CN113009954A - Control method and system for photovoltaic cell working at maximum power point - Google Patents
Control method and system for photovoltaic cell working at maximum power point Download PDFInfo
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- CN113009954A CN113009954A CN202110264199.9A CN202110264199A CN113009954A CN 113009954 A CN113009954 A CN 113009954A CN 202110264199 A CN202110264199 A CN 202110264199A CN 113009954 A CN113009954 A CN 113009954A
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/66—Regulating electric power
- G05F1/67—Regulating electric power to the maximum power available from a generator, e.g. from solar cell
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
Abstract
One embodiment of the invention discloses a control method and a system for a photovoltaic cell to work at a maximum power point, which comprises the following steps: taking the maximum power voltage of the photovoltaic cell panel as a reference value of the direct-current bus voltage of the inverter and an actual direct-current bus voltage value obtained from a direct-current voltage sensor of the inverter to obtain a difference value, and obtaining a first calculation result; regulating the first calculation result by using a first PI regulator, and outputting a second calculation result; taking the second calculation result as an inversion voltage amplitude reference value and taking a difference value between the actual amplitude of the inversion voltage obtained from the alternating voltage sensor of the inverter to obtain a third calculation result; regulating the third calculation result by using a second PI regulator, and outputting an inversion voltage reference amplitude; multiplying the inversion voltage reference amplitude by a sin function to obtain a sine wave; and outputting the result of spwm modulation on the sine wave to an inverter.
Description
Technical Field
The invention relates to the field of inverters of photovoltaic heat storage systems, in particular to a control method and a control system for a photovoltaic cell to work at a maximum power point.
Background
MPPT, which is a short name for Maximum Power Point Tracking, and is called Maximum Power Point Tracking in chinese, refers to adjusting output Power of a photovoltaic array by an inverter according to characteristics such as different external environmental temperatures and illumination intensities, so that the photovoltaic array always outputs Maximum Power.
In the control of the existing photovoltaic off-grid inversion system, a photovoltaic cell panel and a battery for energy storage are generally adopted as a system control scheme. When the sunlight is sufficient, the load power is preferentially provided by the photovoltaic cell, and the energy storage cell is charged. When the light is weak, the load power is provided by the photovoltaic cell and the energy storage cell together, as shown in fig. 1.
In some engineering applications, considering cost and other objective factors, battery energy storage is eliminated, and a control scheme of independent power supply of a photovoltaic cell panel is adopted, as shown in fig. 2, when an off-grid control system adopts a control scheme of constant voltage and constant frequency, the power is determined by load. As can be seen from the photovoltaic power curve, as shown in fig. 3, if the current operating point is point a, as the load increases (or the illumination decreases), the operating point gradually moves to point B of the maximum power point, the voltage of the photovoltaic cell decreases, the power increases accordingly, and the control system is stable. If the working point coincides with the maximum power working point (point B), when the load is increased (or the illumination is reduced), the working point moves to the left of the maximum working point (point A). As seen by the power curve, as the voltage decreases, a decrease in power results; the power reduction results in a voltage reduction. The operating point moves to the C point rapidly, which causes the inverter to alarm under voltage and system failure.
Disclosure of Invention
The invention aims to provide a control method and a control system for a photovoltaic cell to work at a maximum power point.
In order to achieve the above purpose, the invention provides the following scheme:
the invention provides a control method for a photovoltaic cell to work at a maximum power point, which is applied to an off-grid control system independently powered by a photovoltaic cell panel and comprises the following steps:
taking the maximum power voltage of the photovoltaic cell panel as a reference value of the direct-current bus voltage of the inverter and an actual direct-current bus voltage value obtained from a direct-current voltage sensor of the inverter to obtain a difference value, and obtaining a first calculation result;
regulating the first calculation result by using a first PI regulator, and outputting a second calculation result;
taking the second calculation result as an inversion voltage amplitude reference value and taking a difference value between the actual amplitude of the inversion voltage obtained from the alternating voltage sensor of the inverter to obtain a third calculation result;
regulating the third calculation result by using a second PI regulator, and outputting an inversion voltage reference amplitude;
multiplying the inversion voltage reference amplitude by a sin function to obtain a sine wave;
and outputting the result of spwm modulation on the sine wave to an inverter.
The invention provides a system for enabling a photovoltaic cell to work at a maximum power point, which is applied to an off-grid control system independently powered by a photovoltaic cell panel, and comprises the following components:
a difference module, a PI regulator module, a sine wave module, and a spwm modulation module, wherein,
the difference module is used for calculating the difference between each reference value and the actual value and outputting the difference to the PI regulator module;
the PI regulator module is used for carrying out proportional integral regulation on the received difference value;
the sine wave module is used for multiplying the received signal by a sin function to obtain a sine wave and sending the sine wave to the spwm modulation module;
and the spwm modulation module is used for carrying out spwm modulation on the sine wave and sending a modulation result to the inverter.
