CN-121705855-B - Photovoltaic water pump inverter running state analysis method and system

CN121705855BCN 121705855 BCN121705855 BCN 121705855BCN-121705855-B

Abstract

The invention discloses a method and a system for analyzing the running state of a photovoltaic water pump inverter, relates to the technical field of photovoltaic system monitoring, and is used for solving the problem of high false alarm rate of fault identification under complex working conditions. The method comprises the steps of firstly, extracting a direct-current side steady-state power supply component and a dynamic ripple component through frequency domain separation to construct equivalent impedance and mechanical vibration characteristics, then, analyzing power-impedance sensitivity to define a power supply side gradient characteristic interval, meanwhile, utilizing electromechanical energy linear coupling degree to accurately distinguish illumination linear drift and physical nonlinear distortion, and finally, executing multidimensional logic judgment based on sensitivity interval and coupling degree evolution state to realize accurate classification of normal, overload clamping stagnation and no-load dry rotation states of the water spring motor, and improving fault diagnosis precision and environmental adaptability of a photovoltaic power supply system.

Inventors

CHENG HONGWEI
WANG HAIHE
SONG JINXIONG

Assignees

孚瑞肯电气(深圳)有限公司

Dates

Publication Date: 20260508
Application Date: 20260213

Claims (7)

1. The method for analyzing the running state of the photovoltaic water pump inverter is characterized by comprising the following steps of: S1, continuously sampling a voltage signal and a current signal on a direct current side of a photovoltaic water pump inverter, extracting a steady-state direct current component representing the power supply level of a photovoltaic array through frequency domain separation, and a dynamic ripple component representing the mechanical torque characteristic of a water pump unit, constructing an equivalent impedance evolution value according to the steady-state direct current component, and extracting a mechanical load vibration amplitude according to the dynamic ripple component; S2, synchronously monitoring the change trend of the power value in the steady-state direct current component and the evolution value of the equivalent impedance, constructing a power-impedance sensitivity characteristic reflecting the output characteristic of the power supply side, and identifying that the current power-impedance sensitivity characteristic is a negative gradient characteristic interval or a zero gradient characteristic interval; s3, establishing electromechanical energy linear coupling degree of the mechanical load vibration amplitude relative to a power value in a steady-state direct-current component, and monitoring the evolution state of the electromechanical energy linear coupling degree on a time axis so as to distinguish linear drift characteristics caused by illumination irradiance changes from nonlinear distortion characteristics caused by physical structure changes of a water pump unit; S4, executing operation state logic judgment based on the evolution state of the linear coupling degree of the electromechanical energy and the characteristic interval where the power-impedance sensitivity characteristic is located, wherein when the power-impedance sensitivity characteristic is located in the negative gradient characteristic interval and the linear coupling degree of the electromechanical energy shows the linear drift characteristic, the system is judged to be in a normal operation state; when the power-impedance sensitivity characteristic is positioned in a negative gradient characteristic interval, but the power value continuously falls, and the electromechanical energy linear coupling degree is subjected to step-type decline until the loss, the system is judged to be in a water pump idle dry rotation state or a water inlet end suction state; The method comprises the following specific processes of synchronously monitoring the evolution value of equivalent impedance and the change trend of the power value in the steady-state direct current component, and constructing the power-impedance sensitivity characteristic reflecting the output characteristic of the power supply side: Calculating the product of the steady-state direct-current voltage component and the steady-state direct-current component, obtaining a steady-state direct-current power value, and constructing a differential observation window comprising the current moment and the historical moment; in the differential observation window, calculating a first-order differential quantity of a steady-state direct-current power value relative to time and a first-order differential quantity of an equivalent impedance evolution value relative to time; Dividing the first-order difference of the steady-state direct current power value by the first-order difference of the equivalent impedance evolution value to obtain a power-impedance sensitivity coefficient representing the power response intensity caused by unit impedance change, and taking the coefficient as a power-impedance sensitivity characteristic; the specific process of establishing the electromechanical energy linear coupling degree of the mechanical load vibration amplitude relative to the power value in the steady-state direct-current component and monitoring the evolution state of the electromechanical energy linear coupling degree on the time axis is as follows: Calculating the product of the voltage value and the current value of the steady-state direct current component, obtaining a steady-state direct current power value, dividing the vibration amplitude of the mechanical load by the steady-state direct current power value, or dividing the vibration amplitude of the mechanical load by a nonlinear mapping function value of the steady-state direct current power value, and obtaining an instantaneous coupling ratio; a first-in first-out annular buffer area for storing instantaneous coupling ratio is constructed, when each sampling is updated, the latest instantaneous coupling ratio is written into the head of the buffer area and covers the oldest data, the arithmetic average value or weighted average value of all instantaneous coupling ratios in the buffer area is calculated, and the electromechanical energy linear coupling degree is generated, so that a coupling degree evolution sequence which is updated continuously along with time is formed.
