High-power Systems Research Articles

Modeling photothermal effects in high power optical resonators used for coherent levitation

Radiation pressure can be used to enable optomechanical control and manipulation of the quantum state of a mechanical oscillator. Optomechanical interaction can also be mediated by photothermal effects which, although frequently overlooked, may compete with radiation pressure interaction. Understanding of how these phenomena affect the coherent exchange of information between optical and mechanical degrees of freedom is often underdeveloped, particularly in mesoscale high-power systems where photothermal effects can fully dominate the interaction. Here we report an effective theoretical model to predict and successfully reconstruct the dynamics of a unique optomechanical system: a cavity-enhanced setup for macroscopic optical levitation, where a free-standing mirror acts as the optomechanical oscillator. We decompose the photothermal interaction into two opposing light-induced effects, photothermal expansion, and thermo-optic effects. We then reconstruct a heuristic model that links the intracavity field to four types of cavity length changes caused by acoustic (), centre of mass (), photothermal () and thermo-optic () displacements. This offers refined predictions with a higher degree of agreement with experimental results. Our work provides a means to precisely model the photothermal effect of high power optomechanical systems, as well as for developing more precise photothermal modeling of photonics systems for precision sensing and quantum measurements.

Current imbalance analysis of multichip influenced by parasitic inductance within PP-IEGT

The Press-Pack Injection Enhanced Gate Transistor (PP-IEGT) technology is frequently employed in converters for high power systems. In the device packaging, the imbalanced current sharing among chips has become a significant issue for device reliability. Considering the semiconductor structure of IEGT is different from the conventional power devices, the main prerequisite for fully quantifying the current distribution is to establish a suitable electrical model for IEGT. Thus, this paper proposes an IEGT single chip lumped-charge model taking into account the effect of carrier injection enhancement in the emitter. Furthermore, as for the parallel branches in PP-IEGT, the parasitic inductance of the drive board and pillars within the package are extracted by Ansys simulation, and the validity of Ansys simulation is verified by the port S-parameter method. Finally, combining the electrical model and the effect of mutual inductance, the switching inconsistency is evaluated. It is demonstrated that the farther the branch from the gate inlet, the greater the gate inductance withstands. Besides, the mutual inductance is an important factor to influence the electrical parameter distribution. Both mutual coupling coefficient and current density display degressive trends with the increases of the gap between parallel chips.

Mode purity evaluation of high-power millimeter wave transmission line by 3-port directional coupler

In high-power millimeter wave systems, transmission lines based on the circular corrugated waveguide are widely used to realize efficient millimeter wave transmission. The mode purity is a very important parameter for the high-power millimeter wave transmission lines. The main mode in the corrugated waveguide is usually the LP01 mode, while the main spurious modes include the LP02 mode, the LP11 even mode, the LP11 odd mode, and so on. For the mode purity analysis, we designed a 3-port directional coupler, considering 3 major spurious modes. A calculation code was developed for the mode purity investigation. In addition, the error caused by ignoring the minor spurious modes was analyzed with some calculation examples. Finally, high-power experiments were carried out with a 105 GHz millimeter wave system. The mode purity was evaluated with the data measured by the 3-port directional coupler. The results indicated that the content of the main mode LP01 is up to 90.38%, which aligns with the parameters derived from the factory test results of 105 GHz high-power millimeter wave source. It shows that the 3-port directional coupler can be used as an optional method for mode purity estimation of the high-power millimeter wave systems.

Enhanced Energy Storage Properties of Polypropylene/Glycidyl Methacrylate Grafted Polypropylene/Nano-ZrO2 Ternary System

