A single-phase or two-phase to three-phase power supply structure using a YNvd transformer

Abstract

The invention discloses a single-phase or two-phase to three-phase power supply structure using a YNvd transformer, and relates to the technical field of power supply and distribution of electric power grids. A transmission line, a YNvd transformer and a three-phase static VAR generator, the transmission line is connected to the YNvd transformer, when the transmission line is a single-phase transmission line, the transmission line is respectively connected to the P terminal in the input end of the three-phase static VAR generator and the A terminal in the YNvd transformer, the K terminal in the YNvd transformer is grounded, the N terminal of the three-phase static VAR generator is also grounded GND, the B terminal and the C terminal of the YNvd transformer are respectively connected to the M terminal and the N terminal in the output end of the three-phase static VAR generator, and the output ports a phase, b phase and c phase of the YNvd transformer provide three-phase power to users.

Description

Technical Field

[0001] The invention relates to the technical field of power supply and distribution of electric power grids. 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 using a YNvd transformer, which can effectively solve the technical problem of providing three-phase power through a single-phase or two-phase transmission line.

[0006] The purpose of the present invention adopts the following technical solution: a single-phase or two-phase to three-phase power supply structure using a YNvd transformer, the power supply structure includes: a transmission line, a YNvd transformer and a three-phase static VAR generator, the transmission line is connected to the YNvd transformer, 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 YNvd transformer, the K terminal in the YNvd transformer is grounded, the N terminal of the three-phase static VAR generator is also grounded GND, the B terminal and C terminal of the YNvd transformer are respectively connected to the M terminal and N terminal at the output end of the three-phase static VAR generator, and the output ports a phase, b phase and c phase of the YNvd transformer provide three-phase power to users.

[0007] When the transmission line is a two-phase transmission line, the A-phase transmission line L A They are respectively connected to the P terminal of the three-phase static VAR generator input port and the A terminal of the v-type winding of the YNvd transformer; the B-phase transmission line L B They are respectively connected to the N terminal in the input port of the three-phase static VAR generator and the K terminal of the V-type winding of the YNvd transformer.

[0008] The three-phase static VAR generator includes six high-power transistors BG, a DC energy storage capacitor and a pulse width modulator CP; 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 three groups of high-power transistors constitute the external P terminal, M terminal and N terminal of the three-phase static VAR generator; the three groups of high-power transistors are arranged in parallel, their emitter connection points are point e, the collector connection points are point f, and the DC energy storage capacitor is connected in parallel between point e and point f; the control electrode of each high-power transistor BG is connected to the output end of the pulse width modulator CP.

[0009] The input current of the P terminal of the three-phase static VAR generator is equal to half of the input current of the transmission line; the input voltage U between the B terminal and the C terminal of the YNvd transformer B The input voltage U between the A terminal and the K terminal of the YNvd transformer A The magnitudes are equal and the phases are 90 degrees to each other; the input current I B Equal to the input current I2 of the three-phase static VAR generator.

[0010] The high-power transistor BG is an integrated gate-commutated thyristor or an insulated gate bipolar thyristor.

[0011] Compared with the prior art, the beneficial effects of the technology of the present invention are:

[0012] 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;

[0013] 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;

[0014] 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.

[0015] 4. Simple structure, good versatility, good economy and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a basic structural schematic diagram of the present invention.

[0017] Figure 2 It is a schematic diagram of the specific structural connection of the present invention.

[0018] Figure 3 It is a structural schematic diagram of the three-phase static VAR generator of the present invention.

[0019] Figure 4 It is a schematic diagram of the specific structural connection of the second embodiment of the present invention.

[0020] Figure 5 It is a control flow chart of the pulse width modulator of the present invention. DETAILED DESCRIPTION

[0021] 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 in conjunction with the accompanying drawings.

[0022] The basic working principle of the power supply structure described in the present invention is as follows: a pulse width modulator CP (pulse width modulator) is used to perform analog control on an analog circuit using the digital output of a microprocessor. The pulse width modulator 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.

