CN108279362B - Method for identifying turn-to-turn short circuit fault of rotor winding of marine double-fed motor - Google Patents

Abstract

Translated fromChinese

本发明涉及一种海上双馈电机转子绕组匝间短路故障辨识方法，针对双馈风机转子短路的特点，打破了以往的辨识参数受转差率影响较大的特点，引入磁链诊断，将转子绕组匝间短路故障引起的电压、电流两侧磁链观测差为故障特征量，将故障特征参数放大，该特征量可以精确识别双馈电机转子绕组匝间短路故障，且可以准确定位故障相，在获取特征量时滤除了转速测量误差，从而避免了测量误差对故障辨识的影响，以便及时做出处理，能可靠实现双馈电机转子绕组匝间短路早期故障辨识，提高双馈电机的使用寿命，避免灾难性故障的发生减少因故障造成的经济损失。

The invention relates to a fault identification method for short-circuit between turns of the rotor winding of an offshore doubly-fed generator. Aiming at the characteristics of the short-circuit of the rotor of the doubly-fed generator, it breaks the previous characteristics that the identification parameters are greatly affected by the slip rate. The observed difference between the voltage and current flux linkage on both sides of the winding inter-turn short-circuit fault is the fault characteristic quantity, and the fault characteristic parameter is amplified. This characteristic quantity can accurately identify the inter-turn short-circuit fault of the rotor winding of the DFIG, and can accurately locate the faulty phase. The rotational speed measurement error is filtered out when the characteristic quantity is obtained, thereby avoiding the influence of the measurement error on the fault identification, so as to deal with it in time, and can reliably realize the early fault identification of the inter-turn short circuit of the rotor winding of the doubly-fed motor, and improve the service life of the doubly-fed motor. , to avoid catastrophic failures and reduce economic losses caused by failures.

Description

Method for identifying turn-to-turn short circuit fault of rotor winding of marine double-fed motor

Technical Field

The invention relates to a motor fault identification technology, in particular to a method for identifying turn-to-turn short circuit faults of a rotor winding of an offshore double-fed motor based on bilateral flux linkage observation difference.

Background

In recent years, with the increasing prominence of global energy supply, energy safety, ecological environment and other problems, the development and utilization of renewable energy sources become important ways of energy strategies of all countries in the world and important directions for implementing sustainable development strategies. Especially, offshore wind power is favored by various coastal countries due to the characteristics of abundant offshore wind energy resources and proximity to a load center. China has 300 ten thousand square kilometers of Liaoning wide sea area, and offshore wind energy resources are rich, thus having good conditions for developing offshore wind power. By the middle of 2016, the global wind installed capacity has reached 456GW, with the total offshore wind installed capacity reaching 14384 MW. Accounting for 3.15% of the total installed capacity worldwide. However, the offshore wind power plant has a severe environment and complicated and changeable climate, and is far away from the land, so that the offshore wind turbine has high failure rate, inconvenient maintenance and large failure shutdown loss. Early fault identification of the wind power plant is therefore crucial in order to avoid unplanned shutdowns and to reduce maintenance costs of the wind power system.

The stator turn-to-turn short circuit has been widely noticed by researchers at home and abroad, and there are several common characteristic quantities such as negative sequence current, power spectrum, impedance change and the like when identifying the turn-to-turn short circuit fault of the double-fed asynchronous motor, however, the study on the turn-to-turn short circuit of the rotor winding is relatively less, because ① is influenced by the slip ratio of the double-fed motor, the slip power is smaller under the condition that the slip power is closer to the synchronous speed, the rotor turn-to-turn short circuit is smaller compared with fault information generated by the stator turn-to-turn short circuit, and fault characteristics are weaker, the fault characteristic quantity is not easy to extract due to the rotor winding rotating ②, so that difficulty is increased for diagnosing the rotor turn-to-turn short circuit, electric faults in the offshore wind turbine are discovered early stage, destructive accidents caused by the leak judgment of the fault initial stage are avoided, the researchers of li-he, li-mi, Jung J H and the like propose several characteristic quantities of the rotor turn-to-rotor turn short circuit of the double-fed asynchronous motor, and the rotor and the study on the rotor on-rotor frequency spectrum analysis of the double-fed rotor and the harmonic-fed rotor and the on-fed rotor instantaneous rotor power simulation method for realizing the analysis of the double-fed rotor and rotor harmonic-fed rotor short circuit.

