CN103995561B

CN103995561B - A kind of maximum power point tracing method and device

Info

Publication number: CN103995561B
Application number: CN201410230513.1A
Authority: CN
Inventors: 石勇
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Digital Power Technologies Co Ltd
Priority date: 2014-05-28
Filing date: 2014-05-28
Publication date: 2015-12-02
Anticipated expiration: 2034-05-28
Also published as: CN103995561A

Abstract

The embodiment of the invention discloses a kind of maximum power point tracing method, comprising: the output power maintaining the first preset duration internal power transducer is constant, and described power converter comprises DC bus; To sample the magnitude of voltage of described DC bus according to the predeterminated voltage sampling period, described first preset duration comprises the predeterminated voltage sampling period described at least two continuous print; The magnitude of voltage that each predeterminated voltage sampling period relatively in described first preset duration collects, controls the output power of described power converter according to the comparative result of described comparison.Correspondingly, the embodiment of the invention also discloses a kind of maximum power point tracking device.Adopt the embodiment of the present invention, the power error that current sensor causes can be removed, improve MPPT precision, thus improve the whole efficiency of photovoltaic generating system.

Description

A kind of maximum power point tracing method and device

Technical field

The present invention relates to photovoltaic cell technical field, particularly relate to a kind of maximum power point tracing method and device.

Background technology

The output characteristics of photovoltaic cell is non-linear (family curve of photovoltaic cell as shown in Figure 1), and its output affects by intensity of illumination, environment temperature and loading condition.Under certain intensity of illumination and environment temperature, photovoltaic cell can be operated in different output voltage states, but only when a certain output voltage values, the output power of photovoltaic cell just can reach maximal value, at this moment, the power points of photovoltaic cell just reaches maximum power point (MaximumPowerPoint, MPP).Photovoltaic cell is electric energy generation unit the most basic in photovoltaic generating system, therefore the whole efficiency of photovoltaic generating system will be improved, an important approach is exactly the power points adjusting photovoltaic cell in real time, make it to always work near MPP, this process is just referred to as MPPT maximum power point tracking (MaximumPowerPointTracking, MPPT), wherein, disturbance observation (PerturbandObservemethods) and conductance increment method (incrementalconductancemethods) are the MPPT comparatively often used.

Disturbance observation utilizes the characteristic single peak characteristic of photovoltaic array P-V, the output voltage of disturbance light photovoltaic array or electric current, the output voltage of sampling current time and electric current, and according to the output power of this output current and voltage determination current time, the output power of current time and the output power in a upper moment are compared, according to comparative result control disturbance voltage or direction of current, it is made to be operated near MPP; Conductance increment method is also utilize the characteristic single peak characteristic of photovoltaic array P-V, makes dP/dV=0, and therefore will as the condition judging maximum power point, thus realize MPPT maximum power point tracking.Because the output power of monomer photovoltaic cell is little, therefore, need multiple photovoltaic cell connection in series-parallel to form photovoltaic array, thus make photovoltaic generating system have higher output power.

Disturbance observation and conductance increment method all need to sample to output voltage and output current, the output voltage and output current determination output power that obtain according to sampling, suppose that the output voltage that sampling obtains is U+ △ U, output current is I+ △ I, wherein △ U is voltage sample error amount, △ I is current sample error amount, the power error that the output current then obtained according to sampling causes is: △ I*U+ △ U* △ I, this power error may cause perturbation direction mistake, thus away from maximum power point, particularly when current sensor precision is lower, power error is more obvious.

Summary of the invention

The embodiment of the present invention provides a kind of maximum power point tracing method and device, can remove the power error that current sensor causes, and improves MPPT precision.

Embodiment of the present invention first aspect provides a kind of maximum power point tracing method, comprising:

The output power maintaining the first preset duration internal power transducer is constant, and described power converter comprises DC bus;

To sample the magnitude of voltage of described DC bus according to the predeterminated voltage sampling period, described first preset duration comprises the predeterminated voltage sampling period described at least two continuous print;

The magnitude of voltage that each predeterminated voltage sampling period relatively in described first preset duration collects, controls the output power of described power converter according to the comparative result of described comparison.

In the implementation that the first is possible, describedly compare the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, control the output power of described power converter according to the comparative result of described comparison after, also comprise:

Return the step that the output power that performs described maintenance first preset duration internal power transducer is constant, wherein, the output power of described power converter maintains the output power after described control.

In conjunction with the first possible implementation of first aspect or first aspect, in the implementation that the second is possible, before the output power of described maintenance first preset duration internal power transducer is constant, also comprise:

Close the voltage control loop for stablizing described DC bus-bar voltage.

In conjunction with the implementation that the first or the second of first aspect or first aspect are possible, in the implementation that the third is possible, describedly compare the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, the output power controlling described power converter according to the comparative result of described comparison comprises:

The magnitude of voltage that each predeterminated voltage sampling period relatively in described first preset duration collects;

If the magnitude of voltage collected in each predeterminated voltage sampling period described to taper off state along time shaft, then on the basis of the output power of current maintenance, reduce the output power of described power converter;

Otherwise, the basis of the output power of current maintenance increases the output power of described power converter.In conjunction with the implementation that the first or the second of first aspect or first aspect are possible, in the 4th kind of possible implementation, describedly compare the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, the output power controlling described power converter according to the comparative result of described comparison comprises:

When the magnitude of voltage collected in each predeterminated voltage sampling period described along time shaft taper off duration of state reach the second preset duration time, on the basis of the output power of current maintenance, then reduce the output power of described power converter, wherein, described second preset duration is less than described first preset duration.

In conjunction with the 4th kind of possible implementation of first aspect, in the 5th kind of possible implementation, describedly compare the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, the output power controlling described power converter according to the comparative result of described comparison also comprises:

When the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, on the basis of the output power of current maintenance, then increase the output power of described power converter, wherein, described 3rd preset duration is less than described first preset duration.

In conjunction with the implementation that the second of first aspect is possible, in the 6th kind of possible implementation, described closedown for stablize described DC bus-bar voltage voltage control loop before, also comprise:

Using presetting step-length as current step, repeatedly disturbance is carried out to described DC bus-bar voltage, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value, perform the step of described closedown for the voltage control loop of stable DC bus.

In conjunction with the 6th kind of possible implementation of first aspect, in the 7th kind of possible implementation, describedly using presetting step-length as current step, repeatedly disturbance is carried out to described DC bus-bar voltage, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value and comprises:

Using presetting step-length as current step, repeatedly disturbance is carried out to described DC bus-bar voltage, and obtain before each disturbance with disturbance after the output power of described power converter;

When the difference of the output power of described power converter before the output power and disturbance of power converter described after disturbance is in the second predetermined threshold value, then judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value.

