MPPT工作流程及算法和硬件的選擇
時間：2018-04-24 來源：未知
在(zai)(zai)光(guang)伏(fu)控制(zhi)系統中，因為日照、溫(wen)(wen)度等條件的變化(hua)(hua)，光(guang)伏(fu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的輸(shu)出功(gong)率也是(shi)在(zai)(zai)不(bu)斷(duan)變化(hua)(hua)的，為保證使(shi)得光(guang)伏(fu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的輸(shu)出功(gong)率保持(chi)在(zai)(zai)最大(da)(da)點，需(xu)要調整光(guang)伏(fu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(日照強度發生變化(hua)(hua)時，短路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)流變化(hua)(hua)大(da)(da)，開(kai)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)受影(ying)響小(xiao);環(huan)境溫(wen)(wen)度發生變化(hua)(hua)時，短路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)流受影(ying)響小(xiao)，開(kai)路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)變化(hua)(hua)大(da)(da))。另外，光(guang)伏(fu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)和電(dian)(dian)(dian)(dian)(dian)(dian)流也和負載有很大(da)(da)關系，負載大(da)(da)，輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)大(da)(da)，輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)流小(xiao);負載小(xiao)，輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)小(xiao)，輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)流大(da)(da)。光(guang)伏(fu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的MPP中的電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)是(shi)指光(guang)伏(fu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)。
MPPT算(suan)法選擇
目前，MPPT算法有開(kai)路(lu)電壓比率(離線(xian))、短路(lu)電流比率(離線(xian))、觀察調節(jie)(在線(xian))、極限追蹤控制法(在線(xian))。
開(kai)路(lu)電(dian)壓(ya)(ya)比(bi)率(lv)(lv)(lv)(lv)法(fa)(fa)(fa)——這(zhe)可(ke)以說(shuo)是(shi)非常經(jing)典也(ye)相(xiang)(xiang)(xiang)當(dang)古老的(de)方法(fa)(fa)(fa)了，又名(ming)“固定(ding)(ding)(ding)(ding)(ding)電(dian)壓(ya)(ya)法(fa)(fa)(fa)”。簡單來說(shuo)，算(suan)法(fa)(fa)(fa)基于(yu)最(zui)大(da)功(gong)率(lv)(lv)(lv)(lv)電(dian)壓(ya)(ya)和(he)開(kai)路(lu)電(dian)壓(ya)(ya)的(de)線性關系式 ，系數(shu) 取(qu)值(zhi)由設(she)計(ji)師(shi)決(jue)定(ding)(ding)(ding)(ding)(ding)，一(yi)般(ban)介于(yu)0.71到0.78之間，大(da)多數(shu)設(she)定(ding)(ding)(ding)(ding)(ding)為0.76。MPPT在(zai)追(zhui)蹤(zong)時(shi)，首先開(kai)路(lu)DC端來測量(liang)開(kai)路(lu)電(dian)壓(ya)(ya)，然后通(tong)過算(suan)法(fa)(fa)(fa)來計(ji)算(suan)最(zui)大(da)功(gong)率(lv)(lv)(lv)(lv)電(dian)壓(ya)(ya)并且定(ding)(ding)(ding)(ding)(ding)位最(zui)大(da)功(gong)率(lv)(lv)(lv)(lv)點(dian)(dian)(dian)(dian)。