A method for detecting single-phase loss of a variable-frequency compressor

Abstract

The present invention discloses a method for detecting phase loss in a variable frequency compressor. The method comprises the following steps: starting detection, initializing data, and setting the command electrical frequency to fref; sampling the three-phase current; performing principal component analysis on the three-phase current to determine if a phase loss has occurred; performing cross-analysis; and concluding whether a phase loss has occurred based on the cross-analysis results; and completing the detection. The method performs component analysis on the three-phase current using a Fourier analysis scheme. The analysis results are first subjected to principal component comparison analysis, then to pairwise cross-comparison analysis, and finally to DC quantity analysis, ultimately concluding whether a phase loss has occurred. The results are stable and applicable to both high and low current modes, eliminating the need for repeated threshold calibration, or even the need for threshold calibration at all.

Description

Technical Field

[0001] The invention belongs to the technical field of refrigerator control, and in particular relates to a method for detecting phase loss in a variable frequency compressor. Background Art

[0002] At present, phase loss detection is essential in variable frequency compressor control. When the compressor is running in a phase loss state, especially when one phase is missing, the compressor can continue to operate in most cases, but the phase current passing through the compressor is much larger than normal, and is generally accompanied by mechanical conditions such as compressor vibration. This will not only reduce the user experience, but also accelerate the mechanical loss of the compressor, shorten the life of the compressor, and ultimately affect the service life of the entire machine.

[0003] Currently, phase loss detection typically uses the following approach: Three-phase currents are monitored. If the current in a phase is consistently below a small threshold, this phase is considered to have experienced a phase loss. The principle is that when a phase is lost, no current should flow through the coil in that phase, resulting in a theoretical current value of zero.

[0004] The existing technology has the following shortcomings: In the event of a phase loss, the current value should theoretically be zero. However, in practice, the actual current measured is not zero due to various external factors, such as electromagnetic induction of the compressor coil, electromagnetic interference in the circuit, and sampling methods. Under these circumstances, setting the threshold is often difficult. If it is set too low, the phase loss may not be detected due to interference, while if it is set too high, a false alarm may occur when the compressor current is low. Furthermore, different compressors often have different operating currents under the same conditions, resulting in different required threshold values for different compressors. Therefore, the threshold often needs to be recalibrated for different compressors. Summary of the Invention

[0005] The object of the present invention is to provide a method for detecting phase loss in a variable frequency compressor. The method performs component analysis on the three-phase current through a Fourier analysis scheme, first performs principal component comparison analysis on the analysis results, then performs pairwise cross comparison analysis, and finally performs DC quantity analysis to finally conclude whether a phase loss occurs. The result is stable and applicable to both large and small current modes; there is no need to repeatedly calibrate the threshold, or even no need to calibrate the threshold.

[0006] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for detecting phase loss in a variable frequency compressor, comprising the following steps:

[0008] Stp1, start detection, initialize data, set the command electrical frequency to fref;

[0009] Stp2, sampling the three-phase current;

[0010] Stp3, principal component analysis, includes the following sub-steps:

[0011] SS01, perform discrete Fourier analysis on the current frequency point;

[0012] SS02, take the absolute value of the result and then limit it;

[0013] SS03, the maximum value fmax00 is obtained between 0.9 times the current frequency point and 1.1 times the current frequency point, and the frequency point is recorded as f00; the maximum value fmax01 is obtained between 0.5 times the current frequency point and 1.5 times the current frequency point, and the frequency point is recorded as f01;

[0014] SS04, judge f00 and f01, if f00 = f01, it is determined that there is no phase loss, otherwise it is determined that there is a phase loss;

[0015] Step 4, cross-analysis, includes the following sub-steps:

[0016] SS11, judge f20 and f10, if 0.9f20≤f10≤1.1f20, then go to step SS12, otherwise it is determined that there is a phase loss;

[0017] SS12, judging f20 and f30, if 0.9f20≤f30≤1.1f20, then proceed to step SS13, otherwise it is determined that a phase loss occurs;

[0018] SS13, judge f10 and f30, if 0.9f10≤f30≤1.1f10, it is determined that there is no phase loss, otherwise it is determined that there is a phase loss;

[0019] Among them, f10, f20 and f30 are the maximum values and corresponding frequency points of the three-phase current calculated in the frequency domain from 0.1 times fref to 1.1 times fref;

[0020] Step 5: Based on the cross-analysis results, it is concluded whether a phase loss occurs;

[0021] Stp6, complete the test.

