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智能化小區LED路燈光伏充電器

 在各大中型城市中一大批智能化小區、花園別墅、智能大型綜合體育設施等建筑拔地而起, 客觀上要求有與其相配套的高效能環保的照明設備的出現。LED 是發光二極管的統稱, 它工作在低電壓、小電流的狀態下, 所以具有發熱量小、功耗低的顯著特征。而且其使用方面, 可以根據不同場合的使用要求方便地進行多顆LED 的組合。所以在LED 技術基礎上發展起來的LED 光伏路燈是一種新型環保且具有高光效的節能設備, 具有安全抗震、使用方便、費用低、壽命長、節約能源、無污染等優點, 在許多領域可代替現在廣泛使用的白熾燈、日光燈等光效相對較低的照明設備。其工作原理就是通過太陽電池光伏陣列將太陽能轉化為電能, 給蓄電池進行充電, LED 驅動器則通過蓄電池為其提供工作電源, 完成對LED 燈的驅動和保護功能。其優點是克服了目前市場上所使用的其它照明設備普遍存在的耗能大、光效差、不穩定、蓄電池使用壽命短等多種弊端。大功率LED 路燈充電器設計的一個關鍵的部分就是光伏充電器的設計問(wen)題, 因為光(guang)(guang)伏(fu)充(chong)電(dian)器(qi)(qi)不僅完成了(le)(le)把(ba)太陽能轉換(huan)成電(dian)能的重(zhong)任, 而且還對蓄電(dian)池提供了(le)(le)智(zhi)能充(chong)電(dian)管理, 因此(ci)光(guang)(guang)伏(fu)充(chong)電(dian)器(qi)(qi)的性能直接決定(ding)了(le)(le)太陽能能量(liang)利用(yong)的效率和系統(tong)使(shi)用(yong)的壽命。本文從原(yuan)理、控制策(ce)略和實際應(ying)用(yong)等幾個(ge)方面介紹一(yi)種光(guang)(guang)伏(fu)充(chong)電(dian)器(qi)(qi)及其控制系統(tong)的設計思想。

  1 系統構成

  1.1 LED 的工(gong)作特性(xing)

  發(fa)光二極管LED(Light Emitting Diode)的工(gong)作原理(li)是在半導體(ti)p-n 結上加一正向電壓, 從而(er)使其電子(zi)(zi)與空穴(xue)復合(即結區變窄), 這種復合是電子(zi)(zi)從高能級的導帶釋放(fang)能量回到價帶與空穴(xue)復合, 其釋放(fang)的能量以光子(zi)(zi)的形式出現, 即發(fa)光。

  根據半(ban)導(dao)體物(wu)理中的(de)(de)(de)公式: λ=1.24/Eg式中: Eg 為半(ban)導(dao)體材料(liao)導(dao)帶與(yu)價(jia)帶之間的(de)(de)(de)禁帶寬度, λ為波(bo)長(chang)(chang)。從式中可以(yi)(yi)看(kan)出, 對于不同材料(liao)的(de)(de)(de)半(ban)導(dao)體來說, 由于它們(men)的(de)(de)(de)Eg 不同, 因此它們(men)的(de)(de)(de)波(bo)長(chang)(chang)# 也不一樣, 所以(yi)(yi)發光(guang)(guang)(guang)(guang)(guang)的(de)(de)(de)顏(yan)色不同。顯然, 一般LED 多為單顏(yan)色光(guang)(guang)(guang)(guang)(guang), 如紅(hong)光(guang)(guang)(guang)(guang)(guang)、綠光(guang)(guang)(guang)(guang)(guang)、黃光(guang)(guang)(guang)(guang)(guang)、藍(lan)光(guang)(guang)(guang)(guang)(guang)等。所謂白光(guang)(guang)(guang)(guang)(guang)是(shi)多種(zhong)顏(yan)色的(de)(de)(de)光(guang)(guang)(guang)(guang)(guang)混(hun)合(he)而成, 以(yi)(yi)人類眼睛所能見到的(de)(de)(de)白光(guang)(guang)(guang)(guang)(guang)形式至少必須兩種(zhong)以(yi)(yi)上的(de)(de)(de)光(guang)(guang)(guang)(guang)(guang)混(hun)合(he), 一般有下列兩種(zhong)混(hun)合(he)方式: 二波(bo)長(chang)(chang)光(guang)(guang)(guang)(guang)(guang)―――藍(lan)光(guang)(guang)(guang)(guang)(guang)與(yu)黃光(guang)(guang)(guang)(guang)(guang)混(hun)合(he); 三波(bo)長(chang)(chang)光(guang)(guang)(guang)(guang)(guang)―――紅(hong)光(guang)(guang)(guang)(guang)(guang)、綠光(guang)(guang)(guang)(guang)(guang)與(yu)藍(lan)光(guang)(guang)(guang)(guang)(guang)混(hun)合(he)。目前已經(jing)商(shang)品化的(de)(de)(de)白光(guang)(guang)(guang)(guang)(guang)LED 產(chan)品多為二波(bo)段藍(lan)光(guang)(guang)(guang)(guang)(guang)單晶(jing)片(pian)(pian)加上YAG 黃色熒光(guang)(guang)(guang)(guang)(guang)粉(fen); 三波(bo)長(chang)(chang)光(guang)(guang)(guang)(guang)(guang)以(yi)(yi)無機紫外線光(guang)(guang)(guang)(guang)(guang)晶(jing)片(pian)(pian)加R、G、B 三顏(yan)色熒光(guang)(guang)(guang)(guang)(guang)粉(fen)。此外, 有機單層三波(bo)長(chang)(chang)型白光(guang)(guang)(guang)(guang)(guang)LED 也有成本低、制(zhi)作容易等優點。

