A method for excitation enhancement of a self-excited synchronous motor by asymmetric square wave injection

Abstract

The application discloses a kind of asymmetric square wave injection self-excitation synchronous motor excitation enhancement methods, first, the stator winding of motor is injected adjustable duty cycle high-frequency square wave voltage signal, the adjustment range of duty cycle is 0%-100%;Second, the high-frequency injection phase current under natural coordinate system is calculated based on high-frequency square wave voltage signal;Third, the excitation current on the excitation winding in motor is calculated according to high-frequency injection phase current;Finally, the numerical value of high-frequency injection phase current and excitation current corresponding to high-frequency square wave voltage signal under different duty cycles is collected, the corresponding relationship of high-frequency injection phase current, duty cycle and excitation current is established, and the duty cycle is adjusted based on the corresponding relationship, to realize the enhancement regulation of excitation current.

Description

Technical Field

[0001] This invention relates to the field of motor control, and more specifically to a method for enhancing the excitation of a self-excited synchronous motor by asymmetric square wave injection. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) suffer from high cost, non-adjustable rotor magnetic field, and susceptibility to demagnetization at high temperatures, limiting their application in high-temperature and high-pressure environments, such as in multi-electric / all-electric aircraft. To address these shortcomings, electrically excited brushless synchronous motors (WRSMs) have emerged as a new alternative. These motors generate controllable excitation current through rotor-side excitation windings, achieving flexible magnetic field adjustment and offering advantages such as lower cost. Traditional WRSMs are mainly classified into three types based on their excitation method: three-stage starter-generators, wireless power transfer excitation motors, and harmonic excitation synchronous motors. Among these, harmonic excitation synchronous motors possess self-excitation characteristics and are also known as self-excited synchronous motors (SESMs).

[0003] Currently, the high-frequency sinusoidal voltage injection zero-low-speed excitation strategy can effectively solve the zero-speed start-up problem of SESM. However, since the injection frequency of the high-frequency sinusoidal wave is limited by the system carrier frequency, it is difficult to further increase the high-frequency sinusoidal injection frequency, which restricts the further increase of the excitation current.

[0004] Based on this, in order to further improve the zero-low-speed excitation performance, a high-frequency symmetrical square wave injection excitation strategy is proposed. This strategy directly uses high-frequency square wave voltage for excitation. Compared with sinusoidal voltage injection, the frequency of high-frequency square wave voltage can be increased to 1 / 2 of the carrier frequency, which can obtain a larger excitation current. However, the square wave voltage injected by this strategy is symmetrically arranged, with low harmonic content, and the resulting excitation current is still small, which does not fully realize the potential of high-frequency square wave excitation.

[0005] In view of this, this application has conducted in-depth research on this basis, resulting in this case. Summary of the Invention

[0006] The purpose of this invention is to provide a method for enhancing the excitation of a self-excited synchronous motor by asymmetric square wave injection, which obtains higher frequency excitation harmonics under the same square wave voltage, increases the induced electromotive force in the harmonic winding, and thus increases the excitation current.

[0007] To achieve the above objectives, the solution of the present invention is: a method for enhancing the excitation of a self-excited synchronous motor by asymmetric square wave injection, comprising the following steps:

[0008] Step 1: Inject a high-frequency square wave voltage signal with an adjustable duty cycle into the stator winding of the self-excited synchronous motor. The duty cycle is adjustable from 0% to 100%, and is not 50%.

[0009] Step 2: Calculate the high-frequency injected phase current in the natural coordinate system based on the high-frequency square wave voltage signal;

[0010] Step 3: Calculate the excitation current on the excitation winding of the self-excited synchronous motor based on the high-frequency injected phase current described in Step 2.

[0011] Step 4: Collect the values ​​of the high-frequency injected phase current corresponding to the high-frequency square wave voltage signal under different duty cycles, establish the correspondence between the high-frequency injected phase current, the duty cycle and the excitation current, and adjust the duty cycle of the high-frequency square wave voltage signal based on the correspondence to achieve enhanced regulation of the excitation current.

[0012] In step 1, the formula for calculating the high-frequency square wave voltage value is: In the formula, In the stationary coordinate system x The high-frequency square wave voltage value injected into the 2-axis system, n For harmonic order; The angular frequency of the square wave , The period of the square wave; t This refers to the running time of the self-excited synchronous motor. D Duty cycle; This represents the positive amplitude of the square wave.

