A motor system for reducing common mode voltage and a method for determining filter parameters thereof

Abstract

The present invention relates to a motor system for reducing common-mode voltage and a filter parameter determination method thereof. The motor system includes an M-phase voltage source inverter and an M-phase permanent magnet synchronous motor. The M-phase permanent magnet synchronous motor includes M filter branches and M motor branches. The input ends of the M filter branches are respectively connected to each phase of the M-phase voltage source inverter, and the output ends of the M filter branches are respectively connected to the input ends of the motor branches located in the same phase winding. The output ends of each motor branch are connected to each other. The M-phase permanent magnet synchronous motor also includes M passive branches. The connection between the output end of each filter branch and the input end of the motor branch is connected to the input end of a passive branch through a lead tap. This structure can filter out the common-mode voltage through an integrated common-mode voltage filter while reducing the volume of the overall system, thereby improving the functional density, service life and reliability of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motors, and in particular to a motor system for reducing common mode voltage and a method for determining filter parameters thereof. Background Art

[0002] Inverter drive technology, based on pulse-width modulation (PWM) strategies, is widely used in AC motor drive systems. However, the common-mode voltage it generates can negatively impact the performance of the motor drive system, reducing overall system performance, decreasing reliability, and increasing failure rates, hindering the inverter system's long-term stable operation. Furthermore, with the advancement of power electronics technology, the switching frequency of power devices and the voltage levels of motor drive systems have increased, further amplifying the impact of common-mode voltage issues.

[0003] The stray capacitance of the motor creates a loop, which, combined with the common-mode voltage, generates shaft voltage on the motor's shaft, damaging the motor's bearings and shortening their lifespan. The leakage current caused by this common-mode voltage, when applied to the stator windings, accelerates insulation degradation. This leakage current can also cause relays to malfunction, triggering circuit protection mechanisms and causing circuit breakers. Common-mode EMI can increase electromagnetic interference (EMI) in the motor drive system, impacting the normal operation of surrounding electronic equipment. Therefore, suppressing common-mode voltage in motor drive systems is crucial.

[0004] In the prior art, in order to meet the common-mode voltage suppression requirements of the motor drive system, a common-mode filter is usually added between the inverter and the motor. However, this method significantly increases the volume and weight of the system, thereby reducing the power density of the system.

[0005] In summary, research and development of integrated winding structures that reduce common-mode voltage are of great significance for improving the service life, reliability and power density of motor drive systems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a motor system for reducing common-mode voltage and an integrated common-mode voltage filter, which can suppress common-mode voltage, improve system power density, and extend service life, and a method for determining filter parameters thereof.

[0007] In a first aspect, the technical solution adopted by the present invention is a motor system for reducing common mode voltage, comprising a system body, wherein the system body comprises an M-phase voltage source inverter and an M-phase permanent magnet synchronous motor connected to the M-phase voltage source inverter, wherein the winding in each phase of the M-phase permanent magnet synchronous motor is divided into two parts, wherein one part of the winding serves as a filter branch, and the other part of the winding serves as a motor branch, that is, the M-phase permanent magnet synchronous motor comprises M filter branches and M motor branches, wherein the input ends of the M filter branches are respectively connected to each phase of the M-phase voltage source inverter, and the output ends of the M filter branches are respectively connected to the input end of the motor branch in the same phase winding, and the output ends of each motor branch are connected to each other, and the M-phase permanent magnet synchronous motor further comprises M passive branches, wherein the connection between the output end of each filter branch and the input end of the motor branch is connected to the input end of a passive branch through a lead tap, and the output ends of the M passive branches are simultaneously connected to the midpoint of the DC bus of the M-phase inverter, and the passive branch comprises a resistor R f and the resistor R f The series capacitor C f .

