CN114079281A - Low-voltage direct current system and power supply system - Google Patents
Low-voltage direct current system and power supply system Download PDFInfo
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- CN114079281A CN114079281A CN202111388423.1A CN202111388423A CN114079281A CN 114079281 A CN114079281 A CN 114079281A CN 202111388423 A CN202111388423 A CN 202111388423A CN 114079281 A CN114079281 A CN 114079281A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J11/00—Circuit arrangements for providing service supply to auxiliaries of stations in which electric power is generated, distributed or converted
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0063—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with circuits adapted for supplying loads from the battery
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33561—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having more than one ouput with independent control
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J2207/20—Charging or discharging characterised by the power electronics converter
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
Abstract
The application relates to a low-voltage direct-current system and a power supply system. The direct current power supply module is used for outputting a first direct current voltage. The isolated DC-DC conversion module comprises a DC-AC conversion control circuit, an isolation circuit, a filter circuit and a high-frequency transformer, wherein the high-frequency transformer comprises a first winding, a second winding and a third winding. The DC-AC conversion control circuit is used for periodically switching on and off the connection between the second end of the first winding and the ground so as to convert the first direct-current voltage into a first alternating-current voltage; the high-frequency transformer is used for converting the first alternating voltage into a second alternating voltage; the filtering module is used for converting the second alternating-current voltage into a second direct-current voltage and outputting the second direct-current voltage; the isolation circuit is used for isolating the second winding from the load branch circuit and isolating the third winding from the load branch circuit. The method and the device can isolate faults on the corresponding load branch, and improve the power supply reliability of the low-voltage direct-current system.
Description
Technical Field
The present application relates to the field of electronic power technologies, and in particular, to a low voltage dc system and a power supply system.
Background
In recent years, along with the development of power grids, the importance of a low-voltage direct-current system in a transformer substation is increasingly highlighted. The low-voltage direct-current system is widely applied to devices for control, protection, measurement, wave recording and the like and loop power supplies, and a storage battery can be connected into the low-voltage direct-current system, so that the function of an uninterruptible power supply is easy to realize. However, the conventional low-voltage direct-current system is easy to cause relay malfunction, and has the problem of low power supply reliability.
Disclosure of Invention
Accordingly, there is a need for a low-voltage dc system and a power supply system with high power supply reliability.
A low voltage dc system comprising:
the direct current power supply module is used for outputting a first direct current voltage;
the isolated DC-DC conversion module comprises a DC-AC conversion control circuit, an isolation circuit, a filter circuit and a high-frequency transformer, wherein the high-frequency transformer comprises a first winding, a second winding and a third winding; the first end of the first winding is connected with the direct current supply module, the second end of the first winding is connected with the DC-AC conversion control circuit, and the DC-AC conversion control circuit is used for grounding; the first end of the second winding is connected with the isolation circuit, and the second end of the second winding is used for grounding; the first end of the third winding is used for grounding, and the second end of the third winding is connected with the isolation circuit; the isolation circuit is connected with the filter circuit, and the filter circuit is used for connecting a load branch circuit;
wherein the DC-AC conversion control circuit is used for periodically switching on and off the connection between the second end of the first winding and the ground so as to convert the first direct-current voltage into a first alternating-current voltage; the high-frequency transformer is used for converting the first alternating voltage into a second alternating voltage; the filtering module is used for converting the second alternating-current voltage into a second direct-current voltage and outputting the second direct-current voltage; the isolation circuit is used for isolating the second winding from the load branch circuit and for isolating the third winding from the load branch circuit.
In one embodiment, the filter circuit comprises a first capacitor, a second capacitor, a first inductor and a second inductor;
the first end of the first capacitor is connected with the isolation circuit and the first end of the first inductor respectively, the second end of the first inductor is used for connecting the load branch circuit, and the second end of the first capacitor is used for grounding; the first end of the second capacitor is used for grounding, the second end of the second capacitor is respectively connected with the isolation circuit and the first end of the second inductor, and the second end of the second inductor is used for connecting the load branch circuit.
In one embodiment, the filter circuit further comprises a first balancing resistor and a second balancing resistor, wherein the resistance value of the first balancing resistor is the same as that of the second balancing resistor;
the first end of the first balancing resistor is connected with the first end of the first capacitor, and the second end of the first balancing resistor is used for grounding; the first end of the second balance resistor is used for grounding, and the second end of the second balance resistor is connected with the second end of the second capacitor.
