KR101852015B1 - Hybrid PI controller and inverter system having the controller - Google Patents

Abstract

The present invention relates to a hybrid proportional integral controller and an inverter system having the controller. More specifically, when the modulation ratio of an inverter is kept at a maximum and the rate of application of a converter is controlled, the hybrid proportional integral controller can prevent decrease in the efficiency of the inverter and a motor and torque ripple when driving the inverter in a low speed range by compensating the sensing error of input power and voltage drop according to load with a fine duty ratio. The hybrid proportional integral controller includes a command value calculating part; a proportional integral control part; a converter application ratio calculating part; and an adding part.

Description

[0001] Hybrid proportional integral controller and inverter system having the hybrid proportional integral controller [0002]

The present invention relates to a hybrid proportional integral controller and an inverter system having the controller, and more particularly, to a hybrid proportional integral controller and a control method thereof, And more particularly, to a hybrid proportional integral controller capable of reducing the efficiency of the inverter and the motor and improving the torque ripple when the inverter is driven in a low speed region by compensating for a drop ratio with a minute duty ratio, and an inverter system having the controller.

Inverter is a power converter that converts DC voltage to AC voltage and is used in various industries.

The factor that determines the magnitude of the output voltage of the inverter is the input DC voltage and modulation ratio.

In general, the input DC voltage of the inverter is set to be larger than the magnitude of the voltage capable of generating the rated output voltage, and the output voltage is determined by the modulation ratio.

Therefore, when the inverter modulation ratio is low, the high frequency component appears large in the output. This low modulation ratio operation causes the inverter efficiency reduction and high harmonic distortion (THD) to occur.

In recent years, there has been an increasing demand for inverter systems that are combined with various sources such as batteries for multi-functioning of inverters. For this purpose, DC / DC converters for connecting various DC voltage sources and inverters are used.

In the case of using this converter, the input DC voltage of the inverter should be set higher than the voltage capable of generating the rated output voltage from the viewpoint of the inverter output voltage dependency, and the converter should be controlled by the inverter input voltage setpoint regardless of the inverter modulation ratio , The inverter must control the modulation ratio based on this setpoint.

Such a modulation ratio control method has an advantage that the inverter has excellent dynamic characteristics. However, when a low output voltage is required, there is a disadvantage that the efficiency of the inverter is lowered due to a low output current pulse width due to a low modulation ratio.

On the other hand, the inverter of the photovoltaic power generation device is a device which does not require accelerated operation, and the elevator inverter has a predetermined operating pattern of the motor according to the operation time, and it is a system capable of predicting different modulation ratios over time.

In the case of a system in which the acceleration is not required or the modulation ratio can be predicted with a time function, in the case of a configuration in which the output voltage of the converter is fixed in a form of a variable voltage in conjunction with the modulation ratio of the inverter, It is advantageous to improve the efficiency and reduce the high frequency of the output current to improve the efficiency of the plant and to reduce EMI (Electro Magnetic Interference), thereby preventing malfunction of peripheral devices.

Fig. 1 is a diagram showing a general single-phase equivalent circuit connected to an inverter. Fig.

In Fig. 1, the low-temperature component of the equivalent circuit is ignored for convenience of analysis.

1, v _a is _a grid voltage when the inverter is a grid-connected photovoltaic inverter, and a back electromotive force when the load is an electric motor such as an elevator.

The inductor L is a damping inductor for a solar inverter and a leakage inductor for a motor.

On the other hand, in the case of a solar inverter, the inverter is driven by only a specific phase voltage in order to avoid a low modulation ratio operating range to a level at which the phase voltage fluctuation of the system is almost negligible.

Also, in the case of the inverter for driving the motor, v _a is governed by the motor speed term as shown in the following equation (1), and in the low speed region of the variable speed motor system, this voltage is small and the operation of the low modulation ratio is inevitable.

[Equation 1]

Where K _e is the counter-electromotive force constant, and? Is the output frequency.

