Bidirectional converter and modulation method thereof

Abstract

The present application belongs to the technical field of converters, and specifically relates to a bidirectional converter and a modulation method thereof, wherein the bidirectional converter comprises a DC interface, an AC interface, a high-frequency module, an industrial frequency module and a control module; the high-frequency module comprises a high-frequency upper bridge arm and a high-frequency lower bridge arm connected in series, the high-frequency upper bridge arm comprises N cascaded first bridge arm circuits; the high-frequency lower bridge arm comprises N cascaded second bridge arm circuits; the industrial frequency module comprises an industrial frequency upper bridge arm and an industrial frequency lower bridge arm connected in series; the control module is used to control the industrial frequency upper bridge arm and the industrial frequency lower bridge arm to be alternately turned on, and when the industrial frequency upper bridge arm is turned on, the N first bridge arm circuits of the high-frequency upper bridge arm are driven to alternately output full voltage and zero voltage, and when the industrial frequency lower bridge arm is turned on, the N second bridge arm circuits of the high-frequency lower bridge arm are driven to alternately output full voltage and zero voltage; the present application can realize the mutual conversion between DC and AC through only one voltage conversion, thereby reducing the volume and cost of the converter while improving the voltage conversion efficiency.

Description

Technical Field

[0001] The present application belongs to the technical field of converters, and in particular relates to a bidirectional converter and a modulation method thereof. Background Art

[0002] As a power electronic device that can realize bidirectional conversion between direct current and alternating current, the DC-AC bidirectional converter plays an important role in modern power systems. Its high efficiency, intelligence and environmental protection make it widely used in new energy vehicles, renewable energy power generation, energy storage systems and data centers.

[0003] The inverter principle of the existing DC-AC bidirectional converter is generally evolved based on the Buck circuit (i.e., step-down conversion circuit), so its DC bus voltage needs to be greater than or equal to the AC side voltage amplitude, and usually includes one or two stages of DC-DC converters based on high-frequency transformers and DC-AC converters; since the bidirectional converter in the related technology has at least two voltage conversions (DC-DC and DC-AC), it not only reduces the voltage conversion efficiency, but also has the problems of large size and high cost.

[0004] Therefore, how to improve the conversion efficiency of the DC-AC bidirectional converter while reducing the size of the converter is a problem that needs to be solved urgently. Summary of the invention

[0005] The present application provides a bidirectional converter and a modulation method thereof, which solve the problems of low conversion efficiency and large volume of the bidirectional converter in the related art.

[0006] In a first aspect, the present application provides a bidirectional converter, which includes: a DC interface; a high-frequency module, including a high-frequency upper bridge arm and a high-frequency lower bridge arm connected in series, the high-frequency upper bridge arm including N cascaded first bridge arm circuits; the high-frequency lower bridge arm including N cascaded second bridge arm circuits; N is an integer greater than or equal to 2; the first end of the high-frequency upper bridge arm is connected to the first end of the DC interface, and the second end of the high-frequency lower bridge arm is connected to the second end of the DC interface; an industrial frequency module, including an industrial frequency upper bridge arm and an industrial frequency lower bridge arm connected in series, the first end of the industrial frequency upper bridge arm is connected to the first end of the DC interface, and the second end of the industrial frequency lower bridge arm is connected to the DC interface an AC interface, wherein the first end of the AC interface is respectively connected to the second end of the high-frequency upper bridge arm and the first end of the high-frequency lower bridge arm, and the second end of the AC interface is respectively connected to the second end of the power frequency upper bridge arm and the first end of the power frequency lower bridge arm; a control module, wherein the control module is respectively connected to the control ends of the high-frequency module and the power frequency module, and is used to control the power frequency upper bridge arm and the power frequency lower bridge arm in the power frequency module to be alternately turned on, and when the power frequency upper bridge arm is turned on, the N first bridge arm circuits of the high-frequency module are driven to alternately output full voltage and zero voltage, and when the power frequency lower bridge arm is turned on, the N second bridge arm circuits of the high-frequency module are driven to alternately output full voltage and zero voltage.

[0007] Optionally, each first bridge arm circuit includes a control end, a first connection end, and a second connection end, the first connection end of the first first bridge arm circuit is connected to the first end of the DC interface, the first connection end of the nth first bridge arm circuit is connected to the second connection end of the n-1th first bridge arm circuit, and the second connection end of the Nth first bridge arm circuit is connected to the first end of the AC interface;

[0008] Or / and, each second bridge arm circuit includes a control end, a first connection end and a second connection end, the first connection end of the first second bridge arm circuit is connected to the first end of the AC interface, the first connection end of the nth second bridge arm circuit is connected to the second connection end of the n-1th second bridge arm circuit, and the second connection end of the Nth second bridge arm circuit is connected to the second end of the DC interface; wherein n=[1,…,N].

[0009] Optionally, the first bridge arm circuit and / or the second bridge arm circuit includes: a capacitor; a first transistor, the control end of the first transistor is connected to the control module, the first end of the first transistor is connected to the first end of the capacitor, and the second end of the first transistor serves as the first connection end of the first bridge arm circuit and / or the second bridge arm circuit; a second transistor, the control end of the second transistor is connected to the control module, the first end of the second transistor is connected to the second end of the first transistor, the second end of the second transistor is connected to the second end of the capacitor, and the second end of the second transistor serves as the second connection end of the first bridge arm circuit and / or the second bridge arm circuit.

[0010] Optionally, the power frequency upper bridge arm comprises: a third transistor, a control end of the third transistor is connected to the control module, a first end of the third transistor serves as the first end of the power frequency upper bridge arm, and a second end of the third transistor serves as the second end of the power frequency upper bridge arm;

[0011] Or / and, the industrial frequency lower bridge arm includes: a fourth transistor, the control end of the fourth transistor is connected to the control module, the first end of the fourth transistor serves as the first end of the industrial frequency lower bridge arm, and the second end of the fourth transistor serves as the second end of the industrial frequency lower bridge arm.

[0012] Optionally, the control module is configured to: generate a control signal for controlling the alternating conduction of the industrial frequency upper bridge arm and the industrial frequency lower bridge arm according to the modulation signal; compare the absolute value signal of the modulation signal with the carrier signal, and generate a drive signal for controlling the first bridge arm circuit and the first second bridge arm circuit according to the comparison result; compare the absolute value signal of the modulation signal with the delay signal of the carrier signal, and generate a drive signal for controlling the i+1th first bridge arm circuit and the i+1th second bridge arm circuit according to the comparison result; wherein, i=[1,…,N-1].

[0013] Optionally, the control module includes: a first comparison unit, a first input end of the first comparison unit is connected to the threshold output end, a second input end of the first comparison unit is connected to the modulation wave output end, and an output end of the first comparison unit is connected to the control end of the industrial frequency lower bridge arm, for comparing the modulation signal output by the modulation wave output end with the threshold signal output by the threshold output end; a first inverter, an input end of the first inverter is connected to the output end of the first comparison unit, and an output end of the first inverter is connected to the control end of the industrial frequency upper bridge arm.

