A single-phase or two-phase to three-phase power supply structure

Abstract

The present invention discloses a single-phase or two-phase to three-phase power supply structure, which belongs to the technical field of power supply and distribution of electric power grid. The structure includes a transmission line, a power converter and a single-phase combined transformer; the three-phase port of the single-phase combined transformer serves as an output port to provide three-phase power to users, and the input end of the power converter is connected to the transmission line. The single-phase combined transformer is composed of a first single-phase transformer and a second single-phase transformer connected by a power converter. The input side of the first single-phase transformer in the single-phase combined transformer is connected to the transmission line, and the input end of the second single-phase transformer in the single-phase combined transformer is connected to the output end of the power converter. The present invention can realize the function of providing three-phase power to users through single-phase wires and two-phase transmission lines, and is widely applicable to power distribution system transformation and fault repair.

Description

Technical Field

[0001] The invention relates to the technical field of electric power supply and distribution. Background Art

[0002] Among the AC power supply methods of the power system, the three-phase AC power supply system is widely used. In my country's low-voltage power distribution field, single-phase transmission lines are generally used to provide electricity to users. In some areas where users are geographically dispersed, two-phase transmission lines are also used to provide electricity to users. When users who are only connected to single-phase or two-phase transmission lines need to use three-phase power, according to existing technology, they can only re-erect three-phase transmission lines to provide three-phase power to users, which is time-consuming, costly, and uneconomical.

[0003] At the same time, since the transmission lines are generally erected outdoors, the geographical span is wide, and the environmental conditions are changeable, various disconnection faults occur due to long-term mechanical force, electromagnetic force and thermal effect, as well as severe oxidation, poor contact and other reasons, making the equipment unable to operate normally. When the original three-phase transmission line has one or two phase disconnection faults due to external reasons, the three-phase power supply mode becomes a non-three-phase power supply mode, and it is impossible to provide users with the three-phase power supply they need. The existing solution can only provide three-phase power supply in a short time through economical emergency repairs by power maintenance personnel, but emergency repairs in bad weather are very dangerous, and the personal safety of power maintenance personnel is difficult to guarantee.

[0004] If the power quality of the power grid permits, a single-phase or two-phase transmission line can be converted into a three-phase power supply through a relatively simple power equipment structure, so that users can obtain three-phase power in a shorter time and at a lower cost. This can not only save the cost of transmission facilities, but also provide emergency three-phase power when a three-phase transmission line breaks, avoiding power maintenance personnel from having to perform emergency repairs under harsh environmental conditions and ensuring their personal safety. Summary of the invention

[0005] The object of the present invention is to provide a single-phase or two-phase to three-phase power supply structure, which can effectively solve the technical problem of providing three-phase power supply through a single-phase or two-phase transmission line.

[0006] The objective of the present invention is achieved through the following technical solutions: a single-phase or two-phase to three-phase power supply structure, which includes: a transmission line connected to a power grid, a power converter connected to a single-phase transformer, a single-phase combined transformer formed by connecting a first single-phase transformer T1 and a second single-phase transformer T2, wherein the B terminal and the C terminal of the single-phase combined transformer are respectively connected to the M terminal and the N terminal of the output port of the power converter; the input side of the first single-phase transformer T1 is directly connected to the transmission line, the input end of the power converter is connected to the transmission line, and the output end of the power converter is connected to the input end of the second single-phase transformer T2; the k terminal of the output port of the first single-phase transformer T1 is connected to the middle tap e of the output winding of the second single-phase transformer T2, and the a terminal of the output port of the first single-phase transformer T1 and the b terminal and the c terminal of the output side of the second single-phase transformer T2 together form a three-phase output side.

[0007] When the transmission line is a single-phase transmission line, the P terminal in the input end of the power converter is connected to the transmission line, and the Q terminal in its input end is grounded; the A terminal in the single-phase combined transformer is connected to the transmission line, and the K terminal is grounded.

[0008] When the transmission line is a two-phase transmission line, the P terminal and the Q terminal in the input port of the power converter are respectively connected to the A phase transmission line L of the transmission line. A , B-phase transmission line L B The A and K terminals of the single-phase combined transformer are connected to the A-phase transmission line L of the transmission line respectively. A , B-phase transmission line L B connected.

