Motor driver and motor driving system

Abstract

The invention relates to a motor driver and a motor driving system, the motor driver comprises a rectifier circuit, a direct current chain circuit and an inverter circuit, the rectifier circuit comprises a rectifier bridge, a first half bridge, a first switch, a second switch, a third switch and an inductor, the inductor is connected between the c phase of a three-phase power grid and the midpoint of the first half bridge, and the inverter circuit is connected with the DC chain circuit. The first switch is connected with the inductor in parallel, the second switch is connected between the a phase of the three-phase power grid and the midpoint of the first bridge arm of the rectifier bridge, the third switch is connected between the b phase of the three-phase power grid and the midpoint of the second bridge arm of the rectifier bridge, and the direct-current chain circuit comprises a capacitor and a second half bridge, the first end and the second end of the capacitor are respectively connected with the positive electrode output end and the negative electrode output end of the rectifying circuit, the collector electrode of the seventh switching device is connected with the first end of the capacitor, the emitter electrode of the seventh switching device is connected with the collector electrode of the eighth switching device, and the emitter electrode of the eighth switching device is connected with the second end of the capacitor.

Description

Motor drivers and motor drive systems Technical Field

[0001] The present disclosure generally relates to the field of circuit technology, and more particularly, to a motor driver and a motor drive system. Background Art

[0002] Frequency converters (VFCs) are widely used in the motor drive and servo industries. In most cases, capacitors are used in the DC link circuit as power supply decoupling devices. During motor braking, regenerative energy is applied to the DC link circuit capacitors, causing the DC voltage to rise. If the voltage continues to rise above the allowable operating voltage, the capacitors may be damaged. Braking resistors are often used to dissipate the regenerative energy and prevent overvoltage damage to components. However, this introduces other issues, such as heat dissipation and bulk.

[0003] FIG1 shows a topology of a motor drive 10 in the prior art. Ua, Ub, and Uc are the three phases of the power grid. Two single-phase diode rectifier bridges are used at the input. One branch from each rectifier bridge shares a grid phase to support 1AC or 3AC power input. An intelligent power module (IPM) is used in the DC / AC converter to achieve a compact design. A large braking resistor R1 is connected to the DC link through power switch T7. If the DC voltage rises to a limit value, power switch T7 will be activated and R1 will absorb the overvoltage. A freewheeling diode D9 is added to eliminate transient overvoltages caused by the stray inductance of braking resistor R1.

[0004] Because brake resistor R1 needs to dissipate the motor's regenerative energy, it requires a high power capacity and a large size. Furthermore, it is typically custom-made, making it quite expensive. Most importantly, the high power dissipation generates high temperatures within the resistor, sometimes reaching hundreds of degrees Celsius. This poses significant challenges to the heat sink and structural design of the entire system.

[0005] Summary of the Invention

[0006] A brief overview of the present invention is provided below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important aspects of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is simply to present certain concepts in a simplified form as a prelude to the more detailed description discussed later.

[0007] In view of the foregoing, the present disclosure provides a motor driver capable of eliminating overvoltage damage.

[0008] According to one aspect of the present disclosure, a motor driver is provided. The input end of the motor driver is connected to a three-phase power grid, and the output end of the motor driver is connected to a motor. The motor driver includes: a rectifier circuit, a DC link circuit, and an inverter circuit. The inverter circuit includes first, second, and third DC / AC conversion branch circuits arranged in parallel between the positive and negative output ends of the DC link circuit. Each of the first, second, and third DC / AC conversion branch circuits includes first and second, third and fourth, fifth and sixth switching devices, respectively.

[0009] The rectifier circuit includes a rectifier bridge, a first half-bridge, a first switch, a second switch, a third switch, and an inductor. The rectifier bridge includes a first bridge arm and a second bridge arm connected in parallel. The first bridge arm includes a first diode and a second diode connected in series. The second bridge arm includes a third diode and a fourth diode connected in series. The first half-bridge includes a ninth switching device, a ninth freewheeling diode, a tenth switching device, and a tenth freewheeling diode. The ninth freewheeling diode is connected in reverse between the collector and emitter of the ninth switching device, and the tenth freewheeling diode is connected in reverse between the collector and emitter of the tenth switching device. The collector of the ninth switching device is connected to the positive output terminal of the rectifier bridge, the emitter of the ninth switching device is connected to the collector of the tenth switching device, and the emitter of the tenth switching device is connected to the negative output terminal of the rectifier bridge.

