CN107450651B - The control method of maximum power point of photovoltaic power generation system capture system - Google Patents
The control method of maximum power point of photovoltaic power generation system capture system Download PDFInfo
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- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/66—Regulating electric power
- G05F1/67—Regulating electric power to the maximum power available from a generator, e.g. from solar cell
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The invention discloses a kind of maximum power point of photovoltaic power generation system to capture system and control method.The system is made of photovoltaic power generation major loop and photovoltaic power generation control loop；Wherein, photovoltaic power generation major loop is made of photovoltaic array, DC converter, load, and photovoltaic power generation control loop is made of phasor measurement units, MPPC control unit.The quick capture of maximum power point of photovoltaic power generation system of this method canbe used on line, the i.e. technology that step positioning, a step capture；And by setting maximum power point stable region, steady-error coefficient oscillation problem is eliminated；Photovoltaic array output voltage is set substantially to be constantly equal to maximum power point voltage, output power is substantially constantly equal to maximum power.The problem of this method amplitude peak causes photovoltaic array output pulsation when reducing solar energy fluctuation and load fluctuation, especially it is a cancellation issuable problem out of control when solar energy big ups and downs.
Description
Technical field
The present invention relates to solar energy power generating applied technical field, specially a kind of maximum power point of photovoltaic power generation system
Capture system and its control method are suitable for photovoltaic generating system and keep maximum power point output or photovoltaic generating system highest
Photoelectric conversion efficiency power generation.
Background technique
Continuous improvement with the whole society to sustainable development and environmental protection requirement is researched and developed, energetically using renewable
The energy has become global common recognition.Solar energy power generating is one of renewable energy application technology.Since solar energy exists
Generality, attract the application technology that countless scientific workers research and develop it.But since solar energy density is low (general small
In 1000W/m2), along with solar cell photoelectric transfer efficiency it is low (in practical application, generally less than 20%), so, mention
High photovoltaic power generation operation efficiency just becomes the main problem that research and development photovoltaic power generation application technology needs to solve.
So far, maximum power point of photovoltaic power generation system tracking (MPPT) technology, which becomes, improves photovoltaic power generation work effect
The major measure of rate.For many years, scientific worker proposes many kinds of MPPT techniques, and related document has carried out well them
It summarizes compared with.But for MPPT technique, needs continuously to observe and disturb (P&O), so disturbance step-length is direct
It is related to the superiority and inferiority of photovoltaic power generation technology parameter.If disturbed, step-length is small, and photovoltaic power generation parameter static oscillation is small, but dynamic response
Difference, low voltage crossing, high voltage crossing outstanding problem, as shown in Figure 3.If it is big to disturb step-length, photovoltaic power generation dynamic state of parameters is rung
It should improve, but static oscillation problem will become larger, as shown in Figure 4；Response duration, all there is additional energy losses.It says above
The size needs of bright disturbance step-length do a tradeoff between steady-error coefficient and dynamic response, this is existing for photovoltaic power generation technology
One of main problem.In addition, many MPPT techniques based on extremum principle, since the photovoltaic P-V curve of its foundation is imperfect or
Inaccuracy causes when acute variation occurs for solar illuminating intensity, MPPT controller will lead to the problem of it is wrong disturb, such as
Shown in Fig. 5, this is two of main problem existing for photovoltaic power generation technology.
Disturbed in one MPPT technique of problem step-length it is much preferably aiming at the problem that, step is still either become using fixed step size
It grows, so far ununified conclusion, this is the inherent shortcoming of MPPT technique.Its reason be exactly MPPT technique can only judge with
The direction of track maximum power point, the position without knowing maximum power point, it is therefore desirable to a step connect a step ceaselessly disturb, with
Thus a series of problems of steady-error coefficient and dynamic response in tracking is brought in the direction of track (P&O) maximum power point.Obviously, it solves
Certainly the thinking of the problem is exactly to innovate a kind of control method, finds the position of maximum power point online, in real time and captures maximum
Power points.
MPPT technique for problem two based on extremum principle may generate mistake when acute variation occurs for intensity of sunshine
The problem of accidentally disturbing, illustrates its control technology according to problematic.Solving the problems, such as this thinking is: restudying photovoltaic generating system
Electrical external characteristics, find maximum power point of photovoltaic power generation system power generation when correct control foundation.
