Three-phase Vienna rectifier circuit and design method thereof

Abstract

The invention provides a three-phase Vienna rectifier circuit and a design method thereof. The three-phase Vienna rectifier circuit comprises a three-phase alternating current input end, three inductors, three power switch groups, a first capacitor, a second capacitor, a first-class rectifier diode and a second-class rectifier diode. The three inductors are respectively coupled with the three-phase alternating current input end. The inductor comprises a magnetic core and an inductance coil wound on the magnetic core. And the three power switch groups are respectively coupled with the three inductors. The first type rectifier diodes are coupled between the output ends of the corresponding inductors and the input ends of the first capacitors. The second type rectifier diodes are coupled between the output ends of the corresponding inductors and the output ends of the second capacitors. The end, connected with the voltage moving point, of the inductance coil is arranged on the inner layer of the magnetic core.

Description

Three-phase Vienna rectifier circuit and its design method

[0001] This application claims priority to the Chinese patent application with application number 202211299037.X filed on October 21, 2022; priority to the Chinese patent application with application number 202211291264.8 filed on October 21, 2022; and priority to the Chinese patent application with application number 202310166634.3 filed on February 24, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present disclosure relates to the technical field of household appliances, and in particular to a three-phase Vienna rectifier circuit and a design method thereof. Background Art

[0003] As a power factor correction (PFC) circuit, the three-phase Vienna rectifier circuit can avoid bridge arm shoot-through and facilitate three-phase clamping, thereby reducing harmonic pollution and reactive power loss.

[0004] Summary of the Invention

[0005] In one aspect, a three-phase Vienna rectifier circuit is provided. The three-phase Vienna rectifier circuit includes a three-phase AC input terminal, three inductors, three power switch groups, a first capacitor, a second capacitor, three first-type rectifier diodes, and three second-type rectifier diodes. The three inductors are respectively coupled to the three-phase AC input terminal. The inductors include a magnetic core and an inductor coil wound around the magnetic core. The three power switch groups are respectively coupled to the three inductors. The second capacitor is connected in series with the first capacitor to form a capacitive circuit. The three first-type rectifier diodes correspond to the three inductors, respectively, and the first-type rectifier diodes are coupled between the output terminals of the corresponding inductors and the input terminals of the first capacitors. The three second-type rectifier diodes correspond to the three inductors, respectively, and the second-type rectifier diodes are coupled between the output terminals of the corresponding inductors and the output terminals of the second capacitors. One end of the inductor's inductor coil connected to the voltage dynamic point is arranged in the inner layer of the magnetic core; the voltage dynamic point is the transition point where the voltage in the three-phase Vienna rectifier circuit changes from zero to half the voltage of the single-phase AC input end.

[0006] In another aspect, a design method for a three-phase Vienna rectifier circuit is provided. The three-phase Vienna rectifier circuit includes a three-phase AC input terminal, three inductors, three power switch groups, a first capacitor, a second capacitor, three first-type rectifier diodes, and three second-type rectifier diodes. The three inductors are respectively coupled to the three-phase AC input terminal. The inductors include a magnetic core and an inductor coil wound around the magnetic core. The three power switch groups are respectively coupled to the three inductors. The second capacitor is connected in series with the first capacitor to form a capacitive circuit. The three first-type rectifier diodes correspond to the three inductors, respectively, and the first-type rectifier diodes are coupled between the output terminals of the corresponding inductors and the input terminals of the first capacitors. The three second-type rectifier diodes correspond to the three inductors, respectively, and the second-type rectifier diodes are coupled between the output terminals of the corresponding inductors and the output terminals of the second capacitors. The method includes: according to the switching states of the three power switch groups, equating each phase branch in the three-phase Vienna rectifier circuit to an equivalent circuit consisting of a single-phase AC power supply, an equivalent inductor, an equivalent rectifier diode, an equivalent capacitor, and a switch; the single-phase AC power supply, the equivalent inductor, the equivalent rectifier diode, and the equivalent capacitor are connected in series to form a loop, one end of the switch is coupled to the anode of the equivalent rectifier diode, and the other end is coupled to the negative electrode of the equivalent capacitor; the equivalent inductor corresponds to any one of the three inductors; The single-phase AC power supply is any single-phase AC input terminal of the three-phase AC input terminals; the inductance of the equivalent inductor is determined based on the relationship between the inductance of the equivalent inductor and the duty cycle of the switch, the power supply voltage, the change in peak current, and the switching frequency of the switch; the power supply voltage is the input voltage of the single-phase AC power supply; the maximum energy storage of the equivalent inductor is determined based on the inductance of the equivalent inductor; based on the maximum energy storage of the equivalent inductor, the magnetic core material and structure of the equivalent inductor are determined, and the number of turns of the inductor coil is calculated.

[0007] In another aspect, an air conditioner is provided. The air conditioner includes the above-mentioned three-phase Vienna rectifier circuit. The above-mentioned design method of the three-phase Vienna rectifier circuit is applicable to the air conditioner. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG1 is a block diagram of a three-phase Vienna rectification system according to some embodiments;

[0009] FIG2 is a circuit diagram of a three-phase Vienna rectifier circuit according to some embodiments;

[0010] FIG3 is a circuit diagram of another three-phase Vienna rectifier circuit according to some embodiments;

[0011] FIG4 is a flow chart of steps performed by a controller according to some embodiments;

[0012] FIG5 is another flow chart of steps performed by a controller according to some embodiments;

[0013] FIG6 is a schematic diagram of voltage intervals at a three-phase AC input terminal according to some embodiments;

[0014] FIG7 is an equivalent circuit diagram of a plurality of power switch groups in a switching state according to some embodiments;

[0015] FIG8 is an equivalent circuit diagram of a plurality of power switch groups in another switching state according to some embodiments;

[0016] FIG9 is an equivalent circuit diagram of a plurality of power switch groups in another switching state according to some embodiments;

[0017] FIG10 is an equivalent circuit diagram of a plurality of power switch groups in another switching state according to some embodiments;

[0018] FIG11 is an equivalent circuit diagram of a plurality of power switch groups in another switching state according to some embodiments;

[0019] FIG12 is an equivalent circuit diagram of a plurality of power switch groups in another switching state according to some embodiments;

[0020] FIG13 is an equivalent circuit diagram of a plurality of power switch groups in another switching state according to some embodiments;

[0021] FIG14 is an equivalent circuit diagram of a plurality of power switch groups in another switching state according to some embodiments;

[0022] FIG15 is a circuit diagram of a single-phase equivalent circuit according to some embodiments;

[0023] FIG16 is a schematic diagram illustrating the relationship between the variation of the peak current and the peak current according to some embodiments;

[0024] FIG17 is another flow chart of steps performed by a controller according to some embodiments;

[0025] FIG18 is a schematic diagram of a design range of inductance of an inductor according to some embodiments;

[0026] FIG19 is another flow chart of steps performed by a controller according to some embodiments;

[0027] FIG20 is another flow chart of steps performed by a controller according to some embodiments;

[0028] FIG21 is a structural diagram of a magnetic ring in an inductor according to some embodiments;

[0029] FIG22 is a schematic diagram of a DC bias curve according to some embodiments;

[0030] FIG23 is another flow chart of steps performed by a controller according to some embodiments;

[0031] FIG24 is a schematic diagram of a charging circuit and a discharging circuit of a single-phase equivalent circuit according to some embodiments;

[0032] FIG25 is another flow chart of steps performed by a controller according to some embodiments;

[0033] FIG26 is a structural diagram of an inductor in a three-phase Vienna rectifier circuit according to some embodiments;

[0034] FIG27 is a structural diagram of a shielding cover according to some embodiments;

[0035] FIG28 is a structural diagram of another shielding cover according to some embodiments;

[0036] FIG29 is a schematic diagram of a charging loop and a discharging loop generating interference in a three-phase Vienna rectifier circuit according to some embodiments;

[0037] FIG30 is a structural diagram of a printed circuit board (PCB) of a three-phase Vienna rectifier circuit according to some embodiments;

[0038] 31 is a schematic diagram of magnetic fields of a first trace and a second trace in a three-phase Vienna rectifier circuit according to some embodiments;

[0039] 32 is a schematic diagram of a printed wiring board of a three-phase Vienna rectifier circuit according to some embodiments. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe some embodiments of the present disclosure in conjunction with the accompanying drawings. However, the described embodiments are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure.

[0041] Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and its other forms, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" are intended to indicate that the particular features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the particular features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0042] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0043] When describing some embodiments, the expressions "coupled" and "connected" and their derivatives may be used. The term "connected" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For another example, when describing some embodiments, the term "coupled" may be used to indicate that two or more components are in direct physical or electrical contact. However, the term "coupled" or "communicatively coupled" may also refer to two or more components that are not in direct contact with each other, but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the contents of this document.

[0044] “At least one of A, B and C” has the same meaning as “at least one of A, B or C” and both include the following combinations of A, B and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B and C.

[0045] The use of "adapted to" or "configured to" herein is intended to be open and inclusive language that does not exclude devices adapted or configured to perform additional tasks or steps.

