Common-mode voltage analysis and suppression method for fault asymmetric motor system

Abstract

The invention relates to a common-mode voltage analysis and suppression method for a fault asymmetric motor system, and the method comprises the following steps: S1, common-mode voltage modeling: building a common-mode voltage model under an open-circuit fault, and representing the common-mode voltage model as a weighted combination of healthy bridge arm voltages; s2, inductance matrix construction: obtaining self-inductance and mutual inductance of each phase, and constructing an inductance matrix; s3, weighting coefficient calculation: diagonalizing the inductance matrix, and deducing the weighting coefficient by combining the fault phase current as zero; s4, zero-sequence voltage injection: adjusting the zero-sequence voltage according to the duty ratio and the alignment constraint to realize pulse alignment; s5, in-group cancellation: the bridge arms are grouped according to the polarity of the weighting coefficient, and pulse edges are aligned in the group; s6, inter-group cancellation: carrying out inter-group alignment on residual pulse edges, and optimizing common-mode rejection; according to the method, effective suppression of common-mode noise and high adaptability of engineering implementation are realized through accurate modeling of common-mode voltage and low-complexity suppression algorithm design under the fault condition.

Description

Technical Field

[0001] This invention relates to the field of motor drive technology, and in particular to a common-mode voltage analysis and suppression method for faulty asymmetrical motor systems. Background Technology

[0002] Variable frequency drive systems are key devices for converting DC to AC power and are widely used in speed regulation and power control scenarios. In order to obtain controllable AC output, frequency converters often use pulse width modulation (PWM) technology to control the switching devices to turn on and off at high speed, generating high-frequency voltage pulses to simulate modulation waves, thereby optimizing the dynamic performance and speed regulation accuracy of the system. However, while PWM improves performance, it inevitably generates common-mode electromagnetic noise, causing common-mode interference and electromagnetic erosion problems. Especially in harsh environments such as high temperature, high humidity, and high dust, the reliability of frequently switching devices faces challenges.

[0003] Multiphase signal drive systems have gained importance in high-reliability scenarios due to their higher degree of freedom in modulation and control. However, most existing fault-tolerant control research focuses on differential-mode performance indicators, such as stator copper loss, output torque, and torque ripple, while paying insufficient attention to common-mode performance. In addition, existing common-mode voltage suppression methods are mostly based on modulation strategy optimization under symmetrical operating conditions, which are difficult to adapt to actual operating conditions such as open-circuit faults that lead to power supply asymmetry, resulting in a significant decrease in suppression effect and limiting the system's stable operation capability in complex scenarios. Summary of the Invention

[0004] This invention provides a common-mode voltage analysis and suppression method for faulty asymmetric motor systems. By establishing an accurate common-mode voltage expression model and introducing a dynamic modulation control mechanism, the method improves the common-mode voltage characterization and control capability under fault conditions, providing technical support for the stable operation and electromagnetic compatibility design of electric drive systems under all operating conditions.

[0005] A common-mode voltage analysis and suppression method for faulty asymmetrical motor systems includes the following steps:

[0006] S1, Common-mode voltage modeling: Based on the equivalent ground loop of the single-phase winding of the motor, a mathematical model of common-mode voltage under bridge arm open-circuit fault is established, and the common-mode voltage is expressed as a weighted combination of healthy bridge arm voltages;

[0007] S2, Inductance matrix construction: Obtain the self-inductance and mutual inductance of each phase of the motor through finite element simulation or experimental measurement, and construct the inductance matrix;

[0008] S3, Common-mode voltage weighting coefficient calculation: The inductance matrix is ​​similarly diagonalized using an orthogonal matrix, and the motor voltage equation is mapped to the decoupled coordinate system through the orthogonal matrix. Under the decoupled coordinate system, based on the condition that the fault phase current is zero, the relationship between the fault terminal voltage and the healthy bridge arm voltage is derived to obtain the common-mode voltage weighting coefficient.

