Topological conversion type multi-resonance direct-current converter

Abstract

The invention discloses a topological transformation type multi-resonant direct-current converter which comprises an inversion unit, a resonant cavity unit and a rectification unit. The inversion unit is used for converting input direct current into a square wave signal; output nodes on the inversion unit are a node A and a node B respectively; the resonant cavity unit comprises an inductor, a capacitor, a high-frequency transformer and an auxiliary switch tube; the primary side winding of the high-frequency transformer is divided into an A-section winding and a B-section winding; one end of the A-section winding is connected with one end of the inductor, the other end of the inductor is connected with the A node through the capacitor, and the other end of the A-section winding is connected with a segmentation node of the high-frequency transformer; one end of the B-section winding is connected with the B node, and the other end is connected with the segment node of the high-frequency transformer; the auxiliary switch tubes are arranged at two ends of the B-section winding in parallel and are used for controlling the switching of working modes of the B-section winding to realize topological transformation; and the rectification unit comprises four switch tubes and is used for converting the alternating current output by the resonant cavity unit into direct current to be used by a post-stage load.

Description

Technical Field

[0001] The invention relates to the field of direct current converters, and in particular to a topology switching type high-efficiency wide-gain multi-resonance direct current converter. Background Art

[0002] In recent years, with the advancement of science and technology and the continuous breakthroughs in power electronics technology, isolated resonant converters have been widely used in the field of DC buildings and in the construction of power distribution systems, especially in distributed energy storage and new energy scenarios. Topological transformation technology and the application technology of new wide bandgap devices have continued to make progress and breakthroughs, especially in energy storage. Due to the continuous development of electrochemical energy storage, the continuous exploration of sodium sulfide batteries and lithium batteries, and the continuous updating of energy storage battery materials, higher requirements have been put forward for energy storage converters. In order to meet the fluctuation voltage regulation requirements of new materials in a wider voltage range and safety assurance, more stringent requirements have been put forward for isolated wide gain and high-efficiency converters.

[0003] Compared with PWM converters, resonant converters have the advantages of high frequency, high efficiency, high power density and low electromagnetic interference. Under traditional control, resonant converters use frequency modulation control (Pulse frequency modulation, PFM), which has the characteristics of good soft switching performance. However, resonant topologies represented by LLC and CLLC, when using frequency modulation control methods, are mostly adjusted within the standardized voltage gain range of 1 to 1.2 times, and the adjustment range is relatively narrow. The working condition greater than 1.2 requires further reduction of the inductance ratio, which often leads to a decrease in the quality factor of the converter and a decrease in efficiency. It is urgent to propose a new topology or control method to enable the converter to have wide gain adjustment capability and high efficiency operation characteristics. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art, and to provide a topology switching type high-efficiency wide-gain multi-resonant DC converter with a wide voltage gain range and high conversion efficiency in view of the problems such as insufficient wide-gain efficiency faced by the traditional LLC resonant converter. By switching the switch tube, the wide-gain efficiency attenuation problem existing in the traditional LLC resonant topology is compensated, and a new solution is provided for the wide-gain high-efficiency realization method of the resonant converter.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A topology conversion type multi-resonant DC converter comprises an inverter unit, a resonant cavity unit and a rectifier unit; the inverter unit is composed of a full-bridge structure composed of four MOSFET switch tubes, and is used to convert input DC power into a square wave signal; the output nodes on the inverter unit are respectively A node and B node;

[0007] The resonant cavity unit includes an inductor, a capacitor, a high-frequency transformer and an auxiliary switch tube; the primary winding of the high-frequency transformer is divided into a winding section A and a winding section B. The winding section A has a turns ratio relationship of M:1 with the secondary side and the corresponding excitation inductance is L m1 , the winding of section B has a turns ratio relationship of N:1 with the secondary side and the corresponding excitation inductance is L m2 ;

[0008] One end of the winding of section A is connected to one end of the inductor, the other end of the inductor is connected to node A through a capacitor, and the other end of the winding of section A is connected to the segment node of the high-frequency transformer;

[0009] One end of the B-section winding is connected to the B node, and the other end is connected to the segment node of the high-frequency transformer; the auxiliary switch tube is arranged in parallel at both ends of the B-section winding to control the working mode switching of the B-section winding to achieve topology transformation; the auxiliary switch tube is composed of two MOSFET switch tubes connected in reverse series;

[0010] The rectifier unit includes four switch tubes, which are used to convert the AC power output by the resonant cavity unit into DC power for use by the subsequent load;

[0011] By controlling the on and off of the auxiliary switch tube, the multi-resonant DC converter can obtain two different working circuits, namely, LLC circuit and LLCLC circuit.

