CN105807840B - A kind of Maximum power point tracing in photovoltaic system - Google Patents

Abstract

The present invention provides a kind of Maximum power point tracing in photovoltaic system, and it is comprised the following steps：Step S1：Photovoltaic system performance number P is obtained in real time；Step S2：Periodic system performance number P (k), setting limit performance number P are disturbed according to current MPPT_Limit, limit power dead band P_Step, obtain limit value of statistical indicant M；Step S3：Periodic system performance number P (k), a upper MPPT are disturbed according to current MPPT and disturbs periodic system performance number P (k 1), maximal power tracing dead band P_Dead, determine perturbation direction D_Flag；Step S4：According to formula V_mppt(k)=V_mppt(k‑1)+M*D_Flag*V_StepObtain peak power disturbance voltage V_mpptK () carries out maximal power tracing.There is advantages below using technical solution of the present invention：Make more to be smoothed during the fully loaded and limitation power output of photovoltaic DC-to-AC converter；The full-load power of photovoltaic system, limit power more accurate, power output are relatively stable；Busbar voltage is more stablized, system loop is relatively reliable.

Description

A kind of Maximum power point tracing in photovoltaic system

Technical field

The present invention relates to field of photovoltaic power generation, particularly a kind of Maximum power point tracing in photovoltaic system.

Background technology

Accompanying drawing 1 show MPPT algorithm generally MPPT, Voltage loop, the electric current loop three close-loop control fortune of traditional combining inverter OK, one-level limiter is increased in Voltage loop rear class when input power exceedes usual practice when equipment runs power.

Voltage loop rear class increases one-level limiter specific implementation, and when there is limit power, MPPT loops are in and lose Effect state, Voltage loop be in saturation state, exist Voltage loop move back saturation speed it is uncontrollable, MPPT re-execute be tracking error, Or again tracking etc. security risk；The precision for limiting power is not high, and power is easily mutated, and is fully loaded with power output, limit power stability Spend the problem such as inadequate.

The content of the invention

In order to overcome the deficiencies in the prior art, the present invention to provide a kind of Maximum power point tracing in photovoltaic system.Specifically Implementation is as follows：

A kind of Maximum power point tracing in photovoltaic system, it is characterised in that comprise the following steps：Step S1：Obtain in real time Take photovoltaic system performance number P；Step S2：Periodic system performance number P (k), setting limit performance number are disturbed according to current MPPT P_Limit, limit power dead band P_Step, limit value of statistical indicant M is obtained, wherein

Step S3：Periodic system performance number P (k), upper MPPT disturbance periodic system performance numbers P are disturbed according to current MPPT (k-1), maximal power tracing dead band P_Dead, determine perturbation direction D_Flag, wherein

Step S4：According to formula V_mppt(k)=V_mppt(k-1)+M*D_Flag*V_StepObtain peak power disturbance voltage V_mppt K () carries out maximal power tracing, V_StepIt is voltage disturbance step-length.

In an embodiment of the present invention, as P (k)<P_LimitWhen, M values are 1, represent that control photovoltaic generating system is carried out most High-power tracking：As P (k)>P(k-1)+P_DeadWhen, D_FlagValue is 1, represents peak power voltage disturbance direction for positive direction is disturbed It is dynamic, i.e. V_mppt(k)=V_mppt(k-1)+V_StepMaximal power tracing is carried out, as P (k) ＜ P (k-1)-P_DeadWhen, D_FlagValue for- 1, represent that peak power voltage disturbance direction disturbs for negative direction, i.e. V_mppt(k)=V_mppt(k-1)-V_StepCarry out peak power with Track, as P (k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue 0, represents V_mppt(k)=V_mppt(k-1) maximum is carried out Power tracking keeps；As P (k)>P_Limit+P_StepWhen, M values are -1, and representing reduces photovoltaic generating system power：As P (k)>P (k-1)+P_DeadWhen, D_FlagValue is 1, represents V_mppt(k)=V_mppt(k-1)-V_StepDrop power disturbance is carried out, as P (k) ＜ P (k- 1)-P_DeadWhen, D_FlagValue is -1, represents that peak power voltage disturbance direction disturbs for negative direction, i.e. V_mppt(k)=V_mppt(k- 1)+V_StepDrop power disturbance is carried out, as P (k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue 0, represents V_mppt(k) =V_mppt(k-1) limit performance number is reached, is not disturbed；Work as P_Limt≤P(k)≤P_Limt+P_StepWhen, M values 0 are represented and keep photovoltaic hair Electric system power, i.e. V_mppt(k)=V_mppt(k-1) carry out keeping photovoltaic generating system power.

