Multilevel power conversion system and method

Abstract

A system includes a first power conversion device connected to a first power source, a first isolated power conversion device connected to the first power source, and a second power conversion device connected to the first isolated power conversion device, wherein an output of the first power conversion device and an output of the second power conversion device are connected in series, and the series connected output of the first power conversion device and the second power conversion device is used to drive a motor.

Description

Technical Field

[0001] This disclosure relates to a high-efficiency power conversion system, and in certain embodiments, to an integrated motor drive and isolated battery charger system. Background Technology

[0002] The power electronics industry has experienced rapid growth due to the exponential development and continuous improvement of new technologies. With the further development of power electronics technology, on-board battery chargers have become a key element in some new energy applications. One of the most important new energy applications is the electric vehicle (EV). Different EVs are equipped with batteries of different capacities and voltages. EVs require suitable chargers to charge these various batteries.

[0003] An on-board battery charger includes electronic circuitry for converting alternating current (AC) power to direct current (DC) power. The on-board battery charger may include an AC / DC stage and a DC / DC stage. The input to the AC / DC stage is connected to the AC utility line. The AC / DC stage is used to convert the AC input voltage from the AC utility line to a suitable DC bus voltage. The AC / DC stage may include various electromagnetic interference (EMI) filters, a bridge rectifier formed by four diodes, and power factor correction circuitry.

[0004] EMI filters are used to reduce high-frequency noise that may interfere with other devices in the vehicle battery charger. Thanks to the use of EMI filters, the vehicle battery charger can meet various EMI regulations. A bridge rectifier converts AC voltage to full-wave rectified DC voltage. This full-wave rectified DC voltage provides the DC input voltage for a power factor correction (PFCC) circuit. The PFCC circuit can be implemented as a suitable power converter, such as a boost converter. By using appropriate control circuitry, a boost converter can shape the input line current into a sinusoidal shape, making it in phase with the sinusoidal input voltage of the AC input source. Therefore, the power factor of the AC / DC stage can approach the uniformity required by various international standards.

[0005] The DC / DC stage is connected between the output of the AC / DC stage and multiple batteries. The DC / DC stage may include an isolated DC / DC power converter with a primary winding, a secondary winding, and a secondary rectifier for converting DC bus voltage into DC voltage to charge EV batteries.

[0006] EV power systems are highly sensitive to component size, weight, and power conversion efficiency. Integration of the onboard charger with the motor drive unit is necessary to further reduce the size of the EV power system. Summary of the Invention

[0007] These and other problems are solved or circumvented by preferred embodiments of the present disclosure, and technical advantages are generally achieved, with preferred embodiments of the present disclosure providing an integrated motor drive and isolated battery charger system.

[0008] According to one embodiment, a system includes a first power conversion device connected to a first power source, a first isolated power conversion device connected to the first power source, and a second power conversion device connected to the first isolated power conversion device, wherein the outputs of the first power conversion device and the outputs of the second power conversion device are connected in series and used to drive a motor.

[0009] The first power conversion device is a first inverter. The second power conversion device is a second inverter. The first isolated power conversion device is a three-level inductor-inductor-capacitor (LLC) converter.

[0010] The first isolated power conversion device includes a first primary switching network, a first resonant circuit, a first transformer, and a secondary rectifier connected in a cascaded manner.

[0011] The first isolated power conversion device includes a first primary switching network, a first resonant circuit, a first transformer, a second primary switching network, a second resonant circuit, a second transformer, and a secondary rectifier, wherein the primary windings of the first primary switching network, the first resonant circuit, and the first transformer are cascaded, wherein the primary windings of the second primary switching network, the second resonant circuit, and the second transformer are cascaded, and wherein the secondary windings of the first transformer and the second transformer are connected in series and further connected to the secondary rectifier.

[0012] The first isolated power conversion device includes a first primary switching network, a first resonant circuit, a first transformer, and a plurality of secondary rectifiers, wherein the plurality of secondary rectifiers are used to provide isolated power to a plurality of inverter units of the second power conversion device.

[0013] The first power conversion device is a first inverter, which includes a first inverter unit, a second inverter unit, and a third inverter unit connected in parallel, and each inverter unit of the first inverter includes two output terminals. The second power conversion device is a second inverter, which includes a fourth inverter unit, a fifth inverter unit, and a sixth inverter unit connected in parallel, and each inverter unit of the second inverter includes two output terminals. The two output terminals of the first inverter unit and the two output terminals of the fourth inverter unit of the second inverter are connected in series and further connected to a first phase of the motor. The two output terminals of the second inverter unit and the two output terminals of the fifth inverter unit of the second inverter are connected in series and further connected to a second phase of the motor. The two output terminals of the third inverter unit and the two output terminals of the sixth inverter unit of the second inverter are connected in series and further connected to a third phase of the motor.

[0014] The common node of the first inverter unit and the fourth inverter unit is used to connect to the first phase of the three-phase power supply. The common node of the second inverter unit and the fifth inverter unit is used to connect to the second phase of the three-phase power supply. The common node of the third inverter unit and the sixth inverter unit is used to connect to the third phase of the three-phase power supply, and wherein the three-phase power supply is used to charge the first power supply through a power factor correction device formed by the windings of the motor and the switches of the second inverter.

[0015] The first power conversion device is a first inverter, which has three branches and three output terminals. The second power conversion device includes a first inverter unit, a second inverter unit, and a third inverter unit, wherein the first terminal of the first inverter is connected in series with the output of the first inverter unit and further connected to the first phase of the motor, wherein the second terminal of the first inverter is connected in series with the output of the second inverter unit and further connected to the second phase of the motor, and wherein the third terminal of the first inverter is connected in series with the output of the third inverter unit and further connected to the third phase of the motor.

[0016] The first isolated power conversion device is an LLC converter, which includes a primary winding, a first stage winding, a second stage winding, and a third stage winding. The primary winding is connected to the first power supply through a primary switching network. The first stage winding is connected to the first inverter unit through a first rectifier. The second stage winding is connected to the second inverter unit through a second rectifier. The third stage winding is connected to the third inverter unit through a third rectifier.

[0017] The first power conversion device is a first inverter, which has three branches and three output terminals. The second power conversion device includes a first inverter unit with two branches and a second inverter unit with two branches. The first output terminal of the first inverter is connected to both the first phase of the motor and in series with the output of the first inverter unit. The second output terminal of the first inverter is connected to both the second phase of the motor and in series with the output of the second inverter unit. The third output terminal of the first inverter is directly connected to the third phase of the motor.

[0018] The first power conversion device is a first inverter, which has three branches and three output terminals. The second power conversion device includes a first inverter unit with three branches and a second inverter unit with three branches, wherein the first output terminal of the first inverter is connected in series with the output of the first inverter unit and further connected to the first phase of the motor, wherein the second output terminal of the first inverter is connected in series with the output of the second inverter unit and further connected to the second phase of the motor, and wherein the third output terminal of the first inverter is directly connected to the third phase of the motor.

[0019] The first power conversion device is a first inverter, which includes a first inverter unit, a second inverter unit, and a third inverter unit connected in parallel, and each inverter unit of the first inverter includes two output terminals. The second power conversion device includes a second inverter and a third inverter. The second inverter includes a fourth inverter unit, a fifth inverter unit, and a sixth inverter unit connected in series. Each inverter unit of the second inverter includes two output terminals. The third inverter includes a seventh inverter unit, an eighth inverter unit, and a ninth inverter unit connected in series. Each inverter unit of the third inverter includes two output terminals. The two output terminals of the first inverter unit, the two output terminals of the fourth inverter unit, and the two output terminals of the seventh inverter unit are connected in series and further connected to the first phase of the motor. The two output terminals of the second inverter unit, the two output terminals of the fifth inverter unit, and the two output terminals of the eighth inverter unit are connected in series and further connected to the second phase of the motor. The two output terminals of the third inverter unit, the two output terminals of the sixth inverter unit, and the two output terminals of the ninth inverter unit are connected in series and further connected to the third phase of the motor.

[0020] According to another embodiment, a system includes a first inverter having an input connected to a battery, an isolated power converter having an input connected to the battery, and a second inverter having an input connected to the output of the isolated power converter and an output connected in series with the output of the first inverter, wherein the output of the series connection of the first inverter and the second inverter is used to drive a motor.

