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This paper presents a sensorless control scheme for the stand-alone brushless doubly fed induction generator (BDFIG) feeding nonlinear loads. The fundamental and harmonic components of the distorted power winding (PW) voltage caused by the nonlinear loads are extracted and controlled separately. A rotor speed observer is employed to estimate the speed based on the PW voltage and control winding (CW) current without the need of any other machine parameters except for the number of pole pairs. Since the d- and q-axis references of the CW current from the PW voltage control loop contain both dc and ac components, which cannot be tracked easily by conventional PI controllers, a CW predictive current controller is designed to regulate the CW current. Finally, the performance of the proposed control scheme is verified by comprehensive experiments on a 35-kVA prototype BDFIG.

By taking two-coupled duffing oscillator system as the research object, the study found under the synergistic effect of weak periodic signal and noise, the two-coupled duffing oscillator system has typical stochastic resonance and even could achieve better output of stochastic resonance than single duffing oscillator. Based on this phenomenon, this paper proposes a new method to detect the weak periodic signal through the stochastic resonance of two-coupled duffing oscillator. The experimental study indicates that we could achieve excellent detection effect by using the method we mentioned in this paper at low SNR (signal-to-noise ratios), especially, it has excellent filter effect for filtering and shaping of weak square signals and has potential values in the application of digital communications.

The paper proposed a new method for the detection of QPSK carrier signal that based on double duffing oscillator to solve the problems as high attenuation and strong noise interference in the QPSK carrier communication of low voltage power line. This method has making use of the different phase of QPSK carrier signal to stimulate the double duffing oscillators to enter different states and through the judgment of the state of the double duffing oscillators to detect the phase information that the QPSK carrier signal carries. At the same time, through the study of the system solutions of duffing oscillator, obtained the change rule of them, based on these rules, the paper proposed a discriminant algorithm that used the difference distribution, and this algorithm is characterized by small calculating amount and low error judgment rate. The numerical simulation and experimental test show that the double duffing oscillator method can detect the phase information of QPSK carrier signal in low voltage power line accurately with the low SNR environment.

This paper aims to accurately locate underground personnel in coal mines. For this purpose, an underground personnel positioning platform was established on the wireless sensor network (WSN). Specifically, the ultra-wide band (UWB) and the time difference of arrival (TDOA) positioning algorithm were introduced briefly, in view of the underground operation environment. Then, the underground operator monitoring platform was developed based on UWB-WSN and compared it with different positioning techniques through experiments. The results show that the proposed platform achieved a high positioning accuracy and satisfied the needs of real-time monitoring of underground personnel. The research findings shed new light on the mitigation of personnel and property losses in coal mine accidents.