[0012] Furthermore, the four MOSFET switch tubes in the inverter unit are respectively a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube; the first switch tube and the third switch tube are connected in series, the second switch tube and the fourth switch tube are connected in series, and the two groups of series circuits are connected in parallel to form a full-bridge topology; an A node is set between the first switch tube and the third switch tube, and a B node is set between the second switch tube and the fourth switch tube.

[0013] Furthermore, the equivalent output capacitance of the auxiliary switch is C a , equivalent output capacitance C a The value of C oss / 2,C oss It is the output capacitance of a single MOSFET switch tube that constitutes the auxiliary switch tube.

[0014] Furthermore, when the auxiliary switch is turned on, the converter operates in LLC mode; at this time, the B section winding is short-circuited and does not participate in the work; only the inductor, capacitor and A section winding in the circuit constitute an effective circuit for power conversion; in this mode, the converter's equivalent excitation inductance L M_LLC =L m1 , the transformer turns ratio is M:1;

[0015] L M_LLC =L m1 (1)

[0016] LLC converter can improve the operating efficiency at the main resonant frequency point; the LLC converter is modeled using the equivalent fundamental wave analysis method FHA, and the KCL / KVL formula is solved in parallel. Its DC voltage gain V gain_LLC Expressed as

[0017]

[0018] Where ω=2πf s , ω is the angular frequency, L1 and C1 are the inductance and capacitance of the inductor and capacitor respectively, j is the imaginary unit, f s is the switching frequency, R eq is the AC equivalent resistance, which is equal to R o The relationship is as follows:

[0019]

[0020] Let the gain V gain_LLC The imaginary part V gainIm_LLC =0, get the main resonant frequency point f r The expression is

[0021]

[0022] When the auxiliary switch is turned off, the converter operates in LLCLC mode. Since the auxiliary switch is turned off, the equivalent output capacitance C a With L m2 Connect in parallel and participate in the work;

[0023] In this mode, C a With L m2 The equivalent excitation inductance L is formed in parallel M2 , expressed as:

[0024]

[0025] Then the equivalent excitation inductance L of the converter M_LLCLC It is expressed as follows, where the transformer turns ratio is (M+N):1;

[0026]

[0027] Similar to the LLC converter, the LLCLC converter is modeled using the equivalent fundamental wave analysis method FHA, and its DC voltage gain V is solved. gain_LLCLC for

[0028]

[0029] Similarly, let the imaginary part of this mode gain V gainIm_LLCLC =0, get the main resonant frequency point f rThe expression of is the same as that of LLC mode, as shown in formula (5).

[0030] The present invention also provides an application based on the above-mentioned topology transformation type multi-resonance DC converter, which is applied to DC power consumption systems, DC adaptation technology, photovoltaic systems, DC microgrid systems, and electric vehicle fields.

[0031] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0032] 1. Simple topology and low manufacturing cost: The topology conversion type multi-resonant DC converter proposed in the present invention has a similar structure to the traditional LLC converter. The overall topology design is relatively simple, easy to implement, and has a low manufacturing cost. At the same time, by using the equivalent output capacitor C of the auxiliary switch tube a Acting as part of the resonant circuit, it achieves topology switching while avoiding the introduction of additional auxiliary capacitors, thereby simplifying the circuit design. This optimization not only reduces the size of the converter, but also further improves the power density, making it suitable for space-constrained application scenarios.

[0033] 2. Wide voltage gain range, adapting to various application requirements: By introducing a topology switching mechanism, the converter can switch freely between LLC mode and LLCLC mode to achieve a wider voltage gain range. Compared with the traditional LLC converter, which can usually only be adjusted within a gain range of 1 to 1.2 times, the voltage adjustment range of the present invention is larger, and the high-efficiency operation of the two resonance points of M and (N+M) segments can be achieved through the ratio of the number of winding turns, and the variable inductance ratio between M and (N+M) gains can be achieved through the LLCLC variable excitation structure, ensuring high efficiency in the full range, and can better meet the wide voltage fluctuation requirements in multiple scenarios such as energy storage batteries, DC microgrids, and photovoltaic systems.

