The protection of the sensitive unbalanced nonlinear loads from sag/swell, distortion, and unbalance in supply voltage is achieved economically using the dynamic voltage restorer (DVR). A simple ...generalized algorithm based on basic synchronous-reference-frame theory has been developed for the generation of instantaneous reference compensating voltages for controlling a DVR. This novel algorithm makes use of the fundamental positive-sequence phase voltages extracted by sensing only two unbalanced and/or distorted line voltages. The algorithm is general enough to handle linear as well as nonlinear loads. The compensating voltages when injected in series with a distribution feeder by three single-phase H-bridge voltage-source converters with a constant switching frequency hysteresis band voltage controller tightly regulate the voltage at the load terminals against any power quality problems on the source side. A capacitor-supported DVR does not need any active power during steady-state operation because the injected voltage is in quadrature with the feeder current. The proposed control strategy is validated through extensive simulation and real-time experimental studies.
In this paper, a novel generalized circuit topology of the n-time quadrupled-hybrid-neutral-point-clamped (Qn-HNPC) converter and a new decomposed sensor-less modulation method are proposed to ...multiply the number of output voltage levels of the 5L-HNPC converter with a less number of components. The Qn-HNPC converter is realized by applying <inline-formula> <tex-math notation="LaTeX">n </tex-math></inline-formula> number of the proposed voltage-level multiplier modules (VLMMs) to the 5L-HNPC converter. Hence, the number of output voltage levels is n-time quadrupled in the attained Qn-HNPC converter, whereas a less number of components, as well as, low cost and size, are added to the main 5L-HNPC converter. Moreover, a novel generalized decomposed sensor-less modulation method is introduced to decompose the main 5L-HNPC and the proposed VLMMs reference signals in the attained Qn-HNPC converter. Consequently, only four low-voltage and low-power switches operate at switching frequency, whereas the remaining devices commutate at the low or fundamental frequency. Furthermore, employing the proposed modulation method in the attained Qn-HNPC converter causes self-balancing of all the capacitors voltage, doubling the first switching harmonic cluster frequency of the output voltage, as well as a remarkable decrease in the control complexity, the stored energy, and the size of the VLMMs capacitor. The presented simulation and experimental results verify the performance and viability of the proposed Qn-HNPC converter topology, as well as, the suggested decomposed modulation method.
Recently, boost‐type current source inverters (CSIs) have received a considerable attention in grid connected photovoltaic (PV) applications thanks to their salient features such as high reliability ...and the aptitude to operate with a DC‐link voltage lower than the grid side voltage. This paper investigates the performance of three different switching strategies for grid‐connected six‐switch boost‐type CSI employed in a solar power conversion system. These strategies are analyzed in terms of the global average conduction and switching power losses, DC‐link current ripple, and AC power quality. The proposed evaluation is based on experimental investigations of the power devices behavior and computer co‐simulations. The obtained numerical and experimental results prove that the switching strategy with a freewheeling state placed in the middle of the overall pulse‐period is the most appropriate in terms of efficiency and power quality.
This paper shows that the switching strategy with a freewheeling state placed in the middle of the overall pulse‐period are the most appropriate for six‐switch boost‐type current‐source photovoltaic inverters in terms of efficiency and power quality.
Z packed U-cell (ZPUC) converter topology is presented in this paper as a new type of multilevel converter topology that can be operated in a single phase as well as in three-phase configurations ...while using a single DC source. Since each U-cell includes two switches and one capacitor, in this topology, three U-cells are needed to generate 5 or 7 voltage levels. Moreover, the configuration proposed for the ZPUC is more appropriate for high-power application modular multilevel converters (MMCs) to increase the voltage levels compared to other topologies. Accurate voltage balancing on small-sized auxiliary capacitors is due to integrated modulation strategy without using additional controllers; additionally, the reduction of total harmonic distortion (THD) in AC currents for higher voltage levels is an advantage of this configuration. A full topology sequence of operation and performance analysis of ZPUC based on the 5-L inverter is investigated in Matlab-Simulink and experimentally validated on a 3 kVA prototype. The obtained results illustrate the good dynamic performance of the proposed topology and the implemented integrated switching pattern voltage balancing.
