A switching module for a power electronic switching assembly

Abstract

A switching module (1) is described. The switching module (1) includes an H-bridge circuit (2) having four switching assemblies and an active clamp circuit (6) having four controllable semiconductor switches (S5, S6, ..., S8). Each switching assembly includes a pair of controllable semiconductor switches (S1, S2, ..., S4 and S9, S10, ..., S12) electrically connected in reverse series. Alternatively, each switching assembly may include a controllable semiconductor switch and a diode electrically connected in series. The H-bridge circuit (2) includes a first AC bridge terminal (AC1) and a second AC bridge terminal (AC2) electrically connectable to individual coils (4), and a first DC bridge terminal (DC1) and a second DC bridge terminal (DC2) electrically connectable to a DC current source or to a DC bridge terminal of another switching module. The active clamp circuit (6) includes a first DC clamp terminal (DC3) and a second DC clamp terminal (DC4), and an energy storage device (C) is electrically connected between these clamp terminals. A plurality of switching modules can be electrically connected together to provide a power electronic switching assembly.

Description

Technology Field

[0001] The present invention relates to a switching module for a power electronic switching assembly.

[0002] A power electronic switching assembly may include a plurality of switching modules.

[0003] A power electronic switching assembly may be part of a direct current (DC) electric machine comprising a stator having multiple stator coils, each stator coil being electrically connected to a respective switching module. A power electronic switching assembly may also be part of a power converter in which each switching module is electrically connected to a respective coil of a transformer assembly. Background Technology

[0004] EP 23155859 describes a switching module that can be used to provide an active commutation and energy recovery process. In one arrangement, a power electronic switching assembly comprises a plurality of switching modules and can be used, for example, to provide energy-efficient commutation of a direct current (DC) electric machine.

[0005] Referring to FIG. 1, each switching module (100) is:

[0006] - Individual coils (104), for example, a first AC bridge terminal (AC1) and a second AC bridge terminal (AC2) electrically connected to the stator coil of a DC electric machine,

[0007] - A first DC bridge terminal (DC1) and a second DC bridge terminal (DC2) electrically connected to a DC current source,

[0008] - A first switch (S1) electrically connected between the first AC bridge terminal (AC1) and the first DC bridge terminal (DC1),

[0009] - A second switch (S2) electrically connected between the first AC bridge terminal (AC1) and the second DC bridge terminal (DC2),

[0010] - A third switch (S3) electrically connected between the second AC bridge terminal (AC2) and the first DC bridge terminal (DC1), and

[0011] - Includes an H-bridge circuit (102) including a fourth switch (S4) electrically connected between a second AC bridge terminal (AC2) and a second DC bridge terminal (DC2).

[0012] Each switching module (100) also includes an active clamp circuit (106). The active clamp circuit (106) of each switching module (100) is:

[0013] - A first AC clamp terminal (AC3) electrically connected to a first AC bridge terminal (AC1),

[0014] - A second AC clamp terminal (AC4) electrically connected to a second AC bridge terminal (AC2),

[0015] - 1st DC clamp terminal (DC3) and 2nd DC clamp terminal (DC4),

[0016] - A fifth switch (S5) electrically connected between the first AC clamp terminal (AC3) and the first DC clamp terminal (DC3),

[0017] - A sixth switch (S6) electrically connected between the first AC clamp terminal (AC3) and the second DC clamp terminal (DC4),

[0018] - A seventh switch (S7) electrically connected between the second AC clamp terminal (AC4) and the first DC clamp terminal (DC3),

[0019] - An 8th switch (S8) electrically connected between the 2nd AC clamp terminal (AC4) and the 2nd DC clamp terminal (DC4), and

[0020] - Includes an energy storage device (e.g., a capacitor (C)) electrically connected between the first clamp terminal (DC3) and the second DC clamp terminal (DC4).

[0021] In each H-bridge circuit (102), the first switch (S1) and the second switch (S2) are electrically connected in series between the first DC bridge terminal (DC1) and the second DC bridge terminal (DC2) as the first bridge leg. The third switch (S3) and the fourth switch (S4) are electrically connected in series between the first DC bridge terminal (DC1) and the second DC bridge terminal (DC2) as the second bridge leg. The DC terminals of the first bridge leg and the second bridge leg are electrically connected in parallel. The junction (or connection point) between the first switch (S1) and the second switch (S2) defines the first AC bridge terminal (AC1), and the junction between the third switch (S3) and the fourth switch (S4) defines the second AC bridge terminal (AC2).

[0022] In each active clamp circuit, the fifth switch (S5) and the sixth switch (S6) are electrically connected in series between the first DC clamp terminal (DC3) and the second DC clamp terminal (DC4) as first clamp legs. The seventh switch (S7) and the eighth switch (S8) are electrically connected in series between the first DC clamp terminal (DC3) and the fourth DC clamp terminal (DC4) as second clamp legs. The first clamp leg and the second clamp leg are electrically connected in parallel. The junction between the fifth switch (S5) and the sixth switch (S6) defines the first AC clamp terminal (AC3), and the junction between the seventh switch (S7) and the eighth switch (S8) defines the second AC clamp terminal (AC4). An energy storage device (i.e., a capacitor (C)) is electrically connected between the first DC clamp terminal (DC3) and the second DC clamp terminal (DC4) in parallel with the first clamp leg and the second clamp leg.

[0023] Each switch (S1, S2, ..., S8) of the H-bridge circuit (102) and the active clamp circuit (106) may include one or more controllable semiconductor switches. For example, any suitable controllable semiconductor switch or combination of switches may be used, including a metal-oxide-semiconductor field-effect transistor (MOSFET), a vertical junction field-effect transistor (VJFET), an insulated-gate bipolar transistor (IGBT), and a gate rectifier thyristor. A separate diode may optionally be electrically connected in anti-parallel with each semiconductor switch, and the anti-parallel diode may be an inherent feature of the semiconductor switch itself, for example, a body diode of the MOSFET structure. Each controllable semiconductor switch is generally switched on and off by a gate drive signal generated by a gate driver.

[0024] In the H-bridge circuit (102), each switch (S1, S2, ..., S4) may be a bidirectional switch, that is, each switch may provide a gate-controlled bidirectional voltage blocking capability with a unidirectional current. Each bidirectional switch may consist of (a) a pair of controllable semiconductor switches as shown in FIG. 1, or (b) a controllable semiconductor switch and a diode, wherein the pair of semiconductor devices are electrically connected in anti-series (or back-to-back)—that is, so that one of the semiconductor devices in the pair blocks voltage in a second direction opposite to the first direction. (As used herein, the term “semiconductor device” may appropriately refer to a semiconductor switch or a diode.) When current is flowing through one of the semiconductor switches in a particular direction, the current may flow through the anti-parallel diode of the other semiconductor switch connected in anti-series. For example, if each semiconductor switch is a MOSFET, the body diode will essentially function as an antiparallel diode as shown in Fig. 1.

[0025] In one actual arrangement of the switching module (100) illustrated in FIG. 1, each switch (S1, S2, ..., S4) of the H-bridge circuit (102) is implemented as a pair of MOSFETs electrically connected in reverse series (i.e. arranged to conduct in opposite directions), and each switch (S5, S6, ..., S8) of the active clamp circuit (106) is implemented as an IGBT with a reverse parallel diode (D5a, D6a, ..., D8a). However, for this to be possible, a custom pre-packaged module for the H-bridge circuit must be used, in contrast to conventional "off-the-shelf" pre-packaged modules in which controllable semiconductor switches are electrically connected to conduct in the same direction. In particular, each pre-packaged module includes a common source array and a pair of MOSFETs electrically connected in reverse series. These custom pre-packaged modules are generally more expensive than conventional pre-packaged modules and are available from a limited number of suppliers. As used herein, the term “pre-packaged module” refers to a power module comprising semiconductor devices and optionally other electronic components (e.g., temperature sensors) packaged together in a suitable housing. The module may also include, for example, a pre-coated thermal interface material to dissipate heat generated by the semiconductor devices. Such pre-packaged modules are often used in wind and solar power generation, energy storage, transmission and distribution, and traction applications.

[0026] Although the H-bridge circuit (102) can be implemented using a single or individual controllable semiconductor switch instead of a custom pre-packaged module, the voltage and current ratings of such a single switch are generally too low or too high to be implemented in an actual switching module, for example, where a current rating in the range of about 200 to 500 A may be required. On the other hand, many conventional pre-packaged modules use controllable semiconductor switches with the required voltage and current ratings, for example, 1200 to 1700 V and 200 to 500 A. These "off-the-shelf" or conventional pre-packaged modules have the following advantages:

[0027] - Lower cost,

[0028] - Can be obtained from various suppliers,

[0029] - Uses a standardized configuration, and

[0030] - Available as various switch options with the required voltage and current ratings (e.g., SiC MOSFET, Si IGBT).

[0031] Conventional pre-packaged modules (e.g., chopper modules) having controllable semiconductor switches and diodes electrically connected in reverse series can also be used.

[0032] The present invention aims to provide an improved switching module that can be substantially implemented using "off-the-shelf" or conventional pre-packaged modules to solve the problems identified above and to take advantage of the cost and supply benefits mentioned above. The present invention provides a switching module, wherein the switching module comprises:

[0033] H-bridge circuit; and

[0034] It includes an active clamp circuit,

[0035] The H-bridge circuit is:

[0036] A first AC bridge terminal and a second AC bridge terminal electrically connectable to individual coils,

[0037] A first DC bridge terminal and a second DC bridge terminal electrically connectable to a DC current source or to a DC bridge terminal of another switching module,

[0038] A first switch assembly electrically connected between a first AC bridge terminal and a first DC bridge terminal - the first switch assembly comprises a first controllable semiconductor switch and a first semiconductor device (i.e., a controllable semiconductor switch or a diode) electrically connected in series -,

[0039] A second switch assembly electrically connected between a first AC bridge terminal and a second DC bridge terminal - the second switch assembly comprises a second controllable semiconductor switch and a second semiconductor device (i.e., a controllable semiconductor switch or a diode) electrically connected in series -,

[0040] A third switch assembly electrically connected between a second AC bridge terminal and a first DC bridge terminal—the third switch assembly comprises a third controllable semiconductor switch and a third semiconductor device (i.e., a controllable semiconductor switch or a diode) electrically connected in series—and

[0041] A fourth switch assembly electrically connected between a second AC bridge terminal and a second DC bridge terminal—the fourth switch assembly comprises a fourth controllable semiconductor switch and a fourth semiconductor device (i.e., a controllable semiconductor switch or a diode) electrically connected in series—and

[0042] The active clamp circuit is:

[0043] 1st DC clamp terminal and 2nd DC clamp terminal,

[0044] A fifth controllable semiconductor switch electrically connected between a junction (or connection point) between a first controllable semiconductor switch and a first semiconductor device and a first DC clamp terminal,

[0045] A sixth controllable semiconductor switch electrically connected between a junction point between a second controllable semiconductor switch and a second semiconductor device and a second DC clamp terminal,

[0046] A seventh controllable semiconductor switch electrically connected between a junction point between a third controllable semiconductor switch and a third semiconductor device and a first DC clamp terminal,

[0047] An eighth controllable semiconductor switch electrically connected between a junction point between a fourth controllable semiconductor switch and a fourth semiconductor device and a second DC clamp terminal, and

[0048] It includes an energy storage device electrically connected between a first DC clamp terminal and a second DC clamp terminal.

[0049] The junction point between the first controllable semiconductor switch and the second controllable semiconductor switch defines the first AC bridge terminal, and the junction point between the third controllable semiconductor switch and the fourth controllable semiconductor switch defines the second AC bridge terminal.