MPPT會保持在(zai)該功(gong)率(lv)(lv)(lv)(lv)點(dian)(dian)(dian)(dian)一(yi)段時(shi)間，然后重復開(kai)路(lu)測算(suan)并且重新(xin)定(ding)(ding)(ding)(ding)(ding)位。固定(ding)(ding)(ding)(ding)(ding)電(dian)壓(ya)(ya)法(fa)(fa)(fa)的(de)最(zui)大(da)優點(dian)(dian)(dian)(dian)就是(shi)制作(zuo)便宜并且應用簡單。相(xiang)(xiang)(xiang)反，缺點(dian)(dian)(dian)(dian)也(ye)十分(fen)明(ming)顯：精確值(zhi)和(he)追(zhui)蹤(zong)效率(lv)(lv)(lv)(lv)較低。盡(jin)管(guan)固定(ding)(ding)(ding)(ding)(ding)電(dian)壓(ya)(ya)法(fa)(fa)(fa)被稱之為“追(zhui)蹤(zong)”算(suan)法(fa)(fa)(fa)，事(shi)實上它依然是(shi)在(zai)整個(ge)工作(zuo)循環中的(de)一(yi)個(ge)計(ji)算(suan)設(she)定(ding)(ding)(ding)(ding)(ding)值(zhi)而(er)非即時(shi)追(zhui)蹤(zong)值(zhi)。其次(ci)(ci)(ci)，此方法(fa)(fa)(fa)完全且單純依賴于(yu)組串的(de)開(kai)路(lu)電(dian)壓(ya)(ya)值(zhi)而(er)放棄了對于(yu)工作(zuo)電(dian)流(liu)的(de)追(zhui)蹤(zong)。當(dang)局部(bu)陰(yin)影出現在(zai)陣列時(shi)，實際最(zui)大(da)功(gong)率(lv)(lv)(lv)(lv)點(dian)(dian)(dian)(dian)和(he)MPPT設(she)定(ding)(ding)(ding)(ding)(ding)功(gong)率(lv)(lv)(lv)(lv)點(dian)(dian)(dian)(dian)就會出現相(xiang)(xiang)(xiang)當(dang)大(da)的(de)偏(pian)差(cha)，偏(pian)差(cha)范圍取(qu)決(jue)于(yu)陰(yin)影遮(zhe)蓋(gai)程度。最(zui)后，每次(ci)(ci)(ci)機器進行(xing)開(kai)路(lu)電(dian)壓(ya)(ya)測量(liang)時(shi)，太(tai)陽(yang)能(neng)(neng)系統是(shi)無法(fa)(fa)(fa)輸出功(gong)率(lv)(lv)(lv)(lv)的(de)，隨著時(shi)間和(he)次(ci)(ci)(ci)數(shu)累(lei)計(ji)此算(suan)法(fa)(fa)(fa)會造成一(yi)定(ding)(ding)(ding)(ding)(ding)量(liang)的(de)能(neng)(neng)量(liang)流(liu)失(shi)。總體來說(shuo)，差(cha)評(ping)。
短(duan)(duan)路(lu)電(dian)(dian)流比(bi)率法(fa)(fa)——和(he)固定電(dian)(dian)壓法(fa)(fa)的(de)算法(fa)(fa)相似，可以(yi)表述為(wei) ， 是一個(ge)(ge)變量系數，通(tong)常(chang)變化范圍在(zai)0.78至(zhi)0.92。和(he)固定電(dian)(dian)壓法(fa)(fa)不同的(de)是，短(duan)(duan)路(lu)電(dian)(dian)流比(bi)率法(fa)(fa)要(yao)(yao)求在(zai)轉(zhuan)換(huan)器(qi)內(nei)置一個(ge)(ge)高頻開關(guan)來測量短(duan)(duan)路(lu)電(dian)(dian)流。比(bi)較(jiao)推(tui)薦的(de)是在(zai)組串和(he)DC link的(de)電(dian)(dian)容之間(jian)安裝一個(ge)(ge)FET(field-effect transistor)。由于(yu)電(dian)(dian)流受(shou)到光照強度(du)的(de)影響非常(chang)大，通(tong)常(chang)機器(qi)還(huan)需要(yao)(yao)一個(ge)(ge)DSP(digital signal processor)來保證IV曲線的(de)全掃描和(he)數據的(de)準確度(du)。這也讓短(duan)(duan)路(lu)電(dian)(dian)流比(bi)率法(fa)(fa)設計更加復雜且難(nan)以(yi)應用。差(cha)評(ping)。
