A new current control method for energy‐efficient/wide‐speed‐range drive of permanent magnet synchronous motor

Abstract

SUMMARYThis paper proposes a new current control method for energy-efficient and/or wide-speed-range drive of salientpole permanent magnet synchronous motors. The proposed method is distinguished from conventional ones by the following features. (1) The original command is a signed current norm. (2) The exact d-axis and q-axis current commands that perform energy-efficient and/or wide-speedrange drive are analytically and simply determined from the singed current norm command. (3) For speed control mode, the system turns out to be nonlinear, but its stability can be guaranteed based on Popov's stability theorem. (4) It can be applied for a mode similar to torque control. (5) Current limitation can be carried out accurately but very simply. Concrete analytical d-axis and q-axis current commands are presented, which satisfy exactly one of three optimum current control codes such as maximum torque, maximum power factor, and voltage limitation. A design method for PI speed controller that guarantees system stability is also presented.

A New Self‐Tuning Power‐Factor‐Based Vector Control Method for Efficient Wide‐Speed Range Sensorless Drive of Permanent‐Magnet Synchronous Motors

“…where Np and ω * 2m are the number of pole pairs and the command value of mechanical speed ω 2m , respectively, and K 1 , K 2 , and K 3 are the setting parameters, which designers can set by themselves, which are determined using the following conditions [2,13]. (16) where i δ means the rated current value of the stator in Eq. (16).…”

“…It is known that the current which realizes minimum copper loss under voltage limitation is at an intersection point made by a true circle of current and a voltage limitation ellipse [1,16]. A generated stator voltage should be under this limitation.…”

“…As a power-factor-based vector control method constructed on a γδ power factor current frame, there is a current II-based determination method, which is a simplified current I-based determination method [16]. However, the current II-based determination method needs approximation process to compensated frequencies, and the approximation region is excessed at high-speed drive, so that the proposed method cannot be applied.…”

“…The voltage limitation ellipse shrinks toward its center i d = -Φ/L d as the speed is increased. It is known that the current which realizes minimum copper loss under voltage limitation is at an intersection point made by a true circle of current and a voltage limitation ellipse [1,16]. Considering the voltage limitation from this fact, in order to high-speed and efficiency drive, stator current needs to move toward the d-axis to keep it inside the voltage limitation ellipse shrunken according to increase of speed.…”

“…The design parameters K 1 and K 3 in a phase-speed estimator were determined based on the determination policy as shown in Eq. (16).…”