CN102354110B - Control method based on temperature variation for maximum power point tracking of photovoltaic generation system - Google Patents

Abstract

The invention relates to a control method based on temperature variation for maximum power point tracking (MPPT) of a photovoltaic generation system, which mainly aim to solve the technical problems of no temperature tracking and low overall output efficiency in a traditional control method. The invention has the technical scheme: the control method based on the temperature variation for the MPPT of the photovoltaic generation system comprises the following steps: working out a voltage increment, i.e. voltage searching step deltaupv (t, deltaT), on a power voltage performance curve based on the temperature variation for a photovoltaic generation array according to a formula; dynamically searching a real-time power calculated value deltaP (t, deltaT) related with the temperature variation through controlling the voltage increment; if the temperature does not vary, controlling in a traditional method; if the temperature varies, dynamically adjusting the voltage searching step in time, and searching the real-time power calculated value deltaP (t, deltaT) related with the temperature variation to realize the control on the MPPT of the photovoltaic generation array. The device comprises circuits: a real-time environment temperature detection information auxiliary circuit 1, a master control circuit 2 and the like.

Description

Maximum power point of photovoltaic power generation system is followed the tracks of the control method based on temperature variation

Technical field

The present invention relates to a kind of maximum power point of photovoltaic power generation system and follow the tracks of (MPPT) control method based on temperature variation.It belongs to a kind of control method of MPPT during based on the solar energy photovoltaic system temperature variation.

Background technology

The output voltage current curve of solar energy power generating array has nonlinear characteristic.Photovoltaic power generation array can be operated in different output voltages, but only has output when a certain magnitude of voltage, and the output power of photovoltaic system just can reach maximum power point.The disturbance observation has been proposed at present, conductance increment method, the control method of the multiple MPPT maximum power point tracking such as adaptive method (MPPT) both at home and abroad.Because MPPT mainly is subject to the impact of day illuminance and environment temperature, but above-mentioned all control methods consider that day illuminance is the primary variables factor more, and have ignored the restriction of environment temperature to MPPT.Therefore, when externally variation of ambient temperature is slow, above-mentioned all methods are effective, but ambient temperature is while occurring sharply to change, especially on grassland, desert and remote mountain areas, it is low that above-mentioned various control methods are followed the trail of the slack-off and whole output efficiency of speed.Be difficult to fast search to new MPPT, thereby cause energy loss and mistake control may occur.

Summary of the invention

The objective of the invention is to solve existing control method exist tracking speed slow, without temperature, follow the tracks of and the low technical matters of whole output efficiency, provide a kind of and control based on temperature variation the control method of maximum power point of photovoltaic power generation system tracking based on temperature variation that maximum power point of photovoltaic power generation system is followed the tracks of and whole output efficiency is high.

The present invention solves the problems of the technologies described above the technical scheme adopted to be:

Maximum power point of photovoltaic power generation system is followed the tracks of (MPPT) control method based on temperature variation, and it is according to following formula, and the voltage increment calculated on the power voltage operation curve of photovoltaic power generation array based on temperature variation is voltage step-size in search Δ u _pv(t, Δ T) is voltage step-size in search Δ u by the voltage increment of controlling on this array power voltage operation curve _pv(t, Δ T), dynamically find the realtime power calculated value Δ P (t, Δ T) relevant to temperature variation on array power voltage operation curve, if without temperature variation, and Δ T=0, voltage step-size in search Δ u _pv(t, Δ T), realtime power calculated value Δ P (t, Δ T) is the controlled quentity controlled variable on pulse-length modulation (PWM) driving circuit and DC-DC stepping-up/stepping-down chopper circuit, by classic method, controls; If temperature variation, dynamically adjust voltage step-size in search Δ u in time _pv(t+1, Δ T), make it to jump on the power voltage operation curve of temperature of living in, finds the realtime power calculated value Δ P (t, Δ T) relevant to this temperature variation, thereby realize the control to photovoltaic power generation array MPPT maximum power point tracking (MPPT); Described formula is:

Δu ₀(t，ΔT)＝KΔu _pv(t-1，ΔT)(1-aΔT)(1+bΔT) (1)

In formula (1), Δ u ₀(t, Δ T) is the increment of the equivalent open-circuit voltage of the t Real-time Collection calculating that photovoltaic array is relevant to temperature increment Δ T constantly, and K is that DC-DC stepping-up/stepping-down chopper circuit dutycycle is adjusted coefficient, Δ u _pv(t-1, Δ T) is the photovoltaic array Equivalent DC voltage increment relevant to temperature increment Δ T that the Real-time Collection of previous moment calculates, Δ T be t-1 to the t temperature increment in the moment, a, b are temperature varying coefficient: a=0.0025/ ℃, b=0.5/ ℃;

ΔI _sc(t，ΔT)＝ΔI _sc(t-1)(1+aΔT) (2)

In formula (2), Δ I _sc(t, Δ T) is the equivalent short-circuit current increment that the t Real-time Collection that photovoltaic array is relevant to temperature increment Δ T constantly calculates, Δ I _sc(t-1, Δ T) is the photovoltaic array equivalence short-circuit current increment of the Real-time Collection calculating that previous moment is relevant to temperature increment Δ T;

$\mathrm{\Δ}{I}_{\mathrm{pv}}(t,\mathrm{\ΔT})=\mathrm{\Δ}{I}_{\mathrm{sc}}(t,\mathrm{\ΔT})\{1-[\exp \left(\frac{\mathrm{\Δ}{u}_{\mathrm{pv}}(t-1,\mathrm{\ΔT})}{\mathrm{\Δ}{u}_0(t-1,\mathrm{\ΔT})}\right)-1\left]\right\}---\left(3\right)$

