CN114079281B - 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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- CN114079281B CN114079281B CN202111388423.1A CN202111388423A CN114079281B CN 114079281 B CN114079281 B CN 114079281B CN 202111388423 A CN202111388423 A CN 202111388423A CN 114079281 B CN114079281 B CN 114079281B
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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 isolation type 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 the second alternating voltage; the filter circuit is used for converting the second alternating voltage into a second direct voltage and outputting the second direct voltage; the isolation circuit is used for isolating the second winding from the load branch and isolating the third winding from the load branch. The application 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 application relates to the technical field of electronic power, in particular to a low-voltage direct-current system and a power supply system.
Background
In recent years, with the development of the power grid, 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 such as control, protection, measurement and wave recording and loop power supplies, and can be connected with a storage battery, so that the function of the uninterruptible power supply is easy to realize. However, the conventional low-voltage direct current system is prone to malfunction of the relay, and has a problem of low power supply reliability.
Disclosure of Invention
Accordingly, it is necessary to provide a low-voltage dc system and a power supply system having 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 isolation type 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 power 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 being grounded; 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;
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 filter circuit is used for converting the second alternating voltage into a second direct voltage and outputting the second direct voltage; the isolation circuit is used for isolating the second winding from the load branch and isolating the third winding from the load branch.
In one embodiment, the filter circuit includes 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 being connected with the load branch, and the second end of the first capacitor is used for being grounded; the first end of the second capacitor is used for being grounded, the second end of the second capacitor is connected with the isolation circuit and the first end of the second inductor respectively, and the second end of the second inductor is used for being connected with 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 balance resistor is connected with the first end of the first capacitor, and the second end of the first balance resistor is used for being grounded; the first end of the second balancing resistor is used for being grounded, and the second end of the second balancing resistor is connected with the second end of the second capacitor.
In one embodiment, the DC-AC conversion control circuit includes a pulse output chip and a MOS transistor; 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 used for being 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 so as to periodically turn on and 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 drive of the first direct current voltage.
In one embodiment, the high frequency transformer further comprises a fourth winding;
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 being grounded.
In one embodiment, the isolated DC-DC conversion module further includes a voltage stabilizing circuit, where the voltage stabilizing circuit is connected to the first end of the first resistor and the DC power supply module, respectively.
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 includes a first diode, a second diode, a third diode, and a fourth diode;
the positive electrode of the first diode is connected with the first end of the second winding, the negative electrode of the first diode is respectively connected with the negative electrode of the second diode and the filter circuit, and the positive electrode of the second diode is used for grounding; the negative pole of the third diode is used for grounding, the positive poles of the third diode are respectively connected with the filter circuit and the positive pole of the fourth diode, and the negative pole 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 embodiment.
The low-voltage direct current system and the power supply system comprise a direct current power supply module and an isolated DC-DC conversion module, wherein the isolated 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 power 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 an isolation circuit, the isolation circuit is connected with a filter circuit, and the filter circuit is used for connecting a load branch. 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 filter circuit is used for converting the second alternating voltage into a second direct voltage and outputting the second direct voltage. The isolation circuit is used for isolating the third winding from the load branch and isolating the fourth winding from the load branch. Therefore, when alternating current-direct current channeling or direct current grounding occurs in a certain load branch, the low-voltage direct current system can isolate the primary side from the secondary side through the high-frequency transformer and isolate faults on the load branch, so that 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 of the embodiments or the conventional techniques of the present application, the drawings required for the descriptions of the embodiments or the conventional techniques will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.
FIG. 1 is one of the schematic block diagrams of a low voltage DC system in one embodiment;
FIG. 2 is a schematic diagram of a DC-DC system according to one embodiment;
fig. 3 is a second schematic block diagram of a dc-dc system in one embodiment.
Detailed Description
In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Embodiments of the application are illustrated 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 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 the terms first, second, etc. as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element. 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 application. Both the first resistor and the second resistor are resistors, but they are not the same resistor.
It is to be understood that in the following embodiments, "connected" is understood to mean "electrically connected", "communicatively connected", etc., if the connected circuits, modules, units, etc., have electrical or data transfer between them.
As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or the like, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof. Also, the term "and/or" as used in this specification includes any and all combinations of the associated listed items. "plurality" means two or more, such as two, three, five, eight, etc.