[0023] Assume that the current of transmission line 1 is I, the input current of terminal A of YNvd transformer 2 is I1, and the input current of terminal B of YNvd transformer 2 is I BThe input current of the P terminal of the three-phase static VAR generator is I2, and the input voltage between the A terminal and the K terminal of the YNvd transformer 2 is U A , the input voltage between the B terminal and the C terminal of the YNvd transformer 2 is U B The input current I2 of the P terminal of the three-phase static VAR generator 3 is half of the current I of the transmission line 1, and the input current I of the B terminal of the YNvd transformer 2 is B The input voltage U between the B terminal and the C terminal of the YNvd transformer 2 is equal to the input current I2 of the P terminal of the three-phase static VAR generator 3; B The input voltage U between the A terminal and the K terminal of the YNvd transformer 2 A The three-phase side of the YNvd transformer 2 is equal in size and 90 degrees in phase with each other, and provides a symmetrical three-phase power supply to operate the load requiring three-phase power.

[0024] Embodiment 1

[0025] like Figure 1 As shown, the embodiment of the present invention provides a single-phase or two-phase to three-phase power supply structure using a YNvd transformer, and the power supply structure mainly includes a transmission line 1, a YNvd transformer 2 and a three-phase static var generator 3. The transmission line 1 is used to transmit current to the YNvd transformer 2 and the three-phase static var generator 3; the YNvd 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 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 YNvd transformer 2; wherein the transmission line 1 is connected to the three-phase static var generator 3 and the YNvd transformer 2 respectively, the three-phase static var generator 3 is connected to the YNvd transformer 2, and the YNvd transformer 2 provides a three-phase power supply to the user.

[0026] 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. The transmission line 1 is respectively connected to the A terminal of the YNvd transformer 2 and the P terminal of the three-phase static VAR generator 3; the current magnitude of the transmission line 1 input to the A terminal of the YNvd transformer 2 is I1, and the current magnitude of the transmission line 1 input to the P terminal of the three-phase static VAR generator 3 is I2; the K terminal of the YNvd transformer 2 is connected to the N terminal of the three-phase static VAR generator 3 and then grounded; the three-phase static VAR generator 3 includes six high-power transistors BG, a DC energy storage capacitor and a pulse width modulation CP; every two high-power transistors BG are connected in series through the emitter of one high-power transistor BG and the collector of the other high-power transistor BG to form a high-power transistor group; the series connection point of the emitter and the collector in the three high-power transistor groups constitutes the external P terminal, M terminal and N terminal of the three-phase static VAR generator, the three high-power transistor groups are connected in parallel, 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 stage of each high-power transistor BG is connected to the output end of the pulse width modulator CP. The M terminal of the three-phase static VAR generator 3 is connected to the B terminal of the single-three-phase combined transformer 2, and the N terminal of the three-phase static VAR generator 3 is connected to the C terminal of the single-three-phase combined transformer 2; the three-phase port side a, b, c of the single-three-phase combined transformer 2 provides a three-phase symmetrical power supply to the user.

[0027] Among them, the input current I2 of the P terminal of the three-phase static VAR generator is half of the current I of the transmission line 1, and the input current I of the B terminal of the YNvd transformer 2 is B The input current I2 of the three-phase static var generator P terminal is equal to the input voltage U between the B terminal and the C terminal of the YNvd transformer 2. B The input voltage U between the A terminal and the K terminal of the YNvd transformer 2 A The three-phase side of the YNvd transformer 2 is equal in size and 90 degrees in phase with each other, and provides a symmetrical three-phase power supply to operate the load requiring three-phase power.

[0028] Figure 3 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.

[0029] Embodiment 2

[0030] The single-phase or two-phase to three-phase power supply structure using a YNvd 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 YNvd transformer 2 and a three-phase static var generator 3. The transmission line 1 is used to transmit current to the YNvd transformer 2 and the three-phase static var generator 3; the YNvd 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 YNvd transformer 2; wherein the transmission line 1 is connected to the three-phase static var generator 3 and the YNvd transformer 2 respectively, the three-phase static var generator 3 is connected to the YNvd transformer 2, and the YNvd transformer 2 provides a three-phase power supply to the user in the future.

