Control of power components of a variable speed drive based on a predetermined magnetic flux level

Abstract

The invention relates to a method for controlling a variable speed drive arranged for powering an electric motor, the variable speed drive comprising a power part and a control part. The method comprises a preliminary phase (200) of storing (202) a set of predetermined flux levels for the electric motor. Then, during a current phase (201), the method comprises selecting (204) a flux level from among the set of predetermined flux levels, and controlling (205) the power part of the variable speed drive based on the selected flux level as a reference value.

Description

Technical Field

[0001] This invention relates to the control of a variable speed drive, hereinafter simply referred to as a "drive", which is arranged to supply power to a motor. Background Technology

[0002] Depending on the application and nature of the motor (also known as an "electric motor"), different types of drives have been conceived:

[0003] - A driver for a DC motor;

[0004] - Frequency converter for asynchronous AC motors;

[0005] - Dimmer for asynchronous AC motors;

[0006] - The driver for the stepper motor;

[0007] -etc.

[0008] A driver comprises power components and a control component that controls the power components. The power components include power electronic elements such as transistors and insulated-gate bipolar transistors (IGBTs), and their structure depends on the application and nature of the motor powered by the driver. The control component implements a control law that can be optimized for the application. The objective can also be to optimize the energy consumption of the motor used to achieve the application.

[0009] Energy-saving control laws exist, but they present several problems and drawbacks.

[0010] The secondary voltage curve is an easy-to-use control law, but it only applies to secondary load curves starting from zero torque and zero speed up to the nominal torque and nominal speed values. In this control law, the magnetic flux level changes continuously with speed. Furthermore, the torque T can be expressed as T = k * V. 2 Where V is the speed and k is the coefficient. If the application is not perfectly quadratic, or if the coefficient k varies, the motor's operating point may be outside the trajectory of the variable speed drive, and the control law will not be optimal. It is impossible to correct for this, thus quadratic control laws lack flexibility.

[0011] The "Nold" control law is based on automatically adapting the magnetic flux according to the torque and is suitable for all types of applications. However, the flux level varies continuously, and the Nold control law requires a default setting for dynamic control gain. Because the function between torque and flux is dynamic and requires knowledge of nonlinear magnetic relationships, this method cannot precisely control the flux, and the energy efficiency of the Nold control law is not optimal for predicting load disturbances or speed changes.

[0012] Therefore, it is necessary to improve the drive control law in terms of energy efficiency, responsiveness and / or flexibility. Summary of the Invention

[0013] The object of the present invention is to mitigate at least some of the above-mentioned disadvantages.

[0014] A first aspect of the invention relates to a method for controlling a variable speed drive, the variable speed drive being arranged to supply power to an electric motor, the variable speed drive including power components and control components, the method comprising:

[0015] The initial stage includes storing a set of predetermined magnetic flux levels for the electric motor;

[0016] The current stage includes:

[0017] - Select a flux level from the set of predetermined flux levels;

[0018] - The power components of the variable speed drive are controlled based on the selected magnetic flux level as a reference value.

[0019] This allows for prediction by selecting the most suitable flux level for a given speed / torque range, rather than simply reacting as in existing solutions, which is particularly advantageous when the motor's trajectory is known in advance.

[0020] According to some embodiments, each predetermined magnetic flux level may correspond to the operating point range of the motor, and when a command including a first operating point is received, a first magnetic flux level corresponding to the operating point range including the first operating point is selected.

[0021] This enables the implementation of an automatic mode that selects the optimal flux level based on the operating point.

[0022] According to some embodiments, each predetermined magnetic flux level may correspond to the operating point range of the motor, and when a command including a first operating point is received, a first magnetic flux level corresponding to the operating point range including the first operating point is output to the user, and the magnetic flux level may be selected based on user input.

[0023] This enables the implementation of a semi-automatic mode where the final selection depends on input from the operator, user, or external entity. This external entity can be a remote control device, telephone, tablet, or other device that provides control commands to coordinate operation and select the flux level.

[0024] As a supplement, user input can be an acceptance of the output first flux level, thereby selecting the first flux level as a reference value to control the power components of the driver.