[0046] As used herein, the term "if" is optionally interpreted to mean "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined that" or "if [stated condition or event] is detected" are optionally interpreted to mean "upon determining" or "in response to determining" or "upon detecting [stated condition or event]" or "in response to detecting [stated condition or event]," depending on the context.

[0047] As used herein, "about," "substantially," or "approximately" includes the stated value and an average value that is within an acceptable range of deviation from the particular value as determined by one of ordinary skill in the art taking into account the measurements in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0048] As used herein, "parallel," "perpendicular," and "equal" include the stated conditions and conditions approximating the stated conditions within an acceptable range of deviation as determined by one of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0049] Because the rectification effect of the power rectifier in central air conditioning systems is nonlinear, the harmonic content of the current on the grid side increases, which can easily lead to grid pollution and reduced power quality. To address this problem, two methods are usually used: one is to add power compensation devices and filters on the grid side, and the other is to improve the power factor correction performance of the power supply. For example, power factor correction is performed through a three-phase Vienna rectifier circuit. However, the three-phase Vienna rectifier circuit used in central air conditioning systems is a high-power three-phase Vienna rectifier circuit, which requires the design of an inductor that meets the high power requirements.

[0050] In addition, the three-phase Vienna rectifier circuit used in the central air-conditioning system is a high-power three-phase Vienna rectifier circuit. The effective value and peak current in the circuit are large, resulting in strong electromagnetic interference (EMI), which seriously affects surrounding circuits.

[0051] In order to solve the above problems, some embodiments of the present disclosure provide a three-phase Vienna rectifier system 1 .

[0052] Figure 1 is a block diagram of a three-phase Vienna rectifier system according to some embodiments. Figure 2 is a circuit diagram of a three-phase Vienna rectifier circuit according to some embodiments. Figure 3 is a circuit diagram of another three-phase Vienna rectifier circuit according to some embodiments. In Figure 2, the sources of two power switches in the same phase branch are connected, while in Figure 3, the drains of two power switches in the same phase branch are connected.

[0053] As shown in FIG. 1 to FIG. 3 , the three-phase Vienna rectifier system 1 includes a three-phase Vienna rectifier circuit 1000 .

[0054] As shown in FIG2 and FIG3, the three-phase Vienna rectifier circuit 1000 includes a three-phase AC input terminal e a 、e b 、e c (ie, the first phase AC input terminal e a , the second phase AC input terminal e b and the third phase AC input terminal e c ), the first inductor La, the second inductor Lb, and the third inductor Lc. Three-phase AC input terminal e a 、e b 、e c They are respectively coupled to the first inductor La, the second inductor Lb, and the third inductor Lc.

[0055] The three-phase Vienna rectifier circuit 1000 further includes a first power switch group Sa, a second power switch group Sb, and a third power switch group Sc.

[0056] The first power switch group Sa is coupled to the first inductor La and may be comprised of at least two power switches connected in series. For example, as shown in FIG2 , the first power switch group Sa includes a first power switch Q1 and a second power switch Q2 with their sources connected. The output terminal of the first inductor La is coupled to the drain of the first power switch Q1, and the drain of the second power switch Q2 is coupled to the midpoint O of the capacitor circuit 104. Alternatively, as shown in FIG3 , the first power switch group Sa includes a first power switch Q1 and a second power switch Q2 with their drains connected. The output terminal of the first inductor La is coupled to the source of the first power switch Q1, and the source of the second power switch Q2 is coupled to the midpoint O of the capacitor circuit 104.

[0057] The second power switch group Sb is coupled to the second inductor Lb and may be composed of at least two power switches connected in series. For example, as shown in FIG2 , the second power switch group Sb includes a third power switch Q3 and a fourth power switch Q4 with their sources connected. Alternatively, as shown in FIG3 , the second power switch group Sb includes a third power switch Q3 and a fourth power switch Q4 with their drains connected. The second power switch group Sb is coupled between the output terminal of the second inductor Lb and the midpoint O of the capacitor circuit 104.

[0058] The third power switch group Sc is coupled to the third inductor Lc and may be comprised of at least two power switches connected in series. For example, as shown in FIG2 , the third power switch group Sc includes a fifth power switch Q5 and a sixth power switch Q6 with their sources connected. Alternatively, as shown in FIG3 , the third power switch group Sc includes a fifth power switch Q5 and a sixth power switch Q6 with their drains connected. The third power switch group Sc is coupled between the output terminal of the third inductor Lc and the midpoint O of the capacitor circuit 104.

[0059] The power switch tubes in the multiple power switch groups may include insulated-gate bipolar transistors (IGBTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), integrated gate-commutated thyristors (IGCTs), or giant transistors (GTRs).

[0060] As shown in Figures 2 and 3, the three-phase Vienna rectifier circuit 1000 further includes a first capacitor C1 and a second capacitor C2. The capacitor circuit 104 is formed by connecting the first capacitor C1 and the second capacitor C2 in series. The output terminal (i.e., the negative electrode) of the first capacitor C1 is coupled to the input terminal (i.e., the positive electrode) of the second capacitor C2, and the connection point between the first capacitor C1 and the second capacitor C2 is the midpoint O of the capacitor circuit 104.

[0061] The circuit between the midpoint O between the first capacitor C1 and the second capacitor C2 and point F2 is the negative bus, and the circuit between the midpoint O between the first capacitor C1 and the second capacitor C2 and point F1 is the positive bus. The positive bus and the negative bus are each half bus. It should be noted that the three-phase Vienna rectifier circuit 1000 may include multiple first capacitors C1 and multiple second capacitors C2, and the multiple first capacitors C1 are connected in parallel, and the multiple second capacitors C2 are connected in parallel.

[0062] As shown in Figures 2 and 3, the three-phase Vienna rectifier circuit 1000 further includes a first rectifier diode D1, a second rectifier diode D2, a third rectifier diode D3, a fourth rectifier diode D4, a fifth rectifier diode D5, and a sixth rectifier diode D6. The first rectifier diode D1, the second rectifier diode D2, and the third rectifier diode D3 are first-type rectifier diodes 105, and the fourth rectifier diode D4, the fifth rectifier diode D5, and the sixth rectifier diode D6 are second-type rectifier diodes 106.

[0063] The first rectifier diode D1 is coupled between the output end of the first inductor La and the input end (i.e., the positive electrode) of the first capacitor C1. The second rectifier diode D2 is coupled between the output end of the second inductor Lb and the input end of the first capacitor C1. The third rectifier diode D3 is coupled between the output end of the third inductor Lc and the input end of the first capacitor C1. The fourth rectifier diode D4 is coupled between the output end of the first inductor La and the output end (i.e., the negative electrode) of the second capacitor C2. The fifth rectifier diode D5 is coupled between the output end of the second inductor Lb and the output end of the second capacitor C2. The sixth rectifier diode D6 is coupled between the output end of the third inductor Lc and the output end of the second capacitor C2. The anodes of the first rectifier diode D1, the second rectifier diode D2, and the third rectifier diode D3 are coupled to the cathodes of the fourth rectifier diode D4, the fifth rectifier diode D5, and the sixth rectifier diode D6, respectively. The cathodes of the first rectifier diode D1, the second rectifier diode D2 and the third rectifier diode D3 are respectively coupled to the input end of the first capacitor C1, and the anodes of the fourth rectifier diode D4, the fifth rectifier diode D5 and the sixth rectifier diode D6 are respectively coupled to the output end of the second capacitor C2.

[0064] Thus, the circuit formed by the first rectifier diode D1 and the fourth rectifier diode D4 forms the first bridge arm 101, the circuit formed by the second rectifier diode D2 and the fifth rectifier diode D5 forms the second bridge arm 102, and the circuit formed by the third rectifier diode D3 and the sixth rectifier diode D6 forms the third bridge arm 103. The first power switch group Sa is coupled to the first bridge arm 101, the second power switch group Sb is coupled to the second bridge arm 102, and the third power switch group Sc is coupled to the third bridge arm 103. The first bridge arm 101, the second bridge arm 102, and the third bridge arm 103 are connected in parallel.

[0065] In the three-phase Vienna rectifier circuit 1000, the three-phase AC input terminal e a 、e b 、e c The AC input side corresponds to a plurality of inductors and a plurality of power switch groups, respectively, and the DC output side is coupled to the capacitor circuit 104 .

[0066] In some embodiments, as shown in Figures 2 and 3, the three-phase Vienna rectifier circuit 1000 further includes a load RL. The load RL is connected in parallel with the capacitor circuit 104 and may include a compressor, a fan, or other electrical equipment.

[0067] In some embodiments of the present disclosure, by controlling the switching states of multiple power switch tubes in multiple power switch groups, the waveforms and phases of the input current and input voltage can be made consistent, thereby resolving harmonic issues. Furthermore, the three-phase Vienna rectifier circuit 1000 offers advantages such as low ripple, low voltage stress on the power switch tubes, and high overall efficiency. Here, the switching state of a power switch tube includes the on and off states of the power switch tube. Voltage stress refers to the ratio of the operating voltage to the rated voltage.

[0068] As one of the core components of the three-phase Vienna rectifier circuit 1000, the inductor (such as the first inductor La, the second inductor Lb, and the third inductor Lc) is the key to how the three-phase Vienna rectifier circuit 1000 is applied to the central air-conditioning system.

