Voltage balancing circuit with integrated brake chip for series inverter

Abstract

A circuit includes a first power switch, a second power switch, a third power switch, and a fourth power switch in series to form a first branch in parallel with a second branch, the second branch including a first capacitor and a second capacitor in series with a first node between the first capacitor and the second capacitor. A first brake resistor is connected in series with the first chopper switch to form a third branch, and a second brake resistor is connected in parallel with the second chopper switch to form a fourth branch. The third branch is located between the terminal of the first capacitor and a second node, which is located between the first power switch and the second power switch. A third node is arranged between the second power switch and the third power switch. The fourth branch is located between the terminal of the second capacitor and a fourth node, which is located between the third power switch and the fourth power switch. The third capacitor and / or inductor forms a fifth branch between (i) the second node and the fourth node or (ii) the first node and the third node.

Description

Technical Field

[0001] The field of this disclosure relates to AC motor drives, and more particularly to series inverters for powering multiphase AC motors. Background Technology

[0002] When a series inverter (SCI) powers a multiphase AC motor, one requirement is voltage balancing of the DC link capacitors. Since DC link voltage balancing depends on the distribution of active power between the inverter / winding groups, balancing methods are typically employed. Voltage balancing circuits are used when balancing methods involve control modifications that introduce unacceptable complexity at the SCI. Some examples of voltage balancing circuits include: LC-based circuits using soft-switching resonant inductors and capacitors, C-based circuits using switched capacitors, and L-based circuits using inductors.

[0003] Furthermore, since motor drivers with diode rectifiers may enter regenerative mode, braking choppers are typically used. Using a braking chopper outside the voltage balancing circuitry used for SCI increases the complexity and number of components required to drive multiphase AC motors, thereby increasing cost and reducing reliability.

[0004] Therefore, it is desirable to improve the reliability of SCI used to drive multiphase AC motors and reduce their complexity. Summary of the Invention

[0005] In one aspect, an integrated voltage balancing and braking chopper circuit is provided. The circuit includes a first power switch, a second power switch, a third power switch, and a fourth power switch, which are series-coupled to form a first branch, wherein the first branch is connected in parallel with a second branch. The second branch includes a first capacitor and a second capacitor coupled in series, wherein the first capacitor and the second capacitor have a first node disposed therebetween. The circuit also includes a first braking resistor, which is series-coupled with a first chopper switch to form a third branch, wherein the third branch is coupled between a terminal of the first capacitor and a second node, the second node being disposed between the first power switch and the second power switch, and wherein the second power switch and the third power switch have a third node disposed therebetween. The circuit further includes a second braking resistor, which is series-coupled with a second chopper switch to form a fourth branch, wherein the fourth branch is coupled between a terminal of the second capacitor and a fourth node, the fourth node being disposed between the third power switch and the fourth power switch. The circuit also includes a third capacitor and / or inductor forming a fifth branch, wherein the fifth branch is coupled between (i) the second node and the fourth node, or (ii) the first node and the third node.

[0006] On the other hand, a drive system for an AC multiphase motor is provided. The drive system includes a first inverter including a first capacitor; and a second inverter including a second capacitor, wherein the first and second capacitors are coupled in series to form a first branch, and wherein the first and second capacitors have a first node disposed therebetween. The drive system also includes an integrated voltage balancing and braking chopper circuit. The circuit includes a first power switch, a second power switch, a third power switch, and a fourth power switch coupled in series to form a second branch, wherein the second branch is connected in parallel with the first branch. The circuit also includes a first braking resistor coupled in series with a first chopper switch to form a third branch, wherein the third branch is coupled between a terminal of the first capacitor and a second node disposed between the first and second power switches, and wherein the third and fourth power switches have a third node disposed therebetween. The circuit also includes a second braking resistor coupled in series with a second chopper switch to form a fourth branch, wherein the fourth branch is coupled between a terminal of the second capacitor and a fourth node disposed between the third and fourth power switches. The circuit also includes a third capacitor and / or inductor forming a fifth branch, wherein the fifth branch is coupled between (i) the second node and the fourth node, or (ii) the first node and the third node.

[0007] On the other hand, an integrated voltage balancing and braking chopper circuit is provided. The circuit includes a first power switch coupled between the positive terminal of a first capacitor and a first node, a second power switch coupled between the first node and a second node, a third power switch coupled between the second node and a third node, and a fourth power switch coupled between the third node and the negative terminal of the second capacitor, wherein the first and second capacitors are coupled in series. The circuit also includes a first braking chopper coupled between the first node and one of the following: the positive terminal and the negative terminal of the first capacitor; and a second braking chopper coupled between the third node and one of the following: the negative terminal and the positive terminal of the second capacitor. The circuit also includes a third capacitor and / or an inductor coupled between (i) the first node and the third node, or (ii) a fourth node at the connection between the second node and the negative terminal of the first capacitor and the positive terminal of the second capacitor. Attached Figure Description

[0008] These and other features, aspects and advantages of this disclosure will be better understood when the following detailed embodiments are read with reference to the accompanying drawings, wherein the same characters denote the same parts throughout the drawings.

[0009] Figure 1 Electric motor drives known in the art are described.

[0010] Figure 2A Discrete LC-based voltage balancing (VB) and braking chopper (BC) circuits known in the art are depicted.

[0011] Figure 2B An integrated LC-based VB-BC circuit is depicted in an exemplary embodiment.

[0012] Figure 3 A block diagram of a controller in an exemplary embodiment is depicted.

[0013] Figure 4A The illustration depicts, in an exemplary embodiment, the process of the electric motor entering and exiting the power generation mode. Figure 2B Integrated LC-based VB-BC curves showing various electrical and operational states.

[0014] Figure 4B The diagram depicts operation in BC mode as shown in an exemplary embodiment. Figure 2B Integrated LC-based VB-BC curves showing various electrical and operational states.

[0015] Figure 4C The diagram depicts operation in VB mode as shown in an exemplary embodiment. Figure 2B Integrated LC-based VB-BC curves showing various electrical and operational states.

[0016] Figure 5A Discrete C-based VB and BC circuits known in the art are depicted.

[0017] Figure 5B An integrated C-based VB-BC circuit is depicted in an exemplary embodiment.

[0018] Figure 6A The illustration depicts, in an exemplary embodiment, the process of the electric motor entering and exiting the power generation mode. Figure 5B Integrated C-based VB-BC curves showing various electrical and operational states.

[0019] Figure 6B The diagram depicts operation in BC mode as shown in an exemplary embodiment. Figure 5B Integrated C-based VB-BC curves showing various electrical and operational states.

[0020] Figure 6C The diagram depicts operation in VB mode as shown in an exemplary embodiment. Figure 5B Integrated C-based VB-BC curves showing various electrical and operational states.