Extensive research has focused on enhancing the energy storage density of polypropylene (PP) to meet the demands of high-power and compact electronic devices and electrical systems. However, there is a lack of studies addressing the delicate balance between energy storage density and dielectric loss. Dielectric loss can lead to excessive heat generation, posing a threat to the operation of energy storage capacitors. In this study, PP grafted with glycidyl methacrylate (GMA) was used as a compatibilizer and incorporated into a PP/nano ZrO2 blend to form a ternary system of PP/nano ZrO2/PP grafted GMA. A comparative study was conducted to analyze the effects of GMA grafting and individual doping of nano ZrO2 on the dielectric performance of PP. The results demonstrate that the ternary system not only ensures a high breakdown voltage (382.29 MV/m) but also possesses a high dielectric constant (2.67), thereby achieving an energy storage density of 1.7275 J/cm3 while maintaining low dielectric loss. Furthermore, grafting GMA introduces a significant number of deep traps, a phenomenon substantiated by the results of thermal stimulated depolarization current tests and molecular simulation calculations. However, the ternary system partially avoids the introduction of excessive deep traps associated with GMA grafting. This ternary system exhibits excellent energy storage performance, ease of fabrication, and stability, thereby enriching the research on polymer-based high-energy density dielectric materials.

Hybrid energy storage system and management strategy for motor drive with high torque overload

The demand for small-size motors with large output torque in fields such as mobile robotics is increasing, necessitating mobile power systems with greater output power and current within a specific volume and weight. However, conventional mobile power sources like lithium batteries face challenges in surpassing the dual limitations of weight and output power due to constraints imposed by materials and other factors. Therefore, this paper references the approach of high-power hybrid energy systems in automobiles and proposes a battery–supercapacitor hybrid energy storage system (BSHESS) and energy management strategy. The motor is powered by the battery during low torque operating conditions, while the additional output power of the battery is used to charge the supercapacitor. In cases of torque overload, the rapid discharge of the supercapacitor provides the motor with a high current, ensuring instantaneous high output power. Furthermore, the proposed energy management strategy is used to control the charging and discharging processes of the supercapacitor, guaranteeing that the charging process of the supercapacitor does not interfere with the battery’s power supply to the motor, as well as maintaining controllability and stability of the current in the discharge process. The feasibility of the principle is verified through simulations, and we also design a complete prototype of the proposed BSHESS and conduct experiments on the motor. The results demonstrate that the maximum output current to the motor is increased by 150% compared to the original level, and the weight is reduced by 64.7% compared to a pure battery-powered system with same maximum current output. Additionally, the energy management strategy enables a more stable charging and discharging process compared to the unmanaged state.

Mitigating stimulated Brillouin scattering in multimode fibers with focused output via wavefront shaping.

The key challenge for high-power delivery through optical fibers is overcoming nonlinear optical effects. To keep a smooth output beam, most techniques for mitigating optical nonlinearities are restricted to single-mode fibers. Moving out of the single-mode paradigm, we show experimentally that wavefront-shaping of coherent input light to a highly multimode fiber can increase the power threshold for stimulated Brillouin scattering (SBS) by an order of magnitude, whilst simultaneously controlling the output beam profile. The SBS suppression results from an effective broadening of the Brillouin spectrum under multimode excitation, without broadening of transmitted light. Strongest suppression is achieved with selective mode excitation that gives the broadest Brillouin spectrum. Our method is efficient, robust, and applicable to continuous waves and pulses. This work points toward a promising route for mitigating detrimental nonlinear effects in optical fibers, enabling further power scaling of high-power fiber systems for applications to directed energy, remote sensing, and gravitational-wave detection.

Research on load-sharing characteristics of six-branch herringbone gear transmission system

With the continuous development of high-speed and high-power gear transmission technology, as well as the new demand for vibration and noise reduction in high-speed and heavy-duty gear transmission systems in fields such as aviation and navigation, the herringbone gear branch transmission system is subject to higher requirements in terms of its dynamic characteristics. Therefore, it is necessary to conduct research on the dynamic characteristics of high-power and high-torque herringbone gear branch transmission systems. Based on the lumped parameter method, a bending-torsion coupling dynamic model of the transmission system is established, and a calculation method for load-sharing coefficients (LSCs) is proposed. The LSCs are obtained for each gear pair in the same meshing period of the transmission system that is under the interaction of time-varying internal excitation. The meshing force of the six-branch gearing system was calculated in ADAMS to verify the validity of the established dynamic model. The study results indicate that errors have a negative impact on the sharing performance. To maintain a sharing coefficient below 1.15, the manufacturing and installation errors of gears Z5 and Z6 should be restricted to 9 µm and 7 µm, respectively. Special attention should be given to gear Z5 in terms of support stiffness, with a value of 1 × 108 N/m being the most favorable. During the system design, the initial phase of the installation error should be considered and preferably selected near 180°. Additionally, the system exhibits easier load sharing with higher input power. The optimal torsional stiffness of the duplex shaft is 5 × 107 N/m, while the optimal bending stiffness is 5 × 108 N/m. This study aimed to provide a theoretical foundation for the design and optimization of marine high-power gear transmission systems.

