Device direct-series multi-direct-current bus transformer

Abstract

The invention relates to the technical field of direct-current transformers, in particular to a device direct-string multi-direct-current-bus transformer which comprises a direct-current input capacitor, an inverter circuit and a multi-isolation conversion rectifying circuit. The input end of the inverter circuit is connected in parallel with the DC input capacitor and then is used as the input end of the multi-DC bus transformer; the output end of the inverter circuit is connected with the multi-isolation conversion rectification circuit; the multi-isolation conversion rectification circuit is provided with n output ends, and the n output ends serve as n paths of output of the multi-direct-current bus transformer. The topological structure is reasonable in design, can realize single-machine large-capacity and multi-path direct current bus output, has the advantages of compactness, high efficiency and simplicity in control, avoids the production and manufacturing difficulty of a large-capacity alternating current transformer, and greatly improves the capacity of the direct current transformer.

Description

Technical Field

[0001] The invention relates to the technical field of direct current transformers, and in particular to a device direct series multi-direct current bus transformer. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The large-capacity of renewable energy power generation has led to an increase in the capacity of the converter, which requires the use of power devices with larger power levels, or the use of a topological structure of multiple low-voltage converters in parallel to meet the requirements of high-power conversion. Among them, the use of multiple low-voltage converters in parallel has flexible redundant control characteristics, which can effectively improve the reliability of the system. However, when the load is low, its efficiency is much lower than the efficiency under rated conditions. It is necessary to adopt a control strategy to optimize and improve the overall efficiency of the parallel system. At the same time, the number of devices required for multiple low-voltage converters in parallel is large, the cost is high, and the floor space is large. At present, the power of a single low-voltage converter is generally less than 500kW. In addition, as the power consumption of data centers continues to increase, the capacity of the existing DC bus voltage converter will not be able to meet the future high-power conversion needs.

[0004] The existing conventional DC power supply has small capacity, large quantity and large floor space, which cannot meet the needs of compact large-capacity DC bus power conversion in future data centers, large-scale renewable energy DC aluminum production and hydrogen production, and cannot be applied to medium and low voltage large-capacity scenarios. In view of the above defects, the present invention has made improvements. Summary of the invention

[0005] In order to overcome the shortcomings of the background technology, the present invention provides a device direct-series multi-DC bus transformer with a reasonable topological structure design, which can achieve single-machine large capacity and multi-channel DC bus output, has the advantages of compactness, high efficiency and simple control, and can better meet practical application needs.

[0006] To achieve the above-mentioned object, the present invention provides a device direct series multi-DC bus transformer, including a DC input capacitor, an inverter circuit, and a multi-isolation conversion rectifier circuit;

[0007] The input end of the inverter circuit is connected in parallel with the DC input capacitor and serves as the input end of the multi-DC bus transformer;

[0008] The output end of the inverter circuit is connected to the multi-isolation conversion rectifier circuit;

[0009] The multi-isolation conversion and rectification circuit has n output terminals, and the n output terminals are used as n outputs of the multi-DC bus transformer.

[0010] Further,

[0011] The multi-isolation conversion rectifier circuit includes n isolation conversion rectifier circuits;

[0012] The input side of each of the isolated conversion and rectification circuits is connected in parallel to the output end of the inverter circuit, and the output sides of each of the isolated conversion and rectification circuits are independent of each other and form n output ends of the multiple isolated conversion and rectification circuits.

[0013] Further,

[0014] The isolated conversion rectifier circuit includes a resonant inductor, a resonant capacitor, a magnetizing inductor, a step-down AC transformer, a rectifier circuit and an output capacitor;

[0015] One end of the resonant inductor and one end of the resonant capacitor are respectively connected to two ends of the output side of the inverter circuit, the other end of the resonant inductor and the other end of the resonant capacitor are respectively connected to two ends of the input side of the step-down AC transformer, and the magnetizing inductor is connected in parallel to the input side of the step-down AC transformer;

[0016] The output side of the step-down AC transformer is connected to the input side of the rectifier circuit, and the output side of the rectifier circuit is connected in parallel with the output capacitor to serve as the output of the isolation conversion rectifier circuit.

[0017] Further,

[0018] The rectifier circuit adopts a bridge rectifier circuit or a full-wave rectifier circuit.

[0019] Further,

[0020] The step-down AC transformers in each of the isolated conversion and rectification circuits adopt different transformation ratios and capacities.

[0021] Further,

[0022] The inverter circuit is a four-arm switch;

[0023] The bridge arm switch adopts a gate turn-off thyristor;

[0024] The multi-DC bus transformer further includes a clamping circuit, which is arranged between the DC input capacitor and the inverter circuit.

