CN104362977B - Bimodal dynamically/static MPP of a kind of photovoltaic DC-to-AC converter follows the tracks of Efficiency test method - Google Patents

Abstract

The present invention provides bimodal dynamically/static MPP of a kind of photovoltaic DC-to-AC converter to follow the tracks of Efficiency test method, comprises steps of determining that the accessibility maximum power point of DC side photovoltaic array and photovoltaic DC-to-AC converter MPP voltage range；Select photovoltaic array, and mate with photovoltaic DC-to-AC converter；Determine photovoltaic module unimodal P V curve；Photovoltaic array bimodal MPPT testing efficiency P V curve is set, completes MPP bimodal dynamically/static to photovoltaic DC-to-AC converter and follow the tracks of efficiency test.The present invention is by the bimodal I V curve under DC source editor's different capacity and different coverage extent, test and evaluation photovoltaic DC-to-AC converter follows the tracks of the ability of bimodal I V curve maximum power point, and this invention has been filled up at present to the blank in terms of bimodal I V curve MPP tracking efficiency test and evaluation.

Description

Bimodal dynamically/static MPP of a kind of photovoltaic DC-to-AC converter follows the tracks of Efficiency test method

Technical field

The invention belongs to photovoltaic DC-to-AC converter detection field, be specifically related to bimodal dynamically/static MPP of a kind of photovoltaic DC-to-AC converter and follow the tracks of effect Rate method of testing.

Background technology

In the last few years, the new forms of energy with wind energy, solar energy as representative obtained fast development in the whole world.Estimate to the year two thousand twenty, photovoltaic Assembly annual production will reach 40GW.In the case, the generating efficiency of photovoltaic system is the most in widespread attention.And affect photovoltaic The key factor of system generating efficiency is exactly the photovoltaic DC-to-AC converter MPPT maximum power point tracking precision to photovoltaic array P-V curve.

According to photovoltaic module characteristic, its preferable P-V curve is a unimodal parabola.Photovoltaic DC-to-AC converter is carrying out maximum power point During tracking, it is only necessary to follow the tracks of its unimodal top.In actual motion, owing to racking, trees, building and birds row Letting out the impacts such as thing, photovoltaic array can be by partial occlusion, and in this case, the solar irradiance that photovoltaic module is received exists Larger difference, photovoltaic group string output characteristics also can change, and bimodal or multimodal situation occurs in photovoltaic array P-V curve.

At present, conventional photovoltaic inverter only has unimodal MPP (Maximum Power Point) and follows the tracks of, photovoltaic DC-to-AC converter MPPT The development experience of control technology constant voltage control methods^[1], short circuit current ratio method^[2]Etc. the relatively simple but side of being accurately controlled not Method；Until disturbance observation method^[3～7], conductance increment method^[8][9]Etc. widely used MPPT control method and employing Fuzzy Control System, neuroid etc. based on intelligent processing method and other non-linear control strategies in interior MPPT tracing.

Use conventional photovoltaic inverter MPPT tracking, it is impossible to I-V curve bimodal to photovoltaic array is tracked, and causes light Volt system generated energy loses.Accompanying drawing 1 be a nominal installed capacity 500kW photovoltaic array part by shadow occlusion, hidden by shade During gear, the irradiance of shield portions about 50W/m².Under this coverage extent, photovoltaic array P-V curve is as shown in Figure 2. Inverter service behaviour is affected by shadow occlusion, if inverter has bimodal MPPT and follows the tracks of ability, then time by shadow occlusion Peak power P that inverter can reach_array1=443.58kW, whole system power loss is about 56.42kW, power loss percentage Ratio is 11.28%.If inverter does not have bimodal MPPT follows the tracks of ability, peak power can be reached by inverter during shadow occlusion P_array2=406.02kW, whole system power loss is about 93.98kW, power loss percentage ratio 18.80%.

Along with the development of distributed photovoltaic system, application will be more universal in incity, city for distributed photovoltaic system, is characterized in Surrounding is complicated, and array is bigger by the probability of shadow occlusion.It is contemplated that, the photovoltaic with bimodal MPPT control mode is inverse Become device and will become one of important indicator of measurement inverter performance.

At present, method photovoltaic DC-to-AC converter MPP following the tracks of efficiency test and evaluation is mainly seen in European standard EN50530, content Follow the tracks of efficiency test including static MPP, dynamic MPP follows the tracks of efficiency test and inverter start and stop MPP follows the tracks of efficiency test, But above content is all for preferable unimodal P-V curve.Photovoltaic array in actual use, is affected by shadow occlusion etc., its I-V Curve can present multiple flex point, causes photovoltaic array bimodal P-V curve, has a strong impact on photovoltaic system whole efficiency.For bimodal MPPT efficiency test standard and method have no report the most temporarily.

List of references

[1] Yu Shijie, He Huiruo, Cao Renxian, waits the control of CVT and MPPT in photovoltaic water pump system to compare [J] solar energy Report, 1998,19 (4): 394-398.

