1引言

　　現(xiàn)有兩種無(wú)觸點(diǎn)補(bǔ)償式交流穩(wěn)壓電源" title="穩(wěn)壓電源">穩(wěn)壓電源在取代三相柱式交流電力穩(wěn)壓器。一種是變壓器補(bǔ)償式穩(wěn)壓器，其原理是用多個(gè)補(bǔ)償變壓器組合，通過(guò)“多全橋”變換電路，切換補(bǔ)償變壓器的初級(jí)頭、尾連接方式進(jìn)行補(bǔ)償，去掉了機(jī)械傳動(dòng)和觸點(diǎn)，提高了壽命和動(dòng)態(tài)性能。補(bǔ)償是有級(jí)的，而且所需的補(bǔ)償變壓器和切換開(kāi)關(guān)較多，電路相對(duì)復(fù)雜，補(bǔ)償精度低。另一種是PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" 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title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" 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title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" 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title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM" title="PWM">PWM開(kāi)關(guān)式交流穩(wěn)壓器，其原理是從輸入側(cè)取得工頻交流電壓，經(jīng)過(guò)整流、正激高頻PWM變換、相位跟蹤和轉(zhuǎn)換產(chǎn)生交流補(bǔ)償電壓進(jìn)行補(bǔ)償，補(bǔ)償是無(wú)級(jí)的，補(bǔ)償精度高，響應(yīng)速度快。但電路復(fù)雜，還需要一個(gè)固定的逆補(bǔ)償變壓器，不易實(shí)現(xiàn)大功率應(yīng)用。我曾介紹過(guò)的PWM斬波器式交流穩(wěn)壓電源很好地克服了上述缺點(diǎn)，是一種很有發(fā)展前途的交流穩(wěn)壓技術(shù)，但其存在著只能穩(wěn)壓，不能消除市電電壓中諧波成分的缺點(diǎn)。為了擴(kuò)大交流穩(wěn)壓電源的功能，我們又開(kāi)發(fā)研制了利用PWM高頻逆變器" title="逆變器">逆變器進(jìn)行補(bǔ)償?shù)亩喙δ芙涣鞣€(wěn)壓電源，這種穩(wěn)壓電源具有用戶電力綜合調(diào)節(jié)器（Custompower)的功能，使穩(wěn)壓電源的性能又上了一個(gè)臺(tái)階。

　　2 采用PWM高頻逆變器的補(bǔ)償式交流穩(wěn)壓電源

　　采用PWM高頻逆變器的補(bǔ)償式交流穩(wěn)壓電源的原理電路如圖1所示。其中補(bǔ)償電壓uco由單相全橋逆變器產(chǎn)生（也可以采用半橋式或推挽式逆變器），逆變器采用高頻SPWM調(diào)制。單相全橋逆變器的輸出電壓uab通過(guò)輸出變壓器Tr，把電壓uab變成補(bǔ)償電壓uco在Tr的次級(jí)輸出。Tr的次級(jí)串聯(lián)在主電路中以對(duì)市電電壓的變化進(jìn)行補(bǔ)償，保持輸出電壓uo穩(wěn)定不變。圖中LFCF為低通濾波器，以濾掉逆變器輸出電壓uab中的高次諧波。變壓器Tr次級(jí)繞組的電阻和漏感以及市電電源內(nèi)阻共同組成線路阻抗Z，則當(dāng)負(fù)載變化時(shí)在Z上產(chǎn)生的壓降會(huì)使輸出電壓隨之變化。ur為用正弦電壓發(fā)生器和鎖相環(huán)產(chǎn)生的標(biāo)準(zhǔn)參考電壓，鎖相環(huán)是使ur在相位上與市電電壓us同步。用瞬時(shí)值usZisur作為SPWM全橋逆變器控制電路中的調(diào)制電壓，控制電路的原理框圖如圖2所示。按此圖的高頻SPWM調(diào)制原理，當(dāng)用（usZisur）作為正弦調(diào)制波時(shí)，就可以使逆變器的輸出電壓與市電電壓的變化和負(fù)載電壓的變化成比例。

圖1采用逆變器補(bǔ)償?shù)慕涣鞣€(wěn)壓電路

圖2 控制電路原理框圖

　　21逆變器輸出電壓的諧波分析

　　假定逆變器的直流電源電壓為Ud，載波三角波的電壓幅值為Uc，則調(diào)制比M的值為：M=（1）

　　式中：Us、Is、Ur為市電電壓us，市電電流is和基準(zhǔn)參考電壓ur的有效值。載波比：N=，fc為三角波頻率，fs為市電電壓頻率。

　　SPWM波形如圖3所示。由此圖可知，逆變器輸出電壓uab的雙重付里葉級(jí)數(shù)表示為：

uab=ua－ub=MUdsinωt＋·cosmπ·sin〔(mN＋n)ωt〕(2)

