CN213693474U - Bipolar bidirectional direct-current transformer - Google Patents

Bipolar bidirectional direct-current transformer Download PDF

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Publication number
CN213693474U
CN213693474U CN202022696724.8U CN202022696724U CN213693474U CN 213693474 U CN213693474 U CN 213693474U CN 202022696724 U CN202022696724 U CN 202022696724U CN 213693474 U CN213693474 U CN 213693474U
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voltage
insulated gate
direct current
gate bipolar
transformer
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CN202022696724.8U
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Inventor
常潇
王金浩
高乐
唐保国
刘翼肇
刘志良
李胜文
张昊
樊瑞
赵军
张敏
肖莹
冯磊
孟润泉
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Taiyuan University of Technology
Electric Power Research Institute of State Grid Shanxi Electric Power Co Ltd
State Grid Shanxi Electric Power Co Ltd
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Taiyuan University of Technology
Electric Power Research Institute of State Grid Shanxi Electric Power Co Ltd
State Grid Shanxi Electric Power Co Ltd
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Abstract

The present invention relates to the field of electrical power converters. A bipolar bidirectional direct current transformer comprises 4 insulated gate bipolar transistors, 2 inductors and 4 capacitors, wherein a high-voltage positive electrode + HV of the bipolar bidirectional direct current transformer is connected with a collector electrode of a first insulated gate bipolar transistor Q1 and one end of a C1 of a first capacitor, a high-voltage positive electrode-HV of the bipolar bidirectional direct current transformer is connected with an emitter electrode of a third insulated gate bipolar transistor Q3 and one end of a C2 of a second capacitor, and an emitter electrode of the first insulated gate bipolar transistor Q1 is respectively connected with a collector electrode of a second insulated gate bipolar transistor Q2 and one end of a first inductor L1. The invention can realize bipolar power supply, unipolar independent power supply and power supply flexibility and reliability.

Description

Bipolar bidirectional direct-current transformer
Technical Field
The utility model relates to an electric power converter field.
Background
The direct current transformer is an electric power converter based on a power electronic conversion technology, and is a key device for connecting two direct current buses with different voltage values. The low-voltage direct-current power distribution network can be divided into a unipolar power supply and a bipolar power supply, wherein the bipolar power supply has higher flexibility and reliability, and the bipolar power supply has two realization forms of a pseudo bipolar power supply and a true bipolar power supply. In order to satisfy different power supply modes, direct current transformers of different structures are required, and therefore, the direct current transformers can be classified into a unipolar type, a pseudo bipolar type and a true bipolar type according to the polarity of output voltage. The single-pole direct-current transformer only needs to meet two points of power rated value and energy bidirectional flow, and the design cost is lowest; the pseudo-bipolar direct current transformer is generally grounded through the midpoint of a grounding resistor or a capacitor, and is very convenient to design, but the pseudo-bipolar direct current transformer has the defects that a load can only be connected between a positive output bus and a negative output bus, and the positive output bus and the negative output bus cannot be loaded independently; the true bipolar direct current transformer can not only connect the load between the positive output bus and the negative output bus, but also enable the positive output bus and the negative output bus to be independently loaded or unbalanced, but also have more difficult design and limited research results at present. With the increasing requirements of users on the flexibility and reliability of the power distribution network, the direct current transformer with the true bipolar characteristic has wider application prospect and market value.
The direct current transformer can be divided into an isolated type and a non-isolated type according to whether the direct electrical connection exists between the input side and the output side, various direct current transformer main circuit topological circuits with true bipolar characteristics are mostly designed aiming at the isolated type at present, and although the reliability is higher, the improvement of the operation efficiency can be influenced due to the existence of the isolation transformer. Patent CN202010076552.6, "a dc solid-state transformer with bipolar output voltage self-balancing capability", proposes a dc solid-state transformer with bipolar output voltage self-balancing capability, which directly implements bipolar output without additional switching devices. The direct current transformer is suitable for occasions with low requirements on efficiency and high requirements on design cost; patent CN201910962620.6 "bipolar dc transformer, and control method and device thereof" proposes a dc transformer with true bipolar characteristic, which includes multiple power sub-modules, and is suitable for medium-high voltage high-power occasions, and has high reliability, but because the internal topology of the power sub-modules also adopts an isolated topology, it is unable to achieve high efficiency, and its design cost is also high.