[0008] The beneficial effect of the present invention is that: the motor system topology structure for reducing the common mode voltage of the above structure is adopted, each phase winding of the permanent magnet synchronous motor is divided into two parts, the input end of one part of the winding in each phase winding is connected to one phase of the M-phase inverter, and its output end is connected to the input end of the other part of the winding, and then a passive branch is connected at the connection of the two parts of the winding through a tap, and the passive branch includes a resistor R f and the resistor R f The series capacitor C f , the filter branch consists of a tap and a resistor R f Connected inductor L f And resistor R1, inductor L f , resistor R f and capacitor C f In fact, an integrated common-mode voltage filter is formed, that is, an integrated common-mode voltage filter is directly constructed by part of the motor winding, thus omitting the inductance structure of the filter connected to the permanent magnet synchronous motor in the original technology. This structure can filter out the common-mode voltage through the integrated common-mode voltage filter while reducing the volume of the overall system, thereby improving the functional density, service life and reliability of the system.

[0009] Preferably, the M-phase voltage source inverter is a three-phase voltage source inverter, the M-phase permanent magnet synchronous motor is a three-phase permanent magnet synchronous motor, the three-phase permanent magnet synchronous motor is a ten-pole twelve-slot permanent magnet synchronous motor, the permanent magnet synchronous motor includes three filter branches and three motor branches, and the system body includes three passive branches. With this structure, a permanent magnet synchronous motor drive system with an integrated common-mode voltage filter is formed by a three-phase voltage source inverter and a permanent magnet synchronous motor composed of three-phase windings. The system can filter out the common-mode voltage to the maximum extent while reducing the volume of the overall system, thereby improving the functional density, service life and reliability of the system.

[0010] In a second aspect, the technical solution adopted by the present invention is a method for determining filter parameters of a permanent magnet synchronous motor system, the method comprising the following steps:

[0011] S1. A three-phase permanent magnet synchronous motor includes an A-phase winding, a B-phase winding, and a C-phase winding. The inductance value L and the resistance value R of each phase winding in the three-phase permanent magnet synchronous motor are measured by a measurement method. The A-phase winding, the B-phase winding, and the C-phase winding of the permanent magnet synchronous motor are divided into two parts according to the ratio of r1:r2, one part is used to form a filter branch, and the other part is used to form a motor branch, thereby obtaining an A-phase filter branch, a B-phase filter branch, and a C-phase filter branch, and also obtaining an A-phase motor branch, a B-phase motor branch, and a C-phase motor branch;

[0012] S2. A three-phase high-frequency equivalent circuit is constructed based on the permanent magnet synchronous motor system. In the three-phase high-frequency equivalent circuit, the equivalent impedance of each phase filter branch is Z1=sL×r1+R×r1, the equivalent impedance of each phase motor branch is Z2=sL×r2+R×r2, and the equivalent impedance of the corresponding passive branch is Z f =sC f +R f , where s represents the symbol in frequency domain analysis, C f Represents the capacitance C in the passive branch f The capacitance value, R f Represents the resistance R in the passive branch f The resistance value;

[0013] S3. Calculate the voltage difference v between the motor neutral point N and the ground for the three-phase high-frequency equivalent circuit obtained in step S2. N1 , Among them, v com1 represents the common mode voltage value of the three-phase high-frequency equivalent circuit, v N1 =v fa -v am =v fb -v bm =v fc -vcm , v ma ,v mb ,v mc Represents the voltage drop of each phase motor branch winding of the three-phase permanent magnet synchronous motor, v fa , v fb , v fc Represent the voltages at the output ends of the three filter branches respectively; ignore the passive branch in the three-phase high-frequency equivalent circuit, and calculate the voltage difference v between the motor neutral point N and the ground in the three-phase high-frequency equivalent circuit after ignoring the passive branch N2 , Among them, v com2 Indicates the common mode voltage value after the passive branch is ignored in the three-phase high-frequency equivalent circuit, v A , v B , v C They represent the line voltage at the input end of each phase winding of the three-phase permanent magnet synchronous motor after ignoring the passive branch;

