Three-phase first-level energy conversion AC / AC converter and its control method

Abstract

The present invention provides a three-phase single-stage energy conversion AC / AC converter and its control method, which relates to the technical field of converters. The present invention proposes a three-phase single-stage energy conversion AC / AC converter and its control method. This converter realizes AC / AC conversion by adopting single-stage energy conversion, replacing the mainstream AC / DC + DC / AC two-stage architecture, using fewer devices, and achieving high efficiency and low cost. At the same time, this converter can operate in a boost mode or a buck mode. Moreover, this converter has no bus capacitor and will not have the problem of low service life of the bus capacitor.

Description

Technical Field

[0001] The present invention relates to the technical field of converters, and particularly to a three-phase first-level energy conversion AC / AC converter and its control method. Background Art

[0002] During the process of power transmission, the stability of voltage determines the power quality. To ensure the smoothness and diversity of AC / AC conversion, a common solution is to use a back-to-back AC / AC converter. As Figure 1 shown, the front stage is a rectifier circuit that first performs AC / DC conversion, and the rear stage uses an inverter circuit to achieve DC / AC conversion.

[0003] However, the two-stage back-to-back AC / AC converter needs to go through two-level energy conversion of AC / DC - DC / AC. The two-level energy conversion will result in relatively low efficiency. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] Aiming at the deficiencies of the prior art, the present invention provides a three-phase first-level energy conversion AC / AC converter and its control method, which solves the technical problem of low efficiency of the existing two-stage AC / AC converter.

[0006] (II) Technical Solutions

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0008] In the first aspect, the present invention provides a three-phase first-level energy conversion AC / AC converter, which includes a first pair of top switches, a second pair of top switches, a first intermediate inductor, a second intermediate inductor, and three A-phase circuits, B-phase circuits, and C-phase circuits with the same structure;

[0009] Among them, each phase circuit includes two connection ports. The first connection port is connected to the second connection port via an inductor, an intermediate capacitor, and a pair of top switches, and a power line communication capacitor is connected between the first connection port and the second connection port;

[0010] The first end of the first pair of top switches is connected to the common end of the inductor and the intermediate capacitor of the A-phase circuit, and the second end of the first pair of top switches is connected to the common end of the inductor and the intermediate capacitor of the B-phase circuit; the first end of the second pair of top switches is connected to the second end of the first pair of top switches, and the second end of the second pair of top switches is connected to the common end of the inductor and the intermediate capacitor of the C-phase circuit;

[0011] The first end of the first intermediate inductor is connected to the common end of the intermediate capacitor in the A-phase circuit and the anti-parallel switch group, and the second end of the first intermediate inductor is connected to the common end of the intermediate capacitor in the B-phase circuit and the anti-parallel switch group; the first end of the second intermediate inductor is connected to the second end of the first intermediate inductor, and the second end of the second intermediate inductor is connected to the common end of the intermediate capacitor in the C-phase circuit and the anti-parallel switch group;

[0012] By controlling the duty cycle of the five groups of anti-parallel switch groups, the voltage of the input AC power supply is increased or decreased.

[0013] Preferably, a first filter capacitor and a second filter capacitor are further included,

[0014] wherein, the first filter capacitor is connected between the second connection ports of the A-phase circuit and the B-phase circuit;

[0015] The second filter capacitor is connected between the second connection ports of the B-phase circuit and the C-phase circuit.

[0016] Preferably, the first anti-parallel switch group, the second anti-parallel switch group, and the anti-parallel switch groups in each phase circuit each include two IGBTs with their emitters connected.

[0017] Preferably, the first connection ports of each phase circuit are respectively connected to the three-phase power grid, and the second connection ports of each phase circuit are respectively connected to a load common end via a load; or, the second connection ports of each phase circuit are respectively connected to the three-phase power grid, and the first connection ports of each phase circuit are respectively connected to a load common end via a load.

[0018] Preferably, a neutral line is connected between the three-phase power grid common end and the load common end.