[2] Zhou Lin, Wu Jian, summarizes [J] etc. maximum power point of photovoltaic array tracking and controlling method, High-Voltage Technology, and 2008 (6)

[3]Femia N,Petrone G,Spagnuolo G,et al.Optimization of perturb and observe maximum power point tracking method[J].IEEE Transactions on Power Electronics,2005,20(4):963-973

[4]Altas I H,Sharaf A M.A novel on-line MPP search algorithm for PV array[J]IEEE Transactions on Energy Conversion 1996,11(4):748-754

[5]Chee Wei Tan,Green T C,Hernandez-Aramburo C A.An improved maximum power point tracking algorithm with current-mode control for photovoltaic applications[C]International Conference on Power Electronics and Drives Systems Kuala Lumpur,Malaysia 2005:489-494

[6] Sun Wuben, Zeng Yi, Jiang Xiuchen, etc. the design of outdoor on-Line Monitor Device power-supply system and realization [J] High-Voltage Technology, 2007,33 (8): 178-182

[7]D’Souza N S,Lopes L A C,XueJun Liu.An intelligent maximum power point tracker using peak current control[C]IEEE 36th Conference on Power Electronics Specialists.Recife,Brazil: IEEE,2005:172-177]

[8]Hussein K H,Muta I Hoshino T,Osakada M.Maximum Photovoltaic power tracking:an algorithm for rapidly changing atmospherc conditions[J].IEE Proceedings-Generation, Transmission and Distribution,1995,142(1):59-64

[9]Yusof Y,Sayuti S H,Abdul Latif M,et al.Modeling and simulation of maximum power point tracker for photovoltaic system[C]Proceedings of National Power and Energy conference.Kuala Lumpur,Malaysia,2004:88-93.

Summary of the invention

In order to overcome above-mentioned the deficiencies in the prior art, the present invention provides bimodal dynamically/static MPP of a kind of photovoltaic DC-to-AC converter to follow the tracks of effect Rate method of testing, by the bimodal I-V curve under DC source editor's different capacity and different coverage extent, test and evaluation light The ability of bimodal I-V curve maximum power point followed the tracks of by volt inverter, and this invention has been filled up and followed the tracks of bimodal I-V curve MPP at present Blank in terms of efficiency test and evaluation.

In order to realize foregoing invention purpose, the present invention adopts the following technical scheme that:

The present invention provides bimodal dynamically/static MPP of a kind of photovoltaic DC-to-AC converter to follow the tracks of Efficiency test method, and described method includes following Step:

Step 1: determine the accessibility maximum power point of DC side photovoltaic array and photovoltaic DC-to-AC converter MPP voltage range；

Step 2: select photovoltaic array, and mate with photovoltaic DC-to-AC converter；

Step 3: determine photovoltaic module unimodal P-V curve；

Step 4: arrange photovoltaic array bimodal MPPT testing efficiency P-V curve, completes photovoltaic DC-to-AC converter bimodal dynamically/static MPP follows the tracks of efficiency test.

In described step 1, according to photovoltaic DC-to-AC converter run relevant parameter determine the accessibility peak power of DC side photovoltaic array and Photovoltaic DC-to-AC converter MPP voltage range；Photovoltaic DC-to-AC converter runs relevant parameter and includes the minimum MPP voltage of photovoltaic DC-to-AC converter U_mppmin, maximum MPP voltage U_mppmax, optimal MPP running voltage and photovoltaic DC-to-AC converter nominal run power.

Run power according to photovoltaic DC-to-AC converter nominal and determine accessibility peak power P of DC side photovoltaic array₀, the photovoltaic battle array of setting Arrange bimodal P-V curve peak power less than P₀；Minimum MPP voltage U according to photovoltaic DC-to-AC converter_mppmin, maximum MPP electricity Pressure U_mppmaxAnd most preferably MPP running voltage determines photovoltaic array MPP voltage range, bent carrying out the bimodal P-V of photovoltaic array When line sets, the running voltage that on photovoltaic array bimodal P-V curve, all extreme points are corresponding is all at the photovoltaic array MPP determined In voltage range.

In described step 2, select crystal silicon photovoltaic battle array according to the application scenario of photovoltaic DC-to-AC converter MPP voltage range and photovoltaic DC-to-AC converter Row or film photovoltaic array, and mate with photovoltaic DC-to-AC converter, determine photovoltaic according to photovoltaic DC-to-AC converter MPP voltage range simultaneously Serial number n of photovoltaic module and quantity m in parallel of photovoltaic group string that is composed in series by photovoltaic module in array.