[0014] S4, for the three-phase high-frequency equivalent circuit obtained in step S2, the three-phase voltage source inverter includes A-phase voltage source, B-phase voltage source and C-phase voltage source; assume that only A-phase voltage source is working, and B-phase voltage source and C-phase voltage source are in a short-circuit state. In this case, calculate v fa The voltage transfer function TF(1) when only the phase A voltage source is supplying power; assume that only the phase B voltage source is working, and the phase A voltage source and the phase C voltage source are in a short-circuit state. In this case, calculate v fa The voltage transfer function TF(2) when only the B-phase voltage source is supplying power; assume that only the C-phase voltage source is working, and the A-phase voltage source and the B-phase voltage source are in a short-circuit state. In this case, calculate v fa The voltage transfer function TF(3) when only the C-phase voltage source is supplying power; similarly, we can calculate v fb and v fc The voltage transfer function of

[0015] S5. According to the voltage transfer function obtained in step S4, the voltage v at the output of the A-phase filter branch in the three-phase high-frequency equivalent circuit is calculated. fa For: v fa =v fa1 +v fa2 +v fa3 =TF(1)×v A +TF(2)×v B +TF(3)×v C ; Among them, v fa1 It represents the voltage at the output of the A-phase filter branch when only the A-phase voltage source is supplying power, v fa2It represents the voltage at the output of the A-phase filter branch when only the B-phase voltage source is supplying power, v fa3 represents the voltage at the output of the A-phase filter branch when only the C-phase voltage source is supplied; similarly, calculate the voltage v at the output of the B-phase filter branch in the three-phase high-frequency equivalent circuit. fb For: v fb =v fb1 +v fb2 +v fb3 =TF(2)×v A +TF(1)×v B +TF(3)×v C ; Among them, v fb1 It represents the voltage at the output of the B-phase filter branch when only the A-phase voltage source is supplying power, v fb2 It represents the voltage at the output of the B-phase filter branch when only the B-phase voltage source is supplying power, v fb3 represents the voltage at the output of the B-phase filter branch when only the C-phase voltage source is supplied; similarly, calculate the voltage v at the output of the C-phase filter branch in the three-phase high-frequency equivalent circuit. fc For: v fc =v fc1 +v fc2 +v fc3 =TF(2)×v A +TF(3)×v B +TF(1)×v C ; Among them, v fc1 It represents the voltage at the output of the C-phase filter branch when only the A-phase voltage source is supplying power, v fc2 It represents the voltage at the output of the C-phase filter branch when only the B-phase voltage source is supplying power, v fc3 It represents the voltage at the output of the C-phase filter branch when only the C-phase voltage source is supplying power;

[0016] S6, the common mode voltage value v obtained in step S3 com1 and common mode voltage v com2 , calculate the ratio between the two common-mode voltage values, that is, v com1 / v com2 The ratio represents the attenuation of the common-mode voltage at different frequencies compared to the input voltage at the motor input terminal. The attenuation of the common-mode voltage at the selected frequency and the resistance R on the passive path are obtained according to the ratio. f , capacitor C f The selection relationship, when v com1 / v com2 When the resistance R on the passive path reaches its minimum f and capacitor C f The combination of is the optimal solution; among them, BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A topological structure diagram of a motor system for reducing common mode voltage according to the present invention;

[0018] Figure 2 This is a system structure diagram of a motor system for reducing common mode voltage according to the present invention;

[0019] Figure 3 Schematic diagram of the structure of the three-phase high-frequency equivalent circuit of the present invention;

[0020] Figure 4 A comparison diagram of common-mode voltage peak-to-peak curves at different common-mode filter cutoff frequencies in the present invention;

[0021] Figure 5 A comparison diagram of the common-mode voltage RMS value curves at different common-mode filter cutoff frequencies in the present invention;

[0022] Figure 6 1 is a comparison diagram of the high-frequency component curves of the switching frequency (10 kHz) of the common-mode voltage at different common-mode filter cut-off frequencies in the present invention. DETAILED DESCRIPTION

[0023] The invention will be further described below with reference to the accompanying drawings and in combination with specific implementations, so that those skilled in the art can implement the invention with reference to the description. The protection scope of the invention is not limited to the specific implementations.

