CN103513693B - Control method based on single argument current method photovoltaic maximum power tracking control system - Google Patents

Abstract

The invention belongs to field of photovoltaic power generation, it is specifically related to a kind of based on single argument current method photovoltaic maximum power tracking control system and method, the MPPT maximum power point tracking of photovoltaic generating system is realized by controlling the output electric current of photovoltaic battery panel, than controlling, output voltage is the most direct, and have only to detect one variable of output electric current of photovoltaic battery panel, enormously simplify the control process of maximal power tracing, the control mode that this coarse adjustment combines with fine setting accelerates maximal power tracing speed, decrease the power loss caused because of environmental change, substantially improve disturbance quantity problem of left and right concussion near maximum power point in tradition method of perturbation.

Description

Control method based on single argument current method photovoltaic maximum power tracking control system

Technical field:

The invention belongs to field of photovoltaic power generation, be specifically related to a kind of photovoltaic maximum power tracking control system based on single argument current method and method.

Background technology:

In photovoltaic generating system, owing to the output characteristics of photovoltaic cell is affected bigger by intensity of illumination and ambient temperature so that the photoelectric transformation efficiency of photovoltaic generating system is extremely low.MPPT maximum power point tracking (Maximal Power Point Tracking in photovoltaic generating system, MPPT) technology is by controlling the output voltage of photovoltaic battery panel or electric current, make system always work on maximum power point, be efficiently to utilize solar energy, realization optimum output, the effective way improving photovoltaic efficiency and key technology.At present, the maximum power tracking and controlling method of photovoltaic generating system mainly has Voltage Feedback method, Feedback of Power method, disturbance observational method, increment conductance method, straight-line approximation method, actual measurement method etc., wherein conventional method is disturbance observational method, but disturbance observational method is to follow the tracks of maximum power point by output voltage and the power of constantly change photovoltaic battery panel, therefore after reaching near maximum power point, disturbance quantity will near maximum power point not failure of oscillation swing, this will result in energy loss and makes the energy conversion efficiency of system reduce.Therefore, find a kind of efficient, stable maximum power tracking and controlling method and become the important technology difficult problem that big-and-middle-sized field of photovoltaic power generation is urgently to be resolved hurrily.

Summary of the invention

Goal of the invention:

The present invention provides a kind of photovoltaic maximum power tracking control system based on single argument current method and method, its objective is to solve the problems such as relatively low, the less stable of photoelectric transformation efficiency existing for conventional method.

Technical scheme:

Based on single argument current method photovoltaic maximum power tracking control system, it is characterized in that: this system includes photovoltaic battery panel, photovoltaic battery panel is connected with Switching Power Supply, connecting valve power supply is controlled by current control unit, Switching Power Supply is connected with DC/DC power inverter again, output voltage control unit control to connect DC/DC power inverter.

A kind of control method based on single argument current method photovoltaic maximum power tracking control system as mentioned above, it is characterized in that: maximum power tracking and controlling method uses one of following two control method based on single argument current method, i.e. uses single argument current disturbing tracing or single argument conic section extreme value following method.

Based on single argument current method (I_pv) maximal power tracing control basic thought be: photovoltaic battery panel output P_pvMaximum power point and current control unit output P_BuckDutycycle corresponding to maximum power point identical, therefore, obtain P according to calculating formula (5)_BuckDutycycle d that maximum power point is corresponding_{pv_m}, then the dutycycle controlling Switching Power Supply is d_{pv_m}, and then reach to follow the tracks of P_pvThe purpose of maximum power point, thus realize maximal power tracing；

$P_{Buck}=\frac{I_{pv}}{d_{pv}}=P_{Buck}\left(I_{pv}\right)---\left(5\right).$

To dutycycle d_pvBounds be defined, if d_{pv_min}(minimum edge dividing value) < d_pv<d_{pv_max}(maximum boundary value), when dutycycle d_pvOutside the bounds limited, i.e. d_pv<d_{pv_min}Or d_pv>d_{pv_max}Time, then without comparing output, first by dutycycle d_pvAdjust to restriction, limit dutycycle d_pvThe purpose of bounds is to reduce number of comparisons, accelerates tracking velocity；Work as d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv, the dutycycle of subsequent time is d_pv(k+1)=d_pv(k)+Δd_pv；Work as d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv, the dutycycle of subsequent time is d_pv(k+1)=d_pv(k)-Δd_pv。

Employing single argument current disturbing tracing:

By the initial value d of dutycycle_{pv_0}It is set to its minimum edge dividing value d_{pv_min}, incrementally increase dutycycle d_pv, and ensure d_pvAt the bounds [d limited_{pv_min},d_{pv_max}In], at a time, dutycycle is d_pvK (), the output electric current of detection photovoltaic battery panel is I_pvK (), the output of calculating current control unit is P_BuckK (), changes dutycycle d at subsequent time_pv, make d_pv(k+1)=d_pv(k)+Δd_pv, export electric current I_pvWith output P_BuckAll changing, the output electric current detecting photovoltaic battery panel the most again is designated as I_pv(k+1), the output of calculating current control unit is designated as P_Buck(k+1), before and after comparing disturbance, output P_Buck(k) and P_Buck(k+1) between and dutycycle d_pv(k) and d_pv(k+1) magnitude relationship between determines subsequent time dutycycle d_pvAdjustment direction, be summarized as follows:

If P_Buck(k+1)>P_Buck(k), d_pv(k+1)>d_pvK (), illustrates d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv；d_pv(k+1)<d_pvK (), illustrates d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv；

