阅读说明：本技术 一种自适应最大功率追踪控制方法 (Self-adaptive maximum power tracking control method ) 是由 王朝威 邬浩泽 骆利勤 朱晨烜 于 2021-09-28 设计创作，主要内容包括：本发明涉及一种自适应最大功率跟踪控制方法,包括：采集当前电压和电流值；根据当前电压和电流值,分别计算得到当前功率值、电压变化量和功率变化量；根据电压变化量和功率变化量,结合预设的导数阈值,确定出占空比扰动值；根据当前功率值和当前电压值,结合上一次功率值、上一次电压值、上一次占空比以及占空比扰动值,确定当前占空比；基于当前占空比,调制相应的PWM驱动信号,以控制DC/DC变换器的工作状态。与现有技术相比,本发明能够同时保证最大功率跟踪的跟踪速度及稳定性。(The invention relates to a self-adaptive maximum power tracking control method, which comprises the following steps: collecting the current voltage and current value; respectively calculating to obtain a current power value, a voltage variation and a power variation according to the current voltage and current value; determining a duty ratio disturbance value according to the voltage variation and the power variation by combining a preset derivative threshold; determining a current duty ratio according to the current power value and the current voltage value by combining the last power value, the last voltage value, the last duty ratio and the duty ratio disturbance value; and modulating the corresponding PWM driving signal based on the current duty ratio to control the working state of the DC/DC converter. Compared with the prior art, the method can simultaneously ensure the tracking speed and the stability of the maximum power tracking.)

1. A self-adaptive maximum power tracking control method is characterized by comprising the following steps:

s1, collecting the current voltage and current values;

s2, respectively calculating to obtain a current power value, a voltage variation and a power variation according to the current voltage and current value;

s3, determining a duty ratio disturbance value according to the voltage variation and the power variation by combining a preset derivative threshold;

s4, determining the current duty ratio according to the current power value and the current voltage value and by combining the last power value, the last voltage value, the last duty ratio and the duty ratio disturbance value;

and S5, based on the current duty ratio, modulating the corresponding PWM driving signal to control the working state of the DC/DC converter.

2. The adaptive maximum power tracking control method according to claim 1, wherein the step S2 specifically includes the following steps:

s21, calculating to obtain a current power value according to the current voltage and current value;

s22, calculating to obtain power variation according to the current power value and the last power value;

and calculating to obtain the voltage variation according to the current voltage value and the last voltage value.

3. The adaptive maximum power tracking control method according to claim 2, wherein the current power value is specifically:

P_k＝U_k*I_k

wherein, P_kFor the current power value, U_kIs the current voltage value, I_kIs the current value.

4. The adaptive maximum power tracking control method according to claim 3, wherein the power variation is specifically:

ΔP＝P_k-P_k-1

where Δ P is the power variation, P_kFor the current power value, P_k-1Is the last power value.

5. The adaptive maximum power tracking control method according to claim 4, wherein the voltage variation is specifically:

ΔU＝U_k-U_k-1

wherein, Delta U is voltage variation, U_kIs the current voltage value, U_k-1Is the last voltage value.

6. The adaptive maximum power tracking control method according to claim 1, wherein the step S3 specifically includes the following steps:

s31, calculating the ratio of the power variation and the voltage variation;

and S32, comparing the ratio obtained in the step S31 with a preset derivative threshold value to determine a duty ratio disturbance value.

7. The adaptive maximum power tracking control method according to claim 6, wherein the step S32 specifically comprises the following steps:

s321, if the absolute value of the ratio calculated in the step S31 is greater than or equal to the preset derivative threshold, executing the step S322, otherwise executing the step S323;

s322, determining the duty ratio disturbance value as follows:

ΔD＝ΔD_ref*α|ΔP/ΔU|

where Δ D is the duty cycle disturbance value, Δ D_refFor a set reference step length, alpha is a system parameter, delta P is a power variation, and delta U is a voltage variation;

s323, determining the duty ratio disturbance value as follows:

ΔD＝ΔD_ref*[1/(β*P_k)]*|ΔP/ΔU|

where Δ D is the duty cycle disturbance value, Δ D_refFor a set reference step, β is a system parameter, Δ P is a power variation, and Δ U is a voltage variation.

