A permanent magnet synchronous motor freewheeling energy storage demagnetization device and an implementation method thereof

Abstract

The application discloses a kind of permanent magnet synchronous motor freewheeling energy storage degaussing device and its implementation method, device is based on the power driving module of existing permanent magnet synchronous motor, additional freewheeling energy storage module and for different power VDC voltage are uniformly sampled energy storage capacitor voltage variation to monitor degaussing completion condition monitoring module;Freewheeling energy storage module includes MOS tube Q7, diode VD and energy storage capacitor C2;Diode VD is in forward across between power supply anode to the bus of power driving module power supply;Capacitor C2 negative pole is connected with power supply VDC positive pole, MOS tube Q7 drain electrode is connected with capacitor C2 positive pole, source electrode is connected with diode VD cathode, gate electrode is connected with single-chip microcomputer;Single-chip microcomputer A / D input is connected with monitoring module output, indirectly obtains voltage from between capacitor C2 positive pole to power supply negative pole by monitoring module, to reduce the influence of voltage variation after sampling by voltage stabilizing tube voltage stabilizing power supply voltage on sampling accuracy.

Description

Technical Field

[0001] This invention relates to the technical field of permanent magnet synchronous motors, and more specifically to a device and method for eliminating residual magnetism by using a three-phase stator winding star connection for stopping a permanent magnet synchronous motor with continuous current storage during shutdown. Background Technology

[0002] Before introducing the background technology, the applicant first explains the basic theoretical characteristics of the main devices associated with the prior art:

[0003] (1) The following is an explanation of MOSFETs:

[0004] For high-power MOSFETs, there is a parasitic diode (body diode) between the drain (D) and source (S) terminals caused by the manufacturing process. The function of the parasitic diode is to conduct large instantaneous reverse currents through the diode, preventing the MOSFET from breaking down (playing a protective role for the MOSFET). When a high-power MOSFET is used in the power bridge arm of the power drive module of a three-phase permanent magnet synchronous motor, its parasitic diode, together with the external diode for freewheeling (when the parasitic diode can fully handle the freewheeling current, the external diode for freewheeling is not required), performs the following: freewheeling and demagnetizing of the reverse electromotive force generated when the motor switches from energized to de-energized phases during normal operation and when the energized phase is cut off during shutdown.

[0005] MOSFETs come in two types: N-channel and P-channel. In an NMOS transistor, the positive terminal of the parasitic diode is on the source (S) and the negative terminal is on the drain (D), while in a PMOS transistor, the positive terminal of the parasitic diode is on the drain (D) and the negative terminal is on the source (S). When NMOS and PMOS transistors are used as switches, the current direction is different: when an NMOS transistor is used as a switch, the current ID flows from the drain (D) to the source (S); when a PMOS transistor is used as a switch, the current ID flows from the source (S) to the drain (D).

[0006] Unlike transistors, MOSFETs can conduct in reverse. When the control voltage between the gate (G) and source (S) of a MOSFET meets the conduction condition, the current ID can flow from the drain (D) to the source (S), and vice versa. The direction of the current ID depends on the direction of the voltage applied between the drain (D) and the source (S). Specifically:

[0007] ① For NMOS transistors: When the voltage applied between the drain (D) and source (S) points towards the source (S), it is used as a switch, and the current ID points from the drain (D) to the source (S). In this case, the NMOS transistor can only conduct when the control voltage between the gate (G) and source (S) meets the conduction condition; otherwise, the NMOS transistor is cut off. When the voltage applied between the drain (D) and source (S) points towards the drain (D), the parasitic diode of the NMOS transistor conducts, directly generating a current ID from the source (S) to the drain (D), and producing a forward voltage of approximately 0.7V across the parasitic diode. If the control voltage between the gate (G) and source (S) of the MOS transistor meets the conduction condition, the NMOS transistor will conduct, shorting the conducting parasitic diode. This allows the current ID generated by the conduction of the parasitic diode to flow through the conduction path controlled by the NMOS transistor, thus preventing power consumption on the parasitic diode. Therefore, due to the presence of the parasitic diode in the NMOS transistor, when the direction of the voltage applied between the drain (D) and source (S) is towards the drain (D), regardless of whether the control voltage between the gate (G) and source (S) of the MOS transistor meets the conduction condition, there will always be a current ID pointing from the source (S) to the drain (D).

[0008] ② For PMOS transistors: When the voltage applied between the drain (D) and source (S) points towards the drain (D), it is used as a switch, and the current ID points from the source (S) to the drain (D). In this case, the PMOS transistor can only conduct when the control voltage between the gate (G) and source (S) meets the conduction condition; otherwise, the PMOS transistor is cut off. When the voltage applied between the drain (D) and source (S) points towards the source (S), the current ID is directly generated from the drain (D) to the source (S) through the conduction of the parasitic diode of the PMOS transistor, and a forward voltage of approximately 0.7V is generated across the parasitic diode. If the control voltage between the gate (G) and source (S) of the MOS transistor meets the conduction condition, the PMOS transistor will conduct, shorting the conducting parasitic diode. This allows the current ID generated by the conduction of the parasitic diode to flow through the conduction path controlled by the PMOS transistor, thus preventing power consumption on the parasitic diode. Therefore, due to the presence of the parasitic diode in the PMOS transistor, when the voltage applied between the drain (D) and source (S) points towards the source (S), there will be a current ID pointing from the drain (D) to the source (S) regardless of whether the control voltage between the gate (G) and source (S) of the MOS transistor meets the conduction condition.

[0009] As analyzed in ① and ② above, due to the parasitic diode (body diode) between the drain (D) and source (S) of a high-power MOSFET caused by the manufacturing process, a single high-power MOSFET cannot be used as a bidirectional switch. To overcome the technical problem of the parasitic diode affecting the bidirectional switch function of a MOSFET, existing technologies have effectively solved this issue, such as connecting two NMOS transistors back-to-back, with the source and gate terminals of the two NMOS transistors sharing the same terminals. Since the MOSFETs in this application are not used as bidirectional switches, the specific circuit of a bidirectional switch composed of two NMOS transistors will not be described in detail here.

[0010] (2) The IGBT transistor is described as follows:

[0011] Unlike MOSFETs, IGBTs do not have an internal parasitic diode. A typical IGBT is a single component without a freewheeling diode (damping diode). IGBT modules integrate the IGBT and the freewheeling diode (damping diode) into a single unit; therefore, the freewheeling diode (damping diode) in the IGBT module is integrated post-processed. The three terminals of an IGBT are the collector (C), emitter (E), and gate (G) (the gate is equivalent to the base of a transistor). An IGBT is a composite, fully controllable, voltage-driven power electronic device composed of a BJT (bipolar junction transistor) and a MOSFET. Its input stage is a MOSFET, and its output stage is a bipolar junction transistor. Therefore, when a conventional IGBT is used as a switch, it can only be used in unidirectional mode.

[0012] To address the limitation of conventional IGBTs being only unidirectional when used as switches, a novel bidirectional IGBT power semiconductor device with a five-layer, four-segment structure is proposed. Its core is based on a planar gate IGBT, and by employing a symmetrical mechanism and a two-way input control method, bidirectional control of the new device is achieved, enabling both bidirectional conduction and bidirectional blocking. Therefore, in existing technologies, if a bidirectional IGBT is used, it must be specifically stated that a bidirectional IGBT is employed.

[0013] When IGBTs are used in the power bridge arm of the power drive module of a three-phase permanent magnet synchronous motor, the IGBTs are IGBT modules with integrated freewheeling diodes. The integrated freewheeling diodes are used to complete the following: the reverse electromotive force generated when the phase is switched from energized to de-energized during normal motor operation and the phase that is disconnected when the motor stops, and the demagnetization.

[0014] II. Regarding a motor drive system for direct main drive of a loom (application number 2012202368353) related to the prior art in the relevant field (patent application number 2012101639259 filed on the same day for the same invention), the technical solution is described as follows:

[0015] This application adds a capacitor C for energy storage to the existing power converter circuit that drives a three-phase switched reluctance motor. CD Q is a common power switching device used to apply high voltage to the windings A, B, and C of a three-phase switched reluctance motor. CD And power diode VD used to provide a path for normal power supply to the windings A, B, and C of the three-phase switched reluctance motor. CD Power diode VD CD Connected across power supply V DC On the bus supplying power to the power converter circuit that drives the existing three-phase switched reluctance motor, its power diode VD CD anode and power supply V DC Filter capacitor C DC The positive terminal of the power diode VD CD The cathode is connected to the bus supplying power to the power converter circuit; the power switching device Q CD collector and energy storage capacitor C CD Its positive terminal is connected to the power diode VD, and its emitter is connected to the power diode VD. CD The cathode is connected in phase; the energy storage capacitor C CD The negative terminal is connected to the power supply V. DC Filter capacitor C DC The positive terminal is connected; in the power converter circuit that drives the three-phase switched reluctance motor using its existing technology, the power diode VD AH VD BH and VD CH The cathode is moved from the power supply bus and connected to the energy storage capacitor C. CD The positive terminal. Correspondingly, the improved power converter circuit for driving the three-phase switched reluctance motor is controlled to achieve the following: after shutdown, the reverse electromotive force generated by the motor windings A, B, and C passes through the power diode VD. AH VD BH and VD CH To the energy storage capacitor C CD Charging and storing energy generates an energy storage voltage V. CD When starting the motor, the power switching device Q is controlled. CD On, using power supply V DC Superimposed energy storage voltage V CD High-voltage power is supplied to the power bus, allowing a larger current to flow through the motor windings, thereby increasing the motor's starting torque to meet the requirements of rapid starting of the three-phase switched reluctance motor; after the motor starts, the power switching device Q is controlled. CD Off, power supply V DC via power diode VD CD Power is supplied to the power bus to restore the motor windings to normal power supply V. DC Go to work.

[0016] From the icons of the power switching devices in the accompanying drawings and the description of the three polarities of the power switching devices in the specification, those skilled in the art can undoubtedly determine that the seven power switching devices described are IGBT transistors, not IGBT modules. Therefore, the power switching devices described do not include freewheeling diodes (damping diodes). Furthermore, based on analysis, the applicant believes that the motor drive system for direct main drive of a loom, as described in application number 2012202368353, is practically applicable.

[0017] III. The background technology of this application is described as follows:

[0018] Permanent magnet synchronous motors have advantages such as simple structure, small size, light weight, low loss, high efficiency, and high power factor. They are mainly used in high-performance servo drive systems that require fast response, wide speed range, and accurate positioning, as well as as replacement motors for DC motors.

[0019] When a permanent magnet synchronous motor (PMSM) starts under load, residual magnetism remaining in the motor windings after a previous shutdown can affect its starting and speed tracking. Currently, the back electromotive force generated in the stator three-phase windings after a shutdown of a PMSM is demagnetized by a freewheeling diode connected in parallel to the switching transistor in the drive module (or a parasitic diode on the MOSFET if the switching transistor is a MOSFET; if the parasitic diode's power is insufficient, another freewheeling diode is connected in parallel to complete the freewheeling process). However, it is difficult to ascertain the extent of residual magnetism removal, making it impossible to determine whether the residual magnetism has been eliminated to a safe level during the next startup.

[0020] The time it takes for a permanent magnet synchronous motor to reach its normal starting torque during the current-driven excitation process directly affects its starting performance. Current methods use constant voltage excitation, powered by a supply voltage equal to the motor's rated voltage. With constant voltage excitation, the current cannot immediately rise to the required excitation value, resulting in a longer time to reach the normal starting torque, slower starting speed, and ultimately, lower starting efficiency for the permanent magnet synchronous motor.

[0021] To address the problems existing in the prior art, for a permanent magnet synchronous motor with a three-phase stator winding star connection, the same applicant simultaneously applied for three inventions on July 25, 2019, implementing different settings and corresponding methods: during shutdown, the freewheeling current eliminates residual magnetism and uses a capacitor to boost and store energy; during startup, the voltage on the capacitor is applied in series with the power supply for a time-limited period to apply high voltage to the bus of the motor power drive module for high-voltage excitation, shortening the startup process and improving the motor startup efficiency; after the time limit, the power supply returns to normal to maintain normal motor operation; two of the inventions also employ a monitoring circuit to monitor the elimination of residual magnetism during shutdown, thereby effectively avoiding the adverse effects of excessive residual magnetism on motor startup and speed tracking when starting the motor again. The above three inventions are: Application No. 2019106755101, entitled "Excitation Control Device and Method for Using a Synchronous Motor"; Application No. 2019106755296, entitled "Die diode freewheeling device for eliminating residual magnetism in a permanent magnet synchronous motor and method for using it"; and Application No. 2019106755277, entitled "MOSFET freewheeling device for eliminating residual magnetism in a permanent magnet synchronous motor and method for demagnetizing it." All three applications have been examined and confirmed by the art to possess novelty, inventiveness, and industrial applicability.

