变频空调缺陷：引起电网谐波污染及其危害

目前市场中采用交流变频技术的家用空调的核心是变频器，变频器就是电网中的非线性负载，其运行过程中工频电源整流成直流电压信号，经电容滤波及大功率晶体管开关元件逆变为频率可变的交流信号。在整流电路中，输入电流的波形为不规则的矩形波，波形按傅立叶级数分解为基波和各次谐波，其中的高次谐波将干扰输入供电系统。输出回路电流信号也可分解为只含正弦波的基波和其它各次谐波，谐波与电力系统中基波叠加，造成波形畸变从而引起电网谐波污染。     

电网谐波条件下光伏空调系统控制策略研究

电网电压中通常含有一定分量的谐波,会导致网侧电流出现谐波分量而发生畸变,网侧电压谐波分量和电流的正序分量相互作用还将使网侧变换器输出的有功功率、无功功率产生6倍频波动。为提高光伏空调系统中网侧变换器的运行性能,在电网电压畸变条件下建立网侧变换器正负序分量数学模型,利用以5次和7次谐波电流分量为零的控制方法,实现维持直流母线电压恒定、消除网侧变换器5次和7次谐波电流的控制目标。并基于光伏空调系统仿真平台进行验证,结果及分析表明此控制策略能够有效改善光伏空调系统的网侧电流谐波及系统控制性能。     

AVR实现的SVPWM变频调速系统研究

矢量控制变频技术是先进的变频调速技术。异步电机在两相同步旋转坐标系下的数学模型表明:可以实现交流感应电机磁场和转矩的解耦控制。本文提出了使用高性价比嵌入式芯片AVR ATmega8515实现矢量变频调速系统的实施方法。实验结果表明:基于AVR的空间矢量变频调速系统基本达到了预期要求,在实验负载条件下能够进行变频调速,电压输出波形符合理论分析,电流输出为三相对称正弦波。     

变频器谐波危害分析及解决措施

随着科学的进步,电力电子技术突飞猛进,交流电动机变频调速技术正日趋完善,变频器控制交流异步电动机,性能胜过以往任何一种控制方式,且结构简单,容易实现智能化。其最典型的应用是异步电动机变频调速,从而达到节能目的。该技术在煤矿的应用广泛,其中以提升机,输煤皮带机的转速控制最为常见。实践证明,综合节能达到70％以上,效果非常明显。在节能增效方面发挥着巨大作用。但是,变频器的广泛应用同时也带来了一些新问题,由于变频器逆变电路的开关特性,变频器输出侧电压、电流、非正弦或非完全正弦波含有丰富的谐波。干扰供电系统、负载及其它邻近电气设备,造成供电线路一些原因不明的非故障性线路跳闸和电器元件损坏。     

全数字化SVPWM调速系统的设计与仿真

该文提出了使用价格低廉的嵌入式系统实现矢量变频调速系统的实施方案,对系统软件、硬件设计进行了优化,并实施仿真.仿真表明,设计的空间矢量变频调速系统性能优异,各个部分的理论分析正确,参数配合比较恰当,电压、电流输出波形达到要求,转速符合最少拍控制要求,基本无振荡.系统的设计对控制生产成本、增强通用性具有指导意义,系统的仿真对样机制作、缩短设计周期、提高生产效率具有重要意义.     

基于滞环控制的三相电压型PWM整流器仿真研究

针对间接电流控制动态性能的不足,采用滞环比较PWM跟踪控制技术,提高了系统的动态响应速度．分析了开关频率与交流侧滤波电感及环宽的关系,并对系统参数进行了优化．采用MATLAB／Simulink软件搭建系统仿真模型,对方案进行了仿真验证．结果表明：滞环电流控制方案下的交流侧谐波畸变率（THD）值为3．31％．     

浅析中压变频器在管道输油工业生产中的维护意义

变频器可以固定电压、固定频率的电源转换为电压、频率可变的电源。变频器能够实现对交流异步电机的软启动、变频调速、提高运转精度、改变功率因数、过流,过压,过载保护等功能,变频器在现代管道输油工业化生产中占有着重要的作用,随着工业自动化程度的不断提高,变频器也得到了非常广泛的应用。     

基于DSP的航空测试交流电源

介绍了一种基于DSP的航空测试交流电源.该交流电源不仅能够输出飞机交流用电设备在不同工作状况下的频率幅值可调的正弦电压,而且能够输出周期性畸变电压.该电源采用数模混合控制及重复控制方法,数字部分实现高精度的波形发生器和电压有效值控制;模拟部分采用电压电流瞬时值控制,提高响应速度.最后给出测试波形.     

