Current zero-crossing polarity determination device, determination method and application thereof

Abstract

The application discloses a current zero-crossing polarity determination device, a determination method and application thereof, and relates to the technical field of current polarity determination devices. The input end of the filter amplification module is connected with the phase line of a motor inverter, the output end of the filter amplification module is connected with the input end of a zero-crossing determination module, the output end of the zero-crossing determination module is connected with a single-chip microcomputer, the current sampling module comprises a reference voltage generating circuit and a current sampling circuit, the positive-phase input end of the current sampling circuit is connected with the phase current output end of an ADC current collector configured by the single-chip microcomputer, the output end of the reference voltage generating circuit is connected with the positive-phase input end of the current sampling circuit, the positive-phase input end and the inverting input end of the current polarity determination module are both connected with the output end of the current sampling circuit, and the output end of the current polarity determination module is connected with the single-chip microcomputer.

Description

Technical Field

[0001] This invention relates to the field of control technology for permanent magnet synchronous motors, specifically to a current zero-crossing polarity determination device, determination method, and its application. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) possess advantages such as simple control methods, high torque-to-inertia ratio, good dynamic response, high power density, compact structure, and high efficiency, making them a significant force in the increasingly popular new energy vehicle sector. In particular, the emergence of new high-quality rare-earth permanent magnet materials, power electronics technology, and intelligent controllers has driven the research and application of high-power and high-frequency switching electronic devices, leading to the widespread adoption of PMSMs in numerous fields.

[0003] However, due to the influence of the motor's magnetic pole structure and stator slot design, the motor's magnetic field is prone to distortion. Simultaneously, due to circuit nonlinearity factors such as the inherent voltage drop of the drive controller and dead time, harmonics will appear in the three-phase current of the PMSM. These harmonics exacerbate motor losses, affect heat dissipation, generate vibration and noise, and further impact load instability.

[0004] Currently, dead-zone compensation is commonly used to suppress current harmonics caused by inverters and other factors. However, using dead-zone compensation requires determining the current polarity to identify the current region of the three-phase voltage, thereby determining the magnitude of the compensation voltage. Therefore, to improve the accuracy of three-phase current polarity determination in permanent magnet synchronous motors, methods for determining current polarity have been extensively studied.

[0005] Currently available methods for determining current polarity can be divided into three categories, as follows:

[0006] (1) The first type starts directly from the current, splits the current into dq axis voltages through Park transformation, eliminates DC harmonics by filtering and other methods, and then reconstructs the phase current through inverse Park transformation. At this time, the phase current has reduced the influence of the 6th harmonic, and the accuracy of current polarity determination is greatly improved.

[0007] (2) The second type is similar to the first type, but it decomposes, filters and reconstructs the voltage, and the polarity of the current can also be determined by the polarity of the voltage.

[0008] (3) The third approach is to decompose the current vector from a spatial perspective, calculate the angle difference between the decomposed current vector and the standard axis, and directly determine the polarity of the current by comparing the angle difference with the original planned angle and polarity correspondence.

[0009] However, the above three methods are mostly more suitable for polarity detection when the sinusoidal current is normal. When the current is at zero point, once a zero-point clamping phenomenon occurs, the current will be continuously suppressed near zero point. This situation is not caused by harmonics, and simple filtering cannot solve this phenomenon. At this time, the polarity judgment of the current will be wrong, resulting in voltage compensation error and causing abnormal rotation of the motor. Summary of the Invention

[0010] To address the existing technology and the zero-crossing clamping phenomenon, this invention proposes a current zero-crossing polarity determination device, determination method, and its application, in order to reduce the impact of current zero-crossing clamping on current polarity determination and dead-zone voltage compensation, and improve the reliability of existing permanent magnet synchronous motor current polarity detection methods.

[0011] The main technical solution adopted in this invention is as follows:

[0012] A current zero-crossing polarity determination device includes a filtering and amplification module, a zero-crossing determination module, a current sampling module, and a current polarity determination module. The input terminal of the filtering and amplification module is connected to the phase line of a motor inverter, allowing the phase voltage signal to be input into the filtering and amplification module. The output terminal of the filtering and amplification module is connected to the input terminal of the zero-crossing determination module. The output terminal of the zero-crossing determination module is connected to a microcontroller, which sends a sampling command to the current sampling module based on the received electrical signal. The current sampling module includes a reference voltage generation circuit and a current sampling circuit. The non-inverting input terminal of the current sampling circuit is connected to the phase current output terminal of an ADC current acquisition unit configured with the microcontroller, used to acquire the phase current of the motor inverter. The output terminal of the reference voltage generation circuit is connected to the non-inverting input terminal of the current sampling circuit, and the inverting input terminal of the current sampling circuit is connected to its output terminal. Both the non-inverting and inverting input terminals of the current polarity determination module are connected to the output terminal of the current sampling circuit, calculating and outputting the phase currents at two different times. The output terminal of the current polarity determination module is connected to the microcontroller.