In described step 3, photovoltaic module mathematical model is utilized to determine photovoltaic module unimodal MPPT efficiency test P-V curve, light In photovoltaic assembly mathematical model, have:

$I_{\mathrm{PV}}=I_{\mathrm{sc}}-I_0(e^{\frac{U_{\mathrm{PV}}}{U_{\mathrm{oc}}{C}_{\mathrm{AQ}}}}-1)$

Wherein, I_PVElectric current, I is exported for photovoltaic module_scFor photovoltaic module short circuit current, I₀For diode saturation current, U_PVFor Photovoltaic module output voltage, U_ocFor photovoltaic module open-circuit voltage, C_AQFor constant, it is expressed as:

$C_{\mathrm{AQ}}=\frac{{\mathrm{FF}}_U-1}{\ln (1-{\mathrm{FF}}_I)}$

Wherein, FF_UFor voltage activity coefficient, for the crystal silicon component in crystal silicon photovoltaic array, take 0.8, for film photovoltaic battle array Film assembly in row, takes 0.72；FF_IFor electric current activity coefficient, for the crystal silicon component in crystal silicon photovoltaic array, take 0.9, For the film assembly in film photovoltaic array, take 0.8；

N block photovoltaic module is connected into photovoltaic group string, simultaneously m photovoltaic group string when being unified into photovoltaic array, photovoltaic array open circuit electricity Pressure is expressed as with short circuit current:

U_{oc_a}=nU_oc

I_{sc_a}=mI_sc

Wherein, U_{oc_a}For photovoltaic array open-circuit voltage, I_{sc_a}For photovoltaic array short circuit current.

In described step 4, block pattern according to photovoltaic array and shadow occlusion degree arranges photovoltaic array bimodal MPPT test Efficiency P-V curve；The photovoltaic array pattern of blocking includes that permutation is blocked, full line blocks and blocks with monolithic element；

Setting and play voltage 0 from photovoltaic array open-circuit voltage, first peak power extreme value is leading peak, second peak power pole Value for postpeak, photovoltaic DC-to-AC converter carry out bimodal dynamically/static MPPT follow the tracks of time, from open-circuit voltage, reduce direction towards voltage Scan for；

1) if leading peak performance number is more than postpeak performance number, no matter whether photovoltaic DC-to-AC converter possesses bimodal MPPT controls function, all The maximum power point of photovoltaic array can be found；

2) if leading peak performance number is less than postpeak performance number, the photovoltaic DC-to-AC converter only possessing bimodal MPPT control function is the most permissible Search the true maximum of photovoltaic array；When on-the-spot shade changes, photovoltaic DC-to-AC converter is found again according to current working newly Maximum power point on P-V curve.

Arrange photovoltaic array bimodal MPPT testing efficiency P-V curve to specifically include and arrange bimodal static MPPT efficiency test P-V Curve and bimodal dynamic MPPT efficiency test P-V curve.

When arranging bimodal static MPPT efficiency test P-V curve, the photovoltaic battle array being respectively provided with under high irradiance and low irradiance Arrange bimodal static MPPT efficiency test P-V curve, the bimodal static MPPT efficiency eta of photovoltaic DC-to-AC converter_MPPT,statIt is expressed as:

${\mathrm{\η}}_{\mathrm{MPPT},\mathrm{stat}}=\frac{\underset{i=1}{\overset{z}{\mathrm{\Σ}}}{U}_{\mathrm{DC},i}\·I_{\mathrm{DC},i}\·\mathrm{\ΔT}}{P_{\mathrm{MPP},\mathrm{PVS}}\·T_M}$

Wherein, Δ T is the sampling period, less than photovoltaic DC-to-AC converter MPPT minimum interval；U_DC,iFor inputting in the sampling period The meansigma methods of voltage, I_DC,iFor the meansigma methods of input current, P in the sampling period_MPP,PVSExport for photovoltaic arrays simulator is actual High-power value, z is photovoltaic DC-to-AC converter sampled data points sum, T_MFor detecting the time, and there is T_M=z × Δ T.

When arranging bimodal dynamic MPPT efficiency test P-V curve, bimodal dynamic MPPT efficiency test includes unimodal to bimodal Conversion and bimodal to unimodal conversion；The bimodal dynamic MPPT efficiency eta of photovoltaic array after n-th is tested_MPPTdyn,tIt is expressed as:

${\mathrm{\η}}_{\mathrm{MPPTDyn},t}=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\η}}_{\mathrm{MPPTdyn},k}$

Wherein, N is testing time sum, η_MPPTdyn,kThe bimodal dynamic MPPT efficiency of photovoltaic array in testing for kth time, its It is expressed as:

${\mathrm{\η}}_{\mathrm{MPPTdyn}.k}=\frac{\underset{i=1}{\overset{z}{\mathrm{\Σ}}}{U}_{\mathrm{DC},i}\·I_{\mathrm{DC},i}\·\mathrm{\Δ}{T}_i}{\underset{j=1}{\overset{M}{\mathrm{\Σ}}}{P}_{\mathrm{MPP},\mathrm{PVS},j}\·\mathrm{\Δ}{T}_j}$

Wherein, U_DC,iFor the meansigma methods of input voltage, I in the sampling period_DC,iFor the meansigma methods of input current in the sampling period, Δ T_i For photovoltaic DC-to-AC converter DC side data sampling period, Δ T in kth time test_jDefeated for photovoltaic arrays simulator in kth time test Go out power cycle, P_MPP,PVS,jFor photovoltaic arrays simulator Maximum Power Output in kth time test, M is photovoltaic arrays simulation Device sampled data points sum.

