A method for testing the DC-axis inductance of a dual three-phase permanent magnet synchronous motor

Abstract

The present invention discloses a method for testing the DC-axis inductance of a dual three-phase permanent magnet synchronous motor. The method involves passing a sinusoidal alternating current with a DC bias through the B and C phase windings, and recording the voltage and current waveforms of the B and C phase windings at this time. The method then disconnects the power supply, maintains the electrical connection of the B and C phase windings, and introduces a DC current through the B and C phase windings, recording the voltage and current waveforms of the B and C phase windings at this time. The method then disconnects the power supply, passes a sinusoidal alternating current with a DC bias through the B and C phase windings, and simultaneously passes a DC current through the V and W phase windings, recording the voltage and current waveforms of the B and C phase windings at this time. Similarly, a DC current is passed through the V phase winding, and the voltage and current waveforms of the B and C phase windings at this time are recorded. The method then calculates the saturation level and impact of the DC current on the B phase winding using a least squares curve fitting method. The method can simulate the saturation level of a motor during operation by adding a DC bias current to the windings.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor testing, and relates to a method for testing the DC-axis inductance of a dual three-phase permanent magnet synchronous motor, and in particular to a method for testing the DC-axis inductance of a dual three-phase permanent magnet synchronous motor, which takes into account the influence of energizing one set of windings on the other set of windings. Background Art

[0002] Currently, there are many methods for testing the inductance of permanent magnet synchronous motors, including the voltage integration method, self-oscillation theory, direct load method, AC static method, and indirect test method without mechanical load. The AC static method measures inductance at its unsaturated value, and requires an external mechanical device to fix the motor's rotor position when measuring the winding parameters of permanent magnet synchronous motors. The indirect test method without mechanical load measures inductance at its saturated value and does not require an external mechanical device to fix the motor's rotor position during the measurement process. Summary of the Invention

[0003] In view of the above-mentioned existing technology, the technical problem to be solved by the present invention is to provide a testing method for the DC-axis inductance of a dual three-phase permanent magnet synchronous motor, and to calculate the DC-axis inductance value of the dual three-phase permanent magnet synchronous motor when considering the saturation condition, taking into account the influence of DC current flowing into one set of windings on the other set of windings.

[0004] To solve the above technical problems, the present invention provides a method for testing the DC-axis inductance of a dual three-phase permanent magnet synchronous motor, comprising:

[0005] Step 1: Pass a sinusoidal AC current with a DC bias into the B and C phase windings of the first set of windings of the dual three-phase permanent magnet synchronous motor, where the DC current is i dc1 , the AC amplitude is i B , the AC current frequency is f, record the voltage waveform and current waveform of the B and C phase windings at this time;

[0006] Step 2: Disconnect the power supply, keep the electrical connection of the first set of motor windings unchanged, and pass a DC current i through the B and C phase windings. dc1 , record the voltage u of the B and C phase windings at this time dc ;

[0007] Step 3: Disconnect the power supply, keep the electrical connection of the first set of motor windings unchanged, and pass a sinusoidal AC current with a DC bias into the B and C phase windings, where the DC current is i dc1 , the AC current amplitude is i B , the AC current frequency is f, and at the same time, a DC current i is passed through the V and W phase windings in the second set of windings of the motor. dc2 , Record the voltage waveform and current waveform of the B and C phase windings at this time;

[0008] Step 4: Disconnect the power supply, keep the electrical connection of the first set of motor windings unchanged, and pass a sinusoidal AC current with a DC bias into the B and C phase windings, where the DC current is i dc1 , the AC current amplitude is i B , the AC current frequency is f, and at the same time, a DC current i is passed through the V phase winding. dc3 ,i dc3 =2i dc1 , record the voltage waveform of B and C phase windings and the current waveform of B and C phases at this time;