In one embodiment, the DC-AC conversion control circuit comprises a pulse output chip and an MOS tube; the output end of the pulse output chip is connected with the grid electrode of the MOS tube, the source electrode of the MOS tube is grounded, and the drain electrode of the MOS tube is connected with the second end of the first winding;
the pulse output chip is used for outputting pulse signals to periodically turn on and turn off the MOS tube.
In one embodiment, the isolated DC-DC conversion module further comprises a first resistor;
the power supply end of the pulse output chip is connected with the first end of the first resistor, and the second end of the first resistor is connected with the direct current power supply module, so that the pulse output chip works under the driving of the first direct current voltage.
In one embodiment, the high frequency transformer further comprises a fourth winding;
and the first end of the fourth winding is connected with the power supply end of the pulse output chip, and the second end of the fourth winding is used for grounding.
In one embodiment, the isolated DC-DC conversion module further includes a voltage stabilizing circuit, and the voltage stabilizing circuit is respectively connected to the first end of the first resistor and the DC power supply module.
In one embodiment, the isolated DC-DC conversion module further includes a shaping circuit, a first end of the shaping circuit is connected to the DC power supply module, and a second end of the shaping circuit is connected to the drain of the MOS transistor.
In one embodiment, the isolation circuit comprises a first diode, a second diode, a third diode and a fourth diode;
the anode of the first diode is connected with the first end of the second winding, the cathode of the first diode is respectively connected with the cathode of the second diode and the filter circuit, and the anode of the second diode is used for grounding; the negative electrode of the third diode is used for grounding, the positive electrodes of the third diode are respectively connected with the filtering circuit and the positive electrode of the fourth diode, and the negative electrode of the fourth diode is connected with the second end of the third winding.
A power supply system comprises a load branch and the low-voltage direct-current system of any one of the embodiments.
The low-voltage direct current system and the power supply system comprise a direct current power supply module and an isolation type DC-DC conversion module, wherein the isolation type DC-DC conversion module comprises a DC-AC conversion control circuit, an isolation circuit, a filter circuit and a high-frequency transformer, and the high-frequency transformer comprises a first winding, a second winding and a third winding. The first end of the first winding is connected with the direct current supply module, the second end of the first winding is connected with the DC-AC conversion control circuit, and the DC-AC conversion control circuit is used for being grounded. The first end of the second winding is connected with the isolation circuit, and the second end of the second winding is used for grounding. The first end of the third winding is used for grounding, the second end of the third winding is connected with the isolation circuit, the isolation circuit is connected with the filter circuit, and the filter circuit is used for connecting the load branch circuit. The DC-AC conversion control circuit is used for periodically switching on and off the connection between the second end of the first winding and the ground so as to convert the first direct-current voltage output by the direct-current power supply module into a first alternating-current voltage. The high-frequency transformer is used for converting the first alternating voltage into a second alternating voltage. The filtering module is used for converting the second alternating-current voltage into a second direct-current voltage and outputting the second direct-current voltage. The isolation circuit is used for isolating the third winding from the load branch circuit and isolating the fourth winding from the load branch circuit. Therefore, when a certain load branch generates alternating current and direct current channeling or direct current grounding, the primary side and the secondary side of the low-voltage direct current system can be isolated through the high-frequency transformer, faults are isolated on the load branch, the operation of other load branches is prevented from being influenced, and the power supply reliability of the low-voltage direct current system can be improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a block diagram of a schematic configuration of a low voltage DC system in one embodiment;
FIG. 2 is a circuit schematic of a low voltage DC system in one embodiment;
fig. 3 is a second schematic block diagram of a low voltage dc system according to an embodiment.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, a first resistance may be referred to as a second resistance, and similarly, a second resistance may be referred to as a first resistance, without departing from the scope of the present application. The first resistance and the second resistance are both resistances, but they are not the same resistance.
It is to be understood that "connection" in the following embodiments is to be understood as "electrical connection", "communication connection", and the like if the connected circuits, modules, units, and the like have communication of electrical signals or data with each other.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, as used in this specification, the term "and/or" includes any and all combinations of the associated listed items. "plurality" refers to two or more, such as two, three, five, eight, etc.
