A method for optimizing the efficiency of a three-phase four-wire servo motor with high-resistance connection

Abstract

The present invention belongs to the technical field of motor fault optimization, and discloses a method for optimizing the efficiency of a three-phase four-wire servo motor with high-impedance connection. The method comprises the following steps: measuring the phase sequence current under a high-impedance connection fault and converting it into a dq0 axis current; calculating the output power of the motor in combination with the motor phase voltage and phase current, analyzing the power to obtain the second harmonic component and combining the phase current amplitude to obtain the fault resistance value; calculating the motor copper loss after the high-impedance connection fault and the intervention of fault tolerance based on the fault resistance value and in combination with the stator resistance value and the dq0 axis current; derivatizing the motor copper loss to obtain the zero-sequence current after optimization of the fourth bridge arm under the high-impedance connection fault of the motor; and calculating the minimum copper loss under the high-impedance connection fault of the motor based on the zero-sequence current injected into the fourth bridge arm. Efficiency optimization control under high-impedance connection fault operating conditions effectively reduces the system copper loss during high-impedance connection operation and improves system efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor fault optimization, and in particular relates to an efficiency optimization method for a three-phase four-wire servo motor with high resistance connection. Background Art

[0002] Permanent magnet synchronous motor systems are widely used in aerospace servo systems. To improve system efficiency and stability, aerospace servo systems widely adopt a three-phase, four-arm control topology. Servo motor systems used in the aerospace sector typically require high stability and also place great emphasis on system efficiency.

[0003] Aerospace servo motor systems often operate under long-term, high-intensity conditions. Excessive copper loss can lead to excessive thermal effects. During this period of high-intensity operation, high-impedance connections are particularly prone to operational failures. These can significantly increase system operating losses, severely reduce system efficiency, and damage mechanical structures.

[0004] At present, the research on high impedance estimation and location is relatively sufficient. The method of changing the d-axis reference current is often used to reduce its operating losses, but this method is less effective than the method proposed in this paper.

[0005] Therefore, an efficiency optimization method for a three-phase four-wire servo motor with high-resistance connection is proposed. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an efficiency optimization strategy for three-phase four-wire servo motors with high-impedance connections, which solves the problem of reducing the copper loss of the servo motor when high-impedance connections occur in the existing technology.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A method for optimizing the efficiency of a three-phase four-wire servo motor with high resistance connection, comprising the following steps:

[0009] The current of each phase sequence of the motor when it is running under the condition of high impedance connection fault is measured by the current sensor, and the current of each phase sequence of the motor is converted into the current in the dq0 axis coordinate system;

[0010] The output power of the motor during operation is calculated based on the motor phase voltage and phase current under high-impedance connection fault conditions. The second harmonic component is obtained through power analysis, and combined with the phase current amplitude at this time, the fault resistance value when a high-impedance connection fault occurs is calculated.

[0011] Based on the fault resistance value when the motor has a high-impedance connection fault, combined with the motor stator resistance value and the dq0-axis current at the time of the high-impedance connection fault, the motor copper loss after the high-impedance connection fault and fault tolerance intervention in the dq0-axis coordinate system is calculated.

[0012] The motor copper loss formula after a high-impedance connection fault and fault tolerance intervention is derived to obtain the current amplitude and phase injected into the fourth bridge arm of the motor. This is then substituted into the zero-sequence current expression injected into the fourth bridge arm of the motor to obtain the optimized zero-sequence current of the fourth bridge arm under the high-impedance connection fault.

[0013] Based on the optimized zero-sequence current injected into the fourth bridge arm, the minimum copper loss under the high-impedance connection fault of the motor is calculated.

[0014] Furthermore, the current of each phase sequence of the motor is converted into the current in the dq0 axis coordinate system in the following way:

[0015]

[0016] Among them, i a 、i b 、i c is the motor abc phase current; i d is the d-axis current, i q is the q-axis current; i0 is the zero-sequence current, and θ is the motor angle.

[0017] Furthermore, the output power of the motor when operating under a high-impedance connection fault is:

[0018]

[0019] Among them, P a Indicates the power of phase A, u an is the phase A voltage, i a is the phase A current, U an is the voltage amplitude of phase A, I a is the current amplitude of phase A, ΔUI represents the voltage and current change amplitude caused by the additional resistance, ω is the angular frequency, Indicates the phase difference between voltage and current.

[0020] Furthermore, the second harmonic component is:

[0021]

[0022] Among them, ΔUI represents the voltage and current change amplitude caused by the additional resistance, U an is the voltage amplitude of phase A, I a is the current amplitude of phase A, Indicates the phase difference between voltage and current.