[0019] In a second aspect, the present invention provides a control method for a three-phase first-level energy conversion AC / AC converter, which is used to control the three-phase first-level energy conversion AC / AC converter as described in the first aspect. The control method includes:

[0020] Regarding the switches in the first anti-parallel switch group and the second anti-parallel switch group as the first group of switches, with a conduction duty cycle of D; regarding the three groups of anti-parallel switch groups in the A-phase circuit, the B-phase circuit, and the C-phase circuit as the second group of switches, with a conduction duty cycle of 1 - D;

[0021] The voltage of the first connection port of each phase is Vx , x = a , b , c ; the voltage of the second connection port of each phase V1x ; the relationship between the two voltages is: V1x =D / (1 - D)*Vx

[0022] Control the size of the conduction duty cycle D to achieve step-up or step-down.

[0023] Preferably, when the first connection port of each phase is connected to the input voltage, that is Vx is the input voltage, V1x is the output voltage. When D is set to a fixed value greater than 0.5, step-up is achieved; when D is set to a fixed value less than 0.5, step-down is achieved.

[0024] In a third aspect, the present invention provides a three-phase first-level energy conversion AC / AC converter, including a first pair of top switches, a second pair of top switches, a first intermediate inductor, a second intermediate inductor, a third intermediate inductor, and three A-phase circuits, B-phase circuits, and C-phase circuits with the same structure;

[0025] Wherein, each phase circuit includes two connection ports. The first connection port is connected to the second connection port via an inductor, an intermediate capacitor, and a pair of top switches, and a power carrier communication capacitor is connected between the first connection port and the second connection port;

[0026] The first end of the first pair of top switches is connected to the common end of the inductor and the intermediate capacitor of the A-phase circuit, and the second end of the first pair of top switches is connected to the common end of the inductor and the intermediate capacitor of the B-phase circuit; the first end of the second pair of top switches is connected to the second end of the first pair of top switches, and the second end of the second pair of top switches is connected to the common end of the inductor and the intermediate capacitor of the C-phase circuit;

[0027] The first end of the first intermediate inductor is connected to the common end of the intermediate capacitor and the pair of top switches of the A-phase circuit; the first end of the second intermediate inductor is connected to the common end of the intermediate capacitor and the pair of top switches of the B-phase circuit; the first end of the third intermediate inductor is connected to the common end of the intermediate capacitor and the pair of top switches of the C-phase circuit; the second ends of the first intermediate inductor, the second intermediate inductor, and the third intermediate inductor are connected together;

[0028] By controlling the duty cycle of the five pairs of top switches, the voltage of the input AC power supply is increased or decreased.

[0029] In a fourth aspect, the present invention provides a control method for a three-phase first-level energy conversion AC / AC converter, used to control the three-phase first-level energy conversion AC / AC converter as described in the third aspect. The control method includes:

[0030] Regarding the switches in the first pair of top switches and the second pair of top switches as the first group of switches, with a conduction duty cycle of D; regarding the three pairs of top switches in the A-phase circuit, B-phase circuit, and C-phase circuit as the second group of switches, with a conduction duty cycle of 1 - D;

[0031] The voltage of the first connection port of each phase is Vx , x = a , b , c ; The voltage of the second connection port of each phase V1x , and the relationship between the two voltages is: V1x = D / (1 - D) * Vx

[0032] By controlling the size of the conduction duty cycle D, step-up or step-down can be achieved.

[0033] Preferably, when the first connection port of each phase is connected to the input voltage, that is Vx is the input voltage, V1x is the output voltage. When D is set to a fixed value greater than 0.5, step-up is achieved. When D is set to a fixed value less than 0.5, step-down is achieved.