In an embodiment of the present invention, the photovoltaic system performance number P is the output voltage V of photovoltaic module_PVWith output electricity Stream I_PVProduct, i.e. P=U_PV*I_PV。

In an embodiment of the present invention, the photovoltaic system performance number P is the output voltage V of photovoltaic system_OUTWith output electricity Stream I_OUTProduct, i.e. P=U_OUT*I_OUT。

In an embodiment of the present invention, the photovoltaic system performance number P is the DC bus-bar voltage V of photovoltaic system_BUSWith it is straight Stream bus current I_BUSProduct, i.e. P=V_BUS*I_BUS。

In an embodiment of the present invention, limit power dead band P_Step=A*P_Volume, wherein 0.1%≤A≤2%, the P_VolumeFor The rated power of photovoltaic system.

In an embodiment of the present invention, 0.3*P_Volume≤P_Limit≤1.1*P_Volume, the P_VolumeIt is the rated power of photovoltaic system.

In an embodiment of the present invention, maximal power tracing dead band P_Dead, wherein maximal power tracing dead band P_Dead=B* P_Volume, wherein 0.1%≤B≤2%, the P_VolumeIt is the rated power of photovoltaic system.

In an embodiment of the present invention, limit power dead band P_StepEqual to maximal power tracing dead band P_Dead。

Compared to prior art, the invention has the advantages that：

1) a kind of Maximum power point tracing in photovoltaic system of the invention is used so that the fully loaded and limit of photovoltaic DC-to-AC converter More smoothed during power output processed.

2) a kind of Maximum power point tracing in photovoltaic system of the invention, the full-load power of photovoltaic system, limit work(are used Rate is more accurate.

3) use a kind of Maximum power point tracing in photovoltaic system of the invention, the fully loaded power output of photovoltaic system compared with It is stabilization.

4) a kind of Maximum power point tracing in photovoltaic system of the invention is used, MPPT is calculated during limit power or full-load power Method is bypassed situation about switching between not performing and running in the absence of algorithm, and system is more stablized.

5) a kind of Maximum power point tracing in photovoltaic system of the invention is used, system electricity during limit power or full-load power Pressure ring in the absence of saturation and the situation for moving back saturation, more stablize, system loop is relatively reliable by busbar voltage.

Brief description of the drawings

The limit power operation principle of the existing photovoltaic systems with MPPT of Fig. 1；

Fig. 2 limit power operation principles of the invention；

The principle flow chart of Fig. 3 Maximum power point tracing in photovoltaic system of the invention；

Fig. 4 is the limit power flow fundamental diagram of an embodiment；

Fig. 5 is the limit power flow fundamental diagram of another embodiment.

Specific embodiment

Below in conjunction with the accompanying drawings and embodiment the present invention will be further described.

A kind of Maximum power point tracing in photovoltaic system, it is characterised in that comprise the following steps：Step S1：Obtain in real time Take photovoltaic system performance number P；Step S2：Periodic system performance number P (k), setting limit performance number are disturbed according to current MPPT P_Limit, limit power dead band P_Step, limit value of statistical indicant M is obtained, wherein

Step S3：Periodic system performance number P (k), upper MPPT disturbance periodic system performance numbers P are disturbed according to current MPPT (k-1), maximal power tracing dead band P_Dead, determine perturbation direction D_Flag, wherein

Step S4：According to formula V_mppt(k)=V_mppt(k-1)+M*D_Flag*V_StepObtain peak power disturbance voltage V_mppt K () carries out maximal power tracing, V_StepIt is voltage disturbance step-length.

