KR-102962792-B1 - Converter and method for driving an electric machine

KR102962792B1KR 102962792 B1KR102962792 B1KR 102962792B1KR-102962792-B1

Abstract

The present disclosure relates to a converter (101) for driving an electric machine, wherein the stator winding of the electric machine can be changed to a low-speed configuration or to a high-speed configuration having fewer series-connected turns than the low-speed configuration. The converter includes a converter stage (102) for supplying stator voltage to the stator winding, and a control system (103) for controlling the stator winding to the low-speed configuration or the high-speed configuration. The control system disables the converter stage during the change between the low-speed configuration and the high-speed configuration and limits the torque of the electric machine such that the torque limit is higher when the stator winding is in the low-speed configuration than when the stator winding is in the high-speed configuration. As the number of series-connected turns of the stator winding changes, unwanted transient currents may be reduced as the torque limit changes.

Inventors

따르끼아이넨 안띠
또이까 유하
시보 따빠니
삐스빠넨 미꼬
뵈르끄홀름 미까

Assignees

댄포스 아/에스

Dates

Publication Date: 20260508
Application Date: 20211120
Priority Date: 20201204

Claims (14)

As a converter (101) for driving an electric machine, The stator winding of the above electric machine can be changed to a low-speed configuration or to a high-speed configuration having fewer series-connected turns than the low-speed configuration, and The above converter is, - A converter stage (102) configured to supply stator voltage to the above stator winding; and - Includes a control system (103) configured to control the stator winding in the above low-speed configuration or the above high-speed configuration and to control the converter stage to supply the stator voltage, and The above control system is configured to limit the torque of the electric machine such that the torque limit is higher when the stator winding is in the low-speed configuration (T1) than when the stator winding is in the high-speed configuration (T2). The control system is characterized by being configured to disable the converter stage during a change between the low-speed configuration and the high-speed configuration and to perform the change. The above control system is configured to maintain a calculation model of the electric machine and, based on the stator current of the electric machine, the stator voltage, and the calculation model, to control the rotational speed and/or torque of the electric machine. The above control system is configured to change the parameters of the calculation model of the electric machine during the change between the low-speed configuration and the high-speed configuration, Converter for driving electric machinery.
In paragraph 1, The above control system is configured to slope the torque limit value according to the rotational speed, and The above torque limit is a converter that slopes between a higher torque limit (T1) corresponding to the low-speed configuration and a lower torque limit (T2) corresponding to the high-speed configuration.
In paragraph 1 or 2, The above control system is configured to use the following procedure during a change from the current configuration of the stator winding to a new configuration of the stator winding, and The above-mentioned procedure below is, i) set the controllable switches (S1 to S6) of the converter stage (102) to a non-conductive state; ii) monitoring the stator current of the above electric machine; iii) After the stator current is reduced below a threshold, all configuration switches (Cs1 to Cs8) of the stator winding are set to a non-conductive state, and a waiting period is maintained for a predetermined first time; iv) setting the configuration switches (Cs1 to Cs8) of the stator windings to positions corresponding to the new configuration of the stator windings, and waiting for a predetermined second time; v) A converter that activates the converter stage (102) to supply stator voltage to the stator winding.
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In paragraph 1 or 2, A converter configured such that the control system estimates an electromotive force that can be induced in the low-speed configuration of the stator winding as a result of the rotational speed of the rotor of the electric machine and the magnetic flux maintained by the rotor of the electric machine, and allows a change from the high-speed configuration to the low-speed configuration only when the estimated electromotive force is less than a threshold.
In paragraph 1 or 2, A converter configured such that the control system prevents a change from the low-speed configuration to the high-speed configuration when less than a predetermined time has elapsed after a previous change from the high-speed configuration to the low-speed configuration, and prevents a change from the high-speed configuration to the low-speed configuration when less than the predetermined time has elapsed after a previous change from the low-speed configuration to the high-speed configuration.
As a method for driving electric machinery, The stator winding of the above electric machine can be changed to a low-speed configuration or to a high-speed configuration having fewer series-connected turns than the low-speed configuration, and The above method is, - A step (201) of controlling the stator winding in the above low-speed configuration or the above high-speed configuration; and - Includes a step (202) of controlling a converter stage to supply a stator voltage to the stator winding, and The above method is, A step (203) of limiting the torque of the electric machine such that the torque limit is higher when the stator winding is in the low-speed configuration than when the stator winding is in the high-speed configuration; and The method is characterized by including the step of deactivating the converter stage (204) during the change between the low-speed configuration and the high-speed configuration and performing the change, and The above method is, A step of maintaining the calculation model of the above electric machine; A step of controlling the rotational speed and/or torque of the electric machine based on the stator current of the electric machine, the stator voltage, and the calculation model; and The step of changing the parameters of the calculation model of the electric machine during the change between the low-speed configuration and the high-speed configuration, A method for driving an electric machine.
In Paragraph 7, The above method includes the step of sloped torque limit value according to rotational speed, and A method in which the above torque limit is sloped between a higher torque limit corresponding to the low-speed configuration and a lower torque limit corresponding to the high-speed configuration.
In Article 7 or Article 8, The above method includes the step of using the following procedure during a change from the current configuration of the stator winding to a new configuration of the stator winding, and The above-mentioned procedure below is, i) Set the controllable switch of the above converter stage to a non-conductive state; ii) monitoring the stator current of the above electric machine; iii) After the stator current is reduced below a threshold, all configuration switches of the stator winding are set to a non-conductive state, and a waiting period is maintained for a predetermined first time; iv) setting the configuration switch of the stator winding to a position corresponding to the new configuration of the stator winding, and waiting for a predetermined second time; v) A method of activating the converter stage to supply stator voltage to the stator winding.
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In Article 7 or Article 8, The above method is, A step of estimating an electromotive force that can be induced in the low-speed configuration of the stator winding as a result of the rotational speed of the rotor of the electric machine and the magnetic flux maintained by the rotor of the electric machine; and A method comprising the step of allowing a change from the high-speed configuration to the low-speed configuration only when the estimated electromotive force is less than a threshold.
In Article 7 or Article 8, The above method is, A step of preventing a change from the low-speed configuration to the high-speed configuration when less than a predetermined time has elapsed after a previous change from the high-speed configuration to the low-speed configuration; and A method comprising the step of preventing a change from the high-speed configuration to the low-speed configuration when less than the predetermined time has elapsed after a previous change from the low-speed configuration to the high-speed configuration.
As a computer program encoded on a non-volatile computer-readable storage medium for driving an electric machine, The stator winding of the above electric machine can be changed to a low-speed configuration or to a high-speed configuration having fewer series-connected turns than the low-speed configuration, and The above computer program is, - Control the stator winding in the above low-speed configuration or the above high-speed configuration; - To control the converter stage to supply stator voltage to the above stator winding, It includes computer-executable instructions for controlling a programmable processing system, The above computer program is, - Limit the torque of the electric machine such that the torque limit is higher when the stator winding is in the low-speed configuration than when the stator winding is in the high-speed configuration; - To disable the converter stage during the change between the low-speed configuration and the high-speed configuration and to perform the change, Characterized by including computer-executable instructions for controlling the above-mentioned programmable processing system, The above computer program is, Maintain the calculation model of the above electric machine; Based on the stator current of the electric machine, the stator voltage, and the calculation model, the rotational speed and/or torque of the electric machine are controlled; and A computer-executable instruction for controlling the programmable processing system to change the parameters of the computational model of the electric machine during the change between the low-speed configuration and the high-speed configuration, A computer program encoded on a non-volatile computer-readable storage medium for driving an electric machine.
A non-volatile computer-readable storage medium encoded with a computer program pursuant to Paragraph 13.

