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This paper aims to outline the process of dimensioning a controller tailored for a fourth-order step-down converter. In order to conduct a thorough small-signal analysis, it is imperative to find the state–space model in matrices form. Given its fourth-order nature, the control-to-output transfer function also aligns with this order, although its degree is ultimately reduced to a second-order using the tfest function. It is remarkable that the design of the type III error amplifier assumes a central position in the overall controller design process. The theoretical analysis was then subjected to rigorous validation via simulation, with particular attention paid to the step response in both input voltage and output resistance. This study developed from the desire to validate the efficacy of reducing the control-to-output transfer function degree using the tfest function, aiming to highlight a fourth-order converter to which controller design theory can be applied, related to that for a second-order converter. [ABSTRACT FROM AUTHOR]

In response to the challenges faced by traditional LLC resonant converters in simultaneously achieving a wide output voltage and high efficiency, this paper proposes a cascaded DC-DC converter. The front stage of the converter adopts a new LLC topology, and it is cascaded with a boost converter through a reutilization of the output-side inductor. The proposed DC-DC converter leverages the electrical isolation and wide output voltage range advantages of LLC and boost converters, enabling the overall system to achieve broad output voltage regulation and high-efficiency operation. The reutilization of the inductor design further enhances the integration density of the DC-DC converter. A minimum loss collaborative control strategy is introduced for the proposed DC-DC converter. When determining the output voltage and operating the circuit in step-up mode, the duty cycles of the switch in the proposed LLC converter and the switch in the boost converter are adjusted to minimize overall circuit losses while ensuring the rated output voltage. Ultimately, the correctness and practicality of the proposed DC-DC converter and its control strategy are validated through a simulation and an experiment. The overall efficiency of the DC-DC converter can reach up to 94% under optimal conditions. [ABSTRACT FROM AUTHOR]

A totem-pole bridgeless boost converter is one of the most promising topologies for the power factor correction (PFC) stage in high-power applications due to its high efficiency and small number of components. However, due to the totem-pole structure of the field-effect transistor (FET), very high switching loss occurs via the reverse recovery current of the body diode. To solve these problems, critical mode (CRM) control is a good solution to achieve the valley switching technique. With valley switching of CRM control, the switching loss decreases drastically with decreasing turn-on voltage. But, although the CRM control enables valley switching, it is hard to make an exact valley switching control with general zero-voltage detection circuits. In addition, when a frequency limitation scheme is applied to prevent a very high frequency, the switch can operate with hard switching at the boundary of the frequency limitation. Furthermore, the CRM boost PFC has a low PF and high total harmonic distortion (THD) under light-load conditions due to the large negative current resulting from resonance between the inductor and parasitic capacitance. It becomes worse at near-zero input voltage since the resonance current becomes larger near zero-input voltage. Therefore, in this paper, a totem-pole bridgeless boost PFC converter with high efficiency, high PF, and low THD is developed using TMS320F28377 by Texas Instruments. Based on the basic digital structure of the totem-pole bridgeless converter, the proposed controls help with exact valley switching, PF and THD improvement, and frequency limitation. The prototype converter is verified using 90–264 VAC input voltages and 450 V/3.3 kW output specifications. [ABSTRACT FROM AUTHOR]

Integrating energy storage units (ESUs) into part of sub‐modules (SMs) enables the decoupling active power control for the modular multilevel matrix converter (M3C). The low frequency AC (LFAC) system based on M3C with symmetrically integrated energy storage (SI‐AM3C) can provide functions such as renewable power fluctuation smoothing and other power grid auxiliary services, which is attractive in engineering practices. This paper focuses on the design and control of SI‐AM3C. For the converter design, an evaluation method for the number of required active SMs (ASMs) is presented. On this basis, the influences of different system operating conditions on the ASM requirement are analyzed in case studies, and the effects of specific circulating injection strategies are also investigated. The control system targeted at decoupled AC side active power for SI‐AM3C is introduced. A modified inner‐arm capacitor voltage balance strategy is introduced to reduce the capacitor voltage deviation between ASMs and passive SMs (PSMs). The conclusions related to the presented estimation method and converter control strategy are verified by time‐domain simulations in PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

The Modular Multilevel Converter (MMC) has been widely used in high-power applications owing to its inherent advantages, including scalability, modularity, high-power density, and fault tolerance. MMCs have recently been used in Low-Frequency Alternating Current (LFAC) transmission, particularly in the integration of offshore wind power with onshore grids. However, LFAC applications produce significant voltage oscillations in floating capacitor voltages within the MMC. Early research efforts have successfully established and validated decoupled control strategies for LFAC-based MMC systems. However, validations are usually based on simulations or small-scale prototypes equipped with limited power cells. Consequently, this paper presents a decentralized voltage control strategy based on Nearest Level Control for an MMC-based LFAC system. Experimental results obtained with a 120-cell MMC prototype are presented to validate the effectiveness and operation of the MMC in LFAC applications. [ABSTRACT FROM AUTHOR]

For decentralized electrification in remote areas, small-sized wind energy systems (WESs) are considered sustainable and affordable solution when employing an efficient, small-sized component converter integrated with a less-sophisticated, cost-effective MPPT controller. Unfortunately, using a conventional buck DC/DC converter as a MPP tracker suffer from input current discontinuity. The latter results in high ripples in the tracked rectified wind power which reduces the captured power and affects system operation especially in standalone applications which are self-sufficient and independent of grid support. Furthermore, these ripples propagate to the machine side causing vibration and torque stress which impacts turbine performance and safety. To solve this issue, a large electrolytic capacitor is placed at the buck converter input to buffer these ripples, yet at the cost of larger size, losses and reduced reliability. Oppositely, the developed C1, D4 and D6 buck converters have the merit of continuous input current at small component-size. In this paper, dynamic modelling of these three converters is developed to select the one with the least input current ripples to replace the traditional buck converter in the considered WES system. Consequently, fluctuations in the tracked power are minimized and the large buffer capacitor is eliminated. This enhances system lifetime, reduces its cost and increases tracking efficiency. Moreover, mechanical power and torque fluctuations are minimized, thus maintaining machine protection. Furthermore, a sensorless MPPT algorithm, based on converter averaged state-space model, is proposed. Being dependent on variable-step P&O algorithm, the proposed approach features simple structure, ease of control and a compromise between tracking time and accuracy besides reduced cost due to the eliminated current sensor. Simulation results verified the effectiveness of the selected converter applying the proposed MPPT approach to efficiently track the wind power under wind variations with cost-effective realization. [ABSTRACT FROM AUTHOR]

