Common DC bus topology circuit

Abstract

The utility model relates to a common direct current bus topology circuit which comprises an LCL filtering module, an active rectification module, a current transformation module and a common direct current bus. The input end of the LCL filtering module is used for being connected with an alternating current power supply input port, and the output end of the LCL filtering module is connected with the input end of the active rectification module; the output end of the active rectifier module is connected with the input end of the converter module through the common direct current bus, and the output end of the converter module is used for being connected with external target equipment; compared with the prior art, the technical scheme of the utility model can effectively suppress the harmonic component in the DC bus, and ensures the safe and stable operation of the frequency conversion system.

Description

Technical Field

[0001] This application relates to the field of power electronics, and more particularly to a common DC bus topology circuit. Background Technology

[0002] In the field of inverter engineering drives, systems are generally divided into single-machine drive systems and multi-machine drive systems. A single-machine drive system consists of a single rectifier module and a single inverter module, while a multi-machine drive system uses one rectifier module equipped with multiple inverter modules, and the multiple inverter modules are interconnected through a common DC bus. In recent years, with the country's requirements for clean energy and advocacy for energy recycling, multi-machine drive systems have been widely used and further developed in the field of high-power engineering drives due to their flexible networking methods, efficient energy feedback capabilities, wide power range, and compact structural topology.

[0003] However, due to factors such as capacitance, stray inductance of cables, and parasitic resistance, the common DC bus topology in multi-machine drive systems is prone to resonance in the bus circuit under certain operating conditions.

[0004] This resonance phenomenon can cause abnormal oscillations in the DC bus voltage and current, which may seriously damage key components such as bus capacitors and IGBTs, thereby affecting the stability and reliability of the frequency converter system. Therefore, how to effectively avoid DC bus oscillations and ensure the safe and stable operation of the frequency converter system has become an important research topic in frequency converter design. Utility Model Content

[0005] This application provides a common DC bus topology circuit, which can effectively suppress harmonic components in the DC bus and ensure the safe and stable operation of the frequency conversion system.

[0006] In a first aspect, this application provides a common DC bus topology circuit, including: an LCL filter module, an active rectifier module, a converter module, and a common DC bus; the input terminal of the LCL filter module is used to connect to an AC power input port, and the output terminal of the LCL filter module is connected to the input terminal of the active rectifier module; the output terminal of the active rectifier module is connected to the input terminal of the converter module through the common DC bus, and the output terminal of the converter module is used to connect to an external target device.

[0007] In one possible implementation, the LCL filter module includes a first inductor, a second inductor, a third inductor, a fourth inductor, a fifth inductor, a sixth inductor, a first capacitor, a second capacitor, and a third capacitor; wherein, the second terminal of the first inductor is connected to the first terminal of the fourth inductor, the second terminal of the second inductor is connected to the first terminal of the fifth inductor, and the second terminal of the third inductor is connected to the first terminal of the sixth inductor; the first terminals of the first capacitor and the second capacitor are respectively connected to the second terminals of the first inductor and the fourth inductor, the second terminals of the first capacitor and the third capacitor are respectively connected to the second terminals of the second inductor and the fifth inductor, and the second terminals of the second capacitor and the third capacitor are respectively connected to the second terminals of the third inductor and the sixth inductor; the first terminals of the first inductor, the second inductor, and the third inductor are respectively connected to the AC power input port.

[0008] In one possible implementation, the active rectifier module includes a fourth capacitor, a first insulated-gate bipolar transistor (IGBT) module, a second IGBT module, a third IGBT module, a fourth IGBT module, a fifth IGBT module, and a sixth IGBT module; wherein the emitter of the first IGBT module is connected to the collector of the fourth IGBT module, and the emitter of the second IGBT module is connected to the collector of the fifth IGBT module. The emitter of the third insulated-gate bipolar transistor (IGBT) module is connected to the collector of the sixth IGBT module; the collectors of the first, second, and third IGBT modules are respectively connected to the first terminal of the fourth capacitor; the emitters of the fourth, fifth, and sixth IGBT modules are respectively connected to the second terminal of the fourth capacitor.

[0009] In one possible implementation, the first insulated-gate bipolar transistor (IGBT) module includes a first IGBT and a first freewheeling diode; the second IGBT module includes a second IGBT and a second freewheeling diode; the third IGBT module includes a third IGBT and a third freewheeling diode; the fourth IGBT module includes a fourth IGBT and a fourth freewheeling diode; the fifth IGBT module includes a fifth IGBT and a fifth freewheeling diode; and the sixth IGBT module includes a sixth IGBT and a sixth freewheeling diode.