[0021] During the charging process of the battery, the windings of the motor are used as inductors for a three-phase power factor correction converter.

[0022] The first inverter is a three-phase full-bridge inverter, which includes three output terminals. The second inverter includes a first inverter unit, a second inverter unit, and a third inverter unit. The first output terminal of the first inverter is connected in series with the output of the first inverter unit and further connected to the first phase of the motor. The second output terminal of the first inverter is connected in series with the output of the second inverter unit and further connected to the second phase of the motor. The third output terminal of the first inverter is connected in series with the output of the third inverter unit and further connected to the third phase of the motor.

[0023] The isolated power converter is an inductor-inductor-capacitor LLC power converter, which includes a primary winding, a first stage winding, a second stage winding, and a third stage winding. The primary winding is connected to the battery through a primary switching network. The first stage winding is connected to the first inverter unit through a first rectifier. The second stage winding is connected to the second inverter unit through a second rectifier. The third stage winding is connected to the third inverter unit through a third rectifier.

[0024] According to yet another embodiment, a method includes driving a motor using a first inverter and a second inverter connected in series with each other, the first inverter being connected to the battery and the second inverter being connected to the battery via an isolated power converter; and charging the battery via a power factor correction device, the power factor correction device including windings of the motor and a switch of the second inverter.

[0025] The method further includes charging the battery using a three-phase power supply, wherein the power factor correction device is used to adjust the input current flowing into the power factor correction device to achieve a power factor within a uniform threshold range.

[0026] The first inverter includes three branches, each of which has an output terminal. The second inverter includes a first inverter unit, a second inverter unit, and a third inverter unit, wherein a first output terminal of the first inverter is connected in series with the output of the first inverter unit and further connected to a first phase of the motor, a second output terminal of the inverter is connected in series with the output of the second inverter unit and further connected to a second phase of the motor, and a third output terminal of the first inverter is connected in series with the output of the third inverter unit and further connected to a third phase of the motor. The isolated power converter includes a primary winding, a first stage winding, a second stage winding, and a third stage winding, wherein the primary winding is connected to the battery through a primary switching network, the first stage winding is connected to the first inverter unit through a first rectifier, the second stage winding is connected to the second inverter unit through a second rectifier, and the third stage winding is connected to the third inverter unit through a third rectifier.

[0027] The method further includes charging the battery using a three-phase power supply, wherein the three-phase power supply is connected to the first inverter unit via an EMI filter and a first inductor, wherein the three-phase power supply is connected to the second inverter unit via the EMI filter and a second inductor, and wherein the three-phase power supply is connected to the first inverter unit via the EMI filter and a third inductor.

[0028] One advantage of embodiments of this disclosure is that the high-efficiency power conversion system combines the motor drive unit and the isolated battery charger into a single system, thereby improving the efficiency, reliability, and cost of the power conversion system.

[0029] To better understand the detailed description of this disclosure below, the features and technical advantages of this disclosure have been broadly outlined above. Additional features and advantages of this disclosure, which form the subject matter of the claims, will be described below. Those skilled in the art will understand that the disclosed concepts and specific embodiments can readily serve as the basis for modifications or the design of other structures or processes to perform the same purposes of this disclosure. Those skilled in the art will also recognize that these equivalent structures do not depart from the spirit and scope of this disclosure as set forth in the appended claims. Attached Figure Description

[0030] To gain a more complete understanding of this disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein:

[0031] Figure 1 Power conversion systems according to various embodiments of the present disclosure are shown;

[0032] Figure 2 Various embodiments according to this disclosure are illustrated. Figure 1 A block diagram of a first implementation of the power conversion system is shown;

[0033] Figure 3 illustrates various embodiments according to the present disclosure. Figure 2 A schematic diagram of the power conversion system is shown;

[0034] Figure 4 A block diagram of a first implementation of an isolated converter according to various embodiments of the present disclosure is shown in FIG3;

[0035] Figure 5 Various embodiments according to this disclosure are illustrated. Figure 4 A schematic diagram of a first implementation of an isolated converter is shown;

[0036] Figure 6 Various embodiments according to this disclosure are illustrated. Figure 4 A schematic diagram of a second implementation of an isolated converter is shown;

[0037] Figure 7 A block diagram of a second implementation of an isolated converter according to various embodiments of the present disclosure is shown in FIG3;

[0038] Figure 8 Various embodiments according to this disclosure are illustrated. Figure 7 A schematic diagram of a first implementation of an isolated converter is shown;

[0039] Figure 9 Various embodiments according to this disclosure are illustrated. Figure 7 A schematic diagram of a second implementation of an isolated converter is shown;

[0040] Figure 10 A schematic diagram of a first inverter shown in FIG3 according to various embodiments of the present disclosure is illustrated;

[0041] Figure 11 A schematic diagram of an inverter unit shown in FIG3 according to various embodiments of the present disclosure is illustrated;

[0042] Figure 12 Various embodiments according to this disclosure are illustrated. Figure 1 A block diagram of a second implementation of the power conversion system is shown;

[0043] Figure 13 Various embodiments according to this disclosure are illustrated. Figure 12 A schematic diagram of the power conversion system is shown;

[0044] Figure 14 Various embodiments according to this disclosure are illustrated. Figure 1 A block diagram of the third implementation of the power conversion system is shown;

[0045] Figure 15 Various embodiments according to this disclosure are illustrated. Figure 14 A schematic diagram of the power conversion system is shown;

[0046] Figure 16 Various embodiments according to this disclosure are illustrated. Figure 15 A schematic diagram of the inverter unit is shown;

[0047] Figure 17 Various embodiments according to this disclosure are illustrated. Figure 1 A block diagram of the fourth implementation of the power conversion system is shown;

[0048] Figure 18 illustrates various embodiments according to the present disclosure. Figure 17 A schematic diagram of the power conversion system is shown;

[0049] Figure 19 A schematic diagram of a first inverter shown in FIG18 according to various embodiments of the present disclosure is illustrated.

[0050] Figure 20 A schematic diagram of a second inverter shown in FIG18 according to various embodiments of the present disclosure is illustrated.

[0051] Figure 21 Various embodiments according to this disclosure are illustrated. Figure 1 A block diagram of the fifth implementation of the power conversion system is shown;

[0052] Figure 22 illustrates various embodiments according to the present disclosure. Figure 21 A schematic diagram of the power conversion system is shown; and

[0053] Figure 23 Various embodiments according to this disclosure are illustrated. Figure 1 A block diagram of the sixth implementation of the power conversion system is shown;

[0054] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to corresponding parts. The accompanying drawings are provided to clearly illustrate relevant aspects of the various embodiments, and the drawings are not necessarily drawn to scale. Detailed Implementation

[0055] The following describes in detail the making and use of the presently preferred embodiments. However, it should be understood that this disclosure provides many applicable inventive concepts that can be embodied in a variety of specific environments. The specific embodiments discussed merely illustrate specific methods of making and using this disclosure and do not limit the scope of this disclosure.

[0056] This disclosure will describe preferred embodiments in a specific context, namely an integrated motor drive and isolated battery charger power conversion system. However, this disclosure is also applicable to various power conversion systems. Various embodiments will be described in detail below with reference to the accompanying drawings.

[0057] Figure 1 A power conversion system according to various embodiments of the present disclosure is illustrated. The power conversion system 100 includes a direct current (DC) power supply 110, a motor 120, an alternating current (AC) power supply 130, a first inverter 150, and a second inverter 160. (As...) Figure 1 As shown, the input of the first inverter 150 is connected to the DC power supply 110. Similarly, the input of the second inverter 160 is connected to the DC power supply 110. The outputs of the first inverter 150 and the second inverter 160 are connected in series and further connected to the motor 120. More specifically, the first output terminal of the first inverter 150 is directly connected to the motor 120. The second output terminal of the first inverter 150 is connected to the first output terminal of the second inverter 160. The second output terminal of the second inverter 160 is directly connected to the motor 120.

[0058] It should be noted that the connection between inverters 150 and 160 and motor 120 is an exemplary implementation of two inverters connected in series to drive a motor. Those skilled in the art will recognize many variations, substitutions, and modifications. For example, Figure 1 Each inverter shown can have more than two output terminals.