[0024] Example 1:

[0025] In a first aspect, a motor system for reducing common mode voltage includes a system body, such as Figure 1 As shown, the system body includes a three-phase voltage source inverter and a three-phase permanent magnet synchronous motor connected to the three-phase voltage source inverter. Each phase winding of the three-phase permanent magnet synchronous motor is evenly divided into two parts, one part of the winding is used as a filter branch, and the other part of the winding is used as a motor branch. That is, the three-phase permanent magnet synchronous motor includes three filter branches and three motor branches. The three filter branches are Figure 2 The A phase filter branch (A1_F, A12_F), the B phase filter branch (B2_F, B3_F) and the C phase filter branch (C4_F, C5_F) in the three motor branches are Figure 2The A-phase motor branch (A6_M, A7_M), the B-phase motor branch (B8_M, B9_M) and the C-phase motor branch (C10_M, C11_M) in the three-phase voltage source inverter are connected to each phase of the three-phase voltage source inverter, that is, the input end A_F+ of the A-phase filter branch is connected to the A-phase voltage source of the three-phase voltage source inverter, the input end B_F+ of the B-phase filter branch is connected to the B-phase voltage source of the three-phase voltage source inverter, and the input end C_F+ of the C-phase filter branch is connected to the C-phase voltage source of the three-phase voltage source inverter; the output ends of the three filter branches are respectively connected to the input ends of the motor branches located in the same phase winding, that is, the output end A_F- of the A-phase filter branch is connected to the input end A_M+ of the A-phase motor branch, and the output end B_F- of the B-phase filter branch is connected to the input end B_M+ of the B-phase motor branch. , the output end C_F- of the C-phase filter branch is connected to the input end C_M+ of the C-phase motor branch; then the output end A_M- of the A-phase motor branch, the output end B_M- of the B-phase motor branch and the output end C_M- of the C-phase motor branch are connected to each other, and the three-phase permanent magnet synchronous motor also includes three passive branches, the connection between the output end A_F- of the A-phase filter branch and the input end A_M+ of the A-phase motor branch is connected to a passive branch through a tap, the connection between the output end B_F- of the B-phase filter branch and the input end B_M+ of the B-phase motor branch is connected to a passive branch through a tap, the connection between the output end C_F- of the C-phase filter branch and the input end C_M+ of the C-phase motor branch is connected to a passive branch through a tap, and the output ends of the three passive branches are simultaneously connected to the midpoint of the DC bus of the three-phase inverter, and the passive branch includes a resistor R f and the resistor R f The series capacitor C f , the filter branch is equivalent to the tap and resistor R f Connected inductor L f and the inductor L f The motor branch includes a resistor R1 connected in series with the resistor R f The connected resistor R2 and the inductor L in series with the resistor R2 m .

[0026] The motor system with the above structure for reducing common mode voltage is used to divide each phase winding of the permanent magnet synchronous motor into two parts in a ratio of 1:1. The input end of one part of the winding in each phase winding is connected to one phase of the three-phase inverter, and its output end is connected to the input end of the other part of the winding. A passive branch is then connected at the connection between the two parts of the winding through a tap. The passive branch includes a resistor R f and the resistor R f The series capacitor C f, the filter branch is equivalent to the tap and resistor R f Connected inductor L f And resistor R1, inductor L f , resistor R f and capacitor C f In fact, an integrated common-mode voltage filter is formed, that is, an integrated common-mode voltage filter is directly constructed by part of the winding of the motor, thus omitting the inductance structure of the filter connected to the permanent magnet synchronous motor in the original technology. The technical solution of the original technology is to reconstruct a common-mode filter composed of resistors, inductors and capacitors outside the permanent magnet synchronous motor to connect to the permanent magnet synchronous motor. The magnetic inductance of the common-mode filter generally needs to occupy 25% of the volume of the entire motor drive system. Its function is to filter out the common-mode voltage. Then the structure of the original technology has the defects of large volume, large weight, low system power density, low reliability, and low efficiency in suppressing common-mode voltage. However, by adopting the structure described in this embodiment, the common-mode voltage can be filtered out by the integrated common-mode voltage filter while reducing the volume of the overall system, improving the functional density, service life and reliability of the system, and also improving the efficiency of suppressing common-mode voltage.

