CN-121984409-A - Overload protection method for variable frequency driving device under high-load working condition of coal mine

CN121984409ACN 121984409 ACN121984409 ACN 121984409ACN-121984409-A

Abstract

The invention discloses an overload protection method of a variable frequency driving device under a high-load working condition of a coal mine, which particularly relates to the field of industrial control, and aims to realize accurate prediction and grading protection of delayed thermal overload by acquiring rated output power, cooling time constant and historical operation data of the variable frequency driving device, extracting power fluctuation amplitude and duration time of a high-load period, calculating accumulated thermal stress factors, constructing a thermal failure critical model, acquiring working parameters of equipment in real time and calculating thermal stress and outputting an overload risk prediction value in the operation process, and adjusting an output power limit value according to a risk grade when the risk prediction value exceeds a judgment threshold value, and executing frequency reduction or output cutting operation when necessary.

Inventors

ZHU KAI
CUI HAIFENG
Xun Yaru
HAO HAITAO
ZHANG NANA
LIU BO
FAN SIJIA

Assignees

山东海纳智能装备科技股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260210

Claims (7)

1. The overload protection method of the variable frequency driving device under the high-load working condition of the coal mine is characterized by comprising the following steps: obtaining rated output power P0, a cooling time constant T0 and a historical operation data sequence D= { D1, D2, & gt, dn } corresponding to the target variable frequency drive device in the initial operation stage, wherein dn comprises load rate, current, voltage and temperature rise indexes; Based on the historical operation data sequence D, extracting load fluctuation amplitude delta P and power duration t of a target device in different high-load time periods, calculating an accumulated thermal stress factor H of the target device, and constructing a thermal failure critical model MH; According to the current real-time collected operation data, inputting the operation data into the thermal failure critical model MH, and outputting an overload risk prediction value R; Judging whether to trigger a protection mode or not based on the overload risk prediction value R, if so, adjusting the output limit Plim of the variable frequency driving device according to the current system state, and sending out an early warning signal; if the preset protection period Tp is continuously exceeded and R > Rth is still satisfied, the Rth is the set overload judgment threshold value, and then the forced down-conversion operation is triggered or the output is cut off.
2. The method for protecting the frequency conversion driving device under the high-load working condition of the coal mine according to claim 1, wherein the calculating the accumulated thermal stress factor H comprises the following steps: Screening out high-load time period data according to the condition that the load rate is greater than 85%, and carrying out difference analysis on continuous output power data in each time period to extract the power fluctuation amplitude delta P; Marking a time interval in which the continuous power of each section in the high-load time period is not lower than 80% of rated output power P0, and counting the power duration t corresponding to each section; Constructing an accumulated thermal stress factor H based on delta P and T by combining a cooling time constant T0, and realizing thermal stress measurement by adopting an exponential weighting accumulated function form; Fitting the accumulated thermal stress factors H in a plurality of high-load operation periods with corresponding device temperature rise thresholds, establishing a thermal stress-failure relation curve, and constructing a thermal failure critical model MH.
3. The method for protecting the variable frequency drive device under the high-load working condition of the coal mine according to claim 2, wherein the constructing the thermal failure critical model MH comprises the following steps: Correspondingly matching the accumulated thermal stress factor H calculated in each high-load operation period with the highest temperature rise value delta Tmax of the device recorded in the period to form a thermal stress-temperature rise sample pair; Fitting all thermal stress-temperature rise sample pairs by adopting a polynomial regression method to construct a temperature rise prediction function F, wherein F takes an accumulated thermal stress factor H as an independent variable and predicts Wen Sheng T as a dependent variable; Determining a corresponding thermal stress critical value Hc according to a rated safety temperature rise threshold value delta Ts of the device, so that F (Hc) =delta Ts is used as a critical thermal failure point; And constructing a thermal failure critical model MH by the temperature rise prediction function F and the thermal stress critical value Hc together.
4. The method for protecting the frequency conversion driving device under the high-load working condition of the coal mine according to claim 1, wherein the output overload risk prediction value R comprises the following steps: output power, load rate and device temperature rise data in the current operation period of the variable frequency driving device are collected in real time, and power fluctuation amplitude and power duration in the current period are calculated; According to the current power fluctuation amplitude and the power duration, a cooling time constant is combined, and a real-time thermal stress factor Hreal corresponding to the current period is calculated; substituting the real-time thermal stress factor Hreal into a temperature rise prediction function in the thermal failure critical model MH, calculating a predicted temperature rise value, and comparing the predicted temperature rise value with a thermal stress critical value Hc corresponding to a critical temperature rise threshold value according to the predicted temperature rise value; and defining an overload risk prediction value R as a ratio of Hreal to Hc, and judging that the delay type overload risk exists currently when the R is larger than a set overload judgment threshold Rth.
5. The method for protecting the overload of the variable frequency drive device under the high-load condition of the coal mine as claimed in claim 4, wherein the step of adjusting the output limit Plim of the variable frequency drive device according to the current system state comprises the following steps: When R is larger than Rth, confirming that the delay type overload risk exists, and entering a protection judging flow; calculating a risk level coefficient K according to the temperature rise, the load rate and the output power parameters of the currently acquired device; And calculating an output limit Plim according to the risk level coefficient K.
6. The method for protecting the overload of the variable frequency drive device under the high-load working condition of the coal mine as claimed in claim 5, wherein the calculating the output limit Plim according to the risk level coefficient K comprises the following steps: Carrying out ratio operation on the real-time thermal stress factor Hreal and the thermal stress critical value Hc in the current operation period, and defining a risk level coefficient K as a result of dividing Hreal by Hc; classifying the risk level coefficient K in intervals, setting a plurality of risk level intervals, wherein each level corresponds to an output limit value attenuation proportion alpha; selecting a corresponding attenuation proportion alpha according to the risk interval where K is located, and calculating an expression Calculating a current output limit Plim; The output limit value Plim is input into a control loop of the variable frequency driving device, and the maximum output power is limited not to exceed the calculated value, so that the dynamic thermal load reduction control is realized.
7. The method for protecting the overload of the variable frequency drive device under the high-load working condition of the coal mine according to claim 1, wherein the triggering of the forced down-conversion operation or the cutting-off of the output comprises the following steps: setting a protection period Tp, continuously monitoring an overload risk predicted value R at fixed time intervals, and recording the accumulated duration T of which the R is larger than a judgment threshold Rth; When the accumulated duration time T is greater than or equal to the protection period Tp, judging that the current thermal stress reaches an irreversible critical state, and entering a forced protection execution flow; judging whether the frequency-reducing condition is met according to the current running frequency and the load rate, and if so, controlling the variable-frequency driving device to gradually reduce the output frequency according to a set descending gradient; if the equipment operation frequency is reduced to the minimum allowable frequency and is not restored to the safe state, executing the output cut-off command to thoroughly cut off the power output.

