A three-phase inverter circuit

Abstract

The application provides a three-phase inverter circuit, comprising: a front-stage voltage generation sub-circuit for collectively generating a plurality of voltage levels required by three-phase output and outputting via a shared filter inductor; and a rear-stage voltage distribution sub-circuit connected to the output end of the front-stage voltage generation sub-circuit for distributing the plurality of voltage levels generated by the front-stage voltage generation sub-circuit to each phase AC output end as required. Thus, the three-phase inverter circuit of the application decouples voltage generation and voltage distribution functions, so that the switch tubes in the rear-stage voltage distribution sub-circuit only work in a low-frequency commutation state, avoiding the action of high-frequency switching of all switch tubes in the conventional topology. The main high-frequency switching loss of the rear-stage power circuit is fundamentally eliminated, thereby significantly improving the conversion efficiency of the entire three-phase inverter circuit.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a three-phase inverter circuit. Background Technology

[0002] In power systems, residential and industrial electricity is predominantly AC, while photovoltaic (PV) and battery-powered energy generation or storage devices primarily output DC. To achieve efficient utilization of clean energy, DC power must be converted to AC for grid connection or use by loads. For example, in grid-connected PV systems, inverters convert the DC power generated by solar panels into AC power for grid feed. In energy storage systems, the DC power stored in batteries also needs to be released as AC power by inverters. These DC-to-AC conversion devices—inverters—are core equipment in renewable energy integration, off-grid / microgrid power supply, and power quality control. Since commercial, industrial, and power plant applications typically require connection to a three-phase grid, three-phase inverters play a crucial role. Therefore, improving the conversion efficiency, power density, and reliability of three-phase inverters while reducing their system costs is of great significance for promoting energy transition and advancing power electronics technology.

[0003] Existing three-phase inverters commonly fall into two main topologies: two-level and three-level. Two-level topologies are simple in structure, but suffer from high switching losses in transistors and high inductor losses, resulting in low overall system conversion efficiency. Furthermore, optimizing cost, size, and weight is challenging. Three-level topologies, compared to two-level topologies, reduce switching losses and inductor costs, but require more transistors, resulting in higher costs and increased control complexity. Summary of the Invention

[0004] This invention was made to solve the above-mentioned problems, and its purpose is to provide a three-phase inverter circuit.

[0005] This invention provides a three-phase inverter circuit, characterized by: a front-stage voltage generation sub-circuit for centrally generating multiple voltage levels required for the three-phase output and outputting them via a shared filter inductor; and a rear-stage voltage distribution sub-circuit connected to the output terminal of the front-stage voltage generation sub-circuit for distributing the multiple voltage levels generated by the front-stage voltage generation sub-circuit to the AC output terminals of each phase as needed.

[0006] In a three-phase inverter circuit provided by this invention, the following feature may also be included: the front-stage voltage generation sub-circuit comprises: a first capacitor for filtering; a first half-bridge connected to the first capacitor for generating the required instantaneous maximum voltage; a first filter inductor connected to the first half-bridge for filtering; a second half-bridge connected to both the first half-bridge and the first filter inductor for generating the neutral point voltage; a second filter inductor connected to both the second half-bridge and the neutral line for filtering; a third half-bridge connected to the second half-bridge for generating the required instantaneous intermediate voltage; and a third filter inductor connected to the third half-bridge for filtering.

[0007] In a three-phase inverter circuit provided by the present invention, it may also have the following features: wherein the first half-bridge includes: a first switching transistor, the first end of which is connected to the first end of the first capacitor, and the second end of which is connected to the first end of the first filter inductor, for controlling the circuit to turn on and off according to a signal; and a second switching transistor, the first end of which is connected to the first end of the first filter inductor, and the second end of which is connected to the second end of the first capacitor, for controlling the circuit to turn on and off according to a signal.