觀(guan)察調節(jie)法(fa)——站在巨人肩頭發展(zhan)出(chu)來的(de)算法(fa)你(ni)敢不(bu)服?目(mu)前(qian)，P&O依(yi)然(ran)應(ying)用在世界各大(da)(da)主流(liu)的(de)逆變器中也是最廣泛的(de)被應(ying)用的(de)算法(fa)，沒有(you)之一(yi)(yi)。相比(bi)于(yu)(yu)ESC，P&O可(ke)(ke)以(yi)在更(geng)短的(de)時(shi)間內(nei)追(zhui)(zhui)(zhui)蹤(zong)(zong)時(shi)觸碰更(geng)大(da)(da)的(de)區域，掃描更(geng)多地(di)數(shu)據(ju)。這進一(yi)(yi)步提高了P&O的(de)追(zhui)(zhui)(zhui)蹤(zong)(zong)效率和(he)準(zhun)確率。由(you)于(yu)(yu)它在短時(shi)間內(nei)可(ke)(ke)以(yi)處(chu)理大(da)(da)量的(de)數(shu)據(ju)，這也一(yi)(yi)定(ding)程度(du)抵(di)制了突變光照強(qiang)度(du)對(dui)于(yu)(yu)追(zhui)(zhui)(zhui)蹤(zong)(zong)精確度(du)的(de)影響。缺點(dian)的(de)話，由(you)于(yu)(yu)它掃描的(de)范(fan)圍較大(da)(da)，會(hui)一(yi)(yi)定(ding)程度(du)的(de)導致輸出(chu)功率缺乏(fa)穩定(ding)性，但(dan)是抖動程度(du)基(ji)本(ben)都在±4%以(yi)內(nei)。所(suo)以(yi)我還要(yao)給它32個(ge)贊!P&O還有(you)一(yi)(yi)個(ge)姐(jie)妹版(ban)本(ben)，還是“爬山”邏輯，但(dan)是并入了“試錯”法(fa)(trial and error)。處(chu)理器會(hui)根據(ju)下一(yi)(yi)刻追(zhui)(zhui)(zhui)蹤(zong)(zong)點(dian)的(de)移(yi)動趨勢(shi)，比(bi)較功率的(de)正增(zeng)量或(huo)負增(zeng)量。如果功率持續增(zeng)加，處(chu)理器將會(hui)繼(ji)續同方向移(yi)動追(zhui)(zhui)(zhui)蹤(zong)(zong)點(dian)，不(bu)停比(bi)較直到功率達到峰值。
極(ji)限追(zhui)蹤控制法(fa)(fa)——該(gai)算法(fa)(fa)第一(yi)次(ci)提出在19世(shi)紀(ji)20年代，也是目前全球最流(liu)行的(de)“觀測調(diao)節(jie)法(fa)(fa)”(Perturb and Observe)的(de)前身。算法(fa)(fa)的(de)創新點是引入了向量(liang)(liang)(liang)在P-V曲(qu)線中。處理器根據電壓的(de)增(zeng)量(liang)(liang)(liang)或(huo)減量(liang)(liang)(liang)來比較(jiao)對應的(de)功(gong)率增(zeng)減量(liang)(liang)(liang)，進而確(que)定(ding)追(zhui)蹤功(gong)率點的(de)移動方向。具體(ti)判定(ding)方法(fa)(fa)請參照圖二，一(yi)目了然。
ESC算法(fa)(fa)的(de)(de)巨(ju)大(da)成功(gong)(gong)(gong)(gong)是(shi)相比于(yu)(yu)之前的(de)(de)固定(ding)電壓法(fa)(fa),通過漸進向(xiang)(xiang)(xiang)量引入(ru)了(le)(le)(le)“爬山(shan)法(fa)(fa)”的(de)(de)概念(nian)，進而開啟了(le)(le)(le)動(dong)態追(zhui)蹤的(de)(de)算法(fa)(fa)。ESC極大(da)地(di)拓寬了(le)(le)(le)MPPT對(dui)于(yu)(yu)DC端輸(shu)入(ru)能量的(de)(de)捕捉，顯(xian)著地(di)提高了(le)(le)(le)追(zhui)蹤效率(lv)(lv)(lv)(lv)(lv)。由于(yu)(yu)ESC對(dui)于(yu)(yu)后(hou)代MPPT算法(fa)(fa)的(de)(de)影響(xiang)深遠，導致它的(de)(de)短板也一(yi)并被(bei)繼(ji)承下(xia)來(lai)并至今“禍害”眾多(duo)(duo)一(yi)線品牌的(de)(de)逆(ni)變(bian)(bian)器(qi)。