Correspondingly, embodiment of the present invention second aspect additionally provides a kind of maximum power point tracking device, comprising:

Power maintains module, and constant for the output power maintaining the first preset duration internal power transducer, described power converter comprises DC bus;

Voltage sample module, for the magnitude of voltage of described DC bus of sampling according to the predeterminated voltage sampling period, described first preset duration comprises the predeterminated voltage sampling period described at least two continuous print;

Comparison module, for the magnitude of voltage that more described voltage sample module each predeterminated voltage sampling period in described first preset duration collects;

Control module, for controlling the output power of described power converter according to the comparative result of described comparison module.

In the implementation that the first is possible, described control module also for:

After the described comparative result according to described comparison module controls the output power of described power converter in execution, trigger described power maintain output power that module maintains described power converter in the first preset duration equal described control after output power.

In conjunction with the first possible implementation of second aspect or second aspect, in the implementation that the second is possible, described device also comprises:

Voltage loop control module, for closing the voltage control loop for stablizing described DC bus-bar voltage, and the output power triggering described power converter in described first preset duration of described power maintenance module maintenance is constant.

In conjunction with the implementation that the first or the second of second aspect or second aspect are possible, in the implementation that the third is possible, described control module specifically for:

Otherwise, the basis of the output power of current maintenance increases the output power of described power converter.In conjunction with the implementation that the first or the second of second aspect or second aspect are possible, in the 4th kind of possible implementation, described control module specifically for:

In conjunction with the 4th kind of possible implementation of second aspect, in the 5th kind of possible implementation, described control module also for:

In conjunction with the implementation that the second of second aspect is possible, in the 6th kind of possible implementation, described device also comprises:

Disturbance module, for carrying out repeatedly disturbance using presetting step-length as current step to described DC bus-bar voltage, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value, trigger the voltage control loop of described Voltage loop control module closedown for stablizing described DC bus-bar voltage.

In conjunction with the 6th kind of possible implementation of second aspect, in the 7th kind of possible implementation, described disturbance module specifically for:

The embodiment of the present invention is under the constant condition of the output power of maintenance first preset duration internal power transducer, according to the magnitude of voltage of predeterminated voltage sampling period sampling DC bus, by the magnitude of voltage that each predeterminated voltage sampling period of comparing in the first preset duration collects, control the output power of power converter, achieve the change according to magnitude of voltage, control the output power of power converter, eliminate the power error that current sensor causes, improve MPPT precision.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme in the embodiment of the present invention, be briefly described to the accompanying drawing used required in embodiment below, apparently, accompanying drawing in the following describes is some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.

Fig. 1 is the family curve of photovoltaic cell;

Fig. 2 is the schematic flow sheet of a kind of maximum power point tracing method that the embodiment of the present invention provides;

Fig. 3 is the P-V family curve of photovoltaic cell;

Fig. 4 is the schematic flow sheet of a kind of maximum power point tracing method that another embodiment of the present invention provides;

Fig. 5 is the schematic flow sheet of a kind of maximum power point tracing method that another embodiment of the present invention provides;

Fig. 6 is the structural representation of a kind of maximum power point tracking device that the embodiment of the present invention provides;

Fig. 7 is the structural representation of a kind of maximum power point tracking device that another embodiment of the present invention provides.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

Refer to Fig. 2, Fig. 2 is the schematic flow sheet of a kind of maximum power point tracing method that the embodiment of the present invention provides.The maximum power point tracing method that the embodiment of the present invention provides can be implemented in photovoltaic generating system.MPPT maximum power point tracking flow process as shown in Figure 2 in the present embodiment can comprise:

S210, the output power maintaining the first preset duration internal power transducer is constant, and described power converter comprises DC bus.

Power converter can comprise one-level power converter or multiple power levels transducer, and this one-level power converter comprises inverter (DC/AC), is directly converted to alternating current for the direct current produced by photovoltaic array; This multiple power levels transducer comprises dc chopper (DC/DC) and inverter, and the direct current that the magnitude of voltage for being produced by photovoltaic array is fixed first is converted to the direct current of variable values, then the direct current of variable values is converted to alternating current.Wherein, inverter is used for direct current to be converted to alternating current; The direct current that dc chopper is used for being fixed by magnitude of voltage is converted to the direct current of variable values, and DC bus is the part in power converter.

If power converter is one-level power converter, then maintain the constant power being specially inverter AC side in maintenance first preset duration of the output power of the first preset duration internal power transducer constant; If power converter is multiple power levels transducer, then maintain the constant power being specially the secondary DC side of the dc chopper be connected with photovoltaic array in maintenance first preset duration of the output power of the first preset duration internal power transducer constant, wherein, in dc chopper, first DC is elementary, and second DC is secondary.

Wherein, photovoltaic generating system, before the output power of maintenance first preset duration internal power transducer is constant, closes the voltage control loop being used for stable DC busbar voltage.This voltage control loop, when in running order, can provide predeterminated voltage to this DC bus, and maintains this DC bus and be in this predeterminated voltage, thus makes the output of photovoltaic array be in power points corresponding to this predeterminated voltage.When closing the voltage control loop for stablizing this DC bus-bar voltage, and the output power maintaining the first preset duration internal power transducer constant time, composition graphs 3 (the P-V family curve of photovoltaic cell) is analyzed the change of DC bus-bar voltage in the first preset duration, wherein, a, b, c tri-curves represent the P-V family curve of photovoltaic cell under different illumination conditions.

Under the condition that external environment is constant, if the output power of power converter maintains the left side of maximum power point, as the power points 1 in Fig. 3, under the condition of closing voltage control loop, according to the self attributes of photovoltaic cell, the power points meeting disturbance to the right automatically of photovoltaic cell, make the output power of photovoltaic cell, namely the power input of power converter is greater than the output power of power converter, now, DC bus can absorb unnecessary power, according to formula (C is dc-link capacitance, U is DC bus-bar voltage) known, DC bus-bar voltage can raise, thus the power points of control photovoltaic cell is from power points 1 disturbance to the right always, until disturbance is to power points 2, namely when the power input of power converter equals output power, the power points of photovoltaic cell just maintains power points 2, wherein, from power points 1 disturbance in the time period of power points 2, DC bus-bar voltage continues to rise, maintain in the time period of power points 2, DC bus-bar voltage remains unchanged, if also there is no disturbance to just reaching described first preset duration during power points 2 at power points, then in the first preset duration, DC bus-bar voltage continues to rise,

