CN104280682B - A kind of rotor method for diagnosing faults based on Field orientable control - Google Patents

Abstract

The invention discloses a kind of rotor method for diagnosing faults based on Field orientable control, the method passes through the torque current being had calculated that in controller, calculate the amplitude of its DC component and its AC compounent, and then the rotor broken bar number of motor is obtained, so as to realize the accurate detection and quantization of rotor broken strip.The inventive method does not need extra hardware, will not increase system cost；Simultaneously, diagnostic result changes to motor speed and load torque change is insensitive, and remaining parameter that process need not be in addition to the total sliver number of rotor is diagnosed, thus diagnostic result has robustness higher, is particularly suitable for the electric system of orientation on rotor flux.

Description

A kind of rotor method for diagnosing faults based on Field orientable control

Technical field

The invention belongs to Diagnosing Faults of Electrical technical field, and in particular to a kind of rotor based on Field orientable control Method for diagnosing faults.

Background technology

Induction machine has the advantages that simple structure, cheap and be widely used in industrial and agricultural production. However, the problems such as due to design structure and manufacturing process, motor prolonged overload or Fraquent start, braking with Afterwards, in fact it could happen that rotor cage bar is broken.After rotor bar fracture, can be increased adjacent to the electric current of sliver, stress increases, Broken bar fault will further expand, and many broken strips occur, motor is exerted oneself reduction, rotor be there is also when serious and be swept thorax and is spoilt Stator, causes whole machine to be scrapped.Therefore, early stage rotor fault occurs, just fault detect out and to quantify its failure serious Degree, with on-call maintenance accordingly, can avoid the generation of hang-up and serious accident, and tool has very great significance.

When motor hangs over electric online operation, can by detect the rotating speed of motor, noise, electric current, electromagnetic torque, part or Person's whole instantaneous powers, the method such as magnetic flux realize the Rotor Fault Diagnosis of motor, and its fault detect and quantization method base This is perfect.

And with the development of Power Electronic Technique, the frequency control of inverter and motor is widely used.This When, the fault diagnosis of motor also needs to consider change, the influence of the strong noise, closed loop of voltage x current of electric moter voltage power frequency And controller bandwidth the problems such as.Now, original method for diagnosing faults for power network electric power thus supplied can part or complete Full failure.Need especially to be studied for inverter power supply and closed-loop control situation for this.To high performance motor control Occasion, Field orientable control (Field OrientedControl, FOC) is the most frequently used control method, and it is become by coordinate Change, the asynchronous machine of a reality is transformed into virtual Equivalent DC motor, realize the dynamic decoupling of magnetic field and torque, obtain Obtained excellent torque dynamic control performance.

It is existing several authors proposed certain methods, such as referential coordinate transformation method, Vienna for this application scenario Observation procedure (Vienna Monitoring Method, VMM), using controller built-in variable (such as rotor flux, exciting current Deng) and virtual current technical method.However, first three class method only realizes qualitative analysis, without to rotor failure Realize quantifying, although and virtual current technical method can realize that failure quantifies, this method not only calculates complexity, and needs The more parameter of electric machine is used, and some of them parameter such as rotor time constant is difficult accurate acquisition, this is to rotor event Barrier diagnostic result has a certain impact.

The content of the invention

For the above-mentioned technical problem existing for prior art, the invention provides a kind of electricity based on Field orientable control Machine rotor method for diagnosing faults, the rotor that the method only needs to the torque current and motor being had calculated that in electric machine controller is led Bar number, it is possible to realize the Rotor Fault Diagnosis of motor, and accurate quantification motor fault severity level.

A kind of rotor method for diagnosing faults based on Field orientable control, comprises the following steps：

(1) the threephase stator electric current of motor is gathered, it is correspondence to be converted by dq and extract d shaft currents therein and q shaft currents The exciting current and torque current of motor；

(2) exciting current according to obtains the rotor flux of motor by flux observation algorithm, and then according to motor Rotor flux and torque current, be calculated the slip frequency f of motor_s；

(3) LPF is carried out to described torque current, filtered torque current is carried out with time window T then Moving average filter obtains the DC component of torque current,

(4) described torque current is made to subtract the AC compounent that its DC component obtains torque current, and then according to turning Difference frequency f_sGoerzel algorithm treatment is carried out to torque current AC compounent, the amplitude of torque current AC compounent is obtained；

(5) according to torque current DC component and the amplitude of torque current AC compounent, judge whether rotor is deposited In broken strip and broken strip radical.

