Method for measuring phase current for inverter control apparatus using single current sensor and apparatus therefor

• US 20020167300A1
• Filed: 05/08/2002
• Published: 11/14/2002
• Est. Priority Date: 05/10/2001
• Status: Active Grant

• Current Assignee: LG Industrial Systems Co., Ltd (LG Corporation)
• Original Assignee: LG Industrial Systems Co., Ltd (LG Corporation)
• Inventors: Kim, Kyung-Seo
• Granted Patent: US 6,642,690 B2
• Time in Patent Office: Days
• US Class Current: 324/107
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 7/53871 with automatic control of output voltage or current
• CPC Class Codes: H02M 7/5395 by pulse-width modulation
• CPC Class Codes: H02P 27/048 using AC supply for only the rotor circuit or only the stator circuit
• CPC Class Codes: H02P 27/16 using ac to ac converters without intermediate conversion to dc H02P27/05 takes precedence

Abstract

A method for measuring three-phases alternating current using a current sensor and an apparatus therefor, which are capable of not changing an average voltage for a switching period by changing reference voltages for modulating pulse width in a switching period of an inverter and compensating for the changed reference voltages in the same switching period. It is possible to prevent current from being distorted, to detect three-phases output current in all of the switching periods, and to rapidly control instantaneous current by changing the reference voltages of arbitrary two phases in one switching period of an inverter, measuring current of each phase for the switching period using the current sensor, and compensating for the amounts of changes in the changed reference voltages of the two phase in the switching period.

Claims

1. A method for measuring current of each phase for an inverter control apparatus comprising a converter for converting alternating current from a three-phase alternating current power source into direct current, an inverter provided with a pair of switching devices in each phase, the inverter for converting direct current from the converter into alternating current and providing the alternating current to a three-phases induction motor, single current sensor for measuring current of a phase, which flows through the motor, an analog-to digital (A/D) converter for converting an analog measured value of current, which is measured by the current sensor, into a digital measured value, and an inverter controller for generating a reference voltage of each phase and a pulse width modulation (PWM) signal using a triangle wave on the basis of the digital measured value from the analog digital converter, to thus control switching of a is switching device of each phase, the method comprising the steps of:

(a) changing the reference voltages of arbitrary two phases in one cycle of the triangle wave;

(b) measuring current of each phase for the one cycle of the triangle wave using the current sensor; and

(c) compensating for the amount of change in the reference voltages of the two phases in the one cycle of the triangle wave.

2. The method of claim 1, wherein, in the step (a), the reference voltage of one phase having the highest voltage among three-phases reference voltages in a rising period of the triangle wave is increased by a predetermined voltage and the reference voltage of the other phase having the lowest voltage is decreased by the predetermined voltage for the one cycle of the triangle wave,

and wherein, in the step (c), the reference voltage of one phase having the highest voltage among the three-phase reference voltages in a falling period of the triangle wave is decreased by the increased voltage and the reference voltage of the other phase having the lowest voltage is reduced for the one cycle of the triangle wave so that an average reference voltage of each phase does not change for the one cycle of the triangle wave.

3. An inverter control apparatus, comprising:

a converter for converting alternating current from a three-phase alternating current power source into direct current;

an inverter provided with a pair of switching devices in each of the three phases, the inverter for converting direct current from the converter into alternating current and providing the alternating current to a three-phases induction motor;

a current sensor for measuring current of a phase, which flows through the motor;

an A/D converter for converting an analog measured value of current of the phase, which is measured by the current sensor, into a digital measured value; and

;

an inverter controller for generating a reference voltage of each phase and a Pulse Width Modulation signal using a triangle wave on the basis of the digital measured value from the analog digital converter, controlling switching of a switching device of each phase, changing the reference voltages of arbitrary two phases in one cycle of the triangle wave, and compensating for the amounts of changes in the changed reference voltages of the two phases in the one cycle of the triangle wave.

4. The inverter control apparatus of claim 3, wherein the inverter controller controls the switching of the switching device of each phase by generating a Pulse Width Modulation signal using a reference voltage of each phase and a triangle wave, increases the reference voltage of one phase having the highest voltage among three-phases reference voltages in a rising period of one cycle of the triangle wave by a predetermined voltage, decreases the reference voltage of the phase having the lowest voltage among the three-phases reference voltages by the predetermined voltage, decreases the reference voltages by the amount of increase in the reference voltage of one phase having the highest voltage in a falling period of the one cycle of the triangle wave, and increases the reference voltages by the amount of decrease in the reference voltage of the phase having the lowest voltage, so that an average reference voltage of each phase does not change for one switching period.