Search

The transparent [Li 0.04 (K 0.5 Na 0.5) 0.96 ]NbO 3 +0.5mol% Er 2 O 3 (KNNLN-Er) lead-free piezoelectric ceramics were prepared by stereolithography technique. The influence of different sintering holding time (4h∼8h) on the micromorphology, relative density, shrinkage, electric properties, and photoluminescence properties were systematically investigated. The KNNLN-Er ceramics show the coexistence of orthorhombic and tetragonal structures. The grain size increases obviously and then decreases slightly with the holding time increasing. The KNNLN-Er ceramics exhibit good piezoelectric performance (piezoelectric constant d 33 ∼97 pC/N, electromechanical couple coefficient k t ∼0.36) and the moderate transparency of 34% when the holding time is 6h during sintering at 1120°C. Besides, the intensity of the photoluminescence emission spectra increases with the holding time increasing. Furthermore, in order to estimate the properties of the KNNLN-Er transparent ceramics, an ultrasonic transducer with a center frequency of 10.5 MHz was fabricated, which can be used for photoacoustic and fluorescence imaging. The results indicate that the KNNLN-Er ceramics have potential for multimode imaging applications. [ABSTRACT FROM AUTHOR]

A voltage drop normally occurs when a power source runs for a load system through long-distance cables. To compensate for such voltage drops, it is necessary to provide remote detecting and controlling of the load-side voltage and boost to the required voltage. In this article, a novel impedance detection method providing more reliable and accurate resistance and inductance measured results for remote cables is presented. Meanwhile, a digital–analog hybrid control strategy based on the impedance detection method is presented to compensate for the voltage drop and delayed response caused by cable intrinsic impedance. Compared with traditional methods, the proposed strategy performs detection and compensation at the source of the cable, and can be integrated into power source devices without imposing extra burden to the load system, which is more attractive and promising in engineering application. Finally, a prototype is built for experimental verification, and a systematic and intuitive comparison is conducted with existing voltage-drop compensation methods. The experimental and comparative results indicate that the problems of voltage drop and delayed response caused by long-distance cables are solved, and the accurate and rapid regulation of the remote voltage is achieved. [ABSTRACT FROM AUTHOR]

This article presents a partial-power postregulated LLC resonant converter. In the proposed topology, the input power is first transferred to the secondary side of the transformer through the LLC-DC transformer converter to achieve galvanic isolation and voltage conversion functions. Then, most of the power is directly transmitted to the load side, and only a small portion of the power is converted to the output side by the partial-power processing converter. Therefore, unlike the two-stage solution, the converter proposed in this article achieves output voltage regulation while minimizing the efficiency loss caused by the two-stage conversion. The operating principle of the proposed converter is analyzed, and the system prototype is constructed. Experimental result validates the correctness of the analysis and proves the feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

• Theoretical analysis of the combined harmonic response of the structure when it is simultaneously excited by low-frequency vibration and ultrasonic guided waves is completed. • De-icing experiments under low-frequency resonance mode, ultrasonic guided waves, and different types of low-frequency excitation modes combined with ultrasonic guided waves are completed. • The application power of low-frequency vibration and ultrasonic guided wave needs to reach a certain level to achieve effective de-icing. • Experimental results show that the low-frequency vibration can significantly enhance the de-icing efficiency of ultrasonic guided waves. This paper presents a novel hybrid de-icing system combining ultrasonic guided waves and low frequency resonance. This new system uses low-frequency vibration-assisted ultrasonic guided waves to remove ice from the leading edge of the blade. Ultrasonic transducers are used to generate ultrasonic guided waves for breaking and detaching ice, and piezoelectric ceramics are used to excite low-frequency resonant modes of the structure to induce additional acceleration and stress. Theoretical analysis and finite element simulation of the combined harmonic response of the structure when it is simultaneously excited by low-frequency vibration and ultrasonic guided waves is completed. Modal analysis is used to determine the mounting location of the piezoelectric ceramics. Transient analysis is calculated to study the effect of low-frequency resonance on ultrasonic guided wave de-icing. De-icing experiments under low-frequency resonance mode, ultrasonic guided waves, and different types of low-frequency excitation modes combined with ultrasonic guided waves are completed. These results show that the application power of low-frequency vibration and ultrasonic guided wave needs to reach a certain level to achieve effective de-icing, and low-frequency resonance vibration is crucial for ultrasonic guided wave de-icing. Compared with ultrasonic guided wave de-icing technology, the combination of low-frequency excitation vibration and ultrasonic guided wave excitation can greatly improve the de-icing efficiency. [ABSTRACT FROM AUTHOR]

This article deals with the negative effects produced by unexpected energy of solar array and methods of suppressing the effects for the sequential switching shunt regulator (S3R). The complex space operation conditions, such as plasma environment and accidental impact are likely to cause abnormal discharge of solar array, leading to unexpected changes in the input energy of an S3R. Effects of unexpected energy on current stress and power loss of power devices, overregulation of the S3R and quality of output voltage are represented and analyzed in this article. A shunt regulator (SR) topology based on the switch current limiting drive is then proposed to suppress current stress and power loss of power devices, thereby alleviating negative effects. Finally, simulation and experimental results are provided to illustrate the negative effects of unexpected energy and validate the proposed SR. [ABSTRACT FROM AUTHOR]

For boost power factor correction (PFC) converters operating in critical conduction mode (CRM), charge compensation strategies are utilized to improve input current distortion. However, since massive calculations are required under complex working conditions, it is difficult to achieve accurate charge compensation with limited real-time computing resources. To solve this issue, this paper proposes an adaptive charge-compensation-based variable on-time (ACVOT) control strategy. The ACVOT controller calculates the required switching on-time by adding a fundamental value and an extended on-time. The fundamental value is adjusted by the loop compensator in each half-line cycle to provide a basic bias. The extended on-time is calculated based on partial charge compensation equation in each switching cycle to reduce the distortion. Compared with conventional digital variable on-time (VOT) control, the proposed strategy improves the input current total harmonics distortion (THD) and reduces the LUT/register resources by 54%/43% in FPGA realization. To verify the effectiveness of the proposed strategy, a 200 W prototype is built using the GaN HEMT transistor, where the THD is reduced to 1.4% at full load. [ABSTRACT FROM AUTHOR]