[0008] In a three-phase inverter circuit provided by the present invention, the following features may also be included: wherein the second half-bridge includes: a third switching transistor, the first end of which is connected to the second end of the first filter inductor, and the second end of which is connected to the first end of the second filter inductor, for controlling the circuit to turn on and off according to a signal; and a fourth switching transistor, the first end of which is connected to the first end of the second filter inductor, and the second end of which is connected to the second end of the first capacitor, for controlling the circuit to turn on and off according to a signal.

[0009] In a three-phase inverter circuit provided by the present invention, the following features may also be included: wherein the third half-bridge comprises: a fifth switching transistor, the first end of which is connected to the second end of the first filter inductor, and the second end of which is connected to the first end of the third filter inductor, for controlling the circuit to turn on and off according to a signal; and a sixth switching transistor, the first end of which is connected to the first end of the third filter inductor, and the second end of which is connected to the second end of the first capacitor, for controlling the circuit to turn on and off according to a signal.

[0010] In a three-phase inverter circuit provided by this invention, the following features may also be included: the subsequent voltage distribution sub-circuit comprises: a second capacitor connected to the third half-bridge and the third filter inductor respectively, for voltage division of the DC bus; a third capacitor connected to the third half-bridge and the third filter inductor respectively, for voltage division of the DC bus; an intermediate voltage gating unit connected to the second capacitor, the third capacitor and the third filter inductor respectively, for distributing the intermediate voltage; and a maximum and minimum voltage gating unit connected to the second capacitor, the third capacitor and the intermediate voltage gating unit respectively, for distributing the maximum voltage and the minimum voltage.

[0011] In a three-phase inverter circuit provided by this invention, the following feature is also included: the intermediate voltage selection unit comprises: a seventh switch, the first terminal of which is connected to the second terminal of a third filter inductor, used to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal according to the on / off state of the signal control circuit; an eighth switch, the first terminal of which is connected to the second terminal of the seventh switch, used to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal according to the on / off state of the signal control circuit; and a ninth switch, the first terminal of which is connected to the second terminal of the third filter inductor, used to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal according to the on / off state of the signal control circuit. The 10th switch, with its first terminal connected to the second terminal of the 9th switch, is used to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal according to the signal control circuit's on / off state. The 11th switch, with its first terminal connected to the second terminal of the 3rd filter inductor, is used to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal according to the signal control circuit's on / off state. The 12th switch, with its first terminal connected to the second terminal of the 11th switch, is used to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal according to the signal control circuit's on / off state.

[0012] In a three-phase inverter circuit provided by this invention, the following feature is also included: the highest and lowest voltage selection unit comprises: a thirteenth switch, the first terminal of which is connected to the second terminal of the first filter inductor, and the second terminal of which is connected to the second terminal of the eighth switch, used to transmit the instantaneous three-phase highest voltage to the corresponding phase output terminal according to the on / off state of the signal control circuit; a fourteenth switch, the first terminal of which is connected to the second terminal of the first filter inductor, and the second terminal of which is connected to the second terminal of the tenth switch, used to transmit the instantaneous three-phase highest voltage to the corresponding phase output terminal according to the on / off state of the signal control circuit; and a fifteenth switch, the first terminal of which is connected to the second terminal of the first filter inductor, and the second terminal of which is connected to the second terminal of the twelfth switch, used to transmit the instantaneous three-phase highest voltage to the corresponding phase output terminal according to the on / off state of the signal control circuit. The first switch, the 16th switch, has its first terminal connected to the second terminal of the 8th switch and phase A, and its second terminal connected to the second terminal of the first capacitor. It is used to control the on / off state of the circuit according to a signal, transmitting the instantaneous three-phase lowest voltage to the corresponding phase output. The second switch, the 17th switch, has its first terminal connected to the second terminal of the 10th switch and phase B, and its second terminal connected to the second terminal of the first capacitor. It is used to control the on / off state of the circuit according to a signal, transmitting the instantaneous three-phase lowest voltage to the corresponding phase output. The third switch, the 18th switch, has its first terminal connected to the second terminal of the 12th switch and phase C, and its second terminal connected to the second terminal of the first capacitor. It is used to control the on / off state of the circuit according to a signal, transmitting the instantaneous three-phase lowest voltage to the corresponding phase output.