[0059] AC power supply 130 is connected to the common node of the first inverter 150 and the second inverter 160. Depending on the application and design requirements, AC power supply 130 can be implemented as a three-phase AC power supply or a single-phase AC power supply. Similarly, DC power supply 110 can be implemented as a single battery or a battery pack including multiple batteries connected in series and / or in parallel. Depending on the application and design requirements, motor 120 can be implemented as a three-phase motor, a two-phase motor, or a single-phase motor.

[0060] In operation, the first inverter 150 is used to convert the DC waveform from the DC power supply 110 into a first pulse width modulated (PWM) waveform, such as a three-level PWM waveform. The first inverter 150 can be implemented as any suitable inverter topology, such as a full-bridge inverter. The following will refer to... Figure 2-2 2. A detailed implementation of the first inverter 150 is described.

[0061] In operation, an isolated power converter (not shown, but...) can be used. Figure 2(As shown in the diagram) The DC waveform from DC power supply 110 is converted into an intermediate DC waveform. A second inverter 160 is used to convert the intermediate DC waveform into a second PWM waveform, such as a three-level PWM waveform. The second inverter 160 can be implemented as any suitable inverter topology, such as a full-bridge inverter. The isolated power converter can be implemented as any suitable isolated power conversion topology, such as an inductor-inductor-capacitor (LLC) resonant converter. References below will be made to... Figure 2-2 2. A detailed implementation of the second inverter 160 and the isolated power converter is described.

[0062] In operation, a first PWM waveform generated by the first inverter 150 and a second PWM waveform generated by the second inverter 160 are added together to form a multi-level PWM waveform, such as a five-level PWM waveform. In some embodiments, the first PWM waveform and the second PWM waveform are synchronized. The first PWM waveform and the second PWM waveform are directly added together. In an alternative embodiment, there is a phase shift between the first PWM waveform and the second PWM waveform. Due to the phase shift between the first PWM waveform and the second PWM waveform, the voltage waveform applied to the motor 120 is not a three-level PWM waveform. Instead, the voltage waveform applied to the motor 120 is a multi-level waveform. The number of levels of the multi-level waveform can vary depending on the degree of phase shift. In some embodiments, the number of levels of the multi-level waveform is equal to five.

[0063] One advantageous feature of applying multi-level waveforms to motor 120 is that the multi-level waveforms follow a sinusoidal waveform. As a result, the harmonic content is lower. For example, by selecting the phase shift between the first and second PWM waveforms, major harmonics such as the fifth harmonic can be eliminated. Another advantageous feature of having multi-level waveforms is that they help simplify the design of the filter circuits in the motor drive system.

[0064] In some embodiments, the power conversion system 100 is configured to operate in a motor drive mode. The DC voltage from the DC power supply 110 is converted into an AC voltage for driving the motor 120. Alternatively, the power conversion system 100 is configured to operate in a battery charging mode. The battery in the DC power supply 110 is charged using the AC power supply 130.

[0065] During operation, in battery charging mode, AC power supply 130 provides power to charge DC power supply 110. During battery charging mode, the windings of motor 120 and the switches of the second inverter 160 form a power factor correction device. The power factor correction device is configured to adjust the power factor of the power conversion system 100 to approximately a uniform level by adjusting the input current flowing into the power factor correction device. It should be noted that various devices can achieve power factors within different ranges. For example, a range could be from 0.99 to 1. The above range is set for a given device and may depend on various factors.

[0066] In operation, during motor drive mode, to achieve high efficiency, power from DC power supply 110 to motor 120 is transmitted via two paths: a first path including the first inverter 150 and a second path including the second inverter 160 and its associated isolated power converter. In some embodiments, the power flowing from DC power supply 110 to motor 120 via the second inverter 160 is a portion of the power flowing from DC power supply 110 to motor 120 via the first inverter 150. For example, only about 15% of the total power passes through the second inverter 160. The majority (85%) of the total power passes through the first inverter 150. The design of the first inverter 150 and the second inverter 160 can be adjusted accordingly based on the different power distribution between the two paths. For example, the rated voltage of the switch of the second inverter 160 may be lower than the rated voltage of the switch of the first inverter 150. The lower rated voltage of the components (e.g., the switch) of the second inverter 160 helps to reduce costs and improve the efficiency of the second inverter 160. In other words, uneven power distribution between two different power transmission paths helps improve the performance (e.g., efficiency and cost) of the power conversion system 100.

[0067] have Figure 1 Another advantageous feature of the power conversion system 100 shown is that it can provide voltage boost by connecting the outputs of the first inverter 150 and the second inverter 160 in series. This voltage boost helps improve the performance of the motor 120 when it is operating at high speed.

[0068] have Figure 1 Another advantageous feature of the illustrated power conversion system 100 is that it enables fast on-board charging by reusing the windings of the motor 120 as part of a power factor correction circuit. The power conversion system 100 can combine an on-board battery charger (OBC) and a motor control unit (MCU) into a single system.

[0069] Figure 2 Various embodiments according to this disclosure are illustrated. Figure 1 The diagram shows a block diagram of a first implementation of a power conversion system. The power conversion system 200 includes a DC power supply 110, a motor 121, an AC power supply 131, a first inverter 151, a second inverter 161, and an isolated converter 171.

[0070] like Figure 2 As shown, the two inputs of the first inverter 151 are connected to the two outputs of the DC power supply 110. The two inputs of the isolated converter 171 are connected to the two outputs of the DC power supply 110. The isolated converter 171 includes six output terminals that are connected to the six inputs of the second inverter 161. The isolated converter 171 provides electrical isolation between the inputs of the first inverter 151 and the inputs of the second inverter 161, such that the outputs of the first inverter 151 and the second inverter 161 can be added to generate a multi-level PWM waveform for driving the motor 121.

[0071] In some embodiments, the isolated converter 171 is implemented as a high-frequency (HF) bridge LLC power converter. Alternatively, the isolated converter 171 is implemented as a full-bridge LLC power converter. A detailed implementation of the isolated converter 171 will now be discussed with reference to FIG3.

[0072] It should be noted that implementing the isolated converter 171 as an LLC power converter is merely an example and should not unduly limit the scope of the claims. Those skilled in the art will recognize many variations, substitutions, and modifications. For example, the isolated converter 171 can be implemented as any suitable isolated power converter, such as a flyback converter, a forward converter, a push-pull converter, a half-bridge converter, a full-bridge converter, any combination thereof, etc.

[0073] like Figure 2 As shown, the first inverter 151 has three outputs. The second inverter 161 has six outputs. The three outputs of the second inverter 161 are connected to the three outputs of the first inverter 151, respectively. The other three outputs of the second inverter 161 are connected to the three phases (A, B, and C) of the motor 121, respectively. The AC power supply 131 has three outputs, which are connected to the common node of the first inverter 151 and the second inverter 161, respectively. A detailed implementation of the power conversion system 200 will be discussed below with reference to FIG3.

[0074] In some embodiments, the DC power supply 110 is implemented as a battery pack for an electric vehicle. The AC power supply 131 is implemented as a three-phase AC power supply from the power grid. The motor 121 is a three-phase induction motor.

[0075] In operation, the power conversion system 200 can operate in motor drive mode, where power is delivered from DC power supply 110 to motor 121 via first inverter 151 and second inverter 161. The outputs of first inverter 151 and second inverter 161 are connected in series to generate a multi-level waveform for driving motor 121. Alternatively, the power conversion system 200 can operate in battery charging mode, where power is delivered from AC power supply 131 to DC power supply 110 (battery pack) via windings of motor 121, second inverter 161, and isolated converter 171.

[0076] Figure 3A and Figure 3B Various embodiments according to this disclosure are illustrated. Figure 2 A schematic diagram of the power conversion system is shown. Throughout the description, Figure 3A and Figure 3B Collectively referred to as Figure 3. The power conversion system 200 includes a DC power supply 110, a motor 121, an AC power supply 131, a first inverter 151, a second inverter 161, and an isolated converter 171.

[0077] As shown in Figure 3, the DC power supply 110 includes multiple batteries connected in series. The DC power supply 110 also includes an output capacitor C1, a first operation control switch K1, and a second operation control switch Kc. The output capacitor C1 is used to reduce ripple and provide a stable DC voltage to the power conversion system 200.