2. The method for analyzing the running state of the photovoltaic water pump inverter according to claim 1, wherein the method is characterized in that the voltage signal and the current signal on the direct current side of the photovoltaic water pump inverter are continuously sampled, and the specific processes of extracting steady-state direct current components representing the power supply level of the photovoltaic array and dynamic ripple components representing the mechanical torque characteristics of a water pump unit through frequency domain separation are as follows: Establishing a sliding time window containing sampling points with preset length, inputting a direct-current side voltage signal and a current signal in the sliding time window into a digital low-pass filter, filtering high-frequency noise and modulation harmonic wave higher than cut-off frequency, and outputting a steady-state direct-current voltage component and a steady-state direct-current component; The current operation fundamental frequency of the photovoltaic water pump inverter is synchronously tracked, a passband range taking the operation fundamental frequency as a center frequency is set, a direct-current side current signal is input into a digital bandpass filter with variable parameters, alternating-current components in the passband range are intercepted, and dynamic current ripple components are output.
3. The method for analyzing the running state of the photovoltaic water pump inverter according to claim 2, wherein the method is characterized in that an equivalent impedance evolution value is constructed according to a steady-state direct current component, and the specific process for extracting the mechanical load vibration amplitude according to a dynamic ripple component is as follows: performing division operation of a steady-state direct-current voltage component and a steady-state direct-current component, obtaining a real-time impedance sampling value, and performing smoothing treatment on the real-time impedance sampling value of a plurality of continuous sampling periods to generate an equivalent impedance evolution value; and performing Hilbert transformation or absolute value detection operation on the dynamic current ripple component to obtain an instantaneous envelope curve of the dynamic current ripple component, calculating an effective value of the instantaneous envelope curve in a single power frequency period, and generating a mechanical load vibration amplitude.
4. The method for analyzing the running state of the photovoltaic water pump inverter according to claim 1, wherein the specific process of identifying the current power-impedance sensitivity characteristic as a negative gradient characteristic interval or a zero gradient characteristic interval is as follows: detecting the numerical polarity and amplitude range of the power-impedance sensitivity coefficient; if the power-impedance sensitivity coefficient is negative and the amplitude exceeds a preset dead zone threshold, judging that the power is increased along with the decrease of the impedance, and classifying the power into a negative gradient characteristic interval; If the amplitude of the power-impedance sensitivity coefficient falls into a preset zero dead zone range or presents a positive-negative alternating oscillation state near the zero point, judging that the power is not changed along with the impedance or is not obvious in change, and classifying the power into a zero gradient characteristic interval.
5. The method for analyzing the running state of the photovoltaic water pump inverter according to claim 1, wherein the specific process of distinguishing the linear drift characteristic caused by illumination irradiance change from the nonlinear distortion characteristic caused by water pump unit physical structure change is as follows: performing first-order differential operation or standard deviation statistical operation on the coupling degree evolution sequence to obtain a coupling degree change rate index; if the absolute value of the coupling degree change rate index is kept in a preset zero drift tolerance range, judging that the linear coupling degree of the electromechanical energy keeps proportion following along with the change of power, and marking the linear drift characteristic; if the absolute value of the coupling degree change rate index exceeds the zero drift tolerance range and presents continuous positive increase or negative step jump, judging that the electromechanical energy linear coupling degree is out of the proportion constraint of power change, and marking the electromechanical energy linear coupling degree as nonlinear distortion characteristic.
6. The method for analyzing the operation state of the photovoltaic water pump inverter according to claim 1, wherein the operation state logic judgment is performed based on the evolution state of the linear coupling degree of the electromechanical energy and the characteristic interval where the power-impedance sensitivity characteristic is located, and the judgment process is as follows: constructing a multidimensional state identification set containing a sensitivity interval identification, a power trend identification and a coupling degree characteristic identification; outputting a maximum power point tracking closed-loop control instruction when the sensitivity interval identifier corresponds to the negative gradient characteristic interval and the coupling degree characteristic identifier corresponds to the linear drift characteristic, and maintaining the normal operation of the system; when the sensitivity interval mark corresponds to a zero gradient characteristic interval and the coupling degree characteristic mark corresponds to a forward divergence state in the nonlinear distortion characteristic, activating overload protection logic and outputting a shutdown alarm signal; when the sensitivity interval mark corresponds to the negative gradient characteristic interval, the power trend mark shows that the numerical value continuously decays, and the coupling degree characteristic mark corresponds to the negative step jump state in the nonlinear distortion characteristic, the underload protection logic is activated, and the delay restarting action is executed.