[0034] (III) Beneficial effects

[0035] The present invention provides a three-phase first-level energy conversion AC / AC converter and its control method. Compared with the prior art, it has the following beneficial effects:

[0036] The present invention proposes a three-phase first-level energy conversion AC / AC converter and its control method. This converter uses first-level energy conversion to achieve AC / AC conversion, replacing the mainstream AC / DC + DC / AC two-stage architecture. It uses fewer devices, achieving high efficiency and low cost. At the same time, this converter can operate in step-up mode or step-down mode. And this converter has no bus capacitor, so there will be no problem of low bus capacitor life. Description of the drawings

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 is the circuit diagram of the existing back-to-back AC / AC converter;

[0039] Figure 2 is the circuit diagram of the existing cascaded Buck-Boost converter;

[0040] Figure 3It is the circuit diagram of an existing phase - controllable three - phase Buck - type AC / AC converter;

[0041] Figure 4 It is the architecture diagram of a three - phase single - stage energy - conversion AC / AC converter in Embodiment 1;

[0042] Figure 5 It is Figure 4 One of the circuit diagrams of the shown architecture diagram;

[0043] Figure 6 It is the circuit diagram of a three - phase single - stage energy - conversion AC / AC converter with a filter capacitor in Embodiment 1;

[0044] Figure 7 It is the circuit diagram of a three - phase single - stage energy - conversion AC / AC converter with a filter capacitor and a neutral line in Embodiment 1;

[0045] Figure 8 It is the circuit diagram of a three - phase single - stage energy - conversion AC / AC converter with a neutral line in Embodiment 1;

[0046] Figure 9 It is Figure 8 Schematic diagrams of operating mode 1 and operating mode 3 of the shown circuit diagram;

[0047] Figure 10 It is Figure 8 Schematic diagram of operating mode 2 of the shown circuit diagram;

[0048] Figure 11 It is Figure 8 Schematic diagram of operating mode 4 of the shown circuit diagram;

[0049] Figure 12 It is the circuit diagram of a three - phase single - stage energy - conversion AC / AC converter in Embodiment 2. Detailed implementation manners

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0051] It should be noted that for the convenience of description, the switching IGBT is used as a representative of the controllable (turn-on and turn-off) switching tube in the embodiments of the present invention, but the switching tube in the present invention is not limited to IGBT. Taking IGBT as an example for illustration. The first end of the IGBT refers to the collector, the second end refers to the emitter, and the control end refers to the gate. A drive control signal is applied to the control end of each switching tube in the embodiments of the present invention. For the sake of brevity, it will not be elaborated further later. The power switching tube in the embodiments of the present invention can also be implemented by other controllable switching tube devices other than IGBT, such as MOSFET. At the same time, in the embodiments of the present invention, in order to ensure the normal operation of each switching device, a freewheeling diode needs to be connected in parallel to each switching device. The parallel direction of the freewheeling diode is related to the type of the switching device, and those skilled in the art can set it according to the type of the switching device, which is not limited herein. If not specified, it is default that the switching device includes a freewheeling diode, and this will be pointed out in special cases of this embodiment.

[0052] By providing a three-phase first-level energy conversion AC / AC converter and its control method in the embodiments of the present application, the technical problem of low efficiency of the existing two-level AC / AC converter is solved. The AC / AC conversion is realized by using first-level energy conversion, thus improving the efficiency.

[0053] The technical solutions in the embodiments of the present application for solving the above technical problems are generally as follows:

[0054] The existing AC / AC converters mainly include back-to-back AC / AC converters, cascaded Buck-Boost converters, and phase-controlled three-phase Buck-type AC / AC converters. Among them, the back-to-back AC / AC converter is as Figure 1 shown. The front stage is a rectifier circuit, and the rear stage uses an inverter circuit to realize DC / AC conversion.

[0055] Taking the single-phase two-level cascaded converter as an example, the cascaded Buck-Boost converter is as Figure 2 shown. This circuit is composed of two converters, a Buck type and a Boost type, cascaded. According to the comparison of the input voltage and the output voltage amplitude, it has the functions of boosting, filtering, and bucking at the same time. When the front-stage Buck circuit works and the rear-stage Boost circuit does not work, the circuit works in the Buck mode; when the front-stage Buck circuit does not work and the rear-stage Boost circuit works, the circuit works in the Boost mode; when the switching tubes S1 and S4 are turned on and S2 and S3 are turned off, and the input voltage fluctuates slightly, the circuit works in the filtering mode.