Summary of the invention
On the basis of emulation experiment, the present invention provides complete photovoltaics load characteristic curve, as shown in Figure 1 and Figure 2,
This be all photovoltaic power generation technologies should foundation control foundation.When solar energy irradiation level (S) is constant and load (R) becomes, light
It lies prostrate shown in I-V curve such as Fig. 1 (a), wherein
ΔG≤0
Shown in its corresponding photovoltaic P-V curve such as Fig. 1 (b), wherein
At maximum power point, Δ P/ Δ V=0
On the left of maximum power point, Δ P/ Δ V > 0
On the right side of maximum power point, Δ P/ Δ V < 0
When solar irradiance (S) becomes and load (R) is constant, shown in photovoltaic I-V curve such as Fig. 2 (a), in which:
Δ G > 0
Shown in its corresponding photovoltaic P-V curve such as Fig. 2 (b), in which:
Δ P/ Δ V > 0
The above complete photovoltaic have carry characteristic curve for the research and development of all kinds of photovoltaic power generation control technologies provide accurately according to
According to Fig. 1 (a) and Fig. 2 (a) provide I-V characteristic control foundation；Fig. 1 (b) and Fig. 2 (b) provide P-V Characteristics Control foundation.
Clearly for based on the MPPT technique of extremum principle, only considered the P-V curve characteristic of Fig. 1 (b) before, scheme without considering
2 (b) P-V curve characteristic.When encountering Fig. 2 (b) the case where, the disturbance that MPPT controller generates mistake is not just strange.
In order to solve, disturbance step sizes are affected to MPPT technique to the present invention and MPPT technique bring is dynamically loud
Should it is slow, there are problems that mistake disturbance, provide a kind of maximum power point of photovoltaic power generation system and capture (Maximum Power
Point Capturing, abbreviation MPPC) technology.
The present invention is achieved by the following technical solution: MPPC technology is by maximum power point tuning on-line technology and most
The high-power online capturing technology of point is constituted, wherein maximum power point tuning on-line technology by photovoltaic Practical model choosing
It selects, the depression of order of photovoltaic Practical model, maximum power point tuning on-line etc. are constituted；The online capturing technology of maximum power point,
The acquisition and capture of maximum power point duty ratio are then realized by DC converter transmission function: i.e. the method achieve photovoltaic hairs
The quick capture of the online maximum power point of electric system, i.e. a step positioning, a step capture.Meanwhile this method passes through to maximum power
The dynamic setting of point stable region, avoids steady-error coefficient oscillation problem.The control effect of this method is that this method makes photovoltaic array
Output voltage is substantially constantly equal to maximum power point voltage, and output power is substantially constantly equal to maximum power, concrete operations step
It is rapid as follows:
1. according to the prior art parameter on solar panels: short circuit current Iscref, maximum power point electric current Imref, maximum work
Rate point voltage Vmref, open-circuit voltage Vocref, scale parameter K is calculated by short circuit current methodSC=Imref/Iscref, and by opening
Road voltage method calculates KOC=Vmref/Vocref, and custom parameter C is obtained by following formula1、 C2Numerical value:
C2=(KOC-1)[ln(1-KSC)]-1
Meanwhile defining following initial parameter:
Dinitial- duty ratio initial value；Dmax- largest duty cycle value；
Dmin- duty ratio minimum value；Δ D-duty ratio disturbs step-length.
2. entering the startup program of MPPC: find two operating points on same I-V curve:
A. first time disturbance is carried out to system, exports D=DinitialAfterwards, it measures and samples first operating point (Vk, Ik),
D is updated immediatelyold=D, Vk-1=Vk, Ik-1=Ik；
B. second is carried out to system to disturb, export D=DoldAfter+Δ D, measures and sample second operating point (Vk,
Ik), and calculate two o'clock (Vk, Ik) and (Vk-1, Ik-1) between G: Δ G=(I of increment conductance Δk- Ik-1)/(Vk- Vk-1), and
Update Dold=D；
If 1.1 Δ G > 0, continue to run step c or step d；
If 3. 1.2 Δ G≤0, enter step；
If c. Dold+ Δ D > Dmax, return step a, restart starting operation；
If d. Dold+ΔD≤Dmax, enable VK-1=Vk, IK-1=Ik, return step b, then continuous starting operation.