Compared with prior art, the beneficial effects of the present invention is:

1) the method is according to photovoltaic array by shadow occlusion situation, arranges bimodal P-V set of curves under low irradiance and high irradiance, Reach the purpose to bimodal MPPT tracking and testing static under inverter difference operating mode；

2) according to on-the-spot shade situation of change, the lower photovoltaic array P-V set of curves variation pattern of shade change and rate of change are set, Reach the purpose of bimodal MPPT efficiency test dynamic to inverter.

Accompanying drawing explanation

Fig. 1 be in prior art photovoltaic array by shadow occlusion schematic diagram；

Fig. 2 be in prior art photovoltaic array by P-V curve chart during shadow occlusion；

Fig. 3 is bimodal MPPT efficiency test flow chart in the embodiment of the present invention；

Fig. 4 is bimodal static MPPT efficiency test P-V curve chart in the embodiment of the present invention；

Fig. 5 is bimodal dynamic MPPT efficiency test P-V curve chart in the embodiment of the present invention；

Fig. 6 is that in the embodiment of the present invention, photovoltaic array bimodal P-V curvilinear motion speed arranges (test mode is 1.) schematic diagram；

Fig. 7 is that in the embodiment of the present invention, photovoltaic array bimodal P-V curvilinear motion speed arranges (test mode is 2.) schematic diagram；

Fig. 8 is photovoltaic module I-V curve figure in the embodiment of the present invention；

Fig. 9 is photovoltaic module P-V curve chart in the embodiment of the present invention；

Figure 10 is photovoltaic array bimodal P-V curve chart in the embodiment of the present invention；

Figure 11 is bimodal MPPT efficiency test result schematic diagram.

Detailed description of the invention

Below in conjunction with the accompanying drawings the present invention is described in further detail.

Such as Fig. 3, the present invention provides bimodal dynamically/static MPP of a kind of photovoltaic DC-to-AC converter to follow the tracks of Efficiency test method, described method bag Include following steps:

Step 1: determine the accessibility maximum power point of DC side photovoltaic array and photovoltaic DC-to-AC converter MPP voltage range；

Step 2: select photovoltaic array, and mate with photovoltaic DC-to-AC converter；

Step 3: determine photovoltaic module unimodal P-V curve；

Step 4: arrange photovoltaic array bimodal MPPT testing efficiency P-V curve, completes photovoltaic DC-to-AC converter bimodal dynamically/static MPP follows the tracks of efficiency test.

In described step 1, according to photovoltaic DC-to-AC converter run relevant parameter determine the accessibility peak power of DC side photovoltaic array and Photovoltaic DC-to-AC converter MPP voltage range；Photovoltaic DC-to-AC converter runs relevant parameter and includes the minimum MPP voltage of photovoltaic DC-to-AC converter U_mppmin, maximum MPP voltage U_mppmax, optimal MPP running voltage and photovoltaic DC-to-AC converter nominal run power.

Run power according to photovoltaic DC-to-AC converter nominal and determine accessibility peak power P of DC side photovoltaic array₀, the photovoltaic battle array of setting Arrange bimodal P-V curve peak power less than P₀；Minimum MPP voltage U according to photovoltaic DC-to-AC converter_mppmin, maximum MPP electricity Pressure U_mppmaxAnd most preferably MPP running voltage determines photovoltaic array MPP voltage range, bent carrying out the bimodal P-V of photovoltaic array When line sets, the running voltage that on photovoltaic array bimodal P-V curve, all extreme points are corresponding is all at the photovoltaic array MPP determined In voltage range.

In described step 2, select crystal silicon photovoltaic battle array according to the application scenario of photovoltaic DC-to-AC converter MPP voltage range and photovoltaic DC-to-AC converter Row or film photovoltaic array, and mate with photovoltaic DC-to-AC converter, determine photovoltaic according to photovoltaic DC-to-AC converter MPP voltage range simultaneously Serial number n of photovoltaic module and quantity m in parallel of photovoltaic group string that is composed in series by photovoltaic module in array.