  1.2 太陽電(dian)池(chi)的工(gong)作(zuo)特性

  圖1、圖2 分別給出了太陽電(dian)(dian)(dian)池(chi)溫度(du)在(zai)25 ℃時(shi), 工作(zuo)電(dian)(dian)(dian)壓(ya)、電(dian)(dian)(dian)流和日照(zhao)( W/m2) 的(de)關系曲線及太陽電(dian)(dian)(dian)池(chi)的(de)輸出功率和日照(zhao)、電(dian)(dian)(dian)壓(ya)之間(jian)的(de)曲線。


  從圖(tu)1 的(de)(de)(de)I/U 關系(xi)可(ke)以看出(chu)(chu)(chu), 太(tai)陽電(dian)池陣(zhen)列既非(fei)恒壓(ya)(ya)源(yuan),也非(fei)恒流源(yuan), 而是一(yi)種非(fei)線性直流電(dian)源(yuan), 電(dian)池輸出(chu)(chu)(chu)電(dian)流在(zai)大(da)部分(fen)(fen)工作(zuo)電(dian)壓(ya)(ya)范圍內相當(dang)恒定, 最(zui)(zui)終在(zai)一(yi)個(ge)足夠高的(de)(de)(de)電(dian)壓(ya)(ya)之(zhi)后,電(dian)流迅速下降(jiang)至零。由圖(tu)2 可(ke)知, 太(tai)陽電(dian)池的(de)(de)(de)工作(zuo)效(xiao)率(lv)(lv)等于(yu)輸出(chu)(chu)(chu)功(gong)(gong)(gong)率(lv)(lv)與(yu)投射到太(tai)陽電(dian)池面積上(shang)的(de)(de)(de)功(gong)(gong)(gong)率(lv)(lv)之(zhi)比。因此, 為了提高本系(xi)統的(de)(de)(de)工作(zuo)效(xiao)率(lv)(lv), 必須盡可(ke)能地使太(tai)陽電(dian)池在(zai)最(zui)(zui)大(da)功(gong)(gong)(gong)率(lv)(lv)點處工作(zuo), 這(zhe)樣就可(ke)以用功(gong)(gong)(gong)率(lv)(lv)盡可(ke)能小的(de)(de)(de)太(tai)陽電(dian)池獲得(de)最(zui)(zui)大(da)的(de)(de)(de)功(gong)(gong)(gong)率(lv)(lv)輸出(chu)(chu)(chu), 這(zhe)就是進行最(zui)(zui)大(da)功(gong)(gong)(gong)率(lv)(lv)點跟蹤的(de)(de)(de)意義所在(zai)。如圖(tu)1 和(he)圖(tu)2 所示(shi), 圖(tu)中的(de)(de)(de)A、B、C、D、E 點分(fen)(fen)別(bie)對應不同日照時的(de)(de)(de)最(zui)(zui)大(da)功(gong)(gong)(gong)率(lv)(lv)點。