[0013] Step 2 includes the following steps:

[0014] Step 2-1, in the stationary coordinate system x A high-frequency square wave voltage value is injected into the 2-axis system, after... Clarke The inverse transformation, the voltages in the natural coordinate system are as follows:

[0015] ,

[0016] In the formula, For the self-excited synchronous motor a , b ... k The voltage vector of the phase voltage, The fundamental wave plane of the self-excited synchronous motor αβ Axis and each harmonic plane The voltage vector of the axis voltage. To oppose clarke Transformation matrix;

[0017] Step 2-2: Calculate the increased voltage vector of each phase in the natural coordinate system. The calculation formula is as follows:

[0018] ,

[0019] In the formula, The voltage increase for the first phase of the self-excited synchronous motor, For the self-excited synchronous motor, the first k The increase in phase voltage, k For the self-excited synchronous motor, the first k The numerical values ​​of the phases; among which, , ;

[0020] Steps 2-3: Calculate the high-frequency injected phase current. The calculation formula is as follows:

[0021] ,

[0022] In the formula, For the self-excited magneto Phase current, For the self-excited magneto k Phase increase voltage, The resistance of the stator winding, The inductance of the stator winding, The angular frequency of the square wave.

[0023] Step 3 includes the following steps:

[0024] Step 3-1: Calculate the total magnetomotive force of the multiphase self-excited synchronous motor. The calculation formula is as follows:

[0025] ,

[0026] In the formula, for k Total magnetomotive force of the phase motor. for a The magnetomotive force of the phase. for a Phase winding coefficient, for a Phase current, The number of turns in the stator winding. The magnitude of the stator current. For extreme logarithms, The electrical frequency of a high-frequency square wave; It is an angular displacement. , The fundamental frequency of the motor. The initial position angle;

[0027] Step 3-2: After the total magnetomotive force of the multiphase motor is rectified by the rectifier circuit on the rotor of the self-excited synchronous motor, the excitation current obtained on the excitation winding is:

[0028] ,

[0029] In the formula, For excitation current, The number of turns in the stator winding. The magnitude of the stator current. The fundamental wave distribution coefficient of the winding is... The number of turns in series for each phase winding. This refers to the axial length of the motor. Where is the air gap radius, The resistance of the rotor excitation winding. The inductance of the rotor excitation winding, This represents the DC component of the air gap permeability. This represents the first harmonic component of the air gap permeability. The coil span, Stator slot pitch This refers to the number of stator teeth.

[0030] exist k When =1, and the duty cycle of the injected high-frequency square wave voltage signal is 50%, a The phase current of the phase is:

[0031] ;

[0032] When the duty cycle of the injected high-frequency square wave voltage signal is 20%, a The phase current of the phase is:

[0033] ;

[0034] Compared to the high-frequency square wave voltage signal with a duty cycle of 50%, the high-frequency square wave voltage signal with a duty cycle of 20% is injected into the high-frequency square wave voltage signal with a duty cycle of 20%. a The phase current has a richer harmonic content, with cosine components of the same order existing in addition to the sine components.

[0035] With the above structure, the present invention has the following beneficial effects: by changing the duty cycle of the injected high-frequency square wave voltage signal, a higher frequency excitation harmonic can be obtained under the same square wave voltage, increasing the induced electromotive force in the harmonic winding, thereby increasing the excitation current. Attached Figure Description

[0036] Figure 1 This is a topology diagram of the self-excited synchronous motor in this invention.

[0037] Figure 2 This is a schematic diagram of the self-excited synchronous motor in this invention.

[0038] Figure 3 This is a schematic diagram of the energy transfer of the excitation strategy of the self-excited synchronous motor in this invention.

[0039] Figure 4 This is a system block diagram of the present invention.

[0040] Figure 5 This is a square wave waveform diagram of a high-frequency square wave voltage signal with a conventional duty cycle of 50% injected when using a self-excited synchronous motor.

[0041] Figure 6 This is a diagram of the square wave waveform when a high-frequency square wave voltage signal with an asymmetric duty cycle is injected in this invention.

[0042] Figure 7 In this invention a Phase current simulation waveform (orange represents 50% duty cycle, blue represents 20% duty cycle).

[0043] Figure 8 The present invention injects a duty cycle of 50%. a Phase current FFT analysis diagram.

[0044] Figure 9 The present invention injects a duty cycle of 20%. a Phase current FFT analysis diagram.