Fig. 2 is a diagram showing a phasor diagram of the single-phase equivalent circuit of Fig. 1. Fig.

Referring to FIG. 2, in the equivalent circuit of FIG. 1, the inverter voltage for forming the current i _a is calculated by the vector sum of the voltage v _a and the inductor voltage v _L.

Here, the inductor voltage is expressed by Equation (2) below and the inverter voltage is expressed by Equation (3) below.

&Quot; (2) "

&Quot; (3) "

In addition, since the inductor voltage is relatively small compared to the voltage v _a , the output voltage (v _inv ) of the inverter is determined by the voltage v _a .

The relationship between the output voltage of the inverter and the input voltage of the inverter is expressed by Equation (4) below.

The input voltage of the inverter is also referred to as a DC link voltage, which is the voltage of the DC link connecting the converter and the inverter.

&Quot; (4) "

Where K _inv is the conversion efficiency, 0.866 for three-phase inverters, 1.0 for single-phase inverters, M is the modulation ratio, and v _dc is the DC link voltage.

From Equations (3) and (4), the correlation between the output voltage of the inverter and the DC link voltage can be expressed as Equation (5) below.

&Quot; (5) "

As can be seen from Equation (5), when the DC link voltage is large, the modulation ratio becomes low.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method of controlling an inverter, in which a modulation ratio of an inverter is maintained at a unit power factor, And to improve the torque ripple and the efficiency of the inverter and the motor when the inverter is driven in the low speed region by compensating the small proportional ratio of the inverter and the inverter.

According to an aspect of the present invention, there is provided an inverter device including a converter for converting an input voltage into a DC link voltage, which is a DC voltage, and an inverter for outputting an AC output voltage by switching the DC link voltage. A hybrid proportional-plus-integral controller for controlling a duty ratio, comprising: an instruction value calculation unit for calculating an instruction value of the DC link voltage by measuring the output voltage; A hybrid proportional integral controller for receiving a measured value of the command value and the DC link voltage to calculate an error value and outputting a proportional integral control signal from the error value and a control signal for sensing error compensation for correcting a sensing error of the input voltage; A converter ratio calculator for receiving the input voltage, the command value and the sensing error compensation control signal, and calculating a converter ratio of which the sensing error of the input voltage is compensated; And an adder for adding the converter duty ratio and the proportional integral control signal to calculate a proportional integral control converter duty ratio and controlling the switching operation of the converter at the proportional integral control converter duty ratio And provides a hybrid proportional integral controller.

In a preferred embodiment, the command value is an instruction value for maintaining the modulation ratio of the inverter at '1'.

In a preferred embodiment, the hybrid proportional plus integral control unit comprises: an error value calculator that receives an instruction value and a measurement value of the DC link voltage and calculates an error value; An integral controller for receiving the error value and calculating and outputting an integral control signal; A proportional controller connected in parallel with the integral controller, for calculating and outputting a proportional control signal in response to the error value; A proportional integral control signal output unit for adding the integral control signal and the proportional control signal to output a proportional integral control signal; And a sensing error compensation controller receiving the error value and calculating the sensing error compensation control signal.

In a preferred embodiment, the sensing error compensation control signal is calculated by adding the error values input in accordance with the passage of time and multiplying by the time constant integral gain for sensor error compensation.

In a preferred embodiment, the command value calculator includes a coordinate converter for receiving a phase voltage and a phase current of the output voltage and converting the phase voltage and the phase current into a two-phase voltage and a two-phase current on a stationary two-phase coordinate system; A voltage and current maximum value calculator for calculating and outputting the two-phase voltage and the two-phase current as a voltage maximum value and a maximum current value; And an instruction value calculator for calculating the instruction value using the voltage maximum value and the current maximum value.

According to another aspect of the present invention, there is provided an inverter device including a converter for converting an input voltage into a DC link voltage, which is a predetermined DC voltage, and an inverter for switching the DC link voltage to output an AC output voltage; And the hybrid proportional integral controller for controlling the duty ratio of the converter.