[0069] To this end, in some embodiments, as shown in FIG1 , the three-phase Vienna rectifier system 1 further includes a controller 2000 , which can select the inductor of the three-phase Vienna rectifier circuit 1000 used in the central air-conditioning system.

[0070] The controller 2000 includes a processor. The processor may include a central processing unit (CPU), a microprocessor (Microprocessor), or an application-specific integrated circuit (ASIC), and may be configured to perform the corresponding operations described in the controller 2000 when the processor executes a program stored in a non-transitory computer-readable medium coupled to the controller 2000.

[0071] FIG4 is a flow chart of steps executed by a controller according to some embodiments. As shown in FIG4 , the controller 2000 is configured to execute steps 1 to 4.

[0072] In step 1, according to the switching states of the three power switch groups, each phase branch in the three-phase Vienna rectifier circuit 1000 is equivalent to an equivalent circuit consisting of a single-phase AC power supply, an equivalent inductor, an equivalent rectifier diode, an equivalent capacitor and a switch.

[0073] FIG5 is another flow chart of steps executed by a controller according to some embodiments. Here, as shown in FIG5 , step 1 executed by the controller 2000 includes steps 11 to 13.

[0074] In step 11, the three-phase AC input terminal e is set to 0, 1, 2, or 3. Under the condition that the voltages of the two-phase AC input terminals are positive and the voltage of one-phase AC input terminal is negative at the same time, or the voltages of the two-phase AC input terminals are negative and the voltage of one-phase AC input terminal is positive at the same time, a 、e b 、e c The voltage is divided into multiple intervals.

[0075] FIG6 is a schematic diagram of the voltage range of the three-phase AC input terminal according to some embodiments. For example, as shown in FIG6, the voltage zero crossing point is used as the dividing point, and the three-phase AC input terminal e is divided into a 、e b 、e c The voltage is divided into six intervals: I, II, III, IV, V, and VI, with each interval being 60°.

[0076] Here, the three-phase AC input terminal e can be calculated according to Kirchhoff's law (also known as the node current law). a 、e b 、e c The voltage is divided into intervals. Kirchhoff's law: At any node in the circuit, at any time, the sum of the currents flowing into the node is equal to the sum of the currents flowing out of the node. When the three-phase AC input terminal e a 、e b 、e c When the voltages at the two-phase AC input terminals increase or decrease and the voltage at one-phase AC input terminal decreases or increases, the sum of the currents flowing into the midpoint O of the capacitor circuit 104 is equal to the sum of the currents flowing out of the midpoint O.

[0077] In each phase bridge arm (e.g., first bridge arm 101, second bridge arm 102, and third bridge arm 103), the corresponding power switch group has two switching states: on and off. Depending on the switching state, the three power switch groups can have eight operating states within a single interval. When a power switch group is on, the current in the corresponding inductor increases, and the inductor stores energy. When a power switch group is off, the three-phase power supply and the corresponding inductor jointly provide energy to the load RL, increasing the output voltage on the DC side.

[0078] In the positive half cycle of three-phase electricity, the three-phase AC input terminal e a 、e b 、e cThe current flows from the first rectifier diode D1, the second rectifier diode D2, and the third rectifier diode D3 on the bridge arm, or from the first power switch group Sa, the second power switch group Sb, and the third power switch group Sc, to charge at least one of the first capacitor C1 or the second capacitor C2 on the DC side and provide energy to the load RL. The current then flows back to the AC side through the first power switch group Sa, the second power switch group Sb, and the third power switch group Sc, or from the fourth rectifier diode D4, the fifth rectifier diode D5, and the sixth rectifier diode D6 on the bridge arm.

[0079] In the negative half cycle of the three-phase power, the three-phase AC input terminal e a 、e b 、e c The current flows from the fourth rectifier diode D4, the fifth rectifier diode D5, and the sixth rectifier diode D6 on the bridge arm, or from the first power switch group Sa, the second power switch group Sb, and the third power switch group Sc, to charge at least one of the first capacitor C1 or the second capacitor C2 on the DC side and provide energy to the load RL. The current then flows back to the AC side through the first power switch group Sa, the second power switch group Sb, and the third power switch group Sc, or from the first rectifier diode D1, the second rectifier diode D2, and the third rectifier diode D3 on the bridge arm. In this way, by charging and discharging the first capacitor C1 and the second capacitor C2 in the DC side capacitor circuit 104, a rectified output can be achieved. Here, the positive half-cycle of the three-phase power refers to the period when the power supply voltage is positive, and the negative half-cycle of the three-phase power refers to the period when the power supply voltage is negative.

[0080] For the three-phase Vienna rectifier circuit 1000, the current of the inductor and the voltage of the capacitor can be adjusted by controlling the switching states of the first power switch group Sa, the second power switch group Sb and the third power switch group Sc, so as to balance the potential of the midpoint O of the capacitor circuit 104 to 0 and stabilize the voltage of the DC bus output.

[0081] Since the three-phase AC input terminal e a 、e b 、e c The polarity of the input current is different, and the switching states of the first power switch group Sa, the second power switch group Sb, and the third power switch group Sc are different. The voltage between each phase AC input terminal of the three-phase Vienna rectifier circuit 1000 and the midpoint O of the capacitor circuit 104 switches between three levels: -U / 2, 0, and U / 2. Therefore, the three-phase Vienna rectifier circuit 1000 can also be called a three-phase three-level Vienna rectifier circuit. Here, U refers to the three-phase AC input terminal e a 、e b 、e c The input voltage of the single-phase AC input terminal (i.e., the single-phase AC power supply hereinafter) in the circuit.

[0082] In step 12, any interval is selected and the three-phase Vienna rectifier circuit 1000 is equivalently constructed based on the various switching states of the three power switch groups, thereby obtaining various operating states of the three-phase Vienna rectifier circuit 1000. Here, the various operating states of the three-phase Vienna rectifier circuit 1000 refer to operating conditions corresponding to different current flow directions in the three-phase Vienna rectifier circuit 1000 under different switching states of the three power switch groups.

[0083] The following describes the working principle of the three-phase Vienna rectifier circuit 1000 by taking the different switching states of the three power switch groups in the first interval shown in FIG6 as an example. a 、e b 、e c Due to the high frequency characteristics of the capacitor circuit 104, the discharge process of the capacitor circuit 104 is relatively fast. Therefore, the following only describes the charging process of the capacitor circuit 104. In addition, the working principles of the three-phase Vienna rectifier circuit 1000 corresponding to other intervals are similar to those of the first interval and will not be repeated here.

[0084] Figure 7 is an equivalent circuit diagram of multiple power switch groups in a switching state according to some embodiments. Compared to Figures 2 and 3, the power switch groups in Figure 7 are simplified to facilitate the description of multiple power switch groups in different switching states. In some examples, as shown in Figure 7, the first power switch group Sa, the second power switch group Sb, and the third power switch group Sc are respectively disconnected (i.e., SaSbSc=000). The first phase current Ia from the AC side charges the first capacitor C1 and the second capacitor C2 on the DC side from the first rectifier diode D1 on the first bridge arm 101, and then flows back to the AC side through the fifth rectifier diode D5 on the second bridge arm 102 and the sixth rectifier diode D6 on the third bridge arm 103.

[0085] With the midpoint O of capacitor circuit 104 as the reference ground, the potential at point A is U / 2, the potentials at points B and C are -U / 2, and the first-phase current Ia is equal to the sum of the second-phase current Ib and the third-phase current Ic (i.e., Ia = Ib + Ic). The first-phase current Ia charges the first capacitor C1, while the second-phase current Ib and the third-phase current Ic charge the second capacitor C2. In this case, the current flowing through the first inductor La is the first-phase current Ia, the current flowing through the second inductor Lb and the third inductor Lc is half the first-phase current Ia (i.e., Ia / 2), and the voltage across the first capacitor C1 is U / 2.

[0086] Here, the three numbers corresponding to SaSbSc correspond to the first power switch group Sa, the second number corresponds to the second power switch group Sb, and the third number corresponds to the third power switch group Sc. A number equal to 1 indicates that the corresponding power switch group is on, and a number equal to 0 indicates that the corresponding power switch group is off.

[0087] Figure 8 is an equivalent circuit diagram of multiple power switch groups in another switching state according to some embodiments. In other examples, as shown in Figure 8, the first power switch group Sa is off, the second power switch group Sb is off, and the third power switch group Sc is on (i.e., SaSbSc = 001). The first phase current Ia from the AC side charges the first capacitor C1 through the first rectifier diode D1 and then flows back to the AC side through the third power switch group Sc and the fifth rectifier diode D5. During this process, the second capacitor C2 is also charged.

[0088] With the midpoint O of capacitor circuit 104 as the reference ground, the potential at point A is U / 2, the potential at point B is -U / 2, and the potential at point C is 0. The first-phase current Ia is equal to the sum of the second-phase current Ib and the third-phase current Ic. The first-phase current Ia charges the first capacitor C1, and the second-phase current Ib charges the second capacitor C2. The voltage across the first capacitor C1 is U / 2.