As described in the background art, the conventional low-voltage dc system is prone to malfunction of the relay, and has a problem of low power supply reliability. The inventor researches and finds that the problem is caused because in a low-voltage direct-current system, one section of bus is respectively connected with different load branches. For the secondary power supply in the same interval of the transformer substation, the transformer substation is provided with an alternating current loop and a direct current loop. Therefore, in the process of maintenance, the condition that the alternating current loop is lapped on the direct current loop easily occurs, so that alternating current and direct current are mixed, further the relay is mistakenly operated, equipment is mistakenly tripped, and the reliability of a low-voltage direct current system is reduced.
Particularly, in a transformer substation and a converter station, low-voltage alternating current and direct current channeling is serious in damage and serious in consequence. Equipment tripping events that are directly caused by the channeling of ac power into low voltage dc systems have occurred in power systems. In a control cubicle or a terminal box, the situation of using an alternating current power supply and a direct current power supply at the same time is inevitable, and the risk still has uncontrollable factors, and is particularly greatly influenced by human factors. Grounding of a pole of a low voltage dc system may also cause malfunction or failure of protection and automation devices.
In a traditional low-voltage direct-current system, a load branch is directly connected to a direct-current bus, the load branch is not isolated from the direct-current bus, and different load branches are not isolated. When a certain branch enters an alternating current power supply or is grounded, the fault is directly led to a direct current bus through a branch loop, and the normal operation of other branches is further influenced.
Therefore, a low-voltage dc system with high power supply reliability is needed. The application technically reduces the harm of alternating current and direct current channeling electricity, and the alternating current isolating module used on the branch of the low-voltage direct current system of the transformer substation is added. When a certain DC branch circuit is jumped into by an AC power supply, the module can filter AC components and isolate the serially connected AC power supply in the branch circuit, thereby reducing the influence on the whole low-voltage DC system, preventing other branch circuits from being mistakenly moved and further improving the power supply reliability of the low-voltage DC system.
In one embodiment, as shown in FIG. 1, a low voltage DC system is provided. The system comprises a direct current power supply module 10 and an isolated DC-DC conversion module 20. The isolated DC-DC conversion module 20 is an isolated DC-DC conversion module, has the advantages of small size, high reliability, stable output, high cost performance, and the like, and can be widely used in the fields of industrial instruments, digital circuits, electronic communication equipment, satellite navigation, remote sensing and telemetry, ground communication and scientific research equipment, and the like.
Specifically, the isolated DC-DC conversion module 20 includes a DC-AC conversion control circuit 210 (i.e., an AC-DC conversion control circuit), an isolation circuit 220, a filter circuit 230, and a high-frequency transformer 240. The high frequency transformer 240 includes a first winding TR1, a second winding TR2, and a third winding TR 3. The first end of the first winding TR1 is connected to the DC power supply module 10, the second end of the first winding TR1 is connected to the DC-AC conversion control circuit 210, and the DC-AC conversion control circuit 210 is further configured to be grounded. A first end of the second winding TR2 is connected to the isolation circuit 220, and a second end of the second winding TR2 is used for grounding. The first end of the third winding TR3 is used for grounding, the second end of the third winding TR3 is connected with the isolation circuit 220, the isolation circuit 220 is connected with the filter circuit 230, and the filter circuit 230 is used for connecting with one or more load branches 30.
The DC-AC conversion control circuit 210 is used to periodically turn on and off the connection between the first winding TR1 and the ground. That is, the DC-AC conversion control circuit 210 will periodically control the connection between the first winding TR1 and ground, and in each cycle, the DC-AC conversion circuit will turn on the connection between the first winding TR1 and ground in the first period and turn off the connection between the first winding TR1 and ground in the second period. The first period and the second period constitute one cycle. In this way, the voltage received at the first winding TR1 may be changed to convert the first dc voltage output by the dc power supply module 10 into the first ac voltage. The high frequency transformer 240 may receive the first ac voltage, transform the first ac voltage accordingly, and output the transformed voltage (i.e., the second ac voltage) at the second winding TR2 and the third winding TR 3.
