Direct torque control inverter arrangement

An inverter arrangement for simultaneous control of a stator flux and a torque of an electric machine (M) having a number of phases, comprising

• an inverter (AC) having switches (S.sub.wa, S.sub.wb, S.sub.wc) and connected to a direct voltage intermediate circuit (DC) for generating an alternating voltage (u.sub.s) having a corresponding number of main phases (U.sub.a, U.sub.b, U.sub.c) as the electric machine (M), and
• a control system (CS) for controlling an instantaneous value of the alternating voltage (u.sub.s) generated by the inverter (AC);
• the control system (CS) receiving, as input variables, reference values for the torque (T.sub.ref) and stator flux (.psi..sub.ref) and measured values for the stator current (i.sub.s) and stator voltage (u.sub.s) and a stator voltage reference (u.sub.sref), including means (EC) for defining error variables, for the torque (T.sub.err) and the stator flux (.psi..sub.err), said error variables being based on input variables and which describe a difference between the reference values and actual values, and
• means for controlling the switches (Swa, Swb, Swc) of the inverter (AC) on the basis of the error variables, wherein the means for controlling the switches of the inverter includes:
• means (FC, TC, CC) for generating a stator voltage reference (u.sub.sref) in response to the error variables (T.sub.err, .psi..sub.err) of the torque and stator flux,
• means (POL) for generating main voltage reference values (U.sub.acref, U.sub.bcref) in response to the stator voltage reference (U.sub.sref), and
• a feedback voltage controller (VC2;
• VC3) for controlling the main voltages of the stator voltage supplied to the electric machine (M) such that said main voltages correspond to the defined reference values (u.sub.acref, u.sub.bcref) of the main voltages.

An inverter arrangement having at least one phase for connection to an intermediate circuit for simultaneous control of stator flux and torque values of an electric machine having a corresponding number of phases comprising:

• an inverter having switches for generating an alternating voltage having a number of phases corresponding to the phases of the electric machine;
• a control system for controlling an instantaneous value of the alternating voltage generated by the inverter, the control system receiving, as input variables, reference values corresponding to the torque and to the stator flux and measured values corresponding to stator current and to stator voltage including means for defining error variables for the torque and the stator flux based on the input variables and which describe the difference between the reference values and the measured values, and means for controlling the switches of the inverter on the basis of the error variables, means for controlling the switches of the inverter including:
• means for generating a stator voltage reference based on the error variables of the torque and stator flux;
• means for generating reference values on the basis of the stator voltage reference defined for phase voltages of the stator voltage and the reference value for a common-mode voltage of the stator voltage, and
• a feedback voltage controller for controlling the phase voltages of the stator voltage supplied to the electric machine such that said phase voltages correspond to the defined reference values of the phase voltages.

An inverter arrangement having at least one phase for connection to a direct voltage intermediate circuit for simultaneous control of stator flux and torque values of an electric machine having a corresponding number of phases, comprising:

• an inverter connected to a direct voltage intermediate circuit including inverter control switches for generating an alternating voltage that has a corresponding number of phases as the electric machine, and
• a control system for controlling an instantaneous value of the alternating voltage generated by the inverter, the control system receiving, as input variables, reference values corresponding to the torque and to the stator flux and measured values corresponding to stator current (i.sub.s) and to stator voltage including means for defining error variables for the torque and the stator flux based on the input variables for describing the difference between the reference values and the measured values, and
• means for controlling the inverter control switches in accordance with the error variables, including
• means for generating a stator voltage reference in accordance with the error variables of the torque and stator flux values,
• means for generating reference values in accordance with the stator voltage reference, defined for voltages of the strator voltage, and
• a feedback voltage controller for controlling the voltages of the stator voltage supplied to the electric machine corresponding to the defined reference values of the voltages.