A method for realizing synchronous control of rotor series resistance and stator voltage regulation of a wound-rotor asynchronous motor

Abstract

The present invention discloses a method for realizing synchronous control of rotor series resistance and stator voltage regulation of a wound-rotor asynchronous motor, including a main controller. A voltage output slope control unit, a rotor series resistance time control unit, and a rotor series resistance frequency control unit are provided in the main controller. Among them, the voltage output slope control unit presets the motor starting voltage, the target stator voltage corresponding to each operation gear of the motor, the recommended value of the voltage output slope corresponding to different load ratios, and the calculation formula of the voltage output slope. The rotor series resistance time control unit presets a delay count variable C and the delay values corresponding to the removal of each stage of resistance. The rotor series resistance frequency control unit presets the rotor frequency values corresponding to the removal of each stage of resistance. By obtaining the input information of the motor operation gear and load ratio and the selection of the rotor series resistance control mode, the main controller can synchronously output a voltage output control signal and a rotor series resistance control signal, which can be used for the functional transformation of traditional hoisting motors.

Description

Technical Field

[0001] The present invention relates to a method capable of synchronously controlling the rotor resistance series and stator voltage regulation of a wound-rotor asynchronous motor, and belongs to the technical field of wound-rotor asynchronous motor control. Background Art

[0002] The wound-rotor type three-phase asynchronous motor (simply referred to as the wound-rotor asynchronous motor) has three-phase lead-out wires in the rotor winding. By connecting resistors in series in the rotor circuit, the mechanical characteristics of the motor can be improved, and the starting torque can be increased. Therefore, it is widely used in hoisting equipment (such as: crane systems) in industries such as metallurgy and ports. Generally, the service life of the metal structure parts in the crane system is relatively long. The transformation and upgrading of the crane are all carried out on the hoisting motor (i.e., the wound-rotor asynchronous motor) and its control system.

[0003] At present, most of the control of hoisting motors in the metallurgy industry adopts the traditional rotor resistance series control method. This control method uses contactors to turn on and off the three-phase voltage of the motor and changes the method of connecting resistors in series in the motor rotor. The advantages of this method are simple structure and reliable operation. The disadvantages are that it cannot regulate the voltage, the stator voltage of the motor is a full-voltage fixed value, soft start cannot be achieved, and large current impulses will be generated during frequent full-voltage start and braking during operation, which easily causes the contactors and motors to be burned out, resulting in a very large impact on the mechanical structure of the crane, greatly affecting the service life of the entire crane system, and this method cannot dynamically adjust the motor speed. Although the existing variable frequency speed regulators can achieve dynamic voltage regulation and speed regulation, the cost is high. The key is that if the traditional rotor resistance series control method is upgraded to a variable frequency speed regulation control method, the existing entire resistor system needs to be replaced, resulting in waste of resources, high upgrading and transformation costs and long cycles. Therefore, this type of control technology is only applicable to some high-end application occasions and is not suitable for upgrading a large number of traditional crane systems. Most of the existing cranes in the metallurgy industry in China adopt the traditional rotor resistance series control method. With the development of the industry, the requirements for the control characteristics and service life of hoisting motors are getting higher and higher. Therefore, there is an urgent need in this field to develop an optimal transformation and upgrading method that can take into account the control effect and economy of such motors. Summary of the Invention

[0004] In view of the above problems and requirements existing in the prior art, the object of the present invention is to provide a method capable of realizing synchronous control of rotor series resistance and stator voltage regulation of a wound-rotor asynchronous motor, so as to realize the organic combination of the rotor series resistance control mode and the stator voltage regulation control mode, so that the traditional hoisting motor can have the functions of soft start and stator voltage regulation speed control while having the rotor series resistance control function, resulting in more accurate timing for the removal and connection of the rotor resistance, and being able to upgrade and transform the control system of the traditional hoisting motor with the least modification and the lowest cost, thereby maximizing the optimization and best performance of the control performance and mechanical characteristics of the traditional hoisting motor.