[0013] Preferably, the filtering and amplification module includes a filtering module and a signal amplification circuit. The filtering circuit consists of a simple filter composed of capacitor C1. The signal amplification circuit includes resistors R1 and R2 and an operational amplifier D1. One end of capacitor C1 is connected to the phase line of the motor inverter, and the other end is connected to the non-inverting input of operational amplifier D1. The phase voltage waveform V1, after being filtered by the filtering circuit, is connected to the non-inverting input of operational amplifier D1. The inverting input of operational amplifier D1 is divided into two paths. The first path is connected to resistor R1, and the other end of resistor R1 is connected to ground. The second path is connected to resistor R2, and the other end of resistor R2 is connected to the output of operational amplifier D1. The output of operational amplifier D1 outputs a sine wave V2.

[0014] Preferably, the specific circuit structure of the zero-crossing determination module is as follows: the base of transistor Q1 is connected to one end of resistors R3, R4 and R5 respectively; the other ends of resistors R3 and R4 are respectively connected to the output signal sine wave V2 of the filter amplification module; the other end of resistor R5 is grounded; the emitter of transistor Q1 is grounded; the collector of transistor Q1 is divided into two paths; the first path is connected to a 5V working voltage after being connected in series with resistor R6; the second path is used as the output terminal to output signal V3 and then connected to the signal input terminal of the microcontroller.

[0015] Preferably, the reference voltage generation circuit has the following specific structure: capacitor C2 and capacitor C3 are connected in parallel, with one end grounded and the other end connected to the 3.3V operating voltage and resistor R7 respectively. The other end of resistor R7 is connected to resistor R8 and the non-inverting input terminal of operational amplifier D2 respectively. The other end of resistor R8 is grounded, and capacitor C4 is connected in parallel with resistor R8. The inverting input terminal of operational amplifier D2 is connected to the output terminal of operational amplifier D2. The output terminal of operational amplifier D2 is also connected to capacitor C5, with the other end of capacitor C5 connected to ground. The output signal of the output terminal of operational amplifier D2 is the reference voltage Vref.

[0016] Preferably, the specific structure of the current sampling circuit is as follows: the positive input terminal of the operational amplifier D3 is divided into two paths. The first path is connected in series with resistors R12 and R10, and then connected to the reference voltage Vref output by the reference voltage generation circuit after being connected in series with resistor R13. The inverting input terminal of the operational amplifier D3 is divided into two paths. The first path is connected in series with resistor R14 and is connected to the output terminal of the operational amplifier D3. The second path is connected in series with resistors R11 and R9, and the other end of resistor R9 is grounded. The two ends of capacitor C6 are connected to resistors R9 and R10 respectively. The output terminal of the operational amplifier D3 is connected to resistor R14 and then to resistor R15. The other end of resistor R15 is divided into two paths. The first path is connected to capacitor C7 and then grounded. The second path is used as the output terminal to output the sampled current signal Inx at different times, where x is a natural number and n is any one of the three phases.

[0017] Preferably, the specific structure of the current polarity determination module is as follows: the non-inverting input of operational amplifier D4 is divided into two paths. The first path is that the non-inverting input of operational amplifier D4 is connected to resistor R19, and the other end of resistor R19 is grounded. The second path is that the non-inverting input of operational amplifier D4 is connected to resistor R17, and the other end of resistor R17 is connected to the sampling current signal Ia1 output by the current acquisition module. The inverting input of operational amplifier D4 is divided into two paths. The first path is that the inverting input of operational amplifier D4 is connected to resistor R18, and the other end of resistor R18 is connected to the output of operational amplifier D4 and then connected to the microcontroller. The second path is that the inverting input of operational amplifier D4 is connected to resistor R16, and the other end of resistor R16 is connected to the sampling current signal Inx output by the current acquisition module, where x≥2.

[0018] Preferably, resistors R16 and R17 have the same resistance value, and resistors R18 and R19 have the same resistance value.

[0019] Preferably, the microcontroller is an STM32 series microcontroller. The output terminals of the microcontroller are connected to the zero-crossing determination module and the current polarity determination module, and the microcontroller controls the opening and closing of the working voltage in the current sampling module. The microcontroller is equipped with an ADC current acquisition device and transmits the acquired phase current of the motor inverter to the current sampling module.

[0020] A current polarity determination method using a current zero-crossing polarity determination device is disclosed for determining the polarity of each single-phase current in a three-phase permanent magnet synchronous motor. The single-phase voltage is denoted as Vn, and the single-phase current as In, where n is any one of the three phases, representing phase A voltage Va, phase A current Ia, phase B voltage Vb, phase B current Ib, phase C voltage Vc, and phase C current Ic, respectively. The specific determination method is as follows:

[0021] S1: After the single-phase voltage Vn is input to the filter circuit, the filter circuit filters out the noise in the voltage signal to obtain the filtered signal V1. The signal V1 is input to the non-inverting input terminal of the operational amplifier D1. According to formula (1), V1 is amplified to obtain a sine wave V2.

[0022] V2=(1+R2 / R1)*V1(1;

[0023] S2: Input the sine wave V2 to the zero-crossing detection module. Use voltage divider resistors R3 and R4 to attenuate the voltage to the base of transistor Q1. According to the characteristics of the transistor, whenever the sine wave V2 performs a zero-crossing operation, the waveform of signal V3 will show a momentary high level, and the high-level signal will be transmitted to the microcontroller.

