Anti-electromagnetic interference method for electronic device in electric dragging system

Abstract

The invention discloses an anti-electromagnetic interference method for an electronic device in an electric dragging system, which comprises the following steps of: 1, respectively analyzing conduction and radiation type interference in the electric dragging system; 2, a second-order RLC low-pass filter is adopted; 3, selecting a control strategy and an algorithm; fourthly, inductance, capacitance and resistance parameters of the conducted interference filter are calculated; 5, selecting a random switching frequency modulation strategy; and 6, designing a rotary transformer signal processing circuit and filtering an output position angle of a decoding chip of the rotary transformer. In combination with an electrical principle of a motor driving device, firstly, an interference filter is selected, then, algorithm selection operation is performed according to selection of a control strategy, and finally, anti-interference design of electronic devices related to resolver calculation is performed, so that conduction type electromagnetic interference at a power supply end is effectively inhibited, the switching frequency harmonic content is reduced, and the reliability of a resolver is improved. And the rotor position angle is accurately tracked.

Description

Technical Field

[0001] The present invention relates to the field of automatic control, and particularly to an anti-electromagnetic interference method for electronic devices in an electric drive system. Background Art

[0002] The main function implementation entities in an electric drive system are various electronic devices. During the motor control process, since the motor drive system needs to use control devices with a relatively high switching frequency, electromagnetic interference is easily generated, which not only affects the control accuracy and effect of itself, but also transmits the interference to other sensitive devices through conduction or radiation to damage their performance. At the same time, various electromagnetic interferences will also interfere and couple with each other, thus making the electromagnetic environment in which the system operates more complex.

[0003] The power source in an electric drive system is various electronic devices that realize the motor drive function. Among them, most controllers use pulse width modulation (PWM) technology to generate control signals, and realize the conversion and on-demand control of electric energy by controlling the on and off of the power switching tubes of the inverter electronic device. During the high-speed turn-on and turn-off process of the switching tubes, relevant high-order harmonic voltages and currents will be generated, resulting in electromagnetic interference phenomena. In addition, in the electronic device during the drive process of a permanent magnet synchronous motor, a reluctance resolver is commonly used to realize the real-time acquisition of the motor rotor position and angle, and realize the speed closed-loop control. The increase in the switching frequency of the power tube will cause an increase in the electromagnetic interference radiated outward by the motor armature winding. As the electromagnetic interference increases, the accuracy of the resolver decoding chip to realize position detection will also become worse.

[0004] In an actual applied electric drive system, when electromagnetic interference occurs, it is often impossible to quickly locate the interference source. During the design process of the electronic device for motor drive, there is also a lack of reasonable and scientific means to suppress the interference. Summary of the Invention

[0005] The purpose of the present invention is to provide an anti-electromagnetic interference method for electronic devices in an electric drive system to solve the problems proposed in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solution: an anti-electromagnetic interference method for electronic devices in an electric drive system, the anti-electromagnetic interference method includes the following steps:

[0007] In the first step, first, according to the classification of electromagnetic interference, the conducted and radiated interferences in the electric drive system are respectively analyzed. For the conducted interference, combined with the electrical principle of the motor drive device, the power filter, control strategy and algorithm are respectively analyzed, and anti-interference design is carried out for the electronic devices related to resolver calculation.

[0008] In the second step, according to the analysis of the common-mode and differential-mode interference sources of the motor drive device, a second-order RLC low-pass filter is adopted;

[0009] In the third step, for the selection of control strategies and algorithms, on the basis of space vector pulse width modulation, the fixed triangular wave signal is replaced with a triangular carrier signal whose amplitude and frequency both randomly vary, thereby obtaining random pulse width modulation;

[0010] In the fourth step, the inductance, capacitance, and resistance parameters of the conducted interference filter are calculated;

[0011] In the fifth step, based on the random pulse width modulation technology, a random switching frequency modulation strategy is selected;

[0012] In the sixth step, the design of the resolver signal processing circuit and the filtering of the output position angle of the resolver decoding chip are carried out.

[0013] Preferably, in the third step, when the fixed triangular wave signal is replaced with a triangular carrier signal whose amplitude and frequency both randomly vary, the harmonic energy can be extended to a wide range of frequencies, and the content of the switching sub-harmonics of the power switching tube can be reduced.