In formula (3), Δ I _pv(t, Δ T) is the t Equivalent DC current increment relevant to temperature increment Δ T that photovoltaic array sends constantly, Δ u ₀(t-1, Δ T) is the increment of the equivalent open-circuit voltage of the t-1 Real-time Collection calculating that photovoltaic array is relevant to temperature increment Δ T constantly,

Δu _pv(t，ΔT)＝ΔI _pv(t，ΔT)Z _th(t，ΔT) (4)

In formula (4), Δ u _pv(t, Δ T) is the t Equivalent DC voltage increment relevant to temperature increment Δ T that photovoltaic array sends constantly, Z _th(t, Δ T) is t parallel network reverse point X constantly, 2 equivalent Dai Weinan impedances relevant to temperature increment Δ T to the electric system side of common point Y;

ΔP(t，ΔT)＝Δu _pv(t，ΔT)ΔI _pv(t，ΔT) (5)

In formula (5), Δ P (t, Δ T) is the t realtime power calculated value relevant to temperature increment Δ T of photovoltaic array constantly;

The device of described control method, it comprises real time environment temperature detection information auxiliary circuit 1, main control circuit 2, dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, pulse-length modulation (PWM) driving circuit 4, DC current voltage detecting circuit 5, DC current voltage detecting and filtering circuit 6, DC-DC stepping-up/stepping-down chopper circuit 7 and dynamic control variable comparator circuit 8, real time environment temperature detection information auxiliary circuit 1 is connected with dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 with main control circuit 2, and the ambient temperature information detected is real-time transmitted to main control circuit 2 and dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, main control circuit 2 and dynamic control variable comparator circuit 8, dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, DC current voltage detecting and filtering circuit 6, pulse-length modulation (PWM) driving circuit 4, real time environment temperature detection information auxiliary circuit 1 is connected with inversion gird connecting device, with the ambient temperature information transmitted according to real time environment temperature detection information auxiliary circuit 1, the Real Time Observation ambient temperature information is found best power voltage operation curve the optimum dynamically MPPT voltage step-size in search of search, form in real time dynamic power voltage operation curve, by its result feedback to dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 and DC current voltage detecting and filtering circuit 6, when temperature change value Δ T is zero, send trigger pip to pulse-length modulation (PWM) driving circuit 4, dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 is connected with main control circuit 2, will calculate in real time the Equivalent DC voltage u relevant with temperature _pv(t, Δ T), Equivalent DC electric current I _pvwhether (t, Δ T) and Equivalent DC power P (t, Δ T), now need described formula (1) and formula (2) are adjusted to determine, and with main control circuit 2 exchange messages, dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 also is connected with dynamic control variable comparator circuit 8, with as a Δ T and b Δ T when non-vanishing, to dynamic control variable comparator circuit 8 output equivalent DC voltage u _pv(t, Δ T) and Equivalent DC power P (t, Δ T) the temperature independent Equivalent DC voltage u exported with main control circuit 2 _pv(t) and temperature independent Equivalent DC power P (t) compare, and the output Equivalent DC voltage increment Δ u relevant with temperature _pv(t, Δ T) and the Equivalent DC power increment Δ P (t, Δ T) relevant with temperature, be the controlled quentity controlled variable of pulse-length modulation (PWM) driving circuit 4 and DC-DC stepping-up/stepping-down chopper circuit 7, pulse-length modulation (PWM) driving circuit 4 is with dynamically control variable comparator circuit 8, DC-DC stepping-up/stepping-down chopper circuit 7 are connected with main control circuit 2, receive in real time the operation information of dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 and main control circuit 2, send trigger pulse and remove to control the switch in DC-DC stepping-up/stepping-down chopper circuit 7, DC current voltage detecting circuit 5 is connected with photovoltaic array with dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, DC-DC stepping-up/stepping-down chopper circuit 7, detects in real time the equivalent open-circuit voltage u of photovoltaic array ₀and equivalent short-circuit current I (t) _sc(t), and by it send into dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, DC current voltage detecting and filtering circuit 6 are connected with inversion gird connecting device with DC-DC stepping-up/stepping-down chopper circuit 7, main control circuit 2, detect in real time the current/voltage value according to the requirement of parallel network reverse, and filter harmonic wave according to the standard-required of harmonic wave, DC-DC stepping-up/stepping-down chopper circuit 7 is connected with DC current voltage detecting and filtering circuit 6 with pulse-length modulation (PWM) driving circuit 4, dynamically the photovoltaic array output voltage is changed into to the DC current voltage needed before parallel network reverse, dynamically control variable comparator circuit 8 is connected with main control circuit 2 with dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, pulse-length modulation (PWM) driving circuit 4.

Because the present invention has adopted technique scheme, solved existing control method exist tracking speed slow, without temperature, follow the tracks of and the low technical matters of whole output efficiency.Compared with prior art, the present invention have whole output efficiency high, can control based on temperature variation the advantages such as maximum power point of photovoltaic power generation system tracking.

The accompanying drawing explanation

Fig. 1 is the power voltage operation curve figure of photovoltaic array normal temperature during different sunshine;

Fig. 2 is the power voltage operation curve characteristic pattern of photovoltaic generation power when change in voltage;

Power voltage operation curve figure when Fig. 3 is photovoltaic array different temperatures at identical sunshine;

Fig. 4 is the photovoltaic array equivalent circuit diagram;

Fig. 5 is based on the frame principle figure of the MPPT control device of temperature variation;

Fig. 6 is based on the flow chart of the MPPT control method of temperature variation.

