the PV source, for both DC-DC converter, and electrolyzer. The study considers precise modeling of the system, and evaluation of its operation and efficiency over real scenario, with environmental data of three locations considered, with minute-based resolution, allowing precise simulation. Evaluation of EURO and CEC efficiencies for DC-DC converter and electrolyzer demonstrate the accuracy of the FoM with error lower than 1.23% and 3.70% respectively. It is finally recommended the use of weighted efficiencies for the evaluation of off-grid H2production systems, allowing fast and accurate comparison between different electrolyzer and DC-DC converter technologies while designing new plants.

This paper presents a Minimum Stress Factor Tracking (MSFT) algorithm designed for a T-Type Dual Active Bridge (DAB) DC-DC converter, aimed at electric vehicle (EV) charging applications. The proposed system dynamically selects among six different modulation configurations by evaluating a weighted combination of three normalized stress factors: Semiconductor Component Stress Factor (SCSF), Capacitor Component Stress Factor (CCSF), and Transformer Winding Component Stress Factor (WCSF). Each stress factor is mathematically modeled across the full operating range, allowing real-time optimization without dependency on runtime simulations. The weighting factors are user-defined and sum to unity, offering flexibility to adapt the stress minimization strategy according to specific reliability requirements. The results demonstrate that the proposed approach achieves significant stress reduction on critical components while maintaining full controllability and capacitor voltage balance. This methodology addresses a seldom-explored aspect in the current literature, opening a new path for reliability-oriented optimization in T-Type DAB converters for EV charging systems.

This paper presents a hybrid controller based on fractional order control (FOC) with finite control set model predictive control (FCS-MPC) for LCL grid-tied single-phase multilevel inverters. Recently, FCS-MPC has received major interest in fast control tracking and handling several control objectives together in a single cost function. However, in the case of LCL grid-tied inverters, the control of the inverter side current, grid side current, and AC filter capacitor voltage, in addition to the voltage balance of dc-link capacitors, makes the design process of a single cost function more difficult to reach. Therefore, a cascaded FOC resonant controller for grid-side current with inner FCS-MPC for controlling inverter-side current and capacitor voltages is proposed for a single-phase five-level H-bridge T-type grid-tied inverter. The proposed controller merges the characteristics of FOC, FCS-MPC, and resonant controllers, improving system performance. Simulation results are provided to verify the superior tracking and control performance of the new proposed controller.

This paper proposes a DC-coupled PEM electrolyzer current control scheme combined with an Input Capacitors Voltage Balancing (ICVB) strategy for a three-channel interleaved dual buck converter topology, aimed at low-carbon hydrogen production. Input capacitors voltage imbalance can lead to improper operation of the interleaved dual buck converter topology, potentially damaging the power components. To address this issue, a control scheme featuring differential operation is proposed to regulate the input voltages, alongside the current control of the electrolyzer, directly influencing the amount of hydrogen produced. By controlling 5 out of 6 inductor currents, it is possible to leave one degree of freedom to control the voltage balance of the input capacitors, indirectly controlling the remaining current due to the operating principle of the topology. Simulation results are presented to validate the proposed control scheme for the proposed system with a nominal power of 1MW.

Electric vehicle (EV) charging infrastructure is critical, especially considering the exponential increase in electric vehicle adoption over the last decade, leading to a surge in demand for charging stations. However, it is not just about increasing their number; consideration should also be given to the reliability and availability of these chargers. Several factors can affect power converter reliability, many of which have been studied independently of the application. Nevertheless, in addition to those EV chargers are subjected to unique controls and operation that depend on the different battery charging profiles that have been proposed. This work analyzes the impact of different load profiles on semiconductors, using a total of four different load profile strategies. The results show that there is a very similar impact on damage among the most mainstream charging profiles. However, the Pulse Charging (PC) profile stands out as one that accumulates more semiconductor damage, reducing EV charger reliability.

Electromobility has experienced rapid expansion, where electric vehicle (EV) battery and charging processes are of great importance. Charging profiles have been proposed to enhance charging speeds while improving battery lifetime. However, more research is needed in relation to their impact on the charging infrastructure. This paper analyzes the impact of the charging profile over the global efficiency of the power converter of the fast charging station. Both full and partial charges are considered, and four types of charging profiles and variants, for a total of 12 charging profiles are considered. Results of this study show significant efficiency differences depending on the charging profile, being the classical Constant Current Constant Voltage (CCCV) at low charging rate the most efficient charging profile, while Pulse Charging (PC) leads to the lowest. The dependence of the global efficiency of the power converter with the corresponding charging time is also analyzed.