[0034] 3. Excellent soft switching performance, improved efficiency, the converter of the present invention can achieve soft switching characteristics in the full load range:

[0035] The switch tube of the inverter unit can achieve zero voltage switching (ZVS), effectively reducing the turn-on and turn-off losses of the switch tube;

[0036] The rectifier unit can achieve zero current switching (ZCS), further reducing the reverse recovery loss of the diode. Through the optimized soft switching mechanism, the overall efficiency of the converter is significantly improved, while reducing the heat and loss during system operation.

[0037] 4. High power density and low electromagnetic interference:

[0038] The present invention reasonably designs the resonant cavity parameters and topology switching mode, so that the converter can still maintain high power density under high-frequency operation, and effectively reduce electromagnetic interference (EMI) during operation, meeting the modern design requirements of power electronic devices. This feature is particularly suitable for scenarios with high requirements for high efficiency and low interference, such as electric vehicle charging systems, DC building power supply systems, and DC microgrids.

[0039] 5. Modular design facilitates application and promotion: Due to the versatility of topological design and modularity of circuit structure, the present invention can be widely used in DC power systems, photovoltaic systems, energy storage converters, DC adapter technology, electric vehicles and other fields. The modular design makes the present invention easier to integrate with existing power electronic systems, realizing rapid promotion and engineering implementation of the technology.

[0040] In summary, the present invention not only effectively solves the problems of narrow gain range and efficiency attenuation of traditional LLC resonant converters, but also provides a new solution for realizing a DC converter with wide gain, high efficiency and multi-scenario adaptability, and has significant engineering application value and market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of the structure of a topology-changing multi-resonant DC converter is shown.

[0042] Figure 2 A schematic diagram of the LLC converter structure is shown.

[0043] Figure 3 The voltage gain curve of the LLC converter is shown.

[0044] Figure 4 The LLCLC converter schematic diagram is shown

[0045] Figure 5 The voltage gain curve of LLCLC is shown.

[0046] Figure 6 The voltage gain curve of the converter of the present invention is shown. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] Figure 1 The structure diagram of the topology transformation type multi-resonant DC converter is shown, which includes three parts: an inverter unit, a resonant cavity unit and a rectifier unit.

[0049] The inverter unit is used to convert the input direct current into a square wave signal, and is composed of a full-bridge structure consisting of four MOSFET switch tubes. The four MOSFET switch tubes are respectively a first switch tube S1, a second switch tube S2, a third switch tube S3, and a fourth switch tube S4; the first switch tube S1 and the third switch tube S3 are connected in series, the second switch tube S2 and the fourth switch tube S4 are connected in series, and the two groups of series circuits are connected in parallel to form a full-bridge topology; an A node is set between the first switch tube S1 and the third switch tube S3, and a B node is set between the second switch tube S2 and the fourth switch tube S4.

[0050] The resonant cavity unit includes an inductor L1, a capacitor C1, a high-frequency transformer T and an auxiliary switch tube S a The primary winding of the high-frequency transformer T is divided into winding section A and winding section B. The winding section A has a turns ratio relationship of M:1 with the secondary winding and the corresponding excitation inductance is L. m1 , the winding of section B has a turns ratio relationship of N:1 with the secondary side and the corresponding excitation inductance is L m2 ; One end of the winding of section A is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the node A through the capacitor C1, and the other end of the winding of section A is connected to the segment node of the high-frequency transformer T; one end of the winding of section B is connected to the node B, and the other end is connected to the segment node of the high-frequency transformer T;

[0051] Auxiliary switch tube S a It is connected in parallel at both ends of the B winding to control the switching of the working mode of the B winding, thereby realizing the adjustment of the multi-resonance characteristics; the auxiliary switch tube S a It consists of two MOSFET switches connected in reverse series; Figure 1 Middle C a Auxiliary switch S a The equivalent output capacitance is C oss / 2,C oss To form the auxiliary switch tube S a The output capacitance of a single MOSFET switch tube.

[0052] The rectifier unit adopts a full-bridge structure, including four switch tubes SR1-SR4, which are used to convert the AC power output by the resonant cavity unit into DC power for use by the subsequent load;

[0053] In this embodiment, the resonant cavity unit is a key element of the multi-resonant DC converter, which plays a vital role in the operating performance of the entire converter. The multi-resonant DC converter of the present invention combines multi-resonance technology and topology transformation technology to form a new type of resonant network. The auxiliary switch tube S is introduced into the multi-resonant cavity unit. a , by controlling S aBy turning on and off the converter, the converter can obtain two different working circuits, namely LLC circuit and LLCLC circuit. As a result, the converter obtains a wide voltage gain range in a narrow frequency range, which is conducive to high-efficiency operation.

