Non-inductive FOC downwind starting method

Abstract

The invention discloses a non-inductive FOC downwind starting method, and relates to the field of motors, the non-inductive FOC downwind starting method comprises the following steps: step 1, when a motor is in a downwind state or a headwind state, a three-phase lower bridge arm is opened, and the opening time is Tsh; 2, three-phase motor currents Iu, Iv and Iw are obtained, Ialpha and Ibeta are obtained through coordinate transformation, and a phase included angle theta 1 is obtained through arc tangent operation; 3, closing the three-phase lower bridge arm, wherein the closing time lasts for T12; # imgabs0 # omega eMax is the maximum rotating speed of the motor; compared with the prior art, the method has the beneficial effects that a position sensor is not needed, the initial position of the motor rotor is quickly and reliably estimated, the initial position of the motor can be identified in a very short time, and the motor does not rotate in the identification process; compared with a product with a position sensor motor and a driver, the cost of the motor position sensor is saved.

Description

Technical Field

[0001] The invention relates to the field of motors, and in particular to a sensorless FOC downwind starting method. Background Art

[0002] Most traditional permanent magnet synchronous motors are equipped with position sensors so that the controller can use the sensor to obtain the motor rotor position and then drive the motor normally. However, the introduction of position sensors not only increases the cost of hardware, but also increases the difficulty of production and installation, and the requirements for process also increase. In addition, since the position sensor usually requires an additional wiring harness to connect to the controller, the motor drive system often cannot be used normally during use due to factors such as wiring harness aging and poor contact.

[0003] Therefore, products with position sensorless motors and drivers have emerged. In many products equipped with position sensorless motors and drivers, when the controller is turned off, the motor will still rotate freely at a certain speed due to inertia. When the controller is turned on again during this period, it needs to wait until the motor stops completely before restarting the motor. This time may be relatively long, thereby reducing system utilization.

[0004] The solution is that when the load object of the position sensorless motor is a fluid, such as a fan, pump or a motor with large rotational inertia, a quick restart can be achieved without waiting for the motor to come to a stop. However, this is limited to the load object of the position sensorless motor and needs to be improved. Summary of the invention

[0005] The object of the present invention is to provide a sensorless FOC downwind starting method to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A sensorless FOC downwind starting method comprises the following steps:

[0008] Step 1: When the motor is in a downwind or headwind state, the three-phase lower bridge arm is turned on for a time of T. sh ;

[0009] Step 2: Get the three-phase motor current I u , I v , I w , after coordinate transformation, we get I α , I β , and then the inverse tangent operation is used to obtain the angle θ 1 ;

[0010] Step 3: Close the three-phase lower bridge arm for a duration of T 12 ; where ωeMax is the maximum speed of the motor;

[0011] Step 4, repeat steps 1 and 2 to get the angle θ 2 ; And shut down the three-phase lower bridge arm;

[0012] Step 5, by the phase angle θ 1 ,θ 2 , calculate the current electrical angle of the motor;

[0013] Step 6, judging whether the motor is in a downwind state or a headwind state based on the motor speed and the motor rotation direction;

[0014] Step 7: When the calculated motor speed is higher than the set threshold, the calculated angle and speed are brought into the observer to directly enter the closed loop.

[0015] As a further solution of the present invention: in step 1, when the motor is in a downwind state or a headwind state, a lower bridge arm short-circuit pulse mode is adopted to open the three-phase lower bridge arm, and the opening time is T sh .

[0016] As a further solution of the present invention: Under the premise of ensuring sampling reliability and required signal-to-noise ratio, ensure the opening time T sh Short enough.

[0017] As a further solution of the present invention: in step 2, i 1 (T sh ) is the first short pulse current, θ I1 is the angle between the current vector and the U phase, θ 0 is the angle between the current vector and the d-axis, θ 1 The angle between the d-axis and the U-phase is used to obtain the motor back electromotive force angle:

[0018] θ 1 =θ I1 +θ 0 (1).

[0019] As a further solution of the present invention: in step 5, the current motor speed is calculated:

[0020]

[0021] Calculate the current motor electrical angle:

[0022]

[0023] As a further solution of the present invention: in step 6, when the motor speed ω e When the motor rotates in the same direction as the motor, the motor is in a downwind state. eThe direction of rotation is opposite to that of the motor.

[0024] As a further solution of the present invention: in step 7, when the calculated motor speed is higher than the set threshold, that is, |ω e |>ω Thr , then the calculated angle and speed are brought into the observer to directly enter the closed loop.

[0025] Compared with the prior art, the beneficial effects of the present invention are: the present invention does not require a position sensor and can quickly and reliably estimate the initial position of the motor rotor, can identify the initial position of the motor in a very short time, and the motor does not rotate at all during the identification process; compared with products with position sensor motors and drivers, the cost of the motor position sensor is saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the electrical angle of rotation of the motor. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] See also Figure 1 , a non-sensing FOC (field oriented control) downwind starting method, comprising the following steps:

[0029] Step 1: When the motor is in a downwind or headwind state, the three-phase lower bridge arm is turned on for a time of T. sh ;

[0030] Step 2: Get the three-phase motor current I u , I v , I w , after coordinate transformation, we get I α , I β , and then the inverse tangent operation is used to obtain the angle θ 1 ; The specific calculation formula is as follows:

[0031] I α =I u

[0032]

[0033] Step 3: Close the three-phase lower bridge arm for a duration of T 12 ; where ω Maxis the maximum speed of the motor;

[0034] Step 4, repeat steps 1 and 2 to get the angle θ 2 ; And shut down the three-phase lower bridge arm;

[0035] Step 5, by the phase angle θ 1 ,θ 2 , calculate the current electrical angle of the motor;

[0036] Step 6, judging whether the motor is in a downwind state or a headwind state based on the motor speed and the motor rotation direction;

[0037] Step 7: When the calculated motor speed is higher than the set threshold, the calculated angle and speed are brought into the observer to directly enter the closed loop.