Phase-shifted pulse width modulation (PS-PWM) is one of the preferred modulation strategies for cascaded H-bridge (CHB) converters due to its excellent harmonic performance. Nevertheless, this modulation strategy needs a fast sampling frequency, which can increase with the number of H-bridge sub-modules (SMs). Moreover, the advantages related to the harmonic content of the output voltages are usually lost for applications that require unbalanced operation conditions regarding SM power or voltage references, such as solar PV or battery energy storage systems. This work proposes a feed-forward compensation technique that reduces the sampling frequency to two times the carrier frequency while maintaining the good harmonic performance of the CHB output voltages. Simulation results are carried out to compare and demonstrate the superior performance of the proposed technique.

Recently, doubly grounded (DG) photovoltaic (PV) inverters have proven superior performance in total elimination capability of PV leakage currents. This is due to the direct connection of PV side negative terminal with grid side neutral terminal. This paper presents a boost DG-PV five-level (5L) inverter topology based on neutral point clamped (NPC) leg. The proposed DG-PV boost 5L-NPC inverter totally eliminates the existing leakage currents, achieves boost of PV voltage, is considered a single stage PV inverter structure, uses low component count, and has continuous PV current. Moreover, finite control set model predictive control (FCS-MPC) is presented for controlling multiple objectives in a single cost function for the proposed topology. The FCS-MPC also eliminates the cascaded l0ops in the conventional control methods, which facilitates the control design process. A simulation based case study is preformed of the proposed DG-PV boost 5L-NPC inverter with FCS-MPC controller. Superiority of proposed inverter and controller have been verified with various step changes in PV power, power quality of injected grid current, and capacitor voltage control.

Analysis and performance of a three-phase single-stage SEPIC differential-mode inverter (DMI) using a discontinuous modulation scheme (DMS) are presented in this paper. Since the DMS was previously suggested in many inverter topologies to reduce the voltage stress of utilized switching devices and enhance inverter efficiency, a simple design process to integrate DMS into the SEPIC DMI is proposed in this work. With this modulation strategy, the discontinuity of the duty cycle for one-third of the entire grid frequency cycle thoroughly minimizes the conduction losses and switching losses into the SEPIC converters. Also, it is noted that the voltage stress is significantly reduced in passive elements as well as switching devices. Furthermore, the compensation of the negative sequence harmonic components is maintained without adding extra sensors. The inverter operation along with mathematical analysis of the DMS and grid current control is presented. A PSIM simulator is used to evaluate the behavior of the proposed modulation strategy. Finally, a comparison with the conventional continuous modulation scheme (CMS) is performed for a better assessment.

Electric vehicle (EV) charging infrastructure will play a critical role in decarbonization during the next decades, energizing a large share of the transportation sector. This will further increase the enabling role of power electronics converters as an energy transition technology in the widespread adoption of clean energy sources and their efficient use. However, this deep transformation comes with challenges, some of which are already unfolding, such as the slow deployment of charging infrastructure and competing charging standards, and others that will have a long-term impact if not addressed timely, such as the reliability of power converters and power system stability due to loss of system inertia, just to name a few. Nevertheless, the inherent transition toward power systems with higher penetration of power electronics and batteries, together with a layer of communications and information technologies, will also bring opportunities for more flexible and intelligent grid integration and services, which could increase the share of renewable energy in the power grid. This work provides an overview of the existing charging infrastructure ecosystem, covering the different charging technologies for different EV classes, their structure, and configurations, including how they can impact the grid in the future.

Electromobility has been growing rapidly in recent years, as a result of green and sustainability policies that promote it, but its growth has been hampered by having less autonomy than combustion vehicles, not being able to directly replace them especially in heavy-duty electric vehicles powertrains. The main objective of this work is to propose an improvement to an already implemented Bidirectional Dual-Active-Bridge (DAB) Partial Power Converter (PPC) topology, seeking to boost efficiency by testing different modulations. The modulation study applied to PPC is interesting in order to identify the cases where the RMS current in the transformer is minimized. Results of the study shows that efficiency of the DAB-based PPC can be optimized by using the correct modulation, with a possible maximum efficiency of 99.41% at 6.526 kW.

PV microinverters are the preferred choice for the integration of PV systems in rooftop applications. Among them, single stage microinverters are gaining more attention in the last years due to their inherent advantages, where differential mode inverters have been one of the mainstream proposed architectures. In this context, dual boost inverters (DBI) appears as a very attractive alternative, however, control issues and efficiency are still challenges to solve. To overcome these issues, the DBI with bypass switches and half-cycle modulation has been proposed, in order to increase the efficiency and suppress PV leakage currents. In this paper, a simple and efficient control scheme for the DBI with bypass switches is proposed. In order to validate the proposed control scheme, the DBI with bypass switches is simulated operating as PV microinverter under dynamic test conditions.

Power Optimizers are a trending solution for photovoltaic (PV) applications since they allow high energy yield performing energy conversion and distributed maximum power point tracking (DMPPT). Because of its benefits in terms of efficiency, component rating and power density, partial power converter (PPC) is a very attractive solution to operate as power optimizers. In this paper, a new reconfigurable Full-bridge-based PPC is proposed. The reconfigurable scheme allows to take advantage of both step-up PPC of Type I, and step-down PPC of Type II. In order to enlarge the operation range, the proposed converter can also be reconfigured as a classical full-power converter. Theoretical analysis of the converter is provided and simulation results show the correct operation of the proposed reconfigurable PPC, and validate its effectiveness and performances.

