A method for suppressing induced ripple voltage based on low-pass filter circuit

Abstract

The present invention discloses a method for suppressing induced pulsating voltage based on a low-pass filter circuit. This method, based on the high-frequency attenuation characteristics of the low-pass filter circuit, suppresses the high-frequency harmonic components by connecting a low-pass filter circuit in parallel to the input end of the excitation winding, thereby achieving the purpose of suppressing the induced pulsating voltage of the excitation winding. The present invention proposes a method for suppressing the harmonics of the induced pulsating voltage of the excitation winding of a brushless electric excitation magnetic field modulation motor under PWM excitation using a low-pass filter circuit. This method can achieve suppression of the induced pulsating voltage of the excitation winding under PWM excitation by connecting a low-pass filter circuit in parallel to the input end of the excitation winding. Therefore, this method has important reference value for suppressing higher-order harmonics in the induced pulsating voltage of the excitation winding of an electric excitation magnetic field modulation motor under PWM excitation.

Description

Technical Field

[0001] The invention relates to an induced pulsating voltage suppression method based on a low-pass filter circuit, belonging to the technical field of voltage suppression in motor design. Background Art

[0002] Permanent magnet motors (PMMs) are widely used in electric vehicles and aviation due to their high torque density and robust rotors. However, permanent magnets also have drawbacks, such as susceptibility to demagnetization at high temperatures and unstable supply of rare earth permanent magnet materials. To address these issues, renewed interest has been placed on electrically excited synchronous motors (ESMs).

[0003] Electromagnetic motors use field windings instead of permanent magnets for excitation. Electromagnetic field modulation motors are a type of electromagnet synchronous motor. Their stator and rotor are doubly salient, with both the field winding and armature winding located on the stator. This eliminates brushes and slip rings, significantly enhancing the motor's rotor robustness. Consequently, electromagnetic field modulation motors are used in electric vehicles, wind power generation, aerospace, and high-speed motors.

[0004] However, due to the uneven distribution of air gap permeability in electromagnetism-field-modulated motors and the severe magnetic coupling between the excitation winding and the armature winding, induced pulsating voltages in the excitation windings can complicate control of the excitation winding current and, in severe cases, even damage the excitation winding's power supply. When the motor is excited by PWM, the power supply circuit generates high-frequency harmonics around the excitation winding switching frequency and its integer multiples in the induced pulsating voltages in the excitation windings. These harmonics are not beneficial to motor operation. The analysis and suppression of induced pulsating voltages in the excitation windings of electromagnetism-field-modulated motors under PWM excitation has not received much attention and is therefore of great research value. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an induced pulsating voltage suppression method based on a low-pass filter circuit, so as to suppress the induced pulsating voltage of the excitation winding under PWM excitation.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] A method for suppressing induced pulsating voltage based on a low-pass filter circuit, wherein a low-pass filter circuit with specific parameters is connected in parallel to the input end of the excitation winding of an electric excitation magnetic field modulation motor under PWM excitation to suppress the induced pulsating voltage of the excitation winding;

[0008] The design steps of the inductance and capacitance parameters of the low-pass filter circuit with specific parameters are as follows:

[0009] S1. Determine the number of pulsating voltage induced by the motor excitation winding and the motor fundamental frequency according to the number of stator slots, the number of rotor poles and the motor speed of the motor modulated by the electromagnetic excitation magnetic field;

[0010] S2. Select the cutoff frequency of the low-pass filter circuit under no-load and loaded working conditions, and determine the inductance and capacitance parameters of the low-pass filter circuit according to the cutoff frequency.

[0011] As a preferred solution of the present invention, the specific process of S1 is as follows:

[0012] S101, determining the number of pulsations of the induced pulsating voltage of the motor's no-load excitation winding based on the number of stator slots and rotor poles of the motor, and further determining the number of pulsations of the induced pulsating voltage of the motor's loaded excitation winding;

[0013] S102. Determine the motor fundamental frequency based on the motor speed and the number of rotor poles.

[0014] As a preferred solution of the present invention, in said S101, under no-load condition, the pulsation number N of the induced pulsating voltage of the motor no-load excitation winding is pef The expression is:

[0015]

[0016] Among them, N s is the number of stator slots of the motor, N r is the number of rotor poles, LCM represents the least common multiple;

[0017] The pulsation number N of the induced pulsating voltage of the excitation winding caused by the armature reaction pea The expression is:

[0018] N pea =min{3r×Sgn(k w(3r+1) +k w(3r-1) )}

[0019] Among them, Sgn is the sign function, k w(3r+1) 、k w(3r-1) They are the 3r+1 and 3r-1 harmonics of the motor winding factor, respectively, where r is a positive integer;

[0020] Under loading conditions, the motor loaded excitation winding induced pulsation voltage pulsation number N pe The expression is:

[0021] N pe =min{N pef , N pea}.