[0022] Through analysis of the above three inventive solutions, the applicant has unequivocally determined that they are all derived from a technical solution added to a motor drive system for direct main drive of a loom, as described in application number 2012202368353 prior to the application date. Furthermore, research on the technical solutions of the above three inventions has revealed the following defects and technical problems:

[0023] (1) A common problem is that the method and technical solution are undoubtedly based on the absence of parasitic diodes in the MOSFET. Otherwise, the shutdown energy storage and demagnetization methods claimed in applications 2019106755101 and 2019106755277 cannot be reproduced. For application 2019106755296, after removing (and eliminating the need for) diodes VD1, VD2, and VD3, there exists a more effective shutdown energy storage and demagnetization method. And without a doubt... As is well known to those skilled in the art, the MOSFETs in the prior art drive modules are high-power MOSFETs: In applications 2019106755101 and 2019106755277, MOSFETs Q1 (MOSFET T1), Q2 (MOSFET T2), Q3 (MOSFET T3), Q4 (MOSFET T4), Q5 (MOSFET T5), and Q6 (MOSFET T6) effectively maintain the normal operation of the synchronous motor precisely because of the parasitic diodes that provide freewheeling current; In application 2019106755296, since MOSFET Q6 is connected to a diode VD2 for freewheeling current, the MOSFETs Q1, Q2, Q3, Q4, and Q5 in its drive module effectively maintain the normal operation of the synchronous motor precisely because of the parasitic diodes that provide freewheeling current. However, although diode VD1 is equivalent to the corresponding phase freewheeling current when MOSFET Q4 is turned off, diode VD3 is equivalent to... The freewheeling current is used for the corresponding phase when MOSFET Q2 is turned off. The freewheeling current of diodes VD1 and VD3 is used to charge the energy storage capacitor C2 at the higher position, and cannot be freewheeled through the conducting phase of the upper transistor of the bridge arm. Therefore, it is not fast enough to release the reverse electromotive force and demagnetize. So during the operation of the motor, the freewheeling current is only released through the parasitic diodes in MOSFETs Q1 and Q5 (or together with the freewheeling diodes connected in parallel across the MOSFETs). The reverse electromotive force is quickly released and demagnetized through the conducting phase of the upper transistor of the bridge arm, effectively maintaining the normal operation of the synchronous motor.

[0024] (2) The following analysis is provided regarding the excitation control device and its usage method for synchronous motors, with application number 2019106755101:

[0025] The device in this application is designed based on the existing three-phase stator winding star connection permanent magnet synchronous motor drive module with MOSFETs as power transistors, assuming that there are no parasitic diodes in the MOSFETs (T1, T2, T3, T4, T5, T6), and the additional MOSFETs (T7, T8, T9, T10) are also assumed to be free of parasitic diodes. Specifically, the drain (D) of the additional MOSFET T8 is connected to the center point of the three-phase stator winding star connection, and the source (S) is connected to the negative terminal of the power supply (VDC1) that powers the drive module in the existing technology. The positive terminal of the power supply (VDC1) is disconnected from the power supply bus of the drive module in the existing technology, and a diode VD1 is connected in series with the positive terminal of the power supply (VDC1) and the power supply bus of the drive module in the existing technology. Between the power buses, the anode of diode VD1 is connected to the positive terminal of the power supply (VDC1), and the cathode of diode VD1 is connected to the power supply bus of the drive module in the prior art; an energy storage capacitor C2 is added, the negative terminal of capacitor C2 is connected to the positive terminal of the power supply (VDC1), and the positive terminal of capacitor C2 is connected to the drain (D) of the added MOSFET T7, the source (S) of MOSFET T9, and the source (S) of MOSFET T10; a power supply VDC2 is added, its positive terminal is connected to the drain (D) of MOSFET T10, and its negative terminal is connected to the positive terminal of the power supply (VDC1); the source (S) of MOSFET T7 is connected to the power supply bus of the drive module in the prior art; a diode VD2 is added, its anode is connected to the power supply bus of the drive module in the prior art, and its cathode is connected to the drain (D) of MOSFET T9;

[0026] The added MOSFET T8, together with the added MOSFET T9 and diode VD2, is used to store and demagnetize the reverse electromotive force in the three phases of the motor to capacitor C2 after the motor stops.

[0027] If the energy stored in capacitor C2 is insufficient, the control MOSFET T10 is turned on, and the power supply VDC2 replenishes the energy stored in capacitor C2. This technical solution is not within the scope of this application, so the solution of replenishing energy stored in capacitor C2 by power supply VDC2 will not be analyzed.

[0028] The added MOSFET T8, together with the added MOSFET T7, is used to turn on and turn off for a limited time when the motor starts. The energy stored in the capacitor C2 in series with the power supply (VDC1) is used to increase the starting voltage of the motor. All the upper arm MOSFETs in the bridge arm are controlled to conduct to allow current to flow through the corresponding phase. It is claimed that this method can achieve sequential excitation of the three phases of the motor, shorten the starting process of the synchronous motor, and improve the starting efficiency of the synchronous motor.

[0029] After the motor starts, the MOSFET T7 is turned off, and the power supply (VDC1) supplies power to the drive module through the diode VD1. It is claimed that the motor can run normally, but in fact it cannot run normally because the MOSFET in this application must not have parasitic diodes. Otherwise, its shutdown energy storage and demagnetization method will not work.

[0030] The specific analysis of this application is as follows:

[0031] ① Because parasitic diodes actually exist in MOSFETs due to manufacturing processes; therefore, during shutdown: when phase A is the reverse electromotive force generated by the turn-off of the corresponding lower-arm MOSFET T4, the current flows through the parasitic diode in the corresponding upper-arm MOSFET T1, and then through the parasitic diode in MOSFET T7 to charge the energy storage capacitor C2; when phase B is the reverse electromotive force generated by the turn-off of the corresponding lower-arm MOSFET T6, the current flows through the parasitic diode in the corresponding upper-arm MOSFET T3, and then through the parasitic diode in MOSFET T7 to charge the energy storage capacitor C2; when phase C is the reverse electromotive force generated by the turn-off of the corresponding lower-arm MOSFET T2, the current flows through the parasitic diode in the corresponding upper-arm MOSFET T5, and then through the parasitic diode in MOSFET T6... The parasitic diode in MOSFET T7 provides freewheeling current to charge the energy storage capacitor C2. As is well known to those skilled in the art, not all three bridge arms stop when the corresponding phase is energized after the lower MOSFET is turned on. Instead, some bridge arms stop when the upper MOSFET is turned on, and some when the lower MOSFET is turned on. Therefore, during shutdown, the reverse electromotive force generated in the corresponding phase when the lower MOSFET is turned on is actually added in series with the reverse electromotive force generated in the corresponding phase when the upper MOSFET is turned on. This added current then flows through the parasitic diode in the upper MOSFET when the lower MOSFET is turned on, and then through the parasitic diode in MOSFET T7 to charge the energy storage capacitor C2. After passing through capacitor C1 and VDC, the freewheeling current from the parasitic diode in the lower MOSFET when the upper MOSFET is turned on forms the release and charging circuit. Note: The above analysis of shutdown occurs naturally without MOSFET control.

[0032] ② Assuming there are no parasitic diodes in the MOSFET, analyze the usage of the corresponding device:

[0033] Step two of the method for using the corresponding device states that "when the synchronous motor needs to be energized and started: the microcontroller controls MOSFETs T1, T3, and T5 to be turned on, while MOSFETs T2, T4, T6, T8, T9, and T10 remain off. At the same time, the microcontroller controls MOSFET T7 to be turned on for 1 to 2 seconds and then off, using the energy in capacitor C2 for electrical excitation. After excitation is completed, the motor is ready to start." Since MOSFET T8 is off, it is impossible for current to flow through the three phases to form a magnetic field. Even if MOSFET T8 is turned on, the magnetic field formed by current flowing through the three phases would be a fixed magnetic field, not a rotating magnetic field. This fixed magnetic field is not the rotating magnetic field required for starting. However, the device claims that by applying a higher-than-normal driving voltage to the two ends of the motor windings, sequential excitation of the three phases of the motor is achieved. Those skilled in the art truly do not know how this effect is achieved.

[0034] Step two of the usage method for the corresponding device states: "When the synchronous motor stops: the microcontroller controls MOSFETs T8 and T9 to turn on, then sequentially controls MOSFETs T1 to turn on for 0.3s~0.6s, T3 to turn on for 0.3s~0.6s, and T5 to turn on for 0.3s~0.6s. The microcontroller keeps MOSFETs T2, T4, T6, T7, and T10 in the off state. When the remaining energy feedback is complete, the microcontroller controls MOSFETs T8 and T9 to turn off." The question is:

[0035] Assuming that the reverse electromotive force (EMF) generated during shutdown in all three phases is turned off when the lower transistor of the corresponding bridge arm is turned on, the upper transistor of the corresponding bridge arm controlled by the release of the reverse EMF in the corresponding phase is turned on within a time set to 0.3s to 0.6s. If the reverse EMF is released before the time is over within 0.3s to 0.6s, since the power supply VDC1 acts on the drain (D) of the MOSFET through diode VD1, the voltage between the drain (D) and source (S) of the MOSFET in the bridge arm will point towards the drain (D) during the remaining time. This will cause the power supply VDC1 to flow into the released reverse EMF, thus setting the turn-on time. If the on-time is too long, a conduction current will be generated in the remaining time after complete release. If the set on-time is reduced, the reverse electromotive force in the release phase will not be completely released after the MOSFET is turned off at the designated time, meaning the residual magnetism will not reach the safe range. Therefore, the timing control of the corresponding MOSFET to turn on after shutdown is unreliable. Furthermore, the application uses sequential control of MOSFET T1 to turn on for 0.3s to 0.6s, MOSFET T3 to turn on for 0.3s to 0.6s, and MOSFET T5 to turn on for 0.3s to 0.6s, which prolongs the overall release and demagnetization time after shutdown, failing to achieve the desired rapid release.

[0036] Since in a real three-phase system, it is impossible for all the reverse electromotive forces (EMFs) to be generated when the lower transistor of the corresponding bridge arm is turned on and then shut down, there must be a corresponding phase in the three-phase system that generates a reverse EMF when the upper transistor of the bridge arm is turned on and then shut down. When the upper transistor of the bridge arm is turned on again, the corresponding phase that generates the reverse EMF cannot release the reverse EMF in that phase. Instead, the power supply VDC1 superimposes this reverse EMF and generates an inrush current in that phase, thereby damaging the conducting MOSFET.

[0037] ③ Since the MOSFETs used in the three-phase drive modules of existing permanent magnet synchronous motors are high-power MOSFETs, which actually have parasitic diodes, the usage method of the corresponding device in this application is analyzed in the case of parasitic diodes in the MOSFETs:

[0038] Step two of the usage method for the corresponding device states: "When the synchronous motor stops: the microcontroller controls MOSFETs T8 and T9 to turn on, then sequentially controls MOSFETs T1 to turn on for 0.3s~0.6s, T3 to turn on for 0.3s~0.6s, and T5 to turn on for 0.3s~0.6s. The microcontroller keeps MOSFETs T2, T4, T6, T7, and T10 in the off state. When the remaining energy feedback is complete, the microcontroller controls MOSFETs T8 and T9 to turn off." The question is:

[0039] Because of the parasitic diode in MOSFET T7, controlling MOSFET T9 to conduct after shutdown has no effect, since the freewheeling current reaching the bus at this time charges the energy storage capacitor C2 through the parasitic diode in MOSFET T7. If there were no parasitic diode in MOSFET T7, the freewheeling current reaching the bus after shutdown would charge the energy storage capacitor C2 through diode VD2 and the parasitic diode in MOSFET T9. Controlling the conduction of MOSFET T9 would only short-circuit the already conducting parasitic diode on the MOSFET, allowing the freewheeling current generated by the conducting parasitic diode to flow through the conduction path controlled by the MOSFET, thus preventing power consumption on the parasitic diode.

[0040] To control the conduction of MOSFETs T1, T3, and T5, the parasitic diodes already conducting on these MOSFETs are simply shorted, allowing the freewheeling current generated by the conducting diodes to flow through the conduction path controlled by the MOSFETs, thus preventing power consumption on the parasitic diodes. Similarly, to control the conduction of MOSFET T8, the parasitic diode already conducting on this MOSFET is simply shorted, allowing the freewheeling current generated by the conducting diodes to flow through the conduction path controlled by the MOSFETs, thus preventing power consumption on the parasitic diodes.