8. The adaptive maximum power tracking control method according to claim 1, wherein the step S4 specifically includes the following steps:

s41, comparing the current power value with the last power value, if the current power value is larger than or equal to the last power value, executing the step S42, otherwise executing the step S43;

s42, comparing the current voltage value with the last voltage value, and determining the current duty ratio by combining the last duty ratio and the duty ratio disturbance value;

and S43, comparing the current voltage value with the last voltage value, and determining the current duty ratio by combining the last duty ratio and the duty ratio disturbance value.

9. The adaptive maximum power tracking control method according to claim 8, wherein the step S42 specifically includes the following steps:

if the current voltage value is greater than or equal to the last voltage value, determining that the current duty ratio is as follows:

D_k＝D_k-1-ΔD

otherwise, determining that the current duty ratio is:

D_k＝D_k-1+ΔD

wherein D is_kFor the current duty cycle, D_k-1For the last duty cycle, Δ D is the duty cycle disturbance value.

10. The adaptive maximum power tracking control method according to claim 8, wherein the step S43 specifically includes the following steps:

if the current voltage value is greater than or equal to the last voltage value, determining that the current duty ratio is as follows:

D_k＝D_k-1+ΔD

otherwise, determining that the current duty ratio is:

D_k＝D_k-1-ΔD

wherein D is_kFor the current duty cycle, D_k-1For the last duty cycle, Δ D is the duty cycle disturbance value.

Technical Field

The invention relates to the technical field of photovoltaic power generation control, in particular to a self-adaptive maximum power tracking control method.

Background

Maximum Power Point Tracking (MPPT) enables the photovoltaic panel to output more electric energy by adjusting the working state of the electrical module, so that direct current generated by the solar panel is effectively stored in the storage battery, and the MPPT controller can detect the generated voltage of the solar panel in real time and track the Maximum voltage current Value (VI), so that the system charges the storage battery with the Maximum Power output. Currently, MPPT is widely used in a solar photovoltaic system to coordinate the work of a solar cell panel, a storage battery and a load.

The MPPT control is generally performed by a DC/DC converter circuit, a photovoltaic cell array is connected to a load by a DC/DC circuit, and a maximum power tracking device continuously detects a change in current and voltage of the photovoltaic array and adjusts a duty ratio of a PWM driving signal of the DC/DC converter according to the change. The existing MMPT algorithm mainly comprises a constant voltage tracking method, a conductance incremental method and an interference observation method, wherein the voltage of the constant voltage tracking method is a constant value, so that the tracking efficiency is not high; the conductance incremental method has high response speed, but is relatively complex to realize and has high requirement on the precision of the sensor; the interference observation method is simple to implement, but an oscillation phenomenon exists near the MPP point obtained by the method, so that the stability is poor.

Disclosure of Invention

The present invention is directed to overcome the above-mentioned drawbacks of the prior art, and to provide an adaptive maximum power tracking control method to ensure tracking speed and stability.

The purpose of the invention can be realized by the following technical scheme: a self-adaptive maximum power tracking control method comprises the following steps:

s1, collecting the current voltage and current values;

s2, respectively calculating to obtain a current power value, a voltage variation and a power variation according to the current voltage and current value;

s3, determining a duty ratio disturbance value according to the voltage variation and the power variation by combining a preset derivative threshold;

s4, determining the current duty ratio according to the current power value and the current voltage value and by combining the last power value, the last voltage value, the last duty ratio and the duty ratio disturbance value;

and S5, based on the current duty ratio, modulating the corresponding PWM driving signal to control the working state of the DC/DC converter.

Further, the step S2 specifically includes the following steps:

s21, calculating to obtain a current power value according to the current voltage and current value;

s22, calculating to obtain power variation according to the current power value and the last power value;

and calculating to obtain the voltage variation according to the current voltage value and the last voltage value.

Further, the current power value specifically includes:

P_k＝U_k*I_k

wherein, P_kFor the current power value, U_kIs the current voltage value, I_kIs the current value.