[0022] As a preferred solution of the present invention, in S102, the expression of the motor fundamental frequency is:

[0023]

[0024] Among them, f e is the motor fundamental frequency, N r is the number of rotor poles, and n is the motor speed.

[0025] As a preferred solution of the present invention, the specific process of S2 is as follows:

[0026] S201, selecting a cutoff frequency that is smaller than the product of the number of pulsations of the induced pulsating voltage of the motor's no-load excitation winding and the motor's fundamental frequency, thereby suppressing the induced pulsating voltage of the excitation winding under no-load conditions; selecting a cutoff frequency that is smaller than the product of the number of pulsations of the induced pulsating voltage of the motor's loaded excitation winding and the motor's fundamental frequency, thereby suppressing the induced pulsating voltage of the excitation winding under loaded conditions;

[0027] S202 : Obtain a cutoff frequency conversion coefficient and a characteristic impedance conversion coefficient according to the selected cutoff frequency and characteristic impedance, thereby calculating the inductance and capacitance of the low-pass filter circuit.

[0028] As a preferred solution of the present invention, in S202, the expressions of the cutoff frequency conversion coefficient M and the characteristic impedance conversion coefficient K are:

[0029]

[0030] Among them, f c is the cutoff frequency, R c is the characteristic impedance, R c =1Ω, f0 is the cutoff frequency of the normalized filter circuit, f0=1 / (2π)Hz, R0 is the characteristic impedance of the normalized low-pass filter circuit, R0=1Ω;

[0031] The inductance L and capacitance C of the low-pass filter circuit are expressed as:

[0032]

[0033] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0034] 1. Existing measures for suppressing the induced pulsating voltage of the excitation winding ignore PWM excitation. The present invention designs a low-pass filter circuit for the excitation winding of an electric excitation magnetic field modulation motor with arbitrary slot-pole matching. By connecting a low-pass filter circuit in parallel at the input end of the excitation winding, the induced pulsating voltage of the excitation winding under PWM excitation is suppressed.

[0035] 2. The present invention provides a method for determining the parameters of the low-pass filter circuit of the excitation winding of the electric excitation magnetic field modulation motor under PWM excitation, which has a guiding role in suppressing the induced pulsating voltage of the excitation winding of the electric excitation magnetic field modulation motor under PWM excitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of the method for suppressing induced ripple voltage based on a low-pass filter circuit of the present invention;

[0037] Figure 2 This is a topology diagram of a 12-slot, 10-pole electric excitation field modulation motor according to an embodiment of the present invention;

[0038] Figure 3 This is a diagram illustrating the size parameters of a 12-slot, 10-pole electric excitation magnetic field modulation motor according to an embodiment of the present invention;

[0039] Figure 4 Schematic diagram of a 12-slot, 10-pole electric excitation magnetic field modulation motor drive circuit according to an embodiment of the present invention;

[0040] Figure 5 The present invention is a motor excitation winding drive system with a low-pass filter circuit;

[0041] Figure 6 is a Bode diagram of the low-pass filter circuit designed in an embodiment of the present invention;

[0042] Figure 7 This is a comparison of the induced pulsating voltage waveforms of the no-load excitation winding before and after adding a low-pass filter circuit when using the magnetic field-circuit joint simulation of the present invention;

[0043] Figure 8 This is a comparison of the low-frequency harmonic spectrum of the no-load excitation winding induced pulsating voltage before and after adding a low-pass filter circuit when using the magnetic field-circuit joint simulation of the present invention;

[0044] Figure 9 This is a comparison of the harmonic spectrum diagrams near the PWM frequency of the induced pulsating voltage of the no-load excitation winding before and after adding a low-pass filter circuit when using the magnetic field-circuit joint simulation of the present invention;

[0045] Figure 10 The present invention uses the magnetic field-circuit joint simulation to compare the waveforms of the induced pulsating voltage of the excitation winding before and after adding the low-pass filter circuit;

[0046] Figure 11 This is a comparison of the low-frequency harmonic spectrum of the induced pulsating voltage of the excitation winding before and after adding a low-pass filter circuit when using the magnetic field-circuit joint simulation of the present invention;

[0047] Figure 12 This is a comparison of the harmonic spectrum diagrams near the PWM frequency of the induced pulsating voltage of the excitation winding before and after adding a low-pass filter circuit when using the magnetic field-circuit joint simulation of the present invention. DETAILED DESCRIPTION

[0048] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be interpreted as limiting the present invention.