In described step 3, photovoltaic module mathematical model is utilized to determine photovoltaic module unimodal MPPT efficiency test P-V curve, light In photovoltaic assembly mathematical model, have:

$I_{\mathrm{PV}}=I_{\mathrm{sc}}-I_0(e^{\frac{U_{\mathrm{PV}}}{U_{\mathrm{oc}}{C}_{\mathrm{AQ}}}}-1)---\left(1\right)$

Wherein, I_PVElectric current, I is exported for photovoltaic module_scFor photovoltaic module short circuit current, I₀For diode saturation current, U_PVFor Photovoltaic module output voltage, U_ocFor photovoltaic module open-circuit voltage, C_AQFor constant, it is expressed as:

$C_{\mathrm{AQ}}=\frac{{\mathrm{FF}}_U-1}{\ln (1-{\mathrm{FF}}_I)}---\left(2\right)$

Wherein, FF_UFor voltage activity coefficient, for the crystal silicon component in crystal silicon photovoltaic array, take 0.8, for film photovoltaic battle array Film assembly in row, takes 0.72；FF_IFor electric current activity coefficient, for the crystal silicon component in crystal silicon photovoltaic array, take 0.9, For the film assembly in film photovoltaic array, take 0.8；

N block photovoltaic module is connected into photovoltaic group string, simultaneously m photovoltaic group string when being unified into photovoltaic array, photovoltaic array open circuit electricity Pressure is expressed as with short circuit current:

U_{oc_a}=nU_oc (3)

I_{sc_a}=mI_sc (4)

Wherein, U_{oc_a}For photovoltaic array open-circuit voltage, I_{sc_a}For photovoltaic array short circuit current.

In described step 4, block pattern according to photovoltaic array and shadow occlusion degree arranges photovoltaic array bimodal MPPT test Efficiency P-V curve；The photovoltaic array pattern of blocking includes that permutation is blocked, full line blocks and blocks with monolithic element；

Setting and play voltage 0 from photovoltaic array open-circuit voltage, first peak power extreme value is leading peak, second peak power pole Value for postpeak, photovoltaic DC-to-AC converter carry out bimodal dynamically/static MPPT follow the tracks of time, from open-circuit voltage, reduce direction towards voltage Scan for；

1) if leading peak performance number is more than postpeak performance number, no matter whether photovoltaic DC-to-AC converter possesses bimodal MPPT controls function, all The maximum power point of photovoltaic array can be found；

2) if leading peak performance number is less than postpeak performance number, the photovoltaic DC-to-AC converter only possessing bimodal MPPT control function is the most permissible Search the true maximum of photovoltaic array；When on-the-spot shade changes, photovoltaic DC-to-AC converter is found again according to current working newly Maximum power point on P-V curve.

Arrange photovoltaic array bimodal MPPT testing efficiency P-V curve to specifically include and arrange bimodal static MPPT efficiency test P-V Curve and bimodal dynamic MPPT efficiency test P-V curve.

(1) when arranging bimodal static MPPT efficiency test P-V curve, it is respectively provided with under high irradiance and low irradiance The bimodal static MPPT efficiency test P-V curve of photovoltaic array, every set of curves comprises first peak and is more than postpeak, after first peak is slightly less than Peak and first peak are less than the situation of postpeak, such as C in accompanying drawing 4₁、C₂And C₃Shown in.Every curve is tested 2 times, tests 10 every time Minute, test result takes twice testing mean.When test, for C1, inverter should follow the trail of P1 point, for C₂, inverse Become device and should follow the trail of P4 point, it is ensured that inverter running voltage is near optimum operating voltage, for C₃, inverter should follow the trail of P4 point. The bimodal static MPPT efficiency eta of photovoltaic DC-to-AC converter_MPPT,statIt is expressed as:

${\mathrm{\η}}_{\mathrm{MPPT},\mathrm{stat}}=\frac{\underset{i=1}{\overset{z}{\mathrm{\Σ}}}{U}_{\mathrm{DC},i}\·I_{\mathrm{DC},i}\·\mathrm{\ΔT}}{P_{\mathrm{MPP},\mathrm{PVS}}\·T_M}---\left(5\right)$

Wherein, Δ T is the sampling period, less than photovoltaic DC-to-AC converter MPPT minimum interval；U_DC,iFor inputting in the sampling period The meansigma methods of voltage, I_DC,iFor the meansigma methods of input current, P in the sampling period_MPP,PVSExport for photovoltaic arrays simulator is actual High-power value, z is photovoltaic DC-to-AC converter sampled data points sum, T_MFor detecting the time, and there is T_M=z × Δ T.

(2) arranging bimodal dynamic MPPT efficiency test P-V curve, checking photovoltaic array is inverse by photovoltaic under change shadow occlusion Become device and follow the tracks of the performance of real peak.When carrying out bimodal dynamic MPPT efficiency test P-V curve and arranging, bimodal P-V curve also should Comprise leading peak performance number more than postpeak performance number, leading peak performance number less than the point of postpeak power, according to the same degree of the assembly that is blocked And shade situation of change, two kinds of measurement condition are set altogether:

2-1) coverage extent change；

During coverage extent change refers to that photovoltaic array surface occurs that shadow occlusion and shadow occlusion disappear, photovoltaic array P-V Curve is changed between unimodal and multimodal, investigates in transformation process, and the ability of real peak correctly found by inverter.