Since the second terminal of the second winding TR2 and the first terminal of the third winding TR3 are both used for grounding, the second alternating voltage output by the high frequency transformer 240 may be a voltage difference between the first terminal of the second winding TR2 and the second terminal of the third winding TR 3. The second winding TR2, the isolation circuit 220, and the filter circuit 230 are connected in this order, and the third winding TR3, the isolation circuit 220, and the filter circuit 230 are also connected in this order. The second ac voltage may be output to the filter circuit 230 through the isolation circuit 220, so that the filter circuit 230 converts the second ac voltage into a second DC voltage, and the isolated DC-DC conversion module 20 realizes DC-DC conversion. The filter circuit 230 may output the second dc voltage to the load branches 30 to supply power to each load branch 30 through the second dc voltage.
When a certain load branch 30 has an ac ingress or a dc ground fault, since the isolation circuit 220 is disposed between the load branch 30 and the high-frequency transformer 240, the isolation circuit 220 may be configured to isolate the second winding TR2 from the load branch 30, so as to prevent the fault voltage of the load branch 30 from triggering the high-frequency transformer 240 through the second winding TR2 to generate electromagnetic induction, and further isolate the primary side from the secondary side. Similarly, the isolation circuit 220 may also be used to isolate the third winding TR3 from the load branch 30, so as to prevent the fault voltage of the load branch 30 from triggering the high-frequency transformer 240 to generate electromagnetic induction through the third winding TR 3. Therefore, the fault voltage can be prevented from influencing the direct current power supply module 10 or other load branches 30 through the high-frequency transformer 240, and further, the fault can be isolated at the load branches 30, so that the normal operation of other load branches 30 is guaranteed, the power equipment faults caused by alternating current and direct current channeling and direct current branch grounding are effectively prevented, and the reliability of the low-voltage direct current system power supply of the transformer substation is greatly improved.
The low-voltage direct-current system comprises a direct-current power supply module 10 and an isolated DC-DC conversion module 20, wherein the isolated DC-DC conversion module 20 comprises a DC-AC conversion control circuit 210, an isolation circuit 220, a filter circuit 230 and a high-frequency transformer 240, and the high-frequency transformer 240 comprises a first winding TR1, a second winding TR2 and a third winding TR 3. The first end of the first winding TR1 is connected to the DC power supply module 10, the second end of the first winding TR1 is connected to the DC-AC conversion control circuit 210, and the DC-AC conversion control circuit 210 is connected to the ground. A first end of the second winding TR2 is connected to the isolation circuit 220, and a second end of the second winding TR2 is used for grounding. The first end of the third winding TR3 is used for grounding, the second end of the third winding TR3 is connected with the isolation circuit 220, the isolation circuit 220 is connected with the filter circuit 230, and the filter circuit 230 is used for connecting with the load branch 30. The DC-AC conversion control circuit 210 is configured to periodically turn on and off the connection between the second end of the first winding TR1 and the ground, so as to convert the first DC voltage output by the DC power supply module 10 into a first AC voltage. The high frequency transformer 240 is used to convert the first ac voltage into a second ac voltage. The filtering module is used for converting the second alternating-current voltage into a second direct-current voltage and outputting the second direct-current voltage. The isolation circuit 220 is used to isolate the third winding TR3 from the load branch 30 and to isolate the fourth winding TR4 from the load branch 30. Thus, when a certain load branch 30 has an ac/dc power channeling or a dc grounding, the low voltage dc system can isolate the primary side and the secondary side through the high frequency transformer 240 to isolate the fault on the load branch 30, thereby avoiding affecting the operation of other load branches 30, and further improving the power supply reliability of the low voltage dc system.
In one embodiment, as shown in fig. 2, the filter circuit 230 includes a first capacitor C2, a second capacitor C1, a first inductor L1, and a second inductor L2. A first terminal of the first capacitor C2 is connected to the isolation circuit 220 and a first terminal of the first inductor L1, respectively, a second terminal of the first inductor L1 is connected to the load branch 30, and a second terminal of the first capacitor C2 is connected to ground. A first terminal of the second capacitor C1 is connected to ground, a second terminal of the second capacitor C1 is connected to the isolation circuit 220 and a first terminal of the second inductor L2, and a second terminal of the second inductor L2 is connected to the load branch 30. In this embodiment, the LC filter circuit 230 converts the second ac voltage into the second dc voltage, so that the dc loss can be reduced and the filtering effect can be improved.
