Motor drive device and motor drive system

Abstract

This application discloses a motor drive device and a motor drive system. The motor drive device includes a unidirectional freewheeling circuit, an energy storage capacitor, and a three-phase inverter circuit. The input terminal of the unidirectional freewheeling circuit is connected to the first output terminal of a single-phase power supply; the energy storage capacitor is connected to the output terminal of the unidirectional freewheeling circuit; the input terminal of the three-phase inverter circuit is connected to the output terminal of the unidirectional freewheeling circuit, and each phase output terminal of the three-phase inverter circuit is respectively connected to the three-phase windings of the motor; wherein, the second output terminal of the single-phase power supply is connected to the neutral point of the motor. Thus, the motor drive device of this embodiment utilizes the motor windings as PFC inductors and uses the neutral point of the motor to provide a charging and discharging path, eliminating the PFC inductor, switching transistor, and output diode components in the Boost PFC circuit, simplifying the topology of the device while improving the overall circuit efficiency.

Description

Technical Field

[0001] This application relates to motor drive technology, and more particularly to a motor drive device and a motor drive system. Background Technology

[0002] Currently, in high-power motor drive systems powered by single-phase power supplies, in order to improve the power factor and suppress harmonics, motor drive devices typically include a boost power factor correction (BoostPFC) circuit. The AC signal output from the single-phase power supply is rectified and corrected by the Boost PFC circuit to obtain a DC signal, which is then inverted into a three-phase AC signal fed into the motor by the three-phase inverter circuit in the motor drive device.

[0003] However, in order to achieve the power factor correction effect, the aforementioned motor drive device requires the Boost PFC circuit to include a PFC inductor, a switching transistor, and multiple diodes, resulting in a higher cost for the motor drive device. Furthermore, in the inductor discharge loop of the Boost PFC circuit, the current needs to pass through multiple components such as the rectifier bridge and the output diode. The diode voltage drop will cause additional losses, resulting in poor overall circuit efficiency. Utility Model Content

[0004] In view of this, embodiments of this application provide a motor drive device and a motor drive system, which aim to simplify the topology of the motor drive device and improve circuit efficiency.

[0005] The technical solution of this application embodiment is implemented as follows: In a first aspect, embodiments of this application provide a motor drive device, the device comprising: A unidirectional freewheeling circuit, wherein the input terminal of the unidirectional freewheeling circuit is connected to the first output terminal of a single-phase power supply; An energy storage capacitor is connected to the output terminal of the unidirectional freewheeling circuit. A three-phase inverter circuit, wherein the input terminal of the three-phase inverter circuit is connected to the output terminal of the unidirectional freewheeling circuit, and each phase output terminal of the three-phase inverter circuit is respectively connected to the three-phase winding of the motor. The second output terminal of the single-phase power supply is connected to the neutral point of the motor.

[0006] In some implementations, the unidirectional freewheeling circuit includes: The first unidirectional freewheeling element has its input terminal connected to the first output terminal of the single-phase power supply, and its output terminal is the positive output terminal of the unidirectional freewheeling circuit. The second unidirectional freewheeling element has its output terminal connected to the first output terminal of the single-phase power supply, and its input terminal is the negative output terminal of the unidirectional freewheeling circuit.

[0007] In some implementations, the first unidirectional freewheeling element and the second unidirectional freewheeling element are diodes; In the unidirectional freewheeling circuit, the input terminal of the unidirectional freewheeling element is the cathode of the diode, and the output terminal of the unidirectional freewheeling element is the anode of the diode.

[0008] In some implementations, the three-phase inverter circuit includes: The three single-phase bridge arms are respectively connected to one phase winding of the motor; each single-phase bridge arm includes an upper switch tube and a lower switch tube.

[0009] In some implementations, the upper switch and the lower switch are unipolar switches.

[0010] In some implementations, the energy storage capacitor is disposed between the positive and negative output terminals of the unidirectional freewheeling circuit; the first terminal of the upper switching transistor is connected to the positive output terminal of the unidirectional freewheeling circuit, the second terminal of the upper switching transistor is connected to the first terminal of the lower switching transistor and the corresponding phase winding, and the second terminal of the lower switching transistor is connected to the negative output terminal of the unidirectional freewheeling circuit.

[0011] In some embodiments, the motor drive further includes: The control unit is used to control the on / off state of each switching transistor in the three-phase inverter circuit.

[0012] In some implementations, the control unit is configured to: control all the upper switches and all the lower switches to be continuously and alternately turned on during the zero vector phase; In the zero vector phase, all the upper switches are turned on simultaneously or all the lower switches are turned on simultaneously.

[0013] In some implementations, the control unit is configured to: during the non-zero vector phase, control one of the upper switching transistors and two of the lower switching transistors to be turned on simultaneously, or control one of the lower switching transistors and two of the upper switching transistors to be turned on simultaneously; During the non-zero vector phase, each conducting switch belongs to a different single-phase bridge arm.