An Advanced High Dimensional Power System of Optimization Problems Algorithm

New Evolutionary Algorithm-based for High-Dimensional Power System Optimization Problems and Modern power system optimization problems face growing challenges as there are numerous decision variables and unbiased functions. Multi-objective evolutionary algorithms (MOEAs) basically are popularly applied for solving and dealing with such complicated problems in substantial power systems that have several objective functions. However, customary MOEAs works appropriately when the number of objective features comes to be less than three. Generally, the effectiveness of MOEAs begins to decrease apparently with an increase in the number of unbiased functions. This study is devoted to applying an authentic gradable evolutionary algorithm for the purpose of solving power system optimization issues which manifest numerous objective functions. In particular, this seeks an algorithm based upon NSGA-II algorithm dedicated for an efficient solution of multi-objective optimization problems. Here, we attempt to modify NSGA-II algorithm to effectively solve many target optimization problems. A novel effective grouping method is applied in the proposed algorithm in similar to the non-dominant grouping method of NSGA-II algorithm to accelerate decision convergence action in POF. The recommended algorithm is compared with modern numerous objective optimization algorithms following three test problems. The findings reveal that as the number of unbiased functions is noticeably large, the algorithm that we propose is significantly superior to other algorithms.

Design and Implementation of Area Efficient Low Latency Radix-8 Multiplier on FPGA

Abstract: Electronic systems are widely used by humans nowadays in all aspects of daily life. Today, there is no living for humans on Earth without any electronic products. High Speed, Low Power, and Low Area Electronic Systems are what the current generation needs. In digital systems, a variety of arithmetic circuits are employed. Adder, multiplier, divider, and other arithmetic circuits are some examples. To acquire Products from Multiplier and Multiplicand, there are various multipliers with various methods. One of the multipliers is Radix-4 Multiplier. The Radix-4 Multiplier produces n/2 partial products, where n is the multiplier's bit count. This multiplier has a high operating speed, power dissipation, and surface area. Area, power dissipation, and propagation delay can all be reduced by reducing the number of partial products of the n-bit multiplier. Radix-8 uses n-bit multiplier integers that are n/3 for partial products. The Area, Delay, and Power Dissipation are reduced as a result. 8- bit booth multipliers for Radix-4 and Radix-8 are designed and implemented using FPGA. For both multipliers, delay, power dissipation, and area are compared. According to the comparison, Radix8 Booth Multiplier performs better than Radix-4 Booth Multiplier in terms of delay, power dissipation, and area. Therefore, the Radix-4 Booth Multiplier can be swapped out for the Radix-8 Booth Multiplier.

Boosting capacitive performance of lead-free relaxor ferroelectrics by introducing a linear dielectric

As an important core component used in high-power pulse electronic systems, dielectric ceramic capacitors have gained great interest because of their ultrahigh powder density (PD) and fast discharge speed (t0.9). However, inferior energy storage performance (ESP) greatly limits the development of energy storage devices with the requirement of miniaturization and integration. Herein, we propose a feasible approach to introduce linear dielectric CaTiO3 (CT) into (Bi0.5Na0.5)TiO3 (BNT) for the design of engineered relaxor ferroelectrics to tune ESP at the grain, domain, and macroscopic scales. The results demonstrate that introducing CT generates enhanced relaxor behavior with highly dynamic polar nanoregions, refines grain size, and suppresses dielectric loss, synergistically yielding increased breakdown strength, negligible remnant polarization, and a nearly linear polarization hysteresis loop. Consequently, superior ESP is achieved in BNT-0.3CT relaxor ferroelectric ceramics with a large energy density (∼5.65 J/cm3) and a high efficiency (∼88.1 %). Based on CT-induced merits, the excellent temperature/frequency/cycling stabilities and remarkable charge-discharge properties featuring a high PD of 200.4 MW/cm3, high discharge energy density of 2.27 J/cm3 and ultrashort t0.9 of 58 ns of the designed ceramics broaden the actual application prospects. This work demonstrates that introducing linear dielectric CT holds great promise for developing high-performance energy storage dielectrics.

