KR102546709B1 - Voltage compensation method for motor control inverter - Google Patents

Abstract

The present invention is a motor that improves the starting characteristics by adding a compensation voltage so that the motor can be started even when the motor cannot be started by adjusting the output voltage command by receiving feedback of the torque component variable during low-speed overload start-up in the V/F constant control of a general motor. It is about the voltage compensation method of the control inverter. In the present invention, when generating the compensation voltage, different compensation voltages are generated according to the type of the motor using the resistance component of the motor, which is a relatively accurate parameter. Accordingly, the present invention can increase the reliability of driving the motor by performing starting control using the resistance component of the motor, which is a relatively accurate parameter. According to the present invention, the capacity and rated current are different for each motor, so that the difficulty of selecting the motor voltage gain for each system to which the motor is applied can be easily solved, thereby improving start-up control performance in the field of an overload system. In addition, the present invention does not experimentally obtain a voltage gain value for each capacity of the motor and stores it in a memory as a separate parameter, but obtains different resistance components according to the capacity of the motor in real time and compensates for the voltage gain value, thereby reducing the memory load. can reduce

Description

Voltage compensation method of inverter for motor control {VOLTAGE COMPENSATION METHOD FOR MOTOR CONTROL INVERTER}

The present invention relates to a method for compensating voltage of an inverter for motor control, and more particularly, to a method for compensating voltage for an inverter for motor control in which a compensation voltage is generated by determining the capacity of a motor with a resistance component among motor parameters.

In general, a device that performs DC/AC conversion is defined as an inverter, and a device that performs AC/DC conversion is defined as a converter. Here, in the case of a constant V/F control method among motor control inverters, an output voltage command value is obtained at a set operating command frequency, and the motor is controlled by converting it into a voltage suitable for the motor. Here, all motors generally have different capacities, and accordingly, voltage gains are also different. Therefore, in the related art, the output voltage command value is compensated according to a different voltage gain for each motor.

1 is a block diagram of an inverter for motor control according to the prior art.

As shown in FIG. 1, a motor control inverter according to the prior art includes a voltage command generator 10 that obtains an output voltage command value from a set operating command frequency and coordinate conversion from positional information output from the output voltage command value. The first coordinate conversion unit 20 that indicates the 3-phase output voltage command value on the stationary coordinate system, the automatic voltage regulator 30 that outputs the voltage according to the motor rating even if the DC link voltage of the 3-phase output voltage command value fluctuates, and the 3-phase The actual output current between the PWM input voltage command unit 40 and the PWM generator 50 to which the switching technique for applying the pulse width modulation control signal is applied to apply the voltage, and the load motor and the inverter is measured on the magnetic flux side on the synchronous coordinate system. A second coordinate conversion unit 60 that converts the current component (id) and the torque shaft current component (Iq), a filter 70 that removes harmonics based on the torque current component, the motor capacity and and a compensation voltage generator 80 generating a compensation voltage with a voltage gain. Since the initial overcurrent flows greatly when the slip increases in the induction motor, the compensating voltage generating unit 80 goes through the appropriate slip compensation process and the compensating voltage generating unit that puts the boost voltage gain to compensate the voltage for the existing V/F constant control It is used when a large starting torque is required or when an automatic adjustment function is used. Here, the inverter for motor control according to the prior art shown in FIG. 1 is a case in which there is no rotor position sensor in an open loop type V/F constant control method. Of course, a rotor position sensor may be used as needed.

In the conventional motor control inverter having such a structure, when the V/F constant control is performed due to the voltage drop due to the stator resistance at low speed, the air gap magnetic flux decreases and the output torque decreases. Increasing the voltage at low speed to compensate for this is called starting control or torque boost.

The motor control inverter according to the prior art is a torque boost form in general inverter V/F operation. The start control method is independent of the values of the stator resistance (Rs, resistance component), leakage inductance (Ls), and no-load current obtained by auto-tuning. Compensation voltage is generated from current, slip, and motor capacity, and it is a technology required in industrial sites with relatively large loads by relatively simply adding the starting voltage to the output voltage command. Although the q-axis current, which is the torque current, receives feedback, it has a strong advantage against startup failure due to parameter errors because it does not use parameter information about the motor. However, the voltage gain (%) is different for each system because the information on the system to which the motor is applied is uncertain.

In this case, as a solution, at least the basic voltage gain should be experimentally selected for each capacitance and made into a table, and the difference in the experimentally selected range of gain should be considered for each system. Experimentally, a method of storing the basic gain value for each capacity by making a table of the default voltage gain for each capacity for use of a general-purpose inverter can be considered, but this can be seen as a limitation in an economical general-purpose inverter that requires additional use of memory space.