[0027] like Figure 2 As shown, the three-phase permanent magnet synchronous motor is a ten-pole twelve-slot permanent magnet synchronous motor, which includes three filter branches and three motor branches. The system body includes three passive branches. With this structure, a permanent magnet synchronous motor drive system with an integrated common-mode voltage filter is formed by a three-phase voltage source inverter and a permanent magnet synchronous motor composed of six-phase windings. The system can filter out the common-mode voltage to the maximum extent while reducing the volume of the overall system, thereby improving the functional density, service life and reliability of the system.

[0028] Secondly, the filtering effect of the integrated common-mode voltage filter on high-frequency components is determined by the resistor R f and capacitor C f In order to achieve the best filtering effect of common mode voltage, this embodiment of the present invention also provides a method for determining the parameters of the filter of a permanent magnet synchronous motor system, which includes the following steps:

[0029] S1, a three-phase permanent magnet synchronous motor includes an A-phase winding, a B-phase winding, and a C-phase winding. The inductance L and resistance R of each phase winding in the three-phase permanent magnet synchronous motor are measured by measurement. The inductance value of each phase winding is equal, and the resistance value of each phase winding is equal. The A-phase winding, the B-phase winding, and the C-phase winding of the permanent magnet synchronous motor are divided into two parts according to the ratio of r1:r2, one part of which is used to form a filter branch, and the other part is used to form a motor branch, to obtain an A-phase filter branch, a B-phase filter branch, and a C-phase filter branch, an A-phase motor branch, a B-phase motor branch, and a C-phase motor branch; in this embodiment, r1 is 1, and r2 is 1;

[0030] S2. Construct a three-phase high-frequency equivalent circuit based on the permanent magnet synchronous motor system, such as Figure 3 As shown, in Figure 3 In the three-phase high-frequency equivalent circuit, the equivalent impedance of the filter branch is Z1=sL×r1+R×r1, the equivalent impedance of the motor branch is Z2=sL×r2+R×r2, and the equivalent impedance of the passive branch is Z f =sC f +R f , where s represents the frequency domain symbol, C f Represents the capacitance C in the passive branch f The capacitance value, R f Represents the resistance R in the passive branch f The resistance value;

[0031] S3. Calculate the voltage difference v between the motor neutral point N and the ground for the three-phase high-frequency equivalent circuit obtained in step S2. N1 , Among them, v com1 represents the common mode voltage value of the three-phase high-frequency equivalent circuit, v N1 =v fa -v ma =v fb -v mb =v fc -v mc , v ma +v mb +v mc =0,v ma ,v mb ,v mc Represents the voltage drop of each phase winding of the three-phase permanent magnet synchronous motor, v fa , v fb , v fc Represent the voltages at the output ends of the three filter branches respectively; ignore the passive branch in the three-phase high-frequency equivalent circuit, and calculate the voltage difference v between the motor neutral point N and the ground in the three-phase high-frequency equivalent circuit after ignoring the passive branchN2 , Among them, v com2 It represents the common mode voltage value of the three-phase high-frequency equivalent circuit after ignoring the passive branch, v A , v B , v C They respectively represent the line voltage at the input end of each phase winding of the three-phase permanent magnet synchronous motor after ignoring the passive branch; note that the three-phase high-frequency equivalent circuit obtained in step S2 after ignoring the passive branch is the three-phase high-frequency circuit of the three-phase permanent magnet synchronous motor without connecting to the passive branch, which is actually the three-phase high-frequency circuit of the traditional permanent magnet synchronous motor;

