CN112383078A - Local side power supply and alternating current remote power supply system - Google Patents

Local side power supply and alternating current remote power supply system Download PDF

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Publication number
CN112383078A
CN112383078A CN202011357472.4A CN202011357472A CN112383078A CN 112383078 A CN112383078 A CN 112383078A CN 202011357472 A CN202011357472 A CN 202011357472A CN 112383078 A CN112383078 A CN 112383078A
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China
Prior art keywords
power supply
phase
transformer
alternating current
power
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Pending
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CN202011357472.4A
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Chinese (zh)
Inventor
甘鸿坚
蒲波宇
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Zhejiang Kunwu Technology Co ltd
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Zhejiang Kunwu Technology Co ltd
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Priority to CN202011357472.4A priority Critical patent/CN112383078A/en
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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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention provides a local side power supply and an alternating current remote power supply system, comprising: the three-phase alternating current-to-direct current converter comprises a three-phase alternating current-to-direct current module, a direct current-to-alternating current module and a first transformer; the three-phase AC-to-DC conversion module receives a three-phase AC power supply and converts the three-phase AC power supply into a DC power supply; the direct current to alternating current module is connected to the output end of the three-phase alternating current to direct current module and converts the direct current power supply into an alternating current power supply; the primary side of the first transformer is connected with the output end of the direct current-to-alternating current module, and the secondary side of the first transformer is connected with the single-phase alternating current power supply in series to obtain single-phase alternating current output voltage. The local side power supply and the alternating current remote power supply system can effectively reduce the loss in the power transmission process of the remote power supply system and reduce the volume and the cost.

Description

Local side power supply and alternating current remote power supply system
Technical Field
The invention relates to the field of circuit design, in particular to a local side power supply and an alternating current remote power supply system.
Background
The highway electromechanical system is composed of 4 systems of communication, charging, monitoring and power supply, along with the high-speed development of traffic intellectualization, traffic intelligent system equipment is continuously increased, the traffic intelligent system equipment is distributed along the line, the distance is different, the power is different, the requirements of electronic equipment on power supply are different, and the power consumption dilemma is more and more obvious.
In a low-voltage power supply system, the line voltage is 380V/50 Hz, and due to the line impedance, the transmission line has line voltage drop, and the voltage drop at the tail end of the power supply line should not exceed 5 percent according to the current power standard. In order to overcome the disadvantages, an ac remote power supply system is generally used to increase the voltage of the user terminal, and the whole system mainly comprises a local power supply, a long cable and a plurality of remote power supplies. A power electronic converter in the local side power supply converts a three-phase alternating current 380V power supply into a single-phase alternating current 800V-1000V power supply, and the single-phase alternating current 800V-1000V power supply is transmitted to each remote electric equipment end through a long cable; the input voltage of the far end is basically maintained above 800V due to the transmission of high voltage; then converting the single-phase AC 800V-1000V power supply into AC220V power supply for the load through a remote power supply; thereby ensuring stable power supply on the load side.
In the remote power supply system, all loads are output by the local side power supply, the power of the power electronic converter in the local side power supply is high, the manufacturing cost is high, the proportion of loss to total loss is also the largest, and the economic benefit is not high.
Therefore, how to reduce the loss in the power transmission process of the remote power supply system and reduce the size and cost has become one of the problems to be solved by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a local side power supply and an ac remote power supply system, which are used to solve the problems of high loss, high cost, etc. of the ac remote power supply system in the prior art.
To achieve the above and other related objects, the present invention provides a local side power supply, including at least:
the three-phase alternating current-to-direct current converter comprises a three-phase alternating current-to-direct current module, a direct current-to-alternating current module and a first transformer;
the three-phase AC-to-DC conversion module receives a three-phase AC power supply and converts the three-phase AC power supply into a DC power supply;
the direct current to alternating current module is connected to the output end of the three-phase alternating current to direct current module and converts the direct current power supply into an alternating current power supply;
the primary side of the first transformer is connected with an alternating current power supply output by the direct current-to-alternating current module, and the secondary side of the first transformer is connected with a single-phase alternating current power supply in series to obtain a single-phase alternating current output voltage.
Optionally, the secondary side of the first transformer includes two sets of secondary side windings, where one end of the first secondary side winding is connected to one end of the single-phase ac power supply, and the other end of the first secondary side winding is used as a first output end of the local side power supply; and one end of the second secondary winding is connected with the other end of the single-phase alternating-current power supply, and the other end of the second secondary winding is used as a second output end of the local-side power supply.