[0014] Secondly, embodiments of this application provide a motor drive system, the system comprising: a motor drive device as described in the first aspect, a single-phase power supply, and a motor; The first terminal of the single-phase power supply is connected to the input terminal of the motor drive device, the second terminal of the single-phase power supply is connected to the neutral point of the motor, and the output terminals of each phase of the motor drive device are connected to the three-phase windings of the motor.

[0015] The technical solution provided in this application embodiment includes a motor drive device comprising: a unidirectional freewheeling circuit, an energy storage capacitor, and a three-phase inverter circuit. The input terminal of the unidirectional freewheeling circuit is connected to the first output terminal of a single-phase power supply; the energy storage capacitor is connected to the output terminal of the unidirectional freewheeling circuit; the input terminal of the three-phase inverter circuit is connected to the output terminal of the unidirectional freewheeling circuit, and each phase output terminal of the three-phase inverter circuit is respectively connected to the three-phase windings of the motor; wherein, the second output terminal of the single-phase power supply is connected to the neutral point of the motor. Thus, the motor drive device of this application embodiment utilizes the motor windings as PFC inductors and uses the motor's neutral point to provide a charging and discharging path, eliminating the PFC inductor, switching transistor, and output diode components in the Boost PFC circuit, simplifying the device's topology while improving overall circuit efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a motor drive system in related technologies; Figure 2 This is a first structural schematic diagram of the motor drive device provided in the embodiments of this application; Figure 3 This is a schematic diagram of the second structure of the motor drive device provided in the embodiments of this application; Figure 4 This is a schematic diagram of the switching control signals of the three-phase inverter circuit provided in the embodiments of this application.

[0017] It should be noted that the terms "first" and "second" mentioned above are only used to distinguish between different options and do not represent the degree of superiority or inferiority of the options or their priority in the implementation process.

[0018] Explanation of reference numerals in the attached figures: 1. Unidirectional freewheeling circuit; 2. Three-phase inverter circuit; 21. Phase A bridge arm; 22. Phase B bridge arm; 23. Phase C bridge arm; 3. Single-phase power supply; 4. Motor. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In the following description, references are made to “some embodiments,” which describe a subset of all possible embodiments. However, it is understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0022] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] In order to enable those skilled in the art to fully understand the technical concept of this application, before describing in detail the technical solution of the motor drive device provided in the embodiments of this application, the topology and working principle of the motor drive device in the related art will be briefly explained first.

[0024] In high-power drive scenarios, in order to improve the power factor and suppress harmonics, Figure 1 In the motor drive system shown, the motor drive unit typically includes a Boost PFC circuit, a filter capacitor C2, and a three-phase inverter circuit. The Boost PFC circuit includes a bridge rectifier circuit, a PFC inductor, a switching transistor Q7, and an output diode. The bridge rectifier circuit consists of diodes D3, D4, D5, and D6, and the output diode is typically a fast recovery diode (FRD).

[0025] In addition, Figure 1 In the motor drive system shown, the output terminals of the single-phase power supply are all connected to the bridge rectifier circuit. The AC signal output by the single-phase power supply is rectified and power factor corrected by the Boost PFC circuit to obtain a DC signal. The filter capacitor C2 is used to filter the DC signal. The three-phase windings of the motor are connected to the output terminals of each phase in the three-phase inverter circuit. The DC signal output by the Boost PFC circuit is inverted by the three-phase inverter circuit to obtain a three-phase AC signal with a phase difference of 120°. The three-phase AC signal is passed into the three-phase windings of the motor to form an alternating magnetic field, and the rotor of the motor rotates under the action of the alternating magnetic field.

[0026] It should be noted that, Figure 1 When the motor drive system shown is running, taking the single-phase power supply in the positive half-cycle as an example, if the switch Q7 of the Boost PFC circuit is turned on, the PFC inductor is in a charging state. The charging circuit for the PFC inductor is: single-phase power supply - diode D3 - PFC inductor - switch Q7 - diode D6 - single-phase power supply. While the PFC inductor is charging, the input power to the three-phase inverter circuit is provided by the filter capacitor. If the switch Q7 of the Boost PFC circuit is turned off, the PFC inductor is in a discharging state. The discharging circuit for the PFC inductor is: single-phase power supply - diode D3 - PFC inductor - output diode - filter capacitor C2 - diode D6 - single-phase power supply. After rectification, the single-phase power supply, along with the PFC inductor, simultaneously charges the filter capacitor C2 and provides input power to the three-phase inverter circuit. This is easily understood. Figure 1 The motor drive system shown continuously switches the charging and discharging state of the PFC inductor by controlling the on / off state of the switching transistor Q7 of the BoostPFC circuit, thereby achieving the power factor correction function.

[0027] However, although Figure 1 The motor drive system shown above uses an additional BoostPFC circuit at the input of the three-phase inverter circuit to adjust the power factor of the power supply in high-power drive scenarios. However, since the BoostPFC circuit includes multiple components such as a PFC inductor, a switching transistor Q7, and multiple diodes, the cost of the motor drive device is significantly increased, which is not conducive to cost control. In addition, in the discharge circuit of the PFC inductor of the BoostPFC circuit, the current needs to pass through components such as diode D3, output diode, and diode D6. The voltage drop of multiple diodes in the discharge circuit will cause additional losses, resulting in poor overall efficiency of the motor drive device.