Under the condition that external condition is constant, if the output power of power converter maintains the right side of maximum power point, as the power points 2 in Fig. 3, under the condition of closing voltage control loop, because the power input of power converter equals output power, and the ENERGY E of DC bus can not disappear without foundation, namely DC bus-bar voltage can not reduce, then just to maintain power points 2 constant for the power points of photovoltaic cell, and during this period of time, DC bus-bar voltage remains unchanged;

Under the condition of extraneous environmental change, if the output power of power converter maintains the left side of maximum power point, as the power points 1 in Fig. 3, suppose that intensity of illumination strengthens, the P-V family curve of photovoltaic cell is made to change to c from b, in conjunction with above analysis, the power points of photovoltaic cell can disturbance to the right always, until disturbance is to power points 4, power points just maintains power points 4, in the first preset duration, DC bus-bar voltage first continues to increase and remains unchanged, if also there is no disturbance to just reaching described first preset duration during power points 4 at power points, then in the first preset duration, DC bus-bar voltage continues to rise, if the output power of power converter maintains power points 1, suppose that intensity of illumination weakens, the P-V family curve of photovoltaic cell is made to change to a from b, analyze in conjunction with above, the power points meeting first disturbance left of photovoltaic cell, disturbance to the right again, until disturbance is to power points 3, power points just maintains power points 4, in the first preset duration, DC bus-bar voltage first continues reduction and continues to increase and finally remain unchanged, if also there is no disturbance to just reaching described first preset duration during power points 3 at power points, then in the first preset duration, DC bus-bar voltage is that lasting reduction continues to increase again.

Under the condition of extraneous environmental change, if the output power of power converter maintains the right side of maximum power point, as the power points 2 in Fig. 3, suppose that intensity of illumination strengthens, the P-V family curve of photovoltaic cell is made to change to c from b, in conjunction with above analysis, the power points meeting disturbance of photovoltaic cell is to power points 4, and it is constant to maintain power points 4, in the first preset duration, DC bus-bar voltage first continues to increase and remains unchanged, if also there is no disturbance to just reaching described first preset duration during power points 4 at power points, then in the first preset duration, DC bus-bar voltage continues to increase, if the output power of power converter maintains power points 2, suppose that intensity of illumination weakens, make the P-V family curve of photovoltaic cell change to a from b, analyze in conjunction with above, the power points meeting disturbance of photovoltaic cell is to power points 3, and it is constant to maintain power points 3, in the first preset duration, DC bus-bar voltage first continues reduction and remains unchanged, if also do not have disturbance to just reaching described first preset duration during power points 3 at power points again, then in the first preset duration, DC bus-bar voltage continues to reduce,

In change of external conditions, and under the output power of power converter exceedes the condition of the peak power output of current time photovoltaic cell, output power as power converter maintains power points 9, intensity of illumination weakens, the P-V family curve of photovoltaic cell is made to change to b from c, the peak power output of photovoltaic cell can not meet the output power of power converter, now, then provide electric energy to load by photovoltaic cell and DC bus simultaneously, the output power of power converter is made to maintain power points 9, the then voltage of DC bus continuous decrease in the first preset duration.

Further, photovoltaic generating system is before closing the voltage control loop being used for stable DC busbar voltage, repeatedly disturbance can be carried out to DC bus-bar voltage using presetting step-length as current step, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value, namely judge that current power point is near maximum power point, close the voltage control loop being used for stable DC busbar voltage again, reduce the distance of current power point and maximum power point, improve the efficiency of MPPT.Optionally, photovoltaic generating system can carry out repeatedly disturbance using presetting step-length as current step to DC bus-bar voltage, and obtain before each disturbance with disturbance after the output power of power converter, when the difference of the output power of power converter before the output power and disturbance of power converter after disturbance is in the second predetermined threshold value, then judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value, namely judge that current power point is near maximum power point.Such as, second predetermined threshold value is 0.4w, the output power of t (namely after disturbance) power converter is 45.1w, the output power of t-1 moment (namely before disturbance) power converter is 44.9w, and photovoltaic generating system can judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value.

Wherein, when step-length is at every turn carrying out disturbance to DC bus-bar voltage, the magnitude of voltage basis of current DC bus-bar voltage increasing or reduces, this step-length equals presetting step-length, and namely DC bus-bar voltage increases or the magnitude of voltage that reduces is fixed value at every turn.Such as, presetting step-length is 1V, t DC bus-bar voltage is 5v, if power converter is greater than the output power in t-1 moment in the output power of t, photovoltaic generating system then adds on the basis of 5v that 1v is as DC bus-bar voltage described in the t+1 moment, if power converter is greater than the output power of t in the output power in t+1 moment, photovoltaic generating system then adds on the basis of 6v that 1v is as DC bus-bar voltage described in the t+2 moment, by that analogy.

S220, to sample the magnitude of voltage of described DC bus according to the predeterminated voltage sampling period, described first preset duration comprises the predeterminated voltage sampling period described at least two continuous print.

Concrete, close at voltage control loop, and under the constant condition of the output power of holding power transducer, photovoltaic generating system can be sampled the magnitude of voltage of this DC bus according to the predeterminated voltage sampling period, each predeterminated voltage sampling period samples a magnitude of voltage, and the first preset duration comprises at least two continuous print predeterminated voltage sampling periods, thus multiple magnitude of voltage can be obtained in the first preset duration.

S230, compares the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, controls the output power of described power converter according to the comparative result of described comparison.

Photovoltaic generating system compares the magnitude of voltage that each predeterminated voltage sampling period in the first preset duration collects, the output power of power converter is controlled according to this comparative result, achieve the change according to magnitude of voltage, control the output power of power converter, eliminate the power error that current sensor causes, improve MPPT precision.

When the magnitude of voltage that photovoltaic generating system collected in each predeterminated voltage sampling period of comparing in the first preset duration, control the output power of power converter according to comparative result after, return the step that the output power of execution maintenance first preset duration internal power transducer is constant, now, the output power of power converter maintains the output power after control, such as, the output power of photovoltaic generating system holding power transducer is 68.95w in the first preset duration, the output power of power converter is controlled according to comparative result, and the output power after power converter control is 69w, photovoltaic generating system is when returning the output power performing maintenance first preset duration internal power transducer and being constant, the output power of power converter is maintained 69w.