Embodiment

Maximum power point of photovoltaic power generation system in the present embodiment is followed the tracks of (MPPT) control method based on temperature variation, it is according to following formula, and the voltage increment calculated on the power voltage curve of photovoltaic power generation array based on temperature variation is voltage step-size in search Δ u _pv(t, Δ T) is voltage step-size in search Δ u by the voltage increment of controlling on this array power voltage curve _pv(t, Δ T), dynamically find the realtime power calculated value Δ P (t, Δ T) relevant to temperature variation on array power voltage operation curve, if without temperature variation, and Δ T=0, voltage step-size in search Δ u _pv(t, Δ T), realtime power calculated value Δ P (t, Δ T) is the controlled quentity controlled variable on pulse-length modulation (PWM) circuit and stepping-up/stepping-down chopper circuit, by classic method, controls; If temperature variation, dynamically adjust voltage step-size in search Δ u in time _pv(t+1, Δ T), make it to jump on the power voltage operation curve of temperature of living in, finds the realtime power calculated value Δ P (t, Δ T) relevant to this temperature variation, thereby realize the control to photovoltaic power generation array MPPT maximum power point tracking (MPPT); Described formula is:

Δu ₀(t，ΔT)＝KΔu _pv(t-1，ΔT)(1-aΔT)(1+bΔT) (1)

In formula (1), Δ u ₀(t, Δ T) is the increment of the equivalent open-circuit voltage of the t Real-time Collection calculating that photovoltaic array is relevant to temperature increment Δ T constantly, and K is that the stepping-up/stepping-down chopper circuit dutycycle is adjusted coefficient, Δ u _pv(t-1, Δ T) is the photovoltaic array Equivalent DC voltage increment relevant to temperature increment Δ T that the Real-time Collection of previous moment calculates, Δ T be t-1 to the t temperature increment in the moment, a, b are temperature varying coefficient: a=0.0025/ ℃, b=0.5/ ℃;

ΔI _sc(t，ΔT)＝ΔI _sc(t-1)(1+aΔT) (2)

In formula (2), Δ I _sC(t, Δ T) is the equivalent short-circuit current increment that the t Real-time Collection that photovoltaic array is relevant to temperature increment Δ T constantly calculates, Δ I _sc(t-1, Δ T) is the photovoltaic array equivalence short-circuit current increment of the Real-time Collection calculating that previous moment is relevant to temperature increment Δ T;

$\mathrm{\Δ}{I}_{\mathrm{pv}}(t,\mathrm{\ΔT})=\mathrm{\Δ}{I}_{\mathrm{sc}}(t,\mathrm{\ΔT})\{1-[\exp \left(\frac{\mathrm{\Δ}{u}_{\mathrm{pv}}(t-1,\mathrm{\ΔT})}{\mathrm{\Δ}{u}_0(t-1,\mathrm{\ΔT})}\right)-1\left]\right\}---\left(3\right)$

In formula (3), Δ I _pv(t, Δ T) is the t Equivalent DC current increment relevant to temperature increment Δ T that photovoltaic array sends constantly, Δ u ₀(t-1, Δ T) is the increment of the equivalent open-circuit voltage of the t-1 Real-time Collection calculating that photovoltaic array is relevant to temperature increment Δ T constantly,

Δu _pv(t，ΔT)＝ΔI _pv(t，ΔT)Z _th(t，ΔT) (4)

In formula (4), Δ u _pv(t, Δ T) is the t Equivalent DC voltage increment relevant to temperature increment Δ T that photovoltaic array sends constantly, Z _th(t, Δ T) is t X constantly, 2 equivalent Dai Weinan impedances relevant to temperature increment Δ T to the electric system side of Y;

ΔP(t，ΔT)＝Δu _pv(t，ΔT)ΔI _pv(t，ΔT) (5)

In formula (5), Δ P (t, Δ T) is the t realtime power calculated value relevant to temperature increment Δ T of photovoltaic array constantly.

