浅谈变频器控制原理及应用

变频器调速技术有整流电路、平波电路、控制电路、逆变电路等。随着电子技术的发展,交流变频技术从理论到实践逐渐走向成熟。变频器使调速趋于平稳,其调速范围大、效率高,启动电流小、节能效果明显。交流变频器已逐渐取代传统的滑差调速、变极调速、直流调速等调速系统,目前已广泛应用于冶金、纺织生产线、楼宇和供水等领域。     

变频技术在我公司的应用

一、概述 交流变频调速技术已越来越引起人们高度重视。在电机拖动装置中,交流电机和所带的机械负荷一般都有一定的余量,而且也不是始终在最大负荷下运行。在轻载时,如果利用电力电子技术,改变电机外加电压或频率,对电机速度进行控制来适应工况的变化,可达到节电目的。工业生产中使用的风机、水泵、压缩机等机械通常依靠闸门、风门来改变流量,电能浪费严重,如用变频调速技术对电机控制来改变流量则可大大降低电耗。 从异步电机在调速时引起的转子能耗角度来看,变频调速时异步电机的同步转速随频率变化,调速时相应转差变化不大,比有另外的调速方式对异步电动机调速,转差功率损耗更小。 我公司在技改过程中注重节能降耗工作,先后在重要的、需要调速的设备中安装了17台VVVF脉宽调制(PWM)型变频器。 VVVF简称交——直——交变频,它直接将电网交流电变成直流,经逆变后以交流输出。其系统框图如下:     

采用开关电源的电视机省电

<正> 电视机工作时所用的直流电,是由220伏的交流电变压成低压交流电,再经整流成为不稳定的直流,然后由稳压电源电路使其电压趋于基本稳定后供给的。一般电视机采用串联式稳压电源,电路中有一个调整管,当整流电压升高或整机耗电小时,它的电阻变大,电压降就大。一部分电能变成热量耗散掉了。     

逆变器激励方式

逆变器按激励方式．可分为自激式振荡逆变和他激式振荡逆变。主要功能是将蓄电池的直流电逆变成交流电。通过全桥电路．一般采用SPWM处理器经过调制、滤波、升压等,得到与照明负载频率f．额定电压UN等匹配的正弦交流电供系统终端用户使用。     

燃料电池功率调节系统的研究

燃料电池电压输出范围比较宽，电压比较低。针对该特点本文设计了DC/DC和DC/AC两级变换的功率调节系统(PCS)。其中DC/DC将燃料电池输出的低压直流电高频变换成高压直流电，变换器为电压单环控制。DC／AC逆变器采用基于电压电流瞬时值反馈的双闭环控制，将高压直流电逆变为正弦交流电。分析了整个功率调节系统的工作原理及逆变器电路参数对稳定性的影响。0．5KVA佯饥实验结果表明整个系统具有电压输入范围宽、变换效率高、输出波形THD小等优点。为开发高效、高功率密度的燃料电池电源系统提供技术基础。     

基于小型风力发电机的整流系统设计

随着可再生能源技术的发展,需要性能优良的三相整流系统,将风力发电机等清洁能源系统产生的交流电转换为直流电进行储能或供电。针对此问题,提出了一种适用于风能以及太阳能的整流系统设计。该设计方案以三相整流为核心,通过变压器隔离降压,给三相全桥不可控整流电路供电。接着经过boost升压电路将输出的电压升为50 V,再经过buck降压电路将电压降为36 V,最终得到稳定的36 V电压输出。经测试,该方案表现出的平均负载调整率为0.184%,平均电压调整率为0.228%,为满足现代电子设备对直流电源的需求提供了新的思路。     

并网故障下双馈感应风力发电系统的改进控制策略研究

介绍在并网故障下对双馈感应风力发电系统改进的控制策略研究。并网故障分为对称故障和不对称故障,在不对称故障情况下,当电网电压频率为60 Hz并且电机转速接近同步速时,在双馈感应风力发电机的转子中将会出现接近于120 Hz的转子电流主要谐波;在对称故障下,定子电压有一个瞬间跌落,从而会在转子中导致过电流、过电压、过转速的出现。该文中转子侧变频器(RSC)主要用于抑制在并网故障下转子中出现的谐波分量或过电流等现象;网侧变频器(GSC)则用于抑制变频器之间直流电容电压中出现的谐波,以维持直流电容电压恒定。所提出改进控制策略可更好地抑制并网故障,改善整个双馈感应风力发电系统的控制性能,并使用Matlab/Simulink仿真验证了控制效果。     

