低压通用变频(pin)输(shu)出(chu)电(dian)压为380～650V，输(shu)出(chu)功率为0.75～400kW，工作频(pin)率为0～400Hz，它的(de)主电(dian)路都(dou)采用交—直—交电(dian)路。其控制方式经历了以(yi)下四(si)代。

       1U/f=C的正弦脉(mai)宽调制(SPWM)控制方式(shi)：

       其(qi)特(te)点(dian)是控(kong)制电(dian)(dian)(dian)路结构(gou)简单、成本(ben)较低(di)(di)，机械特(te)性(xing)硬(ying)度(du)也(ye)较好，能(neng)够满(man)足一般传动的(de)(de)平滑调速(su)要求，已(yi)在(zai)产(chan)业的(de)(de)各(ge)个领域得到(dao)广泛(fan)应用(yong)。但(dan)是，这种(zhong)控(kong)制方式在(zai)低(di)(di)频时，由于输出电(dian)(dian)(dian)压较低(di)(di)，转(zhuan)(zhuan)矩(ju)受定子(zi)电(dian)(dian)(dian)阻压降的(de)(de)影响比较显著(zhu)，使输出最大转(zhuan)(zhuan)矩(ju)减(jian)小。另外，其(qi)机械特(te)性(xing)终(zhong)究没有直流(liu)电(dian)(dian)(dian)动机硬(ying)，动态转(zhuan)(zhuan)矩(ju)能(neng)力和(he)静态调速(su)性(xing)能(neng)都还不尽如人(ren)意，且系统性(xing)能(neng)不高、控(kong)制曲线(xian)会随负载的(de)(de)变化而(er)变化，转(zhuan)(zhuan)矩(ju)响应慢、电(dian)(dian)(dian)机转(zhuan)(zhuan)矩(ju)利用(yong)率(lv)不高，低(di)(di)速(su)时因定子(zi)电(dian)(dian)(dian)阻和(he)逆(ni)变器死区效(xiao)应的(de)(de)存在(zai)而(er)性(xing)能(neng)下降，稳定性(xing)变差等。因此人(ren)们又(you)研究出矢量控(kong)制变频调速(su)。

       电压空间矢量(SVPWM)控制方式：

       它(ta)是以(yi)三相波(bo)形(xing)整体生成(cheng)效果为前提，以(yi)逼近电机气隙的(de)理(li)想(xiang)圆形(xing)旋转(zhuan)磁场轨迹为目的(de)，一次生成(cheng)三相调制(zhi)(zhi)波(bo)形(xing)，以(yi)内切多边形(xing)逼近圆的(de)方式(shi)进(jin)行(xing)控(kong)制(zhi)(zhi)的(de)。经实践使(shi)用后又有(you)所改(gai)进(jin)，即引(yin)入频率补偿(chang)，能消除速度(du)(du)控(kong)制(zhi)(zhi)的(de)误差；通过反馈(kui)估算磁链(lian)幅值，消除低速时定子电阻的(de)影(ying)响(xiang)；将输出电压、电流闭环，以(yi)提高动态的(de)精度(du)(du)和稳定度(du)(du)。但控(kong)制(zhi)(zhi)电路环节较多，且没(mei)有(you)引(yin)入转(zhuan)矩的(de)调节，所以(yi)系统性能没(mei)有(you)得到根本改(gai)善。