In an embodiment of the present invention, as P (k)<P_LimitWhen, M values are 1, represent that control photovoltaic generating system is carried out most High-power tracking：As P (k)>P(k-1)+P_DeadWhen, D_FlagValue is 1, represents peak power voltage disturbance direction for positive direction is disturbed It is dynamic, i.e. V_mppt(k)=V_mppt(k-1)+V_StepMaximal power tracing is carried out, as P (k) ＜ P (k-1)-P_DeadWhen, D_FlagValue for- 1, represent that peak power voltage disturbance direction disturbs for negative direction, i.e. V_mppt(k)=V_mppt(k-1)-V_StepCarry out peak power with Track, as P (k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue 0, represents V_mppt(k)=V_mppt(k-1) maximum is carried out Power tracking keeps；As P (k)>P_Limit+P_StepWhen, M values are -1, and representing reduces photovoltaic generating system power：As P (k)>P (k-1)+P_DeadWhen, D_FlagValue is 1, represents V_mppt(k)=V_mppt(k-1)-V_StepCarry out drop power disturbance, when P (k-1)- P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue is -1, represents that peak power voltage disturbance direction disturbs for negative direction, i.e., V_mppt(k)=V_mppt(k-1)+V_StepDrop power disturbance is carried out, as P (k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagTake Value 0, represents V_mppt(k)=V_mppt(k-1) limit performance number is reached, is not disturbed；Work as P_Limt≤P(k)≤P_Limt+P_StepWhen, M values 0, Represent and keep photovoltaic generating system power, i.e. V_mppt(k)=V_mppt(k-1) carry out keeping photovoltaic generating system power.

In an embodiment of the present invention, the photovoltaic system performance number P is the output voltage V of photovoltaic module_PVWith output electricity Stream I_PVProduct, i.e. P=U_PV*I_PV。

In an embodiment of the present invention, the photovoltaic system performance number P is the output voltage V of photovoltaic system_OUTWith output electricity Stream I_OUTProduct, i.e. P=U_OUT*I_OUT。

In an embodiment of the present invention, the photovoltaic system performance number P is the DC bus-bar voltage V of photovoltaic system_BUSWith it is straight Stream bus current I_BUSProduct, i.e. P=V_BUS*I_BUS。

In an embodiment of the present invention, limit power dead band P_Step=A*P_Volume, wherein 0.1%≤A≤2%, the P_VolumeFor The rated power of photovoltaic system.

In an embodiment of the present invention, 0.3*P_Volume≤P_Limit≤1.1*P_Volume, the P_VolumeIt is the rated power of photovoltaic system.

In an embodiment of the present invention, maximal power tracing dead band P_Dead, wherein maximal power tracing dead band P_Dead=B* P_Volume, wherein 0.1%≤B≤2%, the P_VolumeIt is the rated power of photovoltaic system.

As shown in Figure 2, the current limliting principle of photovoltaic system of the invention, including band limits MPPT_Limit rings, the electricity of power Pressure ring, the operation of electric current loop three close-loop control.

Embodiment 1：

Photovoltaic system includes photovoltaic polar plate, DC/DC modules (BOOST boosting units), such as DC/AC inversion modules, accompanying drawing 3,4 It is shown, the output valve V of the MPPT_Limit rings with limit power_mpptAs the set-point of Voltage loop, the magnitude of voltage U of photovoltaic polar plate_PV As the value of feedback of Voltage loop, the output I of Voltage loop_{L_ref}As the set-point of electric current loop, the output current value I of DC/DC_boost Used as the value of feedback of electric current loop, the output valve pwm signal of electric current loop produces drive signal to act on DC/DC moulds through PWM generator The switching tube of block.

