Calibration time adaptive MPPT (Maximum Power Point Tracking) method for environment energy collection circuit

Abstract

The invention discloses a calibration time self-adaptive MPPT (Maximum Power Point Tracking) method for an environmental energy collection circuit. The method comprises the following steps of: starting the energy collection circuit; confirming the maximum power point, and recording the characteristic voltage V1 of the input end of the energy collection circuit at the moment; after the interval calibration time T0, the maximum power point is confirmed again, and the characteristic voltage V2 of the input end of the energy collection circuit at the moment is recorded; if V1-V2 is greater than V, reducing T from T0 to obtain new interval calibration time T1, otherwise, increasing T from T0 to obtain T1; and repeating the above process until T1 approaches or reaches the minimum calibration time Tmin, or T1 reaches the maximum calibration time Tmax, and terminating. The method can reduce the tracking power consumption of the energy collection circuit, and is suitable for collecting environment energy such as light energy, electromagnetic energy and heat energy.

Description

Technical Field

[0001] The present invention relates to energy harvesting technology in a passive Internet of Things, and in particular to a calibration time-adaptive Maximum Power Point Tracking (MPPT) method for an ambient energy harvesting circuit. Background Art

[0002] Ambient energy harvesting circuits / systems are widely used in the Internet of Things (IoT). For example, in passive RFID, energy harvesting systems / circuits collect electromagnetic energy from the environment, convert it into electrical energy, and store it in their own energy storage devices. Similarly, passive sensors and other devices in the IoT use energy harvesting circuits / systems to collect light and thermal energy from the environment, converting it into electrical energy to power their own operations.

[0003] Maximum power point tracking (MPPT) is a key technology in ambient energy harvesting systems. Its purpose is to enable ambient energy harvesting circuits to consistently and stably collect maximum power under varying environmental conditions. Currently, it's primarily used in light energy harvesting circuits. In passive IoT systems, which require extremely low power consumption, MPPT circuits typically use an open-circuit voltage proportional method, eliminating the need for real-time tracking and control of the maximum power point.

[0004] Each time an energy harvesting circuit calibrates its maximum power point, it consumes significant energy. If the calibration interval is short and the ambient energy is low, the energy collected by the energy harvesting circuit may be insufficient to support the consumption. If the calibration interval is long, the energy harvesting circuit may not be able to track the maximum power point in a timely manner when the ambient energy fluctuates. Therefore, accurately controlling the calibration time of the energy harvesting circuit is particularly important. Summary of the Invention

[0005] To solve the above problems, a calibration time adaptive maximum power point tracking (MPPT) method is proposed. This method is suitable for ambient energy harvesting systems / circuits of passive devices in passive Internet of Things.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A calibration time adaptive MPPT method for an ambient energy harvesting circuit includes the following steps: S1. Energy harvesting circuit startup: The energy harvesting circuit collects energy (such as light energy, electromagnetic energy, thermal energy, etc.) from the environment to meet the energy requirements for entering the working state; S2. Confirm the maximum power point: Adjust the equivalent input impedance of the energy harvesting circuit, track the maximum power point by comparing the input power collected by the circuit, and record the characteristic voltage V1 at the input end of the energy harvesting circuit at this time; S3. Reconfirm the maximum power point: After the interval calibration time T0, track the maximum power point and record the characteristic voltage V2 at the input end of the energy harvesting circuit at this time; S4, update interval calibration time T1: Comparing V1 and V2, If |V1-V2|>∆V, the interval calibration time T0 is reduced by time T to obtain a new interval calibration time T1; If |V1-V2|≤∆V, then the interval calibration time T0 is increased by time T to obtain a new interval calibration time T1; S5. Repeat the update of calibration time and finally converge: Modify the value of T0 in S3 to the value of T1; Repeat steps S3 and S4 to obtain the new interval calibration time T1; The termination condition of S5 is: When the environmental conditions are constantly changing, T1 tends to decrease continuously and eventually approaches or reaches the minimum calibration time Tmin. Alternatively, when the environment tends to be stable and the external variables no longer change, T1 tends to extend continuously and eventually reaches the maximum calibration time Tmax value, and S5 terminates.

[0007] The time T is preset and is determined based on the range from Tmin to Tmax and the number of steps for the interval calibration time adjustment. T is (Tmax-Tmin) / number of steps.

[0008] The Tmin to Tmax range is determined by the circuit design. For example, if the step range is set to ten, then T is (Tmax - Tmin) / 10. The Tmin to Tmax range is determined by the clock circuit in the circuit design. During design, its value can vary from 10ms to 1s based on scenario requirements.

