Motor control device for reducing high-frequency leakage current

Abstract

The invention provides a motor control device for reducing high-frequency leakage current, and the device is characterized in that a DC power supply module is provided with a DC bus positive electrode and a DC bus negative electrode; the power conversion module is provided with a switch input end and a switch output end, the switch input end is connected with the DC bus anode, and the switch output end is connected with the DC bus cathode; the leakage current compensation module comprises a compensation capacitor, an upper bridge compensation switch device and a lower bridge compensation switch device, the upper bridge compensation switch device and the lower bridge compensation switch device are connected in series, the input end of the upper bridge compensation switch device is connected to the positive electrode of the direct-current bus, and the output end of the lower bridge compensation switch device is connected to the negative electrode of the direct-current bus. A compensation connection point is arranged between the upper bridge compensation switch device and the lower bridge compensation switch device and is grounded through a compensation capacitor; the control module controls the leakage current compensation module to output compensation alternating current, and the compensation alternating current and the leakage current are opposite in phase. The technical problems that in an existing leakage current compensation scheme, the circuit cost is high, the debugging difficulty is large, and the reliability is low are solved.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and more specifically, to a motor control device for reducing high-frequency leakage current. Background Technology

[0002] In air conditioners that use inverters to drive the internal motor of the compressor, there is a leakage current of several MHz flowing from the coils of each phase of the compressor motor through the refrigerant and refrigeration oil to the ground. In order to prevent accidents such as electric shock, the product safety standards have set limits and regulations on this leakage current.

[0003] To reduce this type of leakage current, measures such as installing a choke coil in the connection line between the output of the frequency converter and the compressor motor, or reducing the switching frequency of the frequency converter can be taken.

[0004] However, the relevant technologies have at least one of the following problems: In the existing technologies, whether it is a passive suppression scheme that sets up a choke coil and reduces the switching frequency, or an active compensation scheme that detects the zero-phase current and generates a canceling current, there are obvious defects: the passive scheme has limited suppression effect and affects motor performance, while the active scheme relies on a zero-phase current detection coil and a complex compensation circuit, resulting in high cost, high debugging difficulty, and low reliability. Summary of the Invention

[0005] This invention addresses the technical problems of high circuit cost, difficult debugging, and low reliability in existing leakage current compensation schemes.

[0006] To address the aforementioned problems, this invention provides a motor control device for reducing high-frequency leakage current, comprising: a DC power supply module having a positive DC bus and a negative DC bus; a power conversion module having a switch input terminal and a switch output terminal, the switch input terminal being connected to the positive DC bus and the switch output terminal being connected to the negative DC bus; a leakage current compensation module comprising: a compensation capacitor, an upper bridge compensation switch and a lower bridge compensation switch connected in series, the input terminal of the upper bridge compensation switch being connected to the positive DC bus, the output terminal of the lower bridge compensation switch being connected to the negative DC bus, and a compensation connection point being provided between the upper bridge compensation switch and the lower bridge compensation switch, the compensation connection point being connected to ground through the compensation capacitor; and a control module controlling the leakage current compensation module to output a compensation AC current, the compensation AC current being out of phase with the leakage current.

[0007] Compared with existing technologies, the technical effects achieved by this solution are as follows: The leakage current compensation module in this invention directly reuses the DC bus power supply, eliminating the need for an additional independent power supply unit, simplifying the circuit structure and reducing integration difficulty; in addition, it eliminates the zero-phase current detection coil and complex amplification circuit in traditional active compensation schemes, and significantly reduces hardware costs through the extremely simple design of "leakage current compensation module + control module," while reducing circuit failure points and improving system reliability; the overall solution has strong compatibility and can be directly adapted to existing variable frequency motor systems without modifying the structure of the motor body, equipment housing, etc., making it widely applicable.

[0008] In one embodiment of the present invention, the control module includes: a speed control unit, which receives the speed command value and the speed detection value of the motor, and calculates the current command based on the deviation between the two through speed control gain; a current control unit, which receives the current command, combines the d-axis current and q-axis current obtained by motor current conversion, and calculates the d-axis voltage command and q-axis voltage command through proportional-integral control; a modulation unit, which converts the d-axis voltage command and q-axis voltage command into three-phase AC voltage values, and uses a two-phase modulation strategy to compensate the three-phase AC voltage values ​​to obtain the compensated three-phase output voltage values; and a PWM signal generation unit, which generates peak waveform carriers and valley waveform carriers, selects the corresponding carrier according to the phase interval, compares the compensated three-phase output voltage values ​​with the selected carrier, and generates a PWM drive signal to drive the power conversion module.

[0009] Compared with existing technologies, the technical effects achieved by this technical solution are as follows: In this invention, the two-phase modulation strategy and the PWM signal generation unit work together to make the output line voltage sinusoidal through precise voltage conversion and carrier selection, thereby reducing the common-mode voltage fluctuation amplitude and reducing leakage current generation from the source; the design of peak and valley carriers provides a clear timing reference for the synchronous drive of the subsequent compensation module, ensuring that the phase of the compensation current and the leakage current are precisely opposite, thus improving the cancellation effect.