[0078] As shown in Figure 3, the motor 121 includes three windings arranged in a Y-shape. The common node of the three windings is connected to the neutral point N via switch Q1. The AC power supply 131 can be a three-phase AC power supply. In some embodiments, the output voltage of the AC power supply 131 is in the range of about 220V to about 240V. Alternatively, depending on different design requirements, the AC power supply 131 can be implemented as a two-phase power supply or a single-phase power supply.

[0079] The operation of the power conversion system 200 is controlled using a first operating control switch K1 and a second operating control switch Kc. More specifically, during motor drive mode, both the first and second operating control switches K1 and Kc remain closed. The output of the isolated converter 171 is connected in series with the output voltage of the battery, and the sum of the two can boost the DC voltage of the power conversion system 200. During battery charging mode, the first operating control switch K1 is open. AC power charges the battery through the second inverter 161 and the isolated converter 171. More specifically, the isolated converter 171 operates in reverse power flow mode and charges the battery voltage of the DC power supply 110.

[0080] The first inverter 151 is a full-bridge inverter comprising three branches. The midpoint of each branch is the output of the first inverter 151. As shown in Figure 3, the first inverter 151 has three outputs. The following will refer to... Figure 10 A detailed schematic diagram of the first inverter 151 is discussed.

[0081] The second inverter 161 includes three inverter units, each of which is a full-bridge inverter with two branches. The midpoint of each branch is the output of the full-bridge inverter. As shown in Figure 3, each inverter unit has two outputs. The following will refer to... Figure 11 Detailed example diagrams of the inverter unit are discussed.

[0082] The isolated converter 171 can be implemented as an LLC resonant converter. The isolated converter 171 includes a primary switching network 141, a primary winding NP1, a first-stage winding NS1, a second-stage winding NS2, a third-stage winding NS3, and three rectifiers 142. As shown in Figure 3, the primary winding NP1 is connected to the battery through the primary switching network 141. The first-stage winding NS1 is connected to the first inverter unit through the first rectifier. The second-stage winding NS2 is connected to the second inverter unit through the second rectifier. The third-stage winding NS3 is connected to the third inverter unit through the third rectifier.

[0083] Transformer T1 provides electrical isolation between the primary side (the side with the primary switching network 141) and the secondary side (the side with the rectifier 141) of the isolated converter 171. According to one embodiment, transformer T1 may be formed by one primary transformer winding (e.g., winding NP1) and three secondary transformer windings (e.g., windings NS1-NS3), as shown in FIG3. It should be noted that the transformers shown herein and throughout the description are merely examples and should not unduly limit the scope of the claims. Many variations, substitutions, and modifications will be recognized by those skilled in the art. For example, transformer T1 may also include various bias windings and gate drive auxiliary windings.

[0084] The rectifier (e.g., the first rectifier) ​​converts the alternating polarity waveform received from the secondary winding (e.g., winding NS1) of transformer T1 into a unipolar waveform. (Refer to the following...) Figure 4-9 The detailed operation and structure of the isolated converter 171 are discussed.

[0085] The power conversion system 200 also includes input capacitors C2, C3, and C4, and output capacitors C5, C6, and C7. Input capacitors C2, C3, and C4 are used to reduce ripple and provide stable input DC voltages to the primary switching network 141 and the first inverter 151, respectively. Furthermore, the common node of input capacitors C3 and C4 can be connected to the neutral point of the power conversion system, as indicated by the dashed line in Figure 3. Output capacitors C5, C6, and C7 are used to reduce ripple and provide stable input DC voltages to the second inverter 161, respectively.

[0086] In some embodiments, the isolated converter 171 and the second inverter 161 form a bidirectional power conversion system. In operation, when the power conversion system 200 is used to convert DC power to AC power to drive the motor 121, the isolated converter 171 is configured as an isolated DC / DC converter to convert the battery's output voltage into three suitable DC voltages, respectively applied to the three inverter units. On the other hand, when the power conversion system 200 is used to convert AC power to DC power to charge the battery, the windings of the motor 121 and the switches of the second inverter 161 form a power factor correction device. In some embodiments, the power factor correction device is configured to adjust the power factor of the power conversion system 200 to approximately a uniform level by adjusting the input current flowing into the power factor correction device. The power factor correction device can be implemented as any suitable power factor correction converter, such as a boost power factor correction rectifier. When the power conversion system 200 is used to convert AC power to DC power to charge the battery, the isolated converter 171 operates in reverse power flow mode to charge the battery voltage.

[0087] As shown in Figure 3, the AC power supply 131 also includes an EMI filter and three inductors L1-L3. The EMI filter may include multiple capacitors. Inductors L1-L3 allow DC or low-frequency current to pass through while blocking unwanted high-frequency current. The capacitors of the EMI filter provide a low-impedance path to divert unwanted high-frequency current or noise from the EMI filter. Unwanted high-frequency current either returns to the input power supply or returns to ground. Due to the use of the EMI filter, the power conversion system 200 can meet various EMI regulations.

[0088] The switch shown in Figure 3 can be implemented as an insulated-gate bipolar transistor (IGBT) device. Alternatively, the switch can be formed from other types of controllable devices, such as metal-oxide-semiconductor field-effect transistor (MOSFET) devices, bipolar junction transistor (BJT) devices, super junction transistor (SJT) devices, etc.

[0089] Figure 4 A block diagram of a first implementation of an isolated converter according to various embodiments of the present disclosure is shown in FIG3. The isolated converter 171 includes a primary HF bridge 141, a primary winding NP, a plurality of second windings NS, and a plurality of secondary HF bridges 142. Figure 4 As shown, the primary winding NP and multiple secondary windings NS are magnetically coupled to form transformer T1. The number of secondary windings and associated secondary HF bridges can be selected accordingly based on different design requirements and applications. Referring back to Figure 3, three secondary windings and three secondary HF bridges have been utilized to provide isolated power to the three inverter units of the second inverter 161. The following will refer to... Figure 5-6 The detailed structure of the primary HF bridge 141 and the secondary HF bridge 142 is described. For simplicity, Figure 5-6 It contains only one secondary HF bridge.

[0090] Figure 5 Various embodiments according to this disclosure are illustrated. Figure 4 A schematic diagram of a first implementation of an isolated converter is shown. The isolated converter 171 is implemented as a three-level LLC power converter. Throughout the description, the isolated converter 171 may alternatively be referred to as a three-level LLC power converter. The primary HF bridge 141 may alternatively be referred to as the primary network. The secondary HF bridge 142 may alternatively be referred to as the secondary network.

[0091] In some embodiments, the input of the three-level LLC power converter 171 is connected to the battery shown in FIG3. In some embodiments, the input voltage of the three-level LLC power converter 171 is a first DC voltage in the range of approximately 240V to approximately 490V. The output of the three-level LLC power converter 171 is a second DC voltage in the range of approximately 50V to approximately 200V.

[0092] like Figure 5As shown, the three-level LLC power converter 171 includes a primary network 141, a transformer T1, and a secondary network 142. The primary network 141 includes input capacitors C1 and C2, a switching network, and a resonant circuit. The transformer T1 includes a primary winding NP and a secondary winding NS. The secondary network 142 includes a secondary resonant capacitor Cr2, a rectifier, and output capacitors Co1 and Co2. Figure 5 As shown, the switching network, resonant circuit, transformer T1, and rectifier are coupled to each other and cascaded.

[0093] The switching network includes switches S21, S22, S23, and S24 connected in series between the positive terminal of input capacitor C1 and the negative terminal of input capacitor C2. The common node of switches S22 and S23 is connected to the common node of capacitors C1 and C2. The common node of switches S21 and S22 is connected to the first terminal of transformer T1 via a resonant circuit. The common node of switches S23 and S24 is connected to the second terminal of transformer T1.

[0094] Resonant circuits can be implemented in a variety of ways. For example, a resonant circuit includes a series resonant inductor Lr, a parallel resonant inductor Lm, and a series resonant capacitor Cr1.

[0095] Series resonant inductors and parallel resonant inductors can be implemented as external inductors. Those skilled in the art will recognize that many variations, substitutions, and modifications are possible. For example, a series resonant inductor can be implemented as the leakage inductance of transformer T1.