Optionally, the office power supply further includes a first switch; a first secondary contact of the first switch is connected in series between a first output end of the direct current-to-alternating current module and a first end of a primary winding of the first transformer; the second auxiliary contact of the first switch is connected in series between the second output end of the direct current-to-alternating current module and the second end of the primary winding of the first transformer; the third auxiliary contact of the first switch is connected in series between the first end of the primary winding of the first transformer and the first end of the single-phase alternating-current power supply; the fourth auxiliary contact of the first switch is connected in series between the second end of the primary winding of the first transformer and the second end of the single-phase alternating-current power supply.
Optionally, the local side power supply further includes a second transformer, and a primary side of the second transformer is connected to the secondary side of the first transformer and two ends of the single-phase ac power supply after being connected in series, so as to boost the voltages of the secondary side of the first transformer and two ends of the single-phase ac power supply after being connected in series, and obtain the single-phase ac output voltage.
Optionally, the office power supply further includes a fifth switch, and the fifth switch is connected in parallel to the secondary side of the first transformer.
Optionally, the primary side of the second transformer includes two sets of primary windings, where a first primary winding of the second transformer is connected in series with the secondary side of the first transformer and the single-phase ac power supply, and a second primary winding of the second transformer is connected to the power supply device.
Optionally, each local side power supply receives the same three-phase alternating current power supply and is respectively connected to each phase of the same power grid as a corresponding single-phase alternating current power supply to respectively output a corresponding single-phase alternating current output voltage.
In order to achieve the above and other related objects, the present invention further provides an ac remote power supply system, which at least includes:
the local side power supply and a far-end power supply connected with the output end of the local side power supply through a long cable.
As described above, the local side power supply and the ac remote power supply system of the present invention have the following advantages:
1. the power of the electronic converter in the local side power supply and alternating current remote supply power supply system is far less than the system power, so that the loss in power transmission is effectively reduced, the system efficiency is improved, and the size, the weight and the cost of the electronic converter and the transformer of the local side power supply are reduced.
2. In the local side power supply and the alternating current remote power supply system, when the voltage of a power grid fluctuates within the range of 80-120% of a rated value, the rated voltage and power can still be stably and reliably output.
3. When the single-phase earth fault occurs in the power grid voltage of the local side power supply and the alternating current remote power supply system, partial effective voltage and power can be still output for the load, and the reliability of the system is greatly improved.
4. The local side power supply can be used for boosting and can also be used as an active power filter, so that the THD of the power grid meets the corresponding national standard.
5. The local side power supply and the alternating current remote supply power system of the invention enable the voltages to earth at two ends of the output voltage to be equal through the arrangement of the two controlled voltage sources, thereby reducing the insulation requirement on the output cable and lowering the cost.
6. The local side power supply and the alternating current remote power supply system select the power supply of the first transformer through the switch, so that the flexibility of the system is improved.
Drawings
Fig. 1 is a schematic structural diagram of a first embodiment of an office power supply according to the present invention.
Fig. 2 is a schematic structural diagram of a second embodiment of the local side power supply according to the present invention.
Fig. 3 is a schematic structural diagram of a third embodiment of the local side power supply according to the present invention.
Fig. 4 is a schematic structural diagram of a fourth embodiment of the local side power supply according to the present invention.
Fig. 5 is a schematic timing diagram of an output voltage of a fourth embodiment of the local power supply according to the invention.
Fig. 6 is a schematic structural diagram of a fifth embodiment of the local power supply according to the present invention.
Fig. 7 is a schematic structural diagram of a sixth embodiment of the local side power supply according to the present invention.
Fig. 8 is a schematic structural diagram of a seventh embodiment of the local power supply according to the present invention.
Fig. 9 is a schematic structural diagram of an ac remote power supply system according to the present invention.
Fig. 10 is a schematic diagram of an equivalent circuit of the compensation of the local side power supply with the APF function according to the present invention.
Description of the element reference numerals
1 local side power supply
1a, 1b first and second local side power supplies
11. 111, 112 three-phase AC-DC conversion module
12. 121, 122 DC-AC module
131 energy storage unit
132 DC-AC unit
2 grid power supply
3 remote power supply
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 1 to 10. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Example one
As shown in fig. 1, the present embodiment provides an office side power supply 1, where the office side power supply 1 includes:
a three-phase AC-DC module 11, a DC-AC module 12 and a first transformer T1.