[0028] Based on this, the present application provides a motor drive device suitable for high-power scenarios, which aims to simplify the topology and improve circuit efficiency.

[0029] Exemplary, the motor drive device in this application embodiment is as follows: Figure 2 As shown, the device includes a unidirectional freewheeling circuit 1, an energy storage capacitor C1, and a three-phase inverter circuit 2. The input terminal of the unidirectional freewheeling circuit 1 is connected to the first output terminal of the single-phase power supply. The energy storage capacitor C1 is connected to the output terminal of the unidirectional freewheeling circuit 1. The input terminal of the three-phase inverter circuit 2 is connected to the output terminal of the unidirectional freewheeling circuit 1, and each phase output terminal of the three-phase inverter circuit 2 is connected to the three-phase windings of the motor.

[0030] The second output terminal of the single-phase power supply is connected to the neutral point of the motor.

[0031] Here, the single-phase power supply is an AC power supply, and the first and second output terminals of the single-phase power supply output AC signals; in some embodiments, the single-phase power supply is AC mains power, and the first and second output terminals of the single-phase power supply are the live wire and the neutral wire, respectively.

[0032] Here, the motor drive device in this embodiment is a frequency converter drive device.

[0033] Here, the three-phase inverter circuit 2 is used to convert the input electrical signal into a three-phase AC signal. The three-phase inverter circuit 2 includes three single-phase bridge arms; each single-phase bridge arm is connected to one phase winding of the motor. Each single-phase bridge arm includes an upper switching transistor and a lower switching transistor.

[0034] Specifically, such as Figure 2 As shown, the three-phase inverter circuit 2 includes phase A bridge arm 21, phase B bridge arm 22, and phase C bridge arm 23. Phase A bridge arm 21 includes a first switch Q1 and a fourth switch Q4, phase B bridge arm 22 includes a second switch Q2 and a fifth switch Q5, and phase C bridge arm 23 includes a third switch Q3 and a sixth switch Q6. Specifically, the first switch Q1, the second switch Q2, and the third switch Q3 are upper switches, and the fourth switch Q4, the fifth switch Q5, and the sixth switch Q6 are lower switches.

[0035] Here, each phase output terminal of the three-phase inverter circuit 2 outputs a corresponding phase electrical signal, specifically the phase node of each single-phase bridge arm; wherein, the phase node is the connection point of the upper and lower switching transistors of the single-phase bridge arm, that is, the second end of the upper switching transistor is connected to the first end of the lower switching transistor and the corresponding phase winding. In this embodiment, the A-phase output terminal of the three-phase inverter circuit 2 is connected to the A-phase winding LA of the motor, the B-phase output terminal of the three-phase inverter circuit 2 is connected to the B-phase winding LB of the motor, and the C-phase output terminal of the three-phase inverter circuit 2 is connected to the C-phase winding LC of the motor.

[0036] Here, the motor driven by the motor drive device in this application embodiment adopts a star connection method (also known as a Y connection method). In this case, the first ends of the three-phase windings inside the motor with star connection are respectively led out from the motor housing, and the lead wires are respectively used as the terminals of phase A, phase B and phase C of the motor. The tail ends of the three-phase windings are connected to form a neutral point inside the motor.

[0037] Here, the external wiring methods for a star-connected motor include a neutral point floating connection and a neutral point lead-out connection. In the neutral point floating connection, the motor's external wiring terminals only include the aforementioned A-phase, B-phase, and C-phase terminals. In the neutral point lead-out connection, the motor also has external wiring led out from the neutral point, and in addition to the aforementioned A-phase, B-phase, and C-phase terminals, it also includes an N-point terminal led out from the neutral point. It is readily understood that the motor driven by the motor drive device in this embodiment uses a neutral point lead-out connection, and the neutral point lead-out wire of the motor is connected to the second output terminal of the single-phase power supply.

[0038] Here, the unidirectional freewheeling circuit 1 is used to provide unidirectional freewheeling paths during the positive and negative half-cycles of the single-phase power supply. Exemplarily, the unidirectional freewheeling circuit 1 includes a first unidirectional freewheeling element and a second unidirectional freewheeling element. The input terminal of the first unidirectional freewheeling element is connected to the first output terminal of the single-phase power supply, and the output terminal of the first unidirectional freewheeling element is the positive output terminal of the unidirectional freewheeling circuit 1; the output terminal of the second unidirectional freewheeling element is connected to the first output terminal of the single-phase power supply, and the input terminal of the second unidirectional freewheeling element is the negative output terminal of the unidirectional freewheeling circuit 1.

[0039] Correspondingly, the first end of the upper switching transistor of the single-phase bridge arm is connected to the positive output terminal of the unidirectional freewheeling circuit 1, and the second end of the lower switching transistor of the single-phase bridge arm is connected to the negative output terminal of the unidirectional freewheeling circuit 1.