[0031] The structures of the six high-power transistors BG, the DC energy storage capacitor and the pulse width modulator CP in the three-phase static VAR generator 3 described in 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.

[0032] 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.

[0033] Combination Figure 2 and Figure 4 As shown, the difference between the single-phase or two-phase to three-phase power supply structure using a YNvd transformer in this embodiment and the above-mentioned embodiment 1 is that the transmission line 1 in this embodiment 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 YNvd transformer 2 and the P terminal of the three-phase static var generator 3 are connected respectively. The current input to the A terminal of the YNvd transformer 2 is I1, and the current input to the P terminal of the three-phase static var generator 3 is I2. B They are respectively connected to the K terminal in the YNvd transformer 2 and the N terminal of the three-phase static VAR generator 3; the M terminal and the N terminal of the three-phase static VAR generator 3 are respectively connected to the B terminal and the C terminal in the YNvd transformer 2; the three-phase sides a, b, and c of the YNvd transformer 2 provide three-phase symmetrical power to the user.

[0034] The pulse width modulator control process is as follows Figure 5 As shown, the input current I2 of the P terminal of the three-phase static VAR generator is half of the current I of the transmission line 1, and the input current I of the B terminal of the YNvd transformer 2 is BThe input current I2 of the three-phase static var generator P terminal is equal to the input voltage U between the B terminal and the C terminal of the YNvd transformer 2. B The input voltage U between the A terminal and the K terminal of the YNvd transformer 2 A The three-phase side of the YNvd transformer 2 is equal in size and 90 degrees in phase with each other, and provides a symmetrical three-phase power supply to operate the load requiring three-phase power.

Claims

1. A single-phase or two-phase to three-phase power supply structure using a YNvd transformer, the power supply structure comprising: A transmission line (1), a YNvd transformer (2) and a three-phase static VAR generator (3), wherein the transmission line (1) is connected to the YNvd transformer (2), characterized in that: when the transmission line (1) is a single-phase transmission line, the transmission line (1) is respectively connected to the P terminal at the input end of the three-phase static VAR generator (3) and the A terminal of the YNvd transformer (2), the K terminal of the YNvd transformer (2) is grounded, and the N terminal of the three-phase static VAR generator (3) is also grounded GND, the B terminal and the C terminal of the YNvd transformer (2) are respectively connected to the M terminal and the N terminal at the output end of the three-phase static VAR generator (3), and the output ports a phase, b phase and c phase of the YNvd transformer (2) provide three-phase power to users; When the transmission line (1) is a two-phase transmission line, the A-phase transmission line of the transmission line (1) L A They are respectively connected to the P terminal of the input port of the three-phase static VAR generator (3) and the A terminal of the v-type winding of the YNvd transformer (2); the B-phase transmission line of the transmission line (1) L B They are respectively connected to the N terminal of the input port of the three-phase static VAR generator (3) and the K terminal of the V-type winding of the YNvd transformer (2).

2. According to claim 1, a single-phase or two-phase to three-phase power supply structure using a YNvd transformer is characterized in that: The three-phase static VAR generator (3) comprises six high-power transistors BG, a DC energy storage capacitor and a pulse width modulator CP; 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 three high-power transistor groups form the external P terminal, M terminal and N terminal of the three-phase static VAR generator; the three high-power transistor groups are arranged in parallel, their emitter connection point is point e, the collector connection point is point f, and the DC energy storage capacitor is connected in parallel between point e and point f; the control electrode of each high-power transistor BG is connected to the output end of the pulse width modulator CP.

3. The single-phase or two-phase to three-phase power supply structure using a YNvd transformer according to claim 1, characterized in that: The input current at the P terminal of the three-phase static VAR generator (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 YNvd transformer (2) is U B The input voltage between the A and K terminals of the YNvd transformer (2) U A The input current at the B terminal of the YNvd transformer (2) is equal in magnitude and 90 degrees in phase with each other. I B Equal to the input current of the three-phase static VAR generator (3) I 2.

4. The single-phase or two-phase to three-phase power supply structure using a YNvd transformer according to claim 2, characterized in that: The high-power transistor BG is an integrated gate-commutated thyristor or an insulated gate bipolar thyristor.

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