[0032] S4. For the three-phase high-frequency equivalent circuit obtained in step S2, the three-phase voltage source inverter includes phase A voltage source, phase B voltage source and phase C voltage source. It is assumed that only phase A voltage source is working, and phase B voltage source and phase C voltage source are in a short-circuit state. In this case, calculate v fa The voltage transfer function TF(1) when only the phase A voltage source is supplying power; assume that only the phase B voltage source is working, and the phase A voltage source and the phase C voltage source are in a short-circuit state. In this case, calculate v fa The voltage transfer function TF(2) when only the B-phase voltage source is supplying power; assume that only the C-phase voltage source is working, and the A-phase voltage source and the B-phase voltage source are in a short-circuit state. In this case, calculate v fa The voltage transfer function TF(3) when only the C-phase voltage source is supplying power; similarly, we can calculate v fb and v fc The voltage transfer function of

[0033] S5. According to the superposition theorem of circuits, for a linear system, the response (voltage or current) of any branch of a bilateral linear circuit containing multiple independent sources is equal to the algebraic sum of the responses of each independent source when it acts alone, when all other independent sources are replaced by their respective impedances, that is, Figure 3 The equivalent model shown in fa The voltage can be obtained by the transfer function obtained in step S4 and the input three-phase voltage source, that is: fa =v fa1 +v fa2 +v fa3 =TF(1)×v A +TF(2)×v B +TF(3)×v C , where v fa1 It represents the voltage at the output of the A-phase filter branch when only the A-phase voltage source is supplying power, v fa2 It represents the voltage at the output of the A-phase filter branch when only the B-phase voltage source is supplying power, v fa3represents the voltage at the output of the A-phase filter branch when only the C-phase voltage source is supplied; similarly, calculate the voltage v at the output of the filter branch in the three-phase high-frequency equivalent circuit. fb For: v fb =v fb1 +v fb2 +v fb3 =TF(2)×v A +TF(1)×v B +TF(3)×v C , v fb1 It represents the voltage at the output of the B-phase filter branch when only the A-phase voltage source is supplying power, v fb2 It represents the voltage at the output of the B-phase filter branch when only the B-phase voltage source is supplying power, v fb3 represents the voltage at the output of the B-phase filter branch when only the C-phase voltage source is supplied; similarly, calculate the voltage v at the output of the filter branch in the three-phase high-frequency equivalent circuit. fc For: v fc =v fc1 +v fc2 +v fc3 =TF(2)×v A +TF(3)×v B +TF(1)×v C , v fc1 It represents the voltage at the output of the C-phase filter branch when only the A-phase voltage source is supplying power, v fc2 It represents the voltage at the output of the C-phase filter branch when only the B-phase voltage source is supplying power, v fc3 It represents the voltage at the output of the C-phase filter branch when only the C-phase voltage source is supplying power;

[0034] S6, the common mode voltage value v obtained in step S3 com1 and common mode voltage v com2 , calculate the ratio between the two common-mode voltage values, that is, v com1 / v com2 The ratio represents the attenuation of the common-mode voltage at different frequencies compared to the input voltage at the motor input terminal. The filtering effect of the integrated common-mode voltage filter is evaluated based on the ratio. The attenuation of the common-mode voltage at the selected frequency and the resistance R on the passive path are obtained based on the ratio. f , capacitor C f The selection relationship, when v com1 / v com2 When the resistance R on the passive path reaches its minimum f and capacitor C f The combination of is the optimal solution; among them,

[0035] In step S4, the voltage transfer function Voltage transfer function Voltage transfer function Where a3 = 3C f 2 LR f r1r2,a2=C f 2 R f 2 R1+3C f 2 R f 2 r2+3C f Lr1r2+3C f 2 RR f r1r2, a1=2C f R f r1+6C f R f r2+3C f Rr1r2, a0=r1+3r2, b4=3C f 2 L 2 R1 2 R2, B3 = 3c f 2 LR f R1 2 +6C f 2 LR f r1r2+6C f 2 LRr1 2 r2,b2=3r2C f 2 R 2 r1 2 +3C f 2 RR f r1 2 +6r2C f 2 RR f r1+3C f 2 R f 2 r1+3r2C f 2 R f 2 +3LC f r1 2 +6Lr2C f r1b1=6C f Rf r1+6C f R f r2+3C f Rr1 2 +6C f Rr1r2b0=3r1+3r2,c2=r1C f 2 R f 2 , c1=2C f R f r1, c0 = r1.

