CN107167695B - Permanent magnet synchronous motor interturn short-circuit failure diagnosing method based on Distribution of Magnetic Field monitoring - Google Patents

Abstract

The present invention discloses a kind of permanent magnet synchronous motor interturn short-circuit failure diagnosing method based on Distribution of Magnetic Field monitoring.First in the steady state, equivalent circuit when permanent magnet synchronous motor mutually occurring turn-to-turn short circuit is analyzed, and obtains a series of diagnosis algorithms.By the diagnosis algorithm, diagnosed using the high fdrequency component of stator Tooth flux to whether motor occurs shorted-turn fault.

Description

Fault diagnosis method for inter-turn short circuit of permanent magnet synchronous motor based on magnetic field distribution monitoring

technical field

The invention relates to a fault diagnosis technology for a motor.

Background technique

Permanent magnet synchronous motor has many remarkable advantages, such as simple structure, no brushes and slip rings, no electric excitation system, high operation reliability, high power density, flexible and diverse motor shapes and sizes. In line with the economic development needs of energy saving and emission reduction, it can not only partially replace traditional electric excitation motors, but also achieve high efficiency that is difficult to achieve with electric excitation motors. Therefore, permanent magnet synchronous motors have been widely used in aerospace, CNC machine tools, electric vehicles, robots and other fields.

Because the permanent magnet synchronous motor has a wide range of applications and a harsh working environment, various faults will inevitably occur in the permanent magnet motor. The common faults of permanent magnet synchronous motor include inter-turn short circuit fault, loss of field fault, rotor eccentricity fault and so on. After the motor fails, the motor efficiency will be reduced, and it may even cause the motor to stop or even cause permanent damage to the motor. If not found in time, the fault may cause huge economic losses, so the fault diagnosis of permanent magnet synchronous motor is very important.

With the continuous development of fault diagnosis technology, people are committed to developing various special motor fault diagnosis systems, which have become the focus of research in recent years. Although significant progress has been made in this regard, the high rate of false positives and low accuracy are still a real problem.

SUMMARY OF THE INVENTION

The purpose of the present invention is to address the problems in the prior art, and to provide a method for diagnosing inter-turn short-circuit faults of permanent magnet synchronous motors based on magnetic field distribution monitoring. The method uses the high-frequency harmonics of the magnetic flux to diagnose whether an inter-turn short circuit occurs. Compared with the traditional method, this method has higher sensitivity (the high-frequency harmonics come from the inverter, and no additional equipment is required). The fault characteristic value obtained by this method is not only not affected by the change of the motor running state, but can also accurately reflect the severity of the fault.

It is worth noting that, in steady state, the equivalent circuit of the PMSM phase A when an inter-turn short circuit occurs is shown in Figure 1 (in order to simplify the analysis, it is considered that all short-circuit windings are in one coil):

Ignoring the effect of core saturation, the voltage equation of the motor at this time is:

in

L is the phase inductance, M is the phase-to-phase mutual inductance, and u is the short-circuit ratio (u=N/N _F , N is the total number of turns of a phase winding, and n is the number of short-circuit turns). is the flux linkage generated by permanent magnets in A-phase, B-phase, C-phase and short-circuit winding, R is the phase winding resistance, R _F is the short-circuit winding resistance, and the neutral point of V ₀ is the zero-sequence voltage.

When the motor only has an inter-turn short-circuit fault, the rotor of the motor is still normal, so the same as when the motor is running normally, and

Arranging formula (0.1) and formula (0.2) can be obtained:

Usually the motor is controlled by the controller, and the three-phase stator current of the motor is symmetrical, then set: Equation (0.3) can be simplified as:

Solving the above formula can get:

According to the symmetry of the motor, when the motor is running normally, the voltage across the short-circuit winding is:

Combining equations (0.4) and (0.5), it can be known that the voltage across the faulty winding satisfies:

Usually, the internal resistance of the winding is much smaller than the reactance of the winding, ignoring the internal resistance of the winding, the above formula can be further simplified as:

For a concentrated winding motor, the magnetic flux on the stator teeth at the fault and the fault winding voltage satisfy:

Therefore, when the inter-turn short circuit and normal, the magnetic flux at the fault satisfies:

The above formula shows that the magnetic flux at the fault will be reduced when an inter-turn short circuit occurs, and the magnitude of the reduction of the magnetic flux is related to the relative magnitude of the short-circuit resistance (R _F ) and the fault winding reactance (u ² jωL). The larger the u ² jωL , the more obvious the change of magnetic flux. For fault diagnosis, the more obvious the change caused by the fault, the higher the sensitivity of the diagnosis. For the same fault, the higher the frequency, the larger u ² jωL, so the inter-turn short circuit can be diagnosed by using the high frequency harmonics of the magnetic flux. Permanent magnet synchronous motors are powered by inverters, and there are a large number of high-order harmonics in the power supply itself. Using these high-frequency harmonics to judge faults can improve the sensitivity of diagnosis.