• The spacing of the resistance wires is theoretically determined by a theoretical thermal model. • The water film formed by heating makes up for the problem that the stress generated by the actuator is insufficient for de-icing. • The experiments of ultrasonic guided waves de-icing, electrothermal de-icing and combined electrothermal-ultrasonic de-icing are explored in freezer with airfoil leading edge model, respectively. • Hybrid de-icing method combining electrothermal and ultrasonic is feasible and has great potential to accelerate ice shedding. A novel hybrid de-icing method combining an electrothermal system and ultrasonic guided waves is proposed for the leading edge structure of wind turbine blades. The adhesion strength between the ice layer and the leading-edge structure is reduced by the electrothermal system. Piezoelectric ultrasonic transducers are used to generate shear stresses to crack and remove ice. The heating resistance wires and transducers are pasted onto the inner surface of the leading-edge structure. The spacing of the resistance wires was calculated by a theoretical thermal model. A temperature recorder was used to measure the temperature changes at different measuring points on the leading-edge surface under electric heating. This study conducted ultrasonic guided waves de-icing, electrothermal de-icing, and combined electrothermal–ultrasonic de-icing experiments in a freezer with an airfoil leading edge model. The results reveal that the combined electrothermal–ultrasonic method is feasible and has great potential for ice shedding acceleration. [ABSTRACT FROM AUTHOR]

In a wireless power transfer system, applying power-relay coils is an effective method to achieve both long distance and high efficiency. However, the wireless power-relay system (WPRS) has many variables, which will perplex the system design. In this article, an evaluation method based on the black-box $Z$ -parameter two-port model is introduced for the WPRS. This method can easily obtain the theoretical optimal efficiency and the corresponding load from black-box measurement instead of acquiring all the parameters of the resonant coils. This feature can be used to compare potential performance of different WPRSs. WPRSs based on printed circuit board coils are built to verify black-box $Z$ -parameter two-port modeling. Experiments are also carried out on WPRS ac resonant tanks and WPRS dc–dc converters. [ABSTRACT FROM AUTHOR]

Linear power supplies (LPSs) are widely used in fields including measurement systems, radiofrequency systems, medical applications, nuclear power plants, and spacecraft electronics. Electrolytic capacitors are used in a variety of devices because of their small size, low cost, and large capacity. During the use of electrolytic capacitor, it is very common for the capacitance (C) to decrease and its equivalent series resistance (ESR) to increase, which are typical indicators of capacitor degradation. Electrolytic capacitors are both the weak link and the core component of the LPSs and play a vital role in determining the LPSs lifetime. Under the power frequency condition, the power frequency transformer plays a role in isolation and voltage reduction in the LPSs. The input and output signals of the LPSs are used for condition monitoring of capacitor, and the existence of transformer increases the difficulty of the online noninvasive technique of LPSs. The online noninvasive technique for condition monitoring of capacitor in LPSs proposed in this article can be solved only by using the input current, the magnetizing current, the input voltage, and the load current. Effect of temperature on C and ESR values is incorporated for accurate determination of the parameters of capacitor. The effectiveness of the proposed method is verified through simulations and experiments, and the data obtained are consistent with the results measured using an LCR meter. [ABSTRACT FROM AUTHOR]

This article presents an integrated magnetic buck–boost converter (IMBBC) with a positive output voltage. The input inductor, two power transfer inductors, and an auxiliary inductor in the ripple cancellation network of this converter are integrated in one magnetic core, and an additional capacitor is included for output current ripple cancellation. The IMBBC inherently operates in the continuous conduction mode and exhibits a nonpulsating input current and a very low ripple output current, thereby not only decreasing the current stress on both the input and output capacitors but also reducing the output voltage ripple. Because the input of the IMBBC is connected to the output during the switch-on period (similar to the operation of buck converters), the proposed IMBBC overcomes the right-half-plane zero problem in the buck or boost mode, thus achieving a higher dynamic performance. The use of the magnetic integration technique not only helped realize the aforementioned performance, but can also help reduce the weight and volume of dc–dc converters. Finally, the feasibility and effectiveness of the proposed topology and design approaches are experimentally verified. [ABSTRACT FROM AUTHOR]

The loss of metallic area is the most important factor affecting the quality of wire ropes. Therefore, it is very important to detect the loss of metallic area values of wire rope defects quickly and accurately. At present, the main flux detection approach is one of the most effective methods, and the detection signal is related directly to the metal cross-sectional area of the wire rope. However, when the defect width is less than a specific value, the existence of the leakage magnetic field means that the amount of the magnetic flux change is not only related to the loss of metallic area of the defect but also has a complex nonlinear relationship with the defect width. The resulting calculation is highly complex and means that the loss of metallic area cannot be determined quickly and quantitatively. This article presents an in-depth study of the theoretical basis of magnetic flux detection, analyzes the problems of the main magnetic flux detection method and their causes, and proposes a method to improve main magnetic flux detection using the axial magnetic flux density. Simulation analysis and experimental results show that the method presented in this article can be used to calculate the loss of metallic area values of defects quickly and accurately without the need for complex calculation processes. [ABSTRACT FROM AUTHOR]

Fine wire rope is a type of skeleton material that is used widely in elevator steel belts, conveyor belts, and synchronous belts. When the tension of a fine wire rope changes abnormally, its service life and the safe operation of the system it belongs to will be seriously affected. Therefore, it is particularly important to monitor the tension and detect the defects of fine wire rope. However, traditional nondestructive testing technology only detects the defects or monitors the tension of the tested structure. In this article, longitudinal guided wave sensors are used to measure the tension changes and defects of fine wire rope. When the tension of a fine wire rope changes, the natural frequencies of the fine wire rope change, so the change of natural frequencies of fine wire rope can be used to represent the change of tension. White noise is used to measure the natural frequencies of fine wire rope under varying tension using a low-power circuit to determine the influence of the change of fine wire rope tension on the natural frequencies. Meanwhile, the excitation frequency needed to produce the maximum amplitude of the guided wave is determined according to the natural frequencies detection results to improve the signal-to-noise ratio of the guided wave signal. Additionally, defect detection is realized by analyzing the wave velocity and time of flight of the guided wave signal. [ABSTRACT FROM AUTHOR]