In one embodiment, as shown in fig. 2, the filter circuit 230 further includes a first balancing resistor R2 and a second balancing resistor R21, and the resistance of the first balancing resistor R2 is the same as the resistance of the second balancing resistor R21. The first end of the first balancing resistor R2 is connected to the first end of the first capacitor C2, and the second end of the first balancing resistor R2 is connected to ground. The first end of the second balancing resistor R21 is used for grounding, and the second end of the second balancing resistor R21 is connected with the second end of the second capacitor C1. Because the low-voltage direct current system needs to supply power for the load branch circuit 30 through the two-pole voltage of 55V, therefore, this application accessible sets up two balancing resistors that the resistance is the same in filter circuit 230 department to make filter circuit 230 can be to the two-pole voltage that the load branch circuit 30 output satisfied the requirement, improved the output reliability.
In one embodiment, as shown in fig. 2, the DC-AC conversion control circuit 210 includes a pulse output chip U1 and a MOS transistor Q1. The output end of the pulse output chip U1 is connected with the gate of a MOS tube Q1, the source of the MOS tube Q1 is used for grounding, and the drain of the MOS tube Q1 is used for connecting the second end of the first winding TR 1. The pulse output chip U1 is used for outputting a pulse signal to periodically turn on and off the MOS transistor Q1. When the MOS transistor Q1 is switched on, the first winding TR1 is connected with the ground through the MOS transistor Q1; when the MOS transistor Q1 is disconnected, the connection between the first winding TR1 and the ground is also disconnected. In this way, the switching state of the MOS transistor Q1 may be controlled by the pulse signal output from the pulse output chip U1 to periodically turn on and off the connection between the first winding TR1 and the ground. In one embodiment, the source of the MOS transistor may be grounded through a resistor R1.
In this embodiment, the pulse output chip U1 and the MOS transistor Q1 implement the DC-AC conversion control circuit 210, so that a cost-effective DC-AC conversion circuit can be implemented with fewer components.
In one embodiment, the pulse output chip U1 may be a chip of UC3842 type, and the chip of UC3842 type may be connected to a corresponding peripheral circuit to implement output of the pulse signal. As shown in fig. 2, the peripheral circuit of the chip may include a resistor R3, a resistor R4, a resistor R6, a resistor R25, a capacitor C3, a capacitor C4, and a capacitor C11, and the connection relationship of the devices may be as shown in fig. 2.
In one embodiment, as shown in fig. 2, the isolated DC-DC conversion module 20 further includes a first resistor R5. The power supply end of the pulse output chip U1 is connected to the first end of the first resistor R5, and the second end of the first resistor R5 is connected to the dc power supply module 10, so that the pulse output chip U1 operates under the driving of the first dc voltage. Therefore, the pulse output chip U1 can get power from the dc power supply module 10 through the first resistor R5 without providing an additional power supply, thereby reducing the size of the low voltage dc system.
In one embodiment, as shown in fig. 2, the high frequency transformer 240 further includes a fourth winding TR4, a first end of the fourth winding TR4 is connected to a power supply terminal of the pulse output chip U1, and a second end of the fourth winding TR4 is used for grounding. In one embodiment, the isolated DC-DC conversion module 20 may further include a diode D5 and a resistor R7, a first end of the fourth winding TR4 is connected to the anode of the diode D5, a cathode of the diode D5 is connected to a first end of the resistor R7, and a second end of the resistor R7 is connected to the power supply end of the pulse output chip U1.
Specifically, the fourth winding TR4 serves as a secondary winding in the high frequency transformer 240, and may supply an operating voltage of the chip to the pulse output chip U1 when the high frequency transformer 240 is operated. In this way, the fourth winding TR4 is provided to supply power to the pulse output chip U1, so that, on the one hand, the voltage interference of the dc power supply module 10 can be prevented from affecting the operation of the pulse output chip U1. On the other hand, the pulse output chip U1 can be powered by two power supply modes, so that the working reliability of the low-voltage direct-current system is improved.
