An automatic detection system and method for a permanent magnet synchronous motor drive circuit

Abstract

An automatic detection system for a permanent magnet synchronous motor drive circuit disclosed by the present invention includes a central processing chip, an inverter drive circuit, an optocoupler isolation circuit, an inverter drive output circuit, and a power control module. The central processing chip outputs six drive signals, which enter the optocoupler isolation circuit after passing through the inverter drive circuit, and then enter the power control module through the inverter drive output circuit to output three-phase voltage to the permanent magnet synchronous motor. It includes a sensor that measures the three-phase current signals of the permanent magnet synchronous motor and feeds them back to the central processing chip. The present invention also discloses an automatic detection method for a permanent magnet synchronous motor drive circuit. The present invention applies SVPWM and rotor magnetic field positioning to the functional detection of the drive circuit to complete the automatic detection of the permanent magnet synchronous motor drive circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motor detection, and particularly relates to an automatic detection system and method for a permanent magnet synchronous motor drive circuit. Background Art

[0002] SVPWM and rotor magnetic field orientation are generally used in flux linkage modulation and speed control, and are less used in the functional detection of drive circuits.

[0003] The drive circuit of the frequency converter enables the permanent magnet synchronous motor to correctly control signals, such as PWM output signals. In actual production, the node signals of each drive link are usually manually captured by an oscilloscope to determine which drive circuit fails to work, with low efficiency and insufficient automation. Summary of the Invention

[0004] One of the technical problems to be solved by the present invention is to provide an automatic detection system for a permanent magnet synchronous motor drive circuit in view of the deficiencies of existing permanent magnet synchronous motor drive circuits.

[0005] Another technical problem to be solved by the present invention is to provide an automatic detection method for a permanent magnet synchronous motor drive circuit in view of the deficiencies of existing permanent magnet synchronous motor drive circuits.

[0006] To achieve the above invention object, an automatic detection system for a permanent magnet synchronous motor drive circuit of the present invention includes a central processing chip, an inverter drive circuit, an optocoupler isolation circuit, an inverter drive output circuit, and a power control module. The central processing chip outputs six drive signals, which enter the optocoupler isolation circuit after passing through the inverter drive circuit, and then enter the power control module through the inverter drive output circuit to output three-phase voltage to the permanent magnet synchronous motor. It is characterized in that it further includes a sensor, and the sensor measures the three-phase current signal of the permanent magnet synchronous motor and feeds it back to the central processing chip.

[0007] In a preferred embodiment of the present invention, the central processing chip is a DSP.

[0008] In a preferred embodiment of the present invention, the sensor is a current sensor.

[0009] An automatic detection method for a permanent magnet synchronous motor drive circuit of the present invention includes the following steps:

[0010] Step 1: The central processing chip uses a current loop to send PWM signals to control the permanent magnet synchronous motor drive circuit;

[0011] Step 2: Locate the rotor of the permanent magnet synchronous motor to a specified angle so that two angle positions can complete the conduction of 6 drive loops in the permanent magnet synchronous motor drive circuit;

[0012] Step 3: Determine whether the six drive circuits of the permanent magnet synchronous motor drive circuit are operating normally based on the three-phase feedback current direction and a preset judgment threshold.

[0013] Step 4: Feed back the state of the drive circuit to the host computer.

[0014] In a preferred embodiment of the present invention, the reference current input to the central processing chip is in a two-phase synchronous coordinate system. The current controller in the central processing chip outputs a control voltage, which is transformed into a two-phase stationary coordinate system through coordinate transformation, and then converted into six three-phase PWM drive signals through SVPWM in the central processing chip and output. After passing through the inverter drive circuit in the permanent magnet synchronous motor drive circuit, it enters the opto-isolation circuit in the permanent magnet synchronous motor drive circuit, and then enters the power control module in the permanent magnet synchronous motor drive circuit through the inverter drive output circuit, and outputs three-phase voltage to the permanent magnet synchronous motor.

[0015] In a preferred embodiment of the present invention, the feedback current in Step 3 is sampled by a current sensor. The current sensor samples the three-phase feedback current of the permanent magnet synchronous motor, and then is transformed into a two-phase synchronous coordinate system through a three-phase stationary coordinate system, and the sampled three-phase feedback current is fed back to the central processing chip to form a loop.