As shown in fig. 1, the three-phase dc-to-ac conversion module 11 receives a three-phase ac power source Vin3, and converts the three-phase ac power source Vin3 into a dc power source Vdc.
Specifically, the three-phase ac power Vin3 is a three-phase signal output by a power grid, and the three-phase ac-dc conversion module 11 receives the three-phase signal and converts the three-phase signal into a dc power Vdc for output. As an example, the three-phase ac power source Vin3 is 380V ac, and in actual use, the three-phase ac power source Vin3 may be obtained by selecting ac power sources with different voltages as needed, which is not limited in this embodiment.
As shown in fig. 1, the dc-ac conversion module 12 is connected to an output end of the three-phase ac-dc conversion module 11, and converts the dc power Vdc into an ac power Vac.
Specifically, any structure of dc-to-ac circuit is suitable for the dc-to-ac module 12 of the present invention, which is not listed here.
As shown in fig. 1, the primary side of the first transformer T1 is connected to the ac power Vac output by the dc-to-ac module 12, and the secondary side is connected in series to the single-phase ac power Vin to obtain a single-phase ac output voltage Vout, where the single-phase ac output voltage Vout is used for supplying power to a remote end.
Specifically, in this embodiment, the primary side and the secondary side of the first transformer T1 each include a set of windings, the primary side winding of the first transformer T1 is connected to the ac power Vac, the secondary side winding of the first transformer T1 is connected in series to the single-phase ac power Vin, and both ends of the series-connected secondary side winding of the first transformer T1 and the single-phase ac power Vin serve as output ends of the local-side power supply 1. The first transformer T1 acts as an isolation transformer.
Specifically, the ac power source Vac is converted into a voltage source Vac _ c on the secondary side based on the first transformer T1, and the voltage source Vac _ c is used as a controlled voltage source and is serially superposed with the single-phase ac power source Vin1 to obtain the single-phase ac output voltage Vout, and is output to a remote end through a long cable. By way of example, if the single-phase ac power source Vin1 is set to 380V or 220V ac, the single-phase ac output voltage Vout is 800V-1000V ac. In this embodiment, the single-phase ac power Vin1 is obtained from a grid power source.
It should be noted that, since the voltage source Vac _ c and the single-phase ac power Vin1 are connected in series, the currents flowing through the voltage source Vac _ c are equal, and taking the single-phase ac power Vin1 as 380V and the single-phase ac output voltage Vout as 800V as an example, the voltage source Vac _ c is 420V, so that the power of the three-phase ac-to-dc module 11, the dc-to-ac module 12, and the first transformer T1 only needs to be about 50% of the rated power of the system. The reduction of the power electronic converter (the three-phase alternating current-to-direct current module 11 and the direct current-to-alternating current module 12) in the local side power supply 1 can effectively reduce the loss in power transmission and improve the system efficiency; meanwhile, the weight, the volume and the cost of a power electronic converter and a transformer in the local side power supply can be reduced.
Example two
As shown in fig. 2, the present embodiment provides an office power supply 1, which is different from the first embodiment in that the first transformer T1 includes two sets of secondary windings, and other modules are the same as the first embodiment and are not described herein.
Specifically, one end of a first secondary winding of the first transformer T1 is connected to one end of the single-phase ac power Vin1, and the other end of the first secondary winding is used as a first output end of the local side power supply 1; one end of a second secondary winding of the first transformer T1 is connected to the other end of the single-phase ac power source Vin1, and the other end of the second secondary winding is used as a second output end of the local side power source 1; that is, the first secondary winding and the second secondary winding are respectively connected in series to two ends of the single-phase ac power source Vin 1.
Specifically, the ac power source Vac is converted into a first voltage source Vac _ c1 at a first secondary winding and into a second voltage source Vac _ c2 at a second secondary winding based on the first transformer T1; the first voltage source Vac _ c1 and the second voltage source Vac _ c2 are used as controlled voltage sources and are serially connected and superposed with the single-phase alternating current power source Vin1 to obtain the single-phase alternating current output voltage Vout, and the single-phase alternating current output voltage Vout is output to a far end through a long cable.