Motor slip frequency f is calculated by flux observation algorithm in described step (2)_sTo implement process as follows：

First, the rotor flux ψ of motor is calculated according to following formula_r；

Wherein：L_mAnd i_sdThe respectively magnetizing inductance and exciting current of motor, L_rAnd R_rRespectively the inductor rotor of motor and Rotor resistance, s is Laplace operator；

Then, the slip angular frequency ω of motor is calculated according to following formula_s；

Wherein：i_sqIt is the torque current of motor；

Finally, according to f_s=ω_s/ 2 π determine the slip frequency f of motor_s。

Preferably, in described step (3) by following quadravalence butterworth filter transfer function H (z) to torque current LPF is carried out, to eliminate the switching harmonics in torque current and other noises；

Wherein：g₁、g₂、a₁、a₂、a₃And a₄Filtering parameter is, z is transform operator.

Preferably, before carrying out moving average filter to filtered torque current in described step (3), first to the torque Electric current carries out down-sampled；After torque current is low-pass filtered, the highest frequency of its useful signal is very low, and too high sampling is frequently Rate is nonsensical, while the down-sampled computation burden that can reduce controller.

The method for carrying out Goerzel algorithm treatment to torque current AC compounent in described step (4) is as follows：

First, the sampled point number in signal length N i.e. duration of torque current AC compounent is determined with certain time length；

Then, the torque current AC compounent N-1 and the N-2 signal of sampled point is tried to achieve according to following formula iteration Value s (N-1) and s (N-2)：

S (i)=x (i)+2cos (2 π ω) s (i-1)-s (i-2) i=0,1 ... N-1

Wherein：S (i), s (i-1) and s (i-2) are respectively i-th, the i-th -1 and the i-th -2 of torque current AC compounent The signal value of sampled point, x (i) is the current value of torque current AC compounent ith sample point, ω=4 π f_sT_s, T_sIt is torque electricity The sampling period of stream；

Finally, according to the amplitude of following formula calculating torque current alternating component：

Wherein：It is the amplitude of torque current AC compounent.

Judge that rotor whether there is broken strip and broken strip radical according to below equation in described step (5)：

Wherein：M is the broken strip radical of rotor, and M is the sliver number of rotor,It is torque current AC compounent Amplitude,It is the DC component of torque current.

The present invention calculates the width of its DC component and its AC compounent by the torque current being had calculated that in controller Value, and then the rotor broken bar number of motor is obtained, so as to realize the accurate detection and quantization of rotor broken strip；The method is not required to Extra hardware is wanted, system cost will not be increased；Meanwhile, diagnostic result changes to motor speed and load torque change is unwise Sense, and remaining parameter that diagnosis process need not be in addition to the total sliver number of rotor, thus diagnostic result has robustness higher, It is particularly suitable for the electric system of orientation on rotor flux.

Brief description of the drawings

Fig. 1 is the system schematic of the direct orientation on rotor flux of induction machine and its fault diagnosis.

Fig. 2 is the current model schematic diagram of calculating rotor magnetic linkage under MT coordinate systems.

Fig. 3 is the schematic flow sheet of rotor fault diagnosis of the present invention.

Diagnostic result figure when Fig. 4 is rated speed, different loads torque and different broken strip radicals.

Diagnostic result figure when Fig. 5 is a broken strip, different loads torque and different given rotating speeds.

Specific embodiment

In order to more specifically describe the present invention, below in conjunction with the accompanying drawings and specific embodiment is to technical scheme It is described in detail.

Fig. 1 gives one and is applied to the direct orientation on rotor flux of induction machine and its fault diagnosis system 100 Schematic diagram.The system includes but is not limited to dc bus 101, inverter module 102, current sensor 103, voltage sensor 104th, induction machine 105, tachogenerator 106, control module 110 and Rotor Fault Diagnosis module 130.