[0023] Furthermore, the fault resistance value of the high impedance connection fault is:

[0024]

[0025] Among them, I a is the current amplitude of phase A, FT(P cu_2f ) is the second harmonic component.

[0026] Furthermore, the motor copper loss after the high-impedance connection fails and fault tolerance is intervened is:

[0027]

[0028] in, is the motor copper loss after high impedance connection failure and fault tolerance intervention, R s is the stator resistance, P cu_HRC The loss introduced by the high impedance connection fault, i q is the q-axis current.

[0029] Furthermore, the zero-sequence current injected into the fourth bridge arm of the motor is:

[0030]

[0031] Where A is the injection current amplitude, is the phase of the injected current, and θ represents the motor angle.

[0032] Furthermore, the current amplitude and current phase injected into the fourth bridge arm of the motor are:

[0033]

[0034] Furthermore, the optimized zero-sequence current of the fourth bridge arm under high-impedance connection fault is:

[0035]

[0036] Among them, R add is the fault resistance value of phase A, R s is the stator resistance, I q is the q-axis current amplitude.

[0037] Furthermore, after the optimized zero-sequence current is injected into the fourth bridge arm, the minimum copper loss is:

[0038]

[0039] Among them, R add is the fault resistance value of phase A, R s is the stator resistance, I q is the q-axis current amplitude.

[0040] Beneficial effects of the present invention:

[0041] Efficiency optimization control under high-impedance connection fault operating conditions effectively reduces system copper loss when high-impedance connection is running. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0043] Figure 1 This is the system control block diagram;

[0044] Figure 2 This is the fault simulation diagram of the three-phase four-bridge arm system;

[0045] Figure 3 This is a comparison of three-phase currents in healthy, faulty, and optimized modes with a fault resistance of 67Ω (100 times the stator resistance).

[0046] Figure 4 The following figure shows the speed comparison chart under the three modes of healthy, faulty, and optimized with a fault resistance of 67Ω (100 times the stator resistance).

[0047] Figure 5 The following is a comparison of the output torque under healthy, faulty, and optimized modes with a fault resistance of 67Ω (100 times the stator resistance).

[0048] Figure 6 This is a comparison of copper loss in healthy, faulty, and optimized modes with a fault resistance of 67Ω (100 times the stator resistance).

[0049] Figure 7 This is a comparison diagram of the effects of injecting and changing the d-axis reference current based on the fourth bridge arm. DETAILED DESCRIPTION

[0050] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0051] In the description of the present invention, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inside", "around" and the like indicating orientation or positional relationship are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0052] like Figure 1 As shown, the present invention provides a technical method, a method for optimizing the efficiency of a three-phase four-wire servo motor with high resistance connection.

[0053] The following example takes the high impedance connection fault of phase A as an example. The stator resistance of the motor is R s , a proposed method for optimizing the efficiency of a three-phase four-wire servo motor with high-resistance connection is as follows:

[0054] 1. The current of each phase sequence when the motor is running under high impedance connection fault is measured by current sensor, and the current of each phase sequence of the motor is converted into the current in the dq0 axis coordinate system.

[0055] 1) The current sensor measures the current i of each phase when the motor is running under high impedance connection fault a ,i b ,i c ;

[0056] 2) Convert the current of each phase of the motor into the current i in the dq0 axis coordinate system d ,i q ,i0:

[0057]

[0058] Among them, i a 、i b 、i c is the motor phase current; i d is the d-axis current, i q is the q-axis current; i0 is the zero-sequence current, and θ is the motor angle.

[0059] 2. Calculate the output power of the motor when it is working based on the phase voltage and phase current of the motor under the high-impedance connection fault. Then use Fourier transform FFT to analyze the power to obtain the second harmonic component. Combined with the phase current amplitude at this time, calculate the fault resistance value when the high-impedance connection fault occurs.

[0060] 1) Add resistor R in phase A add , the three-phase resistance becomes unbalanced and the motor has a high impedance connection fault; in the early stage of the fault, due to the existence of the current closed loop, the additional resistance can still operate normally under the control of the proportional integral controller PI, but the copper loss will increase.

[0061] After adding the additional resistance of phase A, according to the theoretical derivation, the output power of phases B and C of the system remains unchanged, so the changed power of phase A is:

[0062]

[0063] Among them, P a Indicates the power of phase A, u an is the phase A voltage, i a is the phase A current, U an is the voltage amplitude of phase A, I a is the current amplitude of phase A, ΔUI represents the voltage and current change amplitude caused by the additional resistance, ω is the angular frequency, Indicates the phase difference between voltage and current.