The magnetostrictive torsional wave sensors are focused on magnetostrictive patch transducer. These transducers use a material with a high magnetostrictive coefficient on the pipe surface to increase the excitation efficiency for detection. However, this approach loses the noncontact characteristic of the magnetostrictive guided waves. To enable noncontact detection in small-diameter pipes using torsional waves, a magnetostrictive torsional wave sensor with a tile-shaped magnet is designed in this article. By optimizing the structure of the static magnetic field, the circumferential magnetic field of the pipe is enhanced. The amplitude and the signal-to-noise ratio of the guided waves are also improved. The tile-shaped magnet with shoving magnetic structure is used to realize a uniform circumferential magnetic field. A solenoid coil is used to provide the axial dynamic magnetic field to generate the torsional waves that are used to detect the pipes. In this article, the principles of torsional wave sensors are studied first. The static magnetic field results for different structures are then analyzed via simulations. Finally, experiments show that the magnetostrictive torsional wave sensors with the tile-shaped magnets can realize the excitation and detection of torsional waves in pipes, which can be used to detect the locations and sizes of defects in these pipes. [ABSTRACT FROM AUTHOR]

DC/DC converters are connected in series at the input so that low power devices can be used in high-voltage conversion applications. This article proposes a building block method for constructing an input-series-connected dc/dc converter, which combines voltage sharing modules (VSM) with voltage source modules or current source modules. A VSM consists of two MOSFETs, an inductor, and an open-loop driver. The input voltage sharing between the individual modules is achieved by connecting one VSM to the inputs of the two power modules. The proposed method makes the standardized functional modules can be combined together like building blocks, which greatly simplifies the converter complexity and shortens the system development cycle without sacrificing the high dynamic response performance and excellent sharing effect. This article first analyzes the working principle of the converter. Second, the stability constraints of the proposed method are revealed, and the effects of various parameters on the performance are discussed. Furthermore, the theoretical analysis results are verified by simulation. Finally, taking the voltage source module as an example, a prototype is built to test its steady-state and dynamic performance. [ABSTRACT FROM AUTHOR]

Sequential switching shunt regulators (S3Rs) are widely used in the satellites owing to their simple structure and high reliability. The high-power communication satellites require a power supply with a high bus voltage and large solar array section current. However, a large solar array capacitance and new time-division multiple access operations complicate the design of a lightweight and cost-effective power supply by increasing the difficulty in dissipation and thermal control. On the basis of passive current limitation, in this article, we propose a novel shunt regulator with only one output diode and a protection strategy to achieve high efficiency, appropriate shunt current limitation, and low turn-off delay. In addition, to reduce the dissipation of an S3R cell when feeding the solar array current to the main bus and to satisfy the single point failure-free requirement, an innovative self-retriggerable diode short-circuit fault detector circuit is proposed, which includes a protection switch for a safe thermal or electrical operation. Finally, simulation and experimental results are presented to validate the proposed shunt regulator and the corresponding control method or protection strategy. [ABSTRACT FROM AUTHOR]

A new bidirectional LCLL-type resonant dc-dc converter (LCLL-BDC) is proposed in this article, which features a wide output voltage range for both ports, thus achieving zero-voltage switching (ZVS) at the input side and zero-current switching (ZCS) at the output side. The snubberless converter is similar to the type-11 LLC-type resonant converter, with the exception of an additional inductor. The auxiliary inductor allows for the converter to achieve a wide voltage range power transfer, thus addressing the inability of the LLC-type converter to be boosted in the reverse mode. The equivalent model and the steady-state operation are presented in this article. Moreover, the design methodology for the resonant network was derived for the LCLL-BDC. A 1-kW prototype, which interfaces two batteries of different energy systems, was developed to verify the validity and applicability of the proposed converter. The input and output voltage range was found to be 80–120 V, and the highest efficiencies for the bidirectional operational modes exceeded 96%. [ABSTRACT FROM AUTHOR]

Wire rope is a chain structure, and the strength of the weakest link is the strength of the entire wire rope. The axial resolution of loss of metallic cross-sectional area (LMA) detection using the induction coil is related to the length of the detection probe, which is usually greater than or equal to the length of the probe. Improving the axial resolution is an important technical indicator of the LMA. In this article, through theoretical analysis based on the principle of magnetic aggregation and 3-D transient magnetic field simulation, a particular kind of magnetic aggregation structure used for winding coil is proposed and optimized. Simulation and experimental results show that for wire rope LMA detection adding the proposed magnetic aggregation structure, the defect signals’ signal-to-noise ratio (SNR) is improved and the axial resolution of the LMA is increased to 20 mm. At the same time, the cross-sectional area loss can be quantitatively evaluated by the magnetic flux peak-to-peak value. The difference between the maximum and minimum values of the derivative of the magnetic flux signal can be used to evaluate the defect length. [ABSTRACT FROM AUTHOR]

Magnetostrictive guided waves are widely used in nondestructive testing and structural health monitoring of pipes to ensure their integrity. These guided waves are mechanical waves, and if the natural frequencies of the pipe are used as excitation frequencies, the mechanical vibration amplitude can be enhanced, which will then improve the amplitude of the guided waves. Comparison of the various methods to determine the natural frequencies of pipes shows that the white noise signals remain relatively smooth in both time and frequency domains. White noise has a wide bandwidth and uniform energy distribution. It does not require high energy within a short time period, so it is easy to generate. In this article, white noise is used to determine the natural frequencies of pipes. Comparison of the white noise spectra produced by analog and digital circuits shows that the energy spectrum of white noise produced by the analog circuit is high and uniform, so the analog circuit is used as the white noise source and this noise is loaded onto a magnetostrictive sensor. The detected signal spectrum is then analyzed and the frequencies with high power density spectra are determined to be the natural frequencies. The natural frequencies of the pipeline detected using white noise are compared with the results of modal analysis. Simulation results and experimental results demonstrate that the use of white noise allows the natural frequencies of pipes to be determined quickly and accurately. These natural frequencies can be used in magnetostrictive guided-wave nondestructive testing. [ABSTRACT FROM AUTHOR]