[0040] Here, the positive output terminal is the current output terminal of the unidirectional freewheeling circuit 1, and the negative output terminal is the current return terminal of the unidirectional freewheeling circuit 1. During the positive half-cycle of the single-phase power supply, the electrical signal output by the single-phase power supply flows out from the first output terminal through the first unidirectional freewheeling element; during the negative half-cycle of the single-phase power supply, the electrical signal output by the single-phase power supply flows back to the first output terminal from the second unidirectional freewheeling element.

[0041] Accordingly, in some embodiments, the first unidirectional freewheeling element and the second unidirectional freewheeling element are diodes. The input terminal of the unidirectional freewheeling element in the unidirectional freewheeling circuit 1 is the cathode of the diode, and the output terminal of the unidirectional freewheeling element in the unidirectional freewheeling circuit 1 is the anode of the diode.

[0042] Specifically, such as Figure 3 As shown, the unidirectional freewheeling circuit 1 includes a first diode D1 and a second diode D2. The cathode of the first diode D1 is connected to the first output terminal of the single-phase power supply, and the anode of the first diode D1 is the positive output terminal of the unidirectional freewheeling circuit 1; the anode of the second diode D2 is connected to the first output terminal of the single-phase power supply, and the cathode of the second diode D2 is the negative output terminal of the unidirectional freewheeling circuit 1.

[0043] It is understood that this embodiment utilizes the unidirectional conduction characteristic of diodes to provide different current outflow paths and current return paths for the first output terminal of a single-phase power supply.

[0044] It should be noted that, in this embodiment of the application, since the first output terminal of the single-phase power supply is connected to the input terminal of the unidirectional freewheeling circuit 1 and the second output terminal is connected to the neutral point of the motor, the power-on circuit of the single-phase power supply is not a conventional closed-loop circuit in which current flows out from the positive output terminal of the unidirectional freewheeling circuit 1 and back from the negative output terminal of the unidirectional freewheeling circuit 1. Instead, the neutral point of the motor is used as the circuit path, and the power-on circuit of the single-phase power supply is either in which current flows out from the positive output terminal of the unidirectional freewheeling circuit 1 and back from the neutral point of the motor, or in which current flows out from the neutral point of the motor and back from the negative output terminal of the unidirectional freewheeling circuit 1.

[0045] For example, the energy storage capacitor C1 is disposed between the positive output terminal and the negative output terminal of the unidirectional freewheeling circuit 1. Specifically, the positive terminal of the energy storage capacitor C1 is connected to the positive output terminal of the unidirectional freewheeling circuit 1 and the first terminal of the upper switching transistor of the single-phase bridge arm, and the negative terminal of the energy storage capacitor C1 is connected to the negative output terminal of the unidirectional freewheeling circuit 1 and the second terminal of the lower switching transistor of the single-phase bridge arm.

[0046] It should be noted that the type of energy storage capacitor C1 is not specifically limited in the embodiments of this application; in some embodiments, energy storage capacitor C1 is a polarized capacitor.

[0047] It should be noted that since the energy storage capacitor C1 is located between the positive and negative output terminals of the unidirectional freewheeling circuit 1, the electrical signal output from the single-phase power supply will charge the energy storage capacitor C1 when it flows out from the positive output terminal or back from the negative output terminal of the unidirectional freewheeling circuit 1. Accordingly, in the motor drive device of this application embodiment, the energy storage capacitor C1 is used to supply power to the three-phase inverter circuit 2 and to filter the passing electrical signal. It is easy to understand that when the energy storage capacitor C1 supplies power to the three-phase inverter circuit 2, the DC signal flows out from the positive terminal of the energy storage capacitor C1 and into the three-phase inverter circuit 2; when the energy storage capacitor C1 is charging, the DC signal flows in from the positive terminal of the energy storage capacitor C1.

[0048] It should be noted that, based on the structure of the motor drive device described above, if the upper and lower switching transistors of different single-phase bridge arms in the three-phase inverter circuit 2 are turned on simultaneously according to a specific timing sequence, the three-phase inverter circuit 2 will convert the DC signal output by the energy storage capacitor C1 into a three-phase AC signal for driving the motor. If only the upper switching transistor or only the lower switching transistor of the three-phase inverter circuit 2 is turned on at the same time, the single-phase power supply and the three-phase windings of the motor form a power-on circuit, and the embodiment of this application utilizes this power-on circuit to realize the power factor correction function.

