阅读说明：本技术 引入改进步长因子的光伏mppt控制方法、系统、介质及设备 (Photovoltaic MPPT control method, system, medium and equipment introducing improved step size factor ) 是由 王洪荣 孙强 施成章 王希乐 刘志峰 于 2021-07-12 设计创作，主要内容包括：本发明提供了一种引入改进步长因子的光伏MPPT控制方法、系统、介质及设备,包括：步骤S1：在光伏电池MPPT控制中,根据扰动观察法原理和光伏电池的功率-电压特性,引入步长因子；步骤S2：基于引入的步长因子,并根据扰动前后功率差值和扰动前后的电压差值确定继续扰动的方向,得到改进后的光伏电池MPPT控制,从而保证在特性曲线两端的收敛速度和精度。本发明引入步长因子,利用它来调节扰动的步长,从而可以动态地调节MPPT的步长,从而保证在特性曲线两端的收敛速度和精度。(The invention provides a photovoltaic MPPT control method, a system, a medium and equipment with an improved step size factor, which comprise the following steps: step S1: in MPPT control of the photovoltaic cell, a step factor is introduced according to a disturbance observation method principle and the power-voltage characteristic of the photovoltaic cell; step S2: and determining the direction of continuous disturbance according to the power difference before and after disturbance and the voltage difference before and after disturbance based on the introduced step length factor to obtain the improved MPPT control of the photovoltaic cell, thereby ensuring the convergence speed and precision at the two ends of the characteristic curve. The invention introduces a step factor, and utilizes the step factor to adjust the disturbed step length, thereby dynamically adjusting the step length of MPPT, and ensuring the convergence speed and precision at the two ends of the characteristic curve.)

1. A photovoltaic MPPT control method introducing an improved step size factor is characterized by comprising the following steps:

step S1: in MPPT control of the photovoltaic cell, a step factor is introduced according to a disturbance observation method principle and the power-voltage characteristic of the photovoltaic cell;

step S2: and determining the direction of continuous disturbance according to the power difference before and after disturbance and the voltage difference before and after disturbance based on the introduced step length factor to obtain the improved MPPT control of the photovoltaic cell, thereby ensuring the convergence speed and precision at the two ends of the characteristic curve.

2. The photovoltaic MPPT control method incorporating the modified step factor as set forth in claim 1, wherein the step S1 includes:

wherein Δ p represents a power difference before and after the disturbance; e denotes a natural constant.

3. The photovoltaic MPPT control method incorporating the modified step factor as set forth in claim 1, wherein the step S2 includes:

step S2.1: detecting the current voltage u (i) and the current i (i);

step S2.2: calculating the current power according to the detected current voltage u (i) and current i (i), and making a difference with the voltage and the power at the last time point to obtain a voltage difference value and a power difference value;

step S2.3: judging whether the product of the voltage difference value and the power difference value is positive, and if so, judging that the disturbance direction is correct; when the current is negative, the disturbance direction is wrong, and the opposite direction is taken.

4. The photovoltaic MPPT control method incorporating an improved step factor as set forth in claim 1, wherein the step S2.3 includes:

△U＝U_i-U_i-1 (2)

△p＝p_i-p_i-1 (3)

wherein, U_iRepresenting the current voltage value; u shape_i+1Representing the voltage value at the last time point; Δ U represents a voltage difference; p is a radical of_iRepresents a current power value; p is a radical of_i-1Representing the power value of the last time point; Δ p represents the power difference;

when the delta U is positive, the working voltage at the moment is modified into Uref + lambda delta U;

when Δ U × Δ p is not positive, the operating voltage at this time is modified to Uref — λ Δ U.

5. A photovoltaic MPPT control system introducing an improved step size factor, comprising:

module M1: in MPPT control of the photovoltaic cell, a step factor is introduced according to a disturbance observation method principle and the power-voltage characteristic of the photovoltaic cell;

module M2: and determining the direction of continuous disturbance according to the power difference before and after disturbance and the voltage difference before and after disturbance based on the introduced step length factor to obtain the improved MPPT control of the photovoltaic cell, thereby ensuring the convergence speed and precision at the two ends of the characteristic curve.

6. The photovoltaic MPPT control system incorporating an improved step-size factor as set forth in claim 5, wherein the module M1 includes:

wherein Δ p represents a power difference before and after the disturbance; e denotes a natural constant.