This study presents a hierarchical control strategy for an auxiliary power unit (APU) for aircraft to coordinate multiple power sources and control developed power electronic interfaces. The study ...benefits from the presence of a hybrid energy system in paralleled structure to the main generator as the complementary system. The employed structure enhances power quality and improves the voltage profile of the high-voltage DC bus. Furthermore, the developed bi-directional topology provides the possibility of interaction with the grid. Considering the APU features in an aircraft, a hierarchical control strategy with different levels of control, timescale, dynamic response, and significance are developed. The developed controller consists of a power management algorithm in the higher level, and local voltage and current controllers in the lower one. The algorithm aims to maximise the PV sub-system utilisation, overcome voltage fluctuations, increase power density, reduce operation costs, and increase system availability while allowing further development to larger systems. Simulation and experimental results confirm the robustness of the algorithm. The result shows that the proposed power sharing strategy optimises the system utilisation while achieving a high-quality voltage profile under severe fluctuations. Moreover, the stress on the battery pack is reduced to improve the life cycle and reduce operation costs.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In this paper, the authors propose a novel six-band hysteresis technique to efficiently control the seven-level packed U cells (PUC) converter. The proposed PUC combines advantages of the flying ...capacitor and the cascaded H-bridge topologies. The novel control strategy is proposed in order to insure a good operation of the PUC converter in both inverter and rectifier modes. In case of rectifier operation, the proposed six-band controller is designed to draw a sinusoidal line current (load current in case of inverter operation) with a unity power factor. Harmonics contents of line current (or load current) and rectifier input voltage (or inverter output voltage) are very low which permits the reduction of the active and passive filters ratings resulting on a very high energetic efficiency and a reduced installation cost. The proposed concept was validated through experimental implementation using real-time controller, the DS1103 of dSpace.
In this study, a real-time controller implementing closed-loop space vector modulation (CLSVM) technique combined with DC bus voltage control is applied on a three-phase four-wire three-level neutral ...point clamped (NPC) inverter to be used in sustainable energy conversion systems with higher efficiency and lower switching frequency than conventional two-level inverters. The redundant switching states of CLSVM is dictated based on the voltage feedback obtained from DC link in order to constantly balance the DC bus capacitors voltages under various load conditions. The main feature of this technique is the use of only voltage sensors for balancing the DC capacitors voltages in four-wire system which makes the algorithm act fast, while permitting reduction of DC bus capacitors voltage ripple significantly and therefore smaller capacitors are used. The NPC inverter has been modelled and effects of redundant switching states have been analysed mathematically on DC capacitors voltages. Comprehensive experimental tests are conducted on a four-wire three-leg NPC operating as uninterruptible power supply application for sustainable energy conversion to validate the designed approach and the dynamic response under various load conditions including linear, non-linear, balanced, unbalanced and motor loads.
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All‐solid‐state lithium (Li) metal batteries combine high power density with robust security, making them one of the strong competitors for the next generation of battery technology. By replacing the ...flammable and volatile electrolytes commonly found in traditional Li‐ion batteries (LIBs) with noncombustible solid‐state electrolytes (SSEs), we have the potential to fundamentally enhance safety measures. Concurrently, SSE would be capable of fitting high specific capacity (3860 mAh g−1) metal Li and is expected to break through the upper limit of mass‐energy density (350 Wh kg−1) of existing LIBs system. Nevertheless, the growth of Li dendrites on the negative side or the nucleation of Li inside SSEs may give rise to battery short circuits, which is the primary factor limiting the application of Li metal. Recognizing this, the focus of this review is to provide a perspective for experimentalists and theorists who closely monitor various surface/interface and microstructure phenomena to understand Li dendrites. The strategies to reveal the complicated deposition mechanism and to control the dendrite growth of metal Li in solid‐state batteries, as well as the advanced characterization methods of metal Li, provide suggestions for the practical research of solid‐state Li metal batteries.
All‐solid‐state batteries have attracted great attention from academia and industry, however, many challenges remain regarding practical applications. This review focuses on systematic discussions classifying the deposition mechanism of lithium (Li) dendrites, examining the ion concentration gradient, morphological characteristics of dendrites, and the nonuniform distribution of internal compressive stress, in the mainstream of solid‐state electrolytes. It delves into strategies for controlling Li metal deposition within the solid‐state electrolyte, compiles characterization methods for assessing Li deposition behavior in solid‐state batteries, and outlines anode design methodologies for industrialization. The review aims to offer some insights into the advancement of solid‐state batteries.
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This paper introduces an enhanced commutation method applied to the indirect matrix converter topology. It is based on the detection of the load current polarity so as to cancel the turn-on delay ...times of the load-side converter's switches. The proposed method allows the grid-side converter devices to commutate at zero current with larger time interval widths provided for this safe commutation. Moreover, it has been shown through experimental results, carried out on a laboratory prototype of the matrix converter, that a substantial improvement of line current total harmonic distortion is achieved.
In this paper, a new cascaded nonlinear controller has been designed and implemented on the packed U-cell (PUC) seven-level inverter. The proposed controller has been designed based on a simplified ...model of PUC inverter and consists of a voltage controller as an outer loop and a current controller as an inner loop. The outer loop regulates the PUC inverter capacitor voltage as the second dc bus. The inner loop is in charge of controlling the flowing current, which is also used to charge and discharge that capacitor. The main goal of the whole system is to keep the dc capacitor voltage at a certain level results in generating a smooth and quasi-sine-wave seven-level voltage waveform at the output of the inverter with low switching frequency. The proposed controller performance is verified through experimental tests. Practical results prove the good dynamic performance of the controller in fixing the PUC capacitor voltage for various and variable load conditions and yet generating low-harmonic seven-level voltage waveform to deliver power to the loads. Operation as an uninterruptible power supply (UPS) or ac loads interface for photovoltaic energy conversion applications is targeted.
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