[0010] In one embodiment of the present invention, the power conversion module includes: three sets of conversion units, each set including an upper bridge switch and a lower bridge switch. The input terminals of the upper bridge switch are connected to the positive terminal of the DC bus, and the output terminals of the lower bridge switch are connected to the negative terminal of the DC bus. Each set of upper bridge switch and lower bridge switch has connection points as U-phase output terminals, V-phase output terminals, and W-phase output terminals, respectively, which are connected to the three-phase windings of the motor. The two-phase modulation strategy divides each output voltage cycle into multiple 120-degree phase intervals. In each phase interval, the switch in one phase conversion unit is fixed in the ON or OFF state, and the switch in the other two phase conversion units is PWM modulated by comparing with the peak wave carrier and the valley wave carrier.

[0011] Compared with existing technologies, the technical effects achieved by this solution are as follows: the division of the 120-degree phase interval and the "1-phase fixed, 2-phase modulated" design reduce the number of switching operations by 1 / 3, significantly reducing switching losses and improving system efficiency. At the same time, it reduces common-mode voltage fluctuations caused by frequent switching operations, suppressing leakage current at the source. The application of the opposite phase carrier makes the voltage changes of the two phases involved in modulation complementary, and the average voltage fluctuation of the motor winding to ground is more regular, which makes it easier for the compensation module to generate a compensation current with a precise opposite phase, improving the accuracy of leakage current cancellation. The standardized design of the three sets of conversion units ensures the symmetry of the three-phase output, avoids additional leakage current caused by three-phase voltage imbalance, and simplifies the circuit design and production debugging process.

[0012] In one embodiment of the present invention, when the modulation unit uses a two-phase modulation strategy to compensate for the three-phase AC voltage value, the compensation formula is as follows: ; ; ;in, , , These are the converted U-phase, V-phase, and W-phase AC voltage values, respectively. It is the minimum value among the three-phase AC voltage values. , , These are the compensated output voltage values ​​for phase U, phase V, and phase W, respectively.

[0013] Compared with existing technologies, the technical effects achieved by this solution are as follows: By subtracting the minimum three-phase voltage, the voltage of the lowest phase after compensation is reduced to zero, ensuring that the switching device of that phase is stably in the OFF state (saturated output), avoiding malfunctions caused by voltage fluctuations, and ensuring the effective implementation of the two-phase modulation strategy; the relative relationship of the three-phase output voltages after compensation remains unchanged, ensuring that the voltage between the output lines is a standard sine wave, with small motor torque pulsation, smooth operation, and reduced leakage current changes caused by torque fluctuations; voltage compensation regularizes the average voltage change of the motor windings to ground, forming a stable two-level rectangular wave characteristic, which facilitates the compensation module to accurately capture the timing of voltage changes and generate a compensation current that is completely opposite in phase to the leakage current, greatly improving the cancellation effect.

[0014] In one embodiment of the present invention, the control module selects the carrier according to the following rules: the output voltage period is divided into three 120-degree phase intervals, S1, S2, and S3; in the S1 phase interval, the U phase is fixed OFF, the V phase output voltage uses a valley carrier, and the W phase output voltage uses a peak carrier; in the S2 phase interval, the U phase output voltage uses a peak carrier, the V phase is fixed OFF, and the W phase output voltage uses a valley carrier; in the S3 phase interval, the U phase output voltage uses a valley carrier, the V phase output voltage uses a peak carrier, and the W phase is fixed OFF; wherein the peak carrier and the valley carrier have the same frequency and are mirror-symmetrically distributed on the time axis.

[0015] Compared with existing technologies, the technical effects achieved by this solution are as follows: the clear carrier selection rule ensures that the two phase carriers participating in modulation in each phase interval are out of phase, ensuring that the voltage changes of the two phases are complementary, the average voltage fluctuation amplitude of the motor winding to ground is consistent and the frequency is stable, providing a clear timing reference for the accurate generation of compensation current; the mirror symmetry design of peak and valley waves makes the timing of the two phase switches participating in modulation complementary, reducing the sudden change of common mode voltage, reducing the peak value of leakage current, and improving the leakage current suppression effect from the source.

[0016] In one embodiment of the present invention, the control module further includes: a compensation device driving unit, which generates a compensation driving signal according to the timing of the PWM driving signal to drive the upper bridge compensation switching device and the lower bridge compensation switching device, so that the leakage current compensation module outputs compensation AC power through the compensation capacitor; wherein, the compensation driving signal is synchronized with the driving time of the switching device of the power conversion module and is opposite in phase.

[0017] Compared with existing technologies, the technical effects achieved by this solution are as follows: the synchronous design of the compensation drive signal and the PWM drive signal ensures that the generation of the compensation current and the generation of the leakage current are perfectly matched in timing, avoiding cancellation failure due to timing deviation and significantly improving the leakage current suppression accuracy; the compensation drive unit directly reuses the timing information of the PWM drive signal, eliminating the need for an additional timing detection module, simplifying circuit design, reducing costs, and improving response speed; the synchronous drive strategy enables the compensation module to track changes in the motor's operating status in real time, and regardless of how the motor speed or load is adjusted, the compensation current can quickly adapt to changes in the leakage current, ensuring stable suppression under all operating conditions.