[0010] In one possible implementation, the output terminal of the LCL filter module is connected to the input terminal of the active rectifier module, specifically including: the output terminal of the LCL filter module includes the second terminal of the fourth inductor, the second terminal of the fifth inductor, and the second terminal of the sixth inductor; the input terminal of the active rectifier module includes the emitter of the first insulated-gate bipolar transistor module, the emitter of the second insulated-gate bipolar transistor module, the emitter of the third insulated-gate bipolar transistor module, the collector of the fourth insulated-gate bipolar transistor module, and the fifth insulated-gate bipolar transistor module. The collector of the first insulated-gate bipolar transistor module and the collector of the sixth insulated-gate bipolar transistor module; the second end of the fourth inductor is connected to the emitter of the first insulated-gate bipolar transistor module and the collector of the fourth insulated-gate bipolar transistor module, respectively; the second end of the fifth inductor is connected to the emitter of the second insulated-gate bipolar transistor module and the collector of the fifth insulated-gate bipolar transistor module, respectively; and the second end of the sixth inductor is connected to the emitter of the third insulated-gate bipolar transistor module and the collector of the sixth insulated-gate bipolar transistor module, respectively.

[0011] In one possible implementation, the converter module includes N converters, where N is a positive integer.

[0012] In one possible implementation, the N converters are N DC-AC converters; the input terminal of the converter module includes the DC input terminal corresponding to each of the N converters; the output terminal of the converter module includes the AC output terminal corresponding to each of the N converters; or, the N converters are N DC-DC converters; the input terminal of the converter module includes the DC input terminal corresponding to each of the N converters; the output terminal of the converter module includes the DC output terminal corresponding to each of the N converters.

[0013] In one possible implementation, the output terminal of the converter module is used to connect to an external target device, specifically including: each of the target devices is connected to the output terminal corresponding to any one of the N converters; and / or, each of the target devices is connected to the output terminals corresponding to multiple converters among the N converters.

[0014] In one possible implementation, the output terminal of the active rectifier module is connected to the input terminal of the converter module via the common DC bus. Specifically, the common DC bus comprises N busbar cable segments, wherein the number of busbar cables is the same as the number of converters. The output terminal of the active rectifier module is connected to each of the N converters via the N busbar cable segments.

[0015] In one possible implementation, the output of the active rectifier module is connected to any converter via a busbar cable to form an RLC series resonant circuit corresponding to any converter.

[0016] The technical solutions provided in this application have the following advantages compared with the prior art:

[0017] This application provides a common DC bus configuration. The input terminal of the LCL filter module is connected to an AC power input port, and the output terminal of the LCL filter module is connected to the input terminal of the active rectifier module. The combination of the LCL filter module and the active rectifier module enables power feedback, reducing harmonic components at the source and preventing bus oscillation. The output terminal of the active rectifier module is connected to the input terminal of the converter module via the common DC bus. The output terminal of the converter module is connected to external target equipment. During this process, the active rectifier module can output a stable and adjustable bus power to the common DC bus. The line voltage converter module, based on its connection to the common DC bus, converts the DC voltage input from the common DC bus into AC power with adjustable frequency and amplitude to drive loads such as motors. Compared with the prior art, the technical solution of this application, through the effective filtering effect of the LCL filter module and the coordinated work of the active rectifier module and the converter module, can effectively suppress the harmonic components in the DC bus, avoiding oscillation of the inverter system at its inherent frequency. Furthermore, the active rectifier module ensures the stability of the DC bus by adjusting the voltage, and the converter module generates a precise AC signal based on the stable DC voltage, further improving the system stability. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0021] Figure 1 This application provides a schematic diagram of a common DC bus topology circuit.

[0022] Figure 2 This is a schematic diagram of the structure of the LCL filter module provided in the embodiments of this application;

[0023] Figure 3 A schematic diagram of the structure of the active rectifier module provided in the embodiments of this application.

[0024] Figure 4 A schematic diagram of the converter module with 3 converters provided in this embodiment of the application;

[0025] Figure 5 A schematic diagram of a simplified DC bus topology circuit for a multi-machine drive frequency converter provided in an embodiment of this application;

[0026] Figure 6 This is another circuit structure diagram of a simplified DC bus topology circuit for a multi-machine drive frequency converter provided in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0029] For ease of description, spatial relative terms may be used in the text to describe the relative position or movement of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "front," "back," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure undergoes a positional flip, orientation change, or change of motion, these directional indications will change accordingly. For instance, an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0030] Figure 1 This application provides a schematic diagram of a common DC bus topology circuit according to an embodiment of the present application; as shown below. Figure 1 As shown, the common DC bus topology circuit includes an LCL filter module 10, an active rectifier module 20, a converter module 30, and a common DC bus 40, as detailed below:

[0031] The input terminal of the LCL filter module 10 is used to connect to the AC power input port, and the output terminal of the LCL filter module 10 is connected to the input terminal of the active rectifier module 20.

[0032] The output terminal of the active rectifier module 20 is connected to the input terminal of the converter module 30 through the common DC bus 40. The output terminal of the converter module 30 is used to connect to the external target device 50.

