Motor driver

Abstract

The invention relates to a motor driver which comprises a rectifying circuit, a direct current chain circuit, an inverter circuit, a filter circuit and a compensating circuit, the inverter circuit comprises a first direct current / alternating current conversion branch, a second direct current / alternating current conversion branch and a third direct current / alternating current conversion branch which are arranged between the positive electrode output end and the negative electrode output end of the direct current chain circuit in parallel, and the filter circuit comprises a three-phase inductor. The head ends of the three inductors of the three-phase inductor are respectively connected with the midpoints of the first to third DC / AC conversion branches, and the tail ends of the three inductors respectively output three-phase voltages; the compensating circuit comprises a coupling inductor with a center tap and a solid-state circuit breaker, the coupling inductor is coupled with the three-phase inductor, a moving point of the solid-state circuit breaker comprises a first switch contact and a second switch contact, the first switch contact is connected with the head end of the coupling inductor, the second switch contact is connected with the center tap of the coupling inductor, and the first switch contact is connected with the head end of the coupling inductor. The solid-state circuit breaker is connected with the midpoint of the half-bridge branch, and the tail end of the coupling inductor is connected with the midpoint of the capacitance branch.

Description

TECHNICAL FIELD

[0002] The present disclosure relates generally to the field of circuit technology, and more specifically, to a motor driver. BACKGROUND

[0004] Variable frequency drives (VFC) are widely used in motor drive and servo industry. VFCs using PWM technique will generate high frequency common mode voltage on motor terminals, which results in bearing current and can cause severe bearing damage. In addition, high frequency common mode voltage will cause EMI problem. In order to suppress these adverse effects on motor drive products and improve system reliability, the output common mode voltage of VFC should be limited.

[0005] Figure 1 is a circuit topology of a motor driver in prior art. It has a three-phase diode rectifier bridge and uses a three-phase two-level half bridge as a DC / AC inverter. R, S, T are three-phase grid input terminals, U, V, W are output terminals to a three-phase motor. C1 is a DC link capacitor. R1, T8 and D7 are used to dissipate transient DC link high voltage generated during motor regeneration. The DC / AC output voltages V1, V2 and V3 contain high frequency common mode voltage, which will be applied to motor terminals and generate harmful motor bearing current.

[0006] In some applications with long motor cables, a three-phase LC filter can be installed to suppress overvoltage at motor terminals. The output filter can reduce high frequency components in differential mode voltage, however, it has no effect on common mode voltage.

[0007] In order to eliminate bearing current caused by common mode voltage, some countermeasures are taken. On the one hand, a ground brush on the motor shaft can be used to bypass the bearing current, but the ground brush is a consumable part and needs regular maintenance and replacement. Increasing bearing insulation is another way to eliminate bearing current, but it increases system cost and can cause additional heat dissipation problem. On the other hand, an improved output filter can be used to suppress common mode voltage. For example, the DC link capacitor is divided into two capacitors in series. A three-phase filter is added on the output side and the star connection point of the filter capacitor is connected to the midpoint of the DC link capacitor. This solution can help reduce high frequency components in both differential mode voltage and common mode voltage. However, in order to obtain better filtering effect, the volume of the output filter is very large, and the common mode voltage cannot be completely eliminated. SUMMARY

[0009] The following presents a simplified summary of the application in order to provide a basic understanding of some aspects of the application. This summary is not an extensive overview of the application. It is not intended to identify key or critical elements of the application or to delineate the scope of the application. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

[0010] In view of the above, the present disclosure provides a motor driver capable of eliminating common-mode voltage.

[0011] According to one aspect of the present disclosure, a motor driver is provided, comprising a rectifier circuit, a DC link circuit, an inverter circuit, a filter circuit and a compensation circuit, wherein,

[0012] The rectifier circuit comprises three AC / DC conversion branches for converting input AC voltage into DC voltage;

[0013] The DC link circuit is connected between the positive output terminal and the negative output terminal of the rectifier circuit, and comprises an energy discharge branch, a capacitor branch and a half-bridge branch connected in parallel, wherein the capacitor branch comprises two capacitors, and the half-bridge branch comprises two switching devices;

[0014] The inverter circuit comprises first to third DC / AC conversion branches arranged in parallel between the positive output terminal and the negative output terminal of the DC link circuit, each of the first to third DC / AC conversion branches comprising two switching devices;

[0015] The filter circuit comprises a three-phase inductor, and the three inductors of the three-phase inductor are respectively connected to the midpoints of the first to third DC / AC conversion branches at their first ends, and the three inductors are respectively connected to output three-phase voltage at their second ends;

[0016] The compensation circuit comprises a center-tapped coupled inductor and a solid-state circuit breaker, the coupled inductor is coupled to the three-phase inductor,

[0017] The moving point of the solid-state circuit breaker comprises a first switching contact and a second switching contact, the first switching contact is connected to the first end of the coupled inductor, the second switching contact is connected to the center tap of the coupled inductor, the solid-state circuit breaker is connected to the midpoint of the half-bridge branch, and the second end of the coupled inductor is connected to the midpoint of the capacitor branch.