[0018] In one embodiment of the present invention, the specific method by which the compensation device driving unit generates the compensation driving signal is as follows: extract the conduction timing of the two-phase switching devices participating in PWM modulation in the PWM driving signal, and determine the conduction time window of the two-phase switching devices; generate a compensation driving signal synchronized with the conduction time window, so that the upper bridge compensation switching device of the leakage current compensation module conducts when the lower bridge switching device of the two-phase switching devices conducts, and the lower bridge compensation switching device conducts when the upper bridge switching device of the two-phase switching devices conducts, so as to ensure that the voltage across the compensation capacitor is out of phase with the average voltage of the three-phase winding of the motor to ground.

[0019] Compared with existing technologies, the technical effects achieved by this solution are as follows: the reverse conduction design of the upper and lower bridge compensation switching devices and the two-phase switching devices involved in modulation makes the voltage across the compensation capacitor completely opposite to the average voltage of the motor winding to ground, maximizing the cancellation effect of compensation current and leakage current, and reducing the average leakage current to the level of several mA; the synchronous design of the conduction time window avoids the mis-conduction of the compensation switching devices, reduces the self-loss of the compensation module, improves system efficiency, and avoids the generation of additional high-frequency interference.

[0020] In one embodiment of the present invention, the control module further includes: a two-phase conversion unit, which is used to convert the motor current into d-axis current and q-axis current, and feed the d-axis current and q-axis current back to the current control unit; wherein, after generating the current command, the speed control unit uses the current phase angle to convert the current command into d-axis current command and q-axis current command.

[0021] Compared with existing technologies, the technical effects achieved by this solution are as follows: The two-phase conversion unit enables accurate detection and coordinate transformation of motor current, providing accurate feedback signals for the current control unit, reducing the deviation between current command and actual current, resulting in more stable motor operation and smaller leakage current fluctuations; The application of current phase angle enables precise decomposition of current command, with d-axis current controlling flux and q-axis current controlling torque, achieving decoupled control of torque and flux, improving motor operating efficiency and dynamic response performance, and indirectly reducing leakage current caused by low efficiency or dynamic fluctuations.

[0022] In one embodiment of the present invention, the control module further includes: a rotational position speed estimation unit, which estimates the rotational speed based on the motor current and the motor inductance value; wherein the rotational speed estimation value is used as the rotational speed detection value.

[0023] Compared with existing technologies, the technical effects achieved by adopting this technical solution are as follows: no additional external speed sensor is required, reducing hardware costs, reducing circuit failure points, and improving system reliability and integration; the speed estimation has strong real-time performance, which can quickly track changes in motor speed, ensuring the dynamic response performance of speed control, enabling the motor to operate stably under conditions such as start-stop and sudden load changes; and the compensation module can adapt to changes in leakage current in a timely manner to ensure the compensation effect.

[0024] By adopting the technical solution of the present invention, the following technical effects can be achieved: (1) The leakage current compensation module in this invention directly reuses the DC bus power supply, without the need to set up an independent power supply unit, which simplifies the circuit structure and reduces the integration difficulty. In addition, it abandons the zero-phase current detection coil and complex amplification circuit in the traditional active compensation scheme. Through the minimalist design of "leakage current compensation module + control module", the hardware cost is greatly reduced, and the circuit failure points are reduced, thus improving the system reliability. (2) The division of the 120-degree phase interval and the design of "1 phase fixed and 2 phase modulated" reduce the number of switching by 1 / 3, significantly reduce switching losses, improve system efficiency, and at the same time reduce common-mode voltage fluctuations caused by frequent switching operations, thus suppressing leakage current from the source. (3) Voltage compensation makes the average voltage change of the motor winding to ground regular, forming a stable 2-level rectangular wave characteristic, which makes it easy for the compensation module to accurately capture the voltage change timing and generate a compensation current that is completely opposite to the phase of the leakage current, greatly improving the cancellation effect. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a structural diagram of a motor control device for reducing high-frequency leakage current provided in Embodiment 1 of the present invention; Figure 2 for Figure 1 Structure diagram of the control module; Figure 3 The switching timing diagram is for a two-phase modulation strategy; Figure 4 This is a diagram illustrating the definition of peak wave carrier and valley wave carrier in this invention; Figure 5 This refers to the carrier wave and switching pulse shifting of the motor control device during the implementation of this invention; Figure 6This is an example of the voltage of U phase and V phase, average voltage, and compensation circuit voltage in the motor control device of the present invention; Figure 7 This is another example of the voltage of U phase and V phase, average voltage, and compensation circuit voltage in the motor control device of the present invention; Figure 8 The simulation results show the leakage current shift after using the leakage current compensation module of this invention; Figure 9 Detailed simulation results of leakage current shift after using the leakage current compensation module of this invention.

