Four quadrant motor controller minimizing distortion index

A motor control apparatus for controlling a multiphase AC motor having stator windings and a rotor and powered by a source of AC power, the apparatus comprising:

• motor command means for defining a reference signal indicative of a desired motor parameter;
• current sensor means for sensing stator currents of the motor;
• a DC voltage link including means for storing energy;
• a self-commutated line-side converter means coupled to the DC voltage link for controlling the bidirectional flow of electrical power between the DC voltage link and the source of AC power, wherein the line-side converter includes active switches coupled in a bridge configuration between the source of AC power and the DC voltage link, and includes line-side control means for controlling the active switches therein to regulate the flow of electrical power therethrough;
• and
• motor-side converter means coupled to the DC voltage link for controlling stator currents of the motor by controlling the bidirectional currents between the DC voltage link and the motor, wherein the motor-side converter includes active switches coupled in a bridge configuration between the DC voltage link and the stator windings of the motor, includes motor-side control means responsive to the reference signal for determining desired stator currents, includes means for periodically determining a distortion index indicative of errors between the desired and actual stator currents, and includes means for controlling the active switches therein to produce stator currents that minimize the distortion index, wherein the means for controlling the active switches generates signals that are complimentary for each pair of active switches, causing one active switch of each pair to switch on and the other active switch of the pair to switch off as appropriate to minimize the distortion index.

A motor control apparatus for controlling a multiphase AC motor having stator windings and a rotor and powered by a source of AC power, the apparatus comprising:

• motor command means for defining a reference signal indicative of a desired motor parameter;
• current sensor means for sensing stator currents of the motor;
• a DC voltage link including means for storing energy;
• a self-commutated line-side converter means coupled to the DC voltage link for controlling the bidirectional flow of electrical power between the DC voltage link and the source of AC power, wherein the line-side converter includes active switches coupled in a bridge configuration between the source of AC power and the DC voltage link, and includes line-side control means for controlling the active switches therein to regulate the flow of electrical power therethrough, wherein the line-side control means includes means for determining desired line currents, includes means for sensing the actual line currents, includes means for periodically determining a distortion index indicative of errors between the desired and actual line currents, and includes means for controlling the active switches therein to produce line currents that minimize the distortion index, wherein the means for controlling the active switches generates signal that are complimentary for each pair of active switches, causing one active switch of each pair to switch on and the other active switch of the pair to switch off as appropriate to minimize the distortion index;
• and
• motor-side converter means coupled to the DC voltage link for controlling stator electrical quantities of the motor by controlling the bidirectional flow of electrical power between the DC voltage link and the motor, wherein the motor-side converter includes active switches coupled in a bridge configuration between the DC voltage link and the stator windings of the motor, and includes motor-side control means responsive to the reference signal for controlling the active switches therein to produce stator electrical quantities that correspond to the reference signal.

A method for controlling currents switched by a self-commutated bridge circuit containing active switches, the method comprising the steps of:

• determining desired bridge circuit currents;
• sensing the actual bridge circuit currents;
• and
• switching the active switches to produce bridge circuit currents that minimize a distortion index indicating the magnitude of current errors between the actual and desired bridge circuit currents, wherein the step of switching the active switches comprises the steps of generating signals that are complimentary for each pair of active switches, and causing one active switch of each pair to switch on and the other active switch of the pair to switch off as appropriate to minimize the distortion index.

A method for controlling stator currents in a multiphase AC motor rotating at variable speeds, wherein the stator currents are switched by a self-commutated bridge circuit that includes active switches, the method comprising the steps of:

• defining a reference signal indicative of a desired motor torque, speed, or position;
• converting the reference signal into desired stator currents;
• sensing the actual stator currents;
• determining a distortion index indicative of the magnitude of current errors between the actual and desired stator currents;
• and
• supplying pulse width modulation signals to the active switches to produce stator currents that minimize the distortion index, wherein the step of supplying pulse width modulation signals comprises the steps of generating signals that are complimentary for each pair of active switches, and causing one active switch of each pair to switch on and the other active switch of the pair to switch off as appropriate to minimize the distortion index.

A method for controlling stator currents in a multiphase AC motor rotating at variable speeds to obtain torque, speed, or position control of the motor, wherein the stator currents are switched by an self-commutated active rectifier that establishes a rotating flux field in the rotor of the motor, the method comprising the steps of:

• defining a reference signal indicative of a desired motor torque, speed, or position;
• determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system;
• converting the reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system;
• sensing the rotational speed of the rotor;
• sensing the actual stator currents;
• determining a rotor flux angle indicative of the instantaneous position of the rotor flux field;
• converting the desired quadrature and direct axis currents into desired stator currents in a stationary stator coordinate system using the rotor flux angle;
• determining a distortion index indicative of the magnitude of current errors between the actual and desired stator currents;
• and
• supplying pulse width modulation signals to the switches of the active rectifier to produce stator currents that minimize the distortion index, wherein the step of supplying pulse width modulation signals comprises the steps of generating signals that are complimentary for each pair of active switches, and causing one active switch of each pair to switch on and the other active switch of the pair to switch off as appropriate to minimize the distortion index.