Adaptive Active Inertia Control Strategy of MMC-HVDC Systems for Flexible Frequency Support

The Modular Multilevel Converter High Voltage Direct Current Transmission (MMC-HVDC) technology is considered to be the most feasible choice for high-voltage and high-power transmission systems, and its flexibility and high controllability provide a new solution for renewable energy grid integration. The MMC topology contains a large number of capacitors, which enables it to provide a certain active inertia support for the connected AC system. Different from a synchronous machine, the active inertia control of an MMC can flexibly adjust a system’s inertia-supporting power by changing the control parameters. By introducing a variation of the Sigmoid function with amplitude-limiting capability, this paper proposes an adaptive active inertia control strategy for the MMC-HVDC system. The proposed scheme adjusts the inertia constant adaptively according to the frequency change rate of the AC system, which can better respond to the frequency recovery performance. Finally, the MMC-HVDC simulation model is established in PSCAD/EMTDC to verify the effectiveness of the proposed control strategy.

Improved energy-storage performance with superior thermal stability of [(Bi0.5Na0.5)TiO3](1-x) – [Ba(Ni0.5Nb0.5)O3]x relaxor ferroelectric ceramics

Dielectric ceramic capacitors have been extensively investigated in electronic and high-power electrical systems due to their high-power density, fast charge-discharge rates, brilliant fatigue endurance, and good high-temperature stability. In this study, the dielectric and energy-storage performance of [(Bi0.5Na0.5)TiO3](1-x) –[Ba(Ni0.5Nb0.5)O3]x (x = 0, 0.02, 0.03, 0.04, 0.05, and 0.06) relaxor ferroelectric ceramics were investigated as a function of electric field and temperature. The splitting of (200) reflections in the XRD pattern confirmed the rhombohedral phase with R3c symmetry of all samples. The scanning electron microscopy confirmed that the average grain size gradually increased with doping. The introduction of BNN reduced the temperature of the ferroelectric-antiferroelectric phase transition (Td) and antiferroelectric - paraelectric phase and enhanced the relaxor behavior of BNT ceramics. The value of the recoverable energy density (Wrec) and efficiency (η) increased from 0.049 J/cm3 to 0.627 J/cm3 and 2.13%–61.71% with an increase of x from 0 to 0.06. Further, the Wrec values also showed temperature stability with a variation of less than 8% in the range RT-383 K. Hence, the substitution of BNN in BNT positively affects the overall properties and makes it a promising candidate for energy storage application with superior thermal stability.

Transforming a Primary Li-SOCl2 Battery into a High-Power Rechargeable System via Molecular Catalysis.

Li-SOCl2 batteries possess ultrahigh energy densities and superior safety features at a wide range of operating temperatures. However, the Li-SOCl2 battery system suffers from poor reversibility due to the sluggish kinetics of SOCl2 reduction during discharging and the oxidation of the insulating discharge products during charging. To achieve a high-power rechargeable Li-SOCl2 battery, herein we introduce the molecular catalyst I2 into the electrolyte to tailor the charging and discharging reaction pathways. The as-assembled rechargeable cell exhibits superior power density, sustaining an ultrahigh current density of 100 mA cm-2 during discharging and delivering a reversible capacity of 1 mAh cm-2 for 200 cycles at a current density of 2 mA cm-2 and 6 mAh cm-2 for 50 cycles at a current density of 5 mA cm-2. Our results reveal the molecular catalyst-mediated reaction mechanisms that fundamentally alter the rate-determining steps of discharging and charging in Li-SOCl2 batteries and highlight the viability of transforming a primary high-energy battery into a high-power rechargeable system, which has great potential to meet the ever-increasing demand of energy-storage systems.

