Multi-output multi-bridge power converter

Abstract

According to one embodiment of the present disclosure, there is provided a power converter including at least two switching bridges connected to a direct current (DC) bus, both of which generate a pulse-width modulated (PWM) voltage at a non-isolated output, and an isolation transformer having a primary winding connected between the outputs of the two switching bridges and a secondary winding connected to the isolated output. In a non-isolated mode, the two switching bridges are configured to operate in a parallel mode, and power is transferred between the DC bus and the non-isolated output. In an isolated mode, the two switching bridges are configured to operate in a full-bridge mode, and power is transferred between the DC bus and the isolated output through the transformer.

Description

Technical Field

[0001] The present disclosure generally relates to the field of power circuits such as power converters used in electric vehicles.

Background Art

[0002] The renewable energy industry has experienced rapid growth in recent years, and along with it, further improvements in power electronics technology are being sought. For example, with the popularization of electric vehicles (EVs), motor drive inverters and battery chargers have become major components of EVs. The continuous requirements for improvements in cost, efficiency, size, and weight pose challenges in the design of EV motor drive inverters and battery chargers.

[0003] Battery packs installed in EVs include those with various different rated voltages and capacities. Therefore, EVs require appropriate chargers for charging at a wide range of battery voltages and current values, which is a major challenge especially for battery charger product suppliers and commercial fast charger stations.

[0004] The power converter of a battery charger is potentially dangerous due to high voltage and large current. Galvanic insulation can reduce the electrical safety risk and may be able to stop the propagation of faults when components within the power converter fail. Therefore, galvanic insulation may be required by some safety standards such as IEC, IEEE, UL, SAE, etc., and this essential requirement applies to off-board chargers as well as on-board battery chargers (OBCs).

[0005] An EV battery charger is equipped with an electrical circuit for converting alternating current (AC) power into direct current (DC) power and is typically designed in two stages, namely, the AC-DC stage and the DC-DC stage. The AC-DC stage converts the AC input voltage (typically from an AC commercial power supply) into a DC bus voltage and adjusts the DC bus voltage to be within a desirable range suitable for the DC-DC stage as a load. The AC-DC stage can include various electromagnetic interference (EMI) filters and a power factor correction (PFC) converter circuit (or namely, a PFC rectifier) employing a plurality of diodes and active switching devices.

[0006] The EMI filter is adopted to reduce high-frequency noise that may cause interference with other devices mounted on the EV in order to meet various EMI regulations. The PFC converter circuit can be implemented as a boost PFC converter that can shape the input line current to be sinusoidal and in phase with the sinusoidal input voltage of the AC power supply and keep the circuit operation at a power factor of 1. On the other hand, the PFC converter circuit adjusts its output to maintain the DC bus voltage within a predetermined target range, realizing a stable power flow and safe operation.

[0007] As the stage following the AC-DC stage in the EV battery charger, the DC-DC stage is connected between the output of the DC bus and a plurality of batteries. The DC-DC stage can typically include a high-frequency switching DC-DC converter that powers an isolation transformer having one primary winding and one secondary winding. On the secondary side, another rectifier circuit is provided for adjusting the output of the secondary winding of the isolation transformer to a DC voltage for charging the EV battery. Also, the DC-DC converter can adjust the battery charging current and maintain the state of charge of the battery.

[0008] To drive the EV running motor with the battery power, an inverter-type motor control unit (MCU) is used. The inverter converts the DC voltage of the battery into a pulse-width modulation (PWM) AC output voltage waveform and adjusts the motor winding current as needed. Its purpose is to generate high torque in the low-speed region of the motor and supply high output according to the commands of the MCU in the high-speed region of the motor, which usually causes problems in the trade-off of the design of the motor and inverter system.

[0009] Normally, a higher torque output of the motor requires more permanent magnet material for the rotor, which reduces the maximum motor winding current, and thus reduces the dimensions of the motor frame. However, having more permanent magnet material in the rotor means that the induced back electromotive force (EMF) is higher. When the back electromotive force reaches the DC bus voltage value, the MCU can no longer supply power to the motor or drive the motor in a higher speed rotation range. This design problem is usually solved by field weakening control, regardless of the adoption of a DC-DC boost converter.

[0010] The technique called field weakening control is used to cancel part of the magnetic flux of the permanent magnet and lower the back electromotive force below the DC bus voltage value in the high-speed rotation range of the motor. The drawback of field weakening control is that the motor efficiency drops dramatically, especially in the case of deep field weakening, where it drops by several percent, which is clearly a high cost for the fuel consumption of the EV. Furthermore, the inverter has to tolerate a large amount of reactive current during field weakening control, which increases the rating and cost of the equipment and further reduces the inverter efficiency.

[0011] The DC-DC boost converter can be used to be inserted between a battery and a DC bus that supplies power to an inverter. When the motor operates at high speed, the boost converter can raise the DC bus voltage. As a result, the inverter can generate a high output voltage across the motor windings to overcome the back electromotive force and achieve continuous power supply in a high motor speed range without field weakening. Although the solution using this boost converter incurs additional costs, the improvement in inverter efficiency and motor efficiency can offset that cost to some extent on the inverter side.

[0012] Power train components such as motors, inverters, and in-vehicle battery chargers account for a significant portion of the total material cost of an EV. A typical EV inverter usually has a rating of 60 kW to 200 kW due to the peak power demand by motor drive. The in-vehicle battery charger usually has a rating of about 6 kW to 22 kW due to cost and space limitations. The inverter does not require insulation, but the OBC power stage requires insulation of the transformer. Therefore, due to the difference in the need for insulation and the rated power, the inverter and OBC are usually implemented by separate hardware and different subsystems respectively.

[0013] For further cost reduction and miniaturization and weight reduction, it is truly necessary to consider the possibility of integrating the inverter and OBC systems and reusing common power converter hardware between EV motor drive and battery charging. In fact, many papers have been published on the integration of the inverter and OBC. However, in an important area of power converter topologies, no appropriate and practical solution has been found to achieve the necessary insulation and compact integration of the inverter and OBC systems. Summary of the Invention

[0014] These and other problems are generally solved or avoided by the preferred embodiments of the present disclosure that propose a new concept of multiple bridge converters (i.e., multi-bridge converters) having multiple outputs, and technical advantages are generally achieved. A multi-bridge converter typically includes two switching bridges connected to a direct current (DC) bus, and each bridge causes a pulse width modulation (PWM) voltage to be generated at a non-isolated output. The isolation transformer includes a primary winding connected between the two bridge outputs and a secondary winding connected to the isolated output. Different gate timing controls are performed to generate different PWM voltage waveforms using the same converter hardware and supply DC bus power to the non-isolated output or the isolated output, but both cannot be supplied simultaneously. In the non-isolated mode, the two switching bridges operate in parallel mode, and power is transmitted between the DC bus and the non-isolated output. In the isolated mode, the two switching bridges operate in full-bridge mode, and power is transmitted between the DC bus and the isolated output through the transformer.

[0015] In the non-isolated mode, the multi-bridge converter bridges operate in parallel mode with their gate switching signals in phase synchronization (i.e., without a phase shift), generating the same PWM voltage waveform across the transformer. As a result, the transformer windings are not excited with the intended significant differential voltage, and no significant power is supplied to the transformer as a whole. Therefore, power is mainly transmitted from the DC bus to the non-isolated output, and bidirectional power flow is possible.

[0016] In the insulation mode, the multi-bridge converter bridges are controlled to operate in the full-bridge mode, and their gate switching signals are phase-shifted and out of phase. Therefore, the transformer windings are excited with the intended significant differential voltage, and power is mainly transmitted from the DC bus through the transformer to the insulated output, enabling bidirectional power flow. At this time, it is necessary to pay attention to minimizing or stopping the power flow to the non-insulated load, and for this purpose, a special arrangement may be required in the configuration of the load segment. In any case, by using the same hardware, the multi-bridge converter can transmit power to the non-insulated output and the insulated output under different gate timing controls.

[0017] Generally, when multiple switching bridges are operated in parallel, it is well-known that interleaved operation with a phase shift between the bridges is performed in the synchronized PWM gate switching signals. The advantages include an increase in the effective PWM switching frequency, a reduction in the switching ripple of the output voltage and current, and a potentially smaller EMI noise spectrum. To achieve interleaved PWM operation in the proposed multi-bridge converter, an open-circuit switch is additionally connected in series to the primary or secondary transformer winding. In the non-insulated operation mode where power is transmitted between the DC bus and the non-insulated output, the open-circuit switch of the transformer is opened, and the PWM switching of the bridges is interleaved synchronously with the phase shift angle. In the insulation operation mode, the open-circuit switch of the transformer is closed, and the two bridges are controlled to operate in the full-bridge mode. The PWM switching signals are phase-shifted and out of phase between the two bridges, and power is transmitted between the DC bus and the insulated output through the transformer.

[0018] Under the same concept of the present disclosure, the switching bridge of the multi-bridge converter can use any multilevel converter topology such as a two-level, three-level, five-level, or diode neutral point clamped (NPC) multilevel converter, an active neutral point clamped (ANPC) multilevel converter, a flying capacitor multilevel converter, or any combination of different multilevel topologies between bridges.

[0019] Similarly, examples are shown in the present disclosure where the multi-bridge converter can include three, four, or any greater number of switching bridges that are connected to a plurality of separate isolation transformers, connected to the same isolation transformer with a plurality of windings coupled, or connected to a mixture of different transformer designs.

[0020] As an exemplary circuit according to various embodiments of the present disclosure, the multi-bridge converter is configured as a three-phase PWM inverter for an integrated EV motor drive and an on-vehicle charging system, and includes a battery pack consisting of a number of battery cells connected to a DC bus through a DC main contactor or switch, three multi-bridge converters that form a DC-AC inverter operation for driving an AC motor with a non-isolated output, and an isolation transformer having a primary coil connected to the converter bridge output and a secondary coil connected to any type of rectifier that outputs a DC power supply for charging the battery pack. The power supply is connected to the DC bus either from an external DC power supply directly connected to the DC bus or from an external AC power supply indirectly connected through an AC-DC rectifier.

[0021] The control unit operates the three-phase multibridge converter while performing PWM synchronization and phase shift. During the inverter drive operation in the non-isolated mode, when the battery contactor is closed and no external power source is plugged in, within each multibridge converter, two switching bridges operate in parallel mode, and power is transmitted between the DC bus and the non-isolated output. During the battery charging operation in the isolated operation mode, while the external power source is connected and the battery contactor is open, within each multibridge converter, the two switching bridges operate in full-bridge mode, and power is mainly transmitted between the DC bus and the isolated output through the transformer.