  1.3 鉛酸蓄電池的(de)工作(zuo)特(te)性

  目前在光伏(fu)充(chong)電(dian)器系統中(zhong)大(da)量使用的(de)是鉛酸(suan)蓄電(dian)池(chi), 它的(de)工作(zuo)原理是依(yi)靠鉛酸(suan)正(zheng)極(ji)(ji)的(de)活(huo)性物質二氧化(hua)鉛( PbO2) 和(he)負極(ji)(ji)的(de)活(huo)性物質海綿狀鉛( Pb) 與電(dian)解(jie)液硫(liu)(liu)酸(suan)( H2SO4) 進行化(hua)學反應生成(cheng)硫(liu)(liu)酸(suan)鉛( PbSO4) , 在此工作(zuo)過程中(zhong)將(jiang)引(yin)起硫(liu)(liu)酸(suan)( H2SO4) 的(de)減少(shao), 而且在正(zheng)極(ji)(ji)板(ban)上不斷生成(cheng)水(shui)( H2O) , 從而引(yin)起電(dian)解(jie)液的(de)密度降(jiang)低。在充(chong)電(dian)期間, 正(zheng)極(ji)(ji)極(ji)(ji)板(ban)上的(de)硫(liu)(liu)酸(suan)鉛( PbSO4) 氧化(hua)成(cheng)了(le)二氧化(hua)鉛( PbO2) , 此時負極(ji)(ji)極(ji)(ji)板(ban)上的(de)硫(liu)(liu)酸(suan)鉛( PbSO4) 還原成(cheng)鉛( Pb) , 同時生成(cheng)硫(liu)(liu)酸(suan)( H2SO4) , 耗(hao)去(qu)了(le)蓄電(dian)池(chi)中(zhong)的(de)水(shui)( H2O) , 使電(dian)池(chi)中(zhong)電(dian)解(jie)液的(de)密度上升, 完成(cheng)充(chong)電(dian)過程。

  2 系統的工作原理

  2.1 系統的(de)主控制芯片介(jie)紹

  充電器(qi)系統的硬(ying)件(jian)框圖(tu)如(ru)圖(tu)3 所(suo)示。


  主控(kong)芯(xin)(xin)片(pian)(pian)采(cai)用Microchip 公司的(de)(de)(de)PIC16F874, 它(ta)采(cai)用RISC 指令(ling)系統, 哈佛總線結構, 低功耗(hao), 高速度。內部(bu)集成了(le)ADC、SPI 和(he)Flash 程(cheng)序存儲器等模塊, 具(ju)有10 位A/ D 轉換、PWM 輸出、LCD 驅動(dong)等功能(neng), 此外它(ta)還帶有128 個(ge)字節的(de)(de)(de)E2PROM 存儲器, 能(neng)方(fang)便寫入調整量(liang)以(yi)備后用。PIC16F874通過SPI 接口(kou)可(ke)以(yi)實(shi)現(xian)與(yu)CAN 控(kong)制器MCP2510 的(de)(de)(de)無縫連(lian)接, 且同時同步串(chuan)行模塊( SSP) 為(wei)以(yi)后與(yu)工控(kong)機聯網奠定了(le)基礎。PIC16F874 的(de)(de)(de)I/O 資(zi)源(yuan)豐富, 共有A、B、C、D、E 五個(ge)I/O口(kou), 每個(ge)I/O 口(kou)除了(le)基本(ben)用途外還有一些特殊功能(neng)。豐富的(de)(de)(de)資(zi)源(yuan)和(he)強大的(de)(de)(de)功能(neng), 使(shi)之十分適合于作為(wei)控(kong)制系統的(de)(de)(de)控(kong)制核心芯(xin)(xin)片(pian)(pian)。

  2.2 系統的工作過程(cheng)分析

  充電器系(xi)統(tong)的控制框圖如圖4 所(suo)示。


  由(you)圖4 可以(yi)看出(chu), 在蓄(xu)(xu)電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)階段, 控制(zhi)回路電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)環僅(jin)由(you)太(tai)(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)構成。此時(shi), 電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)環的(de)輸(shu)(shu)出(chu)為(wei)電(dian)(dian)(dian)(dian)(dian)流(liu)環的(de)給(gei)定(ding),通(tong)過檢測主電(dian)(dian)(dian)(dian)(dian)路中蓄(xu)(xu)電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)與給(gei)定(ding)電(dian)(dian)(dian)(dian)(dian)流(liu)相比較(jiao)來改變SG3525 的(de)輸(shu)(shu)出(chu)脈沖寬度(du), 使太(tai)(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)跟(gen)蹤給(gei)定(ding)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。由(you)圖1 可知(zhi), 當(dang)太(tai)(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)下降, 在穩(wen)態時(shi), 太(tai)(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)等(deng)于給(gei)定(ding)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya), 電(dian)(dian)(dian)(dian)(dian)流(liu)環的(de)給(gei)定(ding)亦為(wei)穩(wen)定(ding)值, 蓄(xu)(xu)電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)等(deng)于給(gei)定(ding)電(dian)(dian)(dian)(dian)(dian)流(liu); 反之(zhi), 當(dang)太(tai)(tai)陽(yang)(yang)電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)小于給(gei)定(ding)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)時(shi),SG3525

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