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In photovoltaic systems, common-mode voltage (CMV) generates leakage current, which shortens the insulation lifespan and causes safety problems. As for neutral-point-clamped (NPC) inverters, zero CMV PWM (ZCMV PWM) can be implemented to eliminate leakage current, but unable to balance neutral-point (NP) voltage in dc side. This article presents a novel modulation technique for NPC PV inverter. The strategy contains ZCMV PWM and another two modulation modes which keeps CMV constant in one switching period, so as to eliminate leakage current. In order to balance NP voltage, NP current is adjusted by selection of optimal modulation mode and the leakage current is still well eliminated during the process of balancing NP voltage. Compared with conventional ZCMV PWM, the proposed scheme can remove both leakage current and NP voltage deviation. The output performance and limitations of the proposed method are also introduced in the paper. Experiments are provided to verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]

Three-port converters with high voltage gain are desirable solutions for integrating renewable energy and energy storage devices into high voltage dc bus. A high gain three-port converter with soft switching is proposed in this paper, which can realize zero voltage switching for all switches and zero current switching for all diodes in various operating modes. Single coupled inductor is used to achieve high voltage gain and to reduce the voltage stress of switches so that switches with low on-resistance can be selected to reduce the conduction loss. In addition, the advantages of fewer components, higher voltage gain, and very low switch voltage stresses make the proposed converter more suitable for application in renewable energy systems than similar solutions. Various operating modes, performance analysis, design considerations, efficiency analysis, and control method of the proposed converter are discussed. A laboratory prototype with 30 V renewable energy source, 48 V energy storage device and 400 V output is designed to verify the performance of the proposed three-port converter. [ABSTRACT FROM AUTHOR]

Finite control set model predictive control (FCS-MPC) strategies for power conversion devices benefit from extending the prediction horizon length. Solving this problem relies on the definition of the underlying integer least-squares problem. Sphere decoding algorithm (SDA) has been extensively used in previous works as an approach to solve this problem. In this article, a parallel and fully scalable K-best SDA hardware design is proposed as an alternative. The K-best SDA establishes a different breadth-first search strategy, which addresses some of the main drawbacks of the SDA. Through experimental tests based on an uninterruptible power supply, the K-best SDA performance for long prediction horizon FCS-MPC is assessed and verified. Results demonstrate key beneficial aspects through which the K-best SDA is capable of rendering an improved control performance when compared to the conventional SDA. [ABSTRACT FROM AUTHOR]

This article proposes a novel control for the multiple-input, single-inductor, multiple-output dc–dc converters. It is digitally and discretely implemented, which can have an outstanding performance in low-power applications so that at the power of 10 mW, it has an efficiency of 92.5%. Conventionally, in this power range, an attempt is made to take advantage of an analog design that is flexible. Thus, a fully programmable (software designed) converter with digital design using a microcontroller is in great demand. This converter design basis is to deploy the microcontroller's central processing unit (CPU) as little as possible. Also, it only turns on the CPU when necessary to be employed in low-power, portable systems, e.g., energy-harvesting technologies. Therefore, construction costs are significantly reduced. Depending on the energy level of the inputs, they can simultaneously be utilized to charge the outputs. This article uses stability analysis, time-multiplexing control method, and variable-frequency pulsewidth modulation in the proposed control design. Each output can be charged with different frequencies according to its load, and the maximum switching frequency is equal to 10 kHz. Also, the proposed technique for zero-current switching has been digitally implemented; it can be utilized to determine the optimal value of the inductor discharge duty cycle based on the inductor's left-side voltage. Comparative simulations and experimental results reveal the superiority and practicality of the proposed approach. [ABSTRACT FROM AUTHOR]

A direct speed control strategy based on finite control set model predictive control (FCS–MPC) with a voltage smoother is presented herein. In the proposed concept, a finite set of smoothed voltage vectors characterized by an adjustable amplitude and a movable origin is introduced as voltage candidates in the FCS–MPC scheme. The controller predicts the future current and speed and outputs the optimal smoothed voltage using pulse-width modulation. Owing to this control scheme, an abrupt change in the output voltage, which causes a large current ripple, is avoided without additional computational costs. Simulation and experimental results obtained using a permanent magnet synchronous motor fed by a two-level three-phase inverter show that the proposed method effectively reduces the current ripple while achieving a high dynamic drive compared with the conventional FCS–MPC scheme. [ABSTRACT FROM AUTHOR]

The current error is hard to avoid for finite control set model predictive current control (FCS-MPCC) in nine-phase open-end winding permanent magnet synchronous motors. To overcome this problem, an online virtual voltage vector (V $^{3}$) synthesis strategy is proposed in this article. First, a group of V $^{3}$ s without harmonic voltage components are designed as the basic vectors for online synthesis. Then, two adjacent basic V $^{3}$ s and a zero vector are used to synthesize a new V $^{3}$ , which can output arbitrary amplitude and phase angle in the fundamental space. The two basic V $^{3}$ s are directly selected from the located sector of the predicted reference voltage vector (RVV), and their duration ratio can be simply calculated according to the angle of the RVV in the sector. In this way, the zero error is realized between the new V $^{3}$ and RVV. Moreover, an online pulse generation algorithm corresponding to the new V $^{3}$ is proposed, which can calculate the symmetrical pulse sequences in real-time for the multiphase OW drive system without the space vector modulator. Finally, experimental results have verified the effectiveness and superiority of the proposed strategy, in comparison to existing FCS-MPCC in multiphase OW motor drive systems. [ABSTRACT FROM AUTHOR]

