Anti-interference method and device for eliminating sudden loading and network quitting of variable-frequency alternating-current power supply system

Abstract

The invention belongs to the technical field of aircraft variable-frequency alternating-current power supply system design, and particularly relates to an anti-interference method and device for eliminating sudden loading and network quitting of a variable-frequency alternating-current power supply system. The method comprises the following steps: periodically collecting frequency signals output by a generator, and storing the frequency signals in a queue with a preset length of N; performing filtering processing on the frequency signals in the queue to obtain a frequency average value for judgment; if the frequency average value is lower than the network exiting frequency threshold value, the overclocking identification position is 1, and the period count values are accumulated; if the frequency average value is not lower than the network exiting frequency threshold value, resetting the overclocking identification bit and the period count value; and when the overclocking identification bit is 1 and the period count value reaches a threshold value, controlling the main contactor of the generator to be switched off, so that the power supply system exits from the power grid, otherwise, carrying out detection of the next period. According to the method and the device, the abnormal network quit phenomenon in the system loading process is avoided, and the reliability of the power supply system is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aircraft variable frequency AC power supply system design, and particularly relates to an anti-interference method and device for eliminating sudden load-off-grid of a variable frequency AC power supply system. BACKGROUND

[0002] The variable frequency AC main power supply system adopts a three-stage variable frequency alternator. According to the working principle of the variable frequency AC power generation system and the fact that modern electronic devices generally adopt switching power supplies which are not sensitive to input frequency and can complete the control function of system on-off-grid through frequency change. However, when a sudden load is added in the normal working system, the power output cannot follow up instantaneously, the kinetic energy of the system is consumed, the output frequency of the generator permanent magnet machine drops instantaneously, and the recovery time after the frequency drops instantaneously is much smaller than the system fault protection time, so the system will not be off-grid due to triggering of the fault protection. When the instantaneous dropped frequency is lower than the frequency threshold of the normal off-grid system, the system will disconnect the connection between the generator and the power grid, resulting in abnormal off-grid of the power supply system. SUMMARY

[0003] The application provides an anti-interference method and device for eliminating sudden load-off-grid of a variable frequency AC power supply system, which solves the problem of abnormal off-grid caused by sudden load after the variable frequency power supply system is put on the grid.

[0004] The first aspect of the application provides an anti-interference method for eliminating sudden load-off-grid of a variable frequency AC power supply system, mainly including the following steps:

[0005] Step S1, system initialization, setting an over-frequency identification bit and a cycle count value, and setting the initial values to be zero;

[0006] Step S2, monitoring whether the variable frequency AC power supply system has been put on the grid, if yes, periodically collecting the frequency signal output by the generator and storing it in a queue with a preset length N;

[0007] Step S3, filtering the frequency signal in the queue to obtain a frequency average value for judgment;

[0008] Step S4, comparing the frequency average value with a preset off-grid frequency threshold value, if the frequency average value is lower than the off-grid frequency threshold value, setting the over-frequency identification bit to 1 and accumulating the cycle count value, if the frequency average value is not lower than the off-grid frequency threshold value, resetting the over-frequency identification bit and the cycle count value;

[0009] Step S5, when the over-frequency identification bit is 1 and the cycle count value reaches a threshold value, controlling the generator main contactor to be disconnected, so that the power supply system exits the grid, otherwise, the next cycle of detection is performed.

[0010] Preferably, step S2 further comprises:

[0011] From the Nth collection cycle, the head frequency value is removed from the queue in a first-in-first-out manner, and the frequency value collected in the current cycle is written at the tail of the queue.

[0012] Preferably, step S3 further comprises:

[0013] When the number of stored frequency values in the queue is less than N, the arithmetic mean of all frequency values in the queue is calculated as the frequency average;

[0014] When the number of stored frequency values in the queue is equal to N, the arithmetic mean of the remaining frequency values is calculated as the frequency average after removing the minimum frequency value in the queue.

[0015] Preferably, step S4 further comprises: during the super frequency identification position 1, if the frequency average occurs once and is not lower than the off-network frequency threshold value, the super frequency identification bit and the cycle count value are reset.

[0016] Preferably, in step S3, the frequency average is corrected by the following formula:

[0017] ;

[0018] Wherein, u is the frequency average before correction, is the frequency average after correction, 、 、 is a weight value, and satisfies , is the dynamic weight of the ith frequency value, , is the standard deviation of the queue frequency, is the ith frequency sampling value in the queue, is the maximum value of the absolute value of the frequency change rate of adjacent cycles in the current queue.

