Apparatus for controlling inverter
An apparatus for controlling an inverter is disclosed. The apparatus for controlling the inverter contained in an inverter system configured to drive a motor determines a slip frequency to be used for compensation of a frequency of a first reference voltage, not only using a first reference voltage (including an amplitude and frequency) of the first reference voltage applied to the inverter, but also using an output current of the motor or a rotor speed of the motor. The apparatus determines not only a frequency of a second reference voltage obtained by compensation of the slip frequency, but also an amplitude of the second reference voltage corresponding to the frequency of the second reference voltage.
1. An apparatus for controlling an inverter contained in an inverter system configured to drive a motor, comprising:
a slip frequency decision unit configured to determine a first slip frequency to be used for compensation of a frequency of a first reference voltage, not only using a first reference voltage (including an amplitude and frequency) of the first reference voltage applied to the inverter, but also using an output current of the motor or a rotor speed of the motor; and
a reference voltage generation unit configured to determine not only a frequency of a second reference voltage achieved by compensation of the first slip frequency, but also an amplitude of the second reference voltage corresponding to the frequency of the second reference voltage, and apply the second reference voltage to the inverter,
wherein the slip frequency decision unit includes:
a closed-loop controller configured to determine a second slip frequency using the rotor speed of the motor; and
an open-loop controller configured to determine a third slip frequency, using an output current of the motor, the amplitude and frequency of the first reference voltage, and a nominal value of the motor.
2. The apparatus according to claim 1 , wherein the closed-loop controller includes:
a comparator configured to compare the first frequency with the rotor speed of the motor; and
a proportional integral (PI) controller configured to output the second slip frequency by PI-controlling an output signal of the comparator.
3. The apparatus according to claim 1 , wherein the open-loop controller includes:
a load power decision unit configured to determine load power in consideration of the amplitude of the first reference voltage, the output current of the motor, and the number of poles of the motor;
a load torque decision unit configured to determine a load torque in consideration of the load power and the frequency of the first reference voltage; and
an open-loop slip frequency decision unit configured to determine the third slip frequency in consideration of the load torque, a rated torque of the motor, and a rated slip frequency of the motor.
4. The apparatus according to claim 3 , wherein the open-loop controller further includes:
a filter configured to perform low pass filtering of an output signal of the open-loop slip frequency decision unit.
5. The apparatus according to claim 1 , wherein the slip frequency decision unit further includes:
an adder configured to add the second slip frequency and the third slip frequency, thereby outputting the first slip frequency.