[0021] Figure 7A Discrete C-based VB and BC circuits known in the art are depicted.

[0022] Figure 7B An integrated L-based VB-BC circuit in an exemplary embodiment is depicted.

[0023] Figure 8A The illustration depicts, in an exemplary embodiment, the process of the electric motor entering and exiting the power generation mode. Figure 7B Integrated L-based VB-BC curves showing various electrical and operational states.

[0024] Figure 8B The diagram depicts operation in BC mode as shown in an exemplary embodiment. Figure 7B Integrated L-based VB-BC curves showing various electrical and operational states.

[0025] Figure 8C The diagram depicts operation in VB mode as shown in an exemplary embodiment. Figure 7B Integrated L-based VB-BC curves showing various electrical and operational states.

[0026] Figure 9A , Figure 9B , Figure 9C , Figure 9D and Figure 9E Depicting an exemplary embodiment Figure 2B , Figure 5B and Figure 7B Various extended circuit topologies of integrated VB-BC circuits based on LC, C and L.

[0027] Unless otherwise stated, the accompanying drawings provided herein are intended to illustrate features of embodiments of this disclosure. These features are considered applicable to various systems including one or more embodiments of this disclosure. Therefore, the drawings are not intended to include all conventional features known to those skilled in the art for practicing the embodiments disclosed herein. Detailed Implementation

[0028] In the following specification and claims, several terms will be referenced, and these terms shall be defined as having the following meanings.

[0029] Unless the context clearly indicates otherwise, the singular forms “a,” “one,” and “the” include plural references.

[0030] "Optional" or "optionally" means that the event or situation described below may or may not occur, and the description includes instances where the event occurs and instances where it does not occur.

[0031] As used herein and throughout the specification and claims, approximate language can be used to modify any permissible variation in quantitative representation without altering its associated essential function. Therefore, values ​​modified by one or more terms (such as “about,” “approximately,” and “substantially”) are not limited to the specified precise values. In at least some cases, approximate language may correspond to the precision of the instrument used to measure the value. Scope limitations may be combined and / or interchanged herein and throughout the specification and claims, and unless otherwise indicated by context or language, these scopes are identified and include all subscopes contained herein.

[0032] As used herein, the terms “processor” and “computer,” as well as related terms such as “processing device,” “computing device,” and “controller,” are not limited to those integrated circuits referred to in the art as computers, but broadly refer to microcontrollers, microcomputers, analog computers, programmable logic controllers (PLCs), application-specific integrated circuits (ASICs), and other programmable circuits. These terms are used interchangeably herein. In the embodiments described herein, “memory” may include, but is not limited to, computer-readable media such as random access memory (RAM) and computer-readable non-volatile media such as flash memory. Alternatively, floppy disks, optical disc read-only memory (CD-ROM), magneto-optical disk (MOD), and / or digital versatile optical disk (DVD) may also be used. Furthermore, in the embodiments described herein, additional input channels may be, but are not limited to, computer peripherals associated with an operator interface, such as touchscreens, mice, and keyboards. Alternatively, other computer peripherals may also be used, such as, but not limited to, scanners. Furthermore, in exemplary embodiments, additional output channels may include, but are not limited to, operator interface monitors or head-up displays. Some embodiments involve the use of one or more electronic or computing devices. Such devices typically include processors, processing devices, or controllers, such as general-purpose central processing units (CPUs), graphics processing units (GPUs), microcontrollers, reduced instruction set computer (RISC) processors, ASICs, programmable logic controllers (PLCs), field-programmable gate arrays (FPGAs), digital signal processing (DSP) devices, and / or any other circuitry or processing devices capable of performing the functions described herein. The methods described herein may be encoded as executable instructions contained in a computer-readable medium, including but not limited to storage devices and / or memory devices. When executed by a processing device, such instructions cause the processing device to perform at least a portion of the methods described herein. The examples above are not intended to limit the definition and / or meaning of the terms processor and processing device in any way.

[0033] As previously discussed, one problem with SCIs supplying multiphase AC motors is the unacceptably high voltage imbalance at the DC link capacitors. During operation, DC voltage balance depends primarily on the distribution of active power between inverter / winding banks. Typically, independent control of the SCIs is used to mitigate voltage imbalance at the DC link capacitors because independent control of SCIs allows for direct control of active power, which in turn can be used to achieve DC voltage balance at the DC link capacitors.

[0034] However, in situations where controlling the SCI to achieve DC voltage balancing introduces unacceptable control complexity and / or SCI operation and / or motor drive performance, specific voltage balancing circuits, such as LC-based, C-based, and L-based circuits, can be used. Furthermore, braking choppers are also used in some applications where motor drivers with diode rectifiers may enter generator mode. For example, during deceleration, the motor can act as a generator and feed energy back to the converter, thus charging the DC link capacitor. This is typically the case when controlling high-inertia loads in applications such as trains, cranes, elevators, centrifuges, large fans, etc. Since this energy cannot be transferred back to the grid via the diode front-end rectifier, the motor drive DC bus voltage will increase. To prevent the DC link voltage from reaching unacceptable levels for both passive and active components in the DC link voltage circuit, a mechanism is needed to dissipate the energy generated by the motor during generator mode. A braking resistor is a component connected to the braking chopper, and this braking resistor is designed to convert excess energy generated by the motor during generator mode into heat energy that can be dissipated as heat. Typically, the braking chopper and / or the control system operating the braking chopper monitors the DC link voltage, and when the DC link voltage reaches a threshold level, the braking chopper switches the braking resistor to the DC link circuit to maintain the DC link voltage at an acceptable level. The braking chopper disconnects when the generator mode ends and the motor no longer supplies power to the DC link circuit.

[0035] Applications utilizing braking chopper circuits and voltage balancing circuits typically require a large number of semiconductor devices and passive components, which increases costs and reduces the reliability of the motor driver.

[0036] Figure 1A motor driver 102, known in the art, is depicted. The motor driver 102 receives three-phase AC power from a power grid 104 and selectively supplies three-phase AC power to a multiphase motor 106. The motor driver 102 includes a diode front end 108 forming a rectifier, an LC-based voltage balancing circuit 110, a first braking chopper 112, a second braking chopper 114, a first inverter 116, and a second inverter 118. The first inverter 116 and the second inverter 118 form a single-phase inductor (SCI) for the multiphase motor 106.

[0037] exist Figure 1 In the motor driver 102, since the multiphase motor 106 enters and exits the power generation mode, at least six additional power switches and two diodes are required to ensure the operation of the motor driver 102, regardless of the topology of the voltage balancing circuit used.