If P_Buck(k+1)<P_Buck(k), d_pv(k+1)>d_pvK (), illustrates d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv；d_pv(k+1)<d_pvK (), illustrates d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv；

If P_Buck(k+1)=P_BuckK (), illustrates d_pv=d_{pv_m}, then dutycycle d is kept_pvConstant；

Constantly repeat said process, make the output P of current control unit_BuckTo the Long-term change trend increased, thus realize maximal power tracing；

Single argument current disturbing tracing is (to compare P based on two discriminants_Buck(k)、P_Buck(k+1) size and d_pv(k)、d_pv(k+1) size), by constantly adjusting dutycycle d_pvChange the output electric current I of photovoltaic battery panel_pv, and then change the output P of current control unit_Buck, make P_BuckTo the direction change increased, it is finally reached the purpose following the tracks of maximum power point.

Single argument conic section extreme value following method to realize step as follows:

(1) in dutycycle d_pvBounds [d_{pv_min},d_{pv_max}Three values, d is taken in]_{pv_min}、d_{pv_int}、d_{pv_max}, wherein d_{pv_int}For d_{pv_min}With d_{pv_max}Between a certain value, and detect that the photovoltaic battery panel 1 that these three dutyfactor value is corresponding respectively exports electric current I_{pv_min}、I_{pv_int}、I_{pv_max}；

(2) above three dutyfactor value d is calculated according to formula (5)_{pv_min}、d_{pv_int}、d_{pv_max}The most corresponding current control unit (2) output P_{Buck_min}、P_{Buck_int}、P_{Buck_max}, it is hereby achieved that three coordinate points (d_{pv_min},P_{Buck_min})、(d_{pv_int},P_{Buck_int})、(d_{pv_max},P_{Buck_max}), as shown in Fig. 7 (A)；

(3) according to above three coordinate points, utilizing Lagrange multinomial can obtain the quadratic curve equation of correspondence, as shown in formula (6), the equation can be regarded as now photovoltaic power conversion diagram equation；

$\begin{array}{c}{\stackrel{\&OverBar;}{P}}_{Buck}=\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\min })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })}{(d_{pv\_\mathrm{int}}-d_{pv\_\min })(d_{pv\_\mathrm{int}}-d_{pv\_\max })}{P}_{Buck\_\mathrm{int}}\\ +\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\min })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })}{(d_{pv\_\max }-d_{pv\_\min })(d_{pv\_\max }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\max }\\ +\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\mathrm{int}})}{(d_{pv\_\min }-d_{pv\_\max })(d_{pv\_\min }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\min }\end{array}---\left(6\right)$

In order to solve the extreme value of quadratic curve equation formula (6), formula (6) is differentiated, and makes it be equal to zero, as shown in formula (7)；

$\begin{array}{c}\frac{d{\stackrel{\&OverBar;}{P}}_{Buck}}{d{\stackrel{\&OverBar;}{d}}_{pv}}=\left(\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\min }+d_{pv\_\max })\&rsqb;}{(d_{pv\_\mathrm{int}}-d_{pv\_\min })(d_{pv\_\mathrm{int}}-d_{pv\_\max })}\right)P_{Buck\_\mathrm{int}}\\ +\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\min }+d_{pv\_\mathrm{int}})\&rsqb;}{(d_{pv\_\max }-d_{pv\_\min })(d_{pv\_\max }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\max }\\ +\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\max }+d_{pv\_\mathrm{int}})\&rsqb;}{(d_{pv\_\min }-d_{pv\_\max })(d_{pv\_\min }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\min }=0\end{array}---\left(7\right)$

The dutycycle that maximum power point (8) is corresponding can be obtained by formula (7)For

${\stackrel{\&OverBar;}{d}}_{pv\_n}=\frac{d_{pv\_\min }^2(P_{Buck\_\max }-P_{Buck\_\mathrm{int}})+d_{pv\_\mathrm{int}}^2(P_{Buck\_\min }-P_{Buck\_\max })+d_{pv\_\max }^2(P_{Buck\_\mathrm{int}}-P_{Buck\_\min })}{2\&lsqb;d_{pv\_\min }(P_{Buck\_\max }-P_{Buck\_\mathrm{int}})+d_{pv\_\mathrm{int}}(P_{Buck\_\min }-P_{Buck\_\max })+d_{pv\_\max }(P_{Buck\_\mathrm{int}}-P_{Buck\_\min })\&rsqb;}---\left(8\right)$

WillSubstitution formula (6), the extreme value of current control unit outputAs shown in Fig. 7 (B)；

(4) extreme valueIt is not the output maximum of actual characteristic curve, therefore, according to dutycycleThe output of actual correspondence can be recordedAs shown in Fig. 7 (C)；

(5) four performance numbers P can be obtained by above-mentioned steps_{Buck_min}、P_{Buck_int}、P_{Buck_max}、Take wherein three relatively high power points, these three power points the curve described just should be closer to the reference characteristic curve of maximal power tracing, as shown in Fig. 7 (D)；

(6) by discriminantJudging, before and after disturbance, whether the relative variation of peak power meets the condition of convergence less than 1%, if it is satisfied, then dutycycle corresponding to Maximum Power Output point is d_{pv_m}If be unsatisfactory for, then returning step (2), again detecting the output electric current of photovoltaic battery panel, till meeting the condition of convergence.

