Photovoltaic energy collection system capable of adaptively adjusting monitoring time

Abstract

The invention belongs to the technical field of energy collection, and relates to a photovoltaic energy collection system capable of adaptively adjusting monitoring time, which comprises a cold start module used for self-starting of an initial no-power state of the system; the maximum power point tracking circuit adopts a fractional open-circuit voltage method to track and control the photovoltaic cell to work at the maximum power point; the clock circuit is used for providing a reference clock signal for the system; the power level circuit is used for storing and releasing energy to realize voltage conversion; the peak current detection circuit is used for detecting and controlling peak inductive current in the power level circuit; the zero current detection circuit is used for detecting an inductive current zero crossing point; and the digital control logic module is used for regulating the operation of the maximum power point tracking circuit, the peak current detection circuit and the zero current detection circuit. Through adaptive maximum power point monitoring time, the tracking speed of the photovoltaic energy collection system under a dynamic illumination condition is remarkably improved, and the method has the characteristic of high energy collection efficiency.

Description

Technical Field

[0001] This invention belongs to the field of energy harvesting technology, specifically relating to a photovoltaic energy harvesting system that adaptively adjusts monitoring time. Background Technology

[0002] Photovoltaic energy harvesting technology provides a sustainable energy solution for low-power electronic devices. Maximum power point tracking (MPPT) circuits are at their core, with the fractional open-circuit voltage method (FPS) being widely adopted due to its simplicity and low power consumption. However, the traditional FPS method uses a fixed monitoring time to sample the open-circuit voltage of the photovoltaic cells and update the operating point. Under strong sunlight, the photovoltaic cells quickly establish an open-circuit voltage, but the energy harvesting system must wait for the fixed monitoring time to end before it can continue harvesting energy, resulting in the waste of some potentially harvestable energy. Conversely, under weak sunlight, the photovoltaic cells require a longer time to establish an open-circuit voltage, and the end of the fixed monitoring time does not necessarily mean that the photovoltaic cell voltage has reached the open-circuit state. The energy harvesting system may collect an incorrect open-circuit voltage value and calculate an incorrect maximum power point voltage, causing the system to deviate from its optimal efficiency point over a long period. Therefore, a maximum power point tracking circuit that can intelligently adapt to different light intensities and dynamically optimize the monitoring time is needed to resolve the above contradictions and improve the overall efficiency of the energy harvesting system under all-weather conditions. Summary of the Invention

[0003] To address the aforementioned technical problems in the existing technology, this invention proposes a photovoltaic energy harvesting system that adaptively adjusts the monitoring time, the specific technical solution of which is as follows: A photovoltaic energy harvesting system that adaptively adjusts monitoring time includes: The cold start module is used to initiate the initial startup process of the system when the system power supply voltage is insufficient. Maximum power point tracking circuit, used to track and control photovoltaic cells to operate at their maximum power point using the fractional open-circuit voltage method; Clock circuit, used to provide a reference clock signal for the system; Power stage circuitry is used to realize energy transfer and voltage conversion between photovoltaic cells and load; A peak current detection circuit is used to detect and control the peak inductor current in the power stage circuit. A zero-current detection circuit is used to detect the zero-crossing point of the inductor current in the power stage circuit. The digital control logic module is used to coordinate the operation of the maximum power point tracking circuit, the peak current detection circuit, and the zero current detection circuit.

[0004] Furthermore, the maximum power point tracking circuit includes: A voltage sampling and conversion unit is used to sample the voltage of the photovoltaic cell and convert it into digital codeword format; An adaptive monitoring time control unit, connected to the voltage sampling and conversion unit, is used to identify changes in photovoltaic cell voltage, determine when it reaches the open-circuit voltage, and output a signal to indicate that maximum power point monitoring has been completed. The fractional calculation unit, connected to the voltage sampling conversion unit and the adaptive monitoring time control unit, is used to calculate the open-circuit voltage after the maximum power point monitoring is completed, so as to generate a digital codeword for the maximum power point reference voltage of the photovoltaic cell. The maximum power point reference voltage generation unit is connected to the fractional calculation unit and is used to generate a corresponding analog voltage based on the digital codeword output by the fractional calculation unit, which serves as the system reference voltage.

[0005] Furthermore, the adaptive monitoring time control unit is configured to determine that the photovoltaic cell voltage has reached a stable open-circuit voltage state when the rate of change of the photovoltaic cell voltage is detected to be lower than a preset threshold.

[0006] Furthermore, the fractional calculation unit generates a digital codeword for the maximum power point reference voltage of the photovoltaic cell by multiplying the digital codeword of the open-circuit voltage by a pre-stored fractional coefficient.

[0007] Furthermore, the digital control logic module dynamically sets the energy transfer parameters based on the maximum power point reference voltage.

