Three-phase single-stage AC / DC isolation conversion circuit

Abstract

The invention relates to a three-phase single-stage AC / DC isolation conversion circuit, which comprises a power frequency voltage selection module, a third harmonic injection module and an isolation DCDC module, and is characterized in that the power frequency voltage selection module is used for carrying out voltage selection based on an input phase voltage so as to control a bus voltage between a positive bus and a negative bus; the isolation DCDC module is used for performing DCDC conversion on the bus voltage to generate an output voltage; the third harmonic injection module is used for controlling neutral current, and the isolation DCDC module is used for controlling bus current. The input phase current of the three-phase single-stage AC / DC isolation conversion circuit follows the input phase voltage to obtain a higher power factor, and meanwhile, a unified positive bus and a unified negative bus are formed through a power frequency voltage selection module and a third harmonic injection module, so that a higher voltage value and a smaller voltage ripple are achieved; the isolation DCDC module is connected between a positive bus and a negative bus, so that the ripple current and the effective value current required by output voltage stabilization are smaller, and the efficiency is higher.

Description

Technical Field

[0001] This invention relates to the field of charging modules, and more specifically, to a three-phase single-stage AC / DC isolation converter circuit. Background Technology

[0002] With the increasing demand for electric vehicle charging equipment, single-stage circuit topologies are receiving more and more attention. Compared to two-stage circuit structures, single-stage structures save on the use of bus electrolytic capacitors and combine the PFC circuit and isolated DC-DC circuit into one, saving on the number of components, improving system efficiency, increasing system power density, and enabling miniaturized power supply design.

[0003] However, when a single-stage structure is applied to a three-phase AC / DC isolation converter circuit, a phase difference can easily occur between the input phase current and the phase voltage, resulting in a low power factor. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a three-phase single-stage AC / DC isolation converter circuit that addresses the above-mentioned deficiencies of the prior art, wherein the input phase current follows the input phase voltage, thus resulting in a high power factor.

[0005] The technical solution adopted by the present invention to solve its technical problem is: to construct a three-phase single-stage AC / DC isolation converter circuit, including: a power frequency voltage selection module, a third harmonic injection module, and an isolation DC / DC module; The input terminal of the power frequency voltage selection module is connected to a three-phase power supply to receive the input phase voltage; the first output terminal is connected to the positive bus; the second output terminal is connected to the negative bus; and the third output terminal is connected to the neutral line. The third harmonic injection module and the isolation DC-DC module are connected sequentially between the positive bus and the negative bus. The power frequency voltage selection module is used to select voltage based on the input phase voltage to control the bus voltage between the positive bus and the negative bus; The isolated DC-DC module is used to perform DC-DC conversion on the bus voltage to generate an output voltage; The third harmonic injection module is used to control the neutral current of the neutral line, and the isolation DC-DC module is used to control the bus current, so that the input phase current of the three-phase single-stage AC / DC isolation converter circuit follows the input phase voltage.

[0006] In the three-phase single-stage AC / DC isolation converter circuit of the present invention, the power frequency voltage selection module includes: a filter unit, a first rectification unit, a second rectification unit, a third rectification unit, a first switch driving unit, a second switch driving unit, and a third switch driving unit; The input terminal of the filter unit is connected to the three-phase power supply. The first output terminal of the filter unit is connected to the first terminal of the first rectifier unit and the first terminal of the first switch driver unit. The second output terminal of the filter unit is connected to the first terminal of the second rectifier unit and the first terminal of the second switch driver unit. The third output terminal of the filter unit is connected to the first terminal of the third rectifier unit and the first terminal of the third switch driver unit. The second end of the first rectifier unit, the second end of the second rectifier unit, and the second end of the third rectifier unit are all connected to the positive bus, and the third end of the first rectifier unit, the third end of the second rectifier unit, and the third end of the third rectifier unit are all connected to the negative bus. The second end of the first switch driving unit, the second end of the second switch driving unit, and the second end of the third switch driving unit are all connected to the neutral line; The control terminals of the first switch driver unit, the second switch driver unit, and the third switch driver unit respectively receive control signals. The power frequency voltage selection module is used to select voltage based on the input phase voltage to control the bus voltage between the positive bus and the negative bus, including: The first switch driving unit, the second switch driving unit, and the third switch driving unit turn on or off based on the absolute values ​​of the first input phase voltage, the second input phase voltage, and the third input phase voltage output by the filter unit to select the maximum and minimum voltages to control the bus voltage between the positive bus and the negative bus.

[0007] In the three-phase single-stage AC / DC isolation converter circuit described in this invention, the filtering unit includes a single-inductor filtering unit, an LCL filtering unit, or an LC filtering unit. The first rectification unit, the second rectification unit, and the third rectification unit each include a diode rectification unit or a switching transistor rectification unit; The first switching transistor driving unit includes a first switching transistor and a second switching transistor. The first end of the first switching transistor is connected to the first output end of the filtering unit, and the second end is connected to the second end of the second switching transistor. The first end of the second switching transistor is connected to the neutral line. The control end of the first switching transistor receives a first control signal, and the control end of the second switching transistor receives a second control signal. The second switching transistor driving unit includes a third switching transistor and a fourth switching transistor. The first end of the third switching transistor is connected to the second output end of the filtering unit, and the second end is connected to the second end of the fourth switching transistor. The first end of the fourth switching transistor is connected to the neutral line. The control end of the third switching transistor receives a third control signal, and the control end of the fourth switching transistor receives a fourth control signal. The third switch driving unit includes a fifth switch and a sixth switch. The first end of the fifth switch is connected to the third output end of the filter unit, and the second end is connected to the second end of the sixth switch. The first end of the sixth switch is connected to the neutral line. The control end of the fifth switch receives a fifth control signal, and the control end of the sixth switch receives a sixth control signal. When the filtering unit is the single-inductor filtering unit or the LCL filtering unit, the first control signal and the second control signal are the same, the third control signal and the fourth control signal are the same, and the fifth control signal and the sixth control signal are the same; When the filtering unit is the LC filtering unit, the first control signal and the second control signal are different, the third control signal and the fourth control signal are different, and the fifth control signal and the sixth control signal are different.

[0008] In the three-phase single-stage AC / DC isolation converter circuit described in this invention, the third harmonic injection module includes a first high-frequency filter capacitor, a second high-frequency filter capacitor, a harmonic inductor unit, a harmonic switching transistor unit, and a bus capacitor. The positive terminal of the first high-frequency filter capacitor is connected to the positive busbar, the negative terminal of the first high-frequency filter capacitor is connected to the neutral line and the positive terminal of the second high-frequency filter capacitor, and the negative terminal of the second high-frequency filter capacitor is connected to the negative busbar. The harmonic switching transistor unit is connected between the positive bus and the negative bus, and the control terminal of the harmonic switching transistor unit receives the harmonic control signal. The positive terminal of the bus capacitor is connected to the positive bus, and the negative terminal is connected to the negative bus. The harmonic inductor unit is connected between the neutral line and the harmonic switching transistor unit. The third harmonic injection module is used to control the neutral current of the neutral line, including: The instantaneous values ​​of the maximum and minimum phase voltages are obtained based on the first, second, and third input phase voltages, and the reference value of the neutral current is obtained based on the maximum and minimum phase voltage values ​​and the set output voltage power. The harmonic control signal is generated based on the real-time sampled value of the neutral current and the reference value of the neutral current, or the harmonic control signal is generated based on the real-time sampled value of the neutral current, the reference value of the neutral current, the instantaneous value of the maximum phase voltage and the instantaneous value of the minimum phase voltage. The harmonic switching transistor unit is controlled based on the harmonic control signal, thereby controlling the neutral current of the neutral line.

[0009] In the three-phase single-stage AC / DC isolation converter circuit of the present invention, the harmonic control signal is generated based on the real-time sampled value of the neutral current and the reference value of the neutral current, including: Calculate the difference between the real-time sampled value of the neutral current and the reference value of the neutral current; The difference is input into the proportional-integral controller to obtain the output value; The output value is sent to the PWM generation unit to generate the harmonic control signal; in, in, This represents a reference value for the neutral current. Indicates the first input phase voltage. Indicates the second input phase voltage. Indicates the third input phase voltage. This represents the instantaneous value of the maximum phase voltage. This represents the instantaneous value of the minimum phase voltage. This indicates the set output voltage and power; = , This represents the phase voltage amplitude of the first input phase voltage. This represents the phase voltage amplitude of the second input phase voltage. This represents the phase voltage amplitude of the third input phase voltage.

[0010] In the three-phase single-stage AC / DC isolation converter circuit of the present invention, the harmonic control signal is generated based on the real-time sampled value of the neutral current, the reference value of the neutral current, the instantaneous value of the maximum phase voltage, and the instantaneous value of the minimum phase voltage, including: Calculate the difference between the real-time sampled value of the neutral current and the reference value of the neutral current; The difference is input into the proportional-integral controller to obtain the output value; The output value is superimposed with the first feedforward signal or the second feedforward signal and then sent to the PWM generation unit to generate the harmonic control signal. in, in, This represents a reference value for the neutral current. Indicates the first input phase voltage. Indicates the second input phase voltage. Indicates the third input phase voltage. This represents the instantaneous value of the maximum phase voltage. This represents the instantaneous value of the minimum phase voltage. This indicates the set output voltage and power; = , This represents the phase voltage amplitude of the first input phase voltage. This represents the phase voltage amplitude of the second input phase voltage. This represents the phase voltage amplitude of the third input phase voltage; The first feedforward signal is The second feedforward signal is ;in This represents the instantaneous value of the intermediate phase.

[0011] In the three-phase single-stage AC / DC isolation converter circuit of the present invention, the harmonic inductor unit includes a harmonic inductor, and the harmonic switching transistor unit includes a first harmonic switching transistor and a second harmonic switching transistor; the first end of the harmonic inductor is connected to the neutral line, the second end of the harmonic inductor is connected to the second end of the first harmonic switching transistor and the first end of the second harmonic switching transistor, the first end of the first harmonic switching transistor is connected to the positive bus, the second end of the second harmonic switching transistor is connected to the negative bus, the positive terminal of the bus capacitor is connected to the positive bus, and the negative terminal is connected to the negative bus; the control terminal of the first harmonic switching transistor receives a first harmonic control signal, and the control terminal of the second harmonic switching transistor receives a second harmonic control signal.

[0012] In the three-phase single-stage AC / DC isolation converter circuit of the present invention, the harmonic inductor unit includes a first harmonic inductor and a second harmonic inductor; the harmonic switch unit includes a first harmonic switch, a second harmonic switch, a third harmonic switch, and a fourth harmonic switch. The first end of the first harmonic inductor is connected to the neutral line, and the second end of the first harmonic inductor is connected to the second end of the first harmonic switch and the first end of the second harmonic switch. The first end of the first harmonic switch is connected to the positive bus, and the second end of the second harmonic switch is connected to the negative bus. The positive terminal of the bus capacitor is connected to the positive bus, and the negative terminal is connected to the negative bus. The control terminal of the first harmonic switch receives a first harmonic control signal, and the control terminal of the second harmonic switch receives a second harmonic control signal. The first end of the second harmonic inductor is connected to the neutral line, and the second end of the second harmonic inductor is connected to the second end of the third harmonic switch and the first end of the fourth harmonic switch. The first end of the third harmonic switch is connected to the positive bus, and the second end of the fourth harmonic switch is connected to the negative bus. The positive terminal of the bus capacitor is connected to the positive bus, and the negative terminal is connected to the negative bus. The control terminal of the third harmonic switch receives a third harmonic control signal, and the control terminal of the fourth harmonic switch receives a fourth harmonic control signal.

[0013] In the three-phase single-stage AC / DC isolation converter circuit of the present invention, the isolation DC-DC module includes multiple isolation DC-DC units; the multiple isolation DC-DC units achieve high-low voltage switching through series-parallel connection of windings or series-parallel connection of output capacitors; The isolated DC-DC module is used to control the bus current, thereby ensuring that the input phase current of the three-phase single-stage AC / DC isolation converter follows the input phase voltage, including: The bus current is used as a reference value for the output current; Based on the reference value of the output current, the sampled value of the output current, and the bus voltage, a power transistor control signal is generated to control the power transistors of the plurality of isolated DC-DC units, thereby making the input phase current of the three-phase single-stage AC-DC isolation converter circuit follow the input phase voltage.

[0014] In the three-phase single-stage AC / DC isolation converter circuit of the present invention, a power transistor control signal for controlling the power transistors of the plurality of isolated DC / DC units is generated based on the reference value of the output current, the sampled value of the output current, and the bus voltage, including: Calculate the difference between the reference value of the output current and the sampled value of the output current; The difference is input into the proportional-integral controller to obtain the output value; The output value is superimposed with a feedforward signal and then sent to a PWM generation unit to generate a power transistor control signal for controlling the power transistors of the plurality of isolated DC-DC units, wherein the feedforward signal is the normalized value of the bus voltage. in, ; ; in, Indicates bus voltage. This represents the absolute value of the line voltage between the first input phase and the second input phase. This represents the absolute value of the line voltage between the second and third input phases. This represents the absolute value of the line voltage between the first input phase and the third input phase; Indicates the bus current; This indicates the set output power.

[0015] The three-phase single-stage AC / DC isolation converter circuit of the present invention includes a power frequency voltage selection module, a third harmonic injection module, and an isolation DC / DC module. The power frequency voltage selection module is used to select the voltage based on the input phase voltage to control the bus voltage between the positive bus and the negative bus. The isolation DC / DC module is used to perform DC / DC conversion on the bus voltage to generate an output voltage. The third harmonic injection module is used to control the neutral current of the neutral line, and the isolation DC / DC module is used to control the bus current. Since the input phase current of the three-phase single-stage AC / DC isolation converter circuit satisfies the condition that the sum of the three-phase input phase currents is 0, the three-phase input phase current of the three-phase single-stage AC / DC isolation converter circuit can actually be controlled by controlling the neutral current and the bus current. This allows the input phase current of the three-phase single-stage AC / DC isolation converter circuit to follow the input phase voltage, thereby obtaining a higher power factor. At the same time, since the power frequency voltage selection module and the third harmonic injection module form a unified positive and negative bus, compared with a single-phase DC bus formed by only using a rectifier bridge, it has a higher voltage value and a smaller voltage ripple. The isolation DC-DC module is connected between the positive and negative buses, resulting in a smaller ripple current and effective current required for output voltage regulation, and higher system efficiency. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a block diagram of a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 2 This is a block diagram of a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 3 This is a circuit diagram of a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 4 This is a circuit diagram of another preferred embodiment of the power frequency voltage selection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 5 This is a circuit diagram of another preferred embodiment of the power frequency voltage selection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 6 The waveforms of the input phase voltage and the switching transistor drive signal of the three-phase single-stage AC / DC isolation converter circuit of the present invention are shown. Figures 7A-7D It shows Figure 5 The switching status of the power frequency voltage selection module is shown. Figure 8 This is a circuit diagram of another preferred embodiment of the power frequency voltage selection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 9 The waveforms of the input phase voltage and harmonic inductance of the three-phase single-stage AC / DC isolation converter circuit of the present invention are shown. Figure 10 This is a circuit diagram of another preferred embodiment of the third harmonic injection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figures 11A-11B This is a circuit diagram of another preferred embodiment of the third harmonic injection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 12 This is a circuit diagram of another preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 13 This is a circuit diagram of another preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 14 These are schematic diagrams illustrating different embodiments of the winding switching of the isolation DC-DC module in the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 15 yes Figure 3 The diagram shows the harmonic control signal generation logic of a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit. Figure 16 yes Figure 3 A schematic diagram of the power transistor control signal generation logic of the isolation DC-DC module in a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit shown. Figure 17 yes Figure 3 The diagram shows the input voltage, current waveform, output current waveform, and bus voltage waveform of a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] Figure 1 This is a block diagram illustrating the principle of the three-phase single-stage AC / DC isolation converter circuit of this invention. Figure 1As shown, the three-phase single-stage AC / DC isolation converter circuit includes: a power frequency voltage selection module, a third harmonic injection module, and an isolation DC-DC module. The input terminal of the power frequency voltage selection module is connected to a three-phase power supply to receive the input phase voltage; the first output terminal is connected to the positive bus P; the second output terminal is connected to the negative bus N; and the third output terminal is connected to the neutral line M. The third harmonic injection module and the isolation DC-DC module are sequentially connected between the positive bus P and the negative bus N. The power frequency voltage selection module is used to select the voltage based on the input phase voltage to control the bus voltage between the positive bus P and the negative bus N. The isolation DC-DC module is used to perform DC-DC conversion on the bus voltage to generate an output voltage. The third harmonic injection module is used to control the neutral current of the neutral line M, and the isolation DC-DC module is used to control the bus current, so that the input phase current of the three-phase single-stage AC / DC isolation converter circuit follows the input phase voltage.

[0019] The three-phase single-stage AC / DC isolation converter circuit of the present invention includes a power frequency voltage selection module, a third harmonic injection module, and an isolation DC / DC module. The power frequency voltage selection module is used to select voltage based on the input phase voltage to control the bus voltage between the positive bus P and the negative bus N. The isolation DC / DC module is used to perform DC / DC conversion on the bus voltage to generate an output voltage. The third harmonic injection module is used to control the neutral current of the neutral line M, and the isolation DC / DC module is used to control the bus current. Since the input phase current of the three-phase single-stage AC / DC isolation converter circuit satisfies the condition that the sum of the three-phase input phase currents is 0, the three-phase input phase current of the three-phase single-stage AC / DC isolation converter circuit can actually be controlled by controlling the neutral current and the bus current. This allows the input phase current of the three-phase single-stage AC / DC isolation converter circuit to follow the input phase voltage after passing through the single-stage AC / DC isolation converter circuit, thereby obtaining a higher power factor. At the same time, since the power frequency voltage selection module and the third harmonic injection module form a unified positive and negative bus, and the isolation DC / DC module is connected between the positive and negative buses, a higher bus voltage can be formed. This reduces the peak current stress on the isolation DC / DC module, improves the full-cycle device utilization rate of the isolation DC / DC module, and reduces the control difficulty of the isolation DC / DC module, thereby reducing the output current ripple.

[0020] In a preferred embodiment of the present invention, the power frequency voltage selection module includes: a filtering unit, a first rectification unit, a second rectification unit, a third rectification unit, a first switching transistor driving unit, a second switching transistor driving unit, and a third switching transistor driving unit; the input terminal of the filtering unit is connected to the three-phase power supply, the first output terminal of the filtering unit is connected to the first terminal of the first rectification unit and the first terminal of the first switching transistor driving unit, the second output terminal of the filtering unit is connected to the first terminal of the second rectification unit and the first terminal of the second switching transistor driving unit, and the third output terminal of the filtering unit is connected to the first terminal of the third rectification unit and the first terminal of the third switching transistor driving unit; the second terminals of the first rectification unit, the second terminals of the second rectification unit, and the second terminals of the third rectification unit are all connected to the positive bus P, and the third terminals of the first rectification unit and the third terminals of the second rectification unit are connected to the positive bus P. The third terminal of the first rectifier unit and the third rectifier unit are all connected to the negative bus N; the second terminals of the first switch driver unit, the second switch driver unit, and the third switch driver unit are all connected to the neutral line M; the control terminals of the first switch driver unit, the second switch driver unit, and the third switch driver unit respectively receive control signals; the power frequency voltage selection module is used to select the bus voltage between the positive bus P and the negative bus N based on the input phase voltage, including: the first switch driver unit, the second switch driver unit, and the third switch driver unit turn on or off based on the absolute values ​​of the first input phase voltage, the second input phase voltage, and the third input phase voltage output by the filter unit to select the maximum voltage and the minimum voltage to control the bus voltage between the positive bus P and the negative bus N.

[0021] In a preferred embodiment of the present invention, the third harmonic injection module includes a first high-frequency filter capacitor, a second high-frequency filter capacitor, a harmonic inductor unit, a harmonic switching transistor unit, and a bus capacitor; the positive terminal of the first high-frequency filter capacitor is connected to the positive bus P, and the negative terminal is connected to the neutral line M and the positive terminal of the second high-frequency filter capacitor; the negative terminal of the second high-frequency filter capacitor is connected to the negative bus N; the harmonic switching transistor unit is connected between the positive bus P and the negative bus N, and the control terminal of the harmonic switching transistor unit receives a harmonic control signal; the positive terminal of the bus capacitor is connected to the positive bus P, and the negative terminal is connected to the negative bus N. The harmonic inductor unit is connected between the neutral line M and the harmonic switching transistor unit; the third harmonic injection module is used to control the neutral line current of the neutral line M, including: obtaining the instantaneous values ​​of the maximum and minimum phase voltages based on the first, second, and third input phase voltages, and obtaining a reference value of the neutral line current based on the instantaneous values ​​of the maximum and minimum phase voltages and a set output voltage power; generating the harmonic control signal based on the real-time sampled value of the neutral line current, the reference value of the neutral line current, the instantaneous value of the maximum and minimum phase voltages; and controlling the harmonic switching transistor unit based on the harmonic control signal, thereby controlling the neutral line current of the neutral line M.

[0022] Figure 2 This is a circuit diagram of a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit of the present invention. (In conjunction with...) Figure 1-2 As can be seen, the three-phase single-stage AC / DC isolation converter circuit of the present invention includes a power frequency voltage selection module, a third harmonic injection module, and an isolation DC / DC module; the input terminal of the power frequency voltage selection module is connected to a three-phase power supply to receive the input phase voltage, the first output terminal is connected to the positive bus P, the second output terminal is connected to the negative bus N, and the third output terminal is connected to the neutral line M; the third harmonic injection module and the isolation DC / DC module are sequentially connected between the positive bus P and the negative bus N. Figure 2In the preferred embodiment shown, the isolated DC-DC module includes multiple isolated DC-DC units 1 to n, which achieve high-low voltage switching through series-parallel connection of windings or series-parallel connection of output capacitors. In a preferred embodiment of the present invention, the isolated DC-DC unit includes a flyback unit, a forward unit, a full-bridge LLC unit, a half-bridge LLC unit, a three-phase LLC unit, a full-bridge DAB unit, a full-bridge quasi-DAB unit, a half-bridge DAB unit, a three-phase DAB unit, a phase-shifted full-bridge unit, an isolated SEPIC unit, an isolated ZETA unit, or an isolated CUK unit. Here, the aforementioned isolated DC-DC units are all known isolated DC-DC units in the art, and their specific structures will not be described in detail. In a preferred embodiment of the present invention, the isolated DC-DC module may include different isolated DC-DC units, such as n sets of flyback units, n sets of full-bridge LLC units, n sets of half-bridge LLC units, n sets of three-phase LLC units, n sets of full-bridge DAB units, n sets of full-bridge quasi-DAB units, n sets of half-bridge DAB units, n sets of three-phase DAB units, or n sets of isolated SEPIC units. Therefore, the three-phase single-stage AC / DC isolation converter circuit of the present invention can connect to different isolated DC-DC modules; the number of connected isolated DC-DC units (n) can vary according to power requirements, and the circuits can be interleaved to reduce ripple; and each isolated DC-DC unit can perform different high-low voltage switching according to high- and low-voltage requirements, such as switching the series and parallel connections of capacitors, switching the series and parallel connections of windings, and switching the number of turns of the windings.

[0023] Figure 3 This is a circuit diagram of a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit of the present invention. (In conjunction with...) Figure 1-3 It is known that the three-phase single-stage AC / DC isolation converter circuit includes: a power frequency voltage selection module, a third harmonic injection module, and an isolation DC-DC module; the input terminal of the power frequency voltage selection module is connected to the three-phase power supply to receive the input phase voltage, the first output terminal is connected to the positive bus P, the second output terminal is connected to the negative bus N, and the third output terminal is connected to the neutral line M; the third harmonic injection module and the isolation DC-DC module are sequentially connected between the positive bus P and the negative bus N. In this invention, the power frequency voltage selection module is directly connected to the power grid (i.e., the three-phase power supply), and then connected to the third harmonic injection module and n isolation DC-DC units respectively. The n isolation DC-DC units can increase power through parallel connection between units, or expand the output voltage through series connection between units. The output of the isolation DC-DC unit is directly connected to the DC load. Figure 3As shown, the power frequency voltage selection module includes: a filtering unit, a first rectification unit, a second rectification unit, a third rectification unit, a first switch driver unit, a second switch driver unit, and a third switch driver unit; the filtering unit includes a single-inductor filter unit (i.e., a filter); the first rectification unit, the second rectification unit, and the third rectification unit each include diodes D1~D2, D3~D4, and D5~D6. The first switch driver unit includes a first switch S1 and a second switch S2; the second switch driver unit includes a third switch S3 and a fourth switch S4; and the third switch driver unit includes a fifth switch S5 and a sixth switch S6. Figure 3 As shown, the first, second, and third input terminals of the single-inductor filter are connected to the first, second, and third phases of a three-phase power supply, respectively. The first terminal of the first switch S1 is connected to the first output terminal of the single-inductor filter unit, and its second terminal is connected to the second terminal of the second switch S2. The first terminal of the second switch S2 is connected to the neutral line M. The control terminal of the first switch S1 receives a first control signal, and the control terminal of the second switch S2 receives a second control signal. The first terminal of the third switch S3 is connected to the second output terminal of the single-inductor filter unit, and its second terminal is connected to the second terminal of the fourth switch S4. The first terminal of the fourth switch S4 is connected to the neutral line M. The control terminal of the third switch S3 receives a third control signal, and the control terminal of the fourth switch S4 receives a fourth control signal. The first terminal of the fifth switch S5 is connected to the third output terminal of the single-inductor filter unit, and its second terminal is connected to the second terminal of the sixth switch S6. The first terminal of the sixth switch S6 is connected to the neutral line M. The control terminal of the fifth switch S5 receives a fifth control signal, and the control terminal of the sixth switch S6 receives a sixth control signal. The first control signal and the second control signal are the same, the third control signal and the fourth control signal are the same, and the fifth control signal and the sixth control signal are the same. The first output terminal of the filter unit is connected to the first terminal of the first rectifier unit (anode of diode D1 and cathode of diode D2), the second output terminal of the filter unit is connected to the first terminal of the second rectifier unit (anode of diode D3 and cathode of diode D4), and the third output terminal of the filter unit is connected to the first terminal of the third rectifier unit (anode of diode D5 and cathode of diode D6). The second terminals of the first rectifier unit (cathode of diode D1), the second rectifier unit (cathode of diode D3), and the third rectifier unit (cathode of diode D5) are all connected to the positive bus P, and the third terminals of the first rectifier unit (anode of diode D2), the second rectifier unit (anode of diode D4), and the third rectifier unit (anode of diode D6) are all connected to the negative bus N.

[0024] Apart from Figure 3 In addition to the power frequency voltage selection module structure described above, Figure 4 This is a circuit diagram of another preferred embodiment of the power frequency voltage selection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention; Figure 5 This is a circuit diagram of another preferred embodiment of the power frequency voltage selection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention. Figure 4 In the preferred embodiment shown, the filtering unit includes an LCL filtering unit, the second rectification unit and the third rectification unit respectively include diodes D1~D2, diodes D3~D4 and diodes D5~D6, the first switching transistor driving unit includes a first switching transistor S1 and a second switching transistor S2, the second switching transistor driving unit includes a third switching transistor S3 and a fourth switching transistor S4, and the third switching transistor driving unit includes a fifth switching transistor S5 and a sixth switching transistor S6. Figure 4 The illustrated embodiments and Figure 3 The only difference in the embodiments shown lies in the construction of the filtering unit, which will be described below. Figure 4 As shown, the LCL filter unit includes filter inductors Lg1~Lg3, Lf1~Lf3, and filter capacitors Cf1~Cf3. The first end of filter inductor Lg1 is connected to the first phase of the three-phase power supply, and the second end is connected to the first end of filter inductor Lf1 and the positive terminal of filter capacitor Cf1. The second end of filter inductor Lf1 is connected to the first terminal of the first rectifier unit (the anode of diode D1 and the cathode of diode D2). The first end of filter inductor Lg2 is connected to the second phase of the three-phase power supply, and the second end is connected to the first end of filter inductor Lf2 and the positive terminal of filter capacitor Cf2. The second end of filter inductor Lf2 is connected to the first terminal of the second rectifier unit (the anode of diode D3 and the cathode of diode D4). The first end of filter inductor Lg3 is connected to the third phase of the three-phase power supply, and the second end is connected to the first end of filter inductor Lf3 and the positive terminal of filter capacitor Cf3. The second end of filter inductor Lf3 is connected to the first terminal of the third rectifier unit (the anode of diode D5 and the cathode of diode D6). The negative terminal of the filter capacitor Cf1 is connected to the negative terminals of the filter capacitor Cf2 and the filter capacitor Cf3.

[0025] exist Figure 5In the preferred embodiment shown, the filtering unit includes an LC filtering unit, the second rectification unit and the third rectification unit respectively include diodes D1~D2, diodes D3~D4 and diodes D5~D6, the first switching transistor driving unit includes a first switching transistor S1 and a second switching transistor S2, the second switching transistor driving unit includes a third switching transistor S3 and a fourth switching transistor S4, and the third switching transistor driving unit includes a fifth switching transistor S5 and a sixth switching transistor S6. Figure 5 The illustrated embodiments and Figure 3 The only difference in the illustrated embodiments lies in the construction of the filter unit and the control of the switching transistor, which will be described below. Figure 5 As shown, the LC filter unit includes filter inductors Lg1~Lg3 and filter capacitors Cf1~Cf3. The first end of filter inductor Lg1 is connected to the first phase of the three-phase power supply, and the second end is connected to the positive terminal of filter capacitor Cf1 and the first terminal of the first rectifier unit (the anode of diode D1 and the cathode of diode D2). The first end of filter inductor Lg2 is connected to the second phase of the three-phase power supply, and the second end is connected to the positive terminal of filter capacitor Cf2 and the first terminal of the second rectifier unit (the anode of diode D3 and the cathode of diode D4). The first end of filter inductor Lg3 is connected to the third phase of the three-phase power supply, and the second end is connected to the positive terminal of filter capacitor Cf3 and the first terminal of the third rectifier unit (the anode of diode D5 and the cathode of diode D6). The negative terminal of filter capacitor Cf1 is connected to the negative terminals of filter capacitors Cf2 and Cf3. Figures 3-5 In the preferred embodiment shown, the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, and the sixth switch S6 operate at the power frequency and are used to select voltages based on the absolute values ​​of the first input phase voltage, the second input phase voltage, and the third input phase voltage, thereby controlling the bus voltage between the positive bus P and the negative bus N. When the filtering unit is the single-inductor filtering unit or the LCL filtering unit, the first control signal and the second control signal are the same, the third control signal and the fourth control signal are the same, and the fifth control signal and the sixth control signal are the same; when the filtering unit is the LC filtering unit, the first control signal and the second control signal are different, the third control signal and the fourth control signal are different, and the fifth control signal and the sixth control signal are different.

[0026] Figure 6 The waveforms of the input phase voltage and the switching transistor drive signal of the three-phase single-stage AC / DC isolation converter circuit of the present invention are shown. Figures 3-5 As shown, the harmonic inductor unit can be as follows: Figure 3 The filter shown can also be Figure 4 The LCL filter unit shown is, or Figure 5 The LC filter unit is shown. The first switch S1 and the second switch S2 are driven by the same drive signal SW1 or separate drive signals SG1 and SG2. The third switch S3 and the fourth switch S4 are driven by the same drive signal SW2 or separate drive signals SG3 and SG4. The fifth switch S5 and the sixth switch S6 are driven by the same drive signal SW3 or separate drive signals SG5 and SG6.

[0027] When the harmonic inductor unit is a single-inductor filter unit or an LCL filter unit, the same group of transverse transistors (i.e., the first switch S1 and the second switch S2, the third switch S3 and the fourth switch S4 or the fifth switch S5 and the sixth switch S6) can use the same drive signal, and their drive logic is as follows: Figure 5 As shown. Figure 5 The relationship between the transverse tube drive signal and the input voltage signal is given in the case of unity power factor. , , These are the first input phase voltage, the second input phase voltage, and the third input phase voltage, respectively. SW1-SW3 are the drive signals for the three-phase horizontal transistors, and their frequency is twice the phase voltage frequency. Specifically, for the drive signal SW1 of the first phase horizontal transistor (i.e., the first switch S1 and the second switch S2), its drive logic is as follows: when... or At that time, that is | When the value of | is the midpoint of the three absolute values, SW1 is high. The logic of SW2 and SW3 is similar to SW1, except that they correspond to | | and | When the voltage is the midpoint of the three voltage values, it is set to high. At the critical switching time ( Figure 5 (As indicated in the transient section), SW1, SW2, and SW3 should not have dead zones (i.e., all drives are low), but should maintain appropriate overlap in their high-level drive regions (i.e., all switches are on simultaneously) to ensure that the larger inductive component of the neutral line M has a continuous current path. Taking the switch from SW2 high level to SW3 high level as an example, SW1 can be turned on earlier, or SW2 can be turned off later, or SW1 can be turned on earlier and SW2 can be turned off later.

[0028] When the harmonic inductor unit is an LC filter, a separate drive unit is required for the horizontal tube. This is because it is necessary to ensure that the capacitor between the two phases does not short-circuit. Specifically, as shown... Figure 5In steady state, the drive signal for each group of transverse transistors is the same as when using the common drive signal. However, in transient state, the switching sequence depends on the relative voltage levels of the capacitors and the direction of the current at the neutral line M. Taking the switching of the third switch S3 and the fourth switch S4 to the first switch S1 and the second switch S2 as an example, the relationship of the capacitor voltage at the neutral line M is as follows: u cf1 > u cf2 , u cf1 This is the voltage between the positive busbar and the neutral line. u cf2 When the voltage across the filter capacitor Cf2 is such that the current at the neutral line M flows into the AC terminal, the switching logic is as follows: Figures 7A-7D As shown. In Figures 7A-7D In the image, the switch tube outlined by the dashed line is in the ON state. Figure 7A In the first switching state, the second switch S2 is turned on. At this time, due to u cf1 > u cf2 When the first switch S1 is turned off, the filter capacitor will not be short-circuited through the first to fourth switches S1-S4, and the current at the neutral line M has a freewheeling loop. Figure 7B To switch to the second state, the fourth switch S4 is turned off, and the current at the neutral line M needs to freewheel through the first switch S1 and the second switch S2. Similarly, because... u cf1 > u cf2 When the first switch S1 is turned off, the filter capacitor will not be short-circuited through the first to fourth switches S1-S4. Figure 7C In the third state of switching, the first switch S1 is turned on, because u cf1 > u cf2 When the fourth switch S4 is turned off, the filter capacitor will not be short-circuited through the first to fourth switches S1-S4. Figure 7D In the final state of the switching, the third switch S3 is turned off, while the first switch S1 and the second switch S2 remain on, and the three-phase single-stage AC / DC isolation converter circuit enters a new stable state. The switching from the third switch S3 and the fourth switch S4 to the fifth switch S5 and the sixth switch S6, and vice versa, follows the same principle and will not be elaborated upon here.

[0029] Figure 8 This is a circuit diagram of another preferred embodiment of the power frequency voltage selection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention. (See diagram below.) Figure 8As shown, the power frequency voltage selection module includes: a filtering unit, a first rectification unit, a second rectification unit, a third rectification unit, a first switch driver unit, a second switch driver unit, and a third switch driver unit. The filtering unit includes a single-inductor filter unit (i.e., a filter). The first rectification unit, the second rectification unit, and the third rectification unit each include switches SD1~SD2, SD3~SD4, and SD5~SD6, respectively. The first switch driver unit includes a first switch S1 and a second switch S2; the second switch driver unit includes a third switch S3 and a fourth switch S4; and the third switch driver unit includes a fifth switch S5 and a sixth switch S6. Replacing diodes D1~D6 with switches SD1~SD6 can achieve synchronous rectification or bidirectional operation.

[0030] Further Return Figure 3 ,exist Figure 3 In the preferred embodiment shown, the third harmonic injection module includes a first high-frequency filter capacitor Cf1, a second high-frequency filter capacitor Cf2, a harmonic inductor unit, a harmonic switching transistor unit, and a bus capacitor Cbus. The positive terminal of the first high-frequency filter capacitor Cf1 is connected to the positive bus P, the negative terminal of the first high-frequency filter capacitor Cf1 is connected to the neutral line M and the positive terminal of the second high-frequency filter capacitor Cf2, and the negative terminal of the second high-frequency filter capacitor Cf2 is connected to the negative bus N. The harmonic switching transistor unit is connected between the positive bus P and the negative bus N, and its control terminal receives a harmonic control signal. The positive terminal of the bus capacitor Cbus is connected to the positive bus P, and its negative terminal is connected to the negative bus N. The harmonic inductor unit is connected between the neutral line M and the harmonic switching transistor unit. The first high-frequency filter capacitor Cf1, the second high-frequency filter capacitor Cf2, and the bus capacitor Cbus are all thin-film capacitors used for high-frequency filtering. The harmonic switching transistor unit operates at high frequency to control the current of the midpoint inductor L1. The third harmonic injection module is used to control the neutral current of the neutral line M, including: obtaining the instantaneous values ​​of the maximum and minimum phase voltages based on the first, second, and third input phase voltages, and obtaining a reference value of the neutral current based on the maximum and minimum phase voltages and a set output voltage power; generating the harmonic control signal based on the real-time sampled value of the neutral current, the reference value of the neutral current, the maximum and minimum phase voltages; and controlling the harmonic switching transistor unit based on the harmonic control signal, thereby controlling the neutral current of the neutral line M. Figure 3In the preferred embodiment shown, the harmonic inductor unit includes a harmonic inductor L1, and the harmonic switching transistor unit includes a first harmonic switch S+ and a second harmonic switch SS-. The first end of the harmonic inductor L1 is connected to the neutral line M, and the second end of the harmonic inductor L1 is connected to the second end of the first harmonic switch S+ and the first end of the second harmonic switch S-. The first end of the first harmonic switch S+ is connected to the positive bus P, and the second end of the second harmonic switch S- is connected to the negative bus N. The positive terminal of the bus capacitor is connected to the positive bus P, and the negative terminal is connected to the negative bus N. The control terminal of the first harmonic switch S+ receives a first harmonic control signal, and the control terminal of the second harmonic switch S- receives a second harmonic control signal.

[0031] Figure 9 The diagram shows the waveforms of the input phase voltage and harmonic inductor of the three-phase single-stage AC / DC isolation converter circuit of the present invention. The harmonic switching transistor unit operates at a high frequency to achieve current control of the midpoint inductor L1. , , These are the first input phase voltage, the second input phase voltage, and the third input phase voltage, respectively. Figure 9 As shown, the current of the harmonic inductor L1 always has the same shape as the input phase voltage whose absolute value is in the middle position, that is, the same phase; the magnitude of the inductor current is determined by the weight of the load.

[0032] Figure 10 This is a circuit diagram of another preferred embodiment of the third harmonic injection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention. Depending on the load power, the third harmonic injection module can also use a multi-channel interleaved structure to reduce the current pressure on each channel. For example... Figure 10 As shown, the third harmonic injection module includes a first high-frequency filter capacitor Cf1, a second high-frequency filter capacitor Cf2, a harmonic inductor unit, a harmonic switching transistor unit, and a bus capacitor Cbus. Figure 3 The difference is that, in Figure 10In the illustrated embodiment, the harmonic inductor unit includes a first harmonic inductor L1 and a second harmonic inductor L2; the harmonic switching transistor unit includes a first harmonic switch S1+, a second harmonic switch S1-, a third harmonic switch S2+, and a fourth harmonic switch S2-; the first end of the first harmonic inductor L1 is connected to the neutral line M, the second end of the first harmonic inductor L1 is connected to the second end of the first harmonic switch S1+ and the first end of the second harmonic switch S1-, the first end of the first harmonic switch S1+ is connected to the positive bus P, the second end of the second harmonic switch S1- is connected to the negative bus N, the positive terminal of the bus capacitor is connected to the positive bus P, and the negative terminal is connected to the negative bus N; the first harmonic switch... The control terminal of transistor S1+ receives the first harmonic control signal, and the control terminal of the second harmonic switch transistor S1- receives the second harmonic control signal; the first terminal of the second harmonic inductor L2 is connected to the neutral line M, the second terminal of the second harmonic inductor L2 is connected to the second terminal of the third harmonic switch transistor S2+ and the first terminal of the fourth harmonic switch transistor S2-, the first terminal of the third harmonic switch transistor S2+ is connected to the positive bus P, the second terminal of the fourth harmonic switch transistor S2- is connected to the negative bus N, the positive terminal of the bus capacitor is connected to the positive bus P, and the negative terminal is connected to the negative bus N; the control terminal of the third harmonic switch transistor S2+ receives the third harmonic control signal, and the control terminal of the fourth harmonic switch transistor S2- receives the fourth harmonic control signal. Figure 10 The illustrated embodiments and Figure 3 The embodiments shown are similar and will not be described again here.

[0033] like Figure 3 As shown, the isolated DC-DC module includes multiple isolated DC-DC units to achieve input / output isolation and stable control of the output voltage. Figure 3 In the illustrated embodiment, the isolated DC-DC module includes eight flyback units, each flyback unit including a flyback transformer, a flyback switch, and an output diode. Figure 3As shown, the isolated DC-DC module includes flyback switches Sa1-Sa8, flyback transformers Tra1-Tra8, and flyback output diodes Dra1-Dra8. Lm1-Lm8 in the circuit are the magnetizing inductances of transformers Tra1-Tra8, i.e., at the actual physical level. Lmx and Trax (x=1,2,...8) are the same component, i.e., the flyback transformer. The control terminals of flyback switches Sa1-Sa8 receive control signals SW1~SW8. The first end of the primary winding of flyback transformers Tra1-Tra8 is connected to the positive busbar, and the second end of the primary winding is connected to the negative busbar via the corresponding first and second ends of flyback switches Sa1-Sa8. The first end of the secondary winding of flyback transformers Tra1-Tra8 is connected to the anode of flyback output diodes Dra1-Dra8, and the first end of the secondary winding is connected to a switching unit composed of relays S1~S3. The cathode of flyback output diodes Dra1-Dra8 is also connected to the switching unit composed of relays S1~S3. Figure 3 In the preferred embodiment shown, the drive signal interleaving angle of each flyback unit is 360° / 8. The output terminals of each flyback unit are widened through relays S1-S3. When a low voltage output is required, relays S2 and S3 are closed, and all flyback units output in parallel. When a high voltage output is required, relays S2 and S3 are opened, S1 is closed, and the upper four sets of parallel flyback modules and the lower four sets of parallel flyback modules output in series, achieving high voltage output. In a preferred embodiment of the invention, the isolated DC-DC converter module is used to control the bus current, thereby making the input phase current of the three-phase single-stage AC / DC isolation converter follow the input phase voltage, including: using the bus current as a reference value for the output current; generating power transistor control signals for controlling the power transistors of the multiple isolated DC-DC converter units based on the reference value of the output current, the sampled value of the output current, and the bus voltage, thereby making the input phase current of the three-phase single-stage AC / DC isolation converter follow the input phase voltage. In a preferred embodiment of the invention, a unified six-pulse bus is provided for the isolated DC-DC module through the power frequency voltage selection module and the third harmonic injection module. Because they share a single bus, some functional circuits of the isolated DC-DC module can be multiplexed. For example, all switches connected to the negative bus can be multiplexed to drive the isolated power supply. For the flyback unit, its active clamping circuit can be multiplexed to reduce cost.

[0034] Figures 11A-11B This is a circuit diagram of another preferred embodiment of the third harmonic injection module of the three-phase single-stage AC / DC isolation converter circuit of the present invention. Figures 11A-11BThe isolated DC-DC module includes three flyback units, which are connected in an interleaved parallel configuration. In practice, the number of interleaved parallel configurations can be increased as needed. Figures 11A-11B In the preferred embodiment shown, each flyback unit's main power transistor (i.e., flyback switches Sa1-Sa3) is equipped with a clamping capacitor (Ccla1, Ccla2, Ccla3). This capacitor needs to be as close as possible to the switch and transformer to better absorb leakage inductance energy. The active clamping discharge transistor Sa4 can be shared by multiple transistors to achieve the discharge of the clamping capacitor. Figures 11A-11B These are the cases of clamping to the negative busbar and the positive busbar, respectively. Figures 11A-11B In the preferred embodiment shown, the isolated DC-DC module includes flyback switches Sa1-Sa3, flyback transformers Tra1-Tra3, and flyback output diodes Dra1-Dra3. Lm1-Lm3 in the circuit are the magnetizing inductances of transformers Tra1-Tra3, respectively. The isolated DC-DC module also includes clamping capacitors Ccla1, Ccla2, and Ccla3; clamping diodes Dcla1 and Dcla2; and a discharge switch Sa4. Figure 11A As shown, the first terminals of the primary windings of flyback transformers Tra1-Tra3 are all connected to the positive busbar. The second terminal of the primary winding of flyback transformer Tra1 is connected to the anode of clamping diode Dcla1 and the first terminal of flyback switch Sa1. The second terminal of flyback switch Sa1 is connected to the negative busbar. The cathode of clamping diode Dcla1 is connected to the positive terminal of clamping capacitor Ccla1, and the negative terminal of clamping capacitor Ccla1 is connected to the negative busbar. The second terminal of the primary winding of flyback transformer Tra2 is connected to the anode of clamping diode Dcla2 and the first terminal of flyback switch Sa2. The second terminal of flyback switch Sa2 is connected to the negative busbar. The cathode of clamping diode Dcla2 is connected to the positive terminal of clamping capacitor Ccla2, and the negative terminal of clamping capacitor Ccla2 is connected to the negative busbar. The second terminal of the primary winding of the flyback transformer Tra3 is connected to the second terminal of the discharge switch Sa4 and the first terminal of the flyback switch Sa3. The second terminal of the flyback switch Sa3 is connected to the negative bus. The first terminal of the discharge switch Sa4 is connected to the positive terminal of the clamping capacitor Ccla3, and the negative terminal of the clamping capacitor Ccla3 is connected to the negative bus. The cathodes of clamping diodes Dcla1 and Dcla2, and the first terminal of the discharge switch Sa4 are also connected. The control terminal of the discharge switch Sa4 receives the discharge control signal. Figure 11B The illustrated embodiments and Figure 11A The difference in the illustrated embodiment lies in the connection relationship of the clamping capacitors Ccla1, Ccla2, and Ccla3; the clamping diodes Dcla1 and Dcla2; and the discharge switch Sa4. The principle is the same as... Figure 11AThe embodiments shown are similar and will not be repeated here. In a further preferred embodiment of the present invention, the isolated DC-DC unit includes a flyback unit, a full-bridge LLC unit, a half-bridge LLC unit, a three-phase LLC unit, a full-bridge DAB unit, a full-bridge quasi-DAB unit, a half-bridge DAB unit, a three-phase DAB unit, or an isolated SEPIC unit. That is, the isolated DC-DC module may include different isolated DC-DC units, such as n sets of flyback units, n sets of full-bridge LLC units, n sets of half-bridge LLC units, n sets of three-phase LLC units, n sets of full-bridge DAB units, n sets of full-bridge quasi-DAB units, n sets of half-bridge DAB units, n sets of three-phase DAB units, or n sets of isolated SEPIC units. Figure 12 This is a circuit diagram of another preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit of the present invention. Figure 13 This is a circuit diagram of another preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit of the present invention. Figure 12 In the preferred embodiment shown, the isolated DC-DC module includes multiple three-phase LLC units. Figure 13 In the preferred embodiment shown, the isolated DC-DC module includes multiple full-bridge quasi-DAB units.

[0035] Figure 14 This is a schematic diagram of different embodiments of the winding switching of the isolation DC-DC module in the three-phase single-stage AC / DC isolation converter circuit of the present invention. Figures 12-13 In the preferred embodiment shown, each isolated DC-DC unit uses series and parallel output capacitors to achieve high-low voltage switching. In a further preferred embodiment of the present invention, each isolated DC-DC unit can perform different high-low voltage switching according to the high-low voltage requirements, such as switching the series and parallel connection of capacitors, switching the series and parallel connection of windings, and switching the number of turns of windings. Figure 14 Different embodiments of winding switching for the isolated DC-DC module are shown, where (a)-(c) are secondary winding series-parallel switching schemes, (d) is the primary winding series-parallel switching scheme, and (e)-(f) are primary and secondary winding switching schemes, respectively. Therefore, the three-phase single-stage AC / DC isolation converter circuit of this invention can connect to different isolated DC-DC modules; the number of connected isolated DC-DC units (n) can vary according to power requirements, and the circuits can be interleaved to reduce ripple; and each isolated DC-DC unit can perform different high-low voltage switching according to high- and low-voltage requirements, such as series-parallel switching of capacitors, series-parallel switching of windings, and switching of the number of turns in the windings.

[0036] Figure 15 yes Figure 3 The diagram shows the harmonic control signal generation logic of a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit. Figure 16 yes Figure 3A schematic diagram of the power transistor control signal generation logic of the isolation DC-DC module in a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit shown. Figure 17 yes Figure 3 The diagram shows the input voltage, current waveform, output current waveform, and bus voltage waveform of a preferred embodiment of the three-phase single-stage AC / DC isolation converter circuit. We will now combine this with... Figure 3 , 15 The principle of the three-phase single-stage AC / DC isolation converter circuit of the present invention is explained below (section 17). For the waveform generation mode of the power frequency voltage selection module and the output waveform of the third harmonic injection module, please refer to [reference needed]. Figures 3-9 The description of the illustrated embodiment will not be repeated here. Since the sum of the three-phase input phase currents of the three-phase single-stage AC / DC isolation converter circuit is zero, the three-phase input phase currents of the three-phase single-stage AC / DC isolation converter circuit can be controlled by controlling the neutral current and the bus current, thereby making the input phase currents of the three-phase single-stage AC / DC isolation converter circuit follow the input phase voltages. Therefore, the current in inductor L1, i.e., the neutral current, is the target object that the three-phase single-stage AC / DC isolation converter circuit needs to control.

[0037] Combination Figure 3 and 15 The specific derivation process is as follows. Indicates the first input phase voltage. Indicates the second input phase voltage. This represents the voltage of the third input phase, and therefore it can be expressed as: .

[0038] This represents the phase voltage amplitude of the first input phase voltage. This represents the phase voltage amplitude of the second input phase voltage. This represents the phase voltage amplitude of the third input phase voltage; in a three-phase balanced state, the three voltage values ​​are equal. . The reference value for the neutral current is the reference value for the current in the neutral point inductor L1, and it is a time-varying nonlinear variable. Under three-phase equilibrium conditions, its expression is: .

[0039] in, This represents a reference value for the neutral current. Indicates the first input phase voltage. Indicates the second input phase voltage. Indicates the third input phase voltage. This represents the instantaneous value of the maximum phase voltage. This represents the instantaneous value of the minimum phase voltage. This indicates the set output voltage and power; = , This represents the phase voltage amplitude of the first input phase voltage. This represents the phase voltage amplitude of the second input phase voltage. This represents the phase voltage amplitude of the third input phase voltage.

[0040] In a preferred embodiment of the present invention, generating the harmonic control signal based on the real-time sampled value of the neutral current, the reference value of the neutral current, the instantaneous value of the maximum phase voltage, and the instantaneous value of the minimum phase voltage includes: calculating the difference between the real-time sampled value of the neutral current and the reference value of the neutral current; inputting the difference into a proportional-integral controller to obtain an output value; and superimposing the output value with a first feedforward signal or a second feedforward signal and then sending it to a PWM generation unit to generate the harmonic control signal, wherein the first feedforward signal is... The second feedforward signal is ;in This represents the instantaneous value of the intermediate phase. The harmonic control signal includes drive signals for the switching transistors S+ and S- with dead zones.

[0041] In another preferred embodiment of the present invention, a feedforward signal may not be used; that is, the harmonic control signal may be generated based on the real-time sampled value of the neutral current and the reference value of the neutral current. In this preferred embodiment, the difference between the real-time sampled value of the neutral current and the reference value of the neutral current is calculated; the difference is input to a proportional-integral controller to obtain an output value; and the output value is sent to a PWM generation unit to generate the harmonic control signal. Here, the feedforward signal can be removed by increasing the bandwidth of the PI controller, modifying the PI controller to a proportional-resonant controller (PR controller), or modifying the PI controller to a repetitive controller. Those skilled in the art can implement the aforementioned modifications based on the teachings of the present invention and common knowledge in the field, and will not be elaborated here. As mentioned above, the harmonic control signal includes drive signals for the switching transistors S+ and S- with dead time.

[0042] For an isolated DC-DC module, the bus voltage on its input bus capacitor Cbus is... When the variable is nonlinear: .in, Indicates bus voltage. This represents the absolute value of the line voltage between the first input phase and the second input phase. This represents the absolute value of the line voltage between the second and third input phases. This represents the absolute value of the line voltage between the first input phase and the third input phase. In this invention, the control objective of the isolated DC-DC module is to achieve constant output power or constant output current. If the current of the isolated DC-DC module is controlled, its current reference value... Selected as bus current . This indicates the set output voltage and power. A closed-loop control system is used. This is a reference value for the output current. The difference between the sampled output current and the input current is fed into the proportional-integral controller (PI). The output is then superimposed with a feedforward signal, which is the normalized voltage signal on bus Cbus. The PWM generation unit generates power transistor control signals for controlling the power transistors of the multiple isolated DC-DC units, namely, 8 interleaved flyback drive signals. Through the above control, the waveforms of the input voltage and current, the output current, and the bus voltage on the bus capacitor Cbus are as follows: Figure 17 As shown, the input phase current is in phase with the phase voltage, exhibiting a high power factor. The current sinusoidal characteristic is high, resulting in low output current ripple. The bus capacitor Cbus is a film capacitor; the bus voltage across it is the envelope of the peak absolute value of the input line voltage, exhibiting a six-pulse waveform with a fluctuation frequency six times the phase voltage frequency.

[0043] The three-phase single-stage AC / DC isolation converter circuit of this invention, in addition to possessing the advantages of high efficiency, high power density, and no bus electrolysis inherent in conventional single-stage circuits, can form a unified three-phase bus through a power frequency voltage selection module and a third harmonic injection module. Compared to other three-phase single-stage circuits with separately controlled three circuits, the three-phase single-stage AC / DC isolation converter circuit of this invention can form a higher bus voltage through coordinated control of the three phases. Compared to the single-stage bus voltage in the form of a "steamer wave," the three-phase single-stage AC / DC isolation converter circuit of this invention, by forming a six-pulse bus voltage, can reduce the peak current stress on the isolated DC-DC modules, improve the full-cycle device utilization of the isolated DC-DC modules, and reduce the control difficulty of the isolated DC-DC modules, thereby reducing output current ripple. Furthermore, by forming a unified DC bus, this invention allows for more flexible selection of the number of isolated DC-DC modules, and parallel isolated DC-DC modules can be completely interleaved, thereby reducing bus capacitor ripple and output capacitor ripple, improving capacitor lifespan, and enhancing system reliability.

[0044] Although this invention has been described through specific embodiments, those skilled in the art should understand that various modifications and equivalent substitutions can be made to this invention without departing from its scope. Furthermore, various modifications can be made to this invention for specific situations or materials without departing from its scope. Therefore, this invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims. The above descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A three-phase single-stage AC / DC isolation converter circuit, characterized in that, include: Power frequency voltage selection module, third harmonic injection module, and isolated DC-DC module; The input terminal of the power frequency voltage selection module is connected to a three-phase power supply to receive the input phase voltage; the first output terminal is connected to the positive bus; the second output terminal is connected to the negative bus; and the third output terminal is connected to the neutral line. The third harmonic injection module and the isolation DC-DC module are connected sequentially between the positive bus and the negative bus. The power frequency voltage selection module is used to select voltage based on the input phase voltage to control the bus voltage between the positive bus and the negative bus; The isolated DC-DC module is used to perform DC-DC conversion on the bus voltage to generate an output voltage; The third harmonic injection module is used to control the neutral current of the neutral line, and the isolation DC-DC module is used to control the bus current, so that the input phase current of the three-phase single-stage AC / DC isolation converter circuit follows the input phase voltage.

2. The three-phase single-stage AC / DC isolation converter circuit according to claim 1, characterized in that, The power frequency voltage selection module includes: a filtering unit, a first rectification unit, a second rectification unit, a third rectification unit, a first switch driver unit, a second switch driver unit, and a third switch driver unit; The input terminal of the filter unit is connected to the three-phase power supply. The first output terminal of the filter unit is connected to the first terminal of the first rectifier unit and the first terminal of the first switch driver unit. The second output terminal of the filter unit is connected to the first terminal of the second rectifier unit and the first terminal of the second switch driver unit. The third output terminal of the filter unit is connected to the first terminal of the third rectifier unit and the first terminal of the third switch driver unit. The second end of the first rectifier unit, the second end of the second rectifier unit, and the second end of the third rectifier unit are all connected to the positive bus, and the third end of the first rectifier unit, the third end of the second rectifier unit, and the third end of the third rectifier unit are all connected to the negative bus. The second end of the first switch driving unit, the second end of the second switch driving unit, and the second end of the third switch driving unit are all connected to the neutral line; The control terminals of the first switch driver unit, the second switch driver unit, and the third switch driver unit respectively receive control signals. The power frequency voltage selection module is used to select voltage based on the input phase voltage to control the bus voltage between the positive bus and the negative bus, including: The first switch driving unit, the second switch driving unit, and the third switch driving unit turn on or off based on the absolute values ​​of the first input phase voltage, the second input phase voltage, and the third input phase voltage output by the filter unit to select the maximum and minimum voltages to control the bus voltage between the positive bus and the negative bus.

3. The three-phase single-stage AC / DC isolation converter circuit according to claim 2, characterized in that, The filtering unit includes a single-inductor filtering unit, an LCL filtering unit, or an LC filtering unit; The first rectification unit, the second rectification unit, and the third rectification unit each include a diode rectification unit or a switching transistor rectification unit; The first switching transistor driving unit includes a first switching transistor and a second switching transistor. The first end of the first switching transistor is connected to the first output end of the filtering unit, and the second end is connected to the second end of the second switching transistor. The first end of the second switching transistor is connected to the neutral line. The control end of the first switching transistor receives a first control signal, and the control end of the second switching transistor receives a second control signal. The second switching transistor driving unit includes a third switching transistor and a fourth switching transistor. The first end of the third switching transistor is connected to the second output end of the filtering unit, and the second end is connected to the second end of the fourth switching transistor. The first end of the fourth switching transistor is connected to the neutral line. The control end of the third switching transistor receives a third control signal, and the control end of the fourth switching transistor receives a fourth control signal. The third switch driving unit includes a fifth switch and a sixth switch. The first end of the fifth switch is connected to the third output end of the filter unit, and the second end is connected to the second end of the sixth switch. The first end of the sixth switch is connected to the neutral line. The control end of the fifth switch receives a fifth control signal, and the control end of the sixth switch receives a sixth control signal. When the filtering unit is the single-inductor filtering unit or the LCL filtering unit, the first control signal and the second control signal are the same, the third control signal and the fourth control signal are the same, and the fifth control signal and the sixth control signal are the same; When the filtering unit is the LC filtering unit, the first control signal and the second control signal are different, the third control signal and the fourth control signal are different, and the fifth control signal and the sixth control signal are different.

4. The three-phase single-stage AC / DC isolation converter circuit according to any one of claims 1 to 3, characterized in that, The third harmonic injection module includes a first high-frequency filter capacitor, a second high-frequency filter capacitor, a harmonic inductor unit, a harmonic switching transistor unit, and a bus capacitor. The positive terminal of the first high-frequency filter capacitor is connected to the positive busbar, the negative terminal of the first high-frequency filter capacitor is connected to the neutral line and the positive terminal of the second high-frequency filter capacitor, and the negative terminal of the second high-frequency filter capacitor is connected to the negative busbar. The harmonic switching transistor unit is connected between the positive bus and the negative bus, and the control terminal of the harmonic switching transistor unit receives the harmonic control signal. The positive terminal of the bus capacitor is connected to the positive bus, and the negative terminal is connected to the negative bus. The harmonic inductor unit is connected between the neutral line and the harmonic switching transistor unit. The third harmonic injection module is used to control the neutral current of the neutral line, including: The instantaneous values ​​of the maximum and minimum phase voltages are obtained based on the first, second, and third input phase voltages, and the reference value of the neutral current is obtained based on the maximum and minimum phase voltage values ​​and the set output voltage power. The harmonic control signal is generated based on the real-time sampled value of the neutral current and the reference value of the neutral current, or the harmonic control signal is generated based on the real-time sampled value of the neutral current, the reference value of the neutral current, the instantaneous value of the maximum phase voltage and the instantaneous value of the minimum phase voltage. The harmonic switching transistor unit is controlled based on the harmonic control signal, thereby controlling the neutral current of the neutral line.

5. The three-phase single-stage AC / DC isolation converter circuit according to claim 4, characterized in that, The harmonic control signal is generated based on the real-time sampled value of the neutral current and the reference value of the neutral current, including: Calculate the difference between the real-time sampled value of the neutral current and the reference value of the neutral current; The difference is input into the proportional-integral controller to obtain the output value; The output value is sent to the PWM generation unit to generate the harmonic control signal; in, in, This represents a reference value for the neutral current. Indicates the first input phase voltage. Indicates the second input phase voltage. Indicates the third input phase voltage. This represents the instantaneous value of the maximum phase voltage. This represents the instantaneous value of the minimum phase voltage. This indicates the set output voltage and power; = , This represents the phase voltage amplitude of the first input phase voltage. This represents the phase voltage amplitude of the second input phase voltage. This represents the phase voltage amplitude of the third input phase voltage.

6. The three-phase single-stage AC / DC isolation converter circuit according to claim 4, characterized in that, The harmonic control signal is generated based on the real-time sampled value of the neutral current, the reference value of the neutral current, the instantaneous value of the maximum phase voltage, and the instantaneous value of the minimum phase voltage, including: Calculate the difference between the real-time sampled value of the neutral current and the reference value of the neutral current; The difference is input into the proportional-integral controller to obtain the output value; The output value is superimposed with the first feedforward signal or the second feedforward signal and then sent to the PWM generation unit to generate the harmonic control signal. in, in, This represents a reference value for the neutral current. Indicates the first input phase voltage. Indicates the second input phase voltage. Indicates the third input phase voltage. This represents the instantaneous value of the maximum phase voltage. This represents the instantaneous value of the minimum phase voltage. This indicates the set output voltage and power; = , This represents the phase voltage amplitude of the first input phase voltage. This represents the phase voltage amplitude of the second input phase voltage. This represents the phase voltage amplitude of the third input phase voltage; The first feedforward signal is The second feedforward signal is ;in This represents the instantaneous value of the intermediate phase.

7. The three-phase single-stage AC / DC isolation converter circuit according to claim 4, characterized in that, The harmonic inductor unit includes a harmonic inductor, and the harmonic switching transistor unit includes a first harmonic switching transistor and a second harmonic switching transistor. The first end of the harmonic inductor is connected to the neutral line, and the second end of the harmonic inductor is connected to the second end of the first harmonic switching transistor and the first end of the second harmonic switching transistor. The first end of the first harmonic switching transistor is connected to the positive busbar, and the second end of the second harmonic switching transistor is connected to the negative busbar. The positive terminal of the busbar capacitor is connected to the positive busbar, and the negative terminal is connected to the negative busbar. The control terminal of the first harmonic switching transistor receives a first harmonic control signal, and the control terminal of the second harmonic switching transistor receives a second harmonic control signal.

8. The three-phase single-stage AC / DC isolation converter circuit according to claim 4, characterized in that, The harmonic inductor unit includes a first harmonic inductor and a second harmonic inductor; the harmonic switch unit includes a first harmonic switch, a second harmonic switch, a third harmonic switch, and a fourth harmonic switch. The first end of the first harmonic inductor is connected to the neutral line, and the second end of the first harmonic inductor is connected to the second end of the first harmonic switch and the first end of the second harmonic switch. The first end of the first harmonic switch is connected to the positive bus, and the second end of the second harmonic switch is connected to the negative bus. The positive terminal of the bus capacitor is connected to the positive bus, and the negative terminal is connected to the negative bus. The control terminal of the first harmonic switch receives a first harmonic control signal, and the control terminal of the second harmonic switch receives a second harmonic control signal. The first end of the second harmonic inductor is connected to the neutral line, and the second end of the second harmonic inductor is connected to the second end of the third harmonic switch and the first end of the fourth harmonic switch. The first end of the third harmonic switch is connected to the positive bus, and the second end of the fourth harmonic switch is connected to the negative bus. The positive terminal of the bus capacitor is connected to the positive bus, and the negative terminal is connected to the negative bus. The control terminal of the third harmonic switch receives a third harmonic control signal, and the control terminal of the fourth harmonic switch receives a fourth harmonic control signal.

9. The three-phase single-stage AC / DC isolation converter circuit according to claim 4, characterized in that, The isolated DC-DC module includes multiple isolated DC-DC units; the multiple isolated DC-DC units achieve high-low voltage switching through series-parallel connection of windings or series-parallel connection of output capacitors. The isolated DC-DC module is used to control the bus current, thereby ensuring that the input phase current of the three-phase single-stage AC / DC isolation converter follows the input phase voltage, including: The bus current is used as a reference value for the output current; Based on the reference value of the output current, the sampled value of the output current, and the bus voltage, a power transistor control signal is generated to control the power transistors of the plurality of isolated DC-DC units, thereby making the input phase current of the three-phase single-stage AC-DC isolation converter circuit follow the input phase voltage.

10. The three-phase single-stage AC / DC isolation converter circuit according to claim 9, characterized in that, Based on the reference value of the output current, the sampled value of the output current, and the bus voltage, a power transistor control signal is generated to control the power transistors of the plurality of isolated DC-DC units, including: Calculate the difference between the reference value of the output current and the sampled value of the output current; The difference is input into the proportional-integral controller to obtain the output value; The output value is superimposed with a feedforward signal and then sent to a PWM generation unit to generate a power transistor control signal for controlling the power transistors of the plurality of isolated DC-DC units, wherein the feedforward signal is the normalized value of the bus voltage. in, ; ； in, Indicates bus voltage. This represents the absolute value of the line voltage between the first input phase and the second input phase. This represents the absolute value of the line voltage between the second and third input phases. This represents the absolute value of the line voltage between the first input phase and the third input phase; Indicates the bus current; This indicates the set output power.

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