[0010] The inductor is connected between phase c of the three-phase grid and the midpoint of the first half-bridge, the first switch is connected in parallel with the inductor, the second switch is connected between phase a of the three-phase grid and the midpoint of the first arm of the rectifier bridge, and the third switch is connected between phase b of the three-phase grid and the midpoint of the second arm of the rectifier bridge.

[0011] The DC link circuit is connected between the rectifier circuit and the inverter circuit, and the DC link circuit includes a capacitor and a second half-bridge. The second half-bridge includes a seventh switching device, a seventh freewheeling diode, an eighth switching device, and an eighth freewheeling diode. The seventh freewheeling diode is reversely connected between the collector and the emitter of the seventh switching device, and the eighth freewheeling diode is reversely connected between the collector and the emitter of the eighth switching device. The first end and the second end of the capacitor are respectively connected to the positive output end and the negative output end of the rectifier circuit, the collector of the seventh switching device is connected to the first end of the capacitor, the emitter of the seventh switching device is connected to the collector of the eighth switching device, and the emitter of the eighth switching device is connected to the second end of the capacitor.

[0012] In this way, overvoltage damage to the capacitor can be avoided.

[0013] Optionally, in an example of the above aspect, a midpoint between the seventh switching device and the eighth switching device is connected to a neutral point of the three-phase power grid.

[0014] When the motor connected to the motor drive operates in a braking regeneration mode, the regenerative energy generated during braking is fed into the c-phase of the power grid.

[0015] In this way, the regenerative energy generated during braking can be fed back into the grid, which helps save energy.

[0016] Optionally, in an example of the above aspect, the first to ninth devices are fully-controlled power transistors.

[0017] Optionally, in an example of the above aspect, the fully-controlled power transistor is an insulated gate bipolar transistor.

[0018] According to another aspect of the present disclosure, a motor driver is provided, wherein an input terminal of the motor driver is connected to a single-phase power grid, and an output terminal of the motor driver is connected to a motor. The motor driver comprises: a rectifier circuit, a DC link circuit, and an inverter circuit. The inverter circuit comprises first, second, and third DC / AC conversion branch circuits arranged in parallel between positive and negative output terminals of the DC link circuit. Each of the first, second, and third DC / AC conversion branch circuits comprises first and second, third and fourth, fifth and sixth switching devices, respectively.

[0019] The rectifier circuit includes a rectifier bridge, a first half-bridge, a first switch, a second switch, and an inductor. The rectifier bridge includes a first bridge arm and a second bridge arm connected in parallel. The first bridge arm includes a first diode and a second diode connected in series. The second bridge arm includes a third diode and a fourth diode connected in series. The first half-bridge includes a ninth switching device, a ninth freewheeling diode, a tenth switching device, and a tenth freewheeling diode. The ninth freewheeling diode is reversely connected between the collector and emitter of the ninth switching device. The tenth freewheeling diode is reversely connected between the collector and emitter of the tenth switching device. The collector of the ninth switching device is connected to the positive output terminal of the rectifier bridge, the emitter of the ninth switching device is connected to the collector of the tenth switching device, and the emitter of the tenth switching device is connected to the negative output terminal of the rectifier bridge.

[0020] The first switch and the inductor are connected in parallel, the input end of the parallel circuit of the first switch and the inductor is connected to the neutral line input end of the single-phase power grid and the midpoint of the second bridge arm of the rectifier bridge, the output end is connected to the midpoint of the first half-bridge, and the second switch is connected between the output end of the single-phase power grid and the midpoint of the first bridge arm of the rectifier bridge.

