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Recently, programmable metamaterials or metasurfaces have been developed to dynamically edit electromagnetic waves for realizing different functions in the same platform. However, the proposed programmable metasurfaces can only control reflected or transmitted wavefronts in half‐space. Here, a “Janus” digital coding metasurface with the capabilities to program various electromagnetic functions in the reflected (with R‐codes) and transmitted (with T‐codes) waves simultaneously is presented. Three PIN diodes are employed to design the metaparticle, and the state of the PIN diodes can be switched to change the reflected and transmitted phases independently. Three schemes achieved by the proposed programmable metasurface are provided as illustrative examples, including anomalous deflections, beam focusing, and scattering reduction in the full space. As a proof‐of‐concept, a prototype composed of 10 × 20 metaparticles is fabricated and the measured results are in good agreement with the designs and numerical results, validating the full‐space modulations enabled by the programmable metasurface. It is expected that the new programmable metasurface can broaden the applications in stealth technologies, imaging systems, and the next generation of wireless communications. A “Janus” coding programmable metasurface is proposed to edit the reflected and transmitted waves simultaneously in real‐time. Benefiting from the design of the separated current paths of diodes, the reflected and transmitted phases can be controlled independently in different polarizations. The proposed metasurface can implement various electromagnetic functions in the reflected (with R‐codes) and transmitted (with T‐codes) regions simultaneously.

The six-phase two-level voltage source inverter (SPTLVSI) fed the six-phase asymmetrical induction motor (SPAIM), which has a stator that splits the three-phase windings into two groups those are shifted electrically by 30 ∘ . It introduces significant current harmonics of the order of 6 k ± 1 k = 1 , 3 , 5 … , which can be mapped into the non-flux/torque producing X - Y sub-plane. These harmonics cause only losses in the motor winding as they do not take part in torque production. The authors propose a new space vector modulation technique named the 48-sector vector space decomposition-based space vector pulse-width modulation (C6 ϕ SVPWM48) technique, which has been verified using MATLAB (Matrix Laboratory) simulation and reported by the authors in the previous work, and the work is extended in this paper. This paper presents a contribution to compare the proposed technique with the 12-sector vector space decomposition-based space vector pulse-width modulation (C6 ϕ SVPWM12) based on CMV (Common mode voltage) , switching loss of the inverter, torque ripple, and stator current distortion. The C6 ϕ SVPWM48 technique has been implemented experimentally on the SPTLVSI fed a prototype of 200 V, 2 kW SPAIM. The C6 ϕ SVPWM48 technique is controlled using the ARM cortex M4 32-bit microcontroller (STM32F407VGT6) and the SPTLVSI during steady-state and dynamic operating conditions. The experimental results of the C6 ϕ SVPWM48 technique are discussed and presented. Furthermore, it reduces the harmonic current drawn by the machine to a large extent, consequently, the copper losses of the machine and also reducing the average switching loss.

In the research field of multilevel converters, three-level NPC (neutral-point-clamped) converters, which unfortunately may cause the deviation of the neutral-point voltage of DC-link capacitors, are widely discussed. Theoretically, virtual space vector modulation (VSVM) could guarantee the balance control of the neutral-point voltage. However, there still exist some uncontrollable space vector regions. Based on VSVM, this paper proposes a varied virtual space vector modulation (VVSVM) method for three-level NPC converters. Under complete modulation conditions, this method can control the balance of the neutral-point voltage of DC-link capacitors by adjusting the duty cycle of small vectors and regulating the current generated by virtual medium vectors. Compared with commonly used VSVM methods and mixed modulation strategies, this method is simpler and more practical. The effectiveness and validity of this method are verified by simulations and experiments.

A simplified space vector modulation (SVM) technique is proposed for the seven-level cascaded H-bridge (CHB) inverter. It is based on decomposing the seven-level space vector hexagon into a number of two-level space vector hexagons. The presented technique significantly reduces the calculation time and efforts involved in the SVM of a seven-level inverter; without any loss in the output voltage magnitude or increase in the total harmonic distortion content. A further simplified technique is also presented in this study, which significantly reduces the complexity and effort involved in the seven-level SVM. Simulation results for the seven-level CHB inverter using the proposed techniques are presented. The results are compared with results using sinusoidal pulse-width modulation (PWM) and third harmonic injection PWM to prove the validity of the proposed techniques. The proposed technique is perfectly general and can be applied to all types of multilevel inverters and extended to higher level inverters.

We consider the boundedness of the n-dimension oscillatory hyper-Hilbert transform along homogeneous curves on the α-modulation spaces, including the inhomogeneous Besov spaces and the classical modulation spaces. The main theorems signicantly improve some known results.