[0041] Because the parasitic diodes in the MOSFETs act as freewheeling diodes, they sequentially control the conduction of MOSFET T1 for 0.3s to 0.6s, MOSFET T3 for 0.3s to 0.6s, and MOSFET T5 for 0.3s to 0.6s. After the conduction of MOSFETs T3 and T5, there is a high probability that the power supply will flow to the corresponding phase.

[0042] Therefore: Due to the presence of parasitic diodes in the MOSFETs: when the power is off, controlling the MOSFET to conduct only shorts the corresponding parasitic diode that is already conducting, allowing the freewheeling current generated by the conducting diode to flow through the conduction path controlled by the MOSFET, thus preventing power consumption on the parasitic diode; and when the reverse electromotive force has not finished releasing, turning off the turned-on MOSFET cannot stop the continued release of the reverse electromotive force, and the freewheeling current will continue through the parasitic diode in the MOSFET; even if the MOSFET is not controlled to conduct after power is off, the reverse electromotive force will still be released naturally through the parasitic diode in the MOSFET for energy storage and demagnetization. Therefore, when the MOSFETs T1, T3, and T5 are turned on in sequence, there is a high probability that the power supply will flow to the corresponding phase.

[0043] If the parasitic diodes of the MOSFETs are not considered to provide freewheeling, the reverse electromotive force in the three phases will not be released when the microcontroller loses power and stops, meaning that energy storage and demagnetization will be impossible.

[0044] (3) For application number 2019106755277, entitled "Device and Demagnetization Method for Residual Magnetism Elimination via MOSFET Freewheeling in Permanent Magnet Synchronous Motors", the analysis is as follows:

[0045] The device in this application is designed based on the existing three-phase stator winding star-connected permanent magnet synchronous motor drive module with MOSFETs as power transistors, assuming that there are no parasitic diodes in the MOSFETs (Q1, Q2, Q3, Q4, Q5, Q6), and the additional MOSFETs (Q7, Q8) are also assumed to be free of parasitic diodes; the specific device design is as follows:

[0046] Disconnect the positive terminal of the power supply (VDC1) from the power supply bus of the existing drive module. Add a diode VD1 connected in series between the positive terminal of the power supply (VDC) and the power supply bus of the existing drive module. The anode of diode VD1 is connected to the positive terminal of the power supply (VDC), and the cathode of diode VD1 is connected to the power supply bus of the existing drive module. Add an energy storage capacitor C2. The negative terminal of capacitor C2 is connected to the positive terminal of the power supply (VDC), and the positive terminal of capacitor C2 is connected to the drain (D) of the added MOSFET Q7. The source (S) of MOSFET Q7... Connect to the existing drive module power supply bus; connect the drain (D) of the added MOSFET Q8 to the center point of the star connection of the three-phase stator winding; add resistor R1, diode VD2 and amplifier circuit, connect the cathode of diode VD2 to the source (S) of MOSFET Q8, connect the anode of diode VD2 in series with resistor R1 to the negative terminal of the power supply (VDC), and lead a wire from the connection line between the anode of diode VD2 and resistor R1 to the input terminal of the amplifier circuit; add a voltage divider circuit from the positive terminal of capacitor C2 to the negative terminal of the power supply (VDC);

[0047] in:

[0048] The voltage divider circuit is used to determine whether demagnetization is complete after shutdown by measuring the rate of change of the sampling voltage between the positive terminal of capacitor C2 and ground when the power supply (VDC) is less than or equal to 48V.

[0049] The resistor R1 and the amplifier circuit are used to determine whether demagnetization is complete after shutdown when the power supply (VDC) is greater than 48V, by collecting the voltage through the resistor R1 and calculating the magnitude of the sampling current.

[0050] The added MOSFET Q7, together with the added MOSFET Q8, is used to store and demagnetize the reverse electromotive force in the three phases of the motor to capacitor C2 after the motor stops.

[0051] The added MOSFET Q7 is also used to turn on and turn off for a limited time when the motor starts. The energy stored in the capacitor C2 is added in series with the power supply (VDC) to increase the starting voltage of the motor. The application does not describe the excitation control method of the MOSFET in the bridge arm of the drive module when the motor starts. Therefore, the applicant believes that it is to maintain the control method of sequential excitation of the three phases of the motor in the prior art. Due to the high voltage applied, the starting process of the synchronous motor is shortened and the starting efficiency of the synchronous motor is improved.

[0052] After the motor starts, MOSFET Q7 is turned off, and power is supplied to the drive module by the power supply (VDC) through diode VD1, and the motor runs normally.

[0053] In fact, the motor in this application cannot operate effectively because the MOSFET in this application must not have parasitic diodes; otherwise, its shutdown energy storage and demagnetization methods will not be valid.

[0054] The specific analysis of this application is as follows:

[0055] This application aims to overcome the unreliability issue in the excitation control device and usage method for synchronous motors (application number 2019106755101), where the upper transistors of the bridge arms are sequentially and periodically turned on to release the corresponding reverse electromotive force after the motor stops. Therefore, after the motor stops, the upper MOSFETs of the corresponding bridge arms are sequentially and in real-time turned on, so that the reverse electromotive force generated on the corresponding phase is fed through the conducting MOSFET and then through the controlled conducting MOSFET Q7 to charge the energy storage capacitor C2.

[0056] When the voltage of the power supply VDC is greater than 48V, when the current of the reverse electromotive force release phase is less than or equal to the first preset value, it is determined that the release and demagnetization of the reverse electromotive force release phase is completed. The corresponding conducting MOSFET of the release phase is turned off, and the upper MOSFET of the next corresponding bridge arm is controlled to turn on. The reverse electromotive force generated on the phase is charged to the energy storage capacitor C2 through the conducting MOSFET and the controlled conducting MOSFET Q7. When the current of the reverse electromotive force release phase is less than or equal to the first preset value, it is determined that the release and demagnetization of the reverse electromotive force release phase is completed. The corresponding conducting MOSFET is turned off. This process is repeated until the release of all three phases is completed. Then the conducting MOSFETs Q7 and Q8 are turned off, and the entire process of eliminating residual magnetism is determined to be complete.

[0057] When the voltage of the power supply VDC is less than or equal to 48V, the system monitors the charging of capacitor C2 by the phase of the reverse electromotive force release. When the rate of change of C2 relative to ground is less than the second preset value, the release and demagnetization of the phase of the reverse electromotive force release is considered complete. The corresponding MOSFET of the release phase is turned off, and the upper MOSFET of the next corresponding bridge arm is turned on. The reverse electromotive force generated on this phase is then fed into the energy storage capacitor C2 through the conducting MOSFET and the controlled conducting MOSFET Q7. When the system monitors the charging of capacitor C2 by the phase of the reverse electromotive force release, and the rate of change of C2 relative to ground is less than the second preset value, the release and demagnetization of the phase of the reverse electromotive force release is considered complete. The corresponding MOSFET is turned off, and so on. After the release of all three phases is completed, the conducting MOSFETs Q7 and Q8 are turned off, and the entire process of eliminating residual magnetism is considered complete.

[0058] In fact, because the parasitic diodes in the MOSFETs act as freewheeling diodes, they sequentially monitor the release current or charging voltage in real time to control the MOSFETs Q1, Q3, and Q5 to turn on or off. After the MOSFETs Q3 and Q5 are turned on, there is a high probability that the power supply will flow to the corresponding phase. This is because the sampling can only be done after the MOSFETs are turned on, and the decision to turn off the turned-on MOSFETs Q3 and Q5 is based on the monitoring results.

[0059] In this application, after controlling MOSFETs Q1, Q3, and Q5 to turn on, if a monitoring error occurs, the upper MOSFET of the bridge arm that is turned on will be turned off late, which will also cause the power supply to flow to the corresponding phase. Therefore, after the motor stops, the application adopts the method of sequentially and in real time controlling the upper MOSFET of the corresponding bridge arm to turn on, so that the reverse electromotive force generated on the corresponding phase will charge the energy storage capacitor C2 through the conducting MOSFET and the controlled conducting MOSFET Q7. In addition to the problem that the release and demagnetization time is prolonged after the machine stops, it does not effectively solve the unreliability problem when controlling the upper MOSFET of the bridge arm to turn on and release the corresponding reverse electromotive force.

[0060] Regarding the application's claim that when the DC power supply VDC voltage is greater than 48V, if a voltage sampling method is used, the amplitude change of the sampled voltage relative to the DC power supply VDC voltage will be insignificant, ultimately leading to insufficient judgment accuracy. Therefore, this application only uses the voltage sampling method when the DC power supply VDC voltage is less than or equal to 48V. Similarly, when the DC power supply VDC voltage is less than or equal to 48V, if a current sampling method is used, the judgment accuracy will be insufficient due to the small sampled current. Therefore, this application only uses the current sampling method when the DC power supply VDC voltage is greater than 48V. However, as is well known to those skilled in the art, during the shutdown freewheeling process, once the current in the freewheeling circuit equals zero or the voltage on the charging and energy storage capacitor remains constant, the freewheeling completely ends. Therefore, the applicant believes that the fundamental reason why the monitoring and elimination of residual magnetism cannot be effectively unified into a voltage sampling method is that it cannot eliminate the influence of the power supply voltage on the sampling voltage divider circuit, thus causing the DC power supply... When the VDC voltage is greater than 48V, the microcontroller cannot effectively acquire the voltage change on the energy storage capacitor. The fundamental reason why the monitoring and elimination of residual magnetism cannot be effectively unified into the sampling current method is that the resistance value of the current sampling resistor cannot be large. A large resistance value not only affects the effective energy storage of the freewheeling current, but also the large current generated by the freewheeling current when the DC power supply VDC voltage is greater than 48V (as claimed in this application) will cause the microcontroller to be unable to effectively acquire the voltage change generated by the large current on the sampling resistor. However, if the resistance value is large, the small current generated by the freewheeling current when the DC power supply VDC voltage is less than or equal to 48V (as claimed in this application) can be effectively acquired by the microcontroller on the sampling resistor. Furthermore, the applicant believes that when using the sampling current method, that is, using the sampling resistor to acquire the freewheeling current, if the current is zero or close to zero, it can be considered that the elimination of residual magnetism during shutdown is complete.

[0061] As for other issues in this application, they are the same as those in application number 2019106755101, entitled "Excitation Control Device and Usage Method of Synchronous Motor," and will not be elaborated further. If the parasitic diodes of the MOSFETs are not considered for their freewheeling function, once the microcontroller loses power and stops, the reverse electromotive force in the three phases will not be released, meaning energy storage and demagnetization will be impossible.

[0062] (4) Regarding application number 2019106755296, entitled "Dietzon Freewheeling Device for Eliminating Residual Magnetism in Permanent Magnet Synchronous Motor and its Usage Method," the specific analysis is as follows:

[0063] This application addresses the issues of unreliability and prolonged release time in applications 2019106755101 and 2019106755277, specifically the failure to release the back electromotive force (EMF) when the MOSFET is turned on after the motor stops, and the inability to release the back EMF in the three phases when the microcontroller loses power. Therefore, after the motor stops, a diode freewheeling high-voltage energy storage method is used to eliminate residual magnetism. The device in this application incorporates the existing three-phase stator winding star-connected permanent magnet synchronous motor drive module, which uses MOSFETs as power transistors, and assumes that the MOSFETs (Q1, Q2, Q3, Q4, Q5, Q6) do not have parasitic diodes. The added MOSFET Q7 is also assumed to be free of parasitic diodes. The specific device scheme is as follows:

[0064] Disconnect the positive terminal of the power supply (VDC) from the existing drive module power supply bus. Add a diode VD4 connected in series between the positive terminal of the power supply (VDC) and the existing drive module power supply bus. Connect the anode of diode VD4 to the positive terminal of the power supply (VDC) and the cathode of diode VD4 to the existing drive module power supply bus. Add an energy storage capacitor C2, with its negative terminal connected to the positive terminal of the power supply (VDC) and its positive terminal connected to the drain (D) of the added MOSFET Q7. Connect the source (S) of MOSFET Q7 to the existing drive module power supply bus. Add diodes VD1, VD2, and VD3. The anode of diode VD1... The source (S) of MOSFET Q1 is connected to the source, and the cathode is connected to the positive terminal of capacitor C2; the anode of diode VD3 is connected to the source (S) of MOSFET Q5, and the cathode is connected to the positive terminal of capacitor C2; the anode of diode VD2 is connected to the source (S) of MOSFET Q6, and the cathode is connected to the drain (D) of MOSFET Q6. Analysis shows that the above circuit can only be used in existing drive modules, stopping the circuit when MOSFETs Q4, Q2, and Q3 are energized and conducting. The reverse electromotive force generated by phases A, B, and C can then charge and demagnetize capacitor C2 through diodes VD1, VD2, and VD3. Stopping the circuit under other energized conditions is either partially or completely invalid.