变频调速技术在工业企业中的应用

一、概述 变频调速技术是现代电力电子技术发展的产物。它以其卓越的性能和高效的节能特性逐步取代了滑差调速、整流子电机调速、串级调速以及直流电机调速。它具有结构简单、稳定可靠,调速范围广,节电效果显著等优点,已成为交流电机调速的最新潮流。 目前,国内变频器市场以日本产品居多,其中日本富士变频器的市场占有率为42％,日本三垦为30％,国产变频器市场占有率很小。随着科技水平的发展,变频器的使用场合越来越多,用户对变频器的要求也越来越高,变频器的功能也越齐全,越实用。 二、变频调速器的应用 变频调速技术已广泛应用于石油、化工、纺织、轻工、机械和造纸等行业,是企业技术改造和产品更新换代的理想设备。以下分别从变频器的使用目的、频率控制方式以及切换方式等几个方面来阐述变频调速的应用情况。     

电流源变频调速及其应用

上海电机厂在上海铁道学院的协助下,研制了50KVA电流源变频装置,1985年4月通过了局级单位的技术鉴定,经工业性运行试验考核,质量和性能均达到预期效果。兹将该变频调速装置的原理框图、特性、节能效益以及装置和电机的配套问题介绍如下: 一、系统简介 电流源变频调速装置由整流器、滤波器和逆变器等三个部分组成,工频电网的交流电经整流器和滤波器变成电压可调的直流电,再通过逆变器变为频率可调的交流电,供异步电动     

脱硫系统增压风机电机变频改造技术分析

通过分析燃煤电厂脱硫系统增压风机的运行特性,找出静叶可调式风机的最佳运行工作点;通过分析三相异步电动机的转速与频率成正比关系,得出采用变频器进行无级调速,调速范围宽且转速变化曲线平滑.介绍了阜阳华润600 MW超临界火电厂对脱硫系统增压风机电机实施变频改造的理论分析和技术改造经验,叙述了对增压风机电机进行变频改造后,脱...     

Equivalent circuit representation of a vortex-induced vibration-based energy harvester using a semi-empirical lumped parameter approach

Small-scale wind energy harvesting from vortex-induced vibrations (VIV) has been introduced in recent years as a renewable power source for microelectronics and wireless sensors. Previous studies have focused on modeling and optimizing the VIV-based piezoelectric energy harvester (VIVPEH) structures and simplified the complicated interface circuits as pure resistors with an alternating current (AC) output. In practice, an AC output is required to be transformed into a direct current (DC) followed by further regulations before being used for real applications. Incorporating the rectification and regulation, traditional theoretical and numerical models will become extremely cumbersome and even impossible. To address this issue, this work proposes an equivalent circuit model (ECM) for a typical VIVPEH. The Scanlan-Ehsan aerodynamic force model is employed to describe the fluid-structure interaction. Wind tunnel experiments are carried out to validate the derived model. The performances of the VIVPEH with AC and DC interface circuits are subsequently analyzed and compared to understand the influences of these circuits on the operational wind speed bandwidth, power output, vibration amplitude, and electrical damping.     

直流微电网微电源接口分析与控制策略设计

多数分布式电源发出的电能需要通过整流逆变后接入交流微电网,增加了电力电子器件的使用,降低了能量转换效率。介绍了更适合直流微电源和高频交流微电源接入的直流微电网拓扑结构,分析了交流微电源、直流微电源、储能装置与直流微电网间的电力电子接口,设计了以上接口的控制器,提出了整个直流微电网的控制策略。在Matlab／Simulink中建立上述直流微电网仿真模型,仿真结果表明,所建立的电力电子接口的正确性和所提出的控制策略的有效性。     

A new DC-link converter for induction motor drives

In this paper, a new DC link power converter is proposed for induction motor drives. It consists of a three-phase adjustable AC/DC power converter as a pre-stage, a three-active-switch power converter to simplify the conventional six-active-switch inverter and eliminate the lock-out time circuit and an adaptive DC-link voltage controller to achieve the optimal DC voltage and minimize the switching frequency of the three-active-switch power converter. The simple rotor-flux-oriented control can also be implemented easily using the proposed power converter to achieve high performance. Finally a prototype circuit is constructed and some experimental results are presented for demonstration     

一种四端口能量路由器的协同控制策略研究

针对研究的四端口能量路由器,首先分析能量路由器拓扑结构,根据能量路由器的功能需求提出各端口的控制方法。电网单元端口为T型三电平拓扑结构,采用电流闭环矢量控制实现直流母线的稳压控制;交流源单元端口为VSR拓扑结构,采用PQ控制实现交流源单元功率的灵活调节;光伏单元端口为Boost电路,采用最大功率点追踪（MPPT）和直流母线恒压控制（CVC）相结合的控制策略;储能单元端口为级联Buck-Boost电路,采用恒流控制。由此,提出一种四端口的协同控制策略,根据能量路由器接入的分布式能源与储能单元荷电状态（SOC）划分能量路由器的工作模态,再通过直流母线电压的波动、储能单元SOC等状态数据实现模态的切换。最后,通过MATLAB软件搭建仿真平台,验证能量路由器模态切换的可行性。     

PWM整流器在变速恒频风力发电系统中的应用

变速恒频风力发电系统要求励磁电源有良好的输入、输出特性和能量双向流动的能力.交-直-交双PWM变频器是理想的励磁电源,而PWM整流器是其中一项关键技术.文章从三相电压型PWM整流器主电路拓扑结构出发,建立了基于三相静止坐标系和两相同步旋转坐标系的数学模型.阐述了电压、电流双闭环控制的基本原理和空间矢量脉宽调制技术在三相PWM整流器中的应用.在Matlab/Simulink环境下,对其进行了单位功率因数整流和逆变的仿真研究.结果证明,该整流器是满足交流励磁需要的理想整流电源.     