In one particular embodiment, the difference module includes a first difference module and a second difference module, and the PI regulator module includes a first PI regulator module and a second PI regulator module, wherein,
the first difference module is used for taking the maximum power voltage of the photovoltaic cell panel as a reference value of the DC bus voltage of the inverter and making a difference value with an actual DC bus voltage value obtained from a DC voltage sensor of the inverter so as to obtain a first difference value;
the first PI regulator module is used for carrying out proportional integral regulation on the result of the first difference module;
the second difference module is used for taking the result output by the first PI regulator module as an inversion voltage amplitude reference value and making a difference value with an actual inversion voltage amplitude obtained from an alternating voltage sensor of the inverter so as to obtain a second difference value;
and the second PI regulator module is used for performing proportional-integral regulation on the result of the second difference module.
In a specific embodiment, the difference module is implemented by a subtractor.
A third aspect of the invention provides a DSP digital signal processor which, when executing a program, implements the method of the first aspect of the invention.
The invention has the following beneficial effects:
according to the technical scheme, the control mode of variable voltage and constant frequency is adopted, so that the problem that the system is out of control when the photovoltaic cell panel works at the left side of the maximum power point in an off-grid system independently powered by the photovoltaic cell panel is solved, and the system has the MPPT function.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 shows a diagram of a photovoltaic cell panel and battery energy storage common power supply system.
Fig. 2 shows a diagram of a photovoltaic panel individual power supply system.
Fig. 3 shows a graph of the voltage power of a photovoltaic cell panel.
Fig. 4 shows a flowchart of a control method for operating a photovoltaic cell at a maximum power point according to an embodiment of the present invention.
Fig. 5 shows a signal flow diagram corresponding to the method shown in fig. 4.
Detailed Description
In order to make the technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
With reference to fig. 4 and 5, a first embodiment of the present invention provides a control method for a photovoltaic cell to operate at a maximum power point, which is applied to an off-grid control system separately powered by a photovoltaic cell panel, and includes the following steps:
taking the maximum power voltage Mppt _ Ref of the photovoltaic cell panel as a reference value of the direct-current bus voltage of the inverter and an actual direct-current bus voltage value Udc _ Feed obtained from a direct-current voltage sensor of the inverter to obtain a first calculation result;
regulating the first calculation result by using a first PI regulator, and outputting a second calculation result;
taking the second calculation result as an inversion voltage amplitude reference value Uac _ Amp and an actual inversion voltage amplitude Uac _ Feed obtained from an alternating voltage sensor of the inverter to obtain a third calculation result;
regulating the third calculation result by using a second PI regulator, and outputting an inversion voltage reference amplitude Uac _ Ref;
multiplying the inversion voltage reference amplitude by a sin function to obtain a sine wave;
and carrying out spwm modulation on the sine wave, namely outputting the result after sine modulation to an inverter.
The inverter sends the obtained result, i.e. the actual voltage, to the load.
The voltage of the load can be controlled through the control method, the voltage of the load is controlled to be reduced, when the voltage of the load is reduced, the load power is reduced according to a calculation formula P (U2)/R of the power, the output power of the photovoltaic cell panel is unchanged, the photovoltaic output power is larger than the actual power of the load, a part of the photovoltaic output power is stored in the direct-current capacitor of the inverter, the voltage of the capacitor is increased, two wires of the photovoltaic cell panel are connected to the direct-current capacitor of the inverter, and therefore the voltage of the graph in figure 3 is increased, and the power point moves from the left side to the peak direction, so that the power point is stabilized at.
In a specific embodiment, the maximum power voltage Mppt — Ref of the photovoltaic panel is calculated according to an algorithm known in the art, and is not described herein again.
A second embodiment of the present invention provides a system for operating a photovoltaic cell at a maximum power point, which is applied to an off-grid control system separately powered by a photovoltaic cell panel, and includes: a difference module, a PI regulator module, a sine wave module and a spwm modulation module,
wherein the content of the first and second substances,
the difference module is used for calculating the difference of input data and outputting the difference to the PI regulator module;
the PI regulator module is used for carrying out proportional integral regulation on the received difference value;
the sine wave module is used for multiplying the received signal by a sin function to obtain a sine wave and sending the sine wave to the spwm modulation module;
and the spwm modulation module is used for carrying out spwm modulation on the sine wave and sending a modulation result to the inverter.