[0065] In order to monitor whether demagnetization is complete after shutdown, the application adopted two methods:

[0066] The first method is to add a voltage divider circuit from the positive terminal of capacitor C2 to the negative terminal of the power supply (VDC) when the power supply (VDC) is less than or equal to 48V. This circuit is used to determine whether demagnetization is complete after shutdown by measuring the rate of change of the sampling voltage between the positive terminal of capacitor C2 and ground.

[0067] The second method involves adding a resistor R1 and an amplifier circuit when the power supply (VDC) is greater than 48V. The added resistor R1 is connected in series with the branch of diode VD2, which is connected to MOSFET Q6 for freewheeling. That is, the anode of diode VD2 is connected in series with resistor R1 and then connected to the source (S) of MOSFET Q6. A wire is led from the connection line between the anode of diode VD2 and resistor R1 to the input terminal of the amplifier circuit. After shutdown, the voltage collected by resistor R1 is used to calculate the magnitude of the sampling current to determine whether demagnetization is complete.

[0068] The added MOSFET Q7 is used to turn on and turn off for a limited time when the motor starts. It uses the energy stored in the power supply (VDC) and capacitor C2 to increase the starting voltage of the motor. The drive module sequentially excites the three phases of the motor, shortens the starting process of the synchronous motor, and improves the starting efficiency of the synchronous motor.

[0069] In fact, the motor in this application cannot operate effectively because the MOSFET in this application must not have parasitic diodes; otherwise, its shutdown energy storage and demagnetization methods will not be valid.

[0070] After the MOSFET Q7 is turned off for a limited time, the power supply (VDC) supplies power to the drive module through diode VD4, and the motor runs normally.

[0071] In fact, the motor in this application also cannot operate effectively because the MOSFET in this application cannot have a parasitic diode; otherwise, its usage method is not valid (e.g., when the voltage of the DC power supply VDC is greater than 48V, the sampling current method cannot be used).

[0072] Regarding the application's claim that when the DC power supply VDC voltage is greater than 48V, if a voltage sampling method is used, the amplitude change of the sampled voltage relative to the DC power supply VDC voltage will be insignificant, ultimately leading to insufficient judgment accuracy. Therefore, this application only uses the voltage sampling method when the DC power supply VDC voltage is less than or equal to 48V. Similarly, when the DC power supply VDC voltage is less than or equal to 48V, if a current sampling method is used, the judgment accuracy will be insufficient due to the small sampled current. Therefore, this application only uses the current sampling method when the DC power supply VDC voltage is greater than 48V. However, as is well known to those skilled in the art, during the shutdown freewheeling process, once the current in the freewheeling circuit equals zero or the voltage on the charging and energy storage capacitor remains constant, the freewheeling completely ends. Therefore, the applicant believes that the fundamental reason why the monitoring and elimination of residual magnetism cannot be effectively unified into a voltage sampling method is that it cannot eliminate the influence of the power supply voltage on the sampling voltage divider circuit, thus causing the DC power supply... When the VDC voltage is greater than 48V, the microcontroller cannot effectively acquire the voltage change on the energy storage capacitor. The fundamental reason why the monitoring and elimination of residual magnetism cannot be effectively unified into the sampling current method is that the resistance value of the current sampling resistor cannot be large. A large resistance value not only affects the effective energy storage of the freewheeling current, but also the large current generated by the freewheeling current when the DC power supply VDC voltage is greater than 48V (as claimed in this application) will cause the microcontroller to be unable to effectively acquire the voltage change generated by the large current on the sampling resistor. However, if the resistance value is large, the small current generated by the freewheeling current when the DC power supply VDC voltage is less than or equal to 48V (as claimed in this application) can be effectively acquired by the microcontroller on the sampling resistor. Furthermore, the applicant believes that when using the sampling current method, that is, using the sampling resistor to acquire the freewheeling current, if the current is zero or close to zero, it can be considered that the elimination of residual magnetism during shutdown is complete.

[0073] Since the MOSFET in the drive module of this application is set to have no parasitic diode, the motor cannot actually operate normally. Of course, when a freewheeling diode is connected in parallel with the MOSFET, it is equivalent to the MOSFET in the drive module having a parasitic diode.

[0074] Based on the above analysis of the technical solutions of application numbers 2019106755101, 2019106755296, and 2019106755277, it is definitively determined that:

[0075] The above three invention patent applications filed on the same day are all impractical. They not only cannot effectively reproduce the technical solutions, but also prevent the motor from operating normally.

[0076] Meanwhile, the three technical solutions filed on the same day teach those skilled in the art that, if the power module of the permanent magnet synchronous motor with a star connection of the three-phase stator winding is kept unchanged in the prior art before the application date, the shutdown energy storage technology solution added in application number 2012202368353 cannot be used to achieve shutdown boost energy storage and demagnetization. Summary of the Invention

[0077] The purpose of this invention is to overcome the shortcomings of existing technologies and, while keeping the power drive module and its control method unchanged in the prior art for permanent magnet synchronous motors with three-phase stator winding star connection, propose a freewheeling energy storage demagnetizing device and its implementation method for permanent magnet synchronous motors. When the motor is stopped, it achieves: effective freewheeling voltage boosting and energy storage, and elimination of residual magnetism; and unifies the monitoring of the completion of residual magnetism elimination under different power supply voltage conditions into a single effective monitoring method.

[0078] To achieve the above objectives, the technical solution of the present invention is as follows:

[0079] A freewheeling energy storage demagnetizing device for a permanent magnet synchronous motor (PMSM) is provided. Based on the power drive module of a PMSM with a three-phase stator winding star connection, a freewheeling energy storage module and a unified monitoring module for monitoring the demagnetizing completion status by detecting changes in the voltage of the energy storage capacitor are added. The freewheeling energy storage module includes a MOSFET Q7, a diode VD, and a storage capacitor C2. The positive terminal of the power supply VDC is disconnected from the busbar supplying the power drive module. A diode VD is connected in series with the positive terminal of the power supply VDC and then connected to the busbar supplying the power drive module. The negative terminal of capacitor C2 is connected to... The positive terminal of the power supply VDC is connected to the circuit. The positive terminal of capacitor C2 is connected to the drain of MOSFET Q7. The source of MOSFET Q7 is connected to the cathode of diode VD. The gate of MOSFET Q7 is connected to the output of the microcontroller. The A / D input of the microcontroller is connected to the output of the monitoring module. The monitoring module directly samples the voltage change of capacitor C2 from both ends of capacitor C2, or indirectly obtains the voltage between the positive terminal of capacitor C2 and the negative terminal of power supply VDC. The voltage change of capacitor C2 is sampled after the voltage is regulated by a Zener diode to reduce the influence of power supply VDC voltage on the sampling accuracy.

[0080] The MOSFET Q7 mentioned above is an NMOS transistor with a parasitic diode.

[0081] The monitoring module described above includes a Zener diode DZ1, a switching transistor T1, a switching transistor T2, and resistors R1, R2, R3, R4, and R5. It is used to obtain the voltage between the positive terminal of capacitor C2 and the negative terminal of the power supply VDC, and indirectly sample the voltage after filtering out interference from the power supply VDC voltage with Zener diode DZ1. The cathode of Zener diode DZ1 is connected to the positive terminal of capacitor C2, and the anode of Zener diode DZ1 is connected to the high-potential terminal of switching transistor T1. The low-potential terminal of switching transistor T1 is connected in series with resistors R1 and R5. 2. Connect the resistor to the negative terminal of the power supply VDC. Connect the resistor R1 and R2 to the A / D input of the microcontroller. Connect the control terminal of the switching transistor T1 to the high potential terminal of the switching transistor T2 after connecting the resistor R3 in series. Connect the low potential terminal of the switching transistor T2 to the negative terminal of the power supply VDC. Connect the control terminal of the switching transistor T2 to one end of the resistor R4 and one end of the resistor R5 respectively. Connect the other end of the resistor R4 to the negative terminal of the power supply VDC. Connect the other end of the resistor R5 to the output of the microcontroller I / O.

[0082] The voltage regulation value of the Zener diode DZ1 should meet the following requirements: the voltage of the power supply VDC minus the voltage regulation value of the Zener diode DZ1 is greater than zero and less than or equal to 48V; preferably, the voltage regulation value of the Zener diode DZ1 is 10V lower than the voltage of the power supply VDC.

[0083] The monitoring module described above also includes a Zener diode DZ2, a switching transistor T3, an optocoupler U1, and resistors R6, R7, R8, R9, and R10. These components are used to obtain voltage from the positive terminal of capacitor C2 to the negative terminal of the power supply VDC. The Zener diode DZ2 is used to regulate and filter out interference from the power supply VDC voltage before indirect sampling. The cathode of the Zener diode DZ2 is connected to the positive terminal of capacitor C2, and the anode of the Zener diode DZ2 is connected to the collector of the phototransistor in the optocoupler U1. The emitter of the phototransistor in the optocoupler U1 is connected in series with resistors R6 and R7, and then connected to the power supply VDC. The negative terminal of C is connected to the microcontroller's A / D input via the connection between resistors R6 and R7. The anode of the LED in optocoupler U1 is connected to the microcontroller's power supply via resistor R8. The cathode of the LED in optocoupler U1 is connected to the high-potential terminal of switch T3. The low-potential terminal of switch T3 is connected to the negative terminal of power supply VDC. The control terminal of switch T3 is connected to one end of resistor R9 and one end of resistor R10. The other end of resistor R9 is connected to the negative terminal of power supply VDC. The other end of resistor R10 is connected to the microcontroller's I / O output.

[0084] The optocoupler U1 described above is a digital optocoupler. When the light-emitting diode in optocoupler U1 is energized, the phototransistor in optocoupler U1 is saturated and conducting. When the light-emitting diode in optocoupler U1 is not energized, the phototransistor in optocoupler U1 is cut off.

[0085] The voltage regulation value of the Zener diode DZ2 should meet the following requirements: the voltage of the power supply VDC minus the voltage regulation value of the Zener diode DZ2 is greater than zero and less than or equal to 48V; preferably, the voltage regulation value of the Zener diode DZ2 is 2V lower than the voltage of the power supply VDC.

[0086] The monitoring module described above also includes resistors R11, R12, R13, R14, R15, and R16, optocoupler U2, optocoupler U3, and switching transistor T4; used to directly obtain voltage from across capacitor C2 for sampling; the anode of the LED in optocoupler U2 is connected to the positive terminal of capacitor C2 via resistor R11; the cathode of the LED in optocoupler U2 is connected to the collector of the phototransistor in optocoupler U3; the emitter of the phototransistor in optocoupler U3 is connected to the negative terminal of capacitor C2; the anode of the LED in optocoupler U3 is connected to the microcontroller power supply via resistor R13. In U3, the cathode of the LED is connected to the high-potential terminal of the switching transistor T4, and the low-potential terminal of the switching transistor T4 is connected to the negative terminal of the power supply VDC. The control terminal of the switching transistor T4 is connected to one end of resistor R14 and one end of resistor R15, respectively. The other end of resistor R14 is connected to the negative terminal of the power supply VDC, and the other end of resistor R15 is connected to the output of the microcontroller I / O. In optocoupler U2, the collector of the phototransistor is connected to the microcontroller power supply after being connected in series with resistor R12, and the emitter of the phototransistor in optocoupler U2 is connected to the negative terminal of the power supply VDC after being connected in series with resistor R16. The emitter lead of the phototransistor in optocoupler U2 is connected to the A / D input of the microcontroller.

[0087] The optocoupler U3 mentioned above is a digital optocoupler.

[0088] The optocoupler U2 described above is a linear optocoupler.

[0089] To achieve the above objectives, another technical solution of the present invention

[0090] A method for implementing a freewheeling energy storage demagnetization device for a permanent magnet synchronous motor includes the following steps:

[0091] (1) For different power supply VDC voltages, the voltage change of monitoring capacitor C2 is used as the condition to determine whether demagnetization is complete. The microcontroller directly samples the voltage change of capacitor C2 from both ends of capacitor C2 through the monitoring module, or indirectly obtains the voltage between the positive terminal of capacitor C2 and the negative terminal of power supply VDC. The voltage change of capacitor C2 is sampled after the voltage is regulated by the Zener diode to reduce the influence of power supply VDC voltage on the sampling accuracy.