A dc–dc converter used for fuel cell vehicles should be characterized by a wide voltage-gain range and low input current ripple. In order to meet the above requirements, a new nonisolated dc–dc converter consisting of an active switched-inductor cell, a zero current ripple cell, and a switched-capacitor (SC) cell was proposed in this article. The proposed converter integrates with the advantages of a wide voltage-gain range, zero input current ripple, low voltage stresses across power semiconductors, and common ground structure. Thanks to the use of a zero current ripple cell, not only the input current ripple is reduced but also the energy transfer path of the SC cell is changed, thereby reducing the instantaneous peak current of the SC structure. The operating principles, the characteristics analysis, and the parameter design of the proposed converter are given. In addition, to show the merits of the proposed converter, a comparison study is demonstrated. Finally, a prototype of 400 V, 1000 W/50 kHz is developed to validate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

This article proposes and studies different sigma–delta ($\Sigma$ $\Delta$) modulation strategies for obtaining a constant common-mode voltage (CMV) by eliminating the CMV level transitions in a five-phase voltage source inverter (VSI). These techniques are based on choosing vectors that generate a constant CMV with values of 0.1 $V_{\text{dc}}$ or –0.1 $V_{\text{dc}}$. Because of the high-switching frequencies used with wide-bandgap semiconductors, pulse-width modulation techniques continually generate high dv/dt values. Therefore, the proposal to combine a $\Sigma$ $\Delta$ modulation strategy with vector selections achieves a constant CMV level due to the elimination of its level transitions, a reduction in conducted electromagnetic interference and a high-efficiency converter operation. The average number of switching per transistor of the VSI is analyzed using the results from MATLAB/Simulink and PLECS simulations. Experimental results are obtained by applying the proposed $\Sigma$ $\Delta$ modulation strategies on a VSI with silicon carbide MOSFETs. The results demonstrate the achievement of the aforementioned features. [ABSTRACT FROM AUTHOR]

In this article, a low computational burden model predictive control (MPC) strategy without weighting factor is proposed for the single-phase cascaded H-bridge CHB converters. To reduce the switching state candidates, a hierarchy control algorithm is proposed. The grid current is controlled by selecting a subregion from the designed 2-D control plane, instead of the entire area. Two vectors are chosen in one sampling period for more accurate tracking. Then, the voltage balancing is achieved by selecting the optimal switching state from the subregion candidates to form the above two vectors. The cost function can be constructed of one variable: load voltage. Therefore, the weighting factor can be eliminated. No tuning or retuning processes are required in the proposed method. To reduce the computational time further, the principle of eliminating the switching state candidates operating the same voltage balancing performance is proposed. Conventional and proposed MPC methods are verified by experimental tests via a laboratory setup of a three-cell connected CHB converter. Steady-state and transient operations demonstrate that the proposed method guarantees less distortion grid current and shorter execution time (reduced from 15 to 3 $\mu s$). Fast response speed to variations in voltage reference and load resistance can be achieved t. [ABSTRACT FROM AUTHOR]

Fault localization is one of the most important issues for modular multilevel converters (MMCs) consisting of numerous switches. This article proposes an isolation forest (IF) based submodule (SM) switch open-circuit fault localization method for MMCs. Based on the continuous sampling SM capacitor voltages, a number of isolation trees (ITs) are produced to construct the IFs for MMCs. Through the comparison of continuous IFs’ outputs, the faulty SM can be effectively localized. The proposed IF-based fault localization method only requires SM capacitor voltages in the MMC to construct concise low-data-volume tree models, and uses sparsity and difference properties of outlier data to localize fault, and accordingly it simplifies calculation complexity. In addition, it does not require the MMC's mathematical models and manual setting of empirical thresholds. Simulation and experiment are conducted, and the results confirm the effectiveness of proposed method. [ABSTRACT FROM AUTHOR]

Multilevel inverters (MLIs) featuring reactive power ability and common ground (CG) have become much popular in transformerless grid-tied photovoltaic applications. A switched-capacitor (SC) based five-level transformerless inverter configuration is thus proposed in this article, which requires only six switches, one diode, three capacitors, and one input dc voltage supply. Notably, only four power switches are operated in high frequency, thus, the switching losses are reduced. Moreover, the presented topology can effectively tackle the leakage current problem using a CG architecture. A multicarrier phase disposition pulsewidth modulation strategy is employed to achieve reactive power regulation and SC voltage self-balancing. To achieve the neutral point voltage balance of the presented five-level inverter, a simple closed-loop voltage-balancing control method is proposed. The operation principles with modulation strategy and voltage self-balancing of SC are discussed in depth. Comparisons between the proposed and the state-of-the-art MLIs are presented in detail. Finally, experimental tests on a single-phase 1.1-kW prototype validate the appropriate performance of the proposed inverter. [ABSTRACT FROM AUTHOR]

This article presents a novel low-cost, single-switch, high-step-upresonant dc–dc converter with high reliability. The proposed converter topology comprises a low count of components and a simple structure and achieves the low ripple input current characteristic. The inductors in the resonant network participate in the resonant process rather than creating voltage spikes across the switch and likely reverse recovery problems. The circuit operates in the soft-switching condition (ZVS–ZCS conditions in the turn-off and turn-on transitions), leading to a significant reduction of the switching losses. Moreover, employing film capacitors instead of electrolytic capacitors reduces the size of the circuit and improves reliability. The operational principle and comprehensive steady-state analysis in the continuous conduction mode are discussed in detail, alongside the design considerations of the proposed converter. The validity of the theoretical equations is investigated via experiments, achieving maximum efficiency of 97.69% for a converter designed at the input of 24.5 V, the negative output of 200 V, and the maximum powerof 200 W. [ABSTRACT FROM AUTHOR]

The switched-capacitor of boost seven-level active neutral-point-clamped inverter has the large voltage ripple due to its inherent long discharging interval. Aiming at reducing the switched-capacitor voltage ripple and subsequently the capacitance, this article proposes a flexible third harmonic voltage modulation method. In specific, the long discharging interval can be divided into short intervals or even avoided by flexibly regulating the amplitude and phase-angle of third harmonic voltage based on various modulation indexes and power factors. An offline particle swarm optimization algorithm is employed to find the corresponding optimal amplitude and phase-angle of third harmonic voltage, which will further be put into the online look-up table to simplify the real time implementation. Experimental results verified the performance of the proposed modulation method. [ABSTRACT FROM AUTHOR]