[0089] Figure 9 is an equivalent circuit diagram of multiple power switch groups in another switching state according to some embodiments. In yet other examples, as shown in Figure 9 , the first power switch group Sa is off, the second power switch group Sb is on, and the third power switch group Sc is off (i.e., SaSbSc = 010). The first phase current Ia from the AC side charges the first capacitor C1 through the first rectifier diode D1 and then flows back to the AC side through the second power switch group Sb and the sixth rectifier diode D6. During this process, the second capacitor C2 is also charged.

[0090] With the midpoint O of capacitor circuit 104 as the reference ground, the potential at point A is U / 2, the potential at point B is 0, and the potential at point C is -U / 2. The first-phase current Ia is equal to the sum of the second-phase current Ib and the third-phase current Ic. The first-phase current Ia charges the first capacitor C1, and the third-phase current Ic charges the second capacitor C2. The voltage across the first capacitor C1 is U / 2.

[0091] FIG10 is an equivalent circuit diagram of multiple power switch groups in another switching state according to some embodiments. In yet other examples, as shown in FIG10 , the first power switch group Sa is off, the second power switch group Sb is on, and the third power switch group Sc is on (i.e., SaSbSc = 0:1). The first phase current Ia from the AC side charges the first capacitor C1 through the first rectifier diode D1 and then flows back to the AC side through the second power switch group Sb and the third power switch group Sc.

[0092] With the midpoint O of capacitor circuit 104 as the reference ground, the potential at point A is U / 2, the potentials at points B and C are both 0, and the first phase current Ia is equal to the sum of the second phase current Ib and the third phase current Ic. The first phase current Ia charges the first capacitor C1, and the voltage across the first capacitor C1 is U / 2.

[0093] Figure 11 is an equivalent circuit diagram of multiple power switch groups in another switching state according to some embodiments. In yet other examples, as shown in Figure 11, the first power switch group Sa is on, the second power switch group Sb is off, and the third power switch group Sc is off (i.e., SaSbSc = 100). The first phase current Ia from the AC side charges the second capacitor C2 from the first power switch group Sa and then flows back to the AC side through the fifth rectifier diode D5 and the sixth rectifier diode D6.

[0094] With the midpoint O of capacitor circuit 104 as the reference ground, the potential at point A is 0, the potentials at points B and C are -U / 2, and the first phase current Ia is equal to the sum of the second phase current Ib and the third phase current Ic. The first phase current Ia charges the second capacitor C2, and the voltage at the first capacitor C1 is zero.

[0095] Figure 12 is an equivalent circuit diagram of multiple power switch groups in another switching state according to some embodiments. In yet other examples, as shown in Figure 12, the first power switch group Sa is on, the second power switch group Sb is off, and the third power switch group Sc is on (i.e., SaSbSc = 101). The first phase current Ia from the AC side charges the second capacitor C2 through the first power switch group Sa, and then flows back to the AC side through the third power switch group Sc and the fifth rectifier diode D5.

[0096] With the midpoint O of capacitor circuit 104 as the reference ground, the potentials at points A and C are 0, and the potential at point B is -U / 2. The first phase current Ia is equal to the sum of the second phase current Ib and the third phase current Ic. The second phase current Ib charges the second capacitor C2, and the voltage on the first capacitor C1 is zero.

[0097] FIG13 is an equivalent circuit diagram of multiple power switch groups in another switching state according to some embodiments. In yet other examples, as shown in FIG13 , the first power switch group Sa is on, the second power switch group Sb is on, and the third power switch group Sc is off (i.e., SaSbSc = 110). The first phase current Ia from the AC side charges the second capacitor C2 through the first power switch group Sa and then flows back to the AC side through the second power switch group Sb and the sixth rectifier diode D6.

[0098] With the midpoint O of capacitor circuit 104 as the reference ground, the potentials at points A and B are 0, and the potential at point C is -U / 2. The first-phase current Ia is equal to the sum of the second-phase current Ib and the third-phase current Ic. The third-phase current Ic charges the second capacitor C2, and the voltage on the first capacitor C1 is zero.

[0099] Figure 14 is an equivalent circuit diagram of multiple power switch groups in another switching state, according to some embodiments. In some embodiments, as shown in Figure 14 , the first power switch group Sa, the second power switch group Sb, and the third power switch group Sc are all turned on (i.e., SaSbSc = 111). The first phase current Ia from the AC side flows from the first power switch group Sa to the midpoint O of the capacitor circuit 104, and then flows back to the AC side through the second power switch group Sb and the third power switch group Sc.

[0100] With the midpoint O of the capacitor circuit 104 as the reference ground, the potentials of points A, B, and C are all zero, the first phase current Ia is equal to the sum of the second phase current Ib and the third phase current Ic, and the voltage of the first capacitor C1 is zero.

[0101] In step 13, according to various working states of the three-phase Vienna rectifier circuit 1000, each phase branch in the three-phase Vienna rectifier circuit 1000 is equivalent to an equivalent circuit consisting of a single-phase AC power supply, an equivalent inductor, an equivalent rectifier diode, an equivalent capacitor and a switch.

[0102] According to the above analysis of the circuits in FIG. 7 to FIG. 14, for the first phase AC input terminal e a Regardless of the switching states of the three power switch groups, when the first power switch group Sa is disconnected, the first phase current Ia charges the first capacitor C1, and the voltage of the first capacitor C1 is U / 2; when the first power switch group Sa is turned on, the first phase current Ia charges the second capacitor C2 or returns to the AC side from the corresponding power switch group. In this case, the voltage of the first capacitor C1 is 0.

[0103] Similarly, for the second phase AC input terminal e b Or the third phase AC input terminal e c Regardless of the switch state combination of the three power switch groups, when the second power switch group Sb is disconnected, the second phase current Ib charges the first capacitor C1; when the second power switch group Sb is closed, the second phase current Ib charges the second capacitor C2 or returns from the corresponding power switch group to the AC side, and the voltage on the first capacitor C1 is 0; when the third power switch group Sc is disconnected, the third phase current Ic charges the first capacitor C1; when the third power switch group Sc is closed, the third phase current Ic charges the second capacitor C2 or returns from the corresponding power switch group to the AC side, and the voltage on the first capacitor C1 is 0.

[0104] FIG15 is a circuit diagram of a single-phase equivalent circuit according to some embodiments. Therefore, as shown in FIG15 , each phase branch can be equivalent to a single-phase equivalent circuit consisting of an equivalent inductor L0, an equivalent rectifier diode D0, a switch Sp, and an equivalent capacitor C. The input end of the equivalent inductor L0 is coupled to the single-phase AC power supply U1, the output end of the equivalent inductor L0 is coupled to the anode of the equivalent rectifier diode D0, the cathode of the equivalent rectifier diode D0 is coupled to the input end of the equivalent capacitor C, the output end of the equivalent capacitor C is grounded, and one end of the switch SP is coupled between the equivalent inductor L0 and the equivalent rectifier diode D0, and the other end is grounded. The voltage of the single-phase AC power supply U1 is equal to U / 2 (i.e., U1=U / 2). When the switch Sp is open, the voltage of the equivalent capacitor C is U / 2; when the switch Sp is closed, the voltage of the equivalent capacitor C is 0.

[0105] It should be noted that the equivalent inductor L0 corresponds to any one of the three inductors in the three-phase Vienna rectifier circuit 1000; the single-phase AC power supply U1 is the three-phase AC input terminal e a 、e b 、e c Any single-phase AC input terminal.

[0106] Based on the above equivalent circuit, the three-phase Vienna rectifier circuit 1000 can be equivalent to three single-phase power supply circuits connected in parallel. Thus, when selecting the three inductors, one inductor can be selected for one phase of the three-phase Vienna rectifier circuit 1000, and the inductors for the other two phases can be selected in the same manner.

[0107] In step 2, the inductance L of the equivalent inductor L0 is determined based on the relationship between the inductance L (also called inductance or self-inductance coefficient) of the equivalent inductor L0 and the duty cycle D of the switch Sp, the power supply voltage Vout, the change ΔI of the peak current Imax, and the switching frequency f of the switch Sp (as shown in formula (1)).

[0108] As shown in the equivalent circuit in Figure 15, the inductance L is calculated according to formula (1):

[0109] D is the duty cycle of the switch Sp, Vout is the power supply voltage, which is the input voltage of the single-phase AC power supply U1 (i.e., Vout = U / 2), ΔI is the change in peak current Imax, and f is the switching frequency of the switch Sp. It should be noted that the duty cycle and switching frequency of the switch Sp are the same as those of the corresponding power switch group.

[0110] FIG16 is a schematic diagram of the relationship between the change in peak current and the peak current according to some embodiments. As shown in FIG16 , the change in peak current Imax ΔI is any value within the range of 20% Imax to 40% Imax (preset range). That is, the peak current Imax can increase or decrease by any value between 20% and 40%. For example, the change in peak current Imax ΔI is 20% Imax, 25% Imax, 30% Imax, 35% Imax, or 40% Imax, etc. Assuming that the inductance L and other parameters are known, the maximum change in peak current Imax ΔI occurs when the duty cycle D is 50%. When the change in peak current Imax ΔI is the largest, the inductance L is the smallest. Therefore, in the selection of the inductor, the inductance L needs to be greater than the minimum inductance corresponding to the maximum change in peak current Imax ΔI.