For some occasions with particularly high requirements on efficiency, a non-isolated topology is generally adopted, wherein the half-bridge non-isolated topology not only can meet the requirement of more than 98% of efficiency, but also is suitable for high-power occasions and is widely applied to low-voltage direct-current transformers. Patent CN201820920739.8 "a low-voltage dc bi-directional bipolar DCDC converter", proposes a non-isolated low-voltage dc bi-directional bipolar DCDC converter, which can realize energy bi-directional flow and ensure bipolar dc voltage balance, but because the upper end of its input side is connected to the positive bus of the previous stage of dc, and the lower end is connected to the negative bus of the previous stage of dc, once the positive bus or the negative bus of the previous stage needs to be disconnected due to reasons such as maintenance, the output side of the dc transformer cannot operate with only single polarity, and its operation reliability is not high.
Disclosure of Invention
The utility model discloses the technical problem that will solve is: the non-isolated DC transformer with the bipolar output characteristic is suitable for a low-voltage distribution network, meets the requirements of energy bidirectional flow and bipolar input and output, and can be operated in a bipolar mode and a unipolar mode independently.
The utility model adopts the technical proposal that: a bipolar bidirectional DC transformer comprises 4 insulated gate bipolar transistors, 2 inductors and 4 capacitors, wherein a high-voltage positive pole + HV of the bipolar bidirectional DC transformer is connected with a collector of a first insulated gate bipolar transistor Q1 and one end of a first capacitor C1, a high-voltage positive pole-HV of the bipolar bidirectional DC transformer is connected with an emitter of a third insulated gate bipolar transistor Q3 and one end of a second capacitor C2, an emitter of the first insulated gate bipolar transistor Q1 is respectively connected with a collector of the second insulated gate bipolar transistor Q2 and one end of a first inductor L1, a collector of the third insulated gate bipolar transistor Q3 is respectively connected with an emitter of a fourth insulated gate bipolar transistor Q4 and one end of a second inductor L2, a low-voltage positive pole + LV of the bipolar DC transformer is connected with the other end of the first inductor L1 and one end of a third capacitor C3, the low-voltage negative electrode-LV of the bipolar bidirectional direct current transformer is connected with the other end of the second inductor L2 and one end of the fourth capacitor C4, and the other end of the first capacitor C1, the other end of the second capacitor C2, the other end of the third capacitor C3, the other end of the fourth capacitor C4, the emitter of the second insulated gate bipolar transistor Q2, and the collector of the fourth insulated gate bipolar transistor Q4 are grounded.
The diode-based IGBT further comprises four diodes, two ends of each IGBT are connected with one diode in an anti-parallel mode, namely the emitter of each IGBT is connected with the anode of each diode, and the collector of each IGBT is connected with the cathode of each diode. The purpose is to transfer the energy in the first inductor L1 and the second inductor L2 to the load during the turn-off period of the igbt, so as to perform voltage reduction or voltage increase.
The first insulated gate bipolar transistor Q1 and the third insulated gate bipolar transistor Q3 control the forward flow of the power of the transformer, and can convert the high-voltage side input voltage into the low-voltage side output voltage; the second and fourth igbts Q2 and Q4 control the forward flow of transformer power and convert the low-side input voltage into a high-side output voltage.
The driving signals of the first insulated gate bipolar transistor Q1, the third insulated gate bipolar transistor Q3, the second insulated gate bipolar transistor Q2 and the fourth insulated gate bipolar transistor Q4 are controlled by independent PWM when the forward and reverse flows of the transformer power are controlled, and the purpose is to prevent the through problem caused by the fact that the Q1 and the Q2 are conducted at the same time and the Q3 and the Q4 are conducted at the same time when the switching frequency is high.
The first inductor L1 and the second inductor L2 have the functions of energy storage and filtering when the direct current transformer works in the forward direction, and only have the function of energy storage when the direct current transformer works in the reverse direction; the C1 of the first capacitor and the C2 of the second capacitor have the functions of voltage stabilization and filtering when the direct-current transformer works reversely; the C3 of the third capacitor and the C4 of the fourth capacitor have the function of filtering when the direct current transformer works in the forward direction.
