A non-three-phase to three-phase power supply structure based on a three-phase transformer

Abstract

The present invention discloses a non-three-phase to three-phase power supply structure based on a three-phase transformer, which includes a transmission line, a three-phase static VAR generator and a three-phase transformer; wherein the three-phase port of the three-phase transformer is used as an output port to provide a three-phase power supply to a user, the input end of the three-phase transformer is respectively connected to the output end of the three-phase static VAR generator and the transmission line, and the input end of the three-phase static VAR compensation generator is connected to the transmission line. The present invention can realize the function of providing a three-phase power supply to a user through a single-phase wire and a two-phase transmission line, and is widely applicable to the transformation of a distribution system and emergency repair of a fault.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power distribution, and in particular to a non-three-phase to three-phase power supply structure based on a three-phase transformer. 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] In view of this, the present invention provides a non-three-phase to three-phase power supply structure based on a three-phase transformer, which solves the technical problem of providing three-phase power through single-phase or two-phase transmission lines. It can provide symmetrical three-phase power to users in areas where non-three-phase transmission lines are installed without the need to re-install the transmission lines. It can also provide three-phase power urgently when one or two phases of the original three-phase transmission lines are broken, avoiding the long-distance installation of transmission lines and reducing the safety hazards caused by emergency repairs by power maintenance personnel.

[0006] In order to solve the problem of obtaining three-phase power supply in a short time for users in non-three-phase transmission line areas and users who cannot obtain three-phase power supply due to three-phase transmission line failures while meeting the requirements of economy, safety and timeliness, the present invention adopts the following technical solutions:

[0007] The present invention provides a non-three-phase to three-phase power supply structure based on a three-phase transformer, which includes a transmission line for supplying power to a three-phase transformer and a three-phase static VAR generator, a three-phase static VAR generator for supplying power to the three-phase transformer after transforming the shunted current in the transmission line, and a three-phase transformer for supplying a symmetrical three-phase power supply to a user after transforming and phase-adjusting the electric energy provided by the transmission line and the three-phase static VAR generator;

[0008] Among them, the three-phase port of the three-phase transformer serves as an output port to provide a symmetrical three-phase power supply to the user, the B terminal, C terminal and D terminal of the three-phase transformer are respectively connected to the Q terminal, M terminal and N terminal of the output port of the three-phase static VAR generator, and the A terminal of the three-phase transformer is connected to the transmission line; the input end of the three-phase static VAR generator is connected to the transmission line, and the triangle winding side of the three-phase transformer provides a symmetrical three-phase power supply to the user.

[0009] Specifically, when the transmission line is a single-phase transmission line, the transmission line is respectively connected to the P terminal at the input end of the three-phase static VAR generator and the A terminal in the three-phase transformer, the B terminal, C terminal and D terminal in the three-phase transformer are respectively connected to the Q terminal, M terminal and N terminal in the output port of the three-phase static VAR generator, and the N terminal of the three-phase static VAR generator is grounded; the triangle winding side of the three-phase transformer provides a symmetrical three-phase power supply to the user.

[0010] Specifically, when the transmission line is a two-phase transmission line, the A-phase transmission line L A The P terminal of the input end of the three-phase static var generator and the A terminal of the three-phase transformer are respectively connected, and the B terminal, C terminal and D terminal of the three-phase transformer are respectively connected to the Q terminal, M terminal and N terminal of the output port of the three-phase static var generator, and the N terminal of the three-phase static var generator is connected to the B phase transmission line L of the transmission line. B The triangle winding side of the three-phase transformer provides users with symmetrical three-phase power.