[0096] In summary, a resonant circuit comprises three key resonant elements: a series resonant inductor, a series resonant capacitor, and a parallel resonant inductor. This configuration is commonly referred to as an LLC resonant converter. Based on the operating principle of an LLC resonant converter, at a switching frequency approximately equal to the resonant frequency of the circuit, the resonant circuit facilitates zero-voltage switching of the primary-side switching elements and zero-current switching of the secondary-side switching elements.

[0097] Transformer T1 can be formed by two transformer windings, i.e. Figure 5 The primary transformer winding NP and the secondary transformer winding NS are shown. Alternatively, transformer T1 may have a center-tapped secondary winding, thus having three transformer windings, including a primary transformer winding, a first secondary transformer winding, and a second secondary transformer winding.

[0098] Secondary network 142 converts the alternating polarity waveform received from the secondary winding NS of transformer T1 into a unipolar waveform, which is applied to the input of the inverter unit (as shown in Figure 3). Two output capacitors, Co1 and Co2, are connected in series between the first and second outputs of the isolated converter 171. Output capacitors Co1 and Co2 are used to reduce ripple components and provide a stable DC voltage to the inverter unit.

[0099] Secondary network 142 includes secondary resonant capacitor Cr2, switches S31, S32, S33 and S34, and diodes D31, D32, D33 and D34. For example... Figure 5 As shown, switches S31, S32, S33, and S34 are connected in series between the first and second outputs of the isolated converter 171. The common node of switches S32 and S33 is connected to the common node of capacitors Co1 and Co2. The common node of switches S31 and S32 is connected to the first terminal of the secondary winding NS through the secondary resonant capacitor Cr2. The common node of switches S33 and S34 is directly connected to the second terminal of the secondary winding NS.

[0100] It should be noted that the schematic diagram of secondary network 142 is merely an example and should not unduly limit the scope of the claims. Those skilled in the art will recognize many variations, substitutions, and modifications. For example, secondary network 142 may include a secondary resonant circuit (resonant inductor and resonant capacitor). In particular, when the isolated power converter 171 operates in reverse power flow mode, the secondary resonant circuit is necessary to improve the efficiency of the isolated power converter 171.

[0101] According to one embodiment, the switches (e.g., switches S21-S24 and S31-S34) can be insulated-gate bipolar transistor (IGBT) devices. Alternatively, Figure 5The switching element shown can be any controllable switch, such as a metal-oxide-semiconductor field-effect transistor (MOSFET) device, an integrated gate-commutated thyristor (IGCT) device, a gate-turn-off thyristor (GTO) device, a silicon-controlled rectifier (SCR) device, a junction-gate field-effect transistor (JFET) device, a MOS controlled thyristor (MCT) device, a gallium nitride (GaN)-based power device, a silicon carbide (SiC)-based power device, etc. Throughout the description, the switch symbols (e.g., the symbol for an IGBT) are merely examples. Depending on the application and design requirements, the switch shown in this disclosure can be any controllable switch.

[0102] It should be noted that when switches S21-S24 and S31-S34 are implemented using MOSFET devices, the body diodes of switches S21-S24 and S31-S34 can be used to provide a freewheeling path. On the other hand, when switches S21-S24 and S31-S34 are implemented using IGBT devices, a separate freewheeling diode is required, connected in parallel with its corresponding switch.

[0103] like Figure 5 As shown, diodes D21-D24 and D31-D34 require a reverse conduction path. In other words, diodes D21-D24 and D31-D34 are anti-parallel diodes. In some embodiments, diodes D21-D24 and D31-D34 are co-packaged with their respective IGBT devices S21-S24 and S31-S34. In alternative embodiments, diodes D21-D24 and D31-D34 are placed outside their respective IGBT devices S21-S24 and S31-S34.

[0104] It should also be noted that, although Figure 5 Each bidirectional switch is shown to be formed by diodes and IGBT devices connected in an anti-parallel arrangement, but those skilled in the art will recognize many variations, substitutions, and modifications. For example, bidirectional switches can be implemented using novel semiconductor switches, such as anti-parallel reverse-blocking IGBT arrangements. The discussion of IGBT devices herein applies to other IGBT devices disclosed herein.

[0105] Figure 5 An advantageous feature of the illustrated three-level LLC power converter 171 is that the power conversion system can achieve high efficiency under a wide range of operating conditions. For example, the battery voltage and output voltage of the power conversion system 200 can vary over a wide range. This wide range may lead to a decrease in efficiency. Figure 5 The illustrated three-level LLC power converter 171 uses a three-level switching bridge on both the primary and secondary sides. The three-level switching bridge is suitable for applications with a wide voltage range. Due to the presence of the three-level LLC power converter 171, the power conversion system 200 can operate at a switching frequency substantially equal to the resonant frequency of the LLC power converter 171, thereby improving the efficiency of the three-level LLC power converter 171.

[0106] Figure 6 Various embodiments according to this disclosure are illustrated. Figure 4 A schematic diagram of a second implementation of an isolated converter is shown. Figure 6 The isolated converter 171 shown is Figure 5 The diagram is similar, except that the isolated converter 171 is implemented as a three-level dual-active-bridge (DAB) converter. Figure 6 The structure of the three-level DAB converter shown is similar to Figure 5 The diagram is similar, except that it does not include the resonant capacitor. Figure 6 The three-level DAB converter shown is well-known, so it will not be discussed in detail here.

[0107] Figure 7 A block diagram of a second implementation of an isolated converter shown in FIG3 according to various embodiments of the present disclosure is illustrated. The isolated converter 171 is implemented as a power converter having an interleaved multi-bridge circuit. The isolated converter 171 includes a first primary network 143, a first transformer T1, a second primary network 144, a second transformer T2, and an interleaved multi-bridge circuit 145.

[0108] The first primary network 143 is connected to the primary winding NP1 of the first transformer T1. The second primary network 144 is connected to the primary winding NP2 of the second transformer T2. The interleaved multi-bridge circuit 145 is connected to the secondary winding NS1 of the first transformer T1 and the secondary winding NS2 of the second transformer T2. (Refer to the following...) Figure 8-9 A detailed schematic diagram of the isolated converter 171 is discussed.

[0109] Figure 8 Various embodiments according to this disclosure are illustrated. Figure 7 A schematic diagram of a first implementation of an isolated converter is shown. Figure 8As shown, the isolated converter 171 includes two transformers T1 and T2. The primary side of transformer T1 is connected to a first primary network 143 including switches S21-S24 and diodes D21-D24. The first primary network 143 also includes a first resonant circuit comprising a resonant inductor Lr1 and a resonant capacitor Cr1. The first primary network 143 is the primary side of the three-level LLC power converter. Similarly, the primary side of transformer T2 is connected to a second primary network 144 including switches S11-S14 and diodes D11-D14. The second primary network 144 also includes a second resonant circuit comprising a resonant inductor Lr3 and a resonant capacitor Cr3. The second primary network 144 is the primary side of the three-level LLC power converter. The primary side of the three-level LLC power converter has already been described above. Figure 5 Since it has already been described, it will not be discussed further in this article.

[0110] The secondary sides of transformer T1 and transformer T2 are connected to an interleaved multi-bridge circuit 145. For example... Figure 8 As shown, the inputs of the interleaved multi-bridge circuit 145 are connected to the secondary windings NS1 and NS2, respectively. The output of the interleaved multi-bridge circuit 145 is connected to the output capacitor Co.

[0111] like Figure 8 As shown, the interleaved multi-bridge circuit 145 includes three branches. The first branch includes a first switch S31 and a second switch S32 connected in series. The second branch includes a third switch S33 and a fourth switch S34 connected in series. The third branch includes a fifth switch S35 and a sixth switch S36 connected in series. The secondary winding NS1 of the first transformer T1 is connected between the common node of the first switch S31 and the second switch S32 and the common node of the third switch S33 and the fourth switch S34 through a resonant capacitor Cr2. The secondary winding NS2 of the second transformer T2 is connected between the common node of the fifth switch S35 and the sixth switch S36 and the common node of the third switch S33 and the fourth switch S34 through a resonant capacitor Cr4.