[0049] Specifically, with Figure 3 Taking the motor drive device shown as an example, when the single-phase power supply is in the positive half-cycle, the output electrical signal flows out from the positive output terminal of the unidirectional freewheeling circuit 1 through the first output terminal; if the lower switch of the three-phase inverter circuit 2 is in the off state and only the upper switch is on, then the single-phase power supply, the motor drive device and the motor form a power-on circuit of single-phase power supply-first diode D1-upper switch-three-phase winding-neutral point-single-phase power supply, at which time the single-phase power supply charges the three-phase winding of the motor; if the upper switch of the three-phase inverter circuit 2 is in the off state and only the lower switch is on, then the single-phase power supply, the motor drive device and the motor form a power-on circuit of single-phase power supply-first diode D1-energy storage capacitor C1-lower switch-three-phase winding-neutral point-single-phase power supply, at which time the three-phase winding of the motor discharges, and the single-phase power supply and the three-phase winding simultaneously charge the energy storage capacitor C1.

[0050] Correspondingly, when the single-phase power supply is in the negative half-cycle, the output electrical signal flows out from the neutral point of the motor through the second terminal; if the upper switch of the three-phase inverter circuit 2 is in the off state and only the lower switch is on, then the single-phase power supply, the motor drive device and the motor form a power-on circuit of single-phase power supply-neutral point-three-phase winding-lower switch-second diode D2-single-phase power supply, at which time the single-phase power supply charges the three-phase winding of the motor; if the lower switch of the three-phase inverter circuit 2 is in the off state and only the upper switch is on, then the single-phase power supply, the motor drive device and the motor form a power-on circuit of single-phase power supply-neutral point-three-phase winding-upper switch-energy storage capacitor C1-second diode D2-single-phase power supply, at which time the three-phase winding of the motor discharges, and the single-phase power supply and the three-phase winding simultaneously charge the energy storage capacitor C1.

[0051] It is understood that the motor drive device in this application embodiment reuses the three-phase windings of the motor as PFC inductors. In different half-cycles of the single-phase power supply, the three-phase windings of the motor are charged or discharged by the three-phase windings of the motor by controlling the on / off state of the switching transistor of the three-phase inverter circuit 2. The current waveform is adjusted based on the switching of the charging and discharging state of the three-phase windings to achieve the power factor correction function.

[0052] It is understood that, in addition to outputting three-phase AC signals, the three-phase inverter circuit 2 in the motor drive device of this application embodiment also works in conjunction with the unidirectional freewheeling circuit 1 during power factor correction. During the three-phase winding discharge stage, it converts the AC signal output by the single-phase power supply into a DC signal to achieve rectification. The DC signal charges the energy storage capacitor C1, thereby enabling the energy storage capacitor C1 to subsequently provide the three-phase inverter circuit 2 with a DC signal for conversion into three-phase AC signals.

[0053] In some embodiments, in order to achieve synchronous rectification, the upper and lower switching transistors of the three-phase inverter circuit 2 are unipolar switching transistors.

[0054] Here, unipolar switching transistors include, but are not limited to: Si MOS transistors, SiC MOS transistors, and group III nitride-based power devices (such as GaN-HEMT transistors).

[0055] It is understood that the motor drive device in the embodiments of this application is similar to... Figure 1 Compared to the motor drive device shown, the unidirectional freewheeling circuit 1, which includes two unidirectional freewheeling elements, replaces the Boost PFC circuit, which includes multiple diodes, a PFC inductor, and a switching transistor Q7. That is, the motor drive device of this application eliminates the two rectifier diodes, the output diode, the PFC inductor, the switching transistor Q7, and the driving circuit of the switching transistor Q7 in the Boost PFC circuit. While realizing the power factor correction function, it simplifies the topology of the motor drive device and reduces the cost of the motor drive device.

[0056] It is understood that when the motor drive device in this embodiment performs power factor correction, the three-phase windings of the motor are in either a charging or discharging state, and the energizing circuit only passes through one diode (first diode D1 or second diode D2) in the unidirectional freewheeling circuit 1. Figure 1 The inductive discharge circuit of the motor drive device shown requires three diodes. Therefore, the motor drive device of this application embodiment reduces the power loss caused by the diode voltage drop, and the overall circuit efficiency of the motor drive device is improved.

[0057] It is understood that the motor drive device in this application embodiment uses the motor winding as the PFC inductor and the neutral point of the motor to provide a charging and discharging path, eliminating the PFC inductor, switching transistor and output diode and other components in the Boost PFC circuit, simplifying the topology of the device while improving the overall circuit efficiency.

[0058] In some embodiments, in order to reduce the conduction loss of the unidirectional freewheeling circuit 1 and improve the overall efficiency of the motor drive device, the first unidirectional freewheeling element and the second unidirectional freewheeling element of the unidirectional freewheeling circuit 1 are switching transistors.

[0059] It is understood that the unidirectional freewheeling path of a single-phase power supply during the positive and negative half-cycles can be switched by controlling the on / off state of the first and second unidirectional freewheeling elements. The types of the first and second unidirectional freewheeling elements include, but are not limited to: MOSFETs, SiC MOSFETs, and group III nitride-based power devices.

[0060] For example, the motor drive device also includes a control unit (not shown in the figure); the control unit is connected to the drive terminals of each switching transistor in the three-phase inverter circuit 2; the control unit is used to control the on / off state of each switching transistor in the three-phase inverter circuit 2.