The Maximum power point tracing in photovoltaic system, comprises the following steps：

Step S1：Photovoltaic system performance number P is obtained in real time, and wherein photovoltaic system performance number P is the output electricity of photovoltaic module Pressure U_PVWith output current I_PVProduct, i.e. P=U_PV*I_PV；

Step S2：Periodic system performance number P (k), setting limit performance number P are disturbed according to current MPPT_Limit, limit power Dead band P_Step, limit value of statistical indicant M is obtained,

Wherein

Step S3：Periodic system performance number P (k), upper MPPT disturbance periodic system performance numbers P are disturbed according to current MPPT (k-1), maximal power tracing dead band P_Dead, determine perturbation direction D_Flag, wherein

Step S4：According to formula V_mppt(k)=V_mppt(k-1)+M*D_Flag*V_StepObtain peak power disturbance voltage V_mppt K () carries out maximal power tracing.

Wherein, limit power dead band P_Step=A*P_Volume, wherein 0.1%≤A≤2%, the P_VolumeIt is specified for photovoltaic system Power；

Wherein, 0.3*P_Volume≤P_Limit≤1.1*P_Volume, the P_VolumeIt is the rated power of photovoltaic system.

Wherein, maximal power tracing dead band P_Dead, wherein maximal power tracing dead band P_Dead=B*P_Volume, wherein 0.1%≤B ≤ 2%.

It should be noted that limit power dead band P_StepWith maximal power tracing dead band P_DeadEqual value can be arranged to.

Concrete operating principle is as follows：

(1) as P (k)<P_LimitWhen, M values are 1, represent that control photovoltaic generating system carries out maximal power tracing：

As P (k)>P(k-1)+P_DeadWhen, D_FlagValue is 1, represents that peak power voltage disturbance direction disturbs for positive direction, That is V_mppt(k)=V_mppt(k-1)+V_StepCarry out maximal power tracing,

As P (k) ＜ P (k-1)-P_DeadWhen, D_FlagValue is -1, represents peak power voltage disturbance direction for negative direction is disturbed It is dynamic, i.e. V_mppt(k)=V_mppt(k-1)-V_StepCarry out maximal power tracing,

P(k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue 0, represents V_mppt(k)=V_mppt(k-1) carry out most High-power tracking keeps；

(2) as P (k)>P_Limit+P_StepWhen, M values are -1, and representing reduces photovoltaic generating system power,

As P (k)>P(k-1)+P_DeadWhen, D_FlagValue is 1, represents V_mppt(k)=V_mppt(k-1)-V_StepCarry out drop power Disturbance,

As P (k) ＜ P (k-1)-P_DeadWhen, D_FlagValue is -1, represents peak power voltage disturbance direction for negative direction is disturbed It is dynamic, i.e. V_mppt(k)=V_mppt(k-1)+V_StepDrop power disturbance is carried out,

P(k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue 0, represents V_mppt(k)=V_mppt(k-1) limit is reached Performance number, does not disturb；

(3) P is worked as_Limit≤P(k)≤P_Limt+P_StepWhen, M values 0 are represented and keep photovoltaic generating system power, i.e. V_mppt(k) =V_mppt(k-1) carry out keeping photovoltaic generating system power.

Embodiment 2：

Photovoltaic system includes photovoltaic polar plate, DC/AC inversion modules, as shown in Figure 5, the MPPT_Limit rings with limit power Output valve V_mpptAs the set-point of Voltage loop, the magnitude of voltage U of photovoltaic polar plate_PVAs the value of feedback of Voltage loop, Voltage loop Output I_{L_ref}As the set-point of electric current loop, the output current value I of DC/AC_outAs the value of feedback of electric current loop, electric current loop it is defeated Go out to be worth pwm signal produces drive signal to act on the switching tube of DC/AC modules through PWM generator.

The Maximum power point tracing in photovoltaic system, comprises the following steps：

Step S1：Photovoltaic system performance number P is obtained in real time, and wherein photovoltaic system performance number P is the output voltage of DC/AC U_outWith output current I_outProduct, i.e. P=U_out*I_out；

Step S2：Periodic system performance number P (k), setting limit performance number P are disturbed according to current MPPT_Limit, limit power Dead band P_Step, limit value of statistical indicant M is obtained,

Wherein

Step S3：Periodic system performance number P (k), upper MPPT disturbance periodic system performance numbers P are disturbed according to current MPPT (k-1), maximal power tracing dead band P_Dead, determine perturbation direction D_Flag, wherein

Step S4：According to formula V_mppt(k)=V_mppt(k-1)+M*D_Flag*V_StepObtain peak power disturbance voltage V_mppt K () carries out maximal power tracing.