[0018] In this way, a compensation voltage can be generated by the coupled inductor to offset the DC / AC common-mode voltage.

[0019] Optionally, in one example of the above aspect, the coupling inductor comprises a first inductor and a second inductor, the center tap is connected between the first inductor and the second inductor, the number of turns of the first inductor is twice the number of turns of the second inductor, and the number of turns of each of the three inductors of the three-phase inductor is equal to the number of turns of the second inductor.

[0020] In this way, the required number of turns of the coupling inductor can be obtained by connecting different switch contacts of the solid-state circuit breaker.

[0021] Optionally, in one example of the above aspect, the switching states of the two switching devices of the half-bridge branch and which of the first contact and the second contact is configured to be controlled according to the switching states of the switching devices of each of the first to third DC / AC conversion branches, so that the coupling inductor generates a compensation voltage with a magnitude equal to that of the common-mode voltage generated by the inverter circuit.

[0022] In this way, a compensation voltage with the same magnitude as the common-mode voltage but opposite polarity can be generated, thereby canceling the common-mode voltage.

[0023] Optionally, in one example of the above aspect, the first ends of the coupling inductor and the three-phase inductor are either the same name end or the different name end, and in both cases, the switching states of the two switching devices of the half-bridge branch are opposite.

[0024] In this way, different connection modes of the coupling inductor can be selected as needed.

[0025] Optionally, in one example of the above aspect, each switching device comprises a fully controlled power switch tube and a power diode connected in antiparallel.

[0026] According to another aspect of the present disclosure, there is provided an electric motor driver, comprising: a rectifier circuit, a DC link circuit, an inverter circuit, a filter circuit and a compensation circuit, wherein,

[0027] The rectifier circuit comprises three AC / DC conversion branch circuits for converting an input AC voltage into a DC voltage;

[0028] The DC link circuit is connected between the positive output end and the negative output end of the rectifier circuit, and comprises: an energy discharge branch connected in parallel, a capacitor branch, a first half-bridge branch and a second half-bridge branch, the capacitor branch comprises two capacitors, and the first half-bridge branch and the second half-bridge branch each comprise two switching devices;

[0029] The inverter circuit comprises first to third DC / AC conversion branches connected in parallel between the positive and negative output terminals of the DC link circuit, each of the first to third DC / AC conversion branches comprising two switching devices;

[0030] The filter circuit comprises a three-phase inductor, three inductors of the three-phase inductor having respective first ends connected to the midpoints of the first to third DC / AC conversion branches and respective second ends outputting three-phase voltages;

[0031] The compensation circuit comprises a first coupling inductor and a second coupling inductor,

[0032] The first coupling inductor has a first end connected to the midpoint of the second half-bridge branch, the second coupling inductor has a first end connected to the midpoint of the first half-bridge branch, and the second coupling inductor and the first coupling inductor have second ends connected to the midpoint of the capacitor branch.

[0033] In this way, the compensation voltage can be generated by the coupling inductor to offset the DC / AC common-mode voltage.

[0034] Optionally, in one example of the above aspect, the second coupling inductor has a number of turns that is three times the number of turns of the first coupling inductor, and the three inductors of the three-phase inductor each have a number of turns that is equal to the number of turns of the first inductor.

[0035] In this way, by controlling the conduction states of the first and second half-bridge branches, it is possible to control which of the first and second coupling inductors is connected to the circuit, thereby obtaining the required number of turns of the coupling inductor.

[0036] Optionally, in one example of the above aspect, the switching states of the switching devices of the first and second half-bridge branches are configured to be controlled according to the switching states of the first to third DC / AC conversion branches, so that the compensation voltage generated by the first coupling inductor or the second coupling inductor has a magnitude equal to that of the common-mode voltage generated by the inverter circuit.

[0037] In this way, by controlling the conduction states of the first and second half-bridge branches, it is possible to generate a compensation voltage having the same magnitude as the common-mode voltage but opposite polarity, thereby offsetting the common-mode voltage.

[0038] Optionally, in one example of the above aspect, the first ends of the first and second coupling inductors are the same terminals, and the first ends of the first and second coupling inductors and the first ends of the three-phase inductor are either the same terminals or different terminals, in which case the switching states of the two switching devices of the half-bridge branch that is turned on are opposite.

[0039] In this way, different connection modes of the coupled inductors can be selected as needed.

[0040] The circuit topology of the motor driver according to the present disclosure can eliminate common-mode voltage and reduce possible damage to the motor bearing, thus improving system reliability. Since the common-mode voltage is eliminated, it is beneficial to EMI performance, thus improving the stability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0042] The above and other objects, features and advantages of the present application will be more apparent from the following description in conjunction with the accompanying drawings. The components in the drawings are merely for illustrating the principles of the present application. In the drawings, the same or similar technical features or components will be designated by the same or similar reference signs. In the drawings:

[0043] Figure 1 is a circuit topology diagram of a motor driver in the prior art.

