Rail locomotive air conditioner low-harmonic variable-frequency power supply system and control method

Abstract

The invention discloses a rail locomotive air conditioner low-harmonic variable-frequency power supply system and a control method, and relates to the technical field of harmonic control. According to the method, historical harmonic fault data are analyzed to determine a harmonic sensitive section, and multiple control strategies are determined based on the harmonic sensitive section; starting the locomotive air conditioner, collecting cold start load data of the locomotive air conditioner in real time, and preprocessing the cold start load data to obtain a standard cold start data set; extracting a cold start load index in the standard cold start data set, when the cold start load is judged to be abnormal based on the cold start load index, extracting harmonic trend data, a harmonic trend index and a frequency output function in the standard cold start data set, calculating and outputting a comprehensive execution risk value, and determining a start risk level based on the comprehensive execution risk value. And selecting and executing a corresponding control strategy, and dynamically adjusting the starting frequency of the locomotive air conditioner based on the control strategy. By means of the method, the air conditioner starting stability under the complex working condition can be greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rail transit technology, in particular to a low-harmonic variable frequency power supply system for rail vehicle air conditioner and a control method. BACKGROUND

[0002] At present, the fixed frequency starting strategy based on traditional PWM modulation technology or the slope limiting type linear variable frequency strategy is generally used in the control system of rail vehicle air conditioner. Although this method has a simple structure, when the train is started for the first time in a low temperature environment, the initial load of the air conditioner compressor is very high, which often leads to a sudden change in starting current and serious distortion of power supply waveform, thereby causing a large number of high-order harmonics at the output end of the variable frequency power supply. These high-order harmonics can easily cause the air conditioning system to malfunction, the frequency output to jump, and even cause the protection trip of the air conditioning system or the whole vehicle power supply system. In addition, the existing control system generally lacks the ability to actively identify the cold start load state, cannot dynamically adjust the starting control strategy, and has a slow control response and poor adaptability, which makes it difficult to adapt to the complex working conditions of high-cold starting. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a low-harmonic variable frequency power supply system for rail vehicle air conditioner and a control method, which solves the problems mentioned in the background art.

[0004] To achieve the above purpose, the present application is realized by the following technical scheme: Obtain historical harmonic fault data of the rail vehicle air conditioner, analyze the historical harmonic fault data to determine a harmonic sensitive section, and determine a plurality of control strategies based on the harmonic sensitive section; Start the rail vehicle air conditioner, and collect the cold start load data of the rail vehicle air conditioner in a first time period in real time, preprocess the cold start load data, and obtain a standard cold start data set; Extract the cold start load index in the standard cold start data set, perform a comparative evaluation on the cold start load index based on a pre-set cold start threshold, and determine the cold start load condition of the rail vehicle air conditioner; When it is determined that the cold start load is abnormal, extract the harmonic trend data in the standard cold start data set, calculate a harmonic trend index based on the harmonic trend data, and calculate a frequency output function based on the harmonic trend index; Calculate an output comprehensive execution risk value based on the cold start load index, the harmonic trend index and the frequency output function, determine a starting risk level based on the comprehensive execution risk value; Select and execute a corresponding control strategy based on the starting risk level, and dynamically adjust the starting frequency of the rail vehicle air conditioner in a second time period based on the control strategy.

[0005] Preferably, the harmonic trend data comprises total harmonic distortion rate, inverter current fluctuation rate and inverter voltage fluctuation rate, the output harmonic trend index is calculated based on the harmonic trend data, the output frequency output function is calculated based on the acquired harmonic trend index, and the output comprehensive execution risk value is calculated based on the cold start load index, the harmonic trend index and the frequency output function.

[0006] Preferably, the start-up risk level comprises a first level, a second level and a third level, the first level executes an A-level control strategy, the second level executes a B-level control strategy, and the third level executes a C-level control strategy. The A-level control strategy is a 3-step frequency slow start, each step stays for 8 seconds, the B-level control strategy is a 5-step frequency slow start, each step stays for 10 seconds, and a proactive suppression mechanism is started, when the harmonic growth rate exceeds 20%, the start-up frequency stay time is locked, and the total harmonic distortion rate over-limit threshold is set to 18%, and the C-level control strategy is a 5-step frequency slow start, each step stays for 15 seconds, and when the monitored total harmonic distortion rate exceeds 22%, the frequency output is immediately frozen.

[0007] Preferably, analyzing the historical harmonic fault data to determine the harmonic sensitive section comprises the following steps: The historical harmonic fault data comprises start-up frequency, start-up frequency duration of each step and disturbance time point of harmonic occurrence, a first sequence of each historical harmonic fault data is generated based on the start-up frequency, the start-up frequency where the disturbance time point is located in the first sequence is located as a first frequency, the first occurrence probability of each numerical value in the historical harmonic fault data is calculated, and the first frequency whose first occurrence probability is greater than a first threshold value is taken as a second frequency. The first sequence where there are at least two second frequencies is located as a second sequence, the earliest occurrence time and the latest occurrence time of each second frequency are located, and the allowed delay of each second frequency is calculated based on the earliest occurrence time and the latest occurrence time. A plurality of frequency combinations are generated based on the second frequencies included in each second sequence, the frequency combinations are time-aligned based on the allowed delay, and the total number of times each frequency combination is successfully aligned is counted. The second occurrence probability of the frequency combination is calculated based on the total number of times, the frequency combination whose second occurrence probability is greater than a second threshold value is defined as a high frequency combination, the first frequency whose first occurrence probability is greater than a second threshold value is taken as the harmonic sensitive section, the high frequency combination is verified, and the second frequency included in the high frequency combination that passes the verification is taken as the harmonic sensitive section.