[0011] Preferably, the three-phase static VAR generator includes eight high-power transistors BG, a DC energy storage capacitor and a pulse modem; every two high-power transistors BG are connected in series through the emitter of one of the high-power transistors BG and the collector of another high-power transistor BG to form a group of high-power transistors; the series connection points of the emitters and collectors in the four groups of high-power transistors constitute the external P terminal, Q terminal, M terminal and N terminal of the three-phase static VAR generator, the four groups of high-power transistors are connected in parallel in the forward direction, the emitter connection point is point e, the collector connection point is point f, and the DC energy storage capacitor is connected between point e and point f; the control electrode of each high-power transistor BG is connected to the pulse width modem;

[0012] Specifically, suppose that the transmission line L A The current of the three-phase static VAR generator is I2, and the input current of the B terminal of the three-phase transformer 2 is I B , the input current of terminal C in three-phase transformer 2 is I C The input voltage of the B terminal of the three-phase transformer 2 relative to the neutral point D terminal is U B The input voltage of the C terminal of the three-phase transformer 2 relative to the neutral point D terminal is U C ; Three-phase transformer input voltage U C =U,U C The phase leads the phase of U by 120°; the input current of the C terminal of the three-phase transformer I C The phase leads the phase of U by 30°; the input voltage of the three-phase transformer is U B =U,U B The input current at the B terminal of the three-phase transformer lags behind the phase of U by 120°. I B The phase lags U by 30°.

[0013] Further preferably, the high-power transistor may be an integrated gate-commutated thyristor.

[0014] Further preferably, the high-power transistor may also be an insulated gate bipolar transistor.

[0015] Compared with the prior art, the beneficial effects of the technology of the present invention are:

[0016] 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;

[0017] 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;

[0018] 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.

[0019] 4. Simple structure, good versatility, good economy and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a basic structural diagram of the power supply structure described in the first embodiment of the present invention.

[0021] 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.

[0022] Figure 3 It is a schematic structural diagram of the three-phase static VAR generator described in Example 1 of the present invention.

[0023] 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.

[0024] Reference numerals:

[0025] 1- Transmission line, L A -A phase transmission line, L B -B-phase transmission line, 2-three-phase transformer, 3-three-phase static VAR generator, BG-high power transistor, U B - Input voltage of terminal B of three-phase transformer relative to neutral point, U C - Input voltage at terminal C of three-phase transformer relative to neutral point, I - Transmission line current, I A - Input current of the A terminal of the three-phase transformer, I2 - Input current of the P terminal of the three-phase static VAR generator, I B - Input current at terminal B of three-phase transformer 2, I C -Input current at terminal C in three-phase transformer 2. DETAILED DESCRIPTION

[0026] 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.

[0027] The basic working principle of the power supply structure of the present invention is as follows:

[0028] Assume that the current of transmission line 1 is I, the input current of terminal P of three-phase static VAR generator 3 is I2, and the input current of terminal A of three-phase transformer 2 is I A , the input current of terminal B in three-phase transformer 2 is I B , the input current of terminal C in three-phase transformer 2 is I C , the input voltage of terminal B relative to the neutral point of three-phase transformer 2 is U B , the input voltage of the C terminal relative to the neutral point of the three-phase transformer 2 is U C ; Input voltage U at terminal C of three-phase transformer C =U,U C The phase leads the phase of U by 120°; the input current of the C terminal of the three-phase transformer I C The phase leads the phase of U by 30°; the input voltage U at the B terminal of the three-phase transformer B =U,U B The input current at the B terminal of the three-phase transformer lags behind the phase of U by 120°. I B The phase lags behind the phase of U by 30°; the delta winding side of the three-phase transformer 2 provides a symmetrical three-phase power supply for the load that requires three-phase power to operate.

[0029] Embodiment 1

[0030] like Figure 1 As shown, the embodiment of the present invention provides a non-three-phase to three-phase power supply structure based on a three-phase transformer, and the power supply structure mainly includes a transmission line 1, a three-phase transformer 2 and a three-phase static VAR generator 3. The transmission line 1 is used to transmit current to the three-phase transformer 2 and the three-phase static VAR generator 3; the three-phase transformer 2 is used to transform and phase-adjust the current provided by the transmission line 1 and the three-phase static VAR generator 3 and then provide a symmetrical three-phase power supply to the user; the three-phase static VAR generator 3 is used to transform the shunted current in the transmission line 1 and then supply power to the three-phase transformer 2; wherein the transmission line 1 is connected to the three-phase static VAR generator 3 and the three-phase transformer 2 respectively, the three-phase static VAR generator 3 is connected to the three-phase transformer 2, and the three-phase transformer 2 provides a three-phase power supply to the user in the back.