As shown in Figure 5, a kind of device of realizing maximum power point of photovoltaic power generation system tracking (MPPT) control method based on temperature variation, it comprises real time environment temperature detection information auxiliary circuit 1, main control circuit 2, dynamic electric voltage step-length MPPT auxiliary control circuit 3, pulse-length modulation (PWM) driving circuit 4, DC current voltage detecting circuit 5, direct current detects and filtering circuit 6, DC-DC stepping-up/stepping-down chopper circuit 7 and dynamic control variable comparator circuit 8, real time environment temperature detection information auxiliary circuit 1 is connected with dynamic electric voltage step-length MPPT auxiliary control circuit 3 with main control circuit 2, and the ambient temperature information detected is real-time transmitted to main control circuit 2 and dynamic electric voltage step-length MPPT auxiliary control circuit 3, main control circuit 2 and dynamic control variable comparator circuit 8, dynamic electric voltage step-length MPPT auxiliary control circuit 3, DC current voltage detecting and filtering circuit 6, PWM driving circuit 4, real time environment temperature detection information auxiliary circuit 1 is connected with inversion gird connecting device, with the ambient temperature information transmitted according to real time environment temperature detection information auxiliary circuit 1, the Real Time Observation ambient temperature information is found best power voltage operation curve the optimum dynamically MPPT voltage step-size in search of search, form in real time dynamic power voltage operation curve, by its result feedback to dynamic electric voltage step-length MPPT auxiliary control circuit 3 and DC current voltage detecting and filtering circuit 6, when temperature change value Δ T is zero, send trigger pip to PWM driving circuit 4, dynamic electric voltage step-length MPPT auxiliary control circuit 3 is connected with main control circuit 2, will calculate in real time the Equivalent DC voltage u relevant with temperature _pv(t, Δ T), Equivalent DC electric current I _pvwhether (t, Δ T) and Equivalent DC power P (t, Δ T), now need above-mentioned formula (1) and formula (2) are adjusted to determine, and with main control circuit 2 exchange messages, dynamic electric voltage step-length MPPT auxiliary control circuit 3 also is connected with dynamic control variable comparator circuit 8, with as a Δ T and b Δ T when non-vanishing, to dynamic control variable comparator circuit 8 output equivalent DC voltage u _pv(t, Δ T) and Equivalent DC power P (t, Δ T) the temperature independent Equivalent DC voltage u exported with main control circuit 2 _pv(t) and temperature independent Equivalent DC power P (t) compare, and the output Equivalent DC voltage increment Δ u relevant with temperature _pv(t, Δ T) and the Equivalent DC power increment Δ P (t, Δ T) relevant with temperature, be the controlled quentity controlled variable of PWM driving circuit 4 and DC-DC stepping-up/stepping-down chopper circuit 7, PWM driving circuit 4 is with dynamically control variable comparator circuit 8, DC-DC stepping-up/stepping-down chopper circuit 7 are connected with main control circuit 2, receive in real time the operation information of dynamic electric voltage step-length MPPT auxiliary control circuit 3 and main control circuit 2, send trigger pulse and remove to control the switch in DC-DC stepping-up/stepping-down chopper circuit 7, DC current voltage detecting circuit 5 is connected with photovoltaic array with dynamic electric voltage step-length MPPT auxiliary control circuit 3, DC-DC stepping-up/stepping-down chopper circuit 7, detects in real time the equivalent open-circuit voltage u of photovoltaic array ₀and equivalent short-circuit current I (t) _sc(t), and by it send into dynamic electric voltage step-length MPPT auxiliary control circuit 3, DC current voltage detecting and filtering circuit 6 are connected with inversion gird connecting device with DC-DC stepping-up/stepping-down chopper circuit 7, main control circuit 2, detect in real time the current/voltage value according to the requirement of parallel network reverse, and filter harmonic wave according to the standard-required of harmonic wave, DC-DC stepping-up/stepping-down chopper circuit 7 is connected with DC current voltage detecting and filtering circuit 6 with PWM driving circuit 4, dynamically the photovoltaic array output voltage is changed into to the DC current voltage needed before parallel network reverse, dynamically control variable comparator circuit 8 is connected with main control circuit 2 with dynamic electric voltage step-length MPPT auxiliary control circuit 3, PWM driving circuit 4.

The function of real time environment temperature detection information auxiliary circuit 1 is that the ambient temperature information will detected is real-time transmitted to main control circuit 2 and dynamic electric voltage step-length MPPT auxiliary control circuit 2, and these two circuit are applied to the temperature information obtained in the MPPT control method based on temperature variation; Related variable is dynamically revised, and dynamically found new power voltage operation curve, and then found new MPPT on new curve.

The function of main control circuit 2 is to find best power voltage operation curve the optimum dynamically MPPT voltage step size of search according to disturbance observation and ambient temperature information, form in real time dynamic power voltage operation curve, by its result feedback to dynamic electric voltage step-length MPPT auxiliary control circuit 3 and DC current voltage detecting and filtering circuit 6, when temperature change value Δ T is zero, to PWM driving circuit 4, send trigger pip.Detect in real time the front DC current voltage signal of parallel network reverse, and carry out the filtering processing.Main control circuit 2 is according to the temperature independent direct current equivalent voltage u of information detected _pv(t), the temperature independent direct current equivalent voltage u of previous time period _pv(t-1), temperature independent direct current equivalent current I _pv(t), the temperature independent direct current equivalent current I of previous time period _pv(t-1), with this tittle, carry out real-time rated output t constantly and temperature independent performance number P (t) and P (t-1) of the t-1 moment, i.e. power difference DELTA P (t)=P (t)-P (t-1), voltage difference Δ u _pv(t)=u _pv(t)-u _pv(t-1), if now working point operates on the power voltage operation curve of temperature-resistantization, as temperature in Fig. 3 according to as shown in 25 ℃ of curves, the power difference DELTA P (t) that main control circuit 2 calculates, temperature independent Equivalent DC voltage increment Δ u _pv(t) be the controlled quentity controlled variable of PWM driving circuit 4 and DC-DC stepping-up/stepping-down chopper circuit 7.If working point operates on the power voltage operation curve of temperature variation, as shown in Figure 3, at t+1 constantly now, dynamically adjust rapidly voltage step size, and by working point from temperature be 25 ℃ of curves to jump to temperature be 50 ℃ of curves, the voltage power information of transmitted power voltage operation curve in real time simultaneously.Now, main control circuit 2 is also in real time by temperature independent direct current equivalent voltage u _pv(t), the t constantly information of power P (t) sends into dynamic control variable comparator circuit 8, the relevant Equivalent DC voltage u with temperature calculated in real time with dynamic electric voltage step-length MPPT auxiliary control circuit 3 _pv(t, Δ T), the Equivalent DC power P relevant with temperature (t, Δ T) compares, and obtains the Equivalent DC voltage increment Δ u relevant with temperature _pv(t, Δ T), the Equivalent DC power increment Δ P (t, Δ T) relevant with temperature, be the controlled quentity controlled variable of PWM driving circuit 4 and DC-DC stepping-up/stepping-down chopper circuit 7.