[0022] Here, the EV motor needs to be a dual-winding motor with two sets of motor windings separated from each other, or a two-split-winding AC motor. Each set of motor windings is most often seen in a Y-shaped configuration. During the battery charging operation in the isolated operation mode, additional gate switching synchronization is applied between those switching bridges connected to the same set of motor phase windings. Thus, each set of motor windings is excited with a differential voltage between the motor terminals being approximately zero to reduce the unintentional motor circulating current.

[0023] As an exemplary circuit according to various embodiments of the present disclosure, the multibridge converter is configured as a DC-DC boost converter for integrated EV drive and in-vehicle charging systems. This device includes two switching bridges formed as a DC-DC boost converter that outputs to the DC bus feeding the EV drive inverter and the AC motor, a primary winding connected between the converter bridge outputs, and an isolation transformer having a secondary winding connected to a rectifier for outputting DC power to charge the battery pack. The same battery pack is connected to the DC contactor, then to the boost inductor, and to the midpoint output of the converter bridge, and further to a power source that is directly or indirectly connected to the DC bus through a power converter.

[0024] The control unit operates the multi-bridge converter while performing PWM synchronization and phase shift. During the EV drive boost operation in the non-isolated operation mode, the battery contactor is closed, the external power supply is not plugged in, and within each multi-bridge converter, the two switching bridges operate in parallel mode, and power is transmitted bidirectionally from the battery to the DC bus. During the battery charging operation in the isolated operation mode, the battery contactor is open, and the external AC power supply is connected. Within each multi-bridge converter, the two switching bridges operate in full-bridge mode, and power is transmitted between the DC bus and the isolated output through the transformer.

[0025] To further reduce costs, part or all of the boost inductor can be incorporated into the magnetic design of the isolation transformer. Through the main contactor, the battery input is connected to the midpoint of the primary winding of the isolation transformer. Therefore, regardless of the presence or absence of an additional separate inductor, the transformer winding is used as a coupled boost inductor.

[0026] According to various embodiments of the present disclosure, the AC-DC converter (i.e., PFC rectifier) is not entirely an additional set of hardware. Rather, the rectifier hardware and the power factor correction function can be integrated and realized by operating part or all of the inverter bridge in the reverse power direction to draw power from the AC power supply, regardless of whether the motor winding is used as the inductor required by the PFC rectifier.

[0027] Optionally, in any of the foregoing embodiments, the plurality of isolation transformers across the multi-bridge converter may be separate transformers, or may be an integrated transformer having a plurality of primary windings coupled on the same core configuration and a common secondary winding.

[0028] Optionally, in any of the foregoing embodiments, the AC motor may have a plurality of sets of separate armature windings, and each set of windings is supplied by a separate inverter phase output of the multi-bridge converter. This separate winding configuration avoids potential circulating currents in the motor windings due to the common mode voltage.

[0029] Optionally, in any of the foregoing forms, the multibridge converter may drive a plurality of separate AC motors, each motor being supplied by a separate inverter phase output of the multibridge converter.

[0030] In a simplified form, the above has rather broadly outlined the features and technical advantages of the present disclosure so that the following detailed description of the present disclosure can be better understood. The additional features and advantages of the present disclosure that form the subject matter of the claims of the present disclosure are described below. It should be understood by those skilled in the art that the disclosed concepts and specific embodiments can be readily utilized as a basis for modifying or designing other configurations or processes for accomplishing the same purposes of the present disclosure. It should also be understood by those skilled in the art that such equivalent configurations do not depart from the spirit and scope of the present disclosure as defined in the appended claims.

[0031] For example, in the present disclosure, in the non-insulated operation mode, it is shown that the multibridge converter is configured as a DC-AC inverter and a DC-DC boost circuit. On the other hand, it is not shown here that in the non-insulated operation mode, the multibridge converter is configured to form a DC-DC buck circuit. In fact, it is much easier to configure the multibridge converter as a DC-DC buck circuit, which is under the same concept and exact concept taught in the present disclosure.

[0032] As another example, in order to enable more functions and better performance, a breaking switch is shown in series with the primary or secondary insulated transformer winding. Similarly, the breaking switch can be connected in series with the non-insulated output of the multibridge converter, whereby unintended power losses can be reduced or simply the control can be facilitated. However, changes such as adding a breaking switch anywhere in the circuit do not depart from the spirit and scope of the present disclosure as defined in the appended claims.

[0033] As another example, the isolated DC-DC charging circuit exemplified in the present disclosure is mainly a full-bridge phase-shift converter, an LLC converter, or a dual active bridge (DAB) converter. It should be understood that other isolated DC-DC topologies or combinations of different topologies are also applicable to the implementation of the multi-bridge converter circuit and are well-suited. Such modifications using other different DC-DC topologies do not depart from the spirit and scope of the present disclosure as defined in the appended claims.

Brief Description of the Drawings

[0034] Embodiments of the present disclosure are described by way of example and are not limited by the accompanying drawings.

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DETAILED DESCRIPTION OF THE INVENTION

[0036] Next, the present disclosure will be generally described with reference to the figures regarding a power circuit that can be used, for example, in an electric vehicle. For example, the circuit described herein can be used to charge a battery from an external power source and to control the power for driving an electric motor using the battery.

[0037] EV power systems are sensitive to component size, weight, and converter efficiency. Conventional mainstream power converter designs using metal-oxide-semiconductor field-effect transistors (MOSFETs) and insulated-gate bipolar transistors (IGBTs) have reached their performance limits, and new-generation power devices such as gallium nitride (GaN) and silicon carbide (SiC) MOSFET transistors have been adopted due to their advantages in terms of efficiency, size, and weight. Also, it is efficient and cost-saving to use a shared hardware circuit to perform different functions such as motor drive and battery charging. Integrating the motor drive and battery charging system can provide further advantages in terms of cost and size.

[0038] Generally, it is desirable for an EV to be able to charge the battery from at least two different power sources, for example, DC power from a charging station and AC power from a commercial AC power grid. Therefore, an EV on-vehicle power system can include both DC and AC charging circuits in addition to an inverter circuit that operates the EV motor during the driving or traction mode.

[0039] Charging of the EV's battery can include the use of an on-vehicle charging circuit. The power from the battery can be used to supply power to one or more electric motors through an inverter to propel the electric vehicle. In some cases, certain components can be shared among these circuits to reduce costs and promote efficiency. Using an advanced high-frequency circuit topology to integrate the on-vehicle charging circuit and the inverter circuit and using a common power conversion stage (e.g., a power bridge) between the on-vehicle charger and the inverter can reduce the overall cost, size, and weight of the EV power system. However, the integrated solution needs to address the technical challenges brought about by different power ratings, insulation requirements, and a wide voltage range.

[0040] It is understood that the embodiments of the present disclosure can be implemented in many different forms and that the claims should not be construed as limited to the embodiments shown herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the inventive embodiments to those skilled in the art. In fact, the present disclosure is intended to cover alternatives, modifications, and equivalents of these embodiments, which are within the scope and spirit of the present disclosure as defined by the appended claims. Furthermore, in the following detailed description of the embodiments of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding. However, it will be apparent to those skilled in the art that the embodiments of the present disclosure can be practiced without such specific details.

[0041] FIG. 1A is a conceptual diagram of a multi-bridge converter 100 including a multi-bridge 110 (composed of two switching bridges, i.e., phase A bridge 111 and phase B bridge 112, but can be composed of two or more switching bridges as desired in various embodiments) coupled to an isolation transformer 120 having a primary winding connected between the output of phase A bridge 111 (i.e., port A) and the output of phase B bridge 112 (i.e., port B) and connected to a DC bus 130. By the control unit 140 generating different PWM gate control signals and supplying them to the multi-bridge converter 100, the multi-bridge converter 100 can operate in at least two different modes: (i) a non-isolated operation mode in which the two switching bridges operate in parallel mode and power is supplied from the DC bus 130 to non-isolated ports A and B, and (ii) an isolated operation mode in which the two switching bridges operate in full-bridge mode and power is supplied from the DC bus 130 through the isolation transformer 120 to isolated ports E and F. Generally, the multi-bridge converter 100 can be used in a DC-DC or DC-AC inverter system.

[0042] FIG. 1B is a diagram showing an example of switching waveforms for the non-isolated operation mode of the multi-bridge converter 100. For simplicity, all dead times in the PWM signals of each bridge are ignored, and the same is true for all other exemplary waveforms throughout the present disclosure. The two switching bridges 111, 112 are synchronized in the gate on-off signals to generate the same PWM voltage waveform without a phase shift between the primary windings of the transformer 120. Thus, the primary winding of the transformer 120 has no significant differential voltage (i.e., the voltage V representing the voltage between port A and port B) AB) It is not excited either, and power is mainly transmitted from the DC bus to the non-insulated ports A and B having the ability of bidirectional power flow. The switching rule in the non-insulated operation mode is that the phases of the phase-A bridge 111 and the phase-B bridge 112 are completely synchronized, and the switching elements S1, S2 (IGBT, silicon MOSFET, silicon carbide MOSFET, etc.) of the phase-A bridge 111 are turned on and off with the same gate signal as the switching elements S3, S4 (IGBT, silicon MOSFET, silicon carbide MOSFET, etc.) of the phase-B bridge 112. That is, since the phase-A bridge 111 and the phase-B bridge 112 are controlled by the same PWM gate signal, they usually operate completely synchronously. And the common PWM gate signal is usually generated by a multi-variable input-output closed-loop rule from the perspective of the duty cycle control or space vector modulation of the converter 100. As a result, the primary winding of the transformer 120 is excited by the same voltage waveform as the voltage V A from the phase-A bridge 111 and the voltage V B from the phase-B bridge 112. Therefore, the voltage V EF applied to the secondary winding of the transformer 120 becomes flat and ideally locates at the "0" voltage. Therefore, power is supplied from the DC bus 130 to the non-insulated ports A and B, but not to the insulated ports E and F. In this non-insulated operation mode with incomplete gate signal synchronization, the switching devices of the phase-A bridge 111 and the phase-B bridge 112 may not turn on and off at the same timing, and short voltage pulses or glitches may be seen at the secondary ports E and F of the transformer 120. However, it should be noted that those short pulses are tolerable due to the fact that they do not supply an important part of the total power flow.