[0045] In the picture:

[0046] 100-Motor body; 11-Stator core; 12-Stator winding; 13-Harmonic winding; 14-Excitation winding; 3-Rectifier plate. Detailed Implementation

[0047] To further explain the technical solution of the present invention, the present invention will be described in detail below through specific embodiments.

[0048] A method for enhancing the excitation of a self-excited synchronous motor by asymmetric square wave injection is proposed, applicable to existing conventional self-excited synchronous motors, such as... Figure 1 As shown, the device includes a motor body 100, which comprises a rotor and a stator. The stator is conventionally mounted on the outside of the rotor. The stator includes a stator core 11 and a stator winding 12. The stator winding 12 is conventionally wound in stator slots on the stator core 11. The rotor is conventionally wound with a harmonic winding 13 and an excitation winding 14. A rectifier board 3 integrating a rectifier circuit is conventionally mounted on the rotor. Figure 2 The arrangement is shown.

[0049] This invention discloses a method for enhancing the excitation of a self-excited synchronous motor by asymmetric square wave injection, such as... Figures 2-4As shown, the steps include the following.

[0050] Step 1: Inject a high-frequency square wave voltage signal with an adjustable duty cycle into the stator winding 12 of the self-excited synchronous motor. The duty cycle adjustment range is 0%-100%, not 50%.

[0051] To elaborate, in a stationary coordinate system x 2 shaft system (i.e.) α - β A high-frequency square wave voltage signal is injected into the coordinate system. The specific process is as follows.

[0052] Step 1-1: Within one cycle, set the high-frequency square wave voltage signal as follows:

[0053] (1);

[0054] In the formula, This is the expression for a high-frequency square wave voltage signal. The period of a high-frequency square wave; Let be the angular frequency, and ; This represents the positive amplitude of a high-frequency square wave. This represents the negative amplitude of a high-frequency square wave. Duty cycle, t This refers to the running time of the self-excited synchronous motor.

[0055] Steps 1-2: In each cycle, it is necessary to ensure the stability of the stationary coordinate system. x Since the rising and falling values ​​of the current in the two-axis system are the same, according to the volt-second balance principle, therefore... ,Right now, (2).

[0056] Steps 1-3, the Fourier series trigonometric function form of the above formula (2) is:

[0057] (3);

[0058] In the formula, In the stationary coordinate system x The high-frequency square wave voltage value injected into the 2-axis system, n This represents the harmonic order.

[0059] Substituting formula (2) into formula (3), we get the following formula:

[0060] (4).

[0061] Step 2: Calculate the high-frequency injected phase current in the natural coordinate system based on the high-frequency square wave voltage value.

[0062] To elaborate, the specific process of step 2 is as follows.

[0063] Step 2-1, the high-frequency square wave voltage value in Step 1 (i.e. )go through Clarke The inverse transformation yields the voltages in the natural coordinate system as follows:

[0064] (5),

[0065] In the formula, For the self-excited synchronous motor a , b ... k The voltage vector of the phase voltage, The fundamental wave plane of the self-excited synchronous motor αβ Axis voltage and each harmonic plane , , , The voltage vector of the axis voltage. To oppose clarke Transformation matrix.

[0066] It is worth mentioning that formula (5) can also be expressed as follows: ;

[0067] In the formula, Self-excited synchronous motor a The voltage vector of the phase voltage, Self-excited synchronous motor b The voltage vector of the phase voltage, Self-excited synchronous motor k The voltage vector of the phase voltage; , These are the fundamental wave planes of the self-excited synchronous motor. αβ The voltage vector of the axis voltage. Harmonic plane of a self-excited synchronous motor The voltage vector of the axis voltage.

[0068] Furthermore, in formula (5), the opposite... clarke The transformation matrix is ​​as follows: .

[0069] Furthermore, due to the harmonic plane x A high-frequency square wave voltage signal is injected into the two axes, so the voltage vector added in the stationary coordinate system is: .

[0070] in, In the formula, For self-excited magneto a ,b ... k The voltage vector of the phase voltage increase This is an added voltage vector to the fundamental and harmonic planes of a self-excited motor.

[0071] Will The formulas for calculating the increased voltage vector of each phase in the natural coordinate system, due to the injection of high-frequency square wave voltage signals, are as follows:

[0072] (6);

[0073] In the formula, , And so on, that is, The first phase of the self-excited synchronous motor (i.e. a The increase in voltage vector of phase), The second phase of the self-excited synchronous motor (i.e. b The increase in voltage vector of phase), For the self-excited synchronous motor k The increase in phase voltage, k For the self-excited synchronous motor, the first k The numerical value of the phase.