[0054] When S a When turned on, the converter operates in LLC mode, and its topology is as follows: Figure 2 As shown. At this time, winding B (L m2 ) and C a is short-circuited and does not participate in the work, the total equivalent excitation inductance L of the transformer M Equal to the excitation inductance of winding A, L m1 There are only L1, C1 and L in the circuit. m1 An effective circuit is formed to perform power conversion.

[0055] There are only L1, C1 and winding A in the circuit (L m1 ) forms an effective circuit for power conversion. In this mode, the converter's equivalent excitation inductance L M_LLC =L m1 , the transformer turns ratio is M:1.

[0056] L M_LLC =L m1 (1)

[0057] Thanks to its simple structure and good soft switching characteristics, the LLC converter can achieve high operating efficiency near the main resonant frequency. The LLC circuit is modeled using the Fundamental Harmonic Approximation (FHA) method, and the KCL / KVL formula is solved in parallel. Its DC voltage gain V gain_LLC It can be expressed as

[0058]

[0059] Where ω=2πf s ,ω is the angular frequency, L1 and C1 are the inductance and capacitance of inductor L1 and capacitor C1 respectively, j is the imaginary unit, f s is the switching frequency. R eq is the AC equivalent resistance, which is equal to R o The relationship is as follows.

[0060]

[0061] Let the gain V gain_LLC The imaginary part V gainIm_LLC =0, we can get the main resonant frequency point f r The expression is

[0062]

[0063] Figure 3 The voltage gain curve of LLC converter is given. r The converter voltage gain is the standard gain, Figure 3 The voltage gain in is normalized. Figure 3 It can be seen that f r The voltage gain of the converter is always 1 at this point and is independent of load changes. The converter achieves higher operating efficiency at this point. The voltage gain at other locations decreases as the load increases.

[0064] When S a When turned off, the converter operates in LLCLC mode, and its topology is as follows: Figure 4 As shown. a Shutdown, S a The equivalent output capacitance C a and the excitation inductance L of winding section B m2 Connect in parallel and participate in the work.

[0065] In this mode, C a With L m2 The parallel connection forms the equivalent excitation inductance L of the winding of section B. M2 , which can be expressed as

[0066]

[0067] Furthermore, the total equivalent excitation inductance L of the converter M At this time, it can be written as L M_LLCLC The specific expression is as follows: the transformer turns ratio is (M+N):1.

[0068]

[0069] Similar to the LLC converter, the LLCLC converter is modeled using FHA and its DC voltage gain V is solved. gain_LLCLC for

[0070]

[0071] Similarly, let the imaginary part of this mode gain V gainIm_LLCLC =0, we can get the main resonant frequency point f r The expression of is the same as that of LLC mode, as shown in formula (5).

[0072] Figure 5 The voltage gain curve of LLCLC converter is given. r The voltage gain of the converter at the position is always 1 and is independent of load changes. The voltage gain at other positions decreases as the load increases.

[0073] Figure 6The voltage gain curve of the converter of the present invention is shown. LLC and LLCLC have their own characteristics. There are similarities and differences. Such as the resonant frequency point, voltage gain range, excitation inductance size, topology complexity and other aspects. In terms of similarities, the two topologies have the same main resonant frequency point; high efficiency can be achieved at the resonant frequency point; and have similar voltage gain curve change trends. In terms of differences, the LLC converter has the following characteristics: ① simple structure; ② the inductance ratio k1 is fixed and has nothing to do with frequency regulation. By utilizing the similarities of the two topological structures (such as the same resonant frequency point and partially shared resonant circuit structure) and combining the different advantages of the two topologies, they can be integrated into a new converter. Utilize the switching of the topology structure by turning on or off the auxiliary switch tube. The key goal of the design of the new topology conversion converter proposed in the present invention is to achieve a wide voltage gain within a narrow frequency range, thereby improving the operating efficiency within the full gain and full load range.

[0074] In LLC mode, taking advantage of its simple structure and good soft switching characteristics, the converter operates near the resonant frequency and achieves high-efficiency operation at the rated operating point.

[0075] In LLCLC mode, the inductance ratio is increased and the C a The advantage of the change helps to further achieve high-efficiency operation within the full gain range.

