智能调节续流模式的步进电机细分控制

针对步进电机在细分控制下使用传统续流模式导致的响应时间和电流纹波问题,提出一种智能调节续流模式策略.首先,详细分析了缓慢续流、快速续流和固定混合续流模式.其次,设计了一种可自动计算最佳续流模式的智能调节方法,该方法基于固定关断时间,可在一个PWM周期内对固定续流时间中快速续流的百分比进行优化,旨在提高电机细分控制运动性能.然后,基于已搭建的实物平台,对比分析了传统续流模式和智能调节续流模式的电流纹波.最后,该方法成功应用于ALNES S7卫星SADA.结果表明所提出的方法在响应时间和电流纹波之间达到了一种平衡,使得细分控制更加平稳.

连续流好氧颗粒污泥技术处理低浓度市政污水的中试研究

基于河北省某污水处理厂原厌氧池构建了中试规模3000 m^(3)·d^(-1)(Ⅰ、Ⅱ系列)的微氧-好氧耦合沉淀一体式反应器,以低浓度市政污水为基质、接种活性污泥,成功在连续流模式下培育了好氧颗粒污泥,并研究了颗粒污泥的形貌、结构特性、污染物去除性能及微生物群落结构变化。结果表明:中试系统形成的颗粒污泥轮廓清晰、呈规则球形和椭球形,平均粒径由接种污泥的28.9μm增至90.1μm,其中粒径>100μm的占47.8%,>200μm的占9.4%;中试系统培养的颗粒污泥机械强度远高于接种污泥的;Ⅰ、Ⅱ系列平均出水NH^(4+)-N分别为1.3和1.0 mg·L^(-1),平均出水TN分别为9.9和9.1 mg·L^(-1),系统具有良好的脱氮效果。此外,高通量测序结果表明中试系统大量富集了好氧反硝化菌Methylophilaceae和Methylotenera,好氧反硝化途径可能在脱氮中起重要作用。本研究可为连续流好氧污泥工艺的升级改造,以及在现有污水处理厂工艺基础上发展高效低碳的连续流AGS工艺提供参考。

A New Zero-Voltage Transition Power Factor Corrected Single-Phase Single-Stage AC-to-DC Converter

This paper presents a new ZVT （zero-voltage transition） single-stage ac-to-dc converter using PWM （pulse width modulation） and HF （high frequency） transformer isolation with capacitive output filter. In this converter a front-end power factor corrected boost stage integrates with a cascaded dc-to-dc bridge HF converter. The front-end boost converter operates in discontinuous current mode and ensures natural power factor correction with very simple control. The auxiliary circuit of this topology deals with very small power and is placed out of the main power path. As a result, the auxiliary circuit components have smaller power rating as opposed to main converter components. Also, output rectifier voltage is clamped to output voltage due to capacitive output filter. Identification and analyses of different operating modes of this converter are presented. Based on these analyses design example of a 50 kHz, 48 V, 1 kW ac-to-dc converter is presented. PSPICE simulation results of the designed converter are presented and explained to verify the performance of this converter.

Constant Ripple Current Control for Switching DC-DC Converter

The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microelectronic load applications. This paper proposes a DC-DC converter using variable on-time and variable switching frequency control enhanced constant ripple current control and reduced magnetic components. The proposed converter is realized by making the turn-offtime proportional to the on-time of the converter, according to the input and output voltage, thereby reducing the corresponding current ripple on output voltage in the continuous conduction mode. A Buck DC-DC converter using the proposed control strategy is analyzed in detail, along with some experimental results to show the performance and effectiveness of this converter.

Modelling and Predictive Control of a Buck-Boost DC-DC Converter

A predictive current control algorithm for the Buck-Boost DC-DC converter is presented in this paper. The continuous time model of the system is properly introduced, then, by imposing a proper PWM modulation pattern, its discrete time model is achieved. This last one is successfully employed in determining the steady state locus of the Buck-Boost converter, both in CCM （continuous conduction mode） and DCM （discontinuous conduction mode）. A novel continuous time equivalent circuit of the converter is introduced too, with the aim of determining a ripple free representation of the state variables of the system, over both transient and steady state operation. Then, a predictive current control algorithm, suitable in both CCM and DCM, is developed and properly checked by means of computer simulations. The corresponding results have highlighted the effectiveness of the proposed modelling and of the predictive control algorithm, both in CCM and DCM.

固定化活性污泥实现短程硝化反硝化处理畜禽废水

以畜禽废水为处理对象,通过分别控制水力停留时间(HRT)、溶解氧(DO)、pH值、温度和碳氮比(C/N)等影响亚硝化的主要单因子,以使固定化活性污泥颗粒实现短程硝化反硝化反应,在连续流运行模式下进行废水脱氮实验,实验结果表明,单因子HRT为10 h,溶解氧为4 mg/L,pH值为8.5,温度为30℃,碳氮比为10时,对TN和COD的去除率分别为81.98%、93.79%;87.32%、98.35%;83.82%、93.93%;85%、97%;85.37%、97.28%,达到了理想的去除效果。