Controllable DC ice melting device with rectifier bridge series-parallel switching function and control method

Abstract

The present invention discloses a controllable DC ice-melting device with a rectifier bridge series-parallel switching function and a control method. The device includes a three-winding transformer, a positive six-pulse rectifier bridge, a negative six-pulse rectifier bridge, a positive switching knife switch, a negative switching knife switch, a positive balancing reactor, a negative balancing reactor, a positive smoothing reactor, a negative smoothing reactor, a positive connection knife switch and a negative connection knife switch. The present invention can take into account both the large current of the conductor ice melting and the high voltage requirements of the ground wire ice melting, and exert the best performance of the DC ice-melting device through the adaptive switching of the topology. Compared with the existing twelve-pulse DC ice-melting device, it can expand the current output range or reduce the device cost.

Description

Technical Field

[0001] The invention belongs to the field of high voltage power transmission, and in particular relates to a direct current ice melting device. Background Art

[0002] The transmission distance span of high-voltage transmission lines is very large, and the lines passing through ice-covered areas need to be de-iced to prevent the collapse of the towers. The towers are generally equipped with both conductors and ground wires, both of which require ice melting. The DC resistance of the conductor is small, so a larger ice-melting current needs to be applied for de-icing; the DC resistance of the ground wire is large, so a smaller ice-melting current needs to be applied for de-icing. Since the heat generated by the line is proportional to the square of the ice-melting current, the voltage drop between the ends of the ground wire is higher than that of the conductor under the same heat generation. In summary, a larger ice-melting current is required to melt the ice on the conductor, and a larger ice-melting voltage is required to melt the ice on the ground wire.

[0003] The DC de-icing device installed in the station generally needs to take into account the de-icing of the conductor and the ground wire, that is, it needs to have the output capacity of high current and high voltage at the same time. The existing de-icing solutions are as follows: Figure 1 As shown, a thyristor with a larger on-state current is selected to output a larger ice-melting current; two six-pulse rectifier bridges are connected in series to output a higher ice-melting voltage. The two six-pulse rectifier bridges and three coil transformers together form an ice-melting device. The ice-melting line is connected to the output end of the ice-melting device, and the ice-melting device provides a DC current to melt the ice through heat.

[0004] One problem with the above scheme is that the ice-melting device is not required to have a high voltage output capability when melting ice on the conductor, and is not required to have a large current output capability when melting ice on the ground wire. Therefore, there is some performance waste when the ice-melting device melts ice on the conductor or the ground wire. Summary of the invention

[0005] In order to solve the technical problems mentioned in the above background technology, the present invention proposes a controllable DC ice melting device and a control method with a rectifier bridge series-parallel switching function to solve the problems existing in the existing technical solutions.

[0006] In order to achieve the above technical objectives, the technical solution of the present invention is:

[0007] A controllable DC ice melting device with a rectifier bridge series-parallel switching function, comprising a three-winding transformer, a positive six-pulse rectifier bridge, a negative six-pulse rectifier bridge, a positive switching knife switch, a negative switching knife switch, a positive balancing reactor, a negative balancing reactor, a positive smoothing reactor, a negative smoothing reactor, a positive connecting knife switch and a negative connecting knife switch; the high-voltage side winding of the three-winding transformer is connected to an AC power supply, a low-voltage side winding of the three-winding transformer is connected to the input end of the positive six-pulse rectifier bridge, and the other low-voltage side winding of the three-winding transformer is connected to the input end of the negative six-pulse rectifier bridge; the output positive pole of the positive six-pulse rectifier bridge is connected to port one of the positive balancing reactor, the output negative pole of the positive six-pulse rectifier bridge is connected to port one of the positive switching knife switch, the output positive pole of the negative six-pulse rectifier bridge is connected to port one of the negative switching knife switch, and the output positive pole of the negative six-pulse rectifier bridge is connected to port one of the negative six-pulse rectifier bridge. The output negative pole is connected to port one of the negative pole balancing reactor; port two of the positive pole switching knife switch is connected to port two of the negative pole switching knife switch and ground, port three of the positive pole switching knife switch is connected to port two of the negative pole balancing reactor, port two of the negative pole switching knife switch is connected to port two of the positive pole switching knife switch and ground, and port three of the negative pole switching knife switch is connected to port two of the positive pole balancing reactor; port three of the positive pole balancing reactor is connected to one end of the positive pole connection knife switch via the positive pole smoothing reactor, and the other end of the positive pole connection knife switch is connected to one end of the ice melting circuit, port three of the negative pole balancing reactor is connected to one end of the negative pole connection knife switch via the negative pole smoothing reactor, and the other end of the negative pole connection knife switch is connected to the other end of the ice melting circuit; the ice melting circuit is formed by connecting the ice-melting line in series with the terminal short-circuit line or short-circuit knife switch.

[0008] Furthermore, the positive six-pulse rectifier bridge and the negative six-pulse rectifier bridge are controllable rectifiers.

