dq0

dq0 is a notation used in electrical engineering and power electronics to describe a three-axis representation of a three-phase quantity after transformation into a direct-quadrature-zero (dq0) frame. The dq0 frame is a rotating reference frame for the direct (d) and quadrature (q) axes, plus a zero-sequence (0) axis. It is obtained by applying Clarke's and Park's transforms to three-phase variables (a, b, c). In this frame, the d-axis is typically aligned with the rotor flux direction, the q-axis is orthogonal to it, and the 0-axis captures the sum or average (zero-sequence) component. In balanced three-phase systems, the 0 component is often negligible, while in unbalanced or multiphase configurations it carries meaningful information.

Applications include vector control of induction and synchronous machines, brushless DC motors, and grid-connected converters. The dq0 representation often linearizes and decouples torque and flux dynamics, enabling separate current control loops for the d and q axes. It is a standard tool in field-oriented control and in the real-time control of electric drives and power electronics.

Beyond engineering, dq0 can appear as a label or code name in software projects or other media; in such cases its meaning is defined by the source and is not part of a standard terminology.

See also: Clarke transform, Park transform, direct-quadrature-0 frame, vector control.