A transformer suitable for common mode noise suppression of a multi-level converter

Abstract

The present application relates to a kind of transformer suitable for multilevel converter common mode noise suppression, the transformer includes main magnetic core and auxiliary magnetic core;Primary winding and balance winding are wound around the main magnetic core of the transformer;Primary auxiliary winding and secondary auxiliary winding are wound around the auxiliary magnetic core of the transformer.The principle of realizing common mode noise suppression of the present application is to introduce a cancellation voltage opposite in phase with the noise voltage of the primary winding of the transformer, to generate a reverse phase displacement current to offset the displacement current caused by the primary winding of the transformer, so as to realize the suppression of common mode noise.

Description

Technical Field

[0001] This invention relates to a transformer suitable for common-mode noise suppression in multilevel converter topologies, belonging to the field of power conversion. Background Technology

[0002] Multilevel converters, as one of the core technologies of modern power electronics, play an irreplaceable role in the field of high-voltage, high-power power conversion. Compared with traditional two-level converters, multilevel structures, through stepped output waveforms, not only significantly reduce the voltage stress on individual switching devices, making it possible to achieve high-voltage, high-power conversion using medium- and low-voltage devices, but also significantly reduce voltage slew rate and total harmonic distortion, while also possessing the ability to adapt to a wide range of input or output voltages. Based on these characteristics, multilevel topologies exhibit significant technical advantages and development potential in high-voltage, wide-gain application scenarios.

[0003] Distributed capacitance in transformers is one of the main transmission paths for common-mode conducted noise. Optimizing noise sources in transformer windings, aiming to reduce common-mode current at its source, is a classic technique for suppressing common-mode conducted noise at its source in the early stages. However, most existing suppression methods are applied to two-level topologies such as full-bridge and half-bridge, and the traditional method of noise cancellation through symmetrical circuits is mainly based on the consistency of the impedances of the two paths and the symmetry of the two separate noise sources in the two-level topology. However, this method is not effective in multi-level topologies. The following example illustrates this using LLC resonant converters employing full-bridge and series half-bridge topologies respectively: exist Figure 1 In the middle, the switching transistor Q 2. Q The voltage at the drain of pin 4 relative to the input ground is one of the two noise sources that cause common-mode interference. v A and v B The method of suppressing common-mode noise caused by the primary winding of the transformer is adopted using a symmetrical resonant inductor. v P The waveform is as follows Figure 2 As shown. Due to the full-bridge topology v A and v B With complementary waveforms, the common-mode noise in the transformer cancels out each other when using the symmetrical resonant inductor suppression method, achieving a better suppression effect.

[0004] exist Figure 3 In the series half-bridge topology shown, the switching transistors Q 2. Drain voltage to ground v A exist V in With 0.5V in The switching transistor jumps between these states. Q 4-Drain voltage to ground v B Then at 0.5 V in The signal jumps between zero and 0. At this point, even with suppression using a symmetrical resonant inductor, the equivalent common-mode noise source generated by the transformer's primary winding remains. v P The waveform is as follows Figure 4 As shown. Therefore, it can be seen that, due to this topology... v A and v B The waveforms are not complementary, and the symmetrical resonant inductor cannot effectively cancel the common-mode noise.

[0005] In multilevel topologies, noise sources are composed of multiple asymmetrically varying voltage levels, making it difficult to achieve ideal noise cancellation results using traditional symmetrical circuit structures. Furthermore, due to the inconsistency between the common-mode and differential-mode voltage waveforms on the transformer windings in multilevel circuits, waveform cancellation methods based on balanced windings have limited effectiveness in suppressing noise in such topologies. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a transformer that achieves common-mode noise suppression and is suitable for multilevel converter topologies.

[0007] To achieve the above objectives, the technical solution proposed by this invention is as follows: a transformer suitable for common-mode noise suppression in a multilevel converter, the transformer comprising a main magnetic core and an auxiliary magnetic core; a primary winding and a balancing winding are wound around the main magnetic core, and a primary auxiliary winding and a secondary auxiliary winding are wound around the auxiliary magnetic core; the two ends of the primary winding are connected to the multilevel converter; the midpoint of the primary winding is connected to one end of the primary auxiliary winding via a capacitor, and the other end of the primary auxiliary winding is connected to the input circuit ground; one end of the secondary auxiliary winding is connected to the midpoint of the balancing winding, and the other end of the secondary auxiliary winding is connected to the input circuit ground; the end of the primary auxiliary winding connected to the primary winding and the grounded end of the secondary auxiliary winding are of the same name.