[0050] The switch assembly of an H-bridge circuit includes a pair of series-connected controllable semiconductor switches:

[0051] In one arrangement, the first semiconductor device, the second semiconductor device, the third semiconductor device, and the fourth semiconductor device are controllable semiconductor switches—that is, each switch assembly of the H-bridge circuit may include a pair of controllable semiconductor switches. The pair of controllable semiconductor switches in each switch assembly are electrically connected in reverse series (i.e., arranged to conduct in opposite directions).

[0052] In this arrangement, for convenience, the first semiconductor device is referred to as the ninth controllable semiconductor switch, the second semiconductor device is referred to as the tenth controllable semiconductor switch, the third semiconductor device is referred to as the eleventh controllable semiconductor switch, and the fourth semiconductor device is referred to as the twelfth controllable semiconductor switch.

[0053] The first controllable semiconductor switch and the ninth controllable semiconductor switch can be electrically connected in reverse series. The first controllable semiconductor switch can be electrically connected to the first AC bridge terminal, and the ninth controllable semiconductor switch can be electrically connected to the first DC bridge terminal.

[0054] The second controllable semiconductor switch and the tenth controllable semiconductor switch can be electrically connected in reverse series. The second controllable semiconductor switch can be electrically connected to the first AC bridge terminal, and the tenth controllable semiconductor switch can be electrically connected to the second DC bridge terminal.

[0055] The third controllable semiconductor switch and the eleventh controllable semiconductor switch can be electrically connected in reverse series. The third controllable semiconductor switch can be electrically connected to the second AC bridge terminal, and the eleventh controllable semiconductor switch can be electrically connected to the first DC bridge terminal.

[0056] The fourth controllable semiconductor switch and the twelfth controllable semiconductor switch can be electrically connected in reverse series. The fourth controllable semiconductor switch can be electrically connected to the second AC bridge terminal, and the twelfth controllable semiconductor switch can be electrically connected to the second DC bridge terminal.

[0057] All controllable semiconductor switches in the switching module may be of the same type. In particular, it will be understood that controllable semiconductor switches of the same type can be used to implement both H-bridge circuits and active clamp circuits. All controllable semiconductor switches may have the same rating.

[0058] For example, any suitable fully-controllable semiconductor switch may be used, including a metal-oxide-semiconductor field-effect transistor (MOSFET), a vertical junction field-effect transistor (VJFET), an insulated-gate bipolar transistor (IGBT), a high-electron-mobility transistor (HEMT), a bipolar junction transition (BJT), and a gate-commutated thyristor (GCT) or a gate turn-off thyristor (GTO). A separate diode may optionally be electrically connected in antiparallel with each semiconductor switch, or the antiparallel diode may be an intrinsic feature of the semiconductor switch itself, for example, a body diode of the MOSFET structure.

[0059] Each controllable semiconductor switch is typically switched on and off by a gate drive signal generated by a gate driver.

[0060] In one particular arrangement, all controllable semiconductor switches of the H-bridge circuit and the active clamp circuit may be implemented as MOSFETs. The first controllable semiconductor switch and the ninth controllable semiconductor switch are preferably electrically connected in reverse series in a common-drain configuration. The second controllable semiconductor switch and the tenth controllable semiconductor switch are preferably electrically connected in reverse series in a common-drain configuration. The third controllable semiconductor switch and the eleventh controllable semiconductor switch are preferably electrically connected in reverse series in a common-drain configuration. The fourth controllable semiconductor switch and the twelfth controllable semiconductor switch are preferably electrically connected in reverse series in a common-drain configuration.

[0061] In one array of switching modules, the first controllable semiconductor switch and the second controllable semiconductor switch may be of the same type and may be implemented as a pre-packaged module in which the first controllable semiconductor switch and the second controllable semiconductor switch are arranged to conduct in the same direction. In other words, the first controllable semiconductor switch and the second controllable semiconductor switch may be implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module.

[0062] The third controllable semiconductor switch and the fourth controllable semiconductor switch may be of the same type and may be implemented as a pre-packaged module in which the third controllable semiconductor switch and the fourth controllable semiconductor switch are arranged to conduct in the same direction. In other words, the third controllable semiconductor switch and the fourth controllable semiconductor switch may be implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module.

[0063] The fifth controllable semiconductor switch and the ninth controllable semiconductor switch may be of the same type and may be implemented as a pre-packaged module in which the fifth controllable semiconductor switch and the ninth controllable semiconductor switch are arranged to conduct in the same direction. In other words, the fifth controllable semiconductor switch and the ninth controllable semiconductor switch may be implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module, despite the fact that they are used in an active clamp circuit and an H-bridge circuit, respectively.

[0064] The sixth controllable semiconductor switch and the tenth controllable semiconductor switch may be of the same type and may be implemented as a pre-packaged module in which the sixth controllable semiconductor switch and the tenth controllable semiconductor switch are arranged to conduct in the same direction. In other words, the sixth controllable semiconductor switch and the tenth controllable semiconductor switch may be implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module, despite the fact that they are used in an active clamp circuit and an H-bridge circuit, respectively.

[0065] The seventh controllable semiconductor switch and the eleventh controllable semiconductor switch may be of the same type and may be implemented as a pre-packaged module in which the seventh controllable semiconductor switch and the eleventh controllable semiconductor switch are arranged to conduct in the same direction. In other words, the seventh controllable semiconductor switch and the eleventh controllable semiconductor switch may be implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module, despite the fact that they are used in an active clamp circuit and an H-bridge circuit, respectively.

[0066] The eighth controllable semiconductor switch and the twelfth controllable semiconductor switch may be of the same type and may be implemented as a pre-packaged module in which the eighth controllable semiconductor switch and the twelfth controllable semiconductor switch are arranged to conduct in the same direction. In other words, the eighth controllable semiconductor switch and the twelfth controllable semiconductor switch may be implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module, despite the fact that they are used in an active clamp circuit and an H-bridge circuit, respectively.

[0067] For example, a pre-packaged module may be a half-bridge module. In other words, each pair of controllable semiconductor switches (e.g., a first controllable semiconductor switch and a second controllable semiconductor switch, a third controllable semiconductor switch and a fourth controllable semiconductor switch, a fifth controllable semiconductor switch and a ninth controllable semiconductor switch, etc.) may be implemented as a separate half-bridge module. In this arrangement, six conventional or "off-the-shelf" pre-packaged half-bridge modules are required to implement each switching module. These half-bridge modules may include a pair of controllable semiconductor switches defining a single leg. However, other pre-packaged modules may also be used to implement the switching module. For example, provided that the leg terminals are not electrically connected together (e.g., the DC terminals are not connected to each other), the pre-packaged module may have two or more pairs of controllable semiconductors defining two or more legs. This will allow multiple pairs of controllable semiconductor switches of a switching module to be implemented within the same pre-packaged module. For example, if each pre-packaged module includes a first pair of controllable semiconductor switches defining a first leg and a second pair of controllable semiconductor switches defining a second leg, only three conventional or "off-the-shelf" pre-packaged modules are required to implement each switching module. If each pre-packaged module also includes a third pair of controllable semiconductor switches defining a third leg, only two conventional or "off-the-shelf" pre-packaged modules are required to implement each switching module. This can provide a more compact switching module and reduce costs. Although combinations of different pre-packaged modules may be used, they will preferably all use the same type of controllable semiconductor switches.

[0068] The switch assembly of the H-bridge circuit includes controllable semiconductor switches and diodes connected in series:

[0069] In another arrangement, the first semiconductor device, the third semiconductor device, and the fourth semiconductor device are diodes—that is, each switch assembly of the H-bridge circuit may include a controllable semiconductor switch and a diode arranged to be electrically connected in series and conduct in the same direction.

[0070] In this arrangement, for convenience, the first semiconductor device is referred to as the first diode, the second semiconductor device is referred to as the second diode, the third semiconductor device is referred to as the third diode, and the fourth semiconductor device is referred to as the fourth diode.

[0071] The first controllable semiconductor switch and the first diode can be electrically connected in series and arranged to conduct in the same direction. The first controllable semiconductor switch can be electrically connected to the first AC bridge terminal, and the first diode can be electrically connected to the first DC bridge terminal.

[0072] The second controllable semiconductor switch and the second diode can be electrically connected in series and arranged to conduct in the same direction. The second controllable semiconductor switch can be electrically connected to the first AC bridge terminal, and the second diode can be electrically connected to the second DC bridge terminal.

[0073] The third controllable semiconductor switch and the third diode can be electrically connected in series and arranged to conduct in the same direction. The third controllable semiconductor switch can be electrically connected to the second AC bridge terminal, and the third diode can be electrically connected to the first DC bridge terminal.

[0074] The fourth controllable semiconductor switch and the fourth diode can be electrically connected in series and arranged to conduct in the same direction. The fourth controllable semiconductor switch can be electrically connected to the second AC bridge terminal, and the fourth diode can be electrically connected to the second DC bridge terminal.

[0075] All controllable semiconductor switches can be of the same type. In particular, it will be understood that the same type of controllable semiconductor switch can be used to implement both H-bridge circuits and active clamp circuits. All controllable semiconductor switches can have the same rating.

[0076] For example, any suitable fully controllable semiconductor switch may be used, including a vertical junction field-effect transistor (VJFET), an insulated gate bipolar transistor (IGBT), a high electron mobility transistor (HEMT), a bipolar junction transistor (BJT), and a gate rectifier thyristor (GCT) or gate turn-off thyristor (GTO). A separate diode may optionally be electrically connected in antiparallel with each semiconductor switch.

[0077] Each controllable semiconductor switch is typically switched on and off by a gate drive signal generated by a gate driver.

[0078] In one particular arrangement, all controllable semiconductor switches of the H-bridge circuit and active clamp circuit can be implemented, for example, as IGBTs having associated antiparallel diodes.

[0079] In one array of switching modules, the first controllable semiconductor switch and the second controllable semiconductor switch may be of the same type and may be implemented as a pre-packaged module in which the first controllable semiconductor switch and the second controllable semiconductor switch are arranged to conduct in the same direction. In other words, the first controllable semiconductor switch and the second controllable semiconductor switch may be implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module.

[0080] The third controllable semiconductor switch and the fourth controllable semiconductor switch may be of the same type and may be implemented as a pre-packaged module in which the third controllable semiconductor switch and the fourth controllable semiconductor switch are arranged to conduct in the same direction. In other words, the third controllable semiconductor switch and the fourth controllable semiconductor switch may be implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module.

[0081] The fifth controllable semiconductor switch and the first diode can be implemented as a pre-packaged module in which the fifth controllable semiconductor switch and the first diode are electrically connected in reverse series, that is, arranged to conduct in opposite directions. In other words, the fifth controllable semiconductor switch and the first diode can be implemented using a controllable semiconductor switch and a diode that are packaged together in a conventional pre-packaged module, despite the fact that they are used in an active clamp circuit and an H-bridge circuit, respectively.

[0082] The sixth controllable semiconductor switch and the second diode can be implemented as a pre-packaged module in which the sixth controllable semiconductor switch and the second diode are electrically connected in reverse series, that is, arranged to conduct in opposite directions. In other words, the sixth controllable semiconductor switch and the second diode can be implemented using a controllable semiconductor switch and a diode that are packaged together in a conventional pre-packaged module, despite the fact that they are used in an active clamp circuit and an H-bridge circuit, respectively.