Nowadays, grid power loss and power quality deterioration are causing many problems, especially for sensitive uses such as data centers, airports, healthcare, banking, insurance, and telecom. These issues must be resolved through energy continuity coverage and optimization. Dynamic voltage restorers (DVR) are generally used to mitigate network voltage disturbances and maintain a constant voltage value between load terminals for a short and limited duration due to limited energy storage facilities. However, this paper's proposed (DVR) system controlled by the adaptive-network fuzzy inference system (ANFIS) controller can compensate for prolonged power quality disturbances by integrating a hybrid renewable energy system (HRES) managed using classical Proportional Integral (PI) controller power management. This paper proposes a new (DVR) topology coupled with a hybrid renewable energy system (HRES) to exploit free and clean energy, consisting of a solar panel, a PEM fuel cell, and a battery storage device connected through DC-DC converters to a DC transmission, the obtained results from the simulation process of the proposed DVR system in the environment of MATLAB / Simulink showed the ability to eliminate sag that exceeded 0.9 pu in a period of more than 3 min and swells that exceeded 1.2 pu in a period that exceeded one minute. In comparison, the load voltage's total harmonic distortion THDv was reduced from 29% to 5%, and the source current total harmonic distortion THDi from 30.25% to 2.79%. [ABSTRACT FROM AUTHOR]

Unequal thermal stress among the phase legs of a multiphase converter leads to a reduction in the useful lifespan and reliability of that converter in general. Increasing the converter's lifespan by relieving the stressed phase leg, which suffers excessive thermal stress due to aging, is crucial. This paper evaluates two control concepts, including two per-phase model predictive control methods for extending the lifespan of a voltage source inverter. These two per-phase techniques alter the switching pattern to reduce the losses of the most aged phase leg. Hence, the loss and the corresponding thermal stress of the leg that has aged the most are reduced. In such a way, the lifespan and reliability of the converter are prolonged. Two per-phase model predictive control techniques are executed in both simulation and experiment environments, where the corresponding results are provided to evaluate the behavior of these control strategies, considering several operational aspects both in steady state and transient operation. In addition to static load conditions, two per-phase techniques are verified for the correct operation under dynamic load (induction motor) conditions. [ABSTRACT FROM AUTHOR]

The application of modular multilevel converters (MMCs) to large drive systems is subject to severe low-frequency operation restrictions. The fluctuation of capacitor voltage and the high amplitude of common mode voltage in sub-modules is a thorny problem. In this paper, a novel fly-across capacitor modular multilevel converter topology is adopted to eliminate low-frequency voltage ripples by using the fly-across capacitor as a power transfer channel between the upper and lower bridge arms of the MMC. A novel finite compensation method is proposed--instead of the traditional full compensation method--that introduces a real-time variable limiting factor to change the amplitude of the mixed injected high-frequency differential-mode voltage and high-frequency differential-mode current and reduce the amplitude of the common-mode voltage on the AC side while lowering the current stress of the power devices. Finally, a complete system simulation model is constructed, and the topology with the proposed control strategy are verified to have good output characteristics under different operating conditions; good results are achieved in suppressing the sub-module fluctuation and common-mode voltage. [ABSTRACT FROM AUTHOR]

Examining impacts of differential mode (DM) filter topologies covering pi, LC with damping, LC, LCL filter through isolated Ćuk single phase PFC converter is realized in this paper regarding to power factor, THD and efficiency. Application of PFC isolated Ćuk converter is conducted with 42 kHz switching frequency and 50 W power. Each filter is modeled, designed, and applied experimentally via isolated PFC Ćuk converter. Average model derivation based on state-space, for DCM operation of input side inductor of isolated PFC Ćuk converter that is not introduced in literature is the main contribution of the paper. Second main contribution is to analyze filter types by linear methods for the transfer functions cascading the converter and filter transfer functions, which is not presented for PFC converters. It is also presented that solely LCL filter which is not analyzed for PFC converters in detail in literature, does not give desired results. So, increasing the effectivity of LCL filter, new filter structure LCL with parallel C filter is proposed and modeled in this paper. Thanks to the applications, presented results of LCL with parallel C filter is better than others with 4.9% current THD and '1' power factor. Proposed LCL filter ensures 45% reduction of total inductor value, comparing to LC filter. Besides, LCL with C filter provides better control characteristics with maximum allowable gain for stability as 0.7585 higher than other topologies. Moreover, practical design methodology of filter types avoiding complex mathematical procedure is given in this paper. Applications with each filters provide THD requirements, obtained 4.9% as a best value, lower than IEC61000-3-2 standard. Maximum percentage improvement comparing to the IEC61000-3-2 is 27.5% for third harmonic. Furthermore, SiC and Si Mosfets are employed separately in the converter and compared by using each DM filters regarding to power factor, THD, efficiency through applications. As a result, better efficiency with SiC Mosfet as 83% and better THD with Si Mosfet as 4.9% are conducted. [ABSTRACT FROM AUTHOR]

Modular multilevel converter (MMC) is a key device of high-voltage-direct circuit (HVDC) transmission system, the sub-module detection technology of which will directly influence the damage severity, and even the reliability of the whole system. In this paper, the open-circuit fault characteristics of an insulated gate bipolar transistor (IGBT) in a sub-module are analyzed, and a fault-tolerant optimal control strategy is proposed for the redundant hot-reserved MMC based on nearest-level modulation (NLM). A fault sub-module diagnosis and location strategy based on the deviation distance of the capacitor voltages is presented. After the faulty sub-module is removed, due to the asymmetric operation of the MMC, odd-order circulating currents are introduced in the faulty phase, in which the fundamental-frequency circulating current is the major component; the fundamental-frequency voltage related to the redundancy rate is injected into the faulty phase, which effectively suppresses the fundamental-frequency circulating current and harmonics in the faulty phase. The proposed method combines fault detection and fault ride-through steps, so it has the features of high reliability and high compatibility. Based on the Matlab/Simulink simulation model, the effectiveness of the proposed strategy is verified. [ABSTRACT FROM AUTHOR]