Since both the input-series–output-series system and the input-series–output-parallel system have a circuit configuration in which the input sides are in series, it is very suitable for applications with high input voltages. This article proposes a simple active voltage sharing module (AVSM) that allows two closed-loop dc/dc converters to be combined directly into an input-series system as power devices to meet various voltage requirements. An AVSM, consisting of one coupled inductor and two metal–oxide–semiconductor field-effect transistors, is connected on the input side of the two submodules. By adopting a control method with fixed frequency and duty cycle, accurate input voltage sharing can be achieved, enabling voltage isolation sampling of the submodules and the voltage sharing regulators of the system to be eliminated, thus greatly simplifying the design process of the input-series system. This article introduces the AVSM working principle and discusses the stability of the proposed input-series system. It then describes a simulation performed to verify the theoretical analysis results and addresses the influences of the AVSM parameters on the system performance. Finally, the use of a prototype to test the steady-state and dynamic performances of the proposed scheme is discussed. [ABSTRACT FROM AUTHOR]

The solar array drive assembly (SADA) slip ring is a critical link that provides electrical power and electric signal transmission between solar arrays and satellite power systems, which is prone to arc faults in the space environment. If these arc faults cannot be detected and eliminated quickly enough, they will seriously threaten the safety of the satellite power system and the satellite. In this paper, a fast arc detection method based on fractal dimension is proposed that adapts to different operating modes of power systems. The detection method collects the current differential signal data flowing through the SADA slip ring, and, according to the trend of the fractal dimension change in this signal, the fault identification algorithm is designed for different operating modes of the power system to achieve real-time and rapid identification of arc faults. Finally, the effectiveness of the proposed method is demonstrated using test data under several different fault conditions. [ABSTRACT FROM AUTHOR]

It is difficult for a single converter to handle the high voltages involved in dc–dc conversion with a high-voltage input bus. Input-series–output-parallel (ISOP) technology can be used to solve this problem. In this paper, an input voltage sharing control scheme based on peak current (IVSPC) control to guarantee power balance between the modules of the ISOP system is studied. Owing to the peak current control, the output voltage of the system has a good ability to suppress input bus perturbations, and it exhibits good dynamic characteristics even when the input voltage changes significantly with a high slope. The IVSPC control method has two kinds of loops: a common output voltage regulation (OVR) loop and individual input voltage sharing (IVS) loops. The OVR loop provides the same current reference component for all modules, whereas the IVS loops provide different components. The peak current reference signal for each module is the sum of the reference components from the OVR and IVS loops. The performance of the IVSPC control scheme is verified using an ISOP-connected prototype consisting of two flyback converters. [ABSTRACT FROM AUTHOR]

The magnetic flux leakage (MFL) technology is one of the most widely used electromagnetic nondestructive testing techniques. To magnetize the detected object near to saturated flux density, the excitation mechanism is heavy and large in the MFL technology. A simple and portable magnetic detector device for shallow defect of ferromagnetic objects based on the magnetic probe structure is designed in this paper. The proposed magnetic detector is very light, cheap, and easy to design and manufacture. The magnetic detector can make the qualitative and quantitative evaluation for shallow defect of ferromagnetic objects. In steel ribbon test, the maximum relative error of quantitative test results is less than 5% by the proposed magnetic detector device. In this paper, the application of the magnetic detection method for wire rope is proposed. By the proposed method, qualitative and positional detection of the wire rope defects can be easily achieved. [ABSTRACT FROM AUTHOR]

This paper presents an interleaved current-driven phase-shift full-bridge converter for plug-in hybrid electric vehicle (PHEV) applications. In the proposed converter, soft switching of the active switches can be realized for a wide range of operating conditions by using a simple auxiliary circuit. Due to the current-driven nature of secondary rectifiers, the proposed converter is able to eliminate the voltage spikes across the output diodes and provides smooth commutations for the secondary rectifiers. Thus, diodes with lower breakdown voltage rate and lower forward voltage drop can be used to further improve the efficiency. All the passive magnetic components are integrated into the main transformer. The numbers of the output diodes are minimized because of the voltage doubler rectifier configuration. The input filtering requirements, as well as the current stresses of the switch devices, are also significantly reduced owing to the interleaving approach. Therefore, the proposed converter would be a good candidate for PHEV applications. The steady-state operation and relevant analysis results of the proposed converter are presented. Experimental results obtained from a 2-kW prototype with a peak efficiency of 97.4% validate feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

Most existing high-power solar array simulators are suitable for simulating solar array energy sources in terrestrial applications. However, they are not sufficiently fast for spacecraft power-system testing using terrestrial testing applications. This paper proposes a UI-RI hybrid lookup table method with high linearity and high-speed convergence performance, which outperforms the traditional single UI lookup table method by employing a field-programmable gate array digital I–V outer loop. The proposed method overcomes the difficulty in guaranteeing stable output characteristics of the current output-type space solar array simulator (SSAS) because of the nonlinear I–V curves and slow convergence speed to the target operating point of the latter. The new lookup method is applied to a 2.4-kW hardware power platform of SSAS, and the SSAS can quickly respond to a load step between the short-circuit and open-circuit (OC) states, which is the harshest working condition, using the UI-RI hybrid lookup table method with a shunt switching frequency of 2 kHz. It can also quickly respond to a load step between the OC and rated-load states using a series-switching frequency of 10 kHz. The experimental data-point distribution trajectory of the switching process shows a greater tendency to converge to the designed I–V curve compared with the single UI lookup table method. [ABSTRACT FROM AUTHOR]