The invention has the beneficial effects as follows:

For photovoltaic generating system, propose two kinds of maximum power tracking and controlling methods based on single argument current method, i.e. single argument current disturbing tracing and single argument conic section extreme value following method, the MPPT maximum power point tracking of photovoltaic generating system is realized by controlling the output electric current of photovoltaic battery panel, than controlling, output voltage is the most direct, and have only to detect one variable of output electric current of photovoltaic battery panel, enormously simplify the control process of maximal power tracing, additionally the bounds of dutycycle is defined, the control mode that this coarse adjustment combines with fine setting accelerates maximal power tracing speed, decrease the power loss caused because of environmental change, substantially improve disturbance quantity problem of left and right concussion near maximum power point in tradition method of perturbation.

Accompanying drawing explanation

Fig. 1 is the structural representation of photovoltaic maximum power tracking control system of the present invention；

Fig. 2 is current control unit hardware circuit figure of the present invention；

Fig. 3 is the relation curve of output of the present invention and dutycycle；

Fig. 4 is that the bounds of dutycycle of the present invention limits schematic diagram；

Fig. 5 is the control flow chart of single argument current disturbing tracing of the present invention；

Fig. 6 is the control flow chart of single argument conic section extreme value following method of the present invention；

Fig. 7 is the MPPT maximum power point tracking process schematic of single argument conic section extreme value following method of the present invention.

Description of reference numerals:

1. photovoltaic battery panel；2. current control unit；3. output voltage control unit；4. Switching Power Supply；5.DC/DC power inverter；6.P_pv-d_pvRelation curve；7.P_Buck-d_pvRelation curve；8. maximum power point.

Detailed description of the invention

The present invention proposes a kind of based on single argument current method photovoltaic maximum power tracking control system, it is characterized in that: this system includes photovoltaic battery panel 1, photovoltaic battery panel 1 is connected with Switching Power Supply 4, current control unit 2 control connecting valve power supply 4, to realize maximal power tracing control；Switching Power Supply 4 is connected with DC/DC power inverter 5 again, output voltage control unit 3 control to connect DC/DC power inverter 5, to reach regulated output voltage U₀Purpose.

Current control unit 2 is main by switching device Q, diode D, electric capacity C₁, electric capacity C₂Constitute with inductance L, the negative electrode of diode D connecting valve device Q and inductance L respectively, the other end of switching device Q and electric capacity C₁One end be connected, the other end of inductance L is even and electric capacity C₂One end be connected, electric capacity C₁The other end and electric capacity C₂The other end connect the anode of diode D respectively.

A kind of maximum power tracking and controlling method based on single argument current method photovoltaic generating system as mentioned above, it is characterized in that: maximum power tracking and controlling method uses one of following two control method based on single argument current method, i.e. use single argument current disturbing tracing or single argument conic section extreme value following method, set about from hardware circuit angle, between photovoltaic battery panel 1 and DC/DC power inverter 5, accessed a current control unit 2.

Described control method based on single argument current method photovoltaic maximum power tracking control system, based on single argument current method (I_pv) maximal power tracing control basic thought be: photovoltaic battery panel 1 output P_pvMaximum power point 8 and current control unit 2 output P_BuckThe dutycycle of maximum power point 8 correspondence identical, therefore, obtain P according to calculating formula (5)_BuckDutycycle d of maximum power point 8 correspondence_{pv_m}, then the dutycycle controlling Switching Power Supply 4 is d_{pv_m}, and then reach to follow the tracks of P_pvThe purpose of maximum power point 8, thus realize maximal power tracing；

$P_{Buck}=\frac{I_{pv}}{d_{pv}}=P_{Buck}\left(I_{pv}\right)---\left(5\right).$

To dutycycle d_pvBounds be defined, if d_{pv_min}(minimum edge dividing value) < d_pv<d_{pv_max}(maximum boundary value), when dutycycle d_pvOutside the bounds limited, i.e. d_pv<d_{pv_min}Or d_pv>d_{pv_max}Time, then without comparing output, first by dutycycle d_pvAdjust to restriction, limit dutycycle d_pvThe purpose of bounds is to reduce number of comparisons, accelerates tracking velocity；Work as d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv, the dutycycle of subsequent time is d_pv(k+1)=d_pv(k)+Δd_pv；Work as d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv, the dutycycle of subsequent time is d_pv(k+1)=d_pv(k)-Δd_pv。

Employing single argument current disturbing tracing:

By the initial value d of dutycycle_{pv_0}It is set to its minimum edge dividing value d_{pv_min}, incrementally increase dutycycle d_pv, and ensure d_pvAt the bounds [d limited_{pv_min},d_{pv_max}In], at a time, dutycycle is d_pvK (), the output electric current of detection photovoltaic battery panel 1 is I_pvK (), the output of calculating current control unit 2 is P_BuckK (), changes dutycycle d at subsequent time_pv, make d_pv(k+1)=d_pv(k)+Δd_pv, export electric current I_pvWith output P_BuckAll changing, the output electric current detecting photovoltaic battery panel 1 the most again is designated as I_pv(k+1), the output of calculating current control unit 2 is designated as P_Buck(k+1), before and after comparing disturbance, output P_Buck(k) and P_Buck(k+1) between and dutycycle d_pv(k) and d_pv(k+1) magnitude relationship between determines subsequent time dutycycle d_pvAdjustment direction, be summarized as follows:

If P_Buck(k+1)>P_Buck(k), d_pv(k+1)>d_pvK (), illustrates d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv；d_pv(k+1)<d_pvK (), illustrates d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv；

If P_Buck(k+1)<P_Buck(k), d_pv(k+1)>d_pvK (), illustrates d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv；d_pv(k+1)<d_pvK (), illustrates d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv；

If P_Buck(k+1)=P_BuckK (), illustrates d_pv=d_{pv_m}, then dutycycle d is kept_pvConstant；

Constantly repeat said process, make the output P of current control unit 2_BuckTo the Long-term change trend increased, thus realize maximal power tracing；

Single argument current disturbing tracing is (to compare P based on two discriminants_Buck(k)、P_Buck(k+1) size and d_pv(k)、d_pv(k+1) size), by constantly adjusting dutycycle d_pvChange the output electric current I of photovoltaic battery panel 1_pv, and then change the output P of current control unit 2_Buck, make P_BuckTo the direction change increased, it is finally reached the purpose following the tracks of maximum power point 8.

Use single argument conic section extreme value following method to realize step as follows:

(1) in dutycycle d_pvBounds [d_{pv_min},d_{pv_max}Three values, d is taken in]_{pv_min}、d_{pv_int}、d_{pv_max}, wherein d_{pv_int}For d_{pv_min}With d_{pv_max}Between a certain value, and detect that the photovoltaic battery panel 1 that these three dutyfactor value is corresponding respectively exports electric current I_{pv_min}、I_{pv_int}、I_{pv_max}；

(2) above three dutyfactor value d is calculated according to formula (5)_{pv_min}、d_{pv_int}、d_{pv_max}The most corresponding current control unit (2) output P_{Buck_min}、P_{Buck_int}、P_{Buck_max}, it is hereby achieved that three coordinate points (d_{pv_min},P_{Buck_min})、(d_{pv_int},P_{Buck_int})、(d_{pv_max},P_{Buck_max}), as shown in Fig. 7 (A)；

(3) according to above three coordinate points, utilizing Lagrange multinomial can obtain the quadratic curve equation of correspondence, as shown in formula (6), the equation can be regarded as now photovoltaic power conversion diagram equation；

$\begin{array}{c}{\stackrel{\&OverBar;}{P}}_{Buck}=\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\min })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })}{(d_{pv\_\mathrm{int}}-d_{pv\_\min })(d_{pv\_\mathrm{int}}-d_{pv\_\max })}{P}_{Buck\_\mathrm{int}}\\ +\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\min })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })}{(d_{pv\_\max }-d_{pv\_\min })(d_{pv\_\max }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\max }\\ +\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\mathrm{int}})}{(d_{pv\_\min }-d_{pv\_\max })(d_{pv\_\min }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\min }\end{array}---\left(6\right)$

In order to solve the extreme value of quadratic curve equation formula (6), formula (6) is differentiated, and makes it be equal to zero, as shown in formula (7)；

$\begin{array}{c}\frac{d{\stackrel{\&OverBar;}{P}}_{Buck}}{d{\stackrel{\&OverBar;}{d}}_{pv}}=\left(\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\min }+d_{pv\_\max })\&rsqb;}{(d_{pv\_\mathrm{int}}-d_{pv\_\min })(d_{pv\_\mathrm{int}}-d_{pv\_\max })}\right)P_{Buck\_\mathrm{int}}\\ +\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\min }+d_{pv\_\mathrm{int}})\&rsqb;}{(d_{pv\_\max }-d_{pv\_\min })(d_{pv\_\max }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\max }\\ +\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\max }+d_{pv\_\mathrm{int}})\&rsqb;}{(d_{pv\_\min }-d_{pv\_\max })(d_{pv\_\min }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\min }=0\end{array}---\left(7\right)$

The dutycycle of maximum power point 8 correspondence can be obtained by formula (7)For

${\stackrel{\&OverBar;}{d}}_{pv\_n}=\frac{d_{pv\_\min }^2(P_{Buck\_\max }-P_{Buck\_\mathrm{int}})+d_{pv\_\mathrm{int}}^2(P_{Buck\_\min }-P_{Buck\_\max })+d_{pv\_\max }^2(P_{Buck\_\mathrm{int}}-P_{Buck\_\min })}{2\&lsqb;d_{pv\_\min }(P_{Buck\_\max }-P_{Buck\_\mathrm{int}})+d_{pv\_\mathrm{int}}(P_{Buck\_\min }-P_{Buck\_\max })+d_{pv\_\max }(P_{Buck\_\mathrm{int}}-P_{Buck\_\min })\&rsqb;}---\left(8\right)$

WillSubstitution formula (6), the extreme value of current control unit 2 outputAs shown in Fig. 7 (B)；

(4) extreme valueIt is not the output maximum of actual characteristic curve, therefore, according to dutycycleThe output of actual correspondence can be recordedAs shown in Fig. 7 (C)；

(5) four performance numbers P can be obtained by above-mentioned steps_{Buck_min}、P_{Buck_int}、P_{Buck_max}、Take wherein three relatively high power points, these three power points the curve described just should be closer to the reference characteristic curve of maximal power tracing, as shown in Fig. 7 (D)；

(6) by discriminantJudging, before and after disturbance, whether the relative variation of peak power meets the condition of convergence less than 1%, if it is satisfied, then the dutycycle of Maximum Power Output point 8 correspondence isIf be unsatisfactory for, then returning step (2), again detecting the output electric current of photovoltaic battery panel, till meeting the condition of convergence.

