Phase distortion compensating apparatus and method for reducing torque ripple in 3-phase motor
First Claim
1. A phase distortion compensating apparatus for reducing a torque ripple in a 3-phase motor, comprising:
- a rectifier unit for rectifying an input AC voltage into a DC voltage;
upper and lower DC link capacitors connected in parallel to the rectifier unit, each of the DC link capacitors serving to conduct charge and discharge operations for the DC voltage;
an inverter connected in parallel to the capacitors and adapted to generate a 3-phase voltage adapted to rotate the 3-phase motor, based on voltages respectively discharged from the capacitors along with a switching signal, and a voltage command generator for calculating compensation components for respective switching operations of switching elements included in the inverter, which are connected to A and B phases of the motor, based on a voltage difference between the capacitors, a difference between an actual rotating speed of the motor and a command speed, and a rotor position of the motor, and providing respective switching times including the calculated compensation components, thereby controlling a rotating speed of the motor, wherein an operational one phase of the 3-phase motor is connected to a connection node between the upper and lower DC link capacitors.
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Abstract
Disclosed are a phase distortion compensating apparatus and method for reducing a torque ripple in a 3-phase motor using four switching elements, which are capable of adjusting respective switching times of phase voltages, to be supplied to the 3-phase motor by an inverter including the switching elements, based on a voltage difference between upper and lower DC link capacitors respectively adapted to supply voltages to the inverter, thereby reducing a torque ripple generated in the motor. The apparatus includes a rectifier unit, upper and lower DC link capacitors connected in parallel to the rectifier unit, each of the capacitors serving to conduct charge and discharge operations for a DC voltage outputted from the rectifier unit, an inverter connected in parallel to the capacitors and adapted to generate a 3-phase voltage adapted to rotate the motor, based on voltages respectively discharged from the capacitors along with a switching signal, and a voltage command generator for calculating compensation components for respective switching operations of switching elements of A and B phases included in the inverter, based on a voltage difference between the capacitors, a difference between an actual motor speed and a command speed, and a rotor position, and providing respective switching times including the calculated compensation components, thereby controlling a rotating speed of the motor.
13 Citations
11 Claims
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1. A phase distortion compensating apparatus for reducing a torque ripple in a 3-phase motor, comprising:
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a rectifier unit for rectifying an input AC voltage into a DC voltage;
upper and lower DC link capacitors connected in parallel to the rectifier unit, each of the DC link capacitors serving to conduct charge and discharge operations for the DC voltage;
an inverter connected in parallel to the capacitors and adapted to generate a 3-phase voltage adapted to rotate the 3-phase motor, based on voltages respectively discharged from the capacitors along with a switching signal, and a voltage command generator for calculating compensation components for respective switching operations of switching elements included in the inverter, which are connected to A and B phases of the motor, based on a voltage difference between the capacitors, a difference between an actual rotating speed of the motor and a command speed, and a rotor position of the motor, and providing respective switching times including the calculated compensation components, thereby controlling a rotating speed of the motor, wherein an operational one phase of the 3-phase motor is connected to a connection node between the upper and lower DC link capacitors. - View Dependent Claims (2, 3)
a speed detector coupled to the motor and adapted to detect the rotating speed of the motor;
a position detector coupled to the speed detector and adapted to detect the rotor position of the motor based on the detected rotating speed;
a subtractor coupled to the position detector and the speed detector and adapted to derive an error of the detected rotating speed from the command speed;
a speed controller coupled to an output of the subtractor and adapted to determine the level of a voltage to be supplied to the motor, based on the derived speed error; and
a voltage detector adapted to derive the voltage difference between the upper and lower DC link capacitors.
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3. The phase distortion compensating apparatus according to claim 2, further comprising, in place of the voltage detector:
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a current detector for detecting a current inputted to a connection node between the upper and lower DC link capacitors to which an optional one phase of the 3-phase motor is connected; and
an integrator for integrating the detected current, thereby indirectly deriving the voltage difference between the capacitors.