[0008] A further design of the above technical solution is as follows: the midpoint voltage amplitude of the primary winding is V P The voltage amplitude across the capacitor between the midpoint of the primary winding and the endpoint of the primary auxiliary winding is V C The midpoint voltage amplitude of the balancing winding V PBsatisfy: ; in: N a1 , N a2 These are the number of turns in the primary auxiliary winding and the secondary auxiliary winding, respectively.

[0009] The main magnetic core and the auxiliary magnetic core are two independent magnetic cores; or the main magnetic core and the auxiliary magnetic core are the same magnetic core.

[0010] A preferred embodiment of the above technical solution is as follows: the transformer further includes a floating ground structure, and the lumped parasitic capacitance between the midpoint of the primary winding and the floating ground structure is... C PF The lumped parasitic capacitance between the midpoint of the balancing winding and the floating structure is C PBF The primary winding and the balance winding have the same winding shape, opposite winding directions, and the same number of turns, making... C PF and C PBF Consistent.

[0011] Another preferred embodiment of the above technical solution is: the main magnetic core is further wound with a secondary winding, and the lumped parasitic capacitance between the midpoint of the primary winding and the midpoint of the secondary winding is... C PS The lumped parasitic capacitance between the midpoint of the balancing winding and the midpoint of the secondary winding is C PBS The primary winding and the balance winding have the same winding shape, opposite winding directions, and the same number of turns, making... C PS and C PBS Consistent.

[0012] The primary winding, balance winding, primary auxiliary winding, and secondary auxiliary winding are made of PCB substrate, solid wire, Litz wire, or copper foil.

[0013] The application topologies of the multilevel converter include series half-bridge topology, module cascade topology, diode clamping type, flying capacitor clamping type, or hybrid multilevel topology.

[0014] Another implementation of the above-mentioned transformer for common-mode noise suppression of multilevel converters is as follows: the transformer includes a main magnetic core and an auxiliary magnetic core with the same structure; a primary winding and a primary auxiliary winding with the same structure are wound around the main magnetic core and the auxiliary magnetic core respectively, and the primary winding and the primary auxiliary winding are respectively connected to multilevel converters with equal voltage magnitude and opposite phase.

[0015] The primary winding and primary auxiliary winding are made of PCB substrate, solid wire, Litz wire or copper foil.

[0016] The application topologies of the multilevel converter include series half-bridge topology, module cascade topology, diode clamping type, flying capacitor clamping type, or hybrid multilevel topology.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The transformer of the present invention, by designing an auxiliary magnetic core and a primary auxiliary winding, forms an auxiliary anti-phase transformer, which can convert the midpoint of the equivalent noise source of the primary winding into a potential point with equal amplitude and opposite phase, and introduce it into a balance winding that is symmetrical with the primary winding structure, thereby canceling the displacement current generated by the primary winding and realizing common-mode noise suppression.

[0018] 2. This invention utilizes the noise source in the circuit to construct another voltage source with equal amplitude and opposite phase, thereby canceling the suppression method of displacement current. It is not affected by changes in circuit topology waveform and can be applied to two-level and multi-level topologies, thus having versatility. Attached Figure Description

[0019] Figure 1 This is a circuit structure diagram of a traditional symmetrical circuit suppression method applied to a full-bridge topology. Figure 2 The waveform suppression effect of traditional symmetrical circuit suppression methods on interference sources in a full-bridge topology application is shown in the figure. Figure 3 The circuit structure diagram is shown for the application of traditional symmetrical circuit suppression methods in a series half-bridge topology. Figure 4 The waveform suppression effect of traditional symmetrical circuit suppression methods on interference sources in a series half-bridge topology application is shown in the figure. Figure 5 This is a schematic diagram of the circuit and transformer using the series half-bridge topology in Example 1; Figure 6 This is a simplified schematic diagram of the common-mode noise conduction path in Example 1; Figure 7 This is a schematic diagram of the circuit and transformer using the series half-bridge topology in Example 2; Figure 8 This is a simplified schematic diagram of the common-mode noise conduction path in Example 2; Figure 9 This is a schematic diagram of the circuit and transformer using the series half-bridge topology in Example 3; Figure 10 This is a simplified schematic diagram of the common-mode noise conduction path in Example 3; Figure 11This is a schematic diagram of the circuit and transformer used in Example 4, which employs a hybrid full-bridge multilevel topology. Figure 12 To verify the common-mode noise spectrum of the present invention on an LLC resonant converter with a series half-bridge topology in Example 1; Detailed Implementation