[0049] like Figure 1 As shown, the method for suppressing induced pulsating voltage based on a low-pass filter circuit includes the following steps:

[0050] S1: The number of stator slots N of the motor s 、Number of rotor poles r Determine the number of ripples N of the induced ripple voltage of the motor excitation winding with the motor speed n pe(f) and the motor fundamental frequency f e .

[0051] S2: Select the cutoff frequency f of the low-pass filter circuit c , and according to f c Determine the inductance and capacitance parameters of the low-pass filter circuit. The low-pass filter circuit obtained with the selected parameters can be used to suppress the induced ripple voltage of the excitation winding.

[0052] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0053] The topology of the 12-slot 10-pole electric excitation magnetic field modulation motor used in this embodiment is as follows: Figure 2 The main parameters of the motor are listed in Table 1, and the size parameter diagram is shown in Figure 3 shown.

[0054] Table 1 Main parameters of 12-slot 10-pole electric excitation field modulation motor

[0055] parameter unit value <![CDATA[Axial stack length, l s > mm 125 Unilateral air gap width, g mm 0.5 <![CDATA[Stator outer diameter, R so > mm 105 <![CDATA[Radius of stator yoke, R sy > mm 98.26 <![CDATA[Width of stator yoke, W sy > mm 6.74 <![CDATA[Inner diameter of stator, R si > mm 58.87 <![CDATA[Stator tooth width, W st > mm 10.33 <![CDATA[Outer diameter of rotor, R ro > mm 59.37 <![CDATA[Radius of rotor yoke, R ry > mm 44.72 <![CDATA[Inner diameter of rotor, R ri > mm 20 <![CDATA[Armature winding radian, θ arm > ° 9.41 <![CDATA[Rotor pole radian, θ rp > ° 10.48 <![CDATA[Number of rotor poles, N r > - 10 <![CDATA[Number of stator slots, N s > - 12 Number of coil turns, N - 24 Number of parallel branches, b - 1 Silicon steel sheet type - DR510-50

[0056] The 12-slot, 10-pole excitation field modulation motor used in this embodiment has its field winding powered by an H-bridge full-bridge with a DC bus voltage of 40Vdc. The armature winding is powered by a three-phase voltage-type full-bridge inverter with a DC bus voltage of 200Vdc. The switching frequency of both the field winding and the armature winding is 10kHz. The motor control mode is zero d-axis current control, and the q-axis current reference value i q * =32.77A, excitation current reference value i f * =32.48Adc, the speed is set to 600 rpm. The drive system of the motor is as follows Figure 4 shown.

[0057] N under no-load condition s Slot N r Pole excitation magnetic field modulation motor no-load excitation winding induced ripple voltage ripple number Npef The expression is:

[0058]

[0059] Among them, LCM is the least common multiple.

[0060] The pulsation number N of the induced pulsating voltage of the excitation winding caused by the armature reaction pea The expression is:

[0061] N pea =min{3r×Sgn(k w(3r+1) +k w(3r-1) )}

[0062] Where min{x} represents the minimum value of set x and x does not contain 0. wk is the kth harmonic of the motor winding factor. Sgn is the sign function.

[0063] The pulsation number N of the induced pulsating voltage of the excitation winding under loading conditions pe The expression is:

[0064] N pe =min{N pef , N pea}

[0065] The number of motor slots N used in this embodiment s =12, number of poles N r =10, and the pulsation number N of the induced pulsating voltage of the no-load excitation winding is obtained. pef =6, load the excitation winding induced pulsating voltage pulsation number N pe =6.

[0066] N s Slot N r The fundamental frequency f of the pole electric excitation magnetic field modulation motor at a speed of n e The expression is:

[0067]

[0068] In this embodiment, the motor speed is 600 rpm, so f e =100Hz, select the low-pass filter circuit cutoff frequency f c Less than N pe(f )f e =600Hz, here we select 160Hz.

[0069] Select characteristic impedance R c If the impedance is 1Ω, the cutoff frequency conversion coefficient M and the characteristic impedance conversion coefficient K can be expressed as:

[0070]

[0071] Wherein, f0=1 / (2π) Hz represents the cutoff frequency of the normalized filter circuit. R0=1Ω represents the characteristic impedance of the normalized low-pass filter circuit. In this embodiment, M=1000 and K=1 are calculated.

[0072] The expressions of capacitance C and inductance L of the RLC low-pass filter circuit are:

[0073]

[0074] The low-pass filter circuit in this example has an inductance of L = 1mH and a capacitance of C = 1000μF. A first-order RLC low-pass filter circuit will resonate near the resonant frequency. To suppress the resonance, a 1Ω resistor is connected in series with the capacitor branch. The motor excitation winding drive system with the RLC low-pass filter circuit is shown in the figure below. Figure 5 As shown, the Bode diagram of the low-pass filter circuit is as follows Figure 6 shown.

