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

Abstract

In a drive system (1) for a tap changer, an electric machine (2) is supplied with current from a voltage source (4) and / or from an energy store (5). At the end of a switching process, mechanical components in the tap changer and the drive system (1) are braked, the kinetic energy of the mechanical components is converted into electrical energy and is fed to the energy store (5).

Description

Technical Field

[0001] The present invention relates to a method for driving a tap changer and a corresponding driving system. Background Technology

[0002] Tap switches are used to switch between the different winding contacts of a transformer. This, in particular, enables the voltage supplied to the grid by the transformer to remain within a defined fluctuation range around a target value, despite variable network load. Tap switches themselves are well known; they include, in particular, on-load tap switches and off-load tap switches, in which the switching process occurs between the different winding contacts of the transformer while the transformer is supplying power to the grid, and in which the transformer disconnects the grid supplied by the transformer for the switching process. Switching between the different winding contacts of the transformer is achieved by mechanically actuating the electrical contacts in the tap switch. This mechanical actuation can be driven by a motor.

[0003] Near the end of the switching process, the mechanical components in the tap changer's drive system that moved for the purpose of the switching process (including the mechanically operated electrical contacts in the tap changer) must decelerate in order to finally occupy their respective predetermined final positions. This typically dissipates the kinetic energy present in the drive system. This energy waste is detrimental. Summary of the Invention

[0004] Therefore, the objective of this invention is to provide a method for driving a tap changer and a corresponding driving system that avoids this energy waste.

[0005] The task is accomplished by the method according to claim 1 and by the drive system according to claim 4. The dependent claims relate to advantageous embodiments, respectively.

[0006] According to the method for driving a tap changer according to the invention, current is supplied to a motor used for the tap changer to implement a switching process. The switching process is monitored by a motor controller, which regulates the current supplied to the motor. According to the invention, current is supplied to the motor from a voltage source and / or from an energy storage device, which is different from the voltage source. In the final stage of the defined switching process, the kinetic energy remaining in the drive system of the tap changer is converted into electrical energy and delivered to the energy storage device.

[0007] In this way, the kinetic energy remaining in the drive system is not wasted, but is used for future drive needs of the tap changer. Here, the motor controller can control whether to supply current to the motor only from the voltage source, only from the energy storage, or from both the voltage source and the energy storage, based on the state of charge of the energy storage.

[0008] The energy storage device can be one or more capacitors. The capacitors can operate at the same voltage level as the voltage source. However, it is also possible to place a voltage transformer between the capacitor and the motor; this allows for greater freedom in selecting the capacitor and thus makes it easier to meet possible further requirements such as structural space requirements, lifespan, and heat resistance.

[0009] The motor is an electric motor; the specific type of electric motor can be appropriately selected by a person skilled in the art. It can be a DC motor, especially a brushless DC motor, without limiting the invention thereto. Since the high torque is provided through the corresponding current supply of the motor even in the phases requiring high torque during the switching process, a mechanical energy storage device (e.g., a spring energy storage device) can become redundant.

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

[0011] In one embodiment, monitoring the switching process via a motor controller includes the motor controller receiving a signal from a rotary encoder representing the angular position of the tap changer's drive shaft. The tap changer's drive shaft is a shaft within the tap changer whose rotation causes mechanical actuation of electrical contacts within the tap changer, and the motor is mechanically coupled to the shaft either directly or via a transmission mechanism to drive the tap changer. The rotary encoder can directly detect the angular position of the drive shaft, or it can detect the angular position of another shaft in the tap changer's transmission system, which may also be, for example, the shaft of the motor itself. Importantly, the angular position of the tap changer's switching process can be inferred from the angular position of the corresponding shaft. It should also be noted that the relationship between the angular position of the shaft and the angular position of the tap changer's drive shaft is derived from the characteristics of the mechanical coupling between the corresponding shaft (e.g., the motor shaft) and the tap changer's drive shaft, for example from the transmission ratio of the transmission mechanism between the corresponding shaft and the tap changer's drive shaft. Thus, the signal from the rotary encoder, for example, giving the angular position of the motor shaft, represents, in the sense of this application, the angular position of the tap changer's drive shaft.

[0012] It should generally be noted that the method for which protection is sought is used to drive a tap changer to implement the tap changer switching process. In practical applications, the tap changer is connected to a transformer supplying power to the grid. Therefore, the method for which protection is sought is integrated into a broader set of methods for controlling the tap changer and regulating the grid. From these broader methods, for example, the necessity of the switching process is determined, and a corresponding signal is sent to the motor controller, using said signal to request such a switching process.

