CN102809980A - Maximum Power Tracking Method Based on Efficient Adaptive Perturbation-and-Observe Method - Google Patents

Abstract

The invention provides a maximum power point tracking method based on efficient adaptive perturbation and observation. By the aid of the maximum power point tracking method, the problem that the step size used in a traditional perturbation and observation method in the photovoltaic-battery maximum power point tracking technology is difficult to balance, completely adaptive perturbation can be realized, and tracking speed, stability precision and universality of a system are high. The maximum power point tracking method with a basic principle includes that computing continuous output power values of a photovoltaic array according to filtered voltage and current signals; generating error signals according to changes among power signals; generating adaptive perturbation voltage values via a PI (proportional plus integral) controller; and finally generating a reference value of voltage of the photovoltaic array according to the basic principle of perturbation and observation. An error signal of an actual value and the reference value of the voltage of the photovoltaic signal is computed, and a duty cycle signal d required by a DC/DC converter is generated by another PI controller, so that on and off time of each power switch tube of a phase-shift full-bridge converter is controlled, power outputted by the photovoltaic array is adjusted, and the maximum power output point of the photovoltaic array can be tracked.

Description

Maximum power tracking method based on efficient self-adapted disturbance observation

Technical field

The present invention relates to the maximal power tracing technology of photovoltaic array (battery).The present invention relates to photovoltaic power generation grid-connecting or leave the net system.The present invention's design belongs to the maximal power tracing technical field.

Background technology

Problems such as the conventional energy resources shortage of the world today, the deterioration of the ecological environment are increasingly serious.As a kind of clean reproducible energy, photovoltaic generation is for solving energy problem and realizing that effective solution route of human social has worldwide obtained unprecedented opportunity to develop and powerful growth momentum.Yet the photoelectric transformation efficiency of photovoltaic cell is very limited, and itself is a kind of extremely unsettled power supply, and output power receives the influence of external environment (like intensity of illumination, environment temperature etc.) and loading condition easily.For making full use of sun power, improve the efficient of photovoltaic parallel in system, the working control circuit need adopt MPPT maximum power point tracking MPPT maximum power point tracking (Maximum Power Point Tracking, MPPT) technology.

Disturbance observe (Perurbation and Observation, P&O) method since its algorithm succinct, be easy to realize, be most widely used MPPT method in the present reality.But but there is defective in traditional fixed step size disturbance observation: when the disturbance step-length hour, oscillation of power will very little also, but the tracking velocity of system but can not get assurance; When the disturbance step-length becomes big, the tracking velocity of system can improve, and but can cause more high-power vibration simultaneously.So the disturbance observation step sizes of fixed step size is difficult to confirm, and is relatively poor to the adaptability of different system.Therefore; The present invention proposes a kind of efficient self-adapted disturbance observation, this method has solved the problem that traditional disturbance observation step sizes is difficult to weigh, and can obtain more excellent performance, is easy to realize, cost is moderate; And its core algorithm has general applicability, need not preset relevant definite value.Can realize complete self-adaptation disturbance, tracking velocity is fast, stable state accuracy is high, system's highly versatile.

Summary of the invention

Technical matters: a kind of maximum power tracking method that the objective of the invention is to propose photovoltaic array based on efficient self-adapted disturbance observation; Solve the problem that traditional disturbance observation step sizes is difficult to weigh; Can realize complete self-adaptation disturbance; Tracking velocity is fast, stable state accuracy is high, system's highly versatile.

Technical scheme: the maximum power tracking method based on efficient self-adapted disturbance observation of the present invention comprises that step is following:

A, the output voltage U of measuring light photovoltaic array at first_Pv(n) and output current I_Pv(n), the n in the symbol representes the n time sampled result.

B, calculate the photovoltaic array output power P of this time through the filtered voltage of low-pass filter, a current signal then_Pv(n)=U_Pv(n) * I_Pv(n), go out the self-adaptation disturbed value according to the change calculations between the power signal.Utilize this to change the error signal as closed-loop control system, it is as far as possible little when stable state to control this error, avoids system that overshoot takes place when starting simultaneously, and the oscillation of power when eliminating stable state.