As the optional embodiment of one, suppose that the magnitude of voltage collected successively in the first preset duration is respectively U1, U2, U3 and U4, photovoltaic generating system compares the magnitude of voltage that each predeterminated voltage sampling period in the first preset duration collects, if the magnitude of voltage collected in each predeterminated voltage sampling period described to taper off state along time shaft, i.e. U1>U2>U3>U4, illustrate that DC bus is providing electric energy to load in the first preset duration always, that is the output power of power converter is greater than the peak power output of current time photovoltaic array, on the basis of the output power of current maintenance, then reduce the output power of power converter,

If the magnitude of voltage collected in each predeterminated voltage sampling period described is not the state of tapering off along time shaft, as U1<U2<U3<U4, U1=U2=U3=U4, U1<U2=U3=U4, U1>U2=U3=U4 or U1>U2<U3=U4 etc., illustrate that the output power of photovoltaic array in the first preset duration finally can be more than or equal to the output power of power converter, on the basis of the output power of current maintenance, then increase the output power of power converter.

As the optional embodiment of another kind, in the magnitude of voltage process that each predeterminated voltage sampling period relatively in the first preset duration collects, when the magnitude of voltage collected in each predeterminated voltage sampling period described along time shaft taper off duration of state reach the second preset duration time, photovoltaic generating system then can reduce the output power of power converter on the basis of the output power of current maintenance, wherein, second preset duration is less than the first preset duration, suppose, first preset duration is 1min, that is, the output power of photovoltaic generating system holding power transducer is constant in 1min, suppose that the output power of now power converter is P1, and the sampling period is 2s, second preset duration is 4s, if U1>U2>U3 detected, photovoltaic generating system can determine that DC bus-bar voltage reaches the second preset duration along taper off duration of state of time shaft, now, photovoltaic generating system then reduces the output power of power converter on the basis of the output power of current maintenance, decrease magnitude of voltage and compare the time, thus the efficiency of MPPT can be improved.

Further, in the magnitude of voltage process that each predeterminated voltage sampling period of comparing in the first preset duration collects, when the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, photovoltaic generating system then can increase the output power of power converter, wherein, 3rd preset duration is less than the first preset duration, suppose, first preset duration is 1min, that is, the output power of photovoltaic generating system holding power transducer is constant in 1min, suppose that the output power of now power converter is P3, and the sampling period is 2s, 3rd preset duration is 4s, if U3=U4=U5 detected, photovoltaic generating system can determine that the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, now, photovoltaic generating system then increases the output power of power converter on the basis of the output power of current maintenance, reduce magnitude of voltage and compare the time, thus the efficiency of MPPT can be improved.

Wherein, photovoltaic generating system can pass through the dutycycle of control PWM (PulseWidthModulation, pulse-length modulation), thus controls the output power of power converter.Concrete, photovoltaic generating system by increasing the dutycycle of PWM, thus can increase output voltage and the electric current of power converter, thus increases the output power of power converter; Photovoltaic generating system by reducing the dutycycle of PWM, thus can reduce output voltage and the electric current of power converter, thus reduces the output power of power converter, and suppose, each power increased or reduce is △ P, can according to formula determine the power at every turn needing to increase or reduce, regulate the dutycycle of PWM, until the difference of increase or the power reduced and △ P is less than or equal to the 3rd predetermined threshold value, wherein, P _outfor the output power of current power transducer, U _pvbe the arbitrary DC bus-bar voltage collected in the first preset duration, η is the conversion efficiency that inverter is corresponding, and U' is the minimum voltage that voltage sensor can be differentiated, the i.e. precision of voltage sensor, and such as, the precision of voltage sensor is 0.001V, then U'=0.001; Photovoltaic generating system can also preset fixed duty cycle by changing, thus increases or reduce the output power of power converter.

Refer to Fig. 4, Fig. 4 is the schematic flow sheet of a kind of maximum power point tracing method that another embodiment of the present invention provides.The maximum power point tracing method that the embodiment of the present invention provides can be implemented in photovoltaic generating system.MPPT maximum power point tracking flow process as shown in Figure 4 in the present embodiment can comprise:

S410, the output power maintaining the first preset duration internal power transducer is constant, and described power converter comprises DC bus.

Concrete, photovoltaic generating system can the dutycycle of control PWM, constant with the output power maintaining described power converter in the first preset duration, if the reference voltage level of current acquisition is less than the last reference voltage level obtained, then increases the dutycycle of PWM; If the reference voltage level of current acquisition is greater than the last reference voltage level obtained, then reduce the dutycycle of described PWM; If the reference voltage level of current acquisition equals the last reference voltage level obtained, then do not change the dutycycle of described PWM, optionally, the DC bus-bar voltage collected can be worth by photovoltaic generating system as the reference voltage.

Wherein, photovoltaic generating system, before the output power of maintenance first preset duration internal power transducer is constant, closes the voltage control loop being used for stable DC busbar voltage.This voltage control loop, when in running order, can provide predeterminated voltage to this DC bus, and maintains this DC bus and be in this predeterminated voltage, thus makes the output of photovoltaic array be in power points corresponding to this predeterminated voltage.

S420, to sample the magnitude of voltage of described DC bus according to the predeterminated voltage sampling period, described first preset duration comprises the predeterminated voltage sampling period described at least two continuous print.

S430, compares the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, and judges whether the magnitude of voltage that collects in each predeterminated voltage sampling period described tapers off state along time shaft.

Photovoltaic generating system can judge whether the magnitude of voltage that collects in each predeterminated voltage sampling period described tapers off state along time shaft, if so, then performs step S440, otherwise performs step S450.

S440, if so, then reduces the output power of described power converter on the basis of the output power of current maintenance, and returns execution step S410.

Concrete, suppose that the magnitude of voltage collected successively in the first preset duration is respectively U1, U2, U3 and U4, photovoltaic generating system compares the magnitude of voltage that each predeterminated voltage sampling period in the first preset duration collects, if the magnitude of voltage collected in each predeterminated voltage sampling period described to taper off state along time shaft, i.e. U1>U2>U3>U4, illustrate that DC bus is providing electric energy to load in the first preset duration always, that is the output power of power converter is greater than the peak power output of current time photovoltaic array, then reduce the output power of power converter, and return execution step S410.

Wherein, in the process comparing the magnitude of voltage that each predeterminated voltage sampling period in the first preset duration gathers, when the magnitude of voltage collected in each predeterminated voltage sampling period described along time shaft taper off duration of state reach the second preset duration time, photovoltaic generating system then reduces the output power of power converter on the basis of the output power of current maintenance, and return execution step S410, wherein, the second preset duration is less than the first preset duration.Photovoltaic generating system can according to formula determine the power needing to reduce, regulate the dutycycle of PWM, until the difference of the power reduced and △ P is less than or equal to the 3rd predetermined threshold value; Photovoltaic generating system by reducing to preset fixing dutycycle, thus can also reduce the output power of power converter.