Bimodal dynamic MPPT efficiency test includes unimodal to bimodal conversion and bimodal to unimodal conversion；On accompanying drawing 4 set of curves basis On, increase unimodal curve, be designated as C₀, wherein, C0 correspondence irradiance is that under S0, C1 correspondence shade, irradiance is S1, C2 Under corresponding shade, irradiance is that under S2, C3 correspondence shade, irradiance is S3.Multimodal P-V curvilinear motion order is: C₀→C₁→ C₀→C₂→C₀→C₃, as shown in Figure 5.Under low irradiance and high irradiance, be respectively provided with P-V curvilinear motion speed with And change frequency, as shown in Figure 6.Under low irradiance with high irradiance, it is respectively provided with photovoltaic curvilinear motion speed such as accompanying drawing Shown in 6, arranging the low irradiation paramount irradiation rise time (t0～t1), retention time (t1～t2) during high irradiation, height is irradiated to low spoke According to fall time (t2～t3) and low irradiance retention time (t3～t4).In this mode, n times test is carried out.Through The bimodal dynamic MPPT efficiency eta of photovoltaic array after n times test_MPPTdyn,tIt is expressed as:

${\mathrm{\η}}_{\mathrm{MPPTDyn},t}=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\η}}_{\mathrm{MPPTdyn},k}$

Wherein, N is testing time sum, η_MPPTdyn,kThe bimodal dynamic MPPT efficiency of photovoltaic array in testing for kth time, its It is expressed as:

${\mathrm{\η}}_{\mathrm{MPPTdyn}.k}=\frac{\underset{i=1}{\overset{z}{\mathrm{\Σ}}}{U}_{\mathrm{DC},i}\·I_{\mathrm{DC},i}\·\mathrm{\Δ}{T}_i}{\underset{j=1}{\overset{M}{\mathrm{\Σ}}}{P}_{\mathrm{MPP},\mathrm{PVS},j}\·\mathrm{\Δ}{T}_j}---\left(7\right)$

Wherein, U_DC,iFor the meansigma methods of input voltage, I in the sampling period_DC,iFor the meansigma methods of input current in the sampling period, Δ T_i For photovoltaic DC-to-AC converter DC side data sampling period, Δ T in kth time test_jDefeated for photovoltaic arrays simulator in kth time test Go out power cycle, P_MPP,PVS,jFor photovoltaic arrays simulator Maximum Power Output in kth time test, M is photovoltaic arrays simulation Device sampled data points sum.

2-2) shielded area is constant, and coverage extent change；

Shielded area is constant, and when coverage extent change refers to block fixing, the partial illumination degree that is blocked changes, big by first peak Be changed to first peak less than secondary peak in secondary peak, such as irradiation change S1 → S3 → S1 in accompanying drawing 5, corresponding multimodal P-V change curve by C1 → C3 → C1 change, in change procedure, inverter, when irradiance profile changes, should be able to be distinguished on bimodal P-V curve Maximum of points and maximum point, tracking maximum power point: P1, P5, P1.It is respectively provided with photovoltaic curvilinear motion speed such as accompanying drawing 7 Shown in, the low irradiation paramount irradiation rise time (t0～t1) is set, retention time (t1～t2) during high irradiation, height is irradiated to low irradiation Fall time (t2～t3) and low irradiance retention time (t3～t4), test repeats n times every time.In this mode, use Formula (6) and (7) calculate photovoltaic array MPPT testing efficiency.

Embodiment

One 500kW photovoltaic array is lost under difference blocks pattern and is analyzed, test low irradiance static state MPPT efficiency. Array is made up of for Suntech 250W 25V Si-poly HiPerforma PLUTO block-type No. 2000.The compound mode of array is 20 block assembly series connection, the connection in series-parallel of 100 groups.Photovoltaic module parameter is as shown in table 1, every piece of photovoltaic module I-V curve in array And P-V curve is as shown in accompanying drawing 8 and accompanying drawing 9.

Table 1

Manufacturer	Suntech	Model	PLUTO250
				Component type	Monocrystal silicon	Short circuit current	8.63A
Open-circuit voltage	37.4V	Peak power electric current	8.15A
				Peak power voltage	30.7V	Nominal power	250W
Conversion efficiency	15.55%	Series resistance	0.152Ω
				Parallel resistance	500Ω	Bypass diode number	3

In the case of underloading, (when i.e. shadow-free blocks, irradiance is 500W/m²), set occlusion area irradiance and be respectively 400W/m²、300W/m²、200W/m²、100W/m²、50W/m²In the case of photovoltaic array P-V curve as shown in Figure 10. According to setting principle 3), choose that to block lower irradiance be 400W/m²、300W/m²And 50W/m²Curve is tested.

