Junlong Fang

The neutral point clamped (NPC) three-level inverter is widely used in highvoltage and high-power applications. However, neutral point voltage oscillation (NPVO) and common-mode voltage (CMV) problems exist in the NPC three-level inverter. In this paper, an improved virtual space vector modulation (VSVM) is proposed based on the reconstruction of a virtual small vector and a virtual medium vector. Compared with the traditional VSVM, an improved VSVM can effectively reduce the CMV. On this basis, a vector conversion method is proposed to further reduce the NPVO in the whole range. Simulation results verify the effectiveness and superiority of the improved VSVM.

To improve the observation accuracy and robustness of the sensorless control of an interior permanent magnet synchronous motor (IPMSM), a sliding mode observer based on the super twisting algorithm (STA-SMO) with adaptive parameters estimation control is proposed, as parameter mismatches are considered. First, the conventional sliding mode observer (CSMO) is analyzed. The conventional exponential approach law produces a large chattering phenomenon in the back EMF estimation, which causes a large observation error when filtering the chattering through the low-pass filter. Second, a high-order approach law of the super twisting algorithm is introduced to observe the rotor position and speed estimation, which uses the integral function to eliminate the chattering of the sliding mode. Third, an adaptive parameter estimation control (APEC) is presented to enhance the observation accuracy caused by parameter mismatches; the motor parameter adaptive law of the APEC is designed by Lyapunov’s stability law. Finally, the proposed method not only reduces both the chattering and the low-pass filter, but it also enhances accuracy and robustness against parameter mismatches, as discussed through simulations and experiments.

Capacitors are critical in voltage regulator modules (VRMs), which contribute to store energy and stabilize the output voltage during load transients. Usually, VRMs work with consecutive load transients, which would bring more electrothermal stress to capacitors and affect the reliability of capacitors compared with the steady-state operation. Recently, some efforts have been made to investigate the reliability of capacitors in power electronic converters. Unfortunately, transient processes are commonly ignored, which can impair the accuracy of the lifetime estimation. Regarding this issue, this letter investigates the influence of transients on the damage of capacitors in VRMs. A 150-W VRM is introduced as a case study. First, the electrothermal stresses during steady state and transients are analyzed. Then, the lifetime calculation is considered from a single capacitor to hybrid capacitor banks. In addition, a suitable capacitor configuration of capacitor banks is also provided in order to maximize its lifetime.

In order to realize the collection, management, visualization, and uploading of real-time information in the paddy field, an information monitoring node based on automatic tracking solar-powered panel is presented in this paper. First, the node consists of information collecting sensors, STM32 MCU, LCD, GPRS module, automatic tracking solar-powered module, and monitoring interface. Second, data gathered from sensors can be displayed on the LCD and sent to the host computer interface. Moreover, host computer can also save the data packages to management server for examination and analysis. Finally, in the practical test, data are gathered every 2 h. At nontest time, the node works in low-power mode to achieve rational use of electric energy. The results of this experiment show that the node can achieve an accurate transmission and display of data, and the power supply system can meet the demand for electricity in continuous rainy days.