[0005] To achieve the above object of the invention, the technical solution adopted by the present invention is as follows:

[0006] A method capable of realizing synchronous control of rotor series resistance and stator voltage regulation of a wound-rotor asynchronous motor, including a main controller, wherein a voltage output slope control unit, a rotor series resistance time control unit, and a rotor series resistance frequency control unit are provided in the main controller; the voltage output slope control unit presets the motor starting voltage, the target stator voltage corresponding to each motor operation gear, and the recommended value of the voltage output slope and the calculation formula of the voltage output slope corresponding to different load ratios (i.e., the ratio of the actual load to the rated load): K = (target stator voltage - motor starting voltage) / Δt, where K represents the voltage output slope value and Δt represents the time taken for the motor starting voltage to rise or fall to the target stator voltage; the rotor series resistance time control unit presets a delay count variable C and the delay values corresponding to the removal of each stage of resistance; the rotor series resistance frequency control unit presets the rotor frequency values corresponding to the removal of each stage of resistance; and the method includes the following steps:

[0007] S1. The main controller obtains the motor operation gear input information, the load ratio input information, and the control mode of the rotor series resistance.

[0008] S2. The voltage output slope control unit determines the corresponding target stator voltage according to the obtained motor operation gear, determines the corresponding recommended value of the voltage output slope according to the obtained load ratio, and then controls the voltage output according to the voltage rise / fall time Δt calculated by the voltage output slope calculation formula to achieve stator voltage regulation and soft start of the motor.

[0009] S3. If the control mode of rotor series resistance is set to the time control mode, once the rotor series resistance time control unit 1 learns that the motor operation gear is not the zero gear, it starts counting the delay count variable C, and dynamically compares the value of C with the delay values corresponding to the removal of each stage of resistance preset. Once the value of C is equal to the delay value corresponding to the removal of a certain stage of resistance preset, it immediately outputs the control information for removing this stage of resistance. If the control mode of rotor series resistance is set to the frequency control mode, once the rotor series resistance frequency control unit 1 learns that the motor operation gear is not the zero gear, it starts dynamically comparing the rotor frequency feedback value with the rotor frequency values corresponding to the removal of each stage of resistance preset. Once the rotor frequency feedback value is equal to the rotor frequency value corresponding to the removal of a certain stage of resistance, it immediately outputs the control information for removing this stage of resistance.

[0010] Moreover, the voltage output control in step S2 and the resistance removal control in step S3 maintain a strictly synchronous relationship in timing.

[0011] In an implementation scheme, the motor operation gears are divided into a zero gear, a low gear, and a high gear, where: the target stator voltage corresponding to the zero gear is 0 V, the target stator voltage corresponding to the high gear is the full voltage of 380 V, and the target stator voltage corresponding to the low gear is 60% - 85% of the full voltage, which is set by the user within the range of AC 228V - AC 323V according to specific needs.

[0012] In an implementation scheme, there is a negative correlation between the load ratio and the recommended value of the voltage output slope, that is: the larger the load ratio, the smaller the recommended value of the voltage output slope.

[0013] In a preferred scheme, the corresponding relationship between the load ratio and the recommended value of the voltage output slope is as follows:

[0014] Load ratio 30％ 50％ 80％ 100％ Recommended value of voltage output slope 2 1 0.5 0.3

[0015] The load ratio therein refers to the percentage value of the actual load to the rated load.

[0016] In an implementation scheme, the voltage output slope control unit evenly divides the calculated Δt into N time segments, and calculates and controls the voltage increment or decrement required for each time segment according to the formula: (target stator voltage - motor starting voltage) / N, where N is a natural number greater than 2.

[0017] In an implementation scheme, as long as the motor operation gear is the zero gear, the counting of the delay count variable C is cleared.