Space solar array simulators (SSASs), which are used for testing space power systems, generally utilize linear power topologies owing to their fast dynamic performance and satisfactory simulation accuracy. However, to output a medium power level from a linear-power-topology SSAS, multiple parallel linear voltage-controlled current sources are required for addressing the redundant power dissipation, thereby limiting the overall mechanical structure and volume optimization; in addition, the presence of multiple parallel sources results in a complex circuit structure with poor reliability. In this context, in this study, we propose a novel three-port linear power composite transistor as a linear power dissipation device, which is composed of multiple cascaded SiC-JFETs to improve on the above-mentioned shortcomings. The proposed 510-W optimized SSAS requires only eight parallel linear current-source paths to form a linear power stage and uses a high-speed field-programmable gate array (FPGA) digital controller to quickly react to a load step between short circuit and open circuit (the harshest working condition for a solar array simulator) at a 1-kHz stepping frequency. Further, the device can react to a load step between short circuit and the nominal working point at 10-kHz stepping frequency, thus, offering a better dynamic performance over other similar devices. [ABSTRACT FROM PUBLISHER]

The solar arrays of space stations, communication satellites and lunar/Mars rovers, are occasionally partially shaded by the vehicles themselves. The shading can cause the output power of the solar array to significantly decrease even when the shaded area is quite small. This effect is stronger in direct energy transfer power systems, which are widely used in space applications because of their simplicity and reliability. In this study, we develop a model of solar arrays to evaluate their power performance under partially shaded conditions. Our analysis considers the various impacts of irradiation, partial shading, and layout of the solar array. Two objective functions that can be used to assess the overall power performance of solar arrays under various conditions are proposed. A multi-objective genetic algorithm with a small population is also proposed to optimize the layout of the solar array. The experimental results on a scaled-down equivalent model verify the effectiveness of the proposed method, and demonstrate that the magnitude of the power reduction and variation under partially shaded conditions decreases without increasing the system complexity. [ABSTRACT FROM AUTHOR]

Cascaded instability of the cascaded power supply system has restricted the development of the dc distributed power system for a long time. In this paper, by analyzing the cascaded instability essential cause of the dc–dc cascaded system, a control method based on output voltage ac signal component sampling feedback is presented to improve the cascaded stability. Meanwhile, the small signal analysis interprets the physical meaning of the cascaded instability, and then analyzed the control method from the frequency characteristics and control loop point of view. Finally, based on the above-mentioned analysis and discussion, a cascaded dc–dc system comprising two Buck converters has been built and tested. The simulation and experimental results verify the validity and reliability of the proposed ac signal sampling component control method on cascaded stability improvement. [ABSTRACT FROM AUTHOR]

With the power of high-orbit satellites now reaching dozens of kilowatts, solar energy sources play an important role in nonterrestrial applications. However, most of the existing high-power solar array simulators (SASs) are designed for simulating energy sources in terrestrial applications, and may not have suitable dynamic performance for nonterrestrial applications. This paper proposes a design for a high-power high-dynamic-performance space solar array simulator (SSAS) system, which combines a linear power stage unit and a multilevel bus tracking converter unit, in order to achieve a fast step-switching capability and high-power-handling capacity. In this paper, we consider the SSAS power system as two separate parts: the I–V power curve simulator that uses a linear power stage with 20 linear voltage-controlled current paths in parallel; and the multilevel bus tracking converter unit that provides the variable voltage levels tracking the SSAS output voltage, in order to decrease the power dissipation in the linear power stage. This paper establishes a mathematical model for the multilevel converter under this particular system architecture, and presents the application qualification conditions and system design principles. The proposed 2.4-kW SSAS can react quickly to a load step between the short-circuit and open-circuit states, which are the most challenging working conditions, at a stepping frequency of 3 kHz; this is a superior dynamic performance compared to other similar devices. The experimental results of testing the spacecraft power supply with a shunt regulator architecture demonstrating better performance, when compared to the results from four SAS modular products in parallel. [ABSTRACT FROM AUTHOR]

The power conditioning unit system is a critical part in a spacecraft and is responsible for converting the solar panel energy into a stable bus voltage. This system requires a high dynamic characteristic solar array simulator (SAS) for testing purposes. Space solar array simulators (SSASs) used for testing space power systems generally use a linear power topology because of its fast dynamic performance and good simulation accuracy. However, commercially available SASs are not sufficiently fast for simulating the actual solar array panel output and, therefore are unreliable for terrestrial testing. In this paper, a highly dynamic SSAS is developed with multipath SiC MOSFET linear voltage-controlled current source paralleling for power regulation. The proposed 510 W SSAS, consisting of 20 linear current paths paralleling the power stage and a high-speed FPGA digital controller, can quickly react to a load step between the nominal and short circuit at 50-kHz stepping frequency. It can also react to a step change from a short circuit to an open circuit perfectly at a 1-kHz stepping frequency offering a superior dynamic performance compared to other similar devices. [ABSTRACT FROM AUTHOR]

Inductive coil is used as the nondestructive testing sensor of a wire rope or a pipe, because of its low cost and high durability. However, the winding structure is complex and difficult to design during the field test. Hundreds or even thousands of turns are needed to improve the signal to noise ratio (SNR) and the data processing is cumbersome. In this paper, based on the theoretical analysis and 3D transient magnetic field simulation, a kind of iron core is presented as coil winding skeleton for the wire rope nondestructive testing. Additional iron core plays a role of magnetism concentration, where the magnetic flux leakage (MFL) path is changed and the MFL of the defect is converged to the core. Therefore, the SNR of the coil which is wound on the iron core is improved, and the coil winding skeleton is simplified with the iron core structure optimization. Meanwhile, the influence of the coil cross-section area on the test result analysis is eliminated, and the influence of the lift-off distance between coil and wire rope on the detection result is also reduced. Finally, it is proved by experiment that the SNR of coil with the iron core proposed in this paper is increased almost six times, which makes it easier for defect analysis. [ABSTRACT FROM AUTHOR]