7. A photovoltaic water pump inverter operation state analysis system, applied to the photovoltaic water pump inverter operation state analysis method as claimed in any one of claims 1-6, characterized by comprising the following modules: The characteristic extraction module is used for continuously sampling voltage signals and current signals on the direct current side of the photovoltaic water pump inverter, extracting steady-state direct current components representing the power supply level of the photovoltaic array and dynamic ripple components representing the mechanical torque characteristics of the water pump unit through frequency domain separation, constructing equivalent impedance evolution values according to the steady-state direct current components, and extracting mechanical load vibration amplitude according to the dynamic ripple components; The characteristic identification module is used for synchronously monitoring the evolution value of the equivalent impedance and the variation trend of the power value in the steady-state direct current component, constructing a power-impedance sensitivity characteristic reflecting the output characteristic of the power supply side, and identifying that the current power-impedance sensitivity characteristic is a negative gradient characteristic interval or a zero gradient characteristic interval; The coupling analysis module is used for establishing electromechanical energy linear coupling degree of the mechanical load vibration amplitude relative to the power value in the steady-state direct-current component, and monitoring the evolution state of the electromechanical energy linear coupling degree on a time axis so as to distinguish linear drift characteristics caused by illumination irradiance changes from nonlinear distortion characteristics caused by physical structure changes of the water pump unit; The state judgment module is used for executing operation state logic judgment based on the evolution state of the characteristic interval where the power-impedance sensitivity characteristic is located and the electromechanical energy linear coupling degree, wherein the state judgment module is used for judging that the system is in a normal operation state when the power-impedance sensitivity characteristic is located in a negative gradient characteristic interval and the electromechanical energy linear coupling degree presents a linear drift characteristic, judging that the system is in a water pump mechanical overload or foreign matter clamping state when the power-impedance sensitivity characteristic is located in a zero gradient characteristic interval and the electromechanical energy linear coupling degree presents a monotonically rising nonlinear distortion characteristic, and judging that the system is in a no-load dry rotation or water inlet end suction state when the power-impedance sensitivity characteristic is located in the negative gradient characteristic interval and the power value continuously falls and the electromechanical energy linear coupling degree is subjected to step-type drop until the electromechanical energy linear coupling degree disappears; The method comprises the following specific processes of synchronously monitoring the evolution value of equivalent impedance and the change trend of the power value in the steady-state direct current component, and constructing the power-impedance sensitivity characteristic reflecting the output characteristic of the power supply side: Calculating the product of the steady-state direct-current voltage component and the steady-state direct-current component, obtaining a steady-state direct-current power value, and constructing a differential observation window comprising the current moment and the historical moment; in the differential observation window, calculating a first-order differential quantity of a steady-state direct-current power value relative to time and a first-order differential quantity of an equivalent impedance evolution value relative to time; Dividing the first-order difference of the steady-state direct current power value by the first-order difference of the equivalent impedance evolution value to obtain a power-impedance sensitivity coefficient representing the power response intensity caused by unit impedance change, and taking the coefficient as a power-impedance sensitivity characteristic; the specific process of establishing the electromechanical energy linear coupling degree of the mechanical load vibration amplitude relative to the power value in the steady-state direct-current component and monitoring the evolution state of the electromechanical energy linear coupling degree on the time axis is as follows: Calculating the product of the voltage value and the current value of the steady-state direct current component, obtaining a steady-state direct current power value, dividing the vibration amplitude of the mechanical load by the steady-state direct current power value, or dividing the vibration amplitude of the mechanical load by a nonlinear mapping function value of the steady-state direct current power value, and obtaining an instantaneous coupling ratio; a first-in first-out annular buffer area for storing instantaneous coupling ratio is constructed, when each sampling is updated, the latest instantaneous coupling ratio is written into the head of the buffer area and covers the oldest data, the arithmetic average value or weighted average value of all instantaneous coupling ratios in the buffer area is calculated, and the electromechanical energy linear coupling degree is generated, so that a coupling degree evolution sequence which is updated continuously along with time is formed.