As described in the background art, the traditional low-voltage direct current system is easy to cause relay misoperation, and has the problem of low power supply reliability. The inventor has found that the problem is caused by the fact that in a low-voltage direct current system, a section of bus is connected with different load branches respectively. For the secondary power supply in the same interval of the transformer substation, an alternating current loop and a direct current loop are arranged. Therefore, in the process of overhauling, the condition that an alternating current loop is overlapped to a direct current loop is easy to occur, so that alternating current and direct current are conducted, and then misoperation of a relay is caused, equipment is tripped by mistake, and the reliability of a low-voltage direct current system is reduced.
In particular, in a transformer substation and a convertor station, the low-voltage alternating current-direct current channeling is huge in damage and serious in consequences. A trip event of the equipment directly caused by the channeling of multiple ac power sources into the low voltage dc system occurs in the power system. In a control box or terminal box, the use of both ac and dc power is unavoidable, and this risk is still an uncontrollable factor, particularly subject to human factors. Grounding of a pole of the low voltage dc system may also cause malfunction or rejection of the protection and automation.
In a traditional low-voltage direct current system, load branches are directly connected to a direct current bus, no isolation exists between the load branches and the direct current bus, and no isolation exists between different load branches. When one branch is led into an alternating current power supply or grounded, the fault is led to a direct current bus directly through a branch loop, so that the normal operation of other branches is influenced.
Accordingly, it is necessary to provide a low-voltage dc system with high power supply reliability. The application technically reduces the harm of alternating current and direct current channeling, and adds an alternating current isolation module for a low-voltage direct current system branch of a transformer substation. When the alternating current power supply is led into a certain direct current branch, the module can filter the alternating current component, isolate the series-connected alternating current power supply at the branch, thereby reducing the influence on the whole low-voltage direct current system, preventing the situation of misoperation of other branches and further improving the power supply reliability of the low-voltage direct current system.
In one embodiment, as shown in FIG. 1, a low voltage DC system is provided. The system includes 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, which has the advantages of small volume, 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 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 TR3. The first end of the first winding TR1 is connected to the DC power module 10, and the second end of the first winding TR1 is connected to the DC-AC conversion control circuit 210, where the DC-AC conversion control circuit 210 is further used for grounding. The first end of the second winding TR2 is connected to the isolation circuit 220, and the second end of the second winding TR2 is used for grounding. The first end of the third winding TR3 is for grounding, the second end of the third winding TR3 is connected to the isolation circuit 220, the isolation circuit 220 is connected to the filter circuit 230, and the filter circuit 230 is for connecting one or more load branches 30.
Wherein the DC-AC conversion control circuit 210 is configured 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 periodically controls the connection between the first winding TR1 and the ground, and in each period, the DC-AC conversion circuit turns on the connection between the first winding TR1 and the ground for a first period and turns off the connection between the first winding TR1 and the ground for a second period. The first period and the second period form a 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 and transform it accordingly, and output the transformed voltage (i.e., the second ac voltage) at the second winding TR2 and the third winding TR3.
Since the second end of the second winding TR2 and the first end of the third winding TR3 are both used for grounding, the second ac voltage output from the high frequency transformer 240 may be a voltage difference between the first end of the second winding TR2 and the second end of the third winding TR3. The second winding TR2, the isolation circuit 220, and the filter circuit 230 are sequentially connected, and the third winding TR3, the isolation circuit 220, and the filter circuit 230 are also sequentially connected. 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 can further realize 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 an ac channeling or dc ground fault occurs in a certain load branch 30, since the isolation circuit 220 is disposed between the load branch 30 and the high-frequency transformer 240, the isolation circuit 220 can be used to isolate the second winding TR2 from the load branch 30, so as to avoid that the fault voltage of the load branch 30 triggers the high-frequency transformer 240 to generate electromagnetic induction through the second winding TR2, and further isolate the primary side from the secondary side. Similarly, the isolation circuit 220 can be further used to isolate the third winding TR3 from the load branch 30, so as to avoid that the fault voltage of the load branch 30 triggers the high-frequency transformer 240 to generate electromagnetic induction through the third winding TR3. 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, so that the fault is isolated at the load branches 30, the normal operation of other load branches 30 is ensured, the faults of power equipment caused by alternating current-direct current channeling and direct current branch grounding are effectively prevented, and the reliability of a low-voltage direct current system power supply of a transformer substation is greatly improved.