[0020] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be arbitrarily combined with each other. Furthermore, the magnetic core of the transformer involved in the embodiments of the present invention can be made of ferromagnetic materials such as silicon steel sheets, ferrite, microcrystalline, ultracrystalline, permalloy, or iron-cobalt-vanadium, etc., and the windings can be made of solid wire, Litz wire, copper foil, or PCB coils. However, the present application does not limit the specific materials of the transformer and windings. Example 1

[0021] Figure 5 As the preferred implementation scheme for the transformer suitable for common-mode noise suppression in multilevel converters proposed in this embodiment, the multilevel converter adopts a series half-bridge topology; the transformer includes a main magnetic core 1 and an auxiliary magnetic core 2; a primary winding 1a, a balancing winding 1b, and a secondary winding 1c are wound around the main magnetic core 1 of the transformer, and the number of turns of the primary winding 1a and the balancing winding 1b are respectively... N 1, N 2; A primary auxiliary winding 2a and a secondary auxiliary winding 2b are wound around the transformer auxiliary magnetic core 2, the number of turns of the primary auxiliary winding 2a and the secondary auxiliary winding 2b being respectively N a1 , N a2 The two ends of the primary winding 1a are respectively connected to the primary side resonant inductor. L r and primary side resonant capacitor C r Connected to a multilevel converter; diodes are connected to both ends of the secondary winding 1c. D 1 and D 2. Positive terminal of diode D 1 and D The negative terminal of winding 2 is connected to the midpoint of the secondary winding 1c. R L And the midpoint of the secondary winding 1c is connected to a capacitor. C S Grounding.

[0022] Specifically, the midpoint of the primary winding 1a P Through capacitor C 1 and one end of the primary auxiliary winding 2a S AThe primary auxiliary winding 2a is connected to the input circuit ground, and one end of the secondary auxiliary winding 2b is connected to the input circuit ground. S B Midpoint of the balancing winding 1b P B The other end of the secondary auxiliary winding 2b is also connected to the input circuit ground. The endpoints of the primary auxiliary winding 2a... S A The terminals that are grounded with the secondary auxiliary winding 2b are terminals with the same name.

[0023] Specifically, the main magnetic core 1 and the auxiliary magnetic core 2 are two independent magnetic cores, and are housed in two separate transformers. Electrically, the voltage amplitude at the midpoint of the primary winding 1a is set to... V P ,capacitance C The voltage amplitude at both ends is V C The voltage amplitude at the midpoint of the balancing winding 1b is... V PB The following relationship must be satisfied to reduce capacitance. C The impact of 1: .

[0024] Specifically, the midpoint of the primary winding 1a P and the midpoint of the secondary winding 1c S The lumped parasitic capacitance between them is C PS The midpoint of the balancing winding 1b P B and the midpoint of the secondary winding 1c S The lumped parasitic capacitance between them is C PBS To ensure C PS and C PBS To compensate for the common-mode noise generated by the primary winding, the winding shape and number of turns of the primary winding 1a and the balancing winding 1b must be the same, and their winding directions must be opposite. Under this condition, based on the star-delta equivalent transformation of the capacitor, the noise source... v P and v PB The common-mode noise simplified conduction path can be as follows Figure 6 Further simplification. At this point, the equivalent parasitic capacitance... C X and C Y The total displacement current generated by the converter is equal to: .

[0025] The transformer proposed in this embodiment, suitable for common-mode noise suppression in multi-level topologies, can be applied not only to series half-bridge topologies, but also to module cascade topologies, diode clamped topologies, flying capacitor clamped topologies, and hybrid multi-level topologies combining different types of topologies. Example 2

[0026] Figure 7 This is another implementation circuit for the transformer proposed in this embodiment for common-mode noise suppression in multi-level topologies. The converter adopts a series half-bridge topology, and the structure of this embodiment is basically the same as that of Embodiment 1. The difference is that the main magnetic core 1 is only wound with the primary winding 1a and the balance winding 1b, and does not include the secondary winding, but there is a floating ground structure 3. In addition, the main magnetic core 1 and the auxiliary magnetic core 2 are the same magnetic core, that is, the main magnetic core 1 and the auxiliary magnetic core 2 are decoupled and integrated in the same transformer.

[0027] Specifically, the midpoint P of the primary winding 1a is connected to a capacitor. C 1 and one end of the primary auxiliary winding 2a S A The primary auxiliary winding 2a is connected to the input circuit ground, and one end of the secondary auxiliary winding 2b is connected to the input circuit ground. S B Midpoint of the balancing winding 1c P B The other end of the secondary auxiliary winding 2b is also connected to the input circuit ground. The endpoints of the primary auxiliary winding 2a... S A The terminals that are grounded with the secondary auxiliary winding 2b are terminals with the same name.