[0061] Here, the control unit can be a digital signal processor (DSP), a programmable logic device (PLD), a complex programmable logic device (CPLD), a field programmable gate array (FPGA), a general-purpose processor, a controller, a micro controller unit (MCU), a microprocessor, or an electronic component. This application embodiment does not specifically limit the specific type of control unit.

[0062] In some embodiments, the first unidirectional freewheeling element and the second unidirectional freewheeling element are switching transistors, and the control unit is connected to the output terminals of the first unidirectional freewheeling element and the second unidirectional freewheeling element to control the on / off state of the first unidirectional freewheeling element and the second unidirectional freewheeling element.

[0063] Here, the operating state of the three-phase inverter circuit 2 is divided into a zero-vector stage and a non-zero-vector stage based on different conduction combinations of the switching transistors. In the zero-vector stage, the vector sum of the output voltages of the three-phase inverter circuit 2 is zero, and the three-phase windings of the motor will not generate torque. In the non-zero-vector stage, the vector sum of the output voltages of the three-phase inverter circuit 2 is not zero, forming an effective voltage to drive the motor.

[0064] It is understandable that by adjusting the duty cycle of the zero-vector phase and the non-zero-vector phase within the switching cycle, the output voltage amplitude and frequency of the three-phase inverter circuit 2 can be adjusted, thereby achieving precise control of the motor speed and torque.

[0065] Accordingly, the control unit is configured to: in the zero vector phase, control all upper switches to be turned on simultaneously or all lower switches to be turned on simultaneously.

[0066] Accordingly, the control unit is also configured to: control one upper switch and two lower switches to be turned on simultaneously, or control one lower switch and two upper switches to be turned on simultaneously, during the non-zero vector phase; wherein, during the non-zero vector phase, each turned-on switch belongs to a different single-phase bridge arm.

[0067] Understandably, when the three-phase inverter circuit 2 is running, the upper and lower switching transistors of the same single-phase bridge arm will not be turned on at the same time to avoid direct short circuit of the single-phase bridge arm.

[0068] It is understandable that the zero-vector stage is a symmetrical conduction mode, meaning that there are two operating states in the zero-vector stage: the first switch Q1, the second switch Q2, and the third switch Q3 are all conducting simultaneously, and the fourth switch Q4, the fifth switch Q5, and the sixth switch Q6 are all conducting simultaneously. The non-zero-vector stage is an asymmetrical conduction mode, meaning that the three switches that are conducting simultaneously in the non-zero-vector stage include at least one upper switch and at least one lower switch, such as the operating state in which the first switch Q1, the third switch Q3, and the fifth switch Q5 are all conducting simultaneously. Here, we will not give examples of each operating state in the non-zero-vector stage of the three-phase inverter circuit 2.

[0069] Understandably, during the non-zero vector phase, due to the simultaneous conduction of the upper and lower switches of different single-phase bridge arms, the energy storage capacitor C1 outputs a DC signal to the three-phase inverter circuit 2. The DC signal is passed through the conducting upper switch to the corresponding phase winding, and then flows back to the energy storage capacitor C1 through the other phase winding and the conducting lower switch, forming a power-on circuit. Taking the simultaneous conduction of the first switch Q1, the third switch Q3, and the fifth switch Q5 as an example, the following power-on circuits are formed: energy storage capacitor C1 - first switch Q1 - A phase winding - neutral point - B phase winding - fifth switch Q5 - energy storage capacitor C1 and energy storage capacitor C1 - third switch Q3 - C phase winding - neutral point - B phase winding - fifth switch Q5 - energy storage capacitor C1.

[0070] It is understandable that during the non-zero vector phase, the three-phase inverter circuit 2 can realize the inverter function. Based on the set switch sequence, the switching transistors of the three-phase inverter circuit 2 are turned on alternately in sequence, so that the three-phase inverter circuit 2 converts the DC signal output by the energy storage capacitor C1 into a three-phase AC signal with a phase difference of 120° to drive the motor.

[0071] For example, based on the control unit being configured to control all upper switches to be turned on simultaneously or all lower switches to be turned on simultaneously during the zero vector phase, the control unit is further configured to: control all the upper switches and all the lower switches to be turned on continuously and alternately during the zero vector phase.

[0072] It should be noted that during the operation of the motor drive device, the zero-vector stage typically maintains a state where all upper switching transistors or all lower switching transistors are simultaneously turned on to reduce switching losses. However, in this embodiment, the zero-vector stage, in addition to adjusting the output voltage amplitude and frequency of the three-phase inverter circuit 2, is also reused as the power factor correction stage. Specifically, during the zero-vector stage, the three-phase inverter circuit 2 is no longer used for inversion but provides a PFC freewheeling path. The control unit controls the three-phase inverter circuit 2 to switch between the two states of "all upper switching transistors simultaneously turned on" and "all lower switching transistors simultaneously turned on" multiple times, thereby achieving the alternating switching of the charging and discharging states of the motor's three-phase windings and thus achieving the power factor correction function.