[0009] S4, Inject zero-sequence voltage: Based on the duty cycle of each phase and pulse alignment constraints, the injected zero-sequence voltage is dynamically adjusted to achieve alignment of bridge arm pulse edges and common-mode cancellation;

[0010] S5, Bridge Arm Grouping and Intra-Group Cancellation: Healthy bridge arms are grouped according to the polarity of the common-mode voltage weighting coefficient, and the pulse alignment order within the group is set according to the principle of similar amplitude to achieve intra-group pulse cancellation;

[0011] S6, Inter-group pulse edge alignment: For bridge arm pulses that cannot be canceled within a group, inter-group edge alignment is performed based on the principle that the absolute values ​​of the common-mode voltage weighting coefficients are similar, thereby optimizing the overall cancellation effect.

[0012] Optionally, the common-mode voltage mathematical model is expressed as:

[0013]

[0014] Where m is the number of phases of the motor, V cm1_F with I cm1_F These are the common-mode voltage and common-mode current under open-circuit fault conditions, V F The voltage to ground at the terminal of the faulty phase winding (F = 1, 2, ... m), V i Let u be the voltage at the midpoint of the healthy bridge arm of phase i to ground. dc This is the DC bus voltage.

[0015] Optionally, the calculation of the common-mode voltage weighting coefficient in S3 includes:

[0016] S31, Diagonalization of the inductance matrix: Select an orthogonal matrix [A] to diagonalize the motor inductance matrix, and then multiply the motor voltage equation by the orthogonal matrix [A] on the left, as follows:

[0017]

[0018] Where dec represents the physical quantity mapped to the decoupled coordinate system through the orthogonal matrix [A], and u, i, L s ψ f These are the motor phase voltage, phase current, stator inductance, and rotor flux linkage, respectively.

[0019] An orthogonal matrix [A] is represented as:

[0020]

[0021] S32, Voltage calculation under fault phase constraint: Based on the forced constraint that the fault phase current is 0, calculate the instantaneous phase voltage of each phase winding;

[0022] S33, Establishment of port voltage mapping relationship: Based on the topological instantaneous voltage, the phase voltage is converted into port voltage, and the mathematical relationship between the port voltage of the faulty phase and the port voltage of the remaining healthy bridge arm is obtained;

[0023] S34, Weighted representation of common-mode voltage switching function: The common-mode voltage under open-circuit fault of bridge arm is defined as the weighted sum of the switching functions of the remaining healthy bridge arms.

[0024] Optionally, the instantaneous phase voltage of the phase winding is expressed as:

[0025]

[0026] Optionally, the mathematical relationship between the faulty phase port voltage and the remaining healthy bridge arm port voltage is expressed as follows:

[0027]

[0028] Optionally, the weighted sum of the remaining healthy bridge arm switching functions is expressed as:

[0029]

[0030] Optionally, the duty cycle of each phase and the pulse alignment constraint are expressed as follows:

[0031]

[0032] in, D is the reference voltage for each phase healthy winding. z The zero-sequence component injected into each phase healthy bridge arm, where integer represents the integer closest to the sum of the duty cycles of each phase healthy bridge arm before the zero-sequence is injected.

[0033] The beneficial effects of this invention are:

[0034] This invention redefines the common-mode voltage expression under open-circuit faults of bridge arms based on the common-mode transmission path of the motor system, and introduces a decoupling method of the inductor matrix to achieve quantitative characterization of the high-frequency common-mode excitation generated by the remaining healthy bridge arms. This enables a more accurate modeling and explanation of the formation mechanism of common-mode voltage under fault asymmetry conditions, and provides a theoretical basis for common-mode noise assessment and common-mode electromagnetic compatibility design under all operating conditions.

[0035] This invention, by constructing an accurate common-mode voltage analytical model and combining it with a carrier comparison strategy to design a suppression algorithm, not only effectively improves the common-mode noise suppression capability under fault conditions and reduces the dependence on common-mode filters and shielding materials, but also significantly reduces the computational complexity of the controller compared to traditional schemes based on the space vector method, thus possessing stronger engineering adaptability and ease of implementation. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the analysis and suppression method according to an embodiment of the present invention;

[0038] Figure 2 This is an equivalent schematic diagram of the common-mode circuit to ground of a single-phase winding of a motor according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the common-mode voltage suppression method based on dynamic zero-sequence injection proposed in an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the voltage waveforms to ground at each bridge arm port under an open-circuit fault in phase A1 of this invention.

