Method for driving a tap changer, and drive system for a tap changer

Abstract

In a drive system (1) for a tap changer, a motor (2) is supplied with current from a voltage supply (4) and / or from an energy storage device (5), and mechanical components in the tap changer and the drive system (1) are braked at the end of a switching process, the kinetic energy of said components being converted into electrical energy and supplied to the energy storage device (5).

Description

[0001] METHOD FOR DRIVING A TAP CHANGER AND DRIVE SYSTEM FOR A TAP CHANGER

[0002] The invention relates to a method for driving a tap changer and a corresponding drive system.

[0003] Tap changers are used to switch between different winding contacts of a transformer. This ensures that the voltage supplied by the transformer to a power grid remains within a defined fluctuation range around a setpoint, despite variable grid load. Tap changers as such are well known; they include, in particular, on-load tap changers, in which the switching process takes place between different winding contacts of the transformer while the transformer is supplying voltage to a power grid, and off-circuit tap changers, in which the transformer is disconnected from the power grid it supplies for the switching process. Switching between different winding contacts of the transformer is achieved by mechanical actuation of electrical contacts in the tap changer. This mechanical actuation can be driven by a motor.

[0004] Towards the end of a switching operation, moving mechanical components in the tap-changer's drive train, including the mechanically operated electrical contacts in the tap-changer, must be decelerated to ultimately assume their intended end positions. Kinetic energy present in the drive train is typically dissipated in the process. This waste of energy is detrimental.

[0005] The object of the invention is therefore to provide a method for driving a tap changer and a corresponding drive system that avoids this waste of energy. This object is achieved by a method according to claim 1 and by a drive system according to claim 4. The subclaims each relate to advantageous embodiments.

[0006] According to the method of the invention for driving a tap changer, current is supplied to a motor for the tap changer to perform a switching operation. The switching operation is monitored by a motor controller; the motor controller regulates the current supplied to the motor. According to the invention, the current is supplied to the motor from a voltage supply and / or from an energy storage device; the energy storage device is different from the voltage supply. In a defined final phase of the switching operation, remaining kinetic energy in a drive train of the tap changer is converted into electrical energy and fed to the energy storage device.

[0007] In this way, any remaining kinetic energy in the drive train is not wasted but is available for future drive requirements of the tap changer. Depending on the charge level of the energy storage device, the motor control system can determine whether power is supplied to the motor solely from the power supply, solely from the energy storage device, or from both the power supply and the energy storage device.

[0008] The energy storage device can consist of one or more capacitors. These capacitors can operate at the same voltage level as the power supply. However, it is also possible to provide a voltage transformer between the capacitors and the motor; this allows greater freedom in the selection of capacitors and therefore makes it easier to meet any additional requirements, such as space requirements, service life, and thermal resistance.

[0009] The motor is an electric motor; the specific type of electric motor can be suitably selected by the person skilled in the art. It can be a DC motor, in particular a brushless DC motor, without limiting the invention to this. Since high torque is also provided by the motor's power supply during phases of the switching process in which this is required, mechanical energy storage devices, such as spring energy storage devices, can be dispensed with.

[0010] In one embodiment, the motor is used as a generator to convert kinetic energy into electrical energy.

[0011] In one embodiment, monitoring the switching process by the motor control system involves the motor control system receiving signals from a rotary encoder that represent an angular position of a drive shaft of the tap changer. The drive shaft of the tap changer is a shaft in the tap changer whose rotation causes the electrical contacts in the tap changer to be mechanically actuated, and to which the motor for driving the tap changer is mechanically coupled, either directly or via a gear. The rotary encoder can directly detect the angular position of the drive shaft or the angular position of another shaft in the drive train of the tap changer, such as a shaft of the motor itself. It is important here that the angular position of the respective shaft can be used to determine which phase the switching process of the tap changer is in.It should also be noted that the properties of the mechanical coupling between the respective shaft, such as the shaft of the motor, and the drive shaft of the tap changer, for example from a transmission ratio of a gear between the respective shaft and the drive shaft of the tap changer, result in a relationship between the angular position of this shaft and the angular position of the drive shaft of the tap changer, so that, for example, signals from the rotary encoder which indicate the angular position of the shaft of the motor also represent the angular position of the drive shaft of the tap changer within the meaning of this application.