AC/DC power conversion interface for self-excited induction generator

A new AC/DC power conversion interface for the self-excited induction generator (SEIG) is proposed here. The proposed AC/DC conversion interface includes an excitation systemand a diode rectifier connected in parallel.The variable frequency AC power generated by the SEIG is converted into DC power by the diode rectifier.The DC power of the diode rectifier can charge a battery set and supply DC loads or be further converted into fixed-frequency AC power by an inverter for AC loads.The DC voltage is expected to be regulated in the above applications.The excitation system supplies an exciting reactive current to maintain the amplitude of the SEIG output voltage to be a constant value. Moreover, it can also serve as an active power filter to suppress the harmonic current generated by the diode rectifier. The excitation system is composed of an AC power capacitor and a power converter connected in series. The AC power capacitor is adapted to provide a basic reactive power, and it can also reduce the voltage rating and the capacity of the power converter. The salient point of the proposed AC/DC power conversion interface is that the capacity of the power converter in the AC/DC power conversion interface can be minimised, and the power loss of the AC/DC power conversion interface can also be reduced. A prototype is developed and tested to verify the performance of the proposed AC/DC power conversion interface.     

Temperature-dependent properties of organic-on-inorganic Ag/p-CuPc/n-GaAs/Ag photoelectric cell

A thin organic film of copper phthalocynanine (CuPc) as p-type semiconductor was deposited by vacuum evaporation on n-type GaAs single-crystal semiconductor substrate. Electrical, photoelectrical and frequency response of the cells were investigated at a temperature interval of 23–74 °C. Photoelectric characteristics were measured under semiconductor laser beam injection illumination (), while frequency response was investigated by laser beam modulated with a frequency range of 10 Hz–100 kHz.It was observed that cell parameters such as rectification ratio; threshold voltage; nonlinearity coefficient; junction, shunt and series resistances; diode ideality factor and power conversion efficiency were temperature-dependent. Moreover, experimental data showed that open-circuit voltage decreases with an increase in frequency whereas short-circuit AC current falls with frequency but remains constant as a function of temperature. It was further observed that the short-circuit DC current remained constant with an increase in frequency as well as temperature. Based on the experimental data an equivalent circuit of photoelectric cell was proposed to explain the observed behavior.     

Autonomous micro hydro power plant with induction generator

Autonomous micro hydro power plants (MHPP) are a reliable solution for supplying small power consumers in areas located far from the distribution grid. When an induction generator (IG) is used in such a power plant, voltage and frequency need to be stabilized. This paper presents a single control structure that ensures both the voltage and frequency regulation of an isolated induction generator (IG). The control structure consists in a voltage source inverter (VSI) with a dump load (DL) circuit on its DC side. The VSI operates at constant frequency, thus stabilizing the IG frequency also. For voltage regulation two cascaded regulators are used, which have as reference the line voltage and the VSI DC voltage, respectively. Simulations and experiments are carried out in order to investigate the reliability of such configuration when supplying static and dynamic loads.     

含VSC换流器的交直流配网潮流算法

随着电力电子技术的发展和应用,直流技术得到了快速发展,交直流网络亦广泛应用于电力系统。建立含电压源型换流器(VSC)交直流配电系统,探讨了VSC换流器损耗及其控制方式,并针对交替迭代法和统一迭代法两种算法的不足,提出了改进交替迭代算法,该算法通过调整交流、直流子系统界限的重新界定,避免了潮流计算迭代的交替,从而大大减少潮流计算量。最后通过改进IEEE 13节点配电系统验证了所提算法的正确性和高效性。     

Flexible control strategy for HVDC transmission system adapted to intermittent new energy delivery

Intermittent new energy delivery requires increasing the flexibility of ultra-high voltage direct current (DC) power adjustment. Based on a converter steady-state model and a DC power model, the control angle constraints of a converter valve are relaxed for power regulation. In this paper, a flexible DC power control method based on a fixed tap changer position is proposed. The initial ratio of the converter transformer is optimized. The effects of the fixed-tap changer position control on the control angle, reactive power compensation, and commutation failure are analyzed. The new control method allows a DC system to operate at a large angle and increase the additional reactive power loss while improving the commutation security margin. Steady-state and electromagnetic transient simulations in the CIGRE test system verify the validity of the method proposed in this paper and the correctness of the analysis conclusions.