[0041] Figure 5 This is a schematic diagram showing the time-domain common-mode voltage comparison results of SPWM, the existing common-mode voltage suppression method ASZPWM, and the proposed common-mode suppression method under an open-circuit fault in phase A1 bridge arm according to an embodiment of the present invention.

[0042] Figure 6 This is a schematic diagram showing the comparison of time-domain common-mode current under an open-circuit fault in phase A1 bridge arm according to an embodiment of the present invention, using SPWM, the existing common-mode voltage suppression method ASZPWM, and the proposed common-mode suppression method.

[0043] Figure 7 This diagram illustrates a comparison of the common-mode current spectrum of SPWM, the existing common-mode voltage suppression method ASZPWM, and the proposed common-mode suppression method under an open-circuit fault in phase A1 bridge arm according to an embodiment of the present invention. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Those skilled in the art may employ other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0045] like Figures 1-7 As shown, a common-mode voltage analysis and suppression method for a faulty asymmetrical motor system includes the following steps:

[0046] (1) Based on the equivalent ground loop model of a single-phase winding of a motor, such as Figure 2 As shown, the mathematical expression for the common-mode voltage is calculated based on circuit theory. In a specific example, taking a single-phase open-circuit fault in a six-phase motor system, the switching action of the remaining bridge arm will generate high-frequency ripple currents in each phase winding. These ripple currents will generate high-frequency voltages at the faulty phase terminals through mutual inductance, making the contribution of the faulty phase to the common-mode voltage non-negligible. The common-mode voltage is defined as:

[0047]

[0048] Among them, V cm1_F with I cm1_F These are the common-mode voltage and common-mode current under open-circuit fault conditions, V 1_F V is the voltage to ground at the terminal of the faulty phase winding. i Let u be the voltage at the midpoint of the healthy bridge arm of phase i to ground. dc S is the DC bus voltage. i Let be the switching function for the i-th phase healthy bridge arm.

[0049] (2) The self-inductance and mutual inductance of each phase winding of the motor are obtained based on finite element simulation or experimental measurement, and an inductance matrix is ​​constructed. It should be noted that the analytical method proposed in this invention does not require the precise actual size of the inductance, only the relative size. The relative value matrix of the inductance of the six-phase permanent magnet motor used in the specific example is shown in Table 1.

[0050] Table 1: Inductance Relative Value Matrix of the Six-Phase Prototype Used in Specific Examples

[0051]

[0052] (3) Calculate the common-mode voltage contribution coefficient k of the remaining healthy bridge arm based on matrix similarity diagonal decoupling. Vi By applying orthogonal matrices, the motor voltage equations are decoupled and mapped to a decoupled coordinate system. Based on the constraint that the fault phase current is forced to zero, the relationship between the voltage to ground at the fault phase port and the switching function of the remaining healthy bridge arms is calculated. Substituting these values ​​into the mathematical expression for common-mode voltage, the common-mode voltage under an open-circuit fault in the bridge arm can be expressed as a weighted sum of the switching functions of each phase bridge arm.

[0053] The proposed calculation of the common-mode voltage contribution coefficient based on matrix similarity diagonalization mainly includes the following steps:

[0054] a. Select a suitable orthogonal matrix [A] to diagonalize the motor inductance matrix, and then multiply the motor voltage equation by the orthogonal matrix [A] on the left:

[0055]

[0056] Where the subscript "dec" represents the physical quantity mapped to the "decoupled coordinate system" through the orthogonal matrix [A], u, i, L s ψ f These represent the motor phase voltage, phase current, stator inductance, and rotor flux linkage, respectively. The orthogonal matrix [A] can be represented as:

[0057]

[0058]

[0059] b. Based on the forced constraint that the fault phase current is 0, calculate the mathematical relationship of the instantaneous phase voltage of each phase winding:

[0060]

[0061] c. Based on the topological instantaneous voltage expression, the phase voltage is converted into port voltage, and the mathematical relationship between the port voltage of the faulty phase and the port voltage of the remaining healthy bridge arm is obtained:

[0062]

[0063] Among them, V i Let be the port-to-ground voltage of the i-th phase bridge arm.