[0038] In the embodiments described herein, integrated voltage balancing (VB) circuits and braking chopper (BC) circuits are depicted, combining typically separate VB and BC circuits into a single circuit to reduce the number of semiconductor devices that are not SCI components. This reduces cost and improves solution reliability compared to two specific circuit implementations typically used for voltage balancing and braking chopper circuits. Various topologies, including integrated LC-based, C-based, and L-based VB and BC circuits, will be discussed in the embodiments described herein.

[0039] Figure 2A A discrete LC-based VB-BC circuit 202 known in the art is depicted. Figure 2B An integrated LC-based VB-BC circuit 204 is depicted in an exemplary embodiment. In this embodiment, the integrated LC-based VB-BC circuit 204 is configured to be electrically coupled to capacitors 206 and 207 arranged in series. For example, capacitor 206 may include a capacitor for a first inverter, and capacitor 207 may include a capacitor for a second inverter. The first and second inverters may include a control circuitry (SCI) for controlling a multiphase motor, such as multiphase motor 106.

[0040] In this embodiment, the integrated LC-based VB-BC circuit 204 includes power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4) arranged in series. Power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4) are arranged in parallel with a series combination of capacitors 206 and 207. The integrated LC-based VB-BC circuit 204 also includes braking resistors 212 and 213, chopper switches 214 and 215 (which may include mechanical switches and / or semiconductor devices), and a series combination of capacitor 216 and inductor 218 forming a resonant LC circuit. Compared to the discrete LC-based VB-BC circuit 202, the integrated LC-based VB-BC circuit 204 achieves the same functionality but utilizes fewer diodes and power semiconductor devices, thereby reducing cost and improving solution reliability.

[0041] Although in this embodiment the series combination of braking resistor 212 and chopper switch 214 is coupled to the negative terminal of capacitor 206, in other embodiments, the series combination of braking resistor 212 and chopper switch 214 may be coupled to the positive terminal of capacitor 206. Similarly, although in this embodiment the series combination of braking resistor 213 and chopper switch 215 is coupled to the negative terminal of capacitor 207, in other embodiments, the series combination of braking resistor 213 and chopper switch 215 may also be coupled to the positive terminal of capacitor 207.

[0042] In this embodiment, the integrated LC-based VB-BC circuit 204 includes a controller 220 that controls the operation of the integrated LC-based VB-BC circuit 204. Specifically, the controller 220 controls the operation of power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4), as well as chopper switches 214 and 215. The controller 220 also measures various electrical parameters of the integrated LC-based VB-BC circuit 204, including the voltages at capacitors 206, 207, and 216 (referred to as V0, ... dc1 V dc2 and V cr ), and the chopper current flowing through chopper switch 214 and chopper switch 215 (referred to as I, respectively). chop1 and I chop2 The controller 220 can also measure the resonant current through the inductor 218, referred to as i. rHowever, the controller 220 can measure any additional electrical parameters of the integrated LC-based VB-BC circuit 204 in order to perform the functions of the controller 220 for the integrated LC-based VB-BC circuit 204 as described herein.

[0043] In this embodiment, the integrated LC-based VB-BC circuit 204 includes multiple nodes 222, 223, 224, and 225, wherein the electrical components of the integrated LC-based VB-BC circuit 204 are electrically connected to each other. Specifically, node 222 is located at the electrical connection between capacitor 206 and capacitor 207, node 223 is located at the electrical connection between power switch 208 (Q1) and power switch 209 (Q2), node 224 is located at the electrical connection between power switch 209 (Q2) and power switch 210 (Q3), and node 225 is located at the electrical connection between power switch 210 (Q3) and power switch 211 (Q4).

[0044] In this embodiment, the series combination of braking resistor 212 and chopper switch 214 is electrically connected between nodes 222 and 223; the series combination of braking resistor 213 and chopper switch 215 is electrically connected between node 225 and the negative terminal of capacitor 207; and the series combination of capacitor 216 and inductor 218 is electrically connected between nodes 223 and 225. In this embodiment, nodes 222 and 224 are electrically connected together.

[0045] During VB operation, controller 220 turns off (disconnects) the chopper switch and operates power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4) to realize a resonant LC circuit formed by capacitor 216 and inductor 218. It also operates power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4) to balance the voltage V at capacitor 206. dc1 and the voltage V at capacitor 207 dc2 When the motor enters generator mode, the voltage V at capacitor 206... dc1 and the voltage V at capacitor 207 dc2The voltage can begin to increase, which is detected by controller 220. If the voltage at capacitors 206 and / or 207 increases to an amount exceeding the threshold voltage, controller 220 switches the integrated LC-based VB-BC circuit 204 from VB mode to BC mode by modifying the operation of power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4) and turning on (closing) chopper switches 214 and / or 215. During BC mode, braking resistors 212 and / or 213 dissipate excess energy transferred from the motor to capacitors 206 and / or 207 as heat. When controller 220 determines that the power generation mode has ended, controller 220 modifies the operation of power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4) and turns off (disconnects) the chopper switch, switching the integrated LC-based VB-BC circuit 204 from BC mode to VB mode to restore the voltage V at capacitor 206. dc1 The voltage V at capacitor 207 dc2 The balance.

[0046] As described above, when the controller 220 operates power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4) simultaneously with chopper switches 214 and 215 open (open circuit), the VB mode is implemented by the integrated LC-based VB-BC circuit 204. The BC mode is implemented when the controller 220 turns on (closes) the chopper switches. To prevent mutual interference between VB and BC modes, when the resonant LC circuit i rWhen the current is approximately zero amperes, controller 220 can turn on (close) the chopper switches during the dead time of power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4). Due to the impedance changes and resulting phase shift when braking resistors 212 and 213 are added to the integrated LC-based VB-BC circuit 204, controller 220 can turn off power switches 209 (Q2) and 211 (Q4) during BC mode to prevent loss of soft switching. This can be performed because VB mode may not be necessary during BC mode, as the voltages of capacitors 206 and 207 can be clamped at threshold voltages when controller 220 transitions the integrated LC-based VB-BC circuit 204 from VB mode to BC mode. When the motor's generator mode terminates, controller 220 turns off (opens) the chopper switch, and controller 220 operates power switches 209 (Q2) and 211 (Q4) without causing voltage overshoot at capacitors 206, 207, and 216, because their voltage V dc1 V dc2 and V cr They can be roughly equal.

[0047] Figure 3 A block diagram of a controller 220 in an exemplary embodiment is depicted. The controller 220 includes any components, systems, or devices that perform the functions described herein. The controller 220 will be described with respect to various discrete elements that perform the functions. These elements may be combined in different embodiments or separated into different discrete elements in other embodiments. In this embodiment, the controller 220 includes at least one processor 302, at least one memory 304, at least one sensor 306, and at least one switch driver 312.