7. The photovoltaic MPPT control system incorporating an improved step-size factor as set forth in claim 5, wherein the module M2 includes:

module M2.1: detecting the current voltage u (i) and the current i (i);

module M2.2: calculating the current power according to the detected current voltage u (i) and current i (i), and making a difference with the voltage and the power at the last time point to obtain a voltage difference value and a power difference value;

module M2.3: judging whether the product of the voltage difference value and the power difference value is positive, and if so, judging that the disturbance direction is correct; when the current is negative, the disturbance direction is wrong, and the opposite direction is taken.

8. The photovoltaic MPPT control system incorporating an improved step-size factor as set forth in claim 5, wherein the module M2.3 includes:

△U＝U_i-U_i-1 (2)

△p＝p_i-p_i-1 (3)

wherein, U_iRepresenting the current voltage value; u shape_i+1Representing the voltage value at the last time point; Δ U represents a voltage difference; p is a radical of_iRepresents a current power value; p is a radical of_i-1Representing the power value of the last time point; Δ p represents the power difference;

when the delta U is positive, the working voltage at the moment is modified into Uref + lambda delta U;

when Δ U × Δ p is not positive, the operating voltage at this time is modified to Uref — λ Δ U.

9. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 4.

10. A photovoltaic MPPT control apparatus incorporating an improved step factor, comprising: a controller;

the controller includes the computer readable storage medium of claim 9 having a computer program stored thereon, which when executed by a processor implements the steps of the photovoltaic MPPT control method incorporating the improved step factor of any of claims 1 to 4; alternatively, the controller includes the photovoltaic MPPT control system incorporating the improved step factor of any one of claims 5 to 8.

Technical Field

The invention relates to the technical field of industry, in particular to a photovoltaic MPPT control method and a photovoltaic MPPT control system introducing an improved step factor, and more particularly to a photovoltaic MPPT control strategy introducing the improved step factor.

Background

At present, the MPPT control of the photovoltaic power generation unit is most widely used by a disturbance observation method, which is also called a hill climbing search method and is divided into a voltage type and a current type, wherein the voltage type is common. When a disturbance observation method is used, a positive disturbance quantity delta U is given to the voltage, the output power P of the photovoltaic cell is calculated, and if the output power is increased, the disturbance direction is correct; conversely, the direction of the disturbance is opposite. However, the traditional method adopts a fixed step length, and the selection of the step length has a large influence on the disturbance effect. When the disturbance step length is too large, although the tracking speed is high, the tracking speed is not accurate enough, and the system is easy to oscillate; when the disturbance step length is too small, although the disturbance step length is accurate, the tracking speed is slow, once the external environment changes fast, a good tracking effect cannot be achieved, and how to determine the appropriate step length can achieve both fast tracking and a good tracking effect is an important subject.

In the prior art, when the disturbance step length is too large, although the tracking speed is high, the tracking speed is not accurate enough, and the system is easy to oscillate; when the disturbance step size is too small, the tracking speed is slow although the disturbance step size is more accurate.

The invention determines the appropriate step length required by the current MPPT control method, thereby obtaining the appropriate tracking speed and tracking accuracy.

Patent document CN110362146A (application number: 201910614450.2) discloses an adaptive MPPT control strategy based on a variable step disturbance observation method, and belongs to the field of photovoltaic power generation. Based on the research of the traditional disturbance observation method, the invention introduces the adaptive variable step factor to further adaptively change the size of the disturbance step, so that the disturbance step can be adaptively adjusted according to the distance between the working point of the photovoltaic power generation system and the maximum power point, thereby improving the dynamic performance of the traditional disturbance observation method and avoiding the erroneous judgment of the system.

Disclosure of Invention

In view of the shortcomings in the prior art, it is an object of the present invention to provide a photovoltaic MPPT control method, system, medium, and apparatus incorporating an improved step factor.

The invention provides a photovoltaic MPPT control method introducing an improved step size factor, which is characterized by comprising the following steps:

step S1: in MPPT control of the photovoltaic cell, a step factor is introduced according to a disturbance observation method principle and the power-voltage characteristic of the photovoltaic cell;

step S2: and determining the direction of continuous disturbance according to the power difference before and after disturbance and the voltage difference before and after disturbance based on the introduced step length factor to obtain the improved MPPT control of the photovoltaic cell, thereby ensuring the convergence speed and precision at the two ends of the characteristic curve.