[0008] Furthermore, the digital control logic module determines the current operating point of the system by comparing the real-time output voltage of the photovoltaic cell with the maximum power point reference voltage output by the maximum power point tracking circuit. If the real-time output voltage is higher than the reference voltage, it indicates that the photovoltaic cell still has a surplus of usable power, and the digital control logic module enables the power stage circuit to continue to extract energy from the photovoltaic cell; otherwise, it disables the power stage circuit, suspends energy harvesting, and waits for the photovoltaic cell to recover to the maximum power point.

[0009] Furthermore, the digital control logic module is also used to periodically trigger the maximum power point tracking circuit to start a new round of sampling and calculation.

[0010] Furthermore, the peak current detection circuit generates a peak current signal and turns off the main power switch by comparing the voltages across the main power switch in the power stage circuit.

[0011] Furthermore, the zero-current detection circuit generates a zero-current detection signal and turns off the synchronous rectifier switch by comparing the voltages across the synchronous rectifier power transistor switch in the power stage circuit.

[0012] This invention has the following advantages: By proposing an adaptive maximum power point monitoring time technology, it can monitor the changes in photovoltaic cell voltage in real time and automatically determine the open-circuit voltage establishment time. Under strong light, it can significantly shorten the invalid waiting time and ensure the accuracy of the sampling voltage under weak light, thus achieving dynamic matching between monitoring time and illumination conditions. This invention can automatically adapt to different illumination conditions without the need for additional configuration of maximum power point monitoring time, and has application flexibility. It is particularly suitable for wearable devices and other low-power devices that need to work stably for a long time in complex illumination environments. Attached Figure Description

[0013] Figure 1 This is a structural principle block diagram of a photovoltaic energy harvesting system that adaptively adjusts monitoring time according to this embodiment; Figure 2 This is the schematic diagram of the maximum power point tracking circuit in this embodiment. Detailed Implementation

[0014] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0015] like Figure 1 As shown, this embodiment discloses a photovoltaic energy harvesting system that adaptively adjusts monitoring time, comprising: The cold start module is used to initiate the initial startup process of the system when the system power supply voltage is insufficient. The maximum power point tracking circuit uses the fractional open-circuit voltage method to track and control the photovoltaic cells to operate at the maximum power point. Clock circuit, used to provide a reference clock signal for the system; Power stage circuitry is used to realize energy transfer and voltage conversion between photovoltaic cells and load; A peak current detection circuit is used to detect and control the peak inductor current in the power stage circuit. A zero-current detection circuit is used to detect the zero-crossing point of the inductor current in the power stage circuit. The digital control logic module is used to coordinate the operation of the maximum power point tracking circuit, the peak current detection circuit, and the zero current detection circuit.

[0016] After the system in this embodiment is started by the cold start module, the maximum power point tracking (MPPT) circuit begins to operate. This circuit dynamically determines the monitoring time required for each MPPT execution through its internal adaptive monitoring time control unit, and ultimately outputs a precise reference voltage for the photovoltaic cell's maximum power point. Simultaneously, a global clock signal generated by the clock circuit synchronizes the entire system timing. During the switching cycle of the power stage circuit, the peak current detection circuit monitors the inductor current according to an internally set fixed threshold and turns off the main power switch when the peak value is reached; subsequently, the zero current detection circuit monitors the decrease in inductor current and turns off the synchronous rectifier switch when the current crosses zero.

[0017] One of the core functions of the digital control logic module is to coordinate the energy harvesting and maximum power point tracking (MPPT) processes. It determines the system's current operating point by comparing the real-time output voltage of the photovoltaic (PV) cells with the reference voltage of the MPPT circuit. If the real-time output voltage is higher than the reference voltage, it indicates that the PV cells still have surplus usable power, and the digital control logic module enables the power stage circuit to continue extracting energy from the PV cells; conversely, it disables the power stage circuit, suspends energy harvesting, and waits for the PV cells to return to their maximum power point. Simultaneously, the digital control logic module is also responsible for periodically triggering the MPPT circuit to start a new round of sampling and calculation.

[0018] like Figure 2 As shown, the maximum power point tracking circuit includes: A voltage sampling and conversion unit is used to sample the voltage of the photovoltaic cell and convert it into digital codeword format; An adaptive monitoring time control unit, connected to the voltage sampling and conversion unit, is used to identify changes in photovoltaic cell voltage, determine when it reaches the open-circuit voltage, and output a signal to indicate that maximum power point monitoring has been completed. The fractional calculation unit, connected to the voltage sampling conversion unit and the adaptive monitoring time control unit, is used to calculate the open-circuit voltage after the maximum power point monitoring is completed, so as to generate a digital codeword for the maximum power point reference voltage of the photovoltaic cell. The maximum power point reference voltage generation unit is connected to the fractional calculation unit and is used to generate a corresponding analog voltage based on its output digital codeword, which serves as the system reference voltage.