[0033] In one embodiment, the LCL filter module 10 is a multi-order filter that effectively suppresses AC voltage and current harmonics through a combination of series and parallel inductors and capacitors. This is because inductors impede AC current, i.e., inductive reactance XL, whose magnitude is proportional to the frequency f and the inductance L, i.e., XL = 2πfL. Therefore, as the frequency increases, the inductor's impediment to current strengthens, resulting in a strong suppression effect on high-frequency harmonic components. On the other hand, capacitors conduct AC current, i.e., capacitive reactance XC, whose magnitude is inversely proportional to the frequency f and the capacitance C, i.e., XC = 1 / (2πfC). Therefore, as the frequency increases, the capacitor's conduction effect on current strengthens, resulting in a stronger conduction effect on high-frequency harmonic components. In the LCL filter module 10, the combination of inductor and capacitor can form a resonant circuit. At the resonant frequency fr, the inductive reactance of the inductor and the capacitive reactance of the capacitor are equal, i.e., XL = XC. At this time, the circuit has the minimum impedance and the maximum current at a specific frequency. That is, for high-frequency components, since the inductive reactance of the inductor increases with frequency and the capacitive reactance of the capacitor decreases with frequency, the LCL filter module 10 can provide a larger impedance, thereby attenuating high-frequency components and effectively suppressing harmonics. Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of the LCL filter module provided in an embodiment of this application.

[0034] In one embodiment, the LCL filter module 10 includes a first inductor L101, a second inductor L102, a third inductor L103, a fourth inductor L104, a fifth inductor L105, a sixth inductor L106, a first capacitor C101, a second capacitor C102, and a third capacitor C103.

[0035] Specifically, the second end of the first inductor L101 is connected to the first end of the fourth inductor L104, the second end of the second inductor L102 is connected to the first end of the fifth inductor L105, and the second end of the third inductor L103 is connected to the first end of the sixth inductor L106; the first end of the first capacitor C101 and the first end of the second capacitor C102 are respectively connected to the second ends of the first inductor L101 and the fourth inductor L104, the second ends of the first capacitor C101 and the first end of the third capacitor C103 are respectively connected to the second ends of the second inductor L102 and the fifth inductor L105, and the second ends of the second capacitor C102 and the third capacitor C103 are respectively connected to the second ends of the third inductor L103 and the sixth inductor L106; the first ends of the first inductor L101, the second inductor L102, and the third inductor L103 are respectively connected to the AC power input port.

[0036] Specifically, by setting multiple inductors and capacitors in the LCL filter module 10 to form multiple series and parallel resonant circuits, this multi-stage filter structure can provide a wider stopband width and a higher suppression effect, especially in the high-frequency range. By adjusting the values ​​of each inductor and capacitor, filters with different resonant frequencies can be designed. In this way, the LCL filter module 10 can provide the maximum impedance for specific harmonic frequencies, thereby achieving effective suppression of these harmonics.

[0037] In one embodiment, the active rectifier module 20 is used to output a stable and adjustable bus voltage to the common DC bus 40. This is because the active rectifier module 20 is equipped with multiple insulated-gate bipolar transistor (IGBT) modules. These IGBT modules utilize a combination of IGBTs and freewheeling diodes, and control the rectification process through pulse width modulation (PWM) technology or phase control technology, thereby achieving precise adjustment of the output voltage. Figure 3 As shown, Figure 3 This is a schematic diagram of the structure of the active rectifier module provided in an embodiment of this application.

[0038] In one embodiment, the active rectifier module 20 includes a fourth capacitor C201, a first insulated gate bipolar transistor module IGBT201, a second insulated gate bipolar transistor module IGBT202, a third insulated gate bipolar transistor module IGBT203, a fourth insulated gate bipolar transistor module IGBT204, a fifth insulated gate bipolar transistor module IGBT205, and a sixth insulated gate bipolar transistor module IGBT206.

[0039] Specifically, the first insulated gate bipolar transistor module I GBT201 includes a first insulated gate bipolar transistor and a first freewheeling diode; wherein, the positive terminal of the first freewheeling diode is connected to the emitter of the first insulated gate bipolar transistor, and the negative terminal of the first freewheeling diode is connected to the collector of the first insulated gate bipolar transistor.

[0040] Specifically, the second insulated gate bipolar transistor module I GBT202 includes a second insulated gate bipolar transistor and a second freewheeling diode; wherein, the positive terminal of the second freewheeling diode is connected to the emitter of the second insulated gate bipolar transistor, and the negative terminal of the second freewheeling diode is connected to the collector of the second insulated gate bipolar transistor.

[0041] Specifically, the third insulated-gate bipolar transistor module I GBT203 includes a third insulated-gate bipolar transistor and a third freewheeling diode; wherein, the positive terminal of the third freewheeling diode is connected to the emitter of the third insulated-gate bipolar transistor, and the negative terminal of the third freewheeling diode is connected to the collector of the third insulated-gate bipolar transistor.

[0042] Specifically, the fourth insulated-gate bipolar transistor module I GBT204 includes a fourth insulated-gate bipolar transistor and a fourth freewheeling diode; wherein, the positive terminal of the fourth freewheeling diode is connected to the emitter of the fourth insulated-gate bipolar transistor, and the negative terminal of the fourth freewheeling diode is connected to the collector of the fourth insulated-gate bipolar transistor.