When power flows in the forward direction, the first insulated gate bipolar transistor Q1 and the third insulated gate bipolar transistor Q3 are controlled to be periodically conducted, and the circuit is equivalent to two buck chopper circuits. When the first igbt Q1 and the third igbt Q3 are turned on, the high-voltage side of the bipolar bidirectional dc transformer supplies power to the inductor L1, the second inductor L2, and the low-voltage side load of the bipolar bidirectional dc transformer, respectively, and when the first igbt Q1 and the third igbt Q3 are turned off, the first inductor L1 and the second inductor L2 freewheel through diodes, and the voltage across the low-voltage side load is 0.
The utility model has the advantages that: the utility model provides a net DC transformer is joined in marriage to low pressure is based on the true bipolar DC transformer of non-isolation half-bridge bidirectional converter, has inherited the topological high efficiency of half-bridge, powerful characteristics, only contains 4 full accuse type power devices, has avoided introducing isolation transformer and the problem of the efficiency reduction that causes, volume increase, the increase of the design degree of difficulty. Compare with current direct current transformer, the utility model discloses both can realize bipolar power supply, have and to realize monopole independent power supply, improved the flexibility and the reliability of power supply.
Drawings
Fig. 1 is a schematic structural diagram of a bipolar bidirectional dc transformer according to the present invention;
fig. 2 is a state diagram of an igbt and a power diode when the dc transformer power flows in the forward direction according to an embodiment of the present invention;
fig. 3 is a state diagram of an igbt and a power diode when the dc transformer power flows in the reverse direction according to an embodiment of the present invention;
fig. 4 is a state diagram of the igbt and the power diode when the positive bus of the dc transformer operates with a single pole according to the embodiment of the present invention;
fig. 5 is a state diagram of the igbt and the power diode when the negative bus of the dc transformer operates with a single pole according to the embodiment of the present invention.
Detailed Description
As shown in fig. 1, a bipolar bidirectional dc transformer includes 4 igbts, 2 inductors, 4 capacitors, and four diodes, the high voltage positive electrode + HV of the bipolar bidirectional dc transformer is connected to the collector of the first igbts Q1 and one end of the C1 of the first capacitor, the high voltage positive electrode-HV of the bipolar bidirectional dc transformer is connected to the emitter of the third igbts Q3 and one end of the C2 of the second capacitor, the emitter of the first igbts Q1 is respectively connected to the collector of the second igbts Q2 and one end of the first inductor L1, the collector of the third igbts Q3 is respectively connected to the emitter of the fourth igbts Q4 and one end of the second inductor L2, the low voltage positive electrode + LV of the bipolar dc transformer is connected to the other end of the first inductor L1 and one end of the C3 of the third capacitor, the low-voltage negative electrode-LV of the bipolar bidirectional direct current transformer is connected with the other end of the second inductor L2 and one end of the fourth capacitor C4, and the other end of the first capacitor C1, the other end of the second capacitor C2, the other end of the third capacitor C3, the other end of the fourth capacitor C4, the emitter of the second insulated gate bipolar transistor Q2, and the collector of the fourth insulated gate bipolar transistor Q4 are grounded. Two ends of each insulated gate bipolar transistor are connected with a diode in an anti-parallel mode, namely the emitter of each insulated gate bipolar transistor is connected with the anode of the diode, and the collector of each insulated gate bipolar transistor is connected with the cathode of the diode. The purpose is to transfer the energy in the first inductor L1 and the second inductor L2 to the load during the turn-off period of the igbt, so as to perform voltage reduction or voltage increase.
The first and third insulated gate bipolar transistors Q1 and Q3 of the direct current transformer control the forward flow of transformer power, and can convert a high-voltage side input voltage into a low-voltage side output voltage; the insulated gate bipolar transistors Q2 and Q4 control the forward flow of transformer power and convert the low-side input voltage to a high-side output voltage.
