改进无差拍控制在单相并网逆变器中的应用

为解决在单相并网逆变器中应用无差拍控制时,由于采样及处理器计算的延时而导致系统不稳定的问题,提出了一种基于CMAC神经网络的无差拍控制策略。控制策略通过MPPT算法跟踪光伏电池的最大输出功率,然后将最大功率减去电路中功率损失后除以电网电压的有效值平方得到逆变器参考电流的系数k,再根据CMAC神经网络预测出下一时刻的电网电压和参考电流,最后计算出下一时刻的开关周期的占空比对逆变器进行控制。此方法实现了对采样及处理器计算的延时的补偿,可提高了系统的稳定性,使并网逆变器的输出电流快速、准确地跟踪电网电压,降低逆变器输出电流中的总谐波歧变。通过对该策略进行了仿真和试验,结果表明该控制策略有效性和可行性。     

基于反推的电液比例系统共振频率控制

针对电液比例系统的非线性以及不确定性因素对破碎频率控制的影响,设计反推的频率控制方法.建立电液比例阀控液压马达的破碎机构的非线性模型,特别是考虑了比例阀的动态频率和阻尼特性,将系统的各不确定性参数对破碎频率的影响等效为液压马达轴上的负载波动;设计基于反推的控制律,构建各步骤的误差信号、虚拟控制信号和目标函数间的关系,在不确定性有界的前提下保证了液压马达输出转速渐近跟踪的稳定性.给出频率控制系统的模型参数,并在基于Matlab6.5的环境下进行了仿真研究以及车载试验,结果表明,对于具有不确定性因素的电液比例频率控制系统,反推控制策略具有较好的控制性能,能够满足共振式破碎机的工程应用要求.     

具有谐波补偿功能的光伏并网逆变器控制策略研究

随着高新能源技术的发展,光伏并网发电在通过逆变器并网时往往会产生大量的不同谐波,并因此消耗大量的电能.接入电网的光伏并网逆变器中存在大量的负载,这将使整体电网质量下降.针对此问题,论文提出一种具有谐波补偿功能的光伏并网逆变器控制方法,通过谐波补偿装置采集电网中的谐波含量,并基于MPPT算法对所采集的谐波进行分析、计算,...     

A computational method based on Gustafson-Kessel fuzzy clustering for a novel islanding detection for grid connected devices and sensors

Fuzzy Clustering-based (G-K) Gustafson-Kessel is used to create the fuzzy rule-based classifier in a grid connected photovoltaic (PV) system where it is tested using specific features in a grid connected PV inverter for detecting islanding condition. It is detected when harmonic content of voltages at the Point of Common Coupling and inverter increases beyond a threshold value. If islanding is not detected, distribution lines are rendered unsafe. The present study uses G-K fuzzy clustering to categorize islanding and nonislanding incidents. Two features based on Total Harmonic Distortion are extracted and used as inputs for the G-K fuzzy clustering classifier. The proposed technique is tested using nonlinear loads and its performance is verified by simulation using MATLAB Simulink. A hardware test set-up is developed to validate the proposed antiislanding technique and the results obtained are discussed.     

纸纱复合制袋机控制系统设计

针对纸纱复合制袋机存在可靠性欠佳、自动化水平不高等问题,提出了一种新型纸纱复合制袋机自动控制系统。该控制系统分别以欧姆龙CP1H PLC和3G3MV变频器为控制核心、以人机界面软件MCGS为开发前台和控制界面,实现了袋速、袋长、纬纱密度与切刀的速度灵活匹配以及胶槽温度、压辊控制的智能调节。生产实践结果表明,该系统运行稳定、可靠,操作界面简单、友好,性能完全满足设计和生产要求。     