[0056] The phase-controlled three-phase Buck-type AC / AC converter is as Figure 3As shown in the figure, it mainly consists of 3 single-phase Buck AC conversion units and a three-phase output filter. Among them, the filter capacitors are connected in a triangular connection. Analyzing each single phase, it includes four switching tubes. For a three-phase circuit, there are 12 switching tubes, and 2 capacitors and 2 inductors are used in each path. This circuit is composed of 3 single-phase Buck AC units and a three-phase output filter. The filter capacitors are connected in a triangular connection, which cancels out the 3rd harmonic voltages in the 3 single-phase Buck AC units. Subsequently, it ensures that no 3rd harmonic current flows through the output filter inductor, and a sinusoidal output line voltage with controllable phase is obtained at the output end.

[0057] However, as Figure 1 shown, the two-stage back-to-back AC-AC converter needs to undergo two-stage energy conversion, which has low efficiency. At the same time, it uses many devices and has a high cost. As Figure 2 shown, for the cascaded Buck-Boost converter, when it is applied to three phases, it uses many devices and has a high cost. As Figure 3 shown, the phase-controlled three-phase Buck-type AC / AC converter topology can only achieve step-down, and it uses many devices and has a high cost.

[0058] To overcome the above problems, the embodiment of the present invention proposes a three-phase one-stage energy conversion AC / AC converter and its control method. This converter realizes AC / AC conversion through one-stage energy conversion, replacing the mainstream AC / DC + DC / AC two-stage architecture. It uses fewer devices, achieves high efficiency, and low cost. At the same time, this converter can operate in step-up mode or step-down mode. In addition, this converter uses an anti-parallel switch to construct a two-way energy path and can achieve two-way operation.

[0059] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners.

[0060] Embodiment 1:

[0061] This embodiment provides a three-phase one-stage energy conversion AC / AC converter. As Figure 4 shown, this converter includes a first anti-parallel switch group, a second anti-parallel switch group, a first intermediate inductor, a second intermediate inductor, and three A-phase circuits, B-phase circuits, and C-phase circuits with the same structure;

[0062] Among them, each phase circuit includes two connection ports. The first connection port is connected to the second connection port via an inductor, an intermediate capacitor, and an anti-parallel switch group, and a power line communication capacitor is connected between the first connection port and the second connection port;

[0063] The first end of the first pair of top switches is connected to the common end of the inductor and the intermediate capacitor in the A-phase circuit, and the second end of the first pair of top switches is connected to the common end of the inductor and the intermediate capacitor in the B-phase circuit; the first end of the second pair of top switches is connected to the second end of the first pair of top switches, and the second end of the second pair of top switches is connected to the common end of the inductor and the intermediate capacitor in the C-phase circuit;

[0064] The first end of the first intermediate inductor is connected to the common end of the intermediate capacitor and the pair of top switches in the A-phase circuit, and the second end of the first intermediate inductor is connected to the common end of the intermediate capacitor and the pair of top switches in the B-phase circuit; the first end of the second intermediate inductor is connected to the second end of the first intermediate inductor, and the second end of the second intermediate inductor is connected to the common end of the intermediate capacitor and the pair of top switches in the C-phase circuit;

[0065] By controlling the duty cycle of the five pairs of top switches, the voltage of the input AC power supply can be increased or decreased.

[0066] It should be noted that in Figure 4 , the inductors in the A, B, and C phase circuits are La, Lb, and Lc respectively, the intermediate capacitors in the A, B, and C phase circuits are Ca, Cb, and Cc respectively, and the power line communication capacitors in the A, B, and C phase circuits are Ca2, Cb2, and Cc2. The first intermediate inductor is Lab, and the second intermediate inductor is Lbc. Of course, in the specific implementation process, the intermediate inductor, intermediate capacitor, etc. can all be an inductor group, capacitor group, etc. composed of multiple devices. In Figure 4 , a single capacitor, inductor, etc. are taken as examples. At the same time, in the embodiments of the present invention, ABC only represents the serial numbers of the three-phase circuits, and does not correspond one-to-one with the phase sequence of the three-phase power grid circuits.