[0043] FIG. 1C is a diagram showing an example of switching waveforms for the isolated operation mode of the multi-bridge converter 100. In this mode, the two switching bridges 111 and 112 operate in full-bridge mode, and the PWM switching signals are phase-shifted by 180°, exactly out of phase between the two bridges. Thus, the windings of the transformer 120 are excited with the intended significant differential voltage, and power is supplied mainly from the DC bus 130 through the transformer 120 to the isolated output (i.e., isolated ports E and F) with the ability of bidirectional power flow. The phase of the A-phase bridge 111 and the B-phase bridge 112 is shifted, and they are not turned on and off with the same gate timing signal. In fact, the two bridges 111 and 112 can be operated out of phase, and the switching device S1 of the A-phase bridge 111 and the switching device S4 of the B-phase bridge 112 are typically turned on simultaneously, and the switching device S2 of the A-phase bridge 111 and the switching device S3 of the B-phase bridge 112 are typically turned on simultaneously, so that the intended phase shift is not performed. As a result, the isolated ports E and F of the transformer 120 generate a square wave or a similar waveform, and thus power is mainly transmitted from the DC bus 130 to the isolated ports E and F. In this isolated operation mode, the purpose is to minimize the power flow to the non-isolated ports A and B, and it should be noted that in order to achieve this purpose, some attention or special arrangements may be required for the load wiring or load configuration connected to the non-isolated ports A and B.

[0044] FIG. 1D is a diagram showing another example of switching waveforms for the isolated operation mode of the multi-bridge converter 100. Here, the two switching bridges operate in full-bridge mode with the intended phase shift of the PWM switching signals (i.e., S1 / S2 pair S3 / S4) between the two phase bridges. For simplicity, the dead time in the PWM signals of each bridge is ignored. As a result, the primary winding V of the transformer ABThe PWM voltage output applied thereto has a bipolar waveform, that is, a waveform having positive and negative DC bus voltages alternately and having a zero voltage transition in the middle. And the same bipolar waveform appears in the secondary winding voltage V of the transformer that ignores all parasitic effects. In fact, the active duty cycle and pulse width of the positive and negative voltage waveforms depend on the phase shift angle. Therefore, by adjusting this phase shift angle between the PWM gate signals of the two bridges, the power flowing through the transformer to the isolated load can be adjusted. The detailed gate timing usually depends on the closed-loop adjustment method of the converter 100, such as PWM, frequency modulation, phase shift control, etc. In fact, it operates in the same way as a conventional full-bridge type phase shift or LLC converter. EF In fact, the active duty cycle and pulse width of the positive and negative voltage waveforms depend on the phase shift angle. Therefore, by adjusting this phase shift angle between the PWM gate signals of the two bridges, the power flowing through the transformer to the isolated load can be adjusted. The detailed gate timing usually depends on the closed-loop adjustment method of the converter 100, such as PWM, frequency modulation, phase shift control, etc. In fact, it operates in the same way as a conventional full-bridge type phase shift or LLC converter.

[0045] Figures 2A to 2B are diagrams showing an example of a multi-bridge converter and its operating waveforms according to various embodiments of the present disclosure. The circuits of FIGS. 2A and 2B are substantially the same as the circuit of FIG. 1A, but an additional open switch 250, that is, Kc is connected between the output port A or B of the multi-bridge 210 and the isolated port E or F sandwiching the transformer 220. This open switch Kc is different from that of FIG. 1 only in that it can be in series with the transformer either on the primary winding side as shown in FIG. 2A or on the secondary winding side of FIG. 2B. With the help of this open switch Kc, a phase shift angle is introduced into the synchronized PWM signal, and the purpose is to realize the PWM interleaving operation between the two bridges 211 and 212 of the multi-bridge converter 200 during the non-isolated operation in parallel mode. This open switch Kc can be anything such as a contactor, a relay, or a semiconductor device switch. The parallel bridge PWM interleaving is well-known for the advantage that it can increase the effective PWM frequency of the output terminal, and as a result, reduce the output voltage and current ripple and mitigate electromagnetic radiation (EMI) and audible noise.

[0046] Figure 2C is a diagram showing an example of the PWM interleaved switching waveform in the non-isolated operation mode of the multi-bridge converter 200. In this mode, the open switch Kc remains open, and thus the isolation transformer is not active in the circuit function. There is a 180° phase shift angle between the synchronized PWM gate signals of the two switching bridges 211 and 212. Thus, due to the load output voltage V AB , the effective PWM switching frequency is doubled, the PWM switching ripple is reduced, and the EMI noise applied to the load and the like is reduced.

[0047] Figure 2D shows that in the isolated operation mode of the multi-bridge converter 200 with the open switch Kc closed, the circuit operation of the multi-bridge converter 200 is the same as that in the full-bridge mode, and the output waveform is the same as that in FIGS. 1A to 1C without the open switch Kc. In short, FIGS. 2A to 2D have additional functions related to PWM phase shift interleaving under the same circuit concept as FIGS. 1A to 1C, and the performance is improved.

[0048] FIG. 3A is a conceptual circuit diagram of a three-level multibridge converter 300 as an example. The multibridge 310 connected to the DC bus 330 is composed of two switching bridges (i.e., the A-phase bridge 311 and the B-phase bridge 312) using the diode NPC three-level topology. Similarly, the same concept can be applied to other multilevel topologies such as ANPC, flying capacitor, or hybrid multilevel converters. The primary winding of the isolation transformer 320 is connected between the outputs of the A-phase bridge 311 and the B-phase bridge 312, i.e., between ports A and B. The secondary winding of the transformer 320 supplies an isolated output to ports E and F. By the control unit 340 generating different PWM gate signals, the three-level multibridge converter 300 can operate in at least two different modes, including: (i) a non-isolated operating mode in which the two switching bridges operate in parallel mode, the PWM switching signals are in phase synchronization between the two bridges, and power is supplied from the DC bus 330 to the non-isolated ports A and B; and (ii) an isolated operating mode in which the two switching bridges operate in full-bridge mode, the PWM switching signals are phase-shifted between the two bridges and out of phase, and thus power is supplied from the DC bus 330 to the isolated ports E and F through the isolation transformer 320. The three-level multibridge converter 300 can be used in a DC-DC or DC-AC inverter system.

[0049] FIG. 3B is a diagram showing an example of switching waveforms in the non-isolated operation mode of the multi-bridge converter 300. The rule of switching in the non-isolated operation mode is that the A-phase bridge 311 and the B-phase bridge 312 are completely synchronized in phase and operate completely in parallel with the same PWM gate signal. As a result, since the primary winding of the transformer 320 is excited by the same voltage waveform from port A and port B, the secondary winding of the transformer 320 will remain at "0" voltage. Therefore, power is mainly supplied from the DC bus 330 to the non-isolated ports A and B, but not to the isolated ports E and F. Note that in this non-isolated operation mode where the gate signal synchronization is not perfect, the switching devices S1 to S4 of the A-phase bridge 311 and the switching devices S5 to S8 of the B-phase bridge 312 may not turn on and off at exactly the same timing, and short voltage pulses or glitches may be seen at the secondary ports E and F of the transformer 320. However, such short voltage pulses are acceptable due to the fact that they do not supply an important part of the total power flow.

[0050] FIG. 3C is a diagram showing an example of switching waveforms in the isolated operation mode of the multi-bridge converter 300. In this mode, the A-phase bridge 311 and the B-phase bridge 312 are out of phase and are not turned on and off with the same gate timing signal. As a result, the isolated ports E and F of the transformer 320 generate a multi-step rectangular-shaped waveform or a similar waveform, and thus, power is mainly supplied from the DC bus 330 to the isolated ports E and F. In fact, the two bridges 311 and 312 operate like a conventional three-level full-bridge phase shift or LLC converter. The detailed gate timing usually depends on the closed-loop adjustment method of the converter 300 such as PWM, frequency modulation, phase shift control, etc. In this isolated operation mode, the purpose is to minimize the power flowing through the non-isolated ports A and B, and it should be noted that in order to achieve this purpose, some special arrangements may be required for the load configuration connected to the non-isolated ports A and B.

[0051] Figure 4A shows a conceptual circuit diagram of a three-bridge multi-bridge converter 410 connected to two separate isolation transformers 420 and 421. There are three switching bridges connected to the DC bus, namely, a phase-A bridge 411 with an output port A, a phase-B bridge 412 with an output port B, and a phase-C bridge 413 with an output port C. The primary winding of isolation transformer 420 is connected between port A and port B, and the primary winding of isolation transformer 421 is connected between port C and port B. The secondary windings of the two transformers 420 and 421 supply isolated outputs to ports E and F, and ports G and H, respectively. Note that the polarities of the multiple transformer windings need to be arranged in the same way as shown in order to match the switching waveforms illustrated below.

[0052] Figure 4B shows a conceptual diagram of a three-bridge multi-bridge converter 410 connected to one integrated transformer 422. The only difference between Figures 4A and 4B lies in the isolation transformers, but the isolation transformers in both Figures 4A and 4B operate basically in the same way. It should be noted that in order to match the switching waveforms illustrated below, the polarities of the multiple transformer windings need to be arranged in the same way as shown.

[0053] Figure 4C is a diagram showing an example of switching waveforms in the non-isolated operating mode of the circuit in Figure 4A. The rule of switching in the non-isolated operating mode is that the phase-A bridge 411, the phase-B bridge 412, and the phase-C bridge 413 operate completely synchronously and in parallel with the same PWM gate signal. As a result, the primary windings of the two transformers 420 and 421 connected to the voltages V A , V B between ports A and B, and the voltages V C , V B between ports C and B are excited with the same voltage waveform. Therefore, the output voltage V EF at the isolated ports E and F of the secondary winding of transformer 420, and the output voltage V GH at the isolated ports G and H of the secondary winding of transformer 421It remains stationary at voltage "0". Therefore, power is mainly supplied from the DC bus to non-insulated ports A and B, and non-insulated ports C and B, but not to insulated ports E and F, or ports G and H. In such a non-insulated operating mode where the synchronization of the gate signals is not perfect, it should be noted that the A-phase, B-phase, and C-phase bridges do not turn on and off at the same timing, and short voltage pulses or glitches may be seen at ports E, F of transformers 420, 421, and ports G, H. However, those short voltage pulses are tolerable due to the fact that they do not supply an important part of the total power flow.

[0054] Figure 4D is a diagram showing an example of switching waveforms in the insulated operating mode of the circuit of Figure 4A. In this mode, the A-phase bridge 411 and the B-phase bridge 412 are out of phase and are not turned on and off by the same gate timing signal. At the same time, the C-phase bridge 413 and the B-phase bridge 412 are also out of phase. As a result, square waves and the like are generated at the insulated ports E, F of transformers 420, 421, and insulated ports G, H, and thus power is mainly transmitted from the DC bus to insulated ports E, F, and insulated ports G, H. In fact, the three bridges 411, 412, 413 operate almost in the same way as a conventional full-bridge phase shift or LLC converter. The detailed gate timing usually depends on the closed-loop adjustment methods of the converter such as PWM, frequency modulation, and phase shift control. In this insulated operating mode, the aim is to minimize the power flowing through non-insulated ports A, B, C, and it should be noted that in order to achieve this aim, some special arrangements may be required for the load wiring and load configuration connected to non-insulated ports A, B, C.