[0014] Preferably, the fundamental voltage drop across the filtering inductor of the conducted interference filter does not exceed 3% - 5%, and the calculation formula for the filtering inductor parameters is:

[0015]

[0016] where I represents the peak current output by the drive of the electric drive system, L f represents the filtering inductor parameter, f0 represents the cut-off frequency of the conducted interference filter, and ΔU represents the voltage difference.

[0017] Preferably, the filtering capacitor of the conducted interference filter is calculated according to the size of the filtering inductor parameter, and the inductive reactance value of the conducted interference filter is greater than the capacitive reactance value in the high-frequency range. The calculation formula is:

[0018]

[0019] where C f represents the filtering capacitor, L f represents the filtering inductor parameter, and f0 represents the cut-off frequency of the conducted interference filter.

[0020] Preferably, the calculation formula for the filtering resistor of the conducted interference filter is:

[0021]

[0022] δ ≤ 1 (4);

[0023] Among them, δ is the damping ratio, representing the relationship between the inductor, capacitor, and filtering resistor, C f represents the filtering capacitor, L f represents the filtering inductor parameter.

[0024] Preferably, the cut-off frequency calculation formula of the conducted interference filter is:

[0025] f0 = k × f1 (5);

[0026] Among them, the value of k is 1 / 3; f1 represents the lowest interference frequency.

[0027] Preferably, the operation of the random switching frequency modulation strategy is as follows: First, the carrier frequency is randomly changed according to a random rule to generate a random number that does not change within each carrier's switching period but changes randomly among different carrier switching periods. Then, the amplitude of the output signal is transformed into the range of 0 to 1, and finally, after dividing by twice the switching frequency, a triangular carrier signal with randomly varying amplitude and frequency is obtained.

[0028] Preferably, the output position angle of the resolver decoding chip is filtered by a phase-locked loop.

[0029] Preferably, the method of phase-locked loop filtering is to use multiple low-pass filters to filter the output speed signal of the decoding chip and filter out the high-frequency components of the error signal respectively.

[0030] Preferably, the phase detector of the phase-locked loop is expressed as:

[0031] sin(θ(n) - θ1(n - 1))(6);

[0032] When the phase output by the phase-locked loop lags behind or leads the calculation result, the output of the phase detector is positive or negative, and the phase-locked loop output is dynamically adjusted to track the position angle signal of the calculation output.

[0033] The technical effects and advantages of the present invention:

[0034] The present invention combines the electrical principle of the motor drive device. First, through the selection of the interference filter and then the selection of the algorithm according to the selection of the control strategy, and finally the anti-interference design of the resolver calculation-related electronic devices is carried out, so as to effectively suppress the conducted electromagnetic interference at the power supply end, reduce the harmonic content of the switching frequency, accurately track the rotor position angle, and the key electrical parameters of the motor can be used to guide the reasonable design of the resolver signal processing circuit. Brief Description of the Drawings

[0035] Figure 1 It is the structural diagram of the second-order RLC low-pass filter of the present invention.

[0036] Figure 2This is the random switching frequency pulse waveform diagram of the present invention.

[0037] Figure 3 This is the schematic diagram of interference coupling of the resolver of the present invention.

[0038] Figure 4 This is the schematic diagram of PLL filtering of the position signal of the present invention.

[0039] Figure 5 This is the resolver processing circuit diagram of Scheme A of the present invention.

[0040] Figure 6 This is the resolver processing circuit diagram of Scheme B of the present invention. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] Embodiment 1, a method for anti-electromagnetic interference of an electronic device in an electric drive system of the present invention, includes the following steps:

[0043] In the first step, first, according to the classification of electromagnetic interference, the conducted and radiated interferences in the electric drive system are respectively analyzed. For the conducted interference, in combination with the electrical principle of the motor drive device, the power filter, control strategy and algorithm are respectively analyzed, and the anti-interference design of the resolver-related electronic device is carried out;

[0044] It should be noted that the conducted interference filter is usually composed of inductors, capacitors and resistors, allowing the frequency components of the useful signal to pass through and blocking the other interference frequency signal components. The main parameter of the electromagnetic interference filter is the insertion loss, and its size determines the quality of the filter performance. The insertion loss of the filter is defined as:

[0045]

[0046] Among them, U1 represents the voltage drop on the load impedance when the signal source passes through the filter, U2 represents the voltage drop of the signal source on the same load without the filter, and IL is the insertion loss (dB)

[0047] In the second step, according to the analysis of the common-mode and differential-mode interference sources of the motor drive device, a second-order RLC low-pass filter is adopted, and its topology reference Figure 1 is shown as follows;

[0048] Specifically, the cut-off frequency calculation formula of the conducted interference filter is:

[0049] f0 = k × f1 (2);

[0050] Wherein, k takes a value of 1 / 3; f1 represents the lowest interference frequency.