[0048] In some embodiments, memory 304 stores programmable instructions that control the operation of processor 302 to implement the functions described herein for controller 220. Sensor 306 includes one or more current sensors 308 and one or more voltage sensors 310, which processor 302 can use to measure voltages and currents at the integrated LC-based VB-BC circuit 204 and other circuitry, as described herein. For example, voltage sensor 310 can be used by processor 302 to measure the voltage V at capacitor 206. dc1 The voltage V at capacitor 207 dc2 The voltage V at capacitor 216 cr The current sensor 308 can be used by the processor 302 to measure the current i at the inductor 218. r The current I through chopper switch 214chop1 and the current I through chopper switch 215 chop2 The switch driver 312 is controlled by the processor 302 to modify the on / off (closed / open) states of the power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4) as well as the chopper switch.

[0049] Figure 4A Graphs 402a, 403a, 404a, 405a, 406a, and 407a are depicted, illustrating various electrical standards of the integrated LC-based VB-BC circuit 204 when the motor enters and exits the generator mode in an exemplary embodiment. Figure 4B Graphs 402b, 403b, 404b, 405b, 406b, and 407b are depicted, illustrating various electrical standards of the integrated LC-based VB-BC circuit 204 operating in BC mode in an exemplary embodiment. Figure 4C Graphs 402c, 403c, 404c, 405c, 406c, and 407c are depicted, illustrating various electrical standards of the integrated LC-based VB-BC circuit 204 operating in VB mode in an exemplary embodiment.

[0050] Specifically, the integrated LC-based VB-BC circuit 204 operates in VB mode at times t0 and t3, enters BC mode from VB mode at time t1, and exits BC mode and returns to VB mode at time t2.

[0051] Graphs 402a, 402b, and 402c show the motor speed (n) and the motor's electrical torque T. e and motor load torque T m Graphs 403a, 403b, and 403c show the voltage V at capacitors 206 and 207. dc1 and V dc2 Graphs 404a, 404b, and 404c show the resonant current i of inductor 218. r Graphs 405a, 405b, and 405c show the resonant capacitor voltage V of capacitor 216. cr Graphs 406a, 406b, and 406c show the chopper current I. chop1 and I chop2Graphs 407a, 406b, and 407c illustrate the control signals for power switches 208 (Q1), 209 (Q2), 210 (Q3), and 211 (Q4). From time t0 to t1, the integrated LC-based VB-BC circuit 204 begins operation in VB mode, where controller 220 simultaneously operates power switches 208 (Q1) and 210 (Q3), and simultaneously and complementaryly operates power switches 209 (Q2) and 211 (Q4) to balance the voltage V at capacitor 206. dc1 and the voltage V at capacitor 207 dc2 When the voltage of capacitors 206 and 207 increases to an amount exceeding the threshold voltage due to the motor operating in generator mode (e.g., T...), e (Negative), controller 220 turns on (closes) the chopper switch, power switch 209 (Q2) and power switch 211 (Q4) turn off, and the integrated LC-based VB-BC circuit 204 operates in BC mode, such as Figure 4B The resonant current i is described. r Approximately zero (e.g., power switches 209 (Q2) and 211 (Q4) are not switching), and the braking chopper current I flowing through braking resistors 212 and 213 respectively. chop1 and I chop2 The energy supplied by the electric motor is dissipated as heat. The integrated LC-based VB-BC circuit 204 converts the BC mode (e.g., T) to BC mode. e After time t2 transitions from negative to positive, controller 220 will switch the integrated LC-based VB-BC circuit 204 from BC mode to VB mode, as follows: Figure 4C As depicted. In VB mode, controller 220 simultaneously operates power switches 208 (Q1) and 210 (Q3), and simultaneously and complementaryly with power switches 208 (Q1) and 210 (Q3) operates power switches 209 (Q2) and 211 (Q4) to make the voltage V at capacitor 206... dc1 The voltage V at capacitor 207 dc2 Mutual balance.

[0052] Figure 5A A discrete C-based VB-BC circuit 502, known in the art, is described, featuring a separate voltage balancing circuit 504 and a braking chopper circuit 506 and a braking chopper circuit 507. Figure 5BAn integrated C-based VB-BC circuit 508 is depicted in an exemplary embodiment. In this embodiment, the integrated C-based VB-BC circuit 508 is configured to be electrically coupled to capacitors 510 and 511 arranged in series. For example, capacitor 510 may include a capacitor for a first inverter, and capacitor 511 may include a capacitor for a second inverter. The first and second inverters may include a control circuit (SCI) for controlling a multiphase motor, such as multiphase motor 106.

[0053] In this embodiment, the integrated C-based VB-BC circuit 508 includes power switches 512 (Q1), 513 (Q2), 514 (Q3), and 515 (Q4), braking resistors 516 and 517, chopper switches 518 and 519 (which may include mechanical switches and / or semiconductor devices), and a capacitor 520 forming part of a switched capacitor circuit. Compared to the discrete C-based VB-BC circuit 502, the integrated C-based VB-BC circuit 508 achieves the same functionality but utilizes fewer diodes and power semiconductor devices, thereby reducing cost and improving the reliability of the solution.

[0054] Although in this embodiment the series combination of braking resistor 516 and chopper switch 518 is coupled to the negative terminal of capacitor 510, in other embodiments, the series combination of braking resistor 516 and chopper switch 518 may be coupled to the positive terminal of capacitor 510. Similarly, although in this embodiment the series combination of braking resistor 517 and chopper switch 519 is coupled to the negative terminal of capacitor 511, in other embodiments, the series combination of braking resistor 517 and chopper switch 519 may also be coupled to the positive terminal of capacitor 511.

[0055] In this embodiment, controller 220 controls the operation of power switches 512 (Q1), 513 (Q2), 514 (Q3), and 515 (Q4), as well as chopper switches 518 and 519 (e.g., via switch driver 312, see [link]). Figure 3 The controller 220 also utilizes sensor 306 to measure various electrical parameters of the integrated C-based VB-BC circuit 508, including measuring the voltage at capacitors 510, 511, and 520 using voltage sensor 310, referred to as V0. dc1 V dc2 and V cr In addition, controller 220 uses current sensor 308 to measure the chopper current flowing through chopper switches 518 and 519, referred to as Ichopper. chop1 and I chop2The controller 220 can also use a current sensor 308 to measure the current through the capacitor 520, referred to as i. r However, controller 220 can measure any additional electrical parameters of the integrated C-based VB-BC circuit 508 in order to perform the functions of controller 220 for the integrated C-based VB-BC circuit 508 as described herein.