[0025] This makes it possible to implement a semi-automatic mode while minimizing the interaction required between the control components and the user.

[0026] According to some embodiments, a flux level can be selected from a set of predetermined flux levels based on input from an operator or external entity.

[0027] This makes it possible to implement manual mode.

[0028] According to some embodiments, the operating point can be defined by torque and / or speed values.

[0029] As a supplement, each predetermined flux level may be associated with two operating point ranges, including a first operating point range for increasing the flux level and a second operating point range for decreasing the flux level.

[0030] This allows for optimized control of power components.

[0031] A second aspect of the invention relates to a non-transitory computer-readable storage medium having a computer program thereon, the computer program including instructions for performing steps of the method according to the first aspect of the invention when executed by a processor.

[0032] A third aspect of the invention relates to a variable speed drive arranged for supplying power to an electric motor, the variable speed drive including a power component and a control component, wherein the control component includes:

[0033] A memory that stores a set of predetermined magnetic flux levels for an electric motor;

[0034] The processor is configured to perform the following operations during the current phase:

[0035] - Select a flux level from the set of predetermined flux levels;

[0036] - The power components of the variable speed drive are controlled based on the selected magnetic flux level as a reference value.

[0037] Referring to the accompanying drawings, other objects, aspects, effects, and details of the invention will be described in the following detailed description of several exemplary embodiments. Attached Figure Description

[0038] By way of example only, embodiments of this disclosure will be described with reference to the accompanying drawings, in which:

[0039] Figure 1 A system according to some embodiments of the present invention is shown;

[0040] Figure 2 This is a flowchart illustrating the steps of a method according to some embodiments of the present invention;

[0041] Figure 3 Curves representing predetermined magnetic flux levels for different operating point ranges are shown according to some embodiments of the present invention; and

[0042] Figure 4 The structure of the control component of a variable speed drive according to some embodiments of the present invention is shown. Detailed Implementation

[0043] refer to Figure 1 The diagram illustrates a power system for controlling the power supplied to the motor 100 according to some embodiments of the present invention.

[0044] The power system includes a variable speed drive, or simply “drive”, which includes a power component 110 and a control component 120.

[0045] The power component 110 can be powered by a transformer 111 connected to the main power grid 112 (e.g., a three-phase power supply network). Alternatively, the power component 110 can be directly powered by the main power grid 112 or any other power source.

[0046] According to some embodiments, power component 110 may include one or more low-voltage power units. However, there are no limitations on the structure of power component 110, depending on the application and type of the motor 100 to which it is connected. Several structures of variable speed drives are known and will not be described further.

[0047] According to existing technical solutions, the control unit 120 controls the power unit 110 based on a target speed or torque specified in a command received from an external entity or based on a control law. However, the magnetic flux continuously varies to achieve the target speed or torque value. Furthermore, this mechanical parameter target exhibits different responsiveness upon reaching the target because the magnetic flux dynamically changes in response to changes in the mechanical set point.

[0048] Figure 2 This is a flowchart illustrating the steps of a method according to some embodiments of the present invention.

[0049] The method includes a preliminary stage 200 and a current stage 201. In the preliminary stage 200, necessary settings and parameters are determined, which are applicable to the current stage 201, i.e., the operation stage. Therefore, the preliminary stage 200 precedes the current stage 201, in which the driver operates to supply power to the motor.

[0050] In step 202 of the preliminary stage, a set of magnetic flux levels (as predetermined as determined during the preliminary stage) are determined and stored in the memory of the control unit 120. The stored magnetic flux levels can be determined based on criteria depending on the application and type of the motor. There are no limitations on the stored magnetic flux levels.

[0051] The magnetic flux level of the predetermined group can be:

[0052] - Defined manually by the operator during the initial phase 200;

[0053] - Determined based on the work points entered by the operator during the initial phase 200; or

[0054] - By default, it is predefined by the manufacturer during the initial phase 200.

[0055] exist Figure 3 In this system, the operating point is defined solely by the torque value, not the speed value. For example... Figure 3 As shown, each flux level can be associated with at least one operating point range (such as an operating point defined by a torque value). Each flux level allows for optimal energy output within its associated torque value range.