[0083] The seventh controllable semiconductor switch and the third diode can be implemented as a pre-packaged module in which the seventh controllable semiconductor switch and the third diode are electrically connected in reverse series, that is, arranged to conduct in opposite directions. In other words, the seventh controllable semiconductor switch and the third diode can be implemented using a controllable semiconductor switch and a diode that are packaged together in a conventional pre-packaged module, despite the fact that they are used in an active clamp circuit and an H-bridge circuit, respectively.

[0084] The eighth controllable semiconductor switch and the fourth diode can be implemented as a pre-packaged module in which the eighth controllable semiconductor switch and the fourth diode are electrically connected in reverse series, that is, arranged to conduct in opposite directions. In other words, the eighth controllable semiconductor switch and the fourth diode can be implemented using a controllable semiconductor switch and a diode that are packaged together in a conventional pre-packaged module, despite the fact that they are used in an active clamp circuit and an H-bridge circuit, respectively.

[0085] The pre-packaged module for the first controllable semiconductor switch and the second controllable semiconductor switch may be the first pre-packaged half-bridge module, and the pre-packaged module for the third controllable semiconductor switch and the fourth controllable semiconductor switch may be the second pre-packaged half-bridge module. Alternatively, the first controllable semiconductor switch, the second controllable semiconductor switch, the third controllable semiconductor switch, and the fourth controllable semiconductor switch may be implemented as a single pre-packaged module having two pairs of controllable semiconductor switches defining two legs as described above. The remaining pre-packaged module may be a chopper module, and each chopper module includes a controllable semiconductor switch (e.g., an IGBT and a counter-parallel diode) electrically connected in series with a diode. If each pre-packaged module includes one controllable semiconductor switch and a diode, five or six conventional or "off-the-shelf" pre-packaged modules are required to implement each switching module. If each pre-packaged chopper module contains two or more legs, and each leg contains a controllable semiconductor switch electrically connected in reverse series with a diode, then fewer pre-packaged modules will be required.

[0086] However, in an actual arrangement, the remaining pre-packaged modules may also be hard-bridge modules, wherein each pre-packaged module includes a first controllable semiconductor switch (e.g., IGBT) and a first antiparallel diode electrically connected in series with a second controllable semiconductor switch (e.g., IGBT) and a second antiparallel diode. The pre-packaged half-bridge modules may have two or more pairs of controllable semiconductors defining two or more legs as described above. This will allow multiple pairs of controllable semiconductor switches of the switching modules to be implemented within the same pre-packaged module. By disabling one of the first controllable semiconductor switch and the second controllable semiconductor switch of each half-bridge module (or each leg) (e.g., by shorting the gate terminal and the emitter terminal in the case of an IGBT), the switch can be effectively made redundant without affecting the individual antiparallel diodes. For example, this allows the switching module to be implemented using six (or fewer) identical pre-packaged modules, but for a pre-packaged module with disabled controllable semiconductor switches, only the non-disabled (or active) controllable semiconductor switches are switched on and off. Other controllable semiconductor switches are disabled, but current can still flow through individual antiparallel diodes. Combinations of different pre-packaged modules (e.g., half-bridge modules and chopper modules) may be used, but they will preferably all use the same type of controllable semiconductor switches.

[0087] Implementing the H-bridge circuit and active clamp circuit with MOSFETs will minimize conduction losses. Using IGBTs may be less expensive, but the switching module will experience higher conduction losses. Both arrays using MOSFETs and IGBTs will require a total of six (or fewer) pre-packaged modules.

[0088] Compared to the actual arrangement of the known switching module described above, each switch of the H-bridge circuit is implemented as a pair of MOSFETs electrically connected in anti-series (i.e., arranged to conduct in opposite directions), and each switch of the active clamp circuit is implemented as an IGBT with an anti-parallel diode; and since the switching on and off can be controlled by using a single gate driver to control the anti-series pair of MOSFETs of each switch in the known switching module, implementing the H-bridge circuit and active clamp circuit of the present invention with MOSFETs would require a slight increase in gate drivers, namely 12 instead of 8. The total chip area of ​​each switch remains the same. If the H-bridge circuit and active clamp circuit are implemented with IGBTs with anti-parallel diodes (or any other suitable type of controllable semiconductor device), only 8 gate drivers are required. This still applies even if the switching module is implemented using six (or fewer) identical pre-packaged modules (e.g., half-bridge modules) and one of the first controllable semiconductor switch and the second controllable semiconductor switch in four of the pre-packaged modules is disabled (e.g., by shorting the gate terminal and the emitter terminal if an IGBT is used).

[0089] All controllable semiconductor switches are preferably of the same type (e.g., all MOSFETs, all IGBTs, or other suitable fully controllable semiconductor switches) and are preferably provided in the form of pre-packaged modules, so they will generally have the same voltage and current ratings. In other words, the controllable semiconductor switches of the active clamp circuit are now rated to handle the total current flowing through the H-bridge circuit, although these switches may have previously had lower ratings. While these higher ratings are not necessary for normal operation—that is, to provide energy recovery during the operation of the switching module—the higher ratings may be useful in specific situations where higher currents may flow through the active clamp circuit, such as in fault conditions, high-frequency applications, or dynamic braking (see below).

[0090] The energy storage device may be a capacitor. Any suitable capacitor with any appropriate rating may be used. Alternatively, the energy storage device may be, for example, a battery or other suitable device.

[0091] The first AC terminal and the second AC terminal of the switching module may be electrically connected to a single coil or to two or more coils electrically connected in series or parallel.

[0092] A switching module may be associated with one or more electronic circuits, such as a control circuit or a gate driver circuit for driving a controllable semiconductor switch. The electronic circuit may communicate with a main controller, for example, via a fiber optic link or other galvanically-isolated communication channel. The electronic circuit will generally require a power supply. In one configuration, power for the electronic circuit may be provided by the energy storage device of the switching module instead of being supplied by a separate power supply. Thus, the switching module may include a power supply circuit (e.g., a low-voltage power supply circuit) electrically connected between a first DC clamp terminal and a second DC clamp terminal in parallel with the energy storage device. The power supply circuit may be electrically connected to one or more local electronic circuits. The power supply circuit may include a power converter, such as a step-down power converter, to derive an appropriate output voltage from the voltage of the energy storage device. A suitable power converter may be a DC / DC power converter, such as a forward converter or a flyback converter. The energy storage device may be charged by a DC current source through the first DC bridge terminal and the second DC bridge terminal, or by a current induced in a coil electrically connected to the first AC bridge terminal and the second AC bridge terminal; in the latter case, the induced current will flow through one or more semiconductor devices of the H-bridge circuit and the clamp circuit. For example, when the energy storage device is charged by performing a pre-charging process, power may be supplied to one or more electronic circuits associated with a switching module using a power supply circuit.

[0093] The switching module may further include a battery (or a battery bank comprising a plurality of electrically connected batteries) electrically connected between a first DC clamp terminal and a second DC clamp terminal in parallel with the energy storage device. Integrating additional energy storage beyond what is required for energy recovery may provide a distributed energy storage network for a power electronic switching assembly comprising a plurality of switching modules. The distributed energy storage network may be used to black-start an electric machine or other load electrically connected to the switching module, for example, by discharging the battery or battery bank or by controlling a controllable semiconductor device of an active clamp circuit for voltage regulation. The battery voltage and the battery state of charge (SoC) may be controlled via the active clamp circuit. The active clamp circuit may be designed to match the battery voltage range across the battery's allowable SoC variation. In some situations, the battery may also be used to absorb excess power induced in a coil electrically connected to the first AC bridge terminal and the second AC bridge terminal during an overspeed condition of a DC electric machine, for example, which includes a plurality of switching modules, and each switching module is electrically connected to the stator coil of the DC electric machine.

[0094] The switching module may further include a dynamic braking system electrically connected between a first DC clamp terminal and a second DC clamp terminal in parallel with the energy storage device. The dynamic braking system may be any suitable type. For example, the dynamic braking system may include a braking resistor and a controllable semiconductor switch electrically connected in series between the first DC clamp terminal and the second DC clamp terminal. The dynamic braking system may also include a diode electrically connected in parallel with the braking resistor. The dynamic braking system may be used, for example, to provide short-term power dissipation during an overspeed condition of a DC electric machine.

[0095] The switching module may have one or more of a power supply circuit electrically connected in parallel with the energy storage device, a battery for distributed energy storage, a dynamic braking system, or any other suitable circuit.

[0096] The present invention also provides a DC electric machine, and the DC electric machine is:

[0097] A stator having multiple stator coils;

[0098] Rotor;

[0099] DC current source; and

[0100] A power electronic switching assembly comprising n switching modules as described above, wherein n is an integer greater than or equal to 2. The first AC bridge terminal and the second AC bridge terminal of each switching module are electrically connected to at least one individual stator coil. The first DC bridge terminal of the first switching module is electrically connected to a DC current source, the second DC bridge terminal of the nth switching module is electrically connected to a DC current source, and the first DC bridge terminal and the second DC bridge terminal of the remaining switching modules are electrically connected in series. For example, the second DC bridge terminal of the (n-1)th switching module is electrically connected to the first DC bridge terminal of the nth switching module, and until the second DC bridge terminal of the nth switching module is electrically connected to a DC current source (e.g., the second DC terminal), the first DC bridge terminal of the first switching module is electrically connected to a DC current source (e.g., the first DC terminal), the second DC bridge terminal of the first switching module is electrically connected to the first DC bridge terminal of the second switching module, the second DC bridge terminal of the second switching module is electrically connected to the first DC bridge terminal of the third switching module, and so on. In other words, switching modules can be electrically connected in a series chain link structure between the DC terminals of DC current sources. Two or more sets of switching modules electrically connected in a series chain link structure can be electrically connected in parallel between the DC terminals of DC current sources. Switching modules may also be electrically connected in other ways to define a power electronic switching assembly.

[0101] Stator coils can be received through slots formed in the stator. Stator coils can be of any suitable type (e.g., single layer, double layer, etc.) and can be arranged around the stator to have any suitable winding topology. The rotor rotates relative to the stationary stator and is spaced apart from the stator by an air gap. The rotor can be of any suitable type (e.g., a wound rotor type with any suitable excitation method, such as a permanent magnet type, a field winding with slip rings, or a brushless type). The rotor can be a synchronous rotor or an asynchronous / inductive rotor.

[0102] The DC current source may be a power converter, such as an AC / DC power converter having, for example, a first DC terminal and a second DC terminal electrically connected to a first switching module and an n-th switching module of a power electronic switching assembly, and two or more AC terminals electrically connected to an AC circuit or a power grid (e.g., a three-phase power grid). The AC / DC power converter may be, for example, a current source inverter or a thyristor converter (6p, 12p, etc.). The DC current source may be a DC / DC power converter having, for example, a first DC terminal and a second DC terminal electrically connected to a first switching module and an n-th switching module of a power electronic switching assembly, and a third DC terminal and a fourth DC terminal electrically connected to a DC circuit or a storage device, for example, a battery. The DC current source may also be another DC electric machine, such as a generator, that provides a DC output voltage.

[0103] Each switching module may further include a controller adapted to rectify the individual switching module according to a coil rectification process (i.e., a process in which the current flowing through the coil is reversed). Alternatively, one or more controllers may be associated with two or more switching modules, and each controller is adapted to rectify the switching module according to an individual coil rectification process. The coils of each switching module may be rectified, and the individual coil rectification processes may be interleaved. The stator coils of a DC electric machine are arranged around the stator to provide multiple phase-shifted coil voltages—usually having multiple phases. For example, a DC electric machine having p phases may include a first group of at least p stator coils, the EMFs of these stator coils are phase-shifted by 360 / p° relative to each other, where p is an integer greater than or equal to 2, one cycle of the stator fundamental frequency occupies 360°, and each EMF experiences two zero crossings per cycle. A DC electric machine according to the present invention may have any convenient number of stator coils and thus may have multiple phases with small phase displacements between EMFs. Since the number of coil rectification events per stator fundamental frequency cycle is equal to twice the number of phases, continuous coil rectification is interleaved. In the case of a DC electric machine having multiple phases, several overlapping coil rectification events may occur at a given time.