[0025] Further,

[0026] The inverter circuit is a four-arm switch;

[0027] The bridge arm switch adopts a high-power transistor, a power field effect transistor or an insulated gate bipolar transistor.

[0028] Further,

[0029] The multi-DC bus transformer further includes a clamping circuit, which is arranged between the DC input capacitor and the inverter circuit.

[0030] Further,

[0031] The input end of the clamp circuit is connected in parallel with the DC input capacitor, and the output end of the clamp circuit is connected to the input end of the inverter circuit;

[0032] The input end of the clamp circuit includes a positive input end and a negative input end, and the output end of the clamp circuit includes a positive output end and a negative output end;

[0033] The clamping circuit includes an anode reactance, a clamping diode, a clamping resistor and a clamping capacitor;

[0034] The first end of the anode reactance is connected to the anode of the clamping diode, and a path is drawn from the first end of the anode reactance and the anode of the clamping diode as the positive output end of the clamping circuit, the clamping resistor is connected in parallel between the second end of the anode reactance and the cathode of the clamping diode, and the second end of the anode reactance is used as the positive input end of the clamping circuit;

[0035] The first end of the clamping capacitor is connected to the cathode of the clamping diode, and the second end of the clamping capacitor is used as the negative input terminal and the negative output terminal of the clamping circuit.

[0036] Further,

[0037] The switch tubes in the four-arm switch are controlled by a fixed duty cycle.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The multi-isolation conversion rectifier circuit has n output terminals, and the output voltages are Vout1 to Voutn, i.e., n-channel voltage outputs of the multi-DC bus transformer; the multi-DC bus transformer of the present invention can realize single-machine large capacity and multi-channel DC bus output, and has the advantages of compactness, high efficiency, and simple control. At the same time, it avoids the difficulty of manufacturing large-capacity AC transformers, and greatly improves the capacity of DC transformers;

[0040] 2. The rectifier circuit in the isolated conversion rectifier circuit adopts a bridge rectifier circuit or a full-wave rectifier circuit, which can reduce the current stress of the rectifier diode and the transformer winding;

[0041] 3. The step-down AC transformer in each isolated conversion and rectification circuit can adopt different transformation ratios and capacities to achieve outputs of different voltage levels and powers;

[0042] 4. When a multi-DC bus transformer adopts a clamping circuit, the clamping circuit can, on the one hand, limit the current change rate when the switch tube in the inverter circuit is turned on, and on the other hand, limit the oscillation amplitude of the inverter circuit AC output voltage.

[0043] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings.

[0044] The present invention will be further described below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0046] Figure 1 A schematic diagram of a topological structure of a multi-DC bus transformer according to an embodiment of the present invention;

[0047] Figure 2 for Figure 1 A partial schematic diagram of the Zhongduo isolated conversion and rectification circuit;

[0048] Figure 3 This is a partial schematic diagram of an embodiment of the present invention in which the four-bridge-arm switch tubes of the inverter circuit adopt insulated gate bipolar transistors and the clamping circuit is removed;

[0049] Figure 4 The figure is a waveform diagram of the basic working principle of a multi-DC bus transformer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the implementation of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] like Figures 1 to 3 As shown, an embodiment of the present invention provides a device direct series multi-DC bus transformer, including a DC input capacitor Cp, an inverter circuit, and a multi-isolation conversion rectifier circuit;

[0052] The input end of the inverter circuit is connected in parallel with the DC input capacitor Cp to serve as the input end of the multi-DC bus transformer;

[0053] The output end of the inverter circuit is connected to the multi-isolation conversion rectifier circuit;

[0054] The multi-isolation conversion and rectification circuit has n output terminals, and the n output terminals are used as n outputs of the multi-DC bus transformer.

[0055] In the above technical solution, the DC input capacitor Cp plays the role of DC voltage support and filtering, the inverter circuit is used to convert the input DC power into AC power, and the multi-isolation conversion rectifier circuit has n output terminals, and the output voltages are Vout1~Voutn, that is, n voltage outputs of the multi-DC bus transformer; the above-mentioned multi-DC bus transformer can achieve single-machine large capacity and multi-channel DC bus output, and has the advantages of compactness, high efficiency and simple control. At the same time, it avoids the difficulty of producing and manufacturing large-capacity AC transformers and greatly improves the capacity of DC transformers.

[0056] The various components of the above-mentioned multi-DC bus transformer will be further described below.