圖3參差相位法獲得三階SPWM波

　　因?yàn)樽儔浩鱐r的變比為ξ，故補(bǔ)償電壓uco的表示式為：

uco=ξMUdsinωt＋ξ·cosmπ·sin〔(mN＋n)ωt〕(3)

　　uco的頻譜如圖4所示，可知：載波比N越大，諧波頻率越高，濾波越容易，所需的LFCF的值越小，當(dāng)fc=12.8kHz時(shí)，LF=10mH，CF=2μF，即可將uco中的高次諧波濾掉。

圖4補(bǔ)償電壓uco的頻譜和諧波分量與M的關(guān)系

　　2 考慮線路阻抗Z的補(bǔ)償分析

　　由于逆變器開(kāi)關(guān)管的正向壓降，開(kāi)關(guān)死區(qū)、變壓器Tr初級(jí)繞組的電阻及漏感和交流濾波電感LF的繞組電阻及電感的影響，會(huì)使補(bǔ)償電壓uco的值減小。但這種影響不大，而且是基本固定的，與負(fù)載的大小變化關(guān)系不大，因此可以通過(guò)增大變壓器Tr的變比ξ來(lái)補(bǔ)償。

　　由圖1考慮到線路阻抗Z時(shí)，在us>ur的情況下輸出電壓的方程式為：

uo=us－Zis－uco(4)

　　假定市電電壓中無(wú)諧波，市電輸入功率因數(shù)cosφ=1，則：us=Ussinωt,is=Issinωt，將方程式（3）uco的值以及us、is的值代入式（4）得：

uo=Ussinωt－ZIssinωt－ξMUdsinωt－cosmπ·sin〔(mN＋n)ωt〕(5)

　　用電路中低通濾波器LFCF濾掉uco中的高次諧波時(shí)，則上式變?yōu)椋?/p>

uo=Ussinωt－ZIssinωt－ξMUdsinωt（6）

       將式（1）的M值及ξ=代入式（6），則得：

uo=Ussinωt－ZIssinωt－(Us－ZIs－Ur)·sinωt=Ursinωt

　　圖5所示SPWM高頻逆變器式交流穩(wěn)壓電源有六種工作狀態(tài)：

　　us>ur＋Zis，此時(shí)uco=us－Zis－ur，輸出電壓uo=us－(us－Zis－ur)－Zis=ur

　　us us=ur，此時(shí)uco=－Zis，輸出電壓uo=us－(－Zis)－Zis=ur

　　空載（is=0)us>ur，此時(shí)uco=us－ur，輸出電壓uo=us－(us－ur)=ur

　　空載（is=0)us 空載（is=0)us=ur，此時(shí)uco=0，不補(bǔ)償。

圖5 SPWM高頻逆變器式交流穩(wěn)壓電源有六種工作狀態(tài)

　　從以上分析可知：當(dāng)市電電壓us或負(fù)載發(fā)生變化時(shí)，用瞬時(shí)值（us－ur－Zis)作為正弦調(diào)制電壓的SPWM高頻逆變器的輸出電壓uco完全可以補(bǔ)償輸出電壓uo的變化，保持uo=ur不變。

　　23對(duì)市電電壓中諧波的補(bǔ)償假定市電電壓的數(shù)值不變，但卻含有諧波Usnsinωt，即：

　　us=Us1sinωt＋Usnsinnωt，us1=ur。

　　為了使推導(dǎo)簡(jiǎn)化，令is=0，則調(diào)制波電壓為：

　　us－Zis－ur=us1sinωt＋Usnsinnωt－Ursinωt=Usnsinnωt(7)調(diào)制比：Mn=，則補(bǔ)償電壓為：=ξMnUdsinnωt＋ξ·

cosm″π·sin〔(m″N＋n′)n′ωt〕(8)

　　將us、is、的值代入式（4），用低通濾波器濾去中的更高次的諧波，并將Mn=，ξ=代入中即得：

uo=Us1sinωt＋Usnsinnωt－Usnsinnωt=Us1sinωt=Ursinωt(9)