3. carrying out maximum power point location and capturing:
A. maximum power point location: target is determining newest maximum power point parameter online, by two sample point parameters
(Vk, Ik)、(Vk-1, Ik-1) V that is substituted into following photovoltaic Practical model equation respectively and I form two equations column in parallel and ask
Solution,
Since above-mentioned equation is nonlinear equation, need using solution by iterative method, therefore calculated using Newton iteration method, i.e.,
The short circuit current I of current photovoltaic array can be quickly obtainedscWith open-circuit voltage Voc；And thereby determine that the electricity of current maximum power point
Pressure, electric current and resistance parameter are as follows:
Vm=KOC×Voc
Im=KSC×Isc
Rm=Vm/Im；
B. maximum power point captures: currently practical operating parameter: D=Dold, Ri=VK/IK, passed by DC converter
Delivery function can establish the relationship between current point of operation and maximum power point parameter, and obtain accounting for for current maximum power point
Sky ratio Dm, operate in photovoltaic power generation major loop at newest maximum power point.For different DC converters, calculation formula
It is as follows:
1.1 for step down DC converter:
1.2 for voltage boosting dc converter:
1.3 for buck-boost DC converter:
With calculated DmIt is disturbed, photovoltaic generating system can be made to operate at maximum power point.
In order to eliminate MPPT technique bring static oscillation problem, the present invention is arranged in real time or updates most in MPPC technology
High-power voltage VmStable region.Stable strategy are as follows: when working voltage is in VmStable region in when, MPPC controller is only seen
Survey does not disturb, and avoids static oscillation；When working voltage crosses the border to VmStable region outside when, MPPC controller carries out new maximum work
The positioning and capture of rate point, and redefine new VmStable region.Specific step is as follows:
4. stable region is arranged: the stable region is the stable domain of static state of maximum power point；The present invention exports photovoltaic
Relative fluctuation degree judgment basis as stable region of the voltage relative to current maximum power point voltage, and set its stable thresholding as
ε, judgment basis are as follows:
If a. | (Vk-Vm)/Vm|≤ε, output duty cycle D=DoldIt is constant, continue sampling and compare, circular flow is only observed
It does not disturb, avoids static concussion；
If b. | (Vk-Vm)/Vm| > ε then presses (Vk-Vm) value disposed respectively:
If 1.1 Vk-Vm> 0 exports D=Dold+ Δ D acquires data and calculates Δ G；
If 1.2 Vk-Vm≤ 0, export D=DoldΔ D acquires data and calculates Δ G；
If Δ G≤0, enters step and 3. carry out new maximum power point location and capture；
If Δ G > 0, enters step and 5. carry out new maximum power point valuation positioning and capture.
5. maximum power point valuation positioning and capture:
A. maximum power point valuation positions: using nearest maximum power point voltage VmFind approximate new maximum power
Point；As Δ G > 0, by newest sample point parameter (Vk, Ik) and the last V being calculatedocSubstitute into following photovoltaic engineering
Utility model equation solution:
It can be obtained the short circuit current I ' of current photovoltaic arraysc, and thereby determine that current maximum power point valuation voltage,
Valuation electric current and valuation resistance parameter are as follows:
V′m=KOC×Voc
I′m=KSC×I′sc
R′m=V 'm/I′m；
B. approximate maximum power point captures: currently practical operating point parameter are as follows: D=Dold, Ri=VK/IK.Need to make be
System operates at current approximate maximum power point, and parameter resistance is R 'm(known), duty ratio D 'm(undetermined).
By analysis, using DC converter transmission function, current point of operation can be established and joined with approximate maximum power point
Relationship between number, for different DC converters, calculation formula is as follows:
1.1 for step down DC converter:
1.2 for voltage boosting dc converter:
1.3 for buck boost converter:
With calculated D 'mIt is disturbed, photovoltaic generating system just operates at approximate maximum power point；Then into
Enter operating procedure 4..
The maximum power point of photovoltaic power generation system capturing technology is compared compared to existing photovoltaic power generation control technology, tool
It has the advantage that
1) compared with all photovoltaic power generation control technologies before based on different principle, the present invention is to have load I- based on photovoltaic
The online Generation Control technology of V characteristic and a kind of photovoltaic Practical model；With all MPPT maximum power point trackings (MPPT) before
Technology is compared, and the present invention is that online maximum power point captures (MPPC) technology.
2) it is that online maximum power point captures (MPPC) technology that the present invention, which changes MPPT maximum power point tracking (MPPT) technology, is disappeared
In addition to (MPPT) technology disturbance step sizes and a step connect step tracking bring a series of problems, such as low voltage crossing problem
Deng.