[0057] As a preferred technical solution, the multi-isolated conversion rectifier circuit includes n isolated conversion rectifier circuits; the input side of each of the isolated conversion rectifier circuits is connected in parallel to the output end of the inverter circuit, and the output sides of each of the isolated conversion rectifier circuits are independent of each other and form n output ends of the multi-isolated conversion rectifier circuit.

[0058] In this embodiment, n isolated conversion rectifier circuits are arranged in the multi-isolated conversion rectifier circuit, the input sides of the n isolated conversion rectifier circuits are connected in parallel, and the output sides are independent of each other; these isolated conversion rectifier circuits are connected in parallel to the output end of the inverter circuit to form n output ends of the multi-isolated conversion rectifier circuit, and the output voltages are Vout1~Voutn (i.e., n voltage outputs).

[0059] As a preferred technical solution, the isolated conversion rectifier circuit includes a resonant inductor Lr, a resonant capacitor Cr, a magnetizing inductor Lm, a step-down AC transformer, a rectifier circuit and an output capacitor; one end of the resonant inductor Lr and one end of the resonant capacitor Cr are respectively connected to the two ends of the output side of the inverter circuit, the other end of the resonant inductor Lr and the other end of the resonant capacitor Cr are respectively connected to the two ends of the input side of the step-down AC transformer, and the magnetizing inductor Lm is connected in parallel to the input side of the step-down AC transformer; the output side of the step-down AC transformer is connected to the input side of the rectifier circuit, and the output side of the rectifier circuit is connected in parallel with the output capacitor as the output of the isolated conversion rectifier circuit. In specific implementation, the resonant inductor can be externally matched, or replaced by the leakage inductance of the step-down AC transformer itself to reduce system cost and volume; the resonant capacitor can be placed on the primary or secondary side of the step-down AC transformer; the magnetizing inductor can be externally matched, or the magnetizing inductance of the step-down AC transformer itself can be used to reduce system cost and volume. The isolated conversion rectifier circuit of this embodiment can realize the isolation function and the conversion function through the step-down AC transformer, and can realize the rectification function through the rectification circuit.

[0060] In some embodiments, the rectifier circuit adopts a bridge rectifier circuit or a full-wave rectifier circuit. In this embodiment, the rectifier circuit adopts a bridge rectifier circuit or a full-wave rectifier circuit, which can reduce the current stress of the rectifier diode and the transformer winding.

[0061] The rectifier circuit of this embodiment adopts a bridge rectifier circuit. The resonant inductor Lr and the resonant capacitor Cr form an LC resonant circuit. The magnetizing inductance Lm helps the switch tubes T1~T4 in the inverter circuit to achieve zero voltage turn-on; the step-down AC transformers Tr1~Trn play the role of electrical isolation and voltage reduction; the full-bridge rectifier circuit composed of diodes Drl~Dr4 plays the role of AC / DC conversion, realizing the conversion of AC voltage into DC voltage.

[0062] like Figure 2 As shown, in the multi-isolation conversion rectifier circuit of the present embodiment, the primary side of each step-down AC transformer has a resonant network (also called a resonant cavity); the resonant network is composed of Lr / Cr / Lm, so the embodiment of the present invention actually provides a multi-resonant cavity type multi-DC bus transformer.

[0063] In some embodiments, the step-down AC transformers in each of the isolated conversion and rectification circuits use different transformation ratios and capacities. In this embodiment, the step-down AC transformers in each of the isolated conversion and rectification circuits can use different transformation ratios and capacities to achieve outputs of different voltage levels and powers.

[0064] As a preferred technical solution, the inverter circuit is a four-arm switch; the arm switch adopts a gate turn-off thyristor; the multi-DC bus transformer also includes a clamping circuit, and the clamping circuit is arranged between the DC input capacitor Cp and the inverter circuit. When the arm switches in the four-arm switch of this embodiment adopt various thyristors (including gate turn-off thyristors), the multi-DC bus transformer is additionally provided with a clamping circuit; the clamping circuit is provided in the multi-DC bus transformer to suppress the oscillation amplitude of the AC voltage output by the inverter circuit.

[0065] As a preferred technical solution, the inverter circuit is a four-arm switch; the arm switch adopts a high-power transistor, a power field effect transistor or an insulated gate bipolar transistor. In this embodiment, when a high-power transistor, a power field effect transistor or an insulated gate bipolar transistor device is adopted, the multi-DC bus transformer may not be provided with a clamping circuit, that is, it is understood that the clamping circuit is removed; here, taking the insulated gate bipolar transistor device as an example, after removing the clamping circuit, Figure 3 As shown, the driving circuit needs to be controlled to limit the turn-on speed of the transistor, thereby reducing the oscillation amplitude of the AC voltage output by the inverter circuit.