[0019] The second aspect of the application provides an anti-interference device for eliminating the sudden load-off-network of a variable frequency AC power supply system, mainly comprising:

[0020] An initialization module for system initialization, setting the super frequency identification bit and the cycle count value, and the initial values are all zero;

[0021] A frequency signal collection module for monitoring whether the variable frequency AC power supply system has been put into grid operation, if so, periodically collecting the frequency signal output by the generator and storing it in a queue with a preset length N;

[0022] a frequency average value calculation module, configured to filter the frequency signals in the queue to obtain a frequency average value for judgment;

[0023] a counting module, configured to compare the frequency average value with a preset off-grid frequency threshold value, if the frequency average value is lower than the off-grid frequency threshold value, set the over-frequency identification bit to 1 and accumulate the cycle count value, if the frequency average value is not lower than the off-grid frequency threshold value, reset the over-frequency identification bit and the cycle count value;

[0024] an off-grid control module, configured to control the generator main contactor to be disconnected to make the power supply system exit the power grid when the over-frequency identification bit is 1 and the cycle count value reaches a threshold value, otherwise, perform detection in the next cycle.

[0025] Preferably, the frequency signal acquisition module comprises:

[0026] a queue control unit, configured to remove the frequency value at the head of the queue from the queue and write the frequency value acquired in the current cycle to the tail of the queue by the first-in first-out mode from the Nth acquisition cycle.

[0027] Preferably, the frequency average value calculation module comprises:

[0028] a queue not full calculation unit, configured to calculate the arithmetic average value of all the frequency values in the queue as the frequency average value when the number of the frequency values stored in the queue is less than N;

[0029] a queue full calculation unit, configured to calculate the arithmetic average value of the remaining frequency values as the frequency average value after removing the minimum frequency value in the queue when the number of the frequency values stored in the queue is equal to N.

[0030] Preferably, the counting module comprises a reset control unit, configured to reset the over-frequency identification bit and the cycle count value when the frequency average value is not lower than the off-grid frequency threshold value once during the over-frequency identification bit is 1.

[0031] Preferably, the frequency average value calculation module further comprises a correction unit, configured to correct the frequency average value by the following formula:

[0032] ;

[0033] wherein, u is the frequency average value before correction, is the frequency average value after correction, 、 、 is a weight value and satisfies , is the dynamic weight of the i th frequency value, , is the standard deviation of the queue frequency, is the i-th frequency sampling value in the queue, is the maximum value of the absolute value of the adjacent period frequency change rate in the current queue.

[0034] The application avoids the abnormal off-grid phenomenon of the system during loading, and improves the reliability of the power supply system.

[0035] The application avoids the abnormal off-grid phenomenon of the system during loading, and improves the reliability of the power supply system. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a flowchart of a preferred embodiment of the anti-interference method for eliminating sudden load off-grid of a variable frequency AC power supply system. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme of the embodiment of the application will be described in more detail below in combination with the drawings of the embodiment of the application. In the drawings, the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The described embodiments are part of the embodiments of the application, not all embodiments. The embodiments described below by reference to the drawings are exemplary and are intended to explain the application, and cannot be understood as limiting the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application. The embodiments of the application will be described in detail below in combination with the drawings.

[0038] The first aspect of the application provides an anti-interference method for eliminating sudden load off-grid of a variable frequency AC power supply system, as shown in Figure 1 mainly includes:

[0039] Step S1, system initialization, setting the over-frequency identification bit and the period count value, the initial value is set to zero;

[0040] Step S2, monitor whether the variable frequency AC power supply system has been put into grid work, if yes, periodically collect the frequency signal output by the generator, and store it in a preset queue with length N;

[0041] Step S3, filtering the frequency signal in the queue to obtain the frequency average value for judgment;

[0042] Step S4, compare the frequency average value with a preset off-grid frequency threshold value, if the frequency average value is lower than the off-grid frequency threshold value, set the over frequency identification bit to 1 and accumulate the cycle count value; if the frequency average value is not lower than the off-grid frequency threshold value, reset the over frequency identification bit and the cycle count value;

[0043] Step S5, when the over frequency identification bit is 1 and the cycle count value reaches a threshold value, control the generator main contactor to be disconnected, so that the power supply system exits the power grid, otherwise, proceed to the detection of the next cycle.