[0043] Specifically, the fifth insulated-gate bipolar transistor module I GBT205 includes a fifth insulated-gate bipolar transistor and a fifth freewheeling diode; wherein, the positive terminal of the fifth freewheeling diode is connected to the emitter of the fifth insulated-gate bipolar transistor, and the negative terminal of the fifth freewheeling diode is connected to the collector of the fifth insulated-gate bipolar transistor.

[0044] Specifically, the sixth insulated-gate bipolar transistor module I GBT206 includes a sixth insulated-gate bipolar transistor and a sixth freewheeling diode, wherein the anode of the sixth freewheeling diode is connected to the emitter of the sixth insulated-gate bipolar transistor, and the cathode of the sixth freewheeling diode is connected to the collector of the sixth insulated-gate bipolar transistor.

[0045] An insulated-gate bipolar transistor (IGBT) is a power electronic device that combines the high input impedance of a MOSFET with the low on-state voltage drop of a bipolar transistor. IGBTs can be used as switches to regulate current flow by controlling their turn-on and turn-off times. A freewheeling diode is used to provide a path for current when the IGBT is turned off, maintaining current continuity and preventing voltage spikes caused by sudden current interruptions.

[0046] Specifically, the emitter of the first insulated-gate bipolar transistor module I GBT201 is connected to the collector of the fourth insulated-gate bipolar transistor module I GBT204; the emitter of the second insulated-gate bipolar transistor module I GBT202 is connected to the collector of the fifth insulated-gate bipolar transistor module I GBT205; and the emitter of the third insulated-gate bipolar transistor module I GBT203 is connected to the collector of the sixth insulated-gate bipolar transistor module I GBT206. The collectors of the first, second, and third insulated-gate bipolar transistor modules I GBT201, I GBT202, and I GBT203 are respectively connected to the first terminal of the fourth capacitor C201. The emitters of the fourth, fifth, and sixth insulated-gate bipolar transistor modules I GBT204, I GBT205, and I GBT206 are all connected to the collector of the fourth insulated-gate bipolar transistor module I GBT206. The emitter of GBT206 is connected to the second terminal of the fourth capacitor C201.

[0047] The active rectifier module 20 provided in this embodiment can control the on and off times of each insulated gate bipolar transistor module through PWM technology, thereby controlling the magnitude of the rectified output voltage. The fourth capacitor serves as a filter capacitor to smooth voltage fluctuations after PWM rectification, reduce ripple, and thus provide a more stable DC bus voltage. In other words, the active rectifier module 20 achieves stable and adjustable control of the output voltage of the common DC bus 40 by precisely controlling the switching action of the insulated gate bipolar transistor modules, combined with PWM or phase control technology, and the use of filter capacitors.

[0048] In one embodiment, the output terminal of the LCL filter module 10 includes the second terminal of the fourth inductor L104, the second terminal of the fifth inductor L105, and the second terminal of the sixth inductor L106.

[0049] In one embodiment, the input terminal of the active rectifier module 20 includes the emitter of the first insulated gate bipolar transistor module I GBT201, the emitter of the second insulated gate bipolar transistor module I GBT202, the emitter of the third insulated gate bipolar transistor module I GBT203, the collector of the fourth insulated gate bipolar transistor module I GBT204, the collector of the fifth insulated gate bipolar transistor module I GBT205, and the collector of the sixth insulated gate bipolar transistor module I GBT206.

[0050] In one embodiment, when the output terminal of the LCL filter module 10 is connected to the input terminal of the active rectifier module 20, the second terminal of the fourth inductor L104 is connected to the emitter of the first insulated gate bipolar transistor module I GBT201 and the collector of the fourth insulated gate bipolar transistor module I GBT204, respectively; the second terminal of the fifth inductor L105 is connected to the emitter of the second insulated gate bipolar transistor module I GBT202 and the collector of the fifth insulated gate bipolar transistor module I GBT205, respectively; and the second terminal of the sixth inductor L106 is connected to the emitter of the third insulated gate bipolar transistor module I GBT203 and the collector of the sixth insulated gate bipolar transistor module I GBT206, respectively.

[0051] In one embodiment, the LCL filter module 10 filters the voltage and current on the power supply side through a combination of inductors and capacitors, reducing high-frequency harmonic components. It provides a smoother and more stable voltage input to the active rectifier module 20 through the output terminal. Furthermore, the second terminal of each inductor at the output terminal of the LCL filter module 10 is connected to the emitter and collector of the corresponding IGBT module, respectively. This connection method helps to distribute the filtered current evenly to each IGBT module, achieving three-phase balance.

[0052] In one embodiment, since the multi-machine drive is a rectifier module equipped with multiple converters, and the multiple converters are interconnected through a common DC bus 40; therefore, in this embodiment, the converter module 30 includes N converters, where N is a positive integer; by integrating multiple converters into one converter module and adjusting the number of converters according to requirements, it is possible to flexibly adapt to different power requirements and application scenarios.

[0053] Preferably, the N converters include, but are not limited to, N DC-DC converters or N DC-AC converters.