Suppose, first preset duration is 1min, that is, the output power of photovoltaic generating system holding power transducer is constant in 1min, suppose that the output power of now power converter is P1, and the sampling period is 2s, second preset duration is 4s, if U1>U2>U3 detected, photovoltaic generating system can determine that DC bus-bar voltage reaches the second preset duration along taper off duration of state of time shaft, now, photovoltaic generating system then reduces the output power of power converter on the basis of the output power of current maintenance, decrease magnitude of voltage and compare the time, thus the efficiency of MPPT can be improved.

S450, otherwise, the basis of the output power of current maintenance increases the output power of described power converter, and returns execution step S410.

Concrete, suppose that the magnitude of voltage collected successively in the first preset duration is still respectively U1, U2, U3 and U4, photovoltaic generating system compares the magnitude of voltage that each predeterminated voltage sampling period in the first preset duration collects, if the magnitude of voltage collected in each predeterminated voltage sampling period described is not the state of tapering off along time shaft, as U1<U2<U3<U4, U1=U2=U3=U4, U1<U2=U3=U4, U1>U2=U3=U4 or U1>U2<U3=U4 etc., illustrate that the output power of photovoltaic array in the first preset duration finally can be more than or equal to the output power of power converter, then increase the output power of power converter, and return execution step S410.

Wherein, comparing in the magnitude of voltage process that the neighbouring sample cycle in the first preset duration collects, when the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, photovoltaic generating system then increases the output power of power converter on the basis of the output power of current maintenance, and return execution step S410, wherein, the 3rd preset duration is less than the first preset duration.Photovoltaic generating system can according to formula determine the power needing to increase, regulate the dutycycle of PWM, until the difference of the power increased and △ P is less than or equal to the 3rd predetermined threshold value; Photovoltaic generating system can also preset fixing dutycycle by increasing, thus increases the output power of power converter.

Suppose, first preset duration is 1min, that is, the output power of photovoltaic generating system holding power transducer is constant in 1min, suppose that the output power of now power converter is P3, and the sampling period is 2s, 3rd preset duration is 4s, if U3=U4=U5 detected, photovoltaic generating system can determine that the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, now, photovoltaic generating system then increases the output power of power converter on the basis of the output power of current maintenance, reduce magnitude of voltage and compare the time, thus the efficiency of MPPT can be improved.

The embodiment of the present invention can according to the magnitude of voltage of predeterminated voltage sampling period sampling DC bus, if the magnitude of voltage collected in each predeterminated voltage sampling period to taper off state along time shaft, illustrate that the output power of power converter is greater than the peak power output of current time photovoltaic array, then reduce the output power of power converter; The magnitude of voltage collected in each predeterminated voltage sampling period is not the state of tapering off along time shaft, illustrate that the output power of photovoltaic array in the first preset duration finally can be more than or equal to the output power of power converter, then increase the output power of power converter, achieve the change according to magnitude of voltage, control the output power of power converter, eliminate the power error that current sensor causes, improve MPPT precision.

Refer to Fig. 5, Fig. 5 is the schematic flow sheet of a kind of maximum power point tracing method that another embodiment of the present invention provides.The maximum power point tracing method that the embodiment of the present invention provides can be implemented in photovoltaic generating system.MPPT maximum power point tracking flow process as shown in Figure 5 in the present embodiment can comprise:

S501, carries out repeatedly disturbance using presetting step-length as current step to DC bus-bar voltage, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value.

As the optional embodiment of one, photovoltaic generating system can carry out repeatedly disturbance using presetting step-length as current step to DC bus-bar voltage, and obtain before each disturbance with disturbance after the output power of power converter, when the difference of the output power of power converter before the output power and disturbance of power converter after disturbance is in the second predetermined threshold value, then judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value, namely judge that current power point is near maximum power point.Such as, second predetermined threshold value is 0.4w, the output power of t (namely after disturbance) power converter is 45.1w, the output power of t-1 moment (namely before disturbance) power converter is 44.9w, and photovoltaic generating system can judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value.

S502, closes the voltage control loop for stablizing described DC bus-bar voltage.

Concrete, when judging that the power difference of current power point and maximum power point is less than the first predetermined threshold value, photovoltaic generating system then closes the voltage control loop for stable DC busbar voltage, this voltage control loop is when being in power rating, predeterminated voltage can be provided to this DC bus, and maintain this DC bus and be in this predeterminated voltage, thus the output of photovoltaic array is made to be in power points corresponding to this predeterminated voltage.

S503, the output power maintaining the first preset duration internal power transducer is constant, and described power converter comprises described DC bus.

Concrete, photovoltaic generating system can the dutycycle of control PWM, constant with the output power maintaining described power converter in the first preset duration, if the reference voltage level of current acquisition is less than the last reference voltage level obtained, then increases the dutycycle of PWM; If the reference voltage level of current acquisition is greater than the last reference voltage level obtained, then reduce the dutycycle of described PWM; If the reference voltage level of current acquisition equals the last reference voltage level obtained, then do not change the dutycycle of described PWM, optionally, photovoltaic generating system can using the DC bus-bar voltage that collects as this reference voltage level.

S504, to sample the magnitude of voltage of described DC bus according to the predeterminated voltage sampling period.

Concrete, photovoltaic generating system can comprise voltage sensor, close at voltage control loop, and under the constant condition of the output power of holding power transducer, photovoltaic generating system can be sampled DC bus-bar voltage by voltage sensor, controls the output power of power converter according to the change of d-c bus voltage value.

S505, compares the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects.

Concrete, the magnitude of voltage that each predeterminated voltage sampling period in the first preset duration can collect by photovoltaic generating system compares, thus the change of DC bus-bar voltage in the first preset duration can be detected, the output power of power converter can be controlled according to the change of this magnitude of voltage, the embodiment of the present invention first carries out disturbance tracking using presetting step-length as current step to DC bus-bar voltage, can fast by near power points disturbance to maximum power point, close voltage control loop again, the output power of power converter is controlled according to the change of DC bus-bar voltage in the first preset duration, on the basis that improve MPPT precision, further improve the efficiency of MPPT.

S506, judges whether the magnitude of voltage that collects in each predeterminated voltage sampling period described reaches the second preset duration along taper off duration of state of time shaft, and described second preset duration is less than described first preset duration.

Concrete, if the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the second preset duration along taper off duration of state of time shaft, then perform step S509; Otherwise, perform step S507.

