太陽能電池板最大功率點跟蹤技術的比較

1、Comparison of Photovoltaic Array Maximum PowerPoint Tracking Techniques光伏陣列最大功率點跟蹤技術的比較Trishan Esram, Student Member, IEEE, and Patrick L. Chapman, Senior Member, IEEEAbstractThe many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed. The techniques are

2、taken from the literature dating back to the earliest methods. It is shown that at least 19 distinct methods have been introduced in the literature, with many variations on implementation. This paper should serve as a convenient reference for future work in PV power generation.摘要：關于光伏陣列最大功率點跟蹤的許多不同技

3、術的討論，著作中的這些方法都可以追溯到最早的方法。結果表明至少有19種方法已經在著作中被介紹，有許多已經實現(xiàn)變形。本文應該對將來的光伏發(fā)電工作提供一個方便的參考。Index TermsMaximum power point tracking (MPPT), photovoltaic (PV).索引詞最大功率點跟蹤，光伏。I. INTRODUCTIONI簡介TRACKING the maximum power point (MPP) of a photovoltaic (PV) array is usually an essential part of a PV system. As such,

4、 many MPP tracking (MPPT) methods have been developed and implemented. The methods vary in complexity, sensors required, convergence speed, cost, range of effectiveness, implementation hardware, popularity, and in other respects. They range from the almost obvious (but not necessarily ineffective) t

5、o the most creative (not necessarily most effective). In fact, so many methods have been developed that it has become difficult to adequately determine which method, newly proposed or existing, is most appropriate for a given PV system.跟蹤光伏陣列的最大功率點通常是光伏系統(tǒng)的主要部分，鑒于此許多最大功率點跟蹤方式已經被開發(fā)和實現(xiàn)。這些方法各不相同，如復雜程度、傳

6、感器需要、收斂速度、花費、范圍的有效性、硬件實現(xiàn)、普及程度以及其他方面。他們幾乎涵蓋了所有的從平淡無奇（但是不一定不起作用）到最具創(chuàng)造性（不一定都有效）。事實上，由于許多的方式已經被開發(fā)，在新提出的或是現(xiàn)存的方法中，對于給定的光伏系統(tǒng)準確的決定最適合方式的變的困難Given the large number of methods for MPPT, a survey of the methods would be very beneficial to researchers and practitioners in PV systems. Fig. 1 shows the total numb

7、er of MPPT papers from our bibliography per year since the earliest MPPT paper we found. The number of papers per year has grown considerably of the last decades and remains strong. However, recent papers have generally had shorter, more cursory literature reviews that largely summarize or repeat th

8、e literature reviews of previous work. This approach tends to repeat what seems to be conventional wisdom that there are only a handful of MPPT techniques, when in fact there are many. This is due to the sheer volume of MPPT literature to review, conflicting with the need for brevity.鑒于大量的方法來研究MPPT，

9、在光伏系統(tǒng)中采用調查的方法對研究人員和實踐者都是非常有益的。圖一給出了自從我們發(fā)現(xiàn)最早MPPT論文以來每年我們文獻目錄中MPPT論文的總數(shù)目，最近幾十年論文的數(shù)量已有了長足的發(fā)展并且發(fā)展仍然很強勁。然而，最近的論文普遍較短，更多粗略的文學評論以致大量的總結或重復前人的總結工作。這種重復方式似乎是傳統(tǒng)的智慧，以至于只有很少的MPPT技術，但事實上有很多。這是由于有大量的公開的MPPT文獻回顧與簡潔的需求相沖突。This survey is a single reference of the great majority of papers and techniques presented on

10、MPPT. We compiled over 90 papers pertaining to different MPPT methods published up to the date of submission of this manuscript. It is not our intention to establish a literal chronology of when various techniques were proposed, since the publication date is not necessarily indicative of when a meth

11、od was actually conceived. As is typical of review papers, we have elected not to reference patents. Papers referencing MPPT methods from previous papers without any modification or improvement have also been omitted. It is possible that one or more papers were unintentionally omitted. We apologize

12、if an important method or improvement was left out.這個調查參考了絕大多數(shù)提出MPPT的論文和技術。我們收集了超過90篇關于MPPT不同方法的論文的手稿提交的日期。我們的意圖不是當不同的技術被提出時建立一個文字年代， 因為出版日期不能表明一種方法是什么時間構思的。作為典型的評論性文章，我們推選不涉及專利。如果論文中所涉及的MPP T的方法來自以前的論文而沒有任何的修改和改善，則論文將被忽略。一篇或更多的論文被無意識的遺漏也是可能的，如果是一種重要的方法或改進被遺漏，我們表示歉意。Manuscript received September 24,

