High-speed permanent magnet synchronous motor control method for lower bridge arm current sampling

Abstract

The invention discloses a high-speed permanent magnet synchronous motor control method for lower bridge arm current sampling, and the method comprises the steps: carrying out the reconstruction of a current detected by a lower bridge arm shunt of a three-phase inverter circuit, obtaining a three-phase output current, and obtaining the angle and speed of a permanent magnet synchronous motor through a sliding-mode observer position-free control algorithm. The time delay caused by current sampling of the shunt is compensated in the dq / alpha beta conversion link, so that the rotor position detection precision under the condition of no position sensor is improved, and the control performance of the high-speed permanent magnet synchronous motor can be further improved.

Description

Technical Field

[0001] The present invention relates to a control method for a high-speed permanent magnet synchronous motor with lower arm current sampling, belonging to the technical field of motor control, and particularly to the technical field of high-speed motor control. Background Art

[0002] With the development of fuel cell air compressors and micro gas turbine generators, the sensorless control technology and high integration in high-speed motor systems have attracted increasing attention. Currently, in this system, isolated drive schemes and current Hall detection schemes on three-phase output lines are often used for power transistor drive and three-phase current detection of the drive controller. This scheme is very suitable for high-speed motor systems with high DC input voltage (such as 400V) or high power (such as 30kW). However, in some mobile or portable application scenarios with low input voltage (such as 48V, 96V) and low power (such as 5kW, 1kW), the isolated drive power supply and current Hall in this scheme will significantly reduce the power density of the drive controller, thereby increasing the volume and weight of the entire system.

[0003] In this regard, a charge pump bootstrap drive scheme and a lower arm shunt current detection scheme can be adopted to improve the power density of the system. Among them, the core of the lower arm shunt current detection scheme is to measure the shunt current of the lower arm of the inverter circuit, combine the switching state of the inverter circuit and the motor winding connection method, and use Kirchhoff's law to reconstruct the motor phase current. The lower arm shunt scheme has significant cost and bandwidth advantages in high-speed motor drive, but it requires comprehensive design of control algorithms (such as delay compensation, observers, etc.) to achieve reliable performance in high-dynamic scenarios. Therefore, this current detection scheme brings new challenges to the control algorithm of high-speed motors. Summary of the Invention

[0004] The purpose of the present invention is to provide a control method for a high-speed permanent magnet synchronous motor with lower arm current sampling in view of the deficiencies of the prior art. The present invention can improve the detection accuracy of the rotor position without a position sensor, and then improve the control performance of the high-speed permanent magnet synchronous motor.

[0005] The purpose of the present invention is achieved through the following technical solutions: A control method for a high-speed permanent magnet synchronous motor with lower arm current sampling includes the following steps:

[0006] (1) Obtain the currents i aL , i bL and i cL flowing through the three lower transistors through the shunt of the lower arm of the three-phase inverter circuit, and input the phase current reconstruction module in combination with the drive signals Gs2, Gs4, and Gs6 of the lower arm switching transistors to calculate and obtain the three-phase output currents i a , i b and i c, which is transformed by abc / αβ transformation to obtain the α-axis and β-axis currents i in the two-phase stationary coordinate system α and i β ;

[0007] (2) The three-phase output voltages u of the inverter circuit are obtained through voltage sampling a , u b and u c , which are transformed by abc / αβ transformation to obtain the α-axis and β-axis voltages u α and u β , and they are jointly input to the sliding mode observer to obtain the detected value ω of the electrical angular velocity of the motor α and the detected value θ of the electrical angle before compensation β , and then the detected value θ of the electrical angle of the motor eg and the detected value n of the motor speed eg1 ; eg2 mg ; ;

[0008] (3) The currents i α , i β and the detected value θ of the electrical angle of the motor eg2 are input to the αβ / dq transformation module to obtain the d-axis and q-axis current feedback values i d and i q ;

[0009] (4) The detected value n of the motor speed mg and the given speed n ref constitute the outer speed loop to obtain the speed deviation value n err , and after passing through the PI regulator, the q-axis current control reference value i q * is output. The i q * , the detected value ω of the electrical angular velocity of the motor eg , i q and i d are used together as the input of the i d =0 control regulator module, and the d-axis and q-axis voltage control quantities u d * and u q * are output. Combining the detected value θ of the electrical angle of the motor eg2 , through the dq / αβ transformation, the α-axis and β-axis voltage control quantities u α * and u β * are obtained, and then six-way switch tube drive signals are generated through the SVPWM module to control each switch tube of the three-phase inverter circuit.