The present invention also relates to the inverter system; And a phase voltage measuring device for measuring the phase angle of the electric motor of the elevator to calculate a phase voltage of the electric motor and inputting the phase voltage as the output voltage to the command value calculation unit. More.

The present invention has the following excellent effects.

According to the hybrid proportional plus integral controller of the present invention and the inverter system having the controller, the modulation ratio of the inverter is kept at the maximum unit power factor, and when controlling the rate of the converter, the sensing error of the input power source and the voltage drop Min, it is possible to reduce the efficiency of the inverter and the motor and improve the torque ripple when the inverter is driven in the low speed region.

Figure 1 shows a general single-phase equivalent circuit connected to an inverter,
Fig. 2 is a phaser of the single-phase equivalent circuit of Fig. 1,
3 is a diagram illustrating a configuration of an inverter system having a hybrid proportional integral controller according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating a configuration of a hybrid proportional-plus-integral control unit of an inverter system according to an embodiment of the present invention;
5 is a diagram illustrating an inverter system for controlling an elevator motor including an inverter system according to an embodiment of the present invention.

Although the terms used in the present invention have been selected as general terms that are widely used at present, there are some terms selected arbitrarily by the applicant in a specific case. In this case, the meaning described or used in the detailed description part of the invention The meaning must be grasped.

Hereinafter, the technical structure of the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings.

However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like reference numerals designate like elements throughout the specification.

3, an inverter system 1000 according to an embodiment of the present invention includes an inverter device 10 that converts a DC input power source and connects the system to the system 20, And a hybrid proportional integral controller (100) for controlling the hybrid proportional integral controller.

In addition, the inverter device 10 can supply power to various loads other than the system 20, and can supply power to, for example, an elevator electric motor.

5 shows an inverter system 2000 for controlling an elevator motor for supplying power to an elevator motor. The inverter system 2000 for controlling an elevator motor includes an inverter system 1000 of the present invention, And a phase voltage measuring device 2100 for measuring the voltage and providing it to the inverter system 1000.

The phase voltage measurement device 2100 is a device that calculates frequency (?) From a rotor phase angle (?) Of an electric motor and calculates a phase voltage (v _abc ) from a frequency.

Also, in the inverter system 1000, only the hybrid proportional plus integral controller 100 may be separately provided.

That is, the present invention can be applied to an inverter system 1000 having the hybrid proportional integral controller 100, the hybrid proportional integral controller 100 or an inverter motor control inverter 1000 having the inverter system 1000 and the phase voltage measurement device 2100 System 2000. In this embodiment,

Hereinafter, the configuration of the inverter system 1000 of the present invention will be described in detail with reference to FIG.

The inverter system 1000 includes an inverter device 10 and a hybrid proportional integral controller 100.

The inverter device 10 converts an input power source v _in , which is a direct current, into an alternating current output power source v _abc .

The inverter apparatus 10 further includes a converter 11 for converting an input voltage v _in to a DC voltage of a predetermined magnitude and outputting the DC voltage, And an inverter 12 for outputting an output power v _abc .

The converter 11 is a female-type converter, and is a DC / DC converter capable of adjusting the magnitude of the DC link voltage by switching.

The hybrid proportional plus integral controller 100 is a controller for controlling a duty ratio of the converter 11 to output a desired command value from the inverter 12. [

The hybrid proportional plus integral controller 100 controls the inverter 11 so that the modulation ratio of the inverter is fixed at a maximum, that is, 1 (unit power factor) .

That is, the hybrid proportional plus integral controller 100 of the present invention is a controller that can improve the efficiency reduction and torque ripple of the inverter device 20 by maximizing the modulation ratio of the inverter 12.

In addition, the hybrid proportional plus integral controller 100 according to an exemplary embodiment of the present invention compensates for the sensing error of the input power source and the voltage drop caused by the load by using a minute ratio, thereby reducing efficiency and torque ripple Can be improved very effectively.