Take a PI controller a to realize above-mentioned control; The PI controller is a pi controller; PI controller a is used as the needed self-adaptation disturbed value of photovoltaic array reference voltage generator, promptly forms error signal △ P through the variation between the continuous power calculation value_Pv(n)=P_Pv(n)-P_Pv(n-1), produce adaptive disturbance magnitude of voltage through this PI controller again

${\mathrm{\&Delta;\; U}}_{\mathrm{Pv}}^{*}\left(n\right)={\mathrm{\&Delta;\; U}}_{\mathrm{Pv}}^{*}(n-1)+K_{p1}[{\mathrm{\&Delta;\; P}}_{\mathrm{Pv}}\left(n\right)-{\mathrm{\&Delta;\; P}}_{\mathrm{Pv}}(n-1)]+{\mathrm{<figure-callout\; label="K\; i"\; filenames="HDA00001953838100011.png"\; state="\{\{state\}\}">K</figure-callout>}}_i{\mathrm{\&Delta;\; T}}_s{\mathrm{\&Delta;\; P}}_{\mathrm{Pv}}\left(n\right),$K_P1, K_I1Be respectively ratio and the integration constant of pi regulator a, △ T_sBe the SI.

C, produce the reference value U of photovoltaic array voltage through disturbance observation principle^*_Mppt(n).Determine by following formula:

$U_{\mathrm{mppt}}^{*}\left(n\right)=\left\{\begin{array}{c}{U}_{\mathrm{mppt}}^{*}(n-1)+{\mathrm{\&Delta;U}}_{\mathrm{pv}}^{*}\left(n\right),{\mathrm{\&Delta;P}}_{\mathrm{pv}}\left(n\right)\&times;{\mathrm{\&Delta;U}}_{\mathrm{pv}}\left(n\right)>0\\ U_{\mathrm{mppt}}^{*}(n-1)-{\mathrm{\&Delta;U}}_{\mathrm{pv}}^{*}\left(n\right),{\mathrm{\&Delta;P}}_{\mathrm{pv}}\left(n\right)\&times;{\mathrm{\&Delta;U}}_{\mathrm{pv}}\left(n\right)<0\end{array}\right.$

In the following formula, U^*_Mppt(n), U^*_Mppt(n-) be the photovoltaic array voltage reference value of this perturbation control and the photovoltaic array voltage reference value of perturbation control last time;

Disturbed value for this perturbation control; △ P_Pv(n) be this and the changing value of photovoltaic array output power last time; △ U_Pv(n) be this and the changing value of photovoltaic array output voltage last time.

The actual output voltage of D, photovoltaic array needs accurately to follow the tracks of this reference voltage U^*_Mppt(n), can realize, calculate the error signal e of photovoltaic array voltage reference value and actual value earlier through another one PI controller b_Pv(n):

Produce the DC/DC needed duty cycle signals d of transducer (n): d (n)=d (n-1)+K through PI controller b again_P2[e_Pv(n)-e_Pv(n-1)]+K_I2△ T_se_Pv(n), K_P2, K_I2Be respectively ratio and the integration constant of pi regulator b; D (n-1) is the duty cycle signals that produced in a last moment; △ T_sBe the SI.Control the make-and-break time of switching tube in the DC/DC transducer through control dutycycle d (n).After the dutycycle of DC/DC transducer changed, corresponding variation can take place in the electric current and voltage that photovoltaic array is exported to the DC/DC transducer, thereby has changed the output power and the dc-link capacitance C of photovoltaic array_DcVoltage, realize the MPPT maximum power point tracking of photovoltaic array.

E, this method comprise like the lower part from view of function altogether: the output voltage of photovoltaic array, current filtering part; Photovoltaic array output power delay link; With photovoltaic array output power changing value is the PI controller a of input; Carry out disturbance according to variable power and observe the link of judging; Carry out voltage-controlled PI controller b according to reference voltage; Suppress the excessive proportional controller of DC bus-bar voltage.

The core concept of F, this method is: be that with traditional fixed step size disturbance observation difference this method does not have fixing disturbance step-length; Thereby but confirm the reference value of output voltage with the change in voltage step-length that the changing value of photovoltaic array output power obtains the disturbance observation through the PI controller, pass through the control dutycycle that the PI controller obtains the DC/DC transducer according to the error of voltage reference value and actual value then.Because adopted the method for variable step, can greatly improve the speed of maximal power tracing and reduce its steady state power vibration, thereby improve the performance of photovoltaic system.