In one particular embodiment, the difference module includes a first difference module and a second difference module, and the PI regulator module includes a first PI regulator module and a second PI regulator module, wherein,
the first difference module is used for taking the maximum power voltage of the photovoltaic cell panel as a reference value of the DC bus voltage of the inverter and making a difference value with an actual DC bus voltage value obtained from a DC voltage sensor of the inverter so as to obtain a first difference value;
the first PI regulator module is used for carrying out proportional integral regulation on the result of the first difference module;
the second difference module is used for taking the result output by the first PI regulator module as an inversion voltage amplitude reference value and making a difference value with an actual inversion voltage amplitude obtained from an alternating voltage sensor of the inverter so as to obtain a second difference value;
and the second PI regulator module is used for performing proportional-integral regulation on the result of the second difference module.
In a specific embodiment, the difference module is implemented by a subtractor.
A third embodiment of the present invention provides a DSP digital signal processor that, when executing a program, implements the method of the first embodiment of the present invention.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (5)
1. A control method for a photovoltaic cell working at a maximum power point is applied to an off-grid control system independently powered by a photovoltaic cell panel, and is characterized by comprising the following steps:
taking the maximum power voltage of the photovoltaic cell panel as a reference value of the direct-current bus voltage of the inverter and an actual direct-current bus voltage value obtained from a direct-current voltage sensor of the inverter to obtain a difference value, and obtaining a first calculation result;
regulating the first calculation result by using a first PI regulator, and outputting a second calculation result;
taking the second calculation result as an inversion voltage amplitude reference value and taking a difference value between the actual amplitude of the inversion voltage obtained from the alternating voltage sensor of the inverter to obtain a third calculation result;
regulating the third calculation result by using a second PI regulator, and outputting an inversion voltage reference amplitude;
multiplying the inversion voltage reference amplitude by a sin function to obtain a sine wave;
and outputting the result of spwm modulation on the sine wave to an inverter.
2. A system for operating a photovoltaic cell at a maximum power point for use in an off-grid control system powered solely by photovoltaic panels, comprising:
a difference module, a PI regulator module, a sine wave module, and a spwm modulation module, wherein,
the difference module is used for calculating the difference between each reference value and the actual value and outputting the difference to the PI regulator module;
the PI regulator module is used for carrying out proportional integral regulation on the received difference value;
the sine wave module is used for multiplying the received signal by a sin function to obtain a sine wave and sending the sine wave to the spwm modulation module;
and the spwm modulation module is used for carrying out spwm modulation on the sine wave and sending a modulation result to the inverter.
3. The system of claim 2, wherein the difference module comprises a first difference module and a second difference module, and the PI regulator module comprises a first PI regulator module and a second PI regulator module, wherein,
the first difference module is used for taking the maximum power voltage of the photovoltaic cell panel as a reference value of the DC bus voltage of the inverter and making a difference value with an actual DC bus voltage value obtained from a DC voltage sensor of the inverter so as to obtain a first difference value;
the first PI regulator module is used for carrying out proportional integral regulation on the result of the first difference module;
the second difference module is used for taking the result output by the first PI regulator module as an inversion voltage amplitude reference value and making a difference value with an actual inversion voltage amplitude obtained from an alternating voltage sensor of the inverter so as to obtain a second difference value;
and the second PI regulator module is used for performing proportional-integral regulation on the result of the second difference module.
4. The system of claim 2, wherein the difference module is implemented by a subtractor.
5. A DSP digital signal processor characterized in that said processor, when executing a program, implements the method of claim 1.
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| CN102780232A (en) * | 2012-07-24 | 2012-11-14 | 华南理工大学 | Three-ring control method and three-ring control device of single-stage type photovoltaic grid-connected inverter system |
| CN102801363A (en) * | 2011-05-24 | 2012-11-28 | 中山大学 | Photovoltaic system MPPT (maximum power point tracking) control method based on adaptive prediction |
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2021
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Patent Citations (7)
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| CN102801363A (en) * | 2011-05-24 | 2012-11-28 | 中山大学 | Photovoltaic system MPPT (maximum power point tracking) control method based on adaptive prediction |
| CN202759253U (en) * | 2012-05-29 | 2013-02-27 | 苏州电器科学研究院股份有限公司 | Novel photovoltaic grid connected inversion control system |
| CN102780232A (en) * | 2012-07-24 | 2012-11-14 | 华南理工大学 | Three-ring control method and three-ring control device of single-stage type photovoltaic grid-connected inverter system |
| KR101403556B1 (en) * | 2012-12-03 | 2014-06-03 | 청주대학교 산학협력단 | Mppt control method for grid-connected pv inverter |
| CN104734323A (en) * | 2013-12-24 | 2015-06-24 | 珠海格力电器股份有限公司 | Hybrid power supply system, power supply method thereof and electrical equipment |
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