Disclosure of Invention

The invention provides a method for identifying turn-to-turn short circuit faults of a rotor winding of an offshore double-fed motor aiming at the problems of few diagnosis methods and high difficulty of the rotor turn-to-turn short circuit of the double-fed asynchronous motor, and aims at the characteristic of the rotor short circuit of a double-fed fan, the characteristic that the conventional identification parameters are greatly influenced by the slip ratio is broken through, and flux linkage diagnosis is introduced. And amplifying the fault characteristic parameters through calculation of the flux linkage. A new fault characteristic quantity, namely a bilateral flux linkage observation difference is provided. Firstly, a mathematical model of the turn-to-turn short circuit fault of a rotor winding of the doubly-fed motor is established, and then a flux linkage difference expression under different working conditions is deduced according to the fault state of the motor; finally, simulation and experimental analysis verify that the double-side flux linkage observation difference provided by the method can reliably realize the early fault identification of the turn-to-turn short circuit of the rotor winding of the double-fed motor.

The technical scheme of the invention is as follows: a method for identifying turn-to-turn short circuit faults of a rotor winding of an offshore double-fed motor specifically comprises the following steps:

1) acquiring three-phase voltage, three-phase current and rotating speed of a stator and a rotor of the marine double-fed motor to be fault-identified;

2) and (3) calculating the effective value delta psi of the double-side flux linkage observation difference caused by the turn-to-turn short circuit fault of the rotor winding by using a flux linkage extraction method for the three-phase voltage and the three-phase current of the rotor:

wherein

Wherein △ psi_sThe difference between the observed value of current-side flux linkage and the observed value of voltage-side flux linkage of the stator winding is △ psi_rFor current-side flux linkage of rotor windingsThe difference value between the observed value and the voltage side flux linkage observed value, mu is the ratio of the number of short circuit turns to the total number of turns of the rotor winding, L_lsFor stator winding leakage inductance, L_lrFor leakage inductance of rotor winding, L_msMutual inductance value of stator and rotor, I_ar、I_br、I_crThe currents of the rotor a, b and c are respectively_as、I_bs、I_csThe current of the stator is A, B, C phase, theta is the included angle between the stator and the rotor, omega is the angular speed of the rotor current, A is the amplitude of the rotor current, and theta is_rA rotor current t is equal to 0 time phase angle;

3) the difference between the faulted phase and the non-faulted phase, delta psi, is calculated to filter out the measurement error, resulting in a fault severity factor ξ, assuming rotor phase a as the faulted phase,

4) judging whether the fault severity factor ξ reaches a fault early warning value, if so, executing the step 5), otherwise, returning to the step 1);

5) and the marine double-fed motor to be subjected to fault identification generates a stator winding turn-to-turn short circuit fault, and carries out fault processing. The flux linkage extraction method in the step 2) comprises the following specific steps:

201) acquiring three-phase signals of the offshore double-fed motor to be fault-identified, wherein the three-phase signals comprise stator three-phase voltage, rotor three-phase voltage, stator three-phase current, rotor three-phase current and rotor rotating speed;

202) calculating to obtain current side flux linkage psi according to stator and rotor three-phase current and motor intrinsic parameters₁；

Wherein the stator is from the inductive array

Rotor self-inductance array

Mutual inductance array of rotor to stator

203) Calculating to obtain voltage side magnetic linkage psi according to three-phase voltage, current and motor impedance parameters of the stator and the rotor₂：

In the formula, p is a differential sign;

204) calculating the observed difference value delta psi of each phase flux linkage₁-ψ₂；

205) 202) because the calculation is complex, introducing a rotor winding turn-to-turn short circuit fault working condition f during theoretical derivation, and assuming that a phase of the rotor is a fault phase, the fault working condition meets a double-fed motor fault equation:

ψ_ffor flux linkage matrices derived from fault equations

Voltage and current U of winding due to turn-to-turn short circuit_ar1、I_ar1Internal voltage and current generated by turn-to-turn short circuit are not easy to measure, and psi is ignored by the magnetic linkage matrix_ar1When the motor fails, the flux linkage change value of each phase calculated through the fault equation and the normal equation can be obtained according to the following formula:

206) for 203) an intermediate process rotor winding turn-to-turn short circuit fault condition f is also introduced,

let I_ar＝Asin(ωt+θ_r) (18)

Then

207) Subtracting the results of 205) and 206) can eliminate the intermediate process f, and obtain the required flux linkage difference of each phase:

the invention has the beneficial effects that: according to the method for identifying the turn-to-turn short circuit fault of the rotor winding of the offshore double-fed motor, the observation difference of the magnetic linkage at two sides of voltage and current caused by the turn-to-turn short circuit fault of the rotor winding is taken as the fault characteristic quantity, the characteristic quantity can accurately identify the turn-to-turn short circuit fault of the rotor winding of the double-fed motor, the fault phase can be accurately positioned, and the rotating speed measurement error is filtered when the characteristic quantity is obtained, so that the influence of the measurement error on the fault identification is avoided, the timely processing is facilitated, the service life of the double-fed motor is prolonged, the occurrence of catastrophic faults is avoided, and the economic loss caused by.

Drawings

FIG. 1 is a diagram showing a simulation result of flux linkage difference change of each phase when a double-fed motor of the present invention fails;

FIG. 2 is a flow chart of a method for identifying turn-to-turn short circuit faults of a rotor winding of an offshore double-fed motor according to the invention;

FIG. 3 is a diagram showing the experimental result of flux linkage difference change of each phase when the doubly-fed motor of the present invention fails;

FIG. 4 is a diagram showing a simulation result of flux linkage differences of each phase of the doubly-fed motor under a 1.43% fault degree according to the present invention;

FIG. 5 is a diagram showing the experimental result of flux linkage difference of each phase of the doubly-fed motor under the 3.57% fault degree of the present invention;

FIG. 6 is a diagram of a simulation result of doubly-fed motor fault phase flux linkage difference with measurement error filtered under different short-circuit coefficients.

Detailed Description

There are many methods for establishing a fault model of a doubly-fed motor, such as a multi-loop method, a finite element method, and the like. However, the structure is complex and is not beneficial to online diagnosis, so that the engineering is rarely applied to online diagnosis. The existing mathematical model of the stator a-phase turn-to-turn short circuit fault of the doubly-fed asynchronous motor under a three-phase static coordinate system (abc coordinate system) can accurately identify the early turn-to-turn short circuit fault, but is not suitable for the working condition of rotor short circuit.

Therefore, the existing stator winding turn-to-turn short circuit mathematical model is improved into a rotor winding turn-to-turn short circuit model. Assuming that the motor is in an ideal state of symmetrical magnetic circuit and uniform air gap distribution, a mathematical model containing a rotor winding fault short circuit loop is established, and a schematic diagram of a phase turn-to-turn short circuit of a rotor of the doubly-fed asynchronous motor is shown in fig. 1.

As shown in a diagram of a simulation result of flux linkage difference change of each phase when the doubly-fed motor fails in FIG. 1, the horizontal axis is time t/s, and the vertical axis is flux linkage difference/Wb. The left side is sequentially provided with a stator ABC three-phase flux linkage difference from top to bottom, and the right side is sequentially provided with a rotor ABC three-phase flux linkage difference from top to bottom. For the operation condition of fig. 1, the mathematical model of the turn-to-turn short circuit of the rotor winding of the doubly-fed motor is as follows:

in the formula, p is a differential sign;

U_s＝[U_asU_bsU_cs]^Tis a stator winding voltage matrix, U_as、U_bs、U_csStator A, B, C three-phase voltages respectively;

U_r＝[U_arU_ar1U_brU_cr]^Tis a rotor winding voltage matrix, U_ar、U_br、U_crThree-phase voltages of rotor a, b and c, U_ar1Voltage of winding of turn-to-turn short circuit part;

R_s＝R_sdiag[1 1 1]a stator winding resistance matrix;

R_r＝R_rdiag[1-μ μ 1 1]a rotor winding resistance matrix;

R_ris the rotor resistance; r_sIs a stator resistor;