[0056] In this embodiment, the integrated C-based VB-BC circuit 508 includes multiple nodes 522, 523, 524, and 525, wherein the electrical components of the integrated C-based VB-BC circuit 508 are electrically connected to each other. Specifically, node 522 is located at the electrical connection between capacitor 510 and capacitor 511, node 523 is located at the electrical connection between power switch 512 (Q1) and power switch 513 (Q2), node 524 is located at the electrical connection between power switch 513 (Q2) and power switch 514 (Q3), and node 525 is located at the electrical connection between power switch 514 (Q3) and power switch 515 (Q4).

[0057] In this embodiment, the series combination of braking resistor 516 and chopper switch 518 is electrically connected between nodes 522 and 523; the series combination of braking resistor 517 and chopper switch 519 is electrically connected between node 525 and the negative terminal of capacitor 511; and capacitor 520 is electrically connected between nodes 523 and 525. In this embodiment, nodes 522 and 524 are electrically connected.

[0058] During VB operation, controller 220 turns off (opens) chopper switches 518 and 519 and operates power switches 512 (Q1), 513 (Q2), 514 (Q3), and 515 (Q4) to implement a switched capacitor circuit including capacitor 520, and also operates power switches 512 (Q1), 513 (Q2), 514 (Q3), and 515 (Q4) to balance the voltage V at capacitor 510. dc1 and the voltage V at capacitor 511 dc2When the motor enters generator mode, the voltage at capacitors 510 and 511 may begin to increase, which is detected by the controller 220 using voltage sensor 310. If the voltage at capacitors 510 and / or 511 increases to an amount exceeding a threshold voltage, the controller 220 switches the integrated C-based VB-BC circuit 508 from VB mode to BC mode by modifying the operation of power switches 512 (Q1), 513 (Q2), 514 (Q3), and 515 (Q4) and turning on (closing) chopper switches 518 and / or 519. During BC mode, braking resistors 516 and 517 dissipate excess energy transferred from the motor to the integrated C-based VB-BC circuit 508 as heat. When the controller 220 determines that the power generation mode has ended, the controller 220 switches the C-based integrated VB-BC circuit 508 from BC mode to VB mode by modifying the operation of power switches 512 (Q1), 513 (Q2), 514 (Q3) and 515 (Q4) and turning off (disconnecting) chopper switches 518 and 519.

[0059] As described above, when the controller 220 operates power switches 512 (Q1), 513 (Q2), 514 (Q3), and 515 (Q4) simultaneously with chopper switches 518 and 519 open (open circuit), the VB operation is implemented by the integrated C-based VB-BC circuit 508. The BC operation is implemented when the controller 220 turns on (closes) chopper switches 518 and 519. To prevent mutual interference between the VB and BC operations, when the current i of capacitor 520... r At approximately zero amperes, controller 220 can turn on (close) chopper switches 518 and 519 during the dead time of power switches 512 (Q1), 513 (Q2), 514 (Q3), and 515 (Q4). Because adding braking resistors 516 and 517 to the integrated C-based VB-BC circuit 508 does not modify the circuit's operation, controller 220 can continue operating power switches 513 (Q2) and 515 (Q4) during BC operation. However, in some embodiments, power switches 513 (Q2) and 515 (Q4) can also be turned off in BC mode.

[0060] Figure 6A Graphs 602a, 603a, 604a, 605a, 606a, and 607a are depicted, illustrating various electrical and operational states of the integrated C-based VB-BC circuit 508 as the motor enters and exits the power generation mode in an exemplary embodiment. Figure 6B Graphs 602b, 603b, 604b, 605b, 606b, and 607b are depicted, illustrating various electrical and operational states of the integrated C-based VB-BC circuit 508 operating in BC mode in an exemplary embodiment. Figure 6C Graphs 602c, 603c, 604c, 605c, 606c, and 607c are depicted, illustrating various electrical and operational states of the integrated C-based VB-BC circuit 508 operating in VB mode in an exemplary embodiment.

[0061] Specifically, the integrated C-based VB-BC circuit 508 operates in VB mode at times t0 and t3, enters BC mode from VB at time t1, and exits BC mode and returns to VB mode at time t2.

[0062] Graphs 602a, 602b, and 602c show the motor speed (n) and the motor's electrical torque T. e and motor load torque T m Graphs 603a, 603b, and 603c show the voltage V at capacitor 510. dc1 and the voltage V at capacitor 511 dc2 Graphs 604a, 604b, and 604c show the current i of capacitor 520. r Graphs 605a, 605b, and 605c show the capacitor voltage V of capacitor 520. cr Graphs 606a, 606b, and 606c show the chopper current I. chop1 and I chop2 Furthermore, graphs 607a, 607b, and 607c illustrate the control signals for power switches 512 (Q1), 513 (Q2), 514 (Q3), and 515 (Q4). From time t0 to t1, the integrated C-based VB-BC circuit 508 begins operation in VB mode, where controller 220 simultaneously operates power switches 512 (Q1) and 514 (Q3), and simultaneously and complementaryly operates power switches 513 (Q2) and 515 (Q4) to cause the voltage V at capacitor 510 to... dc1 and the voltage V at capacitor 511 dc Mutual balance. When the voltage of capacitors 510 and 511 increases to an amount exceeding the threshold voltage due to the motor operating in generator mode (e.g., T... e(Negative), controller 220 turns on (closes) chopper switches 518 and 519, power switches 513 (Q2) and 515 (Q4) remain operational and complement each other, and the integrated C-based VB-BC circuit 508 operates in BC mode, such as Figure 6B The braking chopper current I flowing through braking resistors 516 and 517, respectively, is described. chop1 and I chop2 The energy supplied by the electric motor is dissipated as heat. The integrated C-based VB-BC circuit 508 converts the BC mode (e.g., T) to BC mode. e After time t2 transitions from negative to positive, controller 220 will switch the integrated C-based VB-BB circuit 508 from BC mode to VB mode, as follows: Figure 6C As depicted. In VB mode, controller 220 simultaneously operates power switches 512 (Q1) and 514 (Q3), and simultaneously and complementaryly with power switches 512 (Q1) and 514 (Q3) operates power switches 513 (Q2) and 515 (Q4) to make the voltage V at capacitor 510... dc1 and the voltage V at capacitor 511 dc2 Mutual balance.

[0063] Figure 7A A discrete C-based VB-BC circuit 702 with separate voltage balancing circuit 704 and braking chopper circuit 706 and braking chopper circuit 707, known in the art, is described. Figure 7B An integrated L-based VB-BC circuit 708 is depicted in an exemplary embodiment. In this embodiment, the integrated L-based VB-BC circuit 708 is configured to be electrically coupled to capacitors 710 and 711 arranged in series. For example, capacitor 710 may include a capacitor for a first inverter, and capacitor 711 may include a capacitor for a second inverter. The first and second inverters may include a SCI for controlling a multiphase motor, such as multiphase motor 106.