交流变频调速在转炉倾动控制中的应用

文章介绍了本钢150t转炉倾动装置采用交流变频调速驱动的应用并对电机的选择、变频器的选择、控制方案的确定作了详细说明.采用PROFIBUS-DP网组成控制网络,对系统实行网络控制;用SIMOLIK光纤网解决了同步控制的问题.     

浅谈电力系统中谐波的产生、危害及治理

理想的电力系统向用户提供的应该是一个恒定工频的正弦波形电压,但是由于各种原因,使这种理想状态在实际中无法存在。随着我国工业经济的快速发展,大量非线性负荷,如中频炉、电弧炉、大型轧机、变频设备等接入电网,组成了电网的主要谐波污染源。如果系统中有较强的谐波源,又没有采取有效的限制措施,电网的电压及电流波形就会发生畸变。     

Power calibrator using switched mode voltage source

The paper is focused on a sophisticated switched mode power supply with a pure sinusoidal output voltage waveform with frequency (40-65 Hz) and voltage range (30-500 V). In order to cope with stringent voltage (10.2%) and distortion constraint (THD<0.7%) in a modern calibration system, traditional inverter design with an output LC filter is upgraded with a feedback-feedforward control principle. The paper presents the voltage source topology, analyzes its steady-state response and gives its comprehensive evaluation. Using a simple sensor that is capable to detect a small voltage asymmetry at the presence of a high AC component (500 VRMS), the parasitic DC component is limited below 5 mV. Experimental results demonstrate exceptional voltage accuracy (<0.2%) and low total harmonic distortion (THD)     

A frequency‐dependent droop scheme for parallel control of ups inverters

Abstract

This paper presents a frequency‐dependent droop scheme for paralleling UPS inverters with no control interconnection, so the inverters can be tightly connected with the load. At the fundamental frequency, the reference voltage of the inverter is generated as a reactor connected between the inverter and the load. The intention is to control the real and reactive power sharing of inverters with the Q‐V and P‐ω droop scheme employed in the power system without needing a true transfer reactor. At the harmonic frequency, the reference voltage is generated as a resistor connected between the inverter and the load. The intention is that the load harmonic current can be shared equally and the voltage waveform distortion will be low. Two 1KVA single‐phase inverters are designed and implemented, some simulation and experimental results are provided for demonstrating the effectiveness of the proposed approach.     

1V脉冲驱动型交流量子电压源研究

脉冲驱动型交流量子电压标准ACJVS通过高速脉冲序列驱动约瑟夫森结阵芯片的方式实现宽频带交流量子电压的合成,相比于可编程型交流量子电压标准PJVS,具有免台阶切换、频谱纯净、频带宽等优点。搭建的系统主要包括8位高速脉冲码型发生器、微波放大器、直流阻断、约瑟夫森结阵芯片等。通过驱动包含4个子阵列,每个子阵列含12810个约瑟夫森结的结阵芯片,并结合4通道联合低频补偿的方式,成功产生了1V有效值的脉冲驱动型交流量子电压,为进一步建立交流量子电压基准打下了坚实的基础。最后,展望了脉冲驱动型交流量子电压在量子阻抗桥、交流量子功率源、交流量子功率表方面的应用价值。     

Vector-optimised harmonic elimination for single-phase pulse-width modulation inverters/converters