Suppose that the first preset duration is 1min, that is the output power of photovoltaic generating system holding power transducer is constant in 1min, and the sampling period is 2s, second preset duration is 4s, if the magnitude of voltage in each predeterminated voltage sampling period is followed successively by U1, U2, U3, and there is U1>U2>U3, photovoltaic generating system then can judge that the magnitude of voltage that collects in each predeterminated voltage sampling period described reaches the second preset duration along taper off duration of state of time shaft, then perform step S509.

S507, if magnitude of voltage does not reach the second preset duration along taper off duration of state of time shaft, when judging whether the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, wherein, described 3rd preset duration is less than described first preset duration.

Concrete, if photovoltaic generating system judges that magnitude of voltage that each predeterminated voltage sampling period collects does not reach the second preset duration along taper off duration of state of time shaft, when further can judge whether the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, if when magnitude of voltage reaches the 3rd preset duration along the duration that time shaft remains unchanged, then perform step S510, otherwise, perform step S508.

Suppose that the first preset duration is 1min, that is the output power of photovoltaic generating system holding power transducer is constant in 1min, and the sampling period is 2s, 3rd preset duration is 4s, if the magnitude of voltage collected is U1, U2, U3, and there is U1=U2=U3, when photovoltaic generating system can judge that the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, then perform step S508.

If it is pointed out that, the 3rd preset duration is greater than the second preset duration, then can carry out MPPT maximum power point tracking according to the flow process of the embodiment of the present invention; In other embodiment, second preset duration can be greater than the 3rd preset duration, when namely first judging whether the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, if magnitude of voltage reaches the 3rd preset duration along the duration that time shaft remains unchanged, just perform and judge that the magnitude of voltage that collects in each predeterminated voltage sampling period described reaches the step of the second preset duration along taper off duration of state of time shaft.

S508, if magnitude of voltage does not reach the 3rd preset duration along the duration that time shaft remains unchanged, then compare the magnitude of voltage that the predeterminated voltage sampling period samples always, until all magnitudes of voltage in described first preset duration are compared, on the basis of the output power of current maintenance, just increase the output power of described power converter, and return execution step S503.

Concrete, if magnitude of voltage does not reach the second preset duration along taper off duration of state of time shaft, and magnitude of voltage does not reach the 3rd preset duration along the duration that time shaft remains unchanged, then compare the magnitude of voltage that the predeterminated voltage sampling period samples always, until all magnitudes of voltage collected in the first preset duration are all compared, photovoltaic generating system just increases the output power of described power converter on the basis of the output power of current maintenance, and returns execution step S503.

S509, if magnitude of voltage reaches the second preset duration along taper off duration of state of time shaft, then reduces the output power of described power converter on the basis of the output power of current maintenance, and returns and perform step S503.

Concrete, photovoltaic generating system can according to formula determine the power needing to reduce, regulate the dutycycle of PWM, until the difference of the power reduced and △ P is less than or equal to the 3rd predetermined threshold value; Photovoltaic generating system by reducing to preset fixing dutycycle, thus can also reduce the output power of power converter.

S510, if when magnitude of voltage reaches the 3rd preset duration along the duration that time shaft remains unchanged, then increases the output power of described power converter on the basis of the output power of current maintenance, and returns execution step S503.

Concrete, photovoltaic generating system can according to formula determine the power needing to increase, regulate the dutycycle of PWM, until the difference of the power increased and △ P is less than or equal to the 3rd predetermined threshold value; Photovoltaic generating system can also preset fixing dutycycle by increasing, thus increases the output power of power converter.

The embodiment of the present invention carries out repeatedly disturbance using presetting step-length as current step to DC bus-bar voltage, until when judging that the power difference of current power point and maximum power point is less than the first predetermined threshold value, just close the voltage control loop being used for stable DC busbar voltage, can by near power points rapid perturbations to maximum power point; If magnitude of voltage reaches the second preset duration along taper off duration of state of time shaft, illustrate that the output power of power converter is greater than the peak power output of current time photovoltaic array, then reduce the output power of power converter immediately; If magnitude of voltage reaches the 3rd preset duration along the duration that time shaft remains unchanged, illustrate that the output power of photovoltaic array equals the output power of power converter, then increase the output power of power converter immediately; Compared with a upper embodiment, on the basis that improve MPPT precision, further increase the efficiency of MPPT.

Refer to Fig. 6, Fig. 6 is the structural representation of a kind of maximum power point tracking device that the embodiment of the present invention provides.The maximum power point tracking device that the embodiment of the present invention provides can be applied in photovoltaic generating system.Maximum power point tracking device 600 as shown in Figure 6 in the embodiment of the present invention at least can comprise power and maintain module 610, voltage sample module 620, comparison module 630 and control module 640, wherein:

Power maintains module 610, and constant for the output power maintaining the first preset duration internal power transducer, described power converter comprises DC bus.

Concrete, power maintains module 610 can the dutycycle of control PWM, constant with the output power maintaining described power converter in the first preset duration, if the reference voltage level of current acquisition is less than the last reference voltage level obtained, then increase the dutycycle of PWM; If the reference voltage level of current acquisition is greater than the last reference voltage level obtained, then reduce the dutycycle of described PWM; If the reference voltage level of current acquisition equals the last reference voltage level obtained, then do not change the dutycycle of described PWM, optionally, power maintains module 610 can using the DC bus-bar voltage that collects as this reference voltage level.

Wherein, described maximum power point tracking device 600 can also comprise Voltage loop control module 650, for closing the voltage control loop for stablizing described DC bus-bar voltage, and after the described voltage control loop of closedown, trigger described power maintain output power that module 610 maintains the first preset duration internal power transducer equal described control after output power.

Further alternative, described maximum power point tracking device 600 can also comprise disturbance module 660, for carrying out repeatedly disturbance using presetting step-length as current step to described DC bus-bar voltage, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value, trigger described Voltage loop control module 650 and close voltage control loop for stablizing described DC bus-bar voltage.

Wherein, disturbance module 660 can carry out repeatedly disturbance using presetting step-length as current step to described DC bus-bar voltage, and obtain before each disturbance with disturbance after the output power of described power converter, when the difference of the output power of described power converter before the output power and disturbance of power converter described after disturbance is in the second predetermined threshold value, then judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value.

Voltage sample module 620, for the magnitude of voltage of described DC bus of sampling according to the predeterminated voltage sampling period, described first preset duration comprises the predeterminated voltage sampling period described at least two continuous print.

