Journal of Electrical Engineering & Technology最新文献

The traditional Wireless Power Transfer (WPT) system has the problem that the coupling coefficient has a great influence on the transmission characteristics. The WPT system with PT-symmetric structure can achieve the transmission characteristics independent of the coupling coefficient and maintain stable power and efficiency transmission in the strong coupling region constructed by the PT-WPT system. To further optimize PT-WPT, this paper proposes a PLL controlled wireless power transfer system based on PT-symmetric theory. Phase-locked loop (PLL) is employed to accurately control the power of the transmitter and the system can maintain constant transmission power and efficiency in the strong coupling region. In addition, this control method also reduces the complexity of WPT system. A 10–15 W experimental WPT system platform with a 0–10 cm transmission distance is developed to validate the transmission power and efficiency of the system, The results demonstrate that the output voltage and current of the inverter can always ensure that the system works in the PT-symmetric state and the transmission efficiency is more than 90%, The transmission power is not less than 10 W within the transmission range of 0–10 cm. The designed system can maintain constant high efficiency and high-power transmission in the strong coupling region.

MEMS-based devices have helped in the miniaturization of various transducers, one such being the accelerometer. The current study presents the design and simulation of a MEMS tri-axial resonance-based accelerometer in a differential arrangement to measure acceleration up to 5 g. The final tri-axial accelerometer differential design is derived from five designs which consist of four proof masses, four resonating beams, two vertical and two horizontal hinges. The first three designs are non-differential designs and the next two designs give a differential output only for out-of-plane acceleration. Numerical simulations were carried out in COMSOL Multiphysics for all the designs and the dimensions were optimized to obtain maximum stress on the resonating beam for an applied acceleration. Eigenfrequency analysis was also carried out to estimate the change in resonance frequencies of all the resonating beams in each of the proposed models along with the final differential design. The sensitivities were found to be 33 Hz/g, 33 Hz/g, and 19 Hz/g for the final differential design in X, Y, and Z directions respectively. The differential arrangement will be able to compensate for any temperature variations and the resonance condition can be achieved by piezoelectric excitation and detection.

Switched reluctance machines (SRMAs) have recently received significant attention in the electrical power research community. This attention can be attributed to its outstanding features and traits of being used as generators or engines. An accurate model should be developed to design controllers and drives for these SRMAs properly. Analytical techniques and polynomial degree representation have been used in several attempts to find the SRMA parameters in the literature. However, it is important to note that these techniques are based on many assumptions and approximations. This study develops a precise, analytical model of the SRMA without any assumptions, approximations, or conducting any practical experiments. This analysis is based on frequency techniques using Fourier expansion and spectrum analysis. Then, an identification method is proposed to determine the model parameters, e.g., the inductance parameters. Furthermore, the magnetic field distribution and other performances of the switched reluctance motors, such as the torque, can be given using this method. Comparisons between the outcomes produced by this frequency model and those provided by FEM (Finite Element Method) and the recursive least squares approach were made to demonstrate the efficacy of the suggested study. This comparison shows that the proposed method is more accurate in finding the SRMA parameters than other methods. The proposed approach effectively predicted the motor parameters in about 2% less than other methods.

This paper proposes the lifetime extension of DC-link capacitors in three-level inverters based on the neutral-point (NP) current. High-capacity inverters require large-size capacitors to maintain robust DC-link voltage. The proposed method suppresses the ripple current of the DC-link capacitors by replacing the switching states, which are optimized for two specific modulation index regions in the linear modulation range. The reliability of the DC-link capacitors is analyzed using a capacitor lifetime model. The validation of the proposed method is supported by simulation and experimental results across various conditions.

To obtain the operating status of equipment and loads in buildings without installation of intrusive monitoring devices, non-intrusive load decomposition and monitoring methods have become the research focus of many scholars and researchers. To improve the accuracy of non-intrusive load decomposition, a non-intrusive load decomposition based on parallel connection network and attention mechanism is proposed. This proposed method educes the depth of network by ‘parallel connection’ and reduces the risk of overfitting. In additional, the dilated residual convolutional neural network and the bidirectional long short-term memory network are connected in parallel to extract features respectively, which greatly improves the representation ability of features. The attention mechanism is introduced to eliminate redundant information, focus on important information, and improve the decomposition performance. Finally, the domestic self-assessment data set is used, and different evaluation indicators are used for evaluation and comparison with other commonly used models. The simulation results show that the decomposition accuracy of proposed method is significantly improved.