3) present invention can be arranged in real time, update the steady stability domain of maximum power point voltage.When working voltage is in Vm
Stable region in when, MPPC controller, which is only observed, not to be disturbed, and static oscillation is avoided；When working voltage is in VmStable region outside
When, MPPC controller carries out new maximum power point and captures, and redefines new VmSteady stability domain.
4) it is only necessary to disturb to find new maximum power point and capture maximum power point twice for MPPC technology
(that is, primary positioning, primary to capture), so, through MPPC technical controlling, photovoltaic output voltage is constantly equal to V substantiallym, photovoltaic output
Power is constantly equal to P substantiallym.Compared with existing MPPT photovoltaic power generation technology, photovoltaic power generation all technical can all be obtained greatly
The problem of amplitude improves, MPPT technique based on extremum principle can be well solved (MPPC as shown in Figure 6
In, starting speed is fast, steady-error coefficient dead-beat；Dynamic response is fast and accurate, and problem out of control is not present；Moreover, photoelectric energy turns
It changes efficiency to nearly reach 100%), this method amplitude peak causes photovoltaic array when reducing solar energy fluctuation and load fluctuation
The problem of output pulsation, is especially a cancellation issuable problem out of control when solar energy big ups and downs.
Detailed description of the invention
Fig. 1 be photovoltaic generating system when having load intensity of sunshine it is constant and load corresponding I-V and P-V characteristic curve when becoming.
Fig. 2 is corresponding I-V and P-V characteristic curve when intensity of sunshine becomes and loads constant when photovoltaic generating system has load.
Fig. 3 is the situation of change of parameters when MPPT controller uses microvariations step-length.
Fig. 4 is the situation of change of parameters when MPPT controller uses large disturbances step-length.
Fig. 5 is the change that MPPT controller generates mistake disturbance parameters when solar energy intensity of sunshine occurs persistently to change
Change situation schematic diagram.
Fig. 6 captures the effect of maximum power point for MPPC controller of the present invention when solar energy intensity of sunshine occurs persistently to change
Fruit schematic diagram.
Fig. 7 is that MPPC controls program flow diagram.
Fig. 8 is the structural schematic diagram that maximum power point of photovoltaic power generation system captures system.
Specific embodiment
Specific embodiments of the present invention are illustrated with reference to the accompanying drawing.
A kind of maximum power point of photovoltaic power generation system capture system, as shown in Figure 8: including photovoltaic power generation major loop and photovoltaic
Generation Control circuit；Wherein, photovoltaic power generation major loop is made of photovoltaic array, DC converter, load.Photovoltaic array is by more
Block solar panels form in series and parallel as needed；DC converter selects as needed, selects decompression DC to become in the present embodiment
Parallel operation, voltage boosting dc converter or buck boost converter；It loads and D.C. resistance may be selected, it can also be in DC/AC inversion
AC load is connected after device or two kinds of loads are connected in parallel and also may be used；Photovoltaic array is connected to load by DC converter.
DC converter duty ratio control photovoltaic power generation major loop operating status (or adjust include DC converter and load etc.
Imitate the size of resistance) and form closed-loop control.
And photovoltaic power generation control loop is made of phasor measurement units and MPPC control unit, wherein phasor measurement units are negative
Duty continuously its voltage is sampled with electric current from photovoltaic array output end, MPPC control unit be microprocessor, according to
The sampling of phasor measurement unit, by the maximum power point capturing technology program that designs of the present invention, continuously output duty cycle D, from
And it realizes and the state of photovoltaic power generation main circuit is controlled.
Phasor measurement units measurement period (that is, disturbance period in MPPC) takes 0.01 second in the present embodiment, that is, measurement
Frequency (i.e. forcing frequency) is 100Hz.In general, the disturbance period should be greater than 4 times that are equal to power generation major loop time constant.Due to
MPPC technology and the size of disturbance step-length have no relations；Should be small as far as possible so disturbing step-length in program, reduce disturbance step-length to the greatest extent
It is larger and bring unnecessary error；In normal external interference, as long as before disturbance step-length value can distinguish disturbance
Circuit state afterwards.