Multiphase variable-speed drives and generation systems (systems with more than three phases) have become one of the mainstream research areas during the last decade. The main driving forces are the specific applications, predominantly related to the green agenda, such as electric and hybrid electric vehicles (EVs), locomotive traction, ship propulsion, “more-electric” aircraft, remote offshore wind farms for electric energy generation, and general high-power industrial applications. As a result, produced body of significant work is substantial, making it impossible to review all the major developments in a single paper. This paper therefore surveys the recent progress in two specific areas associated with multiphase systems, namely power electronic supply control and innovative ways of using the additional degrees of freedom in multiphase machines for various nontraditional purposes. [ABSTRACT FROM AUTHOR]

This paper provides a brief idea about modeling of Solar Photovoltaic systems. This paper presents simulation model of PV array which is used to evaluate the electrical performance of PV array with respect to changes in temperature and irradiation. The proposed paper includes design and simulation of a 10 kW Stand-alone solar photovoltaic system. The equivalent circuit model of a cell is simulated using Matlab/Simulink to examine a typical 235 W solar module and 10 kW solar PV array. In this paper, an MPPT tracker using modified Adaptive P & O algorithm is proposed to improve the efficiency of solar photovoltaic system. The algorithm identifies a particular duty ratio at which the DC-DC converter should operate to maximize the power output. The proposed model is designed with the help of Matlab/Simulink. The data provided by the manufacturer are used to calculate the non-linear parameters. The characteristic of the proposed model is compared with reference PV module. The 230 W PV modules manufactured by Sun module SW 230 poly/Version 2.0 and 2.5 Frame are used as a reference. The large solar PV array system is modeled and simulated using the data provided in this module. The proposed model results in improved performance of solar photovoltaic systems. [ABSTRACT FROM AUTHOR]

A modular multilevel converter (MMC) can generate different common-mode voltage (CMV) values due to the high-frequency changing of the switching state under various modulation strategies. The high-frequency dv/dt will produce common-mode current in the equivalent common-mode loop to the ground, which will affect the insulation and shorten the life of the equipment. To eliminate the effect of common-mode voltage on MMC operation, a common-mode voltage elimination strategy (0CMV-SVPWM) is proposed for five-level MMC space vector pulse width modulation (SVPWM) by using the vector that does not generate common-mode voltage as the reference vector in this paper. The proposed strategy is studied and analyzed by the rapid prototype development experimental system based on RT-LAB to verify the feasibility and effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper proposes a new single‐phase direct step‐up ac–ac converter by modifying the p‐type impedance source. It provides a high boost factor as well as high efficiency, while only six parts are required to design it, involving just two bidirectional power switches. A safe commutation method has been applied to power switches to make the converter snubber‐free and high efficient. Input and output harmonic filters are no longer required since input and output currents variate continuously with small ripple and low total harmonic distortion (THD). The proposed topology only modulates the output voltage amplitude, not the phase and frequency, so the output frequency is identical to the input frequency and constant. Thus, it can be utilized in step‐up conversion applications, like inductive power transmission from low ac voltage sources. Input and output have the same ground, which is a good protective feature. In this paper, the operating principle of the converter is demonstrated. Experimental results have been represented to evaluate the performance of the converter. For this purpose, an experimental prototype has been fabricated. Results are investigated and compared with other previous step‐up ac–ac converters. Results confirm the theory, operating principle, and performance of the converter. [ABSTRACT FROM AUTHOR]

The main challenges of the input current control in synchronous DC-DC buck converters are the nonlinear model of the system, changes of the operating point in a wide range, and the need to use an input LC filter for current smoothing, which may result in the instability of the closed-loop system. In this paper, a step-by-step approach is developed for the design and improvement of a PI-feedforward closed-loop controller. It is shown that a linear PI controller cannot stabilize the closed-loop system properly during wide changes in model parameters, e.g., an equivalent series resistance of the input filter. To cope with the stability issues, a fixed-frequency sliding mode controller (SMC) has been developed in this paper for the implementation of an electro-mechanical actuator (EMA) emulator. Moreover, a systematic approach is proposed for controller tuning and the selection of the SMC's gains. To achieve high power efficiency, high-frequency GaN switches are used for the practical implementation of the DC-DC converter. Despite large changes in the load current, the designed nonlinear controller can track the input current reference satisfactorily. Steady-state and dynamic responses of the proposed SMC are compared with conventional linear controllers. Considering the Lyapunov stability theorem, it is proved that the designed SMC can stabilize the closed-loop system in the entire utilizable domain. The proposed nonlinear SMC controller enjoys a very simple control law. Hence, despite having very high switching and sampling frequencies, it can be easily implemented. The experimental response of the designed synchronous DC-DC buck converter is evaluated experimentally by implementing the control strategy in a TMS320F28335PGFA DSP from Texas Instrument. Moreover, the comprehensive comparison of the proposed SMC controller and a PI-feedforward controller proved the superior performance of the developed closed-loop system, in terms of the transient time response, robustness, and stability of the EMA emulator. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a new bidirectional nonisolated DC‐DC (direct current–direct current) converter to interface microgrid energy storage systems is proposed. This converter is based on the classical bidirectional boost/buck converter, the most used converter in microgrids and can operate both in step‐down and step‐up modes. Besides that, this converter presents low number of components, low voltage and current stress on components, simplicity of operation, low current ripple from low‐side power supply, and two different modes of operation: synchronous and asynchronous. In addition, in this paper, the modeling, control, and power losses estimate of the proposed converter are carried out and the performance of the converter in different aspects of the microgrid application is evaluated, such as step load, abrupt power flux change, and transient analysis. A prototype of 1 kW, 144 to 400 V, is developed in the laboratory to validate the theoretical evaluations of the proposed converter. Besides that, the proposed converter is also evaluated under different dynamic condition which illustrates the effectiveness of the converter. Finally, the maximum efficiency obtained is 97.1% for 500 W working in step‐down operation. [ABSTRACT FROM AUTHOR]