[0009] The power converter includes a first high-power switch device SVG1 on the rectifier side, a second high-power switch device SVG2 on the inverter side, a DC energy storage capacitor Cd and a pulse width modulator. The first high-power switch device SVG1 and the second high-power switch device SVG2 are connected in series, and a DC energy storage capacitor Cd is connected between them to provide voltage support between the emitter E and the collector j of the first high-power switch device and the second high-power switch device; the control electrodes G of the first high-power switch device SVG1 and the second high-power switch device SVG2 are both connected to the output end of the pulse width modulator.

[0010] The input current of the first high-power switch device SVG1 of the power converter is equal to half of the input current in the transmission line; the input voltage U between the B terminal and the C terminal of the second single-phase transformer T2 is B The input voltage U between the A terminal and the K terminal of the first single-phase transformer T1 A Equal in magnitude and 90 degrees in phase with each other.

[0011] The first high-power switching device SVG1 includes four high-power transistors BG, and the control electrode G of each high-power transistor BG is connected to the output end of the pulse width modulator; every two high-power transistors BG are connected in series through the emitter E of one of the high-power transistors BG and the collector j of the other high-power transistor BG to form a group of high-power transistors, and the emitters E of the two groups of high-power transistors are connected in pairs, and the collectors j are connected in pairs; the series connection point of the emitter E and the collector j in the two groups of high-power transistors constitutes the P terminal and Q terminal of the current input end of the first high-power switching device SVG1.

[0012] The second high-power switching device SVG2 includes four high-power transistors BG, and the control electrode G of each high-power transistor BG is connected to the output end of the pulse width modulator; every two high-power transistors BG are connected in series through the emitter E of one of the high-power transistors BG and the collector j of the other high-power transistor BG to form a group of high-power transistors, and the emitters E of the two groups of high-power transistors are connected in pairs, and the collectors j are connected in pairs; the series connection point of the emitters E and the collectors j in the two groups of high-power transistors constitutes the current output end of the second high-power switching device SVG2, that is, the M terminal and the N terminal of the output end of the power converter.

[0013] The high-power transistor BG is an integrated gate-commutated thyristor or an insulated gate bipolar transistor.

[0014] Compared with the prior art, the beneficial effects of the technology of the present invention are:

[0015] 1. In a place where only a single-phase transmission line with a grounded neutral point is erected in the distribution network, due to the emergency short-term need for three-phase power supply, and the time for erecting a new three-phase line is not allowed, the power supply structure of the present invention can be used to provide three-phase power supply if the power quality of the power grid allows;

[0016] Second, in places where only two-phase transmission lines are set up in the distribution network, due to the emergency and short-term need for three-phase power supply, and the time for setting up new three-phase lines does not allow, if the power quality of the power grid allows, the power supply structure of the present invention can provide three-phase power supply;

[0017] 3. When one or two phases of a three-phase user are disconnected and the maintenance environment is relatively bad at the time, this method can be used to provide three-phase power and the line can be repaired after the climate environment improves. This reduces the potential safety hazards of outdoor emergency repairs by power maintenance personnel and also reduces the possibility of larger accidents due to emergency situations.

[0018] 4. Simple structure, good versatility, good economy and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a basic structural diagram of the power supply structure described in the first embodiment of the present invention.

[0020] Figure 2 It is a schematic diagram of the specific structural connection of the power supply structure described in the first embodiment of the present invention.

[0021] Figure 3 It is a structural schematic diagram of the power converter described in the first embodiment of the present invention.

[0022] Figure 4 It is a schematic diagram of the specific structural connection of the power supply structure described in the second embodiment of the present invention.

[0023] Figure 5 The pulse width modulator control flow chart of the present invention is DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0025] The basic working principle of the power supply structure described in the present invention is as follows: a pulse width modulator (PWM) is used to perform analog control on an analog circuit using the digital output of a microprocessor. The PWM can modulate the bias of a transistor base or a MOS tube gate according to changes in the corresponding load to achieve a change in the conduction time of the transistor or MOS tube, thereby achieving a change in the output of a switching regulated power supply.

