KR20100033862A

KR20100033862A - Current measurement of inverter using shunt resistor

Info

Publication number: KR20100033862A
Application number: KR1020080092927A
Authority: KR
Inventors: 김승환; 정세종
Original assignee: 현대중공업 주식회사
Priority date: 2008-09-22
Filing date: 2008-09-22
Publication date: 2010-03-31

Abstract

PURPOSE: A current measurement of an inverter using a shunt resistor is provided to increase a control performance by calculating a current on a phase where a sensing current is not flowed without filtering. CONSTITUTION: A phase current, outputting a middle size of a phase voltage as a first current, is measured. A phase current, outputting a minimum size of the phase voltage, is measured as a second current. A phase current, outputting the maximum size of the phase voltage, is calculated from a first and a second current.

Description

Current measurement method of inverter using shunt resistor {Current measurement of inverter using shunt resistor}

The present invention relates to a current measuring method of an inverter using a shunt resistor, and more particularly, to determine the magnitude of a phase voltage reference value output from a controller and output a reference value of a phase current and a minimum size to output a reference value of a medium size. The first and second currents are measured by changing the current measurement order in the order of the phases of the phases, and a shunt resistor is used to calculate the phase current outputting the maximum reference value from the measured first and second currents. It relates to a current measuring method of the inverter.

Generally, as shown in FIG. 1, a plurality of IGBTs Q1 to Q6, which are power switching elements, drive the motor 3 while the on / off switching operation is performed by a PWM control signal output from the controller 1. It is configured to supply a three-phase voltage (U, V, W) for the purpose, in this general motor drive device CT (2) (Current Transfomer) at the output terminal of the inverter to detect the output current supplied to the motor (3) Is installing.

That is, the controller 1 generates and outputs a PWM control signal for switching control of the IGBTs Q1 to Q6 according to the output current detected by the CT 2 so that the inverter outputs the optimum drive voltage to the motor 3. Will be supplied.

However, in low-cost, small inverters, the shunt resistor is used to measure the output current of the inverter.

Figure 2 shows a low-cost inverter drive device using a shunt resistor,

In low-cost inverter driver, N-side power supply of DC terminal and control power supply ground of controller 10 are commonly used to construct products at low cost, and Emitter terminal and DC terminal of N-side IGBT (Q4 ~ Q6) A shunt resistor (Rshunt) is disposed between the N-side power supplies to apply the current measurement signal used for control only by scaling in the controller 10 without any isolation.

However, in a low-cost inverter drive device using a conventional shunt resistor, when the output phase voltage reference value becomes large and the turn-on width of the IGBTs (Q1 to Q3) of the DC voltage P stage becomes larger, the DC voltage N-side IGBTs (Q4 to Q6) Since the turn-on time is short, the conduction time of the current flowing through the shunt resistor is shortened, which makes it difficult to accurately measure phase current.

That is, the turn-on time of the N-side IGBTs (Q4 to Q6) is shortened according to the output phase voltage reference value, so that the time for which current flows through the shunt resistor (Rshunt) of the IGBTs (Q4 to Q6) of the N side is required for signal sampling. It becomes shorter and causes a problem in measuring the output current.

Accordingly, an object of the present invention is to solve the problem that occurs in the actual circuit configuration by reconfiguring and calculating the phase current to be measured as a current flowing through the shunt resistor of another phase.

Current measuring method of the present invention for achieving the above object

In the current measurement method of an inverter using a shunt resistor, a first current measuring a phase current outputting a medium size phase voltage as a first current, and a current measuring a phase current outputting a phase voltage of a minimum magnitude as a second current. Steps; A second step of calculating a phase current outputting the largest phase voltage from the first current and the second current obtained in the first step; Characterized in that configured.

In addition, when the PWM output is generated by the phase voltage reference value calculated by the controller, the magnitude of the phase voltage reference value among the three phases is determined, and the measurement target of the first current and the second current measured in the first step according to the determination result. It is characterized by being variable.

According to the present invention, the current value for the phase outputting the reference voltage of the medium size and the minimum size can be measured sequentially, and the current of the phase outputting the reference value of the maximum magnitude can be calculated based on the measured current value. The current detection operation can be calculated online, and the inverter output current can be known regardless of the output PWM voltage. No additional circuit is required, and the current value for the phase without current sensing signal is calculated without filtering. Therefore, the effect of providing a current measuring method of an inverter using a shunt resistor to improve control performance can be expected.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In describing the present invention, the defined terms are defined in consideration of the function of the present invention, and should not be understood in a limiting sense of the technical elements of the present invention.

2 is a power unit structure of a voltage inverter for current measurement using a shunt resistor, FIG. 3 is a flow chart of a current measurement using a shunt resistor, and FIG. 4 is measured according to an output phase voltage reference value. The order of the current is shown.

