Microprocessor-based efficiency optimization control for an induction motor drive system

Claim 1

A method of controlling an induction machine drive during steady state operation using a microcomputer having stored machine constants, the machine drive having an stator current control loop and a stator frequency control loop, said method comprising the steps of: (1) measuring induction machine slip, torque and air gap flux; (2) determining machine stator copper loss, rotor copper loss and iron loss from measured variables and machine constants; (3) determining machine efficiency from machine losses and power input to the machine; (4) processing machine efficiency as a function of air gap flux to determine whether air gap flux should be increased or decreased to increase machine efficiency; (5) varying air gap flux by a predetermined amount in the direction determined in step 4; (6) varying frequency so that the previously determined torque is maintained; (7) commanding the new values of air gap flux and frequency in said stator current control loop and said stator frequency control loop, respectively; and (8) repeating steps 1-8.

Claim 2

A method of controlling an induction machine drive during steady state operation using a microcomputer having stored machine constants, the machine drive having an stator current control loop and a stator frequency control loop, said method comprising the steps of: (1) measuring induction machine slip, torque and air gap flux; (2) determining machine stator copper loss, rotor copper loss and iron loss from measured variables and machine constants; (3) determining machine efficiency from machine losses and power input to the machine; (4) processing machine efficiency as a function of air gap flux to determine whether air gap flux should be increased or decreased to increase machine efficiency; (5) varying air gap flux by a predetermined amount in the direction determined in step 4; (6) varying frequency so that the previously determined torque is maintained; (7) commanding the new values of air gap flux and frequency in said stator current control loop and said stator frequency control loop, respectively; and (8) repeating steps 1-8.

Claim 4

A method of controlling an induction machine drive during steady state operation using a microcomputer having stored machine constants, the machine drive having a stator voltage control loop and a stator frequency control loop, said method comprising the steps of: (1) determining induction machine slip, torque and air gap flux; (2) determining machine stator copper loss, rotor copper loss and iron loss from measured variables and machine constants; (3) determining machine efficiency from machine losses and power input to the machine; (4) processing machine efficiency as a function of air gap flux to determine whether air gap flux should be increased or decreased to increase machine efficiency; (5) varying air gap flux by a predetermined amount in the direction determined in step 4; (6) varying frequency so that the previously determined torque is maintained; (7) commanding the new values of airgap flux and frequency in said stator voltage control loop and said stator frequency control loop, respectively; and (8) repeating steps 1-8.

Claim 5

A method of controlling an induction machine drive during steady state operation using a microcomputer having stored machine constants, the machine drive having a stator voltage control loop and a stator frequency control loop, said method comprising the steps of: (1) determining induction machine slip, torque and air gap flux; (2) determining machine stator copper loss, rotor copper loss and iron loss from measured variables and machine constants; (3) determining machine efficiency from machine losses and power input to the machine; (4) processing machine efficiency as a function of air gap flux to determine whether air gap flux should be increased or decreased to increase machine efficiency; (5) varying air gap flux by a predetermined amount in the direction determined in step 4; (6) varying frequency so that the previously determined torque is maintained; (7) commanding the new values of airgap flux and frequency in said stator voltage control loop and said stator frequency control loop, respectively; and (8) repeating steps 1-8.

Claim 7

A method of generating an air gap flux command and a slip command for a converter-fed induction motor drive comprising the steps of: (1) determining the torque error and proceeding to step 2 when the torque error is below a predetermined amount; (2) sensing stator current and voltage and machine angular velocity; (3) determining stator fundamental RMS current and ripple current from the sensed stator current; (4) determining machine losses from known machine parameters, machine speed and stator RMS and ripple current, (5) determining machine efficiency from machine losses and machine stator currents and losses; (6) determining machine air gap flux; (7) decreasing machine air gap flux by a predetermined amount to obtain a new value of air gap flux; (8) measuring machine torque; (9) determining a new value of machine slip corresponding to the new value of machine air gap flux to maintain machine torque at its measured value; (10) commanding the new values of machine air gap flux and slip; (11) performing steps 1-4; (12) processing machine efficiency as a function of air gap flux to determine whether air gap flux should be increased or decreased to increase machine efficiency; (--) varying air gap flux by a predetermined amount in the direction determined in step 12; (14) performing steps 8 and 9; (15) repeating steps 1-5, 8, 12, 13, 14 and 15.

Claim 8

A method of generating an air gap flux command and a slip command for a converter-fed induction motor drive comprising the steps of: (1) determining the torque error and proceeding to step 2 when the torque error is below a predetermined amount; (2) sensing stator current and voltage and machine angular velocity; (3) determining stator fundamental RMS current and ripple current from the sensed stator current; (4) determining machine losses from known machine parameters, machine speed and stator RMS and ripple current, (5) determining machine efficiency from machine losses and machine stator currents and losses; (6) determining machine air gap flux; (7) decreasing machine air gap flux by a predetermined amount to obtain a new value of air gap flux; (8) measuring machine torque; (9) determining a new value of machine slip corresponding to the new value of machine air gap flux to maintain machine torque at its measured value; (10) commanding the new values of machine air gap flux and slip; (11) performing steps 1-4; (12) processing machine efficiency as a function of air gap flux to determine whether air gap flux should be increased or decreased to increase machine efficiency; (--) varying air gap flux by a predetermined amount in the direction determined in step 12; (14) performing steps 8 and 9; (15) repeating steps 1-5, 8, 12, 13, 14 and 15.

Claim 9

A method of generating an air gap flux command and a slip command for a converter-fed induction motor drive comprising the steps of: (1) determining the torque error and proceeding to step 2 when the torque error is below a predetermined amount; (2) sensing stator current and voltage and machine angular velocity; (3) determining stator fundamental RMS current and ripple current from the sensed stator current; (4) determining machine losses from known machine parameters, machine speed and stator RMS and ripple current, (5) determining machine efficiency from machine losses and machine stator currents and losses; (6) determining machine air gap flux; (7) decreasing machine slip by a predetermined amount to obtain a new value of slip; (8) measuring machine torque; (9) determining a new value of machine air gap flux corresponding to the new value of machine slip to maintain machine torque at its measured value; (10) commanding the new values of machine air gap flux and slip; (11) performing steps 1-4; (12) processing machine efficiency as a function of slip to determine whether slip should be increased or decreased to increase machine efficiency; (13) varying slip by a predetermined amount in the direction determined in step 12; (14) performing steps 8 and 9; (15) repeating steps 1-5, 8, 12, 13, 14 and 15.

Claim 10

A method of generating an air gap flux command and a slip command for a converter-fed induction motor drive comprising the steps of: (1) determining the torque error and proceeding to step 2 when the torque error is below a predetermined amount; (2) sensing stator current and voltage and machine angular velocity; (3) determining stator fundamental RMS current and ripple current from the sensed stator current; (4) determining machine losses from known machine parameters, machine speed and stator RMS and ripple current, (5) determining machine efficiency from machine losses and machine stator currents and losses; (6) determining machine air gap flux; (7) decreasing machine slip by a predetermined amount to obtain a new value of slip; (8) measuring machine torque; (9) determining a new value of machine air gap flux corresponding to the new value of machine slip to maintain machine torque at its measured value; (10) commanding the new values of machine air gap flux and slip; (11) performing steps 1-4; (12) processing machine efficiency as a function of slip to determine whether slip should be increased or decreased to increase machine efficiency; (13) varying slip by a predetermined amount in the direction determined in step 12; (14) performing steps 8 and 9; (15) repeating steps 1-5, 8, 12, 13, 14 and 15.