Described photovoltaic array to electrical network or load delivering power, is set DC bus-bar voltage higher limit U through DC/DC transducer and dc-link capacitance_Dc_ max, when virtual voltage surpassed the higher limit of setting, difference in magnitude was adjusted the dutycycle of DC/DC transducer through reciprocal regulated quantity of a proportional component output between the two, and it is too high to suppress DC bus-bar voltage, and system is moved continually and steadily.

Described PI controller a and b are made as CVT trigger voltage U with the reference voltage of photovoltaic array earlier in the practical adjustments process_{Pv_ref}, at this moment, PI controller a utilizes ratio, the integral coefficient of Ziegler-Nichols method adjustment PI controller b, up to obtaining satisfied output with inoperative; Enable disturbance then and observe algoritic module, and ratio, the integral coefficient of the adjustment PI controller a that uses the same method, finally make The whole control system obtain good output performance.

Beneficial effect: the efficient self-adapted disturbance observation that the present invention proposes has solved the problem that traditional disturbance observation step sizes is difficult to weigh; Can obtain more excellent performance, be easy to realize, cost is moderate; And its core algorithm has general applicability, need not preset relevant definite value.Can realize complete self-adaptation disturbance, tracking velocity is fast, stable state accuracy is high, system's highly versatile.

Description of drawings

Fig. 1 is the control structure block diagram based on the maximum power tracking method of efficient self-adapted disturbance observation;

Fig. 2 is the dynamic tracking process oscillogram of long fixed step size (step-length is 0.2V) disturbance observation;

Fig. 3 is the dynamic tracking process oscillogram of short fixed step size (step-length is 0.05V) disturbance observation;

Fig. 4 is the dynamic tracking process oscillogram of the efficient self-adapted disturbance observation of the present invention's proposition.

Embodiment

The maximum power tracking method of efficient self-adapted disturbance observation of the present invention, its concrete implementation step is following:

1, the output voltage U of measuring light photovoltaic array at first_Pv(n) and output current I_Pv(n), the n in the symbol representes the n time sampled result.

2, calculate the photovoltaic array output power P of this time then through the filtered voltage of low-pass filter, a current signal_Pv(n)=U_Pv(n) * I_Pv(n), go out the self-adaptation disturbed value according to the change calculations between the power signal.Utilize this to change the error signal as closed-loop control system, it is as far as possible little when stable state to control this error, avoids system that overshoot takes place when starting simultaneously, and the oscillation of power when eliminating stable state.

Take a PI controller a to realize above-mentioned control, PI controller a is used as the needed self-adaptation disturbed value of photovoltaic array reference voltage generator, promptly forms error signal △ P through the variation between the continuous power calculation value_Pv(n)=P_Pv(n)-P_Pv(n-1), produce adaptive disturbance magnitude of voltage through this PI controller again

${\mathrm{\&Delta;\; U}}_{\mathrm{Pv}}^{*}\left(n\right)={\mathrm{\&Delta;\; U}}_{\mathrm{Pv}}^{*}(n-1)+K_{p1}[{\mathrm{\&Delta;\; P}}_{\mathrm{Pv}}\left(n\right)-{\mathrm{\&Delta;\; P}}_{\mathrm{Pv}}(n-1)]+{\mathrm{<figure-callout\; label="K\; i"\; filenames="HDA00001953838100011.png"\; state="\{\{state\}\}">K</figure-callout>}}_i{\mathrm{\&Delta;\; T}}_s{\mathrm{\&Delta;\; P}}_{\mathrm{Pv}}\left(n\right),$K_P1, K_I1Be respectively ratio and the integration constant of pi regulator a, △ T_sBe the SI.

3, produce the reference value U of photovoltaic array voltage through disturbance observation principle^*_Mppt(n).Determine by following formula:

$U_{\mathrm{mppt}}^{*}\left(n\right)=\left\{\begin{array}{c}{U}_{\mathrm{mppt}}^{*}(n-1)+{\mathrm{\&Delta;U}}_{\mathrm{pv}}^{*}\left(n\right),{\mathrm{\&Delta;P}}_{\mathrm{pv}}\left(n\right)\&times;{\mathrm{\&Delta;U}}_{\mathrm{pv}}\left(n\right)>0\\ U_{\mathrm{mppt}}^{*}(n-1)-{\mathrm{\&Delta;U}}_{\mathrm{pv}}^{*}\left(n\right),{\mathrm{\&Delta;P}}_{\mathrm{pv}}\left(n\right)\&times;{\mathrm{\&Delta;U}}_{\mathrm{pv}}\left(n\right)<0\end{array}\right.$