[0054] In this embodiment, the converter module 30 is illustrated using an example where N converters are N DC-AC converters and N is 3. Figure 4 As shown, Figure 4 This is a schematic diagram of the converter module provided in this application embodiment when the number of converters is 3; when N is 3, the N converters include a first DC-AC converter DC-AC301, a second DC-AC converter DC-AC303 and a third DC-AC converter DC-AC303.

[0055] Preferably, the number of multiple converters in the converter module 30 can be set based on actual needs; when N is 2, the N converters include a first converter and a second converter; when N is 4, the N converters include a first converter, a second converter, a third converter, and a fourth converter, and so on.

[0056] Specifically, when the N converters are N DC-AC converters, the input terminal of the converter module includes the DC input terminal corresponding to each of the N DC-AC converters; the output terminal of the converter module includes the AC output terminal corresponding to each of the N DC-AC converters.

[0057] When N is 3, and the N DC-AC converters include a first DC-AC converter DC-AC301, a second DC-AC converter DC-AC303, and a third DC-AC converter DC-AC303, the input terminals of the converter module 30 include the DC input terminals of the first DC-AC converter DC-AC301, the second DC-AC converter DC-AC302, and the third DC-AC converter DC-AC303; the output terminals of the converter module 30 include the AC output terminals of the first DC-AC converter DC-AC301, the second DC-AC converter DC-AC302, and the third DC-AC converter DC-AC303.

[0058] Specifically, the N converters are N DC-DC converters; the input terminal of the converter module includes the DC input terminal corresponding to each of the N DC-DC converters; the output terminal of the converter module includes the DC output terminal corresponding to each of the N DC-DC converters.

[0059] Specifically, when N is 3, and the N converters include a first DC-DC converter DC-AC301, a second DC-DC converter DC-AC303, and a third DC-DC converter DC-AC303, the input terminals of the converter module 30 include the DC input terminals of the first DC-DC converter DC-AC301, the second DC-DC converter DC-AC302, and the third DC-DC converter DC-AC303; the output terminals of the converter module 30 include the AC output terminals of the first DC-DC converter DC-AC301, the second DC-DC converter DC-AC302, and the third DC-DC converter DC-AC303.

[0060] In one embodiment, the output terminal of the converter module 30 is used to connect to an external target device 50.

[0061] Specifically, when the converter is a DC-AC converter, the target device includes, but is not limited to, a three-phase AC motor; in this process, the DC-AC converter converts DC voltage into variable AC voltage and frequency to drive the three-phase AC motor.

[0062] Specifically, when the converter is a DC-DC converter, the target device includes, but is not limited to, a battery energy storage device.

[0063] In one embodiment, the target device 50 may include one or more target devices; preferably, the number of target devices 50 may be set based on actual needs.

[0064] In this embodiment, the target device 20 is a three-phase AC motor and the number of target devices 50 is 2, which is specifically described as follows: the target device 50 includes a first three-phase AC motor and a second three-phase AC motor.

[0065] Specifically, when the output terminal of the converter module 30 is used to connect to an external target device 50, any target device can be connected to the output terminal corresponding to any one of the N converters, or any target device can be connected to the output terminals corresponding to multiple converters among the N converters.

[0066] Taking the example of a three-phase AC motor as the target device 20 and two target devices 50, the AC output terminal of the first DC-AC converter DC-AC301 is connected to the first three-phase AC motor, that is, any one of the target devices is connected to the output terminal of any one of the N converters; the AC output terminals of the second DC-AC converter DC-AC302 and the third DC-AC converter DC-AC303 are respectively connected to the second three-phase AC motor, that is, any one of the target devices is connected to the output terminals of multiple converters among the N converters.

[0067] Preferably, the AC output terminals of the second DC-AC converter DC-AC302 and the third DC-AC converter DC-AC303 are respectively connected to the second three-phase AC motor in order to improve the total power output to the three-phase AC motor, which is not limited by the rated power of a single converter; if one converter fails, the other can continue to operate, thereby improving the redundancy and reliability of the system.

[0068] Preferably, in addition to connecting the outputs of two converters to one target device, multiple converters can also be connected to one target device.

[0069] In one embodiment, the common DC bus includes N busbar cables; wherein the number of busbar cables is the same as the number of converters; that is, when there are N converters in the converter module 30, the common DC bus 40 includes N busbar cables.

[0070] Specifically, if there are three converters in the converter module 30, then the common DC bus includes three busbar cables, that is, the common DC bus 40 includes a first busbar cable 401, a second busbar cable 402 and a third busbar cable 403.

[0071] In one embodiment, taking the common DC bus as an example comprising three busbar cables, when the output terminal of the active rectifier module 20 is connected to the input terminal of the converter module 30 through the common DC bus 40, the output terminal of the active rectifier module 20 is connected to the first DC-AC converter DC-AC301 through the first busbar cable 401, the output terminal of the active rectifier module 20 is connected to the second DC-AC converter DC-AC302 through the first busbar cable 401 and the second busbar cable 402, and the output terminal of the active rectifier module 20 is connected to the third DC-AC converter DC-AC303 through the first busbar cable 401, the second busbar cable 402 and the third busbar cable 403.