[0026] Explanation of reference numerals in the attached figures: 11. AC power supply; 12. Interference filter; 13. Rectifier circuit; 14. Smoothing capacitor; 200. Power conversion module; 15a. First upper bridge switch; 16a. First lower bridge switch; 15b. First upper bridge freewheeling diode; 16b. First lower bridge freewheeling diode; 16c. First connection point; 17a. Second upper bridge switch; 18a. Second lower bridge switch; 17b. Second upper bridge freewheeling diode; 18b. Second lower bridge freewheeling diode; 18c. Second connection point; 19a. Third upper bridge switch; 20a. Third lower bridge switch; 19b. Third upper bridge freewheeling diode ; 20b, Third lower bridge freewheeling diode; 20c, Third connection point; 21, Motor; 22, Compensation device drive unit; 23a, Upper bridge compensation switch device; 24a, Lower bridge compensation switch device; 23b, Upper bridge compensation freewheeling diode; 24b, Lower bridge compensation freewheeling diode; 24c, Compensation connection point; 25, Compensation capacitor; 26, Control module; 260, Speed ​​control unit; 261, Two-phase conversion unit; 262, Current control unit; 263, Modulation unit; 264, PWM signal generation unit; 265, Rotational position and speed estimation unit; 27, Current detection module; 28, Shunt resistor. Detailed Implementation

[0027] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 See Figure 1This invention provides a motor control device for reducing high-frequency leakage current, as shown in the first embodiment. The motor control device includes: a DC power supply module, a power conversion module 200, a leakage current compensation module, and a control module 26. The DC power supply module has a positive DC bus and a negative DC bus. The power conversion module 200 has a switch input terminal and a switch output terminal. The switch input terminal is connected to the positive DC bus, and the switch output terminal is connected to the negative DC bus. The leakage current compensation module includes: a compensation capacitor 25, an upper bridge compensation switch device 23a and a lower bridge compensation switch device 24a connected in series. The input terminal of the upper bridge compensation switch device 23a is connected to the positive DC bus, and the output terminal of the lower bridge compensation switch device 24a is connected to the negative DC bus. A compensation connection point 24c is provided between the upper bridge compensation switch device 23a and the lower bridge compensation switch device 24a. The compensation connection point 24c is connected to ground through the compensation capacitor 25. The control module 26 controls the leakage current compensation module to output a compensation AC current, which is out of phase with the leakage current.

[0029] In one specific embodiment Figure 1 This is a structural diagram of the motor control device of the present invention. The AC power output from the AC power supply 11 is converted into DC power through the interference filter 12, rectifier circuit 13, and smoothing capacitor 14. Then it is supplied to the power conversion module 200 (i.e., frequency converter circuit) composed of switching devices 15a-20a connected in parallel with freewheeling diodes 15b-20b. In the power conversion module 200, the switching devices 15a-20a constitute the upper bridge switching device and the lower bridge switching device. The series conversion unit formed by the two is divided into three phases. The connection point of this conversion unit with the upper bridge and the lower bridge is connected to the load motor 21, and the motor 21 is driven by the above structure.

[0030] The casing of motor 21 and interference filter 12 are grounded, and leakage current flows into the ground through this path. In this invention, the leakage current compensation module generates a current that can cancel the leakage current and flows into the ground, thereby reducing the leakage current. The leakage current compensation module includes: a linear circuit composed of an upper bridge compensation switch 23a and a lower bridge compensation switch 24a connected in series, and both the upper bridge compensation switch 23a and the lower bridge compensation switch 24a are connected in parallel with freewheeling diodes, namely the upper bridge compensation freewheeling diode 23b and the lower bridge compensation freewheeling diode 24b, respectively; the compensation connection point 24c of the upper and lower bridges of the linear circuit is grounded through the compensation capacitor 25. In addition, the upper bridge compensation switch 23a and the lower bridge compensation switch 24a are driven synchronously with the power conversion module 200 through the compensation device driving unit 22. The leakage current compensation module in this invention directly reuses the DC bus power supply, eliminating the need for an additional independent power supply unit, thus simplifying the circuit structure and reducing integration difficulty. In addition, this invention abandons the zero-phase current detection coil and complex amplification circuit in traditional active compensation schemes. Through the extremely simple design of "leakage current compensation module + control module 26", the hardware cost is greatly reduced, while the number of circuit failure points is reduced and the system reliability is improved.

[0031] Further, see Figure 2 The control module 26 includes: a speed control unit 260, a current control unit 262, a modulation unit 263, and a PWM signal generation unit 264. The speed control unit 260 receives the speed command value and the speed detection value of the motor 21, and calculates the current command based on the deviation between the two through speed control gain. The current control unit 262 receives the current command, and calculates the d-axis voltage command and q-axis voltage command through proportional-integral control by combining the d-axis current and q-axis current obtained by motor current conversion. The modulation unit 263 converts the d-axis voltage command and q-axis voltage command into three-phase AC voltage values, and uses a two-phase modulation strategy to compensate the three-phase AC voltage values ​​to obtain the compensated three-phase output voltage values. The PWM signal generation unit 264 is used to generate peak waveform carriers and valley waveform carriers, and selects the corresponding carrier according to the phase interval, compares the compensated three-phase output voltage values ​​with the selected carrier, and generates a PWM drive signal to drive the power conversion module 200.