 ;      矢量控(kong)制(VC)方(fang)式：

       矢(shi)量(liang)控(kong)制(zhi)(zhi)变(bian)频调速(su)的(de)(de)做法是将(jiang)异(yi)步(bu)电(dian)(dian)(dian)动(dong)(dong)(dong)机(ji)(ji)在三相(xiang)(xiang)坐(zuo)标(biao)系(xi)(xi)下(xia)的(de)(de)定子电(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)Ia、Ib、Ic、通过三相(xiang)(xiang)－二相(xiang)(xiang)变(bian)换(huan)(huan)，等(deng)效(xiao)(xiao)成(cheng)两(liang)(liang)相(xiang)(xiang)静(jing)止坐(zuo)标(biao)系(xi)(xi)下(xia)的(de)(de)交流(liu)(liu)(liu)(liu)(liu)电(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)Ia1Ib1，再(zai)通过按转(zhuan)(zhuan)(zhuan)子磁(ci)(ci)场(chang)定向(xiang)旋(xuan)转(zhuan)(zhuan)(zhuan)变(bian)换(huan)(huan)，等(deng)效(xiao)(xiao)成(cheng)同步(bu)旋(xuan)转(zhuan)(zhuan)(zhuan)坐(zuo)标(biao)系(xi)(xi)下(xia)的(de)(de)直(zhi)(zhi)流(liu)(liu)(liu)(liu)(liu)电(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)Im1、It1(Im1相(xiang)(xiang)当于(yu)直(zhi)(zhi)流(liu)(liu)(liu)(liu)(liu)电(dian)(dian)(dian)动(dong)(dong)(dong)机(ji)(ji)的(de)(de)励磁(ci)(ci)电(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)；It1相(xiang)(xiang)当于(yu)与(yu)转(zhuan)(zhuan)(zhuan)矩(ju)(ju)成(cheng)正(zheng)比的(de)(de)电(dian)(dian)(dian)枢电(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu))，然后模仿(fang)直(zhi)(zhi)流(liu)(liu)(liu)(liu)(liu)电(dian)(dian)(dian)动(dong)(dong)(dong)机(ji)(ji)的(de)(de)控(kong)制(zhi)(zhi)方法，求(qiu)得直(zhi)(zhi)流(liu)(liu)(liu)(liu)(liu)电(dian)(dian)(dian)动(dong)(dong)(dong)机(ji)(ji)的(de)(de)控(kong)制(zhi)(zhi)量(liang)，经过相(xiang)(xiang)应(ying)的(de)(de)坐(zuo)标(biao)反变(bian)换(huan)(huan)，实(shi)(shi)现对异(yi)步(bu)电(dian)(dian)(dian)动(dong)(dong)(dong)机(ji)(ji)的(de)(de)控(kong)制(zhi)(zhi)。其实(shi)(shi)质是将(jiang)交流(liu)(liu)(liu)(liu)(liu)电(dian)(dian)(dian)动(dong)(dong)(dong)机(ji)(ji)等(deng)效(xiao)(xiao)为直(zhi)(zhi)流(liu)(liu)(liu)(liu)(liu)电(dian)(dian)(dian)动(dong)(dong)(dong)机(ji)(ji)，分(fen)别(bie)对速(su)度，磁(ci)(ci)场(chang)两(liang)(liang)个分(fen)量(liang)进行独(du)立控(kong)制(zhi)(zhi)。通过控(kong)制(zhi)(zhi)转(zhuan)(zhuan)(zhuan)子磁(ci)(ci)链，然后分(fen)解定子电(dian)(dian)(dian)流(liu)(liu)(liu)(liu)(liu)而获得转(zhuan)(zhuan)(zhuan)矩(ju)(ju)和(he)磁(ci)(ci)场(chang)两(liang)(liang)个分(fen)量(liang)，经坐(zuo)标(biao)变(bian)换(huan)(huan)，实(shi)(shi)现正(zheng)交或解耦控(kong)制(zhi)(zhi)。矢(shi)量(liang)控(kong)制(zhi)(zhi)方法的(de)(de)提出具有划时代的(de)(de)意义(yi)。然而在实(shi)(shi)际(ji)应(ying)用中，由于(yu)转(zhuan)(zhuan)(zhuan)子磁(ci)(ci)链难(nan)以准确观(guan)测，系(xi)(xi)统特性受电(dian)(dian)(dian)动(dong)(dong)(dong)机(ji)(ji)参数的(de)(de)影响较大，且在等(deng)效(xiao)(xiao)直(zhi)(zhi)流(liu)(liu)(liu)(liu)(liu)电(dian)(dian)(dian)动(dong)(dong)(dong)机(ji)(ji)控(kong)制(zhi)(zhi)过程中所用矢(shi)量(liang)旋(xuan)转(zhuan)(zhuan)(zhuan)变(bian)换(huan)(huan)较复杂，使得实(shi)(shi)际(ji)的(de)(de)控(kong)制(zhi)(zhi)效(xiao)(xiao)果难(nan)以达到理想分(fen)析的(de)(de)结果。