[0024] S3: The microcontroller turns on the operating voltage of the current sampling module based on the received high-level signal, and the current sampling module starts working.

[0025] S4: First, the reference voltage generation circuit generates a reference voltage Vref using a 3.3V operating voltage, resistors R7 and R8, and operational amplifier D2. The non-inverting input of operational amplifier D3 in the current sampling circuit is connected to the single-phase current In of the motor inverter and the reference voltage Vref, respectively. When the circuit is sampling, the current sampled at the zero-crossing point is recorded as In1 and stored in the microcontroller. Then, within 1 / 4T after the zero-crossing point, the current sampling module samples the current once at regular intervals Td, recorded as Inx, and stored in the microcontroller. Here, T is the current period, x is a natural number ≥2, and n is a natural number. The current sampling module inputs the currents In1 and Inx to the non-inverting and inverting inputs of operational amplifier D4 in the current polarity determination module, respectively.

[0026] S5: The current polarity determination module calculates the difference T between the two sampled currents based on the received current signal and formula (2). （x-1） :

[0027] T （x-1） =(R18 / R16)*(Inx-In1),x≥2(2);

[0028] S6: Initially, the current sampling module inputs the currents In1 and In2 to the non-inverting and inverting input terminals of the operational amplifier D4 in the current polarity determination module, respectively, and calculates the difference T1 of the sampled currents according to formula (2). The current polarity determination module transmits the difference T1 to the microcontroller for judgment. When the magnitude of the difference T1 is greater than or equal to the preset threshold, it is determined that no current zero-crossing clamping phenomenon has occurred. When T1 is positive, the value at the zero-crossing moment is less than the value after the zero-crossing moment, so it can be determined that the current polarity after the zero-crossing moment is positive. Conversely, when T1 is negative, the current at the zero-crossing moment is greater than the value after the zero-crossing moment, so it can be determined that the current polarity after the zero-crossing moment is negative. At the same time, the microcontroller sends a stop sampling signal to the sampling circuit to stop sampling.

[0029] When the magnitude of the difference T1 is less than the preset threshold, it is determined that the current has experienced a zero-crossing clamping phenomenon. The sampled currents In3 and In1 are then sent to the inverting and non-inverting inputs of operational amplifier D4, respectively, and the difference T2 between In3 and In1 is calculated. The difference T2 is then sent to the microcontroller, which compares the magnitude of T2 with the preset threshold to determine whether the current has released the zero-crossing clamping state at the sampling time of In3. If the current has released the zero-crossing clamping state, the polarity of the current is determined based on the sign of the difference T2. If the current is still in the zero-crossing clamping state, the same operation is performed by sending the currents Inx and In1 to the inverting and non-inverting inputs of operational amplifier D4, respectively, until the current releases the zero-crossing clamping state, and the circuit polarity is determined.

[0030] When the zero-crossing clamping time exceeds 1 / 4T, the current sampling circuit continuously samples the current signal at equal intervals Td until the current Inx, which is released from the zero-crossing clamping state, is sampled. At this time, the polarity of the current Inx is determined by the polarity of the current Inx and the zero-crossing sampling duration T'. To determine the polarity of the sampling point Inx, the reference current value of the reference voltage generation circuit is subtracted from the current value of the sampling point Inx to obtain the actual current value Inx' of the sampling point Inx. The polarity of the current can be determined by the sign of the actual current value Inx'. The zero-crossing clamping duration is approximately (x-1)*Td. Since the polarity of the current alternates between positive and negative in half-cycle units, the phase segment where the sampling point Inx is located can be obtained by dividing the zero-crossing clamping duration by 1 / 2T, starting from the sampling time of In1. Then, the current polarity during the zero-crossing clamping period can be obtained by deducing from the polarity of the sampling point Iax.

[0031] Preferably, the device includes three sets of current zero-crossing polarity determination devices, a permanent magnet synchronous motor, and a microcontroller. The three-phase voltages of the motor inverter of the permanent magnet synchronous motor are respectively connected to the phase voltage input terminals of one set of current zero-crossing polarity determination devices. The three-phase currents of the motor inverter of the permanent magnet synchronous motor are respectively connected to the input terminals of the ADC current acquisition devices configured in the microcontroller. The input terminals of the current sampling circuits in the three sets of current zero-crossing polarity determination devices are connected to the output terminals of the ADC current acquisition devices configured in the microcontroller. The output terminals of the current polarity determination module and the zero-crossing determination module in the three sets of current zero-crossing polarity determination devices are respectively connected to the microcontroller. The microcontroller controls the switching of the current sampling modules in the three sets of current zero-crossing polarity determination devices.

[0032] Beneficial effects: This invention provides a device, method, and application for determining the polarity of a current zero-crossing point, which has the following advantages compared with the prior art:

[0033] (1) Compared with the general zero-crossing current polarity judgment, the present invention adds an extra set of current sampling circuit and current differential circuit to determine whether there is a zero-crossing clamping phenomenon. The polarity change of the current during the zero-crossing clamping period is determined by the polarity of the current at the previous moment and the time difference between the currents.