Wherein, limit power dead band P_Step=A*P_Volume, wherein 0.1%≤A≤2%, the P_VolumeIt is specified for photovoltaic system Power；

Wherein, 0.3*P_Volume≤P_Limit≤1.1*P_Volume, the P_VolumeIt is the rated power of photovoltaic system.

Wherein, maximal power tracing dead band P_Dead, wherein maximal power tracing dead band P_Dead=B*P_Volume, wherein 0.1%≤B ≤ 2%.

It should be noted that limit power dead band P_StepWith maximal power tracing dead band P_DeadEqual value can be arranged to.

Concrete operating principle is as follows：

(1) as P (k)<P_LimitWhen, M values are 1, represent that control photovoltaic generating system carries out maximal power tracing：

As P (k)>P(k-1)+P_DeadWhen, D_FlagValue is 1, represents that peak power voltage disturbance direction disturbs for positive direction, That is V_mppt(k)=V_mppt(k-1)+V_StepCarry out maximal power tracing,

As P (k) ＜ P (k-1)-P_DeadWhen, D_FlagValue is -1, represents peak power voltage disturbance direction for negative direction is disturbed It is dynamic, i.e. V_mppt(k)=V_mppt(k-1)-V_StepCarry out maximal power tracing,

P(k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue 0, represents V_mppt(k)=V_mppt(k-1) carry out most High-power tracking keeps；

(2) as P (k)>P_Limit+P_StepWhen, M values are -1, and representing reduces photovoltaic generating system power,

As P (k)>P(k-1)+P_DeadWhen, D_FlagValue is 1, represents V_mppt(k)=V_mppt(k-1)-V_StepCarry out drop power Disturbance,

As P (k) ＜ P (k-1)-P_DeadWhen, D_FlagValue is -1, represents peak power voltage disturbance direction for negative direction is disturbed It is dynamic, i.e. V_mppt(k)=V_mppt(k-1)+V_StepDrop power disturbance is carried out,

P(k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue 0, represents V_mppt(k)=V_mppt(k-1) limit is reached Performance number, does not disturb；

(3) P is worked as_Limt≤P(k)≤P_Limt+P_StepWhen, M values 0 are represented and keep photovoltaic generating system power, i.e. V_mppt(k) =V_mppt(k-1) carry out keeping photovoltaic generating system power.

These are only in the embodiment of the present invention a preferably embodiment.But, the present invention is not limited to above-mentioned implementation Scheme, all any impartial changes done by the present invention program and modification, produced model of the function without departing from this programme When enclosing, protection scope of the present invention is belonged to.

Claims (9)

1. a kind of Maximum power point tracing in photovoltaic system, it is characterised in that comprise the following steps：

Step S1：Photovoltaic system performance number P is obtained in real time；

Step S2：Periodic system performance number P (k), setting limit performance number P are disturbed according to current MPPT_Limit, limit power dead band P_Step, limit value of statistical indicant M is obtained, wherein

$M=\left\{\begin{array}{cc}1,& P\left(k\right)<P_{Limit}\\ 0,& P_{Limit}\&le;P\left(k\right)\&le;P_{Limit}+P_{Step};\\ -1,& P\left(k\right)>P_{Limit}+P_{Step}\end{array}\right.$

Step S3：Periodic system performance number P (k), upper MPPT disturbance periodic system performance number P (k- are disturbed according to current MPPT 1), maximal power tracing dead band P_Dead, determine perturbation direction D_Flag, wherein

$D_{Flag}=\left\{\begin{array}{cc}1,& P\left(k\right)>P(k-1)+P_{Dead}\\ 0,& P(k-1)-P_{Dead}\&le;P\left(k\right)\&le;P(k-1)+P_{Dead}\\ -1,& P\left(k\right)<P(k-1)-P_{Dead}\end{array}\right.;$

Step S4：According to formula V_mppt(k)=V_mppt(k-1)+M*D_Flag*V_StepObtain peak power disturbance voltage V_mpptK () enters Row maximal power tracing, V_StepIt is voltage disturbance step-length.