Photovoltaic DC-to-AC converter bimodal MPPT efficiency under test low irradiance, photovoltaic array is at 500W/m²Irradiation lower part is hidden by shade Gear, the photovoltaic module surface irradiation degree that is blocked is 300W/m²Making this array P-V curve is a bimodal curve, has two poles Value point, power maximum of points is all 10 minutes in the postpeak of P-V curve, every curve testing time.

Inverter, under not possessing multimodal MPPT tracing mode, is only capable of tracing into lower-wattage extreme value (first peak), such as accompanying drawing 11 Shown star trace point.In this case, photovoltaic DC-to-AC converter MPPT efficiency is 74.84%.

By change programmed instruction, making inverter have simple multimodal MPPT and follow the tracks of ability, now inverter can trace into Maximum power point of photovoltaic array (postpeak), circular trace point as shown in Figure 11.In this case, photovoltaic DC-to-AC converter MPPT Efficiency is 99.55%.

Finally should be noted that: above example only in order to illustrate that technical scheme is not intended to limit, art Those of ordinary skill still the detailed description of the invention of the present invention can be modified or equivalent with reference to above-described embodiment, These are without departing from any amendment of spirit and scope of the invention or equivalent, the claim of the present invention all awaited the reply in application Within protection domain.

Claims (7)

1. bimodal dynamically/static MPP of photovoltaic DC-to-AC converter follows the tracks of Efficiency test method, it is characterised in that: described method includes Following steps:

Step 1: determine the accessibility maximum power point of DC side photovoltaic array and photovoltaic DC-to-AC converter MPP voltage range；

Step 2: select photovoltaic array, and mate with photovoltaic DC-to-AC converter；

Step 3: determine photovoltaic module unimodal P-V curve；

Step 4: arrange photovoltaic array bimodal MPPT testing efficiency P-V curve, completes photovoltaic DC-to-AC converter bimodal dynamically/static MPP follows the tracks of efficiency test；

In described step 1, according to photovoltaic DC-to-AC converter run relevant parameter determine the accessibility peak power of DC side photovoltaic array and Photovoltaic DC-to-AC converter MPP voltage range；Photovoltaic DC-to-AC converter runs relevant parameter and includes the minimum MPP voltage of photovoltaic DC-to-AC converter U_mppmin, maximum MPP voltage U_mppmax, optimal MPP running voltage and photovoltaic DC-to-AC converter nominal run power；

Run power according to photovoltaic DC-to-AC converter nominal and determine accessibility peak power P of DC side photovoltaic array₀, the photovoltaic battle array of setting Arrange bimodal P-V curve peak power less than P₀；Minimum MPP voltage U according to photovoltaic DC-to-AC converter_mppmin, maximum MPP Voltage U_mppmaxAnd most preferably MPP running voltage determines photovoltaic array MPP voltage range, carrying out the bimodal P-V of photovoltaic array During curve setting, the running voltage that on photovoltaic array bimodal P-V curve, all extreme points are corresponding is all at the photovoltaic array MPP determined In voltage range.

Bimodal dynamically/static MPP of photovoltaic DC-to-AC converter the most according to claim 1 follows the tracks of Efficiency test method, and its feature exists In: in described step 2, select crystal silicon photovoltaic battle array according to the application scenario of photovoltaic DC-to-AC converter MPP voltage range and photovoltaic DC-to-AC converter Row or film photovoltaic array, and mate with photovoltaic DC-to-AC converter, determine photovoltaic according to photovoltaic DC-to-AC converter MPP voltage range simultaneously Serial number n of photovoltaic module and quantity m in parallel of photovoltaic group string that is composed in series by photovoltaic module in array.

Bimodal dynamically/static MPP of photovoltaic DC-to-AC converter the most according to claim 1 follows the tracks of Efficiency test method, and its feature exists In: in described step 3, utilize photovoltaic module mathematical model to determine photovoltaic module unimodal MPPT efficiency test P-V curve, light In photovoltaic assembly mathematical model, have:

$I_{PV}=I_{sc}-I_0(e^{\frac{U_{PV}}{U_{oc}{C}_{AQ}}}-1)$

Wherein, I_PVElectric current, I is exported for photovoltaic module_scFor photovoltaic module short circuit current, I₀For diode saturation current, U_PVFor Photovoltaic module output voltage, U_ocFor photovoltaic module open-circuit voltage, C_AQFor constant, it is expressed as:

$C_{AQ}=\frac{{\mathrm{FF}}_U-1}{ln(1-{\mathrm{FF}}_I)}$

Wherein, FF_UFor voltage activity coefficient, for the crystal silicon component in crystal silicon photovoltaic array, take 0.8, for film photovoltaic battle array Film assembly in row, takes 0.72；FF_IFor electric current activity coefficient, for the crystal silicon component in crystal silicon photovoltaic array, take 0.9, For the film assembly in film photovoltaic array, take 0.8；

N block photovoltaic module is connected into photovoltaic group string, simultaneously m photovoltaic group string when being unified into photovoltaic array, photovoltaic array open circuit electricity Pressure is expressed as with short circuit current:

U_{oc_a}=nU_oc

I_{sc_a}=mI_sc

Wherein, U_{oc_a}For photovoltaic array open-circuit voltage, I_{sc_a}For photovoltaic array short circuit current.