This article presents a highly reliable push–pull resonant dc/dc converter for medium-power applications. At medium power, conventional push–pull resonant dc/dc converter experiences a very high current spike at the secondary-side switches, and this spike can destroy the active power components. We eliminate this current spike by connecting clamp diodes to the resonant capacitors. Moreover, the proposed converter achieves fully zero-voltage-switching (ZVS) turn-off at the secondary-side switches when the load exceeds the threshold. Furthermore, the proposed converter is invulnerable to the short-circuit problem at the output. Experimental results are presented to show the effectiveness of the proposed dc/dc converter at the medium power against a conventional solution. [ABSTRACT FROM AUTHOR]

In this article, we propose a switching anti-windup scheme for the aircraft engine control. The linear engine model with asymmetric saturation is first transformed into a switched system, each subsystem of which is subject to symmetric saturation. A state-dependent switching logic is presented to orchestrate the switching among multiple anti-windup compensators. We then establish the sufficient condition to guarantee the regional stability and $\mathcal {L}_{2}$ performance of the resulting closed-loop system. This condition is less conservative since the non-symmetric nature of the saturation nonlinearity can be fully exploited in the control design. Optimization algorithms are further developed for the anti-windup gain design. The theoretical aspect of the proposed method is analyzed rigorously, and the effectiveness is validated through experiments performed on a semi-physical test bed. [ABSTRACT FROM AUTHOR]

This article introduces a new nonisolated soft-switching coupled-inductor (CI) step-up dc/dc converter. The presented topology utilizes a three-winding CI (TWCI) along with a voltage multiplier circuit to increase the voltage conversion ratio without needing a high duty cycle. Using this circuit, a high voltage gain can be achieved without requiring a large number of turns ratio in the CI. The input current ripple of the introduced converter is very low, which is very desirable for renewable energy sources applications. The TWCI also creates an additional design freedom to increase the voltage gain, which indicates more circuit flexibility. Additionally, the voltage stress across the single power switch is limited with the help of a regenerative clamp capacitor. The leakage inductor of the CI is used to create a resonant tank to reduce power losses further. The leakage inductances help provide the zero-current switching conditions for the single power switch and decrease the reverse-recovery issues for all diodes, leading to an efficiency improvement. The operation principle, steady-state analysis, and design considerations are discussed thoroughly. Finally, the theoretical analysis is validated through experimental results obtained from a 200 W prototype with 250 V output voltage. [ABSTRACT FROM AUTHOR]

Unbalanced ac voltages drastically deteriorate the performance of five-level flying capacitor (FC) rectifiers. Without introducing an extra buffering circuit to absorb the second-order oscillating power, it is an incompatible contradiction for realizing both negative-sequence current reduction and second-order voltage ripple suppression. In this article, based on the idea of using FCs in the rectifier to absorb the oscillating power, a second-order voltage ripple suppression strategy for unbalanced ac voltage conditions is proposed. Reducing the negative-sequence currents and suppressing the dc voltage ripples can be simultaneously realized. Simulations and experimental results verified the effectiveness and performance of the proposed scheme well. [ABSTRACT FROM AUTHOR]

Gate driver circuits to ensure proper turn-on and turn-off for power switches are essential parts of a power converter design. They become significantly challenging for multilevel converters, where multiple switches are operated at active voltage domains. The recent favorable use of gallium nitride devices for power switches makes gate driving even more difficult as the switch performance and reliability are very sensitive to the variations of the gate driving signals and power rails compared with traditional power MOSFETs. This article discusses gate driving methods using a multilevel multi-inductor hybrid (MIH) converter as the demonstration prototype to address two key challenges in designing gate drivers: 1) providing level-shifted pulsewidth modulation signals to active voltage domains and 2) powering schemes for gate driver circuits. To solve the first challenge, an optimal use of available half-bridge drivers is proposed to eliminate the need for separate signal isolator chips. This method was implemented and verified in an MIH converter prototype for 48-V point-of-load applications using three different powering schemes for gate drivers, including isolated power modules, regulated supplies from switch blocking voltages, and cascaded bootstrap power rails with regulations. The gate driver techniques and powering schemes are compared experimentally in terms of performance to illustrate their benefits and tradeoffs. [ABSTRACT FROM AUTHOR]

A dual-transformer-based hybrid dual active bridge (DAB) converter for plug-in electric vehicle charging to cope with wide load voltages is introduced in this article. The control degrees of freedom are extended by splitting the leg and transformer of the conventional DAB converter (CDABC) in two parts. Based on the numerical analysis, the full-domain four-variable closed-form optimal trajectories targeting at the minimum root mean square value of the leakage inductor current is attainted, and the unified-segmental control strategy is proposed to handle the working modes shifting without the current inrush. As a result, the conduction losses and switching losses can be significantly reduced in boost mode compared to CDABC. The discussed converter and control strategy are verified by a 1.0-kW prototype. [ABSTRACT FROM AUTHOR]

This article investigates a decoupled vector current control strategy for grid-tied single-phase nine-level Packed E-Cell (PEC) inverters for vehicle-to-grid (V2G) technologies. The control design is based on a loop shaping approach, where performance specifications such as desired closed-loop bandwidth, closed-loop stability, robustness to pure time-delays in control loops/process, and decoupling between direct ($d$) and quadrature ($q$) axis of control signals are specified in the frequency domain. The control design problem is formulated as a convex optimization problem whose solution results in a multivariable controller in the $dq$ framework. The effectiveness of the proposed control strategy in terms of robust stability, current tracking, and improved total harmonic distortion is evaluated by experimental and simulation results under several case studies. The results also show that the designed controller provides the desired transient response as well as decoupling between the $dq$ output currents. [ABSTRACT FROM AUTHOR]