[0021] The DC link circuit is connected between the rectifier circuit and the inverter circuit. The DC link circuit includes a capacitor and a second half-bridge. The second half-bridge includes a seventh switching device, a seventh freewheeling diode, an eighth switching device, and an eighth freewheeling diode. The seventh freewheeling diode is reversely connected between the collector and emitter of the seventh switching device, and the eighth freewheeling diode is reversely connected between the collector and emitter of the eighth switching device. The first end and the second end of the capacitor are respectively connected to the positive output end and the negative output end of the rectifier circuit. The collector of the seventh switching device is connected to the first end of the capacitor, the emitter of the seventh switching device is connected to the collector of the eighth switch device, and the emitter of the eighth switching device is connected to the second end of the capacitor.

[0022] A midpoint between the seventh switching device and the eighth switching device is connected to the a-phase input terminal of the second switch.

[0023] According to another aspect of the present disclosure, a motor drive system is provided, comprising the motor driver described above and a motor, wherein the motor driver is used to drive the motor, wherein when the motor operates in a braking regeneration mode, the regenerative energy generated during the braking process of the motor is fed back to the power grid.

[0024] In the circuit topology of the motor driver according to the present invention, by adding two half-bridge branches, the brake resistor commonly used in the prior art is eliminated. This brake resistor is typically large, generates a lot of heat, and is expensive. Therefore, the circuit topology of the motor driver according to the present invention has at least one of the following technical advantages.

[0025] 1. It is beneficial to the heat dissipation design of the system and can eliminate the influence of the braking resistor on other temperature sensing components.

[0026] 2. Saving volume. In the circuit topology of the prior art, the braking resistor needs to dissipate the regenerated energy, so it is bulky. Removing the resistor in the circuit topology of the present invention helps to save space.

[0027] 3. Compared with expensive brake resistors, the added components can use commercial components, thus reducing costs.

[0028] 4. The regenerative energy generated during braking can be fed back to the grid, which is beneficial to energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and other purposes, features and advantages of the present invention will be more easily understood by referring to the following description of the embodiments of the present invention in conjunction with the accompanying drawings. The components in the accompanying drawings are only for illustrating the principles of the present invention. In the accompanying drawings, the same or similar technical features or components will be represented by the same or similar reference numerals. In the accompanying drawings:

[0030] FIG1 is a circuit topology diagram of a motor driver in the prior art.

[0031] FIG2 is a circuit topology diagram of a motor driver according to an embodiment of the present disclosure.

[0032] FIG3 is a circuit topology diagram of a motor driver according to another embodiment of the present disclosure.

[0033] The accompanying drawings are numerals as follows:

[0034] 10, 20, 30: Motor driver Ua, Ub and Uc: Power grid

[0035] D1-D10: diodes R1: resistor

[0036] T1-T10: first to tenth switching devices 210, 310: rectifier circuit

[0037] 220, 320: DC link circuit 230, 330: Inverter circuit

[0038] M: Motor 2101, 3101: Rectifier bridge

[0039] 2102, 3102: First half bridge 2301, 2302, 2303: First to third DC / AC conversion branch circuits

[0040] L1: Inductor 2202, 3202: Second half bridge

[0041] C1: Capacitor K1-K3: First to third switches DETAILED DESCRIPTION

[0042] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that discussing these embodiments is intended only to enable those skilled in the art to better understand and implement the subject matter described herein, and is not intended to limit the scope of protection, applicability, or examples set forth in the claims. The functions and arrangements of the elements discussed may be changed without departing from the scope of protection of this disclosure. Various examples may omit, replace, or add various processes or components as needed. For example, the described method may be performed in an order different from the described order, and various steps may be added, omitted, or combined. In addition, features described relative to some examples may also be combined in other examples.

[0043] As used herein, the term "including" and its variations are open terms meaning "including but not limited to". The term "based on" means "based at least in part on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment". The term "another embodiment" means "at least one other embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other definitions may be included below, whether explicit or implicit. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout the specification.

[0044] In view of this, the present invention provides a motor driver that can solve the above-mentioned problems existing in the prior art.

[0045] Figure 2 shows an example circuit topology diagram of a motor driver 20 according to an embodiment of the present disclosure. As shown in Figure 2, the input end of the motor driver 20 is connected to the three phases Ua, Ub and Uc of the three-phase grid, and the output end of the motor driver is connected to a motor M.

[0046] The motor driver 20 includes a rectifier circuit 210 , a DC link circuit 220 , and an inverter circuit 230 .