This paper presents an improved sequential model predictive control (MPC) method for single phase photovoltaic (PV) applications. The T-type H-bridge five-level topology is selected in this paper. The proposed method achieves constant switching frequency operation of the inverter, which is advantageous over the variable switching frequency MPC methods. The proposed fixed switching frequency MPC (FSF-MPC) method eliminates the weighting factors, which represent critical element in applying classical MPC methods. Moreover, the proposed FSF-MPC method achieves low dv/dt values through using optimized switching sequences to evaluate the cost function. The simulation results of the proposed FSF-MPC method are provided and compared with variable switching frequency MPC method. The results show the fast tracking in both controllers. Whereas, fixed switching frequency and weighting factorless operation are obtained using the proposed FSF-MPC method. Additionally, lower total harmonic distortion (THD) in the output voltage is obtained using the proposed FSF-MPC method compared to classical MPC method.

Battery energy storage systems (BESSs) have be-come integral parts in photovoltaic (PV) energy systems due to their fluctuated nature. The most common solutions in the literature for hybrid PV-battery systems are based on two-stage power converter solutions with separate power converters. However, these solutions increase the cost of the system and the number of required devices. Additionally, leakage currents represent critical issue for safe and reliable operation of PV systems. This paper presents a three-port configuration for hybrid PV-battery grid-connected systems. The proposed configuration includes a common ground connection between the PV side and grid side, which results in the elimination of leakage current components. Moreover, a finite control set model predictive control (FCS-MPC) is presented in this paper for controlling the proposed three-port configuration. The proposed controller achieves the control of multiple objectives simultaneously in addition to having fast dynamic response. Simulation results of the proposed configuration and control method are provided in this paper. The results show the effectiveness of the proposed configuration for hybrid PV-battery systems.

This paper presents a new common grounded (CG) multilevel boost inverter (MI) topology for single-phase grid-tied photovoltaic (PV) applications. The proposed topology has the capability to fully eliminate the leakage currents in PV systems due to the using of the CG connection. Additionally, the proposed topology benefits the high boosting factor capability of the low PV voltage. The proposed topology represents a single stage power conversion system with reduced power components compared to the traditional two-stage PV power conversion systems. In addition, model predictive controller (MPC) is proposed in this paper to control the proposed topology. The proposed controller can control multiple objectives simultaneously without using cascaded controllers. The simulation results with the different case studies are provided. The results confirm the superiority of the proposed CG boost MI topology and the proposed MPC method. Furthermore, fast tracking of the grid active and reactive power demands is achieved using the proposed MPC method.

Differential-mode inverter is an attractive solution for photovoltaic (PV) microinverter applications since this structure allows to perform both voltage elevation and grid connection in a single conversion stage. In this paper a partial power differential mode inverter (PPDMI) is proposed. It is demonstrated that by using two partial power converter, the proposed solution allows to reduce the power rating of the structure by 15% in comparison to full-power structure. Moreover, averaged power processed by the converter is also reduced by 33%. In order to validate the proposed converter a PV microinverter realized with a flyback-based PPDMI has been simulated. The results show the attractiveness of the solution with estimated efficiency reaching 94.6%.

This paper presents a comparison of buck-boost partial power converters (PPC) for the DC-DC conversion stage of an electrical vehicle (EV) fast charging station. By using a DC-DC buck-boost structure, the proposed fast charger can operate with wide output voltage range. The proposed topology can be used to charge either 400V or 800V batteries. Since the PCC only processes a fraction of the total power, high efficiency is obtained. Two different buck-boost PPC topologies are compared. First structure consider two-quadrant switches in order to obtain bipolar voltage, while the second structure uses an unfolding bridge to change the voltage polarity. Results show that the first solution with two-quadrant switches allows better efficiency. The proposed converter operation is then evaluated for fast charging applications for both 400V and 800V batteries, showing high efficiency up to 99%, making the proposed solution very attractive for fast charging application.

In this paper, a space Vector modulation scheme (SVMS) to enhance the performance of the single-stage three-phase grid-tied SEPIC-based differential inverter is presented. Compared to the traditional modulation schemes, the proposed modulation scheme offers a significant reduction in the peaks of output voltages and input currents of the utilized SEPIC modules at the same voltage gain. Moreover, the peak voltages of the utilized capacitors in SEPIC converters are reduced. Therefore, the voltage stresses, conduction losses, and switching losses have been decreased, and the system efficiency has been increased in accordance. The proposed SVMS is implemented by employing a simple modification to the traditional continuous modulation scheme (CMS) of differential inverters, which keeps the smooth operation of the grid-current control at the inverter side and verifies low execution time. Moreover, a detailed comparison between the proposed modulation scheme and traditional CMS at different power ratings is introduced. The performance of the proposed SVMS is evaluated using the PSIM environment to validate the theoretical features added to the grid-current control and the SEPIC-based differential inverter.

