CN105842577A - Power converter open-circuit fault diagnosis method in AC variable-frequency speed regulation system - Google Patents

Abstract

The invention discloses a method for diagnosing open-circuit faults of a power converter in a frequency conversion speed regulation system, comprising: determining the array length of a complete current cycle sampling array according to a given speed; calculating the variance of the three-phase current sampling array, and determining the relative Variance; calculate the skewness of the three-current sampling array; compare the relative variance with two thresholds to determine whether an open-circuit fault occurs and the bridge arm where the fault occurs; if a single-tube open-circuit fault occurs, then determine whether the fault occurs based on the skewness Top tube or down tube. The present invention calculates the variance Var of the three current sampling arrays by determining the length L of the periodic current signal array, and then calculates the size of the relative variance ε _x , and judges whether there is a fault according to the obtained relative variance ε _x . When a fault occurs, the position of the faulty power tube is further judged by using the skewness γ _x , which improves the accuracy of the fault diagnosis of the power converter of the AC variable frequency speed control system, and the algorithm is simple and easy to implement.

Description

A method for diagnosing open-circuit faults of power converters in AC frequency conversion speed regulation systems

technical field

The invention belongs to the technical field of power converter fault diagnosis, and in particular relates to a power converter open circuit fault diagnosis method in an AC frequency conversion speed regulation system.

Background technique

In the fields of industrial manufacturing, aerospace, transportation, etc., frequency conversion speed regulation systems driven by power converters have been widely used due to their advantages such as high energy density and high energy efficiency. Figure 1 is a traditional three-phase frequency conversion speed regulation system and its basic structure diagram. As the safety and reliability requirements of these systems are getting higher and higher, it is particularly important to detect and locate faults in the components of the system, especially the power converter, which is the most prone to failure. Traditional fault diagnosis methods are mainly divided into two types: one is to directly detect the conduction voltage drop of the power converter or measure the temperature of the power converter by adding sensors, this method can quickly locate the system fault, and this method It is necessary to add hardware such as sensors, which increases the system overhead while diagnosing power tube faults; the second is to use the existing sensor resources in the frequency conversion speed control system to detect faults by comparing the relevant characteristic signals after the fault with the deviation value under normal conditions. Methods of diagnosis and localization. In the second algorithm, the fault diagnosis method based on intelligent classification is commonly used at present, but this method is prone to misjudgment, its application is limited, and it is slightly complicated, requiring a large amount of data for training; the second is to use the correlation coefficient , Euclidean distance, vector angle cosine and Hausdorff distance and other algorithms for fault diagnosis, these methods are slightly complicated in calculation, and in practical applications, because they occupy too many processor resources, they are not economical to implement.

Contents of the invention

In view of the above defects of the prior art, the technical problem to be solved by the present invention is to provide a method for diagnosing open-circuit faults of power converters in AC variable frequency speed regulation systems. By analyzing the distribution of current probability density curves under normal conditions and fault conditions, Using the variance and skewness of the current sampling sequence to measure the similarity, it is more convenient to solve the diagnosis problem when the open circuit fault occurs in the power converter of the variable frequency speed control system.

The invention provides a method for diagnosing an open-circuit fault of a power converter in an AC frequency conversion speed regulation system, which includes the following steps:

S1, determine the length of the periodic current signal array, use where T _s is the sampling period of the controller, p is the number of pole pairs of the motor, and ω ^* is the speed of the motor;

S2. At each sampling moment, write down the current sampling value to obtain three current sampling arrays A(L), B(L), and C(L); calculate the variance Var _x =σ ² = of the three current sampling arrays EX ² -μ ² , where x∈{a,b,c} represent the three phases a, b, and c respectively, and X is one of the three current sampling arrays; then calculate the size of the relative variance

S3. Calculate the skewness of the three current sampling arrays where x∈{a,b,c};

S4. According to the obtained relative variance ε _x , judge whether there is a fault. If there is a fault, it is necessary to judge whether the bridge arm and the fault type are single-pipe fault or double-pipe fault; when a single-pipe fault occurs, then Use the skewness γ _x to further judge the position of the faulty power tube.

Further, in the step S4: according to the calculated relative variance, then there is

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; \&ap;</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; \&ap;</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>& \left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; \&ap;</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right.\\ \mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ,</span>& \left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; \&ap;</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right.\end{array}\right.$

If the value of f _l is 0, then phase x is healthy; if it is 1, there is one tube fault in phase x; if it is 2, then there are two faulty tubes in phase x; if there is one power tube fault, use the skewness γ _x Further determine the location of the fault;

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right.$

When the value of f _s is 0, the lower tube of x-phase is faulty, and when the value of f _s is 1, the upper tube of x-phase is faulty, so as to determine the location of the fault.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

The method for diagnosing the open-circuit fault of the power converter in the AC variable frequency speed regulation system of the present invention calculates the variance Var of the three current sampling arrays by determining the length L of the periodic current signal array, and then calculates the size of the relative variance ε _x , according to the obtained The relative variance ε _x judges whether there is a fault. When a single tube fault occurs, the skewness γ _x is used to further judge the position of the faulty power tube, which improves the accuracy of the fault diagnosis of the power converter of the AC variable frequency speed control system, and the algorithm Simple and easy to implement.

Description of drawings

Figure 1 is a traditional three-phase frequency conversion speed regulation system and its basic structure diagram.