[0018] In a preferred scheme, if the motor operation gear is the low gear, the maximum value among the delay values corresponding to the removal of each stage of resistance preset is set as the counting upper limit value of the delay count variable C.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] By using the method of the present invention, the synchronous control of rotor resistance series and stator voltage regulation of a wound-rotor asynchronous motor can be realized. It can not only achieve the organic combination of the rotor resistance series control mode and the stator voltage regulation control mode, but also enable this type of wound-rotor asynchronous motor in the traditional crane system to have the functions of soft start and stator voltage regulation speed control on the basis of the rotor resistance series control function. It can achieve seamless compatibility with the existing rotor resistance series control, and can make the cut-in and cut-off timing of the rotor resistance series more accurate. The control mode can freely select the time or frequency control mode according to needs, realizing multi-dimensional control of this type of motor. In addition, the method of the present invention does not require replacing the original resistors and other hardware, and can upgrade and transform the control system of the traditional hoisting motor with the least modification and the lowest cost, and can optimize and best play the control performance and mechanical characteristics of the traditional hoisting motor. Therefore, compared with the prior art, the present invention has significant progress and strong industrial application value. Brief Description of the Drawings

[0021] Figure 1 It is a principle block diagram for upgrading and transforming a traditional hoisting motor by using a method provided by an embodiment of the present invention, which can realize the synchronous control of rotor resistance series and stator voltage regulation of a wound-rotor asynchronous motor. Detailed Embodiment

[0022] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0023] Embodiment

[0024] A method provided by this embodiment, which can realize the synchronous control of rotor resistance series and stator voltage regulation of a wound-rotor asynchronous motor, includes a main controller. A voltage output slope control unit, a rotor resistance series time control unit, and a rotor resistance series frequency control unit are provided in the main controller. The voltage output slope control unit preset the motor starting voltage, the target stator voltage corresponding to each operation gear of the motor, and the recommended value of the voltage output slope and the calculation formula of the voltage output slope corresponding to different load ratios (i.e., the ratio of the actual load to the rated load): K = (target stator voltage - motor starting voltage) / Δt, where K represents the voltage output slope value, and Δt represents the time taken for the motor starting voltage to rise or fall to the target stator voltage. The rotor resistance series time control unit preset a delay count variable C and the delay values corresponding to the cut-off of each stage of resistance. The rotor resistance series frequency control unit preset the rotor frequency values corresponding to the cut-off of each stage of resistance. And the method includes the following steps:

[0025] S1. The main controller obtains the motor operation gear input information, the load ratio input information, and the control mode of the rotor resistance series.

[0026] S2. The voltage output slope control unit determines the corresponding target stator voltage according to the known motor operation gear, determines the recommended value of the voltage output slope corresponding to the known load ratio, and then controls the voltage output according to the calculated voltage rise / fall duration Δt of the voltage output slope calculation formula, so as to achieve stator voltage regulation and soft start of the motor;

[0027] S3. If the control mode of the rotor series resistance is set to the time control mode, as soon as the rotor series resistance time control unit knows that the motor operation gear is not the zero gear, it starts the counting of the delay count variable C, and dynamically compares the C value with the delay values corresponding to the removal of each stage of resistance preset. Once the C value is equal to the delay value corresponding to the removal of a certain stage of resistance preset, it immediately outputs the control information for removing this stage of resistance; if the control mode of the rotor series resistance is set to the frequency control mode, as soon as the rotor series resistance frequency control unit knows that the motor operation gear is not the zero gear, it starts the dynamic comparison between the rotor frequency feedback value and the rotor frequency values corresponding to the removal of each stage of resistance preset. Once the rotor frequency feedback value is equal to the rotor frequency value corresponding to the removal of a certain stage of resistance, it immediately outputs the control information for removing this stage of resistance;

[0028] Moreover, the voltage output control in step S2 and the resistance removal control in step S3 maintain a strictly synchronous relationship in timing.

[0029] In this embodiment, the motor operation gears are divided into zero gear, low gear and high gear, where: the target stator voltage corresponding to the zero gear is 0 V, the target stator voltage corresponding to the high gear is the full voltage of 380 V, and the target stator voltage corresponding to the low gear is 60% - 85% of the full voltage, which is set by the user within the range of AC 228V - AC 323V according to specific needs. In addition, as long as the motor operation gear is the zero gear, the counting of the delay count variable C is cleared; if the motor operation gear is the low gear, the maximum value of the delay values corresponding to the removal of each stage of resistance preset is set as the counting upper limit value of the delay count variable C.