In specific implementation, voltage sample module 620 can be sampled the magnitude of voltage of this DC bus according to the predeterminated voltage sampling period, each predeterminated voltage sampling period samples a magnitude of voltage, and the first preset duration comprises at least two continuous print predeterminated voltage sampling periods, thus multiple magnitude of voltage can be obtained in the first preset duration.

Comparison module 630, for the magnitude of voltage that more described voltage sample module 620 each predeterminated voltage sampling period in described first preset duration collects.

Control module 640, for controlling the output power of described power converter according to the comparative result of described comparison module 630.

Comparison module 630 compares the magnitude of voltage that each predeterminated voltage sampling period in the first preset duration collects, control module 640 controls the output power of power converter according to this comparative result, achieve the change according to magnitude of voltage, control the output power of power converter, the power error that current sensor causes can be removed, improve MPPT precision.

Further, described control module 640 after the described comparative result according to described comparison module 630 controls the output power of described power converter in execution, trigger described power maintain output power that module 610 maintains described power converter in the first preset duration equal described control after output power.

As the optional embodiment of one, control module 640 specifically may be used for:

If the magnitude of voltage collected in each predeterminated voltage sampling period described to taper off state along time shaft, then on the basis of the output power of current maintenance, reduce the output power of described power converter.Concrete, if the magnitude of voltage collected in each predeterminated voltage sampling period described to taper off state along time shaft, illustrate that DC bus is providing electric energy to load in the first preset duration always, that is the output power of power converter is greater than the peak power output of current time photovoltaic array, and control module 640 reduces the output power of power converter on the basis of the output power of current maintenance;

If the magnitude of voltage collected in each predeterminated voltage sampling period described is not the state of tapering off along time shaft, then on the basis of the output power of current maintenance, increase the output power of described power converter.Concrete, if the magnitude of voltage collected in each predeterminated voltage sampling period described is not the state of tapering off along time shaft, illustrate that the output power of photovoltaic array in the first preset duration finally can be more than or equal to the output power of power converter, control module 640 increases the output power of power converter on the basis of the output power of current maintenance.

As the optional embodiment of another kind, described control module 640 specifically for:

When the magnitude of voltage collected in each predeterminated voltage sampling period described along time shaft taper off duration of state reach the second preset duration time, on the basis of the output power of current maintenance, then reduce the output power of described power converter, wherein, described second preset duration is less than described first preset duration.Suppose, first preset duration is 1min, that is, the output power that power maintains module 610 holding power transducer is constant in 1min, suppose that the output power of now power converter is P1, and the sampling period is 2s, second preset duration is 4s, if U1>U2>U3 detected, comparison module 630 can determine that DC bus-bar voltage reaches the second preset duration along taper off duration of state of time shaft, now, control module 640 reduces the output power of power converter on the basis of the output power of current maintenance, decrease magnitude of voltage and compare the time, thus the efficiency of MPPT can be improved.

Further, described control module 640 concrete also for:

When the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, on the basis of the output power of current maintenance, then increase the output power of described power converter, wherein, described 3rd preset duration is less than described first preset duration.Suppose, first preset duration is 1min, that is, the output power that power maintains module holding power transducer is constant in 1min, suppose that the output power of now power converter is P3, and the sampling period is 2s, 3rd preset duration is 4s, if U3=U4=U5 detected, comparison module 630 can determine that the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, now, control module 640 increases the output power of power converter on the basis of the output power of current maintenance, reduce magnitude of voltage and compare the time, thus the efficiency of MPPT can be improved.

Optionally, comparison module 630 can detect magnitude of voltage and whether reach the second preset duration along taper off duration of state of time shaft, if detect, magnitude of voltage reaches the second preset duration along taper off duration of state of time shaft, then trigger the output power that described control module 640 reduces described power converter on the basis of the output power of current maintenance; If comparison module 630 detects that magnitude of voltage does not reach the second preset duration along taper off duration of state of time shaft, then can also detect magnitude of voltage further and whether reach the 3rd preset duration along the duration that time shaft remains unchanged, if detect, magnitude of voltage reaches the 3rd preset duration along the duration that time shaft remains unchanged, then trigger the output power that described control module 640 increases described power converter on the basis of the output power of current maintenance; If detect, magnitude of voltage does not reach the 3rd preset duration along the duration that time shaft remains unchanged, then comparison module 630 can compare the magnitude of voltage collected always, until the magnitude of voltage collected in the first preset duration all compares by comparison module 630, just trigger control module 640 increases the output power of power converter on the basis of the output power of current maintenance, wherein, first preset duration is greater than the second preset duration, and the 3rd preset duration is greater than the first preset duration.

Comparison module 630 can detect magnitude of voltage and whether reach the 3rd preset duration along the duration that time shaft remains unchanged, if detect, magnitude of voltage reaches the 3rd preset duration along the duration that time shaft remains unchanged, then trigger the output power that described control module 640 increases described power converter on the basis of the output power of current maintenance; If detect, magnitude of voltage does not reach the 3rd preset duration along the duration that time shaft remains unchanged, then comparison module 630 can detect magnitude of voltage further and whether reaches the second preset duration along taper off duration of state of time shaft, if detect, magnitude of voltage reaches the second preset duration along taper off duration of state of time shaft, then trigger the output power that described control module 640 reduces described power converter on the basis of the output power of current maintenance; If detect, magnitude of voltage does not reach the second preset duration along taper off duration of state of time shaft, then comparison module 630 can compare the magnitude of voltage collected always, until the magnitude of voltage collected in the first preset duration all compares by comparison module 630, just trigger control module 640 increases the output power of power converter on the basis of the output power of current maintenance, wherein, first preset duration is greater than the second preset duration, and the 3rd preset duration is less than the first preset duration.

Wherein, control module 640 by regulating the dutycycle of PWM, thus can control the output power of power converter.Concrete, control module 640 can according to formula determine the power at every turn needing to increase or reduce, regulate the dutycycle of PWM, just stop regulating until the difference of increase or the power reduced and △ P is less than or equal to the 3rd predetermined threshold value; Control module 640 can also preset fixed duty cycle by changing, thus increases or reduce the output power of power converter.

Refer to Fig. 7, Fig. 7 is the structural representation of a kind of maximum power point tracking device that another embodiment of the present invention provides, as shown in Figure 7, this maximum power point tracking device 700 can comprise: photovoltaic array 710, power converter 720 and power cable 730, described power converter 720 comprises storer 7201 and at least one processor 7202.Wherein, photovoltaic array 710 is made up of multiple photovoltaic cell series and parallel, for sun power being converted to the electric energy of DC form; Power converter 720 is converted to alternating current for the direct current energy exported by photovoltaic array; Power cable 730 for alternating current transmission that power converter 720 is exported to electrical network.Storer 7201 can be high-speed RAM storer, also can be non-labile storer (non-volatilememory), such as at least one magnetic disk memory.Store batch processing code in storer 7201, and processor 7202 is for calling the program code stored in storer 7201, for performing following operation:

The output power maintaining the first preset duration internal power transducer 720 is constant, and described power converter 720 comprises DC bus;

The magnitude of voltage that each predeterminated voltage sampling period relatively in described first preset duration collects, controls the output power of described power converter 720 according to the comparative result of described comparison.