Description

Overload protection method for variable frequency driving device under high-load working condition of coal mine Technical Field The invention relates to the field of industrial control, in particular to an overload protection method of a variable frequency driving device under a high-load working condition of a coal mine. Background In the coal mine industry, the variable frequency driving device is used as a key control component of an electric transmission system of a coal mine and is widely applied to high-load equipment such as lifting, transportation, ventilation, drainage and the like. The frequency conversion driving device is limited by underground complex working conditions, runs in severe environments such as high humidity, high dust, severe load fluctuation and the like throughout the year, is extremely easy to generate overload risks such as overcurrent, overheat, bus voltage abnormality and the like under the conditions of heavy load starting, frequent starting and stopping or short-time abrupt load change, and seriously threatens the running safety and the service life of equipment. The overload protection strategy of the existing variable frequency driving device mostly adopts a fixed threshold triggering mode, so that the load dynamic characteristics of equipment in different working periods cannot be identified in real time, and particularly, delay type overload faults caused by short-time high-load accumulation effect are difficult to accurately judge. The overload is not caused by instantaneous abnormality, but is caused by superposition of comprehensive factors such as long-time operation close to rated power boundary, system cooling lag, insufficient recovery due to frequent start-up, and the like, and is characterized in that no obvious characteristic exists in the initial stage, the critical point is instantaneously invalid, so that a power device of a frequency conversion module is burnt out, a motor system is stopped, and even a local electric fire is caused. Disclosure of Invention The invention aims to provide an overload protection method of a variable frequency driving device under a high-load working condition of a coal mine, so as to solve the defects in the background art. In order to achieve the purpose, the invention provides the following technical scheme that the overload protection method of the variable frequency driving device under the high-load working condition of the coal mine comprises the following steps: obtaining rated output power P0, a cooling time constant T0 and a historical operation data sequence D= { D1, D2, & gt, dn } corresponding to the target variable frequency drive device in the initial operation stage, wherein dn comprises load rate, current, voltage and temperature rise indexes; Based on the historical operation data sequence D, extracting load fluctuation amplitude delta P and power duration t of a target device in different high-load time periods, calculating an accumulated thermal stress factor H of the target device, and constructing a thermal failure critical model MH; According to the current real-time collected operation data, inputting the operation data into the thermal failure critical model MH, and outputting an overload risk prediction value R; Judging whether to trigger a protection mode or not based on the overload risk prediction value R, if so, adjusting the output limit Plim of the variable frequency driving device according to the current system state, and sending out an early warning signal; if the preset protection period Tp is continuously exceeded and R > Rth is still satisfied, the Rth is the set overload judgment threshold value, and then the forced down-conversion operation is triggered or the output is cut off. Preferably, wherein said calculating the cumulative thermal stress factor H thereof comprises: Screening out high-load time period data according to the condition that the load rate is greater than 85%, and carrying out difference analysis on continuous output power data in each time period to extract the power fluctuation amplitude delta P; Marking a time interval in which the continuous power of each section in the high-load time period is not lower than 80% of rated output power P0, and counting the power duration t corresponding to each section; Constructing an accumulated thermal stress factor H based on delta P and T by combining a cooling time constant T0, and realizing thermal stress measurement by adopting an exponential weighting accumulated function form; Fitting the accumulated thermal stress factors H in a plurality of high-load operation periods with corresponding device temperature rise thresholds, establishing a thermal stress-failure relation curve, and constructing a thermal failure critical model MH. Preferably, the constructing the thermal failure critical model MH includes: Correspondingly matching the accumulated thermal stress factor H calculated in each high-load operation period with the h