[0075] The magnetic field circuit joint simulation is used to verify the suppression effect of the low-pass filter circuit on the excitation winding induced pulsating voltage. The joint simulation predicts the waveform and spectrum of the no-load excitation winding induced pulsating voltage before and after the addition of the low-pass filter circuit. Figure 7-Figure 9 As shown, the waveform and spectrum of the induced pulsating voltage of the loaded excitation winding are as follows: Figure 10-12 As shown. After adding the low-pass filter circuit, the peak-to-peak value of the induced pulsating voltage of the excitation winding is greatly reduced. In addition, since the low-pass filter circuit is higher than f c =160Hz, it will attenuate. No matter it is unloaded or loaded, its baseband harmonics (600Hz, 1200Hz), sideband harmonics (10kHz±600Hz) and carrier harmonics (10kHz) are significantly suppressed compared with those before the low-pass filter circuit is added.

[0076] The above embodiments are only for illustrating the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for suppressing induced ripple voltage based on a low-pass filter circuit, characterized in that: The method suppresses the induced pulsating voltage of the excitation winding by connecting a low-pass filter circuit with specific parameters in parallel to the input end of the excitation winding of the electric excitation magnetic field modulation motor under PWM excitation; The design steps of the inductance and capacitance parameters of the low-pass filter circuit with specific parameters are as follows: S1. Determine the number of pulsating voltage induced by the motor excitation winding and the motor fundamental frequency based on the number of stator slots, the number of rotor poles, and the motor speed of the motor modulated by the electromagnetic field. The specific process is as follows: S101, determining the number of pulsations of the induced pulsating voltage of the motor's no-load excitation winding based on the number of stator slots and rotor poles of the motor, and further determining the number of pulsations of the induced pulsating voltage of the motor's loaded excitation winding; S102, determining the motor fundamental frequency based on the motor speed and the number of rotor poles; S2. Select the cutoff frequency of the low-pass filter circuit under no-load and loaded conditions, and determine the inductance and capacitance parameters of the low-pass filter circuit according to the cutoff frequency. The specific process is as follows: S201, selecting a cutoff frequency that is smaller than the product of the number of pulsations of the induced pulsating voltage of the motor's no-load excitation winding and the motor's fundamental frequency, thereby suppressing the induced pulsating voltage of the excitation winding under no-load conditions; selecting a cutoff frequency that is smaller than the product of the number of pulsations of the induced pulsating voltage of the motor's loaded excitation winding and the motor's fundamental frequency, thereby suppressing the induced pulsating voltage of the excitation winding under loaded conditions; S202 : Obtain a cutoff frequency conversion coefficient and a characteristic impedance conversion coefficient according to the selected cutoff frequency and characteristic impedance, thereby calculating the inductance and capacitance of the low-pass filter circuit.

2. The method for suppressing induced ripple voltage based on a low-pass filter circuit according to claim 1, characterized in that: In the above S101, under no-load condition, the pulsation number N of the induced pulsating voltage of the motor no-load excitation winding is pef The expression is: Among them, N s is the number of stator slots of the motor, N r is the number of rotor poles, LCM represents the least common multiple; The pulsation number N of the induced pulsating voltage of the excitation winding caused by the armature reaction pea The expression is: N pea =min{3r×Sgn(k w(3r+1) +k w(3r-1) )} Among them, Sgn is the sign function, k w(3r+1) 、k w(3r-1) They are the 3r+1 and 3r-1 harmonics of the motor winding factor, respectively, where r is a positive integer; Under loading conditions, the motor loaded excitation winding induced pulsation voltage pulsation number N pe The expression is: N pe =min{N pef ,N pea }。 3. The method for suppressing induced ripple voltage based on a low-pass filter circuit according to claim 1, characterized in that: In S102, the motor fundamental frequency is expressed as: Among them, f e is the motor fundamental frequency, N r is the number of rotor poles, and n is the motor speed.

4. The method for suppressing induced ripple voltage based on a low-pass filter circuit according to claim 1, characterized in that: In S202, the expressions of the cutoff frequency conversion coefficient M and the characteristic impedance conversion coefficient K are: Among them, f c is the cutoff frequency, R c is the characteristic impedance, R c =1Ω, f0 is the cutoff frequency of the normalized filter circuit, f0=1 / (2π)Hz, R0 is the characteristic impedance of the normalized low-pass filter circuit, R0=1Ω; The inductance L and capacitance C of the low-pass filter circuit are expressed as:

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