Further, the power variation is specifically:

ΔP＝P_k-P_k-1

where Δ P is the power variation, P_kFor the current power value, P_k-1Is the last power value.

Further, the voltage variation is specifically:

ΔU＝U_k-U_k-1

wherein, Delta U is voltage variation, U_kIs the current voltage value, U_k-1Is the last voltage value.

Further, the step S3 specifically includes the following steps:

s31, calculating the ratio of the power variation and the voltage variation;

and S32, comparing the ratio obtained in the step S31 with a preset derivative threshold value to determine a duty ratio disturbance value.

Further, the step S32 specifically includes the following steps:

s321, if the absolute value of the ratio calculated in the step S31 is greater than or equal to the preset derivative threshold, executing the step S322, otherwise executing the step S323;

s322, determining the duty ratio disturbance value as follows:

ΔD＝ΔD_ref*α|ΔP/ΔU|

where Δ D is the duty cycle disturbance value, Δ D_refFor a set reference step sizeα is a system parameter, Δ P is a power variation, and Δ U is a voltage variation;

s323, determining the duty ratio disturbance value as follows:

ΔD＝ΔD_ref*[1/(β*P_k)]*|ΔP/ΔU|

where Δ D is the duty cycle disturbance value, Δ D_refFor a set reference step, β is a system parameter, Δ P is a power variation, and Δ U is a voltage variation.

Further, the step S4 specifically includes the following steps:

s41, comparing the current power value with the last power value, if the current power value is larger than or equal to the last power value, executing the step S42, otherwise executing the step S43;

s42, comparing the current voltage value with the last voltage value, and determining the current duty ratio by combining the last duty ratio and the duty ratio disturbance value;

and S43, comparing the current voltage value with the last voltage value, and determining the current duty ratio by combining the last duty ratio and the duty ratio disturbance value.

Further, the step S42 specifically includes the following steps:

if the current voltage value is greater than or equal to the last voltage value, determining that the current duty ratio is as follows:

D_k＝D_k-1-ΔD

otherwise, determining that the current duty ratio is:

D_k＝D_k-1+ΔD

wherein D is_kFor the current duty cycle, D_k-1For the last duty cycle, Δ D is the duty cycle disturbance value.

Further, the step S43 specifically includes the following steps:

if the current voltage value is greater than or equal to the last voltage value, determining that the current duty ratio is as follows:

D_k＝D_k-1+ΔD

otherwise, determining that the current duty ratio is:

D_k＝D_k-1-ΔD

wherein D is_kFor the current duty cycle, D_k-1For the last duty cycle, Δ D is the duty cycle disturbance value.

Compared with the prior art, the invention provides the self-adaptive maximum power tracking control method based on the selection of the duty ratio disturbance, the problem of contradiction between rapidity and stability in the maximum power tracking process can be effectively solved by acquiring the current voltage and current values and judging the derivative boundary value of power to voltage to select and determine the appropriate duty ratio disturbance value, when the environmental factors change, the maximum power tracking speed of the invention is higher than that of the traditional method, and when the power is stable, the duty ratio fluctuation of the method is lower than that of the traditional duty ratio disturbance method, and the stability is better.

Drawings

FIG. 1 is a schematic flow diagram of the process of the present invention;

fig. 2 is a schematic diagram illustrating a process of determining a current duty ratio in the embodiment.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Examples

As shown in fig. 1, an adaptive maximum power tracking control method includes the following steps:

s1, collecting the current voltage and current values;

s2, respectively calculating a current power value, a voltage variation and a power variation according to the current voltage and current value, specifically:

firstly, according to the current voltage and current value, calculating to obtain a current power value:

P_k＝U_k*I_k

wherein, P_kFor the current power value, U_kIs the current voltage value, I_kIs the current value;

and then calculating to obtain the power variation according to the current power value and the last power value:

ΔP＝P_k-P_k-1

wherein, DeltaP is the amount of power change, P_kFor the current power value, P_k-1Is the last power value;

and calculating to obtain the voltage variation according to the current voltage value and the last voltage value:

ΔU＝U_k-U_k-1

wherein, Delta U is voltage variation, U_kIs the current voltage value, U_k-1Is the last voltage value;

s3, determining a duty ratio disturbance value according to the voltage variation and the power variation by combining a preset derivative threshold, specifically:

firstly, calculating the ratio of the power variation and the voltage variation; and then comparing the calculated ratio with a preset derivative threshold value to determine a duty ratio disturbance value, wherein if the absolute value of the calculated ratio is greater than or equal to the preset derivative threshold value, the duty ratio disturbance value is determined as follows:

ΔD＝ΔD_ref*α|ΔP/ΔU|

where Δ D is the duty cycle disturbance value, Δ D_refFor a set reference step length, alpha is a system parameter, delta P is a power variation, and delta U is a voltage variation;

otherwise, determining the duty ratio disturbance value as:

ΔD＝ΔD_ref*[1/(β*P_k)]*|ΔP/ΔU|

where Δ D is the duty cycle disturbance value, Δ D_refFor a set reference step length, beta is a system parameter, delta P is a power variation, and delta U is a voltage variation;

s4, determining the current duty ratio according to the current power value and the current voltage value, in combination with the previous power value, the previous voltage value, the previous duty ratio, and the duty ratio disturbance value, which specifically includes:

s41, comparing the current power value with the last power value, if the current power value is larger than or equal to the last power value, executing the step S42, otherwise executing the step S43;

s42, comparing the current voltage value with the last voltage value, and if the current voltage value is greater than or equal to the last voltage value, determining that the current duty ratio is:

D_k＝D_k-1-ΔD

otherwise, determining that the current duty ratio is:

D_k＝D_k-1+ΔD

wherein D is_kFor the current duty cycle, D_k-1The duty ratio is the last time, and delta D is a duty ratio disturbance value;

s43, comparing the current voltage value with the last voltage value, and if the current voltage value is greater than or equal to the last voltage value, determining that the current duty ratio is:

D_k＝D_k-1+ΔD

otherwise, determining that the current duty ratio is:

D_k＝D_k-1-ΔD

wherein D is_kFor the current duty cycle, D_k-1The duty ratio is the last time, and delta D is a duty ratio disturbance value;

and S5, based on the current duty ratio, modulating the corresponding PWM driving signal to control the working state of the DC/DC converter.

The specific method process for determining the current duty ratio by applying the method in the embodiment is shown in fig. 2:

firstly, sampling voltage and current values, calculating power, voltage variation and power variation by using a formula of P ═ UI, then calculating a ratio delta P/delta U of the power variation and the voltage variation, and judging the size of the delta P/delta U and a derivative threshold lambda:

if Δ P/Δ U is greater than or equal to λ, Δ D ═ Δ D_ref*α|ΔP/ΔU|；

If Δ P/Δ U is smaller than λ, Δ D ═ Δ D_ref*[1/(βP_k)]*|ΔP/ΔU|；

Wherein Δ D_refFor a set reference step size, α and β are system parameters, P_kIs the power at the current moment;

II, after P is calculated to be UI, judging P_kAnd P_k-1The size of (A) to (B):

(1) if P is_kGreater than P_k-1Then continueJudge U_kAnd U_k-1If U is greater than or equal to_kGreater than U_k-1Then D_k＝D_k-1Δ D, if U_kLess than U_k-1Then D_k＝D_k-1+ΔD；

(2) If P is_kLess than P_k-1Then continue to judge U_kAnd U_k-1If U is greater than or equal to_kGreater than U_k-1Then D_k＝D_k-1+ Δ D, if U_kLess than U_k-1Then D_k＝D_k-1-ΔD；

Finally output D_kAnd re-samples U and I into the next calculation.

In summary, the invention provides an MPPT adaptive hill-climbing method with selective duty ratio disturbance to realize adaptive maximum power tracking control, and switches the duty ratio by judging a derivative decomposition value of power to voltage to solve the contradiction between rapidity and stability in the maximum power tracking process. The determined step size (i.e. duty ratio) is larger at a position farther from the maximum power point, and when the tracking is close to the maximum power point, the step size is switched by judging the derivative of the power to the voltage, so that the step size is switched into a small step size mode.