In strong power part, the front end of DC bus sections 101 is generally three-phase alternating-current supply and uncontrollable rectifier circuit.It is logical Cross 101 obtain more satisfactory DC voltage after, by voltage source inverter module 102 for threephase asynchronous machine 105 is supplied Electricity.

In motor control module 110, motor uses the indirect orientation on rotor flux mode of magnetic linkage amplitude closed loop, this portion Dividing mainly includes coordinate transform and flux observation 123, subtracter 111, subtracter 112, subtracter 115, subtracter 116, magnetic linkage Adjusting means 113, speed adjusting device 114, regulating current device 117, coordinate transformation module 121 and pwm signal generation mould Block 122.Flux regulating device 113, speed adjusting device 114 are with regulating current device 117 typically using PI controls.PWM is generated Module is frequently with sinusoidal pulse width modulation (SPWM) or Voltage space vector PWM (SVPWM).

In this example, coordinate transform uses the current model on MT coordinate systems with flux observation module 123.Its structural frames Figure is as shown in Figure 2.First pass through 3/2 module to transform on α β coordinate systems the electric current of motor from three-phase static coordinate system, then will Two-phase rest frame is transformed in the middle of two-phase synchronous rotating frame, obtains the exciting current i of motor_sdWith torque current i_sq。 According toThe rotor flux amplitude of motor is can obtain,L_rAnd R_rRespectively the inductor rotor of motor and Rotor resistance；And the rotating excitation field angular velocity omega of motor₁=ω+ω_s, ω_sBe motor slip angular frequency and ω is the angular rate of rotor.To the rotating excitation field angular velocity omega of motor₁Integration, can obtain the position of rotor magnetic linkage Put.

What deserves to be explained is, 3/2 module can both be input into three-phase current, it is also possible to be input into biphase current, because three-phase electricity Stream and always zero, the instantaneous value of third phase electric current can be obtained according to biphase current therein.Except the electricity on MT coordinate systems Flow model (as shown in Figure 2) is obtained beyond the rotor flux of motor, can also be using the current model or electricity on α β coordinate systems Pressing mold type etc. obtains the rotor flux of motor.

The model of the three-phase induction motor of rotor fault is：

In formula, u_sdAnd i_sdIt is the voltage and current of motor stator d axles, u_sqAnd i_sqIt is the voltage and electricity of motor stator q axles Stream, ψ_rdAnd ψ_rqIt is rotor d axles and the magnetic linkage of q axles, R_sIt is motor stator resistance, L_m、L_rIt is magnetic linkage inductance and the rotor electricity of motor Sense,And R_rIt is the rotor resistance of motor, n is motor continuously fracture Rotor bar number, N is total rotor bar number.Symbol p=d/dt, ω₁It is the rotary speed of motor synchronous rotating frame, θ_sω It is the slippage angle of motor, the i.e. difference of synchronous rotating frame and rotor electrical angle, s is the revolutional slip of motor.

When motor use Field orientable control and magnetic linkage amplitude closed loop when, when its magnetic linkage is positioned at into d axles, following formulas into It is vertical.

And now d shaft currents are also called exciting current, q shaft currents are also called torque current.

During motor steady-state operation, DC component and 2 times of slip-frequencies are mainly contained in the d axles and q shaft currents of motor stator 2f_s=2sf₁Low frequency component, wherein 2f_sLow frequency component is introduced due to rotor fault, f₁It is the fundamental wave of motor stator electric current Frequency (frequency of supply).Therefore can set：

Wherein,For motor energization current and torque current average value and be direct current；Δi_sd、Δi_sqIt is motor The wave component of exciting current and torque current, its amplitude is smaller, and its frequency is 2f_s。

The above formula is substituted into the fourth line of motor model, had：

In the case of rotor failure,Still set up, substitute into above formula, and ignore second order in a small amount, have：

Ignore the change of motor slip ratio s, the left side of above formula equal sign is AC compounent, and the right is then DC quantity.According to small The concept of signal model, both members are 0, therefore：

I.e.

In formula,It is torque current wave component Δ i_sqAmplitude.

Δ R_rWithSubstitute into, the broken strip number for obtaining rotor is：

Because k is typically small, institute's above formula is approximately written as n ≈ kN.Therefore, by calculating torque electric current i_sqDC componentAnd its amplitude of AC compounentCan be in the hope of the broken strip number of rotor, it is achieved thereby that the diagnosis to rotor fault And quantization.