[0013] The role and effect of invention

[0014] According to the present invention, a three-phase inverter circuit includes: a front-stage voltage generation sub-circuit for centrally generating multiple voltage levels required for the three-phase output and outputting them via a shared filter inductor; and a rear-stage voltage distribution sub-circuit connected to the output terminal of the front-stage voltage generation sub-circuit for distributing the multiple voltage levels generated by the front-stage voltage generation sub-circuit to the AC output terminals of each phase as needed. Therefore, the three-phase inverter circuit of the present invention decouples the voltage generation and voltage distribution functions, allowing the switching transistors in the rear-stage voltage distribution sub-circuit to operate only at the power frequency or twice the power frequency commutation state, avoiding the need for all switching transistors to perform high-frequency switching operations in traditional topologies. This fundamentally eliminates the main high-frequency switching losses in the rear-stage power circuit, thereby significantly improving the conversion efficiency of the entire three-phase inverter circuit. Attached Figure Description

[0015] Figure 1 This is a circuit diagram of the three-phase inverter circuit in Embodiment 1 of the present invention.

[0016] Figure 2 This is a waveform diagram of the three-phase inverter circuit in operation in Embodiment 1 of the present invention.

[0017] Figure 3 This is a circuit diagram of a three-phase inverter circuit with another structure in Embodiment 2 of the present invention. Detailed Implementation

[0018] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between 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.

[0019] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments, in conjunction with the accompanying drawings, provide a detailed description of the three-phase inverter circuit of this invention.

[0020] Example 1

[0021] Figure 1 This is a circuit diagram of a three-phase inverter circuit in an embodiment of the present invention.

[0022] This embodiment provides a three-phase inverter circuit 100, including: a front-stage voltage generation sub-circuit 1 and a rear-stage voltage distribution sub-circuit 2.

[0023] The front-end voltage generation sub-circuit 1 is used to centrally generate multiple voltage levels required for the three-phase output and output them through a common filter inductor. BUS+ is the positive DC bus input terminal, BUS- is the negative DC bus input terminal, and the voltage difference between the two is the DC bus voltage (Vdc).

[0024] The front-end voltage generation sub-circuit 1 includes: a first capacitor C1, a first half-bridge, a first filter inductor L1, a second half-bridge, a second filter inductor L2, a third half-bridge, and a third filter inductor L3.

[0025] The first capacitor C1 is used for filtering. The first terminal of the first capacitor C1 is connected to the BUS+ positive DC bus input terminal, and the second terminal is connected to the BUS- negative DC bus input terminal. The first capacitor C1 is also used to stabilize the DC bus voltage.

[0026] The first half-bridge is connected to the first capacitor C1 to generate the required instantaneous maximum voltage.

[0027] The first half-bridge includes: a first switch S1 and a second switch S2.

[0028] The first terminal of the first switch S1 is connected to the first terminal of the first capacitor C1, and the second terminal is connected to the first terminal of the first filter inductor L1, which is used to control the circuit to turn on and off according to the signal.

[0029] The first terminal of the second switch S2 is connected to the first terminal of the first filter inductor L1, and the second terminal is connected to the second terminal of the first capacitor C1, which is used to control the circuit to turn on and off according to the signal.

[0030] The first filter inductor L1 is connected to the first half-bridge and is used for filtering.

[0031] The second half-bridge is connected to the first half-bridge and the first filter inductor L1 respectively, and is used to generate the neutral point voltage.

[0032] The second half-bridge includes: a third switch S3 and a fourth switch S4.

[0033] The first terminal of the third switch S3 is connected to the second terminal of the first filter inductor L1, and the second terminal is connected to the first terminal of the second filter inductor L2, which is used to control the circuit to turn on and off according to the signal.