It should be noted that the single-phase ac output voltage Vout in this embodiment is the same as that in the first embodiment, but the end of the single-phase ac output voltage Vout connected in series with the voltage source Vac _ c is higher in voltage to ground, and the end not connected in series with the voltage source Vac _ c is lower in voltage to ground; as an example, the single-phase ac power source Vin1 is 380V, the single-phase ac output voltage Vout is 800V, the voltage source Vac _ c is 420V, the voltage to ground of one end of the single-phase ac output voltage Vout is 640V (220V +420V), and the voltage to ground of the other end is 220V; this results in a higher insulation requirement for the long cable at the output end in the first embodiment. In the embodiment, the first voltage source Vac _ c1 and the second voltage source Vac _ c2 are respectively connected in series to two ends of the single-phase ac output voltage Vout, so that the voltage difference between the two ends of the single-phase ac output voltage Vout to the ground is not large; still taking the single-phase ac power source Vin1 as 380V and the single-phase ac output voltage Vout as 800V as an example, the first voltage source Vac _ c1 and the second voltage source Vac _ c2 are 210V, and the voltages to ground at both ends of the single-phase ac output voltage Vout are 430V (220V + 210V); therefore, the requirement for insulation of the cable in the second embodiment is relatively reduced.
EXAMPLE III
As shown in fig. 3, the present embodiment provides a local side power supply 1, which is different from the first embodiment in that the local side power supply 1 further includes a first switch, and other modules are the same as the first embodiment and are not described herein.
Specifically, the first secondary contact of the first switch K1 is connected in series between the first output terminal of the dc-to-ac module 12 and the first end of the primary winding of the first transformer T1; a second secondary contact of the first switch K1 is connected in series between the second output terminal of the dc-to-ac module 12 and the second end of the primary winding of the first transformer T1; the third auxiliary contact of the first switch K1 is connected in series between the first end of the primary winding of the first transformer T1 and the first end of the single-phase alternating-current power source Vin 1; the fourth auxiliary contact of the first switch K1 is connected in series between the second end of the primary winding of the first transformer T1 and the second end of the single-phase alternating-current power source Vin 1; the switch states of the first auxiliary contact and the second auxiliary contact of the first switch K1 are kept consistent, and the switch states of the third auxiliary contact and the fourth auxiliary contact of the second switch K1 are kept consistent, wherein the first auxiliary contact and the second auxiliary contact are set to be normally closed contacts, and the third auxiliary contact and the fourth auxiliary contact are set to be normally open contacts; or the first auxiliary contact and the second auxiliary contact are set as normally open contacts, and the third auxiliary contact and the fourth auxiliary contact are set as normally closed contacts.
Specifically, the first switch K1 includes but is not limited to a button, a knob, a contactor, and a relay, and any device or apparatus capable of performing the above-mentioned switching function is suitable for the present invention.
In addition, under normal conditions, the first auxiliary contact and the second auxiliary contact of the first switch K1 are conducted, and the third auxiliary contact and the fourth auxiliary contact of the first switch K1 are disconnected, so that the three-phase alternating-current power source Vin3 supplies power to the first transformer T1, and the single-phase alternating-current power source Vin1 is bypassed; once any one of the three-phase ac-dc conversion module 11 and the dc-ac conversion module 12 fails, the three-phase ac-dc conversion module 11 and the dc-ac conversion module 12 should stop working, at this time, the first auxiliary contact and the second auxiliary contact of the first switch K1 are disconnected, and the third auxiliary contact and the fourth auxiliary contact of the first switch K1 are connected, so that the single-phase ac power Vin1 supplies power to the transformer T1, and the three-phase ac power Vin3 is bypassed; thereby increasing the flexibility of the office side power supply 1.
It should be noted that each switch is also applicable to the local power supply structure in the second embodiment, and details thereof are not repeated herein.
Example four
As shown in fig. 4, the present embodiment provides a local side power supply 1, which is different from the first embodiment in that the local side power supply 1 further includes a second transformer T2, and other modules are the same as the first embodiment and are not described herein.
Specifically, in this embodiment, the primary side and the secondary side of the second transformer T2 each include a winding set, the primary side winding of the second transformer T2 is connected to the secondary side of the first transformer T1 and the two ends of the single-phase ac power Vin1 after being connected in series, and the secondary side winding of the second transformer T2 outputs the boosted voltage of the voltages at the secondary side of the first transformer T1 and the two ends of the single-phase ac power Vin1 after being connected in series as the single-phase ac output voltage Vout. The second transformer T2 acts as a step-up transformer.