Linear modulation techniques (LMTs) of an asymmetrical six-phase machine (ASPM) with two isolated neutral points synthesize the desired voltage vectors by applying at least five switching states. Different choices of applied voltage vectors, sequences in which they are used, distribution of dwell-times among the redundant switching states give rise to a large number of possible LMTs. It is desirable that these LMTs avoid more than two transitions of a particular inverter leg within a carrier period. Only a subset of existing LMTs of ASPM follows this rule. Through an innovative approach, this article finds a way to account for all possible infinitely many LMTs that follow the rule of at most two transitions per leg. Another important criterion for the selection of an LMT is its current-ripple performance. Therefore, through numerical optimization, this article finds optimal LMTs among the above infinite possible LMTs for all reference voltage vectors in the linear range and for the whole feasible range of a machine parameter. This parameter is related to the leakage inductance of the machine and impacts the current ripple performance of ASPM. An optimal hybrid strategy is proposed with these optimal techniques, which outperforms all existing techniques in terms of the current ripple. The theoretical analysis is validated through simulation in MATLAB and experiments performed up to 3.5 kW on a hardware prototype. [ABSTRACT FROM AUTHOR]

This article presents two techniques to address the reliability issues caused by dv/dt under fast switching conditions of gallium nitride high electron mobility transistors. The first technique called active overdrive voltage control is proposed to adjust the gate driving strength according to the rising speed of the switching node (dv/dt) adaptively and, thus, decrease the dv/dt without increasing too much switching loss. The second technique is three-branch high-voltage level shifter (TBLS), which can improve the dv/dt immunity without compromising the signal transmission speed. The common mode current caused by dv/dt can be copied and then compensated by a transient current provided by the auxiliary branch. Combining the above techniques, a 400 V half bridge gate driver IC is fabricated by silicon-on-insulator BCD process. Compared with the gate driver IC utilizing the conventional open-loop output stage, the proposed gate driver IC reduces the turn-on switching loss by 16.2% for the same level of peak dv/dt at 400 V 10 A application. In addition, the proposed TBLS can achieve the dv/dt immunity up to 100 V/ns meanwhile the propagation delay less than 14 ns, enabling megahertz operation frequency. [ABSTRACT FROM AUTHOR]

In this article, a new stabilization control strategy is designed for a kind of nonholonomic system under full-state constraints and external disturbances. First, a stabilization controller for the first input is proposed to divide the entire control process into two stages. Then, using state transformations, the remaining original system is converted into an unconstrained system for which the stabilization controller is designed based on dynamic surface control. Stability analysis has established that the developed stabilization control algorithm can achieve the desired stabilization control objectives and the predefined full-state constraints. Meanwhile, all closed-loop signals keep bounded in the whole control process. Simulation and experiment results are given finally to demonstrate the effectiveness of the proposed stabilization control algorithm. [ABSTRACT FROM AUTHOR]

A series of three-port forward converters with a compact structure and extended duty cycle range is presented for the standalone renewable energy system. Bidirectional power-flow port embedding and switch device sharing can be used to derive these converters from conventional two-switches forward converters. In comparison to the conventional two-switch forward converter, only one switch and one diode are added to build an energy storage port with bidirectional power flow characteristics, which has the benefits of compact structure and low cost. Meanwhile, the embedding of the energy storage port provides an additional demagnetization loop for the magnetic inductor, which extends the duty cycle range of the forward converter so that the proposed converter no longer requires a duty cycle of less than 0.5 as in the case of conventional forward converters. The proposed converters also offer the advantages of fewer components, easy control, and independent control of power flow between multiple ports when compared to similar solutions. Finally, an experimental setup with a photovoltaic battery as an application is developed, and the experimental results verify the effectiveness and flexibility of the proposed topology and control method. [ABSTRACT FROM AUTHOR]

This article’s primary motivation is to propose a nonsingular and continuous terminal sliding-mode (TSM) control with reduced chattering, which is able to rapidly stabilize the second-order plant with high precision. To this end, a novel sliding-mode manifold, coined as practical TSM (PTSM) one, is first constructed. Once the proposed sliding surface is reached, a Lipschitz-continuous but slope-steep generalized velocity will be established at the origin such that the global nonsingularity of the equivalent control is ensured. The fast dynamic response with local high gain characterizes the sliding behavior inside the unit neighborhood of the origin. Importantly, the analytical solution of the proposed sliding-mode reduced-order system is deduced, which indicates that the finite time taken to slide into a preset small neighborhood of the origin can be calculated. The above designability of convergence time is necessary for control practices with accurate time sequence planning. Further, the corresponding globally singular-free PTSM reaching law with reduced chattering is designed based on the super-twisting algorithm. Finally, several groups of linear-motor-based control experiments verify the superiorities of proposed controllers. [ABSTRACT FROM AUTHOR]

Available capacity of lithium-ion batteries is directly linked to the mileage of the electric vehicle. The cell imbalance is recognized as a significant concern hindering the full utilization of pack capacity. Following the emerging concept of battery reconfiguration, this article proposes a dual-scale hierarchical equalization scheme enabled by a novel four-switch reconfigurable topology. In particular, a four-switch reconfigurable topology is proposed, for the first time, which enjoys the benefits of flexible reconfigurability, moderate complexity, and high fault tolerance. Relying on the new topology, a hierarchical equalization strategy is proposed incorporating the intramodule time-sharing intervention and inter-module splitting recombination. This endeavor contributes to achieving all-cell flexibility, which further promises the all-cell equalization and maximum capacity utilization. Hardware-in-the-loop results validate that the proposed reconfigurable topology-enabled hierarchical equalization strategy can improve the pack capacity utilizing rate by 11.3%. [ABSTRACT FROM AUTHOR]