[0034] The first terminal of the fourth switch S4 is connected to the first terminal of the second filter inductor L2, and the second terminal is connected to the second terminal of the first capacitor C1, which is used to control the circuit to turn on and off according to the signal.

[0035] The second filter inductor L2 is connected to the second half-bridge and the neutral line respectively, and is used for filtering.

[0036] The third half-bridge is connected to the second half-bridge and is used to generate the required instantaneous intermediate voltage.

[0037] The third half-bridge includes: the fifth switch S5 and the sixth switch S6.

[0038] The first terminal of the fifth switch S5 is connected to the second terminal of the first filter inductor L1, and the second terminal is connected to the first terminal of the third filter inductor L3, which is used to control the circuit to turn on and off according to the signal.

[0039] The first terminal of the sixth switch S6 is connected to the first terminal of the third filter inductor L3, and the second terminal is connected to the second terminal of the first capacitor C1, which is used to control the circuit to turn on and off according to the signal.

[0040] The third filter inductor L3 is connected to the third half-bridge and is used for filtering.

[0041] In this embodiment, the switching transistors in the front-end voltage generation sub-circuit 1 are all composed of a power MOSFET and a power diode. The drain of the power MOSFET is connected to the cathode of the power diode, and the source of the power MOSFET is connected to the anode of the power diode. The power MOSFET is used to control the circuit to turn on and off according to the signal, and the power diode is used for freewheeling.

[0042] The subsequent voltage distribution sub-circuit 2 is connected to the output terminal of the preceding voltage generation sub-circuit 1, and is used to distribute the multiple voltage levels generated by the preceding voltage generation sub-circuit 1 to each phase AC output terminal as needed.

[0043] The subsequent voltage distribution sub-circuit 2 includes: a second capacitor C2, a third capacitor C3, an intermediate voltage selection unit 21, and a maximum and minimum voltage selection unit 22.

[0044] The second capacitor C2 is connected to the third half-bridge and the third filter inductor L3 respectively, and is used to divide the DC bus voltage.

[0045] The third capacitor C3 is connected to the third half-bridge and the third filter inductor L3, respectively, and is used to divide the DC bus voltage.

[0046] The intermediate voltage gating unit 21 is connected to the second capacitor C2, the third capacitor C3 and the third filter inductor L3 respectively, and is used to distribute the intermediate voltage.

[0047] The intermediate voltage selection unit 21 includes: a seventh switch S7, an eighth switch S8, a ninth switch S9, a tenth switch S10, an eleventh switch S11, and a twelfth switch S12.

[0048] The first terminal of the seventh switch S7 is connected to the second terminal of the third filter inductor L3, and is used to control the circuit to switch on and off according to the signal, so as to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal.

[0049] The first terminal of the eighth switch S8 is connected to the second terminal of the seventh switch S7, and is used to control the circuit to switch on and off according to the signal, so as to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal.

[0050] The first terminal of the ninth switch S9 is connected to the second terminal of the third filter inductor L3, and is used to control the circuit to switch on and off according to the signal, so as to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal.

[0051] The first terminal of the tenth switch S10 is connected to the second terminal of the ninth switch S9, and is used to control the circuit to switch on and off according to the signal to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal.

[0052] The first terminal of the eleventh switch S11 is connected to the second terminal of the third filter inductor L3, and is used to control the circuit to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal according to the signal control circuit.

[0053] The first terminal of the twelfth switch S12 is connected to the second terminal of the eleventh switch S11, and is used to control the circuit to switch on and off according to the signal, so as to transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal.

[0054] The highest and lowest voltage selection unit 22 is connected to the second capacitor C2, the third capacitor C3 and the intermediate voltage selection unit respectively, and is used to allocate the highest voltage and the lowest voltage.

[0055] The highest and lowest voltage selection unit 22 includes: the thirteenth switch S13, the fourteenth switch S14, the fifteenth switch S15, the sixteenth switch S16, the seventeenth switch S17, and the eighteenth switch S18.

[0056] The first terminal of the thirteenth switch S13 is connected to the second terminal of the first filter inductor L1, and the second terminal is connected to the second terminal of the eighth switch S8. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase highest voltage to the corresponding phase output terminal.

[0057] The first terminal of the fourteenth switch S14 is connected to the second terminal of the first filter inductor L1, and the second terminal is connected to the second terminal of the tenth switch S10. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase highest voltage to the corresponding phase output terminal.

[0058] The first terminal of the fifteenth switch S15 is connected to the second terminal of the first filter inductor L1, and the second terminal is connected to the second terminal of the twelfth switch S12. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase highest voltage to the corresponding phase output terminal.

[0059] The first terminal of the sixteenth switch S16 is connected to the second terminal of the eighth switch S8 and phase A, respectively. The second terminal is connected to the second terminal of the first capacitor C1. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase minimum voltage to the corresponding phase output terminal.

[0060] The first terminal of the seventeenth switch S17 is connected to the second terminal of the tenth switch S10 and phase B, respectively. The second terminal is connected to the second terminal of the first capacitor C1. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase minimum voltage to the corresponding phase output terminal.

[0061] The first terminal of the eighteenth switch S18 is connected to the second terminal of the twelfth switch S12 and phase C respectively. The second terminal is connected to the second terminal of the first capacitor C1. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase lowest voltage to the corresponding phase output terminal.

[0062] In this embodiment, the switching transistors of the subsequent voltage distribution sub-circuit 2 are all composed of an IGBT and a power diode. The collector of the IGBT is connected to the cathode of the power diode, and the emitter of the IGBT is connected to the anode of the power diode. The IGBT is used to control the circuit to turn on and off according to the signal, and the power diode is used for freewheeling.

[0063] Figure 2 This is a waveform diagram of the three-phase inverter circuit in operation in an embodiment of the present invention.

[0064] like Figure 2 As shown, the phase voltages of the 50Hz three-phase AC are all sine waves with an amplitude of 1. The N-line voltage is used as a reference. The three-phase voltages are represented by Ua, Ub, and Uc, and the N-line voltage is represented by Un. The maximum value of Ua, Ub, and Uc is Umax, the minimum value is Umin, and the middle value is Umid. Figure 2 The three-phase voltage waveforms for two power frequency cycles are shown.

[0065] Calculations show that the voltage across the first capacitor C1 on the DC side cannot be lower than sqrt(3). Now, Vdc = sqrt(3) ≈ 1.732 is set for the control scheme description.

[0066] At a specific moment (e.g., 6ms in the waveform shown in the attached figure), the instantaneous values ​​of the three-phase output voltages are as follows: Phase A voltage Ua = 0.95, Phase B voltage Ub = -0.31, and Phase C voltage Uc = -0.71. Among these, the instantaneous maximum voltage Umax = Ua = 0.95, the instantaneous minimum voltage Umin = Uc = -0.71, and the instantaneous intermediate voltage Umid = Ub = -0.31.

[0067] The core task of the front-stage voltage generation sub-circuit 1 is to generate the three-phase voltage required by the back-stage voltage distribution sub-circuit 2 through high-frequency modulation of the three half-bridges.

[0068] The first half-bridge (first switch S1, second switch S2) is responsible for generating the highest voltage Umax = Ua = 0.95. Umax − Umin = 0.95 − (−0.71) = 1.66, and Vdc = 1.732, so the duty cycle of S1 can be obtained:

[0069] duty_S1 = (Umax − Umin) / Vdc = 1.66 / 1.732 ≈ 95.8%. Because the first switch S1 and the second switch S2 are complementary in conduction, duty_S2 = 4.2%.

[0070] The second half-bridge (third switch S3 and fourth switch S4) is responsible for generating the voltage Un=0 at point N. The duty cycle of the third switch S3 can be obtained as follows:

[0071] duty_S3 = (Un−Umin) / (Umax−Umin) = 0.71 / 1.66 ≈ 42.77%. Because the third switch S3 and the fourth switch S4 are complementary in conduction, duty_S4 ≈ 57.23%.

[0072] The third half-bridge (fifth switch S5 and sixth switch S6) is responsible for generating the intermediate voltage Umid = Ub = -0.31. The duty cycle of the fifth switch S5 can be calculated as follows:

[0073] duty_S5 = (Umid − Umin) / (Umax − Umin) = (-0.31 - (-0.71)) / 1.66 ≈ 24.1%. Because the fifth switch S5 and the sixth switch S6 are complementary in conduction, duty_S6 ≈ 75.9%.

[0074] The subsequent voltage distribution sub-circuit 2 distributes the three-phase voltage generated by the preceding voltage generation sub-circuit 1. Since the A-phase voltage Ua=0.95 is the instantaneous maximum value, the thirteenth switch S13 is turned on, and the A-phase output terminal outputs the three-phase maximum value Umax=Ua=0.95.

[0075] Since the C-phase voltage Uc = −0.71 is the instantaneous minimum value, the eighteenth switch S18 is turned on, and the C-phase output terminal outputs the three-phase minimum value Umin = uc = −0.71.

[0076] Since the B-phase voltage Ub = -0.31 is an instantaneous intermediate value, the ninth switch S9 and the tenth switch S10 are turned on, and the B-phase output terminal outputs the three-phase intermediate value Umid = Ub = -0.31. In this operating state, in the front-end voltage generation sub-circuit 1, the first switch S1 to the sixth switch S6 are all in a high-frequency on / off state.

[0077] In the subsequent voltage distribution circuit 2, the thirteenth switch S13, the eighteenth switch S18, the ninth switch S9, and the tenth switch S10 are turned on, while the other switches are turned off.

[0078] This implementation illustrates the control strategy for the first to eighteenth switches (S1-S18) of the front-stage voltage generation sub-circuit 1 and the rear-stage voltage distribution sub-circuit 2 at a selected specific moment. Throughout the entire output cycle, the first to sixth switches (S6) of the front-stage voltage generation sub-circuit 1 employ a high-frequency pulse width modulation strategy that calculates the duty cycle based on the instantaneous output voltage value. The seventh to eighteenth switches (S18) of the rear-stage voltage distribution sub-circuit 2 operate in a low-frequency switching mode at the mains frequency or twice the mains frequency.

[0079] like Figure 2 As shown, taking phase A as an example, within one fundamental cycle of 5 / 3ms to 65 / 3ms, from 5 / 3ms to 25 / 3ms, phase A has the highest three-phase voltage, and the thirteenth switch S13 is turned on. From 25 / 3ms to 35 / 3ms, phase A has the intermediate three-phase voltage, the thirteenth switch S13 is turned off, and the seventh and eighth switches S7 and S8 are turned on. From 35 / 3ms to 55 / 3ms, phase A has the lowest three-phase voltage, the seventh and eighth switches S7 and S8 are turned off, and the sixteenth switch S16 is turned on. From 55 / 3ms to 65 / 3ms, phase A has the intermediate three-phase voltage, the sixteenth switch S16 is turned off, and the seventh and eighth switches S7 and S8 are turned on.

[0080] Based on the above control method, in the subsequent voltage distribution sub-circuit 2, half of the switching transistors complete only one turn-on and one turn-off cycle per output fundamental frequency period, and their switching frequency is equal to the output power frequency. The switching frequency of half of the switching transistors is twice the power frequency. This frequency (typically in the range of 50Hz, 100Hz, 60Hz, or 120Hz) is extremely low compared to the typical high-frequency PWM switching frequency (e.g., 10kHz and above) in the preceding voltage generation sub-circuit 1. Therefore, the switching losses generated by the switching transistors in the subsequent voltage distribution sub-circuit 2 are negligible compared to those in the preceding voltage generation sub-circuit 1, thus achieving a significant reduction in overall system switching losses from a control perspective.

[0081] In practical applications, the switching device can be MOSFET, IGBT, JFET, BJT, etc., without limiting the specific type of switching device.

[0082] Example 2

[0083] Figure 3 This is a circuit diagram of a three-phase inverter circuit with another structure in Embodiment 2 of the present invention.

[0084] like Figure 3 As shown in this embodiment, the DC-side half-bridge does not always have to be connected to the negative terminal of the subsequent bridge arm; it can also be connected to the positive terminal.

[0085] For ease of explanation, the same symbols are used for structures identical to those in Embodiment 1, and the same descriptions are omitted in this embodiment.

[0086] The role and effect of the embodiments

[0087] According to the three-phase inverter circuit involved in this embodiment, it includes: a front-stage voltage generation sub-circuit for centrally generating multiple voltage levels required for the three-phase output and outputting them via a shared filter inductor; and a rear-stage voltage distribution sub-circuit connected to the output terminal of the front-stage voltage generation sub-circuit for distributing the multiple voltage levels generated by the front-stage voltage generation sub-circuit to the AC output terminals of each phase as needed. Therefore, the three-phase inverter circuit of this invention decouples the voltage generation and voltage distribution functions, allowing the switching transistors in the rear-stage voltage distribution sub-circuit to operate only in a low-frequency commutation state, avoiding the need for all switching transistors to perform high-frequency switching operations in traditional topologies. This fundamentally eliminates the main high-frequency switching losses of the rear-stage power circuit, thereby significantly improving the conversion efficiency of the entire three-phase inverter circuit.

[0088] This embodiment reuses the same set of filter inductors in the front-end voltage generation sub-circuit, enabling centralized generation and filtering of multiple voltage levels for a three-phase system. This eliminates the need for independent filter inductors for each phase output, as required in traditional solutions. This directly reduces the total number of filter inductors in the system, lowering the material cost of magnetic components and helping to reduce the overall size and weight of the equipment, thus increasing the system's power density.

[0089] The circuit structure implemented in this embodiment reduces the voltage stress on all switching devices except the first half-bridge. Lower voltage stress allows for the use of semiconductor devices with lower rated voltages, lower cost, and better switching characteristics, thereby further optimizing the overall cost and performance of the system while ensuring reliability.

[0090] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A three-phase inverter circuit, characterized in that, include: The front-end voltage generation sub-circuit is used to centrally generate multiple voltage levels required for the three-phase output and output them through a common filter inductor; The subsequent voltage distribution sub-circuit is connected to the output terminal of the preceding voltage generation sub-circuit and is used to distribute the multiple voltage levels generated by the preceding voltage generation sub-circuit to each phase AC output terminal as needed.

2. A three-phase inverter circuit according to claim 1, Its features are: in, The front-stage voltage generation sub-circuit includes: The first capacitor is used for filtering. The first half-bridge, connected to the first capacitor, is used to generate the required instantaneous maximum voltage; The first filter inductor is connected to the first half-bridge and is used for filtering. The second half-bridge is connected to the first half-bridge and the first filter inductor respectively, and is used to generate the neutral point voltage. The second filter inductor is connected to the second half-bridge and the neutral line respectively, and is used for filtering. The third half-bridge, connected to the second half-bridge, is used to generate the required instantaneous intermediate voltage; The third filter inductor is connected to the third half-bridge and is used for filtering.

3. A three-phase inverter circuit according to claim 2, Its features are: The first half-bridge includes: The first switching transistor has its first terminal connected to the first terminal of the first capacitor and its second terminal connected to the first terminal of the first filter inductor, and is used to control the circuit to turn on and off according to the signal. The second switching transistor has its first terminal connected to the first terminal of the first filter inductor and its second terminal connected to the second terminal of the first capacitor, and is used to control the circuit to turn on and off according to the signal.

4. A three-phase inverter circuit according to claim 3, Its features are: The second half-bridge includes: The third switching transistor has its first terminal connected to the second terminal of the first filter inductor and its second terminal connected to the first terminal of the second filter inductor, and is used to control the circuit to turn on and off according to the signal. The fourth switching transistor has its first terminal connected to the first terminal of the second filter inductor and its second terminal connected to the second terminal of the first capacitor, and is used to control the circuit to turn on and off according to the signal.

5. A three-phase inverter circuit according to claim 1, Its features are: The third half-bridge includes: The fifth switching transistor has its first terminal connected to the second terminal of the first filter inductor and its second terminal connected to the first terminal of the third filter inductor, and is used to control the circuit to turn on and off according to the signal. The sixth switching transistor has its first terminal connected to the first terminal of the third filter inductor and its second terminal connected to the second terminal of the first capacitor, and is used to control the circuit to turn on and off according to the signal.

6. A three-phase inverter circuit according to claim 1, Its features are: The subsequent voltage distribution sub-circuit includes: The second capacitor is connected to the third half-bridge and the third filter inductor respectively, and is used to divide the DC bus voltage. The third capacitor is connected to the third half-bridge and the third filter inductor respectively, and is used to divide the DC bus voltage; The intermediate voltage gating unit is connected to the second capacitor, the third capacitor, and the third filter inductor respectively, and is used to distribute the intermediate voltage; The highest and lowest voltage selection unit is connected to the second capacitor, the third capacitor and the intermediate voltage selection unit respectively, and is used to allocate the highest voltage and the lowest voltage.

7. A three-phase inverter circuit according to claim 6, Its features are: The intermediate voltage gating unit includes: The seventh switch, with its first terminal connected to the second terminal of the third filter inductor, is used to control the circuit's on / off state according to the signal and transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal. The eighth switch, with its first terminal connected to the second terminal of the seventh switch, is used to control the circuit's on / off state according to the signal and transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal. The ninth switching transistor, with its first terminal connected to the second terminal of the third filter inductor, is used to control the circuit's on / off state according to the signal, and transmits the instantaneous three-phase intermediate voltage to the corresponding phase output terminal. The tenth switch, with its first terminal connected to the second terminal of the ninth switch, is used to control the circuit's on / off state according to a signal and transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal. The eleventh switching transistor has its first terminal connected to the second terminal of the third filter inductor, and is used to control the circuit to turn on and off according to the signal, and transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal. The twelfth switch, with its first terminal connected to the second terminal of the eleventh switch, is used to control the on / off state of the circuit according to the signal and transmit the instantaneous three-phase intermediate voltage to the corresponding phase output terminal.

8. A three-phase inverter circuit according to claim 7, characterized in that: in, The highest and lowest voltage gating unit includes: The thirteenth switch has its first terminal connected to the second terminal of the first filter inductor and its second terminal connected to the second terminal of the eighth switch. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase highest voltage to the corresponding phase output terminal. The fourteenth switch has its first terminal connected to the second terminal of the first filter inductor and its second terminal connected to the second terminal of the tenth switch. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase highest voltage to the corresponding phase output terminal. The fifteenth switch has its first terminal connected to the second terminal of the first filter inductor and its second terminal connected to the second terminal of the twelfth switch. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase highest voltage to the corresponding phase output terminal. The sixteenth switch has its first terminal connected to the second terminal of the eighth switch and phase A, and its second terminal connected to the second terminal of the first capacitor. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase lowest voltage to the corresponding phase output terminal. The seventeenth switch has its first terminal connected to the second terminal of the tenth switch and phase B, and its second terminal connected to the second terminal of the first capacitor. It is used to control the circuit to turn on and off according to the signal and transmit the instantaneous three-phase lowest voltage to the corresponding phase output terminal. The eighteenth switch has its first terminal connected to the second terminal of the twelfth switch and phase C, and its second terminal connected to the second terminal of the first capacitor. It is used to control the circuit to switch on and off according to the signal and transmit the instantaneous three-phase minimum voltage to the corresponding phase output terminal.

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