In the dc transformer, the driving signals of the igbt Q1 and Q2, and the igbt Q3 and the igbt Q4 are independently PWM-controlled to control the forward and reverse flows of the transformer power. When power flows in the forward direction, the Q1 and the Q3 are controlled to be switched on or off only through the PWM, and the Q2 and the Q4 are in a switching-off state all the way in one control period of the PWM; when power flows reversely, the Q2 and the Q4 are controlled to be switched on or switched off only through PWM, and the Q1 and the Q3 are in a switched-off state all the way in one control period of PWM, so that the problem of through caused by the fact that the Q1 and the Q2 are switched on simultaneously and the Q3 and the Q4 are switched on simultaneously at high switching frequency is solved.
In the above dc transformer, the power diode is connected in anti-parallel to both ends of the igbt, and the purpose of the power diode is to transfer energy in the energy storage inductors L1 and L2 to the load during the turn-off period of the igbt, thereby performing voltage reduction or voltage increase.
In the direct-current transformer, the inductors L1 and L2 have the functions of energy storage and filtering when the direct-current transformer works in the forward direction, and only have the function of energy storage when the direct-current transformer works in the reverse direction; the capacitors C1 and C2 have the functions of voltage stabilization and filtering when the direct-current transformer works reversely; the capacitors C3 and C4 have the function of filtering when the direct current transformer works in the forward direction.
In the direct current transformer, the input end N1 of the grounded neutral wire is respectively connected with the negative electrode of the high-voltage side direct current power grid DC1 and the positive electrode of the high-voltage side direct current power grid DC2, and the output end N2 is respectively connected with the negative electrode of the low-voltage side direct current power grid DC3 and the positive electrode of the low-voltage side direct current power grid DC4, so that the buses on the high-voltage side and the low-voltage side have bipolar characteristics, namely the buses on the high-voltage side are bipolar direct current buses of + HV and-HV, and the buses on the low-voltage side are bipolar direct current buses of + LV and-LV, and the flexibility and the reliability.
According to the difference of the energy flow directions of the high-voltage side and the low-voltage side of the direct-current transformer, the direct-current transformer has two working modes of forward power flow and reverse power flow; according to whether the positive bus and the negative bus of the direct current transformer have voltage simultaneously, the direct current transformer has two power supply modes of bipolar power supply and unipolar independent power supply.
When power flows in the forward direction, the direct-current transformer respectively controls the insulated gate bipolar transistors Q1 and Q3 to be periodically conducted, and the circuit is equivalent to two buck chopper circuits. When the Q1 and the Q3 are conducted, the high-voltage side direct current grids DC1 and DC2 respectively provide electric energy for the inductors L1 and L2 and the low-voltage side load, and at the moment, the voltages at two ends of the low-voltage side load are DC1 and DC2 respectively; when Q1, Q3 are off, inductors L1, L2 freewheel through the diodes, and the voltage across the low-side load is both approximately 0.
When power reversely flows, the direct current transformer respectively controls the insulated gate bipolar transistors Q2 and Q4 to be periodically conducted, and the circuit is equivalent to two boosting chopper circuits. When Q2 and Q4 are conducted, low-voltage side direct current grids DC3 and DC4 respectively store electric energy to inductors L1 and L2, meanwhile, capacitors C1 and C2 respectively provide electric energy to a high-voltage side load, and output voltage is basically kept to be a constant value; when Q2, Q4 are conducting, low-side DC grids DC3, DC4 and inductors L1, L2 together charge capacitors C1, C2 and supply energy to the high-side load.
When the direct current transformer is used for single-pole independent power supply, only DC1 or DC2 can be input to the high-voltage side, only DC3 or DC4 can be output to the low-voltage side, and the function of bidirectional energy flow of positive bus single-pole power supply or negative bus single-pole power supply can be achieved by independently controlling Q1, Q2 or Q3 and Q4.
The direct current transformer is a true bipolar direct current transformer, and a positive direct current bus and a negative direct current bus on the output side of the direct current transformer can be independently loaded or unbalanced loaded.
When the bipolar power supply mode is adopted, the insulated gate bipolar transistors Q1 and Q3, Q2 and Q4 control the voltages of the high-voltage side positive and negative direct current buses and the low-voltage side positive and negative direct current buses, respectively.