According to the drawings, according to the present invention, in the current measurement method of an inverter using a shunt resistor (Rshunt), the phase current outputting the medium size phase voltage is measured as the first current, and outputs the phase voltage of the minimum magnitude. A first step of measuring the current in the phase as a second current; A second step of calculating a phase current outputting the largest phase voltage from the first current and the second current obtained in the second step; Characterized in that configured.

In addition, when the PWM output is generated by the phase voltage reference value calculated by the controller 10, the magnitude of the phase voltage reference value among the three phases is determined, and the first and second currents measured in the first step according to the determination result. Characterized in that the measurement target of the variable.

Referring to the operation of the present invention configured as described above is as follows.

The operation of the present invention will be described with reference to the waveform diagram of FIG.

First, when the PWM output is generated by the phase voltage reference values Va_ref, Vb_ref, and Vc_ref calculated by the controller 10, the magnitude of the three-phase (Va, Vb, Vc) phase voltage reference values is determined, and the determination result is determined. Accordingly, the first and second measurement targets Ia, Ib, and Ic to be measured are selected.

Taking the T1 section of FIG. 4 as an example, since the phase voltage reference values Va_ref, Vb_ref, and Vc_ref are Vc_ref> Va_ref> Vb_ref, the phase current Ia of the phase Va outputting the medium size phase voltage reference value Va_ref is determined as the first. The phase current Ib of the phase Vb outputting the minimum magnitude phase voltage reference value Vb_ref is measured as the second current, measured as a current, and the combined first reconstruction of the measured first current and the second current is performed to determine the maximum phase voltage. The phase current Ic of the phase Vc outputting the reference value Vc_ref is calculated.

On the other hand, in the section T2 of FIG. 4, Ic and Ib are measured as the first current and the second current, and the phase outputting the maximum phase voltage reference value Va_ref based on the first current Ic and the second current Ib. The current Ia for Va is obtained.

As described above, when the PWM output is generated by the phase voltage reference values Va_ref, Vb_ref, and Vc_ref calculated by the controller 10, the magnitudes of the three-phase (Va, Vb, Vc) phase voltage reference values are determined, and the determination thereof. According to the result, the phase current of the phase outputting the medium size phase voltage reference value is measured as the first current, the phase current of the phase outputting the minimum size phase voltage reference value is measured as the second current, and the measured first and second currents are measured. Based on this, the phase current for the phase outputting the maximum magnitude phase voltage reference value is calculated.

As shown in FIG. 4, the first and second currents are varied for each of the sections T1 to T7. The reason for this is that the PWM output is determined by the phase voltage reference value calculated by the controller 10 as described above. This is because the magnitude of the phase voltage reference value among the three phases is changed by section when it is made.

In current measurement of a low-cost motor drive device using a conventional shunt resistor, when the IGBT (Q1 to Q3) turn-on time of the P side is increased by the output phase voltage reference value, the NGB IQT (Q4 to Q6) turns short the turn-on time. This impossible area will occur.

However, if the present invention is applied, the current measurement method using the shunt resistor of the present invention determines the magnitude of the output voltage from the three-phase output voltage reference value of the controller in order to eliminate the area that cannot be measured, so that a phase current that cannot be measured is not generated. Change the current measurement order of the AD converter so that the phase current, the phase voltage reference value of the medium size, of the three-phase output voltage is measured first, and then the phase current, the phase voltage reference value of the smallest magnitude, is measured. By reconstructing the phase current, the voltage reference, all output currents of the inverter can be measured accurately.

1 is a view showing a conventional inverter drive device.

2 is a view showing an inverter driving device using a shunt resistor.

3 is a flowchart showing a current measuring method of an inverter using the shunt resistor of the present invention.

Figure 4 is a waveform diagram showing the order of the measurement current according to the magnitude of the output phase voltage reference value implemented by the present invention.

* Description of the symbols for the main parts of the drawings *

10: controller, Rshunt: shunt resistor,

3: electric motor, Q1 ~ Q6: IGBT

Claims

In the current measurement method of the inverter using a shunt resistor,

A first step of measuring a current of a phase outputting a medium-sized phase voltage as a first current and a current of a phase outputting a phase voltage of a minimum magnitude as a second current;

A second step of calculating a phase current outputting the largest phase voltage from the first current and the second current obtained in the first step; A method for measuring the current of an inverter using a shunt resistor, characterized in that consisting of.

The method of claim 1,

When the PWM output is generated by the phase voltage reference value calculated by the controller, the magnitude of the phase voltage reference value among the three phases is determined, and the measurement target of the first current and the second current measured in the first step is variable according to the determination result. Inverter current measurement method using a shunt resistor, characterized in that the.

In the current measurement method of the inverter using a shunt resistor,

Determine the magnitude of the phase voltage reference value output from the controller and change the current measurement order in the order of the phase current outputting the reference value of medium size and the phase current outputting the minimum size reference value to measure the first current and the second current, Computing the current of the phase outputting a reference value of the maximum magnitude from the measured first current and the second current current measuring method of the inverter using a shunt resistor.