The low-voltage DC system includes a DC power supply module 10 and an isolated DC-DC conversion module 20, wherein the isolated DC-DC conversion module 20 includes 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 includes a first winding TR1, a second winding TR2, and a third winding TR3. A first end of the first winding TR1 is connected to the DC power supply module 10, and a 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 used for grounding. The first end of the second winding TR2 is connected to the isolation circuit 220, and the 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 to the isolation circuit 220, the isolation circuit 220 is connected to the filter circuit 230, and the filter circuit 230 is used for connecting 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 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 filter circuit is used for converting the second alternating voltage into a second direct voltage and outputting the second direct 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 an ac/dc power channeling or dc grounding occurs in a certain load branch 30, the low-voltage dc system can isolate the primary side from the secondary side through the high-frequency transformer 240 so as 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. The first end of the first capacitor C2 is connected to the isolation circuit 220 and the first end of the first inductor L1, respectively, and the second end of the first inductor L1 is connected to the load branch 30, and the second end of the first capacitor C2 is connected to ground. The first end of the second capacitor C1 is used for grounding, the second end of the second capacitor C1 is respectively connected with the isolation circuit 220 and the first end of the second inductor L2, and the second end of the second inductor L2 is used for connecting the load branch 30. In this embodiment, the LC filter circuit 230 converts the second ac voltage into the second dc voltage, so as to reduce dc loss and improve the filtering effect.
In one embodiment, as shown in fig. 2, the filtering circuit 230 further includes a first balancing resistor R2 and a second balancing resistor R21, where the resistance value of the first balancing resistor R2 is the same as the resistance value 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 grounded. 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 to the load branch 30 through the bipolar voltage of +/-55V, the application can ensure that the filter circuit 230 can output the bipolar voltage meeting the requirement to the load branch 30 by arranging two balance resistors with the same resistance value at the filter circuit 230, thereby improving 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 grid electrode of the MOS tube Q1, the source electrode of the MOS tube Q1 is grounded, and the drain electrode of the MOS tube Q1 is connected with the second end of the first winding TR 1. The pulse output chip U1 is configured to output a pulse signal to periodically turn on and off the MOS transistor Q1. When the MOS tube Q1 is conducted, the first winding TR1 is connected with the ground through the MOS tube Q1; when the MOS transistor Q1 is turned off, the connection between the first winding TR1 and ground is also turned off. Thus, the switching state of the MOS transistor Q1 can be controlled by the pulse signal output by the pulse output chip U1, so as to periodically turn on and off the connection between the first winding TR1 and ground. In one embodiment, the source of the MOS transistor may be grounded through a resistor R1.
In this embodiment, the DC-AC conversion control circuit 210 is implemented by the pulse output chip U1 and the MOS transistor Q1, so that a cost-effective DC-AC conversion circuit can be implemented by fewer components.
In one embodiment, the pulse output chip U1 may be a chip of model UC3842, where the chip of model UC3842 may be connected to a corresponding peripheral circuit to implement output of a 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 with the first end of the first resistor R5, and the second end of the first resistor R5 is connected with the direct current power supply module 10, so that the pulse output chip U1 works under the drive of the first direct current voltage. Therefore, the pulse output chip U1 can take electricity from the direct current power supply module 10 through the first resistor R5 without setting an additional power supply, and the volume of the low-voltage direct current system can be reduced.
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 end 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, wherein the first end of the fourth winding TR4 is connected to the positive electrode of the diode D5, the negative electrode of the diode D5 is connected to the first end of the resistor R7, and the 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 the operating voltage of the chip to the pulse output chip U1 when the high-frequency transformer 240 is operated. In this way, by providing the fourth winding TR4 to supply power to the pulse output chip U1, on the one hand, the voltage interference of the dc power supply module 10 can be avoided 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 turns ratio of the first, second, third and fourth windings TR1, TR2, TR3 and TR4 may be determined according to actual circumstances, and the present application is not particularly limited thereto. In one example, the turns ratio of the first, second, third and fourth windings TR1, TR2, TR3 and TR4 may be 110:57:57:20.
in one embodiment, the isolated DC-DC conversion module 20 further includes a voltage stabilizing circuit, which is connected to the first end of the first resistor and the DC power supply module 10, respectively. In one embodiment, as shown in fig. 2, the voltage stabilizing 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 may be as shown in fig. 2. In this embodiment, by setting the voltage stabilizing circuit, the interference of the unstable voltage of the dc power supply module 10 to 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, where 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 is connected to the drain of the MOS transistor Q1 through a diode D3. Therefore, the drain voltage can be shaped through the shaping circuit, so that the influence of sharp waves generated by switching of the switching state of the MOS tube Q1 on the operation of the MOS tube 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. Wherein, the positive pole of the first diode D1 is connected to one end of the second winding TR2, and the negative pole of the first diode D1 is connected to the negative pole of the second diode D2 and the filter circuit 230, respectively. The anode of the second diode D2 is used for grounding. The negative pole of the third diode D9 is used for grounding, the positive pole of the third diode D9 is respectively connected with the positive poles of the filter circuit 230 and the fourth diode D8, and the negative pole of the fourth diode D8 is connected with the second end of the third winding TR3. Thus, the isolation circuit 220 can be implemented by a diode, thereby reducing the cost and volume of the low voltage dc system.