Multilevel converters (MLCs) are pioneers in the field of electrical energy conversion. From the classification of MLCs, modular multilevel converter (MMC) is top-rated due to its attractive structure and performance. The modular nature and no need for isolated DC resources are two significant advantages of this converter. However, the need for many sensors to control its performance is a considerable drawback. In addition, the internal circulating current in the MMC causes losses, decreases efficiency, and increases the voltage ripple of capacitors. This paper proposes combining a new capacitor voltage sorting method and an open-loop controller based on arms energy estimation to control the MMC using two voltage sensors in the arms and one current sensor at the output. The proposed method ensures continuous voltage balancing of the capacitors and removes multiple voltage sensors from sub-modules (SMs). The simulation and experimental results verify the accuracy and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Transformer-less connection schemes can provide a feasible solution for lowering the economic cost, occupied space, and device weight of modular multilevel converter (MMC) systems. However, due to the reduction in the converter transformer, the current flow loop is changed; as a result, the existing MMC model is not suitable. In this paper, the ac- and dc-side equivalent circuit models of the MMC system using a transformer-less connection scheme are established in both a–b–c stationary and d–q rotating coordinate systems. Then, a highly accurate mathematical analysis model is proposed, in which the interactions among the electrical quantities can be fully seen. The mathematical model is established in the time domain, and hence the amplitude and phase angle of every harmonic component in each quantity can be directly obtained. The proposed model is verified under various typical situations by comparing the calculated values with the actual waveforms. The comparison results prove that the calculation error is small enough to be negligible. The mathematical model in this paper can provide a powerful tool in terms of the performance analysis and the main circuit parameter design for MMCs in transformer-less applications. [ABSTRACT FROM AUTHOR]

This paper presents a novel control scheme based on the fractional order PI controller for a high gain multilevel boost converter. Non-conventional energy resources such as solar PV cells produce DC output voltages, which are continuously change with weather conditions. It is necessary to obtain a constant DC voltage from such systems to use them for battery charging applications. The voltage gain obtained using the traditional boost converter is very limited. Switched capacitor circuit can act as a multiplier circuit and can be combined with boost converters to increase the gain. Even though the output voltage from this converter meets the requirement of high output voltage, but heavy fluctuations in the solar energy makes this system inefficient to use for battery charging applications where a constant DC voltage is required. In this paper, a control scheme is proposed for this high gain multilevel boost converter circuit using Fractional Order PI (FOPI) controller. Modeling of the high gain boost converter is required for the design of fractional order controller. A reduced order model is developed for the high gain DC-DC converter and the transfer function is obtained from this. The parameters of the FOPI controller are designed using the fractional order toolbox FOMCON. The performance of the proposed converter is compared with the conventional PI controller and the superiority of the proposed converter was provedin terms of bench mark performance measures. The simulation was carried out in MATLAB/SIMULINK and the fractional order toolbox FOMCON is used to design and simulate the fractional order PI controller. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMCs) are characterized by modularization and multielectric equality, and the application of this structure to a high-voltage large-capacity static synchronous compensator (STATCOM) shows good potential. In this paper, a modified instantaneous symmetrical component method is proposed for positive- and negative-sequence decomposition, i.e. the critical part of the control device, which can accurately detect the instantaneous value of each sequence component in three-phase asymmetrical phasors in real time. Then, based on this method, the paper proposes a control method for MMC-based STATCOMs that solves the problems of multi-DC (direct current) voltage balance, grid-connected current control, and circulation suppression. Finally, the proposed detection and control methods are verified by performing simulations and experiments. The results show that the proposed method can quickly and accurately detect the positive- and negative-sequence reactive component that should be compensated by the device, thus realizing real-time reactive compensation for MMC-based STATCOMs. [ABSTRACT FROM AUTHOR]

Partial shading condition drastically reduces the maximum power output of photovoltaic array. Partial shading occurs due to several factors, such as flying birds, trees, and passing clouds. Many ways can be mitigated partial shading problems in photovoltaic (PV) array. One among the way is reconfiguration techniques, namely reconfigure the location of PV modules in PV array based on irradiance levels in order to distribute shading effects and increasing maximum power. This paper proposed an optimal SuDoKu reconfiguration pattern for $9\times 9$ total-cross-tied (TCT) PV array to improve maximum power under partial shading conditions. In this approach, the physical location of PV modules in TCT array are rearranged based on optimal SuDoKu style without altering the electrical connections, so that the shading effects can distribute over the array. Further, the performance of proposed pattern investigated with existing SuDoKu pattern under different shading conditions by comparing the global maximum power point, mismatch losses, fill-factor, and efficiency using MATLAB-Simulink. Based on the results of this paper, it concluded that the proposed optimal SuDoKu reconfiguration arrangement is reducing the wiring arrangement and increasing the shading distribution over the array as compared to SuDoKu arrangement. [ABSTRACT FROM AUTHOR]

In this paper, based on the combination scheme of dual-sampling and adaptive predictive PID control, a digital controller for improving the transient performance of Buck DC–DC converters is designed. Due to the inherent loop delay in analog-to-digital (A/D) conversion, the calculation process of the digital controller and digital pulse width modulator (DPWM) of conventional digitally-controlled Buck DC–DC converters limits the system bandwidth and this makes the transient response lower. The designed digital controller can reduce the delay time in analog-to-digital converter (ADC), the digital controller and DPWM of digitally-controlled Buck DC–DC converters. Adaptive predictive control is used to eliminate the delay time of ADC and the digital controller, while dual-sampling scheme is used to reduce the delay time of DPWM in this paper. These are two new control schemes, and they show better performance in improving the transient response than other existing control schemes. Both simulation and experimental results demonstrate that the designed digital controller based on dual-sampling and adaptive predictive PID control is effective in improving the transient performance of Buck DC–DC converters. During experimental verification, for a load step between 0.5 A and 1.0 A, the fastest transient recovery time and the overshoot voltage are found to be 102 μ s and 120 mV, respectively. Compared with the conventional digital PID controller, the transient recovery time and the overshoot voltage of the digital controller designed in this paper are decreased by 40.0% and 27.3%, respectively. [ABSTRACT FROM AUTHOR]

