A motor system current sensor fault-tolerant method

Abstract

This invention belongs to the field of fault tolerance in motor systems, and relates to a fault tolerance method for current sensors in motor systems. The method includes: first, establishing an offset coordinate system using different phase currents as the Clarke coordinate transformation base axes; second, obtaining the β-axis fundamental fault-tolerant current least affected by a fault through the offset coordinate system, and then obtaining the α-axis fundamental fault-tolerant current through a second-order generalized integrator; finally, obtaining the final fault-tolerant current after a current sensor fault through a rotating coordinate transformation, and using it as a current loop feedback quantity to achieve fault isolation. This invention uses phase current as the input quantity for the fault-tolerant algorithm, avoiding the addition of extra detection equipment; the fault-tolerant algorithm does not involve motor parameters, and fault tolerance for current sensors can be achieved solely through a fault isolation algorithm designed using phase current. Therefore, this invention provides a more reliable and effective new approach for achieving fault tolerance for current sensors in AC motor systems.

Description

Technical fields:

[0001] This invention belongs to the field of motor drive technology and relates to a fault-tolerant method for current sensor faults in motor systems, used for fault tolerance research of current sensor faults in motor systems. Background technology:

[0002] The current signal output by the current sensor is an indispensable piece of information for the motor drive control system. In applications with high reliability requirements, it is necessary to smoothly switch to fault-tolerant operation mode in a timely and accurate manner in case of current sensor failure. The output signal of the current sensor involves a variety of complex faults. The occurrence of different faults will cause different types of AC pulsations or DC biases in the drive system, thereby affecting the stable operation of the entire motor system. Therefore, fault tolerance for various current sensor faults is the key to ensuring the continuous safe and reliable operation of the motor system. Summary of the Invention:

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and propose a fault-tolerant method for current sensor faults in motor systems. This method can effectively isolate current sensor output signal faults and provide a more reliable and effective new approach for achieving fault-tolerant operation of AC motor current sensors.

[0004] The technical solution of this invention is implemented as follows:

[0005] A fault-tolerant method for a current sensor in a motor system includes the following steps:

[0006] (1) Establishment of offset coordinate system: Using different phase currents as the Clarke coordinate transformation basis axis, establish an offset coordinate system.

[0007] (2) Fault-tolerant current calculation: The β-axis fundamental current with the least impact from the fault is obtained by offset coordinate system. The α-axis fundamental current with a lag angle of π / 2 is obtained by passing the β-axis fundamental current through a second-order generalized integrator.

[0008] (3) Fault-tolerant operation control: The obtained α-axis fundamental current and β-axis fundamental current are transformed by rotating coordinates to obtain the final fault-tolerant current after the current sensor fails. The final fault-tolerant current is used as the current loop feedback quantity to achieve fault isolation.

[0009] Optionally, the motor is a synchronous motor.

[0010] Optionally, the motor is an asynchronous motor.

[0011] Optionally, the motor can be multi-phase.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] Using different phase currents as the Clarke coordinate transformation basis, an offset coordinate system is established. The fault-tolerant current in the two-phase stationary coordinate system is obtained through the offset coordinate system. Then, the final fault-tolerant current after jamming and open circuit faults is obtained through rotational coordinate transformation. This is used as the current loop feedback quantity to achieve fault isolation. All fault-tolerant strategies use phase current as input quantity, avoiding the addition of additional equipment. The fault-tolerant algorithm does not involve motor parameters. Fault isolation algorithm designed only by phase current quantity can achieve fault tolerance of current sensor faults. Attached image description:

[0014] Figure 1 This is a schematic diagram of the offset coordinate system involved in the present invention;

[0015] Figure 2 This is a schematic diagram of the second-order generalized integral module involved in the present invention. Detailed implementation method:

[0016] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0017] This embodiment uses the failure of various current sensor faults in phase A1 of a nine-phase motor with H-bridge power supply start winding as a case study. The specific fault tolerance process is as follows:

[0018] The current measured by each phase current sensor is expressed as:

[0019] i A1_m =λi A1 +μ=λI am cos(ωt+θ ori )+μ

[0020] i A2_m =i A2

[0021] ···

[0022] i C3_m =i C3

[0023] In the formula, i A1 ...i C3 i represents the actual stator current. A1_m ...i C3_m For current sensors measuring current, λ is the current sensor gain factor, μ is the offset coefficient, and I... am ω is the phase current amplitude, ω is the motor angular frequency, and θ is the phase current amplitude. ori Let t be the initial phase angle and t be the time.