[0104] The timing parameters of each coil rectification event can be changed or adjusted to control the voltage across the energy storage device of the active clamp circuit of the individual switching module in a closed loop.

[0105] The present invention also:

[0106] A transformer assembly comprising a plurality of first coils;

[0107] DC current source; and

[0108] A power converter is provided comprising a power electronic switching assembly including n switching modules as described above, wherein n is an integer greater than or equal to 2. A first AC bridge terminal and a second AC bridge terminal of each switching module are electrically connected to an individual first coil of a transformer assembly. A first DC bridge terminal of a first switching module is electrically connected to a DC current source, a second DC bridge terminal of an nth switching module is electrically connected to a DC current source, and the first DC bridge terminal and the second DC bridge terminal of the remaining switching modules are electrically connected in series. For example, the second DC bridge terminal of the (n-1)th switching module is electrically connected to the first DC bridge terminal of the nth switching module, and until the second DC bridge terminal of the nth switching module is electrically connected to a DC current source (e.g., the second DC terminal), the first DC bridge terminal of the first switching module is electrically connected to a DC current source (e.g., the first DC terminal), the second DC bridge terminal of the first switching module is electrically connected to the first DC bridge terminal of the second switching module, the second DC bridge terminal of the second switching module is electrically connected to the first DC bridge terminal of the third switching module, and so on. In other words, the switching modules can be electrically connected in a series chain link structure between the DC terminals of the DC current sources. The switching modules may also be electrically connected in other ways (e.g., in series, in parallel, or in series-parallel) to define a power electronic switching assembly.

[0109] Each switching module can be electrically connected to an individual first coil through a capacitor.

[0110] Each switching module can function as a DC / AC power converter, and an output current waveform is generated from each first coil. The output current waveform can have any suitable frequency, for example, about 1 to 10 kHz or higher. This allows the size of the transformer assembly to be minimized and high power density to be achieved.

[0111] The transformer assembly may further include a plurality of second coils, each second coil being associated with a first coil (e.g., having a coupled primary coil and a secondary coil). In other words, the transformer assembly may include a plurality of individual transformer units, each transformer unit comprising a physically separated and electromagnetically coupled primary coil and a secondary coil. Each second coil may be electrically connected to an individual AC / DC power converter. Any suitable AC / DC power converter may be used. For example, each AC / DC power converter may have two AC terminals electrically connected to the individual second coil and two DC terminals electrically connected to the DC circuit. Alternatively, the second coil may be electrically connected to a common AC / DC power converter, for example.

[0112] Therefore, the power converter can provide medium-frequency galvanic isolation between the DC current source and the DC circuit. The DC circuit may include one or more energy storage devices, such as, for example, a capacitor.

[0113] If an AC output voltage is required, an AC output voltage can be derived from a DC circuit using any suitable DC / AC power converter. For example, a DC / AC power converter may have two DC terminals electrically connected to a DC circuit and two or more AC terminals that provide a desired AC output voltage at a desired frequency (e.g., 60 Hz).

[0114] Each switching module can also function as a switch-mode converter (e.g., forward or flyback converter, dual active bridge (DAB) converter, Cuk converter, single-ended primary-inductor converter (SEPIC), etc.) or a resonant converter.

[0115] The switching modules of a power electronic switching assembly can be bypassed in the event of a fault in the H-bridge or active clamp circuit. A bypass switch (e.g., a mechanical switch or a controllable semiconductor switch) may be electrically connected between the first DC bridge terminal and the second DC bridge terminal of each switching module. The bypass switch will generally be switched off (or the bypass switch will generally be open so that no current flows through the bypass circuit between the first DC bridge terminal and the second DC bridge terminal), but may be optionally switched on (or closed) to bypass the H-bridge circuit. This allows the power electronic switching assembly to continue operating at a possibly slightly reduced rating if one or more of the switching modules fail and need to be bypassed. Brief explanation of the drawing

[0116] FIG. 1 is a schematic circuit diagram illustrating a known switching module; FIG. 2 is a schematic circuit diagram illustrating a first switching module according to the present invention; FIGS. 3a and 3b are schematic circuit diagrams of the first switching module shown in FIG. 2; FIG. 3c is a schematic diagram of a pre-packaged module that can be used to implement the first switching module illustrated in FIG. 2; FIGS. 4a and 4b are schematic circuit diagrams of a second switching module; FIGS. 4c, 4d, 4e and 4f are schematic circuit diagrams of a pre-packaged module that can be used to implement the second switching module shown in FIGS. 4a and 4b; FIGS. 5a through 5f are schematic circuit diagrams illustrating the coil rectification process of the second switching module shown in FIGS. 4a and 4b; FIG. 6 is a schematic circuit diagram of the second switching module of FIG. 4a and 4b having a power supply circuit; FIG. 7 is a schematic circuit diagram of the second switching module of FIG. 4a and 4b having a battery for distributed energy storage; FIG. 8 is a schematic circuit diagram of the second switching module of FIG. 4a and 4b having a dynamic braking system; FIG. 9 is a schematic circuit diagram of a direct current (DC) electric machine having a power electronic switching assembly having a plurality of switching modules; FIG. 10 is a schematic circuit diagram of a power converter having a power electronic switching assembly having a plurality of switching modules; FIG. 11 is a schematic circuit diagram of the switching module, transformer unit, and AC / DC power converter of the power converter of FIG. 10; and FIG. 12 is a schematic circuit diagram of the second switching module of FIG. 4a and 4b having a bypass switch. Specific details for implementing the invention

[0117] Referring to FIG. 2, the switching module (1) according to the present invention includes an H-bridge circuit (2). The H-bridge circuit (2) is:

[0118] - First bridge terminal (AC1) and second AC bridge terminal (AC2) electrically connectable to individual coils (4),

[0119] - A first DC bridge terminal (DC1) and a first DC bridge terminal (DC2) electrically connectable to a DC current source or to a DC bridge terminal of another switching module,

[0120] - A first switch assembly electrically connected between a first AC bridge terminal (AC1) and a first DC bridge terminal (DC1) - The first switch assembly includes a first controllable semiconductor switch (S1) and a ninth controllable semiconductor switch (S9) electrically connected in series -,

[0121] - A second switch assembly electrically connected between a first AC bridge terminal (AC1) and a second DC bridge terminal (DC2) - The second switch assembly includes a second controllable semiconductor switch (S2) and a first controllable semiconductor switch (S10) electrically connected in series -,

[0122] - A third switch assembly electrically connected between the second AC bridge terminal (AC2) and the first DC bridge terminal (DC1) - The third switch assembly includes a third controllable semiconductor switch (S3) and a first controllable semiconductor switch (S11) electrically connected in series -,

[0123] - A fourth switch assembly electrically connected between the second AC bridge terminal (AC2) and the second DC bridge terminal (DC2) - The fourth switch assembly includes a fourth controllable semiconductor switch (S4) and a 12th controllable semiconductor switch (S12) electrically connected in series -

[0124] The first AC terminal (AC1) and the second AC terminal (AC2) of the switching module (1) are shown as being electrically connected to a single coil (4). However, the switching module (1) may be electrically connected to two or more coils that are electrically connected in series or parallel.

[0125] The switching module (1) also:

[0126] - 1st DC clamp terminal (DC3) and 2nd DC clamp terminal (DC4),

[0127] - A fifth controllable semiconductor switch (S5) electrically connected between a junction (or connection point) between a first controllable semiconductor switch (S1) and a ninth controllable semiconductor switch (S9) and a first DC clamp terminal (DC3),

[0128] - A sixth controllable semiconductor switch (S6) electrically connected between the junction point between the second controllable semiconductor switch (S2) and the tenth controllable semiconductor switch (S10) and the second DC clamp terminal (DC4),

[0129] - A seventh controllable semiconductor switch (S7) electrically connected between the junction point between the third controllable semiconductor switch (S3) and the eleventh controllable semiconductor switch (S11) and the first DC clamp terminal (DC3),

[0130] - An 8th controllable semiconductor switch (S8) electrically connected between the junction point between the 4th controllable semiconductor switch (S4) and the 12th controllable semiconductor switch (S12) and the 2nd DC clamp terminal (DC4), and

[0131] - Includes an active clamp circuit (6) comprising an energy storage device (e.g., a capacitor (C)) electrically connected between a first DC clamp terminal (DC3) and a second DC clamp terminal (DC4).

[0132] The junction point between the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) defines the first AC bridge terminal (AC1), and the junction point between the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) defines the second AC bridge terminal (AC2).

[0133] In the switching module (1) illustrated in FIG. 2, each switch assembly of the H-bridge circuit (2) comprises a pair of controllable semiconductor switches (e.g., a first controllable semiconductor switch (S1) and a ninth controllable semiconductor switch (S9)). The pair of controllable semiconductor switches of each switch assembly is electrically connected in reverse series (i.e., arranged to conduct in opposite directions). In particular:

[0134] - The first controllable semiconductor switch (S1) and the ninth controllable semiconductor switch (S9) are electrically connected in reverse series. The first controllable semiconductor switch (S1) is electrically connected to the first AC bridge terminal (AC1), and the ninth controllable semiconductor switch (S9) is electrically connected to the first DC bridge terminal (DC1).

[0135] - The second controllable semiconductor switch (S2) and the tenth controllable semiconductor switch (S10) are electrically connected in reverse series. The second controllable semiconductor switch (S2) is electrically connected to the first AC bridge terminal (AC1), and the tenth controllable semiconductor switch (S10) is electrically connected to the second DC bridge terminal (DC2).

[0136] - The third controllable semiconductor switch (S3) and the eleventh controllable semiconductor switch (S11) are electrically connected in reverse series. The third controllable semiconductor switch (S3) is electrically connected to the second AC bridge terminal (AC2), and the eleventh controllable semiconductor switch (S11) is electrically connected to the first DC bridge terminal (DC1).

[0137] - The fourth controllable semiconductor switch (S4) and the twelfth controllable semiconductor switch (S12) are electrically connected in reverse series. The fourth controllable semiconductor switch (S4) is electrically connected to the second AC bridge terminal (AC2), and the twelfth controllable semiconductor switch (S12) is electrically connected to the second DC bridge terminal (DC2).

[0138] The controllable semiconductor switches (S1, S2, ..., S12) of the switching module (1) are all of the same type and have the same rating. In the switching module (1) shown in FIG. 2, the controllable semiconductor switches (S1, S2, ..., S12) are all MOSFETs. Each MOSFET includes a body diode as part of the MOSFET structure. It will be understood that other controllable semiconductor switches may also be appropriately used.

[0139] The first controllable semiconductor switch (S1) and the ninth controllable semiconductor switch (S9) are electrically connected in reverse series in a common drain configuration. The second controllable semiconductor switch (S2) and the tenth controllable semiconductor switch (S10) are electrically connected in reverse series in a common source configuration. The third controllable semiconductor switch (S3) and the eleventh controllable semiconductor switch (S11) are electrically connected in reverse series in a common drain configuration. The fourth controllable semiconductor switch (S4) and the twelfth controllable semiconductor switch (S12) are electrically connected in reverse series in a common source configuration.

[0140] The same switching module (1) is shown in FIG. 3a.