The maximum power point capturing technology program of the present embodiment is worked out on the platform of MATLAB 2015a, controls program
Flow chart is as shown in fig. 7, detailed step is as described below:
1. according to the prior art parameter on solar panels: short circuit current Iscref, maximum power point electric current Imref, maximum work
Rate point voltage Vmref, open-circuit voltage Vocref, scale parameter K is calculated by short circuit current methodSC=Imref/Iscref, pass through open circuit electricity
Platen press calculates KOC=Vmref/Vocref, and custom parameter C is obtained by following formula1、C2Numerical value:
C2=(KOC-1)[ln(1KSC)]-1
Meanwhile defining following initial parameter:
Dinitial- duty ratio initial value, takes 0.1；
Dmax- largest duty cycle value, takes 0.9；
Dmin- duty ratio minimum value, takes 0.1；
Δ D-duty ratio disturbs step-length, takes 0.2%.
2. entering the startup program of MPPC, two operating points on same I-V curve are found:
A. first time disturbance is carried out to system, i.e. output D=DinitialAfterwards, it measures and samples first operating point (Vk,
Ik), D is updated immediatelyold=D, Vk-1=Vk, Ik-1=Ik；
B. it carries out second to system to disturb, i.e. output D=DoldAfter+Δ D, measures and sample second operating point (Vk,
Ik), and calculate two o'clock (Vk, Ik) and (Vk-1, Ik-1) between G: Δ G=(I of increment conductance Δk- Ik-1)/(Vk- Vk-1), and
Update Dold=D；
If 1.1 Δ G > 0, continue to start, into operating procedure c or step d；
If 3. 1.2 Δ G≤0, enter step；
If c. Dold+ Δ D > Dmax, return step a, restart starting operation；
If d. Dold+ΔD≤Dmax, enable VK-1=Vk, IK-1=Ik, return step b, then continuous starting operation.
3. carrying out maximum power point location and capturing:
A. maximum power point location: target is determining current maximum power point parameter online, by two sample point parameters
(Vk, Ik)、(Vk-1, Ik-1) V that is substituted into following photovoltaic Practical model equation respectively and I form two equations column in parallel and ask
Solution,
It is calculated in the present embodiment using Newton iteration method, the short circuit current I of current photovoltaic array can be quickly obtainedscWith it is short
Road voltage Voc；And thereby determine that the voltage, electric current and resistance parameter of current maximum power point are as follows:
Vm=KOC×Voc
Im=KSC×Isc
Rm=Vm/Im；
B. maximum power point captures: currently practical operating point parameter are as follows: D=Dold, Ri=VK/IK.It needs to operate in and work as
Preceding maximum power point, parameter resistance are Rm(known), duty ratio Dm(wait ask).
By analysis, using DC converter transmission function, can establish current point of operation and maximum power point parameter it
Between relationship.For different DC converters, calculation formula is as follows:
1.1 for step down DC converter:
1.2 for voltage boosting dc converter:
1.3 for buck boost converter:
With calculated DmIt is disturbed, operates in photovoltaic generating system at maximum power point；
According to analysis, maximum power point voltage VmThe setting of stable region is changeable, depending on being needed according to real work.When
VmWhen stable region setting is larger, photovoltaic output voltage tatic range is wider, but the number of dynamic MPPC is reduced；Work as VmStable region
When being arranged smaller, photovoltaic output voltage tatic range is narrow, but the number of dynamic MPPC increases.
4. stable region is arranged: the stable region is the stable domain of static state of maximum power point；The present embodiment is defeated by photovoltaic
Relative fluctuation degree judgment basis as stable region of the voltage relative to current maximum power point voltage out defines and stablizes thresholding and be
ε；Therefore the judgment basis for defining stable region is as follows:
|(Vk-Vm)/Vm|≤ε, wherein ε is to stablize thresholding；ε=1% is taken in the present embodiment.
If a. | (Vk-Vm)/Vm|≤ε, output duty cycle D=DoldIt is constant, continue sampling and compare, circular flow is only observed
It does not disturb, avoids static concussion；
If b. | (Vk-Vm)/Vm| > ε, then to Vk-VmValue is discussed respectively:
If 1.1 Vk-Vm> 0 exports D=Dold+ Δ D acquires data and calculates Δ G；
If 1.2 Vk-Vm≤ 0, export D=DoldΔ D acquires data and calculates Δ G；
If 3. Δ G≤0, enters step；
If Δ G > 0, enters step and 5. revalue new maximum power point location and carry out maximum power point capture；
5. maximum power point valuation positioning and capture:
A. maximum power point valuation positions: using nearest maximum power point voltage VmFind approximate new maximum power
Point；As Δ G > 0, by newest sample point parameter (Vk, Ik) and the last V being calculatedocSubstitute into following photovoltaic engineering
Utility model equation solution:
It can be obtained the short circuit current I ' of current photovoltaic arraysc, and thereby determine that current maximum power point valuation voltage,
Valuation electric current and valuation resistance parameter are as follows:
V′m=KOC×Voc
I′m=KSC×I′sc
R′m=V 'm/I′m；
B. approximate maximum power point captures: currently practical operating point parameter are as follows: D=Dold, Ri=VK/IK.System needs
It operates at current approximate maximum power point, parameter resistance is R 'm(known), duty ratio D 'm(wait ask).