[0076] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solution of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, a person of ordinary skill in the art can also make many forms of specific changes under the guidance of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A topology conversion type multi-resonant DC converter, characterized in that: It includes an inverter unit, a resonant cavity unit and a rectifier unit; the inverter unit is composed of a full-bridge structure composed of four MOSFET switch tubes, which is used to convert the input direct current into a square wave signal; the output nodes on the inverter unit are node A and node B respectively; The resonant cavity unit includes an inductor (L1), a capacitor (C1), a high-frequency transformer (T) and an auxiliary switch tube (S a ); The primary winding of the high-frequency transformer (T) is divided into section A winding and section B winding. The section A winding has a turns ratio relationship of M:1 with the secondary winding and the corresponding excitation inductance is L m1 , the winding of section B has a turns ratio relationship of N:1 with the secondary side and the corresponding excitation inductance is L m2 ; One end of the winding of section A is connected to one end of the inductor (L1), the other end of the inductor (L1) is connected to the node A through the capacitor (C1), and the other end of the winding of section A is connected to the segment node of the high-frequency transformer (T); One end of the B segment winding is connected to the B node, and the other end is connected to the segment node of the high-frequency transformer (T); the auxiliary switch tube (S a ) is connected in parallel at both ends of the B winding to control the working mode switching of the B winding to achieve topology transformation; the auxiliary switch tube (S a ) consists of two MOSFET switches connected in reverse series; The rectifier unit includes four switch tubes, which are used to convert the AC power output by the resonant cavity unit into DC power for use by the subsequent load; By controlling the auxiliary switch tube (S a ) is turned on and off, the multi-resonant DC converter can obtain two different working circuits, namely LLC circuit and LLCLC circuit.

2. A topology conversion type multi-resonance DC converter according to claim 1, characterized in that: The four MOSFET switch tubes in the inverter unit are respectively a first switch tube (S1), a second switch tube (S2), a third switch tube (S3), and a fourth switch tube (S4); the first switch tube (S1) and the third switch tube (S3) are connected in series, the second switch tube (S2) and the fourth switch tube (S4) are connected in series, and the two groups of series circuits are connected in parallel to form a full-bridge topology; an A node is set between the first switch tube (S1) and the third switch tube (S3), and a B node is set between the second switch tube (S2) and the fourth switch tube (S4).

3. The topology conversion type multi-resonance DC converter according to claim 1, characterized in that: Auxiliary switch tube (S a ) is C a , equivalent output capacitance C a The value of C oss / 2,C oss To form an auxiliary switch tube (S a )’s output capacitance for a single MOSFET switch.

4. The topology conversion type multi-resonance DC converter according to claim 1, characterized in that: When the auxiliary switch tube (S a ) is turned on, the converter operates in LLC mode; at this time, the B section winding is short-circuited and does not participate in the work; only the inductor (L1), capacitor (C1) and the A section winding in the circuit constitute an effective circuit for power conversion; in this mode, the converter's equivalent excitation inductance L M_LLC =L m1 , the transformer turns ratio is M:1; L M_LLC =L m1 (1) LLC converter can improve the operating efficiency at the main resonant frequency point; the LLC converter is modeled using the equivalent fundamental wave analysis method FHA, and the KCL / KVL formula is solved in parallel. Its DC voltage gain V gain_LLC Expressed as Where ω=2πf s , ω is the angular frequency, L1 and C1 are the inductance and capacitance of the inductor (L1) and capacitor (C1), respectively, j is the imaginary unit, and f s is the switching frequency, R eq is the AC equivalent resistance, which is equal to R o The relationship is as follows: Let the gain V gain_LLC The imaginary part V gainIm_LLC =0, get the main resonant frequency point f r The expression is When the auxiliary switch tube (S a ) is turned off, the converter operates in LLCLC mode; due to the auxiliary switch tube (S a ) is turned off, the auxiliary switch tube (S a ) of the equivalent output capacitance C a With L m2 Connect in parallel and participate in the work; In this mode, C a With L m2 The equivalent excitation inductance L is formed in parallel M2 , expressed as: Then the equivalent excitation inductance L of the converter M_LLCLC It is expressed as follows, where the transformer turns ratio is (M+N):1; Similar to the LLC converter, the LLCLC converter is modeled using the equivalent fundamental wave analysis method FHA, and its DC voltage gain V is solved. gain_LLCLC for Similarly, let the imaginary part of this mode gain V gainIm_LLCLC =0, get the main resonant frequency point f r The expression of is the same as that of the LLC model, as shown in (5).

5. An application of a topology conversion type multi-resonance DC converter according to any one of claims 1 to 4, characterized in that: Applied to DC power systems, DC adaptation technology, photovoltaic systems, DC microgrid systems, and electric vehicles.

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