[0031] like Figure 2 and Figure 3As shown, the 220V transmission line 1 of the neutral point grounded power grid is a single-phase transmission line with a current of I, and the transmission line 1 is respectively connected to the A terminal of the three-phase transformer 2 and the P terminal of the three-phase static VAR generator 3; the current magnitude of the P terminal of the three-phase static VAR generator 3 input by the transmission line 1 is I2; the B terminal, C terminal, and D terminal of the three-phase transformer 2 are respectively connected to the Q terminal, M terminal, and N terminal of the three-phase static VAR generator 3, and the N terminal of the three-phase static VAR generator 3 is grounded; the three-phase static VAR generator 3 includes eight high-power transistors BG, a DC energy storage capacitor, and a pulse modem; every two high-power transistors BG forms a group of high-power transistors through the emitter of one high-power transistor BG connected in series with the collector of another high-power transistor BG; the series connection points of the emitters and collectors in the four groups of high-power transistors form the external P terminal, Q terminal, M terminal and N terminal of the three-phase static VAR generator. The four groups of high-power transistors are connected in parallel in the forward direction, the emitter connection point is point e, the collector connection point is point f, and a DC energy storage capacitor is connected between point e and point f; the control electrode of each high-power transistor BG is connected to a pulse width modem; the triangle winding sides a, b, and c of the three-phase transformer 2 provide three-phase symmetrical power to the user.

[0032] Among them, the input voltage U at the C terminal of the three-phase transformer C =U,U C The phase leads the phase of U by 120°; the input current of the C terminal of the three-phase transformer I C The phase leads the phase of U by 30°; the input voltage U at the B terminal of the three-phase transformer B =U,U B The input current at the B terminal of the three-phase transformer lags behind the phase of U by 120°. I B The phase lags behind U by 30°;

[0033] The high-power transistor BG shown in the embodiment of the present invention is an integrated gate-commutated thyristor IGCT; in actual implementation, an insulated gate bipolar transistor IGBT may also be used.

[0034] Embodiment 2

[0035] The non-three-phase to three-phase power supply structure based on the three-phase transformer 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 three-phase transformer 2 and a three-phase static var generator 3. The transmission line 1 is used to transmit current to the three-phase transformer 2 and the three-phase static var generator 3; the three-phase transformer 2 is used to transform and phase-adjust the current provided by the transmission line 1 and the three-phase static var generator 3 and then provide a symmetrical three-phase power supply to the user; the three-phase static var generator 3 is used to transform the shunted current in the transmission line 1 and then supply power to the three-phase transformer 2; wherein the transmission line 1 is connected to the three-phase static var generator 3 and the three-phase transformer 2 respectively, the three-phase static var generator 3 is connected to the three-phase transformer 2, and the three-phase transformer 2 provides the three-phase power supply to the user in the back.

[0036] The structures and mutual connection modes of the eight high-power transistors BG, DC energy storage capacitors and pulse width modems in the three-phase static VAR generator 3 described in the embodiment of the present invention 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.

[0037] 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.

[0038] Combination Figure 2 and Figure 4 As shown, the difference between the non-three-phase to three-phase power supply structure based on the three-phase transformer 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 U is 220V, the input current of the A-phase transmission line in the transmission line 1 is I, and the A-phase transmission line L in the transmission line 1 is A The A terminal of the three-phase transformer 2 and the P terminal of the three-phase static var generator 3 are connected respectively, and the A-phase transmission line L A The current magnitude of the P terminal of the input three-phase static VAR generator 3 is I2; the B terminal, C terminal, and D terminal of the three-phase transformer 2 are respectively connected to the Q terminal, M terminal, and N terminal of the three-phase static VAR generator 3, and the B-phase transmission line L in the transmission line 1 B Connect to the N terminal of the three-phase static VAR generator 3; the triangle winding sides a, b, and c of the three-phase transformer 2 provide three-phase symmetrical power to the user.