Specifically, the second transformer T2 boosts the superimposed voltage of the voltage source Vac _ c and the single-phase ac power source Vin1 to the single-phase ac output voltage Vout (800V to 1000V), and outputs the voltage to a remote end through a long cable.
It should be noted that when the amplitude of the single-phase ac power source Vin1 fluctuates between 80% and 120% of the rated value of the power grid, as long as the voltage of the voltage source Vac _ c is controlled to be at the same frequency as the power grid and 0% to 20% of the rated value, the output of the second transformer T2 can still be maintained at 100% to 120% of the rated value, as shown in fig. 5. Alternatively, when the load becomes larger and the voltage of the secondary side of the second transformer T2 becomes lower, the voltage of the voltage source Vac _ c may be controlled to become larger to compensate for the voltage loss caused by the long cable. In this embodiment, the voltage of the voltage source Vac _ c fluctuates between 0% and 20% of the rated value of the power grid, and the powers of the three-phase ac-to-dc module 11 and the dc-to-ac module 12 are only 20% of the rated power of the system, so that the power of the power electronic converter in the local power supply is further reduced, the loss in power transmission is further reduced, and the system efficiency is improved.
EXAMPLE five
As shown in fig. 6, the present embodiment provides a local side power supply 1, which is different from the fourth embodiment in that the local side power supply 1 further includes a second switch, and other modules are the same as those in the fourth embodiment and are not described herein.
Specifically, the second switch K2 is connected in parallel to the secondary side of the first transformer T1. When any one of the three-phase ac-dc conversion module 11 and the dc-ac conversion module 12 fails, both the three-phase ac-dc conversion module 11 and the dc-ac conversion module 12 should stop working, and at this time, the voltage source Vac _ c can be bypassed by turning on the second switch K2 without affecting the normal power supply of the single-phase ac power source Vin 1. When the single-phase ac power Vin1 is too high (e.g. exceeds 120% of the rated value of the power grid), the three-phase ac-to-dc module 11 and the dc-to-ac module 12 may stop working, and the voltage source Vac _ c is also bypassed by turning on the second switch K2, so as to reduce the loss of the local side power.
It should be noted that, if the single-phase AC power source Vin1 is the phase voltage AC220V, when a single-phase ground short-circuit fault occurs, the single-phase AC power source Vin1 drops to 0V; the voltage drop of the output of the second transformer T2 is about 20% of the rated voltage. If the single-phase alternating-current power source Vin1 is the line voltage AC380V, the single-phase alternating-current power source Vin1 during the single-phase-to-ground short circuit is reduced to AC220V, and the output voltage of the second transformer T2 can still be about 78% of the rated voltage in consideration of the compensation voltage of the first transformer T1. Although the line voltage loss is slightly larger, the far-end power supply is generally provided with a PFC (power factor correction) circuit and an inverter circuit, so that the far-end power supply can still be ensured to output normal AC220V to a load for use. Therefore, when the system has short-circuit fault, the local side power supply can still output partial effective voltage and power for the use of a far-end load, and the reliability of the system is greatly improved.
EXAMPLE six
As shown in fig. 7, the present embodiment provides an office side power supply 1, which is different from the fourth embodiment in that the primary side of the second transformer T2 includes two sets of primary side windings, and other modules are the same as those in the fourth embodiment and are not described herein again.
Specifically, the first primary winding of the second transformer T2 is connected to the secondary side of the first transformer T1 after being connected in series and two ends of the single-phase ac power Vin1 to output the single-phase ac output voltage Vout. The second primary winding of the second transformer T2 is connected to a power supply device to introduce a new power supply. The power supply device is an energy storage device or a new energy power generation device; in this embodiment, the power supply device includes an energy storage unit 131 and a dc-to-ac unit 132, where the energy storage unit 131 is connected to an input end of the dc-to-ac unit 132, and an output end of the dc-to-ac unit 132 is connected to the second primary winding of the second transformer T2; in practical use, the energy storage unit 131 can be replaced by a new energy power generation unit according to needs.
It should be noted that, when the energy storage power is applied, when the power grid operates at 80% or more of the rated voltage, the energy storage unit 131 does not output voltage; and when the power grid works under 80% of rated voltage in case of power failure, the energy storage unit 131 can continuously supply power for the load. Under the condition of applying the new energy to generate electricity (such as a solar power generation panel and a solar inverter), the main load power can be controlled to be provided by the new energy power generation unit.