[0064] In this embodiment, the integrated L-based VB-BC circuit 708 includes power switches 712 (Q1), 713 (Q2), 714 (Q3), and 715 (Q4), braking resistors 716 and 717, chopper switches 718 and 719 (which may include mechanical switches and / or semiconductor devices), an inductor 720 forming part of a switching inductor circuit, and diodes 722 and 723. Compared to the discrete L-based VB-BC circuit 702, the integrated L-based VB-BC circuit 708 achieves the same functionality but utilizes fewer diodes and power semiconductor devices, thereby reducing cost and improving the reliability of the solution.

[0065] In this embodiment, controller 220 controls the operation of power switches 712 (Q1), 713 (Q2), 714 (Q3), and 715 (Q4), as well as chopper switches 718 and 719 (e.g., via switch driver 312, see [link]). Figure 3 The controller 220 also utilizes sensor 306 to measure various electrical parameters of the integrated L-based VB-BC circuit 708, including measuring the voltage at capacitors 710 and 711 (referred to as V1 and V2 respectively) using voltage sensor 310. dc1 and V dc2 The voltage at inductor 720 is called V. lr In addition, the controller 220 uses a current sensor 308 to measure the chopper current flowing through chopper switch 718 and chopper switch 719, referred to as Ic. chop1 and I chop2 The controller 220 can also use a current sensor 308 to measure the current through the inductor 720, referred to as i. r However, controller 220 can measure any additional electrical parameters of the integrated L-based VB-BC circuit 708 in order to perform the functions of controller 220 for the integrated L-based VB-BC circuit 708 as described herein.

[0066] In this embodiment, the integrated L-based VB-BC circuit 708 includes multiple nodes 724, 725, 726, and 727, wherein the electrical components of the integrated L-based VB-BC circuit 708 are electrically connected to each other. Specifically, node 724 is located at the electrical connection between capacitor 710 and capacitor 711, node 725 is located at the electrical connection between power switch 712 (Q1) and power switch 713 (Q2), node 726 is located at the electrical connection between power switch 713 (Q2) and power switch 714 (Q3), and node 727 is located at the electrical connection between power switch 714 (Q3) and power switch 715 (Q4).

[0067] In this embodiment, the series combination of braking resistor 716 and chopper switch 718 is electrically connected between node 724 and node 725, the series combination of braking resistor 717 and chopper switch 719 is electrically connected between node 724 and inductor 727, and inductor 720 is electrically connected between node 724 and node 726.

[0068] During VB operation, controller 220 turns off (opens) chopper switches 718 and 719, and operates power switches 712 (Q1), 713 (Q2), 714 (Q3), and 715 (Q4) to implement a switched inductor circuit including inductor 720. It also operates power switches 712 (Q1), 713 (Q2), 714 (Q3), and 715 (Q4) to balance the voltage V at capacitor 710. dc1 and the voltage V at capacitor 711 dc2 In VB mode, controller 220 simultaneously operates power switches 712 (Q1) and 713 (Q2), and also simultaneously, but complementary to power switches 714 (Q3) and 714 (Q4). Diodes 722 and 723 provide clamping in the event of mismatch. Mismatches may occur, for example, due to the power switches 712 (Q1), 713 (Q2), 714 (Q3), and 715 (Q4) having slightly different on-time and off-time electrical characteristics, and / or due to the switch driver 312 having slightly different on-time and off-time electrical characteristics.

[0069] When the motor enters the generator mode, the voltage V at capacitors 710 and 711 is... dc1 and V dc2The voltage can begin to increase, which is detected by the controller 220 using the voltage sensor 310. If the voltage at capacitors 710 and / or 711 increases to an amount exceeding a threshold voltage, the controller 220 switches the integrated L-based VB-BC circuit 708 from VB mode to BC mode by modifying the operation of power switches 712 (Q1), 713 (Q2), 714 (Q3), and 715 (Q4) and turning on (closing) chopper switches 718 and / or 719. During BC mode, braking resistors 716 and 717 dissipate excess energy transferred from the motor to the integrated L-based VB-BC circuit 708 as heat. During VB mode, power switches 713 (Q2) and 714 (Q3) are off, and power switches 712 (Q1) and 714 (Q4) are switched simultaneously.

[0070] When the controller 220 determines that the power generation mode has ended, the controller 220 switches the integrated L-based VB-BC circuit 708 from BC mode to VB mode, and the controller 220 simultaneously operates power switches 712 (Q1) and 713 (Q2), and also simultaneously, but complementary to power switches 712 (Q1) and 713 (Q2), operates power switches 714 (Q3) and 714 (Q4).

[0071] As described above, when the controller 220 operates power switches 712 (Q1), 713 (Q2), 714 (Q3), and 715 (Q4) simultaneously with chopper switches 718 and 719 open (open circuit), the VB operation is implemented by the L-integrated VB-BC circuit 708. When the controller 220 turns on (closes) chopper switches 718 and 719, the BC operation is implemented. To prevent mutual interference between the VB and BC operations, when the current i of inductor 720... r At approximately zero amperes, controller 220 can turn on (close) chopper switches 718 and 719 during the dead time of power switches 712 (Q1), 713 (Q2), 714 (Q3), and 715 (Q4). Because adding braking resistors 716 and 717 to the integrated L-based VB-BC circuit 708 does not modify the circuit's operation, controller 220 can continue operating power switches 713 (Q2) and 714 (Q3) during BC operation. However, BC operation may not require power switches 713 (Q2) and 714 (Q3), and their operation may incur additional losses. Therefore, power switches 713 (Q2) and 714 (Q3) can be turned off during BC operation.

[0072] Figure 8A Curves 802a, 803a, 804a, 805a, 806a, and 807a are depicted, illustrating various electrical and operational states of the integrated L-based VB-BC circuit 708 as the motor enters and exits the power generation mode in an exemplary embodiment. Figure 8B Graphs 802b, 803b, 804b, 805b, 806b, and 807b are depicted, illustrating various electrical and operational states of the integrated L-based VB-BC circuit 708 during BC mode in an exemplary embodiment. Figure 8C Graphs 802c, 803c, 804c, 805c, 806c, and 807c are depicted, illustrating various electrical and operational states of the integrated L-based VB-BC circuit 708 during VB mode in an exemplary embodiment.

[0073] Specifically, the integrated L-based VB-BC circuit 708 operates in VB mode at times t0 and t3, enters BC mode from VB mode at time t1, and exits VB mode from BC mode at time t2.