13、 2004; revised September 8, 2005. This work was supported by the National Science Foundation ECS-01-34208. Paper no. TEC-00276-2004. The authors are with the Grainger Center for Electric Machinery and Electromechanics, University of Illinois at Urbana-Champaign, Urbana, IL 61801- 2918 USA (e-mail: e

14、; ).Digital Object Identifier 10.1109/TEC.2006.Fig.1. Total number of MPPT papers per year, since 1968.This manuscript steps through a wide variety of methods with a brief discussion and categorization of each. We have avoided discussing slight modifications of existin

15、g methods as distinct methods. For example, a method may have been first presented in context of a boost converter, but later on shown with a boost buck converter, otherwise with minimal change. The manuscript concludes with a discussion on the different methods based on their implementation, the se

16、nsors required, their ability to detect multiple local maxima, their costs, and applications they suit. A table that summarizes the major characteristics of the methods is also provided.這份手稿通過各種各樣的方式進行簡要的討論和分類，我們討論將稍加修改已經存在的方法作為獨特的方法認為無效。例如，一種方法第一次已經在boost升壓電路中提出，但之后又在升降壓變換電路中提出，除此之外，幾乎沒有變化。手稿以實現(xiàn)不同方

17、式結束，根據(jù)他們的實現(xiàn)、所需要的傳感器、檢測最大值的能力、成本和適合的應用程序。我們提供了一個總結主要方法特征的表格。II. PROBLEM OVERVIEWII.問題概述Fig. 2 shows the characteristic power curve for a PV array. The problem considered by MPPT techniques is to automatically find the voltage VMPP or current IMPP at which a PV array should operate to obtain the maxim

18、um power output PMPP under a given temperature and irradiance. It is noted that under partial shading conditions, in some cases it is possible to have multiple local maxima, but overall there is still only one true MPP. Most techniques respond to changes in both irradiance and temperature, but some

19、are specifically more useful if temperature is approximately constant. Most techniques would automatically respond to changes in the array due to aging, though some are open-loop and would require periodic fine-tuning. In our context, the array will typically be connected to a power converter that c

20、an vary the current coming from the PV array.圖二給出了光伏陣列的功率曲線。MPPT技術所要考慮的問題是自動的發(fā)現(xiàn)光伏陣列中電壓最大功率點或電流最大功率點，使該光伏陣列在給定的溫度和光照下得到最大功率輸出。有人指出，在局部遮擋的情況下，有些時候他可能有多個極大值，但總體來說他只有一個真正的最大功率點。大部分技術應對溫度和光照強度的變換，但是假如溫度接近穩(wěn)定一些特別的方法將更加有用。大部分技術能自動的對陣列中由老化引起的變化做出響應，盡管一些是開環(huán)控制需要周期性的微調。本文中，陣列和變流器相連，該變流器可以改變電流來自光伏陣列。III. MPPT TE

21、CHNIQUESIII.MPPT技術We introduce the different MPPT techniques below in an arbitrary order. 我們以任意順序介紹不同的MPPT技術。A. Hill Climbing/P&OAmong all the papers we gathered, much focus has been on hill climbing 18, and perturb and observe (P&O) 925 methods. Hill climbing involves a perturbation in the duty rat

22、io of the power converter, and P&O a perturbation in the operating voltage of the PV array. In the case of a PV array connected to a power converter, perturbing the duty ratio of power converter perturbs the PV array current and consequently perturbs the PV array voltage. Hill climbing and P&O metho

23、ds are different ways to envision the same fundamental method.A 爬坡/擾動與觀察在我們收集的所有論文中， 大多數(shù)集中在爬坡方式1-8,和擾動與觀察方式9-25。在變流器的一個工作周期內爬坡方式包含一個擾動，而擾動與觀察方式是包含光伏陣列工作電壓的一個擾動。就光伏陣列與變流器相連而說，變流器工作周期的擾動擾亂光伏陣列的電流，進而影響光伏陣列的電壓。爬坡方式和擾動與觀察方式是兩種不同的方式來設想相同的基本模型。From Fig. 2, it can be seen that incrementing (decrementing) th

24、e voltage increases (decreases) the power when operating on the left of the MPP and decreases (increases) the power when on the right of the MPP. Therefore, if there is an increase in power, the subsequent perturbation should be kept the same to reach the MPP and if there is a decrease in power, the

25、 perturbation should be reversed. This algorithm is summarized in Table I. In 24, it is shown that the algorithm also works when instantaneous (instead of average) PV array voltage and current are used, as long as sampling occurs only once in each switching cycle.Fig. 2. Characteristic PV array powe