In the end, it reduces the memory burden on economical inverters, and because of parameter errors caused by auto-tuning, the start-up control method that uses torque current, which is the measured value, without using parameters due to parameter errors due to inaccurate voltage gains that vary from system to system causes difficulties in tuning and errors in voltage compensation values. If it becomes large, operation may fail at a large starting torque.

An object of the present invention is to control the voltage of a motor control inverter that operates stably without causing motor failure in the field where a large starting torque is required from the torque component current of the output current or a large load change is applied when controlling the starting torque of a general-purpose inverter. to provide a way to compensate.

The object of the present invention is not limited to the above-mentioned object, and other objects and advantages of the present invention not mentioned above can be understood by the following description and will be more clearly understood by the examples of the present invention. It will also be readily apparent that the objects and advantages of the present invention may be realized by means of the instrumentalities and combinations indicated in the claims.

In order to achieve the above object, the present invention generates different compensation voltages according to the type of motor by using a resistance component of the motor, which is a relatively accurate parameter, when generating the compensation voltage. Specifically, this step involves rectifying AC power to DC power for driving the motor, generating a compensation voltage with the torque shaft current value of the motor, a resistance component among parameters of the motor, and a basic voltage gain value of the motor; and compensating an output voltage command value for controlling the DC power source according to the compensation voltage to drive the motor.

Here, the step of generating the compensation voltage with the torque shaft current value of the motor, the resistance component among the parameters of the motor, and the basic voltage gain value of the motor includes the output current between the motor and a motor control inverter that controls the motor. Converting to a torque shaft current value on the synchronous coordinate system, generating a boost variable by a boost variable generator by multiplying the basic voltage gain value and the resistance component, and multiplying the torque shaft current value by the boost variable to compensate for a voltage. It includes the step of generating.

The step of compensating the output voltage command value for controlling the DC power source according to the compensation voltage to drive the motor comprises: compensating the output voltage command value according to the compensation voltage; Generating a voltage command value, and converting the three-phase output voltage command value into a pulse width modulation method to generate a control signal for controlling the DC power supply.

According to the present invention, reliability of motor driving can be increased by performing start-up control using a resistance component of a motor, which is a relatively accurate parameter.

According to the present invention, the capacity and rated current are different for each motor, so that the difficulty of selecting the motor voltage gain for each system to which the motor is applied can be easily solved, thereby improving start-up control performance in the field of an overload system.

In addition, the present invention does not experimentally obtain a voltage gain value for each capacity of the motor and stores it in a memory as a separate parameter, but obtains different resistance components according to the capacity of the motor in real time and compensates for the voltage gain value, thereby reducing the memory load. can reduce

1 is a block diagram of an inverter for motor control according to the prior art;
2 is a block diagram of an inverter for controlling a motor according to the present invention.
3 is a block diagram of a compensating voltage generator according to the present invention.
4 is a flowchart of a voltage compensation method of an inverter for motor control according to the present invention.

The above objects, features and advantages will be described later in detail with reference to the accompanying drawings, and accordingly, those skilled in the art to which the present invention belongs will be able to easily implement the technical spirit of the present invention. In describing the present invention, if it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

2 is a block diagram of an inverter for motor control according to the present invention.

As shown in FIG. 2, the inverter 100 for motor control according to the present invention includes a rectifying unit 110 for rectifying AC power, and a driver 120 for controlling a motor with the rectified power rectified in the rectifying unit 110, The control unit 1000 controls the driving unit 120 by applying the compensation voltage generated by the resistance component parameter of the motor and the basic gain value to the output voltage generated from the driving command frequency.

The rectifier 110 includes an AC/DC rectifier that converts AC power supplied from the outside into DC. Here, the present embodiment illustrates a three-phase AC power source as an AC power source and an induction motor as a motor. In addition, the rectifying unit 110 applies DC power converted from three-phase AC power applied from the outside to the driving unit 120 to be described later.

The driving unit 120 converts DC power applied from the rectifying unit 110 into induction motor control power according to a control signal applied from a control unit to be described later, and outputs the converted power to the induction motor. Here, the induction motor control power converted by the driving unit 120 is preferably a pulse wave converted by a pulse width modulation (PWM; hereinafter referred to as PWM) method.

The control unit 1000 generates an output voltage from the driving command frequency and outputs a control signal obtained by converting the output voltage into a PWM method to the driving unit 120 . Here, the present invention generates a compensation voltage for compensating the output voltage when generating the output voltage, and accordingly, the controller 1000 includes a voltage command generator 130, a first coordinate conversion unit 140, and an automatic voltage regulator ( 150), a control signal generator 160, a second coordinate conversion unit 170, and a compensation voltage generator 180.

The voltage command generator 130 generates an output voltage command value from the set operating command frequency. Here, the present invention is controlled by the V/F method, and accordingly, the output voltage command value generated by the voltage command generation unit 130 is proportional to the set operating command frequency.