[0047] The rectifier circuit 210 includes a rectifier bridge 2101 , a first half-bridge 2102 , a first switch K1 , a second switch K2 , a third switch K3 , and an inductor L1 .

[0048] The rectifier bridge 2101 includes a first bridge arm and a second bridge arm connected in parallel. The first bridge arm includes a first diode D1 and a second diode D2 connected in series, and the second bridge arm includes a third diode D3 and a fourth diode D4 connected in series. The first half-bridge 2102 includes a ninth switching device T9, a ninth freewheeling diode D9, a tenth switching device, and a tenth freewheeling diode D10. The ninth switching device T9 has the ninth freewheeling diode D9 connected in reverse between its collector and emitter, and the tenth switching device T10 has the tenth freewheeling diode D10 connected in reverse between its collector and emitter. The collector of the ninth switching device T9 is connected to the positive output terminal of the rectifier bridge 2101, the emitter of the ninth switching device is connected to the collector of the tenth switching device, and the emitter of the tenth switching device T10 is connected to the negative output terminal of the rectifier bridge 2101.

[0049] The inductor L1 is connected between the c-phase Uc of the three-phase power grid and the midpoint of the first half-bridge 2102 (i.e., the midpoint where the ninth switching device T9 is connected to the tenth switching device T10), the first switch K1 is connected in parallel with the inductor L1, the second switch K2 is connected between the a-phase Ua of the three-phase power grid and the midpoint of the first bridge arm of the rectifier bridge 2101, and the third switch K3 is connected between the b-phase Ub of the three-phase power grid and the midpoint of the second bridge arm of the rectifier bridge 2101.

[0050] The DC link circuit 220 is connected between the rectifier circuit 210 and the inverter circuit 230 and is used to filter the output voltage of the rectifier circuit.

[0051] The DC link circuit 220 includes a capacitor C1 and a second half-bridge 2202. The second half-bridge 2202 includes a seventh switch device T7, a seventh freewheeling diode D7, an eighth switch device T8, and an eighth freewheeling diode D8. The seventh freewheeling diode D7 is reversely connected between the collector and emitter of the seventh switch device T7, and the eighth freewheeling diode D8 is reversely connected between the collector and emitter of the eighth switch device T8. The first end and the second end of the capacitor C1 are respectively connected to the positive output terminal and the negative output terminal of the rectifier circuit 210. The collector of the seventh switch device T7 is connected to the first end of the capacitor C1, the emitter of the seventh switch device is connected to the collector of the eighth switch device, and the emitter of the eighth switch device T8 is connected to the second end of the capacitor C1.

[0052] It can be seen that the circuit topologies of the first half-bridge 2102 and the second half-bridge 2202 are the same.

[0053] The inverter circuit 230 is connected to the DC link circuit 220 and includes three parallel first, second and third DC / AC (direct current / alternating current) conversion branch circuits for converting the DC voltage output by the DC link circuit into an AC voltage.

[0054] Specifically, the inverter circuit 230 includes first, second and third DC / AC conversion branch circuits 2301, 2302, 2303 arranged in parallel between the positive and negative output terminals of the DC link circuit 220, and each of the first, second and third DC / AC conversion branch circuits 2301, 2302, 2303 includes a first and a second, a third and a fourth, and a fifth and a sixth switching device T1, T2, T3, T4, T5, T6, respectively.

[0055] The topology of the inverter circuit shown in FIG2 is a common circuit in the prior art. The inverter circuit portion of the present disclosure is not limited to that shown in FIG2 , and may also adopt other topologies, which will not be described in detail here.

[0056] In other examples of the present disclosure, the single fully-controlled power transistor can be composed of multiple fully-controlled power transistors in parallel, series, or mixed. Similarly, the single diode can also be composed of multiple diodes in parallel, series, or mixed. In the present disclosure, the fully-controlled power transistor is, for example, an insulated gate bipolar transistor (IGBT). Those skilled in the art will understand that other types of power transistors can also be used, which will not be described in detail here.