[0067] It should be noted that in Figure 5 , the first pair of top switches, the second pair of top switches, and the pairs of top switches in the A, B, and C phase circuits all adopt two opposing IGBTs. In the specific implementation process, other forms of switching tubes, such as MOSFETs, can also be used.

[0068] It should be noted that in the embodiments of the present invention, the three-phase first-level energy conversion AC / AC converter can operate bidirectionally, that is, the objects connected to the two connection ports of each phase circuit can be swapped, and both sides can be connected to the three-phase AC power grid or the load (the load can also be replaced with a charging power supply) respectively.

[0069] Such as Figure 6As shown, in the specific implementation process, in order to better filter (the capacitors Ca2, Cb2, and Cc2 in power line carrier communication also have a filtering effect), a first filter capacitor C1 is connected between the second connection ports of the A-phase circuit and the B-phase circuit, and a second filter capacitor C2 is connected between the second connection ports of the B-phase circuit and the C-phase circuit.

[0070] As Figure 7 shown, in the specific implementation process, a neutral line is connected between the common terminal of the three-phase input power supply and the common terminal of the three-phase output, which is applicable to a three-phase four-wire system and provides a current path for zero-sequence current to flow.

[0071] It should be noted that the converter can also be equipped with a neutral line, but there is no connection method for filter capacitors. As Figure 8 shown, the first connection ports of the A, B, and C phase circuits of the converter are connected to the three-phase power grid, and the second connection ports of the A, B, and C phase circuits are respectively connected to a resistive load.

[0072] Next, taking the Figure 8 shown circuit as an example, modal analysis is carried out on the converter. Since the three-phase voltage is periodic, the modes of this topology also have a periodic variation law. Next, the cases where the A and B phase voltages are greater than zero and the C phase grid voltage is less than zero, and the A phase voltage is greater than zero and the B and C phase grid voltages are less than zero will be mainly analyzed (other modes can be obtained by analogy):

[0073] When the A and B phase voltages are greater than zero and the C phase grid voltage is less than zero:

[0074] Operating mode 1: As Figure 9 shown, the switching transistors T1, T2, T3, and T4 form the first group of switches to conduct (the switching transistors T1 and T3 conduct forward, and the anti-parallel diodes of T2 and T4 conduct), and the switching transistors T5, T6, T7, T8, T9, and T10 form the second group of switches to turn off. In this mode, the power supply voltage charges the input inductors La, Lb, and Lc, and the intermediate capacitors Ca, Cb, and Cc charge the output inductors Lab and Lbc through the switches. The current direction of power line carrier communication is related to the phase voltage difference across itself, and the switching mode has no impact, so it will not be elaborated here.

[0075] Operating mode 2: As Figure 10 shown, the switching transistors T1, T2, T3, and T4 form the first group of switches to turn off, and the switching transistors T5, T6, T7, T8, T9, and T10 form the second group of switches to conduct (the switching transistors T5, T7, and T10 conduct forward, and the anti-parallel diodes of T6, T8, and T9 conduct). In this mode, the input inductors La, Lb, and Lc and the output inductors Lab and Lbc discharge through the second group of switching transistors, releasing the inductor energy to the load.

[0076] When the phase A voltage is greater than zero and the grid voltages of phases B and C are less than zero:

[0077] Operating mode 3: The switching transistors T1, T2, T3, and T4 form the first group of switches to conduct (the switching transistors T1 and T3 conduct forward, and the anti-parallel diodes of T2 and T4 conduct), and the switching transistors T5, T6, T7, T8, T9, and T10 form the second group of switches to turn off. In this mode, the power supply voltage charges the input inductors La, Lb, and Lc, and the intermediate capacitors Ca, Cb, and Cc charge the output inductors Lab and Lbc through the switches. It should be noted that the corresponding circuit schematic diagram of this mode is the same as that of operating mode 1, as Figure 1 shown. Figure 9 shown.

