Single-phase photovoltaic water pump variable frequency control method and system

Abstract

The application provides a single-phase photovoltaic water pump variable frequency control method and system, obtains a maximum power point of a photovoltaic cell array, generates a first target frequency of photovoltaic water pump operation, obtains a first pressure signal of a water supply pipeline, generates a second target frequency of the photovoltaic water pump operation, generates a third target frequency of the photovoltaic water pump operation according to the first target frequency and the second target frequency, and adjusts the photovoltaic water pump according to the third target frequency, so that the system water supply remains stable, thereby facilitating user water use.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic water pump control technology, and in particular to a frequency conversion control method and system for a single-phase photovoltaic water pump. Background Technology

[0002] Water pump systems typically use electric or diesel generators for power, but these systems are not only expensive to operate and maintain, but also consume fossil fuels and damage the environment. In contrast, photovoltaic (PV) water pump systems can be used for water supply. Provided there is ample sunlight and abundant underground or surrounding river and lake water resources, PV water pump systems can be used for agricultural irrigation, desertification control, urban water features, and domestic water supply.

[0003] A photovoltaic (PV) water pump system consists of PV solar panels, a dedicated PV inverter, and a water pump. The water pump is typically driven by a three-phase AC motor with relatively high power. However, with the increasing demand for low-power applications, such as self-service water supply systems in rural courtyards in remote areas, low-power PV water pump systems are often required. The rated power of these pumps generally does not exceed 1.1 kW. In such scenarios, single-phase asynchronous motor water pumps are more suitable. However, traditional single-phase asynchronous motor speed control methods have limited speed range, poor speed control accuracy, and low efficiency. Furthermore, the output power of the PV array varies with sunlight, thus affecting the water pump's output. Therefore, a highly efficient and stable single-phase PV water pump control system is needed. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a method and system for frequency conversion control of a single-phase photovoltaic water pump.

[0005] To achieve the above objectives, the present invention provides a frequency conversion control method for a single-phase photovoltaic water pump, comprising the following steps: S1. Obtain the maximum power point of the photovoltaic array and generate the first target frequency for the operation of the photovoltaic water pump; S2. Obtain the first pressure signal from the water supply pipeline and generate the second target frequency for the operation of the photovoltaic water pump; S3. Generate a third target frequency for the operation of the photovoltaic water pump based on the first target frequency and the second target frequency; S4. Adjust the photovoltaic water pump according to the third target frequency.

[0006] Further, S1, obtaining the maximum power point of the photovoltaic array and generating the first target frequency for the operation of the photovoltaic water pump, specifically involves: S11. Obtain the first voltage signal and the first current signal of the DC bus of the photovoltaic array at the current sampling time, obtain the current output power of the photovoltaic array, and transmit it to the MPPT module and the main control module; S12. The MPPT module determines the maximum power point of the photovoltaic array based on the first voltage signal and the first current signal, and transmits the result to the main control module. S13. The main control module generates the first target frequency of the photovoltaic water pump based on the maximum power point.

[0007] Further, in step S2, acquiring the first pressure signal from the water supply pipeline and generating the second target frequency for the operation of the photovoltaic water pump specifically involves: S21. Obtain the first pressure signal of the water supply pipeline at the current sampling time and transmit it to the main control module; S22. The main control module generates the second target frequency of the photovoltaic water pump based on the first pressure signal.

[0008] Further, in step S3, a third target frequency for the operation of the photovoltaic water pump is generated based on the first target frequency and the second target frequency, specifically as follows: S31. The main control module compares the first target frequency with the second target frequency. When the first target frequency is greater than or equal to the second target frequency, the second target frequency is used as the third target frequency and transmitted to the frequency conversion control module. S32. When the first target frequency is less than the second target frequency, the first target frequency is used as the third target frequency and transmitted to the frequency conversion control module.

[0009] Furthermore, when the first target frequency is less than the second target frequency, the main control module generates a pressure change curve of the water supply pipeline based on the historical pressure signal data of the water supply pipeline; it predicts the pressure change of the water supply pipeline in the next period based on the pressure change curve; if the pressure of the water supply pipeline drops rapidly in the next period, the main control module uses the first target frequency as the third target frequency and transmits it to the frequency converter control module; if the pressure of the water supply pipeline drops gradually in the next period, the main control module uses the first target frequency as the third target frequency, generates a stage control strategy, transmits it to the frequency converter control module, and controls the photovoltaic water pump to reach the third target frequency after a delay.