[0010] The present invention has the following beneficial effects: improving the rotor position detection accuracy of a high-speed motor drive controller adopting a lower-arm shunt current detection scheme without a position sensor, and then improving the control performance of a high-speed permanent magnet synchronous motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. Figure 1 is a schematic diagram of a three-phase inverter circuit adopting lower-arm current sampling;

[0012] FIG. Figure 2 is a schematic diagram of the driving signals of each power switch tube and the lower-arm current sampling moments in the three-phase inverter circuit;

[0013] FIG. Figure 3 is a block diagram of a control method for a high-speed permanent magnet synchronous motor adopting lower-arm current sampling according to the present invention;

[0014] FIG. Figure 4 is a simulation waveform diagram of the rotational speed and angular position error of a high-speed motor after sampling delay compensation in the present invention;

[0015] FIG. Figure 5 is a simulation waveform diagram of the rotational speed and angular position error of a high-speed motor without sampling delay compensation in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] The technical solution of the present invention will be described in detail with reference to the accompanying drawings.

[0017] As shown in FIG. Figure 1 , a three-phase inverter adopts a lower-arm current detection scheme. Figure 1 In it, U in and C in are the input DC voltage and input bus capacitor of the three-phase inverter circuit; u a , u b and u c are the three-phase output voltages of the three-phase inverter circuit; i a , i b and i c are the three-phase output currents of the three-phase inverter circuit; S1, S2, S3, S4, S5 and S6 are the first, second, third, fourth, fifth and sixth MOS-type power switch tubes of the three-phase inverter circuit respectively; R1, R2 and R3 are the first, second and third shunts of the three-phase inverter circuit respectively; i aL , i bL and i cL are the current values flowing through the shunts R1, R2 and R3 respectively.

[0018] Let Gs1, Gs2, Gs3, Gs4, Gs5, and Gs6 be the driving signals of the power switch tubes S1, S2, S3, S4, S5, and S6 of the three-phase inverter circuit respectively. The method of generating the intersection of the triangular carrier waves is as shown in the appendix Figure 2 as follows. Figure 2 Among them, T s is the switching period of the power switch tubes of the three-phase inverter circuit; T1, T2, and T3 are the conduction times of the lower tubes S2, S4, and S6 of the three bridge arms of the three-phase inverter circuit within one switching period. Taking the detection of the current flowing through S2 as an example, only when S2 is turned on, will current flow through R1, and then the current i aL can be detected. Due to the existence of the dead zone between the upper and lower tubes of the bridge arm, the full establishment time of i aL , and the sampling / holding time of analog-to-digital conversion, S2 needs to conduct for a sufficient length of time (that is, T1 in the appendix Figure 2 should not be less than the minimum value T min ) to ensure stable current detection. Similarly, the current detection of the lower tubes of the other two bridge arms is also like this. Based on this, the function of the phase current reconstruction module in the appendix Figure 3 is designed as follows: When S2, S4, and S6 all have sufficient conduction times, the currents i Figure 1 flowing through the three lower tubes in the appendix aL , i bL , and i cL can be detected separately, and then the three-phase output currents i a , i b , and i c of the three-phase inverter can be obtained; in addition, as long as two of the switch tubes S2, S4, and S6 have sufficient conduction times within one switching period, i aL +i bL +i cL =0 can be used for reconstruction and the currents i aL , i bL , and i cL can be detected, and then the three-phase output currents i a , i b , and i c can be obtained.

[0019] As shown in the appendix Figure 3 , the block diagram of the high-speed permanent magnet synchronous motor control method provided in this embodiment Figure 3 Among them, i a , i b , and i c are the three-phase output currents of the inverter circuit obtained after current reconstruction; i α and i β are the α and β axis currents of the inverter circuit in the two-phase stationary coordinate system; i d and i qare the d-axis and q-axis currents of the inverter circuit in the synchronous rotating coordinate system; u α and u β are the α-axis and β-axis voltages of the three-phase inverter circuit in the two-phase stationary coordinate system; i q * 、u d * and u q * are the q-axis current control reference value, d-axis voltage control quantity, and q-axis voltage control quantity of the three-phase inverter circuit in the synchronous rotating coordinate system; u α * and u β * are the α-axis and β-axis voltage control quantities of the three-phase inverter circuit in the two-phase stationary coordinate system; ω eg 、n mg 、θ eg1 and θ eg2 are respectively the detected value of the electrical angular velocity of the motor, the detected value of the rotational speed, the detected value of the electrical angle before compensation, and the detected value of the electrical angle; p n is the number of pole pairs of the permanent magnet synchronous motor; n ref and n err are the given value of the motor rotational speed and the rotational speed error value.