By analysis, using DC converter transmission function, current point of operation can be established and joined with approximate maximum power point
Relationship between number, for different DC converters, calculation formula is as follows:
1.1 for step down DC converter:
1.2 for voltage boosting dc converter:
1.3 for buck boost converter:
With calculated D 'mIt is disturbed, operates in photovoltaic generating system at maximum power point；Then operating procedure
④。
The control effect of the present embodiment is as shown in Figure 6.Fig. 6 and Fig. 5 are compared, i.e., by the control performance of MPPT with
The control performance of MPPC compares, it can be observed that following phenomenon: 1, starting is fast, and MPPC it is only necessary to disturb twice, photovoltaic hair
Electric system enters stable state (i.e. static) operation, and MPPT technique needs a very long time (and disturbance step sizes have
It closes).2, steady-error coefficient.When MPPC control, photovoltaic generating system runs dead-beat, and when MPPT control, photovoltaic generating system
Oscillatory operation (oscillation amplitude is related with disturbance step sizes).3, dynamic response.2 seconds to 4 seconds solar energies of observation slowly decline
The process slowly risen with 6 seconds to 8 seconds solar energies: during solar energy slowly declined in 2 seconds to 4 seconds, compared to figure
5 MPPT techniques based on extremum principle, the MPPC technology of Fig. 6 can preferably capture the maximum power point of photovoltaic array.And 6
During second slowly rose to 8 seconds solar energies, as shown in figure 5, mistake has occurred in the MPPT technique based on extremum principle
Tracking makes photovoltaic generating system operating point gradually deviate from maximum power point until open circuit (i.e. D=0, due to generally setting in program
It is equipped with Dmin, last operating point is very close to open circuit point)；And for MPPC technology, as shown in fig. 6, in 6 seconds to 8 seconds solar energies
During slowly rising, photovoltaic generating system operating point tightly captures maximum power point.In addition, in photovoltaic generating system
During whole service, including dynamic and static operation and dynamic operation are opened, the photovoltaic energy conversion efficiency of MPPC control technology is remote
It is better than the photovoltaic energy conversion efficiency of MPPT control technology, moreover, the photovoltaic energy conversion efficiency of MPPC control technology reaches
It is optimal, nearly close to 100%.
When the present embodiment uses MPPC, it is thus only necessary to which a disturbance carries out maximum power point location, needs another disturbance
Carry out maximum power point capture.That is, needing two disturbances when acute variation occurs for intensity of sunshine or acute variation occurs for load
Period captures new maximum power point.
The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention.
Various modifications to these embodiments will be readily apparent to those skilled in the art, as defined herein
General Principle can be realized in other embodiments without departing from the spirit or scope of the present invention.Therefore, of the invention
It is not intended to be limited to the embodiments shown herein, and is to fit to and the principles and novel features disclosed herein phase one
The widest scope of cause.