[0026] Assume that the transmission line L A The current of the single-phase combined transformer 2 is I, the input current of the A terminal is I1, the input current of the first high-power switching device SVG1 is I2, and the input voltage between the A terminal and the K terminal of the single-phase combined transformer 2 is U A The input voltage between the B terminal and the C terminal of the single-phase combined transformer 2 is U B ; Using the pulse width modulator to control the input current I2 of the first high-power switching device SVG1 in the power converter 3 is the transmission line L A One half of the current I;

[0027] Input voltage U between terminal B and terminal C in single-phase combined transformer 2 B The input voltage U between the A terminal and the K terminal of the single-phase combined transformer 2 A The three-phase side of the single-phase combined transformer 2 is equal in size and 90 degrees in phase with each other, and provides a symmetrical three-phase power supply for the operation of loads requiring three-phase power.

[0028] Embodiment 1

[0029] like Figure 1As shown, the embodiment of the present invention provides a single-phase or two-phase to three-phase power supply structure, which mainly includes a transmission line 1, a single-phase combined transformer 2 and a power converter 3. The transmission line 1 is used to transmit current to the single-phase combined transformer 2 and the power converter 3; the single-phase combined transformer 2 is formed by connecting a first single-phase transformer T1 and a second single-phase transformer T2 in accordance with regulations, and is used to transform and phase-modulate the current provided by the transmission line 1 and the power converter 3 and then provide a symmetrical three-phase power supply to the user; the power converter 3 is used to transform the shunted current in the transmission line 1 and then supply power to the single-phase combined transformer 2; wherein the transmission line 1 is connected to the power converter 3 and the single-phase combined transformer 2 respectively, the power converter 3 is connected to the single-phase combined transformer 2, and the three-phase side of the single-phase combined transformer 2 provides a three-phase power supply to the user.

[0030] like Figure 2 and Figure 3 As shown, the 220V transmission line 1 of the neutral point grounded power grid is a single-phase transmission line with a current of I. The transmission line 1 is respectively connected to the A terminal of the single-phase combined transformer 2 and the P terminal of the power converter 3; the current magnitude of the transmission line 1 input to the A terminal of the single-phase combined transformer 2 is I1, and the current magnitude of the transmission line 1 input to the P terminal of the power converter 3 is I2; the K terminal of the single-phase combined transformer 2 is grounded; the power converter 3 includes a first high-power switching device SVG1 as a rectifier side and a second high-power switching device SVG2 as an inverter side, and the first high-power switching device SVG1 and the second high-power switching device S VG2 is connected in series, and a DC energy storage capacitor Cd is arranged in parallel between them; the DC energy storage capacitor Cd is used to provide voltage support for the emitter E and the collector j of the first high-power switching device and the second high-power switching device; the control electrodes G of the first high-power switching device SVG1 and the second high-power switching device SVG2 are both connected to the output end of the pulse width modulator 4; the Q terminal of the power converter 3 is grounded, and the M terminal and the N terminal of the power converter 3 are respectively connected to the B terminal and the C terminal of the second single-phase transformer 2; the three-phase sides a, b, and c of the single-phase combined transformer 2 provide three-phase symmetrical power to the user.

[0031] The input current I2 of the first high-power switch SVG1 in the power converter 3 is the current of the transmission line L A The input voltage U between the B terminal and the C terminal of the second single-phase transformer T2 is B The input voltage U between the A terminal and the K terminal of the first single-phase transformer T1 A Equal in magnitude and 90° in phase with each other.

[0032] In the embodiment of the present invention, the first high-power switch device SVG1 includes four high-power transistors BG, and the control electrode G of each high-power transistor BG is connected to the output end of the pulse width modulator 4; every two high-power transistors BG are connected in series through the emitter E of one of the high-power transistors BG and the collector j of the other high-power transistor BG to form a group of high-power transistor groups; the series connection point of the emitter E and the collector j in the two groups of high-power transistor groups constitutes the current input terminals P and Q of the first high-power switch device SVG1; the emitters E that are not connected in series in the two groups of high-power transistor groups in the first high-power switch device SVG2 are connected, and the collectors j that are not connected in series in the two groups of high-power transistor groups in the first high-power switch device SVG1 are connected.