The function of dynamic electric voltage step-length MPPT auxiliary control circuit 3 is to calculate in real time the Equivalent DC voltage u relevant with temperature _pv(t, Δ T), the Equivalent DC electric current I _pv(t, Δ T), Equivalent DC power P (t, Δ T), to determine, now whether need the formula in the present invention (1) and formula (2) are adjusted, and with main control circuit 2 exchange messages, when a Δ T, b Δ T are non-vanishing, to the dynamic control variable comparator circuit 8 output Equivalent DC voltage u relevant with temperature _pv(t, Δ T), the Equivalent DC power P relevant with temperature (t, Δ T) the temperature independent Equivalent DC voltage u exported with main control circuit 2 _pv(t), t power P (t) constantly compares, and the output Equivalent DC voltage increment Δ u relevant with temperature _pv(t, Δ T), the Equivalent DC power increment Δ P (t, Δ T) relevant with temperature, be the controlled quentity controlled variable of PWM driving circuit 4 and DC-DC stepping-up/stepping-down chopper circuit 7.

PWM driving circuit 4 receives the operation information of dynamic electric voltage step-length MPPT auxiliary control circuit 3 and main control circuit 2 in real time, sends trigger pulse and removes to operate the switch in DC-DC stepping-up/stepping-down chopper circuit 7.

DC current voltage detecting circuit 5 detects the equivalent open-circuit voltage u of photovoltaic array in real time ₀and equivalent short-circuit current I (t) _sc(t), and by it send into dynamic electric voltage step-length MPPT auxiliary control circuit 3.

The function of DC current voltage detecting and filtering circuit 6 is to detect in real time the current/voltage value according to the requirement of parallel network reverse, and filter relevant harmonic wave according to GB and the international standard of harmonic wave.

DC-DC stepping-up/stepping-down chopper circuit 7, its function is dynamically the photovoltaic array output voltage to be changed into to the DC current voltage needed before parallel network reverse.

Fig. 6 is the flow chart that the present invention is based on the MPPT control method of temperature variation.As shown in the figure, from Real-time Collection short-circuit current and open-circuit voltage values in the middle of photovoltaic array, and input is normal and i-v curve and the parameter limit value of temperature variation, whether with temperature have relation, with temperature, the irrelevant operation curve that all will form in real time power and voltage is arranged if constantly surveying this current/voltage.And initial voltage step-size in search is set, search MPPT on the Power operation curve, and the direction of definite power.If any link of whole system breaks down, system is out of service.If the system normal operation, whether so next Rule of judgment is for operating on the equilibrium temperature curve.Now, if temperature does not change, by the power voltage curve of single power peak feature, search MPPT, by etc. the voltage step size method determine the mode of buck copped wave and obtain voltage and the power increment of corresponding gauge tap, these increments are used to the dutycycle of compute switch, and be used as controlled quentity controlled variable and remove to drive pwm control circuit, until MPPT is locked.If, in the middle of the process of searching MPPT, temperature generation cataclysm, adjust the voltage step-size in search dynamically, jumps to rapidly the power voltage operation curve of another temperature from a kind of power voltage operation curve of temperature.And constantly dynamically adjust voltage step size on new temperature power voltage operation curve, determine the mode of buck copped wave and obtain voltage and the power increment of corresponding gauge tap by dynamic voltage step size method, these increments are used to the dutycycle of compute switch, and be used as controlled quentity controlled variable and remove to drive pwm control circuit, until MPPT is locked.Follow the tracks of (MPPT) control method based on temperature variation in the hope of realizing optimum maximum power point of photovoltaic power generation system.

Below control method of the present invention is described in further detail.

As shown in Figure 1: at normal temperature, during different sunshine, when environment temperature is 25 ℃, and day illumination is from 400W/m ²to 1000W/m ²during variation, the photovoltaic array maximum power point (mpp) presents sharply variation, but output voltage values is stabilized in 440V.Corresponding to different amplitudes at sunshine, the maximum power point on each power voltage operation curve changes, but the relative voltage value stabilization.In such cases, every power voltage operation curve all has the feature of single power peak.This situation can characterize its homogeny with Fig. 2.

As shown in Figure 2, transverse axis u _pvthe VD of photovoltaic array, the output power that P is photovoltaic array.If Δ u in figure _pvfor the voltage step-size in search, and Δ P is corresponding power increment.In Fig. 2, P ₁, P ₂for corresponding power peak P _maxthe corresponding Δ u in left side _pv2 performance numbers, P ₃, P ₄for corresponding power peak P _maxthe corresponding Δ u in right side _pv2 performance numbers.Traditional not stressing considers that the method for temperature variation is all at P ₁, P ₂differentiate positive and negative to the derivative of voltage of its power during variation.If P ₂>P ₁, Δ P/ Δ u _pv>0 explanation power searching point is just by P _maxleft side to MPPT, approach.Otherwise, if P ₃<P ₄, Δ P/ Δ u _pv<0, illustrate that power searching point is just by P _maxright side to MPPT, approach.And if as Δ P/ Δ u _pv=0 o'clock, P _maxpoint is locked.Its corresponding photovoltaic array electrical voltage point is maximum power point P _maxvoltage.