The effect of inter-turn short circuit on the magnetic flux at the fault is:

It can be seen from the above formula that the influence of the inter-turn short circuit on the magnetic flux at the fault is related to the fault parameters ( _RF , u), so the degree of fault can be judged by the change of the magnetic flux. When u ² _jωL is relatively small relative to RF, the influence of inter-turn short circuit on the magnetic flux at the fault is approximately the sum of u ² is proportional. For the same degree of fault, the u ² jωL corresponding to the fundamental frequency is the smallest, so the fault degree can be judged by using the fundamental component of the magnetic flux.

2. Diagnostic steps

1) Measure the magnetic flux of stator teeth

1-1) Winding coils on each stator tooth of the permanent magnet synchronous motor, and sequentially numbering these coils;

1-2) Synchronously measure the voltage on each coil, each phase voltage and phase current from t ₀ to t ₀ +T, and record the motor speed Ru _i at this time, where i is the coil number and T is the synchronous motor cycle.

1-3) Perform Fourier transform on each coil voltage, each phase voltage, and each phase current, and obtain their fundamental wave components as: Obtain their 2h _k -1 (h _k is the carrier ratio) subharmonic components are respectively recorded as: Obtaining their 2h _k +1 harmonic components are respectively recorded as:

1-4) Calculate the fundamental wave and harmonic components of the magnetic flux of each tooth according to the following formulas:

In the formula, j is the imaginary unit, and ω is the angular velocity of the synchronous motor;

2) Calculation of the threshold

2-1) Calculate the threshold for determining the short circuit between turns according to the following formula:

Where E _d is the DC bus voltage; M is the amplitude modulation degree (the ratio of the amplitude of the sine wave to the amplitude of the triangular carrier); J ₁ represents the 1st-order Bessel function; N is the total number of turns of the one-phase winding; α is the Threshold coefficient, usually in the range of 0.5 to 0.8, the larger the value of the coefficient, the higher the diagnostic sensitivity, but the lower the reliability.

3) Whether there is a fault and the determination of the fault location

3-1) Calculate the harmonic amplitude of the magnetic flux corresponding to each tooth Compare with the threshold TH. if all are greater than TH, it is determined that the motor has no inter-turn short circuit; if there are one or more If it is less than TH, it is judged that the motor is short-circuited between turns.

3-2) If the motor is short-circuited between turns, it can be judged The coils on the teeth corresponding to less than TH are short-circuited between turns. Depending on how the motor windings are wound, the faulty phase that has an inter-turn short circuit can be determined.

4) Obtaining the reference value of stator tooth magnetic flux

4-1) Calculate n ₁ according to the following formula:

Where Q is the number of motor stator slots, and m is the number of motor stator winding phases.

4-2) If the inter-turn short circuit occurs on the i- _th tooth, calculate the stator tooth magnetic flux reference value according to the following formula:

Among them, θ is the electrical angle difference between two adjacent teeth.

5) Determination of the degree of failure

5-1) If the motor is short-circuited between turns, the magnetic flux fundamental wave corresponding to the fault position marked as

5-2) According to the judgment result of the faulty phase, record the amplitude of the fundamental wave of the faulty phase voltage as The fault phase voltage and current harmonic amplitudes are respectively recorded as

5-2) Calculate the fault characteristic value according to the following formula:

5-3) According to the magnitude of the fault characteristic value FI, the degree of the fault can be judged.

The advantages and beneficial effects of the present invention are:

1. The present invention can be used to diagnose short-circuit faults between turns of permanent magnet synchronous motors.

2. The present invention proposes to use the high-frequency harmonics generated by the controller to diagnose the inter-turn short-circuit fault. This method does not require additional equipment to inject harmonics, and has higher sensitivity than the traditional diagnosis method.

3. The fault eigenvalue algorithm proposed in the present invention eliminates the influence of motor voltage and iron core saturation changes on the results, which makes the diagnosis results not affected by changes in motor operating conditions.

4. The present invention can accurately identify the location where the inter-turn short circuit occurs and the severity of the inter-turn short circuit fault.

5. The present invention does not depend on motor parameters.

6. The present invention does not need to obtain the reference value of the motor during normal operation in advance.

Description of drawings

Figure 1 short-circuit equivalent circuit between turns;

Figure 2. Harmonic components of stator teeth under different working conditions;

Fig. 3 FI under different working conditions.

Detailed ways

The present invention will be further described below in conjunction with the examples, but it should not be understood that the scope of the above-mentioned subject matter of the present invention is limited to the following examples. Without departing from the above-mentioned technical idea of the present invention, various substitutions and changes can be made according to common technical knowledge and conventional means in the field, which shall be included in the protection scope of the present invention.

Using the finite element simulation software, the simulation calculation of the inter-turn short-circuit fault under normal conditions and under different conditions is carried out. The simulated working conditions are shown in Table 1.