[0032] Specifically, the switching devices 15a to 20a in the power conversion module 200 are driven by the frequency converter module; the speed control unit 260 calculates the current command based on the deviation between the speed command value issued in the previous control process and the estimated speed detection value, combined with the speed control gain. The current command received The speed detection W can be synchronized with the speed command. Current command for: ,in, The current command is given, and W represents the speed detection value. This is the speed command value. For speed control proportional gain, Integral gain for speed control.

[0033] Current command By d-axis current command and q-axis current command composition, Used to adjust the magnetic field Used to adjust torque pulsation; similarly, current control is performed using general vector control, which can control the motor current ( , , It is divided into torque current (q-axis current) ) and the excitation current (d-axis current) that generates a magnetic field in the rotor The current control unit 262 operates according to current commands. , The resulting two-phase current values , The deviation between them, combined with the current control gain, is used to calculate the output voltage of the two axes. , The obtained output voltage , This can make the current value , Synchronized with current command , : ; ;in, This is a d-axis voltage command. This is a q-axis voltage command; These are the proportional gain for d-axis current control and the integral gain for d-axis current control, respectively. These are the q-axis current control proportional gain and the q-axis current control integral gain, respectively.

[0034] Combined with rotation phase angle This is converted into a three-phase AC voltage value. , , : The present invention employs a 2-phase modulation drive mode during implementation, meaning that in all output phases of the inverter, one phase is saturated with output: such as... Figure 3As shown, within the set saturation output range, such as the 120-degree intervals in the scenario shown in the figure, the output is saturated sequentially in the order of U-phase down → V-phase down → W-phase down, which can reduce the total number of switching operations by 1 / 3, thus reducing losses. In addition, the two-phase modulation strategy and the PWM signal generation unit 264 in this invention work together to make the output line voltage sinusoidal through precise voltage conversion and carrier selection, reducing the common-mode voltage fluctuation amplitude and reducing leakage current generation from the source. The design of peak and valley carrier waves provides a clear timing reference for the synchronous drive of the subsequent compensation module, ensuring that the phase of the compensation current and the leakage current are precisely opposite, thus improving the cancellation effect.

[0035] Furthermore, the power conversion module 200 includes: 3 sets of conversion units, each set including an upper bridge switch and a lower bridge switch. The input terminals of the upper bridge switch are connected to the positive terminal of the DC bus, and the output terminals of the lower bridge switch are connected to the negative terminal of the DC bus. Each set of upper and lower bridge switch devices has connection points as U-phase output terminals, V-phase output terminals, and W-phase output terminals, respectively, which are connected to the three-phase windings of the motor 21. The 2-phase modulation strategy divides each output voltage cycle into multiple 120-degree phase intervals. In each phase interval, the switch in one of the three-phase conversion units is fixed in the ON or OFF state, and the switch in the other two phase conversion units is PWM modulated by comparing with the peak wave carrier and the valley wave carrier. The peak wave carrier and the valley wave carrier are opposite in phase.

[0036] Specifically, the power conversion module 200 includes three conversion units: a first conversion unit, a second conversion unit, and a third conversion unit. The first conversion unit includes a first upper bridge switch 15a and a first lower bridge switch 16a connected in series, and a first upper bridge freewheeling diode 15b and a first lower bridge freewheeling diode 16b connected in parallel across the first upper bridge switch 15a and the first lower bridge switch 16a. A first connection point 16c (serving as the U-phase output terminal) is provided between the first upper bridge switch 15a and the first lower bridge switch 16a. The second conversion unit includes a second upper bridge switch 17a and a second lower bridge switch 18a connected in series, and a second upper bridge switch 17a connected in parallel with the first lower bridge switch 18a. The second upper bridge freewheeling diode 17b and the second lower bridge freewheeling diode 18b are connected at both ends of the switching device 17a and the second lower bridge switching device 18a. A second connection point 18c (as the V-phase output terminal) is provided between the second upper bridge switching device 17a and the second lower bridge switching device 18a. The third conversion unit includes: a third upper bridge switching device 19a and a third lower bridge switching device 20a connected in series, and a third upper bridge freewheeling diode 19b and a third lower bridge freewheeling diode 20b connected in parallel at both ends of the third upper bridge switching device 19a and the third lower bridge switching device 20a. A third connection point 20c (as the W-phase output terminal) is provided between the third upper bridge switching device 19a and the third lower bridge switching device 20a.

[0037] In the implementation of this invention, two triangular wave shapes are used as carrier waves, namely... Figure 4 The carrier wave is divided into two types: peak wave and valley wave. The carrier wave is generated by the timer value of the MCU. The carrier wave that increases and decreases is defined as a peak wave carrier wave, and the carrier wave that decreases and increases is defined as a valley wave carrier wave.

[0038] The division of the 120-degree phase interval and the "1-phase fixed, 2-phase modulated" design reduce the number of switching operations by 1 / 3, significantly reducing switching losses and improving system efficiency. At the same time, it reduces common-mode voltage fluctuations caused by frequent switching operations, suppressing leakage current at the source. The application of the opposite phase carrier makes the voltage changes of the two phases involved in modulation complementary, and the average voltage fluctuation of the motor winding to ground is more regular, which makes it easier for the compensation module to generate a compensation current with precise opposite phase, improving the accuracy of leakage current cancellation.