[0064] In a specific example, the calculated weighted common-mode coefficients are shown in Table 2. This indicates that the rising / falling edges of bridge arms 2 and 3 (corresponding to the driving windings B1 and C1) will cause the falling / rising edges of the voltage at the faulty phase A1 port; the rising / falling edges of bridge arms 4-6 (corresponding to the driving windings A2, B2, and C2) will cause the rising / falling edges of the voltage at the faulty phase A1 port, as shown below. Figure 3 As shown.

[0065] Table 2: Weighted Common Mode Coefficient

[0066]

[0067] d. Further simplification allows us to define the common-mode voltage under an open-circuit fault in one arm as a weighted sum of the switching functions of the remaining healthy arms:

[0068]

[0069] (4) Dynamically adjust the injected zero-sequence voltage amplitude based on bridge arm pulse edge alignment constraints. In a specific example, after a bridge arm open-circuit fault occurs, only five phase controlled bridge arms remain. Therefore, the condition for phase-to-phase common-mode cancellation is no longer met, and it is necessary to actively inject zero-sequence voltage to satisfy the bridge arm pulse edge alignment constraint, that is, to ensure that the duty cycles of each phase bridge arm add up to an integer.

[0070]

[0071] in, D is the reference voltage for each phase winding. z The zero-sequence component injected into each phase arm.

[0072] (5) Group the bridge arms based on the polarity of the weighted common mode coefficient. In a specific example, bridge arms 4 to 6 (corresponding to the driving windings A2, B2, and C2) are grouped into group A; bridge arms 2 and 3 (corresponding to the driving windings B1 and C1) are grouped into group B.

[0073] (6) Determine the connection order within a group based on the amplitude of the weighted common-mode system. In a specific example, the rising edges of V2 and V4 are used as the starting reference positions within their respective groups. For group A, the connection order is set so that the falling edge of V4 is aligned with the rising edge of V6, and the falling edge of V6 is aligned with the rising edge of V5. For group B, the connection order is set so that the falling edge of V2 is aligned with the rising edge of V3.

[0074] (7) Alignment of remaining edges between groups is set based on the amplitude of the common-mode voltage coefficient. In a specific example, considering that the common-mode coefficients of the 2nd and 3rd phase bridge arms are equal, the alignment order between groups is determined by sequential connection, such as... Figure 4 As shown. Applying the common-mode rejection algorithm provided by this invention, the effective value of the common-mode voltage is reduced by approximately 82.23% compared to SPWM; and by approximately 71.17% compared to existing common-mode rejection methods, as... Figure 5 As shown, the effective value of the common-mode current is reduced by approximately 55.08% compared to SPWM; and by approximately 36.14% compared to existing common-mode rejection methods. Figure 6 As shown; in the frequency bands of 10kHz-100kHz, 100kHz-300kHz, 300kHz-500kHz, and 500kHz-1MHz, by applying the common-mode rejection method provided by this invention, the common-mode rejection is reduced by 13.2462dBμA, 7.2175dBμA, 3.6460dBμA, and 6.0394dBμA respectively compared to SPWM, and by 8.3629dBμA, 3.5452dBμA, 3.1947dBμA, and 2.6621dBμA respectively compared to existing common-mode rejection methods. Figure 7 As shown.