This paper provides an experimental discussion on a real-time real-power emulator that plays an important role in achieving a total test of medium-voltage, high-power, high-speed induction motor drives. The use of the emulator brings cost and time savings to the test. The test bench including the emulator is characterized by connecting two modular multilevel double-star chopper-cell (DSCC) converters connected in a front-to-front way. This paper designs, builds, and tests a 400- ${\rm V}_{\rm dc}$ , 10-kW downscaled test bench. It mainly consists of the following two identical DSCC converters: 1) one DSCC converter is used as an inverter under test; and 2) the other as a real-time real-power high-fidelity emulator. Experimental waveforms confirm that the emulator can reproduce electrical and mechanical operating performance of the three-phase 200-V, 10-kW, four-pole, 9000-r/min induction motor loaded with a centrifugal compressor. [ABSTRACT FROM AUTHOR]

This paper presents a dc–dc input-parallel output-parallel (IPOP) converter configuration for renewable energy integration with medium-voltage dc grids. A full-bridge zero-current-switching (FB-ZCS) converter with voltage-doubler output is proposed as the fundamental module. To achieve smooth current commutation and ZCS, the leakage inductance of transformer and a resonant capacitor across its secondary are utilized. This resonant capacitor is always charged to its full-rated capacity irrespective of converter loading and requires a dedicated charging interval resulting in duty-cycle loss. For a given leakage inductance, a large resonant capacitor is required for higher current ratings. With a single-centralized converter, these operational and design constraints result in significant duty-cycle loss, restricting the operation range. This paper proposes an IPOP configuration for high-power applications. Phase shedding at reduced loading ensures that individual modules are operated optimally. Input inductance requirement in modules is reduced due to interleaving of the input current. Additionally, voltage stress across converter components and input current ripple are reduced by 50% in the proposed converter modules. Steady-state operation, modeling, current-sharing control, start-up, and shutdown of modules in the IPOP configuration are demonstrated using simulations. Experimental results on a scaled-down prototype are presented to validate its operation. [ABSTRACT FROM AUTHOR]

There has been increasing interest in solid-state transformers (SSTs) as a future replacement for conventional distribution transformers as it is able to provide ancillary services in addition to step-up/step-down of voltages. In SSTs, a common topology used in the ac–dc stage is the cascaded H-bridge (CHB) multilevel converter. This paper proposes a novel dual-model predictive control method for the CHB multilevel converter with faster dynamic response, improved harmonic performance, and voltage balancing of the CHB cells. The primary model enables conventional control over source current and output voltages, whereas the secondary model is able to generate the reference source current through power modeling, which eliminates the need for a proportion-integral (PI) controller, thus resulting in faster dynamic response. A Luenberger-based observer is also implemented to estimate the dc load current in each CHB cell. The second-order harmonic notch filter and the CHB cell dc voltage balancing cost function aim at improving the performance of the source current and CHB cell dc voltages, respectively. The proposed control techniques are then validated under steady-state and transient conditions through simulation and experiment with a laboratory prototype. [ABSTRACT FROM AUTHOR]

Power converters are one of the failure sources in modern power systems, and hence driver of maintenance and downtime costs, which should be reduced by reliable design, control, and operation of converters. This paper proposes a power sharing control strategy for evenly distributing the thermal stresses among dc converters in dc microgrids, and consequently enhancing the overall system reliability. The aim of this paper is to extend the aging process of failure prone converters by adjusting their loadings. The proposed approach employs the prior experienced thermal damages on the converter's fragile components in order to adjust its contribution on demand supply. According to the proposed strategy, the higher the thermal stress on a converter is, the lower the power it will supply. As a result, the overall system reliability will be improved. A numerical case study on a dc microgrid is presented to illustrate the effectiveness of the proposed power sharing strategy. Moreover, experimental tests are provided to demonstrate the applicability of the reliability-oriented power sharing method. [ABSTRACT FROM AUTHOR]

It is very important to obtain high reliability in the high‐voltage direct current (HVDC) system operation because of extremely high and huge power capacity. To guarantee the reliability IEC‐62501 standard requires valve test for the voltage source converter (VSC) HVDC system. This paper proposes a test circuit for modular multilevel converter (MMC)‐based HVDC valve. The proposed scheme has good features of adequate test current generation, considerably reduced power supply voltage, simplified test circuit topology, etc., compared to the conventional test circuits. The validity of the proposed scheme is verified through experimental results. [ABSTRACT FROM AUTHOR]

In the context of weak grids, vector-controlled modular multilevel converters (MMC) suffer from issues such as low inertia, low damping, and poor system stability. To address these challenges, this paper proposes a control strategy for virtual synchronous generators (VSGs) based on a fuzzy logic control algorithm. The conFtrol strategy leverages the capability of fuzzy algorithms to handle the fuzziness and uncertainty of input signals, enabling adaptive control of the virtual inertia and damping coefficient of the VSG, thus empowering the system with autonomous frequency and voltage regulation capabilities. When the system deviates from or approaches the stable operating point, increasing or decreasing the virtual inertia allows for dynamic adjustment of the virtual inertia and damping coefficient in response to load fluctuations during MMC operation. Through simulation verification, it is demonstrated that the proposed control method provides inertia support to the system during sudden changes in active load during MMC grid-connected operation. This control method achieves adaptive adjustment of the virtual inertia and damping coefficient, effectively enhancing system stability. The simulation results validate the effectiveness and correctness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

Hybrid Energy Storage Systems (HESSs) have gathered considerable interest due to their potential to achieve high energy and power density by integrating different storage technologies, such as batteries and capacitors, to name a few. Among the various topologies explored for HESSs, the multi-output multilevel converter stands out as a promising option, offering decoupled operation of the AC ports while maintaining an internal balance among the diverse storage units. In this paper, the operation and restrictions of a HESS based on a multi-output multilevel converter with a carrier-based modulation scheme are presented. The study provides compelling evidence of the correct operation of the proposed modulation scheme and highlights its advantages, including simplicity and stability. [ABSTRACT FROM AUTHOR]