[0009] Step 5: Keep the AC component of the B and C phase windings unchanged, and pass the DC current i through the first set of motor windings. dc1 , every time i changes dc1 The voltage value of the corresponding B-phase winding is recorded. At this time, the motor is positioned on the Q axis and the least squares curve fitting method is used to calculate the DC current i dc1 is the independent variable, the voltage of phase B winding is the dependent variable, and the DC current i is calculated. dc1 The analytical expression of and DC current i dc1 The resulting saturation value

[0010]

[0011]

[0012] in, is the voltage value of the B-phase winding, is the voltage value of the B-phase winding when the motor is positioned at the D / Q axis without adding a DC current component, and k is the voltage value of the B-phase winding when the DC current i is added. dc1 The proportional coefficient of the impact value on the B-phase winding voltage when ;

[0013] Step 6: Pass DC current i through the B and C phase windings dc1 , change the DC current i dc1 The size of the B and C phase windings is recorded. dc , calculate the resistance value of B and C phase windings;

[0014] Step 7: Keep the AC component of the B and C phase windings unchanged, and pass the DC current i through the first set of motor windings. dc1 , every time i changes dc1 The size of i is changed accordingly dc2 The size of the corresponding B-phase winding is recorded. At this time, the motor is positioned on the D axis and the least squares curve fitting method is used to calculate the DC current i dc1is the independent variable, the voltage of phase B winding is the dependent variable, and the DC current i is calculated. dc2 The saturation value generated for the B phase winding

[0015]

[0016] Among them, k1i dc1 for and The sum of The voltage value of the B phase winding when the V and W phase windings are energized, k1 is the DC current i dc1 and i dc2 The proportional coefficient of the impact value on the B-phase winding voltage is:

[0017]

[0018] Step 8: Keep the AC component of the B and C phase windings unchanged, and pass the DC current i through the first set of motor windings. dc1 , every time i changes dc1 The size of i is changed accordingly dc3 The size of the corresponding B-phase winding is recorded. At this time, the motor is positioned on the D axis and the least squares curve fitting method is used to calculate the DC current i dc1 is the independent variable, the voltage of phase B winding is the dependent variable, and the DC current i is calculated. dc3 The saturation value generated for the B phase winding

[0019]

[0020] Among them, k2i dc1 for and The sum of The voltage value of the B phase winding when the V phase winding is energized, k2 is the voltage value of the B phase winding when the DC current i is added. dc1 and i dc3 The proportional coefficient of the influence value on the B-phase winding voltage is

[0021]

[0022] Step 9: Calculate the quadrature-axis inductance L of the dual three-phase permanent magnet synchronous motor considering saturation Q , taking into account the degree of magnetic circuit saturation and ignoring the effect of V and W phase windings on B phase winding, the direct axis inductance L D1 , considering the degree of magnetic circuit saturation and the influence of V and W phase windings on B phase winding, the direct axis inductance L D2 , taking into account the degree of magnetic circuit saturation and ignoring the effect of V-phase winding energization on B-phase winding, the direct-axis inductance L D3, taking into account the degree of magnetic circuit saturation and the effect of V-phase winding energization on B-phase winding, the direct-axis inductance L D4 :

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] Beneficial effects of the present invention:

[0029] The present invention aims to overcome the problem that when an AC static method is currently used to measure the inductance of a dual three-phase permanent magnet synchronous motor, the measured inductance does not take into account the influence of a DC current flowing through one set of windings on the other set of windings. Instead, the present invention provides a method for testing the DC-axis inductance of a dual three-phase permanent magnet synchronous motor that takes into account the influence of a DC current flowing through one set of windings on the other set of windings. This method can calculate the DC-axis inductance value of the dual three-phase permanent magnet synchronous motor when the saturation condition is taken into account.