[0008] Preferably, time-aligning the frequency combination comprises the following steps: The frequency combination with the same second frequency is taken as an alignment target, and two alignment targets for alignment are defined as a first combination and a second combination respectively, the allowed delay of each second frequency in the first combination and the second combination is obtained, and the occurrence time period of the second frequency is obtained, the overlap value range is calculated according to the allowed delay, and if the occurrence time period of the second combination can be moved to be completely the same as the occurrence time period of the first combination in the overlap value range, it is determined that the alignment of the first combination and the second combination is successful.

[0009] Preferably, the verification on the alternative frequency and the high-frequency combination comprises the following steps: The historical harmonic fault data is divided into an analysis part and a verification part, the alternative frequency and the high-frequency combination are obtained based on the historical harmonic fault data in the analysis part, the first occurrence number of the alternative frequency and the second occurrence number of the high-frequency combination are obtained based on the verification part, if the first occurrence number of the alternative frequency is greater than a third threshold value, the verification is passed, and if the second occurrence number of the high-frequency combination is greater than a fourth threshold value, the verification is passed.

[0010] Preferably, the control strategy comprises a plurality of start frequencies, and when the control strategy is determined, the start frequencies of the control strategy are not in the harmonic sensitive section.

[0011] Preferably, the cold start load data comprises an outdoor environment temperature, a low-pressure side initial pressure of refrigerant, a condenser surface temperature, an initial current peak change value, a frequency converter current and a frequency converter voltage.

[0012] The application also provides a rail locomotive air conditioner low-harmonic variable frequency power supply system for the rail locomotive air conditioner low-harmonic variable frequency power supply control method, and the system comprises, The acquisition module is used for obtaining historical harmonic fault data of the locomotive air conditioner, analyzing the historical harmonic fault data to determine a harmonic sensitive section, determining a plurality of control strategies based on the harmonic sensitive section, and collecting cold start load data of the locomotive air conditioner in a first time period in real time after starting the locomotive air conditioner. The processing module is used for pre-processing the cold start load data and obtaining a standard cold start data set. The analysis module extracts the cold start load index in the standard cold start data set, performs a one-time comparative evaluation on the cold start load index based on a pre-set cold start threshold, judges the cold start load condition of the locomotive air conditioner, extracts the harmonic trend data in the standard cold start data set when judging that the cold start load is abnormal, calculates a harmonic trend index based on the harmonic trend data, calculates a frequency output function based on the harmonic trend index, calculates an output comprehensive execution risk value based on the cold start load index, the harmonic trend index and the frequency output function, and determines a start risk level based on the comprehensive execution risk value. The reconstruction module selects and executes a corresponding control strategy based on the start risk level, and dynamically adjusts the start frequency of the locomotive air conditioner in the second time period based on the control strategy.

[0013] The present application provides a low-harmonic variable frequency power supply system and control method for a track locomotive air conditioner, which has the following beneficial effects: The method can accurately quantify the comprehensive load level of the current compressor at the beginning of cold start, and after evaluating the cold start abnormality, the harmonic trend index is calculated, and a dynamic frequency function is constructed accordingly. Finally, based on the joint analysis of the cold start load index, the harmonic trend index and the frequency output function, the comprehensive execution risk value is generated, which is the core basis for the secondary risk evaluation and dynamic classification response of the air conditioner system start strategy, so as to realize the strategy cascade and transition from fast standard slow start to multi-stage residence and real-time harmonic freezing, so that the control response is more adaptive and safe and flexible, and the air conditioner start stability and the overall safety level of the track vehicle power supply system in complex working conditions such as extreme cold, harmonic pollution and high load mutation are greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The present application provides a low-harmonic variable frequency power supply system and control method for a track locomotive air conditioner, which has the following beneficial effects: Figure 2 The present application provides a low-harmonic variable frequency power supply system and control method for a track locomotive air conditioner, which has the following beneficial effects: Figure 3 The present application provides a low-harmonic variable frequency power supply system and control method for a track locomotive air conditioner, which has the following beneficial effects: DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0016] Please refer to Figure 1The application provides a control method for a low-harmonic frequency conversion power supply of a rail locomotive air conditioner, and aims to realize the above object by the following technical scheme. S1, historical harmonic fault data of the locomotive air conditioner is acquired, and a harmonic sensitive section is determined by analyzing the historical harmonic fault data, and a plurality of control strategies are determined based on the harmonic sensitive section.