Below in conjunction with the accompanying drawings the present invention is specifically described:

Fig. 1 is the structural representation of photovoltaic maximum power tracking control system of the present invention, wherein, U_pvAnd I_pvIt is respectively output voltage and output electric current, the I of photovoltaic battery panel 1_pv ^*For electric current I_pvSet-point；U₀For the output voltage of DC/DC power inverter 5, U₀ ^*For voltage U₀Set-point.

Photovoltaic battery panel 1 is connected with Switching Power Supply 4, current control unit 2 control Switching Power Supply 4, to realize maximal power tracing control；Switching Power Supply 4 is connected with DC/DC power inverter 5 again, output voltage control unit 3 control DC/DC power inverter 5, to reach regulated output voltage U₀Purpose.

Maximal power tracing controls to be respectively adopted two kinds of control methods based on single argument current method, i.e. single argument current disturbing tracing and single argument conic section extreme value following method, set about from hardware circuit angle, between photovoltaic battery panel 1 and DC/DC power inverter 5, accessed a current control unit 2.

Fig. 2 is current control unit hardware circuit figure of the present invention.The basic thought of single argument current method is: the output electric current I of photovoltaic battery panel 1_pvFor

$I_{pv}=n_p{I}_{ph}-n_p{I}_{rs}\&lsqb;\exp (\frac{q}{kTA}\&CenterDot;\frac{U_{pv}+I_{pv}{R}_s}{n_s})-1\&rsqb;-\frac{U_{pv}+I_{pv}{R}_s}{R_{sh}}---\left(1\right)$

In formula, n_sAnd n_pIt is respectively series connection number and the number of parallel of photovoltaic battery panel；Q is the quantity of electric charge of an electron institute band, q=1.6 × 10^-19C；K is Boltzmann constant, k=1.38 × 10^-23J/K；T is the surface temperature (unit is K) of photovoltaic battery panel；A is ideality factor, generally takes A=1～2；I_phFor photovoltaic battery panel through current source current produced by illumination；I_rsReverse saturation current for photovoltaic battery panel；R_shAnd R_sIt is respectively equivalent parallel resistance and the series resistance of photovoltaic battery panel.

The then output P of photovoltaic battery panel 1_pvFor

$\begin{array}{c}{P}_{pv}=V_{pv}{I}_{pv}\\ =n_p{V}_{pv}{I}_{ph}-n_p{V}_{pv}{I}_{rs}\&lsqb;\exp \left(\frac{q}{KTA}\&CenterDot;\frac{V_{pv}+I_{pv}{R}_s}{n_s}\right)-1\&rsqb;-V_{pv}\&CenterDot;\frac{V_{pv}+I_{pv}{R}_s}{R_{sh}}\\ =P_{pv}\left(V_{pv}{I}_{pv}\right)\end{array}---\left(2\right)$

The output voltage U of current control unit 2₀₁For

$U_{01}=\frac{t_{on}}{T}{U}_{pv}=d_{pv}{V}_{pv}---\left(3\right)$

In formula, d_pvFor the dutycycle of Switching Power Supply 4, d_pv=t_on/T。

So, the output P of photovoltaic battery panel 1_pvCan also be write as

$P_{pv}=U_{pv}{I}_{pv}=U_{01}\frac{I_{pv}}{d_{pv}}---\left(4\right)$

The output P of current control unit 2_BuckFor

$p_{Buck}=\frac{I_{pv}}{d_{pv}}=P_{Buck}\left(I_{pv}\right)---\left(5\right)$

P can be obtained respectively by formula (4) and formula (5)_pv-d_pvRelation curve 6 and P_Buck-d_pvRelation curve 7, as shown in Figure 3.It can be seen that photovoltaic battery panel 1 output P_pvMaximum power point 8 and current control unit 2 output P_BuckThe dutycycle of maximum power point 8 correspondence identical, therefore, obtain P according to formula (5)_BuckDutycycle d of maximum power point 8 correspondence_{pv_m}, then the dutycycle controlling Switching Power Supply 4 is d_{pv_m}, and then reach to follow the tracks of P_pvThe purpose of maximum power point 8, here it is utilize single argument current method (I_pv) realize the basic thought that maximal power tracing controls.

Fig. 4 is that the bounds of dutycycle of the present invention limits schematic diagram.If d_{pv_min}(minimum edge dividing value) < d_pv<d_{pv_max}(maximum boundary value), when dutycycle d_pvOutside the bounds limited, i.e. d_pv<d_{pv_min}Or d_pv>d_{pv_max}Time, then without comparing output, first by dutycycle d_pvAdjust to restriction, limit dutycycle d_pvThe purpose of bounds is to reduce number of comparisons, accelerates tracking velocity.Work as d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv, the dutycycle of subsequent time is d_pv(k+1)=d_pv(k)+Δd_pv；Work as d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv, the dutycycle of subsequent time is d_pv(k+1)=d_pv(k)-Δd_pv。