26、r curve.TABLE ISUMMARY OF HILL CLIMBING AND P&O ALGORITHM從圖二可以看出，隨著電壓的增長（下降）當作用于最大功率點左側時功率增長（下降），當作用與最大功率點右側時功率下降（增長）。因此，如果功率增長，則隨之而來的擾動將保持相同達到最大功率點；如果功率下降，擾動就會相反。這種算法的總結在表I。在24中，給出當使用瞬時（而不是平均值）光伏陣列電壓和電流時這種算法仍然使用， 只要在一個開關周期內采樣一次即可。圖 2.光伏陣列功率曲線表 I爬坡算法和擾動與觀察方法摘要The process is repeated periodically unt

27、il the MPP is reached. The system then oscillates about the MPP. The oscillation can be minimized by reducing the perturbation step size. However, a smaller perturbation size slows down the MPPT. A solution to this conflicting situation is to have a variable perturbation size that gets smaller towar

28、ds the MPP as shown in 8, 12, 15, and 22. In 24, fuzzy logic control is used to optimize the magnitude of the next perturbation. In 20, a two-stage algorithm is proposed that offers faster tracking in the first stage and finer tracking in the second stage. On the other hand, 21 bypasses the first st

29、age by using a nonlinear equation to estimate an initial operating point close to the MPP. 此過程要反復進行，直到達到最大功率點。然后系統(tǒng)在最大功率點附近震蕩。在一定程度上可以通過減小擾動步長來減小振動。然而一個幅值小的擾動可以降低達到最大功率點的速度。這種矛盾的一種解決辦法是有一個大小可變的擾動以更小的步長向最大功率點移動，在81215和22中給出，其中在24中，模糊邏輯控制使下一個擾動量達到最優(yōu)。在20中提出兩步運算法則，第一步采用快速跟蹤，第二步采用最有追蹤。另一方面，21通過運用非線性方程估計最初

30、的工作點接近最大功率點來避開第一步。Hill climbing and P&O methods can fail under rapidly changing atmospheric conditions as illustrated in Fig. 3. Starting from an operating point A, if atmospheric conditions stay approximately constant, a perturbation V in the PV voltage V will bring the operating point to B and the

31、 perturbation will be reversed due to a decrease in power. However, if the irradiance increases and shifts the power curve from P1 to P2 within one sampling period, the operating point will move from A to C. This represents an increase in power and the perturbation is kept the same. Consequently, th

32、e operating point diverges from the MPP and will keep diverging if the irradiance steadily increases. To ensure that the MPP is tracked even under sudden changes in irradiance, 18 uses a three-point weight comparison P&O method that compares the actual power point to two preceding ones before a deci

33、sion is made about the perturbation sign. In 22, the sampling rate is optimized, while in 24, simply a high sampling rate is used. In 8, toggling has been done between the traditional hill climbing algorithm and a modified adaptive hill climbing mechanism to prevent deviation from the MPP.Fig. 3. Di

34、vergence of hill climbing/P&O from MPP as shown in 9.爬坡方式和擾動與觀察方式在快速變化的大氣環(huán)境中不起作用，如圖3.從工作點A開始，如果大氣條件保持基本不變，光伏陣列電壓V的擾動V將工作點變?yōu)锽，同時由于功率的下降干擾將被反相?？墒?，如果光照強度增加使一個周期內的功率曲線由P1變?yōu)?P2，工作點將由A點移至C點。這表示功率的增長和擾動保持相同。因此，如果光照強度穩(wěn)定的增加，工作點就會偏離最大功率點并且保持這種偏離狀態(tài)。為了保證光強突然變化時最大功率點仍然能夠被追蹤，18應用三點比較P&O重要法，該方法是在擾動信號確定之前將先前的兩個點和真實

35、的功率點作比較。在22中，采樣頻率是最優(yōu)的，而在24中僅僅采用高頻率的采樣信號。在8中，將傳統(tǒng)的爬坡模式算法和改進的自適應的機制相結合，以防止與最大功率點的偏差。圖 3. 9中給出的爬坡和P&O模式最大功率點的差異D. Fractional Short-Circuit CurrentFractional results from the fact that, under varying atmospheric conditions, is approximately linearly related to the of the PV array as shown in 40, 42, and

36、4548 （6）where is a proportionality constant. Just like in the fractional technique, has to be determined according to the PV array in use. The constant is generally found to be between 0.78 and 0.92.D.定電流跟蹤法定電流跟蹤法源于這個事實，在多變的大氣條件下，光伏陣列的與近似的呈線性關系，在論文40，42，4548 給出 （6）其中為正比例常數(shù)。正如定電壓跟蹤技術中，由使用的光伏陣列確定。常數(shù)一般