[0017] S2, the locomotive air conditioner is started, and cold start load data of the locomotive air conditioner in a first time period is collected in real time, the cold start load data is preprocessed, and a standard cold start data set is acquired.

[0018] S3, cold start load indexes in the standard cold start data set are extracted, the cold start load indexes are compared and evaluated based on a pre-set cold start threshold, and a cold start load condition of the locomotive air conditioner is judged.

[0019] S4, when it is judged that the cold start load is abnormal, harmonic trend data in the standard cold start data set is extracted, a harmonic trend index is calculated based on the harmonic trend data, and a frequency output function is calculated based on the harmonic trend index.

[0020] S5, an output comprehensive execution risk value is calculated based on the cold start load indexes, the harmonic trend index and the frequency output function, and a start risk level is determined based on the comprehensive execution risk value.

[0021] S6, a corresponding control strategy is selected and executed based on the start risk level, and a start frequency of the locomotive air conditioner in a second time period is dynamically adjusted based on the control strategy.

[0022] In the embodiment, the sensor group is installed on the rail locomotive, and the Sub-GHz industrial wireless transmission protocol is combined to realize real-time collection and transmission of key load parameters in the whole cold start process. Then, the control center receives the data, and the data is preprocessed by the STM32 embedded module to obtain the standard cold start data set. On this basis, the cold start load indexes are calculated by the load evaluation function, and the cold start load indexes are compared with the set cold start threshold to judge whether the cold start load is abnormal.

[0023] If the abnormal condition is evaluated, further extract real-time THD, current and voltage fluctuation rate and other characteristics, calculate the harmonic trend index, and combine the cold start load index, harmonic trend index and frequency output function to build a comprehensive execution risk index, and according to the index grade division, trigger the corresponding three-level slow start control strategy, accurately control the start path and harmonic suppression strategy, and ensure that the air conditioner can still start smoothly and run with low interference in extremely cold or complex conditions. Through the above implementation, the present application not only realizes the joint identification of the cold start load and harmonic disturbance state, but also breaks through the whole process link from perception, evaluation, modeling and control strategy generation, improves the environmental adaptability and forward control ability of different cold start conditions; through harmonic trend driven control path reconstruction, the harmonic peak value is effectively reduced by more than 40%, and the stability is improved. Through multi-index fusion risk assessment and hierarchical response.

[0024] S2 includes S21 and S22; S21, by installing a sensor group at the key nodes of the rail locomotive, real-time acquisition of cold start load data; The key nodes include the outer wall of the rail locomotive, the condenser, the refrigerant circuit and the air conditioner frequency converter. The sensor group includes a temperature sensor, a refrigerant pressure sensor, a Hall current sensor, a voltage sensor and a condenser temperature probe. The cold start load data includes the vehicle external environment temperature, the refrigerant low pressure side initial pressure, the condenser surface temperature, the initial current peak value, the frequency converter current and the frequency converter voltage.

[0025] The cold start load data includes the vehicle external environment temperature Tamb, the refrigerant low pressure side initial pressure Pref, the condenser surface temperature Tcond, the initial current peak value ΔIstart, the frequency converter current I and the frequency converter voltage V. S22, a control center is built in the control server of the rail locomotive, and a short-distance industrial-grade wireless sensor network Sub-Ghz is set up. The wireless module of the sensor group is interconnected with the air conditioner control center of the rail locomotive, and the data upload frequency is set to 10 seconds per data packet. The real-time collected cold start load data is transmitted to the air conditioner control center.

[0026] In this embodiment, the method is used to collect the cold start load data of the air conditioner in the cold start stage by arranging sensor groups at key nodes such as the outer wall of the rail locomotive, the condenser, the refrigerant circuit and the air conditioner frequency converter. In the control center built on the basis of the rail locomotive control server platform, a short-distance industrial-grade wireless sensor network with Sub-GHz as the core is established. The various sensor modules with wireless communication capability are connected to the air conditioner control center at high speed and low interference. The data upload frequency is set to one data packet every 10 seconds to realize stable and real-time return of the cold start load data. Through the above specific implementation, the collection accuracy and update frequency of the pre-cold start working condition parameters are greatly improved, and a low-power, high-robustness and wiring-free wireless sensing network architecture is successfully built. The technical purpose is to provide a high-consistency, high-integrity and high-real-time data basis for subsequent cold start load level identification, harmonic trend evaluation and frequency control strategy selection, and to avoid control errors and instability caused by parameter collection lag, complex wiring or insufficient sampling resolution.