[0030] The advantage of the present invention is that when the structural characteristics of the two sets of windings of the dual three-phase permanent magnet synchronous motor are combined with the AC static method to test the motor's direct-axis inductance, the saturation level of the motor during operation can be simulated by adding a DC bias current to the winding. At the same time, a DC current is passed through the second set of windings to fix the motor rotor in the direct-axis position. However, when a DC current is passed through the second set of windings, it will affect the test results of the first set of windings. By calculating the impact value of the direct current passed through the second set of windings on the first set of windings and analyzing and processing the test results, the direct-axis inductance of the motor under actual operating conditions can be obtained. In the process of testing the inductance of the dual three-phase permanent magnet synchronous motor using the method of the present invention, the motor housing and shaft extension do not need to be specially fixed, and no mechanical load is required, that is, an external mechanical device is omitted, and the method has a series of advantages such as simple structure, stable performance, and reliable data. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an electrical connection diagram of the first set of windings of a motor when testing the AC and DC axis inductance according to the method of the present invention;

[0032] Figure 2 This is an electrical connection diagram of the second set of windings of the motor when the V and W phase windings are energized to test the AC and DC axis inductances according to the method of the present invention;

[0033] Figure 3 This is an electrical connection diagram of the second set of windings of the motor when the V-phase winding is energized to test the AC and DC axis inductance according to the method of the present invention;

[0034] Figure 4 A schematic diagram of the electromagnetic force when the motor of the method of the present invention is fixed at the cross-axis position;

[0035] Figure 5 Schematic diagram of the electromagnetic force when the V and W phase windings are energized and the motor is fixed in the direct axis position;

[0036] Figure 6 This is a schematic diagram of the electromagnetic force that fixes the motor in the direct axis position when the V-phase winding is energized in the method of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] Step 1: Pass a sinusoidal AC current with a DC bias into the B and C phase windings of the first set of windings (A, B, C three-phase windings) of the dual three-phase permanent magnet synchronous motor, where the DC current is i dc1 , the AC amplitude is i B , the AC current frequency is f, the specific electrical connection diagram is as follows Figure 1 As shown, record the voltage waveforms of the B and C phase windings and the B and C phase current waveforms of the first set of windings at this time.

[0039] Step 2: Disconnect the power supply, keep the electrical connection of the first set of motor windings unchanged, and pass a DC current i through the B and C phase windings. dc1 , record the voltage u of the B and C phase windings at this time dc .

[0040] Step 3: Disconnect the power supply and keep the electrical connection of the first set of motor windings unchanged. Pass a sinusoidal AC current with a DC bias into the B and C phase windings of the first set of motor windings. The DC current of the current is i dc1 , the AC current amplitude is i B , the AC current frequency is f, the specific electrical connection diagram is as follows Figure 2 At the same time, the DC current i flowing into the V and W phase windings of the second set of windings (U, V, W three-phase windings) of the motor is dc2 As shown in formula (1), record the voltage waveforms of the B and C phase windings and the B and C phase current waveforms of the first set of windings of the motor at this time.

[0041]

[0042] Step 4: Disconnect the power supply and keep the electrical connection of the first set of motor windings unchanged. Pass a sinusoidal AC current with a DC bias into the B and C phase windings of the first set of motor windings. The DC current of the current is i dc1 , the AC current amplitude is i B, the AC current frequency is f, the specific electrical connection diagram is as follows Figure 3 At the same time, the DC current i flowing into the V-phase winding of the second set of windings of the motor is dc3 As shown in formula (2), record the voltage waveforms of the B and C phase windings and the B and C phase current waveforms of the first set of windings of the motor at this time.

[0043]

[0044] Step 5: Keep the AC component of the B and C phase windings unchanged, and pass the DC current i through the first set of motor windings. dc1 , each time i changes dc1 Do an experiment with the size of the motor. At this time, the motor is positioned on the Q axis and the voltage value of the B phase winding is recorded. dc1 In the process, the motor magnetic circuit will change, which will affect the voltage value of the B phase winding. In order to calculate the DC current i dc1 The impact on the voltage value of the B-phase winding is calculated using the following least squares curve fitting method:

[0045] Curve fitting involves finding a simple, easily calculated function g(x) for a function f(x), with the goal of minimizing the error between f(x) and g(x) in some metric sense. The value σ = f(x) - g(x) is often called the residual error, and the magnitude of the residual error is a key indicator of the quality of the curve fit. Three commonly used criteria are: minimizing the maximum absolute value of the residual error; minimizing the sum of the absolute values ​​of the residual errors; and minimizing the sum of the squares of the residual errors. Because the first two methods for calculating residual error involve absolute values ​​and are inconvenient to calculate, minimizing the sum of the squares of the residual errors is used instead.