37、在0.78-0.92間取值。Measuring during operation is problematic. An additional switch usually has to be added to the power converter to periodically short the PV array so that can be measured using a current sensor. This increases the number of components and cost. In 48, a boost converter is used, where th

38、e switch in the converter itself can be used to short the PV array. 在運行期間測量是有問題的。因此，在變流器上附加一個開關周期性的短接光伏陣列通過電流傳感器實現(xiàn)對的測量。這就增加了元器件的數(shù)量和成本。在48中，運用一個升壓變換器，變換器上的開關可以用來短接光伏陣列。Power output is not only reduced when finding but also because the MPP is never perfectly matched as suggested by (6). In 46, a way o

39、f compensating is proposed such that the MPP is better tracked while atmospheric conditions change. To guarantee proper MPPT in the presence of multiple local maxima, 45 periodically sweeps the PV array voltage from open-circuit to short-circuit to update. Most of the PV systems using fractional in

40、the literature use a DSP. In 48, a simple current feedback control loop is used instead 功率輸出的降低的原因不僅僅由于尋找而且從提出的公式（6）中可以看到，MPP從來沒有很好地匹配。在46中，提出一種補償?shù)姆椒ㄒ灾劣谠诖髿猸h(huán)境變化時最大功率點能很好地被跟蹤。在存在多個局部最大點時為了保證完全的最大功率跟蹤,45周期性的快速改變開路到短路的電壓來更新。文獻中大多數(shù)運用部分的光伏系統(tǒng)應用DSP。在48中用一個簡單的電流控制回路來代替。E. Fuzzy Logic ControlMicrocontrollers

41、have made using fuzzy logic control 4958 popular for MPPT over the last decade. As mentioned in 57, fuzzy logic controllers have the advantages of working with imprecise inputs, not needing an accurate mathematical model, and handling nonlinearityE模糊邏輯控制 在過去的十年間，微控制器使模糊控制49-58在最大功率跟蹤方面應用變得流行。如57，模糊控

42、制在處理不確定輸入和非線性問題方面處于有利條件，而他不需要一個精確地數(shù)學模型。Fuzzy logic control generally consists of three stages: fuzzification, rule base table lookup, and defuzzification. During fuzzification, numerical input variables are converted into linguistic variables based on a membership function similar to Fig. 5. In this

43、 case, five fuzzy levels are used: NB (negative big), NS (negative small), ZE (zero), PS (positive small), and PB (positive big). In 54 and 55, seven fuzzy levels are used, probably for more accuracy. In Fig. 5, a and b are based on the range of values of the numerical variable. The membership funct

44、ion is sometimes made less symmetric to give more importance to specific fuzzy levels as in 49, 53, 57, and 58.Fig. 5. Membership function for inputs and output of fuzzy logic controller模糊控制一般包括三個階段：模糊化、查找規(guī)則庫表、去模糊化。在模糊化過程中，數(shù)字輸入變量被轉化成基于隸屬度函數(shù)的語言變量，如圖5.如此看來就有五個模糊子集：NB（負方向大的偏差）、NS（負方向小的偏差）、ZE（零）、PS（正方向小

45、的偏差）、PB（正方向大的偏差）。在54和55中，應用了七個模糊子集，可能更精確。在圖5中，a和b的值決定于變量值的范圍。隸屬度函數(shù)有時候是不對稱的來更加重視特殊的模糊子集，像49、53、57、58。圖5 輸入的隸屬度函數(shù)和輸出的模糊控制The inputs to a MPPT fuzzy logic controller are usually an errorand a change in error. The user has the flexibility of choosing how to computeand. Sincevanishes at the MPP, 58 uses

46、the approximation （7）And (8)MPPT模糊控制器的輸入通常是一個錯誤和錯誤變化。用戶可以靈活的選擇如何計算和。鑒于在最大功率點為零，58應用近似值： （7）和 (8)Equivalently, (4) is very often used. Once and are calculated and converted to the linguistic variables, the fuzzy logic controller output, which is typically a change in duty ratio of the power converter

47、, can be looked up in a rule base table such as Table II 50.TABLE IIFUZZY RULE BASE TABLE AS SHOWN IN 50相同的，公式（4）經常用，一旦和被計算出來和轉化為語言變量，模糊控制器輸出，該輸出是典型的一個變流器占空比的變化且能在規(guī)則庫表中被查出，如表II50.表II50中給出的模糊規(guī)則庫表The linguistic variables assigned tofor the different combinations of and are based on the power converter being used and al