ψ_s＝[ψ_asψ_bsψ_cs]t is stator winding flux linkage matrix psi_as、ψ_bs、ψ_csStator A, B, C three-phase flux linkage respectively;

ψ_r＝[(1-μ)ψ_arμψ_arψ_brψ_cr]for a rotor winding flux matrix, psi_ar、ψ_br、ψ_crThe three-phase magnetic flux linkages of the rotors a, b and c are respectively, and mu is a short-circuit coefficient, namely the ratio of the number of short-circuit turns to the total number of turns of the rotor winding;

I_s＝[I_asI_bsI_cs]^Tis a stator winding current matrix, I_as、I_bs、I_csStator A, B, C three-phase current;

I_r＝[I_arI_ar-I_fI_brI_cr]^Tis a rotor winding current matrix, I_ae、I_br、I_crThree-phase currents of rotors a, b, c, I_fIs the rotor short circuit current;

stator self-inductance array:

rotor self-inductance array:

mutual inductance array of rotor to stator:

wherein L is_lsFor stator winding leakage inductance, L_lrFor leakage inductance of rotor winding, L_msThe mutual inductance value of the stator and the rotor is theta, which is the included angle of the stator and the rotor.

In order to quickly detect and identify the turn-to-turn short circuit fault, a method for observing the difference of the bilateral magnetic linkage is provided. And establishing a motor dynamic model in a normal state, comparing the motor dynamic model with the flux linkage difference of the fault double-fed motor to obtain the flux linkage observation difference at two sides, and filtering the flux linkage observation difference to remove measurement errors so as to identify the fault.

Detecting three-phase currents and rotating speeds of the stator and the rotor, and calculating a current side flux linkage observed value psi according to the following formula₁：

Wherein the stator is from the inductive array

Rotor self-inductance array

Mutual inductance array of rotor to stator

θ_rThe phase angle at the moment when the rotor current t is equal to 0, and theta is equal to theta_r。

Detecting three-phase voltage and current of stator and rotor, and calculating differential p psi of voltage side flux linkage observed value by the following formula₂：

In the formula, p is a differential sign; for p psi₂Integrating to obtain voltage measurement magnetic chain observation value psi₂。

Calculating the observed difference value delta psi of each phase flux linkage₁-ψ₂；

Wherein

△ψ_sThe difference between the observed value of current-side flux linkage and the observed value of voltage-side flux linkage of the stator winding is △ psi_rThe difference value of the flux linkage observed value on the current side of the rotor winding and the flux linkage observed value on the voltage side is shown, theta is the included angle of the stator and the rotor, omega is the angular velocity of the rotor current, and A is the amplitude of the rotor current.

It can be seen that: each phase flux linkage is related to a short-circuit coefficient and a short-circuit current, the short-circuit current is mainly influenced by the short-circuit coefficient and a short-circuit additional resistance, the magnitude of flux linkage difference is mainly related to the short-circuit coefficient on the assumption that the short-circuit additional resistance is unchanged, and the larger the short-circuit coefficient is, the larger the flux linkage difference value is.

When the rotor A phase fails, the flux linkage change rules of all phases of the stator are the same; the rotor a phase flux linkage is clearly distinguished from the other phase changes. The fault characteristic quantity can distinguish and determine the rotor fault and can accurately position the fault phase, so the fault characteristic quantity is used for diagnosing the turn-to-turn short circuit fault of the rotor.

Considering the parameter change of the motor influenced by the environment in engineering and the error of signal detection, the flux linkage difference value when the motor is normal is not zero. If the flux linkage difference is directly used as a fault criterion, the accuracy of fault judgment is possibly influenced. Therefore, in order to ensure the reliability and accuracy of the diagnosis result, the initial error of the flux linkage difference needs to be filtered.