[0036] The motor system for reducing common mode voltage proposed in the first embodiment is illustrated by simulation experiments. After simulation verification, the motor system Figure 1 The motor system shown, under open-loop control, can effectively reduce the RMS value, peak-to-peak value, and high-frequency components of the motor's common-mode voltage. The peak-to-peak and RMS values of the common-mode voltage can be reduced to up to 10% of the common-mode voltage of the original motor (i.e., without an integrated common-mode voltage filter), and the high-frequency components at the switching frequency can be reduced by up to 98%. Detailed simulation results can be found in Figure 4 、 Figure 5 and Figure 6 , Figure 4 The peak-to-peak common-mode voltage at different filter cutoff frequencies is shown. Figure 5 The RMS value at different filter cutoff frequencies is shown. Figure 6 The high frequency components at different filter cutoff frequencies are shown. Figure 4 、 Figure 5 and Figure 6 In the figure, the dotted line represents the common-mode voltage of the original motor, the vertical axis represents the voltage value after normalization, and the horizontal axis represents the value of the resistor in the integrated filter.

Claims

1. A method for determining filter parameters of a permanent magnet synchronous motor system for reducing common mode voltage, characterized by: The motor system includes a system body, which includes an M-phase voltage source inverter and an M-phase permanent magnet synchronous motor connected to the M-phase voltage source inverter. The windings in each phase of the M-phase permanent magnet synchronous motor are divided into two parts, one part of the windings serves as a filter branch, and the other part of the windings serves as a motor branch, that is, the M-phase permanent magnet synchronous motor includes M filter branches and M motor branches, the input ends of the M filter branches are respectively connected to each phase of the M-phase voltage source inverter, the output ends of the M filter branches are respectively connected to the input ends of the motor branches in the same phase winding, and the output ends of each motor branch are connected to each other. The M-phase permanent magnet synchronous motor also includes M passive branches, and the connection between the output end of each filter branch and the input end of the motor branch is connected to the input end of a passive branch through a lead-out tap, and the output ends of the M passive branches are simultaneously connected to the midpoint of the DC bus of the M-phase inverter. The passive branch includes a resistor R f and the resistor R f The series capacitor C f ; The method comprises the following steps: S1. A three-phase permanent magnet synchronous motor includes an A-phase winding, a B-phase winding, and a C-phase winding. The inductance value L and the resistance value R of each phase winding in the three-phase permanent magnet synchronous motor are measured by a measurement method. The A-phase winding, the B-phase winding, and the C-phase winding of the permanent magnet synchronous motor are divided into two parts according to the ratio of r1:r2, one part is used to form a filter branch, and the other part is used to form a motor branch, thereby obtaining an A-phase filter branch, a B-phase filter branch, and a C-phase filter branch, and also obtaining an A-phase motor branch, a B-phase motor branch, and a C-phase motor branch; S2. A three-phase high-frequency equivalent circuit is constructed based on the permanent magnet synchronous motor system. In the three-phase high-frequency equivalent circuit, the equivalent impedance of each phase filter branch is Z1 = sL × r1 + R × r1, the equivalent impedance of each phase motor branch is Z2 = sL × r2 + R × r2, and the equivalent impedance of the corresponding passive branch is Z f =sC f +R f , where s represents the symbol in frequency domain analysis, C f Represents the capacitance C in the passive branch f The capacitance value, R f Represents the resistance R in the passive branch f The resistance value; S3. Calculate the voltage difference v between the motor neutral point N and the ground for the three-phase high-frequency equivalent circuit obtained in step S2. N1 , Among them, v com1 represents the common mode voltage value of the three-phase high-frequency equivalent circuit, v N1 =v fa -v am =v fb -v bm =v fc -v cm , v ma ,v mb ,v mc Represents the voltage drop of each phase motor branch winding of the three-phase permanent magnet synchronous motor, v fa , v fb , v fc Represent the voltages at the output ends of the three filter branches respectively; ignore the passive branch in the three-phase high-frequency