[0056] The flux level can also be associated with two torque value ranges (represented on curves 301 and 302), with the first range corresponding to increasing the flux level (curve 301) and the second range corresponding to decreasing the flux level (curve 302).

[0057] Compare Figure 3 More generally, as described in the text, each flux level can be associated with a range of operating points that includes paired torque and speed values.

[0058] like Figure 3 As shown, according to the present invention, the change of magnetic flux is discontinuous, wherein the magnetic flux takes only discrete predetermined magnetic flux levels: this is because the present invention proposes to use the magnetic flux as a reference value for the variable speed drive (rather than as a value that is adjusted to achieve a reference speed or torque value).

[0059] A predetermined flux value can be associated with a control law of the transmission drive according to the invention (e.g., named "predetermined flux control law" or "preset flux control law"). For example, an operator can use the user interface of the transmission drive to select between different control laws (Nold, secondary, predetermined flux according to the invention, etc.). Alternatively, the control law according to the invention can be integrated in parallel with the mechanical control law in the energy control module of the control unit, which uses torque or speed values ​​as input and is implemented by the mechanical control module of the control unit. Both the energy control module and the mechanical control module can control the electrical control module of the control unit, which directly controls the power components of the transmission drive. For this purpose, the energy control module can provide a flux reference value selected according to the invention as an input to the electrical control module. The mechanical control module can provide a mechanical reference value to the electrical control module.

[0060] Back Figure 3 In optional step 203 of the initial stage, a predetermined magnetic flux level sequence is stored in the memory of the control unit 120. The predetermined sequence includes the association between magnetic flux level and time information. Each sequence can be associated with a specific operation / mode of the motor 100 application.

[0061] Optional step 203 applies to the first embodiment, wherein the flux level is automatically selected based on at least one operating point. Before storing the flux level sequence, the operator can input an operating point sequence and derive the flux level sequence based on the operating point sequence and store it in memory. Alternatively, in step 203, the operating point sequence can be stored instead of the flux level sequence.

[0062] For example, in step 203, several sequences can be stored in association with a preset flux control law. Then, after selecting the current flux control law, the operator can then select one of the predetermined sequences to run.

[0063] The current stage 201 includes step 204 of selecting a flux level from a stored set of predetermined flux levels, and step 205 of controlling the power component 120 of the transmission drive based on the selected flux level as a reference value. The reference value specifies a target value that the transmission drive is controlled to reach and maintain.

[0064] The present invention includes several embodiments for selecting magnetic flux levels.

[0065] According to the first embodiment, also known as "fully automatic mode," the selection of the magnetic flux level is performed entirely automatically. For example:

[0066] - The operator or external entity can select a predetermined sequence to run: when at least one sequence is already stored in memory, the flux level is selected based on the current time and the sequence stored in association with time information; or

[0067] - An operator or external entity can input a command indicating the operating point of the motor, and automatically select the flux level based on the operating point in the command and use it as a reference value.

[0068] According to the second embodiment, also known as "manual mode," the selection of the flux level is performed manually by the operator. This may involve the use of a user interface, including buttons, touchpads, keyboards, graphical user interfaces, and / or any other type of user interface. A list corresponding to the set of predetermined flux levels can be output to the user, and the user can select the predetermined flux level to be applied immediately to the power component 120, or to be delayed and operated later on a given date.

[0069] According to the third embodiment, also known as "semi-automatic mode," an operator or external entity can input a command indicating the operating point of the motor 100, and the control unit 120 determines a first magnetic flux level based on the operating point indicated in the command. The first magnetic flux level is suggested to the operator or external entity as the best choice for the indicated operating point, and the suggested first magnetic flux level can be selected or rejected by the operator or external entity.

[0070] refer to Figure 4 The structure of the control component 120 according to some embodiments of the present invention is shown.

[0071] Control unit 120 may include memory 402 and processor 401, configured to execute reference Figure 2 The steps of the described method.

[0072] Memory 402 can be any type of memory, such as random access memory (RAM), read-only memory (ROM), flash memory, etc. Memory 402 can store instructions executable by processor 401 to perform the steps of the method according to the invention. Alternatively, processor 401 can be replaced by dedicated electronic circuitry designed to perform the steps of the method according to the invention.