[0033] In the embodiment of the present invention, the structure of the second high-power switch device SVG2 is exactly the same as that of the first high-power switch device SVG1. The second high-power switch device SVG2 includes four high-power transistors BG, and the control electrode G of each high-power transistor BG is connected to the output end of the pulse width modulator 4; every two high-power transistors BG are connected in series through the emitter E of one of the high-power transistors BG and the collector j of the other high-power transistor BG to form a group of high-power transistor groups; the series connection point of the emitter E and the collector j in the two groups of high-power transistor groups constitutes the current output terminals M and N of the second high-power switch device SVG2; the emitters E that are not connected in series in the two groups of high-power transistor groups in the second high-power switch device SVG2 are connected, and the collectors j that are not connected in series in the two groups of high-power transistor groups in the second high-power switch device SVG2 are connected.

[0034] In the embodiment of the present invention, the first high-power switch device SVG1 and the second high-power switch device SVG2 are connected in series, and a DC energy storage capacitor Cd is connected between them. Figure 4 The high-power transistor BG shown is an integrated gate-commutated thyristor IGCT; in actual implementation, an insulated gate bipolar transistor IGBT may also be used.

[0035] Embodiment 2

[0036] The single-phase or two-phase to three-phase power supply structure described in the embodiment of the present invention is the same as the basic structure of the first embodiment of the present invention described above, that is, Figure 1As shown, the power supply structure mainly includes a transmission line 1, a single-phase combined transformer 2 and a power converter 3. The transmission line 1 is used to transmit current to the single-phase combined transformer 2 and the power converter 3; the single-phase combined transformer 2 is used to transform and phase-adjust the current provided by the transmission line 1 and the power converter 3 and then provide a symmetrical three-phase power supply to the user; the power converter 3 is used to transform the shunted current in the transmission line 1 and then supply power to the single-phase combined transformer 2; wherein the transmission line 1 is connected to the power converter 3 and the single-phase combined transformer 2 respectively, the power converter 3 is connected to the single-phase combined transformer 2, and the single-phase combined transformer 2 provides a three-phase power supply to the user in the back.

[0037] The structures of the first high-power switch device SVG1, the second high-power switch device SVG2 and the DC energy storage capacitor Cd in the power converter 3 of the embodiment of the present invention and the connection method therebetween are similar to those in the first embodiment of the present invention. Figure 3 The structures shown are exactly the same, so they will not be described again here.

[0038] In the embodiment of the present invention, the high-power transistor BG is an integrated gate-commutated thyristor IGCT; in actual implementation, the high-power transistor BG may also be an insulated gate bipolar transistor IGBT.

[0039] Combination Figure 2 and Figure 4 As shown, the difference between the single-phase or two-phase to three-phase power supply structure described in the embodiment of the present invention and the above-mentioned embodiment of the invention is that the transmission line 1 described in the embodiment of the present invention is a two-phase transmission line; L in the two-phase transmission line A , L B The voltage between them is 220V, the input current in transmission line 1 is I, and the A phase transmission line L in transmission line 1 A The A terminal of the single-phase combined transformer 2 and the P terminal of the power converter 3 are connected respectively. The current input to the A terminal of the single-phase combined transformer 2 is I1, and the current input to the P terminal of the power converter 3 is I2. The B-phase transmission line L in the transmission line 1 BThey are respectively connected to the K terminal in the single-phase combined transformer 2 and the Q terminal of the power converter 3; the power converter 3 includes a first high-power switching device SVG1 as a rectifier side and a second high-power switching device SVG2 as an inverter side. The first high-power switching device SVG1 and the second high-power switching device SVG2 are connected back to back, and a DC energy storage capacitor Cd is arranged in parallel between them to provide voltage support for the emitter E and collector j of the first high-power switching device and the second high-power switching device. The control electrodes G of the first high-power switching device SVG1 and the second high-power switching device SVG2 are both connected to the output end of the pulse width modulator 4; the output end of the second high-power switching device SVG2, that is, the M terminal and the N terminal of the power converter 3 are respectively connected to the B terminal and the C terminal in the single-phase combined transformer 2; the three-phase sides a, b, and c of the single-phase combined transformer 2 provide three-phase symmetrical power to the user.

[0040] Figure 5 is a pulse width modulator control flow chart, wherein the input current I2 of the first high power switch device SVG1 in the power converter 3 is the transmission line L A The input voltage U between the B terminal and the C terminal of the second single-phase transformer T2 is B The input voltage U between the A terminal and the K terminal of the first single-phase transformer T1 A Equal in magnitude and 90 degrees in phase with each other.