[0034] (2) In terms of current polarity determination, the present invention focuses on the influence of zero-crossing clamping problem, which is often ignored in existing methods, making the detection more accurate and the motor operation smoother. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the filter amplifier circuit structure of the present invention (taking phase A voltage as an example);

[0036] Figure 2 This is a schematic diagram of the zero-crossing point determination module of the present invention (taking phase A voltage as an example);

[0037] Figure 3 This is a schematic diagram of the reference voltage generation circuit of the present invention (taking phase A voltage as an example);

[0038] Figure 4 This is a schematic diagram of the first current sampling circuit of the present invention (taking phase A voltage as an example);

[0039] Figure 5 This is a schematic diagram of the circuit structure of the current polarity determination module of the present invention (taking phase A voltage as an example);

[0040] Figure 6 This is a pin diagram of the microcontroller portion of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The description of the specific embodiments below is merely exemplary and should be understood as being used only to explain the invention, and not in any way to limit the invention or its applications or uses.

[0042] It should be noted that when an element is said to be "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is said to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. Conversely, when an element is said to be "directly on" another element, there is no intervening element. Conversely, when an element is said to be "directly" connected to another element, there is no intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0043] In the description of this invention, it should be understood that the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] Example 1:

[0045] A current zero-crossing polarity determination device includes a filtering and amplification module, a zero-crossing determination module, a current sampling module, and a current polarity determination module. The input terminal of the filtering and amplification module is connected to the phase line of a motor inverter, allowing the phase voltage signal to be input into the filtering and amplification module. The output terminal of the filtering and amplification module is connected to the input terminal of the zero-crossing determination module. The output terminal of the zero-crossing determination module is connected to a microcontroller, which sends a sampling command to the current sampling module based on the received electrical signal. The current sampling module includes a reference voltage generation circuit and a current sampling circuit. The non-inverting input terminal of the current sampling circuit is connected to the phase current output terminal of an ADC current acquisition unit configured with the microcontroller, used to acquire the phase current of the motor inverter. The output terminal of the reference voltage generation circuit is connected to the non-inverting input terminal of the current sampling circuit, and the inverting input terminal of the current sampling circuit is connected to its output terminal. Both the non-inverting and inverting input terminals of the current polarity determination module are connected to the output terminal of the current sampling circuit, calculating and outputting the phase currents at two different times. The output terminal of the current polarity determination module is connected to the microcontroller.

[0046] like Figure 1 As shown, the filtering and amplification module includes a filtering module and a signal amplification circuit. The filtering circuit consists of a simple filter composed of capacitor C1. The signal amplification circuit includes resistors R1 and R2 and an operational amplifier D1. One end of capacitor C1 is connected to the phase line of the motor inverter, and the other end is connected to the non-inverting input of operational amplifier D1. The phase voltage waveform V1, after being filtered by the filtering circuit, is connected to the non-inverting input of operational amplifier D1. The inverting input of operational amplifier D1 is divided into two paths. The first path is connected to resistor R1, and the other end of resistor R1 is connected to ground. The second path is connected to resistor R2, and the other end of resistor R2 is connected to the output of operational amplifier D1. The output of operational amplifier D1 outputs a sine wave V2.

[0047] like Figure 2As shown, the specific circuit structure of the zero-crossing determination module is as follows: The base of transistor Q1 is connected to one end of resistors R3, R4 and R5 respectively. The other ends of resistors R3 and R4 are respectively connected to the output signal sine wave V2 of the filter amplification module. The other end of resistor R5 is grounded. The emitter of transistor Q1 is grounded. The collector of transistor Q1 is divided into two paths. The first path is connected to a 5V working voltage after being connected in series with resistor R6. The second path is used as the output terminal to output signal V3 and then connected to the signal input terminal of the microcontroller.

[0048] like Figure 3 As shown, the specific structure of the reference voltage generation circuit is as follows: capacitors C2 and C3 are connected in parallel, with one end grounded and the other end connected to the 3.3V operating voltage and resistor R7 respectively. The other end of resistor R7 is connected to resistor R8 and the non-inverting input terminal of operational amplifier D2 respectively. The other end of resistor R8 is grounded, and capacitor C4 is connected in parallel with resistor R8. The inverting input terminal of operational amplifier D2 is connected to the output terminal of operational amplifier D2 to form a voltage follower. The output terminal of operational amplifier D2 is also connected to capacitor C5, with the other end of capacitor C5 connected to ground, thereby filtering out AC harmonics. The output signal of the output terminal of operational amplifier D2 is the reference voltage Vref.