[0044] Figure 2 is an example circuit topology diagram of a motor driver according to one embodiment of the present disclosure.

[0045] Figure 3 is an example circuit topology diagram of a motor driver according to another embodiment of the present disclosure.

[0046] Figure 4 is an example circuit topology diagram of a motor driver according to another embodiment of the present disclosure.

[0047] Figure 5 is an example circuit topology diagram of a motor driver according to yet another embodiment of the present disclosure.

[0048] In the drawings, the following reference signs are used:

[0049] DETAILED DESCRIPTION

[0051] The subject matter described herein will now be discussed with reference to example implementations. It should be understood that these implementations are discussed solely for the purpose of illustrating aspects of the subject matter described herein and are not intended to be a limitation on the scope of protection, applicability, or examples set forth in the claims. Changes in the function and arrangement of elements discussed can be made without departing from the scope of the disclosure. Various examples can omit, substitute, or add various procedures or components as appropriate. For instance, the methods described can be performed in an order different than that described, and / or various steps can be added, omitted, or combined. Also, features described with respect to some examples can be combined in other examples.

[0052] As used herein, the term "includes" and its variants are meant to be interpreted broadly. 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 additional embodiment." The terms "a or an" and "the" mean "one or more." The following detailed description is presented in terms of examples, systems, and methods. It should be understood, however, that these examples, systems, and methods are not intended to constrain the scope, applicability, or configuration of the claimed subject matter. Rather, the foregoing description of examples, systems, and methods should be viewed as being illustrative in nature. Various changes to the examples, systems, and methods can be made without departing from the scope or spirit of the claimed subject matter. It should be further understood that aspects of the examples, systems, and methods discussed can be combined in any combination.

[0053] Figure 2 An example circuit topology of the motor driver 20 according to one embodiment of the disclosure is shown. As shown, the motor driver 20 includes a rectifier circuit 202, a DC link circuit 204, an inverter circuit 206, a filter circuit 208, and a compensation circuit 210. Figure 2 The rectifier circuit 202 is configured to convert an alternating voltage input to the motor driver 20 into a direct voltage.

[0054] The rectifier circuit 202 is configured to convert an alternating voltage input to the motor driver 20 into a direct voltage.

[0055] The rectifier circuit 202 includes three AC / DC conversion branch circuits, each of which includes two diodes connected in the same direction in series, such as diodes D1, D2, D3, D4, D5, and D6. Input terminals R, S, and T of a three-phase power supply of the motor driver are connected to nodes between the two diodes of the corresponding branch circuit.

[0056] The DC link circuit 204 is connected between the positive output terminal and the negative output terminal of the rectifier circuit 202 and is configured to filter the direct voltage output by the rectifier circuit 202.

[0057] In particular, the DC link circuit 204 includes an energy discharge branch 2042, a capacitor branch 2044, and a half-bridge branch 2046 connected in parallel.

[0058] The energy discharge branch 2042 can include, for example, a diode D7 and a resistor R1 connected in parallel, the cathode of the diode connected to the positive output terminal of the rectifier circuit 202, the anode of the diode connected in series to a switching device T8, and the switching device T8 connected to the negative output terminal of the rectifier circuit 202.

[0059] The capacitor branch 2044 includes two capacitors C1 and C2 connected between the positive output terminal and the negative output terminal, and the half-bridge branch includes two switching devices T9 and T10 connected between the positive output terminal and the negative output terminal.

[0060] Each switching device employed in the present disclosure includes a power transistor of the full control type and a power diode connected in anti-parallel. Specifically, it can be composed of a single power transistor of the full control type and a single diode, the anode and cathode of the diode connected to the emitter and collector of the power transistor of the full control type, respectively. In other examples of the present disclosure, the single power transistor of the full control type can be composed of a plurality of power transistors of the full control type in parallel, in series, or in a hybrid connection. Likewise, the single diode can also be composed of a plurality of diodes in parallel, in series, or in a hybrid connection. In the present disclosure, the power transistor of the full control type is, for example, an Insulated Gate Bipolar Transistor (IGBT).

[0061] In other examples of the present disclosure, the switching device can also be composed of a single power field effect transistor of the full control type and a single diode, the anode and cathode of the diode connected to the source and drain of the power field effect transistor of the full control type, respectively. Likewise, in other examples of the present disclosure, the single power field effect transistor of the full control type can be composed of a plurality of power field effect transistors of the full control type in parallel, in series, or in a hybrid connection. Likewise, the single diode can also be composed of a plurality of diodes in parallel, in series, or in a hybrid connection. In the present example, the power field effect transistor of the full control type is, for example, a power field effect transistor of the full control type of the enhancement type, a power field effect transistor of the full control type of the depletion type.