[0044] The variable frequency alternating current power supply system described in the application mainly consists of a three-stage variable frequency alternating current generator, a generator controller and an alternating current control device. The generator main contactor installed in the alternating current control device is responsible for connecting or disconnecting the system and the power grid. The controller collects the frequency signal of the generator permanent magnet machine through the frequency sampling circuit in the signal collection and output module and makes logical processing. When the frequency signal processed by the instantaneous drop is lower than the off-grid threshold value and the over frequency identification bit position cycle is greater than the system preset value, the controller sends a main contactor disconnection instruction and outputs a main contactor driving signal to make the generator main contactor in the alternating current control device disconnected, so that the variable frequency alternating current power supply system exits the power grid.

[0045] Figure 1 The specific control strategy of the controller is given. After the system is initialized, the core work is to continuously sample the generator output frequency in the power supply grid-connected state. Instead of using the original instantaneous frequency for judgment, the application introduces a filtering processing link to generate a "frequency average value" that can reflect the real trend of the frequency. Then, the processed frequency is compared with the preset safety threshold (off-grid frequency threshold value), and the "over frequency identification bit" and "cycle count value" two state variables are used to record the duration of the abnormal state. The final off-grid instruction is not triggered by a momentary abnormality, but is issued based on the condition that the abnormal state lasts for a certain number of cycles.

[0046] Through the double mechanisms of "filtering processing" and "cycle counting", the application effectively filters out the instantaneous frequency drop glitches caused by sudden load, avoids the false off-grid of the system due to temporary and recoverable disturbances, and greatly improves the reliability of the system.

[0047] The application adopts the state machine idea and is realized through identification bits and counters. Only when the frequency abnormality is confirmed to be persistent, the real fault is determined, and the off-grid operation is performed. This simulates the logic of manual judgment and has higher intelligence.

[0048] In an alternative embodiment, in step S4, in addition to the accumulation counter, a "decay mechanism" can also be introduced. For example, if the frequency average value fluctuates frequently above and below the threshold value, but the overall trend is downward, a small decay amount can be set while the counter is accumulating, so that a more persistent and more explicit abnormal signal is needed to trigger the network withdrawal. This can further improve the accuracy of the judgment under complex disturbance conditions.

[0049] In some alternative embodiments, step S2 further comprises:

[0050] From the Nth collection cycle, the frequency value at the head of the queue is removed from the queue in a first-in-first-out manner, and the frequency value collected in the current cycle is written at the tail of the queue.

[0051] In this embodiment, the queue is gradually filled in the initial stage. Once it is filled to N data points, each time new frequency data arrives, the oldest data is removed from the head of the queue, and the new data is placed at the tail of the queue. It is assumed that the data is filled into the queue from the tail. This ensures that the queue always stores the frequency information of the last N cycles, forming a dynamically updated time window.

[0052] In some alternative embodiments, step S3 further comprises:

[0053] When the number of frequency values stored in the queue is less than N, the arithmetic mean of all frequency values in the queue is calculated as the frequency average value;

[0054] When the number of frequency values stored in the queue is equal to N, after removing the minimum frequency value in the queue, the arithmetic mean of the remaining frequency values is calculated as the frequency average value.

[0055] In this embodiment, when the queue is not full, a simple arithmetic mean is used to ensure the timeliness of the initial judgment; after the queue is full, the algorithm of "calculating the average after removing the minimum value" is automatically switched. This method is essentially a simple and effective digital filter for pulse-type interference. The instantaneous drop in frequency caused by the load appears as a sudden minimum value in the data sequence. By actively identifying and removing this minimum value, the negative impact of this instantaneous drop on the overall trend judgment can be significantly reduced.

[0056] In some alternative embodiments, step S4 further comprises: during the super frequency identification position 1, if the frequency average value is not lower than the network withdrawal frequency threshold value once, the super frequency identification bit and the cycle count value are reset.

[0057] This embodiment means that the instantaneous drop of frequency must be continuous, which will eventually lead to off-grid. If the frequency quickly recovers to normal after a short drop, the system will immediately forget this short-term anomaly and continue to work normally. This effectively prevents false actions caused by single interference or measurement noise.