[0049] like Figure 4 As shown, the specific structure of the current sampling circuit is as follows: The positive input terminal of operational amplifier D3 is divided into two paths. The first path is connected in series with resistors R12 and R10, and then connected to the reference voltage Vref output by the reference voltage generation circuit after being connected in series with resistor R13. The inverting input terminal of operational amplifier D3 is divided into two paths. The first path is connected in series with resistor R14 and is connected to the output terminal of operational amplifier D3. The second path is connected in series with resistors R11 and R9, and the other end of resistor R9 is grounded. The two ends of capacitor C6 are connected to resistors R9 and R10 respectively. The output terminal of operational amplifier D3 is connected to resistor R14 and then to resistor R15. The other end of resistor R15 is divided into two paths. The first path is connected to capacitor C7 and then grounded. The second path is used as the output terminal to output the sampled current signal Iax at different times, where x is a natural number.

[0050] like Figure 5As shown, the specific structure of the current polarity determination module is as follows: The non-inverting input of operational amplifier D4 is divided into two paths. The first path connects the non-inverting input of operational amplifier D4 to resistor R19, with the other end of resistor R19 grounded. The second path connects the non-inverting input of operational amplifier D4 to resistor R17, with the other end of resistor R17 connected to the sampling current signal Ia1 output by the current acquisition module. The inverting input of operational amplifier D4 is divided into two paths. The first path connects the inverting input of operational amplifier D4 to resistor R18, with the other end of resistor R18 connected to the output of operational amplifier D4 and then connected to the microcontroller. The second path connects the inverting input of operational amplifier D4 to resistor R16, with the other end of resistor R16 connected to the sampling current signal Iax output by the current acquisition module, where x≥2. The resistance values ​​of resistors R17 and R19 are the same, and the resistance values ​​of resistors R18 and R20 are the same.

[0051] like Figure 6 As shown, the microcontroller is an STM32 series microcontroller. The microcontroller is connected to the output terminals of the zero-crossing determination module and the current polarity determination module, and the microcontroller controls the opening and closing of the working voltage in the current sampling module.

[0052] A method for determining the polarity of a current zero-crossing point polarity determination device, wherein a motor inverter generates three-phase voltages Va, Vb, and Vc, taking phase A as an example, the specific steps are as follows:

[0053] S1: After the A-phase current Va is input to the filter circuit, the filter circuit filters out the noise in the voltage signal to obtain the filtered signal V1. The signal V1 is input to the non-inverting input terminal of the operational amplifier D1. According to formula (1), V1 is amplified to obtain a sine wave V2, which increases the amplitude of its waveform, making it easier to compare the difference between the sampled values ​​and the threshold in the later stage.

[0054] V2=(1+R2 / R1)*V1(1;

[0055] S2: Input the sine wave V2 to the zero-crossing detection module. Use voltage divider resistors R3 and R4 to attenuate the voltage to the base of transistor Q1. According to the characteristics of the transistor, whenever the sine wave V2 performs a zero-crossing operation, the waveform of signal V3 will show a momentary high level, and the high-level signal will be transmitted to the microcontroller.

[0056] S3: The microcontroller turns on the operating voltage of the current sampling module based on the received high-level signal, and the current sampling module starts working.

[0057] S4: Since different voltage polarities can cause errors in the subtraction of later sampled values ​​and polarity determination, before sampling, the reference voltage generation circuit first generates a reference voltage Vref using a 3.3V operating voltage, resistors R7 and R8, and operational amplifier D2, which serves to boost the voltage. When the circuit is sampling, the non-inverting input of operational amplifier D3 is connected to the single-phase current Ia of the motor inverter and the reference voltage Vref, respectively. When the circuit is sampling, the current sampled at the zero-crossing point is recorded as Ia1 and stored in the microcontroller. Then, within 1 / 4T after the zero-crossing point, the current sampling module samples the current once at regular intervals Td, recorded as Iax, and stored in the microcontroller. Here, T is the current period, x is a natural number ≥ 2, and n is a natural number. The current sampling module inputs the currents Ia1 and Iax to the non-inverting and inverting inputs of operational amplifier D4 in the current polarity determination module, respectively.

[0058] S5: The current polarity determination module calculates the difference T between the two sampled currents based on the received current signal and formula (2). （x-1） :

[0059] T （x-1） =(R18 / R16)*(Inx-In1),x≥2(2);

[0060] S6: Initially, the current sampling module inputs currents Ia1 and Ia2 to the non-inverting and inverting input terminals of the operational amplifier D4 in the current polarity determination module, respectively, and calculates the difference T1 of the sampled current according to formula (2). The current polarity determination module transmits the difference T1 to the microcontroller for judgment. When the magnitude of the difference T1 is greater than or equal to the preset threshold, it is determined that no current zero-crossing clamping phenomenon has occurred. When T1 is positive, the value at the zero-crossing moment is less than the value after the zero-crossing moment, so it can be determined that the current polarity after the zero-crossing moment is positive. Conversely, when T1 is negative, the current at the zero-crossing moment is greater than the value after the zero-crossing moment, so it can be determined that the current polarity after the zero-crossing moment is negative. At the same time, the microcontroller sends a stop sampling signal to the sampling circuit to stop sampling.