When power flows in the forward direction, as shown in fig. 2, the high-voltage side dc bus outputs energy to the low-voltage side dc bus, and the insulated gate bipolar transistors Q1 and Q3 are respectively controlled to adjust the voltage of the low-voltage side positive and negative dc buses, and the diodes connected in anti-parallel at the two ends of the diodes are only subjected to reverse voltage, so that the diodes are not conducted in the whole process; the igbt Q2 and Q4 have no driving signal all the time, and the diodes connected in anti-parallel between the two ends thereof bear forward voltage during the turn-off period of Q1 and Q3, so that the current in the inductors L1 and L2 can freewheel.
When power flows in the reverse direction, as shown in fig. 3, the low-voltage side dc bus outputs energy to the high-voltage side dc bus, and the insulated gate bipolar transistors Q2 and Q4 are respectively controlled to adjust the voltage of the high-voltage side positive and negative dc buses, and the diodes connected in anti-parallel at the two ends of the diodes only bear the reverse voltage, so that the diodes are not conducted in the whole process; and the insulated gate bipolar transistors Q1 and Q3 have no driving signal at all times, the diodes connected in anti-parallel at two ends bear forward voltage during the turn-off period of Q2 and Q3, and the inductors L1 and L2 and the low-voltage direct-current power grids DC3 and DC4 can provide energy to the high-voltage direct-current bus and the capacitors C1 and C2.
When the power is supplied independently by the positive bus monopole, as shown in fig. 4, energy flows only between the high-voltage side positive direct current bus and the low-voltage side positive direct current bus, and the directions of the energy flows are controlled by controlling the insulated gate bipolar transistors Q1 and Q2 respectively; and the insulated gate bipolar transistors Q3 and Q4 are always kept off, and the diodes with two ends connected in anti-parallel only bear reverse voltage all the time, so the whole process is not conducted, and no energy transmission exists between the high-voltage side negative direct current bus and the low-voltage side negative direct current bus.
When the power is supplied independently by the negative bus monopole, as shown in fig. 5, energy flows only between the high-voltage side negative direct current bus and the low-voltage side negative direct current bus, and the directions of the energy flows are controlled by respectively controlling the insulated gate bipolar transistors Q3 and Q4; the insulated gate bipolar transistors Q1 and Q2 are always turned off, and the diodes connected in anti-parallel at two ends of the insulated gate bipolar transistors are always only subjected to reverse voltage, so that the insulated gate bipolar transistors are not conducted in the whole process, and no energy is transmitted between the high-voltage side positive direct current bus and the low-voltage side positive direct current bus.

Claims (2)

1. A bipolar bidirectional DC transformer, characterized in that: the high-voltage positive pole-HV of the bipolar bidirectional direct current transformer is connected with the collector of a first insulated gate bipolar transistor Q1 and one end of a first capacitor C1, the high-voltage positive pole-HV of the bipolar bidirectional direct current transformer is connected with the emitter of a third insulated gate bipolar transistor Q3 and one end of a second capacitor C2, the emitter of the first insulated gate bipolar transistor Q1 is respectively connected with the collector of a second insulated gate bipolar transistor Q2 and one end of a first inductor L1, the collector of the third insulated gate bipolar transistor Q3 is respectively connected with the emitter of a fourth insulated gate bipolar transistor Q4 and one end of a second inductor L2, the low-voltage positive pole + LV of the bidirectional direct current transformer is connected with the other end of the first inductor L1 and one end of a third capacitor C3, the low-voltage negative pole-LV of the bipolar direct current transformer is connected with the other end of the second inductor L2 and one end of a fourth capacitor C4, the other terminal of C1 of the first capacitor, the other terminal of C2 of the second capacitor, the other terminal of C3 of the third capacitor, the other terminal of C4 of the fourth capacitor, the emitter of the second insulated-gate bipolar transistor Q2, and the collector of the fourth insulated-gate bipolar transistor Q4 are grounded.
2. A bipolar bi-directional dc transformer as claimed in claim 1, wherein: the diode-based IGBT further comprises four diodes, two ends of each IGBT are connected with one diode in an anti-parallel mode, namely the emitter of each IGBT is connected with the anode of each diode, and the collector of each IGBT is connected with the cathode of each diode.
CN202022696724.8U 2020-11-20 2020-11-20 Bipolar bidirectional direct-current transformer Active CN213693474U (en)

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