Preferably, the step S1 includes:

wherein Δ p represents a power difference before and after the disturbance; e denotes a natural constant.

Preferably, the step S2 includes:

step S2.1: detecting the current voltage u (i) and the current i (i);

step S2.2: calculating the current power according to the detected current voltage u (i) and current i (i), and making a difference with the voltage and the power at the last time point to obtain a voltage difference value and a power difference value;

step S2.3: judging whether the product of the voltage difference value and the power difference value is positive, and if so, judging that the disturbance direction is correct; when the current is negative, the disturbance direction is wrong, and the opposite direction is taken.

Preferably, said step S2.3 comprises:

△U＝U_i-U_i-1 (2)

△p＝p_i-p_i-1 (3)

wherein, U_iRepresenting the current voltage value; u shape_i+1Representing the voltage value at the last time point; Δ U represents a voltage difference; p is a radical of_iRepresents a current power value; p is a radical of_i-1Represents the last hourAn intermediate power value; Δ p represents the power difference;

when the delta U is positive, the working voltage at the moment is modified into Uref + lambda delta U;

when Δ U × Δ p is not positive, the operating voltage at this time is modified to Uref — λ Δ U.

According to the invention, a photovoltaic MPPT control system introducing an improved step size factor is provided, comprising:

module M1: in MPPT control of the photovoltaic cell, a step factor is introduced according to a disturbance observation method principle and the power-voltage characteristic of the photovoltaic cell;

module M2: and determining the direction of continuous disturbance according to the power difference before and after disturbance and the voltage difference before and after disturbance based on the introduced step length factor to obtain the improved MPPT control of the photovoltaic cell, thereby ensuring the convergence speed and precision at the two ends of the characteristic curve.

Preferably, said module M1 comprises:

wherein Δ p represents a power difference before and after the disturbance; e denotes a natural constant.

Preferably, said module M2 comprises:

module M2.1: detecting the current voltage u (i) and the current i (i);

module M2.2: calculating the current power according to the detected current voltage u (i) and current i (i), and making a difference with the voltage and the power at the last time point to obtain a voltage difference value and a power difference value;

module M2.3: judging whether the product of the voltage difference value and the power difference value is positive, and if so, judging that the disturbance direction is correct; when the current is negative, the disturbance direction is wrong, and the opposite direction is taken.

Preferably, said module M2.3 comprises:

△U＝U_i-U_i-1 (2)

△p＝p_i-p_i-1 (3)

wherein, U_iRepresenting the current voltage value; u shape_i+1Representing the voltage value at the last time point; Δ U represents a voltage difference; p is a radical of_iRepresents a current power value; p is a radical of_i-1Representing the power value of the last time point; Δ p represents the power difference;

when the delta U is positive, the working voltage at the moment is modified into Uref + lambda delta U;

when Δ U × Δ p is not positive, the operating voltage at this time is modified to Uref — λ Δ U.

According to the present invention, a computer-readable storage medium is provided, in which a computer program is stored, which, when being executed by a processor, carries out the steps of the method as described above.

According to the invention, the photovoltaic MPPT control device introducing the improved step size factor comprises the following components: a controller;

the controller comprises the computer-readable storage medium storing the computer program, and the computer program is used for realizing the steps of the photovoltaic MPPT control method for introducing the improved step size factor when being executed by a processor; alternatively, the controller comprises the photovoltaic MPPT control system introducing the improved step factor.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention introduces a step factor, and utilizes the step factor to adjust the disturbed step length, thereby dynamically adjusting the step length of MPPT, and ensuring the convergence speed and precision at the two ends of the characteristic curve.

2. The invention can quickly react to the temperature and the illumination intensity change, and can quickly and stably keep near the new output voltage and output power.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a diagram illustrating the variation of the lambda value;

FIG. 2 is a flow chart of an improved variable step MPPT control;

FIG. 3 is a modified step-size factor λ model;

FIG. 4 is a modified step MPPT controller model;

FIG. 5 is a schematic diagram of a photovoltaic cell model;

fig. 6 is a graph of photovoltaic cell model output.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.

Example 1

The invention mainly aims at the problem that the disturbance step length in the MPPT control strategy can not be dynamically adjusted, improves according to a disturbance observation method and the power-voltage characteristic of a photovoltaic cell, introduces a step length factor, and utilizes the step length factor to adjust the disturbance step length, thereby dynamically adjusting the MPPT step length and ensuring the convergence speed and precision at two ends of a characteristic curve.