It is understood that the turn ratios of the first winding TR1, the second winding TR2, the third winding TR3 and the fourth winding TR4 may be determined according to practical situations, and the present application does not specifically limit the same. In one example, the turns ratio of the first, second, third and fourth windings TR1, TR2, TR3, TR4 may be 110:57:57: 20.
in one embodiment, the isolated DC-DC conversion module 20 further includes a voltage regulator circuit, which is respectively connected to the first end of the first resistor and the DC power supply module 10. In one embodiment, as shown in FIG. 2, the voltage regulation circuit may include a diode D4, a diode D6, a diode D7, a diode D10, a capacitor C13, and a resistor R31. The connection relationship of the devices can be as shown in fig. 2. In this embodiment, by providing the voltage stabilizing circuit, the interference of unstable voltage of the dc power supply module 10 on the pulse output chip U1 can be avoided, and the reliability of the low-voltage dc system is improved.
In one embodiment, the isolated DC-DC conversion module 20 further includes a shaping circuit, a first end of the shaping circuit is connected to the DC power supply module 10, and a second end of the shaping circuit is connected to the drain of the MOS transistor Q1. In one embodiment, as shown in fig. 2, the shaping circuit may include a resistor R8 and a capacitor C5, the resistor R8 and the capacitor C5 are connected in parallel, one end of the parallel connection is connected to the dc power supply module 10, and the other end of the parallel connection may be connected to the drain of the MOS transistor Q1 through a diode D3. Therefore, the drain voltage can be shaped by the shaping circuit, so that the influence of sharp waves generated by switching the switching state of the MOS transistor Q1 on the work of the MOS transistor Q1 is avoided, and the reliability of a low-voltage direct-current system is further improved.
In one embodiment, as shown in fig. 2, the isolation circuit 220 includes a first diode D1, a second diode D2, a third diode D9, and a fourth diode D8. The anode of the first diode D1 is connected to one end of the second winding TR2, and the cathode of the first diode D1 is connected to the cathode of the second diode D2 and the filter circuit 230, respectively. The anode of the second diode D2 is used for ground. The cathode of the third diode D9 is used for grounding, the anode of the third diode D9 is connected to the anodes of the filter circuit 230 and the fourth diode D8, respectively, and the cathode of the fourth diode D8 is connected to the second end of the third winding TR 3. Thus, the isolation circuit 220 can be implemented by a diode, thereby reducing the cost and size of the low voltage dc system.
To facilitate understanding of the solution of the present application, a low voltage dc system is provided as shown in fig. 2-3. The dc power supply module 10 includes a 110V dc power supply V3, a third balancing resistor R14, a fourth balancing resistor R15, and other devices. Because the low-voltage direct current load in the transformer substation is more, the cable is longer, and the two-pole cable has certain distributed capacitance (namely, the capacitor C7 and the capacitor C8 in the figure 2) to the ground. R19 is the equivalent resistance of a certain brake-separating relay, and C6 is the cable-to-ground capacitance of the brake-separating branch. When the other branches are subjected to alternating current ingress, if the load branch 30 is directly connected with the dc power supply module 10, a "ground-alternating current power supply-R19-C6-ground" loop is formed due to the existence of the capacitor C6, so that the voltage across the R19 exceeds the action voltage thereof, thereby causing switch malfunction.
In the present application, an isolated DC-DC conversion module 20 is disposed between the DC power supply module 10 and the load branch 30, a UC3842 chip is used to control the turn-off of the MOS transistor Q1, the first winding TR1 of the four-winding high-frequency transformer 240 collects the output of the DC power supply module 10, the second winding TR2 provides a working voltage for the UC3842 chip after starting, and the third winding TR3 and the fourth winding TR4 respectively provide the converted positive and negative output voltages. Since the isolated DC-DC conversion module 20 has a certain voltage loss, the windings of the transformer need to be set in a specific ratio according to the actual setting, for example, the ratio can be set to 110:57:57: 20. The output of the high frequency transformer 240 is converted into a direct current by the filter circuit 230 and converted into a bipolar voltage of ± 55V by the first and second balancing resistors R2 and R21, so that output reliability can be improved. When a certain load branch 30 flees into the alternating current, the voltage on the two sides of the resistor R19 can be maintained at a lower value according to the voltage of other loads on the power supply side, thereby avoiding the malfunction of the relay and improving the reliability of the low-voltage direct current power supply system.
In one embodiment, a power supply system is provided, which includes one or more load branches, and the low-voltage dc system in any of the above embodiments.