2. a kind of Maximum power point tracing in photovoltaic system according to claim 1, it is characterised in that：As P (k)< P_LimitWhen, M values are 1, represent that control photovoltaic generating system carries out maximal power tracing：

As P (k)>P(k-1)+P_DeadWhen, D_FlagValue is 1, represents that peak power voltage disturbance direction disturbs for positive direction, i.e., V_mppt(k)=V_mppt(k-1)+V_StepCarry out maximal power tracing,

As P (k) ＜ P (k-1)-P_DeadWhen, D_FlagValue is -1, represents that peak power voltage disturbance direction disturbs for negative direction, i.e., V_mppt(k)=V_mppt(k-1)-V_StepCarry out maximal power tracing,

As P (k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue 0, represents V_mppt(k)=V_mppt(k-1) maximum is carried out Power tracking keeps；

As P (k)>P_Limit+P_StepWhen, M values are -1, and representing reduces photovoltaic generating system power：

As P (k)>P(k-1)+P_DeadWhen, D_FlagValue is 1, represents V_mppt(k)=V_mppt(k-1)-V_StepDrop power disturbance is carried out,

As P (k) ＜ P (k-1)-P_DeadWhen, D_FlagValue is -1, represents that peak power voltage disturbance direction disturbs for negative direction, i.e., V_mppt(k)=V_mppt(k-1)+V_StepDrop power disturbance is carried out,

As P (k-1)-P_Dead≤P(k)≤P(k-1)+P_DeadWhen, D_FlagValue 0, represents V_mppt(k)=V_mppt(k-1) limit work(is reached Rate value, does not disturb；

Work as P_Limt≤P(k)≤P_Limt+P_StepWhen, M values 0 are represented and keep photovoltaic generating system power, i.e. V_mppt(k)=V_mppt (k-1) carry out keeping photovoltaic generating system power.

3. a kind of Maximum power point tracing in photovoltaic system according to claim 1, it is characterised in that：The photovoltaic system System performance number P is the output voltage V of photovoltaic module_PVWith output current I_PVProduct, i.e. P=U_PV*I_PV。

4. a kind of Maximum power point tracing in photovoltaic system according to claim 1, it is characterised in that：The photovoltaic system System performance number P is the output voltage V of photovoltaic system_OUTWith output current I_OUTProduct, i.e. P=U_OUT*I_OUT。

5. a kind of Maximum power point tracing in photovoltaic system according to claim 1, it is characterised in that：The photovoltaic system System performance number P is the DC bus-bar voltage V of photovoltaic system_BUSWith DC bus current I_BUSProduct, i.e. P=V_BUS*I_BUS。

6. a kind of Maximum power point tracing in photovoltaic system according to claim 1, it is characterised in that：Limit power is dead Area P_Step=A*P_Volume, wherein 0.1%≤A≤2%, the P_VolumeIt is the rated power of photovoltaic system.

7. a kind of Maximum power point tracing in photovoltaic system according to claim 1, it is characterised in that：0.3*P_Volume≤ P_Limit≤1.1*P_Volume, the P_VolumeIt is the rated power of photovoltaic system.

8. a kind of Maximum power point tracing in photovoltaic system according to claim 1, it is characterised in that：Peak power with Track dead band P_Dead, wherein maximal power tracing dead band P_Dead=B*P_Volume, wherein 0.1%≤B≤2%, the P_VolumeIt is photovoltaic system Rated power.

9. a kind of Maximum power point tracing in photovoltaic system according to claim 1, it is characterised in that：Limit power is dead Area P_StepEqual to maximal power tracing dead band P_Dead。