[0141] Referring to FIG. 3b, the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are of the same type and are implemented as a first pre-packaged module (M1) in which the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are arranged to conduct in the same direction. In other words, the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module.

[0142] The third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) are of the same type and are implemented as a second pre-packaged module (M2) in which the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) are arranged to conduct in the same direction. In other words, the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) are implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module.

[0143] The fifth controllable semiconductor switch (S5) and the ninth controllable semiconductor switch (S9) are of the same type and are implemented as a third pre-packaged module (M3) arranged to conduct in the same direction. In other words, the fifth controllable semiconductor switch (S5) and the ninth controllable semiconductor switch (S9) are implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module, despite the fact that they are used in the active clamp circuit (6) and the H-bridge circuit (2), respectively.

[0144] The sixth controllable semiconductor switch (S6) and the tenth controllable semiconductor switch (S10) are of the same type and are implemented as a fourth pre-packaged module (M4) in which the sixth controllable semiconductor switch (S6) and the tenth controllable semiconductor switch (S10) are arranged to conduct in the same direction. In other words, the sixth controllable semiconductor switch (S6) and the tenth controllable semiconductor switch (S10) are implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module, despite the fact that they are used in the active clamp circuit (6) and the H-bridge circuit (2), respectively.

[0145] The seventh controllable semiconductor switch (S7) and the eleventh controllable semiconductor switch (S11) are of the same type and are implemented as a fifth pre-packaged module (M5) in which the seventh controllable semiconductor switch (S7) and the eleventh controllable semiconductor switch (S11) are arranged to conduct in the same direction. In other words, the seventh controllable semiconductor switch (S7) and the eleventh controllable semiconductor switch (S11) are implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module, despite the fact that they are used in the active clamp circuit (6) and the H-bridge circuit (2), respectively.

[0146] The eighth controllable semiconductor switch (S8) and the twelfth controllable semiconductor switch (S12) are of the same type and are implemented as a sixth pre-packaged module (M6) in which the eighth controllable semiconductor switch (S8) and the twelfth controllable semiconductor switch (S12) are arranged to conduct in the same direction. In other words, the eighth controllable semiconductor switch (S8) and the twelfth controllable semiconductor switch (S12) are implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module, despite the fact that they are used in the active clamp circuit (6) and the H-bridge circuit (2), respectively.

[0147] In this arrangement, six conventional or "off-the-shelf" pre-packaged modules (M1, M2, ..., M6) are required to implement the switching module. For example, the pre-packaged modules (M1, M2, ..., M6) may be half-bridge modules. An example of a half-bridge module is shown in FIG. 3c, in which a pair of MOSFETs are electrically connected in series and arranged to conduct in the same direction. As described above, if each pre-packaged module has two or more pairs of controllable semiconductors defining two or more legs, under the condition that the leg terminals are not electrically connected together (e.g., DC terminals are not connected to each other), the switching module can be implemented using a smaller number of pre-packaged modules. This allows multiple pairs of controllable semiconductor switches of the switching module to be implemented within the same pre-packaged module.

[0148] Referring to FIG. 4a, an alternative switching module (10) according to the present invention includes an H-bridge circuit (2). The H-bridge circuit (12) is:

[0149] - A first AC bridge terminal (AC1) and a second AC bridge terminal (AC2) electrically connectable to individual coils (14),

[0150] - A first DC bridge terminal (DC1) and a second DC bridge terminal (DC2) electrically connectable to a DC current source or to a DC bridge terminal of another switching module,

[0151] - A first switch assembly electrically connected between a first AC bridge terminal (AC1) and a first DC bridge terminal (DC1) - The first switch assembly includes a first controllable semiconductor switch (S1) and a first diode (D1) electrically connected in series -,

[0152] - A second switch assembly electrically connected between a first AC bridge terminal (AC1) and a second DC bridge terminal (DC2) - The second switch assembly includes a second controllable semiconductor switch (S2) and a second diode (D2) electrically connected in series -,

[0153] - A third switch assembly electrically connected between the second AC bridge terminal (AC2) and the first DC bridge terminal (DC1) - The third switch assembly includes a third controllable semiconductor switch (S3) and a third diode (D3) electrically connected in series -,

[0154] - A fourth switch assembly electrically connected between the second AC bridge terminal (AC2) and the second DC bridge terminal (DC2) - The fourth switch assembly includes a fourth controllable semiconductor switch (S4) and a fourth diode (D4) electrically connected in series -

[0155] The first AC terminal (AC1) and the second AC terminal (AC2) of the switching module (10) are shown as being electrically connected to a single coil (14). However, the switching module (10) may be electrically connected to two or more coils that are electrically connected in series or parallel.

[0156] The switching module (10) also:

[0157] - 1st DC clamp terminal (DC3) and 2nd DC clamp terminal (DC4),

[0158] - A fifth controllable semiconductor switch (S5) electrically connected between the junction (or connection point) between the first controllable semiconductor switch (S1) and the first diode (D1) and the first DC clamp terminal (DC3),

[0159] - A sixth controllable semiconductor switch (S6) electrically connected between the junction point between the second controllable semiconductor switch (S2) and the second diode (D2) and the second DC clamp terminal (DC4),

[0160] - A seventh controllable semiconductor switch (S7) electrically connected between the junction point between the third controllable semiconductor switch (S3) and the third diode (D3) and the first DC clamp terminal (DC3),

[0161] - An eighth controllable semiconductor switch (S8) electrically connected between the junction point between the fourth controllable semiconductor switch (S4) and the fourth diode (D4) and the second DC clamp terminal (DC4), and

[0162] - Includes an active clamp circuit (16) comprising an energy storage device (e.g., a capacitor (C)) electrically connected between a first DC clamp terminal (DC3) and a second DC clamp terminal (DC4).

[0163] The junction point between the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) defines the first AC bridge terminal (AC1), and the junction point between the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) defines the second AC bridge terminal (AC2).

[0164] The first controllable semiconductor switch (S1) and the first diode (D1) are electrically connected in series and arranged to conduct in the same direction. The first controllable semiconductor switch (S1) is electrically connected to the first AC bridge terminal (AC1), and the first diode (D1) is electrically connected to the first DC bridge terminal (DC1).

[0165] The second controllable semiconductor switch (S2) and the second diode (D2) are electrically connected in series and arranged to conduct in the same direction. The second controllable semiconductor switch (S2) is electrically connected to the first AC bridge terminal (AC1), and the second diode (D2) is electrically connected to the second DC bridge terminal (DC2).

[0166] The third controllable semiconductor switch (S3) and the third diode (D3) are electrically connected in series and arranged to conduct in the same direction. The third controllable semiconductor switch (S3) is electrically connected to the second AC bridge terminal (AC2), and the third diode (D3) is electrically connected to the first DC bridge terminal (DC1).

[0167] The fourth controllable semiconductor switch (S4) and the fourth diode (D4) are electrically connected in series and arranged to conduct in the same direction. The fourth controllable semiconductor switch (S4) is electrically connected to the second AC bridge terminal (AC2), and the fourth diode (D4) is electrically connected to the second DC bridge terminal (DC2).

[0168] The controllable semiconductor switches (S1, S2, ..., S8) of the switching module are all of the same type and have the same rating. In the switching module (10) shown in FIG. 4a, the controllable semiconductor switches (S1, S2, ..., S8) are all IGBTs. Each IGBT is associated with an antiparallel diode (i.e., diodes (D1a, D2a, ..., D8a)). It will be understood that other controllable semiconductor switches may also be used.

[0169] Referring to FIG. 4b, the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are of the same type and are implemented as a first pre-packaged module (M1) in which the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are arranged to conduct in the same direction. In other words, the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module.

[0170] The third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) are of the same type and are implemented as a second pre-packaged module (M2) in which the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) are arranged to conduct in the same direction. In other words, the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) can be implemented using a pair of controllable semiconductor switches that are packaged together in a conventional pre-packaged module.

[0171] The fifth controllable semiconductor switch (S5) and the first diode (D1) are implemented as a third pre-packaged module (M3) in which the fifth controllable semiconductor switch (S5) and the first diode (D1) are electrically connected in reverse series, that is, arranged to conduct in opposite directions. In other words, the fifth controllable semiconductor switch (S5) and the first diode (D1) are implemented using a controllable semiconductor switch and a diode that are packaged together in a conventional pre-packaged module, despite the fact that they are used in the active clamp circuit (16) and the H-bridge circuit (12), respectively.

[0172] The sixth controllable semiconductor switch (S6) and the second diode (D2) are implemented as a fourth pre-packaged module (M4) in which the sixth controllable semiconductor switch (S6) and the second diode (D2) are electrically connected in reverse series, that is, arranged to conduct in opposite directions. In other words, the sixth controllable semiconductor switch (S6) and the second diode (D2) are implemented using a controllable semiconductor switch and a diode that are packaged together in a conventional pre-packaged module, despite the fact that they are used in the active clamp circuit (16) and the H-bridge circuit (12), respectively.

[0173] The seventh controllable semiconductor switch (S7) and the third diode (D3) are implemented as a fifth pre-packaged module (M5) in which the seventh controllable semiconductor switch (S7) and the third diode (D3) are electrically connected in reverse series, that is, arranged to conduct in opposite directions. In other words, the seventh controllable semiconductor switch (S7) and the third diode (D3) are implemented using a controllable semiconductor switch and a diode that are packaged together in a conventional pre-packaged module, despite the fact that they are used in the active clamp circuit (16) and the H-bridge circuit (12), respectively.

[0174] The eighth controllable semiconductor switch (S8) and the fourth diode (D4) are implemented as a sixth pre-packaged module (M6) in which the eighth controllable semiconductor switch (S8) and the fourth diode (D4) are electrically connected in reverse series, that is, arranged to conduct in opposite directions. In other words, the eighth controllable semiconductor switch (S8) and the fourth diode (D4) are implemented using a controllable semiconductor switch and a diode that are packaged together in a conventional pre-packaged module, despite the fact that they are used in the active clamp circuit (16) and the H-bridge circuit (12), respectively.

[0175] In this arrangement, six conventional or "off-the-shelf" pre-packaged modules are required to implement the switching module. For example, the first pre-packaged module (M1) and the second pre-packaged module (M1) may be half-bridge modules. An example of a half-bridge module is shown in FIG. 4c, in which a pair of IGBTs and antiparallel diodes are electrically connected in series and arranged to conduct in the same direction. Alternatively, as described above, under the condition that the leg terminals are not electrically connected together (e.g., the DC terminals are not connected to each other), the first, second, third, and fourth controllable switches (S1, S2, ..., S4) may be implemented using a single pre-packaged module having two pairs of controllable semiconductors defining two legs. The third, fourth, fifth, and sixth pre-packaged modules (M3, M4, ..., M6) may be chopper modules, and each chopper module includes a controllable semiconductor switch (e.g., an IGBT and an antiparallel diode) electrically connected in anti-series with a diode. An example of a chopper module is shown in FIGS. 4d and 4e, in which an IGBT and an antiparallel diode are electrically connected in anti-series with a diode. The IGBT and the diode are arranged to conduct in opposite directions. The third pre-packaged module (M3) and the fifth pre-packaged module (M5) may be implemented using the chopper module shown in FIG. 4d, and the fourth pre-packaged module (M4) and the sixth pre-packaged module (M6) may be implemented using the chopper module shown in FIG. 4e.