[0051] In the third step, select the control strategy and algorithm. On the basis of space vector pulse width modulation, replace the fixed triangular wave signal with a triangular carrier signal whose amplitude and frequency both change randomly, so as to obtain random pulse width modulation;

[0052] It should be noted that space vector pulse width modulation (SVPWM) is a modulation technique used to control the output of power electronic converters (such as inverters). The main purpose of SVPWM is to achieve precise control of the output voltage by adjusting the switching states of the inverter, thereby improving the performance and efficiency of the motor drive system. The basic principles of SVPWM include:

[0053] Space vector representation, in a three-phase power supply system, a space vector is used to represent the state of the three-phase voltage. The three-phase voltage is represented as a vector in the complex plane. The length of this vector is related to the voltage amplitude, and the direction is related to the voltage phase;

[0054] Six main vectors and six zero vectors. In a complete cycle, the output voltage of the inverter is regarded as being composed of six main space vectors and two zero space vectors. The main space vectors correspond to different switching states, while the zero space vectors represent the states where all switches are closed or all switches are open;

[0055] Time allocation, by appropriately selecting and adjusting the application time of each vector, precise control of the output voltage is achieved. In SVPWM, it is usually necessary to calculate the interpolation of the target voltage vector among the main vectors to determine the application time of each main vector;

[0056] Modulation depth, SVPWM achieves a relatively high modulation depth, usually able to reach 1 (i.e., full amplitude modulation), which makes the harmonic content of the output voltage lower, thereby improving the efficiency and performance of the system.

[0057] The advantages of SVPWM include: reducing harmonics, SVPWM can effectively reduce harmonic distortion in motor drives and improve the power quality of the system; improving efficiency, by optimizing the switching states, SVPWM can improve the operating efficiency of the inverter; high control precision, SVPWM can achieve precise control of the output voltage and is suitable for high-performance motor drives.

[0058] Specifically, when the fixed triangular wave signal is replaced by a triangular carrier signal with randomly varying amplitude and frequency, the harmonic energy can be extended to a wide range of frequencies, and the sub-harmonic content of the power switch tube switching can be reduced. A random number that does not change within the switching period of each carrier but varies randomly among different carrier switching periods is generated using a random switching function to obtain a triangular carrier signal that meets the requirements. The generated random switching frequency pulse waveform is referenced Figure 2 as shown

[0059] Step 4: Calculate the inductance, capacitance, and resistance parameters of the conducted interference filter;

[0060] Specifically, the fundamental wave voltage drop across the filter inductor of the conducted interference filter does not exceed 3% - 5%. The calculation formula for the filter inductor parameters is:

[0061]

[0062] where I represents the peak current output by the drive of the electric drive system, L f represents the filter inductor parameter, f0 represents the cut-off frequency of the conducted interference filter, and ΔU represents the voltage difference.

[0063] The filter capacitor of the conducted interference filter is calculated based on the size of the filter inductor parameter, and the inductive reactance value of the conducted interference filter is greater than the capacitive reactance value in the high-frequency range. The calculation formula is:

[0064]

[0065] where C f represents the filter capacitor, L f represents the filter inductor parameter, and f0 represents the cut-off frequency of the conducted interference filter.

[0066] The calculation formula for the filter resistor of the conducted interference filter is:

[0067]

[0068] δ ≤ 1 (6);

[0069] where δ is the damping ratio, representing the relationship between the inductor, capacitor, and filter resistor. C f represents the filter capacitor, and L f represents the filter inductor parameter.

[0070] Step 5: Select a random switching frequency modulation strategy in the random pulse width modulation technology;

[0071] Specifically, the operation of the random switching frequency modulation strategy is as follows: First, the carrier frequency is randomly changed according to a random rule to generate a random number that does not change within each carrier's switching period but varies randomly across different carrier switching periods. Then, the amplitude of the output signal is transformed into the range from 0 to 1. Finally, after dividing by twice the switching frequency, a triangular carrier signal with randomly varying amplitude and frequency is obtained.

[0072] Step 6: Design the resolver signal processing circuit and filter the position angle output by the resolver decoding chip.

[0073] It should be noted that in the transformation control system of a permanent magnet synchronous motor, a reluctance resolver is commonly used to obtain the rotor position and angle to achieve stronger environmental adaptability.