Calculate the difference between the faulted phase and the non-faulted phase Δ ψ to filter out the measurement error, resulting in a fault severity factor ξ (assuming rotor phase a is the faulted phase)

Therefore, as shown in fig. 2, a flowchart of a method for identifying a turn-to-turn short circuit fault of a stator winding of an offshore doubly-fed motor according to the present invention is shown, and the method includes the following steps:

step 1: acquiring three-phase voltage, three-phase current and rotating speed of a stator and a rotor of the marine double-fed motor to be fault-identified;

step 2: calculating the rotor three-phase voltage and the rotor three-phase current by a flux linkage extraction method to obtain a bilateral flux linkage observation difference effective value delta psi caused by the turn-to-turn short circuit fault of a rotor winding:

wherein

And 3, calculating the difference between the fault phase and the non-fault phase delta psi to filter out measurement errors to obtain a fault severity factor ξ (assuming that the rotor a phase is the fault phase)

Step 4, judging whether the fault severity factor ξ reaches a fault early warning value, if so, executing thestep 5, otherwise, returning to thestep 1;

and 5: and the marine double-fed motor to be subjected to fault identification generates a stator winding turn-to-turn short circuit fault, and carries out fault processing.

Thestep 2 specifically comprises the following steps:

(201) acquiring three-phase signals of the offshore double-fed motor to be fault-identified, wherein the three-phase signals comprise stator three-phase voltage, rotor three-phase voltage, stator three-phase current, rotor three-phase current and rotor rotating speed;

(202) calculating to obtain a current side magnetic linkage psi according to the three-phase currents of the stator and the rotor and the intrinsic parameters (leakage inductance, mutual inductance and the like) of the motor₁；

Wherein

(203) Calculating to obtain voltage side magnetic linkage psi according to three-phase voltage, current and motor impedance parameters of the stator and the rotor₂；

In the formula, p is a differential sign;

(204) calculating the observed difference value delta psi of each phase flux linkage₁-ψ₂；

(205) Wherein (202) because of the complex calculation, the turn-to-turn short circuit fault working condition f of the rotor winding is introduced in theoretical derivation, (assuming that the a phase of the rotor is a fault phase)

The fault working condition meets the fault equation of the doubly-fed motor:

ψ_ffor flux linkage matrices derived from fault equations

Voltage and current U of winding due to turn-to-turn short circuit_ar1、I_ar1Internal voltage and current generated by turn-to-turn short circuit are not easy to measure, and a fault equation (magnetic linkage matrix neglects psi) is passed when the motor is in fault_ar1) The flux linkage change value of each phase calculated by the normal equation can be obtained by the following formula:

(206) aiming at (203) the condition f of turn-to-turn short circuit fault of the rotor winding in the middle process is also introduced,

let I_ar＝Asin(ωt+θ) (18)

Then

(207) The intermediate process f can be eliminated by subtracting the results of 205 and 206, and the required flux linkage difference of each phase is obtained:

aiming at simulation and experiment without filtering error processing, the working condition is that the grid voltage is symmetrical three-phase voltage, the rotor slip is 10 percent, the sampling period Ts is 50 mu s during signal measurement, the active power of the stator is given as-3000W (the power flowing into the motor is taken as the positive direction) during normal work, and the reactive power is given as 0_varWhen in simulation, the motor short-circuit coefficient is t equal to 5When s is changed from 0.0143 to 0.0357, the same type of fault occurs when t is about 6.25s in experiments, in order to protect experimental equipment, the system is derated to operate in fault, namely, when turn-to-turn short circuit fault occurs, the active power of a stator is given to-2700W, and the reactive power is given to 0_var. The simulation and experiment results are shown in fig. 1 and 3.

As can be seen from fig. 1 and 3, the simulation is substantially consistent with the experimental results. Compared with a formula, the three-phase flux linkage difference amplitude of the stator is basically consistent; the rotor fault phase is obviously different from other phases, and the amplitude phase angle of the rotor non-fault phase is consistent and is obviously smaller than that of the fault phase. Simulation and experimental results prove the correctness of the theoretical derivation.

Fig. 4 and 5 show the simulated and experimental flux linkage differences under different fault severity degrees. Due to the limitation of experimental conditions (the rotor has only two short-circuit taps), the experiment can only realize the simulation of two fault degrees of 1.43% and 3.57%.

Because simulation aims at an ideal motor, and the parameters of the real motor are influenced by the operating environment and measurement errors, the flux linkage difference value obtained by the experiment is slightly larger than a simulation ideal value. But the change rule of the two is consistent.