[0112] During operation, the secondary windings NS1 and NS2 are connected in parallel or in series depending on the phase shift between the two primary networks 143 and 144. When the phase shift between the switches of primary network 143 and 144 is zero degrees, the secondary windings NS1 and NS2 are connected in series. Switches S31 and S36 are on during the first half-cycle. Switches S32 and S35 are on during the second half-cycle. Conversely, when the phase shift between the switches of primary network 143 and 144 is 180 degrees, the secondary windings NS1 and NS2 are connected in parallel. During the first half-cycle, switches S31 and S34 are on to transfer power from the secondary winding NS1 to the load. Switches S35 and S34 are on to transfer power from the secondary winding NS2 to the load. During the second half-cycle, switches S32 and S33 are on to transfer power from the secondary winding NS1 to the load. Switches S33 and S36 are turned on to transfer power from the secondary winding NS2 to the load.

[0113] An advantageous feature of having a phase shift between the two primary networks 143 and 144 is that the isolated converter 171 is capable of operating with a wide battery input voltage and a wide output voltage.

[0114] Figure 9 Various embodiments according to this disclosure are illustrated. Figure 7 A schematic diagram of a second implementation of an isolated converter is shown. Figure 9 The isolated converter shown is Figure 8 The diagram is similar, except that the three-level LLC converter 171 is replaced by a three-level DAB converter. Three-level DAB converters are well-known and will not be discussed further here.

[0115] Figure 10 A schematic diagram of a first inverter shown in FIG3 according to various embodiments of the present disclosure is illustrated. The first inverter 151 is a three-phase inverter for converting DC voltage into three AC waveforms. The first inverter 151 includes six switches. The six switches form three branches. The first branch includes switches S51 and S52 connected in series between the positive and negative terminals of the input of the first inverter 151. The common node of switches S51 and S52 is connected to the first output terminal V11 of the first inverter 151.

[0116] The second branch includes switches S53 and S54 connected in series between the positive and negative terminals of the input of the first inverter 151. The common node of switches S53 and S54 is connected to the second output terminal V12 of the first inverter 151. The third branch includes switches S55 and S56 connected in series between the positive and negative terminals of the input of the first inverter 151. The common node of switches S55 and S56 is connected to the third output terminal V13 of the first inverter 151. Figure 10 The working principle of the three-phase inverter shown is well known, and will not be discussed further in this article to avoid repetition.

[0117] like Figure 10 As shown, diodes D51-D56 require a reverse conduction path. In other words, diodes D51-D56 are anti-parallel diodes. In some embodiments, diodes D51-D56 are co-packaged with their respective IGBT devices S51-S56. In alternative embodiments, diodes D51-D56 are placed outside their respective IGBT devices S51-S56.

[0118] Figure 11 A schematic diagram of an inverter unit shown in FIG3 according to various embodiments of the present disclosure is illustrated. The three inverter units shown in FIG3 form a three-phase inverter. Each inverter unit is a single-phase inverter. The inverter units shown in FIG3 have the same structure. For simplicity, Figure 11 Only one inverter unit is shown in the diagram.

[0119] Inverter unit 161 is a single-phase inverter used to convert DC voltage into AC waveform. Inverter unit 161 includes four switches. The four switches form two branches. The first branch includes switches S61 and S62 connected in series between the positive and negative terminals of the input of inverter unit 161. The common node of switches S61 and S62 is connected to the first output terminal V11 of inverter unit 161.

[0120] The second branch includes switches S63 and S64 connected in series between the positive and negative terminals of the input of inverter unit 161. The common node of switches S63 and S64 is connected to the second output terminal V12 of inverter unit 161. Figure 11 The operating principle of the single-phase inverter shown is well known, so it will not be discussed further in this article.

[0121] like Figure 11 As shown, diodes D61-D64 require a reverse conduction path. In other words, diodes D61-D64 are anti-parallel diodes. In some embodiments, diodes D61-D64 are co-packaged with their respective IGBT devices S61-S64. In alternative embodiments, diodes D61-D64 are placed outside their respective IGBT devices S61-S64.

[0122] Figure 12 Various embodiments according to this disclosure are illustrated. Figure 1 A block diagram of a second implementation of the power conversion system is shown. Figure 12 The power conversion system 300 shown is Figure 2The power conversion system 200 shown is similar, except that the second inverter 162 includes two inverter units and the isolated converter 172 includes two secondary circuits. Furthermore, the AC power supply 132 can be a single-phase or two-phase power supply.

[0123] Figure 13 Various embodiments according to this disclosure are illustrated. Figure 12 A schematic diagram of the power conversion system is shown. Power conversion system 300 and... Figure 2 The power conversion system 200 shown is similar. Therefore, to avoid repetition, the common parts of the two systems will not be discussed further.

[0124] The isolated converter 172 includes two secondary windings, NS1 and NS2. Two rectifiers 142 are connected to the two secondary windings, respectively. The two rectifiers 142 generate two DC voltages, which are fed into capacitors C5 and C6, respectively.

[0125] like Figure 13 As shown, the second inverter 162 includes two inverter units. The first output of the first inverter 151 is connected to the first output of the first inverter unit. The second output of the first inverter unit is connected to the first phase of the motor 121. The second output of the first inverter 151 is connected to the first output of the second inverter unit. The second output of the second inverter unit is connected to the second phase of the motor 121. The third output of the first inverter 151 is directly connected to the third phase of the motor 121.

[0126] AC power supply 132 is for single-phase or two-phase power. For example... Figure 13 As shown, AC power supply 132 is connected to the second inverter 162 via an EMI filter and two inductors L1 and L2. The operating principle of power conversion system 300 is similar to that of power conversion system 200 described above, and therefore will not be discussed further here.

[0127] Figure 14 Various embodiments according to this disclosure are illustrated. Figure 1 A block diagram of the third implementation of the power conversion system is shown. Figure 14 The power conversion system 400 shown is... Figure 12 The power conversion system 300 shown is similar, except... Figure 14 The inverter unit of the second inverter 163 shown is implemented as a three-phase inverter. Furthermore, the AC power supply 133 can be a single-phase power supply, a two-phase power supply, or a three-phase power supply.

[0128] Figure 15 Various embodiments according to this disclosure are illustrated. Figure 14 A schematic diagram of the power conversion system is shown. Power conversion system 400 and... Figure 13 The power conversion system 300 shown is similar. Therefore, to avoid repetition, the common parts of the two systems will not be discussed further.

[0129] like Figure 15 As shown, the second inverter 163 includes two inverter units. Each inverter unit of the second inverter 163 is implemented as a three-phase inverter with three outputs, similar to the first inverter 151.

[0130] The first output of the first inverter 151 is connected to the first output of the first inverter unit and the first phase of the AC power supply 133. The second output of the first inverter unit is connected to the first phase of the motor 121. The third output of the first inverter unit is connected to the third output of the second inverter unit and the second phase of the AC power supply 133.

[0131] The second output of the first inverter 151 is connected to the first output of the second inverter unit and the third phase of the AC power supply 133. The second output of the second inverter unit is connected to the third phase of the motor 121. The third output of the first inverter 151 is directly connected to the third phase of the motor 121.

[0132] AC power supply 133 is a three-phase power supply. Alternatively, AC power supply 133 can be a single-phase or two-phase power supply. In some embodiments, the output voltage of AC power supply 131 is in the range of approximately 220V to approximately 240V. Figure 15 As shown, AC power supply 133 is connected to the second inverter 162 through an EMI filter.

[0133] Figure 16 Various embodiments according to this disclosure are illustrated. Figure 15 The diagram shows a schematic of the inverter unit. Inverter unit 163 is a three-phase inverter used to convert DC voltage into three AC waveforms. Inverter unit 163 includes six switches. The six switches form three branches. The first branch includes switches S71 and S72 connected in series between the positive and negative terminals of the input of inverter unit 163. The common node of switches S71 and S72 is connected to the first output terminal V11 of inverter unit 163. The second branch includes switches S73 and S74 connected in series between the positive and negative terminals of the input of inverter unit 163. The common node of switches S73 and S74 is connected to the second output terminal V12 of inverter unit 163. The third branch includes switches S75 and S76 connected in series between the positive and negative terminals of the input of inverter unit 163. The common node of switches S75 and S76 is connected to the third output terminal V13 of inverter unit 163. Figure 16 The operating principle of the three-phase inverter shown is well known, so it will not be discussed further in this article.