[0010] Furthermore, the stage control strategy divides the third target frequency into three stage target frequencies: the first stage target frequency is 1 / 4 of the third target frequency and lasts for 5 minutes; the second stage target frequency is 3 / 4 of the third target frequency and lasts for 10 minutes; and the third stage target frequency is the third target frequency and continues indefinitely.

[0011] Furthermore, step S4, adjusting the photovoltaic water pump according to the third target frequency, specifically involves: S41. The frequency conversion control module receives the third target frequency, adjusts the DSVPWM control signal, and adjusts the operating frequency of the photovoltaic water pump. S42. Monitor the operating status of the photovoltaic water pump in real time, obtain the real-time operating frequency, and transmit it to the main control module; S43. The main control module compares the third target frequency with the real-time operating frequency, generates an adjustment strategy based on the result, and transmits it to the frequency conversion control module.

[0012] Furthermore, before adjusting the photovoltaic water pump according to the third target frequency in step S4, the main control module sends a wake-up signal to the frequency conversion control module, and the frequency conversion control module drives the photovoltaic water pump to start according to the wake-up signal.

[0013] Furthermore, the photovoltaic water pump startup includes applying a specific DC voltage to each terminal of the photovoltaic water pump when the photovoltaic water pump is stationary, measuring the current between the middle terminals of the first and third bridge arms, the second and third bridge arms, and the third bridge arm, respectively, to calculate the resistances R1, R2, and R3 between the middle terminals of the first and second bridge arms, and to determine the main and auxiliary windings and terminals of the photovoltaic water pump based on the relationship between R1, R2, and R3.

[0014] On the other hand, the present invention provides a control system based on the single-phase photovoltaic water pump frequency conversion control method, including a photovoltaic cell array, a data acquisition module, a main control module, an MPPT module, a frequency conversion control module, a photovoltaic water pump, and a water supply pipeline; The photovoltaic cell array is used to provide power; The data acquisition module is used to acquire the output voltage and output current of the photovoltaic cell array and transmit them to the MPPT module. It is also used to acquire the pressure data of the water supply pipeline and the operating frequency of the photovoltaic water pump and transmit the acquired data to the main control module. The MPPT module is used to determine the maximum power point of the photovoltaic array and transmit it to the main control module; The main control module generates a first target frequency for the operation of the photovoltaic water pump based on the maximum power point, generates a second target frequency for the operation of the photovoltaic water pump based on the pressure data, generates a third target frequency based on the first target frequency and the second target frequency, and transmits the third target frequency to the frequency conversion control module. The frequency conversion control module controls the photovoltaic water pump according to the third target frequency.

[0015] In summary, the present invention has the following beneficial effects: by collecting real-time data from photovoltaic cell arrays, photovoltaic water pump operation data, and water supply pipeline pressure data, the single-phase photovoltaic water pump frequency conversion control system is monitored. The main control module generates a first target frequency for the operation of the photovoltaic water pump based on the maximum power point, generates a second target frequency for the operation of the photovoltaic water pump based on the pressure data, generates a third target frequency based on the first target frequency and the second target frequency, and transmits the third target frequency to the frequency conversion control module, thereby keeping the system water supply stable and facilitating water use for users. Attached Figure Description

[0016] Figure 1 A schematic diagram of the frequency conversion control method for a single-phase photovoltaic water pump; Figure 2 This is a schematic diagram of a single-phase photovoltaic water pump frequency conversion control system. Figure 3 This is a schematic diagram of a frequency converter control circuit for a single-phase photovoltaic water pump. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to preferred embodiments and accompanying drawings. Obviously, the embodiments described below are only for explaining the present invention and are not intended to limit the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0018] Please see Figure 1 , Figure 1 A single-phase photovoltaic water pump frequency conversion control method according to the present invention includes the following steps: S1. Obtain the maximum power point of the photovoltaic array and generate the first target frequency for the operation of the photovoltaic water pump; S2. Obtain the first pressure signal from the water supply pipeline and generate the second target frequency for the operation of the photovoltaic water pump; S3. Generate a third target frequency for the operation of the photovoltaic water pump based on the first target frequency and the second target frequency; S4. Adjust the photovoltaic water pump according to the third target frequency.