[0016] In a preferred embodiment of the present invention, the steps of transforming the two-phase synchronous coordinate system to the three-phase stationary coordinate system are as follows:

[0017] Step 1: Transform from the two-phase synchronous coordinate system to the two-phase stationary coordinate system;

[0018] Step 2: Transform the two-phase stationary coordinate system to the three-phase stationary coordinate system.

[0019] Due to the adoption of the above technical solutions, the present invention uses SVPWM and rotor magnetic field orientation for the functional detection of the drive circuit to complete the automatic detection of the permanent magnet synchronous motor drive circuit. The present invention focuses on detecting the operating state of the permanent magnet synchronous motor drive circuit through software algorithms, while traditionally, the level of the monitoring points is generally tested manually, thereby improving the detection efficiency and being able to quickly determine the faults of the drive circuit and feedback them to the host computer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the principle of the drive system of the permanent magnet synchronous motor of the present invention.

[0021] Figure 2 It is a schematic diagram of the model of the automatic detection method for the permanent magnet synchronous motor drive circuit of the present invention.

[0022] Figure 3 Schematic diagram for converting from dq coordinate system to αβ coordinate system.

[0023] Figure 4 Schematic diagram for converting from αβ coordinate system to abc coordinate system.

[0024] Figure 5 Simplified diagram of the IPM of the present invention.

[0025] Figure 6 Schematic diagram of the actual measured three-phase phase current image Figure 1 .

[0026] Figure 7 Schematic diagram of the actual measured three-phase phase current image Figure 2 .

[0027] Figure 8 Simplified circuit diagram of the drive end when the upper bridge arm of phase V conducts and the lower bridge arms of U and W conduct.

[0028] Figure 9 Schematic diagram of the space voltage vector synthesized by three-phase voltages.

[0029] Figure 10 Schematic diagram of the flow of the automatic detection method for the drive circuit of the permanent magnet synchronous motor. Detailed implementation manners

[0030] The present invention will be further described below in conjunction with the accompanying drawings and detailed implementation manners.

[0031] Refer to Figure 1 . In the drive system of the permanent magnet synchronous motor shown in the figure, the six drive pins PWM1 - PWM6 of the central processing chip (DSP) respectively output six drive signals, which enter the optocoupler isolation circuit after passing through the inverter drive circuit, and then enter the power control module (IPM) through the inverter drive output circuit, output three-phase voltages to the permanent magnet synchronous motor, and the sensor measures the three-phase current signals and feeds them back to the DSP.

[0032] When performing field-oriented control (FOC) of the rotor of the permanent magnet synchronous motor, the two-phase synchronous coordinate system is generally used in industry. The purpose of choosing the two-phase synchronous coordinate system is to facilitate the decoupling of the permanent magnet synchronous motor and control it equivalently as a DC motor. This requires the coordinate system to be converted from the three-phase stationary coordinate system (i.e., abc coordinate system) to the two-phase synchronous coordinate system (i.e., dq coordinate system). Refer to Figure 2 , that is, the reference current i input by the DSP rIt is two identical synchronous coordinate systems. The output control voltage of the current controller (ACR) is transformed into two-phase stationary coordinates (i.e., αβ coordinate system) through coordinate transformation, and then converted into three-phase PWM signals through SVPWM and output to the permanent magnet synchronous motor. The current sensor samples the three-phase current signals, and then forms a loop by converting the three-phase stationary coordinate system (i.e., abc coordinate system) into two identical synchronous coordinate systems (i.e., dq coordinate system).

[0033] The transformation from two identical synchronous coordinate systems to three-phase stationary coordinate systems needs to go through two steps. See Figure 3 , the first step is to transform from two identical synchronous coordinate systems to two-phase stationary coordinate systems, that is, from the dq coordinate system to the ∝β coordinate system. According to the geometric relationship, the inverse Park transformation is obtained.