[0066] In some embodiments, the multi-DC bus transformer further includes a clamping circuit, and the clamping circuit is arranged between the DC input capacitor Cp and the inverter circuit. In this embodiment, when the bridge arm switches in the four-arm switches use high-power transistors, power field effect transistors or insulated gate bipolar transistor devices, the multi-DC bus transformer can be provided with a clamping circuit. By providing the clamping circuit in the multi-DC bus transformer, the oscillation amplitude of the AC voltage output by the inverter circuit can be suppressed, and the opening speed limit of the transistor can be realized by controlling the driving circuit, thereby further reducing the oscillation amplitude of the AC voltage output by the inverter circuit.

[0067] It can be seen that when the bridge arm switches in the four-arm switches are high-power transistors, power field effect transistors or insulated gate bipolar transistor devices, the multi-DC bus transformer of this embodiment can use a clamping circuit or remove the clamping circuit.

[0068] When the inverter circuit uses four-arm switches, the arm switches can be fully controlled power switches such as gate turn-off thyristors, high-power transistors, power field effect transistors or insulated gate bipolar transistors. In specific implementation, the switch tubes of the four-arm switches (i.e., fully controlled power switches) are all provided with anti-parallel diodes. The anti-parallel diodes belong to the prior art and are not described in detail here.

[0069] In some embodiments, the inverter circuit may also adopt a three-level inverter circuit to further reduce the voltage stress of the power device.

[0070] As a preferred technical solution, the input end of the clamp circuit is connected in parallel with the DC input capacitor Cp, and the output end of the clamp circuit is connected to the input end of the inverter circuit; the input end of the clamp circuit includes a positive input end and a negative input end, and the output end of the clamp circuit includes a positive output end and a negative output end; the clamp circuit includes an anode reactance L buf , clamping diode D buf , Clamping resistor R buf and the clamping capacitor C buf The anode reactance L buf The first end of the clamping diode D buf The positive electrode and the anode reactance L buf The first terminal and the clamping diode D buf A path is drawn between the positive electrodes as the positive output terminal of the clamp circuit, and the anode reactance L buf The second end of the clamping diode D buf The clamping resistor R is connected in parallel between the negative electrodes of buf and the anode reactance L buf The second end of is used as the positive input end of the clamping circuit; the clamping capacitor C buf The first end of the clamping diode D buf the negative terminal and the clamp capacitor C buf The second end serves as the negative input terminal and the negative output terminal of the clamping circuit.

[0071] In this embodiment, if Figure 1 As shown, the clamp circuit is set between the DC input capacitor Cp and the inverter circuit. The clamp circuit consists of an anode reactance L buf , clamping diode D buf , Clamping resistor R buf and the clamping capacitor C buf The clamping circuit can limit the current change rate when the switch tube (here the switch tube refers to the four-arm switch tube T1~T4 in the inverter circuit) is turned on; on the other hand, it can limit the inverter circuit AC input voltage (that is, the inverter circuit AC output voltage V AB ) of the oscillation amplitude. Among them, the anode reactance L buf Limit the current rise rate when the switch is turned on, clamping diode D buf Used to provide a branch for the anode reactance to continue current and block the clamping capacitor C buf Discharge the inverter circuit; clamping capacitor C buf Used to buffer the anode reactance L buf The energy stored in.

[0072] As a preferred technical solution, the switch tube in the four-arm switch is controlled by a fixed duty cycle. The four-arm switch tube of the multi-DC bus transformer in this embodiment is controlled by a fixed duty cycle (preferably about 0.48 in the specific implementation), which can realize the fixed ratio conversion from the medium voltage DC bus to the low voltage bus. For the above-mentioned fixed ratio conversion, for example, when the primary-secondary turns ratio N1:S1 of the AC isolation transformer (i.e., the step-down AC transformer Tr1) is 2:0.75, when the input voltage Vin is 2kV, the output voltage Vout1 is 750V.

[0073] based on Figure 1 The multi-resonant cavity type multi-DC bus transformer shown in the embodiment of the present invention also provides Figure 4 The basic working principle waveform diagram is shown in the figure. The meaning of the symbols in the figure refers to Figure 1 , 2 As shown; this waveform diagram can intuitively demonstrate the basic working principle of the multi-resonant cavity type multi-DC bus transformer according to an embodiment of the present invention.