Integrating Power Electronics Converters (PECs)‐based renewable energy sources can establish a weak grid due to the substantial inertia reduction leading to severe frequency fluctuations. In this paper, a control strategy based on the Virtual Synchronous Generator (VSG) concept is designed for a three‐phase Modular Multilevel Converter (MMC) connected to a weak grid. The proposed VSG control approach improves the frequency response during transient mode, resulting in a 66.7% enhancement at the Point of Common Coupling (PCC). The proposed strategy is shaped within four control loops wherein the VSG‐dependent output current control possesses the duty of enriching the MMC output current tracking capability. Focusing on the MMC output current‐based transfer function, the effectiveness of this capability is guaranteed using the frequency domain analysis including the Nyquist and Bode diagrams. Moreover, a comprehensive discussion was carried out regarding the impact of VSG on the voltage of submodule capacitors and the circulating current. Simulation results in MATLAB/Simulink environment validate the accuracy and weak grid‐connected MMC performance under the proposed VSG‐based control technique. To further verify the superiority of the proposed strategy, two control techniques including Droop and SEBIR are compared with the VSG proposed controller. [ABSTRACT FROM AUTHOR]

This paper introduces advanced control strategies for power electronic converters in distributed generation systems, specifically designed for islanding microgrid systems. The proposed methodology employs a non-linear Sliding Mode Control (SMC) approach, specifically utilizing the Super-Twisting Algorithm (STA) for the regulation of power converters in the GridSupporting Grid-Forming (GSGFm) mode. A cascaded control scheme with an outer-loop voltage controller and an inner-loop current controller utilizes a STA method implemented in the Synchronous Rotating Reference Frame (SRRF). The main advantage of the proposed SMC-STA algorithm in the cascade control methodology is its simple structure and easy implementation. The HIL test under normal conditions typically involves analyzing both transient and steady-state behavior when supplying energy to the load. The stability of both voltage and current is compared between the two control strategies. The experimental results provide confirmation of the control performance of the proposed control methodology based on the STA method. The results demonstrate that the STA-based control methodology effectively regulates voltage levels and minimizes fluctuations, surpassing the performance of a classical PI controller. [ABSTRACT FROM AUTHOR]

Time-relaxed interleaving dynamic element matching return-to-zero (TRI-DEMRZ) is proposed and verified in this paper to improve the spurious-free dynamic range (SFDR) of current-steering digital-to-analog converters (DACs). It incorporates time-relaxed interleaving (TRI), return-to-zero, and the dynamic-element-matching techniques, in a way that fosters the strength of each technique. As analyzed in this paper, merits beyond the combination of these techniques could be achieved. Firstly, TRI-DEMRZ provides a new dimension in the space domain, rather than the time domain, to explore the methods of mitigating nonlinear switching distortions. Secondly, this paper proves that, the image tone caused by typical channel mismatches between interleaved sub-DACs can be randomized into noise with TRI-DEMRZ. Circuit simulations and analysis are provided. An experimental 14-bit 500-MS/s current-steering DAC in 65 nm CMOS has been fabricated and measured, showing 81 dB SFDR at 5.5 MHz and more than 70 dB SFDR up to 211 MHz bandwidth. The SFDR improvement achieved by TRI-DEMRZ is more than 10 dB, which further verifies the effectiveness of TRI-DEMRZ. [ABSTRACT FROM AUTHOR]

In this paper, the procedure for designing a sliding-mode controller for maximum power point tracking photovoltaic (PV) applications is proposed. It is applied to a single-ended primary inductor converter, thus to a fourth-order topology, but it can be extended to a wide class of converters suitable for PV applications. The reachability and existence conditions give rise to a number of design inequalities that add to the classical steady-state conditions in order to have the desired closed-loop converter's performances. The superiority of the control technique over the classical tracking methods is analytically demonstrated through the procedure proposed in this paper. The analytical results have been validated by means of both simulations and experiments. [ABSTRACT FROM PUBLISHER]

In this paper, a new transformerless buck–boost converter is proposed. This converter is based on combining two basic converters, including Cuk and traditional buck–boost converters, along with a voltage multiplier (VM) at the output side. The proposed semi‐quadratic buck–boost converter operates in continuous conduction mode (CCM) and provides two operation modes by turning the switches on and off. This converter has some merits such as a wide conversion ratio and continuous input current. The proposed converter consists of two switches with simultaneous operation resulting in simplicity in control. A modular configuration and a wide range of duty cycles are available through the proposed converter, which causes higher or lower output voltage and facilitates the converter maintenance. The calculations of the ideal and the real voltage gain, voltage stress of switches and diodes, efficiency, and design consideration of elements are given in this paper. Finally, a prototype is implemented, and experimental waveforms are obtained to prove and validate the simulation results as well as the theoretical analysis of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, a steady-state model of an LLC resonant half-bridge converter with internal loss resistance is proposed, in order to maximize power conversion efficiency, and steady-state characteristic equations of DC voltage gain and input impedance are derived for the optimal design of the converter. First, to confirm the validity of the steady-state characteristic equation and the optimal design process, a prototype converter with a maximum output of 2 kW was designed. Through comparison of simulation, calculation, and experimental results obtained from the prototype test, it is shown that the calculation results proposed in this paper were closer to the experimental results than the calculation results obtained under the lossless condition. In addition, the relationship between the switching frequency and the load current of the prototype was compared, in order to determine the operating range of the switching frequency, which is important in the converter design stage. In this case, it was confirmed that the calculated value reflecting the internal loss showed a close result. In conclusion, we confirm the usefulness of the analysis results reflecting the internal loss resistance proposed in this paper and the optimal design process. [ABSTRACT FROM AUTHOR]