[0072] Specifically, by using multiple busbar cables to distribute the output of the active rectifier module 20 to multiple converters, flexible and scalable power distribution can be achieved to adapt to different application requirements and spatial layouts.

[0073] In one embodiment, in a frequency converter system, the inherent oscillation frequency is the characteristic frequency of each subsystem. Different rectification and converter control methods will generate different harmonic frequency components. When the system's harmonic frequency coincides with the system's inherent oscillation frequency, system resonance will occur. Therefore, it is necessary to avoid the harmonic frequency coinciding with the system's inherent oscillation frequency during the design phase.

[0074] For a 50Hz AC input, when rectification uses PWM (Pulse Width Modulation), a relatively high carrier frequency, such as 3kHz, is typically chosen. Due to the presence of the freewheeling diode, the main harmonic components on the DC bus are predominantly 300Hz, along with harmonic components that are integer multiples of the carrier frequency. As the carrier frequency increases, the amplitude of these higher harmonics gradually decreases, and typically, these higher harmonics do not have a significant impact on the system.

[0075] For low-voltage frequency converters, the carrier frequency of converter module 30 is generally set to 1.5kHz. At this frequency, the harmonic components on the DC bus are mainly concentrated around integer multiples of 1.5kHz and their upper and lower sideband frequencies. These harmonic frequencies will have a certain impact on the DC bus, therefore, special attention needs to be paid to the management of these frequency components.

[0076] To effectively manage system harmonics and reduce resonance risks, it is first necessary to determine the main harmonic components of the system through theoretical analysis and simulation verification. By establishing the frequency band of the resonant frequency and ensuring that the system's operating frequency and natural oscillation frequency do not coincide, resonance can be avoided at its source. Specifically, frequency analysis of the bus harmonics should be performed during the design phase to ensure sufficient spacing between the operating frequency and the main harmonic components. This can minimize system instability caused by the coincidence of harmonics and oscillation frequencies.

[0077] In one embodiment, in a multi-motor drive system, the DC bus consists of parasitic resistance, inductance, and capacitance, which are connected together in series and parallel. Compared to a single drive system, the resonant characteristics of the bus become more complex, mainly in the number and nature of the resonant points. Resonance analysis requires comprehensive consideration of these complex factors. Since the electrical characteristics of each branch in the bus are different, each branch can be considered as an RLC series resonant circuit. An RLC series resonant circuit satisfying the resonance condition does not directly cause the entire system to oscillate, but rather exhibits low impedance characteristics. Simultaneously, since other branches do not satisfy the resonance condition, their impedances will not be zero, thus avoiding the formation of low-impedance loops and preventing circulating current phenomena.

[0078] However, in order to accurately and comprehensively analyze the resonant frequency of the bus circuit and study the conditions for bus oscillation, considering the complexity of the system, the DC bus topology circuit of the multi-machine drive frequency converter provided in this embodiment can be simplified. This simplification process can effectively reduce the complexity of the analysis, help us to understand the interaction between various electrical components more clearly, and finally obtain a simplified DC bus topology circuit of a multi-machine drive frequency converter that can more accurately describe the bus oscillation and resonance behavior.

[0079] In one embodiment, each branch can be considered as an RLC series resonant circuit. It is understood that the output of the active rectifier module is connected to any converter via a busbar cable, forming an RLC series resonant circuit corresponding to that converter. Taking a converter count of 3 as an example: the output of the active rectifier module 20 is connected to the first converter via the first busbar cable, forming a first RLC series resonant circuit; the output of the active rectifier module 20 is connected to the second converter via the first and second busbar cables, forming a second RLC series resonant circuit; and the output of the active rectifier module 20 is connected to the third converter via the first, second, and third busbar cables, forming a third RLC series resonant circuit.

[0080] In one embodiment, taking a converter with 3 converters as an example, the simplified DC bus topology circuit of the multi-machine drive frequency converter is constructed, including a first RLC series resonant circuit, a second RLC series resonant circuit, a third RLC series resonant circuit, and a rectifier unit output capacitor.

[0081] Specifically, the first RLC series resonant circuit includes a first parasitic resistance and a first stray inductance equivalent to the first busbar cable segment, and a second parasitic resistance, a second stray inductance, and a second bus capacitance equivalent to the first converter; the second RLC series resonant circuit includes a first parasitic resistance and a first stray inductance equivalent to the first busbar cable segment, a fifth parasitic resistance and a fifth stray inductance equivalent to the second busbar cable segment, and a third parasitic resistance, a third stray inductance, and a third bus capacitance equivalent to the second converter; the third RLC series resonant circuit includes a first parasitic resistance and a first stray inductance equivalent to the first busbar cable segment, a fifth parasitic resistance and a fifth stray inductance equivalent to the second busbar cable segment, and a fourth parasitic resistance, a fourth stray inductance, and a fourth bus capacitance equivalent to the third busbar cable segment and the third converter.