Based on above-mentioned theory, the workflow of present embodiment Rotor Fault Diagnosis, its step is as shown in Figure 3：

(1) first by the torque current i of motor_sqBy a low pass filter 301, with eliminate the switching harmonics in electric current with And other noises.When motor uses direct orientation on rotor flux, inherently there is torque current i in its controller_sq.Its Sample frequency is identical with the frequency of electric machine controller electric current loop, hertz generally thousands of or up to ten thousand, is in this example 8000Hz. Low pass filter 301 is a quadravalence Butterworth lowpass filters.Its cut-off frequency f_cIt is 50Hz.The biography of the low pass filter Delivery function is：

In formula, g₁=3.7978 × 10^-4, g₂=3.7199 × 10^-4, a₁=-1.9689, a₂=0.9704, a₃=- 1.9285, a₄=0.9300.

After the treatment of low pass filter 301, the signal i for obtaining_sq1In only exist in theory DC component and due to Rotor fault and the 2f that introduces_sFrequency component.

(2) to filtered current signal i_sq1Down-sampled 302 treatment is carried out, signal i is obtained_sq2.By the sampling of signal frequently Rate is reduced to 200Hz from 8000Hz, and equivalent in original signal, every 40 points extract a point, i.e., the down-sampled factor is 40. The reason for adding down-sampled is that mainly have two reasons：One because torque current i_sqBy after low pass filter 301, its is effective The highest frequency of signal is very low (generally below 10Hz), and too high sample frequency is nonsensical；The second is because drop Sampling can reduce the computation burden of controller.

(3) to the signal i after down-sampled_sq2Moving average filter is carried out, so as to obtain the average value of torque currentMeter Calculate the cycle of average valueAnd f_sCan be obtained by the controller of motor, it passes through slip angular frequency ω_sObtained divided by 2 π Arrive, specific acquisition process refers to Fig. 2.

(4) the signal i after down-sampled_sq2Subtract its average valueObtain only containing AC compounent that (frequency is 2f_s) Δ i_sq, the purpose is to prevent larger mean componentBecause of spectrum leakage and caused by the relatively low 2f of frequency_sFrequency component crest meter Do not calculate accurately really.

(5) to Δ i_sqGoerzel algorithm treatment is carried out, so that the 2f in extracting signal_sThe amplitude of frequency componentGe Ze The signal length of your algorithm process is N=600 points (data of i.e. 3 seconds).Its calculating process is as follows：

S (i)=x (i)+2cos (2 π ω) s (i-1)-s (i-2) i=0,1 ... N-1

Wherein：S (- 1)=s (- 2)=0, x (i) is the current value of torque current AC compounent ith sample point, ω=4 π f_sT_s, T_sIt is the sampling period of torque current；In this example,

By above formula after N=600 interative computation, s (N-1) and s (N-2) is can obtain, and then can obtain 2f_sFrequency The amplitude of component, its calculation expression is：

(6) basisWithCan try to achieve

(7) according to k values and total rotor bar number of motor, the rotor broken bar radical of motor can be tried to achieve.Its expression is ForThe formula can also approximately be written as n ≈ kN.

(8) according to the size of n, judge motor whether broken strip, and broken strip radical；Take corresponding according to broken strip radical Remedial measure.

Fig. 4 and Fig. 5 give the simulation result for obtaining in the embodiment.Wherein, Fig. 4 is motor in rated speed Diagnostic result in the case of (980rpm), different load torques.It can be seen that, its rotor broken bar number and rotor for calculating Actual broken strip number coincide, and electric motor load torque change on diagnostic result influence it is smaller.Fig. 5 has then considered motor The influence of load torque and given rotating speed to diagnostic result.The result of Fig. 5 proves that the change of motor given rotating speed is proposed to the present invention This diagnostic method influence very little, so as to demonstrate the robustness of the inventive method.