[0092] (2) When the machine is stopped:

[0093] The microcontroller outputs a turn-on control signal to the gate of MOSFET Q7. In the power drive module, a freewheeling diode provides current. Under the action of the freewheeling diode, the reverse electromotive force causes MOSFET Q7 to conduct in reverse. The reverse electromotive force generated by the three-phase windings is effectively connected by the corresponding freewheeling diode in the power drive module. The residual magnetism is eliminated by the conducting MOSFET Q7 and stored in capacitor C2.

[0094] The microcontroller outputs an enable control signal to control the monitoring module to enable voltage monitoring.

[0095] (3) Demagnetization is completed based on the trend of sampling voltage changes:

[0096] The microcontroller outputs a shutdown control signal to the gate of MOSFET Q7, turning off MOSFET Q7.

[0097] The microcontroller outputs a shutdown control signal to control the monitoring module to shut down voltage monitoring, effectively preventing the loss of charge on capacitor C2 and saving energy.

[0098] (4) When the demagnetization is confirmed to be complete, the parasitic diode in MOSFET Q7 takes over the conduction of MOSFET Q7 to participate in the freewheeling to eliminate residual magnetism and store energy in capacitor C2 until the freewheeling is completely finished.

[0099] (5) When the lag determines that demagnetization is complete, MOSFET Q7 becomes forward-biased during the lag time. However, since the power drive module uses a freewheeling diode for freewheeling, the charge stored in capacitor C2 will not be mistakenly transferred to the motor windings.

[0100] (6) During startup, the microcontroller controls the MOSFET Q7 to turn on and turn off for a limited time, thereby starting the motor with high-voltage excitation within the limited time.

[0101] Beneficial effects:

[0102] The present invention provides a freewheeling energy storage demagnetization device and its implementation method for a permanent magnet synchronous motor. This not only maintains the power drive module and its control method for the three-phase stator winding star connection of the permanent magnet synchronous motor unchanged in the prior art, thereby effectively keeping the motor working, but also achieves:

[0103] ① By directly sampling the voltage change of capacitor C2 from both ends, or indirectly obtaining the voltage between the positive terminal of capacitor C2 and the negative terminal of power supply VDC, and using a Zener diode to regulate the voltage and reduce the influence of power supply VDC voltage on the sampling accuracy, the voltage change of capacitor C2 is sampled. This effectively overcomes the defect in the prior art where the power supply voltage affects the accuracy of the microcontroller's sampling of the voltage change on the energy storage capacitor during shutdown and freewheeling energy storage demagnetization. Thus, it realizes the unification of the sampling method under different power supply voltages into an effective sampling voltage method, recognizes the completion of demagnetization with the same judgment accuracy, and performs corresponding control and prompts to the user.

[0104] ② The monitoring module is in a closed state and not powered during periods when it is not monitoring changes in the voltage of the energy storage capacitor, which effectively prevents the loss of charge on capacitor C2 and saves energy;

[0105] ③ Because the reverse electromotive force generated during shutdown is carried over by a freewheeling diode in the power drive module, the reverse electromotive force generated in the three-phase windings of the motor can effectively carry over and store energy and eliminate residual magnetism when the motor stops in any operating state. Furthermore, if there is an error in determining that demagnetization is complete: if it causes a delayed determination that demagnetization is complete and the MOSFET Q7 is turned off, there will be no reverse current flowing into the motor windings; if it causes an advanced determination that demagnetization is complete and the MOSFET Q7 is turned off, because there is a parasitic diode in the MOSFET Q7, the parasitic diode in the MOSFET Q7 will take over its conduction and participate in the freewheeling to eliminate residual magnetism and store energy in the energy storage capacitor until the freewheeling is completely finished.

[0106] ④ Because the reverse electromotive force generated during shutdown is carried by the freewheeling diode in the power drive module, and there is a parasitic diode in MOSFET Q7, once the microcontroller loses power and shuts down, the reverse electromotive force in the three phases will still carry the current through the freewheeling diode in the power drive module and the parasitic diode in MOSFET Q7 to charge capacitor C2 and eliminate residual magnetism until the freewheeling ends.

[0107] ⑤ When the machine is stopped, the MOSFET Q7 is turned on to allow freewheeling. The main purpose is to reduce the burden on the parasitic diode in the MOSFET Q7 when it is used for freewheeling. Of course, the freewheeling of the MOSFET Q7 can effectively increase the voltage on the capacitor. Attached Figure Description

[0108] Figure 1 This is a schematic diagram of the power drive module of a permanent magnet synchronous motor with a star-connected three-phase stator winding in the prior art.

[0109] Figure 2 This is a schematic diagram of the principle of a permanent magnet synchronous motor freewheeling energy storage demagnetization device based on monitoring the voltage change of the energy storage capacitor in this invention.

[0110] Figure 3 for Figure 2 A schematic diagram of the circuit principle of the first embodiment of the monitoring module;

[0111] Figure 4 for Figure 2 A schematic diagram of the circuit principle of the second embodiment of the monitoring module;

[0112] Figure 5 for Figure 2 A schematic diagram of the circuit principle of the third embodiment of the monitoring module;

[0113] Figure 6This is a schematic diagram of the principle of a permanent magnet synchronous motor freewheeling energy storage demagnetization device based on monitoring the change of current in the charging circuit of the energy storage capacitor in this invention.

[0114] In the diagram: Q1, Q2, Q3, Q4, Q5, Q6 are power drive transistors; VDC is the power supply; C1, C2, C3 are capacitors; VCC+ is the positive terminal of the DC power supply; VCC_ is the negative terminal of the DC power supply; Q7 is a MOSFET; DZ1 and DZ2 are Zener diodes; T1, T2, T3, T4, T8 are switching transistors; U1, U2, U3, U4 are optocouplers; R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, R19 are resistors; VD, VD1, VD2, VD3 are diodes. Detailed Implementation

[0115] like Figure 1 As shown, power drive transistors Q1, Q2, Q3, Q4, Q5, and Q6 are six power drive transistors with freewheeling diodes on the bridge arm of the power drive module of a permanent magnet synchronous motor with a star-connected three-phase stator winding in the prior art. They are NMOS transistors or N-type IGBT modules. The power supply VDC is the DC power supply used in the prior art to normally power the power drive module of the permanent magnet synchronous motor with a star-connected three-phase stator winding. The capacitor C1 is the capacitor used in the prior art to filter the power supply VDC. The output terminals of the microcontroller D1, D2, D3, D4, D5, and D6 are connected to the gates (control terminals) of the corresponding power drive transistors Q1, Q2, Q3, Q4, Q5, and Q6, respectively, and it is assumed that the negative terminal of the microcontroller's operating power supply is connected to the negative terminal of the power supply VDC. The power drive module is used to drive the permanent magnet synchronous motor.

[0116] like Figure 1 , Figure 2 , Figure 3 Figure 4 and Figure 5As shown, this invention discloses a freewheeling energy storage demagnetizing device for a permanent magnet synchronous motor based on monitoring changes in the energy storage capacitor voltage. It adds a freewheeling energy storage module and a unified monitoring module for monitoring the demagnetizing completion status by monitoring changes in the energy storage capacitor voltage, based on the power drive module of a permanent magnet synchronous motor with a three-phase stator winding star connection. The freewheeling energy storage module includes a MOSFET Q7, a diode VD, and an energy storage capacitor C2. The positive terminal of the power supply VDC is disconnected from the busbar supplying the power drive module. A diode VD is connected in series with the positive terminal of the power supply VDC and then connected to the busbar supplying the power drive module. Online; the negative terminal of capacitor C2 is connected to the positive terminal of power supply VDC, the positive terminal of capacitor C2 is connected to the drain of MOSFET Q7, the source of MOSFET Q7 is connected to the cathode of diode VD, and the gate of MOSFET Q7 is connected to the output of the microcontroller; the A / D input of the microcontroller is connected to the output of the monitoring module. The monitoring module directly samples the voltage change of capacitor C2 from both ends of capacitor C2, or indirectly obtains the voltage between the positive terminal of capacitor C2 and the negative terminal of power supply VDC. The voltage change of capacitor C2 is sampled after the voltage is regulated by a Zener diode to reduce the influence of power supply VDC voltage on the sampling accuracy.

[0117] The microcontroller is equipped with a program module for controlling the on / off state of the MOSFET Q7 and the on / off state of the monitoring module, as well as a program module for voltage sampling, calculating the rate of change, and judging the corresponding values. It also includes an output terminal that is compatible with the connection of the MOSFET Q7, and a control output terminal and an A / D input terminal that are connected to the monitoring module.

[0118] The MOS transistor Q7 is an NMOS transistor with a parasitic diode (the existence of a parasitic diode should not be mentioned, but since three inventions filed on the same day in the background art identify MOS transistors without parasitic diodes, this application makes a special mention of it to distinguish them).

[0119] The capacitor C2 is used for energy storage. It is charged and stored when the motor stops and the residual magnetism is eliminated by the follow current. When the motor starts, it is superimposed with the power supply VDC voltage to apply high voltage to the bus of the power drive module of the permanent magnet synchronous motor with star connection of three-phase stator winding, so that the motor starts under high voltage, shortens the starting process and improves the starting efficiency.

[0120] The diode VD is used to supply power from the power supply VDC to the bus of the power drive module when the motor is running normally, and to prevent the freewheeling current from directly forming a loop from the power supply VDC when the motor is stopped.

[0121] When the machine stops, the electromotive force generated in the three-phase winding is led to the bus via the corresponding freewheeling diode in the power drive module. The microcontroller controls the MOSFET Q7 to conduct, which is reverse conduction. The electromotive force generated in the three-phase winding is freewheeled to the bus via the corresponding freewheeling diode in the power drive module. The freewheeling current from the conducting MOSFET Q7 is directed to the capacitor C2 for charging and demagnetizing.

[0122] When the machine stops, if the microcontroller keeps the control MOSFET Q7 off, the electromotive force generated in the three-phase windings will continue to the bus via the corresponding freewheeling diode in the power drive module, and the freewheeling current from the parasitic diode in MOSFET Q7 will charge and demagnetize capacitor C2.

[0123] When the system stops, the microcontroller controls MOSFET Q7 to turn on. During the process of charging and demagnetizing capacitor C2 by freewheeling current from the turned MOSFET Q7, the microcontroller samples the voltage on capacitor C2 through the monitoring module and calculates the rate of change to determine whether demagnetization is complete. When the rate of change is less than the set value, demagnetization is considered complete, and the microcontroller controls MOSFET Q7 to turn off. The parasitic diode in MOSFET Q7 continues to participate in freewheeling current to charge capacitor C2 until the freewheeling current ends and demagnetization is complete.

[0124] During startup, the microcontroller controls MOSFET Q7 to turn on and sets a time-limited turn-off. Within this time limit, the voltage across capacitor C2 is superimposed with the power supply VDC voltage, which then applies high voltage to the bus supplying power to the power drive module of the three-phase stator winding star-connected permanent magnet synchronous motor via the turned-on MOSFET Q7. This high voltage then excites and starts the three-phase motor. After MOSFET Q7 is turned off, power is supplied to the power drive module via diode VD, and the motor operates normally. The time-limited turn-off period for MOSFET Q7 is set to 0.5S to 1S, as described in existing technologies.

[0125] Because the reverse electromotive force generated during shutdown still drives the freewheeling diode in the power drive module using existing technology, it can effectively store energy and demagnetize regardless of whether the power is on or off. Even if there is an error in the monitored completion of residual magnetization removal, resulting in actual demagnetization being completed while MOSFET Q7 is still conducting, no reverse current flow will occur. Furthermore, because MOSFET Q7 contains a parasitic diode, even if there is an error in the monitored completion of residual magnetization removal, resulting in incomplete demagnetization, the controlled conduction... When MOSFET Q7 is turned off, although MOSFET Q7 is off, the parasitic diode in MOSFET Q7 will continue to participate in freewheeling energy storage and demagnetization until the freewheeling ends and demagnetization is complete. When the machine stops, it can not only effectively store high voltage energy to eliminate residual magnetism, but also start high voltage excitation during startup, without affecting the normal operation of the motor. In addition, once the microcontroller loses power and stops, the reverse electromotive force in the three phases will still charge the energy storage capacitor and eliminate residual magnetism through the freewheeling diode in the power drive module and the parasitic diode in MOSFET Q7 until the freewheeling ends and demagnetization is complete.