The switched-quasi-Z-source bidirectional dc–dc converter (SQBC) has the characteristics of wide voltage gain and low voltage stress, and is suitable for the power interface between the supercapacitors and the dc bus in the multisource system of electric vehicles. On the basis of the SQBC, an optimal design method for inductance parameters and variable switching frequency control strategy are proposed in this article. While remaining the wide voltage gain and low voltage stress characteristics of the topology, the soft-switching operation within the full voltage gain range is achieved without adding additional auxiliary devices. The variable switching frequency control strategy keeps the converter operating at the critical soft-switching point with the lowest switching losses per switching cycle, further improving the operation efficiency of the converter. Finally, an experimental prototype with a rated power of P = 300 W, input voltage of Ulow = 50–150 V and output voltage of Uhigh = 300 V was built, and its maximum efficiency is 98.28%, which verified the correctness and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Domain-based electronic and electrical (E/E) architectures have been regarded as a possible upgrade to distributed E/E architectures currently used in electric vehicles. In a distributed E/E design, E/E components are directly connected to the automobile bus. Domain-based architectures split E/E components into distinct domains depending on their functions, which clearly benefits software upgrading and wire harness reduction. However, due to its heterogeneous topology with multiple network protocols, domain-based E/E architecture introduces complicated multilink and multinode delays into the control loop. The delays may degrade and even deteriorate the stability of adaptive cruise control (ACC) employing domain-based E/E architecture. To this end, this article proposes a heterogeneous-topology loop delay analysis by introducing a notion of poly-service loop delay. With a graphical pattern, the analytical process is presented in depth. The worst-case loop delay is calculated using an upper-boundary mathematic equation. Then, a hierarchical cyber-physical control method for ACC is designed. The upper level is intended to achieve desired acceleration based on vehicle and intervehicle motion states. And the lower level is intended to mitigate the negative impact of loop delays and provide reliable acceleration tracking. The results of cosimulation and hardware-in-loop experiment verify effectiveness of proposed approaches. [ABSTRACT FROM AUTHOR]

The introduction of the switched affine system opens new perspectives for the control design of dc–dc converters. In order to overcome the drawbacks of the continuous-time switching control methods, several sampled-data-based switching control approaches have been proposed in the literature. However, in these works, the solution of control parameters involves a nonlinear optimization problem. In addition, the designed switching laws are nonlinear functions about the system state, which require higher computational resources. In this article, a periodic time-triggered hybrid control is proposed based on a new design framework. All the design conditions are in linear matrix inequality formulations, which can be conveniently solved by common semidefinite programming software. Moreover, the proposed switching law is a linear function about the state, reducing the online computing burden. Finally, a unified view of the classical continuous-time switching scheme and the proposed method is established. Simulation and experiment tests on a buck–boost converter demonstrate the good performance of the proposed control strategy. [ABSTRACT FROM AUTHOR]

Cascaded split-source inverter (CSSI) is a single-stage modular multilevel structure. This article proposes the multidimensional pulsewidth modulation (MD-PWM) for this topology. All multilevel modulations are a particular version of this approach. The principles of this geometrical method are based on selecting the optimal points and determining the switching sequences and time intervals. By considering the operational principles of CSSI, this method is modified to accurately control the voltage of dc links, charge inductors with constant duty cycles, control dc and ac sides of cells independently, and reduce the reverse recovery effects of input diodes. MD-PWM, with a low computational burden, can be implemented for CSSI with any number of voltage levels. The output power can be distributed equally or unequally among cells, and both buck and boost operation modes are realized for each cell. Also, this method is extended for the operation of the converter with unequal input sources. For an asymmetric topology with N cells, harmonics are located at multiples of N times switching frequency. Thus, this strategy eliminates low-frequency distortions from the output voltage of asymmetric CSSI. The simulation and experimental results verify the performance and accuracy of the proposed technique and mathematical relations. [ABSTRACT FROM AUTHOR]

This article proposes a new single switch trans-inverse high step-up converter applicable in sustainable sources of energies such as photovoltaic (PV) and fuel cell (FC). Through developing a single-ended primary-inductor converter by a three-winding built-in transformer (BIT) mixed with a switched-capacitor voltage multiplier cell, high voltage gains as well as low voltage stress across the mosfet can be achieved to reduce the required duty cycle and the conduction losses. The third winding of the BIT acts in a trans-inverse manner whose turns ratio should be lower than unity. Hence, with a lower number of windings the voltage gain can also be improved. Furthermore, the quasi-resonance operation of the proposed converter, reduces the associated switching losses of the mosfet and also guarantees zero current switching of diodes through the whole switching cycle. Meanwhile, low input current of the proposed converter serves as an interesting feature to maintain PV and FC lifetime. The detailed steady-state analysis of the proposed high-efficiency converter is presented with an extensive performance comparison to explore its advantages. Finally, a 200-W prototype with 20–250-V voltage conversion is developed in the laboratory to examine the carried steady-state analysis. [ABSTRACT FROM AUTHOR]

This article presents a multiobjective control scheme for a bidirectional interlinking converter (ILC) of renewable energy based ac–dc hybrid microgrid. The prime focus of the power management algorithm is to feed the ac loads, and dc loads from ac source, and photovoltaic battery energy storage (BES), respectively. The second objective is to utilize the solar power to maximum capacity, by feeding it to dc load, BES, and ac load, in the given order of priority. The ac and dc subgrids operate independently, while supporting each other in case of overloading/underloading, thus reducing the amount of power reserve required in each, and eliminating the need of dump loads. The ANFIS-MN-based power quality control is integrated in order to ensure the total harmonics distortion of ac source current remains below 5% as per IEEE 519 standard, irrespective of the nature of load connected. In addition, the ILC control prevents any negative sequence currents from entering the ac source, even if there is any open circuit fault leading to unbalanced loading on the three phases. The performance of ANFIS-MN-based ILC control is demonstrated to be superior when compared with the conventional and contemporary techniques under different scenarios. [ABSTRACT FROM AUTHOR]