[0027] In this embodiment, when the control center receives the cold start load data in real time, the cold start load data is preprocessed, including data cleaning, filtering processing and standardization processing to obtain a standard cold start data set. Data cleaning is used to clean the cold start load data by using upper and lower threshold exclusion and change rate exclusion to remove obviously erroneous, jumping and physically unreasonable data values. Filtering processing is used to filter the cold start load data by using sliding average filtering to remove random jitter and small fluctuations and retain trend characteristics. Standardization processing is used to standardize the cold start load data after data cleaning and filtering processing by using Z-score standardization processing to eliminate the dimensional influence between all parameters in the cold start load data. Step S3 includes S31 and S32. S31, a cold start load algorithm model is constructed. The real-time standard cold start data set before the cold start of the rail train is extracted and input into the cold start load algorithm model for calculation to output a cold start load index Lload, which quantifies the load index of the air conditioner compressor in the cold start stage under the current working condition. The cold start load index Lload is calculated and output by the following load algorithm model: ; In the formula, log represents the logarithmic function, A small constant is represented to prevent the instability caused by zero division error or extremely small number in the formula, n1 represents the environmental impact coefficient, which is used to control the degree of dominance of temperature factors in the model, n2 represents the electrical impact factor weight, which is used to control the proportion of initial current jump in the overall load level judgment, n3 represents the thermal state reaction coefficient, which adjusts the action weight of the initial pressure Pref of the low-pressure side of the refrigerant and the condenser surface temperature Tcond; A nonlinear weight factor of environmental temperature is represented to avoid unreasonable calculation logic caused by negative temperature in the formula, and the absolute value is taken to measure the deviation from the warm environment, and the index is a nonlinear amplification factor; The electrical load is represented, and the greater the starting current peak value is, the greater the rotating resistance is; The thermal load is represented, and the lower the refrigerant pressure is and the colder the condenser is, the more serious the cold state is, and the higher the load is; The physical meaning of the formula is to integrate the three factors of cold-state thermal, electrical and environmental into a unified load level evaluation function, directly quantify the cold start complexity through the mathematical model, and drive the subsequent control logic to adapt dynamically.

[0028] S32, set the cold start threshold F1 based on the user's setting of the upper limit value of the cold start load of the rail locomotive air conditioner compressor, judge the load situation under the cold start condition of the rail train, and the specific evaluation content is as follows; When the cold start load index Lload is less than the cold start threshold F1, it indicates that the cold start load is normal, and the rail locomotive air conditioner is started normally at this time; When the cold start load index Lload is greater than or equal to the cold start threshold F1, it indicates that the cold start load is abnormal, and the frequency ladder reconstruction mechanism driven by the harmonic trend is triggered at this time.

[0029] In this embodiment, the method constructs a cold start load algorithm model, before the cold start of the rail train, calls the standard cold start data set matched with the current working condition in the database, inputs into the cold start load algorithm model for calculation, and outputs the cold start load index Lload. The load index is obtained by calculating the algorithm model composed of parameters such as environmental temperature, initial current peak change, initial refrigerant pressure and condenser surface temperature. And the user can set a cold start load upper limit value as the cold start threshold F1 according to the performance requirements of the air conditioner compressor carried. Then the actual calculated load index Lload is compared with the threshold in real time. Through the above implementation, the rail vehicle air conditioner control has the ability to evaluate the complex load condition in real time in the cold start stage, realizes the closed loop logical link from "perception, modeling and discrimination" to "control trigger". This way can identify the cold start risk brought by high load, high resistance or extremely cold environment in time before starting, avoid the current impact, control jump or harmonic burst caused by blind start, so as to significantly improve the starting safety, intelligent adaptability and control accuracy of rail vehicle air conditioner in multiple working conditions.

[0030] The harmonic trend data of the embodiment includes total harmonic distortion rate, frequency converter current fluctuation rate and frequency converter voltage fluctuation rate, the harmonic trend index is calculated based on the harmonic trend data, the frequency output function is calculated based on the obtained harmonic trend index, and the comprehensive execution risk value is calculated based on the cold start load index, the harmonic trend index and the frequency output function.

[0031] Specifically, in the determination of the cold start load abnormality, the standard cold start data set acquired in real time is extracted, feature extraction is performed, and harmonic trend data is acquired; the harmonic trend data includes total harmonic distortion rate THD, frequency converter current fluctuation rate and frequency converter voltage fluctuation rate ; wherein the total harmonic distortion rate THD is obtained by calculating the ratio of the energy between the high harmonic component and the fundamental wave in the frequency converter voltage V, d represents the differential variable, dt represents the time differential variable, dI represents the differential variable of the current frequency converter current fluctuation rate, and dV represents the differential variable of the frequency converter voltage fluctuation rate; then the harmonic trend index Htrend is calculated based on the harmonic trend data, the extreme harmonic fluctuation risk of the current rail vehicle in the cold start is analyzed, and the harmonic trend index Htrend is calculated and output by the following algorithm formula: ; In the formula, THD(t) represents the total harmonic distortion rate at time t, dI(t) represents the differential variable of the current frequency converter current fluctuation rate at time t, dV(t) represents the differential variable of the frequency converter voltage fluctuation rate at time t, a1, a2 and a3 respectively represent the frequency converter current fluctuation rate , the frequency converter voltage fluctuation rate and the preset weight value of the total harmonic distortion rate THD, the specific value of which is set by the user, and a1+a2+a3=1. Finally, based on the obtained harmonic trend index Htrend, the frequency output function Fstep is calculated and output, and the target value of the output frequency of the frequency converter in the current cold start process is dynamically generated, which is calculated by the following algorithm formula: ; In the formula, Fstep(t) represents the frequency output function at time t, f0 represents the initial frequency, which is dimensionless, J represents the total number of frequency steps, e represents the exponential function, represents the jump amplitude of the jth frequency step, which is set by the controller, and the larger the value, the faster the frequency rises, represents the risk sensitivity of the jth frequency stage, which is used to control the influence degree of the harmonic trend index Htrend, t j represents the starting time of the jth frequency stage, t j+1 represents the end time of the jth frequency stage, represents the time window at time t.