This study proposes a space vector modulation (SVM) strategy to balance the neutral-point voltage of three-level inverter systems. The proposed method is implemented by combining conventional symmetric SVM with nearest three-vector (NTV) modulation. The conventional SVM is converted to NTV modulation by properly adding or subtracting a minimum gate-on time. In addition, using this method, the switching frequency is reduced and a decrease of switching loss would be yielded. The neutral-point voltage is balanced by the proposed SVM strategy without additional hardware or complex calculations. Simulation and experimental results are shown to verify the validity and feasibility of the proposed SVM strategy.

The total harmonic distortion and switching stress of a three-level direct matrix converter (TLDMC) is greatly reduced in comparison with those of a conventional matrix converter (MC). Meanwhile, the TLDMC leads to major advantages in comparison with existing multi-level AC–DC–AC converter topologies in terms of reduced switch counts and lowered switching power loss. In this paper, a space vector pulse width amplitude modulation (SVPWAM) strategy for the TLDMC is proposed, which can reduce the number of switching actions and improve the voltage utilization by eliminating the zero vector of each sector. An indirect modulation model of a TLDMC is discussed according to the topology of TLDMC in this paper. For the space vector modulation of the TLDMC, the space vector pulse width modulation (SVPWM) with a zero-vector of the fictitious rectifier stage is improved to form the SVPWAM. In addition, the virtual space vector pulse width modulation (VSVPWM) strategy is used for the fictitious inverter stage. Finally, simulation and experimental results verify the correctness of the proposed method.

Recently, space‐time modulation has revolutionized the wave engineering technologies, providing unprecedented opportunities beyond traditional static systems. This advancement is crucial across diverse fields, ranging from non‐reciprocal transmission to wireless communication. However, the current approaches to sound modulation require bulky artificial structures and are limited in achieving space‐time‐variable sound‐matter interactions. Here, a prototype of space‐time acoustic metasurface (STAM) is proposed and implemented, consisting of a reflective piezoelectric array controlled by a field‐programmable gate array. Leveraging the spatiotemporally programmable phases of the STAM, this is experimentally achieved Doppler‐like chirp modulation and space‐time modulation with deterministic frequency and momentum shifts of waterborne acoustic waves. Furthermore, based on this flexible and efficient modulation strategy, a stochastic space‐time modulation method is introduced, showcasing its applications in single‐channel direction‐of‐arrival estimation. The proposed STAM extends the frontier of wave control and thereby lays the foundation for versatile space‐time applications involving sound. This article introduces a novel space‐time acoustic metasurface (STAM) to overcome the limitations of bulky structures in sound modulation. Using a programmable piezoelectric array, the STAM precisely controls waterborne acoustic waves through spatiotemporal phase modulation. Doppler‐like chirp modulation and stochastic modulation are demonstrated, with applications shown in single‐channel direction‐of‐arrival estimation, opening new avenues for wave control.

Parallel multilevel inverter becoming a very attractive structure for medium- and high-power/voltage applications. This is mainly due to the fact that it can achieve high-power level and overcome voltage /current limitations of switching devices. However due to the differences in hardware parameters, the circulating current appears in this structure and degrades its performance. This paper presents a circulating current control method for paralleled three-level neutral point clamped (NPC) inverter. The analytical model that describes the circulating current generation and behaviors is demonstrated, and then using this model, a control method to eliminate the circulating current is proposed. The proposed strategy is realized by introducing a control variable adjusting the application times of the redundant vectors of the three-level space vector modulation (SVPWM). In addition, a PI-controller based on closed loop control is synthetized to determine automatically the appropriate adjustable duration, during which the redundant vectors will be applied to eliminate the circulating current among the paralleled inverter. Finally, the effectiveness of the proposed circulating current control method under different operating conditions is confirmed through experimental validation.

This paper presents a current source inverter (CSI) with zero-voltage-switching (ZVS) for low-input voltage PMSM application. And its working principle, space vector modulation (SVM) method, high-frequency switching process are analyzed in detail. The detailed ZVS realization conditions are also designed. The proposed circuit is consisted of a high-gain buck-boost chopper circuit, a three-phase bridge and a C filter, it has the advantage of a wide output voltage range. The proposed modulation method realizes SVM control due to the optimized energy storage mode. The proposed soft-switching scheme realizes the ZVS of the energy storage switch by designing the resonance parameters and controlling the turn-on time of the active clamp circuit. The feasibility and advancement of the proposed CSI drive system are verified by 24VDC/1 kW prototype experiments.