The diameter of fine steel wire rope (FSWR) is generally a few millimeters. Its magnetic flux leakage (MFL) signal is weak, and the number of magnetic sensors installed for defect detection is limited because of the small diameter. In FSWR production workshops, different kinds of machinery work together, deteriorating the power quality and making the spatial electromagnetic environment complex; the weak MFL is thus interfered with further. It is difficult to carry out online nondestructive testing (NDT) of FSWR in the process of manufacturing. In this paper we present a novel MFL method for FSWR NDT in a strong electromagnetic interference environment. We use a three-dimensional finite element method (FEM) to analyze the MFL signals. A simplified magnetic circuit is presented to excite the FSWR; the circuit comprises two half-sized radial magnetizing ring NdFeB magnets, and because there is no need for a magnetic yoke, the device is simple and light. A single Hall sensor is used to measure the flux leakage field. A stable performance power system is designed for the NDT power supply, which is not only resistant to voltage sags, but also has very low output noise. To enhance the signal-to-noise ratio (SNR) of the MFL defects signal, a signal conditioning and processing circuit are designed to enhance the detectability of signals in MFL data. The novel and small FSWR NDT system realizes on-line testing in an environment of strong electromagnetic interference, and for the experiment with a 1.5-mm-diameter wire rope twisted by 19 wires, the minimum damage of a pit on half of a wire can be identified. [ABSTRACT FROM AUTHOR]

This paper proposes a novel electrical power supply system architecture (power conditioning and processing unit, PCPU) for high-power all-electric propulsion spacecraft platform with high-voltage power bus (HVBUS) powering thrusters and regulated power bus (VBUS) powering onboard payloads, respectively. The design principle of function modules in PCPU has been analyzed. Besides, the test on electrical characteristic of VBUS and HVBUS in prototyped system proves the stable and reliable work of buses in PCPU. [ABSTRACT FROM AUTHOR]

DC/DC converters connected in series or parallel allow low power devices to be used in high power conversions. The input series output series (ISOS) connection is suitable for situations where both the input and output sides are high voltage fields. To ensure that each module shares voltage with the other, this paper proposes an active output voltage sharing (AOVS) control scheme. The scheme introduces sharing control in the output side so that the isolation is not needed between the input and output sides in the control loop. The AOVS control scheme, consisting of a common output voltage loop and individual output voltage sharing loop, has a master–slave structure. To improve the reliability and realize a hot-plug, this paper also provides an automatic master–slave form of the AVOS control scheme. A simulation of the frequency and time domains is used to verify the accuracy of the small signal model, and an ISOS-connected prototype consisting of three forward converters is made to test the steady and dynamic characteristics of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents a coupling method of power supplies to improve power density, efficiency, and dynamic response by taking the case of heater supply, ignitor supply, and keeper supply for hollow cathode of an all electric propulsion (AEP) Hall thruster. The working principle and timing characteristic of the coupled supply, as well as the three-loop control, current sampling and chopping switch control are also illustrated. With the proposed coupling method, the power density is improved since three supplies are coupled into one supply. Additionally, the test on the coupled supply prototype with 200 W maximum output power shows that the efficiency of the coupled supply could reach up to 89.7%, increasing by 3.9%–14.2% as being compared with that of traditional three supplies with heater current between 4 and 10 A, and the joint test of the coupled supply with an AEP hall thruster proves the achievement of fast dynamic response and the ability to extend useful life of hollow cathode. Hence, the coupling method proposed in this paper could achieve the power supply system with high power density, efficiency, and fast dynamic response. [ABSTRACT FROM AUTHOR]

This paper proposes an output current-differential (OCD) control scheme that has a master–slave structure. It can be applied in dc/dc converters to connect the input in series and the output in parallel. All of the control and sample circuits in the proposed control scheme are on the output side, which means that there is no further isolation in the control loops. The proposed control scheme, consisting of one output voltage regulator loop and individual load-current-sharing loops, will enable low-voltage converters to be used for high-voltage specifications. The master module regulates the output voltage through a common output voltage loop and provides current references to slave modules. The individual current-sharing loops residing in the slave modules regulate the current in each module equally. According to the power balance, input-voltage sharing is realized simultaneously. To prevent a situation in which system failure is caused by master module failure, a fault-tolerant automatic master–slave output current-differential (FOCD) control scheme is developed. The performance of the OCD and FOCD control schemes is validated on a 450-W prototype input-series–output-parallel system comprising three forward converters. [ABSTRACT FROM AUTHOR]

Interleaving is a technique that is commonly used due to its inherent reduction of current ripple and filter capacitance size. However, optimal interleaving is only achieved when the switching cells are identical. Variations of the filter inductance, which are caused by the manufacturing process or magnetic material properties, may lead to the total current ripple of all phases significantly larger than that of the ideal case in steady state, and slow down the energy transfer speed during the transient response. Consequently, in order to meet the voltage ripple and dynamic response requirements of multiphase converters, the calculation of the output capacitor under inductance mismatches has to be reconsidered, which has been rarely mentioned previously. This paper proposes a method to estimate the effect of inductance mismatches on output capacitance selection from two aspects including steady state and transient state. The proposed methodology enables mathematical expressions that allow us to calculate the maximum value of the capacitor considering nonidealities. Monte Carlo simulation is also used during the analysis by varying all of the inductors’ values with respect to tolerance and distribution type to identify the worst case values in real applications, according to this approach, the principle of when the worst condition happens is summarized. Simulated and experimental results of a four-phase buck converter are presented in this study. Good agreement between the estimates and the measured values is demonstrated. [ABSTRACT FROM AUTHOR]

This paper presents a novel two-phase interleaved inverse-coupled inductor boost (IICIB) without right half-plane (RHP) zeros. The input and output inductors in the IICIB have been all integrated into one magnetic core, and there is a 180° phase shift between the driving signals. Thanks to the coupling relationship between the four inductors in the new proposed converter, a smaller core size and higher power density can be achieved because the core size is normally determined by the energy storage requirement. Meanwhile, with the RHP zeros eliminate, a higher bandwidth with wide range of control over the applied input or output voltage can be achieved. The new converter not only has the aforementioned advantages, but also shows great potential for current ripple reduction as a result of the interleaved structure. Finally, experimental verification is provided to illustrate the effectiveness of the theoretical findings and design approaches. [ABSTRACT FROM AUTHOR]