[0039] Among them, the input voltage U at the C terminal of the three-phase transformer C =U,U C The phase leads the phase of U by 120°; the input current of the C terminal of the three-phase transformer I CThe phase leads the phase of U by 30°; the input voltage U at the B terminal of the three-phase transformer B =U,U B The input current at the B terminal of the three-phase transformer lags behind the phase of U by 120°. I B The phase lags U by 30°.

Claims

1. A non-three-phase to three-phase power supply circuit based on a three-phase transformer, characterized in that: The power supply structure includes: A transmission line (1) for supplying power to a three-phase transformer (2) and a three-phase static VAR generator (3); A three-phase transformer (2) is used to transform and phase-modulate the current provided by the transmission line (1) and the three-phase static VAR generator (3) to provide a symmetrical three-phase power supply to users; A three-phase static VAR generator (3) is used to transform the shunted current in the transmission line (1) and supply power to the three-phase transformer (2); The three-phase port of the three-phase transformer (2) is used as an output port to provide a three-phase power supply to a user, the input end of the three-phase transformer (2) is respectively connected to the output end of the three-phase static VAR generator (3) and the transmission line (1), and the input end of the three-phase static VAR generator (3) is connected to the transmission line (1); The A terminal, the B terminal and the C terminal of the three-phase transformer (2) are the A, B and C three-phase input terminals of the three-phase transformer respectively, and the D terminal is the midpoint of the three-phase transformer; The three-phase static VAR generator (3) is a three-phase four-wire structure, and the P terminal, Q terminal, M terminal and N terminal are the midpoints of the four bridge arms respectively; The B terminal, C terminal and D terminal of the three-phase transformer (2) are respectively connected to the Q terminal, M terminal and N terminal of the three-phase static VAR generator (3); The transmission line (1) is a single-phase transmission line, and the transmission line (1) is connected to the A terminal of the three-phase transformer (2) and the P terminal of the three-phase static VAR generator (3) respectively; the N terminal of the three-phase static VAR generator (3) is grounded; or the transmission line (1) is a two-phase transmission line, and the A-phase transmission line (L) of the transmission line (1) is connected to the ground. A ) are connected to the A terminal of the three-phase transformer (2) and the P terminal of the three-phase static VAR generator (3) respectively; the B-phase transmission line (L) in the transmission line (1) B ) is connected to the N terminal of the three-phase static VAR generator (3).

2. The non-three-phase to three-phase power supply circuit based on a three-phase transformer according to claim 1 is characterized in that: Input voltage U between terminals C and D of three-phase transformer (2) C Equal to the voltage U of the transmission line (1), U C The phase leads the phase of U by 120°; the input current I at the C terminal of the three-phase transformer (2) C Equal to the current I of the transmission line (1) times, I C The phase leads the phase of U by 30°; the input voltage U between the B terminal and the D terminal of the three-phase transformer (2) B Equal to the voltage U of the transmission line (1), U B The phase lags U by 120°, and the input current I at the B terminal of the three-phase transformer (2) B Equal to the current I of the transmission line (1) times, I B The phase lags U by 30°.

3. The non-three-phase to three-phase power supply circuit based on a three-phase transformer according to claim 1 or 2, characterized in that: The three-phase static VAR generator (2) comprises eight high-power transistors (BG), a DC energy storage capacitor and a pulse modem; every two high-power transistors (BG) are connected in series through the emitter of one of the high-power transistors (BG) and the collector of another high-power transistor (BG) to form a high-power transistor group; the series connection points of the emitters and collectors in the four high-power transistor groups form the external P terminal, Q terminal, M terminal and N terminal of the three-phase static VAR generator; the four high-power transistor groups are connected in parallel in the forward direction, the emitter connection point is point e, the collector connection point is point f, and the DC energy storage capacitor is connected between point e and point f; the control electrode of each high-power transistor (BG) is connected to the pulse modem.

4. The non-three-phase to three-phase power supply circuit based on a three-phase transformer according to claim 3 is characterized in that: The high-power transistor (BG) adopts an integrated gate-commutated thyristor.

5. The non-three-phase to three-phase power supply circuit based on a three-phase transformer according to claim 3, characterized in that: The high-power transistor (BG) is an insulated gate bipolar transistor.

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