　　由式（9）可知：當(dāng)市電電壓us中含有諧波時(shí)用瞬時(shí)值(us－ur－Zis)作調(diào)制波的SPWM逆變器的輸出電壓uco即可以補(bǔ)償?shù)魎s中的諧波，尤其是5次以下的低次諧波。

　　此外從物理上看，由于控制電路采用的是市電電壓與純正弦波參考基準(zhǔn)電壓ur的瞬時(shí)值進(jìn)行比較，所得到的瞬時(shí)值之差作為調(diào)制波進(jìn)行控制補(bǔ)償?shù)?，?dāng)市電電壓us是正弦波時(shí)，us>ur時(shí)是負(fù)補(bǔ)償，即us－uco；us2.4逆變器型式與參數(shù)

　　穩(wěn)壓電源中的逆變器，可以用全橋式、半橋式或推挽式，其補(bǔ)償效果基本相同。不用高頻SPWM調(diào)制而改用線性Delta滯環(huán)PWM控制也可以達(dá)到相同的效果。唯一應(yīng)指出的一點(diǎn)是逆變器的直流電源電壓一定要穩(wěn)定，它對(duì)電壓的補(bǔ)償精度有直接影響。變壓器Tr的變比ξ=的值取決于市電電壓的最大變化范圍，市電電壓的最大允許變化范圍為±10％，實(shí)際有的地方可高達(dá)±20％，所以變比ξ一般?。?0～25)％，相應(yīng)補(bǔ)償變壓器Tr的容量應(yīng)取穩(wěn)壓電源標(biāo)稱(chēng)容量的（20～25)％。

　　3三相補(bǔ)償式交流穩(wěn)壓電源

　　三相補(bǔ)償式交流穩(wěn)壓電源的原理電路如圖6所示，它由主電路、控制電路和檢測(cè)電路三部分組成。主電路又由并聯(lián)部分、串聯(lián)部分和直流部分的濾波儲(chǔ)能電容 Cd三部分組成。并聯(lián)部分是由低通濾波器和三相PWM開(kāi)關(guān)整流器組成，開(kāi)關(guān)整流器實(shí)際上就是一個(gè)三相電壓型逆變器，它的主要作用是為串聯(lián)部分的單相補(bǔ)償逆變器提供整流直流電源，保持直流電容Cd上的電壓恒定。直流電容Cd起濾波和儲(chǔ)能作用。采用三相開(kāi)關(guān)整流器的目的有兩個(gè)，一是保持市電輸入功率因數(shù) cosφ=1，并使輸入電流的波形接近正弦，以減小對(duì)市電的污染；二是可以使電能雙向流動(dòng)，使逆變器負(fù)載中的無(wú)功能量可以反饋回市電電源，提高補(bǔ)償器的效率。此外，如果在直流電容Cd上并聯(lián)儲(chǔ)能蓄電池，當(dāng)市電故障停電時(shí)，三相PWM開(kāi)關(guān)整流器轉(zhuǎn)換到逆變狀態(tài)工作，又可以短時(shí)作為在線式UPS使用。如果再附加一部分控制電路，三相電壓型逆變器又可以作為無(wú)功補(bǔ)償器或有源濾波器使用，以濾掉負(fù)載電流中的諧波。串聯(lián)部分是由三個(gè)單相全橋逆變器及其輸出變壓器（亦即補(bǔ)償變壓器）組成，其作用就是對(duì)市電電壓的高低變化、三相不對(duì)稱(chēng)、諧波、閃變等進(jìn)行補(bǔ)償；串聯(lián)部分之所以采用三個(gè)單相逆變器及輸出變壓器，其原因有兩個(gè)，一是由于三相四線制的市電系統(tǒng)所帶的負(fù)載多數(shù)情況下是不對(duì)稱(chēng)的，因此三相電壓也不對(duì)稱(chēng)，必須用互無(wú)聯(lián)系的單相逆變器獨(dú)立進(jìn)行補(bǔ)償。二是也可以提高三相四線制電源的可靠性，萬(wàn)一有一相出現(xiàn)故障另外兩相還可以繼續(xù)供電。三個(gè)單相逆變器也都是可以雙向工作的，當(dāng)市電電壓us等于標(biāo)稱(chēng)基準(zhǔn)電壓時(shí)，三個(gè)單相逆變器由逆變的補(bǔ)償狀態(tài)轉(zhuǎn)換到開(kāi)關(guān)整流狀態(tài)向直流電容Cd或蓄電池供電，以保證并聯(lián)電路的三相電壓型逆變器正常工作。這樣，三相交流穩(wěn)壓電源就變成了用戶電力綜合調(diào)節(jié)器（Custompower)。