[0058] In some optional embodiments, in step S3, the frequency average value is corrected by the following formula:

[0059] ;

[0060] wherein u is the frequency average value before correction, is the frequency average value after correction, 、 、 is a weight value, and satisfies , is the dynamic weight of the i-th frequency value, , is the standard deviation of the queue frequency, is the i-th frequency sampling value in the queue, is the maximum value of the absolute value of the frequency change rate in the adjacent period in the current queue.

[0061] This embodiment gives a more accurate filtering method. The first term in the formula uses Gaussian weighting, so that the frequencies close to the average value have a larger weight, effectively suppressing abnormal value interference. The second term in the formula introduces the standard deviation, reflecting the degree of frequency fluctuation. The third term in the formula captures extreme cases of frequency changes, improving the response speed to sudden loads. The weight coefficients of the three terms can be dynamically adjusted according to the system state, realizing an intelligent anti-interference strategy. Through the optimization of the above mathematical model, the accuracy and reliability of the anti-interference method can be significantly improved.

[0062] The second aspect of the present application provides an anti-interference device for eliminating the sudden load off-grid of the variable frequency alternating current power supply system, which corresponds to the above method, mainly comprising:

[0063] An initialization module is used for system initialization, setting the over-frequency identification bit and the period count value, and the initial values are all set to zero;

[0064] A frequency signal acquisition module is used for monitoring whether the variable frequency alternating current power supply system has been put into grid work. If yes, the frequency signal output by the generator is periodically acquired and stored in a queue with a preset length N;

[0065] A frequency average value calculation module is used for filtering processing of the frequency signal in the queue to obtain the frequency average value for judgment;

[0066] a counting module, configured to compare the frequency average value with a preset off-grid frequency threshold value, if the frequency average value is lower than the off-grid frequency threshold value, set the over-frequency identification bit to 1 and accumulate the cycle count value; if the frequency average value is not lower than the off-grid frequency threshold value, reset the over-frequency identification bit and the cycle count value;

[0067] an off-grid control module, configured to control the generator main contactor to be disconnected when the over-frequency identification bit is 1 and the cycle count value reaches a threshold value, so that the power supply system exits the power grid, otherwise, detection of the next cycle is performed.

[0068] In some optional embodiments, the frequency signal acquisition module comprises:

[0069] a queue control unit, configured to remove the frequency value at the head of the queue from the queue and write the frequency value acquired in the current cycle to the tail of the queue by means of first-in first-out from the Nth acquisition cycle.

[0070] In some optional embodiments, the frequency average value calculation module comprises:

[0071] a queue-underflow calculation unit, configured to calculate the arithmetic average value of all the frequency values in the queue as the frequency average value when the number of the frequency values stored in the queue is less than N;

[0072] a queue-full calculation unit, configured to remove the minimum frequency value in the queue and then calculate the arithmetic average value of the remaining frequency values as the frequency average value when the number of the frequency values stored in the queue is equal to N.

[0073] In some optional embodiments, the counting module comprises a reset control unit, configured to reset the over-frequency identification bit and the cycle count value when the frequency average value is not lower than the off-grid frequency threshold value once during the period when the over-frequency identification bit is 1.

[0074] In some optional embodiments, the frequency average value calculation module further comprises a correction unit, configured to correct the frequency average value by the following formula:

[0075] ;

[0076] wherein u is the frequency average value before correction, is the frequency average value after correction, 、 、 is a weight value and satisfies , is the dynamic weight of the ith frequency value, , is the standard deviation of the queue frequency, For the i-th frequency sample value in the queue, It represents the maximum absolute value of the rate of change of frequency between adjacent periods in the current queue.

[0077] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for eliminating interference during sudden load disconnection in a variable frequency AC power supply system, characterized in that, Includes the following steps: Step S1: System initialization, set the overclocking flag and cycle count value, and set the initial values ​​to zero; Step S2: Monitor whether the variable frequency AC power system has been put into operation on the power grid. If so, periodically collect the frequency signal output by the generator and store it in a queue with a preset length of N. Step S3: Filter the frequency signals in the queue to obtain the average frequency for judgment; Step S4: Compare the average frequency with a preset decommissioning frequency threshold. If the average frequency is lower than the decommissioning frequency threshold, set the overclocking flag to 1 and increment the cycle count. If the average frequency is not lower than the decommissioning frequency threshold, reset the overclocking flag and the cycle count. Step S5: When the overclocking flag is 1 and the cycle count value reaches the threshold, control the generator main contactor to disconnect, so that the power system is disconnected from the power grid; otherwise, proceed with the detection of the next cycle.