[0030] In this embodiment, there is a negative correlation between the load ratio and the recommended value of the voltage output slope, that is: the larger the load ratio, the smaller the recommended value of the voltage output slope. The corresponding relationship between the load ratio and the recommended value of the voltage output slope is preferably as follows:

[0031] Load ratio 30％ 50％ 80％ 100％ Recommended value of voltage output slope 2 1 0.5 0.3

[0032] The load ratio therein refers to the percentage value of the actual load to the rated load.

[0033] As a preferred solution, the voltage output slope control unit in this embodiment divides the calculated Δt into N time segments, and calculates and controls the voltage increment or decrement required for each time segment according to the formula: (target stator voltage - motor starting voltage) / N, where N is a natural number greater than 2.

[0034] Please refer to Figure 1 as shown, the method for upgrading and transforming a traditional hoisting motor by using a method for realizing synchronous control of rotor series resistance and stator voltage regulation of a wound-rotor induction motor provided by an embodiment of the present invention is as follows:

[0035] Connect the main controller of the present invention to the master switch, the key input unit, and the resistance mode switch respectively. Collect the motor operation gear input information through the master switch, obtain the load ratio input information through the key input unit, and obtain the selection information of the rotor series resistance control mode through the resistance mode switch;

[0036] Connect the rotor frequency signal output terminal of the hoisting motor itself to the signal input terminal of the rotor frequency feedback circuit that realizes rotor frequency signal acquisition and signal processing (converting the sine wave signal into a square wave signal), and connect the signal output terminal of the rotor frequency feedback circuit to a signal input terminal of the main controller of the present invention;

[0037] Connect the signal output terminals of the rotor series resistance time control unit and the rotor series resistance frequency control unit in the main controller of the present invention to the signal input terminals of the multi-channel relay switch module that can convert the control level signals output by the corresponding control units into 220V AC signals respectively. The signal output terminal of the multi-channel relay switch module is connected to the signal input terminal of the resistor in the original hoisting motor control system;

[0038] Connect the signal output terminal of the voltage output slope control unit in the main controller of the present invention to the signal input terminal of the voltage output circuit that is used to collect the D / A signal output by the control unit and perform boosting, isolation, and output processing on the D / A signal. The signal output terminal of the voltage output circuit is connected to the signal input terminal of the thyristor phase-shifting trigger module that is used to convert the collected control voltage signal into a thyristor phase angle control signal, and connect the signal output terminal of the thyristor phase-shifting trigger module to the signal input terminal of the thyristor drive module that is used to control the forward and reverse operation of the original hoisting motor;

[0039] Since the voltage output slope control unit in the main controller according to the present invention can easily achieve precise regulation of the output voltage based on the motor operation gear, the actual load ratio, and the recommended value of the voltage output slope preset according to years of practical experience, thereby realizing the soft start function and the stator voltage regulation speed control function of the motor; at the same time, the main controller according to the present invention can, according to different control modes of the rotor series resistance selected, achieve synchronous control of the rotor series resistance as soon as the motor operation gear information is received; thus it can be seen that: since the method according to the present invention can achieve synchronous control of the rotor series resistance and the stator voltage regulation of the wound rotor asynchronous motor, and can achieve an organic combination of the rotor series resistance control mode and the stator voltage regulation control mode, so that this type of wound rotor asynchronous motor in the traditional crane system can, on the basis of having the rotor series resistance control function, also have the soft start and stator voltage regulation speed control functions at the same time. Therefore, it can achieve seamless compatibility with the existing rotor series resistance control, make the cut-off and access timing of the rotor series resistance more accurate, the control mode can be freely selected according to needs, and multi-dimensional control of this type of motor can be achieved; moreover, applying the method according to the present invention to upgrade the control mode of the traditional hoisting motor does not require replacing the original resistors and other hardware, and the required auxiliary hardware are all common modules that can be commercially purchased or integrated using existing technologies, with the advantages of low cost and easy implementation. It can upgrade the control system of the traditional hoisting motor with the least modification and the lowest cost, so as to maximize the optimization and best play of the control performance and mechanical characteristics of the traditional hoisting motor.