[0019] Further, S1, obtaining the maximum power point of the photovoltaic array and generating the first target frequency for the operation of the photovoltaic water pump, specifically involves: S11. Obtain the first voltage signal and the first current signal of the DC bus of the photovoltaic array at the current sampling time, obtain the current output power of the photovoltaic array, and transmit it to the MPPT module and the main control module; S12. The MPPT module determines the maximum power point of the photovoltaic array based on the first voltage signal and the first current signal, and transmits the result to the main control module. S13. The main control module generates the first target frequency of the photovoltaic water pump based on the maximum power point.

[0020] The MPPT module, based on the output characteristics of the photovoltaic array, establishes appropriate judgment conditions by detecting the output voltage and current. For example, using the commonly used constant voltage method, when the measured voltage during operation is greater than the target voltage, the output frequency is increased; conversely, the output frequency is decreased, thus adjusting the operating point of the photovoltaic array. Due to the response speed delay of the photovoltaic water pump supply system, a corresponding delay setting should be made when setting the control cycle of the MPPT.

[0021] Further, in step S2, acquiring the first pressure signal from the water supply pipeline and generating the second target frequency for the operation of the photovoltaic water pump specifically involves: S21. Obtain the first pressure signal of the water supply pipeline at the current sampling time and transmit it to the main control module; S22. The main control module generates the second target frequency of the photovoltaic water pump based on the first pressure signal.

[0022] Further, in step S3, a third target frequency for the operation of the photovoltaic water pump is generated based on the first target frequency and the second target frequency, specifically as follows: S31. The main control module compares the first target frequency with the second target frequency. When the first target frequency is greater than or equal to the second target frequency, the second target frequency is used as the third target frequency and transmitted to the frequency conversion control module. S32. When the first target frequency is less than the second target frequency, the first target frequency is used as the third target frequency and transmitted to the frequency conversion control module.

[0023] Furthermore, when the first target frequency is less than the second target frequency, the main control module generates a pressure change curve of the water supply pipeline based on the historical pressure signal data of the water supply pipeline; it predicts the pressure change of the water supply pipeline in the next period based on the pressure change curve; if the pressure of the water supply pipeline drops rapidly in the next period, the main control module uses the first target frequency as the third target frequency and transmits it to the frequency converter control module; if the pressure of the water supply pipeline drops gradually in the next period, the main control module uses the first target frequency as the third target frequency, generates a stage control strategy, transmits it to the frequency converter control module, and controls the photovoltaic water pump to reach the third target frequency after a delay.

[0024] If the first target frequency is lower than the second target frequency, it means the output power of the photovoltaic array cannot meet the water pressure requirements of the water supply pipeline. Therefore, based on historical pressure data of the water supply pipeline, the pressure changes are statistically analyzed, and a pressure change curve is generated to display the pressure situation of the water supply pipeline in each time period, thereby understanding the water usage in each period. The pressure change curve is then used to predict the pressure changes of the water supply pipeline in the next time period. For example, if the pressure change curve shows a rapid drop in the pressure of the water supply pipeline in the next time period, it indicates that the next period is a peak water demand period, requiring the photovoltaic water pump to operate at a high frequency to maintain stable water pressure. Therefore, the main control module sets the first target frequency as the third target frequency, making the photovoltaic water pump operate at the maximum power point that the photovoltaic array can provide. If the pressure change curve shows a gradual drop in the pressure of the water supply pipeline in the next time period, it indicates that the next period has low water demand, and maintaining stable water pressure does not require high-frequency operation of the photovoltaic water pump. Therefore, the main control module can adjust the frequency in stages.

[0025] Furthermore, the stage control strategy divides the third target frequency into three stage target frequencies. The first stage target frequency is 1 / 4 of the third target frequency, lasting for 5 minutes. If the water supply pipeline pressure continues to drop, the photovoltaic water pump is adjusted to set the second stage target frequency to 3 / 4 of the third target frequency, lasting for 10 minutes. If the water supply pipeline pressure continues to drop, the photovoltaic water pump is adjusted to set the third stage target frequency to the third target frequency and continues to operate.

[0026] Furthermore, step S4, adjusting the photovoltaic water pump according to the third target frequency, specifically involves: S41. The frequency conversion control module receives the third target frequency, adjusts the DSVPWM control signal, and adjusts the operating frequency of the photovoltaic water pump. S42. Monitor the operating status of the photovoltaic water pump in real time, obtain the real-time operating frequency, and transmit it to the main control module; S43. The main control module compares the third target frequency with the real-time operating frequency, generates an adjustment strategy based on the result, and transmits it to the frequency conversion control module.