圖6三相補(bǔ)償式交流穩(wěn)壓電源原理電路

　　三相補(bǔ)償式穩(wěn)壓電源的工作原理與單相相同，都是通過(guò)檢測(cè)電路將需要補(bǔ)償?shù)母鞣N電壓分量檢測(cè)出來(lái)進(jìn)行補(bǔ)償，以保持輸出電壓為正弦穩(wěn)定的電壓。由于三相四線制系統(tǒng)存在著三相電壓不對(duì)稱(chēng)的問(wèn)題，雖然單相電路使用的正弦瞬時(shí)值比較法也可以采用，但為了能檢測(cè)出三相電壓的不對(duì)稱(chēng)性，采用了基于廣義瞬時(shí)無(wú)功理論的檢測(cè)方法是更合適的，此法可以對(duì)三相四線制電路的非正弦電壓和非對(duì)稱(chēng)電壓進(jìn)行檢測(cè)，能更有效地檢測(cè)出三相電壓不對(duì)稱(chēng)時(shí)的補(bǔ)償值。其原理電路如圖7所示：將檢測(cè)到的電壓信號(hào)經(jīng)過(guò)Park變換，然后通過(guò)低通濾波器濾掉d、q分量中的直流分量，最后再經(jīng)過(guò)Park反變換，即可得到三相需要補(bǔ)償?shù)碾妷骸?/p>

圖7廣義瞬時(shí)無(wú)功理論諧波檢測(cè)原理圖

　　3.1仿真結(jié)果

　　圖8及圖9分別為給定的三相電壓補(bǔ)償前和補(bǔ)償后的仿真波形。由這兩種波形可以看出：補(bǔ)償前的圖8波形的THD分別為15％、1732％、2449％，基波有不對(duì)稱(chēng)現(xiàn)象。補(bǔ)償后的圖9波形的THD下降到3％以內(nèi)，是一組比較理想的正弦波，基波的不對(duì)稱(chēng)現(xiàn)象也基本消除了。

圖8補(bǔ)償前的三相電壓仿真波形

圖9補(bǔ)償后的三相電壓仿真波形

　　3.2實(shí)驗(yàn)結(jié)果

　　為了進(jìn)一步驗(yàn)證補(bǔ)償效果，又進(jìn)行了實(shí)驗(yàn)。實(shí)驗(yàn)參數(shù)為：變壓器變比為1∶4；串聯(lián)部分電路的濾波器參數(shù)為：LF=10mH,CF=2μF；并聯(lián)部分電路的濾波器參數(shù)為：LF=10mH,CF=1μF。串聯(lián)部分及并聯(lián)部分逆變器的開(kāi)關(guān)管為PM50RSK060，開(kāi)關(guān)頻率為12.8kHz，標(biāo)準(zhǔn)電壓有效值為110V（峰值為15556V），頻率為50Hz。圖10及圖11分別為補(bǔ)償前和補(bǔ)償后A相電壓的實(shí)驗(yàn)波形。圖10補(bǔ)償前的電壓幅值為120V（有效值為8485V）下降了2286％，而補(bǔ)償后的圖11的電壓幅值為154V（有效值為109V），下降1％。可見(jiàn)對(duì)電壓的高低變化進(jìn)行了補(bǔ)償，補(bǔ)償精度為1％；THD由補(bǔ)償前的32％下降到補(bǔ)償后的27％。

圖10補(bǔ)償前電壓實(shí)驗(yàn)波形

圖11補(bǔ)償后電壓實(shí)驗(yàn)波形

　　4結(jié)語(yǔ)

　　通過(guò)仿真和實(shí)驗(yàn)表明，采用PWM高頻逆變器的補(bǔ)償式交流穩(wěn)壓電源，既可以補(bǔ)償市電電壓的高低變化，也可以補(bǔ)償諧波和閃變等，對(duì)于三相穩(wěn)壓電源還可以補(bǔ)償三相電壓的不對(duì)稱(chēng)，從而有效地提高了電能質(zhì)量，是一種很有前途的交流穩(wěn)壓電源。

　　適當(dāng)?shù)丶尤胍恍┛刂齐娐?，還可以使其具有無(wú)功補(bǔ)償、有源濾波的作用。在直流電容Cd上并聯(lián)蓄電池以后，還可以當(dāng)短時(shí)在線UPS使用，是一種較好的多功能電能質(zhì)量補(bǔ)償器，具有廣泛的用途，應(yīng)大力發(fā)展，以取代陳舊的交流穩(wěn)壓電源。