Claims (4)
1. the control method that a kind of maximum power point of photovoltaic power generation system captures system, it is characterised in that: the following steps are included:
1. according to the prior art parameter on solar panels: short circuit current Iscref, maximum power point electric current Imref, maximum power point
Voltage Vmref, open-circuit voltage Vocref, calculate scale parameter KSC=Imref/IscrefWith KOC=Vmref/Vocref, and by following public
Formula obtains custom parameter C1、C2Numerical value:
C2=(KOC-1)[ln(1-KSC)]-1
Meanwhile defining following initial parameter:
Dinitial- duty ratio initial value；Dmax- largest duty cycle value；
Dmin- duty ratio minimum value；Δ D-duty ratio disturbs step-length；
2. entering the startup program of MPPC:
A. first time disturbance is carried out to system, exports D=Dinitial, measure and sample first operating point (Vk, Ik), immediately more
New Dold=D, Vk-1=Vk, Ik-1=Ik；
B. second is carried out to system to disturb, export D=DoldAfter+Δ D, measures and sample second operating point (Vk, Ik), and count
Calculate two o'clock (Vk, Ik) and (Vk-1, Ik-1) between G: Δ G=(I of increment conductance Δk- Ik-1)/(Vk- Vk-1), and update Dold=
D；
If 1.1 Δ G > 0, continue to run step c or step d；
If 3. 1.2 Δ G≤0, enter step；
If c. Dold+ Δ D > Dmax, return step a, then restart operation；
If d. Dold+ΔD≤Dmax, enable VK-1=Vk, IK-1=Ik, return step b, then continuous starting operation；
3. carrying out maximum power point location and capturing:
A. maximum power point location: current maximum power point parameter is determined, by two sample point parameter (Vk, Ik)、(Vk-1, Ik-1)
The V and I substituted into following photovoltaic Practical model equation respectively forms two equation connection column and solves,
It is calculated using Newton iteration method, can be obtained the short circuit current I of current photovoltaic arrayscWith open-circuit voltage Voc；And thus really
The voltage of settled preceding maximum power point, electric current and resistance parameter are as follows:
Vm=KOC×Voc
Im=KSC×Isc
Rm=Vm/Im；
B. maximum power point captures: by DC converter transmission function, obtaining the duty ratio of current maximum power point, makes photovoltaic
Power generation major loop operates at newest maximum power point, and calculates the duty ratio D at maximum power pointm；
According to currently practical operating parameter: D=Dold, Ri=VK/IK, for different DC converters, calculation formula is as follows:
1.1 for step down DC converter:
1.2 for voltage boosting dc converter:
1.3 for buck boost converter:
With calculated DmIt is disturbed, operates in photovoltaic generating system at maximum power point.
2. the control method that maximum power point of photovoltaic power generation system according to claim 1 captures system, it is characterised in that:
It is further comprising the steps of:
4. stable region is arranged: the stable region is the stable domain of static state of maximum power point；It defines and stablizes thresholding as ε, stablize
The judgment basis in domain is as follows:
If a. | (Vk-Vm)/Vm|≤ε, output duty cycle D=DoldIt is constant, continue sampling and compare, circular flow, only observation is not disturbed
It is dynamic；
If b. | (Vk-Vm)/Vm| > ε, then according to Vk-VmValue is disposed respectively:
If 1.1 Vk-Vm> 0 exports D=Dold+ Δ D acquires data and calculates Δ G；
If 1.2 Vk-Vm≤ 0, export D=DoldΔ D acquires data and calculates Δ G；
If Δ G≤0, enters step and 3. carry out new maximum power point location and capture；
If Δ G > 0, enters step and 5. carry out new maximum power point valuation positioning and capture；
5. maximum power point valuation positioning capturing:
A. maximum power point valuation positions: using nearest maximum power point voltage VmFind approximate new maximum power point；Work as Δ
When G > 0, by newest sample point parameter (Vk, Ik) and the last V being calculatedocSubstitute into following photovoltaic Practical model
Equation solution:
It can be obtained the short circuit current I ' of current photovoltaic arraysc, and thereby determine that the valuation voltage of current maximum power point, valuation
Electric current and valuation resistance parameter are as follows:
V′m=KOC×Voc
I′m=KSC×I′sc
R′m=V 'm/I′m；
B. approximate maximum power point captures: by DC converter transmission function, obtaining the duty ratio of current maximum power point, makes
Photovoltaic power generation major loop operates at newest maximum power point, and calculates the duty ratio D ' at maximum power pointm；
According to currently practical operating parameter are as follows: D=Dold, Ri=Vk/Ik, for different DC converters, calculation formula is such as
Under:
1.1 for step down DC converter:
1.2 for voltage boosting dc converter:
1.3 for buck boost converter:
With calculated D 'mIt is disturbed, operates in photovoltaic generating system at maximum power point；Then operating procedure is 4..
3. the control method that maximum power point of photovoltaic power generation system according to claim 1 captures system, it is characterised in that:
DinitialTake 0.1；DmaxTake 0.9；DminTake 0.1；Δ D takes 0.2%.
4. the control method that maximum power point of photovoltaic power generation system according to claim 2 captures system, it is characterised in that:
The stable thresholding ε is 1%.
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