[0074] Steps 2-3: Calculate the high-frequency injected phase current. The calculation formula is as follows:

[0075] (7);

[0076] In the formula, For the self-excited magneto Phase current, For the self-excited magneto k Phase increase voltage vector, The resistance of the stator winding, The inductance of the stator winding, The angular frequency of the square wave k For the self-excited synchronous motor, the first k The numerical value of the phase.

[0077] In this embodiment, a self-excited synchronous motor is used. a For example, that is k =1, when the duty cycle of the injected high-frequency square wave voltage signal is 50% (symmetrical duty cycle). a The phase current of the phase is:

[0078] (8).

[0079] When the duty cycle of the injected high-frequency square wave voltage signal is 20% (i.e., asymmetrical duty cycle), a The phase current of the phase is:

[0080] (9).

[0081] like Figures 5-9 As shown, comparing equations (8) and (9), it is found that the injected high-frequency square wave voltage signal with a duty cycle of 20% is significantly more efficient than that with a duty cycle of 50%. a The phase current has a richer harmonic content, with cosine components of the same order existing in addition to the sine components.

[0082] It should be noted that in a self-excited synchronous motor, other phases (such as...) b Mutually, c Mutually,..., k The phase currents of the phases are all calculated using the above formula (7), and other corresponding k values ​​need to be substituted in.

[0083] Step 3: Calculate the excitation current on the excitation winding of the self-excited synchronous motor based on the high-frequency injected phase current in Step 2 (Formula (7)).

[0084] To elaborate, step 3-1 involves calculating the total magnetomotive force of the multiphase self-excited synchronous motor. The calculation formula is as follows:

[0085] (10);

[0086] In the formula, for k Total magnetomotive force of a self-excited synchronous motor; for a The magnetomotive force of the phase, and The magnetomotive force of the other phases of the stator can be obtained in the same way.

[0087] for a Phase winding coefficient, for a Phase current, The number of turns in the stator winding. The magnitude of the stator current. For extreme logarithms, The electrical frequency of a high-frequency square wave; For angular displacement, , The fundamental frequency of a self-excited synchronous motor. This is the initial position angle.

[0088] It should be noted that the formula for calculating the total magnetomotive force of the multiphase motor mentioned above was derived using conventional methods, and will not be elaborated further here.

[0089] Step 3-2, Total magnetomotive force of the multiphase motor (e.g., in this embodiment, an 11-phase self-excited synchronous motor is used as an example, i.e.) k =11) After rectification by the rectifier circuit on the rotor of the self-excited synchronous motor, the final excitation current obtained on the excitation winding is:

[0090] (11);

[0091] In the formula, For excitation current, The number of turns in the stator winding. The magnitude of the stator current. The fundamental wave distribution coefficient of the winding is... The number of turns in series for each phase winding. This refers to the axial length of the motor. Where is the air gap radius, The resistance of the rotor excitation winding, The inductance of the rotor excitation winding, This represents the DC component of the air gap permeability. This represents the first harmonic component of the air gap permeability. The coil span, Stator slot pitch This refers to the number of stator teeth.

[0092] Step 4: Collect the values ​​of high-frequency injection phase current and excitation current corresponding to the high-frequency square wave voltage signal under different duty cycles, establish the correspondence between high-frequency injection phase current, duty cycle and excitation current, and adjust the duty cycle of the high-frequency square wave voltage signal based on the correspondence to achieve enhanced regulation of excitation current.

[0093] To elaborate further, from Figures 5-9 It is known that the greater the difference between the duty cycle value and the 50% duty cycle, the richer the harmonic content that can be generated, the larger the excitation current that can be obtained, and the better the enhancement effect of the excitation current. However, as the difference between the duty cycle value and the 50% duty cycle increases, the effective value of the stator current required for excitation also increases, which leads to a decrease in the maximum value of the electromagnetic torque formed. Therefore, the duty cycle of the injected high-frequency square wave voltage signal should be selected according to the actual situation and actual needs of the self-excited synchronous motor.

[0094] It should be noted that, in this embodiment, the above-mentioned high-frequency square wave voltage signal is described using an asymmetric 20% duty cycle.