[0082] Specifically, such as Figure 5 As shown, Figure 5This is a schematic diagram of a simplified DC bus topology circuit for a multi-machine drive frequency converter provided in this application embodiment. In the simplified DC bus topology circuit, the second terminal of the rectifier unit output capacitor is connected to the first terminal of the first parasitic resistor R1. The second terminal of the first parasitic resistor R1 is connected to the first terminal of the first stray inductor L1. The second terminal of the first stray inductor L1 is connected to the first terminals of the second parasitic resistor R2 and the fifth parasitic resistor R5. The second terminal of the second parasitic resistor R2 is connected to the first terminal of the second stray inductor L2 and the first terminal of the second bus capacitor C2. The second terminal of the fifth parasitic resistor R5 is connected to the first terminal of the fifth stray inductor L5. The second terminal of the fifth stray inductor L5 is connected to the third parasitic resistor R... The first end of the third parasitic resistor R3 is connected to the first end of the third stray inductor L3. The second end of the third stray inductor L3 is connected to the first end of the third bus capacitor. The second end of the fourth parasitic resistor R4 is connected to the first end of the fourth stray inductor L4. The second end of the fourth stray inductor L4 is connected to the first end of the fourth bus capacitor C3. The second ends of the second bus capacitor C2, the third bus capacitor L3, and the fourth bus capacitor C3 are respectively connected to the first end of the rectifier unit output capacitor C1. Bus harmonic components exist in the connections between the second ends of the second bus capacitor C2, the third bus capacitor L3, and the fourth bus capacitor C3 and the rectifier unit output capacitor C1.

[0083] Analysis of the total impedance of a multi-machine drive frequency converter based on a simplified DC bus topology circuit:

[0084] Taking a copper core cable with a cross-sectional area of ​​150 mm², a length of 1 meter, and an ambient temperature of 20°C as an example, the formula for calculating the parasitic resistance is as follows:

[0085]

[0086] The formula for calculating parasitic inductance under the same specifications is as follows:

[0087]

[0088] Taking the 300Hz harmonic component as the object of study, the capacitive reactance is approximately 1600 times that of the parasitic resistance. Therefore, the influence of parasitic resistance can be ignored in the overall system analysis. The parasitic resistance of the bus capacitors, especially electrolytic capacitors, is relatively large, reaching the mΩ level, and cannot be ignored; it must be considered in the resonance analysis.

[0089] Since C1 represents the output capacitor of the rectifier unit, Hw represents the bus harmonic component, R1 and L1 represent the first parasitic resistance and the first stray inductance on the first busbar cable; R2, L2 and C2 represent the second parasitic resistance (ESR), the second stray inductance and the second busbar capacitor of the first converter module 30, respectively; R5 and L5 represent the fifth parasitic resistance and the fifth stray inductance on the second busbar cable; R3, L3 and C3 represent the third parasitic resistance (ESR), the third stray inductance and the second busbar capacitor of the second converter module 30, respectively. Stray inductance and third bus capacitor; R4, L4, and C4 represent the fourth parasitic resistance (ESR), fourth stray inductance, and fourth bus capacitor of the third converter module 30, respectively; from the above analysis, it can be seen that the influence of the first parasitic resistance R1 and the fifth parasitic resistance R5 of the bus cable can be ignored. The ESR of the electrolytic capacitor of the converter module 30, i.e., the second parasitic resistance R2, the third parasitic resistance R3, and the fourth parasitic resistance R4, needs to be taken into account. The impedance of the entire system can be expressed as a series-parallel combination of X1-X4, such as... Figure 6 As shown, Figure 6 This application provides another simplified circuit diagram of a DC bus topology for a multi-machine drive frequency converter, where the total system impedance XT can be expressed as:

[0090] X T =X1+X2 / / (X5+X3 / / X4);

[0091] Since only AC components can cause resonance, we only consider the imaginary part of the total impedance. When the imaginary part is zero, the total impedance is minimized, and the bus oscillates. Based on the above analysis, according to the topology and algorithm structure of the rectifier and converter, we determine the components of the bus harmonics, and then determine a safe frequency band so that all the system's inherent resonant frequencies are within this band, and the harmonic components are outside this band, thus minimizing the possibility of bus oscillation. Based on this principle, we proceed with the selection of bus capacitors and cables.

[0092] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0093] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0094] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0095] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0096] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0097] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0098] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Since these modifications and variations fall within the scope of the claims and their equivalents, this application also intends to include these modifications and variations.

[0099] The above description describes specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A common DC bus topology circuit, characterized by, The utility model relates to a kind of active rectifier module and a kind of active rectifier module control method. It includes: LCL filter module, active rectifier module, current conversion module and common DC bus; The input end of the LCL filter module is connected with the AC power input port, and the output end of the LCL filter module is connected with the input end of the active rectifier module.