EXAMPLE seven
As shown in fig. 8, the present embodiment includes at least two local side power supplies, each local side power supply receives the same three-phase ac power supply, and is respectively connected to each phase of the same power grid as a corresponding single-phase ac power supply, so as to respectively output a corresponding single-phase ac output voltage to power each group of users. The local side power supply adopts the structure of the first embodiment or the fourth embodiment.
Specifically, in this embodiment, two central office side power supplies of the fourth embodiment are adopted, which are the first central office side power supply 1a and the second central office side power supply 1b respectively. The first local side power supply 1a receives the three-phase alternating current power supply Vin3 output by the grid power supply 2, and outputs a direct current power supply Vdc1 through a three-phase alternating current to direct current module 111, the direct current power supply Vdc1 is converted into an alternating current power supply Vac1 through a direct current to alternating current module 121, the alternating current power supply Vac1 is converted into a voltage source Vac1_ c on the secondary side of a first transformer T11, and a signal obtained by superimposing the voltage source Vac1_ c and the single-phase alternating current power supply Vin11 is boosted through a second transformer T21 to obtain a single-phase alternating current output voltage Vout1 of the first local side power supply 1 a; the single-phase AC power Vin11 is provided by a grid power 2 (for example, the grid power 2 is a three-phase four-wire grid), including but not limited to an AC phase or a CN phase of the grid power 2. The second local side power supply 1b receives the three-phase alternating current power supply Vin3 output by the grid power supply 2, and outputs a direct current power supply Vdc2 through a three-phase alternating current-to-direct current module 112, the direct current power supply Vdc2 is converted into an alternating current power supply Vac2 through a direct current-to-alternating current module 122, the alternating current power supply Vac2 is converted into a voltage source Vac2_ c on the secondary side of the first transformer T12, and a signal obtained by superimposing the voltage source Vac2_ c and the single-phase alternating current power supply Vin12 is boosted through a second transformer T22 to obtain a single-phase output alternating current voltage Vout2 of the second local side power supply 1 b; the single-phase ac power Vin12 is provided by the grid power 2, and includes, but is not limited to, an AB phase or a BN phase of the grid power 2.
The loads of the ABC three phases in the power grid 2 of this embodiment are more balanced, and the local side power supplies are independent of each other.
Example eight
As shown in fig. 9, the present embodiment provides an ac remote power supply system, which includes an office side power supply 1 according to any one of the first to seventh embodiments, and a remote side power supply 3 connected to the office side power supply 1.
Specifically, in this embodiment, the central office power supply 1 of the first embodiment is adopted, an output end of the central office power supply 1 is connected to input ends of two remote power supplies 3 through a long cable, and each remote power supply 3 converts the power supplied by the central office power supply 1 into an alternating current with a set voltage (for example, the set voltage is 220V) to supply power to corresponding loads (a first load and a second load). By way of example, the remote power supply 3 includes a buck converter 31 (including but not limited to a transformer), an ac-to-dc module 32, and a dc-to-ac module 33.
It should be noted that the number of the remote power supplies 3 can be set according to the needs, and is not limited to this embodiment.
As shown in fig. 9, the ac-to-dc conversion module 32 is generally composed of a PFC module or an uncontrolled rectifier module. If the rectifier is composed of uncontrolled rectifier modules, low-order harmonic currents such as 3, 5 and 7 are generated to pollute the power grid. The local side power supply 1 in the present invention may also function as a series type APF (active power filter) that prevents harmonics generated by the remote power supply 3 from flowing into the grid. At this time, the dc-to-ac module 12 in the local side power supply 1 and the first transformer T1 together generate the fundamental voltage compensation grid voltage having the same frequency as the grid, so that the amplitude of the input voltage of the remote side power supply 3 is within a certain range; meanwhile, the low-order harmonic voltage of the power grid is generated to offset the harmonic voltage generated by the load, so that the THD (total harmonic distortion) of the power grid current meets the related requirement.
Fig. 10 shows an equivalent circuit of local-side power compensation with APF function, where Zs Is an equivalent internal impedance of a power grid, Is a power grid current, Ish Is a harmonic of the power grid current, Isf Is a fundamental wave of the power grid current, and Is ═ Ish + Isf; uc is the output voltage of the secondary side of the first transformer T1, Ul is the load voltage, Ulh is the harmonic of the load voltage, Ulf is the fundamental of the load voltage, and Ul is Ulh + Ulf; us is the grid voltage, Ush is the harmonic wave of the grid voltage, Usf is the fundamental wave of the grid voltage, and Us Ush + Usf. When Uc is controlled to-Ulh, Ish is Ush/Zs. Then Ish is 0 when the grid voltage is not distorted. In conjunction with the use of a remote power source, Uc ═ -Ulh + k × Usf; it is possible to compensate for both the fundamental wave of the output voltage and to cancel the harmonics of the load voltage. Where k is the compensation component of the fundamental.