[0176] The third, fourth, fifth, and sixth pre-packaging modules (M3, M4, ..., M6) may be half-bridge modules as shown in FIG. 4c, but by deactivating one of the pair of IGBTs, the corresponding switch is rendered unnecessary without affecting the individual antiparallel diode. This is illustrated in FIG. 4f, where one of the IGBTs is ghosted to indicate that it is unnecessary. It can be seen that the gate and emitter terminals of the ghosted IGBT are short-circuited. In this way, the switching module (10) can be implemented using six (or fewer) identical pre-packaging half-bridge modules—where for the third, fourth, fifth, and sixth pre-packaging modules (M3, M4, ..., M6), only one of the IGBTs is switched on and off. The other IGBT is deactivated, but current can still flow through its individual antiparallel diode.

[0177] As shown in FIGS. 2 and 3a through 3c, implementing the H-bridge circuit and active clamp circuit with MOSFETs will minimize conduction losses. As shown in FIGS. 4a through 4f, using IGBTs may be less expensive, but the switching module will experience higher conduction losses. Both arrangements using MOSFETs and IGBTs will require a total of six (or fewer) pre-packaged modules (M1, M2, ..., M6).

[0178] The following description refers to a switching module (10) using an IGBT, but it will be understood that other types of controllable semiconductor switches, such as MOSFETs shown in FIG. 2 and 3a to 3b, may also be used.

[0179] The coil rectification process of the switching module (10) implemented using an IGBT is described with reference to FIGS. 5a through 5f.

[0180] In the first step illustrated in FIG. 5a, I 코일 = + I dc is, I 코일 is the coil current, and I dc is a DC current, for example, a DC current supplied by a DC current source (56) described below. The first controllable semiconductor switch (S1) and the fourth controllable semiconductor switch (S4) are switched on. All other controllable semiconductor switches are switched on. Current flows through the coil (14) in the direction indicated by the arrow in FIG. 5a—that is, from the first DC bridge terminal (DC1) to the second DC bridge terminal (DC2) through the first diode (D1), the first controllable semiconductor switch (S1), the coil (14), the fourth controllable semiconductor switch (S4), and the fourth diode (D4).

[0181] In the second step illustrated in FIG. 5b, the first controllable semiconductor switch (S1) and the fourth controllable semiconductor switch (S4) are kept in a switched-on state. The second controllable semiconductor switch (S2), the third controllable semiconductor switch (S3), the sixth controllable semiconductor switch (S6), and the seventh controllable semiconductor switch (S7) are switched-on. As a result, a negative voltage is applied across the coil (14). V 코일 = - V 클램프 and, here V 코일 is the coil voltage, and V 클램프 is the DC voltage across the capacitor (C) of the active clamp circuit (16) (i.e., the capacitor voltage). The coil current begins to decrease and the capacitor (C) discharges. When the coil current reaches a threshold value (e.g., I 코일 = + I dc / 2), the process transitions to the third step shown in Fig. 5c.

[0182] In the third step, the first controllable semiconductor switch (S1) is switched off. The second controllable semiconductor switch (S2), the third controllable semiconductor switch (S3), the fourth controllable semiconductor switch (S4), the sixth controllable semiconductor switch (S6), and the seventh controllable semiconductor switch (S7) remain switched on. This maintains a negative voltage across the coil (14). The coil current continues to decrease and approaches zero. The capacitor (C) is charged. When the coil current reaches zero, the process transitions to the fourth step shown in FIG. 5d.

[0183] In the fourth step, the second controllable semiconductor switch (S2), the third controllable semiconductor switch (S3), the fourth controllable semiconductor switch (S4), the sixth controllable semiconductor switch (S6), and the seventh controllable semiconductor switch (S7) are kept in a switched-on state. This maintains a negative voltage across the coil (14). The coil current, which is now negative, continues to become even more negative. The capacitor (C) is discharged. When the coil current reaches a threshold value (e.g., I 코일 = - I dc / 2), the process transitions to the fifth step shown in Fig. 5e.

[0184] In the fifth step, the fourth controllable semiconductor switch (S4) is switched off. The second controllable semiconductor switch (S2), the third controllable semiconductor switch (S3), the sixth controllable semiconductor switch (S6), and the seventh controllable semiconductor switch (S7) remain switched on. This maintains a negative voltage across the coil (14). The coil current continues to become increasingly negative, and - I dc It approaches. The capacitor (C) is charged. The coil current is - I dcWhen approaching, the process transitions to the sixth step illustrated in FIG. 5f. Although the sixth switch (S6) and the seventh switch (S7) may remain switched on until the end of the fifth step, these switches may also be switched off during the fifth step because the antiparallel diodes (D6a, D7a) of these switches will carry current. The advantage of switching off the sixth switch (S6) and the seventh switch (S7) during the fifth step is that the coil current - I dc This means that the 5th stage automatically terminates when it is reached, and if the switches remain in the switched-on state, the coil current is - I dc There is a risk that it may exceed, that is, the coil current may overshoot.

[0185] In step 6, I 코일 = - I dc (i.e., the coil current +I dc at -I dc (rectified to) and the second semiconductor switch (S2) and the third semiconductor switch (S3) are maintained in a switched-on state.

[0186] The net charge flowing into or out of the capacitor (C) during the coil rectification process will be determined by the duration of each of the second through fifth stages. The total duration of these stages will remain the same for a given clamp voltage, DC current, and coil inductance. However, the transition points between the second and third stages, and between the fourth and fifth stages, will determine the change in the net capacitor charge and, consequently, the capacitor voltage. For example, if the second and fourth stages are shortened while the third and fifth stages are extended by the same amount, there will be a net charge in the capacitor (C), and the capacitor voltage at the end of the coil rectification process will be greater than at the start of the process. The stage durations can be adjusted, for example, by adjusting the coil current threshold value that triggers the end of each stage.

[0187] Although not shown, the coil current using a corresponding coil rectification process -I dc from + I dc It can be rectified. In particular, in the first stage, I 코일 = - I dc The second controllable semiconductor switch (S2) and the third controllable semiconductor switch (S3) are switched on. All other controllable semiconductor switches are switched off. Current flows from the first DC bridge terminal (DC1) to the second DC bridge terminal (DC2) through the third diode (D3), the third controllable semiconductor switch (S3), the coil (14), the second controllable semiconductor switch (S2), and the second diode (D2).

[0188] In the second step, the second controllable semiconductor switch (S2) and the third controllable semiconductor switch (S3) are kept in a switched-on state. The first controllable semiconductor switch (S1), the fourth controllable semiconductor switch (S4), the fifth controllable semiconductor switch (S5), and the eighth controllable semiconductor switch (S8) are switched on. As a result, a positive voltage is applied across the coil (14). V 코일 = + V 클램프 is. The coil current begins to decrease to a negative value and the capacitor (C) discharges. When the coil current reaches a threshold value (e.g., I 코일 = - I dc / 2), the process transitions to the third stage.

[0189] In the third step, the third controllable semiconductor switch (S3) is switched off. The first controllable semiconductor switch (S1), the second controllable semiconductor switch (S2), the fourth controllable semiconductor switch (S4), the fifth controllable semiconductor switch (S5), and the eighth controllable semiconductor switch (S8) remain switched on. This maintains a positive voltage across the coil (14). The coil current continues to decrease in negative value and approaches zero. The capacitor (C) is charged. When the coil current reaches zero, the process transitions to the fourth step.

[0190] In the fourth step, the first controllable semiconductor switch (S1), the second controllable semiconductor switch (S2), the fourth controllable semiconductor switch (S4), the fifth controllable semiconductor switch (S5), and the eighth controllable semiconductor switch (S8) are kept in a switched-on state. This maintains a positive voltage across the coil (14). The coil current, which has now become positive, continues to increase. The capacitor (C) discharges. When the coil current reaches a threshold value (e.g., I 코일 = + Idc / 2), the process transitions to the 5th stage.

[0191] In the fifth step, the second controllable semiconductor switch (S2) is switched off. The first controllable semiconductor switch (S1), the fourth controllable semiconductor switch (S4), the fifth controllable semiconductor switch (S5), and the eighth controllable semiconductor switch (S8) remain switched on. This maintains a positive voltage across the coil (14). The coil current continues to increase, + I dc It approaches. The capacitor (C) is charged. The coil current is + I dc When it is reached, the process transitions to the sixth stage. Although the fifth switch (S5) and the eighth switch (S8) may remain switched on until the end of the fifth stage, these switches may also be switched off during the fifth stage because the antiparallel diodes (D5a, D8a) of these switches will carry current. The advantage of switching off the fifth switch (S5) and the eighth switch (S8) during the fifth stage is that the coil current is + I dc This means that the 5th stage automatically terminates when it is reached, and if the switches remain in the switched-on state, the coil current is + I dc There is a risk that it may exceed, that is, the coil current may become excessively high.

[0192] In step 6, I 코일 = + I dc (i.e., the coil current - I dc at + I dc (rectified to) and the first semiconductor switch (S1) and the fourth semiconductor switch (S4) are maintained in a switched-on state.

[0193] If the switching module (10) is implemented using a MOSFET, the MOSFET may need to be switched off just before current flows through the individual antiparallel diode and switched on just after current starts flowing through the individual antiparallel diode. In other words, it is generally necessary to add deadtime to the coil rectification process to prevent short circuits in the capacitor (C) of the active clamp circuit (16). For example, in the third step illustrated in FIG. 5c, but implemented using a MOSFET instead of an IGBT, it is necessary to switch off the ninth controllable semiconductor switch (S9) just before switching off the first controllable semiconductor switch (S1). Switching off the first controllable semiconductor switch (S1) causes the body diode of the eleventh controllable semiconductor switch (S11) to be switched on. Thus, the eleventh controllable semiconductor switch (S11) is switched on immediately after the first controllable semiconductor switch (S1) is switched off.

[0194] The switching module (10) may be associated with one or more electronic circuits, such as a control circuit, a gate driver circuit for driving a controllable semiconductor switch, for example. The electronic circuit may communicate with the main controller, for example, via a fiber optic link or other galvanically isolated communication channel. The electronic circuit will generally require a power supply. In one arrangement, power for the electronic circuit may be provided by a capacitor (C) of the switching module (10) instead of being supplied by a separate power supply. Referring to FIG. 6, therefore, the switching module (10) may include a power supply circuit (18) (e.g., a low-voltage power supply circuit) electrically connected between a first DC clamp terminal (DC3) and a second DC clamp terminal (DC4) in parallel with the capacitor (C). The power supply circuit (18) may be electrically connected to one or more local electronic circuits (20, 22). The power supply circuit may be a power converter, for example, a step-down power converter for deriving an appropriate output voltage from the capacitor voltage. A suitable power converter may be a DC / DC power converter, such as a forward converter or a flyback converter. The capacitor (C) may be charged by a DC current source through the first DC bridge terminal (DC1) and the second DC bridge terminal (DC2) or by a current induced in a coil (14) electrically connected to the first AC bridge terminal (AC1) and the second AC bridge terminal (AC2), in the latter case, the induced current will flow through one or more semiconductor devices of the H-bridge circuit (12) and the clamp circuit (16). For example, if the capacitor (C) is charged by a pre-charging process, power may be supplied to one or more electronic circuits (20, 22) associated with the switching module (10) using the power supply circuit (18).

[0195] Referring to FIG. 7, the switching module (10) may further include a battery (24) (or a battery bank including a plurality of electrically connected batteries) electrically connected between a first DC clamp terminal (DC3) and a second DC clamp terminal (DC4) in parallel with the capacitor (C). Incorporating additional energy storage beyond what is required for energy recovery may provide a distributed energy storage network for a power electronic switching assembly including a plurality of electrically connected switching modules. The battery voltage and battery state of charge (SoC) of the battery (24) may be controlled by an active clamp circuit (16). The active clamp circuit (16) may be designed to match the battery voltage range across the allowable SoC variation of the battery (24). In some situations, the battery (24) may also be used to absorb excess power induced in a coil electrically connected to the first AC bridge terminal (AC1) and the second AC bridge terminal (AC2) during an overspeed condition of a DC electric machine, for example, comprising a plurality of switch modules, and each switching module is electrically connected to the stator coil of the DC electric machine. An example of a DC electric machine is described below with reference to FIG. 9.