An open-end high-power microwave-induced fracturing system for hard rock

Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-power microwave subsystem (100 kW), a true triaxial testing machine, a dynamic monitoring subsystem, and an electromagnetic shielding subsystem. It can realize rapid microwave-induced fracturing, intelligent tuning of impedance, dynamic feedback under strong microwave fields, and active control of microwave parameters by addressing the following issues: the instability and insecurity of the system, the discharge breakdown between coaxial lines during high-power microwave output, and a lack of feedback of rock-microwave response. In this study, microwave-induced surface and borehole fracturing tests under true triaxial stress were carried out. Experimental comparisons imply that high-power microwave irradiation can reduce the fracturing time of hard rock and that the fracture range (160 mm) of a 915-MHz microwave source is about three times that of 2.45 GHz. After microwave-induced borehole fracturing, many tensile cracks occur on the rock surface and in the borehole: the maximum reduction of the P-wave velocity is 12.8%. The test results show that a high-power microwave source of 915 MHz is more conducive to assisting mechanical rock breaking and destressing. The system can promote the development of microwave-assisted rock breaking equipment.

Mode analysis and fault-tolerant method of open-circuit fault for a three-level dual active bridge DC-DC converter

The three-level dual-active-bridge (TL-DAB) DC-DC converter is a promising dc-dc converter for high-voltage and high-power systems. Open-circuit faults on power switches are crucial issues for the TL-DAB dc-dc converters, resulting in various performance degradations such as dc bias and divided capacitor voltage imbalance. The mode analysis after fault is necessary for fault detection and fault-tolerant control. Subsequently, fault-tolerant control is essential to reduce or overcome these issues. In the proposed fault-tolerant method, when the primary side inner switch or the secondary side switch breaks down, the gate-driving signal of the complementary switch is recommended to block and the effects can be removed. Finally, experiment results demonstrate that the issues caused by open-circuit faults can be reduced significantly with the proposed fault-tolerant method.

Development of high-power microwave mechanical integrated continuous mining device

This article introduces a high-power microwave mechanical integrated continuous mining device, which can achieve synchronous cutting of hard rocks by microwave and machinery. The device includes a cutting system, a rotary translation system, a loading system, a high-power microwave system, and a control and monitoring system. The technology of “master-slave follow-up” disc cutter alternating side cutting of rock was proposed, which could improve the effectiveness of rock breaking. The integrated structure of a microwave-cut system was then proposed, and synchronous motion of the microwave-cut system and adjustment of the loading system could be realized. The automatic adjustment technology of the microwave working distance was developed to dynamically control the optimal microwave working distance. The basic functions of the equipment were verified by tests. By comparing the two types of disk cutters, it is found that the master-slave follow-up disk cutter can improve significantly the dust removal effect and rock breaking efficiency in rock breaking process versus the conventional large disc cutter. Cutting tests of slate with or without microwave were conducted using a master-slave follow-up disk cutter. The results show that the cutting patterns of slates change from intermittent chunks (without microwave irradiation) to persistent debris (with microwave irradiation), and the cutting speed is significantly improved (170%). The development of the device provides a scientific basis for changing the conventional mining technology of metal mines and realizing the mechanical continuous mining in hard metal mines.

Ultrafast Yb:YAG laser oscillator with gigahertz repetition rate.

We present a SESAM modelocked Yb:YAG solid-state laser providing low-noise narrowband pulses with a pulse duration of 606 fs at a 1.09-GHz repetition rate, delivering up to 2.5 W of average output power. This laser provides access to a new parameter space that could previously not be reached by solid-state lasers and, to the best of our knowledge, is the first modelocked solid-state Yb:YAG laser in the gigahertz regime. This is achieved by introducing a single additional intracavity element, specifically a nonlinear birefringent YVO4 crystal, for soliton formation, polarization selection, and cavity intensity clamping. The isotropic pump absorption in Yb:YAG allows for stable and low-noise operation with multimode fiber pumping. This laser is ideally suited as a seed source for many commercial high-power Yb-doped amplification systems operating at a center wavelength around 1.03 µm. The laser exhibits a high power per comb line of 5.0 mW which also makes it interesting for applications in frequency comb spectroscopy, especially if it is used to pump an optical parametric oscillator. We measure a relative intensity noise (RIN) of 0.03%, integrated from 1 Hz to 10 MHz. Furthermore, we show that the laser timing jitter for noise frequencies >2 kHz is fully explained by a power-dependent shift in the center wavelength of 0.38 nm/W due to the quasi-three-level laser gain material. The narrow gain bandwidth of Yb:YAG reduces this contribution to noise in comparison to other SESAM modelocked Yb-doped lasers.