[0009] Furthermore, the positive pole switching knife switch and the negative pole switching knife switch are single-pole double-throw switches, or are composed of two single-pole single-throw switches with selected connection points respectively.

[0010] Furthermore, the positive electrode balancing reactor and the negative electrode balancing reactor are split reactors with intermediate taps, or two reactors are connected in series and wired out from an intermediate connection point.

[0011] The control method for the above-mentioned controllable DC ice melting device includes the following steps:

[0012] (1) Select the series-parallel mode of two six-pulse rectifier bridges according to the line type;

[0013] (2) The three-winding transformer is connected to AC power, the valve groups of the two six-pulse rectifier bridges are in a locked state, there is no DC output, and the positive and negative connection knife switches are in the open position;

[0014] (3) Close the positive and negative connection switches;

[0015] (4) Unlock the two six-pulse rectifier bridges to increase the current.

[0016] Furthermore, in step (1), when the conductor is to be de-iced, port 1 of the positive switching switch is connected to port 3, and port 1 of the negative switching switch is connected to port 3, and at this time, the two six-pulse rectifier bridges are in parallel working mode; when the ground wire is to be de-iced, port 1 of the positive switching switch is connected to port 2, and port 1 of the negative switching switch is connected to port 2, and at this time, the two six-pulse rectifier bridges are in series working mode.

[0017] The beneficial effects brought by adopting the above technical solution are:

[0018] The present invention can realize adaptive switching of topology through series-parallel switching of the rectifier bridge. Under the condition that the six-pulse rectifier bridge is the same, it can output a DC current twice that of the existing ice-melting device, and has a wider range of applications. Under the condition that the output parameters of the ice-melting device are the same, a thyristor on-state current half that of the existing ice-melting device can be selected, effectively reducing the device cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the principle diagram of the existing twelve-pulse DC ice melting device;

[0020] Figure 2 This is a diagram of an embodiment of a controllable DC ice melting device with a rectifier bridge series-parallel switching function proposed by the present invention;

[0021] Figure 3 It is another embodiment diagram of the controllable DC ice melting device with rectifier bridge series-parallel switching function proposed by the present invention.

[0022] Explanation of reference numbers: 1. Three-winding transformer; 2. Positive six-pulse rectifier bridge; 3. Negative six-pulse rectifier bridge; 4. Positive switching switch; 4-1, 4-2, 4-3, three ports of the positive switching switch; 5. Negative switching switch; 5-1, 5-2, 5-3, three ports of the negative switching switch; 6. Positive balancing reactor; 7. Negative balancing reactor; 8. Positive smoothing reactor; 9. Negative smoothing reactor; 10. Positive connecting switch; 11. Negative connecting switch. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] The present invention designs a controllable DC ice melting device with rectifier bridge series-parallel switching function, such as Figure 2As shown, it includes three-winding transformer, positive six-pulse rectifier bridge, negative six-pulse rectifier bridge, positive switching knife switch, negative switching knife switch, positive balancing reactor, negative balancing reactor, positive smoothing reactor, negative smoothing reactor, positive connecting knife switch and negative connecting knife switch. The high-voltage side winding of the three-winding transformer is connected to the AC power supply, one low-voltage side winding of the three-winding transformer is connected to the input end of the positive six-pulse rectifier bridge, and the other low-voltage side winding of the three-winding transformer is connected to the input end of the negative six-pulse rectifier bridge. The output positive pole of the positive six-pulse rectifier bridge is connected to port one of the positive balancing reactor, the output negative pole of the positive six-pulse rectifier bridge is connected to port one of the positive switching knife switch, the output positive pole of the negative six-pulse rectifier bridge is connected to port one of the negative switching knife switch, and the output negative pole of the negative six-pulse rectifier bridge is connected to port one of the negative balancing reactor. Port 2 of the positive switching knife switch is connected to port 2 of the negative switching knife switch and ground, port 3 of the positive switching knife switch is connected to port 2 of the negative balancing inductor, port 2 of the negative switching knife switch is connected to port 2 of the positive switching knife switch and ground, and port 3 of the negative switching knife switch is connected to port 2 of the positive balancing inductor. Port 3 of the positive balancing inductor is connected to one end of the positive connecting knife switch via the positive smoothing inductor, and the other end of the positive connecting knife switch is connected to one end of the ice melting circuit, port 3 of the negative balancing inductor is connected to one end of the negative connecting knife switch via the negative smoothing inductor, and the other end of the negative connecting knife switch is connected to the other end of the ice melting circuit. The ice melting circuit is formed by connecting the ice melting line to be melted and the terminal short-circuit wire or short-circuit knife switch in series.

[0025] In this embodiment, preferably, the positive six-pulse rectifier bridge and the negative six-pulse rectifier bridge adopt

[0026] A controlled rectifier implemented by power electronic devices such as thyristors.

[0027] In this embodiment, preferably, the positive switching knife switch and the negative switching knife switch adopt single-pole double-throw switches, and the positive balancing reactor and the negative balancing reactor are split reactors with intermediate taps, such as Figure 2 shown.