[0074] In summary, in response to the needs of compact large-capacity DC bus power conversion in data centers, large-scale renewable energy DC aluminum production, and hydrogen production, the embodiments of the present invention propose a multi-resonant cavity type multi-DC bus transformer for low-voltage scenarios. The capacity of a single unit can reach hundreds of kilowatts to megawatts, and can achieve multi-channel DC bus isolation output. It has the characteristics of compactness, high efficiency, and simple control. Among them, the capacity of a single unit refers to the output power of a DC / DC converter. The multi-DC bus transformer proposed in the embodiment of the present invention is based on a large-capacity crimped IGCT device and a modular multi-resonant cavity structure. The crimped IGCT device has a large capacity, and the multi-resonant cavity output structure can effectively reduce the current stress on a single output side. Therefore, the capacity of a single unit can reach hundreds of kilowatts to megawatts.

[0075] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0076] Parts not involved in the above embodiments are the same as the prior art or can be implemented by using the prior art, and will not be further described here.

[0077] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device directly connected in series with multiple DC bus transformers, characterized in that: Including DC input capacitor, inverter circuit, multi-isolation conversion rectifier circuit; The input end of the inverter circuit is connected in parallel with the DC input capacitor and serves as the input end of the multi-DC bus transformer; The output end of the inverter circuit is connected to the multi-isolation conversion rectifier circuit; The multi-isolation conversion and rectification circuit has n output terminals, and the n output terminals are used as n outputs of the multi-DC bus transformer.

2. The device direct series multi-DC bus transformer according to claim 1, characterized in that: The multi-isolation conversion rectifier circuit includes n isolation conversion rectifier circuits; The input side of each of the isolated conversion and rectification circuits is connected in parallel to the output end of the inverter circuit, and the output sides of each of the isolated conversion and rectification circuits are independent of each other and form n output ends of the multiple isolated conversion and rectification circuits.

3. The device direct series multi-DC bus transformer according to claim 2, characterized in that: The isolated conversion rectifier circuit includes a resonant inductor, a resonant capacitor, a magnetizing inductor, a step-down AC transformer, a rectifier circuit and an output capacitor; One end of the resonant inductor and one end of the resonant capacitor are respectively connected to two ends of the output side of the inverter circuit, the other end of the resonant inductor and the other end of the resonant capacitor are respectively connected to two ends of the input side of the step-down AC transformer, and the magnetizing inductor is connected in parallel to the input side of the step-down AC transformer; The output side of the step-down AC transformer is connected to the input side of the rectifier circuit, and the output side of the rectifier circuit is connected in parallel with the output capacitor to serve as the output of the isolation conversion rectifier circuit.

4. The device direct series multi-DC bus transformer according to claim 3, characterized in that: The rectifier circuit adopts a bridge rectifier circuit or a full-wave rectifier circuit.

5. The device direct series multi-DC bus transformer according to claim 3, characterized in that: The step-down AC transformers in each of the isolated conversion and rectification circuits adopt different transformation ratios and capacities.

6. The device direct series multi-DC bus transformer according to claim 1, characterized in that: The inverter circuit is a four-arm switch; The bridge arm switch adopts a gate turn-off thyristor; The multi-DC bus transformer further includes a clamping circuit, which is arranged between the DC input capacitor and the inverter circuit.

7. The device direct series multi-DC bus transformer according to claim 1, characterized in that: The inverter circuit is a four-arm switch; The bridge arm switch adopts a high-power transistor, a power field effect transistor or an insulated gate bipolar transistor.

8. The device direct series multi-DC bus transformer according to claim 7, characterized in that: The multi-DC bus transformer further includes a clamping circuit, which is arranged between the DC input capacitor and the inverter circuit.

9. A device direct series multi-DC bus transformer according to claim 6 or 8, characterized in that: The input end of the clamp circuit is connected in parallel with the DC input capacitor, and the output end of the clamp circuit is connected to the input end of the inverter circuit; The input end of the clamp circuit includes a positive input end and a negative input end, and the output end of the clamp circuit includes a positive output end and a negative output end; The clamping circuit includes an anode reactance, a clamping diode, a clamping resistor and a clamping capacitor; The first end of the anode reactance is connected to the anode of the clamping diode, and a path is drawn from the first end of the anode reactance and the anode of the clamping diode as the positive output end of the clamping circuit, the clamping resistor is connected in parallel between the second end of the anode reactance and the cathode of the clamping diode, and the second end of the anode reactance is used as the positive input end of the clamping circuit; The first end of the clamping capacitor is connected to the cathode of the clamping diode, and the second end of the clamping capacitor is used as the negative input terminal and the negative output terminal of the clamping circuit.

10. A device direct series multi-DC bus transformer according to any one of claims 6 to 8, characterized in that: The switch tubes in the four-arm switch are controlled by a fixed duty cycle.

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