[0046] Assume that a set of experimental data (x i ,f(x i )), i=0,1,2,···,m, and the weight coefficient a of each point k , the relationship between the independent variable x and the dependent variable g(x) is obtained as shown in equation (3). The sum of squares of the errors is calculated as shown in equation (4). The value of Δ is the smallest, which is the curve fitting of the least squares method.

[0047] g(x)=a0δ0(x)+a1δ1(x)+…+a n δ n (x) (3)

[0048] Among them, a k ,k=0,1,2,···,n is the experimental data (x i ,f(x i ))The weight coefficients corresponding to each point.

[0049]

[0050] Among them, λ i ,i=0,1,2,···,m is the experimental data (x i ,f(x i )) corresponds to a set of weights.

[0051] The partial derivative of Δ is obtained as shown in formula (5).

[0052]

[0053] According to the definition of inner product, the corresponding weighted inner product notation is introduced as shown in equations (6) and (7).

[0054]

[0055]

[0056] Then formula (5) can be written as formula (8).

[0057] (δ0,δ k )a0+(δ1,δ k )a1+...+(δ n , δ k )a n =(f(x),δ k )k=0,1,2,···,n (8)

[0058] Formula (8) is expressed in matrix form, as shown in Formula (9).

[0059]

[0060] Since δ0(x), δ1(x)···δ n (x) is linearly independent, so a k There is a unique solution. In summary, we can find the analytical expression g(x) for x.

[0061] Using the least squares curve fitting method mentioned above, the DC current i dc1 is the independent variable, the voltage of phase B winding is the dependent variable, and the DC current i is calculated. dc1 The analytical expression of And the DC current i dc1 The resulting saturation value at this time, The value of ki dc1 .

[0062]

[0063] in, is the voltage value of the B-phase winding;

[0064] i dc1 is the DC current component;

[0065] The voltage value of the B-phase winding when the motor is positioned at the D / Q axis without adding a DC current component;

[0066] k is the added DC current i dc1 The proportional coefficient of the impact value on the B-phase winding voltage when .

[0067] Step 6: Pass DC current i through the B and C phase windings dc1 , change the DC current i dc1 The resistance of the B-phase winding and the C-phase winding is u. dc / i dc1 .

[0068] Step 7: Keep the AC component of the B and C phase windings unchanged, and pass the DC current i through the first set of motor windings. dc1 , each time i changes dc1 The size of i is changed accordingly according to formula (1) dc2 The motor is positioned on the D axis and the voltage value of the B phase winding is recorded. dc1 and i dc2 In the process of , it will cause the change of the motor magnetic circuit, which will affect the voltage value of the B phase winding. In order to calculate the DC current i dc1 and i dc2 The impact value on the voltage value of the B phase winding. Use the least squares curve fitting method in step 5 above to calculate the DC current i dc1 is the independent variable, the voltage of phase B winding is the dependent variable, and the DC current i is calculated. dc2 The saturation value of the B-phase winding As shown in formula (11). At this time, and The sum of the values ​​is k1i dc1 When the DC current i dc1 In the same situation, use k1i dc1 Subtract the value of The value of value.

[0069]

[0070] in, When the V and W phase windings are energized, the impact of the V phase winding and the W phase winding on the B phase winding voltage;

[0071] The voltage value of the B phase winding when the V and W phase windings are energized.

[0072] k1 is the DC current i dc1 and i dc2 The proportional coefficient of the impact value on the B-phase winding voltage when .