[0126] like Figure 3As shown, the first embodiment of the monitoring module circuit obtains voltage from the positive terminal of capacitor C2 to the negative terminal of power supply VDC, and indirectly samples the voltage after filtering out interference from power supply VDC voltage with Zener diode DZ1. The monitoring module includes Zener diode DZ1, switching transistors T1 and T2, resistors R1, R2, R3, R4, and R5. The cathode of Zener diode DZ1 is connected to the positive terminal of capacitor C2, and the anode of Zener diode DZ1 is connected to the high-potential terminal of switching transistor T1. The low-potential terminal of switching transistor T1 is connected in series with... Resistors R1 and R2 are connected to the negative terminal of the power supply VDC. A lead is then connected from the connection point of resistors R1 and R2 to the A / D input of the microcontroller. The control terminal of switch T1 is connected in series with resistor R3 and then to the high potential terminal of switch T2. The low potential terminal of switch T2 is connected to the negative terminal of the power supply VDC. The control terminal of switch T2 is connected to one end of resistor R4 and one end of resistor R5. The other end of resistor R4 is connected to the negative terminal of the power supply VDC. The other end of resistor R5 is connected to the output of the microcontroller's I / O.

[0127] The aforementioned switching transistor T1 can be a PNP type switching transistor, a PMOS type, or a P-type IGBT type. When T1 is a PNP type switching transistor, the high-potential terminal is the emitter, the low-potential terminal is the collector, and the control terminal is the base. When T1 is a PMOS type switching transistor, the high-potential terminal is the source, the low-potential terminal is the drain, and the control terminal is the gate. When T1 is a P-type IGBT type switching transistor, the high-potential terminal is the emitter, the low-potential terminal is the collector, and the control terminal is the gate. Preferably, T1 is a PNP type switching transistor.

[0128] The aforementioned switch T2 can be an NPN transistor, an NMOS transistor, or an N-type IGBT. When switch T2 is an NPN transistor, the high-potential terminal is the collector, the low-potential terminal is the emitter, and the control terminal is the base. When switch T2 is an NMOS transistor, the high-potential terminal is the drain, the low-potential terminal is the source, and the control terminal is the gate. When switch T2 is an N-type IGBT, the high-potential terminal is the collector, the low-potential terminal is the emitter, and the control terminal is the gate. Preferably, switch T2 is an NPN transistor.

[0129] The voltage regulation value of Zener diode DZ1 should meet the following requirements: the voltage of the power supply VDC minus the voltage regulation value of Zener diode DZ1 should be greater than zero and less than or equal to 48V. Considering that when the capacitor C2 used for energy storage stops without voltage, it is possible to promptly and effectively control the switching transistor T1 in the monitoring module to saturate and conduct. Therefore, the voltage regulation value of Zener diode DZ1 is not selected to be equal to the voltage of the power supply VDC. However, the closer the voltage regulation value of Zener diode DZ1 is to the voltage of the power supply VDC, the smaller the impact of the power supply VDC voltage on the monitoring effect. In order to promptly and effectively control the switching transistor T1 in the monitoring circuit to saturate and conduct when the capacitor C2 stops without voltage, the preferred voltage regulation value of Zener diode DZ1 is the voltage regulation value plus the basic voltage required to effectively control the switching transistor T1 in the monitoring circuit to saturate and conduct, which is equal to the voltage of the power supply VDC. That is, it is preferable to choose the voltage regulation value of Zener diode DZ1 plus 10V to equal the voltage of the power supply VDC. If the voltage of the power supply VDC of the permanent magnet synchronous motor is less than or equal to 10V, Zener diode DZ1 can be removed.

[0130] The resistors R1 and R2 described above are connected in series to form a sampling circuit. The voltage change on capacitor C2 is obtained by voltage division and output to the microcontroller. That is, the microcontroller samples the voltage from resistor R2, which is the voltage divider formed by resistors R1 and R2 connected in series.

[0131] Resistor 4 and resistor R5 are limit / current limiting resistors for the control terminal of switch T2.

[0132] Resistor 3 is the limit / current limiting resistor for the control terminal of switch T1.

[0133] The working process of the circuit in the first embodiment of the monitoring module above is as follows:

[0134] When the system stops, the microcontroller controls MOSFET Q7 to turn on and outputs a high level to the control terminal of switch T2. Switch T2 then saturates and conducts. Since the voltage regulation value of Zener diode DZ1 is set to be 10V lower than the power supply VDC voltage, 10V is applied between the high potential terminal of switch T1 and the negative terminal of power supply VDC. This 10V is then sent to the control terminal of switch T1 via resistor R3, causing switch T1 to saturate and conduct. After conduction, capacitor C2 is charged, and the voltage across capacitor C2 is indirectly reflected across the series connection of resistors R1 and R2. The power supply VDC voltage only has a 10V effect on the series connection of resistors R1 and R2, thus effectively controlling the voltage across the circuit. The DZ1 Zener diode eliminates the defect of insignificant voltage change on the sampling capacitor C2 of the microcontroller due to the power supply VDC voltage. It effectively expands the range of voltage change on capacitor C2 during the power-off freewheeling process sampled by the microcontroller through resistor R2. Thus, regardless of whether the power supply VDC is less than or equal to 48V or greater than 48V, the microcontroller can effectively calculate the rate of change by sampling the voltage change on capacitor C2 during the power-off freewheeling process through resistor R2. When the rate of change is detected to be close to zero or less than the set value, demagnetization is considered complete, and the MOSFET Q7 is turned off. The parasitic diode in MOSFET Q7 continues to flow to capacitor C2 to store energy and eliminate residual magnetism until the freewheeling ends and demagnetization is complete.

[0135] Once demagnetization is confirmed to be complete, the MOS transistor Q7, which is in control, is turned off, and a low level is output to the control terminal of the switching transistor T2. Switching transistor T2 is turned off, and switching transistor T1 is turned off. The monitoring module of the circuit in the first embodiment is not powered on for energy saving.

[0136] like Figure 4 As shown, the second embodiment of the monitoring module circuit obtains voltage from the positive terminal of capacitor C2 to the negative terminal of power supply VDC, and indirectly samples the voltage after filtering out interference from power supply VDC voltage with Zener diode DZ2. The monitoring module includes Zener diode DZ2, switching transistor T3, optocoupler U1, resistors R6, R7, R8, R9, and R10. The cathode of Zener diode DZ2 is connected to the positive terminal of capacitor C2, and the anode of Zener diode DZ2 is connected to the collector of the phototransistor in optocoupler U1. The emitter of the phototransistor in optocoupler U1 is connected in series with resistors R6 and R10. 7 is connected to the negative terminal of the power supply VDC. A lead is connected to the A / D input of the microcontroller from the connection between resistors R6 and R7. The anode of the LED in optocoupler U1 is connected to the microcontroller power supply after being connected in series with resistor R8. The cathode of the LED in optocoupler U1 is connected to the high potential terminal of switch T3. The low potential terminal of switch T3 is connected to the negative terminal of the power supply VDC. The control terminal of switch T3 is connected to one end of resistor R9 and one end of resistor R10 respectively. The other end of resistor R9 is connected to the negative terminal of the power supply VDC. The other end of resistor R10 is connected to the output of the microcontroller I / O.

[0137] The aforementioned switch T3 can be an NPN transistor, an NMOS transistor, or an N-type IGBT. When T3 is an NPN transistor, the high-potential terminal is the collector, the low-potential terminal is the emitter, and the control terminal is the base. When T3 is an NMOS transistor, the high-potential terminal is the drain, the low-potential terminal is the source, and the control terminal is the gate. When T3 is an N-type IGBT, the high-potential terminal is the collector, the low-potential terminal is the emitter, and the control terminal is the gate. Preferably, T3 is an NPN transistor.

[0138] The optocoupler U1 described above is a digital optocoupler. When the light-emitting diode in optocoupler U1 is energized, the phototransistor in optocoupler U1 is saturated and conducting. When the light-emitting diode in optocoupler U1 is not energized, the phototransistor in optocoupler U1 is cut off.

[0139] Resistor R8 is the current-limiting resistor for the light-emitting diode in optocoupler U1.

[0140] Resistors R9 and R10 are limit / current limiting resistors for the control terminal of switch T3.

[0141] The voltage regulation value of Zener diode DZ2 should meet the following requirements: the voltage of the power supply VDC minus the voltage regulation value of Zener diode DZ2 should be greater than zero and less than or equal to 48V. Considering that when the capacitor C2 used for energy storage is de-energized and shuts down, it can effectively and promptly turn on the phototransistor in optocoupler U1, the voltage regulation value of Zener diode DZ2 is not chosen to be equal to the voltage of the power supply VDC. However, the closer the voltage regulation value of Zener diode DZ2 is to the voltage of the power supply VDC, the smaller the impact of the power supply VDC voltage on the monitoring effect. In this embodiment, the voltage regulation value of Zener diode DZ2 is preferably less than 2V compared to the voltage of the power supply VDC.

[0142] The resistors R6 and R7 described above are connected in series to form a sampling circuit. The voltage change on capacitor C2 is obtained by voltage division and output to the microcontroller. That is, the microcontroller samples the voltage from resistor R7, which is the voltage divider formed by resistors R6 and R7 connected in series.

[0143] The working process of the second embodiment of the monitoring module described above is as follows:

[0144] When the system stops, the microcontroller controls the MOSFET Q7 to turn on, and then outputs a high level to the control terminal of the switching transistor T3. Switch T3 saturates and conducts, causing the LED in optocoupler U1 to emit light. The phototransistor in optocoupler U1 also saturates and conducts. This conduction charges capacitor C2, and the voltage across C2 is indirectly reflected across the series connection of resistors R6 and R7. The power supply VDC voltage is filtered out by the Zener diode DZ2, and the remaining portion is then applied across the series connection of resistors R6 and R7. This effectively filters out the influence of the power supply VDC voltage on the system's voltage regulation. The defect of insignificant voltage change on capacitor C2 sampled by the microcontroller is effectively addressed by expanding the range of the microcontroller's sampling of voltage change on capacitor C2 during the power-off freewheeling process via resistor R7. Thus, regardless of whether the power supply VDC is less than or equal to 48V or greater than 48V, the microcontroller can effectively calculate the rate of change by sampling the voltage change on capacitor C2 during the power-off freewheeling process via resistor R7. When the rate of change is detected to be close to zero or less than the set value, demagnetization is considered complete, and the MOSFET Q7 is turned off. The parasitic diode in MOSFET Q7 continues to provide freewheeling current to capacitor C2 for energy storage and removal of residual magnetism until the freewheeling ends and demagnetization is complete.

[0145] Once demagnetization is complete, the MOS transistor Q7, which is in control, is turned off, and a low level is output to the control terminal of the switching transistor T3. When the switching transistor T3 is turned off, the light-emitting diode in the optocoupler U1 is not energized, and the phototransistor in the optocoupler U1 is turned off. The monitoring module of the circuit in the second embodiment is not energized for energy saving.

[0146] like Figure 5As shown, the third embodiment of the monitoring module directly samples the voltage across capacitor C2 to eliminate the influence of the power supply VDC voltage on the insignificant voltage change across the microcontroller's sampling capacitor C2. The monitoring module includes resistors R11, R12, R13, R14, R15, and R16, optocouplers U2 and U3, and a switching transistor T4. The anode of the LED in optocoupler U2 is connected to the positive terminal of capacitor C2 via resistor R11. The cathode of the LED in optocoupler U2 is connected to the collector of the phototransistor in optocoupler U3. The emitter of the phototransistor in optocoupler U3 is connected to the negative terminal of capacitor C2. The anode of the LED in optocoupler U3... The collector of the phototransistor in optocoupler U2 is connected to the microcontroller power supply via a series resistor R13. The cathode of the LED in optocoupler U3 is connected to the high-potential terminal of the switching transistor T4, and the low-potential terminal of the switching transistor T4 is connected to the negative terminal of the power supply VDC. The control terminal of the switching transistor T4 is connected to one end of resistor R14 and one end of resistor R15, respectively. The other end of resistor R14 is connected to the negative terminal of the power supply VDC, and the other end of resistor R15 is connected to the output of the microcontroller I / O. The collector of the phototransistor in optocoupler U2 is connected to the microcontroller power supply via a series resistor R12, and the emitter of the phototransistor in optocoupler U2 is connected to the negative terminal of the power supply VDC via a series resistor R16. The emitter lead of the phototransistor in optocoupler U2 is connected to the A / D input of the microcontroller.

[0147] The aforementioned switching transistor T4 can be an NPN transistor, an NMOS transistor, or an N-type IGBT. When T4 is an NPN transistor, the high-potential terminal is the collector, the low-potential terminal is the emitter, and the control terminal is the base. When T4 is an NMOS transistor, the high-potential terminal is the drain, the low-potential terminal is the source, and the control terminal is the gate. When T4 is an N-type IGBT, the high-potential terminal is the collector, the low-potential terminal is the emitter, and the control terminal is the gate. Preferably, T4 is an NPN transistor.

[0148] The optocoupler U3 described above is a digital optocoupler. When the light-emitting diode in optocoupler U3 is energized, the phototransistor in optocoupler U3 is saturated and conducting. When the light-emitting diode in optocoupler U3 is not energized, the phototransistor in optocoupler U3 is cut off.