In the following formula, U^*_Mppt(n), U^*_Mppt(n-1) be the photovoltaic array voltage reference value of this perturbation control and the photovoltaic array voltage reference value of perturbation control last time;

Disturbed value for this perturbation control; △ P_Pv(n) be this and the changing value of photovoltaic array output power last time; △ U_Pv(n) be this and the changing value of photovoltaic array output voltage last time.

4, the actual output voltage of photovoltaic array needs accurately to follow the tracks of this reference voltage U^*_Mppt(n), can realize, calculate the error signal e of photovoltaic array voltage reference value and actual value earlier through another one PI controller b_Pv(n):

Produce the DC/DC needed duty cycle signals d of transducer (n): d (n)=d (n-1)+K through PI controller b again_P2[e_Pv(n)-e_Pv(n-1)]+K_I2△ T_se_Pv(n), K_P2, K_I2Be respectively ratio and the integration constant of pi regulator b, △ T_sBe the SI.Control the make-and-break time of switching tube in the DC/DC transducer through control dutycycle d (n).After the dutycycle of DC/DC transducer changed, corresponding variation can take place in the electric current and voltage that photovoltaic array is exported to the DC/DC transducer, thereby has changed the output power and the dc-link capacitance C of photovoltaic array_DcVoltage, realize the MPPT maximum power point tracking of photovoltaic array.

5, be connected by dc bus between DC/DC transducer and the DC/AC inverter, realize that through dc-link capacitance power is by the transmission of photovoltaic array to electrical network or load.For guaranteeing the reliability service of system, set DC bus-bar voltage higher limit U_Dc_ max, when virtual voltage surpassed the higher limit of setting, difference in magnitude was adjusted the dutycycle of DC/DC transducer through reciprocal regulated quantity of a proportional component output between the two, and it is too high to suppress DC bus-bar voltage, and system is moved continually and steadily.

6, described PI controller a and b are made as CVT trigger voltage U with the reference voltage of photovoltaic array earlier in the practical adjustments process_{Pv_ref}, at this moment, PI controller a utilizes ratio, the integral coefficient of Ziegler-Nichols method adjustment PI controller b, up to obtaining satisfied output with inoperative; Enable disturbance then and observe algoritic module, and ratio, the integral coefficient of the adjustment PI controller a that uses the same method, finally make The whole control system obtain good output performance.

7, the tracking effect during practical application is as shown in Figure 4; The dynamic tracking effect of the traditional fixed step size disturbance observation when Fig. 2 and Fig. 3 are respectively long step-length with the weak point step-length, wherein U_Pv, I_Pv, P_PvBe respectively output voltage, output current and the output power of photovoltaic array.Can find out that on scheming the compare disturbance observation of fixed step size of the algorithm that the present invention proposes can improve the speed of power tracking well, reduces the oscillation of power in the tracing process simultaneously, has greatly improved the output performance of photovoltaic system.

8, the above only is the embodiment that the present invention is directed to photovoltaic system, is noted that this method also can be extended to wind-power electricity generation, fuel cell etc. other needs the field of maximal power tracing technology.

Claims (3)

1. maximum power tracking method based on efficient self-adapted disturbance observation is characterized in that its controlled step is following:

A, the output voltage U of measuring light photovoltaic array at first_Pv(n) and output current I_Pv(n), wherein n representes the n time sampled result;

B, calculate the photovoltaic array output power P of this time through the filtered voltage of low-pass filter, a current signal then_Pv(n)=U_Pv(n) * I_Pv(n); Go out the self-adaptation disturbed value according to the change calculations between the power signal, utilize this to change the error signal as closed-loop control system, it is as far as possible little when stable state to control this error; Avoid system that overshoot takes place when starting simultaneously; And the oscillation of power when eliminating stable state, take a proportional integral PI (Proportional-Integral) controller a to realize above-mentioned control; PI controller a is used as the needed self-adaptation disturbed value of photovoltaic array reference voltage generator, promptly forms error signal △ P through the variation between the continuous power calculation value_Pv(n)=P_Pv(n)-P_Pv(n-1), produce adaptive disturbance magnitude of voltage through this PI controller a again