[0055] FIG. 5A is a diagram showing an embodiment of a multi-bridge converter-based single-phase inverter integrated with a battery charging system. There are two multi-bridges 510 and 520 connected to a DC bus, and each multi-bridge 510 or 520 has two switching bridges. The multi-bridge 510 includes a 1A-phase bridge and a 1B-phase bridge, and the multi-bridge 520 includes a 2A-phase bridge and a 2B-phase bridge. The two multi-bridges 510 and 520 form a non-insulated single-phase output at port 1A of the 1A-phase bridge and port 2A of the 2A-phase bridge, and form a parallel single-phase non-insulated output at port 1B of the 1B-phase bridge and port 2B of the 2B-phase bridge. The multi-bridges 510, 520 are respectively connected to isolation transformers 530, 531. Power converters 550, 551 are connected to the secondary windings of the transformers 530, 531, function as rectifiers, and generate a DC voltage for charging the battery 570 through an optional contactor K2. Also, the same battery 570 is connected to the DC bus through a main contactor K1. Usually, the battery 570 is filled with a number of modules of a plurality of cells having a battery management system (BMS) 570 for electrical safety and thermal protection. Further, a PFC rectifier 580 is also connected between the DC bus and an external AC power supply. The control unit 590 controls the gate timing of the phase bridges of the multi-bridges 510 and 520 according to two different operating modes. Note that both the inverter drive operation and the battery charging operation are characterized by a bidirectional power flow function.

[0056] Figure 5B shows an equivalent active circuit portion of the circuit shown in Figure 5A in a non-isolated operation mode, together with exemplary switching waveforms. In this non-isolated operation mode, battery 570 supplies power to the DC bus with K1 closed, and multibridges 510 and 520 supply a pair of single-phase outputs to ports 1A and 2A and ports 1B and 2B connected in parallel as single-phase inverter outputs. As shown in the example of the switching waveforms, the 1A-phase bridge and the 1B-phase bridge of multibridge 510 are completely synchronized with the same gate timing signal, and the 2A-phase bridge and the 2B-phase bridge of multibridge 520 are also completely synchronized with the same gate timing signal. Therefore, the 1A-phase bridge and the 1B-phase bridge generate the same PWM voltage waveform between the primary windings of transformer 530. Therefore, the secondary winding of transformer 530 has a "0" voltage V EF across ports E and F under ideal conditions. The same applies to transformer 531, and its secondary winding generates a flat voltage V GH that remains "0" at ports G and H. Note that in this non-isolated operation mode where the synchronization of the gate signals is not perfect, the 1A-phase bridge and the 1B-phase bridge, as well as the 2A-phase bridge and the 2B-phase bridge, do not turn on and off at the same timing, and short voltage pulses or glitches may be seen at secondary ports E and F of transformer 530 and secondary ports G and H of transformer 531. However, those short voltage pulses are acceptable due to the fact that they do not supply an important part of the total power flow.

[0057] Figure 5C shows an equivalent active circuit portion of the circuit shown in Figure 5A in an isolated operating mode having an exemplary switching waveform. In this mode, the PFC rectifier 580 is operating actively to support the DC bus by drawing power from an external AC power source. The multi-bridges 510 and 520 operate in opposite phases. Thus, the isolation transformers 530 and 531 are excited with rectangular voltage waveforms, and power is supplied between the isolation transformers to charge the battery 570. However, the non-isolated output ports 1A and 2A or ports 1B and 2B of the single-phase multi-bridges 510 or 520 do not have a large power flow as shown in the exemplary switching waveform. The 1A-phase bridge of the multi-bridge 510 and the 2A-phase bridge of the multi-bridge 520 are completely synchronized with the same gate timing signal, and similarly, the 1B-phase bridge of the multi-bridge 510 and the 2B-phase bridge of the multi-bridge 520 are completely synchronized. Thus, the 1A-phase bridge and the 2A-phase bridge generate the same PWM voltage waveform, and the differential voltage between the non-isolated ports 1A and 2A becomes "0". The same applies to the 1B-phase bridge and the 2B-phase bridge, and the differential voltage between the non-isolated ports 1B and 2B becomes "0". In this isolated operating mode, the purpose is to minimize the power flowing through the non-isolated ports 1A, 2A, and ports 1B, 2B. It should be noted that in order to achieve this purpose, some special arrangements may be required for the load configurations connected to the non-isolated ports 1A, 2A, and ports 1B, 2B.

[0058] FIG. 6A is an exemplary circuit diagram of a multi-bridge converter-based three-phase inverter system according to various embodiments of the present disclosure. There are three multi-bridge converters 610, 611, 612 configured to drive a dual-winding AC motor 660 and coupled to three isolation transformers 620, 621, 622 and their rectifiers 630, 631, 632 to charge a battery 670. A PFC rectifier 640 and an EMI filter 650 are connected between the DC bus and an external AC power source. Also, a plug port for an external DC power source for charging is provided. FIG. 6A shows an example of an in-vehicle integrated circuit for an EV that can efficiently execute the functions of battery charging and inverter motor driving by a control unit 680. By sharing the main power components (i.e., the hardware of the same multi-bridges 610, 611, 612) between the battery charging mode and the driving mode, the component cost, size, and weight of the circuit are reduced. It is characterized by a bidirectional power flow function that enables both inverter driving operation and battery charging operation. Also, circuit breakers Kc1, Kc2, Kc3 are connected in series to the primary windings of transformers T1, T2, T3, respectively. And during non-insulated operation in parallel mode, these circuit break switches enable the multi-bridge converter to operate in PWM phase interleaving, increasing the effective switching frequency of the PWM voltage between the motor terminals. The advantages include reducing motor torque ripple, audible noise, etc.

[0059] FIG. 6B is a diagram showing an example of switching waveforms in the non-insulated operation mode of the multi-bridge converter-based three-phase inverter system shown in FIG. 6A. In this non-insulated operation mode, i.e., the motor driving mode, the main contactor switch K1 for the battery is closed, and the three multi-bridge converters 610, 611, 612 cooperate to function as a three-phase inverter and are controlled in real time by PWM or SVM (space vector modulation) according to motor speed and torque closed-loop regulation. Inside each multi-bridge converter, pairs of two phase bridges (e.g., 1A and 1B, 2A and 2B, 3A and 3B) are phase-synchronized and always turn the gates on and off at the same timing, so that the PWM output voltage (i.e., V 1A =V1B , V 2A = V 2B , V 3A = V 3B ) is configured so as to have the same waveform. Also, even when there is no disconnection switch (for example, Kc1, Kc2, Kc3), the differential voltage applied to the primary windings of the three transformers becomes almost "0". Therefore, as a result, the differential voltage applied to the secondary winding of the isolation transformer (that is, the voltage V EF , V GH , V JK ) also remains "0". Therefore, the power of the battery is mainly supplied to drive the motor through its double winding, and no significant power flow is supplied between the three isolation transformers.

[0060] FIG. 6C is a diagram showing an example of switching waveforms for the isolation operation mode of the multi-bridge converter-based three-phase inverter system shown in FIG. 6A. In this isolation operation mode, that is, in the battery charging mode, the main contactor switch K1 for the battery remains open, and the phase bridges of the multi-bridge converters 610, 611, and 612 are not turned on and off at the same timing. Actually, each multi-bridge operates like a standard LLC or phase-shifted full-bridge converter, and PWM regulation or frequency modulation is generally used to adjust the battery charging DC voltage and charging current. The charging power of the battery can be supplied from the AC power source by the PFC rectifier, or can also be supplied by an external DC power source.

[0061] Furthermore, here in FIG. 6C, there is another important thing about the battery charging mode. The A-phase bridges of the three multi-bridge converters 610, 611, and 612 (that is, the 1A-phase bridge, 2A-phase bridge, and 3A-phase bridge) are all in phase synchronization, and the output voltages of these A-phase bridges (that is, V 1A = V 2A = V 3A ) are the same in the PWM waveform. Also, the output voltages of all B-phase bridges of the three multi-bridge converters 610, 611, and 612 (that is, V 1B = V 2B = V 3B) Similarly, it will result in the same waveform. As a result, especially because the two sets of motor double windings are separated from each other, the motor windings will not be excited by a significant differential voltage that could cause a circulating current.

[0062] FIG. 6D is a diagram showing another embodiment of a three-phase multi-bridge inverter having two isolation transformers for a battery charging system. Here, in the circuit of the three-phase multi-bridge inverter, an LLC converter having resonance capacitors Cr1 and Cr2 is explicitly shown. This circuit operates in the same manner as the three-transformer type of FIG. 6A, and the only difference is that the rating of the battery charging power capacity is reduced. Both the inverter driving operation and the battery charging operation are characterized by the ability of bidirectional power flow.

[0063] FIG. 6E is a diagram showing another embodiment of a three-phase multi-bridge inverter having one isolation transformer for a battery charging system. Here, in the circuit of the three-phase multi-bridge inverter, an LLC converter having a resonance capacitor Cr1 is explicitly shown. This circuit operates in the same manner as the three-transformer type of FIG. 6A and the two-transformer type of FIG. 6D, and the only difference is that the rating of the battery charging power capacity is further reduced. Both the inverter driving operation and the battery charging operation are characterized by the ability of bidirectional power flow.

[0064] As described above, although the resonance capacitor may not be explicitly shown in all circuit diagrams of the present disclosure for all the exemplary circuits shown, they can be configured as LLC resonant converters. In fact, throughout the embodiments of the present disclosure, the isolated DC-DC charging circuit is illustrated as a full-bridge phase shift converter, an LLC converter, or a dual active bridge (DAB) converter. It should be understood that other isolated DC-DC topologies or combinations of different topologies may also be applicable and may be well-suited for the implementation of the multi-bridge converter circuit. And such modifications using other different topologies do not depart from the spirit and scope of the present disclosure as defined in the appended claims.