In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A low voltage dc system, comprising:
the direct current power supply module is used for outputting a first direct current voltage;
the isolated DC-DC conversion module comprises a DC-AC conversion control circuit, an isolation circuit, a filter circuit and a high-frequency transformer, wherein the high-frequency transformer comprises a first winding, a second winding and a third winding; the first end of the first winding is connected with the direct current supply module, the second end of the first winding is connected with the DC-AC conversion control circuit, and the DC-AC conversion control circuit is used for grounding; the first end of the second winding is connected with the isolation circuit, and the second end of the second winding is used for grounding; the first end of the third winding is used for grounding, and the second end of the third winding is connected with the isolation circuit; the isolation circuit is connected with the filter circuit, and the filter circuit is used for connecting a load branch circuit;
wherein the DC-AC conversion control circuit is used for periodically switching on and off the connection between the second end of the first winding and the ground so as to convert the first direct-current voltage into a first alternating-current voltage; the high-frequency transformer is used for converting the first alternating voltage into a second alternating voltage; the filtering module is used for converting the second alternating-current voltage into a second direct-current voltage and outputting the second direct-current voltage; the isolation circuit is used for isolating the second winding from the load branch circuit and for isolating the third winding from the load branch circuit.
2. The low voltage direct current system of claim 1, wherein the filter circuit comprises a first capacitor, a second capacitor, a first inductor, and a second inductor;
the first end of the first capacitor is connected with the isolation circuit and the first end of the first inductor respectively, the second end of the first inductor is used for connecting the load branch circuit, and the second end of the first capacitor is used for grounding; the first end of the second capacitor is used for grounding, the second end of the second capacitor is respectively connected with the isolation circuit and the first end of the second inductor, and the second end of the second inductor is used for connecting the load branch circuit.
3. The low voltage direct current system according to claim 2, wherein the filter circuit further comprises a first balancing resistor and a second balancing resistor, wherein the first balancing resistor has the same resistance value as the second balancing resistor;
the first end of the first balancing resistor is connected with the first end of the first capacitor, and the second end of the first balancing resistor is used for grounding; the first end of the second balance resistor is used for grounding, and the second end of the second balance resistor is connected with the second end of the second capacitor.
4. The low-voltage direct-current system according to claim 1, wherein the DC-AC conversion control circuit comprises a pulse output chip and an MOS (metal oxide semiconductor) tube; the output end of the pulse output chip is connected with the grid electrode of the MOS tube, the source electrode of the MOS tube is grounded, and the drain electrode of the MOS tube is connected with the second end of the first winding;
the pulse output chip is used for outputting pulse signals to periodically turn on and turn off the MOS tube.
5. The low voltage direct current system of claim 4, wherein the isolated DC-DC conversion module further comprises a first resistor;
the power supply end of the pulse output chip is connected with the first end of the first resistor, and the second end of the first resistor is connected with the direct current power supply module, so that the pulse output chip works under the driving of the first direct current voltage.
6. The low voltage direct current system according to claim 5, wherein said high frequency transformer further comprises a fourth winding;
and the first end of the fourth winding is connected with the power supply end of the pulse output chip, and the second end of the fourth winding is used for grounding.
7. The low-voltage direct-current system according to claim 5 or 6, wherein the isolated DC-DC conversion module further comprises a voltage stabilizing circuit, and the voltage stabilizing circuit is respectively connected with the first end of the first resistor and the direct-current power supply module.
8. The low-voltage direct-current system according to any one of claims 4 to 6, wherein the isolated DC-DC conversion module further comprises a shaping circuit, a first end of the shaping circuit is connected with the direct-current power supply module, and a second end of the shaping circuit is connected with the drain of the MOS transistor.
9. The low voltage dc system according to any of claims 1 to 6, wherein the isolation circuit comprises a first diode, a second diode, a third diode, and a fourth diode;
the anode of the first diode is connected with the first end of the second winding, the cathode of the first diode is respectively connected with the cathode of the second diode and the filter circuit, and the anode of the second diode is used for grounding; the negative electrode of the third diode is used for grounding, the positive electrodes of the third diode are respectively connected with the filtering circuit and the positive electrode of the fourth diode, and the negative electrode of the fourth diode is connected with the second end of the third winding.
10. A power supply system comprising a load branch and a low voltage dc system according to any one of claims 1 to 9.
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