[0064] By the A phase power P a Analysis shows that the 2ωt component is due to the additional resistance R add Therefore, this component is recorded as the second harmonic component FT(P cu_2f ):

[0065]

[0066] Among them, ΔUI represents the voltage and current change amplitude caused by the additional resistance, U an is the voltage amplitude of phase A, I a is the current amplitude of phase A, Indicates the phase difference between voltage and current.

[0067] 2) Based on the second harmonic component FT(P cu_2f ), combined with the current amplitude of phase A at this time, the fault resistance value when phase A has a high impedance connection fault is calculated as:

[0068]

[0069] Among them, I a is the current amplitude of phase A, FT(P cu_2f ) is the second harmonic component.

[0070] 3. Based on the fault resistance value when the motor has a high-impedance connection fault, combined with the motor stator resistance value and the dq0-axis current when the high-impedance connection fault occurs, calculate the motor copper loss after the high-impedance connection fault occurs and fault tolerance is introduced in the dq0-axis coordinate system.

[0071] 1) Calculate the motor copper loss after a high-impedance connection fault and fault tolerance intervention in the dq0 axis coordinate system

[0072]

[0073] in, is the motor copper loss after high impedance connection failure and fault tolerance intervention, R s is the stator resistance, P cu_HRC The loss introduced by the high impedance connection fault, i q is the q-axis current.

[0074] 2) At this time, according to the three-phase current representation of the motor, it is converted into:

[0075]

[0076]

[0077]

[0078] Among them, i a 、i b 、i c is the motor phase current, θ is the motor angle, A is the injected current amplitude, Indicates the phase of the injected current; (x represents 1, 2, 3) corresponds to the three-phase current bias angle, i d is the d-axis current, i q is the q-axis current; i0 is the zero-sequence current.

[0079] 4. Based on the periodic characteristics of current, it is assumed that the zero-sequence current injected into the fourth bridge arm of the motor is:

[0080]

[0081] Where A is the injection current amplitude, is the phase of the injected current, and θ represents the motor angle.

[0082] 5. Derivate the motor copper loss formula after the motor high-impedance connection fault and fault tolerance intervention to obtain the current amplitude and current phase injected into the fourth bridge arm of the motor. Substitute these into the zero-sequence current expression injected into the fourth bridge arm of the motor to obtain the optimized zero-sequence current of the fourth bridge arm under the motor high-impedance connection fault.

[0083] 1) The motor copper loss formula after the motor high-impedance connection fault and fault tolerance is derived as follows:

[0084]

[0085] Among them, P cu_HRC is the power loss caused by high impedance connection fault, R s is the stator resistance, A is the injected current amplitude, Indicates the phase of the injected current, i a 、i b 、i c is the three-phase current of the motor; i d is the d-axis current, i q is the q-axis current; i0 is the zero-sequence current.

[0086] At this time, without considering the output performance and only considering the motor copper loss efficiency, the partial differential can be used to obtain:

[0087]

[0088] The solution is:

[0089] 2) Substitute the solved current amplitude and current phase into the zero-sequence current expression injected into the fourth bridge arm of the motor, and the optimized zero-sequence current of the fourth bridge arm under the high-impedance connection fault of the motor is obtained as:

[0090]

[0091] Among them, R add is the fault resistance value of phase A, R s is the stator resistance, I q is the q-axis current amplitude.

[0092] 6. Under the condition of high-impedance connection fault of the motor, after the optimized zero-sequence current is injected into the fourth bridge arm, the minimum copper loss is:

[0093]

[0094] Among them, R add is the fault resistance value of phase A, R s is the stator resistance, I q is the q-axis current amplitude.

[0095] The present invention uses the following motor parameters for simulation verification, the specific parameters are as follows:

[0096]

[0097] Set the phase A high impedance connection fault level to 67 ohms. Figure 3 The comparison of three-phase currents under three modes of healthy, faulty and optimized fault resistance is given. Figure 4 The comparison of the speed under the three modes of healthy, fault and optimized is given. Figure 5 The comparison of output torque under three modes of healthy, fault and optimized is given. Figure 6 A comparison of copper loss in three modes, healthy, faulty, and optimized, is given under fault resistance. Figure 7A comparison diagram of the effects of injecting and changing the d-axis reference current based on the fourth bridge arm is given.

[0098] like Figure 2 As shown in the figure, R add The resistance value of the fault in phase A is expressed as the value of the resistance value. The motor continues to operate stably in the three-phase four-leg system, but the system losses are no longer minimal. The severity of the fault resistance can be determined based on the collected three-phase current and the above.