[0020] Among them, Figure 3 and the phase current reconstruction module involved in the method of the present invention mainly realizes the conversion between the three-phase output currents i a 、i b 、i c and the currents i aL 、i bL 、i cL in the shunt. According to the current directions defined in Appendix Figure 1 , the transformation relationship between i a 、i b 、i c and i aL 、i bL 、i cL is shown in Table 1.

[0021] Table 1 Transformation relationship between the three-phase output current and the sampling current of the lower bridge arm in the three-phase inverter circuit

[0022]

[0023] Among them, Figure 3 and the SMO sliding mode observer module, αβ / dq transformation module, i d =0 control regulator module, and SVPWM module involved in the method of the present invention are all existing modules in the art, and their functions and roles are well known in the art. The SMO sliding mode observer module mainly based on the α-axis and β-axis voltages u α, u β and current i α , i β The detected value ω of the electrical angular velocity of the motor is obtained through observation eg and the detected value θ of the electrical angle before compensation eg1 ; The αβ / dq transformation module mainly realizes the transformation of variables from the αβ two-phase stationary coordinate system to the dq synchronous rotating coordinate system, and is the basic transformation module in the motor control method; i d =0 control regulator module mainly realizes the control of the motor i d =0, which is a common control method for permanent magnet synchronous motors; The SVPWM module generates six drive signals for the three-phase inverter circuit according to the voltage control quantities u α * and u β *

[0024] Reference Figure 3 , the control method for the high-speed permanent magnet synchronous motor of the present invention specifically includes the following steps:

[0025] (1) The currents i aL , i bL and i cL flowing through the three lower transistors are detected through the shunt resistor of the lower bridge arm of the three-phase inverter circuit, and together with the current drive signals Gs2, Gs4 and Gs6 of the three lower bridge arm switching transistors at present, they are used as the input of the phase current reconstruction module. After calculation, the three-phase output currents i a , i b and i c of the inverter circuit are obtained, and through abc / αβ transformation, the α and β axis currents i α and i β in the two-phase stationary coordinate system are obtained;

[0026] (2) The three-phase output voltages u a , u b and u c of the three-phase inverter circuit are obtained through voltage sampling, and through abc / αβ transformation, the α and β axis voltages u α and u β in the two-phase stationary coordinate system are obtained. They are jointly input to the SMO sliding mode observer module together with the currents i α and i β obtained in step (1) to obtain the detected value ω of the electrical angular velocity of the motor eg and the detected value θ of the electrical angle before compensation eg1 , ω eg is multiplied by the coefficient 1 / (2T s ) brought by the sampling delay of the lower bridge arm current and added to θ eg1 to obtain the detected value θ of the electrical angle of the motor eg2 , ω​eg Divide by the number of motor pole pairs p n Then multiply by the coefficient 30 / π to get the motor speed detection value n mg ;

[0027] (3) The current i obtained in step (1) α 、i β and the motor electrical angle detection value θ obtained in step (2) eg2 The αβ / dq conversion module is input together to obtain the d and q axis current feedback values ​​i in the synchronous rotating coordinate system. d and i q ;

[0028] (4) The motor speed detection value n obtained in step (2) is mg Through negative feedback, with the given speed n ref The speed outer loop is formed, and the speed deviation value n is obtained by subtracting the two err The deviation value is output as the q-axis current control reference value i after passing through the PI regulator. q * , and compare it with the motor electrical angular velocity detection value ω obtained in step (2) eg , the quadrature-axis current feedback value i obtained in step (3) q and the direct axis current feedback value i d Together as i d =0 controls the input of the regulator module, and after adjustment, it outputs the d and q axis voltage control quantity u in the synchronous rotating coordinate system d * and u q * , and the motor electrical angle detection value θ obtained in step (2) eg2 The dq / αβ conversion module is input together to output the α and β axis voltage control quantity u in the two-phase stationary coordinate system. α * and u β * , the SVPWM module generates six drive signals Gs1, Gs2, Gs3, Gs4, Gs5 and Gs6 to control the on and off of each power tube in the three-phase inverter circuit.