Description

Converter and method for driving an electric machine The present disclosure generally relates to a converter for driving an electric machine. More specifically, the present disclosure relates to a converter for driving an electric machine, wherein the stator winding of the electric machine can be changed to a low-speed configuration or to a high-speed configuration in which the number of series connected turns is less than that of the low-speed configuration. Additionally, the present disclosure relates to a method and a computer program for driving an electric machine of the aforementioned type. In the typical design of a permanent magnet machine, the nominal rotational speed of the permanent magnet machine cannot be safely exceeded by more than about 40%. For example, if the nominal rotational speed is 2000 rpm (revolutions per minute), this means that the maximum recommended speed is about 2800 rpm. These limits are due to the back electromotive force ("EMF") of the permanent magnet machine, which increases linearly with the rotational speed of the permanent magnet machine. In a fault situation, the alternating current ("AC") system (e.g., a converter) connected to the permanent magnet machine is not necessarily able to suppress the back EMF of the permanent magnet machine. Unsuppressed back EMF during the aforementioned types of fault situations and overspeeding will cause an overvoltage situation that can damage the permanent magnet machine and/or the AC system connected to the permanent magnet machine. Often, the aforementioned technical problem is resolved by selecting a permanent magnet machine with a higher nominal rotational speed that is otherwise required. However, this suboptimal solution limits the maximum peak torque achievable with a given peak current. Therefore, the AC system (e.g., converter) connected to the permanent magnet machine must be designed for higher peak currents. Furthermore, since the achievable steady-state torque achievable with a given steady-state current is reduced, the AC system must also be designed for higher steady-state currents. Variable speed drive units implemented as induction machines have their own issues regarding the selection of the induction machine's nominal rotational speed. The nominal rotational speed is the speed achievable with the nominal stator voltage without field weakening, that is, without reducing the breakdown torque of the induction machine. The faster the aforementioned nominal rotational speed, the higher the stator current required to generate the required torque with the given magnetic flux (e.g., nominal flux) of the induction machine. EP3723276 describes an electric machine comprising a multiphase winding in which the number of series-connected turns of the multiphase winding can be changed using a configuration switch connected to the multiphase winding section. Thus, the nominal rotational speed of the electric machine can be changed using the aforementioned configuration switch. However, a converter (e.g., a frequency converter) for driving the electric machine of the aforementioned type has a problem, particularly when it is necessary to change the winding configuration during the operation of the electric machine. One of the problems is related to the need to prevent excessively high current transients during the change of winding configuration. A simplified summary is provided below to provide a basic understanding of some aspects of various embodiments. This summary is not a comprehensive overview of the invention. It is not intended to identify the core or important elements of the invention or to describe the scope of the invention. The following summary provides only a simplified representation of some concepts of the invention as an introduction to a more detailed description of exemplary embodiments. According to the present invention, a new converter for driving an electric machine is provided, wherein the stator winding of the electric machine can be changed to a low-speed configuration or to a high-speed configuration in which the number of series-connected turns is less than that of the low-speed configuration. The converter according to the present invention comprises - A converter stage configured to supply stator voltage to the stator windings; - Includes a control system configured to control the stator windings in a low-speed or high-speed configuration and to control the converter stage to supply the stator voltage. The control system is configured to limit the torque of the electric machine such that the torque limit is higher when the stator winding is in a low-speed configuration than when the stator winding is in a high-speed configuration. The control system is configured to disable the transducer stage during the change between the low-speed and high-speed configurations and to perform the change. It should be noted that torque limiting is performed only when necessary, that is, only when the actual torque