2. The common DC bus topology circuit of claim 1, wherein, The output end of the active rectifier module is connected with the input end of the current conversion module through the common DC bus, and the output end of the current conversion module is connected with the external target device. The LCL filter module includes first inductor, second inductor, third inductor, fourth inductor, fifth inductor, sixth inductor, first capacitor, second capacitor and third capacitor. The second end of the first inductor is connected with the first end of the fourth inductor, the second end of the second inductor is connected with the first end of the fifth inductor, and the second end of the third inductor is connected with the first end of the sixth inductor. The first end of the first capacitor and the first end of the second capacitor are respectively connected with the second end of the first inductor and the second end of the fourth inductor, the second end of the first capacitor and the first end of the third capacitor are respectively connected with the second end of the second inductor and the second end of the fifth inductor, and the second end of the second capacitor and the second end of the third capacitor are respectively connected with the second end of the third inductor and the second end of the sixth inductor.

3. The common DC bus topology circuit of claim 2, wherein, The first end of the first inductor, the first end of the second inductor and the first end of the third inductor are respectively connected with the AC power input port. The active rectifier module includes fourth capacitor, first insulated gate bipolar transistor module, second insulated gate bipolar transistor module, third insulated gate bipolar transistor module, fourth insulated gate bipolar transistor module, fifth insulated gate bipolar transistor module and sixth insulated gate bipolar transistor module. The emitter of the first insulated gate bipolar transistor module is connected with the collector of the fourth insulated gate bipolar transistor module, the emitter of the second insulated gate bipolar transistor module is connected with the collector of the fifth insulated gate bipolar transistor module, and the emitter of the third insulated gate bipolar transistor module is connected with the collector of the sixth insulated gate bipolar transistor module. The collector of the first insulated gate bipolar transistor module, the collector of the second insulated gate bipolar transistor module and the collector of the third insulated gate bipolar transistor module are respectively connected with the first end of the fourth capacitor.

4. The common DC bus topology circuit of claim 3, wherein, The emitter of the fourth insulated gate bipolar transistor module, the emitter of the fifth insulated gate bipolar transistor module and the emitter of the sixth insulated gate bipolar transistor module are respectively connected with the second end of the fourth capacitor. The first insulated gate bipolar transistor module includes first insulated gate bipolar transistor and first freewheeling diode. The second insulated gate bipolar transistor module includes second insulated gate bipolar transistor and second freewheeling diode. The third insulated gate bipolar transistor module includes third insulated gate bipolar transistor and third freewheeling diode. The fourth insulated gate bipolar transistor module comprises a fourth insulated gate bipolar transistor and a fourth freewheeling diode; The fifth insulated gate bipolar transistor module comprises a fifth insulated gate bipolar transistor and a fifth freewheeling diode; The sixth insulated gate bipolar transistor module comprises a sixth insulated gate bipolar transistor and a sixth freewheeling diode.

5. The common DC bus topology circuit of claim 3, wherein, The output end of the LCL filter module is connected with the input end of the active rectifier module, and specifically comprises: The output end of the LCL filter module comprises the second end of the fourth inductor, the second end of the fifth inductor and the second end of the sixth inductor; The input end of the active rectifier module comprises the emitter of the first insulated gate bipolar transistor module, the emitter of the second insulated gate bipolar transistor module, the emitter of the third insulated gate bipolar transistor module, the collector of the fourth insulated gate bipolar transistor module, the collector of the fifth insulated gate bipolar transistor module and the collector of the sixth insulated gate bipolar transistor module; The second end of the fourth inductor is connected with the emitter of the first insulated gate bipolar transistor module and the collector of the fourth insulated gate bipolar transistor module respectively, the second end of the fifth inductor is connected with the emitter of the second insulated gate bipolar transistor module and the collector of the fifth insulated gate bipolar transistor module respectively, and the second end of the sixth inductor is connected with the emitter of the third insulated gate bipolar transistor module and the collector of the sixth insulated gate bipolar transistor module respectively.

6. The common DC bus topology circuit of claim 1, wherein, The current conversion module comprises N current converters, wherein N is a positive integer.

7. The common DC bus topology circuit of claim 6, wherein, The N current converters are N DC-AC current converters; The input end of the current conversion module comprises the DC input end corresponding to each of the N current converters; The output end of the current conversion module comprises the AC output end corresponding to each of the N current converters; Or, The N current converters are N DC-DC current converters; The input end of the current conversion module comprises the DC input end corresponding to each of the N current converters; The output end of the current conversion module comprises the DC output end corresponding to each of the N current converters.

8. The common DC bus topology circuit of claim 7, wherein, The output end of the current conversion module is used for being connected with an external target device, and specifically comprises: Any target device is connected with the output end corresponding to any current converter in the N current converters respectively; And / or, Any target device is connected with the output end corresponding to multiple current converters in the N current converters respectively.

9. The common DC bus topology circuit of claim 6, wherein, The output end of the active rectifier module is connected with the input end of the current conversion module through the common DC bus, and specifically comprises: The common DC bus comprises N busbar cables; wherein the number of the busbar cables is the same as the number of the current converters, The output end of the active rectifier module is connected with the N current converters through the N busbar cables respectively.

10. The common DC bus topology circuit of claim 8, wherein, The output end of the active rectifier module is connected with any current converter through a busbar cable, thereby forming an RLC series resonant circuit corresponding to the any current converter.

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