Splitting and placing interfacing inductance on both sides of the transformer has been proven to be an effective method, which extends the zero-voltage switching region for all the switching devices in the dual active bridge (DAB) converter. With the trend toward operating in higher frequency, achieving higher power density and higher efficiency, the converter model becomes more complex due to the non-negligible parasitic components that brings new challenges to DAB converter design. Traditional analytical methods have made it hard to imitate the proposed converter easily and precisely. Thus, artificial intelligence techniques are able to be utilized to assist the design process. When considering the converter system as a gray-box model, the metaheuristic algorithm can be implemented for the targeted design inside such a gray-box. In this article, a genetic algorithm (GA) is employed in the DAB converter parametric design with an explicit fitness desire to help in discovering the high frequency oscillation (HFO) problem. Consequently, the splitting inductance tuning method is proposed for eliminating the HFO problem and minimizing inductors’ loss. The methodology of implementing GA into converter parametric design, and the proposed splitting inductance tuning method are introduced and verified with a 1 MHz gallium nitride high-electron-mobility transistor based DAB converter prototype. The comparitive experimental results prove the effectiveness of the splitting inductance tuning method and achieve 4% efficiency enhancement with 200 W power delivering. [ABSTRACT FROM AUTHOR]

This article explores a single-source UXE-type asymmetrical multilevel inverter for its operation on 13-, 11-, and 9-levels with boosted output voltage. The 13- and 11-level operations require a single voltage sensor to maintain the auxiliary dc link at $V_{\text{dc}}/2$ and produce 1.5 and 1.25 boosting using redundant states and exhibit lower capacitor inrush currents. For the 9-level operation, the topology exhibits self-balancing of the dc-link at $V_{\text{dc}}$ and a boosting of 2. With a conventional pulsewidth modulation (PWM) for the 13-level operation, the inverter can drive a predominantly inductive load of 0.35 lagging at unity modulation index. For the 11-level operation, the levels cease to maintain beyond the modulation of 0.95. Thus, a hybrid PWM is proposed to fully utilize the redundant states for the charging of the switched-capacitors and enhance the inverter active load capability in the 13-level mode by 21% at unity modulation index ($m_a$) and address a 0.8 power factor load at the $m_a$ of 0.9. For the 11-level operation, the levels are maintained at any $m_a$ with the hybrid PWM. The operation of the inverter is also verified for nonlinear load. Further, the 9-level operation with twice boosting and self-balancing is presented. The results are verified on MATLAB/Simulink and validated experimentally. [ABSTRACT FROM AUTHOR]

For the dual three-phase interior permanent magnet synchronous machines (DT-IPMSMs), open-phase fault can cause current unbalance and degrade the drive performance. This article proposes a fault tolerant maximum torque per ampere (FT-MTPA) control for DT-IPMSMs, which can maximize the ratio of the average torque to the stator current and minimize the fault-induced torque ripple. In the proposed approach, optimal FT-MTPA solution is derived and theoretically proven, and current rms is considered as one design constraint to ensure the equivalent loss to the healthy condition. The proposed FT-MTPA control ensures the smooth switching between fault tolerant control and healthy control without inducing noticeable torque ripple. Compared with existing methods, the proposed approach is computation-efficient and fast in achieving the FT-MTPA control, which is critical to practical applications with fast changing loads. Moreover, this article derives the optimal solution from the faulty MTPA model with fault induced terms considered to ensure high torque. Experiments and comparisons with existing methods are conducted to evaluate the proposed approach on a laboratory DT-IPMSM. [ABSTRACT FROM AUTHOR]

This article introduces a nonisolated, high step-up voltage multiplier cell (VMC)-based dc–dc converter for applications such as module-integrated converter and power optimizers. The VMC combines switched capacitor with autotransformer techniques and active clamp circuit. The autotransformer tertiary winding is employed to increase voltage gain without operating the main switch under extreme duty cycle condition, to reduce the current through the main switch before it turns offand to ensure its zero-voltage switching (ZVS) operation on a wide operation range. The auxiliary switch in the clamp circuit provides ZVS for the main switch and vice-versa. Thus, both switches are turned on with zero voltage and there is no switching loss. Hence, high switching frequency is used to reduce the passive components’ volume and weight. Besides, the low dc-bias and bidirectional magnetizing current allows a smaller magnetizing inductance in the autotransformer to further minimizing the dimensions of the magnetic core. The leakage inductances are used to provide zero-current switching condition for the diodes, eliminating their reverse-recovery losses. The operation principle, steady-state analysis, and design guidelines are depicted and validated through experimental results obtained from a 350-W prototype of the proposed converter. Efficiency of 96.5% at full load is also reported. [ABSTRACT FROM AUTHOR]

Existing dc and ac bypass-assisted two-level three-φ inverter topologies can only reduce the peak-to-peak (P-to-P) common mode voltage (CMV) value by 66.6%. However, the dv/dt of CMV remains unchanged. This issue can be easily addressed by using a multilevel inverter but it increases the size, cost, and complexity of the system. As an alternative, this article proposes a novel three-phase inverter topology where one leg (out of three) of the inverter is configured to produce three-level pole voltage while the other two legs produce two-level pole voltages. This results in a unique space vector (SV) diagram with 12 SVs, whereas a 2-level inverter has only 8 SVs. A new pulsewidth modulation scheme is proposed that can utilize the SV diagram in such a way that dv/dt of CMV is reduced by 50% along with a 66.6% reduction in CMV P-to-P value in each switching cycle. Another advantage of the proposed topology is the reduced conduction losses due to fewer switches conducting at any given time. The proposed topology is compared with the existing solutions to prove its advantages. Simulation and experimental results are presented for a three-phase induction motor load to validate the various claims. [ABSTRACT FROM AUTHOR]