[0061] When the magnitude of the difference T1 is less than the preset threshold, it is determined that the current has experienced zero-crossing clamping. The sampled currents Ia3 and Ia1 are then fed into the inverting and non-inverting inputs of operational amplifier D4, respectively. The difference T2 between Ia3 and Ia1 is calculated and sent to the microcontroller. The magnitude of T2 is compared with the preset threshold to determine whether the current has released the zero-crossing clamping state at the sampling time of Ia3. If the current has released the zero-crossing clamping state, the polarity of the current is determined based on the sign of the difference T2. If the current is still in the zero-crossing clamping state, the same operation is performed by feeding the currents Iax and Ia1 into the inverting and non-inverting inputs of operational amplifier D4, respectively, until the current releases the zero-crossing clamping state, and the circuit polarity is determined.

[0062] When the zero-crossing clamping time exceeds 1 / 4T, the current sampling circuit continuously samples the current signal at equal intervals Td until the current Iax, which is released from the zero-crossing clamping state, is sampled. At this time, the polarity of the current is determined by the polarity of the current Iax and the zero-crossing sampling duration T'. To determine the polarity of the sampling point Iax, the reference current value of the reference voltage generation circuit is subtracted from the current value of the sampling point Iax to obtain the actual current value Iax' of the sampling point Iax. The polarity of the current can be determined by the sign of the actual current value Iax'. The zero-crossing clamping duration is approximately (x-1)*Td. Since the polarity of the current alternates between positive and negative in half-cycle units, the phase segment where the sampling point Iax is located can be obtained by dividing the zero-crossing clamping duration by 1 / 2T, starting from the sampling time of Ia1. Then, the current polarity during the zero-crossing clamping period can be obtained by deducing from the polarity of the sampling point Iax.

[0063] The three sets of current zero-crossing polarity determination devices described in Embodiment 1 can be used to determine the current polarity of the three-phase current of a permanent magnet synchronous motor after it crosses the zero point. The specific connection structure is as follows: the three-phase voltages of the motor inverter of the permanent magnet synchronous motor are respectively connected to the phase voltage input terminals of one set of current zero-crossing polarity determination devices. The three-phase currents of the motor inverter of the permanent magnet synchronous motor are respectively connected to the input terminals of the ADC current acquisition device configured by the microcontroller. The input terminals of the current sampling circuits in the three sets of current zero-crossing polarity determination devices are connected to the output terminals of the ADC current acquisition devices configured by the microcontroller. The output terminals of the current polarity determination module and the zero-crossing determination module in the three sets of current zero-crossing polarity determination devices are respectively connected to the microcontroller. The microcontroller controls the switching of the current sampling modules in the three sets of current zero-crossing polarity determination devices.

[0064] The current sampling module in this embodiment 1 can also use two identical current sampling circuits to collect current at different times. One circuit is used to collect the current value at the zero crossing point, save it, and input it to the non-inverting input of the operational amplifier D4. The other circuit is used to collect the current value after the zero crossing point at equal intervals, save it, and input it to the inverting input of the operational amplifier D4. Its working principle is the same as that of the current sampling circuit in embodiment 1.

[0065] It will be apparent 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 invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0066] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A device for determining the polarity of a current zero-crossing point, characterized in that: The system includes a filtering and amplification module, a zero-crossing point determination module, a current sampling module, and a current polarity determination module. The input terminal of the filtering and amplification module is connected to the phase line of the motor inverter, allowing the phase voltage signal to be input into the filtering and amplification module. The output terminal of the filtering and amplification module is connected to the input terminal of the zero-crossing point determination module, and the output terminal of the zero-crossing point determination module is connected to a microcontroller. The microcontroller sends a sampling command to the current sampling module based on the received electrical signal. The current sampling module includes a reference voltage generation circuit and a current sampling circuit. The non-phase input terminal of the current sampling circuit is connected to the phase current output terminal of the ADC current acquisition unit configured on the microcontroller, used to collect the phase current of the motor inverter. The output terminal of the reference voltage generation circuit is connected to the non-phase input terminal of the current sampling circuit, and the inverting input terminal of the current sampling circuit is connected to its output terminal. The non-phase input terminal and the inverting input terminal of the current polarity determination module are both connected to the output terminal of the current sampling circuit, calculating and outputting the phase currents at two different times. The output terminal of the current polarity determination module is connected to the microcontroller. The specific circuit structure of the zero-crossing point determination module is as follows: The base of transistor Q1 is connected to one end of resistors R3, R4 and R5 respectively. The other ends of resistors R3 and R4 are respectively connected to the output signal sine wave V2 of the filter amplification module. The other end of resistor R5 is grounded. The emitter of transistor Q1 is grounded. The collector of transistor Q1 is divided into two paths. The first path is connected to a 5V working voltage after being connected in series with resistor R6. The second path is used as the output terminal to output signal V3 and then connected to the signal input terminal of the microcontroller. The specific structure of the current polarity determination module is as follows: The non-inverting input of operational amplifier D4 is divided into two paths. The first path connects the non-inverting input of operational amplifier D4 to resistor R19, with the other end of resistor R19 grounded. The second path connects the non-inverting input of operational amplifier D4 to resistor R17, with the other end of resistor R17 connected to the sampling current signal Ia1 output by the current acquisition module. The inverting input of operational amplifier D4 is divided into two paths. The first path connects the inverting input of operational amplifier D4 to resistor R18, with the other end of resistor R18 connected to the output of operational amplifier D4 and then connected to the microcontroller. The second path connects the inverting input of operational amplifier D4 to resistor R16, with the other end of resistor R16 connected to the current Inx output by the current acquisition module, where x≥2. The current polarity determination module first calculates the difference T1 between the sampled currents Ia1 and Ia2. If the magnitude of the difference T1 is greater than or equal to the preset threshold, it is determined that no current zero-crossing clamping phenomenon has occurred. The current polarity is determined according to the sign of T1, and the sampling circuit is notified to stop sampling. If the magnitude of the difference T1 is less than the preset threshold, it is determined that the current has experienced zero-crossing clamping. The difference T between the two sampled currents is then calculated by sequentially calculating the difference between the two sampled currents Inx and Ia1. （x-1） And compare it with a preset threshold until the current releases the zero-crossing clamp state, and then calculate the difference T. （x-1） Determine polarity; When the current zero-crossing clamping time continues for more than 1 / 4 of the current cycle T, the current sampling circuit continuously collects the current signal at equal intervals Td until the current Iax that is released from the zero-crossing clamping state is collected. The polarity of the current is determined by the polarity of the current Iax and the zero-crossing sampling duration T'. When determining the polarity of the current Iax at the sampling point, the reference current value of the reference voltage generation circuit is subtracted from the current value of the current Iax at the sampling point to obtain the actual current value Iax' of the current Iax at the sampling point. The polarity of the current is determined by the sign of the actual current value Iax'. Combined with the alternation of current polarity in half-cycles, the polarity of the current during the clamping period can be calculated.