[0028] Specifically, in terms of electrical relationships, the voltage amplitude at the midpoint of the primary winding 1a is set to be... V P ,capacitance C The voltage amplitude at both ends is V C The voltage amplitude at the midpoint of the balancing winding 1b is... V PB The relationship needs to be satisfied to reduce capacitance. C The impact of 1: ; Specifically, the midpoint of the primary winding 1a P The lumped parasitic capacitance between the ground structure 3 and the floating structure 3 is C PF The midpoint of the balancing winding 1b P B The lumped parasitic capacitance between the ground structure 3 and the floating structure 3 is C PBF The primary winding 1a and the balance winding 1b have the same winding shape, but opposite winding directions and different number of turns.N 1 and N 2. Same to ensure C PF and C PBF Consistent, canceling common-mode noise between the primary winding and the floating ground structure.

[0029] Under this condition, the star-delta equivalent transformation based on capacitance, noise source v P and v PB The common-mode noise simplified conduction path can be as follows Figure 8 Further simplification. At this point, the equivalent parasitic capacitance... C X' and C Y' The total displacement current generated by the converter is equal to: .

[0030] The transformer proposed in this embodiment for common-mode noise suppression in multilevel topologies can also be applied to other types of multilevel topologies. Example 3

[0031] Figure 9 This is another implementation scheme for the transformer proposed in this embodiment for common-mode noise suppression in multi-level topologies. The converter adopts a series half-bridge topology, and the structure of this embodiment is basically the same as that of Embodiment 1. The difference is that the main magnetic core 1 is wound with only the primary winding, excluding the secondary winding and the balancing winding, but there is a floating ground structure 3; in addition, the auxiliary magnetic core 2 is wound with only the primary auxiliary winding, excluding the secondary auxiliary winding; there is no circuit connection between the primary winding 1a and the primary auxiliary winding 2a. The primary winding 1a and the primary auxiliary winding 2a are respectively connected to a series half-bridge topology as input sources. The two input sources are equal in magnitude and opposite in phase.

[0032] Specifically, the midpoint of the primary winding 1a P The lumped parasitic capacitance between the ground structure 3 and the floating structure 3 is C PF The midpoint of the primary auxiliary winding 2a P B The lumped parasitic capacitance between the ground structure 3 and the floating structure 3 is C PBF The primary winding 1a and the primary auxiliary winding 2a have the same winding shape and direction, and the number of turns is the same. N 1 and N 2. Same to ensure C PF and C PBF Consistent, only input source v AB andv ab The magnitudes are equal, but the phases are opposite. This ensures that the noise source... v P and v PB They are equal in size but opposite in phase to cancel common-mode noise between the primary winding and the floating ground structure.

[0033] Under this condition, the star-delta equivalent transformation based on capacitance, noise source v P and v PB The simplified conduction path for common-mode noise can be similarly described in Example 2. Figure 8 The form is further simplified, specifically as follows: Figure 10 As shown. At this point, the equivalent parasitic capacitance... C X' and C Y' The total displacement current generated by the converter is equal to: .

[0034] The transformer proposed in this embodiment for common-mode noise suppression in multilevel topologies can also be applied to other types of multilevel topologies. Example 4

[0035] Figure 11 This is another implementation scheme for the transformer suitable for common-mode noise suppression in multi-level topologies proposed in this embodiment. This embodiment has the same structure as Embodiment 1, except that the multi-level converter used is a hybrid full-bridge multi-level topology. Verification example:

[0036] This verification example uses the method described in Example 1. Figure 5 The circuit structure shown was experimentally verified.

[0037] L r — Primary side resonant inductor C r —Primary-side resonant capacitor. The circuit parameters are: inverter circuit input voltage. V in It is 800V, rated output power 100W, and switching frequency 140kHz; L r = 40μH, C r = 25nF; primary winding has 6 turns, secondary winding is a full-wave winding with 3 turns. The inverter circuit uses a controllable switching transistor... Q 1. Q 2.Q 3. Q The model number of 4 is C3M0025065D.

[0038] Figure 12 This demonstrates the difference between conventional suppression methods for existing symmetrical circuits and the method proposed in Example 1. Figure 5 The common-mode noise spectrum comparison is shown in the series half-bridge topology. The switching transistors used are... Figure 4 The driving method shown uses DMR96A magnetic core material. The red curve in the figure corresponds to the common-mode noise of the converter when using the traditional symmetrical circuit suppression method, while the blue curve represents the common-mode noise when using the transformer proposed in this invention.