[0062] In the present disclosure, the specific type of the switching device is not limited, and for the sake of simplicity, it is referred to as a switching device in the present specification.

[0063] The inverter circuit 206 is connected to the DC link circuit 204, and includes three parallel first to third DC / AC (Direct Current / Alternating Current) conversion branches provided between the positive output terminal and the negative output terminal of the DC link circuit 204, for converting the DC voltage output from the DC link circuit into an AC voltage.

[0064] Specifically, each of the first to third DC / AC conversion branch circuits comprises two switching devices T1, T2, T3, T4, T5, T6, respectively, wherein the switching devices T1, T2, T3, T4, T5 and T6 are the same switching devices as the switching devices T8, T9 and T10.

[0065] The filter circuit 208 is configured to filter the voltage output by the inverter circuit 206.

[0066] Specifically, the filter circuit 208 comprises a three-phase inductor Labc, and three inductances of the three-phase inductor Labc are connected to the midpoints V1, V2, V3 of the first to third DC / AC conversion branch circuits, respectively, and the three inductances output three-phase voltages U, V, W, respectively.

[0067] The compensation circuit 210 comprises a coupled inductor L12 with a center tap and a solid-state circuit breaker K1. The coupled inductor L12 is coupled to the three-phase inductor Labc.

[0068] The solid-state circuit breaker K1 is configured to switch between a first switching contact 1 and a second switching contact 2, the first switching contact 1 is connected to the start of the coupled inductor L12, the second switching contact 2 is connected to the center tap CP of the coupled inductor L12, and the other end of the solid-state circuit breaker K1 is connected to the midpoint V4 of the half-bridge branch 2046, and the end of the coupled inductor L12 is connected to the midpoint O (i.e., the point between the two capacitors) of the capacitor branch 2044.

[0069] Specifically, the coupled inductor L12 comprises a first inductor L1 and a second inductor L2, and the first inductor L1 and the second inductor L2 have a center tap CP, wherein the number of turns of the first inductor L1 is twice the number of turns of the second inductor L2, and the number of turns of the three inductances of the three-phase inductor Labc are equal to each other and equal to the number of turns of the second inductor L2. Table 1 below shows the relationship between the number of turns of the three inductances (denoted as La, Lb and Lc in the table below) of the three-phase inductor Labc and the first inductor L1 and the second inductor L2.

[0070]

[0071] Table 1. Number of turns of inductors

[0072] It can be understood that when the solid-state circuit breaker K1 is connected to the first switching contact 1, both the first inductor L1 and the second inductor L2 are connected to the circuit, and the equivalent number of turns of the inductors is equivalent to 3N; when the solid-state circuit breaker K1 is connected to the second switching contact 2, only the second inductor L2 is connected to the circuit, and the number of turns of the inductor is N.

[0073] Capacitors C1 and C2 share the DC-link voltage Vdc, so each capacitor bears half of the DC bus voltage Vdc / 2. The common-mode voltage can be expressed as Vcm = (V1 + V2 + V3) / 3. According to the principle of SVPWM (Space Vector Pulse Width Modulation), the common-mode voltage will have 4 possible values (relative to the O point), as shown in Table 2. The common-mode voltage will vary according to different switching vectors. Table 2 below shows the magnitude of the common-mode voltage corresponding to different switching vectors. Among them, the three numbers of the DC / AC switching vector represent the closing and opening states of the switching devices of the three DC / AC conversion branches, "1" represents that the switching device (i.e. T1, T3 and T5) above the DC / AC conversion branch is closed, "0" represents that the switching device (i.e. T2, T4, T6) below the DC / AC conversion branch is closed, and only one of the two switching devices of a branch is in the closed state at the same time.

[0074]

[0075] Table 2. Switching vectors and common-mode voltage

[0076] The switching states of the two switching devices of the half-bridge branch and the connection mode of the solid-state circuit breaker K1 can be controlled according to the switching state (i.e. which switching device is closed and which is open) of each branch in the first to third DC / AC conversion branches, so that the coupling inductors L1 or L2 generate a suitable compensation voltage on the three-phase inductor Labc, which can offset the common-mode voltage, and even theoretically completely eliminate the common-mode voltage.

[0077]

[0078] Table 3. Switching vectors and compensation voltage

[0079] The data in Table 3 represent the states of T9, T10 and K1 and the magnitude of the generated compensation voltage under different DC / AC switching vectors. The data in Table 3 will be explained in detail below.

[0080] 1) When the switching vector is 111, the generated common-mode voltage is Vdc / 2. In this case, T9 is controlled to be open, T10 is controlled to be closed, and K1 is connected to the second switching contact 2. A voltage of -Vdc / 2 will be applied to the inductor L2, and a coupling voltage -Vdc / 2 will be generated on the three windings of Labc, thereby offsetting the common-mode voltage.