ESC對(dui)于(yu)(yu)陡然(ran)變(bian)(bian)化(hua)的(de)(de)光(guang)照(zhao)反應強烈，舉個通俗(su)例子，MPPT正(zheng)專注的(de)(de)比較著功(gong)(gong)(gong)(gong)率(lv)(lv)(lv)(lv)(lv)和電壓的(de)(de)變(bian)(bian)量，“嗯，正(zheng)向(xiang)(xiang)(xiang)移(yi)動(dong)的(de)(de)電壓同步伴隨(sui)著功(gong)(gong)(gong)(gong)率(lv)(lv)(lv)(lv)(lv)的(de)(de)增加，明(ming)顯(xian)最大(da)功(gong)(gong)(gong)(gong)率(lv)(lv)(lv)(lv)(lv)點(dian)還在(zai)正(zheng)向(xiang)(xiang)(xiang)(右(you)(you)邊)，那我繼(ji)續向(xiang)(xiang)(xiang)右(you)(you)移(yi)動(dong)”。此(ci)時云(yun)層擋住了(le)(le)(le)陽光(guang)，稍(shao)稍(shao)影響(xiang)了(le)(le)(le)輸(shu)入(ru)的(de)(de)直流功(gong)(gong)(gong)(gong)率(lv)(lv)(lv)(lv)(lv)，使之略(lve)微下(xia)降，“慢(man)著!正(zheng)向(xiang)(xiang)(xiang)移(yi)動(dong)的(de)(de)電壓竟然(ran)導致功(gong)(gong)(gong)(gong)率(lv)(lv)(lv)(lv)(lv)減小了(le)(le)(le)!我肯定(ding)錯過了(le)(le)(le)最大(da)功(gong)(gong)(gong)(gong)率(lv)(lv)(lv)(lv)(lv)點(dian)，快掉頭!”于(yu)(yu)是(shi)，追(zhui)蹤點(dian)就離(li)它的(de)(de)歸宿越(yue)來(lai)越(yue)遠的(de)(de)地(di)方飄去。。。我在(zai)實(shi)驗室(shi)模擬測(ce)試時，親(qin)眼看到最多(duo)(duo)達到70%左右(you)(you)的(de)(de)偏差。基于(yu)(yu)ESC這(zhe)種一(yi)級(first stage)追(zhui)蹤的(de)(de)設計(ji)理(li)念(nian)，這(zhe)種現象，無解。但是(shi)欣(xin)賞(shang)它對(dui)后(hou)世(shi)的(de)(de)正(zheng)面(mian)影響(xiang)以及(ji)理(li)念(nian)創新，還是(shi)好評!
綜(zong)合考慮，MPPT的算法采用極限追蹤控(kong)制法來進行軟件實現，即采集PN側電(dian)壓(ya)(ya)、流向PN側的電(dian)流數據(ju)，計算 、 和 ，判(pan)斷(duan) 與 的關系， 大于 ，此(ci)時應(ying)按 減(jian)小PN側的目標電(dian)壓(ya)(ya);若 小于 ，此(ci)時應(ying)按 增加PN側的目標電(dian)壓(ya)(ya)。
MPPT硬(ying)件選擇
MPPT的(de)實(shi)現(xian)(xian)是(shi)(shi)通(tong)過(guo)(guo)調(diao)節光(guang)(guang)(guang)伏電(dian)池(chi)輸出(chu)電(dian)壓(ya)來實(shi)現(xian)(xian)的(de)，若光(guang)(guang)(guang)伏電(dian)池(chi)輸出(chu)電(dian)壓(ya)直接(jie)連接(jie)到(dao)DC/AC的(de)PN側，那么光(guang)(guang)(guang)伏電(dian)池(chi)輸出(chu)電(dian)壓(ya)波動就會(hui)直接(jie)影響(xiang)PN側電(dian)壓(ya)，最好是(shi)(shi)在光(guang)(guang)(guang)伏電(dian)池(chi)和DC/AC之間加一個(ge)中間環節，通(tong)過(guo)(guo)這(zhe)個(ge)中間環節來調(diao)整(zheng)輸入電(dian)壓(ya)，保(bao)持輸出(chu)電(dian)壓(ya)穩定(ding)，增加或(huo)減(jian)小輸出(chu)電(dian)流。這(zhe)個(ge)功能一般(ban)(ban)有(you)BUCK、BOOST、BUCK-BOOST、CUK電(dian)路(lu)(lu)和開關電(dian)路(lu)(lu)可(ke)以選擇(ze)，但BUCK電(dian)路(lu)(lu)是(shi)(shi)連續向負載(zai)供電(dian)、間接(jie)從(cong)電(dian)源取(qu)電(dian);BOOST電(dian)路(lu)(lu)時間接(jie)向負載(zai)供電(dian)、連續從(cong)電(dian)源取(qu)電(dian)，為保(bao)證光(guang)(guang)(guang)伏電(dian)池(chi)板的(de)發電(dian)效率得到(dao)較好使用(yong)，一般(ban)(ban)選擇(ze)BOOST電(dian)路(lu)(lu)來實(shi)現(xian)(xian)MPPT。