An interleaved DC/DC power cells-based topology is proposed in combination with a control method for photovoltaic plants. For this, two partial power and two interleaving methods are evaluated in terms of efficiency and performance. The selected topology consists of input-parallel-output-parallel interleaved DC/DC converters, which together with the control strategy, allows a high efficiency photovoltaic system, unlike conventional topologies. However, this type of topology is prone to present an unbalanced power distribution between the DC/DC power cells, mainly due to the natural differences between their components. This paper shows the application of a power balancing control strategy for interleaved partial power converters, which guarantees an equitable power distribution, therefore, it enables a correct sizing of the components. The simulation results show the correct operation of the power cells, in terms of overall high efficiency and power distribution among the power cells.

Transformerless photovoltaic (PV) inverter topologies have proven superior performance over transformer-based inverter topologies. However, they face challenges due to their high leakage currents and voltage step-up requirements. There-fore, modified topologies and/or modulation techniques are essential to limit the current leakages to standard limits. The doubly grounded (DG) inverter topologies represent efficient solutions for totally limiting the leakage currents. This paper presents a finite control set (FCS) model predictive controller (MPC) method for DG step-up five-level PV inverter topology. The proposed FCS-MPC method can control the injected grid currents and multiple capacitors voltages simultaneously with high power quality output. The modelling and design of the step-up inverter topology and the FCS-MPC method are given in the paper. Simulation results with step-up DG five-level PV inverter topology are performed to validate the proposed FCS-MPC method. Moreover, the proposed FCS-MPC method has been validated using simulation results at the various operating conditions of PV inverters.

Leakage currents represent critical issues for the operation of conventional photovoltaic (PV) inverter topologies. Recently, the common grounded (CG) PV inverter topologies have presented superior performance over the conventional PV inverter topologies from the leakage currents elimination point of view. The multilevel CG-PV inverter topologies combine both features of the multilevel output voltage and the CG connection. Among the existing CG topologies, the switched capacitor types have found wide applications due to the lower cost, volume, and losses on the passive inductors. However, burdens have been risen for the control system to achieve multi-objectives, which includes controlling the output current of the inverter and the capacitor voltages. Therefore, this paper presents a Finite Control Set Model Predictive Control (FCS-MPC) method for five-level CG single-phase PV inverter topology. The FCS-MPC method presents reduced harmonic contents of the output currents and precise tracking to its reference value. The design guidelines of the FCS-MPC method and weighting factor adjustments are provided in this paper. Simulation results are presented in order to validate the effectiveness of the FCS-MPC method.

Fault tolerant (FT) operation in photovoltaic (PV) inverters is gaining increased attention in order to improve system availability. Conventional string PV inverters lack the ability to eliminate the leakage currents of the system during fault modes of operation. Therefore, traditional PV inverters are modified through modulations and structures to tolerate such faults. However, proper operation and control of FT-PV-inverters remain challenging, particularly on the better utilization of the extra added components. This paper proposes a new modulation method for eliminating the PV inverter leakage current in normal and faulty modes of operations. The sinusoidal based pulse width modulation (PWM) scheme is modified for implementing the new proposed modulation. In addition, the proposed PWM is capable of preserving full rating and energy efficiency operation of the inverter with leakage current elimination in both the normal and faulty operating modes. The proposed inverter and modulation method are implemented and tested at various conditions. The results confirm the superiority and leakage current elimination capability of the new proposed PWM method.

Novel reconfigurable rectifier circuit is presented. It features three operating modes: full-bridge rectifier, voltage doubler rectifier, voltage quadrupler rectifier. After the rectifier topology is introduced, a case study dc-dc converter based on quasi-Z-source full-bridge topology is presented. An experimental prototype was assembled to verify concept feasibility. The assembled converter is suitable for the global maximum power point tracking owing to the wide input voltage range achieved. DC voltage gain theoretical expressions are verified experimentally, and measured efficiency is given.

Increasing the amount of energy extracted from a large-scale photovoltaic (PV) plant directly impacts its profitability. Obtaining higher energy yields depends heavily on the efficiency of the power conversion stages, but also on the configuration of the PV plant. More distributed maximum power point tracking (MPPT) among PV modules, allows maximizing the amount of energy extracted, especially under non-uniform conditions. To deal with partial shading conditions at module level, a sub-module power optimizer based on partial power converters is proposed. The configuration employs an isolated partial DC-DC power converters allowing to decouple the shaded parts from the unshaded at PV module level, maximizing the energy extracted. The behavior of the proposed configuration is verified through simulation, which is compared with a classic string configuration through analysis based on performance, improvements, and drawbacks of the proposed structure under mismatching scenarios.