[0057] In normal operation, the first, second, and third switches K1, K2, and K3 of the motor driver 20 are all closed, while the seventh, eighth, ninth, and tenth switches T7, T8, T9, and T10 are inactive. In this case, the inductor L1 is bypassed. The rectifier bridge, along with the ninth and tenth freewheeling diodes D9 and D10, function as a three-phase rectifier bridge.

[0058] When the DC link voltage rises to the protection level, the braking function is activated. At this point, the DC link voltage is greater than the peak grid voltage, blocking bridge rectifier 2101. When the motor operates in braking regeneration mode, the first, second, and third switches K1, K2, and K3 are simultaneously turned on, activating switching devices T7, T8, T9, and T10. The resulting circuit can be viewed as an H-bridge converter, reducing the DC voltage.

[0059] As shown in Figure 2, the midpoint between the seventh and eighth switching devices T7 and T8 is connected to the neutral point of the three-phase grid. In this case, DC link energy (i.e., regenerative energy generated during braking) can be fed into the grid's C phase Uc via inductor L1, effectively utilizing the regenerative energy. Furthermore, the fed current can be controlled to be a sinusoidal wave to avoid injecting harmonics into the grid.

[0060] FIG3 shows an exemplary circuit topology diagram of a motor driver 30 according to another embodiment of the present disclosure.

[0061] As shown in FIG3 , an input end of the motor driver 30 is connected to a single-phase power grid Ua, and an output end of the motor driver is connected to a motor M.

[0062] The motor driver 30 includes a rectifier circuit 310 , a DC link circuit 320 , and an inverter circuit 330 .

[0063] The circuit topology of the DC link circuit 320 and the inverter circuit 330 is substantially the same as that of the DC link circuit 220 and the inverter circuit 230 in the motor driver 20 shown in FIG. 2 , and will not be described again here.

[0064] The rectifier circuit 310 in FIG3 is connected to a single-phase power grid, so its circuit topology is different from that of the rectifier circuit 210 shown in FIG2 .

[0065] Specifically, the rectifier circuit 310 includes a rectifier bridge 3101, a first half-bridge 3102, a first switch K1, a second switch K2 and an inductor L1. The circuit topology of the rectifier bridge 3101 and the first half-bridge 3102 is the same as the circuit topology of the rectifier bridge 2101 and the first half-bridge 2102, and will not be described in detail here.

[0066] In the rectifier circuit 310, the first switch K1 and the inductor L1 are connected in parallel. The input end of the parallel circuit of the first switch K1 and the inductor L1 is connected to the neutral line end of the single-phase power grid Ua and the midpoint of the second bridge arm of the rectifier bridge 3101, and the output end is connected to the midpoint of the first half bridge 3102. The second switch K2 is connected between the output end of the single-phase power grid Ua and the midpoint of the first bridge arm of the rectifier bridge 3101.

[0067] The midpoint between the seventh switching device T7 and the eighth switching device T8 is connected to the input terminal of the a-phase of the second switch K2.

[0068] In normal operation, both the first switch K1 and the second switch K2 are closed, while the seventh, eighth, ninth, and tenth switches T7, T8, T9, and T10 are inactive. In this case, the inductor L1 is bypassed. The rectifier bridge converts AC power from the single-phase grid into DC power, which is then supplied to the DC link circuit 320.

[0069] When the motor operates in braking regeneration mode, the first and second switches K1 and K2 are simultaneously opened, activating the seventh, eighth, ninth, and tenth switching devices T7, T8, T9, and T10, forming an H-bridge converter to reduce the DC voltage. Furthermore, the regenerative energy generated during braking can be fed to the single-phase grid Ua via inductor L1.

[0070] In the circuit topology of the motor driver according to the present invention, by adding two half-bridge branches, the braking resistor commonly used in the prior art is eliminated. This braking resistor is typically large, generates a lot of heat, and is expensive. Therefore, the circuit topology of the motor driver according to the present invention has at least one of the following technical advantages.

[0071] 1. It is beneficial to the heat dissipation design of the system and can eliminate the influence of the braking resistor on other temperature sensing components.

[0072] 2. Saving volume. In the circuit topology of the prior art, the braking resistor needs to dissipate the regenerated energy, so it is bulky. Removing the resistor in the circuit topology of the present invention helps to save space.

[0073] 3. Compared with expensive brake resistors, the added components can use commercial components, thus reducing costs.