[0075] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for common-mode voltage analysis and suppression in a faulty asymmetrical motor system, characterized in that, Includes the following steps: S1, Common-mode voltage modeling: Based on the equivalent ground loop of the single-phase winding of the motor, a mathematical model of common-mode voltage under bridge arm open-circuit fault is established, and the common-mode voltage is expressed as a weighted combination of healthy bridge arm voltages; S2, Inductance matrix construction: Obtain the self-inductance and mutual inductance of each phase of the motor through finite element simulation or experimental measurement, and construct the inductance matrix; S3, Common-mode voltage weighting coefficient calculation: The inductance matrix is ​​similarly diagonalized using an orthogonal matrix, and the motor voltage equation is mapped to a decoupled coordinate system. Under the decoupled coordinate system, based on the condition that the fault phase current is zero, the relationship between the fault terminal voltage and the healthy bridge arm voltage is derived to obtain the common-mode voltage weighting coefficient. S4, Inject zero-sequence voltage: Based on the duty cycle of each phase and pulse alignment constraints, the injected zero-sequence voltage is dynamically adjusted to achieve alignment of bridge arm pulse edges and common-mode cancellation; S5, Bridge Arm Grouping and Intra-Group Cancellation: Healthy bridge arms are grouped according to the polarity of the common-mode voltage weighting coefficient, and the pulse alignment order within the group is set according to the principle of similar amplitude to achieve intra-group pulse cancellation; S6, Inter-group pulse edge alignment: For bridge arm pulses that cannot be canceled within a group, inter-group edge alignment is performed according to the common-mode voltage weighting coefficient matching principle to optimize the overall cancellation effect.

2. The common-mode voltage analysis and suppression method for a faulty asymmetrical motor system according to claim 1, characterized in that, The common-mode voltage mathematical model is expressed as follows: Where m is the number of phases of the motor, V cm1_F with I cm1_F These are the common-mode voltage and common-mode current under open-circuit fault conditions, V F V is the voltage to ground at the terminal of the faulty phase winding. i Let u be the voltage at the midpoint of the healthy bridge arm of phase i to ground. dc This is the DC bus voltage.

3. The common-mode voltage analysis and suppression method for a faulty asymmetrical motor system according to claim 2, characterized in that, The calculation of the common-mode voltage weighting coefficient in S3 includes: S31, Diagonalization of the inductance matrix: Select an orthogonal matrix [A] to diagonalize the motor inductance matrix, and then multiply the motor voltage equation by the orthogonal matrix [A] on the left, as follows: Where dec represents the physical quantity mapped to the decoupled coordinate system through the orthogonal matrix [A], and u, i, L s ψ f These are the motor phase voltage, phase current, stator inductance, and rotor flux linkage, respectively. The orthogonal matrix [A] is represented as follows: S32, Voltage calculation under fault phase constraint: Based on the forced constraint that the fault phase current is 0, calculate the mathematical relationship of the instantaneous phase voltage of each phase winding; S33, Establishment of port voltage mapping relationship: Based on the topological instantaneous voltage, the phase voltage is converted into port voltage, and the mathematical relationship between the port voltage of the faulty phase and the port voltage of the remaining healthy bridge arm is obtained; S34, Weighted representation of common-mode voltage switching function: The common-mode voltage under open-circuit fault of bridge arm is defined as the weighted sum of the switching functions of the remaining healthy bridge arms.

4. The common-mode voltage analysis and suppression method for a faulty asymmetrical motor system according to claim 3, characterized in that, Based on the mandatory constraint that the fault phase current is 0, the mathematical relationship of the instantaneous phase voltage of each phase winding is expressed as:

5. The common-mode voltage analysis and suppression method for a faulty asymmetrical motor system according to claim 4, characterized in that, The mathematical relationship between the faulty phase port voltage and the remaining healthy bridge arm port voltage is expressed as follows:

6. The common-mode voltage analysis and suppression method for a faulty asymmetrical motor system according to claim 5, characterized in that, The weighted sum of the remaining healthy bridge arm switching functions is expressed as:

7. The common-mode voltage analysis and suppression method for a faulty asymmetrical motor system according to claim 6, characterized in that, The duty cycle of each phase and the pulse alignment constraint are expressed as follows: Among them, V i * D is the reference voltage for each phase healthy winding. z The zero-sequence component injected into each phase healthy bridge arm, where integer represents the integer closest to the sum of the duty cycles of each phase healthy bridge arm before the zero-sequence is injected.

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