[0074] The resolver signal processing circuit and the resolver are two important components of the resolver transformation and calculation system. Among them, the resolver is a sensor used to obtain the angle information of rotating objects such as motors and spacecraft. Its working principle is based on electromagnetic induction and usually consists of a stator and a rotor. The stator winding generates a rotating magnetic field, usually a three-phase winding. The rotor is a component that rotates together with the stator. There is a set of windings on the rotor that interact with the stator windings. When the rotor rotates, the induced voltage in the rotor winding is proportional to the angle (position) of the rotor. By measuring the voltage output by the stator winding, the position and speed information of the rotor can be deduced. Its characteristics include: high precision, the resolver provides high-precision angle measurement; strong anti-interference ability, compared with optical sensors, the resolver is less affected by environmental light and dust; high temperature resistance, suitable for harsh environments such as high temperature and high pressure.

[0075] The design of the resolver signal processing circuit aims to convert the analog signal output by the resolver into a digital signal and perform further processing to achieve high-precision angle measurement. The elements of its design include signal conditioning, analog-to-digital conversion, angle calculation, data fusion, and software algorithms.

[0076] Signal conditioning includes: an amplifier, using an operational amplifier to amplify the output signal to increase the signal amplitude and overcome noise; a filter, designing a low-pass filter to remove high-frequency noise and ensure signal clarity.

[0077] Analog-to-digital conversion includes an ADC (analog-to-digital converter) to convert the conditioned analog signal into a digital signal for subsequent digital processing.

[0078] Angle calculation includes the arctangent function. By processing the sine and cosine components (usually output by different windings of the resolver), the rotation angle is calculated using the arctangent function.

[0079] Data fusion includes Kalman filtering. If there are other sensors in the system (such as gyroscopes, accelerometers), the Kalman filtering algorithm can be used to fuse multi-sensor data to improve the accuracy and robustness of angle measurement.

[0080] The software algorithm includes a microprocessor or GA. The signal processing algorithm is implemented in the microprocessor or FPGA to calculate the angle in real time and control the feedback.

[0081] The interference coupling principle of the resolver refers to Figure 3 As shown, the power tubes in the motor drive controller switch at high frequency and quickly, acting on the motor armature winding to form an EMI source. H and E respectively represent the magnetic field coupling and electric field coupling of the EMI source. The magnetic field coupling radiates the magnetic field outward with the armature winding as the antenna, and the electric field coupling couples the interference to the controller case through the parasitic capacitance between the armature winding and the case to form a common-mode voltage. The radiated magnetic field is coupled with the sine winding Nsin and cosine winding Ncos in the resolver to generate an interference voltage. The common-mode voltage is coupled through the parasitic capacitance between the sine winding Nsin and cosine winding Ncos and the case, generating an interference voltage on the winding. Eventually, the position signal output by the resolver decoding chip will have a large error.

[0082] Specifically, the position angle output by the resolver decoding chip is filtered by a phase-locked loop. The method of phase-locked loop filtering is to use multiple low-pass filters to filter the speed signal output by the decoding chip and filter out the high-frequency components of the error signal respectively.

[0083] It should be noted that referring to Figure 4 As shown, LPF1 and LPF2 are low-pass filters, which respectively implement the filtering of the speed signal output by the decoding chip and filter out the high-frequency components of the error signal e rr .

[0084] Furthermore, the phase detector of the phase-locked loop is expressed as:

[0085] sin(θ(n)-θ1(n-1))(7);

[0086] When the phase output by the phase-locked loop lags behind or leads the calculation result, the phase detector outputs e rr as positive or negative, and the phase-locked loop output is dynamically adjusted to track the position angle signal output by the calculation output.

[0087] In the second embodiment, taking the torque permanent magnet synchronous motor shown in Table 1 below as an example, different resolver signal processing circuits will affect the accuracy of resolver calculation;

[0088] Table 1 Permanent Magnet Synchronous Motor Parameter Table

[0089] Serial number Parameter Value Remark 1 Rated power 200W 2 Rated bus DC voltage 220VDC 3 Rated speed 800n / min 4 Peak torque 108Nm 5 Rated torque 30Nm 6 Line back electromotive force coefficient 0.21V / rpm 7 Line resistance 1.15 ohm 8 Line inductance 7.9 - 9.1mH 9 Number of pole pairs 11 pole pairs 10 Feedback method Resolver 11 Duty cycle Continuous

[0090] The resolver signal effect of Solution A is better than that of Solution B. Among them, the circuit principle of Solution A is shown in Figure 5 the following figure; the circuit principle of Solution B is shown in Figure 6 the following figure.