[0196] Referring to FIG. 8, the switching module (10) may further include a dynamic providing system (26) electrically connected between a first DC clamp terminal (DC3) and a second DC clamp terminal (DC4) in parallel with a capacitor (C). The dynamic braking system (26) may be of any suitable type. For example, as shown in FIG. 8, the dynamic braking system (26) includes a braking resistor (28) and a controllable semiconductor switch (30) electrically connected in series between the first DC clamp terminal (DC3) and the second DC clamp terminal (DC4). The dynamic braking system (26) also includes a diode (32) electrically connected in parallel with the braking resistor (28). The dynamic braking system (26) may be used, for example, to provide short-term power loss during an overspeed condition of a DC electric machine.

[0197] Referring to FIG. 9, the DC electric machine (50) is:

[0198] - Multiple stator coils (541, 542, ..., 54 n A stator (52) having ) - where n is an integer greater than or equal to 2 -,

[0199] - Rotor (not shown),

[0200] - DC current source (56), and

[0201] - Includes a power electronic switching assembly (58).

[0202] The power electronic switching assembly (58) comprises n switching modules (101, 102, ..., 10) as described above. n It will be understood that the power electronic switching assembly (58) may be implemented using the switching module shown in FIG. 2, 3a and 3b, where the controllable semiconductor switch is a MOSFET, or the switching module shown in FIG. 4a and 4b, where the controllable semiconductor switch is an IGBT. Switching modules implemented using other types of controllable semiconductor switches may also be used.

[0203] Each switching module (101, 102, ..., 10 n The first AC bridge terminal (AC1) and the second AC bridge terminal (AC2) of ) are individual stator coils (541, 542, ..., 54 n It is electrically connected to ). The first DC bridge terminal (DC1) of the first switching module (101) is electrically connected to the first DC terminal (60) of the DC current source (56), and the nth switching module (10 n The second DC bridge terminal (DC2) of the ) is electrically connected to the second DC terminal (62) of the DC current source (56), and the first DC bridge terminal (DC1) and the second DC bridge terminal (DC2) of the remaining switching module are electrically connected in series. For example, the (n-1)th switching module (10 (n-1) The second DC bridge terminal (DC2) of the nth switching module (10 n Until it is electrically connected to the first DC bridge terminal (DC1) of the first switching module (101), the second DC bridge terminal (DC2) of the first switching module (101) is electrically connected to the first DC bridge terminal (DC1) of the second switching module (102), and the second DC bridge terminal (DC2) of the second switching module (102) is electrically connected to the first DC bridge terminal of the third switching module, and so on. In other words, the switching modules (101, 102, ..., 10 n As shown in FIG. 9, ) can be electrically connected in a serial chain link structure between the first DC terminal (60) and the second DC terminal (62) of the DC current source (56).

[0204] FIG. 9 shows a first set of switching modules (101, 102, ..., 10 nA second set of switching modules connected in parallel with the first DC terminal and the second DC terminal of the DC current source (56) via a serial chain link structure is also illustrated. In practice, three or more sets of switching modules connected via a serial chain link structure may be electrically connected in parallel between the first DC terminal and the second DC terminal of the DC current source (56).

[0205] Stator coils (541, 542, ..., 54 n ) can be received through a slot formed in the stator (52). Stator coils (541, 542, ..., 54 n The rotor (not shown) can be of any suitable type (e.g., single layer, double layer, etc.) and can be arranged around the stator to have any suitable winding topology. The rotor (not shown) rotates relative to the stationary stator (52) and is spaced apart from the stator (52) by an air gap. As described above, the rotor (not shown) can have any suitable configuration.

[0206] The DC current source (56) illustrated in FIG. 9 is, for example, a first switching module (101) and an nth switching module (10) of a power electronic switching assembly (58). n It may be a power converter, such as an AC / DC power converter, having a first DC terminal (60) and a second DC terminal (62) electrically connected to ), and three AC terminals (64) electrically connected to an AC circuit or power grid (e.g., a three-phase power grid). Although not illustrated, the DC current source may be another DC electric machine, such as a generator that provides a DC output voltage, for example. The DC electric machine (50) may operate as a motor or a generator. In particular, power is supplied from the DC current source (56) to the switching module (101, 102, ..., 10 nPower is supplied to ) to drive a rotor (not shown), or the rotor can be driven to rotate (e.g., by a prime mover), and power is supplied to the stator coils (541, 542, ..., 54 n Generated in ) switching module(101, 102, ..., 10 n It can be supplied to a DC current source (56) from ). Other DC current sources may also be used.

[0207] Each switching module (101, 102, ..., 10 n ) is a coil rectification process (i.e., when the DC electric machine (50) is operating here, the stator coils (541, 542, ..., 54 n It may further include a controller (not shown) adapted to rectify individual switching modules according to the (repeated reversal of the current flowing through it). Alternatively, one or more controllers may be associated with two or more switching modules, and each controller is adapted to rectify a switching module according to an individual coil rectification process. Each switching module (101, 102, ..., 10 n Stator coils (541, 542, ..., 54) of ) n ) can be rectified, and the individual coil rectification processes can be interleaved. Stator coils (541, 542, ..., 54) of a DC electric machine (50) n) can be arranged around the stator (52) to provide multiple phase-shifted coil voltages—usually having multiple phases. For example, a DC electric machine (50) having p phases may include a first group of at least p stator coils, the EMFs of these stator coils being phase-shifted by 360 / p° relative to each other, where p is an integer greater than or equal to 2, one cycle of the stator fundamental frequency occupies 360°, and each EMF experiences two zero crossings per cycle. The DC electric machine (50) may have any convenient number of stator coils (i.e., n can be any appropriate number) and thus may have a larger number of phases with small phase shifts between the EMFs. Since the number of coil rectification events per cycle of the stator fundamental frequency is equal to twice the number of phases, consecutive coil rectifications are interleaved. Multiple overlapping coil rectification events may occur at any given time.

[0208] The timing parameters of each coil rectification event are individual switching modules (101, 102, ..., 10 n The voltage across the capacitor (C) of the active clamp circuit (16) can be changed or adjusted to control the closed loop.

[0209] Referring to FIGS. 10 and 11, the power converter (70) is:

[0210] - Multiple first coils (741, 742, ..., 74) that are combined n ) and a plurality of second coils (761, 762, ..., 76 n A transformer assembly (72) having )

[0211] - DC current source (78), and

[0212] - Includes a power electronic switching assembly (80).

[0213] The power electronic switching assembly (80) comprises n switching modules (101, 102, ..., 10) as described above.n It will be understood that the power electronic switching assembly (80) may be implemented using the switching module illustrated in FIG. 2, 3a and 3b, where the controllable semiconductor switch is a MOSFET, or the switching module illustrated in FIG. 4a and 4b, where the controllable semiconductor switch is an IGBT. Switching modules implemented using other types of controllable semiconductor switches may also be used. FIG. 11 illustrates a switching module implemented using a MOSFET as an example.

[0214] Each switching module (101, 102, ..., 10 n The first AC bridge terminal (AC1) and the second AC bridge terminal (AC2) of the transformer assembly (72) are the individual first coils (741, 742, 744) n It is electrically connected to ). FIG. 11 illustrates an optional series capacitor (SC) connected between the first AC terminal (AC1) of the switching module (101) and the individual first coil (741). The first DC bridge terminal (DC1) of the first switching module (101) is electrically connected to the first DC terminal (82) of the DC current source, and the nth switching module (10 n The second DC bridge terminal (DC2) of the (n-1)th switching module can be electrically connected to the second DC terminal (84) of the DC current source (78), and the first DC bridge terminal (DC1) and the second DC bridge terminal (DC2) of the remaining switching module are electrically connected in series. For example, the second DC bridge terminal (DC2) of the (n-1)th switching module is connected to the nth switching module (10 nUntil it is electrically connected to the first DC bridge terminal (DC1) of the first switching module (101), the second DC bridge terminal (DC2) of the first switching module (101) is electrically connected to the first DC bridge terminal (DC1) of the second switching module (102), and the second DC bridge terminal (DC2) of the second switching module (102) is electrically connected to the first DC bridge terminal (DC1) of the third switching module, and so on. In other words, the switching modules (101, 102, ..., 10 n As shown in FIG. 10, the first DC terminal (82) and the second DC terminal (84) of the DC current source (78) can be electrically connected in a series chain link structure.

[0215] Each switching module (101, 102, ..., 10 n ) can function as a DC / AC power converter, and each first coil (741, 742, ..., 74 n An output current waveform is generated in the ). For example, to generate a positive voltage in an individual first coil, the first controllable semiconductor switch (S1), the fourth controllable semiconductor switch (S4), the fifth controllable semiconductor switch (S5), and the eighth controllable semiconductor switch (S8) of the switching module can be switched on, while the remaining controllable semiconductor switches are switched off. To generate a negative voltage in an individual first coil, the second controllable semiconductor switch (S2), the third controllable semiconductor switch (S3), the sixth controllable semiconductor switch (S6), and the seventh controllable semiconductor switch (S7) of the switching module can be switched on, while the remaining controllable semiconductor switches are switched off. The output current waveform can have any appropriate frequency, for example, about 1 to 10 kHz or higher. This allows the size of the transformer assembly (72) to be minimized and high power density to be achieved.

[0216] More specifically, to generate a positive voltage in an individual first coil, the first controllable semiconductor switch (S1), the fourth controllable semiconductor switch (S4), the fifth controllable semiconductor switch (S5), and the eighth controllable semiconductor switch (S8) may be switched on. In this state, either the second controllable semiconductor switch (S2) or the third controllable semiconductor switch (S3) may be switched on to short-circuit the DC current source (State A). If neither the second controllable semiconductor switch (S2) nor the third controllable semiconductor switch (S3) is switched on (State B), the voltage of the DC current source is equal to the clamp voltage.

[0217] To generate a negative voltage in an individual first coil, the second controllable semiconductor switch (S2), the third controllable semiconductor switch (S3), the sixth controllable semiconductor switch (S6), and the seventh controllable semiconductor switch (S7) can be switched on. In this state, either the first controllable semiconductor switch (S1) or the fourth controllable semiconductor switch (S4) can be switched on to short-circuit the DC current source (State C). If neither the first controllable semiconductor switch (S1) nor the fourth controllable semiconductor switch (S4) is switched on (State D), the voltage of the DC current source is equal to the clamp voltage.

[0218] Therefore, the voltage of the DC current source is a square wave with the same amplitude as the clamp voltage. The average voltage is set by the duty ratio of state A and state B, and by the duty ratio of state C and state D. The applied switching pattern—including for the 9th, 10th, 11th, and 12th controllable semiconductor switches (S9, S10, ..., S12)—can be optimally selected to minimize the number of switching events, and the power flowing from the DC current source into the circuit can be controlled by controlling the average DC input voltage.

[0219] Each second coil (761, 762, ..., 76 n ) are individual AC / DC power converters (861, 862, ..., 86 n It is electrically connected to ). Any suitable AC / DC power converter may be used. For example, as shown in FIG. 10, each AC / DC power converter (861, 862, ..., 86 n ) is individual second coils (761, 762, ..., 76 n It has two AC terminals electrically connected to ) and two DC terminals electrically connected to a DC circuit (88). The DC circuit (88) includes a capacitor (90). AC / DC power converters (861, 862, ..., 86 n Other arrangements of ) may be used, and these AC / DC power converters may be electrically connected in different ways, for example, such as AC / DC power converters being electrically connected in series, parallel, or series-parallel.