2. The current zero-crossing polarity determination device according to claim 1, characterized in that, The filtering and amplification module includes a filtering circuit and a signal amplification circuit. The filtering circuit consists of a simple filter formed by capacitor C1. The signal amplification circuit includes resistors R1 and R2 and an operational amplifier D1. One end of capacitor C1 is connected to the phase line of the motor inverter, and the other end is connected to the non-inverting input of operational amplifier D1. The phase voltage waveform, after being filtered by the filtering circuit, is connected to the non-inverting input of operational amplifier D1. The inverting input of operational amplifier D1 is divided into two paths. The first path is connected to resistor R1, the other end of which is connected to ground. The second path is connected to resistor R2, the other end of which is connected to the output of operational amplifier D1. The output of operational amplifier D1 outputs a sine wave V2.

3. The current zero-crossing polarity determination device according to claim 2, characterized in that, The specific structure of the reference voltage generation circuit is as follows: capacitors C2 and C3 are connected in parallel, with one end grounded and the other end connected to the 3.3V operating voltage and resistor R7 respectively. The other end of resistor R7 is connected to resistor R8 and the non-inverting input terminal of operational amplifier D2 respectively. The other end of resistor R8 is grounded, and capacitor C4 is connected in parallel with resistor R8. The inverting input terminal of operational amplifier D2 is connected to the output terminal of operational amplifier D2. The output terminal of operational amplifier D2 is also connected to capacitor C5, with the other end of capacitor C5 connected to ground. The output signal of the output terminal of operational amplifier D2 is the reference voltage Vref.

4. The current zero-crossing polarity determination device according to claim 2, characterized in that, The specific structure of the current sampling circuit is as follows: The positive input terminal of operational amplifier D3 is divided into two paths. The first path is connected in series with resistors R12 and R10, and then connected to the reference voltage Vref output by the reference voltage generation circuit after being connected in series with resistor R13. The inverting input terminal of operational amplifier D3 is divided into two paths. The first path is connected in series with resistor R14 and is connected to the output terminal of operational amplifier D3. The second path is connected in series with resistors R11 and R9, and the other end of resistor R9 is grounded. The two ends of capacitor C6 are connected to resistors R9 and R10 respectively. The output terminal of operational amplifier D3 is connected to resistor R14 and then to resistor R15. The other end of resistor R15 is divided into two paths. The first path is connected to capacitor C7 and then grounded. The second path is used as the output terminal to output the current Inx at different times, where x≥2.

5. The current zero-crossing polarity determination device according to claim 4, characterized in that, The resistors R16 and R17 have the same resistance value, and the resistors R18 and R19 have the same resistance value.

6. The current zero-crossing polarity determination device according to claim 2, characterized in that, The microcontroller is an STM32 series microcontroller. The output terminals of the microcontroller are connected to the zero-crossing determination module and the current polarity determination module, and the microcontroller controls the opening and closing of the working voltage in the current sampling module. The microcontroller is equipped with an ADC current acquisition device and transmits the acquired phase current of the motor inverter to the current sampling module.