[0039] Furthermore, when the modulation unit 263 uses a two-phase modulation strategy to compensate for the three-phase AC voltage value, the compensation formula is as follows: ; ; ;in, , , These are the converted U-phase, V-phase, and W-phase AC voltage values, respectively. It is the minimum value among the three-phase AC voltage values. , , These are the compensated output voltage values ​​for phase U, phase V, and phase W, respectively.

[0040] Specifically, the two-phase modulation compensates for the AC voltage value in the following way: ; ; ,in, The minimum phase voltage is obtained by the PWM signal generation unit 264 using pulse width modulation (PWM) to output a switching mode, thus achieving the voltage value obtained in the previous step. , , Therefore, a generation method that compares the carrier wave with the modulation wave corresponding to the output voltage is required.

[0041] This invention reduces the minimum three-phase voltage to zero after compensation, ensuring that the switching device in that phase remains stably in the OFF state (saturated output). This avoids malfunctions caused by voltage fluctuations and guarantees the effective implementation of the two-phase modulation strategy. The relative relationship of the three-phase output voltages remains unchanged after compensation, ensuring that the voltage between the output lines is a standard sine wave, resulting in small motor torque ripple, smooth operation, and reduced leakage current changes caused by torque fluctuations. Voltage compensation regularizes the average voltage change of the motor windings to ground, forming a stable two-level rectangular wave characteristic. This allows the compensation module to accurately capture the timing of voltage changes and generate a compensation current that is completely opposite in phase to the leakage current, significantly improving the cancellation effect.

[0042] Furthermore, the control module 26 selects the carrier according to the following rules: the output voltage period is divided into three 120-degree phase intervals, S1, S2, and S3; in the S1 phase interval, the U phase is fixed OFF, the V phase output voltage uses a valley carrier, and the W phase output voltage uses a peak carrier; in the S2 phase interval, the U phase output voltage uses a peak carrier, the V phase is fixed OFF, and the W phase output voltage uses a valley carrier; in the S3 phase interval, the U phase output voltage uses a valley carrier, the V phase output voltage uses a peak carrier, and the W phase is fixed OFF; wherein, the peak carrier and the valley carrier have the same frequency and are mirror-symmetrically distributed on the time axis.

[0043] Specifically, Figure 5 This invention describes the shift of the carrier waves of the three phases (U phase, V phase, W phase) and the switching pulses of the upper and lower bridge devices of each phase when the carrier wave is a peak wave or a valley wave during the implementation of the invention. The carrier shape of each phase is fixed once every 120 degrees of phase angle. The carrier shape of each phase interval of the three phases is selected according to Table 1, and the corresponding switching pulse is output (↑ indicates peak wave carrier, ↓ indicates valley wave carrier).

[0044] Table 1. Carrier selection method during the implementation of this invention. The mirror-symmetric design of peak and trough waves in this invention makes the timing of the two-phase switches involved in modulation complementary, reducing the sudden change of common-mode voltage and lowering the peak value of leakage current, thus improving the leakage current suppression effect from the source. The precise matching of carrier selection and phase interval allows the compensation module to quickly judge the voltage change trend according to the carrier type and adjust the conduction timing of the compensation switching device in advance, ensuring that the compensation current and leakage current are reversed in real time, resulting in higher cancellation accuracy.

[0045] Furthermore, the control module 26 also includes a compensation device driving unit 22, which generates a compensation driving signal according to the timing of the PWM driving signal to drive the upper bridge compensation switch 23a and the lower bridge compensation switch 24a, so that the leakage current compensation module outputs compensation AC power through the compensation capacitor 25; wherein, the compensation driving signal is synchronized with the driving time of the switching devices of the power conversion module 200 and is opposite in phase.

[0046] Specifically, the carrier selection method described above can reduce the variation in the average voltage of the motor winding, thereby simplifying the structure of the leakage current compensation module. The specific operation is as follows: the compensation device drive unit 22 outputs a compensation drive signal, which is in opposite phase to the switching signal output by the control module 26; that is, the compensation switching device is driven to make the leakage current compensation module output a compensation current (i.e., compensation AC current) to offset the leakage current flowing out through the stray capacitance between the winding of the motor 21 and the housing of the motor 21.

[0047] Furthermore, the specific method by which the compensation device drive unit 22 generates the compensation drive signal is as follows: extract the conduction timing of the two-phase switching devices participating in PWM modulation from the PWM drive signal, determine the conduction time window of the two-phase switching devices; generate a compensation drive signal synchronized with the conduction time window, so that the upper bridge compensation switch 23a of the leakage current compensation module conducts when the lower bridge switch of the two-phase switching device conducts, and the lower bridge compensation switch 24a conducts when the upper bridge switch of the two-phase switching device conducts, so as to ensure that the voltage across the compensation capacitor 25 is out of phase with the average voltage of the three-phase winding of the motor to ground.