Take the case of parallel modules in battery discharging regulator of power conditioning unit, which is based on Weinberg topology, a conductance compensator used in average current mode control is proposed in this paper, which could ensure constant loop bandwidth and output impedance when the number of operating parallel modules changes. The design principle of conductance compensator is shown as that the total conductance coefficient keeps constant when the number of operating parallel modules changes. Besides, a circuit of the conductance compensator, and the timing between the regulation of conductance compensator and ON/OFF of parallel modules, as well as the frequency-domain constraints of each function part in outer voltage control loop, are also illustrated. Additionally, measurements of the loop characteristic and output impedance of regulated power bus with different numbers of operating parallel modules, as well as the voltage ripple and current waveforms at the ON/OFF moment of parallel modules (four parallel modules in total), have been carried out, validating the design purpose of the proposed conductance compensator. [ABSTRACT FROM AUTHOR]

This paper proposes a novel phase-shift dual full-bridge converter with shared leading leg and dual outputs in series. Full soft-switching range of the active switches can be achieved based on the parallel full-bridge configuration of the converter, and the dual outputs of the proposed converter are connected in series. The output voltage can be regulated by primary-side phase-shift and secondary-side phase–shift dual-mode control scheme, and a wide conversion range can be achieved. Furthermore, the circulating current in the primary-side full-bridge circuits can be extinguished. Therefore, the proposed converter would be useful for constant peak power and wide output voltage range applications. Steady-state operation and relevant analysis results of the proposed converter are presented and verified on a 1.5-kW hardware prototype. The experimental results show that the proposed converter can achieve a peak efficiency of 95.3%. [ABSTRACT FROM PUBLISHER]

Envelope elimination and restoration technique and envelope tracking technique are proposed to enhance efficiency of radio frequency power amplifier (RFPA), and both of them take envelope amplifier (EA) as a high slew-rate variable voltage source. Serial linear-assisted switching converter, one of the solutions of EA, has benefits in high tracking bandwidth, high tracking accuracy, and relatively low switching losses. Among those many types of linear-assisted switching converter, the design of a linear regulator is rarely mentioned. This paper proposes a new design of linear regulator to supply a higher voltage and maintain high tracking bandwidth by dividing a linear regulator into four different parts. Beyond that, an input filter is recommended to increase the power supply rejection ratio (PSRR) of a linear regulator in high frequency, which is able to reduce the glitch caused by multilevel voltage power supply. An EA prototype is composed of the proposed linear regulator, the PSRR improvement filter, and the multilevel voltage power supply. To align signals, circular convolution is suggested as a modified algorithm. Experiments show that this prototype has a maximum output of 40 V, a tracking bandwidth of about 2 MHz for a full-range sinusoidal signal, and a tracking ability for OFDM envelope signal with a subcarrier up to 5 MHz. [ABSTRACT FROM AUTHOR]

This paper presents a new application of power and voltage balance control schemes for the cascaded H-bridge multilevel inverter (CHMI)-based solid-state transformer (SST) topology. To reduce load on the controller and simplify modulation algorithm, a master–slave control (MSC) strategy is designed for the dual active bridge (DAB) stage. The master controller executes all control and modulation calculations, and the slave controllers manage only device switching and protection. Due to the inherent power and dc-link voltage unbalance in cascaded H-bridge-based SST, this paper presents a compensation strategy based on three-phase dq decoupled current controller. An optimum zero-sequence component is injected in the modulation scheme so that the three-phase grid currents are balanced. Furthermore, to tightly regulate the output voltage of all the DAB modules to target value, a dynamic reference voltage method is also implemented. With this proposed control method, the three-phase grid currents and dc-link voltage in each module can be simultaneously balanced. Finally, simulation and experimental results are presented to validate the performance of the controller and its application to microgrid SST. [ABSTRACT FROM PUBLISHER]

This paper presents a novel integrated magnetic three-port converter (IMTPC) with high power density and all three ports’ current ripple cancellation. The proposed IMTPC can interface one PV port, one bidirectional battery port, and one load port of the PV-battery dc power system. Only two high power magnetic devices are needed in an IMTPC for realizing power conversion, ripple cancellation, and switch driver simultaneously. Three extra capacitors were added to achieve three ports’ current ripple cancellation. Therefore, the port of the IMTPC will always in continuous-conduction mode with “zero current ripple,” thus, size of passive filter can be reduced and accuracy of maximum power point tracking can be improved. Meanwhile, simple driving of the high-side switch can be realized by integrated magnetic winding, which is responsible for MOSFET driver's voltage level shift. The using of the integrated magnetic technique not only performs aforementioned advantages but also shows great potential for reducing the weight and volume of the dc–dc converter. Finally, experimental verifications are given to illustrate the feasibility and effectiveness of the proposed topology and control method. [ABSTRACT FROM PUBLISHER]

In order to interface one photovoltaic (PV) port, one bidirectional battery port, and one load port of a PV-battery dc power system, a novel nonisolated three-port dc/dc converter named boost bidirectional buck converter (B3C) and its control method based on three-domain control are proposed in this paper. The power flow and operating principles of the proposed B3C are analyzed in detail, and then, the dc voltage relation between three ports is deduced. The proposed converter features high integration and single-stage power conversion from both PV and battery ports to the load port, thus leading to high efficiency. The current of all three ports is continuous; hence, the electromagnetic noise can be reduced. Furthermore, the control and modulation method for B3C has been proposed for realizing maximum power point tracking (MPPT), battery management, and bus voltage regulation simultaneously. The operation can be transited between conductance mode and MPPT mode automatically according to the load power. Finally, experimental verifications are given to illustrate the feasibility and effectiveness of the proposed topology and control method. [ABSTRACT FROM PUBLISHER]