Inductors with soft saturation cores built on compressed iron powder have higher saturation flux densities in comparison to ferrite gapped inductors, exhibiting a gradual drop of permeability for increasing magnetic field strength. This behavior yields to a gradual drop of differential inductance for increasing current, which avoids sudden core saturation and overcurrent produced in hard saturation cores as the inductance plummets when the maximum flux density is reached. However, the inductance in soft saturation cores starts dropping in the wide range of nominal current operation, increasing the complexity of the converter model and the control scheme. In this work, an interleaved dc-dc converter for supercapacitor management is modeled in continuous and discontinuous conduction mode, considering an inductor core with a linear drop in the differential inductance. A suitable current control strategy is proposed. Analysis of the model is given and simulated results that confirm the performance of the proposed control strategy are shown.

This paper proposes a new topology with reduced switch count for a regenerative flying capacitor multilevel inverter. This paper also introduces a new control strategy, the use of Predictive Control. The resulting control scheme is extremely simple to understand and to implement. In addition, simulation results present a very good performance of the converter.

This paper proposes an algorithm that effectively allows a PV plant to inject a given amount of reactive power into the grid regardless of the irradiance and temperature levels. In the presence of irradiance (daylight hours), the system injects active and reactive power into the grid, and the losses of the topology are supplied from the PV. Under absence of irradiance (clouds and at night) the system keeps the reactive power level into the grid, and the losses of the converter are supplied by the grid. Moreover, the proposed algorithm is capable of injecting a constant and given amount of reactive power during the transitions among the operating modes regardless of the active power level being injected into the grid. Thus, providing an overall robust ancillary service to support the grid.

In photovoltaic (PV) systems, module level power electronics has focused a lot of attention in the last years. The microinverter, also known as AC module, has shown to be an interesting solution. For this purpose, PV microinverter architectures with pseudo DC-link consisting in a DC-DC converter followed by an unfolding inverter have been analyzed as good alternatives. This paper proposes a new push-pull based pseudo DC-link microinverter. Simulation results are provided to validate the behavior of the proposed microinverter. Comparison with the classical interleaved flyback pseudo DC-link microinverter is given to show the interest of the proposed structure. Results show improvement in terms of conversion efficiency and power quality.

The search of efficient, robust and fault-tolerant electronic power converters is a challenge for the industry and academia. Nowadays, the integration and exploitation of the renewable energy sources and energy storage systems is required. In these terms, the multilevel power converters and specifically the cascaded H-bridge (CHB) power converter is a very good candidate. However, if a CHB power converter operates under an unbalanced operation a low-frequency high-distortion content appears in the output voltage spectrum. In order to reduce this problem, an extra cell, equipped with a low voltage battery or supercapacitor, is added to the original CHB converter. The idea is to operate the extra cell with the convenient duty cycle value in order to eliminate the low-order harmonic distortion generated by the unbalanced operation. This makes the proposed method very interesting because it leads to a reduction of the grid connection filter.

Induction machines with double-star stator winding configuration, has extend the redundancy capability of the FEP based ship propulsion systems. However, under winding faulty conditions, the presence of negative sequence torque components introduce torque pulsations which are responsible for the torsional vibration stress. The classical Field Oriented Control (FOC) scheme approach, has a PI controller performance, because of the oscillating components, due to the development of negative sequence current components. On this matter, several approaches have been proposed, based on an alternative rotation matrix, which is dependant on the nature of the fault. In order to deal with this uncertainty, the present work presents a new approach, with the implementation of sliding current controllers in the synchronous reference frame.

This paper proposes an interleaved partial power converter (PPC) for the DC-DC conversion stage of electric vehicles (EVs) fast charging stations. The proposed converter topology is based on the H-bridge DC-DC converter. PPC allows the converter to process only a fraction of the total power, the rest being bypassed and directly supplied to the load. This increases the converter efficiency, as only a portion of the power goes through the converter, thus increasing its efficiency. The principle of operation of the proposed PPC is theoretically analyzed. Simulations of the behavior of the proposed PPC are provided for the charging of an EV battery. Results show the good behavior of the proposed system. It is in particular verified that the proposed converter only process a fraction of the power around 36% for the entire output power range. Comparison with a classical full power converter is provided showing that the proposed topology leads to a significant improvement in terms of conversion efficiency, from 95.1% to 98.3%.

Tow-stage configurations used in photovoltaic (PV) architectures (microinverter, string inverter or multistring inverter), are commonly used because of the advantages in front of mismatch conditions. In case of a partial shading scenario (produced by cloudy days and dust accumulation), two-stage architectures reach higher efficiencies compared with the traditional central inverter. It is because, the DC-stage allows a wide voltage range in order to perform maximum power point tracking (MPPT). On the other hand, the additional stage increase the component counts and the conversion losses, which leads to a reduced efficiency compared with the single-stage inverters. This work presents a solution for the traditional two-stage configurations, where the partial power conversion (PPC) concept is implemented in the DC-stage. In that way, the DC-DC converter handles a reduced power allowing a volume reduce and increased power density. Moreover, the AC-stage is made using a cascaded H-bridge topology, which improves the power quality and reduces the components size. Simulations are implemented in order to validate the proposed work.