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4. A phase distortion compensating apparatus for reducing a torque ripple in a 3-phase motor, comprising:
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a rectifier unit for rectifying an input AC voltage into a DC voltage;
upper and lower DC link capacitors connected in parallel to the rectifier unit, each of the DC link capacitors serving to conduct charge and discharge operations for the DC voltage;
an inverter connected in parallel to the capacitors and adapted to generate a 3-phase voltage adapted to rotate the 3-phase motor, based on voltages respectively discharged from the capacitors along with a switching signal;
a voltage command generator for calculating compensation components for respective switching operations of switching elements included in the inverter, which are connected to A and B phases of the motor, based on a voltage difference between the capacitors, a difference between an actual rotating speed of the motor and a command speed, and a rotor position of the motor, and providing respective switching times including the calculated compensation components, thereby controlling a rotating speed of the motor, wherein the voltage command generator calculates the compensation components for respective switching operations of the switching elements of A and B phases, based on the voltage difference derived by the integrator, the rotor position detected by the position detector, and the voltage level determined by the speed controller;
a speed detector coupled to the motor and adapted to detect the rotating speed of the motor;
a position detector coupled to the speed detector and adapted to detect the rotor position of the motor based on the detected rotating speed;
a subtractor coupled to the position detector and the speed detector and adapted to derive an error of the detected rotating speed from the command speed;
a speed controller coupled to an output of the subtractor to determine the level of a voltage to be supplied to the motor, based on the derived speed error;
a current detector for detecting a current input to a connection node between the upper and lower DC link capacitors to which an optional one phase of the 3-phase motor is connected; and
an integrator for integrating the detected current, thereby indirectly deriving the voltage difference between the capacitors.
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5. The phase distortion compensating apparatus for reducing a torque ripple in a 3-phase motor, comprising:
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a rectifier unit for rectifying an input AC voltage into a DC voltage;
upper and lower DC link capacitors connected in parallel to the rectifier unit, each of the DC link capacitors serving to conduct charge and discharge operations for the DC voltage;
an inverter connected in parallel to the capacitors and adapted to generate a 3-phase voltage adapted to rotate the 3-phase motor, based on voltages respectively discharged from the capacitors along with a switching signal;
a voltage command generator for calculating compensation components for respective switching operations of switching elements included in the inverter, which are connected to A and B phases of the motor, based on a voltage difference between the capacitors, a difference between an actual rotating speed of the motor and a command speed, and a rotor position of the motor, and providing respective switching times including the calculated compensation components, thereby controlling a rotating speed of the motor; and
a speed detector coupled to the motor and adapted to detect the rotating speed of the motor;
a position detector coupled to the speed detector and adapted to detect the rotor position of the motor based on the detected rotating speed;
a subtractor coupled to the position detector and the speed detector and adapted to derive an error of the detected rotating speed from the command speed;
a speed controller coupled to an output of the subtractor to determine the level of a voltage to be supplied to the motor, based on the derived speed error; and
a current detector comprising a diode and a capacitor and serving to detect a current inputted to the connection node.
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6. A phase distortion compensating method for reducing a torque ripple in a 3-phase motor, comprising the steps of:
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(a) calculating respective switching times (Ta and Tb) for upper ones of four switching elements respectively associated with A- and B-phase legs in an inverter, the A- and B-phase legs being connected to A and B phases of the motor, respectively, based on a voltage command for driving the 3-phase motor;
(b) comparing the calculated switching times (Ta and Tb) with each other;
(c) calculating on-time t1 of lower switch in the A- and B-phase legs switching status from the Ta and Tb and on-time t2 of upper switch in the A- and B-phase legs switching status from the Ta and Tb;
(d) detecting a current inputted to a connection node between upper and lower DC link capacitors respectively connected to the A- and B-phase legs of the inverter after completion of the calculation of the switching times (t3 and t3), and integrating the detected current, thereby deriving a difference between a voltage across the upper DC link capacitor and a voltage across the lower DC link capacitor;
(e) calculating respective compensation components (Δ
Ta and ATb) for the switching times (Ta and Tb), based on the derived voltage difference; and
(f) producing new switching times (Ta′ and
Tb′
) respectively reflecting the calculated compensation components, and supplying the new switching times to the inverter.- View Dependent Claims (7, 8, 9, 10, 11)
where, “
ma”
represents a modulation rate, and “
Tsamp”
represents a sampling time.
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9. The phase distortion compensating method according to claim 6, wherein the calculation of On times (t1 and t3) at the step (c) is carried out using the following equations
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10. The phase distortion compensating method according to claim 6, wherein the calculation of the compensating components (Δ
- Ta and Δ
Tb) for the switching times (Ta and Tb) at the step (e) is carried out using the following equations;
- Ta and Δ
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11. The phase distortion compensating method according to claim 6, wherein the calculation of the new switching times (Ta′
- and Tb′
) at the step (f) is carried out using the following equation;
- and Tb′
Specification