Fig. 2 is a flow chart of a method for diagnosing an open-circuit fault of a power converter in an AC frequency conversion speed regulation system according to the present invention.

detailed description

The specific implementation of the present invention will be described in detail below in conjunction with the accompanying drawings. As a part of this specification, the principles of the present invention will be described through examples. Other aspects, features and advantages of the present invention will become clear through the detailed description. In the referenced drawings, the same reference numerals are used for the same or similar components in different drawings. In order to make the present invention easier to understand, specific embodiments of the present invention will be further described below.

As shown in Figure 2, the power converter open circuit fault diagnosis method in the AC frequency conversion speed regulation system of the present invention comprises the following steps:

S1, determine the length of the periodic current signal array, use where T _s is the sampling period of the controller, p is the number of pole pairs of the motor, and ω ^* is the speed of the motor.

S2. At each sampling moment, write down the current sampling value to obtain three current sampling arrays A(L), B(L), and C(L); calculate the variance Var _x =σ ² = of the three current sampling arrays EX ² -μ ² , where x∈{a,b,c} represent the three phases a, b, and c respectively, and X is one of the three current sampling arrays; then calculate the size of the relative variance

S3. Calculate the skewness of the three current sampling arrays where x∈{a,b,c}, using the formula Calculate the magnitude of the skewness of the current sampling sequence.

S4. According to the obtained relative variance ε _x , judge whether there is a fault. If there is a fault, it is necessary to judge whether the bridge arm and the fault type are single-pipe fault or double-pipe fault; when a single-pipe fault occurs, then Use the skewness γ _x to further judge the position of the faulty power tube.

According to the calculated relative variance, we have

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; \&ap;</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; \&ap;</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>& \left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; \&ap;</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right.\\ \mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ,</span>& \left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; \&ap;</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; \&ap;</span>\mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right.\end{array}\right.$

If the value of f _l is 0, then phase x is healthy; if it is 1, phase x has one faulty tube; if it is 2, phase x has two faulty tubes. If there is a power tube failure, use the skewness γ _x to further judge the location of the failure

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& {\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; ></span>\mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right.$

When the f _s value is 0, the lower tube of the x phase is faulty, and when the f _s value is 1, the upper tube of the x phase is faulty. From this, it is determined which one or two of T ₁ , T ₂ , T ₃ , T ₄ , T ₅ , T ₆ where the fault occurs, see Table I.

Table 1 is the fault type table of the detection method.

Table I

According to the given speed, the present invention determines the array length of a complete current cycle sampling; calculates the variance of the three-phase current sampling array, and determines the relative variance; calculates the skewness of the three-current sampling array; compares the relative variance with two thresholds Determine whether an open-circuit fault occurs and the bridge arm where the fault occurs; if a single-tube open-circuit fault occurs, then determine whether the fault occurs on the upper tube or the lower tube according to the deflection.

The method for diagnosing the open-circuit fault of the power converter in the AC variable frequency speed regulation system of the present invention calculates the variance Var of the three current sampling arrays by determining the length L of the periodic current signal array, and then calculates the size of the relative variance ε _x , according to the obtained The relative variance ε _x judges whether there is a fault. When a single tube fault occurs, the skewness γ _x is used to further judge the position of the faulty power tube, which improves the accuracy of the fault diagnosis of the power converter of the AC variable frequency speed control system, and the algorithm Simple and easy to implement.

Claims (2)

1. power inverter open fault diagnostic method in an AC variable-frequency speed regulation system, it is characterised in that include following step Rapid:

S1, determine the length of periodic current signal array, useRepresent, wherein T_sIt it is the sampling week of controller Phase, p is the number of pole-pairs of motor, ω^*It is the speed of motor；

S2, in each sampling instant, write down current flow sampled value, obtain three current sample arrays A (L), B (L), C (L)； Calculate variance Var of three current sample arrays_x=σ²=EX²-μ², wherein { a, b, c} represent a, b, c three-phase to x ∈ respectively, and X is In three current sample arrays one；Then contra extent is calculated

S3, the degree of bias of three current sample arrays of calculatingWherein x ∈ a, b, c}；

S4, relative variance ε according to gained_xJudge whether faulty generation, if faulty generation, also failure judgement to send out accordingly Raw brachium pontis and fault type are single tube fault or two-tube fault；When there is single tube fault, then utilize degree of bias γ_xFurther The position of failure judgement power tube.

Power inverter open fault diagnostic method in AC variable-frequency speed regulation system the most according to claim 1, its feature It is, in described step S4: according to the relative variance calculated, then have

$f_l=\left\{\begin{array}{cc}0,& {\mathrm{\&epsiv;}}_x\&ap;{\mathrm{\&epsiv;}}_y\&ap;{\mathrm{\&epsiv;}}_z\&ap;1\\ 1,& \left\{\begin{array}{c}{P}_1<{\mathrm{\&epsiv;}}_x<P_2\\ {\mathrm{\&epsiv;}}_y\&ap;{\mathrm{\&epsiv;}}_z\&ap;1\end{array}\right.\\ 2,& \left\{\begin{array}{c}{\mathrm{\&epsiv;}}_x<P_1\\ {\mathrm{\&epsiv;}}_y\&ap;{\mathrm{\&epsiv;}}_z\&ap;1\end{array}\right.\end{array}\right.$

If f_lValue is 0, then x phase is healthy；If 1, then x phase has a pipe fault；If 2, then x phase has two fault pipes；If having one Individual power tube fault, then utilize degree of bias γ_xDetermine whether location of fault；

$f_s=\left\{\begin{array}{cc}1,& {\mathrm{\&gamma;}}_x<0\\ 0,& {\mathrm{\&gamma;}}_x>0\end{array}\right.$

Work as f_sValue is 0, then x phase down tube fault, works as f_sValue is 1, then pipe fault in x phase, thereby determines that the position that fault occurs.