Fig. 5 is the control flow chart of single argument current disturbing tracing of the present invention.By the initial value d of dutycycle_{pv_0}It is set to its minimum edge dividing value d_{pv_min}, incrementally increase dutycycle d_pv, and ensure d_pvAt the bounds [d limited_{pv_min},d_{pv_max}In], at a time, dutycycle is d_pvK (), the output electric current of detection photovoltaic battery panel 1 is I_pvK (), the output of calculating current control unit 2 is P_BuckK (), changes dutycycle d at subsequent time_pv, make d_pv(k+1)=d_pv(k)+Δd_pv, export electric current I_pvWith output P_BuckAll changing, the output electric current detecting photovoltaic battery panel 1 the most again is designated as I_pv(k+1), the output of calculating current control unit 2 is designated as P_Buck(k+1), before and after comparing disturbance, output P_Buck(k) and P_Buck(k+1) between and dutycycle d_pv(k) and d_pv(k+1) magnitude relationship between determines subsequent time dutycycle d_pvAdjustment direction, be summarized as follows:

If P_Buck(k+1)>P_Buck(k), d_pv(k+1)>d_pvK (), illustrates d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv；d_pv(k+1)<d_pvK (), illustrates d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv。

If P_Buck(k+1)<P_Buck(k), d_pv(k+1)>d_pvK (), illustrates d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv；d_pv(k+1)<d_pvK (), illustrates d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv。

If P_Buck(k+1)=P_BuckK (), illustrates d_pv=d_{pv_m}, then dutycycle d is kept_pvConstant.

Constantly repeat said process, make the output P of current control unit 2_BuckTo the Long-term change trend increased, thus realize maximal power tracing.

Single argument current disturbing tracing is (to compare P based on two discriminants_Buck(k)、P_Buck(k+1) size and d_pv(k)、d_pv(k+1) size), by constantly adjusting dutycycle d_pvChange the output electric current I of photovoltaic battery panel 1_pv, and then change the output P of current control unit 2_Buck, make P_BuckTo the direction change increased, it is finally reached the purpose following the tracks of maximum power point 8.

Fig. 6 is the control flow chart of single argument conic section extreme value following method of the present invention, and Fig. 7 is the MPPT maximum power point tracking process schematic of single argument conic section extreme value following method of the present invention.The step that realizes of single argument conic section extreme value following method is summarized as follows:

1) in dutycycle d_pvBounds [d_{pv_min},d_{pv_max}Three values, d is taken in]_{pv_min}、d_{pv_int}、d_{pv_max}, wherein d_{pv_int}For d_{pv_min}With d_{pv_max}Between a certain value, and detect that the photovoltaic battery panel 1 that these three dutyfactor value is corresponding respectively exports electric current I_{pv_min}、I_{pv_int}、I_{pv_max}。

2) above three dutyfactor value d is calculated according to formula (5)_{pv_min}、d_{pv_int}、d_{pv_max}The most corresponding current control unit 2 output P_{Buck_min}、P_{Buck_int}、P_{Buck_max}, it is hereby achieved that three coordinate points (d_{pv_min},P_{Buck_min})、(d_{pv_int},P_{Buck_int})、(d_{pv_max},P_{Buck_max}), as shown in Fig. 7 (A).

3) according to above three coordinate points, utilizing Lagrange multinomial can obtain the quadratic curve equation of correspondence, as shown in formula (6), the equation can be regarded as now photovoltaic power conversion diagram equation.

$\begin{array}{c}{\stackrel{\&OverBar;}{P}}_{Buck}=\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\min })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })}{(d_{pv\_\mathrm{int}}-d_{pv\_\min })(d_{pv\_\mathrm{int}}-d_{pv\_\max })}{P}_{Buck\_\mathrm{int}}\\ +\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\min })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })}{(d_{pv\_\max }-d_{pv\_\min })(d_{pv\_\max }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\max }\\ +\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\mathrm{int}})}{(d_{pv\_\min }-d_{pv\_\max })(d_{pv\_\min }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\min }\end{array}---\left(6\right)$

In order to solve the extreme value of quadratic curve equation formula (6), formula (6) is differentiated, and makes it be equal to zero, as shown in formula (7).

$\begin{array}{c}\frac{d{\stackrel{\&OverBar;}{P}}_{Buck}}{d{\stackrel{\&OverBar;}{d}}_{pv}}=\left(\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\min }+d_{pv\_\max })\&rsqb;}{(d_{pv\_\mathrm{int}}-d_{pv\_\min })(d_{pv\_\mathrm{int}}-d_{pv\_\max })}\right)P_{Buck\_\mathrm{int}}\\ +\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\min }+d_{pv\_\mathrm{int}})\&rsqb;}{(d_{pv\_\max }-d_{pv\_\min })(d_{pv\_\max }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\max }\\ +\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\max }+d_{pv\_\mathrm{int}})\&rsqb;}{(d_{pv\_\min }-d_{pv\_\max })(d_{pv\_\min }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\min }=0\end{array}---\left(7\right)$

The dutycycle of maximum power point 8 correspondence can be obtained by formula (7)For

${\stackrel{\&OverBar;}{d}}_{pv\_n}=\frac{d_{pv\_\min }^2(P_{Buck\_\max }-P_{Buck\_\mathrm{int}})+d_{pv\_\mathrm{int}}^2(P_{Buck\_\min }-P_{Buck\_\max })+d_{pv\_\max }^2(P_{Buck\_\mathrm{int}}-P_{Buck\_\min })}{2\&lsqb;d_{pv\_\min }(P_{Buck\_\max }-P_{Buck\_\mathrm{int}})+d_{pv\_\mathrm{int}}(P_{Buck\_\min }-P_{Buck\_\max })+d_{pv\_\max }(P_{Buck\_\mathrm{int}}-P_{Buck\_\min })\&rsqb;}---\left(8\right)$

WillSubstitution formula (6), the extreme value of current control unit 2 outputAs shown in Fig. 7 (B).