[0220] If an AC output voltage is required, an AC output voltage can be derived from the DC circuit (88) using any suitable DC / AC power converter (92). For example, as shown in FIG. 10, the DC / AC power converter (92) has two DC terminals (94, 96) electrically connected to the DC circuit (88) and three AC terminals (98) that provide a desired AC output voltage at a desired frequency (e.g., 60 Hz).

[0221] Switching modules (101, 102, ..., 10) of a power electronic switching assembly (e.g., the power electronic switching assembly (58) shown in FIG. 9 or the power electronic switching assembly (80) shown in FIG. 10). n) can be bypassed in the event of a fault in the H-bridge or active clamp circuit. Referring to FIG. 12, a bypass switch (Q1) (e.g., a mechanical switch or a controllable semiconductor switch) may be electrically connected between the first DC bridge terminal (DC1) and the second DC bridge terminal (DC2) of each switching module (10). The bypass switch (Q1) will generally be switched off (or the bypass switch (Q1) will generally be open so that no current flows through the bypass circuit between the first DC bridge terminal and the second DC bridge terminal), but may be optionally switched on (or closed) to bypass the H-bridge circuit (12). This allows the power electronic switching assembly to continue operating at a possibly slightly reduced rating if one or more of the switching modules fail and need to be bypassed. Instead of applying a direct short circuit across the first DC bridge terminal (DC1) and the second DC bridge terminal (DC2), the bypass switch (Q1) may be electrically connected in series with an energy-absorbing device (not shown), such as a varistor or capacitor, for example. This may be advantageous in certain applications where a direct short circuit may not be recommended.

Claims

Claim 1 A switching module (1; 10) comprises an H-bridge circuit (2; 12); and an active clamp circuit (6; 16), wherein the H-bridge circuit (2; 12) is: A first bridge terminal (AC1) and a second AC bridge terminal (AC2) electrically connectable to individual coils (4; 14), A first DC bridge terminal (DC1) and a second DC bridge terminal (DC2) electrically connectable to a DC current source (56; 78) or to a DC bridge terminal of another switching module, A first switch assembly electrically connected between the first AC bridge terminal (AC1) and the first DC bridge terminal (DC1) - the first switch assembly includes a first controllable semiconductor switch (S1) and a first semiconductor device (S9; D1) electrically connected in series -, A second switch assembly electrically connected between the first AC bridge terminal (AC1) and the second DC bridge terminal (DC2) - the second switch assembly includes a second controllable semiconductor switch (S2) and a second semiconductor device (S10; D2) electrically connected in series -, A third switch assembly electrically connected between the second AC bridge terminal (AC2) and the first DC bridge terminal (DC1) - the third switch assembly includes a third controllable semiconductor switch (S3) and a third semiconductor device (S11; D3) electrically connected in series -, and A fourth switch assembly electrically connected between the second AC bridge terminal (AC2) and the second DC bridge terminal (DC2) - the fourth switch assembly includes a fourth controllable semiconductor switch (S4) and a fourth semiconductor device (S12; D4) electrically connected in series - and the active clamp circuit (6; 16) comprises: 1st DC clamp terminal (DC3) and 2nd DC clamp terminal (DC4), A fifth controllable semiconductor switch (S5) electrically connected between the junction point between the first controllable semiconductor switch (S1) and the first semiconductor device (S9; D1) and the first DC clamp terminal (DC3), A sixth controllable semiconductor switch (S6) electrically connected between the junction point between the second controllable semiconductor switch (S2) and the second semiconductor device (S10; D2) and the second DC clamp terminal (DC4), A seventh controllable semiconductor switch (S7) electrically connected between the junction point between the third controllable semiconductor switch (S3) and the third semiconductor device (S11; D3) and the first DC clamp terminal (DC3), An eighth controllable semiconductor switch (S8) electrically connected between the junction point between the fourth controllable semiconductor switch (S4) and the fourth semiconductor device (S12; D4) and the second DC clamp terminal (DC4), and A switching module (1; 10) comprising an energy storage device (C) electrically connected between the first DC clamp terminal (DC3) and the second DC clamp terminal (DC4). Claim 2 A switching module (1) wherein, in claim 1, the first semiconductor device is a ninth controllable semiconductor switch (S9), the second semiconductor device is a tenth controllable semiconductor switch (S10), the third semiconductor device is a eleventh controllable semiconductor switch (S11), and the fourth semiconductor device is a twelfth controllable semiconductor switch (S12). Claim 3 In paragraph 2, the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are of the same type and are implemented as a pre-packaged module (M1) in which the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are arranged to conduct in the same direction; the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) are of the same type and are implemented as a pre-packaged module (M2) in which the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) are arranged to conduct in the same direction; the fifth controllable semiconductor switch (S5) and the ninth controllable semiconductor switch (S9) are of the same type and are implemented as a pre-packaged module (M3) in which the fifth controllable semiconductor switch (S5) and the ninth controllable semiconductor switch (S9) are arranged to conduct in the same direction; and the sixth controllable semiconductor switch (S6) and the tenth controllable semiconductor A switching module (1) in which the switch (S10) is of the same type and is implemented as a pre-packaged module (M4) in which the sixth controllable semiconductor switch (S6) and the tenth controllable semiconductor switch (S10) are arranged to conduct in the same direction, the seventh controllable semiconductor switch (S7) and the eleventh controllable semiconductor switch (S11) are of the same type and are implemented as a pre-packaged module (M5) in which the seventh controllable semiconductor switch (S7) and the eleventh controllable semiconductor switch (S11) are arranged to conduct in the same direction, and the eighth controllable semiconductor switch (S8) and the twelfth controllable semiconductor switch (S12) are of the same type and are implemented as a pre-packaged module (M6) in which the eighth controllable semiconductor switch (S8) and the twelve controllable semiconductor switch (S12) are arranged to conduct in the same direction. Claim 4 A switching module (1) wherein, in claim 1 or 2, all of the controllable semiconductor switches (S1, S2, ..., S12) of the H-bridge circuit (2) and the active clamp circuit (6) are MOSFETs. Claim 5 A switching module according to claim 4, wherein the first controllable semiconductor switch (S1) and the ninth controllable semiconductor switch (S1) are electrically connected in anti-series in a common drain configuration, the second controllable semiconductor switch (S2) and the tenth controllable semiconductor switch (S10) are electrically connected in anti-series in a common drain configuration, the third controllable semiconductor switch (S3) and the eleventh controllable semiconductor switch (S11) are electrically connected in anti-series in a common drain configuration, and the fourth controllable semiconductor switch (S4) and the twelfth controllable semiconductor switch (S12) are electrically connected in anti-series in a common drain configuration. Claim 6 A switching module (10) wherein, in claim 1, the first semiconductor device is a first diode (D1), the second semiconductor device is a second diode (D2), the third semiconductor device is a third diode (D3), and the fourth semiconductor device is a fourth diode (D4). Claim 7 In claim 6, the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are of the same type and are implemented as a pre-packaged module (M1) in which the first controllable semiconductor switch (S1) and the second controllable semiconductor switch (S2) are arranged to conduct in the same direction; the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) are of the same type and are implemented as a pre-packaged module (M2) in which the third controllable semiconductor switch (S3) and the fourth controllable semiconductor switch (S4) are arranged to conduct in the same direction; the fifth controllable semiconductor switch (S5) and the first diode (D1) are implemented as a pre-packaged module (M3) in which the fifth controllable semiconductor switch (S5) and the first diode (D1) are electrically connected in reverse series and arranged to conduct in opposite directions; and the sixth controllable semiconductor switch (S6) and the second A switching module (10) wherein the diode (D2) is implemented as a pre-packaged module (M4) in which the sixth controllable semiconductor switch (S6) and the second diode (D2) are electrically connected in reverse series and arranged to conduct in opposite directions, the seventh controllable semiconductor switch (S7) and the third diode (D3) are implemented as a pre-packaged module (M5) in which the seventh controllable semiconductor switch (S7) and the third diode (D3) are electrically connected in reverse series and arranged to conduct in opposite directions, and the eighth controllable semiconductor switch (S8) and the fourth diode (D4) are implemented as a pre-packaged module (M6) in which the eighth controllable semiconductor switch (S8) and the fourth diode (D4) are electrically connected in reverse series and arranged to conduct in opposite directions. Claim 8 A switching module (10) in which, in claim 6 or 7, all of the controllable semiconductor switches (S1, S2, ..., S8) of the H-bridge circuit (12) and the active clamp circuit (16) are IGBTs. Claim 9 A switching module (1; 10) wherein, in any one of claims 1 to 8, the energy storage device is a capacitor (C). Claim 10 A switching module (10) according to any one of claims 1 to 9, further comprising a power supply circuit (18) electrically connected between the first DC clamp terminal (DC3) and the second DC clamp terminal (DC4) in parallel with the energy storage device (C), wherein the power supply circuit (18) is electrically connectable to one or more electronic circuits (20, 22) associated with the switching module (10). Claim 11 A switching module (10) further comprising, in any one of claims 1 to 10, a battery (24) electrically connected between the first DC clamp terminal (DC3) and the second DC clamp terminal (DC4) in parallel with the energy storage device (C). Claim 12 A switching module (10) further comprising, in any one of claims 1 to 11, a dynamic braking system (26) electrically connected between the first DC clamp terminal (DC3) and the second DC clamp terminal (DC4) in parallel with the energy storage device (C). Claim 13 In a direct current (DC) electric machine (50), a plurality of stator coils (541, 542, ..., 54 n A stator (52) having ); a rotor; a DC current source (56); and n switching modules (101, 102, ..., 10) according to any one of claims 1 to 12 n It includes a power electronic switching assembly (58) comprising ), where n is an integer greater than or equal to 2, and each switching module (101, 102, ..., 10 n The first AC bridge terminal (AC1) and the second AC bridge terminal (AC2) of ) each have at least one individual stator coil (541, 542, ..., 54 n ) is electrically connected to, and the first DC bridge terminal (DC1) of the first switching module (101) is electrically connected to the DC current source (56), and the nth switching module (10 n A direct current (DC) electric machine (50) wherein the second DC bridge terminal (DC2) of the above-mentioned ) is electrically connected to the DC current source (56), and the first DC bridge terminal (DC1) and the second DC bridge terminal (DC2) of the remaining switching module are electrically connected in series. Claim 14 In paragraph 13, the above DC current source (56) is a direct current (DC) electric machine (50) which is a power converter, for example, an AC / DC converter, or another DC electric machine. Claim 15 In the power converter (70), a plurality of first coils (741, 742, ..., 74 n A transformer assembly (72) including ); a DC current source (78); and n switching modules (101, 102, ..., 10) according to any one of claims 1 to 9 n A power electronic switching assembly (80) comprising ) and n is an integer greater than or equal to 2, and each switching module (101, 102, ..., 10 n The first AC bridge terminal (AC1) and the second AC bridge terminal (AC2) of the above are individual first coils (741, 742, ..., 74 n ) is electrically connected to, and the first DC bridge terminal (DC1) of the first switching module (101) is electrically connected to the DC current source (78), and the nth switching module (10 n A power converter (70) wherein the second DC bridge terminal (DC2) of the above-mentioned switch module is electrically connected to the DC current source (78), and the first DC bridge terminal (DC1) and the second DC bridge terminal (DC2) of the remaining switch module are electrically connected in series.

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