This paper presents the design of a model predictive controller for grid-tie multilevel photovoltaic inverters. The proposed control scheme has a cascade-free structure and it uses a simple cost function optimization algorithm to compute the control action to be applied at the next sampling period. The cost function is designed by merging the grid current tracking with the overall dc-link voltage control and the neutral-point voltage minimization, avoiding the extra linear controllers used by conventional schemes. The strategy is validated in a three-level inverter connected to the mains trough simulation results using measured irradiance and temperature profiles.

Commercial photovoltaic microinverter topologies are normally composed of two stages: a step-up dc-dc stage and a step-down dc-ac stage. Nevertheless, to achieve high-ratio conversion, a high frequency transformer is used in the dc-dc stage, resulting in a bulky configuration with a high cost of implementation. To minimize these issues, a single stage boost inverter is proposed, composed by two bidirectional boost dc-dc converter. The control of this topology is complex due to its high non-linearity behaviour. Therefore, this paper presents a control methodology based on Finite Control Set Model Predictive Control (FCS-MP) algorithm with predictions of the system variables through the inverter model and an optimization process. Each boost dc-dc converter of the inverter is regulated to achieve an output signal composed of the sinusoidal wave with a dc bias. The main features of the boost inverter and predictive control are analysed. Simulations are shown in order to validate the proposed control and the converter for grid-connected PV applications.

In order to increase the conversion efficiency in photovoltaic (PV) systems, different configurations and topologies were developed. Depending on the application, the converters used for grid connection are built using one or two conversion stages. The advantages of the converters with a DC-stage are mainly the distributed maximum power point tracking algorithm per PV string or PV module and, when required for grid connection, the possibility of voltage elevation. However, the conversion efficiency is lower than configurations with a single-stage as the central inverter. Therefore, the proposed work presents a Partial Power DC-DC converter (PPC) which process part of the entire system power, and the remaining power is directly supplied to the output side. A topology is proposed and the details of its operation are explained based on the operating principle. Simulations are performed in order to evaluate the converter performance.

This paper presents an electrorefining plant operating with a photovoltaic dc-dc direct power interface. Different PV dc-dc power configurations are presented as alternative to partially feed the electrorefining process. The proposed power configuration is based on a multi-string dc-dc conversion system to achieve maximum power point tracking on each string, the electrorefining plant is fed through an interleaved isolated H-bridge dc-dc converter. The proposed configuration and control scheme are validated trough simulation results and tested under dynamic conditions.

Multilevel converters are an attractive alternative for medium voltage applications. The Stacked Multicell Converter (SMC), in particular, is a multilevel converter that allows to increase the output voltage level compared with the classical Flying Capacitor Converter, while decreasing the stored energy in the converter. This paper presents the application of Finite Control Set Model Predictive Control (FCS-MPC) in a three phase SMC with two cells and two stacks. The strategy controls simultaneously the load currents and capacitor voltages. simulation results show that the FCS-MPC strategy produces an effective control of the load current, while keeping balanced capacitor voltages. In addition, it is demonstrated that FCS-MPC outperforms Phase Shifted Pulse Width Modulation with linear controllers in transient and steady state operation.

Among multilevel converters, the cascaded H-bridge topology is one of the most industrially accepted solution for multiple applications, mostly for motor drives and flexible AC transmissions systems. Besides, other applications are being considered taking advantage of its modularity. The conventional phase-shifted PWM is the common method to generate the power devices switching of the converter. However, the performance is poor when an unbalanced operation is present. In this paper, an adaptive modulation method is presented where the angle to be applied to the phase-shifted PWM modulator is not fixed, but it is variable and calculated in real time depending on the operational conditions. Some simulation results are presented in order to demonstrate the good performance of the system.

Multilevel converters are an attractive alternative for medium voltage applications. The Stacked Multicell Converter (SMC), in particular, is a multilevel converter that allows to increase the output voltage level compared with the classical Flying Capacitor Converter, while decreasing the stored energy in the converter. This paper presents the application of Model Predictive Control (MPC) in a three phase SMC with three cells and two stacks (3×2). The strategy controls simultaneously the load currents and capacitor voltages. A problem about the implementation of MPC is the computational cost, which is bigger for multilevel converters. In the case of SMC 3×2 it is necessary to do 19683 iterations, for This paper proposed a new method to implement MPC reducing the necessary iterations from 19683 to 343. Simulation results show that the proposed MPC strategy produces an effective control of the load current, while keeping balanced capacitor voltages and lower THD that classical MPC with 57.38 times lower iterations.