Table 1 Simulation calculation conditions

serial number Load torque/Nm Speed/rpm Fault Condition 1 50 3000 none Condition 2 50 3000 2 turns of 0.1Ω turn-to-turn short circuit Condition 3 50 3000 2 turns of 0.05Ω turn-to-turn short circuit Condition 4 25 3000 2 turns of 0.1Ω turn-to-turn short circuit Condition 5 75 3000 2 turns of 0.1Ω turn-to-turn short circuit Condition 6 50 2000 2 turns of 0.1Ω turn-to-turn short circuit

In each state, the harmonic components of the stator tooth magnetic flux and the corresponding thresholds (dotted lines) are shown in Figure 2, respectively. When calculating the threshold, take the threshold coefficient α=0.7.

It can be seen from Figure 2 that the magnetic flux harmonics corresponding to all teeth are greater than the threshold when the motor is running normally. Under different torques, rotational speeds and fault resistances, the harmonic components of the magnetic flux where the inter-turn short circuit occurs are far less than the threshold value, while the harmonic components of the magnetic flux at other positions are all greater than the threshold value. According to the method of fault judgment, the inter-turn short-circuit fault and the location of the fault can be easily determined.

The fault characteristic value FI under different conditions is shown in Figure 3:

It can be seen from Figure 3(a) that when the short-circuit conductance is small, FI is proportional to the short-circuit conductance, which indicates that the relationship between FI and the fault degree is linear at this time, and the fault degree can be more accurately judged according to the size of FI. It can be seen from Figure 3(b) and Figure 3(c) that under different load torques and rotational speeds, the size of FI corresponding to the same fault is basically unchanged, indicating that the diagnosis results are not affected by changes in the motor operating state.

Claims (4)

1. a kind of permanent magnet synchronous motor interturn short-circuit failure diagnosing method based on Distribution of Magnetic Field monitoring, which is characterized in that including Following steps:

1) stator Tooth flux is measured

1-1) the coiling on each described stator tooth of permanent magnet synchronous motor, and to these coil number consecutivelies；

1-2) synchro measure t₀To t₀Voltage in+T time on each coil, each phase voltage, phase current record motor speed at this time Ru_i, wherein i is coil number, T is the synchronous motor period；

Fourier transformation 1-3) is carried out to each coil voltage, each phase voltage, each phase current；

Obtain the fundamental wave of each coil voltage

Obtain the 2h of each coil voltage_k- 1 order harmonic components2h_k+ 1 order harmonic componentsh_kIt is carrier wave ratio；

1-4) calculate the fundametal compoment of each Tooth flux:

Calculate the harmonic component of each Tooth flux:

In formula, j is imaginary unit, and ω is synchronous motor angular speed；

2) calculating of threshold value

The threshold value for determining turn-to-turn short circuit 2-1) is calculated according to the following formula:

Wherein E_dIt is DC bus-bar voltage；M is amplitude modulation degree；J1 indicates 1 rank Bessel function；N is total circle of a phase winding Number；α is threshold coefficient, and ω is synchronous motor angular speed；

3) whether break down and the judgement of abort situation

Respectively by the corresponding magnetic flux harmonic amplitude of each toothIt is compared with threshold value TH；If allIt is all larger than TH, then is determined Turn-to-turn short circuit does not occur for motor；If there is one or moreThen determine that turn-to-turn short circuit occurs for motor less than TH.

2. a kind of permanent magnet synchronous motor interturn short-circuit failure diagnosing side based on Distribution of Magnetic Field monitoring according to claim 1 Method, it is characterised in that: if turn-to-turn short circuit occurs for motor, may determine thatTurn-to-turn occurs for the coil on tooth corresponding less than TH Short circuit.

3. a kind of permanent magnet synchronous motor shorted-turn fault based on Distribution of Magnetic Field monitoring according to claim 1 or 2 is examined Disconnected method, it is characterised in that: if it is determined that the coil generation turn-to-turn short circuit on some tooth can according to the winding method of machine winding To determine specific location and failure phase that turn-to-turn short circuit occurs.

4. a kind of permanent magnet synchronous motor interturn short-circuit failure diagnosing side based on Distribution of Magnetic Field monitoring according to claim 3 Method, it is characterised in that:

Pass through step 4~5) carry out fault degree judgement

4) acquisition of stator tooth flux reference

N 4-1) is calculated according to the following formula₁:

Wherein Q is motor stator slot number, and m is the motor stator winding number of phases；

If 4-2) turn-to-turn short circuit occurs i-th_FNumber tooth calculates stator tooth flux reference according to the following formula:

Wherein, θ is the electrical angle of adjacent two teeth difference, and j is imaginary unit；

5) judgement of fault degree

If 5-1) turn-to-turn short circuit occurs for motor, by the corresponding magnetic flux fundamental wave of abort situationIt is denoted as

5-2) according to faulted phase decision as a result, faulted phase voltage fundamental voltage amplitude is denoted asBy faulted phase voltage current harmonics Amplitude is denoted as respectively

Wherein subscript h₁Indicate 2h_k- 1 order harmonic components, h₂Indicate 2h_k+ 1 order harmonic components；

5-2) calculating fault features value according to the following formula:

It is faulted phase voltage fundamental wave；

5-3) according to the size of fault eigenvalue FI, i.e. the degree size of faults.