[0111] FIG17 is another flow chart of the steps executed by the controller according to some embodiments. In some embodiments, as shown in FIG17 , the controller 2000 is configured to execute step 20 .

[0112] In step 20, the peak current Imax is determined according to the power, power factor and line voltage of the three-phase AC input terminal.

[0113] Since the change ΔI of the peak current Imax is related to the peak current Imax, it is necessary to calculate the peak current Imax. According to the following formula (2), when the input voltage of the AC power supply is minimum, the peak current Imax is maximum.

[0114] Here, Pin is the power at the three-phase AC input terminal, PF is the power factor, and Vin_ll (RMS) is the line voltage.

[0115] The line voltage Vin_ll (RMS) is any value within the set range of AC380±20%V. Different input voltages result in different inductances. The higher the input voltage, the greater the inductance L under the same conditions. Therefore, the calculated inductance L in some embodiments of the present disclosure is a range value.

[0116] Figure 18 is a schematic diagram illustrating a design range for the inductance of an inductor according to some embodiments. The design range for the inductance is shown in Figure 18. For example, when the switching frequency f is 40 kHz, the change ΔI of the peak current Imax is 20% Imax, the input voltage is AC304V, and the output voltage is DC650V, the inductance L can be approximately 379uH.

[0117] FIG19 is another flow chart of the steps executed by the controller according to some embodiments. In some embodiments, as shown in FIG19 , the controller 2000 is further configured to execute step 21 .

[0118] In step 21 , the saturation current of the equivalent inductor L0 (eg, the first inductor L1 , the second inductor L2 , or the third inductor L3 ) is determined according to the anti-saturation parameter α, the peak current Imax, and the variation ΔI of the peak current Imax.

[0119] In order to avoid inductor saturation, the saturation current Ilmax of the equivalent inductor L0 needs to satisfy formula (3):

[0120] Here, α is an anti-saturation parameter, and the anti-saturation parameter α is greater than 1. For example, the anti-saturation parameter α is equal to 1.1. Based on the peak current Imax (i.e., the maximum input current), the current variation is increased, and the sum of the peak current Imax and the current variation is increased by a preset multiple, thereby obtaining a saturation current Ilmax that meets the requirements. For example, when the anti-saturation parameter α is equal to 1.1, the sum of the peak current Imax and the current variation is increased by 10% to obtain the saturation current Ilmax. Otherwise, the equivalent inductor L0 may experience inductor saturation.

[0121] In some embodiments of the present disclosure, each phase branch of a three-phase Vienna rectifier circuit 1000 is equivalent to a simplified circuit consisting of an equivalent inductor, an equivalent rectifier diode, a switch, and an equivalent capacitor, based on the switching states of multiple power switch groups. Based on this simplified circuit, the inductance is calculated by combining the duty cycle, current variation, and switching frequency. The equivalent inductor's ability to withstand saturation current is considered, and the input current is combined with the ripple current and the anti-saturation parameter α to design an integrated PFC inductor that meets the requirements.

[0122] In step 3, the maximum stored energy of the equivalent inductor L0 is determined according to the inductance L of the equivalent inductor L0.

[0123] After calculating the inductance L, it is necessary to perform closed-loop selection of the inductor in the three-phase Vienna rectifier circuit 1000 at the application level to convert the calculated parameters into practical applications, thereby selecting appropriate magnetic materials and structures for the actual design of the high-power inductor in the three-phase Vienna rectifier circuit 1000. Therefore, the equivalent inductor L0 can be selected based on the inductor energy storage formula (4). W = L × I 2 (4)

[0124] Here, W is the energy stored in the inductor, L is the inductance, and I is the current in the inductor.

[0125] For example, when the power supply power is 10 kW, the input voltage is AC304V, the output voltage is DC650V, the switching frequency f is 40 kHz, and the change ΔI of the peak current Imax is 20% of Imax, the peak current Imax is approximately equal to 35.35A, the inductance L is approximately equal to 379uH, and the energy stored in the inductor W is approximately equal to 473mJ. For another example, when the power supply power is 10 kW, the input voltage is AC460V, the output voltage is DC650V, the switching frequency f is 40 kHz, and the change ΔI of the peak current Imax is 20% of Imax, the peak current Imax is approximately equal to 23.56A, the inductance L is approximately equal to 568uH, and the energy stored in the inductor W is approximately equal to 315mJ.

[0126] From the above data, we can see that when the input voltage is low, the inductor's peak current Imax is large. Although the inductance L is small, the inductor's overall energy is large (i.e., the inductor's stored energy W is large). When the input voltage is high, the inductor's peak current Imax is small. Although the inductance L is large, the inductor's overall energy is small (i.e., the inductor's stored energy W is small). Therefore, inductor selection should be based on the most stringent conditions. Here, the most stringent conditions refer to the case where the input voltage is low and the inductor current is high.

[0127] The present disclosure can design an inductor based on an example where the power supply is 10KW, the input voltage is AC304V, the output voltage is DC650V, the switching frequency f is 40KHz, the change ΔI of the peak current Imax is 20% Imax, the inductance L is 379uH, and the energy storage W is 473mJ. It should be noted that when the change ΔI of the peak current Imax is 40% Imax, the inductance L becomes 189uH and the energy storage W becomes 322mJ. Therefore, the inductor corresponding to the energy storage W of 473mJ is the most stringent design selection. In other words, the inductor is selected based on its maximum energy storage.

[0128] In step 4, the core material and structure of the equivalent inductor L0 are determined according to the maximum stored energy of the equivalent inductor L0, and the number of turns of the inductor coil is calculated.

[0129] For the energy storage W of the inductor, different magnetic materials correspond to different curves and different magnetic cores. Here, the magnetic core of the inductor can be made of ferrite material, such as sendust, iron-nickel-molybdenum, iron-nickel, iron-silicon, etc. In addition, the magnetic core can be a magnetic powder core, for example, a ring-shaped, EE-shaped, or U-shaped magnetic core. Here, the curve may refer to a curve representing the energy storage capacity of the magnetic material. The magnetic powder core is a soft magnetic material made by mixing ferromagnetic powder particles and an insulating medium and pressing them. In addition, the EE-shaped magnetic core means that the magnetic core is composed of two structures roughly in the shape of a capital English letter "E".

[0130] For example, the inductor uses a Sendust toroidal core, which has a maximum energy storage capacity of 1000 mJ and is greater than 473 mJ, thus meeting the required specifications. In this case, the corresponding magnetic permeability μ of the Sendust toroidal core is less than 26.

[0131] It should be noted that when the maximum energy storage of a magnetic core of corresponding shape and material cannot meet the design requirement of energy storage W being 473 mJ, the volume of the magnetic core can be increased to meet the design requirement.

[0132] After determining the inductance L, the core size, and the magnetic permeability μ, the controller 2000 can calculate the number of turns of the inductor coil. For example, if the equivalent inductor L0 uses a Sendust toroidal core with a magnetic permeability μ equal to 26, the inductance AL of a single turn coil of the core is 30nH / T. 2 At this time, according to the inductance calculation formula (5), it can be determined that when the inductance L is 380uH, the corresponding number of inductor turns is 112 turns. L = AL × N 2 (5)

[0133] In this way, after determining the inductance L, core size, magnetic permeability μ, and number of turns of the inductor coil, the selection of the inductor is roughly completed.

[0134] FIG20 is another flow chart of steps executed by the controller according to some embodiments. In some embodiments, as shown in FIG20 , after determining the selection of the equivalent inductor L0 , the controller 2000 is further configured to execute steps 5 and 6 .

[0135] In step 5, the magnetic field strength of the equivalent inductor L0 after DC bias is calculated according to the equivalent circuit.

[0136] After determining the selection of the equivalent inductor L0, the equivalent inductor L0 can be DC biased and verified, and the magnetic field strength of the equivalent inductor L0 after DC bias can be calculated according to formula (6):

[0137] Here, H is the magnetic field intensity, I is the current of the equivalent inductor L0 (such as the peak current Imax), and le is the effective magnetic path length.

[0138] For example, when the peak current Imax is equal to 35.35 A, the number of turns N of the inductor coil is 112, and the effective magnetic path length le is equal to 19.6 cm, according to formula (6), the magnetic field intensity H is approximately equal to 251 Oersteds.

[0139] In step 6, the structure of the equivalent inductor L0 is determined according to the magnetic field strength after the DC bias and the initial magnetic permeability corresponding to the magnetic field strength.

[0140] Figure 21 is a structural diagram of a magnetic ring in an inductor according to some embodiments. Figure 22 is a schematic diagram of a DC bias curve according to some embodiments.

[0141] When the magnetic field strength H reaches 251oersreds, the initial magnetic permeability of the magnetic core changes from 1 to 0.45. In this case, if the number of turns N of the inductor coil is adjusted, the magnetic field strength H value will also change when the current remains unchanged, thereby affecting the adjustment of the initial magnetic permeability of the magnetic core. Therefore, as shown in Figure 21, one magnetic ring can be replaced with two magnetic rings with an initial magnetic permeability of 0.45, and the two magnetic rings are coupled to each other, so that the initial magnetic permeability of the entire magnetic core composed of the two magnetic rings becomes 0.9, which makes it easier to reduce the number of turns of the inductor coil and thus meet the demand.