[0032] In this embodiment, the method dynamically predicts the power quality disturbance risk in the cold start process through the harmonic trend modeling mechanism, and reconstructs the frequency converter output frequency control path in real time based on the prediction result, thereby realizing a soft start control strategy with adaptability. In the preliminary comparative evaluation, when the cold start load is abnormal, the frequency step reconstruction mechanism driven by the harmonic trend is triggered, and the current real-time collected standard cold start data set is extracted for feature extraction to obtain the harmonic trend data. The harmonic trend data includes three key parameters: first, the total harmonic distortion rate THD, which is obtained by calculating the ratio of the high harmonic component in the frequency converter voltage signal to the fundamental energy; second, the frequency converter current fluctuation rate, which is represented by the first derivative of the current with respect to time; and third, the frequency converter voltage fluctuation rate. These parameters can comprehensively reflect the power disturbance trend and fluctuation intensity currently experienced in the cold start process.

[0033] Based on the above three characteristic data, the harmonic trend index Htrend is constructed to quantify the risk level of the harmonic disturbance in the current cold start process. The trend index is calculated by the following function: based on the harmonic trend index Htrend calculated at the current time, the frequency output function Fstep is constructed to dynamically control the target value of the output frequency of the frequency converter. Through the complete implementation, not only does it have the ability to accurately model and predict the harmonic disturbance trend in the cold start process, but it can also actively reconstruct the frequency step according to the power quality risk and dynamically adjust the output frequency rise speed and node setting, thereby effectively suppressing the sudden growth of high harmonics and reducing the current jump phenomenon caused by frequency mutation.

[0034] In the calculation of the comprehensive execution risk value, based on the cold start load index Lload, the harmonic trend index Htrend and the frequency output function Fstep, the output comprehensive execution risk value Cexec is calculated by summarizing calculation, and the linkage risk of harmonic explosion, load impact and control climb loss of control in the cold start stage of the track is comprehensively analyzed. The comprehensive execution risk value Cexec is calculated by the following algorithm formula.

[0035] ; In the formula, Htrend(t) represents the upper limit value of the harmonic trend index at time t, dFstep(t) represents the frequency output function fluctuation rate at time t, i.e. the current frequency climb speed, b1, b2 and b3 represent the preset weight values of the cold start load index Lload, the harmonic trend index Htrend and the frequency output function Fstep respectively, the specific numerical values of which are set by the user, and b1+b2+b3=1, dFstep(t) represents the frequency output function differential variable at time t.

[0036] The start-up risk level includes a first level, a second level and a third level, the first level executes an A-level control strategy, the second level executes a B-level control strategy, and the third level executes a C-level control strategy.

[0037] The A-level control strategy is a 3-step frequency slow start, each step stays for 8 seconds, the B-level control strategy is a 5-step frequency slow start, each step stays for 10 seconds, and an active suppression mechanism is started, when the harmonic growth rate exceeds 20%, the start-up frequency stay time is locked, and the total harmonic distortion rate over-limit threshold is set to 18%, and the C-level control strategy is a 5-step frequency slow start, each step stays for 15 seconds, and when the total harmonic distortion rate is monitored to exceed 22%, the frequency output is immediately frozen.

[0038] As shown in Figure 2 When the comprehensive execution risk value Cexec is less than 4.0, the current cold start risk is divided into a first level risk, and the A-level control strategy is executed; when 4.0≤the comprehensive execution risk value Cexec is less than 7.5, the current cold start risk is divided into a second level risk, and the B-level control strategy is executed; when the comprehensive execution risk value Cexec is greater than or equal to 7.5, the current cold start risk is divided into a third level risk, and the C-level control strategy is executed.

[0039] The A-level control strategy is to start 3-stage slow start, for example, 3-stage slow start is to control the cold start frequency path to be 15 Hz, 30 Hz and 45 Hz, and to gradually advance, each stage stays for 8 seconds; the B-level control strategy is to start 5-stage slow start, for example, 5-stage slow start is to control the cold start frequency path to be 12 Hz, 25 Hz, 36 Hz, 45 Hz and 50 Hz, and to gradually advance, each stage stays for 10 seconds, and a positive inhibition mechanism is started, when the harmonic growth rate exceeds 20%, the cold start frequency stay delay is automatically locked, and the total harmonic distortion rate THD over-limit threshold is set to 18%; the C-level control strategy is to start 7-stage slow start, for example, 7-stage slow start is to control the cold start frequency path to be 10 Hz, 15 Hz, 20 Hz, 28 Hz, 34 Hz, 42 Hz and 50 Hz, and to gradually advance, each stage stays for 15 seconds, and the total harmonic distortion rate THD is monitored in real time, when the total harmonic distortion rate THD exceeds 22%, the frequency output is immediately frozen.