[0009] Compared with the prior art, the advantages or beneficial effects of the present invention include: (1) The present invention compares the characteristic voltages at the input end of the maximum power point tracked by the energy harvesting circuit at adjacent time nodes and adaptively adjusts the calibration time interval based on the comparison results, thereby allowing the energy harvesting circuit to quickly adapt to changes in the external environment. When the external environment changes significantly, the calibration time interval of the energy harvesting circuit is shortened, thereby achieving the purpose of rapid calibration. When the external environment does not change, the calibration time interval of the energy harvesting circuit is extended, thereby reducing the tracking power consumption of the energy harvesting circuit.

[0010] (2) The method of the present invention is not limited to light energy collection, and can be used in a variety of passive IoT energy collection circuits and maximum power tracking point methods such as electromagnetic energy and thermal energy, and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic flow chart of the steps of the method of the present invention.

[0012] Figure 2 This is a flow chart of the adaptive adjustment of the maximum power point calibration time of the present invention.

[0013] Figure 3 This is a schematic diagram of the principle of a typical energy (light energy) collection circuit used in the present invention. DETAILED DESCRIPTION

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0015] The embodiment of the present invention provides a calibration time adaptive MPPT method for an ambient energy harvesting circuit, such as Figure 1 As shown, specifically including: S1. Energy harvesting circuit startup: When the ambient energy meets the cold-start conditions of the energy harvesting circuit, the energy harvesting circuit wakes up and collects the corresponding type of energy from the environment. For example, if the voltage of the electrical energy converted by the photovoltaic cell is higher than the cold-start voltage of the solar energy harvesting circuit, the cold-start circuit of the solar energy harvesting circuit begins to collect energy for the normal operation of other circuits.

[0016] S2. Confirm the maximum power point: After the energy harvesting circuit is officially operational, adjust its equivalent input impedance up and down. By comparing the input energy detected by the circuit, the maximum power point is determined, and the characteristic voltage V1 detected by the energy harvesting circuit at this time is recorded.

[0017] It's important to note that under varying external conditions, the maximum power point (MPP) determined by the energy harvesting circuit will vary, and the characteristic voltage V1 detected at the input terminal will also fluctuate. For example, if the illuminated surface of the photovoltaic cell is blocked by a shadow, the output power will decrease, and the maximum power point (MPP) determined by the energy harvesting circuit will also decrease. At this point, the characteristic voltage detected at the input terminal of the energy harvesting circuit will also fluctuate.

[0018] S3. Reconfirm the maximum power point: After the interval calibration time T0, the environment may change, and the internal circuit impedance of the energy harvesting circuit may also change. Therefore, it is necessary to adjust the circuit equivalent input impedance again to determine the maximum power point and record the characteristic voltage V2 at the input end of the energy harvesting circuit at this time.

[0019] It should be noted that trial calibration and comparison can be performed in high-power photovoltaic energy harvesting circuits without the need for a calibration interval. Calibration intervals are often required in passive IoT devices because calibration consumes a lot of energy, and passive IoT devices require extremely low-power circuits.

[0020] S4. Update the calibration interval time T1: The calibration interval time is adjusted based on the difference between the two input characteristic voltages. When |V1-V2| > ∆V, T0 is reduced by time T; otherwise, T0 is increased by time T, resulting in a new calibration interval time T1. The value of ∆V determines the sensitivity of the calibration time update and should be determined based on the actual application scenario. For example, in photovoltaic energy harvesting circuits, it can be set to 0.05-0.2V. The comparison between V1 and V2 is performed by a comparison and judgment circuit.

[0021] S5. Calibration Time Convergence: Repeat steps S3 and S4 to obtain a new interval calibration time. The maximum calibration time in the circuit is Tmax, and the minimum calibration time is Tmin. When the external environment changes significantly, the calibration time tends to move toward the minimum calibration time, ensuring real-time tracking of the maximum power point and maximum efficiency in converting external energy. When the external environment conditions tend to be stable, the circuit calibration time also tends to Tmax, reducing the system power consumption caused by circuit calibration.

[0022] The specific adjustment process in this example is as follows Figure 2 As shown in the figure, the circuit continuously compares the characteristic voltage difference detected between two consecutive calibration times. When the difference is greater than ∆V, the calibration time is reduced; when it is less than or equal to ∆V, the calibration time is increased. Because the environment always tends to change toward a stable state, the calibration time will eventually become Tmax. If the calibration time is continuously maximum (that is, the characteristic voltage difference is continuously less than or equal to ∆V), the calibration time is temporarily fixed at Tmax until a significant change in the characteristic voltage at the input is detected, at which point a new round of adaptive adjustment begins.