[0013] The drive system for a tap changer according to the present invention includes a motor for driving the tap changer, a motor controller for the motor, a voltage source, and an energy storage device. The drive system is configured to implement the method according to the present invention described above. This includes: the motor controller being configured, and in particular programmed, to receive and process information related to the switching process and to control the current flow of the motor based on the result of the information processing, thereby executing the switching process according to the method steps.

[0014] In one embodiment, the motor controller includes a management unit configured to regulate whether current is supplied to the motor from a voltage source and / or an energy storage device. This includes the management unit checking the state of charge (SBC) of the energy storage device. For example, when the SBC of the energy storage device exceeds a defined minimum level, current can be supplied to the motor from the energy storage device.

[0015] In a further extended embodiment, the management unit is also configured to regulate the charge amount of the energy storage device by means of electrical energy converted from the kinetic energy of the drive system of the tap changer.

[0016] In a more specific embodiment, the motor controller further includes a power output stage and a regulating unit. In the power output stage, the current supplied to the motor is switched. The regulating unit regulates the switching process of the tap changer by evaluating a signal from a rotary encoder representing the angular position of the drive shaft of the tap changer and by correspondingly controlling the switching of the current in the power output stage. Here, the regulating unit is configured to regulate whether the current to be switched in the power output stage is supplied to the power output stage from a voltage source and / or from an energy storage device, or whether electrical energy is delivered from the power output stage to the energy storage device. The latter occurs when kinetic energy in the drivetrain is converted into electrical energy, which must then be conducted to the energy storage device. Attached Figure Description

[0017] The invention and its advantages are further illustrated below with the aid of the accompanying drawings.

[0018] Figure 1 An embodiment of the drive system according to the present invention is illustrated schematically.

[0019] Figure 2 The diagram schematically illustrates the variation curve of the current intensity used for the motor during the switching process. Detailed Implementation

[0020] These figures only illustrate various embodiments of the invention and should not be construed as limiting the invention to the embodiments shown.

[0021] Figure 1A drive system 1 according to the invention is schematically shown. A motor 2 is configured to drive a tap changer. For this purpose, the motor 2 is controlled by a motor controller 3, which receives signals from a rotary encoder 6, in this example, indicating the angular position of the motor 2's shaft. The motor 2 can be powered by the motor controller 3 using current from a voltage source 4 and / or from an energy storage device 5.

[0022] The motor controller 2 includes a management unit 31, a power output stage 32, and a regulation unit 33. The power output stage 32 switches the current to the motor 2. This current is provided to the power output stage 32 via the management unit 31, which controls whether the current is supplied to the power output stage 32 from the voltage source 4, the energy storage device 5, or both. Depending on the detailed configuration of the drive system 1, the current supplied from the energy storage device 5 may be alternative to or supplemented to the current supplied from the voltage source 4. The management unit 31 also regulates the delivery of electrical energy to the energy storage device 5, which is converted from kinetic energy in the drive system of the tap changer.

[0023] The regulating unit 33 regulates the switching process of the tap changer. Information about the phase of the switching process is obtained from the signal from the rotary encoder 6; other measurement information, such as the current intensity and phase in the components of the tap changer, may also be considered for this purpose. Based on the information about the phase of the switching process, the regulating unit 33 controls the switching of the current in the power output stage 32. This may include: as the defined phase of the switching process is reached, the switching of the current in the power output stage 32 is controlled such that the motor 2 operates as a generator and delivers electrical energy to the management unit 31 via the power output stage 32, which then delivers the electrical energy to the energy storage unit 5. For example, the reaching of the defined phase can be confirmed by the tap changer's drive shaft reaching a defined angular position; in the example shown, the regulating unit 33 determines this from the signal transmitted by the rotary encoder 6 (which gives the angular position of the motor 2's shaft).

[0024] Figure 2 Figure 100 is shown, which has an abscissa 101 corresponding to the change curve of the tap changer switching process and a ordinate 102 showing the current intensity to the motor 2 of the drive system 1 (see Figure 100). Figure 1 The drive system drives the tap changer during the switching process. For example, the change curve of the switching process can be given by the corresponding angular position of the shaft (e.g., the drive shaft of the tap changer or the shaft of motor 2). Without limiting the invention, it is possible, for example, that a complete rotation of the drive shaft of the tap changer corresponds to a complete switching process; in this case, the current intensity change curve shown in Figure 100 extends along the horizontal axis 101 over a range of more than 360 degrees. Similarly, the change curve of the switching process can be described by the angular position of the shaft of motor 2.