Claims

1. A single-phase or two-phase to three-phase power supply structure, the power supply structure comprising: A power transmission line (1) connected to a power grid, and a power converter (3) connected to a single-phase transformer, characterized in that: a first single-phase transformer T1 and a second single-phase transformer T2 are connected to form a single-phase combined transformer (2), and a B terminal and a C terminal of the single-phase combined transformer (2) are respectively connected to an M terminal and an N terminal of an output port of the power converter (3); the input side of the first single-phase transformer T1 is directly connected to the power transmission line (1), the input end of the power converter (3) is connected to the power transmission line (1), and the output end of the power converter (3) is connected to the input end of the second single-phase transformer T2; the power converter (3) includes a first high-power switch device SVG1 on the rectifier side, a second high-power switch device SVG2 on the inverter side, and a first high-power switch device SVG1 on the inverter side. The first high-power switch device SVG1 and the second high-power switch device SVG2 are connected in series, and the DC energy storage capacitor Cd is connected between them to provide voltage support between the emitter E and the collector j of the first high-power switch device and the second high-power switch device; the control electrodes G of the first high-power switch device SVG1 and the second high-power switch device SVG2 are both connected to the output end of the pulse width modulator (4); the input current of the first high-power switch device SVG1 of the power converter (3) is equal to half of the input current in the transmission line (1); the input voltage between the B terminal and the C terminal of the second single-phase transformer T2 is equal to the input current of the first high-power switch device SVG1 of the power converter (3); U B The input voltage between the A terminal and the K terminal of the first single-phase transformer T1 U A The sizes are equal and the phases are 90 degrees to each other; the k terminal in the output port of the first single-phase transformer T1 is connected to the middle tap e of the output winding of the second single-phase transformer T2, and the a terminal in the output port of the first single-phase transformer T1 and the b terminal and c terminal on the output side of the second single-phase transformer T2 together constitute a three-phase output side.

2. A single-phase or two-phase to three-phase power supply structure according to claim 1, characterized in that: When the transmission line (1) is a single-phase transmission line, the P terminal at the input end of the power converter (3) is connected to the transmission line (1), and the Q terminal at the input end is grounded; the A terminal of the single-phase combined transformer (2) is connected to the transmission line (1), and the K terminal is grounded.

3. A single-phase or two-phase to three-phase power supply structure according to claim 1, characterized in that: When the transmission line (1) is a two-phase transmission line, the P terminal and the Q terminal in the input port of the power converter (3) are respectively connected to the A phase transmission line of the transmission line (1). L A , B-phase transmission line L B The A terminal and the K terminal of the single-phase combined transformer (2) are respectively connected to the A phase transmission line of the transmission line (1). L A , B-phase transmission line L B connected.

4. A single-phase or two-phase to three-phase power supply structure according to claim 1, characterized in that: The first high-power switch device SVG1 comprises four high-power transistors BG, wherein the control electrode G of each high-power transistor BG is connected to the output end of the pulse width modulator (4); each two high-power transistors BG are connected in series via the emitter E of one of the high-power transistors BG and the collector j of the other high-power transistor BG to form a group of high-power transistors, wherein the emitters E of the two groups of high-power transistors are connected in pairs, and the collectors j are connected in pairs; and the series connection point between the emitters E and the collectors j in the two groups of high-power transistors forms the P terminal and the Q terminal of the current input end of the first high-power switch device SVG1.

5. A single-phase or two-phase to three-phase power supply structure according to claim 1, characterized in that: The second high-power switch device SVG2 comprises four high-power transistors BG, wherein the control electrode G of each high-power transistor BG is connected to the output end of the pulse width modulator (4); each two high-power transistors BG are connected in series via the emitter E of one of the high-power transistors BG and the collector j of the other high-power transistor BG to form a group of high-power transistors, wherein the emitters E of the two groups of high-power transistors are connected in pairs, and the collectors j are connected in pairs; and the series connection point between the emitters E and the collectors j in the two groups of high-power transistors forms the current output end of the second high-power switch device SVG2, i.e., the M terminal and the N terminal of the output end of the power converter (3).

6. A single-phase or two-phase to three-phase power supply structure according to claim 5, characterized in that: The high-power transistor BG is an integrated gate-commutated thyristor or an insulated gate bipolar transistor.

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