[0065] FIG. 7A is a diagram showing another embodiment of a three-phase multi-bridge inverter that uses one isolation transformer 720 having three coupled primary windings for a battery charging system. This circuit of the three-phase multi-bridge inverter operates in the same manner as the three-transformer type shown in FIG. 6A, and the only difference between them is related to the design of the magnetic transformer. Alternatively, it is shown that a passive rectifier 730 can be used for the secondary winding of the isolation transformer 720 for battery charging, and the main advantage would be the low cost compared to the active switching rectifier 630. Note that both the inverter drive operation and the battery charging operation are characterized by the possibility of bidirectional power flow.

[0066] FIG. 7B is a diagram showing another embodiment of a three-phase multi-bridge inverter that uses one isolation transformer 721 having two coupled primary windings for a battery charging system. This circuit of the three-phase multi-bridge inverter operates in the same manner as the two-transformer type shown in FIG. 6D, and the only difference between them is related to the design of the magnetic transformer. Alternatively, it is shown that a Vienna rectifier 741 is used in the boost PFC converter to draw power from an external AC power source and obtain the advantage of cost reduction by reducing the voltage stress and current on the active switching device.

[0067] FIG. 8A is a diagram showing an embodiment of a three-phase multi-bridge inverter without additional PFC rectifier hardware. Instead, the phase bridge 812 is used as a boost PFC rectifier operating in reverse power flow, and the winding inductance of the motor 860 is used as a boost inductor. Thereby, the cost of the charging hardware can be further reduced. FIG. 8A shows two isolation transformers 820, 821 and two rectifiers 830, 831 for battery charging. A single-phase AC power supply is connected to the neutral point of the dual winding of the EV motor 860 through the EMI filter 850. In the EV drive mode, the circuit shown in FIG. 8A operates in the same manner as described above, and within each multi-bridge, two phase bridges operate in parallel mode. Since no PFC rectifier is added, there are differences in the battery charging mode. During battery charging in the isolated operation mode, within each multi-bridge, two phase bridges operate in full-bridge mode. Further, the PWM duty cycle of each multi-bridge in full-bridge mode needs to be modulated by the AC voltage reference waveform for the power factor correction function. This is basically the same mechanism as that of an inherently single-stage PFC-compatible isolated DC-DC converter. Also, since the envelope of the AC current rides on the PWM switching ripple, it is a drawback that the size of the magnetic core of the isolation transformer becomes large. When the phase bridges 810, 811, 812 operate as a PFC rectifier and draw current through the motor winding, they need to be adjusted together from the perspective of the synchronization of the PWM gate timing in order to minimize the circulating current of the motor winding. Also, attention is required in the design of the control unit to suppress the pulsating torque of the motor and prevent the rotor from moving during charging. Note that it should be noted that both the inverter drive operation and the battery charging operation are characterized by the ability of bidirectional power flow.

[0068] FIG. 8B is a diagram showing another embodiment of a three-phase multi-bridge inverter without additional PFC rectifier hardware. Similarly, phase bridges 810, 811, 812 are used as boost PFC rectifiers operating in reverse power flow, and the winding inductance of motor 860 is used as a boost inductor. The AC power supply is connected to two neutral points of the dual winding of motor 860 through EMI filter 850. FIG. 8B is a diagram showing one isolation transformer 820 for a battery charging system. During battery charging in the isolation mode, phase bridges 810, 811, 812 operate as a single-stage PFC-compatible DC-DC converter, similar to FIG. 8A. Also, the gate timing control of phase bridges 810, 811, 812 needs to synchronize the phases in order to minimize the circulating current in the motor windings. Attention is required in the design of the control unit to suppress the pulsating torque of the motor and prevent the rotor from moving during charging. In addition, the circuit of this three-phase multi-bridge inverter basically operates in the same manner as the circuit of FIG. 8A. Note that it should be noted that both the inverter drive operation and the battery charging operation are characterized by the ability of bidirectional power flow.

[0069] FIG. 8C is a diagram showing an embodiment of a three-phase multi-bridge inverter having two isolation transformers 820 and 821 used for charging. Again, no additional PFC rectifier hardware is used. Instead, phase bridge 812 is used as a boost PFC rectifier operating in reverse power flow, and two inductors La and Lb are used as boost inductors. The three multi-bridge converters formed by phase bridges 810, 811, 812 are used to drive the dual-winding motor 860, and two isolation transformers 820, 821 and two rectifiers 830, 831 are used to charge the battery 870. A single-phase AC power supply is connected to the dual-winding terminals 3A, 3B of the EV motor 860 through an EMI filter 850 and through inductors La, Lb. In the EV drive mode, the circuit shown in FIG. 8C operates in the same manner as described above. During battery charging in the isolation operation mode, phase bridge 812 operates as a PFC rectifier to draw current from the external AC power supply, and the other phase bridges 810, 811 need to be synchronized with phase bridge 812 in terms of PWM gate timing to minimize the winding circulating current of the motor 860. Ideally, when the gate timings are synchronized among the three multi-bridges, the PWM output voltages at ports 1A, 2A, 3A will be the same, and no circulating current will flow through the A-phase winding of the motor 860. Similarly, since the PWM output voltages of 1B, 2B, 3B will be the same, no circulating current will flow through the B-phase winding of the motor 860. Therefore, the rotor of the motor 860 will not move during battery charging. Note that both the inverter drive operation and the battery charging operation are characterized by the ability to have bidirectional power flow.

[0070] FIG. 8D is a diagram showing another embodiment of a three-phase multi-bridge inverter having one isolation transformer 820 used for charging. Similarly, here, no additional PFC rectifier hardware is used. Instead, phase bridge 812 is used as a boost PFC rectifier operating in reverse power flow, and two inductors La and Lb are used as boost inductors. For the same reason, the PWM gate timings of the three multi-bridges are synchronized, and the same PWM output voltage is generated across the A-phase winding (i.e., ports 1A, 2A, 3A) and the B-phase winding (i.e., ports 1B, 2B, 3B) of motor 860. An AC voltage is applied across winding terminals 3A, 3B of motor 860, but the circulating current through the windings of motor 860 is not excited, and thus the rotor of motor 860 does not move during battery charging. During battery charging in the isolation mode, phase bridge 812 operates as a PFC rectifier, but the PWM gate timings of phase bridges 810, 811, 812 need to be phase-synchronized to minimize the circulating current in the motor windings so that the motor does not move during charging. Note that it should be noted that both the inverter drive operation and the battery charging operation are characterized by the ability of bidirectional power flow.

[0071] FIG. 9A is a diagram showing an embodiment of a three-phase multi-bridge inverter that drives two AC motors 960 and 961. Here, no additional PFC rectifier hardware is used. Instead, phase bridge 912 is used as a boost PFC rectifier operating in reverse power flow, and two inductors La and Lb are used as boost inductors. There are two isolation transformers 920 and 921, and two rectifiers 930 and 931 for charging battery 970. The single-phase AC power supply is connected through EMI filter 950, through inductors La and Lb, to the winding terminals 3A and 3B of motors 960 and 961. Another inductor Lc is connected to the midpoint of the DC bus to form the third line of the AC input as three-phase AC or split single-phase AC. In the EV drive mode, the circuit shown in FIG. 9A operates as described above. During battery charging in the isolation operation mode, phase bridge 912 mainly operates as a PFC rectifier to draw current from the external AC power supply, and the other phase bridges 910 and 911 need to be coordinated with phase bridge 912 from the perspective of PWM gate timing to minimize the circulating current through the windings of motors 960 and 961. Here, again, an AC voltage is applied between the winding terminals 3A and 3B of motors 960 and 961, but the circulating current through the windings of motors 960 and 961 is not excited, and thus the rotors of motors 960 and 961 do not move during battery charging. Note that both the inverter drive operation and the battery charging operation are characterized by the ability of bi-directional power flow.

[0072] FIG. 9B is a diagram showing another embodiment of a three-phase multi-bridge inverter that drives two AC motors 960 and 961, and one isolation transformer 920 is used for battery charging. Similarly, no additional PFC rectifier hardware is used here. Instead, phase bridge 912 is used as a boost PFC rectifier operating in reverse power flow, and two inductors La and Lb are used as boost inductors. Another inductor Lc is connected to the midpoint of the DC bus to form the third line of the AC input as three-phase AC or split single-phase AC. For the same reason, an AC voltage is applied to the winding terminals 3A and 3B of motors 960 and 961, but the circulating current through the windings of motors 960 and 961 is not excited, and thus motors 960 and 961 do not move during battery charging. In order to minimize any high-frequency component of the circulating current through the windings of motors 960 and 961, care must be taken in the design to adjust the gate timing control of phase bridges 910, 911, and 912. Note that both the inverter drive operation and the battery charging operation are characterized by the ability to have bidirectional power flow.

[0073] FIG. 10A is a diagram showing a circuit example of a multi-bridge based DC-DC boost converter and a battery charging system according to various embodiments of the present disclosure. The multi-bridge 1010 having two phase bridges 1011, 1012 is shown as a boost converter that converts the DC voltage of the battery 1070 to a higher voltage for driving the inverter 1040 with respect to the DC bus that supports an AC load (e.g., an AC motor load for EV driving). Between the main contactor K1 for the battery 1070 and the non-insulated output ports A and B of the phase bridges 1011, 1012, two boost inductors 1060, namely L1 and L2, are respectively connected. Note that the inductor 1060 may be a coupled inductor. The bidirectional PFC rectifier 1030 is provided to draw current from an external AC power source during charging and supply it to the DC bus. The primary winding of the isolation transformer 1020 is connected between the output ports A and B of the multi-bridge 1010. At the output formed by the ports E and F of the secondary winding of the transformer 1020, the bidirectional power converter 1050 adjusts the AC voltage from the transformer 1020 to a DC voltage and is used to charge the battery 1070. Note that both the inverter driving operation and the battery charging operation are characterized by the possibility of bidirectional power flow.

[0074] Figure 10B is a diagram showing the equivalent active switching circuit of the circuit shown in Figure 10A in the non - isolated operation mode with exemplary switching waveforms. During inverter operation in the non - isolated mode, the battery contactor K1 is closed, the external power supply is disconnected, and the multi - bridge 1010 operates as a DC - DC boost converter. The phase bridges 1011, 1012 of the multi - bridge 1010 operate in parallel mode with their PWM gate - switching signals synchronized in the same phase. Therefore, the same PWM voltage waveform is generated across the primary windings of the isolation transformer 1020, and the transformer windings are not excited with a significant differential voltage. As a result, the power flow is mainly supplied to the inverter 1040 and further to the AC load, and except for some transformer core losses, little power flows through the isolation transformer 1020. Also, short pulses or voltage glitches may be seen at the secondary ports E and F of the transformer, but those short pulses are acceptable due to the fact that they do not supply a significant portion of the total power flow.