To facilitate an understanding of the aspects 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 source V3, a third balancing resistor R14, a fourth plane Heng Dianzu 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 a certain distributed capacitance (namely a capacitance C7 and a capacitance C8 in fig. 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 other branches are in ac, if the load branch 30 is directly connected with the dc power supply module 10, a loop of "ground-ac power supply-R19-C6-ground" will be formed due to the capacitor C6, resulting in the voltage across R19 exceeding the operating voltage thereof, thereby causing malfunction of the switch.
In the application, an isolated DC-DC conversion module 20 is arranged between a DC power supply module 10 and a load branch 30, a UC3842 chip is used to control a MOS transistor Q1 to be turned off, a first winding TR1 of a four-winding high-frequency transformer 240 collects the output of the DC power supply module 10, a second winding TR2 provides a working voltage for the UC3842 chip after starting, and a third winding TR3 and a fourth winding TR4 respectively provide 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 to a specific ratio according to the actual setting, for example, 110:57:57:20. The output of the high frequency transformer 240 is converted into a direct current through the filter circuit 230 and converted into a bipolar voltage of ±55v through the first balancing resistor R2 and the second balancing resistor R21, so that the output reliability can be improved. When a certain load branch 30 is led into alternating current, the voltage at two sides of the resistor R19 can be maintained at a lower value according to the voltage of other loads at the power supply side, so that misoperation of a relay can be avoided, and the reliability of a low-voltage direct current power supply system is improved.
In one embodiment, a power supply system is provided that includes one or more load branches, and the low voltage dc system of any of the above embodiments.
In the description of the present specification, reference to the terms "some embodiments," "other embodiments," "desired embodiments," and the like, means 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, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (8)
1. A low voltage dc system, comprising:
the direct current power supply module is used for outputting a first direct current voltage;
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, 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 power 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 being grounded; 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;
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 filter circuit is used for converting the second alternating voltage into a second direct voltage and outputting the second direct voltage; the isolation circuit is used for isolating the second winding from the load branch and isolating the third winding from the load branch;
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 being connected with the load branch, and the second end of the first capacitor is used for being grounded; 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;
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 used for being 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 so as to periodically turn on and off the MOS tube.
2. The low voltage dc system of claim 1, wherein the filter circuit further comprises a first balancing resistor and a second balancing resistor, the first balancing resistor having a same resistance as the second balancing resistor;
the first end of the first balance resistor is connected with the first end of the first capacitor, and the second end of the first balance resistor is used for being grounded; the first end of the second balancing resistor is used for being grounded, and the second end of the second balancing resistor is connected with the second end of the second capacitor.
3. The low voltage direct current system of claim 1 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 drive of the first direct current voltage.
4. The low voltage dc system of claim 3 wherein the high frequency transformer further comprises a fourth winding;
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 being grounded.
5. The low voltage DC system of claim 3 or 4, wherein the isolated DC-DC conversion module further comprises a voltage stabilizing circuit connected to the first end of the first resistor and the DC power supply module, respectively.
6. The low voltage DC system of any one of claims 1 to 4, wherein the isolated DC-DC conversion module further comprises 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 a drain of the MOS transistor.
7. The low voltage dc system of any one of claims 1 to 4, wherein the isolation circuit comprises a first diode, a second diode, a third diode, and a fourth diode;
the positive electrode of the first diode is connected with the first end of the second winding, the negative electrode of the first diode is respectively connected with the negative electrode of the second diode and the filter circuit, and the positive electrode of the second diode is used for grounding; the negative pole of the third diode is used for grounding, the positive poles of the third diode are respectively connected with the filter circuit and the positive pole of the fourth diode, and the negative pole of the fourth diode is connected with the second end of the third winding.
8. A power supply system comprising a load branch and a low voltage direct current system according to any one of claims 1 to 7.
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