[0073] In some embodiments, the control signals for the upper and lower switching transistors of the three-phase inverter circuit 2 during the zero-vector phase are as follows: Figure 4 As shown. During the positive half-cycle of the single-phase power supply, at the set moment of the zero vector phase, the control unit controls all upper switching transistors to conduct simultaneously. The positive output terminal of the unidirectional freewheeling circuit 1 is connected to the three-phase winding of the motor based on the conducting upper switching transistors. Since the lower switching transistors are all in the off state at this time, the energy storage capacitor C1 cannot output a DC signal to the three-phase inverter circuit 2. Therefore, the single-phase power supply can output an electrical signal from the positive output terminal of the unidirectional freewheeling circuit 1. In the energizing circuit of single-phase power supply - first diode D1 - upper switching transistors (first switching transistor Q1, second switching transistor Q2 and third switching transistor Q3) - three-phase winding - neutral point - single-phase power supply, the single-phase power... The power source charges the three-phase windings of the motor; at the next switching moment, the control unit switches the on / off state of the upper and lower switching transistors. At this time, all lower switching transistors are turned on at the same time. The connection path between the positive output terminal of the unidirectional freewheeling circuit 1 and the three-phase windings of the motor is switched from the upper switching transistor to the turned-on lower switching transistor and the energy storage capacitor C1. In the power-on circuit of single-phase power supply - first diode D1 - energy storage capacitor C1 - lower switching transistor (fourth switching transistor Q4, fifth switching transistor Q5 and sixth switching transistor Q6) - three-phase windings - neutral point - single-phase power supply, the single-phase power supply and the three-phase windings charge the energy storage capacitor C1 used to supply power in the non-zero vector phase.

[0074] Correspondingly, during the negative half-cycle of the single-phase power supply, at the set moment of the zero vector phase, the control unit controls all lower switches to be turned on simultaneously. In the energizing circuit of single-phase power supply - neutral point - three-phase winding - lower switches (fourth switch Q4, fifth switch Q5 and sixth switch Q6) - second diode D2 - single-phase power supply, the single-phase power supply charges the three-phase winding of the motor. At the next switching moment, the control unit switches the on / off state of the upper and lower switches. At this time, in the energizing circuit of single-phase power supply - neutral point - three-phase winding - upper switches (first switch Q1, second switch Q2 and third switch Q3) - energy storage capacitor C1 - second diode D2 - single-phase power supply, the single-phase power supply and the three-phase winding charge the energy storage capacitor C1 used for power supply in the non-zero vector phase.

[0075] Accordingly, the control unit is also configured to: control all upper switches to turn on based on a first duty cycle during the switching cycle of the zero vector phase, and control all lower switches to turn on based on a second duty cycle.

[0076] Here, the first duty cycle and the second duty cycle are determined based on the power factor correction strategy.

[0077] It is understandable that by configuring the duty cycle of the upper and lower switching transistors in the zero vector phase, and the motor drive device controlling all the upper and lower switching transistors to conduct continuously and alternately in the zero vector phase based on the duty cycle, the power factor correction function can be achieved. Since the voltage vector sum in the zero vector phase is always zero, the motor will not generate torque after an electrical signal is applied, and the realization of the power factor correction function will not affect the operation of the motor.

[0078] It should be noted that during the zero vector phase, the single-phase power supply and the three-phase windings of the motor simultaneously charge the energy storage capacitor C1. Therefore, after charging, the terminal voltage of the energy storage capacitor C1 is higher than the output voltage of the single-phase power supply. Based on this, during the positive half-cycle of the single-phase power supply, even if the second output terminal of the single-phase power supply is connected to the neutral point of the motor during the non-zero vector phase, and the upper switching transistor in the three-phase inverter circuit 2 connects the positive output terminal of the unidirectional freewheeling circuit 1 to at least one phase winding of the motor, the first diode D1 is in a reverse bias state because the terminal voltage of the energy storage capacitor C1 is higher than the output voltage of the single-phase power supply. Therefore, the single-phase power supply cannot output an electrical signal to the motor drive device at this time; the same applies during the negative half-cycle of the single-phase power supply. Therefore, the direct connection method between the single-phase power supply and the neutral point of the motor in this embodiment will not affect the operation of the motor.

[0079] It is understood that, in the embodiments of this application, during the non-zero vector phase of the three-phase inverter circuit, the motor drive system is powered only by the energy storage capacitor C1 of the motor drive device, and the single-phase power supply is not connected to the energizing circuit; during the zero vector phase of the three-phase inverter circuit, the single-phase power supply is connected to the energizing circuit based on the unidirectional freewheeling circuit 1 and the neutral point of the motor, providing stored electrical energy to the energy storage capacitor C1 while performing power factor correction. Therefore, the unidirectional freewheeling circuit 1 is essentially used to control the single-phase power supply to only be connected during the zero vector phase of the three-phase inverter circuit.

[0080] Based on the above-described motor drive device, embodiments of this application also provide a motor drive system, such as... Figure 2 As shown, the system includes the aforementioned motor drive device, single-phase power supply 3, and motor 4.