As shown in Figure 3, at identical sunshine, during different temperatures, not only photovoltaic array voltage occurs sharply to change, and significant change also occurs MPPT maximum power point tracking (MPPT).Its main performance characteristic is that the power voltage operation curve is all moving up and down at great-jump-forward of MPPT.If it is obviously invalid still with traditional voltage step-size in search, approaching MPPT.Therefore the present invention propose following during for temperature variation the dynamic change voltage step size calculate the control method of MPPT.

In fact, from Fig. 3, can draw when temperature changes, larger variation occurs in the output voltage of photovoltaic power generation array, thereby causes the variation that MPPT is ordered.DC voltage booster circuit in traditional photovoltaic generating system (BOOST) circuit application is more, if when temperature sharply raises, the MPPT point moves to the low-voltage direction fast.If adjust not in time step-length, booster circuit (BOOST) circuit can obviously lose efficacy, unless the starting potential value is established very lowly, but so not only can make system effectiveness greatly reduce, also can make system not only complexity but also understable when gating pulse width modulated (PWM) dutycycle.The present invention uses stepping-up/stepping-down chopper circuit (BUCKBOOST), and the voltage-regulation scope of straight-flow system is increased.By the voltage increment on control system power voltage curve, be the voltage step-size in search, the dynamic searching system power voltage operation curve variation relation relevant with temperature.Thereby adjust traditional control method, and find a kind of method removal search by the dynamic control voltage step-length to follow the tracks of (MPPT) control method based on temperature variation based on maximum power point of photovoltaic power generation system.

As shown in Figure 3, this suite line is the system voltage Power operation curve curve relevant with temperature.Longitudinal axis P (W) is the power shaft that power constantly changes with temperature, transverse axis u _pv(v) be the temperature variant output voltage axle of photovoltaic array.If system now operates on the power voltage curve that temperature is 25 ℃, and voltage step-size in search now is Δ u _pv(t-1, Δ T), corresponding power increment Δ P (t-1, Δ T), the voltage step size of search naturally in next time period is Δ u _pv(t, Δ T), with previous moment Δ u _pv(t-1, Δ T) equates, corresponding power increment Δ P (t, Δ T), if now temperature does not change, above-mentioned in Δ T in all subscript variables be zero.If without temperature variation, Δ u _pv(t, Δ T), Δ P (t, Δ T) is the controlled quentity controlled variable on pwm circuit and stepping-up/stepping-down chopper circuit, and as shown in Figure 2, available traditional method is asked for Δ u _pv(t), Δ P (t) (now, Δ T is zero).If but, now because of temperature variation, when the voltage power operation curve jumps on the curve that temperature of living in is 50 ℃, as the method for voltage step-size in searchs such as still continuing to use, and be operated on the curve that temperature is 25 ℃, obviously search was lost efficacy, and caused mistake control.So, now must dynamically adjust rapidly Δ u _pvthe step-length of (t+1, Δ T), make it to jump on the power voltage operation curve that temperature is 50 ℃, on this curve, searches for MPPT.

According to Fig. 1 photovoltaic array power voltage operation curve, can obtain:

$S\underset{\underset{\mathrm{\&Delta;P}\&RightArrow;0}{\mathrm{\&Delta;}{u}_{\mathrm{pv}}\&RightArrow;0}}{=}N\frac{\mathrm{dP}}{d{u}_{\mathrm{pv}}}---\left(6\right)$

In formula (6), S is slope or the derivative on the power voltage operation curve, and N is constant, Δ u _pvbe the voltage disturbance step-length on the power voltage operation curve, Δ P is corresponding to Δ u _pvpower step size, dP is as Δ u _pv, Δ P photovoltaic array while going to zero the power limit value, i.e. differential value.Du _pvas Δ u _pv, Δ P photovoltaic array while going to zero the output voltage ultimate value, i.e. differential value.

Photovoltaic array equivalent electrical circuit in Fig. 4 is known, and the power that photovoltaic array sends is:

P _pv＝I _pvu _pv (7)

In formula (7), I _pvthe Equivalent DC electric current that photovoltaic array sends, u _pvthe Equivalent DC voltage that photovoltaic array sends, P _pvthe Equivalent DC power that photovoltaic array sends.

$I_{\mathrm{pv}}=I_{\mathrm{sc}}\{1-[\exp \left(\frac{u_{\mathrm{pv}}}{u_0}\right)-1\left]\right\}---\left(8\right)$

In formula (8), I _scthe short-circuit current that photovoltaic array sends, u ₀it is the open-circuit voltage of photovoltaic array.

Above formula is traditional MPPT computing formula while not considering temperature variation.When temperature variation, the dynamic change step size increments that must introduce while considering temperature variation removes to control pwm circuit and stepping-up/stepping-down chopper circuit, and its formula is:

Δu ₀(t，ΔT)＝KΔu _pv(t-1，ΔT)(1-aΔT)(1+bΔT) (1)

In formula (1), Δ u ₀(t, Δ T) is the increment of the equivalent open-circuit voltage that calculates of Real-time Collection relevant with temperature increment Δ T in t time chart 4, and K is that the stepping-up/stepping-down chopper circuit dutycycle is adjusted coefficient, Δ u _pv(t-1, Δ T) is the photovoltaic array Equivalent DC voltage increment relevant with temperature increment Δ T that the Real-time Collection of previous moment calculates, Δ T be t-1 to the t temperature increment in the moment, a, b is temperature varying coefficient: a=0.0025/ ℃, b=0.5/ ℃

ΔI _sc(t，ΔT)＝ΔI _sc(t-1)(1+aΔT) (2)

In formula (2), Δ I _sc(t) be the equivalent short-circuit current increment that Real-time Collection relevant with temperature increment Δ T in t time chart 4 calculates, Δ I _sc(t-1, Δ T) is the photovoltaic array equivalence short-circuit current increment that the previous moment Real-time Collection relevant with temperature increment Δ T calculates.