[0142] For example, two magnetic rings are provided with insulating brackets at both ends in the height direction. The inductor coil can be wound with flat wire in a single layer to minimize the distributed capacitance of the inductor. The corresponding DC bias curve is shown in Figure 22.

[0143] Figure 23 is another flow chart of steps executed by the controller according to some embodiments. In some embodiments, as shown in Figure 23 , after calculating the number of turns of the inductor coil of the equivalent inductor L0 , the controller 2000 is further configured to execute steps 7 and 8 .

[0144] In step 7, the window fill factor of the equivalent inductor L0 is calculated.

[0145] In step 8, it is determined that the window filling factor of the equivalent inductor L0 is less than or equal to a set factor, which is 50%.

[0146] In the process of designing the inductor, it is also necessary to confirm the window filling factor Ku of the equivalent inductor L0 and limit the window filling factor Ku to less than 50% to facilitate the heat dissipation of the equivalent inductor L0. For example, the window area WA without winding on the core is 1820mm 2 The cross-section of the flat inductor is 4 mm long and 1 mm wide, and the number of turns N of the inductor is 112. The total area of ​​the inductor is the product of the cross-sectional area Aw of the inductor and the number of turns N of the inductor, which is equal to 448 mm. 2 (i.e., Aw×N=4×1×112=448mm 2 Thus, the window filling factor Ku is 24.6% (ie, 448 / 1820=24.6%), and the window filling factor Ku is less than 50%, which meets the design requirements.

[0147] In some embodiments of the present disclosure, a three-phase Vienna rectifier system 1 can be used to select the inductor in the three-phase Vienna rectifier circuit 1000, so that the three-phase Vienna rectifier circuit 1000 can be applied to a central air-conditioning system and used as a power factor correction converter to solve problems such as harmonic pollution and reactive power loss.

[0148] The structure of the inductor in the three-phase Vienna rectifier circuit 1000 is described in detail below.

[0149] In the three-phase Vienna rectifier system 1 designed above, since the power supply power can reach 10KW, the effective current can reach 19A, and the peak current Imax can reach 35A, the current in the three-phase Vienna rectifier circuit 1000 is relatively large, which easily leads to strong electromagnetic compatibility (EMC) interference. The EMC interference formula is as follows: E=K×(F×As×Iy) / R (7)

[0150] Here, E represents energy (i.e., electric field strength), K is a constant, F is the current frequency, As is the loop area of ​​the circuit through which the current flows, Iy is the effective value of the current in the loop, and R is the distance between the device and the EMC test antenna. For a circuit, K and R are generally constants. Thus, the parameters relevant to EMC are the current frequency F, the loop area As, and the effective value of the current Iy. Therefore, the greater the current in the three-phase Vienna rectifier circuit 1000, the greater the EMC interference of the circuit. Furthermore, since all inductors in the three-phase Vienna rectifier circuit 1000 have exposed magnetic powder cores, the EMC energy of each inductor is very high, seriously interfering with surrounding circuits.

[0151] Figure 24 is a schematic diagram of the charging and discharging circuits of a single-phase equivalent circuit according to some embodiments. As shown in Figures 2, 3, and 24, when switch Sp is closed, equivalent inductor L0 stores energy, and the current path follows the Ion-phase loop, indicated by the first dotted line in Figure 24. The current flows from point A11 through equivalent inductor L0, then from point B11 to point D11, and finally to point E11. The reference voltage at point B11 is 0.

[0152] When switch Sp turns off, the equivalent inductor L0 releases energy, and the current path follows the Ioff-phase loop, indicated by the second dotted line in Figure 24. The current flows from point A11 through the equivalent inductor L0 to point B11, then through the equivalent rectifier diode D0 to point C11, and finally from points C11 and D11 to point E11. The reference voltage at point B11 is U / 2. It should be noted that the "hot loop" in Figure 24 refers to a loop with a sudden change in current.

[0153] In this case, point B11 is the transition point where the voltage changes from zero to U / 2, which can be called a voltage swing point, and the loop associated with point B11 is a hot loop. Therefore, point B11 is the location where EMC interference is greatest in the three-phase Vienna rectifier circuit 1000.

[0154] FIG25 is another flow chart of the steps executed by the controller according to some embodiments. In this case, as shown in FIG25 , the controller 2000 is further configured to execute step 9.

[0155] In step 9, the voltage swing point in the three-phase Vienna rectifier circuit 1000 is determined.

[0156] The voltage dynamic point is the transition point where the voltage in the three-phase Vienna rectifier circuit 1000 changes from zero to U / 2.

[0157] The voltage swing point can be determined based on the charge and discharge loop of the equivalent circuit of Figure 24. Of course, in some embodiments, the voltage swing point from zero to U / 2 can also be determined in combination with the charge and discharge loop of Figure 2 or Figure 3, and this disclosure does not limit this.

[0158] Figure 26 is a structural diagram of an inductor in a three-phase Vienna rectifier circuit according to some embodiments. In some embodiments, since the voltage swing point is connected to one end of the inductor coil, the end of the inductor coil connected to the voltage swing point can be arranged in the inner layer of the magnetic core.

[0159] For example, as shown in FIG24 , the voltage pivot point B11 is a point on the equivalent inductor L0 (i.e., one end of the equivalent inductor L0 coupled to the switch Sp and the equivalent rectifier diode D0). As shown in FIG26 , the inductor includes a magnetic core 801 and an inductor coil 802 wound around the magnetic core 801. If the end of the equivalent inductor L0 connected to the switch Sp and the equivalent rectifier diode D0 is wound on the outermost layer of the magnetic core 801, severe EMC interference is likely to occur. Therefore, as shown in FIG26 , the voltage pivot point B11 and the end B12 of the equivalent inductor L0 connected to the voltage pivot point B11 can be set in the innermost layer of the magnetic core 801. In this way, EMC radiation can be limited to the inner side of the enclosed area of ​​the inductor coil 802, and the interference caused by the EMC radiation to the outside is relatively small.

[0160] FIG27 is a structural diagram of a shielding cover according to some embodiments. FIG28 is a structural diagram of another shielding cover according to some embodiments. In some embodiments, as shown in FIG27 and FIG28 , the three-phase Vienna rectifier circuit 1000 further includes a shielding cover 50 , which is provided over the inductor in the three-phase Vienna rectifier circuit 1000 to shield against EMC interference.

[0161] In some embodiments, the shield 50 can be made of nickel-zinc ferrite, eliminating the need for conductive material (such as aluminum or copper) between the shield 50 and the inductor. Alternatively, the shield 50 can be made of stainless steel or copper-nickel-zinc alloy, with conductive material provided between the shield 50 and the inductor, or the inductor can be wrapped with high-temperature insulating tape.

[0162] In some embodiments, as shown in FIG27 , the upper side of the shielding cover 50 can be open to form an opening 500 to facilitate heat dissipation from the inductor. Alternatively, as shown in FIG28 , the upper side of the shielding cover 50 can be closed. It should be noted that whether the upper side of the shielding cover 50 is open can be determined based on EMC considerations and the temperature rise of the inductor.

[0163] In some embodiments, the shielding cover 50 may cover one inductor. Of course, the shielding cover 50 may also cover multiple inductors.

[0164] In some embodiments, the inductor housing can be made of a low-permeability material, such as silicon steel sheet. Thus, the inductor housing can also function as a shielding medium, enclosing the inductor coil and further reducing EMC interference.

[0165] 29 is a schematic diagram of a charging loop and a discharging loop generating interference in a three-phase Vienna rectifier circuit according to some embodiments.

[0166] In some embodiments, as shown in FIG29 , in a three-phase Vienna rectifier circuit 1000, the area surrounded by the thick black line is the EMC interference area 70. Interference sources can be divided into two categories: one is the discharge interference of the inductor, corresponding to the discharge loop represented by the dotted arrow, and the other is the charging interference of the inductor, corresponding to the charging loop represented by the dotted arrow. According to formula (7), because the magnitude of the current frequency F and the current effective value Iy cannot be changed, therefore, in the process involving the printed circuit board (PCB), it is necessary to minimize the area of ​​the interference source as much as possible.

[0167] Therefore, the first rectifier diode D1, the first capacitor C1, the second capacitor C2, the fifth rectifier diode D5, and the sixth rectifier diode D6 are connected in sequence to form a discharge circuit, which needs to be small in area. The circuit from point A through the first power switch group Sa to the midpoint O forms a charging circuit, which also needs to be small in area.

[0168] By analogy, another discharge circuit composed of the second rectifier diode D2, the first capacitor C1, the second capacitor C2, the fourth rectifier diode D4 and the sixth rectifier diode D6, another discharge circuit composed of the third rectifier diode D3, the first capacitor C1, the second capacitor C2, the fourth rectifier diode D4 and the fifth rectifier diode D5, another charging circuit composed of point B, the second power switch group Sb and the midpoint O, and another charging circuit composed of point C, the third power switch group Sc and the midpoint O also need to have a smaller area.