2. The method for eliminating interference caused by sudden load disconnection from the grid in a frequency conversion AC power supply system according to claim 1, characterized in that, Step S2 further includes: Starting from the Nth acquisition cycle, the frequency value at the head of the queue is removed from the queue in a first-in-first-out manner, and the frequency value acquired in the current cycle is written to the tail of the queue.

3. The method for eliminating interference during sudden load disconnection of a frequency conversion AC power supply system according to claim 1, characterized in that, Step S3 further includes: When the number of frequency values ​​stored in the queue is less than N, the arithmetic mean of all frequency values ​​in the queue is calculated as the frequency average. When the number of frequency values ​​stored in the queue is equal to N, after removing the minimum frequency value from the queue, the arithmetic mean of the remaining frequency values ​​is calculated as the average frequency value.

4. The method for eliminating interference during sudden load disconnection of a frequency conversion AC power supply system according to claim 1, characterized in that, Step S4 further includes: if, during the overclocking flag position 1, there is a situation where the average frequency is not lower than the decommissioning frequency threshold, then the overclocking flag and the cycle count value are reset.

5. The method for eliminating interference during sudden load disconnection of a frequency conversion AC power supply system according to claim 1, characterized in that, In step S3, the average frequency is corrected using the following formula: ； Where u is the average frequency before correction. This is the corrected average frequency. , , Let be the weight value, and satisfy... , The dynamic weight for the i-th frequency value. , The standard deviation of the queue frequency, For the i-th frequency sample value in the queue, It represents the maximum absolute value of the rate of change of frequency between adjacent periods in the current queue.

6. An anti-interference device for eliminating sudden load disconnection from the grid in a variable frequency AC power supply system, characterized in that, include: The initialization module is used for system initialization, setting the overclocking flag and cycle count value, with the initial values ​​set to zero. The frequency signal acquisition module is used to monitor whether the variable frequency AC power system has been put into operation on the power grid. If so, it periodically acquires the frequency signal output by the generator and stores it in a queue with a preset length of N. The frequency average value calculation module is used to filter the frequency signals in the queue to obtain the frequency average value for judgment. The counting module is used to compare the average frequency with a preset decommissioning frequency threshold. If the average frequency is lower than the decommissioning frequency threshold, the overclocking flag is set to 1 and the cycle count is incremented. If the average frequency is not lower than the decommissioning frequency threshold, the overclocking flag and the cycle count are reset. The grid disconnection control module is used to control the generator main contactor to disconnect when the overclocking flag is 1 and the cycle count value reaches the threshold, so that the power system disconnects from the grid; otherwise, the detection of the next cycle is performed.

7. The anti-interference device for eliminating sudden load disconnection of a frequency conversion AC power supply system according to claim 6, characterized in that, The frequency signal acquisition module includes: The queue control unit is used to remove the frequency value at the head of the queue from the queue and write the frequency value collected in the current cycle to the tail of the queue, starting from the Nth acquisition cycle, using a first-in-first-out (FIFO) method.

8. The anti-interference device for eliminating sudden load disconnection of a frequency conversion AC power supply system according to claim 6, characterized in that, The frequency average value calculation module includes: The calculation unit when the queue is not full is used to calculate the arithmetic mean of all frequency values ​​in the queue as the frequency average when the number of frequency values ​​stored in the queue is less than N. The queue full calculation unit is used to calculate the arithmetic mean of the remaining frequency values ​​as the average frequency value after removing the minimum frequency value from the queue when the number of frequency values ​​stored in the queue is equal to N.

9. The anti-interference device for eliminating sudden load disconnection of a frequency conversion AC power supply system according to claim 6, characterized in that, The counting module includes a reset control unit, which is used to reset the overclocking flag bit and the period count value if, during the overclocking flag position 1, the average frequency value is not lower than the decommissioning frequency threshold.

10. The anti-interference device for eliminating sudden load disconnection of a frequency conversion AC power supply system according to claim 6, characterized in that, The frequency average calculation module further includes a correction unit, used to correct the frequency average using the following formula: ； Where u is the average frequency before correction. This is the corrected average frequency. , , Let be the weight value, and satisfy... , The dynamic weight for the i-th frequency value. , The standard deviation of the queue frequency, For the i-th frequency sample value in the queue, It represents the maximum absolute value of the rate of change of frequency between adjacent periods in the current queue.

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