${\mathrm{\&Delta;\; U}}_{\mathrm{Pv}}^{*}\left(n\right)={\mathrm{\&Delta;\; U}}_{\mathrm{Pv}}^{*}(n-1)+K_{p1}[{\mathrm{\&Delta;\; P}}_{\mathrm{Pv}}\left(n\right)-{\mathrm{\&Delta;\; P}}_{\mathrm{Pv}}(n-1)]+K_{i1}{\mathrm{\&Delta;\; T}}_s{\mathrm{\&Delta;\; P}}_{\mathrm{Pv}}\left(n\right),$K_P1, K_I1Be respectively ratio and the integration constant of pi regulator a, △ T_sBe the SI;

C, produce the reference value U of photovoltaic array voltage through disturbance observation principle^*_Mppt(n), by following formula decision:

$U_{\mathrm{mppt}}^{*}\left(n\right)=\left\{\begin{array}{c}{U}_{\mathrm{mppt}}^{*}(n-1)+{\mathrm{\&Delta;U}}_{\mathrm{pv}}^{*}\left(n\right),{\mathrm{\&Delta;P}}_{\mathrm{pv}}\left(n\right)\&times;{\mathrm{\&Delta;U}}_{\mathrm{pv}}\left(n\right)>0\\ U_{\mathrm{mppt}}^{*}(n-1)-{\mathrm{\&Delta;U}}_{\mathrm{pv}}^{*}\left(n\right),{\mathrm{\&Delta;P}}_{\mathrm{pv}}\left(n\right)\&times;{\mathrm{\&Delta;U}}_{\mathrm{pv}}\left(n\right)<0\end{array}\right.$

In the following formula, U^*_Mppt(n), U^*_Mppt(n-1) be the photovoltaic array voltage reference value of this perturbation control and the photovoltaic array voltage reference value of perturbation control last time;

Disturbed value for this perturbation control; △ P_Pv(n) be this and the changing value of photovoltaic array output power last time; △ U_Pv(n) be this and the changing value of photovoltaic array output voltage last time;

The actual output voltage of D, photovoltaic array needs accurately to follow the tracks of this reference voltage U^*_Mppt(n), realize, calculate the error signal e of photovoltaic array voltage reference value and actual value earlier through another one PI controller b_Pv(n):

Produce the DC/DC needed duty cycle signals d of transducer (n): d (n)=d (n-1)+K through PI controller b again_P2[e_Pv(n)-e_Pv(n-1)]+K_I2△ T_se_Pv(n), K_P2, K_I2Be respectively ratio and the integration constant of pi regulator b; D (n-1) is the duty cycle signals that produced in a last moment; △ T_sBe the SI.Control the make-and-break time of switching tube in the DC/DC transducer through control dutycycle d (n); After the dutycycle of DC/DC transducer changed, corresponding variation can take place in the electric current and voltage that photovoltaic array is exported to the DC/DC transducer, thereby has changed the output power and the dc-link capacitance C of photovoltaic array_DcVoltage, realize the MPPT maximum power point tracking of photovoltaic array.

2. maximum power tracking method based on efficient self-adapted disturbance observation as claimed in claim 1; It is characterized in that described photovoltaic array; To electrical network or load delivering power, set DC bus-bar voltage higher limit U through DC/DC transducer and dc-link capacitance_Dc_ max, when virtual voltage surpassed the higher limit of setting, difference in magnitude was adjusted the dutycycle of DC/DC transducer through reciprocal regulated quantity of a proportional component output between the two, and it is too high to suppress DC bus-bar voltage, and system is moved continually and steadily.

3. the maximum power tracking method based on efficient self-adapted disturbance observation as claimed in claim 1 is characterized in that described PI controller a and PI controller b, and elder generation is made as CVT trigger voltage U with the reference voltage of photovoltaic array in the practical adjustments process_{Pv_ref}, at this moment, PI controller a utilizes ratio, the integral coefficient of Ziegler-Nichols method adjustment PI controller b, up to obtaining satisfied output with inoperative; Enable disturbance then and observe algoritic module, and ratio, the integral coefficient of the adjustment PI controller a that uses the same method, finally make The whole control system obtain good output performance.

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