[0048] Specifically, Figure 6 In the motor control device of this invention, within the interval (phase interval S3) when the W-phase output is 0V, the voltages of the U-phase and V-phase, the average voltage, and the voltage of the compensation module are considered. Here, the compensation module voltage refers to the voltage at compensation connection point 24c. The timing value corresponding to the U-phase output voltage is compared. The U-phase voltage corresponding to the U-phase output time width Pu pulse and carrier wave 1; by comparing the timing value corresponding to the V-phase output voltage. With carrier wave 2, the V-phase output pulse with a time width Pv corresponds to the V-phase voltage; at this time, the average three-phase voltage of the motor is calculated according to... Figure 8 The trajectory of the penultimate line shifts; due to the difference in the generation time points of the Pu and Pv pulses of the U and V phases, the voltage waveform of the output three-phase average voltage is a rectangular wave with an amplitude H of 2 levels.

[0049] To reduce the leakage current caused by this voltage, simply adjust the voltage level output by the leakage current compensation module according to... Figure 8The output should be a 2-level rectangular wave signal as shown in the bottom row waveform. In summary, in the leakage current compensation module, the inline circuit composed of the upper bridge compensation switch 23a and the lower bridge compensation switch 24a can be composed of only one phase, and the upper and lower compensation switches are driven by a 2-level rectangular wave signal; that is, driving the upper and lower compensation switches generates a voltage value opposite to the average voltage of the phase in which the switches are operating; subsequently, the compensation module voltage is as follows... Figure 8 The bottom line shows the application to one end of the compensation capacitor 25; finally, the compensation capacitor 25 outputs a compensation current that is in the opposite phase to the leakage current flowing to the ground wire.

[0050] Figure 7 In the motor control device of the present invention, during the interval (phase interval S3) when the W phase output is 0V, there is another case regarding the voltage, average voltage, and compensation module voltage of the U phase and V phase: at this time, the voltage of the U phase and V phase is relatively high, and there is a portion of the output pulse width time that overlaps with each other; in addition, the average voltage of the motor winding forms a 2-level rectangular wave signal, and the leakage current compensation module with 2-level output can output compensation current to reduce the leakage current.

[0051] Furthermore, the control module 26 also includes a two-phase conversion unit 261, which is used to convert the motor current into d-axis current and q-axis current, and feed the d-axis current and q-axis current back to the current control unit 262; wherein, after generating the current command, the speed control unit 260 uses the current phase angle to convert the current command into d-axis current command and q-axis current command.

[0052] Specifically, the two-phase conversion unit 261 converts the motor current detected by the current detection module 27 ( , , The current is converted into d-axis and q-axis currents and sent to the current control unit 262 and speed control unit 260 to provide suitable current parameters for vector control and improve the accuracy of current control. ;in, For the rotation phase angle, For d-axis current, This is the q-axis current.

[0053] Using the current phase angle to transmit the current command The conversion to d-axis current command and q-axis current command is calculated using the following formula: , ,in, The current phase angle, This is the d-axis current command. This is the q-axis current command; the current phase angle β is the value that defines the current phase. The setting of the current phase angle β needs to meet the load conditions and parameter characteristics of the motor 21. By setting the current phase angle β to the optimal value that meets the current load conditions, the motor 21 can achieve high-performance operation in a wide load range.

[0054] Furthermore, the control module 26 also includes a rotational position and speed estimation unit 265, which estimates the rotational speed based on the motor current and the motor inductance value; wherein the estimated rotational speed value is used as the rotational speed detection value.

[0055] Specifically, the rotational position and speed estimation unit 265 detects the three-phase AC current value through the current detection module 27 based on the voltage across the shunt resistor 28. , , ), used to estimate the rotational phase angle of motor 21 Rotational speed detection value W.

[0056] Preferably, the speed control unit 260, two-phase conversion unit 261, current control unit 262, modulation unit 263, signal generation unit and rotational position and speed estimation unit 265 in the control module 26 utilize the timing function inside the chip to output the command speed of the motor 21 to the power conversion module 200 by outputting a switch signal.

[0057] Figure 8 The simulation results are shown below when the motor 21 is driven using the leakage compensation circuit of the present invention. From top to bottom, they are motor current, leakage current, compensation current, leakage current after compensation, and average leakage current after compensation. Similar to the prior art, by adding a compensation current to offset the leakage current, the leakage current is significantly reduced after compensation. Figure 9 Is Figure 8 Under the same conditions, a detailed trajectory after the device drive signal was added; compared with the leakage current generated at the switching pulse time points of each phase upper and lower bridge device, the leakage current after compensation was significantly reduced after adding the compensation current with opposite phase.

[0058] The leakage current compensation module of the present invention described above reduces the leakage current during motor 21 driving at low cost without requiring a leakage current detector.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A motor control device for reducing high frequency leakage current, characterized by, The motor control device comprises: A direct current power supply module provided with a direct current bus positive pole and a direct current bus negative pole; A power conversion module (200) provided with a switch input end and a switch output end, the switch input end being connected to the direct current bus positive pole, and the switch output end being connected to the direct current bus negative pole; A leakage current compensation module comprising a compensation capacitor (25), an upper bridge compensation switch device (23a) and a lower bridge compensation switch device (24a) connected in series, the input end of the upper bridge compensation switch device (23a) being connected to the direct current bus positive pole, the output end of the lower bridge compensation switch device (24a) being connected to the direct current bus negative pole, and a compensation connection point (24c) being provided between the upper bridge compensation switch device (23a) and the lower bridge compensation switch device (24a) and connected through the compensation capacitor (25); A control module (26) for controlling the leakage current compensation module to output compensation alternating current, the compensation alternating current being opposite in phase to the leakage current.