In summary, the present invention provides a local side power supply and an ac remote power supply system, including: the three-phase alternating current-to-direct current converter comprises a three-phase alternating current-to-direct current module, a direct current-to-alternating current module and a first transformer; the three-phase AC-to-DC conversion module receives a three-phase AC power supply and converts the three-phase AC power supply into a DC power supply; the direct current to alternating current module is connected to the output end of the three-phase alternating current to direct current module and converts the direct current power supply into an alternating current power supply; the primary side of the first transformer is connected with the output end of the direct current-to-alternating current module, and the secondary side of the first transformer is connected with the single-phase alternating current power supply in series to obtain single-phase alternating current output voltage. The local side power supply and the alternating current remote power supply system can effectively reduce the loss in the power transmission process of the remote power supply system and reduce the volume and the cost. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (8)

1. A local side power supply, comprising:
the three-phase alternating current-to-direct current converter comprises a three-phase alternating current-to-direct current module, a direct current-to-alternating current module and a first transformer;
the three-phase AC-to-DC conversion module receives a three-phase AC power supply and converts the three-phase AC power supply into a DC power supply;
the direct current to alternating current module is connected to the output end of the three-phase alternating current to direct current module and converts the direct current power supply into an alternating current power supply;
the primary side of the first transformer is connected with an alternating current power supply output by the direct current-to-alternating current module, and the secondary side of the first transformer is connected with a single-phase alternating current power supply in series to obtain a single-phase alternating current output voltage.
2. The office side power supply according to claim 1, wherein: the secondary side of the first transformer comprises two sets of secondary side windings, wherein one end of the first secondary side winding is connected with one end of the single-phase alternating-current power supply, and the other end of the first secondary side winding is used as a first output end of the local side power supply; and one end of the second secondary winding is connected with the other end of the single-phase alternating-current power supply, and the other end of the second secondary winding is used as a second output end of the local-side power supply.
3. The office-side power supply according to claim 1 or 2, wherein: the local side power supply also comprises a first switch; a first secondary contact of the first switch is connected in series between a first output end of the direct current-to-alternating current module and a first end of a primary winding of the first transformer; the second auxiliary contact of the first switch is connected in series between the second output end of the direct current-to-alternating current module and the second end of the primary winding of the first transformer; the third auxiliary contact of the first switch is connected in series between the first end of the primary winding of the first transformer and the first end of the single-phase alternating-current power supply; the fourth auxiliary contact of the first switch is connected in series between the second end of the primary winding of the first transformer and the second end of the single-phase alternating-current power supply.
4. The office side power supply according to claim 1, wherein: the local side power supply further comprises a second transformer, wherein the primary side of the second transformer is connected to the secondary side of the first transformer and two ends of the single-phase alternating-current power supply after being connected in series, so that the voltage of the secondary side of the first transformer and two ends of the single-phase alternating-current power supply after being connected in series is boosted to obtain the single-phase alternating-current output voltage.
5. The office-side power supply according to claim 4, wherein: the local side power supply further comprises a second switch, and the second switch is connected in parallel with the secondary side of the first transformer.
6. The office-side power supply according to claim 4, wherein: the primary side of the second transformer comprises two groups of primary side windings, wherein the first primary side winding of the second transformer is connected with the secondary side of the first transformer and the single-phase alternating-current power supply in series, and the second primary side winding of the second transformer is connected with a power supply device.
7. The office-side power supply according to claim 1 or 4, wherein: and each local side power supply receives the same three-phase alternating current power supply and is respectively connected with each phase of the same power grid as a corresponding single-phase alternating current power supply so as to respectively output corresponding single-phase alternating current output voltage.
8. An ac remote power supply system, comprising:
the office side power supply according to any one of claims 1 to 7, and a remote side power supply connected to an output terminal of the office side power supply through a long cable.
CN202011357472.4A 2020-11-27 2020-11-27 Local side power supply and alternating current remote power supply system Pending CN112383078A (en)

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