Claims (6)

1. a kind of rotor method for diagnosing faults based on Field orientable control, it is characterised in that comprise the following steps：

(1) the threephase stator electric current of motor is gathered, it is correspondence motor to be converted by dq and extract d shaft currents therein and q shaft currents Exciting current and torque current；

(2) exciting current according to obtains the rotor flux of motor, and then turning according to motor by flux observation algorithm Sub- magnetic linkage and torque current, are calculated the slip frequency f of motor_s；

(3) LPF is carried out to described torque current, line slip is then entered to filtered torque current with time window T Average filter obtains the DC component of torque current,

(4) described torque current is made to subtract the AC compounent that its DC component obtains torque current, and then according to slip frequently Rate f_sGoerzel algorithm treatment is carried out to torque current AC compounent, the amplitude of torque current AC compounent is obtained；

(5) according to torque current DC component and the amplitude of torque current AC compounent, judge rotor with the presence or absence of disconnected Bar and broken strip radical.

2. rotor method for diagnosing faults according to claim 1, it is characterised in that：Pass through in described step (2) Flux observation algorithm calculates motor slip frequency f_sTo implement process as follows：

First, the rotor flux ψ of motor is calculated according to following formula_r；

$\begin{array}{cc}{\mathrm{\ψ}}_r=\frac{L_m{i}_{sd}}{T_{r}s+1}& T_r=\frac{L_r}{R_r}\end{array}$

Wherein：L_mAnd i_sdThe respectively magnetizing inductance and exciting current of motor, L_rAnd R_rThe respectively inductor rotor and rotor of motor Resistance, s is Laplace operator；

Then, the slip angular frequency ω of motor is calculated according to following formula_s；

${\mathrm{\ω}}_s=\frac{L_m{i}_{sq}}{T_r{\mathrm{\ψ}}_r}$

Wherein：i_sqIt is the torque current of motor；

Finally, according to f_s=ω_s/ 2 π determine the slip frequency f of motor_s。

3. rotor method for diagnosing faults according to claim 1, it is characterised in that：Pass through in described step (3) Following quadravalence butterworth filter transfer function H (z) carries out LPF to torque current：

$H\left(z\right)=g_1\frac{1+2z^{-1}+z^{-2}}{1+a_1{z}^{-1}+a_2{z}^{-2}}\×g_2\frac{1+2z^{-1}+z^{-2}}{1+a_3{z}^{-1}+a_4{z}^{-2}}$

Wherein：g₁、g₂、a₁、a₂、a₃And a₄Filtering parameter is, z is transform operator.

4. rotor method for diagnosing faults according to claim 1, it is characterised in that：To filter in described step (3) Before torque current after ripple carries out moving average filter, first the torque current is carried out down-sampled.

5. rotor method for diagnosing faults according to claim 1, it is characterised in that：To turning in described step (4) The method that square current alternating component carries out Goerzel algorithm treatment is as follows：

First, the sampled point number in signal length N i.e. duration of torque current AC compounent is determined with certain time length；

Then, the torque current AC compounent N-1 and the N-2 signal value s of sampled point is tried to achieve according to following formula iteration And s (N-2) (N-1)：

S (i)=x (i)+2cos (2 π ω) s (i-1)-s (i-2) i=0,1 ... N-1

Wherein：S (i), s (i-1) and s (i-2) are respectively i-th, the i-th -1 and the i-th -2 sampling of torque current AC compounent The signal value of point, x (i) is the current value of torque current AC compounent ith sample point, ω=4 π f_sT_s, T_sIt is torque current Sampling period；

Finally, according to the amplitude of following formula calculating torque current alternating component：

${\hat{i}}_{sq}=\sqrt{s^2(N-1)+s^2(N-2)-2\cos \left(2\mathrm{\π}\mathrm{\ω}\right)s(N-1)s(N-2)}$

Wherein：It is the amplitude of torque current AC compounent.

6. rotor method for diagnosing faults according to claim 1, it is characterised in that：Basis in described step (5) Below equation judges that rotor whether there is broken strip and broken strip radical：

$\begin{array}{cc}m=\frac{k}{1+2k}M& k=\frac{{\hat{i}}_{sq}}{{\stackrel{\‾}{i}}_{sq}}\end{array}$

Wherein：M is the broken strip radical of rotor, and M is the sliver number of rotor,It is the amplitude of torque current AC compounent,It is the DC component of torque current.