[0034]

[0035] Then transform the two-phase stationary coordinate system into a three-phase stationary coordinate system. See Figure 4 , that is, from the αβ coordinate system to the abc coordinate system. According to the geometric relationship, the inverse Clarke transformation is obtained:

[0036]

[0037] When is an equal-power transformation, m′ = 1 is an equal-amplitude transformation

[0038] To sum up, the transformation matrix from the dq coordinate system to the abc coordinate system is

[0039]

[0040] Adopt i q = 0 control, that is, when the rotor angle is positioned, we get:

[0041]

[0042] As Figure 5 is a simplified diagram of the IPM. PN are the positive and negative ends of the bus. There are a total of six drive bridge arms (IGBTs) in three phases, two for each phase up and down, equipped with freewheeling diodes. The permanent magnet synchronous motor is equivalent to an inductor, and the connection method is Y-N.

[0043] From Figure 5It can be seen that to test whether the six-way drive signals are conducting, it is necessary to apply currents in both positive and negative directions to the three-phase circuit. When the current in one phase is positive, the upper bridge arm of the IPM conducts, and the current of this phase flows into the permanent magnet synchronous motor from the upper bridge arm of the drive circuit; when the current in one phase is negative, the lower bridge arm of the IPM conducts, and the current of this phase flows from the permanent magnet synchronous motor into the lower bridge arm of the drive circuit. Then, it is transformed into a mathematical problem of how to test that each of the six ways of the drive circuit conducts once through two positioning angles. Two ideas are given below:

[0044] Idea 1:

[0045] Define the scheme as

[0046] Phase \ Current Direction \ Times First time Second time A ＞0 ＜0 B ＜0 ＜0 C ＜0 ＜0

[0047] That is, to satisfy

[0048]

[0049] That is, it is necessary to solve the above constraints,

[0050] Take an embodiment. Assume that the required rotor angle for positioning is in [0, π]. Then,

[0051] For the first positioning, select

[0052] ① It is automatically satisfied,

[0053] ② Get

[0054] ③ It also holds in this interval because both sinθ and cosθ are greater than 0;

[0055] For the second positioning, select

[0056] (4) It is automatically satisfied,

[0057] (5) It also holds in this interval because sinθ > 0 and cosθ < 0,

[0058] (6) Get

[0059] Assume that the first positioning selects 0° and the second positioning selects 165°. Then,

[0060] When calculating the trigonometric functions of 165°, the half-angle formula needs to be used, that is:

[0061]

[0062] It depends on whether it is positive or negative on the position of the angle

[0063] then

[0064]

[0065] the following table can be obtained

[0066]

[0067] See Figure 6 , for the first actual test, the three-phase phase current image is when the rotor is positioned at 0°, see Figure 7 For the second actual test, the three-phase phase current image is when the rotor is positioned at 165°.

[0068] It can be seen from this embodiment that the two-positioning ensures that all six drive branches are conducted, that is, the automatic detection work is carried out. The six drive circuits are judged whether they are operating normally by the feedback current direction of the three phases and the set judgment threshold, and the state of the drive circuit is fed back to the host computer.

[0069] Idea 2:

[0070] According to the SVPWM space vector synthesis relationship described by Xu Jinbo in the literature (Space Voltage Vector Modulation SVPWM Technology) to determine the positioning angle. Since there are 6 switching tubes in the three-phase bridge arm of the drive circuit, in order to study the space vectors output when different switches of the upper and lower bridge arms of each phase are closed, the switching function S x (a, b, c) is defined. When any of a, b, c is equal to 1, it means that the upper bridge arm of the corresponding phase is conducted, and when it is equal to 0, it means that the lower bridge arm of the corresponding phase is conducted. Then there are 8 switching combinations for the three phases, including 6 non-zero vectors S1(0, 0, 1), S2(0, 1, 0), S3(0, 1, 1), S4(1, 0, 0), S5(1, 0, 1), S6(1, 1, 0), and two zero vectors S0(0, 0, 0) and S7(1, 1, 1). Taking S2(0, 1, 0) as an example, the circuit schematic diagram of its drive end is Figure 8

[0071] According to Figure 8 it can be obtained that

[0072] U BN -U CN =U dc

[0073] U BN -U AN =U dc

[0074] U AN +U BN +UCN = 0

[0075] It can be solved that

[0076]