[0040] In the embodiment, the method performs comprehensive summary analysis by taking the cold start load index Lload, the harmonic trend index Htrend and the frequency output function Fstep calculated in the previous steps as input variables, and constructs a comprehensive execution risk value Cexec to reflect the linkage risk level jointly constituted by high load, high frequency climbing rate and strong harmonic disturbance in the cold start process.

[0041] The embodiment analyzes historical harmonic fault data to determine the harmonic sensitive section, including the following steps: The historical harmonic fault data includes the start frequency, the duration of each stage start frequency and the disturbance time point of the harmonic occurrence, a first sequence of each piece of historical harmonic fault data is generated based on the start frequency, the start frequency where the disturbance time point is located in the first sequence is located as a first frequency, the first occurrence probability of various numerical first frequencies in the historical harmonic fault data is counted, and the first frequency with the first occurrence probability greater than a first threshold is set as a second frequency.

[0042] The historical harmonic fault data is data caused by the occurrence of harmonics leading to system failure, which includes the start frequency of the air conditioner at each time point, and the first sequence generated according to the historical harmonic fault data is, for example, [15, 17, 19, 21], wherein the numerical value is the start frequency, and the unit is omitted for convenience of description. The disturbance time point corresponds to the frequency 19, and the frequency 19 is set as the first frequency. If 100 pieces of historical harmonic fault data are collected, the frequency 19 (the first frequency) appears 90 times, and the corresponding first occurrence probability is 90 / 100=0.9. The first threshold is set to 0.8 in the embodiment, and since 0.9 is greater than 0.8, the frequency 19 is set as the second frequency.

[0043] The first sequence in which the second frequencies exist is defined as a second sequence, the earliest occurrence time and the latest occurrence time of each second frequency are located, and the allowed delay of each second frequency is calculated based on the earliest occurrence time and the latest occurrence time.

[0044] Based on the above method, two or more second frequencies can exist in a first sequence. As in the example described above, both frequency 17 and frequency 19 are determined as second frequencies, and the first sequence is defined as a second sequence. The earliest occurrence time and the latest occurrence time of each second frequency in each second sequence are obtained, and the occurrence time is the position of the frequency in the first sequence. In combination with the first sequence described above, for frequency 17, the occurrence time is 2, and if there is a first sequence [13, 15, 17, 19, 21], the occurrence time is 3. Finally, in combination with all first sequences, the minimum and maximum values of the occurrence time of the frequencies are determined, and are respectively the earliest occurrence time and the latest occurrence time. Then, the allowed delay of each second frequency is calculated based on the earliest occurrence time and the latest occurrence time. The calculation process of the allowed delay is described below. The allowed delay is calculated by the following formula, . Wherein, is the allowed delay, is the latest occurrence time, is the earliest occurrence time, for example, for frequency A, the earliest occurrence time is 2, and the latest occurrence time is 6, then the allowed delay is 2. In particular, if the allowed delay is not an integer, rounding is performed.

[0045] Based on the second frequencies included in each second sequence, a plurality of frequency combinations are generated, the frequency combinations are time-aligned based on the allowed delay, and the total number of times each frequency combination is successfully aligned is counted.

[0046] Specifically, the frequency combinations with the same second frequencies are taken as the alignment target, and the two alignment targets for alignment are defined as the first combination and the second combination, the allowed delay of each second frequency in the first combination and the second combination is obtained, and the occurrence time period of the second frequency is obtained, the overlap value range is calculated according to the allowed delay, and if the occurrence time period of the second combination can be moved to be completely the same as the occurrence time period of the first combination in the overlap value range, it is determined that the alignment of the first combination and the second combination is successful.

[0047] For example, the second sequence 1 includes the second frequencies A and B, and the second sequence 2 includes the second frequencies A and B, the second sequence 1 and the second sequence 2 are taken as the alignment target, the second frequencies A and B in the second sequence 1 are taken as the first combination, and the second frequencies A and B in the second sequence 2 are taken as the second combination. The overlap value range is the smaller value of the allowed delay of the two second frequencies in the combination, and the calculated allowed delay of the second frequencies A and B is 1 and 2 respectively, so the overlap value range is 1. For another example, the calculated allowed delay of the second frequencies A and B is 3 and 5 respectively, so the overlap value range is 3. The alignment process is introduced below. For the second sequence 1, the occurrence time of the second frequencies A and B is 2 and 4 respectively, for the second sequence 2, the occurrence time of the second frequencies A and B is 3 and 5 respectively, the overlap value range is 1, so the occurrence time of the second frequencies A and B in the second sequence 2 is shifted to the left by one time unit, which can be the same as the occurrence time of the second frequencies A and B in the second sequence 1, so it is determined that the first combination and the second combination can be aligned.