[0027] DSVPWM (Double Sine Wave Pulse Width Modulation) is an improved space vector pulse width modulation (SVPWM) control method. It reduces harmonic content and improves the quality of the inverter output voltage by modulating the comparator output signal over two sinusoidal cycles. The amplitude, frequency, and phase of the DSVPWM control signal are adjusted according to the pump's load characteristics and requirements to ensure stable operation under different conditions. The control signal parameters can be adjusted based on the needs during pump startup, operation, and shutdown to ensure pump performance and safe operation.

[0028] Furthermore, before adjusting the photovoltaic water pump according to the third target frequency in step S4, the main control module sends a wake-up signal to the frequency conversion control module, and the frequency conversion control module drives the photovoltaic water pump to start according to the wake-up signal.

[0029] Furthermore, please refer to Figure 3 , Figure 3 This is a schematic diagram of the frequency conversion control circuit for a single-phase photovoltaic water pump according to the present invention. The first power switch T1 and the second power switch T4 constitute the first bridge arm, the third power switch T3 and the fourth power switch T6 constitute the second bridge arm, and the fifth power switch T5 and the sixth power switch T2 constitute the third bridge arm. When the photovoltaic water pump is stationary, a specific DC voltage is applied between each terminal of the photovoltaic water pump. The currents between the middle terminals of the first and third bridge arms, the second and third bridge arms, and the third bridge arm are measured respectively. The resistances R1, R2, and R3 between the middle terminals of the first and second bridge arms are then calculated. Based on the relationship between R1, R2, and R3, the main and auxiliary windings of the photovoltaic water pump and their corresponding terminals are determined.

[0030] Please see Figure 2 , Figure 2 The present invention provides a control system based on the single-phase photovoltaic water pump frequency conversion control method, comprising a photovoltaic cell array, a data acquisition module, a main control module, an MPPT module, a frequency conversion control module, a photovoltaic water pump, and a water supply pipeline; The photovoltaic cell array is used to provide power; The data acquisition module is used to acquire the output voltage and output current of the photovoltaic cell array and transmit them to the MPPT module. It is also used to acquire the pressure data of the water supply pipeline and the operating frequency of the photovoltaic water pump and transmit the acquired data to the main control module. The MPPT module is used to determine the maximum power point of the photovoltaic array and transmit it to the main control module; The main control module generates a first target frequency for the operation of the photovoltaic water pump based on the maximum power point, generates a second target frequency for the operation of the photovoltaic water pump based on the pressure data, generates a third target frequency based on the first target frequency and the second target frequency, and transmits the third target frequency to the frequency conversion control module. The frequency conversion control module controls the photovoltaic water pump according to the third target frequency.

[0031] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, it should be noted that, for ease of description, the accompanying drawings only show the parts relevant to the present invention, not all of them.

[0032] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0033] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A single phase photovoltaic water pump variable frequency control method, characterized by, Includes the following steps: S1. Obtain the maximum power point of the photovoltaic array and generate the first target frequency for the operation of the photovoltaic water pump; S2. Obtain the first pressure signal from the water supply pipeline and generate the second target frequency for the operation of the photovoltaic water pump; S3. Generate a third target frequency for the operation of the photovoltaic water pump based on the first target frequency and the second target frequency; S4. Adjust the photovoltaic water pump according to the third target frequency; Specifically, step S3 generates a third target frequency for the operation of the photovoltaic water pump based on the first target frequency and the second target frequency, as follows: S31. The main control module compares the first target frequency with the second target frequency. When the first target frequency is greater than or equal to the second target frequency, the second target frequency is used as the third target frequency and transmitted to the frequency conversion control module. S32. When the first target frequency is less than the second target frequency, the first target frequency is used as the third target frequency and transmitted to the frequency conversion control module. When the first target frequency is less than the second target frequency, the main control module generates a pressure change curve of the water supply pipeline based on the historical pressure signal data of the water supply pipeline; it then predicts the pressure change of the water supply pipeline in the next time period based on the pressure change curve; if the pressure of the water supply pipeline drops rapidly in the next time period, the main control module uses the first target frequency as the third target frequency and transmits it to the frequency converter control module; if the pressure of the water supply pipeline drops gradually in the next time period, the main control module uses the first target frequency as the third target frequency, generates a stage control strategy, transmits it to the frequency converter control module, and controls the photovoltaic water pump to reach the third target frequency after a delay.