[0078] Operating mode 4: As Figure 11 shown, the switching transistors T1, T2, T3, and T4 form the first group of switches to turn off, and the switching transistors T5, T6, T7, T8, T9, and T10 form the second group of switches to conduct (the switching transistors T5, T8, and T10 conduct forward, and the anti-parallel diodes of T6, T7, and T9 conduct). In this mode, the input inductors La, Lb, and Lc and the output inductors Lab and Lbc freewheel through the second group of switching transistors, releasing the inductor energy to the load.

[0079] Embodiment 2:

[0080] This embodiment provides a three-phase first-level energy conversion AC / AC converter, as Figure 12 shown (in Figure 12 , two opposing IGBTs are used for the opposing switch group). The converter includes a first opposing switch group, a second opposing switch group, a first intermediate inductor, a second intermediate inductor, a third intermediate inductor, and three A-phase circuits, B-phase circuits, and C-phase circuits with the same structure;

[0081] Each phase circuit includes two connection ports. The first connection port is connected to the second connection port via an inductor, an intermediate capacitor, and an opposing switch group, and a power line carrier communication capacitor is connected between the first connection port and the second connection port;

[0082] The first end of the first opposing switch group is connected to the common end of the inductor and the intermediate capacitor of the A-phase circuit, and the second end of the first opposing switch group is connected to the common end of the inductor and the intermediate capacitor of the B-phase circuit; the first end of the second opposing switch group is connected to the second end of the first opposing switch group, and the second end of the second opposing switch group is connected to the common end of the inductor and the intermediate capacitor of the C-phase circuit;

[0083] The first end of the first intermediate inductor is connected to the common end of the intermediate capacitor in the A-phase circuit and the antipodal switch group; the first end of the second intermediate inductor is connected to the common end of the intermediate capacitor in the B-phase circuit and the antipodal switch group; the first end of the third intermediate inductor is connected to the common end of the intermediate capacitor in the C-phase circuit and the antipodal switch group; the second ends of the first intermediate inductor, the second intermediate inductor, and the third intermediate inductor are connected together;

[0084] By controlling the duty cycles of the five groups of antipodal switch groups, the voltage of the input AC power supply can be increased or decreased.

[0085] Embodiment 3:

[0086] The embodiment of the present invention provides a control method for a three-phase first-level energy conversion AC / AC converter, and the method includes:

[0087] The following gives the mathematical relationship between the input and output voltages: If the conduction duty cycle of the first group of switches composed of the switching tubes T1, T2, T3, and T4 is D, and the duty cycle of the second group of switches composed of the switching tubes T5, T6, T7, T8, T9, and T10 is 1-D (Note: According to the partial modes given by the circuit, when each switch group works, one switch is always conducting forward and the other switch is conducting through the anti-parallel diode, which is determined by the drive signal and the voltage of the switch group. Therefore, the duty cycle in the control method refers to the duty cycle of the switch group). Taking the input voltage as the voltage connected to the first connection port of each phase Vx as an example, the output voltage of each phase V1x = D / (1-D) * Vx ( x = a 、 b 、 c ). It can be obtained that the magnitude of the output voltage of each phase is only related to the input voltage of the corresponding phase and the conduction duty cycle of the switch group. And when the conduction duty cycle D of the first group of switches composed of the switching tubes T1, T2, T3, and T4 is > 0.5, a boost change can be achieved, and when the conduction duty cycle D of the first group of switches composed of the switching tubes T1, T2, T3, and T4 is < 0.5, a buck change can be achieved.

[0088] The input voltage is an AC voltage. According to the output voltage V1x = D / (1-D) * Vx ( x = a 、 b 、 c ), in order to achieve AC / AC conversion, only the duty cycle needs to be fixed. When a boost is required, the duty cycle D > 0.5 takes a fixed value; when a buck is required, the duty cycle D < 0.5 takes a fixed value;

[0089] Due to the turn-on and turn-off characteristics of fully controlled devices, the first switch group shares a driving signal, and the second switch group shares a driving signal. By fixing the duty cycle that generates the target output voltage, AC / AC conversion can be achieved (since the driving of the first switch group and the second switch group is complementary, a switching dead zone needs to be added in practical applications).