Meanwhile, when the modulation ratio of the inverter 12 is fixed to 1, the DC link voltage can be converted from Equation (5) as shown in Equation (6) below.

&Quot; (6) "

Also, as can be seen from Equation (6), when the inverter modulation ratio is kept at 1, the DC link voltage (v _dc ) is determined by v _a and i _a , and when the output voltage is three phases, , And then calculating the maximum value as shown in equation (8).

&Quot; (7) "

Here, v _abc denotes a three-phase voltage as an output voltage of the inverter 21, and v _? And v _{? Are} voltages on stationary two-phase coordinates.

Also, the two-phase voltage of Equation (7) can be calculated as a maximum voltage value by calculating the maximum value as shown in Equation (8) below.

&Quot; (8) "

Also, in the case of the two-phase current, the current maximum value can be calculated in the same manner as in Equations (7) and (8).

In order to fix the modulation ratio of the inverter 12 to '1', a function of the voltage and current of the DC link may be set to Equation (6), where v _dc is the set value of the DC link voltage (v _{dc_ref} ) .

The duty ratio of the converter 11 for the command value control of the DC link voltage is expressed by Equation (9) below.

&Quot; (9) "

Here, d _b is the converter ratio, v _{dc_ref} is the set value of the DC link voltage, v _in is the input voltage of the converter, and d _step is the _{microcomputing} rate for compensating the sensing error.

9, the hybrid proportional plus integral controller 100 adds a proportional integral control signal for compensating a voltage drop due to a load to the converter duty ratio at which the sensing error is compensated to calculate a proportional integral control converter duty ratio And finally controls the duty ratio of the converter 11 using the proportional integral control converter duty ratio.

The hybrid proportional plus integral controller 100 includes a command value calculation unit 110, a hybrid proportional integral control unit 120, and a converter ratio calculation unit 130.

The command value calculation unit 110 receives the output voltage v _abc and the output current i _abc of the inverter 12 and calculates the two-phase voltage v? _Beta and the two-phase current i _αβ) the calculated coordinate converter 111, the two-phase voltages (v _αβ) and 2-phase currents (i _αβ) the current maximum value with the use of the equation 8 (i _p) and the voltage maximum value (v _p) (V _a ) and the output current (i _a ) of Equation (6) by using the voltage and current maximum value calculator 112, the maximum current value i _p and the maximum voltage value v _p , And a command value calculator 113 for calculating the DC link voltage v _dc and outputting the calculated DC link voltage to the voltage command value v _{dc_ref} of the DC link.

The hybrid proportional plus integral control unit 120 outputs a proportional integral control signal PI _out for proportional integral control and a control signal for sensing error compensation which is a small error rate d _step for compensating the sensing error.

3, the hybrid proportional _plus integral control unit 120 receives the command value v _{dc_ref} and the measured value v _dc of the DC link calculated by the command value calculation unit 110, An error value calculator 121 for calculating an error value e _k which is a difference between the measured values, an integrating controller 130 for integrating the error value inputted in accordance with the passage of time and multiplying the error value K _i by an integral gain K _i , (122), a proportional controller (123) for multiplying the error value by a proportional gain (K _d ) to output a proportional control signal, and a proportional integral control signal PI _out outputting a sum of the integral control signal and the proportional control signal And a proportional integral control signal output unit 124. [

Further, a limiter 125 for limiting the value of the integral control signal may further be provided at the rear end of the integral controller 122. [

In addition, the hybrid proportional plus integral control unit 120 sums the error values inputted in accordance with the passage of time and multiplies the error value by a time constant integral gain K _d for sensing error compensation to obtain the sensing error compensation control signal d _step , .

That is, the hybrid proportional-plus-integral control unit 120 outputs a control signal (d _step ) for sensing error compensation in addition to the proportional integral control signal PI _{out in} comparison with a general proportional-integral controller.