Description

Photovoltaic water pump inverter running state analysis method and system Technical Field The invention relates to the technical field of photovoltaic system monitoring, in particular to a method and a system for analyzing the running state of a photovoltaic water pump inverter. Background The photovoltaic water pump system is used as an application form for directly driving a water pump to lift water by utilizing solar energy, and is widely applied to agricultural irrigation, desert control, domestic water in remote areas and other scenes. The inverter is used as a core control unit for connecting the photovoltaic array and the water pump unit, and the running state of the inverter directly determines the water lifting efficiency and the service life of the system. Because the photovoltaic water pump system is generally deployed in an outdoor unattended environment, and the output power of the photovoltaic array is obviously nonlinear fluctuation influenced by meteorological conditions such as illumination intensity, temperature and the like, the real-time and accurate sensing of the running state of the inverter has important significance for guaranteeing continuous and stable running of the system and reducing operation and maintenance cost. The state monitoring method for the photovoltaic water pump inverter generally relies on setting a fixed threshold value for a single electrical parameter such as voltage and current to determine. However, this monitoring method has substantial drawbacks in practical applications. Firstly, under the working condition that the illumination intensity is changed drastically or clouds are blocked, the normal maximum power point tracking adjustment can cause great fluctuation of electrical parameters, and the fluctuation is easily misjudged as a system fault by the existing method, so that unnecessary shutdown is caused. Secondly, the prior art often ignores the mechanical load characteristics contained in the electrical signals, is difficult to effectively establish deep association between the electrical parameters and the mechanical state of the water pump, and has low sensitivity in identifying early mechanical faults such as dry rotation of the water pump and impeller clamping stagnation, protection can be triggered after the faults evolve into serious overcurrent or stalling accidents, and early warning and accurate positioning of the faults cannot be realized. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a method and a system for analyzing the running state of a photovoltaic water pump inverter, which solve the problems of the background art. S1, continuously sampling voltage signals and current signals on a direct current side of the photovoltaic water pump inverter, extracting steady-state direct current components representing the power supply level of a photovoltaic array through frequency domain separation, and extracting dynamic ripple components representing the mechanical torque characteristics of a water pump unit, constructing equivalent impedance evolution values according to the steady-state direct current components, and extracting mechanical load vibration amplitude according to the dynamic ripple components; S2, synchronously monitoring the evolution value of equivalent impedance and the change trend of a power value in a steady-state direct current component, constructing a power-impedance sensitivity characteristic reflecting the output characteristic of a power supply side, identifying that the current power-impedance sensitivity characteristic is a negative gradient characteristic interval or a zero gradient characteristic interval, S3, establishing electromechanical energy linear coupling degree of a mechanical load vibration amplitude relative to the power value in the steady-state direct current component, monitoring the evolution state of the electromechanical energy linear coupling degree on a time axis to distinguish linear drift characteristics caused by illumination irradiance change from nonlinear distortion characteristics caused by physical structure change of a water pump unit, S4, executing operation state logic judgment based on the characteristic interval where the power-impedance sensitivity characteristic is positioned and the evolution state of the electromechanical energy linear coupling degree, judging that the system is in a normal operation state when the power-impedance sensitivity characteristic is positioned in the negative gradient characteristic interval and the electromechanical energy linear coupling degree presents the linear drift characteristic, and judging that the power-impedance sensitivity characteristic is positioned in the zero gradient characteristic interval and the electromechanical energy linear coupling degree presents the nonlinear distortion characteristics that monotonically rises, and when the power-impedance sensitivity characteristic is positioned in a nega