Analyses on an electronic voltage transformer's failure by its resonance with very fast transient overvoltage and suppression

AbstractAs voltage measuring devices are widely used in the high voltage power system with a primary‐secondary‐fusion structure, electronic voltage transformers are directly connected to the primary conductor and would face much more serious electromagnetic environments than general secondary equipment. As a result, they would still experience failures even when general protection measures are adopted to suppress overvoltages' amplitudes. To address this issue, an innovative method is proposed after analyses are conducted on the resonance between a transformer and an overvoltage. Within this method, an air‐cored coil is installed in a transformer to artificially shift its natural frequency and to dodge the high‐frequency dominant component of a transient overvoltage, avoiding the aforementioned resonance and suppressing the secondary overvoltage. In addition, simulations and laboratory tests are conducted to prove this method's validity.

A New 3D Frequency-Selective Structure for 5G Communication

Background: In this paper, a new frequency-selective structure (FSS) for 3 to 4 GHz frequency band of fifth generation (5G) is proposed as a result of an analytical mode-matching method. Methods: A new periodic structure with stepped rods is designed using a closed-form equation derived by the analytical mode-matching method. Performance of the structure is simulated by different numerical packages. Results: The analytical and simulation results demonstrate that the designed structure transmits incident waves in 3.4 to 3.9 GHz frequency range with return loss lower than 10 dB and insertion loss of about 0.5 dB. The structure reflects the frequencies out of this range, especially wireless local area network (WLAN) 5 GHz, which is adjacent to this band. Furthermore, the performance of the proposed structure is independent of the TE and TM polarization of the incident wave and relative to the angle of the incident wave up to 60 degrees from perpendicular to the FSS surface, it has minor variations of about 8% in the transmitted frequency bandwidth. In addition, the average value of maximum field enhancement factor (MFEF) as the ratio of maximum field magnitude on the FSS surface to the magnitude of the incident field, used for assessing power handling capability of the structure, is about 4.5. Conclusion: Therefore, these features make the proposed structure suitable for 5G communication and high power systems.

Reduction of CO2 Emissions from Offshore Combined Cycle Diesel Engine-Steam Turbine Power Plant Powered by Alternative Fuels

Abstract Diverse forms of environmental pollution arise with the introduction of materials or energy that exert adverse effects on human health, climate patterns, ecosystems, and beyond. Rigorous emission regulations for gases resulting from fuel combustion are being enforced by the European Union and the International Maritime Organization (IMO), directed at maritime sectors to mitigate emissions of SOx, NOx, and CO2. The IMO envisions the realisation of its 2050 targets through a suite of strategies encompassing deliberate reductions in vessel speed, enhanced ship operations, improved propulsion systems, and a transition towards low and zero-emission fuels such as LNG, methanol, hydrogen, and ammonia. While the majority of vessels currently depend on heavy fuel or low-sulphur fuel oil, novel designs integrating alternative fuels are gaining prominence. Technologies like exhaust gas purification systems, LNG, and methanol are being embraced to achieve minimised emissions. This study introduces the concept of a high-power combined ship system, composed of a primary main engine, a diesel engine, and a steam turbine system, harnessing the energy contained within the flue gases of the main combustion engine. Assumptions, constraints for calculations, and a thermodynamic evaluation of the combined cycle are outlined. Additionally, the study scrutinises the utilisation of alternative fuels for ship propulsion and their potential to curtail exhaust emissions, with a specific focus on reducing CO2 output.