The converter ratio calculation unit 130 inputs the input voltage v _in , the command value v _{dc_ref} and the control signal d _step for sensing error compensation, And calculates the rate (d _b ).

The adder 140 receives the converter duty ratio d _b and the proportional integral control command PI _out and adds the converter duty ratio and the proportional integral control signal to calculate a final proportional integral control Calculates the converter duty ratio d, and controls the switching operation of the converter 11 with the proportional integral control converter duty ratio d.

Therefore, according to the hybrid proportional plus integral controller 100 according to the embodiment of the present invention, when the modulation ratio of the inverter 12 is maintained at a unit power factor (maximum modulation ratio) and the rate of application of the converter 11 is controlled, The efficiency of inverter and motor can be reduced and the torque ripple can be improved when the inverter is driven in the low speed range by compensating the sensing error of the input power source and the voltage drop due to the load with the minute ratio.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, Various changes and modifications will be possible.

1000: Inverter system
2000: Inverter system for elevator motor control
100: Hybrid proportional integral controller 110: Setpoint calculation unit
120: Hybrid proportional-integral control unit 121: Error value calculator
122: Integral controller 123: Proportional controller
124: proportional integral control signal thruster 125: limiter
126: sensing error compensation controller 130: converter ratio calculation section
140:

Claims (7)

A hybrid proportional integral controller for controlling an application rate of the converter in an inverter device including a converter for converting an input voltage into a DC link voltage of a predetermined DC voltage and an inverter for switching the DC link voltage to output an AC output voltage ,
An instruction value calculation unit for calculating an instruction value of the DC link voltage by measuring the output voltage;
A hybrid proportional integral controller for receiving a measured value of the command value and the DC link voltage to calculate an error value and outputting a proportional integral control signal from the error value and a control signal for sensing error compensation for correcting a sensing error of the input voltage;
A converter ratio calculator for receiving the input voltage, the command value and the sensing error compensation control signal, and calculating a converter ratio of which the sensing error of the input voltage is compensated; And
And an adder for adding the converter duty ratio and the proportional integral control signal to calculate a proportional integral control converter duty ratio and to control the switching operation of the converter with the proportional integral control converter duty ratio. Proportional Integral Controller.
The method according to claim 1,
Wherein the command value is an instruction value for maintaining the modulation ratio of the inverter at " 1 ".
The method according to claim 1,
The hybrid proportional plus integral control unit includes:
An error value calculator for receiving an instruction value and a measurement value of the DC link voltage and calculating an error value;
An integral controller for receiving the error value and calculating and outputting an integral control signal;
A proportional controller connected in parallel with the integral controller, for calculating and outputting a proportional control signal in response to the error value;
A proportional integral control signal output unit for adding the integral control signal and the proportional control signal to output a proportional integral control signal; And
And a sensing error compensation controller receiving the error value and calculating a control signal for compensating the sensing error.
The method of claim 3,
Wherein the sensing error compensating control signal is calculated by adding error values inputted in accordance with the passage of time and multiplying the error value by a time constant integral gain for sensor error compensation.
The method of claim 3,
Wherein the command value calculation unit receives a phase voltage and a phase current of the output voltage and converts the phase voltage and the phase current of the output voltage into a two-phase voltage and a two-phase current on the stopping two-phase coordinate system;
A voltage and current maximum value calculator for calculating and outputting the two-phase voltage and the two-phase current as a voltage maximum value and a maximum current value; And
And a command value calculator for calculating the command value using the voltage maximum value and the current maximum value.
A converter for converting an input voltage into a DC link voltage which is a predetermined DC voltage; and an inverter for switching the DC link voltage to output an AC output voltage; And
And a hybrid proportional integral controller according to any one of claims 1 to 5 for controlling the duty ratio of the converter.
An inverter system according to claim 6; And
And a phase voltage measuring device for measuring the phase angle of the electric motor of the elevator to calculate a phase voltage of the electric motor and inputting the phase voltage as the output voltage to the command value calculation unit.

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