[0023] The schematic diagram of the light energy collection circuit using this method is as follows Figure 3 As shown, the solar cell converts received light into electrical energy and transmits it to the light energy collection circuit. This circuit periodically monitors the solar cell voltage and transmits the detected characteristic voltage to the comparison and judgment circuit. The comparison and judgment circuit compares two consecutive characteristic voltage values. If the difference between the two characteristic voltage values ​​is greater than ∆V, a low-level signal is transmitted to the MPPT circuit, indicating that the calibration time is reduced by T. If the difference between the two characteristic voltage values ​​is less than or equal to ∆V, a high-level signal is transmitted to the MPPT circuit, indicating that the calibration time is increased by T. The MPPT circuit defaults to a calibration time of Tmax for each calibration, and subsequent calibration times are adjusted based on the comparison and judgment circuit's results. When the continuous calibration time reaches Tmax, the comparison and judgment circuit stops to reduce power consumption until the voltage monitoring circuit detects a significant change in the input voltage, at which point a new round of calibration time adjustment begins.

Claims

1. A calibration time adaptive MPPT method for ambient energy harvesting circuits, characterized by The following steps are involved: S1. Energy harvesting circuit startup: The energy harvesting circuit collects energy from the environment to meet the energy requirements for entering the working state; S2. Confirm the maximum power point: Adjust the equivalent input impedance of the energy harvesting circuit, track the maximum power point by comparing the input power collected by the circuit, and record the characteristic voltage V1 at the input end of the energy harvesting circuit at this time; S3. Reconfirm the maximum power point: After the interval calibration time T0, track the maximum power point and record the characteristic voltage V2 at the input end of the energy harvesting circuit at this time; S4, update interval calibration time T1: Comparing V1 and V2, If |V1-V2|>∆V, the interval calibration time T0 is reduced by time T to obtain a new interval calibration time T1; If |V1-V2|≤∆V, then the interval calibration time T0 is increased by time T to obtain a new interval calibration time T1; S5. Repeat the update of calibration time and finally converge: Modify the value of T0 in S3 to the value of T1; Repeat steps S3 and S4 to obtain the new interval calibration time T1; The termination condition of S5 is: When the environmental conditions are constantly changing, T1 tends to decrease continuously and eventually approaches or reaches the minimum calibration time Tmin. Alternatively, when the environment tends to be stable and the external variables no longer change, T1 tends to extend continuously and eventually reaches the maximum calibration time Tmax value, and S5 terminates.

2. The MPPT method with adaptive calibration time for environmental energy harvesting circuit according to claim 1, characterized in that In S1, the energy in the environment includes light energy, electromagnetic energy or thermal energy.

3. The MPPT method with adaptive calibration time for an ambient energy harvesting circuit according to claim 1, Its characteristic is that in S1, the ambient energy meets the cold start condition of the energy harvesting circuit, the energy harvesting circuit is awakened, and the corresponding type of energy is collected from the environment; In S2, after the energy harvesting circuit officially starts working, it adjusts its equivalent input impedance up and down, determines the maximum power point by comparing the input energy detected by the circuit, and records the input terminal characteristic voltage V1 detected by the energy harvesting circuit at this time; In S2, when the environmental conditions change, the maximum power point obtained by adjusting the energy harvesting circuit changes, and the detected V1 also changes.

4. The MPPT method for calibration time adaptation of an environmental energy harvesting circuit according to claim 1, wherein the environmental If the energy is light energy, then In S1, when the voltage of the electric energy converted by the photovoltaic cell is higher than the cold start voltage of the light energy collection circuit, the cold start circuit of the light energy collection circuit starts to collect light energy for the normal operation of the energy consumption circuit; In S4, the value of ∆V determines the sensitivity of the calibration time update; in the photovoltaic energy harvesting circuit, ∆V is set to 0.05~0.2V.

5. The MPPT method with adaptive calibration time for environmental energy harvesting circuit according to claim 1, characterized in that Ambient energy harvesting circuit for passive devices in passive IoT applications.

6. The calibration time adaptive MPPT method for an ambient energy harvesting circuit according to claim 1, characterized in that: The time T is preset and is determined based on the range from Tmin to Tmax and the number of steps for the interval calibration time adjustment. T is (Tmax-Tmin) / number of steps.

Images