[0025] The switching process shown in Figure 100 is identifiable as being divided into multiple phases 110-150.

[0026] In phase 110, the switching process begins. First, the stationary mechanical components (including the electrical contacts in the tap changer and, for example, possible transmission devices or the rotor of the motor) must be put into motion, i.e., accelerated. The torque required for this must be provided by motor 2, which requires a high current intensity.

[0027] In phase 120, the previously accelerated mechanical components move. All that is needed is to maintain this movement. This requires torque and, correspondingly, a current intensity significantly lower than the maximum current intensity observed in phase 110.

[0028] In phase 130, contact occurs between the different mechanical components of the tap changer, which is necessary for the switching process. Continuing this movement and thus the switching process requires torque and current values ​​significantly higher than those in phase 120.

[0029] In phase 140, the mechanical components move further, reaching their predetermined final positions after the switching process. Only the movement needs to be maintained, similar to that in phase 120.

[0030] In phase 150, the moving mechanical component must be decelerated so that it stops at its corresponding predetermined final position. This braking process results in a current whose absolute value can exactly match the values ​​appearing in phases 110 or 130, but with the opposite sign. The energy corresponding to this current is supplied to the energy storage device 5. The energy stored in the energy storage device 5 is used to drive the motor 2 during future tap changers. It is conceivable that the energy from the energy storage device 5 will be used selectively in the phases during the switching process where high torque from the motor 2 is required and correspondingly low high current is needed on the motor 2. The reference current intensity in... Figure 2 The curves shown represent phases 110 and 130.

[0031] Figure Labels

[0032] 1. Drive System

[0033] 2 motors

[0034] 3 Motor controller

[0035] 4. Voltage source

[0036] 5. Energy Storage

[0037] 6. Rotary encoder

[0038] 31 Management Unit

[0039] 32 power output stages

[0040] 33 Adjustment Unit

[0041] 100 charts

[0042] 101. Horizontal axis (the curve showing changes during the switching process)

[0043] 102. Vertical axis (current intensity at the motor)

[0044] Phase of the 110-150 switching process

Claims

1. A method for driving a tap changer, the method comprising the following steps: Current is supplied to the motor (2) used for the tap changer to carry out the switching process; The switching process is monitored by the motor controller (3), wherein The motor controller (3) regulates the current supplied to the motor (2); Its features are, Current is supplied to the motor (2) from a voltage source (4) and / or from an energy storage device (5) different from the voltage source (4); and In the final stage of the switching process, the kinetic energy remaining in the drive system of the tap changer is converted into electrical energy and the electrical energy is delivered to the energy storage device (5).

2. The method of claim 1, wherein, In order to convert kinetic energy into electrical energy, the motor (2) is used as a generator.

3. The method according to claim 1 or 2, wherein, Monitoring the switching process via the motor controller (3) includes the motor controller (3) receiving a signal from the rotary encoder (6) representing the angular position of the drive shaft of the tap changer.

4. A drive system (1) for a tap changer, the drive system (1) comprising: Motor (2) used to drive tap changer; Motor controller (3) for motor (2); Voltage source (4); Energy storage device (5); Its features are, The drive system (1) is configured to implement the method according to any one of claims 1-3.

5. The drive system (1) according to claim 4, wherein, The motor controller (3) includes a management unit (31) configured to regulate whether current is supplied to the motor (2) from a voltage source (4) and / or from an energy storage device (5).

6. The drive system (1) according to claim 5, wherein, The management unit (31) is also configured to regulate the charge amount of the energy storage device (5) by means of electrical energy converted from the kinetic energy of the drive system of the tap changer.

7. The drive system (1) according to any one of claims 5 or 6, wherein, The motor controller (3) also includes: A power output stage (32) configured to switch the current to be supplied to the motor (2); Adjustment unit (33) is configured to adjust the switching process of the tap switch by evaluating a signal representing the angular position of the drive shaft of the rotary encoder (6) and by correspondingly controlling the switching of the current in the power output stage (32). The management unit (31) is configured to regulate whether to supply the current to be switched in the power output stage (32) from the voltage source (4) and / or from the energy storage (5) to the power output stage (32), or to deliver electrical energy from the power output stage (32) to the energy storage (5).

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