The correctness of the fault model and the mathematical derivation of the fault characteristic quantity is verified by the aid of the method shown in the figures 1 and 3, and the method can be used for distinguishing and determining turn-to-turn short circuit faults of rotor windings and accurately positioning fault phases. The method can be suitable for early diagnosis of the turn-to-turn short circuit of the rotor winding.

Fig. 6 is a simulation result of filtering out errors by using an equation (9) when a detection error exists in a rotating speed signal, and it can be seen that a fault threshold of a fault severity factor ξ is set to be 0.005Wb, so that short circuits with more than 2 turns can be accurately identified, and misjudgment caused by over sensitivity is avoided.

In summary, by eliminating the influence of the inherent error, the diagnosis method provided herein can accurately identify the turn-to-turn short circuit fault of the rotor winding of the doubly-fed motor, can accurately locate the fault phase, and has robustness to the measurement error of the rotating speed signal.

Claims (2)

1. A method for identifying turn-to-turn short circuit faults of a rotor winding of an offshore double-fed motor is characterized by comprising the following steps:

1) acquiring three-phase voltage, three-phase current and rotating speed of a stator and a rotor of the marine double-fed motor to be fault-identified;

2) and (3) calculating the effective value delta psi of the double-side flux linkage observation difference caused by the turn-to-turn short circuit fault of the rotor winding by using a flux linkage extraction method for the three-phase voltage and the three-phase current of the rotor:

wherein

Wherein △ psi_sThe difference between the observed value of current-side flux linkage and the observed value of voltage-side flux linkage of the stator winding is △ psi_rIs the difference value of the flux linkage observed value of the current side and the flux linkage observed value of the voltage side of the rotor winding, mu is the ratio of the number of short circuit turns to the total number of turns of the rotor winding, I_fFor short-circuit currents of the rotor, L_lrFor leakage inductance of rotor winding, L_srFor mutual inductance value of stator and rotor, I_ar、I_br、I_crThe currents of the rotor a, b and c are respectively_as、I_bs、I_csThe current of the stator is A, B, C phase, theta is the included angle between the stator and the rotor, omega is the angular speed of the rotor current, A is the amplitude of the rotor current, and theta is_rA rotor current t is equal to 0 time phase angle;

3) the difference between the faulted phase and the non-faulted phase, delta psi, is calculated to filter out the measurement error, resulting in a fault severity factor ξ, assuming rotor phase a as the faulted phase,

4) judging whether the fault severity factor ξ reaches a fault early warning value, if so, executing the step 5), otherwise, returning to the step 1);

5) and the marine double-fed motor to be subjected to fault identification generates a rotor winding turn-to-turn short circuit fault and carries out fault processing.

2. The method for identifying turn-to-turn short circuit faults of the marine doubly-fed motor rotor winding according to claim 1, wherein the flux linkage extraction method in the step 2) comprises the following specific steps:

201) acquiring three-phase signals of the offshore double-fed motor to be fault-identified, wherein the three-phase signals comprise stator three-phase voltage, rotor three-phase voltage, stator three-phase current, rotor three-phase current and rotor rotating speed;

202) calculating to obtain current side flux linkage psi according to stator and rotor three-phase current and motor intrinsic parameters₁；

Wherein the stator is from the inductive array

Rotor self-inductance array

Mutual inductance array of rotor to stator

203) Calculating to obtain voltage side magnetic linkage psi according to three-phase voltage, current and motor impedance parameters of the stator and the rotor₂：

In the formula, p is a differential sign;

204) calculating the observed difference value delta psi of each phase flux linkage₁-ψ₂；

205) 202) because the calculation is complex, introducing a rotor winding turn-to-turn short circuit fault working condition f during theoretical derivation, and assuming that a phase of the rotor is a fault phase, the fault working condition meets a double-fed motor fault equation:

when the motor fails, the flux linkage change value of each phase calculated through a fault equation and a normal equation is obtained according to the following formula:

206) for 203) an intermediate process rotor winding turn-to-turn short circuit fault condition f is also introduced,

let I_ar＝Asin(ωt+θ_r)

Then

207) Subtracting the results of 205) and 206) can eliminate the intermediate process f, and obtain the required flux linkage difference of each phase:

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