[0038] In a specific embodiment: the motor is in the state of forward and reverse wind, and the three-phase lower bridge arm is opened at the same time, and the opening time is T sh The following is the motor stator dq voltage equation:

[0039]

[0040] When T sh Small enough to satisfy Then R s It can be approximated to 0. Opening the three-phase lower bridge arm is equivalent to U d =0,U q =0The above formula can be transformed into:

[0041]

[0042] After Lass transformation, we get:

[0043]

[0044] Due to the short circuit time T sh Short enough so For surface mount motors L q and L d Can be nearsighted, so Since the back EMF leads the flux phase Therefore, the current motor electrical angle is:

[0045]

[0046] In this embodiment: In step 1, when the motor is in a downwind state or a headwind state, a lower bridge arm short-circuit pulse mode is adopted to open the three-phase lower bridge arm, and the opening time is T sh .

[0047] In this embodiment: firstly, the sampling must be reliable, that is, the opening time must be greater than the current sampling time, and the current sampling time is related to the driver chip; secondly, the required signal-to-noise ratio must be guaranteed, that is, the current signal at the end of the lower tube opening must reach a relatively stable state, which is usually affected by the motor parameters; under the above two conditions, the opening time T sh Should be short enough, generally, T sh Take the range of 1 / 100 to 1 / 10 of the control period.

[0048] In this example: See Figure 1 , in step 2, i 1 (T sh ) is the first short pulse current, θ I1 is the angle between the current vector and the U phase, θ 0 is the angle between the current vector and the d-axis, θ 1 The angle between the d-axis and the U-phase is used to obtain the motor back electromotive force angle:

[0049] θ 1 =θ I1 +θ 0 (1).

[0050] θ 2 Calculation method and θ 1 The difference is that the motor rotation angle changes at intervals.

[0051] In this embodiment: In step 5, the current motor speed is calculated:

[0052]

[0053] Calculate the current motor electrical angle:

[0054]

[0055] In this embodiment: In step 6, when the motor speed ω e When the motor rotates in the same direction as the motor, the motor is in a downwind state. e The direction of rotation is opposite to that of the motor.

[0056] In this embodiment: In step 7, when the calculated motor speed is higher than the set threshold, that is, |ω e |>ω Thr , then the calculated angle and speed are brought into the observer to directly enter the closed loop.

[0057] The present invention does not require a position sensor and can quickly and reliably estimate the initial position of the motor rotor. It can identify the initial position of the motor in a very short time, and the motor does not rotate during the identification process. Compared with products with position sensor motors and drivers, the cost of the motor position sensor is saved.

[0058] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered as exemplary and non-restrictive in all respects.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A non-sensing FOC downwind starting method, characterized in that: The sensorless FOC downwind starting method comprises the following steps: Step 1: When the motor is in a downwind or headwind state, the three-phase lower bridge arm is turned on for a time of T. sh ; Step 2: Get the three-phase motor current I u , I v , I w , after coordinate transformation, we get I α , I β , and then the inverse tangent operation is used to obtain the angle θ1; Step 3: Close the three-phase lower bridge arm for a duration of T 12 ; where ω eMax is the maximum speed of the motor; Step 4, repeat steps 1 and 2 to obtain the phase angle θ2; and turn off the three-phase lower bridge arm; Step 5, calculate the current electrical angle of the motor through the phase angles θ1 and θ2; Step 6, judging whether the motor is in a downwind state or a headwind state based on the motor speed and the motor rotation direction; Step 7: When the calculated motor speed is higher than the set threshold, the calculated angle and speed are brought into the observer to directly enter the closed loop.

2. The non-sensing FOC downwind starting method according to claim 1 is characterized in that: In step 1, when the motor is in a downwind or headwind state, the lower bridge arm short-circuit pulse method is adopted to open the three-phase lower bridge arm for a time of T. sh .

3. The non-sensing FOC downwind starting method according to claim 1 or 2, characterized in that: Ensure the opening time T under the premise of ensuring sampling reliability and required signal-to-noise ratio sh Short enough.

4. The non-sensing FOC downwind starting method according to claim 1, characterized in that: In step 2, i1(T sh ) is the first short pulse current, θ I1 is the angle between the current vector and the U phase, θ0 is the angle between the current vector and the d axis, θ1 is the angle between the d axis and the U phase, and the motor back electromotive force angle is obtained: θ1=θ I1 +θ0 (1).

5. The non-sensing FOC downwind starting method according to claim 1, characterized in that: In step 5, the current motor speed is calculated: Calculate the current motor electrical angle:

6. The non-sensing FOC downwind starting method according to claim 5, characterized in that: In step 6, when the motor speed ω e When the motor rotates in the same direction as the motor, the motor is in a downwind state. e The direction of rotation is opposite to that of the motor.

7. The non-sensing FOC downwind starting method according to claim 5, characterized in that: In step 7, when the calculated motor speed is higher than the set threshold, i.e. |ω e |>ω Thr , then the calculated angle and speed are brought into the observer to directly enter the closed loop.

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