[0081] 2) When the switching vector is 000, the generated common-mode voltage is -Vdc / 2. In this case, T9 is controlled to be closed, T10 is controlled to be open, and K1 is connected to the second switching contact 2. A voltage of Vdc / 2 will be applied to the inductor L2, and a coupling voltage Vdc / 2 will be generated on the three windings of Labc, thereby offsetting the common-mode voltage.

[0082] 3) When the switch vector is 110, 101 or 011, the common-mode voltage generated is Vdc / 6. In this case, control T9 is open, T10 is closed, K1 is connected to the first switch contact 1, and the total number of turns of L1+L2 is 3N. A voltage of -Vdc / 2 will be applied to the inductor L1+L2, generating a coupling voltage -Vdc / 6 on the three windings of Labc, thereby canceling the common-mode voltage.

[0083] 4) When the switch vector is 001, 010 or 100, the common-mode voltage is -Vdc / 6. In this case, control T9 is closed, T10 is open, K1 is connected to the first switch contact 1, and the total number of turns of L1+L2 is 3N. A voltage of Vdc / 6 will be applied to the inductor L1+L2, generating a coupling voltage Vdc / 6 on the three windings of Labc, thereby canceling the common-mode voltage.

[0084] In this way, according to the switching state of the switching devices in each of the first to third DC / AC conversion branches, the switching state of the two switching devices T9, T10 of the half-bridge branch 2046, and which of the first contact 1 and the second contact 2 the solid-state circuit breaker K1 is connected to, a compensation voltage equal in size to the common-mode voltage generated by the inverter circuit can be generated, thereby canceling the common-mode voltage.

[0085] Figure 2 The circuit topology of the motor driver shown is only one specific embodiment, and in fact, the rectifier circuit, the inverter circuit, the filter circuit, and the energy discharge circuit, the capacitor circuit, etc. in the DC link circuit can adopt the circuit topology in the prior art, and the specific circuit topology can be the same as the circuit shown or can not be the same, which is not limited by the present application. Figure 1 The circuit topology of the motor driver shown is only one specific embodiment, and in fact, the rectifier circuit, the inverter circuit, the filter circuit, and the energy discharge circuit, the capacitor circuit, etc. in the DC link circuit can adopt the circuit topology in the prior art, and the specific circuit topology can be the same as the circuit shown or can not be the same, which is not limited by the present application.

[0086] In order to verify the performance of the motor driver adopting the circuit topology of one embodiment of the present application shown in Figure 2 , the inventors have carried out simulation experiments. According to the experimental results, without using the common-mode voltage compensation circuit according to the present application, the common-mode voltage generated has 4 voltage levels, and the peak voltage is equal to the DC bus voltage. While using the compensation circuit, the common-mode voltage can be greatly reduced.

[0087] Figure 3 An example circuit topology diagram of a motor driver according to another embodiment of the present application is shown.

[0088] In the circuit topology of the motor driver shown in Figure 3 , the connection direction of the coupling inductor in the compensation circuit is opposite to that of the coupling inductor L12 in the circuit topology shown in Figure 2 Figure 1 ​In the diagram, the starting terminals of the coupled inductor L12 and the three-phase inductor Labc are of the same name, while... Figure 2 In the diagram, the starting terminals of the coupled inductor L12 and the three-phase inductor Labc are opposite-named terminals.

[0089] exist Figure 3 In the motor driver shown, the switching states of the two switching devices T9 and T10 in the half-bridge branch, as well as which contact point K1 is connected to, can be controlled according to Table 4 below. It can be seen that, in this case, the switching states of T9 and T10 are... Figure 1 The switching states of the coupled inductor L12 and the three-phase inductor Labc are opposite when their starting terminals are of the same name. The connection method of K1 is the same as... Figure 1 The situation is the same as in [the previous sentence].

[0090]

[0091] Table 4

[0092] Apart from the fact that the coupling capacitors are connected in opposite directions, Figure 3 The circuit topology of the motor driver shown is similar to... Figure 2 The circuit topology for the motor drive is the same, and the same circuit components use the same reference numerals, so they will not be described again here.

[0093] Figure 4 An example circuit topology diagram of a motor driver 40 according to another embodiment of this disclosure is shown. Figure 4 As shown, the motor driver 40 includes: a rectifier circuit 402, a DC link circuit 404, an inverter circuit 406, a filter circuit 408, and a compensation circuit 410.

[0094] The rectifier circuit 402 is used to convert the input AC voltage into DC voltage.

[0095] The rectifier circuit 402 includes three AC / DC conversion branch circuits, each branch circuit including two diodes connected in series in the same direction, such as diodes D1, D2, D3, D4, D5, and D6. The input terminals R, S, and T of the three-phase power supply of the motor driver are respectively connected to the nodes between the two diodes in the corresponding branch circuits.

[0096] The DC link circuit 404 is connected between the positive output terminal and the negative output terminal of the rectifier circuit 402.