[0012] Generally, it should be noted that the claimed method serves to drive a tap changer to perform a switching operation of the tap changer. In practical use, the tap changer is connected to a transformer that feeds a power grid. Accordingly, the claimed method is integrated into more comprehensive methods for controlling the tap changer and regulating the power grid. These more comprehensive methods then result in, for example, the determination of the need for a switching operation and corresponding signals to the motor control system requesting such a switching operation.

[0013] The drive system according to the invention for a tap changer comprises a motor for driving the tap changer, a motor controller for the motor, a power supply, and an energy storage device. The drive system is configured to carry out the method according to the invention described above. This includes the motor controller being designed, in particular programmed, to receive and process information relevant to a switching operation and, depending on the results of this information processing, to control the current flow to the motor such that the switching operation is carried out according to the method steps.

[0014] In one embodiment, the motor controller comprises a management unit configured to regulate whether power is supplied to the motor from the voltage supply and / or from the energy storage device. This includes the management unit checking the charge level of the energy storage device. For example, power can be supplied to the motor from the energy storage device if the charge level of the energy storage device exceeds a defined minimum level.

[0015] In a further development, the management unit is further designed to regulate a charge of the energy storage device by means of electrical energy converted from kinetic energy of the drive train of the tap changer.

[0016] In an even more specific embodiment, the motor controller further comprises a power output stage and a control unit. The current supplied to the motor is switched in the power output stage. The control unit controls a switching process of the tap changer by evaluating signals from a rotary encoder, which represent an angular position of a drive shaft of the tap changer, and by correspondingly controlling the switching of the current in the power output stage. The management unit is designed to regulate whether the current to be switched in the power output stage is provided to the power output stage from the voltage supply and / or from the energy storage device, or whether electrical energy is supplied from the power output stage to the energy storage device. The latter is the case when kinetic energy in the drive train is converted into electrical energy, which must then be fed to the energy storage device.

[0017] The invention and its advantages are explained in more detail below with reference to the attached drawings.

[0018] Figure 1 shows schematically an embodiment of a drive system according to the invention.

[0019] Figure 2 shows schematically the course of a current for the motor during a switching process.

[0020] The figures refer only to embodiments of the invention and are not to be construed as limiting the invention to the embodiments shown.

[0021] Fig. 1 schematically shows a drive system 1 according to the invention. The motor 2 is intended to drive a step switch. For this purpose, the motor 2 is controlled by a motor controller 3, which for this purpose receives signals from a rotary encoder 6, which in this example indicate an angular position of a shaft of the motor 2. The motor 2 can be supplied with power from a voltage supply 4 and / or from an energy storage device 5 via the motor controller 3.

[0022] The motor controller 2 includes a management unit 31, a power output stage 32, and a control unit 33. The power output stage 32 switches the current to the motor 2. This current is supplied to the power output stage 32 via the management unit 31, with the management unit 31 controlling whether the current is supplied to the power output stage 32 from the voltage supply 4 and / or from the energy storage device 5. Depending on the detailed design of the drive system 1, the current from the energy storage device 5 can be supplied alternatively to or in addition to the current from the voltage supply 4. The management unit 31 also controls the supply of electrical energy to the energy storage device 5, which energy was converted from kinetic energy in the drive train of the tap changer.

[0023] The control unit 33 controls the switching process of the tap changer. The signals from the rotary encoder 6 provide information about the phase of the switching process; further measured data, such as current intensities and current phases in components of the tap changer, can also be used for this purpose. Depending on the information about the phase of the switching process, the control unit 33 controls the switching of the current in the power output stage 32. This can include, upon reaching a defined phase of the switching process, controlling the switching of the current in the power output stage 32 such that the motor 2 acts as a generator and supplies electrical energy via the power output stage 32 to the management unit 31, which then feeds this electrical energy to the energy storage device 5.The achievement of this defined phase can be determined, for example, by the drive shaft of the tap changer reaching a defined angular position; in the example shown, the control unit 33 would determine this from the signals transmitted by the rotary encoder 6, which indicate the angular position of the shaft of the motor 2.

[0024] Fig. 2 shows a diagram 100, with an abscissa 101 corresponding to the course of a switching operation of a tap changer, and an ordinate 102 on which a current intensity to the motor 2 of the drive system 1 (cf. Fig. 1) is shown, which drives the tap changer during this switching operation. The course of a switching operation can be specified, for example, via the respective angular position of a shaft, such as the drive shaft of the tap changer or a shaft of the motor 2. Without limiting the invention thereto, it may be the case that a full revolution of the drive shaft of the tap changer corresponds to a complete switching operation; in this case, the current intensity course shown in diagram 100 extends over a range of 360 degrees along the abscissa 101. In the same way, the course of the switching operation could also be described via an angular position of a shaft of the motor 2.