In view of the temperature control system with Programmable Logic Controller (PLC) as the core, the main problems focus on the inability to realize wireless communication, remote downloading, poor temperature stability and poor anti-interference ability. A multi-channel Proportional Integral Differential (PID) temperature control system based on PLC and Internet of Things (IOT) is designed. It can not only adjust the temperature in real time. But also, the thirdparty cloud platform can be used through Message Queuing Telemetry Transport (MQTT) protocol, wireless data monitoring and remote control can also be carried out, and PLC programs can be downloaded remotely. Compared with the traditional wired monitoring system, it has great advantages and brings unprecedented convenience to the maintenance of the equipments. Based on the prototype, the multi-channel temperature stability and anti-interference tests, and wireless communication monitoring and alarm tests are carried out. The results show that the actual temperature of the system can change with the set value by PID control algorithm with the multi-channel heaters, and the temperature stability can reach ± 0.1 °C in steady state. In addition, real-time data such as temperature, voltage and current can be obtained through the cloud platform monitoring interface. And after triggering the alarm, the mobile devices (such as mobile phones) receive messages in real time.

The state of the polyvinyl chloride (PVC) outer sheath of cable before combustion has not been fully clarified, especially in relation to thermal decomposition gas research. To further establish the cable fire warning technology based on thermal decomposition gas, the author of this paper sets up an experimental platform for thermal decomposition of high voltage cable outer sheath. The objective is to investigate the thermal decomposition characteristics of 110 kV high voltage cable PVC outer sheath in oxygen-free and oxygen conditions. The thermal decomposition behavior of PVC outer sheath in nitrogen and air atmospheres were studied by Fourier Transform Infrared (FTIR) spectroscopy. The characteristic gases produced by thermal decomposition were revealed by infrared spectroscopy. The effects of heating temperature and heating time on these characteristic gases were investigated. The results showed that the thermal decomposition gases of the PVC outer sheath of 110 kV high voltage cable in two atmospheres were mainly H₂O, CO₂. Also found were small amounts of alkanes, as well as dioctyl phthalate (DOP) and 2-ethylhexanol (2-EH). The peak absorbance of DOP was influenced by the heating temperature and heating time, while that of 2-ethylhexanol was almost not influenced by the heating temperature. The experimental results of this paper will provide theoretical and technical support for the early warning of cable fires.

In order to enhance the state feedback accuracy of permanent magnet synchronous motor (PMSM), magnetic simulation analysis, magnetic simulation analyses were initially conducted on a 10-pole, 12-slot motor to investigate the reliability of PMSM under long-term operational conditions. Subsequently, we considered the impact of current disturbances on position observation, along with the harmonic disturbances of stator current and permanent magnet flux, to rectify the observed errors of the state observer. A novel error-corrected extended state observer is proposed to enhance the observed accuracy of PMSM. Finally, acceleration and deceleration experiment, as well as load disturbance experiment, were performed. The results of the experiments and observed simulations demonstrate that the designed state observer achieves faster dynamic response and higher observed precision compared to the state observer that does not utilize the method presented in this paper. Moreover, it exhibits excellent sinusoidal properties of the current waveform and strong anti-disturbance ability.

Accurate measurement of blood flow velocity profiles is important for diagnosing diseases such as heart failure, carotid stenosis, and renal failure. Speckle decorrelation (SDC) was developed to measure 2D out-of-plane blood flow over the entire luminal area using a conventional 1D array transducer. One of the main challenges in SDC is the tissue clutter interference with blood. Adaptive clutter filters can suppress the clutter from backscattered signals in ultrasound blood-flow imaging. This study aims to evaluate the performance of adaptive clutter filters, including the discrete cosine transform (DCT), polynomial regression (PR), and singular value decomposition (SVD), for SDC-based blood flow velocity measurement via ultrasound simulations. Among the adaptive clutter filters, the SVD filter with Pareto scaling exhibits the best performance for clutter rejection and SDC-based flow velocity measurements. The benefit of this study is that it significantly improves the accuracy of SDC-based blood flow velocity measurements.

This paper presents a method for field-weakening control on the induction motor of a low-speed vehicle (LSV) using look-up tables (LUTs). In LSV induction motors that are characterized by low voltage and high current, field-weakening control involves complex calculations that consider stator resistance. This approach has limitations in accurately reflecting motor parameter variations, which impacts its ability to achieve the maximum torque. Therefore, we utilized LUTs to achieve the maximum torque by considering motor parameter changes. In field-weakening region I, a LUT of the d-axis feedforward current was created based on speed and the q-axis reference current. In addition, the d-axis feedback current was calculated to compensate for the parameter discrepancies. In field-weakening region II, a LUT of the q-axis current limit was created based on speed and the d-axis reference current. The design with the proposed method is robust against parameter changes, ensuring the maximum torque per ampere throughout the entire field-weakening region. The experimental results confirm the validity of the proposed method.