[0134] like Figure 16As shown, diodes D71-D76 require a reverse conduction path. In other words, diodes D71-D76 are anti-parallel diodes. In some embodiments, diodes D71-D76 are co-packaged with their respective IGBT devices S71-S76. In alternative embodiments, diodes D71-D76 are placed outside their respective IGBT devices S71-S76.

[0135] Figure 17 Various embodiments according to this disclosure are illustrated. Figure 1 The block diagram shown is for the fourth implementation of the power conversion system. Figure 17 The power conversion system 500 shown is... Figure 2 The power conversion system 200 shown is similar, except that the isolated converter has a single output, and both the first inverter 152 and the second inverter 164 include three inverter units. Furthermore, the motor 122 is implemented as an open-phase winding motor.

[0136] like Figure 17 As shown, the first inverter 152 has six outputs. The first output of the first inverter 152 is connected to winding terminal A of the motor 122. The second output of the first inverter 152 is connected to the first output of the second inverter 164 and further connected to the first phase of the AC power supply 131. The third output of the first inverter 152 is connected to winding terminal B of the motor 122. The fourth output of the first inverter 152 is connected to the third output of the second inverter 164 and further connected to the second phase of the AC power supply 131. The fifth output of the first inverter 152 is connected to winding terminal C of the motor 122. The sixth output of the first inverter 152 is connected to the fifth output of the second inverter 164 and further connected to the third phase of the AC power supply 131. The second output of the second inverter 164 is connected to winding terminal A'. The fourth output of the second inverter 164 is connected to winding terminal B'. The sixth output of the second inverter 164 is connected to winding terminal C'.

[0137] It should be noted that winding terminals A and A' are the two terminals of the first open-phase winding of motor 122. Winding terminals B and B' are the two terminals of the second open-phase winding of motor 122. Winding terminals C and C' are the two terminals of the first open-phase winding of motor 122. The detailed structure of motor 122 will be described below with reference to FIG18.

[0138] Figure 18A and Figure 18B Various embodiments according to this disclosure are illustrated. Figure 17 A schematic diagram of the power conversion system is shown. Throughout the description, Figure 18A and Figure 18BCollectively referred to as Figure 18. The power conversion system 500 is similar to the power conversion system 200 shown in Figure 3. Therefore, to avoid repetition, the common parts of the two systems will not be discussed further.

[0139] The first inverter 152 includes three inverter units connected in parallel between the positive and negative terminals of capacitor C3. Each inverter unit of the first inverter 152 is a single-phase inverter with two outputs. The first inverter 152 is a three-phase inverter with six outputs.

[0140] The second inverter 164 comprises three inverter units connected in parallel between the positive terminal of capacitor C6 and the negative terminal of capacitor C7. Each inverter unit of the second inverter 164 is a single-phase inverter with two outputs. The second inverter 164 is a three-phase inverter with six outputs.

[0141] The first output of the first inverter unit of the first inverter 152 is connected to the first output of the first inverter unit of the second inverter 164 and the first phase of the AC power supply 131. The second output of the first inverter unit of the first inverter 152 and the second output of the first inverter unit of the second inverter 164 are respectively connected to the two terminals of the first open-phase winding of the motor 122.

[0142] The first output of the second inverter unit of the first inverter 152 is connected to the first output of the second inverter unit of the second inverter 164 and the second phase of the AC power supply 133. The second output of the second inverter unit of the first inverter 152 and the second output of the second inverter unit of the second inverter 164 are respectively connected to the two terminals of the second open-phase winding of the motor 122.

[0143] The first output of the third inverter unit of the first inverter 152 is connected to the first output of the third inverter unit of the second inverter 164 and the third phase of the AC power supply 133. The second output of the third inverter unit of the first inverter 152 and the second output of the third inverter unit of the second inverter 164 are respectively connected to the two terminals of the third open-phase winding of the motor 122.

[0144] AC power supply 131 can be a three-phase AC power supply. In some embodiments, the output voltage of AC power supply 131 is in the range of about 220V to about 240V. Alternatively, depending on different design requirements, AC power supply 131 can be implemented as a two-phase power supply or a single-phase power supply.

[0145] Figure 19A schematic diagram of a first inverter shown in FIG18 according to various embodiments of the present disclosure is illustrated. The first inverter 152 is a three-phase inverter for converting DC voltage into three AC waveforms. The first inverter 152 includes three inverter units. The switches of the first inverter 152 form six branches. The first branch includes switches S11 and S12 connected in series between the positive and negative terminals of the input of the first inverter 152. The common node of switches S11 and S12 is connected to the first output terminal V11 of the first inverter 152. The second branch includes switches S13 and S14 connected in series between the positive and negative terminals of the input of the first inverter 152. The common node of switches S13 and S14 is connected to the second output terminal V12 of the first inverter 152. The first branch and the second branch form the first inverter unit of the first inverter 152.

[0146] The third branch includes switches S21 and S22 connected in series between the positive and negative terminals of the input of the first inverter 152. The common node of switches S21 and S22 is connected to the third output terminal V21 of the first inverter 152. The fourth branch includes switches S23 and S24 connected in series between the positive and negative terminals of the input of the first inverter 152. The common node of switches S23 and S24 is connected to the fourth output terminal V22 of the first inverter 152. The third and fourth branches form the second inverter unit of the first inverter 152.

[0147] The fifth branch includes switches S31 and S32 connected in series between the positive and negative terminals of the input of the first inverter 152. The common node of switches S31 and S32 is connected to the fifth output terminal V31 of the first inverter 152. The sixth branch includes switches S33 and S34 connected in series between the positive and negative terminals of the input of the first inverter 152. The common node of switches S33 and S34 is connected to the sixth output terminal V32 of the first inverter 152. The fifth and sixth branches form the third inverter unit of the first inverter 152. Figure 19 The operating principle of the three-phase inverter shown is well known, so it will not be discussed further in this article.

[0148] like Figure 19 As shown, diodes D11-D14, D21-D24, and D31-D34 require a reverse conduction path. In other words, diodes D11-D14, D21-D24, and D31-D34 are anti-parallel diodes.

[0149] Figure 20A schematic diagram of a second inverter according to various embodiments of the present disclosure is shown in FIG18. The second inverter 164 includes switches S41-S44, S51-S54, and S61-S64. The second inverter 164 also includes diodes D41-D44, D51-D54, and D61-D64. The structure of the second inverter 164 is similar to that of the first inverter 152, and therefore will not be discussed further herein.

[0150] Figure 21 Various embodiments according to this disclosure are illustrated. Figure 1 The block diagram shown is for the fifth implementation of the power conversion system. Figure 21 The power conversion system 600 shown is... Figure 17 The power conversion system 500 shown is similar, except that three inverters are connected in series to drive motor 123.

[0151] like Figure 21 As shown, the first inverter 153 is directly connected to the DC power supply 110. The second inverter 165 is connected to the DC power supply 110 via a first isolation converter 174. The third inverter 166 is connected to the DC power supply 110 via a second isolation converter 175. The first isolation converter 174 and the second isolation converter 175 provide isolated power to the second inverter 165 and the third inverter 166, respectively. Due to the isolated power, the outputs of the three inverters can be summed to achieve a higher voltage.

[0152] Figure 21 Each inverter shown has six outputs. Three outputs of the third inverter 166 are connected to winding terminals A, B, and C, respectively. The other three outputs of the third inverter 166 are connected to the three outputs of the first inverter 153, respectively. The other three outputs of the first inverter 153 are connected to the three outputs of the second inverter 165, respectively. The other three outputs of the second inverter 165 are connected to winding terminals A', B', and C', respectively. The three outputs of the AC power supply 134 are connected to the three windings of the motor 123, respectively.

[0153] Figure 22A , Figure 22B and Figure 22C Various embodiments according to this disclosure are illustrated. Figure 21 A schematic diagram of the power conversion system is shown. Throughout the description, Figure 22A , Figure 22B and Figure 22C Collectively referred to as Figure 22. The power conversion system 600 is similar to the power conversion system 500 shown in Figure 18. Therefore, to avoid repetition, the common parts of the two systems will not be discussed further.