[0090] In summary, compared with the prior art, the following beneficial effects are achieved:

[0091] 1. The embodiment of the present invention proposes a three-phase first-level energy conversion AC / AC converter and its control method. This converter uses first-level energy conversion to achieve AC / AC conversion, replacing the mainstream AC / DC + DC / AC two-stage architecture. With fewer devices, high efficiency and low cost are achieved. At the same time, this converter can operate in step-up mode or step-down mode.

[0092] 2. The three-phase first-level energy conversion AC / AC converter in the embodiment of the present invention is coupled in circuit form. Through mathematical analysis, the output voltage of each phase is only related to the input voltage of the corresponding phase. Therefore, the three-phase circuit is decoupled in mathematical relationship, and thus the control is relatively easy.

[0093] 3. The embodiment of the present invention uses an anti-parallel switch to construct a bidirectional energy path. The proposed three-phase first-level energy conversion AC / AC converter can achieve bidirectional operation.

[0094] 4. The embodiment of the present invention does not use a bus capacitor, avoiding the problem of the short service life of the bus capacitor in the two-stage scheme.

[0095] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of another identical element in the process, method, article or device including the element.

[0096] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A three-phase primary energy conversion AC / AC converter, characterized in that: It includes a first pair of top switch groups, a second pair of top switch groups, a first intermediate inductor, a second intermediate inductor, and three A-phase circuits, B-phase circuits, and C-phase circuits with the same structure; Each phase circuit includes two connection ports, the first connection port is connected to the second connection port via an inductor, an intermediate capacitor and a top switch group, and a power carrier communication capacitor is connected between the first connection port and the second connection port; The first end of the first pair of top switch groups is connected to the common end of the inductor and the middle capacitor of the A phase circuit, and the second end of the first pair of top switch groups is connected to the common end of the inductor and the middle capacitor of the B phase circuit; the first end of the second pair of top switch groups is connected to the second end of the first pair of top switch groups, and the second end of the second pair of top switch groups is connected to the common end of the inductor and the middle capacitor of the C phase circuit; The first end of the first intermediate inductor is connected to the common end of the intermediate capacitor of the A-phase circuit and the top switch group, and the second end of the first intermediate inductor is connected to the common end of the intermediate capacitor of the B-phase circuit and the top switch group; the first end of the second intermediate inductor is connected to the second end of the first intermediate inductor, and the second end of the second intermediate inductor is connected to the common end of the intermediate capacitor of the C-phase circuit and the top switch group; By controlling the duty cycle of the five groups of top switch groups, the voltage of the input AC power supply can be increased or decreased; the switches in the first pair of top switch groups and the second pair of top switch groups are regarded as the first group of switches, and the three groups of top switch groups in the A phase circuit, the B phase circuit and the C phase circuit are the second group of switches, and the first group of switches and the second group of switches are complementarily turned on; the first group of switches shares a control signal; the second group of switches shares a control signal.

2. The three-phase primary energy conversion AC / AC converter according to claim 1, characterized in that: Also includes a first filter capacitor and a second filter capacitor, Wherein, the first filter capacitor is connected between the second connection port of the A-phase circuit and the B-phase circuit; The second filter capacitor is connected between the second connection ports of the B-phase circuit and the C-phase circuit.

3. The three-phase primary energy conversion AC / AC converter according to claim 1, characterized in that: The first pair of top switch groups, the second pair of top switch groups, and the pair of top switch groups in each phase circuit all include two IGBTs with connected emitters.

4. The three-phase primary energy conversion AC / AC converter according to claim 1, characterized in that: The first connection port of each phase circuit is connected to the three-phase power grid, and the second connection port of each phase circuit is connected to a load common terminal via the load; or, the second connection port of each phase circuit is connected to the three-phase power grid, and the first connection port of each phase circuit is connected to a load common terminal via the load.

5. The three-phase primary energy conversion AC / AC converter according to claim 1, characterized in that: A neutral line is connected between the common end of the three-phase power grid and the common end of the load.