選(xuan)擇(ze)BOOST電路來實現MPPT算法，其(qi)結構拓撲(pu)如(ru)下(xia)圖。
考(kao)慮成(cheng)本問(wen)題，再加(jia)上(shang)光伏電(dian)池輸出(chu)的所有(you)最大功率(lv)點(dian)對應的輸出(chu)電(dian)壓差(cha)別不是(shi)很大，MPPT不使用DC/DC電(dian)路來實現(xian)，在現(xian)有(you)的DC/AC平臺上(shang)進行(xing)實現(xian)。
MPPT程序實現(xian)
變流器的工(gong)作流程為：
啟動——預充電——PN側抬壓——接入光伏電池——輸出(MPPT)。
可以確定，MPPT的(de)作(zuo)用(yong)是(shi)在電壓(ya)環上作(zuo)用(yong)，并且是(shi)在變(bian)流(liu)器進入工作(zuo)狀態后開(kai)始工作(zuo)。
采(cai)用(yong)現有的DC/AC平臺來實現MPPT，存在(zai)兩個(ge)問(wen)題(ti)(ti)：控制步長(chang)(時間間隔)問(wen)題(ti)(ti)、擾動步長(chang) 問(wen)題(ti)(ti)、判(pan)斷(duan)精度問(wen)題(ti)(ti)。
控制步長(chang)(chang)問題(ti)——PN側(ce)電(dian)壓在(zai)MPPT過程中會產生一(yi)定的波動，但因為(wei)對(dui)于光伏電(dian)池來說(shuo)(結合下(xia)面兩圖)，其最大功率點(dian)對(dui)應的電(dian)壓大致都在(zai)一(yi)個(ge)不大的范圍(wei)內，并且(qie)都接近(jin)開路電(dian)壓，所以(yi)，對(dui)于在(zai)DC/AC上實現(xian)MPPT，要考慮(lv)多長(chang)(chang)時間對(dui)PN側(ce)目(mu)標(biao)電(dian)壓進行一(yi)次更新。目(mu)前(qian)State Manage函數是(shi)0.1ms進入一(yi)次，可以(yi)考慮(lv)MPPT的控制步長(chang)(chang)為(wei)0.2~0.5ms，步長(chang)(chang)暫定為(wei)0.3ms。
相同光照、不同溫度
相同溫度(du)，不同光(guang)照
擾動步(bu)長(chang)(chang)問題——考慮在(zai)變(bian)(bian)流(liu)器進(jin)(jin)入工(gong)作狀態后，其PN側電(dian)壓為(wei)較穩定(ding)的值(zhi)，即使光(guang)(guang)照強度(du)、環(huan)境溫度(du)發生(sheng)變(bian)(bian)化，光(guang)(guang)伏電(dian)池的最大功(gong)率點(dian)(dian)電(dian)壓的變(bian)(bian)動范圍不(bu)會很大。根據其采集回來的PN側電(dian)壓和光(guang)(guang)伏電(dian)池輸出電(dian)流(liu)，并計算和前一(yi)時刻(ke)的功(gong)率差值(zhi) ，根據電(dian)導增量法進(jin)(jin)行(xing)判(pan)斷，然后在(zai)目(mu)標(biao)跟蹤電(dian)壓上增加或減小一(yi)定(ding)的步(bu)長(chang)(chang) 。因(yin)為(wei)在(zai)光(guang)(guang)伏電(dian)池開(kai)始工(gong)作后，PN側電(dian)壓不(bu)是從0開(kai)始的，而是在(zai)光(guang)(guang)伏電(dian)池最大功(gong)率點(dian)(dian)對(dui)應電(dian)壓附近，所(suo)以 的值(zhi)會比(bi)較小，K值(zhi)的設置通(tong)過調(diao)試程序(xu)獲(huo)得，K暫定(ding)為(wei)5。
判(pan)斷精度問題——由導納法的(de)工(gong)作流程圖(tu)(tu)(下圖(tu)(tu))可以知道，在(zai)流程中存在(zai) 、 與0的(de)關系的(de)判(pan)斷，程序中總是會存在(zai)誤(wu)差(cha)，并且檢測中也會存在(zai)，如果以0為判(pan)斷準值，考慮(lv)實際應(ying)用中的(de)誤(wu)差(cha)因(yin)素，用一個小的(de)閥(fa)(fa)值來替代0。閥(fa)(fa)值暫定(ding)為0.1V和(he)0.1A。
MPPT算(suan)法C程(cheng)序實現
#include "16F877.h"
#device ADC = 8 // 一個(ge)8位寄存器ADC模式