equivalent circuit, and calculate the voltage difference v between the motor neutral point N and the ground in the three-phase high-frequency equivalent circuit after ignoring the passive branch N2 , Among them, v com2 Indicates the common mode voltage value after the passive branch is ignored in the three-phase high-frequency equivalent circuit, v A , v B , v C They represent the line voltage at the input end of each phase winding of the three-phase permanent magnet synchronous motor after ignoring the passive branch; S4, for the three-phase high-frequency equivalent circuit obtained in step S2, the three-phase voltage source inverter includes A-phase voltage source, B-phase voltage source and C-phase voltage source; assume that only A-phase voltage source is working, and B-phase voltage source and C-phase voltage source are in a short-circuit state. In this case, calculate v fa The voltage transfer function TF(1) when only the phase A voltage source is supplying power; assume that only the phase B voltage source is working, and the phase A voltage source and the phase C voltage source are in a short-circuit state. In this case, calculate v fa The voltage transfer function TF(2) when only the B-phase voltage source is supplying power; assume that only the C-phase voltage source is working, and the A-phase voltage source and the B-phase voltage source are in a short-circuit state. In this case, calculate v fa The voltage transfer function TF(3) when only the C-phase voltage source is supplying power; similarly, we can calculate v fb and v fc The voltage transfer function of S5. According to the voltage transfer function obtained in step S4, the voltage v at the output of the A-phase filter branch in the three-phase high-frequency equivalent circuit is calculated. fa For: v fa =v fa1 +v fa2 +v fa3 =TF(1)×v A +TF(2)×v B +TF(3)×v C ; Among them, v fa1 It represents the voltage at the output of the A-phase filter branch when only the A-phase voltage source is supplying power, v fa2 It represents the voltage at the output of the A-phase filter branch when only the B-phase voltage source is supplying power, v fa3 represents the voltage at the output of the A-phase filter branch when only the C-phase voltage source is supplied; similarly, calculate the voltage v at the output of the B-phase filter branch in the three-phase high-frequency equivalent circuit. fb For: v fb =v fb1 +v fb2 +v fb3 =TF(2)×v A +TF(1)×v B +TF(3)×v C ; Among them, v fb1 It represents the voltage at the output of the B-phase filter branch when only the A-phase voltage source is supplying power, v fb2 It represents the voltage at the output of the B-phase filter branch when only the B-phase voltage source is supplying power, v fb3 represents the voltage at the output of the B-phase filter branch when only the C-phase voltage source is supplied; similarly, calculate the voltage v at the output of the C-phase filter branch in the three-phase high-frequency equivalent circuit. fc For: v fc =v fc1 +v fc2 +v fc3 =TF(2)×v A +TF(3)×v B +TF(1)×v C ; Among them, v fc1 It represents the voltage at the output of the C-phase filter branch when only the A-phase voltage source is supplying power, v fc2 It represents the voltage at the output of the C-phase filter branch when only the B-phase voltage source is supplying power, v fc3 It represents the voltage at the output of the C-phase filter branch when only the C-phase voltage source is supplying power; S6, according to the obtained common mode voltage value v com1 and common mode voltage v com2 , calculate the ratio between the two common-mode voltage values, that is, v com1 / v com2 The ratio represents the attenuation of the common-mode voltage at different frequencies compared to the input voltage at the motor input terminal. The attenuation of the common-mode voltage at the selected frequency and the resistance R on the passive path are obtained according to the ratio. f , capacitor C f The selection relationship, when v com1 / v com2 When the resistance R on the passive path reaches its minimum f and capacitor C f The combination of is the optimal solution; among them, 2. The method for determining filter parameters of a permanent magnet synchronous motor system for reducing common mode voltage according to claim 1, wherein: The M-phase voltage source inverter is a three-phase voltage source inverter, the M-phase permanent magnet synchronous motor is a three-phase permanent magnet synchronous motor, the three-phase permanent magnet synchronous motor is a ten-pole twelve-slot permanent magnet synchronous motor, the three-phase permanent magnet synchronous motor includes three filter branches and three motor branches, and the system body includes three passive branches.

Images