7. The current polarity determination method of the current zero-crossing polarity determination device according to any one of claims 2-6, characterized in that, This is used to determine the polarity of each single-phase current in the three-phase current of a permanent magnet synchronous motor. The single-phase voltage is denoted as Vn, and the single-phase current as In, where n is any one of the three phases. In represents phase A voltage Va, phase A current Ia, phase B voltage Vb, phase B current Ib, phase C voltage Vc, and phase C current Ic, respectively. The specific determination method is as follows: S1: After the single-phase voltage Vn is input to the filter circuit, the filter circuit filters out the noise in the voltage signal to obtain the filtered signal V1. The signal V1 is input to the non-inverting input terminal of the operational amplifier D1. According to formula (1), the signal V1 is amplified to obtain the sine wave V2. ； S2: Input the sine wave V2 to the zero-crossing detection module. Use resistors R3 and R4 to attenuate the voltage to the base of transistor Q1. According to the characteristics of the transistor, whenever the sine wave V2 performs a zero-crossing operation, the waveform of signal V3 will show a momentary high level, and the high-level signal will be transmitted to the microcontroller. S3: The microcontroller turns on the operating voltage of the current sampling module based on the received high-level signal, and the current sampling module starts working. S4: First, the reference voltage generation circuit generates a reference voltage Vref using a 3.3V operating voltage, resistors R7 and R8, and operational amplifier D2. The non-inverting input of operational amplifier D3 in the current sampling circuit is connected to the single-phase current In of the motor inverter and the reference voltage Vref, respectively. When the circuit is sampling, the current sampled at the zero-crossing point is recorded as In1 and stored in the microcontroller. Then, within 1 / 4T after the zero-crossing point, the current sampling module samples the current once every certain time interval Td, recorded as Inx, and stored in the microcontroller. Here, T is the current period and x is a natural number ≥2. The current sampling module inputs the currents In1 and Inx to the non-inverting and inverting inputs of operational amplifier D4 in the current polarity determination module, respectively. S5: The current polarity determination module calculates the difference T between the two sampled currents based on the received current signal and formula (2). （x-1） : ； S6: Initially, the current sampling module inputs the currents In1 and In2 to the non-inverting and inverting input terminals of the operational amplifier D4 in the current polarity determination module, respectively, and calculates the difference T1 of the sampled currents according to formula (2). The current polarity determination module transmits the difference T1 to the microcontroller for judgment. When the magnitude of the difference T1 is greater than or equal to the preset threshold, it is determined that no current zero-crossing clamping phenomenon has occurred. When T1 is positive, the value at the zero-crossing moment is less than the value after the zero-crossing moment, so it can be determined that the current polarity after the zero-crossing moment is positive. Conversely, when T1 is negative, the current at the zero-crossing moment is greater than the value after the zero-crossing moment, so it can be determined that the current polarity after the zero-crossing moment is negative. At the same time, the microcontroller sends a stop sampling signal to the sampling circuit to stop sampling. When the magnitude of the difference T1 is less than the preset threshold, it is determined that the current has experienced a zero-crossing clamping phenomenon. The sampled currents In3 and In1 are then sent to the inverting and non-inverting inputs of operational amplifier D4, respectively, and the difference T2 between In3 and In1 is calculated. The difference T2 is then sent to the microcontroller, which compares the magnitude of T2 with the preset threshold to determine whether the current has released the zero-crossing clamping state at the sampling time of In3. If the current has released the zero-crossing clamping state, the polarity of the current is determined based on the sign of the difference T2. If the current is still in the zero-crossing clamping state, the same operation is performed by sending the currents Inx and In1 to the inverting and non-inverting inputs of operational amplifier D4, respectively, until the current releases the zero-crossing clamping state, and the circuit polarity is determined. When the zero-crossing clamping time exceeds 1 / 4T, the current sampling circuit continuously samples the current signal at equal intervals Td until it detects the current Inx when the zero-crossing clamping state is released. At this point, the polarity of the current Inx is determined by its polarity and the zero-crossing sampling duration T'. To determine the polarity of the current Inx, the reference current value of the reference voltage generation circuit is subtracted from the current value of Inx to obtain the actual current value Inx'. The polarity of the current can be determined based on the sign of the actual current value Inx'. The zero-crossing clamping duration is approximately... Since the polarity of the current alternates between positive and negative in half-cycle units, taking the sampling time of In1 as the starting point, the zero-crossing clamping duration is divided by 1 / 2T to obtain the phase segment where the current Inx is located. Then, the polarity of the current during the zero-crossing clamping period can be obtained by deducing from the polarity of the current Iax at the sampling point.

8. A permanent magnet synchronous motor using the current zero-crossing polarity determination device as described in any one of claims 1-6, characterized in that, The system includes three sets of current zero-crossing polarity determination devices, a permanent magnet synchronous motor, and a microcontroller. The three-phase voltages of the motor inverter of the permanent magnet synchronous motor are connected one-to-one to the phase voltage input terminals of each set of current zero-crossing polarity determination devices. The three-phase currents of the motor inverter of the permanent magnet synchronous motor are connected to the input terminals of the ADC current acquisition devices configured in the microcontroller. The input terminals of the current sampling circuits in the three sets of current zero-crossing polarity determination devices are connected to the output terminals of the ADC current acquisition devices configured in the microcontroller. The output terminals of the current polarity determination modules and the zero-crossing determination modules in the three sets of current zero-crossing polarity determination devices are respectively connected to the microcontroller. The microcontroller controls the switching of the current sampling modules in the three sets of current zero-crossing polarity determination devices.

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