[0169] Figure 30 is a structural diagram of a printed circuit board of a three-phase Vienna rectifier circuit according to some embodiments. Figure 30 only shows a partial circuit structure of the three-phase Vienna rectifier circuit 1000.

[0170] In some embodiments, as shown in FIG30 , the three-phase Vienna rectifier circuit 1000 further includes a power integrated module (Converter-Inverter-Braker, CIB) 100. The power integrated module 100 is a module formed by integrating a rectifier diode and a power switch group to minimize EMC interference. The power switch group is arranged in the innermost layer of the power integrated module 100. It should be noted that the power integrated module 100 can also be called an intelligent power module (IPM), which can be composed of one or more IGBTs. The area 1001 indicated by the dotted box in FIG30 is the area where the power switch group is located.

[0171] Because the power switch group in power integrated module 100 is the core component of the charging circuit, it generates the greatest EMC interference. Therefore, the power switch group can be placed in the innermost layer of the power integrated module (i.e., the charging circuit corresponding to the power switch group is surrounded by other circuits in power integrated module 100) to minimize the area occupied by the charging circuit of three-phase Vienna rectifier circuit 1000 on the PCB.

[0172] In some embodiments, as shown in FIG30 , the DC positive output terminal DC+ of the power integrated module 100 is connected to the positive terminal 1002 of the capacitor circuit 104 (corresponding to point F1 in FIG2 ) through the first terminal group CN1 and the first jumper 81 , thereby wiring the core components in the discharge circuit of the inductor to minimize the discharge circuit.

[0173] For example, as shown in FIG30 , the DC positive output terminal DC+ of the power integrated module 100 includes a first DC positive output terminal DC1+ and a second DC positive output terminal DC2+, and the first terminal group CN1 includes a first external terminal CN12 and a second external terminal CN13. The first DC positive output terminal DC1+ is connected to the second external terminal CN13, and the positive terminal 1002 of the capacitor circuit 104 is connected to the first external terminal CN12. The first external terminal CN12 and the second external terminal CN13 are connected via a first jumper 81. The second DC positive output terminal DC2+ is connected to the first DC positive output terminal DC1+. The first capacitor C1 is located between the second DC positive output terminal DC2+ and the first DC positive output terminal DC1+, thereby reducing the wiring between the second DC positive output terminal DC2+ and the first DC positive output terminal DC1+, thereby minimizing the discharge loop.

[0174] In some embodiments, the DC negative output terminal DC- of the power integrated module 100 can be connected to the negative terminal 1003 of the capacitor circuit 104 (corresponding to point F2 in Figure 2) through the second terminal group CN2 and the second jumper 82, thereby wiring the core components in the discharge circuit of the inductor to minimize the discharge circuit.

[0175] For example, as shown in FIG30 , the DC negative output terminal DC- of the power integrated module 100 includes a first DC negative output terminal DC1- and a second DC negative output terminal DC2-, and the second terminal group CN2 includes a third external terminal CN11 and a fourth external terminal CN10. The second DC negative output terminal DC2- is connected to the fourth external terminal CN10, and the negative terminal 1003 of the capacitor circuit 104 is connected to the third external terminal CN11. The third external terminal CN11 and the fourth external terminal CN10 are connected via a second jumper 82. The second DC negative output terminal DC2- is connected to the first DC negative output terminal DC1-. The second capacitor C2 is located between the second DC negative output terminal DC2- and the first DC negative output terminal DC1-, thereby reducing the wiring between the second DC negative output terminal DC2 and the first DC negative output terminal DC1-, thereby minimizing the discharge loop.

[0176] 31 is a schematic diagram illustrating magnetic fields of a first trace and a second trace in a three-phase Vienna rectifier circuit according to some embodiments.

[0177] In some embodiments, a first jumper 81 connected to the positive terminal 1002 of the capacitor circuit 104 and a second jumper 82 connected to the negative terminal 1003 of the capacitor circuit 104 are arranged in a cross-route. For example, as shown in Figures 30 and 31, the first jumper 81 connected to the positive terminal 1002 of the capacitor circuit 104 and the second jumper 82 connected to the negative terminal 1003 of the capacitor circuit 104 are arranged in a cross-route, so that the magnetic fields generated by the two can cancel each other out, thereby reducing EMC interference. In Figure 31, the first mark 83 represents the first direction of the magnetic field, the second mark 84 represents the second direction of the magnetic field, and the arrows represent the direction of current, with the first direction being opposite to the second direction.

[0178] 32 is a schematic diagram of a printed wiring board of a three-phase Vienna rectifier circuit according to some embodiments.

[0179] In some embodiments, the capacitor circuit 104 may surround the power integrated module 100. For example, as shown in FIG32 , multiple capacitors (such as a first capacitor C1 and a second capacitor C2) surround the power integrated module 100 to limit the interference range to a small area as much as possible.

[0180] In some embodiments of the present disclosure, by adjusting the PFC inductor and the PCB layout process, the EMC interference problem of the high-power three-phase Vienna rectifier circuit can be solved, so that the three-phase Vienna rectifier circuit can be applied to the central air-conditioning system.

[0181] Some embodiments of the present disclosure also provide a design method for a three-phase Vienna rectifier circuit, which is applied to the above-mentioned three-phase Vienna rectifier circuit 1000. The method includes: based on the switching states of the three power switch groups, equating each phase branch in the three-phase Vienna rectifier circuit to an equivalent circuit consisting of a single-phase AC power supply, an equivalent inductor, an equivalent rectifier diode, an equivalent capacitor, and a switch; determining the inductance of the equivalent inductor based on the relationship between the inductance of the equivalent inductor and the duty cycle of the switch, the power supply voltage, the change in peak current, and the switching frequency of the switch; determining the maximum energy storage of the equivalent inductor based on the inductance of the equivalent inductor; and determining the magnetic core material and structure of the equivalent inductor based on the maximum energy storage of the equivalent inductor, and calculating the number of turns of the inductor coil.

[0182] In some embodiments, based on the switching states of the three power switch groups, each phase branch in the three-phase Vienna rectifier circuit is equivalent to an equivalent circuit consisting of a single-phase AC power supply, an equivalent inductor, an equivalent rectifier diode, an equivalent capacitor, and a switch. This includes: dividing the voltage of the three-phase AC input terminal into multiple intervals based on the conditions that the voltages of two-phase AC input terminals are positive and the voltage of one-phase AC input terminal is negative at the same time, or the voltages of two-phase AC input terminals are negative and the voltage of one-phase AC input terminal is positive at the same time; selecting any interval and equating the three-phase Vienna rectifier circuit with the multiple switching states of the three power switch groups to obtain multiple operating states of the three-phase Vienna rectifier circuit; based on the multiple operating states of the three-phase Vienna rectifier circuit, equating each phase branch in the three-phase Vienna rectifier circuit to an equivalent circuit consisting of the single-phase AC power supply, the equivalent inductor, the equivalent rectifier diode, the equivalent capacitor, and the switch.

[0183] In some embodiments, the method includes: determining the peak current based on the power, power factor and line voltage of the three-phase AC input terminal; the line voltage is any value within a set range.

[0184] In some embodiments, the method further includes: determining a saturation current of the inductor according to an anti-saturation parameter, the peak current, and a change in the peak current.

[0185] In some embodiments, the method further comprises: after determining the selection of the equivalent inductor, calculating the magnetic field strength of the equivalent inductor after DC bias according to the equivalent circuit; and adjusting the structure of the equivalent inductor according to the magnetic field strength after DC bias and the initial magnetic permeability corresponding to the magnetic field strength. The anti-saturation parameter is greater than 1.

[0186] In some embodiments, the method further includes: after determining the selection of the equivalent inductor, calculating the magnetic field strength of the equivalent inductor after DC bias according to the equivalent circuit; and adjusting the structure of the equivalent inductor according to the magnetic field strength after DC bias and the initial magnetic permeability corresponding to the magnetic field strength.

[0187] In some embodiments, the method further includes: calculating the window filling coefficient of the equivalent inductor after calculating the number of turns of the inductor coil of the equivalent inductor; and adjusting the structure of the equivalent inductor so that the window filling coefficient of the equivalent inductor is less than or equal to a set coefficient.

[0188] In some embodiments, the method further includes: determining a voltage swing point in the three-phase Vienna rectifier circuit; and placing an end of the inductor coil connected to the voltage swing point in an inner layer of the magnetic core. The voltage swing point is the transition point where the voltage in the three-phase Vienna rectifier circuit changes from zero to half the voltage at the single-phase AC input terminal.

[0189] In some embodiments, determining the voltage rotating point in the three-phase Vienna rectifier circuit includes: determining a transition point where the voltage in the equivalent circuit changes from zero to half the voltage of the single-phase AC input terminal as the voltage rotating point.

[0190] It should be noted that the details of the steps in the above method can be found in the relevant content of the steps executed by the controller 2000 in the above text, and will not be repeated here. In addition, some embodiments of the present disclosure are not limited to the order of the steps described above. Those skilled in the art may change the order of the steps described above according to actual needs, or may omit one or more of the steps described above, or may add one or more steps to the steps described above.