[0095] This invention discloses an excitation enhancement method for a self-excited synchronous motor using asymmetric square wave injection. Traditional harmonic excitation methods inject a symmetrical high-frequency square wave voltage with low harmonic content, resulting in a small excitation current and thus failing to fully unleash the potential of the high-frequency square wave excitation strategy. In this embodiment, under the same high-frequency square wave voltage, the duty cycle of the injected high-frequency square wave voltage is changed to obtain higher-frequency excitation harmonics, thereby increasing the induced electromotive force in the harmonic winding and consequently increasing the excitation current.

[0096] The above description is only a preferred embodiment of this invention. Any equivalent changes and modifications made within the scope of the claims of this invention shall fall within the scope of the claims of this invention.

Claims

1. A method for enhancing the excitation of a self-excited synchronous motor by asymmetric square wave injection, characterized in that, Includes the following steps: Step 1: Inject a high-frequency square wave voltage signal with an adjustable duty cycle into the stator winding of the self-excited synchronous motor. The duty cycle is adjustable from 0% to 100%, and is not 50%. Step 2: Calculate the high-frequency injected phase current in the natural coordinate system based on the high-frequency square wave voltage signal; Step 3: Calculate the excitation current on the excitation winding of the self-excited synchronous motor based on the high-frequency injected phase current described in Step 2. Step 4: Collect the values ​​of the high-frequency injection phase current and excitation current corresponding to the high-frequency square wave voltage signal under different duty cycles, establish the correspondence between the high-frequency injection phase current, the duty cycle and the excitation current, and adjust the duty cycle of the high-frequency square wave voltage signal based on the correspondence to achieve enhanced regulation of the excitation current. In step 1, the formula for calculating the high-frequency square wave voltage value is: In the formula, In the stationary coordinate system x The high-frequency square wave voltage value injected into the 2-axis system, n For harmonic order; The angular frequency of the square wave , The period of the square wave; t This refers to the running time of the self-excited synchronous motor. D Duty cycle; This represents the positive amplitude of the square wave.

2. The method for enhancing the excitation of a self-excited synchronous motor by asymmetric square wave injection according to claim 1, characterized in that, Step 2 includes the following steps: Step 2-1, in the stationary coordinate system x A high-frequency square wave voltage value is injected into the 2-axis system, after... Clarke The inverse transformation, the voltages in the natural coordinate system are as follows: ， In the formula, For the self-excited synchronous motor a , b ... k The voltage vector of the phase voltage, The fundamental wave plane of the self-excited synchronous motor αβ Axis and each harmonic plane The voltage vector of the axis voltage. To oppose clarke Transformation matrix; Step 2-2: Calculate the increased voltage vector of each phase in the natural coordinate system. The calculation formula is as follows: ， In the formula, The voltage increase for the first phase of the self-excited synchronous motor, For the self-excited synchronous motor, the first K The increase in phase voltage, K For the self-excited synchronous motor, the first K The numerical values ​​of the phases; among which, , ; Steps 2-3: Calculate the high-frequency injected phase current. The calculation formula is as follows: ， In the formula, For the self-excited magneto K Phase current, For the self-excited magneto K Phase increase voltage, The resistance of the stator winding, The inductance of the stator winding, The angular frequency of the square wave.

3. The method for enhancing the excitation of a self-excited synchronous motor by asymmetric square wave injection according to claim 2, characterized in that, Step 3 includes the following steps: Step 3-1: Calculate the total magnetomotive force of the multiphase self-excited synchronous motor. The calculation formula is as follows: ， In the formula, for K Total magnetomotive force of the phase motor. for a The magnetomotive force of the phase. for a Phase winding coefficient, for a Phase current, The number of turns in the stator winding. The magnitude of the stator current. For extreme logarithms, The electrical frequency of a high-frequency square wave; For angular displacement, , The fundamental frequency of the motor. The initial position angle; Step 3-2: After the total magnetomotive force of the multiphase motor is rectified by the rectifier circuit on the rotor of the self-excited synchronous motor, the excitation current obtained on the excitation winding is: ， In the formula, For excitation current, The number of turns in the stator winding. The magnitude of the stator current. The fundamental wave distribution coefficient of the winding is... The number of turns in series for each phase winding. This refers to the axial length of the motor. Where is the air gap radius, The resistance of the rotor excitation winding, The inductance of the rotor excitation winding, This represents the DC component of the air gap permeability. This represents the first harmonic component of the air gap permeability. The coil span, Stator slot pitch This refers to the number of stator teeth.

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