[0014] Optionally, the control module also includes: an absolute value unit, the input end of the absolute value unit is connected to the modulation wave output end, and is used to take the absolute value of the modulation signal output from the modulation wave output end; a second comparison unit, the first input end of the second comparison unit is connected to the output end of the absolute value unit, and the second input end of the second comparison unit is connected to the carrier output end, and is used to compare the output waveform of the absolute value unit with the output waveform of the carrier output end; a first gating unit, the input end of the first gating unit is connected to the output end of the second comparison unit, and the output end of the first gating unit is respectively connected to the control ends of the first first bridge arm circuit and the first second bridge arm circuit, and is used to output multiple drive signals under the action of the output signal of the second comparison unit.

[0015] Optionally, the control module also includes: N-1 delay units, the input end of the i-th delay unit is connected to the carrier output end, and is used to delay the carrier signal output from the carrier output end, and the delay time is (Ts / N)×i; Ts represents the carrier period; N-1 third comparison units, the first input end of the i-th third comparison unit is connected to the output end of the absolute value unit, and the second input end of the i-th third comparison unit is connected to the output end of the i-th delay unit, and is used to compare the output waveform of the i-th delay unit with the output waveform of the absolute value unit; N-1 second selection units, the input end of the i-th second selection unit is connected to the output end of the i-th third comparison unit, and the output end of the i-th second selection unit is respectively connected to the control ends of the i+1-th first bridge arm circuit and the i+1-th second bridge arm circuit, and is used to output multiple drive signals under the action of the output signal of the third comparison unit; wherein, i=[1,…,N-1].

[0016] Optionally, the first gating unit or / and the second gating unit includes: a first throw switch, the control end of the first throw switch is connected to the enable signal output end, and the fixed end of the first throw switch is connected to the output end of the second comparison unit or the third comparison unit; a second inverter, the input end of the second inverter is connected to the fixed end of the first throw switch; a second throw switch, the control end of the second throw switch is connected to the enable signal output end, and the fixed end of the second throw switch is connected to the output end of the second inverter; a third throw switch, the control end of the third throw switch is connected to the output end of the first comparison unit, the first fixed end of the third throw switch is connected to the throw end of the first throw switch, the second fixed end of the third throw switch is connected to the throw end of the second throw switch, the first throw end and the second throw end of the third throw switch are connected to the control end of the first bridge arm circuit, and the third throw end and the fourth throw end of the third throw switch are connected to the control end of the second bridge arm circuit.

[0017] In a second aspect, the present application provides a bidirectional converter modulation method, the modulation method comprising: obtaining a target number of first bridge arm circuits in a high-frequency upper bridge arm; calculating the delay duration of each first bridge arm circuit and each second bridge arm circuit according to the target number; wherein the delay duration of the nth first bridge arm circuit and the nth second bridge arm circuit is: (Ts / N)×(n-1), Ts represents the carrier period, and N represents the target number; generating a control signal for controlling the alternating conduction of the industrial frequency upper bridge arm and the industrial frequency lower bridge arm according to the modulation signal; phase-shifting the carrier signal according to the delay duration of each first bridge arm circuit and each second bridge arm circuit, and generating a drive signal corresponding to each first bridge arm circuit and each second bridge arm circuit.

[0018] The technical solution provided by this application has at least the following beneficial effects:

[0019] When the industrial frequency upper bridge arm is turned on, the present application drives the N first bridge arm circuits of the high-frequency upper bridge arm to alternately output full voltage and zero voltage through the control module, and when the industrial frequency lower bridge arm is turned on, drives the N second bridge arm circuits of the high-frequency lower bridge arm to alternately output full voltage and zero voltage, and the obtained AC voltage is the sum of the full voltages output by the N first bridge arm circuits or the N second bridge arm circuits; conversely, the obtained DC voltage is also the sum of the full voltages output by the N first bridge arm circuits or the N second bridge arm circuits, thereby realizing the mutual conversion between DC and AC; therefore, compared with at least two voltage conversions in the related art, the present application can realize the mutual conversion between DC and AC through only one voltage conversion, while improving the voltage conversion efficiency and reducing the size and cost of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0021] Figure 1 Shown is a schematic structural diagram of a bidirectional converter provided in an embodiment of the present application.

[0022] Figure 2 Shown is a schematic structural diagram of another bidirectional converter provided in an embodiment of the present application.

[0023] Figure 3 Shown is a schematic diagram of the structure of a control module provided in an embodiment of the present application.

[0024] Figure 4Shown is a schematic structural diagram of a gating unit provided in an embodiment of the present application.

[0025] Figure 5 Shown is a circuit diagram of a bidirectional converter provided in an embodiment of the present application.

[0026] Figure 6 Shown is a circuit diagram of an example of a control module provided in an embodiment of the present application.

[0027] Figure 7 Shown is a schematic diagram of a modulation waveform provided in an embodiment of the present application.

[0028] Figure 8 The figure is a flow chart of a bidirectional converter modulation method provided in an embodiment of the present application.

[0029] Description of reference numerals:

[0030] 100, bidirectional converter; 110, DC interface; 120, high frequency module; 121, high frequency upper bridge arm; 1211, first bridge arm circuit; 122, high frequency lower bridge arm; 1221, second bridge arm circuit; 130, power frequency module; 131, power frequency upper bridge arm; 132, power frequency lower bridge arm; 140, AC interface; 150, control module; 151, first comparison unit; 152, absolute value unit; 153, second comparison unit; 154, first selection unit; 155, delay unit; 156, third comparison unit; 157, second selection unit;

[0031] 210, threshold output terminal; 220, modulation wave output terminal; 230, carrier output terminal;

[0032] Cp, capacitor; Q1, first transistor; Q2, second transistor; Q3, third transistor; Q4, fourth transistor; U1, first inverter; U2, second inverter; S1, first throw switch; S2, second throw switch; S3, third throw switch. DETAILED DESCRIPTION

[0033] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more comprehensive and complete and fully convey the concept of the example embodiments to those skilled in the art.

[0034] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, known methods, devices, realizations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0035] The present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be understood as limiting the present application.

[0036] In a first aspect, the present application provides a bidirectional converter, which specifically includes the following embodiments:

[0037] Figure 1 FIG. 1 is a schematic diagram of a bidirectional converter provided in an embodiment of the present application; Figure 1 As shown, the bidirectional converter 100 includes a DC interface 110, a high frequency module 120, an industrial frequency module 130, an AC interface 140 and a control module 150; wherein the DC interface 110 is used to connect to a DC bus or a DC power supply, the first end of the DC interface 110 can be a positive end, and the second end of the DC interface 110 can be a negative end; the AC interface 140 is used to connect to an external AC power supply or an AC load, and can also be connected to an external filter.

[0038] In this embodiment, if Figure 1 As shown, the high-frequency module 120 includes a high-frequency upper bridge arm 121 and a high-frequency lower bridge arm 122 connected in series, the first end of the high-frequency upper bridge arm 121 is connected to the first end of the DC interface 110, and the second end of the high-frequency lower bridge arm 122 is connected to the second end of the DC interface 110; the industrial frequency module 130 includes an industrial frequency upper bridge arm 131 and an industrial frequency lower bridge arm 132 connected in series, the first end of the industrial frequency upper bridge arm 131 is connected to the first end of the DC interface 110, and the second end of the industrial frequency lower bridge arm 132 is connected to the second end of the DC interface 110.

[0039] Figure 2 for Figure 1 Specific structural diagram of Figure 2As shown, the high-frequency upper bridge arm 121 includes N cascaded first bridge arm circuits 1211; the high-frequency lower bridge arm 122 includes N cascaded second bridge arm circuits 1221; N is an integer greater than or equal to 2; the control module 150 is respectively connected to the control end of each first bridge arm circuit 1211, the control end of each second bridge arm circuit 1221, the control end of the power frequency upper bridge arm 131 and the control end of the power frequency lower bridge arm 132 in the high-frequency module, and is used to control the power frequency upper bridge arm 131 and the power frequency lower bridge arm 132 in the power frequency module to be alternately turned on, and when the power frequency upper bridge arm 131 is turned on, the N first bridge arm circuits 1211 of the high-frequency module are driven to alternately output full voltage and zero voltage, and when the power frequency lower bridge arm 132 is turned on, the N second bridge arm circuits 1221 of the high-frequency module are driven to alternately output full voltage and zero voltage.

[0040] It should be noted that the control module 150 controls the power frequency upper bridge arm 131 and the power frequency lower bridge arm 132 to be turned on alternately, and drives the N first bridge arm circuits 1211 of the high frequency upper bridge arm 121 when the power frequency upper bridge arm 131 is turned on, and drives the N second bridge arm circuits 1221 of the high frequency lower bridge arm 122 when the power frequency lower bridge arm 132 is turned on; in addition, each first bridge arm circuit 1211, driven by the control module 150, alternately outputs full voltage and zero voltage; wherein the full voltage is equal to , Vdc represents the DC bus voltage output by the DC interface 110 .

[0041] The specific working principle of the bidirectional converter 100 provided in this embodiment is as follows: when the control module 150 controls the power frequency upper bridge arm 131 to be in the on state, the control module 150 outputs a plurality of high-frequency driving signals to drive the N first bridge arm circuits 1211 of the high-frequency upper bridge arm 121 to alternately output full voltage and zero voltage; and because the output voltage of the high-frequency upper bridge arm 121 is the sum of the output voltages of the N cascaded first bridge arm circuits 1211, during the time period in which the power frequency upper bridge arm 131 is in the on state, the AC voltage at each moment is the sum of the full voltages outputted by the N first bridge arm circuits 1211; similarly, when the control module 150 controls the power frequency lower bridge arm 132 to be in the on state, the control module Block 150 outputs several high-frequency driving signals to drive the N second bridge arm circuits 1221 of the high-frequency lower bridge arm 122 to alternately output full voltage and zero voltage. The specific working principle is the same as that of the upper bridge arm, and will not be repeated here. It can be seen that the function of the control module 150 is to output control signals and high-frequency driving signals. The industrial frequency module is used to control the connection status of the high-frequency upper bridge arm and the high-frequency lower bridge arm with the second end of the AC interface respectively under the action of the control signal output by the control module. The high-frequency module is used to control the N first bridge arm circuits 1211 to alternately output full voltage and zero voltage, and the N second bridge arm circuits 1221 to alternately output full voltage and zero voltage under the action of the high-frequency driving signal output by the control module.

[0042] In one embodiment, if Figure 2 As shown, the DC interface 110 of this embodiment also includes a DC capacitor Cdc, a first end of the DC capacitor Cdc is connected to the first end of the DC interface 110, and a second end of the DC capacitor Cdc is connected to the second end of the DC interface 110, which mainly filters and stabilizes the DC voltage input or output of the DC interface.

[0043] It should be noted that: at the same time, the number of circuits outputting full voltage in the N first bridge arm circuits 1211 may be 0, may be N, or may be any number between 0 and N. The specific number can be adjusted according to actual application requirements so that the maximum value of the output AC power can be equal to the input DC power, thereby improving the utilization rate of the DC voltage and improving the inverter efficiency.

[0044] In summary, when the industrial frequency upper bridge arm 131 is turned on, the control module 150 drives the N first bridge arm circuits 1211 of the high-frequency upper bridge arm 121 to alternately output full voltage and zero voltage, and when the industrial frequency lower bridge arm 132 is turned on, drives the N second bridge arm circuits 1221 of the high-frequency lower bridge arm 122 to alternately output full voltage and zero voltage, and the obtained AC voltage is the sum of the full voltages output by the N first bridge arm circuits 1211 or the N second bridge arm circuits 1221; conversely, the obtained DC voltage is also the sum of the full voltages output by the N first bridge arm circuits 1211 or the N second bridge arm circuits 1221, thereby realizing the mutual conversion between DC and AC; therefore, compared with at least two voltage conversions in the related art, the present application can realize the mutual conversion between DC and AC through only one voltage conversion, thereby improving the voltage conversion efficiency while reducing the size and cost of the converter.

[0045] In one embodiment, if Figure 2 As shown, each first bridge arm circuit 1211 includes control terminals a1 and a2, a first connection terminal b1 and a second connection terminal b2, the first connection terminal of the first first bridge arm circuit 1211 is connected to the first terminal of the DC interface 110, the first connection terminal of the nth first bridge arm circuit 1211 is connected to the second connection terminal of the n-1th first bridge arm circuit 1211, and the second connection terminal of the Nth first bridge arm circuit 1211 is connected to the first terminal of the AC interface 140. In other words, each first bridge arm circuit 1211 includes two different control terminals, and both of the two control terminals are connected to the control module 150, and the first connection terminal of the next first bridge arm circuit 1211 is connected to the second connection terminal of the previous first bridge arm circuit 1211, thereby realizing the cascade of N first bridge arm circuits 1211.

[0046] Similarly, each second bridge arm circuit 1221 includes control terminals c1 and c2, a first connection terminal d1, and a second connection terminal d2. The first connection terminal of the first second bridge arm circuit 1221 is connected to the first terminal of the AC interface 140, the first connection terminal of the nth second bridge arm circuit 1221 is connected to the second connection terminal of the n-1th second bridge arm circuit 1221, and the second connection terminal of the Nth second bridge arm circuit 1221 is connected to the second terminal of the DC interface 110. In other words, each second bridge arm circuit 1221 includes two different control terminals, and both control terminals are connected to the control module 150. The first connection terminal of the next second bridge arm circuit 1221 is connected to the second connection terminals of the previous two first bridge arm circuits 1211, thereby realizing the cascade of N second bridge arm circuits 1221.

[0047] In this embodiment, n is a variable, and its value range is an integer in [1, ..., N]; N is a constant, and is an integer greater than or equal to 2.

[0048] It should be noted that the circuit structures of the first bridge arm circuit 1211 and the second bridge arm circuit 1221 may be the same or different; for the convenience of control, this embodiment sets the first bridge arm circuit 1211 and the second bridge arm circuit 1221 to have the same circuit structure; in addition, the first bridge arm circuit 1211 and the second bridge arm circuit 1221 may be half-bridge circuits or full-bridge circuits.

[0049] In this embodiment, a half-bridge circuit is taken as an example. Figure 2 As shown: each first bridge arm circuit 1211 and each second bridge arm circuit 1221 includes: a capacitor Cp, a first transistor Q1 and a second transistor Q2; the control end of the first transistor Q1 is connected to the control module 150, the first end of the first transistor Q1 is connected to the first end of the capacitor Cp, and the second end of the first transistor Q1 serves as the first connection end of the first bridge arm circuit 1211 and / or the second bridge arm circuit 1221; the control end of the second transistor Q2 is connected to the control module 150, the first end of the second transistor Q2 is connected to the second end of the first transistor Q1, the second end of the second transistor Q2 is connected to the second end of the capacitor Cp, and the second end of the second transistor Q2 serves as the second connection end of the first bridge arm circuit 1211 and / or the second bridge arm circuit 1221.

[0050] In one embodiment, the first end of the capacitor Cp is also connected to the positive terminal of the energy storage battery, and the second end of the capacitor Cp is also connected to the negative terminal of the energy storage battery.

[0051] It should be noted that Sp11 and Sp12 are driving signals for the control terminals of the first transistor Q1 and the second transistor Q2 in the first bridge arm circuit 1211, respectively. Cp is a DC capacitor of the half-bridge circuit, which can be suspended, directly connected to the energy storage battery, or connected via a DC-DC converter. In other words: Figure 2 As shown, the first end and the second end of the capacitor Cp are respectively connected to the first end of the first transistor Q1 and the second end of the second transistor Q2. This connection method is used as a suspended setting of the DC capacitor Cp. At this time, the DC voltage of the bidirectional converter 100 comes from the input through the DC interface 110.

[0052] In addition, in addition to the two ends of the capacitor Cp being respectively connected to the first transistor Q1 and the second transistor Q2, an energy storage battery or a DC-DC converter can also be externally connected; in this case, the DC voltage of the bidirectional converter 100 comes from the input of the energy storage battery or the DC-DC converter; on this basis, the present embodiment can also realize charging of the energy storage battery through the DC interface 110 or the AC interface 140, thereby improving the application scenario of the bidirectional converter 100.

[0053] Under ideal conditions, the capacitor Cp voltage of each bridge arm circuit is equal, that is: Vp1=Vp2=…=VpN=Vdc / N, Vn1=Vn2=…=VnN=Vdc / N, that is, the DC bus voltage Vdc is equal to the sum of the capacitor Cp voltages of the N bridge arm circuits of the high-frequency upper bridge arm 121 or the high-frequency lower bridge arm 122.

[0054] In one embodiment, the power frequency upper bridge arm 131 includes: a third transistor Q3, the control end of the third transistor Q3 is connected to the control module 150, the first end of the third transistor Q3 serves as the first end of the power frequency upper bridge arm 131, and the second end of the third transistor Q3 serves as the second end of the power frequency upper bridge arm 131.

[0055] In one embodiment, the power frequency lower bridge arm 132 includes: a fourth transistor Q4, the control end of the fourth transistor Q4 is connected to the control module 150, the first end of the fourth transistor Q4 serves as the first end of the power frequency lower bridge arm 132, and the second end of the fourth transistor Q4 serves as the second end of the power frequency lower bridge arm 132.

[0056] It should be noted that, in this embodiment, the control module 150 controls the alternating conduction of the third transistor Q3 and the fourth transistor Q4, so that the second end of the AC interface 140 is alternately connected to the high-frequency upper bridge arm 121 and the high-frequency lower bridge arm 122, thereby achieving the inversion of the output voltage and obtaining an AC voltage.

[0057] In one embodiment, the control module 150 is configured to: generate a control signal for controlling the alternating conduction of the industrial frequency upper bridge arm 131 and the industrial frequency lower bridge arm 132 according to the modulation signal; compare the absolute value signal of the modulation signal with the carrier signal, and generate a drive signal for controlling the first first bridge arm circuit 1211 and the first second bridge arm circuit 1221 according to the comparison result; compare the absolute value signal of the modulation signal with the delay signal of the carrier signal, and generate a drive signal for controlling the i+1th first bridge arm circuit 1211 and the i+1th second bridge arm circuit 1221 according to the comparison result; wherein, i=[1,…,N-1].

[0058] It should be noted that the control module 150 can be a single chip microcomputer, MCU or FPGA, and the generation of control signals and drive signals is achieved through a software control method.

[0059] In this embodiment, a control signal for controlling the alternating conduction of the industrial frequency upper bridge arm 131 and the industrial frequency lower bridge arm 132 is generated according to the modulation signal. Specifically, the control signal for controlling the industrial frequency upper bridge arm 131 is generated in the negative half cycle of the modulation signal, and the control signal for controlling the industrial frequency lower bridge arm 132 is generated in the positive half cycle of the modulation signal.

[0060] In this embodiment, the absolute value signal of the modulated signal is compared with the carrier signal, and a drive signal for controlling the first bridge arm circuit 1211 and the first second bridge arm circuit 1221 is generated according to the comparison result. Specifically, when the absolute value signal is greater than the carrier signal, a high-frequency drive signal for the first bridge arm circuit 1211 is generated; when the absolute value signal is less than the carrier signal, a high-frequency drive signal for the first second bridge arm circuit 1221 is generated.

[0061] In this embodiment, the absolute value signal of the modulation signal and the delay signal of the carrier signal are compared, and a drive signal for controlling the i+1th first bridge arm circuit 1211 and the i+1th second bridge arm circuit 1221 is generated according to the comparison result. Specifically, when the absolute value signal is greater than the delay signal, a high-frequency drive signal is generated for the i+1th first bridge arm circuit 1211 or the i+1th second bridge arm circuit 1221, and the high-frequency drive signal is valid when and only when the corresponding industrial frequency bridge arm is turned on.

[0062] Figure 3 FIG. 1 is a schematic diagram of a control module provided in an embodiment of the present application; Figure 3As shown, the control module 150 includes: a first comparison unit 151 and a first inverter U1; the first input end of the first comparison unit 151 is connected to the threshold output end 210, the second input end of the first comparison unit 151 is connected to the modulation wave output end 220, and the output end of the first comparison unit 151 is connected to the control end of the power frequency lower bridge arm 132; the first inverter U1, the input end of the first inverter U1 is connected to the output end of the first comparison unit 151, and the output end of the first inverter U1 is connected to the control end of the power frequency upper bridge arm 131.

[0063] Optionally, the first comparison unit 151 is used to compare the modulation signal output by the modulation wave output terminal 220 with the threshold signal output by the threshold output terminal 210; the first inverter U1 is used to invert the signal output by the first comparison unit 151; wherein the modulation signal can be a sine wave signal or a square wave signal.

[0064] Specifically, the threshold output terminal 210 is used to output a threshold signal, and any threshold value can be set according to the actual scenario. In this embodiment, the threshold value is equal to 0 as an example; the modulation wave output terminal 220 is used to output a sinusoidal wave modulation signal or a square wave modulation signal, and can be a sinusoidal wave generator or a square wave generator; in this embodiment, the modulation signal is a sinusoidal wave as an example. When the sinusoidal wave signal output by the modulation wave output terminal 220 is greater than 0, the first comparison unit 151 outputs a high level to control the fourth transistor Q4 to be turned on, and at the same time, the high level output by the first comparison unit 151 is outputted as a low level after passing through the first inverter U1, and the third transistor Q3 is turned off; conversely, when the sinusoidal wave signal output by the modulation wave output terminal 220 is less than 0, the first comparison unit 151 outputs a low level to control the fourth transistor Q4 to be turned off, and at the same time, the low level output by the first comparison unit 151 is outputted as a high level after passing through the first inverter U1, and the third transistor Q3 is turned on.

[0065] Therefore, in this embodiment, the unit module composed of the first comparison unit 151 and the first inverter U1 can obtain a driving signal for controlling the alternating conduction of the power frequency upper bridge arm 131 and the power frequency lower bridge arm 132 .

[0066] In another embodiment, if Figure 3As shown, the control module 150 also includes: an absolute value unit 152, a second comparison unit 153 and a first gating unit 154; the input end of the absolute value unit 152 is connected to the modulation wave output end 220, and is used to take the absolute value of the modulation signal output by the modulation wave output end 220; the first input end of the second comparison unit 153 is connected to the output end of the absolute value unit 152, and the second input end of the second comparison unit 153 is connected to the carrier output end 230, and is used to compare the output waveform of the absolute value unit 152 with the output waveform of the carrier output end 230; the input end of the first gating unit 154 is connected to the output end of the second comparison unit 153, and the output end of the first gating unit 154 is respectively connected to the control ends of the first first bridge arm circuit 1211 and the first second bridge arm circuit 1221, and is used to output multiple drive signals under the action of the output signal of the second comparison unit 153.

[0067] It should be noted that, in this embodiment, the absolute value unit 152 performs an absolute value operation on the sine wave output from the modulation wave output terminal 220 to obtain a pre-processed wave, that is, a duty cycle (similar to a steamed bun wave) of the DC-AC bidirectional converter 100; further, the pre-processed wave is compared with the triangular carrier input to the second comparison unit 153 output from the carrier output terminal 230 to obtain a first selection signal; for example, when the pre-processed wave is greater than the triangular wave, the second comparison unit 153 outputs a high level, and when the pre-processed wave is less than the triangular wave, the second comparison unit 153 outputs a low level; vice versa; wherein the first selection signal is a high level signal or a low level signal; after the first selection signal passes through the first selection unit 154, the high-frequency drive signals Sp11 and Sp12 of the first first bridge arm circuit 1211 and the high-frequency drive signals Sn11 and Sn12 of the first second bridge arm circuit 1221 can be obtained.

[0068] Therefore, in this embodiment, the driving signal for driving the first first bridge arm circuit 1211 and the first second bridge arm circuit 1221 can be obtained through the unit module composed of the absolute value unit 152 , the second comparison unit 153 and the first selection unit 154 .

[0069] In another embodiment, if Figure 3As shown, the control module 150 also includes: N-1 delay units 155, N-1 third comparison units 156 and N-1 second selection units 157; the input end of the i-th delay unit 155 is connected to the carrier output end 230, and is used to delay the carrier signal output by the carrier output end 230; the first input end of the i-th third comparison unit 156 is connected to the output end of the absolute value unit 152, and the second input end of the i-th third comparison unit 156 is connected to the output end of the i-th delay unit 155, and is used to compare the output waveform of the i-th delay unit 155 with the output waveform of the absolute value unit 152; the input end of the i-th second selection unit 157 is connected to the output end of the i-th third comparison unit 156, and the output end of the i-th second selection unit 157 is respectively connected to the control ends of the i+1-th first bridge arm circuit 1211 and the i+1-th second bridge arm circuit 1221, and is used to output multiple drive signals under the action of the output signal of the third comparison unit 156.

[0070] It should be noted that, in this embodiment, the delay length of the i-th delay unit 155 is: (Ts / N)×i; wherein Ts represents the carrier period of the carrier signal, N represents the number of the first bridge arm circuit 1211 or the second bridge arm circuit 1221, and i represents the serial number of the delay unit 155; that is to say: the delay length of each delay unit 155 is different, when i=1, the delay length of the first delay unit 155 is: Ts / N; when i=2, the delay length of the second delay unit 155 is: (Ts / N)×2; and so on, when i=N-1, the delay length of the N-1th delay unit 155 is: (Ts / N)×(N-1).

[0071] In this embodiment, the carrier signal output from the carrier output terminal 230 is phase-shifted by the i-th delay unit 155 to obtain the i-th phase-shifted carrier; further, the pre-processed wave and the phase-shifted carrier output by the i-th delay unit 155 are input into the second comparison unit 153 for comparison to obtain the second selection signal; for example, when the pre-processed wave is greater than the phase-shifted carrier, the third comparison unit 156 outputs a high level, and when the pre-processed wave is less than the phase-shifted carrier, the third comparison unit 156 outputs a low level; vice versa; wherein the second selection signal is a high level signal or a low level signal; after the second selection signal passes through the second selection unit 157, the high-frequency drive signal of the i+1th first bridge arm circuit 1211 and the high-frequency drive signal of the i+1th second bridge arm circuit 1221 can be obtained.

[0072] Therefore, this embodiment can obtain a driving signal for driving the i+1th first bridge arm circuit 1211 and the i+1th second bridge arm circuit 1221 through a unit module composed of an absolute value unit 152, an i-th delay unit 155, an i-th third comparison unit 156 and an i-th second selection unit 157.

[0073] Figure 4 FIG. 1 is a schematic diagram of the structure of a gating unit provided in an embodiment of the present application; Figure 4 As shown, the first gating unit 154 and / or the second gating unit 157 include: a first throw switch S1, a second inverter U2, a second throw switch S2 and a third throw switch S3; the control end of the first throw switch S1 is connected to the enable signal output end, and the fixed end of the first throw switch S1 is connected to the output end of the second comparison unit 153 or the third comparison unit 156; the input end of the second inverter U2 is connected to the fixed end of the first throw switch S1; the control end of the second throw switch S2 is connected to the enable signal output end, and the input end of the second inverter U2 is connected to the fixed end of the first throw switch S1; The fixed end is connected to the output end of the second inverter U2; the control end of the third throwing switch S3 is connected to the output end of the first comparing unit 151, the first fixed end of the third throwing switch S3 is connected to the throwing end of the first throwing switch S1, the second fixed end of the third throwing switch S3 is connected to the throwing end of the second throwing switch S2, the first throwing end and the second throwing end of the third throwing switch S3 are connected to the control end of the first bridge arm circuit 1211, and the third throwing end and the fourth throwing end of the third throwing switch S3 are connected to the control end of the second bridge arm circuit 1221.

[0074] It should be noted that the gating unit in this embodiment can be the first gating unit 154 or the second gating unit 157. The gating unit includes a gating signal terminal, an enable signal terminal and a drive signal terminal. The gating signal terminal is connected to the output terminal of the first comparison unit 151, so that the signal output by the first comparison unit 151 controls the throwing of the third throw switch S3; the enable signal terminal is connected to the external enable signal output terminal, so that the enable signal output by the external enable signal output terminal controls the throwing of the first throw switch S1 and the second throw switch S2. Figure 4 In the figure, g1 represents the first fixed end of the third throwing switch S3, g2 represents the second fixed end of the third throwing switch S3, z11 represents the first throwing end of the third throwing switch S3, z21 represents the second throwing end of the third throwing switch S3, z12 represents the third throwing end of the third throwing switch S3, and z22 represents the fourth throwing end of the third throwing switch S3.

[0075] To illustrate: Taking the first selection unit as an example, the specific working principle is: its input signals include the selection signal A, the drive signal X, and the enable signal EN, and the output signals include four drive signals Sp11, Sp12, Sn11, and Sn12. When the enable signal EN is high level 1 and the selection signal A is low level 0, Sp11 and Sp12 are respectively the complementary signals of X and X, and Sn11 and Sn12 are both low level 0; when the enable signal EN is high level 1 and the selection signal A is high level 1, Sp11 and Sp12 are both low level 0, and Sn11 and Sn12 are respectively the complementary signals of X and X; when the enable signal EN is low level 0, the four outputs Sp11, Sp12, Sn11, and Sn12 are all low level 0.

[0076] In one embodiment, if Figure 2 As shown, assuming that in the positive half cycle of the AC modulation wave, the high level of the industrial frequency lower bridge arm is turned on, and the low level of the working upper bridge arm is turned off at this time, the corresponding N sub-modules of the high frequency lower bridge arm are put into use, and the voltage Vp of the industrial frequency lower bridge arm is 0V. From KVL, it can be obtained that Vlower=Vao+Vp (Vlower is the output voltage of the high frequency lower bridge arm), that is, Vao = Vlower, the AC output voltage Vao is equal to the output voltage Vlower of the high frequency lower bridge arm, Vlower is equal to (Vdc / N)×Nlow, Nlow is the number of sub-modules of the high frequency lower bridge arm that output the full voltage (0≤Nlow≤N), then the output voltage Vlower of the high frequency lower bridge arm can output N+1 levels (including a zero level and a full level Vdc).

[0077] Similarly, assuming that in the negative half cycle of the AC modulation wave, the high level of the industrial frequency upper bridge arm is turned on, and the low level of the working lower bridge arm is turned off, the corresponding N bridge arm circuits of the high frequency upper bridge arm are put into operation, and the voltage of the industrial frequency upper bridge arm Vn=0V. From KVL, it can be obtained that Vupper=Vn-Vao (Vupper is the output voltage of the high frequency upper bridge arm), that is, Vao = -Vupper, the AC output voltage Vao is equal to the opposite of the output voltage Vupper of the high frequency upper bridge arm, Vupper is equal to (Vdc / N)×Nup, Nup is the number of sub-modules of the high frequency upper bridge arm outputting the full voltage (0≤Nup≤N), then the output voltage Vupper of the high frequency upper bridge arm can output N+1 levels (including a zero level and a full level Vdc).

[0078] In summary, in a complete cycle of an AC modulation wave, the AC output voltage Vao can include N positive levels, N negative levels and a zero level, totaling 2N+1 levels. The larger the number of cascaded submodules N, the closer the AC output voltage Vao is to a sine wave, and its equivalent carrier frequency is N×fs (fs is the reference carrier frequency). Its harmonic spectrum is mainly distributed near N×fs and its integer multiples, that is, the more submodules N, the further away the harmonic spectrum of the AC output voltage Vao is from the fundamental frequency, so the cutoff frequency of the AC filter is higher. The higher the cutoff frequency, the smaller the inductance L of the AC filter, that is, the smaller the volume.

[0079] Here, taking N=2 as an example, the specific working principle and modulation process of the bidirectional converter are described in detail; Figure 5 This is the circuit diagram of the bidirectional converter when N=2. Figure 6 This is the structural diagram of the control module when N=2. Figure 7 Schematic diagram of the modulation waveform.

[0080] like Figure 5 As shown, the upper arm of the high-frequency bridge is composed of two identical bridge arm circuits in cascade, the two transistors of the first bridge arm circuit are driven by Sp11 and Sp12 respectively, the capacitor Cp1 can be directly connected to the energy storage battery, can be connected through a DC-DC converter, or can be suspended, the two transistors of the second bridge arm circuit are driven by Sp21 and Sp22 respectively, and the size and interface form of the capacitor Cp2 are consistent with that of the capacitor Cp1; similarly, the lower arm of the high-frequency bridge is also composed of two identical bridge arm circuits in cascade, the two transistors of the first bridge arm circuit are driven by Sn11 and Sn12 respectively, the size and interface form of the capacitor Cn1 are consistent with that of the capacitor Cp1, the two transistors of the second bridge arm circuit are driven by Sn21 and Sn22 respectively, and the size and interface form of the capacitor Cn2 are consistent with that of the capacitor Cp1. In addition, the driving signal of the upper arm of the industrial frequency bridge is Sn, and the driving signal of the lower arm of the industrial frequency bridge is Sp.

[0081] The two bridge arm circuits of the high-frequency bridge upper arm and the high-frequency bridge lower arm are driven by the high-frequency signal obtained by comparing the same modulation wave (duty cycle of the DC-AC converter) with two carriers. The phase shift time of the second carrier is Ts / 2, that is, the carrier phase of the second bridge arm circuit lags the carrier of the first bridge arm circuit by 180°. If the EPWM module of the TI C2000 series is used, the carrier with a 180° phase shift can be realized by the A and B channels of an EPWM module, which can save the peripheral resources of the MCU. If N=8, the carrier of the fifth bridge arm circuit and the first bridge arm circuit has a 180° phase shift, the carrier of the sixth bridge arm circuit and the second bridge arm circuit has a 180° phase shift, the carrier of the seventh bridge arm circuit and the third bridge arm circuit has a 180° phase shift, and the carrier of the eighth bridge arm circuit and the fourth bridge arm circuit has a 180° phase shift. That is, in the case of N=8, only four EPWM modules can be used to realize eight drives, which greatly saves resources.

[0082] In addition, the two bridge arm circuits of the upper bridge arm of the high-frequency bridge are in a locked state in the positive half cycle of the modulation wave, that is, the four drive signals Sp11, Sp12, Sp21, and Sp22 are all 0, and the two bridge arm circuits of the lower bridge arm of the high-frequency bridge are in a locked state in the negative half cycle of the modulation wave, that is, the four drive signals Sn11, Sn12, Sn21, and Sn22 are all 0; the upper bridge arm and the lower bridge arm of the power frequency bridge are alternately turned on according to the power frequency period of the modulation wave, Sp is turned on at a high level in the positive half cycle, and Sn is turned on at a high level in the negative half cycle.

[0083] like Figure 6 As shown, 220 is the output terminal of the sinusoidal modulation signal of the DC-AC converter, 230 is the output terminal of the reference isosceles triangle carrier signal (i.e., the carrier signal of the first bridge arm circuit), 154 is the first selection unit driven by the switch, whose input signal includes the selection signal A, the drive signal X, and the enable signal EN, and the output signal includes four drive signals Sp11, Sp12, Sn11, and Sn12. When the enable signal EN is at a high level 1 and the selection signal A is at a low level 0, Sp11 and Sp12 are respectively the complementary signals of X and X, and Sn11 and Sn12 are both at a low level 0; when the enable signal EN is at a high level 1 and the selection signal A is at a high level 1, Sp11 and Sp12 are both at a low level 0, and Sn11 and Sn12 are respectively the complementary signals of X and X. When the enable signal EN is at low level 0, the four outputs Sp11, Sp12, Sn11, and Sn12 are all at low level 0; 155 is a delay unit, the delay time is Ts / 2, Ts is the carrier period of the reference carrier, that is, the reference carrier 11 is delayed by Ts / 2 (that is, 180° carrier phase shift) and then compared with the duty cycle to output a high-frequency drive signal for the second bridge arm circuit; 157 is the second selection unit driven by the switch.

[0084] Figure 6The specific working process is: when the modulation wave is greater than 0, Sp is turned on at a high level and Sn is turned off at a low level; conversely, when the modulation wave is less than or equal to 0, Sp is turned off at a low level and Sn is turned on at a high level. That is, Sp is only turned on at a high level in the positive half cycle of the modulation wave, and Sn is only turned on at a high level in the negative half cycle of the modulation wave.

[0085] By performing an absolute value operation on the modulated wave, the duty cycle of the DC-AC converter (similar to a steamed bun wave) can be obtained. Furthermore, by comparing the duty cycle with the reference carrier, the high-frequency drive signal of the first bridge arm circuit of the upper and lower bridge arms of the high-frequency bridge can be obtained. Furthermore, by driving the selection unit through the switch, the high-frequency drive signal Sp11, Sp12 of the first bridge arm circuit of the upper bridge arm of the high-frequency bridge and the high-frequency drive signal Sn11, Sn12 of the first bridge arm circuit of the lower bridge arm of the high-frequency bridge can be obtained.

[0086] Similarly, the high-frequency driving signal of the second bridge arm circuit of the upper and lower bridge arms of the high-frequency bridge is obtained by comparing the second carrier obtained by shifting the reference carrier phase by Ts / 2 with the duty cycle of the DC-AC converter; further, through the second selection unit, the high-frequency driving signals Sp21 and Sp22 of the second bridge arm circuit of the upper bridge arm of the high-frequency bridge and the high-frequency driving signals Sn21 and Sn22 of the second bridge arm circuit of the lower bridge arm of the high-frequency bridge can be obtained.

[0087] like Figure 7 As shown, the carrier C1 of the first bridge arm circuit and the carrier C2 of the second bridge arm circuit are phase-shifted by 180°, and compared with the duty cycle Duty (similar to a steamed bun wave) of the DC-AC converter to obtain a high-frequency driving signal, Sp and Sn are alternately turned on with the industrial frequency cycle, Sp is turned on in the positive half cycle of the modulation wave, Sn is turned on in the negative half cycle of the modulation wave, Sn11 and Sn12 are turned on with high frequency complementation in the positive half cycle, Sn21 and Sn22 are also turned on with high frequency complementation in the positive half cycle, Sn11, Sn12, Sn21, and Sn22 are all turned off in the negative half axis, Sp11 and Sp12 are turned on with high frequency complementation in the negative half cycle, Sp21 and Sp22 are also turned on with high frequency complementation in the negative half cycle, Sp11, Sp12, Sp21, and Sp22 are all turned off in the positive half axis. The normalized waveform (Vao / Vdc) of the AC output Vao of the DC-AC converter pulsates in the form of five levels of 0, ±0.5, and ±1.

[0088] In a second aspect, the present application provides a bidirectional converter modulation method, which specifically includes the following embodiments:

[0089] Figure 8 FIG. 1 is a flow chart of a bidirectional converter modulation method provided in an embodiment of the present application; Figure 8 As shown, the modulation method specifically includes the following steps:

[0090] Step S100, obtaining a target number of first bridge arm circuits in the high-frequency upper bridge arm.

[0091] It should be noted that since the number of first bridge arm circuits in the high-frequency upper bridge arm of the bidirectional converter is the same as the number of second bridge arm circuits in the high-frequency lower bridge arm, obtaining the target number of first bridge arm circuits in the high-frequency upper bridge arm is equivalent to obtaining the number of second bridge arm circuits in the high-frequency lower bridge arm.

[0092] Step S200: Calculate the delay time of each first bridge arm circuit and each second bridge arm circuit according to the target quantity.

[0093] In this embodiment, the delay duration of the nth first bridge arm circuit and the nth second bridge arm circuit is: (Ts / N)×(n-1), Ts represents the carrier period, N represents the target number, n=[1,…,N]; when n=1, it means that the delay duration of the first bridge arm circuit is 0.

[0094] Step S300: Generate a control signal for controlling the alternating conduction of the power frequency upper bridge arm and the power frequency lower bridge arm according to the modulation signal.

[0095] Step S400: phase-shift the carrier signal according to the delay time length of each first bridge arm circuit and each second bridge arm circuit to generate a drive signal corresponding to each first bridge arm circuit and each second bridge arm circuit.

[0096] In this embodiment, the specific process of generating the control signal and the driving signal in step S300 and step S400 is the same as the principle of the above embodiment, and will not be repeated here.

[0097] Therefore, through the bidirectional converter modulation method provided in this embodiment, the bidirectional converter can achieve mutual conversion between direct current and alternating current through only one voltage conversion, thereby improving the voltage conversion efficiency while reducing the size and cost of the converter.

[0098] In addition, the terms "first", "second", "third", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third" may explicitly or implicitly include one or more of the feature. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0099] In the description of this specification, the description with reference to the terms "some embodiments", "exemplarily", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0100] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application. Therefore, any changes or modifications made in accordance with the claims and description of the present application should fall within the scope of the patent of this application.

Claims

1. A bidirectional converter, characterized in that: The bidirectional converter comprises: DC interface; A high-frequency module, comprising a high-frequency upper bridge arm and a high-frequency lower bridge arm connected in series, wherein the high-frequency upper bridge arm comprises N cascaded first bridge arm circuits; the high-frequency lower bridge arm comprises N cascaded second bridge arm circuits; N is an integer greater than or equal to 2; the first end of the high-frequency upper bridge arm is connected to the first end of the DC interface, and the second end of the high-frequency lower bridge arm is connected to the second end of the DC interface; The power frequency module comprises a power frequency upper bridge arm and a power frequency lower bridge arm connected in series, wherein a first end of the power frequency upper bridge arm is connected to a first end of the DC interface, and a second end of the power frequency lower bridge arm is connected to a second end of the DC interface; An AC interface, wherein a first end of the AC interface is respectively connected to a second end of the high-frequency upper bridge arm and a first end of the high-frequency lower bridge arm, and a second end of the AC interface is respectively connected to a second end of the power frequency upper bridge arm and a first end of the power frequency lower bridge arm; A control module, wherein the control module is connected to the control ends of the high-frequency module and the industrial frequency module respectively, and is used to control the industrial frequency upper bridge arm and the industrial frequency lower bridge arm in the industrial frequency module to be alternately turned on, and when the industrial frequency upper bridge arm is turned on, drive the N first bridge arm circuits of the high-frequency module to alternately output full voltage and zero voltage, and when the industrial frequency lower bridge arm is turned on, drive the N second bridge arm circuits of the high-frequency module to alternately output full voltage and zero voltage.

2. The bidirectional converter according to claim 1, characterized in that: Each first bridge arm circuit includes a control end, a first connection end, and a second connection end. The first connection end of the first first bridge arm circuit is connected to the first end of the DC interface, the first connection end of the nth first bridge arm circuit is connected to the second connection end of the n-1th first bridge arm circuit, and the second connection end of the Nth first bridge arm circuit is connected to the first end of the AC interface; Or / and, each second bridge arm circuit includes a control end, a first connection end, and a second connection end, the first connection end of the first second bridge arm circuit is connected to the first end of the AC interface, the first connection end of the nth second bridge arm circuit is connected to the second connection end of the n-1th second bridge arm circuit, and the second connection end of the Nth second bridge arm circuit is connected to the second end of the DC interface; Where n=[1,…,N].

3. The bidirectional converter according to claim 2, characterized in that: The first bridge arm circuit and / or the second bridge arm circuit comprises: capacitance; a first transistor, wherein a control end of the first transistor is connected to the control module, a first end of the first transistor is connected to a first end of the capacitor, and a second end of the first transistor serves as a first connection end of the first bridge arm circuit and / or the second bridge arm circuit; a second transistor, wherein the control end of the second transistor is connected to the control module, the first end of the second transistor is connected to the second end of the first transistor, the second end of the second transistor is connected to the second end of the capacitor, and the second end of the second transistor is used as the second connection end of the first bridge arm circuit and / or the second bridge arm circuit.

4. The bidirectional converter according to claim 1, characterized in that: The power frequency upper bridge arm comprises: a third transistor, a control end of the third transistor is connected to the control module, a first end of the third transistor serves as the first end of the power frequency upper bridge arm, and a second end of the third transistor serves as the second end of the power frequency upper bridge arm; Or / and, the industrial frequency lower bridge arm includes: a fourth transistor, the control end of the fourth transistor is connected to the control module, the first end of the fourth transistor serves as the first end of the industrial frequency lower bridge arm, and the second end of the fourth transistor serves as the second end of the industrial frequency lower bridge arm.

5. The bidirectional converter according to any one of claims 1 to 4, characterized in that: The control module is configured to: Generate a control signal for controlling the alternating conduction of the power frequency upper bridge arm and the power frequency lower bridge arm according to the modulation signal; Comparing the absolute value signal of the modulation signal with the carrier signal, and generating a driving signal for controlling the first first bridge arm circuit and the first second bridge arm circuit according to the comparison result; The absolute value signal of the modulation signal and the delay signal of the carrier signal are compared, and a drive signal for controlling the i+1th first bridge arm circuit and the i+1th second bridge arm circuit is generated according to the comparison result; wherein i=[1, ..., N-1].

6. The bidirectional converter according to any one of claims 1 to 4, characterized in that: The control module comprises: a first comparison unit, wherein a first input end of the first comparison unit is connected to a threshold output end, a second input end of the first comparison unit is connected to a modulation wave output end, and an output end of the first comparison unit is connected to a control end of the power frequency lower bridge arm, and is used to compare a modulation signal output from the modulation wave output end with a threshold signal output from the threshold output end; A first inverter, wherein an input end of the first inverter is connected to an output end of the first comparison unit, and an output end of the first inverter is connected to a control end of the power frequency upper bridge arm.

7. The bidirectional converter according to claim 6, characterized in that: The control module also includes: An absolute value unit, the input end of which is connected to the modulation wave output end, and is used to obtain an absolute value of the modulation signal output by the modulation wave output end; a second comparing unit, wherein a first input terminal of the second comparing unit is connected to the output terminal of the absolute value unit, and a second input terminal of the second comparing unit is connected to the carrier output terminal, and is used to compare the output waveform of the absolute value unit with the output waveform of the carrier output terminal; A first gating unit, wherein the input end of the first gating unit is connected to the output end of the second comparing unit, and the output end of the first gating unit is respectively connected to the control ends of the first first bridge arm circuit and the first second bridge arm circuit, for outputting a plurality of driving signals under the action of the output signal of the second comparing unit.

8. The bidirectional converter according to claim 7, characterized in that: The control module also includes: N-1 delay units, the input end of the i-th delay unit is connected to the carrier output end, and is used to delay the carrier signal output from the carrier output end, and the delay time is (Ts / N)×i; Ts represents the carrier period; N-1 third comparison units, a first input end of the i-th third comparison unit is connected to the output end of the absolute value unit, a second input end of the i-th third comparison unit is connected to the output end of the i-th delay unit, and is used to compare the output waveform of the i-th delay unit with the output waveform of the absolute value unit; N-1 second gating units, the input end of the i-th second gating unit is connected to the output end of the i-th third comparing unit, and the output end of the i-th second gating unit is respectively connected to the control ends of the i+1-th first bridge arm circuit and the i+1-th second bridge arm circuit, for outputting a plurality of driving signals under the action of the output signal of the third comparing unit; Where i=[1,…,N-1].

9. The bidirectional converter according to claim 8, characterized in that: The first gating unit and / or the second gating unit include: A first throw switch, wherein a control end of the first throw switch is connected to an enable signal output end, and a fixed end of the first throw switch is connected to an output end of the second comparison unit or the third comparison unit; A second inverter, wherein an input terminal of the second inverter is connected to a fixed terminal of the first throw switch; a second throw switch, wherein a control end of the second throw switch is connected to the enable signal output end, and a fixed end of the second throw switch is connected to the output end of the second inverter; A third throwing switch, wherein the control end of the third throwing switch is connected to the output end of the first comparing unit, the first fixed end of the third throwing switch is connected to the throwing end of the first throwing switch, the second fixed end of the third throwing switch is connected to the throwing end of the second throwing switch, the first throwing end and the second throwing end of the third throwing switch are connected to the control end of the first bridge arm circuit, and the third throwing end and the fourth throwing end of the third throwing switch are connected to the control end of the second bridge arm circuit.

10. A bidirectional converter modulation method, characterized in that: Applied to the bidirectional converter according to any one of claims 1 to 9, the modulation method comprises: Obtaining the target number of the first bridge arm circuit in the high-frequency upper bridge arm; The delay time length of each first bridge arm circuit and each second bridge arm circuit is calculated according to the target number; wherein the delay time length of the nth first bridge arm circuit and the nth second bridge arm circuit is: (Ts / N)×(n-1), Ts represents the carrier cycle, N represents the target number, and n=[1, ..., N]; Generate a control signal for controlling the alternating conduction of the power frequency upper bridge arm and the power frequency lower bridge arm according to the modulation signal; The carrier signal is phase-shifted according to the delay duration of each first bridge arm circuit and each second bridge arm circuit to generate drive signals corresponding to each first bridge arm circuit and each second bridge arm circuit.

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