The two-level voltage source inverter fed dual three-phase motor (DTPM) induces the high-frequency common-mode voltage (CMV) and generates the unwanted adverse effects. As one of the effective common-mode suppression methods, the conventional CMV elimination (CMVE) pulsewidth modulation (PWM) schemes are generally based on the voltage-balance mode for DTPM systems which suffer from the parameter asymmetry induced phase current imbalance. This article proposes two current-balance mode unified CMVE PWM schemes which has no restriction on the reference voltages and angle displacement between the two sets of three-phase windings. Thus, the proposed methods can be utilized in different types of DTPMs with different angle displacements between the two winding sets, and the CMVE effect can be retained both in the conditions of symmetrical and asymmetrical system parameters which is more practical than conventional CMVE schemes in real application. The function and performance of the proposal is proved by simulations and experiments. [ABSTRACT FROM AUTHOR]

In this article, a nine-level multilevel topology is proposed by stacking of low voltage basic inverter cells and then cascading with H-bridges. The dc-link is split into four equal halves by series-connected capacitors from a common dc-link. Three common coupling points (CCPs) are formed due to the stacking of four capacitors, which are connected across the dc-link. The CCP voltage balancing is ensured by drawing or injecting zero instantaneous currents from each of these points at any instant. A six-phase symmetrical IM is used to generate equal and opposite instantaneous phase currents by applying exactly equal and opposite phase voltages for two opposite phases from the six-phase inverter. Simultaneously, the capacitor voltage balancing of H-bridge inverter cells is also achieved by proper selection of redundancies from the available pole voltage redundancies. The concept is verified with a nine-level inverter laboratory prototype, which consists of a five-level stacked inverter, and followed by two low voltage cascaded H-bridge inverters in each phase. Detailed experimental results of steady-state and transient conditions are included to validate the proposed scheme. [ABSTRACT FROM AUTHOR]

Four-switch buck-boost (FSBB) converter features positive output voltage and low voltage stress of power switches. In this article, a pulsewidth modulation plus phase-shift control scheme is proposed to achieve zero-voltage-switching for all the power switches in full input voltage and load range and minimize the inductor current ripple and root mean square (RMS) value. The implementation of the proposed control scheme is given. A prototype of a 500-W FSBB converter is built and tested in the lab, and the experimental results verify the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Three-phase voltage source inverters (VSIs) with output $ LC$ filter are preferred topologies to provide voltage and frequency support for islanded ac microgrids. This article proposes a finite-set quasi-sliding model predictive control (FS-QSMPC) scheme for $LC$ -filtered VSIs to improve the output-voltage quality. By explicitly including a predictive sliding-mode function into the cost function, reduced steady-state ripple and enhanced robustness are achieved compared to typical FS-MPC. Besides, theoretical analysis of stability and robustness for FS-QSMPC is given. Analytical tuning of the weighting factor is also derived to decrease the tuning effort. Comparative simulations and experiments verify the presented approach. [ABSTRACT FROM AUTHOR]

In this article, a family of nonisolated zero voltage switching (ZVS) bidirectional dc–dc converters (BDCs) with simple auxiliary circuit and continuous current at low voltage side source ($V_L$) is proposed. The auxiliary circuit is only composed of a single switch, a capacitor, and a small inductor which is applied to all proposed nonisolated BDCs to provide soft switching condition for all semiconductor elements. Thus, in terms of components count, the presented converters are superior to other counterpart BDCs. In addition, the continuous current at $V_L$ is maintained, while the main and auxiliary switches in both operating modes are turned on and off at ZVS. Moreover, all diodes turn off at zero current switching which mitigate the reverse recovery problem. Hence, a suitable overall efficiency is achieved in all proposed BDCs. The proposed bidirectional buck/boost converter is analyzed for both step-up and step-down operating modes in details and a 100 W converter prototype is implemented to verify the main converter features and the theoretical analysis. [ABSTRACT FROM AUTHOR]

Three-phase electric spring (TPES) was originally proposed to solve three-phase imbalance issues in power systems. So far, several attempts have been reported on proposing power control methods for it. However, existing solutions on TPES either depend on circuit parameters or have relatively slow dynamic responses. In this article, a novel power control strategy that incorporates the advantages of direct power control (DPC) is proposed to solve the above issues. It might be the first attempt to propose a simple power control strategy with rapid dynamic response and independent with circuit parameters for TPES. Besides, the relationship between power operating range and circuit parameters is well analyzed, which provides a way for parameter optimization. To restrain the resonance phenomenon caused by the TPES topology, the passive and active damping methods are compared, revealing that power quality of the control objective can be greatly improved with the active damping. Finally, the proposed DPC with both damping methods is validated by simulations and experimental results. [ABSTRACT FROM AUTHOR]

Power filters have been widely used to suppress switching harmonics caused by the modulation of grid-connected inverters. In order to save the total inductance and cost and reduce the volume, different power filters were proposed for the three-phase three-wire grid-connected voltage source inverter. However, in industrial applications, due to the consideration of production cost, the difficulties caused by the deviation of actual parameters have to be addressed. In this article, we propose a new three-phase three-wire power filter with a simple structure, almost the smallest total inductance, and strong resistance to the adverse effects of parameter shifts. The parameters of the proposed filter and the design of the grid-connected system controller are introduced in detail. When studying the influence of parameter offset, a comparison between different types of notch power filters is also given. Simulation and experimental results on a 380 V/50 Hz/6 kW three-phase inverter prototype verify the performance of the proposed power filter. [ABSTRACT FROM AUTHOR]