The first coordinate conversion unit 140 generates a three-phase output voltage command value on a stationary coordinate system through coordinate conversion from positional information of the output voltage command value generated by the voltage command generation unit 130 .

The automatic voltage adjusting unit 150 outputs a three-phase output voltage according to the rating of the induction motor by automatic voltage regulation even if the DC link voltage of the three-phase output voltage command value generated by the first coordinate conversion unit 140 fluctuates.

The control signal generator 160 generates a control signal by converting the three-phase output voltage adjusted by the automatic voltage regulator 150 into a pulse width modulation method. Here, the control signal generator 160 goes through a switching technique process for applying a PWM control signal to an insulated gate bipolar mode transistor (IGBT) in order to apply a three-phase output voltage.

The second coordinate conversion unit 170 converts an actual output current between an induction motor that is a load and an inverter. Here, the converted output current is the magnetic flux axis and torque axis current components on the synchronous coordinate system, and the magnetic flux axis is converted into Id and the torque axis current component is converted into Iq.

3 is a block diagram of the compensation voltage generator 180 according to the present invention.

The compensation voltage generation unit 180 generates different compensation voltages according to the type of induction motor by using a resistance component, that is, a stator resistance (Rs) component among the parameter information of the induction motor obtained through auto-tuning. The output voltage command value generated by the voltage command generator 130 is compensated. To this end, the compensation voltage generator 180 includes a filter 181, an amplifier 182, and a boost variable generator 183.

The filter 181 removes harmonics of the torque current component. To this end, the filter 181 may include a low pass filter (LPF) that removes harmonics by passing low frequencies of the torque current component. Here, the filter 181 is input with Iq, which is a torque axis current component converted by the second coordinate conversion unit 170, and a filter gain.

The amplification unit 182 compares the torque-shaft current component from which the harmonics have been filtered out by the filter 181 with the current compensation reference value, and when the filtered torque-shaft current component is greater than or equal to the current compensation reference value, compensates by a value exceeding the current compensation reference value. Of course, when the filtered torque shaft current component is less than or equal to the current compensation reference value, the filtered torque shaft current component is used as it is without compensation.

The boost variable generation unit 183 generates a boost variable by multiplying the basic voltage gain and the stator resistance component, which is a resistance component obtained through the aforementioned auto-tuning. The slip is different for each induction motor, and the larger the slip, the larger the initial starting current of the induction motor to reduce the slip. At this time, in order to protect the induction motor from a sudden increase in the initial starting current of the induction motor, when an initial slip occurs, a compensation voltage is added to control the starting of the induction motor. In addition, the voltage is compensated by multiplying only the resistance component, which is relatively more accurate parameter information than other induction motor parameters, such as internal inductance of the induction motor, by the voltage gain. Accordingly, since the present invention obtains information of the induction motor through the resistance component and corrects the basic voltage gain value accordingly, it is not necessary to modify the basic voltage gain value for each capacity of the induction motor. In addition, since a voltage gain value can be found relatively easily with a resistance component, it is possible to easily select a different voltage gain value for each induction motor.

In addition, the present invention generates the compensation voltage Vcomp by multiplying the boost variable generated by the boost variable generator 183 and the torque shaft current component that has passed through the amplification unit 182 . In addition, the generated compensation voltage is input to the voltage command generator 130 and compensates for the output voltage command value generated by the voltage command generator 130 in accordance with the induction motor.

Meanwhile, the present invention may further include a compensating voltage limiting unit 184 that restricts an excessively large compensating voltage from being input to the voltage command generating unit 130 .

As described above, according to the present invention, when the slip increases in the induction motor, the initial overcurrent flows in the induction motor to reduce the slip, so appropriate slip compensation is provided. In addition, in the case of a general-purpose inverter, in order to solve the memory burden by adding a different basic gain to the memory due to different basic gains for each capacity, the present invention uses resistance information, which is relatively accurate parameter information. Accordingly, even if the basic gain is constant, the compensation voltage generator 180 adds a boost voltage gain to compensate the voltage for the existing V/F constant control, and when a large starting torque is required or an automatic adjustment function is used, the induction motor start-up failure can be prevented.

Next, a voltage compensation method of an inverter for motor control according to the present invention will be described with reference to the drawings. Among the contents to be described later, contents overlapping with the description of the motor control inverter according to the present invention described above will be omitted or briefly described.

4 is a flow chart of a voltage compensation method of an inverter for motor control according to the present invention.

As shown in FIG. 4, a method for compensating voltage of an inverter for controlling a motor according to the present invention includes steps of rectifying AC power (S1), generating a compensation voltage (S2), and controlling a motor according to the compensation voltage. (S3) is included.

In step S1 of rectifying the AC power, the rectifier converts the externally applied AC power into DC power. This embodiment exemplifies a three-phase AC power source as an AC power source, and an induction motor is exemplified as a motor operated by the three-phase AC power source.