[0091] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electromagnetic interference resistance method for an electronic device in an electric drive system, characterized in that The anti-electromagnetic interference method includes the following steps: In the first step, first, according to the classification of electromagnetic interference, the conducted and radiated interferences in the electric drive system are analyzed respectively. For the conducted interference, combined with the electrical principle of the motor drive device, the power filter, control strategy and algorithm are analyzed respectively, and the anti-interference design of the relevant electronic devices for resolver calculation is carried out; In the second step, according to the analysis of the common-mode and differential-mode interference sources of the motor drive device, a second-order RLC low-pass filter is adopted; In the third step, the control strategy and algorithm are selected. Based on space vector pulse width modulation, the fixed triangular wave signal is replaced with a triangular carrier signal whose amplitude and frequency both change randomly, so as to obtain random pulse width modulation; In the fourth step, the inductance, capacitance and resistance parameters of the conducted interference filter are calculated; In the fifth step, on the basis of random pulse width modulation technology, a random switching frequency modulation strategy is selected; In the sixth step, the resolver signal processing circuit is designed and the output position angle of the resolver decoding chip is filtered.

2. The anti-electromagnetic interference method of an electronic device in an electric drive system according to claim 1, characterized in that, In the third step, when the fixed triangular wave signal is replaced with a triangular carrier signal whose amplitude and frequency both change randomly, the harmonic energy can be extended to a wide range of frequencies and the sub-harmonic content of the power switch tube switching can be reduced.

3. A method for electromagnetic interference resistance of an electronic device in an electric drive system according to claim 1, characterized in that, The fundamental wave voltage drop on the filtering inductor of the conducted interference filter does not exceed 3% - 5%, and the calculation formula for the filtering inductor parameters is: Among them, I represents the peak current output by the drive of the electric drive system, L f represents the filter inductance parameter, f0 represents the cut-off frequency of the conducted interference filter, and ΔU represents the voltage difference.

4. A method for electromagnetic interference resistance of an electronic device in an electric drive system according to claim 3, wherein The filtering capacitance of the conducted interference filter is calculated according to the size of the filtering inductor parameters, and the inductive reactance value of the conducted interference filter is greater than the capacitive reactance value in the high-frequency range. The calculation formula is: Among them, C f represents a filtering capacitor, and L f represents a filtering inductance parameter, and f0 represents the cut-off frequency of the conducted interference filter.

5. A method for anti-electromagnetic interference of an electronic device in an electric drive system according to claim 4, characterized in that, The calculation formula for the filtering resistance of the conducted interference filter is: δ≤1 (4); Among them, δ is the damping ratio, representing the relationship between the inductor, capacitor, and filtering resistor, where C f represents the filtering capacitor, and L f represents the filtering inductor parameter.

6. A method for anti-electromagnetic interference of an electronic device in an electric drive system according to claim 4, characterized in that, The calculation formula for the cut-off frequency of the conducted interference filter is: f0 = k×f1 (5); Among them, the value of k is 1 / 3; f1 represents the lowest interference frequency.

7. A method for anti-electromagnetic interference of an electronic device in an electric drive system according to claim 1, characterized in that, The operation of the random switching frequency modulation strategy is as follows: first, the carrier frequency changes randomly according to a random rule, generating a random number that does not change during the switching period of each carrier but changes randomly during different carrier switching periods. Then, the amplitude of the output signal is changed to the range of 0 to 1, and finally, after dividing by twice the switching frequency, a triangular carrier signal whose amplitude and frequency both change randomly is obtained.

8. A method for anti-electromagnetic interference of an electronic device in an electric drive system according to claim 1, characterized in that, The output position angle of the resolver decoding chip is filtered by a phase-locked loop.

9. A method for electromagnetic interference resistance of an electronic device in an electric drive system according to claim 8, characterized in that, The method of phase-locked loop filtering is to use multiple low-pass filters to filter the output speed signal of the decoding chip and filter out the high-frequency components of the error signal respectively.

10. A method for anti-electromagnetic interference of an electronic device in an electric drive system according to claim 9, characterized in that, The phase detector of the phase-locked loop is expressed as: sin(θ(n)-θ1(n - 1))(6); When the phase output by the phase-locked loop lags behind or leads the calculation result, the output of the phase detector is positive or negative, and the phase-locked loop output is dynamically adjusted to track the position angle signal of the calculation output.

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