[0019] The working process of the maximum power point tracking circuit described in this invention is as follows: After the digital control logic module issues a start command, the circuit enters the maximum power point monitoring (MPP) phase. At this time, the voltage sampling and conversion unit begins periodically sampling the photovoltaic cell voltage VIN at a fixed frequency and outputs a series of continuous digital codewords. The adaptive monitoring time control unit continuously compares the latest codeword with the previous codeword. If the difference is small, below a preset change threshold, the photovoltaic cell voltage is considered to have stabilized within this time period, triggering an internal counter to accumulate. If the difference is large, above the change threshold, the voltage is considered to be still changing rapidly and has not yet stabilized, at which point the counter is reset to zero. This comparison and counting process continues. Once the accumulated value of the counter reaches another preset threshold for consecutive stable counts, it is determined that the photovoltaic cell voltage has experienced a sufficiently long period of stable state, i.e., the open-circuit voltage has been established. At this time, the unit immediately outputs a monitoring completion signal and locks the latest sampled value as the final open-circuit voltage value. Subsequently, after receiving the monitoring completion signal, the fraction calculation unit multiplies the locked open-circuit voltage value by a preset fraction coefficient to calculate the digital value of the maximum power point voltage. Finally, the maximum power point reference voltage generation unit converts the above digital values ​​into an accurate maximum power point analog reference voltage VMPP for subsequent system control.

[0020] The photovoltaic energy harvesting system provided in this invention effectively solves the contradictions of traditional fixed monitoring time methods, such as excessively long waiting time under strong light and inaccurate sampling under weak light, through an adaptive monitoring time mechanism. It can intelligently optimize the monitoring process under different lighting conditions, thereby improving the overall energy harvesting efficiency of the system. It is particularly suitable for low-power devices such as IoT terminals and wireless sensor nodes that need to work stably for a long time in complex lighting environments.

[0021] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the implementation process of the present invention has been described in detail above, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A photovoltaic energy harvesting system that self-adapts monitoring time, characterized by, The application relates to a photovoltaic power generation system, which comprises the following parts: a cold start module for realizing initial self-start of the system; a maximum power point tracking circuit for tracking and controlling the photovoltaic cell to work at the maximum power point by using a fractional open circuit voltage method; a clock circuit for providing a reference clock signal for the system; a power stage circuit for realizing energy transmission and voltage conversion between the photovoltaic cell and a load; a peak current detection circuit for detecting and controlling the peak inductance current in the power stage circuit; a zero current detection circuit for detecting the zero point of the inductance current in the power stage circuit; a digital control logic module for coordinating the operation of the maximum power point tracking circuit, the peak current detection circuit and the zero current detection circuit.

2. The photovoltaic energy-harvesting system of claim 1, wherein, The maximum power point tracking circuit comprises: a voltage sampling and conversion unit for sampling the photovoltaic cell voltage and converting the photovoltaic cell voltage into a digital code word form; an adaptive monitoring time control unit connected to the voltage sampling and conversion unit, for judging the change of the photovoltaic cell voltage, determining the time when the open circuit voltage is reached, and outputting a signal to indicate that the maximum power point monitoring has been completed; a fraction calculation unit connected to the voltage sampling and conversion unit and the adaptive monitoring time control unit, for calculating the open circuit voltage after the maximum power point monitoring is completed, so as to generate a digital code word of the photovoltaic cell maximum power point reference voltage; a maximum power point reference voltage generation unit connected to the fraction calculation unit, for generating an analog voltage corresponding to the digital code word output by the fraction calculation unit as a system reference voltage.

3. The photovoltaic energy-harvesting system of claim 2, wherein, The adaptive monitoring time control unit is configured to determine that the photovoltaic cell voltage has reached a stable open circuit voltage state when the change rate of the photovoltaic cell voltage is detected to be lower than a preset threshold.

4. The photovoltaic energy-harvesting system of claim 2, wherein, The fraction calculation unit generates the digital code word of the photovoltaic cell maximum power point reference voltage by multiplying the digital code word of the open circuit voltage by a pre-stored fraction coefficient.

5. The photovoltaic energy-harvesting system of claim 2, wherein, The digital control logic module dynamically sets the energy transmission parameter according to the maximum power point reference voltage.

6. The photovoltaic energy-harvesting system of claim 5, wherein, The digital control logic module judges the current working point of the system by comparing the real-time output voltage of the photovoltaic cell with the maximum power point reference voltage output by the maximum power point tracking circuit. If the real-time output voltage is higher than the reference voltage, it indicates that the photovoltaic cell still has surplus available power, and the digital control logic module enables the power stage circuit to continue extracting energy from the photovoltaic cell; otherwise, it disables the power stage circuit, suspends energy collection, and waits for the photovoltaic cell to recover to the maximum power point.

7. The photovoltaic energy-harvesting system of claim 5, wherein, The digital control logic module is used for periodically triggering the maximum power point tracking circuit to start a new round of sampling and calculation.

8. The photovoltaic energy-harvesting system of claim 1, wherein, The peak current detection circuit generates a peak current signal and turns off the main power switch tube by comparing the voltage across the main power switch tube in the power stage circuit.

9. The photovoltaic energy-harvesting system of claim 1, wherein, The zero current detection circuit generates a zero current detection signal and turns off the synchronous rectification switch tube by comparing the voltage across the synchronous rectification power switch in the power stage circuit.

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