The step of generating a compensation voltage (S2) generates a compensation voltage to compensate for the DC power rectified in the step (S1) of rectifying the three-phase AC power. In this way, in order to generate the compensation voltage, the step of generating the compensation voltage (S2) is the step of converting the torque axis current value (S2-1), the step of generating a boost variable (S2-2), and the torque axis and generating a compensation voltage with the current value and the boost variable (S2-3).

In the step of converting the torque shaft current value (S2-1), the second coordinate conversion unit converts the actual output current between the induction motor and the inverter as a load. Accordingly, the torque shaft current value on the synchronous coordinate system is converted.

In the step of generating the boost variable (S2-2), the boost variable generator multiplies the basic voltage gain and the resistance component to generate the boost variable. Here, the basic voltage gain is a voltage gain that is basically set, and the resistance component is one of the components included in the parameter information of the motor. That is, the basic voltage gain is information stored in the memory, and the resistance component is information acquired from the motor in real time. Of course, resistance components can also be stored in a table according to the type of motor, but the present invention exemplifies obtaining from a motor in real time in order not to additionally use memory.

The step of generating the compensation voltage with the torque shaft current value and the boost variable (S2-3) is the step of generating the torque shaft current value and the boost variable converted in the step of converting the torque shaft current value (S2-1) (S2-3). The compensation voltage is generated by multiplying the boost variable generated in 2).

The step of controlling the induction motor according to the compensation voltage (S3) generates a motor control signal according to the compensation voltage generated in the step of generating the compensation voltage (S2). The step of controlling the induction motor according to the compensation voltage (S3) includes compensating the output voltage command value according to the compensation voltage (S3-1), generating a three-phase output voltage command (S3-2), and automatically A voltage adjustment step (S3-3) and a control signal generating step (S3-4) are included.

Compensating the output voltage command value according to the compensating voltage (S3-1) is as much as the compensating voltage generated in the step (S2) of generating the compensating voltage when the voltage command generator generates the output voltage command value from the set operating command frequency. Compensate the output voltage command value.

The step of generating the 3-phase output voltage command (S3-2) is the output voltage command value compensated by the compensated voltage in the step of compensating the output voltage command value according to the compensation voltage (S3-1), and the voltage command generation unit outputs the 3-phase output voltage. Generates a voltage reference. Here, the voltage command generating unit may generate a three-phase output voltage command value on a stationary coordinate system through coordinate conversion from positional information of an output voltage command value compensated by the compensation voltage.

In the automatic voltage regulating step (S3-3), the automatic voltage regulating unit automatically adjusts the voltage of the 3-phase output voltage command value generated in the step of generating the 3-phase output voltage command (S3-2). Accordingly, the voltage of the three-phase output voltage command value is automatically adjusted according to the rating of the motor without shaking.

In the step of generating the control signal (S3-4), the control signal generating unit converts the 3-phase output voltage command value whose voltage is automatically adjusted in the automatic voltage adjustment step (S3-3) into a pulse width modulation method to generate a control signal. do. In addition, in step S1 of rectifying the AC power according to the generated control signal, the rectified DC power is controlled and applied to the motor.

The above-described present invention, since various substitutions, modifications, and changes are possible to those skilled in the art without departing from the technical spirit of the present invention, the above-described embodiments and accompanying drawings is not limited by

Claims (3)

Rectifying AC power to DC power for driving the motor;
Generating a compensation voltage using a torque shaft current value of the motor, a stator resistance component among parameters of the motor, and a basic voltage gain value of the motor; and
Compensating an output voltage command value for controlling the DC power supply according to the compensation voltage to drive the motor;
The step of generating the compensation voltage,
Converting an output current between the motor and a motor control inverter that controls the motor into a torque shaft current value on a synchronous coordinate system;
filtering high frequencies from the torque shaft current value through a low pass filter receiving the torque shaft current value and a filter gain;
Comparing the torque shaft current component from which the high frequency is filtered with a current compensation reference value and outputting a signal for determining whether to compensate according to the comparison result;
generating a boost variable by a boost variable generator by multiplying the basic voltage gain value by the stator resistance component; and
Generating a compensation voltage by multiplying the torque shaft current value and the boost variable according to the signal for determining whether to compensate or using the torque shaft current component for driving the motor without generating the compensation voltage,
Voltage compensation method of inverter for motor control.
delete According to claim 1,
The step of driving the motor by compensating the output voltage command value for controlling the DC power supply according to the compensation voltage,
compensating an output voltage command value according to the compensation voltage;
Generating a three-phase output voltage command value with the output voltage command value, and
and generating a control signal for controlling the DC power supply by converting the three-phase output voltage command value into a pulse width modulation method.

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