[0048] The second occurrence probability of the frequency combination is calculated based on the total number of times, the frequency combination with the second occurrence probability greater than the second threshold value is defined as a high-frequency combination, the first frequency with the first occurrence probability greater than the second threshold value is taken as a harmonic sensitive section, and the high-frequency combination is verified, and the second frequency included in the high-frequency combination that passes the verification is taken as the harmonic sensitive section.

[0049] The verification of the alternative frequency and the high-frequency combination in the embodiment includes the following steps: The verification of the high-frequency combination in the embodiment includes the following steps: The historical harmonic fault data is divided into an analysis part and a verification part, the high-frequency combination is obtained based on the historical harmonic fault data in the analysis part, the number of occurrences of the high-frequency combination is obtained based on the verification part, and if the number of occurrences of the high-frequency combination is greater than a third threshold value, the verification passes.

[0050] 30 second sequences in which a certain frequency combination (including the second frequency A and the second frequency B) exists are aligned, and the total number of times is 30, the second occurrence probability is calculated according to the total number of times and the number of first sequences, and the second occurrence probability is 30 / 100=0.3. In the embodiment, the second threshold value is set to 0.9, after the second occurrence probability of each frequency combination is calculated, the first occurrence probability of the second frequency is compared with the second threshold value, the second threshold value is greater than the first threshold value, for example, the second threshold value is 0.9, the first frequency greater than the second threshold value is taken as a harmonic sensitive section, for example, the first occurrence probability of the frequency 17 is greater than the second threshold value, which indicates that the frequency 17 is prone to harmonic interference. For the high-frequency combination that passes the verification, it is indicated that the second frequency combination in the high-frequency combination appears at the same time, and there is a great probability of harmonic interference, so the second frequency included in the high-frequency combination is taken as the harmonic sensitive section.

[0051] The third threshold is determined according to the number of historical harmonic fault data included in the analysis part and the verification part. The present application divides the historical harmonic fault data into the analysis part and the verification part, determines the high-frequency combination in the analysis part, and verifies it through the verification part, thereby further ensuring the reliability of the analysis result.

[0052] The control strategy includes a plurality of start frequencies, and when the control strategy is determined, the start frequencies of the control strategy are not in the harmonic sensitive section.

[0053] The present application avoids these harmonic sensitive sections when formulating the control strategy by determining the harmonic sensitive sections in advance, which are sections where harmonics are prone to occur, thereby further reducing the risk of harmonic occurrence.

[0054] Please refer to Figure 3 The present application also provides a low-harmonic variable frequency power supply system for rail locomotive air conditioners, which is used for the above-mentioned low-harmonic variable frequency power supply control method for rail locomotive air conditioners, and the system comprises: The acquisition module is used to acquire historical harmonic fault data of the locomotive air conditioner, analyze the historical harmonic fault data to determine a harmonic sensitive section, determine a plurality of control strategies based on the harmonic sensitive section, and acquire cold start load data of the locomotive air conditioner in a first time period in real time after starting the locomotive air conditioner.

[0055] The processing module is used to preprocess the cold start load data and acquire a standard cold start data set.

[0056] The analysis module is used to extract a cold start load index in the standard cold start data set, perform a one-time comparison and evaluation on the cold start load index based on a pre-set cold start threshold, judge the cold start load condition of the locomotive air conditioner, extract harmonic trend data in the standard cold start data set when the cold start load is judged to be abnormal, calculate a harmonic trend index based on the harmonic trend data, calculate a frequency output function based on the harmonic trend index, calculate an output comprehensive execution risk value based on the cold start load index, the harmonic trend index and the frequency output function, and determine a start risk level based on the output comprehensive execution risk value.

[0057] The reconstruction module is used to select and execute a corresponding control strategy based on the start risk level, and dynamically adjust the start frequency of the locomotive air conditioner in a second time period based on the control strategy.

[0058] Although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application.

Claims

1. A method for controlling a low-harmonic variable-frequency power supply for a rail vehicle air conditioner, characterized in that: The following steps are involved: Obtain historical harmonic fault data of locomotive air conditioners, analyze the historical harmonic fault data to determine harmonic sensitive sections, and determine multiple control strategies based on the harmonic sensitive sections; Starting the locomotive air conditioner, collecting cold start load data of the locomotive air conditioner in a first time period in real time, preprocessing the cold start load data, and obtaining a standard cold start data set; Extract the cold start load index from the standard cold start data set, perform a comparative evaluation on the cold start load index based on the pre-set cold start threshold, and determine the cold start load condition of the locomotive air conditioner; When it is determined that the cold start load is abnormal, the harmonic trend data in the standard cold start data set is extracted, the harmonic trend index is calculated based on the harmonic trend data, and the frequency output function is calculated based on the harmonic trend index; Calculate and output a comprehensive execution risk value based on the cold start load index, harmonic trend index and frequency output function, and determine the startup risk level based on the comprehensive execution risk value; A corresponding control strategy is selected and executed based on the startup risk level, and the startup frequency of the locomotive air conditioner in the second time period is dynamically adjusted based on the control strategy.

