System and method for consistent speed regulation in a variable frequency drive

A method of controlling a variable frequency drive (VFD) circuit via a control system comprising a feedforward controller and a feedback controller, the method comprising:

• measuring or estimating a motor speed of a motor being controlled by the VFD circuit according to an introductory torque command;
• providing an input to the feedback controller comprising the motor speed;
• introducing a speed reference input in the feedforward controller;
• modifying the motor speed input in the feedback controller to generate a modified feedback controller output;
• modifying the speed reference input in the feedforward controller to generate a modified feedforward controller output;
• calculating an updated torque command based on the modified outputs of the feedback and feedforward controllers;
• and
• controlling the VFD circuit to supply power to the motor based on the torque command.

A regulator for controlling the output of a variable frequency drive (VFD) circuit, the regulator programmed to:

• sense or estimate a motor speed of a motor driven by the VFD circuit according to an initial torque command;
• receive a speed reference value;
• filter the speed reference value;
• manipulate the motor speed in a feedback controller according to the filtered speed reference value;
• manipulate the speed reference value in a feedforward controller according to the filtered speed reference value;
• determine a modified torque command value according to the manipulated motor speed and manipulated speed reference value;
• and
• control the VFD circuit to drive the motor in conformance with the modified torque command value.