[0097] The DC link circuit 404 includes: an energy discharge branch 4042, a capacitor branch 4044, a first half-bridge branch 4046, and a second half-bridge branch 4048 connected in parallel.

[0098] The energy discharge branch 4042 can use a common circuit topology, which will not be described in detail here.

[0099] The capacitance branch 4044 includes two capacitors C1 and C2 connected between the positive output terminal and the negative output terminal.

[0100] The first half-bridge branch 4046 includes two switching devices T9 and T10, and the second half-bridge branch 4048 includes two switching devices T11 and T12.

[0101] The inverter circuit 406 includes first to third DC / AC conversion branches arranged in parallel between the positive and negative output terminals of the DC link circuit 404, each of the first to third DC / AC conversion branches including two switching devices T1, T2, T3, T4, T5, T6, respectively.

[0102] The filter circuit 408 includes a three-phase inductor Labc, three inductors of the three-phase inductor Labc each having a first end connected to a midpoint V1, V2, V3 of the first to third DC / AC conversion branches, respectively, and each having a second end outputting a three-phase voltage U, V, W, respectively.

[0103] The compensation circuit 410 includes a first coupling inductor L11 and a second coupling inductor L22.

[0104] The first end of the first coupling inductor L11 is connected to the midpoint V6 of the second half-bridge branch 4048, the first end of the second coupling inductor L22 is connected to the midpoint V5 of the first half-bridge branch 4046, and the second ends of the first and second coupling inductors L11 and L22 are connected to the midpoint O of the capacitance branch 4044.

[0105] The number of turns of the second coupling inductor L22 is three times the number of turns of the first coupling inductor L11, and the numbers of turns of the three inductors of the three-phase inductor Labc are equal to each other and equal to the number of turns of the first coupling inductor L11.

[0106]

[0107] Table 5. Numbers of turns of inductors

[0108] Capacitors C1 and C2 share the DC link voltage Vdc, so each capacitor bears half of the DC bus voltage Vdc / 2. The common mode voltage can be expressed as Vcm = (V1 + V2 + V3) / 3. According to the principle of SVPWM, the common mode voltage will have 4 possible values (relative to the O point), as shown in Table 6. The common mode voltage will vary according to different switching vectors. Table 6 below shows the magnitude of the common mode voltage corresponding to different switching vectors. Among them, the three numbers of the DC / AC switching vector represent the closing and opening states of the switching devices of the three DC / AC conversion branches, "1" represents that the switching devices (i.e. T1, T3 and T5) above the DC / AC conversion branch are closed, "0" represents that the switching devices (i.e. T2, T4, T6) below the DC / AC branch are closed, and only one of the two switching devices of a branch is in a closed state at the same time.

[0109]

[0110] Table 6. Switching vectors and common mode voltage

[0111] The switching states of the switching devices of the first half-bridge branch and the second half-bridge branch can be controlled according to the switching vectors (the switching states of each branch in the first to third DC / AC conversion branches), so that the first coupling inductance L11 or the second coupling inductance L22 generates a suitable compensation voltage on the three-phase inductance Labc, which can offset the common mode voltage, and even theoretically completely eliminate the common mode voltage.

[0112]

[0113] Table 7. Switching vectors and compensation voltage

[0114] The data in Table 7 represent the states of T9, T10 and K1 and the magnitude of the generated compensation voltage under different DC / AC switching vectors. The data in Table 7 will be explained in detail below.

[0115] 1) When the switching vector is 111, the generated common mode voltage is Vdc / 2. In this case, T9, T10 and T11 are controlled to be open, and T12 is closed. The voltage of -Vdc / 2 will be applied to the inductance L1, generating a coupling voltage -Vdc / 2 on the three windings of Labc, thereby offsetting the common mode voltage.

[0116] 2) When the switching vector is 000, the generated common mode voltage is -Vdc / 2. In this case, T9, T10 and T12 are controlled to be open, and T11 is closed. The voltage of Vdc / 2 will be applied to the inductance L1, generating a coupling voltage Vdc / 2 on the three windings of Labc, thereby offsetting the common mode voltage.

[0117] 3) When the switching vector is 110, 101, or 011, the resulting common-mode voltage is Vdc / 6. In this case, controls T9, T11, and T12 are open, and T10 is closed. A voltage of -Vdc / 2 will be applied to inductor L2, generating a coupling voltage of -Vdc / 6 across the three windings of Labc, thereby canceling the common-mode voltage.

[0118] 4) When the switch vector is 001, 010, or 100, the common-mode voltage is -Vdc / 6. In this case, controls T10, T11, and T12 are open, and T9 is closed. The Vdc / 6 voltage will be applied to inductor L2, generating a coupling voltage Vdc / 6 across the three windings of Labc, thereby canceling the common-mode voltage.

[0119] Figure 4 The circuit topology of the motor driver shown is only a specific embodiment. In reality, the rectifier circuit, inverter circuit, filter circuit, and energy discharge circuit and capacitor circuit in the DC link circuit can adopt existing circuit topologies. The specific circuit topology can be similar to... Figure 4 The circuits shown may be the same or different; this invention does not limit this.