[0081] The first terminal of the single-phase power supply 3 is connected to the input terminal of the motor 4 drive device, the second terminal of the single-phase power supply 3 is connected to the neutral point of the motor 4, and the output terminals of each phase of the motor drive device are connected to the three-phase windings of the motor 4.

[0082] It is understandable that the input terminal of the motor drive device is the input terminal of the unidirectional freewheeling circuit 1, that is, the connection point of the first unidirectional freewheeling element and the second unidirectional freewheeling element.

[0083] Here, the single-phase power supply 3 is an AC power supply, and the first and second output terminals of the single-phase power supply 3 output AC signals; in some embodiments, the single-phase power supply 3 is AC mains power, and the first and second output terminals of the single-phase power supply 3 are the live wire and the neutral wire, respectively.

[0084] Here, the motor 4 in this embodiment of the application adopts a star connection (also known as a Y-connection), wherein the starting end and neutral point of the three-phase winding of the motor 4 are provided with lead wires.

[0085] Here, the motor driven by the motor drive device in this embodiment adopts a neutral point lead-out connection, and the lead-out line of the neutral point of the motor is connected to the second output terminal of the single-phase power supply.

[0086] It is understood that the motor drive system of this application embodiment uses the motor winding as the PFC inductor and the neutral point of the motor to provide a charging and discharging path, eliminating the PFC inductor, switching transistor and output diode and other components in the Boost PFC circuit, simplifying the topology of the motor drive device while improving the overall circuit efficiency.

[0087] It should be noted that terms such as "first" and "second" are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0088] Furthermore, the technical solutions described in the embodiments of this application can be combined arbitrarily without conflict.

[0089] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A motor drive device, characterized in that, The device includes: A unidirectional freewheeling circuit, wherein the input terminal of the unidirectional freewheeling circuit is connected to the first output terminal of a single-phase power supply; An energy storage capacitor is connected to the output terminal of the unidirectional freewheeling circuit. A three-phase inverter circuit, wherein the input terminal of the three-phase inverter circuit is connected to the output terminal of the unidirectional freewheeling circuit, and each phase output terminal of the three-phase inverter circuit is respectively connected to the three-phase winding of the motor. The second output terminal of the single-phase power supply is connected to the neutral point of the motor.

2. The apparatus according to claim 1, characterized in that, The unidirectional freewheeling circuit includes: The first unidirectional freewheeling element has its input terminal connected to the first output terminal of the single-phase power supply, and its output terminal is the positive output terminal of the unidirectional freewheeling circuit. The second unidirectional freewheeling element has its output terminal connected to the first output terminal of the single-phase power supply, and its input terminal is the negative output terminal of the unidirectional freewheeling circuit.

3. The apparatus according to claim 2, characterized in that, The first unidirectional freewheeling element and the second unidirectional freewheeling element are diodes; In the unidirectional freewheeling circuit, the input terminal of the unidirectional freewheeling element is the cathode of the diode, and the output terminal of the unidirectional freewheeling element is the anode of the diode.

4. The apparatus according to any one of claims 1 to 3, characterized in that, The three-phase inverter circuit includes: The three single-phase bridge arms are respectively connected to one phase winding of the motor; each single-phase bridge arm includes an upper switch tube and a lower switch tube.

5. The apparatus according to claim 4, characterized in that, The upper and lower switching transistors are unipolar switching transistors.

6. The apparatus according to claim 4, characterized in that, The energy storage capacitor is disposed between the positive output terminal and the negative output terminal of the unidirectional freewheeling circuit; the first terminal of the upper switching transistor is connected to the positive output terminal of the unidirectional freewheeling circuit, the second terminal of the upper switching transistor is connected to the first terminal of the lower switching transistor and the corresponding phase winding, and the second terminal of the lower switching transistor is connected to the negative output terminal of the unidirectional freewheeling circuit.

7. The apparatus according to claim 6, characterized in that, The motor drive device also includes: The control unit is used to control the on / off state of each switching transistor in the three-phase inverter circuit.

8. The apparatus according to claim 7, characterized in that, The control unit is configured to: during the zero vector phase, control all the upper switching transistors and all the lower switching transistors to be continuously and alternately turned on; In the zero vector phase, all the upper switches are turned on simultaneously or all the lower switches are turned on simultaneously.

9. The apparatus according to claim 7, characterized in that, The control unit is configured to: during the non-zero vector phase, control one of the upper switching transistors and two of the lower switching transistors to be turned on simultaneously, or control one of the lower switching transistors and two of the upper switching transistors to be turned on simultaneously; During the non-zero vector phase, each conducting switch belongs to a different single-phase bridge arm.

10. A motor drive system, characterized in that, The system includes: a motor drive device, a single-phase power supply, and a motor as described in any one of claims 1 to 9; The first terminal of the single-phase power supply is connected to the input terminal of the motor drive device, the second terminal of the single-phase power supply is connected to the neutral point of the motor, and the output terminals of each phase of the motor drive device are connected to the three-phase windings of the motor.

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