The following work introduces the use of nine-switch converter in a multi-channel dual configuration for its use with multiphase permanent magnet synchronous generator, based wind energy conversion systems (WECS). The converter topology consists of a nine-switch dual channel three-phase voltage source converter capable of controlling two sets of three-phase variables without voltage limitations when operating both three-phase systems at same frequency. This feature is exploited to control both ends of the PMSG and both terminals of a 12 pulse transformer for grid connection.

The development of different configurations and topologies implemented in photovoltaic (PV) plants have made possible the increase of efficiency of the system. The traditional configurations of grid-connected PV systems, centralized, string, multi-string and ac-module, have been analyzed and actually most of them are controlled using classic PI control. Furthermore, each of them has different efficiency values due to the inherent associated problems. The large-scale PV plants do not work properly when the modules do not work at the same conditions, for example when some atmospheric and environmental problems are involved, it reduces the reliability of the system. The traditional small-scale PV configurations have a low efficiency due to the dc-boosting stage in order to reach the grid levels. This work presents a grid-connected PV configuration, focused in the improve of the efficiency of the traditional ac-module configuration, a flyback topology for the dc-side and a H-bridge topology for the grid connection will be implemented. Moreover, the proposed control scheme is based on FCS-MPC algorithm.

Solar photovoltaic (PV) energy has grown significantly during the last years. However, despite of the increase in installed capacity penetration, this energy source still arises important concerns due to the variability of power production. The short-term effects such as cloud shadowing and supply interruptions, as well as long-term effects such as dust accumulation, seasonal variation and ageing of PV modules can generate variability of power production. Therefore, the analysis of all the variability sources in order to provide a statistically consistent power production data represents an important challenge. This work presents a methodology to analyze data from a PV plant located in Chile by isolating the effect produced by soiling and, with this information a cost based cleaning program is proposed.

This paper presents a comprehensive study on the state-of-the-art and emerging wind energy technologies from the electrical engineering perspective. In an attempt to decrease cost of energy, increase the wind energy conversion efficiency, reliability, power density, and comply with the stringent grid codes, the electric generators and power electronic converters have emerged in a rigorous manner. From the market based survey, the most successful generator-converter configurations are addressed along with few promising topologies available in the literature. The back-to-back connected converters, passive generator-side converters, converters for multiphase generators, and converters without intermediate dc-link are investigated for high-power wind energy conversion systems (WECS), and presented in low and medium voltage category. The onshore and offshore wind farm configurations are analyzed with respect to the series/parallel connection of wind turbine ac/dc output terminals, and high voltage ac/dc transmission. The fault-ride through compliance methods used in the induction and synchronous generator based WECS are also discussed. The past, present and future trends in megawatt WECS are reviewed in terms of mechanical and electrical technologies, integration to power systems, and control theory. The important survey results, and technical merits and demerits of various WECS electrical systems are summarized by tables. The list of current and future wind turbines are also provided along with technical details.

This investigation presents a grid-connected five-level H-bridge neutral-point-clamped converter operating with a single dc-link as photovoltaic power source. The operation with a single dc-bus is enabled by adding a transformer with open-end winding secondary, where each power cell of the converter is connected. The proposed control scheme is validated trough simulation results and tested under dynamic conditions. It can be implemented with a good tracking of the active and reactive power references injected to the grid. The results serve as a preliminary validation to potential utilization of the converter in large scale photovoltaic energy conversion systems.

Large-scale grid-connected photovoltaic (PV) energy conversion systems operate at low voltage and are interfaced to medium-voltage and high-voltage ac utility grids through one or two step-up voltage transformer stages. In addition, the power conversion is performed with either a single stage dc-ac converter (central inverter) or a two stage dc-dc/dc-ac (string or multi-string inverter). However, prime solar irradiation regions in the world are not always located close to available utility lines, and in some cases are far away from main consumption areas. Furthermore, long overhead transmissions lines (>400km) and underwater transmission lines above 70kM, HVDC has become the most cost-effective solution. Among HVDC technologies, voltage source converter based HVDC system, mainly based on the modular multilevel converter (MMC), have become popular due to smaller filters, multi-network connection and decoupling of active and reactive power. This paper explores a new large-scale PV plant configuration based on a dc-dc stage interfaced directly to an MMC based HVDC system. Since PV systems are dc by nature, the proposed solution has several advantages, particularly if combined directly with the HVDC power station. Some power circuit topologies are presented, including their corresponding control schemes. Simulation results are presented to provide a preliminary evaluation on the operation and performance of the proposed system.

This paper describes control and modulation algorithm of a simplified multilevel AC-DC-AC converter for small power generation system which is based on well known Neutral Point Clamped (NPC) topology. Main advantage of this approach allows single 3-phase, 3-level converter to be utilized as a full interface between Permanent Magnet Synchronous Generator (PMSG) and the single-phase grid. Study of control and modulation for simplified converter are supported by simulation and experimental results. The three-phase AC-DC converter is controlled with regard of Field Oriented Control (FOC) principle. The current control of the single-phase DC-AC converter is based on the P+Multi-Resonant controller and Second Order Generalized Integrator Phase Locked Loop (SOGI-PLL). The multi resonant structure in single-phase converter allows a proper operation under non-ideal grid voltage.