Step-up converters are widely used in many applications, such as renewable energy generation with photovoltaic panels and fuel cell stacks. In many cases, the required voltage gain is larger for those applications than a traditional boost converter can achieve. Several large-voltage gain converters have been recently studied. This paper introduces a converter topology in which the voltage gain is larger than a traditional boost converter. The main advantages of the proposed topology are: (i) it provides a large voltage gain without the use of an extreme duty cycle; (ii) its capacitors require a smaller voltage to be sustained compared with other, similar state-of-the-art converters; (iii) the voltage among the ground input and output is not pulsating; and (iv) it can be synthesized with commercial, off-the-shelf half-bridge packed transistors. The proposed converter can be employed in different applications, such as distributed generation and microgrids. This paper presents the steady-state analysis of the proposed converter in the continuous conduction mode, a short comparison with similar topologies, and their voltage on capacitors. Computer-based simulation results are provided to verify the principle of the proposed converter in different operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents a passivity-based control (PBC) based on the Euler–Lagrange (EL) model for dual active bridge (DAB) converters in the constant power load (CPL) condition. The EL model, which is derived from Kirchhoff's current equations at the input and output nodes, is first presented in the DAB application, and the bidirectional CPL is considered in the theoretical analysis, simulation, and physical verification. The PBC has strong robustness to large-signal disturbance and negative incremental resistance load, and it is suitable for DAB converters in the CPL condition. In this paper, the DAB's EL model, passivity analysis, stability analysis, and controller design are described in detail. The simulation results based on SIMULINK are also given in this paper. Finally, a DAB converter prototype is built to demonstrate the validity and feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, a grid-connected converter is investigated. Since the AC side of the grid-connected converter is the LC filter, there is a second-order system resonance problem, and the conventional passive damping control has an inherent limitation of excessive power loss. Based on the mathematical model, a new damping control method is proposed in this paper. It is compared with the traditional solution in terms of damping effect, power loss and system stability. The optimal inductor split ratio is also discussed. The theoretical analysis demonstrates that the proposed method can not only achieve almost the same damping effect as the conventional solution, but also reduce the power loss of the damping resistor. The experimental tests are carried out and the experimental results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Summary: Although LLC converters have widespread applications due to their advantages of high efficiency, high power density, and soft switching, in wide voltage gain range applications, a large switching frequency range is inevitably required, which may bring difficulties in converter design and efficiency improvement. In this paper, a dual LC parallel multi‐resonant converter (MRC) is introduced. The converter contains two parallel LC resonant branches in the resonant tank, which exhibit the notch filter characteristic on the gain curve. It enables the converter to provide wide voltage gain regulation, soft startup, and overcurrent protection over a limited frequency range. Compared to other five‐element MRCs, since the converter provides different current loops for the fundamental wave and the third harmonic to transmit active power, the circulating reactive energy and stress on the resonant components are reduced. Finally, a detailed design procedure for a 3.3 kW converter prototype with an output voltage range of 250–450 V is provided. [ABSTRACT FROM AUTHOR]

In order to address the issues of complexity, high cost, large volume, and low reliability associated with traditional H‐bridge cascaded converters when operating under high voltage, high capacity, and dual electric motor loads, the authors propose the utilisation of a nine‐switch converter as an alternative to the conventional H‐bridge converter for implementing cascaded multilevel converters in dual electric motor drive systems. After conducting an analysis and research on the topology and operational control strategy of cascaded multilevel converters based on the nine‐switch converter, a design is presented using six individual nine‐switch converter units to develop a cascaded multilevel converter capable of driving two 3 MW asynchronous electric motors at a 6 kV voltage level. Simulation verification is performed, and a scaled‐down prototype is built for experimental validation. The results demonstrate that, in comparison to traditional H‐bridge cascaded converters, the proposed cascaded multilevel converter can effectively drive dual electric motors at the same or different frequencies while reducing the number of switches to 1/4, the total transformer windings to 1/2, and Direct Current‐side capacitors to 1/6. This improvement enhances system reliability, portability, and load adaptability, thus offering increased versatility in dual electric motor drive applications. [ABSTRACT FROM AUTHOR]

The cascade converter system has been widely concerned along with the medium power operating conditions, and it is crucial to address the intricate interplay among individual modules to ensure stability of both the source and load subsystems. This paper analyzes the DC‐link voltage stability based on impedance matching and proposes a normalized sensitivity calculation method based on the control strategy, which prevents the complex products and matrix calculations of traditional methods. The three‐level boost (TLB) output impedance model is derived based on state‐space averaging for open‐loop and considering the double‐loop, and the full‐bridge LLC (FBLLC) input impedance model is derived based on the fundamental equivalent circuit. Then the effect of the double‐loop PI parameters on the output impedance of the TLB is analyzed in detail based on the normalized sensitivity and verified by the Bode plots. The experimental results of the 30 kW prototype indicate that the control parameters were varied by a factor of 10 compared to the theoretical control group. The most significant alteration was the modification of the kp_i, resulting in an 8.9% increase in the DC‐link voltage ripple, while the ki_v was modified, resulting in a 0.53% increase, indicating that the effects of the PI parameter are consistent with the normalized sensitivity results. [ABSTRACT FROM AUTHOR]

This paper proposes fractional delay filter-based repetitive controllers (FDF-RCs) for grid-tied converters. Finite impulse response filters and infinite impulse response filters are used to estimate the fractional-order delay filter in a conventional repetitive controller. To do this, both the Lagrange filter-based repetitive controller (LF-RC) and Thiran filter-based repetitive controller (TF-RC) are utilized as FDF-RCs to compensate a fractional delay. The operating principle, the ladder structure, and the performance analysis of FDF-RCs are addressed. The simulation and the experimental results on a single-phase grid-tied converter verify the harmonic suppression ability and reference-tracking performance of the proposed FDF-RC under the grid frequency variation. Moreover, the advantages of the TF-RC over the LF-RC are discussed by comparing and analyzing the simulation and experimental results. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a high voltage gain hybrid interleaved DC‐DC converter (HIC) with quadratic voltage gain is proposed that is suitable for renewable energy systems. The hybrid technique is used in this converter to increase the output voltage. The proposed DC‐DC converter utilizes the interleaved boost converter on the input side, and the input current is shared with a low ripple that lengthens the lifetime of the renewable power source. In addition, the proposed converter has low voltage stress across the components that can be adopted to reduce conduction losses and the cost of the elements. In addition, the proposed converter share ground between the input and output and has high efficiency. The operation modes of the proposed converter are analyzed, and its equations are calculated. Then, the elements of the proposed converter are designed in continuous conduction mode. A comprehensive comparison of the proposed converter with other recently presented existing converters is discussed to show the advantages and disadvantages of the proposed structure. Finally, to verify the performance of the proposed converter and the obtained relations, a 400 W prototype is built to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