[0075] Figure 10C is a diagram showing the equivalent active switching circuit of Figure 10A in the isolated operation mode with exemplary switching waveforms. During battery charging operation in the isolated mode, the battery contactor K1 is open, an external AC or DC power supply is connected, and the two phase bridges 1011 and 1012 of the multi - bridge 1010 operate in full - bridge mode. The PWM gate - switching signals are phase - shifted between the two bridges and out of phase. In fact, since the two bridges 1011 and 1012 can be adjusted as a normal LLC or DAB converter with PWM regulation, frequency modulation, or phase - shift control, the power from the AC power supply is mainly supplied to the isolated output (i.e., the isolated ports E and F) through the transformer 1020.

[0076] FIG. 10D is a diagram showing a modified example of a circuit having an additional switch added to the circuit shown in FIG. 10A. In particular, FIG. 10D shows a modified equivalent active switching circuit in the non-insulated operation mode, together with exemplary switching waveforms. The circuit of FIG. 10D is simply different from the circuit of FIG. 10A in that a transformer open switch, i.e., Kc, is connected between the output of the multi-bridge 1010 and the winding terminal of the transformer 1020. The purpose of this open switch Kc is to introduce a phase shift angle into the synchronized PWM signal and to realize an interleaved operation between the switching bridges 1011 and 1012 during the non-insulated operation mode. This open switch Kc may be anything such as a contactor, a relay, or a semiconductor device switch. Also, this open switch Kc can be arranged in series with the transformer either on the primary winding side or on the secondary winding side (not shown) as shown in FIG. 10D. Parallel bridge interleaving is well known to have the advantage of increasing the effective PWM frequency of the entire load, and thus reducing the load voltage and current ripple, and potentially reducing electromagnetic radiation (EMI) and audible noise.

[0077] FIG. 11A is a diagram showing another exemplary circuit of a multi-bridge based DC-DC boost converter and a battery charging system according to various embodiments of the present disclosure. Different from the previous circuit shown in FIG. 10A, here, the battery 1180, the main DC contactor K1, the inductor L1, and the midpoint of the primary winding of the isolation transformer 1120 are connected in series. During the EV driving operation in the non-insulated operation mode, the primary winding of the transformer 1120 is used as a combined boost inductor. If the inductance of the transformer 1120 is properly designed, the inductor L1 may become unnecessary or may be represented as parasitic inductance such as wiring and cables.

[0078] FIG. 11B is a diagram showing an equivalent active switching circuit of the circuit shown in FIG. 11A in a non-insulated operation mode with exemplary switching waveforms. During inverter operation in the non-insulated operation mode, contactor K1 is closed, the external power supply is disconnected, and multibridge 1110 operates as a DC-DC boost converter. Similar to the case of FIG. 10B, the two-phase bridges operate in parallel mode, and their gate switching signals are synchronized in the same phase. Therefore, the same PWM voltage waveform is generated across the primary winding of transformer 1120, and the transformer winding is not excited with a significant differential voltage. As a result, the power flow is mainly supplied to inverter 1150 and further to an AC load (e.g., AC motor 1160 as shown), but not much to the entire isolation transformer 1120 except for transformer core losses and other parasitic losses.

[0079] FIG. 11C is a diagram showing the equivalent active switching circuit of FIG. 11A in an insulated operation mode with exemplary switching waveforms. During battery charging operation in the insulated mode, contactor K1 is open and an external AC or DC power supply is connected. Similar to the case of FIG. 10C, the two-phase bridges of multibridge 1110 operate in full-bridge mode, and the PWM switching signals are phase-shifted and out of phase between the two bridges. In practice, the two-phase bridges can be operated as a normal LLC or DAB converter with PWM regulation, frequency modulation, or phase-shift control, so that power is transmitted between the DC bus and the isolated output (i.e., isolated ports E and F) through transformer 1120.

[0080] FIG. 11D is a diagram showing a modification of the circuit having an additional switch added to the circuit shown in FIG. 11A. In particular, FIG. 11D shows a modified equivalent active switching circuit in the non-insulated operation mode, together with exemplary switching waveforms. The circuit of FIG. 11D differs from the circuit of FIG. 11A only in that the transformer open switch, i.e., Kc is connected to the output terminal of the secondary winding of transformer 1120. The purpose of this open switch Kc is to introduce a phase shift angle into the synchronized PWM signal and to realize an interleaved operation between the two phase bridges during the non-insulated boost mode. This open switch Kc may be anything such as a contactor, a relay, or a semiconductor device switch. Parallel bridge interleaving is well known for the advantage of increasing the effective PWM frequency on the load, thus reducing the load current and voltage ripple, and potentially reducing electromagnetic radiation (EMI) and audible noise.

[0081] FIG. 12 is a diagram showing another exemplary circuit of a multi-bridge based DC-DC boost converter and a battery charging system according to various embodiments of the present disclosure. The PWM inverter 1230 is provided to drive the AC traveling motor 1240, and the neutral point of the motor winding is connected to the AC power supply and referenced to the DC bus midpoint. Here, the voltage doubler circuit 1260 is connected between the DC buses, which includes two diodes D1 and D2, and split capacitors C1 and C2 connected in series with the contactor switch Q2. By selectively closing the contactor switch Q2 by the control unit 1290, the voltage doubling function can be enabled (i.e., the voltage doubling is effective when the switch Q2 is closed, and the voltage doubling is ineffective when the switch Q2 is open). Thereby, the flexibility corresponding to a wide range of AC power supply voltages is further enhanced. The effect of using the voltage doubler 1260 is to supply the same stable high voltage to the DC bus both in the case of low AC input and high AC input. The voltage doubler 1260 needs to be disabled during inverter operation. Note that both the inverter driving operation and the battery charging operation are characterized by the possibility of bidirectional power flow. Alternatively, for cost reduction, a passive rectifier can be used at the output of the secondary winding of the isolation transformer 1220 instead of the active switching rectifier 1270.

[0082] FIG. 13 is a diagram showing another exemplary circuit of a multi-bridge based DC-DC boost converter and a battery charging system according to various embodiments of the present disclosure. There are two AC traveling motors 1350, 1351 driven by two inverters 1330, 1331. The single-phase AC power supply 1340 is connected between the neutral points of the windings of the two motors 1350, 1351, and both of the two inverters 1330, 1331 are used for charging with bidirectional power capability. Since a balanced charging current flows between the three-phase motor windings, a large rotational magnetic force is not generated in the motors 1350, 1351, and the motor pulsating torque becomes negligible. Otherwise, the multi-bridge circuit shown in FIG. 13 operates basically in the same manner as FIG. 11.

[0083] FIG. 14 is a diagram showing another embodiment of a multi-bridge DC-DC boost converter and a transformer-isolated battery charging system. The circuit shown in FIG. 14 differs in that two inverters 1430 and 1431 drive an AC running motor 1450 having a dual winding in a conventional Y-shaped configuration. A single-phase AC power supply is connected to two neutral points of the dual winding of the motor 1450 through an EMI filter 1460 for charging with bidirectional power capability. Since a balanced charging current flows between each pair of the three-phase motor windings, a large rotational magnetic force is not generated in the motor 1450, and the motor pulsating torque becomes negligible. And this circuit operates in the same manner as the other circuits described above.

[0084] FIG. 15A is a diagram showing another exemplary circuit of a multi-bridge-based DC boost converter and a transformer-isolated battery charging system according to various embodiments of the present disclosure. The circuit shown in FIG. 15A differs in that two inverters 1530 and 1531 drive an AC running motor 1550 having an open winding configuration. A three-phase AC power supply is connected to three intermediate points of the windings of a charging motor 1550 having bidirectional power capability through an EMI filter 1560 and an AC contactor switch Q1. During charging of the battery 1580, both inverters 1530 and 1531 operate as a boost PFC rectifier and evenly distribute current among all three-phase windings of the motor 1550. As a result of these balanced currents, the motor windings do not generate a large rotational magnetic force, and the motor pulsating torque becomes negligible. Otherwise, the multi-bridge circuit of FIG. 15A operates in the same manner as FIG. 11.

[0085] Figure 15B shows another embodiment of a multi-bridge DC boost converter, where a three-phase or split-phase AC input is connected to the midpoint of the open winding of the battery charging motor 1550. The circuit shown in Figure 15B is different in that it is configured to have a common neutral point that can change the motor winding to a double-Y configuration when the AC contactor switch Q1 is enabled. Since the common neutral point is connected, the double-Y configuration has the flexibility to operate the motor in a six-phase mode versus a three-phase double-wound mode. This difference is the relative current phase relationship between the motor windings from the perspective of space vector control. The advantage is to reduce the back electromotive force voltage reflected on the DC bus during high-speed motor rotation and improve the motor current capacity during low-speed motor rotation.

[0086] Figure 15C shows another embodiment of a multi-bridge DC-DC boost converter, where a single-phase AC input is connected to a three-phase motor 1550 at its open winding midpoint for battery charging. Note that only two of the motor windings with the midpoint connected to the AC input, which is common for a single-phase AC power supply. In this case, the motor is a special type and needs to be a commonly seen double-wound motor, where each phase winding basically has two half windings, and the two double windings overlap in the same slot with the same current direction. By flowing equal currents from the midpoint of the winding to both half windings, the induced magnetic forces are always balanced and canceled out. Therefore, the balanced motor winding current during the operation of the PFC rectifier does not cause significant pulsating torque or vibration problems.

[0087] Embodiments of the present technology can be applied to a wide range of electric motors in various arrangements (e.g., multiple motors within an EV). Here, several examples are illustrated, but these are not limiting, and it will be understood that the present technology is applicable to more types of electric motors in more configurations.

[0088] Embodiments of the present technology are not limited to any single type of electric motor and can be used with different electric motor designs, including single-wound motors, double-wound motors, and open-wound motors, and any number of motors (either of the same type or different types).

[0089] For the purposes of this specification, it should be noted that the dimensions of the various features depicted in the figures may not necessarily be drawn to scale.

[0090] For the purposes of this specification, references to "an embodiment", "one embodiment", "some embodiments", or "another embodiment" in this specification may be used to describe different embodiments or the same embodiment.

[0091] For the purposes of this specification, a connection may be a direct connection or an indirect connection (e.g., through one or more other components). In some cases, when an element is referred to as being connected or coupled to another element, that element may be directly connected to the other element or indirectly connected to the other element through intervening elements. When an element is referred to as being directly connected to another element, there are no intervening elements between that element and the other element. Two devices are "in communication" if they are directly or indirectly connected and are capable of communicating an electronic signal between them.

[0092] For the purposes of this specification, the term "based on" may be read as "based at least in part on".