[0099] After a system high impedance connection fault occurs, the system zero axis reference current change module takes effect, that is, Figure 1 As indicated by the Id / I0 REFERENCE, the coordinate transformation module generates a three-phase current reference value, which is compared with the actual current signal collected by the current sensor. After being transformed by the integral controller (PI), it is input into the PWM carrier modulation module to achieve motor drive. The reference value is changed from 0 to the optimized current derived in this article, thus achieving efficiency-optimized control under high-impedance connection operating conditions.

[0100] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0101] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A method for optimizing the efficiency of a three-phase four-wire servo motor with high-resistance connection, characterized in that: The following steps are involved: The current of each phase sequence of the motor when it is running under the condition of high impedance connection fault is measured by the current sensor, and the current of each phase sequence of the motor is converted into the current in the dq0 axis coordinate system; The output power of the motor during operation is calculated based on the motor phase voltage and phase current under high-impedance connection fault conditions. The second harmonic component is obtained through power analysis, and combined with the phase current amplitude at this time, the fault resistance value when a high-impedance connection fault occurs is calculated. Based on the fault resistance value when the motor has a high-impedance connection fault, combined with the motor stator resistance value and the dq0-axis current at the time of the high-impedance connection fault, the motor copper loss after the high-impedance connection fault and fault tolerance intervention in the dq0-axis coordinate system is calculated. The motor copper loss formula after a high-impedance connection fault and fault tolerance intervention is derived to obtain the current amplitude and phase injected into the fourth bridge arm of the motor. This is then substituted into the zero-sequence current expression injected into the fourth bridge arm of the motor to obtain the optimized zero-sequence current of the fourth bridge arm under the high-impedance connection fault. Based on the optimized zero-sequence current injected into the fourth bridge arm, the minimum copper loss under the high-impedance connection fault of the motor is calculated; The output power of the motor when it is working under high impedance connection fault is: Among them, P a Indicates the power of phase A, u an is the phase A voltage, i a is the phase A current, U an is the voltage amplitude of phase A, I a is the current amplitude of phase A, ΔUI represents the voltage and current change amplitude caused by the additional resistance, ω is the angular frequency, Indicates the phase difference between voltage and current; The second harmonic component is: Among them, ΔUI represents the voltage and current change amplitude caused by the additional resistance, U an is the voltage amplitude of phase A, I a is the current amplitude of phase A, Indicates the phase difference between voltage and current.

2. The method for optimizing the efficiency of a three-phase four-wire servo motor with high-resistance connection according to claim 1, characterized in that: The current of each phase sequence of the motor is converted into the current in the dq0 axis coordinate system as follows: Among them, i a 、i b 、i c is the motor abc phase current; i d is the d-axis current, i q is the q-axis current; i0 is the zero-sequence current, and θ is the motor angle.

3. The method for optimizing the efficiency of a three-phase four-wire servo motor with high-resistance connection according to claim 1, wherein: The fault resistance value of a high impedance connection fault is: Among them, I a is the current amplitude of phase A, FT(P cu_2f ) is the second harmonic component.

4. The method for optimizing the efficiency of a three-phase four-wire servo motor with high-resistance connection according to claim 1, wherein: The motor copper loss after the high-impedance connection fails and fault tolerance intervenes is: in, is the motor copper loss after high impedance connection failure and fault tolerance intervention, R s is the stator resistance, P cu_HRC The loss introduced by the high impedance connection fault, i q is the q-axis current.

5. The method for optimizing the efficiency of a three-phase four-wire servo motor with high resistance connection according to claim 1, characterized in that: The zero-sequence current injected into the fourth bridge arm of the motor is: Where A is the injection current amplitude, is the phase of the injected current, and θ represents the motor angle.

6. The method for optimizing the efficiency of a three-phase four-wire servo motor with high-resistance connection according to claim 5, characterized in that: The current amplitude and current phase of the fourth bridge arm of the motor are:

7. The method for optimizing the efficiency of a three-phase four-wire servo motor with high-resistance connection according to claim 6, characterized in that: The optimized zero-sequence current of the fourth bridge arm under high-impedance connection fault is: Among them, R add is the fault resistance value of phase A, R s is the stator resistance, I q is the q-axis current amplitude.

8. The method for optimizing the efficiency of a three-phase four-wire servo motor with high-resistance connection according to claim 7, characterized in that: After the optimized zero-sequence current is injected into the fourth bridge arm, the minimum copper loss is: Among them, R add is the fault resistance value of phase A, R s is the stator resistance, I q is the q-axis current amplitude.

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