[0073] Step 8: Keep the AC component of the B and C phase windings unchanged, and pass the DC current i through the first set of motor windings. dc1 , each time i changes dc1 The size of i is changed accordingly according to formula (2) dc3 The motor is positioned on the D axis and the voltage value of the B phase winding is recorded. dc1 and i dc3 In the process of , it will cause the change of the motor magnetic circuit, which will affect the voltage value of the B phase winding. In order to calculate the DC current i dc1 and i dc3 The impact value on the voltage value of the B phase winding. Use the least squares curve fitting method in step 5 above to calculate the DC current i dc1 is the independent variable, the voltage of phase B winding is the dependent variable, and the DC current i is calculated. dc3 The saturation value of the B-phase winding As shown in formula (12). At this time, and The sum is k2i dc1 When the DC current i dc1 In the same situation, use k2i dc1 Subtract the value of The value of value.

[0074]

[0075] in, When the V-phase winding is energized, the impact of the V-phase winding on the B-phase winding voltage;

[0076] The voltage value of the B-phase winding when the V-phase winding is energized.

[0077] k2 is the added DC current i dc1 and i dc3 The proportional coefficient of the impact value on the B-phase winding voltage when .

[0078] After testing according to the above steps, the specific calculation method of the DC-axis inductance of the dual three-phase permanent magnet synchronous motor is as follows:

[0079] According to the constraint of passing the DC current component into the first set of windings of the motor in step 1, the motor will be fixed at the quadrature axis position, and its specific synthetic vector is as follows: Figure 4 Therefore, the inductance measured at this time is the quadrature-axis inductance of the motor.

[0080] Separate the DC component from the voltage and current waveforms of the B-phase winding recorded in step 1, and obtain the AC component amplitude of the B-phase current i B , the AC voltage amplitude of phase B is u B The quadrature axis inductance L of the dual three-phase permanent magnet synchronous motor considering the saturation condition is Q The expression of is shown in formula (13):

[0081]

[0082] According to the DC current i passed through the first set of motor windings in step 3 dc1 The second set of motor windings is connected to a DC current i dc2 The motor will be fixed at the direct axis position, and its specific synthetic vector is as follows: Figure 5 As shown. Separate the DC component from the voltage waveform of the B-phase winding and the B-phase current waveform recorded in step 3, and obtain the AC component amplitude of the B-phase current i B , the AC voltage amplitude of phase B is u B1 . Record the DC current i in step 5 dc1 The resulting saturation value Record the DC current i in step 7 dc2 Impact value on B phase winding At this time, considering the degree of magnetic circuit saturation and ignoring the effect of V and W phase windings on B phase winding, the direct axis inductance L D1 As shown in formula (14). Taking into account the degree of magnetic circuit saturation and the influence of the V and W phase windings on the B phase winding, the direct axis inductance L D2 As shown in formula (15).

[0083]

[0084]

[0085] According to the DC current i passed through the first set of motor windings in step 4 dc1 The second set of motor windings is connected to a DC current i dc3 The motor will be fixed at the direct axis position, and its specific synthetic vector is as follows: Figure 6 As shown. Separate the DC component of the terminal voltage waveform of the B-phase winding and the B-phase current waveform recorded in step 3, and obtain the AC component amplitude of the B-phase current i B , the AC voltage amplitude of phase B is uB2 . Record the DC current i in step 5 dc1 The resulting saturation value Record the DC current i in step 7 dc3 Impact value on B phase winding At this time, considering the degree of magnetic circuit saturation and ignoring the effect of V-phase winding energization on B-phase winding, the direct-axis inductance L D3 As shown in formula (16). Taking into account the influence of magnetic circuit saturation and V-phase winding energization on B-phase winding, the direct axis inductance L D4 As shown in formula (17).