[0093] For the purposes of this specification, in the absence of additional context, the use of numerical terms such as "a first" object, "a second" object, and "a third" object, etc., does not imply an ordering of the objects, but rather may be used for identification purposes to distinguish different objects.

[0094] Although the present disclosure has been described with reference to its particular features and embodiments, it will be apparent that various modifications and combinations can be made thereto without departing from the scope of the present disclosure. Accordingly, the specification and drawings are to be regarded as merely illustrative of the present disclosure as defined by the appended claims, and it is contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present disclosure.

[0095] The foregoing detailed description is presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the subject matter claimed herein to the exact forms disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments described were chosen to best explain the principles of the disclosed technology and its practical application, thereby enabling others skilled in the art to best utilize the technology in various embodiments and with various modifications suited to the particular uses contemplated. It is intended that the scope be defined by the claims appended hereto.

Description of Reference Numerals

[0096] 110, 210, 310, 410, 510, 520, 610, 611, 612, 710, 711, 712, 810, 811, 812, 910, 911, 912, 1010, 1110, 1210, 1310, 1410, 1510 Multi-bridge 111, 112, 211, 212, 311, 312, 411, 412, 413, 1011, 1012 Phase bridge 120, 220, 320, 420, 421, 422, 530, 531, 620, 621, 622, 720, 721, 820, 821, 920, 921, 1020, 1120, 1220, 1320, 1420, 1520 Transformer 130, 230, 330, 430, 540, 1090 DC bus 140, 240, 340, 440, 590, 680, 780, 880, 980, 1080, 1190, 1290, 1380, 1490, 1590 Control Unit 580, 640, 740, 741, 1030, 1130 PFC Rectifier 1040, 1150, 1230, 1330, 1331, 1430, 1431, 1530, 1531 Inverter 660, 760, 860, 960, 961, 1160, 1240, 1350, 1351, 1450, 1550 Motor 550, 551, 630, 631, 730, 731, 830, 831, 930, 931, 1050, 1170, 1270, 1360, 1470, 1570 Power Converter on the Secondary Side of Transformer 570, 670, 770, 870, 970, 1070, 1180, 1280, 1370, 1480, 1580 Battery, Battery Management System (BMS) 650, 750, 850, 950, 1140, 1250, 1340, 1460, 1560 EMI Filter

Claims

1. A multi-bridge power converter (100), A multi-bridge (110) comprising first and second switching bridges (111, 112) connected to a common DC bus (130) having a common positive terminal (p) and a common negative terminal (n), wherein the first switching bridge (111) has a first non-insulated output (A) of the non-insulated outputs (A, B), the second switching bridge (112) has a second non-insulated output (B) of the non-insulated outputs (A, B), and pulse width modulation (PWM) voltages (V A , V B ) are generated at the first and second non-insulated outputs (A, B). having an isolation transformer (120) having a primary winding (Np1) connected between the first non-isolated output (A) of the first switching bridge (111) and the second non-isolated output (B) of the second switching bridge (112), and a secondary winding (Ns1) connected to the isolated outputs (E, F), comprising: In the non-isolated mode, the first and second switching bridges (111, 112) are controlled to operate in a parallel mode, and power is transmitted between the DC bus (130) and a load coupled to the non-isolated outputs (A, B). In the isolated mode, the first and second switching bridges (111, 112) are controlled to operate in a full-bridge mode, and power is transmitted between the DC bus (130) and a load coupled to the isolated outputs (E, F) through the isolation transformer (120). A multi-bridge power converter (100).

2. A control unit (140) operates the first and second switching bridges (111, 112) at least according to the non-isolated mode and the isolated mode, In the non-isolated mode, the first and second switching bridges (111, 112) are controlled by PWM switching signals with synchronized phases, In the isolated mode, the first and second switching bridges (111, 112) are controlled by PWM switching signals with phase shifts, The multi-bridge power converter according to Claim 1.

3. A multi-bridge power converter (200), A multi-bridge (210) comprising first and second switching bridges (211, 212) connected to a common DC bus (230) having a common positive terminal (p) and a common negative terminal (n), wherein the first switching bridge (211) has a first non-insulated output (A) of the non-insulated outputs (A, B), the second switching bridge (212) has a second non-insulated output (B) of the non-insulated outputs (A, B), and pulse-width modulation (PWM) voltages (V A , V B ) are generated at the first and second non-insulated outputs (A, B). having an isolation transformer (220) having a primary winding (Np1) connected between the first non-isolated output (A) of the first switching bridge (211) and the second non-isolated output (B) of the second switching bridge (212), and a secondary winding (Ns1) connected to the isolated outputs (E, F), at least one transformer open-circuit switch (250, Kc) connected in series to either the primary winding (Np1) or the secondary winding (Ns1) and operating at least according to the non-isolated mode and the isolated mode, comprising: In the non-insulated mode, the transformer disconnection switch (250, Kc) remains open, the first and second switching bridges (211, 212) are controlled in an interleaved parallel mode, and the PWM switching signals are synchronized and interleaved with a phase shift angle so as to increase the effective PWM switching frequency between the first and second non-insulated outputs (A, B). In the insulated mode, the transformer disconnection switch (250, Kc) remains closed, and the first and second switching bridges (211, 212) are controlled in a full bridge mode. Multi-bridge power converter.

4. The multi-bridge (110; 310) is a two-level switching bridge (111, 112), or a three-level switching bridge (311, 312), or a five-level switching bridge, or any multi-level converter topology such as a diode neutral point clamped (NPC) multi-level converter (311, 312), an active NPC (ANPC) multi-level converter, or a flying capacitor multi-level converter. is used. The multi-bridge power converter according to claim 1.

5. A multi-bridge power converter, comprising A multi-bridge (410) comprising first, second, and third switching bridges (411, 412, 413) connected to a common DC bus (430) having a common positive terminal (p) and a common negative terminal (n), wherein the first switching bridge (411) has a first non-insulated output (A) among non-insulated outputs (A, B, C), the second switching bridge (412) has a second non-insulated output (B) among the non-insulated outputs (A, B, C), the third switching bridge (413) has a third non-insulated output (C) among the non-insulated outputs (A, B, C), and pulse width modulation (PWM) voltages (V A , V B , V C ) are generated at the first, second, and third non-insulated outputs (A, B, C). a first insulated transformer (420) having a first primary winding (Np1) and a second insulated transformer (421) having a second primary winding (Np2), or an integrated insulated transformer (422) having a first primary winding (Np1) and a second primary winding (Np2); is provided with connecting the first primary winding (Np1) between the first non-insulated output (A) of the first switching bridge (411) and the second non-insulated output (B) of the second switching bridge (412), and connecting the second primary winding (Np2) between the second non-insulated output (B) of the second switching bridge (412) and the third non-insulated output (C) of the third switching bridge (413); the multi-bridge power converter is operated at least according to a non-insulated mode and an insulated mode, In the non-insulated mode, the first, second, and third switching bridges (411, 412, 413) are controlled to operate in a parallel mode, and power is transmitted between the DC bus (430) and a load coupled to the non-insulated outputs (A, B, C). In the insulation mode, the first, second, and third switching bridges (411, 412, 413) are controlled to operate in a full bridge mode (411, 412; 412, 413), and power is transmitted through the first and second insulation transformers (420, 421) or the integrated insulation transformer (422). Multi-bridge power converter. **Claim 6** A multi-bridge power converter, configured as a non-insulated pulse width modulation (PWM) inverter integrated with an insulation battery charging system, Two or three multi - bridges (510, 520; 610, 611, 612), each multi - bridge having two switching bridges, each switching bridge being connected to a common DC bus (540) having a common positive terminal (p) and a common negative terminal (n), each switching bridge having each non - isolated output (1A, 1B; 2A, 2B; 3A, 3B), and a DC - AC inverter (510, 520; 610, 611, 612) that generates a PWM voltage (V 1A , V 1B ; V 2A , V 2B ; V 3A , V 3B ) for each non - isolated output (1A, 1B; 2A, 2B; 3A, 3B), two or three multi - bridges (510, 520; 610, 611, 612) forming, a battery (570; 670) connected to the DC bus (540) through a battery main contactor (K1), two or three insulation transformers (530, 531; 620, 621, 622), each insulation transformer having a primary winding (Np1, Np2, Np3) connected between non-insulated outputs (1A, 1B; 2A, 2B; 3A, 3B) of two switching bridges of the corresponding multi-bridge among the two or three multi-bridges (510, 520; 610, 611, 612), and corresponding to the primary winding (Np1, Np2, Np3), each having a secondary winding (Ns1, Ns2, Ns3) connected to each insulation output (E, F; G, H; J, K), two or three insulation transformers (530, 531; 620, 621, 622); two or three power converters (550, 551; 630, 631, 632) corresponding to the two or three insulation transformers (530, 531; 620, 621, 622), connected to the corresponding insulation outputs (E, F; G, H; J, K) to generate a DC voltage for charging the battery (570; 670); comprising the multi-bridge power converter is operated at least according to a non-insulated mode and an insulation mode, in the non-insulated mode during inverter operation, the battery main contactor (K1) remains closed, and within each multi-bridge (510, 520; 610, 611, 612), two switching bridges operate in a parallel mode, in the insulation mode during battery charging operation, the battery main contactor (K1) remains open, and within each multi-bridge (510, 520; 610, 611, 612), two switching bridges operate in a full bridge mode. Multi-bridge power converter. **Claim 7** Each non-insulated output (1A, 1B; 2A, 2B; 3A, 3B) of the two or three multi-bridges (610, 611, 612) supplies power for driving an AC motor (660) having two or three sets of motor windings (1A - 2A - 3A; 1B - 2B - 3B) separated from each other, and during the battery charging operation in the insulation mode, additional PWM gate switching synchronization is performed between the switching bridges connected between the motor windings of the same set (1A - 2A - 3A; 1B - 2B - 3B), so that each set of motor windings has a differential voltage (V 1A-2A , V 2A-3A , V 3A-1A ; V 1B-2B , V 2B-3B , V 3B-1B ) between the terminals (1A, 2A, 3A; 1B, 2B, 3B) of the AC motor excited to be approximately and substantially zero. The multi-bridge power converter according to claim 6. **Claim 8** A multi-bridge power converter, configured as a non-insulated DC boost converter integrated with an insulated battery charging system, a multi-bridge (1010), wherein the multi-bridge has two switching bridges (1011, 1012), each switching bridge is connected to a common DC bus (1090) having a common positive terminal (p) and a common negative terminal (n), each switching bridge has each non-insulated output (A, B), and each non-insulated output (A, B) of the two switching bridges (1011, 1012) is connected to the battery (1070) through a battery main contactor (K1) and each boost inductor (L1, L2), the multi-bridge (1010); an isolation transformer (1020), having a primary winding (Np1) connected between each non-insulated output (A, B) of the two switching bridges (1011, 1012), having a secondary winding (Ns1) connected to an insulated output (E, F), and the insulated output (E, F) is connected to a power converter (1050) that generates a DC voltage to charge the battery (1070), the isolation transformer (1020); comprising the multi-bridge power converter is operated at least according to a non-insulated mode and an insulated mode, in the non-insulated mode during DC boost operation, the battery main contactor (K1) remains closed, and within the multi-bridge, the two switching bridges (1011, 1012) are controlled to operate in a parallel mode, and power is transmitted from the battery (1070) to the DC bus (1090), in the insulated mode during battery charging operation, the battery main contactor (K1) remains open, and within the multi-bridge, the two switching bridges (1011, 1012) are controlled to operate in a full-bridge mode, and power is transmitted from the DC bus (1090) to the battery (1070), a multi-bridge power converter.