A new soft-switching dual-switch forward converter with self-driven synchronous rectifier is presented in this article. The proposed converter operates under discontinuous conduction mode; therefore, compared with the two-switch forward (TSF) converter, one diode along with one inductor is removed from the output side. The leakage inductance of the transformer is employed to transfer the power from the input side to the output side. To provide the zero-current switching (ZCS) condition for all semiconductor devices in both on and off instants, a delay time between the off-command signals of main switches along with a capacitor is used as auxiliary circuit, which eliminates the required additional switch for soft switching. Moreover, the auxiliary circuit in addition to provide soft-switching condition, resets the transformer core, resonantly. Compared with the TSF converter with the help of the new auxiliary circuit, two reset diodes at the input side can be removed. The proposed converter is controlled with duty cycle using the pulsewidth modulation. Also, a winding is added at the output side of transformer to drive the MOSFET of synchronous rectification. Thus, a ZCS TSF converter with the minimum number of components is proposed. The operating modes of the proposed converter along with the design approach and the stress analysis are completely considered. To verify the theoretical results, a prototype is implemented and the theoretical results are compared with the experimental results. [ABSTRACT FROM AUTHOR]

This article proposes a fixed switching frequency (FSF)-based improved model predictive control (MPC) for a five-level active neutral-point clamped (5L-ANPC) converter. Compared to the conventional MPC for 5L-ANPC converter, the proposed MPC significantly reduces the computational burden while ensuring the balance of dc-link and flying capacitor voltages. The proposed MPC optimally selects the control voltage vectors to reduce common mode voltage (CMV), leading to a small CMV of the converter. Using three voltage vectors action per control cycle in MPC, FSF is achieved. Steady-state and dynamic performances of the proposed MPC have been evaluated by experiments. The results verify the feasibility and effectiveness of the proposed MPC method. [ABSTRACT FROM AUTHOR]

Zero-voltage zero-current switching (ZVZCS) phase-shift full-bridge (PSFB) dc–dc converters are candidate converters for high-power switching mode power supply because of their low cost and high efficiency. However, these converters still have some definite weaknesses, e.g., resetting obstacles of high-value currents, extra electrical stress on the power devices. Hence, customers seldom adopt these topologies in high-power applications. This article proposes a new ZVZCS PSFB dc–dc converter to solve the above problems. A clamping circuit with two mosfets, two diodes, and a resetting transformer ensures ZCS of the lagging-leg switches over a wide load range, and no extra electrical stress arises on the primary or secondary components. The clamping circuit has a high current reset ability and can break through the power limitation of conventional ZVZCS PSFB dc–dc converters. The volume of the resetting transformer is small because of the low voltage-second product, and the added mosfets cause low power loss because of the wide soft-switching load range and low on-resistance. The experimental results from a 12-kW prototype prove the rightness and advantages of the proposed converter. [ABSTRACT FROM AUTHOR]

In this article, a low-ripple continuous control set (CCS) model predictive torque control (MPTC) method for switched reluctance machines (SRMs) is proposed. The inherent high nonlinearity of the SRMs makes it difficult to solve the optimization problem in the CCS MPTC algorithm analytically. To address this issue, an equivalent linear SRM model is adopted, and the cost function is also properly modified. Then, with the torque boundary values provided by executing the voltage vectors of an improved switching table, the optimization problem in the CCS MPTC method becomes simple and analytically solvable. The Lagrange multiplier method is employed to solve this optimization problem analytically and generate the optimum torque reference values for the active phases. Based on the estimated torque variation rates, the duty cycles for each phase are calculated. Extensive simulation and experimental tests are carried out in a four-phase 8/6 SRM setup. These testing results reveal that the proposed CCS MPTC method shows much lower torque ripples and current ripples in a wide speed range with a low computational burden than the existing finite control set MPTC methods. [ABSTRACT FROM AUTHOR]

High-performance comprehensive optimization of line current ripple, zero-sequence circulating current (ZSCC), and switching losses is a challenge for parallel interleaved inverters. This article proposes a modified discontinuous pulse width modulation (PWM) method for two parallel interleaved two-level voltage-source inverters (2L-VSIs), which are regarded as a single 3L-VSI to optimize its vector sequence. The line current ripple is the priority optimization target to guarantee the principle of the nearest three vectors is applied in each subsector. To reduce the ZSCC and switching losses, the vector combinations with smaller changing rate of ZSCC are selected, and the phase-leg carrying the highest current is clamped. The detailed design procedure of 3L-vector sequence and how to distribute to 2L-VSIs are revealed. The quantitative performance comparison between the proposed PWM method and existing ones in terms of line current ripple, ZSCC, and switching losses are made. Experimental results confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this work, a multilevel 42-sided polygonal space vector structure for suppression of lower order harmonics for open-end induction motor (OEIM) drive applications is proposed. The proposed power circuit topology consists of two inverters feeding an OEIM from either side. The main inverter fed with a single dc-link providing active power for motoring operation is switched at low switching frequency. The secondary inverter fed with a capacitive supply is switched at high frequency to suppress lower order harmonics upto 39th order, up to the base speed of operation allowing maximum utilization of the dc-link. The advantages of lower order harmonic suppression in motor phase voltage, for polygonal space vector structures, are combined with multilevel inverter topology. This offers various advantages like multilevel operation with low inverter switching for the main power delivery inverter and harmonic suppression throughout the modulation range. The low switching frequency primary inverter generates harmonics of the order $6*k \pm 1$ , where $k = 1, 2, 3,{\ldots }$. The harmonics are suppressed by the capacitor-fed secondary inverter, which supplies only reactive power for suppression of lower order harmonics in motor phase voltage. Use of a single dc-link facilitates four-quadrant operation of the inverter. The proposed scheme is validated for steady-state and dynamic performance by experimental results. [ABSTRACT FROM AUTHOR]