6. A control method for a three-phase primary energy conversion AC / AC converter, characterized in that: Used to control the AC / AC converter for three-phase primary energy conversion as claimed in any one of claims 1 to 5, the control method comprising: The switches in the first pair of top switch groups and the second pair of top switch groups are regarded as the first group of switches, and the on-duty cycle is D; the three pairs of top switch groups in the A phase circuit, the B phase circuit and the C phase circuit are regarded as the second group of switches, and the on-duty cycle is 1-D, the first group of switches share a driving signal, and the second group of switches share a driving signal; The voltage at the first connection port of each phase is Vx , x = a , b , c ; The voltage of the second connection port of each phase V1x ; The relationship between the two voltages is: V1x =D / (1-D)* Vx Control the size of the on-duty cycle D to achieve voltage boost or voltage reduction.

7. The control method of the AC / AC converter for three-phase primary energy conversion according to claim 6, characterized in that: When the first connection port of each phase is connected to the input voltage, that is Vx is the input voltage, V1x For the output voltage, when D is set to a fixed value greater than 0.5, boost is achieved, and when D is set to a fixed value less than 0.5, buck is achieved.

8. A three-phase primary energy conversion AC / AC converter, characterized in that: It includes a first pair of top switch groups, a second pair of top switch groups, a first intermediate inductor, a second intermediate inductor, a third intermediate inductor, and three A-phase circuits, B-phase circuits, and C-phase circuits with the same structure; Each phase circuit includes two connection ports, the first connection port is connected to the second connection port via an inductor, an intermediate capacitor and a top switch group, and a power carrier communication capacitor is connected between the first connection port and the second connection port; The first end of the first pair of top switch groups is connected to the common end of the inductor and the middle capacitor of the A phase circuit, and the second end of the first pair of top switch groups is connected to the common end of the inductor and the middle capacitor of the B phase circuit; the first end of the second pair of top switch groups is connected to the second end of the first pair of top switch groups, and the second end of the second pair of top switch groups is connected to the common end of the inductor and the middle capacitor of the C phase circuit; The first end of the first intermediate inductor is connected to the common end of the intermediate capacitor of the A-phase circuit and the top switch group; the first end of the second intermediate inductor is connected to the common end of the intermediate capacitor of the B-phase circuit and the top switch group; the first end of the third intermediate inductor is connected to the common end of the intermediate capacitor of the C-phase circuit and the top switch group; the second end of the first intermediate inductor, the second end of the second intermediate inductor, and the second end of the third intermediate inductor are connected together; By controlling the duty cycle of the five groups of top switch groups, the voltage of the input AC power supply can be increased or decreased; the switches in the first pair of top switch groups and the second pair of top switch groups are regarded as the first group of switches, and the three groups of top switch groups in the A phase circuit, the B phase circuit and the C phase circuit are the second group of switches, and the first group of switches and the second group of switches are complementarily turned on; the first group of switches shares a control signal; the second group of switches shares a control signal.

9. A control method for a three-phase primary energy conversion AC / AC converter, characterized in that: For controlling the AC / AC converter for three-phase primary energy conversion as claimed in claim 8, the control method comprises: The switches in the first pair of top switch groups and the second pair of top switch groups are regarded as the first group of switches, and the on-duty cycle is D; the three pairs of top switch groups in the A phase circuit, the B phase circuit and the C phase circuit are regarded as the second group of switches, and the on-duty cycle is 1-D, the first group of switches share a driving signal, and the second group of switches share a driving signal; The voltage at the first connection port of each phase is Vx , x = a , b , c ; The voltage of the second connection port of each phase V1x ; The relationship between the two voltages is: V1x =D / (1-D)* Vx Control the size of the on-duty cycle D to achieve voltage boost or voltage reduction.

10. The control method of the AC / AC converter for three-phase primary energy conversion according to claim 9, characterized in that: When the first connection port of each phase is connected to the input voltage, that is Vx is the input voltage, V1x For the output voltage, when D is set to a fixed value greater than 0.5, boost is achieved, and when D is set to a fixed value less than 0.5, buck is achieved.

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