[0074] Graphs 802a, 802b, and 802c show the motor speed (n) and the motor's electrical torque T. e and motor load torque T m Graphs 803a, 803b, and 803c show the voltage V at capacitor 710. dc1 and the voltage V at capacitor 711 dc2 Graphs 804a, 804b, and 804c show the current i of inductor 720. r Graphs 805a, 805b, and 805c show the voltage V of inductor 720. lr Graphs 806a, 806b, and 806c show the chopper current I. chop1 and I chop2 Furthermore, graphs 807a, 807b, and 807c illustrate the control signals for power switches 712 (Q1), 713 (Q2), 714 (Q3), and 715 (Q4). From time t0 to t1, the integrated L-based VB-BC circuit 708 begins operation in VB mode, where controller 220 operates power switches 712 (Q1) and 713 (Q2) to switch simultaneously, and operates power switches 714 (Q3) and 715 (Q4) to switch simultaneously, but complementaryly to power switches 712 (Q1) and 713 (Q2), so that the voltage V at capacitor 710 is... dc1 and the voltage V at capacitor 711 dc2 They are mutually balanced. When the voltage V between capacitors 710 and 711...dc1 and V dc2 When the voltage increases to a level exceeding the threshold voltage due to the motor operating in generator mode (e.g., T...), e (Negative), controller 220 turns on (closes) chopper switches 718 and 719, disables power switches 713 (Q2) and 714 (Q3), and continues to operate power switches 712 (Q1) and 715 (Q4). The integrated L-based VB-BC circuit 708 operates in BC mode, as... Figure 8B The braking chopper current I flowing through braking resistors 716 and 717, respectively, is depicted. chop1 and I chop2 The energy supplied by the electric motor is dissipated as heat. The integrated L-based VB-BC circuit 708 converts the BC mode (e.g., T) to BC mode. e After time t2 transitions from negative to positive, controller 220 will switch the integrated L-based VB-BB circuit 708 from BC mode to VB mode, as follows: Figure 8C As depicted. In VB mode, controller 220 operates power switches 712 (Q1) and 713 (Q2) to switch simultaneously, and operates power switches 714 (Q3) and 715 (Q4) to switch simultaneously, but complementary to power switches 712 (Q1) and 713 (Q2), to balance the voltage V at capacitor 710. dc1 and the voltage V at capacitor 711 dc2 .

[0075] Although the embodiments described herein illustrate their use in a dual-stator AC motor, each of the integrated LC-based VB-BC circuit 204, the integrated C-based VB-BC circuit 508, and the integrated L-based VB-BC circuit 708 is scalable and capable of performing both VB and BC functions for any number of DC link capacitors connected in series to power the inverter / winding group. Two expansion methods, series expansion and rainpipe expansion, will be described below, although each of the integrated LC-based VB-BC circuit 204, the integrated C-based VB-BC circuit 508, and the integrated L-based VB-BC circuit 708 can be scaled using other techniques not described.

[0076] The series expansion method can have a lower number of active switches, but switching should be synchronized. All top devices in a half-bridge may need to switch simultaneously, and all bottom devices in a half-bridge may need to switch simultaneously and complementaryly with each other. The rain duct expansion method can have a larger number of active switches, but they may not need to be synchronized between different rain duct modules.

[0077] Figure 9A , Figure 9B , Figure 9C , Figure 9D and Figure 9E Various extended circuit topologies of the integrated LC-based VB-BC circuit 204, the integrated C-based VB-BC circuit 508, and the integrated L-based VB-B circuit 708 in the exemplary embodiments are depicted. Figure 9A A series approach for an integrated LC-based VB-BC circuit 204 is described, which has (n-1) resonant loops (L and C) and n chopper branches (BR and SW). Figure 9B A method for extending a rain tube using an integrated LC-based VB-BC circuit 204 is described, wherein, in order to avoid duplication of the chopper circuit, the VB portion of the integrated LC-based VB-BC circuit 204, labeled "B", is used instead of the integrated LC-based VB-BC circuit 204, labeled "A". Figure 9C The series extension circuit topology of the integrated C-based VB-BC circuit 508 is depicted, and Figure 9D The rain tube circuit topology for the integrated C-based VB-BC circuit 508 is depicted, wherein, in order to avoid duplication of the chopper circuit, the VB portion of the integrated C-based VB-BC circuit 508 labeled "B" is used instead of the integrated C-based VB-BC circuit 508 labeled "A". Figure 9E The topology of the rain tube extension circuit of the integrated L-based VB-BC circuit 708 is depicted, since the integrated L-based VB-BC circuit 708 may not be extended in series. To avoid duplication of the chopper circuit, the VB portion of the L-based VB-BC circuit 708, labeled "B", is used instead of the integrated L-based VB-BC circuit 708, labeled "A".

[0078] The exemplary technical effects of the embodiments described herein include one or more of the following: (a) a reduction in the number of components while maintaining the same functionality as discrete VB and BC implementations; (b) a lower number of components reducing the cost of the solution; (c) a lower number of components improving the reliability of the solution; and (d) the embodiments described herein are scalable for topologies with more than two series-connected main capacitors.

[0079] While specific features of various embodiments of this disclosure may be shown in some drawings but not in others, this is merely for convenience. Any feature of any of the drawings may be referenced and / or claimed in accordance with the principles of this disclosure, in conjunction with any feature of any other drawing.

[0080] This written specification uses examples to disclose embodiments, including best practices, and also enables those skilled in the art to practice the embodiments, including making and using any device or system and performing any combined methods. The patentable scope of this disclosure is defined by the claims and may include other examples that would occur to those skilled in the art. Such other examples should be within the scope of the claims if they have structural elements that are not indistinguishable from the literal language of the claims, or if they include equivalent structural elements that are not substantially indistinguishable from the literal language of the claims.

Claims

1. An integrated voltage balancing and braking chopper circuit, comprising: A first power switch, a second power switch, a third power switch, and a fourth power switch are connected in series to form a first branch, wherein the first branch is connected in parallel with a second branch, the second branch includes a first capacitor and a second capacitor connected in series, and wherein the first capacitor and the second capacitor have a first node disposed therebetween. A first braking resistor is coupled in series with a first chopper switch to form a third branch, wherein the third branch is coupled between the terminal of the first capacitor and a second node, the second node being disposed between the first power switch and the second power switch, and wherein the second power switch and the third power switch have a third node disposed therebetween. The second braking resistor is coupled in series with the second chopper switch to form a fourth branch, wherein the fourth branch is coupled between the terminal of the second capacitor and the fourth node, and the fourth node is disposed between the third power switch and the fourth power switch. as well as A third capacitor and / or inductor forms a fifth branch, wherein the fifth branch is coupled between (i) the second node and the fourth node, or (ii) the first node and the third node.