This paper proposes a new power converter topology for the Wave Dragon multi-megawatt wave energy conversion platform. The current wave dragon power converter system is composed of several low-voltage two-level voltage source converters in back-to-back configuration; one per turbine-generator. Although this is a well known and proven technology, the use of distributed power electronic converters among all turbines does not bring any additional benefit in terms of efficiency and power quality. The proposed topology remains operating at low voltage and distributed at the generator side, but is combined at the grid side into a three-phase cascaded H-bridge (CHB) multilevel converter operating at medium voltage. This is achieved interfacing each PMSG through a low-voltage full bridge diode rectifier, followed by a boost dc-dc converter connected to the dc-link of the power cells of a 7-level CHB. The proposed configuration allows to concentrate the whole Wave Dragon platform into a single grid-tied converter with higher power quality and efficiency. Control schemes for both grid- and generator-side converters, and simulation results are presented in this paper.

Modular multilevel converter features high power quality and has high availability due to its inherent modularity. Those characteristics make this converter well suited for high voltage DC transmission applications. In this paper, a new application of modular multilevel converter in solar photovoltaic plants is proposed. The proposed structure can use higher voltages than standard photovoltaic plants, hence reducing internal losses. Additionally, an storage element can be integrated with the converter in order to perform peak shaving. The proposed topology and control strategy are shown and simulation results confirm their performance.

The automotive industry is making important changes towards the electrified transportation. Several Electric Vehicles (EVs) and Plug-in Hybrid EVs are currently on the market offering a clean and environment friendly alternative to conventional vehicles. However, limited mileage capacity and long refueling times have lead to a lukewarm reception from the consumers. In order to reduce the charging time fast charging architectures are being developed, usually as off-board solutions located in public installations. This paper presents a centralized charging station architecture, using a bipolar dc grid to power off-board chargers and integrate of DGs and storage systems. The central converter topology is an NPC and a novel balancing technique is implemented to extend the operating range of the power converter.

This paper presents a new small-scale single-phase photovoltaic (PV) energy conversion system. The topology is based on the series connection of two three-level T-type converters, which form a 5-level converter with two independent maximum power point tracking (MPPT) string connections. The topology merges benefits of string and multi-string PV configurations. The operating principle, the switching states, modulation scheme and control method are addressed in the paper. Simulation results are presented under dynamic conditions and different operating points for the two PV strings, to provide a preliminary validation of the topology and its performance.

A new predictive control strategy for current source rectifiers which allows an effective control of source and load currents is presented in this paper. This method uses the commutation states of the converter in the subsequent sampling time according to an optimization algorithm given by a cost function and the discrete system model. The two control goals are: (a) regulation of dc-link current according to an arbitrary reference, and (b) a good tracking of the source current to its sinusoidal reference. The feasibility of the proposed method is verified by MATLAB/Simulink software.

Large-scale photovoltaic energy conversion systems (LS-PECS) are currently well into the megawatt range. Therefore multilevel converters have been proposed as an attractive solution due to medium voltage operation, higher efficiency, power quality, and possibility to connect PV strings separately to each dc-link. However, the latter advantage makes the inverter susceptible to severe voltage unbalances due to the inherent power unbalance produced by the individual maximum power point tracking (MPPT) of the PV strings. This is particularly the case of the cascaded H-bridge inverter (CHB) where power cell and phase unbalances occur. In this work a new single dc-bus collector bus bar CHB is proposed for a multistring LS-PECS configuration. The operation with a single dc-bus is enabled by adding an isolation dc-dc converter stage to each power cell of the CHB. This allows inherent balanced operation of the CHB while fully decoupling the multistring PV-system from the grid tie inverter. This also greatly extends the operating range of the system compared to previous solutions. Simulation results for a 3.3kV 7-level CHB tested under dynamic conditions are presented and serve as a preliminary validation of the configuration and control schemes.

This paper presents a novel model predictive control method for current source converters (CSC) following the duality with voltage source converters (VSC). In VSC the predictive control is applied to the output current, while in this work the CSC is controlled through the output voltage. The method is based on the discrete prediction model of the system, including the converter and output filter. The model is used to predict future behavior of the system variables for each switching state of the converter. The predictions are evaluated in a cost function that weights the level of accomplishment of the control goals. The switching state with best performance is then generated. The proposed algorithm predicts the output terminal voltages (includes the output filter capacitors), ensuring sinusoidal voltage generation without the need of cascaded control loops, coordinate transformations and modulation schemes found in classic solutions. In addition, low switching frequency is imposed by including the switching frequency in the cost function. Simulation results show a preliminary validation of the proposed control scheme, with comparable performance to the classical solutions, especially in terms of the current and voltage harmonic distortion.

Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.