[0025] The switching process shown in diagram 100 is clearly divided into several phases 110 - 150.

[0026] The switching process begins in phase 110. First, stationary mechanical components (including the electrical contacts in the tap changer, as well as any gears and the rotor of the electric motor) must be set in motion, i.e., accelerated. The torque required for this must be supplied by motor 2, which requires high currents for this purpose.

[0027] In phase 120, the previously accelerated mechanical components move. It is only necessary to maintain this movement. This requires torques and corresponding currents that are significantly lower than the maximum currents occurring in phase 110.

[0028] In phase 130, the contact required for the switching process occurs between various mechanical components of the tap changer. Continuing the movement, and thus the switching process, requires torques and currents that are significantly higher than in phase 120.

[0029] In Phase 140, the mechanical components continue to move toward their respective designated end positions after the switching process. It is only necessary to maintain this movement, similar to Phase 120.

[0030] In phase 150, the moving mechanical components must be decelerated so that they come to a stop at their respective intended end positions. This braking process results in currents whose magnitude can certainly reach the values ​​occurring in phases 110 or 130, but with the opposite sign. The energy corresponding to these currents is fed to energy storage device 5. The energy stored in energy storage device 5 is used to drive motor 2 during future switching operations of the tap changer.

[0031] It is conceivable to use the energy from energy storage device 5 specifically in those phases of the switching process in which high torques from motor 2 and correspondingly high currents to motor 2 are required. With reference to the current intensity curve shown in Fig. 2, these would be phases 110 and 130.

[0032] List of reference symbols:

[0033] 1 drive system

[0034] 2 engines

[0035] 3 Motor control 4 Power supply

[0036] 5 energy storage

[0037] 6 rotary encoders

[0038] 31 administrative unit

[0039] 32 Power amplifier 33 Control unit

[0040] 100 diagram

[0041] 101 Abscissa (switching process)

[0042] 102 Ordinate (current to motor)

[0043] 110 - 150 phases of a switching process

Claims

Claims 1. Method for driving a tap changer, the method comprising the steps: Providing power to a motor (2) for the step switch to carry out a switching operation; Monitoring the switching process by a motor controller (3), wherein the motor controller (3) regulates the current supplied to the motor (2); characterized in that the current is supplied to the motor (2) from a voltage supply (4) and / or from an energy storage device (5) which is different from the voltage supply (4); and in that, in a defined final phase of the switching process, kinetic energy remaining in a drive train of the tap changer is converted into electrical energy and supplied to the energy storage device (5).

2. Method according to claim 1, wherein the motor (2) is used as a generator to convert the kinetic energy into electrical energy.

3. The method according to claim 1 or 2, wherein monitoring the switching process by the motor control (3) comprises the motor control (3) receiving signals from a rotary encoder (6) which represent an angular position of a drive shaft of the tap changer.

4. Drive system (1) for a tap changer, the drive system (1) comprising: a motor (2) for driving the tap changer; a motor controller (3) for the motor (2); a voltage supply (4); an energy storage device (5); characterized in that the drive system (1) is configured to carry out the method according to one of claims 1-3.

5. Drive system (1) according to claim 4, wherein the motor control (3) comprises a management unit (31) which is designed to regulate whether current is provided to the motor (2) from the voltage supply (4) and / or from the energy storage device (5).

6. Drive system (1) according to claim 5, wherein the management unit (31) is further designed to regulate a charge of the energy storage device (5) by electrical energy converted from kinetic energy of the drive train of the tap changer.

7. Drive system (1) according to one of claims 5 or 6, wherein the motor controller (3) further comprises: a power output stage (32) configured to switch the current to be supplied to the motor (2); a control unit (33) configured to control a switching operation of the tap changer by evaluating signals from a rotary encoder (6) representing an angular position of a drive shaft of the tap changer, and by appropriately controlling the switching of the current in the power output stage (32); wherein the management unit (31) is designed to regulate whether the current to be switched in the power output stage (32) is provided from the voltage supply (4) and / or from the energy store (5) to the power output stage (32), or whether electrical energy is supplied from the power output stage (32) to the energy store (5).

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