This article proposed an off-board bidirectional battery charger for electric vehicles (EVs) that have been designed to perform various modes of operation of EVs like grid-to-vehicle (G2V) and vehicle-to-grid (V2G) while improving the grid power quality (PQ). During the charging process, the charger operates in the G2V mode. In this mode, power flows from the utility grid to the EV, ensuring a smooth and efficient transfer, which has the ability to maintain a sinusoidal grid current waveform and a unity power factor throughout the operation. This not only ensures efficient power transfer but also minimizes disruptions and distortions in the grid. On the other side of the operational spectrum lies the discharging phase, governed by the V2G mode. This mode allows the charger to deliver power from the EV's batteries back to the utility grid. This capability is a significant step toward establishing a two-way relationship between EVs and the grid, enabling EVs to act as energy reservoirs and support grid stability during peak demand or emergencies. This paper presents the proposed adaptive direct power control (ADPC) theory for the proposed electric vehicle charger (EVC), which consists of a grid-side converter and an EV side converter. The proposed control algorithm on both sides of the converters plays a significant role in various operating modes. The ADPC employs a control strategy referred to as the second-order generalized integrator to estimate the actual synchronizing voltage templates specifically designed for single-phase grid-side converters. Consequently, the appropriate current reference used by the charger is to ensure that the power factor remains unity throughout various operating modes. Similarly, for the EV side converter, the integration of the power delivery error further enhances steady-state responses with the proposed ADPC by generating actual phase shifted pulses for the DAB. The overall performance under similar conditions is studied with virtual direct power control to further check the robustness of the proposed ADPC. The adopted topology and control technique further implemented in the prototype of an off-board EVC to verify the various operating conditions to demonstrate its effectiveness and justified as per the IEEE 519-2022 standard. [ABSTRACT FROM AUTHOR]

The buck converter is generally utilized in many applications because of various advantages like maintaining high efficiency for the wide range of input voltage, cost reduction, low output voltage, protection against inrush current and lifetime improvement. However, when on-time of buck converter is kept constant, the input voltage and current remains out of phase that cause's low PF and high total harmonic distortion (THD). Therefore a power factor improvement technique is implemented in this paper that permits the average input current sinusoidal without need of extra converter to work in cascade with buck converter. The critical conduction mode (CRM) buck converter operating with constant on-time (COT) control scheme have low PF because of harmonic contained input current waveform. So in order to make the input current waveform as a sinusoidal by changing the on-time of buck switch, a variable-on-time (VOT) control scheme for CRM buck converter is proposed in this paper. The theoretical analysis is given, and the simulation results confirm the advantages of the proposed control scheme. The object of the research paper is to propose the control scheme to realize high PF for CRM buck converter by only modulating the on-time of buck switch and without need of extra converter to work with buck converter. [ABSTRACT FROM AUTHOR]

In [[5]] is proposed a novel control method intended for compensating the micro-grid power factor and load asymmetries by utilizing advanced functionalities enabled by grid-tied inverters of photovoltaics (PV) and energy storage system (ESS). The main objective of the paper is a control-oriented full-order model and the design of a control strategy for a PV-fed grid-tied boost inverter as a whole system is presented without any decoupling between the two loops in the control system. Accordingly, in [[2]], the authors represent a grid-connected PV system based on a differential step-up inverter working as an adaptive DC-AC inverter topology providing voltage boost capability and it could be one of the future candidates for many DC-AC electrical energy conversion applications. 10.3390/app10041303 2 El Aroudi A., Haroun R., Al-Numay M., Huang M. Multiple-Loop Control Design for a Single-Stage PV-Fed Grid-Tied Differential Boost Inverter. [Extracted from the article]

The Medium Voltage DC (MVDC) architecture for All Electric Ships (AES) has the potential to provide superior features compared to traditional 60-HZ AC distribution systems in terms of power density, power quality, and system stability. The MVDC system introduces extensive use of power electronics equipment into the shipboard power system (SPS) design that brings complexity to the system design. These power electronics equipment connect the power sources and load centers to the MVDC bus and play a major role in handling system faults. This paper focuses on developing a framework to determine the volume and failure rate of a Modular Multilevel Converter (MMC) for early stage ship design. Two different methodologies (Taguchi method and a genetic algorithm) were used to determine the best design from a robust set of design options. Once the design parameters have been identified, the Taguchi method forms orthogonal array to explore and evaluate designs. At the end of the design cycle, it identifies the best parameters from a large set of design parameters to achieve lower volume and failure rate. These parameters are used as input to the optimization process. This helps to narrow out the number of inputs for optimization algorithm. The Nondominated Sorting Genetic Algorithm II (NSGA-II) has been integrated with converter design tool to minimize the volume and failure rate of MMC. The results show that the optimization algorithm coupled with Taguchi Method provides the lowest volume and failure rate for MMC. One of the goals of early-stage ship design is to develop preliminary design and evaluation of trade space to narrow it down. This paper is expected to aid early-stage ship design of power electronics converter design for MVDC systems in SPS. [ABSTRACT FROM AUTHOR]

Advanced cascade design theories and methods are crucial to the rapid development of torque converters. Therefore, the study proposed a new parametric design method for a hydrodynamic torque converter cascade. The method is embodied by using a cubic non-uniform rational B-splines (NURBS) open curve and closed curve, respectively, to carry out the parametric design of the unit blade camberline and unit blade thickness distribution, and the curvature of the designed blade curve is continuous. Then, the author developed batch and script files in the Isight platform for a fully automated integrated design of the hydrodynamic torque converter, including cascade parametric modeling, meshing, computational fluid dynamics (CFD) simulation, post-processing, and optimization design. A three-dimensional cascade integrated optimization design system of the hydrodynamic torque converter is established with CFD technology as the bottom layer design, a control file as the middle layer, and an optimization algorithm as the top layer drive. Finally, multi-objective optimization was carried out for the key cascade parameters (camberline peak height). Compared with the original blade, the optimized NURBS blade increased by 7.207% in high-efficiency region width (Gη), and the optimized blade increased by 2.673% in peak efficiency (ηmax) to meet the actual engineering requirements. The new parametric design method of the blade shape and the integrated optimization design system of a three-dimensional cascade of torque converter proposed in this paper significantly reduces the design costs and shortens the design cycle of the torque converter, which will provide a valuable reference for engineers of turbomachinery. [ABSTRACT FROM AUTHOR]