Load commutated current source inverter

A current-source inverter circuit for a motor drive system comprising:

• a direct current source;
• a reference current, wherein the reference current defines a switching signal to control the current-source inverter;
• a first silicon-controlled rectifier connected in series with a second silicon-controlled rectifier, wherein a cathode of the first silicon-controlled rectifier is connected to an anode of the second-silicon-controlled rectifier at a first node;
• and
• a third silicon-controlled rectifier connected in series with a fourth silicon-controlled rectifier;
• wherein a cathode of the third silicon-controlled rectifier is connected to an anode of the second silicon-controlled rectifier at a second node;
• wherein the anodes of the first and third silicon-controlled rectifiers are coupled to the direct current source;
• wherein the cathodes of the second and fourth silicon-controlled rectifiers are coupled to the reference current;
• and wherein switching on the third silicon-controlled rectifier results in the switching off of the first silicon-controlled rectifier.

A control system for controlling the operations of a motor drive system, comprising:

• an estimator configured to calculate estimated magnitudes and positions of a rotor flux of an induction motor based on signals from a motor terminal of a motor drive system;
• a speed control configured to provide first motor current information based on signals received from the estimator;
• a flux control configured to provide second motor current information based on signals received from the estimator;
• a current reference generator configured to provide reference current information based on signals received from the motor terminal, the speed control, the flux control, and the estimator;
• an active filter current control configured to provide active filter control information based on signals from the motor terminal and the estimator;
• a VSI in-phase sine triangle pulsewidth modulator (IP-SPWM) configured to control transistors in an active filter in the motor drive system based on signals received from the active filter current control;
• a DC control configured to provide DC control information based on signals from a DC link inductor in the motor drive system and signals received from the current reference generator;
• a CSI gate configured to control a current-source inverter in the motor drive system based on signals received from the current reference generator;
• and
• a rectifier gate configured to control thyristors in an inverter in the motor drive system based on signals received from the DC control.