4) extreme valueIt is not the output maximum of actual characteristic curve, therefore, according to dutycycleThe output of actual correspondence can be recordedAs shown in Fig. 7 (C).

5) four performance numbers P can be obtained by above-mentioned steps_{Buck_min}、P_{Buck_int}、P_{Buck_max}、Take wherein three relatively high power points, these three power points the curve described just should be closer to the reference characteristic curve of maximal power tracing, as shown in Fig. 7 (D).

6) by discriminantJudging, before and after disturbance, whether the relative variation of peak power meets the condition of convergence less than 1%, if it is satisfied, then the dutycycle of Maximum Power Output point 8 correspondence isIf be unsatisfactory for, then returning step (2), again detecting the output electric current of photovoltaic battery panel, till meeting the condition of convergence.

The two kinds of maximum power tracking and controlling methods based on single argument current method proposed, i.e. single argument current disturbing tracing and single argument conic section extreme value following method, the MPPT maximum power point tracking of photovoltaic generating system is realized by controlling the output electric current of photovoltaic battery panel, than controlling, output voltage is the most direct, and have only to detect one variable of output electric current of photovoltaic battery panel, enormously simplify the control process of maximal power tracing, additionally the bounds of dutycycle is defined, the control mode that this coarse adjustment combines with fine setting accelerates maximal power tracing speed, decrease the power loss caused because of environmental change, substantially improve disturbance quantity problem of left and right concussion near maximum power point in tradition method of perturbation.

The present invention is based on single argument current method, it is provided that two kinds of photoelectric transformation efficiency height, the photovoltaic generating system of good stability and maximum power tracking and controlling method thereof.

Claims (3)

1. control method based on single argument current method photovoltaic maximum power tracking control system, it is characterised in that: this system Including photovoltaic battery panel (1), photovoltaic battery panel (1) is connected with Switching Power Supply (4), current control unit (2) control even Connecing Switching Power Supply (4), Switching Power Supply (4) is connected with DC/DC power inverter (5) again, by output voltage control unit (3) Control to connect DC/DC power inverter (5)；

Maximum power tracking and controlling method uses one of following two control method based on single argument current method, i.e. uses single argument Current disturbing tracing or single argument conic section extreme value following method；

Based on single argument current method (I_pv) maximal power tracing control basic thought be: photovoltaic battery panel (1) output P_pvMaximum power point (8) and current control unit (2) output P_BuckDutycycle corresponding to maximum power point (8) Identical, therefore, obtain P according to calculating formula (5)_BuckDutycycle d that maximum power point (8) is corresponding_{pv_m}, then control Switching Power Supply (4) dutycycle is d_{pv_m}, and then reach to follow the tracks of P_pvThe purpose of maximum power point (8), thus realize maximal power tracing；

$P_{Buck}=\frac{I_{pv}}{d_{pv}}=P_{Buck}\left(I_{pv}\right)---\left(5\right);$

To dutycycle d_pvBounds be defined, if minimum edge dividing value d_{pv_min}<d_pv< maximum boundary value d_{pv_max}, when Dutycycle d_pvOutside the bounds limited, i.e. d_pv<d_{pv_min}Or d_pv>d_{pv_max}Time, then without comparing output, First by dutycycle d_pvAdjust to restriction, limit dutycycle d_pvThe purpose of bounds be reduce number of comparisons, accelerate with Track speed；Work as d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv, the dutycycle of subsequent time is d_pv(k+1)=d_pv(k)+Δd_pv； Work as d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv, the dutycycle of subsequent time is d_pv(k+1)=d_pv(k)-Δd_pv。

Control method based on single argument current method photovoltaic maximum power tracking control system the most according to claim 1, It is characterized in that: employing single argument current disturbing tracing:

By the initial value d of dutycycle_{pv_0}It is set to its minimum edge dividing value d_{pv_min}, incrementally increase dutycycle d_pv, and ensure d_pvIn limit Fixed bounds [d_{pv_min},d_{pv_max}In], at a time, dutycycle is d_pv(k), the output of detection photovoltaic battery panel (1) Electric current is I_pvK (), the output of calculating current control unit (2) is P_BuckK (), changes dutycycle d at subsequent time_pv, Make d_pv(k+1)=d_pv(k)+Δd_pv, export electric current I_pvWith output P_BuckAll change, detect photovoltaic battery panel the most again (1) output electric current is designated as I_pv(k+1), the output of calculating current control unit (2) is designated as P_Buck(k+1), by than Before and after relatively disturbance, output P_Buck(k) and P_Buck(k+1) between and dutycycle d_pv(k) and d_pv(k+1) magnitude relationship between Determine subsequent time dutycycle d_pvAdjustment direction, be summarized as follows:

If P_Buck(k+1)>P_Buck(k), d_pv(k+1)>d_pvK (), illustrates d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv； d_pv(k+1)<d_pvK (), illustrates d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv；

If P_Buck(k+1)<P_Buck(k), d_pv(k+1)>d_pvK (), illustrates d_{pv_m}<d_pv<d_{pv_max}, then dutycycle d is reduced_pv； d_pv(k+1)<d_pvK (), illustrates d_{pv_min}<d_pv<d_{pv_m}, then dutycycle d is increased_pv；

If P_Buck(k+1)=P_BuckK (), illustrates d_pv=d_{pv_m}, then dutycycle d is kept_pvConstant；

Constantly repeat said process, make the output P of current control unit (2)_BuckTo the Long-term change trend increased, thus real Existing maximal power tracing；

Single argument current disturbing tracing is based on comparing P_Buck(k)、P_Buck(k+1) size and d_pv(k)、d_pv(k+1) size, passes through Constantly adjust dutycycle d_pvChange the output electric current I of photovoltaic battery panel (1)_pv, and then change current control unit (2) Output P_Buck, make P_BuckTo the direction change increased, it is finally reached the purpose following the tracks of maximum power point (8).