2. The motor control device according to claim 1, characterized by The control module (26) comprises: A speed control unit (260) for receiving a speed instruction value and a speed detection value of a motor, calculating a current instruction according to a deviation between the two values through a speed control gain; A current control unit (262) for receiving the current instruction, combining d-axis current and q-axis current obtained through motor current conversion, and calculating d-axis voltage instruction and q-axis voltage instruction through proportional integral control; A modulation unit (263) for converting the d-axis voltage instruction and the q-axis voltage instruction into three-phase alternating voltage values, compensating the three-phase alternating voltage values through a 2-phase modulation strategy, and obtaining compensated three-phase output voltage values; A PWM signal generation unit (264) for generating peak waveform carriers and valley waveform carriers, selecting corresponding carriers according to the phase interval, comparing the compensated three-phase output voltage values with the selected carriers, and generating PWM drive signals for driving the power conversion module (200).

3. The motor control device according to claim 2, wherein The power conversion module (200) comprises three groups of conversion units, each conversion unit comprising an upper bridge switch device and a lower bridge switch device, the input end of the upper bridge switch device being commonly connected to the direct current bus positive pole, the output end of the lower bridge switch device being commonly connected to the direct current bus negative pole, and a connection point being provided between the upper bridge switch device and the lower bridge switch device of each group as a U-phase output end, a V-phase output end and a W-phase output end, and being connected to three-phase windings of the motor correspondingly. The 2-phase modulation strategy is to divide a plurality of 120-degree phase intervals in each output voltage period, and in each phase interval, the switching device in the 1-phase conversion unit is fixed to the ON or OFF state, and the switching device in the remaining 2-phase conversion unit is PWM modulated by comparing with the peak wave carrier and the valley wave carrier. The peak wave carrier and the valley wave carrier are opposite phases.

4. The motor control device according to claim 3, characterized by When the modulation unit (263) compensates the three-phase alternating voltage value by using the 2-phase modulation strategy, the compensation formula is as follows: ； ； ； Wherein, , , are converted U-phase, V-phase, W-phase AC voltage values respectively; is the minimum value in the three-phase AC voltage values, , , are compensated U-phase, V-phase, W-phase output voltage values respectively.

5. The motor control device of claim 3, wherein The control module (26) selects the carrier according to the following rules: The output voltage period is divided into S1, S2 and S3 three 120-degree phase intervals; In the S1 phase interval, the U-phase is fixed OFF, the V-phase output voltage selects the valley wave carrier, and the W-phase output voltage selects the peak wave carrier; In the S2 phase interval, the U-phase output voltage selects the peak wave carrier, the V-phase is fixed OFF, and the W-phase output voltage selects the valley wave carrier; In the S3 phase interval, the U-phase output voltage selects the valley wave carrier, the V-phase output voltage selects the peak wave carrier, and the W-phase is fixed OFF; The peak wave carrier and the valley wave carrier have the same frequency and are mirror-symmetrically distributed on the time axis.

6. The motor control device of claim 2, wherein The control module (26) further comprises: The compensation device driving unit (22) generates a compensation driving signal according to the timing of the PWM driving signal to drive the upper bridge compensation switching device (23a) and the lower bridge compensation switching device (24a), so that the leakage current compensation module outputs the compensation alternating current through the compensation capacitor (25); The compensation driving signal is synchronous and opposite in phase with the switching device driving time point of the power conversion module (200).

7. The motor control device of claim 6, wherein The specific way of the compensation device driving unit (22) to generate the compensation driving signal is as follows: Extract the conduction timing of the 2-phase switching device involved in PWM modulation in the PWM driving signal to determine the conduction time window of the 2-phase switching device; The compensation driving signal is generated synchronously with the conduction time window, so that the upper bridge compensation switching device (23a) of the leakage current compensation module is turned on when the lower bridge switching device of the 2-phase switching device is turned on, and the lower bridge compensation switching device (24a) is turned on when the upper bridge switching device of the 2-phase switching device is turned on, so as to ensure that the voltage across the compensation capacitor (25) is opposite in phase to the average voltage of the three-phase winding of the motor.

8. The motor control device of claim 2, wherein The control module (26) further comprises: The two-phase conversion unit (261) is used to convert the motor current into the d-axis current and the q-axis current, and feed back the d-axis current and the q-axis current to the current control unit (262); The speed control unit (260) converts the current instruction into a d-axis current instruction and a q-axis current instruction by using a current phase angle after generating the current instruction.

9. The motor control device of claim 8, wherein The control module (26) further comprises: A rotational position and speed estimation unit (265) estimates the rotational speed estimation value from the motor current and a motor inductance value. The rotational speed estimation value is used as the rotational speed detection value.

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