Wind speed follows the Weibull probability distribution and wind power can have a significant influence on power system voltage stability. In order to research the influence of wind plant correlation on power system voltage stability, in this paper, the stochastic response surface method (SRSM) is applied to voltage stability analysis to establish the polynomial relationship between the random input and the output response. The Kendall rank correlation coefficient is selected to measure the correlation between wind farms, and the joint probability distribution of wind farms is calculated by Copula function. A dynamic system that includes system node voltages is established. The composite matrix spectral radius of the dynamic system is used as the output of the SRSM, whereas the wind speed is used as the input based on wind farm correlation. The proposed method is compared with the traditional Monte Carlo (MC) method, and the effectiveness and accuracy of the proposed approach is verified using the IEEE 24-bus system and the EPRI 36-bus system. The simulation results also indicate that the consideration of wind farm correlation can more accurately reflect the system stability.

The quartz double-ended tuning fork (DETF) resonator is well known to be sensitive to longitudinal force and is widely used as the sensing element in modern accelerometer, force and pressure sensors. The quartz DETF resonator works in-plane, with anti-phase flexural mode vibration, which is driven into oscillation by internal strains created by AC voltages applied to electrode patterns on the beams. The DETF vibration modes and vibration characteristics are determined by the electrode pattern and its electromechanical coupling efficiency. Presented are three kinds of electrode patterns for different applications, and the effect of electrode patterns on the vibration performances are investigated experimentally. With the fundamental frequency at 65 KHz, the DETF resonator is designed and fabricated using the wet etching-based quartz MEMS technique. The vibration characteristics including Q-value, and equivalent parameters, are evaluated using a 4294 A impedance analyser. Experimental results demonstrated that the vibration characteristics of quartz DETFs are affected by the electrode patterns including pattern location and widths. These results are expected to be useful for designing quartz DETF based devices.

Aiming at the current oscillation and delay of traditional limited control set model predictive control (FCS-MPC), an improved FCS-MPC is proposed. Eliminate current oscillation by using two adjacent voltage vectors and zero voltage vector to work together in one sampling period. In order to reduce the switching frequency, the effects of the voltage vectors are sequentially ordered to obtain an optimal voltage vector sequence (OVVS). In the high-power five-level NPC/H-bridge inverter, the modulation control experiment is carried out, and the simulation model is built by Simulink software. The simulation results verify that the proposed improved FCS-MPC model is in the high-power multi-level NPC/H inverter. Predictive control effectiveness.