Bimodal dynamically/static MPP of photovoltaic DC-to-AC converter the most according to claim 1 follows the tracks of Efficiency test method, and its feature exists In: in described step 4, block pattern according to photovoltaic array and shadow occlusion degree arranges photovoltaic array bimodal MPPT test Efficiency P-V curve；The photovoltaic array pattern of blocking includes that permutation is blocked, full line blocks and blocks with monolithic element；

Setting and play voltage 0 from photovoltaic array open-circuit voltage, first peak power extreme value is leading peak, second peak power pole Value for postpeak, photovoltaic DC-to-AC converter carry out bimodal dynamically/static MPPT follow the tracks of time, from open-circuit voltage, reduce direction towards voltage Scan for；

1) if leading peak performance number is more than postpeak performance number, no matter whether photovoltaic DC-to-AC converter possesses bimodal MPPT controls function, all The maximum power point of photovoltaic array can be found；

2) if leading peak performance number is less than postpeak performance number, the photovoltaic DC-to-AC converter only possessing bimodal MPPT control function is the most permissible Search the true maximum of photovoltaic array；When on-the-spot shade changes, photovoltaic DC-to-AC converter is found again according to current working newly Maximum power point on P-V curve.

5. following the tracks of Efficiency test method according to bimodal dynamically/static MPP of the photovoltaic DC-to-AC converter described in claim 1 or 4, it is special Levy and be: photovoltaic array bimodal MPPT testing efficiency P-V curve is set and specifically includes bimodal static MPPT efficiency test is set P-V curve and bimodal dynamic MPPT efficiency test P-V curve.

Bimodal dynamically/static MPP of photovoltaic DC-to-AC converter the most according to claim 5 follows the tracks of Efficiency test method, and its feature exists In: when arranging bimodal static MPPT efficiency test P-V curve, the photovoltaic battle array being respectively provided with under high irradiance and low irradiance Arrange bimodal static MPPT efficiency test P-V curve, the bimodal static MPPT efficiency eta of photovoltaic DC-to-AC converter_MPPT,statIt is expressed as:

${\mathrm{\η}}_{MPPT,stat}=\frac{\underset{i=1}{\overset{z}{\Σ}}{U}_{DC,i}\·I_{DC,i}\·\mathrm{\Δ}T}{P_{MPP,PVS}\·T_M}$

Wherein, Δ T is the sampling period, less than photovoltaic DC-to-AC converter MPPT minimum interval；U_DC,iFor inputting in the sampling period The meansigma methods of voltage, I_DC,iFor the meansigma methods of input current, P in the sampling period_MPP,PVSExport for photovoltaic arrays simulator is actual High-power value, z is photovoltaic DC-to-AC converter sampled data points sum, T_MFor detecting the time, and there is T_M=z × Δ T.

Bimodal dynamically/static MPP of photovoltaic DC-to-AC converter the most according to claim 5 follows the tracks of Efficiency test method, and its feature exists In: when arranging bimodal dynamic MPPT efficiency test P-V curve, bimodal dynamic MPPT efficiency test includes unimodal to bimodal Conversion and bimodal to unimodal conversion；The bimodal dynamic MPPT efficiency eta of photovoltaic array after n-th is tested_MPPTdyn,tIt is expressed as:

${\mathrm{\η}}_{MPPTdyn,t}=\frac{1}{N}\underset{k=1}{\overset{N}{\Σ}}{\mathrm{\η}}_{MPPTdyn,k}$

Wherein, N is testing time sum, η_MPPTdyn,kThe bimodal dynamic MPPT efficiency of photovoltaic array in testing for kth time, its It is expressed as:

${\mathrm{\η}}_{MPPTdyn.k}=\frac{\underset{i=1}{\overset{z}{\Σ}}{U}_{DC,i}\·I_{DC,i}\·{\mathrm{\ΔT}}_i}{\underset{j=1}{\overset{M}{\Σ}}{P}_{MPP,PVS,j}\·{\mathrm{\ΔT}}_j}$

Wherein, U_DC,iFor the meansigma methods of input voltage, I in the sampling period_DC,iFor the meansigma methods of input current in the sampling period, Δ T_i For photovoltaic DC-to-AC converter DC side data sampling period, Δ T in kth time test_jDefeated for photovoltaic arrays simulator in kth time test Go out power cycle, P_MPP,PVS,jFor photovoltaic arrays simulator Maximum Power Output in kth time test, M is photovoltaic arrays simulation Device sampled data points sum.