[0024] When the gain factor or offset coefficient takes different values, the current sensor outputs different types of fault signals, which in turn have different degrees of impact on the drive system.

[0025] (1) Establishment of offset coordinate system: Establish Clarke coordinate systems with different offset angles based on different phase currents (e.g., Figure 1 As shown), the established offset coordinate system can be represented as:

[0026]

[0027] Where σ=π / 9, m is the position of the winding axis of the semi-symmetrical nine-phase motor, m=0,1,2,6,7,8,12,13,14; h is each harmonic; h=1,3,5,7; γ is the electrical angle between the α axis and the a1 phase winding axis, that is, the offset angle of the offset coordinate system.

[0028] (2) Determination of fault-tolerant current: The fault-tolerant current i in the two-phase stationary coordinate system is obtained by offset coordinate system. α1_n and i β1_n Based on the principle of Clarke transform, the current i that is least affected by current sensor failure is selected. β1_n Then, the lag i is obtained by using the second-order generalized integral module. β1_n Current i of π / 2 α1_n Among them, the second-order generalized integral module (such as...) Figure 2 The transfer function (shown) can be expressed as:

[0029]

[0030] Where k is the system gain, s is the complex Laplace transform, and ω is the resonant frequency.

[0031] (3) The required fault-tolerant current i α1_n and i β1_n Then, the final q-axis fault-tolerant current i is obtained through coordinate transformation. q1 The faulty q-axis current is replaced by this current as the current loop feedback in the control system, achieving fault-tolerant control. The rotating coordinate transformation can be expressed as:

[0032] i q1 =i β1_n ×cos(θ e -θ n )+i α1_n ×sin(θ e -θ n )

[0033] Where, θ n (θ n =0,π / 9...14π / 9) represents the offset angle of the offset coordinate system.

[0034] The final fault-tolerant current after the current sensor fault is calculated is used as the current loop feedback quantity to replace the fault i. q1This enables fault isolation.

[0035] This invention uses phase current as an input variable, enabling accurate fault tolerance for current sensor failures. Compared to existing technologies, using phase current as an input variable avoids the need for additional detection equipment, and effectively isolates current sensor failures by switching the correct q-axis current.

Claims

1. A fault-tolerant method for a current sensor in a motor system, characterized in that, Includes the following steps: (1) Establishment of offset coordinate system: Using different phase currents as the Clarke coordinate transformation basis axes, establish an offset coordinate system; (2) Fault-tolerant current calculation: The β-axis fundamental current with the least impact from the fault is obtained by offset coordinate system. The α-axis fundamental current with a lag angle of π / 2 is obtained by passing the β-axis fundamental current through a second-order generalized integrator. (3) Fault-tolerant operation control: The obtained α-axis fundamental current and β-axis fundamental current are transformed by rotating coordinates to obtain the final fault-tolerant current after the current sensor fails. The final fault-tolerant current is used as the current loop feedback quantity to achieve fault isolation. The motor is a semi-symmetrical nine-phase motor, and the offset coordinate system is as follows: Where σ=π / 9, m is the position of the winding axis of the semi-symmetrical nine-phase motor, m=0,1,2,6,7,8,12,13,14; h is each harmonic; h=1,3,5,7; γ is the electrical angle between the α axis and the a1 phase winding axis, that is, the offset angle of the offset coordinate system. The transfer function of the second-order improper integral module is expressed as: Where k is the system gain, s is the complex Laplace transform, and ω is the resonant frequency; The rotation coordinate transformation is expressed as: Where, θ n =0,π / 9...14π / 9, θ n This indicates the offset angle of the offset coordinate system.

2. The fault-tolerant method for current sensor in motor system according to claim 1, characterized in that, The motor is a synchronous motor.

3. The fault-tolerant method for current sensor in a motor system according to any one of claims 1, characterized in that, The motor is an asynchronous motor.

4. The fault-tolerant method for current sensor in a motor system according to any one of claims 1, characterized in that, The motor has multiple phases.

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