#fuses HS, NOWDT, PUT, NOPROTECT, BROWNOUT, NODEBUG, NOLVP // High-Speed 20MHz, No Watchdog, No Protection, Brownout Protection,
#use delay(clock=20000000) // 20MHz Crystal
//int is defined as 8-bit unsigned integer using CCS compiler
void main (void)
{
signed int direction;
int delta;
int pwm;
int upperbound;
int lowerbound;
float power;
float powerold;
float voltage;
float voltagedrop;
float voltagedifference;
float currentma;
float measuredvoltage;
float measuredvoltagedrop;
direction = 1; // Set initial direction to positive
delta = 1; // Amount by which to adjust the PWM - 7-bit resolution so duty step of 2%
pwm = 26; // Initial position of the PWM - 50% Duty Cycle with 7-bit resolution.
upperbound = 49; // Upper bound of the PWM %
lowerbound = 1; // Lower bound of the PWM %
power = 0; // Initial Value of Power
setup_adc(ADC_CLOCK_DIV_32); // ADC clock
setup_adc_ports(ALL_ANALOG); // Set all inputs to analog
output_low(PIN_C1); // Set CCP1 output low
setup_ccp1(ccp_pwm); // setup pin CCP1 (RC2) to do PWM
setup_timer_2(T2_DIV_BY_1,12,1); // 384.615kHz
while (1)
{
//delay_ms(1000) // Wait 1 Second
set_adc_channel(0); // Select RA0
//delay_ms(20); // Wait to Read ADC
measuredvoltage = read_adc(); // Read the voltage input from ADC channel 0
set_adc_channel(1); // Select RA1
//delay_ms(20); // Wait to Read ADC
measuredvoltagedrop = read_adc(); // Read the Voltage dropped across the R from ADC channel 1
voltage = measuredvoltage/51; // Measured Voltage is 51 steps per Volt at a Reference Voltage of 5V
voltagedrop = measuredvoltagedrop/51;
voltagedifference = voltage - voltagedrop;
currentma = voltagedifference; // Calculating Current using 1K Resistance
powerold = power; // Calculate the Power from the inputs
power = voltage * currentma;
pwm = pwm + direction*delta; // Adjust Pulse Width Modulation Value by Delta value
if (power < powerold) // If at top of curve, change direction
{
direction = -direction;
continue;
}
if (pwm >; upperbound) // If at maximum PWM, Stop here
{
pwm = upperbound;
continue;
}
if (pwm < lowerbound) // If at mi
nimum PWM, Stop here
{
pwm = lowerbound;
continue;
}
set_pwm1_duty(pwm); // Set PWM Mark-Space Radio to approx 50%
}
}