[0022] Preferably, if two or more phases are missing in step Stp03, the current determination of phase missing is abandoned and the current process ends directly;

[0023] Preferably, if a phase loss occurs in step Stp03, the phase that is found to be missing is compared with the other two phases, and the comparison conditions are as follows:

[0024] 0.9f20 < f11 < 1.1f20, 0.9f30 < f11 < 1.1f30; When both conditions are not satisfied, step Stp04 is skipped and it is directly determined that the phase is missing, and a missing phase fault is output.

[0025] Where f11, f21, and f31 are the maximum values and the corresponding frequency points calculated in the frequency domain of the three-phase current from 0.5 times fref to 1.5 times fref respectively.

[0026] The present invention has the following beneficial effects:

[0027] The present invention analyzes the components of the three-phase current through a Fourier analysis scheme. First, a principal component comparison analysis is performed on the analysis results, then a pairwise cross-comparison analysis is performed, and finally a direct current analysis is performed. Finally, a conclusion on whether there is a missing phase is obtained. The result is stable and applicable to both large current and small current modes; there is no need to repeatedly calibrate the threshold, and even no need to calibrate the threshold.

[0028] Of course, any product implementing the present invention does not necessarily need to achieve all the above-mentioned advantages simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 A method for detecting missing phase of a variable frequency compressor according to the present invention;

[0031] Figure 2 A flowchart of the principal component analysis of three-phase current;

[0032] Figure 3 A flowchart of the cross-analysis of three-phase current. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] Please refer to Figure 1 As shown, the present invention is a method for detecting missing phase of a variable frequency compressor, including the following steps:

[0035] Stp1, start detection, initialize data, set the command electrical frequency to fref;

[0036] Stp2, sampling the three-phase current;

[0037] Stp3, such as Figure 2 As shown, principal component analysis is performed on the three-phase currents, including the following sub-steps:

[0038] SS01, perform discrete Fourier analysis on the current frequency point;

[0039] SS02, take the absolute value of the result and then limit it;

[0040] SS03, the maximum value fmax00 is obtained between 0.9 times the current frequency point and 1.1 times the current frequency point, and the frequency point is recorded as f00; the maximum value fmax01 is obtained between 0.5 times the current frequency point and 1.5 times the current frequency point, and the frequency point is recorded as f01;

[0041] SS04, judge f00 and f01, if f00 = f01, it is determined that there is no phase loss, otherwise it is determined that there is a phase loss;

[0042] Stp4, such as Figure 3 As shown, the three-phase currents are cross-analyzed in pairs, including the following sub-steps:

[0043] SS11, judge f20 and f10, if 0.9f20≤f10≤1.1f20, then go to step SS12, otherwise it is determined that there is a phase loss;

[0044] SS12, judging f20 and f30, if 0.9f20≤f30≤1.1f20, then proceed to step SS13, otherwise it is determined that a phase loss occurs;

[0045] SS13, judge f10 and f30, if 0.9f10≤f30≤1.1f10, it is determined that there is no phase loss, otherwise it is determined that there is a phase loss;

[0046] Among them, f10, f20 and f30 are the maximum values and corresponding frequency points of the three-phase current calculated in the frequency domain from 0.1 times fref to 1.1 times fref;

[0047] Step 5: Based on the cross-analysis results, it is concluded whether a phase loss occurs;

[0048] Stp6, complete the test.

[0049] Example 1:

[0050] like Figure 2As shown, in this embodiment, principal component analysis is performed on the three-phase currents respectively, and Fourier analysis is performed on the three-phase currents in a frequency domain from 0.5 times fref to 1.5 times fref at a certain frequency interval (such as 0.02 times fref).

[0051] The maximum value and the corresponding frequency point are calculated in the frequency domain from 0.1 times fref to 1.1 times fref, and are recorded as (fumax0, fu0), (fvmax0, fv0), and (fwmax0, fw0) respectively.