模糊控制在湿式复合机张力控制系统中的应用

湿式复合机张力控制系统具有非线性、时变的特点,对其进行恒张力控制具有一定的难度,传统的PID控制不能很好地满足要求。本文采用偏差e和偏差变化率ec的变化规律为依据的模糊PID控制算法,对湿式复合机张力进行在线修改,建立模糊控制规则的监控系统表,并利用MATLAB进行计算机仿真。对比两种控制仿真曲线,可以看出模糊控制系统抗干扰能力强,能取得良好的调节品质。     

基于STM32的电液比例模糊PID控制系统设计

本文以电液比例阀为研究对象,针对被控对象的非线性和时变性特点,应用STM32技术设计了模糊PID控制器,使电液比例模糊PID控制系统具备了实时性好、响应速度快、稳定性高、超调小等特点,较好的满足了工业控制要求.     

An application of PSO technique for harmonic elimination in a PWM inverter

Harmonic elimination problem in PWM inverter is treated as an optimization problem and solved using particle swarm optimization (PSO) technique. The derived equation for computation of total harmonic distortion (THD) of the output voltage of PWM inverter is used as the objective function in the PSO algorithm. The objective function is minimized to contribute the minimum THD in the voltage waveform and the corresponding switching angles are computed. The method is applied to investigate the switching patterns of both unipolar and bipolar case. While minimizing the objective function, the individual selected harmonics like 5th, 7th, 11th and 13th can be controlled within the allowable limits by incorporating the constraints in the PSO algorithm. The results of the unipolar case using five switching angles are compared with that of a recently reported work and it is observed that the proposed method is effective in reducing the voltage THD in a wide range of modulation index. The simulated results are also validated through suitable experiments.     

基于复合控制的电力系统稳定器设计

针对传统电力系统稳定器(PSS)的缺点,提出一种基于复合控制的电力系统稳定器,可以根据实际的运行情况在模糊和比例积分微分(Fuzzy-PID)控制中进行选择性的控制,使电力系统稳定器既具有模糊控制简单有效的非线性控制作用,又具有比例和积分控制的快速性和跟踪能力。理论分析及仿真结果均表明所提出的方案正确可行并具有良好的性能。     

小信号放大电路任意波形THD全自动测量系统研究

总谐波失真THD是衡量信道非线性程度的重要指标,应用于音频小信号放大电路的任意输出波形识别和总谐波失真的全自动测量系统成为检测信号放大性能的有效手段。为准确计算放大后的波形总谐波失真度,采用了快速傅里叶变换FFT技术。从提高系统效率角度,使用高频率采样并半数提取的技术方案。通过动态控制继电器、阻容元件及多级放大等手段,合理调整放大系统静态工作点的位置和输入波形大小,实现不同类型的失真波形输出。基于stm32f103c6单片机,联动开关一键式完成任意波形采集、识别、计算和显示,极大提升了小信号放大电路失真度测量的工作效率。Matlab运算仿真、Multisim电路仿真及实物测试表明,多级晶体管放大一致性调节电路和单片机FFT运算组成的小信号放大电路任意波形THD全自动测量系统,可准确、实时识别波形并计算出总谐波失真,一键式切换设计操作方便、节约成本,颇具实用价值。     

Online Learning Control for Harmonics Reduction Based on Current Controlled Voltage Source Power Inverters

Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components. Shunt active filters (SAF) with current controlled voltage source inverters (CCVSI) are usually used to obtain balanced and sinusoidal source currents by injecting compensation currents. However, CCVSI with traditional controllers have a limited transient and steady state performance. In this paper, we propose an adaptive dynamic programming (ADP) controller with online learning capability to improve transient response and harmonics. The proposed controller works alongside existing proportional integral (PI) controllers to efficiently track the reference currents in the d -q domain. It can generate adaptive control actions to compensate the PI controller. The proposed system was simulated under different nonlinear (three-phase full wave rectifier) load conditions. The performance of the proposed approach was compared with the traditional approach. We have also included the simulation results without connecting the traditional PI control based power inverter for reference comparison. The online learning based ADP controller not only reduced average total harmonic distortion by 18.41 %, but also outperformed traditional PI controllers during transients.