The invention provides a photovoltaic MPPT control method introducing an improved step size factor, which comprises the following steps:

in the MPPT control of the common photovoltaic cell, the adopted step length is a fixed step length, and the problem of slow oscillation or tracking can exist, so that the MPPT step length can be changed by introducing a step length factor, and the problems of oscillation and tracking speed can be solved.

Where Δ p represents the power difference before and after disturbance, and e represents a natural constant

It is used to adjust the step size at the perturbation. Lambda and distance P_mThe longer the distance, the larger the value of lambda, thus ensuring the convergence speed at both ends of the characteristic curve, i.e. improving the characteristic curve to the correct direction of the disturbance U_i+1＝U_i+ λ Δ U or U in case of disturbance directional error_i+1＝U_i+ λ Δ U. The lambda value versus voltage power plot is shown in fig. 1:

wherein, U_i+1Representing the voltage at the next point in time; u shape_iRepresents the current voltage; delta U represents the amplitude of the disturbance voltage

The variable step-size factor lambda has a value range of (0,1), and the distance P is obtained during tracking_mThe more recent, i.e. the larger the power difference Δ P, the larger the λ value, the smaller the power difference Δ P, and the smaller the λ value, the more detailed improved variable step disturbance observation process flow is shown in fig. 2:

step S1: detecting the voltage and current u (i), i (i) at the moment;

step S2: calculating the lambda at the moment through the delta P at the last time point;

step S3: calculating the power at the moment according to the numerical value of the first step, and subtracting the power from the voltage at the last time point to obtain a voltage difference value and a power difference value;

step S4: judging whether the voltage difference value and the power difference value are positive, if so, modifying the working voltage at the moment into Uref + Lambda Delta U, and if not, modifying the working voltage at the moment into Uref-Lambda Delta U;

the improved variable-step disturbance observation method is different from the traditional disturbance observation method in that a variable-step factor lambda is introduced, and the value of the variable-step factor lambda is related to the output power difference delta P before and after disturbance. By measuring the photovoltaic output voltage U_(i)And an output current I_(i)The output power P can be calculated_(i)And using the voltage U of the last operating point_(i-1)And power P_(i-1)Δ U and Δ P are calculated. Determining the direction of continuous disturbance according to the positive and negative conditions of the delta U and the delta P, and if the direction is positive, determining the direction is the correct disturbance direction; when the direction is negative, the direction is wrong, and the opposite direction is taken.

According to the improved variable-step-size MPPT control flow chart, a control circuit is built in Simulink, as shown in figure 3, a step-size factor lambda model is improved, as shown in figure 4, the step-size MPPT control circuit is improved.

The whole photovoltaic module is divided into three parts, namely a photovoltaic cell output circuit, a booster circuit and a load circuit, and a specific circuit schematic diagram is shown in fig. 5:

wherein, the left side of the converter comprises an output circuit of C1 and L, the converter comprises a booster circuit of VD, C2 and R1, and a load point circuit of R2 and switch

The circuit parameters are shown in Table 1

TABLE 1 photovoltaic cell model parameters

The corresponding photovoltaic cell parameter variation, output voltage, output current, output power, as shown in fig. 6:

under the condition that the temperature and the illumination intensity are unchanged, even if a load is added, the power is almost unchanged and is maintained at the maximum power point. After the temperature is reduced, the output power of the photovoltaic cell is reduced, but the amplitude is not large. After the illumination intensity is reduced, the power is greatly reduced. After the illumination intensity, the temperature and the power are changed, the power, the current and the voltage can be quickly recovered to a stable value.

The photovoltaic MPPT control system introducing the improved step size factor can be realized through the step flow in the photovoltaic MPPT control method introducing the improved step size factor. The photovoltaic MPPT control method introducing the improved step-size factor can be understood as a preferred example of the photovoltaic MPPT control system introducing the improved step-size factor by those skilled in the art.

Those skilled in the art will appreciate that, in addition to implementing the systems, apparatus, and various modules thereof provided by the present invention in purely computer readable program code, the same procedures can be implemented entirely by logically programming method steps such that the systems, apparatus, and various modules thereof are provided in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system, the device and the modules thereof provided by the present invention can be considered as a hardware component, and the modules included in the system, the device and the modules thereof for implementing various programs can also be considered as structures in the hardware component; modules for performing various functions may also be considered to be both software programs for performing the methods and structures within hardware components.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.