[0074] 4. The regenerative energy generated during braking can be fed back to the grid, which is beneficial to energy saving.

[0075] The specific embodiments described above in conjunction with the accompanying drawings describe exemplary embodiments, but do not represent all embodiments that can be implemented or fall within the scope of protection of the claims. The term "exemplary" used throughout this specification means "used as an example, instance or illustration" and does not mean "preferred" or "having advantages" over other embodiments. For the purpose of providing an understanding of the described technology, the specific embodiments include specific details. However, these technologies can be implemented without these specific details. In some instances, in order to avoid obscuring the concepts of the described embodiments, well-known structures and devices are shown in block diagram form.

[0076] The foregoing description of the present disclosure is provided to enable any person skilled in the art to implement or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but is intended to be consistent with the widest range of principles and novel features disclosed herein.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A motor driver (20), wherein an input end of the motor driver (20) is connected to a three-phase power grid (Ua, Ub, Uc), an output end of the motor driver (20) is connected to a motor (M), and the motor driver (20) comprises: A rectifier circuit (210), a DC link circuit (220) and an inverter circuit (230), wherein the inverter circuit (230) comprises first, second and third DC / AC conversion branch circuits (2301, 2302, 2303) arranged in parallel between the positive and negative output terminals of the DC link circuit (220), and each of the first, second and third DC / AC conversion branch circuits (2301, 2302, 2303) comprises first and second, third and fourth, fifth and sixth switching devices (T1, T2, T3, T4, T5, T6), respectively, characterized in that: The rectifier circuit (210) comprises a rectifier bridge (2101), a first half-bridge (2102), a first switch (K1), a second switch (K2), a third switch (K3), and an inductor (L1); the rectifier bridge (2101) comprises a first bridge arm and a second bridge arm connected in parallel; the first bridge arm comprises a first diode (D1) and a second diode (D2) connected in series; the second bridge arm comprises a third diode (D3) and a fourth diode (D4) connected in series; the first half-bridge (2102) comprises a ninth switch device (T9), a ninth freewheeling diode (D9), a tenth switch device (T9), and a ninth freewheeling diode (D9). (T10) and a tenth freewheeling diode (D10), wherein the ninth freewheeling diode (D9) is reversely connected between the collector and the emitter of the ninth switching device (T9), the tenth freewheeling diode (D10) is reversely connected between the collector and the emitter of the tenth switching device (T10), the collector of the ninth switching device (T9) is connected to the positive output terminal of the rectifier bridge (2101), the emitter of the ninth switching device (T9) is connected to the collector of the tenth switching device (T10), and the emitter of the tenth switching device (T10) is connected to the negative output terminal of the rectifier bridge (2101), The inductor (L1) is connected between the c-phase (Uc) of the three-phase power grid and the midpoint of the first half-bridge (2102); the first switch (K1) is connected in parallel with the inductor (L1); the second switch (K2) is connected between the a-phase (Ua) of the three-phase power grid and the midpoint of the first bridge arm of the rectifier bridge (2101); and the third switch (K3) is connected between the b-phase (Ub) of the three-phase power grid and the midpoint of the second bridge arm of the rectifier bridge (2101). The DC link circuit (220) is connected between the rectifier circuit (210) and the inverter circuit (230), the DC link circuit (220) comprises a capacitor (C1) and a second half-bridge (2202), the second half-bridge (2202) comprises a seventh switch device (T7), a seventh freewheeling diode (D7), an eighth switch device (T8), and an eighth freewheeling diode (D8), the seventh freewheeling diode (D7) being reversely connected between the collector and emitter of the seventh switch device (T7), and the eighth switch device (T8). An eighth freewheeling diode (D8) is reversely connected between the collector and emitter of the seventh switching device (T8), wherein the first end and the second end of the capacitor (C1) are respectively connected to the positive output end and the negative output end of the rectifier circuit (210), the collector of the seventh switching device (T7) is connected to the first end of the capacitor (C1), the emitter of the seventh switching device (T7) is connected to the collector of the eighth switching device (T8), and the emitter of the eighth switching device (T8) is connected to the second end of the capacitor (C1).