$\mathrm{\&Delta;}{I}_{\mathrm{pv}}(t,\mathrm{\&Delta;T})=\mathrm{\&Delta;}{I}_{\mathrm{sc}}(t,\mathrm{\&Delta;T})\{1-[\exp \left(\frac{\mathrm{\&Delta;}{u}_{\mathrm{pv}}(t-1,\mathrm{\&Delta;T})}{\mathrm{\&Delta;}{u}_0(t-1,\mathrm{\&Delta;T})}\right)-1\left]\right\}---\left(3\right)$

In formula (3), Δ I _pv(t, Δ T) is the t Equivalent DC current increment relevant with temperature increment Δ T that photovoltaic array sends constantly.Δ u ₀(t-1, Δ T) is the increment of the equivalent open-circuit voltage that calculates of Real-time Collection relevant with temperature increment Δ T in t-1 time chart 4,

Δu _pv(t，ΔT)＝ΔI _pv(t，ΔT)Z _th(t，ΔT) (4)

In formula (4), Δ u _pv(t, Δ T) is the t Equivalent DC voltage increment relevant with temperature increment Δ T that photovoltaic array sends constantly, Z _th(t, Δ T) be in t time chart 4 from X, 2 of Y see the equivalent Dai Weinan impedance relevant with temperature increment Δ T to the electric system side.

ΔP(t，ΔT)＝Δu _pv(t，ΔT)ΔI _pv(t，ΔT) (5)

In formula (5), Δ P (t, Δ T) is the t realtime power calculated value relevant with temperature increment Δ T of photovoltaic array constantly.

When ambient temperature does not change, a Δ T=0 in above-mentioned formula, b Δ T=0.

So in the present invention, all formula emphasis are applicable to when temperature changes, the maximum power point of photovoltaic array calculates, and simultaneously, also can calculate maximum power value calculating in difference situation at sunshine when constant temperature.

As shown in Figure 4, the represented I of dotted line in figure _scequivalent short-circuit current while being the photovoltaic array short circuit.Electric capacity of voltage regulation when in Fig. 4, capacitor C is the photovoltaic array open circuit, be connected side by side with photovoltaic array, and the upside of capacitor C is connected with the DC-DC stepping-up/stepping-down chopper circuit, and the downside of capacitor C is connected with common port Y point.U ₀it is the photovoltaic array open-circuit voltage at capacitor C two ends.The left side of DC-DC stepping-up/stepping-down chopper circuit is connected with the upper end of capacitor C, and the lower end of DC-DC stepping-up/stepping-down chopper circuit is connected with common point Y, and the right-hand member of DC-DC stepping-up/stepping-down chopper circuit is connected with parallel network reverse point X.I _pvthe photovoltaic array photovoltaic Equivalent DC electric current that backward electric system provides through the DC-DC stepping-up/stepping-down chopper circuit, u _pvthe photovoltaic array photovoltaic Equivalent DC voltage that backward electric system provides through the DC-DC buck-boost chopper.Z _thfrom X, 2 equivalent Dai Weinan impedances to the electric system side of Y.

Claims (1)

1. a maximum power point of photovoltaic power generation system is followed the tracks of (MPPT) control method based on temperature variation, it is characterized in that: according to following formula, the voltage increment calculated on the power voltage operation curve of photovoltaic power generation array based on temperature variation is voltage step-size in search Δ u _pv(t, Δ T) is voltage step-size in search Δ u by the voltage increment of controlling on this array power voltage operation curve _pv(t, Δ T), dynamically find the realtime power calculated value Δ P (t, Δ T) relevant to temperature variation on array power voltage operation curve, if without temperature variation, and Δ T=0, voltage step-size in search Δ u _pv(t, Δ T), realtime power calculated value Δ P (t, Δ T) is the controlled quentity controlled variable on pulse-length modulation (PWM) driving circuit and DC-DC stepping-up/stepping-down chopper circuit, by classic method, controls; If temperature variation, dynamically adjust voltage step-size in search Δ u in time _pv(t+1, Δ T), make it to jump on the power voltage operation curve of temperature of living in, finds the realtime power calculated value Δ P (t, Δ T) relevant to this temperature variation, thereby realize the control to photovoltaic power generation array MPPT maximum power point tracking (MPPT); Described formula is:

Δu ₀(t，ΔT)＝KΔu _pv(t-1，ΔT)(1-aΔT)(1+bΔT) (1)

In formula (1), Δ u ₀(t, Δ T) is the increment of the equivalent open-circuit voltage of the t Real-time Collection calculating that photovoltaic array is relevant to temperature increment Δ T constantly, and K is that DC-DC stepping-up/stepping-down chopper circuit dutycycle is adjusted coefficient, Δ u _pv(t-1, Δ T) is the photovoltaic array Equivalent DC voltage increment relevant to temperature increment Δ T that the Real-time Collection of previous moment calculates, Δ T be t-1 to the t temperature increment in the moment, a, b are temperature varying coefficient: a=0.0025/ ℃, b=0.5/ ℃;

ΔI _sc(t，ΔT)＝ΔI _sc(t-1)(1+aΔT) (2)

