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本文通过对1993年局属电厂垢及腐蚀产物模拟试样统检中氧化钙、氧化钙和氧化镁测定结果偏低问题的分析、试验,查明了影响氧化钙和氧化镁测定结果偏低的主要原因,即氢氧化铁胶体的干扰影响。通过试验,提出了在酸性条件下加掩蔽剂三乙醇胺的掩蔽方法,从而消除了氢氧化铁胶体的干扰,扩大了测定方法的适用范围,提高了分析结果的准确度。 相似文献
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研究了基于实时操作系统内核AR166的控制软件开发过程,解决了任务划分及协调工作等问题,提出了采用冗余的容错设计,给出了性能评价的方法,并结合全数字化智能电梯控制系统的软件设计,进行了深入分析。 相似文献
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建立了基于d-q同步旋转坐标系下的三相电压型PWM整流器(VSR)解耦状态方程,给出了双闭环控制策略,即电流内环实现指令电流跟踪控制,电压外环实现稳压输出。在此基础上,提出了SVPWM快速算法,完成了指令电压矢量所在扇区的判断和不同扇区PWM调制波占空比计算方法,避免了非线性运算,提高了运算速度和计算精度。最后,在MATLAB/SIMULINK环境下建立了系统的仿真模型,并进行实验样机的研制,仿真和实验结果表明:所设计的三相PWM整流器实现了单位功率因数运行,输入电流谐波含量低,输出直流电压稳定。 相似文献
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阐述了画家座椅的基本工作原理,通过PLC控制电机等设备实现了座椅的升降与移动,提出了具体的升降传动方案和PLC控制流程。系统具有操作简便、运行稳定流畅、安全可靠的特点,既保证了画家的人身安全,又节省了创作时间,提高了创作效率。 相似文献
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在许多大功率交流传动场合下,开关损耗大。为了降低开关损耗,提高逆变器效率,开关频率一般限制在1 kHz以下,导致牵引逆变器中含有大量的谐波。以应用于大功率电力机车的三电平逆变器为特定的研究对象,建立了三电平逆变器最小相电流总谐波畸变率谐波优化模型。采用分子动理论优化算法求解模型时施加了消除窄脉冲算法,完成全调制范围、多种脉波条件下优化函数的求解。与传统SPWM和SHEPWM比较,MMTPWM具有良好的谐波优化效果。最后,通过仿真实验和硬件实验结果验证了理论分析的正确性。 相似文献
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In this paper, a new approach for the detection and classification of single and combined power quality (PQ) disturbances is proposed using fuzzy logic and a particle swarm optimization (PSO) algorithm. In the proposed method, suitable features of the waveform of the PQ disturbance are first extracted. These features are extracted from parameters derived from the Fourier and wavelet transforms of the signal. Then, the proposed fuzzy system classifies the type of PQ disturbances based on these features. The PSO algorithm is used to accurately determine the membership function parameters for the fuzzy systems. To test the proposed approach, the waveforms of the PQ disturbances were assumed to be in the sampled form. The impulse, interruption, swell, sag, notch, transient, harmonic, and flicker are considered as single disturbances for the voltage signal. In addition, eight possible combinations of single disturbances are considered as the PQ combined types. The capability of the proposed approach to identify these PQ disturbances is also investigated, when white Gaussian noise, with various signal to noise ratio (SNR) values, is added to the waveforms. The simulation results show that the average rate of correct identification is about 96% for different single and combined PQ disturbances under noisy conditions. 相似文献
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易于FPGA实现的最优移相PWM控制策略 总被引:7,自引:2,他引:5
在综合考虑波形特性、开关损耗、电压利用率及易实现性的基础上,提出一种新的最优移相脉宽调制(PWM)控制策略。从线电压出发,指出电压利用率的提高实质上是一个非线性规划问题,并就此非线性规划问题分8种情况进行讨论,系统地分析了谐波注入正弦脉宽调制(SPWM)电压利用率可以达到的极限值。采用数字仿真得出易于现场可编程门阵列(FPGA)实现的最优移相PWM调制波数据,并对其进行频谱分析。论证了移相法和堆波法在开关损耗上的一致性,以及移相法具有开关动作均匀、易于FPGA实现的特点。最后给出了最优移相PWM策略MATLAB仿真波形以及在SIGA(system in gate array)多电平高压变频器模型机中应用的实验波形。 相似文献
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基于多层前馈神经网络的并联型电能质量控制器 总被引:1,自引:0,他引:1
神经网络用于电力系统电能质量分析和控制是一个新研究领域.快速可靠地提取谐波分量决定着并联型电能质量控制器的整体性能,构造了一种和理论分析相一致的基于反向传播算法的三层前馈神经网络,离线训练收敛后可用来在线检测电力系统谐波电流.系统中逆变器补偿电流的产生对系统的补偿性能至关重要,提出了一种基于神经网络的逆变器瞬时电流PWM控制.并联型电能质量控制器投入系统后电流总畸变率由26.29%下降为5.25%.仿真实例表明,所提并联型电能质量控制器动态响应快,可改善电力系统电流波形畸变,提高电能质量. 相似文献
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This paper presents a novel algorithm for identifying and measuring the symmetrical components of distorted three phase voltage or current waveforms in electrical power systems. The proposed algorithm is capable of estimating the symmetrical components as well as the harmonic contents of a given unbalanced distorted signal. The proposed technique is based on stochastic estimation theorem. The problem is formulated as an estimation problem and presented in state space form. The proposed algorithm used to estimate the positive, negative and zero components of unsymmetrical waveforms as well as the harmonic content of a given distorted signal. Application of the proposed algorithm has been conducted on various test cases. Among which a practical simulated power system has been implemented using EMTP. Various scenarios are carried out to simulate realistic situations of unsymmetrical waveforms. Effects of bad data on the solution accuracy are also studied. The speed of convergence is examined by changing the estimator initial conditions. Results obtained show that the proposed technique can estimate and track the symmetrical components of non-stationary three phase unbalance voltage or current waveforms in noisy environments. Fast accurate solutions are guaranteed regardless of the initial conditions. It is also shown that bad measurements have no effects on the final accuracy of the estimation. 相似文献
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Keiju Matsui Yasutaka Kawata Tadashi Yamaguchi Fukashi Ueda 《Electrical Engineering in Japan》1997,120(2):49-58
The neutral point clamped (NPC)-PWM inverter has significant advantages, such as its ability to operate motors with nearly sinusoidal current waveforms. For this reason, in larger-capacity inverter systems, NPC-PWM inverters using GTOs and the like have been put into practical use, because of great advantages to large-capacity ac motor drives, such as lower ripple currents and higher output voltages. With the spread of applications, inverters of still larger capacity are expected. However, since the capacities of such switching devices are insufficient, a certain technique and controlling method are proposed for the parallel connection of NPC inverters. In this paper, conventional modulation techniques are extended to improve the inverter characteristics; asymmetrical modulation and overmodulation techniques are introduced for the parallel-connected NPC inverter. In the proposed modulation strategies, the waveforms become more complicated, so that it is difficult to analyze the output waveforms. For those waveforms, an analytical waveform analysis method using the switching function is proposed. With such a method, the physical meaning of harmonic generation can be realized to some extent. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 49–58, 1997 相似文献