[0029] From the above process, it can be seen that the high-speed permanent magnet synchronous motor control method of the present invention performs sampling delay compensation on the angle position. Figure 4 It is a simulation waveform diagram of the rotation speed and angular position error after sampling delay compensation in the present invention, Figure 4 In, n m is the actual speed of the motor, θ err The actual motor angle minus the motor electrical angle detection value θ eg2 The motor angle position error is obtained after the simulation. In the simulation, the motor speed given value n is setref is a fixed value of 160,000 revolutions per minute. The simulation results show that as the motor output speed n m increases, the angular position error θ of the motor err gradually increases after a short initial identification period until it stabilizes, and the error value is less than 0.04 rad. Figure 5 is the simulation waveform diagram of the speed and angular position error without using the sampling delay compensation in the present invention. The simulation results show that the angular position error θ of the motor err reaches 0.124 rad, which is much larger than Figure 4 that.

[0030] According to the description of the above embodiments, the present invention can improve the rotor position detection accuracy of a high-speed motor drive controller using a lower-bridge arm current detection scheme without a position sensor, and thus can improve the control performance of a high-speed permanent magnet synchronous motor.

[0031] What is described above in this specification is only an example of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the content of this specification of the present invention or exceed the scope defined by this claims, they should all fall within the protection scope of the present invention.

Claims

1. A high-speed permanent magnet synchronous motor control method with lower bridge arm current sampling, characterized in that: The following steps are involved: (1) The current i flowing through the three lower tubes is obtained through the shunt of the lower bridge arm of the three-phase inverter circuit aL 、i bL and i cL , combined with the lower bridge arm switch tube drive signals Gs2, Gs4 and Gs6, the input phase current reconstruction module is solved to obtain the three-phase output current i a 、i b and i c , after abc / αβ transformation, we can get the α and β axis current i in the two-phase stationary coordinate system. α with i β ; (2) Obtain the three-phase output voltage u of the inverter circuit through voltage sampling a 、u b and u c , after abc / αβ transformation, we can get the α and β axis voltage u α with u β , and compare it with the current i α with i β The two are input to the sliding mode observer to obtain the motor electrical angular velocity detection value ω. eg and the electrical angle detection value θ before compensation eg1 , and then get the motor electrical angle detection value θ eg2 And the motor speed detection value n mg ; (3) The current i α 、i β and the motor electrical angle detection value θ eg2 Input to the αβ / dq conversion module to obtain the d and q axis current feedback values ​​i in the synchronous rotating coordinate system d and i q ; (4) The motor speed detection value n mg With given speed n ref The speed outer loop is formed to obtain the speed deviation value n err , after the PI regulator, the q-axis current control reference value i is output q * , change i q * 、Motor electrical angular velocity detection value ω eg 、i q with i d Together as i d =0 controls the input of the regulator module and outputs the d and q axis voltage control quantities u in the synchronous rotating coordinate system d * and u q * , combined with the motor electrical angle detection value θ eg2 , after dq / αβ transformation, we can get the α and β axis voltage control quantity u α * and u β * , and then generate six switch tube drive signals through the SVPWM module to control each switch tube of the three-phase inverter circuit.

2. The high-speed permanent magnet synchronous motor control method with lower bridge arm current sampling according to claim 1 is characterized in that: In the step (1), within a switching cycle, it is necessary to ensure that at least two of the three lower bridge arm switch tubes have sufficient conduction time to ensure that the current flowing through at least the two lower tubes can be detected separately.

3. The high-speed permanent magnet synchronous motor control method for lower bridge arm current sampling according to claim 2 is characterized in that: When the current flowing through the two lower tubes is obtained, according to i aL +i bL +i cL =0 to obtain the current flowing through the third lower tube.

4. The high-speed permanent magnet synchronous motor control method with lower bridge arm current sampling according to claim 1 is characterized in that: In step (2), the motor electrical angular velocity detection value ω is obtained eg and the electrical angle detection value θ before compensation eg1 After that, ω eg Multiply the coefficient caused by the bridge arm current sampling delay 1 / (2T s ) and θ eg1 Add together to get the motor electrical angle detection value θ eg2 .

5. The high-speed permanent magnet synchronous motor control method with lower bridge arm current sampling according to claim 1, characterized in that: In step (2), the motor electrical angular velocity detection value ω eg Divide by the number of motor pole pairs p n Then multiply by the coefficient 30 / π to get the motor speed detection value n mg .

6. The high-speed permanent magnet synchronous motor control method with lower bridge arm current sampling according to claim 1 is characterized in that: In step (4), the motor speed detection value n obtained in step (2) is mg Through negative feedback, with the given speed n ref The speed outer loop is formed, and the speed deviation value n is obtained by subtracting the two err .

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