[0120] To verify the adoption Figure 4 The inventors conducted simulation experiments to assess the performance of the motor driver based on the circuit topology of another embodiment of the present invention. According to the experimental results, without the common-mode voltage compensation circuit according to the present invention, the generated common-mode voltage has four voltage levels, with the peak voltage equal to the DC bus voltage. However, with the compensation circuit, the common-mode voltage can be significantly reduced.

[0121] Figure 5 An example circuit topology diagram of a motor driver according to another embodiment of the present invention is shown.

[0122] exist Figure 5 In the circuit topology of the motor driver shown, the connection direction of the first coupling inductor L11 and the second coupling inductor L22 in the compensation circuit 408 is the same as... Figure 4 In the circuit topology shown, the first coupled inductor L11 and the second coupled inductor L22 are connected in opposite directions. Figure 4 In the diagram, the first coupling inductor L11 and the second coupling inductor L22 have the same name as the start terminal of the three-phase inductor Labc, while... Figure 5 In the three-phase inductor Labc, the first coupling inductor L11 and the second coupling inductor L22 are opposite to each other.

[0123] exist Figure 5In the motor driver shown, the switching states of the switching devices T9, T10, T11, T12 of the first half-bridge branch 4046 and the second half-bridge branch 4048 can be controlled according to Table 8 below. It can be seen that, in this case, compared with the case where the first coupling inductor L11, the second coupling inductor L22 and the first ends of the three-phase inductor Labc are the same-named ends, the switched half-bridge branches are the same, and the switched switching devices in the switched half-bridge branch are opposite. Figure 4

[0124]

[0125] Table 8. Switching vector and compensation voltage

[0126] In addition to the connection direction of the coupling capacitor being opposite, Figure 5 The circuit topology of the motor driver shown is the same as that of the motor driver in Figure 2 The same circuit components are denoted by the same reference numerals, and will not be described here.

[0127] According to the motor driver of the present disclosure, the coupling inductor is used to generate a compensation voltage, which can offset the common-mode voltage. The technical solution according to the present disclosure has at least one of the following advantages:

[0128] In one embodiment, a half-bridge branch and a coupling tap inductor are added to the circuit topology of the motor driver, so that a compensation voltage of appropriate size can be generated to offset the DC / AC common-mode voltage; and the motor bearing current can be eliminated, reducing the possible damage to the motor bearing, thereby improving the system reliability.

[0129] In another embodiment, a H-bridge branch (two half-bridge branches) and two coupling inductors are added to the circuit topology of the motor driver, so that a compensation voltage of appropriate size can be generated to offset the DC / AC common-mode voltage, and the motor bearing current can be eliminated, reducing the possible damage to the motor bearing, thereby improving the system reliability.

[0130] In addition, the motor driver according to the present disclosure can eliminate the common-mode voltage, thus being beneficial to the EMI performance and improving the system stability.

[0131] ​The detailed description set forth above describes exemplary embodiments but is not intended to represent the only embodiments in which the application can be practiced. The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Thus, the description is not intended to represent an exhaustive or exhaustive list of alternatives or equivalents. The detailed description includes specific details for the purpose of providing a thorough understanding of the techniques described herein. However, these techniques can be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described embodiments.

[0132] The above description of the disclosure has been presented to enable any person skilled in the art to implement or use the disclosure. Various modifications to the disclosure will be apparent to those skilled in the art, and the general principles defined herein can also be applied to other variations without departing from the scope of protection of the disclosure. Therefore, the disclosure is not limited to the examples and designs described herein, but is consistent with the broadest scope of the principles and novel features disclosed herein.

[0133] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A motor driver (20), comprising: The circuit includes a rectifier circuit (202), a DC-DC link circuit (204), an inverter circuit (206), a filter circuit (208), and a compensation circuit (210). The rectifier circuit (202) includes three AC / DC conversion branches for converting the input AC voltage into DC voltage; The DC link circuit (204) is connected between the positive output terminal and the negative output terminal of the rectifier circuit (202). The DC link circuit (202) includes: an energy discharge branch (2042), a capacitor branch (2044) and a half-bridge branch (2046) connected in parallel. The capacitor branch (2044) includes two capacitors (C1) and (C2), and the half-bridge branch (2046) includes two switching devices (T9) and (T10). The inverter circuit (206) includes a first to a third DC / AC conversion branch arranged in parallel between the positive and negative output terminals of the DC link circuit (204), and each of the first to third DC / AC conversion branches includes two switching devices (T1, T2, T3, T4, T5, T6). The filter circuit (208) includes a three-phase inductor (Labc), the first ends of the three inductors (Labc) are respectively connected to the midpoints (V1, V2, V3) of the first to third DC / AC conversion branches, and the ends of the three inductors respectively output three-phase voltages (U, V, W). The compensation circuit (210) includes a center-tapped coupled inductor (L12) and a solid-state circuit breaker (K1), the coupled inductor (L12) being coupled to the three-phase inductor (Labc). The moving part of the solid circuit breaker (K1) includes a first switch contact (1) and a second switch contact (2). The first switch contact (1) is connected to the beginning of the coupling inductor (L12), and the second switch contact (2) is connected to the center tap (CP) of the coupling inductor (L12). The solid circuit breaker (K1) is connected to the midpoint (V4) of the half-bridge branch (2046), and the end of the coupling inductor (L12) is connected to the midpoint (O) of the capacitor branch.