[0040] In summary, compared with the prior art, the present invention has significant progress and strong industrial application value.

[0041] Finally, it is necessary to point out here that: the above description is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for realizing synchronous control of rotor series resistance and stator voltage regulation of a wound-rotor asynchronous motor, characterized in that: It includes a main controller, and a voltage output slope control unit, a rotor series resistance time control unit, and a rotor series resistance frequency control unit are provided in the main controller; the voltage output slope control unit presets a motor starting voltage, target stator voltages corresponding to each motor operation gear, recommended values of voltage output slopes corresponding to different load ratios, and a calculation formula for the voltage output slope: K = (target stator voltage - motor starting voltage) / Δt, where K represents the voltage output slope value, and Δt represents the time taken for the motor starting voltage to rise or fall to the target stator voltage; the rotor series resistance time control unit presets a delay count variable C and delay values corresponding to the removal of each stage of resistance; the rotor series resistance frequency control unit presets rotor frequency values corresponding to the removal of each stage of resistance; and the method includes the following steps: S1. The main controller obtains motor operation gear input information, load ratio input information, and the control mode of the rotor series resistance. S2. The voltage output slope control unit determines the corresponding target stator voltage according to the obtained motor operation gear, determines the recommended value of the corresponding voltage output slope according to the obtained load ratio, and then controls the voltage output according to the time duration Δt of voltage rise / fall calculated by the voltage output slope calculation formula to achieve stator voltage regulation and soft start of the motor. S3. If the control mode of the rotor series resistance is set to the time control mode, once the rotor series resistance time control unit knows that the motor operation gear is not the zero gear, it starts the counting of the delay count variable C, and dynamically compares the value of C with the preset delay values corresponding to the removal of each stage of resistance. Once the value of C is equal to the preset delay value corresponding to the removal of a certain stage of resistance, it immediately outputs the control information for removing this stage of resistance. If the control mode of the rotor series resistance is set to the frequency control mode, once the rotor series resistance frequency control unit knows that the motor operation gear is not the zero gear, it starts the dynamic comparison between the rotor frequency feedback value and the preset rotor frequency values corresponding to the removal of each stage of resistance. Once the rotor frequency feedback value is equal to the rotor frequency value corresponding to the removal of a certain stage of resistance, it immediately outputs the control information for removing this stage of resistance. Moreover, the voltage output control in step S2 and the resistance removal control in step S3 maintain a strictly synchronous relationship in timing.

2. The method according to claim 1, wherein: The motor operation gears are divided into the zero gear, the low gear, and the high gear, where: the target stator voltage corresponding to the zero gear is 0 V, the target stator voltage corresponding to the high gear is the full voltage of 380 V, and the target stator voltage corresponding to the low gear is 60% - 85% of the full voltage, which is set by the user within the range of AC 228 V - AC 323 V according to specific needs.

3. The method according to claim 1, wherein: There is a negative correlation between the load ratio and the recommended value of the voltage output slope, that is: the larger the load ratio, the smaller the recommended value of the voltage output slope.

4. The method according to claim 1 or 3, characterized in that: The corresponding relationship between the load ratio and the recommended value of the voltage output slope is as follows: The load ratio herein refers to the percentage value of the actual load to the rated load.

5. The method according to claim 1, wherein: The voltage output slope control unit evenly divides the calculated Δt into N time segments, and calculates and controls the voltage increment or decrement required for each time segment according to the formula: (target stator voltage - motor starting voltage) / N, where N is a natural number greater than 2.

6. The method according to claim 1, characterized in that: As long as the motor operation gear is in the zero gear, the count of the delay count variable C is cleared.

7. The method according to claim 1, wherein: If the motor operation gear is in the low gear, the maximum value among the corresponding delay values for cutting off each level of resistance is set as the upper limit value of the count of the delay count variable C.

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