[0039] As can be seen from the comparison, at the switching frequency of 140kHz and its multiple harmonics, the common-mode noise of the method of the present invention is significantly reduced, with a maximum reduction of about 20dB compared with the traditional method, indicating that it has a better common-mode noise suppression effect.

[0040] Those skilled in the art will understand that all or part of the steps in the above methods can be implemented by a program instructing related hardware, and the program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk. Optionally, all or part of the steps in the above embodiments can also be implemented using one or more integrated circuits. Accordingly, each module / unit in the above embodiments can be implemented in hardware or as a software functional module. This application is not limited to any particular combination of hardware and software.

[0041] The above-described design examples of rotary transformers are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A transformer suitable for common-mode noise suppression in multilevel converters, characterized in that: The transformer includes a main magnetic core and an auxiliary magnetic core; a primary winding and a balancing winding are wound around the main magnetic core, and a primary auxiliary winding and a secondary auxiliary winding are wound around the auxiliary magnetic core. The two ends of the primary winding are connected to a multilevel converter; the midpoint of the primary winding is connected to one end of the primary auxiliary winding through a capacitor, and the other end of the primary auxiliary winding is connected to the input circuit ground; one end of the secondary auxiliary winding is connected to the midpoint of the balancing winding, and the other end of the secondary auxiliary winding is connected to the input circuit ground; the end of the primary auxiliary winding connected to the primary winding and the grounded end of the secondary auxiliary winding are of the same name.

2. The transformer for common-mode noise suppression in multilevel converters according to claim 1, characterized in that: The midpoint voltage amplitude of the primary winding is V P The voltage amplitude across the capacitor between the midpoint of the primary winding and the endpoint of the primary auxiliary winding is V C The midpoint voltage amplitude of the balancing winding V PB satisfy: ； in: N a1 , N a2 These are the number of turns in the primary auxiliary winding and the secondary auxiliary winding, respectively.

3. The transformer for common-mode noise suppression in multilevel converters according to claim 2, characterized in that: The main magnetic core and the auxiliary magnetic core are two independent magnetic cores; or the main magnetic core and the auxiliary magnetic core are the same magnetic core.

4. The transformer for common-mode noise suppression in multilevel converters according to claim 3, characterized in that: The transformer also includes a floating ground structure, and the lumped parasitic capacitance between the midpoint of the primary winding and the floating ground structure is: C PF The lumped parasitic capacitance between the midpoint of the balancing winding and the floating structure is C PBF The primary winding and the balance winding have the same winding shape, opposite winding directions, and the same number of turns, making... C PF and C PBF Consistent.

5. The transformer for common-mode noise suppression in multilevel converters according to claim 3, characterized in that: The main magnetic core is also wound with a secondary winding, and the lumped parasitic capacitance between the midpoint of the primary winding and the midpoint of the secondary winding is... C PS The lumped parasitic capacitance between the midpoint of the balancing winding and the midpoint of the secondary winding is C PBS The primary winding and the balance winding have the same winding shape, opposite winding directions, and the same number of turns, making... C PS and C PBS Consistent.

6. The transformer for common-mode noise suppression in multilevel converters according to claim 4 or 5, characterized in that: The primary winding, balance winding, primary auxiliary winding, and secondary auxiliary winding are made of PCB substrate, solid wire, Litz wire, or copper foil.

7. The transformer for common-mode noise suppression in multilevel converters according to claim 6, characterized in that: The application topologies of the multilevel converter include series half-bridge topology, module cascade topology, diode clamping type, flying capacitor clamping type, or hybrid multilevel topology.

8. A transformer suitable for common-mode noise suppression in multilevel converters, characterized in that: The transformer includes a main magnetic core and an auxiliary magnetic core with identical structures; a primary winding and a primary auxiliary winding with identical structures are wound around the main magnetic core and the auxiliary magnetic core respectively, and the primary winding and the primary auxiliary winding are respectively connected to a multilevel converter with equal voltage magnitude and opposite phase.

9. The transformer for common-mode noise suppression in multilevel converters according to claim 8, characterized in that: The primary winding and primary auxiliary winding are made of PCB substrate, solid wire, Litz wire or copper foil.

10. The transformer for common-mode noise suppression in multilevel converters according to claim 9, characterized in that: The application topologies of the multilevel converter include series half-bridge topology, module cascade topology, diode clamping type, flying capacitor clamping type, or hybrid multilevel topology.

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