In formula (2), Δ I _sc(t, Δ T) is the equivalent short-circuit current increment that the t Real-time Collection that photovoltaic array is relevant to temperature increment Δ T constantly calculates, Δ I _sc(t-1, Δ T) is the photovoltaic array equivalence short-circuit current increment of the Real-time Collection calculating that previous moment is relevant to temperature increment Δ T;

$\mathrm{\&Delta;}{I}_{\mathrm{pv}}(t,\mathrm{\&Delta;T})=\mathrm{\&Delta;}{I}_{\mathrm{sc}}(t,\mathrm{\&Delta;T})\{1-[\exp \left(\frac{\mathrm{\&Delta;}{u}_{\mathrm{pv}}(t-1,\mathrm{\&Delta;T})}{\mathrm{\&Delta;}{u}_0(t-1,\mathrm{\&Delta;T})}\right)-1\left]\right\}---\left(3\right)$

In formula (3), Δ I _pv(t, Δ T) is the t Equivalent DC current increment relevant to temperature increment Δ T that photovoltaic array sends constantly, Δ u ₀(t-1, Δ T) is the increment of the equivalent open-circuit voltage of the t-1 Real-time Collection calculating that photovoltaic array is relevant to temperature increment Δ T constantly,

Δu _pv(t，ΔT)＝ΔI _pv(t，ΔT)Z _th(t，ΔT) (4)

In formula (4), Δ u _pv(t, Δ T) is the t Equivalent DC voltage increment relevant to temperature increment Δ T that photovoltaic array sends constantly, Z _th(t, Δ T) is t parallel network reverse point X constantly, 2 equivalent Dai Weinan impedances relevant to temperature increment Δ T to the electric system side of common point Y;

ΔP(t，ΔT)＝Δu _pv(t，ΔT)ΔI _pv(t，ΔT) (5)

In formula (5), Δ P (t, Δ T) is the t realtime power calculated value relevant to temperature increment Δ T of photovoltaic array constantly;

The device of described control method, it comprises real time environment temperature detection information auxiliary circuit 1, main control circuit 2, dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, pulse-length modulation (PWM) driving circuit 4, DC current voltage detecting circuit 5, DC current voltage detecting and filtering circuit 6, DC-DC stepping-up/stepping-down chopper circuit 7 and dynamic control variable comparator circuit 8, real time environment temperature detection information auxiliary circuit 1 is connected with dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 with main control circuit 2, and the ambient temperature information detected is real-time transmitted to main control circuit 2 and dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, main control circuit 2 and dynamic control variable comparator circuit 8, dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, DC current voltage detecting and filtering circuit 6, pulse-length modulation (PWM) driving circuit 4, real time environment temperature detection information auxiliary circuit 1 is connected with inversion gird connecting device, with the ambient temperature information transmitted according to real time environment temperature detection information auxiliary circuit 1, the Real Time Observation ambient temperature information is found best power voltage operation curve the optimum dynamically MPPT voltage step-size in search of search, form in real time dynamic power voltage operation curve, by its result feedback to dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 and DC current voltage detecting and filtering circuit 6, when temperature change value Δ T is zero, send trigger pip to pulse-length modulation (PWM) driving circuit 4, dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 is connected with main control circuit 2, will calculate in real time the Equivalent DC voltage u relevant with temperature _pv(t, Δ T), Equivalent DC electric current I _pvwhether (t, Δ T) and Equivalent DC power P (t, Δ T), now need described formula (1) and formula (2) are adjusted to determine, and with main control circuit 2 exchange messages, dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 also is connected with dynamic control variable comparator circuit 8, with as a Δ T and b Δ T when non-vanishing, to dynamic control variable comparator circuit 8 output equivalent DC voltage u _pv(t, Δ T) and Equivalent DC power P (t, Δ T) the temperature independent Equivalent DC voltage u exported with main control circuit 2 _pv(t) and temperature independent Equivalent DC power P (t) compare, and the output Equivalent DC voltage increment Δ u relevant with temperature _pv(t, Δ T) and the Equivalent DC power increment Δ P (t, Δ T) relevant with temperature, be the controlled quentity controlled variable of pulse-length modulation (PWM) driving circuit 4 and DC-DC stepping-up/stepping-down chopper circuit 7, pulse-length modulation (PWM) driving circuit 4 is with dynamically control variable comparator circuit 8, DC-DC stepping-up/stepping-down chopper circuit 7 are connected with main control circuit 2, receive in real time the operation information of dynamic electric voltage step-size in search MPPT auxiliary control circuit 3 and main control circuit 2, send trigger pulse and remove to control the switch in DC-DC stepping-up/stepping-down chopper circuit 7, DC current voltage detecting circuit 5 is connected with photovoltaic array with dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, DC-DC stepping-up/stepping-down chopper circuit 7, detects in real time the equivalent open-circuit voltage u of photovoltaic array ₀and equivalent short-circuit current I (t) _sc(t), and by it send into dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, DC current voltage detecting and filtering circuit 6 are connected with inversion gird connecting device with DC-DC stepping-up/stepping-down chopper circuit 7, main control circuit 2, detect in real time the current/voltage value according to the requirement of parallel network reverse, and filter harmonic wave according to the standard-required of harmonic wave, DC-DC stepping-up/stepping-down chopper circuit 7 is connected with DC current voltage detecting and filtering circuit 6 with pulse-length modulation (PWM) driving circuit 4, dynamically the photovoltaic array output voltage is changed into to the DC current voltage needed before parallel network reverse, dynamically control variable comparator circuit 8 is connected with main control circuit 2 with dynamic electric voltage step-size in search MPPT auxiliary control circuit 3, pulse-length modulation (PWM) driving circuit 4.

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