9. further comprising a PWM inverter (1230; 1330, 1331) connected to the DC bus for driving an AC motor (1240; 1350, 1351), and the PWM inverter (1230; 1330, 1331) operates in a reverse power flow as an AC-DC rectifier to draw power from an AC power source, the multi-bridge power converter according to claim 8.

10. A method for converting power, A multi-bridge (110) is formed, comprising first and second switching bridges (111, 112) connected to a common DC bus (130) having a common positive terminal (p) and a common negative terminal (n), wherein the first switching bridge (111) has a first non-insulated output (A) among non-insulated outputs (A, B), the second switching bridge (112) has a second non-insulated output (B) among the non-insulated outputs (A, B), and pulse-width modulation (PWM) voltages (V A , V B ) are generated at the first and second non-insulated outputs (A, B). A step of arranging an isolation transformer (120) having a primary winding (Np1) connected between the first non-isolated output (A) of the first switching bridge (111) and the second non-isolated output (B) of the second switching bridge (112), and having a secondary winding (Ns1) connected to the isolated outputs (E, F). Including In the non-isolated mode, a step of transmitting power between the DC bus (130) and a load coupled to the non-isolated outputs (A, B) by operating the first and second switching bridges (111, 112) in a parallel mode. In the isolated mode, a step of transmitting power between the DC bus (130) and a load coupled to the isolated outputs (E, F) through the isolation transformer (120) by operating the first and second switching bridges (111, 112) in a full-bridge mode. Including A method of converting power.

11. Further including a step of controlling the first and second switching bridges (111, 112) using a control unit (140) at least according to the non-isolated mode and the isolated mode. In the non-isolated mode, a step of operating the first and second switching bridges (111, 112) with a PWM switching signal having a synchronized phase. In the isolated mode, a step of operating the first and second switching bridges (111, 112) with a PWM switching signal having a phase shift. The method of converting power according to claim 10, including

12. A method of converting power, A first and a second switching bridge (211, 212) connected to a common DC bus (230) having a common positive terminal (p) and a common negative terminal (n), wherein the first switching bridge (211) has a first non-insulated output (A) of the non-insulated outputs (A, B), and the second switching bridge (212) has a second non-insulated output (B) of the non-insulated outputs (A, B), and a pulse width modulation (PWM) voltage (V A , V B ) is generated to form a multi-bridge (210). A step of arranging an isolation transformer (220) having a primary winding (Np1) connected between the first non-isolated output (A) of the first switching bridge (211) and the second non-isolated output (B) of the second switching bridge (212), and having a secondary winding (Ns1) connected to the isolated outputs (E, F). A step of connecting at least one transformer open-circuit switch (250, Kc) connected in series to either the primary winding (Np1) or the secondary winding (Ns1) and operating at least according to the non-isolated mode and the isolated mode. Including In the non-insulated mode, the transformer disconnection switch (250, Kc) is kept open, the first and second switching bridges (211, 212) are operated in an interleaved parallel mode, and the PWM switching signals are synchronized and interleaved at a phase shift angle so that the effective PWM switching frequency increases between the first and second non-insulated outputs (A, B). In the insulated mode, the transformer disconnection switch (250, Kc) is kept closed, the first and second switching bridges (211, 212) are operated in a full bridge mode, and the PWM switching signals are phase shifted so that the phases are shifted. including A method for converting power.

13. A multi-bridge power converter, comprising Two or three multi-bridges (510, 520; 610, 611, 612), each multi-bridge having two switching bridges, each switching bridge being connected to a common DC bus (540) having a common positive terminal and a common negative terminal, each switching bridge having each non-insulated output (1A, 1B; 2A, 2B; 3A, 3B), and a PWM voltage (V 1A , V 1B ; V 2A , V 2B ; V 3A , V 3B ) being generated to form a DC-AC inverter (510, 520; 610, 611, 612), two or three multi-bridges (510, 520; 610, 611, 612), and a battery (570; 670) connected to the DC bus (540) through a battery main contactor (K1); two or three insulated transformers (530, 531; 620, 621, 622), each insulated transformer having a primary winding (Np1, Np2, Np3) connected between non-insulated outputs (1A, 1B; 2A, 2B; 3A, 3B) of two switching bridges of the corresponding multi-bridge among the two or three multi-bridges (510, 520; 610, 611, 612), and corresponding to the primary winding, each having a secondary winding (Ns1, Ns2, Ns3) connected to each insulated output (E, F; G, H; J, K), two or three insulated transformers (530, 531; 620, 621, 622); two or three power converters (550, 551; 630, 631, 632) corresponding to the two or three insulated transformers (530, 531; 620, 621, 622), connected to the corresponding insulated outputs (E, F; G, H; J, K) and generating a DC voltage for charging the battery (570; 670); A multi-bridge power converter comprising the multi-bridge power converter is operated at least according to a non-insulated mode and an insulated mode, In the non-insulated mode during inverter operation, the battery main contactor (K1) remains closed, and within each multi-bridge (510, 520; 610, 611, 612), the two switching bridges operate in parallel mode. In the insulation mode during battery charging operation, the battery main contactor (K1) remains open, and within each multi-bridge (510, 520; 610, 611, 612), two switching bridges operate in full-bridge mode. Electric vehicle.

14. The inverter operation is executed in the non-insulated mode, and each non-insulated output (1A, 1B; 2A, 2B; 3A, 3B) of the two or three multi-bridges (610, 611, 612) supplies power for driving an AC motor (660) having two or three sets of motor windings (1A-2A-3A; 1B-2B-3B) separated from each other. During the battery charging operation in the insulated mode, additional PWM gate switching synchronization is performed between the switching bridges connected between the motor windings of the same set (1A-2A-3A; 1B-2B-3B). Therefore, each set of motor windings has a differential voltage (V 1A-2A , V 2A-3A , V 3A-1A ; V 1B-2B , V 2B-3B , V 3B-1B ) between the terminals (1A, 2A, 3A; 1B, 2B, 3B) of the AC motor excited to be approximately and substantially zero to reduce any unintended motor circulating current. The electric vehicle according to claim 13.

15. A multi-bridge power converter, configured as a non-insulated DC boost converter integrated with an insulated battery charging system, a multi-bridge (1010), wherein the multi-bridge has two switching bridges (1011, 1012), each switching bridge is connected to a common DC bus (1090) having a common positive terminal (p) and a common negative terminal (n), each switching bridge has each non-insulated output (A, B), and each non-insulated output (A, B) of the two switching bridges (1011, 1012) is connected to a battery (1070) through a battery main contactor (K1) and one or more boost inductors (L1, L2), the multi-bridge (1010); an isolation transformer (1020), having a primary winding (Np1) connected between each non-insulated output (A, B) of the two switching bridges (1011, 1012), having a secondary winding (Ns1) connected to an insulated output (E, F), and the insulated output (E, F) is connected to a power converter (1050) that generates a DC voltage for charging the battery (1070), the isolation transformer (1020); comprising a multi-bridge power converter, the multi-bridge power converter is operated at least according to a non-insulated mode and an insulated mode, In the non-insulated mode during DC boost operation, the battery main contactor (K1) remains closed, and power is transmitted from the battery (1070) to the DC bus (1090) through the battery main contactor (K1). In the insulation mode during battery charging operation, the battery main contactor (K1) remains open, and power is transmitted from the DC bus (1090) to the battery (1070) through the isolation transformer (1020). Electric vehicle.

16. comprising a control unit (1080) for operating the two switching bridges (1011, 1012) of the multi-bridge (1010) at least according to the non-insulated mode and the insulated mode. In the non - isolation mode, the two switching bridges (1011, 1012) are controlled to operate in a parallel mode, and the PWM switching signals are phase - synchronized. In the isolation mode, the two switching bridges (1011, 1012) are controlled to operate in a full - bridge mode, and the PWM switching signals are out of phase. The electric vehicle according to claim 15.

17. At least one transformer disconnection switch (Kc) is connected in series to either the primary winding (Np1) or the secondary winding (Ns1). It operates at least according to the non - isolation mode and the isolation mode. In the non - isolation mode, the transformer disconnection switch (Kc) remains open, the two switching bridges (1011, 1012) are controlled in an interleaved parallel mode, and the PWM switching signals are synchronized and interleaved at a phase - shift angle so as to increase the effective PWM switching frequency between the non - isolated outputs (A, B). In the isolation mode, the transformer disconnection switch (Kc) remains closed, the two switching bridges (1011, 1012) are controlled in a full - bridge mode, and the PWM switching signals are out of phase. The electric vehicle according to claim 15.

18. Some or all of the one or more boost inductors (L1, L2) are incorporated into the design of the isolation transformer (1120; 1520). The battery (1180) is connected to the mid - point of the primary winding (Np1) of the isolation transformer (1120) through the battery main contactor (K1). When some of the one or more boost inductors (L1, L2) are incorporated into the design of the isolation transformer (1120), the one or more boost inductors (L1, L2) are composed of a single small inductor (L1) and the primary winding (Np1). When all of the one or more boost inductors (L1, L2) are incorporated into the design of the isolation transformer (1520), the one or more boost inductors (L1, L2) are composed of the primary winding. The electric vehicle according to claim 15.

19. The multi - bridge (1010) is a two - level switching bridge (1011, 1012), or a three - level switching bridge (311, 312), or a five - level switching bridge, or Any multilevel converter topology, such as a diode neutral point clamped (NPC) multilevel converter (311, 312), an active NPC (ANPC) multilevel converter, or a flying capacitor multilevel converter, is used for the electric vehicle according to claim 15.

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