2. The single-phase photovoltaic water pump frequency conversion control method according to claim 1, characterized in that, S1, obtaining the maximum power point of the photovoltaic array and generating the first target frequency for the operation of the photovoltaic water pump, specifically involves: S11. Obtain the first voltage signal and the first current signal of the DC bus of the photovoltaic array at the current sampling time, obtain the current output power of the photovoltaic array, and transmit it to the MPPT module and the main control module; S12. The MPPT module determines the maximum power point of the photovoltaic array based on the first voltage signal and the first current signal, and transmits the result to the main control module. S13. The main control module generates the first target frequency of the photovoltaic water pump based on the maximum power point.

3. The single-phase photovoltaic water pump frequency conversion control method according to claim 1, characterized in that, S2, acquiring the first pressure signal from the water supply pipeline and generating the second target frequency for the operation of the photovoltaic water pump, specifically involves: S21. Obtain the first pressure signal of the water supply pipeline at the current sampling time and transmit it to the main control module; S22. The main control module generates the second target frequency of the photovoltaic water pump based on the first pressure signal.

4. The single-phase photovoltaic water pump frequency conversion control method according to claim 3, characterized in that, The phased control strategy involves dividing the third target frequency into three phased target frequencies. The first phase target frequency is set to 1 / 4 of the third target frequency, lasting for 5 minutes. If the water supply pipeline pressure continues to drop, the photovoltaic water pump is adjusted, setting the second phase target frequency to 3 / 4 of the third target frequency, lasting for 10 minutes. If the water supply pipeline pressure continues to drop, the adjustment continues... The photovoltaic water pump is set to the third target frequency and kept running continuously.

5. The single-phase photovoltaic water pump frequency conversion control method according to claim 1, characterized in that, S4, adjusting the photovoltaic water pump according to the third target frequency, specifically involves: S41. The frequency conversion control module receives the third target frequency, adjusts the DSVPWM control signal, and adjusts the operating frequency of the photovoltaic water pump. S42. Monitor the operating status of the photovoltaic water pump in real time, obtain the real-time operating frequency, and transmit it to the main control module; S43. The main control module compares the third target frequency with the real-time operating frequency, generates an adjustment strategy based on the result, and transmits it to the frequency conversion control module.

6. The single-phase photovoltaic water pump frequency conversion control method according to claim 5, characterized in that, Before adjusting the photovoltaic water pump according to the third target frequency in step S4, the main control module sends a wake-up signal to the frequency conversion control module, and the frequency conversion control module drives the photovoltaic water pump to start according to the wake-up signal.

7. The single-phase photovoltaic water pump frequency conversion control method according to claim 6, characterized in that, The photovoltaic water pump startup process includes applying a specific DC voltage to each connection point of the photovoltaic water pump while the pump is stationary, measuring the current between the middle connection points of the first and third bridge arms, the second and third bridge arms, and the third bridge arm, respectively, to calculate the resistances R1, R2, and R3 between the middle connection points of the first and second bridge arms. Based on the relationship between R1, R2, and R3, the main and auxiliary windings of the photovoltaic water pump and their corresponding connection points are determined.

8. The control system of the single-phase photovoltaic water pump frequency conversion control method according to claim 7, characterized in that, Includes photovoltaic cell array, data acquisition module, main control module, MPPT module, frequency conversion control module, photovoltaic water pump and water supply pipeline; The photovoltaic cell array is used to provide power; The data acquisition module is used to acquire the output voltage and output current of the photovoltaic cell array and transmit them to the MPPT module. It is also used to acquire the pressure data of the water supply pipeline and the operating frequency of the photovoltaic water pump and transmit the acquired data to the main control module. The MPPT module is used to determine the maximum power point of the photovoltaic array and transmit it to the main control module; The main control module generates a first target frequency for the operation of the photovoltaic water pump based on the maximum power point, generates a second target frequency for the operation of the photovoltaic water pump based on the pressure data, generates a third target frequency based on the first target frequency and the second target frequency, and transmits the third target frequency to the frequency conversion control module. The frequency conversion control module controls the photovoltaic water pump according to the third target frequency.

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