[0086]

[0087]

Claims

1. A method for testing the DC-axis inductance of a dual three-phase permanent magnet synchronous motor, characterized in that: include: Step 1: Pass a sinusoidal AC current with a DC bias into the B and C phase windings of the first set of windings of the dual three-phase permanent magnet synchronous motor, where the DC current is i dc1 , the AC amplitude is i B , the AC current frequency is f, record the voltage waveform and current waveform of the B and C phase windings at this time; Step 2: Disconnect the power supply, keep the electrical connection of the first set of motor windings unchanged, and pass a DC current i through the B and C phase windings. dc1 , record the voltage u of the B and C phase windings at this time dc ; Step 3: Disconnect the power supply, keep the electrical connection of the first set of motor windings unchanged, and pass a sinusoidal AC current with a DC bias into the B and C phase windings, where the DC current is i dc1 , the AC current amplitude is i B , the AC current frequency is f, and at the same time, a DC current i is passed through the V and W phase windings in the second set of windings of the motor. dc2 , Record the voltage waveform and current waveform of the B and C phase windings at this time; Step 4: Disconnect the power supply, keep the electrical connection of the first set of motor windings unchanged, and pass a sinusoidal AC current with a DC bias into the B and C phase windings, where the DC current is i dc1 , the AC current amplitude is i B , the AC current frequency is f, and at the same time, a DC current i is passed through the V phase winding. dc3 ,i dc3 =2i dc1 , record the voltage waveform of B and C phase windings and the current waveform of B and C phases at this time; Step 5: Keep the AC component of the B and C phase windings unchanged, and pass the DC current i through the first set of motor windings. dc1 , every time i changes dc1 The voltage value of the corresponding B-phase winding is recorded. At this time, the motor is positioned on the Q axis and the least squares curve fitting method is used to calculate the DC current i dc1 is the independent variable, the voltage of phase B winding is the dependent variable, and the DC current i is calculated. dc1 The analytical expression of and DC current i dc1 The resulting saturation value in, is the voltage value of the B-phase winding, is the voltage value of the B-phase winding when the motor is positioned at the D / Q axis without adding a DC current component, and k is the voltage value of the B-phase winding when the DC current i is added. dc1 The proportional coefficient of the impact value on the B-phase winding voltage when ; Step 6: Pass DC current i through the B and C phase windings dc1 , change the DC current i dc1 The size of the B and C phase windings is recorded. dc , calculate the resistance value of B and C phase windings; Step 7: Keep the AC component of the B and C phase windings unchanged, and pass the DC current i through the first set of motor windings. dc1 , every time i changes dc1 The size of i is changed accordingly dc2 The size of the corresponding B-phase winding is recorded. At this time, the motor is positioned on the D axis and the least squares curve fitting method is used to calculate the DC current i dc1 is the independent variable, the voltage of phase B winding is the dependent variable, and the DC current i is calculated. dc2 The saturation value generated for the B phase winding Among them, k1i dc1 for and The sum of The voltage value of the B phase winding when the V and W phase windings are energized, k1 is the DC current i dc1 and i dc2 The proportional coefficient of the impact value on the B-phase winding voltage is: Step 8: Keep the AC component of the B and C phase windings unchanged, and pass the DC current i through the first set of motor windings. dc1 , every time i changes dc1 The size of i is changed accordingly dc3 The size of the corresponding B-phase winding is recorded. At this time, the motor is positioned on the D axis and the least squares curve fitting method is used to calculate the DC current i dc1 is the independent variable, the voltage of phase B winding is the dependent variable, and the DC current i is calculated. dc3 The saturation value generated for the B phase winding Among them, k2i dc1 for and the sum of The voltage value of the B phase winding when the V phase winding is energized, k2 is the voltage value of the B phase winding when the DC current i is added. dc1 and i dc3 The proportional coefficient of the influence value on the B-phase winding voltage is Step 9: Calculate the quadrature-axis inductance L of the dual three-phase permanent magnet synchronous motor considering saturation Q , taking into account the degree of magnetic circuit saturation and ignoring the effect of V and W phase windings on B phase winding, the direct axis inductance L D1 , considering the degree of magnetic circuit saturation and the influence of V and W phase windings on B phase winding, the direct axis inductance L D2 , taking into account the degree of magnetic circuit saturation and ignoring the effect of V-phase winding energization on B-phase winding, the direct-axis inductance L D3 , taking into account the degree of magnetic circuit saturation and the effect of V-phase winding energization on B-phase winding, the direct-axis inductance L D4 :

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