2. The motor driver (20) as claimed in claim 1, wherein, The coupling inductor (L12) includes a first inductor (L1) and a second inductor (L2), with the center tap (CP) connected between the first inductor (L1) and the second inductor (L2), wherein the number of turns of the first inductor (L1) is twice the number of turns of the second inductor (L2), and the number of turns of each of the three inductors of the three-phase inductor (Labc) is equal to the number of turns of the second inductor (L2).

3. The motor driver (20) as described in claim 1 or 2, wherein, The switching states of the two switching devices (T9, T10) of the half-bridge branch (2046) and which of the solid-state circuit breakers (K1) connected to the first switch contact (1) and the second switch contact (2) is configured to be controlled according to the switching states of the switching devices of each branch in the first to third DC / AC conversion branches, so that the magnitude of the compensation voltage generated by the coupling inductor (L12) is equal to the magnitude of the common-mode voltage generated by the inverter circuit (206).

4. The motor driver (20) as described in claim 1 or 2, wherein, The first ends of the coupling inductor (L12) and the three-phase inductor (Labc) are either the same name end or the opposite name end. In both cases, the switching states of the two switching devices (T9, T10) of the half-bridge branch (2046) are opposite.

5. The motor driver (20) as described in claim 1 or 2, wherein, Each switching device includes a fully controlled power switch and an anti-parallel power diode.

6. A motor driver (40), comprising: The circuit consists of a rectifier circuit (402), a DC-DC link circuit (404), an inverter circuit (406), a filter circuit (408), and a compensation circuit (410), among which... The rectifier circuit (402) includes three AC / DC conversion branch circuits for converting the input AC voltage into DC voltage; The DC link circuit (404) is connected between the positive output terminal and the negative output terminal of the rectifier circuit (402). The DC link circuit (404) includes: an energy discharge branch (4042), a capacitor branch (4044), a first half-bridge branch (4046), and a second half-bridge branch (4048) connected in parallel. The capacitor branch (4044) includes two capacitors (C1, C2). The first half-bridge branch (4046) and the second half-bridge branch (4048) each include two switching devices (T9, T10, T11, T12). The inverter circuit (406) includes a first to a third DC / AC conversion branch arranged in parallel between the positive and negative output terminals of the DC link circuit (404), and each of the first to third DC / AC conversion branches includes two switching devices (T1, T2, T3, T4, T5, T6). The filter circuit (408) includes a three-phase inductor (Labc), the first ends of the three inductors (Labc) are respectively connected to the midpoints (V1, V2, V3) of the first to third DC / AC conversion branches, and the ends of the three inductors respectively output three-phase voltages (U, V, W). The compensation circuit (410) includes a first coupling inductor (L11) and a second coupling inductor (L22). The first end of the first coupling inductor (L11) is connected to the midpoint (V6) of the second half-bridge branch (4048), the first end of the second coupling inductor (L22) is connected to the midpoint (V5) of the first half-bridge branch (4046), and the ends of the second coupling inductor (L22) and the first coupling inductor (L11) are connected to the midpoint (O) of the capacitor branch (4044).

7. The motor driver (40) as claimed in claim 6, wherein, The number of turns of the second coupling inductor (L22) is three times the number of turns of the first coupling inductor (L11), and the number of turns of each of the three inductors of the three-phase inductor (Labc) is equal to the number of turns of the first coupling inductor (L11).

8. The motor driver (40) as claimed in claim 6 or 7, wherein, The switching states of the switching devices of the first half-bridge branch (4046) and the second half-bridge branch (4048) are configured to be controlled according to the switching states of each branch in the first to third DC / AC conversion branches, so that the magnitude of the compensation voltage generated by the first coupling inductor (L11) or the second coupling inductor (L22) is equal to the magnitude of the common-mode voltage generated by the inverter circuit (406).

9. The motor driver (40) as claimed in claim 6 or 7, wherein, The first and second coupled inductors (L11 and L22) are of the same name. The first and second coupled inductors (L22) are either of the same name or different name from the first and second coupled inductors (L11 and L22) of the three-phase inductor (Labc). In both cases, the switching states of the two switching devices in the connected half-bridge branch are opposite.

10. The motor driver (40) as claimed in claim 6 or 7, wherein, Each switching device includes a fully controlled power switch and an anti-parallel power diode.

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