2. The method according to claim 1, wherein: The harmonic trend data includes the total harmonic distortion rate, the inverter current fluctuation rate and the inverter voltage fluctuation rate. The output harmonic trend index is calculated based on the harmonic trend data. The output frequency output function is calculated based on the obtained harmonic trend index. The comprehensive execution risk value is calculated and output based on the cold start load index, harmonic trend index and frequency output function.

3. The method according to claim 1, wherein: The startup risk levels include the first, second and third levels. The first level implements the A-level control strategy, the second level implements the B-level control strategy, and the third level implements the C-level control strategy; The Class A control strategy is a 3-order frequency slow start with a dwell time of 8 seconds per step. The Class B control strategy is a 5-order frequency slow start with a dwell time of 10 seconds per step. The active suppression mechanism is activated. When the harmonic growth rate exceeds 20%, the dwell time of the start frequency is locked, and the total harmonic distortion rate exceeding the limit threshold is set to 18%. The Class C control strategy is a 5-order frequency slow start with a dwell time of 15 seconds per step. When the monitored total harmonic distortion rate exceeds 22%, the frequency output is immediately frozen.

4. The method according to claim 1, wherein: Analyzing historical harmonic fault data to determine harmonic sensitive sections includes the following steps: The historical harmonic fault data includes the starting frequency, the duration of each order of the starting frequency, and the interference time point of the harmonic. A first sequence of each piece of historical harmonic fault data is generated based on the starting frequency. The starting frequency at the interference time point in the first sequence is located as the first frequency. The first occurrence probability of various numerical first frequencies in the historical harmonic fault data is counted, and the first frequency with a first occurrence probability greater than a first threshold is used as the second frequency. Positioning a first sequence with at least two second frequencies as a second sequence, positioning the earliest appearance time and the latest appearance time of each second frequency, and calculating the allowed delay of each second frequency based on the earliest appearance time and the latest appearance time; generating a plurality of frequency combinations based on the second frequencies included in each second sequence, performing time alignment on the frequency combinations based on an allowed delay, and counting a total number of successful alignments for each frequency combination; The second occurrence probability of the frequency combination is calculated based on the total number of times, the frequency combination with a second occurrence probability greater than the second threshold is defined as a high-frequency combination, the first frequency with a first occurrence probability greater than the second threshold is used as a harmonic-sensitive section, the high-frequency combination is verified, and the second frequency included in the verified high-frequency combination is used as the harmonic-sensitive section.

5. The method according to claim 4, characterized in that: Time-aligning a frequency combination involves the following steps: A frequency combination with the same second frequency is used as the alignment target, and the two alignment targets to be aligned are defined as the first combination and the second combination, respectively. The allowed delay of each second frequency in the first combination and the second combination, as well as the time period of occurrence of the second frequency, are obtained. The overlapping numerical range is calculated based on the allowed delay. If the time period of occurrence of the second combination can be moved to be exactly the same as the time period of occurrence of the first combination within the overlapping numerical range, then it is determined that the alignment of the first combination and the second combination is successful.

6. The method according to claim 4, characterized in that Verification of the high frequency combination includes the following steps; The historical harmonic fault data is divided into an analysis part and a verification part. The high-frequency combination is obtained based on the historical harmonic fault data in the analysis part, and the number of occurrences of the high-frequency combination is obtained based on the verification part. If the number of occurrences of the high-frequency combination is greater than the third threshold, the verification is passed.

7. The method according to claim 1, characterized in that: The control strategy includes multiple starting frequencies. When determining the control strategy, the starting frequency of the control strategy is not within the harmonic sensitive section.

8. The method according to claim 1, characterized in that The cold start load data includes the outside ambient temperature, the initial pressure of the refrigerant low-pressure side, the condenser surface temperature, the initial current peak change value, the inverter current and the inverter voltage.

9. A low-harmonic variable-frequency power supply system for a railway locomotive air conditioner, used to implement the railway locomotive air conditioner low-harmonic variable-frequency power supply control method according to any one of claims 1 to 8, characterized in that: The system includes, An acquisition module is used to obtain historical harmonic fault data of the locomotive air conditioner, analyze the historical harmonic fault data to determine the harmonic sensitive section, and determine multiple control strategies based on the harmonic sensitive section. After the locomotive air conditioner is started, the acquisition module collects the cold start load data of the locomotive air conditioner in the first time period in real time; A processing module is used to pre-process the cold start load data to obtain a standard cold start data set; An analysis module extracts a cold start load indicator from a standard cold start data set, performs a comparative evaluation of the cold start load indicator based on a preset cold start threshold, determines the cold start load condition of the locomotive air conditioner, extracts harmonic trend data from the standard cold start data set when the cold start load is determined to be abnormal, calculates a harmonic trend index based on the harmonic trend data, calculates a frequency output function based on the harmonic trend index, calculates and outputs a comprehensive execution risk value based on the cold start load indicator, the harmonic trend index, and the frequency output function, and determines the startup risk level based on the comprehensive execution risk value; The reconstruction module selects and executes a corresponding control strategy based on the startup risk level, and dynamically adjusts the startup frequency of the locomotive air conditioner in the second time period based on the control strategy.

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