A photovoltaic (PV)-based stand-alone power system is usually used to manage the energy supplied from several power sources such as PV solar arrays and battery and deliver a continuous power to the users in an appropriate form. Traditionally, three different dc/dc converters would have been used. To reduce the cost and improve the power density of the power system, an integrated solution of PV isolated dc/dc three-port converter (TPC) is proposed in this paper. Zero current switching can be achieved for all main diodes and MOSFETs to improve the efficiency, and a continuous input current of solar array is maintained by adding a magnetic switch derived from a fourth winding of the half-bridge transformer. Based on the energy-balancing part formed by boost, the control methods for the single module to realize maximum power point tracking (MPPT), battery charge control, and main bus regulation are proposed. The power system control method for multimodules in parallel is also derived, and the operation of the TPC power system can be transited between conductance mode and MPPT mode automatically. Finally, the experimental results verify that the proposed TPC, together with the proposed control method, meets the requirements of a high-power-density stand-alone PV-battery power system. [ABSTRACT FROM PUBLISHER]

Simultaneous switching noise (SSN) is verified as a serious impact on the quality of power distribution and accuracy of the data acquisition system in the mixed signal circuits by modeling and simulating the single-stage output buffer at the driver side. To reduce SSN, a board-level slit-surface disturbance lattice electromagnetic bandgap structure is proposed. The corresponding 1-D equivalent transmission line model is established and lower and upper bound cutoff frequencies of the bandgap are derived. Suitable test boards are fabricated and measured to demonstrate the accuracy of the design concept. The measured SSN reduced to 65% and the signal jitter is decreased by 75% comparing with the solid power/ground plane, which proves that the isolation between the analog and the digital signals can be enhanced to improve the quality of power distribution, and provides a new method to improve precision for data acquisition and transmission in power monitoring system. The results show that the simulated, modeled, and measured results are consistent. [ABSTRACT FROM AUTHOR]

As a rapid, noncontact, and nondestructive technology, magnetostrictive guided waves have been widely used for the quality inspection of pipes and stay cables. Traditionally, a single-frequency signal with a high amplitude and a long pulse duration is used to increase the excitation energy and detection distance. However, the longer the pulse duration of a single-frequency signal is, the lower the resolution of adjacent defects and the accuracy of defect location will be. A novel method of addressing this problem is proposed in this paper. An encoded multifrequency excitation signal, whose frequency range is selected from a calculated dispersion curve, is used to excite the guided wave. After passing through the signal-conditioning board, the detected defect signals are sampled, averaged, and then filtered using a matched filter. In this manner, the pulse width of echoes can be greatly compressed. Our experimental results demonstrate that our proposed method can improve the resolution of adjacent defects and the accuracy of defect location in the propagation direction of the magnetostrictive guided wave. [ABSTRACT FROM AUTHOR]

This paper presents a boost converter with a proposed tapped inductor ripple cancellation network. Based on the conventional boost converter (CBC), a small capacitor and a small inductor are added as the ripple cancellation network (RCN) in the proposed converter. Meanwhile, the tapped inductor can be easily realized by adding an extra tap in the main inductor of the CBC. Since the capacitor and inductor in the RCN do not need to handle the main power as the conventional LC input filter, the size and weight of the proposed converter are relatively small comparing the CBC with the LC input filter. The small signal and dynamic characteristics analyses show that the proposed converter has the same static and dynamic responses as the CBC, and the input current ripple cancellation can be achieved in all power ranges without significantly increasing the losses. Finally, three 36–50-V, 500-W prototypes operating at 100 kHz are implemented to verify the expected performance. The simulation and experimental results show that the proposed converters can achieve input current ripple cancellation with efficiency higher than 97.4% in all power ranges. [ABSTRACT FROM PUBLISHER]

A 3-D model of multichip module (MCM) is built with ANSYS and the temperature field distribution is studied. A regression equation describing the relationship of structure parameters and material properties with the maximum chip junction temperature of MCM is made, which integrates the response surface methodology and ANSYS. Quantitative analysis of the effect of four design parameters on the maximum chip junction temperature of MCM is studied. The four design parameters are the thickness of the substrate, thermal conductivity of the substrate, thermal conductivity of the thermal grease, and convection heat transfer coefficient, respectively. The accuracy and validity of the regression equation are validated by simulation with ANSYS. In addition, the maximum error between the calculation value of the regression equation and the simulation value with ANSYS is 0.541^\circC. With the regression equation, the thermal optimization design results of the four parameters are Ktg=5~W/m~^{\circ}C, \delta=2.5~mm, Ks=290~W/m~^{\circ}C, and h=55~W/m^2~^\circC, which lead to the maximum chip junction temperature Tjmax=89.172^{\circ}C as the minimum value. [ABSTRACT FROM AUTHOR]

This paper presents an interleaved boost converter (IBC) with ripple cancellation network (RCN). Based on the conventional IBC, two capacitors, two coupled inductors, and two inductors are added as RCN in the proposed converter. Therefore, the proposed converter shares the same advantages of the conventional IBC and achieves input current ripple cancellation without significantly increasing the current stress and loss of the converter. Finally, a 36-V input voltage, 50-V output voltage, and 1-kW output power prototype circuit operating at 100 kHz is implemented in the laboratory to verify the expected performance. The proposed converter can achieve input current ripple cancellation in all power range with the efficiency higher than 96%. The simulation and experimental results show that the proposed IBC with RCN has great potential to be applied in high-power, high-efficiency dc/dc conversion. [ABSTRACT FROM AUTHOR]

Magnetic flux leakage (MFL) techniques are used extensively for non-intrusively detecting and characterizing wire rope defects. Traditionally, MFL signals are captured with induction coil sensors. However, the output of coil sensors is related to the wire rope speed, and they can only provide the axial distribution along the wire rope. Hall sensors array are designed due to the limitation of coil sensors. In this paper, a Hall sensors array was designed to capture the MFL signals both axially and circumferentially. 30-channel data from Hall sensors are processed to compose a MFL image. A digital image process technique is introduced to preprocess the MFL image, the MFL images from different types of defects show different texture characteristics. Gray level co-occurrence matrix is utilized for feature extraction of the texture in the MFL image. Five typical eigenvalues (contrast, correlation, energy, homogeneity and entropy) are used as the inputs of back propagation (BP) networks. After training with typical samples, the BP networks show good performance in the quantitative recognition of different defects. The result of this work shows that texture analysis method for MFL image is suitable for feature extraction and quantitative detection of wire rope defects. [ABSTRACT FROM AUTHOR]