[0149] Resistor R13 is the current-limiting resistor for the light-emitting diode in optocoupler U3.

[0150] Resistors R14 and R15 are limit / current limiting resistors for the control terminal of switch T4.

[0151] The optocoupler U2 described above is a linear optocoupler. Its light-emitting diode indirectly obtains the voltage change on capacitor C2 through current response, and is coupled to its corresponding phototransistor in a linear relationship. The current in the phototransistor changes linearly with the current change in the light-emitting diode, so the microcontroller indirectly samples the voltage change on capacitor C2 through resistor R16 and calculates the rate of change.

[0152] Resistor R11 and the LED in optocoupler U2 are connected in series to form a sampling circuit to obtain the voltage change across capacitor C2 and convert it into a corresponding current. That is, the LED in optocoupler U2 indirectly obtains the voltage change across capacitor C2 through current response, and couples linearly with its corresponding phototransistor. The current in the phototransistor changes linearly with the current in the LED, and the current in the phototransistor then shows a corresponding voltage change across resistor R16. In other words, the monitoring module is equivalent to directly obtaining the voltage change across capacitor C2 and outputting it to the microcontroller.

[0153] Resistor R11 is the current-limiting resistor for the LEDs in optocoupler U2 and optocoupler U3.

[0154] Resistor R12 is the current-limiting resistor for the phototransistor in optocoupler U2.

[0155] The working process of the circuit in the third embodiment of the monitoring module above is as follows:

[0156] When the system stops, the microcontroller controls the MOSFET Q7 to turn on, and then outputs a high level to the control terminal of the switching transistor T4. Switch T4 saturates and turns on, causing the LED in optocoupler U3 to emit light. The phototransistor in optocoupler U3 also saturates and turns on, charging capacitor C2. The voltage across capacitor C2 is reflected across resistor R11 and the LED in optocoupler U2. The current flowing through the LED in optocoupler U2 changes linearly with the voltage across capacitor C2, coupling to the phototransistor in optocoupler U2 to form a corresponding linearly changing current. This indirectly reflects the sampled current across resistor R16. This overcomes the defect that the voltage change on the sampling capacitor C2 of the microcontroller is not obvious due to the power supply VDC voltage. It effectively expands the range of voltage change on capacitor C2 during the sampling stop-and-go flow process. Thus, regardless of whether the power supply VDC is less than or equal to 48V or greater than 48V, the microcontroller can effectively indirectly sample the voltage change on capacitor C2 during the stop-and-go flow process through resistor R16 and calculate the rate of change. When the rate of change is detected to be close to zero or less than the set value, it is determined that demagnetization is complete. The MOSFET Q7, which is turned on, is turned off, and the parasitic diode in MOSFET Q7 continues to flow to capacitor C2 to store energy and eliminate residual magnetism until the freewheeling ends and demagnetization is complete.

[0157] Once demagnetization is complete, the MOS transistor Q7, which is in control, is turned off, and a low level is output to the control terminal of the switching transistor T4. When the switching transistor T4 is turned off, the light-emitting diode in the optocoupler U3 is not energized, and the phototransistor in the optocoupler U3 is turned off. The monitoring module of the circuit in the third embodiment is not energized for energy saving.

[0158] A method for implementing a freewheeling energy storage demagnetization device for a permanent magnet synchronous motor based on monitoring changes in the voltage of the energy storage capacitor, according to the present invention, includes the following steps:

[0159] (1) For different power supply VDC voltages, the voltage change of monitoring capacitor C2 is used as the condition to determine whether demagnetization is complete. The microcontroller directly samples the voltage change of capacitor C2 from both ends of capacitor C2 through the monitoring module, or indirectly obtains the voltage between the positive terminal of capacitor C2 and the negative terminal of power supply VDC. The voltage change of capacitor C2 is sampled after the voltage is regulated by the Zener diode to reduce the influence of power supply VDC voltage on the sampling accuracy.

[0160] (2) When the machine is stopped:

[0161] The microcontroller outputs a turn-on control signal to the gate of MOSFET Q7. In the power drive module, a freewheeling diode provides current. Under the action of the freewheeling diode, the reverse electromotive force causes MOSFET Q7 to conduct in reverse. The reverse electromotive force generated by the three-phase windings is effectively connected by the corresponding freewheeling diode in the power drive module. The residual magnetism is eliminated by the conducting MOSFET Q7 and stored in capacitor C2.

[0162] The microcontroller outputs an enable control signal to control the monitoring module to enable voltage monitoring.

[0163] (3) Demagnetization is completed based on the trend of sampling voltage changes:

[0164] The microcontroller outputs a shutdown control signal to the gate of MOSFET Q7, turning off MOSFET Q7.

[0165] The microcontroller outputs a shutdown control signal to control the monitoring module to shut down voltage monitoring, effectively preventing the loss of charge on capacitor C2 and saving energy.

[0166] (4) When the demagnetization is confirmed to be complete, the parasitic diode in MOSFET Q7 takes over the conduction of MOSFET Q7 to participate in the freewheeling to eliminate residual magnetism and store energy in capacitor C2 until the freewheeling is completely finished.

[0167] (5) When the lag determines that demagnetization is complete, MOSFET Q7 becomes forward-biased during the lag time. However, since the power drive module uses a freewheeling diode for freewheeling, the charge stored in capacitor C2 will not be mistakenly transferred to the motor windings.

[0168] (6) During startup, the microcontroller controls the MOSFET Q7 to turn on and turn off for a limited time, thereby starting the motor with high-voltage excitation within the limited time.

[0169] like Figure 6 As shown, this invention discloses a freewheeling energy storage demagnetizing device for a permanent magnet synchronous motor based on monitoring the current changes in the charging circuit of the energy storage capacitor. It adds a freewheeling energy storage module and a unified monitoring module for monitoring the demagnetizing completion status by monitoring the current changes in the charging circuit of the energy storage capacitor, based on the power drive module of a permanent magnet synchronous motor with a three-phase stator winding star connection. The freewheeling energy storage module includes a switching transistor T8, diodes VD1, VD2, and VD3, and an energy storage capacitor C3. The positive terminal of the power supply VDC is connected to the power drive module for power supply. The busbar is disconnected, and diode VD1 is connected in series with the positive terminal of power supply VDC and then connected to the busbar supplying power to the power drive module. The negative terminal of capacitor C3 is connected to the positive terminal of power supply VDC, the positive terminal of capacitor C3 is connected to the high potential terminal of switching transistor T8, the low potential terminal of switching transistor T8 is connected to the cathode of diode VD1, and the control terminal of switching transistor T8 is connected to the output of the microcontroller. Diodes VD3 and VD2, connected in series in the forward direction, form the freewheeling diode in the freewheeling energy storage module, and are used for the sampling circuit in the monitoring module. The sampling voltage is obtained across diodes VD3 and VD2, enabling the microcontroller to effectively sample the small current in the capacitor charging circuit through the monitoring module. The cathode of diode VD2 is connected to the high potential terminal of switch T8, and the anode of diode VD2 is connected to the cathode of diode VD3. The anode of diode VD3 is connected to the busbar supplying power to the power drive module. The monitoring module includes an optocoupler U4, resistors R17, R18, and R19. Resistor R19 and the light-emitting diode in optocoupler U4 are connected in series. In the sampling circuit, the anode of the LED in optocoupler U4 is connected to the anode of diode VD3. The cathode of the LED in optocoupler U4 is connected to the cathode of diode VD2 after being connected in series with resistor R19. The emitter of the phototransistor in optocoupler U4 is connected to the negative terminal of power supply VDC after being connected in series with resistor R18, and the emitter lead of the phototransistor in optocoupler U4 is connected to the A / D input of the microcontroller. The collector of the phototransistor in optocoupler U4 is connected to the microcontroller power supply after being connected in series with resistor R17.

[0170] The microcontroller is equipped with a program module that controls the switching transistor T8 to turn on / off, as well as a program module for current sampling and change judgment. It also includes an output terminal that is compatible with the connection of the switching transistor T8 and an A / D input terminal that is connected to the output of the monitoring module.

[0171] The switching transistor T8 is either an NPN transistor or an N-type IGBT. When T8 is an NPN transistor, the high-potential terminal is the collector, the low-potential terminal is the emitter, and the control terminal is the base. When T8 is an N-type IGBT, the high-potential terminal is the collector, the low-potential terminal is the emitter, and the control terminal is the gate. An N-type IGBT is preferred for T8. T8 is only turned on during motor startup.

[0172] The capacitor C3 is used for energy storage. It is charged to store energy when the motor stops and the residual magnetism is eliminated by the follow current. When the motor starts, it is superimposed with the power supply VDC voltage to apply high voltage to the bus of the power drive module of the permanent magnet synchronous motor with star connection of three-phase stator winding, so that the motor starts under high voltage, shortens the starting process and improves the starting efficiency.

[0173] The diode VD1 is used to supply power from the power supply VDC to the bus of the power drive module when the motor is running normally, and to prevent the freewheeling current from directly forming a loop from the power supply VDC when the motor is stopped.

[0174] During startup, the microcontroller controls the switching transistor T8 to turn on and sets a time-limited turn-off. Within this time limit, the voltage across capacitor C3 is superimposed with the power supply VDC voltage, which then applies high voltage to the busbar supplying the power drive module of the three-phase stator winding star-connected permanent magnet synchronous motor via the conducting switching transistor T8. This high voltage then excites and starts the three-phase motor. After switching transistor T8 is turned off, the power supply VDC supplies power to the power drive module via diode VD1, and the motor operates normally. The time-limited turn-off period for controlling the switching transistor T8 is 0.5S to 1S, as described in existing technologies.

[0175] The optocoupler U4 described above is a linear optocoupler used for current sampling during the shutdown, freewheeling, energy storage, and demagnetization process. The LED in optocoupler U4 is used for sampling the current in the capacitor charging circuit, linearly controlling the current change of the phototransistor within U4. This current change in the phototransistor generates a corresponding voltage change across resistor R18. The microcontroller calculates the current flowing through the LED in optocoupler U4 based on the voltage across resistor R18. Resistor R19 is used for current limiting protection and current adjustment of the LED in optocoupler U4.

[0176] Resistor R17 is the current-limiting resistor for the phototransistor in optocoupler U4.

[0177] The diodes VD3 and VD2, connected in series in the forward direction, are used for freewheeling during shutdown energy storage and demagnetization. The purpose of using two diodes in series as freewheeling diodes is that the LED in the optocoupler U4 of the monitoring module obtains the sampling voltage from the two ends of the freewheeling diode. To ensure the effective operation of the LED in optocoupler U4, two diodes are connected in series in the forward direction for the freewheeling diode in the capacitor charging circuit. In this embodiment, both diodes VD3 and VD2 are selected as silicon diodes, or one is a silicon diode and the other is a germanium diode.

[0178] During the demagnetization process of the freewheeling energy storage system during shutdown, when the voltage across the capacitor charging circuit after diodes VD3 and VD2 are connected in the forward direction is equal to the sum of the forward voltages of diodes VD3 and VD2, it indicates that the freewheeling energy storage demagnetization is proceeding normally, meaning that the demagnetization has not yet been effectively completed. Furthermore, when diodes VD3 and VD2 are conducting, the voltage across the LED connected in series with resistor R19 in optocoupler U4 is a constant voltage, which is equal to the sum of the forward voltages of diodes VD3 and VD2. Therefore, when diodes VD3 and VD2 are conducting, the current flowing through the LED in optocoupler U4 is a constant current, the magnitude of which depends on the resistance value of resistor R19.

[0179] During the demagnetization process of freewheeling energy storage, the current in the capacitor charging circuit is equal to the sum of the current flowing through the LED in optocoupler U4 and the current flowing through the series diodes VD3 and VD2. When diodes VD3 and VD2 are conducting, the current in the capacitor charging circuit almost flows through the conducting diodes VD3 and VD2, which is the sum of the currents of the conducting diodes VD3 and VD2 and the constant current flowing through the LED in optocoupler U4. As the demagnetization process of freewheeling energy storage progresses, the freewheeling energy gradually weakens, and diodes VD3 and VD2 will gradually change from conducting to ineffectively conducting and then to non-conducting, thus ending the demagnetization process of freewheeling energy storage.

[0180] When diodes VD3 and VD2 become ineffectively conducting and non-conducting, the voltage across the forward-connected diodes VD3 and VD2 is less than the sum of their forward voltages. Consequently, the current flowing through the LED in optocoupler U4 is less than the constant current flowing through it, and at this time, the current flowing through the LED in optocoupler U4 is equal to the current in the capacitor charging circuit.