[0154] The power conversion system 600 includes two isolated converters 174 and 175. The first isolated converter 174 has an input connected to a DC power supply 110 via a switch Kc. Capacitor C2 is an input capacitor used to provide a stable DC voltage. Capacitors C7 and C8 are output capacitors. As shown in Figure 22, capacitors C7 and C8 are connected in series.

[0155] The second isolated converter 175 has an input connected to a DC power supply 110 via a switch Kc. Capacitor C3 is an input capacitor used to provide a stable DC voltage. Capacitors C9 and C10 are output capacitors. As shown in Figure 22, capacitors C9 and C10 are connected in series.

[0156] The power conversion system 600 includes three inverters 153, 165, and 166. The outputs of the three inverters are connected in series to drive the motor 123. The AC power supply 134 has three outputs, which are respectively connected to the midpoints of the three open-phase windings of the motor 123, as shown in Figure 22.

[0157] Figure 23 Various embodiments according to this disclosure are illustrated. Figure 1 The block diagram shown is for the sixth implementation of the power conversion system. Figure 23 The power conversion system 700 shown includes multiple inverters 150, 151, and 153. The outputs of the multiple inverters are connected in series to drive the motor 120. Figure 2-2 The various embodiments discussed in section 2 are applicable to Figure 23 The power conversion system 700 is shown.

[0158] While embodiments of the present disclosure and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made without departing from the spirit and scope of the present disclosure as defined by the appended claims.

[0159] Furthermore, the scope of this application is not intended to be limited to the specific embodiments of the processes, machines, articles, compositions of matter, apparatuses, methods, and steps described in the specification. Those skilled in the art will readily understand from the disclosure of this publication that processes, machines, articles, compositions of matter, apparatuses, methods, or steps that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized using existing or future developments. Therefore, the appended claims are intended to encompass such processes, machines, production processes, compositions of matter, means, methods, or steps within their scope. Accordingly, this specification and the accompanying drawings should be simply regarded as illustrative of the invention as defined by the appended claims and are intended to cover any and all modifications, variations, combinations, or equivalent substitutions falling within the scope of the invention.

Claims

1. A system comprising: a first power conversion device connected to a first power source; a first isolated power conversion device connected to the first power source; and a second power conversion device connected to the first isolated power conversion device, wherein an output of the first power conversion device and an output of the second power conversion device are connected in series and used to drive a motor; wherein the first power conversion device is a first inverter comprising a first inverter unit, a second inverter unit, and a third inverter unit connected in parallel, and wherein each inverter unit of the first inverter comprises two output terminals; and wherein the second power conversion device is a second inverter comprising a fourth inverter unit, a fifth inverter unit, and a sixth inverter unit connected in parallel, and wherein each inverter unit of the second inverter comprises two output terminals, wherein the two output terminals of the first inverter unit and the two output terminals of the fourth inverter unit of the second inverter are connected in series and further connected to a first phase of the motor, wherein the two output terminals of the second inverter unit and the two output terminals of the fifth inverter unit of the second inverter are connected in series and further connected to a second phase of the motor, and wherein the two output terminals of the third inverter unit and the two output terminals of the sixth inverter unit of the second inverter are connected in series and further connected to a third phase of the motor. The first isolated power conversion device is a three-level inductor-inductor-capacitor converter.

2. The system of claim 1, wherein, The first isolated power conversion device comprises a first primary switch network, a first resonant tank, a first transformer, and a secondary rectifier connected in cascade.

3. The system of claim 1 or 2, wherein, The first isolated power conversion device comprises a first primary switch network, a first resonant tank, a first transformer, a second primary switch network, a second resonant tank, a second transformer, and a secondary rectifier, 4. The system of claim 1 or 2, wherein, wherein the first primary switch network, the first resonant tank, and a primary winding of the first transformer are connected in cascade, wherein the second primary switch network, the second resonant tank, and a primary winding of the second transformer are connected in cascade, and wherein a secondary winding of the first transformer and a secondary winding of the second transformer are connected in series and further connected to the secondary rectifier. The first isolated power conversion device comprises a first primary switch network, a first resonant tank, a first transformer, and a plurality of secondary rectifiers, and wherein the plurality of secondary rectifiers are used to provide isolated power for a plurality of inverter units of the second power conversion device.

5. The system of claim 1 or 2, wherein, a common node of the first inverter unit and the fourth inverter unit is used to be connected to a first phase of a three-phase power source, 6. The system of claim 1, wherein, wherein a common node of the second inverter unit and the fifth inverter unit is used to be connected to a second phase of the three-phase power source, and wherein a common node of the third inverter unit and the sixth inverter unit is used to be connected to a third phase of the three-phase power source. wherein a common node of the third inverter cell and the sixth inverter cell is configured to be connected to a third phase of the three-phase power supply, and wherein the three-phase power supply is configured to charge the first power supply through a power factor correction device formed by windings of the motor and switches of the second inverter.

7. A system comprising: a first inverter having an input connected to a battery; an isolated power converter having an input connected to the battery; and a second inverter having an input connected to an output of the isolated power converter and an output connected in series with an output of the first inverter, wherein the series connected outputs of the first inverter and the second inverter are configured to drive a motor; the first inverter is a three-phase full-bridge inverter comprising three output terminals; and wherein the second inverter comprises a first inverter cell, a second inverter cell, and a third inverter cell, wherein a first output terminal of the first inverter is connected in series with an output of the first inverter cell and further connected to a first phase of the motor, wherein a second output terminal of the first inverter is connected in series with an output of the second inverter cell and further connected to a second phase of the motor, and wherein a third output terminal of the first inverter is connected in series with an output of the third inverter cell and further connected to a third phase of the motor. During charging of the battery, windings of the motor are configured to operate as inductors of a three-phase power factor correction converter.

8. The system of claim 7, wherein, the isolated power converter is an Inductor-Inductor-Capacitor (LLC) power converter comprising a primary winding, a first secondary winding, a second secondary winding, and a third secondary winding, 9. The system of claim 7 or 8, wherein, wherein the primary winding is connected to the battery through a primary switch network, wherein the first secondary winding is connected to the first inverter cell through a first rectifier, wherein the second secondary winding is connected to the second inverter cell through a second rectifier, and wherein the third secondary winding is connected to the third inverter cell through a third rectifier.

10. A method comprising: driving a motor using a first inverter and a second inverter connected in series with each other, the first inverter connected to a battery, the second inverter connected to the battery through an isolated power converter; and charging the battery through a power factor correction device comprising windings of the motor and switches of the second inverter; wherein the first inverter comprises three branches, each branch of the three branches having an output terminal; wherein the second inverter comprises a first inverter cell, a second inverter cell, and a third inverter cell, wherein a first output terminal of the first inverter is connected in series with an output of the first inverter cell and further connected to a first phase of the motor, wherein a second output terminal of the first inverter is connected in series with an output of the second inverter cell and further connected to a second phase of the motor, and wherein a third output terminal of the first inverter is connected in series with an output of the third inverter cell and further connected to a third phase of the motor. wherein a second output terminal of the first inverter is connected in series with an output of the second inverter unit and further connected to a second phase of the motor, and wherein a third output terminal of the first inverter is connected in series with an output of the third inverter unit and further connected to a third phase of the motor; and wherein the isolated power converter comprises a primary winding, a first secondary winding, a second secondary winding, and a third secondary winding, wherein the primary winding is connected to the battery through a primary switching network, wherein the first secondary winding is connected to the first inverter unit through a first rectifier, wherein the second secondary winding is connected to the second inverter unit through a second rectifier, and wherein the third secondary winding is connected to the third inverter unit through a third rectifier.

11. The method of claim 10, further comprising: charging the battery using a three-phase power source, wherein the power factor correction device is used to adjust an input current flowing into the power factor correction device to achieve a power factor within a unity threshold range.

12. The method of claim 11, further comprising charging the battery using a three-phase power source, wherein, the three-phase power source is connected to the first inverter unit through an EMI filter and a first inductor, wherein the three-phase power source is connected to the second inverter unit through the EMI filter and a second inductor, and wherein the three-phase power source is connected to the first inverter unit through the EMI filter and a third inductor.

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