[0052] The maximum values and corresponding frequency points are calculated within the frequency domains of 0.5 to 0.9 and 1.1 to 1.5 times fref, and are recorded as (fumax, fu1), (fvmax1, fv1), and (fwmax1, fw1), respectively. For the same phase, if fu0 is greater than 2*fu1, the phase is considered to be present; otherwise, a phase is considered to be missing.

[0053] Example 2: This example based on Example 1 is an additional judgment case for phase loss, as shown below:

[0054] If two or more phases are missing in step Stp03, the current phase missing determination is abandoned and the current process is terminated directly without further phase missing determination.

[0055] Example 3: Based on Example 1

[0056] If a phase loss occurs in step Stp03, the following conditions are determined for the phase f11 where the phase loss occurs: 0.9f20 <f11<1.1f20、0.9f30<f11<1.1f30;

[0057] If a phase loss occurs in step Stp03, the following conditions are determined for the phase f21 where the phase loss occurs: 0.9f10 <f21<1.1f10、0.9f30<f21<1.1f30;

[0058] If a phase loss occurs in step Stp03, the following conditions are determined for the phase f31 where the phase loss occurs: 0.9f20 <f31<1.1f20、0.9f10<f31<1.1f10;

[0059] Among them, f11, f21 and f31 are the maximum values and corresponding frequency points of the three-phase current calculated in the frequency domain from 0.5 times fref to 1.5 times fref;

[0060] When both conditions are not met at the same time, it is directly determined that the phase is missing and the output phase is missing fault.

[0061] Assume that there is a phase loss in the w phase, and determine the following conditions: 0.9*fu0 < fw1 < 1.1*fu0, 0.9*fv0 < fw1 < 1.1*fv0; when both conditions are not satisfied, it is determined that there is a phase loss in the w phase.

[0062] It should be noted that in the above system embodiments, the included units are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be realized; in addition, the specific names of the functional units are only for the convenience of mutual distinction and do not limit the protection scope of the present invention.

[0063] In addition, those of ordinary skill in the art can understand that all or part of the steps in the methods of the above embodiments can be completed by instructing relevant hardware through a program, and the corresponding program can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk or optical disc, etc.

[0064] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for detecting phase loss in a variable frequency compressor, characterized in that: The steps include: Stp1, start detection, initialize data, set the command electrical frequency to fref; Stp2, sampling the three-phase current; Stp3, principal component analysis, includes the following sub-steps: SS01, perform discrete Fourier analysis on the current frequency point; SS02, take the absolute value of the result and then limit it; SS03, the maximum value fmax00 is obtained between 0.9 times the current frequency point and 1.1 times the current frequency point, and the frequency point is recorded as f00; the maximum value fmax01 is obtained between 0.5 times the current frequency point and 1.5 times the current frequency point, and the frequency point is recorded as f01; SS04, judge f00 and f01, if f00=f01, it is determined that there is no phase loss, otherwise it is determined that there is a phase loss; Step 4, cross-analysis, includes the following sub-steps: SS11, judge f20 and f10, if 0.9f20≤f10≤1.1f20, then go to step SS12, otherwise it is determined that there is a phase loss; SS12, judging f20 and f30, if 0.9f20≤f30≤1.1f20, then proceed to step SS13, otherwise it is determined that a phase loss occurs; SS13, judge f10 and f30, if 0.9f10≤f30≤1.1f10, it is determined that there is no phase loss, otherwise it is determined that there is a phase loss; Among them, f10, f20 and f30 are the maximum values and corresponding frequency points of the three-phase current calculated in the frequency domain from 0.1 times fref to 1.1 times fref; Step 5: Based on the cross-analysis results, it is concluded whether a phase loss occurs; Stp6, complete the test.

2. A method for detecting phase loss in a variable frequency compressor according to claim 1, characterized in that: If two or more phases are missing in step Stp3, the current determination of phase missing is abandoned and the current process ends directly.

3. The method for detecting phase loss in a variable frequency compressor according to claim 1, wherein: If a phase is missing in step Stp3, the phase missing is compared with the other two phases. The comparison conditions are as follows: 0.9f20 <f11<1.1f20、0.9f30<f11<1.1f30; When both conditions are not met at the same time, step Stp4 is skipped and the phase is directly determined to be missing, and a phase missing fault is output.

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