[0181] Furthermore, as is well known to those skilled in the art, during demagnetization with stop-current freewheeling, the demagnetization can be considered complete when the freewheeling diode changes from being on to being ineffectively on and then not on.

[0182] In this embodiment, the constant current flowing through the light-emitting diode in the optocoupler U4 can be obtained by pre-measurement or calculation, or it can be sampled in real time during shutdown, continuous current storage, and demagnetization.

[0183] In this embodiment, when diodes VD3 and VD2 are conducting, the resistance value of resistor R19 is selected to ensure that the constant current is within the effective operating region of the LED in optocoupler U4. Due to the physical characteristics of optocoupler U4, the current in the effective region is less than 0.5% of the rated current of the motor in the prior art. If the constant current is greater than 0.5% of the rated current of the motor in the prior art, the resistance value of resistor R19 is increased to ensure that the constant current is less than 0.5% of the rated current of the motor in the prior art.

[0184] Therefore, in this embodiment, during the demagnetization process of the power-off follow-current energy storage, the microcontroller can determine that demagnetization is complete when the current flowing through the LED in its optocoupler U4 is less than the constant current, as sampled by the monitoring module. For more effective determination of demagnetization completion, preferably, when monitoring the current change in the energy storage capacitor charging circuit to assess demagnetization completion, the microcontroller determines that demagnetization is complete when the current flowing through the LED in its optocoupler U4 is less than 50% of the constant current, as sampled by the monitoring module.

[0185] A method for implementing a freewheeling energy storage demagnetization device for a permanent magnet synchronous motor based on monitoring changes in the charging circuit current of an energy storage capacitor, comprising the following steps:

[0186] (1) For different power supply VDC voltages, the change in current of the energy storage capacitor charging circuit is uniformly used as a condition to determine whether demagnetization is completed. The freewheeling diode in the freewheeling energy storage module is composed of diode VD3 and diode VD2 connected in series in the forward direction. In the monitoring module, resistor 19 and the light-emitting diode in optocoupler U4 are connected in series to form a sampling circuit, which is connected in parallel across diode VD3 and diode VD2 connected in the forward direction. The sampling circuit samples the conduction voltage and small current in the capacitor charging circuit current across diode VD3 and diode VD2 after series connection.

[0187] (2) When the machine stops, the reverse electromotive force generated by the three-phase winding drives the freewheeling diode in the power drive module to continue the flow and the diodes VD3 and VD2 connected in series in the freewheeling energy storage module to continue the flow, storing energy in capacitor C3 to eliminate residual magnetism. At the same time, the microcontroller collects the current flowing through its acquisition circuit when diodes VD3 and VD2 are conducting through the monitoring module, sets the current as a constant current and temporarily stores it.

[0188] (3) After the constant current is temporarily stored, the microcontroller continues to monitor the current in its acquisition circuit through the monitoring module and compares it with the temporarily stored constant current. When the current in the acquisition circuit is less than 50% of the constant current, the demagnetization is considered to be complete.

[0189] (4) During startup, the microcontroller controls the switch T8 to turn on and turn off within a time limit, thereby starting the motor with high-voltage excitation within the time limit.

[0190] The beneficial effects of the above-described permanent magnet synchronous motor freewheeling energy storage demagnetization device and its implementation method based on monitoring the current change in the charging circuit of the energy storage capacitor are as follows:

[0191] Not only does it maintain the power drive module and its control method for the three-phase stator winding star connection of the permanent magnet synchronous motor in the existing technology, thus effectively keeping the motor working effectively, it also achieves:

[0192] ① By using a sampling circuit connected in parallel with the freewheeling diode in the freewheeling energy storage module, the small current in the capacitor charging circuit is effectively sampled. This overcomes the defect in the existing technology that the large and small circuit currents cannot be effectively taken into account. It effectively unifies the monitoring of the change in the capacitor charging circuit current for different power supply VDC voltages as a condition for judging whether demagnetization is completed. Once demagnetization is completed, the user is notified, and the effective operation of the motor is not affected.

[0193] ② The reverse electromotive force generated by the three-phase winding drives the freewheeling diode in the power drive module and the freewheeling diode in the freewheeling energy storage module to continue flowing. Therefore, once the microcontroller loses power and stops, it will not affect the freewheeling of the reverse electromotive force in the three-phase winding to charge capacitor C3 and eliminate residual magnetism until the freewheeling ends.

[0194] ③ Due to the reverse current blocking effect of the optocoupler U4 light-emitting diode in the sampling circuit of the monitoring module, the charge on capacitor C3 is effectively prevented from being lost during the non-stop follow-up energy storage demagnetization period.

Claims

1. A freewheeling energy storage demagnetization device for a permanent magnet synchronous motor, characterized in that, The system includes a power drive module for a permanent magnet synchronous motor with a three-phase stator winding star connection, a freewheeling energy storage module, and a monitoring module that uses the voltage change of the energy storage capacitor to monitor the demagnetization completion status for different power supply VDC voltages. The freewheeling energy storage module includes a MOSFET Q7, a diode VD, and a storage capacitor C2. The positive terminal of the power supply VDC is disconnected from the busbar supplying the power drive module. A diode VD is connected in series with the positive terminal of the power supply VDC and then connected to the busbar supplying the power drive module. The negative terminal of capacitor C2 is connected to the positive terminal of the power supply VDC. The positive terminal of the transistor is connected to the drain of MOSFET Q7, the source of MOSFET Q7 is connected to the cathode of diode VD, and the gate of MOSFET Q7 is connected to the output of the microcontroller. MOSFET Q7 contains a parasitic diode. The A / D input of the microcontroller is connected to the output of the monitoring module. The monitoring module indirectly samples the voltage change of capacitor C2 from its positive terminal to the negative terminal of power supply VDC. A Zener diode is used to regulate the voltage, reducing the impact of power supply VDC voltage on the sampling accuracy. The monitoring module includes a Zener diode DZ1, switching transistors T1 and T2, resistor R1, and resistor R...

2. Resistors R3, R4, and R5 are used to obtain voltage between the positive terminal of capacitor C2 and the negative terminal of power supply VDC. After filtering out interference from the power supply VDC voltage using Zener diode DZ1, the voltage is indirectly sampled. The cathode of Zener diode DZ1 is connected to the positive terminal of capacitor C2, and the anode of Zener diode DZ1 is connected to the high-potential terminal of switching transistor T1. The low-potential terminal of switching transistor T1 is connected in series with resistors R1 and R2 and then to the negative terminal of power supply VDC. A lead is connected to the A / D input of the microcontroller from the connection point of resistors R1 and R2. The control terminal of switching transistor T1 is connected in series with... Resistor R3 is connected to the high-potential terminal of switch T2, and the low-potential terminal of switch T2 is connected to the negative terminal of power supply VDC. The control terminal of switch T2 is connected to one end of resistor R4 and one end of resistor R5, respectively. The other end of resistor R4 is connected to the negative terminal of power supply VDC, and the other end of resistor R5 is connected to the output of microcontroller I / O. The Zener diode DZ1 is selected such that the voltage of power supply VDC minus its regulated value is greater than zero. Resistors R1 and R2 are connected in series to form a sampling circuit to obtain the voltage change on capacitor C2 by voltage division and output it to the microcontroller.

2. The permanent magnet synchronous motor freewheeling energy storage demagnetization device according to claim 1, characterized in that, The switching transistor T1 is a PNP type switching transistor, a PMOS transistor, or a P-type IGBT transistor, and the switching transistor T2 is an NPN type switching transistor, an NMOS transistor, or an N-type IGBT transistor.

3. A freewheeling energy storage demagnetization device for a permanent magnet synchronous motor, characterized in that, The system includes a power drive module for a permanent magnet synchronous motor with a three-phase stator winding star connection, a freewheeling energy storage module, and a monitoring module that uses the voltage change of the energy storage capacitor to monitor the demagnetization completion status for different power supply VDC voltages. The freewheeling energy storage module includes a MOSFET Q7, a diode VD, and a storage capacitor C2. The positive terminal of the power supply VDC is disconnected from the busbar supplying the power drive module. A diode VD is connected in series with the positive terminal of the power supply VDC and then connected to the busbar supplying the power drive module. The negative terminal of capacitor C2 is connected to the positive terminal of the power supply VDC, and the positive terminal of capacitor C2 is connected to the drain of the MOSFET Q7. The source of MOSFET Q7 is connected to the cathode of diode VD, and the gate of MOSFET Q7 is connected to the output of the microcontroller. MOSFET Q7 contains a parasitic diode. The A / D input of the microcontroller is connected to the output of the monitoring module. The monitoring module indirectly samples the voltage change of capacitor C2 from its positive terminal to the negative terminal of power supply VDC. A Zener diode is used to regulate the voltage, reducing the impact of power supply VDC on the sampling accuracy. The monitoring module includes a Zener diode DZ2, a switching transistor T3, an optocoupler U1, and resistors R6, R7, R8, R9, and R10. It is used to sample the voltage change of capacitor C2 from its positive terminal to the negative terminal of power supply VDC. A voltage is obtained between the positive terminal of capacitor C2 and the negative terminal of power supply VDC. This voltage is then indirectly sampled after filtering out interference from the power supply VDC voltage using Zener diode DZ2. The cathode of Zener diode DZ2 is connected to the positive terminal of capacitor C2, and the anode of Zener diode DZ2 is connected to the collector of the phototransistor in optocoupler U1. The emitter of the phototransistor in optocoupler U1 is connected to the negative terminal of power supply VDC via resistors R6 and R7 in series. A lead is then connected to the A / D input of the microcontroller from the connection point of resistors R6 and R7. The anode of the LED in optocoupler U1 is connected to the microcontroller power supply via resistor R8 in series. In coupler U1, the cathode of the LED is connected to the high-potential terminal of the switching transistor T3, and the low-potential terminal of the switching transistor T3 is connected to the negative terminal of the power supply VDC. The control terminal of the switching transistor T3 is connected to one end of resistor R9 and one end of resistor R10, respectively. The other end of resistor R9 is connected to the negative terminal of the power supply VDC, and the other end of resistor R10 is connected to the output of the microcontroller I / O. The Zener diode DZ2 is selected such that the voltage of the power supply VDC minus its regulated value is greater than zero. Resistors R6 and R7 are connected in series to form a sampling circuit to obtain the voltage change on capacitor C2 by voltage division and output it to the microcontroller.

4. The permanent magnet synchronous motor freewheeling energy storage demagnetization device according to claim 3, characterized in that, The switching transistor T3 is an NPN type switching transistor, an NMOS transistor, or an N-type IGBT transistor, and the optocoupler U1 is a digital optocoupler.

5. A method for implementing the freewheeling energy storage demagnetization device for a permanent magnet synchronous motor according to any one of claims 1 or 3, characterized in that, Includes the following steps: (1) For different power supply VDC voltages, the voltage change of the sampling monitoring capacitor C2 is uniformly used as a condition to determine whether demagnetization is complete. The microcontroller indirectly obtains the voltage between the positive terminal of capacitor C2 and the negative terminal of power supply VDC through the monitoring module. After the voltage is regulated by the Zener diode to reduce the influence of power supply VDC voltage on the sampling accuracy, the voltage change of sampling capacitor C2 is sampled. (2) When the machine is stopped: The microcontroller outputs a turn-on control signal to the gate of MOSFET Q7. In the power drive module, a freewheeling diode provides current. Under the action of the freewheeling diode, the reverse electromotive force causes MOSFET Q7 to conduct in reverse. The reverse electromotive force generated by the three-phase windings is effectively connected by the corresponding freewheeling diode in the power drive module. The residual magnetism is eliminated by the conducting MOSFET Q7 and stored in capacitor C2. The microcontroller outputs an enable control signal to control the monitoring module to enable voltage monitoring. (3) Demagnetization is completed based on the trend of sampling voltage changes: The microcontroller outputs a shutdown control signal to the gate of MOSFET Q7, turning off MOSFET Q7. The microcontroller outputs a shutdown control signal to control the monitoring module to shut down voltage monitoring, effectively preventing the loss of charge on capacitor C2 and saving energy. (4) When the demagnetization is confirmed to be complete, the parasitic diode in MOSFET Q7 takes over the conduction of MOSFET Q7 to participate in the freewheeling to eliminate residual magnetism and store energy in capacitor C2 until the freewheeling is completely finished. (5) When the lag determines that demagnetization is complete, MOSFET Q7 becomes forward-biased during the lag time. However, since the power drive module uses a freewheeling diode for freewheeling, the charge stored in capacitor C2 will not be mistakenly transferred to the motor windings. (6) During startup, the microcontroller controls the MOSFET Q7 to turn on and turn off for a limited time, thereby starting the motor with high-voltage excitation within the limited time.

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