A new approach for calculating single-phase inverters/converters-optimised pulse-width modulation (PWM) switching angles for harmonic and voltage control is proposed. This approach takes into account the DC-link voltage ripple, due to the finite DC-link capacitance, in the optimised switching-angles calculation, using its harmonic content. New expressions for the evaluation of the PWM waveform harmonic spectrum are derived. Output voltage quarter-wave symmetry is thus not assumed and the pulse position is no longer fixed, resulting in two simultaneous sets of nonlinear equations in twice as many unknowns as in the case of conventional-optimised PWM strategy with smooth DC input/output voltage. The performance of this latter technique is hence retained while the size of the DC-link capacitor is reduced to a limit depending on the filter capacitance, the number of pulses per half modulation period and the modulation depth. The compensation of the reactive power (exchanged between the AC source/AC load and the DC link due to the rectifying/inverting process and the low-link capacitance) is also included; the converter then plays the additional role of an active power filter. Simulation examples and experimental results are used to validate the proposed method     

Feedforward simple control technique for on-chip all-digital three-phase AC/DC power-MOSFET converter with least components

A novel simple control technique for on-chip all-digital three-phase alternating current to direct current (AC/DC) power-metal oxide semiconductor field-effect transistors (MOSFET) converter with least components, which is employed to obtain small current and DC output voltage ripples as well as excellent performance, and using a feedforward simple control method for DC output voltage regulation is proposed. The proposed all-digital feedforward controller has the features of low cost, simple control, fast response, independence of load parameters and the switching frequency, it has no need for compensation, and high stability characteristics; moreover, the proposed controller consists of three operation amplifiers and few digital logic gates that are directly applied to the three-phase converter. The power-MOSFETs are also known as power switches, whose control signals are derived from the proposed all-digital feedforward controller. Instead of thyristors or diodes, the application of power-MOSFETs can reduce the loss of AC/DC converter that is proper to the power supply system. The input stage of an AC/DC converter functions as a rectifier and the output stage is a low pass inductor capacitor (LC) filter. The input AC sources may originate from miniature three-phase AC generator or low-power three-phase DC/AC inverter. The maximum output loading current is 0.8 A and the maximum DC output ripple is less than 200 mV. The prototype of the proposed AC/DC converter has been fabricated with Taiwan Semiconductor Manufacturing Company (TSMC) 0.35 mum 2P4M complementary MOS (CMOS) processes. The total chip area is 2.333 1.960 mm². The proposed AC/DC converter is suitable for the following three power systems with the low power, DC/DC converter, low-dropout linear regulator and switch capacitor. Finally, the theoretical analysis is verified to be correct by simulations and experiments.     

基于高低压电源切换的双环恒流控制电磁流量计励磁控制系统

为了提高电磁流量计高频方波励磁性能,基于励磁恒流控制仿真分析,采用外环高低压电源切换和内环电流微调的双环励磁恒流控制方式,以保证电磁流量计高频方波励磁时一次仪表输出信号零点稳定、电源利用效率高。设计方波励磁控制系统,以实现高频方波精确励磁。仿真结果表明,高压源电压越高越有利于拓宽励磁频率范围。实验结果表明,系统在高频方波励磁时,励磁电流响应速度快且电磁流量计传感器输出信号零点稳定。     

单相无电解电容永磁同步电机驱动系统控制方法研究

针对传统单相无电解电容电机驱动系统中直流母线电压波动较大而导致控制不稳的问题,提出一种单相无电解电容永磁同步电机驱动系统控制方法。通过对传统单相无电解电容电机驱动系统输入、输出功率进行分析,在q轴电流注入正弦分量,对输出功率进行控制,调节输入功率,达到改善输入电流波形的目的;通过设计一种积分比例控制器替代传统的比例积分控制器对母线电压进行调节,能够有效抑制母线电容充电时的电流、电压过冲。理论分析、仿真结果与试验结果均验证所提控制策略的有效性。     

前端调速型风电机组动力学建模与运行特性研究

基于先进的机械调速与伺服控制技术,提出了一种带有发电机前端无极调速器的混合传动风电机组方案,以实现变速恒频。利用集中质量与拉格朗日方法,建立该机组传动系统动力学模型。并利用动力学方程建立1.5 MW前端调速型风电机组的Simulink仿真,实现对机组调速精度、功率消耗、电流谐波与低电压穿越能力等运行特性的深入研究。结果表明:在不同的风速条件下,所提机组不仅可以在调速功率消耗较小的情况下输出恒频电能(占比小于输出功率的15.25%),还可以有效抑制电流谐波污染,改善机组低电压穿越能力。理论分析与仿真研究验证了该机组的实用性和优越性。