Further, processor 7202 compares the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, and after controlling the output power of described power converter 720, also performs following operation according to the comparative result of described comparison:

Return the step that the output power that performs described maintenance first preset duration internal power transducer 720 is constant, wherein, the output power of described power converter 720 maintains the output power after described control.

Wherein, processor 7202 maintain the output power of the first preset duration internal power transducer 720 constant before, also perform following operation:

Close the voltage control loop for stablizing described DC bus-bar voltage.

As the optional embodiment of one, processor 7202 compares the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, and the output power controlling described power converter 720 according to the comparative result of described comparison is specifically as follows:

If the magnitude of voltage collected in each predeterminated voltage sampling period described to taper off state along time shaft, then on the basis of the output power of current maintenance, reduce the output power of described power converter 720;

Otherwise, the basis of the output power of current maintenance increases the output power of described power converter 720.

As the optional embodiment of another kind, processor 7202 compares the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, and the output power controlling described power converter 720 according to the comparative result of described comparison is specifically as follows:

When the magnitude of voltage collected in each predeterminated voltage sampling period described along time shaft taper off duration of state reach the second preset duration time, on the basis of the output power of current maintenance, then reduce the output power of described power converter 720, wherein, described second preset duration is less than described first preset duration.

Further, processor 7202 compares the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, and the output power controlling described power converter 720 according to the comparative result of described comparison can also be specifically:

When the magnitude of voltage collected in each predeterminated voltage sampling period described reaches the 3rd preset duration along the duration that time shaft remains unchanged, on the basis of the output power of current maintenance, then increase the output power of described power converter 720, wherein, described 3rd preset duration is less than described first preset duration.

Optionally, before processor 7202 cuts out the voltage control loop for stablizing described DC bus-bar voltage, also perform following operation:

Wherein, described in processor 7202, using presetting step-length as current step, repeatedly disturbance is carried out to described DC bus-bar voltage, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value and is specifically as follows:

Using presetting step-length as current step, repeatedly disturbance is carried out to described DC bus-bar voltage, and obtain before each disturbance with disturbance after the output power of described power converter 720;

When the difference of the output power of described power converter 720 before the output power and disturbance of power converter 720 described after disturbance is in the second predetermined threshold value, then judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value.

It should be noted that, in the above-described embodiments, the description of each embodiment is all emphasized particularly on different fields in certain embodiment, there is no the part described in detail, can see the associated description of other embodiments.Secondly, those skilled in the art also should know, the embodiment described in instructions all belongs to preferred embodiment, and involved action and module might not be that the embodiment of the present invention is necessary.

Step in embodiment of the present invention method can be carried out order according to actual needs and be adjusted, merges and delete.

Module in embodiment of the present invention device can carry out merging, divide and deleting according to actual needs.

Module described in the embodiment of the present invention, universal integrated circuit can be passed through, such as CPU (CentralProcessingUnit, central processing unit), or realized by ASIC (ApplicationSpecificIntegratedCircuit, special IC).

One of ordinary skill in the art will appreciate that all or part of flow process realized in above-described embodiment method, that the hardware that can carry out instruction relevant by computer program has come, described program can be stored in a computer read/write memory medium, this program, when performing, can comprise the flow process of the embodiment as above-mentioned each side method.Wherein, described storage medium can be magnetic disc, CD, read-only store-memory body (Read-OnlyMemory, ROM) or random store-memory body (RandomAccessMemory, RAM) etc.

Above disclosedly be only present pre-ferred embodiments, certainly can not limit the interest field of the present invention with this, therefore according to the equivalent variations that the claims in the present invention are done, still belong to the scope that the present invention is contained.

Claims

1. a maximum power point tracing method, is characterized in that, comprising:

Close the voltage control loop of the voltage being used for stable DC bus;

The output power maintaining the first preset duration internal power transducer is constant, and described power converter comprises described DC bus;

2. the method for claim 1, it is characterized in that, describedly compare the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, control the output power of described power converter according to the comparative result of described comparison after, also comprise:

3. the method as described in any one of claim 1-2, it is characterized in that, describedly compare the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, the output power controlling described power converter according to the comparative result of described comparison comprises:

Otherwise, the basis of the output power of current maintenance increases the output power of described power converter.

4. the method as described in any one of claim 1-2, it is characterized in that, describedly compare the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, the output power controlling described power converter according to the comparative result of described comparison comprises:

5. method as claimed in claim 4, is characterized in that, describedly compares the magnitude of voltage that each predeterminated voltage sampling period in described first preset duration collects, and the output power controlling described power converter according to the comparative result of described comparison also comprises:

6. the method for claim 1, is characterized in that, described closedown also comprises before being used for the voltage control loop of the voltage of stable DC bus:

Using presetting step-length as current step, repeatedly disturbance is carried out to described DC bus-bar voltage, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value, perform the step of described closedown for the voltage control loop of the voltage of stable DC bus.

7. method as claimed in claim 6, is characterized in that, describedly carries out repeatedly disturbance using presetting step-length as current step to described DC bus-bar voltage, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value and comprises:

8. a maximum power point tracking device, is characterized in that, comprising:

Voltage loop control module, for closing the voltage control loop of the voltage for stable DC bus;

Power maintains module, and constant for the output power maintaining the first preset duration internal power transducer, described power converter comprises described DC bus;

9. device as claimed in claim 8, is characterized in that, described control module also for:

10. as claimed in claim 8 or 9 device, is characterized in that, described control module specifically for:

11. devices as claimed in claim 8 or 9, is characterized in that, described control module specifically for:

12. devices as claimed in claim 11, is characterized in that, described control module concrete also for:

13. devices as claimed in claim 8, is characterized in that, also comprise:

Disturbance module, for carrying out repeatedly disturbance using presetting step-length as current step to described DC bus-bar voltage, until judge that the power difference of current power point and maximum power point is less than the first predetermined threshold value, trigger the voltage control loop of described Voltage loop control module closedown for the voltage of stable DC bus.

14. devices as claimed in claim 13, is characterized in that, described disturbance module specifically for: