Alternating current to alternating current conversion circuit and motor device

Abstract

The invention discloses an AC-to-AC conversion circuit and a motor device, the AC-to-AC conversion circuit comprises a voltage source input module and a conversion module, the voltage source input module is connected with the conversion module and is used for providing a capacitor voltage, and the conversion module is used for providing an output voltage for a load based on the capacitor voltage. The voltage source input module comprises two bidirectional switches and an output capacitor, and the bidirectional switches are used for controlling the capacitance voltage output by the output capacitor; the conversion module comprises three phases of bridge arms which are respectively a first phase bridge arm, a second phase bridge arm and a third phase bridge arm, and each phase bridge arm comprises two bidirectional switches which are connected in series; and the voltage source input module and the conversion module are respectively configured to be connected with the control module, so that the control module controls the on and off of all the bidirectional switches, and the voltage transformation and frequency conversion control of the AC-to-AC conversion circuit is realized. According to the AC-to-AC conversion circuit, intermediate links of DC conversion are reduced, and the efficiency of the conversion circuit can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, in particular to an AC-AC conversion circuit and a motor device. BACKGROUND

[0002] With the vigorous development of the power electronics industry, power electronic devices are constantly updated and upgraded, which provides the possibility for the efficiency and power density of the converter circuit to be improved. As a bridge for AC-AC power conversion, single-phase / three-phase AC-AC converters have wide applications in household appliances and industrial production. Traditional single-phase / three-phase AC-AC converters mostly adopt a two-stage structure, and the power needs to be converted through two stages of AC-DC and DC-AC, which has a low efficiency. Therefore, it is of great significance to study the single-phase / three-phase AC-AC converter circuit.

[0003] In addition, due to the limitation of the number and size of the devices in the traditional circuit, the size of the traditional circuit structure is difficult to be further reduced, thereby limiting the improvement of the power density. How to improve the power density and save the space occupied by the converter is a technical problem to be solved. SUMMARY

[0004] The present application provides an AC-AC conversion circuit and a motor device, which aims to solve the above problems.

[0005] To solve the above technical problems, one technical solution adopted by the present application is to provide an AC-AC conversion circuit, which comprises a voltage source input module and a conversion module. The voltage source input module is connected with the conversion module and is used to provide a capacitor voltage. The conversion module is used to provide an output voltage for a load based on the capacitor voltage. The voltage source input module comprises two bidirectional switches and an output capacitor. The bidirectional switches are used to control the size of the capacitor voltage output by the output capacitor. The conversion module comprises three-phase bridge arms, i.e. a first-phase bridge arm, a second-phase bridge arm and a third-phase bridge arm. Each phase bridge arm comprises two series-connected bidirectional switches. The voltage source input module and the conversion module are respectively configured to be connected with a control module, so that the control module controls the conduction and shutdown of all bidirectional switches, thereby realizing the voltage and frequency conversion control of the AC-AC conversion circuit.

[0006] The voltage source input module comprises an AC power source, an inductor, a seventh bidirectional switch, an eighth bidirectional switch and an output capacitor. The first end of the AC power source is connected with the first end of the inductor. The second end of the inductor is respectively connected with the first pass-through end of the seventh bidirectional switch and the first pass-through end of the eighth bidirectional switch. The second pass-through end of the eighth bidirectional switch is connected with the first end of the output capacitor. The second pass-through end of the seventh bidirectional switch and the second end of the output capacitor are connected with the second end of the AC power source. The two ends of the output capacitor are used to provide the capacitor voltage for the conversion module. The seventh bidirectional switch and the eighth bidirectional switch are complementary.

[0007] When the seventh bidirectional switch is in the on state and the eighth bidirectional switch is in the off state, the alternating current power charges the inductor, and the inductor current rises; when the eighth bidirectional switch is in the on state and the seventh bidirectional switch is in the off state, the voltage of the inductor is superimposed with the voltage of the alternating current power to charge the output capacitor, so that the capacitor voltage rises.

[0008] The output voltage includes a first output voltage, a second output voltage and a third output voltage, the first phase bridge arm includes the first bidirectional switch and the second bidirectional switch connected in series, the second phase bridge arm includes the third bidirectional switch and the fourth bidirectional switch connected in series, and the third phase bridge arm includes the fifth bidirectional switch and the sixth bidirectional switch connected in series. The first pass end of the first bidirectional switch, the first pass end of the third bidirectional switch and the first pass end of the fifth bidirectional switch are connected with the second end of the output inductor, and the second pass end of the second bidirectional switch, the second pass end of the fourth bidirectional switch and the second pass end of the sixth bidirectional switch are connected with the second end of the alternating current power supply. The connection between the second pass end of the first bidirectional switch and the first pass end of the second bidirectional switch, the connection between the second pass end of the third bidirectional switch and the first pass end of the fourth bidirectional switch, and the connection between the second pass end of the fifth bidirectional switch and the first pass end of the sixth bidirectional switch are respectively used as the output ends of the first phase bridge arm, the second phase bridge arm and the third phase bridge arm to output the first output voltage, the second output voltage and the third output voltage respectively. At the same time, only one bidirectional switch in each phase of the first phase bridge arm, the second phase bridge arm and the third phase bridge arm is turned on.

[0009] When the first bidirectional switch, the third bidirectional switch and the fifth bidirectional switch are in the on state or the second bidirectional switch, the fourth bidirectional switch and the sixth bidirectional switch are in the on state, the conversion module outputs a zero voltage vector; when the first bidirectional switch, the third bidirectional switch and the sixth bidirectional switch are in the on state, the first bidirectional switch, the fourth bidirectional switch and the fifth bidirectional switch are in the on state, the first bidirectional switch, the fourth bidirectional switch and the sixth bidirectional switch are in the on state, the second bidirectional switch, the third bidirectional switch and the fifth bidirectional switch are in the on state, the second bidirectional switch, the third bidirectional switch and the sixth bidirectional switch are in the on state, or the second bidirectional switch, the fourth bidirectional switch and the fifth bidirectional switch are in the on state, the conversion module outputs a valid voltage vector.

[0010] The input current of the alternating current power supply and the voltage of the alternating current power supply are configured as in-phase sine waves.

[0011] The capacitor voltage of the output capacitor and the voltage of the alternating current power supply are configured as alternating voltages of the same frequency, and the peak value of the capacitor voltage is greater than the voltage of the alternating current power supply.

[0012] The bidirectional switch includes a bidirectional gallium nitride switch, a bidirectional insulated gate bipolar transistor switch or a bidirectional metal oxide semiconductor field effect transistor switch.

[0013] The bidirectional switch can be configured as two unidirectional switches connected in series.

[0014] To solve the above technical problems, the application adopts another technical solution: providing a motor device, which includes the AC-AC conversion circuit and the control module of any one of the above, the control module is connected with the voltage source input module and the conversion module respectively, and is used for controlling the turn-on and turn-off of all bidirectional switches, so that the AC-AC conversion circuit realizes variable voltage and variable frequency control.

[0015] The control module is further used for sampling the input current of the voltage source input module and the load current of the load, and performing closed-loop control on the input current and the load current based on the output demand, to obtain the instantaneous modulation ratio of each phase bridge arm, wherein the instantaneous modulation ratio is used for adjusting the amplitude and frequency of the output voltage of each phase bridge arm, so that the AC-AC conversion circuit realizes variable voltage and variable frequency control.

[0016] The beneficial effects of the application are: different from the prior art, the AC-AC conversion circuit of the application includes a voltage source input module and a conversion module, the voltage source input module is connected with the conversion module, and is used for providing a capacitor voltage, the conversion module is used for providing an output voltage for a load based on the capacitor voltage; the voltage source input module includes two bidirectional switches and an output capacitor, the bidirectional switches are used for controlling the size of the capacitor voltage output by the output capacitor; the conversion module includes three phase bridge arms, namely a first phase bridge arm, a second phase bridge arm and a third phase bridge arm, each phase bridge arm includes two bidirectional switches connected in series; the voltage source input module and the conversion module are respectively configured to be connected with the control module, so that the control module controls the turn-on and turn-off of all bidirectional switches, thereby realizing variable voltage and variable frequency control of the AC-AC conversion circuit. In the above manner, the AC-AC conversion circuit of the application reduces the intermediate link of direct current conversion, effectively improves the efficiency of the converter circuit, and at the same time reduces the dependence of the converter circuit on the capacity of the capacitor and the inductance, thereby reducing the volume of the converter circuit and improving the power density and reliability of the converter circuit. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings are incorporated into the specification and form part of the specification, which show embodiments consistent with the application, and together with the specification, serve to explain the technical solutions of the application.

[0018] Figure 1 is a circuit structure schematic diagram of an embodiment of the AC-AC conversion circuit provided by the application;

[0019] Figure 2 is a vector diagram of an embodiment of the voltage space provided by the present application;

[0020] Figure 3 is a structural diagram of an embodiment of the motor device provided by the present application;

[0021] Figure 4 is an algorithm flow diagram of an embodiment of the control module provided by the present application. DETAILED DESCRIPTION

[0022] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0024] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0025] In this paper, the "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connection", "fixing" and other terms should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanical connection, or it can be electrical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0027] With the vigorous development of the power electronics industry, power electronic devices are constantly updated and upgraded, which provides the possibility for the efficiency and power density of the converter circuit to be improved. As a bridge for AC-AC power conversion, single-phase / three-phase AC-AC converters have a wide range of applications in household appliances and industrial production. Traditional single-phase / three-phase AC-AC converters mostly use a two-stage structure, and the power needs to go through two-stage conversion of AC to DC and DC to AC, which is low in efficiency. Therefore, it is of great significance to study the single-phase / three-phase AC-AC converter circuit.

[0028] In addition, limited by the number and size of the devices in the traditional circuit, the size of the traditional circuit structure is difficult to further reduce, thereby limiting the improvement of the power density. How to improve the power density and save the space occupied by the converter is a technical problem to be solved.

[0029] To solve the above problems, the present application first proposes an AC-AC conversion circuit, please refer to Figure 1 , Figure 1 is a circuit structure schematic diagram of an embodiment of the AC-AC conversion circuit provided by the present application. As Figure 1 shown, the AC-AC conversion circuit 100 of the embodiment includes a voltage source input module 10 and a conversion module 20.

[0030] Among them, the voltage source input module 10 is connected with the conversion module 20, and is used to provide a capacitor voltage u ac , the conversion module 20 is used to provide an output voltage for a load based on the capacitor voltage u ac ; the voltage source input module 10 includes two bidirectional switches and an output capacitor C ac , the bidirectional switch is used to control the size of the capacitor voltage u ac output by the output capacitor C ac ; the conversion module 20 includes three-phase bridge arms, which are a first-phase bridge arm, a second-phase bridge arm and a third-phase bridge arm, each phase bridge arm includes two series-connected bidirectional switches; the voltage source input module 10 and the conversion module 20 are respectively configured to be connected with a control module, so that the control module controls the conduction and turn-off of all bidirectional switches, thereby realizing the voltage and frequency conversion control of the AC-AC conversion circuit 100.

[0031] In the embodiment, the voltage source input module 10 of the embodiment includes two bidirectional switches, which are series-connected and jointly control the size of the capacitor voltage u ac output by the voltage source input module 10 to the outside; the conversion module 20 is directly connected with the voltage source input module 10 and based on the capacitor voltage u acThe AC-to-AC converter 100 provides output voltage to the load. During operation, the control module can sample the signals on the input and output sides of the AC-to-AC converter 100, and perform closed-loop control based on the input and output signals and output requirements to generate corresponding modulation signals. It also generates drive signals based on PWM modulation, hysteresis control, and other methods to control the conduction and cutoff of all bidirectional switches in the voltage source input module 10 and the conversion module 20, thereby enabling the AC-to-AC converter 100 to achieve voltage and frequency conversion.

[0032] In this embodiment, all switches in the voltage source input module 10 and the conversion module 20 are bidirectional switches. The bidirectional switches can conduct positive and negative bidirectional currents when they are on and block bidirectional currents when they are off.

[0033] Unlike existing technologies, the AC-to-AC converter circuit 100 of this application includes a voltage source input module 10 and a conversion module 20. The voltage source input module 10 is connected to the conversion module 20 and is used to provide capacitor voltage u. ac The conversion module 20 is used for conversion based on capacitor voltage u ac Provides output voltage to the load; the voltage source input module 10 includes two bidirectional switches and an output capacitor C. ac A bidirectional switch is used to control the output capacitor C. ac Output capacitor voltage u ac The size of the converter module 20 is as follows: The converter module 20 includes three phase arms, namely the first phase arm, the second phase arm, and the third phase arm. Each phase arm includes two bidirectional switches connected in series. The voltage source input module 10 and the converter module 20 are respectively configured to be connected to the control module, so that the control module controls the on and off of all bidirectional switches, thereby realizing the voltage and frequency conversion control of the AC-to-AC converter circuit 100. Through the above method, the AC-to-AC converter circuit 100 of this application reduces the intermediate links in DC-DC conversion, effectively improving the efficiency of the converter circuit, while reducing the dependence of the converter circuit on capacitor capacity and inductor inductance, thereby reducing the size of the converter circuit and improving the power density and reliability of the converter circuit.

[0034] Optionally, such as Figure 1 As shown, in this embodiment, the voltage source input module 10 includes an AC power supply e in Inductor L, seventh bidirectional switch S7, eighth bidirectional switch S8, and output capacitor C ac AC power e in The first terminal is connected to the first terminal of inductor L. The second terminal of inductor L is connected to the first pass terminal of the seventh bidirectional switch S7 and the first pass terminal of the eighth bidirectional switch S8. The second pass terminal of the eighth bidirectional switch S8 is connected to the output capacitor C. acThe first terminal is connected to the second terminal of the seventh bidirectional switch S7 and the output capacitor C. ac The second terminal is connected to the AC power supply e in The second terminal is connected to the output capacitor C. ac The two ends are used to provide capacitor voltage u to the conversion module 20. ac The seventh bidirectional switch S7 and the eighth bidirectional switch S8 are complementary.

[0035] In this embodiment, the complementarity of the seventh bidirectional switch S7 and the eighth bidirectional switch S8 means that only one of the seventh bidirectional switch S7 and the eighth bidirectional switch S8 is on at any given time. That is, when the seventh bidirectional switch S7 is on, the eighth bidirectional switch S8 is off; when the seventh bidirectional switch S7 is off, the eighth bidirectional switch S8 is on.

[0036] Furthermore, in this embodiment, the voltage source input module 10 can guarantee the capacitor voltage u. ac It cannot undergo sudden changes and maintains voltage stability.

[0037] Optionally, based on the above embodiments, in this embodiment, when the seventh bidirectional switch S7 is in the ON state and the eighth bidirectional switch S8 is in the OFF state, the AC power supply e in When inductor L is charged, its inductor current increases; when the eighth bidirectional switch S8 is in the on state and the seventh bidirectional switch S7 is in the off state, the voltage across inductor L is equal to the voltage across the AC power supply e. in The voltage superposition affects the output capacitor C. ac Charge so that the capacitor voltage u ac rise.

[0038] In this embodiment, when the seventh bidirectional switch S7 is in the ON state and the eighth bidirectional switch S8 is in the OFF state, current flows from the AC power source e. in The current flows out, through inductor L and the seventh bidirectional switch S7, and returns to the AC power source e. in That is, AC power e in The inductor L is charged, causing its inductor current to increase; when the eighth bidirectional switch S8 is in the on state and the seventh bidirectional switch S7 is in the off state, current flows from the AC power source e. in Starting from the eighth bidirectional switch S8 and the output capacitor C, the current flows through... ac Return to and back to AC power e in At this moment, the inductor L and AC power supply e that were charged in the previous moment... in Together they form the output capacitor C ac Charging, output capacitor C ac capacitor voltage u ac The voltage rise enables the AC-to-AC converter circuit 100 to perform a voltage boost function.

[0039] Optionally, as shown in the embodiment, the output voltage includes a first output voltage u Figure 1 U , a second output voltage u V , and a third output voltage u W , the first phase bridge arm includes a first bidirectional switch S1 and a second bidirectional switch S2 connected in series, the second phase bridge arm includes a third bidirectional switch S3 and a fourth bidirectional switch S4 connected in series, the third phase bridge arm includes a fifth bidirectional switch S5 and a sixth bidirectional switch S6 connected in series, the first pass-through end of the first bidirectional switch S1, the first pass-through end of the third bidirectional switch S3, and the first pass-through end of the fifth bidirectional switch S5 are all connected to the second end of the output inductor L, the second pass-through end of the second bidirectional switch S2, the second pass-through end of the fourth bidirectional switch S4, and the second pass-through end of the sixth bidirectional switch S6 are all connected to the second end of the alternating current power source e in , wherein the connection between the second pass-through end of the first bidirectional switch S1 and the first pass-through end of the second bidirectional switch S2, the connection between the second pass-through end of the third bidirectional switch S3 and the first pass-through end of the fourth bidirectional switch S4, and the connection between the second pass-through end of the fifth bidirectional switch S5 and the first pass-through end of the sixth bidirectional switch S6 are respectively the output ends of the first phase bridge arm, the second phase bridge arm, and the third phase bridge arm to output the first output voltage u U , the second output voltage u V , and the third output voltage u W , respectively; at the same time, only one bidirectional switch in each phase of the first phase bridge arm, the second phase bridge arm, and the third phase bridge arm is turned on.

[0040] In the embodiment, the purpose of only one bidirectional switch in each phase of the first phase bridge arm, the second phase bridge arm, and the third phase bridge arm being turned on is to avoid the situation of the output capacitor C ac being short-circuited caused by the bridge arm shoot-through.

[0041] Optionally, in the embodiment, the conversion module 20 outputs a voltage zero vector when the first bidirectional switch S1, the third bidirectional switch S3, and the fifth bidirectional switch S5 are in the on state or the second bidirectional switch S2, the fourth bidirectional switch S4, and the sixth bidirectional switch S6 are in the on state; the conversion module 20 outputs a voltage active vector when the first bidirectional switch S1, the third bidirectional switch S3, and the sixth bidirectional switch S6 are in the on state, the first bidirectional switch S1, the fourth bidirectional switch S4, and the fifth bidirectional switch S5 are in the on state, the first bidirectional switch S1, the fourth bidirectional switch S4, and the sixth bidirectional switch S6 are in the on state, the second bidirectional switch S2, the third bidirectional switch S3, and the fifth bidirectional switch S5 are in the on state, the second bidirectional switch S2, the third bidirectional switch S3, and the sixth bidirectional switch S6 are in the on state, or the second bidirectional switch S2, the fourth bidirectional switch S4, and the fifth bidirectional switch S5 are in the on state.​

[0042] In the embodiment, referring to Figure 2 , Figure 2 is a schematic diagram of an embodiment of the voltage space vector provided by the present application. As shown in Figure 2 , U0 and U7 are voltage zero vectors, and U1-U6 are six voltage effective vectors. That is, in the embodiment, as described above, according to the different on-state of the bidirectional switch, the conversion module 20 can output the six voltage effective vectors U1-U6 and the two voltage zero vectors U0 and U7.

[0043] Alternatively, based on the above embodiment, in the embodiment, the input current i in of the alternating current power supply e in is configured as a positive sine wave in phase with the voltage of the alternating current power supply e in .

[0044] In the embodiment, the input current i in of the alternating current power supply e in is configured as a positive sine wave in phase with the voltage of the alternating current power supply e in , which can ensure high power factor and low current harmonic of the input.

[0045] Alternatively, based on the above embodiment, in the embodiment, the capacitor voltage u ac of the output capacitor C ac is configured as an alternating voltage in the same frequency as the voltage of the alternating current power supply e in , and the peak value of the capacitor voltage u ac is greater than the voltage of the alternating current power supply e in .

[0046] In the embodiment, since the inductor L can store energy when the seventh bidirectional switch S7 is in the on-state, when the eighth bidirectional switch S8 is in the on-state, the inductor L and the alternating current power supply e in supply power to the output capacitor C ac at the same time, and the peak value of the capacitor voltage u ac is greater than the voltage of the alternating current power supply e in .

[0047] Alternatively, based on the above embodiment, in the embodiment, the bidirectional switch includes a bidirectional gallium nitride switch, a bidirectional insulated gate bipolar transistor switch, or a bidirectional metal oxide semiconductor field effect transistor switch.

[0048] In the embodiment, the bidirectional switch is preferably a bidirectional gallium nitride switch. The bidirectional switch is a bidirectional gallium nitride switch, which can improve the switching speed, reduce the switching loss and improve the efficiency. In other embodiments, the bidirectional switch can also be a bidirectional insulated gate bipolar transistor switch or a bidirectional metal oxide semiconductor field effect transistor switch, wherein the bidirectional insulated gate bipolar transistor switch needs to be reversely connected in series.

[0049] Optionally, based on the above embodiment, in the embodiment, the bidirectional switch can be two unidirectional switches connected in series, wherein the drain or source of the two unidirectional switches are connected.

[0050] In the embodiment, the bidirectional switch can also be two unidirectional switches connected in series. If the unidirectional switch is an insulated gate bipolar transistor switch or a metal oxide semiconductor field effect transistor switch, the application needs 16 unidirectional switches. In addition, if the two unidirectional switches are connected in series, the two unidirectional switches need to be connected in back-to-back series, that is, the drain or source of the two unidirectional switches are connected.

[0051] Optionally, please refer to Figure 3 , Figure 3 is a structural schematic diagram of an embodiment of the motor device provided by the application. As shown in Figure 3 , the motor device 200 of the embodiment includes the AC-AC conversion circuit 100 and the control module 110 of any one of the above embodiments.

[0052] The control module 110 is connected with the voltage source input module 10 and the conversion module 20, respectively, and is used to control the conduction and turn-off of all bidirectional switches, so that the AC-AC conversion circuit 100 realizes the variable voltage and variable frequency control.

[0053] That is, as described above, in the embodiment, the control module 110 of the embodiment can realize the control of the output voltage by reasonably combining the switching sequence of the above eight bidirectional switches, so as to achieve the purpose of variable voltage and variable frequency control.

[0054] In other embodiments, the AC-AC conversion circuit 100 of the embodiment can also be applied to other electronic devices that need to be converted to AC, and is not limited to the motor device 200.

[0055] Optionally, based on the above embodiment, in the embodiment, the control module 110 is also used to sample the input current i in of the voltage source input module 10 and the load current of the load, and based on the output demand, the input current i inThe input current and the load current are closed-loop controlled to obtain the instantaneous modulation ratio of each phase bridge arm, wherein the instantaneous modulation ratio is used to adjust the amplitude and frequency of the output voltage of each phase bridge arm, so that the AC-to-AC conversion circuit 100 realizes the variable-voltage and variable-frequency control.

[0056] In the embodiment, the first output voltage u U , the second output voltage u V and the third output voltage u W of the conversion module 20 have the following relationship with the capacitor voltage u ac :

[0057]

[0058] wherein u U represents the first output voltage, u V represents the second output voltage, u W represents the third output voltage, m a , m b and m c respectively represent the instantaneous modulation ratio of each phase bridge arm, and u ac represents the capacitor voltage. Taking a permanent magnet synchronous motor as an example, in the permanent magnet synchronous motor control, the outer loop is the speed loop, and the inner loop is the current loop. The output of the current loop is subjected to coordinate transformation and modulation to obtain m a , m b and m c . In the embodiment, the variable-voltage and variable-frequency control can be achieved by changing the frequency and amplitude of m a , m b and m c .

[0059] Please refer to Figure 4 , Figure 4 which is the algorithm flowchart of an embodiment of the control module. As shown in Figure 4 , the control module 110 can sample the input side to obtain the input current i in of the voltage source input module 10, and sample the output side to obtain the load current of the load. According to the output power, voltage and other requirements, the input current i in and the load current are closed-loop controlled based on the output requirements to generate the corresponding modulation ratio signals as described above. Then, the drive signals are generated by the PWM modulation, hysteresis control and other methods based on the modulation ratio signals, and the drive signals are used to control the conduction and turn-off of the eight bidirectional switches described above, so that the AC-to-AC conversion circuit 100 realizes the variable-voltage and variable-frequency control.

[0060] The above merely describes the embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which is made by using the content of the present application specification and drawings, is also included in the patent protection scope of the present application.

Claims

1. An AC to AC conversion circuit, characterized by comprising: The voltage source input module is connected with the conversion module, and is configured to provide a capacitor voltage; the conversion module is configured to provide an output voltage for a load based on the capacitor voltage. The voltage source input module includes two bidirectional switches and an output capacitor, and the bidirectional switches are configured to control the capacitor voltage output by the output capacitor; the conversion module includes three-phase bridge arms, i.e., a first-phase bridge arm, a second-phase bridge arm, and a third-phase bridge arm, each of which includes two bidirectional switches connected in series; the voltage source input module and the conversion module are respectively configured to be connected with a control module, so that the control module controls the on and off of all the bidirectional switches, thereby realizing the voltage and frequency conversion control of the AC-AC conversion circuit.

2. The AC to AC converter circuit of claim 1, wherein, The voltage source input module includes an AC power source, an inductor, a seventh bidirectional switch, an eighth bidirectional switch, and the output capacitor; a first end of the AC power source is connected with a first end of the inductor; a second end of the inductor is respectively connected with a first path end of the seventh bidirectional switch and a first path end of the eighth bidirectional switch; a second path end of the eighth bidirectional switch is connected with a first end of the output capacitor; a second path end of the seventh bidirectional switch and a second end of the output capacitor are connected with a second end of the AC power source; and two ends of the output capacitor are configured to provide the capacitor voltage for the conversion module. The seventh bidirectional switch and the eighth bidirectional switch are complementary.

3. The AC to AC converter circuit of claim 2, wherein, When the seventh bidirectional switch is in an on state and the eighth bidirectional switch is in an off state, the AC power source charges the inductor, and an inductor current of the inductor rises. When the eighth bidirectional switch is in an on state and the seventh bidirectional switch is in an off state, a voltage of the inductor and a voltage of the AC power source are superimposed, the output capacitor is charged, and the capacitor voltage rises.

4. The AC to AC converter circuit of claim 2, wherein, The output voltage includes a first output voltage, a second output voltage and a third output voltage, the first phase bridge arm includes a first bidirectional switch and a second bidirectional switch connected in series, the second phase bridge arm includes a third bidirectional switch and a fourth bidirectional switch connected in series, the third phase bridge arm includes a fifth bidirectional switch and a sixth bidirectional switch connected in series, the first pass-through end of the first bidirectional switch, the first pass-through end of the third bidirectional switch and the first pass-through end of the fifth bidirectional switch are all connected to the second end of the output inductor, the second pass-through end of the second bidirectional switch, the second pass-through end of the fourth bidirectional switch and the second pass-through end of the sixth bidirectional switch are all connected to the second end of the AC power supply, wherein the connection between the second pass-through end of the first bidirectional switch and the first pass-through end of the second bidirectional switch, the connection between the second pass-through end of the third bidirectional switch and the first pass-through end of the fourth bidirectional switch and the connection between the second pass-through end of the fifth bidirectional switch and the first pass-through end of the sixth bidirectional switch are respectively the output ends of the first phase bridge arm, the second phase bridge arm and the third phase bridge arm to output the first output voltage, the second output voltage and the third output voltage respectively. At the same time, only one bidirectional switch in each phase of the first phase bridge arm, the second phase bridge arm and the third phase bridge arm is turned on.

5. The AC to AC converter circuit of claim 4, wherein, When the first bidirectional switch, the third bidirectional switch and the fifth bidirectional switch are in the on state or the second bidirectional switch, the fourth bidirectional switch and the sixth bidirectional switch are in the on state, the conversion module outputs a voltage zero vector. When the first bidirectional switch, the third bidirectional switch and the sixth bidirectional switch are in the on state, the first bidirectional switch, the fourth bidirectional switch and the fifth bidirectional switch are in the on state, the first bidirectional switch, the fourth bidirectional switch and the sixth bidirectional switch are in the on state, the second bidirectional switch, the third bidirectional switch and the fifth bidirectional switch are in the on state, the second bidirectional switch, the third bidirectional switch and the sixth bidirectional switch are in the on state, or the second bidirectional switch, the fourth bidirectional switch and the fifth bidirectional switch are in the on state, the conversion module outputs a voltage effective vector.

6. The AC to AC converter circuit of claim 2, wherein, The input current of the AC power supply and the voltage of the AC power supply are configured as in-phase sine waves.

7. The AC to AC converter circuit of claim 2, wherein, The capacitor voltage of the output capacitor and the voltage of the AC power supply are configured as AC voltages of the same frequency, wherein the peak value of the capacitor voltage is greater than the voltage of the AC power supply.

8. The AC to AC converter circuit of claim 1, wherein, The bidirectional switch includes a bidirectional gallium nitride switch, a bidirectional insulated gate bipolar transistor switch or a bidirectional metal oxide semiconductor field effect transistor switch.

9. The AC to AC converter circuit of claim 1, wherein, The bidirectional switch can be configured as two unidirectional switches connected in series, wherein the drain or source of the two unidirectional switches are connected when the two unidirectional switches are connected in series.

10. An electric machine arrangement, characterized in that The AC-AC conversion circuit and the control module of any one of claims 1-9 are connected with the voltage source input module and the conversion module respectively, and are used for controlling the on and off of all the bidirectional switches, so that the AC-AC conversion circuit realizes variable voltage and variable frequency control.

11. The electric machine device of claim 10, wherein, The control module is also used for sampling the input current of the voltage source input module and the load current of the load, and performing closed-loop control on the input current and the load current based on output demand, so as to obtain the instantaneous modulation ratio of each phase bridge arm, wherein the instantaneous modulation ratio is used for adjusting the amplitude and frequency of the output voltage of each phase bridge arm, so that the AC-AC conversion circuit realizes variable voltage and variable frequency control.

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