[0191] Some embodiments of the present disclosure further provide an air conditioner, comprising the three-phase Vienna rectifier circuit 1000 in the three-phase Vienna rectifier system 1 described above. It is understood that the design method of the three-phase Vienna rectifier circuit in the three-phase Vienna rectifier system 1 in some embodiments of the present disclosure can be applied to the air conditioner.

[0192] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0193] Those skilled in the art will understand that the scope of the present disclosure is not limited to the above specific embodiments, and that certain elements of the embodiments may be modified and replaced without departing from the spirit of the present disclosure. The scope of the present disclosure is limited by the appended claims.

Claims

1. A three-phase Vienna rectifier circuit comprising: Three-phase AC input terminal; three inductors, respectively coupled to the three-phase AC input terminals, the inductors comprising a magnetic core and an inductor coil, the inductor coil being wound around the magnetic core; three power switch groups, coupled to the three inductors respectively; a first capacitor; a second capacitor connected in series with the first capacitor to form a capacitive circuit; three first-type rectifier diodes, corresponding to the three inductors respectively, wherein the first-type rectifier diodes are coupled between the output end of the corresponding inductor and the input end of the first capacitor; as well as three second-type rectifier diodes, corresponding to the three inductors respectively, the second-type rectifier diodes being coupled between the output end of the corresponding inductor and the output end of the second capacitor; Among them, one end of the inductor's inductor coil connected to the voltage dynamic point is arranged in the inner layer of the magnetic core; the voltage dynamic point is the transition point where the voltage in the three-phase Vienna rectifier circuit changes from zero to half the voltage of the single-phase AC input end.

2. The three-phase Vienna rectifier circuit according to claim 1, wherein: The three-phase Vienna rectifier circuit also includes a power integrated module. The rectifier diodes and the power switch group in the three-phase Vienna rectifier circuit are integrated to form the power integrated module; the three power switch groups are arranged in the innermost layer of the power integrated module to minimize the area of ​​the charging loop in the three-phase Vienna rectifier circuit.

3. The three-phase Vienna rectifier circuit according to claim 2, wherein: The DC positive output terminal of the power integrated module is connected to the positive terminal of the capacitor circuit through a first terminal group and a first jumper; The DC negative output terminal of the power integrated module is connected to the negative terminal of the capacitor circuit via a second terminal group and a second jumper.

4. The three-phase Vienna rectifier circuit according to claim 3, wherein: The DC positive output terminal includes: a first DC positive output terminal; and a second DC positive output terminal connected to the first DC positive output terminal, wherein the first capacitor is located between the second DC positive output terminal and the first DC positive output terminal; The first terminal group includes: a first external terminal connected to the positive terminal of the capacitor circuit; and The second external terminal is connected to the first DC positive output terminal, and the first external terminal and the second external terminal are connected via the first jumper.

5. The three-phase Vienna rectifier circuit according to claim 3, wherein: The DC negative output terminal includes: a first DC negative output terminal; and a second DC negative output terminal connected to the first DC negative output terminal, wherein the second capacitor is located between the second DC negative output terminal and the first DC negative output terminal; The second terminal group includes: a third external terminal connected to the negative terminal of the capacitor circuit; and The fourth external terminal is connected to the second DC negative output terminal, and the third external terminal and the fourth external terminal are connected via the second jumper.

6. The three-phase Vienna rectifier circuit according to claim 3, wherein: The first jumper wire and the second jumper wire are arranged crosswise.

7. The three-phase Vienna rectifier circuit according to any one of claims 2 to 6, wherein: The capacitor circuit surrounds the power integrated module.

8. The three-phase Vienna rectifier circuit according to any one of claims 1 to 7, wherein: The three-phase Vienna rectifier circuit further includes a shielding cover, wherein the shielding cover covers at least one inductor; The shielding cover satisfies one of the following conditions: The shielding cover is made of nickel-zinc ferrite; and, The shielding cover is made of stainless steel and nickel silver, and a conductive material is provided between the shielding cover and the inductor.

9. The three-phase Vienna rectifier circuit according to claim 8, wherein: The shielding cover covers the three inductors.

10. The three-phase Vienna rectifier circuit according to any one of claims 1 to 9, wherein: The shell of the inductor is made of low magnetic permeability material.

11. A design method for a three-phase Vienna rectifier circuit, wherein: The three-phase Vienna rectifier circuit comprises: Three-phase AC input terminal; three inductors, respectively coupled to the three-phase AC input terminals, the inductors comprising a magnetic core and an inductor coil, the inductor coil being wound around the magnetic core; three power switch groups, coupled to the three inductors respectively; a first capacitor; a second capacitor connected in series with the first capacitor to form a capacitive circuit; three first-type rectifier diodes, corresponding to the three inductors respectively, wherein the first-type rectifier diodes are coupled between the output end of the corresponding inductor and the input end of the first capacitor; and three second-type rectifier diodes, corresponding to the three inductors respectively, the second-type rectifier diodes being coupled between the output end of the corresponding inductor and the output end of the second capacitor; The method comprises: According to the switching states of the three power switch groups, each phase branch in the three-phase Vienna rectifier circuit is equivalent to an equivalent circuit consisting of a single-phase AC power supply, an equivalent inductor, an equivalent rectifier diode, an equivalent capacitor, and a switch; the single-phase AC power supply, the equivalent inductor, the equivalent rectifier diode, and the equivalent capacitor are connected in series to form a loop, one end of the switch is coupled to the anode of the equivalent rectifier diode, and the other end is coupled to the negative electrode of the equivalent capacitor; the equivalent inductor corresponds to any one of the three inductors; the single-phase AC power supply is any single-phase AC input terminal of the three-phase AC input terminals; The inductance of the equivalent inductor is determined according to a relationship between the inductance of the equivalent inductor and a duty cycle of the switch, a power supply voltage, a change in peak current, and a switching frequency of the switch; the power supply voltage is an input voltage of the single-phase AC power supply; determining a maximum stored energy of the equivalent inductor according to the inductance of the equivalent inductor; and According to the maximum energy storage of the equivalent inductor, the magnetic core material and structure of the equivalent inductor are determined, and the number of turns of the inductor coil is calculated.

12. The method according to claim 11, wherein According to the switching states of the three power switch groups, each phase branch in the three-phase Vienna rectifier circuit is equivalent to an equivalent circuit consisting of a single-phase AC power supply, an equivalent inductor, an equivalent rectifier diode, an equivalent capacitor and a switch, including: Dividing the voltage of the three-phase AC input terminal into a plurality of intervals based on the conditions that the voltages of the two-phase AC input terminals are positive and the voltage of one-phase AC input terminal is negative at the same time, or the voltages of the two-phase AC input terminals are negative and the voltage of one-phase AC input terminal is positive at the same time; Select any interval and respectively use the multiple switch states of the three power switch groups as conditions to equalize the three-phase Vienna rectifier circuit to obtain multiple working states of the three-phase Vienna rectifier circuit; and According to various working states of the three-phase Vienna rectifier circuit, each phase branch in the three-phase Vienna rectifier circuit is equivalent to an equivalent circuit consisting of the single-phase AC power supply, the equivalent inductor, the equivalent rectifier diode, the equivalent capacitor and the switch.

13. The method according to claim 11 or 12, wherein: The method comprises: The peak current is determined according to the power, power factor and line voltage of the three-phase AC input terminal; the line voltage is any value within a set range.

14. The method according to any one of claims 11 to 13, wherein The method further comprises: determining a saturation current of the inductor according to an anti-saturation parameter, the peak current, and a change in the peak current; Wherein, the anti-saturation parameter is greater than 1.

15. The method according to any one of claims 11 to 14, wherein The method further comprises: After determining the selection of the equivalent inductor, Calculating the magnetic field strength of the equivalent inductor after DC bias according to the equivalent circuit; and The structure of the equivalent inductor is adjusted according to the magnetic field strength after the DC bias and the initial magnetic permeability corresponding to the magnetic field strength.

16. The method according to any one of claims 11 to 15, wherein The method further comprises: After calculating the number of turns of the inductor coil of the equivalent inductor, calculating the window filling factor of the equivalent inductor; and The structure of the equivalent inductor is adjusted so that the window filling factor of the equivalent inductor is less than or equal to a set factor.

17. The method according to any one of claims 11 to 16, wherein The method further comprises: Determining a voltage dynamic point in the three-phase Vienna rectifier circuit; the voltage dynamic point is a transition point where the voltage in the three-phase Vienna rectifier circuit changes from zero to half the voltage at the single-phase AC input terminal; One end of the inductor coil connected to the voltage moving point is arranged in the inner layer of the magnetic core.

18. The method according to claim 17, wherein Determining the voltage moving point in the three-phase Vienna rectifier circuit includes: A transition point where the voltage in the equivalent circuit changes from zero to half the voltage of the single-phase AC input terminal is determined as the voltage moving point.

19. The method according to any one of claims 11 to 18, wherein The variation of the peak current is any value within a preset range.

20. An air conditioner comprising the three-phase Vienna rectifier circuit according to any one of claims 1 to 10, wherein: The design method of the three-phase Vienna rectifier circuit according to any one of claims 11 to 19 is applicable to the air conditioner.

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