[0073] The control unit 120 also includes an input interface 403, which may be a user interface or an interface for communicating with external entities (e.g., via a wired or wireless connection) to receive commands and input. There is no limitation on the meaning of a user interface; a user interface may include buttons, touchpads, keyboards, graphical user interfaces and / or any other type of user interface, or any combination of these types of interfaces.

[0074] The control unit 120 also includes a control interface 404 configured to control the power unit 110 based on a flux level selected by the processor 401. For example, it can control the commutation of the IGBTs of the power unit 110 to achieve speed / torque commands while reaching and maintaining the selected flux level.

[0075] This invention allows for prediction by selecting the most suitable flux level for a given speed / torque range (instead of reacting as with existing solutions), which is particularly advantageous when the motor trajectory is known in advance.

[0076] For example, the trajectory of the motor can be predetermined and can include different stages corresponding to the corresponding operation of the motor, so a sequence of magnetic flux levels can be defined and stored in memory.

[0077] Furthermore, the responsiveness of the control of the power components 110 increases as the target flux parameters no longer change due to anticipation. Their application allows flux to be established in the motor via electrical control, thus preparing it for mechanical control.

[0078] Although the invention has been described above with reference to specific embodiments, it is not limited to the specific forms set forth herein. Rather, the invention is limited only by the appended claims, and other embodiments besides the specific embodiments described above are also possible within the scope of these appended claims.

[0079] Furthermore, although exemplary embodiments have been described above with reference to some exemplary combinations of components and / or functions, it should be understood that alternative embodiments may be provided by different combinations of components and / or functions without departing from the scope of this disclosure. In particular, it is contemplated that specific features described separately or as part of an embodiment may be combined with other separately described features or as part of other embodiments.

Claims

1. A method for controlling a variable speed drive, the variable speed drive being arranged to supply power to an electric motor (100), the variable speed drive including a power component (110) and a control component (120), the method comprising: The initial stage (200) includes storing (202) a set of predetermined magnetic flux levels of the electric motor; The current phase (201) includes: - Select the (204) flux level from the set of predetermined flux levels; - The power components of the variable speed drive are controlled based on the selected magnetic flux level as a reference value; - wherein each predetermined magnetic flux level corresponds to the operating point range of the motor (100), and wherein, upon receiving a command including a first operating point, a first magnetic flux level corresponding to the operating point range including the first operating point is selected, or a first magnetic flux level corresponding to the operating point range including the first operating point is output to the user, and the magnetic flux level is selected based on the user input. -In this context, each predetermined magnetic flux level is associated with two operating point ranges, which include a first operating point range for increasing the magnetic flux level and a second operating point range for decreasing the magnetic flux level.

2. The method according to claim 1, wherein, The user input is an acceptance of the output first magnetic flux level, thereby selecting the first magnetic flux level as a reference value to control the power components of the variable speed drive.

3. The method according to claim 1, wherein, Based on input from the operator or an external entity, a flux level is selected from the set of predetermined flux levels.

4. The method according to claim 1, wherein, The operating point is defined by the torque value and / or speed value.

5. A non-transitory computer-readable storage medium having a computer program stored thereon, the computer program comprising instructions for performing the steps of the method according to any one of claims 1 to 4 when executed by a processor.

6. A variable speed drive for supplying power to an electric motor, the variable speed drive including a power component (110) and a control component (120), wherein the control component includes: Memory (402) stores a set of predetermined magnetic flux levels of the electric motor; The processor (401) is configured to perform the following operations during the current phase: - Select a flux level from the set of predetermined flux levels; - The power components of the variable speed drive are controlled based on the selected magnetic flux level as a reference value; - wherein each predetermined magnetic flux level corresponds to the operating point range of the motor (100), and wherein, upon receiving a command including a first operating point, a first magnetic flux level corresponding to the operating point range including the first operating point is selected, or a first magnetic flux level corresponding to the operating point range including the first operating point is output to the user, and the magnetic flux level is selected based on the user input. -In this context, each predetermined magnetic flux level is associated with two operating point ranges, which include a first operating point range for increasing the magnetic flux level and a second operating point range for decreasing the magnetic flux level.

Images