2. The motor driver (20) of claim 1, wherein: The midpoint of the seventh switching device (T7) and the eighth switching device (T8) is connected to the neutral point of the three-phase power grid, When the motor connected to the motor driver (20) operates in a braking regeneration mode, the regenerative energy generated during braking is fed into the c-phase of the power grid.

3. The motor driver (20) according to claim 1 or 2, wherein: The first to tenth devices ( T1 , T2 , T3 , T4 , T5 , T6 , T7 , T8 , T9 , T10 ) are fully controlled power transistors.

4. The motor driver (20) of claim 3, wherein: The fully controlled power transistor is an insulated gate bipolar transistor.

5. A motor driver (30), wherein an input end of the motor driver (30) is connected to a single-phase power grid (Ua), an output end of the motor driver (30) is connected to a motor (M), and the motor driver (30) comprises: A rectifier circuit (310), a DC link circuit (320) and an inverter circuit (330), wherein the inverter circuit (330) comprises first, second and third DC / AC conversion branch circuits (2301, 2302, 2303) arranged in parallel between the positive and negative output terminals of the DC link circuit (320), each of the first, second and third DC / AC conversion branch circuits (2301, 2302, 2303) comprising first and second, third and fourth, fifth and sixth switching devices (T1, T2, T3, T4, T5, T6), respectively, characterized in that: The rectifier circuit (310) comprises a rectifier bridge (3101), a first half-bridge (3102), a first switch (K1), a second switch (K2), and an inductor (L1); the rectifier bridge (3101) comprises a first bridge arm and a second bridge arm connected in parallel; the first bridge arm comprises a first diode (D1) and a second diode (D2) connected in series; the second bridge arm comprises a third diode (D3) and a fourth diode (D4) connected in series; the first half-bridge (3102) comprises a ninth switch device (T9), a ninth freewheeling diode (D9), a tenth switch device (T11), and a tenth freewheeling diode (T12). 10) and a tenth freewheeling diode (D10), the ninth freewheeling diode (D9) is reversely connected between the collector and emitter of the ninth switching device (T9), the tenth freewheeling diode (D10) is reversely connected between the collector and emitter of the tenth switching device (T10), the collector of the ninth switching device (T9) is connected to the positive output terminal of the rectifier bridge (3101), the emitter of the ninth switching device (T9) is connected to the collector of the tenth switching device (T10), and the emitter of the tenth switching device (T10) is connected to the negative output terminal of the rectifier bridge (3101), The first switch (K1) and the inductor (L1) are connected in parallel, the input end of the parallel circuit of the first switch (K1) and the inductor (L1) is connected to the neutral terminal of the single-phase power grid and the midpoint of the second bridge arm of the rectifier bridge (3101), and the output end is connected to the midpoint of the first half-bridge (3102), and the second switch (K2) is connected between the output end of the single-phase power grid and the midpoint of the first bridge arm of the rectifier bridge (3101). The DC link circuit (320) is connected between the rectifier circuit (310) and the inverter circuit (330), the DC link circuit (320) includes a capacitor (C1) and a second half-bridge (3202), the second half-bridge includes a seventh switch device (T7), a seventh freewheeling diode (D7), an eighth switch device (T8), and an eighth freewheeling diode (D8), the seventh freewheeling diode (D7) being reversely connected between the collector and emitter of the seventh switch device (T7), and the eighth freewheeling diode (D8) being reversely connected between the collector and emitter of the eighth switch device (T8), wherein the first end and the second end of the capacitor (C1) are respectively connected to the positive output end and the negative output end of the rectifier circuit (310), the collector of the seventh switch device (T7) is connected to the first end of the capacitor (C1), the emitter of the seventh switch device (T7) is connected to the collector of the eighth switch device (T8), and the emitter of the eighth switch device (T8) is connected to the second end of the capacitor (C1); A midpoint between the seventh switching device and the eighth switching device is connected to the a-phase input terminal of the second switch.

6. A motor drive system comprising a motor driver according to any one of claims 1 to 5 and a motor, wherein the motor driver is used to drive the motor, wherein: When the motor operates in a braking regeneration mode, the regenerative energy generated during the braking of the motor is fed back to the grid.

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