 ;      直接转矩控(kong)制(zhi)(DTC)方式：

       1985年(nian)，德国鲁尔(er)大学(xue)的(de)DePenbrock教(jiao)授首次提出(chu)了直(zhi)接转矩控(kong)制(zhi)(zhi)(zhi)变频(pin)技(ji)术。该技(ji)术在很大程度上(shang)(shang)解决了上(shang)(shang)述(shu)矢量控(kong)制(zhi)(zhi)(zhi)的(de)不足，并以(yi)新颖的(de)控(kong)制(zhi)(zhi)(zhi)思想、简洁明了的(de)系统结构、优良(liang)的(de)动(dong)(dong)(dong)静态性能(neng)得到了迅速发展。目前，该技(ji)术已(yi)成功地应用(yong)在电力(li)机(ji)车牵(qian)引的(de)大功率(lv)交流传(chuan)动(dong)(dong)(dong)上(shang)(shang)。 直(zhi)接转矩控(kong)制(zhi)(zhi)(zhi)直(zhi)接在定(ding)子坐标(biao)系下分析交流电动(dong)(dong)(dong)机(ji)的(de)数学(xue)模(mo)型，控(kong)制(zhi)(zhi)(zhi)电动(dong)(dong)(dong)机(ji)的(de)磁链和转矩。它不需要(yao)将交流电动(dong)(dong)(dong)机(ji)等效为直(zhi)流电动(dong)(dong)(dong)机(ji)，因而(er)省去了矢量旋转变换(huan)中(zhong)的(de)许多复杂计算(suan)；它不需要(yao)模(mo)仿(fang)直(zhi)流电动(dong)(dong)(dong)机(ji)的(de)控(kong)制(zhi)(zhi)(zhi)，也不需要(yao)为解耦而(er)简化交流电动(dong)(dong)(dong)机(ji)的(de)数学(xue)模(mo)型。

       矩阵式交(jiao)—交(jiao)控制方式：

       VVVF变频(pin)、矢量(liang)控制变频(pin)、直(zhi)(zhi)(zhi)(zhi)接(jie)转矩(ju)控制变频(pin)都(dou)是交(jiao)—直(zhi)(zhi)(zhi)(zhi)—交(jiao)变频(pin)中(zhong)的(de)(de)一种。其共同缺点是输(shu)(shu)入(ru)功(gong)(gong)率(lv)因(yin)数(shu)低(di)，谐波电(dian)(dian)(dian)(dian)流大(da)，直(zhi)(zhi)(zhi)(zhi)流电(dian)(dian)(dian)(dian)路需要大(da)的(de)(de)储能(neng)电(dian)(dian)(dian)(dian)容，再生能(neng)量(liang)又不(bu)能(neng)反馈回电(dian)(dian)(dian)(dian)网，即不(bu)能(neng)进行四象(xiang)限运行。为此，矩(ju)阵式交(jiao)—交(jiao)变频(pin)应运而生。由于矩(ju)阵式交(jiao)—交(jiao)变频(pin)省去了中(zhong)间(jian)直(zhi)(zhi)(zhi)(zhi)流环节，从而省去了体积大(da)、价格贵的(de)(de)电(dian)(dian)(dian)(dian)解(jie)电(dian)(dian)(dian)(dian)容。它能(neng)实现(xian)(xian)功(gong)(gong)率(lv)因(yin)数(shu)为l，输(shu)(shu)入(ru)电(dian)(dian)(dian)(dian)流为正弦且能(neng)四象(xiang)限运行，系统的(de)(de)功(gong)(gong)率(lv)密度大(da)。该(gai)技术(shu)目(mu)前虽(sui)尚未成(cheng)熟，但仍吸(xi)引着(zhe)众多的(de)(de)学者深入(ru)研究(jiu)。其实质不(bu)是间(jian)接(jie)的(de)(de)控制电(dian)(dian)(dian)(dian)流、磁链等量(liang)，而是把转矩(ju)直(zhi)(zhi)(zhi)(zhi)接(jie)作(zuo)为被(bei)控制量(liang)来(lai)实现(xian)(xian)的(de)(de)。具体方法是：

       1、控制定(ding)(ding)子磁链引入定(ding)(ding)子磁链观测器，实现无速度传感器方(fang)式；

       2、自(zi)动识别(ID)依(yi)靠精(jing)确的电机数(shu)学模型(xing)，对电机参数(shu)自(zi)动识别；

       3、算出(chu)(chu)实(shi)际值对(dui)应定子阻抗、互(hu)感、磁(ci)饱和因(yin)素、惯量(liang)等算出(chu)(chu)实(shi)际的转矩(ju)、定子磁(ci)链、转子速度进(jin)行实(shi)时控(kong)制；

       4、实现(xian)Band—Band控制按磁(ci)链和转矩的Band—Band控制产生PWM信号，对(dui)逆变器开关状(zhuang)态进行(xing)控制。

       矩阵式交—交变频具(ju)有(you)快速(su)的(de)转矩响应(<2ms)，很高(gao)(gao)的(de)速(su)度(du)精度(du)(±2%，无PG反馈)，高(gao)(gao)转矩精度(du)(<+3%)；同(tong)时还具(ju)有(you)较高(gao)(gao)的(de)起动(dong)转矩及高(gao)(gao)转矩精度(du)，尤(you)其在低速(su)时(包括0速(su)度(du)时)，可输出(chu)150%～200%转矩。

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