[0077] Similarly, the space voltage vectors under other various combinations can be calculated as shown in the following table

[0078]

[0079]

[0080] According to the space phase relationship of the three phases, it can be obtained that Figure 9 , which is a regular hexagon, where the amplitudes of the non-zero vectors are the same, the adjacent vectors are spaced 60°, and the amplitudes of the two zero vectors are zero and are located at the center

[0081] By positioning the rotor to any one of the three groups of S1 / S6, S2 / S5, and S3 / S4 with an angle difference of 180°, the detection of 6 drive circuits can be achieved. Whether the 6 drive circuits are operating normally is judged by the feedback current direction of the three phases and the set judgment threshold, and the state of the drive circuit is fed back to the host computer

[0082] See Figure 10 , an automatic detection method for a permanent magnet synchronous motor drive circuit, includes the following steps

[0083] Step 1: The central processing chip uses the current loop to send PWM signals to control the permanent magnet synchronous motor drive circuit

[0084] Step 2: Position the rotor of the permanent magnet synchronous motor to a specified angle so that the conduction of 6 drive circuits in the permanent magnet synchronous motor drive circuit can be completed by two angle positions

[0085] Step 3: Judge whether the 6 drive circuits of the permanent magnet synchronous motor drive circuit are operating normally through the feedback current direction of the three phases and the preset judgment threshold

[0086] Step 4: Feed back the state of the drive circuit to the host computer

Claims

1. An automatic detection method for a permanent magnet synchronous motor drive circuit, including an automatic detection system for the permanent magnet synchronous motor drive circuit, the automatic detection system for the permanent magnet synchronous motor drive circuit includes: A central processing chip, an inverter drive circuit, an optocoupler isolation circuit, an inverter drive output circuit, and a power control module. The central processing chip outputs six drive signals, which enter the optocoupler isolation circuit after passing through the inverter drive circuit, and then enter the power control module through the inverter drive output circuit to output three-phase voltage to the permanent magnet synchronous motor. It is characterized in that it further includes a current sensor, and the current sensor measures the three-phase current signals of the permanent magnet synchronous motor and feeds them back to the central processing chip The automatic detection method of the above permanent magnet synchronous motor drive circuit includes the following steps: Step 1: The central processing chip uses the current loop to send PWM signals to control the permanent magnet synchronous motor drive circuit; Step 2: Locate the rotor of the permanent magnet synchronous motor to a specified angle so that two angle positions can complete the conduction of the 6 drive circuits in the permanent magnet synchronous motor drive circuit; Step 3: Determine whether the 6 drive circuits in the permanent magnet synchronous motor drive circuit are operating normally based on the feedback current directions of the three phases and a preset judgment threshold; Step 4: Feed back the state of the drive circuit to the host computer.

2. The automatic detection method of a permanent magnet synchronous motor drive circuit according to claim 1, wherein, The central processing chip is a DSP.

3. The automatic detection method of a permanent magnet synchronous motor drive circuit according to claim 1, characterized in that, The reference current input to the central processing chip is in a two-phase synchronous coordinate system. The current controller in the central processing chip outputs a control voltage, which is transformed into a two-phase stationary coordinate system through coordinate transformation, and then converted into six three-phase PWM drive signals through SVPWM in the central processing chip. After passing through the inverter drive circuit in the permanent magnet synchronous motor drive circuit, it enters the optocoupler isolation circuit in the permanent magnet synchronous motor drive circuit, and then enters the power control module in the permanent magnet synchronous motor drive circuit through the inverter drive output circuit in the permanent magnet synchronous motor drive circuit to output three-phase voltage to the permanent magnet synchronous motor.

4. The automatic detection method of a permanent magnet synchronous motor drive circuit according to claim 3, characterized in that, The feedback current in Step 3 is sampled by a current sensor. The current sensor samples the feedback current of the three phases of the permanent magnet synchronous motor, and then converts it into a two-phase synchronous coordinate system through a three-phase stationary coordinate system, and feeds back the sampled feedback current of the three phases to the central processing chip to form a loop.

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