Controlling party based on single argument current method photovoltaic maximum power tracking control system the most according to claim 1 Method, it is characterised in that:

Employing single argument conic section extreme value following method:

(1) in dutycycle d_pvBounds [d_{pv_min},d_{pv_max}Three values, d is taken in]_{pv_min}、d_{pv_int}、d_{pv_max}, wherein d_{pv_int}For d_{pv_min}With d_{pv_max}Between a certain value, and detect the photovoltaic battery panel (1) that these three dutyfactor value is respectively corresponding Output electric current I_{pv_min}、I_{pv_int}、I_{pv_max}；

(2) above three dutyfactor value d is calculated according to formula (5)_{pv_min}、d_{pv_int}、d_{pv_max}The most corresponding current control unit (2) output P_{Buck_min}、P_{Buck_int}、P_{Buck_max}, it is hereby achieved that three coordinate points (d_{pv_min},P_{Buck_min})、(d_{pv_int}, P_{Buck_int})、(d_{pv_max},P_{Buck_max})；

(3) according to above three coordinate points, Lagrange multinomial is utilized can to obtain the quadratic curve equation of correspondence, such as formula (6) Shown in, the equation can be regarded as now photovoltaic power conversion diagram equation；

$\begin{array}{c}{\stackrel{\&OverBar;}{P}}_{Buck}=\frac{({\stackrel{\&OverBar;}{d}}_{dv}-d_{pv\_\min })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })}{(d_{dv\_\mathrm{int}}-d_{pv\_\min })(d_{pv\_\mathrm{int}}-d_{pv\_\max })}=P_{Buck\_\mathrm{int}}\\ +\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\min })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\mathrm{int}})}{(d_{pv\_\max }-d_{pv\_\min })(d_{pv\_\max }-d_{pv\_\mathrm{int}})}=P_{Buck\_\max }\\ +\frac{({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\max })({\stackrel{\&OverBar;}{d}}_{pv}-d_{pv\_\mathrm{int}})}{(d_{pv\_\min }-d_{pv\_\max })(d_{pv\_\min }-d_{pv\_\mathrm{int}})}=P_{Buck\_\min }\end{array}---\left(6\right)$

In order to solve the extreme value of quadratic curve equation formula (6), formula (6) is differentiated, and makes it be equal to zero, as shown in formula (7)；

$\begin{array}{c}\frac{d{\stackrel{\&OverBar;}{P}}_{Buck}}{d{\stackrel{\&OverBar;}{d}}_{pv}}=\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\min }-d_{pv\_\max })\&rsqb;}{(d_{dv\_\mathrm{int}}-d_{pv\_\min })(d_{pv\_\mathrm{int}}-d_{pv\_\max })}{P}_{Buck\_\mathrm{int}}\\ +\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\min }+d_{pv\_\mathrm{int}})\&rsqb;}{(d_{pv\_\max }-d_{pv\_\min })(d_{pv\_\max }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\max }\\ +\frac{\&lsqb;2{\stackrel{\&OverBar;}{d}}_{pv}-(d_{pv\_\max }+d_{pv\_\mathrm{int}})\&rsqb;}{(d_{pv\_\min }-d_{pv\_\max })(d_{pv\_\min }-d_{pv\_\mathrm{int}})}{P}_{Buck\_\min }=0\end{array}---\left(7\right)$

The dutycycle that maximum power point (8) is corresponding can be obtained by formula (7)For

${\stackrel{\&OverBar;}{d}}_{pv\_m}=\frac{d_{pv\_\min }^2(P_{Buck\_\max }-P_{Buck\_\mathrm{int}})+d_{pv\_\mathrm{int}}^2(P_{Buck\_\min }-P_{Buck\_\max })+d_{pv\_\max }^2(P_{Buck\_\mathrm{int}}-P_{Buck\_\min })}{2\&lsqb;d_{pv\_\min }(P_{Buck\_\max }-P_{Buck\_\mathrm{int}})+d_{pv\_\mathrm{int}}(P_{Buck\_\min }-P_{Buck\_\max })+d_{pv\_\max }(P_{Buck\_\mathrm{int}}-P_{Buck\_\min })\&rsqb;}---\left(8\right)$

WillSubstitution formula (6), the extreme value of current control unit (2) output

(4) extreme valueIt is not the output maximum of actual characteristic curve, therefore, according to dutycyclePermissible Record the output of actual correspondence

(5) four performance numbers P can be obtained by above-mentioned steps_{Buck_min}、P_{Buck_int}、P_{Buck_max}、, take wherein that three relatively High-power, these three power points the curve described just should be closer to the reference characteristic curve of maximal power tracing；

(6) by discriminantJudging, before and after disturbance, the relative variation of peak power is The no satisfied condition of convergence less than 1%, if it is satisfied, then the dutycycle of Maximum Power Output point (8) correspondence is, as Fruit is unsatisfactory for, then return step (2), again detect the output electric current of photovoltaic battery panel, till meeting the condition of convergence.