2. The integrated voltage balancing and braking chopper circuit according to claim 1 further includes: The controller is configured to modify the operation of the first power switch, the second power switch, the third power switch, the fourth power switch, the first chopper switch, and the second chopper switch to (i) balance the first voltage of the first capacitor with the second voltage of the second capacitor using the third capacitor and / or the inductor, and (ii) dissipate the energy stored in the first capacitor and the second capacitor using the first braking resistor and the second braking resistor.

3. The integrated voltage balancing and braking chopper circuit according to claim 2, wherein the controller is further configured to: Determine whether at least one of the first voltage and the second voltage is greater than a threshold voltage; and In response to determining that at least one of the first voltage and the second voltage is greater than the threshold voltage, at least one of the first chopper switch and the second chopper switch is closed to dissipate the energy stored in at least one of the first capacitor and the second capacitor.

4. The integrated voltage balancing and braking chopper circuit according to claim 3, wherein: The fifth branch includes the third capacitor, which is coupled in series with the inductor. The fifth branch is electrically coupled between the second node and the fourth node, and The controller is also configured to turn off the second power switch and the fourth power switch when the first chopper switch and the second chopper switch are closed.

5. The integrated voltage balancing and braking chopper circuit according to claim 3, wherein: The fifth branch only includes the inductor. The inductor is coupled between the first node and the third node, and The controller is also configured to turn off the second power switch and the third power switch when the first chopper switch and the second chopper switch are closed.

6. The integrated voltage balancing and braking chopper circuit according to claim 3, wherein: The fifth branch includes only the third capacitor. The third capacitor is coupled between the second node and the fourth node, and The controller is also configured to, when the first chopper switch and the second chopper switch are closed: Simultaneously operate the second power switch and the fourth power switch; as well as Simultaneously, the first power switch and the third power switch are operated in a complementary manner to the second power switch and the fourth power switch.

7. The integrated voltage balancing and braking chopper circuit according to claim 1, wherein: The fifth branch includes the third capacitor coupled in series with the inductor, and The fifth branch is electrically coupled between the second node and the fourth node.

8. The integrated voltage balancing and braking chopper circuit according to claim 1, wherein: The fifth branch includes only the third capacitor, and The third capacitor is coupled between the second node and the fourth node.

9. The integrated voltage balancing and braking chopper circuit according to claim 1, wherein: The fifth branch includes only the inductor, and The inductor is coupled between the first node and the third node.

10. The integrated voltage balancing and braking chopper circuit according to claim 9, wherein: The third branch is coupled between the second node and the negative terminal of the first capacitor, and The fourth branch is coupled between the fourth node and the positive terminal of the second capacitor.

11. The integrated voltage balancing and braking chopper circuit according to claim 1, wherein: The third branch is coupled between the second node and the negative terminal of the first capacitor, and The fourth branch is coupled between the fourth node and the negative terminal of the second capacitor.

12. The integrated voltage balancing and braking chopper circuit according to claim 1, wherein: At least one of the first chopper switch and the second chopper switch includes a mechanical switch.

13. A drive system for an alternating current (AC) multiphase motor, the drive system comprising: The first inverter includes a first capacitor; The second inverter includes a second capacitor, wherein the first capacitor and the second capacitor are coupled in series to form a first branch, and wherein the first capacitor and the second capacitor have a first node disposed therebetween. Integrated voltage balancing and braking chopper circuit, including: A first power switch, a second power switch, a third power switch, and a fourth power switch are connected in series and coupled to form a second branch, wherein the second branch is connected in parallel with the first branch; A first braking resistor is coupled in series with a first chopper switch to form a third branch, wherein the third branch is coupled between the terminal of the first capacitor and a second node, the second node being disposed between the first power switch and the second power switch, and wherein the third power switch and the fourth power switch have a third node disposed therebetween. A second braking resistor is coupled in series with a second chopper switch to form a fourth branch, wherein the fourth branch is coupled between the terminals of the second capacitor and a fourth node, the fourth node being disposed between the third power switch and the fourth power switch; and A third capacitor and / or inductor forms a fifth branch, wherein the fifth branch is coupled between (i) the second node and the fourth node, or (ii) the first node and the third node.

14. The drive system according to claim 13, further comprising: The controller is configured to modify the operation of the first power switch, the second power switch, the third power switch, the fourth power switch, the first chopper switch, and the second chopper switch to (i) balance the first voltage of the first capacitor with the second voltage of the second capacitor using the third capacitor and / or the inductor, and (ii) dissipate the energy stored in the first capacitor and the second capacitor using the first braking resistor and the second braking resistor.

15. The drive system of claim 14, wherein the controller is further configured to: Determine whether at least one of the first voltage and the second voltage is greater than a threshold voltage; and In response to determining that at least one of the first voltage and the second voltage is greater than the threshold voltage, at least one of the first chopper switch and the second chopper switch is closed to dissipate the energy stored in at least one of the first capacitor and the second capacitor.

16. The drive system according to claim 15, wherein: The fifth branch includes the third capacitor connected in series with the inductor. The fifth branch is coupled between the second node and the fourth node, and The controller is also configured to turn off the second power switch and the fourth power switch when the first chopper switch and the second chopper switch are closed.

17. The drive system according to claim 15, wherein: The fifth branch only includes the inductor. The inductor is coupled between the first node and the third node, and The controller is also configured to turn off the second power switch and the third power switch when the first chopper switch and the second chopper switch are closed.

18. The drive system according to claim 15, wherein: The fifth branch includes only the third capacitor. The third capacitor is coupled between the second node and the fourth node, and The controller is also configured to, when the first chopper switch and the second chopper switch are closed: Simultaneously operate the second power switch and the fourth power switch; and Simultaneously and complementaryly to the second power switch and the fourth power switch, the first power switch and the third power switch are operated.

19. The drive system according to claim 14, wherein: At least one of the first chopper switch and the second chopper switch includes a mechanical switch.

20. An integrated voltage balancing and braking chopper circuit, comprising: A first power switch is coupled between the positive terminal of the first capacitor and the first node; A second power switch is coupled between the first node and the second node; A third power switch is coupled between the second node and the third node; A fourth power switch is coupled between the third node and the negative terminal of the second capacitor, wherein the first capacitor and the second capacitor are coupled in series. A first braking chopper is coupled between the first node and one of the following: the positive terminal of the first capacitor and the negative terminal of the first capacitor; A second braking chopper is coupled between the third node and one of the following: the positive terminal of the second capacitor and the negative terminal of the second capacitor; as well as A third capacitor and / or inductor is coupled between (i) the first node and the third node, or (ii) a fourth node at the connection between the second node and the negative terminal of the first capacitor and the positive terminal of the second capacitor.

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