[0028] In this embodiment, preferably, the positive switching knife switch and the negative switching knife switch are composed of two single-pole single-throw switches respectively selecting connection points, and the positive balancing inductor and the negative balancing inductor are two inductors connected in series and then connected from the middle connection point.

[0029] The present invention also proposes a control method for the above-mentioned controllable DC ice melting device, comprising the following steps:

[0030] Step 1: Select the series-parallel mode of two six-pulse rectifier bridges according to the line type;

[0031] Step 2: The three-winding transformer is connected to AC power, the valve groups of the two six-pulse rectifier bridges are in a locked state, there is no DC output, and the positive and negative pole connection switches are in the open position;

[0032] Step 3: Close the positive and negative connection switches;

[0033] Step 4: Unlock the two six-pulse rectifier bridges to increase the current.

[0034] In step 1, when the conductor is to be de-iced, port 1 of the positive switching switch is connected to port 3, and port 1 of the negative switching switch is connected to port 3. At this time, the two six-pulse rectifier bridges are in parallel working mode, which can output a larger de-icing current to meet the large current demand for conductor de-icing; when the ground wire is to be de-iced, port 1 of the positive switching switch is connected to port 2, and port 1 of the negative switching switch is connected to port 2. At this time, the two six-pulse rectifier bridges are in series working mode, which can output a higher de-icing voltage to meet the high voltage demand for ground wire de-icing.

[0035] The embodiments are only for illustrating the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A controllable DC ice melting device with rectifier bridge series-parallel switching function, characterized in that: It includes a three-winding transformer, a positive six-pulse rectifier bridge, a negative six-pulse rectifier bridge, a positive switching knife switch, a negative switching knife switch, a positive balancing inductor, a negative balancing inductor, a positive smoothing inductor, a negative smoothing inductor, a positive connecting knife switch and a negative connecting knife switch; the high-voltage side winding of the three-winding transformer is connected to an AC power supply, a low-voltage side winding of the three-winding transformer is connected to the input end of the positive six-pulse rectifier bridge, and the other low-voltage side winding of the three-winding transformer is connected to the input end of the negative six-pulse rectifier bridge; the output positive pole of the positive six-pulse rectifier bridge is connected to port one of the positive balancing inductor, the output negative pole of the positive six-pulse rectifier bridge is connected to port one of the positive switching knife switch, the output positive pole of the negative six-pulse rectifier bridge is connected to port one of the negative switching knife switch, and the output negative pole of the negative six-pulse rectifier bridge is connected to the negative balancing Port one of the reactor; Port two of the positive switching switch is connected to Port two of the negative switching switch and ground, Port three of the positive switching switch is connected to Port two of the negative balancing reactor, Port two of the negative switching switch is connected to Port two of the positive switching switch and ground, and Port three of the negative switching switch is connected to Port two of the positive balancing reactor; Port three of the positive balancing reactor is connected to one end of the positive connecting switch via the positive smoothing reactor, and the other end of the positive connecting switch is connected to one end of the ice melting circuit, Port three of the negative balancing reactor is connected to one end of the negative connecting switch via the negative smoothing reactor, and the other end of the negative connecting switch is connected to the other end of the ice melting circuit; The ice melting circuit is formed by connecting the ice-melting line in series with the terminal short-circuit line or short-circuit switch.

2. According to claim 1, the controllable DC ice melting device with rectifier bridge series-parallel switching function is characterized in that: The positive six-pulse rectifier bridge and the negative six-pulse rectifier bridge are controllable rectifiers.

3. The controllable DC ice melting device with rectifier bridge series-parallel switching function according to claim 1 is characterized in that: The positive pole switching knife switch and the negative pole switching knife switch are single-pole double-throw switches, or are composed of two single-pole single-throw switches with connection points selected respectively.

4. The controllable DC ice melting device with rectifier bridge series-parallel switching function according to claim 1 is characterized in that: The positive electrode balancing reactor and the negative electrode balancing reactor are split reactors with middle taps, or two reactors are connected in series and wired out from a middle connection point.

5. The control method for the controllable DC ice melting device according to claim 1 is characterized in that: The following steps are involved: (1) Select the series-parallel mode of two six-pulse rectifier bridges according to the line type; (2) The three-winding transformer is connected to AC power, the valve groups of the two six-pulse rectifier bridges are in a locked state, there is no DC output, and the positive and negative connection knife switches are in the open position; (3) Close the positive and negative connection switches; (4) Unlock the two six-pulse rectifier bridges to increase the current.

6. The control method according to claim 5, characterized in that: In step (1), when the conductor is to be de-iced, port 1 of the positive switching switch is connected to port 3, and port 1 of the negative switching switch is connected to port 3. At this time, the two six-pulse rectifier bridges are in parallel working mode; when the ground wire is to be de-iced, port 1 of the positive switching switch is connected to port 2, and port 1 of the negative switching switch is connected to port 2. At this time, the two six-pulse rectifier bridges are in series working mode.

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